Constant velocity universal joint

Abstract: A constant velocity ratio universal tripod joint (300) comprises on each tripod arm (327) a glider (331) having flat surfaces (335a,335b) and spherical surfaces (337a,337b) all contacting internal surfaces (336a,336b,338a,338b) of a holder (334) whose external faces (340a,340b) parallel to the axis of rotation have grooves (342a-342d) receiving balls (346a-346d) in a retainer (352), the balls engaging the races (322a,322b) of the joint outer member (312).

Description: BACKGROUND OF THE INVENTION Field of the Invention: The present invention relates to a constant velocity universal joint according to the pre-characterizing part of claim 1. The joint is to be used, for example, for a driving force-transmitting section of an automobile. A universal joint of this type is known from US-A 3,381,497. It has gliding members with recesses of curved sectional shape. A constant velocity universal joint has been hitherto used for a driving force-transmitting section of an automobile in order to transmit a rotary power or a torque of a driving shaft to respective axles through a driven shaft. A constant velocity universal joint concerning the conventional technique is known, for example, as illustrated in FIG. 11, in which three track grooves 2 are formed along the axial direction on an inner surface of an outer wheel 1. Leg shafts 4, which protrude in the radial direction, are provided on a tripod member 3 which is arranged inside the outer wheel 1. A spherical roller 6 is fitted rotatably and slidably in the axial direction to an outer circumferential surface of each of the leg shafts 4 via a plurality of needle bearings 5. The spherical roller 6 is allowed to engage with a roller guide surface 7 disposed on both sides of the track groove 2. However, in the case of the constant velocity universal joint concerning the conventional technique as described above, when a high load is applied in a state in which the tripod member 3 is inclined by a predetermined angle with respect to the axis of the outer wheel 1, then the force to press the roller guide surface 7 by the spherical roller 6, i.e., the surface pressure exerted on the roller guide surface 7 is increased, because each of the spherical rollers 6 linearly contacts with the roller guide surface 7 of the track groove 2. As a result, oil film breakage occurs at the contact surface between the spherical roller 6 and the roller guide surface 7, and lubrication failure occurs. Further, the following inconveniences take plate. That is, the lubrication failure causes formation of small holes on the surface of the spherical roller 6, i.e., so-called pits are generated. In other cases, irregularities are formed on the surface of the spherical roller 6, i.e., so-called adhesive wear occurs. On the other hand, in the case of the constant velocity universal joint concerning the conventional technique as described above, when the tripod member 3 is inclined by a predetermined angle with respect to the axis of the outer wheel 1, a relationship is given as shown in FIG. 12, in which each of the spherical rollers 6 obliquely intersects the roller guide surface 7 of the cylindrical track groove 2 with each other. In such a state, it is impossible to allow the spherical roller 6 to perform proper rolling motion. That is, the spherical roller 6 intends to perform rolling motion in the direction indicated by an arrow A or an arrow B shown in FIG. 11, while the track groove 2 is cylindrical and it extends substantially in parallel to the axis of the outer wheel 1. Therefore, the spherical roller 6 is moved while being restricted by the track groove 2. As a result, a thrust force in the axial direction is induced by the slippage which is caused between the roller guide surface .7 of the track groove 2 and the spherical roller 6. The induced thrust force is increased in proportion to the increase of the angle of inclination of the tripod member 3 with respect to the outer wheel 1. It is feared to be difficult to smoothly transmit the rotary power of the driving shaft to the driven shaft. It is noted that a frictional resistance is generated by the reciprocating motion effected by the spherical roller 6 along the roller guide surface 7. In this context, the induced thrust force refers to a load resulting from the frictional resistance. In order to solve the problem as described above, a constant velocity universal joint is known, which is disclosed, for example, in Japanese Laid-Open Patent Publication No. 3-168416. In this constant velocity universal joint, three ball grooves are formed in the axial direction at the inside of an outer wheel. Three pairs of balls are held in the respective ball grooves by the aid of holders respectively. A tripod member is incorporated into the inside of the outer wheel. Three leg shafts extending in the radial direction, which are arranged between the adjacent pairs of balls, are provided on the tripod member. Each of the leg shafts is formed with a spherical surface. A ball guide, which is formed