CN100476227C

CN100476227C - Constant velocity joint

Info

Publication number: CN100476227C
Application number: CNB2005800024522A
Authority: CN
Inventors: 中尾彰一; 井户一树; 横山晃
Original assignee: Honda Motor Co Ltd
Current assignee: Honda Motor Co Ltd
Priority date: 2004-01-15
Filing date: 2005-01-13
Publication date: 2009-04-08
Anticipated expiration: 2025-01-13
Also published as: CN101493119A; CN101493120A; CN1910380A; JP2005201371A; JP4681235B2

Abstract

Lateral cross-sections of first guiding grooves (26a-26f) provided in the inner wall surface of an outer cup (16) are formed in a circular arc shape for one point (B) contact with balls (28), and lateral cross-sections of second guiding grooves (32a-32f) provided in the outer wall surface of an inner ring (34) are formed in an elliptic arc shape for two-point contact with the balls (28). The diameter (N) of a ball (28) and an offset amount (T) between a first and second groove (26a, 32a) is set to satisfy the expression of 0.12 | V | 0.14 with V being the ratio (T/N) of the two values.

Description

Constant velocity joint

Technical Field

The present invention relates to a constant velocity joint used, for example, to connect one propeller shaft to another propeller shaft in a drive force transmission portion of an automobile.

Background

In a driving force transmitting portion of an automobile, a constant velocity universal joint is conventionally used in which one propeller shaft is connected to another propeller shaft to transmit rotational force to each axle. In recent years, there has been an increasing demand for a constant velocity joint to be lighter in weight, and it is desired to further reduce the size of the constant velocity joint. In this case, the strength, durability, load capacity, and the like of the constant velocity joint are set individually according to the basic dimensions of each element constituting the constant velocity joint, and it is necessary to set dimensions corresponding to downsizing while maintaining various characteristics of the constant velocity joint such as strength, durability, load capacity, and the like.

As a technical idea regarding the basic setting of such a constant velocity joint, japanese patent laid-open No. 2001-: in a fixed constant velocity universal joint having an outer joint member, an inner joint member, eight torque transmission balls, and a retainer, a ratio Rw (═ W/PCR) of an axial width (W) of the inner joint member and a length (PCR) of a line segment connecting a center of a guide groove of the inner joint member and a center of the torque transmission balls is set to 0.69 Rw 0.84.

Further, Japanese patent laid-open No. 2003-97590 discloses the following: in a fixed type constant velocity universal joint having an outer race (outer race), an inner race (inner race), six torque transmission balls, and a cage (cage), a diameter of a drive shaft is D, a diameter of the torque transmission balls is DB, and a pitch circle diameter of the six torque transmission balls is D_PIn the case of (2), the diameter D of the torque transmission ball_BRatio D of diameter D of the drive shaft_BThe value of/d is set to 0.65 to 0.72, pitch diameter D_PDiameter D relative to torque transmission ball_BRatio D of_P/D_BThe range of 3.4 to 3.8.

Further, as constant velocity joints relating to such prior art, for example, Charles e.cooney, Jr, united states, AND DRIVESHAFT digital and manual ADVANCES IN ENGINEERING SERIES No.7, No. 2 edition, that family OF autokinetic ENGINEERS, INC.1991, p.145-149 (hereinafter referred to as THE plain document) discloses such a ball type constant velocity joint: there are the center of the ball groove of the outer race and the center of the ball groove of the inner race on the joint shafts (drive shaft and driven shaft), and the center of the ball groove of the outer race and the center of the ball groove of the inner race are disposed at equal distances from the joint center on both sides of the joint center.

In this ball-type constant velocity universal joint, the six balls held in the cage are positioned on the angular bisector between the constant velocity plane and the joint axis by the relative movement of the ball grooves of the outer race and the ball grooves of the inner race, whereby the drive contact is always held on the constant velocity plane, and the constant velocity is ensured.

In this case, the above-mentioned general documents describe the following: the common normal line of the ball groove (guide groove) of the outer race and the load-side contact point of the ball, and the wedge angle, which is the angle formed by the common normal line of the ball groove (guide groove) of the inner race and the load-side contact point of the ball, are set to approximately 15 to 17 degrees. This is for: when the rzeppa constant velocity universal joint performs a drift angle action when the included angle of the universal joint is about 0 degree, the ball is prevented from being locked due to friction.

The above-mentioned general documents also describe the following: the commonly used spherical groove is formed in an arc shape or an elliptic arc shape in cross section (cross section in a direction orthogonal to the joint axis), and the contact angle of the elliptic arc shaped spherical groove with the ball therein is set to 30 degrees to 45 degrees, and the most commonly used contact angle is 45 degrees.

Further, japanese patent laid-open publication nos. 2003-4062 and 9-317784 disclose a fixed type constant velocity universal joint including a bell housing, a planetary sleeve, eight balls, and a cage, wherein the center of a curved portion of a groove bottom of a guide groove (track groove) of the bell housing is offset in opposite directions in an axial direction by an equal distance (F) with respect to the center of an inner diameter surface, and the center of a curved portion of a groove bottom of a guide groove (track groove) of the planetary sleeve is offset in opposite directions in an axial direction with respect to the center of an outer diameter surface.

In Japanese patent application laid-open No. 2003-4062, it is described that the offset amount (F) and the ratio R1(═ F/PCR) of the length (PCR) of the line segment connecting the center of the guide groove of the bell housing or the center of the guide groove of the star hub and the center of the ball are set in the range of 0.069 ≦ R1 ≦ 0.121.

Further, Japanese patent application laid-open No. 9-317784 discloses: the offset (F) and the ratio R1(═ F/PCR) of the length of a line segment connecting the center of the guide groove of the bell housing or the center of the guide groove of the star hub and the center of the ball are set in the range of 0.069 ≦ R1 ≦ 0.121, and the contact angle between each guide groove and the ball is set to 37 degrees or less.

Further, japanese patent laying-open No. 2002-323061 discloses a fixed type constant velocity universal joint including: the present invention is a torque transmission device comprising an outer joint member, an inner joint member, eight torque transmission balls, and a cage, and the patent document also describes: the center of the ball groove (track groove) of the outer joint member and the center of the ball groove (track groove) of the inner joint member are offset by an equal distance in the axial direction toward opposite sides, and the PCD clearance (difference between the pitch circle diameter of the ball groove of the outer joint member and the pitch circle diameter of the ball groove of the inner joint member) on the ball track is 5 to 50 [ mu ] m.

In the aforementioned japanese patent application laid-open No. 2002-323061, by setting the PCD gap to 5 to 50 μm, durability at the time of a high load can be improved and life variation can be stabilized in a fixed type constant velocity universal joint having eight torque transmission balls.

