JP2012087847A - Fixed type constant velocity universal joint - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fixed type constant velocity universal joint of an undercut free type in which the load acting on a cage becomes more ballanced condition at high operation angle, and thereby a stable high strength can be obtained.SOLUTION: The center of a track groove 32 of the outside joint member 33 and the center of a track groove member 35 of the inside joint member 36 are spaced apart from the joint center face to both sides in the axial direction, respectively. The ratio R4(=F/fr) of F and fr is R4≥tan[(θmax)/2], wherein an axial directional distance between the center of the track groove 32 of the outside joint member 33 or the center of the track groove 35 of the inside joint member 36 and the joint center face is F, a radial directional offset quantity which is a distance from the center of the track groove 32 of the outside joint member 33 or the center of the track groove 35 of the inside joint member 36 and the joint center axis is fr, and the maximum operation angle is θmax.

Description

  The present invention relates to a fixed type constant velocity universal joint, and in particular, is a type that allows only angular displacement between two connected drive and driven shafts, and is used in power transmission systems of automobiles and various industrial machines. The present invention relates to an undercut-free type fixed type constant velocity universal joint including eight torque transmission balls.

  The fixed type constant velocity universal joint includes a Rzeppa type (BJ) (for example, Patent Document 1) and an undercut free type (UJ). As shown in FIG. 13, the Rzeppa type fixed type constant velocity universal joint includes an outer joint member 3 in which a plurality of track grooves 2 are formed in the inner spherical surface 1 along the axial direction at equal intervals in the circumferential direction, and the outer spherical surface 4. A plurality of track grooves 5 paired with the track grooves 2 of the outer joint member 3 are formed along the axial direction at equal intervals in the circumferential direction, and the track grooves 2 and the inner joint of the outer joint member 3 A plurality of balls 7 that transmit torque by being interposed between the track grooves 5 of the member 6 and the balls 7 that are interposed between the inner spherical surface 1 of the outer joint member 3 and the outer spherical surface 4 of the inner joint member 6. The cage 8 to hold | maintain is provided. A plurality of window portions 9 in which the balls 7 are accommodated are arranged in the cage 8 along the circumferential direction.

  The cage 8 is in spherical contact with the inner spherical surface of the outer joint member 3 and the outer spherical surface of the inner joint member 6. The curvature centers (O2, O1) of the ball center locus lines of the track grooves 2 and 5 of the outer joint member 3 and the inner joint member 6 are respectively symmetrical with respect to the joint center Oj. In other words, the curvature center O1 and the curvature center O2 are offset from the joint center Oj by an equal distance in the opposite direction and offset in the axial direction. That is, the track groove 2 of the outer joint member 3 is offset from the joint center Oj by a predetermined distance along the joint center axis X toward the joint opening side, and the track groove 5 of the inner joint member 6 is moved from the joint center Oj to the joint center axis X. A predetermined distance is offset along the joint back side. Here, the joint center axis X is a straight line including the axis of the outer joint member 3 and the axis of the inner joint member 6 in a state where the joint operating angle is 0 °, and the joint center plane is the center of the torque transmission ball 7. A plane that is perpendicular to the joint center axis and the joint center Oj is an intersection of the joint center plane and the joint center axis.

  For this reason, the torque transmission ball track formed by the track groove 2 of the outer joint member 3 and the track groove 5 of the inner joint member 6 has a wedge shape that gradually spreads from one to the other in the axial direction. Each ball 7 is accommodated in this wedge-shaped torque transmitting ball track, and transmits torque between the outer joint member 3 and the inner joint member 6. A cage 8 is incorporated to hold all the balls 7 in the joint plane (plane perpendicular to the bisector of the operating angle).

Also, the fixed-type constant velocity universal joint of the Rzeppa type has a structure with six torque transmission balls that has been used for many years as a technical standard, and has gained the support of many users in terms of performance and reliability. However, the present applicant has achieved a high-efficiency, drastic light weight and compactness while ensuring strength, load capacity and durability equivalent to or better than the six-ball zeppa joint as the technical standard. A single ball zeppa joint has been developed and already proposed (for example, Patent Document 1 below).

  Next, as shown in FIG. 14, the UJ type fixed type constant velocity universal joint includes an outer joint member 13 in which a plurality of track grooves 12 are formed on the inner diameter surface 11 along the axial direction at equal intervals in the circumferential direction. An inner joint member 16 in which a plurality of track grooves 15 paired with the track grooves 12 of the outer joint member 13 are formed on the outer diameter surface 14 along the axial direction at equal intervals in the circumferential direction, and the track of the outer joint member 13 Between a plurality of balls 17 that transmit torque between the groove 12 and the track groove 15 of the inner joint member 16, and between the inner diameter surface 11 of the outer joint member 13 and the outer diameter surface 14 of the inner joint member 16. And a cage 18 for interposing and holding the ball 17. A plurality of window portions 19 in which the balls 17 are accommodated are arranged in the cage 18 along the circumferential direction.

  In this case, the track groove 12 of the outer joint member 13 has an opening in which the track groove ball center locus line is an arcuate portion and the track groove ball center locus line is a straight portion parallel to the outer joint member axis. The side track groove 12b. The back side track groove 12a has its center of curvature O2 shifted from the joint center Oj in the axial direction toward the opening side of the outer joint member 13. Further, the track groove 15 of the inner joint member 16 includes an inner track groove 15a in which the track groove ball center locus line is a straight portion parallel to the inner joint member axis, and an opening side in which the track groove ball center locus line is an arc portion. It consists of a track groove 15b. The center of curvature O1 of the opening side track groove 15b is provided at an equal distance F away from the joint center Oj in the axial direction on the back side opposite to the center of curvature O2 of the back side track groove 12a of the outer joint member 13.

  Thus, the track shape of the outer joint member 13 of the UJ type is an undercut free whose opening side is a straight shape, as opposed to the Rzeppa type in which the entire region has an arc shape. For this reason, since the ball position is on the outer diameter side at the opening compared to the BJ type, the interference angle between the shaft (the shaft fitted into the inner joint member) and the track groove 12 of the outer joint member 13 is increased, and the UJ type Has a larger operating angle than the BJ type. Further, since the track shape of the UJ type outer joint member 13 is a straight shape on the opening side, the movement amount of the ball 17 in the radial direction is increased in the outer diameter side direction. In order to hold, the outer diameter of the cage 18 is also increased. From this, the inner spherical surface diameter of the outer joint member 13 is increased.

