TELESCOPIC TRIPOT UNIVERSAL JOINT

Abstract: A telescopic tripot universal joint comprises an inner drive member (12) which has three radial trunnions (26), an outer drive member (14) which has three radial drive channels (20), and three drive assemblies (16) which comprise drive blocks (32), bearing rollers (34) and cage structure (36) which is effective to retain the bearing rollers and is attached to the drive block in a fixed relationship. The radial trunnions have outer radial projections (29) which are disposed in outer radial grooves (23) of the radial drive channels, and engage radial end walls (25) in the radial grooves to limit the inward stroke of the inner drive member and prevent the drive assemblies from engaging (bottoming out on) an inner end wall (21) of the outer drive member.

Description: This invention relates generally to a telescopic tripot universal joint as specified in the preamble of claim l, for example as disclosed in EP-A-O 244 064. Such telescopic (stroking-type) tripot universal joints are employed in automotive vehicle axle drive shafts, and especially in front-wheel drive vehicles between a transaxle differential and a drive wheel of the vehicle. There is a need in telescopic tripot universal joints of this type to limit the stroke of the inner drive member in the outer drive member in a manner which avoids any possibility of damage to the drive assemblies, particularly the bearing rollers and cage means for retaining the bearing rollers. The present invention is concerned with the provision of a telescopic tripot universal joint of the above-noted type having means to limit the stroke of the inner drive member in a manner which avoids the possibility of damage to the drive assemblies, particularly the bearing rollers and cage means for retaining the bearing rollers. To this end a telescopic tripot universal joint assembly in accordance with the present invention is characterised by the features specified in the characterising portion of claim 1. A telescopic tripot universal joint in accordance with the present invention is particularly well suited for use with drive assemblies which have recirculating bearing rollers disposed on an endless (continuous) roller track of the drive block. In a telescopic tripot universal joint in accordance with the present invention, the means to limit the stroke of one drive member with respect to the other drive member preferably comprises co-operating portions of the drive members which are spaced from the drive assemblies in the radial direction. The means to limit the stroke of one drive member with respect to the other drive member has the potential to prevent the drive assemblies which are mounted on the trunnions of one drive member from engaging (bottoming out on) the other drive member. For the purpose of limiting the stroke of the one drive member with respect to the other drive member, preferably the radial trunnions have radial projections that are disposed in radial grooves in the radial drive channels which end short of the drive channels in the longitudinal direction, to limit the stroke of the drive member carrying the drive assemblies while preventing any engagement of the drive assemblies with the other drive member at the stroke limit, and thus avoiding any possibility of damage to the drive assemblies even when recirculating bearing rollers are used. It is preferred for radial projections of the radial trunnions to be spaced from the longitudinal walls of the radial grooves when the telescopic tripot universal joint is at zero angle (that is, when the longitudinal axes of the inner and the outer drive members coincide), to permit orbiting of the centre of one drive member about the joint centre during operation of the universal joint at an angle. Preferably the radial projections have termini (advantageously rounded termini) which are spaced from the longitudinal walls of the radial grooves in the drive channels in the radial direction when the telescopic tripot universal joint is at zero angle, and the radial grooves in the drive channels are larger than the radial projections in the circumferential direction, so that the centre of one drive member is free to orbit about the joint centre during operation of the tripot universal joint at an angle. In the drawing: Figure 1 is a fragmentary longitudinal. section showing a preferred embodiment of a telescopic tripot universal joint in accordance with the invention; Figure 2 is an end view substantially on the line 2--2 of Figure l, in the direction of the arrows; Figure 3 is a fragmentary enlarged longitudinal section of the telescopic tripot universal joint substantially on the line 3--3 of Figure 2, in the direction of the arrows; and Figure 4 is a perspective view of a typical drive assembly of the telescopic tripot universal joint shown in Figures 1, 2 and 3. With reference now to the drawing, the invention is illustrated in the form of a telescopic tripot universal joint 10 which comprises an inner drive member 12, an outer drive member 14 and a plurality of intermediate drive assemblies 16. The outer drive member 14 has a longitudinal axis 18 about which it rotates, and three radial drive channels 20 which are equally spaced at substantially 120° from each other and extend inwardly to an end wall 21 of the outer drive member 14. Each radial drive channel 20 includes two radially extending planar surfaces 22 which extend parallel to each other and to the longitudinal axis 18. Each radial drive channel 20 further includes an outer radial groove 23 which likewise extends parallel to the longitudinal axis 18 and which ends short of the radial drive channel 20 at an end wall 25 that is spaced in the longitudinal direction from the end wall 21 of the outer drive member 14. The inner drive member 12 has a longitudinal axis 24 about which it rotates. The longitudinal axes 18 and 24 coincide when the tripot universal joint 10 is at zero angle, as shown in solid lines in Figure 1, and intersect at a joint centre 0 when the tripot universal joint is articulated (bent) at an angle, as shown in phantom lines in Figure 1. The inner drive member 12 has three radial trunnions 26 equally spaced at substantially 120 degrees from each other on coplanar radial axes 27 which intersect the longitudinal axis 24 perpendicularly at a centre A. The centre A of the inner drive member 12 is displaced from the longitudinal axis 18 of the outer drive member 14, and orbits around the joint centre 0 at three times the joint speed when the tripot universal joint 10 is articulated and rotated at a given speed. The radial trunnions 26 comprise