JP2000024737A - Manufacture of stabilizer bar - Google Patents

Abstract

PROBLEM TO BE SOLVED: To secure the uniformly and sufficiently high strength in a bend-formed part while reducing the manufacturing cost and to obtain high durability and reliability by applying an induction hardening to the bend-formed part after bend-forming a stabilizer bar blank at cold-state. SOLUTION: The stabilizer bar blank cut to a prescribed length, i.e., a raw member of the stabilizer bar 20 is put into a cold-bending process. The stabilizer bar blank is composed of a hollow material (steel pipe) made of a carbon steel, spring steel, etc., and very light in comparison with a solid material. In this process, the bend formation is executed for a prescribed shape in the room temp. state, simultaneously, both end parts 22, 22 are crushed into plate-state in order to bore holes 23, 23 fitting to a car body. Since the stabilizer bar blank is in raw member state, the strength is low and the bend formation is extremely easy. In the successive induction hardening process, the induction hardening is executed for the range (slanted-line part) shown with D in the stabilizer bar 20.

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 stabilizer bar, and more particularly to a method for forming and quenching a stabilizer bar.

[0002]

2. Related Background Art In recent years, vehicles having a structure in which a stabilizer bar (stabilizing bar) is provided between left and right suspensions has been increasing in order to prevent the vehicle from leaning outward when traveling on a curved road or the like.

However, since this stabilizer bar is usually manufactured by bending the vicinity of both ends of a solid bar-shaped steel material, when the vehicle is large and the stabilizer bar is required to have high strength, the stabilizer bar is required. There is a problem that the outer diameter of the bar increases and the weight inevitably increases.

For example, a large passenger vehicle such as a recreational vehicle (RV vehicle) is considerably heavy, for example, about 8 kg per vehicle, which is a factor of increasing the vehicle weight.

[0005] Therefore, it has been considered to manufacture the stabilizer bar with a hollow steel pipe instead of a solid one, thereby reducing the weight of the vehicle.

[0006]

When the stabilizer bar is hollow as described above, it is necessary to make the section modulus the same as that of a solid member of the same strength in order to ensure sufficient strength. This means that the outer diameter of the member must be larger than the solid member of the same strength.

However, increasing the outer diameter in this manner results in extremely large stresses (tensile and compressive stresses) generated at the outer periphery of the bent portion, and such a large stress The challenge is to ensure the strength to withstand the pressure.

In other words, usually, a method is employed in which a member is heated by a flame or the like to perform hot bending and then quenching is performed continuously. In the quenching method, the above-mentioned large strength cannot be obtained due to the limitation in the construction method, and it is no longer possible to obtain sufficient durability.

In the case of a hollow stabilizer bar having a space inside, if the quenching time is prolonged, the air existing in the hollow portion is heated to a high temperature, and the air heated to the high temperature is cooled when cooling the members. There is also a problem in that the cooling of the inner peripheral side of the stabilizer bar is hindered, the strength is not uniform between the outer peripheral side and the inner peripheral side, and thermal distortion occurs, resulting in poor reliability.

[0010] In order to solve such a problem, for example, a manufacturing method having a configuration in which a hollow stabilizer bar is subjected to induction hardening with a short quenching time and then bent at the time of tempering is disclosed in Japanese Unexamined Patent Publication (Kokai). 2-3469
No. 3 and Japanese Patent Publication No. 2-61338.

However, it is not easy to bend the member after quenching and hardening as in the methods disclosed in each of the above-mentioned publications. Setting the temperature to be higher than the tempering temperature (for example, 200 ° C. or higher) is a factor that lowers the strength while favoring the bending formability, and is hardly realistic.

Further, in order to realize such a manufacturing method, it is necessary to introduce expensive equipment capable of plastically deforming even a high-strength member after quenching, which increases the manufacturing cost, which is not preferable.

The present invention has been made in view of the above-mentioned circumstances, and an object of the present invention is to ensure uniform and sufficient high strength in a bent-formed portion while reducing manufacturing costs, and to improve durability and reliability. To provide a method of manufacturing a stabilizer bar with high reliability.

[0014]

According to the first aspect of the present invention, a bar-shaped stabilizer bar material is cold-bent and then induction hardened to the bent portion. Like that.

Therefore, the stabilizer bar is bent in a relatively soft green state, so that the bending can be easily realized with simple equipment, and the manufacturing cost can be reduced.

Further, since quenching can be completed locally at a high temperature and in a short time without requiring pressure restraint, the quenching strength is increased as a whole, and when the stabilizer bar is a hollow member, the quenching can be completed. The air in the part does not become hot, and good quenching without heat distortion can be realized in the bent part, and the difference between the strength on the outer circumference side and the strength on the inner circumference side is suitably prevented. You.

That is, according to the present invention, even if the stabilizer bar is formed not only of a solid member but also of a hollow member, it is possible to secure a uniform and sufficiently high strength in the bent portion which is a quenched portion. Thus, it is possible to realize a stabilizer bar having high durability and high reliability.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings.

Referring to FIG. 1, there is shown a manufacturing flow of the stabilizer bar according to the present invention, which will be described below with reference to FIG.

