WO2001013012A1

WO2001013012A1 - Motor vehicle automatic transmission

Info

Publication number: WO2001013012A1
Application number: PCT/FR2000/002303
Authority: WO
Inventors: Randolph Victor Toom
Original assignee: Antonov Automotive Technologies B.V.
Priority date: 1999-08-18
Filing date: 2000-08-11
Publication date: 2001-02-22
Also published as: AU7011700A; TW470831B; FR2797666B1; JP2003507671A; EA200200218A1; AR025315A1; FR2797666A1; EP1210533A1

Abstract

The invention concerns a transmission system wherein, when a torque to be transmitted by the transmission device exceeds the value transmissible by a direct drive clutch (18), on account of the application force defined by the centrifugal counter-weights (29), said clutch slips, the planet pinion carrier (13) coupled to the output shaft (2b) slows down, the planetary gear (9) slows down further and ends up being immobilised by a free wheel (16). This causes a reaction force of the teeth (PAC) in the ring (8), which is urged, via an axial stop (B2) to release the clutch (18) so as to eliminate therein all friction while the resulting reduction operates. Said axial motion of the ring (8) is enabled by a coupling device (17) which transmits the engine (5) torque while enabling the member (17a) bearing the ring (8) to slide relative to the input member (17b). The coupling device (17) is a frictionless device, for example operating by elastic material deformation. The invention is useful for enhancing smooth engagement of ratio shifts by eliminating in the axial motion frictions which increase with the transmitted torque, often non-linearly.

Description

DESCRIPTION

AUTOMATIC TRANSMISSION OF A MOTOR VEHICLE

The present invention relates to a transmission device, in particular for a land vehicle.

The present invention relates more particularly but not limited to an automatic transmission device in which the quality of the gear changes is improved, in particular with regard to progressiveness, and this even after a long cumulative period of use.

In transmission devices, in particular automatic ones, gear changes are made by activating selective coupling devices and deactivation of other such selective coupling devices. These selective coupling devices can be clutches or brakes, in particular of the multi-disc type.

The quality, and more particularly the smoothness of the gear change, depends in particular on good control of the movement of the movable member which comes, in the example of a multi-disc clutch, to tighten the stack of discs. In certain applications, such a clamping member is at the same time a torque transmission member which slides by means of grooves relative to another transmission member, which is for example immobilized axially relative to the casing of the transmission device.

It has been found according to the invention that these splines, although universally used, in fact have numerous drawbacks and inadequacies. If they are formed along a circumference of small diameter, they must be given a long axial length so that the sliding guide is correct and so that the pressure between the flank sides does not exceed a predetermined limit value. These difficulties can be overcome to some extent by forming the grooves on a circumference of larger diameter, but the cost, weight and radial bulk of the coupling can become prohibitive. In addition, the grooves wear out, take up play, and provide guidance which degrades over time, so that the quality of the gear changes caused by a sliding movement in such grooves degrades with the aging of the device. of transmission.

The object of the present invention is to provide a transmission device, in particular for a land vehicle, in which the quality of the gear changes is improved when the device is new, and keeps better during the aging of the device.

According to the invention, the transmission device, in particular for land vehicle, comprising:

- torque transmission members, comprising a rotary input member and a rotary output member; - a selective coupling means mounted between two of the torque transmission members;

- a combination of teeth connecting by meshing at least some of the torque transmission members and producing between the input and output members two transmission ratios depending on whether the selective coupling means is in a coupled state or in a released state respectively, and in which,

a first of the transmission members is mounted to control the state of the selective coupling means by axial displacement, and

- rotational connection means with possibility of axial relative displacement are installed between said first transmission member and a second of said transmission members, is characterized in that the connection means are of a type essentially without friction during axial displacement of the first transmission member with respect to the second transmission member. According to a first version, the connection means comprise at least one deformable element having a variable dimension parallel to the axis. This deformable element transmits the torque around the axis while allowing the first transmission member to move axially relative to the second transmission member, without significant friction between them during such a movement.

According to a second version, the connection means are of a rolling type.

Elements mounted in rotation between a first track belonging to the first transmission member and a second track belonging to the second transmission member, transmit the torque from one track to another. Again, any significant friction is eliminated between the two transmission members during a relative axial displacement between them. Other features and advantages of the invention will emerge from the description below, relating to non-limiting examples.

