FR2878596A1 - Internal control device for e.g. transmission controlled with simple clutch, of motor vehicle, has driving spindle including respective cam forming bosses for permitting to engage and disengage odd and even gear ratios - Google Patents

Abstract

The device has a driving spindle (2) with cam forming bosses (4, 7) permitting to engage an odd gear ratio. The spindle has cam forming bosses (5, 8) allowing a selection change of a pair of yokes of shift forks, to disengage the engaged odd gear ratio and to move the selected yoke pair, for engaging an even gear ratio. The spindle has cam forming bosses (6, 9) allowing to disengage an even gear ratio.

Description

The present invention relates to an internal control device of a

  controlled gearbox with single clutch of a motor vehicle.

  The current gearboxes use mechanical internal control devices comprising a control shaft for selecting and shifting gear ratios of the gearbox and which is provided with a passage finger of a selected gear ratio allowing to move the corresponding fork by engaging between the two ends of the fork to ensure the interconnection of a synchronizer on gears that correspond to the selected gear ratio.

  Such a control device must therefore from a single gear shift finger actuate several synchronizers via their control ranges. In addition, the internal control device must also support operational safety elements constituting a so-called "interlocking" device that allows the engagement of only one gear ratio at a time.

  Several variants of gearboxes use this control device and include in particular the manual gearbox, the robotized gearbox or single-clutch controlled gearbox and the robotized gearbox with double clutch.

  Robotic gearboxes with conventional architecture use a single actuator actuating the passage finger which itself actuates the gearshift forks selected gears.

  These conventional architectures superimpose the sticks or shifter nuts and position the synchronizers so as to find a coherent shifting grid according to which the reverse ratio is engaged by a reverse fork, the first or the second gear ratio. forward is engaged by a corresponding fork, the third or fourth forward gear is engaged by a corresponding fork and the fifth or sixth forward gear is engaged by a corresponding fork.

  In this case, the actuator must first drive in translation the passage finger to select a passage passage, for example of the first and second gear ratio, and rotate this finger to engage the gear selected .

  The passage from the first to the second gear ratio, from the third to the fourth gear ratio or from the fifth gear to the sixth gear ratio is effected without problem by a single rotational movement of the control shaft and its passage finger. On the other hand, during the passage from the second to the third speed ratio or from the fourth to the fifth gear ratio, the actuator must either break down the movement of the control shaft into three phases: a rotation of the second gear ratio at dead point, followed by a translation of the control shaft to change the passageway, then finally a rotation of the control shaft to engage the third gear ratio, or make a passage in "S" by a device to cam by means of a very precise study of the movement of the finger of passage in the corresponding sticks or nuts passage. This last mode of passage "S" penalizes the passage times, causes risks of blockage and results in a very complex operating kinematics.

  The present invention provides an internal control device of a gearbox controlled including a single clutch of a motor vehicle using a cam device that can move in translation and rotate between brackets or gear shifters and allowing a selection of the corridor passing in even or odd gear engaged, the gearshifts then being made by a single rotational movement.

  For this purpose, the internal control device of a gearbox controlled particular single clutch of a motor vehicle, of the type comprising an actuator for moving a control axis in translation along its longitudinal axis and in rotation about its longitudinal axis for the selection and shifting of gear ratios, via at least one passage element carried by the control shaft selectively engaging between two ends of a fork among a plurality of forks associated with synchronizers to ensure the interconnection of the corresponding synchronizer on gears corresponding to the selected gear ratio, is characterized in that the control axis passes through the fork brackets perpendicularly to the plane of these sticks and carries at least one set of three passage elements comprising respectively three eccentric bosses forming cams extending perpendicular to the axis of comma nde and being arranged relative to the control axis to be able to cooperate, by the actuator moving in translation and in rotation the control axis in a predetermined sequence, with each pair of brackets of a fork to move it in translation in the direction corresponding to the commitment of the gear selected.

  The three cam bosses include a first camming boss for moving a selected pair of engagement forks to an odd gear ratio, a second cam boss for changing selection of a pair of sticks, disengaging the pre-engaged odd gear ratio and moving a selected pair of engagement forks of an even gear ratio, and a third camming boss for moving a pair of fork brackets to disengage it from the gear ratio. even speed previously engaged.

