JP4041657B2 - Constant velocity universal joint - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
TECHNICAL FIELD The present invention relates to a constant velocity universal joint, and more particularly, is used in a power transmission system of automobiles and various industrial machines, and is a fixed type constant velocity universal that allows only operating angular displacement between two axes of a driving side and a driven side. Related to fittings.
[0002]
[Prior art]
For example, fixed type constant velocity universal joints (Zeper type constant velocity universal joints: BJ) used as coupling joints for automobile drive shafts, etc., have curved track grooves in the axial direction on the spherical inner surface. The outer joint member, the inner joint member in which a curved track groove is formed on the spherical outer diameter surface in the axial direction, the track groove of the outer joint member, and the track groove of the corresponding inner joint member cooperate with each other. A plurality of torque transmission balls disposed on a ball track formed in this manner, and a cage having a pocket for holding the torque transmission balls. The plurality of torque transmission balls are accommodated in pockets formed in the cage and arranged at equal intervals in the circumferential direction.
[0003]
The center of the track groove of the outer joint member is opposite to the spherical center of the inner surface, and the center of the track groove of the inner joint member is opposite to the spherical center of the outer surface by an equal distance in the axial direction. It is offset. Therefore, the ball track formed by the cooperation of the track groove of the outer joint member and the corresponding track groove of the inner joint member has a shape opened in a wedge shape toward one side in the axial direction. The spherical center of the inner surface of the outer joint member and the spherical center of the outer surface of the inner joint member are both within the joint center plane including the center of the torque transmitting ball.
[0004]
In this constant velocity universal joint, when the outer joint member and the inner joint member are angularly displaced, the torque transmitting ball accommodated in the cage pocket is always maintained within the bisector of the operating angle at any operating angle. Thus, the constant velocity of the joint is ensured. Here, the operating angle means an angle formed by the rotating shaft of the outer joint member and the rotating shaft of the inner joint member.
[0005]
In recent years, the wheelbase may be lengthened from the viewpoint of improving the collision safety of automobiles, but in order to prevent the turning radius of the vehicle from increasing accordingly, the steering angle of the front wheels is increased by increasing the angle of the fixed type constant velocity universal joint. There is a need for an increase. To meet this need for higher angles, an undercut-free type fixed constant velocity universal joint (UJ) is used in which the shape of the track groove on the opening side of the outer joint member is parallel to the axial direction. In this type of constant velocity universal joint, both the track grooves of the outer joint member and the inner joint member have no undercut and have a structure capable of taking a large operating angle.
[0006]
[Problems to be solved by the invention]
In this type of fixed constant velocity universal joint (BJ, UJ), it is important how to determine the PCD (pitch circle diameter) clearance in the ball track.
[0007]
That is, if the PCD clearance is too small, it becomes difficult to incorporate the ball when inserting the torque transmission ball into the ball track, and the restraint force on the torque transmission ball is increased, which hinders smooth rolling of the torque transmission ball. Is done. Therefore, when the joint rotates, a rolling motion accompanied by slip occurs at the contact portion between the torque transmitting ball and the ball track, which increases the temperature inside the joint and thereby contributes to a decrease in life.
[0008]
On the other hand, if the PCD clearance is too large, there is an undesirable effect on the joint performance (NVH, durability), for example, a hitting sound is generated between the pocket and the torque transmission ball or the joint vibration is increased. Arise.
[0009]
In particular, when the load is high, the contact ellipse between the torque transmitting ball and the track groove protrudes from the track groove, and there are cases in which chipping occurs to cause flaking. Here, if the PCD clearance is small, it effectively works to prevent the contact ellipse from protruding from the track groove. Conversely, if the PCD clearance is large, the ball contact point moves due to the PCD clearance, and the contact ellipse moves. However, it is easy to protrude from the track groove.
