CN118829799A - Tripod type constant velocity universal coupling - Google Patents

Abstract

A tripod-type constant velocity universal joint (1) comprises an outer coupling member (2) having three rolling grooves (5) extending in the axial direction formed at three equal parts of the inner circumference in the circumferential direction and roller guide surfaces (6) arranged opposite to each other in the circumferential direction in the rolling grooves, a tripod member (3) having three foot shafts (7) protruding radially outward from the three equal parts of the circumferential direction, and a roller assembly (4) externally embedded in the foot shaft, the roller assembly comprising an inner ring (12) externally embedded in the foot shaft, a roller (12) inserted in the roller guide surface, and a roller assembly (12) externally embedded in the foot shaft. 1) A plurality of needle rollers (13) arranged between the cylindrical outer peripheral surface (12b) of the inner ring and the cylindrical inner peripheral surface (11b) of the roller 11, and a pair of washers (14, 15) arranged on both axial sides of the needle rollers and the inner ring and having their outer peripheral edges mounted on the inner periphery of the roller, characterized in that when the maximum diameter of the needle rollers (13) in each roller assembly is set to φdmax and the minimum diameter of the needle rollers (13) in each roller assembly is set to φdmin, φdmax-φdmin≤0.002mm.

Description

Tripod type constant velocity universal coupling

Technical Field

The invention relates to a tripod type constant velocity universal coupling.

Background Art

The constant velocity universal coupling constituting the power transmission system of automobiles and various industrial machines connects two shafts on the driving side and the driven side in a manner capable of torque transmission, and can transmit the rotational torque at a constant speed even if the two shafts take a working angle. Constant velocity universal couplings are generally divided into fixed constant velocity universal couplings that only allow angular displacement and sliding constant velocity universal couplings that allow both angular displacement and axial displacement. For example, in the drive shaft that transmits power from the engine of an automobile to the drive wheels, a sliding constant velocity universal coupling is used on the differential side (inner side), and a fixed constant velocity universal coupling is used on the drive wheel side (outer side).

As one of the sliding type constant velocity universal couplings, there is a tripod type constant velocity universal coupling. In the tripod type constant velocity universal coupling, as for the rollers as the torque transmission member, there are known single-row roller type and double-row roller type. The main parts of the double-row roller type tripod type constant velocity universal coupling (hereinafter, also referred to as the tripod type constant velocity universal coupling) include an outer coupling member, a tripod member as an inner coupling member, and a roller assembly as a torque transmission member.

In the outer coupling member, three linear raceway grooves extending in the axial direction are formed at the positions of the inner circumference in the circumferential direction of the outer coupling member, and roller guide surfaces are formed on both sides of each raceway groove, which are arranged opposite to each other in the circumferential direction and extend in the axial direction respectively. A tripod member and a roller assembly are accommodated inside the outer coupling member. The tripod member has three foot shafts protruding in the radial direction. The main part of the roller assembly includes a roller, an inner ring arranged on the inner side of the roller and embedded in the foot shaft, and a plurality of needle rollers sandwiched between the roller and the inner ring, and the roller assembly is accommodated in the raceway groove of the outer coupling member. The roller assembly including the inner ring, the needle roller and the roller is a structure that is not separated by a pair of washers. The washer is disconnected at a position in the circumferential direction and is assembled in the annular groove of the cylindrical inner circumferential surface of the roller in an elastically reduced diameter state. The inner circumferential surface of the inner ring is an arc-shaped convex surface in the longitudinal section containing the axis of the inner ring.

The outer peripheral surface of each foot shaft of the tripod member is straight in the longitudinal section including the axis of the foot shaft, and is roughly elliptical in the cross section orthogonal to the axis of the foot shaft. It contacts the inner peripheral surface of the inner ring in the direction orthogonal to the axis of the coupling, and forms a gap between the inner peripheral surface of the inner ring in the axial direction of the coupling. In this tripod type constant velocity universal joint, the rollers of the roller assembly assembled on the foot shaft of the tripod member roll on the roller guide surface of the rolling groove of the outer coupling member. The cross section of the foot shaft is roughly elliptical, so when the tripod type constant velocity universal joint takes the working angle, the axis of the tripod member is inclined relative to the axis of the outer coupling member, but the roller assembly can be inclined relative to the axis of the foot shaft of the tripod member. Therefore, the roller rolls correctly on the roller guide surface, so that the induced thrust and sliding resistance can be reduced, and the vibration of the coupling can be reduced (for example, patent documents 1 and 2). The shapes of the three raceway grooves having the roller guide surfaces formed in the outer joint member mainly employ angular contact and annular contact.

Prior art literature

Patent Literature

Patent Document 1: Japanese Patent Application Publication No. 2000-320563

Patent Document 2: Japanese Patent Application Publication No. 2001-132766

Summary of the invention

Problems to be solved by the invention

When the tripod type constant velocity universal joint takes a working angle, the center of the joint is geometrically inconsistent with the center of the tripod member and the center of the shaft member. Therefore, the axis of the tripod member's foot shaft is slightly tilted relative to the center line of the raceway groove formed in three equal parts of 120° along the circumferential direction while rotating. During the rotation, the inner ring of the roller assembly moves relatively in the up-down direction on the tripod member's foot shaft, and the relationship between the up-down load at this time and the tilt of the roller assembly relative to the center of the roller guide surface of the outer coupling member in the rotation direction (also called left-right tilt) was studied. In this state, the contact between the cylindrical outer peripheral surface of the inner ring, the needle roller, and the cylindrical inner peripheral surface of the outer roller is repeatedly contacted in the offset direction. It was found that when there is an excessive load in this state, in a specific large-diameter needle roller, the load is concentrated in the offset load state, so the surface pressure increases significantly, and the durability of the roller assembly may be reduced. Patent documents 1 and 2 do not focus on such problems.

In view of the above problems, an object of the present invention is to provide a tripod type constant velocity universal joint capable of performing smooth rotational motion while alleviating the concentration of stress acting on a needle roller during rotational motion in a working angle state, thereby improving durability.

Solutions to Solve Problems

In order to achieve the above-mentioned purpose, the inventors have explored the behavior of the components of the roller assembly when the double-row roller type tripod type constant velocity universal joint takes a working angle. As a result, it was concluded that the rolling amount of the components of the roller assembly of the tripod type constant velocity universal joint is small compared to ordinary rolling bearings, but the relative behavior of the components of the roller assembly is extremely harsh compared to ordinary rolling bearings. Based on this result, a new concept related to the unique internal specifications that take into account the above-mentioned relative behavior of the components of the roller assembly and the single-row roller was obtained, forming the present invention. The detailed behavior, action, and insights into the development process of the present invention are described below.

