JP2001280360A - Outer joint member of constant velocity universal joint - Google Patents

Abstract

PROBLEM TO BE SOLVED: To manufacture an outer joint member with a hollow shaft at a low cost with high accuracy while ensuring the sufficient strength. SOLUTION: This outer joint member 1 has a mouth part 10 provided with plural guide grooves 13 on an inner peripheral surface 11, and a shaft part 20 extended from the mouth part 10. This outer joint member 1 is manufactured by integrally molding the shaft part 20 and the mouth part 10, a steel material is preformed by sub-hot forging, and then the shaft part 20 is cold forged, and finished, in particular, by ironing work. The shaft part 20 is a bottomed hollow member having a cavity part 21, and a solid part 25 has a toothed part 27 for transmitting the torque.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an outer joint member of a constant velocity universal joint used for power transmission in automobiles and various industrial machines, and a method of manufacturing the same.

[0002]

2. Description of the Related Art For example, various types of constant velocity universal joints are used for connecting a propeller shaft and a drive shaft of an automobile. Constant velocity universal joints are roughly classified into a fixed type that allows only relative angular displacement between the outer joint member and the inner joint member, and a sliding type that allows relative angular displacement and axial displacement. The former includes a ball fixed joint, and the latter includes a double offset joint, a tripod joint, a cross groove joint, and the like. Among the constant velocity universal joints, a tripod joint uses a spherical roller as a torque transmitting member, and the other uses a ball as a torque transmitting member.

Conventionally, for the outer joint member of a constant velocity universal joint, a steel material is preformed into a substantially predetermined shape by sub-hot forging, and then the inner peripheral surface and the guide groove of the mouth portion are cold forged (ironing or rolling). Process) to form the final shape and dimensions.

[0004]

In recent years, it has been strongly desired to reduce the weight of a constant velocity universal joint from the viewpoint of improving the fuel efficiency of a vehicle and the like. It is thought that.

Conventionally, an outer joint member is obtained by welding a separately finished hollow shaft and a mouth portion. However, such a procedure requires a large number of processing steps and increases costs. Further, when two members are welded, the accuracy such as the coaxiality may be deviated.

Accordingly, an object of the present invention is to make it possible to manufacture an outer joint member having a hollow shaft at low cost and with high accuracy while securing sufficient strength.

[0007]

According to the present invention, there is provided an outer joint member having a mouth portion having a plurality of guide grooves formed on an inner peripheral surface thereof and a shaft portion extending from the mouth portion. The part and the mouth part were integrally formed, and the shaft part was a hollow bottomed part having a hollow part and a tooth part for torque transmission in a solid part.

As described above, since the shaft of the outer joint member is formed as a hollow with a bottom having a cavity, the weight of the outer joint member and, consequently, the constant velocity universal joint can be reduced by the amount of the cavity, and the vehicle can be lightened. It can contribute to weight reduction. Further, since the heat radiation area is increased by the amount of the cavity, the effect of suppressing the temperature rise of the grease sealed in the mouth portion is obtained, and the life of the constant velocity universal joint is improved. Since the outer joint member is formed as one part, the conventional welding of the mouth portion and the shaft portion is not required, and therefore, it is possible to reduce the cost and also to prevent the deterioration of accuracy due to welding.

The outer joint member is obtained by preforming a steel material by sub-hot forging and then finishing at least the shaft portion by cold forging. By finishing the shaft portion by cold forging, work hardening occurs on the shaft portion surface, so that the shaft diameter can be reduced and the hollow portion can be made thinner, and further reduction in size and weight can be achieved. As cold forging, for example, ironing may be performed on the shaft portion.

[0010] By providing a shaping portion with a working degree adjusting portion for alleviating a sudden change in the working degree near the bottom of the hollow portion during ironing, cracking or breaking of the material can be avoided. .

As the working degree adjusting portion, an inner diameter of the shaft portion is made smaller toward the shaft end near the bottom of the hollow portion.
It is conceivable that the outer diameter of the shaft portion is made smaller toward the shaft end near the bottom of the hollow portion.