[0010]
On the other hand, with this type of constant velocity universal joint, compared to the one using six torque transmission balls, it is possible to further reduce the size and weight while ensuring the same level of strength, load capacity and durability. To achieve this, there is a constant velocity universal joint with eight torque transmission balls. This constant velocity universal joint is different in basic structure from the constant velocity universal joint having six torque transmission balls, and it is considered that there is a unique value suitable for the structure of the setting value of the PCD clearance. In particular, the constant velocity universal joint with 8 torque transmission balls, compared to the 6 constant velocity universal joint using 6 torque transmission balls, has a small track diameter and a short PCD clearance, and has a durable PCD clearance. Great effect on sex.
[0011]
Accordingly, the present invention has been proposed in view of the above-mentioned problems, and its object is to improve durability at high loads in a fixed type constant velocity universal joint including eight torque transmission balls. In addition, it is possible to stabilize the variation in life.
[0012]
[Means for Solving the Problems]
As technical means for achieving the above object, the present invention provides an outer joint member in which eight curved track grooves extending in the axial direction are formed on a spherical inner surface, and a shaft on a spherical outer surface. The inner joint member formed with eight curved track grooves extending in the direction, the track groove of the outer joint member and the corresponding track groove of the inner joint member formed in cooperation with each other. In a constant velocity universal joint for a drive shaft provided with eight torque transmission balls arranged on a ball track and a cage having a pocket for holding the torque transmission ball, the PCD clearance in the ball track is 5 to 50 μm. The axial clearance between the pocket of the cage and the torque transmission ball is set to −30 to +10 μm . Here, the “PCD clearance” means a difference between the pitch circle diameter of the track groove of the outer joint member and the pitch circle diameter of the track groove of the inner joint member.
[0013]
In the present invention, in the constant velocity universal joint for drive shafts having eight torque transmission balls, the PCD clearance in the ball track is set to a positive clearance of 5 to 50 μm. contact ellipse is less likely to protrude from the track groove of that Do easy to suppress the occurrence of chipping and flaking. Further, since the axial clearance between the cage pocket and the torque transmission ball is set to -30 to +10 μm, the torque transmission ball per one torque transmission ball compared with the constant velocity universal joint having six torque transmission balls. Since the load applied to the pocket is small and the amount of wear on the pocket is small, the restraint force of the torque transmission ball by the pocket can be reduced to ensure smooth rolling of the torque transmission ball. That is, in the case of a constant velocity universal joint having six torque transmission balls (shift in the axial direction is −50 to −10 μm), it is shifted to the plus side, and the axial clearance of the present invention is −30 to +10 μm, preferably By making it within the range of −10 to +10 μm, the temperature rise inside the joint can be reduced by reducing the heat generated by the contact of the torque transmitting ball in the pocket.
[0014]
In the present invention, (1) the center of the track groove of the outer joint member is in the axial direction with respect to the spherical center of the inner surface and the center of the track groove of the inner joint member is in the axial direction. A fixed type constant velocity universal joint (BJ) that is offset to the opposite side by an equal distance; and (2) the track groove of the inner joint member with respect to the spherical center of the inner surface of the outer joint member. The center of the straight is offset to the opposite side by an equal distance in the axial direction with respect to the spherical center of the outer diameter surface, and each track groove of the outer joint member and the inner joint member has a straight groove bottom It is applicable to a fixed type constant velocity universal joint (UJ) provided with a portion.
[0017]
Moreover, in the said structure, it is desirable for the radial clearance between the said holder | retainer and an outer joint member to be 20-100 micrometers, Furthermore, the radial clearance between the said retainer and an inner joint member is 20-100 micrometers. Is desirable. In this way, the operability between the cage and the outer joint member and between the cage and the inner joint member is improved, and between the cage and the outer joint member, the cage and the inner joint. It is possible to prevent a hitting sound from occurring between the members and an increase in joint vibration.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of a constant velocity universal joint according to the present invention will be described in detail below with reference to FIGS. 1 to 3. 2 shows a fixed type constant velocity universal joint (BJ) which is a Zepper type constant velocity universal joint, and FIG. 3 shows an undercut free type fixed type constant velocity universal joint (UJ), which is taken along the line AA in FIG. Since the cross-section and the cross-sectional structure taken along line BB in FIG. 3 are common, FIG.
