JP2008051273A - Fixed type constant velocity universal joint and method of manufacturing outer ring of the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enhance the strength of an outer ring of a fixed type constant velocity universal joint at a high operation angle. <P>SOLUTION: The fixed type constant velocity universal joint includes the outer ring 10 having axially-extending ball grooves 20 formed at a plurality of positions in a circumferential direction of a spherical inner peripheral surface 18 of the outer ring 10, an inner ring 30 having axially-extending ball grooves 34 formed at a plurality of positions in a circumferential direction of a spherical outer peripheral surface 32 of the inner ring 30, balls 40 interposed between the ball grooves 20 of the outer ring 10 and the ball grooves 34 of the inner ring 30, and a cage 50 arranged between the spherical inner peripheral surface 18 of the outer ring 10 and the spherical outer peripheral surface 32 of the inner ring 30 so as to retain all the balls 40 in the same plane. Each ball groove 20 of the outer ring 10 comprises a circular arc part 20a on the bottom side of the outer ring 10 and a straight part 20b positioned on the large end face side and extending parallel to the axial line. An intersecting point P<SB>0</SB>of an extension line of the straight part 20b and a shaft chamfer tapered surface 22 is on the inner side of the large end face 16. A portion including the intersecting point P<SB>0</SB>and extending from the groove bottom to the large end face 16 is removed after quenching. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a fixed type constant velocity universal joint, and more particularly to an undercut free type fixed type constant velocity universal joint. The fixed type constant velocity universal joint is a constant velocity universal joint 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.

  As shown in FIGS. 5 and 6, in the fixed type constant velocity universal joint, a ball 40 is incorporated between the ball groove 20 of the outer ring 10 and the ball groove 34 of the inner ring 30, and all the balls 40 are made identical by the cage 50. The ball 40 is oriented in the bisecting plane P when it is held in a plane and the operating angle θ is taken, so that the constant velocity is maintained. FIG. 6 shows an undercut free type, in which the groove bottom of the ball groove 20 of the outer ring 10 is composed of an arc portion 20a and a straight portion 20b, and the groove bottom of the ball groove 34 of the inner ring 10 is an arc portion 34a and a straight portion 34b. It is made up of.

In the fixed type constant velocity universal joint, as shown in FIG. 7, since the inner diameter D ₁ at the open end of the outer ring 10 is smaller than the outer diameter D _{2 of the} cage 50, the inner ring 30 and the cage 50 are assembled in the outer ring 10. The ball 40 needs to be incorporated into the pocket 56 with the inner ring 30 and the cage 50 tilted so that one of the pockets 56 of the cage 50 faces outward from the open end of the outer ring 10. As shown in FIG. 8, first, the inner ring 30 and the cage 50 are inclined by 90 °, and the inner ring 30 is inserted into the cage 50 in this state. The inner ring 30 is assembled in the cage 50 by rotating both parts relatively 90 ° in the direction in which the axis and the axis of the inner ring 30 coincide. Next, as shown in FIG. 9, the inner ring 30 with cage and the outer ring 10 are relatively inclined by 90 °, and after inserting the inner ring 30 with cage into the outer ring 10, the axes of the outer ring 10 and the inner ring 30 coincide. The inner ring 30 with cage is assembled in the outer ring 10 by tilting both parts by 90 ° in the direction.

Here, in the fixed type constant velocity universal joint, when the operating angle θ is taken and torque is transmitted between the outer ring 10 and the inner ring 30 (see FIG. 6), the ball 40 is surrounded by the circumference of the cage 50 in the pocket 56. Move in the direction. The amount of movement of the ball 40 increases in proportion to the operating angle θ. The inclination angle of the cage 50 with respect to the outer ring 10 is maximized when the ball 40 is assembled as shown in FIG. 7 (this angle is referred to as a ball assembly angle), and the pocket 56 is based on the amount of movement of the ball 40 at this time. It is necessary to determine the length in the circumferential direction. Therefore, as the ball assembly angle increases, the width (circumferential dimension) of the column portion 58 between the adjacent pockets 56 decreases, and the area of the spherical outer peripheral surface 52 and the spherical inner peripheral surface 54 of the cage 50 also decreases. It has a relationship of
Japanese Patent Laid-Open No. 11-101256

