Tripod constant velocity universal joint

Abstract

In a tripod constant velocity universal joint of the double row roller type, an outer ring (11) has a cylindrical outer peripheral surface (15). A pair of roller guide surfaces (6) of each track groove (5) are flat surfaces parallel to each other. A pair of guide surfaces (7) that can come into contact with the outer ring (11) from both sides in the axial direction thereof are provided on both sides in the width direction of the roller guide surface (6). The inner ring (12) has a cylindrical inner peripheral surface (18). The outer peripheral surface (33) of the leg shaft (32) has a convex curve protruding toward both sides in the torque transmission direction (X) in a longitudinal section and a cross section. A convex curve (arc (33b)) in the cross section of the outer peripheral surface of the leg shaft (32) is farther away from the inner peripheral surface (18) of the inner ring (12) from the X-direction end toward both Z-direction sides. The radius of curvature (r) of a convex curve (arc (33a)) in the longitudinal section of the outer peripheral surface of the leg shaft (32) is larger than the radius of curvature (R) of a convex curve (arc (33b)) in the cross section of the outer peripheral surface of the leg shaft (32).

Description

Technical Field

[0001] The present invention relates to a tripod constant velocity universal joint. Background Art

[0002] In a drive shaft used in a power transmission system of a motor vehicle, it is common to provide a sliding constant velocity universal joint on the inner side (the center side in the vehicle width direction) and a fixed constant velocity universal joint on the outer side (the outer side in the vehicle width direction). Here, the sliding constant velocity universal joint is a constant velocity universal joint that allows both angular displacement and axial relative movement between two shafts, and the fixed constant velocity universal joint is a constant velocity universal joint that allows angular displacement between two shafts but does not allow axial relative movement between the two shafts.

[0003] As the sliding constant velocity universal joint, the tripod constant velocity universal joint is well-known. As this tripod constant velocity universal joint, there are a single-row roller type and a double-row roller type. In the single-row roller type tripod constant velocity universal joint, rollers inserted into the raceway grooves of the outer joint member are rotatably mounted on the leg shafts of the tripod member via a plurality of needle rollers. The double-row roller type tripod constant velocity universal joint has rollers 111 disposed in the raceway grooves 105 of the outer joint member 102 and an inner ring 112 that is externally fitted to the leg shafts 132 of the tripod member 103 and supports the rollers 111 so as to be rotatable, as shown in FIGS. 7 and 8 (for example, refer to Patent Documents 1 and 2 described below). Figure 7 As shown in FIGS. 7 and 8, the double-row roller type tripod constant velocity universal joint has rollers 111 disposed in the raceway grooves 105 of the outer joint member 102 and an inner ring 112 that is externally fitted to the leg shafts 132 of the tripod member 103 and supports the rollers 111 so as to be rotatable (for example, refer to Patent Documents 1 and 2 described below).

[0004] In the double-row roller type tripod constant velocity universal joint, as shown in FIG. 9, the cross section of the leg shaft 132 (the section orthogonal to the axis of the leg shaft) is formed in an elliptical shape, and as shown in FIG. 10, the inner peripheral surface of the inner ring 112 is formed in a convex arc-shaped cross section. Thus, as shown in FIG. 11, the rollers 111 can be swung relative to the leg shafts 132, and therefore, compared with the single-row roller type, there is an advantage that the induced thrust (axial force induced by friction between components inside the coupling) and the sliding resistance can be reduced. Figure 9 As shown in FIG. 9, the cross section of the leg shaft 132 (the section orthogonal to the axis of the leg shaft) is formed in an elliptical shape, and as shown in FIG. 10, the inner peripheral surface of the inner ring 112 is formed in a convex arc-shaped cross section. Thus, as shown in FIG. 11, the rollers 111 can be swung relative to the leg shafts 132, and therefore, compared with the single-row roller type, there is an advantage that the induced thrust (axial force induced by friction between components inside the coupling) and the sliding resistance can be reduced. Figure 7 As shown in FIG. 10, the inner peripheral surface of the inner ring 112 is formed in a convex arc-shaped cross section. Thus, as shown in FIG. 11, the rollers 111 can be swung relative to the leg shafts 132, and therefore, compared with the single-row roller type, there is an advantage that the induced thrust (axial force induced by friction between components inside the coupling) and the sliding resistance can be reduced. Figure 10 As shown in FIG. 11, the rollers 111 can be swung relative to the leg shafts 132, and therefore, compared with the single-row roller type, there is an advantage that the induced thrust (axial force induced by friction between components inside the coupling) and the sliding resistance can be reduced.

