JP2009197946A - Fixed type constant velocity joint - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To further improve transmission efficiency of a fixed type constant velocity joint. <P>SOLUTION: This fixed type constant velocity joint includes an outside joint member 10, in which ball grooves 14 extending in an axial direction are formed on an inner sphere 12 at a predetermined interval, an inside joint member, in which ball grooves extending in the axial direction are formed on an outer sphere at a predetermined interval, paired balls interposed between the ball grooves 14 of the outside joint member 10 and the ball grooves of the inside joint member, and a cage interposed between the inner sphere 12 of the outside joint member 10 and the outer sphere of the inside joint member to keep all of the balls on the same plane. The center of the ball groove 14 of the outside joint member 10 and the center of the ball groove of the inside joint member are offset from each other in an opposite and axial direction. All of the balls transmit torque in a high angle area, and a smaller number of the balls than the high angle are transmit the torque in a low angle area. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a fixed constant velocity joint used for a power transmission device of an automobile or various industrial machines. A fixed type constant velocity joint is a type of constant velocity joint that uses a ball as a torque transmission element and can only be angularly displaced but cannot be displaced in the axial direction. A barfield type, an undercut free type, and the like are known.

  A fixed constant velocity joint for automobiles will be described. In a front wheel drive vehicle, power from an engine is transmitted to the front wheels using a drive shaft. The drive shaft is a fixed constant velocity joint and a sliding constant velocity joint attached to both ends of the intermediate shaft. The fixed constant velocity joint is connected to the front wheel axle, and the sliding constant velocity joint is connected to the differential output shaft. Connect to. Drive shaft expansion and contraction caused by bouncing is absorbed by plunging of the sliding constant velocity joint. As for the fixed type constant velocity joint, the steering angle is increased when the automobile turns, so that the operating angle becomes large. However, the operating angle in the straight traveling state of the automobile is set low. Therefore, it is an important factor to improve the efficiency of the fixed type constant velocity joint in the straight traveling state that occupies most of the usage state.

Patent Document 1 and Patent Document 2 describe a fixed type constant velocity joint that is made highly efficient and compact by reducing the number of balls to be used to 8 and reducing the ball diameter and the track offset amount. By adopting a small-diameter ball / small track offset configuration, the distance that the ball moves along the ball groove of the inner ring (contact point locus) and the distance that the ball moves along the ball groove of the outer ring (contact point locus) Therefore, the sliding speed between the ball and the ball groove is reduced, and the torque transmission efficiency is improved. The following is a description with reference to FIGS. FIG. 10A is a longitudinal sectional view of a six-ball fixed type constant velocity joint, and FIG. 10B is a partially enlarged view around the ball in FIG. FIG. 11A is a longitudinal sectional view of a fixed constant velocity joint of eight balls, and FIG. 11B is a partially enlarged view around the ball in FIG. 10 and 11 show a state where the operating angle is 0 degree, and FIG. 12 shows a state where the operating angle is 40 degrees. The locus of the contact point between the inner ring and the ball is indicated by a bold line above the center line in FIG. 12, and the locus of the contact point between the outer ring and the ball is indicated by a thick line below the center line. The length ratio of the contact point trajectory is shown in Table 1.

  When the fixed constant velocity joint rotates while transmitting torque, the ball pushes the cage window in the direction in which the wedge angle is open, so that the outer ring spherical surface portion (spherical surface close to the opening side) and the cage outer spherical surface are in contact with each other. Since the cage is pushed by the ball and pushed toward the opening, the inner spherical surface of the cage contacts the outer spherical surface of the inner ring. The force generated between the spherical fitting portions is called a spherical force. As can be seen from a comparison between FIG. 10 and FIG. 11, by setting the small track offset (f: FIG. 11), the pinching angle (2β) of the ball becomes smaller than the large track offset (F: FIG. 10). The force pushing the ball in the axial direction is reduced (M> M ′). The forces M and M ′ pushing the ball in the axial direction are transmitted to the cage, and as a result, the spherical force between the cage and the outer ring inner spherical surface and the spherical force between the cage and the inner ring outer spherical surface are reduced, and the friction loss at the contact portion is reduced. Less and transmission efficiency is improved.