  For example, when a constant velocity universal joint used in an automobile is used for a drive shaft of a front wheel drive vehicle, a slide type constant velocity universal joint is arranged on the differential side and a fixed type constant velocity universal joint is arranged on the wheel side. The two are connected by a shaft. The fixed type constant velocity universal joint is linked with the steering movement of the steering wheel and moves in the same way as the wheel, so it needs to operate at a high operating angle. As described above, the fixed type constant velocity universal joint rotates and transmits torque at a high operating angle, so that sufficient rigidity, strength and durability are required. Therefore, the outer ring 10, inner ring 30, ball 40 and cage 50 of the fixed type constant velocity universal joint are hardened and used by heat treatment such as carburizing and high frequency. Usually, the weakest part of the fixed type constant velocity universal joint during high-angle operation is the cage 50. As the cage 50 becomes higher in angle, the portion overhanging from the spherical inner peripheral surface 18 of the outer ring 10 and the spherical outer peripheral surface 32 of the inner ring 30 increases (see FIG. 6), and the axial force of the ball 40 further increases. When the cage 50 becomes a high angle, the strength rapidly decreases.

  Recently, improvement in fuel efficiency of vehicles has been desired. However, as a countermeasure, weight reduction of vehicles is the most effective means, and constant velocity universal joints are also strongly desired to be lightweight and compact. In order to reduce the weight and size of the fixed type constant velocity universal joint, it is essential to increase the strength of the cage 50, which is the weakest part during high-angle operation. As countermeasures for this, increasing the strength of materials, increasing the strength by heat treatment, and the like have been proposed, but both have the problem of increasing costs. Increasing the thickness of the cage 50 increases the strength, but the ball groove depth of the outer ring 10 and the inner ring 30 decreases, so that the allowable load torque decreases and the durability significantly decreases. . Further, a portion where the breakage of the cage 50 easily occurs is a pocket 56 into which the ball 40 enters and a column portion 58 between the pockets 56. Therefore, if the width of the column part 58 is increased, the strength is improved. For this purpose, it is conceivable to reduce the ball diameter or increase the PCD of the ball. However, the former is not preferable because the durability of the joint is lowered and the outer diameter of the joint is increased.

FIG. 10 shows an entrance portion of the ball groove 20 of the outer ring 10 in a conventional fixed type constant velocity universal joint. The inlet portion of the ball groove 20 is cut by a tapered surface 22 defined by the shaft 38 when the maximum operating angle θ is taken (see FIG. 6), and the position of the large end surface 16 is a taper including the ball groove cut section. It was outside the surface 22. However, it is necessary to secure the width of the column portion 58 of the cage 50 when a reduction in size is achieved by reducing the PCD of the ball 40, especially when a large number (seven or more) of balls are provided. Therefore, the ball assembly angle α for assembling the ball 40 must be set smaller than before. However, as shown in FIG. 11, when the ball assembly angle α is reduced (α ₁ > α ₂ ), the large end surface 16 must be set at a position in the middle of the track groove cut section of the tapered surface 22. That is, the large end surface 16 of the outer ring 10 is retracted more than before (A ₁ > A ₂ ). This means that the outer ring shape intended for downsizing as described above has a lower outer ring strength at a high operating angle than the conventional one.

  In addition, when a repeated torque load is received at a high operating angle, a crack develops from the bottom of the opening groove of the ball ring of the outer ring and breaks. An object of the present invention is to improve the breaking strength and enable further miniaturization.