First, a rod-shaped stabilizer bar material cut into a predetermined length, that is, a raw material of a stabilizer bar is put into a cold bending forming step 10. Here, the stabilizer bar material is made of a hollow material made of carbon steel, spring steel, or the like, that is, a steel pipe, and the weight per piece is, for example, about 6 kg, which is considerably larger than the solid member (about 8 kg). It is light.

In the cold bending forming step 10, the stabilizer bar material made of a green member is bent into a predetermined shape in a cold state, that is, at room temperature. FIG. 2 shows the stabilizer bar 20 in a bent state. In the cold bending step 10, the stabilizer bar material is formed into a shape as shown in FIG. That is, a position at a predetermined distance from both ends of the member is bent by a predetermined angle. At this time, the both ends 22 and 22 are simultaneously crushed into a plate shape, and the stabilizer bars 20 are attached to the mounting holes 23 and 2 in the vehicle body.
Drill 3

At this time, since the stabilizer bar material has not been heat-treated yet and is in a green state, its strength is low (for example, Vickers hardness of 150).
HV), bending is extremely easy. Therefore, a special jig for forming and processing is used for bending the stabilizer bar and processing the both ends 22, 22, and the jig has a general configuration and is simple and inexpensive. Things are used.

After the stabilizer bar material is formed by bending the stabilizer bar 20, the process proceeds to the induction hardening step 12.

In the induction hardening step 12, induction hardening is performed in a range (shaded area) indicated by D in FIG. 2 of the stabilizer bar 20.

The range (shaded area) indicated by D is a range that is set in advance by experiments or the like and is determined to require quenching, and a procedure for setting the range will be described below.

Referring to FIG. 3, the stabilizer bar 20
One end of the stabilizer bar 20 is shown in an enlarged manner. When the range is set, first, as shown in FIG. 3, each of a, b, c, d, and e is sequentially provided from the end of the stabilizer bar 20. Set points arbitrarily.

Then, when it is assumed that the vehicle has traveled after the stabilizer bar 20 is actually mounted on the vehicle body, the maximum load received by the stabilizer bar 20 is added to the stabilizer bar 20 under the same conditions as the actual vehicle. b,
The stress σ generated at each of the points c, d, and e is measured. More specifically, a strain gauge is attached to each of the points a, b, c, d, and e in advance, and a stress σ generated at each point is detected based on information from the strain gauge.

When the stress σ generated at each of the measurement points a, b, c, d, and e is measured in this manner, these data are used to determine the relationship between each measurement point and the stress σ as shown in FIG. Are plotted on a graph indicating, and linear interpolation is performed between adjacent plots.

In FIG. 3, the strength (specifically, the fatigue strength) of the stabilizer bar material is indicated by a two-dot chain line, and the point at which the two-dot chain line indicating the strength intersects the straight line interpolated is shown. These points are referred to as point P and point P ', respectively.
The range slightly wider than the range between the points P 'is defined as the range indicated by D, that is, the quenching range.

That is, in the induction hardening step 12,
Induction quenching is performed only on the portion where quenching is necessary for strength and in the vicinity thereof.

Induction hardening is a method in which a high-frequency current is passed through an induction heating coil, thereby inducing a high-frequency current in a member to perform quenching. Here, for example, a method as shown in FIG. 5 is used. Adopted.

In the example shown in FIG.
The induction heating coil 30 and the induction heating coil 32 are arranged so as to be separated from the surface of the antenna by a predetermined distance and sandwich the stabilizer bar 20 from above and below. That is,
The induction heating coils 30 and 32 are arranged so as to follow the bent portion of the stabilizer bar 20 in the range indicated by D, that is, the bent portion. A high-frequency current flows through the induction heating coil 30 and the induction heating coil 32 in the same direction in synchronization with each other.
Note that cooling water passages are provided in the induction heating coils 30 and 32, and the cooling water circulates through the cooling water passages. This allows the induction heating coil 3 to be energized
The heating of 0,32 itself is prevented.

Actually, the induction heating coil 30 and the induction heating coil 32 are fixed to the quenching jig with the above positional relationship.
The stabilizer bar 20 is set on the quenching jig such that the quenching range indicated by D is located between the quenching jig and the induction heating coil 32.

When a high-frequency current is applied to the induction heating coils 30 and 32 configured as described above, as indicated by broken lines in FIG. 5, the directions around the induction heating coils 30 and 32 depend on the frequency. A reverse magnetic flux is generated, and a high-frequency current is induced in the stabilizer bar 20 member. The induced current causes the member to reach a predetermined high temperature (a temperature higher than the normal quenching temperature) due to the internal resistance of the member.
To be heated. In general, induction quenching has a characteristic of rapidly reaching a high temperature, so that it is heated to a predetermined high temperature in a short time.

When the member is heated to a predetermined high temperature, the stabilizer bar 20 is removed from the jig or the like, and the high temperature portion is immersed in a cooling liquid or the cooling liquid is sprayed on the high temperature portion. Thereby, quenching is completed. Here, the cooling liquid is generally oil or water, but water is more preferable in consideration of hardenability. Since the induction hardening is performed at a temperature higher than the normal quenching temperature as described above, the strength after quenching in the range indicated by D is higher than that in the normal quenching.