As described above, in Patent Document 1 and Patent Document 2, the frictional heat generated by the spherical contact is reduced by reducing the spherical force generated between the spherical surfaces for the above reasons as compared with the fixed type constant velocity joints before that. In addition, since there is little slip between the ball and the ball groove, the transmission efficiency is improved.
Japanese Patent No. 3460107 Japanese Patent No. 3859267

  In addition to the configuration of the small-diameter ball and the small offset that improve the efficiency of the fixed type constant velocity joint described in Patent Document 1 and Patent Document 2, the problem of the present invention is further improved by a configuration other than that. It is to improve transmission efficiency.

  The fixed constant velocity joint of the present invention includes an outer joint member in which ball grooves extending in the axial direction on the inner spherical surface are formed at predetermined intervals in the circumferential direction, and ball grooves extending in the axial direction on the outer spherical surface at predetermined intervals in the circumferential direction. Between the inner joint member formed in the above, the ball interposed between the ball groove of the outer joint member and the ball groove of the inner joint member, and the inner spherical surface of the outer joint member and the outer spherical surface of the inner joint member. And a cage for holding all the balls in the same plane, and the center of the ball groove of the outer joint member and the center of the ball groove of the inner joint member are offset in the axial direction opposite to each other from the joint center. In addition, all the balls share the torque transmission in the high angle region, and the torque transmission is performed in the low angle region with a smaller number of balls than in the high angle region.

  With respect to the ball grooves of the outer joint member and the ball grooves of the inner joint member, the predetermined interval in the circumferential direction is intended to include unequal intervals, that is, unequal pitches, in addition to equal intervals in the circumferential direction. In any case, the ball grooves of the outer joint member and the ball grooves of the inner joint member are arranged in pairs.

As a result of investigating the effect of changing the number of balls inside the constant velocity joint on the transmission efficiency by mechanism analysis, it was found that in the low angle region (the region used in regular use), the torque loss is reduced when the number of balls is reduced. That is, as shown in FIG. 13, in the low angle region, the smaller the number of balls, the smaller the rolling / sliding friction amount, and the torcross is reduced. FIG. 13 shows four types of fixed constant velocity joints with internal clearance conditions A _{1 to} A ₄ and B _{1 to} B _{4 on} the horizontal axis, and torque crosses on the vertical axis, and the numbers of balls are ₃ , ₅ , 6, and 7. This shows the change in transmission efficiency due to the difference in the number of balls.

It was also found that in the high angle range (used when turning in a vehicle), the number of balls increases as the number of balls increases (see FIG. 14). FIG. 14 shows four types of fixed constant velocity joints with internal clearance conditions A _{1 to} A ₄ and B _{1 to} B _{4 on} the horizontal axis, and torcross on the vertical axis, and the number of balls is ₃ , ₅ , 6, and 7. This shows the change in transmission efficiency due to the difference in the number of balls. In the high angle region, if the number of balls is small, the load received by the ball groove on the non-load side increases, resulting in a torque cross. Therefore, it is advantageous to increase the number of balls in the high angle range (see FIGS. 15 and 16). FIG. 15 shows a comparison of non-load-side track loads at an operating angle of 44 degrees for four types of fixed constant velocity joints having the number of balls of 3, 5, 6, and 7. The horizontal axis represents the phase angle, and the vertical axis represents the load. Represents. FIG. 16 is an explanatory diagram of the phase angle.

  Here, the internal clearance condition A means the effect of the PCD clearance. The PCD clearance is the difference between the pitch circle diameter (PCD) of the inner ring ball groove and the pitch circle diameter (PCD) of the outer ring ball groove. The internal clearance condition B means the effect of spherical clearance. There are two types of spherical clearance. One is up to the clearance between the inner ring outer spherical surface and the cage inner spherical surface, and the other is up to the clearance between the outer ring inner spherical surface and the cage outer spherical surface. Here, the sum of the two values is the spherical clearance.