[0005] Prior Art Documents

[0006] Patent Documents

[0007] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2000-320563

[0008] Patent Document 2: Japanese Patent No. 2957121 Summary of the Invention

[0009] Problems to be Solved by the Invention

[0010] In the above-described tripod constant velocity universal joint, as Figure 8 shown, the outer peripheral surface 115 of the roller 111 is a convex surface with an arc-shaped generatrix, and the roller guide surface 106 in contact therewith has a concave cross-sectional shape (cusp shape) in accordance with the shape of the outer peripheral surface 115 of the roller 111, and they form an angular contact. Therefore, in terms of structure, when the constant velocity universal joint rotates in a state of taking a working angle, in the cross-section orthogonal to the axial direction of the coupling as shown in Figure 11 , a phenomenon occurs in which the roller unit 104 including the roller 111 and the inner ring 112 inclines in the direction of arrow B (hereinafter referred to as "left-right inclination"). In the cross-section parallel to the axial direction of the coupling as shown in Figure 12 , a phenomenon occurs in which the roller unit 104 inclines in the direction of arrow C (hereinafter referred to as "front-back inclination"). When left-right inclination and front-back inclination occur in the roller unit 104, the rolling-sliding resistance at the contact portion where the roller 111 contacts the roller guide surface 106 and the rotational resistance of the roller unit 104 with respect to the stub shaft 32 increase. Also, the needle rollers 117 in the roller unit 104 cannot roll in the axial direction of the outer coupling member 102 with respect to the roller guide surface 106, so the sliding resistance increases. In the case where these factors are significant, the induced thrust and sliding resistance increase, and there is a problem that the NVH (Noise, Vibration, Harshness) characteristics of the constant velocity universal joint deteriorate.

[0011] In addition, in the above-described tripod constant velocity universal joint, the cross-section of the stub shaft 132 is an elliptical shape, and the inner peripheral surface of the inner ring 112 is a convex arc shape in cross-section. Therefore, the contact between the inner ring 112 and the stub shaft 132 becomes a substantially point contact, and the frictional torque that acts to incline the roller unit 104 along with the movement of the stub shaft 132 can be suppressed. Also, even when the coupling takes an angle, the stub shaft 132 contacts the central portion in the width direction (axial direction of the stub shaft 132) of the inner ring 112, so it has a structure that suppresses left-right inclination. However, when the coupling takes a large angle, since the cross-section of the stub shaft 132 is elliptical, a force is generated that causes the roller unit 104 to have front-back inclination (refer to Figure 12 ). In addition, the contact area between the stub shaft 132 and the inner ring 112 is small, so when there is a high torque under extremely strict vehicle usage conditions, etc., the surface pressure of the contact surface between the two becomes large, and there is a concern about the influence on the durability of the stub shaft 132.

[0012] On the other hand, the tripod constant velocity universal joint shown in the above-mentioned Patent Document 2 is as shown in Figure 13 and Figure 14As shown, the outer peripheral surface of the stub shaft 226 of the three-ball pin member 230 is spherical, and the cylindrical inner peripheral surface of the cage 236 is fitted and held on this spherical outer peripheral surface. Further, the roller guide surface 224 is a flat surface, and the outer peripheral surface of the roller 222 that slidably contacts therewith is a cylindrical surface.

[0013] In this three-ball pin type constant velocity universal joint, the inclination of the roller is restricted by the following actions.

[0014] · The first action of restricting the inclination of the roller 222 by the end face 236 on the outer diameter side of the coupling of the cage 234 abutting against the flat portion 220 of the raceway groove

[0015] · The second action of restricting the inclination of the roller 222 by the roller 222 sliding and displacing in the axial direction ( Figure 13 the E direction) of the stub shaft 226 along the roller guide surface 224

[0016] · The third action of restricting the inclination of the roller 222 by the roller 222 rolling while contacting the bulging portion 228 formed at the inner diameter side end of the roller guide surface 224

[0017] In this three-ball pin type constant velocity universal joint, since the inner peripheral surface of the cage 234 is a cylindrical surface and the outer peripheral surface of the stub shaft 226 is spherical, when a torque is applied, the inner peripheral surface of the cage 234 contacts the stub shaft 226, and their contact portion P' ( Figure 14 the scatter region) has an elongated elliptical shape that is long in the circumferential direction of the stub shaft 226. Therefore, when the coupling takes a working angle, it is easy to generate a frictional torque acting to incline the roller 222 along with the movement of the stub shaft 226 at the above-mentioned contact portion P'. Therefore, even if it has a structure that exhibits the above-mentioned first to third actions, it is easy to generate forward and backward inclination of the roller 222, and the sliding resistance generated by the contact between the roller 222 and the bulging portion 228 and the flat portion 220 of the raceway groove increases.

[0018] Accordingly, an object of the present invention is to prevent inclination of a roller unit while suppressing the contact pressure between a stub shaft and an inner ring and maintaining durability in a double-row roller type three-ball pin type constant velocity universal joint, thereby reducing the contact resistance between components and improving NVH characteristics.

[0019] Means for Solving the Problem

[0020] In order to solve the above problems, the present invention provides a tripod constant velocity universal joint, which comprises: an outer joint member having three raceway grooves formed on its inner peripheral surface and extending along the axial direction of the joint, and a pair of roller guide surfaces opposed to each other in the circumferential direction of the joint are provided in each raceway groove; a tripod member disposed on the inner periphery of the outer joint member and having three foot shafts protruding in the radial direction of the joint toward the raceway grooves; and three roller units each having a roller disposed on the outer periphery of the foot shaft and an inner ring disposed between the roller and the foot shaft, and being supported on the foot shaft in a rotatable and swingable state and received in the raceway groove.

