JP2024086277A - Fixed type constant velocity universal joint - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make a fixed type constant velocity universal joint of an undercut free type with 6 balls compact and light, and achieve strength, a load capacity, durability and low transmission torque cross equal to or more than a conventional one.

SOLUTION: A curvature center Oto of a ball center locus of a circular arc part 22a of an outer ring track groove 22, and a curvature center Oti of a ball center locus L2 of a circular arc part 32b of an inner ring track groove 32 are offset from a joint center O by an equal distance on opposite axial sides. A curvature center Oco of an outer spherical periphery 52 of a cage 5, and a curvature center Oci of an inner spherical periphery 53 are offset from the joint center O by an equal distance on opposite sides. An offset angle η is 7°-7.1°, and a ratio f2/F of a cage offset amount f2 to a total offset amount F is 0.143-0.145.

SELECTED DRAWING: Figure 1

COPYRIGHT: (C)2024,JPO&INPIT

Description

The present invention relates to a fixed constant velocity universal joint.

As a fixed constant velocity universal joint capable of handling high operating angles of 50° or more, an undercut-free type fixed constant velocity universal joint (hereinafter referred to as a "UJ type constant velocity universal joint") is known, in which the ball center locus of the track groove has an arc portion and a straight portion. UJ type constant velocity universal joints that have six balls are often used, but there are also known joints that have eight balls and each ball has a small diameter, thereby achieving lighter weight and compactness (see, for example, Patent Document 1 below).

JP 2003-004062 A

Compared to an eight-ball constant velocity universal joint, a six-ball constant velocity universal joint reduces costs by reducing the machining costs of the track grooves and cage pockets. In addition, by reducing the number of balls, the circumferential spacing between the balls, i.e., the circumferential width of the pillars between the cage pockets, increases, making it possible to reduce the diameter of the constant velocity universal joint while maintaining the circumferential width of the cage pillars.

The objective of this invention is to provide a six-ball UJ type constant velocity universal joint that can be manufactured at low cost, while being compact and lightweight, and achieving strength, load capacity, durability, and low transmission torque loss equal to or greater than those of conventional products.

In a six-ball UJ-type constant velocity universal joint, reducing the diameter of the balls and the ball pitch circle can reduce weight and size. However, reducing the diameter of the balls and ball pitch circle raises concerns that the strength of each component may decrease. This makes it necessary to strengthen the cage, for example, but to increase the cage strength, it is necessary to increase the wall thickness. In this case, the track grooves of the inner joint member (hereinafter referred to as the "inner ring track groove") and the track grooves of the outer joint member (hereinafter referred to as the "outer ring track groove") become shallower, making it easier for the balls to ride up onto the edges of the track grooves.

As a measure to prevent the balls from riding up due to the increase in cage thickness as described above, it is effective to reduce the contact angle α between the ball and the track groove (see Figure 3). In addition, by reducing the axial offset of the center of curvature of the outer track groove from the joint center (= the axial offset of the center of curvature of the inner track groove from the joint center; hereafter referred to as the "track offset"), the depth of the outer track groove at the end can be increased, preventing the balls from riding up on the edge of the outer track groove at high angles.

However, reducing the contact angle α increases the surface pressure at the contact point between the ball and the track groove, reducing durability. On the other hand, reducing the track offset amount as described above reduces the difference between the length of the contact point locus between the inner track groove and the ball and the length of the contact point locus between the outer track groove and the ball (L1-L2<L1'-L2' in Figure 4). This reduces the amount of slippage between the outer track groove and the ball, reducing fatigue on the metal surface and improving durability. This effect offsets the decrease in durability that accompanies the increase in surface pressure caused by reducing the contact angle between the ball and the track groove as described above, thereby maintaining durability.

