JP2002005186A - Constant velocity universal joint - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance the durability of a constant velocity universal joint. SOLUTION: A retainer 4 is furnished with eight window-shaped pockets 4c accommodating torque transmitting balls and holding and column parts 4d between the pockets 4c ajoining in the circumferential direction. The difference between the axial direction dimension L of each pocket 4c in the initial period of the joint operation and the diameter of the balls, i.e., the axial direction initial gap between the two, is managed in the range -30 thru +10 μm, favorably between -10 and +10 μm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a constant velocity universal joint capable of transmitting a rotational torque at a constant speed even when a drive shaft and a driven shaft are at an angle. Constant velocity universal joints
Fixed type constant velocity universal joints that allow only angular displacement between two axes, and sliding type constant velocity universal joints that allow angular displacement and axial displacement between two axes, and the present invention is the former of the former For fixed type constant velocity universal joints.

[0002]

2. Description of the Related Art FIG. 6 shows a fixed type constant velocity universal joint (zepper type constant velocity universal joint: ball fixed joint) conventionally used as a coupling for connecting a drive shaft of an automobile. The constant velocity universal joint includes an outer joint member 11 having six curved guide grooves 11b formed in a spherical inner surface 11a in an axial direction, and a spherical outer surface 12a.
a, an inner joint member 12 in which six curved guide grooves 12b are formed in the axial direction and a fitting portion 12c having a tooth shape (serration or spline) on an inner diameter surface, and a guide groove of the outer joint member 11 11b and the corresponding inner joint member 1
A cage 14 having six torque transmission balls 13 arranged on six ball tracks formed in cooperation with two guide grooves 12b, and a window-shaped pocket 14c for holding the torque transmission balls 13. It is composed of

The center A of the guide groove 11b of the outer joint member 11
Is the inner joint member 12 with respect to the center of the spherical surface of the inner surface 11a.
The center B of the guide groove 12b is opposite to the center of the spherical surface of the outer diameter surface 12a by an equal distance in the axial direction, respectively (in the example shown in the figure, the center A is the opening side of the joint, and the center B is the depth of the joint. Part side). Therefore, the guide groove 11b
And the corresponding guide groove 12b cooperate with each other, the ball track is formed in a wedge-like shape toward one of the axial directions (in the example shown in the figure, the opening side of the joint). The spherical center of the inner diameter surface 11a of the outer joint member 11 and the spherical center of the outer diameter surface 12a of the inner joint member 12 are both in the joint center plane O including the center of the torque transmitting ball 13.

When the outer joint member 11 and the inner joint member 12 are angularly displaced by an angle θ, the torque transmitting ball 13 guided by the retainer 14 always has a bisector (θ) of the angle θ at any operating angle θ. / 2), and the constant velocity of the joint is ensured.

[0005]

In such a fixed type constant velocity universal joint, it is important how the axial gap between the pocket of the retainer and the torque transmitting ball is determined. That is, if the interference (negative gap) between the pocket of the retainer and the torque transmitting ball is excessive, the force for restraining the torque transmitting ball becomes large, and smooth rolling of the torque transmitting ball is hindered. 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 causes a rise in the temperature inside the joint and a shortening of the life. Conversely, if the play (positive gap) between the cage pocket and the torque transmitting ball is excessive, a tapping sound is generated between the pocket and the torque transmitting ball, and joint vibration increases. This has an undesirable effect on joint performance. In addition, since the axial wall surface of the pocket is worn by contact with the torque transmitting ball, the initial clearance may become excessive due to use even if it is not so at the initial stage. Furthermore, dimensional variations within manufacturing tolerances are inevitable for the dimensions of each component. In consideration of these points, in the above-described conventional constant velocity universal joint (fixed constant velocity universal joint having six balls), the initial axial gap between the pocket of the retainer and the torque transmitting ball is -50 to less. It is set within the range of −10 μm.

[0006] On the other hand, the present applicant has further improved strength, load capacity and durability equal to or higher than those of the conventional constant velocity universal joint (fixed constant velocity universal joint having six balls) shown in FIG. In order to reduce the size and weight of the vehicle, a fixed type constant velocity universal joint having eight ball tracks and eight torque transmitting balls has already been proposed (Japanese Patent Application No. 8-259484).
No.). The constant velocity universal joint according to this proposed proposal is the conventional constant velocity universal joint described above (fixed constant velocity universal joint with six balls).
Is different from the basic structure, and it is considered that the set value of the initial gap in the axial direction has a unique value suitable for the structure.

