A differential system and method for vehicles

Abstract

The differential of the present invention is designed to permit a finite amount of differentiation and / or yaw between the rotation of at least two (2) wheels of a vehicle. The novel differential, differential mechanism and method of differentiation includes the provision to replenish the finite differentiation. The present invention can also be used to differentiate between the front and rear axles of a 4-wheel drive or all-wheel drive vehicle or a multi-axle vehicle.

Description

A DIFFERENTIAL SYSTEM AND METHOD FOR VEHICLESBackground of the Invention1. Technical Field

[0001] The subject matter described herein relates, in general, to differentials of vehicles; and, more specifically, to an improved vehicle differential system that could (a) in general, provide an improved mechanism with a sum total of a maximum of 4 (four) inputs and outputs together, of which three (3) are rotary and one (1) is linear; and (b) also provide "yaw", the rotation of a vehicle around a vertical axis.2. Background Art

[0002] The subject matter discussed in the background section should not be assumed to be prior art merely because of its mention in the background section. Similarly, a problem mentioned in the background section or associated with the subject matter of the background section should not be assumed to have been previously recognized in the prior art. The subject matter in the background section merely represents different approaches that, in and of themselves, may also correspond to implementations of the claimed technology.

[0003] A differential plays a crucial role in a vehicle by allowing the wheels of at least (1) pair of wheels on the vehicle to rotate at different speeds when turning while still transmitting power from the prime mover or prime movers to both wheels in a wheel pair. However, the traditional differential design, which is based on the planetary gear system invented two centuries ago, has limitations because of its complex design, its need for a high level of maintenance, its high radius of gyration, its high un-sprung weight in rear axle driven vehicles, and its relatively poor overall performance. The entire vehicle is immobilized if one (1) wheel slips relative to the road surface.

[0004] There are many mechanisms known in the current art for transmitting motion from one (1) input to two (2) or more outputs. Some permit the outputs to move equally, and some unequally. Among these, some mechanisms, including the current state of the art in automobile differentials, permit "random unequal" movement of the two (2) outputs. "Random unequal" means that the two (2) outputs are driven unequally based on their respective resistances, and the mechanism does not fix or order any specific ratio or relationship between the two (2) outputs' movements. The most common example of "random unequal" movement being implemented is the current state-of-the-art in automobile differentials, which utilises planetary gearing. In such current wheeled vehicle differentials, the total of inputs and outputs is three (3).

[0005] If "specific unequal" movement is needed, meaning, if yaw of the vehicle is to be inputted, as in a vehicle with a continuous band of treads and vehicles with two (2) wheels, at present, sophisticated drive, feedback and control systems would be needed to give motion to the two (2) wheels or bands. Such specific unequal movement, in addition to propelling the vehicle, also performs the function of steering / navigating / manoeuvring the vehicle (i.e., providing the yaw). For purposes of this disclosure, the terms “bands with treads” or “bands” refers to the continuous band of track plates or treads typically used by snowmobiles, tractors, bulldozers and other similar vehicles or machines as their means of propulsion.

[0006] One example of the prior art of mechanisms for transmitting motion is U.S. Patent No. 3,174,361 to Jack M. Deline (hereinafter, “Deline”). According to Deline, a positive drive axle construction is adapted as a substitute for the differential gearing of automobile vehicles and the like and includes a central bevel drive gear adapted to be rotated in a conventional manner by a suitable shaft-driven pinion for driving the vehicle forward and in a second direction for driving the vehicle in reverse. The gear drives the vehicle through oppositely extending splined wheel axles. In other words, Deline is simply a mechanism for transmitting equal motion to two wheels when going straight, and disengaging (freewheeling) the outer wheel on a turn such that torque is transmitted only to the inner wheel during the turn. Otherwise, Deline does not disclose or suggest any structure or operation for a differential.

[0007] When the total consists of one (1) input and two (2) outputs, the two outputs are driven such that their average is the same as the input. When the "driven" wheels are driving the prime mover or generator, the differential serves to permit random inputs from the two (2) wheels driving the prime mover or generator at the average speed of the two (2) wheels.

[0008] The present state-of-the-art differential does not provide yaw. It is complicated, has a high radius of gyration due to the planetary gears, and permits infinite differentiation. So, if one wheel slips relative to the road or surface on which the vehicle is, the other wheel does not receive any torque, and the vehicle is immobilised. Numerous devices have been invented and are in use to give "limited slip" and other solutions of this problem. The present invention, when used as automobile differential, by itself has a finite amount of differentiation, unless replenished, thereby eliminating this problem.

[0009] Existing differentials have a large radius of gyration. In case of rear axle driven vehicles, a large bevel gear located physically within the differential, reduces ground clearance, increases the radius of gyration, and increases the un-sprung weight. Large inequality of size between the two (2) gears of the bevel pair in the current differential results in quick wear and damage of the pinion, which in turn damages the large bevel gear too.

[0010] The present invention enables specific, unequal differentiation that enables yaw, steering or manoeuvring, which current differentials are unable to do. The "Present invention" means the invention being disclosed in this application.Summary of Invention

[0011] The methods and devices disclosed herein overcome the above disadvantages and improves the state-of-the-art by way of an improved differential that allows for a large magnitude of finite amount of differentiation between the rotation of the two (2) wheels and a provision to replenish this differentiation when needed and further described below in the detailed description. This summary is not intended to identify essential features of the claimed subject matter nor is it intended for use in determining or limiting the scope of the claimed subject matter.

[0012] The present disclosure is about the development of a novel differential, differential mechanism, differential system and differential method. The term "differential" used hereinafter in the disclosure will be used to refer to a mechanical device that eliminates the use of gears in performing its function and, in addition, is capable of dividing the input torque ofone (1) shaft between two (2) output shafts where the two (2) shafts are likely to rotate at different speeds, as when a vehicle is turning. In conventional terms as known in the art, such mechanical device is typically formed from a system of gears, wherein the differential is used as the final drive of vehicles with two or more driven wheels (see for example Goodsell, Don (1995) Dictionary oj Automotive Engineering (2nd ed.) Warrendale, PA: Society of Automotive Engineers, Inc. ISBN 1-56091-683-4).

[0013] The differential of the present invention is designed to permit a finite amount of differentiation between the rotation of two (2) wheels of a wheeled vehicle. In vehicles, with more than one (1) wheel on the left and more than one (1) wheel on the right, both sets being differentiated by the differential, the term “left wheel” will mean all the wheels on the left side of the vehicle, and the term “right wheel” will mean all the wheels on the right side relative to a person sitting in the vehicle facing toward the front of the vehicle. In some embodiments, the novel differential, differential mechanism and method of differentiation includes the provision to replenish the finite differentiation. In some embodiments, the novel differential, differential mechanism and method will include the provision to uncouple the wheel(s) at the outside or inside of the curve being negotiated by the vehicle from the differential when the finite differentiation is exhausted, and replenishment is not possible or provided. The present invention can also be used to differentiate between the front and rear axles of a 4-wheel drive or all-wheel drive vehicle or a multi-axle vehicle.

[0014] The differential is a totally novel applied mechanics concept that employs inclined planes and, in terms of engineering design, utilises helical grooves / projections / constraints and / or balls / ball screws and / or roller screws to permit random unequal movement of two (2) outputs and / or to order specific unequal movement of two (2) outputs from an input.

[0015] The claims also include provisions for periodically bringing the differential back to a mean, baseline or desired position for replenishment, and for uncoupling one of the driven wheels when necessary.

[0016] The present invention can have a maximum sum of inputs plus outputs of four (4), including up to three (3) rotational inputs / outputs Ea, Eb, and Ec, and linear input / output Ed. The applied mechanics concept in the present invention is based on inclined planes, and some actual engineering designs, which employ balls, ball screws or roller screws, as will be disclosed in Detailed Description hereinbelow.

[0017] The relative position of the working elements is dependent on the net differentiation made, and right overdrive and left overdrive cancel each other out in terms of the relative positions of working parts of the differential. Furthermore, optionally, the differential is brought back to its mean position ("Mean Position") or desirable position ("Desirable Position") periodically before or after each time when, and whenever the engine or the prime mover and / or the driven wheel / driven wheels is / are uncoupled from the mechanism by a natural event and / or by design and / or when any of the driven wheels lose contact with the road or while braking, or in-between while shifting to / from the powered state from / to the regenerative braking state or when the vehicle is coasting, or when the finite limit of differentiation is near exhaustion.

[0018] Another embodiment may involve the use of synchrocones for disengaging and synchronizing the differential while / after replenishing the differentiation. This device can beused to uncouple the driven wheels or output elements from Elements Ea, Eb, and / or Ec to restore their relative positions to the mean baseline or desired position, as needed.

[0019] All the embodiments discussed above can be used in various applications, including as automobile differentials, as connectors between two (2) vehicle wheels driven by separate electric motors or prime movers, as torque transmitters to two (2) wheels of a two-wheeler with an ordered ratio of speeds, or as the sole steering or supplement or complement to other steering mechanism or systems. In addition, the embodiments of the invention are applicable for use as the differentials in other types of vehicles or other mobile machines, including but not limited to trucks, buses, and all other wheeled vehicles, such as electric vehicles (including those having regenerative braking), bicycles, powered scooters, personal transport devices (i.e., Segway), manually driven vehicles (i.e., operator-powered, animal drawn, wind driven), wheelchairs, steam driven vehicles, vehicles using other forms of locomotion, and generally all other vehicles with two (2) or more wheels (i.e., three-wheelers).

[0020] The objects and advantages will also be realized and attained by means of the elements and combinations particularly pointed out in the appended claims. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the claimed present invention.Brief Description of Drawings

[0021] The detailed description of the invention is described with reference to the accompanying drawings. The same references will be used throughout the drawings to refer to like features and components, except where repugnant to the context, wherein:

[0022] Fig. 1 illustrates the path a wheeled vehicle denoting the degrees of overdrive that occurs when the wheeled vehicle turns;

[0023] Fig. 2 shows a graph that illustrates a comparison between the gross overdrive in the right wheel versus the gross overdrive in the left wheel occurs in a wheeled vehicle travelling the route shown in Fig. 1;

[0024] Figs. 3A-3C show three (3) alternative forms of inclined planes illustrating the applied mechanics concept of a first embodiment of the claimed invention;

[0025] Figs. 4A-4B shows two alternative forms of inclined planes illustrating the applied mechanics concept of a second embodiment of the claimed invention;

[0026] Figs. 5A-5D show an implementation of the first embodiment of the structure of the claimed invention implementing the applied mechanics concept of Figs. 3A-3C;

[0027] Fig. 6A-6C show an implementation of the second embodiment of the structure of the claimed invention implementing the applied mechanics concept of Figs. 4A-4B;

[0028] Fig. 7A shows a third further embodiment of the structure of the claimed invention further implementing the applied mechanics concept of Figs. 4A-4B, including additional features and elements or alternatives;

[0029] Figs. 7B-7C show further embodiments of ball screw structures applicable to the claimed invention further implementing the applied mechanics concept of Figs. 3A-3C; and

[0030] Fig. 8 shows one embodiment for a computer or processor-based control system for the differential system of the claimed invention;

[0031] Fig. 9 shows a block diagram illustrating the operation of the computer or processorbased control system shown in Fig. 8 for the differential system of the claimed invention;

[0032] Figs. 10A-10C illustrate the structure and operation of an embodiment of the splitter as applied in the differential system of the present invention; and

[0033] Fig. 11 illustrates a fourth embodiment of a structure further implementing the applied mechanics of the present invention.Detailed Description of the Invention

[0034] By way of example and without implying any limitation as to applicability of the present invention, this disclosure will describe present state of the art as well as the present invention with respect to rear-axle driven vehicles. This present invention is not limited just to rear-axle driven vehicles or to powered vehicles and may also be used for two-wheelers. Even more, while the present invention will be described with reference to wheeled vehicle differentials hereinbelow, it has broader applicability. It is a mechanism whose inputs and outputs total four, of which three (3) are rotational, and one (1) is linear.

[0035] In the current state-of the-art differential, the engine (or another motive power) drives the bigger bevel gear of the bevel gear pair of the differential through a power train. This power train will consist of many elements including the bevel-gear pair housed within the differential which changes the direction of motion from the propeller shaft and usually also changes the ratio. This bevel pair is not part of the differential or of the present invention, although this pair is normally located within the "differential housing", and so is physically a part of the differential. For ease of description, the present invention is described in terms of internal combustion engine driven automobiles, but is also applicable to trucks, buses and all other wheeled vehicles, including but not limited to electric vehicles (including those having regenerative braking), bicycles, powered scooters, personal transport devices (i.e., Segway), manually driven vehicles (i.e., human drawn, animal drawn, wind driven), wheelchairs, steam driven vehicles, other electric vehicles, and generally all other vehicles with two (2) or more wheels.

[0036] The current state-of-the-art differential, such as that used in automobiles, drives the two (2) driven wheels such that the average of the revolutions per minute (RPM) of the two (2) driven wheels is equal to the RPM of the bigger bevel gear that houses the planets of the planetary system. For convenience of describing, the engine side or motor side of the differential is the "driving side" and "input" and the wheels side of the differential is the "driven side" and "output." However, when the vehicle is braking, or during regenerative braking, the wheels side is actually driving while the engine / motor / generator side is being driven.

[0037] Hereinbelow, for explanatory purposes only, the letter "Ea" will be used to reference the "driving side" ("input") of the differential mechanism of the present invention, while theletters "Eb" and "Ec" will be used to reference the "driven side" ("output"). Further, depending on the embodiment being discussed, the letter "Ed" will also be used to reference an additional input / output of the differential mechanism of the present invention. For the sake of simplicity, embodiments of the present invention will be based on vehicles with two (2) wheels per axle. For vehicles having more than two (2) wheels per propelled axle, the term "right wheel" will be construed to include a pair of wheels at the right side of the vehicle, and the term "left wheel" includes a pair of wheels at the left side of the vehicle. For vehicles that instead use continuous bands of treads, the terms "right wheel" and “left wheel” will be construed to include the sprocket or other means driving the right or left band of treads, respectively.

[0038] Figs. 1 and 2 illustrate how, in any actual travel of a wheeled vehicle, the gross overdrive on the left wheel plus the gross overdrive on the right wheel, as required by any number of turns in the travel, will result in a large magnitude of gross overdrive. Yet, this will result in a very low amount of net differentiation if, and only if, a differential can be designed such that the left and right overdrives compensate each other (i.e., cancel each other out) within the differential.

[0039] Fig. 1 shows a simplified example of the route taken by a vehicle in a country where vehicles are driven on the left of the road, which was initially parked at place "A" facing, say, east and moves to location "Z", again facing east. While moving from "A" to "Z" the vehicle encounters three major turns, A to D, H to L and since the road where it is to be parked is too narrow to take a "U" turn, a left turn followed “U” turn followed by right turn at V to Z. One of the road comers being too sharp, the vehicle has to butt into road centre at J to obtain a higher radius of turn. On the straight runs as well, the vehicle will not be going dead straight as it is driven by a human and also since other vehicles and / or obstacles need to be dodged. For brevity of description, it will be assumed that, on straight stretches, the vehicle deviates from the road's direction by exactly 15 (fifteen) degrees both ways every time. Fig. 1 also names the points A to Z and next to each of the positions A to Z the direction which the vehicle is facing in degrees. Thus, at G, the vehicle orientation is -90 (meaning it is at 90 degrees anti-clockwise of the orientation at A), which we arbitrarily take to be 0 degrees.

[0040] At every point of inflexion (i.e., when the vehicle is moving dead straight in between changing from a left turn to a right turn or vice-a-versa), there is a local maxima in terms of the orientation (direction) of the vehicle. These points (D, F, G, I, L, N, P, R, T, V and W) along with A and Z directly determine the differentiation required so as to eliminate tire wear and prevent under-steer or over-steer.

[0041] Fig. 2 shows the "overdrive" required for the path of Fig. 1. In Fig. 2, the Y-axis represents the overdrive required. In this disclosure, the overdrive required is treated as positive for the right wheel overdrive and negative for left wheel overdrive. The units shown on the Y- axis of Fig. 2 is degrees. The overdrive required in distance measured in the same unit of length as "W, is ^4 x 7t x 2 x W ^- 360 where "A" is the angle by which the vehicle turns in degrees, 7t is the mathematical constant "pi" (approximately 3.1428), and W is the horizontal distance between the wheels. In terms of revolutions, if wheel diameter is "d”, overdrive required would be {(A x 71 x W) (180 x d) } revolutions. The X-axis in Fig. 2 is arbitrary and not to any scale of time or distance. Points on the X-axis merely represent events / locations A to Z of Fig. 1.

[0042] By "overdrive", the description means the magnitude of inequality in the motion of the right wheel over the left wheel. Thus, arbitrarily and for ease of description in this application, when the right wheel moves more than the left wheel, it will be described as Positive Overdriveand when the left wheel moves more than the right wheel, it will be described as Negative Overdrive. Overdrive is required in order to compensate for the difference in the lengths of the paths of each wheel due to the vehicle turning. The exact curve followed by the vehicle is immaterial; only the orientation (direction faced) of the vehicle at every local maxima is relevant for calculating the differentiation required.

[0043] In Fig. 2, the graphed continuous lines GR and GL, one above and one below the X- axis, respectively, represent the gross corrections which will be made by a differential as right wheel overdrive and left wheel overdrive, respectively. The total of the gross corrections thus made in normal running is very high. In the simple example of Figs. 1 and 2, the gross overdrive required is as much as four hundred and twenty (420) degrees right overdrive and four hundred and twenty (420) degrees left overdrive. This means a gross overdrive of eight hundred and forty (840) degrees, even though the vehicle has never turned by more than 270 (two hundred and seventy) degrees vis-a-vis its starting position.

[0044] The dashed curved line ND in-between the GR and GL lines represents positive overdrive and negative overdrive. This dotted curved line ND represents the net correction made (after cancelling out the right overdrive against left overdrive). Unless the vehicle goes around in circles (such as around a traffic island, or on clover-leaf flyovers or some other road configuration) repeatedly, the net correction will rarely exceed the value for a full revolution in the orientation of the vehicle as exemplified in Fig. 1. Even if the same vehicle were to take a "U" turn at A, the net correction would still have been limited to three hundred and sixty (360) degrees.

[0045] The present invention proposes a mechanism which permits equal or random unequal motion of the driven wheels without the drawbacks of the current automobile differential. Further, it also provides a mechanism to facilitate specific unequal motion, with features which eliminate the drawbacks of current automobile differential and offer certain improvements. Optionally, it also provides means to manoeuvre the vehicle in and out of tight parking spots.

[0046] In particular, in at least one embodiment, the present invention proposes a mechanism to permit finite amount of differentiation, i.e., finite amount of unequal motion and, in which, the differentiation of left and differentiation of right cancel each other out. In another embodiment of the present invention, the finite differentiation is replenished. In a further embodiment, the present invention proposes a mechanism to implement finite differentiation that then provides an internal system for setting off or compensating left or right overdrive with the other. Among the features of the present invention in the various embodiments, the differential mechanism permits left overdrive and right overdrive to cancel each other out, such that it is not necessary for the mechanism to manage the gross differentiation.

[0047] The possibility of two (2) driven wheels having different effective diameters is obviated in current automobiles due to the tyre pressure monitoring system (TPMS) which is mandatory in major automobile markets such as the US, EU, Japan and South Korea.

[0048] In vehicles driven by only two (2) wheels, and vehicles driven by continuous bands of treads, the disclosed differential will permit ordered differentiation which will provide yaw. The present propulsion systems of vehicles with continuous bands of treads propel as well as provide yaw. However, the systems to provide exact yaw are extremely complicated, mostly based on costly and elaborate logic and control systems with feedback.

[0049] The present invention provides a method to steer / manoeuvre (i.e., provide yaw) through the differential mechanism. In particular, "specific unequal" differentiation as achieved by the present invention provides yaw (i.e., steering or manoeuvring of the vehicle) that can undertake, supplement or completely take over the steering function. Thus, the vehicle will have better control and stability. In the present invention, the vehicle will go straight merely by preventing differentiation. Further, the present invention as applied in a vehicle with only two (2) wheels can be steered using the yaw function of the differential according to the present invention.

[0050] This present invention is an improved mechanism where the number of inputs plus number of outputs can be a maximum of four (4), for transmitting motion from the input(s) to the output(s). In at least one embodiment, the present invention is used to give two (2) rotary outputs from one (1) rotary input. This can either be used to permit the outputs "random unequal" movement or to provide ordered equal or unequal movement to the outputs. The present invention can also be used to permit random unequal movement and to provide an output which could be used as the measure of the inequality, or as an output depending upon the extent of inequality.

[0051] Figs. 3A-3C show at least a first embodiment of the present invention illustrated again using the applied mechanics concept. As will be discussed further hereinbelow, Element Ea is a primary component of the mechanism that has a pair of inclined planes, both of which are at an equal angle to the X-axis. Element Ea is movable along the X- or Y- directions, but is not free to rotate within the coordinate system. Element Eb and Element Ec reference output elements whose movements are determined by their maintaining contact with Element Ea. Element Eb is free to slide or roll on one of the inclined planes of Element Ea without losing contact with Element Ea and without overshooting the inclined plane of Element Ea. Similarly, Element Ec is free to slide or roll on the other inclined plane of Element Ea without losing contact with and overshooting Element Ea. The centre points of Elements Eb and Ec are constrained to move on respective straight-line paths, as shown in Figs. 3A-3B, which are parallel to the Y-axis. Alternatively, the centre points of Elements Eb and Ec are free to move along the X-direction, but constrained such that the perpendicular distance between their paths is unchangeable, or constrained such that the linear distance between their centre-points is unchangeable.

[0052] For purposes of a differential system according to the present invention, Element Ea implements a main shaft whose movement within the coordinate system of this mechanical concept translates into the movement of the main shaft along its longitudinal axis during rotation. Element Eb and Element Ec reference output elements coupled to the two (2) driven wheels, left and right, respectively. Freedom of motion as defined herein relate to the freedom of motion vis-a-vis the vehicles' chassis. For ease of explanation, the X-axis in the diagrams of Figs. 3A-3C is defined to illustrate movement parallel to the axis of the driven wheels. The Y- axis is defined to be parallel to the front-to-back axis of the vehicle.

[0053] Figs. 3A-3C further show rolling elements Rb and Rc, which are incorporated into the operation of Elements Eb and Ec, respectively, but are not themselves coupled to two (2) driven wheels. Rather, rolling elements Rb and Rc are defined to be constrained to move only in the Y-direction along the straight-line paths in which they are constrained.

[0054] The degrees of freedom of moving along the X-axis may vary, but at least one of two situations will be given this freedom: (1) Element Ea but not Element Eb, not Element Ec; or(2) not Element Ea, but Elements Eb and Ec together; or (3) all three elements have the freedom, but Elements Eb and Ec can only move equally. Elements Eb and Ec being together means that both Element Eb and Ec can move, but the distance between them remains unchanged. For ease of description, as an example, constraints will be described as along straight lines, such as rolling elements Rb and Rc not being free to move along the X-axis.

[0055] A fourth input or output represented as Element Ed may be employed to provide yaw to the vehicle and to return Element Ea to a mean position, baseline or desired position. As an input or an output, Element Ed may be used to initiate motion between Elements Ea, Eb and Ec according to a specific ratio. For example, if the prime mover is inactive or at a standstill, Elements Ea, Eb and Ec will also be inactive. If Element Ed is activated and made to move Element Ea, Elements Eb and Ec will move equally in opposite directions. If the vehicle implementing the differential of the present invention is equipped so that the wheels on the other axle(s) of the vehicle do not prevent the movement of Elements Ea, Eb and Ec while at a standstill, or if the vehicle has only two (2) wheels, the entire vehicle will be able to turn around a vertical axis passing through midpoint of the two (2) wheels driven by Element Eb and Ec. Thus, in such situations, the present invention may also be used as an aid for manoeuvring a vehicle in or out of a tight spot.

