JPH07310156A - Automobile frame structure its manufacture - Google Patents

Abstract

PURPOSE:To produce an automotive frame structure having excellent energy absorbing characteristic without deterioration change in the lapse of time at low manufacturing cost. CONSTITUTION:At the time of forming a front frame member 10R, a JIS 7003 aluminum alloy is used and a T5 material is extrusion-formed from this alloy, which has a hollow square shape in its cross section. This front side frame member 10R formed is butted to a front side cross member 30 and welded, covering the whole circumference A, to manufacture a test material. To this test material, the heating treatment at 160 deg.C for 20min is applied in the atmosphere. Then, a test for loading the compressive force in the axial direction is executed by using the test material and the result is shown as (b) in the figure. The comparing example leaving the test material for seven days in the room temp. as it is, is also shown in the figure (b). It is clear in this figure that the one by this invention has larger energy absorbing quantity than the comparing example.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of a frame serving as an automobile skeleton, and more particularly, it is provided with a strength member such as a side member arranged to extend in the front-rear direction of a vehicle body to absorb impact energy. TECHNICAL FIELD The present invention relates to a frame structure and a manufacturing method thereof.

[0002]

2. Description of the Related Art Generally, an automobile uses a monocoque body. In this method, a plate member is press-molded, and these are combined to form a box-shaped member to form a strength member.

By the way, various measures have been taken in automobiles to secure the safety of passengers by absorbing the impact force from the front and rear directions. The side frame members extending in the front-rear direction of the vehicle body are designed to be deformed and absorb collision energy when a certain load is applied. That is, the side frame member is formed with, for example, an oval projecting portion that is orthogonal to the front-rear direction of the vehicle body, and this portion serves as the starting point of deformation at the time of a vehicle collision, so that the impact force is suppressed and the amount of energy absorbed thereafter. Is designed to increase

Further, the frame type vehicle body has an advantage that it is strong against a shock or a load in a frontal collision or a rearward collision direction and has high durability, although the vehicle weight itself is increased as compared with a frameless type vehicle body. is doing. Recently, it is considered to use an aluminum alloy for a vehicle body for the purpose of weight reduction as a measure against environmental problems, and in addition to the monocoque system, an automobile frame structure using an aluminum extruded material called a space frame structure is being studied. Also in this frame structure, similarly to the above, an overhang portion is adopted as a measure for energy absorption.

Further, in Japanese Unexamined Patent Publication No. 64-67482, a plurality of weld beads are formed at intervals on the outer periphery of a frame part of aluminum light alloy to form an absolute low rigidity part in a node shape. Then, by easily causing deformation in the frame member in the longitudinal direction at the low rigidity portion,
A frame structure for absorbing impact force is disclosed.

[0006]

However, the processing of the overhanging portion for absorbing the impact force as described above complicates the mold structure, and particularly in the processing of the extrusion mold material, the processing method itself needs to be changed. However, there is a problem that the cost is increased.

Further, according to Japanese Patent Laid-Open No. 64-67482, aluminum alloys generally used as structural members for automobiles are JIS 6000 series or 7000 series.
Among the heat-treated alloys of the series, especially the 7000 series alloy has the property that, when left at room temperature after welding, it age-hardens and the strength of the welded portion once reduced is recovered. For this reason,
The 7000 series alloy exhibits excellent energy absorption characteristics immediately after welding, but the hardness of the welded portion increases with the lapse of time, and along with this, the energy absorption characteristics deteriorate and even become a dangerous state. There are also points. 600
Even if the 0-based alloy is left in a room temperature atmosphere after welding, the strength of the welded portion does not recover.

The present invention has been made in view of the problems of the above-mentioned prior art, and does not require an overhanging portion to prevent cost increase, and has an excellent energy absorption characteristic that does not change over time. It is an object to provide a structure and a manufacturing method thereof.

[0009]

Means for Solving the Problems The present invention for attaining the above-mentioned object comprises Zn3.5-7.0 wt% and Mg0.4-
Includes 2.5 wt% and further contains Cu 0.01 to 0.20 w
t%, Mn 0.1 to 1.0 wt%, Zr 0.05 to 0.
A frame structure for an automobile, comprising an extrusion-molded or press-molded frame member made of an aluminum alloy containing 25% by weight of Cr and 0.01 to 0.30% by weight of Cr and having a closed cross-section structure extending in the front-rear direction of the vehicle body. , The frame member is heated to a temperature of 120 to 250 ° C.
It is characterized in that the heat treatment of (1) is performed within 60 minutes. Further, before performing the heat treatment, a joint portion between another energy absorbing member that constitutes the vehicle body and the tip of the frame member is welded. Further, the energy absorbing member is a side frame member. The joint may be welded all around, the joint may be formed at one location, and the vehicle body may be made of the same aluminum alloy as the frame member. The production method of the present invention is Zn3.5-7.0w.
t%, containing 0.4 to 2.5 wt% of Mg, and further Cu
0.01 to 0.20 wt%, Mn 0.1 to 1.0 wt
%, Zr 0.05 to 0.25 wt%, Cr 0.01 to
An aluminum alloy containing one or more of 0.30 wt% is extruded or press-formed into a closed cross-section to produce a frame member, and the joint between the frame member and another energy absorbing member constituting the vehicle body is entirely formed. Circumferentially welded to the frame member and the energy absorbing member,
It is characterized in that a heat treatment is carried out at a temperature of up to 250 ° C. for 60 minutes or less. Further, the heat treatment can be performed by a heat treatment for paint baking of an automobile.

