JP2007107568A - Fixed constant velocity universal joint - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fixed constant velocity universal joint wherein an elliptic contact face is restrained from jutting out of a groove when an outer ring, together with an inner ring, forms a high-operating angle with respect to either ball which is positioned on the shallow side or deep side in the track groove. <P>SOLUTION: The fixed constant velocity universal joint comprises an outer ring 23 in which a plurality of track grooves 22 are formed on an inner spherical surface 21 axially at regular intervals in the circumferential direction, an inner ring 26 in which a plurality of track grooves 25 making a pair with the track groove 22 of the outer ring 23 are formed on an outer spherical surface 24 axially at regular intervals in the circumferential direction, a plurality of torque-transmitting balls 27 positioned respectively between the track groove 22 of the outer ring 23 and the track groove 25 of the inner ring 26, and a cage 28 for retaining the balls 27 between the inner spherical surface 21 of the outer ring 23 and the outer spherical surface 24 of the inner ring 26. In the constant velocity universal joint, the contact rate of the ball with both the track grooves 22, 25 of the outer and inner rings 23, 26 respectively is gradually increased axially from the center of the track grooves 22, 25 axially to both the ends. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a fixed type constant velocity universal joint, and more particularly to a fixed type constant velocity joint that is used in a power transmission system of an automobile or various industrial machines and allows only angular displacement between two axes of a driving side and a driven side. It relates to a universal joint.

  For example, there is a fixed type constant velocity universal joint as a kind of constant velocity universal joint used as means for transmitting rotational force from an engine of an automobile to wheels at a constant speed. This fixed type constant velocity universal joint has a structure in which two shafts on the driving side and the driven side are connected and the rotational torque can be transmitted at a constant speed even if the two shafts have an operating angle. In general, as the above-mentioned fixed type constant velocity universal joint, a Barfield type (BJ) and an undercut free type (UJ) are widely known.

  For example, a BJ type fixed type constant velocity universal joint has an outer ring 3 as an outer member in which a plurality of track grooves 2 are formed along the axial direction at equal intervals in the circumferential direction on the inner spherical surface 1 as shown in FIG. An inner ring 6 as an inner member in which a plurality of track grooves 5 paired with the track grooves 2 of the outer ring 3 are formed on the outer spherical surface 4 along the axial direction at equal intervals in the circumferential direction, and the track grooves of the outer ring 3 2 and the track groove 5 of the inner ring 6 are interposed between the plurality of balls 7 for transmitting torque and the inner spherical surface 1 of the outer ring 3 and the outer spherical surface 4 of the inner ring 6 to hold the balls 7. And a cage 8. The plurality of balls 7 are accommodated in pockets 9 formed in the cage 8 and arranged at equal intervals in the circumferential direction.

In this constant velocity universal joint, to a structure capable of having a large operating angle, and a curvature center O ₂ of the track grooves 5 of the center of curvature O ₁ and the inner ring 6 of the track grooves 2 of the outer ring 3, the joint comprising a ball center O The center plane P is offset in the axial direction by an equal distance f. By providing the track offset in this way, each of the track grooves 2 and 5 is shallow from the center in the axial direction on the bottom side of the outer ring and deep on the opening side of the outer ring. As a result, from the bottom side of the outer ring 3 A wedge-shaped ball track in which the radial interval gradually increases toward the opening side is formed.

Each of the track grooves 2 and 5 of the outer ring 3 and the inner ring 6 has a single arcuate surface shape in which the cross section along the axial direction has the aforementioned curvature centers O ₁ and O ₂ . 8A is a cross-sectional view showing the track groove 2 formed on the inner spherical surface 1 of the outer ring 3, and FIG. 8B is a cross-sectional view showing the track groove 5 formed on the outer spherical surface 4 of the inner ring 6. FIG. As shown in the figure, the cross-sectional shape of the track grooves 2 and 5 is a Gothic arch shape formed by machining or cold forging with a radius of curvature R larger than the radius r of the ball 7, and this Gothic arch shape. As a result, the contact between the track grooves 2 and 5 and the ball 7 is angular contact. The ball 7 is in contact with the track grooves 2 and 5 with an elliptical contact surface (contact ellipse M) and a contact rate at a ball contact center P forming a contact angle α with respect to the track grooves 2 and 5 (for example, patents). Reference 1-6).