As a technical solution for achieving the aforementioned purpose, the present invention is a tripod-type constant velocity universal joint, which comprises: an outer coupling member, which has three rolling grooves extending in the axial direction formed at the circumferential trisection positions of the inner circumference, and the rolling grooves have roller guide surfaces arranged opposite to each other in the circumferential direction; a tripod member, which has three foot shafts protruding radially outward from the circumferential trisection positions; and a roller assembly, which is externally embedded in the foot shaft, and the roller assembly includes: an inner ring, which is externally embedded in the foot shaft; a roller, which is embedded in the roller A guide surface; a plurality of needle rollers, which are arranged between the cylindrical outer circumferential surface of the inner ring and the cylindrical inner circumferential surface of the roller; and a pair of washers, which are arranged on both axial sides of the needle rollers and the inner ring and have their outer circumferential edges mounted on the inner circumference of the roller. The tripod type constant velocity universal coupling is characterized in that when the maximum diameter of the plurality of needle rollers in each of the roller assemblies is set to φdmax and the minimum diameter of the plurality of needle rollers in each of the roller assemblies is set to φdmin, φdmax-φdmin≤0.002mm.

The above structure can realize a double-row roller type tripod constant velocity universal joint that can alleviate the concentration of stress acting on the needle rollers in the roller assembly during rotational motion at the working angle, thereby improving durability and enabling smooth rotational motion.

Specifically, the inner circumference of the inner ring is formed as an arc-shaped convex surface in the longitudinal section of the inner ring, the outer circumference of the foot shaft is straight in the longitudinal section including the axis of the foot shaft, and is substantially elliptical in the cross section orthogonal to the axis of the foot shaft, the outer circumference of the foot shaft abuts against the inner circumference of the inner ring in the direction orthogonal to the axis of the coupling, and a gap is formed between the outer circumference of the foot shaft and the inner circumference of the inner ring in the axial direction of the coupling, and the roller can tilt in the raceway groove. As a result, the roller tilts smoothly in the raceway groove, which can alleviate the concentration of stress acting on the needle roller in the roller assembly and improve durability, and promote smooth rotation, thereby achieving further reduction of induced thrust, sliding resistance, and low vibration of the coupling.

The second invention is a tripod-type constant-velocity universal joint, which comprises: an outer coupling component, which has three rolling grooves extending axially at three equal parts of the inner circumference in the circumferential direction, and the rolling grooves have roller guide surfaces arranged opposite to each other in the circumferential direction; a tripod component, which has three foot shafts protruding radially outward from the three equal parts of the circumferential direction; and a roller, which has a plurality of needle rollers arranged on the outer circumferential surface of the foot shaft, and is assembled to be rotatable by means of the needle rollers, and the rollers are guided by the roller guide surfaces of the rolling grooves. The tripod-type constant-velocity universal joint is characterized in that when the maximum diameter of the plurality of needle rollers arranged on the outer circumferential surface of each of the foot shafts is set to φdmax, and the minimum diameter of the plurality of needle rollers arranged on the outer circumferential surface of each of the foot shafts is set to φdmin, φdmax-φdmin≤0.002mm.

With the above configuration, it is possible to realize a single-row roller type tripod constant velocity universal joint that can alleviate the concentration of stress acting on the needle roller during rotational motion at the operating angle, thereby improving durability and enabling smooth rotational motion.

As a contact method between the roller and the roller guide surface, either angular contact or annular contact can be applied.

Effects of the Invention

According to the present invention, a tripod type constant velocity universal joint can be realized which can alleviate the concentration of stress acting on the roller assembly and the needle rollers in the single-row rollers during the rotational operation at the operating angle, thereby improving durability and enabling smooth rotational operation.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a longitudinal sectional view of a tripod type constant velocity universal joint according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view taken along the line AA in FIG. 1 .

FIG. 3 is a plan view of the roller assembly and the leg shaft viewed from the line BB in FIG. 1 .

FIG. 4 is a longitudinal sectional view of the roller assembly taken along line EE of FIG. 3 .

5 is a diagram illustrating one roller assembly on the upper side of FIG. 2 and a contact state between the rollers and the roller guide surface in a cross section of approximately 1/3 in the circumferential direction of the outer joint member.

6 is a longitudinal sectional view showing a state where the tripod type constant velocity universal joint of FIG. 1 takes an operating angle.

7 is a longitudinal sectional view of the raceway groove of the leg shaft and the roller assembly at the top dead center (0° phase) of the outer joint member in the working angle state, with the plane E including the axis of the leg shaft of the tripod member added to FIG. 6 .

8a is a longitudinal sectional view illustrating the state, movement and action of the ball bearing groove of the foot shaft and the roller assembly at the top dead center (0° phase) of the outer coupling member in the state of taking the working angle.

8b is a cross-sectional view illustrating the state, movement, and behavior of the ball bearing groove of the foot shaft and the roller assembly at the top dead center (0° phase) of the outer coupling member in the state of taking the working angle.

FIG. 9 a is a longitudinal cross-sectional view illustrating the state, movement, and behavior of the roller assembly 4 ( 1 ) of FIG. 8 b when the roller assembly 4 ( 1 ) rotates clockwise to a phase of 90°.

FIG. 9 b is a cross-sectional view illustrating the state, movement, and behavior of the roller assembly 4 ( 1 ) of FIG. 8 b when the roller assembly 4 ( 1 ) rotates clockwise to a phase of 90°.

FIG. 10 a is a longitudinal cross-sectional view illustrating the state, movement, and behavior of the roller assembly 4 ( 1 ) of FIG. 8 b when the roller assembly 4 ( 1 ) is further rotated in the clockwise direction to a phase of 180°.

FIG. 10 b is a cross-sectional view illustrating the state, movement, and behavior of the roller assembly 4 ( 1 ) of FIG. 8 b when the roller assembly 4 ( 1 ) is further rotated in the clockwise direction to a phase of 180°.

FIG. 11 a is a diagram showing in a composite manner the left-right tilting motion and behavior of the roller assembly in the raceway groove.

FIG. 11 b is a left-right inclined cross-sectional view showing a right rotation of the roller assembly in the raceway groove.

FIG. 11c is a cross-sectional view showing a horizontal state of the roller assembly in the raceway groove.

FIG. 11 d is a left-right tilted cross-sectional view showing the left rotation of the roller assembly in the raceway groove.

FIG. 12 is an enlarged longitudinal sectional view of the roller assembly according to the present embodiment.

FIG. 13 is an enlarged cross-sectional view of the roller assembly taken along line FF in FIG. 4 .

14 is a partial cross-sectional view showing a modified example in which the contact state between the roller and the roller guide surface of the first embodiment is made into an annular contact.

15 is a cross-sectional view of a tripod type constant velocity universal joint according to a second embodiment of the present invention.

16 is a cross-sectional view of a modified example of the tripod type constant velocity universal joint according to the second embodiment of the present invention.

17 is a cross-sectional view of a tripod type constant velocity universal joint according to a third embodiment of the present invention.