In the accompanying drawings: FIG. 1 is a schematic longitudinal sectional half-view of a powerplant comprising a motor and a two-speed transmission device according to the invention, at rest, and with cutaway;

- Figure 2 is a view similar to Figure 1, but relating to the reduction gear operation; - Figure 3 is a schematic, partial cross section of the transmission of Figures 1 and 2, showing the deformable connecting means in a first embodiment;

- Figure 4 is a view substantially along IV-IV of Figure 3;

- Figure 5 is a longitudinal sectional view of an alternative embodiment of the slats;

- Figure 6 is a partial view, in axial section, of a second embodiment of the connecting means; FIG. 7 shows in two axial half-sections two variants of a third embodiment of the connecting means; - Figure 8 is a partial view in axial section showing a fourth embodiment of the connecting means;

- Figures 9, 11 and 15 are axial sections showing three other embodiments of the connecting means;

- Figures 10, 12 and 16 are cross-sectional views of the embodiments of Figures 9, 11 and 15 respectively; - Figure 13 is a sectional view along XIII-XIII of Figure 12;

- Figure 14 is a perspective view of a cage for retaining the rolling needles;

- Figure 17 is a perspective view of a truncated roller of the embodiment of Figures 15 and 16;

- Figure 18 is a top view of the roller of Figure 17; Figure 19 is an axial sectional view of a variant for the embodiment of Figure 15; - Figure 20 is a cross-sectional view relating to a variant of the arrangement shown in Figure 16; FIG. 21 is a partial end view illustrating a means for retaining the rollers; - Figure 22 is a sectional view along XXII-XXII of Figure 21;

FIG. 23 is a partial front view illustrating another embodiment of the retaining means, and

FIG. 24 is a partial perspective view illustrating the retaining means of FIG. 23.

The two-speed transmission device shown in FIG. 1, intended in particular for an automobile, comprises an input shaft 2a and an output shaft 2b aligned along their common axis of rotation 12, which constitutes the main axis of the device . The input shaft 2a is connected to the output shaft of the engine 5 of a motor vehicle with the interposition of an input clutch 3 and possibly other means of transmission not shown. The output shaft 2b is intended to drive the driving wheels of a vehicle directly or indirectly. Between the output shaft 2b and the wheels of the vehicle can for example be interposed another transmission device with two or more reports and / or a reverse gear reverse - reverse gear with manual control, and / or a differential movement distribution between the drive wheels of the vehicle.

The input shafts 2a and output 2b are immobilized axially relative to a casing 4 of the transmission device, which is only very partially shown.

The transmission device comprises a differential gear formed by a planetary gear 7. The train 7 comprises a ring gear 8 with internal teeth and a planetary wheel 9 with external teeth, both meshing with satellites 11 distributed around the axis 12 of the device of transmission. The satellites 11 are supported in rotation by eccentric pins 14 of a planet carrier 13 rigidly connected to the output shaft 2b. The planetary wheel 9 can rotate freely around the axis 12 of the transmission device relative to the output shaft 2b which it surrounds. However, a freewheel device 16 prevents the planetary wheel 9 from rotating in reverse, that is to say in the opposite direction to the normal direction of rotation of the input shaft 2a, relative to the casing 4 of the transmission.

The crown 8 is linked in rotation, but free in axial sliding, relative to the input shaft 2a, by means of a connecting device 17, simply symbolized in Figures 1 and 2, which more particularly object of the invention and will be described in more detail below with reference to the other figures.

The connecting device 17 is formed between a first transmission member 17a rigidly carrying the crown 8 and a second transmission member 17b rigidly secured to the input shaft 2a.

A multi-plate clutch 18 selectively couples the crown 8 with the planet carrier 13. The alternating stack of disks 19 and disks 2 ₂ of the clutch 18 can be clamped axially between a retaining plate 26 secured to the planet carrier 13 and a movable plate 27 which belongs to a cage 20, linked in rotation with the planet carrier 13, but capable of sliding relative to the latter. The cage 20 carries internal grooves 23 with which mesh peripheral teeth of the discs 22 as well as peripheral teeth 24 of the retaining plate 26. The first transmission member 17a carries external grooves 33 with which mesh internal peripheral teeth of the discs 19 .