When the quenching is completed, the tempering step 1 shown in FIG.
In 4, the stabilizer bar 20 is set in a tempering furnace and tempered. Thereby, tempering of the quenched portion is performed. Here, the tempering is performed at a temperature of, for example, 200 ° C. or lower, similarly to the normal tempering.

By the way, the induction heating coils 30 and 32
As described above, the stabilizer bar 20 is spaced apart from the surface of the stabilizer bar 20 by a predetermined distance, and has a shape along the bent shape of the stabilizer bar 20. Therefore, the quenching and tempering are performed uniformly from the outer peripheral surface of the stabilizer bar 20 to the inner peripheral surface thereof and sufficiently performed.

That is, referring to FIG. 6, A- in FIG.
FIG. 4 is a cross-section of the bent portion of the stabilizer bar 20 along the line A ′ after quenching, in which the stabilizer bar 20 is divided into eight at equal intervals, and the respective division positions are denoted by reference numerals 1 to 8 from the A ′ side. 7, and with reference to FIG. 7, the results of measuring the Vickers hardness (HV) of the outer peripheral surface, the core portion, and the inner peripheral surface at each of the division positions 1 to 8 are indicated by circles ( (Solid line), △ (dashed line)
And □ (dash-dot line), the Vickers hardness for all of these measurement points is the target value X1 (for example,
(500 HV). Here, the target value X1 (for example, 500 HV) is a threshold value of Vickers hardness necessary for securing a sufficiently high strength, and is a value set in advance by an experiment or the like.

As described above, in the method of manufacturing a stabilizer bar according to the present invention, first, a stabilizer bar material, which is a raw member, is cold-bent and then subjected to induction hardening at a portion requiring strength. Like that.

Therefore, the molding of the stabilizer bar is easy, and the quenching can be locally completed in a short time without the need for pressure restraint, so that the molding equipment can be simplified and the manufacturing cost can be reduced. As well as good quenching without heat distortion can be realized.

Therefore, even when the stabilizer bar is formed of a hollow member having a large diameter, the quenching range indicated by the above D, that is, the uniform and sufficient high strength is applied to the portion requiring high strength while reducing the weight. As a result, it is possible to realize a stabilizer bar having high durability and high reliability.

In the above embodiment, the case where the stabilizer bar is mainly a hollow member has been described.
The present invention is not limited to this, and similar effects can be obtained by applying the present invention to a solid member.

Further, the induction hardening method is not limited to the above-described method, and any other method can be applied as long as the induction heating coil can be arranged along the bent shape.

[0044]

As is apparent from the above description, claim 1
According to the method of manufacturing a stabilizer bar, since the stabilizer bar is bent in a relatively soft green state, the bending can be easily realized with simple equipment, and the manufacturing cost can be reduced.

In addition, since quenching can be completed locally at a high temperature and in a short time without the need for pressure restraint, the quenching strength can be increased as a whole,
In the case where the stabilizer bar is a hollow member, the air in the hollow portion can be prevented from being heated to a high temperature, and therefore, good quenching without thermal distortion can be realized in the bent portion, and the strength difference between the outer peripheral side and the inner peripheral side can be realized. Can be prevented from occurring.

That is, according to the present invention, even if the stabilizer bar is formed not only of a solid member but also of a hollow member, uniform and sufficient high strength can be ensured in the bent portion which is a quenched portion. In addition, a highly reliable and durable stabilizer bar can be realized.

[Brief description of the drawings]

FIG. 1 is a view showing a manufacturing flow of a stabilizer bar according to the present invention.

FIG. 2 is a view showing a stabilizer bar in a bent state and a range in which induction hardening is performed.

FIG. 3 is an enlarged view of one end side of a stabilizer bar, showing a stress measurement point.

FIG. 4 is a diagram showing a relationship between each measurement point in FIG. 3 and a generated stress σ and for setting a range in which induction hardening is performed.

FIG. 5 is a diagram showing an example of an induction hardening method.

FIG. 6 is a cross-sectional view of the stabilizer bar taken along the line AA ′ in FIG. 3, showing a dividing position for hardness measurement.

FIG. 7 is a view showing a measurement result of Vickers hardness (HV) of the outer peripheral surface, the core, and the inner peripheral surface at each division position in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Cold bending forming process 12 Induction hardening process 14 Tempering process 20 Stabilizer bar 30, 32 Induction heating coil D Quenching range

Continued on the front page (72) Inventor Yoshiharu Matsumura 5-33-8 Shiba, Minato-ku, Tokyo Inside Mitsubishi Motors Corporation (72) Inventor Isao Murasaki 5-33-8 Shiba, Minato-ku, Tokyo Mitsubishi Motors Co., Ltd. F term (reference) 3D001 AA17 DA06

Claims (1)

[Claims] 1. A method for manufacturing a stabilizer bar, comprising: bending a rod-shaped stabilizer bar material in a cold state; and performing induction hardening on the bent portion.