An object of the present invention is to optimally set an initial axial clearance between a pocket of a cage and a torque transmitting ball in a constant velocity universal joint according to the above-mentioned proposal, while considering the performance of the joint. Accordingly, it is intended to further improve the durability.

[0008]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention provides an outer joint member having eight curved guide grooves extending in the axial direction on a spherical inner surface, and a spherical outer member. An inner joint member formed with eight curved guide grooves extending in the axial direction on a radial surface, a guide groove of the outer joint member and a corresponding guide groove of the inner joint member are formed in cooperation with each other. Eight torque transmitting balls arranged in a ball track,
A cage having a pocket for holding the torque transmitting ball, wherein the center of the guide groove of the outer joint member is relative to the center of the spherical surface of the inner diameter surface, and the center of the guide groove of the inner joint member is relative to the center of the spherical surface of the outer diameter surface. And a constant velocity universal joint offset to the opposite side by an equal distance (F) in the axial direction, wherein the initial axial gap between the pocket of the retainer and the torque transmitting ball is −30 to +10 μm. Provide configuration.

The constant velocity universal joint according to the present invention has eight torque transmitting balls, and the torque transmitting ball occupies the entire load capacity of the joint as compared with the conventional joint (fixed constant velocity universal joint having six balls). The load ratio per unit is small. Therefore, the contact stress between the pocket wall surface of the retainer and the torque transmitting ball when the joint transmits the rotational torque while maintaining the operating angle is reduced as compared with the conventional joint (fixed constant velocity universal joint with six balls). The amount of wear on the pocket walls of the cage is reduced. Then, the value of the initial gap in the axial direction can be shifted to the plus side from the conventional joint (fixed constant velocity universal joint with six balls) by the reduced amount of wear on the pocket wall surface of the cage. However, the use does not cause an adverse effect of an excessively large gap, and the performance of the joint is maintained. On the other hand, by shifting the value of the initial gap in the axial direction to the plus side, the restraining force of the torque transmission ball by the pocket of the retainer can be reduced, and smooth rolling of the torque transmission ball can be ensured. As a result, heat generation at the contact portion between the torque transmitting ball and the ball track is reduced, and the temperature rise inside the joint is reduced, so that the durability of the joint is improved. Many tests have shown that the initial axial clearance between the cage pocket and the torque transmitting ball is -30 to +10 [mu] m, preferably -10.
By setting it within the range of +10 μm, the axial gap between the cage pocket and the torque transmitting ball is prevented from becoming too large or too small, and the durability of the joint is improved while ensuring the performance of the joint. It was confirmed that it was possible.

Further, the present invention provides an outer joint member having eight curved guide grooves extending in the axial direction on a spherical inner diameter surface, and eight curved lines extending in the axial direction on a spherical outer diameter surface. Eight ball tracks arranged on eight ball tracks formed in cooperation with the guide groove of the inner joint member, the guide groove of the outer joint member, and the guide groove of the corresponding inner joint member having the guide groove formed in the shape of a circle. A torque transmission ball, and a retainer having a pocket for holding the torque transmission ball, wherein the center of the guide groove of the outer joint member is the center of the spherical surface of the inner diameter surface, and the center of the guide groove of the inner joint member is the outer diameter surface. Are provided in the guide grooves of the outer joint member and the inner joint member, each of which has a straight portion that is offset to the opposite side by the same distance (F) in the axial direction with respect to the center of the spherical surface. The constant velocity universal joint has a pocket Axial initial clearance between the torque transmitting balls -30 to + 10 [mu] m, preferably -10
Provides a configuration that is +10 μm.

The constant velocity universal joint of the present invention is provided with a straight portion having a linear groove bottom in each of the guide grooves of the outer joint member and the inner joint member. Therefore, there is a feature that a large operating angle can be obtained. Other matters are the same as those of the above-described constant velocity universal joint.

In the above construction, a hardened layer is provided on the retainer, and the surface hardness of the hardened layer is adjusted to HRC58-58.
63, the hardness of the core part can be HRC35-45. Here, HRC represents the C scale of Rockwell hardness. The surface hardened layer is, for example, a carburized layer formed by carburizing. Preferably, at least in the cross section of the pillar portion located between the pockets, the area ratio of the core portion to the entire area is 40 to 55%. According to this configuration, the cage has a surface layer with excellent wear resistance and a core with excellent toughness. Therefore, the cage has a high contact fatigue life and a high cracking strength.

