JPH05330342A - Steel pipe for automobile door reinforcement material - Google Patents

Abstract

PURPOSE:To propose a steel pipe for an automobile door reinforcement material with high bending absorbing energy irrespective of loading position of a load, etc., and secure the safety of occupants in the vehicle in a collision accident from the side of the automobile. CONSTITUTION:A steel pipe for an automobile door reinforcement material is so constructed that flat cross-sectional section parts 1 and circular cross-sectional parts 2 are arranged alternately in longitudinal direction. Because the steel pipe for the automobile door reinforcement material is not deformed concentratedly at one point of it irrespective of position of a load point and a width of obstacle to be loaded, its final bending absorbing energy is increased.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reinforcing member (hereinafter referred to as a door impact bar) equipped inside a vehicle door to protect an occupant in the event of a side collision.

[0002]

2. Description of the Related Art In the recent automobile industry, importance is attached to safety against side collision, and almost all doors of passenger cars for domestic as well as for export are equipped with impact bars. On the other hand, from the viewpoint of environmental problems, improvement of fuel efficiency of automobiles is aimed, and weight reduction of vehicles has become a major issue. Therefore, it is desired to reduce the weight of the door impact bar as much as possible. From the viewpoint of reducing the weight of the door impact bar, a conventional one, for example, as disclosed in JP-A-56-50813,
Since pipes are more advantageous than plates, steel pipes have recently been used more frequently as door impact bars. Furthermore, for example, JP-A-01-20503
As disclosed in Japanese Patent No.
It is intended to be thin.

Further, in the door impact bar disclosed in Japanese Patent Application Laid-Open No. 51-42216, the central section modulus from both ends is increased stepwise so that it buckles stepwise when a bending load is applied. Therefore, it is possible to reduce the weight of the bar having a uniform cross section. That is, as shown in FIG. 2, an outer beam 6 is added as a reinforcing material to the center of the door impact bar inner beam 5 in the longitudinal direction, and both ends of the outer beam 6 are welded to the door 4. The fulcrum distance BB when the outer beam 6 is present is shorter than the fulcrum distance AA when the beam 6 is not present, and the bending moment is reduced, which enables weight reduction.

[0004]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
The door impact bar with a varied section modulus disclosed in Japanese Patent No. 2216 is very effective when a load is applied to the central part thereof, but the actual side collision position is not always the same position of the door. However, in some cases, a load may act at a position deviating from the center, and in that case, a door impact bar having a higher section modulus only in the center is disadvantageous. Furthermore, since the load point is considered to have a width rather than a single point, a door impact bar that can withstand a load system having a width is required.

Further, since the load after the door impact bar buckles is almost not taken by the door impact bar, the load is almost applied to the door impact bar mounting portion (hereinafter referred to as a bracket). If the load point deviates from the center in the length direction, the load acting on the bracket will increase, and the bracket will be damaged immediately after buckling. Therefore, in order to take full advantage of the door impact bar, it is necessary to reduce the load on the bracket. The present invention is a door / door that can fulfill such purposes.
To provide steel pipes for impact bars.

[0006]

The feature of the present invention resides in a steel pipe for automobile door reinforcing material having flat cross-section portions and circular cross-section portions alternately in the longitudinal direction.

The details of the present invention will be described below. As shown in FIG. 1, the door impact bar of the present invention has flat cross-section portions 1 and circular cross-section portions 2 that alternate in the lengthwise direction. Deformation is not concentrated at one point on the door impact bar, regardless of the width of the object, and the final bending absorbed energy increases. That is, when a load is applied to the center in the length direction as shown in FIG. 5A, the flat portions on both sides of the load point are bent first. For this reason, the maximum load is somewhat reduced compared to a steel pipe having a uniform cross section, but since the load point is not bent, the load is maintained to some extent after that, so that the final bending absorbed energy becomes equal to or higher than that. Further, even if a load is applied to the position as shown in FIG. 5 (b), the flat portion in the vicinity bends first and the steel pipe bears the load until it buckles at the position of the load point. The load acting on the bracket can be reduced as compared with the steel pipe. Even when a punch having a width like a bumper of an actual vehicle is loaded as shown in FIG. 5C, the steel pipe is effective as in the case of FIG. 5B.

A method of forming flat portions and non-flat portions alternately in the length direction is, for example, a roller 8 having several small rollers 7 as shown in FIG.
There is a method of rolling the impact bar 3 continuously.
The pitch and shape of the unevenness can be easily changed by changing the number and size of the small rollers 7.

When the door impact bar of the present invention is installed in a door, as shown in FIG. 4, the oblong side of the flat cross section of the door impact bar 3 is attached to the inner plate and the outside of the door 4. It is arranged so that it faces the plate side, and the oval side is arranged so as to face vertically in the vertical direction. In addition, the position in the length direction is set so that the true circular cross section is arranged in the center.

[0010]

[Example] Currently, a door impact bar is generally used as an outer diameter of 31.8 mm, wall thickness of 2.8 mm, and length of 9
It was manufactured using a 50 mm steel pipe. The width of the flat portion on the short circle side was 20 mm, and the pitch was 100 mm. Table 1 shows the bending test results of the entire door with the product (A) incorporated in the door.
And shown in FIG. For comparison, the results of the case of a steel pipe (B) made of the same material and having a uniform cross section are also shown.

[0011]

[Table 1]

From this, when the door impact bar (A) of the present invention and the steel pipe (B) of uniform cross section are compared, the maximum load of the door impact bar of the present invention is somewhat lower, Maximum displacement and final bending absorption energy (load −
It can be seen that the area enclosed by the displacement curve) is large.

[0013]

According to the present invention, the safety of the occupant in the vehicle can be ensured regardless of the position of the door in the actual side collision.

[Brief description of drawings]

FIG. 1 is a door impact bar obtained by the present invention.

FIG. 2 is an explanatory view of a door impact bar disclosed in Japanese Patent Laid-Open No. 51-42216.

FIG. 3 is an explanatory view for manufacturing the door impact bar of the present invention.

FIG. 4 is a layout diagram when the door impact bar of the present invention is installed inside the door.

FIG. 5 is a deformation diagram when a load is applied to the door impact bar of the present invention.

FIG. 6 is a bending load-displacement diagram of a door impact bar of the present invention and a steel pipe having a uniform cross section.

[Explanation of symbols]

 1 Flat part 2 True circle part 3 Door impact bar 4 Door 5 Door impact bar inner beam 6 Door impact bar outer beam 7 Small roller 8 Roller 9 Punch

Claims (1)

[Claims] 1. A steel pipe for a vehicle door reinforcing material, which has flat cross-sections and circular cross-sections alternately in the length direction.