JP5031397B2 - Cross groove type constant velocity universal joint - Google Patents

Description

  The present invention relates to a cross groove type constant velocity universal joint.

  In the cross groove type constant velocity universal joint, the ball groove of the inner ring and the ball groove of the outer ring that form a pair are inclined in opposite directions with respect to the axis, and the torque transmission ball is held at the intersection of both ball grooves. ing. Because of such a structure, rattling between the torque transmitting ball and the ball groove can be reduced, and it is particularly used for a drive shaft of an automobile that does not like rattling.

  Non-Patent Document 1 shows the most basic cross groove type constant velocity universal joint. In Non-Patent Document 1, the number of rolling elements is four or more, and generally six, and the inclination angle between the ball grooves is the opposite of the inner ring and the outer ring with the constant velocity universal joint taking the maximum operating angle. It is assumed that the ball grooves to be designed are designed so as not to be parallel to each other, and the axis and the crossing angle of each inner ring or outer ring are generally 13 to 19 °. Moreover, it is described that the cross section of the groove is a gothic arch, and the groove diameter is generally 1.01 to 1.04 times the ball diameter. Furthermore, it is described that the contact angle is 30 to 45 °.

  It is said that the cross groove type constant velocity universal joint cannot basically have a large operating angle. This is because there is an angle (limit angle) where the wedge angle formed by the ball grooves of the inner ring and the outer ring is reversed when the joint takes an operating angle. When the operating angle of the joint exceeds the limit angle, the cage cannot maintain the balance of force and becomes unstable, and it is considered that the function of the constant velocity universal joint is lost.

  Therefore, it is conceivable to prevent the reversal of the wedge angle by forming the ball grooves of the inner ring and the outer ring so that the crossing angle of the axis of each inner ring or outer ring is large. However, since the inner and outer rings are alternately arranged in the circumferential direction with ball grooves inclined in opposite directions with respect to the axis, it is necessary to avoid the interference between adjacent ball grooves, and to increase the crossing angle. There are limits.

  The crossing angle between the inner and outer ball grooves of the cross groove type constant velocity universal joint and the axis of each inner or outer ring is also related to the sliding amount of the joint. It is effective to make it smaller.

  However, if the crossing angle is reduced to increase the sliding amount of the joint, the maximum operating angle as a constant velocity universal joint is reduced. The maximum operating angle is an angle at which a maximum torque (hereinafter referred to as a bending torque) appears when an operation of bending and returning the joint is performed without rotating. In the worst case, there is a phenomenon that the angle does not return, that is, it is caught. Such hooking at the time of bending becomes a problem when the constant velocity universal joint is assembled to an automobile.

  When assembling the constant velocity universal joint to the automobile, it is necessary to return it after bending it once. For this reason, when the operating angle is small and a catch is generated at the time of bending, the workability of assembling the constant velocity universal joint to the automobile is poor.

  Therefore, in Patent Document 1, in order to increase the sliding amount without reducing the maximum operating angle, the ball grooves of the inner ring and the outer ring have an intersection angle with the axis of each inner ring or outer ring of 4.5 ° or more and 8.5. A cross groove type constant velocity universal joint having a torque transmission ball of less than 0 and 8 torque transmission balls has been proposed.

  The cross-groove type constant velocity universal joint of Patent Document 1 is superior in bending torque characteristics to the conventional six joints by setting the number of torque transmission balls to eight. However, when the number of torque transmitting balls is eight, the inclination directions of the pair of ball grooves corresponding to the diameter direction provided on the outer ring or the inner ring are opposite to each other. Therefore, the pair of ball grooves can be processed simultaneously. This is not possible, resulting in poor processability, a decrease in productivity, and an increase in cost.

Therefore, in Patent Document 2, in order to ensure the maximum operating angle without causing an increase in cost, the ball grooves of the inner ring and the outer ring have an intersection angle with the axis of each inner ring or outer ring of 10 ° or more and 15 ° or less. A cross groove type constant velocity universal joint having 10 torque transmitting balls has been proposed. When there are ten torque transmitting balls as in Patent Document 2, the inclination directions of the pair of ball grooves corresponding to the diameter direction provided on the outer ring or the inner ring are the same direction. Therefore, the pair of ball grooves can be processed simultaneously, the workability of the ball grooves is good, the productivity is excellent, and the cost can be reduced.
JP 2006-132669 A JP 2006-266423 A ER Wagner, "Universal Joint and Driveshaft Design Manual", SAE, 1991, p.163-166

  In recent years, with the reduction of fuel consumption and higher functionality of automobiles, there is an increasing demand for a longer slide length in addition to lighter and more compact cross groove type constant velocity universal joints.

