JPH06182472A - Production method of rack bar - Google Patents

Abstract

PURPOSE:To sufficiently keep a wall thickness of a tooth series forming part of a tube material and to surely form a scheduled tooth shape. CONSTITUTION:A process forming a mountain shaped projecting part 5 on a tube material 2 by pressing a side surface of a tooth series forming range L of the tube material 2 with a press die 4 sinking to a section area of almost mountain shape like, a flattening process by pressing this mountain shaped projecting part 5 with a press and flattening, and a process where a normal tooth shape 9 is formed with a tooth series forming press die 8 or by cutting, are provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a rack bar.

[0002]

2. Description of the Related Art For example, as a steering mechanism of an automobile, there is a rack and pinion system in which a pinion fixed to a steering shaft and a rack on a front wheel steering side are meshed with each other to steer the front wheels by rotating the steering shaft. is there.

The rack used in this type of mechanism had one side of a metal round bar cut to form rack teeth, but the rack bar made in this way requires a lot of man-hours and a large weight. However, since there is a problem that the cost increases, a technique for forming the rack bar 1 as shown in FIG. 4 from a pipe material has been recently developed (for example, Japanese Patent Publication No. 3-58).
No. 92).

In the technique described in this publication, the pipe material is placed in a manufacturing die, the upper surface of the pipe material is heated and softened from an opening portion opened in the longitudinal direction of the die, and then the press die is opened from the opening portion. After processing it into a flat shape by taking out, the pipe material is taken out and put in a tooth mold manufacturing die having a manufacturing tooth mold row on the inner surface, the core metal is pressed into the pipe material and the flat surface is pressed into the tooth mold. To form a dentition.

[0005]

However, in the above conventional technique, a flat pipe is used to press a part of the peripheral surface of the round pipe in a flat shape to form a flat surface, and the flat surface has a tooth profile. Since it is manufactured by extruding from the inside, it is difficult to secure the wall thickness of the flat surface because the meat is compressed to both sides at the time of the first flattening process, and it is pressed from the inside to the tooth mold row of the tooth mold manufacturing tooth mold during tooth mold manufacturing. There was a problem that the tooth profile was not sufficiently filled when the tooth was made, it was difficult to obtain the expected tooth shape, and the material thickness of the tooth bottom portion was thin.

In view of this, the present invention provides a method for manufacturing a rack bar which can secure a sufficient thickness of a tooth row forming portion of a round pipe and can manufacture a tooth row having a predetermined tooth height. The purpose is to do.

[0007]

As a means for solving the problems of the above-mentioned prior art, the present invention uses a press die in which the side surface of the tooth row manufacturing range of the pipe material is depressed into a substantially mountain-shaped cross section. A step of pressurizing to form a mountain-shaped convex portion in cross section on the pipe material, a flattening step of flatly pressing the mountain-shaped convex portion by a press, and a dentition on this flat surface for press forming or cutting of a dentition The present invention is characterized in that it has a tooth profile manufacturing step formed by the above, and a press die having a coarse tooth die row may be used during the flattening process.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the embodiments shown in the drawings. The first step, the mountain-shaped convex portion manufacturing process, is shown in FIG.
As shown in the cross section in (A), the pipe material 2 having a circular cross section (for example, a round pipe material having an outer diameter of 25 to 30 mm and a wall thickness of 5 to 6 mm) is pressed by the holding molds 3 to fix the pipe material 2 As shown in FIG. 1 (B), the press die 4 has a length corresponding to the rack manufacturing range L (see FIG. 4) and has a concave die surface 4a in which a cross section orthogonal to the longitudinal direction is recessed into a substantially mountain shape. The rack manufacturing range of No. 2 is pressurized to form the convex portion 5 having a mountain-shaped cross section.

At the time of this processing, the meat on the upper surface of the pipe member 2 is manufactured only by deforming into a ridge-shaped cross-sectional shape without escaping to both sides.

