JPS5992141A - Manufacture of hollow rack shaft - Google Patents

Abstract

PURPOSE:To obtain a hollow rack shaft having sufficient strength by combining an upper mandrel having rack-shaped ruggedness and a lower mandrel, inserting it into a hollow pipe and forging with a die, and after forming, pulling out the lower mandrel and extracting the upper mandrel. CONSTITUTION:An upper mandrel 21 having rack-shaped ruggedness and a lower mandrel 22 having no ruggedness are combined and inserted into a hollow pipe material 1. By forging with an upper die 3 having a rack die and a lower die 4, rack is formed on the hollow pipe material 1. Then, the lower mandrel 22 is pulled out, and the upper mandrel 21 is shifted downward in the hole and extracted. By this way, the hollow pipe material 1 becomes a rack shaft free from abnormal deformation. Correct forming of a rack shaft can be performed efficiently by simple mandrels.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a rack shaft for a rack-pinion type steering device which is generally used as a steering device for automobiles.

A rack shaft or rack that has a pinion that rotates as the steering shaft is rotated, and rack teeth that mesh with the pinion, and that slides in the axial direction as the pinion rotates and rotates the steered wheels in the steering direction. -Pinion type steering devices are widely used as steering devices for automobiles.The above-mentioned rack and pinion type steering devices have already been developed in which the rack shaft is constructed with a hollow vibe shape to reduce weight. (Unexamined Japanese Patent Publication No. 55-1230
(See Publication No. 44).

However, although hollow pipe-shaped rack shafts are very superior in that they can reduce weight as described above, on the other hand, it is difficult to form rack teeth on the surface of the pipe, and in the past, the rank teeth were In order to maintain sufficient strength, a fairly thick material must be used as the hollow pipe material, and the current situation is that the weight reduction effect cannot be sufficiently achieved.

By providing a specific method for forming rack shafts from hollow pipe materials, the present invention significantly simplifies the work of forming hollow rack shafts, and also increases the strength of the rack teeth using relatively thin pipe materials. The present invention will be described below with reference to the embodiments shown in the accompanying drawings.

In the figure, 1 is a material made of hollow pipe material;
A part of the top surface has an uneven portion 21α that roughly matches the rack tooth profile.
Insert the divided core metal 2 into the upper core metal 21 and the lower core metal 22, which has an arc-shaped peripheral surface that fits a part of the inner peripheral surface of the material 1, and match the outer peripheral surface of the material 1. an upper mold 3 having a groove 3a with a semicircular cross section and a concavo-convex portion 3b in a part of the groove 3a that almost matches the external shape of the rack tooth; and a lower mold having a groove 4α with a semicircular cross section that matches the outer peripheral surface of the material 1. 4, after applying molding pressure from the outside to the material 1 into which the core bar 2 is inserted, the lower core bar 22 is removed, and the upper core bar 21 is shifted downward and removed, thereby forming a part of the hollow shaft. A hollow rack shaft with rack teeth can be obtained.

The uneven portions 21α of the upper core metal 21 are formed on both sides of the uneven portions 21α and the inner periphery of the material 1 when the upper core metal 21 is inserted into the material 1 in combination with the lower core metal 22 as shown in FIG. A predetermined gap δ is formed between the upper mold 3 and the outer circumferential surface of the material 1, and both sides of the uneven portion 3b of the upper mold 3 have a predetermined gap δ between the outer circumferential surface of the material 1 and the outer peripheral surface of the material 1, as shown in FIG. The structure is configured such that a gap δ2 is formed between the two knees, and when molding pressure is applied by the upper die 3 and the lower die 4, galling of the core metal 2 is prevented and the flow of the material 1 is controlled. In addition, as shown in Fig. 3, the rack teeth are plastically deformed in a state that bulges into the gap, and the effective tooth trace length of the rack teeth after molding is approximately equal to the diameter of material 1. It can be made longer, and it is possible to improve the meshing strength with the pinion and to make the meshing smoother.