  According to the present invention, all balls share torque transmission in the high angle region, and torque transmission is performed in the low angle region with a smaller number of balls than in the high angle region. As a specific example, it is a fixed constant velocity joint having a ball groove having a region where there is no contact with the ball and a ball groove of a normal shape by forming a recess in the ball groove of the inner ring or the outer ring or both, Taking this case as an example, the operation will be described as follows.

In the low-angle region, since the ball groove having the depression cannot transmit torque with the ball, this fixed type constant velocity joint reduces the number of balls that transmit torque and decreases the torque cross. In the high angle range, contact between the ball groove and the ball occurs on the non-load side other than the torque load side, which causes a torque cross. However, in the ball groove in which the depression is formed, the load generated on the non-load side coincides with the phase where the ball is positioned in the depression, so that torque transmission is not performed between the ball and the non-load side. Therefore, the torque cross is suppressed and transmission efficiency equal to or higher than that of the conventional type can be obtained. As a result, the torque cross can be reduced as compared with the conventional format.

The ball groove and the ball normally contact the inner ring → ball → outer ring to apply a load and transmit torque. If a recess is provided in the side wall of the ball groove in a low angle region (operating angle 0 to 10 degrees), the clearance between the ball and the outer ring is increased between the inner ring and the ball because the clearance between the balls is increased at the recess. The contact becomes insufficient, the load is not transmitted to the side wall of the ball groove, and torque transmission is not performed. Of course, torque is transmitted as usual in a ball groove without a recess. In the low angle region, the number of ball grooves obtained by subtracting the number of ball grooves provided with depressions from the number of all ball grooves receives a load and transmits torque.

In a normal ball groove, the ball and the side wall of the ball groove contact and receive a load. When the operating angle is 0 degree or more, the ball moves on the side wall of the ball groove, and the ball groove and ball of the inner ring and the ball groove and ball of the outer ring Then, a trajectory difference arises from the difference in the contact position. Therefore, a torcross is generated between the ball and the ball groove due to rolling / sliding friction. In the ball groove provided with the depression, when the ball is in the depression, there is no contact between the ball and the side wall of the ball groove.

  In a high angle range, if the number of balls is small, the load received by the ball groove on the non-load side increases, and torque cross occurs. In the high angle range, the load on the load side is the same as the number of ball grooves, and in the phase angle where the load on the non-load side is generated, there is no contact on the non-load side in the ball groove with the depression, and the torque cross Is suppressed. Since the torque cross in the low angle region and the high angle region is reduced, the torque cross can be reduced as compared with the conventional fixed constant velocity joint, and the transmission efficiency is improved.

Embodiments of the present invention will be described below with reference to the drawings.
First, the basic configuration of a fixed type constant velocity joint will be described with reference to FIG. 10. The fixed type constant velocity joint includes an outer ring 10 as an outer joint member, an inner ring 20 as an inner joint member, and a torque transmission element. The ball 30 and the cage 40 that holds the ball 30 are main components.

  The outer ring 10 has a spherical inner peripheral surface (hereinafter referred to as an inner spherical surface) 12, and ball grooves 14 extending in the axial direction are formed at equal intervals in the circumferential direction of the inner spherical surface 12. The inner ring 20 has a spherical outer peripheral surface (hereinafter referred to as an outer spherical surface) 22, and ball grooves 24 extending in the axial direction are formed at equal intervals in the circumferential direction of the outer spherical surface 22. The ball groove 14 of the outer ring 10 and the ball groove 24 of the inner ring 20 make a pair, and one ball 30 is incorporated between each pair of ball grooves 14, 24.