[0056] In this first embodiment, only Element Ea has a pair of inclined planes, both of which are at an equal angle to the X-axis. Element Ea is movable along the X- or Y-directions, but not rotatable within the coordinate system. Element Eb is slidable or rollable on one of the inclined planes of Element Ea without losing contact with Element Ea. Similarly, Element Ec is slidable or rollable on the other inclined plane of Element Ea without losing contact with Element Ea. The centre points of Elements Eb and Ec are constrained to move on their respective straight- line paths, as shown in Figs. 3A-3C, which straight line paths are parallel to the Y-axis. Otherwise, the centre points of Elements Eb and Ec are free to move along X-direction, but constrained such that the perpendicular distance between their paths is unchangeable, or constrained such that the linear distance between their centre-points is unchangeable. Here as well, for ease of description, as an example, constraints will be described as along straight lines, such as rolling elements Rb and Rc not being free to move along the X-axis.

[0057] In this first embodiment, Fig. 3A illustrates the mechanics of the situation when a vehicle that implements the differential system of the present invention is going straight. In Fig. 3B, the functioning of the differential when the vehicle having steering wheels is taking a turn is explained with this example of a right turn, which applies equally to a left turn. The two (2) driven wheels will have a certain ratio of displacement which will be determined by wheelbases in the X and Y-directions and the angle of the steering wheels.

[0058] In Fig. 3A, the two (2) wheels coupled to Elements Eb and Ec are compelled to turn equally because the vehicle is going straight, whereby both wheels provide equal resistance to the movement. Elements Eb and Ec are constrained to move only in the Y- direction in the same paths in which they are constrained. Correspondingly, Element Ea reacts, in the X-direction based on the resistance to turning of Elements Eb and Ec, derived from the resistance to turning of the left and right wheels respectively, rightward from Element Eb, and leftward from Element Ec. They will be equal because the inclined planes are at equal angle, and the wheels will offer equal resistance. Thus, the reaction in the X-direction upon Element Ea from Elements Eb and Ec will be equal and opposite when the vehicle is going straight, and Element Ea will not move in X- direction. The movement of Element Ea in the Y-direction will be transferred to Elements Eb and Ec equally, and thus, Element Ea will transfer torque to bothwheels. Conversely, if Element Ea is kept stationary in the X-direction, the vehicle will be propelled straight.

[0059] In Fig. 3B, the functioning of the differential when the vehicle is taking a turn, such as with the operation of a steering wheel or yaw-providing mechanism of the differential is explained with this example of a right turn. The functioning as explained will be equally applicable to a left turn, except in the converse. The two (2) propelled wheels will have a certain ratio of displacement which will be determined by wheelbases in the X- and Y-directions and the angle of the steering wheel, steering mechanism or steerable wheels.

[0060] As noted above, Fig. 3 A represents the situation of when the vehicle is going straight. It also illustrates at the beginning of when the vehicle makes a turn. Fig. 3B represents the situation in which the vehicle initiates and progresses through the right turn. When the vehicle initiates a right turn, the Element Ea in reaction moves to the left in the X-direction along the axis of the wheels, wherein Element Eb connected to the left driven wheel is compelled to move along the Y-direction more than Element Ec connected to the driven right wheel (i.e., the left wheel has a higher radius of travel than the right wheel during the turn). Further, the resistance to rotation of the right wheel will be greater than the resistance to rotation of the left wheel, and the X-direction component of the reaction from Ec will be higher than the X- direction component of the reaction from Eb, which then results in the leftward X-direction displacement of Element Ea until the displacements of Elements Eb and Ec match the displacement determined by the necessary negative overdrive, namely an excess of displacement of the left wheel over the right wheel. Given that (a) the inclined planes are of equal angle; (b) if Elements Eb and Ec are constrained to move in their given paths (i.e., only along the Y direction); and (c) if they retain contact with the inclined planes, the inclined planes of Ea will be pushed leftward due to the excess of reaction of Ec along the X-axis over the reaction of Eb along the X-axis. Since the contact of Eb and Ec is retained with the inclined planes, torque will continue to be delivered to both wheels.

[0061] Conversely, if Element Ea is moved via an external input thereto, yaw is achieved. For example, if an external input moves Element Ea to the left in the X-direction along the axis of the wheels, Element Eb connected to the left driven wheel is compelled to move along the Y- direction more than Element Ec connected to the driven right wheel. This forces the left wheel to increase its travel and the right wheel to decrease its travel, thus effecting the right turn. Since the contact of Elements Eb and Ec is retained with the inclined planes, torque will again continue to be delivered to both wheels.

[0062] Fig. 3C represents a variation of the mechanics wherein Element Eal is a different configuration still having inclined planes that are equal to one another but reversed and opposite in direction from those in the configuration of Element Ea in Fig. 3 A. In this variation, the displacement of Element Eal will be rightward due to the excess of reaction of Ec along the X-axis over the reaction of Eb along the X-axis. When the vehicle is turning, Element Eal will move towards the centre of rotation of the vehicle. Any permutation or combination of inclined planes can be used, such that the reactions from the two (2) wheels enable Element Eal to move so as to permit differentiation.

[0063] The movement of Element Ea in the X-direction can be translated into an input, such as to provide yaw as discussed above, or it can be an output. In at least one embodiment of the present invention, the input or output is implemented as Element Ed of the differentialmechanism. As shown, the movement / direction of Element Ed is based on its connection to and / or inter-operation with Element Ea.

[0064] Conversely, instead of permitting the resistance of Elements Eb and Ec to determine the movement or position of Element Ea, and consequently that of Element Ed randomly, if the movement / direction of Element Ed is controlled and provided from an external source, then Elements Eb and Ec would be provided the desired amount of differentiation, which then provides the operation of yaw. When the movement / direction of Element Ed is permitted to result from the differentiation necessary and happening passively, it is possible to provide the movement of Element Ed as an external output. Just as the inclined planes get X-direction travel (Element Ed as an output) to accommodate the difference in travel of the two (2) wheels as determined by the angle of the steering wheel or mechanism, the converse also applies. Meaning, if Element Ed is from an external input source instead of being a passive output, such as if Element Ea is given specific movement in the X-direction, that will determine and impose the sense and magnitude of overdrive. By “sense” here is meant positive or negative overdrive. This means that by treating Element Ed as an input to impose an external motion to Element Ea in the X-direction, it is possible to provide yaw to the vehicle. This yaw, obtained from the externally delivered Element Ed, which determines the degree of overdrive, is used, either as yaw assisting the steering provided by the steering wheel or steering mechanism in order to improve the stability and cornering ability of the vehicle, or it can be employed as the sole means to manoeuvre the vehicle. This operation of Element Ed applies whether the vehicle uses at least two (2) drive wheels or two (2) bands of treads.

[0065] Thus, Element Ed, either by transmitting movement into or by reacting from the motion of Element Ea in the X-direction can be utilised as a fourth input or output, respectively. If the operation of Element Ed results passively (i.e., the differential is not used to actively provide yaw), but merely as a reaction to allow differential motion between two (2) wheels, then Element Ed can be used as an output to indicate the amount of differentiation occurring, or in other words, to indicate the direction in which the vehicle is facing. When Element Ed is used to provide yaw, either as a mechanism to specifically provide yaw for the vehicle, or to supplement the steering as determined by the steering wheels, then Element Ed is implemented as a fourth input, in addition to Elements Ea, Eb and Ec.

[0066] As discussed above, the examples of Elements Ea and “Eal” incorporate inclined planes of equal angles. It is also possible to have unequal angles of the inclined planes with the inequality compensated by a speed change by any means such that the reaction of the two (2) wheels along the X-axis remains equal and opposite, while the vehicle is going straight, and unequal and opposite when the vehicle turns. For example, if the inclined plane contacting Element Ec is configured with a steeper angle as the inclined plane in contact the Element Eb, Element Ec would then move twice as much as Element Eb along the Y-axis, then the wheel coupled to Element Eb will be turned at half the speed provided by Element Ec. It is also possible for both Elements Eb and Ec to be configured to contact the same inclined plane (not shown), with Elements Eb and Ec constrained to move equally and oppositely on the same inclined plane.

[0067] Figs. 4A-4B illustrate a second embodiment to explain a variation of the applied mechanics concept applied to the first embodiment of the present invention. As will be discussed further hereinbelow, as with the first embodiment, Element Ea is a primary component of the mechanism that has a pair of inclined planes, both of which are at an equal angle to the X-axis. Element Ea is movable along the X- or Y- directions, but is not free torotate within the coordinate system. Element Eb and Element Ec reference output elements whose movements are determined by their maintaining contact with Element Ea. Element Eb is free to slide or roll on one of the inclined planes of Element Ea without losing contact with Element Ea and without overshooting the inclined plane of Element Ea. Similarly, Element Ec is free to slide or roll on the other inclined plane of Element Ea without losing contact with and overshooting Element Ea. The centre points of Elements Eb and Ec are constrained to move on respective straight-line paths, as shown in Figs. 4A-4B, which are parallel to the Y-axis. Alternatively, the centre points of Elements Eb and Ec are free to move along the X-direction, but constrained such that the perpendicular distance between their paths is unchangeable, or constrained such that the linear distance between their centre-points is unchangeable.

[0068] For purposes of a differential system according to this second embodiment, Element Ea implements a main shaft whose movement within the coordinate system of this mechanical concept translates into the movement of the main shaft along its longitudinal axis during rotation. Element Eb and Element Ec reference output elements coupled to the two (2) driven wheels, left and right, respectively. Freedom of motion as defined herein relate to the freedom of motion vis-a-vis the vehicles' chassis. For ease of explanation, the X-axis in the diagrams of Figs. 4A-4B is defined to illustrate movement parallel to the axis of the driven wheels. The Y- axis is defined to be parallel to the front-to-back axis of the vehicle.

[0069] Figs. 4A-4B further show rolling elements Rb and Rc, which are incorporated into the operation of Elements Eb and Ec, respectively, but are not themselves coupled to two (2) driven wheels. Rather, inclined planes Pb an PC are defined to be constrained to move only in the Y- direction along the straight-line paths in which they are constrained. Rolling elements Rb, Rc are used to maintain the connection between the inclined planes of Element Ea with corresponding inclined planes Pb, Pc, respectively. The inclined planes Pb and Pc are implemented as the structure that is coupled to the two (2) driven wheels.

[0070] Element Eb is slidable or rollable on one of the inclined planes of Element Ea and on the corresponding inclined plane Pb without losing contact with either Element Ea or inclined plane Pb. Similarly, Element Ec is slidable or rollable on the other inclined plane of Element Ea and on the inclined plane Pc without losing contact with either Element Ea or inclined plane Pc. As noted above, the centre points of inclines planes Pb and Pc are constrained to move on their respective straight-line paths, as shown in Figs. 4A-4B, which are also parallel to the Y- axis. Otherwise, the centre points of inclined planes Pb and Pc are movable along the X- direction, but constrained such that the perpendicular distance between their paths is unchangeable, or constrained such that the linear distance between their centre-points is unchangeable.

[0071] The degrees of freedom of moving along the X-axis may vary, but at least one of two situations will be given this freedom: (1) Element Ea but not Element Eb, not Element Ec; or (2) not Element Ea, but Elements Eb and Ec together; or (4) all three elements have the freedom, but Elements Eb and Ec can only move equally. Elements Eb and Ec being together means that both Element Eb and Ec can move, but the distance between them remains unchanged.

[0072] Fig. 4A illustrates the mechanics of the situation when a vehicle that implements the differential system of the present invention is going straight. Operationally, the two (2) driven wheels coupled to the inclined planes Pb and Pc are compelled to rotate equally because the vehicle is going straight. Correspondingly, Element Ea reacts, in the X-direction based on theresistance to turning of the inclined planes Pb and Pc, derived from the resistance to turning of the left and right wheels respectively, rightward from Eb, and leftward from Ec. They will be equal because the inclined planes are at equal angle and both wheels offer equal resistance to turning. Thus, the reaction in the X-direction upon Ea from the inclined planes Pb and Pc will be equal and opposite when the vehicle is going straight, and Ea will not move in “X” direction. The movement of Ea in the Y-direction will be transferred to inclined planes Pb and Pc equally, and thus, Ea will transfer torque to both wheels.

[0073] In Fig. 4B, the functioning of the differential when the vehicle is taking a turn is explained with this example of a right turn, which applies equally to a left turn. The two (2) driven wheels will have a certain ratio of displacement which will be determined by wheelbases in the X and Y-directions and the angle of the steering wheels.

[0074] Fig. 4A represents the situation of when the vehicle is going straight and also illustrates at the beginning of when the vehicle makes a turn. Fig. 4B represents the situation where the vehicles initiates and progresses through a right turn. As shown, when the Element Ea moves to the left in the X-direction, the left wheel is compelled to move along the Y-direction more than the right wheel. The resistance to turning of the right wheel will be higher than the resistance to turning of the left wheel, and the X-direction component of the reaction from inclined plane Pc will be higher than the X-direction component of the reaction from Pb, resulting in X-direction displacement of Ea until the displacements of inclined planes Pb and Pc, match the displacement determined by the necessary negative overdrive, namely an excess of displacement of the left wheel over the right wheel. Given that (a) the inclined planes are of equal angle; (b) if inclines planes Pb and Pc are constrained to move in their given paths (i.e., only along the Y direction); and (c) if they retain contact with the inclined planes, the inclined planes of Ea will be pushed leftward due to the excess of reaction of inclined plane Pc along the X-axis over the reaction of inclined plane Pb along the X-axis. Since the contact of rolling elements Rb and Rc is retained with the inclined planes of Ea and the inclined planes Pb and Pc, torque will continue to be delivered to the driven wheels.

[0075] A fourth input or output represented as Element Ed may be employed to provide yaw to the vehicle and also to return Element Ea to a mean position, baseline or desired position. As an input or an output, Element Ed may be used to initiate motion between Elements Ea, Eb and Ec according to a specific ratio. For example, if the prime mover is inactive or at a standstill, Elements Ea, Eb and Ec will also be inactive. If Element Ed is activated and made to move Element Ea, Elements Eb and Ec will move equally in opposite directions. If the vehicle implementing the differential of the present invention is equipped so that the wheels on the other axle(s) of the vehicle do not prevent the movement of Elements Ea, Eb and Ec while at a standstill, or if the vehicle has only two (2) wheels, the entire vehicle will be able to turn around a vertical axis passing through midpoint of the two (2) wheels driven by Element Eb and Ec. Thus, in such situations, the present invention may also be used as an aid for manoeuvring a vehicle in or out of a tight spot.

[0076] With each of the inclined planes, including the inclines planes of the Element Ea and the inclined planes Pb,Pc, the travel of the Elements Eb and Ec along the inclined planes is defined to be limited to be only within the lengths of the inclined planes. As will be explained in more detail hereinbelow, the implementation of these defined travel limits is intended to prevent immobilization of the vehicle when one wheel slips.

[0077] In at least one embodiment, unequal angle inclined planes may be implemented by providing gearing for each element such that the pitch multiplied by the gearing ratio of one element is the same as the pitch multiplied by the gearing ratio of the other element. Even if both inclined planes are equal, in another embodiment, it might be expedient to use gearing, either to increase the number of turns of differentiation possible, or to reduce the axial loading on the ball screws. This would be especially necessary in an embodiment of the present invention in which the two (2) ball screws are located one inside the other in order to obtain the maximum number of turns of differentiation within the available length / space restraints of the vehicle or differential system.

[0078] The above is implemented by a first inclined plane or pair of inclined planes rolled over or inside a cylinder or cylinders, rotated by the prime mover, and the inclined planes carry rollers which are kept in contact with and cannot overshoot the inclined planes, which rollers mesh with a second pair of inclined planes rolled into cylinders carried coaxial and inside / outside the rollers, and the cylinders carrying the second pair of inclined planes are connected to the wheels; such that the movement in the Y axis, i.e. the rotation, is conveyed to the wheels as rotation, with rotation of the two (2) wheels averaging the rotation of the first inclined plane / s, the axial reactions upon the system due to resistance to turning of the two (2) wheels is opposite, and is equal and opposite when the vehicle is going straight. Any combination of inclined plane / s, rollers, carriers, or ratio-change can be employed so far as the axial component of the reaction of the wheels due to their resistance to turning is opposite, and is equal and opposite when the vehicle is going straight.

[0079] Figs. 5A-5D illustrate one embodiment and variation of the central structure of the present invention implementing the applied mechanics of Figs. 3A-3C. As shown in Fig. 5 A, Element Ea is implemented as a main shaft 50 having helical grooves 50a which is turned by a prime mover (not shown) around its longitudinal axis. The main shaft 50 is formed with two (2) opposite sets or "hands" of threading grooves 50a and 50b on both sides of a central shaft portion 50c. Each of the two (2) threading grooves 50a, 50b engage one (1) or more follower discs Rb and Rc, which rotate around axis Xb and axis Xc, respectively. The follower discs Rb and Rc rotate along their respective axes and their axes rotate around the axis of the main shaft 50 and within their housing (not shown) in the differential. The rotation of the axes of the follower discs Rb and Rc rotate their housing and hence and the wheels.

[0080] Whatever the orientations or handedness (left or right hand) of the main shaft and the corresponding ball screws may be, it is understood that they are configured to ensure that the axial reactions from the two (2) driven wheels counter each other, so that the wheel offering higher resistance will move less, and the average of the two will equal the input. As a preferred implementation, the combination of orientations or handedness will be selected so as to tense (not compress) the main shaft 50 when the vehicle is going forward, wherein, for example, the main shaft 50 will rotate clockwise from the right, which requires that the helical grooves 50a are formed as a righthanded helix and the helical grooves 50b are formed as a lefthanded helix. In other embodiments, the main shaft may also rotate counterclockwise, which then requires forming the orientation or handedness of the helical grooves to be reversed. This requirement for the orientation and / or handedness of the helical grooves applies to all of the embodiments of the invention disclosed herein, as well as those that would be foreseeable given this disclosure.

[0081] In the embodiment shown in Fig. 5A, the main shaft 50 (Element Ea) is connected to be driven by the prime mover. For example, and without implying any limitation of the presentinvention, the prime mover may be implemented as, for example, a conventional internal combustion engine system. As noted above, in alternative implementations, the prime mover may be an electric motor, a hybrid engine powered by both electric battery or fuel cell and internal combustion, or other motive power delivering source known in the art.

[0082] In the at least one embodiment, as shown in Fig. 5B, the prime mover 56 is connected via a bevel gear pair 52,54 that may incorporate a spline or ball spline (not shown) to transmit motion to the main shaft 50. The main shaft 50 is configured to freely rotate on its longitudinal axis Xm as determined by the configuration of the prime mover 56, and in particular the configuration of the clutch 56a, a gear box 56b (if applicable) and / or transmission 56c of the prime mover 56. The main shaft 50 is configures to be freely movable along its longitudinal axis.

[0083] Also as shown in Fig. 5B, the follower discs Rb and Rc are respectively mounted in carriers 58a, 58b and configured to rotate along their respective axes Xb and Xc. The carriers 58a, 58b are each connected to rotate along the longitudinal axis of the main shaft 50 and respectively connected to drive the driven wheels 510a, 510b.

[0084] Follower discs Rb and Rc are configured to freely rotate on their respective axes Xb and Xc, which axes are rotatable around the longitudinal axis of the main shaft 50. Depending on the embodiment, follower discs Rb and Rc may be configured to move longitudinally left or right along the axis of the main shaft 50 or to be fixed longitudinally relative to the chassis or housing. Otherwise, the follower discs Rb and Rc are mounted so as to not have any other degrees of freedom. If in the embodiment the follower discs Rb and Rc are able to move longitudinally left and right, the follower discs Rb and Rc would be mounted with a fixed or constant distance between them such that the fixed distance between the follower wheels Rb and Rc would be maintained relative one another while moving left or right. For ease of explanation, the operation of all embodiments are described herein where the main shaft 50 is permitted longitudinal motion, while the carriers 58 a, 58b of the follower discs Rb and Rc are not permitted longitudinal motion.

[0085] As noted above, the main shaft 50 (Element Ea) is formed with helical grooves 50a, 50b contoured to engage with the follower discs Rb and Rc. In other embodiments, the follower discs may be implemented as spheres (balls), disks, cylinders (rollers) or similar shapes that can perform similar functions with the same or similar characteristics. At least in this first embodiment described above, Elements Eb and Ec are each implemented as single follower discs Rb and Rc and configured to be mounted at a fixed distance apart with their axes Xb and Xc permitted to rotate around the common longitudinal axis of Elements Ea, Eb and Ec.

[0086] Fig. 5A further shows that in the main shaft 50, the groove 50a is formed as a right- handed helical groove and the groove 50b is formed as a left-handed helical groove, wherein the follower disc Rb engages with and runs along the right-handed helical groove 50a, while the follower disc Rc engages with and runs along the left-handed helical groove 50b. In this first example embodiment, the pitch of the right-handed groove 50a and the pitch of the lefthanded groove 50b are equal to one another.

[0087] In this first embodiment, based on the mechanics as illustrated and explained in connection with Figs. 3 A-3B, the main shaft 50 rotates clockwise during operation (see arrow CW in Fig. 5A), and the axes of the follower discs Rb and Rc (Elements Eb and Ec) generate equal resistance to turning, as when the vehicle is going straight. As the prime mover 56 issupplying power to the wheels 60a, 60b, the axial reaction of the follower discs Rb and Rc (Elements Eb and Ec) on the main shaft 50 (Element Ea) will be balanced and will tense the main shaft 50. Since there is no relative axial motion between the main shaft 50 (Element Ea) and the follower disc Rb (Element Eb), the axis of the follower disc Rb will rotate along the longitudinal axis of the main shaft 50 at the same speed as the main shaft 50. Similarly, since there is no relative axial motion between the main shaft 50 (Element Ea) and the follower disc Rc (Element Ec), the axis of the follower disc Rc will also rotate along the axis of the main shaft 50 at the same speed as the main shaft 50.

[0088] However, if resistance occurs as a result of a difference in rotational speed between the main shaft 50 and the carriers 58a, 58b of the follower discs Rb and Rc, as would occur when the vehicle turns, the main shaft 50 (Element Ea) will move along its longitudinal axis. At the same time, the axes of the follower discs Rb and Rc will both rotate along the longitudinal axis of main shaft 50. Specifically, depending on the type of turn being performed, one of the carriers 58a, 58b will be the inner wheel of the turn while the other will be the outer wheel of the turn. In particular, the inner wheel will move less than the outer wheel.

[0089] For example, the carrier 58a of the follower disc Rb is connected to drive the left driven wheel 510a, while the carrier 58b of the follower disc Rc is connected to drive the right driven wheel 510b. In this example, the vehicle will make a left turn. As the vehicle is turning to the left, the right driven wheel 510b will turn more due to its greater radius of travel relative to the vehicle’s axis of rotation, while the left driven wheel 510a will turn less due its smaller radius of travel. At the same time, the main shaft 50 will move along its longitudinal axis to the left and towards the vehicle’s vertical axis of rotation.

[0090] In alternative embodiments, Elements Eb and Ec may each be implemented as two (2) or more follower elements Rb’ and Rc’ (see Fig. 5C), each follower element being a sphere (balls), a convex-shaped disk, a cylinder (rollers) or similar shape that can perform similar functions with the same or similar characteristics. Further, the helical grooves 50a, 50b on the main shaft may be formed as single start (see Fig. 5 A) or multistart grooves or threads 50a’, 50b’ (see Fig. 5D). In the example shown in Fig. 5D, the helical grooves 50b are formed with a triple start thread with three follower elements Rc’. Though not shown only for purposes of brevity, the helical grooves 50a would also be formed with a triple start thread with three follower elements Rb’. In addition, the triple start threads of the helical grooves 50a would have a winding direction opposite the helical grooves 50b. Multistart grooves will reduce the axial forces on the main shaft 50. Further alternative embodiments of the present invention may implement the grooves 50a, 50b or 50a’, 50b’ in other forms that embody a rod having a helical structure that allows follower elements to engage with and move along the helical structure, including but not limited to projections that form the helical structure (not shown).