[0021] It is characterized in that

[0022] the roller has a cylindrical outer peripheral surface,

[0023] the pair of roller guide surfaces of each raceway groove are flat surfaces parallel to each other,

[0024] a pair of guide surfaces capable of abutting against the roller from both sides in the axial direction of the roller are provided on both sides in the width direction of the roller guide surface,

[0025] the inner ring has a cylindrical inner peripheral surface,

[0026] the outer peripheral surface of the foot shaft has a convex curve bulging toward both sides in the torque transmission direction in a longitudinal section including the axis of the foot shaft and a cross section orthogonal to the axis of the foot shaft,

[0027] the convex curve in the cross section of the outer peripheral surface of the foot shaft is farther away from the cylindrical inner peripheral surface of the inner ring as it approaches both sides in the axial direction of the joint from the end in the torque transmission direction,

[0028] the radius of curvature (r) at both ends in the torque transmission direction of the convex curve in the longitudinal section of the outer peripheral surface of the foot shaft is larger than the radius of curvature (R) at both ends in the torque transmission direction of the convex curve in the cross section of the outer peripheral surface of the foot shaft.

[0029] In the present invention, as described above, the roller has a cylindrical outer peripheral surface and the roller guide surface is a flat surface. In this case, when a torque is applied, the flat roller guide surface and the cylindrical outer peripheral surface of the roller are pressed against each other via a linear contact portion, so that the left and right tilting of the roller can be suppressed (see Figure 11 ). Further, a pair of guide surfaces capable of abutting against the roller from both sides in the axial direction of the roller are provided on both sides in the width direction of the roller guide surface, so that the left and right tilting of the roller can be more reliably prevented.

[0030] In addition, in the present invention, the inner ring has a cylindrical inner peripheral surface, and a convex curve that bulges toward the inner peripheral surface of the inner ring in the longitudinal section and the cross section is provided on the outer peripheral surface of the shaft pin. Moreover, the convex curve in the cross section of the outer peripheral surface of the shaft pin has a shape that is farther away from the cylindrical inner peripheral surface of the inner ring as it moves from the end in the torque transmission direction toward both sides in the axial direction of the coupling. As a result, the length in the circumferential direction of the shaft pin of the contact portion where the outer peripheral surface of the shaft pin contacts the inner peripheral surface of the inner ring in the cross section (i.e., the major axis of the contact ellipse) becomes shorter, so the force (moment) that causes the roller to tilt decreases. However, in this case, the contact area between the shaft pin and the inner ring becomes smaller, so there is a concern about an increase in the surface pressure at their contact portion. Thus, in the present invention, as described above, the radius of curvature (r) of the convex curve in the longitudinal section of the outer peripheral surface of the shaft pin is made larger than the radius of curvature (R) of the convex curve in the cross section of the outer peripheral surface of the shaft pin. As a result, the length in the axial direction of the shaft pin of the contact portion where the outer peripheral surface of the shaft pin contacts the inner peripheral surface of the inner ring (i.e., the minor axis of the contact ellipse) becomes longer, so an increase in the surface pressure at their contact portion can be suppressed.

[0031] In the above-mentioned tripod constant velocity universal joint, for example, if a chamfer is provided on the roller to connect the cylindrical outer peripheral surface and the end faces on both sides in the axial direction of the axis, the chamfer can be brought into contact with the guide surface in the axial direction (width direction) of the roller.

[0032] Preferably, the radius of curvature r of the convex curve in the longitudinal section of the outer peripheral surface of the shaft pin is larger than half of the maximum dimension (A / 2) of the shaft pin in the torque transmission direction. In addition, preferably, the radius of curvature (R) of the convex curve in the cross section of the outer peripheral surface of the shaft pin is smaller than half of the maximum dimension (A / 2) of the shaft pin in the torque transmission direction.

[0033] In the above-mentioned tripod constant velocity universal joint, it can be such that the outer peripheral surface of the shaft pin contacts the cylindrical inner peripheral surface of the inner ring in the torque transmission direction, and a gap is provided between the outer peripheral surface of the shaft pin and the cylindrical inner peripheral surface of the inner ring in the axial direction of the coupling.

[0034] In the above-mentioned three-ball pin type constant velocity universal joint, when a torque is applied, the rollers press against one roller guide surface of each raceway groove. At this time, a gap is formed between the rollers and the other roller guide surface of each raceway groove. In the present invention, since the roller guide surface formed of a flat surface faces the cylindrical surface of the outer periphery of the roller, and guide surfaces are provided on both sides in the width direction of the roller guide surface, there is a possibility that due to a slight inclination of the roller, the outer peripheral surface and chamfer of the roller come into contact with the roller guide surface and the guide surfaces on the torque non-loaded side, increasing the contact resistance. Therefore, it is preferable to design the initial clearance (the difference between the interval of a pair of roller guide surfaces and the outer diameter of the roller), the shape of the guide surfaces, etc., such that when a torque is applied, the rollers come into contact with one (torque-loaded side) roller guide surface of each raceway groove and do not come into contact with the other (torque non-loaded side) roller guide surface of each raceway groove and the guide surfaces on both sides in its width direction.