DETAILED DESCRIPTION

FIG. 1 to FIG. 13 show a tripod type constant velocity universal joint according to a first embodiment of the present invention. First, the overall structure of the tripod type constant velocity universal joint according to the present embodiment is described based on FIG. 1 to FIG. 6. FIG. 1 is a longitudinal sectional view of the tripod type constant velocity universal joint according to the present embodiment, and FIG. 2 is a transverse sectional view obtained by viewing along the A-A line of FIG. 1. However, in FIG. 2, the tripod member and the two roller assemblies on the lower side are not shown in cross section, and the shaft member is omitted from the illustration. The two roller assemblies on the lower side of FIG. 2 are not shown in FIG. 1 which is a longitudinal sectional view. FIG. 3 is a top view of the roller assembly and the foot shaft obtained by viewing along the B-B line of FIG. 1, and FIG. 4 is a longitudinal sectional view of the roller assembly at the E-E line of FIG. 3. FIG. 5 is a diagram illustrating a roller assembly on the upper side of FIG. 2, and the contact state between the roller and the roller guide surface in a cross section of approximately 1/3 of the circumferential direction of the outer coupling member. The cross-sectional line is omitted. 6 is a longitudinal sectional view showing a state where the tripod type constant velocity universal joint of FIG. 1 takes an operating angle.

As shown in Fig. 1 and Fig. 2, the main parts of the tripod type constant velocity universal joint 1 include an outer coupling member 2, a tripod member 3 as an inner coupling member, and a roller assembly 4 as a torque transmission member. The outer coupling member 2 has a cup portion 2a with one end open, and three linear rolling grooves 5 extending in the axial direction are formed at three equal positions in the circumferential direction of the inner circumference, and roller guide surfaces 6 are formed on both sides of each rolling groove 5, which are arranged oppositely in the circumferential direction and extend in the axial direction respectively. The roller guide surface 6 has a cross section that is roughly partially cylindrical. The tripod member 3 and the roller assembly 4 are accommodated inside the outer coupling member 2.

The tripod member 3 has three foot shafts 7 protruding radially outward from the circumferentially divided third position. The shaft member 9 is splined with the center hole 8 of the tripod member 3 and fixed in the axial direction by the retaining ring 10. The main part of the roller assembly 4 includes a roller 11, an inner ring 12 arranged on the inner side of the roller 11 and externally fitted on the foot shaft 7, and a plurality of needle rollers 13 sandwiched between the roller 11 and the inner ring 12. The roller assembly 4 is accommodated in the raceway groove 5 of the outer coupling member 2, and the center Cr (refer to FIG. 4) of the roller assembly 4 (roller 11) is located on the pitch circle PC of the raceway groove 5.

As shown in FIG4 , the needle roller 13 is arranged between the cylindrical inner circumferential surface 11b of the roller 11 and the cylindrical outer circumferential surface 12b of the inner ring 12 in a so-called full roller state without a retainer, and the cylindrical inner circumferential surface 11b of the roller 11 is used as the outer raceway surface, and the cylindrical outer circumferential surface 12b of the inner ring 12 is used as the inner raceway surface. The inner circumferential surface 12a of the inner ring 12 is an arc-shaped convex surface in a longitudinal section including the axis of the inner ring 12. In order to allow the left and right inclination of the foot shaft 7 relative to the inner ring 12 caused by the whirling that is unique to the tripod type constant velocity universal joint, the curvature radius ri of the arc-shaped convex surface is set to be about 30 mm, for example. In addition, as shown in Figure 3, the foot shaft 7 having a roughly elliptical cross-section contacts the inner ring 12 having a circular inner circumferential surface 12a to transmit torque. Therefore, in order to alleviate the surface pressure at the contact portion between the foot shaft 7 and the inner ring 12 and ensure the strength of the foot shaft 7, the ellipticity b/a of the major axis a and the minor axis b of the roughly elliptical shape of the foot shaft 7 and the curvature radius ri of the inner circumferential surface 12a of the inner ring 12 are set (refer to Figure 4).

As shown in FIG4, the outer peripheral surface 11a of the roller 11 is formed by a partial spherical surface of a curvature radius ro with the center of curvature set on the axis 4x of the roller assembly 4, in other words, on the axis 7x of the foot shaft 7 shown in FIG3. The roller assembly 4 including the inner ring 12, the needle roller 13 and the roller 11 is formed into a structure that is not separated by the washers 14 and 15. The washers 14 and 15 are disconnected at one position in the circumferential direction (see FIG3), and are assembled in the annular groove of the cylindrical inner peripheral surface 11b of the roller 11 in a state of elastically reduced diameter.

As shown in Fig. 1 and Fig. 2, the outer peripheral surface 7a of each leg shaft 7 of the tripod member 3 is straight in a longitudinal section including the axis 7x of the leg shaft 7 (see Fig. 3). In addition, as shown in Fig. 3, the outer peripheral surface 7a of the leg shaft 7 is substantially elliptical in a cross section perpendicular to the axis 7x of the leg shaft 7, and contacts the inner peripheral surface 12a of the inner ring 12 in a direction perpendicular to the axis of the coupling, i.e., in the direction of the major axis a, and forms a gap m between the inner peripheral surface 12a of the inner ring 12 in the axial direction of the coupling, i.e., in the direction of the minor axis b. In the tripod type constant velocity universal joint 1, the rollers 11 of the roller assembly 4 mounted on the leg shaft 7 of the tripod member 3 roll on the roller guide surface 6 of the raceway groove 5 of the outer coupling member 2.

As shown in FIG. 5 , the outer peripheral surface 11a of the roller 11 is formed by a partial spherical surface with a curvature radius ro having a curvature center Or set on the axis 7x of the foot shaft 7. The curvature center Or is also the center Cr of the roller assembly. The roller guide surface 6 is formed by a cross section of a pointed arch shape with a curvature radius Rt having a curvature center Ort set at a position beyond the center line 5x of the track groove 5 on a line passing through the intersection T of the pitch circle PC of the track groove 5 and the center line 5x of the track groove 5 and at a contact angle α, and extends parallel to the axis of the coupling. The curvature radius Rt is set to be appropriately larger than the curvature radius ro. Therefore, the outer peripheral surface 11a of the roller 11 and the roller guide surface 6 are in angular contact with each other at a contact angle α with respect to the horizontal line X-X passing through the intersection T. A track gap δ of a small size is provided between the roller guide surface 6 and the outer peripheral surface 11a of the roller 11. In FIG. 5 , the center line 5x of the track groove is shown to be consistent with the axis 7x of the foot shaft 7. Therefore, the raceway clearance on one side becomes δ/2.

