JPH07165086A - Manufacture of core for steering wheel - Google Patents

Abstract

PURPOSE:To provide the manufacture of a core for steering wheel, which can prevent the lowering of strength at a welding part of a metal pipe core for rim and which eliminates the holing phenomenon easy to be generated at the time of welding. CONSTITUTION:A pin hole-like small hole 2 is formed at a desired part of a core 1 for rim part, which is made of sealed pipe material, and end surface of a solid core 3 for spoke part is made to abut on a predetermined position of the core 1 for rim part, and welded thereto, and thereafter, the small hole 2 is sealed. Even at the time of welding under the high heat condition, since the air is ventilated between the outside an the inside of the pipe core 1 for rim part through the small hole 2, the air pressure inside of the pipe, which is cooled before the welding and left under the negative pressure condition, becomes equal to the outer air pressure to prevent the generation of holing phenomenon in the welding part, and stability at the time of welding is secured, and the malfunction to be generated in a following process is eliminated.

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 metal cored bar which is applied to a steering wheel of an automobile composed of a rim part, a spoke part and a boss part. Therefore, when welding a solid spoke core metal to the rim core metal, we manufacture a core metal that eliminates the influence of the air inside the rim core metal and can perform stable welding. On how to do.

[0002]

2. Description of the Related Art In recent years, an annular hollow iron pipe has been widely used as a core metal material applied to a rim portion of a steering wheel as part of weight reduction of an automobile. As is well known, the bending process of the core metal for the rim uses a roll bender, in which a straight hollow pipe is wound around a main roll, which is cut into a predetermined length and the ends thereof are joined together. While being pressed against each other, arc welding is used to form a complete ring. The center boss is integrated with the ring-shaped core metal for the rim via the spokes to form the core metal of the steering wheel.

On the other hand, it is general that the core metal made of a pipe material for the rim portion and the core metal for the spoke portion are connected and integrated by arc welding. In order to avoid the decrease, for example, as disclosed in Japanese Utility Model Publication No. 53-87539, the core metal part for the rim to which the core metal for the spoke part is connected is made thicker than the other core metal parts. Proposals to make up are made.

[0004]

However, the core metal for the rim portion made of the metal pipe disclosed in the above publication requires a complicated process at the stage of pipe production due to its special structure, which leads to high cost. In addition, when welding the core metal for the spokes, it is necessary to use extra nerves to specify the thick portion of the pipe material to be the weld.

On the other hand, when the end faces of the solid spoke core metal are butted against the annular metal core for the rim portion and welded, the weight reduction and the strength are satisfied at the same time. Minimum thickness of 1.8mm and 2mm depending on specifications
Often set to two types. In welding the solid spoke core metal as described above to such a thick closed pipe material, various problems occur in addition to the problems recognized heretofore.

One of them is that an opening is formed in the pipe portion of the welded portion. This phenomenon was first recognized by the inventors. When such a phenomenon occurs, foreign matter is more likely to enter through this opening,
When the entire cored bar is cleaned after welding, the cleaning liquid enters the inside of the pipe, and when the cored bar is covered with the synthetic resin molding material by the injection molding in the next step, the surface condition of the open part is evenly formed. Instead, the rate of defective products increases. In addition, during the above welding, there is also a problem that spatter and droplets enter the inside of the pipe through the same opening, resulting in abnormal noise during steering operation.

The present invention has been made to solve the above-mentioned problems, and its purpose is to prevent a decrease in the strength of a welded portion of a core metal for a rim portion made of a pipe, and particularly to solve the problems due to the above-mentioned opening phenomenon. To do.

[0008]

The above object is a method of manufacturing a metal cored bar, which is applied to a steering wheel having a rim portion, a spoke portion and a boss portion, which is a main constitution of the present invention. The core metal for the rim portion is made of an annular pipe material, and a small hole is formed at an arbitrary portion of the pipe material, and then the end surface of the solid core metal for the spoke portion is provided at a predetermined portion of the core metal for the rim portion. The method of manufacturing a core metal for a steering wheel is characterized by comprising the steps of butting and welding, and then closing the small holes.

[0009]

The present inventors, upon recognizing the occurrence of the above-mentioned opening phenomenon, immediately conducted a study to elucidate the mechanism of occurrence of the phenomenon. As a result, they have found that the above-mentioned openings are formed by the following generation mechanism.

Usually, the core metal for a rim portion made of the above-mentioned pipe is formed by winding a linear metal pipe around a main roll of a roll bender into a coil and cutting the pipe into a predetermined length while bending the pipe. The ends are butted against each other and pressed together, and are joined by arc welding to form a ring. The internal air of the pipe-made rim core made in this way is
Air that has been thermally expanded due to a high temperature of 00 ° C to 800 ° C is enclosed, and is cooled and contracted between the end of welding and the time when the spoke core metal is welded. It is under pressure. In this state, when the spoke core metal is welded to a part of the rim core metal, a part of the rim core metal that is softened by heating and melting in the welded part is It is sucked by pressure and an opening is formed in the same portion.

From this, it can be understood that the above phenomenon will not occur if the air pressure existing inside the pipe is always made equal to the external pressure before and after welding. Therefore, in the present invention, the above-mentioned means is adopted to manufacture the core metal for the steering wheel by welding and integrating the core metal for the spoke portion with the core metal for the rim portion.

