JPH115138A - Making of rack bar - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light rack bar at a low price by pressing the peripheral part of the longitudinal required range of a thick walled pipe material and processing a tooth form on the flat thick part and by squeezing an outer diameter of the longitudinal part of the other part of the pipe material to the small diameter so that the thickness of the other part is thinner than the thickness of the flat part. SOLUTION: The broach moves down in the longitudinal direction to contact with the flat part of the pipe material 1 and by front-back direction movement, it processes the tooth form of the rack 6. A core metal 7 with the outer diameter approximately similar to the inner diameter of the pipe material 1 is inserted to the pipe 1 from the edge opposite to the tooth form to the position close to the tooth form. And also the circumference side of the pipe 1 close to the tooth form is made constricted before squeezing, the die 8 installed outside of the pipe material 1 moves in an arrow direction for squeezing, and the thickness of the pipe material 1 is decreased. In this case, as the thickness of the pipe material 1 becomes, for example, 1/2 by squeezing, the length of the pipe material 1 is extended accordingly.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rack bar used for a steering mechanism and the like of an automobile and a method of manufacturing the same.

[0002]

2. Description of the Related Art As a steering mechanism of an automobile, for example, a rack and pinion system in which a pinion fixed to a steering shaft and a rack on a front wheel steering side are engaged with each other so that the front wheels are steered by rotation of the steering shaft. is there.

[0003] The rack used in this type of mechanism has a rack tooth formed by cutting one surface of a metal round bar. However, the rack bar manufactured in this manner requires many man-hours and is heavy. However, there has been a problem that the size of the rack bar is large and the cost is high. Therefore, a technique for forming a rack bar from a pipe material has recently been disclosed in, for example, Japanese Patent Publication No. 3-5892. Further, the technique described in Japanese Patent Application Laid-Open No. Hei 6-246379, which is an application of the present applicant, includes placing a pipe material in a manufacturing mold and heating the upper surface of the pipe material from an opening portion opened in the longitudinal direction of the mold. After softening, and then processed into a flat surface by a press die from the opening, take out the pipe material, put it into a tooth mold manufacturing die having manufacturing teeth on the inner surface, and press-fit a metal core into the pipe material. A method for forming a tooth row by pressing the flat surface into a tooth profile is disclosed.

[0004]

However, in the above prior art, a part of the peripheral surface of a round pipe is flatly pressed by a flat mold to form a flat surface, and a tooth mold is formed on the flat surface from the inside. Since it is manufactured by extrusion, the meat is compressed to both sides during the first flattening process, making it difficult to secure the thickness of the flat surface. There is a problem that it is not sufficiently filled, it is difficult to obtain a desired tooth shape, and the thickness of the material at the bottom of the tooth becomes thin.

[0005] The same applies to the case where a round pipe is flatly pressed to form a flat surface on a part of its peripheral surface by a flat mold, and a tooth mold is formed on the flat surface by broaching from the outside. It is said that if the thickness of the round pipe is thin, sufficient tooth height cannot be obtained, and if a thick pipe is used in order to obtain a sufficient tooth height, the weight increases as in the case of the round bar, and the cost increases. The problem was inevitable.

[0006]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and it is an object of the present invention to provide a rack bar made of a thick pipe and a method of manufacturing the same. The measure is to make the tooth profile thicker and the other parts thinner.

That is, the first aspect of the present invention provides a first step of forming a peripheral portion of a thick pipe material in a required range in the longitudinal direction into a flat surface by press working, and forming a longitudinal portion on the flat portion forming the flat portion. A second step of processing a plurality of rows of tooth profiles perpendicular to the direction, and ironing the outer diameter of the other portion of the pipe material in the longitudinal direction to a small diameter so as to be thinner than the thickness of the flat surface. And a third step of performing the following.

The invention according to claim 2 is the one in which the order of the tooth profile processing and the diameter reduction processing is reversed, and the peripheral portion of the thick pipe material in a required range in the longitudinal direction is formed into a flat surface by pressing. A second step of forming the outer diameter of another portion of the pipe member in the longitudinal direction to a small diameter by ironing so as to be thinner than the thickness of the flat surface; And a third step of machining a plurality of rows of tooth profiles at right angles to the longitudinal direction on the flesh portion forming the shape.

A third aspect of the present invention is characterized in that, in the invention of the first or second aspect, the tooth profile processing is broaching.

According to a fourth aspect of the present invention, a plurality of rows of tooth profiles perpendicular to the longitudinal direction of the pipe material are formed on a flat surface formed in a required range in the longitudinal direction of the pipe material, The range is that the rack bar is formed to be thinner than the wall portion of the flat bearing surface.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to embodiments shown in the drawings.

FIGS. 1 to 8 show a method of manufacturing a rack bar according to the first aspect of the present invention. FIG. 1 is an external perspective view of a pipe material 1 for manufacturing a rack bar.

The pipe material 1 is made of STKM15-
A steel pipe having a large carbon content of 16 is used. For example, a steel pipe having an outer diameter of 30 mm and a wall thickness of 4 to 6 mm (usually 2 to 3 mm in the case of the outer diameter) is used.