  Here, the contact angle α of the ball 7 with respect to the track grooves 2 and 5 (hereinafter referred to as the ball contact angle) is the ball contact center at which the ball 7 and the track grooves 2 and 5 contact with respect to the center O of the ball 7. It means an angle formed by P and the groove bottom center Q of the track groove 5.

  The ball contact center P means a point where the major axis and the minor axis of the elliptical contact surface (contact ellipse M) formed by the contact between the track grooves 2 and 5 and the ball 7 intersect. The long axis refers to the axis that is the longest part in the longitudinal direction of the contact ellipse M, and the short axis refers to the axis that is the longest part in the short direction perpendicular to the long axis.

  Further, the contact ratio of the ball 7 with respect to the track grooves 2 and 5 (hereinafter referred to as the ball contact ratio) is the ratio of the radius of curvature R that forms a Gothic arch-shaped arc surface to the radius r of the ball 7 (R / r). If the ball contact rate is increased, the contact ellipse M is decreased. Conversely, if the ball contact rate is decreased, the contact ellipse M is increased.

When this type of constant velocity universal joint is used, for example, in a drive shaft of an automobile, the outer ring 3 is connected to a driven shaft, and the drive shaft extends from a sliding type constant velocity universal joint attached to the inner ring 6 on the differential on the vehicle body side. Are connected by spline fitting. In this constant velocity universal joint, when an operating angle is given between the outer ring 3 and the inner ring 6 as shown in FIG. 9, the ball 7 accommodated in the cage 8 always has an operating angle of any operating angle. It is maintained in the bisection plane and the constant velocity of the joint is ensured.
Japanese Patent Publication No. 3-40251 Japanese Utility Model Publication No. 64-6412 Japanese Utility Model Publication No. 60-167817 No. 8-3712 JP 2002-310180 A JP 2004-11780 A

  By the way, in the above-mentioned conventional fixed type constant velocity universal joint, the ball contact angle and the ball contact rate of the outer ring 3 and the inner ring 6 are usually the axis center of the track grooves 2 and 5 or the axis separated from the axis center. Since both ends in the direction are the same, as shown in FIG. 9, when the outer ring 3 and the inner ring 6 have a high operating angle and receive a certain amount of torque, the both ends in the axial direction of the track grooves 2 and 5 are shallow. On either the deep side or the deep side, the contact ellipse M between the track grooves 2 and 5 and the ball 7 protrudes from the track grooves 2 and 5.

  That is, FIG. 10A shows the positional relationship between the ball 7 and the track groove 2 of the outer ring 3 that are in a phase that is most likely to jump out of the outer ring 3 when the outer ring 3 and the inner ring 6 take a high operating angle. The ball 7 is positioned on the deep side of the track groove 2 of the outer ring 3. As shown in the figure, a shaft (not shown) connected to the inner ring 6 interferes with the outer ring 3 when the outer ring 3 and the inner ring 6 have a high operating angle at the opening end of the outer ring 3. A chamfer unit 10 is provided to prevent this. FIG. 2B shows the positional relationship between the ball 7 in the innermost phase of the outer ring 3 and the track groove of the outer ring 3. In this case, the ball 7 is positioned on the shallow side of the track groove 2 of the outer ring 3. It will be.

  In this way, the ball 7 positioned on the deep side of the track groove 2 of the outer ring 3 has a contact ellipse M with the track groove 2 protruding from the track groove 2, and similarly, the track groove 2 of the outer ring 3 is shallow in the track groove 2. As for the ball 7 located on the side, the contact ellipse M with the track groove 2 protrudes from the track groove 2. This is the same when the ball 7 is positioned on the shallow side of the track groove 5 of the inner ring 6 or when the ball 7 is positioned on the deep side of the track groove 5 of the inner ring 6.

  When such protrusion of the contact ellipse M occurs, the track grooves 2 and 5 may be damaged, and it is difficult to maintain the strength of the outer ring 3 and the inner ring 6, thereby reducing the life of the joint. was there.

  Therefore, the present invention has been proposed in view of the above-described problems, and the object of the present invention is to provide a ball positioned on the shallow side of the track groove or on the deep side when the outer ring and the inner ring have a high operating angle. It is an object of the present invention to provide a fixed type constant velocity universal joint that can prevent any contact ellipse with a track groove from protruding for any of the balls positioned.

