WO2016110626A1

WO2016110626A1 - Motor vehicle gearbox

Info

Publication number: WO2016110626A1
Application number: PCT/FR2015/053505
Authority: WO
Inventors: Xavier Lelasseux; Marc Falcoz; Michael Wascheul; Grzegorz MITUKIEWICZ
Original assignee: Peugeot Citroen Automobiles Sa
Priority date: 2015-01-06
Filing date: 2015-12-15
Publication date: 2016-07-14
Also published as: FR3031377A1; FR3031377B1

Abstract

The invention relates to a gearbox which includes a shaft (200) and gears (300), said shaft (200) furthermore being hollow, the gearbox also including, concentric with said hollow shaft (200) and on the inside thereof, a control cylinder (100) movable at least by longitudinal translation relative to said hollow shaft (200), in order to engage by longitudinal translation with control pins passing through the wall of the hollow shaft (200) in order to control the rigid connection of the gears (300) with the hollow shaft (200), the cylinder (100) being held in position relative to the shaft (200) by a rounded component (160), and controlled by a first rod driving the cylinder during a relative longitudinal movement in a first direction in order to overcome the holding force imposed by the rounded component and retracting due to the ramp effect caused by said holding force during a relative movement in the opposite direction.

Description

GEARBOX FOR MOTOR VEHICLE

The invention relates to a gearbox for a motor vehicle, for example a motor vehicle, whose engine can be a heat engine.

[0002] Gearboxes for a motor vehicle typically comprise two shafts, one driven by the motor and described as a primary shaft, and the other driving the axes of the drive wheels and being referred to as a secondary shaft. The two shafts are connected by as many pairs of gears as the gearbox offers gear ratios, one gear of each pair being fixed on one of the shafts and the other on the other shaft. The selection of an idler gear among the various idle gears and its securing with the shaft which carries it allows the engagement of the gear ratio, the rotation of the primary shaft then being transmitted to the secondary shaft by the torque of gears including the selected gear.

In known gearboxes, the idle gears are secured to the shaft that carries them using claws or synchronizers. These are actuated by a fork that approaches the shaft laterally and whose control elements occupy a space outside the plane defined by the two shafts of the box. It follows from this provision that the gearbox is cumbersome in its thickness relative to the plane of the two shafts. Moreover, the assembly is complex since to control the passage of a gear ratio it is necessary to have a control shaft in selection and a control axis in passing, a barrel beside the shafts, levers and control fingers .

Document US7997159 discloses a system in which a shaft carrying idle gears comprises, coaxial with it, a tube rotated relative to the shaft, which controls the fastening of the idler gears. But the order is complex, and the system bulky, with actions rotating outside the tree system.

The invention aims to solve these problems and provide a simple and compact system outside the plane occupied by trees.

To solve these problems, it is proposed a gearbox for a motor vehicle comprising a shaft and mounted gears for transmitting power with a gear ratio determined by the gear selected from said gears, the selection of the gear is making by its solidarity with the tree, said tree being more hollow, characterized in that the gearbox further comprises, concentric to said hollow shaft and in its interior, a control cylinder movable at least in longitudinal translation vis-à-vis said hollow shaft, to act in longitudinal translation on pawns control device through the wall of the hollow shaft to control the securing or the separation of the pinions with the hollow shaft, the cylinder being held in position vis-à-vis the shaft by a blasting, and controlled by a first rod driving the barrel, during a relative longitudinal movement in a first direction to overcome the holding force imposed by the blasting, and fading by the effect of a ramp due to said holding force during a displacement relative longitudinal in the opposite direction.

These principles allow to control the cylinder only in translation which is easily achievable even if the assembly rotates at the speed of the shaft relative to the housing.

With these principles, it implements a gearbox control concentric to one of the shafts of the box, which saves space around the gears, and to define a sump of smaller size and less heavy. The number of rooms is reduced, and the system is therefore more solid.

The invention may further comprise the following characteristics, which are advantageous: a second rod impulsively controls the barrel while abutting during a relative longitudinal displacement in the opposite direction and fading away by a damping effect; ramps during relative movement in the first direction;

the control of the barrel being ensured by at least two first rods symmetrical with respect to the longitudinal axis of the barrel; - An engagement or disengagement of the first rod is controlled by a neck of the shaft, which interacts with an outgrowth or lug on the first rod to push it towards the longitudinal axis or let it return to the periphery;

the first rod is guided in translation by an external control element with means for not transmitting the rotational movement of said hollow shaft to said external control element; the first rod drives the barrel acting by bearing in said first direction between parallel planes perpendicular to the longitudinal axis on an edge of a barrel groove, the barrel comprising a groove for each gear ratio, and the first rod a head having a ramp to fade when it meets an edge of the groove in said opposite direction;

- An external control element including a biasing element to cause a return to position of a lever to be actuated by a user in one direction to make a rising speed passage and in another direction to perform a downward passage of speed.

