KR20100077393A

KR20100077393A - Manufacturing method of the worm-shaft for mdps

Info

Publication number: KR20100077393A
Application number: KR1020080135316A
Authority: KR
Inventors: 이양화
Original assignee: 주식회사 보은금속
Priority date: 2008-12-29
Filing date: 2008-12-29
Publication date: 2010-07-08

Abstract

The present invention relates to a method of manufacturing a worm shaft used in a motor driven power-steering system (MDPS), which is an electric power steering system of a vehicle steering apparatus, wherein the worm shaft includes a head part and a shaft part, and among the shaft parts. A first forging step in which a worm gear is formed in a portion, and the head-shaft portion is continuously formed while varying the diameter of the smooth rod-shaped member made of carbon steel; A secondary precursor step of forming a concave shape so that a plurality of protrusions are formed on the head portion; A precursor step of processing the worm gear at a portion where the worm gear is to be formed; The CNC finishing step of holding the center on the same axis of both ends of the rolled product to perform the finishing operation for the whole including the worm gear formed by the roll in the CNC; it is configured to include a reduction in raw materials to reduce manufacturing costs The worm gear is a final process with respect to the center shaft of the worm shaft to provide a method for manufacturing a worm shaft for MDPS, characterized in that it can provide a worm shaft of excellent quality.

Description

Manufacturing method of the worm-shaft for MDPS

The present invention relates to a method of manufacturing a worm shaft used in a motor driven power-steering system (MDPS), which is an electric power steering system of a vehicle steering apparatus.

MDPS is a futuristic steering device that is one step ahead of the existing hydraulic power steering system. If the hydraulic power steering system is a first-generation power steering system that can be used to easily operate the steering wheel, MDPS is a power steering system. (ECU) is attached to enable optimal steering performance according to the driving conditions of the vehicle.

A brief description will be made of the elements constituting the MDPS, and the attached FIG. 1 shows the main components used in the MDPS.

As shown, a worm shaft 20, a sleeve 30, an output shaft 40, an input shaft 50, and the like are provided in the housing 10, and the worm shaft 20 is connected to a worm wheel (not shown). Corresponds to the part to transmit the rotational force.

2 is a schematic perspective view showing the final shape of the worm shaft, and as shown, the worm shaft 20 may be divided into a head part 20a and a shaft part 20b and the shaft part 20b. ), A worm gear 21 is formed, and the head portion 20a is provided with a plurality of protrusions 22.

A method of manufacturing the worm shaft as described above according to the prior art will be introduced.

In the manufacture of a worm shaft according to the conventional method was prepared by cutting the rod-shaped member to a predetermined length after cutting while reducing the diameter to match the dimensions of each part. In addition, the worm gear was designed to perform gear processing in a separate process, and since there were many cutting processes, the free cutting steel was used. In addition, since it was manufactured through cutting, it took a lot of time and there was a problem that a lot of cutting tools were consumed. In addition, the worm gear should be formed as a separate process in the shaft part. In this case, since the center axis of the worm shaft is not a standard, the entire rotation center of the manufactured worm shaft and the rotation center of the worm gear are not exactly matched. There was a fatal defect that caused a lot of vibration.

Recently, the automotive industry is trying to increase the market share by strengthening competitiveness through quality improvement and cost reduction under the global infinite competition system. Conventional worm shaft manufacturing methods used for MDPS were often difficult to have sufficient competitiveness. Therefore, the need for a new method of manufacturing a warm shaft is urgently required.

Therefore, in the present invention, it is possible to supply the worm shaft used for the MDPS at a lower cost while securing high productivity, and at the same time, the quality of the final product is also improved to minimize the noise and vibration that may be caused by the worm gear part. It is a main problem to provide a manufacturing method of a worm shaft.

The present invention for achieving the problem as described, relates to a method of manufacturing a worm shaft used in the MDPS which is an electric power steering system of an automobile, wherein the worm shaft is composed of a head portion and a shaft portion and in some sections of the shaft portion A first forging step in which a worm gear is formed, and the head-shaft portion is continuously formed while varying the diameter of the smooth rod-shaped member made of carbon steel; A secondary forging step of forming a concave shape so that a plurality of protrusions are formed on the head portion; A precursor step of processing the worm gear at a portion where the worm gear is to be formed; The CNC finishing step of holding the center on the same axis of both ends of the rolled product to perform the finishing operation for the whole including the worm gear formed by the roll in the CNC; it is configured to include a reduction in raw materials to reduce manufacturing costs It proposes a method for manufacturing a worm shaft for MDPS, characterized in that the worm gear is finally processed about the center shaft of the worm shaft can provide a worm shaft of excellent quality.

According to the manufacturing method of the worm shaft for MDPS according to the present invention can reduce the manufacturing cost and ensure the price competitiveness, the noise or vibration that can be caused by the worm gear is reduced and the effect that it can take a comparative advantage in terms of quality have.

Hereinafter will be described in more detail with respect to the manufacturing method of the worm shaft for MDPS according to the present invention, it will be referred to the related drawings as a means for helping the understanding of the present invention.

Figure 3 corresponds to a flow chart according to the work process, Figure 4 corresponds to a work flow chart. The worm shaft 20 used as a part of the MDPS constituting the steering device of the vehicle is divided into a head portion 20a and a shaft portion 20b, and a worm gear 21 is formed in a portion of the shaft portion 20b. By connecting with the worm wheel (not shown) is the transmission of the rotational force is made.