[0019]
First, the constant velocity universal joint (BJ) of the embodiment shown in FIG. 2 includes an outer joint member 1 in which eight curved track grooves 1b are formed in an axial direction on a spherical inner surface 1a, and a spherical outer surface. An inner joint member 2 in which eight curved track grooves 2b are formed in the axial direction on the radial surface 2a, and a serration fitting portion 2c with the end of the intermediate shaft 5 of the drive shaft is formed on the inner radial surface; Eight torque transmission balls 3 arranged on eight ball tracks formed by cooperation of the track groove 1b of the member 1 and the track groove 2b of the inner joint member 2 corresponding thereto, and the torque transmission ball 3 It is comprised with the holder | retainer 4 which hold | maintains. The eight torque transmission balls 3 are accommodated in pockets 4c formed in the cage 4 and arranged at equal intervals in the circumferential direction.
[0020]
Against the spherical centers of O ₁ of the outer joint member 1 of the track grooves 1b are inner surface 1a, also, the center O ₂ of the inner joint member 2 of the track grooves 2b with respect to the spherical center of the outer surface 2a, respectively In the axial direction, the distance is offset to the opposite side (in the example shown in the figure, the center O ₁ is the opening side of the joint and the center O ₂ is the back side of the joint). For this reason, the ball track formed by the cooperation of the track groove 1b of the outer joint member 1 and the corresponding track groove 2b of the inner joint member 2 has one axial direction (in the example shown in FIG. (Open side).
[0021]
The spherical center of the outer diameter surface 4 a of the cage 4 and the spherical center of the inner diameter surface 1 a of the outer joint member 1 that serves as a guide surface for the outer diameter surface 4 a of the cage 4 are both the center O of the torque transmission ball 3. ₃ in the joint center plane O. Further, the spherical center of the inner diameter surface 4b of the cage 4 and the spherical center of the outer diameter surface 2a of the inner joint member 2 that serves as a guide surface for the inner diameter surface 4b of the cage 4 are both within the joint center plane O. is there. Therefore, the offset F of the center O ₁ of the outer joint member 1 of the track grooves 1b, the center O ₁ and the axial distance between the joint center plane O, offset of the center O ₂ of the inner joint member 2 of the track grooves 2b The quantity F is the axial distance between the center O ₂ and the joint center plane O and they are equal.
[0022]
Next, the constant velocity universal joint (UJ) of the embodiment shown in FIG. 3 is different from the constant velocity universal joint (BJ) of the embodiment shown in FIG. 2 described above in that the track groove 1b and the inner side of the outer joint member 1 are different. Only the straight portions U1 and U2 each having a linear groove bottom are provided in the track groove 2b of the joint member 2, and the description overlapping the description of the above-described embodiment is omitted. The constant velocity universal joint (UJ) of this embodiment is provided with straight portions U1, U2 in the track groove 1b of the outer joint member 1 and the track groove 2b of the inner joint member 2, respectively. The maximum operating angle can be increased as compared with the constant velocity universal joint (BJ).
[0023]
In the constant velocity universal joints of FIGS. 2 and 3, when the outer joint member 1 and the inner joint member 2 are angularly displaced, the torque transmitting ball 3 accommodated in the pocket 4c of the cage 4 is always at any operating angle. The operating angle is maintained within the bisecting plane, and the constant velocity of the joint is ensured.
