Fixed type constant velocity universal joint

Abstract

To enable light weight and compactification while securing high efficiency, strength and durability in a track groove intersection type fixed type constant velocity universal joint.SOLUTION: A ratio PCDBALL / DBALL between a pitch circle diameter PCDBALL of each of a plurality of balls 4 and a diameter DBALL of the ball 4 is set in a range of 3.89-4.48. When an axial offset amount between a joint center O and a curvature center Oo1 of an arc ball raceway central line Xa of a first track groove part 7a is defined as f, an upper limit value of a ratio f / PCDBALL between the offset amount f and the pitch circle diameter PCDBALL of the ball 4 is set to 0.009.SELECTED DRAWING: Figure 7

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 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. 10 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 that holds the balls 104. Eight balls 104 that transmit torque are incorporated in arc-shaped track grooves 107, 109 that extend axially in the outer joint member 102 and the inner joint member 103, and are held by the cage 105.

[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. 11 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 that holds the balls 154. Eight balls 154 that transmit torque are incorporated in crossed arc-shaped track grooves 157, 159 that extend axially in the outer joint member 152 and the inner joint member 153, and are held by the cage 155.

[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] Various means have been considered for making the eight-ball type Rzeppa-type fixed constant velocity universal joint as shown in Patent Document 1 more compact, but these cannot be applied because the structure is different from that of the track groove crossing type fixed constant velocity universal joint as shown in Patent Document 2 above.

[0008] Furthermore, with regard to fixed constant velocity universal joints of the track groove intersection type, Patent Document 3 considers increasing efficiency, and Patent Document 4 considers increasing angle, but no attention is paid to the issue of making them lightweight and compact while ensuring high efficiency, strength, and durability.

[0009] In view of the above problems, the present invention aims to provide a fixed type constant velocity universal joint of the track groove intersection type that is lightweight and compact while ensuring high efficiency, strength, and durability. [Means for solving the problem]

[0010] As technical means for achieving the above-mentioned object, the present invention provides a fixed type constant velocity universal joint including: an outer joint member having a plurality of track grooves formed on its spherical inner peripheral surface extending in the axial direction and having an open side and a deep side spaced apart in the axial direction; an inner joint member having a plurality of track grooves formed on its spherical outer peripheral surface forming pairs with the track grooves of the outer joint member; a plurality of balls interposed between the track grooves of the outer joint member and the track grooves of the inner joint member to transmit torque; and a cage for holding the balls and having a spherical outer peripheral surface and a spherical inner peripheral surface that fits with the spherical inner peripheral surface of the outer joint member and the spherical outer peripheral surface of the inner joint member, wherein the track grooves of the outer joint member comprise a first track groove portion 7a located on the deep side and a second track groove portion 7b located on the open side, and the first track groove portion 7a has an arc-shaped ball raceway center line Xa having a center of curvature that is offset in the axial direction with respect to a joint center O, and the cage has a radius of curvature that is greater than or equal to the radius of curvature of the ball raceway center line Xa and the joint center O. a plane M inclined with respect to the joint axis NN, and the inclination directions are opposite to each other in the first track groove portions 7a adjacent to each other in the circumferential direction; when a ball track center line Xb of the second track groove portion 7b is projected onto the plane M, the ball track center line Xb has a straight line portion, and this straight line portion is formed to be inclined so as to approach the joint axis NN as it approaches the opening side; an end A of the ball track center line Xa of the first track groove portion 7a is located on the opening side of the joint center O, and this end A is connected to the ball track center line Xb of the second track groove portion 7b; a ball track center line Y of the track groove of the inner joint member is formed as a mirror image of the ball track center line X of the mating track groove of the outer joint member, with respect to a plane P which includes the joint center O and is perpendicular to the joint axis NN when the operating angle is 0°; BALL and the diameter of the ball D BALL Ratio of PCD to BALL / D BALL is set in the range of 3.89 to 4.48, and the axial offset amount between the joint center O and the center of curvature of the arc-shaped ball raceway center line Xa of the first track groove portion 7a is set to f, the relationship between the offset amount f and the pitch circle diameter PCD of the ball BALLRatio of f / PCD BALL The upper limit value of is set to 0.009. With the above configuration, it is possible to realize a fixed type constant velocity universal joint of the track groove crossing type that is lightweight and compact while ensuring high efficiency, strength, and durability.

