Transmission shaft coupling system

Abstract

The present invention relates to a transmission shaft coupling system (1), comprising: - a drive shaft (2); - a driven shaft (3) coaxial with the drive shaft; - a dog clutch sleeve (30) comprising a spline (33) capable of rotating the drive shaft (2) about a first axis of rotation (X) and a spline (34) capable of rotating the driven shaft (3); and - an actuating device (10) comprising an output shaft (12) rotating about a second axis of rotation (Y), wherein the output shaft (12) is arranged to pivot within a receiving recess formed in the dog clutch sleeve, the dog clutch sleeve is able to move axially about the first axis of rotation (X) between an uncoupling position and a coupling position when the output shaft pivots through a predetermined angular range, and an elastic damping means (50) is positioned axially along the first axis of rotation (X) between the output shaft (12) and the dog clutch sleeve (30).

Description

[0001] DESCRIPTION

[0002] Title: Driveshaft Coupling System

[0003] The present invention relates to the field of transmission shaft coupling systems.

[0004] The driveshaft coupling system is, for example, integrated into the electric transmission of a motor vehicle, which includes an electric motor and an associated speed reducer. The coupling system is positioned, in particular, between the output of the speed reducer and the vehicle wheel. The motor vehicle may be electric or hybrid.

[0005] In the example of a hybrid motor vehicle comprising an internal combustion engine and an electric transmission, such coupling systems can be used to connect the electric transmission to the rear wheels of the vehicle when its use becomes necessary to supplement the internal combustion engine, which provides torque and power to the front wheels. Such a driveshaft coupling system is known from document WO2016 / 096769 AL

[0006] In this document, the transmission shaft coupling system is interposed between a drive transmission shaft comprising a first internal spline and a driven transmission shaft coaxial to the drive shaft comprising a second external spline.

[0007] The coupling system also includes a double-spline connector for connecting the driving shaft to the driven shaft when electric transmission is required. The double-spline connector is mounted longitudinally on the driven transmission shaft. The connector is driven along the axis of rotation of the driven transmission shaft by means of an actuation device comprising an electric motor coupled to a speed reduction device, for example, a planetary gear train.

[0008] For this purpose, an internal surface of the double-spline connector is provided with an internal spline that mates with the external spline of the driven transmission shaft and an external spline that mates with the internal spline of the driving transmission shaft. When the coupling system is in an uncoupled position, the external spline of the connector is not engaged with the first internal spline of the driving shaft. The driving shaft and the connector have different rotational speeds. To engage the connection between the driving and driven transmission shafts, the electric motor of the actuation device is used to rotate an eccentric control rod within an annular groove in the double-spline connector. The rotation of the eccentric control rod around a central axis of the planetary gear train allows the connector to move longitudinally.

[0009] When the coupling system is in a coupling position, the rotational speeds of the driven shaft, the driving shaft, and the double-spline connector are identical.

[0010] It is therefore clear that the engagement of the connector spline teeth within the internal spline of the driving shaft can only occur under certain conditions. The geometry of the teeth is a key factor in facilitating insertion. The speed differential during engagement must also be small to allow the connector spline teeth to engage. To achieve this, the electrical drive system is used to adjust the rotational speed of the driving shaft as close as possible to the rotational speed of the driven shaft. Once the target speed is reached, the connector spline teeth are inserted by axially moving the connector.

[0011] However, the insertion attempt may fail simply because the time allowed for the internal and external splines to fully align is insufficient. The teeth of the connector spline will then encounter the top of the drive shaft spline.

[0012] During these failed insertion attempts, shocks can occur at the splines, which are transmitted through the eccentric control rod of the actuation device. Repeated shocks can propagate along the central axis of the actuation device and travel up into the speed reduction mechanism as a temporary overtorque. This shock transmission can damage the epicyclic gear train of the actuation device, which includes teeth not designed to withstand such a temporary overtorque. The present invention aims to overcome these drawbacks by providing a transmission shaft coupling system in which the shocks associated with a tooth engagement failure are absorbed outside the actuation device.

[0013] The main object of the present invention is a transmission shaft coupling system comprising:

[0014] - a drive shaft comprising a first drive spline;

[0015] - a coaxial transmission shaft driven by the driving shaft comprising a second drive spline;

[0016] - a dog clutch sleeve comprising at least a first connecting spline suitable for driving the driving shaft in rotation around a first axis of rotation and a second connecting spline suitable for driving the driven shaft in rotation;

[0017] - an actuation device comprising an electric motor kinematically linked to a speed reduction device and an output shaft of the speed reduction device rotating about a second axis of rotation, the output shaft is arranged to pivot within a receiving housing formed directly or indirectly in the dog clutch sleeve, the dog clutch sleeve being able to move axially along the first axis of rotation between a first extreme disengagement position and a second extreme coupling position when the output shaft pivots according to a predetermined angular sector.

