Fixed type constant velocity universal joint

Abstract

To avoid a decrease in the strength of a cage in a fixed type constant velocity universal joint of the track groove crossing type.SOLUTION: A diameter E of a cylindrical surface 5d of a cage 5 is smaller than an apparent maximum outer diameter D1 of an inner joint member 3 when the inner joint member 3 is viewed from the axial direction of the cage 5 in a state where the axis of the inner joint member 3 and the axis of the cage 5 are orthogonal to each other, and two track grooves 90, 91 of the inner joint member 3 having a phase difference of 180 degrees face each other in the diameter direction of the cage 5. Moreover, the diameter E of the cylindrical surface 5d of the cage 5 is larger than an apparent maximum outer diameter D3 of the inner joint member 3 when the inner joint member 3 is viewed from the axial direction of the cage 5 in a state where the axis of the inner joint member 3 is inclined by an angle α with respect to a plane orthogonal to the axis of the cage 5, and two track grooves 90, 91 of the inner joint member 3 having a phase difference of 180 degrees face an inner peripheral surface of the cage 5.SELECTED DRAWING: Figure 8

Description

[Technical Field]

[0001] This invention relates to a fixed type constant velocity universal joint, which is used in the power transmission systems of automobiles and various industrial machines and allows only angular displacement between two shafts on the driving and driven sides. [Background technology]

[0002] For example, the front drive shaft of an automobile typically incorporates a sliding constant velocity universal joint on the inboard side (differential gear side) that has a relatively small maximum operating angle but is capable of axial displacement while taking an operating angle, while the outboard side (wheel side) incorporates a fixed constant velocity universal joint that has a large operating angle but does not displace axially, as the wheels are steered.

[0003] Known fixed-type constant velocity universal joints include Rzeppa-type constant velocity universal joints (also referred to as BJ types) and undercut-free type constant velocity universal joints (also referred to as UJ types). Among these, an eight-ball type fixed-type constant velocity universal joint shown in FIG. 17 exists as a means for achieving further compactness while reducing temperature rise and torque loss during operation and ensuring strength, load capacity, and durability (Patent Document 1). This fixed-type constant velocity universal joint 101 is a Rzeppa-type constant velocity universal joint, and is mainly composed of an outer joint member 102, an inner joint member 103, balls 104 that transmit torque, and a cage 105. Eight balls 104 that transmit torque are incorporated into arc-shaped track grooves 107, 109 that extend axially in the outer joint member 102 and the inner joint member 103, and each ball 104 is held in a pocket 105a of the cage 105. A cylindrical surface 105c for fitting the inner joint member 103 is provided on the inner peripheral surface of an annular portion 105b provided on one axial side (the right side in FIG. 17(A)) of the pocket 105a of the cage 105. The centers of curvature of the track grooves 107, 109 are offset by an equal distance f on the opposite axial side from the joint center.

[0004] Recently, with the aim of improving the environmental performance of automobiles, there has been a demand for even higher efficiency, and in order to achieve even higher performance than the aforementioned eight-ball type fixed constant velocity universal joint, a track groove crossing type fixed constant velocity universal joint shown in Fig. 19 has been proposed, which aims to reduce heat generation by reducing contact between the spherical outer peripheral surface and the spherical inner peripheral surface of the cage (Patent Document 2). This fixed constant velocity universal joint 151 mainly comprises an outer joint member 152, an inner joint member 153, balls 154 that transmit torque, and a cage 155. Eight balls 154 that transmit torque are incorporated in arc-shaped track grooves 157 and 159 that extend axially of the outer joint member 152 and the inner joint member 153, and each ball 154 is held in a pocket 155a of the cage 155. The cage 155 has an annular portion 155b provided on one axial side (the right side in FIG. 19(A)) of the pocket 155a. A cylindrical surface 155c for fitting the inner joint member 153 is provided on the inner peripheral surface of the annular portion 155b. The track grooves 157, 159 adjacent to each other in the circumferential direction are inclined in opposite directions with respect to the axis. The track grooves 157, 159 facing each other in the radial direction are inclined in opposite directions with respect to the axis. The centers of curvature of the track grooves 157, 159 coincide with the joint center.

[0005] Furthermore, various studies have been conducted on improving the efficiency (Patent Document 3) and increasing the angle (Patent Document 4) of fixed constant velocity universal joints of the track groove intersection type. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent No. 3859267 [Patent Document 2] Patent No. 5138449 [Patent Document 3] Patent No. 6113459 [Patent Document 4] Patent No. 5912419 Summary of the Invention [Problem to be solved by the invention]

[0007] 18 , in the Rzeppa-type fixed constant velocity universal joint of eight balls disclosed in Patent Document 1, the axis of the inner joint member 103 and the axis of the cage 105 are orthogonal to each other and the phase of the inner joint member 103 is adjusted so that two track grooves 109 (the track grooves 109 at the upper and lower ends in the figure) that are out of phase with each other by 180 degrees of each other face the inner circumferential surface of the cage. When the inner joint member 103 is viewed from the axial direction of the cage 105 (direction T in the figure), the apparent outer diameter D' of the inner joint member 103 is slightly smaller than the diameter E' of the cylindrical surface 105c of the cage 105 (E'>D'). This allows the inner joint member 103 to be fitted into the inner periphery of the cage 105 via the cylindrical surface 105c (see arrow U).

[0008] On the other hand, in a track groove tolerance type fixed constant velocity universal joint, adjacent track grooves 159 of an inner joint member 153 are inclined toward opposite sides with respect to the axis, as shown in Fig. 10 , and therefore the circumferential width of a spherical portion 153a provided between the track grooves 159 narrows toward one axial side or the other axial side. For this reason, when the axis of the inner joint member 153 and the axis of the cage 155 are made orthogonal to each other and the phase of the inner joint member 153 is adjusted so that two track grooves 159 of the inner joint member 153 that are 180 degrees out of phase with each other face the inner circumferential surface of the cage, the apparent outer diameter of the inner joint member 153 becomes non-uniform when viewed from the axial direction of the cage 155 (a direction perpendicular to the plane of the paper in Fig. 10 ). Specifically, the apparent outer diameter D1 of the inner joint member 153 at a portion where the circumferential width of the spherical portion 153a is wide is slightly larger than the apparent outer diameter D2 at a portion where the circumferential width of the spherical portion 153a is narrow (D1>D2). As shown in the figure, if the apparent maximum outer diameter (≈D1) of the inner joint member 153 is larger than the diameter E of the cylindrical surface 155c of the cage 155, the inner joint member 153 cannot be fitted to the inner periphery of the cage 155. This requires increasing the diameter of the cylindrical surface 155c of the cage 155, which reduces the radial thickness of the annular portion 155b of the cage 155, resulting in a decrease in the strength of the cage 155.

