Device for changing the caster angle on a motorcycle by means of an articulated quadrilateral

Abstract

A device for changing the caster angle of the front system (1) of a motorcycle, through an articulated quadrilateral, characterized in that the supporting carrier (60) of the steering shaft (5) of the above mentioned front system (1) is connected to the frame (4) of the motorcycle, by two articulated links (14), so that the relative position of the above mentioned carrier (60) in relation to the frame (4) is changeable and determined by the current state of an activator (15), which consists of its primary member (15 A) and its secondary member (15B), wherein the secondary member (15B) is moving relative to the primary member (15A) when the activator (15) is operating, following an electrical signal sent by an electronic Control Unit (11) which receives and processes electrical signals relating to the instantaneous motorcycle kinetic state of the motorcycle, coming from at least one sensor (12).

Description

[0001] DEVICE FOR CHANGING THE CASTER ANGLE ON A MOTORCYCLE

[0002] BY MEANS OF AN ARTICULATED QUADRILATERAL

[0003] DESCRIPTION

[0004] The invention refers to a device for achieving a changeable, at will, driving behavior of the motorcycle, through fee. management of two opporing and conflicting characteristics of the motorcycle, in real time:

[0005] A) Stability

[0006] B) Agility

[0007] This is achieved by using an innovative apparatus, which, depending on the motorcycle's cunent kinetic state, modifies a fundamental geometric characteristic of the motorcycle, that determines - for the moat part - the motorcycle's road behavior.

[0008] STATE OF THE ART figure 1a illustrates foe as of now called ‘front system' (1) of a motorcycle, which in its most common commercial form is also called “fork” Uris system basically consists of the suspension (2) of the front wheti (3) which, typically, is a tdescopic device consisting of a fixed member (2A) and a sliding member (2B) and which inride contains springs and hydraulic dampers. hi general, foe so called as “front system” (1) of a motorcycle is an apparatus via which the front wheel is connected to the frame (4) of foe motorcycle and consists of

[0009] (a) the suspension (2) which is, as previously described, usually of the telescopic' type and which contains foe springs and the hydraulic dampers, which ensure that the front wheel rolls smoothly over the irregularities of the road surface.

[0010] (b) the steering system which allows, through < "front steering shaft" mounted inside the neck (which will be explained later) of the frame (4), the angular movement of the front steering system around foe (imaginary) "steering axis" (5) in order to perform the desired change of (mentation of the front wheel (3).

[0011] In summary, the front system (1) provides the front whed axis with two degrees of freedom:

[0012] A) A "parallel, towards itself movement of the shaft of the wheel, during compression and decompression of the telescopic suspension elements and

[0013] B) A rotation of the draft of the wheel (3) around the imaginary steering axis (5), which steering axis is coaxial with the neck axis (this will be mentioned below) and perpendicular to the shaft of the whed. Figure lb also shows a (commercially available) alternative form of tdescopic system (BMWs “Tdeleva^: Here, the telescopic system is connected at its upper.end to the frame by an upper joint (180), while its sliding member (2A) is connected to the frame (4) by a swing arm (40) which at one end is hinged - via an horizontal shaft (41) - to the frame (4) and at the other end is connected to the sliding member (2A) by a lower ball joint (400). As is evident, the steering axis (5) is, in this case, an imaginary straight line defined by the upper joint (180) and by the lower joint (400). In this system, the wheel axis has three degrees of freedom. The two mentioned above for the conventional telescopic system and an additional one as the telescopic system (but also the steering axis (5) ) constantly varies its relative inclination, in relation to the frame, since, during the operation of the suspension, the ball joint (400) does not follow a straight line but follows the arc of a circle dictated by the length of the swingarm (40). In this case, the two supports of the front system, namely, the upper joint (180) and the lower joint (400) form a virtual support of the steering axis which, hereinafter, will be called as “virtual neck”.

[0014] Figure 1c illustrates a rarely used form of front system, the " articulated system " (known internationally as the " girder " or, in a specialised form, as the " Hossack System"). This system suspends the front wheel by means of an articulated quadrilateral where, especially in the case of the Hossack system, the lengths of the articulated members are chosen so that the front wheel axle, during compression and extension of the suspension, follows a certain path so the distance between the front and rear wheel axles is kept constant, and therefore the motorcycle's wheelbase remains constant.

[0015] Figure 2 shows, in cross section, how the front system (1) is connected to the frame (4) of the motorcycle. The 'steering axle' (8) is supported inside a “tube” which is a part of the frame (4), hereinafter referred to as the 'motorcycle neck' - and for short 'neck' (6) - which is fitted with roller bearing housings (7) which allow the steering system to rotate freely to the right and left in accordance with the movements of the rider-during the directional control of the steering handlebar (not shown).

[0016] Figure 3 shows the front of the motorcycle, when it is in a vertical position and in a standing position.

[0017] The imaginary axis of rotation of the steering system (5) and the vertical imaginary axis (9) form an angle (a) which, from now on, will be called the 'caster angle' (10).

[0018] As shown in the drawing, both the telescopic suspension system (2) and the axle (5) of the neck (6) ate inclined relative to the horizontal level.

[0019] The imaginary extension of the axle (5) meets the road surface (100) at point B, which is in front the point of contact of the wheel with the road surface (point A).

[0020] The distance AB is called the 'track* (16) and is determined by the geometric characteristics of many elements, such as the wheel size, the dimensions of the 'steering plates' (17) (by means of which the front system is connected to the neck axle), etc.), but the most important of these elements is the caster angle (a) which is formed between the imaginary axis of rotation (5) of the front system and the vertical axis (9) in relation to the horizontal level.

[0021] It is obvious that, during the movement of the motorcycle, the caster angle does not remain constant as the wheel passes over road bumps or is subjected to node-diving during braking which results in compression of the front suspension (thus reducing the caster angle and therefore the track and consequently the stability of the front system).

