JPH09207566A - Reinforcing pipe for automobile door - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress bending deformation in a boundary part, between a door reinforcing pipe and a bracket, which is used for installing the reinforcing pipe to a door, in compressive destruction by cutting a pipe end part, into a split shape consisting of a pair of opposed mounting pieces, which are fixed on the door side while their width directions are faced to the working direction of a compressive destruction load. SOLUTION: In a reinforcing pipe 1, each end part is cut into a split shape consisting of a pair of opposed mounting pieces 4, and the pair of mounting pieces 4 are fixed on the inside of a door with their width directions faced to the working direction of a possible compressive destruction load F. That is, a mounting recess part, 5 provided with a semicircular cross section whose inside diameter equals the outside diameter of the reinforcing pipe 1 is formed in a bracket 3 on the door side, and in the recess part 5, the pair of mounting pieces 4 are fitted vertically. The back faces of the respective mounting pieces 4 are fixed in the edge part of the mounting recess part 5 by means of electric resistance welding 6, and consequently, the end part of the reinforcing pipe 1 is fixed in the bracket 3 on the door side.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reinforcing pipe for an automobile door, and more particularly to a reinforcing pipe for an automobile door which is excellent in crushing property and productivity due to having a specific end cut shape. It is a thing.

[0002]

2. Description of the Related Art In recent years, in the automobile industry, with the increasing demand for safety of automobiles, the use of reinforcing members made of high-strength steel plates for protecting passengers in the event of a collision has been promoted. Among them, in order to protect an occupant against a collision on the side surface of an automobile, a reinforcing pipe called a door impact beam as shown in FIG. 2 is mounted inside the door along the traveling direction of the vehicle.

Conventionally, this reinforcing pipe has a tensile strength of 5
When a 88 N / mm ² grade steel plate is formed into a pipe and then used by being hardened to improve the tensile strength to 1275 N / mm ² or more, for example, JP-A-4-131327.
As disclosed in Japanese Patent Laid-Open No. Hei 4-135013,
It has been used as a door reinforcing pipe by pipe-forming a cold-rolled steel sheet having a tensile strength improved to 980 N / mm ² or more by water quenching with a continuous annealing equipment.

On the other hand, at present, there is an increasing demand for weight reduction of an automobile body due to automobile fuel consumption regulations and demands for cost reduction. It is possible to reduce the weight and productivity of such a reinforcing member. There is a strong demand. In response to such a demand, a method for cutting the weight of the reinforcing pipe by cutting the end portion of the reinforcing pipe into a spiral shape has been developed, as shown in US Pat. No. 5,123,694.

[0005]

This method not only can reduce the weight of the reinforcing pipe in comparison with the original one in which the end of the pipe is cut (circular cut) at right angles to the longitudinal direction of the pipe. The maximum load has the characteristic that it can be improved instead. However, when the pipe end is cut into a spiral shape, there is a problem that the bending rigidity at the initial stage when the pipe is crushed is low and the displacement becomes large in the process of reaching the maximum load.

When a reinforcing pipe having a problem of crushing characteristics is mounted on an automobile body as described above, when a large load acts on the reinforcing pipe due to a side collision, the reaction force of the reinforcing pipe acts on the mounting portion of the reinforcing pipe to the vehicle body. It is necessary to have a structure that bears power. For this reason, the reinforcing pipe itself is required to have an effect of reducing the amount of pushing of the door into the vehicle during a light side collision.

That is, such a reinforcing pipe for an automobile door is not only capable of reducing the weight and improving the maximum load, but also has a high bending rigidity in the initial stage of crushing of the reinforcing pipe and a high absorbed energy in a low displacement range. It is required. The present invention has been made in order to meet such a demand, and an object thereof is to provide a lightweight reinforcing pipe for an automobile door, which has excellent crushing characteristics and productivity.

[0008]

DISCLOSURE OF THE INVENTION The present inventors compared the conventional case where the pipe end is cut at a right angle to the longitudinal direction of the pipe with the bending rigidity and the low displacement range in the initial stage of crushing the reinforcing pipe of the door. In order to cut and reduce the weight without lowering the absorbed energy, we conducted extensive experiments and research. As a result, in order not to lower the bending rigidity in the initial stage of crushing and the absorbed energy in the low displacement range, suppress the bending deformation of the boundary part between the door reinforcement pipe and the bracket for mounting it on the door during crushing. We found that is the most important and decided to take the following technical measures.

That is, according to the present invention, in a reinforcing pipe for an automobile door which is attached to the inside of the automobile door for protection against a side collision, a relative pipe fixed to the door side so that its width direction is oriented in the direction of the crush load. The pipe end is cut into a bifurcated shape composed of a pair of facing mounting pieces. In addition to the above configuration, the present invention is characterized in that the pipe is cut so that the forked shape of the pipe end is the same as the bifurcated shape of the other party generated by the cutting.