[0009] SUMMARY OF THE INVENTION It is therefore an object of the present invention to avoid a decrease in the strength of the cage in a track groove intersecting type fixed type constant velocity universal joint. [Means for solving the problem]

[0010] The present invention, which has been made to solve the above problems, provides a fixed type constant velocity universal joint comprising: an outer joint member having eight track grooves formed on a spherical inner peripheral surface; an inner joint member having eight track grooves formed on a spherical outer peripheral surface; eight balls that are interposed between the track grooves of the outer joint member and the track grooves of the inner joint member to transmit torque; a spherical outer peripheral surface that fits with the spherical inner peripheral surface of the outer joint member; a spherical inner peripheral surface that fits with the spherical outer peripheral surface of the inner joint member; eight pockets that hold the balls one by one; and a cage that has a cylindrical surface provided at an axial end of the inner peripheral surface, the outer joint member has a first track groove portion having an arc-shaped ball raceway center line Xa, and the inner joint member has a first track groove portion having an arc-shaped ball raceway center line Ya, a plane including a ball raceway center line Xa of a first track groove portion of each track groove of the outer joint member and a plane including the ball raceway center line Xa of the first track groove portion of an adjacent track groove are inclined by an angle γ toward opposite sides with respect to the axial direction, a plane including a ball raceway center line Ya of a first track groove portion of each track groove of the inner joint member and a plane including the ball raceway center line Ya of the first track groove portion of an adjacent track groove are inclined by an angle γ toward opposite sides with respect to an axial direction, a plane including a ball raceway center line Xa of a first track groove portion of the track groove of the outer joint member and a plane radially opposing thereto and including a ball raceway center line Ya of the first track groove portion of the track groove of the inner joint member are inclined toward opposite sides with respect to the axial direction, The diameter E of the cylindrical surface of the cage is is smaller than the apparent maximum outer diameter D1 of the inner joint member when the inner joint member is viewed from the axial direction of the cage with the axis of the inner joint member and the axis of the cage perpendicular to each other and with the two track grooves of the inner joint member that are out of phase with each other by 180 degrees facing the inner circumferential surface of the cage, and the apparent maximum outer diameter D3 of the inner joint member when viewed from the axial direction of the cage in a state in which the axis of the inner joint member is inclined by an angle α with respect to a plane perpendicular to the axis of the cage and the two track grooves of the inner joint member which are out of phase with each other by 180 degrees face each other and the inner circumferential surface of the cage.

[0011] The inventors have noticed that the apparent maximum outer diameter of the inner joint member of a track groove intersecting type fixed constant velocity universal joint is smaller when the axis of the inner joint member is inclined with respect to a plane perpendicular to the axis of the cage (see FIG. 8) than when the axis of the inner joint member and the axis of the cage are perpendicular to each other (see FIG. 10). By making the diameter E of the cylindrical surface of the cage larger than the apparent maximum outer diameter D3 of the inner joint member when the axis of the inner joint member is inclined with respect to a plane perpendicular to the axis of the cage, it becomes possible to incorporate the inner joint member into the inner periphery of the cage (see FIG. 8). Furthermore, by making the diameter E of the cylindrical surface of the cage smaller than the apparent maximum outer diameter D1 of the inner joint member when the axis of the inner joint member and the axis of the cage are perpendicular to each other, it is possible to ensure the thickness of the cage and maintain its strength (see FIG. 10).

[0012] If the axial width of the inner joint member is too large, it is necessary to increase the diameter of the cylindrical surface of the cage so that the inner joint member can be fitted to the inner periphery of the cage. Therefore, the axial width W of the inner joint member and the diameter D of the balls are required to be large. BALL Ratio of W / D BALL In particular, when the axial distance W2 between the end face on one axial side of the inner joint member and the joint center is larger than the axial distance W1 between the end face on one axial side of the inner joint member and the joint center, the axial distance W2 between the end face on the other axial side of the inner joint member and the joint center and the ball diameter D BALLRatio of W2 / D BALL is preferably set to 0.99 to 1.13.

[0013] For example, by setting the angle α between the axis of the inner joint member and the axis of the cage to be three or more times the inclination angle γ of each track groove with respect to the axial direction of the plane including the ball raceway center lines X and Y, it is possible to make the apparent maximum outer diameter D3 of the inner joint member smaller than the diameter E of the cylindrical surface of the cage.

[0014] The inclination angle γ of the track grooves with respect to the axial direction is preferably 4° to 8°, which prevents inevitable malfunction of the joint and a decrease in constant velocity performance, and ensures the circumferential thickness of the cage pillar portions and the thickness of the spherical portion of the inner joint member, thereby ensuring joint strength.

[0015] In the fixed type constant velocity universal joints mentioned above, the pitch circle diameter of the ball is PCD BALL and the diameter of the ball D BALL Ratio of PCD to BALL / D BALL is preferably set in the range of 3.89 to 4.48.

[0016] Each track groove of the outer joint member may have the following configuration (see FIG. 1 for symbols). The second track groove portion 7b is continuous with one axial end of the first track groove portion 7a and has a linear ball track center line Xb. The connection point A between the ball raceway center line Xa of the first track groove portion 7a and the ball raceway center line Xb of the second track groove portion 7b is located on one axial side of the joint center O. The ball raceway center line Xb of the second track groove portion 7b is inclined so as to approach the axis of the outer joint member as it moves toward one axial side.

[0017] In this case, each track groove of the inner joint member has the following configuration (see FIG. 1 for symbols). The second track groove portion is continuous with the other axial end of the first track groove portion and has a linear ball raceway center line Yb. The connection point B between the ball raceway center line Ya of the first track groove portion and the ball raceway center line Yb of the second track groove portion is located on the other axial side of the joint center O. The ball raceway center line Yb of the second track groove portion is inclined so as to approach the axis of the inner joint member toward the other axial side.

[0018] By providing the above-described linear second track groove portions in the track grooves of the outer joint member and the inner joint member, the effective track length can be increased to achieve a high operating angle. Furthermore, because the balls can be brought into contact with the arc-shaped first track groove portions within the common angle range, torque loss and heat generation within the common angle range can be suppressed, thereby achieving high efficiency. [Effects of the Invention]

[0019] As described above, according to the present invention, in a fixed type constant velocity universal joint of the track groove intersection type, it is possible to avoid a decrease in the strength of the cage. [Brief explanation of the drawings]