In the above-mentioned outer joint member, an inner joint member incorporated into a mouth portion of the outer joint member, and a space between the outer joint member and the inner joint member interposed between the guide groove of the outer joint member and the inner joint member. A constant velocity universal joint can be obtained by incorporating a plurality of torque transmitting members that transmit torque at the same time.

In summary, the manufacturing process of the outer joint member is a procedure of preforming a steel material by sub-hot forging and then finishing at least the shaft portion by cold forging. Cold forging of the shaft can be performed by ironing. Also,
The teeth for transmitting torque are formed in a solid portion of the shaft portion after ironing of the shaft portion. At the time of ironing, it is desirable to mitigate a sudden change in the degree of processing near the bottom of the cavity by the degree-of-work adjusting section provided on the shaft. It is conceivable to reduce the inner diameter of the portion toward the shaft end or to reduce the outer diameter of the shaft near the bottom of the hollow portion of the material before ironing toward the shaft end.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS.

FIG. 1 is a sectional view of a double offset type constant velocity universal joint which is a kind of a sliding type constant velocity universal joint. This constant velocity universal joint has a plurality of (for example, 6
The outer joint member 1 having a mouth portion 10 in which a linear guide groove 13 is formed in the axial direction, and a plurality of (for example, six) linear guide grooves 2b are formed in the spherical outer peripheral surface 2a in the axial direction. Inner joint member 2 formed and guide groove 13 of outer joint member 1
And a guide groove 2b of the inner joint member 2 cooperate to form a plurality of (for example, six) torque transmitting balls 3 disposed on a ball track, and holding the torque transmitting balls 3. And the container 4. The constant velocity universal joint includes a spherical center of an outer peripheral surface 4a of the cage 4 and an inner peripheral surface 4a.
Since the center of the spherical surface b is offset in the axial direction on the opposite side by the same distance from the center of the pocket, it is called a double offset type.

When a constant velocity universal joint of this type transmits a rotational torque while maintaining an operating angle, the retainer 4 is attached to the inner joint member 2.
Rotates to the position of the torque transmitting ball 3 moving on the ball track in accordance with the inclination of the ball, and holds the torque transmitting ball 3 in the angle bisecting plane of the operating angle. Outer joint member 1
When the inner joint member 2 and the inner joint member 2 move relative to each other in the axial direction, a slip occurs between the outer peripheral surface 4a of the retainer 4 and the inner peripheral surface 11 of the outer joint member 1, thereby enabling smooth axial movement (plunging). To

The outer joint member 1 has a cup-shaped mouth portion 10.
And the long shaft portion 20 are integrally formed. Here, “integral molding” means that the outer joint member 1 including the mouth part 10 and the shaft part 20 is molded as one part.

The inner peripheral surface of the mouth portion 10 is in contact with the outer peripheral surface 4a of the cage 4,
And a guide groove 13 which is in contact with.

The shaft portion 20 includes a cylindrical hollow portion 23 having a bottom having a hollow portion 21 and a solid portion 25 provided at a shaft end portion. The hollow portion 23 has a uniform inner and outer diameter except for the vicinity of the bottom 23a and the vicinity of the opening 23b.
The hollow portion 21 of the hollow portion 23 has a circular cross section. One end of the hollow portion 23 is opened to the internal space of the mouth portion 10 while expanding in diameter, and the other end is tapered and reduced in diameter to be closed by the bottom portion 23a. The reduced diameter portion at the other end of the hollow portion 21 is a portion that functions as the workability adjusting portion 26 at the time of cold forging of the shaft portion 20 described later remains in the final product. Serrations (or splines) 27 are formed on the outer periphery of the shaft end of the solid portion 25 as torque transmission teeth for transmitting torque to other members. A tapered portion 29 is interposed between the tooth portion 27 and the hollow portion 23, and has an outer diameter of the solid portion 25 (tooth portion 2).
7) is smaller than the outer diameter of the hollow portion 23.

The outer joint member 1 is made of, for example, medium carbon steel,
Alternatively, it is manufactured using carburized steel through the manufacturing steps shown in FIGS. The carbon content in the steel material is desirably about 0.4% to 0.7% by weight, which corresponds to S48C, S50 for medium carbon steel.
C, S53C, S55C etc., and SCr41 for carburized steel
5 and the like.