Further, Japanese patent application laid-open No. 2002-323061 discloses: the radial gap between the outer joint member and the retainer is set to 20 to 100 μm, and the radial gap between the retainer and the inner joint member is set to 20 to 100 μm.

Further, the constant velocity joint according to the related art includes, for example, as shown in fig. 24: an outer member (bell-shaped member) 1 having a spherical inner diameter surface 1a with a plurality of guide grooves 1b formed therein in a curved shape in an axial direction; and an inner member (a star type sleeve member) 2 having a spherical outer surface 2a formed with a plurality of curved guide grooves 2b in the axial direction and an inner diameter surface provided with splines 2 c. The curved guide groove 1b of the outer member 1 and the curved guide groove 2b of the inner member 2 form a ball rolling groove integrally, and a ball 3 for torque transmission is disposed in the ball rolling groove. The ball 3 is held by a holding window 4a formed in the substantially annular retainer 4.

In this case, the joint strength when an angle is given to the outer member 1 and the inner member 2 is determined by the strength of the cage 4. Therefore, in order to increase the joint strength when the angle is given, it is necessary to increase the strength of the retainer 4 itself.

Here, in order to increase the strength of the holder 4 itself, it is possible to cope with this by increasing the sectional area of the holder 4. Examples of the method include the following methods: a method of increasing the thickness of the cage 4 by reducing the diameter of the inner spherical surface of the cage and increasing the diameter of the outer spherical surface of the cage (hereinafter referred to as a first method), a method of increasing the cross-sectional area of the cage 4 on the side receiving the ejection force of the ball 3 generated when the angle is applied to the gimbal (hereinafter referred to as a second method), and a method of increasing the cross-sectional area of the column portion 4b located between the holding windows 4a (hereinafter referred to as a third method).

However, the first and second methods have the following problems: the weight of the cage 4 becomes large or the width dimension becomes wide, and the balls 3 intrude into the curved guide grooves 1b, resulting in a decrease in durability of the outer member 1. Also, since the width of the retainer 4 is widened, it may be impossible to fit the retainer 4 into the outer member 1.

On the other hand, in the above-described third method, when the length of the pillar portion 4b is increased to reduce the opening area of the holding window 4a, the ball 3 is easily brought into contact with the pillar portion 4b, so that there is a problem that the poor assembly of the ball 3 occurs. Further, since the holding window 4a is too small, there is a problem that the inner member 2 cannot be easily assembled into the holder 4.

Therefore, for example, japanese patent laid-open publication No. 2002-: the holding window 4a is provided with an angular radius part 4c, and the ratio R/D of the curvature radius R of the angular radius part 4c to the diameter D of the ball 3 is 0.22R/D.

However, the technical idea disclosed in the above-mentioned Japanese patent laid-open No. 2001-330051 has such a problem that: the number of parts is large, which results in high manufacturing cost and great technical difficulty in actual production.

Further, in the technical idea disclosed in japanese patent application laid-open No. 2003-97590, the constant velocity joint cannot be downsized because the dimensions are set to increase the strength of the retainer that retains the torque transmission balls.

In addition, the ball track formed by the ball groove of the outer race and the ball groove of the inner race is formed as: a wedge shape gradually increasing from the inner side of the opening portion of the bell-shaped case toward the opening portion side in the axial direction. Therefore, since the respective ball grooves on the bell-shell side and the spider side are located at positions offset by equal distances with respect to the joint center, the depths of the two ball grooves are not uniform in the axial direction.

In the structure disclosed in the above-mentioned conventional document, since the depth of each ball groove of the outer race and the inner race is shallow, at a large connection angle or a high load action, the contact ellipse of the ball may be detached from the ball groove and moved to the shoulder (end) of the ball groove, or the ball groove shoulder may be damaged or worn, etc., thereby decreasing the durability. In addition, cases are also envisaged in which: when a high load is applied, the ball groove and ball contact position is close to the end of the star sleeve, causing the contact ellipse to protrude, thereby increasing the contact surface pressure against the ball groove.

Further, the contents of these are disclosed in the above-mentioned Japanese patent laid-open Nos. 2003-4062 and 9-317784: the offset amount (F) and the ratio R1 (F/PCR) of the length (PCR) of the line segment connecting the center of the guide groove of the outer race or the center of the guide groove of the inner race and the center of the ball are set to predetermined values, but in this case, if the diameter of the ball is set to be small, the constant velocity joint itself is made smaller, and the thickness of the retainer which is the weakest member is ensured, the depth of the guide groove of the outer race and the inner race cannot be ensured sufficiently, and there is a problem such as breakage or abrasion of the shoulder portion of the guide groove as described above.

In addition, japanese patent application laid-open No. 2002-323061 describes that a constant velocity universal joint having eight torque transmission balls is different from a constant velocity universal joint having six torque transmission balls in the basic structure, and the set value of the PCD clearance also has an inherent value suitable for the structure, but the set values of the PCD clearance and the like of the constant velocity universal joint having six torque transmission balls are not mentioned or suggested at all.

That is, in such a constant velocity universal joint, the ball track is formed by a pair of ball grooves of the outer joint member and the inner joint member which face each other, and how to set a PCD (pitch circle diameter) clearance with respect to the ball track is important. This is because if the PCD gap is too small, the ball assembling work when inserting the ball into the ball track is difficult, and the ball is restrained by a large force, which hinders the smooth rolling operation of the ball. On the other hand, if the PCD gap is too large, there is a problem that collision noise is generated between the holding window portion of the holder and the ball, or joint vibration increases.

Further, according to the technical idea disclosed in japanese patent application laid-open No. 2002-.

Disclosure of Invention

The invention provides a constant velocity universal joint which can reduce surface pressure generated on a guide groove due to contact with a ball so as to improve durability.

The invention provides a constant velocity universal joint which can prevent the shoulder part of a guide groove from being damaged or abraded, and can improve the durability.

The present invention provides a constant velocity joint having six balls, in which various clearances or the offset amounts of holding windows of a cage are set to be optimum, and which can reduce surface pressures between an outer guide groove and a ball and between an inner guide groove and a ball, which directly affect the life of the joint, and can improve durability.

The invention aims to provide a constant velocity universal joint which can maintain various characteristics such as strength, durability and load capacity and can be set in various sizes corresponding to miniaturization.

The invention aims to provide a constant velocity universal joint which can well ensure the strength of a retainer and can improve the assembling workability.

According to the present invention, the cross section of the first guide groove of the outer member is formed in the shape of an arc and is in contact with the ball at one point, and the cross section of the second guide groove of the inner ring is formed in the shape of an elliptical arc and is in contact with the ball at two points, whereby the surface pressure to the first and second guide grooves due to the contact with the ball can be reduced as compared with the prior art, and the durability can be improved.