  However, in the UJ type, by increasing the inner diameter surface (inner spherical surface) of the outer joint member 13, the arc track groove of the outer joint member 13 is offset toward the opening side, so that the depth of the inner track is shallow. Become. For this reason, if the inner spherical surface of the outer joint member 13 is increased as described above, the depth of the inner track groove is further reduced. Here, the track depth refers to the joint internal force analysis in the rotating state, and from the ball contact point at the position where the contact ellipse of the ball moving in the axial direction and the contact angle direction in the single rotation is closest to the spherical surface. Expressed as the distance to the sphere.

  Also, because the balls 7 and 17 are held in the cages 8 and 18 and the track depth is secured, the UJ type has a larger ball diameter than the Zepper type at the same size, and the pitch circle PCD of the ball, and thus the outer joint member. The outer diameter is also increased.

  The UJ type shown in FIG. 14 has a cage offset shape that is effective in securing the outer joint member back side track depth. That is, with respect to the joint center Oj, the center O4 of the outer spherical surface 18a of the cage 18 is offset by fc toward the axial opening side, and the center O3 of the inner spherical surface 18b of the cage 18 is offset by fc toward the rear side in the axial direction. . Such a cage offset type is called a track direction cage offset. In FIG. 14, fa is the axial distance between the center of curvature O2 of the track groove 12 and the center of curvature of the inner surface of the outer joint member 13, or the outer diameter of the center of curvature O1 of the track groove 15 and the inner joint member 16. The axial distance from the center of curvature of the surface.

  In recent years, an 8-ball UJ type joint having a reduced outer diameter compared to the 6-ball type has also been proposed (Patent Document 1). The 8-ball UJ type joint has a ball diameter smaller than that of the 6-ball. Therefore, regardless of the size or number of balls, PCR (the center of the arc of the track groove of the outer joint member or the track groove of the inner joint member). The offset amount is set to be small so that the radial dimension (thickness) of the cage corresponding to the radial movement amount determined by the offset amount and the length of the line segment connecting the arc center and the ball center can be secured. As shown in FIG. 14, a cage offset is employed.

  And in such eight UJ types, the improvement at the time of a high angle is regarded as an important subject for the further improvement in durability.

  By the way, conventionally, in the six-ball Rzeppa type, it is disclosed that the center of the track groove is offset from the joint central axis to a position spaced away from the track groove in the radial direction opposite to the track groove (Patent Document 2, Patent Document 3 and Patent Document 4).

  In Patent Document 2, the track groove of the outer joint member includes an opening-side first guide groove centered on the joint center, and a back-side second guide groove centered on a point offset from the joint center to the radially opposite side. It is formed with. Further, the track groove of the inner joint member is further radiused from the center of the back side second track groove centered on the point offset from the joint center to the back side along the joint center axis, and from the center of the back side second guide groove. The opening side second guide groove is centered on a point offset in the opposite direction.

  With such a configuration, the depth of the back side first guide groove of the outer joint member is increased, and the thickness of the inner joint member is increased at the opening side second guide groove portion of the inner joint member. Therefore, when the joint takes a high operating angle, the ball does not ride on the back side first guide groove of the outer joint member and the edge portion of the groove is not chipped. The member will not be damaged.

  In Patent Document 3, the center of the track groove of the outer joint member and the center of the track groove of the inner joint member are spaced apart from each other by an equal distance from the diameter direction surface (joint center surface) in the axial direction. Is offset to a position spaced apart by a predetermined amount on the opposite side in the radial direction. With such a configuration, the contact force between the ball and the track groove is reduced when the joint takes the maximum operating angle and the ball is extremely close to the entrance edge of the track groove of the outer joint member. Damage to the inlet edge of the is prevented.

  In Patent Document 4, the center of curvature of the groove center line of the track groove of the outer joint member and the track groove of the inner joint member is decentered on both sides of the joint center surface, and on the plane including the groove center line and the axis. It is set to be on the opposite side beyond the axis. Thereby, the maximum allowable angle of the joint angle can be increased, and the strength is ensured without increasing the outer diameter of the outer joint member.

  Conventionally, there is one that allows the maximum bending angle to be increased without affecting running characteristics or the like (Patent Document 5). That is, in Patent Document 5, the intersection angle between the tangent to the trajectory curve and the joint rotation axis monotonously increases starting from the point where the distance between the base of the traveling path and the joint rotation axis is the maximum value. It is what you do.

  For Rzeppa type constant velocity universal joints, reduce the axial offset of the center of the track groove (the axial distance between the center of the track groove and the joint center plane) or the radial offset (track groove center and joint center) When the radial distance from the axis is provided, the peak value of the track load during the joint rotation (the load acting on the contact portion between the torque transmission ball and the track groove) tends to increase. In Cited Documents 2 and 3, a radial offset is provided at the center of the track groove for the six-ball Zepper joint. This is intended to prevent damage, and does not take into consideration the problem of ensuring durability in the low and medium operating angle regions.

  In particular, in the ones described in Patent Documents 2 to 4, all are six balls, and the track groove is composed of a single arc portion. Also in Patent Document 5, the number of balls is six, and the straight portion of the track groove is not provided. For this reason, there is a UJ type constant velocity universal joint with 8 balls that can improve the torque capacity at a high operating angle while ensuring durability at a low operating angle. I did not.

  Therefore, an undercut-free type fixed constant velocity universal joint with 8 balls that can improve the torque capacity at a high operating angle while ensuring durability at a low operating angle has been proposed ( Patent Document 6).

  That is, the constant velocity universal joint described in Patent Document 6 is an undercut free type with eight balls, and the center of the track groove of the outer joint member and the center of the track groove of the inner joint member are the center of the joint. It is assumed that they are offset from the axis to positions spaced away from these track grooves in the radial direction. Further, durability and high angle strength are improved by limiting numerical values such as the ratio R1 (= F / Rt) between F and Rt and the ratio R3 (= fr / Rt) between fr and Rt. F is an axial distance between the center of the track groove of the outer joint member and the joint center plane, and Rt is the center of the track groove of the outer joint member or the center of the track groove of the inner joint member and the torque transmitting ball. It is a distance between the centers, and fr is a radial offset amount that is a distance from the track groove of the outer joint member to the central joint central axis.