However, it has been found from experience that if the torque offset is reduced, the pocket load (the load that the cage pocket exerts on the ball), which is the force for controlling the ball on the bisecting plane of both joint components, is reduced, and when the joint angle is taken under conditions of no torque input, the bending torque increases and sticking occurs. In this case, in addition to the track offset, the center of curvature of the outer spherical surface of the cage and the center of curvature of the inner spherical surface are offset axially opposite the joint center (hereinafter referred to as "cage offset") to complement the pocket load and avoid sticking during bending. However, adding a cage offset has disadvantages, such as uneven thickness of the cage and increased internal forces such as track load. Therefore, when both track offset and cage offset are added, the total offset of these affects the constant velocity universal joint.

The smaller the total offset, the smaller the spherical force (the force that presses the spherical surfaces together) between the cage and each joint component, and therefore the smaller the torque loss rate. However, if the total offset is made too small, as mentioned above, the joint will jam when in operation. Therefore, until now, it has been customary to set the total offset as small as possible without causing jamming when bending the joint.

The inventors investigated the relationship between the operating angle and the torque loss rate for several types of UJ type constant velocity universal joints (TYPES 1 to 5) with different total offset amounts. The results are shown in Figure 5. The total offset amount increases in the order of TYPES 1 to 5. As a result, as shown in Figure 5, when the operating angle is 7.5° or less, the torque loss rate is smaller as the total offset amount is smaller, but when the operating angle is greater than 7.5°, the torque loss rate is smaller as the total offset amount is larger. Since the normal angle of a UJ type constant velocity universal joint is usually about 5 to 8°, it is necessary to suppress the torque loss to some extent even when it is used at a normal angle exceeding 7.5°. Therefore, the total offset amount is not necessarily the smaller the better, even if it is within a range where no snagging occurs when bending, and it is preferable that it is a somewhat large value.

Based on the above findings, it has become clear that by setting the offset angle to about 7° and the ratio of the cage offset to the total offset in a UJ type constant velocity joint higher than in conventional products, it is possible to achieve strength, load capacity, durability, and low transmission torque loss equal to or greater than that of conventional products, even when aiming for weight reduction and compactness.

Specifically, the fixed type constant velocity universal joint according to the present invention comprises an outer joint member having six track grooves formed at equal intervals in the circumferential direction on its spherical inner peripheral surface, an inner joint member having six track grooves formed at equal intervals in the circumferential direction on its spherical outer peripheral surface, six balls arranged between the track grooves of the outer joint member and the track grooves of the inner joint member, a spherical outer peripheral surface that fits with the spherical inner peripheral surface of the outer joint member, a spherical inner peripheral surface that fits with the spherical outer peripheral surface of the inner joint member, and a cage having six pockets for holding the six balls,
In an undercut-free type fixed constant velocity universal joint, track grooves of the outer joint member and the inner joint member have arc portions and straight portions,
a center of curvature Oto of a ball center locus of a circular arc portion of the track groove of the outer joint member and a center of curvature Oti of a ball center locus of a circular arc portion of the track groove of the inner joint member are offset by an equal distance on opposite sides in the axial direction with respect to a joint center O,
The center of curvature Oco of the spherical outer peripheral surface of the cage and the center of curvature Oci of the spherical inner peripheral surface are offset by an equal distance on opposite sides with respect to the joint center O,
when an angle formed by a straight line connecting a center of curvature Oto of a ball center locus of an arc portion of a track groove of the outer joint member and the center of the ball, and a plane P that passes through a joint center and is perpendicular to an axis, is defined as an offset angle η, the offset angle η is 7° to 7.1°,
When the axial distance between the center of curvature Oco of the spherical outer peripheral surface of the cage and the joint center O is defined as a cage offset amount f2, and the axial distance between the center of curvature Oto of the ball center locus of the arc portion of the track groove of the outer joint member and the joint center O is defined as a total offset amount F,
The ratio f2/F of the cage offset amount f2 to the total offset amount F is 0.143 to 0.145.