[0011] In the above-described fixed type constant velocity universal joint, for example, the spherical outer peripheral surface of the cage can have a center of curvature Oc1 that is not offset in the axial direction from the joint center O, and the ball raceway center line Xa of the first track groove portion 7a can have a center of curvature Oo1 that is offset in the axial direction from the center of curvature Oc1 of the spherical outer peripheral surface of the cage.

[0012] In the above-described fixed type constant velocity universal joint, the spherical outer peripheral surface of the cage can have a center of curvature Oc1 that is offset in the axial direction from the joint center O, and the ball raceway center line Xa of the first track groove portion 7a can have a center of curvature Oo1 that is not offset in the axial direction from the center of curvature Oc1 of the spherical outer peripheral surface of the cage.

[0013] Furthermore, in the above-described fixed type constant velocity universal joint, the spherical outer peripheral surface of the cage can have a center of curvature Oc1 that is offset in the axial direction from the joint center O, and the ball raceway center line Xa of the first track groove portion 7a can have a center of curvature Oo1 that is offset in the axial direction from the center of curvature Oc1 of the spherical outer peripheral surface of the cage.

[0014] Specifically, the inclination angle γ of the plane M including the ball raceway center line Xa of the first track groove portion 7a and the joint center O with respect to the joint axis NN is set in the range of 4° to 8°. This prevents inevitable malfunctions and deterioration of constant velocity of the joint, ensures the circumferential thickness of the cage pillar portion and the thickness of the spherical portion of the inner joint member, and ensures joint strength.

[0015] The angle β that a straight line L that connects an end A on the opening side of the ball raceway center line Xa of the first track groove portion 7a and the joint center O makes with a plane P that includes the joint center O and is perpendicular to the joint axis NN 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, particularly of the outer joint member, and to prevent the generation of abnormal noise.

[0016] By setting the number of balls to eight or more, it is possible to realize a lightweight, compact, and highly efficient fixed-type constant velocity universal joint. [Effects of the Invention]

[0017] According to the present invention, it is possible to realize a fixed type constant velocity universal joint of the track groove crossing type that is lightweight and compact while ensuring high efficiency, strength, and durability. [Brief explanation of the drawings]

[0018] [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] FIG. 2 is an enlarged partial vertical cross-sectional view of the fixed type constant velocity universal joint of FIG. 1(A). [Figure 7] FIG. 2 is an enlarged partial vertical cross-sectional view of the fixed type constant velocity universal joint of FIG. 1(A). [Figure 8] 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 9] 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 10] FIG. 1A is a longitudinal 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 11] FIG. 1A is a longitudinal 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

[0019] An embodiment of the present invention will be described with reference to the drawings.

[0020] 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.

[0021] 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.

[0022] 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.

[0023] 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.

[0024] 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.

[0025] 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.

[0026] 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.

[0027] 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.

[0028] 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.

[0029] 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.

[0030] 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.

[0031] 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°.

[0032] 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.

[0033] 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.

[0034] 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°.

[0035] 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.

[0036] 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.

[0037] 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.

[0038] The overall configuration of the fixed type constant velocity universal joint 1 according to this embodiment is as described above. Next, the matters taken into consideration in the process of arriving at the characteristic configuration of the fixed type constant velocity universal joint 1 according to this embodiment are as follows. <Considerations> (A) When a fixed constant velocity universal joint is used as the front drive shaft of an automobile, a maximum operating angle greater than the wheel turning angle is required, and generally the operating angle required for a fixed constant velocity universal joint is 40° or greater. (B) The function of a constant velocity universal joint is based on the pitch circle diameter (PCD) of the balls of the constant velocity universal joint. BALL and ball diameter D BALL is determined by. (C) In a fixed constant velocity universal joint of the track groove crossing type, in which the track grooves are inclined circumferentially with respect to the axis NN of the joint and the inclination directions are opposite to each other for adjacent track grooves in the circumferential direction, a special dimension setting is required as a result of examining the function with a focus on achieving lightweight and compactness while ensuring high efficiency, strength, and durability.