The cross section of the foot shaft 7 is substantially elliptical, so at a commonly used relatively small working angle, as shown in FIG6 , the axis of the tripod member 3 is inclined relative to the axis of the outer coupling member 2, but the roller assembly 4 can be inclined relative to the axis of the foot shaft 7 of the tripod member 3. Therefore, the roller 11 of the roller assembly 4 is prevented from being in an oblique state with the roller guide surface 6, and rolls correctly, so that the induced thrust and sliding resistance can be reduced, and the vibration of the coupling can be reduced. In this specification and technical solution, the substantially elliptical shape is not limited to an elliptical shape as shown in the text, and also includes shapes generally referred to as an egg shape, an oblong shape, etc.

On the other hand, when the angle is larger than a predetermined angle (for example, about 15°) exceeding the normal working angle, the outer peripheral surface 7a of the foot shaft 7 shown in FIG. 3 interferes with the inner peripheral surface 12a of the inner ring 12, and the roller assembly 4 (roller 11) cannot be further tilted relative to the foot shaft 7. The angle at which the roller assembly 4 can tilt relative to the foot shaft 7 is limited, so when the angle is larger than the predetermined angle exceeding the normal working angle, the roller assembly 4 needs to tilt relative to the raceway groove 5 by an insufficient angle, but as shown in FIG. 4, the outer peripheral surface 11a of the roller 11 is formed by a partial spherical surface of a curvature radius ro with a curvature center set on the axis 7x of the foot shaft 7, so the roller assembly 4 can tilt in the raceway groove 5, and can cope with even a large working angle.

The overall structure of the tripod type constant velocity universal joint 1 of the present embodiment is as described above. Next, the characteristic structure will be described. The characteristic structure is as follows.

(1) In a double-row roller type tripod constant velocity universal joint, when the maximum diameter of the plurality of needle rollers in each roller assembly is φdmax and the minimum diameter of the plurality of needle rollers in each roller assembly is φdmin, φdmax-φdmin≤0.002 mm.

(2) In a single-row roller type tripod constant velocity universal joint, when the maximum diameter of the plurality of needle rollers arranged on the outer peripheral surface of each leg shaft is φdmax and the minimum diameter of the plurality of needle rollers arranged on the outer peripheral surface of each leg shaft is φdmin, φdmax-φdmin≤0.002 mm.

In order to promote the understanding of the above-mentioned characteristic structure, the research results and insights on the movement and behavior of the roller assembly of the tripod type constant velocity universal joint during the development process are explained based on Figures 7 to 11. First, the axial relative movement and left-right tilt of the roller assembly and the foot shaft corresponding to the specific phase are explained in detail based on Figures 7 to 10, and the left-right tilting behavior of the roller assembly in the raceway groove is briefly explained based on Figure 11.

FIG7 is a longitudinal sectional view obtained by adding plane E including axis 7x of foot shaft 7 of tripod member 3 to FIG6 in which foot shaft and roller assembly are located at the top dead center (0° phase) of outer coupling member in the state of taking working angle, and the following description is based on this figure. FIG8a is a longitudinal sectional view for explaining the state, movement and action of foot shaft and roller assembly at the top dead center (0° phase) of outer coupling member in the state of taking working angle, and FIG8b is a transverse sectional view for explaining the state, movement and action of foot shaft and roller assembly at the top dead center (0° phase) of outer coupling member in the state of taking working angle. In FIG8b, the axis 7x of foot shaft is illustrated by a single dot-dash line with a thick line for tripod member, and the outline of tripod member is omitted. The two roller assemblies 4 on the lower side of FIG2 mentioned above are not shown in FIG8a and FIG7 as longitudinal sectional views.

As shown in FIG. 7 , when the coupling takes the working angle θ, the plane E including the axis 7x of the leg shaft 7 of the tripod member 3 is tilted at the working angle θ. The tripod member 3 rotates on the plane E. Even when the working angle θ is taken, the center Cr of the roller assembly 4 (see FIG. 4 ) is located on the axis 7x of the leg shaft 7 of the tripod member 3 and is constrained on the pitch circle PC of the raceway groove 5. As shown in FIG. 8a and FIG. 8b , the upper roller assembly 4 (1) is located at the 0° phase (ψ=0°) on the opening side I of the cup portion 2a of the outer coupling member 2. This state is referred to as the 0° phase state. In this state, the upper roller assembly 4 (1) is in a horizontal posture, and the axis 4x of the roller assembly 4 (1) does not tilt left and right relative to the vertical plane including the center line 5x of the raceway groove 5. In addition, the axis 7x of the upper leg shaft 7 of the tripod member 3 does not tilt left and right relative to the vertical plane including the center line 5x of the raceway groove 5. The arrows shown radially outward of the outer coupling member 2 indicate that a rotational torque in the direction of the arrow is applied to the outer coupling member 2. That is, the left side of the roller assembly 4 is the load side. The same is true for Figs. 9b and 10b described later.

The three legs 7 of the tripod member 3 are formed to protrude outward in the radial direction from the position of the three equal parts in the circumferential direction, and the positional relationship of the three legs is fixed. In addition, the center Cr (see FIG. 4 ) of each roller assembly 4 is located on the axis 7x of the legs 7 of the tripod member 3 and is constrained on the pitch circle PC of the raceway groove 5. Therefore, as shown in FIG. 8 b , when the working angle θ is taken, the axis 7x of the three legs 7 is located on the inclined plane E, and the center Ct of the tripod member 3 is offset downward relative to the coupling center Cj, and the tripod member 3 is tilted at the working angle θ. As a result, the roller assembly 4 (1) and the axis 7x of the legs 7 for the roller assembly 4 (1) to be fitted outside do not tilt left and right relative to the vertical plane including the center line 5x of the raceway groove 5, but an axial relative movement occurs between the inner ring 12 of the roller assembly 4 (1) and the legs 7.

On the other hand, the axis 4x of the two roller assemblies 4 (2) and 4 (3) on the lower side and the axis 7x of the foot shaft 7 on which these roller assemblies 4 (2) and 4 (3) are embedded are tilted left and right as the foot shaft 7 moves axially relative to the inner ring 12. According to the direction of the left and right tilt of the axis 7x of the foot shaft 7 and the direction of the axial relative movement of the foot shaft 7 relative to the inner ring 12, as shown in FIG. 8b, the roller assembly 4 (2) on the lower right side is tilted left and right by β0 as indicated by the arrow, and the roller assembly 4 (3) on the lower left side is tilted right by β0 as indicated by the arrow.

The coupling center Cj is the curvature center of the pitch circle radius PCR of the raceway groove 5 of the outer coupling member 2. The center Ct of the tripod member 3 coincides with the center Cs of the shaft member. This state is also the same in Figures 9b and 10b described later. In addition, in Figure 8b, for easy understanding, the offset of the center Ct of the tripod member 3 relative to the coupling center Cj and the left and right inclination β are exaggeratedly illustrated as a schematic diagram in which the working angle θ is about 30°. The same is also illustrated in Figures 9b and 10b described later.