  However, the cross-groove type constant velocity universal joint of Patent Document 2 has an intersection angle between the ball grooves as large as 10 ° or more and 15 ° or less, and interference between adjacent ball grooves occurs when the sliding amount is increased. In order to prevent such interference of the ball grooves, it is necessary to increase the diameters of the outer ring and the inner ring, resulting in an increase in size of the joint. That is, it is difficult for the cross groove type constant velocity universal joint disclosed in Patent Document 2 to achieve both an increase in slide amount and a compact size.

  Therefore, an object of the present invention is to provide a cross-groove type constant velocity universal joint that can achieve both a long slide and a compact size.

In order to solve the above problems, a cross-groove type constant velocity universal joint according to claim 1 includes an inner ring having an outer peripheral surface in which ball grooves inclined in opposite directions with respect to the axis are alternately formed in the circumferential direction, and an axis. An outer ring having an inner peripheral surface in which ball grooves inclined in opposite directions to each other in the circumferential direction are alternately formed, and an intersection of an inner ring ball groove and an outer ring ball groove inclined in opposite directions with respect to the axis. And a cage that is interposed between the outer peripheral surface of the inner ring and the inner peripheral surface of the outer ring and holds the torque transmission balls at predetermined intervals in the circumferential direction, and is inclined in opposite directions. The ball groove of the inner ring and the ball groove of the outer ring have an intersecting angle with the axis of each inner ring or outer ring of 7 ° to 10 °, a groove contact angle of 30 ° to less than 40 °, and a groove contact rate of 1 .04 to 1.1 and the torque transmission ball There are 10, and characterized in that it is used as a sliding type constant velocity joint of the drive shaft of a motor vehicle.

  According to the above configuration, since the number of torque transmitting balls is 10 and the crossing angle of the ball grooves of the inner ring and the outer ring is 7 ° or more and 10 ° or less, the sliding amount between the outer ring and the inner ring is increased. However, there is no interference between adjacent ball grooves as in the prior art. Therefore, since the slide amount can be increased without increasing the diameters of the outer ring and the inner ring, it is possible to achieve both a long slide and a compact size of the cross groove type constant velocity universal joint.

  Here, when the crossing angle of the ball grooves is less than 7 °, the operating angle becomes too small, and the function as a constant velocity universal joint may be lost.

  Increasing the sliding amount between the outer ring and the inner ring tends to decrease the maximum operating angle and increase the bending torque, but the groove contact angle is 30 ° or more and 40 ° or less, and the groove contact rate is 1.04 or more. Since it is 1.1 or less, it is possible to prevent an increase in bending torque, and therefore it is possible to prevent the occurrence of a catching phenomenon during bending.

  Here, if the groove contact angle is less than 30 °, the load at the ball contact portion is large, and the durability may deteriorate. On the other hand, if the groove contact angle exceeds 40 °, the ball easily protrudes from the ball groove, the contact state of the ball is deteriorated, and the durability may be deteriorated. On the other hand, if the groove contact ratio is less than 1.04, the ball easily protrudes from the ball groove, the contact state of the ball is deteriorated, and the durability may be deteriorated. On the other hand, if the groove contact ratio exceeds 1.1, the load at the ball contact portion is large, and the durability may deteriorate.

  In addition, since there are ten torque transmission balls, the torque transmission efficiency, which is the main function of the joint, can be improved as compared with the case where there are six transmission balls.

  A cross groove type constant velocity universal joint according to a second aspect is the cross groove type constant velocity universal joint according to the first aspect, wherein a large number of minute recesses are randomly provided on the surface of the torque transmitting ball.

  According to the above embodiment, the ability to form an oil film on the surface of the torque transmitting ball is improved, surface damage can be prevented, and the cross groove type constant velocity universal joint can have a long life.

  The cross groove type constant velocity universal joint according to claim 3 is the cross groove type constant velocity universal joint according to claim 1 or 2, wherein a lubricant having a friction coefficient of 0.07 or less is applied.