[0018] The transmission shaft coupling system is remarkable in that at least one elastic damping means is interposed axially along the first axis of rotation between the output shaft and a part of the dog clutch sleeve, said elastic damping means acting in the direction of the first axis of rotation.

[0019] This driveshaft coupling system architecture prevents damage to the speed reduction mechanism of the actuation device by damping the shock generated by the teeth of the dog clutch sleeve spline when they strike the top of the spline of the driving or driven shaft. This significantly reduces the temporary overtorque that could build up within the gear teeth of the speed reduction device when the insertion attempt is aborted. The actuation device remains compact because the elastic damping means are located outside of it.

[0020] Preferably, the predetermined angular sector is between 20° and 180° allowing the dog clutch sleeve to move from the first extreme disengagement position, in which one of the first or second connecting splines is disengaged from either the first drive spline of the driving shaft or the second drive spline of the driven shaft, to the second extreme coupling position, in which the first and second connecting splines are engaged respectively in the first drive spline of the driving shaft and the second drive spline of the driven shaft.

[0021] According to one aspect of the invention, the receiving housing of the dog clutch sleeve supports at least one elastic damping means and also receives an interface end of the output shaft, the receiving housing being in the form of a groove composed of two lateral rims and a cylindrical bottom.

[0022] Preferably, one of the side edges is made of the same material as the dog clutch sleeve.

[0023] Advantageously, at least one of the lateral edges is formed by a component attached to the dog clutch sleeve, the attached component being for example a circlip, or a threaded ring or a press-fit ring.

[0024] The available space between the side edges and the cylindrical bottom is large enough to accommodate a number of components such as one or more elastic damping means, part of the output shaft, but also other components which will be described later such as an intermediate bushing or a needle bearing.

[0025] According to one aspect of the invention, the dog clutch sleeve supports an intermediate bushing inserted into the receiving housing. The intermediate bushing is annular in shape and includes a groove into which the interface end of the output shaft is inserted. The intermediate bushing is movable relative to the dog clutch sleeve. The intermediate bushing provides an additional degree of freedom at the interface between the actuating device and the dog clutch sleeve. The intermediate bushing contributes to shock absorption during an aborted insertion attempt. Relative movement of the intermediate bushing with respect to the actuating cam is possible, particularly if the intermediate bushing rotates about the first axis of rotation.

[0026] In one example, the intermediate sleeve is free to rotate relative to the dog clutch sleeve.

[0027] In another example, the intermediate sleeve is driven in rotation with the dog clutch sleeve by means of a spline, a tooth, or a key. This limits wear on the intermediate sleeve relative to the dog clutch sleeve.

[0028] Preferably, the intermediate sleeve is made of a material with properties that promote sliding relative to the dog clutch sleeve, for example, a PVD-type surface treatment. The sliding movement of the intermediate sleeve on the dog clutch sleeve along the first axis of rotation can be a translational and / or rotational movement.

[0029] According to one aspect of the invention, the elastic damping means is a spring washer concentric with the first axis of rotation. For example, said spring washer is disposed between the intermediate sleeve and one of the lateral edges of the receiving housing. For example, the elastic damping means is a conical spring washer. For example, the elastic damping means is an open corrugated spring washer. For example, the elastic damping means is an elastomer component.

[0030] The intermediate sleeve provides an additional degree of freedom at the interface between the actuating device and the dog clutch sleeve. This degree of freedom is used to utilize the damping properties of the spring washer.

[0031] Preferably, the spring washer applies an axial preload force between the intermediate sleeve and the lateral edge of the receiving housing.

[0032] Advantageously, the intermediate sleeve moves axially relative to the dog clutch sleeve by the maximum compression value of the spring washer. Preferably, a needle bearing is interposed axially between the intermediate sleeve and the elastic damping means. Advantageously, the axial preload force passes through the needle bearing. In this way, the needle bearing constantly operates under an axial preload, thus ensuring improved durability of the coupling system.

[0033] According to one variant of the invention, the dog clutch sleeve comprises at least one first internal connecting groove arranged to drive the driving shaft in rotation and a second internal connecting groove arranged to drive the driven shaft in rotation, the first and second internal grooves being engaged respectively in a first external transmission groove of the driving shaft and a second external transmission groove of the driven shaft when the dog clutch sleeve is in the second extreme coupling position.

[0034] According to another variant of the invention, the dog clutch sleeve comprises at least a first external connecting groove arranged to drive the driving shaft in rotation and a second internal connecting groove arranged to drive the driven shaft in rotation, the first and second internal grooves being engaged respectively in a first internal transmission groove of the driving shaft and a second external transmission groove of the driven shaft when the dog clutch sleeve is in the second extreme coupling position.

[0035] According to one aspect of the invention, the end of the output shaft interfacing with the dog clutch sleeve is an eccentric actuating rod with respect to the second axis of rotation of the actuating device.