[0022] Obviously, there is a need to control the caster angle at any time and for each different state of the motorcycle’s movement (straight or turning, acceleration or deceleration, high or low speed). Something that Previous Art motorcycles are not able to do, contrary to the current invention, which suggests that this is

[0023] (a) feasible,

[0024] (b) "industrially applicable" and c) innovative.

[0025] The caster angle plays an important role in the handling of the motorcycle since its size determines two -opposite- competitive characteristics of the motorcycle: Directional stability and agility to directional changes.

[0026] Large caster angles (>30°) give the motorcycle increased stability when riding in a straight line, but, in return, they make it "disobedient" - to a certain extent - to the rider's commands to change direction.

[0027] Small caster angles (20-25°) provide increased agility to the motorcycle when enforced to change direction but, on the other hand, they result in an "unstable" wheel steering at high speeds that exhibits angular oscillations (named as “tank slapping” at their extreme), which require the existence of a "steering damper" to limit them before they become dangerously uncontrollable due to the gyroscopic phenomena that occur at high motorcycle speeds, where the front wheel has a high frequency of rotation.

[0028] Understandably, heavy motorcycles intended for open road travel, at relatively high speeds, are chosen to have a large caster, so that they are stable (even in gusts of wind) and "comfortable" during tong hours of riding.

[0029] On the contrary, motorcycles intended for racing use, in closed tracks with consecutive turns (racing tracks) are equipped with small caster angles so that they can easily change direction requiring the minimum effort from the rider.

[0030] From the above-mentioned it is evident that the choice of one certain value for caster angle makes it ideal for a single and only one corresponding kinetic condition of the motorcycle, while it is a "compromise deviation" for the whole remaining spectrum of kinetic conditions of a motorcycle.

[0031] At first view, it could be said that the ideal caster angle is different for each different speed of the motorcycle.

[0032] But this is also just an ’"approximate" view of reality.

[0033] From experience, it has been observed that for a given motorcycle speed, the ideal caster angle is different when the motorcycle is braking, different when accelerating, different when changing direction at the entry of a turn and different when it is already inclined inside a turn. At an even more detailed level (and especially at a racing level where milliseconds matter), additional factors come into play that affect the ideal value of the caster angle at a given moment in time, such as the magnitude of the angle of inclination of a motorcycle inside a comer, the moment of corner entry, the cross-sectional configuration of the tires, their material, their instantaneous temperature, etc.

[0034] Following the above, the logical conclusion is that the selection of the caster angle to maximize the quality of a motorcycle's behavior at any given moment in time is a multi-factorial problem, which is not yet tackled sufficiently by the State of the Art.

[0035] It is known, from the Previous Art, some (non-commercially available) attempts via which the caster angle has a provision for static adjustment at a certain-and fixed- value, each time when the motorcycle is stopped. But it is not a solution to the problem due to the fact that every new -static- value of caster corresponds to a very limited spectrum of kinetic behavior of the motorcycle.

[0036] Certain Prior Art

[0037] In a prior application of the same applicant of the present one (GR2023010103I) it was proposed an innovative way of changing the caster angle in real time.

[0038] In the aforementioned application, the applicant presents a method for continuously changing caster angle, on a motorcycle, based on a number of parameters emanating from the instantaneous kinetic state of the motorcycle.

[0039] The implementation of that prior invention is based on an innovative way of connecting the neck of the motorcycle to the frame, via a hinge, while the operation of the invention is based on fire (also innovative) utilization of known elements of the State of the Art, most of which are commercially available.

[0040] Figure 4 illustrates the basic principle of the prior invention:

[0041] The neck (6) through which the steering shaft (5) passes is not fixedly mounted on the frame (4) but is connected to it by a joint (13).

[0042] Figure 4a illustrates the connection of the neck (6) with the frame (4), where the neck is directly connected to the frame by a joint (13) that provides only one, single, Degree of Freedom (i.e. the angular displacement of the neck around the imaginary axis of this joint).

[0043] In accordance with the fundamental innovation of the present invention, the way of changing the caster angle is illustrated in figure 4b.

[0044] In the illustrated example, the movable position of the neck (6), in relation to the frame (4), depends on the respective state of an actuator, which actuator (15) is adapted (in this example) between the frame (4) and the neck (6) and, by means of its varying length, redefines, in real time, the position of the neck (6) in relation to the frame (4) according to commands received from an electronic unit (11). In turn, the aforementioned electronic unit (11) receives signals (relating to the current instantaneous motorcycle kinetic state) from at least one sensor (12) or, in complex implementations, a number of sensors.

[0045] This device, although functional, exhibits two features which, in some cases, are undesirable:

[0046] 1 In most alternative implementations of that invention (as in that of figure 4b) the actuator (15) itself is a structural element for supporting the neck (6) of the motorcycle, which requires a robust construction of the frame, at this point, with the consequent cost and weight disadvantages.

[0047] 2 The angular displacement of the entire front system, around the joint (13) causes large (parallel to itself) movements of the front wheel axle. This happens due to the magnitude of the radial distance between the front wheel axle and the axis of rotation of the front system, at the joint (13). This, however, results in large variations in the value of the wheelbase of the motorcycle during the desired changes in the caster angle (wheelbase ~ the distance between the front wheel axle and the rear wheel axle), which variations are desirable in some applications and undesirable in others.

[0048] (On "touring” motorcycles, for example, this is desirable: There, the goal is a long wheelbase that provides stability and comfortable riding on the highway straights and a shorter wheelbase that offers some agility in tight comers. On the contrary, on track racing motorcycles, front wheel travel (during suspension movements) is defined by the minimized space available between the engine and front wheel, so that as much as possible of the weight of the bike is distributed to the front wheel. In this case, it is probably impossible to find a space that will allow the front wheel to "retract" rearwards after a wheelbase reduction.)

[0049] 3 The momentarily reduction of the caster angle, according to this Prior Art invention, results to the raising of the front end of the motorcycle.