  In addition, conventionally, the center of the track groove of the outer joint member and the center of the track groove of the inner joint member are offset to a position spaced away from the joint center axis in the radial direction opposite to the track groove. , The intersection point between the joint center plane and the joint center axis is the joint center, and the angle between the straight line including the guide groove center of the outer joint member and the joint center and the joint center plane is β (°) And 15 ° ≦ β <24 ° (Patent Document 7). Thereby, the durability of the joint is improved.

JP-A-9-317783 JP-A-4-228925 JP-T-2002-541395 JP-A-8-128454 JP 59-106724 A JP 2009-299810 A JP 2008-151182 A

  However, in the said patent document 6, the subject which the constant velocity universal joint of patent document 2-patent document 5 comprises was able to be solved. However, in the constant velocity universal joint described in Patent Document 6, when the release angle (or R1) is set to a small value and a high operating angle is taken, the cage may have a position where the torque balance cannot be balanced at the joint centerline. is there. If such a position occurs, it can be a serious drawback in terms of strength at high operating angles. Further, even in the constant velocity universal joint described in Patent Document 7, an unstable position may occur similarly.

  An object of the present invention is to provide an undercut-free type fixed type constant velocity universal joint capable of obtaining a more balanced and balanced state of loads acting on a cage at a high operating angle. It is in.

  The fixed type constant velocity universal joint of the present invention includes an outer joint member in which a track groove extending in the axial direction is formed on the inner diameter surface, an inner joint member in which a track groove extending in the axial direction is formed on the outer diameter surface, and an outer joint member. A torque transmission ball disposed in each of the torque transmission ball tracks formed by cooperation of the track groove and the corresponding track groove of the inner joint member, and a cage having a pocket for holding the torque transmission ball, An undercut free type fixed constant velocity universal joint having a curved portion and a straight portion on the track groove bottom surface of the outer joint member and the track groove bottom surface of the inner joint member, wherein the joint operating angle is 0 °, A straight line including the axis of the outer joint member and the axis of the inner member is a joint center axis, and a plane that includes the center of the torque transmission ball and is orthogonal to the joint center axis is a joint. When the center surface is used, the center of the track groove of the outer joint member and the center of the track groove of the inner joint member are spaced apart from the joint center surface in the axial direction, respectively, and the track grooves are separated from the joint center axis. The axial distance between the center of the track groove of the outer joint member or the center of the track groove of the inner joint member and the joint center plane is F. When the radial offset amount, which is the distance between the center of the track groove of the outer joint member or the center of the track groove of the inner joint member and the joint center axis, is fr and the maximum operating angle is θmax, F And fr ratio R4 (= F / fr) is R4 ≧ tan [(θmax) / 2]. That is, when the maximum operating angle is 50 deg, the ratio R4 (= F / fr) between F and fr is R4 ≧ 0.466. Further, R4 ≦ 0.521.

  Even when the maximum operating angle (about 50 degrees) is taken, in this constant velocity universal joint, since R4 ≧ [tan (θmax) / 2] is set, it is positioned at the innermost side of the outer joint member. The wedge angle (open angle) of the ball 37 to be turned faces the joint opening side. For this reason, the rotational force of the cage is suppressed and balanced, and a stable state can be maintained. Further, there is a relation that the spherical force increases when R4 is increased. An increase in spherical force leads to an increase in the amount of heat generated, leading to a decrease in durability at high angles. Therefore, it is preferable to set R4 as small as possible, and since it is preferable to set R4 ≧ tan [(θmax) / 2], R4 = tan (θmax / 2) is optimal. On the other hand, in the case of R4 <tan [(θmax) / 2], the rotational force acts on the cage at a high operating angle, resulting in an unstable state.

  The number of torque transmitting ball tracks formed by the cooperation of the track grooves of the outer joint member and the corresponding track grooves of the inner joint member may be six.

  Further, there are eight torque transmitting ball tracks formed by cooperation of the track groove of the outer joint member and the corresponding track groove of the inner joint member, and the center of the outer spherical surface of the cage and the inner spherical surface of the cage. Rt is the distance between the center of the track groove of the outer joint member or the center of the track groove of the inner joint member and the center of the torque transmitting ball, and the center of the track groove of the outer joint member. Or, when the axial distance between the center of the track groove of the inner joint member and the joint center plane is F, the ratio R1 (= F / Rt) of F and Rt is 0.061 ≦ R1 ≦ 0. When the radial offset amount, which is the distance from the center of the track groove of the outer joint member or the center of the track groove of the inner joint member to the joint center axis line, is fr, the ratio of fr to the Rt R3 = Fr / Rt) may be those which are 0.07 ≦ R3 ≦ 0.19.

  There are eight torque transmitting ball tracks formed by cooperation of the track groove of the outer joint member and the corresponding track groove of the inner joint member, and the center of the outer spherical surface of the cage and the center of the inner spherical surface of the cage Are offset from the joint central axis to positions spaced radially opposite to the track grooves, the cage offset amount R2 is 0.1 or more, and the center of the track groove of the outer joint member Alternatively, the distance between the center of the track groove of the inner joint member and the center of the torque transmission ball is Rt, the center of the track groove of the outer joint member or the center of the track groove of the inner joint member and the center surface of the joint F1 is a ratio R1 (= F / Rt) of F and Rt is 0.044 ≦ R1 ≦ 0.087, and the center or front of the track groove of the outer joint member When the radial offset amount, which is the distance from the center of the track groove of the inner joint member to the joint central axis, is fr, the ratio R3 (= fr / Rt) of fr to Rt is 0.07 ≦ R3 ≦ 0. .19 may be used.

  The track depth at the maximum operating angle is deeper as the R3 value is larger, and the track depth is deeper as the R1 value is smaller. At the R1 value of 0.087, when the R3 value is 0.07, the depth is the same as the conventional depth.

  In the structure in which the track grooves are offset in the radial direction, the operability is good up to an R1 value that is even smaller than the conventional product that is not offset. In the normal angle (operating angle 6 °), the smaller the R1 value, the deeper the track depth, and the smaller the R3 value, the deeper the track depth. Here, the track depth refers to the joint internal force analysis in the rotating state, and from the ball contact point at the position where the contact ellipse of the ball moving in the axial direction and the contact angle direction in the single rotation is closest to the spherical surface. The distance to the sphere. The greater the distance from the ball contact point to the spherical surface, the better the durability.