When the above-mentioned fixed type constant velocity universal joint (UJ type constant velocity universal joint) has a shaft connected to the inner joint member in a manner capable of transmitting torque, the dimensions of each part can be set as follows, based on the diameter Ds of the smallest diameter part of this shaft.
The ratio Do/Ds of the outer diameter Do of the outer joint member to the diameter Ds of the minimum diameter portion of the shaft is 3.76 to 3.80.
The ratio Db/Ds of the diameter Db of the ball to the diameter Ds of the minimum diameter portion of the shaft is 0.748 to 0.752.
The ratio PCD(BALL)/Ds of the pitch circle diameter PCD(BALL) of the ball to the diameter Ds of the smallest diameter part of the shaft is 2.47 to 2.51.
The ratio Tc/Ds of the radial thickness Tc of the cage to the diameter Ds of the minimum diameter portion of the shaft is 0.209 to 0.214.

As described above, the six-ball UJ type constant velocity universal joint of the present invention is compact and lightweight, while achieving strength, load capacity, durability, and low transmission torque loss equal to or greater than those of conventional products.

1 is an axial cross-sectional view of a fixed type constant velocity universal joint according to one embodiment of the present invention. FIG. 2 is a front view of the fixed type constant velocity universal joint as viewed from the axial direction. 3 is a cross-sectional view taken in a direction perpendicular to the axis at a contact point between a ball and a track groove of the fixed type constant velocity universal joint. FIG. The upper half is an axial cross-sectional view of the above-mentioned fixed type constant velocity universal joint, and the lower half is an axial cross-sectional view of a conventional fixed type constant velocity universal joint. 4 is a graph showing the relationship between the operating angle and the torque loss rate of a fixed type constant velocity universal joint. 4 is a graph showing the relationship between the operating angle and spherical force of a fixed type constant velocity universal joint. 4 is a graph showing the relationship between the operating angle and the spherical force of a fixed type constant velocity universal joint according to the present invention and a conventional product.

The following describes an embodiment of the present invention with reference to the drawings.

1 and 2 show an undercut-free type fixed constant velocity universal joint (UJ type constant velocity universal joint 1) which is a fixed constant velocity universal joint according to one embodiment of the present invention. This UJ type constant velocity universal joint 1 includes an outer joint member 2, an inner joint member 3, six balls 4, and a cage 5. A shaft 10 is connected to the inner joint member 3, and this shaft 10 protrudes from the outer joint member 2 to one axial side (the right side in FIG. 1). This UJ type constant velocity universal joint 1 is provided, for example, at the outboard end of an automobile drive shaft, and a sliding type constant velocity universal joint is attached to the opposite end (the inboard end) of the shaft 10 (intermediate shaft). Hereinafter, in the axial direction of the UJ type constant velocity universal joint 1, the side where the shaft 10 protrudes from the outer joint member 2 (the right side in FIG. 1) is referred to as the "joint opening side", and the opposite side (the left side in FIG. 1) is referred to as the "joint inner side".

The outer joint member 2 integrally comprises a cup portion 23 having six track grooves 22 formed on a spherical inner peripheral surface 21, and a shaft portion (not shown) protruding from the bottom wall of the cup portion 23. Six track grooves 32 that form pairs with the track grooves 22 of the outer joint member 2 are formed on the spherical outer peripheral surface 31 of the inner joint member 3. One ball 4 is disposed between each of the outer ring track grooves 22 and the inner ring track grooves 32. Six pockets 51 are provided in the cage 5, and one ball 4 is accommodated in each of the pockets 51.

As shown in FIG. 2, the outer ring track grooves 22 and the inner ring track grooves 32 are each formed at a predetermined pitch (60° pitch in this case) along the circumferential direction. Therefore, the six balls 4 as torque transmission members are arranged at an equal pitch (60° pitch) along the circumferential direction.