The cage 20 supports a centrifugal actuator 25 intended to apply to the stack of discs 19, 22 an axial clamping force varying as a function of the speed of rotation of the cage 20 and therefore of the planet carrier 13 and the shaft of outlet 2b around the main axis 12. The centrifugal actuator 25 comprises centrifugal weights 29 arranged in a ring around the clutch 18. The weights are supported by the cage 20 and therefore linked in rotation to the output shaft 2b of the transmission device.

The rotation of the planet carrier 13 around the main axis 12 tends to make a body 31 of each flyweight 29 pivot radially outwards around its tangential pivot axis 28 under the action of centrifugal force, to pass the counterweights from a rest position E _R defined by pressing an abutment 36 of the counterweights against the cage 20 (solid lines in FIGS. 1 and FIG. 2) at a position E more or less radially spaced apart, visible in dotted lines in Figure 1. This then results in a relative axial displacement between a spout 32 of each counterweight and the pivot axis 28 of the counterweight. This displacement, which brings the spout 32 closer to the movable plate 27, can correspond to a compression of a spring element 34 mounted between the spout 32 and the retaining plate 26 and / or to a displacement of the movable plate 27 towards the retaining plate 26 in the direction of clutch clutch 18. In the example shown, the spring element 34 is constituted by two belleville washers mounted one after the other and in opposition to each other.

When the transmission device is at rest as shown in solid lines in FIG. 1, the spring element 34 transmits to the cage 20, by means of the counterweights 29 in abutment in the rest position E _R , a prestressing force which tightens the clutch 18 so that the input 2a of the transmission device is coupled in rotation with the output 2b and the transmission device constitutes a direct connection capable of transmitting torque up to a certain maximum defined by the prestressing force of the spring element 34.

The teeth of the crown 8, of the satellites 11 and of the planetary wheel 9 are of the helical type. Thus, in each pair of teeth meshing under load, there appear opposite axial thrusts proportional to the circumferential force transmitted, therefore to the torque on the input shaft 2a and to the torque on the output shaft 2b. The helical inclination direction of the teeth is chosen so that the axial thrust Pac (FIG. 2) originating in the crown 8 when it transmits a driving torque, is exerted in the direction where the crown 8, via the first transmission member 17a and an axial stop B2, pushes the movable plate 27, in the direction separating the plates 26 and 27, therefore loosening the clutch 18. The force Pac also tends to move towards one another the spout 32 of the flyweights 29 and the retaining plate 26, therefore to bring back or to maintain the flyweights 29 in their rest position E _R and to compress the spring element 34. The satellites 11, which not only mesh with the crown 8 but also with the planetary wheel 9, undergo two opposite axial reactions PSI and PS2, which balance each other, and the planetary wheel 9 undergoes, taking into account its meshing with the satellites 11, an axial thrust Pap which is equal in intensity and opposed to thrust axial Pac of the crown 8. The thrust Pap of the planetary wheel 9 is transmitted to the casing 4 by means of an axial stop B3.

Such a situation is shown in Figure 2. Assuming this situation has been achieved, we will now describe the basic operation of the transmission device. As long as the torque transmitted by the input shaft 2a is such that the axial thrust Pac in the crown 8 is sufficient to push back the spouts 32 of the counterweights 29 by means of the spring element 34, the spacing between the plate 26 and the movable plate 27 of the clutch is such that the discs 19 and 22 slide against each other without transmitting torque between them.

The planet carrier 13 can then rotate at a speed different from that of the input shaft 2a, and it tends to be immobilized by the load that the output shaft 2b must drive. As a result, the satellites 11 tend to behave as motion inverters, that is to say to rotate the planetary wheel 9 in the opposite direction to the direction of rotation of the crown 8. But this is prevented by the freewheel 16. The planetary wheel 9 is therefore immobilized by the free wheel 16 and the planet carrier 13 rotates at a speed which is intermediate between the zero speed of the planetary wheel 9 and the speed of the crown 8 and of the input shaft 2a . The transmission device therefore operates as a reduction gear. If, for example, the speed of rotation increases and the torque remains unchanged, there comes a time when the centrifugal force of the counterweights 29 produces on the movable plate 27 relative to the retaining plate 26 an axial clamping force greater than the axial thrust Pac, the counterweights 25 are raised towards the position E (FIG. 1) and the movable plate 27 is pushed towards the plate 26 to produce a direct engagement which differs from that shown in FIG. 1 only in that the spring is more compressed by the spout 32 of the flyweights. The clutch 18, as it is tightened during the transition to direct drive, transmits more and more power directly from the crown 8 linked to the input shaft 2a, to the planet carrier 13 linked to the output shaft 2b. Consequently, the teeth of the planetary gear 7 work less and less, that is to say that they transmit less and less force. The axial thrust Pac decreases and eventually cancels out. Thus, the axial thrust due to the centrifugal force can exercise fully to tighten the plates 26 and 27 towards each other.