In this case, the ratio of the groove radius (M) of the cross section of the first guide groove to the groove radius (P, Q) of the cross section of the second guide groove to the diameter (N) of the ball is set to be in the range of 0.51 to 0.55, respectively, and the contact angle of the first guide groove to the ball is set to zero degrees with respect to the vertical line (L), and the contact angle (α) of the second guide groove to the ball is set to be in the range of 13 to 22 degrees with respect to the vertical line (L), whereby the surface pressure can be reduced, and the durability can be further improved.

Further, it is more preferable that the contact angle (α) between the second guide groove and the ball is set within a range of 15 degrees to 20 degrees with respect to the vertical line (L).

In addition, according to the present invention, the PCD gap is set in the range of 0 μm to 100 μm because: if the PCD gap is less than 0 μm, the fitting property of the ball into the hole portion of the outer member is deteriorated, and the smooth rolling motion of the ball is hindered, resulting in a decrease in durability. Another aspect is because: if the PCD gap exceeds 100 μm, contact ellipses of the ball and the first and second guide grooves protrude from the shoulder portion, which is the groove end, at the time of high load, increasing the surface pressure, and causing the shoulder portion to break, resulting in a decrease in durability.

In this case, the spherical gap is obtained by adding the following two differences: a difference between an outer member inner spherical surface diameter of the inner diameter surface of the outer member and a cage outer spherical surface diameter of the outer surface of the cage, and a difference between a cage inner spherical surface diameter of the inner surface of the cage and an inner ring outer spherical surface diameter of the outer surface of the inner ring, the spherical clearance [ (outer member inner spherical surface diameter) - (cage outer spherical surface diameter) ] + [ (cage inner spherical surface diameter) - (inner ring outer spherical surface diameter) ] is set in a range of 50 to 200 μm.

This is because: if it is less than 50 μm, ablation may occur between the inner surface of the outer member and the outer surface of the cage and between the outer surface of the inner ring and the inner surface of the cage due to poor lubrication, which may adversely affect the performance. Another aspect is because: if the spherical gap exceeds 200 μm, collision noise is generated between the outer member and the inner ring and the cage, which may affect the merchantability.

Further, the center of the width of the holding window formed in the holding window of the holder may be set at a position where: and a position shifted from the spherical centers of the outer surface and the inner surface of the retainer in the range of 20 to 100 [ mu ] m in the axial direction of the retainer.

This is because: if the offset amount between the holding window width center of the retainer and the spherical surface center is less than 20 μm, the restraining force for the ball is insufficient, and it is difficult to ensure the constant velocity, and if the offset amount is greater than 100 μm, the restraining force becomes too large, which hinders the smooth rolling operation of the ball, and deteriorates the durability.

Further, according to the present invention, by setting the ratio V (T/N) of the diameter (N) of the ball to the offset amount T of the center of curvature (H, R) of the first and second guide grooves to satisfy the relational expression (0.12. ltoreq. V.ltoreq.0.14), it is possible to effectively prevent the ball from moving to the shoulder portions formed at the end portions of the first and second guide grooves, or to prevent the shoulder portions from being defective, worn, or the like, and thus to improve the durability of the constant velocity joint.

In this case, if the ratio V (T/N) of the diameter (N) of the ball to the offset amount (T) is less than 0.12, the wedge angle formed by the first guide groove and the second guide groove is extremely small, and when the rotation operation is not performed, the locked state of the ball is likely to occur, and the workability at the time of assembly is lowered. On the other hand, if the ratio V (T/N) of the diameter (N) of the ball to the offset amount (T) exceeds 0.14, the depth of the first and second guide grooves is shallow, and it is difficult to prevent the ball from moving onto the shoulder portions formed at the ends of the first and second guide grooves, or to prevent the shoulder portions from being broken or worn, or the like.

Further, according to the present invention, the outer PCD is made identical to the inner PCD and is an outer/inner PCD, an inner ring serration inner diameter portion is formed on an inner wall surface of a hole portion of the inner ring, and a ratio (Dp/D) of a size (Dp) of the outer/inner PCD to a diameter (D) of the inner ring serration inner diameter portion is preferably set in a range of 1.9 ≦ Dp (Dp/D) ≦ 2.2. If the size ratio (Dp/D) of the outer/inner PCD size (Dp) to the inner ring serration inner diameter portion diameter (D) is less than 1.9, there is a problem that the inner ring wall thickness is too thin and the strength is lowered, and on the other hand, if the size ratio (Dp/D) exceeds 2.2, the constant velocity joint cannot be miniaturized.

Further, the outer PCD is made identical to the inner PCD and is made as outer/inner PCD, and the ratio (Db/Dp) of the diameter (Db) of the balls to the size (Dp) of the outer/inner PCD is preferably set in the range of 0.2 ≦ (Db/Dp) ≦ 0.5. In this case, if the size ratio (Db/Dp) is less than 0.2, there is a disadvantage that the diameter of the ball is excessively small to cause a reduction in durability, and on the other hand, if the size ratio (Db/Dp) exceeds 0.5, the ball is large and the wall thickness of the outer member is relatively thin to cause a reduction in strength.

Further, with the outer PCD being the same as the inner PCD and being outer/inner PCD, the ratio (Do/Dp) of the outer diameter (Do) of the outer member to the size (Dp) of the outer/inner PCD is preferably set in the range of 1.4 ≦ Do/Dp ≦ 1.8. In this case, if the dimensional ratio (Do/Dp) is less than 1.4, the outer member may be thin and the strength may be reduced, whereas if the dimensional ratio (Do/Dp) exceeds 1.8, the outer diameter of the outer member may be large and the outer member cannot be made compact.

The outer PCD is made identical to the inner PCD and is an outer/inner PCD, an inner ring serration inner diameter portion is formed on an inner wall surface of a hole portion of the inner ring, a ratio (Dp/D) of a dimension (Dp) of the outer/inner PCD to a diameter (D) of the inner ring serration inner diameter portion is preferably set in a range of 1.9 ≦ Dp/D ≦ 2.2, and a ratio (Db/Dp) of a diameter (Db) of the ball to a dimension (Dp) of the outer/inner PCD is preferably set in a range of 0.2 ≦ Db/Dp ≦ 0.5, and a ratio (Do/Dp) of an outer diameter (Do) of the outer member to a dimension (Dp) of the outer/inner PCD is preferably set in a range of 1.4 ≦ Do/Dp ≦ 1.8.

