JP7110944B2 - vehicle front structure - Google Patents

Description

This specification discloses a vehicle front structure having a pair of front side members extending in the vehicle front-rear direction and an MC cross member arranged between the pair of front side members.

2. Description of the Related Art Conventionally, electric vehicles that run on motors are widely known. Such an electric vehicle is equipped with a power unit having a driving motor, a transmission, and the like, which are used for running the vehicle. A power unit is usually held in a power unit compartment (corresponding to an engine compartment in a gasoline engine automobile, also called a "motor compartment") provided in the front part of the vehicle. Conventionally, structures for stably holding such power units have been proposed.

For example, Patent Literature 1 discloses such a power unit holding structure. A pair of side frames (corresponding to the side members) extending in the longitudinal direction of the vehicle are provided at the front of the vehicle disclosed in Patent Document 1, and the power plant (corresponding to the power unit) is connected via the EV frame. , supported by a pair of side frames. The EV frame includes two left and right members that are spaced apart in the vehicle front-rear direction and extend in the vehicle left-right direction so as to bridge between the left and right side frames, and extend in the vehicle front-rear direction near the inside of each of the left and right side frames, and two front and rear members connecting the two left and right members. The power plant is suspended by this EV frame, and auxiliary equipment and an inverter are installed on the top of the EV frame.

JP 2015-182749 A

By the way, when a vehicle collides with an obstacle in front of the vehicle, it is desired that the collision energy can be quickly absorbed in order to appropriately protect the high-voltage parts, the cabin, and the like. In order to meet these demands, various ideas have been conventionally applied to the front structure of a vehicle. For example, the vehicle front portion is provided with a front side member extending in the vehicle front-rear direction. Conventionally, in a full-wrap collision, in which an obstacle hits the entire width of the front of the vehicle, or in an offset collision, in which an obstacle hits about half of the front of the vehicle, a part of the front side member is positioned inward in the vehicle width direction. The collision energy is absorbed by positively folding it.

However, when the front and rear members of the EV frame are provided immediately inside the front side members as in Patent Document 1, even if the front side members try to bend inward in the vehicle width direction, the front side members interfere with the front and rear members. and cannot be broken. As a result, there was a possibility that the collision energy could not be absorbed appropriately.

Therefore, this specification discloses a vehicle front structure that can more reliably absorb collision energy while appropriately holding a drive motor.

The vehicle front structure disclosed in this specification includes a pair of front side members spaced apart in the vehicle width direction, each extending in the vehicle front-rear direction, and the pair of front side members extending in the vehicle front-rear direction. An MC cross member, which is arranged between the side members and supports the drive motor and is substantially rectangular in plan view, is provided with a portion of the side portion of the MC cross member having lower strength than other portions. A fragile portion is provided into which the front side member that is broken inward in the vehicle width direction can enter, and the front side member is set to be broken inward in the vehicle width direction by receiving a collision load at the time of a frontal collision. and the fragile portion is provided at a position facing the portion to be bent in the vehicle width direction .

With such a configuration, when the front side member is bent inward in the vehicle width direction, the fragile portion is easily deformed, so that the bending of the front side member is facilitated. As a result, it is possible to more reliably absorb the collision energy while properly holding the driving motor.

With such a configuration, the front side member bent inward in the vehicle width direction more reliably abuts the fragile portion. This makes it easier for the MC cross member to deform around the weakened portion, so that collision energy can be absorbed more reliably.

Further, the fragile portion may be formed by providing a notch in the side portion of the MC cross member so that the broken side member can enter.

By using the notch as the weakened portion, the front side member that is bent inward in the vehicle width direction can more reliably bite into the width of the MC cross member. As a result, the front side member can be folded more smoothly, and the collision energy can be absorbed more reliably.

Also, the weakened portion may form a hole or bead in the side portion of the MC cross member, or may locally reduce the wall thickness.

With such a configuration, the front side member bent inward in the vehicle width direction more reliably abuts the fragile portion. This makes it easier for the MC cross member to deform around the weakened portion, so that collision energy can be absorbed more reliably.