[0050] As a result, there was a need for an innovative, alternative implementation of this prior invention, as will be explained below.

[0051] DETAILED DESCRIPTION OF THE INVENTION

[0052] The fundamental, evolutionary proposition of the present invention (Figure 5) consists in that:

[0053] The steering shaft does not perform a simple angular motion of "one degree of freedom" - i.e. rotation around a joint (13), as in Pat. GR20230101031,- but in this application it performs a complex motion, of two degrees of freedom, around instantaneous (imaginary) rotation centers at each intermediate change of the caster angle.

[0054] Several advantages arise in this way:

[0055] 1 Stronger connection of the steering system, to the frame (in most of the feasible alternative implementations of the present invention). 2 Ability to determine, in advance, the position of the front wheel axis, at each change of the caster angle, and therefore of the wheelbase. (As opposed to the prior invention of the same, where the wheel, " retracts " at each reduction of the caster angle). ;

[0056] 3 Ability, by choice, to determine whether the front of the bike will be raised or lowered, at each reduction of the caster angle.

[0057] Figure 5 illustrates: some proposed examples of the present invention (where the innovation step is presented) in which the steering shaft can undergo desired changes in its position, and thus Changes in the caster angle (a), by moving with two degrees of freedom, i.e. displacement in space and a simultaneous angular displacement around sequential instantaneous centers of rotation (50) .

[0058] Figure 5a illustrates the kinetics of the present invention which are performed via a "quadrilateral articulated connection” through two links (14) connecting the neck (6) to the frame (4) at their relevant end joints (13). A telescopic actuator (15), of variable length, moves the neck (6) in a controlled manner according to commands received from an electronic control unit (11) through signals received from at least one sensor (12) of the instantaneous motorcycle kinetic state.

[0059] Figure 5b illustrates a device / assembly similar to that shown in Figure 5a, wherein the (conventional) neck of the front system is absent and the steering shaft (8) is resting on a pair of ball-joint sockets, named “supports” (80) which are mounted (and, preferably, hinged) to the respective ends of the links (14). In this alternative embodiment, the bearing carrier (60) of the steering shaft is not a "solid part", such as the conventional neck -(6), in the previous drawings - but imaginary, defined by the two sockets (80). From now on, the neck will also be considered as a ’carrier1(60), though in the following diagrams, for the sake of simplicity, only fhe ('material') neck and not the 'virtual* neck of figure 5b will be shown.

[0060] By definition, hereinafter, whenever the word “neck” is used, it will represent either a “real” neck, as in the examples in Figs 2 and 4, or a “virtual neck” between two support sockets (80) like the carrier (60) in Fig 5b.

[0061] 'Fhe links (14) can be either of equal length, as in figures 5c and 5d» or unequal, as in figure 5e.

[0062] Since the required changes in the caster angle (of the order of 3-8 degrees) are very small, it goes without saying that the required displacements (hence the dimensions) of the links (14) of the example of figure 5 are also infinitesimal, in order to achieve the required angular displacements of the steering shaft.

[0063] In figure 6 are presented indicative examples of “miniaturized” links.

[0064] In Figure 6a at least one of the links (14) - or both (Figure 6b)- has the form of a circular crank (14A), which gives alternative possibilities (compared to the existing options of the State of the Art) in the design of fhe frame (4) in order to achieve increased robustness of its connection to the front system. According to design preferences, this kind of circular crank can be supported by fhe frame either via a a central shaft or via a peripheral bearing, encircling the crank, resembling thus an “eccentric" (where the “follower of the eccentric” is considered the frame, relative to the road surface, as reference point). This certain embodiment is provided with an increased rigidity due to the fact that the loads are spread in a large area of the frame..

[0065] Figure 7 illustrates alternative ways of connecting the links (14) to the actuator (15) in order to achieve the desired effect

[0066] Either by directly connecting the actuator to the links (14) as in the indicative (and not binding) example of figure 7a or indirectly, by means of at least one lever (17) which rotates about a shaft (170) and moves a push rod (171), as in the indicative example of figure 7b. In general, it is obvious that there is an unlimited number of alternative connections, always in accordance with the spirit of the present invention.

[0067] In the examples so far, and for the sake of simplifying the description, only a -variable length- telescopic actuator has been exclusively proposed. However, as will be demonstrated below, the present invention can also be implemented with a multitude of different shaped actuators, with much better functional results in certain circumstances.

[0068] Regarding its operation, the actuator, according to the present invention, can be either a) Passive, wherein its activation is performed by utilizing the forces applied to the neck due to a specific motorcycle kinetic state (e.g. braking). b) Active, where its operation is based on the activation of an electric motor or an electric fluid pump.

[0069] In the following, the structure and operation of the present invention with a variety of different actuators will be described (always remaining in the spirit of the present invention) in order to demonstrate that its feasibility is not univocal but, on the contrary, unlimited alternative versions are offered which derive from the same operating principle.

[0070] Figure 8 illustrates an indicative - and not binding - implementation of a 'passive actuator’, which has a telescopic structure and hydraulic operation.

[0071] Figure 8a illustrates an example for a recommended position of the passive actuator (15), between frame (4) and neck (6).

[0072] Figure 8b illustrates, indicatively, the individual elements on which the operating mode of this passive actuator is based.

[0073] The actuator (15) comprises a primary member (15A) and a secondary member (15B) which, under specified conditions, can move relative to each other, thus varying the total length of the actuator between its two ends (150A and 150B).

[0074] The primary member of this actuator (15) consists of an outer shell (151) enclosing a chamber (152) in which a piston / plunger (153) moves which is part of the secondary member (15B).

[0075] Between the bottom (152A) of the chamber (152) and the face of the piston / plunger (153 A) a spring is interposed, hereinafter referred to as the 'return spring' (155), which reacts elastically to the movement of the piston / pluhger (153) towards the bottom (l52A) ofthe aforementioned chamber (152).