  The cage 40 has pockets 42 arranged at predetermined intervals in the circumferential direction, and each pocket 42 penetrates the cage 40 in the radial direction. The balls 30 are received in the pockets 42 of the cage 40, so that all the balls 30 are held in the same plane. The outer peripheral surface of the cage 40 is spherical, and comes into spherical contact with the inner spherical surface 12 of the outer ring 10 with a predetermined clearance (spherical clearance). The inner peripheral surface of the cage 40 is spherical, and is in spherical contact with the outer spherical surface 22 of the inner ring 20 with a predetermined clearance (spherical clearance).

The center O ₁ of the ball groove 14 of the outer ring 10 and the center O ₂ of the ball groove 24 of the inner ring 20 are offset from the joint center O by an equal distance f in the axial direction in opposite directions. As described above, the fixed type constant velocity joint of FIG. 10 forms a track with the arc-shaped ball grooves 14 and 24 offset from the centers O ₁ and O ₂ , and the track is on the side opposite to the opening of the outer ring 10. It has a wedge shape that gradually decreases toward the surface (barfield type). In order to be able to take a high angle of operation, straight portions parallel to the axis are respectively formed on a part of the ball groove 14 on the opening side of the outer ring 10 and on a part of the ball groove 24 on the side opposite to the opening of the outer ring 10. There are also known an undercut free type in which the undercut of the ball groove is eliminated, and a type in which the linear portion is tapered, and any of them can be applied.

  Next, FIGS. 1 to 4 show an example of the outer ring 10 of a fixed type constant velocity joint in which a recess 16 is formed in the ball groove 14. 5 to 9 show examples of the inner ring 20 of the fixed type constant velocity joint in which the recess 26 is formed in the ball groove 24. The positions of the depressions 16 and 26 are positions where the ball 30 occupies in a low angle region (for example, 0 to 10 degrees) in the longitudinal direction of the ball groove. When the ball 30 is in the position of the recess, there is a clearance between the ball 30 and the outer ring 10 and between the ball 30 and the inner ring 20, and torque cannot be transmitted.

  The number of balls used in one fixed type constant velocity joint, and therefore the number of ball grooves 14 and 24 of the outer ring 10 and the inner ring 20 is arbitrary, but 5 is the lower limit. In order to improve the torque transmission efficiency, the number of balls (contributing to torque transmission) is small when the operating angle is low, and the number of balls (contributing to torque transmission) is not reduced at high angles, that is, many. However, if the number of balls is small, a change (variation) between the number of balls that contribute to torque transmission and the number of balls that do not contribute cannot be provided. In addition, it is difficult to establish a constant velocity joint with one or two. Further, from the experimental results (including the analysis experiment), it was determined that the four-ball case does not hold as a constant velocity joint because there is a region that does not rotate at a constant velocity. Therefore, the minimum number of balls that can be used as a constant velocity joint is set to 3, and the number of balls that can have a certain number of changes beyond that is 5 is the lower limit.

  The number of ball grooves without the depressions 16 and 26 is set to 3 or more. In other words, the lower limit of the number of balls 30 that transmit torque in the low angle region is 3. The smaller the number of balls 30 that transmit torque in the low-angle region, the higher the efficiency. However, as described above, when the number of balls is 1, 2, and 4, the constant velocity joint cannot be realized. Therefore, the minimum number of balls 30 that transmit torque is also set to 3. For example, in the case of a 6-track fixed constant velocity joint, the number of conventional ball grooves is 3, 4 or 5. Similarly, in the case of an 8-track fixed constant velocity joint, the number of conventional ball grooves is 4, 5, 6, or 7.

  The upper limit of the interval between the balls 30 that transmit torque in the low angle region is 120 degrees. In order for the constant velocity joint to operate, it is ideal that the cage 40 is disposed on the bisection plane with respect to the outer ring 10 and the inner ring 20. The force for moving the cage 40 is generated when the ball 30 sandwiched between the wedge-shaped tracks pushes the cage 40. Therefore, when the arrangement of the balls 30 is too biased, the cage 40 does not operate and a problem occurs. When the number of balls 30 is 3, the interval is 120 degrees, and when the number of balls 30 is more than 3, the interval is smaller than 120 degrees.