[0039] The fixed type constant velocity universal joint 1 according to this embodiment has the following characteristic configuration. (1) Ball pitch circle diameter PCD BALL and ball diameter D BALL Ratio of PCD to BALL / D BALL is set in the range of 3.89 to 4.48. (2) The first track groove portion has an arc-shaped ball raceway centerline with a curvature center offset in the axial direction from the joint center O, and the axial offset amount f between the joint center O and the curvature center of the arc-shaped ball raceway centerline and the ball pitch circle diameter PCD BALL Ratio of f / PCD BALL The upper limit value is set to 0.009 (when the offset is applied only to the track groove). Also, as an advantageous configuration, (3) 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 set in the range of 4° to 8°. (4) The angle β formed by the straight line connecting the end of the ball track center line of the first track groove portion and the joint center O with a plane P that includes the joint center O and is perpendicular to the joint axis NN is set in the range of 8° to 12°.

[0040] The characteristic features (1) to (4) of this embodiment will be described below with reference to FIGS. 1 to 7 as appropriate.

[0041] (1) Ball pitch circle diameter PCD BALL and ball diameter D BALL Ratio of PCD to BALL / D BALL Regarding setting the range of 3.89 to 4.48 As shown in Figure 6, the pitch circle diameter PCD of the ball BALL is the pitch circle diameter connecting the centers of the balls 4 arranged on the joint center O. The ball diameter D BALL is the ball diameter D BALL 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.

[0042] <ratio PCD BALL / D BALL Setting range study results> 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 Ball diameter D BALL If the ball diameter D becomes too large, the circumferential distance between the outer diameters of the balls 4 becomes close, and the thickness of the spherical portion between the track grooves (see F in Fig. 3(C)) and the cross-sectional area of ​​the cage pillar portion (see 5e in 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. On the other hand, the ball diameter 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 Ball diameter D BALL If the ball diameter D becomes too small, the contact pressure between the track grooves 7, 9 and the balls 4 becomes large relative 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.

[0043] (2) The first track groove portion has an arc-shaped ball raceway centerline with a curvature center offset in the axial direction from the joint center O, and the axial offset amount f between the joint center O and the curvature center of the arc-shaped ball raceway centerline and the ball pitch circle diameter PCD BALL Ratio of f / PCD BALL Regarding setting the upper limit to 0.009 (when offset is applied only to the track groove) As shown in FIG. 7 , in this embodiment, the center of curvature of the ball raceway 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 raceway 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 this embodiment, the outer track center Oo1 is disposed on the opening side and the inner track center Oi1 is disposed on the rear side with respect to the joint center O, but the outer track center Oo1 may be disposed on the rear side and the inner track center Oi1 on the opening side with respect to the joint center O. FIG. 7 illustrates a state in which the inclination angle γ of the track grooves 7, 9 is 0°.

[0044] <ratio f / PCD BALL Setting range study results> 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, contact occurs between the spherical inner peripheral surface (spherical portion 6) of the outer joint member 2 and the spherical outer peripheral surface 12 of the cage 5, and between the spherical outer peripheral surface (spherical portion 8) of the inner joint member 3 and the spherical inner peripheral surface 13 of the cage 5. Friction occurs at these contact points, resulting in energy loss commensurate with the friction force. 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.

[0045] 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.

[0046] (3) Regarding setting the inclination angle γ of the plane including the ball raceway center line of the first track groove portion and the joint center O to the joint axis NN in the range of 4° to 8° The tilt angle γ is as shown in FIGS. 2(A) and 3(B). <Results of study on the setting range of the tilt angle γ> If the inclination angle γ is less than 4°, the force with which the crossing angle (2γ) controls the ball will be small, resulting in unavoidable malfunction of the joint and a decrease in uniform velocity. On the other hand, if the inclination angle γ 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 column portion of the cage [see 5e in Fig. 1(B)] and the thickness of the spherical portion of the inner joint member [see F in Fig. 3(C)] become insufficient, making it impossible to ensure sufficient strength.