The worm shaft manufacturing method of the present invention has two major characteristics which are largely different from those of the conventional manufacturing method. First, the material itself should be replaced with inexpensive carbon steel, and second, the concrete manufacturing process will be more reasonably improved to provide a warm worm shaft suitable for mass production.

In terms of material, expensive free-cutting steel was used in the past, which was important because the shape of the worm shaft was mainly formed by cutting. In the present invention, however, carbon steel such as S45C is used in comparison with free cutting steel.

As a concrete manufacturing process, it consists of 1st forging stage (I), 2nd forging stage (II), rolling stage (III), and CNC finishing stage (IV). After forming the basic shape, it is possible to minimize the waste of materials by rolling and CNC finishing, and to reduce the cause of noise or vibration by increasing the processing accuracy of the worm gear 21 to be formed on the shaft portion 20b. To provide a feature.

More specifically, to prepare a smooth rod-like member (M) made of carbon steel, to cut to a suitable length and 1 divided into the head portion 20a and the shaft portion 20b while varying the diameter through the first forging step (I). Mold shut-off products. As shown, the forging after the primary forging is composed of a head portion of the upper end portion having the largest diameter and a shaft portion which is gradually reduced in diameter while being connected to the lower portion thereof.

After the first forging is completed, the second forging step (II) is followed. In the second forging step (II), the shape is formed to be closer to the outer shape of the final worm shaft, and in particular, the upper surface of the head portion 20a. Forging is performed so that the plurality of divided projections 22 are formed to be concave.

Since the worm gear 21 must be provided in a portion of the shaft portion 20b connected to the lower side of the head portion 20a, the rolling step (III) is continued to the third process, using a rolling machine to form the worm gear in the shaft portion. Gear machining will be performed. The detailed description of the rolling work itself is omitted.

After shaping the worm gear 21 by rolling on the shaft portion 20b, a CNC finishing step (IV) follows to make the final worm shaft of the correct dimensions. In this CNC finishing step, the surface part of the head part 20a and the shaft part 20b of the finished product until the primary molding of the worm gear 21 through rolling is turned, especially the head part 20a and the shaft part ( 20b) It is possible to process the worm gear more precisely by performing a total turning process based on the center of each distal end portion. In other words, CNC turning is performed by holding the center so that the centers of both ends (head and shaft ends) of the finished product are in the same axis, and the degree of machining of the worm gear 21 formed in the previous rolling step is based on the entire center of the worm shaft. Secondary precision machining is possible.

In addition, the metal finishing process is performed after forming the mold close to the outer shape of the final worm shaft through two forging steps, which minimizes waste of material and reduces cutting volume, thus reducing processing time and consumption of cutting tools. It also has a feature that can be greatly reduced.

On the other hand, more preferably in the implementation of the manufacturing method of the worm shaft for MDPS according to the present invention to improve the surface strength and especially the worm gear portion through the predetermined heat treatment after the rolling step (III) or after CNC finishing to loosen the structure This is preferred, and this heat treatment is generally sufficient with known quenching and tempering treatments.

According to the worm shaft manufacturing method of the present invention, it is very suitable for mass production systems compared to the conventional manufacturing method, the cutting amount is drastically reduced, the processing time can be shortened and the material saving effect can be obtained, which can greatly contribute to enhancing the competitiveness.

Above all, according to the manufacturing method according to the prior art, since the worm gear portion formed in the shaft portion and the center axis of the whole worm shaft do not exactly match, the worm shaft which is connected to the worm wheel and rotates generates a lot of noise and vibration. According to the manufacturing method, the final CNC finishing processing is performed with the center axis of the worm gear and the worm shaft being matched, so that the precision of the worm gear can be increased to reduce noise and vibration, thereby providing excellent worm shafts.

Due to the global recession in the automobile industry and the difficulties of the related parts industry, there is an urgent need to increase the competitiveness. Therefore, the present invention seeks to enhance the competitiveness of the domestic parts industry by improving productivity and cost reduction in this context. Will contribute.

The manufacturing method of the worm shaft for MDPS according to the present invention is applied to replace the existing worm shaft manufacturing technology can provide an effect such as cost reduction is a technology that is likely to be used in practice.

1 is a block diagram showing the main components used in MDPS.

Figure 2 is a schematic perspective view showing the shape of the completed worm shaft.

Figure 3 is a flow chart according to the working process by the manufacturing method of the present invention.

4 is a work flow chart.

20: warm shaft 20a: head

22: protrusion 20b: shaft portion

21: Worm Gear

Claims

The present invention relates to a method of manufacturing a worm shaft for use in an MDPS, which is an electric power steering system of an automobile. The worm shaft includes a head part and a shaft part, and a worm gear is formed in a portion of the shaft part.

A primary forging step of molding the smooth rod-shaped member made of carbon steel so as to continuously connect the head portion and the shaft portion with different diameters;

A secondary precursor step of forming a concave shape so that a plurality of protrusions are formed on the head portion;

A precursor step of processing the worm gear at a portion where the worm gear is to be formed;

The CNC finishing step of holding the center on the same axis of both ends of the rolled product to perform the finishing operation for the whole including the worm gear formed by the roll in the CNC; it is configured to include a reduction in raw materials to reduce manufacturing costs Method of manufacturing a worm shaft for MDPS, characterized in that the worm gear is finally processed about the center axis of the worm shaft can provide a good quality worm shaft.