Fixed-type constant-velocity universal joint

Abstract

Provided is a fixed-type constant-velocity universal joint 1 of a track groove crossing type, wherein a ratio PCDBALL / DBALL of a pitch circle diameter PCDBALL of a plurality of balls 4 to a diameter DBALL of each of the balls 4 is set in a range of 3.89 to 4.48. A ratio DINLET / DBALL of an inlet spigot diameter DINLET of an outer joint member 2 to the diameter DBALL of each of the balls 4 is set in a range of 4.18 to 4.76.

Description

Fixed constant velocity universal joint

[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.

[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 is capable of a large operating angle but does not displace axially, as the wheels are steered.

[0003] Known fixed constant velocity universal joints include Rzeppa-type constant velocity universal joints (also referred to as BJ types) and undercut-free constant velocity universal joints (also referred to as UJ types). Among these, an eight-ball fixed constant velocity universal joint shown in FIG. 12 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 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 into 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. 13 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.

[0006] Patent No. 3859267 Patent No. 5138449 Patent No. 6113459 Patent No. 5912419

[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, an object of the present invention is 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.

[0010] The present invention, which has been made as a technical means for achieving the above-mentioned object, comprises: 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 rear side spaced apart in the axial direction; an inner joint member having a plurality of track grooves formed on its spherical outer peripheral surface, 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 plurality of balls, and has a spherical outer peripheral surface which fits with the spherical inner peripheral surface of the outer joint member and a spherical inner peripheral surface which fits with the spherical outer peripheral surface of the inner joint member, wherein the track grooves of the outer joint member consist of a first track groove portion (7a) located on the rear side and a second track groove portion (7b) located on the open side, the first track groove portion (7a) has an arc-shaped ball raceway centerline (Xa) having a center of curvature offset in the axial direction from the joint center (O), a plane (M) including the ball raceway centerline (Xa) and the joint center (O) is inclined with respect to the joint axis (N-N), and the inclination directions are opposite to each other in the first track groove portions (7a) adjacent in the circumferential direction, when the ball raceway centerline (Xb) of the second track groove portion (7b) is projected onto the plane (M), the ball raceway centerline (Xb) has a straight line portion, and this straight line portion is inclined so as to approach the joint axis (N-N) as it approaches the opening side, an end portion (A) of the ball raceway centerline (Xa) of the first track groove portion (7a) is located closer to the opening side than the joint center (O), and the ball raceway centerline (Xb) of the second track groove portion (7b) is connected to this end portion (A), The present invention relates to a track groove crossing type fixed constant velocity universal joint in which a ball raceway center line (Y) of the track groove of the inner joint member is mirror-symmetrical to a ball raceway center line (X) of a mating track groove of the outer joint member, with respect to a plane (P) that includes the joint center (O) and is perpendicular to the joint axis (N-N) when the operating angle is 0°.

[0011] The above-mentioned track groove crossing type fixed constant velocity universal joint comprises: an outer joint member having a plurality of track grooves formed on a spherical inner circumferential surface; an inner joint member having a plurality of track grooves formed on a spherical outer circumferential surface; a plurality of 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 circumferential surface that fits with the spherical inner circumferential surface of the outer joint member; a spherical inner circumferential surface that fits with the spherical outer circumferential surface of the inner joint member; a plurality of pockets that hold the balls one by one; and a cage that has a cylindrical surface provided at an axial end of the inner circumferential surface; and the outer joint member has a first track groove portion that has an arc-shaped ball raceway center line (Xa) and 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), and 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 goes to one axial side, the inner joint member has a first track groove portion having an arc-shaped ball raceway center line (Ya) and a second track groove portion which is continuous with an end portion of the first track groove portion on the other axial side and has a linear ball raceway center line (Yb), and a 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), and 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 as it goes to the other axial side, 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 a first track groove portion of an adjacent track groove are inclined 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 a ball raceway center line (Ya) of a first track groove portion of an adjacent track groove are inclined toward opposite sides with respect to the axial direction,It can also be characterized as 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 including a ball raceway center line (Ya) of a first track groove portion of the track groove of the inner joint member, which plane is radially opposed to the plane including the ball raceway center line (Xa) of a first track groove portion of the track groove of the inner joint member, being inclined in opposite directions relative to the axial direction.