In the figures, (a) to (e) are steps of preforming a hot-rolled material of the steel material into a predetermined shape by sub-hot forging, and (f) to (h) are steps of cold forging the material. This is the step of finish-molding to the final shape and dimensions. Between the sub-hot forging steps (a) to (e) and the cold forging steps (f) to (h), if necessary, insoluble phosphate on the surface of the mouth portion 10 and the shaft portion 20 In some cases, a bond processing (bond light processing) for forming a film is performed.

In the cold forging steps (f) to (h),
(F) is a step of forming the outer periphery of the mouth part 10 by ironing, and (g) is a step of forming the inner surface (the inner peripheral surface 11 and the guide groove 13) of the mouth part 10 by cold forging (die forging). And a step of first forming the outer periphery of the shaft portion 20 by ironing. (H) is a step of secondary forming the outer periphery of the shaft portion 20 by ironing.

In the ironing process of steps (g) and (h), cracks or breakage of the material occur near the bottom 23a of the hollow portion 23 due to the formation of the hollow portion 21 having a small diameter and being long in the axial direction. Cheap. As shown in FIG. 3, ironing is performed by closely inserting the mandrel 6 into a portion 21 ′ which will later become the cavity 21, disposing the die 7 around the steel material 1 ′, and forming the steel material 1 ′ (the mandrel 6). And the die 7 is relatively moved in the axial direction (at this time, the ironing direction is the direction from the shaft end toward the mouse unit 10), but if no countermeasures are taken, the same figure is taken. As shown in the middle graph, in the vicinity A of the bottom 21a 'of the cavity 21',
Since the working ratio (rate of decrease in sheet thickness) rapidly increases with the progress of ironing, the material is likely to crack or break due to rapid elongation or pulling of this portion.

In the present invention, as means for alleviating the sudden change in the degree of work, a work degree adjuster 26 is provided on the steel material 1 'before ironing (hereinafter referred to as "material before ironing"). 1, 2, and 4 illustrate the working degree adjustment unit 26.
In the example, the bottom 21 of the hollow portion 21 'of the material before ironing 1'
In the vicinity of a ′, the inner diameter of the shaft portion 20 ′ is reduced toward the shaft end (note that in FIGS. 2 to 5, portions corresponding to the respective portions of the final product shown in FIG. With the same reference numbers). In order to ensure the close contact with the working degree adjusting portion 26, the outer periphery of the tip of the mandrel 7 is also reduced in diameter toward the tip.

By providing the degree-of-work adjusting portion 26 on the shaft portion 20 ', as shown in FIG. 4, the rate of increase of the sheet thickness reduction near the bottom of the hollow portion 21' is reduced. Cracks and breaks can be prevented. The broken line in the figure represents the shape of the material 1 'before ironing, and the two-dot chain line represents the corresponding shape in FIG. 3 (the same applies to FIG. 5). In addition, as described above, the working degree adjustment unit 26 remains on the shaft unit 20 even after becoming a final product (see FIG. 1).

FIG. 5 shows another example of the degree-of-work adjusting section 26, in which the bottom 21a 'of the hollow portion 21' of the blank before ironing 1 'is formed.
In the vicinity, the outer diameter of the shaft portion 20 'is reduced toward the shaft end. Also in this case, the rate of increase in the sheet thickness reduction rate near the bottom 21a 'of the hollow portion 21' is reduced, so that the material 1 'can be prevented from cracking or breaking. After the working degree adjustment unit 26 is also a final product, a part thereof is
0 Remains on the outer peripheral surface.

In the above embodiment, the ironing of the shaft portion 20 is performed in two steps. However, if the material 1 'is not cracked, the ironing may be finished by one ironing.
Alternatively, ironing may be performed three or more times as necessary. By providing the working degree adjusting unit 26 as described above, if the reduction rate of the sheet pressure per ironing operation is 35% or less, it is possible to perform processing without cracking or breaking without fail. The lower limit of the thickness reduction rate is usually set to 10% or more.