According to the vehicle front structure disclosed in this specification, it is possible to more reliably absorb collision energy while appropriately holding the drive motor.

FIG. 2 is a schematic plan view of the front portion of the vehicle; 4 is an exploded perspective view around the MC cross member; FIG. FIG. 4 is a plan view of the MC cross member; 4 is an exploded perspective view of the MC cross member; FIG. 4 is an end view taken along line AA of FIG. 3; FIG. It is the perspective view which looked at the side part of MC cross member from the lower side. It is a perspective view of the front end periphery of a front side member. It is a perspective view which shows the mode of attachment of a bracket. FIG. 11 is a plan view showing a state in which a small wrap collision or an oblique collision occurs; FIG. 4 is a plan view showing a situation in a full-wrap collision or an offset collision;

The vehicle front structure 10 will be described below with reference to the drawings. FIG. 1 is a schematic plan view of a vehicle front structure 10. FIG. Also, FIG. 2 is an exploded perspective view around a motor compartment cross member (hereinafter referred to as "MC cross member 20"). In the drawings, the longitudinal direction of the vehicle is indicated by the axis Fr, the width direction of the vehicle is indicated by the axis Rw, and the height direction of the vehicle is indicated by the axis Up. In addition, left and right in the following description mean left and right as viewed from the vehicle occupant, unless otherwise specified.

First, the overall configuration of the vehicle front structure 10 will be briefly described. This vehicle front structure 10 is incorporated in an electric vehicle (for example, an electric vehicle, a fuel cell vehicle, etc.) that runs on power generated by the rotary electric machine MG. A power unit room 11 (also referred to as a "motor compartment") in which a power unit is installed is provided in the front part of the vehicle. The power unit generates driving power for the vehicle, and in this example, a rotating electric machine unit 22, which will be described later, functions as the power unit.

A bumper reinforcement (hereinafter abbreviated as “bumper RF”) 14 extending in the vehicle width direction is provided at the front end of the power unit chamber 11 . The bumper RF 14 is curved in plan view so as to be convex forward of the vehicle. Front side members 12 are connected via crash boxes 16 to the vicinity of both ends of the bumper RF 14 in the vehicle width direction. The crash box 16 is compressed and deformed in the longitudinal direction of the vehicle, thereby absorbing collision energy at the time of vehicle collision. Therefore, the crash box 16 usually has a shape that is easily compressed and deformed in the longitudinal direction of the vehicle, for example, a shape in which a plurality of concave beads are formed on the outer peripheral surface.

A front side member 12 is connected to the rear of the crash box 16 . The front side member 12 is a frame member extending in the vehicle front-rear direction. As shown in FIG. 1, two front side members 12 are arranged substantially parallel to each other with a sufficient gap in the vehicle width direction. The front side member 12 is provided with bending portions 48 and 50 that are positively bent when receiving a collision load directed toward the rear of the vehicle, which will be described later.

A gusset 18 is attached to the outer surface of each front side member 12 in the vehicle width direction. The gusset 18 is a substantially triangular member in a plan view whose dimension in the vehicle width direction decreases toward the rear of the vehicle. The front end of this gusset 18 is substantially the same as the front end of the front side member 12 . The gusset 18 protrudes outward in the vehicle width direction from the front side member 12 and receives a load input from the front side member 12 from the outside in the vehicle width direction.

An MC cross member 20 is provided between the pair of front side members 12 . The MC cross member 20 is connected to the front side member 12 via a bracket (not shown in FIG. 1). In other words, the MC cross member 20 spans between the pair of front side members 12 . However, the MC cross member 20 is not in contact with the front side member 12, and both 12 and 20 face each other while being spaced apart in the vehicle width direction. In other words, a slight gap exists between the MC cross member 20 and the front side member 12 . In addition, a weakened portion 44 is formed by notching a portion of the side portion of the MC cross member 20 . The reason why the gap and the fragile portion 44 are provided is to allow the front side member 12 to bend, which will be described later.