  By providing a radial offset at the center of the track groove of the outer joint member (the center of curvature of the curved portion), the groove depth of the inner side of the joint of the track groove is relatively less than when no radial offset is provided. Become bigger. For this reason, the rigidity of the joint groove side wall of the track groove increases, so that the joint takes a high operating angle, and the torque is transmitted when the torque transmission ball is close to the joint groove deep side of the track groove. Deformation of the edge portion of the side wall of the groove at the back of the joint is suppressed, and the torsional strength of the joint at a high operating angle region is improved. In addition, the torque capacity in the high operating angle region is increased, and the edge load at the side wall of the joint in the track groove is reduced. As a result, the durability of the joint in the high operating angle region is improved. Here, the torque capacity is a torque at which the end of the contact ellipse of the contact portion between the torque transmission ball and the track groove overlaps with the edge line of the track groove when the torque is transmitted while taking a certain operating angle. is there.

  The lower limit value of R1 is a limit value of operability, and the upper limit value of R1 is a range in which the service angle durability and the track depth can be secured more than the conventional products. Moreover, by making R2 0.01 or less, it is possible to prevent the thickness on the opening side of the cage from being reduced. The smaller the R1 value, the smaller the PV value (multiplied by the sliding speed between the ball and the track and the track load). The smaller the PV value, the better the durability.

  In this fixed type constant velocity universal joint, it is preferable that the curved portion has a single arc on the track groove bottom surface of the outer joint member and the track groove bottom surface of the inner joint member. This is because processing is easy and the manufacturing cost is low. The ratio R1 (= F / Rt) between F and Rt is preferably 0.070 or less, and the ratio R3 (= fr / Rt) between fr and Rt is preferably 0.15 or more.

  The constant velocity universal joint is used for a drive shaft of an automobile, for example.

  According to the present invention, the load acting on the cage at a high operating angle is in a more balanced and balanced state, and a stable high strength can be obtained. Since the allowable load on the back side of the outer joint member increases at a high operating angle, the rigidity of the track wall surface is improved, the deformation of the track edge portion is suppressed, and the torsional strength is improved. Since the track depth on the back side of the outer joint member increases at a high operating angle, the riding torque is improved, the edge load is reduced, and the durability at a high operating angle is improved. For this reason, since it can be applied to high durability requirements, the size can be reduced, the weight can be reduced, and the cost can be reduced.

  In addition, by providing a radial offset at the center of the track groove of the outer joint member (the center of curvature of the curved portion), the groove depth of the inner part of the joint of the track groove can be reduced compared to the case where no radial offset is provided. It becomes relatively large. For this reason, the rigidity of the joint groove side wall of the track groove increases, so that the joint takes a high operating angle, and the torque is transmitted when the torque transmission ball is close to the joint groove deep side of the track groove. Deformation of the edge portion of the side wall of the groove at the back of the joint is suppressed, and the torsional strength of the joint at a high operating angle region is improved. Moreover, the torque capacity in the high operating angle region increases. Here, the torque capacity is a torque at which the end of the contact ellipse of the contact portion between the torque transmission ball and the track groove overlaps with the edge line of the track groove when the torque is transmitted while taking a certain operating angle. is there.

  If the torque capacity on the back side of the outer joint member is increased at a high operating angle, the rigidity of the track groove wall surface is improved, the deformation of the track edge portion is suppressed, and the torsional strength is improved. Since the track depth on the back side of the outer joint member increases at a high operating angle, the riding torque is improved, the edge load is reduced, and the durability at a high operating angle is improved. With the regular angle, the track depth can be secured as usual, and the durability is equal to or higher than the conventional one. In particular, if R1 = 0.071 or less, the track depth is deeper, the PV value is lowered, and the durability is improved. As described above, the fixed type constant velocity universal joint can be applied to high durability requirements, so that the size can be reduced, the weight can be reduced, and the cost can be reduced. Further, when R1 = 0.087 or less and a value lower than that of the conventional product, the efficiency is improved by reducing the load from the ball in the axial direction to the cage and the amount of movement of the ball 37 in the radial direction. For this reason, the fixed type constant velocity universal joint of the present invention is most suitable for an automobile drive shaft.

  Although it is not particularly limited to the number of balls, the optimum is the adaptation to a fixed constant velocity universal joint of 8 balls.

As described above, the fixed type constant velocity universal joint of the present invention is most suitable for a drive shaft of an automobile.

It is sectional drawing of the fixed type constant velocity universal joint which shows 1st Embodiment of this invention. It is an expanded sectional view which shows the track groove shape of the said fixed type constant velocity universal joint. It is sectional drawing of the fixed type constant velocity universal joint which shows 2nd Embodiment of this invention. It is sectional drawing of a bending state. It is a graph which shows the relationship between an operating angle and the torque of an operating angle direction. It is a graph which shows the relationship between R1 and the torque of an operating angle direction. It is a graph which shows the relationship between R1 and an outer ring track depth. It is a graph which shows the relationship between R3 and an outer ring track depth. It is a graph which shows the relationship between R1 and an outer ring PV value. It is a graph which shows the relationship between R3 and track depth. It is sectional drawing when the constant velocity universal joint which satisfy | fills R4 <tan [((theta) max) / 2)] takes the maximum operating angle (50deg). It is sectional drawing when the constant velocity universal joint which satisfy | fills tan [((theta) max) / 2)] <= R4 <= tan [((theta) max + 5) / 2] takes the maximum operating angle (50deg). It is sectional drawing of a fixed type constant velocity universal joint of a Rzeppa type. It is sectional drawing of the conventional fixed type constant velocity universal joint of an undercut free type.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  The fixed type constant velocity universal joint of this embodiment is arranged on the fixed side (wheel side) of the drive shaft of an automobile, for example, and as shown in FIG. 1, a plurality (eight) track grooves are formed on the inner diameter surface 31. The outer joint member 33 is formed along the axial direction at equal intervals in the circumferential direction, and a plurality of (eight) track grooves 35 that are paired with the track grooves 32 of the outer joint member 33 on the outer diameter surface 34 are circular. Eight ball tracks formed by cooperation of the inner joint member 36 formed along the axial direction at equal intervals in the circumferential direction, the track groove 32 of the outer joint member 33 and the track groove 35 of the inner joint member 36. 8 torque transmission balls 37 respectively disposed on the outer joint member 33, and a cage 38 interposed between the inner diameter surface 31 of the outer joint member 33 and the outer diameter surface 34 of the inner joint member 36 to hold the balls 37. Yes. The cage 38 is provided with a plurality of window portions 39 in which the balls 37 are accommodated along the circumferential direction. In addition, a tooth mold (serration or spline) 36 a for connecting the shaft portion to the inner diameter surface of the inner joint member 36 is formed.