Then, the required area (the dotted line area in FIG. 1B) including the ridge line portion 5a of the mountain-shaped convex portion 5 is heated (high frequency heating) to be red, and the mountain-shaped convex portion 5 is formed by the flat press die 6. Press to flatten (FIG. 1 (C)).

Thus, the rack manufacturing range L of the pipe material 2
Since the mountain-shaped convex portion 5 is pressed into the upper surface of the, the two sides 5b, 5b of the mountain shape are compressed only in the direction of the ridge line portion 5a and the meat is brought close to each other, resulting in sufficient meat as shown in FIG. 1C. The flat surface 7 has a thickness.

On the flat surface 7 thus formed, the tooth pattern row 8a is formed.
A rack rod as shown in FIG. 4 is obtained by forming the tooth profile 9 by press working with the tooth profile manufacturing press die 8 having the above or by cutting (broaching).

At the time of the flattening step, the press die 10 having the rough tooth die 10a that approximates the final tooth profile as shown in FIG. 2C.
If it is pressed and flattened, the rough tooth profile 9
Since a is formed, the machining allowance is reduced when the tooth profile is manufactured by the press die 8 for manufacturing the final tooth profile or the tooth profile is cut by the broaching, and the tooth profile can be easily manufactured by these. Note that FIGS. 2A and 2B are the same steps as those in FIG.

When the thickness of the pipe material 2 having the tooth profile 9 formed as described above outside the tooth row manufacturing range L is thicker than the required strength, as shown in FIG. Insert the cored bar 11 having the outer diameter, and insert the die 1
By reducing the wall thickness of the pipe material 2 by moving it in the direction of the arrow 2 and drawing it in a squeezing manner, the weight of the completed rack bar can be reduced and the strength can be increased by increasing the processing hardness. .

Although it is possible to manufacture the mountain-shaped convex portion 5 without using a cored bar, it is also possible to manufacture it with a cored bar. The same applies to flattening and rough dentition.

[0016]

As described above, according to the present invention, it is possible to manufacture a rack tooth with sufficient gingiva without causing shrinkage of the flesh of the tooth row manufacturing portion when manufacturing the rack tooth on the pipe material, A rack rod having a sufficient tooth height can be obtained.

[Brief description of drawings]

1A to 1D are explanatory views showing steps of an embodiment of the present invention.

2A to 2D are explanatory views showing the steps of another embodiment.

FIG. 3 is an explanatory sectional view showing still another embodiment.

FIG. 4 is a perspective view showing an example of a rack rod obtained by the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Rack rod 2 Pipe material 3 Holding type 4 Press type 4a Crest-shaped concave part 5 Crest-shaped convex part 5a Ridge line part 5b Side part 9 Flat press type 8 Tooth profile manufacturing press type 10 Core type press type 11 Core metal 12 dice

Claims (3)

[Claims] 1. A step of pressurizing a side surface of a tooth row manufacturing range of a pipe material with a press die recessed into a substantially mountain-shaped cross section to form a mountain-shaped convex section in the pipe material, and pressing the mountain-shaped convex section. A method of manufacturing a rack bar, comprising: a flattening step of flatly pressing by means of; and a tooth profile manufacturing step of forming a tooth row on this flat surface by a tooth row manufacturing press die or cutting. 2. A step of forming a mountain-shaped convex portion on the pipe material by pressurizing a side surface of a tooth row manufacturing range of the pipe material with a press die recessed into a substantially mountain-shaped cross section, and forming the mountain-shaped convex portion on the rough teeth. And a step of pressurizing with a press die having a die row to flatten the mountain-shaped convex portions and simultaneously forming a coarse tooth row, and a step of producing a regular tooth profile by a press die for tooth row production or cutting. Characteristic rack bar manufacturing method. 3. The method for manufacturing a rack bar according to claim 1, further comprising the step of thinning the pipe material outside the range of manufacturing the tooth row by drawing.