[0036] According to one embodiment of the invention, a roller or a ball bearing is disposed at the end of the eccentric actuating rod.

[0037] According to one aspect of the invention, the end of the output shaft interfacing with the dog clutch sleeve is an actuating cam pivoting relative to the second axis of rotation of the actuating device.

[0038] Preferably, the interface end of the output shaft of the actuation device is an actuating cam arranged to pivot in three adjacent angular sectors: a first angular sector, a second angular sector adjacent to the first angular sector, and a third angular sector adjacent to the second actuation angular sector; the sum of the three angular sectors corresponds to the predetermined angular sector.

[0039] and in which the dog clutch sleeve moves axially between two extreme positions when the output shaft rotates through the entire second angular sector, the dog clutch sleeve remaining axially fixed in a first extreme position when the output shaft rotation is within the first angular sector, and the dog clutch sleeve remaining axially fixed in a second extreme position when the output shaft rotation is within the third angular sector. This actuation device, thanks in particular to the first and third angular sectors, allows for two stable extreme actuation positions because an angular variation of a few degrees on the output shaft does not cause any displacement of the receiving part.Since the two extreme actuation positions are stable, it is possible to cut off the power supply within the actuation device, thus reducing the vehicle's electrical consumption.

[0040] The angle value of the second angular sector is strictly less than 180°. Thus, the angular travel of the output shaft is reduced, which in turn reduces the actuation time.

[0041] The actuating cam can have two contact areas bearing on the parallel surfaces of the intermediate sleeve groove; the contact width along the first axis of rotation separating the two contact areas is constant over the three angular sectors of rotation of the output shaft. This improves the actuation accuracy.

[0042] Advantageously, an operating clearance can be defined between the bearing width of the actuating cam and the axial distance along the first axis of rotation between the two parallel surfaces of the intermediate sleeve groove. This operating clearance is constant across all three angular sectors of rotation of the output shaft. The operating clearance is on the order of 0.1 mm to 0.6 mm. This improves actuation accuracy.

[0043] The actuating cam may comprise three actuating faces formed in the form of cylindrical segments. The three centers of these cylindrical segments form an isosceles triangle, with the principal vertex of the isosceles triangle coinciding with the second axis of rotation of the output shaft. The geometry of the actuating cam's contact areas utilizes large-diameter cylindrical segments, thereby reducing the contact pressure with the parallel surfaces of the intermediate bushing. Advantageously, the actuating cam may have a symmetrical actuating profile whose axis of symmetry passes through the bisector of the isosceles triangle, the bisector of the isosceles triangle corresponding to the midpoint of the second angular sector. The actuating cam thus has a symmetrical profile passing through the second axis of rotation of the output shaft.

[0044] The actuation device for the transmission shaft coupling system according to the invention may have one or more of the characteristics described below, either combined or taken independently of each other:

[0045] - the actuation device is mounted on a fixing housing;

[0046] - the first axis of rotation is perpendicular to the second axis of rotation;

[0047] - the first axis of rotation does not intersect the second axis of rotation;

[0048] - the angle value of the first angular sector is greater than 3°;

[0049] - the angle value of the second angular sector is between 20° and 174°;

[0050] - the angle value of the third angular sector is greater than 3°;

[0051] - the angle value of the first angular sector is identical to the angle value of the third angular sector;

[0052] - the angle value of the first angular sector is different from the angle value of the third angular sector;

[0053] - the angle value of the second angular sector is greater than the angle value of the first angular sector;

[0054] - the angle value of the second angular sector is greater than the angle value of the third angular sector;

[0055] - the interface end is rotationally fixed to the output shaft.

[0056] The invention also relates to a motor vehicle with hybrid or electric transmission comprising a transmission shaft coupling system as previously mentioned.

[0057] Other features, details and advantages of the invention will become clearer from the reading of the following description on the one hand, and of examples of embodiment given by way of indication and not limitation with reference to the attached drawings on the other hand, on which: [Fig. 1] is a cross-sectional view of a transmission shaft coupling system according to a first embodiment of the invention;

[0058] [Fig. 2] is an isometric view of the transmission shaft coupling system of Figure 1;

[0059] [Fig. 3] is a detailed view of the transmission shaft coupling system of Figure 1;

[0060] [Fig. 4] is a top view of the actuation cam of the transmission shaft coupling system of Figure 1;

[0061] [Fig. 5] is a simplified view of the interface end of the output shaft of the actuation device in Figure 1;

[0062] [Fig. 6] is a detailed view of a transmission shaft coupling system according to a second embodiment of the invention;

[0063] [Fig. 7] is a detailed view of a transmission shaft coupling system according to a third embodiment of the invention.