  The track groove 32 of the outer joint member 33 is a back side track groove 32a in which the track groove ball center locus line is a curved portion (arc portion), and a track groove ball center locus line is a straight portion parallel to the outer joint member axis. It consists of an opening side track groove 32b. The track groove 35 of the inner joint member 36 includes a back-side track groove 35a in which the track groove ball center locus line is a straight portion parallel to the inner joint member axis, and a track groove ball center locus line is a curved portion (arc portion). And an opening-side track groove 35b.

  The track groove 32 of the outer joint member 33 and the track groove 35 of the inner joint member 36 have a Gothic arch shape formed only by forging, or by shaving after forging. As shown in FIG. 3, the track grooves 32, 35 and the ball 37 are in an angular contact by using a Gothic arch shape. That is, the ball 37 is in contact with the track groove 32 of the outer joint member 33 at two points C11 and C12, and is in contact with the track groove 35 of the inner joint member 36 at two points C21 and C22. An angle formed by contact points C11, C12, C21, and C22 between the center Ob of the ball 37 and the track grooves 32 and 35 with respect to the line segment P1 passing through the center Ob of the ball 37 and the joint center Oj is a contact angle α. The contact angles α of the contact points C11, C12, C21, C22 are all set equal.

  1 and 2 show a state in which the operating angle θ of the joint is 0 °. In this state, the axis of the outer joint member 33 and the axis of the inner joint member 36 coincide on the straight line X, and The plane P including the center Ob of all the torque transmission balls 37 is orthogonal to the straight line X. Hereinafter, the straight line X is referred to as a joint center axis X, the plane P is referred to as a joint center plane P, and the intersection of the joint center plane P and the joint center axis X is referred to as a joint center Oj.

  As shown in FIG. 1, the center (curvature center) O2 of the inner side track groove 32a of the track groove 32 of the outer joint member 33 is an axial distance F from the joint center plane P to the joint opening side (right side in FIG. 1). They are spaced apart and offset from the joint center axis X to a position separated from the track groove 32 by a radial distance fr on the opposite side in the radial direction. Further, the center O1 of the opening side track groove 35b of the track groove 35 of the inner joint member 36 is separated from the joint center plane P by the axial distance F from the joint back side (left side in the figure), and the joint center axis The track groove 35 is offset from X by a radial distance fr on the opposite side in the radial direction.

  Hereinafter, the axial distance (F) between the centers O2, O1 of the track grooves 32, 35 and the joint center plane P is defined as the axial offset amount F, and the radial distance (fr) between the curvature centers O2, O1 and the joint center axis X. Is referred to as a radial offset amount fr. In this embodiment, the track groove 32 of the outer joint member 33 and the track groove 35 of the inner joint member 36 have the same axial offset amount F and the same radial offset amount fr.

  In this embodiment, as shown in FIG. 1, the center O4 of the outer spherical surface 38a of the cage 38 and the center O3 of the inner spherical surface 38b of the cage 38 are both on the joint center Oj.

  As shown in FIG. 1, between the center (curvature center) O2 of the track groove 32 of the outer joint member 33 or the center (curvature center) O1 of the track groove 35 of the inner joint member 36 and the center Ob of the torque transmission ball 37. The distance is Rt, and the axial distance (the axial offset amount) between the center O2 of the track groove 32 of the outer joint member 33 or the center O1 of the track groove 35 of the inner joint member 36 and the joint center plane P is F. Then, the ratio R1 (= F / Rt) of F and Rt is set to satisfy 0.061 ≦ R1 ≦ 0.087. For this reason, this R1 can be called a value representing the degree of offset (axial offset).

  The radial offset amount, which is the distance between the center (curvature center) O2 of the track groove 32 of the outer joint member 33 or the center (curvature center) O1 of the track groove 35 of the inner joint member 36 and the joint center axis X, is fr. Then, the ratio R3 (= fr / Rt) of fr and Rt is set to satisfy 0.07 ≦ R1 ≦ 0.19. For this reason, R3 can be called a value representing the degree of offset (radial offset).

  Next, FIG. 3 shows a second embodiment of the present invention. The outer spherical center O4 of the cage 38 is disposed on the joint back side with respect to the joint center Oj, and the inner spherical surface center O3 of the cage 38 is disposed on the joint opening side with respect to the joint center Oj. That is, the outer spherical surface center O4 of the cage 38 and the inner spherical surface center O3 of the cage 38 are offset from the joint center Oj by fc in the axial direction. Such a cage offset type is called a track-direction cage offset, whereas it is called an anti-track-direction cage offset. In FIG. 3, fa is the axial distance between the center of curvature O2 of the track groove 32 and the center of curvature of the inner diameter surface of the outer joint member 33, or the center of curvature O1 of the track groove 35 and the outer diameter surface of the inner joint member 36. The axial distance from the center of curvature.

  Also in this case, the center (curvature center) O2 of the inner side track groove 32a of the track groove 32 of the outer joint member 33 is separated from the joint center plane P by the axial distance F from the joint opening side, and the joint center axis X Are offset from the track groove 32 by a radial distance fr on the opposite side in the radial direction. Further, the center O1 of the opening side track groove 35b of the track groove 35 of the inner joint member 36 is separated from the joint center plane P by the axial distance F from the joint back side, and the track groove 35 from the joint center axis X. Is offset to a position separated by a radial distance fr on the opposite side in the radial direction.

  The ratio R1 (= F / Rt) between F and Rt is set to be 0.044 ≦ R1 ≦ 0.087, and the ratio R3 (= fr / Rt) between fr and Rt is 0.07 ≦ R1. Set so that ≦ 0.19. The axial distance between the outer spherical surface center O4 of the cage 38 (center of the inner surface of the outer joint member 33) or the inner spherical surface center O3 of the cage 38 (center of the outer surface of the inner joint member 36) and the joint center surface P is fc. When the distance from the center Ob of the torque transmission ball 37 to the joint center axis X is R, the ratio R2 (= fc / R) of fc and R is 0.01 or less. The other configuration of the fixed type constant velocity universal joint shown in FIG. 3 is the same as that of the fixed type constant velocity universal joint shown in FIG.

