JP2001315539A - Drive shaft - Google Patents

Abstract

PROBLEM TO BE SOLVED: To use a lightweight shaft of high-quality and inexpensive manufacturing cost as an intermediate shaft for a drive shaft of an automobile. SOLUTION: The intermediate shaft 21 for joining constant velocity universal joints 2 and 3 to both end parts is formed by joining mutual end surfaces of stub shafts 22 and 23 formed by cold forging by frictional welding, etc. The respective stub shafts 22 and 23 have shaft parts 22a and 23a and cylindrical parts 22b and 23b, and the cylindrical parts and a spline part are accurately plastically worked by cold-forging these parts to easily improve a quality of the intermediate shaft 21. The intermediate shaft 21 can be mass-produced by reducing a material cost and a manufacturing equipment cost, and is suitable for the drive shaft of the automobile of small lot multi-production.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drive shaft used as a rotational force transmitting means for an automobile or the like and having a constant velocity universal joint connected to both ends of an intermediate shaft.

[0002]

2. Description of the Related Art A drive shaft for transmitting a driving force from an automobile engine to wheels has a unit structure in which a pair of constant velocity universal joints are coupled to both ends of a single intermediate shaft so as to transmit torque. Many types of intermediate shafts of this drive shaft are mass-produced depending on the type of vehicle to be applied, and the types are roughly classified according to the basic structure. There is a hollow shaft type machined from such as. Due to the demand for improved vehicle interior silence by reducing the weight of automobiles and increasing the rigidity of drive shafts, hollow shaft type intermediate shafts tend to be used for many types of vehicles.

[0003] The hollow shaft type intermediate shaft is also roughly divided into an integral hollow shaft obtained by plastically processing a pipe material such as a steel pipe, and a pair of stub shafts pressed and welded to a single pipe material. There is a pipe joint type hollow shaft of a jointed two-point joint type. FIGS. 4 and 5 show a conventional example of a drive shaft using these two types of intermediate shafts, and FIGS. 3B and 3C show schematic structures of the two types of intermediate shafts.

The intermediate shaft 1 of the drive shaft shown in FIG. 4 is an integral hollow shaft as described above. Both ends of the intermediate shaft 1 are formed into thick shafts 1a and 1c having the same outer diameter, and the center is formed as a shaft. It is plastically worked into a thin cylindrical portion 1b having a larger diameter than 1a and 1c. A sliding type constant velocity universal joint 2 is coupled to one shaft portion 1a of the intermediate shaft 1 by a spline so as to transmit torque, and a fixed type constant velocity universal joint 3 is coupled to the other shaft portion 1c by a spline to transmit torque. You. One constant velocity universal joint 2 is connected to the drive shaft side of the engine of the automobile, and the other constant velocity universal joint 3 is connected to the wheel side.

[0005] Each of the constant velocity universal joints 2 and 3 has a tripod member 2 connected to an intermediate shaft 1 by a spline.
a, an inner wheel 3a, and outer wheels 2b, 3b and the like connected to the engine side and the wheel side of the automobile, respectively, and boots 2c, 3c are provided between the open ends of the outer wheels 2b, 3b and the intermediate shaft 1.
Is installed.

The intermediate shaft 11 of the drive shaft shown in FIG.
Is a two-position pressure welding type pipe-joined hollow shaft as shown in the schematic structure of FIG. 3 (C), and coaxially connects a pair of left and right stub shafts 12, 13 and a central pipe member 14. The two stub shafts 12 and 13 are manufactured by subjecting a solid bar to machining (turning, spline rolling) from hot forging (sub-hot forging) and then heat-treating. Each of the stub shafts 12 and 13 has solid rod-shaped shaft portions 12a and 13a formed by hot forging of a solid bar material, and shaft portions 12a and 13a.
Has cylindrical parts 12b and 13b machined to a large diameter at one end. The cylindrical portions 12b, 13b and the pipe member 14 have the same diameter, and the opening end surface of the cylindrical portion 12b and the opening end surface of the cylindrical portion 13b abut on both end surfaces of the pipe member 14 and are joined by welding or pressure welding to form one intermediate shaft. 11 is manufactured.

[0007]

The hollow shaft type intermediate shaft has been applied to various kinds of vehicles because of its light weight and excellent shaft rigidity. However, the following problems arise in the manufacturing method based on the structure. Was.