  According to the above embodiment, the friction between the torque transmission ball and the ball groove is reduced, and further improvement in transmission efficiency and reduction in bending torque can be achieved. In particular, by using a lubricant that has a friction coefficient of 0.07 or less as measured by a friction coefficient measurement with a Sabang type frictional wear tester, it is possible to secure an improvement in transmission efficiency and a reduction in bending torque.

  The cross groove type constant velocity universal joint according to claim 4 is the cross groove type constant velocity universal joint according to claim 3, wherein the low friction coefficient lubricant is urea grease, and the lower limit of the consistency of the urea grease. No. 0 and the upper limit of the consistency of the urea grease was No. 2.

  According to the above embodiment, sufficient lubricity is maintained even at high temperatures, so that stable seizure resistance can be ensured even during high rotation or long time operation.

  The cross groove type constant velocity universal joint according to claim 5 is the cross groove type constant velocity universal joint according to claims 2 to 4, wherein the lower limit value of the surface roughness of the ball having a large number of minute recesses is Ra 0.03 μm. In addition, the upper limit value of the surface roughness is set to Ra 0.6 μm, the upper limit value of the parameter SK value of the surface roughness of the ball is set to −1.0, and the large number of minute recesses with respect to the surface area of the ball The lower limit value of the total area ratio was set to 10%, and the upper limit value of the ratio was set to 40%.

  If it is within the range of the upper and lower limit values, stable seizure resistance can be ensured, but if these upper and lower limit values are exceeded, it is difficult to ensure seizure resistance.

  A cross groove type constant velocity universal joint according to a sixth aspect of the present invention is the cross groove type constant velocity universal joint according to the fifth aspect, wherein the lower limit value of the surface roughness of the ball having a large number of minute recesses is set to Ra 0.05 μm. The upper limit value of the surface roughness is set to Ra 0.15 μm, the lower limit value of the parameter SK value of the surface roughness of the ball is set to −4.9, and the upper limit value of the parameter SK value is set to −1.0. Was set.

  If it is within the range of the upper and lower limit values, stable seizure resistance can be ensured, but if these upper and lower limit values are exceeded, it is difficult to ensure seizure resistance.

  In the cross groove type constant velocity universal joint of the present invention, the ball grooves inclined in the opposite directions of the inner ring and the outer ring have an intersection angle of 7 ° or more and 10 ° or less with the axis of each inner ring or outer ring, and the groove contact angle Is 30 ° or more and 40 ° or less, the groove contact ratio is 1.04 or more and 1.1 or less, and the number of torque transmitting balls is 10, so that even if the sliding amount between the outer ring and the inner ring is increased, Interference between adjacent ball grooves can be prevented, and since it is not necessary to increase the diameters of the outer ring and the inner ring, it is possible to achieve both a long slide and a compact size. In addition, it is possible to prevent the occurrence of a catching phenomenon during bending. Further, torque transmission efficiency can be increased.

  An embodiment of the present invention will be described with reference to the drawings. This cross groove type constant velocity universal joint includes an inner ring 2, an outer ring 4, a torque transmission ball 6, and a cage 8 as main components. As shown in FIG. 1A, in this cross groove type constant velocity universal joint, an inner ring 2 is coupled to a first shaft 12 (stub shaft), and the first shaft 12 and the constant velocity universal joint are internally connected. A boot 11 with an adapter for sealing is attached. A second shaft (not shown) provided with a companion flange is coupled to the end of the outer ring 4 of the constant velocity universal joint. An end plate 10 that is located between the companion flange of the second shaft and the constant velocity universal joint and seals the inside is attached to the end of the outer ring 4.

  The inner ring 2 has a spline hole 21 at the center, and a plurality of ball grooves 2a and 2b are formed on a spherical outer peripheral surface. The first shaft 12 is fitted into the spline hole 21 of the inner ring 2 so that torque can be transmitted, and the first shaft 12 is attached to the inner ring by a snap ring or a circlip attached to the ring groove of the first shaft 12. Position and fix to 2 in the axial direction. The outer ring 4 is located on the outer periphery of the inner ring 2, and the same number of ball grooves 4a and 4b as the ball grooves 2a and 2b of the inner ring 2 are formed on the inner peripheral surface. The ball grooves 2a and 2b of the inner ring 2 and the ball grooves 4a and 4b of the outer ring 4 will be described in detail later.