  In each of the fixed type constant velocity universal joints, when the maximum operating angle is θmax, it is preferable to set the ratio R4 (= F / fr) between F and fr small, and R4 ≧ tan [(( θmax) / 2]. Furthermore, R4 ≦ tan [(θmax + 5) / 2]. Preferably, R4 = tan [(θmax / 2)]. For example, when the maximum operating angle θmax is 50 deg, the range is 0.466 ≦ R4 ≦ 0.521.

  As in the first embodiment and the second embodiment, the structure offset in the radial direction has good operability up to an offset amount smaller than that of the conventional product. This is because the amount of deviation from the joint center Oj of the inner joint member 36 mainly caused by the gap is smaller than that of the conventional product. This is because, in the product of the present invention, the track groove in which eight track loads are generated in the state where the working angle is taken is caused by the fact that the track groove is positioned radially outward from the joint center axis X as compared with the conventional product. This is because the position and amount of displacement of the inner joint member 36 differ depending on the difference in the positional relationship of the balls supporting the inner joint member 36.

  Next, the optimum range of the ratio R1 (= F / Rt) will be described. As shown in FIG. 4, the shaft is bent in the operating angle direction from the operating angle of −20 ° to + 20 ° with no torsional torque. That is, the bending resistance torque value in the working angle direction when bent was calculated by mechanism analysis.

  In this case, as for the joint internal clearance, the clearance between the ball 37 and the track groove 35 of the inner joint member 36 and between the ball 37 and the track groove 32 of the outer joint member 33 is usually mass-produced in this type of fixed type constant velocity universal joint. It was a gap of what is. The gap between the inner spherical surface (inner diameter surface) 31 of the outer joint member 33 and the cage outer spherical surface is smaller than the actual gap, and the gap between the outer spherical surface (outer diameter surface) 34 of the inner joint member 36 and the cage inner spherical surface 38b is usually normal. The gap amount was larger than that of the above. Further, the gap between the window portion 39 of the cage 38 and the ball 37 is a negative gap smaller than the normal negative gap. That is, the bending resistance torque value in the operating angle direction is likely to be generated and the operability is deteriorated.

  FIG. 5 shows the analysis result of eight balls having a conventional structure that is not offset in the radial direction (cage offset from the joint center plane P toward the track center). In FIG. 5, the thin line indicates the case where R1 is 0.070, the thick line indicates the case where R1 is 0.078, and the middle line indicates the case where R1 is 0.087. As can be seen from FIG. 5, when R1 is set to 0.070 and R1 is set to 0.078, the torque value rises from around + 7.5 ° and the peak value is confirmed at + 13 °. The Further, from the analysis result, when the R1 value is 0.087, no torque is generated and the motor operates smoothly, and when the R1 value becomes small, the bending resistance torque increases. In other words, the conventional product with the gap under the analysis condition has good operability until the R1 value is 0.087, but the operability is deteriorated when the value is smaller than that.

  Next, FIG. 6 shows the result of comparing the R1 value for the product of the present invention under the same gap condition and comparing the maximum torque value with the conventional product from the above analysis for the R1 value. In FIG. 6, the solid line indicates a conventional product (track groove that is not offset in the radial direction and has a cage offset shape), and the alternate long and short dash line indicates the product of the present invention (referred to as product A of the present invention) shown in FIG. The broken line indicates the product of the present invention (referred to as product B of the present invention) shown in FIG. As shown in FIG. 14, the conventional product is a track direction cage offset type, in which R2 = 0.996 and R3 = 0. Further, as shown in FIG. 1, the invention product A is a type without cage offset, and R2 = 0 and R3 = 0.167. As shown in FIG. 3, the invention product B is an anti-track direction cage offset type, and R2 = 0.0005 and R3 = 0.167.

  Thus, the structure offset in the radial direction as the product of the present invention has good operability up to the offset amount further reduced as compared with the conventional product. This is because the amount of deviation from the joint center of the inner joint member generated mainly due to the gap is reduced in the developed product compared to the conventional product. This is because the track position where the track load is generated in the state where the working angle is taken is the conventional position because the track of the invention product is positioned radially outward from the center axis than the conventional product. This is because the product is different from the developed product. That is, this is because the direction and amount of displacement of the inner joint member differ depending on the positional relationship of the balls supporting the inner joint member.

  From the analysis results, it can be seen that the B type (invention product B) has better operability up to the smaller R1 value than the A type (invention product A). In the product A of the present invention, 0.01 or more can be said to have good operability as R1, and in the product B of the present invention, 0.045 or more can be said to have good operability as R1. Moreover, the same result was confirmed also in the manufactured sample.

  Next, FIG. 7 and FIG. 8 show the values of the track depth of the outer joint member 33 under the durability test conditions at the normal angle (6 °). FIG. 7 shows the relationship between R1 and the track depth of the outer joint member 33. In FIG. 7, ● is a type A without cage offset, R2 = 0, R3 = 0.167, R1 = 0.087 (that is, A2 type). (2) is the anti-track direction cage offset type B, R2 = 0.0005, R3 = 0.167, and in particular, □ is R1 = 0.071. ▲ is A type without cage offset, R2 = 0, R3 = 0.221, and in particular, Δ is R1 = 0.096 (that is, A1 type). * Is a conventional product, R1 = 0.087, R2 = 0.0096, and R3 = 0.

  FIG. 8 shows the relationship between R3 and the track depth of the outer joint member 33. In FIG. 7, ○ is A2 type, R3 = 0.167, R1 = 0.087, R2 = 0. is there. ▲ is A type, R3 = 0.221, R1 = 0.087, R2 = 0.

  At the common angle (6 °), the track depth increases as the R1 value decreases, and the track depth increases as the R3 value decreases. The B type (cage offset product) is advantageous because a small R1 value can be obtained. Here, the track depth is a ball that moves in the axial direction and the contact angle α direction in the track during one rotation by analyzing the internal force of the joint in a rotating state under a normal condition of a large torque (operating angle 6 °). Is a distance L (see FIG. 2) from the ball contact point to the spherical surface at a position where the contact ellipse 51 is closest to the spherical surface.

  In the normal angle endurance test, particularly in a test with a large torque, the ball contact ellipse 51 increases as the load on the track increases, and the contact ellipse 51 protrudes from the inner diameter surface of the outer joint member 33 and peels off from the edge load. In order to improve durability, durability increases as the distance L from the ball contact point to the spherical surface portion increases.