As described above, in the present invention, since the shaft portion 20 of the outer joint member 1 is formed as a hollow with a bottom provided with the hollow portion 21, the outer joint member 1 and, consequently, the constant velocity can be freely adjusted by the hollow portion 21. Lightening of the joint is achieved, which can contribute to weight reduction of the vehicle. Further, since the heat radiation area is increased by the amount of the hollow portion 21, the effect of suppressing the temperature rise of the grease sealed in the mouth portion 10 is obtained, and the life of the constant velocity universal joint is improved. Since the outer joint member 1 is formed as one part as is clear from the above process, the conventional welding of the mouth portion 10 and the shaft portion 20 is unnecessary, and therefore, the welding can be performed while achieving low cost. The accompanying deterioration in accuracy can be avoided.

Further, since the shaping of the shaft portion 20 is performed by cold forging, particularly by ironing, work hardening occurs on the surface layer after ironing. Therefore, the diameter of the shaft portion 20 and the thickness of the hollow portion 23 can be reduced, which can contribute to downsizing of the joint. If the hardness of the ironed surface after the ironing is too high, problems occur in terms of tool life and machining cycle time in the subsequent machining process.
05 or less (HRB = 100 to 105 is preferable).

In the sub-hot forging steps (a) to (e), FIG.
The solid portion 25 'is formed as shown in FIG. 5, but by setting the outer diameter of the solid portion 25' smaller than the final outer diameter of the hollow portion 23, In the forging steps (f) to (h), the forging pressure surface does not contact the outer peripheral surface of the solid portion 25 '. Therefore, work hardening due to cold forging does not occur on the surface of the solid portion 25 ', and the load on the rolling tool at the time of rolling of the serration 27 described later is reduced, so that variations in finish dimensions, molding unnecessary and tool It is possible to avoid shortening the service life and the like.

The outer joint member 1 that has been subjected to the cold forging steps (f) to (h) is subjected to machining. Machining is
Normally, the inner periphery (peripheral portion of the retaining ring groove), the end surface, and the outer periphery (peripheral portion of the boot mounting portion) of the opening side end of the mouth portion 10 and the outer periphery of the bottom end portion of the mouse portion 10 to the shaft portion 20 Is done on the part.

Thereafter, a serration 27 is rolled on the outer periphery of the solid portion 25, and the inner peripheral surface 11 of the mouth portion 10 and the guide groove 13 are formed.
And the like are subjected to heat treatment such as induction hardening, and then subjected to grinding at required locations to obtain a final product. The surface hardness after the heat treatment is set to HRC 63 or less (HRC = 53 to 63 is preferable).

The constant velocity universal joint shown in FIG. 1 is completed by incorporating the inner joint member 2, the torque transmitting ball 3, the retainer 4 and the like into the mouth portion 10 of the outer joint member 1. This constant velocity universal joint is installed, for example, on the inboard side of a drive shaft of an automobile.
Of teeth 27 are differentially coupled.

The embodiment applied to the outer joint member of the double offset type constant velocity universal joint has been described above.
The present invention can also be applied to outer joint members such as tripod joints and cross groove joints. These joints are sliding type constant velocity universal joints that can take relative angular displacement and axial displacement between the outer joint member 1 and the inner joint member 2. The present invention can be similarly applied to an outer joint member of a fixed type constant velocity universal joint which can take only a relative angular displacement of a joint or the like (it cannot take an axial displacement).

[0035]

According to the present invention, since the weight of the outer joint member (constant velocity universal joint) can be reduced, it is possible to contribute to the weight reduction of the vehicle and the improvement of fuel efficiency. Further, since the heat radiation area is increased by the amount of the cavity, the temperature rise of the grease sealed in the mouth portion can be suppressed, and the life of the constant velocity universal joint can be improved by improving the life of the grease. Since the outer joint member is formed integrally with the mouth part and the shaft part and is formed as one part, the conventional welding of the mouth part and the shaft part is unnecessary. Therefore, cost reduction can be achieved, and deterioration of accuracy due to welding can be avoided.

Since the shaping of the shaft is performed by cold forging, particularly by ironing, work hardening occurs on the surface layer after ironing. Therefore, the diameter and thickness of the shaft can be reduced, and the size and weight of the joint can be reduced.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a constant velocity universal joint using an outer joint member according to the present invention.