  The second and third cam bosses are superimposed adjacently with the third boss located above the second boss and the first cam boss is angularly offset from the second and third bosses by about 90 by being axially offset relative thereto so that the upper planar face of the first boss is located substantially in the same plane as the lower planar face of the second boss, this plane extending transversely to the control axis.

  The actuator translates the control shaft to bring the second boss between the two sticks of a selected range and then moves the control shaft in rotation to move these two sticks in translation by the first or second boss forming a cam in a direction of engagement of an odd or even gear ratio.

  The device comprises a fourth cam-forming integral with the control pin perpendicular to the latter being superimposed contiguously with the first cam-shaped boss and making it possible to hold the two ends of a fork at the engaged position with an odd speed ratio. while the actuator translational moves the control shaft to a selection position of the two pair of gear forks of the next even gear ratio and the third boss maintains locked two gear sticks to their engaged position of a gear of even speed while the actuator translational moves the control shaft to a selection position of a next odd speed ratio.

  According to one embodiment, the device comprises four pairs of overlapping forks, spaced from each other equidistantly, allowing the engagement of six gears 2878596 forward gears and a reverse gear ratio and successively comprising a pair of reversing engagement forks, a pair of engagement forks of the first and second gear ratios, a pair of engagement forks of the third and fourth gear ratios, and a pair of fifth and sixth gear engagement forks, the control shaft carrying a single set of three passage members and being sequentially displaced in translation and rotation by the actuator to allow the camming bosses to alternatively move the pairs of fork ends to engage the different gear ratios ava nt and reverse gear selected.

  According to another embodiment, the device comprises four pairs of superimposed fork brackets allowing the engagement of six forward gears and one reverse gears ratio and successively comprising two upper pairs of spaced fork rods. the other respectively engaging the reverse gear ratio and the first and second forward gears and two lower pairs of forks spaced from each other the same distance as the one separating the two upper pairs of forks and allowing the engagement of the third and fourth forward gears and the fifth and sixth gears respectively, the upper pairs of forks being spaced from the lower pairs of gears; forks of a greater distance than those separating one from the other two pairs of upper or lower forks, the control shaft carrying two sets of three passage members spaced axially from each other along the control axis which can be sequentially moved in translation and rotation by the actuator so that the camming bosses of one of the sets of three passage members can cooperate with the two upper pairs of forks to engage one of the corresponding gear ratios and the camming bosses of the other game three passage elements can cooperate with the two pairs of lower forks to engage one of the corresponding gear ratios.

  The cam bosses of a game are integral with a cylinder coaxially traversed by the control pin and of a diameter substantially equal to the distance between two brackets of a fork so as to lock in the neutral position the sticks of forks for which no gear ratio is engaged.

  The cylinder of the control shaft comprises, opposite each cam boss, a recessed portion of substantially conjugate shape to that of the end of each of the two ends of a fork and intended to receive an end of a stock when the associated camming boss bears on the opposite end of the other stock so as to lock the two end caps to their engagement position of the corresponding gear ratio.

  The recessed portion and cam boss of a passage member are disposed symmetrically to the plane containing the longitudinal axis of the control shaft and passing through the rounded free end of the cam boss.

  The invention will be better understood, and other objects, characteristics, details and advantages thereof will appear more clearly in the explanatory description which will follow with reference to the accompanying drawings given solely by way of example illustrating an embodiment. of the invention and in which: - Figure 1 is a perspective view of an internal control gearbox driven single clutch motor vehicle according to the invention; FIG. 2 shows the internal gearbox gate made with a conventional gear ratio gear control; FIG. 3 shows an external gearbox gate produced by the control device 10 of the invention; FIG. 4 and a perspective view along the arrow IV of FIG. 1 without some of the gear sticks in order to better represent the passage elements of the control shaft according to the invention and occupying their point position. death of the gearbox; - Figure 5 is a front view along the arrow V of Figure 4; Figure 6 is a sectional view along the line VI-VI of Figure 5; - Figure 7 is a sectional view along the line VII-VII of Figure 5; - Figure 8 is a sectional view along the line VIII-VIII of Figure 5; FIG. 9 is a view from above of the two butts or forks of passage of the first and second gear ratios at the engaged position of the second gear ratio and locked at this position by a passage element according to FIG. 'invention; - Figures 10 to 15 are perspective views showing the operation of the control device of the invention to allow successive commitments in ascending order of the first to third gear ratio forward.