In order to achieve the above-described object, the present invention provides an outer member in which a plurality of track grooves are formed on the inner spherical surface along the axial direction at equal intervals in the circumferential direction, and a track groove of the outer member is paired with the outer spherical surface. Torque is transmitted between an inner member in which a plurality of track grooves are formed along the axial direction at equal intervals in the circumferential direction, and between the track groove of the outer member and the track groove of the inner member. A fixed type constant velocity universal joint including a plurality of balls and a cage for holding the balls interposed between the inner spherical surface of the outer member and the outer spherical surface of the inner member is characterized by the following points.
(I) The ball contact rate of both track grooves of the outer member and the inner member is gradually increased from the axial center (or joint center position) of the track groove toward both axial ends.
(Ii) The ball contact rate on the track groove bottom side opposite to the track groove bottom side, with the ball contact center as a boundary, at both ends in the axial direction of both track grooves of the outer member and the inner member. The contact rate must be greater.

  In (i) of the present invention, the outer member and the inner member are obtained by gradually increasing the ball contact ratio of both the track grooves of the outer member and the inner member from the center in the axial direction of the track groove toward both ends in the axial direction. Since the contact ellipse with the track groove can be made smaller than the conventional case for the balls positioned at both ends in the axial direction of the track groove, the contact ellipse is eroded from the track groove. It can be prevented in advance.

  In (ii) of the present invention, the ball contact rate on the track groove open side opposite to the track groove bottom side is defined as the track at both ends in the axial direction of both track grooves of the outer member and the inner member with the ball contact center as a boundary. When the outer member and the inner member have a high operating angle by increasing the ball contact rate on the groove bottom side, the ball located at both ends in the axial direction of the track groove has an elliptical contact with the track groove. Among them, since the semi-elliptical part on the track groove open side can be made smaller than the semi-elliptical part on the track groove bottom side, it is possible to prevent the contact ellipse from protruding from the track groove.

In the present invention, it is desirable that the ball contact angles of the track grooves of the outer member and the inner member are gradually reduced from the center in the axial direction of the track groove toward both ends in the axial direction.
Thus, if the ball contact angles of the track grooves of the outer member and the inner member are gradually reduced from the center in the axial direction of the track groove toward the both ends in the axial direction, the track groove and the ball at both ends in the axial direction of the track groove. The contact ellipse approaches the bottom side of the track groove, and the protrusion of the contact ellipse can be further suppressed.

  Note that the present invention relates to a barfield type fixed constant velocity universal joint including an outer member and an inner member having track grooves having a single arcuate cross section in the axial direction, and parallel to the axial direction. The present invention can be applied to both an outer member having a track groove having a straight bottom and an undercut free type fixed constant velocity universal joint having an inner member. The present invention is also applicable to other fixed type constant velocity universal joints having track groove shapes other than these bar field type and undercut free type.

  According to the present invention, the ball contact rate of both the track grooves of the outer member and the inner member is gradually increased from the center in the axial direction of the track groove toward both ends in the axial direction. By making the ball contact rate on the track groove open side opposite to the track groove bottom side larger than the ball contact rate on the track groove bottom side, with the ball contact center as a boundary at both axial ends of both track grooves, When the outer member and the inner member have a high operating angle, the contact ellipse with the track groove can be made smaller than in the conventional case for the balls located at both ends in the axial direction of the track groove. The oval can be prevented from protruding from the track groove, and the strength of the outer member and the inner member can be ensured without damaging the track groove, so that the joint life can be improved.

  An embodiment of a fixed type constant velocity universal joint according to the present invention will be described in detail. In the following embodiment, a Barfield type fixed constant velocity universal joint (BJ) is illustrated.

  As shown in FIG. 1, the constant velocity universal joint includes an outer ring 23 as an outer member in which a plurality of track grooves 22 are formed along the axial direction at equal intervals in the circumferential direction on an inner spherical surface 21, and an outer spherical surface 24. An inner ring 26 as an inner member in which a plurality of track grooves 25 paired with the track grooves 22 of the outer ring 23 are formed along the axial direction at equal intervals in the circumferential direction, and the track grooves 22 of the outer ring 23 and the tracks of the inner ring 26 A plurality of balls 27 that transmit torque by interposing between the grooves 25 and a cage 28 that interposes between the inner spherical surface 21 of the outer ring 23 and the outer spherical surface 24 of the inner ring 26 and holds the balls 27 are provided. Yes. The plurality of balls 27 are accommodated in pockets 29 formed in the cage 28 and arranged at equal intervals in the circumferential direction. A chamfer portion is provided at the open end of the outer ring 23 to prevent a shaft (not shown) connected to the inner ring 26 from interfering with the outer ring 23 when the outer ring 23 and the inner ring 26 have a high operating angle. 30 is provided.