The inner joint member 3 has an inner hole in which a female spline portion 33 is formed (see FIG. 1). The end of the shaft 10 is fitted into the inner hole of the inner joint member 3, and the male spline portion 11 formed on the end of the shaft 10 fits into the female spline portion 33 of the inner joint member 3, connecting the two so as to transmit torque. A circumferential groove 12 is formed on the end of the shaft 10, and a retaining ring 6 attached to this circumferential groove 12 prevents the shaft 10 and the inner joint member 3 from coming loose in the axial direction.

The outer ring track groove 22 has an arc portion 22a provided on the rear side of the joint and a straight portion 22b provided on the joint opening side. The inner ring track groove 32 has a straight portion 32a provided on the rear side of the joint and an arc portion 32b provided on the joint opening side. The ball center trajectories of the arc portions 22a, 32b of each track groove 22, 32 form an arc shape, and the ball center trajectories of the straight portions 22b, 32a of each track groove 22, 32 form a straight line. The ball center trajectory is the trajectory that the center of the ball 4 passes through when the ball is moved along the track grooves 22, 32.

The center of curvature Oto of the ball center locus of the arc portion 22a of the outer ring track groove 22 and the center of curvature Oti of the ball center locus of the arc portion 32b of the inner ring track groove 32 are offset in the axial direction by equal distances F, F from the joint center O. In the illustrated example, the center of curvature Oto of the ball center locus of the arc portion 22a of the outer ring track groove 22 is offset toward the joint opening side from the joint center O, and the center of curvature Oti of the ball center locus of the arc portion 32b of the inner ring track groove 32 is offset toward the joint rear side from the joint center O. The straight portion 22b of the outer ring track groove 22 extends in the tangential direction from the end of the arc portion 22a on the joint opening side, and in the illustrated example, is parallel to the axial direction. The straight portion 32a of the inner ring track groove 32 extends in the tangential direction from the end of the arc portion 32b on the joint rear side, and in the illustrated example, is parallel to the axial direction.

The spherical outer peripheral surface 52 of the cage 5 is engaged with the spherical inner peripheral surface 21 of the outer joint member 2, and the spherical inner peripheral surface 53 of the cage 5 is engaged with the spherical outer peripheral surface 31 of the inner joint member 3. The diameter of the outer peripheral surface 52 of the cage 5 is approximately equal to the diameter of the inner peripheral surface 21 of the outer joint member 2, and the diameter of the inner peripheral surface 53 of the cage 5 is approximately equal to the diameter of the outer peripheral surface 31 of the inner joint member 3. The center of curvature Oco of the outer peripheral surface 52 of the cage 5 (i.e., the center of curvature of the inner peripheral surface 21 of the outer joint member 2) and the center of curvature Oci of the inner peripheral surface 53 of the cage 5 (i.e., the center of curvature of the outer peripheral surface 31 of the inner joint member 3) are offset in the axial opposite direction by an equal distance f2 from the joint center O. In the illustrated example, the center of curvature Oco of the outer peripheral surface 52 of the cage 5 is offset toward the joint opening side relative to the joint center O, and the center of curvature Oci of the inner peripheral surface 53 of the cage 5 is offset toward the back side of the joint relative to the joint center O.

Here, the axial distance between the center of curvature Oto of the ball center locus of the arc portion 22a of the outer ring track groove 22 and the joint center O (= the axial distance between the center of curvature Oti of the ball center locus of the arc portion 32b of the inner ring track groove 32 and the joint center O) is the total offset amount F. Also, the axial distance between the center of curvature Oco of the outer peripheral surface 52 of the cage 5 and the joint center O (= the axial distance between the center of curvature Oci of the inner peripheral surface 53 of the cage 5 and the joint center O) is the cage offset amount f2. Also, the difference between the total offset amount F and the cage offset amount f2 is the track offset amount f1.