The gearbox may further be a sequential gearbox.

[001 1] The gearbox may further be a pulse control box.

The hollow shaft may be the primary shaft or the secondary shaft.

The invention further relates to a motor vehicle comprising a gearbox as evoked.

The invention will be better understood, and other objects, features, details and advantages thereof will appear more clearly in the explanatory description which follows with reference to the accompanying drawings given solely by way of example illustrating a embodiment of the invention and in which:

- Figure 1 shows a cylinder of a gearbox according to one embodiment of the invention;

- Figure 2 shows a developed tracks of the barrel of Figure 1;

- Figure 3 shows a sectional view of a shaft of a gearbox according to one embodiment of the invention;

- Figure 4 shows a view of the same shaft, in another section, after various movements of the barrel

FIG. 5 is a view of a particular element of the gearbox according to one embodiment of the invention FIG. 6 is a view of the same particular element during a gearshift.

Referring to Figure 1 there is shown a control cylinder 100 used in the invention. This cylinder 100 has a general shape of a cylinder of revolution having a longitudinal axis. Control tracks 1 10, 120 and 130 are visible on the outer surface of the control cylinder 100. These control tracks 1 10, 120 and 130 are separated from each other and distributed over three consecutive sections of the control cylinder 100, succeeding one another along the longitudinal axis. Each of the tracks 1 10, 120 and 130 constitutes a groove in the material of the control cylinder 100 opening to the surface, delimited by walls and a bottom. The grooves are adapted to receive pins directed radially from outside the control cylinder 100, and to act on them to move them parallel to the longitudinal axis by pushing them with the walls. Each of the tracks 1 10, 120 and 130 is more generally a helicoid along the surface of the barrel 100, rotating one turn or more than one turn thereof while progressing parallel to the longitudinal axis.

Always visible in Figure 1 we see at one end of the barrel 100, visible on the section thereof which is a straight section, the mouth of a bore 140 internal barrel 100. We distinguish on the inner surface of this bore 140, elements of a ball screw 150 disposed in an internal groove formed on the inner surface of the bore 140.

In Figure 2 there is shown a developed tracks 1 10, 120 and 130. The track 1 10, for example is adapted to the passage of the fourth speed ratio and the fifth speed ratio. The track 120 is adapted to the passage of the second gear ratio and the third gear ratio. The track 130 is adapted to the passage of the first gear ratio, neutral (N) and reverse (R).

Each of these tracks comprises on a major part of the track a non-engagement section of the pawn. This non-engagement section of the pin is inclined relative to a straight section of the barrel 100, an angle X ° defining a helicoid, as already mentioned. In addition, the tracks 1 10, 120 and 130 comprise sections adapted to the displacement of the corresponding pin for the engagement of evoked speed ratios. These engagement sections are inclined relative to the main non-engagement section on one side or the other. The positions corresponding to the speed ratios R 1, 2, 3, 4 and 5 are all stable positions.

It is noted that the track 1 10 is provided for, upon disengagement of the fourth speed ratio, proceed to the commitment of the fifth gear ratio, without a stable position is provided between the two commitments. In the same way the track 120 is adapted for, upon disengagement of the second gear ratio, cause the engagement of the third gear ratio. Conversely, the track 130 is configured to provide a stable stall transition between the first gear ratio and the reverse gear.

In Figure 3 there is shown in longitudinal section, a shaft of a gearbox according to the invention. This hollow shaft 200, of general shape corresponding to a cylinder of revolution, carries idle gears cooperating with fixed gears of another shaft of the gearbox (not shown). For simplicity has been shown only one idle gear, referenced 300. The idle gears are secured to the hollow shaft 200 using synchronizers, which has been shown the sleeves 310, 312 and 314. The sleeve 314 is that of a synchronizer which is applied to the idler gear 300. The synchronizers are actuated by pins 320, 322 and 324, respectively acting on the sleeves 310, 312 and 314. The pins 320, 322 and 324 pass through the wall of the hollow shaft 200 and are controlled from the inside thereof by the cylinder 100 which occupies the cylindrical internal cavity of the hollow shaft 200. More specifically, the pins 320, 322 and 324 pass through the hollow shaft 200 by means of lights allowing them to act on the corresponding synchronizer in the longitudinal direction in one direction or in the opposite direction.

