JP4104530B2 - Door beam - Google Patents

Description

  The present invention relates to a door beam installed inside a door of an automobile.

  As a shock-absorbing member of an automobile, a reinforcing lateral beam (door beam) is mounted inside the door in order to protect an occupant from the impact of a collision from the side. The door beam is mainly intended to prevent obstacles from entering the door as much as possible. It is required to have high rigidity and high ability to absorb energy at the time of collision. Made door beams have come to be used.

An aluminum alloy door beam currently used in mass-produced vehicles in Japan is composed of a single hollow extruded shape, and has a uniform cross-sectional shape in the longitudinal direction except for attachment portions at both ends. However, when the door beam is regarded as a beam that receives a bending moment, it is not necessary to have a uniform cross section in the longitudinal direction, and there is room for reducing the weight by setting the bending rigidity at both ends to be smaller than the bending rigidity at the center. For example, the door beam described in the following Patent Documents 1 to 5 has been proposed based on such an idea.
On the other hand, when extruding a hollow extruded shape, there are problems such as a decrease in extrusion speed, limitations on material selection, and uneven cooling. In order to solve this, in Patent Document 6 below, extruded profiles having different lengths are fitted along the longitudinal direction, and a hollow closed cross section is formed between the fitted extruded profiles along the longitudinal direction. A door beam is described which is constructed and has an attachment formed at the end of the longer extruded profile.

JP-A-4-266524 JP-A-5-4518 JP-A-5-270263 JP-A-6-227254 Japanese Utility Model Publication No. 7-23617 JP-A-10-94444

  SUMMARY OF THE INVENTION An object of the present invention is to provide a door beam of the type described in Patent Document 6 with an increased bending rigidity at a central portion in the length direction to reduce the weight of the entire door beam and to provide an optimum structure thereof.

In the present invention, a plurality of short aluminum alloy extruded shapes are fitted in a line along the longitudinal direction of the long shape base material, and the end surfaces of the short aluminum alloy extruded shapes are in contact with each other. In the door beam in which a hollow cross section is formed between the combined long shape member and the short aluminum alloy extruded shape and mounting portions are formed at both ends of the long shape member, the short aluminum alloy extruded shape members are mutually connected. When the total length of the short aluminum alloy extruded shape is L, the cross-sectional shape of both ends and the cross-sectional shape of the central portion are different within the range of the length L. The cross-sectional secondary moment at the center is set to be larger than I, where I is the cross-sectional secondary moment at both ends.

As a concrete form of the door beam, (1) in order to increase the cross-sectional secondary moment of the central part, the height of the central part when viewed in the thickness depth direction of the door is set to be larger than the heights of both ends. 2) The number of short aluminum alloy extruded shapes is at least three. (3) The long shape material and the short aluminum alloy extruded shape are joined by, for example, caulking or bonding so that they do not shift in the length direction. And so on.
Further, as the long shape material, a shape steel (press-formed shape steel or rolled shape steel) or an aluminum alloy extruded shape is desirable, and the material and alloy type of the short aluminum alloy extruded shape can be changed.

  According to the present invention, it is possible to increase the bending rigidity of the central portion in the length direction and to reduce the weight of the entire door beam.

Hereinafter, the door beam according to the present invention will be described more specifically with reference to FIGS.
A door beam 1 shown in FIG. 1 (a) is a combination of four aluminum alloy extruded profiles, and is a long aluminum alloy extruded profile 2 (hereinafter referred to as a profile 2) having attachment portions 2a formed at both ends. ), Short aluminum alloy extruded shapes 3 to 5 (hereinafter referred to as a shape 3, a shape 4, and a shape 5, respectively) fitted in a line along the longitudinal direction of the shape 2. The long shape member 2 and the short shape members 3 to 5 are fitted along the longitudinal direction at two places. In this example, the four shape members 2 to 5 are all open cross sections, but are fitted. The cross section constituted by the shaped material 2 and the shaped materials 3 to 5 is a hollow closed cross section. After the fitting, it is desirable to join the shape member 2 and the shape members 3 to 5 by caulking or bonding so as not to be displaced in the length direction.

In this door beam 1, the shape members 3 and 5 at both end portions have the same cross-sectional shape, and the cross-sectional shape of the shape member 4 at the center portion is in the depth direction of the door (in a horizontal plane) as compared to the shape members 3 and 5 at both end portions. The height h is set high. Thereby, when the sectional secondary moments 3 and 5 of the shape members at both ends are Ie, the sectional secondary moment Ic of the shape member 4 at the central portion can be set larger than Ie. However, it is desirable to set Ic smaller than 2Ie. This is because when the sectional moment of inertia Ic of the central shape member 4 is increased, the bending rigidity thereof is increased and the initial rigidity is increased. However, if this is too high, the shape members 3 and 5 at both ends are added to the bending rigidity of the central portion. This is because it cannot follow, and the cross-section collapses or breaks at the boundary. In addition, when Ic = Ie, it becomes the same as the uniform cross section, and as a result, the weight reduction effect is lost.
On the other hand, when the total length of the short shape members 3 to 5 is L, the length Lc of the center shape member 4 is preferably set in the range of (3/8 to 5/8) L. This is because if Lc is reduced, the weight can be reduced. However, if this is too small, the boundary between the shape 4 at the center and the shapes 3 and 5 at both ends cannot withstand bending, and the cross-section collapses. The reason is that if it is too large, it becomes close to a uniform cross section and the effect of reducing weight is reduced.

