Device for changing the caster angle of the front system of the front system of a motorcycle

Abstract

A device for changing the caster angle of the front system (1) of a motorcycle, characterized in that the neck (6) through which the steering shaft (5) of the above mentioned front system (1) passes, is connected to the frame (4) of the motorcycle by a joint (13), in that relative position at any given time of the above mentioned neck (6) in relation to the frame (4) is changeable, determined by the current state of an actuator (15), consisting of its primary member (15 A) and its secondary member (15B), wherein the secondary member (15B) is moving in relation to the primary member (15 A), when the actuator (15) is working, so that the relative movement between the primary (15 A) and the secondary (15B) member causes an angular adjustment of the neck (6) around the joint (13), thereby changing the caster angle of the motorcycle from an initial value to a desired final value on the basis of an electrical signal sent by an electronic control unit (11) which receives and processes electrical signals relating to the current instantaneous kinetic state of the motorcycle derived from at least one sensor (12).

Description

[0001] DEVICE FOR CHANGING THE CASTER ANGLE OF THE FRONT SYSTEM OF A MOTORCYCLE

[0002] DESCRIPTION

[0003] The invention refers to a device for achieving a changeable, at will, driving behaviour of the motorcycle, through the management of two opposing and conflicting characteristics of the motorcycle, in real time:

[0004] A) Stability

[0005] B) Agility

[0006] This is achieved by using an innovative apparatus, which, depending on the motorcycle's current kinetic state, modifies a fundamental geometric characteristic of the motorcycle, that determines - for the most part - the motorcycle's road behavior.

[0007] STATE OF THE ART

[0008] Figure 1a illustrates the as of now called 'front system' (1) of a motorcycle, which in its most common commercial form is also called “fork”. This system basically consists of the suspension (2) of the front wheel (3) which, typically, is a telescopic device consisting of a fixed member (2A) and a sliding member (2B) and which inside contains springs and hydraulic dampers.

[0009] In general, the so called as ”front system” (1) of a motorcycle is an apparatus via which the front wheel is connected to the frame (4) of the motorcycle and consists of

[0010] (a) the suspension (2) which is, as previously described, usually of the 'telescopic' type and which contains the springs and the hydraulic dampers, which ensure that the front wheel rolls smoothly over the irregularities of the road surface.

[0011] (b) the steering system which allows, through a "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 the (imaginary) "steering axis" (5) in order to perform the desired change of orientation of the front wheel (3).

[0012] In summary, the front system (1) provides the front wheel axis with two degrees of freedom:

[0013] A) A "parallel, towards itself' movement of the shaft of the wheel, during compression and decompression of the telescopic suspension elements and

[0014] B) A rotation of the shaft 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 wheel.

[0015] Figure 1b also shows a (commercially available) alternative form of telescopic system (BMW's “Telelever”): 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 and the lower joint form a virtual support of the steering axis which, hereinafter, will be called as “virtual neck”.

[0016] It is obvious that the Telelever has a continuously varying “inclination angle” of its virtual steering axis according to the frame, during compression and decompression of the front suspension. And this angle depends solely and exclusively on the instantaneous position of the sliding member (2B) relative to the fixed member (2A) and not on the kinetic state of the motorcycle which, as will be exposed below, is the core of the present invention.

[0017] 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 orientation of the front wheel axle is such that the distance between the front and rear wheel axles is kept constant, and therefore the size of the motorcycle's wheelbase remains constant when the front suspension is compressed during its travel through the irregularities of the road surface.

[0018] Nowadays, the "Hossack-type" articulated front suspension (https: / / www.angelfire.com / biz5 / hossack / oldindex.html) has shown an excellent behavior (compared to conventional telescopic systems) as it is proved on the Britten motorcycles (https: / / en.wikipedia.org / wiki / Briten V 1000), an extremely limited production example.

[0019] 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).

[0020] Figure 3 shows the front of the motorcycle, when it is in a vertical position and in a standing position.

[0021] 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). As shown in the drawing, both the telescopic suspension system (2) and the axle (5) of the neck (6) are inclined relative to the horizontal level.

[0022] 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). 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.

[0023] 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).

[0024] 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 , (a) feasible,

[0025] (b) "industrially applicable" and c) innovative.

[0026] 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.

[0027] 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.

[0028] 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. 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 long 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. 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.

[0030] At first view, it could be said that the ideal caster angle is different for each different speed of the motorcycle.