[0010]

The function of the aluminum alloy is determined by the strength required for the purpose of use as an automobile frame. In the JIS 6000 series or 7000 series heat treated alloys, the precipitates that contribute to strength improvement are solid-solved by welding heat and the strength decreases. However, in the 7000 series heat treated alloy, strength recovery occurs during room temperature storage. I will end up. However, if the heat treatment is performed for a short time of 60 minutes or less, the precipitation state changes and the strength decreases, so that there is an energy absorption effect similar to that of the conventional structure having the overhanging portion. This led to the present invention. Further, the frame member is not limited to aluminum, but the entire vehicle body may be made of aluminum alloy. This facilitates welding and also improves the strength of the welded portion.

[0011]

Embodiments of the present invention will now be described with reference to the drawings. Here, the present invention will be described by taking a frame structure including a front side frame member and a rear front side frame member as an example.

(First Embodiment) As shown in FIG. 1, a pair of front side frame members 10R, 10 as frame members made of an aluminum alloy of a vehicle body 1.
Of the L, the front side frame member 10R on the front right side of the vehicle body 1 will be described.
c and the rear end portion 10a are linear, but the intermediate portion 10b connecting these linear portions 10c and 10a is
In order to avoid interference with the front wheel 2, it is bent three-dimensionally downward and outward while extending rearward. The front side frame member 10R is integrally provided with a vertically extending flange 10d for connecting to a panel member (not shown) such as a front wheel apron. Both front side frame members 1
The tips of 0R and 10L are connected to a front side cross member 30 to which a bumper (not shown) is attached.

Similarly, of the pair of rear side frame members as frame members of the vehicle body 1, the front end portion 20c and the rear end portion 20a of the rear right side rear member 20 of the vehicle body 1 shown in FIG. Although it is linear, these linear portions 20c, 2
In order to avoid interference with the rear wheel 3, the intermediate portion 20b connecting 0a is extended toward the upper side and the inner side of the vehicle body while extending rearward.
It is bent into a dimension. Further, a pair of flanges 20 extending in the horizontal direction for connection with a trunk floor or the like.
The d and 20e are integrally erected, and the extension 20f adjacent to the rear wheel 3 of the one flange 20d is extended vertically upward in order to connect with the rear wheel apron. The rear ends of the pair of rear side frame members are joined to a rear cross member (not shown) to which a bumper (not shown) is attached.

The characteristic part of this embodiment will be described below. As shown in FIG. 2 (a), when molding the front side frame member 10R, JIS 70
03 (Al-5.5% Zn-0.7% Mg) alloy is used, and the T5 material of this alloy is extruded into a hollow cross section. The front side frame member 10R is butt-welded to the front side cross member 30 made of the same aluminum alloy as the front side frame member 10R and welded, and this welded portion is welded all around as shown by symbol A. . The test material produced in this way has 16
A short heat treatment for 20 minutes was performed in an atmosphere of 0 ° C. A test for applying a compressive force in the axial direction was conducted using this test material, and the result is shown in FIG. 2 (b). As a comparative example, an example in which the test material was left at room temperature for 7 days was given. As is clear from this figure, the energy absorption amount (indicated by the area surrounded by the horizontal axis and the curve) in the present example is large, and in the comparative example, fracture occurs from the vicinity of the welded portion at the initial stage of deformation However, the amount of energy absorbed is also small.

Table 1 below shows experimental data of heat treatment time of 60 minutes or less, experiment data of more than 60 minutes, and heat treatment temperature of 120 to 250 ° C., 110 ° C. or less and 260 ° C. or more, respectively. It is as follows.

[Table 1] As is clear from the results in Table 1, the more preferable ranges of the heating temperature and the heating time are 120 to 200 ° C., respectively.
Within 40 minutes.

(Second Embodiment) As shown in FIG. 3A, when molding the rear side frame member 20R, JIS7N01 (Al-4.5% Zn-1.3%) is used.
Mg) alloy was used, and T4 material of this alloy was press-formed into a hat shape, and then the lid material 50 was joined thereto by spot welding to form the rear side frame member 20R having a hollow cross section. The lid member 50 is also made of JIS7N01 alloy. This rear side frame member 20R
Is abutted and welded to the rear side cross member 40 made of the same aluminum alloy as the rear side frame member 20R, and this welding is, as indicated by the symbol B, the entire circumference of the joint. For the test material produced in this way, 1
A short-time heat treatment was performed for 20 minutes in an atmosphere of 50 ° C.
A test for applying a compressive force in the axial direction was conducted using this test material, and the result is shown in FIG. 3 (b). As a comparative example, an example after the test material was left at room temperature for 30 days was given. As is clear from this figure, it can be seen that also in this example, the energy absorption is excellent.