with a spherical recess for engaging with the spherical surface, is provided between the spherical surface and the balls. However, in the case of the constant velocity universal joint disclosed in Japanese Laid-Open Patent Publication No. 3-168416, when the operating angle between the first shaft provided at the closed end of the outer wheel and the second shaft provided on the tripod member is increased, there is a fear of occurrence of vibration in the direction of rotation and so-called beat sound resulting from backlash. The beat sound described above refers to a sound generated by looseness in the direction of rotation. Further, there is a fear that the following inconveniences may occur. That is, the balls tend to be disengaged from the holder upon assembly, it is difficult to retain the balls in the ball guide, a high technique is required for assembling, the assembling time is prolonged, and the operation efficiency is lowered. A three-plane constant velocity joint is disclosed in Japanese Laid-Open Patent Publication No. 6-74243. In this case, an inner joint member is inserted into the inside of an outer joint member, and trunnions are provided on the inner joint member. Each of the trunnions is provided with a plurality of spherical balls. The spherical balls are constructed so that they are rollable along side walls which constitute a longitudinal chamber formed in the outer joint member. The spherical balls are held on the trunnion by the aid of a positioning spring installed to the trunnion. However, also in the case of the three-plane constant velocity joint disclosed in Japanese Laid-Open Patent Publication No. 6-74243, when the operating angle between the outer joint member and the inner joint member is increased, there is a fear of occurrence of vibration in the direction of rotation and so-called beat sound resulting from backlash. Further, it is difficult to retain the spherical balls on the trunnion upon assembling. It is feared that the efficiency of the assembling operation is lowered. Another constant velocity universal joint concerning the conventional technique is known, which is constructed, for example, as illustrated in FIG. 13. In this case, a pair of track surfaces 2a, 2b, which are opposed to one another and which have a circular arc-shaped cross-section, are formed in the axial direction on an inner wall surface of an outer joint member 1a. An inner joint member 3a, which is disposed between the pair of track surfaces 2a, 2b, is arranged in an internal hollow space of the outer joint member 1a. Further, a plurality of ball members 9 are provided rollably along the track surfaces 2a, 2b by the aid of a retainer 8 (see Japanese Patent Publication No. 7-74649). However, in the case of the constant velocity universal joint concerning the conventional technique, when the spacing distance S between the pair of track surfaces 2a, 2b is smaller than a predetermined value, a large load is exerted on the ball members 9 which roll along the pair of track surfaces 2a, 2b. On the other hand, when the spacing distance S between the pair of track surfaces 2a, 2b is larger than a predetermined value, looseness occurs due to the gap between the ball members 9 and the pair of track surfaces 2a, 2b. As described above, the constant velocity universal joint concerning the conventional technique involves the inconvenience that the durability and the vibration characteristics are deteriorated by any dimensional error depending on the machining accuracy for the pair of track surfaces 2a, 2b which are formed on the inner wall surface of the outer joint member 1 in the mutually opposing manner. Further, it is necessary that the pair of track surfaces 2a, 2b of the outer joint member 1 on which the ball members 9 roll have a hardness not subjected to plasticization caused by the contact surface pressure generated between the track surfaces 2a, 2b and the ball members 9. For this reason, it is necessary to apply a heat treatment to the pair of track surfaces 2a, 2b, which results in an inconvenience that the production cost becomes expensive. A general object of the present invention is to provide a constant velocity universal joint which makes it possible to reduce the induced thrust force so that the driving force may be still more smoothly transmitted from one transmission shaft to the other transmission shaft. This is achieved by the universal joint having the features of claim 1. Preferred embodiment are defined by the dependent claim. This constant velocity universal joint which makes it possible to avoid occurrence of vibration in the direction of rotation and beat sound resulting from backlash even when the operating angle between one transmission shaft and the other transmission shaft is increased. It is possible to stabilize lubrication performance and avoid occurrence of pits and adhesive wear. It is also possible to shorten the assembling time and improve the operation efficiency by reliably holding ball members upon assembling without any disengagement of the ball members. Specifically, the spacing distance between a pair of mutually opposing rolling surfaces is not affected by any dimensional error. It is possible to reduce the production cost by omitting the heat treatment step which would be otherwise required for rolling surfaces of an outer member. The above and other objects, features, and advantages of the present invention will become more apparent from the following description when taken in conjunction with the accompanying drawings in which a preferred embodiment of the present invention is shown by way of illustrative example. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows a longitudinal sectional view taken along an axial direction of a constant velocity universal joint. FIG. 2 shows a sectional view taken along a line II-II shown in FIG. 1. FIG. 3 shows a perspective view illustrating a trunnion and a pair of slipper members engaging with the trunnion. FIG. 4A to 4C show longitudinal sectional views, wherein figs. 4B and 4C illustrate embodiments of the slipper member shown in FIG. 3 according to the invention. FIG. 5 shows a perspective view illustrating a modified embodiment of the slipper member shown in FIG. 3. FIG. 6 shows a sectional view taken along a line VI-VI shown in FIG. 2. FIGs. 7A and 7B illustrate the relationship between the angle of inclination of the second shaft and the induced thrust force. FIGs. 8A and 8B illustrate shapes of lubricating grooves formed on outer surfaces of the trunnions respectively. FIG. 9 shows a cross-sectional view, with partial omission, illustrating lubricating grooves formed on sliding surfaces of a guide groove. FIG. 10 shows a cross-sectional view illustrating application of the constant velocity universal joint shown in FIG. 2 to a bipod type. FIG. 11 shows a partial sectional side view illustrating a constant velocity universal joint concerning the conventional technique. FIG. 12 shows a magnified perspective view illustrating a state in which a spherical roller used for the constant velocity universal joint shown in FIG. 11 is inclined by a predetermined angle with respect to a roller guide groove. FIG. 13 shows a partial sectional view illustrating a constant velocity universal joint concerning the conventional technique DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIGs. 1 and 2, reference numeral 10 indicates a constant velocity universal joint. The constant velocity universal joint 10 is basically comprises a cylindrical outer cup (outer member) 12 having an opening and integrally coupled to one end of an unillustrated first shaft, and an inner member 16 fixedly fixedly secured to one end of a second shaft 14 and accommodated in a hole of the outer cup 12. As shown in FIG. 2, three guide grooves 18a to 18c, which extend along the axial direction and which are spaced apart from each other by 120 degrees about the center of the axis, are formed on an inner circumferential surface of the outer cup 12. Each of the guide grooves 18a to 18c comprises a curved section 20 which is formed to have a curved cross section, and sliding surfaces (flat surface sections) 24 which are formed mutually opposingly on both sides of the curved section 20 for sliding slipper members 22a, 22b thereon as described later on. The sliding surface 24 is formed to have a flat configuration which extends along the axial direction of the outer cup 12. A ring-shaped spider 25 is externally fitted to the second shaft 14. Three trunnions 26a (26b, 26c), which expand toward the guide grooves 18a (18b, 18c) respectively and which are spaced apart from each other by 120 degrees about the center of the axis, are formed integrally on an outer circumferential surface of the spider 25. An outer surface of each of the trunnions 26a (26b, 26c) facing with the sliding surface 24 is formed to be spherical. A pair of slipper members (gliding members) 22a, 22b, each of which has an identical shape, are interposed between the trunnion 26a (26b, 26c) and the sliding surface 24. The pair of slipper members 22a, 22b are formed to make surface-to-surface contact with the trunnion 26a (26b, 26c) and the sliding surface 24 respectively. As shown in FIG. 3, one side surface of the slipper member 22a, 22b, which makes surface-to-surface contact with the trunnion 26a (26b, 26c), is composed of a recess 28 having its inner wall surface which is formed to have a spherical configuration corresponding to the spherical surface of the trunnion 26a (26b, 26c). The other side surface, which makes surface-to-surface contact with the sliding surface 24, is formed to be a flat surface 30 corresponding to the sliding surface 24. Conventionally, the shape of the recess 28 of the slipper member 22a, 22b contacting with the trunnion 26a (26b, 26c) is a spherical surface formed to have a circular arc-shaped cross section (see FIG. 4A). According to the present invention, the recess 28a is formed to have a substantially v-shaped cross section to make line-to-line contact with the trunnion 26a (26b, 26c) (see FIG. 4B). Alternatively, a hole 32, which penetrate through