[0064] The features, variations, and different embodiments of the invention can be combined in various ways, provided they are not mutually exclusive or incompatible. In the figures, elements common to several figures retain the same reference numeral. In the description and claims, the terms "external" and "internal," as well as the orientations "axial" and "radial," will be used to designate elements of the transmission system, as defined in the description. By convention, the "radial" orientation is directed orthogonally to the first axis of rotation X of the coupling system that determines the "axial" orientation. From the inside out, away from said axis, the "circumferential" orientation is directed orthogonally to the first axis of rotation X and orthogonally to the radial direction.Figures 1 to 5 illustrate a transmission shaft coupling system 1 according to a first embodiment of the invention.

[0065] The driveshaft coupling system 1 is a connecting clutch between two shafts 2 and 3, used in a vehicle's drivetrain to transmit torque from a combustion or electric motor (not shown) to a wheel shaft 7 of a motor vehicle. Such a driveshaft coupling system can, for example, be part of a secondary drivetrain capable of transmitting torque from a secondary motor of the vehicle, such as an electric motor, to a rear or front axle, while a primary drivetrain is capable of transmitting torque from a main motor, such as a combustion engine, to the wheel shafts of another axle of the vehicle. When the reversible electric machine associated with the speed reducer is inactive, there is no benefit to leaving the machine connected to the vehicle wheel. The connecting clutch is then disengaged.

[0066] The drive shaft coupling system 1 is kinematically interposed between a speed reducer and the vehicle's wheel shaft 7. The output of the speed reducer is rotationally fixed to a drive shaft 2 about a first axis of rotation X. The drive shaft 2 has a first transmission spline 2a machined on its end; in this example, the first transmission spline is external.

[0067] The driveshaft coupling system 1 also includes a driven shaft 3 coaxial with the driving shaft 2, comprising a second transmission spline 3a, the second transmission spline being external in this example. The driven shaft 3 is inserted into the driving shaft 2 and guided in rotation by a guide bearing 4 around the first axis of rotation X. The driven shaft 3 also includes an internal torque output spline 3b rotationally connected to the vehicle's wheel shaft 7.

[0068] The drive shaft coupling system 1 uses a dog clutch sleeve 30 to connect the two drive and driven shafts 2, 3. The dog clutch sleeve 30 is axially movable about the first axis of rotation X and includes a first connecting spline 33 for rotating the drive shaft 2 and a second connecting spline 34 for rotating the driven shaft 3. In this example, the first and second connecting splines 33, 34 are external and complement the first and second transmission splines 2a, 3a. To actuate the drive shaft coupling system 1, an electrically powered actuator 10 is used. The actuator 10 comprises an electric motor 11 kinematically linked to a speed reduction device 13 and an output shaft 12 of the speed reduction device rotating about a second axis of rotation Y.An actuating cam 20 is disposed at the interface end of the output shaft 12. The actuating cam 20 is rotationally fixed to the output shaft 12 and interacts with the dog clutch sleeve 30. The output shaft 12 is arranged in particular to pivot within a receiving housing 31 formed directly or indirectly in the dog clutch sleeve 30. As illustrated in Figure 3, the actuating cam 20 is fixed to the end of the output shaft 12, for example press-fitted.

[0069] This actuation device 10 also includes a protective housing 18 which protects the electric motor 11 and supports the speed reduction device 13. The protective housing 18 is mounted on a protective sleeve 9 of the transmission system 1. The protective sleeve 9 is cylindrical in shape with its axis coinciding with the first axis of rotation X and has an opening for the output shaft 12 of the actuation device.

[0070] As illustrated in Figure 5, the dog clutch sleeve 30 moves axially between two extreme positions of disengagement and engagement when the output shaft 12 pivots about its second axis of rotation Y by a predetermined angular sector oc. The dog clutch sleeve 30 moves axially by a value Dx relative to the driven transmission shaft 3, which is axially fixed.

[0071] When the dog clutch sleeve 30 is in the first extreme disengagement position, the second connecting spline 34 is disengaged from the second drive spline of the driven shaft 3. The second connecting spline 34 is broken to reduce the engagement stroke.

[0072] When the dog clutch sleeve 30 is in the second extreme coupling position, the first and second connecting splines 33, 34 are engaged respectively in the first drive spline 2a of the driving shaft 2 and the second drive spline 3a of the driven shaft 3.

[0073] The receiving housing 31 for the dog clutch sleeve 30 is in the form of a groove composed of two lateral flanges 31a and a cylindrical bottom 31b, and receives the interface end of the output shaft 12. In this case, the interface end is formed by the actuating cam 20. One lateral flange 31a is formed from the same material as the dog clutch sleeve, and the other lateral flange 31a is formed by a component attached to the dog clutch sleeve, the attached component being, for example, a threaded ring. The dog clutch sleeve 30 supports an intermediate bushing 40 inserted into the receiving housing 31.

