A tripod joint has an outer joint part with three circumferentially distributed, axis-parallel recesses forming circumferentially distributed opposed tracks. An inner joint part has a star-shaped cross-section and three circumferentially distributed arms engaging the recesses in the outer joint part. The arms support roller assemblies. When torque is transmitted with the joint in an extended position, the resultant K1 of the forces acting from the inner joint part directly on a roller forms a shorter perpendicular distance from the joint axis than the resultant K2 of the counter forces acting from the outer joint part on the roller, so that, when torque is introduced into the joint, at any angle of articulation of the operating range, the roller is subject to a tilting moment.
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11. A tripod joint comprising:
an outer joint part with three circumferentially distributed, axis-parallel recesses forming circumferentially opposed tracks; an inner joint part having a star-shaped cross-section and three circumferentially distributed arms engaging the recesses in the outer joint part, said inner and outer joint parts defining a joint axis; roller assemblies supported on said arms, each roller assembly including a roller carrier assembly and a roller, with at least said roller relative to the respective arm, being axially movable relative to the arm axis and angularly movably pivotable relative to the arm axis; spherical faces at the arms or at the roller carrying assembly of the respective roller assembly and internally spherical or internally cylindrical counter faces at the roller carrier assembly of the roller assembly or at the rollers, providing first mutually contacting surfaces on the one hand, and the outer surfaces of the rollers and the track surfaces in contact therewith, providing second mutually contacting surfaces on the other hand, when torque is transmitted with the joint being in a non-articulated position, a first resultant of the forces acting from the inner joint part directly on the roller between the spherical arm or roller carrier assembly faces and the internally spherical or internally cylindrical faces is at a greater perpendicular distance from the joint axis than a second resultant of the counter forces acting at from the outer joint part on the roller between the internally spherical or internally cylindrical faces outer surfaces of the rollers and track surfaces in contact therewith so that the first resultant is offset from the second resultant, at any angle of articulation in the operating range, the roller is subject to a tilting moment which tilts the roller outwardly around its region of contact at the loaded track.
1. A tripod joint comprising:
an outer joint part with three circumferentially distributed, axis-parallel recesses forming circumferentially opposed tracks; an inner joint part having a star-shaped cross-section and three circumferentially distributed arms engaging the recesses in the outer joint part, said inner and outer joint parts defining a joint axis; roller assemblies supported on said arms, each including a roller carrier assembly and a roller, with at least the roller, relative to the respective arm, arranged axially movable relative to the arm axis and angularly movably pivotable relative to the arm axis; spherical faces at the arms or at the roller carrying assembly of the respective roller assembly and internally spherical or internally cylindrical counter faces of the roller carrier assembly or the rollers, providing first mutually contacting surfaces on the one hand, and the outer surfaces of the rollers and the track surfaces in contact therewith, providing second mutually contacting surfaces on the other hand, when torque is transmitted with the joint being in a non-articulated position, a first resultant of the forces acting from the inner joint part directly on the roller between the arm faces or roller assembly faces and the internally spherical or internally cylindrical counter faces of the roller carrier assembly is at a shorter perpendicular distance from the joint axis than a second resultant of the counter forces acting at from the outer joint part on the roller between the internally spherical or internally cylindrical counter faces of the roller carrier assembly outer surfaces of the rollers and track surfaces in contact therewith so that the first resultant is offset from the second resultant, and so that, when torque is introduced into the joint, at any angle of articulation in the operating range, the roller is subject to a tilting moment which tilts the roller inwardly towards the joint axis around the contact faced at the loaded track.
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The invention relates to a tripod joint having an outer joint part with three circumferentially distributed, axis-parallel recesses which form circumferentially distributed opposed tracks. An inner joint part having a star-shaped cross-section and three circumferentially distributed arms engaging the recesses in the outer joint part. The arms support roller assemblies. Each roller assembly includes a roller carrying assembly and a roller. The roller, with respect to the arm, is axially movable relative to the arm axis and angularly movably pivotable relative to the arm axis.
Tripod joints which provide movability are described, for example, in DE 28 31 044 (Honda), DE 39 36 601 (GKN) and DE 37 16 962 (NTN).