[0076] The chamber (152) contains incompressible hydraulic fluid, which, under conditions to be explained below, moves between the chamber (152) and a reservoir (156). 'the passage between the chamber (152) and the reservoir (156) is controlled by an electrically controlled valve (154) (hereinafter called as "control valve") which, in turn, is controlled by an electronic control unit (11) which sends commands to the electromechanism of the valve (154) after receiving and processing signals from at least one sensor (12) regarding the instantaneous kinetic state of the motorcycle.

[0077] The operation of the above-mentioned device is as follows:

[0078] During the braking of the motorcycle, on a straight line, there is the (largely abusive, as will be explained later) hypothesis that the motorcycle is about to execute a change of direction, at a new speed, which is reduced in relation to the initial speed. Therefore, there is a need to adjust the caster angle to a new (reduced) value which will favor a seamless course change.

[0079] In this case, the Control Unit (11) commands (either immediately, if occasion arises, or within a predetermined period of time after the "detection" of the start of deceleration) the valve (154) to allow fluid to pass from the chamber (152) to the reservoir (156). During this period, an additional vertical force (in addition to the weight of the motorcycle) is applied to the front system due to the braking force developed at the point of contact of the wheel with the road. As a result, the whole motorcycle tends to rotate around the instantaneous point of contact of the front wheel with the road, increasing the compressive loads on the neck (6) and, consequently, on the actuator (15). While the Control Unit (11) keeps the valve (154) open, the secondary member (15B) otters the chamber (152), reducing the total length of the actuator (15), thus reducing the caster angle, since the neck (6) is allowed to perform controlled micro-rotation around consecutive instantaneous rotation points as defined by the geometry of the articulated quadrilateral which is composed of the two links (14) and the distances between their joints (13) on the neck (6) and the frame (4), respectively.

[0080] Figure 8a illustrates an angular displacement sensor, hereinafter referred to as a "position sensor" (120) mounted on the joint (13) of one of the two links. Through this sensor, the Control Unit receives a signal for the instantaneous value of the caster angle. Obviously, the angular displacements received by the sensor are different from the actual values of the caster angle in reference to the road surface. It is understood, of course, that the electronic memory of the control unit can be programmed to perform calculations in order to match, the angle values which are measured by the sensor to the actual (according to the road surface) caster values, provided that there are additional sensors indicating the momentarily amount of compression / extension of the front and rear suspensions.

[0081] The opening of the valve (154) is strictly adjustable, at each instant of the braking process, so that each instantaneous value of the caster angle, during its gradual reduction, is not less than that value which, after tests, has been found to ensure the stability of the motorcycle at the intermediate speeds between the initial speed (at the start of braking) and the final speed (at the end of braking). And, from a certain moment onwards, at the end of braking, the Control Unit (11) commands the valve (154) to close, in order to stabilize the caster angle (a) at its new value, which is the desired one, with respect to the new current kinetic state of the motorcycle.

[0082] The Control Unit (11) then monitors, via the “kinetic state” sensor (12), the end of the condition that dictated the need to reduce the caster angle. So, for example, when it detects that the motorcycle is re-accelerating, it gradually reopens the valve (154) to allow the return spring (155) (which is compressed during the braking phase) to redeploy, pushing the piston / plunger (153) backwards (downwards in the illustration 8a). This piston / plunger (153), in turn, draws fluid into the chamber (152) and pulls away from the bottom (152A) of the chamber (152), pushing the neck (6) towards a larger caster angle that is now suitable for the new, increased motorcycle travel speed.

[0083] Figure Sc illustrates a simplified version of that of Figure 8b where the reservoir (156) is of variable volume and occupies the space of the chamber (152) located behind the piston / plunger (153). At the same time, the "rod" (157) of the piston / plunger (153) is so configured that there are equal volumes of fluid inflows and outflows to and from the chamber (152) and the reservoir (156).

[0084] The oversimplified "passive" system just described has the unique advantage of simplicity and low cost

[0085] However, it still has disadvantages, the most important of which is that it is "passive". This means that it works only when the rider activates the front brake, so that an increased vertical force is developed al the point of contact between the front wheel and the road surface, and therefore also on the return spring (155), so that it retracts to the desired point.

[0086] Also, the Control Unit does not have - in this particular application - the ability to distinguish whether the braking applied is due to the rider's desire to decelerate in order to change (or not) the direction of the motorcycle. Nor can it 'predict' that a change of direction of the motorcycle will occur if the rider slows down with only the rear brake or by simply closing the throttle.

[0087] Of course, the above-mentioned "kinetic state" sensor (through the instantaneous speed it detects) may enable the control unit to detect deceleration (from whatever source), but not to enable the device to operate while no deceleration of sufficient magnitude is applied (in advance) to ensure that the spring (155) retracts to the desired point.

[0088] For the abovementioned reasons, the present invention suggests a more complex implementation using an "active (hydraulic) actuator ", which is based on the operation of an electric motor that draws power from the electrical system of the motorcycle and operates regardless of the rider's action on the front brake.

[0089] This implementation can be carried out with unlimited variations of active hydraulic actuators, largely derived from (different types of) applications of the State of the Art, one of which is indicated, as an example, in Figure 9. In Figure 9, a pump (157) supplies fluid to the chamber (152) through the non-return valve:(159). While the control valve (154) is closed, the fluid pushes out the piston / plunger (153) which, in turn, compresses the return spring (155) and, at the same time, moves the neck (6) to a larger caster angle until a predetermined value is reached, based on the signal sent by the position sensor (120) to the Control Unit (11). When a reduction in caster angle is required, the Control Unit (11) commands the control valve (154) to open, thereby allowing the piston / plunger (153), which is pushed by the return spring (155), to displace fluid to the reservoir (156) until the position sensor (120) sends a signal to the Control Unit (11) that the neck (6) has reached the desired caster angle.