[0074] To precisely axially move the dog clutch sleeve 30, the output shaft 12 pivots within the intermediate sleeve 40, which is held within the receiving housing 31. The intermediate sleeve 40 is annular in shape and includes a groove 41 into which the interface end of the output shaft 12 is inserted. The intermediate sleeve 40 remains movable relative to the dog clutch sleeve 30 and provides an additional degree of freedom at the interface between the actuating device 10 and the dog clutch sleeve 30. In particular, the intermediate sleeve 40 is free to rotate relative to the dog clutch sleeve.

[0075] In this example, the actuating cam 20 is received directly in the groove 41 of the intermediate sleeve. The space available between the lateral edges 31a and the cylindrical base 31b is large enough to accommodate several components, such as the intermediate sleeve 40 and part of the output shaft 12, as well as other components that will be described later, such as an elastic damping means 50.

[0076] To improve the reliability of the transmission shaft coupling system 1, an elastic damping means 50 is interposed axially along the first axis of rotation X between the output shaft 12 and a part of the dog clutch sleeve 30, said elastic damping means 50 acting in the direction of the first axis of rotation X.

[0077] In this first embodiment of the invention, the elastic damping means 50 is an elastic washer concentric to the first axis of rotation X. The elastic washer 50 is disposed between the intermediate sleeve 40 and one of the edges 31a of the receiving housing 31 of the dog clutch sleeve.

[0078] The spring washer 50 is axially oriented along the first axis of rotation X in the direction of the transition from the first extreme disengagement position to the second extreme engagement position. This means that the spring washer will be able to compress during this actuation phase.

[0079] We will now describe the characteristics of the elastic damping device and its operation within the transmission shaft coupling system. The spring washer 50 is annular and conical in shape, exhibiting the elastic characteristics of a Belleville washer. More precisely, the outer diameter of the spring washer 50 bears against the lateral flange 31a, and the inner diameter of the spring washer 50 bears against the intermediate bushing 40. The spring washer may include a series of bearing tabs distributed around a conical ring.

[0080] The spring washer 50 applies an axial preload force between the intermediate sleeve 40 and the rim 31a of the receiving housing. The spring washer is therefore in a state of low compression when installed in the receiving housing 31.

[0081] When the drive shaft coupling system 1 is in its first extreme disengagement position, the electric transmission is stopped. The electric machine's rotor does not rotate, so the speed of the driving shaft 2 differs from the rotational speed of the driven shaft 3, which corresponds to that of the vehicle's wheels.

[0082] When engaging the teeth of the internal spline of the dog clutch sleeve 30 with the second transmission spline 3a of the driven shaft 3, the rotational speed of the driving shaft 2 is first adjusted to be as close as possible to the rotational speed of the driven shaft 3, while maintaining a slight speed differential between the two shafts 2 and 3. Once the target speed of the driving shaft 2 is reached, the teeth of the internal spline of the dog clutch sleeve 30 are inserted. The dog clutch sleeve 30 is then axially moved by rotating the output shaft 12 of the actuation device 10 around the second axis of rotation Y.

[0083] In the favorable case where the teeth of the internal spline of the dog clutch sleeve 30 are aligned with the grooves of the second transmission spline 3a of the driven shaft 3, the dog clutch sleeve 30 slides axially along the driven shaft 3 and transmits only a small parasitic axial force to the actuating cam 20 generated by the friction between the splines. The spring washer 50 is not stressed or only slightly stressed in this favorable case.

[0084] In a first unfavorable case, where the teeth of the internal spline of the dog clutch sleeve 30 are aligned with the crests of the second transmission spline 3a of the driven shaft 3, the dog clutch sleeve 30 cannot slide axially. The pivoting of the output shaft 12 causes the intermediate sleeve 40 to move axially relative to the dog clutch sleeve 30, while the dog clutch sleeve remains axially fixed. The spring washer 50 compresses to compensate for the displacement of the intermediate sleeve 40 up to a certain compression value. The spring washer 50 dampens the displacement of the intermediate sleeve 40 and prevents a shock from being transmitted back into the speed reduction device 13 of the actuation device 10.

[0085] In a second unfavorable case, where the teeth of the internal spline of the dog clutch sleeve 30 are almost aligned with the grooves of the second transmission spline 3a of the driven shaft 3, the dog clutch sleeve 30 begins to slide axially, and the teeth of the spline of the dog clutch sleeve begin to engage with the spline of the driven shaft. It can happen, when the speed differential between the driven shaft 3 and the driving shaft 2 is too great, that the insertion attempt fails simply because the time allowed for the internal and external splines to be fully aligned is too short. The teeth of the spline of the dog clutch sleeve are then abruptly ejected from the spline of the driven shaft 3 while the rotation of the output shaft 12 continues. The intermediate sleeve 40 moves toward the driven shaft 3 while the dog clutch sleeve 30 moves backward toward the driving shaft.This combination of movement causes the compression of the elastic washer 50 which dampens the movement of the intermediate sleeve 40 and prevents a shock from being sent back into the speed reduction device 13 of the actuation device 10. This prevents the shock from being sent back into the output shaft 12 and prevents damage to the speed reduction device 13 of the actuation device which includes teeth not dimensioned to receive such a temporary overtorque.