[0047] In the fixed type constant velocity universal joint 1 of this embodiment, the inclination angle γ 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 portion and the thickness of the spherical portion of the inner joint member, and ensures joint strength.

[0048] (4) The angle β formed by the line connecting the end of the ball raceway center line of the first track groove portion and the joint center O with the plane P that includes the joint center O and is perpendicular to the joint axis NN is set in the range of 8° to 12°. The angle β is as shown in Figures 4 and 5. The angle β that a straight line connecting the end of the ball raceway center line of the first track groove portion and the joint center O forms with a plane P that includes the joint center O and is perpendicular to the joint axis NN is the angle β formed by the connection point (ends A and B) of the arc-shaped ball raceway center line of the first track groove portion and the linear ball raceway center line of the second track groove portion.

[0049] To achieve lightweight and compact design while ensuring the maximum operating angle (40° or more) corresponding to the required wheel turning angle and strength, it is necessary to ensure the length of the track grooves and reduce the force pushing out the balls at high operating angles. In this case, it is useful to provide the track grooves 7, 9 of the outer joint member 2 and the inner joint member 3 with the first track groove portions 7a, 9a having the arc-shaped ball raceway center lines Xa, Ya described above and the second track groove portions 7b, 9b having linear ball raceway center lines Xb, Yb to ensure the length of the track grooves 7, 9. However, the issues described below must be considered.

[0050] <Results of study on the setting range of angle β> If the angle β formed by the connection points (ends A and B) of the arc-shaped ball track center lines Xa, Ya of the first track groove portions 7a, 9a and the linear ball track center lines Xb, Yb of the second track groove portions 7b, 9b is smaller than 8°, the angle between the ball 4 and the track grooves 7, 9 of the outer joint member 2 and the inner joint member 3 at a high operating angle becomes large, and the force pushing out the ball 4 also increases accordingly, making it difficult to ensure strength. On the other hand, if the angle β is greater than 12°, it is particularly difficult to ensure the length of the track grooves 7 of the outer joint member 2, and therefore there will be no contact points between the balls 4 and the track grooves 7 at high operating angles. This raises concerns about an increase in the load distribution on the balls 4 in other rotational phases and the generation of abnormal noise when the balls 4 move in and out of the ends of the track grooves 7.

[0051] In the fixed type constant velocity universal joint 1 of this embodiment, the angle β that the straight line connecting the end of the ball raceway center line of the first track groove portion and the joint center O makes with a plane P that includes the joint center O and is perpendicular to the joint axis NN 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, particularly of the outer joint member, and to prevent the generation of abnormal noise.

[0052] A fixed type constant velocity universal joint according to a second embodiment of the present invention will be described with reference to Figure 8. The fixed type constant velocity universal joint according to this embodiment differs from the fixed type constant velocity universal joint according to the first embodiment described above in that the track offset amount f1 is set to 0 and a cage offset amount f2 is added. The overall configuration and its effects shown in Figures 1 to 6 in the first embodiment described above are also the same for the fixed type constant velocity universal joint according to this embodiment, and so they apply mutatis mutandis. Portions having the same functions as those of the fixed type constant velocity joint according to the first embodiment will be given the same reference numerals, and only the main points will be described.

[0053] The fixed type constant velocity universal joint according to the second embodiment has the following characteristic configuration. (1) Ball pitch circle diameter PCD BALL and ball diameter D BALL Ratio of PCD to BALL / D BALL is set in the range of 3.89 to 4.48. The characteristic configuration (1) is the same as that of the fixed type constant velocity universal joint according to the first embodiment, and therefore the above content applies mutatis mutandis. (2') Offset amount f (= cage offset amount f2) and ball pitch circle diameter PCD BALL Ratio of f / PCD BALL The upper limit value is set to 0.009 (when the track offset amount f1 is set to 0). Also, as an advantageous configuration, (3) 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 set in the range of 4° to 8°. Since this characteristic configuration (4) is the same as that of the fixed type constant velocity universal joint according to the first embodiment, the above content applies mutatis mutandis. (4) The angle β that the straight line connecting the end of the ball raceway center line of the first track groove portion and the joint center O makes with a plane P that includes the joint center O and is perpendicular to the joint axis NN is set in the range of 8° to 12°. Since this characteristic configuration (4) is the same as that of the fixed type constant velocity universal joint according to the first embodiment, the above content applies mutatis mutandis.