[0091] Figs. 6A-6C illustrate the second embodiment of the engineering design which follows the applied mechanics concept of Figs. 4A-4B. For purposes only of brevity in both the description herein and int eh drawings, only one (1) side of the structure of the differential is discussed and / or illustrated (i.e., the driven wheel 66a, the drive shaft 618a). However, as those of skill in the art would understand, the same or equivalent structure and operation described for one (1) such side equally apply to the other side. In the embodiment shown in Figs. 6A-6C, Element Ea is implemented as a main shaft 60 having helical grooves 60al,60bl which is turned by prime mover (not shown) around its longitudinal axis. Further, Element Ea is mounted to rotate along its longitudinal axis and to be axially movable, and formed with opposite sets or “hands” of threading grooves. Elements Eb and Ec are mounted to be rotatablearound their respective axes, but not axially movable, and corresponding threading grooves relative to Element Ea. As noted above, the prime mover may be implemented as, for example, a conventional internal combustion engine system of a rear axle-driven vehicle, wherein the internal combustion engine system includes an engine, a clutch, a gearbox (if applicable), a propeller shaft, universal couplings and a bevel gear pair.

[0092] Alternatively, in a variation of this second embodiment, Elements Ea, Eb and Ec may be mounted to be axially movable with Elements Eb and Ec operatively connected so that they are constrained to move together. In another variation, Element Ea is formed with the same hand of threading grooves throughout its length and Elements Eb and Ec are formed with corresponding threading grooves such that Elements Eb and Ec are compelled to move equally opposite to one another. Otherwise, the crux of the interaction between Elements Ea, Eb and Ec is that Elements Eb and Ec create axial thrust upon Element Ea, which in turn are opposite to each other, while being equal and opposite when the vehicle is travelling straight.

[0093] The main shaft 60 is formed with two (2) opposite sets or "hands" of threading grooves 60al and 60b 1 on both sides of a central shaft portion 60c. The threaded grooves 60al and 60b 1 are formed as the bolt elements 60a, 60b of ball screw assemblies 62a, 62b respectively. The bolt elements 60a, 60b of ball screw assemblies 62a, 62b engage the nut elements 64a, 64b, respectively, which surround the threaded grooves 60a, 60b and implement the inclined planes Pb and Pc, respectively. The nut elements 64a, 64b similarly have defined along their inner surfaces threaded grooves 64al,64bl. The rolling elements Rb and Rc are positioned to engage between the respective bolt elements 60a, 60b and the nut elements 64a, 64b along and in between the threaded grooves 60al,60bl,64al,64bl. All the elements of the ball screw assemblies 62a, 62b which implement Elements Ea, Eb and Ec rotate around the longitudinal axis of the main shaft 60. The nut elements 64a, 64b are operatively connected to drive the driven wheels 66a, 66b, respectively. The driven wheels 66a, 66b in at least one embodiment may be connected to the nut elements, 64a, 64b and then the drive shafts 618a, 618b. In this embodiment, the rolling elements Rb and Rc are implemented as a plurality of balls in the ball screws.

[0094] In at least one embodiment where the differential system of the present invention is implemented in a rear- wheel drive vehicle (not shown), the driven wheels 66a, 66b may be connected to the nut elements, 64a, 64b and the drive shafts 618a,618b directly. Alternatively, in another embodiment where the differential system is implemented in a front-wheel drive vehicle (not shown), the driven wheels 66a, 66b may each be connected to the corresponding nut elements, 64a, 64b and drive shafts 618a, 618b via one (1) or more constant velocity joint assemblies (not shown). The inner halves of constant velocity joint assemblies may be configured to be mounted or positioned inside or outside the differential housing (not shown).

[0095] As shown in Fig. 6B, as an alternative implementation, Element Ea is implemented as a hollow component 60’ having two (2) inner cylindrical bolt elements 60a’, 60b’ with threaded groove surfaces 60al’, 60b 1’ formed on either side of a central portion 60c’, wherein the inner threaded groove surfaces 60a’, 60b’ implement the bolt element of the ball screw assembly 62a’, 62b’. Nut elements 64a’, 64b’ are formed as threaded groove rods that engage with the inner threaded groove surfaces of the bolt elements 60a’, 60b’, and implement the inclined planes Pb and Pc, respectively. Here as well, the rolling elements Rb’ and Rc’ are positioned to engage between the respective bolt elements 60a’, 60b’ and the nut elements 64a’, 64b’ along and in between the threaded grooves 60al’,60br,64al’,64br.

[0096] As shown in Fig. 6C in accordance with the implementation of at least Fig. 6A, the prime mover 616 is connected via a bevel gear pair 612 that incorporates a spline or ball spline (not shown) to transmit motion to the main shaft 60. The main shaft 60 is configured to rotate on its longitudinal axis as determined by the configuration of the prime mover 616 (i.e., the internal combustion engine or other system), and in particular the configuration of the clutch 616a, gearbox 616b and / or transmission 616c of the prime mover 616. In this specific example embodiment, the main shaft 60 is mounted to be axially movable on its longitudinal axis, while nut elements 64a, 64b are not free to be axially movable. In other configurations, the main shaft 60 may or may not be free to move along its longitudinal axis.

[0097] Fig. 6A further shows that in the bolt elements 60a, 60b of the main shaft 60, the groove 60al is formed as a right-handed helical groove and the groove 60b 1 is formed as a left-handed helical groove. Correspondingly, in the nut elements 64a, 64b, the groove 64al is formed as a left-handed helical groove and the groove 64b 1 is formed as a right-handed helical groove, wherein the pitch of the right-handed grooves 60a, 64b and the pitch of the left-handed groove 60b, 64a are equal to one another.

[0098] In this embodiment as shown in Fig. 6A, based on the mechanics as illustrated and explained in connection with Figs. 4A-4B and using the structure in Fig. 4A as an example, in the operation of the invention, the main shaft 60 and correspondingly the bolt elements 60a, 60b rotates clockwise during operation when viewed from the right (see arrow CW in Fig. 6A), while nut elements 64a, 64b with the rolling elements Rb and Rc (Elements Eb and Ec) generate equal resistance to turning, as when the vehicle is going straight. As the prime mover 616 is supplying power to the wheels 66a, 66b, the axial reaction of the nut elements 64a, 64b through the rolling elements Rb and Rc (Elements Eb and Ec) on the main shaft 60 (Element Ea) will be balanced and will tense the main shaft 60. Since there is no relative axial motion between the main shaft 60 (Element Ea) and the nut elements 64a with the follower disc Rb (Element Eb), the follower disc Rb will rotate at the same speed as the main shaft 60. Similarly, since there is no relative axial motion between the main shaft 60 (Element Ea) and nut elements 64b with the follower disc Rc (Element Ec), the follower disc Rc will also rotate at the same speed as the main shaft 60.

[0099] However, if unequal resistance occurs as a result of a difference in rotational speed between the main shaft 60 and the nut elements 64a, 64b with the rolling elements Rb and Rc, as would occur when the vehicle turns, the main shaft 60 (Element Ea) will move along its longitudinal axis towards the vertical axis of rotation of the vehicle as it is turning. At the same time, the nut elements 64a, 64b with the rolling elements Rb and Rc will both rotate. Specifically, depending on the type of turn being performed, one (1) of the nut elements 64a, 64b with the corresponding rolling element Rb or Rc will be the inner wheel of the turn while the other will be the outer wheel of the turn. In particular, the inner wheel will move less than the outer wheel.

[0100] For example, referring to Fig. 6A, it is assumed that the nut element 64a with rolling element Rb is connected to the drive shaft 618a which is connected to drive the left driven wheel 66a, while the rolling element Rc is connected to the opposite drive shaft (not shown) which is connected to drive the right driven wheel (not shown). In this example, the vehicle will make a right turn. As the vehicle is turning to the right, the right driven wheel 66b will turn less due to its smaller radius of travel relative to the vehicle’s axis of rotation, while the left driven wheel 66a will turn more due its greater radius of travel. At the same time, the mainshaft 60 will move along its longitudinal axis to the right toward the vehicle’s vertical axis of rotation.

[0101] When the vehicle is making a left turn, the right driven wheel 66a is compelled to move more than the left driven wheel 66b. The resistance to turning of the right wheel 66b will be higher than the resistance to turning of the left wheel 66a, and the reaction from the nut element 64b (inclined plane Pc) will be higher than the reaction from nut element 64a (the inclined plane Pb), resulting in displacement of the main shaft 60 until the displacements of the nut elements 64a, 64b (the inclined planes Pb and Pc), match the displacement determined by the necessary negative overdrive, namely an excess of displacement of the right wheel over the left wheel. Since the contact of rolling elements Rb and Rc is retained between the bolt elements 60a, 60b of the main shaft 60 with the nut elements 64a, 64b, torque is delivered to the driven wheels 66a, 66b.

[0102] Fig. 7A illustrates a third embodiment of the present invention that embodies features and elements similar to those of the second embodiment shown in at least Fig. 6A, but incorporating further additional elements and details implementing the mechanics as illustrated and explained in connection with Figs. 4A-4B. In this embodiment, for purposes of an example only, a bevel gear pair is operatively mounted to the main shaft in order to provide connection the drive means. Alternatively, as will be readily understood from the description hereinbelow, the bevel gear pair structure may be replaced with other known motion transmission structures and operations including those that incorporate other combinations of gears, a drive belt system, a sprocket connected to a chain or bands of treads, or other devices know in the art. As another alternative, the differential of the invention may be directly joined and mounted inside a hollow shaft electric motor, such as an axial flux electric motor which are amenable to larger inner diameters for a hollow shaft than conventional radial flux motors.

[0103] As shown in Fig. 7A, this third embodiment incorporates a main shaft 70 having helical grooves 70al,70bl formed on bolt elements 70a, 70b of ball screw assemblies 72a, 72b respectively, on either side of a central shaft portion 70c of the main shaft 70. The helical grooves 70al,70bl are formed as opposite “hands” or opposite directions to each other. The threaded grooves 70al and 70b 1 are formed on the bolt elements 70a, 70b of the ball screw assemblies 72a, 72b to engage the nut elements 74a, 74b, respectively, which surround the threaded grooves 70a, 70b and implement the inclined planes Pb and Pc, respectively. The nut elements 74a, 74b similarly have defined along their inner surfaces threaded grooves 74al,74bl. The rolling elements Rb and Rc are positioned to engage between the respective bolt elements 70a, 70b and the nut elements 74a, 74b along and in between the threaded grooves 70al,70bl,74al,74bl. All the elements of the ball screw assemblies 72a, 72b which implement Elements Ea, Eb and Ec rotate around the longitudinal axis of the main shaft 70. The nut elements 74a, 74b are operatively connected to drive the driven wheels 76a, 76b, respectively.

[0104] In this specific embodiment, the driven wheels 76a, 76b are formed with wheel flanges 77a, 77b respectively that are fixed to bearings 79a, 79b. One (1) or a plurality of dowel elements 715 are positioned between the wheel flanges 77a, 77b and the outer plates of the coupling plate pairs 71 la, 71 lb. The inner plates of the coupling plate pairs 71 la, 71 lb are in turn mounted on the outer ends of the nut elements 74a, 74b respectively. Operationally, nut elements 74a, 74b are connected to the driven wheels 76a, 76b via the coupling plate pairs 711a and 711b which are configured to be in a default position that is 'engaged' unless disengaged by a control circuit 724 (explained further hereinbelow) or by manual control.

[0105] In this third embodiment, the central shaft portion 70c is shown to be operatively connected to the prime mover and transmission 719 via a bevel gear pair structure 78 that includes drive gear 78a and shaft gear 78b. The drive gear 78a is connected to a drive shaft 710 which connects to the prime mover and transmission 719. The shaft gear 78b is mounted on the central shaft portion 70c of the main shaft 70. Splines of the shaft gear 78b interconnect with the splines of the main shaft 70 such that rotation of the drive shaft 710 and the drive gear 78a in turn drives and rotates the main shaft 70 via the shaft gear 78b. To prevent the drive shaft 710 and the gears 78a, 78b from moving in the axial direction of the main shaft 70, a thrust bearing 712 is fixedly mounted to the chassis or housing (not shown) of the vehicle in which the differential system is implemented. With the shaft gear 78b mounted to the main shaft 70 via splines, the shaft gear 78b is held in place between the thrust bearing 712 and drive gear 78a but freely rotatable with the rotational motion of the drive shaft 710 and the drive gear 78a.

[0106] In an alternative variation of the central shaft portion 70c described above, also as shown in Fig. 7A, to actively control or at least passively detect and / or measure, movement of the main shaft 70 in an axial direction along its longitudinal axis, a yaw / replenishment mechanism 714 is added to the differential system in order to provide at least one of active yaw for the vehicle or passive detection of the amount of differentiation being performed by the differential system. Specifically, the yaw mechanism 714 includes a rotary bearing structure 716 is connected to the central shaft portion 70c of the main shaft 70. The inner ring 716a of the rotary bearing 716 is fixedly mounted on the central shaft portion 70c. The outer ring 716b of the rotary bearing structure 716 is fixed to a control arm 718 that is then connected to an axial motion device 720. In this third embodiment of the invention, the axial motion device 720 is implemented as a linear actuator that controllably moves the main shaft 70 along its longitudinal axis with positional feedback, and facilitates replenishment.

[0107] In this implementation of the axial motion device 720 as a linear actuator, controllable yaw is achieved. Using the axial motion device 720, axial motion is transmitted to the main shaft 70 via the yaw mechanism 714 that includes the rotary bearing 716 and the control arm 718. The operation of these elements causes a differential motion with one of the two wheels turning more than the other, thus causing yaw. As in the second embodiment, if resistance occurs as a result of a difference in rotational speed between the main shaft 70 and the nut elements 74a, 74b with the rolling elements Rb and Rc, as would occur when the vehicle turns, the main shaft 70 (Element Ea) will move along its longitudinal axis towards the vertical axis of rotation of the vehicle as it is turning. At the same time, the nut elements 74a, 74b with the rolling elements Rb and Rc will both rotate relative to the movement of the main shaft 70. Depending on the type of turn being performed, one (1) of the nut elements 74a, 74b with the corresponding rolling element Rb or Rc will be the inner wheel of the turn while the other will be the outer wheel of the turn, wherein the inner wheel will move less than the outer wheel.

[0108] As an example, it is again assumed that the nut element 74a with rolling element Rb is connected to the drive shaft 718a which is connected to drive the left driven wheel 76a, while the rolling element Rc is connected to the drive shaft 718b which is connected to drive the right driven wheel 76b. In this example, the vehicle will make a left turn. As the vehicle is turning to the left, the right driven wheel 76b will turn more due to its greater radius of travel relative to the vehicle’s axis of rotation, while the left driven wheel 76a will turn less due its smaller radius of travel. At the same time, the main shaft 70 will move along its longitudinal axis to the left toward the vehicle’s vertical axis of rotation.

[0109] Correspondingly, the ball screw assemblies 72a, 72b will react to the movement of the main shaft 70. Specifically, when the main shaft 70 is moved to implement the left turn, the right driven wheel 76b is compelled to move more than the left driven wheel 76a. The resistance to turning of the left wheel 76a will be higher than the resistance to turning of the right wheel 76b, and the reaction from the nut element 74a (inclined plane Pb) will be higher than the reaction from nut element 74b (the inclined plane Pc), resulting in displacement of the main shaft 70 until the rotation of the nut elements 74a, 74b (the inclined planes Pb and Pc), match the displacement determined by the necessary negative overdrive, namely an excess of displacement of the right wheel over the left wheel. As the main shaft 70 moves axially to the left, the bolt element 70a will translate deeper into the nut element 74a, while the bolt element 70b will translate further out of the nut element 74b. Since the contact of rolling elements Rb and Rc is retained between the bolt elements 70a, 70b of the main shaft 70 with the nut elements 74a, 74b, torque is delivered to the driven wheels 76a, 76b.

[0110] The axial motion device 720 as a linear actuator may compensate for or control the amount or degree of yaw that occurs when the vehicle is making the turn. In particular, the axial motion device 720 may at least one of (1) control the amount or degree of yaw by controlling the degree or amount that the main shaft 70 moves axially along its longitudinal axis depending on factors such as the turning rate of the vehicle, the movement of the vehicle’s steering control (i.e., the turning of the steering wheel), the speed of the vehicle (i.e., the wheels) during the turn, etc.; (2) compensate for the amount or degree of yaw in the vehicle while making a turn above predetermined thresholds for the turning rate of the vehicle, the movement of the vehicle’s steering control (i.e., the turning of the steering wheel), the speed of the vehicle (i.e., the wheels) during the turn, etc.; and (3) restore the main shaft 70 to a mean or baseline position, or as close to such mean or baseline position as possible. The factors for determining how much control the axial motion device 720 will exert may be measured and then converted into control signals for the axial motion device 720 via a sensor in the axial motion device 720 that is provided to operate with the differential system of the present invention or other data generating sources in the vehicle, as will be explained in further detail hereinbelow.[OHl] In an alternative implementation, the axial motion device 720 may instead be implemented as a linear actuator and passive sensor, or as a passive sensor alone that measures the amount or degree of yaw that occurs when the vehicle is making the turn. In its function as a sensor, the axial motion device 720 is configured to sense and / or measure the position of the main shaft 70 and then communicate that data to the computer control (see Fig. 8) of the vehicle. The data from the sensor of the axial motion device 720 may then be used by the differential system of the present invention, or other data gathering / generating components in the vehicle.

[0112] When a vehicle using the differential system of the present invention has completed one (1) or more turns, the main shaft 70 will have shifted from its mean or baseline position. If the right overdrive and left overdrive have compensated each other as explained above, finite differentiation is unlikely to be exhausted. However, the structure and operation of the present invention provides a system for returning the main shaft 70 to the mean or baseline position. This process or system for returning the main shaft 70 will be referred to herein as replenishment. As will be explained in more detail hereinbelow, when a vehicle using the differential system of the present invention has completed a journey, or is coasting, or the prime mover 719 or the differential is disengaged from the driven wheels 76a, 76b for any reason, or if the finite differentiation is exhausted before end of the vehicle’s journey (for example, themain shaft 70 has axially moved left or right to its maximum limit), the main shaft 70 should be returned to its mean or baseline position.

[0113] In a further alternative variation of the differential system of the present invention as illustrated in Fig. 7A, the replenishment process or system is achieved via an outer ball screw structure surrounding the main shaft 70. Specifically, outer ball screw assemblies 722a, 722b are formed wherein the outer elements 722al,722bl are positioned to surround the outer nut elements 722a2,722b2, which surround the bolt elements 70b, 70c, respectively, of the main shaft 70 via roller elements (i.e., balls) therebetween. The outer nut elements 722a2,722b2 are formed to operate in a manner similar to and coaxial to the nut elements 74a, 74b, but positioned closer to both sides of the central shaft portion 70c.

[0114] The outer nut elements 722al,722bl are mounted to the structure of the vehicle or housing so as to prevent rotation, while the outer nut elements 722a2,722b2 are positioned to rotate with the bolt elements 70a, 70b during operation. Each of the outer elements 722a2,722b2 are connected to a control circuit 723 which selectively determines to engage with either of the outer elements 722a2,722b2 so as to temporarily stop rotation of the selected one of the outer elements 722a2,722b2 relative to the corresponding bolt element 70a, 70b.

[0115] In one example of the operation of the replenishment system using the differential system of the present invention as described above, using the prior example of the vehicle making a right turn as described above, the left driven wheel 76a will turn more due to its greater radius of travel relative to the vehicle’s axis of rotation, while the right driven wheel 76b will turn less due its smaller radius of travel. At the same time, the main shaft 70 will move along its longitudinal axis to the left toward the vehicle’s vertical axis of rotation until the displacements of the nut elements 74a, 74b (the inclined planes Pb and Pc), match the displacement determined by the excess of displacement of the right wheel over the left wheel. Again, as the main shaft 70 moves axially to the left, the bolt element 70a will translate further out of the nut element 74a, while the bolt element 70b will translate deeper into the nut element 74b. After the turn is completed and the vehicle goes back to moving straight, to replenish the differential system, one (1) or both of the outer bolt elements 722a2,722b2 is controllably stopped from rotating with the corresponding one of the bolt elements 70a, 70b so as to move the main shaft 70 back to or at least towards the mean or baseline position.

[0116] In this one example operation, to make the main shaft 70 move or translate back to the left, the outer bolt element 722a2 is stopped via the control circuit 724 from continuing to rotate with the bolt element 70a. As the main shaft 70 and thus the bolt element 70a continue to rotate with the movement of the vehicle, outer bolt element 722a2 is held stationary by the control circuit 724 relative vehicle and the main shaft 70, whereby the rotation of the bolt element 70 relative to the temporarily stationary outer bolt element 722a2 forces the main shaft 70 to move to the left. Correspondingly, if the main shaft 70 had moved to the left initially as a result of making a turn, to make the main shaft 70 move or translate back to the right, the outer bolt element 722b2 is stopped via the control circuit 724 from continuing to rotate with the bolt element 70b. As the main shaft 70 and thus the bolt element 70b continue to rotate with the movement of the vehicle, outer bolt element 722b2 is held stationary by the control circuit 723 relative vehicle and the main shaft 70, whereby the rotation of the bolt element 70b relative to the temporarily stationary outer bolt element 722b2 forces the main shaft 70 to move to the right.

[0117] The above-noted example is one implementation of a replenishment operation using the differential system of the present invention. Other implementations of a replenishment operation applying the present invention are possible and all within the scope and spirit of the present invention, as would be understood by those of ordinary skill in the art given this disclosure of the present invention.

[0118] As noted above, the coupling plate pairs 71 la, 71 lb are mounted to the outer ends of the nut elements 74a, 74b. When the main shaft 70 moves to the left or right as a result of making a turn or providing yaw, and if replenishment is being performed, the corresponding coupling plate pairs 711a and 711b will disengage the coupling and the corresponding driven wheel 76a or 76b. The axial motion device 720 as a linear actuator or the replenishment structure described above may then be used to replenish the finite differentiation by then moving the main shaft 70 back to the mean or baseline position.

[0119] The coupling plate pairs 71 la, 71 lb also provides a structure for extreme cases wherein the vehicle has performed more consecutive turns in one direction than the other, which would reach the limit of the number of rotations that the bolt elements 70a, 70b could make into the corresponding nut element 74a, 74b, thereby exhausting the finite differentiation. Also, this structure would be available to at least partially compensate for finite differentiation, if the structure for providing replenishment as described hereinabove is not implemented. In such extreme situations, if the main shaft 70 moves to the extreme left or right (i.e., the bolt element 70a rotates up to its limit into the nut element 74a, or the bolt element 70b rotates up to its limit into the nut element 74b), the corresponding coupling plate pairs 711a and 711b will again disengage the coupling and the corresponding driven wheel 76a or 76b, in order to allow replenishment to occur.

[0120] The control circuit 724 may be implemented as part of a control processor or circuit, or may be provided as a separate control processor specifically for the differential system of the claimed invention. As with the axial motion device 720, the control circuit 724 may control the amount or degree of replenishment on the main shaft 70 depending on factors such as the turning rate of the vehicle, the movement of the vehicle’s steering control (i.e., the turning of the steering wheel), the speed of the vehicle (i.e., the wheels) during the turn, etc. The factors for determining the operation of the control circuit 724 may be measured and then converted into control signals via sensors (see Fig. 8) provided to operate with the differential system of the present invention or other data generating sources in the vehicle, as will be explained in further detail hereinbelow.

[0121] Alternatively, the operational control of either or both of the axial motion device 720 as a linear actuator and the control circuit 724 may also be implemented using manual control levers or other mechanisms (not shown) that would be manipulated by the driver or vehicle operator. As a further alternative, the operational control of the axial motion device 720 as a linear actuator and the control circuit 724 may also be implemented using a combination of a control processor or circuit and manual control levers or other mechanisms (not shown) manipulated by the driver / operator, wherein for example the driver / operator can selectively engage or disengage the control processor / circuit in favour of the manual control levers, or vice versa.