Further, according to the present invention, the holding window has an opening length (WL) in a circumferential direction of the holder, and a ratio (WL/N) of the opening length (WL) to a diameter (N) of the ball is preferably set in a range of 1.30 ≦ WL/N ≦ 1.42. The holding window has a corner portion with a radius of curvature R, and the ratio (R/N) of the radius of curvature (R) to the diameter (N) of the ball is preferably set in the range of 0.23 ≦ R/N ≦ 0.45.

By setting the relationship of 0.23 ≦ (R/N), the maximum principal stress load of the column portion between the holding windows can be reduced, and the strength of the retainer can be improved. On the other hand, by setting the relation of (R/N) to 0.45 or less, the corner of the holding window can be effectively prevented from being excessively large, thereby avoiding poor assembly of the ball and the inner ring.

In addition, the first guide groove and the second guide groove may be formed to have a curved shape portion and a linear shape portion along a length direction (S1, S2). Preferably, the first guide groove and the second guide groove are formed to have only curved portions along the longitudinal direction.

Drawings

Fig. 1 is a longitudinal sectional view of a constant velocity joint according to an embodiment of the present invention in an axial direction.

Fig. 2 is a partially enlarged longitudinal sectional view of the constant velocity joint shown in fig. 1.

Fig. 3 is a partial cross-sectional side view of the constant velocity joint shown in fig. 1, as viewed in the axial direction (the direction of arrow X).

Fig. 4 is an enlarged partial cross-sectional view perpendicular to the axial direction of the constant velocity joint shown in fig. 1.

Fig. 5 is a partially enlarged vertical sectional view showing the depth of the first guide groove of the constant velocity joint according to the present embodiment.

Fig. 6 is a partially enlarged longitudinal sectional view showing the depth of the first guide groove of the constant velocity joint of the comparative example.

Fig. 7 is an explanatory diagram showing a relationship between the contact angle of the second guide groove with the ball and the durability.

Fig. 8A is a longitudinal sectional view illustrating an outer PCD as a pitch circle diameter of a first guide groove formed in an outer cup (outer cup), and fig. 8B is a longitudinal sectional view illustrating an inner PCD as a pitch circle diameter of a second guide groove formed in an inner ring (inner ring).

FIG. 9A is a longitudinal sectional view showing the inner diameter of the outer cup, and FIG. 9B is a view showing the inner diameter of the outer cup

31. The constant velocity joint according to claim 28,

the first guide grooves (26 a-26 f) and the second guide grooves (32 a-32 f) have only curved portions along the longitudinal direction.

32. A constant velocity joint, comprising:

an outer member (16) having an open end, the outer member (16) being connected to one of two intersecting shafts (12, 18) and having an inner diameter surface formed of a spherical surface, and the outer member (16) having a plurality of first guide grooves (26 a-26 f) formed therein and extending in the axial direction;

an inner ring (34) connected to the other of the two shafts, and having second guide grooves (32 a-32 f) extending in the axial direction and having the same number as the first guide grooves (26 a-26 f);

six balls (28) rollably disposed between the first guide grooves (26 a-26 f) and the second guide grooves (32 a-32 f) for transmitting torque between the first guide grooves (26 a-26 f) and the second guide grooves (32 a-32 f); and

a retainer (38) formed with a retaining window (36) for receiving each ball (28),

wherein,

the first guide grooves (26 a-26 f) formed in the outer member (16) are formed such that: a cross section orthogonal to the axial direction is formed in a single circular arc shape, and the first guide grooves (26 a-26 f) are in contact with the ball (28) at one point,

second guide grooves (32 a-32 f) formed in the inner ring (34) are formed such that: a cross section thereof orthogonal to the axial direction is formed in an elliptical arc shape, and the second guide grooves (32 a-32 f) are in contact with the ball (28) at two points,

when the pitch circle diameter of the first guide grooves (26 a-26 f) is defined as outer PCD and the pitch circle diameter of the second guide grooves (32 a-32 f) of the inner ring (34) is defined as inner PCD, the PCD gap defined by the difference between the outer PCD and the inner PCD (outer PCD-inner PCD) is set to be in the range of 0 to 100 [ mu ] m,

first guide grooves (26 a-26 f) are formed in the outer member (16), longitudinal sections of the first guide grooves (26 a-26 f) in the axial direction are curved, second guide grooves (32 a-32 f) are formed in the inner ring (34), longitudinal sections of the second guide grooves (32 a-32 f) in the axial direction are curved, and centers of curvature (H) of the first guide grooves (26 a-26 f) and centers of curvature (R) of the second guide grooves (32 a-32 f) are arranged at positions where: from the above

Detailed Description

In fig. 1, reference numeral 10 denotes a constant velocity joint according to an embodiment of the present invention. In the following description, the longitudinal section means a section along the axial direction of the first shaft 12 and the second shaft 18, and the transverse section means a section orthogonal to the axial direction.

The constant velocity joint 10 basically includes: a bottomed cylindrical outer cup (outer member) 16 integrally connected to one end portion of the first shaft 12 and having an opening 14; and an inner member 22 fastened to one end of the second shaft 18 and accommodated in the hole of the outer cup 16.

As shown in fig. 1 and 3, the inner wall of the outer cup 16 has an inner diameter surface 24 formed of a spherical surface, six first guide grooves 26a to 26f extending in the axial direction are formed in the inner diameter surface 24, and the six first guide grooves 26a to 26f are arranged at 60-degree intervals around the axial center.

As shown in fig. 2, the first guide grooves 26a (26b to 26f) formed in the outer cup 16 and having a curved longitudinal section in the axial direction have a point H as a curvature center. In this case, the point H is arranged at a position: the outer cup 16 is axially offset toward the opening 14 by a distance T1 from the spherical center K of the inner diameter surface 24 (the intersection of the imaginary plane connecting the center point O of the ball 28 (the center plane of the ball) and the joint axis 27.

As shown in fig. 4, the cross sections of the first guide grooves 26a to 26f formed in the outer cup 16 are each formed in a single arc shape having a center of curvature a on a straight line L passing through the center O of the ball 28, and the first guide grooves 26a to 26f are formed so as to contact a point B on the drawing surface with the outer surface of the ball 28, which will be described later.

In practice, when a load is applied by transmitting a rotational torque, the outer surface of the ball 28 and the first guide grooves 26a to 26f are not in point contact but in surface contact.

The inner diameter surface 24 is continuously formed on both sides of the first guide grooves 26a to 26f in the cross section, and a set of chamfered

first shoulders

30a and 30b are formed at the boundary portions between the end portions of the first guide grooves 26a to 26f and the inner diameter surface 24.