FIG. 2 is a sectional view showing a manufacturing process of the outer joint member according to the present invention.

FIG. 3 is an enlarged cross-sectional view of the vicinity of the bottom of the cavity, and a graph showing a relationship between a cross-sectional position in the axial direction and a thickness reduction rate.

FIG. 4 is an enlarged cross-sectional view of the vicinity of the bottom of the hollow portion, and a graph showing a relationship between a cross-sectional position in the axial direction and a thickness reduction rate.

FIG. 5 is an enlarged cross-sectional view of the vicinity of the bottom of the hollow portion, and a graph showing the relationship between the cross-sectional position in the axial direction and the thickness reduction rate.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Outer joint member 2 Inner joint member 3 Torque transmitting member 4 Cage 10 Mouth part 11 Inner peripheral surface of mouse part 13 Guide groove 20 Shaft part 21 Cavity part 21a Bottom of cavity part 23 Hollow part 25 Solid part 26 Processing degree adjustment part 27 Tooth (serration)

Continued on the front page (72) Inventor Kenichi Nakano 1578 Higashikaizuka, Iwata-shi, Shizuoka F-term (reference) 4E087 AA10 BA02 CA21 CB02 DB06 HA22 HB01

Claims (13)

[Claims] An outer joint member having a mouth portion having a plurality of guide grooves formed on an inner peripheral surface thereof and a shaft portion extending from the mouth portion, wherein the shaft portion and the mouth portion are integrally formed, and the shaft portion is formed as a hollow portion. An outer joint member for a constant velocity universal joint, characterized in that the outer joint member has a bottomed hollow shape and has a torque transmitting tooth portion in a solid portion. 2. After preforming steel material by sub-hot forging,
The outer joint member of the constant velocity universal joint according to claim 1, wherein at least a shaft portion is finished by cold forging. 3. The outer joint member of a constant velocity universal joint according to claim 2, wherein the shaft portion is subjected to ironing as the cold forging. 4. The outer joint member of a constant velocity universal joint according to claim 3, wherein the shaft portion has a working degree adjusting portion for reducing a sudden change in the working degree near the bottom of the hollow portion during ironing. 5. The outer joint member of a constant velocity universal joint according to claim 4, wherein the working degree adjusting portion is configured such that the inner diameter of the shaft portion is reduced toward the shaft end near the bottom of the hollow portion. 6. The outer joint member for a constant velocity universal joint according to claim 4, wherein the working degree adjusting portion is configured such that the outer diameter of the shaft portion is reduced toward the shaft end near the bottom of the hollow portion. 7. An outer joint member according to claim 1, an inner joint member incorporated in a mouth portion of the outer joint member, and interposition between a guide groove of the outer joint member and the inner joint member. And a plurality of torque transmitting members for transmitting torque between the outer joint member and the inner joint member. 8. When manufacturing an outer joint member integrally provided with a mouth portion having a plurality of guide grooves formed on an inner peripheral surface thereof and a hollow shaft having a bottom having a hollow portion, a steel material is subjected to sub-hot heating. A method for producing an outer joint member for a constant velocity universal joint, wherein at least the shaft is finished by cold forging after preforming by forging. 9. The method for producing an outer joint member for a constant velocity universal joint according to claim 8, wherein the cold forging of the shaft portion is performed by ironing. 10. The method for manufacturing an outer joint member for a constant velocity universal joint according to claim 9, wherein a torque transmitting tooth portion is formed in a solid portion of the shaft portion after ironing of the shaft portion. 11. The manufacturing method for an outer joint member for a constant velocity universal joint according to claim 9, wherein a sudden change in the working ratio near the bottom of the hollow portion during the ironing process is reduced by a working ratio adjusting portion provided on the shaft portion. Method. 12. The method for manufacturing an outer joint member for a constant velocity universal joint according to claim 10, wherein the inner diameter of the shaft portion near the bottom of the hollow portion of the material before ironing is reduced toward the shaft end. 13. The method for manufacturing an outer joint member for a constant velocity universal joint according to claim 10, wherein the outer diameter of the shaft portion near the bottom of the hollow portion of the material before ironing is reduced toward the shaft end.