[0020] [Figure 1] 1A and 1B show a fixed type constant velocity universal joint according to one embodiment of the present invention, in which FIG. 1A is a partial longitudinal cross-sectional view of the fixed type constant velocity universal joint, and FIG. 1B is a front view of the fixed type constant velocity universal joint of FIG. 1A as viewed from the axial direction. [Figure 2] 2A and 2B show an outer joint member of the fixed type constant velocity universal joint of FIG. 1, in which FIG. 2A is a partial vertical cross-sectional view of the outer joint member, and FIG. 2B is a front view of the outer joint member of FIG. 2A as viewed from the axial direction. [Figure 3] 2A and 2B show an inner joint member of the fixed type constant velocity universal joint of FIG. 1, in which FIG. 2A is a front view of the inner joint member as seen from one axial side, FIG. 2B is a side view of the inner joint member as seen from the outer periphery, and FIG. 2C is a back view of the inner joint member as seen from the other axial side. [Figure 4] FIG. 2 is a partial vertical cross-sectional view showing details of track grooves of the outer joint member of FIG. 1(A). [Figure 5] FIG. 2 is a vertical cross-sectional view showing details of a track groove of the inner joint member of FIG. [Figure 6] 5A and 5B are diagrams showing a method of assembling the cage and the inner joint member, in which FIG. 5A is a partial vertical cross-sectional view seen from the radial direction of the cage, and FIG. 5B is a front view seen from the axial direction of the cage. [Figure 7] 5A and 5B are diagrams showing a method of assembling the cage and the inner joint member, in which FIG. 5A is a partial vertical cross-sectional view seen from the radial direction of the cage, and FIG. 5B is a front view seen from the axial direction of the cage. [Figure 8] 5A and 5B are diagrams showing a method of assembling the cage and the inner joint member, in which FIG. 5A is a partial vertical cross-sectional view seen from the radial direction of the cage, and FIG. 5B is a front view seen from the axial direction of the cage. [Figure 9] 5A and 5B are diagrams showing a method of assembling the cage and the inner joint member, in which FIG. 5A is a partial vertical cross-sectional view seen from the radial direction of the cage, and FIG. 5B is a front view seen from the axial direction of the cage. [Figure 10] FIG. 2 is a front view of the cage and the inner joint member, viewed from the axial direction of the cage, with the axis of the cage and the axis of the inner joint member being perpendicular to each other. [Figure 11] FIG. 2 is an enlarged partial vertical cross-sectional view of the fixed type constant velocity universal joint of FIG. 1(A). [Figure 12] FIG. 2 is an enlarged partial vertical cross-sectional view of the fixed type constant velocity universal joint of FIG. 1(A). [Figure 13] FIG. 1A is a partial vertical cross-sectional view of an outer joint member, FIG. 1B is a front view of the outer joint member and a cage assembled together, as seen from the axial direction of the outer joint member, and FIG. 1C is a front view of the cage, as seen from the axial direction. [Figure 14] FIG. 1A is a partial vertical cross-sectional view of an outer joint member, and FIG. 1B is a cross-sectional view taken along line PP in FIG. 1A. [Figure 15] FIG. 10 is a partial vertical cross-sectional view of a fixed type constant velocity universal joint according to another embodiment of the present invention. [Figure 16] FIG. 10(A) is a partial vertical cross-sectional view of a fixed type constant velocity universal joint according to still another embodiment of the present invention, and FIG. 10(B) is an enlarged view of a portion T in FIG. 10(A). [Figure 17]FIG. 1A is a partial longitudinal cross-sectional view of a conventional fixed type constant velocity universal joint (Rzeppa type), and FIG. 1B is a front view of the fixed type constant velocity universal joint of FIG. 1A as viewed from the axial direction. [Figure 18] 18 is a front view of an inner joint member of the fixed type constant velocity universal joint of FIG. 17 as viewed from the axial direction, and a vertical sectional view of a cage. FIG. [Figure 19] FIG. 1A is a partial longitudinal cross-sectional view of a conventional fixed type constant velocity universal joint (cross track groove type), and FIG. 1B is a front view of the fixed type constant velocity universal joint of FIG. 1A as viewed from the axial direction. DETAILED DESCRIPTION OF THE INVENTION

[0021] An embodiment of the present invention will be described with reference to the drawings.

[0022] First, the basic configuration of a track groove intersecting type fixed type constant velocity universal joint 1 according to this embodiment will be described with reference to Figures 1 to 5. The fixed type constant velocity universal joint 1 mainly includes an outer joint member 2, an inner joint member 3, balls 4, and a cage 5.

[0023] Eight track grooves 7 are formed on the spherical inner peripheral surface of the outer joint member 2, and eight track grooves 9 are formed on the spherical outer peripheral surface of the inner joint member 3 {see Fig. 1(B)}. Spherical portions 6 are left between the track grooves 7 in the circumferential direction on the inner peripheral surface of the outer joint member 2, and spherical portions 8 are left between the track grooves 9 in the circumferential direction on the outer peripheral surface of the inner joint member 3 {see Fig. 1(A)}. The centers of curvature of the spherical portions 6 on the inner peripheral surface of the outer joint member 2 and the spherical portions 8 on the outer peripheral surface of the inner joint member both coincide with the joint center O. One ball 4 is disposed between each of the track grooves 7, 9 that face each other in the radial direction. The cage 5 has a spherical outer peripheral surface 12 that fits into the spherical portion 6 on the inner peripheral surface of the outer joint member 2, a spherical inner peripheral surface 13 that fits into the spherical portion 8 on the outer peripheral surface of the inner joint member 3, and eight pockets 5a that each hold one ball 4. The cage 5 has a pair of annular portions 5b, 5c provided on both axial sides of the pocket 5a, and a pillar portion 5e (see Figure 1(B)) that connects the pair of annular portions 5b, 5c in the axial direction. A cylindrical surface 5d centered on the axis NN is provided on the axial end of the inner peripheral surface of the cage 5, i.e., on the inner peripheral surface of one of the annular portions 5c in the illustrated example.

[0024] In the following description, the opening side of the cup-shaped outer joint member 2 in the axial direction (the right side in FIG. 1(A)) will be referred to as the "joint opening side," and the opposite side (the left side in FIG. 1(A)) will be referred to as the "joint inner side." To accurately indicate the inclination, curvature, and other shapes and configurations of the track grooves 7, 9, the term "ball track center line" will be used in this specification. Here, the ball track center line refers to the path traced by the center of a ball placed in the track groove as it moves along the track groove. Therefore, the inclination of the track groove is the same as the inclination of the ball track center line, and the arc-shaped or linear shape of the track groove is the same as the arc-shaped or linear shape of the ball track center line.

[0025] As shown in FIG. 1(A), the track grooves 7 of the outer joint member 2 have a ball track centerline X. Specifically, the track grooves 7 are composed of a first track groove portion 7a having an arc-shaped ball track centerline Xa and a second track groove portion 7b having a linear ball track centerline Xb. The center of curvature of the ball track centerline Xa of the first track groove portion 7a (i.e., the center of the sphere containing all of the ball track centerlines Xa) is offset axially by f toward the joint opening from the joint center O (the intersection of a plane P containing the centers of the eight balls 4 and the axis N-N when the operating angle is 0°). The ball track centerline Xa of the first track groove portion 7a and the ball track centerline Xb of the second track groove portion 7b are smoothly continuous. That is, the ball track centerline Xb of the second track groove portion 7b coincides with a tangent to the ball track centerline Xa of the first track groove portion 7a at the joint opening end.

[0026] The track grooves 9 of the inner joint member 3 have a ball track center line Y. Specifically, the track groove 9 is composed of a first track groove portion 9a having an arc-shaped ball track center line Ya and a second track groove portion 9b having a linear ball track center line Yb. The center of curvature of the ball track center line Ya of the first track groove portion 9a (i.e., the center of the sphere containing all the ball track center lines Ya) is offset in the axial direction by an amount f toward the joint rear side from the joint center O. The ball track center line Ya of the first track groove portion 9a and the ball track center line Yb of the second track groove portion 9b are smoothly connected. That is, the ball track center line Yb of the second track groove portion 9b coincides with a tangent to the ball track center line Ya of the first track groove portion 9a at the joint rear end.