[0024]
In the Zepper type constant velocity universal joint (BJ) of FIG. 2 and the undercut free type constant velocity universal joint (UJ) having the above-described configuration, as shown in FIG. 1, the PCD clearance in the ball track, that is, The difference between the pitch circle diameter PCD _OUT of the track groove 1b of the outer joint member 1 and the pitch circle diameter PCD _IN of the track groove 2b of the inner joint member 2 is 5 to 50 μm. If the PCD clearance is smaller than 5 μm, the assembling property and the operability of the torque transmitting ball 3 may be deteriorated. Conversely, if the PCD clearance is larger than 50 μm, the contact ellipse between the torque transmitting ball 3 and the track grooves 1b and 2b is likely to be deteriorated. However, it becomes easy to protrude from the track grooves 1b and 2b, and it becomes difficult to improve durability.
[0025]
2 and 3, the axial clearance between the pocket 4c of the retainer 4 and the torque transmission ball 3, that is, the axial dimension D _P of the pocket 4c and the diameter D _{B of the} torque transmission ball 3 are used. Is within the range of −30 to +10 μm, preferably −10 to +10 μm. When the tightening allowance (negative gap) between the pocket 4c of the cage 4 and the torque transmission ball 3 becomes excessively smaller than −30 μm, the force that restrains the torque transmission ball 3 is increased, and the torque transmission ball 3 is smooth. Rolling is inhibited. Therefore, when the joint rotates, a rolling motion accompanied by slip occurs at the contact portion between the torque transmission ball 3 and the track grooves 1b and 2b, which causes a rise in temperature inside the joint and thereby a decrease in life. On the other hand, if the play (normal gap) between the pocket 4c of the cage 4 and the torque transmission ball 3 is larger than +10 μm and excessive, a hitting sound is generated between the pocket 4c and the torque transmission ball 3. Adverse effects on the joint performance, such as increased joint vibration.
[0026]
Further, the radial clearance between the cage 4 and the outer joint member 1, that is, the difference between the inner diameter D _O of the outer joint member 1 and the outer diameter D _K1 of the cage 4 is set to 20 to 100 μm. 4 and radial clearance between the inner joint member 2, i.e., the difference between the inner diameter D _K2 of the cage 4 and the outer diameter D _I of the inner joint member 2, 20 to 100 [mu] m. When these radial clearances are smaller than 20 μm, the operability between the cage 4 and the outer joint member 1 and between the cage 4 and the inner joint member 2 is deteriorated, and conversely, the radial clearance is 100 μm. If it becomes larger than this, a hitting sound is generated between the cage 4 and the outer joint member 1, and between the cage 4 and the inner joint member 2, and joint vibration increases.
[0027]
【Example】
FIG. 4 shows the results of a high load endurance test on the PCD clearance for the constant velocity universal joint of the embodiment shown in FIG. 2, that is, the Zepper type constant velocity universal joint (BJ) having eight torque transmission balls. This test was performed by operating the test joint under the test conditions of load torque T = 726 N · m, rotation speed N = 230 rpm, and operating angle θ = 6 deg, and measuring the operation time when the malfunction occurred. The high load endurance test was conducted on two test joints A and B.
[0028]
From the results shown in FIG. 4, a constant velocity universal joint with a PCD clearance of 30 and 50 μm can ensure stable durability, while a constant velocity universal joint with a PCD clearance of 70 and 100 μm can achieve the specifications. Even if it can be cleared, there is a variation in life, and in the constant velocity universal joint with a PCD clearance of 120 μm, it is the limit to clear the specification, and furthermore, in the constant velocity universal joint with a PCD clearance of 130 μm, It is difficult to clear the specifications.
[0029]
Next, FIG. 5 shows the results of an endurance test on the axial clearance in the cage pocket for the Zepper type constant velocity universal joint (BJ). This test was performed by operating the test joint under the test conditions of load torque T = 186 N · m, rotation speed N = 1700 rpm, operating angle θ = 6 deg, and measuring the operation time when the malfunction occurred. This durability test was conducted on two test joints A and B.
[0030]
From the results shown in FIG. 5, the constant velocity universal joint with the axial clearance of −20 and −30 μm can secure stable durability, whereas the constant velocity universal joint with the axial clearance of −45 μm Durability was reduced and lifespan varied.