In this constant velocity universal joint, in order to obtain a structure capable of obtaining a large operating angle, the center of curvature O ₁ of the track groove 22 of the outer ring 23 and the center of curvature O ₂ of the track groove 25 of the inner ring 26 include the ball center O. The center plane P is offset in the axial direction by an equal distance f. By providing the track offset in this way, each of the track grooves 22 and 25 is shallow from the axial center to the outer ring bottom side and deeper from the outer ring opening side, and as a result, from the bottom side of the outer ring 23. A wedge-shaped ball track in which the radial interval gradually increases toward the opening side is formed.

The outer ring 23 and the inner ring 26 that constitute a part of the constant velocity universal joint of this embodiment are a single unit in which the cross section along the axial direction has the aforementioned curvature centers O ₁ and O ₂ on the inner spherical surface 21 and the outer spherical surface 24, respectively. It has a structure in which track grooves 22 and 25 having one circular arc shape are formed. 2A is a cross-sectional view showing a track groove 22 formed on the inner spherical surface 21 of the outer ring 23, and FIG. 2B is a cross-sectional view showing a track groove 25 formed on the outer spherical surface 24 of the inner ring 26. As shown in the figure, the cross-sectional shape of the track grooves 22 and 25 is a Gothic arch shape formed by machining or cold forging with a radius of curvature R larger than the radius r of the ball 27, and this Gothic arch shape. As a result, the contact between the track grooves 22 and 25 and the ball 27 is an angular contact having a ball contact angle and a ball contact rate. That is, the ball 27 is in contact with the track grooves 22 and 25 with an elliptical contact surface (contact ellipse M) and a contact rate at the ball contact center P forming a contact angle α with respect to the track grooves 22 and 25.

  Here, the ball contact angle α is an angle formed by the ball contact center P where the ball 27 and the track grooves 22 and 25 are in contact with the center O of the ball 27 and the groove bottom center Q of the track grooves 22 and 25. means.

  The ball contact center P means a point where the major axis and the minor axis of the elliptical contact surface (contact ellipse M) formed by the contact between the track grooves 22 and 25 and the ball 27 intersect. The long axis refers to the axis that is the longest part in the longitudinal direction of the contact ellipse M, and the short axis refers to the axis that is the longest part in the short direction perpendicular to the long axis.

  Further, the ball contact rate is the ratio (R / r) of the radius of curvature R that forms a Gothic arch-shaped arc surface to the radius r of the ball 27. If this ball contact rate increases, the contact ellipse M If the ball contact ratio decreases, the contact ellipse M increases.

  When this type of constant velocity universal joint is used for a drive shaft of an automobile, for example, an outer ring 23 is connected to a driven shaft, and a drive shaft extending from a sliding type constant velocity universal joint attached to the inner ring 26 on a differential on the vehicle body side. Are connected by spline fitting. In this constant velocity universal joint, when an operating angle is given between the outer ring 23 and the inner ring 26 as shown in FIG. 3, the ball 27 accommodated in the cage 28 always has an operating angle of any operating angle. It is maintained in the bisection plane and the constant velocity of the joint is ensured.

In the constant velocity universal joint of this embodiment, the ball contact ratios of the track grooves 22 and 25 of the outer ring 23 and the inner ring 25 are gradually increased from the center in the axial direction of the track grooves 22 and 25 toward both ends in the axial direction. In this way, the ball contact rate of both the track grooves 22 and 25 of the outer ring 23 and the inner ring 26 is gradually increased from the center in the axial direction of the track grooves 22 and 25 toward both ends in the axial direction. When the inner ring 26 and the inner ring 26 have a high operating angle, as shown in FIG. 4 (a), the outer ring 23 has a ball 27 positioned on the deep side of the track groove 22, as shown in FIG. ) to the ball 27 positioned in a shallow side of the track groove 22 in the outer ring 23 as shown, the contact ellipse M ₁ between the track grooves 22 can be made smaller than in conventional, its contact ellipse M ₁ track Protruding from the groove 22 can be prevented beforehand. This is the same when the ball 27 is positioned on the shallow side of the track groove 25 of the inner ring 26 or when the ball 27 is positioned on the deep side of the track groove 25 of the inner ring 26.

