JP2017019299A - Vehicle body front part structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently absorb impact accompanied by a head-on collision.SOLUTION: A vehicle body front part structure is, on a front end part of a vehicle, provided with: a front end cross member 10 extended in a vehicle width direction; a suspension cross member 31 extended in the vehicle width direction on a backward side than the front end cross member 10; a bracket 20 fixed on the front end cross member 10; a sub frame 30 which is extended in a longitudinal direction of the vehicle, and has a rear end part fixed on the suspension cross member 31 and a front end part relatively movable in the vehicle longitudinal direction with respect to the bracket 20; and a fixing member 40 which fixes the sub frame 30 and the bracket 20 in a state that the sub frame 30 is positioned on a rearmost end in a movable range of the sub frame 30 with respect to the bracket 20, and releases fixation when a predetermined load or more is acted in the vehicle longitudinal direction to allow relative movement of the sub frame 30 with respect to the bracket 20.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a vehicle body front part structure that absorbs the impact of a collision when the vehicle collides forward.

  In order to protect the safety of the occupant at the time of a frontal collision of the vehicle, an impact absorbing structure for absorbing an impact at the time of the frontal collision is adopted at the front of the vehicle body.

  For example, the structure which concerns on patent document 1 is provided with the under member which consists of a hollow front | former stage part, an intermediate | middle stage part, and a back | latter stage part under the front side member. The front stage part and the middle stage part, and the middle stage part and the rear stage part can slide with respect to each other in the front-rear direction of the vehicle. Each step is joined by welding. When an impact is applied due to a frontal collision, the front side member is deformed, the under member is disengaged and the steps slide to each other, and the impact is absorbed.

  Moreover, the structure which concerns on patent document 2 is arrange | positioned under the vehicle body frame | frame frame which has the extension part extended in the vehicle front-back direction, the sub-frame which supports an engine, and an extension part. And a connecting member that connects the subframe. According to this configuration, even in the arrangement in which there is a vertical distance between the vehicle body frame and the sub frame, the vehicle body frame deformation mode is dominant in the vehicle frame structure deformation mode at the time of a collision from the vehicle longitudinal direction. As a result, collision energy can be absorbed efficiently.

  Moreover, the structure which concerns on patent document 3 is provided with the sub-frame extended in the front-back direction of a vehicle under the side member. When a collision load is input from the front of the vehicle, the subframe is bent in a predetermined direction together with the side members, and the impact due to the collision is absorbed.

JP 2011-240808 A JP 2012-71837 A JP2013-6518A

  In each composition of patent documents 1-3, a front side member (or body frame frame, a side member) and an under member (or subframe) are arranged up and down. In this case, when an impact due to a forward collision is applied, the front side member and the under member are simultaneously deformed, and the time for absorbing the impact remains in a short time. Then, the problem which the impact which acts on the passenger | crew in a vehicle interior is not absorbed efficiently may arise.

  Therefore, an object of the present invention is to efficiently absorb an impact caused by a forward collision.

  In order to solve the above problems, according to the present invention, a front end cross member extending in the vehicle width direction at the front end portion of the vehicle, and extending in the vehicle width direction behind the front end cross member. A suspension cross member provided, a bracket fixed to the front end cross member, a vehicle extending in the front-rear direction, a rear end portion fixed to the suspension cross member, and a front end portion relative to the bracket. The subframe and the bracket are fixed in a state in which the subframe is provided so as to be relatively movable in the front-rear direction, and the subframe is positioned at the end of the subframe within the movable range of the subframe with respect to the bracket. When the load more than a predetermined value is applied in the vehicle longitudinal direction, the fixing is released and the sub-frame with respect to the bracket is released. A fixing member to allow relative movement of the beam, to constitute a vehicle body front structure, characterized in that it comprises a.

  In the vehicle body front structure, the sub-frame has a long hole extending in the longitudinal direction of the vehicle along the longitudinal direction, and the fixing member penetrates the bracket and is inserted into the long hole and fastened. It is preferable to have a bolt, and the bolt is configured to fix the bracket and the subframe in a state where the bolt is inserted through the front end of the elongated hole.

  In the configuration employing the bolt, the elongated hole has a width of the front end portion that is the same as or wider than the shaft diameter of the bolt, and a width of a portion on the rear side of the front end portion is the bolt. It is preferable to use a configuration that is narrower than the shaft diameter.

  In the vehicle body front structure, the subframe is bent and deformed at the rear end portion of the bracket when the subframe moves relative to the bracket to the foremost end within the movable range. It is preferable to have a configuration having a fragile part that induces the phenomenon.