  Next, FIG. 9 shows the PV value of the outer joint member from the analysis result under the service angle (6 °) durability test condition. The PV value is obtained by multiplying the sliding speed between the ball and the track and the track load. As the PV value decreases, the durability improves. From the analysis results, the PV value decreases as the R1 value decreases. However, when the R1 value is 0.071 or less, the decrease in the PV value slows down. The B type (cage offset product) is advantageous because a small R1 value can be obtained. Further, the PV value of the inner joint member 36 has a relationship that increases in reverse to the outer joint member by decreasing the R1 value. Therefore, the durability of the inner joint member is decreased due to the increase of the PV value of the inner joint member 36. Is concerned. At the R1 value of 0.071, no malfunction of the inner joint member is recognized. In addition, each ■, □, ▲, △, ●, ○ invented product in FIG. 9 indicates a fixed type constant velocity universal joint of the same type as each ■, □, ▲, △, ●, ○ shown in FIG. Yes.

  Next, FIG. 10 shows the track depth from the analysis result when a torque of 250 Nm is applied at an operating angle of 46 °. In FIG. 10, □ is the B type of the anti-track direction cage offset, R1 = 0.071, R2 = 0.0005, and R3 = 0.167 (that is, the B1 type). ● is A type without cage offset, R1 = 0.087, R2 = 0, in particular, ○ is R3 = 0.167 (that is, A2 type). ▲ is A type without cage offset, R1 = 0.996, R2 = 0, and in particular, △ is R3 = 0.221 (that is, A1 type).

  Thus, at an operating angle of 46 °, the greater the R3 value, the deeper the track depth, and the smaller the R1 value, the deeper the track depth. At the R1 value of 0.087, when the R3 value is 0.07, the depth is the same as the conventional depth.

Table 1 shows the values of R1, R2, and R3 for each type of the conventional product and each of the invention products, and the types of cage offsets. Further, R1, R2, and R3 in the related art also have a ratio R1 (= F / Rt), a ratio R2 (= fc / R), and a ratio R3 (= fr / Rt).

  As can be seen from FIGS. 5 to 10, in the preferred range of R1, the A type is 0.061 to 0.087, and the B type is 0.044 to 0.087. The lower bound value in this case is the limit value of operability, as can be seen from FIG. The upper limit is a range in which a normal angle durability test result and a track depth, which will be described later, can be secured more than the conventional products. In particular, 0.061 to 0.071 for the A type and 0.044 to 0.071 for the B type are more preferable ranges. This is a range in which the PV value is below the conventional product from FIG. By setting the upper limit range, the track depth is further increased and the durability is further improved.

  R2 is preferably 0.01 or less. This is because if R2 exceeds 0.01, the wall thickness on the opening side (joint opening side) of the cage 38 becomes thin, and the strength may decrease.

  R3 is preferably 0.07 to 0.19. That is, as can be seen from FIG. 10, at a suitable R1 value of 0.087, the track depth is set to 0.07 or more, which is assured as in the conventional product. In addition, it is set to 0.19 or less that can be secured to the level of the conventional product from the track depth at the time of normal angle durability described later (see FIG. 8). In particular, R3 is more preferably 0.15 to 0.19. 0.15 is the R3 value corresponding to R1 = 0.087 for the track depth level of the product A1 of the present invention in FIG.

  Even when the maximum operating angle (about 50 degrees) is taken, in this constant velocity universal joint, R4 (F / fr) ≧ [tan (θmax) / 2] is set, so the rotational force of the cage Is suppressed and balanced, and a stable state can be maintained. Further, there is a relation that the spherical force increases when R4 is increased. An increase in spherical force leads to an increase in the amount of heat generated, leading to a decrease in durability at high angles. Therefore, it is necessary to set R4 as small as possible. In this case, it is preferable to set R4 (F / fr) ≦ tan [(θmax + 5) / 2)], and R4 = tan (θmax / 2) is satisfied. Is optimal.

  If R4 <tan [(θmax) / 2] when the maximum operating angle is taken (about 50 degrees), as shown in FIG. 11, a force F1 from the ball 37 acts and a rotational force is exerted on the cage 38. Acts and becomes unstable. In contrast, when [tan (θmax) / 2] ≦ R4 ≦ tan [(θmax + 5) / 2] when the maximum operating angle (about 50 degrees) is taken, the innermost side of the outer joint member 33 The wedge angle (open angle) of the ball 37 positioned at is directed toward the joint opening side. For this reason, as shown in FIG. 12, the force F2 from the ball | bowl 37 acts, the rotational force of the cage 38 is suppressed and it will be in the balanced state.

  According to the present invention, the load acting on the cage 38 at a high operating angle is in a more balanced state and a stable high strength can be obtained. Since the allowable load on the back side of the outer joint member increases at a high operating angle, the rigidity of the track wall surface is improved, the deformation of the track edge portion is suppressed, and the torsional strength is improved. Since the track depth on the back side of the outer joint member increases at a high operating angle, the riding torque is improved, the edge load is reduced, and the durability at a high operating angle is improved. For this reason, since it can be applied to high durability requirements, the size can be reduced, the weight can be reduced, and the cost can be reduced.

  Further, by providing a radial offset at the center of the track groove 32 of the outer joint member 33 (the center of curvature of the curved portion), the groove on the joint back side portion of the track groove 32 is compared to a case where no radial offset is provided. The depth becomes relatively large. Therefore, when the rigidity of the joint back side wall portion of the track groove 32 is increased, the joint takes a high operating angle, and the torque transmission ball 37 transmits torque at a position close to the joint back side of the track groove 32. The deformation of the edge portion of the joint back side wall portion of the track groove 32 is suppressed, and the torsional strength of the joint in the high operating angle region is improved. Moreover, the torque capacity in the high operating angle region increases. Here, the torque capacity means that the end of the contact ellipse of the contact portion between the torque transmission ball 37 and the track groove 32 is the edge line of the track groove 32 when transmitting torque while taking a certain operating angle. Overlapping torque.

  With the regular angle, the track depth can be secured as usual, and the durability is equal to or higher than the conventional one. In particular, if R1 = 0.071 or less, the track depth is deeper, the PV value is lowered, and the durability is improved. As described above, the fixed type constant velocity universal joint can be applied to high durability requirements, so that the size can be reduced, the weight can be reduced, and the cost can be reduced. Further, when R1 = 0.087 or less and a lower value than the conventional product, the efficiency is improved by reducing the load from the axial ball 37 to the cage 38 and the radial movement amount of the ball 37. For this reason, the fixed type constant velocity universal joint of the present invention is most suitable for an automobile drive shaft.

