WO2008123654A1

WO2008123654A1 - Automobile hollow style steering rack bar and the manufacture method

Info

Publication number: WO2008123654A1
Application number: PCT/KR2008/000463
Authority: WO
Inventors: Ho Jin Hwang
Original assignee: Yoonsong Tech Co., Ltd.
Priority date: 2007-04-06
Filing date: 2008-01-25
Publication date: 2008-10-16
Also published as: KR100794927B1

Abstract

The present invention relates to a steering rack bar, which is one of the important parts for transferring steering force to wheels, when a steering wheel is turned for the steering in an automobile, and more particularly, to a method of manufacturing a steering rack bar for an automobile, which can manufacture the steering rack bar more simply and efficiently, thereby achieving lightness of the steering rack, and a steering rack bar manufactured thereby. The method of manufacturing the steering rack bar for the automobile according to the present invention comprises the steps of cutting a prepared hollow tubular material 10 into a desired length; primarily extruding the cut material to have a desired maximum diameter in the whole; secondary extruding the extruded material so that only a gear portion 14 for forming a rack gear 13 is extruded to reduce an outer diameter thereof thereof; tertiarily extruding one side of the gear portion 14 for forming a plane portion 15; forming a rack gear 13 at the gear portion 14 through a broach working or a hot forging; performing a heat-treatment on the worked rack gear 13 to thereby improve a hardness; and grinding the entire outer diameter of the steering rack bar to make a surface thereof to be neat, and the like.

Description

AUTOMOBILE HOLLOW STYLE STEERING RACK BAR AND

THE MANUFACTURE METHOD

Technical Field

[1] The present invention relates to a steering rack bar which is an important part of a steering system of an automobile for transferring directional manipulation of the steering wheel to wheels, and more particularly, to a method of manufacturing a steering rack bar more effectively, which improves the steering rack bar from a conventional solid type steering rack bar to a hollow type steering rack bar, thereby simplifying the construction of the steering rack bar and lightening the weight, and increasing efficiency of the manufacturing process. Background Art

[2] As well known in the art, when a driver turns a steering wheel to convert a traveling direction in an automobile, the steering rack bar in a power cylinder is moved by a hydraulic pressure introduced upon the opening and closing of a pinion valve in response to the rotational displacement of a torsion bar so as to transfer the steering force to the wheels.

[3] Such a conventional steering rack bar can be called a solid type steering rack bar, which is manufactured by machining a round rod to thereby form a rack gear having a desired diameter and outer appearance. Thus, the conventional steering rack bar manufactured by the machining was significantly heavy, which is one of the important factors obstructing the fuel reduction and the lightness of the automobile.

[4] In addition, since it is required to process an outer surface to obtain the desired diameter or to form holes, rack gears and the like along with the machining of the round rod to manufacture the steering rack bar, much time and cost are spent for the working due to lots of machining processes, so that a large amount of material is dissipated. Disclosure of Invention

Technical Problem

[5] Accordingly, the present invention has been devised to solve such conventional problems, and an object of the present invention is to provide a steering rack bar which can be manufactured by extruding a tubular material to obtain a desired thickness and length of the material and forming a rack gear through a cutting or a hot forging, thereby reducing the weight and manufacturing cost of the steering rack bar and minimizing the dissipation of material. Technical Solution [6] To achieve the above object, the present invention provides a method of manufacturing a steering rack bar for an automobile, comprising the steps of cutting a prepared hollow tubular material 10 into a desired length in consideration of a length of a product to be manufactured and an extrusion degree; primarily extruding the cut material to have a desired maximum diameter in the whole; secondarily extruding the extruded material so that one side of the primarily extruded material, in other words, a gear portion 14 for forming a rack gear 13, is extruded to reduce an outer diameter thereof; tertiarily extruding the secondarily extracted material to form a plane portion 15 by compressing only one side of the gear portion 14 reduced through the secondary extruding process; working a rack gear for forming a rack gear 13 at the gear portion 14 through a broach working or a hot forging; heat treating the rack gear for improving a hardness by performing a heat- treatment of the worked rack gear 13; and grinding an entire outer periphery of the steering rack bar to make a surface thereof smooth.

[7] The present invention is also characterized in that it is manufactured through an extrusion of a pipe shape (tubular shape) material 10, and is shaped into a tubular body having a hole passing through an entire length of the material, wherein a portion for forming a rack gear 13 is made thicker than a remaining portion, and the rack gear 13 is formed by performing a broach working or a hot forging on a plane portion 15, which is formed again after the reduction of a diameter by the extrusion.

Advantageous Effects

[8] Therefore, the present invention as described above is a useful invention, which can assist the technical development of the automobile industry, because it is possible to simply and easily manufacture a steering rack bar, which is one of the substantially important parts of the automobile steering system, and it is also possible to manufacture it with low cost and achieve lightness of the steering rack bar to thereby contribute to the fuel reduction, and it is possible to provide a steering rack bar with more rigid and improved strength as compared to the conventional rack bar, and the like. Brief Description of the Drawings

[9] FIG. 1 is a process diagram showing a manufacturing method of the present invention;

[10] FIG. 2 is a view showing sequential states of the manufacturing method of the present invention.