the center of the recess 28 having the substantially v-shaped cross section as described above, may be formed (see FIG. 4C). The provision of the hole 32 is advantageous in that the concentration of stress is avoided, and lubricating oil can be easily poured and applied to the sliding surface of the trunnion 26a (26b, 26c) and the slipper member 22a, 22b. Preferably, the slipper member 22a, 22b may be formed to have the disk-shaped configuration as shown in FIG. 3 or a rectangular configuration as shown in FIG. 5, by using a material made of metal or resin. The constant velocity universal joint 10 according to this embodiment of the present invention is basically constructed as described above. Next, its operation, function, and effect will be explained. When the unillustrated first shaft is rotated, then its rotary power is transmitted to the inner member 16 via the outer cup 12, and the second shaft 14 is rotated in a predetermined direction by the aid of the trunnions 26a to 26c formed to be spherical. That is, the rotary power of the outer cup 12 is transmitted to the slipper members 22a, 22b which make displacement along the guide grooves 18a (18b, 18c), and it is further transmitted to the trunnions 26a (26b, 26c) which make surface-to-surface contact with the slipper members 22a, 22b. Thus, the second shaft 14, which is engaged with the trunnions 26a (26b, 26c), is rotated. During this process, when the second shaft 14 is inclined by a predetermined angle with respect to the outer cup 12 having the first shaft, the trunnion 26a (26b, 26c), which is formed to have the spherical configuration, makes sliding displacement by predetermined angles in the directions indicated by an arrow C (see FIG. 2) and an arrow D (see FIG. 6) along the recesses 28 of the spherical surfaces formed on one side surfaces of the slipper members 22a, 22b. Simultaneously with the sliding displacement of the trunnion 26a (26b, 26c), the slipper members 22a, 22b make sliding displacement along the sliding surfaces 24 via the flat surfaces 30 formed on the other side surfaces. In this embodiment, the slipper members 22a, 22b are provided slidably displaceably in all directions concerning the sliding surfaces 24 including the direction indicated by an arrow E (see FIG. 1) parallel to the axis of the sliding surfaces 24 and the direction indicated by an arrow F (see FIG. 2) perpendicular to the axis. Accordingly, the rotational motion of the first shaft is transmitted to the second shaft 14 without being affected by the angle of inclination of the second shaft 14 with respect to the outer cup 12. As described above, in this embodiment, the pair of slipper members 22a, 22b, which are slidably displaceable while making surface-to-surface contact with the trunnions 26a (26b, 26c) and the sliding surfaces 24, are interposed between the trunnions 26a (26b, 26c) and the sliding surfaces 24. Therefore, in the first embodiment, the surface pressure at the sliding section is lowered as compared with the conventional technique which is based on the linear contact with the sliding section. Thus, it is possible to stabilize the lubricating performance without causing any oil film breakage at the sliding section. As a result, it is possible to avoid, for example, occurrence of pits and adhesive wear resulting from lubrication failure. The relationship between the induced thrust force and the relative angle of inclination of the second shaft 14 with respect to the first shaft is shown in FIGs. 7A and 7B. The term "induced thrust force" described above refers to the load resulting from frictional resistance generated by the sliding displacement of the slipper members 22a, 22b along the guide grooves 18a to 18c. As shown in FIG. 7B, in the case of a constant velocity universal joint concerning the conventional technique '(straight line G), the induced thrust force is rapidly increased in accordance with the increase in the angle of inclination of the second shaft 14. On the contrary, as shown in FIG. 7A, in the case of the constant velocity universal joint 10 according to the first embodiment (straight line H), the induced thrust force is maintained to be approximately constant even when the angle of inclination is increased. Therefore, in the constant velocity universal joint 10 according to this embodiment, the induced thrust force, which is generated resulting from the frictional resistance, is not increased rapidly even when the angle of inclination of the second shaft 14 with respect to the outer cup 12 is increased. Thus, it is possible to stabilize the induced thrust force. In this embodiment, for example, a plurality of lubricating grooves 34, which are arranged longitudinally and latitudinally, are formed to make intersection (see FIG. 8A), or lubricating grooves 36, which extend outwardly in a curved configuration, are formed in four directions (see FIG. 8B) on outer surfaces of the trunnions 26a (26b, 26c) which contact with the slipper members 22a, 22b. Thus, it is possible to further improve the lubricating performance at