  In the configuration having the fragile portion, the subframe includes a first long hole formed in a first surface of the subframe, and a second long hole formed in a second surface facing the first surface. The bolt is inserted through the front end portions of the first elongated hole and the second elongated hole, and fixes the bracket and the subframe in a state of passing through the first surface and the second surface. The first elongated hole is longer than the second elongated hole, and the subframe is moved relative to the bracket to the foremost end within the movable range. In this case, it is preferable that the rear end is extended so as to be located further rearward than the rear end portion of the bracket to form the fragile portion.

  In the configuration in which the subframe includes the first surface and the second surface, it is preferable that the first surface is a lower surface of the subframe and the second surface is an upper surface of the subframe.

  According to the present invention, the fixing member that fixes the bracket and the subframe is removed, and the shock absorption effect that accompanies the relative movement of the subframe to the front of the vehicle with respect to the bracket, and the impact that accompanies the bending deformation of the subframe. Since the absorption action is exhibited sequentially, the impact can be sufficiently absorbed in the first half of the deformation of the vehicle, and a high protection effect for the passenger is exhibited.

Side view showing a vehicle body front structure according to the present invention Plan view of the vehicle body front structure shown in FIG. FIG. 1 is a longitudinal sectional view showing a state before the main part of the vehicle body front structure shown in FIG. Plan view of the main part of the vehicle body front structure shown in FIG. 1 is an exploded perspective view of the vehicle body front structure shown in FIG. FIG. 1 is a longitudinal sectional view showing a state in which a main part of the vehicle body front structure shown in FIG. 1 is a longitudinal sectional view showing a deformation state of a main part of the vehicle body front structure shown in FIG. A diagram showing a comparison of the relationship between the amount of deformation of the vehicle body and the magnitude of acceleration acting on the vehicle body during a forward collision

  One embodiment of a vehicle body front structure according to the present invention is shown in FIGS. 1 is a side view and FIG. 2 is a plan view. The main part of this vehicle body front structure is shown in FIGS. 3 is a longitudinal sectional view, FIG. 4 is a plan view, and FIG. 5 is an exploded perspective view. This vehicle body front structure is a structure for absorbing the impact against a collision from the front of the vehicle, and includes a front end cross member 10, a side member 12, a bracket 20, a sub frame 30, a suspension cross member 31, And the volt | bolt 40 as a fixing member is made into the main components.

  As shown in FIGS. 1 and 2, the front end cross member 10 is a member extending in the vehicle width direction below the front end of the vehicle. A connecting member 11 is fixed in the vicinity of both ends of the front end cross member 10, and left and right side members 12, 12 extending in the front-rear direction of the vehicle are connected to the connecting member 11. A bumper beam 13 extends from the front end of the side member 12 in the vehicle width direction. The side member 12 has a role of crushing from the front side when an impact is applied to the vehicle due to a forward collision and absorbing the impact.

  Also, on the rear side of the front end cross member 10, suspension cross members 31 are provided extending in the vehicle width direction and supporting left and right front wheels via suspension arms (not shown) at both left and right ends in the vehicle width direction. ing. The suspension cross member 31 is connected to the lower side of the side member 12.

  As shown in FIG. 3, the bracket 20 is a hollow member having a U-shaped vertical cross section that extends in the vehicle front-rear direction and opens at the rear end side, and the front end portion thereof is the left and right end portions of the front end cross member 10. It is fixed to. A bolt hole 21 (see FIG. 5) for inserting the bolt 40 from the upper surface side to the lower surface side of the bracket 20 is formed on the rear end side. The white arrow in this figure indicates the front of the vehicle (the same applies to FIGS. 6 and 7 described later).

  The subframe 30 is a long member extending in the front-rear direction of the vehicle, and a rear end portion thereof is fixed to the suspension cross member 31 (see FIG. 1 and the like). The front end portion of the subframe 30 is inserted from the opening at the rear end of the bracket 20 and is provided in the bracket 20 so as to be movable relative to the bracket in the vehicle front-rear direction (longitudinal direction of the subframe 30). (See FIG. 3).

  On the lower surface 30a (first surface) side of the subframe 30 and the upper surface 30b (second surface) side facing the lower surface 30a, a long hole 32 extending in the longitudinal direction of the subframe 30 in the longitudinal direction of the vehicle. Is formed. A bolt 40 penetrating through the bolt hole 21 of the bracket 20 is inserted into the long hole 32, and the bolt 40 together with the bracket 20 extends along the long hole 32 in the longitudinal direction of the subframe 30, that is, the vehicle. Relative movement is possible in the front-rear direction. Hereinafter, the long hole 32 formed in the lower surface 30a is referred to as a first long hole 32a, and the long hole 32 formed in the upper surface 30b is referred to as a second long hole 32b.

