Motorcycle gearbox

Abstract

The invention relates to a motorcycle gearbox provided with: a cam selector drum (2), rotatable about an axis (2a) through rotational steps determined to sequentially reach the positions corresponding to a plurality of gears and a neutral gear; a stop element (3), integral with the cam selector drum (2) and indexed to the position corresponding to the neutral gear; a locking element (4), cooperating with the stop element (3) to block the rotation of the cam selector drum (2) and prevent the neutral gear from being reached or passed through; and a control device (5), which is positioned and configured to interact with the locking element (4) and is operable by the motorcyclist to release the rotation of the cam selector drum (2) and allow the neutral gear to be reached or passed through. The locking element (4) is defined by the rod (6) of a piston (7) with variable configuration and the control device (5) is adapted to give the piston (7) a first configuration having a first end stop, which allows the neutral gear to be reached or passed through, or, alternatively, a second configuration having a second end stop, of different longitudinal extension with respect to the first end stop, which prevents the neutral gear from being reached or passed through; the stroke of the rod (6) towards the bottom of the piston (7) being determined by the thrust of the stop element (3) on the rod (6) following the rotation of the selector drum (2).

Description

[0001] DESCRIPTION

[0002] MOTORCYCLE GEARBOX

[0003] Technical field

[0004] The present invention relates to a motorcycle gearbox.

[0005] In the context of the present invention, the term motorcycle is generically understood as a motor vehicle with two or more wheels provided with a saddle to be mounted, preferably straddled, which defines the driving position of the motorcyclist.

[0006] Background art

[0007] Evidently, motorcycles are commonly provided with a pedal gearbox shift lever that is operable by the motorcyclist, through the foot, to control a cam selector drum for sequentially engaging the gears.

[0008] The sequence of lever positions, to which the respective angular positions of the selector drum and thus the respective gears correspond, is commonly referred to as the "shift pattern".

[0009] The most widespread shift pattern is the one that has the position corresponding to the neutral gear (or even simply "neutral"), interposed between the position corresponding to the first gear and the position corresponding to the second gear.

[0010] For example, in a six-gear gearbox, a shift pattern of the type indicated above has the sequence 1 -N-2-3-4-5-6, where N (neutral) indicates the neutral position and 1 , 2, 3, 4, 5, 6 indicates the positions of the first, second, third, fourth, fifth, sixth gear, respectively.

[0011] In such a configuration, usually the first gear is selected by pushing the pedal lever down from the position corresponding to neutral, while all other gears are selected upwards by raising the lever up with the foot and are selected downwards by pushing the lever down with the foot. Therefore, position 1 (corresponding to the first gear) is the lowest position of the pedal lever while position 6 (corresponding to the sixth gear) is the highest position. Such a configuration is also known in jargon as "1 down-all up". The vast diffusion of the shift pattern that includes the position corresponding to neutral interposed between the position corresponding to the first gear and the position corresponding to the second gear, in particular in the 1 down-all up configuration, derives from a standardization decided in the mid-1970s for safety reasons, introduced to eliminate the possibility of inadvertently selecting neutral by pushing the gear lever downwards beyond the position of the first gear.

[0012] In fact, in the 1960s and even in the early 1970s, shift patterns of the all- up type were very common, with the position corresponding to neutral at the bottom of the sequence of gearbox lever positions.

[0013] With such a configuration, found for example in Kawasaki Mach IV H2 750, produced from 1971 to 1975 and provided with a gearbox having a shift pattern N-1 -2-3-4-5, the motorcyclist could inadvertently insert neutral while braking, downshifting quickly, with the risk of falling.

[0014] If, on the one hand, the shift pattern that includes the position corresponding to neutral at the bottom of the sequence of positions of the gearbox lever allows an easy identification and selection of neutral, although to the detriment of safety, on the other hand, the shift pattern that includes the position corresponding to neutral interposed between the position corresponding to the first gear and the position corresponding to the second gear, which is safer, does not allow an easy identification and selection of neutral, as the latter is positioned "in transit" between the first and second gears. In fact, it may happen that the motorcyclist, in an attempt to select neutral, unintentionally passes from first gear to second gear or vice versa.

[0015] Both drawbacks have been solved by selector drum stop devices configured to be able to block / release the rotation thereof so as to prevent / allow neutral gear to be reached or passed through and operable by the motorcyclist through a block / release command mounted on the handlebar of the motorcycle.