As another embodiment, the ball contact ratio on the track groove open side opposite to the track groove bottom side is defined with the ball contact center P as a boundary at both ends in the axial direction of the track grooves 22 and 25 of the outer ring 23 and the inner ring 26. There is a means for making the ball contact rate larger than the track groove bottom side. In this way, when the outer ring 23 and the inner ring 26 have a high operating angle (see FIG. 3), the balls 27 positioned on the deep side of the track groove 22 of the outer ring 23 as shown in FIG. As shown in FIG. 5B, the asymmetrical contact between the track groove bottom side and the track groove open side with the ball contact center P as a boundary for any of the balls 27 positioned on the shallow side of the track groove 22 of the outer ring 23. elliptical M _2, that is, because it can be a small contact ellipse M ₂ than semi-elliptical portion of the semi-elliptical partial track groove bottom side of the track groove open side, protrudes the contact ellipse M ₂ from the track grooves 22 This can be prevented beforehand. This is the same when the ball 27 is positioned on the shallow side of the track groove 25 of the inner ring 26 or when the ball 27 is positioned on the deep side of the track groove 25 of the inner ring 26. If the ball contact ratios on the track groove bottom side and the track groove open side are the same except at both ends of the track grooves 22 and 25 in the axial direction, for example, in the center in the axial direction, the track groove bottom is centered on the ball contact center P. A symmetric contact ellipse M is obtained on the side and the track groove open side.

  In addition, by combining the above-described embodiment (see FIG. 4) and this embodiment (see FIG. 5), the ball contact ratio of both the track grooves 22 and 25 of the outer ring 23 and the inner ring 26 is determined in the axial center of the track grooves 22 and 25. Gradually increases toward the both ends in the axial direction, and at both ends in the axial direction of the track grooves 22 and 25, the ball contact ratio on the track groove open side opposite to the track groove bottom side is defined as the track groove with the ball contact center P as a boundary. It is also possible to make it larger than the ball contact rate on the bottom side.

  In this way, when the outer ring 23 and the inner ring 26 have a high operating angle, both the ball 27 positioned on the deep side of the track groove 22 or the ball 27 positioned on the shallow side of the track groove 22 The entire contact ellipse with the groove 22 can be made small, and the contact ellipse asymmetrical between the track groove bottom side and the track groove open side with the ball contact center P as the boundary, that is, the semi-elliptical part on the track groove open side is tracked. Since the contact ellipse can be made smaller than the semi-elliptical portion on the groove bottom side, the contact ellipse can be further reliably prevented from protruding from the track groove 22. This is the same when the ball 27 is positioned on the shallow side of the track groove 25 of the inner ring 26 or when the ball 27 is positioned on the deep side of the track groove 25 of the inner ring 26.

Further, the ball contact angle α (see FIGS. 2A and 2B) of both the track grooves 22 and 25 of the outer ring 23 and the inner ring 26 is gradually decreased from the center in the axial direction of the track grooves 22 and 25 toward both ends in the axial direction. For example, contact ellipses M ₁ , M ₁ of the track grooves 22, 25 and the ball 27 are formed at both ends in the axial direction of the track grooves 22, 25, that is, on the deep side of the track groove 22 of the outer ring 23 and the shallow side of the track groove 25 of the inner ring 26. ₂ approaches the bottom side of the track grooves 22 and 25, and the protrusion of the contact ellipses M ₁ and M ₂ can be further suppressed. This is the same when the ball 27 is positioned on the shallow side of the track groove 22 of the outer ring 23 or when the ball 27 is positioned on the deep side of the track groove 25 of the inner ring 26.

  In the above-described embodiment, the present invention is applied to a Barfield type fixed constant velocity universal joint including an outer ring 23 and an inner ring 26 having track grooves 22 and 25 having a single arcuate cross section in the axial direction. However, the present invention is not limited to this, and as shown in FIG. 6, an outer ring 23 ′ and an inner ring 26 ′ having track grooves 22 ′ and 25 ′ having straight bottoms parallel to the axial direction are provided. It can also be applied to an undercut-free type fixed constant velocity universal joint. Furthermore, the present invention can also be applied to other fixed type constant velocity universal joints having track groove shapes other than these bar field type and undercut free type.