The contact angle between the ball 28 and the first guide grooves 26a to 26f of the outer cup 16 is set to zero degrees with reference to the vertical line L. In addition, the ratio (M/N) of the groove radius M to the diameter N of the ball 28 in the cross section of the first guide grooves 26a to 26f may be set in the range of 0.51 to 0.55 (refer to fig. 4).

The inner part 22 is constituted to include: an inner ring 34 having a plurality of second guide grooves 32a to 32f formed on an outer circumferential surface thereof in a circumferential direction, the second guide grooves corresponding to the first guide grooves 26a to 26 f; a plurality of (six in the present embodiment) balls 28 that are arranged so as to be capable of rolling between first guide grooves 26a to 26f formed in an inner wall surface of the outer cup 16 and second guide grooves 32a to 32f formed in an outer diameter surface 35 (see fig. 4) of the inner ring 34, and that have a rotational torque transmission function; and a retainer 38 having a plurality of retaining windows 36 formed along a circumferential direction of the retainer 38 to retain the balls 28, and the retainer 38 is interposed between the outer cup 16 and the inner ring 34.

The inner ring 34 is spline-fitted to the end of the second shaft 18 through a hole formed in the center, or is integrally fixed to the end of the second shaft 18 by an annular locking member 40 fitted to an annular groove of the second shaft 18. A plurality of second guide grooves 32a to 32f are formed in the outer diameter surface 35 of the inner ring 34 at equal angular intervals in the circumferential direction, and the plurality of second guide grooves 32a to 32f are arranged so as to correspond to the first guide grooves 26a to 26f of the outer cup 16.

As shown in fig. 2, the second guide grooves 32a to 32f formed in the inner ring 34 and having a curved longitudinal section in the axial direction have a point R as a center of curvature. In this case, the point R is disposed at a position: the position is axially offset by a distance T2 from the spherical center K of the inner diameter surface 24 (the intersection of an imaginary plane connecting the center point O of the ball 28 (the center plane of the ball) and the joint axis 27 at right angles).

The point H as the center of curvature of the first guide grooves 26a to 26f of the outer cup 16 and the point R as the center of curvature of the second guide grooves 32a to 32f of the inner ring 34 are arranged at positions: positions shifted by equal distances (T1 ═ T2) in opposite directions from the spherical center K of the inner diameter surface 24 (the intersection point where the central surface of the ball is orthogonal to the joint axis 27) in the circumferential direction. The point H is disposed on the opening 14 side of the outer cup 16 with respect to the spherical center K, the point R is located on the deep portion 46 side of the outer cup 16, and the curvature radius of the point H and the curvature radius of the point R are set to intersect (see fig. 2).

In this case, when the diameter of the ball 28 is N, the offset amounts (the distances from the spherical center K in the axial direction) of the centers of curvature (the points H and R) of the first guide grooves 26a to 26f of the outer cup 16 and the second guide grooves 32a to 32f of the inner ring 34 are T, and the ratio between the diameter N and the offset amount T is V, the diameter N and the offset amount T of the ball 28 are preferably set so that the ratio V (T/N) satisfies the relational expression of 0.12V 0.14.

As shown in fig. 4, the second guide grooves 32a to 32f are formed in cross-sections: an elliptical arc shape having a pair of centers C, D spaced apart by a predetermined distance in the horizontal direction, and the second guide grooves 32a to 32f are formed to contact the outer surface of the ball 28 at two points E, F on the drawing. In practice, when a load is applied by transmitting a rotational torque, the outer surface of the ball 28 and the second guide grooves 32a to 32f are not in point contact but in surface contact.

Outer diameter surfaces 35 are continuously formed on both sides of the second guide grooves 32a to 32f in the cross section, and a set of chamfered

second shoulders

42a and 42b are formed at the boundary portions between the end portions of the second guide grooves 32a to 32f and the outer diameter surfaces 35.

The contact angle α between the ball 28 and the second guide grooves 32a to 32f is set to an angle α equal to the distance between the right and left sides with respect to the vertical line L. In this case, as shown in fig. 7, when the contact angle α between the ball 28 and the second guide grooves 32a to 32f is set to be in the range of 13 degrees to 22 degrees, the durability is good, and when the contact angle α between the ball 28 and the second guide grooves 32a to 32f is set to be in the range of 15 degrees to 20 degrees, the durability is excellent. Further, the ratio (P/N, Q/N) of the groove radius P, Q to the diameter N of the ball 28 in the cross section of the second guide grooves 32a to 32f may be set to 0.51 to 0.55 (see fig. 4).

The ball 28 is made of, for example, a steel ball, and is configured to: one guide groove is disposed between each of the first guide grooves 26a to 26f of the outer cup 16 and the second guide grooves 32a to 32f of the inner ring 34, and is capable of rolling in the circumferential direction. The balls 28 transmit the rotational torque of the second shaft 18 to the first shaft 12 through the inner ring 34 and the outer cup 16, and roll along the first guide grooves 26a to 26f and the second guide grooves 32a to 32f, thereby allowing the second shaft 18 (the inner ring 34) and the first shaft 12 (the outer cup 16) to be displaced relative to each other in the intersecting angular direction. In addition, the rotational torque can be transmitted between the first shaft 12 and the second shaft 18 in any direction.

As shown in fig. 8A and 8B, when the pitch circle diameters of the first guide grooves 26a to 26f are set as outer PCD in a state where the six balls 28 are in point contact with the first guide grooves 26a to 26f of the outer cup 16, respectively, and the pitch circle diameters of the second guide grooves 32a to 32f are set as inner PCD in a state where the six balls 28 are in point contact with the second guide grooves 32a to 32f of the inner ring 34, respectively, in this case, a PCD gap is determined by a difference between the outer PCD and the inner PCD (outer PCD — inner PCD).

In addition, as shown in fig. 9A to 9C, the spherical gap is determined by adding the following two differences: the difference between the outer cup inner spherical surface diameter on the inner diameter surface 24 of the outer cup 16 and the retainer outer spherical surface diameter of the outer diameter surface of the retainer 38, and the difference between the retainer inner spherical surface diameter of the inner diameter surface of the retainer 38 and the inner ring outer spherical surface diameter of the outer diameter surface of the inner ring 34.

In other words, it is set according to the following formula: the spherical clearance ═ [ (inner spherical diameter of the outer cup) - (outer spherical diameter of the retainer) ] + [ (inner spherical diameter of the retainer) - (outer spherical diameter of the inner ring) ].

As shown in fig. 10, the holding window 36 of the holder 38 has a holding window width center (with the axial direction of the holder 38 as the width direction) and spherical centers of the outer surface 38a and the inner surface 38b of the holder 38, which are arranged at positions shifted by a predetermined distance along the axial direction of the holder 38.

