JP2001079639A - Manufacture of steering rack - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of a steering rack, with which the precision of a product can be improved by executing a deburring work on the product after forge-forming by using full enclosed dies when the forge- forming is executed. SOLUTION: After forge-forming a blank heated to the suitable temp. to a warm-forging by using the full enclosed dies M forming a run-off absorbing part 43 having a volume matched to the run-off amount in the blank with a plastic deformation along the side part of blank holding parts 30, 40 in the full enclosed dies M, the burr formed at the run-off absorbing part 43 is pressed off or mechanically cut off so as to finish the product to a prescribed dimension.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a steering rack, and more particularly to a method for manufacturing a steering rack suitable for manufacturing a variable steering rack (variable speed steering rack) having a complicated shape.

[0002]

2. Description of the Related Art At present, a constant steering rack having a simple shape can be manufactured relatively easily and at low cost by machining or cold forming.

On the other hand, a variable steering rack having a complicated shape is manufactured by a mechanical working method or various plastic working methods.

[0004] Among them, the mechanical processing method has a problem that it takes time for processing and the manufacturing cost is increased.

[0005] In the plastic working method, it is difficult to employ cold forming in order to mass-produce the mold in relation to the life of the mold and the like. Forging) is adopted.

[0006] When a long product such as a steering rack is forged, the material undergoes plastic deformation in the longitudinal and circumferential directions according to the shape of the product to be formed, ie, the shape of the mold. Therefore, conventionally, forging molding has been performed using an open mold capable of absorbing the plastic deformation. Then, the plastic deformation in the longitudinal direction of the material is eliminated by finishing to a predetermined size when performing mechanical finishing for attaching a tie rod or the like to the product after forging.

[0007]

As described above, since an open mold is used for the forging of the steering rack, the accuracy of the product is limited. There is a problem in that it cannot be provided, the position where burrs are generated is not specified, a cutting process for removing burrs requires time, and manufacturing costs increase.

The present invention has been made in view of the above-mentioned problems of the conventional method of manufacturing a steering rack, and in the case of forging, after forging using a closed mold, deburring of the product is performed. It is an object of the present invention to provide a method for manufacturing a steering rack capable of improving the accuracy of the steering rack.

[0009]

In order to achieve the above object, a method of manufacturing a steering rack according to the present invention comprises a method of manufacturing a steering rack, comprising the steps of: After forging the material heated to a temperature suitable for warm forging using a closed mold formed along the side of the material accommodating part, press-cut the burr formed at the escape absorption part Alternatively, it is characterized in that it is mechanically cut to finish it to a predetermined size.

[0010] This method of manufacturing a steering rack is characterized in that an escape absorbing portion having a capacity suitable for the amount of material escaped by plastic deformation is formed along the side of the material accommodating portion in the closed mold. Since the material is forged by using a mold, the product can be formed with high precision, and the position where burrs occur can be specified.

In this case, the escape absorbing portion can be formed in accordance with the amount of material escaped by plastic deformation in the same cross section.

Thus, plastic deformation can be performed smoothly, and a product can be formed with higher precision.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a method for manufacturing a steering rack according to the present invention will be described below with reference to the drawings.

Referring to FIG. 1, the steps of the method for manufacturing a steering rack according to the present invention include a variable steering rack 2 (hereinafter simply referred to as a "steering rack") having rack teeth 21 and 22 having different shapes shown in FIG. ) Will be described as an example.

First, a material 1 suitable for a steering rack to be manufactured, for example, a round bar-shaped material 1 such as medium carbon steel is cut into a predetermined length (FIG. 1 (1)).
The rough lace processing is performed according to the shape of the steering rack to be formed as necessary (FIG. 1 (2)).

Next, the raw material 11 which has been subjected to rough lace processing as required is heated to a temperature suitable for warm forging, for example, 75 ° C.
Heat to 0 ° C. to 900 ° C. (this temperature varies depending on the material 11) (FIG. 1 (2)). The heating of the material 11 can be performed using a heating furnace, but is performed by induction heating or energization heating, more specifically, by applying an electric current through electrodes connected to both ends of the material 11 to a predetermined set temperature for each part. It can be performed by heating rapidly. As a result, it is possible to heat to a predetermined temperature in a short time, to prevent the generation of oxide scale and decarburization, and to precisely control the temperature for each part according to the shape of the steering rack to be molded. What you can do.

Next, the heated material 12 is placed in the upper mold 3
Forging (FIG. 1 (3), (4)) is performed by the closed mold M including the lower mold 4 so as to have a predetermined shape.

As shown in FIGS. 2 to 4, the upper mold 3 is provided on the outer periphery of the steering rack 2 and in particular, on the rack tooth 2
The outer shape on the side opposite to the side on which the first and second 22 are formed is adjusted to a columnar shape which is the outer peripheral shape of the steering rack 2.
A bar-shaped material housing portion 30 for housing the heated material 12 is formed in the longitudinal direction.

As shown in FIGS. 2, 3 and 5, the lower mold 4 is formed by heating the raw material 12 having the outer periphery of the rack tooth profile of the steering rack 2, particularly the rack tooth profiles 21 and 22 being prepared and heated. A groove-shaped material accommodating portion 40 for accommodating the material is formed in the longitudinal direction thereof, and rack tooth-shaped recesses 41 and 42 for forming rack tooth shapes 21 and 22 are formed on the bottom surface of the material accommodating portion 40. I do. Further, the position of the side of the material accommodating portion 40, for example, FIGS.
As shown in FIG. 5, escape absorbing portions 43, 43 for absorbing escape of the material due to plastic deformation are formed on both sides of the material accommodating portion 40 and along the longitudinal direction of the material accommodating portion 40.