[0016] For example, a solution has been proposed by patent US6487927, according to which, through a device mounted on the handlebar, the motorcyclist can command a solenoid or a mechanical drive to impart, against the opposing action of a spring, the axial movement of a piston rod to block / release the rotation of the selector drum. The rod, in the radial movement thereof with respect to the selector drum, can cooperate with a recess (blind hole) or with a radial projection (tooth) of the selector drum itself.

[0017] In other words, patent US6487927 describes a motorcycle gearbox comprising:

[0018] - a cam selector drum, rotatable about an axis through rotation steps determined for sequentially reaching the positions corresponding to a plurality of gears and a neutral gear;

[0019] - a stop element on the cam selector, in the form of a blind hole or a tooth, indexed to the position corresponding to the neutral gear;

[0020] - a locking element, in the form of a piston rod, cooperating with the stop element to block the rotation of the cam selector and prevent the neutral gear from being passed through (starting from the first gear or from the second gear); and

[0021] - a control device of the locking element, operable by the motorcyclist to disengage the stop element from the locking element, releasing the rotation of the cam selector and allowing the neutral gear to be passed through (starting from the first gear or from the second gear).

[0022] A different solution has been proposed by patent application W02020 / 194108, in particular with reference to a shift pattern of the type in which the position corresponding to neutral is arranged at one end of the sequence of positions corresponding to the gears.

[0023] According to such a solution, instead of the linearly moving blocking / release rod, radially with respect to the selector drum, an oscillating element is provided which is capable of rotating about a rotation axis thereof by virtue of a system of levers. In this case, the oscillating element cooperates with a radial projection (tooth) of a bushing integral with the selector drum and the release of the rotation of the selector drum occurs following a spacing of the oscillating element from the radial projection. A control device of the locking element is also included here, which can be operated by the motorcyclist to disengage the stop element (the radial projection) from the locking element (the oscillating element), in this case to release the rotation of the cam selector and allow the neutral gear to be reached (starting from the first gear).

[0024] Further solutions for blocking / releasing the rotation of the selector drum are known from patents US8438942, US7854178 and patent application JP2014199104 A.

[0025] All of the above known solutions are relatively complex and expensive. They are also unreliable due to the complexity thereof, in particular the versions with oscillating elements, which are more subject to clearances over time, which can lead to jamming in the blocking or release operations.

[0026] Object of the invention

[0027] The object of the present invention is to provide a motorcycle gearbox which, in a simple and reliable manner, allows blocking / releasing the rotation of the selector drum thereof to prevent / allow the neutral gear to be reached or passed through.

[0028] Said object is fully achieved by the motorcycle gearbox that is the subject of the present invention, which is characterized by the contents of the claims below.

[0029] Brief description of the drawings

[0030] The features of the finding will be more apparent from the following description of a preferred embodiment, shown merely by way of nonlimiting example in the accompanying drawings, in which:

[0031] - Figure 1 is an exploded view of a component of a motorcycle gearbox made in accordance with the present invention;

[0032] - Figure 1A is a diagrammatic perspective view of a cam selector drum cooperating with the piston 7 with variable configuration; and

[0033] - Figures 2 to 6 show respective different operating steps of the component of Figure 1 .

[0034] According to what is illustrated in the accompanying figures, a motorcycle gearbox is shown overall with the reference numeral 1 .

[0035] Detailed description of preferred embodiments of the invention

[0036] The gearbox 1 is shown only in the parts thereof which are the subject of the present invention, and in particular a selector drum 2 is shown with a cam rotatable about a central axis 2a through predetermined rotational steps to sequentially reach the positions corresponding to a plurality of gears and a neutral gear (or simply neutral).

[0037] In particular, the selector drum 2 has an end disc, indicated as well as selector drum 2.

[0038] The motorcycle, not shown, is provided with a pedal gearbox shift lever, which is operable by the motorcyclist via the foot to control, in a known manner, the cam selector drum 2 for sequentially engaging the gears.

[0039] For example, the gearbox 1 can be six-speed with a sequence of the type 1 -N-2-3-4-5-6, where N (neutral) indicates the neutral position of the pedal lever and 1 , 2, 3, 4, 5, 6 indicate the positions referring to the first, second, third, fourth, fifth, sixth gear, respectively, or of the type N-1 -2-3-4-5-6, typically used in motor racing. Furthermore, the sequence can be run in the so-called "standard" direction, i.e., with successive lifts of the pedal lever, or in the reverse manner, as in the case of so-called "inverted gears" for more sporty motorcycles.