The barrel 100 is present in the internal cavity of the hollow shaft 200, the barrel and the shaft being positioned coaxially. A longitudinal connecting member 210 closes the end section of the hollow shaft 200. It has a cylindrical extension 21 1 coaxial with the barrel 100 and the hollow shaft 200, directed inside the hollow shaft 200. This extension cylindrical 21 1 carries at its surface grooves for the purpose of creating a threaded system or ball screw type performing a helical movement with a complementary shape of the barrel 100. This complementary shape is the cylindrical bore 140 inside the barrel 100, also coaxial with the cylindrical extension 21 1 and the hollow shaft 200. The ball screw 150 thus allows the helical connection between the longitudinal connecting element 210 and the barrel 100. The longitudinal connecting element 210 being fixed by fitting to the hollow shaft 200, it follows that the barrel 100 evolves in helical connection vis-à-vis the hollow shaft 200. A blasting 160 directed radially and supported on the body of the barrel 100 ensures the stabilization thereof vis-à-vis the hollow shaft 200 by pressing its head on a blasting track 220 of the inner surface of the hollow shaft 200 and thereby applying a holding force.

The pins 320, 322 and 324 are respectively introduced into the grooves 1 10, 120 and 130, and are guided by them. These tracks have on average the angle of inclination X ° on the barrel 100 with respect to a cross section thereof to compensate for the translation that the barrel 100 undergoes during a rotation due to the helical connection created by the ball screw 150 and move each pin 320, 322 or 324 only when the corresponding gear ratio is to be actuated, in which case, on the corresponding section of the track 1 10, 120 or 130, it deviates from the mean angle of inclination X ° from one side or the other, as has been shown in the diagram of FIG.

A control 400 is introduced from outside the system by an open mouth 201 of the hollow shaft 200, opposite the longitudinal connecting member 210, and a corresponding mouth 101 of an inner zone of the barrel 100 , disposed in the continuity of the open mouth 201 of the hollow shaft 200. The control 400 interacts with the cylinder 100 in this inner zone which is elongate on the longitudinal axis and which comprises a succession of internal grooves 170. Precisely, seven successive grooves, parallel to each other, and separated by edges of grooves are present in the succession 170. The edges of grooves define a small diameter.

The groove in which the control interacts with the barrel in the view of Figure 3 is the sixth groove from the mouth 201 of the hollow shaft 200.

In Figure 4 there is shown the system shown in Figure 3, after mutual displacement of the barrel 100 and the hollow shaft 200. The view is a longitudinal sectional view offset by an angle of 90 ° by contribution to FIG. 3 shows the blasting track 220 formed on the inner surface of the hollow shaft 200 and on which the blasting 160 supports its head, to stabilize the mutual positioning of barrel 100 and the hollow shaft 200, in a position chosen from among several, each corresponding to a speed ratio.

Compared to the view of Figure 3, we see that the barrel 100 has moved to the longitudinal connecting member 210 and, conversely, has departed from the mouth 201 open the hollow shaft 200 through which the control 400 enters. It is also noted that the control element 400 interacts with the barrel 100 at the inlet of the succession of internal grooves 170 (more precisely in the first groove) whereas in the position of FIG. 3 the control 400 interacts with the barrel 100 at a deeper level of the succession of internal grooves 170 (in the sixth groove), farther from the mouth 101.

The barrel 100 has progressed along the cylindrical extension 21 1 of the longitudinal connecting element 210, according to the helical movement defined with the aid of the ball screw 150. The cylindrical extension 21 1 penetrates more deep in the bore 140.

One of the tracks 1 10, 120 or 130 has actuated one of the pins 320, 322 and 324 (not visible in this figure), and one of the synchronizers, such as the synchronizer using the sleeve 314 , has secured an idle gear, such as for example the idler gear 300.

It is specified that a gear ratio can be made by distributing a passage force on several pins (variant not shown). This is made possible because the tracks are inclined at an angle X ° with respect to a cross section of the barrel 100, and this makes it possible to produce several tracks or parallel track sections for distributing the force, for the passage of a report. , on several pawns.