The basic structure of the constant velocity joint 10 of the present embodiment is as described above, and the operation and operational effects thereof will be described below.

When the second shaft 18 rotates, the rotational torque thereof is transmitted from the inner race 34 to the outer cup 16 through the balls 28, and the first shaft 12 rotates in a predetermined direction while maintaining the same speed as the second shaft 18.

At this time, when the intersection angle (operating angle) of the first shaft 12 and the second shaft 18 changes, the retainer 38 tilts by a predetermined angle by the action of the balls 28 rolling between the first guide grooves 26a to 26f and the second guide grooves 32a to 32f, and the angle change is allowed.

In this case, the six balls 28 held in the holding windows 36 of the retainer 38 are positioned on the constant velocity plane or the bisector of the angle between the first shaft and the

second shaft

12 and 18, so that the driving contact points are always held on the constant velocity plane, and the constant velocity can be ensured. In this way, while maintaining the constant velocity of the first and

second shafts

12, 18, appropriate angular variations therebetween are also permitted.

In the present embodiment, the ratio V (═ T/N) of the diameter N of the ball 28 and the offset amount (distance in the axial direction from the spherical center K) T from the centers of curvature (points H, R) of the first guide grooves 26a to 26f of the outer cup 16 and the second guide grooves 32a to 32f of the inner ring 34 is set so as to satisfy: 0.12. ltoreq. V.ltoreq.0.14 (see FIG. 2).

In this case, if the ratio V of the diameter N of the ball 28 to the offset amount T is less than 0.12, the wedge angle formed by the first guide grooves 26a to 26f and the second guide grooves 32a to 32f is extremely small, and when the turning operation is not performed, the locked state of the ball 28 is likely to occur, which may cause a problem that workability in assembly is deteriorated.

On the other hand, if the ratio V of the diameter N of the ball 28 to the offset amount T exceeds 0.14, since the depths of the first guide grooves 26a to 26f and the second guide grooves 32a to 32f are shallow, it is difficult to avoid the occurrence of the situation where the ball 28 moves to the first and

second shoulders

30a, 30b, 42a, 42b formed at the ends of the first and second guide grooves 26a to 26f, 32a to 32f, or the situation where the first and

second shoulders

30a, 30b, 42a, 42b are broken or worn, or the like.

By setting the offset T between the diameter N of the ball 28 and the center of curvature (point H, point R) of the first and second guide grooves 26a to 26f, 32a to 32f to satisfy the relational expression (0.12V 0.14) as described above, it is possible to effectively prevent the ball 28 from moving to the first and

second shoulders

30a, 30b, 42a, 42b formed at the end portions of the first and second guide grooves 26a to 26f, 32a to 32f, or from breaking or wearing the first and

second shoulders

30a, 30b, 42a, 42b, and the like, and to further improve the durability of the constant velocity joint 10.

Fig. 5 is a partially enlarged longitudinal sectional view of the constant velocity joint 10 according to the present embodiment, and the offset amount T1 is set small because the relationship between the diameter N of the ball 28 and the offset amount T of the curvature centers (point H, point R) of the first and second guide grooves 26a to 26f, 32a to 32f satisfies the relational expression. On the other hand, fig. 6 is a partially enlarged longitudinal sectional view of the constant velocity joint 10 of the comparative example, and the offset amount T2 is set to be larger than that of the present embodiment (T1 < T2).

In this case, when the depths of the first guide grooves 26a to 26f of the outer cup 16 are compared at a portion inclined by about 15 degrees with respect to a straight line S (the straight line S is orthogonal to the joint axis 27 and passes through the center of the ball 28), the depth DP1 of the first guide grooves 26a to 26f of the present embodiment can be formed to be larger than the depth DP2 of the first guide groove of the comparative example (DP1 > DP2), and therefore, it is possible to effectively avoid the occurrence of the situation where the ball 28 moves to the first and

second shoulders

30a, 30b, 42a, and 42b formed at the end portions of the first guide grooves 26a to 26f, or breaks or wears the first and

second shoulders

30a, 30b, 42a, and 42 b.

In the present embodiment, the cross section of the first guide grooves 26a to 26f of the outer cup 16 is formed in an arc shape and contacts the ball 28 at one point, and the cross section of the second guide grooves 32a to 32f of the inner ring 34 is formed in an elliptical shape and contacts the ball 28 at two points, whereby the surface pressure on the first guide grooves 26a to 26f and the second guide grooves 32a to 32f caused by the contact with the ball 28 is reduced as compared with the conventional art, and the durability can be improved.

In this case, in the present embodiment, the ratios (M/N, P/N, Q/N) of the groove radius (M, P, Q) to the diameter N of the ball 28 in the cross sections of the first guide grooves 26a to 26f and the second guide grooves 32a to 32f are set in the range of 0.51 to 0.55, respectively, and the contact angle between the first guide grooves 26a to 26f and the ball 28 is set to zero degrees with reference to the vertical line L, and the contact angle α between the second guide grooves 32a to 32f and the ball 28 is set in the range of 13 to 22 degrees with reference to the vertical line L, whereby the surface pressure can be reduced, and the durability can be further improved.

The ratio of the groove radius (M, P, Q) to the diameter N of the ball 28 in the cross section of the first guide grooves 26a to 26f and the second guide grooves 32a to 32f is set to 0.51 to 0.55 because: if this ratio is less than 0.51, the groove radius (M, P, Q) and the diameter N of the ball 28 are too close to each other, and the ball 28 is in a state of almost full contact (contact over the entire surface), and therefore, rolling of the ball 28 is not facilitated, and durability is reduced, whereas if it exceeds 0.55, on the contrary, the contact ellipse of the ball 28 is reduced, and therefore, contact surface pressure is increased, and durability is impaired.

Further, the ratio V (T/N) of the diameter N of the ball 28 to the offset T of the centers of curvature (point H, point R) of the first and second guide grooves 26a to 26f, 32a to 32f in the longitudinal section, the contact angle α of the second guide grooves 32a to 32f to the ball 28, and the ratio of the groove radius (M, P, Q) in the cross-section of the first guide grooves 26a to 26f and the second guide grooves 32a to 32f to the diameter N of the ball 28 are optimum values obtained from the results of repeated simulations and tests, respectively.

In addition, the contact angle α between the second guide grooves 32a to 32f and the ball 28 is set in the range of 13 to 22 degrees because: if the contact angle α is less than 13 degrees, the load on the ball 28 increases, so that the surface pressure increases, and the durability deteriorates, on the other hand, if the contact angle α exceeds 22 degrees, the contact positions of the end portions (

second shoulders

42a, 42b) of the second guide grooves 32a to 32f and the ball 28 approach, causing the contact ellipse to protrude, increasing the surface pressure, and deteriorating the durability.

