JP2005170269A - Vehicle body structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a vehicle body structure that moderates stress concentration to the vehicle body structure around a front side frame, reduces the weight of the vehicle body, suppresses deformation of the front side frame or vibration caused by an engine, and can improve steering stability of the vehicle. <P>SOLUTION: In the vehicle body structure, front suspensions 28 are attached to a pair of right and left front side frames 2, respectively, and front bumpers 32 extending in the vehicle width direction are connected with front ends of these front side frames. The vehicle body structure has a viscoelastic member 42 which is disposed between the front end of each front side frame and each front bumper and connects the front side frame to the front bumper, and the viscoelastic member has a viscoelasticity damping characteristic where a viscoelasticity damping force is generated by a relative displacement between the front side frame and the front bumper. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a vehicle body structure of a vehicle, and in particular, a vehicle body structure of a vehicle in which front suspensions are respectively attached to a pair of left and right front side frames, and front bumpers extending in the vehicle width direction are connected to front end portions of these front side frames. Concerning.

The body of an automobile is deformed by receiving a force from the road surface when traveling, for example, the floor of the body is mainly torsionally deformed when turning, and is bent and deformed mainly in the front-rear direction during braking or acceleration.
Since these deformations of the vehicle body affect the operability of the vehicle, conventionally, reinforcing members that reinforce each part of the vehicle body have been provided around the front of the engine room, around the vehicle compartment, and around the rear near the rear wheel. It is provided in the basic structure of the vehicle body to increase the rigidity of the vehicle body.

As such a reinforcing member, there is a suspension tower bar that connects the suspension towers of the front wheels or the rear wheels to increase rigidity. This suspension tower bar is a reinforcing member that is integrally formed of an elastic body such as metal, and energy due to deformation of the reinforcing member acts on the vehicle body as a repulsive force, so that there is a problem that steering stability and riding comfort are impaired. there were. Moreover, if the rigidity of the reinforcing member is increased in order to keep the deformation amount of the reinforcing member small, there is a problem that the weight increases and stress concentration around the mounting portion is caused.
Patent Document 1 proposes a reinforcing member including a hydraulic damper or a viscoelastic member that generates a viscous damping force in order to solve the problem of such a reinforcing member.

Japanese Patent Laid-Open No. 2002-211437

  On the other hand, in order to reduce the weight of the car body as much as possible while ensuring the desired car body rigidity, limit the number of points and points of use of the reinforcing members so as not to increase the rigidity and strength of each part of the car body more than necessary. Therefore, it is necessary to optimally design the cross-sectional dimensions and thickness of the vehicle body constituent members. In particular, in open cars, lightweight sports cars, etc., there is a strong demand for ensuring the desired vehicle body rigidity and reducing the weight.

  Here, in general, an engine and a front suspension are attached to a pair of so-called front side frames extending in the longitudinal direction of the vehicle body in the engine room of the vehicle body. When the pair of front side frames are deformed by an input from the front suspension, the stability of the vehicle is adversely affected. Further, the vibration of the engine transmitted to the front side frame is transmitted to the floor panel constituting the floor portion of the passenger compartment, thereby increasing noise.

  In general, the pair of front side frames has their front end portions connected to a front bumper extending in the vehicle width direction via an impact absorbing member (so-called crash can) to enhance rigidity. Further, in order to reduce noise due to vibration transmitted from the engine, the rigidity of the front side frame itself may be increased, or a larger engine mount may be used.

  However, if the rigidity around the front side frame is greatly increased locally in this way, stress concentrates on other members such as the body structure around the front side frame, for example, pillars of the vehicle body, and cracks occur. It may lead to breakage or the spot welding that holds the structural parts of the car body may come off. For this reason, reinforcing members must be placed in various parts of the body of the vehicle where stress is concentrated, and the cross-sectional dimensions must be increased and the plate thickness increased in order to increase the rigidity and strength of the pillars described above. It was difficult to achieve weight reduction. Further, if the rigidity of the front side frame is increased so as to reduce the noise described above, it has been difficult to achieve weight reduction.

