JPH0986442A - Front body structure for vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To collapse-deform crush boxes at the time of a head-on collision and improve the collision energy absorbing function by fixing the crush boxes having a box-shaped cross section on bend sections fitted at the lower sections of the right and left body frames of a front body and provided at the middle in the longitudinal direction of a sub-frame. SOLUTION: A sub-frame 2 is constituted of the right and left vertical frames 3 fitted to the lower section of a body frame 1 and the front and rear horizontal frames 4, 5 connecting them at the front and rear, and bend sections 31 are formed at the middle sections of the vertical frames 3. The front portions 33 of the vertical frames 3 are offset downward against the rear portions 32 by the bend sections 31, and gaps are formed between the bend sections 31 and the lower face section of the body frame 1. Crush boxes 6 having a box-shaped cross section are fitted at the upper face sections of the bend sections 31, and the gaps between the lower face section of the body frame 1 and the bend sections 31 are shrunk. The collision energy absorbing capability is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a front vehicle body structure of a vehicle, and particularly to an improvement of collision energy absorption characteristics of a sub-frame provided at a lower portion of a frame at a front portion of the vehicle body.

[0002]

2. Description of the Related Art A subframe is provided under a frame of a front body of a vehicle, a suspension and an engine are mounted on the subframe, and a collision energy absorbing function is effective for inputting a large load at the time of a frontal collision of the vehicle. Has been developed in the past, for example, the actual Kaihei 4-518
No. 4 publication.

[0003]

However, as shown in FIG. 4, the subframe a is bent downward in the middle because the suspension and engine mounting functions are prioritized due to layout restrictions. Bending part b
In many cases, the bent portion b has a structure in which the front portion of the subframe a is offset downward with respect to the vehicle body frame c. Thus, the sub-frame structure having the curved portion b is extremely disadvantageous as an effective drag member at the time of frontal collision. In order to make the curved sub-frame a function as a target drag member, the sub-frame a
It is common to deal with this by increasing the plate thickness, but if the plate thickness is increased, there arises a problem that the weight increases and the cost increases.

Further, the G waveform (energy absorption waveform) at the time of a collision of the front vehicle body provided with the sub-frame having a curved portion shows the characteristic as shown by the solid line in FIG.

That is, since the drag increases almost linearly from the initial stage of the collision shown in FIG. 5 (A) and the bumper beam is crushed as shown in FIG. 5 (B), the drag is temporarily increased as shown in FIG. Decrease. When the bumper beam is completely crushed,
As shown in (C), the vehicle body frame c and the subframe a
A buckling drag force with and is generated, and the drag force increases linearly again. However, when the peak of the drag force shown in Fig. 6 is exceeded,
As shown in FIG. 5 (D), bending deformation begins at the bending portion b of the sub-frame a, and the vehicle body frame c also begins to bend accordingly, and the drag changes to a decreasing tendency. An increase in the drag force appears temporarily while the drag force is decreasing. This is because the bending of the sub-frame a pushes up the vehicle body frame c as shown in FIG. Is not enough to affect.

If an attempt is made to increase the drag by increasing the plate thickness of the sub-frame a, as shown by the dotted line in FIG. 6, the drag is generally increased with a waveform having the same shape as the characteristic shown by the solid line. , After the peak, the drag force rapidly decreases,
That characteristic does not change.

In order to effectively absorb the collision energy, it is desirable that the peak of the drag force has a waveform that lasts for a certain period of time. However, as described above, due to the bending deformation of the subframe a, the drag force exceeds the drag force. Has a characteristic of rapidly decreasing, and it is difficult to obtain an effective collision energy absorption effect even if the plate thickness of the subframe a is increased.

An object of the present invention is to solve the above conventional problems.

[0009]

According to the present invention, as described above, in a subframe in which a bent portion is provided in the middle of a vertical frame and a front portion is offset downward from a rear portion, the bent portion or the front portion is formed. When a crash box with a box-shaped cross section is mounted on the upper surface of the sub-frame and the vertical frame of the sub-frame tries to bend and deform from the bending part during a frontal collision, the crash-box is pushed onto the front mount part of the sub-frame or the body frame. It is crushed so that the function of absorbing collision energy can be improved.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to FIG.
It will be described with reference to FIGS.

In FIG. 1, reference numerals 1 and 1 denote left and right body frames vertically passing along a front portion of a vehicle body, that is, right and left side walls of an engine room. The body frame 1 has a box shape as is well known in the art. Make a cross section.

Reference numeral 2 denotes a subframe. The subframe 2 includes left and right vertical frames 3 and 3 which are attached and fixed to the lower surface of the vehicle body frame 1, and the vertical frames 3 and 3 are a front portion and a rear portion. The front horizontal frame 4 and the rear horizontal frame 5 are connected to each other. The vertical frame 3, the front horizontal frame 4 and the rear horizontal frame 5 are each formed of a box-shaped cross-section member.

A bent portion 31 which bends downward is formed in a substantially middle portion of the vertical frame 3 in the front-rear direction, and the bent portion 31 substantially extends along the lower surface of the vehicle body frame 1 to form a rear portion 32 of the vertical frame 3. On the other hand, the front portion 33 is offset downward, and a gap is formed between the curved portion 31 and the front end portion of the front portion 33 and the lower surface portion of the vehicle body frame 1. A front mount portion 33a that protrudes upward is provided near the front end portion of the front portion 33, and the sub-frame 2 includes the rear mount portion 32a provided at the rear portion of the rear portion 32 and the front mount portion 33a. It is attached to the lower surface of the.