In the present embodiment, the PCD gap (see fig. 8A and 8B) formed by the difference between the outer PCD and the inner PCD (outer PCD — inner PCD) is set to 0 to 100 μm, and preferably, 0 to 60 μm. The clearance of the PCD is 0-100 mu m because: if it is less than 0 μm, the assembling property of the ball 28 is lowered and the smooth rolling action of the ball 28 is hindered, so that the durability is deteriorated. Another aspect is because: if the PCD gap exceeds 100 μm, contact ellipses of the ball 28 and the first and second guide grooves 26a to 26f, 32a to 32f are made to protrude from the first and

second shoulders

30a, 30b, 42a, 42b, which are groove ends, at the time of high load, increasing the surface pressure, and causing breakage of the first and

second shoulders

30a, 30b, 42a, 42b, resulting in deterioration of durability. In this case, as shown in the test results of fig. 11, by setting the range of the PCD to 0 to 60 μm, excellent durability can be obtained.

In the present embodiment, as shown in fig. 9A to 9C, the spherical gap set by [ (inner spherical surface diameter of outer cup) - (outer spherical surface diameter of retainer) ] + [ (inner spherical surface diameter of retainer) - (outer spherical surface diameter of inner ring) ] is set to 50 to 200 μm, and preferably, may be set to 50 to 150 μm. This is because: if it is less than 50 μm, ablation may occur between the inner surface of the outer cup 16 and the outer surface 38a of the retainer 38 and between the outer surface of the inner ring 34 and the inner surface 38b of the retainer 38 due to poor lubrication, which may adversely affect the performance. Another aspect is because: if it exceeds 200 μm, collision noise is generated between the outer cup 16 and the inner ring 34, and the holder 38, which may affect the merchantability. In this case, as shown in the test result of fig. 12, by setting the spherical gap to be in the range of 50 to 150 μm, excellent durability can be obtained.

In the present embodiment, as shown in fig. 10, the holding window width center of the holding window 36 of the holder 38 (the axial direction of the holder 38 is taken as the width direction) is arranged at a position: the position is shifted by 20 to 100 [ mu ] m from the spherical center of the outer surface 38a and the inner surface 38b of the holder 38 in the axial direction of the holder 38. This is because: if the offset amount between the center of the holding window width of the holding window 36 of the retainer 38 and the center of the spherical surface is less than 20 μm, the restraining force on the ball 28 is insufficient, and it is difficult to ensure the constant velocity, whereas if the offset amount is greater than 100 μm, the restraining force is too large, which hinders the smooth rolling operation of the ball 28, and deteriorates the durability. In this case, as shown in the test result of fig. 13, the retainer 38 has excellent durability by setting the offset amount between the center of the width of the retaining window and the center of the spherical surface to be 40 to 80 μm.

As a result, in the present embodiment, in the constant velocity universal joint 10 having six balls 28, even in the case of a high load, the protrusion of the contact ellipse of the ball 28 can be suppressed, and the durability can be improved.

The setting of the various dimensions of the constant velocity joint 10 will be described in detail below.

In this case, the outer PCD and the inner PCD shown in fig. 8A and 8B are set to be equal (outer PCD is equal to inner PCD), so that the difference between the outer PCD and the inner PCD is set to zero. In the following description, both the outer PCD and the inner PCD will be collectively referred to as "outer/inner PCD".

The diameter (D) of the inner ring serration inner diameter portion 39 is arbitrarily set, and the size of the outer/inner PCD, which is the minimum wall thickness of the inner ring 34, is set according to the diameter (D) of the inner ring serration inner diameter portion 39 (see fig. 14 and 15).

The diameter (D) of the inner ring serration inner diameter portion 39 is: a dimension (maximum diameter) between a bottom of a valley portion of one inner ring serration inner diameter portion 39 and a bottom of a valley portion of the other inner ring serration inner diameter portion 39 in a direction passing through the center of the hole portion of the inner ring 34 (see fig. 15). The predetermined joining strength is ensured by the minimum wall thickness of the inner ring 34. As shown in fig. 16, the value of the outer/inner PCD is determined from a characteristic straight line L of the relationship between the diameter of the inner ring serration inner diameter portion 39 and the outer/inner PCD.

In this case, when the diameter of the inner ring serration inner diameter portion 39 is D and the outer/inner PCD is Dp (see fig. 14 and 15), the size ratio (Dp/D) of the outer/inner PCD (Dp) to the diameter (D) of the inner ring serration inner diameter portion 39 is preferably set in the range of 1.9 ≦ (Dp/D) ≦ 2.2.

This is because: if the dimension ratio (Dp/D) is less than 1.9, there is a problem that the strength is lowered due to an excessively thin wall thickness of the inner ring 34, while if the dimension ratio (Dp/D) exceeds 2.2, the constant velocity joint 10 cannot be downsized.

As shown in fig. 17, the outer diameter of the outer cup 16 is set based on a characteristic straight line M of the relationship between the outer diameter of the cup portion of the outer cup 16 and the outer/inner PCD. In this case, as shown in FIGS. 14 and 15, assuming that the outer diameter of the outer cup 16 is Do, the size ratio (Do/Dp) of the outer diameter (Do) of the outer cup 16 to the outer/inner PCD (Dp) is preferably set in the range of 1.4. ltoreq. Do/Dp.ltoreq.1.8.

This is because: if the dimension ratio (Do/Dp) is less than 1.4, there is a disadvantage that the strength is lowered due to the excessively thin wall thickness of the outer cup 16, and on the other hand, if the dimension ratio (Do/Dp) exceeds 1.8, the outer diameter of the outer cup 16 is large and miniaturization cannot be achieved.

As shown in fig. 18, the inner ring width of the inner ring 34 is set according to a characteristic straight line of the relationship between the ring width of the inner ring 34 in the axial direction of the second shaft 18 and the outer/inner PCD. In this case, assuming that the inner ring width of the inner ring 34 is W, the size ratio (W/Dp) of the inner ring width (W) of the inner ring 34 to the outer/inner PCD (Dp) is preferably set in the range of 0.38 ≦ W/Dp ≦ 0.42.

As shown in fig. 19, the diameter of the ball 28 is set according to a characteristic straight line Q of the relationship between the diameter of the ball 28 and the outer/inner PCD. In this case, as shown in FIGS. 14 and 15, assuming that the diameter of the balls 28 is Db, the size ratio (Db/Dp) of the diameter (Db) of the balls 28 to the outer/inner PCD (Dp) is preferably set in the range of 0.2. ltoreq. Db/Dp.ltoreq.0.5.

