JPH0356805B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing a rack shaft used in a rack and pinion type steering device for a vehicle such as an automobile.

[Prior art and its problems] Rack shafts have generally been obtained by cutting a solid bar. However, in recent years, due to the desire to reduce the weight of equipment, attempts have been made to obtain the rack shaft from a hollow bar, but cutting the hollow bar makes the rack tooth part thinner and reduces its strength. There is a problem with doing so. For this purpose, Japanese Patent Application Laid-Open No. 195960/1983 discloses that a solid or hollow auxiliary rod is inserted into the inner hole of the hollow rod to form the rack teeth. However, when inserting a hollow auxiliary rod into a hollow bar and press-forming the hollow bar and the auxiliary rod at the same time, plastic flow may not occur smoothly, resulting in problems such as thinner parts and cracks. There is. In particular, if different materials are used for the hollow rod and the auxiliary rod, cracks will occur because the plastic flow of one of them will not occur smoothly due to differences in ductility and fluidity. If cracks occur in the hollow bar or auxiliary bar, the strength of the rack shaft cannot be obtained.

The present invention has been made in view of these points. When press-molding a rack tooth by inserting an auxiliary hollow material into the inner hole of a hollow bar and applying plastic working to one side of the hollow bar, the hollow bar and the auxiliary hollow material are It is an object of the present invention to provide a method for manufacturing a rack shaft that can obtain a rack shaft with sufficient strength without causing any inconvenience to the hollow material.

[Means for Solving the Problems] The object is to provide a method for manufacturing a rack shaft in which an auxiliary hollow member is inserted into an inner hole of a hollow bar and a rack tooth is formed on the side surface of the hollow bar by plastic working. A flat part is formed in advance on the side surface of the auxiliary hollow material,
The flat part is inserted into the hollow bar so that it corresponds to the toothed molded part, and the hollow bar is plastically deformed by pressing with the die with the toothed pattern, and in the final process of the pressing, the auxiliary hollow This is achieved by plastically deforming the flat part of the material to engage the hollow bar and the auxiliary hollow member.

[Function] Since the present invention is as described above, a flat part is formed on the side surface of the auxiliary hollow member in advance, this flat part is positioned within the molding position of the rack teeth of the hollow bar, and the rack teeth are formed using a pressing die. By press-forming, until the hollow bar deforms and comes into contact with the auxiliary hollow member, only the hollow bar is plastically deformed, and plastic flow is performed smoothly. After the hollow bar comes into contact with the auxiliary hollow material, the hollow bar and the auxiliary hollow material are only deformed into a toothed shape, and there is no large plastic flow, resulting in cracks during plastic working. Never.

[Embodiment] FIGS. 1 to 5 show embodiments of the present invention. First, the auxiliary hollow member 2 made of a tempered S45C material is inserted into the inner hole 4 of the cylindrical hollow bar 1 made of an S43C material. At this time, the auxiliary hollow material 2 may be press-fitted if necessary. This auxiliary hollow member 2 has a flat portion 10 having a uniform thickness formed in advance on one side by plastic working. As a method for inserting the auxiliary hollow material 2 into the inner hole 4 of the hollow bar 1, as shown in FIG. 6, the auxiliary hollow member 2 is inserted with the flat part 10 of the auxiliary hollow member 2 facing the flat surface 5 of the core mold 6, and the core mold 6 is inserted into the inner hole 4 of the hollow bar 1 that is held and fixed. , and insert the auxiliary hollow member 2. As a result, the auxiliary hollow member 2 is positioned in the inner hole of the hollow bar 1 at the position where the rack teeth are formed. Next, the press die 9 attached to the upper die 7 and having a tooth pattern engraved thereon is advanced, and the hollow bar 1 and the auxiliary hollow member 2 are plastically deformed between the press die 9 and the core die 6. Press mold the teeth. By forming the flat part 10 on the auxiliary hollow material 2, when press-molding the rack teeth, the power to advance the press mold 9 is reduced in order to initially plastically deform only the hollow bar 1. . Then, the press die 9 is retreated,
The core mold 6 is removed from the auxiliary hollow member 2 to obtain the rack shaft 3. This rack shaft 3 is later subjected to finishing processing such as cutting as required, and a refrigerant is introduced into the rack shaft 3, and the rack teeth are induction hardened. As shown in FIG. 5, it is supported by a housing 12 as a rack shaft 3 of a rack and pinion type steering device, and meshed with a pinion 13.

[Effects of the Invention] The present invention uses the method for manufacturing a rack shaft as described above, in which an auxiliary hollow member is inserted into the inner hole of a hollow bar material, one side of the auxiliary hollow member is subjected to plastic working, and a rack tooth is press-molded. When doing so, sufficient strength of the rack shaft can be obtained without causing any cracks or other inconveniences to the hollow bar or auxiliary hollow material. By leaving a hollow part in the auxiliary hollow member, the hollow part can be used as an air passage in the boots at both ends of the rack and pinion type steering device during steering. Furthermore, since the hollow bar and the auxiliary hollow material are plastically deformed in the final process of press molding, there is no need to take measures to prevent the auxiliary hollow material from falling off, and the easy shaft can be manufactured extremely easily.

[Brief explanation of drawings]

Figures 1 to 5 show examples of the present invention. Figure 1 is a perspective view of the hollow bar and the auxiliary hollow member, and Figure 2 is a longitudinal section showing the auxiliary hollow member inserted into the hollow bar. 3 is a sectional view taken along the line A-A in FIG. 2, FIG. 4 is a longitudinal sectional view showing the state in which the rack teeth are press-molded, and FIG. 5 is a longitudinal sectional view of the rack and pinion type steering device. It is. Explanation of symbols, 1...Hollow bar material, 2...Auxiliary hollow material, 3...Rack shaft, 4...Inner hole, 6...Core type,
7...Upper die, 8...Lower die, 9...Press die, 10...
Tairabu.

Claims (1)

[Claims] 1. In a method for manufacturing a rack shaft in which an auxiliary hollow member is inserted into an inner hole of a hollow bar material and a rack tooth is formed on the side surface of the hollow bar material by plastic working, a flat portion is previously formed on the side surface of the auxiliary hollow member. Then, the flat part is inserted into the hollow bar so that it corresponds to the toothed molded part, and the hollow bar is plastically deformed by pressing with the die with the teeth carved therein, and at the end of the pressing. A method for manufacturing a rack shaft, which comprises plastically deforming a flat part of the auxiliary hollow member in the process to lock the hollow bar and the auxiliary hollow member.