  As shown in FIG. 3, the first long hole 32a is formed longer than the second long hole 32b. Further, as shown in FIG. 4, the width of each of the long holes 32a and 32b is the same as the bolt shaft diameter of the bolt 40 or wider than the bolt shaft diameter at their front end portions, whereas On the rear side of the part, it is slightly narrower than the bolt shaft diameter, so that the bolt 40 inserted through the front end part of each of the long holes 32a and 32b cannot easily move to the rear end side.

  The sub frame 30 is located at the rearmost end (most vehicle rear side) of the vehicle within a movable range that can move relative to the bracket 20 (the front end portions of the first and second long holes 32a and 32b). In a state where the positions of the bolt holes 21 formed in the bracket 20 coincide with each other, the bolt 40 and the nut 41 are fastened to the bracket 20. That is, the bolt 40 is inserted into the front end portions of the first and second elongated holes 32a and 32b and fastened in a state of passing through the lower surface 30a and the upper surface 30b of the subframe 30, so that the bracket 20 and the sub The frame 30 is configured to be fixed.

  At this time, a gap g having a predetermined size is formed between the front end portion of the bracket 20 and the front end portion of the subframe 30 (see FIG. 3). “Fixing” here does not mean that the subframe 30 and the bracket 20 are firmly fixed so as not to move relative to each other, but when the magnitude of the load input in the vehicle front-rear direction exceeds a predetermined value. This means a state in which the sub frame 30 and the bracket 20 are fixed with a fixing force that allows relative movement. The “predetermined” size allowing the relative movement is appropriately determined. That is, the bolt 40 and the nut 41 are fastened to such an extent that the fixing of the subframe 30 and the bracket 20 is released when a predetermined load or more is applied in the vehicle longitudinal direction.

  When a load of a predetermined magnitude or more is applied to the bracket 20 from the front side of the vehicle due to an impact caused by a frontal collision of the vehicle, the bolt 40 is detached from the front end portions of the first and second long holes 32a and 32b. And the subframe 30 are released from being fixed. Then, the bolt 40 relatively moves toward the rear of the first and second long holes 32a and 32b while widening the widths of the first and second long holes 32a and 32b. It moves relative to the vehicle front side within the bracket 20 while absorbing the impact. As shown in FIG. 6, when the front end portion of the bracket 20 and the front end portion of the subframe 30 come into contact with each other and the gap g (see FIG. 3) between them disappears, the relative movement of the subframe 30 toward the front of the vehicle stops. . In a state where the sub frame 30 is moved to the foremost end of the movable range with respect to the bracket 20, the rear end of the second long hole 32 b (on the upper surface 30 b side) is positioned on the front side of the rear end of the bracket 20. On the other hand, the rear end of the first long hole 32 a (on the lower surface 30 a side) is located further rearward than the rear end portion of the bracket 20.

  When the first elongated hole 32a is arranged as described above with respect to the position of the rear end portion of the bracket 20, when a load in the front-rear direction is further applied from the state shown in FIG. 6, as shown in FIG. The frame 30 can be bent and deformed at the rear end portion of the bracket 20 so as to be bent downward (so that the lower surface 30a side becomes a valley fold shape).

  That is, the rear end of the first long hole 32a is positioned further to the vehicle rear side than the rear end portion of the bracket 20 in a state in which the sub frame 30 is moved relative to the bracket 20 to the foremost end of the movable range. By doing so, the strength of the rear end portion of the bracket 20 on the lower surface 30a side of the subframe 30 is relatively lower than the strength of the upper surface 30b side. Thus, the subframe 30 is induced to bend downward at the rear end portion of the bracket 20 because the lower surface 30a side having relatively low strength is deformed first in the vehicle rear portion of the bracket 20. That is, when the subframe 30 moves relative to the bracket 20 to the foremost end of the movable range, a portion formed on the rear side of the rear end portion of the bracket 20 of the first long hole 32a is the rear of the bracket 20. It is comprised so that it may function as a weak part which induces the bending deformation of the sub-frame 30 in an edge part.

  On the other hand, the rear end portion of the subframe 30 is fixed to the suspension cross member 31 and cannot be displaced up and down. In an intermediate portion with the fixing portion to the member 31, it bends upward toward the rear end side (the lower surface 30a side of the intermediate portion is folded in a mountain shape). That is, the subframe 30 is bent so that an intermediate portion between the bent portion at the rear end portion of the bracket 20 and the fixing portion to the suspension cross member 31 protrudes downward.