Figure 3 is a cross-sectional view (cross-sectional view perpendicular to the axis) at the contact point between the ball 4 and the track grooves 22, 32. The cross-sectional shapes of the track groove 22 of the outer joint member 2 and the track groove 32 of the inner joint member 3 are elliptical or gothic arch shapes. The ball 4 is in angular contact with the track groove 22 of the outer joint member 2 at two points C1, C2, and with the track groove 32 of the inner joint member 3 at two points C3, C4.

The dimensions of each part of the above UJ type constant velocity universal joint 1 are as shown in Table 2 below. Note that the "conventional product" in Table 2 is a conventional UJ type constant velocity universal joint, which has the same reference shaft diameter as the UJ type constant velocity universal joint of this embodiment.

The definition of each item in Table 1 above is as follows:

・Offset angle η
In the axial cross section shown in FIG. 1, when the operating angle is 0°, the angle between a plane P that passes through the joint center O and is perpendicular to the axis and a straight line connecting the center of the ball 4 and the center of curvature Oti of the ball center locus of the arc portion 32b of the inner ring track groove 32 (= the angle between the plane P and the straight line connecting the center of the ball 4 and the center of curvature Oto of the ball center locus of the arc portion 22a of the outer ring track groove 22) is defined as the offset angle η.

Contact angle α
In the cross section shown in Figure 3, the angle formed by a straight line passing through the center of the ball 4 and each of the contact points C1, C2, C3, and C4 between the ball 4 and the track grooves 22 and 32, and a plane P that passes through the joint center O and is perpendicular to the axis, is defined as a contact angle α.

Reference shaft diameter Ds
The outer diameter of a minimum diameter portion 13 of the shaft 10 in a torque load region (an axial region between the male spline portions formed on both axial ends) is defined as a reference shaft diameter.

・Ball pitch circle diameter PCD (BALL)
The distance between the center of curvature Oto of the ball center locus of the arc portion 22a of the outer ring track groove 22 and the center of the ball (= the distance between the center of curvature Oti of the ball center locus of the arc portion 32b of the inner ring track groove 32 and the center of the ball) is PCR (see Figure 1), and twice the PCR is the pitch circle diameter PCD (BALL) of the ball.

・Cage thickness Tc
When the operating angle is 0°, the radial thickness of the cage 5 on a plane P that passes through the joint center O and is perpendicular to the axis is defined as a cage thickness Tc (see FIG. 1).

Below we explain why the dimensions of each part were set as above.

In the product of the present invention, the diameter Db of the ball 4, the pitch circle diameter PCD (BALL), and the outer diameter Do of the outer joint member 2 are smaller than those of the conventional product (see (3), (4), and (5) in Table 1). This makes the UJ type constant velocity universal joint 1 lighter and more compact.

As mentioned above, if the diameter of the balls or the ball pitch circle is reduced, there is a concern that the strength of each part will decrease. Therefore, in the product of the present invention, the cage thickness Tc is made larger than that of the conventional product (see (6) in Table 1).

When the cage thickness Tc is increased as described above, the track grooves 22, 32 of the outer joint member 2 and the inner joint member 3 become shallow, so that the ball 4 is more likely to ride up on the edge of the track groove 22, 32. Therefore, in the product of the present invention, the contact angle α (see FIG. 3) between the ball 4 and the track groove 22, 32 is made smaller than that of the conventional product (see (2) in Table 1). In addition, in the product of the present invention, the offset angle η is made smaller than that of the conventional product (see (1) in Table 1), and the ratio of the cage offset amount f2 to the total offset amount F is made larger than that of the conventional product (see (7) in Table 1). In other words, the track offset amount f1 is smaller than that of the conventional product. This makes it possible to deepen the depth of the track groove 22 of the outer joint member 2 at the joint inner end. As described above, by reducing the contact angle α and deepening the track groove 22, it is possible to prevent the ball 4 from riding up on the edge of the track groove 22 at a high angle.