  Between the one end of the outer ring 4 in the axial direction and the first shaft 12, the inside of the constant velocity universal joint is provided to prevent leakage of grease filled in the constant velocity universal joint and to prevent foreign matter from entering from the outside. A boot 11 with an adapter that seals from one end side is attached. This boot 11 with an adapter includes a bellows-like rubber or resin boot 11a having a small-diameter end and a large-diameter end, and a metal adapter 11b having a cylindrical portion at one end. The large-diameter end portion of the boot 11 and the other end portion of the adapter 11b are joined by caulking, and the small-diameter end portion of the boot 11 is fastened to the first shaft 12 by a boot band, and the cylindrical portion of the adapter 11b is attached to the outer ring. 4 and is fixed to the outer ring 4 with bolts 13.

  Between the other axial end of the outer ring 4 and a companion flange (not shown), in order to prevent leakage of grease filled in the constant velocity universal joint and to prevent foreign matters from entering, An end plate 10 that seals from the other end side is mounted. The end plate 10 has a cylindrical shape having a cylindrical portion 10 a at one end, and is fitted between the end of the outer ring 4 with the cylindrical portion 10 b fitted between the end of the outer ring 4 and the companion flange. And is fixed by bolts 13.

  By the way, as one of the structural features of the cross groove type constant velocity universal joint, when the operating angle is 0 °, when the inner ring slides in the axial direction with respect to the outer ring, the movement amount of the inner ring is the movement amount of the ball. There is a point that becomes twice. FIG. 2 is a cross-sectional view showing the inner ring 2, the outer ring 4, the torque transmission ball 6, and the cage 8 which are main components extracted from the cross groove type constant velocity universal joint of the present embodiment. FIG. 2A shows a state in which the center of the inner ring 2 in the axial direction coincides with the center of the outer ring 4 in the axial direction. From this state, the inner ring 2 is moved to the outer ring 4 as shown in FIG. When sliding, a sliding amount twice as long as the moving amount of the torque transmitting ball 6 is obtained. With this feature, the length of the rolling grooves (ball grooves 2a, 2b, 4a, 4b) with respect to a predetermined slide amount can be shortened as compared with other sliding type constant velocity universal joints. Therefore, the cross groove type constant velocity universal joint has an advantage that the axial dimension can be reduced and a space can be secured in the axial direction, thereby increasing the degree of freedom in peripheral design.

  FIG. 3 is a developed view of the ball groove. As shown by the solid line in FIG. 3, the ball grooves 2a and 2b inclined in opposite directions with respect to the axis of the inner ring 2 are alternately positioned in the circumferential direction. . Further, as indicated by a two-dot chain line, ball grooves 4 a and 4 b inclined in opposite directions with respect to the axis of the outer ring 4 are alternately positioned in the circumferential direction.

  The crossing angle of each ball groove 2a, 2b, 4a, 4b with respect to the axis is represented by symbol β. The crossing angle β is in the range of 7 ° to 10 °.

  A torque transmitting ball 6 is incorporated at the intersection of the ball groove 2a and the ball groove 4a or the ball groove 2b and the ball groove 4b forming a pair. As shown in FIG. 6A, here, there are 10 ball grooves 2a, 2b of the inner ring 2, 10 ball grooves 4a, 4b of the outer ring 4, and 10 torque transmitting balls 6. The torque transmission ball 6 is held in a pocket of a cage 8 interposed between the inner ring 2 and the outer ring 4.

  As shown in FIG. 4, the ball grooves 2a, 2b, 4a, 4b of the inner ring 2 and the outer ring 4 generally have a Gothic arch or elliptical cross-sectional shape, and the torque transmission ball 6 and the ball grooves 2a, 2b, 4a , 4b is an angular contact. The groove contact angle α of the angular contact ranges from 30 ° to 40 °.

  Further, the groove diameter D of the ball grooves 2a, 2b, 4a, 4b of the inner ring 2 and the outer ring 4 and the diameter d of the torque transmitting ball 6 are 1.04 as the ball contact ratio represented by (groove diameter D / ball diameter d). The value is set in the range of 1.1 or less.