[0012] The present invention provides a fixed type constant velocity universal joint of the above-mentioned track groove intersection type, in which the pitch circle diameter PCD of the plurality of balls arranged at the joint center O is ＢＡＬＬ and the diameter D of the ball ＢＡＬＬ PCD ratio ＢＡＬＬ / D ＢＡＬＬ is set in the range of 3.89 to 4.48, and the inlet spigot diameter (D ＩＮＬＥＴ ) and the diameter of the ball (D ＢＡＬＬ ) ratio D ＩＮＬＥＴ / D ＢＡＬＬ The present invention is characterized in that the above-described track groove crossing type fixed type constant velocity universal joint ...

[0013] 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 track center line Xa of the first track groove portion 7 a 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] 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 track center line Xa of the first track groove portion 7 a 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.

[0015] 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 track center line Xa of the first track groove portion 7 a 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.

[0016] 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 N-N 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.

[0017] 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 with the joint center O forms with a plane P that includes the joint center O and is perpendicular to the joint axis N-N 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.

[0018] In the above-mentioned fixed type constant velocity universal joint, when the offset amount in the axial direction between the joint center O and the center of curvature Oo1 of the arc-shaped ball track center line Xa of the first track groove portion 7a is f, the relationship between the offset amount f and the pitch circle diameter PCD of the ball is ＢＡＬＬ The ratio f / PCD ＢＡＬＬ The upper limit may be set to 0.009.

[0019] 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.

[0020] 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.

[0021] FIG. 3 is a partial longitudinal sectional view of a fixed type constant velocity universal joint according to an embodiment of the present invention. FIG. 4 is a front view of the fixed type constant velocity universal joint of FIG. 1A, as seen from the axial direction. FIG. 5 is a partial longitudinal sectional view of an outer joint member of the fixed type constant velocity universal joint of FIG. 1. FIG. 6 is a front view of the outer joint member of FIG. 1A, as seen from the axial direction. FIG. 7 is a front view of the inner joint member of FIG. 1, as seen from one axial side. FIG. 8 is a side view of the inner joint member of FIG. 3A, as seen from the outer periphery. FIG. 9 is a rear view of the inner joint member of FIG. 3A, as seen from the other axial side. FIG. 10 is a partial longitudinal sectional view showing details of track grooves of the outer joint member of FIG. 1A. FIG. 11 is a longitudinal sectional view showing details of track grooves of the inner joint member of FIG. 1A. FIG. 12 is a partial longitudinal sectional view showing an enlarged view of the fixed type constant velocity universal joint of FIG. 1A. FIG. 13 is a partial longitudinal sectional view of the outer joint member. FIG. 14 is a front view of the outer joint member and the cage when assembled, as seen from the axial direction of the outer joint member. FIG. 15 is a front view of the cage when seen from the axial direction. FIG. 16 is a partial longitudinal sectional view of the outer joint member. FIG. 11A is a cross-sectional view taken along line P-P of FIG. 9A. FIG. 11B is a partial longitudinal cross-sectional view of a fixed type constant velocity universal joint according to another embodiment of the present invention. FIG. 11C is a partial longitudinal cross-sectional view of a fixed type constant velocity universal joint according to yet another embodiment of the present invention. FIG. 11D is an enlarged view of part T of FIG. 11A. FIG. 11E is a longitudinal cross-sectional view of a conventional fixed type constant velocity universal joint (Rzeppa type). FIG. 12A is a front view of the fixed type constant velocity universal joint of FIG. 12A, as viewed from the axial direction. FIG. 12F is a longitudinal cross-sectional view of a conventional fixed type constant velocity universal joint (track groove intersection type). FIG. 13A is a front view of the fixed type constant velocity universal joint of FIG. 13A, as viewed from the axial direction.

