Constant velocity universal joint

Abstract: A constant velocity universal joint (10) comprises a plurality of trunnions (26a) formed to have a spherical configuration and expanding toward guide grooves (18a), cylindrical holders (32) for surrounding the trunnions (26a), to which roller members (24) displaceable along said guide grooves (18a) are externally fitted, and cutouts (34) formed on surfaces of the trunnions (26a).

Description: The present invention relates to a constant velocity universal joint according to the pre-characterizing part of the patent claim. A constant velocity universal joint has been hitherto used for a driving force-transmitting section of an automobile in order to transmit a rotary driving force or torque of a driving shaft to respective axles through a driven shaft. Such a conventional constant velocity universal joint is based on, for example, technical concepts disclosed in Japanese Laid-Open Patent Publication Nos. 4-282028 and 5-215141. A system is adopted in Japanese Laid-Open Patent Publication Nos. 4-282028 and 5-215141, which comprises a trunnion formed to be spherical, in which the trunnion is surrounded by a cylindrical ring (holder). In this system, a surface of the spherical trunnion and an inner circumferential surface of the ring are formed to make point-to-point contact with each other. However, in the case of the conventional constant velocity universal joint, when the trunnion is tilted at a predetermined angle with respect to the ring, the trunnion slides along the inner circumferential surface of the ring while maintaining the state of point-to-point contact. Namely, the trunnion is slidably displaced along an axial direction or along a direction substantially perpendicular to the axial direction while maintaining the state of point-to-point contact at one point with respect to the ring. Such sliding displacement of the trunnion, which is made while maintaining the state of point-to-point contact at one point, scrapes off an oil film formed by a lubricating oil enclosed in an outer member. As a result, a disadvantage arises in that the driving force is not smoothly transmitted from a driving shaft to a driven shaft. On the other hand, when the driving force is transmitted from the driving shaft to the driven shaft while maintaining the state in which the trunnion and the ring make point-to-point contact at one point, the driving torque is concentrated on the contact point between the trunnion and the ring. As a result, a disadvantage arises in that the pressing force, which is applied to an inner circumferential surface of the ring to make point-to-point contact with the trunnion, becomes excessively large. In accordance with the pre-characterizing part of the patent claim and FR-A-2 698 928 (nearest prior art) a constant velocity universal joint is disclosed in which the oil-reserving section is comprised of two flat planar cutouts opposing each other with respect to the longitudinal axis of the trunnion. GB-A-2 252 144 discloses a constanct velocity universal joint in which the roller (rather than the trunnions) comprise oil receiving grooves. A general object of the present invention is to provide a constant velocity universal joint which makes it possible to more smoothly transmit the driving force from a driving shaft to a driven shaft even when the driven shaft is relatively inclined at a predetermined angle with respect to the driving shaft. A principal object of the present invention is to provide a constant velocity universal joint which makes it possible to restrain the pressing force applied to an inner circumferential surface of a holder. According to the present invention this is achieved by the characterising features defined the patent claim 1. When a trunnion is inclined at a predetermined angle with respect to a holder, the lubricating performance is maintained by the aid of an oil-reserving section formed between the holder and the trunnion. Accordingly, a contact portion between a surface of the trunnion and an inner circumferential surface of the holder is protected. As a result, the driving force can be more smoothly transmitted from a driving shaft to a driven shaft. Thus it is possible to obtain good transmitting efficiency. Further, the force to press the inner circumferential surface of the holder is dispersed owing to the change in contact portion between the holder and the trunnion to make contact at one point, two points, and a line segment. Accordingly, it is possible to restrain the pressing force. 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 the accompanying drawings in which preferred embodiments of the present invention is shown by way of illustrative example. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows a vertical cross-sectional view illustrating a constant velocity universal joint intended to explain the present invention. FIG. 2 shows a vertical cross-sectional view taken along a line II-II shown in FIG. 1. FIG. 3 shows a perspective view illustrating an embodiment of the oil-reserving section formed on the trunnion. FIG. 4 shows a perspective view illustrating an modified embodiment of the oil-reserving section formed on the trunnion. DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIGs. 1 and 2, reference numeral 10 indicates a constant velocity universal joint intended to explain the present invention. The constant velocity universal joint 10 basically comprises a cylindrical outer cup (outer member) 12 integrally coupled to one end of an unillustrated driving shaft and having an opening, and an inner