  Next, the hooking at the time of bending the cross groove type constant velocity universal joint will be described. Hooking is a phenomenon in which excessive torque is required when a joint attempts to return at an operating angle. FIG. 5 is a diagram showing the bending torque experimental results when the bending angle is 12 ° for the cross groove constant velocity universal joint of the present embodiment and the cross groove constant velocity universal joint of the comparative example. is there. In FIG. 5, the vertical axis represents the bending torque (Nm), and the horizontal axis represents the bending angle (°). In the constant velocity universal joint of the present embodiment, the number of torque transmission balls 6 is 10, and the crossing angle β is 8 °. In the constant velocity universal joint of the comparative example, the number of torque transmission balls was six, and two types of crossing angles β of 10 ° and 16 ° were tested. As can be seen from FIG. 5, in the constant velocity universal joint of the present embodiment, the bending torque is set to a low bending torque equivalent to the case where the number of torque transmitting balls is six and the crossing angle β is 16 °. Can do. Since the bending torque can be lowered in this way, the maximum operating angle can be made relatively large, and therefore the workability of the work of assembling the constant velocity universal joint to the automobile can be improved.

  In general, the bending torque can be reduced by increasing the crossing angle β as in the comparative example. However, when the number of torque transmitting balls is 10, if the crossing angle β is increased, the adjacent ball grooves Since mutual interference occurs, it is difficult to earn a slide amount. On the other hand, the constant velocity universal joint of the present embodiment has an angular contact groove contact angle α of 30 ° to 40 ° and a ball contact rate of 1.04 to 1.1. The bending torque can be reduced while keeping the cross angle β relatively small. Although the case where the crossing angle β is 8 ° is illustrated in FIG. 5, the bending torque can be reduced when the crossing angle β is in the range of 7 ° to 10 °.

  FIG. 6 is a diagram for explaining the interference between the ball grooves 4 a and 4 b of the outer ring 4. FIG. 6B is a view of the outer ring 4 in the present embodiment as viewed from the end surface side, and FIG. 6C is a view of the outer ring 40 in the comparative example as viewed from the end surface side. In this embodiment, the intersection angle β of the ball grooves 4a and 4b is 8 °, and in the comparative example, the intersection angle β of the ball grooves 40a and 40b is 11 °. As can be seen from FIG. 6, in the outer ring 4 of the present embodiment, adjacent ball grooves 4a and 4b inclined in opposite directions can be arranged at a sufficient distance. On the other hand, in the outer ring 40 of the comparative example, the separation between the adjacent ball grooves 40a and 40b is substantially lost, causing interference between the ball grooves 40a and 40b.

  Thus, in the cross groove type constant velocity universal joint of the present embodiment, the number of torque transmission balls 6 is 10 and the intersection angle β is 7 ° or more and 10 ° or less. The sliding amount between the outer ring 4 and the inner ring 2 can be ensured without causing interference of the grooves 2a, 2b, 4a, 4b. Therefore, since the slide amount can be increased without increasing the diameters of the outer ring 4 and the inner ring 2, the cross-slot type constant velocity universal joint can be made long and compact.

  The cross groove type constant velocity universal joint according to the present embodiment can improve the torque transmission efficiency in addition to the reduction of the bending torque. FIG. 7 is a diagram showing the results of experiments conducted on torque transmission loss when a torque of 300 Nm was input at a rotation speed of 100 rpm for six and ten torque transmission balls. In FIG. 7, the vertical axis represents transmission loss (%), and the horizontal axis represents the operating angle (°). The transmission loss (%) is calculated by (input torque−output torque) × 100 / input torque. As can be seen from FIG. 7, when there are 10 torque transmitting balls, there is less torque transmission loss at any operating angle than when there are 6 balls. Furthermore, the rate of increase in transmission loss accompanying an increase in the operating angle is smaller for 10 torque transmitting balls than for 6 torque transmitting balls. That is, by using ten torque transmission balls, the torque transmission efficiency can be improved and an increase in transmission loss accompanying an increase in operating angle can be reduced.

  As described above, the cross groove type constant velocity universal joint of the present embodiment has a cross angle β of 7 ° to 10 °, a groove contact angle α of 30 ° to 40 °, and a ball contact rate. Since it is 1.04 or more and 1.1 or less, the bending torque is low, the assembling work can be facilitated, a long slide and compactness can be achieved at the same time, and the torque transmission efficiency can be improved.

  In the cross-groove type constant velocity universal joint of the present embodiment, it is preferable that a minute concave recess is randomly provided on the surface of the torque transmission ball and a lubricant having a low friction coefficient is applied. As a result, the ability to form an oil film on the surface of the torque transmission ball is improved, so that the film breakage of the lubricant can be prevented for a long time, the surface damage can be suppressed for a long time, and the long life of the cross groove type constant velocity universal joint Can be achieved.