[0090] Indicatively, in this particular case, it has been chosen that the reduction of the caster angle is achieved by means of the energy provided by the expanding spring and not by - means of tile pump, whose response has a time lag, Instead, foe pump is used to increase the caster angle, which, upon acceleration of foe motorcycle, exhibits a lower rate of change of its gradual increase requirements.

[0091] The exemplary option to “return” to larger caster angles via the extension of a spring is not mandatory by the present invention (the embodiment of Fig.9 can be designed in order to perform the opposite procedure, where the operation of the pump performs an increase of the caster angle) but it is preferable for safety reasons. Obviously, it is safer for the stability of the front system of the motorcycle to return, automatically, to a greater caster angle in case there is a malfuntion of the pump or the tubing.

[0092] Since, at times, hydraulic devices "fail" without warning, the present invention additionally suggests a series of entirely electromechanical actuators which are preferably applicable to motorcycles for everyday use which do not receive the thorough maintenance that purely racing motorcycles enjoy.

[0093] Figures 10, 11 and 14 illustrate, indicatively, a variety of recommended '"electric" actuators, but obviously the range of potentially applicable types of actuators of this type is not limited to these three.

[0094] Figure 10 illustrates an actuatetor (15) whose primary member (15 A) comprises a shell (25), and a stepping electric motor (158) whose output is configured as a spline (26).

[0095] On the shell (25) of the primary member (15 A) there is a static "output thread" in foe form of a nut (22) which is fixedly attached to the shell (25) of the primary member (15A).

[0096] The secondary member (15B) consists of a screw (23) which passes through the static nut (22) and is connected at one end, directly or indirectly, to the electric motor (20) through the spline (26). At its other end, is connected to the neck (6). Preferably and not bindingly, with a ball joint (130).

[0097] When it is "desired" -by the Control Unit (11) to increase the caster angle, in this particular, indicative example, the electric motor (158) is turning in the selected direction (determined by the direction of the aforementioned threads) and then the secondary member (15B) starts to "unscrew" -while, at the same time, it slides axially on the spline (26), pushing the neck (6) relatively to the frame (4) and thus changing the magnitude of the caster angle (Increase, for example). On the contrary, when it is desired to reduce the caster angle, the electric motor (158) turns in the opposite direction and "screws" the secondary member (15B), pulling the neck (6) towards the frame.

[0098] The State of the Art, obviously, provides an unlimited number of electric actuators which can be derived / ”loaned” from various irrelevant engineering applications and utilized in embodiments of the present invention.

[0099] . For example, in Fig 10b there is the example of a possible alternative version of an electric actuator in which the connection between the electric motor (158) and the spline (26) is made by a pair of gears (123, 124) in an arrangement known in the State of the Art as an "helical shaft" (worm) or “worm / worm wheel”.

[0100] Figure 10c illustrates a different arrangement from that shown in Figure 10b, wherein the spline has been replaced by a rotating pin carrier (26B) where the pins (26A) slide axially in relation to the “wheel gear” of the worm gear (124) during the rotation of the pin carrier (26B).

[0101] It goes without saying that there is an unlimited number of alternative implementations of the aforementioned "screw" active actuator (15), and the so-far description has been given for illustrative purposes in order to understand the principle of its operation.

[0102] Figure 11 illustrates an alternative form of the aforementioned "screw" electromechanical actuator (15) where this particular implementation aims at avoiding the existence of a multi-spline and its consequent friction over time.

[0103] Hereon, the output of the electric actuator (158) has adapted, on its shaft, a primary gear (28). The input of the secondary member (15B) also has a corresponding (secondary) gear (29).

[0104] During the rotation of the electric motor (as described above), the primary gear (28) performs a motion with one degree of freedom (simple rotation about its axis) while the secondary gear (29) performs a complex motion, with two degrees of freedom: One rotation - in synchronization with the primary gear (28) of the electric motor (158), with which it is meshed - and one axial displacement as the thread of the screw (23) is "screwed" and "unscrewed" into the thread of the nut (22) of the primary member (15A).

[0105] In the so far suggested alternative implementations of the present invention, applications were demonstrated where the actuator was in direct connection with the steering shaft carrier (" material" or "notional / virtual" neck of the motorcycle). This is not necessary, and in many cases not even desirable (e g. for reasons of space or mass distribution on the motorcycle).

[0106] Figure 12 illustrates a support of the neck (6) through an intermediate "link arm" (14) extending between a rotating -about axis 131- lever (130) and the neck (6) The actuator (15) rotates the lever(130) and the lever moves the link (14) accordingly. Figure 13 shows the aforementioned lever (130) in the form of a crank (132), rotating about an axis (131).

[0107] Figure 14 illustrates, indicatively, an alternative arrangement of figure 10 where the connection between the actuator (15) and the crank (132) is made via a "helical shaft (worm)” system, wherein the worm gear (123) is rotated by an electric motor (158) and is part of the primary' member (15A) of the actuator (15), while the secondary member (15B) starts from the toothing which gives rotational movement to the crank (132).

[0108] Regarding to the processes for activating the innovative devices which are already described by the present application, it is obvious that a wide range of "potential options" exists, through which the road behavior of the motorcycle is improved, based on the above-mentioned innovative concept.

[0109] In the first instance, the simplest method of activating the device, at the moment the rider so desires, is by pressing an electrical switch mounted on the handlebars of the motorcycle. And in the simplest of cases, the system may be programmed between only two positions:

[0110] 1. Caster angle for straight line stability and

[0111] 2. Caster angle for agility in changes of direction.

[0112] It is understood, of course, that the proposed device, in all its suggested variations, can satisfy much more complex requirements.

[0113] Many modem motorcycles are equipped with a multitude of sensors for the real-time reading and calibration of the complete picture of the current, at any given time, motorcycle’s kinetic state.

[0114] Thus, in addition to speed sensors (for the speedometer and ABS systems, on each of the two wheels), there are motorcycles that have a cornering angle sensor and also sensors of the compression-extension status of the suspensions, front and rear. They even have 'g* sensors for measuring lateral and longitudinal acceleration.

