JPH1096430A - Tripod type constant velocity universal joint - Google Patents

Abstract

PROBLEM TO BE SOLVED: To ensure the sufficient strength of the root part of a leg shaft. SOLUTION: A tripod type constant velocity universal joint is provided with a trunnion member 22 formed such that a serration hoe 9 is formed through, three flat surfaces 11 are formed at equal intervals in a peripheral direction on the outer periphery of a boss part 10, leg shafts 1 are radially protruded from the respective flat surfaces 11, and a plurality of needle rollers are arranged in a rolling manner on the outside diameter surfaces 12 of each leg shaft 1. In the trunnion member 22, the root part 23 of the leg shaft 1 forming a boundary between the outside diameter surface 12 of the leg shaft 1 and the flat surface 11 of the boss part 10 crossing the outside diameter surface 12 forms a continuous rounding surface with a given curvature r1 with radius through simultaneous grinding of the outside diameter surface of the leg shaft and the flat surface of the boss part after heat treatment.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tripod type constant velocity universal joint, and more particularly to a tripod type constant velocity universal joint used for power transmission in automobiles and various industrial machines.

[0002]

2. Description of the Related Art For example, a tripod type constant velocity universal joint [TJ] used for a drive shaft or a propeller shaft of an automobile has three leg shafts 1 as shown in FIGS. 3 (a) and 3 (b). A trunnion member 2 integrally protruding in the radial direction at circumferential intervals of ° and three leg shafts 1 of the trunnion member 2 are fitted into a track groove 5 via a needle roller 3 and a spherical roller 4. And the two shafts 7 and 8 provided on the trunnion member 2 and the outer ring 6 respectively transmit rotational torque at a constant speed even when the two shafts 7 and 8 have an operating angle. Is also allowed.

The trunnion member 2 (see FIG. 4A)
Boss 1 having a serration hole 9 formed at its center
Three flat surfaces 1 at circumferential intervals of 120 ° on the outer circumference of 0
1 are formed, and the leg shaft 1 is integrally provided on each flat surface 11 in the radial direction. The outer diameter surface 12 of the leg shaft 1 is a cylindrical surface, and a plurality of needle rollers 3 are arranged on the outer diameter surface 12 so as to roll freely, and the spherical roller 4 is rotatably fitted via the needle roller 3. You.

The needle roller 3 comprises a pair of washers 13 and 14 mounted on the distal end and the proximal end of the leg shaft 1 and the leg shaft 1.
The displacement of the leg shaft 1 in the axial direction is restricted by the retaining ring 15 fitted to the end of the leg shaft 1, and the spherical roller 4 can rotate smoothly by rolling on the outer diameter surface of the leg shaft 1. To The spherical roller 4 has a cylindrical inner surface 17 in line contact with the needle roller 3 and a convex spherical outer surface 18 fitted into the track groove 5 of the outer ring 6, and extends in the axial direction of the leg shaft 1. Is permitted.

[0005] One shaft 7 is fitted into the serration hole 9 of the boss portion 10, and is held between the step portion 19 and the clip 20 on both sides in the axial direction.

The outer race 6 has a substantially cylindrical cup shape with one end opened and the other end closed, and the other shaft 8 is integrally provided at the other end, and is recessed on the inner peripheral surface at circumferential intervals of 120 °. Three spherical track grooves 5 are formed along the axial direction.

[0007] Torque transmission between the outer ring 6 and the trunnion member 2 is performed by contacting the track groove 5 with the outer diameter surface 18 of the spherical roller 4, the inner diameter surface 17 of the spherical roller 4 and the needle roller 3
And the outer diameter surface 1 of the needle roller 3 and the leg shaft 1
2 through a contact portion.

[0008]

By the way, in response to a demand from users for cost reduction of the drive shaft and the like, it is necessary to realize the miniaturization and high strength of the drive shaft and the like. Therefore, the tripod-type constant velocity universal joint used for the drive shaft and the like also conventionally has a structure in which the number of teeth of the serration holes 9 of the trunnion member 2 is increased to reduce the stress per tooth of the serration holes 9 or to reduce the trunnion. Attempts have been made to improve the strength of the boss 10 by devising a heat treatment such as carburizing, quenching and tempering of the member 2.

However, since the strength of the boss 10 of the trunnion member 2 is improved, the strength of the root 21 of the leg shaft 1 becomes the weakest part.

That is, since the outer diameter surface 12 of the leg shaft 1 becomes the rolling surface of the needle roller 3 at the base 21 of the leg shaft 1, after heat treatment such as carburizing, quenching and tempering, it is shown in FIG. As shown in the figure, the outer diameter surface 12 of the leg shaft 1 is
The grinding is performed to the position indicated by. As a result, a small radius of curvature r ₂ [e.g., 0.9 to 1.0] between the ground lower end portion of the outer diameter surface 12 of the leg shaft 1 and the flat surface 11 of the boss portion 10.
R surface of about 2 mm) remains. Therefore, the R surface of the root portion 21 of the leg shaft 1 and the flat surface 11 on which the washer 13 is mounted are in an unground state while being turned.