Since the intermediate shaft 1 of the integral hollow shaft shown in FIGS. 4 and 3B is formed by plastically processing a pipe material such as a long steel pipe, a swaging for plastically processing the same. Equipment costs such as machines and molds increase. Further, a pipe material is used as a raw material, and the cost of the pipe material is higher than that of a solid rod material, and the material cost is higher. for that reason,
The intermediate shaft 1 is unsuitable for a vehicle intermediate shaft for high-mix low-volume production due to a high manufacturing cost, and is inferior in versatility. In addition, after forming the intermediate shaft 1 from the pipe material, it is difficult to inspect the inner surface of the central cylindrical portion 1b for the presence or absence of a flaw or a defect, and the size thereof. This increases the number of man-hours for quality control of the entire intermediate shaft and increases the accuracy. Inspection is difficult.

A pair of stub shafts 12 and 13 constituting an intermediate shaft 11 of a pipe-joined hollow shaft shown in FIGS. 5 and 3 (C) are machined by hot forging (sub-hot forging) a solid bar. It is manufactured by processing (turning, spline rolling), heat-treating and joining with the pipe material 14. At the time of this machining, the cylindrical portions 12b and 13b are turned into hollow portions and the shaft portions 12a are formed. , 13a are formed by rolling the outer periphery of the spline portion, so that it is technically difficult to finish the spline portion with high accuracy such as coaxiality, and the equipment cost for finishing with high accuracy is increased. . Also, the intermediate shaft 11
Is two stub shafts 12 and 13 and one pipe material 1
4 requires a total of three cables, which makes the maintenance management complicated. In addition, in order to connect the stub shafts 12, 13 and the pipe member 14, a total of two places must be joined by welding or pressure welding, and the two joining steps increase the manufacturing cost.

Accordingly, the present invention has been proposed in view of the above problems, and has as its object to provide a low-cost, high-precision drive shaft having an intermediate shaft.

[0011]

According to a first aspect of the present invention, there is provided a drive shaft in which a constant velocity universal joint is connected to both ends of an intermediate shaft. The stub shaft includes a pair of stub shafts having a shaft portion and a cylindrical portion formed by forging, and the cylindrical portions of the stub shaft are coaxially joined.

[0012] Here, the stub shaft is formed by cold forging a solid bar, so that the number of parts to be machined is greatly reduced, and mass productivity and accuracy are improved accordingly. Also,
The structure in which the intermediate shaft is formed by joining a pair of stub shafts is manufactured at a low cost because the joining point is one.

The invention according to claim 2 is characterized in that the shaft spline of the stub shaft connected to the constant velocity universal joint is formed by ironing. That is, when the stub shaft is cold forged, if the spline is formed by ironing by cold forging without machining the end of the shaft, the coaxiality of the shaft spline can be finished with high accuracy.

According to a third aspect of the present invention, the cylindrical portion of the stub shaft is formed by ironing.
Also in this case, when the stub shaft is cold forged, if the cylindrical portion is formed by ironing by cold forging without machining, the cylindrical portion can be finished with high precision.

According to a fourth aspect of the present invention, the cylindrical portions of the stub shaft are joined by friction welding.
That is, welding between the stub shafts can be performed by welding, but in a cold-forged stub shaft, joining by friction welding is advantageous in terms of strength and equipment.

The invention according to claim 5 is characterized in that the opening side of the cylindrical portion of the stub shaft is formed to have a larger diameter than the shaft portion side opposite to the opening side. By forming the cylindrical portion of the stub shaft in such a manner that the diameter of the cylindrical portion is increased toward the opening side, the diameter of the joining portion of the stub shaft increases, and the joining strength increases.

According to a sixth aspect of the present invention, a hardened surface layer is formed on at least a shaft portion of the stub shaft by induction hardening. The shaft portion of the stub shaft has a spline formed on its outer periphery, has a smaller section modulus than the cylindrical portion, and has a lower torsional strength. Therefore, if a surface hardened layer is formed on the shaft portion, high strength is obtained. Is preferred.