[0122] As noted above, the travel of the Elements Eb and Ec along the inclined planes of Element Ea and the inclined planes Pb, Pc are defined to be limited. In at least one implementation, this travel limit is achieved by configuring all ball screw elements of thedifferential system to have travel-end collars (not shown) as known in the art. In operation, if one of the wheels slip relative to the ground, the differential system will reach a maximum travel limit (i.e., the main shaft 70 reaches a maximum left or right axial position), and prevents the vehicle from being immobilized. In embodiments where a control circuit (see Fig. 8) is implemented, the control circuit will compensate for wheel slippage. Alternatively, in embodiments where the differential system does not include a control circuit and is manually operated, this feature is achieved by the difference in rotation between the wheels 76a, 76b will move the main shaft 70. Specifically, when the main shaft 70 reaches its maximum axial position, axial motion of the main shaft 70 will stop such that both nut elements 74a, 74b will rotate at the same RPM as the main shaft 70. The vehicle will then be able to move out of the area where the slipping occurred, even if one wheel continues to slip.

[0123] In the general operation of the differential system of the present invention, as implemented in any of the embodiments shown in Figs. 5A-5D, 6A-6C and 7, if differential control does occur during the operation of the vehicle, an event may occur to trigger the subsequent replenishment of the differential system. Depending on the implementation of the differential system, replenishment need not occur after every turn or automatically, but rather only when certain triggering events occur. One such triggering event is when the prime mover (engine / motor / other) is disconnected from the of the differential. In conventional engine-driven vehicles, this happens when the vehicle is in the neutral gear or when the clutch is disengaged, or due to any other event, or when the vehicle is being braked and the clutch disengaged, or disconnected by design to enable replenishment. In electric vehicles, this could also happen while changing over from the state of motor driving the vehicle to vehicle driving the motor so as to regeneratively charging the batteries, or vice versa.

[0124] Other triggering events include (1) when the automatic transmission of the vehicle (is so equipped) disconnects the differential, and hence the wheels from the prime mover; (2) when the vehicle’s brakes are applied, such as if the brakes are applied without the clutch being disengaged, disengaging the wheels from the differential would relieve the brakes of the added burden of braking the angular momentum of the prime mover and the drive train; (3) when one or both driven wheels slip or lose contact / traction with the surface on which the vehicle is moving, or just after the finite differentiation has been utilised to get out of a difficult driving situation (i.e., when one wheel slips relative to the ground, the other wheel will lose torque, wherein the differential of the present invention would allow the wheel to slip until the finite differentiation is exhausted, then the non-slipping wheel will receive torque, and the replenishment could be activated after the vehicle is out of the situation; and (3) when one or both devices that implement Elements Eb and Ec have exhausted all or a pre-determined extent of the finite possible differentiation that the devices are designed to do.

[0125] If any one of the above triggering events occurs, the replenishment system of the differential may be initiated depending on how that system is implemented in the vehicle. For example, as will be discussed further hereinbelow, a control circuit of the vehicle may be configured to monitor and / or control the operation of the differential system in conjunction with the other controlled elements of the drive system of the vehicle. When replenishment is initiated, the differential system of the present invention would accomplish the replenishment by, using the elements shown in Fig. 7 as an example: (a) by moving the main shaft 70 using the axial motion device 720; (b) by energizing the appropriate outer ball screw assembly 722a or 722b under the control of the control circuit 724, even under load; or (c) in an extreme situation, such as when replenishment is not possible using (a) or (b) (i.e., the vehicle has made too many consecutive turns in the same direction thereby exhausting the differential system),by uncoupling the outer wheel via one of the coupling plate pairs 71 la, 71 lb, whereby the differential system will mechanically and automatically replenish when the vehicle makes a turn in the direction opposite to the one which caused the exhaustion. It should be noted that the coupling plate pairs 7 Ila, 71 lb and their associated elements as described herein may also be configured to uncouple the driven wheels whenever the brakes are applied, even if replenishment is not required. This achieves the effect of reducing the effort required to brake and conserving the momentum and / or energy of the prime mover and transmission of the vehicle.

[0126] Regarding the process of replenishment by moving the main shaft 70 using the axial motion device 720, one alternative to implementing the axial motion device 720 would be using a spring or spring structure (not shown) attached to both ends of the main shaft 70 positioned to urgingly move the main shaft 70 back to the mean or baseline position.

[0127] With respect to accomplishing replenishment by energizing the appropriate outer ball screw assembly 722a or 722b under the control of the control circuit 724, even under load, one way the control circuit 724 would control the outer ball screw assemblies 722a or 722b is to selectively send pulse-width modulation (PWM) signals to the outer ball screw assemblies. By varying the frequency and / or width of the pulse signals, the control circuit 724 can vary the occurrence and amount of replenishment or yaw. In addition, this method of controlling replenishment and / or yaw may supersede or replace the need to disengage the wheels for purposes of replenishment or recovery.

[0128] In operation, before and after every journey of the vehicle, and every time the vehicle is braked, or is coasting, or in the case of an implementation using an electric motor-generator, while moving from traction to regeneration, the coupling plate pairs 711a and 711b are disengaged, and the main shaft 70 is brought back to the mean position using either of the outer ball screw assemblies 722a or 722b (depending on the direction required), or the axial motion device 720. In the case of implementing the invention in a small vehicle, for example a small automotive or car, given the dimensions of the smallest cars currently on the market, the differential of the invention provides the ability to make more than 25 successive turns in the same direction (left or right) before exhausting its finite differentiation. Those of skill in the art would understand that there can be many journeys requiring 25 or more left turns. However, it would be a rare journey requiring 25 or more turns in the same direction, without any turn in the reverse direction at all in-between. Despite these unknown potentials and possible limitations, if the main shaft 70 reaches its end position, without any of the above events facilitating replenishment, in the event of computer control (i.e., operation of the control circuit 724) and such computer control being fed the route while starting the journey, such computer control may be programmed to examine the next turn coming up, and if it is the reverse of previous successive turns which caused the main shaft 70 to reach the end position, the main shaft 70 need not be replenished. Even more, in any of the implementations of the replenishment system of the invention, especially where computer control is used, such computer control may be configured to move the main shaft 70 not necessarily to a single, specifically defined or established mean or baseline position. Rather, such computer control may be programmed to, depending on current driving conditions or other data input, (a) move the main shaft as close to the pre-defined mean or baseline position but not necessarily to the exact same position; or (b) re-calculate the mean or baseline position and then move the main shaft 70 accordingly. In addition, moving the main shaft 70 to locations other than the same exact mean or baseline position may be used to avoid or limit local wear on the main shaft 70 and / or other components in the differential system.

[0129] If replenishing the differential “on the fly” is required, one (1) of the two (2) wheels will be disengaged via the coupling plate pairs 71 la or 71 lb, and the propulsion continued with the other wheel, and replenishment achieved under load by activating 722a or 722b, as required. Thus the vehicle will be propelled with one (1) wheel, and simultaneously the differential will be replenished, after which the coupling plate pairs 711a or 711b will be returned to their default states so that the vehicle will revert back to propulsion via both the driven wheels 76a, 76b.

[0130] Fig. 7B illustrates a further embodiment of the ball screw structure implementing Elements Ea, Eb and Ec according to the implementation of the differential system illustrated in Fig. 7A which implements the applied mechanics of Figs. 3A-3B. Except as otherwise provided hereinbelow, all other features and elements shown and disclosed with respect to Fig. 7A apply to this further embodiment. In Fig. 7B, only one (1) side of the entire structure is shown which would be applicable to both Elements Eb and Ec (i.e., the structures on both ends of the main shaft) only for purposes of brevity. In this embodiment, nut element 74' is handneutral, meaning its general design is mountable on the main shaft 70, both lefthanded and righthanded, and will perform as per the direction of the thread on which it is mounted. In this embodiment, two (2) nut elements 74’ engage and are mounted on the main shaft 70 at the two (2) opposite ends, which implements the operation of both Elements Ea and Eb.

[0131] Specifically, the nut element 74’ engages with the main shaft 70 via the roller discs 74’ a which are rotatably mounted within the nut element 74’ to carry the axial thrust and rotation of the main shaft 70. The nut element 74’ further incorporates bearings 74', outer race 74'c and balls 74'd. Discs 74'a riding spindle 74'b carry the forces to and from 70 and resulting from resistance of the connected driven wheel to the rotation. Spindle 74'b, through bearings 74', transmit entire end thrust to the rest of the structure of the bearing 74'. While ball bearings are shown, they may be replaced by simple journal bearings with rubbing friction, or tapered or flat roller bearings. While odd number of spindles 74'b are shown in the drawing, they can be even, and any number. While drawing shows two (2) discs mounted on two (2) bearings, there could be many discs and one (1) to many bearings.

[0132] In operation, as the main shaft 70 rotates via power from the prime mover (see Fig. 7A), axial components of the reaction from the driven wheels while the vehicle driving straight will be equal and opposite. Thus, the main shaft 70 will not move axially relative to the nut element 74’, but will rotate at the same speed as the main shaft 70. Movement of the driven wheels is transmitted from the main shaft 70 via the nut element 74’.

[0133] When the vehicle makes a turn, the inner wheel in the direction of the turn will tend to rotate less than the outer wheel. Differential motion will occur wherein the main shaft will move axially in reaction to the turn along with its continuing to rotate. As in previous embodiment shown in Fig. 7A, axial motion of the main shaft 70 may be inputted or imposed from an external source (i.e., axial motion device 720) so as to provide or modulate yaw.

[0134] Fig. 7C illustrates a further embodiment of the ball screw structure implementing Elements Ea, Eb and Ec according to the implementation of the differential system implementing the applied mechanics of Figs. 3A-3C. Except as otherwise provided hereinbelow, all other features and elements shown and disclosed with respect to Fig. 7A apply to this further embodiment. In Fig.7C, only one (1) ball screw structure is shown which would be applicable to either Element Eb or Ec for purposes of brevity. In this embodiment, nutelement 714 is shown which engages and is co-axial with the main shaft 70 which implements the operation of Element Ea.

[0135] Specifically, the nut element 74” engages with the main shaft 70 via the balls 730 which are rotatably mounted in the space between the grooves of the nut element 74” and the threaded grooves of the main shaft 70 to carry the axial thrust and rotation of the main shaft 70. The grooves in 74" can be cylindrical, conical, tear shaped, or any shape which, alone or together with the helical groove in 70, captures the location of each ball. In this embodiment as well, nut element 74" is hand-neutral, meaning its general design is mountable on the main shaft 70, both lefthanded or righthanded, and will perform as per the direction of the thread on which it is mounted.

[0136] In this operation, as the main shaft 70 rotates via power from the prime mover (not shown), axial components of the reaction from the driven wheels while the vehicle driving straight will be equal and opposite. Thus, the main shaft 70 will not move axially relative to the nut element 74”, and both nut elements 74” will rotate at the same speed as the main shaft 70. Movement of the driven wheels is transmitted from the main shaft 70 via the nut element 74”. Again, when the vehicle makes a turn, the inner wheel in the direction of the turn will tend to rotate less than the outer wheel, and differential motion will occur wherein the main shaft will move axially in reaction to the turn along with its continuing to rotate. As in previous embodiment shown in Fig.7A, axial motion of the main shaft 70 may be inputted or imposed from an external source (i.e., axial motion device 720) so as to provide or modulate yaw.

[0137] Fig. 8 shows one embodiment for a computer or processor-based control system 80 for the differential system of the claimed invention. In particular, Fig. 8 is a system block diagram of one implementation for a control circuit for the differential system. As an example, this implementation is for a vehicle with one (1) axle. However, as will be discussed hereinbelow, this implementation may also be used in a vehicle with two (2) axles by incorporating, for example, a splitting device.

[0138] As shown in Fig. 8, the control system 80 may be organized in three (3) sections, namely a mechanical power section MP; a computer or processor section CP; and an input and output section IO. The mechanical power section MP represents the flow of mechanical energy, wherein the prime mover 82 may, depending on the type of implementation for the prime mover, transit or receive motion through the splitter 84, through the axles 86a, 86b, through the differentials 88a, 88b for the axle 86a, 86b, respectively, and then to / from the wheels 810a-810d. In the embodiment illustrated in Fig. 8, the vehicle is equipped with a drive system with two (2) axles in order to illustrate the operation of the differential system of the present invention incorporating the optimum realization of the splitter 84. However, the differential system of the present invention including a splitter is equally applicable to a vehicle with a two-wheel drive system or a four-wheel drive system or other multi-axle drive systems, as those of skill in the art would understand given this disclosure of the present invention.

[0139] Even more, as those of skill in the art would understand given this disclosure of the present invention, the differential system of the present invention with or without a splitter would be equally applicable to vehicles with other configurations currently known or that would be foreseeable, and not be limited just to those with two-wheel drive systems or multiaxle drive systems. The differential system of the present invention is particularly applicable to vehicles that are equipped with continuously variable drive (CVD) transmissions orinfinitely variable drive (IVD) transmissions. In addition, when applied to vehicles using CVD / IVD transmissions, the use of the present invention especially when implementing the splitter has the potential of dispensing with the need for gear boxes and even clutches as now known in the art, as the present invention provides for splitting the drive between two (2) axles at their respective speeds depending on the steering angle.

[0140] In embodiments in which the prime mover 82 is an electric motor, the splitter 84, axles 86a, 86b and differentials 88a, 88b would be configured to transmit the mechanical power or motion both from and to the prime mover 82. For example, when the prime mover 82 is receiving electrical energy from its energy source (not shown) such as a battery, an internal combustion engine or other electrical energy generating device, the prime mover 82 in turn converts the electrical energy to mechanical motion so as to activate the splitter 84, turn the axle and activate the differentials 88a, 88b, and then rotate the wheels 810a-810d to move the vehicle or other implement connected to the entire system.

[0141] Conversely, unpowered rotation of some or all of the wheels 810a-810d, such as when the vehicle or other implement is being moved using another source of motion (i.e., the four- wheel drive system set in two-wheel drive mode, another engine is pushing / pulling / moving the vehicle, or the vehicle is coasting downhill), the mechanical motion generated by the rotating wheels 810a-810d is transmitted through the differentials 88a, 88b, through the axles 86a, 86b, through the splitter 84 and then to the prime mover 82. The rotation in the electric motor that is the prime mover 82 converts the mechanical motion into electrical energy that can then be transmitted and stored in the vehicle’s batteries (not shown).

[0142] In the computer or processor section CP, as shown in Fig. 8, the vehicle’s main computer 812 may be implemented as a conventional computer circuit or other data processing circuit known in the art to be used in automotive applications, including but not limited to controlling and / or monitoring internal combustion engine vehicles, electric vehicles, engine controls, electric motors, industrial machines, power systems and other similar devices. The terms “monitor” or “monitoring” as used herein means that at least one of the occurrence, presence and / or magnitude of an operation is being detected and / or measured.

[0143] The splitter control 814 of the main computer 812 is used to monitor and control the operation of the splitter 84 of the mechanical power section MP. The splitter control 814 may be implemented as a separate computer circuit or other data processing circuit, or as software code incorporated into the software of the main computer 812, as known in the art.

[0144] The differential control 815 of the main computer 812 is used to monitor and control the operation of the differentials 88a, 88b of the mechanical power section MP. The differential control 815 may be implemented as a separate computer circuit or other data processing circuit, or as software code incorporated into the software of the main computer 812, as known in the art.

[0145] The processor section CP may also include a transmission control 816 that is configured to control and / or monitor operation of the transmission system of the vehicle. In an embodiment wherein the vehicle incorporates an automatic transmission system, the transmission control 816 may be implemented as software incorporated into the automatic transmission control circuit as known and used in the art, or as a separate computer or data processing circuit compatible known in the art for use in automotive applications as noted above, or even as software code incorporated into the main computer 812 to control and / or monitor operation ofthe automatic transmission. In this embodiment that incorporates automatic transmission, the transmission control 816 is configured to receive data signals from sensors 817 which include at least a clutch sensor 817a, brake sensors 817b and accelerator sensor 817c. The sensors 817 which are designed to monitor operation of each of the above-noted components are implemented using components known in the art for use in automotive applications as noted above.

[0146] Alternatively, if in the embodiment the vehicle incorporates a manual transmission system, the transmission control 816 may be implemented as the plurality of sensors 817a-817c connected to the main computer 812. In another embodiment, if the vehicle incorporates an anti-lock braking system (ABS) which includes an ABS control circuit 817d as known in the art, the transmission control 816 is configured to receive data signals from the ABS control circuit 817d, in addition to at least the clutch sensor 817a, brake sensors 817b and accelerator sensor 817c.

[0147] In the input and output section IO, a plurality of sensor / actuator elements 818 are connected to either provide data signals to at least the main computer 812, or receive control signal from at least the main computer 812 in order to operate the various functions of the differential system as discussed hereinabove. As shown in Fig. 8, and with reference to Fig. 7, the sensor / actuator elements 818 include at least a drive sensor 818a that monitors operation and condition of the bevel gear pair structure 78 that connects to a drive shaft 710 and the prime mover 719; coupling sensors 818bl,818b2 that monitor and control the operation of the coupling plate pairs 71 la, 71 lb, respectively; an axial motion sensor / actuator 818c that monitors and / or controls the axial motion device 720; wheel sensors 818d 1 -818d4 that monitor the rotation and condition of each of the driven wheels, respectively; and replenishment sensor / actuators 818el,818e2 that control operation of the outer ball screw assemblies 722a, 722b, respectively. Each of the sensor / actuator elements 818 are implemented using components known in the art for use in automotive applications as noted above.

[0148] Further, the input and output section IO includes the steering control structure 820 of the vehicle, a manual override structure 822 and a display 823. The steering control structure 820 and the display 823 are implemented using components known in the art for use in automotive applications as noted above. The manual override structure 822 is used to provide control of, for example, either or both of the axial motion sensor / actuator 818c that monitors and / or controls the axial motion device 720 and the replenishment sensor / actuators 818el,818e2 that control operation of the outer ball screw assemblies 722a, 722b using manual control levers or other mechanisms (not shown) that would be manipulated by the driver or vehicle operator (see Fig. 7). For example, the manual override structure 822 may be implemented using at least one of software in the main computer 812, a separate override control processor or circuit, manual control levers or other mechanisms (not shown) or a combination thereof that can be accessed or manipulated by the driver / operator, such that the driver / operator can selectively engage or disengage the elements or operations of the differential system as determined by the main computer 812 in favour of control selections made by the driver or operator via electronic input or manual control levers, or both.

[0149] The steering control structure 820 implements the operation of the Element Ed as explained hereinabove, wherein the movement of the main shaft 70 and the ball screw assemblies 72a, 72b in the X direction can be translated into inputs (i.e., sensor data signals) to the main computer 812 to help control steering, or as outputs (i.e., steering control signals or movement depending on the implementation of the steering column structure 820 as known inthe art) from the main computer 812 or the steering control structure 820 so as to help control steering, monitor and / or control operation of the ball screw assemblies 72a, 72b, monitor and / or control replenishment, and / or provide and control yaw in the vehicle.

[0150] The steering control structure 820 in conjunction with the axial motion sensor / actuator 818c; wheel sensors 818dl-818d4; and the replenishment sensor / actuators 818el,818e2, together implementing Element Ed, either transmits movement into or reacts from the motion of the main shaft 70 and the ball screw assemblies 72a, 72b in the X-direction. In a passive operation wherein only the sensors are used to monitor the movement of the main shaft 70 and the ball screw assemblies 72a, 72b, the data signals from the sensors to the main computer 812 will indicate the amount of differentiation occurring, or in other words, to indicate the direction in which the vehicle is facing. In the embodiments where the steering control structure 820 in conjunction with the sensors / actuators are fully implemented, controlled yaw is provided based on the operation of the differential 88 with the steering control structure 820.

[0151] As described hereinabove, with reference to Fig. 7A, the coupling plate pairs 71 la, 71 lb mounted to the outer ends of the nut elements 74a, 74b provide a structure for extreme cases wherein the vehicle has performed more turns in one direction than the other, which would reach the limit of the number of rotations that the bolt elements 70a, 70b could make into the corresponding nut element 74a, 74b, thereby exhausting the finite differentiation possible by the differentiation system. Also, this structure may at least partially compensate for finite differentiation, depending on the embodiment of the differential system implemented. If the main shaft 70 moves to the extreme left or right (i.e., the bolt element 70a rotates up to its limit into the nut element 74a, or the bolt element 70b rotates up to its limit into the nut element 74b), the corresponding coupling plate pairs 711a or 711b will be disengaged and the corresponding driven wheel 76a or 76b. The coupling actuators 818b 1,818b2 will then signal the main computer 812 that at least one of the coupling plate pairs 71 la or 71 lb has disengaged the corresponding driving wheel 76a or 76b from the main shaft 70. This will then either (1) signal the main computer 812 to initiate on-load replenishment of the differential system while the vehicle is still moving; (2) signal the main computer to send a message signal to the display 823 notifying the driver or operator that the driven wheels have been disengaged and are now freely rotating, whereby the driver / operator can select what step(s) to take next.

[0152] Regarding the axial motion sensor / actuator 818c that monitors and / or controls the axial motion device 720, as described above, if the axial motion device 720 is implemented as a linear actuator, the axial motion sensor / actuator 818c, as an actuator, may be activated to replenish the differential system by moving the main shaft 70 back to the mean or baseline position according to data signals received from the main computer 812. Alternatively, if the axial motion device 720 is implemented as a sensor (i.e., embodying axial motion sensor / actuator 818c) or as a combination of a sensor and an actuator, the axial motion sensor / actuator 818c would provide data signals for the main computer 812 to at least notify that the main shaft 70 has moved in one direction or the other and / or to measure the extent of the movement of the main shaft 70. It is noted that the axial motion device 720 implemented as a linear actuator as known in the art may not have the power or structural capacity to perform on-load replenishment. Rather, on-load replenishment would be performed using a more robust structure such as the outer ball screw assemblies 722a, 722b. Linear actuators would be more suitable when replenishment is performed during braking or when the driven wheels are uncoupled.

[0153] As discussed above with reference to Fig. 7A, the control circuit 723 is provided to make the main shaft 70 move or translate back to the mean or baseline position by selectively stopping / braking and releasing the outer bolt elements 722a2,722b2 relative to the rotation of the bolt element 70a. In this embodiment, the control circuit 723 is implemented as the replenishment sensor / actuators 818el,818e2 that are connected to the main computer 812 and the differential control 815, depending on the type of implementation for the differential control as discussed above. In the process of replenishment, as the main shaft 70 and thus the bolt element 70a continue to rotate with the movement of the vehicle, thereby continuing to propel the vehicle, either of the outer bolt elements 722a2,722b2 is held stationary by the replenishment sensor / actuators 818el,818e2 relative to the vehicle and the main shaft 70, whereby the rotation of the bolt element 70a or 70b relative to the temporarily stationary outer bolt element 722a2 or 722b2, respectively, forces the main shaft 70 to move to the right or left, respectively, back to the mean or baseline position.

[0154] As noted above, the splitter control 813 of the main computer 812 is used to monitor and control the operation of the splitter 84 of the mechanical power section MP. In the embodiment represented in Fig. 8, the vehicle is equipped with a four-wheel drive system that implements the use of two (2) axles. In operation, when a vehicle is turning as is known in the art, the four rotating wheels 810a-810d each have a different path length. Specifically, the path traversed by the steered wheels (i.e., the wheels connected to the steering system as is known in the art) is longer than the path of the non-steered wheels, while the path of the wheels on the inside radius of a turn is shorter than the path of the wheels on the outside radius of the turn. According to the present invention, when a vehicle turns, each of the four wheels will be given different rotations according to each wheel's path length. This will be accomplished by operation of the splitter 84 that controls the speed of each of the rotating wheels 810a-810d according to a ratio as determined by the steering angle.

[0155] The operation of the control system 80, and in particular the splitter 84 will be described hereinbelow with reference to Fig. 9. As shown, the general operation 90 of the control system 80 (see Fig. 8) illustrates the driving of a vehicle that implements the differential system of the present invention, incorporating the control system 80. For example, when the vehicle is driving along a straight path (assuming no other factors are considered, including but not limited to road conditions, weather, etc.), in the control system 80, the differentials 88a, 88b drives the wheels 810a-810d (or at least two (2) wheels 810a,810b if in a two-wheel drive system or mode) at same speed based on the input mechanical energy from the prime mover 82 via the splitter 84. In this situation, axial components of the reaction forces (i.e., along the longitudinal axis of the main shaft 70) from opposing wheels will balance each other, whereby the main shaft 70 will not move axially (Step 92).