[0022] An embodiment of the present invention will be described with reference to the drawings.

[0023] First, the basic configuration of a track groove crossing 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 comprises an outer joint member 2, an inner joint member 3, balls 4, and a cage 5.

[0024] 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. 1B). 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. 1A). 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 facing each other in the radial direction. The cage 5 has a spherical outer peripheral surface 12 that fits into the spherical portions 6 on the inner peripheral surface of the outer joint member 2, a spherical inner peripheral surface 13 that fits into the spherical portions 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 FIG. 1B) that axially connects the pair of annular portions 5b, 5c. A cylindrical surface 5d centered on the axis N-N is provided on the axial end portion of the inner peripheral surface of the cage 5, that is, on the inner peripheral surface of one of the annular portions 5c in the illustrated example.

[0025] In the following description, the opening side of the cup-shaped outer joint member 2 in the axial direction (the right side in FIG. 1A ) will be referred to as the "joint opening side," and the opposite side (the left side in FIG. 1A ) will be referred to as the "joint inner side." Furthermore, in order to accurately indicate the form and shape of the track grooves 7, 9, such as their inclination and curvature, 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.

[0026] As shown in FIG. 1A , 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.

[0027] 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 including all of 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.

[0028] 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 come into contact with each other at a contact angle (approximately 30° to 45°), which is known as angular contact. Therefore, the ball 4 comes into contact with the side surface of the track grooves 7, 9, which is slightly away from the groove bottom. It is also possible to make the cross-sectional shape of the track grooves 7, 9 circular, and have the track grooves 7, 9 and the ball 4 come into so-called circular contact.

[0029] 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 N-N). 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.

[0030] 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.

[0031] 2A , 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 by an angle γ with respect to the joint axis N-N. Then, 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 by an angle γ with respect to the joint axis N-N in the opposite direction to the inclination direction of the track groove 7A.

[0032] 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 of the track grooves 9A. As shown in FIG. 3B , a plane Q including the ball track center line Y of the track groove 9A (more specifically, a plane including the ball track 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 N-N. Furthermore, although not shown, the track groove 9B adjacent to the track groove 9A in the circumferential direction has a plane Q including the ball track center line Y of the track groove 9B (more specifically, a plane including the ball track 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 N-N 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 FIG. 1A ) 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 N-N.

[0033] The track grooves 7A of the outer joint member 2 will be described in detail with reference to Figure 4. Figure 4 is a cross-sectional view of the track grooves 7A of Figure 2A described above, taken on a plane M including the ball raceway center line X. Therefore, strictly speaking, Figure 4 is not a longitudinal cross-sectional view on a plane including the joint axis N-N, but rather shows a cross-section inclined by an angle γ. Figure 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.

[0034] The track groove 7A is composed of a first track groove portion 7Aa having an arc-shaped ball track centerline Xa with a center of curvature offset axially from the joint center O, and a second track groove portion 7Ab having a linear ball track centerline Xb. The linear ball track centerline Xb of the second track groove portion 7Ab smoothly connects to the joint opening-side end of the ball track centerline Xa of the first track groove portion 7Aa. In the illustrated example, since the connection point A of the ball track centerlines Xa and Xb is located closer to the joint opening than the joint center O, the linear ball track centerline Xb is inclined so as to approach the joint axis N-N (see FIG. 1A) as it moves closer to the joint opening. This ensures an effective track length at the maximum operating angle and prevents the wedge angle from becoming excessively large. FIG. 1A illustrates a state in which the inclination angle γ of the track grooves 7 and 9 is set to 0°.