  Accordingly, the present invention has been made to solve the above-described problems of the prior art, and alleviates stress concentration on the vehicle body structure around the front side frame, reduces the weight of the vehicle body, An object of the present invention is to provide a vehicle body structure capable of suppressing the vibration caused by the engine and enhancing the operability of the vehicle.

In order to achieve the above object, the present invention provides a vehicle body structure in which a front suspension is attached to each of a pair of left and right front side frames, and a front bumper extending in the vehicle width direction is connected to a front end portion of these front side frames. The viscoelastic member is provided between the front end of the front side frame and the front bumper and connects the front side frame and the front bumper. The viscoelastic member is viscoelastic due to relative displacement between the front side frame and the front bumper. It is characterized by having a viscoelastic damping characteristic that generates a damping force.
In the present invention configured as described above, there is provided a viscoelastic member having a viscoelastic damping characteristic that generates a viscoelastic damping force by a relative displacement between the front end portion of the front side frame to which the front suspension is attached and the front bumper. Since it is provided, the viscoelastic member absorbs (attenuates) deformation energy of the front side frame mainly caused by the input from the front suspension and allows a predetermined amount of deformation. Furthermore, the deformation of the front side frame is suppressed by the reaction force due to the deformation of the viscoelastic member. As a result, according to the present invention, the concentration of stress on the vehicle body structure around the front side frame and the weight reduction of the vehicle body are achieved, and deformation of the front side frame and vibration caused by the engine are suppressed, thereby improving vehicle stability. Can be increased.

In the present invention, preferably, the front side frame has a first cylindrical member extending in the front-rear direction of the vehicle body at a front end portion thereof, and the front bumper is connected to the first cylindrical member of the front side frame. The first cylindrical member and the second cylindrical member are configured to be relatively rotatable by a viscoelastic member provided between the first and second cylindrical members. ing.
In the present invention configured as above, the first cylindrical member of the front side frame and the second cylindrical member of the front bumper are formed by the viscoelastic member provided between the first and second cylindrical members. Since it is configured to be relatively rotatable, the first cylindrical member and the second cylindrical member can rotate relative to each other when the front side frames are deformed in the vertical direction of the vehicle body. As a result, according to the present invention, the viscoelastic member undergoes shear deformation in the circumferential direction along with this relative rotation, so that the deformation energy of the front side frame is greatly attenuated.

Preferably, in the present invention, the front bumper is provided so as to be displaceable in the vehicle front-rear direction with respect to the front side frame via a viscoelastic member, and the viscoelastic member is deformed by the displacement of the front bumper and is deformed by the viscous damping force. It is configured to absorb the collision energy in the front-rear direction.
In the present invention configured as above, the viscoelastic member is deformed by the displacement of the front bumper with respect to the front side frame, and the collision energy in the longitudinal direction of the vehicle body is absorbed by the viscous damping force. When the collision load is relatively small, the collision energy can be absorbed by the viscoelastic member.

In the present invention, preferably, the front side frame or the front bumper is a collision energy that deforms itself and absorbs the collision energy in the longitudinal direction of the vehicle body when the vehicle collides with the front side frame and the front bumper together with the viscoelastic member. It has an absorption part.
In the present invention configured as described above, when the collision load with the obstacle is large and the collision energy cannot be absorbed by the viscoelastic member, the collision energy absorbing unit can absorb the collision energy.

In the present invention, preferably, the viscoelastic member has an elastic characteristic that functions as a dynamic damper at a predetermined frequency together with the front bumper.
In the present invention configured as described above, the viscoelastic member has an elastic characteristic that functions as a dynamic damper at a predetermined frequency together with the front bumper. Therefore, the viscoelastic member suppresses the deformation of the front side frame and the vibration caused by the engine, and at the same time. For example, the vibration at the frequency of the secondary vibration or torsional vibration of the vehicle body can be further greatly suppressed.

  According to the present invention, the concentration of stress on the vehicle body structure around the front side frame is reduced and the vehicle body is lightened, and the vehicle side operation is improved by suppressing the deformation of the front side frame and the vibration caused by the engine. I can do it.