[0156] When the vehicle makes a turn or has to drive along a curved road or path, the steering control structure 820 signals the differential control 815 the main computer 812 about the occurrence and magnitude of the turn being performed (Step 94). The differential control 815 will then signal the axial control device 720 (implemented as a linear actuator and sensor) or at least one of the outer ball screw assemblies 722a, 722b, or to move the main shaft 70 axially in a direction and at a rate commensurate with the turn continuously until the turn is completed and the vehicle resumes driving along a straight path (Step 96). In this situation, the amount of force that the axial control device 720 is required to exert on the main shaft 70 will be consistent with merely complying with the requirement of differential motion between the opposing wheels, and the axial movement of the main shaft 70 is determined by the differential control 815 in response to the type, duration and degree of the turn or curve of the road. If the steeringcontrol structure 820 signals that compensation for the turn requires any modulation of the yaw, the differential control 815 will signal the axial control device 720 accordingly (Step 98). It is noted that if the vehicle is equipped with a two-wheel drive system or band of treads and the wheels connected to the differential system of the present invention are not connected to the steering controls of the vehicle, the axial control device 720 and at least of the outer ball screw assemblies 722a, 722b will be the sole source of yaw in the vehicle.

[0157] If differential control does occur during the operation of the vehicle, an event may occur to trigger the subsequent replenishment of the differential system (Step 910). One such triggering event is when the prime mover (engine / motor / other) and at least one of the driven wheels are disconnected from the of the differential (Step 901). In conventional engine-driven vehicles, this happens when the vehicle is in the neutral gear or when the clutch is disengaged, or due to any other event, or when the vehicle is being braked and the clutch disengaged, or disconnected by design to enable replenishment. In electric vehicles, this could also happen while changing over from the state of motor driving the vehicle to vehicle driving the motor so as to regeneratively charging the batteries, or vice versa.

[0158] Another triggering event would be when the automatic transmission of the vehicle (is so equipped) disconnects the differential, and hence the wheels from the prime mover (Step 902).

[0159] Another triggering event would be when the vehicle’s brakes are applied (Step 903). If the brakes are applied without the clutch being disengaged, disengaging the wheels from the differential would relieve the brakes of the added burden of braking the angular momentum of the prime mover and the drive train. In the case of some electric vehicles, even otherwise, the prime mover is not disengaged from the differential.

[0160] Another triggering event would be when one or both driven wheels slip or lose contact / traction with the surface on which the vehicle is moving, or just after the finite differentiation has been utilised to get out of a difficult driving situation (Step 904). For example, when one wheel slips relative to the ground, the other wheel will lose torque. In such situations, the differential of the present invention would allow the wheel to slip until the finite differentiation is exhausted, and then the non-slipping wheel will receive torque. The replenishment could be activated after the vehicle is out of the situation.

[0161] Another triggering event would be when one or both devices that implement Elements Eb and Ec have exhausted all or a pre-determined extent of the finite possible differentiation that the devices are designed to do (Step 905).

[0162] If any one of the above triggering events occurs, the replenishment system of the differential may be initiated (Step 9010) depending on how that system is implemented in the vehicle. For example, the control circuit of the vehicle may be configured to perform the replenishment automatically, or to schedule the replenishment at a predetermined time or when the condition of the vehicle allows, or to just warn the driver or operator that replenishment is needed.

[0163] As discussed above, the differential system of the present invention, and in particular in the embodiments wherein the differential system is applied to vehicles that are equipped with four-wheel drive systems or other multi -axle drive systems, a splitter 84 (with reference to Fig. 8 as an example) is incorporated to transmit in proper ratios the mechanical motion fromthe prime mover 82 to the differentials 88a, 88b. In the operation of the vehicle that incorporates the differential system, it is understood that when the vehicle is going straight, all four wheels 810a-810d will traverse equal paths. On curves, the steered outer wheel has the longest path, and the non-steered inner wheel will have the shortest path. The other two (2) wheels will have path length that are somewhere between the two extremes. It is also understood that the average of the path lengths of non-steered wheels will be less than the average of the steered wheels.

[0164] The function of the splitter, such as that implemented for the present invention, is to transmit the mechanical motion to the two (2) axles (i.e., axles 86a, 86b) proportionate to the difference in the path lengths between the averages of the steered and non-steered wheels, such that the differences in the path lengths differentiate between the two (2) wheels of each axle.

[0165] Fig. 10A illustrates the mechanics of a conventional continuously variable drive (CVD) transmission. As shown, the CVD transmission incorporates two (2) rollers 1010 and 1012, which are frustums of cones mounted to their respective shafts and supported via bearings. The roller 1010 is the driver roller, the roller 1012 the driven roller. A roller element 1014 (implemented as a resilient cord or belt) runs between them. Roller element 1014 transmits motion between the two (2) rollers 1010 and 1012. As known in the art, the ratio between the driver roller 1010 and the driven roller 1012 is varied by the movement of the roller element 1014 between the two (2) rollers.

[0166] In at least one embodiment, as shown in Figs. 10B and 11C, the splitter such as that implemented in Fig. 8, incorporates rollers 1011, 1013 and 1015, wherein all three rollers are also frustums of cones mounted to their respective shafts and supported via bearings, and positioned such that the narrower conical ends of the two (2) outer rollers 1011, 1015 are pointed in the same direction, while the narrower conical end of the middle roller 1013 is pointed in the opposite direction. Roller element 1017 is positioned to run between roller 1011 and 1013, while roller element 1019 is positioned to run between roller 1013 and roller 1015. Depending on the specific implementation, the middle roller 113 is the driver roller that connects to the prime mover and the two (2) outer rollers 1011,1015 are driven and connect to the differentials 86a, 86b, respectively (see Fig. 10B). Alternatively, as shown in Fig. 10C, one of the outer rollers 1011,1015 is the driver (in this example, roller 1011) and connects to the prime mover, while the adjacent rollers 1013,1015 are driven and connect to the differentials 86a, 86b, respectively.

[0167] Other variations of the splitter as described hereinabove include rollers that are frustumshaped toroids. As is known in the art, cone-based CVD systems are not infinitely variable, while toroid-based CVD transmissions are capable of being infinitely variable, such as in IVD systems are infinitely variable including zero. Also, the use of a splitter as part of the differential system of the present invention eliminates the need of a gearbox in the vehicle.

[0168] In operation, using the embodiment where the outer roller 1011 is the driver and the adjacent rollers 1013,1015 are driven as an example, the ratio between the outer roller 1101 and adjacent roller 1013 would be the desired ratio between the prime mover speed and vehicle speed. In this example, adjacent roller 1013 drives the steered wheels, and adjacent 1015 drives the non-steered wheels. When the vehicle is travelling straight, the roller element 1019 betweenthe lower two (2) rollers 1013,1015 is positioned at the location where the diameters of the lower two (2) rollers 1013,1015 at the point of contact are equal. Thus, both rollers are driven at the same speed, which in turn drives the two (2) differentials 88a, 88b at equal speed, and drives all four wheels 810a-810d at the same speed.

[0169] During turns, the roller element 1019 between the lower two (2) rollers 1013,1015 will be positioned such that the adjacent roller 1013 which is driving the steered wheels will be at the exact overdrive speed vis-a-vis the non-steered wheels driven by the adjacent roller 1015, which is required per the angle of the steered wheels. Thus, as between the differentials 86a, 86b, the specific ratio of the speed of the two (2) non-steered wheels vis-a-vis the two (2) steered wheels will be commensurate with the angle of the steered wheels. Further, the differentials will overdrive the outer wheels based on the angle of the steered wheels.

[0170] Alternatively, in a vehicle equipped with manual system, (all not shown) one implementation would be two (2) cams on the steered wheel / steering chain providing mechanical input through the roller element between the two (2) conical rollers which are coupled to the differentials, thereby determining the overdrive of steered wheels vis-a-vis nonsteered wheels. The other cam determines the motion of the main shaft of the differential so as to provide correct overdrive to the outer wheels. In such an implementation, the two (2) driven wheels may be coupled in order to compensate for the driven rollers 1013,1015 that are counterrotating, via for example gears or other coupling devices known in the art. Other alternative embodiments of the splitter include providing a separate CVD structure for each axle, or constructing the splitter with five (5) rollers.

[0171] In another embodiment of the present invention, as shown in Fig. 11, in the implementation of at least applied mechanics of Figs. 4A-4B, Element Ea consists of two (2) sub-elements, EaSl and EaS2, which are driven by the primary Element Ea. In this example, sub-elements, EaSl and EaS2 are coupled to the primary Element Ea via bevel gears mounted on the ends of sub-elements, Element Eb and Ec are each configured to be co-axial with subelements, EaSl and EaS2, respectively, and to operate in the same manner and function as in the other embodiments described hereinabove.

[0172] The primary Element Ea and the sub-elements EaS 1 and EaS2 are interlocked with each other via bevel gears 1102, 1104 and 1106, respectively, wherein the bevel gear 1102 drives the bevel gears 1104, 1106. Sub-element EaSl and Element Eb are operatively connected to one another, while sub-element EaS2 and Element Ec are similarly configured with one another. The sub-elements EaSl, EaS2 and their corresponding Elements Eb, Ec are in turn constructed such that an axial change in distance between sub-element EaSl and Element Eb will always equal the axial change in distance between sub-element EaS2 and Element Ec, either in the same or opposite direction.

[0173] The axial distance is defined to be along the axes Xb and Xc. The “hand” of the helical grooves formed between the sub-elements EaSl, EaS2 and their corresponding Elements Eb, Ec will be either in the same direction or opposite. As such, the direction of rotation of subelement EaSl may be same or opposite of sub-element EaS2. In this example as illustrated in Fig. 11, a change in the axial distance between the elements is same, whereby the handednessof sub-element EaSl is opposite of sub-element EaS2, and the direction of rotation is same. Other combinations of operation that would be possible include: (1) direction of rotation is same, handedness is the same, and changes in axial direction are opposite; (2) directions of rotation are opposite, handedness is same, and changes in axial direction are same; and (3) direction of rotation, handedness and changes in axial direction are all opposite. Whatever the orientations and handedness (left or right) of the helical grooves, the arrangement of components in this embodiment ensures that the axial reactions from the two (2) driven wheels (not shown) connected to Elements Eb, Ec would counter each other, and the axial resistances from the two (2) wheels will be equal and opposite when the vehicle is going straight, such that the wheel offering higher resistance will move less, and the average of the two will equal the input.

[0174] In view of the above description, those of ordinary skill in the art would be able to practice various aspects of the present invention, including but not limited to a first aspect of a differential for a vehicle, having: a main shaft operatively mounted to rotate along a longitudinal axis thereof, the main shaft being operatively connected to a prime mover so as to rotate in response to motive power therefrom; and first and second roller elements operatively connected to the main shaft to rotate at least parallel to the longitudinal axis of the main shaft, the main shaft being formed with a first shaft portion that inter-engages with first roller element and a second shaft portion that inter-engages with the second roller element, wherein the first and second roller elements are operatively connected to first and second wheels of a vehicle, respectively, such that the motive power from the prime mover is transferred to the first and second wheels via co-rotation of the first and second roller elements with the main shaft so as to propel the vehicle, the first and second wheels being in contact with a surface on which the vehicle is propelled, and the main shaft is configured to laterally move between the first and second roller elements along the longitudinal axis thereof in response to a difference in at least one of speed and travel distance during a turn between the first and second wheels while in contact with the surface as the vehicle is propelled.

[0175] In that same first aspect, the first shaft portion is formed with a first threading direction that is opposite a second threading direction formed on the second shaft portion, the first roller element is formed with a first roller threading corresponding to the first threading direction of the first shaft portion, and the second roller element is formed with a second roller threading corresponding to the second threading direction of the second shaft portion.

[0176] In that same first aspect, the differential further includes: a first ball screw assembly including the first shaft portion inter-engaged with the first roller element, the first roller element being a first nut element of the first ball screw assembly; and a second ball screw assembly including the second shaft portion inter-engaged with the second roller element, the second roller element being a second nut element of the first ball screw assembly, wherein the first shaft portion is formed as a first bolt element of the first ball screw assembly, and the second shaft portion is formed as a second bolt element of the second ball screw assembly.

[0177] In that same first aspect, the main shaft includes a bevel gear pair structure operatively connected between the main shaft and a drive shaft connected to the prime mover so as to transfer the motive power from the prime mover to the main shaft.

[0178] In that same first aspect, the differential further includes: an axial motion element operatively connected to the main shaft and configured to controllably and laterally move the main shaft between the first and second roller elements along the longitudinal axis thereof so as to at least one of restore to a baseline position the main shaft moving in response to a difference in at least one of speed and travel distance during a turn between the first and second wheels while in contact with the surface as the vehicle is propelled and compensate for the difference in at least one of speed and travel distance during a turn between the first and second wheels while in contact with the surface.

[0179] In that same first aspect, the differential further includes: an axial motion element operatively connected to the main shaft and configured to at least one of detect and measure lateral movement of the main shaft between the first and second roller elements along the longitudinal axis thereof in response to the difference in at least one of speed and travel distance during a turn between the first and second wheels.

[0180] In that same first aspect, the differential further includes: first and second replenishing elements operatively connected to the main shaft, wherein the first and second replenishing elements are configured to controllably and laterally move the main shaft along the longitudinal axis thereof so as to at least one of restore to a baseline position the main shaft moving in response to the difference in the at least one of speed and travel distance during a turn between the first and second wheels while in contact with the surface as the vehicle is propelled and compensate for the difference in the at least one of speed and travel distance during a turn between the first and second wheels while in contact with the surface.

[0181] In that same first aspect, the differential further includes: a first coupling plate structure operatively connected between the first roller element and first wheel; a second coupling plate structure operatively connected between the second roller element and second wheel, wherein each of the first and second coupling plates is configured to disengage at least one of the first and second wheel from the corresponding first and second roller element when the main shaft reaches a predetermined limit of rotations relative to at least one of the first and second roller elements.

[0182] In that same first aspect, the main shaft includes a bearing fixedly mounted around a center shaft portion of the main shaft, the bearing being operatively connected to the axial motion element.

[0183] In a second aspect, a differential system for a vehicle that provides yaw, includes: a prime mover for providing motive power; a differential structure that includes a main shaft operatively mounted to rotate along a longitudinal axis thereof, the main shaft being operatively connected to the prime mover so as to rotate in response to motive power therefrom, and first and second roller elements operatively connected to the main shaft to rotate at least parallel to the longitudinal axis of the main shaft, the main shaft being formed with a first shaft portion that inter-engages with first roller element and a second shaft portion that inter-engages with the second roller element; first and second drive wheels operatively connected to the first and second roller elements, respectively, such that the motive power from the prime mover istransferred to the first and second wheels via co-rotation of the first and second roller elements with the main shaft so as to propel the vehicle, the first and second wheels being in contact with a surface on which the vehicle is propelled; and a control circuit for at least one of monitoring and controlling operation of the differential structure, wherein the main shaft is configured to laterally move between the first and second roller elements along the longitudinal axis thereof in response to a difference in at least one of speed and travel distance during a turn between the first and second wheels while in contact with the surface as the vehicle is propelled.

[0184] In that same second aspect, the first shaft portion is formed with a first threading direction that is opposite a second threading direction formed on the second shaft portion, the first roller element is formed with a first roller threading corresponding to the first threading direction of the first shaft portion, and the second roller element is formed with a second roller threading corresponding to the second threading direction of the second shaft portion.

[0185] In that same second aspect, the differential system, further includes: a first ball screw assembly including the first shaft portion inter-engaged with the first roller element, the first roller element being a first nut element of the first ball screw assembly; a second ball screw assembly including the second shaft portion inter-engaged with the second roller element, the second roller element being a second nut element of the first ball screw assembly, wherein the first shaft portion is formed as a first bolt element of the first ball screw assembly, and the second shaft portion is formed as a second bolt element of the second ball screw assembly.

[0186] In that same second aspect, the differential system further includes: an axial motion element operatively connected to the main shaft and the control circuit, the control circuit being configured to control the axial motion element to laterally move the main shaft between the first and second roller elements along the longitudinal axis thereof so as to at least one of restore to a baseline position the main shaft moving in response to the difference in at least one of speed and travel distance during a turn between the first and second wheels while in contact with the surface as the vehicle is propelled and compensate for the difference in at least one of speed and travel distance during a turn between the first and second wheels while in contact with the surface.

[0187] In that same second aspect, the differential system further includes: an axial motion element operatively connected to the main shaft and the control circuit, the control circuit being configured to at least one of detect and measure lateral movement of the main shaft between the first and second roller elements along the longitudinal axis thereof in response to a difference in at least one of speed and direction between the first and second wheels in response to the axial motion element.

[0188] In that same second aspect, the differential system further includes: first and second replenishing elements operatively connected to the main shaft and to the control circuit wherein the control circuit is configured to control the first and second replenishing elements to laterally move the main shaft along the longitudinal axis thereof so as to at least one of restore to a baseline position the main shaft moving in response to the difference in at least one of speed and travel distance during a turn between the first and second wheels while in contact with the surface as the vehicle is propelled and compensate for the difference in at least one ofspeed and travel distance during a turn between the first and second wheels while in contact with the surface.

[0189] In that same second aspect, the first replenishing element is a first replenishing ball screw assembly incorporating a first replenishing nut element inter-engaged with the first shaft portion that inter-engages with the first roller element, the first shaft portion inter-engaging with the first roller element being a first replenishing bolt element of the first replenishing ball screw assembly; the second replenishing element is a second replenishing ball screw assembly including a second replenishing nut element inter-engaged with the second shaft portion that inter-engages with the second roller element, the second shaft portion inter-engaging with the second roller element being a second replenishing bolt element of the second replenishing ball screw assembly.

[0190] In that same second aspect, the control circuit is configured to selectively engage at least one of the first and second replenishing elements and thereby at least one of restore to a baseline position the main shaft and compensate for movement of the main shaft.

[0191] In that same second aspect, the main shaft includes a bearing fixedly mounted around a center shaft portion of the main shaft, the bearing being operatively connected to the axial motion element. Comment: This is a limitation on the axial motion element, not the control circuit.

[0192] In that same second aspect, the differential system further includes: a steering control structure operatively connected to the control circuit and the differential structure, wherein the main shaft is configured to laterally move along the longitudinal axis thereof relative to the first and second roller elements in response to a steering angle signal from the steering control structure to the first and second wheels.

[0193] In that same second aspect, the main shaft is configured to laterally move along the longitudinal axis thereof relative to the first and second roller elements in response to a yaw signal from the steering control structure.

[0194] In a third aspect, a differential structure, includes: a main shaft first and second helical shaft portions opposite each; first and second helical wheel shafts operatively positioned to inter-engage with the first and second helical portions, respectively, of the main shaft; first and second driven wheels operatively mounted to outer shaft ends of the first and second helical wheel shafts, respectively; a steering wheel operatively connected to the first and second driven wheels and to the main shaft, wherein the main shaft is configured, during rotation of the first and second helical wheel shafts and the first and second driven wheels, to move coaxially along a common longitudinal axis in response to a steering angle of the steering wheel.

[0195] In that same third aspect, the first and second helical wheel shafts are operatively positioned to inter-engage with the first and second helical portions, respectively, of the main shaft via a plurality of roller balls positioned therebetween.

[0196] In that same third aspect, the differential structure 21, further includes: first and second carriers operatively connected to the first and second helical wheel shafts, respectively, and operatively positioned to inter-engage with the first and second helical portions, respectively, of the main shaft, wherein the first and second carriers are configured to rotate along the common longitudinal axis with the main shaft.

[0197] In that same third aspect, the first and second carriers are operatively positioned to interengage with the first and second helical portions, respectively, of the main shaft via a plurality of roller disks mounted in each of the first and second carriers and inter-engaging with the first and second helical portions.

[0198] In that same third aspect, the first and second carriers are each formed as cylinders with interior helical threads therein, the interior helical threads of the first and second carriers being operatively positioned to inter-engage with the first and second helical portions, respectively, of the main shaft via a plurality of roller balls positioned therebetween.

[0199] In a fourth aspect, a method of operating a differential for a vehicle to provide yaw, incorporates the steps of: providing a differential structure that includes a main shaft operatively mounted to rotate along a longitudinal axis thereof, and first and second roller elements operatively connected to the main shaft to rotate at least parallel to the longitudinal axis of the main shaft, the main shaft being formed with a first shaft portion that inter-engages with first roller element and a second shaft portion that inter-engages with the second roller element, and the first and second roller elements being operatively connected to first and second wheels of a vehicle, respectively; inputting motive power via a prime mover into the main shaft so as to transfer the motive power to first and second wheels of a vehicle such that co-rotation of the first and second roller elements with the main shaft propels the vehicle, the first and second wheels being in contact with a surface on which the vehicle is propelled; and laterally moving the main shaft between the first and second roller elements along the longitudinal axis thereof in response to a difference in at least one of speed and travel distance during a turn between the first and second wheels while in contact with the surface as the vehicle is propelled.

[0200] In that same fourth aspect, the method further includes the step of: controllably and laterally move the main shaft between the first and second roller elements along the longitudinal axis thereof so as to at least one of restore to a baseline position the main shaft moving in response to a difference in at least one of speed and travel distance during a turn between the first and second wheels while in contact with the surface as the vehicle is propelled and compensate for the difference in at least one of speed and travel distance during a turn between the first and second wheels while in contact with the surface.

[0201] In that same fourth aspect, the method further includes the step of: at least one of detecting and measuring lateral movement of the main shaft between the first and second roller elements along the longitudinal axis thereof in response to the difference in at least one of speed and travel distance during a turn between the first and second wheels.

[0202] In that same fourth aspect, the method further includes the step of: providing at least one replenishing element operatively connected to the main shaft; and controllably and laterally moving the main shaft along the longitudinal axis thereof via the at least one replenishment element so as to least one of restore to a baseline position the main shaft moving in response to the difference in at least one of speed and travel distance during a turn between the first and second wheels while in contact with the surface as the vehicle is propelled and compensate for the difference in at least one of speed and travel distance during a turn between the first and second wheels while in contact with the surface.

[0203] In that same fourth aspect, the method further includes the step of: providing a coupling plate structure operatively connected between the first and second roller elements with the first second wheels, respectively; selectively disengaging at least one of the first and second wheels from the corresponding first and second roller element when the main shaft reaches a predetermined limit of rotations relative to at least one of the first and second roller elements.

[0204] In a fifth aspect, a method for operating a differential system for a vehicle, incorporates the steps of: providing a prime mover for providing motive power, a differential structure that includes a main shaft operatively mounted to rotate along a longitudinal axis thereof and operatively connected to the prime mover, and first and second roller elements operatively connected to the main shaft to rotate at least parallel to the longitudinal axis of the main shaft, the main shaft being formed with a first shaft portion that inter-engages with first roller element and a second shaft portion that inter-engages with the second roller element, first and second drive wheels operatively connected to the first and second roller elements, respectively, and a control circuit for at least one of monitoring and controlling operation of the differential structure; inputting motive power from the prime mover to the differential structure; laterally moving the main shaft between the first and second roller elements along the longitudinal axis thereof in response to a difference in at least one of speed and travel distance during a turn between the first and second wheels while in contact with the surface as the vehicle is propelled.

[0205] In that same fifth aspect, the method for operating a differential system according to claim 31, further includes the step of: providing an axial motion element operatively connected to the main shaft and the control circuit; and controlling the axial motion element via the control circuit to laterally move the main shaft between the first and second roller elements along the longitudinal axis thereof.

[0206] In that same fifth aspect, the method for operating a differential system according to claim 31, further includes the step of: providing an axial motion element operatively connected to the main shaft and the control circuit; at least one of detecting and measuring lateral movement of the main shaft between the first and second roller elements along the longitudinal axis thereof.

[0207] In that same fifth aspect, the method for operating a differential system further includes the steps of: providing at least one replenishing element operatively connected to the first and second ball screw assemblies, respectively, and to the control circuit; and selectively activating via the control circuit the first and second replenishing elements to laterally move the main shaft along the longitudinal axis thereof so as to at least one of restore to a baseline positionthe main shaft relative to the first and second roller elements and compensate for the difference in at least one of speed and travel distance during a turn between the first and second wheels.