Based on FIG9, the state in which the coupling is rotated in the clockwise direction and the roller assembly 4 (1) is located at a 90° phase is described. FIG9a is a longitudinal sectional view illustrating the state in which the roller assembly 4 (1) of FIG8b is rotated in the clockwise direction to a 90° phase and the movement and action, and FIG9b is a transverse sectional view illustrating the state in which the roller assembly 4 (1) of FIG8b is rotated in the clockwise direction to a 90° phase and the movement and action. As shown in FIG9b, when the roller assembly 4 (1) is located at a 90° phase (ψ=90°), the axis 4x of the roller assembly 4 (1) does not tilt left or right relative to the horizontal plane containing the center line 5x of the rolling groove 5. In addition, the axis 7x of the foot shaft 7 also does not tilt left or right relative to the horizontal plane containing the center line 5x of the rolling groove 5.

The center Cr (see FIG. 4 ) of each roller assembly 4 is located on the axis 7x of the foot shaft 7 of the tripod member 3 and is constrained on the pitch circle PC of the raceway groove 5. Therefore, as shown in FIG. 9 b , when the roller assembly 4 (1) is in a 90° phase, the center Ct of the tripod member 3 is offset to the right of the drawing relative to the center Cj of the coupling. As a result, the axis 4x of the roller assembly 4 (1) and the axis 7x of the foot shaft 7 on which the roller assembly 4 (1) is fitted do not tilt left and right relative to the horizontal plane including the center line 5x of the raceway groove 5, but axial relative movement occurs between the inner ring 12 of the roller assembly 4 (1) and the foot shaft 7. The axis 4x of the roller assembly 4 (2) on the lower side and the axis 7x of the foot shaft 7 are tilted right and left as indicated by the arrow as the foot shaft 7 moves axially relative to the inner ring 12. The axis 4x of the roller assembly 4 (3) on the upper side and the axis 7x of the foot shaft 7 are tilted leftward and rightward by a leftward tilt β90 as indicated by the arrow as the foot shaft 7 moves relative to the axial direction of the inner ring 12 .

The state in which the roller assembly 4 (1) is located at a phase of 180° when the coupling is further rotated in the clockwise direction is described based on FIG10. FIG10a is a longitudinal sectional view illustrating the state in which the roller assembly 4 (1) of FIG8b is rotated in the clockwise direction to a phase of 180° on the inner side II of the cup portion 2a of the outer coupling member 2, and the movement and action thereof, and FIG10b is a transverse sectional view illustrating the state in which the roller assembly 4 (1) of FIG8b is rotated in the clockwise direction to a phase of 180° on the inner side II of the cup portion 2a of the outer coupling member 2, and the movement and action thereof. The center Cr (see FIG. 4 ) of each roller assembly 4 is located on the axis 7x of the foot shaft 7 of the tripod member 3 and is constrained on the pitch circle PC of the rolling groove 5. As shown in FIG. 10 b , when the roller assembly 4 (1) is in a state of 180° phase (ψ=180°), the roller assembly 4 (1) returns to a horizontal posture, and the axis 4x of the roller assembly 4 (1) does not tilt left or right relative to the vertical plane containing the center line 5x of the rolling groove 5. In addition, the axis 7x of the foot shaft 7 on which the roller assembly 4 (1) is externally mounted also does not tilt left or right relative to the vertical plane containing the center line 5x of the rolling groove 5.

Since the center Ct of the tripod member 3 is offset upward relative to the center Cj of the coupling, the roller assembly 4 (1) and the foot shaft 7 fitted outside the roller assembly 4 (1) do not tilt left and right relative to the vertical plane including the center line 5x of the raceway groove 5, but an axial relative movement occurs between the inner ring 12 of the roller assembly 4 (1) and the foot shaft 7. The axis 4x of the roller assembly 4 (2) on the upper left side and the axis 7x of the foot shaft 7 fitted outside the roller assembly 4 (2) tilt left and right by β180 as indicated by the arrow as the foot shaft 7 moves axially relative to the inner ring 12. In addition, the axis 4x of the roller assembly 4 (3) on the upper right side and the axis 7x of the foot shaft 7 fitted outside the roller assembly 4 (3) tilt right and left by β180 as indicated by the arrow as the foot shaft 7 moves axially relative to the inner ring 12.

In the above, for ease of understanding, it is specifically described that the axis 4x of the roller assembly 4 and the axis 7x of the foot shaft 7 on which the roller assembly 4 is fitted are tilted to the left and right, or the foot shaft 7 moves relative to the inner ring 12 in the axial direction, corresponding to the state where the roller assembly 4 (1) is in the 0° phase (ψ=0°), 90° phase (ψ=90°), and 180° phase (ψ=180°). In fact, in the double-row roller type tripod type constant velocity universal joint 1 of the present embodiment, the axis 4x of the roller assembly 4 and the axis 7x of the foot shaft 7 on which the roller assembly 4 is fitted are tilted to the left and right, and the foot shaft 7 moves relative to the inner ring 12 in the axial direction while changing.

The left-right tilting action of the roller assembly in the raceway groove is schematically described based on Figure 11. Figure 11a is a diagram showing the left-right tilting action of the roller assembly in the raceway groove in a composite manner, Figure 11b is a cross-sectional view showing the right-hand rotation of the roller assembly in the raceway groove, Figure 11c is a cross-sectional view showing the horizontal state of the roller assembly in the raceway groove, and Figure 11d is a cross-sectional view showing the left-hand rotation of the roller assembly in the raceway groove.

As shown in FIG. 11a, the roller assembly 4 generates a horizontal posture, right rotation or left rotation leftward tilt corresponding to the above-mentioned phase. The horizontal posture of the roller assembly 4 in FIG. 11c is supplemented by the state of phase 0° (ψ=0°) in FIG. 8a and FIG. 8b. The foot shaft 7 is tilted at an operating angle θ (refer to FIG. 7). When the roller assembly 4 (1) reaches the phase 0° (ψ=0°) from the phase before the phase 0° (ψ=0°) through the rotation action, the roller assembly 4 (1) becomes a horizontal posture. Although the foot shaft 7 is tilted at the operating angle θ, when observed through a cross section orthogonal to the axis of the outer coupling member, it becomes a horizontal posture relative to the foot shaft 7. This is because, at the moment of reaching the phase 0° (ψ=0°), the axial relative movement of the foot shaft 7 with respect to the inner ring 12 of the roller assembly 4 (1) instantly becomes 0, and the load of the foot shaft 7 that causes the inner ring 12 to move in the vertical direction disappears. Therefore, the roller assembly 4 (1) is in a horizontal posture as described above, and the inner ring 12 and the needle roller 13 are located in the axial center between the washers 14 and 15. The two ends of the inner ring 12 form an axial gap (1/2 of the axial movement amount Ia) divided into two equal parts with respect to the washers 14 and 15. It should be noted that in the horizontal posture of the roller assembly 4 (1), there is also a horizontal posture in which the axis 7x of the foot shaft 7 is consistent with the axis 4x of the roller assembly 4 (1) as shown in the state of 90° (ψ=90°) in the phase of Figures 9a and 9b.