member 16 secured to one end of a driven shaft 14 and accommodated in a hole of the outer cup 12. Three guide grooves 18a to 18c are formed on an inner circumferential surface of the outer cup 12. The guide grooves 18a to 18c extend along an axial direction, and they are spaced apart from each other by an angle of 120 degrees about the axial center respectively. Each of the guide grooves 18a (18b, 18c) comprises a plane section 20 formed at a substantially central portion, an inclined section 22 formed to be inclined on both sides of the plane section 20 at a predetermined angle, and a rolling surface 27 formed to be substantially perpendicular to the plane section 20, for allowing a roller member 24 described later on to roll thereon. An end surface-regulating section 28, which protrudes toward the roller member 24 by a predetermined length for regulating the angle of inclination of the roller member 24, is formed at a lower portion of the rolling surface 27. A ring-shaped spider 30 is externally fitted to the driven shaft 14. Three trunnions 26a (26b, 26c), which expand toward the guide grooves 18a (18b, 18c) and are spaced apart from each other by an angle of 120 degrees about the axial center respectively, are secured to an outer circumferential surface of the spider 30. Each of the trunnions 26a (26b, 26c) is formed to be spherical and surrounded by a cylindrical holder 32 with a predetermined clearance intervening therebetween. The trunnion 26a (26b, 26c) is tiltable within a predetermined angle with respect to the holder 32. An oil-reserving section, which has a predetermined width A and extends along a direction substantially perpendicular to the axis, is formed at a portion having the longest circumference on the trunnion 26a (26b, 26c). The oil-reserving section is composed of a cutout 34 formed by chamfering the portion having the longest circumference on the surface of the trunnion 26a (26b, 26c). The cutout 34 comprises a circumferential section 36 having a substantially linear cross section formed by cutting out the spherical surface in the circumferential direction, and first and second annular ridges 38a, 38b provided at both ends of the circumferential section 36 along its widthwise direction to form boundaries between the circumferential section 36 and the spherical surface (see FIG. 3). In this joint, the cutout 34 is formed such that it makes point-to-point contact at one or two points or makes line-to-line contact with the inner circumferential surface of the holder 32 as described later on. An upper end of the holder 32 is formed such that the upper end is capable of abutting against and being separated from the plane section 20 of the guide groove 18a (18b, 18c). Namely, the upper end of the holder 32 is positioned, in an ordinary state, to have a slight clearance with respect to the plane section 20 of the guide groove 18a (18b, 18c). Further, the upper end of the holder 32 is formed to abut against the plane section 20 when the driving shaft or the driven shaft 14 is relatively inclined at a predetermined angle. The roller member 24 is externally fitted to an outer circumferential section of the holder 32 through a plurality of needle bearings 40. The roller member 24 has its outer circumferential surface with a cross section formed to be linear corresponding to the cross-sectional configuration of the guide groove 18a (18b, 18c). The respective needle bearings 40 and the roller member 24 are held by a set of circlips 42a, 42b and washers 44a, 44b fitted to annular grooves of the holder 32. It is possible to hold the needle bearings 40 and the roller member 24 only by using the circlips 42a, 42b without using the washers 44a, 44b. The outer circumferential surface of the roller member 24 makes line-to-line contact with the rolling surface 27 of the guide groove 18a (18b, 18c). Thus the roller member 24 is slidable in its axial direction (in a direction indicated by an arrow X in FIG. 1). Moreover, the roller member 24 is rollable laterally (in a direction indicated by an arrow Y in FIG. 2) along the rolling surface 27. The constant velocity universal joint 10 is basically constructed as described above. Now, the operation, function, and effect of the constant velocity universal joint 10 will be explained. When the unillustrated driving shaft is rotated, its rotary driving force or torque is transmitted to the inner member 16 through the outer cup 12. Accordingly, the driven shaft 14 is rotated in a predetermined direction by the aid of the trunnions 26a to 26c formed to have the spherical configuration. Namely, the rotary driving force of the outer cup 12 is transmitted to the roller members 24 which are displaceable along the guide grooves 18a (18b, 18c). The force is further transmitted to the trunnions 26a (26b, 26c) through the holders 32 held by the roller members 24. Thus the driven shaft 14 is rotated. In this operation, if the unillustrated driving shaft or the driven shaft 14 is inclined, the roller members 24 roll along the guide grooves 18a to 18c. Accordingly, the velocity of rotation of the driving shaft is not affected by the angle of inclination of the driven shaft 14 with respect to the outer cup 12, and the force is always transmitted to the driven shaft 14 at a constant velocity of rotation. When the trunnion 26a (26b, 26c) is inclined at a predetermined angle the inner circumferential surface having the columnar configuration of the holder 32 and the first and second annular ridges 38a, 38b of the trunnion 26a (26b, 26c) make point-to-point contact at two points. As a