[0086] The compression can reach up to the maximum crushing value of the elastic washer. In this first embodiment of the invention, the shocks associated with a failure of tooth engagement are absorbed outside the actuation device of the transmission shaft coupling system.

[0087] We will now describe the general operation of the drive shaft coupling system when the teeth of the dog clutch sleeve 30 are engaged with those of the driven shaft 3 in the first favorable case. The actuating cam 20 has two contact areas 20a, 20b bearing on the parallel surfaces 42 of the groove 41 of the intermediate sleeve 40. The bearing width L along the first axis of rotation X separating the two contact areas is constant throughout the rotation of the output shaft 12. To ensure free movement of the actuating cam 20 within the groove 41 without unwanted friction, an operating clearance is defined between the bearing width L of the actuating cam and the axial distance D separating the two parallel surfaces 42 of the groove 4L along the first axis of rotation X.

[0088] As illustrated in Figures 4 and 5, the actuating cam 20 comprises three actuating faces 21 formed in the form of cylindrical segments. The three centers 22 of these cylindrical segments form an isosceles triangle, the principal vertex of which coincides with the second axis of rotation Y of the output shaft. The geometry of the contact areas 20a, 20b of the actuating cam utilizes large-diameter cylindrical segments to reduce the contact pressure with the parallel surfaces of the receiving housing. During rotation of the actuating cam, the actuating face 21 slides on one of the parallel surfaces 42.

[0089] In this first embodiment, the actuating cam 20 has a symmetrical actuation profile whose axis of symmetry passes through the bisector 37 of the isosceles triangle, the bisector of the isosceles triangle corresponding to the midpoint of the second angular sector oc2. The isosceles triangle has a principal angle [3, for example, between 45° and 150°. The actuating cam 20 thus has a symmetrical profile passing through the axis of rotation Y.

[0090] Thanks to the specific geometry of the actuating cam profile, the operating clearance between the bearing width L of the actuating cam and the distance D is constant throughout the rotation of the output shaft. This operating clearance is on the order of 0.1 mm to 0.6 mm. The actuation accuracy is thus improved. To ensure free movement of the actuating cam 20 within the annular groove 31 without unwanted friction, the actuating faces 21 of the actuating cam 20 are connected by a cylindrical connecting face 23 with a radius R2 smaller than the radius RI of the cylindrical segments, the connecting radius being between 1 and 5 mm. During the rotation of the actuating cam, the cylindrical connecting face 23 also slides on one of the parallel surfaces 42.The contact areas 20a, 20b of the actuating cam are alternately formed by an actuating face 21 and / or a cylindrical connecting face 23. The geometry of the contact area 20a, 20b then has a radius RI or a radius R2.

[0091] The actuating cam 20 also includes an end radius R3 arranged to interact with the parallel surfaces 42 of the intermediate sleeve 40 and tangentially connecting two actuating faces 21, the center of this end radius R3 being concentric with the axis of rotation Y. The center of the end radius R3 passes through the bisector 37 of the isosceles triangle. The dimension of the radius R3 is defined so as to respect the bearing width L. Thus, the sum of the radius RI of the cylindrical portion forming the actuating face 21 associated with the principal vertex of the isosceles triangle and the radius R3 is equal to the bearing width L.

[0092] For example, the end radius R3 is greater than the radius R2 of the cylindrical bonding faces.

[0093] We will now describe the operation of the actuation device which allows the transition from the first extreme uncoupling position to the second extreme coupling position with a reduced actuation time.

[0094] As illustrated in Figure 5, the output shaft 12 is arranged to rotate within three adjacent angular sectors a1, a2, a3: a first angular sector a1, a second angular sector a2 adjacent to the first angular sector a1, and a third angular sector a3 adjacent to the second angular sector a2. The sum of the three angular sectors a1, a2, a3 corresponds to the predetermined angular sector a. Initially, the dog clutch sleeve 30 is in the first extreme disengagement position. The dog clutch sleeve 30 remains axially fixed in this first extreme position when the output shaft rotates within the first angular sector. The angle value of the first angular sector a1 is 15°.On this first angular sector al, the dog clutch sleeve 30 remains in a stable position which allows the electrical supply to be cut off within the actuation device, thus reducing the electrical consumption of the vehicle.