[0035] As shown in FIG. 4, L denotes the straight line connecting the joint center O and the connection point A of the ball track center lines Xa, Xb. The joint axis N'-N' projected onto a plane M (see FIG. 2A) containing the ball track center line X of the track groove 7A is inclined by γ with respect to the joint axis N-N, and β' denotes the angle formed by the line L and a perpendicular line K at the joint center O to 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 N-N. 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 N-N is expressed as sin β = sin β' × cos γ.

[0036] 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. 3B described above. Therefore, as with Fig. 4, strictly speaking, it is not a longitudinal cross section on a plane including the joint axis N-N, but rather 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.

[0037] The track groove 9A is composed 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, since the connection point B of the ball track centerlines Ya and Yb is located closer to the joint rear side than the joint center O, the linear ball track centerline Yb is inclined so as to approach the joint axis N-N (see FIG. 1A) 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 excessively large. As mentioned above, FIG. 1A illustrates a state in which the inclination angle γ of the track grooves 7 and 9 is 0°.

[0038] As shown in Figure 5, R denotes the straight 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 Figure 3B) containing the ball track center line Y of the track groove 9A is inclined by γ with respect to the joint axis N-N, and the angle β' is defined as the angle between the line R and a perpendicular line K at the joint center O to 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 N-N. 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 N-N is expressed as sin β = sin β' × cos γ.

[0039] Next, we will explain the angle β that the lines L and R form with respect to a plane P that contains the joint center O and is perpendicular to the joint axis N-N when the operating angle is 0°. When the operating angle is θ, the balls 4 move by θ / 2 with respect to a 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 balls 4 contact within the frequently used operating angle range is determined. Here, we will define the frequently used operating angle. First, the common operating angle of the joint refers to the operating angle generated in the fixed constant velocity universal joint of the front drive shaft 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 this angle is also determined according to the design conditions of each vehicle model, but is larger than the normal 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.

[0040] 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 furthest toward the opening 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 furthest toward the rear along the axial direction at a frequently used operating angle. Because the angle β is set in this way, within a frequently used operating angle range, the ball 4 is located on the 7Ba and 9Ba (see Figs. 2 and 3) which are inclined in the opposite direction to the first track groove portions 7Aa and 9Aa of the outer joint member 2 and the inner joint member 3.

[0041] The overall configuration of the fixed type constant velocity universal joint 1 according to this embodiment is as described above. Next, the matters considered 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 type constant velocity universal joint is applied to the front drive shaft of an automobile, a maximum operating angle equal to or greater than the wheel turning angle is required, and the operating angle required for a fixed type constant velocity universal joint is generally 40° or more. (B) Furthermore, the basis of the function of a constant velocity universal joint is the pitch circle diameter PCD of the balls of the constant velocity universal joint. ＢＡＬＬ and the diameter of the ball D ＢＡＬＬ (C) In a fixed constant velocity universal joint of the track groove crossing type in which the track grooves are inclined in the circumferential direction with respect to the axis N-N of the joint and the inclination directions are opposite to each other in adjacent track grooves in the circumferential direction, a special dimension setting is required as a result of studying the function with a focus on achieving lightweight and compactness while ensuring high efficiency, strength, and durability.

[0042] The fixed type constant velocity universal joint 1 according to this embodiment has the following characteristic configurations: (1) Pitch circle diameter PCD of the ball 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. (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 pitch circle diameter PCD of the ball ＢＡＬＬ The ratio f / PCD ＢＡＬＬ The upper limit value of is set to 0.009 (when the offset is applied only to the track grooves). (3) Inlet spigot diameter D of outer joint member ＩＮＬＥＴ and ball diameter D ＢＡＬＬ Relative to D ＩＮＬＥＴ / D ＢＡＬＬ is set in the range of 4.18 to 4.76. Also, as an advantageous configuration, (4) 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 N-N is set in the range of 4° to 8°. (5) The outer diameter D of the outer joint member ＯＵＴＥＲand ball pitch circle diameter PCD ＢＡＬＬ Relative to D ＯＵＴＥＲ / PCD ＢＡＬＬ is set in the range of 1.34 to 1.44.