[0027] The cross-sectional shape of the track grooves 7, 9 is formed into an elliptical shape or a Gothic arch shape. The track grooves 7, 9 and the ball 4 are in contact with each other at a contact angle (approximately 30° to 45°), which is what is called angular contact. Therefore, the ball 4 is in contact with the side surface of the track grooves 7, 9, which is slightly away from the groove bottom. The cross-sectional shape of the track grooves 7, 9 may be formed into an arc shape, and the track grooves 7, 9 and the ball 4 may be in so-called circular contact.

[0028] 2 and 3, the track grooves 7, 9 of the outer joint member 2 and the inner joint member 3 are inclined in the circumferential direction with respect to the axial direction (the direction of the joint axis NN). Adjacent track grooves in the circumferential direction are inclined in opposite directions with respect to the axial direction. Radially opposing track grooves 7, 9 are inclined in opposite directions with respect to the axial direction, and one ball 4 is disposed at each intersection of these grooves.

[0029] The track grooves 7 of the outer joint member 2 will be described in detail with reference to FIG. 2. The track grooves 7 of the outer joint member 2 are denoted by the reference symbols 7A and 7B depending on the inclination direction thereof. The reference symbol 7 is used to refer to the entire track groove of the outer joint member 2, with the reference symbol 7a denoting the first track groove portion and the reference symbol 7b denoting the second track groove portion. The reference symbols 7A and 7B are used to distinguish between track grooves with different inclination directions, with the reference symbols 7Aa and 7Ba denoting the first track groove portions and the reference symbols 7Ab and 7Bb denoting the second track groove portions, respectively. The track grooves of the inner joint member 3, which will be described later, are also denoted by the reference symbols in a similar manner.

[0030] 2(A), a plane M including the ball track center line X of the track groove 7A (more specifically, a plane including the ball track center line Xa of the first track groove portion 7Aa of the track groove 7A and its center of curvature) is inclined at an angle γ with respect to the joint axis NN. Furthermore, although not shown, a track groove 7B adjacent to the track groove 7A in the circumferential direction has a plane including the ball track center line X of the track groove 7B (more specifically, a plane including the ball track center line Xa of the first track groove portion 7Ba of the track groove 7B and its center of curvature) inclined at an angle γ with respect to the joint axis NN in the opposite direction to the inclination direction of the track groove 7A.

[0031] Next, the track grooves 9 of the inner joint member 3 will be described in detail with reference to Fig. 3. The track grooves 9 of the inner joint member 3 are denoted by the reference symbols 9A and 9B depending on the inclination direction thereof. As shown in Fig. 3(B) , a plane Q including the ball raceway center line Y of the track groove 9A (more specifically, a plane including the ball raceway center line Ya of the first track groove portion 9Aa of the track groove 9A and its center of curvature) is inclined by an angle γ with respect to the joint axis NN. Furthermore, although not shown, a track groove 9B adjacent to the track groove 9A in the circumferential direction has a plane Q including the ball raceway center line Y of the track groove 9B (more specifically, a plane including the ball raceway center line Ya of the first track groove portion 9Ba of the track groove 9B and its center of curvature) inclined by an angle γ with respect to the joint axis NN in the opposite direction to the inclination direction of the track groove 9A. When the operating angle is 0°, the ball raceway center line Y of each track groove 9 of the inner joint member 3 is formed in mirror symmetry with the ball raceway center line X (see Figure 1(a)) of the track groove 7 of the outer joint member 2 that faces it in the radial direction, with respect to a plane P that includes the joint center O and is perpendicular to the joint axis NN.

[0032] The track grooves 7A of the outer joint member 2 will be described in detail with reference to Fig. 4. Fig. 4 is a cross-sectional view of the track grooves 7A of Fig. 2(A) as viewed on a plane M including the ball raceway center line X. Therefore, strictly speaking, Fig. 4 is not a longitudinal cross-sectional view on a plane including the joint axis NN, but shows a cross-section inclined by an angle γ. Fig. 4 shows the track grooves 7A of the outer joint member 2, but track groove 7B has the same configuration as track groove 7A except that its inclination direction is opposite to that of track groove 7A, and therefore a description thereof will be omitted.

[0033] The track groove 7A consists of a first track groove portion 7Aa with an arc-shaped ball track centerline Xa whose center of curvature is offset axially from the joint center O, and a second track groove portion 7Ab with a linear ball track centerline Xb. The linear ball track centerline Xb of the second track groove portion 7Ab smoothly connects to the end of the ball track centerline Xa of the first track groove portion 7Aa on the joint opening side. In the illustrated example, the connection point A between the ball track centerlines Xa and Xb is located closer to the joint opening than the joint center O, so the linear ball track centerline Xb is inclined toward the joint axis NN (see Figure 1(A)) as it approaches the joint opening side. This ensures the effective track length at the maximum operating angle and prevents the wedge angle from becoming excessive. Figure 1(A) shows the track grooves 7 and 9 with an inclination angle γ of 0°.

[0034] As shown in FIG. 4, L denotes the line connecting the joint center O and the connection point A of the ball track center lines Xa and Xb. The joint axis N'-N' projected onto a plane M (see FIG. 2(A)) containing the ball track center line X of the track groove 7A is inclined by γ with respect to the joint axis NN, and the angle β' is defined as the angle between the line L and a perpendicular line K at the joint center O of the axis N'-N'. The perpendicular line K lies on a plane P that contains the joint center O when the operating angle is 0° and is perpendicular to the joint axis NN. Therefore, the angle β that the line L forms with the plane P that contains the joint center O when the operating angle is 0° and is perpendicular to the joint axis NN is expressed as sinβ = sinβ' × cosγ.

[0035] Similarly, the track grooves 9A will be described in detail with reference to Fig. 5 from a longitudinal cross section of the inner joint member 3. The longitudinal cross section of Fig. 5 is a cross section seen on a plane Q including the ball raceway center line Y of the track groove 9A in Fig. 3(B) described above. Therefore, as with Fig. 4, strictly speaking, it is not a longitudinal cross section on a plane including the joint axis NN, but shows a cross section inclined by an angle γ. Fig. 5 shows the track grooves 9A of the inner joint member 3, but the track groove 9B has the same configuration as the track groove 9A except that its inclination direction is opposite to that of the track groove 9A, and therefore description thereof will be omitted.

[0036] The track groove 9A consists of a first track groove portion 9Aa having an arc-shaped ball track centerline Ya with a center of curvature offset axially from the joint center O, and a second track groove portion 9Ab having a linear ball track centerline Yb. The linear ball track centerline Yb of the second track groove portion 9Ab smoothly connects to the end of the ball track centerline Ya of the first track groove portion 9Aa on the joint rear side. In the illustrated example, the connection point B of the ball track centerlines Ya and Yb is located closer to the joint rear than the joint center O, so the linear ball track centerline Yb is inclined to approach the joint axis NN (see Figure 1(A)) as it moves toward the joint rear side. This ensures the effective track length at the maximum operating angle and prevents the wedge angle from becoming excessive. As mentioned above, Figure 1(A) illustrates the track grooves 7 and 9 with an inclination angle γ of 0°.