  As described above, the embodiment of the present invention has been described. However, the present invention is not limited to the above-described embodiment, and various modifications are possible. For example, the axial offset amount, the radial offset amount, the cage offset amount, etc. , R1, R2, and R3 can be arbitrarily set within a range where the optimum values are obtained. Further, since the R1 value can be set low by improving the operability due to the radial offset, the outer spherical surface center O4 of the cage 38 is disposed closer to the center O2 side of the track groove 32 of the outer joint member 33 than the joint center Oj. The inner spherical surface center O3 of 38 may be disposed closer to the center O1 side of the track groove 35 of the inner joint member 36 than the joint center Oj. The fixed type constant velocity universal joint according to the present invention is not limited to a drive shaft, but can be used for a propeller shaft and a power transmission system of various other industrial machines. In addition, even if it is the fixed type constant velocity universal joint shown in FIG. 1 or the fixed type constant velocity universal joint shown in FIG. 3, the curved portions of the track grooves 32 and 35 are formed as a single arc. You may form with a circular arc. If the curved portion is a single circular arc, there are advantages that the processing is easy and the manufacturing cost is low.

  These track groove shapes are cut into a plane perpendicular to the axial direction, measured by a circle (PCD), and controlled by PCD and the axial height dimension. Further, during normal mass production, simple management is possible by defining the diameters of the straight portions of the track grooves of the outer joint member and the inner joint member.

31 Inner diameter surfaces 32, 35 Track groove 32a Back side track groove 32b Open side track groove 33 Outer joint member 34 Outer surface 35 Track groove 35a Back side track groove 35b Open side track groove 36 Inner joint member 37 Torque transmission ball 38 Cage 38a Outer spherical surface 38b Inner spherical surface

Claims (10)

An outer joint member formed with an axially extending track groove on the inner diameter surface, an inner joint member formed with an axially extending track groove on the outer diameter surface, an outer joint member track groove and an inner joint member corresponding thereto. A torque transmission ball disposed on each of the torque transmission ball tracks formed in cooperation with the track groove, and a cage having a pocket for holding the torque transmission ball, the track groove bottom surface of the outer joint member and the inner joint member An undercut-free type fixed constant velocity universal joint with a curved part and a straight part on the bottom of the track groove,
In a state where the operating angle of the joint is 0 °, a straight line including the axis of the outer joint member and the axis of the inner member is a joint center axis, a plane including the center of the torque transmission ball is perpendicular to the joint center axis. When using the joint center plane,
The center of the track groove of the outer joint member and the center of the track groove of the inner joint member are spaced apart from both sides of the joint center surface in the axial direction, and the radius from the joint center axis to the track grooves. When the distance in the axial direction between the center of the track groove of the outer joint member or the center of the track groove of the inner joint member and the joint center plane is F, When the radial offset amount, which is the distance from the center of the track groove of the joint member or the center of the track groove of the inner joint member to the joint center axis line, is fr, and the maximum operating angle is 50 deg, F and fr A fixed type constant velocity universal joint, wherein the ratio R4 (= F / fr) is R4 ≧ 0.466.   2. The fixed type constant velocity universal joint according to claim 1, wherein the ratio R4 (= F / fr) is R4 ≦ 0.521.   3. The fixing according to claim 1, wherein when the operating angle is taken, the wedge angle of the ball located on the innermost side of the outer joint member faces the joint opening side. 4. Type constant velocity universal joint. 4. The torque transmission ball track formed by cooperation of the track groove of the outer joint member and the track groove of the inner joint member corresponding to the outer joint member is defined in any one of claims 1 to 3. The fixed type constant velocity universal joint according to item 1.   There are eight torque transmitting ball tracks formed by cooperation of the track groove of the outer joint member and the corresponding track groove of the inner joint member, and the center of the outer spherical surface of the cage and the center of the inner spherical surface of the cage Rt, the distance between the center of the track groove of the outer joint member or the center of the track groove of the inner joint member and the center of the torque transmitting ball, When the axial distance between the center of the track groove of the inner joint member and the joint center plane is F, the ratio R1 (= F / Rt) of F and Rt is 0.061 ≦ R1 ≦ 0.087. Yes, when the radial offset amount, which is the distance from the track groove center of the outer joint member or the track groove center of the inner joint member to the joint center axis line, is fr, the ratio R3 of fr to Rt ( = F / Rt) are fixed type constant velocity universal joint according to any one of claims 1 to 3, characterized in that the 0.07 ≦ R3 ≦ 0.19.   There are eight torque transmitting ball tracks formed by cooperation of the track groove of the outer joint member and the corresponding track groove of the inner joint member, and the center of the outer spherical surface of the cage and the center of the inner spherical surface of the cage Are offset from the joint central axis to positions spaced radially opposite to the track grooves, the cage offset amount R2 is 0.1 or more, and the center of the track groove of the outer joint member Alternatively, the distance between the center of the track groove of the inner joint member and the center of the torque transmission ball is Rt, the center of the track groove of the outer joint member or the center of the track groove of the inner joint member and the center surface of the joint F1 is a ratio R1 (= F / Rt) of F and Rt is 0.044 ≦ R1 ≦ 0.087, and the center or front of the track groove of the outer joint member When the radial offset amount, which is the distance from the center of the track groove of the inner joint member to the joint central axis, is fr, the ratio R3 (= fr / Rt) of fr to Rt is 0.07 ≦ R3 ≦ 0. The fixed type constant velocity universal joint according to any one of claims 1 to 3, wherein the fixed type constant velocity universal joint is .19.   The fixed type constant velocity universal joint according to any one of claims 1 to 6, wherein the curved portions of the track groove bottom surface of the outer joint member and the track groove bottom surface of the inner joint member are formed as a single arc. .   The fixed type constant velocity universal joint according to any one of claims 1 to 7, wherein a ratio R1 (= F / Rt) of F and Rt is set to 0.07 or less.   The fixed type constant velocity universal joint according to any one of claims 1 to 8, wherein a ratio R3 (= fr / Rt) of fr to Rt is 0.15 or more.   The fixed type constant velocity universal joint according to any one of claims 1 to 9, which is used for coupling a drive shaft of an automobile.

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