[0054] As shown in FIG. 8 , the center of curvature Oc1 of the spherical outer peripheral surface 12 of the cage 5 of the fixed type constant velocity universal joint 1 of this embodiment and the center of curvature Oc2 of the spherical inner peripheral surface 13 are offset by equal amounts on opposite axial sides with respect to the joint center O. In this case, the center of curvature Oo1 of the ball raceway center line Xa of the first track groove portion 7a of the outer joint member 2 coincides with the center of curvature Oc1 of the spherical outer peripheral surface 12 of the cage 5, and the center of curvature Oi1 of the ball raceway center line Ya of the first track groove portion 9a of the inner joint member 3 coincides with the center of curvature Oc2 of the spherical inner peripheral surface 13 of the cage 5. That is, the track offset amount f1 is 0, and the offset amount f and the cage offset amount f2 are equal. In this way, 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 caused by the balls 4 riding up onto the first track groove portions 7a, 9a. In the present embodiment, the center of curvature Oc1 is disposed on the opening side and the center of curvature Oc2 is disposed on the rear side with respect to the joint center O, but conversely, the center of curvature Oc1 may be disposed on the rear side and the center of curvature Oc2 may be disposed on the opening side with respect to the joint center O. Fig. 8 illustrates a state in which the inclination angle γ of the track grooves 7 and 9 is 0°.

[0055] A fixed constant velocity universal joint according to a third embodiment of the present invention will be described with reference to FIGS. 9(A) and 9(B). FIG. 9(B) is an enlarged view of a portion T in FIG. 9(A). The fixed constant velocity universal joint according to this embodiment is provided with both a track offset amount f1 and a cage offset amount f2. The outer ring track center Oo1 and the cage outer spherical surface center Oc1 are offset in the same axial direction (toward the opening in the illustrated example) from 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 (toward the rear in the illustrated example) from 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). The overall configuration and effects thereof shown in FIGS. 1 to 5 of the first embodiment described above are also applicable to the fixed constant velocity universal joint according to this embodiment, and therefore apply mutatis mutandis. Portions having the same functions as those of the fixed constant velocity joint according to the first embodiment are designated by the same reference numerals, and only the essential points will be described.

[0056] The fixed type constant velocity universal joint according to the third embodiment has the following characteristic configuration. (1) Ball pitch circle diameter PCD BALL and ball diameter D BALL Ratio of PCD to BALL / D BALL is set in the range of 3.89 to 4.48. The characteristic configuration (1) is the same as that of the fixed type constant velocity universal joint according to the first embodiment, and therefore the above content applies mutatis mutandis. (2") Offset amount f (= track offset amount f1 + cage offset amount f2) and ball pitch circle diameter PCD BALL Ratio of f / PCD BALL Set the upper limit to 0.009. Also, as an advantageous configuration, (3) 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 set in the range of 4° to 8°. Since this characteristic configuration (4) is the same as that of the fixed type constant velocity universal joint according to the first embodiment, the above content applies mutatis mutandis. (4) The angle β that the straight line connecting the end of the ball raceway center line of the first track groove portion and the joint center O makes with a plane P that includes the joint center O and is perpendicular to the joint axis NN is set in the range of 8° to 12°. Since this characteristic configuration (4) is the same as that of the fixed type constant velocity universal joint according to the first embodiment, the above content applies mutatis mutandis.