In each of the above-mentioned embodiments, the welding portion of the side frame member and the cross member is one portion of the joint portion, and the welding man-hour is greatly reduced. That is, a plurality of welding beads may be formed at the welding location as disclosed in JP-A-64-67482, but this requires a large number of welding steps and is not economical. As described above, it is preferable to employ full-circumferential welding at one joint.

The heat treatment of the frame may be performed separately in the automobile manufacturing process, but the present invention is not limited to this, and when painting is performed in the above-mentioned manufacturing process, it is performed by the heat treatment for paint baking treatment. Is also possible, and the production cost is reduced. In this case, the heat treatment temperature should be set to 150 ° C. to 200 ° C. which is the same as the coating baking temperature, and the heat treatment time should be set to 10 minutes to 30 minutes. Further, it goes without saying that the present invention is not limited to the frame-type vehicle body and can be applied to a frameless-type vehicle body.
A heat treatment type alloy of IS6000 series may be used. Not only the frame as the energy absorbing member is made of aluminum, but the entire vehicle body may be made of aluminum alloy.

[0019]

Since the present invention is configured as described above, it has the following effects. In the invention according to claim 1, it is not necessary to provide the overhanging portion as in the conventional case. It is possible to provide a frame structure that has energy absorption characteristics that do not change over time and that is low in manufacturing cost.
As a result, safety can be efficiently added, which has great industrial significance. In addition to the above effects, the invention according to claim 2 reduces the number of welding steps and further reduces the manufacturing cost. The invention according to claim 3 can provide a side frame member that does not change with time. As in the invention according to claim 4 or 5, the welded portion can be welded all around or in one place. According to the sixth aspect of the present invention, the vehicle body and the frame member are made of the same type of aluminum alloy, so that welding is facilitated and welding strength is also improved. The invention according to claim 7 can easily provide the frame structure of the automobile. Claim 8
The invention described in (1) reduces energy cost and eventually production cost.

[Brief description of drawings]

FIG. 1 is a perspective view of an automobile showing an outline of a frame structure of the automobile of the present invention.

FIG. 2 is a diagram showing a first embodiment of the present invention, (a)
Is an enlarged view of a test material which is a bonding material of the front side frame member and the cross member, and (b) is a graph of load-displacement characteristics of the test material and the comparative example.

FIG. 3 is a diagram showing a second embodiment of the present invention, (a)
Is an enlarged view of a test material which is a bonding material between the rear side frame member and the cross member, and (b) is a graph of load-displacement characteristics of the test material and the comparative example.

[Explanation of symbols]

1 vehicle 2 front wheel 3 rear wheel 10R, 10L front side frame member 20R rear side frame member 10a rear end portion 10b straight portion 10c front end portion 10d, 20d, 20e flange 20f extension portion 30 front side cross member 40 rear side cross member 50 cover material

Claims (8)

[Claims] 1. Zn3.5-7.0 wt%, Mg0.4
.About.2.5 wt%, further Cu 0.01 to 0.20
wt%, Mn 0.1-1.0 wt%, Zr 0.05-
A frame of an automobile, which is made of an aluminum alloy containing at least one of 0.25 wt% and 0.01 to 0.30 wt% Cr, and which is provided with an extrusion-molded or press-molded frame member having a closed cross-sectional structure extending in the front-rear direction of the vehicle body. In the structure, the frame member of the automobile is characterized in that the frame member is subjected to a heat treatment at a heating temperature of 120 to 250 ° C. for 60 minutes or less. 2. The frame structure for an automobile according to claim 1, wherein a joint portion between another energy absorbing member constituting the vehicle body and a tip end of the frame member is welded before the heat treatment. 3. The frame structure for an automobile according to claim 2, wherein the energy absorbing member is a side frame member. 4. The frame structure for an automobile according to claim 2, wherein the joint portion is welded all around. 5. The automobile frame structure according to claim 2, wherein the joint portion is provided at one place. 6. A frame structure for an automobile, wherein the vehicle body is made of the aluminum alloy according to claim 1. 7. Zn3.5-7.0 wt%, Mg0.4
.About.2.5 wt%, further Cu 0.01 to 0.20
wt%, Mn 0.1-1.0 wt%, Zr 0.05-
An aluminum alloy containing one or more of 0.25 wt% and 0.01 to 0.30 wt% Cr is extruded or press-formed into a closed cross-section to produce a frame member, and the frame member and other components constituting the vehicle body are formed. The entire circumference of the joint with the energy absorbing member is welded, and 1 is attached to the frame member and the energy absorbing member.
A method for manufacturing an automobile frame structure, which comprises performing a heat treatment at 20 to 250 ° C. for 60 minutes or less. 8. The method for manufacturing an automobile frame structure according to claim 7, wherein the heat treatment is performed by a heat treatment for paint baking of an automobile.