[0040] Of course, the invention can also be applied if there are more or less than six gears.

[0041] In addition to the drum 2, the gearbox 1 comprises a stop element 3, integral with the cam selector drum 2 and indexed to the position corresponding to the neutral gear, and a locking element 4, cooperating with the stop element 3 to block the rotation of the cam selector drum 2 and prevent the neutral gear from being reached or passed through.

[0042] The gearbox 1 further comprises a control device 5 (Fig. 6), which is positioned and configured to interact with the locking element 4 and which can be operated by the motorcyclist to release the rotation of the cam selector drum 2 and allow the neutral gear to be reached or passed through.

[0043] The locking element 4 is defined by the rod 6 of a piston 7 with variable configuration.

[0044] The control device 5 is designed to give or allow the piston 7 a first configuration having a first end stop (Fig. 6) which allows the neutral gear to be reached or passed through, or, alternatively, a second configuration having a second end stop (Fig. 5) of different longitudinal extension with respect to the first end stop, which prevents the neutral gear from being reached or passed through.

[0045] Therefore, the two alternative configurations of the piston 7 derive from the two possible end stops which can be taken by the piston 7 itself, as a result of the different operating states thereof.

[0046] As will become clearer below, the stroke of the rod 6 towards the bottom of the piston 7 is determined by the thrust of the stop element 3 on the rod 6 following the rotation of the selector drum 2. In particular, the stop element 3 pushes, causing a rolling thereof about the central axis thereof, an end ball 6a of the rod 6, which is opposite the bottom of the piston 7. In other words, the rod 6 is provided with a ball tip and the contact with which the rod 6 and the stop element 3 cooperate with each other in the movement of the rod 6 is a rolling contact adapted to favor the mutual sliding of the contact surfaces. This reduces the chance of jamming and reduces wear on the parts.

[0047] The linear movement of the rod 6 occurs along a radial direction of the selector drum 2. That is, the longitudinal axis of the piston 7 is arranged along a radial direction of the selector drum 2.

[0048] The second end stop has a smaller longitudinal extension than the first end stop. The second end stop can be configured to allow the rod 6 to have a stroke substantially equal to zero starting from a position (Fig. 5) in which the rod 6 cooperates, or begins to cooperate, with the stop element 3 in blocking the rotation of the selector drum 2. It may be preferable that such a stroke is not exactly zero to allow the absorption of manufacturing and assembly tolerances, however, it is also preferable that such a stroke is very small, for example a few tenths or a few millimeters, to limit an empty stroke of the rod 6 starting from the position thereof (Fig. 5) in which it cooperates, or begins to cooperate, with the stop element 3 in blocking the rotation of the selector drum 2 (Fig. 5).

[0049] Preferably, the position of the rod 6 in which the latter cooperates, or begins to cooperate, with the stop element 3 in blocking the rotation of the selector drum 2 corresponds to the position of maximum extraction of the rod 6 from the piston 7 (Fig. 5).

[0050] In the example described below, with reference to the accompanying figures, reference will be made to a sequence (shift pattern) of the type N- 1 -2-3-4-5-6. In particular, by way of a purely non-limiting example, reference will be made to a sequence of gears travelled with successive lifts of the pedal lever. Observing Figures 2 to 6, the gears are selected sequentially upwards following certain rotation steps performed counterclockwise.

[0051] In such a gear arrangement, in which the position corresponding to neutral is arranged at one end of the sequence of positions corresponding to the gears, the aforementioned first end stop allows the neutral gear to be reached (starting from the first gear), while the second end stop prevents the neutral gear from being reached (starting from the first gear). In such a case, the stop element 3 is preferably in the form of a tooth 8 integral with the cam selector drum 2, i.e., made on the drum 2 or on a disc integral with the drum 2. Such a tooth 8 centrally has a depression 3a between two humps 3b, 3c which give it a saddle-like shape. The depression 3a defines a stable position for receiving the end of the rod 6 (ball 6a), corresponding to the neutral gear.