[0031] But this is also just an '"approximate" view of reality.

[0032] 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.

[0033] 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 tyres, 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. 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] DETAILED DESCRIPTION OF THE INVENTION

[0037] The present invention relies on the innovative proposal of a continuously adjustable caster angle, on a moving motorcycle, based on a number of factors deriving from the instantaneous kinetic state of the motorcycle which are transmitted via electric signals to the apparatus which controls, in real time, the desired value of caster angle.

[0038] The implementation of the invention is based on an apparatus which connects the neck of the motorcycle to the frame, while the operation of the invention is based on the (innovative) utilization of known components of the State of the Art, most of which are commercially available for other appliances.

[0039] The fundamental mechanical concept of the present invention (Figure 4) consists in the fact that the neck (6) through which the steering shaft (5) passes is not permanently mounted on the frame (4) but is connected to it by a joint (13) which act as the fundamental pivot via which the present invention is realized.

[0040] Figure 4a illustrates the connection of the neck (6) with the frame, where the neck is directly connected to the frame via a joint (13) that provides a single Degree of Freedom (i.e. the angular movement of the neck around the imaginary axis of this joint),

[0041] In accordance with the fundamental mechanical apparatus of the present invention, the way of changing the caster angle is illustrated, simplistically, in Figure 4b.

[0042] In this demonstrative example, the current relative position of the neck (6) in relation to the frame (4) depends on the respective state of an actuator, which actuator (15) is positioned (in this example) directly between the frame (4) and the neck (6) and, through its varying length, redefines, in real time, the relative position of the neck (6) in relation to the frame (4) according to the commands received from an electronic unit (11). An electronic unit, named hereinafter as Control Unit (11) receives signals (relating to the instantaneous kinetic state of the motorcycle) from at least one sensor (12) or, in complex applications, from a number of sensors. The actuator, according to the present invention, may be either

[0043] (A) Passive, wherein the activation is performed by “external” forces applied to the neck due to a specific kinetic state of the motorcycle (e.g. braking).

[0044] (B) Active, where its operation is based on the activation of an electric motor or an electric fluid pump.

[0045] 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) so as to demonstrate that its feasibility is not univocal but, on the contrary, there are unlimited alternative versions which are offered, arising from the same operating principle. Accordingly, the same procedure is applied for the controlling of the momentary value of caster angle in motorcycles where the support of the front system is performed via a “virtual neck” and not by a “solid tube”. Hereinafter the word “neck”, according to the spirit of the present invention, will corresponds to any type of neck, solid or virtual.

[0046] Figure 5 illustrates a first, indicative, example of a "passive actuator", which has a telescopic structure and hydraulic operation.

[0047] Figure 5a illustrates a recommended position of the passive actuator (15), between frame (4) and neck (6), where the kinetic relation betwwen neck and frame is of "one degree of freedom", as usual, while Figure 5b illustrates, indicatively, the individual elements on which the operation of this passive actuator is based.

[0048] The actuator (15) consists of a primary member (15A) and a secondary member (15B) which can, under specified conditions, move relative to each other, thereby changing the total length of the actuator between its two ends (150A and 150B).

[0049] 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 a part of the secondary member (15B).

[0050] Between the bottom (152 A) of the chamber (152) and the forehead of the piston / plunger (153 A) a spring is interposed, hereinafter referred to as the '"return spring" (155), which reacts flexibly to the movement of the piston / plunger (153) towards the bottom (152A) of the aforementioned chamber (152). The chamber (152) contains incompressible hydraulic fluid which, under conditions to be explained later, 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) ('"control valve") which, in tum, is controlled by a digital control unit (11) which sends commands to the electromechanical controller of the valve (154) after receiving and processing a signal from at least one sensor (12) regarding the instantaneous kinetic state of the motorcycle.

[0051] The operation of the above-mentioned device is as follows:

[0052] During the braking of the motorcycle, on straight line, there is the (largely abusive, as will be explained later) assumption that the motorcycle is about to execute a change of direction, at a new speed which is reduced in comparison 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.

[0053] 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, a bending moment +(M) is applied to the front system (Figure 5c) due to the braking force (F) developed at the point of contact of the wheel (3) with the road. As a result of this torque, the neck (6) tends to rotate around its joint (13) (clockwise, in this illustration) and compress the actuator (15). While the Control Unit is holding the valve (154) open, the secondary member (15B) enters the chamber (152) reducing the total length of the actuator (15), therefore the caster angle, since the neck (6) is allowed to perform a controlled micro-rotation around its joint (13).