FIG. 2 shows a flat surface 2 of the pipe blank 1 shown in FIG.
FIG. 2 (A) shows a state in which the left and right sides of the outer peripheral surface other than the upper surface of the pipe blank 1 to be machined are pressed by two holding dies 2a and 2b, and the pipe blank 1 is machined from above. The first press die 3 having a length corresponding to the flat surface to be formed and having a concave surface 3a in which the lower surface perpendicular to the concave surface is depressed in a substantially mountain shape, is first pressed into a cross section at the upper part of the pipe blank 1. The convex portion 1a having a mountain shape is formed as shown in FIG. 2B, the convex portion 1a is heated, and then the convex portion 1a having the mountain shape is pressed by a second press die 4 having a flat lower surface. 2
A flat surface 1b is formed as shown in FIG.

In the embodiment of FIG. 2, the case where the flat surface 2 is formed sequentially by the first press die 3 and the second press die 4 has been described. However, the flat surface 2 is formed by one press die at a time. It may be.

FIG. 4 shows a configuration in which a plurality of rows of teeth are formed on the flat surface 1b of FIG. 3 by broaching. This broach 5 has a plurality of rows of teeth as shown by a two-dot chain line. The height of the teeth is 5a, 5b. 5c, ...
The one provided from a low state to a high state is used.

Accordingly, as shown in the figure, the broach 5 is lowered as shown by the arrow at right angles to the longitudinal direction of the pipe blank 1, and moved in the front-rear (arrow) direction while making contact with the flat surface 1b to process the tooth profile 6 of the rack. I do. Thereby, the tooth profile 6 as shown in FIG. 5 is formed.

FIG. 6 shows an example of a step of thinning the other portion of the pipe material 1 in the longitudinal direction by ironing. From the end of the pipe material 1 on the opposite side to the tooth profile 6,
After inserting a metal core 7 having an outer diameter close to the inner diameter up to a position close to the tooth form 6, a constriction 1 c is formed on the outer peripheral side of the pipe material 1 close to the tooth form 6 before ironing. The die 8 attached to the outer periphery of the pipe material 1 is moved in the direction of the arrow to squeeze it, thereby reducing the thickness of the pipe blank 1. In the figure, 8a is a blade. In this case, the thickness of the pipe blank 1 is reduced to about 1/2 of that of the pipe blank 1, so that the length of the pipe blank 1 is extended accordingly.

FIG. 7 is a perspective view showing the appearance of the rack bar 1A which has been completed by the ironing process shown in FIG. 6. In this case, the end of the tooth profile 6 is not ironed, but this part may be omitted if necessary. May be ironed.

FIG. 8 is a longitudinal sectional view of FIG. 7, where t ₁ is the thickness on the flat surface 1b side and t ₂ is the thickness on the squeezed side, and 2t ₂ = t It is desirable to set it to ₁ .

The method of manufacturing a rack bar according to the second aspect of the present invention is obtained by reversing the second and third steps of the first aspect of the invention. It is possible to

[0022]

As described above, according to the present invention, a rack bar manufactured from the same pipe material does not suffer from the shrinkage of the teeth forming portion, the tooth profile portion of the rack is thick, and portions other than the rack are formed. Can be molded into a thin wall and the strength is increased by work hardening, so that even if a sufficient tooth height is obtained, the weight is light and the strength is not inferior to the case of manufacturing from a round bar material, and therefore, a light weight rack Bars can be provided cheaply.

[Brief description of the drawings]

FIG. 1 is an external perspective view of a pipe material for obtaining a rack bar according to the present invention.

FIGS. 2A and 2B are cross-sectional views showing a process of forming a flat surface on the pipe material of FIG. 1, wherein FIG. 2A is a state before processing, FIG. 2B is a state during processing, and FIG.

FIG. 3 is an external perspective view showing a state where a flat surface is formed on the pipe material of FIG. 1;

FIG. 4 is an external perspective view showing a state in which broaching for forming teeth is performed on the flat surface of FIG. 3;

FIG. 5 is an external perspective view in which a tooth profile of a rack is formed by the tooth forming profile of FIG. 4;

6 is an external perspective view showing a state where ironing is performed on the other side in the longitudinal direction without the rack in FIG. 5;

7 is an external perspective view showing a state where the rack bar of the present invention is completed by the ironing process of FIG. 6;

8 is a longitudinal sectional view of FIG. 7;

[Explanation of symbols]

 Reference Signs List 1 pipe material 1A rack bar 1b flat surface 2a, 2b mold 3 first press 4 second press 5 broach 6 rack 7 cored bar 8 die

Claims (4)

[Claims] 1. A first step of forming a peripheral portion of a thick pipe material in a required range in a longitudinal direction into a flat surface by press working, and forming a plurality of rows at right angles in a longitudinal direction to a wall portion forming the flat surface. A second step of processing the tooth profile; and a third step of forming the outer diameter of the other portion of the pipe material in the longitudinal direction to a smaller diameter by ironing so as to be thinner than the thickness of the flat surface. A method for manufacturing a rack bar. 2. A first step of forming a peripheral portion of a thick pipe material in a required range in the longitudinal direction into a flat surface by press working, and ironing the outer diameter of another portion of the pipe material in the longitudinal direction by pressing. A second step of forming a small diameter so as to be thinner than the thickness of the flat surface, and a third step of processing a plurality of rows of tooth profiles at right angles to a longitudinal direction in the wall portion forming the flat surface. A method for manufacturing a rack bar. 3. The rack bar manufacturing method according to claim 1, wherein the tooth profile processing is broaching. 4. A plurality of rows of tooth profiles perpendicular to the longitudinal direction of the pipe material are formed on a flat surface formed in a required range in the longitudinal direction of the pipe material, and the other range of the pipe material is defined by the flat surface. A rack bar characterized by being formed thinner than a meat portion.