In addition, as the diameter of the barrel 100 is small compared to the usual control barrels, which are not to be integrated in a tree, unlike the barrel 100, it is necessary to incline the sections of the tracks accordingly. deviating from the average inclination X ° to cause the passage of a speed ratio, without which the corresponding pawn can not be put in the track which would not be wide enough.

Finally, according to the sizing, it can be achieved several rotations of the barrel 100 to obtain a passage of all speed reports, from the neutral to fifth gear. This makes it possible to set up optimum angles for the slopes of the sections of the tracks to improve the efficiency of the cylinder. In FIGS. 5 and 6, the operation of the control 400 is shown. It is pointed out that FIG. 6 is a view in a section offset by 90 ° with respect to the section of FIG. 5.

The command 400 consists of four branches of the same length attached to each other at their base which is common. These branches are parallel to each other and flexible at the base. They face two by two thus defining two pairs of branches, or clamps, each clamp constituting a very elongated U. The two planes in which the two clamps are located are perpendicular to each other and intersect on the longitudinal axis. The branches are each arranged at rest parallel to the longitudinal axis.

The succession of inner grooves 170 comprises, in the figure, three visible grooves, numbered 171, 172 and 173, from the mouth 201 the hollow shaft 200 through which is introduced the command 400, via the mouth 101 of the barrel. These grooves are parallel, straight with respect to the longitudinal axis and concentric. They each have the same diameter and the same geometric characteristics. They have an upstream edge (opposite the mouth 201 of the hollow shaft 200), for example referenced 171 1 for the groove 171, and a downstream edge (on the side of the mouth 201 of the hollow shaft 200), for example referenced 1712 for the groove 171.

Each of the branches of the control 400 comprises, opposite the base of the control 400, a head which projects outwardly, opposite the longitudinal axis.

A first branch 410 (visible in Figure 5 and invisible in Figure 6) of the control 400 has a head 412 which comprises a flat surface 4122 configured to abut plan on the upstream edge of the groove in which the head is inserted, here the edge 171 1 of the groove 171, during a movement of the branch 410 in the direction of the introduction thereof into the hollow shaft 200. This abutment is in a plane perpendicular to the longitudinal axis.

The head 412 comprises, on the opposite side, on its side disposed on the side of the base of the control 400, a ramp 4121 which allows, in case of movement of the branch 410 vis-à-vis the shaft hollow 200 in the direction of the disengagement of the branch of the hollow shaft 200, to produce by a ramp effect against the downstream edge of the groove, here the edge 1712 of the groove 171, a slight rotation of the first branch 410 around of its junction with the other branches at the base of the control 400, towards the axis longitudinal, so as to allow the deletion of the head 412 to the axis and the passage thereof next to the downstream edge of the groove, here always the edge 1712 of the groove 171.

A second branch 420 of the control 400, arranged at 90 ° relative to the first branch 410 next to it, comprises a head 422 whose two faces are arranged opposite to that of the head 412 (see Figure 6 for a view in the plane of the branches 420 and the symmetrical branch 440). Thus, the head 422 has a ramp 4221 opposite the base of the control 400 and an abutment surface 4222, perpendicular to the longitudinal axis towards the base of the control 400.

In case of displacement of the second branch 420 in the direction of engagement with the hollow shaft 200, the head 422, due to the effect of its ramp 4221, is caused to deviate from the edge of the 171 and go past it. Conversely, in case of displacement to extract the branch 420 of the hollow shaft 200, the face 4222 of the head 422 abutting encounters the edge 1712 of the groove 171, causing the stop displacement. The third branch 430 which faces the first branch 410 is symmetrically configured thereto and therefore has a stop face operating during a relative movement of the branch 430 towards the inside of the shaft 200, and a ramp for spacing the head 432 during a relative movement for the extraction of the branch 430 from the hollow shaft 200. The fourth branch 440 (not shown in Figure 5, but visible in Figure 6) is symmetrical to the second branch 420.

The set of four heads is sized so that the four heads engage the groove in which they are placed when the control 400 is centered on the longitudinal axis. The mouth 201 of the hollow shaft 200 by which the control 400 is introduced comprises a neck 240. This neck is a straight cut cylinder portion concentric with the other cylinders of the device about the longitudinal axis. From the mouth 201 of the hollow shaft 200, the neck 240 is disposed inside thereof. The neck 240 has an upstream ramp 241 and a downstream ramp 242 at both ends on its inner surface. The length of the neck 240 between these two ramps constitutes a bottleneck through which the four branches of the control 400 are introduced. The first and third branches 410 and 430 comprise lugs 41 1 and 431 (or protuberances) arranged radially outwardly, at a distance from both the heads 412 and 432 and the base of the control 400. From the Similarly, the second and fourth branches 420 and 440 have lugs 421 and 441 (see Figure 6 in particular) directed radially outward distance of the corresponding heads and the base of the control 400.