[0054] 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.

[0055] The Control Unit (11) then monitors, via the sensor (12), the end of the condition that has dictated the need to reduce the caster angle. Thus, 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 (to the right in the illustration). This piston / plunger (153), in tum, 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.

[0056] Figure 5d illustrates a simplified version of that of Figure 5b 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 configured to undergo equal volume fluid inflows and outflows, to and from the chamber (152) and the reservoir (156).

[0057] The oversimplified "passive" system just described has the unique advantage of simplicity and low cost.

[0058] 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 a braking force is applied at the point of contact between the front wheel and the road surface.

[0059] Therefore, the Control Unit is not able to distinguish whether the braking being applied is due to the rider's intention 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.

[0060] Of course, the aforementioned speed sensor may enable the control unit to detect deceleration (from whatever source), but it cannot enable the device to operate while no braking is applied to the front wheel.

[0061] For the abovementioned reasons, the present invention suggests, also, an alternative 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.

[0062] This implementation can be carried out with unlimited variations of active actuators, largely derived from (different types of) applications of the State of the Art, one of which is indicated (indicatively and non-binding) in Figure 6.

[0063] In Figure 6, a pump (157) supplies fluid to the chamber (152) through the non-retum 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), 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.

[0064] 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 displacing spring and not by means of the pump, whose response has a time lag. Instead, the pump is used to increase the caster angle which, upon acceleration of the motorcycle, exhibits a lower rate of change of its gradual increase requirements. Since, at times, hydraulic devices may "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.

[0065] Figure 7 illustrates, indicatively, a number of recommended electric actuators although, obviously, the range of potentially applicable types of actuators of this type is not limited to these three.

[0066] Figure 7a illustrates an actuator (15) whose primary member (15 A) comprises an outer shell (25), which includes a stepping electric motor (158) “step-motor”, according to its commercial name) whose output shaft is formed as a spline (26).

[0067] On the shell (25) of the primary member (15A) there is mounted an "output thread" in the form of a nut (22) which is fixedly attached to the primary member (15 A).

[0068] 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 a spline (26). At its other end, it is connected to the neck (6) with a joint (130) -and preferably with a ball joint.

[0069] When it is commanded -by the Control Unit (11)- to increase the caster angle, in this particular, indicative example, the electric motor (158) is turning in a 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) away from the frame (4) and thus increasing the caster angle.

[0070] 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.

[0071] Figure 7b illustrates an 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 a "worm- worm wheel pair of gears”.

[0072] Figure 7c illustrates a different arrangement from that shown in Figure 7b, wherein the spline has been replaced by a rotating pin carrier (26B) where the pins (26A) slide axially inside the worm wheel (124) during the rotation of the pin earner (26B).

[0073] It is obvious 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.

[0074] Figure 8 illustrates an alternative form of the aforementioned "screw" electromechanical actuator (15) where this particular implementation aims at avoiding the existence of a spline and its consequent static friction over time.

[0075] 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). 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 (15 A).

[0076] 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 (" physical" or "notional" 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).

[0077] Figure 9 illustrates a support of the neck (6) by means of an intermediate "link arm" (14) and the engagement of the actuator (15) through a lever (130) -which is rotating around an axis (131)- on which lever (130) the aforementioned link (14) is connected.

[0078] Figure 10 shows the aforementioned lever (130) in the form of a crank (132), rotating about an axis (131), inside a bearing (133) mounted on the frame (4).

[0079] Figure 11 illustrates , indicatively, an alternative arrangement of figure 10 where the connection between the actuator (15) and the crank (132) is made via a “worm-worm wheel” pair of gears, wherein the screw (123) is rotated by an electric motor (158) and is part of the primary member (15 A) of the actuator (15), while the secondary member (15B) starts from the contact with the screw (123) of the toothed gear (124) which gives rotational movement to the crank (132) and ends at the joint (13) of the "follower" (138).

[0080] In order to prove that the spirit of the present invention can be applied to any type of front system for a motorcycle, Figure 12 illustrates -indicatively, also- an application of the present invention to a motorcycle where a “virtual neck” supports its front system.