[0208] In a sixth aspect, a differential for a vehicle for at least one of controlling and measuring yaw, incorporates: a differential motion element configured to move along a longitudinal axis thereof while transferring motive power from a prime mover to first and second drive wheels; and first and second roller elements rotationally coupled between the differential motion element and first and second drive wheels, respectively, wherein the axial motion element is configured to move axially relative to the first and second roller elements in response to differentiation between the first and second drive wheels.

[0209] In that same sixth aspect, the differential motion element is configured to move axially relative to the first and second roller elements in response to a difference in at least one of speed and travel distance between the first and second drive wheels while transferring motive power from the prime mover to the first and second drive wheels.

[0210] In that same sixth aspect, the differential motion element is further configured to move axially relative to the first and second roller elements in response to input from a steering element operatively connected thereto.

[0211] In that same sixth aspect, the differential for a vehicle further includes: replenishing elements operatively connected to the differential motion element and configured to axially move the differential motion element in opposite reaction to the axial moving of the differential motion element in response to the differentiation between the first and second drive wheels.

[0212] In that same sixth aspect, the first and second roller elements are rotationally coupled between and coaxially with the differential motion element and the first and second drive wheels.

[0213] In that same sixth aspect, the first and second roller elements are rotationally coupled between the differential motion element and the first and second drive wheels, and parallel to the differential motion element.

[0214] In a seventh aspect, a differential system for a vehicle, incorporates: a prime mover for providing motive power; first and second differential structures, each of the first and second differential structures including a main shaft operatively mounted to rotate along a longitudinal axis thereof, the main shaft being operatively connected to the prime mover so as to rotate in response to motive power therefrom, and first and second roller elements operatively connected to the main shaft to rotate at least parallel to the longitudinal axis of the main shaft, the main shaft being formed with a first shaft portion that inter-engages with first roller element and a second shaft portion that inter-engages with the second roller element; first and second drive wheel pairs operatively connected to the first and second differential structures, respectively, such that the motive power from the prime mover is transferred to the first and second wheel pairs via co-rotation of the first and second roller elements with the main shaft so as to propel the vehicle, the first and second wheel pairs being in contact with a surface on which the vehicle is propelled; a control circuit for at least one of monitoring and controlling operation of thefirst and second differential structures, wherein in each of the first and second differential structures, the main shaft is configured to laterally move between the first and second roller elements along the longitudinal axis thereof in response to a difference in at least one of speed and travel distance during a turn between the first and second wheels while in contact with the surface as the vehicle is propelled; and a splitter element operatively connected between the prime mover and the first and second differential structures, the splitter element being configured to distribute motive power from the prime mover between the first and second differential structures in response to the control circuit.

[0215] In that same seventh aspect, in each of the first and second differential structures, the first shaft portion is formed with a first threading direction that is opposite a second threading direction formed on the second shaft portion, the first roller element is formed with a first roller threading corresponding to the first threading direction of the first shaft portion, and the second roller element is formed with a second roller threading corresponding to the second threading direction of the second shaft portion.

[0216] In that same seventh aspect, each of the first and second differential structures includes: a first ball screw assembly having the first shaft portion inter-engaged with the first roller element, the first roller element being a first nut element of the first ball screw assembly; a second ball screw assembly having the second shaft portion inter-engaged with the second roller element, the second roller element being a second nut element of the first ball screw assembly, wherein the first shaft portion is formed as a first bolt element of the first ball screw assembly, and the second shaft portion is formed as a second bolt element of the second ball screw assembly.

[0217] In that same seventh aspect, each of the first and second differential structures includes: an axial motion element operatively connected to the main shaft and the control circuit, the control circuit being configured to control the axial motion element to laterally move the main shaft between the first and second roller elements along the longitudinal axis thereof so as to at least one of restore to a baseline position the main shaft moving in response to the difference in at least one of speed and travel distance during a turn between the first and second wheels while in contact with the surface as the vehicle is propelled and compensate for the difference in at least one of speed and travel distance during a turn between the first and second wheels while in contact with the surface.

[0218] In that same seventh aspect, the each of the first and second differential structures includes: an axial motion element operatively connected to the main shaft and the control circuit, the control circuit being configured to at least one of detect and measure lateral movement of the main shaft between the first and second roller elements along the longitudinal axis thereof in response to a difference in at least one of speed and direction between the first and second wheels in response to the axial motion element.

[0219] In that same seventh aspect, the each of the first and second differential structures includes: first and second replenishing elements operatively connected to the main shaft and to the control circuit wherein the control circuit is configured to control the first and second replenishing elements to laterally move the main shaft along the longitudinal axis thereof so asto at least one of restore to a baseline position the main shaft moving in response to the difference in at least one of speed and travel distance during a turn between the first and second wheels while in contact with the surface as the vehicle is propelled and compensate for the difference in at least one of speed and travel distance during a turn between the first and second wheels while in contact with the surface.

[0220] In that same seventh aspect, the in each of the first and second differential structures, the first replenishing element is a first replenishing ball screw assembly having a first replenishing nut element inter-engaged with the first roller element, the first roller element being a first replenishing bolt element of the first replenishing ball screw assembly; the second replenishing element is a second replenishing ball screw assembly having a second replenishing nut element inter-engaged with the second roller element, the second roller element being a second replenishing bolt element of the second replenishing ball screw assembly.

[0221] In that same seventh aspect, in each of the first and second differential structures, the control circuit is configured to selectively engage at least one of the first and second replenishing elements and thereby at least one of restore to a baseline position the main shaft and compensate for movement of the main shaft.

[0222] In that same seventh aspect, in each of the first and second differential structures, the main shaft includes a bearing fixedly mounted around a center shaft portion of the main shaft, the bearing being operatively connected to the axial motion element.

[0223] In that same seventh aspect, the differential system further includes: a steering control structure operatively connected to the control circuit and each of the first and second differential structures, wherein in each of the first and second differential structures, the main shaft is configured to laterally move along the longitudinal axis thereof relative to the first and second roller elements in response to a steering angle signal from the steering control structure to the first and second wheels.

[0224] In that same seventh aspect, in each of the first and second differential structures, the main shaft is configured to laterally move along the longitudinal axis thereof relative to the first and second roller elements in response to a yaw signal from the steering control structure.

[0225] In that same seventh aspect, the splitter is configured as a continuously variable drive transmission structure that includes first, second and third rollers, the first roller being operatively connected to the prime mover, the second and third rollers each being operatively connected to first and second differential structures, respectively, the first roller inter-engaging with the second and third rollers so as to rotatively drive the second and third rollers.

[0226] In that same seventh aspect, the splitter is configured as a continuously variable drive transmission structure that includes first, second and third rollers, the first roller being operatively connected to the prime mover, the second and third rollers each being operatively connected to first and second differential structures, respectively, the first roller inter-engagingwith the second roller, and the third roller inter-engaging with the second roller such that the first roller rotatively drives, and the second roller rotatively drives the third roller.

[0227] In that same seventh aspect, each of the first, second and third rollers is shaped as a frustum of a cone.

[0228] In that same seventh aspect, the first, second and third rollers are formed as a toroidal infinitely variable drive.

[0229] In an eighth aspect, a differential for a vehicle that provides yaw, incorporates: a main shaft operatively mounted to rotate along a first longitudinal axis thereof, the main shaft being operatively connected to a prime mover so as to rotate in response to motive power therefrom; first and second sub -shafts operatively and rotatively connected to the main shaft, and each mounted to rotate along first and second longitudinal sub-axes, respectively; and first and second roller elements operatively connected to the first and second sub-shafts, respectively, to rotate at least parallel to the first and second longitudinal sub-axes of the first and second sub-shafts, respectively, the first sub-shaft being formed with a first shaft portion that interengages with first roller element and the second sub-shaft being formed with a second shaft portion that inter-engages with the second roller element, wherein the first and second roller elements are operatively connected to first and second wheels of a vehicle, respectively, such that the motive power from the prime mover is transferred to the first and second wheels via co-rotation of the first and second roller elements with the main shaft and the first and second sub-shafts so as to propel the vehicle, the first and second wheels being in contact with a surface on which the vehicle is propelled, and the main shaft with the first and second sub-shafts are configured to laterally move between the first and second roller elements along the longitudinal axis thereof in response to a difference in at least one of speed and travel distance during a turn between the first and second wheels while in contact with the surface as the vehicle is propelled.

[0230] In a ninth aspect, a vehicle differential consists of a first inclined plane or first pair of inclined planes rolled over in the form of a cylinder or cylinders, rotated by the prime mover, the inclined planes carrying rollers inside or outside, which are kept in contact with and constrained from overshooting the inclined planes, the rollers meshing with a second pair of inclined planes rolled into cylinders carried coaxial and outside or inside the rollers, respectively, and the cylinders carrying the second pair of inclined planes are connected to the wheels, such that the movement in the Y axis, namely the rotation, is conveyed to the wheels as rotation, with rotation of the two wheels averaging the rotation of the first inclined planes, the axial reactions upon the first inclined plane(s) due to resistance to turning of the two wheels is opposite, and is equal and opposite when the vehicle is going straight.

[0231] In that same ninth aspect, any combination of inclined plane(s), rollers, carriers, or ratio-change may be applied such that the axial component of the reaction of the wheels due to their resistance to turning is opposite, and is equal and opposite when the vehicle is going straight.

[0232] In a tenth aspect, a vehicle differential consists of a first inclined plane or first pair of inclined planes rolled over in the form of a cylinder or cylinders, rotated by the prime mover,the inclined planes carrying rollers inside or outside, which are kept in contact with and constrained from overshooting the inclined planes, the rollers being carried in two carriers coaxial and inside or outside the cylinder(s) carrying the inclined planes, which carriers remain a fixed distance apart from each other, or are constrained to move equally and opposite to each other, and the carriers are connected to the wheels, characterized in that the movement of the carriers in the Y axis is conveyed to the wheels as rotation, such rotation averaged to the rotation of the cylinder / s carrying the inclined planes, the axial reactions upon the first inclined plane(s) due to resistance to turning of the two wheels being opposite, and being equal and opposite when the vehicle is going straight.

[0233] In that same tenth aspect, any combination of inclined plane(s), rollers, carriers, or ratiochange is employed such that the axial components of the reaction of the wheels due to their resistance to turning is opposite, and is equal and opposite when the vehicle is going straight.

[0234] In an eleventh aspect, a vehicle differential is configured to permit a finite amount of differentiation between the two wheels.

[0235] In that same eleventh aspect, the finite differentiation is replenished.

[0236] In that same eleventh aspect, the replenishment is done before or after a journey or when the vehicle is braked, coasting, and in the case of electric motor driven vehicle with regeneration, at the time between motive power and regeneration.

[0237] In that same eleventh aspect, the two wheels are uncoupled while replenishing.

[0238] In that same eleventh aspect, an internal arrangement is provided such that the overdrive of left wheel due to vehicle turning right, is compensated or cancelled by the overdrive of the right wheel due to vehicle turning left, so that the differential needs to manage only the net overdrive.

[0239] In a twelfth aspect, a vehicle differential configured to determine the ratio of overdrive, thus enabling or modulating yaw.

[0240] In a thirteenth aspect, a vehicle differential is configured to measure or impose yaw based on the implementation of inclined planes and rollers in the form of helical threads or ball screws, wherein the driving inclined planes are rotationally coupled to the prime mover and carry rollers which optionally carry a pair of inclined planes, and the rollers or inclined planes driven by the rollers are rotationally coupled to the two driven wheels, such that the axial components, preferably components parallel to the axle, whether the axle is real or virtual, of reaction forces from the two wheels, which reaction arises from the resistance offered by the driven wheels to rotation fed by the differential, are opposed to each other, and are equal and opposite to each other and hence cancel each other out when the vehicle is going straight, and such that when the vehicle is yawing, namely turning on a vertical axis, whether induced by this differential artificially or occurring naturally due to steering wheels, the driving inclined planes move axially or are moved in relation to the driven inclined planes, axially, i.e. parallel to the axle, so as to permit or order the differentiation arising out of, or imposed upon by thedifferential, on the vehicle, and the wheels obtain rotary motion from the rotation of the driven rollers or inclined planes.

[0241] In a fourteenth aspect, a vehicle differential is configured to measure or impose yaw, containing two ball screws, wherein the driving halves of ball screws are rotationally coupled to the prime mover and the driven halves of ball screws are rotationally coupled to the two driven wheels, such that the axial components, namely components parallel to the axle, whether real or virtual axle, of reaction forces from the two driven wheels, which reaction arises from the resistance offered by the driven wheels to rotation fed by the differential, are opposed to each other, and are equal and opposite to each other when the vehicle is going straight, and such that when the vehicle is on a turn, whether induced by this differential artificially or occurring naturally due to steering wheels, the driving halves of the ball screws move relative to the driven halves of the ball screws, axially, or are moved axially, namely parallel to the axle, so as to permit or order the differentiation and hence yaw arising out of steering wheels, or imposed upon by the differential, on the vehicle, respectively.

[0242] The various implementations of the present invention described hereinabove encompass any and all wheeled and / or vehicles with bands of treads, machines and other motive implements that incorporate at least two (2) wheels mounted on opposite ends of a single axle, including but not limited to automobiles, trucks, vans, tractors, wheelchairs, scooters and hoverboards. These implementations are intended only to illustrate some of the embodiments of the invention that are either intended or foreseeable. Other embodiments that would be within the scope of the invention include but not limited to a differential system for two-wheeled vehicles, machines or other motive implements that incorporate at least two (2) wheels mounted one behind the other along the same plane, including but not limited to bicycles, motorcycles, motorbikes and their equivalents. It is possible to drive the two (2) wheels of a two-wheeler having front and rear wheels, providing torque to both wheels, and driving the front wheel faster than the rear wheel, at the specific inequality required by the speed difference necessitated by the specific turn-radius / turn angle of the two-wheeler. In such implementations, the differential system of the present invention would be uses to control the distance between the front and rear wheels, rather than the axial distance. Further, other embodiments within the scope of the invention would also include but not limited to a differential system for three-wheeled vehicles such as minicars, tricycles and three-wheeled cross-country motorcycles.

[0243] The foregoing discussion discloses and describes merely exemplary embodiments of the present invention. One skilled in the art will readily recognize from such discussion, that various changes, modifications and variations can be made therein without departing from the spirit and scope of the invention as defined in the present disclosure. Thus, while the present invention has been described in connection with exemplary embodiments thereof, it will be understood that many modifications in structure, operation, design and use will be apparent to those of ordinary skill in the art, and this application is intended to cover any adaptations or variations thereof. Accordingly, the particular arrangements disclosed are meant to be illustrative only and not limiting as to the scope of the invention, which is to be given the full breadth of the appended claims and any and all equivalents thereof.

Claims

AMENDED CLAIMS received by the International Bureau on July 21 , 2025 (21.07.2025)I / We claim:

1. (Currently Amended) A differential that provides yaw for a vehicle, comprising: a main shaft operatively mounted to rotate along a longitudinal axis thereof, the main shaft being operatively connected to a prime mover so as to rotate in response to motive power therefrom; and first and second roller elements operatively connected to the main shaft to rotate at least parallel to the longitudinal axis of the main shaft, the main shaft being formed with a first shaft portion that inter-engages with first roller element and a second shaft portion that inter-engages with the second roller element, wherein the first and second roller elements are operatively connected to first and second wheels of a vehicle, respectively, such that the motive power from the prime mover is transferred to the first and second wheels via co-rotation of the first and second roller elements with the main shaft so as to propel the vehicle, the first and second wheels being in contact with a surface on which the vehicle is propelled, and the main shaft is configured to laterally move between the first and second roller elements along the longitudinal axis thereof to generate a difference in at least one of speed and travel distance during a turn between the first and second wheels while in contact with the surface as the vehicle is propelled, wherein each of the first and second roller element is formed of at least one of a ball screw and roller screw.

2. (Currently Amended) The differential according to claim 1 , wherein the first shaft portion is formed with a first threading direction that is opposite in hand to a second threading direction formed on the second shaft portion, the first roller element is formed with a first roller threading corresponding to the first threading hand of the first shaft portion, and the second roller element is formed with a second roller threading corresponding to the second threading hand of the second shaft portion.A differential that provides yaw for a vehicle, comprising: a main shaft operatively mounted to rotate along a longitudinal axis thereof, the main shaft being operatively connected to a prime mover so as to rotate in response to motive power therefrom; and first and second roller elements operatively connected to the main shaft to rotate at least parallel to the longitudinal axis of the main shaft, the main shaft being formed with a first shaft portion that inter-engages with first roller element and a second shaft portion that inter-engages with the second roller element, wherein the first and second roller elements are operatively connected to first and second wheels of a vehicle, respectively, such that the motive power from the prime mover is transferred to the first and second wheels via co-rotation of the first and second roller elements with the main shaft so as to propel the vehicle, the first and second wheels being in contact with a surface on which the vehicle is propelled; and a first screw element assembly comprising the first shaft portion inter-engaged with the first roller element, the first roller element being a first nut element of the first screw element assembly; and a second screw element assembly comprising the second shaft portion interengaged with the second roller element, the second roller element being a second nut element of the first screw element assembly, wherein the first shaft portion is formed as a first bolt element of the first screw element assembly, and the second shaft portion is formed as a second bolt element of the second screw element assembly, wherein at least one of balls and rollers are inter-engaged between the first nut element and the first bolt element of the first screw element assembly and between the second nut element and the second bolt element of the second screw element assembly; and the main shaft is configured to laterally move between the first and second roller elements along the longitudinal axis thereof to generate a difference in at least one of speed and travel distance during a turn between the first and second wheels while in contact with the surface as the vehicle is propelled, wherein each of the first and second roller element is formed of at least one of a ball screw and roller screw.

4. The differential according to claim 1 , wherein the main shaft includes a bevel gear pair structure operatively connected between the main shaft and a drive shaft connected to the prime mover so as to transfer the motive power from the prime mover to the main shaft.

5. The differential according to claim 1, further comprising: an axial motion element operatively connected to the main shaft and configured to controllably and laterally move the main shaft between the first and second roller elements along the longitudinal axis thereof so as to at least one of restore to a baseline position the main shaft moving in response to a difference in at least one of speed and travel distance during a turn between the first and second wheels while in contact with the surface as the vehicle is propelled and generate the difference in at least one of speed and travel distance during a turn between the first and second wheels while in contact with the surface.

6. The differential according to claim 1, further comprising: an axial motion element operatively connected to the main shaft and configured to at least one of detect and measure lateral movement of the main shaft between the first and second roller elements along the longitudinal axis thereof to generate the difference in at least one of speed and travel distance during a turn between the first and second wheels.

7. The differential according to claim 1, further comprising: first and second axial motion elements operatively connected to the main shaft, wherein the first and second axial motion elements are configured to controllably and laterally move the main shaft along the longitudinal axis thereof so as to generate yaw and to at least one of restore to a baseline position the main shaft moving in response to the difference in the at least one of speed and travel distance during a turn between the first and second wheels while in contact with the surface as the vehicle is propelled and togenerate the difference in the at least one of speed and travel distance during a turn between the first and second wheels while in contact with the surface.

8. The differential according to claim 1, further comprising: a first coupling structure operatively connected between the first roller element and first wheel; a second coupling structure operatively connected between the second roller element and second wheel, wherein each of the first and second coupling structures is configured to disengage at least one of the first and second wheel from the corresponding first and second roller element when the main shaft reaches a predetermined limit of operation relative to at least one of the first and second roller elements.

9. The differential according to claim 8, wherein each of the first and second coupling structure is further configured to disengage at least one of the first and second wheel from the corresponding first and second roller element when the vehicle is braking or coasting.

10. A differential system for a vehicle that provides yaw, comprising: a prime mover for providing motive power; a differential structure that includes a main shaft operatively mounted to rotate along a longitudinal axis thereof, the main shaft being operatively connected to the prime mover so as to rotate in response to motive power therefrom, and first and second roller elements operatively connected to the main shaft to rotate at least parallel to the longitudinal axis of the main shaft, the main shaft being formed with a first shaft portion that inter-engages with first roller element and a second shaft portion that inter-engages with the second roller element; first and second drive wheels operatively connected to the first and second roller elements, respectively, such that the motive power from the prime mover is transferred to the first and second wheels via co-rotation of the first and second roller elements with the main shaft so as to propel the vehicle, the first and second wheels being in contact with a surface on which the vehicle is propelled; anda control circuit for at least one of monitoring and controlling operation of the differential structure, wherein the main shaft is configured to laterally move between the first and second roller elements along the longitudinal axis thereof in response to generate a difference in at least one of speed and travel distance during a turn between the first and second wheels while in contact with the surface as the vehicle is propelled[[.]], wherein each of the first and second roller element is formed of at least one of a ball screw and roller screw.

11. (Currently Amended) The differential system according to claim 10, wherein the first shaft portion is formed with a first threading hand that is opposite a second threading hand formed on the second shaft portion, the first roller element is formed with a first roller threading corresponding to the first threading hand of the first shaft portion, and the second roller element is formed with a second roller threading corresponding to the second threading hand of the second shaft portion.

12. A differential system for a vehicle that provides yaw, comprising: a prime mover for providing motive power; a differential structure that includes a main shaft operatively mounted to rotate along a longitudinal axis thereof, the main shaft being operatively connected to the prime mover so as to rotate in response to motive power therefrom, and first and second roller elements operatively connected to the main shaft to rotate at least parallel to the longitudinal axis of the main shaft, the main shaft being formed with a first shaft portion that inter-engages with first roller element and a second shaft portion that inter-engages with the second roller element; the first shaft portion is formed with a first threading hand that is opposite a second threading hand formed on the second shaft portion, the first roller element is formed with a first roller threading corresponding to the first threading hand of the first shaft portion, andthe second roller element is formed with a second roller threading corresponding to the second threading hand of the second shaft portion; a first screw element assembly comprising the first shaft portion inter-engaged with the first roller element, the first roller element being a first nut element of the first roller assembly; a second screw element assembly comprising the second shaft portion interengaged with the second roller element, the second roller element being a second nut element of the first second screw element assembly, wherein the first shaft portion is formed as a first bolt element of the first screw element assembly, and the second shaft portion is formed as a second bolt element of the second screw element assembly, wherein at least one of balls and rollers are inter-engaged between the first nut element and the first bolt element of the first screw element assembly and between the second nut element and the second bolt element of the second screw element assembly; and first and second drive wheels operatively connected to the first and second roller elements, respectively, such that the motive power from the prime mover is transferred to the first and second wheels via co-rotation of the first and second roller elements with the main shaft so as to propel the vehicle, the first and second wheels being in contact with a surface on which the vehicle is propelled; and a control circuit for at least one of monitoring and controlling operation of the differential structure, wherein the main shaft is configured to laterally move between the first and second roller elements along the longitudinal axis thereof to generate a difference in at least one of speed and travel distance during a turn between the first and second wheels while in contact with the surface as the vehicle is propelled, wherein each of the first and second roller element is formed of at least one of a ball screw and roller screw.

13. The differential system according to claim 10, further comprising: an axial motion element operatively connected to the main shaft and the control circuit, the control circuit being configured to control the axial motion element tolaterally move the main shaft between the first and second roller elements along the longitudinal axis thereof so as to at least one of restore to a baseline position the main shaft moving in response to the difference in at least one of speed and travel distance during a turn between the first and second wheels while in contact with the surface as the vehicle is propelled and generate the difference in at least one of speed and travel distance during a turn between the first and second wheels while in contact with the surface.

14. The differential system according to claim 10, further comprising: an axial motion element operatively connected to the main shaft and the control circuit, the control circuit being configured to at least one of detect and measure lateral movement of the main shaft between the first and second roller elements along the longitudinal axis thereof to generate a difference in at least one of speed and direction between the first and second wheels in response to the axial motion element.

15. The differential system according to claim 10, further comprising: first and second axial motion elements operatively connected to the main shaft and to the control circuit, wherein the control circuit is configured to control the first and second replenishing axial motion elements to laterally move the main shaft along the longitudinal axis thereof so as to at least one of restore to a baseline position the main shaft moving in response to the difference in at least one of speed and travel distance during a turn between the first and second wheels while in contact with the surface as the vehicle is propelled and the difference in at least one of speed and travel distance during a turn between the first and second wheels while in contact with the surface and generate yaw.