In the above construction, the offset (F) between the center of the guide groove of the outer joint member and the center of the guide groove of the inner joint member is preferably 2 to 4 mm. When an offset is provided in the guide groove, the groove depth of the guide groove is not uniform in the axial direction. Therefore, when the offset amount (F) is excessively large, when the torque transmitting ball transmits a high load at a small groove depth (when a large operating angle is taken), the contact ellipse of the contact portion with the torque transmitting ball is reduced. A situation in which the protrusion protrudes from the guide groove is expected. Offset amount (F) is 2
By setting it to 4 mm, it is possible to prevent the protrusion of the contact ellipse, thereby preventing the shoulder of the guide groove from being chipped, and to increase the strength and durability of the outer joint member and the inner joint member. Further, since the thickness of the cage can be increased, the strength and durability of the cage can be improved.

[0014]

Embodiments of the present invention will be described below with reference to the drawings.

FIGS. 1 and 2 show a fixed type constant velocity universal joint according to a first embodiment of the present invention. The constant velocity universal joint of this embodiment has an outer joint member 1 in which eight curved guide grooves 1b are formed in a spherical inner surface 1a in an axial direction, and eight curved surfaces in a spherical outer surface 2a. An inner joint member 2 in which an annular guide groove 2b is formed in the axial direction, and a fitting portion 2c having a tooth profile (serration or spline) is formed on the inner diameter surface;
Eight torque transmitting balls 3 arranged on eight ball tracks formed in cooperation with the guide groove 1b of the outer joint member 1 and the corresponding guide groove 2b of the inner joint member 2; And a holder 4 for holding the ball 3.
The shaft end of, for example, a drive shaft of an automobile is engaged with the fitting portion 2c of the inner joint member 2 by tooth-shaped fitting (serration fitting or spline fitting).

The center O1 of the guide groove 1b of the outer joint member 1 is relative to the center of the spherical surface of the inner surface 1a, and the center O2 of the guide groove 2b of the inner joint member 2 is relative to the center of the spherical surface of the outer surface 2a. In the example shown in the drawing, the center O1 is offset to the opposite side by an equal distance F in the axial direction (the center O1 is the opening side of the joint, and the center O2 is the back side of the joint). For this reason, the ball track formed by the guide groove 1b and the corresponding guide groove 2b cooperating with each other has a wedge-like shape that opens toward one of the axial directions (in the example shown in the drawing, the joint opening side). become.

The center of the spherical surface of the outer diameter surface 4a of the retainer 4 and the center of the spherical surface of the inner diameter surface 1a of the outer joint member 1 serving as a guide surface of the outer diameter surface 4a of the cage 4 Are located in the joint center plane O including the center O3. Also,
The center of the spherical surface of the inner diameter surface 4b of the retainer 4, and the outer diameter surface 2a of the inner joint member 2 serving as a guide surface of the inner diameter surface 4b of the retainer
Are in the joint center plane O. Therefore, the offset amount F of the center O1 of the guide groove 1b is
The axial distance between 1 and the joint center plane O and the offset amount F of the center O2 of the guide groove 2b are the axial distance between the center O2 and the joint center plane O, and both are equal. In this embodiment, the offset amount F between the center O1 and the center O2 is 2 to 4 mm, respectively.

The pitch circle diameter of the torque transmitting ball (PCD
_BALL) And diameter (D_BALL) And r1 (= PCD)_BALL/ D
_BALL) Is 3.3 ≦ r1 ≦ 5.0, preferably 3.5 ≦ r
It is set to a value within the range of 1 ≦ 5.0. Where
Pitch circle diameter of luk transmission ball (PCD_BALL) Is the PCR
Twice as large as (PCD_BALL= 2 x PCR). Outside
Center O1 of guide groove 1b of joint member 1 and torque transmitting ball
Length of line connecting center O3 of 3 and guide of inner joint member 2
The center O2 of the groove 2b and the center O3 of the torque transmitting ball 3 are connected.
The length of the line segment is PCR, and both are equal.
No. Further, the outer diameter (D_OUTER) And inner joint
Tooth profile (serration or spur) of the fitting portion 2c of the hand member 2
In) Pitch circle diameter (PCD)_SERR) And r2 (= D
_OUTER / PCD _SERR) Is in the range of 2.5 ≦ r2 <3.5.
Is set to the value in Therefore, the constant velocity of this embodiment
The universal joint is a conventional joint (fixed type constant velocity universal joint with 6 balls).
It has strength and durability equal to or better than that of hand, and outer diameter
The dimensions are compact.