1 is a cross-sectional view showing an overall configuration of a Barfield type constant velocity universal joint in an embodiment of a fixed type constant velocity universal joint according to the present invention. (A) is sectional drawing which shows the contact state of the track groove and ball | bowl of an outer ring | wheel, (b) is sectional drawing which shows the contact state of the track groove | channel and ball | bowl of an inner ring | wheel. It is sectional drawing which shows the state which the constant velocity universal joint of FIG. 1 took the operating angle. In the constant velocity universal joint of FIG. 1, (a) is an enlarged view of a main part showing an example of a contact ellipse in which the track groove and the ball are in contact with each other on the deep side of the track groove of the outer ring, and (b) is an illustration of the track groove of the outer ring. It is a principal part enlarged view which shows an example of the contact ellipse which the track groove and a ball contact on a shallow side. In the constant velocity universal joint of FIG. 1, (a) is an enlarged view of a main part showing another example of a contact ellipse where the track groove and the ball are in contact with each other on the deep side of the track groove of the outer ring, and (b) is a track groove of the outer ring. FIG. 10 is an enlarged view of a main part showing another example of a contact ellipse in which the track groove and the ball are in contact with each other on the shallow side. It is sectional drawing which shows the whole structure of the undercut free type constant velocity universal joint in other embodiment of this invention. It is sectional drawing which shows the whole barfield type constant velocity universal joint in the prior art example of a fixed type constant velocity universal joint. (A) is sectional drawing which shows the contact state of the track groove and ball | bowl of an outer ring | wheel, (b) is sectional drawing which shows the contact state of the track groove | channel and ball | bowl of an inner ring | wheel. It is sectional drawing which shows the state which the constant velocity universal joint of FIG. 7 took the operating angle. In the constant velocity universal joint of FIG. 7, (a) is an enlarged view of the main part showing a contact ellipse where the track groove and the ball are in contact with the deep side of the track groove of the outer ring, and (b) is a shallow side of the track groove of the outer ring. FIG. 6 is an enlarged view of a main part showing a contact ellipse in which the track groove and the ball are in contact with each other.

Explanation of symbols

21 inner spherical surface 22 track groove 23 outer member (outer ring)
24 outer spherical surface 25 track groove 26 inner member (inner ring)
27 Ball 28 Cage α Ball contact angle

Claims (5)

  An outer member in which a plurality of track grooves are formed on the inner spherical surface along the axial direction at equal intervals in the circumferential direction, and a plurality of track grooves that are paired with the track grooves of the outer member on the outer spherical surface are in the circumferential direction, etc. An inner member formed along the axial direction at intervals, a plurality of balls that are interposed between the track grooves of the outer member and the track grooves of the inner member, and transmit torque; and In a fixed type constant velocity universal joint having a cage for holding a ball interposed between an inner spherical surface and an outer spherical surface of an inner member, the ball contact ratio of both track grooves of the outer member and the inner member is determined. A fixed type constant velocity universal joint characterized in that the track groove is gradually increased from the axial center to both axial ends.   An outer member in which a plurality of track grooves are formed on the inner spherical surface along the axial direction at equal intervals in the circumferential direction, and a plurality of track grooves that are paired with the track grooves of the outer member on the outer spherical surface are in the circumferential direction, etc. An inner member formed along the axial direction at intervals, a plurality of balls that are interposed between the track grooves of the outer member and the track grooves of the inner member, and transmit torque; and In a fixed type constant velocity universal joint provided with a cage for holding a ball interposed between an inner spherical surface and an outer spherical surface of the inner member, at both axial ends of both track grooves of the outer member and the inner member. A fixed type constant velocity universal joint characterized in that the ball contact rate on the track groove open side opposite to the track groove bottom side is larger than the ball contact rate on the track groove bottom side with the ball contact center as a boundary.   The fixed constant velocity universal joint according to claim 1 or 2, wherein ball contact angles of both track grooves of the outer member and the inner member are gradually reduced from the center in the axial direction of the track groove toward both ends in the axial direction.   The fixed type constant velocity universal joint according to any one of claims 1 to 3, wherein the track groove of the outer member and the track groove of the inner member have a single circular arc surface shape in an axial cross section.   The track groove of the outer member has a straight bottom parallel to the axial direction toward the outer member opening side, and the track groove of the inner member extends axially toward the outer member non-opening side. The fixed type constant velocity universal joint according to claim 1, wherein the fixed type constant velocity universal joint has parallel straight bottoms.

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