Thus, the outer diameter surface 12 of the leg shaft 1 and the boss 1
The R surface located between the flat surface 11 and the zero flat surface 11 tends to cause stress concentration due to its small radius of curvature r ₂ , and the R surface is unturned together with the flat surface 11 on which the washer 13 is mounted while being turned. Therefore, the surface roughness is as coarse as about 25 μm, and a surface abnormal layer (grain boundary oxide layer) is formed by heat treatment. Due to these synergistic effects, when a large force is applied to the leg shaft 1, a phenomenon has occurred in which a crack m is generated on the R surface of the root portion 21 of the leg shaft 1 (see FIG. 4B).

Therefore, even if the number of teeth of the serration holes 9 of the trunnion member 2 is increased, it is difficult to improve the strength of the entire trunnion member unless the strength of the root 21 of the leg shaft 1 is also improved. .

In view of the above, the present invention has been proposed in view of the above problems, and an object of the present invention is to provide a tripod-type constant velocity freely adjustable trunnion member capable of securing sufficient strength at the base of a leg shaft. It is to provide a joint.

[0014]

As a technical means for achieving the above object, the present invention provides three flat surfaces formed at equal intervals in the circumferential direction on the outer periphery of a boss portion having a serration hole formed therethrough. A tripod-type constant velocity universal joint comprising a trunnion member in which a leg shaft protrudes in a radial direction on each flat surface and a plurality of needle rollers are rotatably arranged on an outer diameter surface of each leg shaft, The trunnion member defines the root of the leg shaft forming the boundary between the outer diameter surface of the leg shaft and the flat surface of the boss perpendicular to the outer diameter surface, with one continuous R surface having a predetermined radius of curvature. It is characterized by having done.

The rounded surface of the root of the leg shaft of the trunnion member can be formed by simultaneous grinding of the outer diameter surface of the leg shaft and the flat surface of the boss after heat treatment.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a tripod type constant velocity universal joint according to the present invention will be described below. 3 and 4
The same reference numerals are given to the same parts.

A tripod type constant velocity universal joint [FIG. 3 (a)]
(Refer to (b))] is a trunnion member 22 in which three leg shafts 1 are integrally protruded in the radial direction at circumferential intervals of 120 °.
And an outer ring 6 which integrally rotates with the three leg shafts 1 of the trunnion member 22 fitted into the track grooves 5 via the needle roller 3 and the spherical roller 4. The feature of the present invention is the trunnion. Member 22.

A trunnion member 22 (see FIG. 1A)
Is a boss 1 having a serration hole 9 formed at the center.
Three flat surfaces 1 at circumferential intervals of 120 ° on the outer circumference of 0
1 are formed, and the leg shaft 1 is integrally provided on each flat surface 11 in the radial direction. The outer diameter surface 12 of the leg shaft 1 is a cylindrical surface, and a plurality of needle rollers 3 are arranged on the outer diameter surface 12 so as to roll freely, and the spherical roller 4 is rotatably fitted via the needle roller 3. You.

The needle roller 3 includes a pair of washers 13 and 14 attached to the distal end and the proximal end of the leg shaft 1 and the leg shaft 1.
The displacement of the leg shaft 1 in the axial direction is restricted by the retaining ring 15 fitted to the end of the leg shaft 1, and the spherical roller 4 can rotate smoothly by rolling on the outer diameter surface of the leg shaft 1. To The spherical roller 4 has a cylindrical inner surface 17 in line contact with the needle roller 3 and a convex spherical outer surface 18 fitted into the track groove 5 of the outer ring 6, and extends in the axial direction of the leg shaft 1. Is permitted.

The feature of the present invention resides in the root portion 23 of the leg shaft 1 of the trunnion member 22 described above. The outer diameter surface 12 of the leg shaft 1 needs to be ground in order to be a rolling surface that comes into contact with the needle roller 3, but in the present invention, not only the outer diameter surface 12 of the leg shaft 1 but also the boss 10 The flat surface 11 is also ground. That is, after heat treatment such as carburizing, quenching and tempering, FIG.
As shown in (b), the outer diameter surface 12 of the leg shaft 1 and the flat surface 11 of the boss 10 are simultaneously ground with a grindstone or the like.