It can then happen that the speed of rotation of the output shaft 2b decreases, and / or that the torque to be transmitted increases, to the point that the weights 29 no longer provide in the clutch 18 a sufficient clamping force to transmit the couple. In this case, the clutch 18 begins to slip. The speed of the planetary wheel 9 decreases until it cancels out. The freewheel 16 immobilizes the planetary wheel and the tooth force Pac reappears to loosen the clutch, so that the transmission device then operates as a reduction gear. Thus, each time there is a change from the reduction gear operation to the direct drive operation, or vice versa, the axial force Pac varies in the direction which stabilizes the newly instituted transmission ratio. This is very advantageous on the one hand to avoid too frequent gear changes around certain critical operating points, and on the other hand so that the slippage situations of the clutch 18 are only transient.

In the example shown in Figures 3 and 4, the connecting device 17 is mounted between the elements 17a and 17b both having in this region the shape of a radial plate relative to the axis 12, according to the illustration more schematic of Figure 1.

The connecting device 17 comprises flexible blades 37 having a first end 37a secured by a rivet 41a with the first transmission member 17a and a second end 37b secured by a rivet 41b with the second transmission member 17b. Between the first and second transmission members 17a, 17b, the blades 37 have a zone 37c adjacent to the first end 37a and curved towards the second transmission member 17b and a zone 37d adjacent to the second end 37b and curved in the another direction, that is to say towards the first transmission member 17a. When the first transmission member 17a moves axially relative to the second transmission member 17b, the curvature of the zones 37c and 37d increases or decreases. There are several sets of blades 37 as shown in FIG. 4 which are distributed around the axis 12, as shown in FIG. 3. The blades 37 are oriented approximately tangentially so as to transmit the engine torque by a tensile stress in the blades 37. An arrow 39 indicates the direction of the engine torque. As shown in dotted lines, it is possible to provide other blades 37e, oriented circumferentially in the other direction from the second transmission member 17b, for transmitting by negative tensile stress of the blades 37e the negative torque (contrary to the direction 39) produced by the engine when operating in restraint. In the absence of such additional blades 37e, it is the blades 37 which transmit this torque by a compressive stress. The thickness, length, width, and material of the blades 37 are chosen to provide the following functions and results:

- The blades 37 flex elastically, practically without resistance, during the axial displacements of the first 17a relative to the second transmission member 17b;

- The blades 37 are capable of transmitting the torque of the motor 5 from the second transmission member 17b to the first transmission member 17a; and

the blades 37 ensure sufficient centering of the first transmission member 17a around the axis 12.

For this, the blades 37 are very thin to be very flexible, relatively wide to have, despite their thinness, a cross section sufficient to transmit the torque, and long enough to remain roughly in a radial plane whatever the relative axial position. the first and second transmission members 17a, 17b.

According to an exemplary embodiment, the blades 37 can be made of spring steel with a thickness of for example 0.7 mm and a length of 3 or 4 cm, to allow an axial stroke of approximately 2 mm. It is advantageous, as shown, to stack the slides at least ^'two. A stack of two blades 37 has the same torque transmission capacity only one blade of double thickness, but greater flexibility.

In service, the crown 8 tends to center spontaneously around the satellites 11 which are angularly distributed around the axis 12. This centering effect is due to the teeth repulsion forces, directed radially with respect to the axis 12, and which arise between the teeth of the crown 8 and the teeth of each satellite 11. The connecting device 17 therefore only partially ensures the centering of the first transmission member 17a relative to the second transmission member 17b.

If necessary, additional sliding centering means can be provided without detracting from the good results of the invention since this complementary centering device will be arranged so as not to transmit the torque which will remain transmitted exclusively by the device 17.