[11] <Description of the numerals in the drawings>

[12] 10: material 10a: steering rack bar

[13] 11: small diameter hole 12: large diameter hole

[14] 13: rack gear 14: gear portion [15] 15: plane portion 16: foaming portion

[16] 17: hoi

Mode for the Invention

[17] The present invention is characterized by obtaining a length and a thickness required for a steering rack bar by extruding a solid tubular material, and completing the steering rack bar by performing a minimum machining work. Hereinafter, the concrete method of manufacturing a steering rack bar of the present invention, and a preferred embodiment of the present invention will be described in detail with reference to the appended drawings.

[18] Herein, FIG. 1 is a view showing a sequence of the manufacturing process of the present invention, and FIG. 2 is a view showing respective state of the sequence of the manufacturing process of the present invention.

[19] Hereinafter, the method of manufacturing the steering rack bar of the automobile steering wheel of the present invention will be at first described in detail.

[20] Material cutting process

[21] In this process, a hollow pipe shaped material 10 is prepared and is cut into a desired length, which can be previously designed according to a length of a product to be manufactured and an extrusion degree.

[22] Primary extrusion process

[23] In this process, the cut material is extruded to have a maximum diameter required in the whole. In this case, a small diameter hole 11 having a small inside diameter is formed at one portion of the material where a rack gear will be formed, and a larger diameter hole 12 having a diameter larger than that of the small diameter hole is formed at the remaining portion of the material.

[24] Secondary extrusion process

[25] An extrusion is carried out on one side of the material extruded primarily, i.e., a gear portion 14 where the rack gear 13 will be formed to reduce an outer diameter.

[26] Tertiary extrusion process

[27] A compressing work is carried out on only one side of the gear portion 14 with a diameter reduced through the secondary extrusion process to thereby form a plane portion 15.

[28] Foaming process of both ends

[29] A foaming process is carried out on a partial region at both ends of the material to thereby form a foaming portion 16 where a diameter thereof is reduced, and simultaneously a hole 17 with a predetermined depth is formed at the inside of the foaming portion 16 located at the end of the gear portion 14. In this case, a process of calibrating a bending of the material may be further carried out in addition to the above process.

[30] Fitting of the section and the entire length

[31] The entire length of the material is fitted through a lathe cutting work so that it falls within the predetermined length range together with a finishing of both sections of the material. In this case, a thread is formed at the hole 17 formed at the previous process through a tapping work.

[32] Forming process of a rack gear

[33] A rack gear 13 is formed at the gear portion 14 through a broaching work. In this case, the rack gear 13 may be formed by a different method, which is carried out by a hot forging after heating the gear portion 14 locally.

[34] Precious cutting of a rack gear

[35] A precision may be improved by a further precious cutting of the rack gear 13 when the rack gear 13 is formed through the hot forging.

[36] Heat-treatment process of the rack gear

[37] A hardness of the rack gear 13 is improved by carrying out the heat-treatment on the worked rack gear 13.

[38] Grinding process

[39] A neat surface is achieved through a grinding of the entire outer periphery.

[40] Bending calibration process

[41] A bending calibration is carried out to complete the manufacture of the rack bar

10a.

[42] Thus, the steering rack bar 10a manufactured through the above processes is characterized in that it is manufactured through an extrusion of the pipe shape (tubular shape) material 10, and it is shaped as a hollow body (tubular shape) having a larger diameter hole 11 and a small diameter hole 12, and a portion for forming a rack gear 13 is constructed to be thicker than a different portion.

[43] In addition, the rack gear 13 is characterized by formed by performing a broach working or a hot forging on the plane portion 15, which is obtained after the reduction of the diameter by the extrusion.

[44] According to the steering rack bar of the automobile steering system of the present invention, which is manufactured by the method of the present invention and constructed as above, a substantial shape of the steering rack bar is completed through the extrusion of the tubular material 10 in the whole to minimize the work. Accordingly, structure of the obtained steering rack bar becomes to be very precious in comparison with that of the conventional steering rack bar, which was manufactured by a cutting entirely, so that a wear-resistant property is greatly increased and a hardness and a rigidity are largely improved.

[45] Especially, since the plane portion 15 is made thicker than a remaining portion of the material to form the rack gear 13, and then it is worked or hot forged into the rack gear 13, the rack gear 13 can well endure a large force and stress applied thereon. [46] Moreover, it is possible to relatively reduce the weight of the steering rack bar in comparison with the conventional steering rack bar because it is manufactured by the extrusion and has a hollow hole formed at the center thereof.

Claims

[1] A method of manufacturing a steering rack bar for an automobile, comprising the steps of: cutting a prepared hollow tubular material 10 into a desired length in consideration of a length of a product to be manufactured and an extrusion degree; primarily extruding the cut material to have a desired maximum diameter in the whole; secondarily extruding the extruded material so that one side of the primarily extruded material, which is a gear portion 14 for forming a rack gear 13, is extruded to reduce an outer diameter thereof; tertiarily extruding the secondarily extracted material to form a plane portion 15 by compressing only one side of the gear portion 14 reduced through the secondary extruding process; forming a rack gear 13 at the gear portion 14 through a broach working or a hot forging; performing a heat- treatment on the worked rack gear 13 to thereby improve a hardness; and grinding an entire outer periphery of the steering rack bar to make a surface thereof smooth. [2] A steering rack bar for an automobile, which is manufactured through an extrusion of a pipe shape (tubular shape) material 10, and is shaped into a tubular body having a hole passing through an entire length of the material, and in which a portion for forming a rack gear 13 is made thicker than a remaining portion, and the rack gear 13 is formed by performing a broach working or a hot forging on a plane portion 15, which is formed again after the reduction of a diameter by the extrusion.