[0052] In a different gear arrangement, not shown, in which the position corresponding to the neutral gear is interposed between the position corresponding to the first gear and the position corresponding to the second gear (shift pattern of the type 1 -N-2-3-4-5-6), the aforementioned first end stop allows the neutral gear to be passed through (from the first to the second gear and vice versa), while the second end stop prevents the neutral gear from being passed through (from the first to the second gear and vice versa). In such a case, the stop element can preferably be in the form of a cavity integral with the cam selector drum, i.e., made on the drum or on a disc integral with the drum.

[0053] In the example described below with reference to the accompanying figures, the locking element 4, i.e., the rod 6, cooperates with the stop element 3 to unidirectionally block the rotation of the cam selector drum 2 and prevent the neutral gear from being reached starting from the first gear. In such a context, the first end stop allows the neutral gear to be reached starting from the first gear, while the second end stop prevents the neutral gear from being reached starting from the first gear. In particular, the first end stop allows the neutral gear to be reached starting from the first gear but also vice versa.

[0054] The piston 7 further comprises a hollow cylinder 9, inside which the rod 6 is slidably coupled, and a first spring 10, which is interposed between the bottom of the cylinder 9, in particular defined by a cap 9a, and the bottom of the rod 6, i.e., it is interposed between the bottom of the cylinder 9 and the end of the rod 6, which is opposite the end ball 6a of the rod 6 itself.

[0055] The cylinder 9 is positioned in a fixed position, facing the lateral periphery of the selector drum 2, with the longitudinal axis thereof transverse to the axis 2a of the selector drum.

[0056] In the aforementioned position of maximum extraction of the rod 6 from the piston 7, the spring 10 pushes the end ball 6a of the rod 6 into abutment against the edge of a circular retaining mouth 11 of the cylinder 9, which ensures a partial exit of the ball 6a from the cavity of the cylinder 9 while preventing the total exit thereof (Figures 4 and 5).

[0057] In the aforementioned stable position, corresponding to the neutral gear, in which the ball 6a of the rod 6 is received in the depression 3a of the tooth 8 (Figure 2), the spring 10 pushes the ball 6a on the tooth 8, centrally with respect to the aforementioned depression 3a. In such a position, the rod 6 is slightly recessed in the piston 7 with respect to the aforementioned position of maximum extraction. In fact, such a position is ensured and maintained by the thrust action of the spring 10

[0058] The second end stop is defined by at least one obstructing element 12, radially and partially extractable from the inner periphery of the cylinder 9 towards the inside of the cylinder 9 itself and cooperating, when in the extracted position, with a groove 13 positioned on the outer lateral periphery of the rod 6.

[0059] In more detail, the second end stop is defined by at least one obstructing element 12 housed at least in part in the thickness of the side wall of the cylinder 9, in particular within a radial through hole positioned along an annular band of the side wall. Inside such a hole, the obstructing element 12 is radially movable with respect to the cylinder 9 to cooperate, when in the extracted position, i.e., when arranged at least in part inside the cavity of the cylinder 9, with the groove 13 positioned on the outer lateral periphery of the rod 6. The obstructing element 12 is radially slidable within the through hole between the aforementioned extracted position and a retracted position in which it is fully recessed in the through hole, without therefore protruding towards the inside of the cavity of the cylinder 9.

[0060] The groove 13 is in particular an annular groove obtained on the outer periphery of the rod 6. In particular, moreover, the obstructing element 12 is in the form of a ball, to which the same reference numeral 12 is hereinafter assigned.

[0061] In more detail, the side wall of the cylinder 9 houses three balls 12, positioned along an annular band of the wall itself inside respective radial through holes and angularly equidistant from each other by 120°. Therefore, the second end stop is defined by three balls 12 radially and partially extractable from the inner periphery of the cylinder 9 towards the inside of the cylinder 9 itself and angularly equidistant from each other by 120°.

[0062] The even distribution at 120° of the balls 12 ensures a perfect axial balance in the definition of the second end stop in the step in which such balls 12, engaging the groove 13, obstruct the axial sliding of the rod 6 inside the cylinder 9 of the piston 7.

[0063] It should be noted that the balls 12 could be provided in a number greater than three, or in a number lower than three, for example two or only one. The piston 7 further comprises a sleeve 14 telescopically coupled to the outer periphery of the cylinder 9 and provided with at least one seat 15, configured to accommodate at least in part the aforementioned obstructing element 12.