Although the type of constant velocity universal joints connected to both ends of the intermediate shaft as described above is not limited, in a drive shaft of an automobile, one of the constant velocity universal joints at both ends of the intermediate shaft is a fixed type constant velocity universal joint. It is practically preferable that the other universal joint is a sliding type constant velocity universal joint (the invention of claim 7). In particular, in the case of a drive shaft of an automobile, it is desirable to couple a fixed type constant velocity universal joint to the vehicle wheel side of the intermediate shaft and a sliding type constant velocity universal joint to the automobile engine side.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a first embodiment, FIG. 2 shows a second embodiment, and FIG. 3 (A) shows a schematic structure of an intermediate shaft in these embodiments. This will be described in detail with reference to FIG. 1 (A) and 2 (A) show partial cross sections of the entire drive shaft, and FIGS. 1 (B) and 2 (B) show exploded cross sections of an intermediate shaft used for the drive shaft. . Further, the drive shaft shown in the figure is for transmitting the driving force of the automobile engine to the wheels, and the same or corresponding parts as those of the drive shaft of FIGS. 4 and 5 are denoted by the same reference numerals.

The drive shaft shown in FIG. 1A has an intermediate shaft 2 having constant velocity universal joints 2 and 3 attached to both ends.
1 is characterized in that the hollow end faces of a pair of stub shafts 22 and 23 formed by cold forging a solid bar are joined together and formed. A pair of stub shafts 22,
23 has a solid shaft portion 22a, 23a and a cylindrical portion 22b, 23b of a base end closed distal end opening integrally and coaxially. Cylindrical part 2 of stub shafts 22 and 23 joined to each other
2b and 23b may have the same dimensions and shape, and the shaft portions 22a and 2b
Reference numeral 3a is a size and shape corresponding to the constant velocity universal joints 2 and 3 to be connected. In FIG. 1A, a sliding type constant velocity universal joint 2 is coupled to one stub shaft 22 side, and a fixed type constant velocity universal joint 3 is coupled to the other stub shaft 23 side.
This constitutes a drive shaft suitable for an automobile.

Each of the pair of stub shafts 22 and 23 is formed by cold forging a solid bar material, and the end faces of the cylindrical portions 22b and 23b are simultaneously butted and joined. Since both stub shafts 22 and 23 are made of a solid bar material that is cheaper than a pipe material, it can be manufactured with a low material cost. Both stub shafts 22,
In the cold forging process 23, the cylindrical portion, the spline portion, and the like are plastically worked. In addition, each stub shaft 22,
In the cold forging of 23, if it is necessary to change the length of the cylindrical portions 22b and 23b, it is possible to cope with the short one by controlling the input weight of the material (solid bar), and a new one can be provided. It is not necessary to manufacture a simple mold, and for a long one, the normal stub shaft manufacturing mold is molded with two molds, the shaft side and the cylindrical side. Yes, with little increase in equipment costs. Also, the cylindrical portions 22b, 23 of the stub shafts 22, 23
By forming b by cold forging, it is easy to freely change the shape in order to adjust the bending rigidity and the like of this portion, and an example of this shape change is shown in the embodiment of FIG.

At the time of cold forging of each of the stub shafts 22, 23, the required accuracy is obtained by ironing the splines of the cylindrical portions 22b, 23b themselves and the shaft end. Thus, the stub shafts 22, 2
By ironing the cylindrical part and shaft spline of No.3, the machined part is greatly reduced and the manufacturing man-hour and equipment can be advantageously manufactured, and it is easy to finish each part with high precision by ironing. Becomes In addition, each stub shaft 2
The equipment and cost required for cold forging and ironing of 2, 23 are about half that of the equipment for forming by machining. Production becomes easy. In addition, in each of the stub shafts 22 and 23, there is a place where turning is necessary, and such a turning place is a minimum necessary place such as a clip groove and the like, and is easy to turn. It will not be high.

Before joining the pair of stub shafts 22, 23, a surface hardened layer is formed by induction hardening to strengthen the stub shafts. This induction hardening is performed at least on the stub shafts 22, 2 connected to the constant velocity universal joints 2, 3.
What is necessary is just to perform about 3 shaft parts 22a and 23a. These end portions 22a and 23a have a smaller section modulus and lower torsional strength than the cylindrical portion. Therefore, in order to obtain the required strength, it is effective to form a surface hardened layer at least at this portion by induction hardening to strengthen the portion. Before joining the two stub shafts, the inner surfaces of the cylindrical portions 22b and 23b are inspected for flaws and defects. This inspection can be easily performed with high reliability by visual inspection. In addition, the inspection can be easily automated.

After the above induction hardening and inspection, the pair of stub shafts 22 and 23 are joined to form one intermediate shaft 2.
1 is produced. The stub shafts 22 and 23 can be joined by either pressure welding or welding. However, in the cold-forged stub shafts 22 and 23, joining by friction welding is advantageous in terms of strength and equipment. In addition, since the two stub shafts 22 and 23 are directly joined without using an intermediate member such as a pipe material, the joining portion becomes a single portion, and the joining can be advantageously performed in terms of equipment and man-hours. Cost reduction is further facilitated, and quality control of the entire intermediate shaft is facilitated by quality control in a small number of places.