[0115] Based on the existence of the above sensors, it is obvious that it is possible to provide the control unit with an integrated programming ('multi-parameter mapping*) in order to mandate the optimum caster angle in each specific case, regardless of the speed value alone. This proves to be a most important aid in racing applications, where the motorcycle is subjected to actions, by the rider, which are beyond the "normal" of everyday use, on public roads, either for simple transportation or for "sport-recreation" riding.

[0116] For example, racing riders - on a racetrack - tend to apply prolonged braking, right up tothe apex of the comer, while they have already given their bike a big lean.

[0117] This means that in special cases, such as the one mentioned above, a different caster angle is required for optimum results in order for the rider to exhaust the potential of the '"crown" of the racing tire and gain those infinitesimal fractions of time that he claims through his advanced riding.

[0118] In this case, it is certain that a device like the proposed by the present invention will prove to be extremely useful and competitive, where the aim of the rider's entire effort is to make positive use of micro-details, such as, for example, the different "ideal" caster angle in two comers that are drawn at similar speeds but where one comer shows different road grip variations from the other, during the course of a race.

[0119] Full utilization of the present invention, at a racing level, within a closed race track (which is lapped repetitively while changing the dynamic characteristics of the motorcycle as the weight of the fuel in the tank decreases and while tire wear progresses) will be carried out under the following status:

[0120] 1. The Control Unit, after testing, is programmed to have the optimum caster angle for each comer, separately, of the track where the race is being held.

[0121] 2. Since all motorcycles participating in a speed race pass through approximately the same points on each lap, the Control Unit determines - via GPS installed on the motorcycle - which is the next coma: of the track and retrieves from its digital memory the appropriate caster angle which is already programmed for that comer. (In this case, during free practice on a track, it is feasible for the mechanics of a racing team to adjust -remotely, via radio signals- the caster angle of the motorcycle for each section of the track and decide for the ideal value according to the “time gains” of the motorcycle in each section. This procedure cannot be considered as “innovation” since it is common practice, nowadays, to adjust -via remote control- the dynamic behavior of a racing vehicle, especially its engine performance).

[0122] SPECIAL CASES OF APPLICATION OF THE INVENTION

[0123] 1. The simplest implementation of the invention consists in an actuator which causes a change in the caster angle exclusively between two extreme positions: a) A large value of the caster angle for straight line stability, b) A small caster angle for flexibility in changing direction.

[0124] This simplifies the system and eliminates the need for a 'position sensor* (marked as (120) in the drawings). This application is suitable for everyday motorcycles where 'micrometric' adjustment of the caster angle is almost redundant. To activate this version, the following procedure is provided (indicative and not binding): a) The rider acts on the front brake to reduce speed. In this case, all motorcycles generate, in their electrical system, a signal to light the rear brake light bulb. Therefore, the Control Unit does not need an additional sensor to detect the change in kinetic state, other than by being connected to the existing electrical system of the motorcycle. b) After receiving a signal from the Central Unit that a deceleration has occurred through the braking system (during which the brake light remains on), the Control Unit waits for the end of the action on the front brake to start the process of reducing the caster angle in view of the presumed change of direction of the motorcycle.

[0125] 2. All references to alternative implementations of the present invention to this point have been exclusively .referring to the "nominal" caster angle. Namely, the one measured when the motorcycle is unloaded (from rider and fuel) and in a static state.

[0126] And the signals from the 'position sensor* (marked as (120) in the relevant figures) refer to changes in the angle of the front system in relation to the frame and not in relation to the road surface, as is 'essentially desirable', especially in racing applications. As is obvious, the "nominal" - or "static" - caster angle is different from the '"actual, in-operation" caster angle, as the respective movements of the suspension (with the associated compressions and rebounds) cause changes in the caster angle and deviations from its nominal value.

[0127] The present invention has the potential to provide the motorcycle with the desired - optional - caster angles, regardless of the momentary compressions or extensions of the suspensions due to the road surface, or the decelerations / accelerations applied to the motorcycle. This is achieved by sensors in the suspension, which provide signals to the Control Unit about their degree of extension or compression.

[0128] Similarly, the Control Unit can calculate and calibrate the actual caster angle value in relation to the road surface - and not in relation to the frame, as calculated approximately by the position sensor alone (120).

[0129] In this way, a much better management of the stability of the front system can be achieved, aiming at managing the values of the front system track and the wheelbase through the changes of the caster angle during the operation of the suspensions.

[0130] In Summary, and contrary to the Prior Art (which proposes “static” apparatuses for the “fixed at a time” set-up of the caster angle in a motorcycle while it is stopped), the present invention differentiates itself in the following inventive steps:

[0131] 1. Provides the opportunity to alter the caster angle in real time, according to the exact behavioral demands of a moving motorcycle. 2. Explores, in certain embodiments, the full spectrum of dynamic parameters : which affect the kinetic response of a motorcycle, according to the external conditions which affect its performance,

Claims

CLAIMS1. A device for changing the caster angle of the front system (1) of a motorcycle by means of a articulated quadrilateral, the caster angle being determined by the relative position, in relation to the rest of the frame (4) of the motorcycle, of the member defining the position of steering shaft (5) of the motorcycle, hereafter referred to as the "carrier" (60), regardless of whether it is a single solid element, known as “carrier ” (6) or a pair of separate bearing elements, named “supports” (80) on which the steering shaft (8) is resting and characterized in that the carrier (60) of the steering shaft (5) of the aforementioned front system (1) is connected to the frame (4) of the motorcycle by means of two articulated links (14), so that a) the two links (14), b) the part of the frame (4) between the points of articulation of the links (14) to it and c) the part of the carrier (60) between the points of articulation of the links (14) to it, form an "articulated quadrilateral", wherein the relative position of the aforementioned carrier (60) in relation to the frame (4) is variable, in that the change in the relative position of the carrier (60) in relation to the frame (4) is determined by the respective state of an activator (15), which activator (15) consists of its primary member (15 A) and its secondary member (15B), wherein the secondary member (15B) moves relative to the primary member (15 A), when the activator ( 15) is operating, in that one of the two aforementioned members of the activator (15), primary (15 A) or secondary (15B), is connected to the frame (4) of the motorcycle while the other member of the activator (15) is connected to a movable point, moving simultaneously with the carrier (60), in that, when the activator (15) receives an electrical signal, from a Control Unit (11), it performs a movement of one of its members relative to the other and in that the relative movement between the primary (15 A) and secondary (15B) member causes a displacement of the carrier (60) around successive instantaneous centers of rotation, determined by the respective instantaneous positions of the members of the aforementioned articulated quadrilateral,modifying the relative position of the carrier (60) in relation to the frame (4) and thus changing the caster angle of the motorcycle from an initial value to a desired final value.