[0095] In a second step, the dog clutch sleeve 30 moves axially between the two extreme disengagement and engagement positions as the output shaft 12 pivots through the entire second angular sector a2. The displacement Dx of the receiving part 30 is shown in Figure 5. The angle value of the second angular sector a2 is approximately 100°. This small angle value, less than 180°, reduces the actuation time. Figure 3 illustrates the position of the actuating cam 20 in the first extreme disengagement position. The dog clutch sleeve 30 is positioned axially thanks to the actuation faces 21 of the actuating cam 20, which are flush with the parallel surfaces 42 of the groove 4L. Figure 4 illustrates the position of the actuating cam 20 in the second extreme engagement position.

[0096] In a third step, the dog clutch sleeve 30 remains axially fixed in the second extreme position when the output shaft rotation is within the third angular sector œ3. The angle of the third angular sector œ3 is approximately 5°. Within this third angular sector œ3, the dog clutch sleeve 30 remains in a stable position, allowing the electrical supply to the actuation device to be cut off, thus reducing the vehicle's electrical consumption. Thanks to the specific geometry of the actuating cam profile, the contact width L along the first axis of rotation X, separating the two contact zones 20a, 20b, is constant over the three angular sectors 1a1, 1a2, œ3 of output shaft rotation. Figure 5 illustrates the different angular positions assumed by the actuating cam 20 during the displacement Dx of the dog clutch sleeve 30.

[0097] Advantageously, the intermediate sleeve moves axially relative to the dog clutch sleeve by the maximum compression value of the elastic washer. A second embodiment of the invention, which differs from the previous one in that the intermediate sleeve 40 is driven in rotation with the dog clutch sleeve via an intermediate spline 45, will now be described with reference to Figure 6. The elastic damping means 50, acting in the direction of the first axis of rotation X, is still located between the output shaft 12 and the dog clutch sleeve 30. The elastic damping means 50 is held axially by two components that have the same rotational speed.

[0098] The receiving housing 31 of the dog clutch sleeve 30 receiving the elastic damping means 50 is in the form of a groove composed of two lateral rims 31a and a cylindrical bottom 31b and receives the interface end 20 of the output shaft 12. In this second embodiment, one lateral rim 31a is formed from the material with the dog clutch sleeve and the other lateral rim 31a is formed by a component attached to the dog clutch sleeve, the attached component being a circlip.

[0099] In this second embodiment of the invention, the elastic damping means 50 is an open corrugated spring washer. The open corrugated spring washer is concentric with the first axis of rotation X. The open corrugated spring washer 50 is positioned between the intermediate bushing 40 and one of the flanges 31a of the receiving housing 31 of the dog clutch sleeve. The open corrugated spring washer 50 is interposed axially along the first axis of rotation X between the output shaft 12 and a portion of the dog clutch sleeve 30.

[0100] The open corrugated spring washer 50 is axially oriented along the first axis of rotation X in the direction of the transition from the first extreme disengagement position to the second extreme engagement position. This means that the spring washer will be able to compress during this actuation phase. The open corrugated spring washer 50 acts in the direction of the first axis of rotation.

[0101] We will now describe, with reference to Figure 7, a third embodiment of the invention, which differs from the first embodiment in that two elastic damping means 50 are arranged within the receiving housing 31 of the dog clutch sleeve, and the end of the output shaft 12 interfacing with the dog clutch sleeve 30 is an actuating rod 25 eccentric with respect to the second axis of rotation Y of the actuating device. The actuating rod 25 is cylindrical.

[0102] The two elastic damping means 50 act in the direction of the first axis of rotation X and are placed on either side of the intermediate sleeve 40.

[0103] The receiving housing 31 of the dog clutch sleeve 30, which receives the elastic damping means 50, is in the form of a groove composed of two lateral edges 31a and a cylindrical bottom 31b, and receives the interface end of the output shaft 12. In this third embodiment, one lateral edge 31a is formed from the same material as the dog clutch sleeve, and the other lateral edge 31a is formed by a component attached to the dog clutch sleeve, the attached component being a circlip. In this third embodiment of the invention, the two elastic damping means 50 are open-wave spring washers. The open-wave spring washers are concentric with the first axis of rotation X. Each open-wave spring washer 50 is disposed between the intermediate bushing 40 and one of the edges 31a of the receiving housing 31 of the dog clutch sleeve.Each open wavy elastic washer 50 acts in the direction of the first axis of rotation.

[0104] Preferably, a needle bearing 60 is axially interposed between the intermediate sleeve and each of the elastic damping means. The axial preload force is thus transmitted through the needle bearing. In this way, the needle bearing constantly operates under an axial preload, thereby ensuring improved durability of the coupling system. Furthermore, the intermediate sleeve no longer rubs against the elastic damping means but rolls on the needles of the bearing, which reduces wear at the interfaces of the intermediate sleeve 40.

[0105] The present invention is not limited to the means and configurations described and illustrated herein, and also extends to any equivalent means and configuration as well as any technically operative combination of such means.