This is because: if the size ratio (Db/Dp) is less than 0.2, there is a disadvantage that the diameter of the ball 28 is excessively small to cause a reduction in durability, and on the other hand, if the size ratio (Db/Dp) exceeds 0.5, the ball 28 is large and the wall thickness of the outer cup 16 is relatively thin to cause a reduction in strength. Further, the inner spherical surface diameter and the outer spherical surface diameter of the retainer 38 that retains the ball 28 are arbitrarily set according to the respective designs.

By setting the respective dimensions in this manner, it is possible to set various dimensions corresponding to the downsized constant velocity universal joint 10 while maintaining various characteristics such as strength, durability, and load capacity.

Next, the relationship between the opening length (WL) of the holding window 36 formed in the retainer 38 in the circumferential direction and the diameter (N) of the ball 28 will be described in detail with reference to fig. 20 to 23.

As shown in fig. 20, six first guide grooves 26a to 26f are formed in the inner diameter surface 24 of the outer cup 16, the six first guide grooves 26a to 26f extending in the axial direction (arrow X direction) and being provided at intervals of 60 degrees around the axial center, and the first guide grooves 26a to 26f have a linear portion S1 integrated with the curved portion along the longitudinal direction (arrow X direction).

Second guide grooves 32a to 32f, which extend in the axial direction and are equal in number to the first guide grooves 26a to 26f, are formed on an outer diameter surface 35 of the inner ring 34. Each of the second guide grooves 32a to 32f has a linear portion S2 integrated with a curved portion along the longitudinal direction (arrow X direction), and the linear portions S1 and S2 are provided in opposite directions along the arrow X direction.

As shown in fig. 21 and 22, the retainer 38 is substantially annular, and six retaining windows 36 that retain the respective balls 28 are formed at equal angular intervals along the circumferential direction of the retainer 38.

As shown in FIG. 22, each holding window 36 has an opening length (WL) in the circumferential direction of the holder 38, and the ratio (WL/N) of the opening length (WL) to the diameter (N) of the ball 28 is set in a relationship of 1.30. ltoreq. WL/N. ltoreq.1.42. Each holding window 36 has a corner 36a with a radius of curvature R, and the ratio R/N of the radius of curvature R to the diameter N of the ball 28 is set in a relationship of 0.23. ltoreq. R/N.ltoreq.0.45.

As shown in FIG. 22, in the constant velocity joint 10, in each of the holding windows 36 of the retainer 38, the opening length (WL) of the retainer 38 in the circumferential direction and the diameter (N) of the ball 28 are set in a relationship of WL/N ≦ 1.42. Therefore, the retainer 38 can effectively maintain the circumferential length of the pillar portion 136 between the retaining windows 36, and the cross-sectional area of the pillar portion 136 can be increased without setting the thickness of the retainer 38 large.

Therefore, the strength of the retainer 38 can be effectively increased without setting the inner spherical surface diameter to be small, the outer spherical surface diameter to be large, or increasing the width in the axial direction, for example.

In the constant velocity joint 10, the opening length (WL) of the holding window 36 and the diameter (N) of the ball 28 are set in a relationship of 1.30. ltoreq. WL/N. This can increase the opening area of each holding window 36, and can effectively prevent poor assembly of the ball 28, poor assembly of the inner ring 34, and the like. Therefore, in the constant velocity joint 10, the workability of the assembling work can be easily improved with a simple structure.

Further, by setting the radius of curvature R of the corner portion 36a of the holding window 36 and the diameter (N) of the ball 28 to a relationship of 0.23. ltoreq.R/N, the maximum principal stress load of the column portion 136 between the holding windows 36 can be reduced, and the strength of the retainer 38 can be improved.

On the other hand, by setting the relationship of R/N ≦ 0.45, it is possible to effectively prevent the occurrence of: the corner 36a of the retaining window 36 is too large, resulting in poor assembly of the ball 28 and the inner ring 34.

In the constant velocity joint 10, the first guide grooves 26a to 26f have linear portions S1 along the longitudinal direction, and the second guide grooves 32a to 32f have linear portions S2 along the longitudinal direction. Therefore, the maximum operating angle of the constant velocity joint 10 can be set effectively large.

As shown in fig. 23, the first guide grooves 26a to 26f and the second guide grooves 32a to 32f may be formed to have only curved portions along the longitudinal direction.

Claims

1. A constant velocity joint, comprising:

an outer member (16) having an open end, the outer member (16) being connected to a first shaft (12) of the two intersecting shafts (12, 18) and having an inner peripheral surface, and the outer member (16) having a plurality of first guide grooves (26 a-26 f) formed therein and extending in the axial direction of the first shaft (12);

an inner ring (34) connected to a second shaft (18) of the two shafts, and having second guide grooves (32 a-32 f) formed therein, the number of the second guide grooves being the same as the number of the first guide grooves (26 a-26 f), the second guide grooves extending in the axial direction of the second shaft (18);

balls (28) rollably disposed between the first guide grooves (26 a-26 f) and the second guide grooves (32 a-32 f) for transmitting torque between the first guide grooves (26 a-26 f) and the second guide grooves (32 a-32 f); and

a retainer (38) formed with a retaining window (36) for receiving the ball (28),

wherein,

the first guide grooves (26 a-26 f) formed in the outer member (16) are formed such that: the first guide grooves (26 a-26 f) are formed in a single circular arc shape in a cross section orthogonal to the axial direction of the first shaft (12), and the first guide grooves (26 a-26 f) are in contact with the balls (28) at one point,

second guide grooves (32 a-32 f) formed in the inner ring (34) are formed such that: the second guide grooves (32 a-32 f) are formed in an elliptical arc shape in a cross section orthogonal to the axial direction of the second shaft (18), and the second guide grooves (32 a-32 f) contact the balls (28) at two points.

2. The constant velocity joint according to claim 1,

the ratio of the groove radius (M) of the cross section of the first guide grooves (26 a-26 f) to the diameter (N) of the ball (28) is set within the range of 0.51-0.55, the ratio of the groove radius (P, Q) of the cross section of the second guide grooves (32 a-32 f) to the diameter (N) of the ball (28) is set within the range of 0.51-0.55, the contact angle of the first guide grooves (26 a-26 f) to the ball (28) is set to zero degrees with respect to the vertical line (L), and the contact angle (alpha) of the second guide grooves (32 a-32 f) to the ball (28) is set within the range of 13-22 degrees with respect to the vertical line (L).

3. The constant velocity joint according to claim 2,

the contact angle (alpha) between the second guide grooves (32 a-32 f) and the ball (28) is set within the range of 15-20 degrees with respect to the vertical line (L).