As shown in FIG. 2, the charger 26 and the PCU 24 are mounted on the upper surface of the MC cross member 20 and fastened. Further, below the MC cross member 20, a left motor mount 28L and a right motor mount 28R (hereinafter referred to as "motor mounts 28" with the suffixes L and R omitted when the left and right are not distinguished) are provided. A unit 22 is suspended and held. The rotary electric machine unit 22 includes a rotary electric machine MG (driving motor) and a transmission (transaxle) TA, which serve as a driving source of the vehicle. In the example shown in FIG. 2, the rotary electric machine unit 22 is placed horizontally, and is arranged in the power unit chamber 11 so that the longitudinal direction of the rotary electric machine unit 22 faces the vehicle width direction. A plurality of fastening holes 23 are provided in the upper surface and both width direction end surfaces of the rotary electric machine unit 22 . The motor mount 28 is fastened to the rotary electric machine unit 22 by aligning these fastening holes 23 with the fastening holes 53 of the motor mount 28 and bolting them. Also, the motor mount 28 is threadedly fastened to the front and rear portions of the MC cross member 20 so as to traverse an opening 34 of the MC cross member 20, which will be described later.

The PCU 24 is a power converter provided in an electric circuit connecting the rotating electric machine MG and a battery (not shown). The PCU 24 includes power conversion circuits such as a DC/DC converter and an inverter, for example. A plurality of fastening holes 25 are formed in a leg portion 24 a extending downward from the PCU 24 . The PCU 24 is fastened to the upper surface of the MC cross member 20 via fastening bolts (not shown) inserted through the plurality of fastening holes 25 .

The charger 26 is connected to a battery (not shown), and includes a booster circuit for power conversion, a transformer circuit for blocking DC components, and the like. Moreover, a plurality of fastening holes 27 are formed in a leg portion 26a extending downward from the charger 26. As shown in FIG. The charger 26 is fastened to the upper surface of the MC cross member 20 via fastening bolts (not shown) inserted through the plurality of fastening holes 27 .

A high-voltage cable (not shown) is routed between the rotating electric machine unit 22, the PCU 24, the charger 26, and the battery (not shown) for transmitting and receiving electric power. A portion of this high voltage cable is passed through an opening 34 provided in the center of the MC cross member 20 .

Next, the configuration of the MC cross member 20 will be described with reference to FIGS. 3 to 6. FIG. 3 is a plan view of the MC cross member 20, and FIG. 4 is an exploded perspective view of the MC cross member 20. FIG. 5 is an end view taken along line AA of FIG. 3. FIG. Furthermore, FIG. 6 is a perspective view of the side portion of the MC cross member 20 viewed from below.

As described above, the MC cross member 20 is a member that spans between the pair of front side members 12, on which the PCU 24 and the charger 26 are placed, and that suspends and holds the rotating electric machine unit 22. . As shown in FIG. 3, the MC cross member 20 has a substantially rectangular shape elongated in the vehicle width direction in a plan view. An elongated opening 34 is formed in the center of the MC cross member 20 in the vehicle width direction, and the MC cross member 20 as a whole has a substantially square shape. A part of a high-voltage cable connected to the rotary electric machine unit 22, the PCU 24, and the charger 26 is routed through the opening 34. As shown in FIG.

As shown in FIGS. 4 to 6, the MC cross member 20 is configured by combining one upper member 36 and two lower members 38F and 38R. In FIG. 6, the lower members 38F and 38R are hatched. The upper member 36 has a top surface with a large opening in the center, a peripheral surface that hangs down from the periphery of the top surface, and a completely open bottom surface. The front lower member 38F and the rear lower member 38R are members attached to the lower side of the upper member 36, and are formed with several steps in the vehicle front-rear direction. In the following, when the front side and the rear side are not distinguished from each other, the suffixes F and R are omitted and simply referred to as the "lower member 38".

The front lower member 38F and the rear lower member 38R form a closed cross section with the upper member 36 as shown in FIG. That is, the front lower member 38F is close to or in contact with the upper member 36 at its uppermost surface and front end surface, but is sufficiently separated from the upper member 36 at other locations. Similarly, the rear lower member 38R is close to or in contact with the upper member 36 at its uppermost surface and rear end surface, but is sufficiently separated from the upper member 36 at other locations.