16. The differential system according to claim 15, wherein the first axial motion element is a first yaw and replenishing nut inter-engaged with a bolt part of the first screw element of the first shaft portion that inter-engages with the first roller element,the second axial motion element is a second yaw and replenishing nut interengaged with a bolt part of the second screw element of the second shaft portion that inter-engages with the second roller element, wherein at least one of balls and rollers are inter-engaged between the first yaw and replenishing nut element and the first yaw and replenishing bolt element of the first yaw and replenishing screw element assembly and between the second yaw and replenishing nut element and the second yaw and replenishing bolt element of the second yaw and replenishing screw element assembly.

17. The differential system according to claim 15, wherein the control circuit is configured to selectively engage at least one of the first and second yaw and replenishing elements and thereby generate yaw and to at least one of restore to a baseline position the main shaft and compensate for movement of the main shaft.

18. The differential system according to claim 13, wherein the main shaft includes a bearing fixedly mounted around a center shaft portion of the main shaft, the bearing being operatively connected to the axial motion element.

19. The differential system according to claim 10 further comprising: a steering control structure operatively connected to the control circuit and the differential structure, wherein the main shaft is configured to laterally move along the longitudinal axis thereof relative to the first and second roller elements in response to a steering angle signal from the steering control structure to the first and second wheels.

20. The differential system according to claim 19, wherein the main shaft is configured to laterally move along the longitudinal axis thereof relative to the first and second roller elements in response to a yaw signal from the steering control structure.

21. A differential structure that provides yaw, comprising: a main shaft having first and second helical shaft portions opposite each;first and second wheel shafts operatively positioned to inter-engage with the first and second helical portions, respectively, of the main shaft; first and second driven wheels operatively mounted to outer shaft ends of the first and second wheel shafts, respectively; a steering wheel operatively connected to the first and second driven wheels and to the main shaft, wherein the main shaft is configured, during rotation of the first and second wheel shafts and the first and second driven wheels, to move co-axially along a common longitudinal axis in response to a steering angle of the steering wheel, each of the first and second helical portions comprise at least one of ball screws and roller screws.

22. A differential structure that provides yaw, comprising: a main shaft having first and second helical shaft portions opposite each; first and second wheel shafts operatively positioned to inter-engage with the first and second helical portions, respectively, of the main shaft; first and second driven wheels operatively mounted to outer shaft ends of the first and second wheel shafts, respectively; a steering wheel operatively connected to the first and second driven wheels and to the main shaft, wherein the main shaft is configured, during rotation of the first and second wheel shafts and the first and second driven wheels, to move co-axially along a common longitudinal axis in response to a steering angle of the steering wheel, wherein the first and second wheel shafts are operatively positioned to inter-engage with the first and second helical portions, respectively, of the main shaft via a plurality of roller balls positioned therebetween, wherein each of the first and second helical portions comprise at least one of ball screws and roller screws.

23. The differential structure of claim 21, further comprising:first and second carriers operatively connected to the first and second wheel shafts, respectively, and operatively positioned to inter-engage with the first and second helical portions, respectively, of the main shaft, wherein the first and second carriers are configured to rotate along the common longitudinal axis with the main shaft.

24. The differential structure of claim 21, wherein the first and second carriers are operatively positioned to inter-engage with the first and second helical portions, respectively, of the main shaft via a plurality of roller disks mounted in each of the first and second carriers and inter-engaging with the first and second helical portions.

25. A differential structure that provides yaw, comprising: a main shaft having first and second helical shaft portions opposite each; first and second wheel shafts operatively positioned to inter-engage with the first and second helical portions, respectively, of the main shaft; first and second driven wheels operatively mounted to outer shaft ends of the first and second wheel shafts, respectively; a steering wheel operatively connected to the first and second driven wheels and to the main shaft, wherein the main shaft is configured, during rotation of the first and second wheel shafts and the first and second driven wheels, to move co-axially along a common longitudinal axis in response to a steering angle of the steering wheel, wherein the first and second carriers are each formed as cylinders with interior helical threads therein, the interior helical threads of the first and second carriers being operatively positioned to interengage with the first and second helical portions, respectively, of the main shaft via a plurality of roller balls positioned therebetween, wherein each of the first and second helical portions comprise at least one of ball screws and roller screws.

26. A method of operating a differential for a vehicle to provide yaw, comprising the steps of:providing a differential structure that includes a main shaft operatively mounted to rotate along a longitudinal axis thereof, and first and second roller elements operatively connected to the main shaft to rotate at least parallel to the longitudinal axis of the main shaft, the main shaft being formed with a first shaft portion that inter-engages with first roller element and a second shaft portion that inter-engages with the second roller element, and the first and second roller elements being operatively connected to first and second wheels of a vehicle, respectively; inputting motive power via a prime mover into the main shaft so as to transfer the motive power to first and second wheels of a vehicle such that co-rotation of the first and second roller elements with the main shaft propels the vehicle, the first and second wheels being in contact with a surface on which the vehicle is propelled; and laterally moving the main shaft between the first and second roller elements along the longitudinal axis thereof to generate a difference in at least one of speed and travel distance during a turn between the first and second wheels while in contact with the surface as the vehicle is propelled, wherein each of the first and second roller element is formed of at least one of a ball screw and roller screw.

27. The method according to claim 26, further comprising the step of: controllably and laterally move the main shaft between the first and second roller elements along the longitudinal axis thereof so as to at least one of restore to a baseline position the main shaft moving in response to a difference in at least one of speed and travel distance during a turn between the first and second wheels while in contact with the surface as the vehicle is propelled and generate the difference in at least one of speed and travel distance during a turn between the first and second wheels while in contact with the surface.

28. The method according to claim 27, further comprising the step of: at least one of detecting and measuring lateral movement of the main shaft between the first and second roller elements along the longitudinal axis thereof togenerate the difference in at least one of speed and travel distance during a turn between the first and second wheels.

29. The method according to claim 27, further comprising the step of: providing at least one axial motion element operatively connected to the main shaft; and controllably and laterally-moving the main shaft along the longitudinal axis thereof via the at least one axial motion element so as to least one of restore to a baseline position the main shaft moving in response to the difference in at least one of speed and travel distance during a turn between the first and second wheels while in contact with the surface as the vehicle is propelled and generate the difference in at least one of speed and travel distance during a turn between the first and second wheels while in contact with the surface.

30. The method according to claim 27, further comprising the step of: providing a coupling structure operatively connected between the first and second roller elements with the first second wheels, respectively; selectively disengaging at least one of the first and second wheels from the corresponding first and second roller element when the main shaft reaches a predetermined limit of rotations relative to at least one of the first and second roller elements.

31. (Currently Amended) A method for operating a differential system for a vehicle, comprising the steps of: providing a prime mover for providing motive power, a differential structure that includes a main shaft operatively mounted to rotate along a longitudinal axis thereof and operatively connected to the prime mover, and first and second roller elements operatively connected to the main shaft to rotate at least parallel to the longitudinal axis of the main shaft, the main shaft being formed with a first shaft portion that inter-engages with first roller element and a second shaft portion that inter-engages with the second roller element, first and second drive wheels operatively connected to the first and secondroller elements, respectively, and a control circuit for at least one of monitoring and controlling operation of the differential structure; inputting motive power from the prime mover to the differential structure; laterally moving the main shaft between the first and second roller elements along the longitudinal axis thereof to generate a difference in at least one of speed and travel distance during a turn between the first and second wheels while in contact with the surface as the vehicle is propelled, wherein each of the first and second roller element is formed of at least one of a ball screw and roller screw.

32. A method for operating a differential system according to claim 31, further comprising the step of: providing an axial motion element operatively connected to the main shaft and the control circuit; and controlling the axial motion element via the control circuit to laterally move the main shaft between the first and second roller elements along the longitudinal axis thereof.

33. A method for operating a differential system according to claim 31, further comprising the step of: providing an axial motion element operatively connected to the main shaft and the control circuit; at least one of detecting and measuring lateral movement of the main shaft between the first and second roller elements along the longitudinal axis thereof.

34. A method for operating a differential system according to claim 31, further comprising the steps of: providing first and second axial motion elements operatively connected to the first and second screw element assemblies, respectively, and to the control circuit; and selectively activating via the control circuit the first and second axial motion elements to laterally move the main shaft along the longitudinal axis thereof so as to atleast one of restore to a baseline position the main shaft relative to the first and second roller elements and generate the difference in at least one of speed and travel distance during a turn between the first and second wheels.

35. A differential for a vehicle for at least one of controlling and measuring yaw, comprising: a differential motion element configured to move along a longitudinal axis thereof while transferring motive power from a prime mover to first and second drive wheels; and first and second roller elements rotationally coupled between the differential motion element and first and second drive wheels, respectively, wherein the axial motion element is configured to move axially relative to the first and second roller elements in response to differentiation between the first and second drive wheels, wherein each of the first and second roller element is formed of at least one of a ball screw and roller screw.

36. A differential for a vehicle according to claim 35, wherein the differential motion element is configured to move axially relative to the first and second roller elements in response to a difference in at least one of speed and travel distance between the first and second drive wheels while transferring motive power from the prime mover to the first and second drive wheels.

37. A differential for a vehicle according to claim 36, wherein the differential motion element is further configured to move axially relative to the first and second roller elements in response to input from a steering element operatively connected thereto.

38. A differential for a vehicle according to claim 35, further comprising: yaw and replenishing elements operatively connected to the differential motion element and configured to axially move the differential motion element in oppositereaction to the axial moving of the differential motion element in response to the differentiation between the first and second drive wheels.

39. A differential for a vehicle according to claim 36, wherein the first and second roller elements are rotationally coupled between and coaxially with the differential motion element and the first and second drive wheels.

40. A differential for a vehicle according to claim 36, wherein the first and second roller elements are rotationally coupled between the differential motion element and the first and second drive wheels, and parallel to the differential motion element.

41. A differential system for a vehicle, comprising: a prime mover for providing motive power; first and second differential structures, each of the first and second differential structures including a main shaft operatively mounted to rotate along a longitudinal axis thereof, the main shaft being operatively connected to the prime mover so as to rotate in response to motive power therefrom, and first and second roller elements operatively connected to the main shaft to rotate at least parallel to the longitudinal axis of the main shaft, the main shaft being formed with a first shaft portion that inter-engages with first roller element and a second shaft portion that inter-engages with the second roller element; first and second drive wheel pairs operatively connected to the first and second differential structures, respectively, such that the motive power from the prime mover is transferred to the first and second wheel pairs via co-rotation of the first and second roller elements with the main shaft so as to propel the vehicle, the first and second wheel pairs being in contact with a surface on which the vehicle is propelled; a control circuit for at least one of monitoring and controlling operation of the first and second differential structures, wherein in each of the first and second differential structures,the main shaft is configured to laterally move between the first and second roller elements along the longitudinal axis thereof to generate a difference in at least one of speed and travel distance during a turn between the first and second wheels while in contact with the surface as the vehicle is propelled, wherein each of the first and second roller element is formed of at least one of a ball screw and roller screw; and a splitter element operatively connected between the prime mover and the first and second differential structures, the splitter element being configured to distribute motive power from the prime mover between the first and second differential structures in response to the control circuit.

42. The differential system according to claim 41, wherein in each of the first and second differential structures, the first shaft portion is formed with a first threading hand that is opposite a second threading hand formed on the second shaft portion, the first roller element is formed with a first roller threading corresponding to the first threading hand of the first shaft portion, and the second roller element is formed with a second roller threading corresponding to the second threading hand of the second shaft portion.

43. The differential system according to claim 42, wherein each of the first and second differential structures includes: a first screw element assembly comprising the first shaft portion inter-engaged with the first roller element, the first roller element being a first nut element of the first screw element assembly; a second screw element assembly comprising the second shaft portion interengaged with the second roller element, the second roller element being a second nut element of the first second screw element assembly, wherein each of the first and second roller element is formed of at least one of a ball screw and roller screw, andthe first shaft portion is formed as a first bolt element of the first screw element assembly, and the second shaft portion is formed as a second bolt element of the second screw element assembly[[.]], wherein at least one of balls and rollers are inter-engaged between the first nut element and the first bolt element of the first screw element assembly and between the second nut element and the second bolt element of the second screw element assembly.

44. The differential system according to claim 41, wherein each of the first and second differential structures includes: an axial motion element operatively connected to the main shaft and the control circuit, the control circuit being configured to control the axial motion element to laterally move the main shaft between the first and second roller elements along the longitudinal axis thereof so as to at least one of restore to a baseline position the main shaft moving in response to the difference in at least one of speed and travel distance during a turn between the first and second wheels while in contact with the surface as the vehicle is propelled and generate the difference in at least one of speed and travel distance during a turn between the first and second wheels while in contact with the surface.

45. The differential system according to claim 41, wherein each of the first and second differential structures includes: an axial motion element operatively connected to the main shaft and the control circuit, the control circuit being configured to at least one of detect and measure lateral movement of the main shaft between the first and second roller elements along the longitudinal axis thereof to generate a difference in at least one of speed and direction between the first and second wheels in response to the axial motion element.

46. The differential system according to claim 41, wherein each of the first and second differential structures includes: first and second axial motion elements operatively connected to the main shaft and to the control circuit whereinthe control circuit is configured to control the first and second axial motion elements to laterally move the main shaft along the longitudinal axis thereof so as to at least one of restore to a baseline position the main shaft moving in response to the difference in at least one of speed and travel distance during a turn between the first and second wheels while in contact with the surface as the vehicle is propelled and generate the difference in at least one of speed and travel distance during a turn between the first and second wheels while in contact with the surface.

47. The differential system according to claim 46, wherein in each of the first and second differential structures, the first axial motion element is a first yaw and replenishing screw element assembly comprising a first yaw and replenishing nut element inter-engaged with the first roller element, the first roller element being a first yaw and replenishing bolt element of the first yaw and replenishing screw element assembly; the second axial motion element is a second yaw and replenishing screw element assembly comprising a second yaw and replenishing nut element inter-engaged with the second roller element, the second roller element being a second yaw and replenishing bolt element of the second yaw and replenishing screw element assembly, wherein at least one of balls and rollers are inter-engaged between the first yaw and replenishing nut element and the first yaw and replenishing bolt element of the first yaw and replenishing screw element assembly and between the second yaw and replenishing nut element and the second yaw and replenishing bolt element of the second yaw and replenishing screw element assembly, and each of the first and second roller element is formed of at least one of a ball screw and roller screw.

48. The differential system according to claim 46, wherein in each of the first and second differential structures, the control circuit is configured to selectively engage at least one of the first and second yaw and replenishing elements and thereby at least one of restore to a baseline position the main shaft and compensate for movement of the main shaft.

49. The differential system according to claim 44, wherein in each of the first and second differential structures, the main shaft includes a bearing fixedly mounted around a center shaft portion of the main shaft, the bearing being operatively connected to the axial motion element.

50. The differential system according to claim 41 further comprising: a steering control structure operatively connected to the control circuit and each of the first and second differential structures, wherein in each of the first and second differential structures, the main shaft is configured to laterally move along the longitudinal axis thereof relative to the first and second roller elements in response to a steering angle signal from the steering control structure to the first and second wheels.

51. The differential system according to claim 50, wherein in each of the first and second differential structures, the main shaft is configured to laterally move along the longitudinal axis thereof relative to the first and second roller elements in response to a yaw signal from the steering control structure.

52. The differential system according to claim 41, wherein the splitter is configured as a continuously variable drive transmission structure that includes first, second and third rollers, the first roller being operatively connected to the prime mover, the second and third rollers each being operatively connected to first and second differential structures, respectively, the first roller inter-engaging with the second and third rollers so as to rotatively drive the second and third rollers.

53. The differential system according to claim 41, wherein the splitter is configured as a continuously variable drive transmission structure that includes first, second and third rollers, the first roller being operatively connected to the prime mover, the second and third rollers each being operatively connected to first and second differential structures, respectively, the first roller inter-engaging with the second roller, and the third rollerinter-engaging with the second roller such that the first roller rotatively drives, and the second roller rotatively drives the third roller.

54. The differential system according to claim 52, wherein each of the first, second and third rollers is shaped as a frustum of a cone.

55. The differential system according to claim 53, wherein the first, second and third rollers are formed as a toroidal infinitely variable drive.

56. A differential for a vehicle that provides yaw, comprising: a main shaft operatively mounted to rotate along a first longitudinal axis thereof, the main shaft being operatively connected to a prime mover so as to rotate in response to motive power therefrom; first and second sub-shafts operatively and rotatively connected to the main shaft, and each mounted to rotate along first and second longitudinal sub-axes, respectively; and first and second roller elements operatively connected to the first and second subshafts, respectively, to rotate at least parallel to the first and second longitudinal sub-axes of the first and second sub-shafts, respectively, the first sub-shaft being formed with a first shaft portion that inter-engages with first roller element and the second sub-shaft being formed with a second shaft portion that inter-engages with the second roller element, wherein the first and second roller elements are operatively connected to first and second wheels of a vehicle, respectively, such that the motive power from the prime mover is transferred to the first and second wheels via co-rotation of the first and second roller elements with the main shaft and the first and second sub-shafts so as to propel the vehicle, the first and second wheels being in contact with a surface on which the vehicle is propelled, and the main shaft with the first and second sub-shafts are configured to laterally move between the first and second roller elements along the longitudinal axis thereof in response to generate a difference in at least one of speed and travel distance during a turnbetween the first and second wheels while in contact with the surface as the vehicle is propelled, wherein each of the first and second roller element is formed of at least one of a ball screw and roller screw.

57. A vehicle differential consisting of a first inclined plane or first pair of inclined planes rolled over in the form of a cylinder or cylinders, rotated by the prime mover, the inclined planes carrying rollers inside or outside, which are kept in contact with and constrained from overshooting the inclined planes, the rollers meshing with a second pair of inclined planes rolled into cylinders carried coaxial and outside or inside the rollers, respectively, and the cylinders carrying the second pair of inclined planes are connected to the wheels, such that the movement in the Y axis, namely the rotation, is conveyed to the wheels as rotation, with rotation of the two wheels averaging the rotation of the first inclined planes, the axial reactions upon the first inclined plane(s) due to resistance to turning of the two wheels is opposite, and is equal and opposite when the vehicle is going straight.

58. The vehicle differential of claim 57, characterized in that any combination of inclined plane(s), rollers, carriers, or ratio-change may be applied such that the axial component of the reaction of the wheels due to their resistance to turning is opposite, and is equal and opposite when the vehicle is going straight.

59. A vehicle differential consisting of a first inclined plane or first pair of inclined planes rolled over in the form of a cylinder or cylinders, rotated by the prime mover, the inclined planes carrying rollers inside or outside, which are kept in contact with and constrained from overshooting the inclined planes, the rollers being carried in two carriers coaxial and inside or outside the cylinder(s) carrying the inclined planes, which carriers remain a fixed distance apart from each other, or are constrained to move equally and opposite to each other, and the carriers are connected to the wheels, characterized in that the movement of the carriers in the Y axis is conveyed to the wheels as rotation, such rotation averaged to the rotation of the cylinder / s carrying the inclined planes, the axialreactions upon the first inclined plane(s) due to resistance to turning of the two wheels being opposite, and being equal and opposite when the vehicle is going straight.

60. The vehicle differential of claim 59, characterized in that any combination of inclined plane(s), rollers, carriers, or ratio-change is employed such that the axial components of the reaction of the wheels due to their resistance to turning is opposite, and is equal and opposite when the vehicle is going straight.

61. A vehicle differential is configured to permit a finite amount of differentiation between the two wheels.

62. The vehicle differential of claim 61, characterized in that the finite differentiation is replenished.

63. A vehicle differential is configured to permit a finite amount of differentiation between the two wheels, with provision for replenishment of the finite differentiation, characterized in that the replenishment is done before or after a journey and when the vehicle is braked, coasting, and in the case of electric motor driven vehicle with regeneration, at the time between motive power and regeneration.

64. The vehicle differential of claim 63, characterized in that the two wheels are uncoupled while replenishing.

65. A vehicle differential is configured to permit a finite amount of differentiation between the two wheels, characterized in that an internal arrangement is provided such that the overdrive of left wheel due to vehicle turning right, is compensated or cancelled by the overdrive of the right wheel due to vehicle turning left, so that the differential needs to manage only the net overdrive.

66. A vehicle differential configured to determine the ratio of overdrive, thus enabling or modulating yaw.

67. A vehicle differential configured to measure or impose yaw based on the implementation of inclined planes and rollers in the form of helical threads or screw elements, wherein the driving inclined planes are rotationally coupled to the prime mover and carry rollers which optionally carry a pair of inclined planes, and the rollers or inclined planes driven by the rollers are rotationally coupled to the two driven wheels, such that the axial components, preferably components parallel to the axle, whether the axle is real or virtual, of reaction forces from the two wheels, which reaction arises from the resistance offered by the driven wheels to rotation fed by the differential, are opposed to each other, and are equal and opposite to each other and hence cancel each other out when the vehicle is going straight, and such that when the vehicle is yawing, namely turning on a vertical axis, whether induced by this differential artificially or occurring naturally due to steering wheels, the driving inclined planes move axially or are moved in relation to the driven inclined planes, axially, i.e. parallel to the axle, so as to permit or order the differentiation arising out of, or imposed upon by the differential, on the vehicle, and the wheels obtain rotary motion from the rotation of the driven rollers or inclined planes, wherein the screw elements have at least one of balls and rollers inter-engaged between the driving halves and the driven halves.

68. A vehicle differential configured to measure or impose yaw, containing two screw elements, wherein the driving halves of screw elements are rotationally coupled to the prime mover and the driven halves of screw elements are rotationally coupled to the two driven wheels, such that the axial components, namely components parallel to the axle, whether real or virtual axle, of reaction forces from the two driven wheels, which reaction arises from the resistance offered by the driven wheels to rotation fed by the differential, are opposed to each other, and are equal and opposite to each other when the vehicle is going straight, and such that when the vehicle is on a turn, whether induced by this differential artificially or occurring naturally due to steering wheels, the driving halves of the screw elements move relative to the driven halves of the screw elements, axially, or are moved axially, namely parallel to the axle, so as to permit or order the differentiationand hence yaw arising out of steering wheels, or imposed upon by the differential, on the vehicle, respectively, wherein each of the two screw elements have at least one of balls and rollers inter-engaged between the driving halves and the driven halves.

69. A differential for a vehicle, comprising: a main shaft operatively mounted to rotate along a longitudinal axis thereof, the main shaft being operatively connected to a prime mover so as to rotate in response to motive power therefrom; and first and second roller elements operatively connected to the main shaft to rotate at least parallel to the longitudinal axis of the main shaft, the main shaft being formed with a first shaft portion that inter-engages with first roller element and a second shaft portion that inter-engages with the second roller element, wherein the first and second roller elements are operatively connected to first and second wheels of a vehicle, respectively, such that the motive power from the prime mover is transferred to the first and second wheels via co-rotation of the first and second roller elements with the main shaft so as to propel the vehicle, the first and second wheels being in contact with a surface on which the vehicle is propelled; and a first screw element assembly comprising the first shaft portion inter-engaged with the first roller element, the first roller element being a first bolt element of the first screw element assembly; and a second screw element assembly comprising the second shaft portion interengaged with the second roller element, the second roller element being a second bolt element of the second screw element assembly, wherein the first shaft portion is formed as a first nut element of the first screw element assembly, and the second shaft portion is formed as a second nut element of the second screw element assembly, wherein at least one of balls and rollers are inter-engaged between the first nut element and the first bolt element of the first screw element assembly and between the second nut element and the second bolt element of the second screw element assembly; andthe main shaft is configured to laterally move between the first and second roller elements along the longitudinal axis thereof to generate a difference in at least one of speed and travel distance during a turn between the first and second wheels while in contact with the surface as the vehicle is propelled, wherein each of the first and second roller element is formed of at least one of a ball screw and roller screw.

70. The differential according to claim 69, further comprising: first and second axial motion elements operatively connected to the main shaft, wherein the first and second axial motion elements are configured to controllably and laterally move the main shaft along the longitudinal axis thereof so as to at least one of restore to a baseline position the main shaft moving in response to the difference in the at least one of speed and travel distance during a turn between the first and second wheels while in contact with the surface as the vehicle is propelled and generate the difference in the at least one of speed and travel distance during a turn between the first and second wheels while in contact with the surface.