[0057] As shown in FIG. 9 , in the fixed type constant velocity universal joint 1 of this embodiment, the center of curvature Oc1 of the spherical outer peripheral surface 12 of the cage 5 and the center of curvature Oc2 of the spherical inner peripheral surface 13 are offset by equal amounts on opposite axial sides with respect to the joint center O. The center of curvature Oo1 of the ball raceway center line Xa of the first track groove portion 7a of the outer joint member 2 is offset axially toward the opening side with respect to the center of curvature Oc1 of the spherical outer peripheral surface 12 of the cage 5. The offsets of the center of curvature Oc1 of the spherical outer peripheral surface 12 of the cage 5 and the center of curvature Oo1 of the arc-shaped ball raceway center line Xa of the first track groove portion 7a with respect to the joint center O are imparted in the same direction. The center of curvature Oi1 of the ball raceway center line Ya of the first track groove portion 9a of the inner joint member 3 is offset axially toward the back side with respect to the center of curvature Oc2 of the spherical inner peripheral surface 13 of the cage 5. The center of curvature Oc2 of the spherical inner peripheral surface 13 of the cage 5 and the center of curvature Oi1 of the arc-shaped ball raceway center line Ya of the first track groove portion 9a are offset in the same direction relative to the joint center O. The center of curvature Oc1 of the spherical outer peripheral surface 12 of the cage 5 is also the center of curvature of the spherical inner peripheral surface 6 of the outer joint member 2, and the center of curvature Oc2 of the spherical inner peripheral surface 13 of the cage 5 is also the center of curvature of the spherical outer peripheral surface 8 of the inner joint member 3. Figure 9 shows a state where the inclination angle γ of the track grooves 7, 9 is 0°.

[0058] In this embodiment, the cage offset amount f2 and the pitch circle diameter PCD of the ball BALL The ratio of f2 / PCD BALL is set to 0.0045, and the track offset amount f1 and ball pitch circle diameter PCD BALL The ratio of f1 / PCD BALLis set to 0.0045. Note that, in this embodiment, the centers of curvature Oo1 and Oc1 are disposed on the opening side and the centers of curvature Oi1 and Oc2 are disposed on the rear side with respect to the joint center O, but conversely, the centers of curvature Oo1 and Oc1 may be disposed on the rear side with respect to the joint center O, and the centers of curvature Oi1 and Oc2 may be disposed on the opening side. Also, although the example has been given in which the offset amount f is divided equally between the track offset amount f1 and the cage offset amount f2, the offset amount f may be divided differently between the track offset amount f1 and the cage offset amount f2.

[0059] The fixed type constant velocity universal joint 1 according to the embodiment described above includes the characteristic configurations (1), (2), (2'), (2"), (3), and (4) described above, and therefore, in a track groove crossing type fixed type constant velocity universal joint in which the track grooves 7, 9 are inclined in the circumferential direction with respect to the axis line NN of the joint and the inclination directions of the track grooves 7, 9 adjacent to each other in the circumferential direction are opposite to each other, it is possible to achieve lightweight and compact design while ensuring high efficiency, strength, and durability.

[0060] In the embodiment described above, the fixed type constant velocity universal joint has been exemplified as having eight balls, but the number of balls is not limited to eight, and the number of balls may be more than eight as appropriate.

[0061] 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]

[0062] 1 Fixed constant velocity universal joint 2 Outer joint member 3 Inner joint member 4 balls 5 cages 6 Spherical inner surface 7 Track groove 7a first track groove portion 7b Second track groove portion 8 Spherical outer surface 9 Track groove 9a first track groove portion 9b second track groove portion 12 Spherical outer surface 13 Spherical inner surface D BALL Ball diameter M Plane containing the ball track centerline N Axis of joint O Joint center 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 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