  Indentations 16 and 26 are formed in the ball grooves 14 and 24 at the angular positions occupied by the balls 30 in the low angle region. Specifically, the low angle region is in the range of 0 to 10 degrees. The angle at which the constant velocity joint is used in a normal automobile (ordinary angle: the angle used when the automobile goes straight) is about this level. In addition, as the operating angle of the constant velocity joint increases, heat generation, transmission efficiency deteriorates, and durability also decreases. Although the operating angle increases when the vehicle turns, there is no problem because it is a short time. However, when the normal angle is 10 degrees or more, the durability is greatly reduced due to the above-described characteristics.

  The ball groove provided with the recess is the ball groove 14 of the outer ring 10, the ball groove 24 of the inner ring 20, or both 14, 24 of them. Various specific shapes of the recesses 16 and 26 can be considered in consideration of workability in addition to the function of the recesses, but at least the cross-sectional shape along the length direction of the ball grooves is smooth on the surfaces of the ball grooves 14 and 24. It is preferable that the groove shape is continuous with the groove. 9A shows an example of a recess 26 in the form of an arc groove, FIG. 9B shows an example of a recess 26 in the form of a triangular groove, and FIG. 9C shows an example of a recess 26 in the form of a rectangular groove. Indicates.

  The dents 16 and 26 can be formed by plastic working with forging as a representative example, or by plastic working and subsequent cutting. In order to produce a constant velocity joint with good torque transmission efficiency, the outer ring 10 and the inner ring 20 need to be processed with high precision, and in particular, the ball grooves 14 and 24 need to be finished by cutting (grinding or turning). By forming the ball grooves 14 and 24 by, for example, forging, the cutting allowance can be reduced as compared with the case of cutting all. In addition, if the recesses 16 and 26 are simultaneously forged in the process of forging the ball grooves 14 and 24, they can be processed at low cost. By finishing the forged and formed recesses 16 and 26 by cutting, the position, width, depth, etc. of the recesses 16 and 26 can be adjusted to adjust characteristics other than the improvement in transmission efficiency.

  The ball grooves 14 and 24 may be arranged at equal intervals (equal pitch) in the circumferential direction, or may be unequal pitches. As a means for making the constant velocity joint compact, it is known that the balls 30 are arranged at unequal pitches. As an example, there is an eight ball specification in which the minimum number of balls that receive torque in a low angle region is three, the ball arrangement is 120 degrees equidistant, and the remaining five balls are arranged at unequal pitches. . In order to achieve both high efficiency in the high angle range and improvement in efficiency in the low angle range, a proportion of unequal pitch is possible.

  The track offset amount of the outer ring 10 and the track offset amount of the inner ring 20 may be different. For example, the track offset amount of the inner ring 20 is made smaller than the track offset amount of the outer ring 10. Alternatively, the track offset amount of the inner ring 20 is made larger than the track offset amount of the outer ring 10. A clearance is set in spherical fitting portions between parts such as the outer ring 10, the inner ring 20, and the cage 40 of the constant velocity joint. When the constant velocity joint is operated with torque input, the clearance of the spherical surface portion is clogged, resulting in a deviation from an ideal arrangement that does not consider the clearance. In the low angle region, the offset of the outer ring 10 is small and the offset of the inner ring 20 is large due to clogging of the spherical surface clearance. In the high angle region, the offset of the outer ring 10 is large and the offset of the inner ring 20 is small. Therefore, by changing the offset amount (F: FIG. 10, f: FIG. 11) in advance to bring it closer to the ideal state, it becomes possible to prevent the efficiency from deteriorating in the required angular range.

  As described above, the basic configuration of the fixed type constant velocity joint is based on the conventional configuration shown in FIG. 10 as well as the configuration of the small-diameter ball / small track offset shown in FIG. In the latter case, a synergistic effect of both can be expected.