truncated spherical (ball-like) portions which have been truncated to provide spherical bearing surfaces 28 in the longitudinal direction of the inner drive member 12 and flat surfaces 30 which are perpendicular to the longitudinal axis 24, as is best seen in Figure 3. The flat surfaces 30 are provided for assembly purposes, as explained below. Each radial trunnion 26 further comprises a concentric radial projection 29 which projects outwardly of the ball-like portion and has a rounded terminus 31. The radial trunnions 26 are disposed in the respective radial drive channels 20 such that the spherical bearing surfaces 28 are in confronting relation with the planar surfaces 22 of the respective radial drive channels 20 and the concentric radial projections 29 are disposed in the respective outer radial grooves 23, as is seen in Figures 1, 2 and 3. The three drive assemblies 16 are disposed in the respective radial drive channels 20, and are pivotally mounted on the respective radial trunnions 26. Each drive assembly 16 comprises a drive block 32, a plurality of bearing rollers 34, and cage means 36 for retaining the bearing rollers 34. The drive block 32 has an endless (continuous) roller track 40 which circumscribes an imaginary radial centre-line 38 in a parallel fashion. The continuous roller track 40 includes a pair of planar surfaces 42 which are parallel to each other and to the radial centre-line 38 and which are disposed parallel to and facing the planar surfaces 22 of the radial drive channel 20 in which the drive block 32 is disposed. The drive block 32 also has a concentric spherical socket 44 which fits on to the spherical bearing surfaces 28 of the radial trunnion 26, whereby the drive block 32 is pivotally mounted on the radial trunnion 26 disposed in the radial drive channel 20 in which the drive block 32 is disposed. A full complement of bearing rollers 34 is disposed on the continuous roller track 40 such that a plurality of bearing rollers 34 are disposed between the planar surfaces 42 of the drive block 32 and the planar surfaces 22 of the radial drive channel 20 in which the drive block 32 is disposed. The roller cage means 36 is carried by the drive block 32 and retains the bearing rollers 34 for rotation about axes which are substantially parallel to the radial centre-line 38 of the drive block 32 and in engagement with the planar surfaces 22 of the radial drive channel 20 to transfer torque via the drive block 32. In this particular instance the roller cage means 36 comprise upper and lower ledges 46 and 48 of the drive block 32 which retain the bearing rollers 34, and two sheet metal cage pieces 50 and 52 which are attached to the longitudinal ends of the drive block 32. The sheet metal cage pieces 50 and 52 provide overhanging flanges 54 at the longitudinal ends of the continuous roller track 40, and also provide covers 56 at the corners leading to the two planar surfaces 42. The overhanging flanges 54 and the covers 56 retain the bearing rollers 34 in the direction radially of the centre-line 38 for the portions of the continuous roller track 40 between the two planar surfaces 42. For the two planar surface portions of the continuous roller track 40, the bearing rollers 34 are retained by grease until the tripot universal joint 10 is assembled, whereupon the planar surfaces 22 of the associated radial drive channel 20 retain the bearing rollers 34. The upper and lower ledges 46 and 48 and the sheet metal cage pieces 50 and 52 are fixedly mounted on the drive block 32 so that the roller cage means 36 is not displaced relative to the drive block 32 during operation of the tripot universal joint 10. The bearing rollers 34 roll along the continuous roller track 40 in the manner of a recirculating roller bearing as the radial trunnions 26 and the drive blocks 32 are displaced relative to the radial drive channels 20 during operation of the tripot universal joint 10. A slight clearance is provided between the planar surfaces 22 of the radial drive channel 20 and the intermediate drive assembly 16 so that when the joint is stroked axially with torque applied in one direction of rotation, only the active bearing rollers 34 on the torque side of the drive block 32 are under load while rolling in a given direction. Thus, the bearing rollers 34 on the opposite side of the drive block 32 are unloaded and free to travel without interference in the opposite linear direction, as they must do since all the bearing rollers 34 in the assembly are part of a recirculatory train. The radial projections 29 of the radial trunnions 26 which are disposed in the outer radial grooves 23 of the drive channels 20 can engage the end walls 25 of the outer radial grooves to limit inward plunge movement of the inner drive member 12 such that the drive assemblies 16 cannot engage the end wall 21 of the outer drive member 14, as is seen in Figures 1 and 3, thus avoiding possible damage during stroking operation. It will be observed that the radial projections 29 of the radial trunnions 26 are spaced from the longitudinal walls 23a of the outer radial grooves 23 when the telescopic tripot universal joint 10 is at zero angle (that is, when the longitudinal axes 18, 24 of the inner and outer drive members coincide), to permit orbiting of the centre A of the inner drive member 12 when the telescopic tripot universal joint 10 is articulated (bent) at an angle, as shown in phantom in Figure 1, and operated in such an angulated condition. As is best seen in Figure 2, the longitudinal outer (bottom) walls 23a of the outer radial grooves 23 are spaced outwardly of the rounded termini 31 of the radial projections 29, and the outer radial grooves 23 are larger than the radial projections 29 in the circumferential direction when the telescopic tripot universal joint 10 is at zero angle, so that the centre 0 of the inner drive member 12 is free to orbit during operation of the telescopic tripot universal joint at an angle. The drive blocks 32, the bearing rollers 34 and the sheet metal cage pieces 50 and 52 are manufactured as unit-handled drive assemblies 16, such as the unit-handled drive assembly 16 shown in Figure 4. A typical drive assembly 16 is mounted on its associated radial trunnion 26 by inserting the spherical bearing surfaces 28 of the radial trunnion 26 into the socket 44 through assembly slots (not shown), and then indexing the drive assembly through an angle of 90° so that the spherical bearing surfaces 28 are trapped in the unslotted spherical portions of the socket 44, as is seen in Figure 2 and is more particularly described in the aforesaid EP-A-O 244 064.