[0064] In particular, the seat 15 is defined by an annular groove of the sleeve 14 which faces the outer lateral periphery of the cylinder 9.

[0065] The sleeve 14 is slidable between a first retracted position (Figures 2, 3 and 6), from which a non-interference condition of the sliding of the rod 6 inside the cylinder 9 results, and a second advanced position (Figures 4 and 5), from which a sliding interference condition of the rod 6 inside the cylinder 9 results.

[0066] In the first retracted position, the sleeve 14 is spaced from an abutment shoulder 9b of the cylinder 9 and is telescopically extracted with respect to the cylinder 9 on the opposite side to that according to which the cylinder 9 faces the selector drum 2 in a fixed position.

[0067] In such a first retracted position, each seat 15 is aligned with the respective through hole in which the corresponding obstructing element 12 is housed to receive the latter in the aforementioned retracted position with respect to the cylinder 9. In such a first retracted position, each obstructing element 12 is radially and partially extracted / extractable from the outer periphery of the cylinder 9 towards the outside of the cylinder 9 itself and partially housed / housable in the respective seat 15.

[0068] In the second advanced position, the sleeve 14 abuts on the shoulder 9b of the cylinder 9 and is telescopically fully recessed with respect to the cylinder 9.

[0069] In such a second advanced position, each seat 15 is not aligned with respect to the respective through hole in which the corresponding obstructing element 12 is housed to maintain the latter in the aforementioned extracted position with respect to the cylinder 9. Such misalignment is given in particular by a position of the seats 15, which are closer (in particular adjacent) to the shoulder 9b with respect to the aforementioned radial holes for housing the obstructing elements 12 (balls 12).

[0070] The control device 5 comprises an actuator element (not shown) positioned on the handlebar of the motorcycle and connected to the sleeve 14.

[0071] Starting from the second advanced position, the first retracted position of the sleeve 14 can only be reached through the aforementioned actuator element against the opposing action of a second spring 16 of the piston 7, which is functionally interposed between the cylinder 9 and the sleeve 14. (Fig. 6)

[0072] In more detail, the piston 7 comprises an outer jacket 17 integral with the cylinder 9, in particular fixed to the cylinder 9 which in turn is fixed, and to which the sleeve 14 is slidably coupled internally by interposing the second spring 16 positioned on the bottom of the jacket 17.

[0073] It should be noted that the actuator element of the control device 5 can be electronic or mechanical. In the first case, the handlebar of the motorcycle can be provided with a control button, in the second case with a lever acting in turn, for example, on a tie rod. It should further be noted that the first retracted position of the sleeve 14 is maintained, against the opposing action of the first spring 10 and the second spring 16 of the piston 7, by the relative retracted positioning of the rod 6 inside the cylinder 9 during the period in which the stop element 3 and the locking element are in contact with each other.

[0074] The operation of the gearbox 1 is described below starting from the state, shown in Figure 2, in which the neutral gear is selected through the pedal shift lever, and then through the selector drum 2.

[0075] In such a state, the central depression 3a of the tooth 8 is aligned with the longitudinal axis of the piston 7 and the tooth 8 pushes the ball 6a, and therefore the rod 6, towards the first end stop (without reaching it) against the opposing action of the first spring 10, stably maintaining the rod 6 in a slightly retracted position, i.e., recessed, in the piston 7 with respect to the aforementioned position of maximum extraction. In such a position, the ball 6a is slightly recessed in the cavity of the cylinder 9 with respect to the position of maximum extraction of the rod 6, in which the ball 6a is pushed into abutment against the edge of the circular retaining mouth 11 of the cylinder 9.

[0076] In such a state, moreover, the sleeve 14 is in the retracted position thereof, which is maintained, against the opposing action of the first spring 10 and the second spring 16 of the piston 7, by the retracted positioning of the rod 6 inside the cylinder 9. In such a state, in fact, the rod 6, due to the longitudinal misalignment between the annular groove 13 of the rod 6 and the aforementioned through holes obtained in the side wall of the cylinder 9, forces the three balls 12 to remain partially and radially extracted from the outer periphery of the cylinder 9 towards the outside of the cylinder 9 itself and partially housed in the respective seats 15, consequently forcing the sleeve 14 to remain in the retracted position thereof against the opposing action of the second spring 16.