Claims

1. CLAIMS 1. Transmission shaft coupling system (1), comprising: 3.- a transmission drive shaft (2) comprising a first drive spline (2a); 4.- a driven shaft (3) coaxial to the driving shaft comprising a second drive spline (3a); 5.- a dog clutch sleeve (30) comprising at least a first connecting groove (33) suitable for driving the driving shaft (2) in rotation about a first axis of rotation (X) and a second connecting groove (34) suitable for driving the driven shaft (3) in rotation; 6.- an actuation device (10) comprising an electric motor (11) kinematically linked to a speed reduction device (13) and an output shaft (12) of the speed reduction device rotating about a second axis of rotation (Y), the output shaft (12) is arranged to pivot within a receiving housing (31) formed directly or indirectly in the dog clutch sleeve (30), the dog clutch sleeve being able to move axially along the first axis of rotation (X) between a first extreme disengagement position and a second extreme engagement position when the output shaft (12) pivots along a predetermined angular sector (a), 7. characterized in that at least one elastic damping means (50) is interposed axially along the first axis of rotation (X) between the output shaft (12) and a part of the dog clutch sleeve (30), said elastic damping means (50) acting in the direction of the first axis of rotation (X).

2. A drive shaft coupling system (1) according to claim 1, wherein the predetermined angular sector (a) is between 20° and 180°, allowing the dog clutch sleeve to move from the first extreme disengagement position, in which one of the first or second connecting splines (33, 34) is disengaged from either the first drive spline (2a) of the driving shaft or the second drive spline (3a) of the driven shaft, to the second extreme coupling position, in which the first and second connecting splines (33, 34) are engaged respectively in the first drive spline (2a) of the driving shaft and the second drive spline (3a) of the driven shaft.

3. Transmission shaft coupling system (1) according to claim 1 or 2, wherein the receiving housing (31) of the dog clutch sleeve supports at least one elastic damping means (50) and also receives an interface end (20) of the output shaft (12), the receiving housing being in the form of a groove composed of two lateral rims (31a) and a cylindrical bottom (31b).

4. Transmission shaft coupling system (1) according to any one of claims 1 to 3, wherein at least one of the lateral flanges (31a) is formed by a component attached to the dog clutch sleeve (30), the attached component being for example a circlip, or a threaded ring or a press-fit ring.

5. Transmission shaft coupling system (1) according to claim 3 or 4, wherein the dog clutch sleeve (30) supports an intermediate bushing (40) inserted in the receiving housing (31), the intermediate bushing is annular in shape and includes a groove (41) into which the interface end (20) of the output shaft is inserted, the intermediate bushing (40) being movable relative to the dog clutch sleeve (30).

6. Transmission shaft coupling system (1) according to any one of the preceding claims, wherein the elastic damping means (50) is an elastic washer concentric to the first axis of rotation (X).

7. Transmission shaft coupling system (1) according to the combination of claims 5 and 6, wherein the spring washer is disposed between the intermediate sleeve (40) and one of the lateral edges (31a) of the receiving housing (30).

8. Transmission shaft coupling system (1) according to the preceding claim, wherein the elastic washer (50) applies an axial preload force between the intermediate sleeve (40) and the lateral rim (31a) of the receiving housing.

9. Transmission shaft coupling system (1) according to any one of claims 6 to 8, wherein the intermediate bushing (40) moves axially relative to the dog clutch sleeve (30) by the maximum crush value of the spring washer.

10. Transmission shaft coupling system (1) according to any one of claims 5 to 9, wherein a needle bearing (60) is axially interposed between the intermediate sleeve (40) and the elastic damping means (50).

11. Transmission shaft coupling system (1) according to any one of claims 5 to 10, wherein the intermediate bushing (40) is free to rotate relative to the dog clutch sleeve (30).

12. Transmission shaft coupling system (1) according to any one of claims 5 to 9, wherein the intermediate sleeve (40) is driven in rotation with the dog clutch sleeve (30) by means of an intermediate spline (45), or a tooth, or a key.

13. Transmission shaft coupling system (1) according to any one of the preceding claims, wherein the dog clutch sleeve comprises at least a first internal connecting spline (33) arranged to drive the driving shaft (2) in rotation and a second internal connecting spline (34) arranged to drive the driven shaft (3) in rotation, the first and second internal splines (33, 34) being engaged respectively in a first external transmission spline (2a) of the driving shaft and a second external transmission spline (3a) of the driven shaft when the dog clutch sleeve (30) is in the second extreme coupling position.

14. Transmission shaft coupling system (1) according to any one of the preceding claims, wherein the end of the output shaft (12) interfacing with the dog clutch sleeve is an actuating cam (20) pivoting about the second axis of rotation (Y) of the actuating device.

15. Transmission shaft coupling system (1) according to any one of claims 1 to 13, wherein the end of the output shaft (12) interfacing with the dog clutch sleeve is an actuating rod (25) eccentric with respect to the second axis of rotation (Y) of the actuating device.

Images