As shown in Fig. 4, the hollow rack shaft has, in addition to the rack teeth α, holes for air passage, grooves C for inserting tie rod rotation prevention pieces, or flat surfaces d for receiving spanners, which improve ease of assembly and disassembly. However, by providing molding elements other than the rack teeth a in the semicircular cross-section grooves 3α and 4α of the upper mold 3 and lower mold 4, it is possible to form a single-processed culm. You can obtain a rack shaft with a completed shape.

Moreover, by constructing the upper core metal 21 and the lower core metal 22 with a material having appropriate flexibility, such as SK material,
It may also be possible to obtain a rack shaft having an arbitrary shape suitable for the mold consisting of the lower mold 4 and the lower mold 4.

In other words, the rack shaft on which the rack teeth α are formed in a part is slightly deformed on the side where the rack teeth α are provided after molding [7, and correction work is required, but as described above, the core metal 2 is moderately deformed. By simply constructing the upper mold 3 and the lower mold 4 into a desired shape by using a material with flexibility of It can be easily formed, and correction work for deformation after molding can be largely omitted.

More racks! By arbitrarily selecting the shape of the uneven portion 3b of the upper die 3, the shape of #α is not limited to the 1GHj shape, but can also be modified as shown in FIG. 5
As shown in Figure (B), any tooth profile such as a rowing tooth profile can be easily obtained without additional processing or special processing.

As described above, according to the present invention, the upper core metal has an uneven portion on its upper surface that roughly matches the rack tooth profile, and the lower core has an arcuate peripheral surface that matches a part of the inner peripheral surface of the hollow pipe-shaped material. We use a core metal made of a combination of gold and plastically deform a hollow pipe-shaped material using the core metal and upper and lower molds to form a hollow rack shaft that partially has rack teeth. Forming the rack teeth is extremely simple and easy, and not only can the tooth profile of the rack teeth be freely selected without the need for additional or special processing, but the plate thickness at the bottom of the rack teeth can be made almost equal to the thickness of the material. , which is very advantageous in terms of strength, and it is possible to obtain a hollow rack shaft with sufficient strength without using unnecessarily thick pipe material, resulting in a significant weight reduction. It can be used to improve productivity and reduce costs, which can bring great practical effects.

[Brief explanation of drawings]

Figure 1 is a perspective view schematically showing the core metal and mold used in the present invention, Figure 2 is a cross-sectional view showing the core metal inserted into the material, and Figure 6 is pressure forming using the mold. A cross-sectional view of the state
FIG. 4 is a perspective view showing a rack shaft 81I formed by the method of the present invention, and FIGS. It is. 1...Material, 2...Core metal, 21...Upper core metal, 2
2...Lower core metal, 3...Upper mold, 4...Lower mold, 21
α, 3b...Uneven portion. Above bone 7 figure 265 spear 2!2] wa figure e. Confrontation (I) (0)

Claims (2)

[Claims] (1) An upper core metal having an uneven portion on its upper surface that matches the rack tooth profile, and a lower core metal having an arc-shaped peripheral surface that approximately matches a part of the inner peripheral surface of a material made of hollow pipe material, The inner and lower parts are inserted into the material made of the hollow pipe material, and the upper and lower molds are shaped to fit the outer shape of the rack shaft, which is densely packed with uneven parts that almost match the outer sides of the rack teeth. A method for manufacturing a hollow rack shaft, characterized in that after processing and forming a material into which a core metal is inserted, the lower core metal is extracted, and then the upper core metal is shifted downward and extracted to obtain a hollow rack shaft. . (2) The upper core metal and the lower core metal are made of IM material with appropriate flexibility, and the upper and lower molds are shaped to accommodate the necessary amount of deformation after forming the hollow rack shaft. 2. The method for manufacturing a hollow rack shaft according to claim 1, wherein the hollow rack shaft is processed and molded.