  The control device of the invention which will be described applies in particular to a gearbox controlled single clutch.

  Referring to the figures, the reference 1 designates this control device comprising a control shaft 2 which can be driven in translation and in rotation in a gearbox housing, not shown, by an actuator also not shown to select and engage a gear ratio among a plurality of gears including, in the present case, a reverse gears ratio and six gears speeds. As is known in itself, the actuator of the control shaft 2 can be constituted by an electric or hydraulic motor coupled to the axis 2 in a suitable manner.

  The control shaft 2 has over a large part of its length a cylinder 3 of larger diameter coaxial with the axis 2.

  The cylinder 3 carries a first set said higher with respect to Figures 1, 4 and 5 of identical passage elements 4, 5, 6 and a second lower set of passage elements 7, 8, 9 identical to the passage elements 4 , 5, 6.

  Each passage element is constituted by an eccentric boss forming cam protruding from the cylinder 3 in a plane perpendicular to the control axis 2. Each boss 4-9 is delimited in the axial direction to the control axis 2 by two planar faces parallel upper and lower and has in cross section to the axis 2 a substantially isosceles triangle shape with rounded free end comparable to a finger pass.

  The two respectively lower and upper camming bosses 6 of the upper set of passage elements are contiguously superimposed and the two cam bosses respectively lower 8 and upper 9 of the lower set of passage elements are also joined together superimposed, the bosses forming cams 5, 6 of the upper set being aligned with the bosses 8, 9 of the lower set along a generatrix of the cylinder 3 and spaced axially from each other.

  The third boss 4, 7 of each set of passage elements is angularly offset from the other two bosses 5, 6; 8, 9 of about 90 and is axially offset at a lower level with respect to the bosses 5; 8 so that its upper planar face is substantially located in the same plane passing through the lower planar face of the boss 5; 8. A fourth boss 10, identical to the bosses 4, 5, 6 of the upper set of passage elements is superposed adjacent to the lower boss 4. Similarly, a fourth boss 11, identical to the bosses 7-9 of the lower game of passage elements is superimposed adjacent to the lowest boss 7.

  In addition, the boss 10 is located at the same level as the boss 5 of the upper set of passage elements and the boss 11 is located at the same level as the boss 8 of the lower set of passage elements.

  The cylinder 3 comprises recessed portions 12 respectively made opposite the bosses 4-11 and having a determined width in the axial direction of the control pin 2. The role of these recesses or notches 12 will be explained later. Each recess 12 has its convex bottom towards the axis 2 constituted by two planar faces respectively belonging to two ropes of the same length crossing the circle defined by a cross section of the cylinder 3. Each recess 12 and the corresponding boss 4-11 are arranged symmetrically to a plane containing the longitudinal axis of the control shaft 2 and passing through the rounded free end of this boss.

  The control device further comprises four pairs of hooks 13, 14, 15, 16 superimposed parallel to each other, two pairs of upper hooks 13, 14 and two pairs of lower hooks 15, 16. The two upper pairs of hooks 13 , 14 are spaced one above the other by a relatively short distance as well as the two pairs of lower hooks 15, 16 and the two upper pairs of hooks 13, 14 are spaced from the two lower pairs of hooks 15 , 16 a distance greater than that separating the two pairs of upper or lower sticks. However, the butts may be spaced differently from each other. Thus, they can be equidistantly spaced to be driven by three cam bosses. Such an arrangement allows a height implantation of the highly compacted device.

  Each pair of sticks 13-16 is connected by a corresponding arm 17, 18, 19, 20 to a fork 21, 22, 23, 24 of passage of a given speed ratio. More precisely, the two sticks 13 make it possible to move the fork 21 of passage of the reverse ratio on a support pin 25 fixed in the gearbox housing, the two sticks 14 make it possible to move the fork 22 on the axis of the gearbox. support 25 in one direction to engage the first or second forward gear, the two sticks 15 can move the fork 23 on a support shaft 26 housed in the gearbox housing in a direction to engage the third or fourth forward gear ratio and the two sticks 16 can move the fork 24 on the support shaft 26 in a direction to engage the fifth or sixth gear ratio forward.

  The shifting gears is effected by interconnection of a player or synchronizer on gears corresponding to the selected speed ratio, these gears being connected to primary and secondary transmission shafts, the player being movable in translation on the shaft primary or secondary school under the effect of the corresponding range 21-24.