[0037] As shown in FIG. 5, R denotes the line connecting the joint center O and the connection point B of the ball track center lines Ya, Yb. The joint axis N'-N' projected onto a plane Q (see FIG. 3(B)) containing the ball track center line Y of the track groove 9A is inclined by γ with respect to the joint axis NN, and the angle β' is defined as the angle between the line R and a perpendicular line K at the joint center O of the axis N'-N'. The perpendicular line K lies on a plane P that contains the joint center O when the operating angle is 0° and is perpendicular to the joint axis NN. Therefore, the angle β that the line R forms with the plane P that contains the joint center O when the operating angle is 0° and is perpendicular to the joint axis NN is expressed as sinβ = sinβ' × cosγ.

[0038] Next, we will explain the angle β that the lines L and R make with the plane P, which contains the joint center O and is perpendicular to the joint axis NN when the operating angle is 0°. When the operating angle is θ, the ball 4 moves by θ / 2 with respect to the plane that contains the joint center O and is perpendicular to the axis of the outer joint part 2 (or inner joint part 3). The angle β is determined by half the frequently used operating angle, and the range of the track grooves in which the ball 4 contacts within the frequently used operating angle range is determined. Here, we will define the frequently used operating angle. First, the common operating angle of a joint refers to the operating angle generated in the fixed constant velocity universal joint of the front driveshaft when the steering is in a straight-ahead position in a vehicle with one occupant on a horizontal, flat road. The common operating angle is selected and determined according to the design conditions of each vehicle model. The frequently used operating angle does not refer to the high operating angle that occurs when the vehicle, for example, turns right or left at an intersection, but rather to the operating angle that occurs in a fixed constant velocity universal joint when the vehicle travels on a continuously curved road, and is also determined according to the design conditions of each vehicle model, but is larger than the common angle. In this embodiment, the angle β is set in the range of 8° to 12°. This makes it possible to ensure the length of the track grooves and the joint strength of the outer joint member in particular, and to prevent the generation of abnormal noise, etc.

[0039] Due to the angle β, in Fig. 4, the connection point A between the ball track center line Xa of the first track groove portion 7Aa and the ball track center line Xb of the second track groove portion 7Ab is the center position of the ball when it moves to the furthest opening side along the axial direction at a frequently used operating angle. Similarly, in the inner joint member 3, in Fig. 5, the connection point B between the ball track center line Ya of the first track groove portion 9Aa and the ball track center line Yb of the second track groove portion 9Ab is the center position of the ball when it moves to the furthest rear side along the axial direction at a frequently used operating angle. Due to the setting in this manner, within a frequently used operating angle range, the ball 4 is positioned at 7Ba, 9Ba (see Figs. 2 and 3) which have an inclination direction opposite to that of the first track groove portions 7Aa, 9Aa of the outer joint member 2 and the inner joint member 3.

[0040] The overall configuration of the fixed type constant velocity universal joint 1 according to this embodiment is as described above. Next, a procedure for assembling the inner joint member 3 onto the inner periphery of the cage 5 will be described with reference to Figs.

[0041] First, as shown in FIG. 6 , with the axis of the inner joint member 3 and the axis of the cage 5 being approximately perpendicular to each other, a part of the inner joint member 3 is inserted into the inner periphery of the cage 5 from the joint opening side (the cylindrical surface 5d side). Then, one of the track grooves 9 (the track groove at the lower end in FIG. 6(A). This track groove is also referred to as a "track groove 90") of the inner joint member 3 is fitted into the annular portion 5c of the cage 5 on the joint opening side from the inner periphery side. In this embodiment, as shown in FIG. 6(B) , the axis of the inner joint member 3 is slightly inclined with respect to a direction perpendicular to the axis of the cage 5. Specifically, the axis of the inner joint member 3 is inclined approximately by the inclination angle γ of the track groove 9 (see FIG. 3(B)). As a result, the extending direction of the track groove 90 (the center line X of the ball raceway) is approximately perpendicular to the axial direction of the cage 5 and is arranged approximately parallel to the annular portion 5c of the cage 5.

[0042] Then, while rotating the inner joint member 3 counterclockwise in the drawing around the fitting portion C between the track groove 90 and the annular portion 5c of the cage 5 {see the arrow in FIG. 6(A)}, the inner joint member 3 is moved to the rear part of the inner circumference of the cage 5 (the rear side of the joint). Then, as shown in FIG. 7, the track groove 90 of the inner joint member 3 and a track groove that is 180 degrees out of phase with the track groove 90 {the track groove at the upper end in FIG. 7(A). This track groove is also referred to as "track groove 91"} are arranged on the inner circumference of the annular portion 5c of the cage 5.

[0043] At this time, as shown in Fig. 7(B), adjacent track grooves 9 of the inner joint member 3 are inclined in opposite directions relative to the axial direction, so that the circumferential width of the spherical portion 8 formed between adjacent track grooves 9 narrows toward one axial side or the other axial side. Therefore, the apparent outer diameter of this inner joint member 3 when viewed from the axial direction of the cage 5 (the direction perpendicular to the plane of the paper in Fig. 7(B)) is non-uniform. 10 , when the axis of the inner joint member 3 and the axis of the cage 5 are orthogonal to each other and the phase of the inner joint member 3 is adjusted so that two track grooves 90, 91 of the inner joint member 3 that are 180 degrees out of phase with each other face the cylindrical surface 5d of the inner circumferential surface of the cage 5, the apparent outer diameter D1 of the inner joint member 3 at a portion where the circumferential width of the spherical portion 8 is wide is larger than the apparent outer diameter D2 of the inner joint member 3 at a portion where the circumferential width of the spherical portion 8 is narrow (D1 > D2). In the illustrated example, the apparent maximum outer diameter (≈ D1) of the inner joint member 3 in the state shown in FIG. 10 is larger than the diameter E of the cylindrical surface 5d of the cage 5. In this case, if the inner joint member 3 is translated toward the rear of the joint in this state, the inner joint member 3 and the cage 5 will interfere with each other.

[0044] Therefore, as shown by arrow J in Fig. 8(A) , the inner joint member 3 is rotated around a central axis S (the vertical direction in Fig. 8(A) ) perpendicular to both the axis of the inner joint member 3 and the axis of the cage 5, so that the axis of the inner joint member 3 is inclined by an angle α with respect to a plane perpendicular to the axis of the cage 5. At this time, the two track grooves 90, 91 of the inner joint member 3, which are 180 degrees out of phase with each other, are maintained in a state facing the cylindrical surface 5d of the inner circumferential surface of the cage 5. This makes it possible to make the apparent maximum outer diameter D3 of the inner joint member 3, when viewed from the axial direction of the cage 5 (the direction perpendicular to the plane of the paper in Fig. 8(B) ), smaller than the diameter E of the cylindrical surface 5d of the cage 5. For example, by setting the angle α between the axis of the inner joint member 3 and the axis of the cage 5 to be three times or more the inclination angle γ with respect to the axis of the track groove 9, the apparent maximum outer diameter D3 of the inner joint member 3 can be made smaller than the diameter E of the cylindrical surface 5d of the cage 5. Furthermore, if the angle α is made too large, the apparent maximum outer diameter of the inner joint member 3 will instead become larger. Therefore, it is preferable to set the angle α so that the apparent maximum outer diameter of the inner joint member 3 is minimized.