The outer joint member 1 and the inner joint member 2 are preformed into a substantially predetermined shape from a steel material by hot forging or sub-hot forging, respectively, and finished to a final shape by cold forging or grinding. It has been experimentally confirmed that the constant velocity universal joint according to this embodiment has a small torque loss and low heat generation. (Fixed constant velocity universal joint with six balls). Focusing on this point, the guide groove 1b and the inner diameter surface 1a of the outer joint member 1 are formed as cold forged surfaces (no grinding), and the guide groove 2b and the outer diameter surface 2a of the inner joint member 2 are formed. Can be a cold forged surface (without grinding). As a result, it is possible to simplify the manufacturing process and thereby reduce the manufacturing cost.

In the above construction, when the outer joint member 1 and the inner joint member 2 are angularly displaced by the angle θ, the torque transmission ball 3 guided by the retainer 4 always has the angle θ of 2 at any operating angle θ. Maintained within the dividing plane (θ / 2), the constant velocity of the joint is ensured. FIG. 3 shows the retainer 4. The retainer 4 accommodates and holds the torque transmission ball 3.
It has a plurality of window-shaped pockets 4c and pillars 4d between the pockets 4c adjacent in the circumferential direction. The difference between the axial dimension L of the pocket 4c and the diameter D _BALL of the torque transmitting ball 3 (= L-D _BALL ) at the initial operation of the joint, that is, the initial axial gap between the two is -30 to +10 μm, preferably It is controlled within the range of −10 to +10 μm.

The retainer 4 is made of, for example, carburizing steel.
The surface layer is provided with a carburized layer formed by carburizing, quenching and tempering. As the carburizing steel, chromium steel, chromium molybdenum steel, nickel chromium molybdenum steel, or the like can be used. In this embodiment, the chromium molybdenum steel SCM4
15B is used. Surface hardness of carburized layer is HRC58 ~
63, hardness of core (excluding carburized layer) is HRC35 ~
45. Also, a predetermined cross section of the retainer 4, particularly the column portion 4d
In the cross section, the area ratio of the core to the total area is 4
0 to 55%.

FIG. 5 shows a constant velocity universal joint according to a second embodiment of the present invention. The constant velocity universal joint of this embodiment is different from the constant velocity universal joint of the first embodiment described above in that the guide groove 1b of the outer joint member 1 and the inner joint member 2
Is provided at the point where straight portions U1 and U2 each having a linear groove bottom are provided in the guide groove 2b. The constant velocity universal joint of this embodiment has the straight portions U1 and U2 in the guide groove 1b of the outer joint member 1 and the guide groove 2b of the inner joint member 2, respectively. The maximum operating angle can be increased as compared with the universal joint.

[0023]

The wear depth of the cage pocket was determined using the constant velocity universal joint of the first embodiment. The exam is
Load torque T = 412 N · m, rotation speed N = 1300 rp
The test joint was operated at m and an operating angle θ of 6 deg., and after 200 hours, 450 hours, and 650 hours of operation, the wear depth of the axial wall surface of the pocket 4c was measured. FIG. 4 shows the results. The test was performed on two test joints (No. 1: ○, No. 2: Δ), and the wear depth was an average value of a plurality of measurements.

From the results shown in FIG. 4, the wear depth sharply increased up to 200 hours, and initial wear was observed. However, after 200 hours, there was no significant change in the wear depth.
It was confirmed that the wear progressed to a calm state.
In addition, the wear depth after the operation for 650 hours was the same as the test bearing No. 1
No., test bearing No. 2 was 11.9 μm, and it was confirmed that the wear depth was reduced by about 20 μm as compared with the conventional joint (fixed constant velocity universal joint having six balls). Therefore, the value of the initial gap in the axial direction between the pocket of the retainer and the torque transmitting ball is shifted to the plus side by 20 μm as compared with the conventional joint (fixed constant velocity universal joint having six balls) to be -30 to +10 μm. When used, the gap does not become too large and the performance of the joint can be ensured. Further, by shifting the value of the initial gap in the axial direction to the plus side, the restraining force of the torque transmitting ball by the pocket of the retainer can be reduced, and smooth rolling of the torque transmitting ball can be ensured.