That is, in the present invention, at least before the spoke core metal is welded to the rim core metal, a pin having a diameter of 0.5 to 1.0 mm that communicates with the inside of the rim core metal. Hole-shaped small holes are formed in advance. By doing so, at the time of joining the cut ends of the bent pipes by welding, even if the internal air of the core metal for the rim portion is enclosed in a thermally expanded state, the internal pressure drops due to subsequent cooling. Also, not only does the pressure difference between the inside and outside of the pipe disappear when the small holes are formed, but also in the next welding step of the spoke core metal, air constantly flows through the inside and outside of the rim core metal through the small holes. In order to equalize the inner and outer pressures of the rim core metal, the negative pressure from the inside of the pipe acts on the welded part at the time of welding the spoke core metal and the rim core metal, as described above. No holes are formed.

However, if the small holes previously formed in the core metal for the rim portion are left as they are, various foreign substances will invade from the small holes as described above, resulting in various harmful effects. At the time when the spoke core metal and the rim core metal are welded, the small holes are plugged again with, for example, synthetic resin to close them.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below based on illustrated embodiments. The drawings all relate to the present invention, and FIG. 1 shows a material of a core metal for a rim portion obtained by bending a linear pipe material into a circle. The same material 1'is obtained by bending a linear metal pipe with a roll bender as in the conventional case. The material 1'which has been bent in this way and cut into a predetermined length is connected by arc welding while the ends thereof are butted and pressed against each other. The state at the end of the connection is shown in FIG. Figure 2
In FIG. 1, reference numeral 1a is a bead formed at the time of welding, and the bead 1a is cut off by grinding or the like in order to prevent the flow of the molten resin raw material from being obstructed when molding the synthetic resin coating by the subsequent injection molding. To adapt the weld to the other surface. These processes are also commonly performed conventionally.

According to the present invention, when the bead 1a is cut off as described above, it has a desired diameter so that the inside and outside communicate with the core metal 1 for the rim portion made of a pipe material as shown in FIG. The pinhole-shaped small hole 2 is formed using a drill or the like. Due to the formation of the small holes 2, outside air flows into the rim core 1 through the small holes 2 to eliminate the pressure difference between the inside and the outside. The small holes 2 may be formed at any position other than the welded portion of the rim core metal 1 to which the spoke core metal 3 is welded, and the number thereof is not limited to one. .

After the core metal 1 for the rim portion having the small holes 2 is manufactured in this manner, one end of the core metal 3 for the spoke portion is attached to a predetermined portion of the core metal 1 by a known welding method as shown in FIG. Welded. At this time, in the conventional case, an opening may be formed in the welded portion as described above, but according to the present invention, the small hole 2 previously formed in the core metal 1 for the rim portion is formed.
By the presence of, air flows through the small hole 2 inside and outside,
Since the inner pressure and the outer pressure of the core metal 1 are always equal to each other, no hole is formed in the welded portion, and therefore foreign matters such as spatter and droplets generated during welding are inside the core metal 1 for the rim portion. There is no noise when you operate the steering wheel.

The spoke core metal 3 is welded to a predetermined portion of the rim core metal 1 and a boss core metal plate 4 is formed on the free end of the spoke core metal 3 according to a normal procedure as shown in FIG. As shown, the steering wheel core metal 6 is also integrally formed by welding together with the boss 5. However, at this time, since the small holes 2 are still formed, as it is, the cleaning liquid flows from the small holes 2 into the inside of the core metal 1 for the rim portion during the subsequent cleaning as described above. If the vicinity of the hole 2 is coated with synthetic resin in the subsequent injection process, uniform molding cannot be performed. Therefore, in the present invention, after the welding of the core metal for the boss portion is completed, the small hole 2 is closed by using a closing plug 7 made of, for example, a synthetic resin material or a metal material as shown in FIG.

[0018]

As is apparent from the above description, according to the method of manufacturing a core metal for a steering wheel of the present invention, before the spoke core metal is welded to the metal pipe rim core metal, Since a small hole is formed in advance at a desired portion of the core metal for the rim portion, even if air flows through the small hole and the welding does not always cause a difference in internal and external pressure of the core metal for the rim portion, the welding is performed. Even when the rim core metal bar made of a thin pipe does not have a unique opening phenomenon, stable welding without deterioration of strength is possible, and foreign matter such as spatter enters the rim core metal bar. In the present invention, since the small hole is closed again after the welding is completed, for example, there is no inflow of liquid at the time of cleaning, and the synthetic resin coating by injection molding is performed thereafter. The entire surface of the molded product Without causing a defective part in,
An extremely high quality product is obtained.

[Brief description of drawings]

FIG. 1 is a plan view showing an overall shape of a pipe core metal for a rim portion obtained by bending.

FIG. 2 is a partial plan view showing a welding structure of end portions of the core metal for the rim portion.

FIG. 3 is a partial cross-sectional view showing a state where small holes are formed in the core metal for the rim portion.

FIG. 4 is a partial perspective view showing a welding structure of a spoke core metal with respect to the rim core metal.

FIG. 5 is an overall plan view showing an example of a core metal structure of a steering wheel of the present invention in which spoke and boss cores are integrally welded to a rim core.

FIG. 6 is a partial sectional view showing an example of a closed structure of a small hole formed in the core metal for a rim portion.

[Explanation of symbols]

 1 core metal for rim 1'material 1a bead 2 small hole 3 core for spoke 4 core metal for boss 5 boss 6 core for steering wheel 7 plug

Claims (1)

[Claims] 1. A method of manufacturing a metal cored bar applied to a steering wheel comprising a rim part, a spoke part and a boss part, wherein the rim part core bar is made of an annular pipe material. To form a small hole in any part of the core metal, and then to butt and weld the end surface of the solid spoke core metal to a predetermined part of the rim core metal, and then to form the small hole. A method of manufacturing a core metal for a steering wheel, which comprises a step of performing a closing process.