[0045] In this state, as shown by arrow I in Fig. 9(A), the inner joint member 3 is moved toward the rear of the joint and rotated in the direction of arrow J' (the opposite direction to arrow J in Fig. 8(A)), whereby the spherical portion 8 of the inner joint member 3 and the spherical inner peripheral surface 13 of the cage 5 are fitted together. Thereafter, the inner joint member 3 is further rotated relative to the cage 5 to align the axial center of the inner joint member 3 with the axial center of the cage 5, thereby completing the assembly of the inner joint member and the cage 5.

[0046] As described above, even when the diameter E of the cylindrical surface 5d of the cage 5 is smaller than the apparent maximum outer diameter D1 of the inner joint member 3 when viewed in a direction perpendicular to the plane of the paper in Fig. 10, by inclining the axis of the inner joint member 3 with respect to a plane perpendicular to the axis of the cage 5 as shown in Fig. 8, the apparent maximum outer diameter D3 of the inner joint member 3 can be made smaller than the diameter E of the cylindrical surface 5d of the cage 5, and the inner joint member 3 can be incorporated into the inner periphery of the cage 5. Therefore, the diameter E of the cylindrical surface 5d of the cage 5 can be made smaller than the apparent maximum outer diameter D1 of the inner joint member 3 when viewed in a direction perpendicular to the plane of the paper in Fig. 9, and this ensures the radial thickness of the annular portion 5c of the cage 5, thereby maintaining the strength of the cage 5.

[0047] The fixed type constant velocity universal joint 1 according to this embodiment has the following configuration in addition to the above.

[0048] (1) Axial width W of the inner joint member and diameter D of the ball BALL Ratio of W / D BALL is 1.74 to 1.99. (2) The axial distance W2 between the end face of the inner joint member on the far side and the joint center and the ball diameter D BALL Ratio of W2 / D BALL is 0.99 to 1.13.

[0049] When the axial width W {see FIG. 3(B)} of the inner joint member 3 is increased, the spherical portion 8 extends in the axial direction. Therefore, even if the axial center of the inner joint member 3 is inclined with respect to a plane perpendicular to the axial center of the cage 5 as shown in FIG. 8, it may not be possible to make the apparent maximum outer diameter D3 of the inner joint member 3 smaller than the diameter E of the cylindrical surface 5d of the cage 5. In this case, it becomes necessary to increase the diameter of the cylindrical surface 5d of the cage 5, which leads to a decrease in the strength of the cage 5. Therefore, it is preferable to keep the axial width W of the inner joint member 3 equal to or less than a predetermined value. In particular, when the axial distance W2 between the joint innermost end face of the inner joint member 3 and the joint center O is larger than the axial distance W1 between the joint opening-side end face of the inner joint member 3 and the joint center O as in the present embodiment, it is preferable to keep the axial distance W2 between the joint innermost end face of the inner joint member 3 and the joint center O equal to or less than a predetermined value.

[0050] On the other hand, if the axial width W of the inner joint member 3 is too small, the track length becomes too short, making it difficult to ensure contact points between the balls 4 and the track grooves 7, 9 at a high operating angle, resulting in a significant deterioration in function at a high angle. Therefore, it is preferable that the axial width W of the inner joint member 3, in particular the axial distance W2 between the end face of the inner joint member 3 on the joint inner side and the joint center O, be equal to or greater than a predetermined value.

[0051] (3) Ball pitch circle diameter PCD BALL and ball diameter D BALL Ratio of PCD to BALL / D BALL is 3.89 to 4.48.

[0052] As shown in Figure 11, the pitch circle diameter PCD of the ball BALL is the pitch circle diameter between the centers of the plurality of balls 4 arranged on the joint center O, and more specifically, is the diameter of a sphere including the ball track center lines Xa and Ya of the first track groove portions 7a and 9a of all the track grooves 7 and 9. The fixed type constant velocity universal joint 1 of this embodiment has a ball diameter D BALL PCD: Pitch circle diameter of the ball based on the BALL Ratio of PCD BALL / D BALL is set in the range of 3.89 to 4.48. Fig. 11 shows a state in which the inclination angle γ of the track grooves 7 and 9 is set to 0°.

[0053] Ball diameter D BALL PCD: Pitch circle diameter of the ball based on the BALL Ratio of PCD BALL / D BALL If is less than 3.89, the ball pitch diameter PCD BALL Whereas the diameter of the ball is D BALL If the diameter D of the balls 4 becomes too large, the distance between the outer diameters of the balls 4 in the circumferential direction becomes close, and the circumferential width F of the spherical surface portion 8 between the track grooves (see FIG. 3(C)) and the cross-sectional area of ​​the pillar portion 5e of the cage 5 (see FIG. 1(B)) become small, making it impossible to ensure the strength of each part. BALL Ball pitch diameter PCD BALLIf the distance between the balls 4 and the balls 4 is too small, the load to be shared by each ball 4 increases, and it becomes impossible to ensure the strength of each part.

[0054] On the other hand, the diameter of the ball D BALL PCD: Pitch circle diameter of the ball based on the BALL Ratio of PCD BALL / D BALL If is greater than 4.48, the ball pitch diameter PCD BALL Whereas the diameter of the ball is D BALL If the diameter D of the ball is too small, the contact pressure between the track grooves 7, 9 and the ball 4 increases with respect to the input torque, and durability cannot be ensured. BALL Whereas, the pitch circle diameter of the ball is PCD BALL becomes too large, the outer diameter of the outer joint member 2 becomes large, and it becomes impossible to maintain compactness.

[0055] (4) The axial offset f between the joint center O and the center of curvature of the arc-shaped ball raceway center line and the ball pitch circle diameter PCD BALL Ratio of f / PCD BALL is less than or equal to 0.009.

[0056] 12 , in the present embodiment, the center of curvature of the ball track center line Xa of the first track groove portion 7a provided in the track groove 7 of the outer joint member 2 (hereinafter referred to as the "outer track center Oo1") and the center of curvature of the ball track center line Ya of the first track groove portion 9a provided in the track groove 9 of the inner joint member 3 (hereinafter referred to as the "inner track center Oi1") are offset in the axially opposite direction with respect to the joint center O (this axial offset amount is referred to as the "offset amount f"). Note that, in the present embodiment, the outer track center Oo1 is disposed closer to the joint opening and the inner track center Oi1 is disposed closer to the joint inner side with respect to the joint center O, but the outer track center Oo1 may be disposed closer to the joint inner side and the inner track center Oi1 may be disposed closer to the joint opening.