In the example shown in Figure 5, the blade 37 is made with a greater thickness at the ends 37a and 37b, than in the bending zones 37c and 37d. In the example shown in Figure 6, the connecting device 17 comprises a metal bellows 47 having a tubular end 47a welded to the first transmission member 17a having for this purpose an end in the form of a shaft end along the axis 12 , and a second tubular end 47b welded to the second transmission member 17b, also terminated in the form of a shaft end for this purpose. The bellows 47 is axially compressible without significant elastic resistance, while being capable of transmitting the torque of the motor without excessive torsional deformation and while ensuring proper centering of the shaft end of the first transmission member 17a relative to 1 ' axis 12.

In the example shown at the top of FIG. 7, the connecting device 17 comprises a disc 57 having annular undulations around the axis 12. The annular disc 57 has an outer peripheral edge 57a welded to the first transmission member 17a and a welded inner peripheral edge 57b to the second transmission member 17b. The disc 57 allows without significant elastic resistance, by bending, to the first transmission member 17a to move axially relative to the second transmission member 17b while ensuring proper centering of the first transmission member 17a relative to the second transmission member 17b around the axis 12 and transmitting the torque from the transmission member 17b to the transmission member 17a practically without deformation. The variant shown at the bottom of FIG. 7 is distinguished only by a different shape from the first transmission member 17a, for the case (different from that shown in FIGS. 1 and 2) where the first transmission member 17a should be made integral by example of an external toothing 58 carried by a shaft 59. One of the transmission members (17a in the example) then comprises a rigid flange 61 connecting the shaft 59 to the area of the weld with the outer peripheral edge 57a of the corrugated disc 57.

In the variant of FIG. 8, the disc 57e is made planar. This variant may be suitable when the axial displacements are very small, or when the radial space available makes it possible to produce a large diameter disc, or even when the torque to be transmitted is relatively small and makes it possible to produce the disc thinner than at the figure 7.

In the example shown in Figures 9 and 10, the connecting device 17 comprises spherical balls 67 arranged in four axial rows distributed around one axis 12. Each row is arranged in a corridor 68 of generally cylindrical shape formed for half by a groove 68a of semi-circular profile belonging to the first transmission member 17a and for the other half by a groove of semi-circular profile 68b belonging to the second transmission member 17b. The grooves 68a and 68b have a slightly larger diameter than the balls 67. The grooves 68a, formed on a cylindrical bore of the first transmission member 17a, open radially towards the axis 12. The grooves 68b, formed in a male cylindrical surface of the second transmission member 17b, open radially in the opposite direction to the axis 12. There is a slight radial clearance 71 between the cylindrical wall 69a of the bore of the first member transmission 17a and the cylindrical wall maie 69b, slidably engaged in the bore 69a and belonging to the second transmission member 17b. The spherical balls 67 are mounted substantially without radial clearance between the respective tracks 68a and 68b, thus ensuring, without friction, the centering of the first transmission member 17a relative to the second transmission member 17b. By the presence of at least two balls 67 per row, the connecting device 17 simultaneously ensures rigorous axial alignment of the first transmission member 17a with the second transmission member 17b.

When the first transmission member 17a slides axially relative to the second transmission member 17b, each ball 67 rolls on each of the two tracks 68a and 68b between which it is installed. During the transmission of a torque according to arrow 39, a face 72b of each groove 68b bears laterally on the balls 67 and presses the balls 67 against an opposite face 72a of each groove 68a. The faces 72a and 72b are inclined relative to a circumferential direction around the axis 12. The balls 67, which are for example of steel of the type used for rolling bearing balls, transmit the torque of the member transmission 17b to the first transmission member 17a by their resistance to shear stress along the cylindrical interface between the transmission members 17a and 17b, and to the compressive stress between the faces 72b and 72a of the grooves.

As the axial travel of the transmission member 17a is moreover limited, there is no risk that the transmission member 17a escapes beyond the end of the transmission member 17b. There could however be a risk that the balls 67 escape through the left end of Figure 9, where the two grooves 68a and 68b of each corridor are made open. To avoid this, an elastic retaining ring 74 mounted in an appropriate groove of the first transmission member 17a serves as an axial stop for the ball 67 located closest to this end in each passage 68. In the example shown, at other end, that is to say on the right side, the grooves 68b belonging to the second transmission member 17b are made closed at 75.

In the example shown in Figures 11 and 12, the connecting device 17 comprises cylindrical needles 77 whose axis 77a is radial with respect to the axis 12. The needles 77 are distributed in four rows angularly equidistant around the axis 12, in four corridors 78 parallel to axis 12 and having a rectangular cross section. Each passage is defined jointly by the radially inner surface 69a of the first transmission member 17a and by the radially outer surface 69b of the second transmission member 17b.