[0035] The above-mentioned three-ball pin type constant velocity universal joint can have rolling elements disposed between the rollers and the inner ring. The rolling elements can be, for example, a plurality of needle rollers arranged in a full complement state between the rollers and the inner ring.

[0036] Advantages of the Invention

[0037] As described above, according to the double-row roller type three-ball pin type constant velocity universal joint of the present invention, while suppressing the contact pressure between the stub shaft and the inner ring and maintaining durability, it prevents the left-right inclination and front-back inclination of the rollers, reducing the contact resistance other than the torque transmission part, and thus can improve the NVH characteristics of the constant velocity universal joint. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 is a cross-sectional view taken along the axial direction of the coupling of the double-row roller type three-ball pin type constant velocity universal joint.

[0039] Figure 2 is Figure 1 a partial cross-sectional view taken along line K-K of

[0040] Figure 3 is Figure 2 an enlarged view of

[0041] Figure 4 is Figure 1 a cross-sectional view taken along line L-L of

[0042] Figure 5 is a side view showing an enlarged three-ball pin member of Figure 1

[0043] Figure 6 is a cross-sectional view showing the state in which the three-ball pin type constant velocity universal joint of Figure 1 takes a working angle.

[0044] Figure 7 is a cross-sectional view of a prior art three-ball pin type constant velocity universal joint in the axial direction of the joint.

[0045] Figure 8 is Figure 7 a partial cross-sectional view taken along line K-K of

[0046] Figure 9 is Figure 7 a cross-sectional view taken along line L-L of

[0047] Figure 10 represents Figure 7 a cross-sectional view of a three-ball pin type constant velocity universal joint of

[0048] Figure 11 is Figure 7 a cross-sectional view of a three-ball pin type constant velocity universal joint of

[0049] Figure 12 is Figure 7 a cross-sectional view of a three-ball pin type constant velocity universal joint of

[0050] Figure 13 a cross-sectional view of a prior art other three-ball pin type constant velocity universal joint in a direction orthogonal to the axial direction of the joint.

[0051] Figure 14 is Figure 13 a cross-sectional view of a three-ball pin member of a three-ball pin type constant velocity universal joint of DETAILED DESCRIPTION

[0052] An embodiment of a three-ball pin type constant velocity universal joint according to the present invention will be described based on the accompanying drawings.

[0053] Figures 1 to 4 The three-ball pin type constant velocity universal joint 1 of the present embodiment shown is of a double-row roller type. It should be noted that in the following description, the axial direction of the three-ball pin type constant velocity universal joint in a state where the working angle is 0° will be referred to as the "axial direction of the joint", and the circumferential direction and the radial direction centered on the axis at this time will be referred to as the "circumferential direction of the joint" and the "radial direction of the joint", respectively.

[0054] As Figure 1 and Figure 2 shown, the three-ball pin type constant velocity universal joint 1 includes an outer joint member 2, a three-ball pin member 3 as an inner joint member, and a roller unit 4 as a torque transmission member.

[0055] The outer coupling member 2 has a cup shape with an open end and a blocked end in the axial direction of the coupling (refer to Figure 1 ). On the inner circumferential surface of the outer coupling member 2, three linear raceways 5 extending in the axial direction of the coupling are formed at equal intervals in the circumferential direction of the coupling (refer to Figure 2 ). A pair of roller guide surfaces 6 opposing each other in the circumferential direction of the coupling are formed in each raceway 5. Each roller guide surface 6 extends in the axial direction of the coupling. A three-ball pin member 3 and a roller unit 4 are housed inside the outer coupling member 2.

[0056] The three-ball pin member 3 integrally has: a main body portion 31 (trunnion main body portion) having a central hole 30; and three leg shafts 32 (trunnion journals) protruding radially from the circumferential direction of the outer peripheral surface of the main body portion 31 at the three equal division positions. By fitting the external spline formed on the shaft 8 with the internal spline formed on the central hole 30 of the main body portion 31 and fixing them in the axial direction of the coupling using a snap ring or the like, the three-ball pin member 3 and the shaft 8 are coupled so as to be able to transmit torque.

[0057] The roller unit 4 is provided on the outer periphery of each leg shaft 32 of the three-ball pin member 3 and is respectively housed in the raceway 5 of the outer coupling member 2. The roller unit 4 includes an outer ring 11 as an annular roller centered on the axis of the leg shaft 32, an inner ring 12 configured on the inner circumference of the outer ring 11 and externally fitted to the leg shaft 32, and rolling elements 13 sandwiched between the outer ring 11 and the inner ring 12. In the present embodiment, as an example of the rolling elements 13, a plurality of full complement needles in a state without a cage are used. The needles 13 use the cylindrical inner circumferential surface of the outer ring 11 as the outer raceway surface, the cylindrical outer circumferential surface of the inner ring 12 as the inner raceway surface, and are configured to be freely rotatable between the above-mentioned outer raceway surface and inner raceway surface. The roller unit 4 including the outer ring 11, the inner ring 12, and the needles 13 has a structure that does not naturally disassemble by a pair of snap rings 14.