[0043] The characteristic features (1) to (5) of this embodiment will be described below with reference to FIGS. 1 to 9 as appropriate.

[0044] (1) Ball pitch circle diameter PCD ＢＡＬＬ and the diameter of the ball D ＢＡＬＬ PCD ratio ＢＡＬＬ / D ＢＡＬＬ Regarding setting the pitch circle diameter (PCD) of the ball in the range of 3.89 to 4.48, as shown in Figure 6, 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 Pitch circle diameter PCD of the ball based on ＢＡＬＬ PCD ratio ＢＡＬＬ / D ＢＡＬＬ is set in the range of 3.89 to 4.48.

[0045] <ratio PCD ＢＡＬＬ / D ＢＡＬＬ Setting range study results > Ball diameter D ＢＡＬＬ Pitch circle diameter PCD of the ball based on ＢＡＬＬ PCD ratio ＢＡＬＬ / D ＢＡＬＬ If is less than 3.89, the pitch circle diameter PCD of the ball ＢＡＬＬ Ball diameter D ＢＡＬＬ becomes too large, the distance between the outer diameters of the balls 4 in the circumferential direction becomes close, the thickness of the spherical portion between the track grooves (see F in FIG. 3C) and the cross-sectional area of ​​the cage pillar portion (see 5e in FIG. 1B) become small, and it becomes impossible to ensure the strength of each part. ＢＡＬＬ Ball pitch circle diameter PCD ＢＡＬＬ If the ball diameter D becomes too small, the load shared by each ball 4 becomes large and it becomes impossible to ensure the strength of each part. ＢＡＬＬ Pitch circle diameter PCD of the ball based on ＢＡＬＬPCD ratio ＢＡＬＬ / D ＢＡＬＬ If is greater than 4.48, the pitch circle diameter PCD of the ball ＢＡＬＬ Ball diameter D ＢＡＬＬ becomes too small, the contact surface pressure between the track grooves 7, 9 and the balls 4 increases with respect to the input torque, and durability cannot be ensured. ＢＡＬＬ whereas the pitch circle diameter PCD of the ball ＢＡＬＬ becomes too large, the outer diameter of the outer joint member 2 becomes large, and it becomes impossible to maintain compactness.

[0046] (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 pitch circle diameter PCD of the ball ＢＡＬＬ The ratio f / PCD ＢＡＬＬ 7 , in this 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 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 may be disposed 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°.

[0047] <Ratio f / PCD ＢＡＬＬResults of Study on Setting Ranges for the Outer Track Center Oo1 and the Inner Track Center Oi1 > When the outer track center Oo1 and the inner track center Oi1 are offset as described above, a force is generated in which the balls 4 push 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 corresponding to 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, which may result in variations in functionality. Therefore, it is desirable to offset the outer track center Oo1 and the inner track center Oi1 axially opposite to 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 The ratio f / PCD ＢＡＬＬ On the other hand, the upper limit of f / PCD is 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.

[0048] 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.

[0049] (3) Inlet spigot diameter D of outer joint member ＩＮＬＥＴ and ball diameter D ＢＡＬＬ Relative to D ＩＮＬＥＴ / D ＢＡＬＬ Regarding setting the range of 4.18 to 4.76: In a fixed constant velocity universal joint of the crossed track groove type, the track grooves are inclined in the circumferential direction with respect to the axis of the joint, and the inclination directions are opposite to each other in adjacent track grooves in the circumferential direction, so that it is possible to provide portions with large and small spherical widths between the track grooves on the open end side of the outer joint member.