[0081] In this exemplary case, the device of Figure 11 is applied to the suspension with the trade name "BMW Telelever", which is already described, with reference to Figure lb. In this indicative embodiment, the rotation of the lever arm (130) about its axis (131) by the actuator (15) causes a controlled displacement of the bearing axis (41) of the awing arm (40). Consequently, the arm (40), via its lower ball joint (400), moves (“forward” or “backward”) the lower edge of a “virtual neck” providing, therefore, the desired change of the caster angle by the angular motion of said “neck” around a [pivot which, in this case, is the upper joint (180). The same application, obviously, may be implemented by means of a crank, as in figure 10, while, alternatively, the movement of said crank may result from a “worm / worm wheel” pair of gears of figure 11 rotated by the electric motor (158). All the above can be applies also in the case of a “Hossack” type system, as described according to Fig 1c. These alternative embodiments are mentioned in order to illustrate the inexhaustible different possibilities of implementing the present invention by combining elements already presented or arising, in an obvious manner, while remaining in the spirit of the invention.

[0082] 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.

[0083] 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:

[0084] 1. Caster angle for straight line stability and

[0085] 2. Caster angle for agility in changes of direction.

[0086] It is understood, of course, that the proposed device, in all its suggested variations, can satisfy much more complex requirements.

[0087] Example:

[0088] 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.

[0089] 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.

[0090] 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, either for simple transportation or for "sport-recreation" riding. For example, racing riders - on a racetrack - tend to apply prolonged braking, right up to the apex of the comer, while they have already given their bike a big lean.

[0091] 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.

[0092] 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.

[0093] 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 earned out under the following status:

[0094] 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.

[0095] 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 corner of the track and retrieves from its digital memory the appropriate caster angle which is already programmed for that corner. (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).

[0096] SPECIAL CASES OF APPLICATION OF THE INVENTION

[0097] 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.

[0098] 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. 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.

[0099] 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.

[0100] The present invention has the potential to provide the motorcycle with the desired optimal 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.

[0101] 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).

[0102] In this way, a much better management of the stability of the front system can be achieved, aiming at managing, also, the values of the front system track and the wheelbase through the changes of the favored value of caster angle during the operation of the suspensions and providing the best synthesis of stability parameters..

[0103] In Summary, and contrary to the Prior Art (which proposes “static” apparatuses for the “fixed, once at every time” set-up of the caster angle in a motorcycle while it is stopped, motionless), the present invention differentiates itself in the following inventive steps:

[0104] 1. Provides the opportunity to continuously alter the caster angle in real time, according to the exact behavioral demands of a MOVING motorcycle.

[0105] 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.

[0106] 3. It can be applied on any known type of front suspension / steering system.

Claims

CLAIMS1. A device for changing the caster angle of the front system (1) of a motorcycle, the caster angle being determined by the relative position, in relation to the rest of the frame (4) of the motorcycle, of that member which defines the position of the steering axis (5) of the motorcycle, and the aforementioned member hereinafter referred to as the "neck" (6) and characterized in that the neck (6), through which the position of the steering axis (5) of the aforementioned front system (1) is determined, is connected to the frame (4) of the motorcycle, in such a way that the relative position of the aforementioned neck (6), in relation to the frame (4), is variable, in that there is a direct connection of the neck (6) with the frame (4) via a pivot and an indirect connection of the neck (6) with the frame via a device called hereinafter, as “actuator” (15), in that the variation of the relative position of the neck (6) in relation to the frame (4) is determined by the current state of said actuator (15), which actuator (15) comprises a primary member (15A) and a secondary member (15B), wherein the secondary member (15B) moves in relation to the primary member (15A) when the actuator (15) is operated, in that one of the two aforementioned members of the actuator (15), primary (15 A) or secondary (15B), is connected to the frame (4) of the motorcycle while the other member of the actuator (15) is attached on a connection with the neck (6), in that when the actuator (15) receives an electrical signal, performs a motion of one of its members relative to the other and in that the relative movement between primary (15A) and secondary (15B) members causes an angular displacement of the neck (6) around the said pivot, 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 according to claim 1 , characterized in thatthe operation of the aforementioned actuator (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 of a motorcycle according to claim 1 or 2, characterized in that the relative movement between primary (15 A) and secondary (15B) members of the aforementioned actuator (15) is caused by the operation of at least one electric motor (158) and which operation is controlled via electrical signals sent by the aforementioned Control Unit (11).