Embodiments of the present invention will be described below with reference to the accompanying drawings.
FIG. 1 is a plan view of an underbody 1 of a vehicle body having a vehicle body structure according to an embodiment of the present invention as viewed from below the vehicle body. As shown in FIG. 1, an underbody 1 of a vehicle body having a vehicle body structure according to an embodiment of the present invention includes a pair of front side frames 2 and a pair of front side frames 2 extending in the longitudinal direction of the vehicle body as basic reinforcing frames of the vehicle body. The side sill 4, the pair of floor side frames 6, and the pair of rear side frames 8, No. 2 respectively extending in the vehicle width direction. 1 cross member 10, no. 2 Cross member 12, No. 2 3 cross member 14, no. 4 cross member 16 and no. 5 cross members 18.

  The underbody 1 further includes a floor panel connected to the plurality of frame members described above, and a floor tunnel 22 is formed in the floor panel 20. The lower edge of the dash panel 24 that partitions the vehicle compartment and the engine room is joined to the end edge of the floor panel 20 on the vehicle body side by spot welding or the like. The vehicle side body (not shown) is attached to each other, and the dash panel 24 and the side body are connected to pillars and ceiling parts (not shown) constituting the passenger compartment. Yes.

  The pair of front side frames 2 are constituted by hollow members having a rectangular cross section, and suspension towers 26 are respectively attached to the outer sides in the vehicle width direction by welding or the like. Is installed. An engine 34 is attached to the inside of the pair of front side frames 2 in the vehicle width direction. Rear suspension towers 36 are attached to the outer sides in the vehicle width direction of the pair of rear side frames 8 by welding or the like, and rear suspensions 36 are attached to these suspension towers.

Next, the vehicle body structure of the vehicle according to the embodiment will be described with reference to FIGS. FIG. 2 is an enlarged plan view showing a main part of a vehicle body structure according to an embodiment of the present invention, and FIG. 3 is a cross-sectional view taken along line III-III in FIG.
As shown in FIG.2 and FIG.3, a pair of front side frame 2 has the 1st connection member 40 attached to the front-end part 2a, respectively. These first connection members 40 have an attachment portion 40a attached to the front end portion of the front side frame 2 having a rectangular cross section by welding, and a cylindrical portion 40b welded to the attachment portion and extending forward in the longitudinal direction of the vehicle body. The front end 2a of the front side frame and the front bumper 32 are connected by the first connecting member 40, the second connecting member 30 and the viscoelastic member 42 described later.

  Here, the front side frame 2 is deformed by input from the front suspension 28, and this deformation causes torsional deformation or bending deformation of the vehicle body, which adversely affects the operability of the vehicle. It is known that these torsional deformations and bending deformations mainly involve vibrations of 15 to 25 Hz. In the present embodiment, deformation of the front side frame 2 is suppressed by the viscoelastic member 42. Hereinafter, the structure of the front end portion of the vehicle body including the viscoelastic member 42 will be specifically described.

  The front bumper 32 is configured by a hollow member having a rectangular cross section extending in the vehicle width direction, and has second connection members 30 attached to the side surfaces of the vehicle body rear side at both ends thereof. These second connecting members 30 have a mounting portion 30a whose four corners are attached to the side surface of the front bumper on the rear side of the vehicle body with bolts (not shown), and a cylindrical shape that is welded to the mounting portion and extends rearward in the longitudinal direction of the vehicle body. And the collision energy absorbing portion 30b. The collision energy absorbing unit 30b absorbs the impact energy received by the front bumper 32 when the vehicle collides with an obstacle ahead of the vehicle by deforming the collision energy absorbing unit itself so as to buckle in the longitudinal direction of the vehicle body. Yes, it functions as a so-called crash can. In addition, each connection member 30 so that the 1st connection member 40 of the front side frame 2 may function as a crash can, or so that both the 1st connection member 40 and the 2nd connection member 30 may function as a crash can, 40 may be configured.