Each passage 78 is defined by two concave dihedral conformations 78a, 78b, one belonging to the first transmission member 17a, the other to the second transmission member 17b. Each dihedral conformation comprises a planar raceway 82a, 82b and an end stop face

83a, 83b for the needles 77. The tracks 82a, 82b are parallel to the spokes passing through the axis of the needles

77, and therefore perpendicular to a circumferential direction around the axis 12. The end abutment faces 83a and 83b are oriented tangentially with respect to the axis 12. The rolling tracks 82a of the first transmission member 17a are rotated alternately clockwise and counterclockwise around axis 12 so that the hands 77 of two diametrically opposed lanes 78 transmit the torque in one direction and the needles 77 of the other two lanes transmit torque of rotation in the other direction. When the needles transmit the torque, they are under compression stress between the two opposite tracks 82a and 82b of their respective lane 78. FIG. 14 illustrates that the needles 77 of the same lane can be mounted in a cage 84 in which the needles can turn on themselves. When the first 17a and second 17b transmission members move axially with respect to each other, the cage 84 moves at intermediate speed between the two members 17a and 17b in the respective corridor 78.

The example of Figures 15 to 18 will only be described for its differences from the previous one. Each row of needles 77 is replaced by a single roller 87 whose radius R (FIG. 18) is large enough for the roller to pivot only around 15 to 20 ° when the first transmission member 17a performs all of its axial sliding stroke relative to the second transmission member 17b. Thus, the roller does not need to have a complete cylindrical surface, but only two diametrically opposite cylindrical rolling arcs 87a and 87b, separated by two parallel and opposite flats 87c. In service, as shown in FIG. 15, the two flats 87c are oriented transversely with respect to the axis 12. Consequently, the axial dimension of the connecting device 17 according to this embodiment is particularly reduced. In the corridors 78, the distance between the opposite tracks 82a and 82b is equal to 2R, it is therefore much greater than in the example of FIGS. 11 to 14.

Such an embodiment requires ensuring that the rollers 87 will not slide on the tracks instead of rolling there. For this, each rolling surface 87a or 87b carries a gear pattern 89a or 89b, respectively adjacent to the middle of one of the curved edges of the surface 87a or 87b. Each of the patterns 89a or 89b is a gear tooth developing from a circle in the example shown. Each tooth 89a or 89b is in service engaged in a complementary gear pattern (toothing) 91a or 91b formed in the corresponding rolling track 82a or 82b. The primitive circle C _p (Figure 18) of the two teeth 89a and 89b of the same roller 87 coincides with the circle of the rolling surfaces 8 ₇ a and 87b.

As illustrated in Figure 17, there is thus at each cylindrical end of the roller an area shown with cross hatching for the rolling contact with the corresponding track 82a or 82b and next to this a non-hatched strip in the middle of which is the tooth and which is used for meshing with the toothed recess 91a or 91b for the angular indexing of the roller with respect to each of the two transmission members 17a and 17b. The diameter of the pitch circle C _P and the geometry of the teeth are chosen, relative to the axial travel provided between the two transmission members 17a and 17b, so that the teeth 89a and 89b remain in a state of engagement with the teeth of the teeth correspondents 91a and 91b throughout the relative axial travel between the two transmission members 17a and 17b.

The example shown in FIG. 19 differs from that of FIG. 15 only in that the second transmission member 17b is now radially inside and the first transmission member 17a is in the form of a crown rigidly carrying the teeth. 8 of Figure 1.

The example of FIG. 20 comprises, compared with that of FIG. 16, two differences which can be implemented independently of one another: - Two rollers 87d of larger diameter alternate with two other rollers 87e of smaller diameter. The larger diameter rollers 87d are those which will be under stress for the transmission of the engine torque and the other two rollers 87e are those which will be under stress during the transmission of the retaining torque, which is lower than the engine torque.

- The rollers are off-center with respect to the diameters D passing through the axis 12, one out of two rollers being off-center in a circumferential direction and the other in the other circumferential direction. The rollers are thus gathered in two groups instead of being distributed regularly around the axis 12. This results for the internal transmission member (17a in this example) a more compact and therefore more robust form than that resulting from the embodiment of FIG. 16.

In the example of FIG. 20, an indexing tooth has not been shown for the rollers, but such teeth may be provided.