result of inclination of the axis of the trunnion 26a (26b, 26c) at a predetermined angle with respect to the axis of the holder 32, a state is given in which the trunnion 26a (26b, 26c) makes the point-to-point contact at the two points of the point a 1 and the point a 2 . In the inclined state, the surface of the trunnion 26a (26b, 26c) is not contacted with the inner circumferential surface of the holder 32 at all portions. Therefore, a clearance (for example, 70 µ to 100 µ) is formed between the surface of the trunnion 26a (26b, 26c) and the inner circumferential surface of the holder 32 except for said points. Accordingly, a lubricating oil enclosed in the outer cup 12 enters the clearance. As a result, an oil film formed by the lubricating oil is allowed to exist between the surface of the trunnion 26a (26b, 26c) and the inner circumferential surface of the holder 32. Thus the surface of the trunnion 26a (26b, 26c) and the inner circumferential surface of the holder 32 are protected by the oil film respectively. Next, when the trunnion 26a (26b, 26c) is inclined at a predetermined angle 5, the axis of the holder 32 may be coincident with the axis of the trunnion 26a (26b, 26c), giving a state in which the inner circumferential surface of the holder 32 and the circumferential section 36 of the trunnion 26a (26b, 26c) make line-to-line contact at a line segment. At this moment, the portion to make the line-to-line contact is protected by the oil film intervening between the inner circumferential surface of the holder 32 and the circumferential section 36 of the trunnion 26a (26b, 26c). It is noted that the oil film for protecting the circumferential section 36 is not scraped off because the circumferential section 36 does not contact with the inner circumferential surface of the holder 32. As described above, when the trunnion 26a (26b, 26c) is inclined at a predetermined angle with respect to the holder 32, the inner circumferential surface of the holder 32 and the surface of the trunnion 26a (26b, 26c) undergo the change in contact state including the state of point-to-point contact at the two points, the state of line-to-line contact at said line segment, and the state of point-to-point contact at the one point wherein the contact portion is protected by the oil film intervening between the surface of the holder 32 and the inner circumferential surface of the trunnion 26a (26b, 26c) in response to the foregoing change. As a result, the driving force can be more smoothly transmitted from the driving shaft to the driven shaft 14, and thus good transmitting efficiency can be obtained. In addition, the pressing force exerted on the inner circumferential surface of the holder 32 is dispersed owing to the change of the contact portion between the holder 32 and the trunnion 26a (26b, 26c) to make contact at the one point, two points, and line segment. Thus it is possible to restrain the pressing force. As described above, an advantage is obtained in that the width of the cutout 34 (circumferential section 36) can be decreased when the amount of the lubricating oil enclosed in the outer cup 12 is increased by a predetermined amount as compared with an ordinary state. Explanation has been made by using the cutout 34 which extends in the direction substantially perpendicular to the axis of the trunnion 26a (26b, 26c). However, there is no limitation thereto. According to an embodiment of the invention shown in FIG. 3, a cutout 34b is provided, in which a circular flat section 46 is formed at the transmitting, point for the driving force. As an alternative embodiment, in place of the flat section 46, the spherical surface is formed with a substantially circular recess, 48 having a predetermined curvature exceeding a curvature of the spherical surface (see FIG. 4).

Claims: A constant velocity universal joint having a cylindrical outer member (12) coupled to one transmitting shaft and having, on an inner circumferential surface, a plurality of guide grooves (18a to 18c) spaced apart from each other by a predetermined spacing and extending along an axial direction, and an inner member (16) coupled to the other transmitting shaft and inserted into an opening inner space of said outer member (12), said constant velocity universal joint comprising: a plurality of trunnions (26a to 26c) each having a spherical surface and expanding toward said guide grooves (18a to 18c); cylindrical holders (32) for surrounding said trunnions (26a to 26c), to which roller members (24) displaceable along said guide grooves (18a to 18c) are externally fitted; and an oil-reserving section disposed on each of said trunnions (26a to 26c) at a position at which said trunnions (26a to 26c) contact with inner wall surfaces of said holders (32), characterized in that said oil-reserving section comprises a substantially circular flat section (46) or recess (48) having a diameter, which is small in comparison to the surface of said trunnion, a centre of said circular flat section being provided at a driving force-transmitting point on said trunnion (26a to 26c).

Inventors: KAWAKATSU TSUTOMU, KAYANO TAKESHI, KUDO SATORU, NAGAOKA ATSUSHI, NAKAO SHOUICHI, KAWAKATSU, TSUTOMU, KAYANO, TAKESHI, KUDO, SATORU, Kawakatsu, Tsutomu, c/o Honda Giken Kogyo K.K., Kayano, Takeshi, c/o Honda Giken Kogyo K.K., Kudo, Satoru, c/o Honda Giken Kogyo K.K., Nagaoka Atsushi, c/o Honda Giken Kogyo K.K., Nakao Shouichi, c/o Honda Giken Kogyo K.K.
Applicants: HONDA MOTOR CO LTD, HONDA GIKEN KOGYO KABUSHIKI KAISHA
Application year: 1997
Main classification: F16D3
IPC codes: F16D3