When the right-hand rotation and left-right tilt of the roller assembly 4 of FIG. 11b are supplemented, for example, regarding the axis 7x of the foot shaft 7 into which the roller assembly 4 (3) on the lower left side shown in FIG. 8b is fitted, when the inner ring 12 of the roller assembly 4 moves relative to the foot shaft 7 of the tripod member 3 due to the rotation of the outer coupling member in the direction of the arrow, the foot shaft 7 pulls the inner ring 12 of the roller assembly 4 (3) downward, and the axis 7x is tilted left-right in a right-hand rotation, and the lower end face of the inner ring 12 and the lower end face of the needle roller 13 abut against the lower washer 15, and the upper end face of the inner ring 12 and the upper end face of the needle roller 13 are separated from the upper washer 14 to generate an axial gap (axial movement amount Ia). The axial movement amount Ia of the inner ring 12 needs to be an appropriate size in consideration of mass production and actual effect.

When the left-rotation and left-right tilt of the roller assembly 4 of Figure 11d is supplemented, for example, with respect to the axis 7x of the foot shaft 7 for embedding the roller assembly 4 (2) on the lower right side shown in Figure 8b, when the inner ring 12 of the roller assembly 4 moves relative to the foot shaft 7 of the tripod member 3 due to the rotation of the outer coupling member in the direction of the arrow, the foot shaft 7 pushes the inner ring 12 of the roller assembly 4 (2) upward, and the axis 7x produces a left-rotation and left-right tilt, and the upper end face of the inner ring 12 and the upper end face of the needle roller 13 abut against the upper washer 14, and the lower end face of the inner ring 12 and the lower end face of the needle roller 13 are separated from the lower washer 15 to produce an axial gap (axial movement amount Ia).

The rolling amount of the components of the roller assembly 4 of the tripod type constant velocity universal joint 1 is small compared with that of a normal rolling bearing, but the relative movement of the components of the roller assembly 4 is significantly different and extremely severe compared with that of a normal rolling bearing. Under such conditions, when the inner ring 12 of the roller assembly 4 repeatedly moves relative to each other in the up-down direction (axial direction) on the foot shaft 7 of the tripod member 3, the cylindrical outer peripheral surface 12b of the inner ring 12, the needle roller 13, and the cylindrical inner peripheral surface 11b of the roller 11 repeatedly contact in an offset direction under the action of the up-down direction load. It was found that when an excessive load is applied in this state, the load is concentrated in the needle roller 13 with a specific large diameter under an offset load state, so the surface pressure increases significantly, and the durability of the roller assembly may be reduced. As a result, a new concept was obtained that although the rolling amount of the needle roller 13 of the roller assembly 4 of the tripod type constant velocity universal joint 1 is small compared with the rolling bearing, when considering the offset load state, concentrated load, and surface pressure increase, the needle roller 13 needs to have the same internal specifications (difference between needle roller diameters) as the rolling bearing. In addition, a characteristic structure was formed in which, in the double-row roller tripod type constant velocity universal joint, when the maximum diameter of the plurality of needle rollers in each roller assembly is set to φdmax and the minimum diameter of the plurality of needle rollers in each roller assembly is set to φdmin, φdmax-φdmin≤0.002mm.

The characteristic structure of the present embodiment will be specifically described based on FIGS. 12 and 13 . FIG. 12 is an enlarged longitudinal sectional view of the roller assembly of the present embodiment. FIG. 13 is an enlarged transverse sectional view of the roller assembly at the line F-F of FIG. 4 . The roller assembly 4 shown in FIG. 12 is shown in a state where the left ends of the inner ring 12 and the needle roller 13 are in contact with the washer 15 and the right ends are separated from the washer 14 in the upper half above the axis 4x (forming an axial movement amount Ia), and the inner ring 12 and the needle roller 13 are located in the axial center between the washers 14 and 15 in the lower half below the axis 4x. An axial gap (axial movement amount Ia/2) divided into two equal parts is formed at both ends of the inner ring 12 with respect to the washers 14 and 15.

As shown in Fig. 12, chamfered portions C are formed at both axial ends of the cylindrical outer peripheral surface 12b of the inner ring 12, and the cylindrical outer peripheral surface 12b of the inner ring 12 is connected to the chamfered portion C at the connection point Pi. The end face of the needle roller 13 is flat and has an end face fillet, and is connected to the cylindrical outer peripheral surface at the connection point Pr.

In the roller assembly 4, when the lower end face (left end face) of the inner ring 12 and the lower end face (left end face) of the needle roller 13 are respectively in contact with the washer 15, the connection point Pr of the end face fillet of the needle roller 13 is approximately aligned in the axial direction with the connection point Pi of the cylindrical outer peripheral surface 12b of the inner ring 12. At the right end portion of FIG. 12 , due to the axial movement amount Ia of the inner ring 12, the connection point Pr of the end face fillet of the needle roller 13 is located axially inward of the connection point Pi of the cylindrical outer peripheral surface 12b of the inner ring 12, that is, inside the cylindrical outer peripheral surface 12b of the inner ring 12.

As shown in FIG. 13 , a plurality of needle rollers 13 are arranged between the cylindrical inner circumferential surface 11b of the roller 11 and the cylindrical outer circumferential surface 12b of the inner ring 12 of the roller assembly 4 in a so-called full roller state without a retainer, with the cylindrical inner circumferential surface 11b of the roller 11 serving as the outer raceway surface and the cylindrical outer circumferential surface 12b of the inner ring 12 serving as the inner raceway surface. For example, in this embodiment, 46 needle rollers are arranged between the cylindrical inner circumferential surface 11b of the roller 11 and the cylindrical outer circumferential surface 12b of the inner ring 12. The maximum diameter of the plurality of needle rollers 13 in each roller assembly 4 is φdmax, and the minimum diameter of the plurality of needle rollers 13 in each roller assembly 4 is φdmin. The characteristic structure of this embodiment is that the difference between the maximum diameter φdmax and the minimum diameter φdmin of the plurality of needle rollers 13 in each roller assembly 4 is set to φdmax-φdmin≤0.002mm, and the internal specification (the difference between the needle roller diameters of the needle rollers) is set to the same level as that of a rolling bearing. Thus, even in a state where the load is concentrated under an offset load state, the increase in surface pressure can be suppressed, and the durability of the roller assembly 4 can be ensured.