[0050] As shown in Figure 8B, the cage 5 is assembled into the spherical inner peripheral surface 6 of the outer joint member 2 with the axis of the cage 5 perpendicular to the axis of the outer joint member 2. 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 8A ＩＮＬＥＴ As shown in FIG. 8C, it is necessary to set the width W5 larger than the window height H determined by the window length W5 of the cage 5.

[0051] <Ratio D ＩＮＬＥＴ / DＢＡＬＬ As shown in Figure 8A, 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, but this reduces the circumferential length of the cage pillar portion (see 5e in FIG. 1B), making it difficult to ensure the strength of the cage 5. ＩＮＬＥＴ / D ＢＡＬＬ If σ is greater than 4.76, when the spherical inner peripheral surface 6 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.

[0052] 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 6 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.

[0053] (4) Regarding setting the inclination angle γ, the inclination angle of the plane including the ball raceway center line of the first track groove portion and the joint center O relative to the joint axis N-N, in the range of 4° to 8°, the inclination angle γ is as shown in Figures 2A and 3B. <Results of study on the setting range of the inclination angle γ> When the inclination angle γ 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, when 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 cage pillar portion (see 5e in Figure 1B) and the thickness of the spherical portion of the inner joint member (see F in Figure 3C) become insufficient, making it impossible to ensure strength.

[0054] 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°, which 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.

[0055] (5) Outer diameter D of outer joint member ＯＵＴＥＲ and ball pitch circle diameter PCD ＢＡＬＬ Relative to D ＯＵＴＥＲ / PCD ＢＡＬＬ Regarding setting the outer diameter D of the outer joint member 2 in the range of 1.34 to 1.44 ＯＵＴＥＲ and ball pitch circle diameter PCD ＢＡＬＬ The ratio D is shown in Figures 9A and 9B. ＯＵＴＥＲ / PCD ＢＡＬＬ Result of study on the setting range of outer joint member outer diameter D 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 larger 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.

[0056] The fixed type constant velocity universal joint 1 of this embodiment has an outer diameter D of the outer joint member 2. ＯＵＴＥＲ and ball pitch circle diameter PCD ＢＡＬＬ Relative to D ＯＵＴＥＲ / PCD ＢＡＬＬ is set in the range of 1.34 to 1.44. This ensures the strength of the outer joint member 2 and makes it possible to make it lightweight and compact.

[0057] A fixed type constant velocity universal joint according to a second embodiment of the present invention will be described with reference to Figure 10. 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 applied. The overall configuration and effects thereof shown in Figures 1 to 5 of the first embodiment described above are also the same for the fixed type constant velocity universal joint according to this embodiment, and so apply mutatis mutandis. Parts 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.

[0058] The fixed type constant velocity universal joint according to the second embodiment has the following characteristic configuration: (1) Pitch circle diameter PCD of the ball ＢＡＬＬ and ball diameter D ＢＡＬＬ PCD ratio 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, so the above content applies mutatis mutandis. (2') Offset amount f (= cage offset amount f2) and pitch circle diameter PCD of the ball ＢＡＬＬ The ratio f / PCD ＢＡＬＬ The upper limit value of is set to 0.009 (when the track offset amount f1 is set to 0). (3) Inlet spigot diameter D of outer joint member ＩＮＬＥＴ and ball diameter D ＢＡＬＬ Relative to D ＩＮＬＥＴ / D ＢＡＬＬ is set in the range of 4.18 to 4.76. This characteristic configuration (3) 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. In addition, as an advantageous configuration, (4) 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 N-N is set in the range of 4° to 8°. This characteristic configuration (4) 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. (5) The outer diameter D of the outer joint member ＯＵＴＥＲ and ball pitch circle diameter PCD ＢＡＬＬ Relative to D ＯＵＴＥＲ / PCD ＢＡＬＬis set in the range of 1.34 to 1.44. The characteristic configuration (5) 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.

[0059] 10 , 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. In other words, 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 example has been given in which 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. Figure 10 illustrates a state in which the inclination angle γ of the track grooves 7 and 9 is 0°.