When the contact angle α is reduced as described above, the surface pressure of the contact portion between the ball 4 and the track grooves 22, 32 increases, and durability decreases. Therefore, by reducing the track offset amount f1 as described above, the difference between the length of the contact point locus L1 between the inner ring track groove 32 and the ball 4 and the length of the contact point locus L2 between the outer ring track groove 22 and the ball 4 is reduced. That is, the difference ΔL (= L1-L2) between the length of the contact point locus L1 between the inner ring track groove 32 and the ball 4 of the product of the present invention shown in the upper half of FIG. 4 and the length of the contact point locus L2 between the outer ring track groove 22 and the ball 4 is smaller than the difference ΔL' (= L1'-L2') between the length of the contact point locus L1' between the inner ring track groove 32' and the ball 4' of the conventional product shown in the lower half of FIG. 4. This reduces the amount of slip between the outer ring track groove 22 and the ball 4, reducing fatigue of the metal surface and improving durability. This effect offsets the decrease in durability caused by the increased surface pressure resulting from reducing the contact angle α between the ball 4 and the track grooves 22, 32 as described above, thereby maintaining durability.

It has been found from experience that if the torque offset amount f1 is reduced as described above, the pocket load (the load that the pocket 51 of the cage 5 exerts on the ball 4), which is the force for controlling the ball 4 on the bisecting plane of both joint members 2 and 3, is reduced, and the bending torque increases and sticking occurs when the joint is angled under conditions of no torque input. Therefore, by providing a cage offset f2 in addition to the track offset f1 as described above and ensuring the total offset amount F, it is possible to complement the pocket load and maintain the bending operability of the joint.

On the other hand, the smaller the total offset amount F, the smaller the spherical force between the cage 5 and each joint member 2, 3 (the force pressing against each other between the spherical outer peripheral surface 52 of the cage 5 and the spherical inner peripheral surface 21 of the outer joint member 2, or between the spherical inner peripheral surface 53 of the cage 5 and the spherical outer peripheral surface 31 of the inner joint member 3), and therefore the smaller the torque loss rate. Therefore, until now, it has been customary to set the total offset amount as small as possible within a range that does not cause snagging when bending.

The inventors therefore investigated the relationship between the operating angle and the torque loss rate for several types of UJ-type constant velocity universal joints with different offset angles. The track offset amount (offset angle) of each sample used here is shown in Table 2 below.

As a result, as shown in Figure 5, at operating angles of 7.5° or less, the smaller the offset angle, the smaller the torque loss rate. On the other hand, at operating angles of 7.5° or more, TYPE 1 and TYPE 2, which have relatively small offset angles, have greater torque loss than TYPE 3 to 5, which have relatively large offset angles. Since the normal angle of a UJ type constant velocity joint is usually around 5 to 8°, it is necessary to suppress torque loss to some extent not only when the normal angle is 7.5° or less, but also when the normal angle exceeds 7.5°. Therefore, the smaller the offset angle, the better, and TYPE 3 (offset angle of approximately 7°), which suppresses torque loss to some extent even when the operating angle exceeds 7.5°, is most preferable.

Based on the above findings, in the UJ type constant velocity universal joint of this embodiment, the offset angle is set to about 7° {see (1) in Table 1}, and the ratio of the cage offset amount to the total offset amount is set higher than in conventional products {see (7) in Table 1}. From the above, it has become clear that even when the UJ type constant velocity universal joint is made lighter and more compact, it is possible to achieve strength, load capacity, durability, and low transmission torque loss equal to or greater than those of conventional products.

However, as mentioned above, if the offset angle η (total offset amount F) is small, snagging occurs when bending, but the cause of this snagging is unclear, and the correlation between the track offset amount and snagging is unclear.

The inventor therefore investigated the relationship between the operating angle and spherical force of a UJ-type constant velocity universal joint. As a result, as shown in Figure 6, fluctuations in the spherical force occurred at an operating angle of approximately 10°. Since the catching that occurs when bending in an actual machine occurs at an operating angle of approximately 10°, it is expected that the fluctuations in the spherical force affect the catching.