  In the first connecting member 40 and the second connecting member 30, the inner diameter d1 of the collision energy absorbing portion 30b of the second connecting member is larger than the outer diameter d2 of the cylindrical portion 40b of the first connecting member. And a cylindrical viscoelastic member 42 extending in the longitudinal direction of the vehicle body is provided between the collision energy absorbing portion 30b and the cylindrical portion 40b.

The viscoelastic member 42 is made of a silicon-based or diene-based viscoelastic material (viscoelastic material), and generates a predetermined viscous damping force and reaction force according to the deformation speed and the deformation amount. As a characteristic value unique to the viscoelastic material, a tan delta value (tan δ _K ) is 0.7 to 1.0. Further, the real number component (K ′) and the imaginary number component (K ″) of the rigidity value in a state where the viscoelastic member 42 is provided on each of the connection members 30 and 40 are 100 in the range of about 15 Hz to 25 Hz at room temperature. To 700 N / mm and 80 to 500 N / mm.

  The viscoelastic members 42 are respectively bonded to the inner peripheral surface of the collision energy absorbing portion 30b of the second connecting member and the outer peripheral surface of the cylindrical portion 40b of the first connecting member to connect the front side frame 2 and the front bumper 32. The front side frame 2 and the front bumper 32 are deformed by relative displacement to generate a viscous damping force and a reaction force.

  Further, the cylindrical portion 40b of the first connecting member and the collision energy absorbing portion 30b of the second connecting member are each formed in a cylindrical shape, and the front side frame 2 and the front bumper 32 are arranged between them. The elastic member 42 is capable of relative rotation by shear deformation in the circumferential direction.

  Further, the viscoelastic member 42 and the front bumper 32 constitute a spring mass system based on the elastic characteristic of the characteristics of the viscoelastic member 42 and the characteristic as the mass of the front bumper 32, and function as a dynamic damper at a predetermined frequency. It is like that. In the present embodiment, it mainly functions as a dynamic damper in the vicinity of 20 Hz (about 15 Hz to 25 Hz) which is a resonance frequency of bending vibration in the longitudinal direction of the entire vehicle body (so-called secondary vibration of the vehicle body) and torsional vibration of the vehicle body. It has become.

  Further, the rear end portion 30c of the collision energy absorbing portion 30b of the second connection member is separated from the front end portion of the front side frame 40, in this embodiment, the attachment portion 40a of the connection member, and the front bumper 32 is a viscoelastic member. The front side frame 2 can be displaced in the longitudinal direction of the vehicle body via 42. Thus, the viscoelastic member 42 is shear-deformed in the longitudinal direction of the vehicle body due to the relative displacement in the longitudinal direction of the vehicle body so that the front bumper 32 approaches the front side frame 2, and the collision energy with the front obstacle of the vehicle is absorbed. I try to do it.

Next, the operation of this embodiment will be described.
In the present embodiment, the viscoelastic member 42 is deformed by the relative displacement between the front side frame 2 and the front bumper 32 to generate a viscous damping force and a reaction force. Specifically, the viscoelastic member 42 absorbs (attenuates) the deformation energy of the front side frame 2 generated by the input from the front suspension 28 and allows a predetermined amount of deformation. Further, the deformation of the front side frame 2 is suppressed by the reaction force due to the deformation of the viscoelastic member 42. Therefore, the deformation of the front side frame 2 can be suppressed without greatly increasing the rigidity of the front side frame 2, and the operability of the vehicle can be improved.

  In particular, since the viscoelastic member 42 is provided between the cylindrical portion 40b of the first connecting member and the collision energy absorbing portion 30b of the second connecting member each formed in a cylindrical shape, the connecting member 40 of the front side frame 2 is provided. And the second connecting member 30 of the front bumper 32 are easily rotated relative to each other. For example, when the front suspension on one side moves up and down due to the unevenness of the road surface, or when the load applied to the left and right front suspensions is different during turning, the left and right front side frames 2 move in the vertical direction of the vehicle as shown by arrow A in FIG. When the first connecting member 40 of the front side frame 2 and the second connecting member 30 of the front bumper 32 rotate relative to each other, the viscoelastic member 42 shears and deforms in the circumferential direction, so that the front side frames are vertically Energy that deforms in the direction is greatly attenuated.