[0058] Hereinafter, Figure 3 and Figure 4 will be used to Figure 3 and Figure 4 describe in detail the shapes of the roller guide surface 6 and the outer peripheral surface 15 of the outer ring 11, which are one of the characteristic structures of the present invention. It should be noted that in Figure 3 and Figure 4 , the axial direction of the coupling is set as the Z direction, the axial direction of the leg shaft 32 is set as the Y direction, and the torque transmission direction orthogonal to both the axial direction of the coupling Z and the axial direction of the leg shaft Y is set as the X direction and shown.

[0059] The outer peripheral surface 15 of the outer ring 11 is a cylindrical surface centered on the axis of the leg shaft 32. The end faces 16 on both sides of the axis direction of the outer ring 11 itself are flat surfaces orthogonal to its own axis (refer to Figure 3). The outer peripheral surface 15 of the outer ring 11 and the both end surfaces 16 are continuous via the chamfer 17. The chamfer 17 includes, for example, a tapered surface with a linear cross-section and a convex curved surface with a curved cross-section (e.g., an arc shape) that smoothly connects the tapered surface to the outer peripheral surface 15 and the both end surfaces 16.

[0060] A pair of roller guide surfaces 6 of each raceway groove 5 of the outer coupling member 2 are flat surfaces parallel to each other. A pair of guide surfaces 7 are provided on both sides in the width direction (Y direction) of each roller guide surface 6. The guide surfaces 7 stand up from both ends in the width direction of the roller guide surface 6 toward the side closer to the axis Y of the foot shaft 32. The shapes of the roller guide surface 6 and the guide surfaces 7 conform to the shape of the outer peripheral surface 15 and the chamfer 17 of the outer ring 11. Specifically, in Figure 3 the cross-section shown, the roller guide surface 6 is parallel to the outer peripheral surface 15 of the outer ring 11, and the interval W between the pair of opposed roller guide surfaces 6 is slightly larger than the diameter of the outer peripheral surface 15 of the outer ring 11. Thus, a minute gap in the X direction is formed between the roller guide surface 6 and the outer peripheral surface 15 of the outer ring 11. In addition, the guide surface 7 is substantially parallel to the chamfer 17 of the outer ring 11 in Figure 3 the cross-section shown, and includes, for example, an inclined surface with a linear cross-section and a concave curved surface with a curved cross-section (e.g., an arc shape) that smoothly connects the inclined surface to the roller guide surface 6. The interval in the Y direction between the pair of guide surfaces 7 provided on both sides in the width direction of the roller guide surface 6 is slightly larger than the interval in the Y direction between the pair of chamfers 17 provided on both sides in the width direction of the outer peripheral surface 15 of the outer ring 11. Thus, a minute gap in the Y direction is formed between the guide surface 7 and the chamfer 17 of the outer ring 11.

[0061] When a torque in the direction of the arrow T is applied to the outer coupling member 2, Figure 3 the outer peripheral surface 15 of the outer ring 11 is pressed against the roller guide surface 6 on the left side in the figure. In the present embodiment, as described above, the roller guide surface 6 is a flat surface and the outer peripheral surface 15 of the outer ring 11 is a cylindrical surface, so they are pressed against each other via a linear contact portion. Thus, in Figure 3 the cross-section shown, the attitude of the outer ring 11 is corrected so that the outer peripheral surface 15 of the outer ring 11 becomes parallel to the roller guide surface 6, and thus the left-right tilt of the outer ring 11 can be suppressed (refer to Figure 11 ). In addition, the guide surface 7 abuts against the chamfer 17 of the outer ring 11 in the Y direction, thereby restricting the front-back tilt of the outer ring 11 (refer to Figure 12 ), and further suppressing the left-right tilt of the outer ring 11.

[0062] When a torque is applied to the outer coupling member 2 as described above, Figure 3When applying torque in the direction of arrow T, the outer peripheral surface 15 of the outer ring 11 is pressed against the roller guide surface 6 on the left side in the figure (hereinafter referred to as "the roller guide surface 6 on the torque load side"). On the other hand, a gap is formed between the roller guide surface 6 on the right side in the figure (hereinafter referred to as "the roller guide surface 6 on the torque non-load side") and the guide surfaces 7 on both sides in its width direction, the outer peripheral surface 15 of the outer ring 11, and the chamfer 17. At this time, when the roller unit 4 tilts and the outer peripheral surface 15 and chamfer 17 of the outer ring 11 come into contact with the roller guide surface 6 on the torque non-load side and the guide surface 7, the rotational resistance of the outer ring 11 increases.