In addition, the gap between the cylindrical inner circumferential surface 11b of the roller 11 and the cylindrical outer circumferential surface 12b of the inner ring 12 is determined based on the maximum diameter φdmax of the needle roller 13. Therefore, when the difference between the maximum diameter φdmax and the minimum diameter φdmin is large, the gap in the circumferential direction becomes larger when the needle roller 13 is arranged between the cylindrical inner circumferential surface 11b of the roller 11 and the cylindrical outer circumferential surface 12b of the inner ring 12, so the play (backlash) also becomes larger. However, in the present embodiment, the difference between the maximum diameter φdmax and the minimum diameter φdmin of the plurality of needle rollers 13 in each roller assembly 4 is set to φdmax-φdmin≤0.002mm, so that the play can be suppressed.

FIG14 shows the case of annular contact. FIG14 is a partial cross-sectional view showing a modified example in which the contact state between the roller and the roller guide surface of the first embodiment is set to annular contact. In the case of annular contact, the roller guide surface 6 of the rolling groove 5 is formed into a partial cylindrical shape with a curvature radius Rt' having a curvature center ORt' set on a horizontal line X-X passing through the intersection T of the center line 5x of the rolling groove 5 and the pitch circle PC of the rolling groove 5. The roller guide surface 6 and the roller 11 are in contact with the horizontal line X-X passing through the intersection T. The case of annular contact can also be applied in the same way as the case of angular contact.

The tripod type constant velocity universal coupling of the second embodiment of the present invention is described based on Figure 15. Figure 15 is a cross-sectional view of the tripod type constant velocity universal coupling of the present embodiment. However, the two rollers and the tripod member on the lower side are not shown in cross section, and the shaft member is omitted from the illustration. The present embodiment is a double-row roller type tripod type constant velocity universal coupling, but the shape of the foot shaft and the shape of the roller assembly are different from the double-row roller type tripod type constant velocity universal coupling 1 of the first embodiment. The same figure marks are marked on the parts with the same functions and the main points are explained.

As shown in FIG. 15 , in the tripod type constant velocity universal joint 1 of the present embodiment, the outer peripheral surface 7a of the foot shaft 7 of the tripod member 3 is formed into a spherical shape, and the inner ring 12 of the roller assembly 4 has a cylindrical inner peripheral surface 12a, and the cylindrical inner peripheral surface 12a of the inner ring 12 can be slidably fitted on the spherical outer peripheral surface 7a of the foot shaft 7 of the tripod member 3. The outer peripheral surface 11a of the roller 11 is formed into a circular ring shape with a relatively small curvature radius ro" having a curvature center at a position Or" offset in the radial direction from the axis 7x of the foot shaft 7. As for other structures, they are the same as those of the first embodiment, so the same figure marks are marked on the parts with the same functions, and the main points are explained.

The main part of the roller assembly 4 includes the roller 11, the inner ring 12, and a plurality of needle rollers 13 assembled between the roller 11 and the inner ring 12 in a fully loaded roller state. The roller 11 has a cylindrical inner peripheral surface 11b. Washers 14 and 15 are assembled in an annular groove of the cylindrical inner peripheral surface 11b of the roller 11 in an elastically reduced state, and the roller assembly 4 including the inner ring 12, the needle rollers 13 and the roller 11 is formed into a structure that is not separated by the washers 14 and 15. The inner ring 12 has a cylindrical outer peripheral surface 12b, and has a drop-shaped portion D (not shown) at both axial ends of the cylindrical outer peripheral surface 12b. The roller assembly 4 is accommodated in the raceway groove 5 of the outer coupling member 2, and the center of the roller assembly 4 (roller 11) in the width direction is located on the pitch circle PC of the raceway groove 5.

The tripod member 3 has three foot shafts 7 protruding in the radial direction. The outer peripheral surface 7a of the foot shaft 7 is formed into a spherical shape with the center of curvature set on the axis 7x of the foot shaft 7, and the cylindrical inner peripheral surface 12a of the inner ring 12 of the roller assembly 4 is slidably fitted on the spherical outer peripheral surface 7a. When the coupling takes an operating angle, the roller assembly 4 can be tilted relative to the axis of the foot shaft 7 of the tripod member 3 and can move in the axial direction. Therefore, the roller 11 of the roller assembly 4 is prevented from being in an oblique state with the roller guide surface 6, and can roll correctly.

The roller guide surface 6 is formed by a local cylindrical surface having a relatively small curvature radius Rt" with a center of curvature set at a position ORt" offset in the radial direction from the center line 5x of the rolling groove 5 on the horizontal line XX passing through the intersection T of the pitch circle PC of the rolling groove 5 and the center line 5x of the rolling groove 5, and extends parallel to the axis of the coupling. In the present embodiment, an example in which a flange portion 5a is provided on one side of the rolling groove 5 is illustrated, but a flange portion may not be provided on one side of the rolling groove 5 as in the modified example shown in FIG16.

In the second embodiment shown in FIG. 15 and the tripod type constant velocity universal joint 1 of the modified example shown in FIG. 16, a plurality of needle rollers 13 are also arranged between the cylindrical inner peripheral surface 11b of the roller 11 and the cylindrical outer peripheral surface 12b of the inner ring 12, and the needle rollers 13 are arranged in a so-called full roller state without a retainer. In addition, as a characteristic structure, the difference between the maximum diameter φdmax and the minimum diameter φdmin of the plurality of needle rollers 13 in each roller assembly 4 is set to φdmax-φdmin≤0.002mm, and the internal specification (the difference between the needle roller diameters of the needle rollers) is set to the same level as that of a rolling bearing. As a result, even in a state where the load is concentrated under an offset load state, the surface pressure increase can be suppressed, and the durability of the roller assembly 4 can be ensured. The above-mentioned characteristic structure is the same as that described in the tripod type constant velocity universal joint of the first embodiment, and therefore applies to the tripod type constant velocity universal joint of the present embodiment.

The tripod type constant velocity universal coupling of the third embodiment of the present invention is described based on Figure 17. Figure 17 is a cross-sectional view of the tripod type constant velocity universal coupling of this embodiment. However, the two rollers and the tripod member on the lower side are not shown in cross section, and the shaft member is omitted from the illustration. This embodiment is a single-row roller type tripod type constant velocity universal coupling, which is different from the double-row roller type of the first and second embodiments in that it is a single-row roller type. The same figure marks are marked on the parts with the same functions and the main points are explained.

As shown in FIG. 17 , the tripod type constant velocity universal joint 1 includes an outer coupling member 2, a tripod member 3 as an inner coupling member, and rollers 11 as torque transmission members. The outer coupling member 2 has a cup portion 2a with one end open, and three linear raceway grooves 5 extending in the axial direction are formed on the inner circumferential surface at equal intervals in the circumferential direction, and roller guide surfaces 6 are formed on both sides of each raceway groove 5 and are arranged opposite to each other in the circumferential direction and extend in the axial direction. The tripod member 3 and the rollers 11 are accommodated inside the outer coupling member 2.