When the joint rotates in an articulated condition with reference to the inner joint part, there occurs radially oscillating movement of the rollers relative to the axis of the inner joint part and pivoting movement of the rollers on the arms. At the same time, during the articulated condition with reference to the outer joint part, there occurs longitudinally extending oscillating rolling movement of the rollers along the tracks. The first mentioned radial and pivot movements are accompanied by sliding friction whereas the next mentioned movements are predominantly rolling contact movements. Because of said friction forces, prior art tripod joints with an increasing angle of articulation, are subject to a considerable increase in joint excitation forces, e.g. cyclic forces generated in the joint and transmitted to the driveline. Because of the wear caused in the driveline and the development of noise, such forces are highly undesirable.
In addition, in some cases such joint excitation forces scatter from joint to joint, sometimes even within the individual joint during operation. The cause of the scatter may be an unstable behavior of the roller in the tracks of a joint rotating in the articulated condition. This may lead to different and changing contact and friction conditions on various contact faces of the roller assembly relative to the recesses.
In view of the above, it is an object of the invention to develop a joint that improves the friction conditions in the joint and, in consequence, reduces and predetermines the joint excitation forces.
A first solution provides spherical faces at the arms or at elements of the respective roller assembly. Internally spherical or internally cylindrical counter faces at elements of the roller assembly or at the rollers, on the one hand, and the outer surfaces of the rollers and the track surfaces in contact therewith, on the other hand, are designed such that when torque is transmitted, with the joint in an extended position, the resultant of the forces acting from the inner joint part directly on a roller between the first mentioned faces features a shorter perpendicular distance from the joint axis than the resultant of the counter forces acting from the outer joint part on the roller between the next mentioned faces. Thus, when torque is introduced into the joint, at any angle of articulation in the operating range, the roller is subject to a tilting moment which tilts the roller inwardly towards the joint axis around its contact face at the loaded track.
In principle, this means that the force application point for the forces applied by the respective tripod arm is asymmetrically located directly to the inner surface of the roller. Thus, the roller is radially inwardly offset relative to the force application point of the forces applied by the surface of the respective track to the outer surface of the roller to generate the tilting moment. It is appreciated that roller assembly elements are provided between the 11 111 with one of three radially adjoining, circumferentially distributed, externally spherical arms 112, inserted into an outer joint part 113. The outer joint part 113 is shown with one of three circumferentially distributed recesses 114. A roller assembly is provided between he the arm and the recess. The roller assembly includes a roller carrier 116 with an internally cylindrical inner aperture. The carrier 116 is radially movably held on the arm 112 relative to the joint axis and pivotable relative to the arm axis. The roller carrier 116, via a needle bearing 117, supports a roller 118. The needle bearing 117 and roller 118, with reference to the joint axis, are held on the roller carrier 116 via a radially inner collar 119, an outer disc 120 and a retaining ring 121. The two halves of the recess 114, on opposite sides, each have internally cylindrical tracks 122 and radially inner shoulders 124. Furthermore, the recess 114 includes an outer supporting face 125.
FIG. 7a shows the joint at the moment when torque is introduced. Assuming that the inner joint part is the driving component and the outer joint part the driven component, torque introduction would be clockwise. The track 122 shown on the right is in contact with the roller.
FIG. 7b, while containing the same illustration as 7a, shows a tilting clockwise moment TR which acts on the roller as a result of a distance OFF between the force application line of a resulting force F, applied by the arm 112 to the roller carrier 16 116 and thus indirectly to the roller 118 (on the radial outside), and the force application line of a resulting force -F, applied by the torque-loaded right hand track 122 to the roller directly (on radial inside) with the line of force F being above the line of force -F.
FIG. 7c shows how, as a result of the tilting moment TR applied to the roller, the roller assumes a position tilted in the track around an axis which is parallel to the joint axis. In the process, the collar 119 is supported on the shoulder 124 on the loaded half of the recess 114, whereas the roller carrier 116, with its radially outer head face, is supported on the outer supporting face 125 of the track. A supporting moment acting against the tilting moment TR is generated through the supporting force FS by the lever arm RR. The distance OFF between the two force application lines of the forces F and -F is to remain positive at all angles of articulation. Thus, the friction forces acting on the supporting face 125 on the roller carrier 116 are low. Therefore, no rotational movement occurs relative to the spherical arm 112. Thus, any wear between the two is avoided at the substantially linear contact face.