[0063] Therefore, in the present embodiment, the initial clearance (the difference between the distance W between the pair of opposed roller guide surfaces 6 and the outer diameter of the outer ring 11), the shape of the guide surface 7, etc. are designed such that when torque is applied to the three-ball pin member 3, the outer ring 11 contacts the roller guide surface 6 on the torque load side, while the outer ring 11 does not contact the roller guide surface 6 on the torque non-load side and the guide surfaces 7 on both sides in its width direction.

[0064] Next, use Figure 3 and Figure 4 to describe in detail the shapes of the inner peripheral surface 18 of the inner ring 12 and the outer peripheral surface 33 of the foot shaft 32, which are other characteristic structures of the present invention.

[0065] The inner peripheral surface 18 of the inner ring 12 is a cylindrical surface parallel to the foot shaft axis direction Y, and this cylindrical inner peripheral surface 18 fits with the outer peripheral surface 33 of the foot shaft 32.

[0066] As Figure 3 shown, in a plan view of the foot shaft 32 observed from the coupling axis direction (the direction orthogonal to the paper surface of Figure 3 ), that is, in a longitudinal section including the axis of the foot shaft 32 itself, the outer peripheral surface 33 of the foot shaft 32 has a convex curve bulging toward both sides in the torque transmission direction X. In the illustrated example, the convex curve in the longitudinal section of the outer peripheral surface of the foot shaft 32 is composed of an arc 33a with a radius of curvature r. Thus, the top (end in the X direction) of the arc 33a of the outer peripheral surface of the foot shaft 32 contacts the cylindrical inner peripheral surface 18 of the inner ring 12, and the gap between the outer peripheral surface 33 of the foot shaft 32 and the inner peripheral surface 18 of the inner ring 12 gradually increases as it moves from the top of the arc 33a toward both sides in the Y direction.

[0067] In Figure 4 the cross-section in the direction orthogonal to the axis of the foot shaft 32 itself shown (a plane passing through both ends in the torque transmission direction of the foot shaft 32 ( Figure 3{in the cross-section in the line X), the outer peripheral surface of the foot shaft 32 has a convex curve bulging on both sides in the torque transmission direction X. In the illustrated example, the convex curve in the cross-section of the outer peripheral surface of the foot shaft 32 is constituted by an arc 33b with a radius of curvature R. When the maximum dimension in the torque transmission direction X of the foot shaft 32 is set as A, the radius of curvature R of the arc 33b is smaller than half of it, A / 2 (≈ the radius of the cylindrical inner peripheral surface 18 of the inner ring 12). Therefore, the arc 33b on the outer peripheral surface of the foot shaft 32 contacts the cylindrical inner peripheral surface 18 of the inner ring 12 at its top (the end in the X direction), and the farther it is from the top towards both sides in the Z direction, the farther it is from the inner peripheral surface 18 of the inner ring 12. Thus, the outer peripheral surface 33 of the foot shaft 32 contacts the inner peripheral surface 18 of the inner ring 12 in the X direction, and a gap G is provided between them in the Z direction. In the illustrated example, in the region including both ends in the Z direction in the cross-section of the outer peripheral surface 33 of the foot shaft 32, flat surfaces 33c orthogonal to the Z direction are provided. Thereby, the gap G in the Z direction between the flat surface 33c of the outer peripheral surface 33 of the foot shaft 32 and the inner peripheral surface 18 of the inner ring 12 becomes larger.

[0068] As described above, the outer peripheral surface 33 of the foot shaft 32 has an aspherical shape in which the radius of curvature r of the convex curve (arc 33a) in the longitudinal section is different from the radius of curvature R of the convex curve (arc 33b) in the cross-section.

[0069] Since the inner peripheral surface 18 of the inner ring 12 is a cylindrical surface, and the longitudinal section and the cross-section of the outer peripheral surface of the foot shaft 32 have convex curves, the inner ring 12 can swing relative to the foot shaft 32. As described above, the inner ring 12 and the outer ring 11 are assembled to be relatively rotatable via the needle rollers 13, so the outer ring 11 can swing relative to the foot shaft 32 integrally with the inner ring 12. That is, in the plane including the axis of the foot shaft 32, the axes of the outer ring 11 and the inner ring 12 can be inclined relative to the axis of the foot shaft 32 (refer to Figure 6 ).

[0070] As Figure 6 shown, when the three-ball pin type constant velocity universal joint 1 rotates at a working angle, the axis of the three-ball pin member 3 is inclined relative to the axis of the outer coupling member 2, but the roller unit 4 can swing, so the state where the outer ring 11 and the roller guide surface 6 are skewed can be avoided. Thereby, the outer ring 11 rolls horizontally relative to the roller guide surface 6, so the reduction of the induced thrust and the sliding resistance can be achieved, and the low vibration of the three-ball pin type constant velocity universal joint 1 can be realized.