As a result, the outer diameter surface 12 of the leg shaft 1 and the boss 1
0, that is, one continuous R having a larger radius of curvature r ₁ at the root 23 of the leg shaft 1 than before.
Form a surface. The radius of curvature r ₁ of the R surface is, for example,
About 0.4 to 1.4 mm is desirable. It should be noted that an R surface having a radius of curvature smaller than 0.4 mm is unsuitable because cracks are likely to occur as in the prior art, and a flat surface 11 of the boss 10 and a needle are not suitable for an R surface having a radius of curvature larger than 1.4 mm. It is difficult to arrange the washer 13 disposed between the roller 3 and the roller 3 at an appropriate position, which is inappropriate.

As described above, the outer diameter surface 12 of the leg shaft 1 and the boss 1
In the R-plane located between the flat surface 11 and the zero, the radius of curvature r ₁ is larger than that in the conventional art, so that stress concentration is reduced. Also, the outer diameter surface 12 of the leg shaft 1 and the flat surface 1 of the boss 10
Surface roughness on the R-plane of the root 23 of the leg shaft 1 is as fine as about 2 μm by simultaneous grinding with the shaft 1, and the abnormal surface layer (grain boundary oxide layer) formed by the heat treatment is removed by grinding. I do. Due to these synergistic actions, the root portion 23 of the leg shaft 1 is formed.
The fatigue strength of the R-plane is significantly improved.

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present applicant has proposed a tripod type constant velocity universal joint [T
J71], the pulsating torsional fatigue strength was tested for the conventional product and the product of the present invention under the test conditions of the mounting angle θ = 0 ° and the load torque T = 0 to 71 kgfm. The test results are shown in the Weibull diagram of FIG. 2, where the horizontal axis in the Weibull diagram is the number of repetitions up to breakage (times) and the vertical axis is the cumulative breakage probability (%).

As is apparent from FIG.
In the case of the conventional product (straight line in the figure) in which only the base 2 is ground and the root 21 of the leg shaft 1 is a small R surface (the straight line in FIG.
%, The number of repetitions up to breakage at 50% is 2.264 × 10
^{The number of} times becomes 3.581 × 10 ⁵ times, and it is difficult to obtain a stable and desired strength with variation.

On the other hand, the outer diameter surface 12 of the leg shaft 1 and the flat surface 11 of the boss 10 are simultaneously ground to grind the base portion 2 of the leg shaft 1.
In the case of the product of the present invention (straight line a in the figure) in which No. 3 is a large R surface, the number of repetitions up to breakage was 2.0 × 10 ⁶ or more for both 10% and 50% of the cumulative breakage probability. The desired strength can be obtained.

[0026]

According to the present invention, the base of the leg shaft, which forms the boundary between the outer diameter surface of the leg shaft and the flat surface of the boss perpendicular to the outer diameter surface, is formed by a predetermined radius of curvature. By providing the trunnion member having two continuous R surfaces, stress concentration at the base of the leg shaft is reduced. In addition, the aforementioned R
Since the surface is formed by simultaneous grinding after the heat treatment, the surface roughness can be improved and the abnormal surface layer (grain boundary oxide layer) can be removed by the heat treatment. To provide a tripod-type constant velocity universal joint that can prevent the root portion of the leg shaft from being damaged due to the synergistic action, easily realize high strength of the root portion of the leg shaft, and have high quality and high reliability. Can be.

[Brief description of the drawings]

1A is a front view showing a trunnion member of the present invention used in a tripod type constant velocity universal joint. FIG. 1B is an enlarged sectional view of a portion A in FIG.

FIG. 2 is a Weibull diagram of pulsating torsional fatigue strength

3A is a cross-sectional view showing a specific structure of a tripod type constant velocity universal joint. FIG. 3B is a cross-sectional view showing a state where the tripod type constant velocity universal joint shown in FIG.

FIG. 4A is a front view showing a conventional trunnion member used for a tripod type constant velocity universal joint. FIG. 4B is an enlarged sectional view of a portion B of FIG.

[Explanation of symbols]

Reference Signs List 1 leg shaft 3 needle roller 9 serration hole 10 boss portion 11 flat surface 12 outer diameter surface 22 trunnion member 23 root portion of leg shaft r ₁ radius of curvature

Claims (2)

[Claims] 1. Three flat surfaces are formed at equal intervals in a circumferential direction on an outer periphery of a boss portion through which a serration hole is formed, and a leg is projected on each flat surface in a radial direction. A tripod-type constant velocity universal joint comprising a trunnion member having a plurality of needle rollers rotatably disposed on a radial surface, wherein the trunnion member has an outer diameter surface of the leg shaft and a boss orthogonal to the outer diameter surface. A tripod type constant velocity universal joint, wherein a root portion of a leg shaft forming a boundary with the flat surface of the portion is formed as one continuous R surface having a predetermined radius of curvature. 2. The trunnion member according to claim 1, further comprising:
The surface is formed by simultaneous grinding of an outer diameter surface of a leg shaft and a flat surface of a boss portion after heat treatment.
The described tripod type constant velocity universal joint.