[0060] A fixed constant velocity universal joint according to a third embodiment of the present invention will be described with reference to FIGS. 11A and 11B. FIG. 11B is an enlarged view of the T portion in FIG. 11A. 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, while 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 of the first embodiment shown in FIGS. 1 to 5 are similar to those of the fixed constant velocity universal joint according to this embodiment, and therefore apply mutatis mutandis. Components 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.

[0061] The fixed type constant velocity universal joint according to the third embodiment has the following characteristic configuration: (1) Pitch circle diameter PCD of the ball ＢＡＬＬ and ball diameter D ＢＡＬＬ PCD ratio 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, so the above content applies mutatis mutandis. (2") The offset amount f (= track offset amount f1 + cage offset amount f2) and the pitch circle diameter PCD of the ball ＢＡＬＬ f / PCD ＢＡＬＬ The upper limit value of is set to 0.009. (3) Inlet spigot diameter D of outer joint member ＩＮＬＥＴ and ball diameter D ＢＡＬＬ Relative to D ＩＮＬＥＴ / D ＢＡＬＬis set in the range of 4.18 to 4.76. This characteristic configuration (3) 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. In addition, as an advantageous configuration, (4) 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 N-N is set in the range of 4° to 8°. This characteristic configuration (4) 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. (5) The outer diameter D of the outer joint member ＯＵＴＥＲ and ball pitch circle diameter PCD ＢＡＬＬ Relative to D ＯＵＴＥＲ / PCD ＢＡＬＬ is set in the range of 1.34 to 1.44. The characteristic configuration (5) 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.

[0062] 11 , 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 11 shows a state in which the inclination angle γ of the track grooves 7, 9 is 0°.

[0063] In this embodiment, the cage offset amount f2 and the pitch circle diameter PCD of the ball ＢＡＬＬ The ratio f2 / PCD ＢＡＬＬ is set to 0.0045, and the track offset amount f1 and the ball pitch circle diameter PCD ＢＡＬＬ The ratio f1 / PCD ＢＡＬＬ is set to 0.0045. Note that, in the present 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 present embodiment has been exemplified where 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.

[0064] The fixed type constant velocity universal joint 1 according to the embodiment described above comprises the characteristic configurations (1), (2), (2'), (2"), (3), (4) and (5) 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 circumferentially with respect to the axis N-N of the joint and the inclination directions are opposite to each other for circumferentially adjacent track grooves 7, 9, it is possible to achieve lightweight and compact design while ensuring high efficiency, strength and durability.

[0065] In the embodiment described above, the fixed type constant velocity universal joint has eight balls, but the number of balls is not limited to eight, and the number of balls may be more than eight as appropriate.

[0066] 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.

[0067] REFERENCE SIGNS LIST 1 Fixed type constant velocity universal joint 2 Outer joint member 3 Inner joint member 4 Ball 5 Cage 6 Spherical inner peripheral surface 7 Track groove 7a First track groove portion 7b Second track groove portion 8 Spherical outer peripheral surface 9 Track groove 9a First track groove portion 9b Second track groove portion 12 Spherical outer peripheral surface 13 Spherical inner peripheral surface D ＢＡＬＬ Ball diameter M Plane including the ball raceway center line N Axis of the joint O Joint center Oo1 Outer ring track center Oi1 Inner ring track center Oc1 Cage outer spherical surface center Oc2 Cage inner spherical surface center f Offset amount f1 Track offset amount f2 Cage offset amount X Ball raceway center line of the track groove of the outer joint member Xa Ball raceway center line of the first track groove portion Xb Ball raceway center line of the second track groove portion Y Ball raceway center line of the track groove of the inner joint member Ya Ball raceway center line of the first track groove portion Yb Ball raceway center line of the second track groove portion