The lugs 41 1 and 431 are arranged at the same height of the corresponding branches and the lugs 421 and 441 carried by the second and fourth branches are also arranged at the same height on these two branches. By against the lugs are not arranged at the same height on the two pairs of branches. The lugs 41 1 and 431 are arranged so as to interact with the upstream ramp 241 while the lugs 421 and 441 of the second and fourth branches are arranged to interact with the downstream ramp 242.

It follows from this arrangement that a relative displacement of the control 400 and the hollow shaft 200 for the introduction of the control 400 into the hollow shaft 200 causes a ramping effect on the pins 421 and 441. (outgrowths) of the second and fourth branches, via the downstream ramp 242. The branches 420 and 440 are pushed towards the longitudinal axis.

This ramp effect induces the closure of the clamp defined by the second and fourth branches 420 and 440 and the controlled erasure heads 422 and 442 of these two branches, which can not interact, therefore, with the edges grooves of the succession of internal grooves 170. Thus the branches 420 and 440 are disengaged from the barrel 100.

Conversely, a displacement of the control 400 towards the outside of the hollow shaft 200 causes the controlled closure of the clamp defined by the first and third branches 410 and 430, by the action of the upstream ramp. 241 on the pins 41 1 and 431. As a result, the heads 412 and 432 are erased and can no longer interact with the groove edges of the succession of internal grooves 170. The branches 410 and 430 are pushed towards the longitudinal axis and are disengaged from the groove. barrel 100. It follows from these principles that a pulse control and sequential can be implemented for the movement of the cylinder 100 in the interior of the hollow shaft 200. A sequence will be presented later.

With respect to the position shown in FIG. 5, the control 400 is, in this sequence, displaced towards the outside of the hollow shaft 200. This results in the controlled closure of the clamp defined by the first branch and third branch 410 and 430, by interaction of the lugs 41 1 and 431 with the ramp 241. But by cons, the clamp defined by the second and fourth branches 420 and 440 abuts against the edge of the groove in which the heads are positioned and pulls the cylinder 100 in the direction of the mouth 201 of the shaft 200.

If the force applied by the control 400 overcomes the resistance opposed by the blasting 160 (see FIGS. 3 and 4), the barrel 100 then follows a helical movement as defined by the ball screw system 150 (see FIGS. , 3 and 4). One of the tracks 1 10, 120 or 130 (previous figures) then imposes a longitudinal translation movement to one of the pins 320, 322 and 324 (Figures 3 and 4) and a gear ratio is then engaged, and / or a report that was engaged is disengaged. The blasting 160 stabilizes the barrel 100 in a new position corresponding to this new speed gear engaged or in neutral. For example, it is a higher gear ratio.

The command 400 can then be released. It can be returned to its initial position with respect to the shaft 200 by means of a spring (not shown), or another return element. The clamp defined by the branches 410 and 430 being closed at the beginning of this movement, it does not prevent the set of heads to pass inside the small diameter defined by the edge of the groove in which the heads were until then placed.

The clamp defined by the second and fourth branches 420 and 440 closes as for it then by action of the ramps (in particular the ramp 4221) carried by the corresponding heads which meet the upstream edge of the groove (in particular the edge upstream 171 1).

The set of heads is able to pass the small diameter and the heads are then found in a subsequent groove of the succession of inner grooves 170, further from the mouth 201 of the hollow shaft 200 that the groove in which the heads were present until then. The structure is thus represented in FIG. 6, moving just after the heads have left the groove 171 and before the heads are inserted into the groove. Once the groove 172 has been reached by the heads, the tongs open again because of the elasticity of the material at the base of the control 400, the neck 240 allowing in particular to leave the branches 410 and 430 return to the periphery, in their initial conformations, since the lugs 41 1 and 431 descend the ramp 241. The heads then engage the throat 172.