[0077] In the transition from neutral to first gear, shown in Figure 3, the tooth 8 maintains contact with the ball 6a of the rod 6 but, as a result of the rear hump 3b thereof with respect to the direction with which the selector drum 2 is rotated to select the first gear (counterclockwise observing Figure 3), further pushes the ball 6a and therefore the rod 6 towards the first end stop (without necessarily reaching it), again against the opposing action of the first spring 10.

[0078] The sleeve 14 remains in the retracted position thereof, as a longitudinal misalignment between the annular groove 13 of the rod 6 and the aforementioned through holes obtained in the side wall of the cylinder 9 remains. In other words, the three balls 12 continue to be forced into the position thereof inside the seats 15, and the sleeve 14 is still longitudinally blocked in the retracted position thereof against the opposing action of the second spring 16 by the three balls 12, in turn blocked longitudinally, i.e., along the longitudinal axis of the piston 7, in the fixed longitudinal position of the aforementioned through holes.

[0079] Upon reaching the first gear, illustrated in Figure 4, the ball 6a of the rod 6, no longer engaged by the tooth 8, snaps in abutment against the edge of the circular retaining mouth 11 of the cylinder 9, since the thrust action of the first spring 10, no longer counteracted, pushes the rod 6 towards the position of maximum extraction thereof from the cylinder 9. Such a condition remains even after passing the first gear towards the next gears. The reaching by the rod 6 of the position of maximum extraction thereof from the cylinder 9 determines a longitudinal alignment between the annular groove 13 of the rod 6 and the aforementioned through holes obtained in the side wall of the cylinder 9.

[0080] As a result, the three balls 12, no longer radially blocked by the rod 6, are forced to travel through the respective through holes to exit from the seats 15 and re-enter the groove 13 under the thrust that the sleeve 14 undergoes from the second spring 16. The sleeve 14 then snaps towards the advanced position thereof and the sliding of the rod 6 is limited by the new position taken by the three balls 12 which thereby define the aforementioned second end stop. A subsequent passage from the first gear towards neutral is blocked by the second end stop, insufficient to make the rod 6 return inside the cylinder 9 enough to allow the tooth 8 to return the ball 6a of the rod 6 to the position between the humps 3b and 3c (Fig. 5).

[0081] To allow a subsequent passage from the first gear towards neutral, the motorcyclist can operate the control device 5 and impart a forced translation with telescopic retraction to the sleeve 14 with respect to the cylinder 9 against the opposing action of the second spring 16, i.e., from the advanced blocking position to the retracted release position, actually bringing the seats 15 into alignment with the through holes of the cylinder 9 through which the three balls 12 are again free to slide towards the seats 15.

[0082] It should be noted that the control device 5 "frees" the first end stop to the place of the second end stop, however the passage from the first gear towards the neutral gear is accompanied by a continuous contact between the tooth 8 and the ball 6a of the rod 6 and by a thrust that the rod 6 undergoes from the tooth 8 against the opposing action of the first spring 10. In other words, the passage from the neutral to the first gear and vice versa, resulting from opposite shifting directions, i.e., from opposite movements of the pedal lever and therefore of the selector drum 2, provides a sliding / rolling contact in both cases, according to respective opposite directions, of the tooth 8 on the ball tip 6a of the rod 6.

[0083] It is evident that the mutual contact is always ensured between the ball tip 6a and the tooth 8, without the two elements being mutually separated or spaced apart.

[0084] The "release" of the first end stop to the place of the second end stop to allow a passage from the first gear toward the neutral occurs by intentional action of the motorcyclist (through the control device 5) and is necessary because, as mentioned, the second end stop, which "snaps" following the passage from the neutral gear to the first gear, would be insufficient to make the rod 6 re-enter the cylinder 9 enough to allow the aforementioned hump 3b of the tooth 8 to slide on the ball tip of the rod 6 to return the tooth 8 to the position corresponding to neutral, in which the depression 3a is aligned with the sliding axis of the rod 6.