the sliding section between the trunnions 26a (26b, 26c) and the slipper members 22a, 22b. In this embodiment, the location of the lubricating grooves 34, 36 is not limited to the outer surfaces of the trunnions 26a (26b, 26c). The lubricating grooves 34, 36 may be formed on the spherical surfaces of the trunnions 26a (26b, 26c), the recesses 28 of the slipper members 22a, 22b which make surface-to-surface contact with the sliding surfaces 24 of the guide grooves 18a (18b, 18c), and the flat surfaces 30 respectively. Further, the lubricating performance may be improved by forming oil sumps such as dimples (not shown) on the outer surfaces of the trunnions 26a (26b, 26c). In addition, as shown in FIG. 9, at least one stripe of lubricating groove 38, which extends substantially in parallel to the axis of the outer cup 12, may be formed on the sliding surface 24 of the guide groove 18a (18b, 18c). The sectional configuration of the lubricating groove 38 may be V-shaped, circular arc-shaped, or rectangular. The lubricating groove 38 may be provided as a plurality of individuals. Further, it is possible to reduce the coefficient of friction by applying a coating treatment to any one of or both of the surfaces of the trunnions 26a (26b, 26c) and the slipper members 22a, 22b. In this embodiment, it is enough to provide only the pair of slipper members 22a, 22b, as compared with the conventional technique. Therefore, this embodiment is advantageous in that the number of parts is decreased, and the production cost can be reduced. The embodiment has been explained with reference to the tripod type constant velocity universal joint 10 provided with the three trunnions 26a (26b, 26c). However, the present invention is not limited thereto. It is a matter of course that the present invention can be applied to a constant velocity universal joint 10a of the bipod type as shown in FIG. 10.

Claims: A constant velocity universal joint having a cylindrical outer member (12) which is provided on its inner circumferential surface with a plurality of guide grooves (18a to 18c) spaced apart from each other by a predetermined spacing distance and extending along an axial direction and which is coupled to one transmission shaft, and an inner member (16) which is inserted into an open internal hollow space of said outer member (12) and which is coupled to the other transmission shaft, said constant velocity universal joint comprising: a plurality of trunnions (26a to 26c) which are formed to be spherical and which expand toward said guide grooves (18a to 18c); flat surface sections (24) which are formed on mutually opposing side surfaces of said guide grooves (18a to 18c) and which extend in a flat surface configuration along said axial direction of said outer member (12); and pairs of gliding members (22a, 22b) having an identical shape each of which is interposed between said flat surface section (24) and said trunnion (26a to 26c), each of which has one side surface formed with a recess (28a) to make contact with a spherical surface of said trunnion (26a to 26c), and each of which has the other side surface formed with a flat surface (30) to make contact with said flat surface section (24), wherein: said pairs of gliding members (22a, 22b) are provided slidably with respect to said flat surface sections (24) of said guide grooves (18a to 18c) and said spherical surfaces of said trunnions (26a to 26c) characterized in that said recess (28a) of said gliding member (22a, 22b) has a sectional shape formed to be a substantially v-shaped sectional configuration involving linear inclination at a predetermined angle from ends to a center. The constant velocity universal joint according to claim 1, wherein a penetrating hole (32) is formed through a central portion of said recess (28a) of said gliding member (22a, 22b). The constant velocity universal joint according to claim 1, wherein lubricating grooves (34, 36) are formed on said spherical surface of said trunnion (26a to 26c) or on said recess (28a) of said gliding member (22a, 22b) contacting with said spherical surface. The constant velocity universal joint according to claim 1, wherein lubricating grooves (34, 36) are formed on said flat surface (30) of said gliding member (22a, 22b) contacting with said flat surface section (24) of said guide groove (18a to 18c). The constant velocity universal joint according to claim 1, wherein at least one or more stripes of lubricating grooves (38) are formed on said flat surface section (24) of said guide groove (18a to 18c) substantially in parallel to said axial direction of said outer member (12).

Inventors: KAYANO TAKESHI, KITA KANJI, KUDO SATORU, MIYATA KAZUNORI, KAYANO, TAKESHI, KITA, KANJI, KUDO, SATORU, MIYATA, KAZUNORI, Kayano, Takeshi, c/o Honda Giken Kogyo K. K., Kita, Kanji, c/o Honda Giken Kogyo K. K., Kudo, Satoru, c/o Honda Giken Kogyo K. K., Miyata, Kazunori, c/o Honda Giken Kogyo K. K.
Applicants: HONDA MOTOR CO LTD, HONDA GIKEN KOGYO KABUSHIKI KAISHA
Application year: 1998
Main classification: F16D3
IPC codes: F16D3