[0057] When the outer track center Oo1 and the inner track center Oi1 are offset as described above, the balls 4 generate a force pushing against the cage 5 during torque transmission. In this case, the spherical inner peripheral surface (spherical portion 6) of the outer joint member 2 contacts the spherical outer peripheral surface 12 of the cage 5, and the spherical outer peripheral surface (spherical portion 8) of the inner joint member 3 contacts the spherical inner peripheral surface 13 of the cage 5. This generates frictional forces at these contact points, resulting in energy losses commensurate with the frictional forces. However, if the outer track center Oo1 and the inner track center Oi1 are not intentionally offset from the joint center O, the offset directions of the outer track center Oo1 and the inner track center Oi1 from the joint center O become random, potentially resulting in inconsistent performance. Therefore, it is desirable to offset the outer track center Oo1 and the inner track center Oi1 axially opposite the joint center O at a level that does not cause practically significant energy loss. Therefore, focusing on an offset angle of 1°, the offset amount f and the ball pitch circle diameter PCD BALL Ratio of f / PCD BALL The upper limit of f / PCD was set to 0.009. On the other hand, focusing on the offset angle of 0.02° where the offset becomes significant, BALL The lower limit is set to 0.0002.

[0058] In the illustrated example, the center of curvature of the spherical portion 6 of the inner peripheral surface of the outer joint member 2, i.e., the center of curvature of the spherical outer peripheral surface 12 of the cage 5 (hereinafter referred to as the "cage outer spherical center Oc1"), and the center of curvature of the spherical portion 8 of the outer peripheral surface of the inner joint member 3, i.e., the center of curvature of the spherical inner peripheral surface 13 of the cage 5 (hereinafter referred to as the "cage inner spherical center Oc2"), both coincide with the joint center O. That is, the axial offset amount of the cage outer spherical center Oc1 and the cage inner spherical center Oc2 from the joint center O (hereinafter referred to as the "cage offset amount f2") is 0. In this case, the offset amount f is equal to the axial offset amount of the outer ring track center Oo1 and the inner ring track center Oi1 from the cage outer spherical center Oc1 and the cage inner spherical center Oc2 (hereinafter referred to as the "track offset amount f1"). In this way, by setting the cage offset amount f2 to 0, the radial thickness of the cage 5, more specifically, the radial distance between the spherical outer surface 12 and the spherical inner surface 13, becomes uniform, thereby ensuring the strength of the cage.

[0059] (5) Inlet spigot diameter D of outer joint member INLET and ball diameter D BALL Relative to D INLET / D BALL is 4.18~4.76.

[0060] In a fixed constant velocity universal joint of the crossed track groove type, the track grooves are inclined circumferentially with respect to the axis of the joint, and the inclination directions of adjacent track grooves in the circumferential direction are opposite to each other. Therefore, portions where the spherical width (the circumferential width of the spherical surface portion between the track grooves) is large and portions where it is small are provided between the track grooves on the open end side of the outer joint member.

[0061] As shown in Figure 13(B), the cage 5 is assembled to the inner periphery of the outer joint member 2 with the axis of the cage 5 and the axis of the outer joint member 2 perpendicular to each other. At this time, the cage 5 can be inserted from a position where the spherical width W4 of the outer joint member 2 is smaller than the window width W3 of the pocket 5a of the cage 5. Also, the inlet spigot diameter D of the outer joint member 2 shown in Figure 13(A) INLETmust be set to be larger than the window height H determined by the window length W5 of the cage 5 shown in FIG. 13(C).

[0062] As shown in Figure 13(A), the inlet spigot diameter D INLET and ball diameter D BALL Relative to D INLET / D BALL If the ratio D is smaller than 4.18, it is necessary to increase the window length W5 of the cage 5 (reduce the window height H) to enable the cage 5 to be inserted into the outer joint member 2. However, since the circumferential length of the cage pillar portion 5e becomes small, it becomes difficult to ensure the strength of the cage 5. On the other hand, INLET / D BALL If ρ is greater than 4.76, when the spherical inner peripheral surface of the outer joint member 2 and the spherical outer peripheral surface 12 of the cage 5 come into contact with each other at a high operating angle, the contact area becomes smaller, which leads to an increase in surface pressure and a decrease in durability.

[0063] In the fixed type constant velocity universal joint 1 of this embodiment, the inlet spigot diameter D INLET and ball diameter D BALL Relative to D INLET / D BALL is set in the range of 4.18 to 4.76, thereby ensuring the strength of the cage 5 and suppressing the contact pressure between the spherical inner peripheral surface of the outer joint member 2 and the spherical outer peripheral surface 12 of the cage 5 at a high operating angle, thereby ensuring durability.

[0064] (6) The inclination angle γ of the plane including the ball raceway center line of the first track groove portion and the joint center O with respect to the joint axis NN is 4° to 8°.

[0065] If the inclination angle γ of the first track groove portions 7a, 9a with respect to the axial direction (see Figures 2(A) and 3(B)) is less than 4°, the force with which the crossing angle (2γ) controls the balls becomes small, resulting in unavoidable malfunction of the joint and a decrease in constant velocity. On the other hand, if the inclination angle γ of the first track groove portions 7a, 9a with respect to the axial direction is greater than 8°, the amount of circumferential movement of the balls when an operating angle is taken becomes large, and the circumferential thickness of the pillar portions 5e of the cage 5 (see Figure 1(B)) and the circumferential width F of the spherical portion 8 of the inner joint member 3 (see Figure 3(C)) become insufficient, making it impossible to ensure sufficient strength.

[0066] In the fixed type constant velocity universal joint 1 of this embodiment, the inclination angle γ of the first track groove portions 7a, 9a with respect to the axial direction is set in the range of 4° to 8°. This prevents inevitable malfunctions and deterioration of constant velocity performance of the joint, ensures the circumferential thickness of the cage pillar portions and the thickness of the spherical portion of the inner joint member, and ensures joint strength.

[0067] (7) Outer diameter D of outer joint member OUTER and ball pitch circle diameter PCD BALL Relative to D OUTER / PCD BALL is 1.34 to 1.44.

[0068] Outer diameter D of outer joint member 2 OUTER and ball pitch circle diameter PCD BALL The outer diameter D of the outer joint member is shown in Fig. 14. OUTER and ball pitch circle diameter PCD BALL Relative to D OUTER / PCD BALL If the ratio D is smaller than 1.34, the thickness of the outer joint member 2 becomes too small, making it difficult to ensure the strength of the outer joint member 2. OUTER / PCD BALL If the ratio is greater than 1.44, the thickness of the outer joint member 2 becomes too large, which increases the weight and makes it difficult to achieve a lightweight and compact design.

[0069] The fixed type constant velocity universal joint 1 of this embodiment has an outer diameter D OUTER and ball pitch circle diameter PCD BALL Relative to DOUTER / PCD BALL is set in the range of 1.34 to 1.44, thereby ensuring the strength of the outer joint member 2 and making it lightweight and compact.

[0070] The present invention is not limited to the above-described embodiment. Other embodiments of the present invention will be described below, but redundant description of the same points as those in the above-described embodiment will be omitted.

[0071] In the above embodiment, the track grooves 7, 9 are formed of the first track groove portions 7a, 9a having arcuate ball track center lines Xa, Ya and the second track groove portions 7b, 9b having linear ball track center lines Xb, Yb. However, the present invention is not limited to this. For example, the track grooves 7, 9 may be formed only with the first track groove portions having arcuate ball track center lines Xa, Ya.