In the reinforcing pipe 1 of the present invention, the pipe end is cut into a bifurcated shape composed of a pair of mounting pieces 4 and 4, and the crushing load F acts in the width direction of the pair of mounting pieces 4 and 4. It is fixed to the door 2 side along the direction. For this reason,
The pair of attachment pieces 4 and 4 forming the bifurcated shape are joined so as to form a vertical wall against the bending deformation of this portion due to the crush load F, whereby the pipe end is cut. In order to reduce the weight, it is possible to prevent the bending rigidity in the initial stage of crushing and the reduction of absorbed energy in the low displacement region.

Further, when the bifurcated shape of the pipe end is cut so as to be the same as the bifurcated shape of the other party caused by the cutting, both pipe materials separated by this cutting can be used as the reinforcing pipe 1 as they are. Become.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an end shape of a reinforcing pipe 1 for an automobile door adopted in this embodiment. The reinforcing pipe 1 is formed into a hollow cylindrical shape having a circular cross section by cold roll rolling or extrusion molding of a steel plate. As shown in FIG. 2, the door 2 is mounted inside the door 2 along the vehicle traveling direction by welding both ends to the bracket 3 on the door 2 side, and prevents the door 2 from being deformed in the case of a side collision. Functions as an impact beam.

As shown in FIG. 1, the reinforcing pipe 1 is
The both ends thereof are cut into a bifurcated shape composed of a pair of mounting pieces 4 facing each other, and the pair of mounting pieces 4 are oriented so that the width direction thereof is oriented in the expected crushing load F acting direction. Fixed inside. That is, the bracket 3 on the door 2 side is formed with a mounting recess 5 having a semicircular cross section with an inner diameter equal to the outer diameter of the reinforcing pipe 1.
The pair of mounting pieces 4 are vertically inserted (vertical direction in FIG. 1A). The end of the reinforcing pipe 1 is fixed to the bracket 3 on the door 2 side by fixing the back surface of each mounting piece 4 to the edge of the mounting recess 5 by electric resistance welding 6.

In this case, in this embodiment, when the bifurcated shape of the pipe end is not cut so as to be the same as the bifurcated shape of the other party caused by the cutting, as will be described later,
In practice, the dimensions of each part are defined so as to satisfy the conditions of the following equations. ΔL / L ≦ 0.24 (1) Lw ≧ 15 mm (2) 0.5D ≦ h ≦ 0.9D (3) Here, L: total length of the reinforcing pipe 1 ΔL: cutting of the end of the reinforcing pipe 1 Overall length Lw: Welding length of the reinforcing pipe 1 to the bracket 3 D: Outer diameter of the reinforcing pipe 1 h: Height at the bracket joint edge of the mounting piece 4 That is, the condition of the formula (1) is defined by ΔL 0.
If it is larger than 24 L, it tends to buckle from this cut portion during crushing, and it becomes impossible to satisfy the required initial rigidity and strength. Although the lower limit of ΔL / L is not specified in the equation (1), if ΔL / L is too small, the effect of weight reduction is also small.
It is desirable to choose as large a value as possible within the range of the formula.

If the welding length Lw is less than 15 mm, there is a high possibility that the required joining strength with the bracket 3 cannot be obtained. Further, in the present embodiment, the pair of identically-shaped mounting pieces 4 are arranged in parallel with each other with respect to the crush load F, that is, in the recess 5 of the bracket 3 so as to form a vertical wall in the load F direction. The height h of the attachment piece 4 at the joint edge of the bracket 3 at this time is adjusted so as to satisfy the above expression (3).

Here, the upper limit of the outer shape D of the reinforcing pipe 1 is not specified, but the largest value is selected within the range that can be installed inside the door 2. And the height h is 0.5D
If it is smaller than that, buckling may occur at the joint between the bracket 3 and the reinforcing pipe 1 during crushing, and there is a strong possibility that the required initial rigidity and strength cannot be satisfied. on the other hand,
If the height h is larger than 0.9D, the mounting piece 4 becomes too wide, and the reinforcing pipe 1 cannot be made so lightweight.

Further, in the reinforcing pipe 1 shown in FIG. 1 of the present embodiment, the bifurcated shape of the pipe end is cut so as to be the same as the bifurcated shape of the mating member caused by the cutting. The two pipe materials produced by the above are used as they are as the reinforcing pipe 1 to improve the material yield. In this case, the dimensions of each part are actually defined so as to satisfy the conditions of the following equations.

ΔL / L ≦ 0.24 (4) Lw ≧ 15 mm (5) 0.5D ≦ h ≦ 1 / √2 × D (6) (where ΔL ≧ 2Lw) 0.5D ≦ h ≦ 0.9D (7) (However, when ΔL ≦ 2Lw) Of these, (4)
Expression (5) is defined in the same manner as expressions (1) and (2) above.