The tripod member 3 has three foot shafts 7 protruding in the radial direction. The roller 11 is externally fitted on the cylindrical outer peripheral surface 7a of the foot shaft 7 via a plurality of needle rollers 13, and is rotatably supported on the foot shaft 7. The cylindrical outer peripheral surface 7a of the foot shaft 7 constitutes the inner raceway surface of the needle roller 13, and the cylindrical inner peripheral surface 11a of the roller 11 constitutes the outer raceway surface of the needle roller 13. The roller 11 has a spherical outer peripheral surface 11b with a curvature radius r whose curvature center is set on the axis 7x of the foot shaft 7. The contact between the outer peripheral surface 11b of the roller 11 and the roller guide surface 6 can apply any of the angular contact and annular contact described above in the first embodiment.

A plurality of needle rollers 13 are assembled between the cylindrical outer peripheral surface 7a of the foot shaft 7 and the cylindrical inner peripheral surface 11a of the roller 11 in a fully loaded roller state. The needle rollers 13 are in contact with the inner washer 15 externally fitted at the root of the foot shaft 7 on the inner side in the radial direction, and are in contact with the outer washer 14 externally fitted at the front end of the foot shaft 7 on the outer side in the radial direction. The outer washer 14 is prevented from coming off by fitting a retaining ring 21 in an annular groove 20 formed at the front end of the foot shaft 7. The outer washer 14 includes a disc portion 14a extending in the radial direction of the foot shaft 7 and a cylindrical portion 14b extending in the axial direction of the foot shaft 7. The cylindrical portion 14b of the outer washer 14 has an outer diameter smaller than the inner peripheral surface 11a of the roller 11, and the outer end 14c of the cylindrical portion 14b viewed in the radial direction of the tripod member 3 is formed to have a larger diameter than the inner peripheral surface 11a of the roller 11. Therefore, the roller 11 can move in the axial direction of the leg shaft 7 and is prevented from falling off by the end portion 14c.

The single-row roller type tripod type constant velocity universal joint 1 of the present embodiment has a characteristic structure. In the single-row roller type tripod type constant velocity universal joint, when the maximum diameter of the plurality of needle rollers arranged on the outer peripheral surface of each leg shaft is set to φdmax and the minimum diameter of the plurality of needle rollers arranged on the outer peripheral surface of each leg shaft is set to φdmin, φdmax-φdmin≤0.002mm, and the internal specification (the difference between the needle roller diameters of the needle rollers) is set to be equal to that of a rolling bearing. Thus, even in a state where the load is concentratedly received under an offset load state, the surface pressure increase can be suppressed, and the durability of the roller assembly 4 can be ensured. The contents described in the tripod type constant velocity universal joint of the first embodiment are also the same in the tripod type constant velocity universal joint of the present embodiment, and therefore are applicable.

The present invention is not limited to the aforementioned embodiments, and can of course be implemented in various ways without departing from the gist of the present invention. The scope of the present invention is shown by the technical solutions, and also includes the equivalent meanings and all changes within the scope recorded in the technical solutions.

Description of Reference Numerals

1 Tripod type constant velocity universal coupling

2 Outer coupling member

3 Tripod components

4 Roller assembly

5 Roller groove

5x Centerline of raceway groove

6 Roller guide surface

7-pin shaft

7x Axis of the foot shaft

11 Roller

11a Outer surface

11b Cylindrical inner surface

12 Inner circle

12a Inner circumference

12b Cylindrical outer surface

13 Roller needle

Cr Center of inner circle

Ct The center of the tripod component

Ia Axial movement

Or Center of Curvature

Or” Center of curvature

ORt Center of curvature

ORt’ Center of curvature

ORt” Center of curvature

PC raceway groove pitch circle

Rt Radius of curvature

Rt’ radius of curvature

Rt” Radius of curvature

T intersection

X－X horizontal line

a Major axis

b Short axis

m Gap

r Axial dimension of the end fillet

ro Radius of curvature

ro” Radius of curvature

α Contact angle

β Left-right tilt

θ Working angle

δ Raceway clearance

φdmax Maximum diameter

φdmin minimum diameter.

Claims (5)

1. A tripod-type constant velocity universal joint, comprising: an outer coupling member, which has three rolling grooves extending in the axial direction at three equal parts of the circumferential direction of the inner circumference, and the rolling grooves have roller guide surfaces arranged opposite to each other in the circumferential direction; a tripod member, which has three foot shafts protruding radially outward from the three equal parts of the circumferential direction; and a roller assembly, which is externally embedded in the foot shaft, and the roller assembly includes: an inner ring, which is externally embedded in the foot shaft; a roller, which is inserted in the roller guide surface; a plurality of needle rollers, which are arranged between the cylindrical outer circumferential surface of the inner ring and the cylindrical inner circumferential surface of the roller; and a pair of washers, which are arranged on both axial sides of the needle rollers and the inner ring, and the outer circumferential edges are mounted on the inner circumference of the rollers, The tripod type constant velocity universal coupling is characterized in that: When the maximum diameter of the plurality of needle rollers in each of the roller assemblies is φdmax and the minimum diameter of the plurality of needle rollers in each of the roller assemblies is φdmin, φdmax-φdmin≤0.002 mm. 2. The tripod type constant velocity universal coupling according to claim 1, characterized in that: The inner circumferential surface of the inner ring is formed as an arc-shaped convex surface in the longitudinal section of the inner ring, the outer circumferential surface of the foot shaft is straight in the longitudinal section including the axis of the foot shaft, and is roughly elliptical in the cross section orthogonal to the axis of the foot shaft, the outer circumferential surface of the foot shaft abuts against the inner circumferential surface of the inner ring in a direction orthogonal to the axis of the coupling, and a gap is formed between the outer circumferential surface of the foot shaft and the inner circumferential surface of the inner ring in the axial direction of the coupling, and the roller can tilt in the raceway groove. 3. A tripod-type constant velocity universal joint, comprising: an outer coupling member, wherein three rolling grooves extending in the axial direction are formed at three equal parts of the inner circumference in the circumferential direction, and the rolling grooves have roller guide surfaces arranged opposite to each other in the circumferential direction; a tripod member, wherein three foot shafts protrude radially outward from the three equal parts in the circumferential direction; and a roller, wherein a plurality of needle rollers are arranged on the outer circumferential surface of the foot shaft, and the roller is rotatably assembled by means of the needle rollers, and the roller is guided by the roller guide surface of the rolling groove, The tripod type constant velocity universal coupling is characterized in that: When the maximum diameter of the plurality of needle rollers arranged on the outer peripheral surface of each of the pin shafts is φdmax and the minimum diameter of the plurality of needle rollers arranged on the outer peripheral surface of each of the pin shafts is φdmin, φdmax-φdmin≤0.002 mm. 4. The tripod type constant velocity universal coupling according to any one of claims 1 to 3, characterized in that: The roller is in angular contact with the roller guide surface. 5. The tripod type constant velocity universal coupling according to any one of claims 1 to 3, characterized in that: The rollers are in annular contact with the roller guide surfaces.