  The cylinder 3 of the control shaft 2 passes through the forks 13-16 perpendicular to the plane thereof so as to be housed in large part between two butts 13a, 13b; 14a, 14b; 15a, 15b; 16a, 16b of the same pair. In addition, the diameter of the cylinder or drum 3 is substantially equal to the minimum distance separating two butts of each pair. The height or width of each recess 12 is slightly greater than the thickness of the forks 13-16 fork so that the end of a stick can engage in the corresponding recess 12 in the engaged position of the corresponding report. In addition, the thickness of each pair of sticks is substantially equal to the thickness of each boss 4-11.

  The operation of the control device of the invention will be described in the context of forward gears speed gears increasing from the starting condition at which the control is in neutral, as shown in particular in Figures 1, 4 and 10.

  At this position, all the pairs of sticks 13-16 are locked to their position of dead point disengagement gear by the circular peripheral portion of the cylinder 3 being in contact between the two sticks of each pair as shown in particular in Figures 6 and 8 with regard to the locking of the two pairs of hooks 13, 14.

  The actuator is controlled so as to rotate the axis 2 and the cylinder 3 as indicated by the arrow F1 in FIG. 10 by an angle value of approximately 45 to move a corresponding angle value by boss 6 which is at the two sticks 13, the boss 5 which is between the two pairs of sticks 13, 14 and the boss 4 which, being at the two sticks 14a, 14b of the pair 14, comes into play. support on the butt 14a to move the two sticks 14 in the direction indicated by the arrow F2 so as to engage the first gear ratio forward as shown in Figure 11. This figure shows that the sticks of the pair 14 are locked to the engagement position of the first forward gear in the manner shown in Figure 9 where the end of the butt 14b is engaged in the recess 12 opposite the boss 4 bearing on the end of the opposite butt 14a. The bosses 7-9 and 11 of the lower set of passage elements produce no effect during the rotational movement of the axis 2 along the arrow F1 as situated between the two upper and lower pairs of fork caps as shown in FIG. 11 also showing the cylinder 3 maintaining in their locked dead-center position the forks 13, 15 and 16. It should be noted that in Figure 11, the two fork brackets 13 are omitted to better represent the relative positions of different bosses of the control shaft 2.

  To ensure the passage from the first to the second forward speed ratio, the actuator is controlled to move the control axis 2 in translation in the direction indicated by the arrow F3 in FIG. 11 so as to bring the cam boss 5 into position. to engage in the space between the two brackets 14a, 14b of the pair 14 as shown in Figure 12 to thereby select the pair of fork brackets 14. During this movement in translation, the cam forming boss 4s is disengaged from the butt 14a of the pair 14 but the boss 10 comes opposite the butt 14a to maintain the forks 14 at their engagement position of the first gear ratio forward. In the position shown in Figure 12, the cylinder 3 maintains in their locked position of dead point forks fork 13, 15 and 16.

  Then, the actuator rotates the control shaft 2 in the direction indicated by the arrow F4 in FIG. 12 by an angular value of approximately 90 so that the cam boss 5 moves the forks 14 into the direction indicated by the arrow F5 in Figure 13 to disengage the first gear ratio forward and engage the second gear ratio forward as shown in this figure. The fork sticks 14 are locked at their engagement position of the second gear ratio by the butt 14a engaged in the recessed portion 12 as shown in Figure 9. The cylinder 3 always maintains in their locked position of dead point forks of forks 13, 15 and 16.

  To enable the engagement of the third gear ratio, the actuator translates the control shaft 2 in the direction indicated by the arrow F6 in FIG. 13 to bring the cam boss 7 to select the fork sticks. 15 as shown in FIG. 14 which also shows that during this phase of selection of the third gear ratio, the second gear ratio is maintained engaged by the boss 6 resting on the butt 14b of the forks 14. fork sticks 13, 15 and 16 in their locked neutral position.

  Then, the actuator rotates the control spindle 2 in the direction indicated by the arrow F7 by an angular value of about 90 at the position shown in FIG. 15 at which the cam-forming boss 7 moves the butts in translation. fork 15 in the direction indicated by the arrow F8 to engage the third gear, the cam boss 6 having disengaged from between the two sticks 14a, 14b to disengage the second gear and lock the pair of sticks 14 to its position of dead point by the cylinder 3 as clearly shown in Figure 15. Of course, the cylinder 3 maintains in their locked position of dead point forks fork 13, 14 and 16, the fork sticks 15 being maintained at their locked third gear engagement position in the manner shown in Figure 9.