4. A device for changing the caster angle of the front system of a motorcycle (1), according to claim 3, characterized in that the electric motor (158) rotates at least one screw (23) which passes through the static nut (22) attached on the actuator (15) and said screw (23) has a connection with the neck and the rotation, in one direction or the other, of said screw (23) increases or reduces the caster angle by means of the axial displacement, in one direction or the other, of its movement where, said movement results in an angular displacement of the neck around its pivot..

5. A device for changing the caster angle of the front system of a motorcycle (1), 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 (23).

6. A device for changing the caster angle of the front system (1) of a motorcycle, according to claim 4, characterized in that the electric motor (158) of the primary member (15A) of the actuator (15) is coaxially connected to the secondary member (15B) of the actuator (15), by means of an "axially sliding member” and, preferably, a spline (26), so as to transmit torque from the electric motor to the secondary member (15B), and, at the same time, to allow axial displacement of the secondary member (15B) in relation to the fixed primary member (15 A), in thatthe secondary member (15B) of the actuator (15) is formed as a screw (23) which runs through the interior of a nut (22) which is fitted to the primary member (15 A), 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) causing its axial displacement along said axially sliding member and in that the rotation of the electric motor (158) is performed 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, according to claim 4, characterized in that the electric motor (158) of the primary member (15 A) of the actuator (15) has at its output a primary gear (28) meshed with a secondary gear (29) attached to the secondary member (15B) of the actuator (15), in that the secondary member (15B) of the actuator (15) is connected to said secondary gear (29) and is formed as a screw (23) which runs through the interior of a nut (22) which is attached to the primary member (15 A), in that the rotation of the primary gear (28) causes rotation of the meshed secondary gear (29) and, consequently, the rotation of the secondary member (15B), in that the forced rotation of the secondary member (15B), in one or the other direction, results in the "screwing" or "unscrewing" of the screw (23) within the nut (22) resulting in its axial displacement, as well as the relative axial sliding between the teeth of the gears (28), (29) involved and in that the rotation of the primary gear (28) by the electric motor (158) is performed 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, according to claims 1 or 2, characterized in that the actuator (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 moment of operation of the actuator (15), within the chamber (152) of the actuator (15).

9. A device for changing the caster angle of the front system (1) of a motorcycle, according to claim 8, characterized in that the primary member of the actuator (15) consists of an outer shell which encloses 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 (153A) there is a "return spring" (155) which reacts, elastically, to the movement of the piston / plunger (153) towards the bottom (152 A) of the aforementioned chamber (152), in that the chamber (152) contains an incompressible hydraulic fluid which moves, in a controlled manner, between the chamber (152) and a reservoir (156), wherein the passage between the chamber (152) and the reservoir (156) has an electrically controlled valve, hereafter referred to as a "control valve" (154) which is controlled by an electronic Control Unit (11) and wherein the Control Unit (11) sends commands to the electro-mechanism of the aforementioned control valve (154) after receiving and processing signals received from at least one sensor (12) regarding the instantaneous kinetic state of the motorcycle, in that at a certain 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 passing of fluid from the chamber (152) to the reservoir (156), in that the decelerating bending moment applied to the front system (1) forces the neck (6) to rotate around its pivot for as long as the control valve (154) allows fluid to pass from the chamber (152) to the reservoir (156), resulting in the actuator (15) contracting, the return spring (155) being compressed until the desired degree of change in the caster angle is achieved 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 neck (6) to its "pre-braking" position.

10. A device for changing the caster angle of the front system (1) of a motorcycle, according to claim 8, characterized in that the primary member (15 A) of the actuator (15) consists 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 the chamber(152) contains incompressible hydraulic fluid which moves between the chamber (152) and a reservoir (156) in a controlled manner, 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 (15 A), in that the aforementioned movement of the piston / plunger (153) results in the neck (6) rotating around its joint (13) towards a larger caster angle until a predetermined value is reached, on the basis of the signal sent by the position sensor (120) to the Control Unit (11), and in that when a reduction in the caster angle is required, the Control Unit (11) commands the control valve (154) to open, thereby allowing the piston / plunger (153) to be pushed by the return spring (155) and the fluid to return in 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.

11. A device for changing the caster angle of the front system (1) of a motorcycle according to any one of claims 1 to 10, characterized in that the movable end of the actuator (15) is hinged to a lever (130), which lever (130) is connected to the motorcycle frame (4) by means of a joint so as to rotate about an axis ( 131 ), and in that the neck (6) is connected to aforementioned lever (130) by means of an intermediate link arm (14).