  The fixed type constant velocity universal joint of the present invention includes an outer ring formed with ball grooves extending in the axial direction at a plurality of circumferential positions on the spherical inner peripheral surface, and an axial direction at a plurality of circumferential positions on the spherical outer peripheral surface. An inner ring having a ball groove extending to the inner ring, a ball interposed between the ball groove of the outer ring and the ball groove of the inner ring, and a spherical inner peripheral surface of the outer ring and a spherical outer peripheral surface of the inner ring. A cage for holding all the balls in the same plane, and the ball groove of the outer ring is composed of an arc portion on the back side and a straight line portion parallel to the axis located on the large end surface side. The intersection of the groove bottom extension line and the shaft chamfered taper surface is on the inner side of the large end surface, and a portion from the groove bottom to the large end surface including the intersection is removed after quenching.

  The invention of claim 2 is characterized in that in the fixed type constant velocity universal joint of claim 1, it is removed in the same cross-sectional shape over the entire circumference from the bottom of the ball groove to the large end surface at a position inside the intersection. It is.

  The invention of claim 3 is a method for manufacturing the outer ring of the fixed type constant velocity universal joint of claim 1 or 2, wherein the portion from the groove bottom to the large end surface of the ball groove including the intersection is removed after quenching. It is characterized by a process.

  According to a fourth aspect of the present invention, in the method for manufacturing a fixed type constant velocity universal joint according to the third aspect, the spherical inner peripheral surface of the outer ring and the removal portion are turned in the same process.

According to the present invention, the surface roughness after quenching is improved, the concave portions on the surface are removed, and the strength due to repeated torque load is improved. Moreover, the removal process (turning or grinding) after quenching gives compressive residual stress to the removal surface, and the strength by repeated torque load is improved. Therefore, according to the present invention, the strength of the outer ring of the fixed type constant velocity universal joint is improved, and the compactness can be achieved.
In addition, the angle of inclination of the inner ring when the ball is assembled is reduced, and the cage window length can be reduced, thereby improving the strength of the cage.
Furthermore, the removal portion can be implemented at low cost by processing the spherical inner peripheral surface of the outer ring and the removal portion in the same turning process.

  Embodiments of the present invention will be described below with reference to the drawings. First, since the basic configuration of the fixed type constant velocity universal joint is the same as that of the prior art, it will be described again with reference to FIG. 6. The fixed type constant velocity universal joint includes an outer ring 10 as an outer joint member, and an inner joint. The main components are an inner ring 30 as a member, a ball 40 as a torque transmission element, and a cage 50 for holding the ball.

  Here, the case where the outer ring 10 is composed of a stem portion 12 and a mouse portion 14 is illustrated, and the stem portion 12 is coupled to one of the two shafts to be connected. The mouse part 14 has a bell shape opened at one end, and the end face indicated by reference numeral 16 is referred to as a large end face. Inside the mouse portion 14, ball grooves 20 extending in the axial direction of the outer ring 10 are formed at equal intervals in the circumferential direction of the spherical inner peripheral surface 18. The vertical cross-sectional shape of the groove bottom of the ball groove 20 includes an arc portion 20a having a center of curvature Oo on the axis X of the outer ring 10 and a straight portion 20b parallel to the axis X on the large end face 16 side. Due to the presence of the straight portion 20b, the ball groove 20 has no undercut. In this sense, this type of constant velocity universal joint is called an undercut free joint (UJ). The outer end of the ball groove 18 is open to the large end surface 16. The entrance of the ball groove 20 is cut by a tapered surface 22 defined by the shaft 38 when the maximum operating angle θ is taken.

  The inner ring 30 has a spline hole 36 for spline coupling with the other of the two shafts to be connected, that is, here the shaft 38. Ball grooves 34 extending in the axial direction of the inner ring 30 are formed on the spherical outer peripheral surface 32 of the inner ring 30 at equal intervals in the circumferential direction and the same number as the ball grooves 20 of the outer ring 10. The vertical cross-sectional shape of the groove bottom of the ball groove 34 is parallel to the axis Y of the inner ring 30 on the side opposite to the arc portion 34a having the center of curvature Oi on the axis Y of the inner ring 30 and the large end surface 16 of the outer ring 10. It consists of a straight part 34b.