A crash box 6 having a box-shaped cross section is attached to the upper surface of the bent portion 31 of the vertical frame 3 by welding or fixing with a bolt or the like, and the lower surface of the vehicle body frame 1 is attached by the crash box 6. The structure is such that the gap between the curved portion 31 of the vertical frame 3 and the curved portion 31 is reduced. The mounting position of the crush box 6 is not limited to the bent portion 31 shown in the figure, but may be mounted on the upper surface of the front portion 33 in front of the bent portion 31, and the height, width and length of the crush box 6 can be arbitrarily set. Can be set. The crash box 6 is made of a plate material thinner than the plate material forming the sub-frame 2, but may be integrally formed of one thin plate, or may be formed by welding a plurality of thin plates. .

In the above-mentioned structure, the deformation mode of the vehicle body frame 1 and the sub-frame 2 at the time of a frontal collision of the vehicle is shown in FIG.
(A), (B), and (C) in order, and the collision energy absorption characteristics at that time are as shown by the G waveform shown by the solid line in FIG.

That is, the drag force increases almost linearly from the initial stage of the collision, and after the bumper beam is crushed, the drag force decreases a little, as shown in FIG. Occurs and the drag force increases linearly. The G waveform so far is the G waveform of the conventional structure shown in FIG.
It is the same as the waveform.

When the drag force reaches a peak as shown in FIG. 3 and a bend is generated from the bent portion 31 of the vertical frame 3, the drag force tends to decrease, but when the vertical frame 3 begins to bend, the drag force shown in FIG. ) To (C), the crush box 6 is pressed against the lower surface portion of the vehicle body frame 1 and is pressed by the front mount portion 33a to be gradually crushed in the vertical direction and the front-back direction. When the dragging force is generated, the G waveform rises again as shown in FIG. The crushing deformation resistance of the crush box 6 and the buckling deformation time of the vertical frame 3 due to the bending of the vertical frame 3 being suppressed to some extent by the crush box 6 provide a high resistance value close to the peak. The state shown lasts for a predetermined time, and the collision energy can be effectively absorbed only in the shaded portion, as compared with the case of the conventional structure.

The collision energy absorption characteristics shown by the solid line in FIG. 3 are obtained by tuning the height, width, length, plate thickness, mounting position, etc. of the crash box 6, for example, as shown by the chain line in FIG. It is also possible to obtain the collision energy absorption characteristic, and the collision energy absorption characteristic can be easily tuned only by the crash box 6 when the subframe 2 is used for different vehicle types.

[0019]

As described above, according to the present invention, the left and right vertical frames joined and fixed to the lower surface portions of the left and right vehicle body frames, and the front side horizontal frame connecting the left and right vertical frames with the front and rear portions thereof. And a rear horizontal frame, wherein the vertical frame is formed with a bent portion that bends downward, and the front portion is offset downward with respect to the rear portion, the bent portion of the vertical frame or the front side By installing a crash box having a box-shaped cross section on the upper surface of the part, when the front frame collides and the vertical frame is bent and deformed, the crash box is crushed and deformed, thereby improving the collision energy absorption function. In addition, the crash energy absorption characteristics can be tuned easily with the crash box. The scan is not a structured weight gain in a relatively thin plate material, in which costs I coupled with the like that is easy assembling at low cost, can lead to practical effect considerable.

[Brief description of drawings]

FIG. 1 shows an embodiment of the present invention, in which (A) is a perspective view and (B) is a cross-sectional view taken along line BB of (A).

2 (A), (B) and (C) are side explanatory views sequentially showing deformation modes of a vehicle body frame and a sub-frame at the time of a frontal collision.

FIG. 3 is a diagram for explaining a collision energy absorption characteristic during a frontal collision according to the present invention.

FIG. 4 is a perspective view showing an example of a conventional subframe structure.

5A to 5E are side explanatory views sequentially showing deformation modes at the time of a frontal collision of a vehicle equipped with the sub-frame shown in FIG.

FIG. 6 is a diagram for explaining collision energy absorption characteristics of a conventional structure at the time of frontal collision.

[Explanation of symbols]

 1 Body Frame 2 Sub-frame 3 Vertical Frame 4 Front Frame 5 Rear Frame 6 Crash Box 31 Bending Part 32 Rear Part 32a Rear Mount Part 33 Front Part 33a Front Mount Part

Claims (3)

[Claims] 1. A subframe which is attached to a lower part of a left and right body frame of a front vehicle body, wherein a front part is located below the body frame at a predetermined interval at a curved portion in the middle of the front-rear direction. In the vehicle, a crash box having a box-shaped cross section is fixed on the bent portion of the subframe, and the distance between the bent portion of the subframe and the body frame is reduced by the crash box. Front body structure. 2. A sub-frame mounted on the lower part of the left and right vehicle body frames of the front vehicle body, wherein the front portion is located below the vehicle body frame at a predetermined interval at a curved portion in the middle of the front-rear direction. In the above, a crash box having a box-shaped cross section is fixed to the upper surface of the front part of the bent portion of the subframe, and the distance between the front part of the subframe and the vehicle body frame is reduced by the crash box. The front body structure of the vehicle characterized by the above. 3. The front vehicle body structure for a vehicle according to claim 1, wherein a front mount portion is formed so as to project upward at a front end portion of a front portion of the subframe, and the front mount portion is provided at the front side. The crash box fixed on the sub-frame is configured to be attached to the lower part of the vehicle body frame, and is crushed by the vehicle body frame and the front mount portion in the case of a frontal collision of the vehicle. The front body structure of the vehicle.