The relationship between the operating angle and spherical force for the product of the present invention and the conventional product is shown in Figure 7. From this figure, it can be seen that the fluctuation range of the spherical force of the product of the present invention is equal to or less than that of the conventional product, and therefore the bending torque when there is no torque input is also equal to or less than that of the conventional product.

1. Fixed constant velocity universal joint (UJ type constant velocity universal joint)
2 Outer joint member 21 Inner peripheral surface 22 Track groove 22a Arc portion 22b Straight portion 3 Inner joint member 31 Outer peripheral surface 32 Track groove 32a Straight portion 32b Arc portion 4 Ball 5 Cage 10 Shaft 13 Minimum diameter portion Db Ball diameter Do Outer diameter Ds of outer joint member Reference shaft diameter F Total offset amount f1 Track offset amount f2 Cage offset amount O Joint center Oti Center of curvature Oto of ball center locus of arc portion of inner ring track groove Center of curvature Oci of ball center locus of arc portion of outer ring track groove Center of curvature Oco of cage inner peripheral surface Center of curvature PCD (BALL) of cage outer peripheral surface Ball pitch circle diameter Tc Cage wall thickness α Contact angle η Offset angle

Claims (2)

an outer joint member having six track grooves formed at equal intervals in the circumferential direction on its spherical inner peripheral surface; an inner joint member having six track grooves formed at equal intervals in the circumferential direction on its spherical outer peripheral surface; six balls disposed between the track grooves of the outer joint member and the track grooves of the inner joint member; and a cage having a spherical outer peripheral surface that fits with the spherical inner peripheral surface of the outer joint member, a spherical inner peripheral surface that fits with the spherical outer peripheral surface of the inner joint member, and six pockets that hold the six balls,
In an undercut-free type fixed constant velocity universal joint, track grooves of the outer joint member and the inner joint member have arc portions and straight portions,
a center of curvature Oto of a ball center locus of a circular arc portion of the track groove of the outer joint member and a center of curvature Oti of a ball center locus of a circular arc portion of the track groove of the inner joint member are offset by an equal distance on opposite sides in the axial direction with respect to a joint center O,
The center of curvature Oco of the spherical outer peripheral surface of the cage and the center of curvature Oci of the spherical inner peripheral surface are offset by an equal distance on opposite sides with respect to the joint center O,
when an angle formed by a straight line connecting a center of curvature Oto of a ball center locus of an arc portion of a track groove of the outer joint member and the center of the ball, and a plane P that passes through a joint center and is perpendicular to an axis, is defined as an offset angle η, the offset angle η is 7° to 7.1°,
a cage offset amount f2 being the axial distance between the center of curvature Oco of the spherical outer peripheral surface of the cage and the joint center O, and a total offset amount F being the axial distance between the center of curvature Oto of the ball center locus of the arc portion of the track groove of the outer joint member and the joint center O, a ratio f2/F of the cage offset amount f2 to the total offset amount F being 0.143 to 0.145. a shaft connected to the inner joint member so as to be capable of transmitting torque;
a ratio Do/Ds of an outer diameter Do of the outer joint member to a diameter Ds of a minimum diameter portion of the shaft is 3.76 to 3.80,
a ratio Db/Ds of a diameter Db of the ball to a diameter Ds of a minimum diameter portion of the shaft is 0.748 to 0.752;
a ratio PCD(BALL)/Ds of a pitch circle diameter PCD(BALL) of the ball to a diameter Ds of a minimum diameter portion of the shaft is 2.47 to 2.51;
2. A fixed type constant velocity universal joint according to claim 1, wherein a ratio Tc/Ds of a radial thickness Tc of said cage to a diameter Ds of a minimum diameter portion of said shaft is 0.209 to 0.214.

Images