[0031]
【The invention's effect】
According to the present invention, since the PCD clearance in the ball track is set to a positive clearance of 5 to 50 μm , the ball diameter is small as in the constant velocity universal joint including eight torque transmission balls, so that the track depth is small. even during high load, the contact ellipse between the torque transmitting ball and the track groove hardly protrudes from the track groove, it becomes easy to suppress the occurrence of chipping or flaking, and the pockets and the torque transmitting balls of the cage Since the axial clearance between -30 and +10 μm is smaller than the constant velocity universal joint with six torque transmission balls, the load applied to the pocket per torque transmission ball is small. Because the amount is small, the torque transmission ball's restraining force by the pocket is reduced to ensure smooth rolling of the torque transmission ball. Can, because it can reduce the temperature rise inside the joint in the reduction of heat generation due to contact of the torque transmitting balls in the pockets, the stabilization of improved and unevenness in life durability of the constant velocity universal joint can be reduced.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view taken along the line AA in FIG. 2 or the line BB in FIG. 3 in the embodiment of the constant velocity universal joint according to the present invention.
FIG. 2 is a longitudinal sectional view showing an example applied to a Zepper type constant velocity universal joint (BJ) in the embodiment of the present invention.
FIG. 3 is a longitudinal sectional view showing an example applied to an undercut free type constant velocity universal joint (UJ) in another embodiment of the present invention.
FIG. 4 is a diagram showing the results of a high load endurance test for a PCD clearance.
FIG. 5 is a diagram showing a result of an endurance test on an axial clearance in a pocket of a cage.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Outer joint member 1a Outer joint member inner diameter surface 1b Outer joint member track groove 2 Inner joint member 2a Inner joint member outer diameter surface 2b Inner joint member track groove 3 Torque transmission ball 4 Cage 4c Pocket PCD _OUT -PCD PCD clearance D _P -D _B- axis clearance in _IN ball track

Claims (4)

An outer joint member in which eight curved track grooves extending in the axial direction are formed on the spherical inner diameter surface, and an inner joint in which eight curved track grooves extending in the axial direction are formed on the spherical outer diameter surface Member, eight torque transmission balls arranged on eight 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 torque thereof A cage having a pocket for holding a transmission ball, and the center of the track groove of the outer joint member is centered on the spherical surface of the inner diameter surface, and the center of the track groove of the inner joint member is centered on the spherical surface of the outer diameter surface. On the other hand, each is a constant velocity universal joint for a drive shaft offset to the opposite side by an equal distance in the axial direction,
A constant velocity universal joint characterized in that a PCD clearance in the ball track is a positive clearance of 5 to 50 μm and an axial clearance between a pocket of the cage and a torque transmitting ball is −30 to +10 μm . An outer joint member in which eight curved track grooves extending in the axial direction are formed on the spherical inner diameter surface, and an inner joint in which eight curved track grooves extending in the axial direction are formed on the spherical outer diameter surface Member, eight torque transmission balls arranged on eight 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 torque thereof A cage having a pocket for holding a transmission ball, and the center of the track groove of the outer joint member is centered on the spherical surface of the inner diameter surface, and the center of the track groove of the inner joint member is centered on the spherical surface of the outer diameter surface. in contrast, respectively, it is offset by the opposite side an equal distance in the axial direction, and, for the outer joint member and the drive shaft straight portion is provided with a straight groove bottom on each track grooves of the inner joint member A constant velocity joint,
A constant velocity universal joint characterized in that a PCD clearance in the ball track is a positive clearance of 5 to 50 μm and an axial clearance between a pocket of the cage and a torque transmitting ball is −30 to +10 μm . The constant velocity universal joint according to claim 1 or 2, characterized in that the radial clearance between the cage and the outer joint member and 20 to 100 [mu] m. The constant velocity universal joint according to any one of claims 1 to 3 , wherein a radial clearance between the cage and the inner joint member is 20 to 100 µm.

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