  Although this is not shown in the figures, the passage of the following gear ratios is easily understood.

  Thus, to enable the engagement of the fourth gear ratio, the actuator translates the control shaft 2 as indicated by the arrow F9 in FIG. 15 so as to cause the cam boss 8 to select the fork brackets 15 , the third gear ratio being maintained engaged by the boss 11 coming opposite the butt 15a, the bosses 4-6 and 10 of the upper game being in the space between the forks 14 and 15. Then, the actuator rotates the control spindle 2 in the same direction as indicated by the arrow F4 in FIG. 12 and an angular value of approximately 90 so as to allow the boss 8 to translate the forks 15 in translation. in the direction opposite to the arrow F8 of FIG. 15 and, consequently, to engage the fourth gear ratio with disengagement of the third gear ratio, the forks 13, 14 and 16 being kept locked at the the neutral position of the cylinder 3.

  The sequence of displacement in translation and in rotation of the control shaft 2 by the actuator to select the fifth gear ratio and engage it and select the sixth gear ratio and engage it is the same in relation to Figures 13 to 15 with the difference that the bosses 7-9 and 11 replace the bosses 4-6 and 10 to move the pairs of forks fork 15 and 16.

  As represented in FIG. 3, the external grid of the gearbox of the invention, by virtue of its control device, allows rectilinear passages between each speed ratio by means of a change of selection corridor between each of these passages, the circles of Figure 3 materializing the possible changes of direction at each intersection. Thus, it is possible to have the rectilinear ratio of passes between the speeds while preserving the possibility of skipping speed report or fast return of dead center through the central corridor. The device of the invention proposes six channels of selection of gear ratios while a normal gearbox geared grid generally offers four.

  According to an alternative embodiment, the cylinder 3 of the control spindle 2 may be provided with a single set of 4-6 and 10 cam bosses passage elements in the configuration according to which the four pairs of fork brackets 14-16 are arranged equidistantly from each other in the axial direction of the control shaft 2, the distance separating them corresponding to that separating two pairs of upper forks 13, 14 or lower 15, 16.

  The control device of the invention is designed in such a way that the bosses 4 and 7 allow the engagement of the odd-speed ratios, the bosses 5 and 8 allow the change of selection line, release the odd gear ratio and engage the corresponding even gear ratio and the bosses 6, 9 allow clearance of even gear ratios. The boss device forming cams pivoting and translating between the butts or speed passage nuts allows a selection of even gear ratio gear engaged and the gearshifts are then always to achieve by a single movement of rotation of the axis control. The device finally allows the interlocking of all gear ratios engaged or not engaged.

  The control device of the invention is extremely reliable since it is impossible to engage two gear ratios at a time by its interlocking means and impossible to have a loss of kinematics through the control of the actuator. Finally, this device is of a relatively simple structure and the performance of passage is equivalent on all gear ratios.

Claims (9)