71. A differential system for a vehicle that provides yaw, comprising: a prime mover for providing motive power; a differential structure that includes a main shaft operatively mounted to rotate along a longitudinal axis thereof, the main shaft being operatively connected to the prime mover so as to rotate in response to motive power therefrom, and first and second roller elements operatively connected to the main shaft to rotate at least parallel to the longitudinal axis of the main shaft, the main shaft being formed with a first shaft portion that inter-engages with first roller element and a second shaft portion that inter-engages with the second roller element; the first shaft portion is formed with a first threading hand that is opposite a second threading hand formed on the second shaft portion, the first roller element is formed with a first roller threading corresponding to the first threading hand of the first shaft portion, andthe second roller element is formed with a second roller threading corresponding to the second threading hand of the second shaft portion; a first screw element assembly comprising the first shaft portion inter-engaged with the first roller element, the first roller element being a first bolt element of the first screw element assembly; a second screw element assembly comprising the second shaft portion interengaged with the second roller element, the second roller element being a second bolt element of the second screw element assembly, wherein the first shaft portion is formed as a first nut element of the first screw element assembly, and the second shaft portion is formed as a second nut element of the second screw element assembly, wherein at least one of balls and rollers are inter-engaged between the first nut element and the first bolt element of the first screw element assembly and between the second nut element and the second bolt element of the second screw element assembly; and first and second drive wheels operatively connected to the first and second roller elements, respectively, such that the motive power from the prime mover is transferred to the first and second wheels via co-rotation of the first and second roller elements with the main shaft so as to propel the vehicle, the first and second wheels being in contact with a surface on which the vehicle is propelled; and a control circuit for at least one of monitoring and controlling operation of the differential structure, wherein the main shaft is configured to laterally move between the first and second roller elements along the longitudinal axis thereof to generate a difference in at least one of speed and travel distance during a turn between the first and second wheels while in contact with the surface as the vehicle is propelled, wherein each of the first and second roller element is formed of at least one of a ball screw and roller screw.

72. A differential system for a vehicle that provides yaw, comprising: a prime mover for providing motive power;a differential structure that includes a main shaft operatively mounted to rotate along a longitudinal axis thereof, the main shaft being operatively connected to the prime mover so as to rotate in response to motive power therefrom, and first and second roller elements operatively connected to the main shaft to rotate at least parallel to the longitudinal axis of the main shaft, the main shaft being formed with a first shaft portion that inter-engages with first roller element and a second shaft portion that inter-engages with the second roller element; first and second drive wheels operatively connected to the first and second roller elements, respectively, such that the motive power from the prime mover is transferred to the first and second wheels via co-rotation of the first and second roller elements with the main shaft so as to propel the vehicle, the first and second wheels being in contact with a surface on which the vehicle is propelled; and a control circuit for at least one of monitoring and controlling operation of the differential structure, wherein the main shaft is configured to laterally move between the first and second roller elements along the longitudinal axis thereof to generate a difference in at least one of speed and travel distance during a turn between the first and second wheels while in contact with the surface as the vehicle is propelled; and first and second yaw and replenishing elements operatively connected to the main shaft and to the control circuit wherein the control circuit is configured to control the first and second yaw and replenishing elements to laterally move the main shaft along the longitudinal axis thereof so as to at least one of restore to a baseline position the main shaft moving in response to the difference in at least one of speed and travel distance during a turn between the first and second wheels while in contact with the surface as the vehicle is propelled and generate the difference in at least one of speed and travel distance during a turn between the first and second wheels while in contact with the surface; the first yaw and replenishing element is a first yaw and replenishing screw element assembly comprising a first yaw and replenishing bolt element inter-engaged with the first shaft portion that inter-engages with the first roller element, the first shaftportion inter-engaging with the first roller element being a first yaw and replenishing nut element of the first yaw and replenishing screw element assembly; the second yaw and replenishing element is a second yaw and replenishing screw element assembly comprising a second yaw and replenishing bolt element inter-engaged with the second shaft portion that inter-engages with the second roller element, the second shaft portion inter-engaging with the second roller element being a second yaw and replenishing nut element of the second yaw and replenishing screw element assembly, wherein each of the first and second roller element is formed of at least one of a ball screw and roller screw, and at least one of balls and rollers are inter-engaged between the first yaw and replenishing nut element and the first yaw and replenishing bolt element of the first yaw and replenishing screw element assembly and between the second yaw and replenishing nut element and the second yaw and replenishing bolt element of the second yaw and replenishing screw element assembly.

73. A differential system that provides yaw for a vehicle, comprising: a prime mover for providing motive power; first and second differential structures, each of the first and second differential structures including a main shaft operatively mounted to rotate along a longitudinal axis thereof, the main shaft being operatively connected to the prime mover so as to rotate in response to motive power therefrom, and first and second roller elements operatively connected to the main shaft to rotate at least parallel to the longitudinal axis of the main shaft, the main shaft being formed with a first shaft portion that inter-engages with first roller element and a second shaft portion that inter-engages with the second roller element; first and second drive wheel pairs operatively connected to the first and second differential structures, respectively, such that the motive power from the prime mover is transferred to the first and second wheel pairs via co-rotation of the first and second roller elements with the main shaft so as to propel the vehicle, the first and second wheel pairs being in contact with a surface on which the vehicle is propelled;a control circuit for at least one of monitoring and controlling operation of the first and second differential structures, wherein in each of the first and second differential structures, the main shaft is configured to laterally move between the first and second roller elements along the longitudinal axis thereof to generate a difference in at least one of speed and travel distance during a turn between the first and second wheels while in contact with the surface as the vehicle is propelled; a splitter element operatively connected between the prime mover and the first and second differential structures, the splitter element being configured to distribute motive power from the prime mover between the first and second differential structures in response to the control circuit; in each of the first and second differential structures, the first shaft portion is formed with a first threading hand that is opposite a second threading hand formed on the second shaft portion, the first roller element is formed with a first roller threading corresponding to the first threading hand of the first shaft portion, and the second roller element is formed with a second roller threading corresponding to the second threading hand of the second shaft portion; each of the first and second differential structures includes: a first screw element assembly comprising the first shaft portion inter-engaged with the first roller element, the first roller element being a first bolt element of the first screw element assembly; a second screw element assembly comprising the second shaft portion interengaged with the second roller element, the second roller element being a second bolt element of the second screw element assembly, wherein each of the first and second roller element is formed of at least one of a ball screw and roller screw, and the first shaft portion is formed as a first nut element of the first screw element assembly, and the second shaft portion is formed as a second nut element of the second screw element assembly, andat least one of balls and rollers are inter-engaged between the first nut element and the first bolt element of the first screw element assembly and between the second nut element and the second bolt element of the second screw element assembly.

74. A differential system for a vehicle, comprising: a prime mover for providing motive power; first and second differential structures, each of the first and second differential structures including a main shaft operatively mounted to rotate along a longitudinal axis thereof, the main shaft being operatively connected to the prime mover so as to rotate in response to motive power therefrom, and first and second roller elements operatively connected to the main shaft to rotate at least parallel to the longitudinal axis of the main shaft, the main shaft being formed with a first shaft portion that inter-engages with first roller element and a second shaft portion that inter-engages with the second roller element; first and second drive wheel pairs operatively connected to the first and second differential structures, respectively, such that the motive power from the prime mover is transferred to the first and second wheel pairs via co-rotation of the first and second roller elements with the main shaft so as to propel the vehicle, the first and second wheel pairs being in contact with a surface on which the vehicle is propelled; a control circuit for at least one of monitoring and controlling operation of the first and second differential structures, wherein in each of the first and second differential structures, the main shaft is configured to laterally move between the first and second roller elements along the longitudinal axis thereof to generate a difference in at least one of speed and travel distance during a turn between the first and second wheels while in contact with the surface as the vehicle is propelled; and a splitter element operatively connected between the prime mover and the first and second differential structures, the splitter element being configured to distribute motive power from the prime mover between the first and second differential structures in response to the control circuit, wherein each of the first and second differential structures includes:first and second yaw and replenishing elements operatively connected to the main shaft and to the control circuit wherein the control circuit is configured to control the first and second yaw and replenishing elements to laterally move the main shaft along the longitudinal axis thereof so as to at least one of restore to a baseline position the main shaft moving in response to the difference in at least one of speed and travel distance during a turn between the first and second wheels while in contact with the surface as the vehicle is propelled and generate the difference in at least one of speed and travel distance during a turn between the first and second wheels while in contact with the surface; and in each of the first and second differential structures, the first yaw and replenishing element is a first yaw and replenishing screw element assembly comprising a first yaw and replenishing bolt element inter-engaged with the first roller element, the first roller element being a first yaw and replenishing nut element of the first yaw and replenishing screw element assembly; the second yaw and replenishing element is a second yaw and replenishing screw element assembly comprising a second yaw and replenishing bolt element inter-engaged with the second roller element, the second roller element being a second yaw and replenishing nut element of the second yaw and replenishing screw element assembly, wherein at least one of balls and rollers are inter-engaged between the first yaw and replenishing nut element and the first yaw and replenishing bolt element of the first yaw and replenishing screw element assembly and between the second yaw and replenishing element and the second yaw and replenishing bolt element of the second yaw and replenishing screw element assembly, wherein each of the first and second roller element is formed of at least one of a ball screw and roller screw.

75. A differential with yaw for a vehicle, comprising: a main shaft operatively mounted to rotate along a longitudinal axis thereof, the main shaft being operatively connected to a prime mover so as to rotate in response to motive power therefrom; and first and second follower elements operatively connected to the main shaft via first and second screw elements, respectively, the screw elements being at least one ofroller screws and ball screws, the main shaft being configured to move axially and rotationally parallel to the first and second follower elements, the first and second follower elements being configured to rotate parallel to the main shaft, wherein the first screw element connects the main shaft with the first follower element, the second screw element connecting the main shaft with the second follower element, the second screw element having a same pitch and an opposite hand direction as the first screw element, the prime mover is configured to transfer motive power to a first wheel of the vehicle via co-rotation of the first screw element with the first follower element, and to transfer motive power to a second wheel of the vehicle via co-rotation of the second screw element with the second follower element so as to propel the vehicle, the first and second wheels being in contact with a surface on which the vehicle is propelled, the main shaft is configured to laterally move between and parallel to the first and second follower elements so as to at least one of measure and generate a difference in rotation of the two first and second wheels, whereby the first and second wheels move axially opposite each other relative to the main shaft in response to resistance in the vehicle turning, and move equal and opposite to each other when the vehicle is going straight, whereby first and second follower elements rotate equally and opposite each other in response to axial movement of the main shaft between the first and second follower elements, the axial movement of the main shaft generating yaw.

76. The differential according to claim 75, wherein a pitch of each of the first and second screw elements are unequal to each other, and one or both wheels are rotated via a ratio or ratios, such that the pitch ratio and rotation ratio together are such that the axial reaction of the opposition to rotation of two wheels is equal and opposite when the vehicle is going straight.

77. A splitter for providing continuously variable drive transmission, comprising: first, second and third rollers, the first roller being operatively connected to the prime mover;first and second differential structures, the second and third rollers each being operatively connected to the first and second differential structures, respectively, the first roller inter-engaging with the second and third rollers so as to rotatively drive the second and third rollers; and means for transmitting motion between a pair of rollers from among the first, second and third rollers that are equal across entire lengths thereof so as to vary a relative speed therebetween, wherein a predetermined gap between the pair of rollers is substantially equal along a length of the first, second and third rollers that form the pair of rollers.

78. The splitter according to claim 77, wherein the means for transmitting motion includes at least one of a resilient cord and belt configured to transmit motion between the pair of rollers.

79. The splitter according to claim 77, wherein the splitter is configured to provide continuously variable drive transmission via at least three rollers.

80. The splitter according to claim 77, further comprising: at least one rotating wheel operatively connected to receive mechanical motion from at least one of the first, second and third rollers, wherein a speed of the at least one rotating wheel is generated in response to a path length of the at least one rotating wheel based on a ratio relating the speed of the at least one rotating wheel and a steering angle of the at least one rotating wheel.

81. The splitter according to claim 77, wherein each of the first, second and third rollers is shaped as a frustum of a cone.

82. The splitter according to claim 77, wherein each of the first, second and third rollers is formed as a toroid.

83. A splitter for providing continuously variable drive transmission, comprising:first, second and third rollers, the first roller being operatively connected to a prime mover; first and second differential structures, the second and third rollers each being operatively connected to the first and second differential structures, respectively, the first roller inter-engaging with the second roller, and the third roller inter-engaging with the second roller such that the first roller rotatively drives, and the second roller rotatively drives the third roller; and means for transmitting motion between a pair of rollers from among the first, second and third rollers that are equal across entire lengths thereof so as to vary a relative speed therebetween.

84. The splitter according to claim 83, wherein the means for transmitting motion includes at least one of a resilient cord and belt configured to transmit motion between the pair of rollers.

85. The splitter according to claim 83, wherein the splitter is configured to provide continuously variable drive transmission via at least three rollers.

86. The splitter according to claim 83, further comprising: at least one rotating wheel operatively connected to receive mechanical motion from at least one of the first, second and third rollers, wherein a speed of the at least one rotating wheel is generated in response to a path length of the at least one rotating wheel based on a ratio relating the speed of the at least one rotating wheel and a steering angle of the at least one rotating wheel.

87. The splitter according to claim 83, wherein each of the first, second and third rollers is shaped as a frustum of a cone.

88. The splitter according to claim 83, wherein each of the first, second and third rollers is formed as a frustum-shaped toroid.

89. The differential according to claim 1 , wherein the main shaft is configured to move at least one of laterally and coaxially relative to the first and second roller elements.

90. The differential according to claim 1 , wherein each of the first and second roller elements are configured to rotate at least one of parallel and coaxially to the longitudinal axis of the main shaft.

91. The differential according to claim 10, wherein the main shaft is configured to move at least one of laterally and coaxially relative to the first and second roller elements.

92. The differential according to claim 10, wherein each of the first and second roller elements are configured to rotate at least one of parallel and coaxially to the longitudinal axis of the main shaft.

93. The differential according to claim 21, wherein the main shaft is configured to move at least one of laterally and coaxially relative to the first and second roller elements.

94. The differential according to claim 21, wherein each of the first and second roller elements are configured to rotate at least one of parallel and coaxially to the longitudinal axis of the main shaft.

95. The method according to claim 26, wherein the main shaft is configured to move at least one of laterally and coaxially relative to the first and second roller elements.

96. The method according to claim 26, wherein each of the first and second roller elements are configured to rotate at least one of parallel and coaxially to the longitudinal axis of the main shaft.

97. The method according to claim 31 , wherein the main shaft is configured to move at least one of laterally and coaxially relative to the first and second roller elements.

98. The method according to claim 31, wherein each of the first and second roller elements are configured to rotate at least one of parallel and coaxially to the longitudinal axis of the main shaft.

99. The differential according to claim 41, wherein the main shaft is configured to move at least one of laterally and coaxially relative to the first and second roller elements.

100. The differential according to claim 41, wherein each of the first and second roller elements are configured to rotate at least one of parallel and coaxially to the longitudinal axis of the main shaft.

101. The differential according to claim 56, wherein each of the first and second sub-shafts are configured to move at least one of laterally and coaxially relative to the first and second roller elements.

102. The differential according to claim 56, wherein each of the first and second roller elements are configured to rotate at least one of parallel and coaxially to the first and second longitudinal sub-axes of the first and second sub-shafts, respectively.

103. A differential that provides yaw for a vehicle, comprising: a main shaft operatively mounted to rotate along a longitudinal axis thereof; and first and second roller elements operatively connected to the main shaft to rotate at least parallel to the longitudinal axis of the main shaft, , the main shaft being configured to rotate relative to the first and second roller elements, the main shaft beingformed with a first shaft portion that inter-engages with first roller element and a second shaft portion that inter-engages with the second roller element, wherein the first and second roller elements are operatively connected to first and second wheels of a vehicle, respectively, such that motive power is transferred to the first and second wheels via co-rotation of the first and second roller elements with the main shaft so as to propel the vehicle, the first and second wheels being in contact with a surface on which the vehicle is propelled, and the main shaft is configured to laterally move between the first and second roller elements along the longitudinal axis thereof in response to generate a difference in at least one of speed and travel distance during a turn between the first and second wheels while in contact with the surface as the vehicle is propelled, wherein each of the first and second roller element is formed of at least one of a ball screw and roller screw.

104. A method of operating a differential for a vehicle to provide yaw, comprising the steps of: providing a differential structure that includes a main shaft operatively mounted to rotate along a longitudinal axis thereof, and first and second roller elements operatively connected to the main shaft to rotate at least parallel to the longitudinal axis of the main shaft, the main shaft being formed with a first shaft portion that inter-engages with first roller element and a second shaft portion that inter-engages with the second roller element, and the first and second roller elements being operatively connected to first and second wheels of a vehicle, respectively; inputting motive power into the main shaft so as to transfer the motive power to first and second wheels of a vehicle such that co-rotation of the first and second roller elements with the main shaft propels the vehicle, the first and second wheels being in contact with a surface on which the vehicle is propelled; and laterally moving the main shaft between the first and second roller elements along the longitudinal axis thereof in response to generate a difference in at least one of speed and travel distance during a turn between the first and second wheels while in contact with the surface as the vehicle is propelled, whereineach of the first and second roller element is formed of at least one of a ball screw and roller screw.

105. A differential for providing yaw in a vehicle, comprising: a main motion transfer structure operatively mounted to rotate along a longitudinal axis thereof; and first and second sub-motion transfer structures operatively connected to the main motion transfer structure so as to receive rotational motion from the main motion transfer structure, wherein each of the first and second sub-motion transfer structures includes first and second roller elements, respectively, wherein each of the first and second roller elements includes a receiving end and transmitting end, each of the first and second sub-motion transfer structures being operatively connected to the main motion transfer structure at respective receiving ends thereof to corotate in response to rotation of the main motion transfer structure, first and second roller elements, respectively, are operatively connected the first and second sub-motion transfer structures at the transmitting ends thereof, the first and second sub-motion transfer structures being configured to rotate relative to the first and second roller elements, respectively, the first and second roller elements are operatively connected to first and second wheels of a vehicle, respectively, such that rotational motion is transferred to the first and second wheels via co-rotation of the first and second roller elements with the first and second sub-motion transfer structures, the first and second wheels being in contact with a surface on which the vehicle is propelled, and the first and second roller elements are configured to laterally move relative to the first and second sub-motion transfer structures along respective longitudinal axes thereof to generate a difference in at least one of speed and travel distance during a turn between the first and second wheels while in contact with the surface as the vehicle is propelled, wherein each of the first and second roller element is formed of at least one of a ball screw and roller screw.

106. The differential according to claim 105, wherein main motion transfer structure includes a driving bevel gear, each of the first and second sub-motion transfer structures includes a receiving bevel gear, the driving gear and the receiving bevel gears being interlocked with each other so as to co-rotate relative to each other.

107. The differential according to claim 105, wherein the first and second sub-motion transfer structures and the first and second roller elements are configured such that an axial change in distance between the first sub-motion transfer structure and the first roller element is equal to an axial change in distance between the second sub-motion transfer structure and the second roller element.

108. The differential according to claim 1, wherein the main shaft is further configured to laterally move between the first and second roller elements along the longitudinal axis thereof to generate a difference in path length during a turn between the first and second wheels while in contact with the surface as the vehicle is propelled.

109. The differential according to claim 10, wherein the main shaft is further configured to laterally move between the first and second roller elements along the longitudinal axis thereof to generate a difference in path length during a turn between the first and second wheels while in contact with the surface as the vehicle is propelled.

110. The differential according to claim 21, wherein the main shaft is further configured to laterally move between the first and second roller elements along the longitudinal axis thereof to generate a difference in path length during a turn between the first and second driven wheels in response to the steering angle of the steering wheel.

111. The method according to claim 26, wherein the step of laterally moving the main shaft between the first and second roller elements along the longitudinal axis thereof generates a difference in path length during a turn between the first and second wheels while in contact with the surface as the vehicle is propelled.

112. The method according to claim 31 , wherein the step of laterally moving the main shaft between the first and second roller elements along the longitudinal axis thereof generates a difference in path length during a turn between the first and second wheels while in contact with the surface as the vehicle is propelled.

113. The differential according to claim 41, wherein the main shaft is further configured to laterally move between the first and second roller elements along the longitudinal axis thereof to generate a difference in path length during a turn between the first and second wheels while in contact with the surface as the vehicle is propelled.

114. The differential according to claim 56, wherein the main shaft is further configured to laterally move between the first and second roller elements along the longitudinal axis thereof to generate a difference in path length during a turn between the first and second wheel shafts in response to the steering angle of the steering wheel.

115. The differential according to claim 10, further comprising: a first coupling structure operatively connected between the first roller element and first drive wheel; a second coupling structure operatively connected between the second roller element and second drive wheel, wherein each of the first and second coupling structures is configured to disengage at least one of the first and second drive wheel from the corresponding first and second roller element when the main shaft reaches a predetermined limit of operation relative to at least one of the first and second roller elements.

116. The differential according to claim 115, wherein each of the first and second coupling structure is further configured to disengage at least one of the first and second wheel from the corresponding first and second roller element when the vehicle is braking or coasting.

117. The differential according to claim 21, further comprising:a first coupling structure operatively connected between the first roller element and first drive wheel; a second coupling structure operatively connected between the second roller element and second drive wheel, wherein each of the first and second coupling structures is configured to disengage at least one of the first and second drive wheel from the corresponding first and second roller element when the main shaft reaches a predetermined limit of operation relative to at least one of the first and second roller elements.

118. The differential according to claim 117, wherein each of the first and second coupling structure is further configured to disengage at least one of the first and second wheel from the corresponding first and second roller element when the vehicle is braking or coasting.

119. The method according to claim 26, further comprising: providing a first coupling structure operatively connected between the first roller element and the first driven wheel, and a second coupling structure operatively connected between the second roller element and the second driven wheel; and disengaging at least one of the first and second driven wheels from the corresponding first and second roller element via each of the first and second coupling structures when the main shaft reaches a predetermined limit of operation relative to at least one of the first and second roller elements.

120. The method according to claim 119, wherein each of the first and second coupling structure is further configured to disengage at least one of the first and second wheel from the corresponding first and second roller element when the vehicle is braking or coasting.

121. The method according to claim 31, further comprising: providing a first coupling structure operatively connected between the first roller element and first drive wheel, and a second coupling structure operatively connected between the second roller element and second drive wheel; anddisengaging at least one of the first and second drive wheel from the corresponding first and second roller element via the first and second coupling structures when the main shaft reaches a predetermined limit of operation relative to at least one of the first and second roller elements.

122. The differential according to claim 121, wherein the step of disengaging at least one of the first and second drive wheel from the corresponding first and second roller element via the first and second coupling structures is performed when the vehicle is braking or coasting.

123. The differential according to claim 41, further comprising: a first coupling structure operatively connected between the first roller element and first drive wheel; a second coupling structure operatively connected between the second roller element and second drive wheel, wherein each of the first and second coupling structures is configured to disengage at least one of the first and second drive wheel from the corresponding first and second roller element when the main shaft reaches a predetermined limit of operation relative to at least one of the first and second roller elements.

124. The differential according to claim 123, wherein each of the first and second coupling structure is further configured to disengage at least one of the first and second wheel from the corresponding first and second roller element when the vehicle is braking or coasting.

125. The differential according to claim 56, further comprising: a first coupling structure operatively connected between the first roller element and first drive wheel; a second coupling structure operatively connected between the second roller element and second drive wheel, wherein each of the first and second coupling structures is configured to disengage at least one of the first and second drive wheel from the corresponding first and second rollerelement when the main shaft reaches a predetermined limit of operation relative to at least one of the first and second roller elements.

126. The differential according to claim 125, wherein each of the first and second coupling structure is further configured to disengage at least one of the first and second wheel from the corresponding first and second roller element when the vehicle is braking or coasting.

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