2. A device for changing the caster angle of the front system (1) of a motorcycle, by means of an articulated quadrilateral, according to claim 1 , characterized in that the operation of the aforementioned activator (15) is determined by an electrical signal sent by an electronic Control Unit (11) which receives and processes electrical signals relating to the instantaneous kinetic state of the motorcycle, coming from at least one sensor (12).

3. A device for changing the caster angle of the front system (1 ) of a motorcycle, by means of an articulated quadrilateral, according to claim 1 or 2, characterized in that the relative movement between primary (15A) and secondary (15B) members of the aforementioned activator (15) is caused by the operation of at least one electric motor (158) and which operation is: controlled by the aforementioned Control Unit (11).

4. A device for changing the caster angle of the front system (I) of a motorcycle, by means of an articulated quadrilateral, according to claim 3, characterized in that said electric motor (158) rotates at least one screw joint-bolt (23) whose rotation, in one or the other direction, fluctuates the caster angle, by moving the carrier (60), in one or the other direction of its movement.

5. A device for changing the caster angle of the front system (1) of a motorcycle, by means of an articulated quadrilateral, according to claim 4, characterized in that a pair of gears of the "worm / worm wheel" type is interposed between the electric motor (158) and the screw joint-bolt (23).

6. A device for changing the caster angle of the front system (1) of a motorcycle, by means of a articulated quadrilateral, according to claim 4, characterized in that the electric motor (158) of the primary member (15A) of the activator (15) is coaxially connected to the secondary member (15B) of the activator (15), by means of an "axially sliding spline" (26), so as to transfer torque from the electric motor to the secondary member (15B), and, at the same time, to allowaxial displacement of the secondary member (15B) in relation to the fixed primary member (15A), in that the secondary member (15B) of the activator (15) is formed in a screw (23) which runs through the interior of a nut (22) fixedly mounted on the primary member (15A), in that the forced rotation of the secondary member (15B), in one direction or the other, results in its "screwing" or "unscrewing" within the nut (22) resulting in its axial displacement along the spline (26) and in that the rotation of the electric motor (158) is carried out in response to a signal from the electronic Control Unit (11).

7. A device for changing the caster angle of the front system (1 ) of a motorcycle, by means of an articulated quadrilateral, according to claim 4, characterized in that the electric motor (158) of the primary member of the activator (15) has at its output a primary gear (28) meshing with a secondary gear (29) mounted on the secondary member (15B) of the activator (15), in that the secondary member (15B) of the activator (15) is formed into a screw (23) which passes through the inside of a nut (22) fixedly mounted on the primary member (15 A), in that the rotation of the primary gear (28) causes rotation of the meshed secondary gear (29) and, consequently, rotation of the secondary member (15B), in that the forced rotation of the secondary member (15B), in one direction or the other, results in the "screwing" or "unscrewing" of the screw joint-bolt (23) within the nut (22) resulting in its axial displacement, as well as the relative axial sliding between the teeth of the meshed gears (28), (29) and in that the rotation of the primary gear (28) by the electric motor (158) is carried out in response to a signal from the electronic control unit (11).

8. A device for changing the caster angle of the front system (1) of a motorcycle, by means of an articulated quadrilateral, according to claims 1 or 2, characterized in that the activator (15) is a hydraulic telescopic device and the movement between its primary (15 A) and secondary (15B) members is determined by the amount of fluid present, at any given moment of operation of the activator (15), within the chamber (152) of the activator (15).

9. A device for changing the caster angle of the front system (1 ) of a motorcycle, by means of an articulated quadrilateral, according to claim 8, characterized in that the primary member of the activator (15) consi sts of an outer shell enclosing a chamber (152) within which a piston / plunger (153) moves, which is part of the secondary member (15B), in that between the bottom (152A) of the chamber (152) and the front of the piston / plunger (153 A) a "return spring" (155) is interposed which reacts, elastically, to the movement of the piston / plunger (153) towards the bottom (152A) of the aforementioned chamber (152), in that the chamber (152) contains incompressible hydraulic fluid which moves in a controlled manner, between the chamber (152) and a reservoir (156), where the passage between the chamber (152) and the reservoir (156) has an electrically controlled valve, hereinafter referred to as "control valve" (154) which is controlled by an electronic Control Unit (11) and wherein the control unit (11) sends commands to the electromechanism of the aforementioned control valve (154) after receiving and processing a signal received from at least one sensor (12) regarding the instantaneous kinetic state of the motorcycle, in that at a specified moment, during the braking of the motorcycle on the straight line, the Control Unit (11) gives an “open" command to the control valve (154) to allow the passage of fluid from the chamber (152) to the reservoir (156), in that the deceleration external torque exerted on the front system (1) forces the articulated quadrilateral to change its shape, and therefore the relative position of the carrier (60) in relation to the frame (4) for as long as the control valve (154) allows fluid to pass from the chamber (152) to the reservoir (156), resulting in the contraction of the activator (15) and the compression of the return spring (155) until the desired degree of change in the caster angle is achieved, in that when the desired degree of change in the caster angle is achieved, the Control Unit (11) commands the control valve (154) to “close” in order to stabilize the desired extension of the secondary member (15B) and in that at a later time, where no braking of the motorcycle will occur, the Control Unit (11) commands the control valve (154) to open to allow fluid to return to the chamber (152) while the return spring (155) extends and moves the carrier (60), through the movement of the quadrilateral, to its "pre-braking" position.