Further, in the case of ΔL ≧ 2Lw, if h is smaller than 0.5D, there is a possibility that the initial rigidity and strength required at the time of crushing cannot be satisfied as described above.
on the other hand. If h is larger than 1 / √2 × D, the root becomes thinner than the bifurcated tip, and the mounting piece 4
The risk of buckling at the root of the pipe becomes great, and it becomes difficult to separate the two pipes 1 after cutting, and productivity is hindered. In the case of ΔL ≦ 2Lw, it is defined in the same manner as the equation (3).

In the present embodiment, in order to prevent stress concentration from occurring in the cut bifurcated root portion 7 during crushing, the root portion 7 has a smooth radius as shown in FIG. 1 (a). It is preferably cut to form.
The present invention, as the reinforcing pipe for the door, the strength of the material,
It is possible to obtain the effect regardless of the plate thickness.

As a method of cutting the end of the pipe, it is desirable to use a high energy beam such as laser or plasma, but cutting by any other method does not affect the effect of the present invention.

[0022]

EXAMPLES As shown in Table 1 below, crushing tests shown in FIG. 3 were performed on reinforced pipes having various dimensional specifications and product weights. However, in this experiment, a method of cutting the pipe end portion so that the bifurcated shape of the end portion of the pipe is the same as the bifurcated shape of the mating member (claim 2) was performed.

[0023]

[Table 1]

A crush test was performed on these reinforcing pipes 1 by a test method of crushing the reinforcing pipe 1 with a punch having a radius of 152.5 mm as shown in FIG. The test results are shown in FIGS. 4 and 5 (load displacement curve). In these figures, as compared with the conventional door reinforcing pipes (conventional examples A and B) in which the pipe ends are cut at right angles, comparative examples C, D, and
Each of E and F has an effect of reducing the weight by about 12 to 15%, and has a higher maximum load as compared with the conventional example.

However, in this comparative example, since the cut shape of the end portion is not appropriate in all cases, the pipe end portion is deformed at the time of crushing, resulting in a lower load at the initial stage of deformation as compared with the conventional example. Has become. The reason is that in these comparative examples C to F, the above formulas (4) to
This is because either (7) is not satisfied. On the other hand, the products G, H, I, and J of the present invention each have a crushing property almost equal to that of the conventional examples A and B, but are 1
It is possible to obtain a weight reduction effect of about 2 to 18%.

FIG. 6 shows a comparison of absorbed energy in the initial stage of deformation. Here, the absorbed energy at the initial stage of deformation is represented by the displacement until the pipes of the conventional examples A and B buckle, that is, the area surrounded by the load displacement curve up to 75 mm, and comparative examples C, D and In the invention examples G and H, the absorbed energy of the conventional example A is 100
, Comparative Examples E and F and Invention Example I,
Regarding J, the absorbed energy of Conventional Example B is shown as 100.

As can be seen from FIG. 6 and Table 1, it is clear that Examples G, H, I and J of the present invention have excellent crushing characteristics and can be significantly reduced in weight.

[0028]

As described in detail above, according to the present invention,
The pipe end is cut into a bifurcated shape consisting of a pair of mounting pieces facing each other, and this mounting piece is fixed in the door so that the width direction thereof is oriented in the direction of the crushing load. Even in this case, it is possible to prevent the flexural rigidity in the initial stage of crushing and the reduction of absorbed energy in the low displacement region. Therefore, a lightweight reinforcing pipe having excellent crushing properties can be obtained, which greatly contributes to the safety and weight reduction of an automobile.

According to the second aspect of the present invention, the pipe is cut so that the forked shape of the pipe end is the same as the forked shape of the other side generated by the cutting, so that both pipe materials produced by the cutting are directly processed. It can be used as a reinforcing pipe, which can significantly improve the material yield.

[Brief description of drawings]

FIG. 1 shows an end structure of a reinforcing pipe of the present invention, (a)
Is a plan view thereof, and (b) is a side view thereof.

FIG. 2 is a perspective view showing a state where a door impact beam (reinforcement pipe) is attached to an automobile door.

FIG. 3 is a side view showing a procedure of a crushing test of a reinforcing pipe.

FIG. 4 is a diagram showing a load displacement curve of a reinforced pipe after a crush test.

FIG. 5 is a diagram showing a load displacement curve after a collapse test of a reinforcing pipe.

FIG. 6 shows punch displacement of 7 in a crush test of a reinforced pipe.
It is a bar graph which compared the absorbed energy up to 5 mm.

[Explanation of symbols] 1 Reinforcement pipe 2 Door 3 Bracket 4 Mounting piece 5 Mounting recess 6 Welding 7 Root F Crushing load

Claims (2)

[Claims] 1. A reinforcing pipe for an automobile door, which is attached to the inside of the automobile door for protection against a side collision, has a pair of opposed pipes fixed to the door side so that its width direction is oriented in the direction of the crush load. A reinforcing pipe for an automobile door, characterized in that the pipe end is cut into a bifurcated shape composed of a mounting piece. 2. The reinforcing pipe for an automobile door according to claim 1, wherein the bifurcated shape of the pipe end is cut so as to be the same as the bifurcated shape of the other party generated by the cutting.