Claims

CLAIMS1 . A motorcycle gearbox, comprising:- a cam selector drum (2) rotatable about an axis (2a) through predetermined rotational steps in order to sequentially reach the positions corresponding to a plurality of gears and to a neutral gear;- a stop element (3), integral with the cam selector drum (2) and indexed to the position corresponding to the neutral gear;- a locking element (4), cooperating with the stop element (3) to block the rotation of the cam selector drum (2) and prevent the neutral gear from being reached or passing through; and- a control device (5), which is positioned and configured to interact with the locking element (4) and which can be operated by the motorcyclist to release the rotation of the cam selector drum (2) and allow the neutral gear to be reached or passed through; characterised in that the locking element (4) is formed by the rod (6) of a piston (7) with a variable configuration; said control device (5) being designed to give the piston (7) a first configuration having a first end stop or, alternatively, a second configuration having a second end stop whose longitudinal extension is different to the first end stop; the stroke of the rod (6) towards the bottom of the piston (7) being determined by the thrust of the stop element (3) on the rod (6) following the rotation of the selector drum (2); said first end stop allowing the neutral gear to be reached or passed through; and said second end stop preventing the neutral gear from being reached or passed through.

2. The motorcycle gearbox according to claim 1 , wherein said second end stop has a longitudinal extension less than the first end stop.

3. The motorcycle gearbox according to claim 2, wherein said second end stop allows the rod (6) to have a stroke substantially equal to zero starting from a relative position in which it cooperates, or starts to cooperate, withthe stop element (3) in blocking the rotation of the selector drum (2).

4. A motorcycle gearbox according to claim 3, wherein said position of the rod (6) in which the rod cooperates, or starts to cooperate, with the stop element (3) in blocking the rotation of the selector drum (2) corresponds to the position of maximum extraction of the rod (6) from the piston (7).

5. A motorcycle gearbox according to any one of claims 1 to 4, wherein said locking element (4) cooperates with the stop element (3) to unidirectionally block the rotation of the cam selector drum (2) and prevent the reaching of the neutral gear starting from the first gear; said first end stop allowing the neutral gear to be reached starting from the first gear; and said second end stop preventing the reaching of the neutral gear starting from the first gear.

6. The motorcycle gearbox according to claim 5, wherein said first end stop allows the neutral gear to be reached starting from the first gear and vice versa; and said second end stop prevents the neutral gear from be reached starting from the first gear.

7. The motorcycle gearbox according to claim 5 or 6, wherein said piston (7) comprises a cylinder (9) to which said rod (6) is slidably coupled and a first spring (10) interposed between the bottom of the cylinder (9) and the rod (6); said second end stop being defined by at least one obstructing element (12) which is radially extractable from the inner periphery of the cylinder (9) towards the inside of the cylinder (9) and cooperating, when in the extracted position, with a groove (13) located on the outer periphery of the rod (6).

8. The motorcycle gearbox according to claim 7, wherein said piston (7) comprises a sleeve (14) coupled telescopically to the outer periphery ofsaid cylinder (9) and provided with at least one seat (15) configured to accommodate said obstructing element (12); said sleeve (14) being slidable between a first position in which the seat (15) is aligned with the corresponding obstructing element (12) for housing it in a retracted position with respect to the cylinder (9), not interfering with the sliding of the rod (6) inside the cylinder (9), and a second position in which the seat (15) is not aligned with respect to the obstructing element (12) for keeping it in said extracted position with respect to the cylinder (9), interfering with the sliding of the rod (6) inside the cylinder (9).

9. The motorcycle gearbox according to claim 8, wherein said obstructing element (12) is in the form of a ball (12).

10. The motorcycle gearbox according to claim 9, wherein said second end stop is defined by three balls (12) which can be radially extracted from the inner periphery of the cylinder (9) towards the inside of the cylinder (9) and equidistant from each other by 120° along an annular band of the side wall of the cylinder (9).

11. The motorcycle gearbox according to any one of claims 8 to 10, wherein said control device (5) comprises an actuator element positioned on the handlebar of the motorcycle and connected to said sleeve (14), and wherein the first position of the sleeve is reached using said actuator element against the opposing action of a second spring (16) of the piston interposed functionally between the cylinder (9) and the sleeve (14).

12. The motorcycle gearbox according to claim 11 , wherein the first position of the sleeve (14) is maintained, against the opposing action of said first spring (10) and of said second spring (16) of the piston, by the relative retracted positioning of the rod (6) inside the cylinder (9) during the period in which the stop element (3) and the locking element (4) are incontact with each other.

13. The motorcycle gearbox according to claim 12, wherein said piston (7) also comprises an outer jacket (17) integral with the cylinder (9) and to which the sleeve (14) is slidably coupled internally by interposing said second spring (16) positioned on the bottom of said jacket (17).

Images