12. A device for changing the caster angle of the front system (1) of a motorcycle, according to any one of claims 1-10, characterized in that the movable end of the actuator (15) is hinged on a circular carrier, hereinafter referred to as "crank" (132), rotating about an axis (131) and in that the neck (6) is connected to the aforementioned crank (132) by means of an intermediate link arm (14).

13. A device for changing the caster angle of the front system (1) of a motorcycle, according to any one of claims 1-10, characterized in thatthe neck (6) is connected by means of a "follower" link (138) to a rotating around axis (130) carrier, hereinafter referred to as "crank" (132), , in that the crank (132) is provided with peripheral toothing (124) and in that the connection of the crank (132) to the electric motor (158) is made by a pair of "worm-worm wheel" type gears, where the aforementioned toothing (124) is formed on one of the two aforementioned gears.

14. A device for changing the caster angle of the front system (1) of a motorcycle, 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 of the parameters of the instantaneous kinetic and dynamic state of the motorcycle, and in that at least one of the parameters of the kinetic / dynamic state of the motorcycle is the speed, the linear acceleration, the linear- deceleration, the centripetal acceleration, the transverse angle / tilt of the motorcycle, the longitudinal angle / tilt during diving or rebound of the front of the motorcycle, the degree of compression of each of the suspensions, the status of action from the rider on the brake system.

15. A device for changing the caster angle of the front system (1) of a motorcycle, 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) with respect to the current value of the caster angle in relation to the frame (4) and performs calculations, according to signals of sensors which monitor the state of the momentarily compression of the suspensions, in order to extract the value of caster angle relatively to the road surface.

16. A device for changing the caster angle of the front system (1) of a motorcycle, according to any one of claims 1 to 15, characterized in thatthe initiation of the process for changing the caster angle takes place at a moment in time which follows 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, according to any one of claims 1 to 16, characterized in that the relative movement of the secondary (15B) to the primary (15 A) member of the actuator (15) depends on the coordinates of the instantaneous position of the motorcycle within a predefined route (race track) onto which route the motorcycle laps repeatedly, in that the instantaneous position of the motorcycle within the aforementioned race track is determined by a satellite geographic coordinate system (GPS) signal receiving unit, which GPS unit is carried by the motorcycle, in that the aforementioned GPS unit is connected to the electronic Control Unit (11) of the actuator (15), to which it sends signals, in real time, concerning the instantaneous position of the motorcycle, in that the Control Unit (11) is programmed to vary its signal to the actuator (15) according to the instantaneous position of the motorcycle within the aforementioned racetrack and in that the aforementioned programming of the Control Unit (11) consists of a file stored in its memory in which the geographical coordinates of each point of the “racing route”, within the racetrack, are matched with the desired caster angle value for each separate section of the track.18 A device for changing the caster angle of the front system (1) of a motorcycle, according to claim 17, characterized in that during the tests, prior to the race, a record is made of the various caster angles at which the motorcycle was repeatedly driven through the same comer, in order to select the value of the caster angle at which the best time through that comer was achieved.19 A device for changing the caster angle of the front system (1) of a motorcycle, according to any one of the claims 1 to 18,where the steering axis (5) is supported via a “virtual neck”, hereinafter called as neck, which consists of an upper joint (180) and a lower ball joint (400) which lower joint (400) is mounted to the front edge of a swing arm (40) which is attached to the movable member of the front suspension and said swing arm (40) performs angular movements around the axis of a bearing shaft (41) according to the movements of the front suspension and is characterized in that said bearing shaft (41) of the swing arm (40) is carried on an intermediate rotating member which is connected to the frame (4) of the motorcycle via a shaft and performs angular movements around its axis (131) and the shape of said rotating member is selected among a lever (130) and a crank (132), in that between said rotating member and the frame (4) is interposed an actuator (15) which actuator (15) rotates said rotating member according to commands sent from a Control Unit (11) and in that the angular movement of said rotating member displaces the bearing shaft (41) and consequently the center of rotation of the arm (40), moving, in space, the related joint (400) and, consequently, changing the position of the imaginary steering axis (5) of the front system (1), thus changing the caster angle, via an enforced angular movement of said “neck” around said upper joint (180) which is the aforementioned pivot of the neck.

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