Claims

1. a fixed type constant velocity universal joint comprising: an outer joint member having an open side and a rear side spaced apart in the axial direction and having a plurality of track grooves formed on a spherical inner peripheral surface thereof and extending in the axial direction; an inner joint member having a plurality of track grooves formed on its spherical outer peripheral surface thereof, each pairing with the track grooves of the outer joint member; a plurality of balls interposed between the track grooves of the outer joint member and the track grooves of the inner joint member to transmit torque; and a cage which holds the balls and has a spherical outer peripheral surface and a spherical inner peripheral surface fitted to the spherical inner peripheral surface of the outer joint member and the spherical outer peripheral surface of the inner joint member, The track grooves of the outer joint member are composed of a first track groove portion (7a) located on the deep side and a second track groove portion (7b) located on the opening side, the first track groove portion (7a) has an arc-shaped ball raceway center line (Xa) having a center of curvature offset in the axial direction with respect to the joint center (O), a plane (M) including at least the ball raceway center line (Xa) and the joint center (O) is inclined with respect to the joint axis (N-N), and the inclination directions are formed in opposite directions in the first track groove portions (7a) adjacent to each other in the circumferential direction, and when the ball raceway center line (Xb) of the second track groove portion (7b) is projected onto the plane (M), the ball raceway center line ( the first track groove portion (7a) has a straight line portion, and this straight line portion is formed so as to approach the axis line (N-N) of the joint as it approaches the opening side, an end (A) of a ball raceway center line (Xa) of the first track groove portion (7a) is located closer to the opening side than the joint center (O), and the ball raceway center line (Xb) of the second track groove portion (7b) is connected to this end (A), and the ball raceway center line (Y) of the track groove of the inner joint member is formed in mirror symmetry with the ball raceway center line (X) of the mating track groove of the outer joint member, with respect to a plane (P) which includes the joint center (O) and is perpendicular to the axis line (N-N) of the joint in a state of 0° operating angle, The pitch circle diameter (PCD) of the plurality of balls arranged at the joint center (O) ＢＡＬＬ ) and the diameter of the ball (D ＢＡＬＬ ) PCD ratio ＢＡＬＬ / D ＢＡＬＬ is set in the range of 3.89 to 4.48, When the offset amount in the axial direction between the joint center (O) and the curvature center (Oo1) of the arc-shaped ball track center line (Xa) of the first track groove portion (7a) is f, the ratio of the offset amount (f) to the pitch circle diameter (PCD) of the ball is ＢＡＬＬ ) ratio f / PCD ＢＡＬＬ The upper limit value of the fixed type constant velocity universal joint is set to 0.

009.

2. The spherical outer peripheral surface of the cage has a center of curvature (Oc1) that is not offset in the axial direction from the joint center (O), 2. The fixed type constant velocity universal joint according to claim 1, wherein a ball raceway center line (Xa) of the first track groove portion (7a) has a center of curvature (Oo1) that is offset in the axial direction from a center of curvature (Oc1) of the spherical outer peripheral surface of the cage.

3. The spherical outer peripheral surface of the cage has a center of curvature (Oc1) offset in the axial direction from the joint center (O), The ball raceway center line (Xa) of the first track groove portion (7a) has a curvature center (Oo1) that is not offset in the axial direction from the curvature center (Oc1) of the spherical outer circumferential surface of the cage.

2. The fixed type constant velocity universal joint according to claim 1.

4. The spherical outer peripheral surface of the cage has a center of curvature (Oc1) offset in the axial direction from the joint center (O), 2. The fixed type constant velocity universal joint according to claim 1, wherein the ball raceway center line (Xa) of the first track groove portion (7a) has a center of curvature (Oo1) that is offset in the axial direction from the center of curvature (Oc1) of the spherical outer peripheral surface of the cage.

5. The fixed type constant velocity universal joint according to any one of claims 1 to 4, characterized in that an inclination angle (γ) of a plane (M) including the ball raceway center line (Xa) of the first track groove portion (7a) and the joint center (O) with respect to the joint axis (N-N) is set in the range of 4° to 8°.

6. 5. The fixed type constant velocity universal joint according to any one of claims 1 to 4, characterized in that an angle (β) formed by a straight line (L) connecting an end (A) on an opening side of the ball raceway center line (Xa) of the first track groove portion (7a) and a joint center (O) with a plane (P) that includes the joint center (O) and is perpendicular to the axis line (N-N) of the joint is set in the range of 8° to 12°.

7. 5. A fixed type constant velocity universal joint according to claim 1, wherein the number of the balls is eight or more.

Images