Figures 21 and 22 illustrate an improvement that can be made to the examples of Figures 15 to 20 to ensure the stability of the coupling before mounting in the transmission device. It will be understood in particular from FIG. 15 that the indexing teeth ensure the stability of the coupling only if the first transmission member 17a is prevented from moving too far to the left of the figure. In the example of FIG. 19, it is also necessary to prevent the transmission member 17a from moving too far to the right. Such excessive movements are, at least in the example of Figures 1 and 2, prevented by the rest of the transmission device. But they may occur before mounting. To avoid this, a spring wire retaining device 92 is provided, comprising a central part 93 which is fixed to the radially inner transmission member.

(17b in this example) and two retaining tabs 94 located on either side of the central part 93 and coming to bear against the flat 87c of a respective roller, and more particularly in a groove 96 formed for this purpose on the flat. The central part 93 passes through a milling 97 passing through the second transmission member 17b and loops back on the other side of the member 17b by a hook configuration 98. Between the central part 93 and each wing 94 the spring wire passes under a positioning hook 99 formed on the corresponding front face of the transmission member 17b.

With this device, when the first transmission member 17a moves axially in the direction causing movement of the rollers 87 towards the side where the retaining tabs 94 are located, these deform elastically and then end up preventing the continuation of the movement of the roller. As the latter is indexed by the teeth 89a and 89b relative to the two transmission members 17a and 17b, the immobilization of the roller prevents the continuation of the relative axial movement between the two transmission members 17a and 17b. FIG. 21 also illustrates that another retaining device intended to be placed on the other face of the transmission member 17b can be installed in the same milling 97 to rest on the other side of the rollers and thus limit the relative axial movement in the other direction of movement. In theory, it suffices to immobilize a single roller to immobilize the two transmission members axially with respect to each other. Each retainer shown immobilizes two rollers with respect to a direction of movement. We can further strengthen the immobilizing action by mounting one or two retaining devices on the other two rollers of the connecting device.

In the example of FIGS. 23 and 24, where the rollers such as 87 are omitted to simplify the representation, the retaining device comprises a spring wire 102 in the shape of a U. A central part 103 of the U is held by hooks 109 on the front face of one (17b) of the transmission members. The two ends 94 of the U form elastic axial stop lugs for the corresponding front face of the other (17a) transmission member. There may be two diametrically opposite retaining devices (only one is shown), and possibly two others (not shown) on the other front face of the members 17a and 17b.

Of course, the invention is not limited to the examples described and shown. In particular, the application of the invention is not limited to a transmission device such as that described with reference to FIGS. 1 and 2. It is for example possible that the first transmission member is integral with the planetary wheel 9 of a planetary train. Furthermore, the numbers of blades, rollers, rows of balls or needles may be different from those shown in the different examples.

Claims

1- Transmission device, in particular for land vehicle, comprising:

- torque transmission members, comprising a rotary inlet member (2a) and a rotary outlet member

(2b);

- a selective coupling means (18) mounted between two of the torque transmission members (17a, 13); a combination of teeth (7) connecting by meshing at least some of the torque transmission members and producing between the input and output members two transmission ratios depending on whether the selective coupling means (18) is in a coupled state or in a released state respectively, and in which,

- A first (17a) of the transmission members is mounted to control by axial displacement the state of the selective coupling means (18), and means (17) for connection in rotation with the possibility of axial relative displacement are installed between said first (17a) transmission member and a second (17b) of said transmission members, characterized in that the connecting means (17) are of an essentially frictionless type during axial movement of the first transmission member (17a) by report to the second transmission member (17b).

2- Device according to claim 1, characterized in that the connecting means comprise at least one deformable element (37, 47, 57) having a variable dimension parallel to the axis (12).

3- Device according to claim 2, characterized in that the deformable element is a bellows (47).

4- Device according to claim 2, characterized in that the deformable element is a thin disc (57, 57e). 5- Device according to claim 4, characterized in that the disc (57) has at least one annular corrugation centered on the axis (12). 6- Device according to claim 2, characterized in that said at least one deformable element comprises at least one flexible blade (37) disposed with its thickness substantially in the axial direction and fixed by a first end (37a) to the first transmission member (17a) and by a second end (37b) to the second transmission member (17b).