Claims: 1. A telescopic tripot universal joint in which a first drive member (14) has a first longitudinal axis (18) and three radial drive channels (20) which are equally spaced at substantially 120° from each other and extend in the longitudinal direction, a second drive member (12) has a second longitudinal axis (24) and three radial trunnions (26) which are equally spaced at substantially 120° from each other and are disposed in the respective radial drive channels (20) of the first drive member (14), and three drive assemblies (16) are disposed in the respective radial drive channels (20) and are pivotally mounted on the respective radial trunnions (26) and each include a drive block (32), bearing rollers (34) disposed between the drive block (32) and the radial drive channel (20) in which the drive block (32) is disposed, and cage means (36) for retaining the bearing rollers (34) which is attached to the drive block (32) in a fixed relationship, characterised in that means to limit the inward stroke of the second drive member (12) with respect to the first drive member (14) comprises portions (29) of the radial trunnions (26) which are spaced from the drive assemblies (16) in the radial direction and co-operate with portions of the first drive member (14) that are also spaced from the drive assemblies (16) in the radial direction. 2. A telescopic tripot universal joint according to claim 1, characterised in that the drive block (32) has a continuous roller track (40) with a full complement of the bearing rollers (34) disposed on the continuous roller track (40) for recirculation along the continuous roller track (40). 3. A telescopic tripot universal joint according to claim 1 or 2, characterised in that the means to limit the inward stroke of the second drive member (12) with respect to the first drive member (14) comprises a radial groove (23) in each drive channel (20) which ends short of the drive channel (20) in the longitudinal direction, and a radial projection (29) on each radial trunnion (26) which is disposed in a respective one of the radial grooves (23). 4. A telescopic tripot universal joint according to claim 3, characterised in that the radial groove (23) in each drive channel (20) has an end wall (25) which is spaced from an inner end wall (21) of the first drive member (14) in the longitudinal direction, and the radial projection (29) on each radial trunnion (26) engages the end wall (25) of the radial groove (23) in which it is disposed such that the drive assemblies (16) cannot engage the inner end wall (21) of the first drive member (14). 5. A telescopic tripot universal joint according to claim 3 or 4, characterised in that the radial groove (23) in each drive channel (20) has a longitudinal wall (23a), and the radial projection (29) on each radial trunnion (26) is spaced from the longitudinal wall (23a) of the radial groove (23) in which it is disposed when the tripot universal joint (10) is at zero angle, to permit orbiting of the centre (A) of the second drive member (12) during operation of the universal joint (10) at an angle. 6. A telescopic tripot universal joint according to claim 5, characterised in that the radial projections (29) have termini which are spaced from the longitudinal walls (23a) of the radial grooves (23) in the radial direction when the tripot universal joint (10) is at zero angle, and the radial grooves (23) in the drive channels (20) are larger than the radial projections (29) in the circumferential direction such that the centre (A) of the second drive member (12) is free to orbit during operation of the tripot universal joint (10) at an angle. 7. A telescopic tripot universal joint according to claim 6, characterised in that the radial projections (29) have rounded termini. 8. A telescopic tripot universal joint according to any one of claims 1 to 7, characterised in that the first drive member (14) comprises an outer drive member, and the second drive member (12) comprises an inner drive member.

Inventors: STENGLEIN, PAUL ROBERT
Applicants: GENERAL MOTORS CORPORATION
Application year: 1988
Main classification: F16D3
IPC codes: F16D3