In addition, as a method of increasing the cross-sectional secondary moment Ic of the profile 4, there are a method of increasing the height in the depth direction of the door as shown in FIG. 1 and a method of widening in the vertical direction (in the vertical plane). . The former has a great effect of increasing the moment of inertia of the cross section while minimizing the increase in weight. Also, as shown in FIGS. 2 and 3, the outer panel 6 of the door and the outer side of the door beam are compared with those of the uniform cross section. Since the distance is shortened (X ₀ → X ₁ ), the distance until the door beam 1 starts to absorb the collision energy when the load P is applied at the time of collision, that is, the idle travel distance is shortened. Will increase. In particular, when the door outer panel 6 has an outwardly convex shape, the effect of shortening the idling distance is great. The latter has an effect of dispersing the load because it takes a large load surface to be subjected to a side collision. Any of these methods can be used individually or in combination as appropriate.

  The door beam shown in FIG. 4 shows various planar shapes of a short extruded shape, and (a) and (b) are obtained by obliquely cutting the abutting end surfaces of the shape 3 and the shape 4 and 5. 1 and (c) are obtained by obliquely cutting both ends of the projecting portion of the central shape member 4, and (d) is obtained by obliquely cutting both of them. By cutting diagonally the end surfaces where the shape members 3 and 4 and the shape members 4 and 5 are in contact with each other, there is an advantage that the contact length between the two increases and the two are easily deformed as a unit. In addition, by cutting the both ends of the protruding portion of the central shape member 4 at an angle, the change in the moment of inertia in the cross section in the longitudinal direction, that is, the change in the bending rigidity is alleviated, and the cross-section collapse or breakage occurs at the boundary. Can be suppressed. If it is made like (d), both advantages can be enjoyed.

  Since the long shape member 2 is located on the inner side, it becomes a bending tension side at the time of collision, and is easy to break. Therefore, a material having higher ductility than the short shape members 3 to 5 is desirable. In that sense, it is desirable to have a fibrous structure in the case of an aluminum alloy extruded shape. Or it can also be set as the molded article of a steel plate with high drawability as the shape material 2. FIG. In that case, in order to prevent galvanic corrosion, it is necessary to use a galvanized steel sheet or to apply a structural adhesive to the short shape members 3 to 5 made of an aluminum alloy extruded shape. It is desirable to do. Bonding with such an adhesive also has the effect of increasing the bonding strength of the sheared portion.

As shown in Fig. 1, when using a long aluminum alloy extruded profile 2 directly on the vehicle body side (usually the inner panel side of the door) (bracketless), workability and SCC resistance (corresponding to corrosion) From the viewpoint of property, it is desirable to be made of 6000 series aluminum alloy. In addition, the post-quenching state (T1, T4) is more preferable than the strong state (T5, T6) that is artificially aged, and a fibrous structure is preferable. When the vehicle body to be attached is made of aluminum, welding can be considered, but a fibrous structure is better from the viewpoint of weldability.
Although only three examples of the short aluminum alloy extruded shape have been shown so far, it is also possible to form a plurality of the shapes 4 in the central portion within the length L.

It is the top view (a) of a door beam , and sectional drawing (b) of each part. It is a top view of the door beam with which the inside of a door was mounted | worn. It is a top view of the door beam similarly mounted inside the door. It is a top view of the door beam of other forms .

Explanation of symbols

1 Door beam
2 Long profile
3-5 short profile
6 Door outer panel 7 Door inner panel

Claims (5)

A plurality of short aluminum alloy extruded shapes are fitted in a line along the longitudinal direction of the base long shape material, and the end surfaces of the short aluminum alloy extruded shapes are in contact with each other and are fitted. In a door beam in which a hollow cross section is formed between the profile and the short aluminum alloy extruded profile, and mounting portions are formed at both ends of the long profile, the short aluminum alloy extruded profile is cut obliquely. When the total length of the short aluminum alloy extruded shapes is L, the cross-sectional shape of both ends and the cross-sectional shape of the center are different within the length L. A door beam characterized in that, when the cross-sectional secondary moment is I, the cross-sectional secondary moment of the central portion is larger than I. The door beam according to claim 1, wherein the height of the central portion when viewed in the depth direction of the door is set to be larger than the height of both ends. The door beam according to claim 1 or 2, wherein a total of three short aluminum alloy extruded shapes forming the central portion and both end portions are fitted to the long shape material. The door beam according to any one of claims 1 to 3, wherein a long shape member and a short aluminum alloy extruded shape member are joined to prevent displacement in the length direction. 5. The door beam according to claim 1 , wherein the long shape member is made of a shape steel or an aluminum alloy extruded shape member.

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