[0025]

The present invention has the following effects.

(1) In a constant velocity universal joint having eight ball tracks and eight torque transmitting balls, the initial axial gap between the cage pocket and the torque transmitting balls is in the range of -30 to +10 μm. Since it is inside, it is possible to prevent the axial gap between the two from becoming excessively large or too small, and to improve the durability while securing the performance of the joint.

(2) A surface hardened layer is provided on the cage, the surface hardness of the hardened layer is HRC 58 to 63, the hardness of the core is HRC 35 to 45, and the area ratio of the core is 40 to 55. %, The surface layer of the cage has excellent wear resistance and the core has excellent toughness. Therefore, the cage has a high contact fatigue life and a high cracking strength.

(3) The offset amount (F) between the center of the guide groove of the outer joint member and the center of the guide groove of the inner joint member is 2 to 4
mm, the contact ellipse protrudes at the contact portion between the guide groove and the torque transmission ball, thereby preventing the shoulder of the guide groove from being chipped, thereby increasing the strength and durability of the outer joint member and the inner joint member. be able to. Further, since the thickness of the cage can be increased, the strength and durability of the cage can be improved.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a constant velocity universal joint according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view of the constant velocity universal joint according to the first embodiment of the present invention.

FIG. 3 is a front view {FIG. 3 (a)} and a longitudinal sectional view {FIG. 3 (b)} of the cage.

FIG. 4 is a view showing a test result of a wear depth of a cage pocket.

FIG. 5 is a longitudinal sectional view of a constant velocity universal joint according to a second embodiment of the present invention.

FIG. 6 is a longitudinal sectional view showing a conventional constant velocity universal joint.
(A)} and {FIG. 6 (b)}.

[Explanation of symbols]

 Reference Signs List 1 outer joint member 1a inner diameter surface 1b guide groove 2 inner joint member 2a outer diameter surface 2b guide groove 3 torque transmitting ball 4 cage

Claims (6)

[Claims] An outer joint member formed with eight curved guide grooves extending in the axial direction on a spherical inner diameter surface, and eight curved guide grooves extending in an axial direction on a spherical outer diameter surface. And eight torque transmitting balls disposed on eight ball tracks formed by cooperation of the guide groove of the outer joint member and the corresponding guide groove of the inner joint member. ,
A cage having a pocket for holding the torque transmitting ball, wherein the center of the guide groove of the outer joint member is relative to the center of the spherical surface of the inner diameter surface, and the center of the guide groove of the inner joint member is relative to the center of the spherical surface of the outer diameter surface. And a constant velocity universal joint offset to the opposite side by an equal distance (F) in the axial direction, wherein an initial axial gap between the pocket of the retainer and the torque transmitting ball is -30 to +10 μm. A constant velocity universal joint. 2. An outer joint member formed with eight curved guide grooves extending in the axial direction on a spherical inner diameter surface, and eight curved guide grooves extending in the axial direction on a spherical outer diameter surface. And eight torque transmitting balls disposed on eight ball tracks formed by cooperation of the guide groove of the outer joint member and the corresponding guide groove of the inner joint member. ,
A cage having a pocket for holding the torque transmitting ball, wherein the center of the guide groove of the outer joint member is relative to the center of the spherical surface of the inner diameter surface, and the center of the guide groove of the inner joint member is relative to the center of the spherical surface of the outer diameter surface. And a constant velocity universal joint which is offset by the same distance (F) in the axial direction on the opposite side, and provided with a straight portion having a linear groove bottom in each guide groove of the outer joint member and the inner joint member. The constant velocity universal joint, wherein an initial axial gap between the pocket of the retainer and the torque transmitting ball is −30 to +10 μm. 3. The cage has a hardened surface layer and a core,
The surface hardness of the surface hardened layer is HRC 58 to 63,
3. The constant velocity universal joint according to claim 1, wherein the core has a hardness of 35 to 45 HRC. 4. 4. The constant velocity universal joint according to claim 3, wherein the surface hardened layer is a carburized layer. 5. The cross-section of a column located at least between pockets of the retainer, wherein the area ratio of the core to the entire area is 40 to 55%. Constant velocity universal joint. 6. The constant velocity universal joint according to claim 1, wherein the offset amount (F) is 2 to 4 mm.