  1. Internal control device of a single clutch driven gearbox of a motor vehicle comprising an actuator for moving a control shaft (2) in translation along its longitudinal axis and in rotation about its longitudinal axis for the selection and the passage of gear ratios, via at least one passage element carried by the control shaft (2) selectively engaging between two butts of a fork among a plurality of forks (13-16) associated with synchronizers to ensure the interconnection of the corresponding synchronizer on gears corresponding to the gear ratio selected, characterized in that the control shaft (2) passes through the fork caps (13-16) perpendicularly to the plane of these sticks and carries at least one set of three passage elements respectively comprising three cam-shaped eccentric bosses (4-6) extending perpendicularly to the control axis nde (2) and being arranged relatively to the control axis to be able to cooperate, by the actuator moving in translation and in rotation the control shaft (2) in a predetermined sequence, with each pair of butts (13; 14; 15; 16) of a fork (21; 22; 23; 24) to move it in translation in the direction corresponding to the engagement of the selected gear ratio.   2. Device according to claim 1, characterized in that the three camming bosses comprise a first cam boss (4; 7) for moving a selected pair of engagement forks of an odd gear ratio, a second camming boss (5; 8) for selectively changing a pair of hooks, disengaging the odd gear ratio previously engaged, and moving a selected pair of engagement fork sticks with an even gear ratio , and a third cam boss (6; 9) for moving a pair of forks to disengage it from the even gear ratio previously engaged.   3. Device according to claim 2, characterized in that the second (5; 8) and third bosses (6; 9) forming cams are superimposed contiguously with the third boss (6; 9) located above the second boss (5). 8) and the first cam boss (4; 7) is angularly offset from the second and third bosses by about 90 by being axially offset relative thereto so that the upper planar face of the first boss (4; 7) is located substantially in the same plane as the lower planar face of the second boss (5; 8), this plane extending transversely to the control axis (2).   4. Device according to claim 3, characterized in that the actuator moves in translation the control shaft (2) to bring the second boss (5; 8) between the two ends of a selected fork and then moves the control spindle (2) in rotation to move these two sticks in translation by the first (4; 7) or second boss (5; 8) forming a cam in a direction of engagement of an odd or even gear ratio.   5. Device according to claim 4, characterized in that it comprises a fourth cam boss (10; 11) integral with the control shaft (2) perpendicular to the latter being superimposed contiguously to the first cam boss (4). 7) and making it possible to hold the two sticks of a fork at the engaged position by an odd gear ratio while the actuator moves the control pin (2) in translation to a position for selecting the two sticks. the next pair of gear ratios and the third boss (6; 9) maintains locked two forks at their engaged position of an even gear ratio while the actuator moves the control shaft in translation ( 2) at a selection position of a next odd speed ratio.   6. Device according to claim 5, characterized in that it comprises four pairs of superposed forks fork (13-16), equidistantly spaced from each other and allowing the engagement of six gears forward gears and a reverse gear ratio and successively comprising a pair of reverse gear forks (13), a pair of engagement forks (14) for engagement of the first and second gear ratios, a pair of forks (15) for engaging the third and fourth gear ratios and a pair of fifth gear forks (16) for engagement of the fifth and sixth gear ratios, and that for the drive shaft (2). carries a single set of three passage members and is sequentially displaced in translation and rotation by the actuator to allow the camming bosses (4,5, 6) to alternately move the pairs of forks ( 13-16) to engage the selected forward and reverse gears.   7. Device according to claim 5, characterized in that it comprises four pairs of superimposed forks (13-16) allowing the engagement of six gears forward gears and a reverse gear ratio and comprising successively two upper pairs of forks (13, 14) spaced apart from one another respectively engaging the reverse gear ratio and the first and second forward gears ratios and two lower pairs of gait hooks. forks (15, 16) spaced from each other by the same distance as that separating the two upper pair of forks (13, 14) and allowing engagement of the third and fourth forward gears, respectively and fifth and sixth forward gear ratios, the upper pairs of forks (13, 14) being spaced apart from the lower pairs of forks (15, 16) of a no distance greater than that separating two pairs of upper or lower forks from each other and in that the control shaft (2) carries two sets of three passage elements spaced axially one of the another along the control axis (2) which can be sequentially displaced in translation and in rotation by the actuator so that the cam bosses (4, 5, 6) of one of the sets of three passage elements can cooperating with the two upper pairs of forks (13, 14) to engage one of the corresponding gear ratios and the camming bosses (7, 8, 9) of the other set of three passage elements can cooperate with the two pairs of lower forks (15,16) to engage one of the corresponding gear ratios.   8. Device according to one of the preceding claims, characterized in that the cam bosses (4, 5, 6, 10; 7, 8, 9, 11) of a set are integral with a cylinder (3) crossed coaxially by the control shaft (2) and a diameter substantially equal to the distance between two brackets of a fork so as to lock in the neutral position forks of forks for which no gear ratio is engaged .   9. Device according to claim 8, characterized in that the cylinder (3) of the control shaft (2) has, opposite to each cam-forming boss, a recessed portion (12) of substantially conjugate shape to that the end of each of the two ends of a fork and intended to receive one end of a stick when the associated camming boss bears against the opposite end of the other stick so as to lock the two sticks ( 13; 14; 15; 16) at their engagement position of the corresponding gear ratio.   W. Device according to claim 9, characterized in that the recessed portion (12) and the cam boss of a passage member are arranged symmetrically to the plane containing the longitudinal axis of the control shaft (2) and passing by the rounded free end of the cam boss.