Further, the vibration of the engine 34 attached to the front side frame 2 is attenuated by the viscoelastic member 42, the vibration transmitted from the front side frame 2 to the floor panel 20 is reduced, and the noise in the vehicle interior is reduced.
Furthermore, since the viscoelastic member 42 and the front bumper 32 function as a dynamic damper with respect to the front side frame 2, it is possible to suppress vibrations of a predetermined frequency such as secondary vibrations and torsional vibrations of the vehicle body. I can do it.

  Further, since the rear end portion 30c of the collision energy absorbing portion 30b of the second connecting member is separated from the front side frame 2, the front bumper 32 receives the front-rear direction when the vehicle collides with an obstacle ahead of the vehicle. First, the front bumper 32 is relatively displaced so as to approach the front side frame 2 by the impact force, and the viscoelastic member 42 is shear-deformed in the longitudinal direction of the vehicle body by such relative displacement to absorb the collision energy. Thereafter, the rear end portion 30c of the collision energy absorbing portion 30b comes into contact with the front side frame 2, in this embodiment, the first connecting member 40 provided at the front end portion 2a of the front side frame, and the collision energy absorbing portion 30b is It is deformed so as to buckle in the longitudinal direction of the vehicle body, and the collision energy is greatly absorbed. Therefore, for example, when the collision load with the obstacle of the vehicle is relatively small, the collision energy can be absorbed by the viscoelastic member 42 without deforming the collision energy absorbing portion 30b. Furthermore, when the collision load is relatively large and the collision energy cannot be absorbed by the viscoelastic member 42, the collision energy can be absorbed by the collision energy absorbing portion 30b.

It is the top view which looked at the underbody of the vehicle body which has the vehicle body structure of the vehicle by embodiment of this invention from the vehicle body downward direction. It is a principal part enlarged plan view which shows the vehicle body structure of the vehicle by embodiment of this invention. It is sectional drawing seen along the III-III line of FIG. It is a principal part expansion perspective view which shows the vehicle body structure of the vehicle by embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Underbody of vehicle body 2 Front side frame 28 Front suspension 30 Second connection member 32 Front bumper 34 Engine 40 First connection member 42 Viscoelastic member

Claims (5)

A vehicle body structure in which front suspensions are respectively attached to a pair of left and right front side frames, and front bumpers extending in the vehicle width direction are connected to front end portions of these front side frames,
A viscoelastic member provided between the front end portion of the front side frame and the front bumper and connecting the front side frame and the front bumper, and the viscoelastic member is moved by relative displacement between the front side frame and the front bumper; A vehicle body structure having a viscoelastic damping characteristic that generates a viscoelastic damping force.   The front side frame has a first cylindrical member extending in the longitudinal direction of the vehicle body at a front end portion thereof, and the front bumper is connected to the first cylindrical member of the front side frame and extends in the longitudinal direction of the vehicle body. The first cylindrical member and the second cylindrical member have a member, and are configured to be relatively rotatable by the viscoelastic member provided between the first and second cylindrical members. 1. A vehicle body structure according to 1.   The front bumper is provided to be displaceable in the vehicle longitudinal direction with respect to the front side frame via the viscoelastic member, and the viscoelastic member is deformed by the displacement of the front bumper and collides in the vehicle longitudinal direction by a viscous damping force. The vehicle body structure according to claim 1 or 2, wherein the vehicle body structure is configured to absorb energy.   The front side frame or the front bumper has a collision energy absorbing portion that connects the front side frame and the front bumper together with the viscoelastic member and deforms itself when the vehicle collides to absorb the collision energy in the longitudinal direction of the vehicle body. Item 4. A vehicle body structure according to Item 3.   The vehicle body structure according to any one of claims 1 to 4, wherein the viscoelastic member has an elastic characteristic of functioning as a dynamic damper at a predetermined frequency together with the front bumper.

Images