  The ball groove 18 of the outer ring 10 and the ball groove 34 of the inner ring 30 make a pair, and a ball 40 is incorporated between each pair of ball grooves 20 and 34 to transmit torque between the outer ring 10 and the inner ring 30. FIG. 5C illustrates an example in which the ball grooves 20 and 34 have a Gothic arch cross-sectional shape and form an angular contact with the ball 40.

  As shown in FIG. 5 (a), the center of curvature Oo of the ball groove 20 of the outer ring 10 and the center of curvature Oi of the ball groove 34 of the inner ring 30 are the joint center O (the spherical inner peripheral surface of the outer ring, the inner ring It is also the center of curvature of the spherical outer peripheral surface. Therefore, the ball track formed by each pair of ball grooves 20 and 34 has a wedge shape that gradually spreads from one to the other in the axial direction. As shown in FIG. 6, when torque is transmitted with the joint at an operating angle θ, an axial force that moves the ball 40 from the narrower side to the wider side of the wedge-shaped ball track acts on the ball 40. To do. With this axial force, the ball 40 is oriented in a plane P (see FIG. 6) perpendicular to the bisector of the operating angle θ, and the constant velocity of the joint is ensured.

  The cage 50 is interposed between the outer ring 10 and the inner ring 30 and plays a role of always holding all the balls 40 in the same plane. The cage 50 includes a spherical outer peripheral surface 52 that makes spherical contact with the spherical inner peripheral surface 22 of the outer ring 10, and a spherical inner peripheral surface 54 that contacts the spherical outer peripheral surface 32 of the inner ring 30. Pockets 56 for accommodating the balls 40 are formed at equal intervals in the circumferential direction of the cage 50. The dimension of the pocket 56 in the axial direction of the cage 50 is usually such that an appropriate margin is given to the ball 40. The circumferential length of the pocket 56 is as described above with reference to FIG. 7 when the ball is assembled so that the outer ring 10 and the cage 50 are relatively inclined so that the pocket 56 faces the outside from the open end of the outer ring 10. In consideration of the amount of movement of the ball in the circumferential direction, the length is such that the ball 40 does not interfere. The relationship between the circumferential length of the pockets 56 is the width of the column portion 58 between the adjacent pockets 56.

Next, the embodiment of the present invention will be described. As shown in FIGS. 1 and 2, as shown in FIG. 1 and FIG. 2, the intersection P between the shaft chamfered tapered surface 22 of the outer ring 10 and the extended line of the straight portion 20 b of the groove bottom of the ball groove 20. ₀ has an opening shape that is from the large end face 16 inwardly, the range of the depth a of the large end face 16 includes an intersection P ₀ are removed after hardening. Although the number of balls 40 is not particularly limited, FIG. 1B illustrates the case of eight balls.

End becomes P ₁ of the groove bottom of the ball groove 20 after the removal, since the back side of the P _0, as shown in FIG. 3, the inclination angle α of the cage 50 in order to put the ball 40 decreases. Therefore, the circumferential length L of the pocket 56 of the cage 50 shown in FIG. 4 can be reduced, and the width of the column 58 between the pocket 56 and the pocket 56 can be increased, so that the cage 50 is strengthened. In order to increase the cross-sectional area of the column 58 of the cage 50 without lowering other characteristics, it is necessary to reduce the circumferential length L of the pocket 56. The circumferential length L is determined by a request for assembling the constant velocity universal joint. That is, when the outer ring 10, the inner ring 30, the cage 50, and the ball 40 are assembled, a large operating angle (ball assembly angle α) is required when the last ball 40 is assembled, but a sufficient circumferential length is allowed to allow this. Is necessary. When the constant velocity universal joint takes an operating angle θ, the position of each ball 40 advances or lags in the circumferential direction with respect to the pocket 56. As the ball assembly angle α increases, the amount of movement of the ball 40 in the circumferential direction increases. When the last ball 40 is assembled, the position of the ball 40 on both sides of the ball 40 moves maximum in the circumferential direction with respect to the pocket 56, and interference between the ball 40 and the column 58 of the pocket 56 occurs. Therefore, if the ball insertion angle α for incorporating the last ball 40 can be reduced, the interference between the adjacent balls 40 and the columns 58 does not occur, and the circumferential length L of the pocket 56 can be reduced. As a result, the columns The cross-sectional area of 58 increases.