7- Device according to claim 2, characterized in that said at least one deformable element comprises at least two flexible blades (37) arranged with their thickness substantially in the axial direction and grouped in at least one stack, each stack being fixed by a first end (37a) to the first transmission member (17a) and by a second end (37b) to the second transmission member (17b).

8- Device according to one of claims 2 to 7, characterized in that 1 'at least one deformable element (37, 47,

57) is, once mounted, substantially rigid in torsion around the axis (12) so as to be able to transmit the torque between the first (17a) and the second (17b) torque transmitting member. 9- Device according to claim 8, characterized in that 1 'at least one deformable element (37e) is, at least when mounted, more rigid against a direction of relative rotation between the first (17a ) and the second (17b) transmission member that is against the other direction. 10- Device according to one of claims 2 to 9, characterized in that the at least one deformable element (37, 37e, 47, 57) is mounted to ensure at least partially between the first (17a) and the second ( 17b) transmission member, centering relative to the axis (12). 11- Device according to claim 1, characterized in that the connecting means (17) are of a rolling type.

12- Device according to claim 11, characterized in that the connecting means comprise elements (67, 77, 87, 87d, 87e) mounted in rotation between a first track (67a, 78a, 82a) belonging to the first transmission member (17a) is a second track (68b, 78b 82b) belonging to the second transmission member (17b). 13- Device according to claim 12, characterized in that the tracks comprise opposite faces (72a, 72b, 82a, 82b) inclined relative to a circumferential direction. 14- Device according to claim 13, characterized in that the facing faces (82a, 82b) are planar and the elements (77, 87, 87d, 87e) are cylindrical.

15- Device according to claim 12 or 13, characterized in that the elements (67) have a curved rolling surface and the tracks are grooves (68a, 68b) having a corresponding curved profile.

16- Device according to claim 15, characterized in that the tracks (68a, 68b) open in the radial direction.

17- Device according to one of claims 12 to 15, characterized in that seen in cross section the tracks

(82a, 82b) are oriented in a direction forming an angle with a tangent.

18- Device according to claim 17, characterized in that each of the first (17a) and second (17b) transmission members carries at least two tracks oriented in opposite directions (82a, 82b) for the transmission of the torque in both direction of rotation between the first (17a) and the second (17b) transmission member.

19- Device according to one of claims 11 to 18, characterized in that the elements (87, 87d, 87e) have radii (R) large enough to be able to perform only a fraction of a turn when the first and the second transmission member cover their entire axial travel relative to each other, and in that the elements are truncated by two opposite flats (87c).

20- Device according to claim 19, characterized in that the rolling element comprises a gear pattern (teeth 89a, 89b), having a pitch circle (C _P ) which coincides with the rolling surface (87a, 87b) , and the corresponding track has a complementary gear pattern (hollow 91a, 91b). 21- Device according to one of claims 11 to 1 ₉ , characterized by gear means (89a, 89b; 91a, 91b) between at least some of the rolling elements (87) and at least one of the two tracks (82a, 82b) between which they are mounted.

22- Device according to claim 20 or 21, characterized in that the gear means (89a, 89b; 91a, 91b) occupy only part of the width of a track (82a, 82b) and the corresponding dimension of the rolling elements (87).

23- Device according to one of claims 11 to 19, characterized in that there are between two tracks (68a, 68b; 82a, 82b) each belonging to one of the first and second transmission members (17a, 17b ) at least two rolling elements (67, 77).

24- Device according to claim 23, characterized in that the at least two rolling elements (77) are held in a cage (84) movable in translation relative to each of the two tracks (82a, 82b). 25- Device according to one of claims 11 to 24, characterized by retaining means (74; 92) carried by one of the first and second transmission members and preventing the rolling elements (67, 87) from s' escape from the tracks. 26- Device according to one of claims 11 to 24, characterized by retaining means (74; 92) carried by one of the first and second transmission members and preventing the transmission members from escaping one of the other before mounting. 27- Device according to one of claims 1 to 26, characterized in that the first transmission member (17a) is connected axially to a helical toothing (8) forming part of the combination of toothing (7).

28- Device according to claim 27, characterized in that said helical toothing (8) is rigidly secured to the first transmission member (17a). 29- Device according to claim 27 or 28, characterized in that the first transmission member (17a) is supported by means of an axial stop (B2) against a movable plate (27) of the selective coupling means ( 18), so that the axial reaction of the helical teeth (8) acts on the movable plate (27) in the opposite direction to actuating forces.