[0071] When a load torque is applied to the three-ball pin member 30, the outer peripheral surface 33 of the foot shaft 32 is pressed against the inner peripheral surface 18 of the inner ring 12, forming a contact portion P as Figure 5 shown. In the present embodiment, as described above, the radius of curvature R of the arc 33b in the cross-section of the outer peripheral surface 33 of the foot shaft 32 (refer toFigure 4 is smaller than half (A / 2) of the maximum dimension A in the torque transmission direction X of the foot shaft 32, and thus, compared with the case where they are equal, it is possible to shorten Figure 5 the length in the Z direction (i.e., the major axis a of the contact ellipse) of the contact portion P shown in the figure. Thereby, the force (moment) that causes the roller unit 4 including the inner ring 12 to tilt with respect to the coupling axis is reduced.

[0072] In this way, when the major axis a of the contact portion P where the outer peripheral surface 33 of the foot shaft 32 contacts the inner peripheral surface 18 of the inner ring 12 becomes shorter, the area of the contact portion P becomes smaller, and thus there is a concern about an increase in the surface pressure at the contact portion P. In the present embodiment, the curvature radius r of the arc 33a in the longitudinal section of the outer peripheral surface 33 of the foot shaft 32 (refer to Figure 3 is larger than the curvature radius R of the arc 33a in the cross-sectional view of the outer peripheral surface 33 of the foot shaft 32 (refer to Figure 4 ), and further larger than half (A / 2) of the maximum dimension A in the torque transmission direction X of the foot shaft 32. Thereby, Figure 5 the length in the Y direction (i.e., the minor axis b of the contact ellipse) of the contact portion P where the outer peripheral surface 33 of the foot shaft 32 shown in the figure contacts the inner peripheral surface 18 of the inner ring 12 becomes longer, and thus an increase in the surface pressure can be suppressed.

[0073] As described above, by adjusting the curvature radius R of the arc 33b in the cross-sectional view of the outer peripheral surface 33 of the foot shaft 32 and the curvature radius r of the arc 33a in the longitudinal section of the outer peripheral surface 33 of the foot shaft 32, it is possible to adjust the ratio of the major axis a to the minor axis b of the contact portion P where the outer peripheral surface 33 of the foot shaft 32 contacts the inner peripheral surface 18 of the inner ring 12. That is, the above-described curvature radii r and R are set in such a manner that while suppressing the surface pressure of the contact portion P where the inner ring 12 and the foot shaft 32 are in contact within an allowable range to ensure durability, the inclination of the outer ring 11 is suppressed within an allowable range to sufficiently reduce the induced thrust and sliding resistance. Specifically, for example, the above-described curvature radii r and R are set in such a manner that the ratio a / b of the major axis a to the minor axis b of the contact portion P is in the range of 2 to 10, preferably in the range of 3 to 6.

[0074] The present invention is not limited to the above-described embodiment. Hereinafter, other embodiments of the present invention will be described, but redundant descriptions of the same points as those in the above-described embodiment will be omitted.

[0075] In the above-described embodiment, a case where the convex curves in the longitudinal section and the cross-section of the outer peripheral surface of the shaft journal 32 are both formed by circular arcs is shown, but it is not limited thereto. For example, the convex curve in the longitudinal section of the outer peripheral surface of the shaft journal 32 may be formed by a non-circular arc curve such as an ellipse. In this case, the radius of curvature (since it is a non-circular arc, it is the radius of curvature of the pseudo-circular arc at both ends in the torque transmission direction. The same applies hereinafter) at at least both ends in the torque transmission direction (i.e., the contact portions in contact with the inner ring 12) of the convex curve (ellipse) in the longitudinal section of the outer peripheral surface of the shaft journal 32 is larger than the radius of curvature R of the convex curve (circular arc 33b) in the cross-section of the outer peripheral surface of the shaft journal 32, and is preferably larger than half (A / 2) of the maximum dimension A of the shaft journal 32 in the torque transmission direction X.

[0076] Alternatively, the convex curve in the cross-section of the outer peripheral surface of the shaft journal 32 may be formed by a non-circular arc curve such as an ellipse. In this case, the radius of curvature at at least both ends in the torque transmission direction (i.e., the contact portions in contact with the inner ring 12) of the convex curve (ellipse) in the cross-section of the outer peripheral surface of the shaft journal 32 is smaller than half (A / 2) of the maximum dimension A of the shaft journal 32 in the torque transmission direction X.

[0077] Alternatively, both the convex curves in the longitudinal section and the cross-section of the outer peripheral surface of the shaft journal 32 may be formed by non-circular arc curves such as an ellipse. In this case, the radius of curvature at at least both ends in the torque transmission direction (i.e., the contact portions in contact with the inner ring 12) of the convex curve (ellipse) in the longitudinal section of the outer peripheral surface of the shaft journal 32 is larger than the radius of curvature at at least both ends in the torque transmission direction (i.e., the contact portions in contact with the inner ring 12) of the convex curve (ellipse) in the cross-section of the outer peripheral surface of the shaft journal 32. Preferably, the radius of curvature at at least both ends in the torque transmission direction of the convex curve (ellipse) in the longitudinal section of the outer peripheral surface of the shaft journal 32 is larger than half (A / 2) of the maximum dimension A of the shaft journal 32 in the torque transmission direction X, and the radius of curvature at at least both ends in the torque transmission direction of the convex curve (ellipse) in the cross-section of the outer peripheral surface of the shaft journal 32 is smaller than half (A / 2) of the maximum dimension A of the shaft journal 32 in the torque transmission direction X.