  The outer ring is manufactured through processes of forging, turning, rolling, heat treatment, grinding and turning. 2 (b) and 3 (b) show the heat treatment part by hatching in the same cross section as FIG. 2 (a) and FIG. 3 (a). In FIG. 1A, the spherical inner peripheral surface 18 of the outer ring 10 indicated by symbol B and the removal portion 24 indicated by symbol A are cut in the same process (with the same tool in the same chuck state) after quenching. Therefore, it can be implemented at low cost.

  The assembly of the constant velocity universal joint having the above-described configuration is the same as that of the conventional case already described with reference to FIGS.

  The present invention can be applied to the case where the number of balls is 7 or more in addition to the case where the number of balls is 6, and the effect becomes more remarkable as the number of balls increases.

(A) is a longitudinal sectional view of the outer ring showing the embodiment, (b) is an end view. (A) is the elements on larger scale of FIG. 1 (a), (b) is a figure which shows a heat processing part. (A) is a longitudinal sectional view of the outer ring and the cage showing the ball assembly process, (b) is a diagram showing the heat treatment part Cage top view (A) is a longitudinal sectional view of a fixed type constant velocity universal joint, (b) is a transverse sectional view, and (c) is a partially enlarged view of FIG. 5 (b). Longitudinal section of fixed constant velocity universal joint with undercut free type at maximum operating angle Longitudinal section showing the process of ball assembly Longitudinal section showing the process of assembling the inner ring and cage Longitudinal section showing the process of incorporating the inner ring with cage into the outer ring (A) is a partial end view of the outer ring large end face, and (b) is a longitudinal sectional view. (A) is a partial end view of the outer ring large end face, and (b) is a longitudinal sectional view.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Outer ring 12 Stem part 14 Mouse part 16 Large end surface 18 Spherical inner peripheral surface 20 Ball groove 20a Arc part O _A Curvature center 20b Linear part 22 Tapered surface 24 Removal part 30 Inner ring 32 Spherical outer peripheral surface 34 Ball groove 34a Arc part O _B center of curvature 34b straight portion 36 spline hole 38 shaft 40 ball 50 cage 52 spherical outer peripheral surface 54 spherical inner peripheral surface 56 pocket 58 column part O joint center P bisector α ball assembly angle θ working angle

Claims (4)

An outer ring in which ball grooves extending in the axial direction are formed at a plurality of circumferential positions on the spherical inner peripheral surface, an inner ring in which ball grooves extending in the axial direction are formed in a plurality of circumferential positions on the spherical outer peripheral surface, and an outer ring A cage interposed between the ball groove of the inner ring and the ball groove of the inner ring and between the spherical inner peripheral surface of the outer ring and the spherical outer peripheral surface of the inner ring to hold all the balls in the same plane And
The ball groove of the outer ring is composed of an arc portion on the back side and a straight line portion parallel to the axis located on the large end surface side, and the intersection of the straight line portion extension line and the shaft chamfer taper surface is on the inner side of the large end surface. A fixed type constant velocity universal joint including a portion from the groove bottom to the large end surface including the intersection and removed after quenching.   The fixed constant velocity universal joint according to claim 1, wherein the fixed constant velocity universal joint is removed with the same cross-sectional shape from the bottom of the ball groove to the large end surface at a position inside the intersection.   A method of manufacturing an outer ring of a fixed type constant velocity universal joint according to claim 1 or 2, wherein the portion including the intersection and extending from the groove bottom to the large end surface is removed after quenching. Manufacturing method of outer ring.   The method for manufacturing a fixed type constant velocity universal joint according to claim 3, wherein the spherical inner peripheral surface of the outer ring and the removal portion are turned in the same process.

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