[0072] In the above-described embodiment, the cage offset amount f2 is 0, and the offset amount f and the track offset amount f1 are equal. However, this is not limiting. For example, in the embodiment shown in FIG. 15, the track offset amount f1 is set to 0 by aligning the outer ring track center Oo1 with the cage outer spherical surface center Oc1 and the inner ring track center Oi1 with the cage inner spherical surface center Oc2. In this case, the offset amount f and the cage offset amount f2 are equal. By setting the track offset amount f1 to 0, the depths of the first track groove portions 7a, 9a can be made uniform, thereby preventing a decrease in durability due to the balls 4 riding up onto the first track groove portions 7a, 9a. Note that FIG. 15 illustrates a state in which the inclination angle γ of the track grooves 7, 9 is 0°.

[0073] Alternatively, as shown in Fig. 16, both a track offset amount f1 and a cage offset amount f2 may be applied. In this case, the outer ring track center Oo1 and the cage outer spherical surface center Oc1 are offset in the same axial direction (towards the joint opening in the illustrated example) with respect to the joint center O, and the inner ring track center Oi1 and the cage inner spherical surface center Oc2 are offset in the same axial direction (towards the rear of the joint in the illustrated example) with respect to the joint center O. The sum of the track offset amount f1 and the cage offset amount f2 is the offset amount f (f = f1 + f2). Note that Fig. 16 shows a state in which the inclination angle γ of the track grooves 7, 9 is 0°.

[0074] Furthermore, if no malfunction of the joint occurs, both the track offset amount f1 and the cage offset amount f2 may be set to 0, and the offset amount f may be set to 0.

[0075] The present invention is not limited to the above-described embodiments, and can of course be embodied in various other forms without departing from the spirit of the present invention. The scope of the present invention is indicated by the claims, and further includes the equivalent meanings set forth in the claims, and all modifications within the scope of the claims. [Explanation of symbols]

[0076] 1 Fixed constant velocity universal joint 2 Outer joint member 3 Inner joint member 4 balls 5 cages 5d cylindrical surface 6 Spherical part 7 Track groove 7a first track groove portion 7b Second track groove portion 8 Spherical part 9 Track groove 9a first track groove portion 9b second track groove portion 12 Spherical outer surface 13 Spherical inner surface D1, D2, D3 Apparent outer diameter of inner joint member E diameter of the cylindrical surface of the cage O Joint center X: Center line of the ball raceway of the track groove of the outer joint member Xa: Center line of the ball raceway of the first track groove Xb: Center line of the ball raceway of the second track groove Y Center line of ball raceway of track groove of inner joint member Ya: Center line of the ball raceway of the first track groove Yb: Center line of the ball raceway of the second track groove Oo1 Outer track center Oi1 Inner track center Oc1 Cage outer sphere center Oc2 Cage inner sphere center f offset amount f1 Track offset amount f2 Cage offset amount

Claims

1. a fixed type constant velocity universal joint comprising: an outer joint member having eight track grooves formed on a spherical inner peripheral surface; an inner joint member having eight track grooves formed on a spherical outer peripheral surface; eight balls interposed between the track grooves of the outer joint member and the track grooves of the inner joint member to transmit torque; a spherical outer peripheral surface that fits with the spherical inner peripheral surface of the outer joint member; a spherical inner peripheral surface that fits with the spherical outer peripheral surface of the inner joint member; eight pockets that hold the balls one by one; and a cage having a cylindrical surface provided at an axial end of the inner peripheral surface, the outer joint member has a first track groove portion having an arc-shaped ball raceway center line (Xa), and the inner joint member has a first track groove portion having an arc-shaped ball raceway center line (Ya), a plane including a ball raceway center line (Xa) of a first track groove portion of each track groove of the outer joint member and a plane including a ball raceway center line (Xa) of the first track groove portion of an adjacent track groove are inclined by an angle γ on opposite sides with respect to the axial direction, a plane including a ball raceway center line (Ya) of a first track groove portion of each track groove of the inner joint member and a plane including a ball raceway center line (Ya) of the first track groove portion of an adjacent track groove are inclined by an angle γ toward opposite sides with respect to an axial direction, a plane including a ball raceway center line (Xa) of a first track groove portion of the track groove of the outer joint member and a plane radially opposing thereto and including a ball raceway center line (Ya) of the first track groove portion of the track groove of the inner joint member are inclined toward opposite sides with respect to the axial direction, The diameter (E) of the cylindrical surface of the cage is is smaller than the apparent maximum outer diameter (D1) of the inner joint member when the inner joint member is viewed from the axial direction of the cage in a state in which the axis of the inner joint member and the axis of the cage are perpendicular to each other and the two track grooves of the inner joint member that are out of phase with each other by 180 degrees are opposed to the inner circumferential surface of the cage, and a fixed type constant velocity universal joint, wherein the apparent maximum outer diameter (D3) of the inner joint member is larger than the apparent maximum outer diameter (D3) of the inner joint member when the inner joint member is viewed from the axial direction of the cage with the axis of the inner joint member inclined by an angle α with respect to a plane perpendicular to the axis of the cage and the two track grooves of the inner joint member that are 180 degrees out of phase with each other are opposed to the inner circumferential surface of the cage.

2. The axial width W of the inner joint member and the diameter D of the ball ＢＡＬＬ Ratio of W / D ＢＡＬＬ 2. The fixed type constant velocity universal joint according to claim 1, wherein is 1.74 to 1.

99.

3. an axial distance W2 between an end face on one axial side of the inner joint member and the joint center is larger than an axial distance W1 between an end face on one axial side of the inner joint member and the joint center, The axial distance W2 between the other axial end face of the inner joint member and the joint center and the diameter D of the ball ＢＡＬＬ The ratio W2 / D ＢＡＬＬ 3. The fixed type constant velocity universal joint according to claim 1, wherein is 0.99 to 1.

13.

4. 3. A fixed type constant velocity universal joint according to claim 1, wherein said angle α is at least three times as large as said angle γ.

5. 3. The fixed type constant velocity universal joint according to claim 1, wherein the angle γ is 4° to 8°.

6. The pitch circle diameter (PCD) of the ball ＢＡＬＬ ) and the diameter of the ball (D ＢＡＬＬ ) PCD ratio ＢＡＬＬ / D ＢＡＬＬ 3. The fixed type constant velocity universal joint according to claim 1 or 2, wherein is 3.89 to 4.

48.

7. Each track groove of the outer joint member is a second track groove portion that is continuous with one axial end of the first track groove portion and has a linear ball raceway center line (Xb); a connection point (A) between a ball raceway center line (Xa) of the first track groove portion and a ball raceway center line (Xb) of the second track groove portion is located on one axial side of a joint center (O), a ball raceway center line (Xb) of the second track groove portion (7b) is inclined so as to approach the axis of the outer joint member toward one axial side, Each track groove of the inner joint member is a second track groove portion that is continuous with the other axial end of the first track groove portion and has a linear ball raceway center line (Yb); a connection point (B) between a ball raceway center line (Ya) of the first track groove portion and a ball raceway center line (Yb) of the second track groove portion is located on the other axial side of the joint center (O), 3. The fixed type constant velocity universal joint according to claim 1, wherein a ball raceway center line (Yb) of the second track groove portion is inclined so as to approach the axis of the inner joint member toward the other axial side.

Images