[0078] In addition, in the above-described embodiment, as Figure 4 shown, a case where flat surfaces 33c are provided at both ends of the shaft journal 32 in the coupling axial direction is shown, but the flat surfaces 33c may be omitted even when there are no flat surfaces 33c as long as there is sufficient clearance formed between the shaft journal 32 and the inner ring 12 in the coupling axial direction to allow the roller unit 4 to swing relative to the shaft journal 32.

[0079] The three-ball pin constant velocity universal joint 1 described above is not limited to being applied to the drive shaft of a motor vehicle, but can be widely used in power transmission paths such as motor vehicles and industrial equipment.

[0080] Description of Reference Numerals

[0081] 1 Tripod Constant Velocity Universal Joint

[0082] 2 Outer Coupling Member

[0083] 3 Tripod Member

[0084] 4 Roller Unit

[0085] 5 Raceway Groove

[0086] 6 Roller Guide Surface

[0087] 7 Guide Surface

[0088] 8 Shaft

[0089] 11 Outer Ring (Roller)

[0090] 12 Inner Ring

[0091] 13 Rolling Element

[0092] 14 Snap Ring

[0093] 31 Main Body Portion

[0094] 32 Stub Shaft

[0095] 33 Outer Peripheral Surface

[0096] 33a Arc (Convex Curve)

[0097] 33b Arc (Convex Curve)

[0098] P Contact Portion

[0099] X Torque Transmission Direction

[0100] Y Stub Shaft Axis Direction

[0101] Z Coupling Axial Direction

Claims

1. A tripod constant velocity universal joint, comprising: An outer joint member having three raceways extending in the joint axial direction on its inner peripheral surface, and a pair of roller guide surfaces opposed to each other in the circumferential direction of the joint provided in each raceway; A tripod member disposed on the inner periphery of the outer joint member and having three foot shafts protruding in the radial direction of the joint toward the raceways; and Three roller units each having a roller disposed on the outer periphery of the foot shaft and an inner ring disposed between the roller and the foot shaft, being supported on the foot shaft in a rotatable and swingable state and received in the raceways, wherein, The roller has a cylindrical outer peripheral surface, The pair of roller guide surfaces of each raceway are flat surfaces parallel to each other, A pair of guide surfaces capable of abutting against the roller from both sides in the axial direction of the roller are provided on both sides in the width direction of the roller guide surface, The inner ring has a cylindrical inner peripheral surface, The outer peripheral surface of the foot shaft has a convex curve bulging toward both sides in the torque transmission direction in a longitudinal section including the axis of the foot shaft and a cross section orthogonal to the axis of the foot shaft, The convex curve in the cross section of the outer peripheral surface of the foot shaft is farther away from the cylindrical inner peripheral surface of the inner ring as it tends toward both sides in the joint axial direction from the end in the torque transmission direction, The radius of curvature (r) at both ends in the torque transmission direction of the convex curve in the longitudinal section of the outer peripheral surface of the foot shaft is larger than the radius of curvature (R) at both ends in the torque transmission direction of the convex curve in the cross section of the outer peripheral surface of the foot shaft.

2. The tripod constant velocity universal joint according to claim 1, wherein, The roller has a chamfer connecting the cylindrical outer peripheral surface and the end surfaces on both sides in the axial direction of the roller, The chamfer can abut against the guide surface in the axial direction of the roller.

3. The tripod constant velocity universal joint according to claim 1 or 2, wherein, The radius of curvature (r) at both ends in the torque transmission direction of the convex curve in the longitudinal section of the outer peripheral surface of the foot shaft is larger than half of the maximum dimension (A / 2) of the foot shaft in the torque transmission direction, The radius of curvature (R) at both ends in the torque transmission direction of the convex curve in the cross section of the outer peripheral surface of the foot shaft is smaller than half of the maximum dimension (A / 2) of the foot shaft in the torque transmission direction.

4. The tripod constant velocity universal joint according to claim 1 or 2, wherein, The outer peripheral surface of the foot shaft is in contact with the cylindrical inner peripheral surface of the inner ring in the torque transmission direction, and a gap is provided between the outer peripheral surface of the foot shaft and the cylindrical inner peripheral surface of the inner ring in the joint axial direction.

5. The tripod constant velocity universal joint according to claim 1 or 2, wherein, When torque is applied, the roller is in contact with one of the roller guide surfaces of each raceway, and the roller is not in contact with the other roller guide surface of each raceway and the guide surfaces on both sides in the width direction of the roller guide surface.

6. The tripod constant velocity universal joint according to claim 1 or 2, wherein, The three-ball-pin constant velocity universal joint has rolling elements disposed between the rollers and the inner ring.

7. The three-ball-pin constant velocity universal joint according to claim 6, wherein the rolling elements are a plurality of needle rollers arranged in a full complement roller state between the rollers and the inner ring.

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