Claims

1. A fixed type constant velocity universal joint comprising: an outer joint member having a plurality of axially extending track grooves formed on its spherical inner peripheral surface and having an open side and a rear side spaced apart in the axial direction; an inner joint member having a plurality of track grooves formed on its spherical outer peripheral surface, each paired with the track grooves of said outer joint member; a plurality of balls for transmitting torque by being interposed between the track grooves of said outer joint member and the track grooves of said inner joint member; and a cage for holding said plurality of balls, having a spherical outer peripheral surface that fits with the spherical inner peripheral surface of said outer joint member and a spherical inner peripheral surface that fits with the spherical outer peripheral surface of said inner joint member, wherein the track grooves of said outer joint member consist of a first track groove portion (7a) located on the rear side and a second track groove portion (7b) located on the open side, the first track groove portion (7a) has an arc-shaped ball raceway centerline (Xa) having a center of curvature offset in the axial direction from the joint center (O), a plane (M) including the ball raceway centerline (Xa) and the joint center (O) is inclined with respect to the joint axis (N-N), and the inclination directions are opposite to each other in the first track groove portions (7a) adjacent in the circumferential direction, when the ball raceway centerline (Xb) of the second track groove portion (7b) is projected onto the plane (M), the ball raceway centerline (Xb) has a straight line portion, and this straight line portion is inclined so as to approach the joint axis (N-N) as it approaches the opening side, an end portion (A) of the ball raceway centerline (Xa) of the first track groove portion (7a) is located closer to the opening side than the joint center (O), and the ball raceway centerline (Xb) of the second track groove portion (7b) is connected to this end portion (A), The ball raceway center line (Y) of the track groove of the inner joint member is mirror-symmetrical with the ball raceway center line (X) of the mating track groove of the outer joint member, with respect to a plane (P) that includes the joint center (O) and is perpendicular to the joint axis (N-N) when the operating angle is 0°, and the pitch circle diameter (PCD) of the plurality of balls arranged at the joint center (O) is 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, and the inlet spigot diameter (D ＩＮＬＥＴ ) and the diameter of the ball (D ＢＡＬＬ ) ratio D ＩＮＬＥＴ / D ＢＡＬＬ A fixed constant velocity universal joint with a constant velocity angle set in the range of 4.18 to 4.

76.

2. A fixed type constant velocity universal joint as set forth in claim 1, wherein 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), and 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.

3. A fixed type constant velocity universal joint as set forth in claim 1, wherein the spherical outer peripheral surface of the cage has 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) has 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.

4. A fixed type constant velocity universal joint as set forth in claim 1, wherein the spherical outer peripheral surface of the cage has a center of curvature (Oc1) offset in the axial direction from the joint center (O), and the ball raceway center line (Xa) of the first track groove portion (7a) has a center of curvature (Oo1) offset in the axial direction from the center of curvature (Oc1) of the spherical outer peripheral surface of the cage.

5. When the axial offset between the joint center (O) and the center of curvature of the arc-shaped ball track center line (Xa) of the first track groove portion (7a) is f, what is the ratio between the offset (f) and the pitch circle diameter (PCD) of the ball? ＢＡＬＬ ) ratio f / PCD ＢＡＬＬ 2. A fixed type constant velocity universal joint according to claim 1, wherein the upper limit of is set to 0.

009.

6. A fixed type constant velocity universal joint as set forth in claim 1, wherein the inclination angle (γ) of the plane (M) containing the ball raceway center line (Xa) of the first track groove portion (7a) and the joint center (O) relative to the joint axis (N-N) is set in the range of 4° to 8°.

7. The outer diameter (D ＯＵＴＥＲ ) and ball pitch circle diameter (PCD) ＢＡＬＬ ) ratio D ＯＵＴＥＲ / PCD ＢＡＬＬ 2. The fixed type constant velocity universal joint according to claim 1, wherein the value of the constant velocity is set in the range of 1.34 to 1.

44.

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

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