  Thus, the subframe 30 can be bent and deformed in a desired direction in accordance with the relationship between the length and position of the long holes 32a and 32b and the position of the rear end portion of the bracket 20. In addition, if the weak part for inducing the folding direction is provided also in the intermediate part of the subframe 30, the folding direction of the subframe 30 can be controlled more reliably. For example, in the present embodiment, it is preferable to provide a weak portion such as a notch or a hole on the upper surface 30b side of the intermediate portion.

  Thus, after the sub-frame 30 is moved relative to the bracket 20 in the vehicle front-rear direction, the sub-frame 30 is bent and deformed, so that the bolt 40 is connected to the front end portions of the first and second long holes 32a and 32b. The shock absorption by moving away from the first and second elongated holes 32a and 32b and the shock absorption accompanying the bending deformation of the subframe 30 are continuously performed while shifting the timing of the shock absorption. It is possible to absorb the impact caused by the forward collision effectively.

  Moreover, there are the following merits by bending and deforming the subframe 30 downward at the rear end portion of the bracket 20 as described above. In general, peripheral parts such as an engine (not shown) and the side member 12 are arranged on the upper side of the subframe 30. For example, the subframe 30 faces upward at the rear end portion of the bracket 20. When bent, the intermediate portion of the subframe 30 is bent and deformed so as to protrude upward, so that the subframe 30 comes into contact with peripheral parts, and the subframe 30 cannot be deformed as prescribed, and the impact absorbing function is reduced. There is a risk of damaging peripheral components.

  Further, the side member 12 which is one of the peripheral parts is a main part for absorbing the impact at the time of a forward collision. However, the contact with the subframe 30 may adversely affect the impact absorbing function. . Therefore, the subframe 30 is bent and deformed downward at the rear end portion of the bracket 20 so that the intermediate portion of the subframe 30 protrudes downward to prevent contact between the subframe 30 and peripheral components. Thus, the impact absorbing action by the subframe 30 can be sufficiently exerted, the peripheral parts can be protected, and the impact absorbing action by the side member 12 can be ensured.

  Depending on the positional relationship between the subframe 30 and peripheral parts, the first and second long holes 32a and 32b may be formed so that the subframe 30 is bent and deformed laterally (in the vehicle width direction) at the rear end portion of the bracket 20. You may form in the side surface of the sub-frame 30. FIG. Further, if it is not necessary to limit the deformation direction of the subframe 30 to a specific direction, instead of forming the long holes 32 (32a, 32b) in the subframe 30, the long holes 32 are formed in the bracket 20, The bolt 40 fixed to the 30 side may be configured to pass through the long hole 32 formed in the bracket 20.

  Further, in the above-described embodiment, the configuration has been described in which the bolt 40 performs shock absorption by relatively moving the first and second elongated holes 32a and 32b while widening the width thereof, but this is only an example. Only. For example, the width of the long hole 32 is set to the same constant width as the bolt diameter of the bolt 40, and the bolt 40 is moved through the first and second long holes 32 a and 32 b by a bolt fastening force when the subframe 30 is fixed to the bracket 20. By adjusting the magnitude of resistance at the time of relative movement, the magnitude of shock absorption due to the detachment of the bolt 40 can be adjusted. Further, the bracket 20 and the subframe 30 may be fixed by welding, and the place where the welding is performed may be broken by a predetermined load or more.

  FIG. 8 shows a comparison of the relationship between the amount of deformation of the vehicle body and the acceleration acting on the vehicle body at the time of a frontal collision between the vehicle employing the vehicle body front structure according to the present invention and the vehicle employing the conventional vehicle body front structure. Show. The horizontal axis represents the amount of vehicle body deformation, and the vertical axis represents the magnitude of acceleration acting on the vehicle body. In this figure, the line marked with A is fixed to the vehicle body front structure according to the present invention (the long holes 32 (32a, 32b) and the bolt 40 so that the subframe 30 and the bracket 20 can be moved relative to each other in the vehicle longitudinal direction). As a result, the line marked with B is the result of the vehicle body front structure having a general subframe, and the line marked with C is the result of the vehicle body front structure (only the side member 12) not employing the subframe. is there.

  In a vehicle employing the vehicle body front structure according to the present invention (see symbol A in the figure), there are two prominent features in the first half of the vehicle body deformation (range of arrow Z in the figure) accompanying a collision. Acceleration peaks a1 and a2 appear. The peak a1 is caused by the bolt 40 moving from the front end portions of the first long hole 32a and the second long hole 32b and moving in the long holes 32a and 32b while widening the width, and the peak a2 is This is because the subframe 30 is bent and deformed downward. The height of each peak a1, a2 corresponds to the magnitude of the absorbed impact. It can be seen that the peaks a1 and a2 appear with a certain time difference, and the shock absorption in the first half of the deformation is effectively performed.