10. A device for changing the caster angle of the front system (1) of a motorcycle, by means of an articulated quadrilateral, according to claim 8, characterized in that the primary member (15 A) of the activator (15) consists of an outer shell enclosing a chamber (152) in which a piston / plunger (153) moves which is part of the secondary member (15B), in that the chamber (152) contains an incompressible hydraulic fluid which moves, in a controlled manner, between the chamber (152) and a reservoir (156), in that a pump (157) supplies fluid to the chamber (152) via the non-retum valve (159) and while the control valve (154) is closed, the fluid displaces the piston / plunger (153) which, in turn, compresses a return spring (155) located within the primary member (15A), in that the aforementioned movement of the piston / plunger (153) results in a change of shape of the articulated quadrilateral, and the consequent rotation of the carrier (60) around an imaginary instantaneous rotation axis, towards a different caster angle, until a predetermined value is reached, based on the signal sent by the position sensor (120) to the Control Unit (11) and in that, when a reset of the caster angle to a previous value is required, the control unit (11) commands the control valve (154) to open, thereby allowing the piston / plunger (153), pushed by the return spring (155), to displace fluid towards the reservoir (156) until the position sensor (120) sends a signal to the Control Unit (11) that the carrier (60) has reached the desired caster angle.

11. A device for changing the caster angle of the front system (1 ) of a motorcycle, by means of an articulated quadrilateral, according to any one of claims 1 to 10, characterized in that the movable end of the activator (15) is hinged to a lever (17), which lever (17) is connected to the motorcycle frame (4) by means of a shaft (170) so as to rotate about the axis of said shaft (170), and in that the carrier (60) is connected to the aforementioned lever of an intermediate link arm (171).

12. A device for changing the caster angle of the front system (1) of a motorcycle, by means of a articulated quadrilateral, according to any one of claims 1-10, characterized in that at least one of the links (14) is connected via an articulated joint (141) to a lever (17) and said lever (17) rotates about an axle (131) via the action of an activator (15) whose movable end is connected to the aforementioned lever (17).

13. A device for changing the caster angle of the front system (1) of a motorcycle, by means of a articulated quadrilateral, according to any one of claims 1-10, characterized in that, at least one link (14) of the articulated quadrilateral is mounted "eccentrically ", via a joint (141) on a pivoting member (132) which has peripheral toothing (124) and which toothing is a member of a “worm / worm wheel type” pair of gears (123, 124, respectively) through which pair of gears an electric motor (158), connected with tlie worm gear (123), drives the aforementioned pivoting member (132) in order to obtain, by means of the displacement of the link (14), the desired caster angle.

14. A device for changing the caster angle of the front system (1) of a motorcycle, by means of a articulated quadrilateral, according to any one of claims 1-13, characterized in that the Control Unit (11) receives a signal from at least one sensor (12) regarding at least one parameter of the instantaneous kinetic and dynamic state of the motorcycle and in that at least one of the parameters of the kinetic and dynamic state of the motorcycle is speed, linear acceleration, linear deceleration, centripetal acceleration, transverse angle / tilt of the motorcycle, compression of the suspensions and 1 longitudinal angle / tilt of the motorcycle during the pitch and drop of the front of the motorcycle15. A device for changing the caster angle of the front system of a motorcycle, by means of a articulated quadrilateral, according to any one of claims 1- 14, characterized in that the Control Unit (11) receives a signal from at least one position sensor (120) regarding the current existing value of the caster angle and the Control Unit (11) calculates the actual caster angle, relative to the road surface, according to signals from sensors which monitor the state of compression / extension of thw front and the rear suspension of the motorcycle.

16. A device for changing the caster angle of the front system of a motorcycle, by means of an articulated quadrilateral, according to any one of claims 1 to 15, characterized in that the initiation of the process for changing the caster angle takes place at a time which is subsequent to the activation of a ’"start switch" by the rider of the motorcycle.

17. A device for changing the caster angle of the front system (1 ) of a motorcycle, by means of an articulated quadrilateral, according to any one of claims 1 -16, characterized in that the relative movement of the secondary (15B) to the primary (15A) member of the activator (15) depends on the coordinates of the instantaneous position of the motorcycle within a defined route, inside a race track, which route the motorcycle repeatedly laps along, in that the instantaneous position of the motorcycle within the aforementioned racetrack is determined by a satellite geographic coordinate system (GPS), which the motorcycle carries, in that the aforementioned GPS unit is connected to the digital Control Unit (11) of the activator (15), to which it sends signals, in real time, concerning the instantaneous position of the motorcycle, in that the digital Control Unit (11) is programmed to modulate its signal to the activator (15) according to the instantaneous position of the motorcycle on the aforementioned racetrack, and in that the aforementioned programming of the Control Unit (11) consists of a digital file stored in its memory, where the geographical coordinates of each point of the 'racing route’ within the race track are matched with the desired value of the caster angle.

18. A device for changing the caster angle of the front system (1) of a motorcycle, by means of an articulated quadrilateral, according to claim 17, characterized in that during the tests, prior to the race, the various caster angles at which the motorcycle is repeatedly driven through the same comer are recorded, in order to select the value of the caster angle at which the best time for driving through the comer was achieved.

19. A device for changing the caster angle of the front system (1) of a motorcycle, by means of an articulated quadrilateral, according to any one of claims 1-18, characterized in that the carrier (60) is connected, by a joint (13), to at least one rotating cylindrical “eccentric” (14A) which rests in a respective cavity of the frame (4), and which eccentric (14A) substitutes a link arm (14) extending, via respective joints (13), between the frame (4) and the carrier (60).

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