  As the lubricant to be applied to the surface of the torque transmission ball, it is preferable to use a lubricant that has a friction coefficient of 0.07 or less as measured by a Sabang type frictional wear tester. By using this lubricant, it is possible to effectively extend the life. In particular, it is preferable to use urea grease having a consistency of No. 1 or No. 2 as a lubricant. Since urea grease retains sufficient lubricity even at high temperatures, stable seizure resistance can be ensured even at high speeds or for long periods of operation.

FIG. 1A is a sectional view of a cross groove type constant velocity universal joint, and FIG. 1B is an end view of the cross groove type constant velocity universal joint. FIG. 2A is a cross-sectional view showing main components of the cross groove type constant velocity universal joint, and FIG. 2B is a cross-sectional view showing a state in which the inner ring is slid. It is a development view of a ball groove of a cross groove type constant velocity universal joint. It is sectional drawing which shows the contact state of the torque transmission ball | bowl in the ball groove | channel of an inner ring | wheel and an outer ring | wheel. It is the figure which piled up and showed the experimental result of bending torque about the cross groove type constant velocity universal joint of this embodiment and a comparative example. FIG. 6B is a view of the outer ring in the embodiment as seen from the end face side, and FIG. 6C is a view of the outer ring in the comparative example as seen from the end face side. It is the figure which piled up and showed the experimental result of the transmission loss of torque about the cross groove type constant velocity universal joint of this embodiment and a comparative example.

Explanation of symbols

2 Inner ring 2a, 2b Ball groove 4 Outer ring 4a, 4b Ball groove 6 Torque transmission ball 8 Cage

Claims (6)

An inner ring having an outer peripheral surface alternately formed in the circumferential direction with ball grooves inclined in opposite directions with respect to the axis, and an inner ring having ball grooves inclined in the opposite directions with respect to the axis in the circumferential direction. An outer ring having a peripheral surface, a torque transmitting ball incorporated at the intersection of the ball groove of the inner ring and the ball groove of the outer ring inclined in opposite directions with respect to the axis, and the outer peripheral surface of the inner ring and the inner peripheral surface of the outer ring. And a cage for holding the torque transmitting balls at a predetermined interval in the circumferential direction, and the ball grooves of the inner ring and the ball grooves of the outer ring inclined in opposite directions are in contact with the axis of each inner ring or outer ring. The crossing angle is 7 ° or more and 10 ° or less, the groove contact angle is 30 ° or more and less than 40 °, the groove contact rate is 1.04 or more and 1.1 or less, and the number of torque transmitting balls is 10. as a sliding type constant velocity joint of an automobile drive shaft Cross groove constant velocity universal joint, characterized in that it is needed. In the cross groove type constant velocity universal joint according to claim 1,
A cross groove type constant velocity universal joint characterized in that a large number of minute recesses are randomly provided on the surface of a torque transmitting ball. In the cross groove type constant velocity universal joint according to claim 1 or 2,
A cross groove type constant velocity universal joint, wherein a lubricant having a friction coefficient of 0.07 or less is applied. In the cross groove type constant velocity universal joint according to claim 3,
The lubricant having a low friction coefficient is urea grease, the lower limit of the consistency of the urea grease is 0, and the upper limit of the consistency of the urea grease is 2; Universal joint.   The lower limit value of the surface roughness of the ball having a large number of minute recesses is set to Ra 0.03 μm, the upper limit value of the surface roughness is set to Ra 0.6 μm, and the upper limit value of the parameter SK value of the surface roughness of the ball is set. The value is set to -1.0, the lower limit value of the ratio of the total area of the large number of minute recesses to the surface area of the ball is set to 10%, and the upper limit value of the ratio is set to 40%. The cross groove type constant velocity universal joint according to any one of claims 2 to 4.   The lower limit value of the surface roughness of the ball having a large number of minute recesses is set to Ra 0.05 μm, the upper limit value of the surface roughness is set to Ra 0.15 μm, and the lower limit value of the parameter SK value of the surface roughness of the ball is set. The cross groove type constant velocity universal joint according to claim 5, wherein the value is set to -4.9, and the upper limit value of the parameter SK value is set to -1.0.

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