The escape absorbing portion 43 for absorbing the escape of the material due to the plastic deformation further depends on the tooth shape to be formed by the lower mold 4, that is, the shape of the rack-shaped recesses 41 and 42, and the like. Is formed in such a shape that the middle portion becomes wide as shown in FIG. 5, for example, in accordance with the position where the plastic deformation of the material occurs and to have a volume corresponding to the amount of plastic deformation of the material. To do. In this embodiment, the escape absorbing portion 43 is provided with a rack-shaped recess 4.
1 and the shape of the depression 42 are different, and accordingly, the amount of plastic deformation of the material is different. Therefore, the shape of the escape absorbing portion 43 is determined and formed so as to absorb the deformation amount.

In this case, in particular, by forming the escape absorbing portion 43 in accordance with the amount of material escaped by plastic deformation in the same cross section, plastic deformation can be performed smoothly.
The product can be molded with higher precision.

Further, in the embodiment, the escape absorbing portion 43
Although the depth of each of them is made constant and the width is changed, the width may be made constant and the depth may be made different.

Thus, even in the case of a product such as a variable steering rack, which has a complicated shape and the amount of plastic deformation of the material is different for each part, the escape of the material due to the plastic deformation is reliably absorbed by absorbing. In addition, the plastic change in the circumferential direction is generated as a burr in a shape constrained at a predetermined position, and the forming accuracy of the material accommodating portion 40 and the rack-shaped recesses 41 and 42 can be improved. It will be. When the steering rack 2 thus formed penetrates a steering housing (not shown), the steering rack 2 can slide smoothly.

The material 12 is divided into an upper mold 3 and a lower mold 4.
When pressed by a predetermined pressing force by the closed mold M composed of:
Part escapes and burrs occur. However, since the position of the burr is specified by the escape absorbing portion 43, the material 12
In a step after forging the burrs, the formed burrs can be uniformly and mechanically cut to finish to a predetermined size. For this reason, deburring can be performed easily, the manufacturing cost can be reduced, and the accuracy of the product can be improved.

When a mechanical finishing process for attaching a tie rod or the like to a product is performed, the product is finished to a predetermined size so that longitudinal plastic deformation is eliminated. FIG. 6 shows the steering rack 2 thus formed. This steering rack 2 is provided with rack tooth profiles 21 and 22 having different shapes at the tip of a round bar-shaped main body 20.
Is formed.

In the above embodiment, the rack-shaped recesses 41, 22 forming the rack-tooth shapes 21, 22 are formed in the lower mold 4.
Although 42 and the escape absorbing portion 43 are formed, they can be formed in the upper mold 3 or both the upper mold 3 and the lower mold 4.

[0027]

According to the manufacturing method of the steering rack of the present invention, the escape absorbing portion having a capacity adapted to the amount of material escaped by plastic deformation is formed along the side of the material accommodating portion in the closed mold. Since the material is forged using a closed mold formed by molding, the product can be molded with high accuracy, the position where burrs are generated is specified, and burrs are formed by mechanical cutting in the subsequent process. The machining can be easily performed, and the manufacturing cost of the steering rack can be reduced.

Further, since the escape of the material due to the plastic deformation is absorbed in accordance with the shape of the steering rack to be formed and in accordance with the position where the plastic deformation of the material occurs, the deburring process is simplified. And the accuracy of the product can be improved.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing an example of steps of a method for manufacturing a steering rack according to the present invention.

FIG. 2 is a front sectional view of a mold used in the method of manufacturing a steering rack according to the present invention.

FIG. 3 is a side sectional view showing the same mold.

FIG. 4 is a plan view showing the same mold, with the upper mold facing upward;

FIG. 5 is a plan view showing the lower mold.

FIG. 6 shows a steering rack manufactured by the manufacturing method of the present invention, wherein (A) is a plan view, (B) is a front view,
(C) is a bottom view, and (D) is a side view.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Material 11 Cutting material 12 Heated material 2 Steering rack 20 Main part 21 Rack teeth 22 Rack teeth 3 Upper die 30 Material storage part 4 Lower die 40 Material storage part 41 Rack tooth-shaped hollow 42 Rack tooth-shaped hollow 43 Escape absorbing part M Closed mold

[Procedure amendment]

[Submission Date] September 17, 1999 (1999.9.1)
7)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0027

[Correction method] Change

[Correction contents]

[0027]

According to the manufacturing method of the steering rack of the present invention, the escape absorbing portion having a capacity adapted to the amount of material escaped by plastic deformation is formed along the side of the material accommodating portion in the closed mold. Since the material is forged using a closed mold formed by molding, the product can be molded with high accuracy, and the burr generation position is specified, making it easy to remove deburring in the subsequent process The manufacturing cost of the steering rack can be reduced.

Claims (2)

[Claims] An escape absorbing portion having a capacity adapted to an amount of material escaped by plastic deformation is warmed by using a closed mold formed along a side of a material accommodating portion in the closed mold. After forging a material heated to a temperature suitable for forging, a burr formed at the escape absorbing portion is pressed or mechanically cut to finish it to a predetermined size. Manufacturing method. 2. The steering rack manufacturing method according to claim 1, wherein the escape absorbing portion is formed in accordance with an escape amount of the material due to plastic deformation in the same cross section.