We will now describe the reverse movement, corresponding, in the case considered, to the passage of a lower gear ratio. This is induced by an action of the control 400 towards the inside of the hollow shaft 200. This action induces a pressure exerted by the heads 412 and 432, which overcomes the stabilization effort exerted by the blasting 160. barrel 100 then follows a helical movement in the interior of the hollow shaft 200, away from the mouth 201 of the hollow shaft 200. The barrel 100 causes the commitment of a speed ratio by action on a pawn via one of the tracks 1 10, 120 or 130.

Furthermore, the lugs 421 and 441 cause, by their meeting of the ramp 242, the controlled closure of the clamp constituted by the branches 420 and 440, the branches 420 and 440 being pushed towards the longitudinal axis by the slope 242.

The control 400 is then released, and as the clamp defined by the branches 420 and 440 is closed, and as defined by the branches 410 and 430 meets the upstream edge of the groove via the ramps of the heads 412 and 432, the heads are able to pass the edge of the throat and to insert into the next groove, towards the mouth 101.

The lugs 421 and 441 descend the slope 242 and the branches 420 and 440 return to the periphery. The heads engage the next throat.

The shaft 200 may be the secondary shaft of the gearbox, or one of the secondary shafts if it has two, in which case each secondary shaft has a cylinder 100. Alternatively, the cylinder 100 may be incorporated in the primary shaft.

The control is sequential, the reports being engaged in the order, and impulse, because the user has only to give an instruction in the form of a pulse to make upward or downward passages. The control external to the box includes for example a return element to cause a return in position of a lever to be actuated by a user in a direction for move up and down in another direction to make a downshift.

The rods and the entire control 400 may be guided in longitudinal translation by an external control element with a means for not transmitting the rotational movement of the hollow shaft 200 to said external control element.

The invention is not limited to the embodiment shown but extends to all variants within the scope of the claims.

Claims

1. Gearbox for a motor vehicle comprising a shaft (200) and pinions (300) mounted to transmit power with a gear ratio determined by the gear selected from said gears (300), the selection of the pinion being done by its integral with the shaft (200), said shaft (200) being further hollow, characterized in that the gearbox further comprises, concentric with said hollow shaft (200) and in its interior, a control cylinder (100) mobile at least in longitudinal translation vis-à-vis said hollow shaft (200), to act in longitudinal translation on control pins (320, 322, 324) passing through the wall of the hollow shaft (200) to control the fastening or detaching the pinions (300) from the hollow shaft (200), the barrel (100) being held in position relative to the shaft (200) by a blasting (160), and controlled by a first rod (410) driving the barrel (100) during a displacement lon relative slope in a first direction to overcome the holding force imposed by the blasting (160), and fading by the effect of a ramp (4121) due to said holding force during a relative longitudinal movement in the opposite direction.

2. Gearbox according to claim 1, wherein a second rod (420) impulse control the barrel (100) abutting during a relative longitudinal movement in the opposite direction and fading by a ramp effect (422) during relative movement in the first direction.

3. Transmission according to claim 1 or claim 2, the control of the barrel (100) being provided by at least two first rods (410, 430) symmetrical with respect to the longitudinal axis of the barrel (100).

4. Gearbox according to one of claims 1 to 3, wherein an engagement or disengagement of the first rod (410) with the cylinder (100) is controlled by a neck (240) of the shaft (200) which interacts with a protrusion on the first rod (410) to push it towards the longitudinal axis or let it return towards the periphery.

5. Transmission according to one of claims 1 to 4, wherein the first rod (410) is guided in translation by an external control member with means for not transmitting the rotational movement of said hollow shaft (200) to said external control element.

6. Gearbox according to one of claims 1 to 5, wherein the first rod (410) drives the cylinder acting by pressing in said first direction between parallel planes (4122, 171 1) perpendicular to the longitudinal axis on an edge (171 1) of a groove (171, 172, 173) of the barrel (100), the barrel (100) comprising a groove (171, 172, 173) for each gear ratio, and the first rod (410 ) having a head (412) having a ramp (4121) to fade when it encounters an edge (1712) of the groove (171, 172, 173) in said opposite direction.

7. Gearbox according to one of claims 1 to 6, comprising an external control element including a biasing element for causing a return to position of a lever to be actuated by a user in one direction to effect a gear change amount and in another direction to perform a descending gear change.

8. Gearbox according to one of claims 1 to 7, which is a sequential box.

9. Gearbox according to one of claims 1 to 8, wherein the shaft (200) is the primary shaft or the secondary shaft.

10. Motor vehicle comprising a gearbox according to one of claims 1 to 9.