(A) is a longitudinal sectional view of the outer ring of the fixed type constant velocity joint, and (B) is an end view. It is a perspective view of the outer ring | wheel of FIG. It is the elements on larger scale of the outer ring | wheel of FIG. (A) (B) (C) is an enlarged view of the hollow part in FIG. It is an end view of the inner ring of a fixed type constant velocity joint. It is VI arrow directional view of the inner ring | wheel of FIG. It is a perspective view of the inner ring | wheel of FIG. It is sectional drawing of the outer ring | wheel of FIG. (A) (B) (C) is an enlarged view of the hollow part in FIG. (A) is a longitudinal sectional view of a fixed type constant velocity joint having 6 balls, and (B) is an enlarged view around the balls. (A) is a longitudinal sectional view of a fixed type constant velocity joint having 8 balls, and (B) is an enlarged view around the balls. (A) is a longitudinal cross-sectional view of a state in which the joint of FIG. 10 (A) takes an operating angle, and (B) is a longitudinal cross-sectional view of a state in which the joint of FIG. 11 (A) takes an operating angle. It is a diagram which shows the change of the transmission efficiency by the difference in the number of balls in a low angle area. It is a diagram which shows the change of the transmission efficiency by the difference in the number of balls in a high angle area. It is a diagram which shows the relationship of the load with respect to a phase angle. It is explanatory drawing of a phase angle, Comprising: (A) is a side view, (B) is an end view.

Explanation of symbols

10 Outer ring (outer joint member)
12 Inner peripheral surface 14 Ball groove 16 Recess 20 Inner ring (inner joint member)
22 outer peripheral surface 24 ball groove 26 dent 30 ball (torque transmission element)
40 cage 42 pocket 44 outer peripheral surface 46 inner peripheral surface

Claims (10)

  An outer joint member in which ball grooves extending in the axial direction on the inner spherical surface are formed at predetermined intervals in the circumferential direction, and an inner joint member in which ball grooves extending in the axial direction on the outer spherical surface are formed at predetermined intervals in the circumferential direction are paired. All balls are flush with the ball interposed between the ball groove of the outer joint member and the ball groove of the inner joint member, and between the inner spherical surface of the outer joint member and the outer spherical surface of the inner joint member. And the center of the ball groove of the outer joint member and the center of the ball groove of the inner joint member are offset from each other in the axial direction in the opposite direction from each other. A fixed type constant velocity joint that shares torque transmission and transmits torque with a smaller number of balls in the low angle range than in the high angle range.   The fixed type constant velocity joint according to claim 1, wherein the total number of balls is 5 as a lower limit.   The fixed type constant velocity joint according to claim 1 or 2, wherein the number of balls transmitting torque in a low angle region is 3 as a lower limit.   The fixed constant velocity joint according to claim 1, 2 or 3, wherein an interval between balls transmitting torque in a low angle region is 120 degrees as an upper limit.   The fixed constant velocity joint according to any one of claims 1 to 4, wherein the low angle region is in a range of 0 to 10 degrees, and a depression is formed in a ball groove at an angular position occupied by the ball at that time.   The fixed constant velocity joint according to claim 5, wherein the ball groove is a ball groove of an inner joint member or a ball groove of an outer joint member, or a ball groove of an inner joint member and a ball groove of an outer joint member.   The fixed constant velocity joint according to claim 5 or 6, wherein a cross-sectional shape of the recess is a groove shape that is smoothly connected to a surface of the ball groove.   The fixed type constant velocity joint according to claim 5, 6 or 7, wherein the recess is formed by plastic processing, or formed by plastic processing and subsequent cutting processing.   The fixed constant velocity joint according to any one of claims 1 to 8, wherein the pitches of the ball grooves are unequal.   The fixed constant velocity joint according to any one of claims 1 to 9, wherein a track offset amount of the outer joint member and a track offset amount of the inner joint member are different.

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