  On the other hand, in a vehicle having a front body structure employing a general subframe (see symbol B in the figure), one remarkable acceleration peak b appears in the first half of the deformation. The peak b is due to the deformation of the subframe. Further, in a vehicle having a vehicle body front structure that does not employ a subframe (see symbol C in the figure), one relatively small acceleration peak c1 appears in the first half of the deformation, and a comparison is made in the second half of the deformation. Large peaks c2 and c3 appear.

  In order to protect passengers, it is generally said that it is desirable to form a plurality of peaks in the first half of deformation to absorb as much impact as possible. By doing so, it is possible to reduce the burden on the occupant by reducing the force received by the occupant from the seat belt or airbag in the latter half of the deformation. In a vehicle (see reference numeral A in the figure) employing the vehicle body front structure according to the present invention, two peaks a1 and a2 are formed in the first half of the deformation, and many impacts are absorbed in the first half. The force that the occupant receives from the seat belt or the like in the second half of the deformation can be greatly reduced.

  However, in a vehicle employing a general subframe (see symbol B in the figure), although a relatively prominent peak b can be confirmed in the first half of the deformation, there is only one peak b. The shock absorption in the first half becomes insufficient, and the force received by the occupant in the second half of the deformation may increase. Further, in a vehicle that does not employ a subframe (see symbol C in the figure), the peak c1 in the first half of the deformation is small, and shock absorption is mainly performed in the second half of the deformation, so that the force received by the occupant increases. There are many.

  Thus, according to the configuration of the present invention, compared to the conventional configuration, the force that the occupant receives from the seat belt or the airbag can be greatly reduced, and sufficient occupant protection can be achieved.

  The above embodiment is merely an example, and the shape and arrangement of each member such as the bracket 20 and the subframe 30 are appropriately set as long as the problem of the present invention that efficiently absorbs the impact caused by the forward collision can be solved. It is allowed to change.

10 Front end cross member 11 Connecting member 12 Side member 13 Bumper beam 20 Bracket 21 Bolt hole 30 Subframe 30a (Subframe) lower surface (first surface)
30b Upper surface (sub-frame) (second surface)
31 Suspension cross member 32 Long hole 32a First long hole 32b Second long hole 40 Bolt (fixing member)
41 Nut (fixing member)

Claims (6)

A front end cross member extending in the vehicle width direction at the front end of the vehicle;
A suspension cross member extending in the vehicle width direction on the rear side of the front end cross member;
A bracket fixed to the front end cross member;
A subframe that extends in the front-rear direction of the vehicle, has a rear end portion fixed to the suspension cross member, and a front end portion that is movable relative to the bracket in the vehicle front-rear direction;
The sub-frame and the bracket are fixed in a state where the sub-frame is positioned at the end of the sub-frame within the movable range of the sub-frame with respect to the bracket, and a load of a predetermined level or more is applied in the vehicle front-rear direction. A fixing member that releases fixation and allows relative movement of the subframe with respect to the bracket;
A vehicle body front structure characterized by comprising: The sub-frame has a long hole extending in the longitudinal direction of the vehicle along the longitudinal direction, and the fixing member has a bolt that penetrates the bracket and is fastened through the long hole.
2. The vehicle body front structure according to claim 1, wherein the bolt fixes the bracket and the sub frame in a state where the bolt is inserted into a front end portion of the elongated hole.   The long hole is formed such that the width of the front end portion is the same as or wider than the shaft diameter of the bolt, and the width of the rear portion of the front end portion is narrower than the shaft diameter of the bolt. The vehicle body front part structure according to claim 2.   The sub-frame has a fragile portion that induces bending deformation of the sub-frame at the rear end portion of the bracket when the sub-frame moves relative to the bracket relative to the foremost end within the movable range. The vehicle body front part structure according to any one of claims 1 to 3. The subframe has a first long hole formed in the first surface of the subframe, and a second long hole formed in the second surface facing the first surface,
The bolt is inserted through the front end portions of the first long hole and the second long hole, and is provided so as to fix the bracket and the subframe in a state of passing through the first surface and the second surface. And
The first long hole is longer than the second long hole, and in a state where the subframe is relatively moved to the foremost end within the movable range with respect to the bracket, The vehicle body front part structure according to claim 4, wherein the weakened part is formed so as to extend further to the rear side than the rear end part of the bracket.   The vehicle body front structure according to claim 5, wherein the first surface is a lower surface of the subframe and the second surface is an upper surface of the subframe.

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