The drive shaft of the embodiment shown in FIG. 2 (A) has cylindrical portions 22b, 23 of stub shafts 22, 23 as shown in an exploded cross section of the intermediate shaft 21 in FIG. 2 (B).
The shape of b is changed. As shown in FIG. 2 (B), the open openings of the cylindrical portions 22b and 23b are formed to have a larger diameter than the shaft portion, and the large-diameter openings 22c and 23c are joined together. To form the intermediate shaft 21. The intermediate shaft 21 of FIG. 2 is manufactured in the same manner as the intermediate shaft of FIG. 1, and constant velocity universal joints 2 and 3 are connected to both ends thereof.

In the intermediate shaft 21 shown in FIG. 2, the cylindrical large-diameter openings 22c, 23 of the pair of stub shafts 22, 23 are provided.
The diameter of the joint between the pair of stub shafts increases in accordance with the increase in the diameter of c, and the joining strength increases, which is suitable for a drive shaft of a vehicle type that requires higher strength.

[0027]

According to the present invention, a pair of stub shafts manufactured by cold forging are coaxially joined to form an intermediate shaft, so that the intermediate shaft is manufactured at low material cost and at low cost. It is possible to provide a drive shaft having an intermediate shaft which can be manufactured with good mass productivity using a low-cost cold forging facility which is suitable for small-scale production and suitable for multi-product small-quantity production. Also, at the time of cold forging of a pair of stub shafts constituting the intermediate shaft, the cylindrical portion of the stub shaft, the shaft portion spline, etc. have high dimensional precision by minimizing the places to be machined by ironing important points. Molding makes it easy to improve the quality of the intermediate shaft.
In addition, since the intermediate shaft is formed by directly joining the stub shafts to each other, there is only one joint that requires quality control of the intermediate shaft, and quality control is easy and reliable by reducing the number of quality control points. The reliability of the intermediate shaft is improved.

[Brief description of the drawings]

FIG. 1A is a side view including a partial cross section of a drive shaft showing a first embodiment, and FIG. 1B is an exploded side view including a partial cross section of an intermediate shaft.

FIG. 2A is a side view including a partial cross section of a drive shaft according to a second embodiment, and FIG. 2B is an exploded side view including a partial cross section of an intermediate shaft.

3A and 3B are diagrams for comparing the present invention with a conventional drive shaft intermediate shaft, wherein FIG. 3A is a schematic sectional view of the intermediate shaft of FIGS. 1 and 2, and FIGS. It is a schematic sectional drawing of a shaft.

FIG. 4 is a side view including a partial cross section of a conventional drive shaft.

FIG. 5 is a side view including a partial cross section of another conventional drive shaft.

[Explanation of symbols]

 2 Sliding constant velocity universal joint 3 Fixed constant velocity universal joint 21 Intermediate shaft 22 Stub shaft 22a Shaft part 22b Cylindrical part 22c Large diameter opening 23 Stub shaft 23a Shaft part 23b Cylindrical part 23c Large diameter opening

Claims (7)

[Claims] 1. A drive shaft in which a constant velocity universal joint is coupled to both ends of an intermediate shaft, wherein the intermediate shaft comprises a pair of stub shafts having a shaft portion and a cylindrical portion formed by cold forging, A drive shaft, wherein cylindrical portions of the stub shaft are coaxially joined. 2. The drive shaft according to claim 1, wherein a shaft spline of the stub shaft connected to the constant velocity universal joint is formed by ironing. 3. The drive shaft according to claim 1, wherein the cylindrical portion of the stub shaft is formed by ironing. 4. The drive shaft according to claim 1, wherein the cylindrical portions of the stub shaft are joined by friction welding. 5. The drive shaft according to claim 1, wherein an opening side of the cylindrical portion of the stub shaft is formed to have a larger diameter than a shaft portion side opposite to the opening side. . 6. The drive shaft according to claim 1, wherein a hardened surface layer is formed on at least a shaft portion of the stub shaft by induction hardening. 7. The constant velocity universal joint according to claim 1, wherein one of the constant velocity universal joints at both ends of the intermediate shaft is a fixed type constant velocity universal joint and the other is a sliding type constant velocity universal joint. Drive shaft as described.