In FIGS. 8a to 8c, any parts corresponding to FIGS. 7a to 7c have been given reference numbers increased by 20. In contrast to the joint illustrated in FIGS. 7a to 7c, the tracks 142 each include two cylindrical portions 147,148 whose central axes are offset relative to one another and whose cross-section has the shape of a so-called Gothic arch. In the section shown, the radius of curvature of the two arch parts is greater than the radius of curvature of the roller 138. This joint differs further in that the roller 138 is secured to the roller carrier 136 both on the radial outside by the disc and securing ring 140, 141 and on the radial inside by the disc and securing ring 149, 150. The design of the track ensures that, independently of the application point of the force F-, the application point of the force -F changes only slightly.
In FIGS. 9a to 9c, again, any components corresponding to FIGS. 8a to 8c have been given reference numbers increased by 20. In contrast to the previous figures, reference has to be made to the shape of the tracks 162 and the roller 158. The cross-section of the track 162 is convex in its central region and forms two shoulders 167, 168. The roller 158, in its central region, is externally cylindrical and is provided with counter-shoulders which stop against the shoulders 167, 168 of the tracks 162. This track shape ensures that with a radially changing force F, the counter force -F substantially retains the same application point.
FIG. 10 shows only part of a section through an inner joint part 171 with one of three circumferentially distributed, radial, cylindrical arms 172 and an outer joint part 173 with one of three circumferentially distributed recesses 174. The arm engages the recess and a roller assembly is arranged on the arm.
The roller assembly includes an inner ring 175 with an internally cylindrical inner surface and an externally spherical outer surface. The inner ring 175 may radially oscillate on the arm 172 with reference to the joint axis. The inner ring 175 holds a roller carrier 176 which, via an internally spherical recess, is pivotably positioned on the externally spherical outer surface of the inner ring 175. A roller 178 is rotatably held on the roller carrier 176 via needle bearing 177. The needle bearing and roller, with reference to the joint axis, are held by a radially inner collar 179, a radially outer disc 180 and a securing ring 181.
When torque is introduced, the externally spherical roller 178 rolls on one of the tracks 182 in the recess 174. On the radial inside of the roller assembly, the recess 174, on both halves, includes shoulders 184, with the shoulder positioned on the recess half not subjected to loads remaining contact-free when torque is introduced. The roller carrier 179, on the other hand, on the half of the recess 174 not subjected to loads, when torque is introduced, may support itself with its head face on a supporting face 185 on the radial outside of the roller assembly. On each half of the recess, the supporting face 185, by radial extensions 186, is restricted to a region close to the arm axis.
Two dash-dot lines indicate the force application line of a resulting force acting from the arm to the inner ring 175, and thus indirectly to the roller 178 (on the radial outside), and the force application line of a resulting force acting from the tracks 182 directly on the roller 178 (on the radial inside). The lines maintain a positive radial distance from one another at all operating angles of articulation. As a result, a tilting moment is applied to the roller clockwise and outwardly around the right hand track if it is assumed that the track is loaded when torque is introduced.
FIG. 11 shows only part of an inner joint part 191 with one of three circumferentially distributed radial arms 192 and an outer joint part 193 with one of three circumferentially distributed recesses 194 engaged by the arm. A roller assembly, for torque transmitting purposes, is provided between the armand arm and recess.
The cylindrical arm 192 rotatably supports an inner roller 196 via a needle bearing 197. The roller 196 has a spherical outer surface and supports a roller 198. The roller 198 has an internally cylindrical inner surface radially movable with reference to the joint axis and pivotable with reference to the arm axis. The roller 198 moves in track 202 in both halves of the recess 194. The needle bearing 197 and the inner roller 196 are axially secured to the arm via a disc 100 200 and a securing ring 101 201 and a stop ring 103 203.
The force application line of the resulting force indirectly applied by the inner joint part 191, via the inner roller 196, to the roller 198 and the force application line of the resulting force applied by the outer joint part 193 to the roller 198 are indicated by dash-dot lines. The former line is located on the radial outside and the latter line on the radial inside. Under all operating conditions, at all angles of articulation, a positive distance is maintained between the two force application lines. Thus, assuming the track is loaded when torque is introduced, a tilting moment is applied to the roller clockwise and outwardly around the right hand track. When the roller 198 is tilted as a result, it is supported on supporting faces 206 in the recess 194.
While the above detailed description describes the preferred embodiment of the present invention, the invention is susceptible to modification, variation, and alteration without deviating from the scope and fair meaning of the subjoined claims.
Hofmann, Norbert, John, Friedhelm, Krude, Werner, Ricks, Michael, Harz, Peter, Bensinger, Jorg, Jost, Dieter
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| Apr 10 1996 | GKN Automotive AG | (assignment on the face of the patent) | / |
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