By forming the MC cross member 20 into a hollow shape composed of the upper member 36 and the lower member 38 in this manner, the strength of the MC cross member 20 is greatly improved compared to the case where the MC cross member 20 is composed of a single plate material. can. In particular, by adopting such a configuration, compressive deformation of the MC cross member 20 in the vehicle width direction is effectively prevented. Although FIGS. 4 and 6 show the upper member 36 and the lower member 38 as simple shapes without beads or recesses, these members 36 and 38 may be provided with a plurality of beads or recesses. By appropriately providing beads and recesses, the strength of the MC cross member 20 can be further improved.

A side portion of the MC cross member 20 is provided with a stepped portion 62 and a weakened portion 44 . The stepped portion 62 widens outward in the vehicle width direction in the process from the front to the rear. Such a stepped portion 62 hooks the broken front side member 12 in the event of a small wrap collision or an oblique collision to restrict rearward movement of the front side member 12, which will be described later. The stepped portion 62 is provided at the rear end of the gusset 18 or slightly rearward from the rear end.

The fragile portion 44 is provided behind the stepped portion 62 . The weakened portion 44 is a portion having a lower strength than other portions so that the front side member 12 that is bent inward in the vehicle width direction can bite into the width of the MC cross member 20 . In this example, a notch 46 provided in the side portion of the MC cross member 20 is used as the weakened portion 44 .

More specifically, as shown in FIG. 6, the upper member 36 is formed with a substantially rectangular notch 46 extending from the lower end of the side surface to the upper surface. Further, the rear end of the front lower member 38F is positioned forward of the front end of the cutout 46, and the front end of the rear lower member 38R is positioned rearward of the rear end of the cutout 46. As a result, of the upper surface of the MC cross member 20, only the portion adjacent to the notch 46 is composed of only one plate material (upper member 36), and its strength is reduced. With such a configuration, the front side member 12 more reliably folds inward in the vehicle width direction in the event of a full-wrap collision or an offset collision, thereby effectively absorbing the collision energy, which will also be described later. .

Next, the front side member 12 and the gusset 18 will be described with reference to FIG. FIG. 7 is a perspective view of the periphery of the front end of the front side member 12. FIG. The front side member 12 is a frame member extending in the vehicle front-rear direction, and is a hollow rectangular pipe-shaped member. The front side member 12 is provided with several breakable portions 48 and 50 that are likely to break at the time of collision. One of the expected folds 48 is near the rear end of the gusset 18 . The load input via the gusset 18 tends to concentrate near the rear end of the gusset 18 . The front side member 12 tends to bend inward in the vehicle width direction in the vicinity of the rear end of the gusset 18 during a minor lap collision or an oblique collision. As described above, the stepped portion 62 of the MC cross member 20 is provided slightly behind the rear end of the gusset 18 in the vehicle.

Further, another planned folding portion 50 is a discontinuous portion 42 of the bead 40 . That is, a reinforcing bead 40 is provided on the outer side surface 12o of the front side member 12 in the vehicle width direction. The reinforcing bead 40 is a linear bead elongated in the longitudinal direction of the vehicle. However, the reinforcing bead 40 is not continuous in the longitudinal direction of the vehicle and is interrupted in the middle. The strength of the interrupted portion 42 of the reinforcing bead 40 is locally reduced, and stress tends to concentrate there. Therefore, the front side member 12 is likely to break at the discontinuous portion 42 during a full-wrap collision or an offset collision. Stress is easily concentrated. The weakened portion 44 of the MC cross member 20 is provided at a position corresponding to the interrupted portion 42 in the vehicle width direction.

Front side member 12 and MC cross member 20 are connected to each other via bracket 32 . FIG. 8 is a perspective view showing how the bracket 32 is attached. The bracket 32 connects the vicinity of the fragile portion 44 of the MC cross member 20 and the vicinity of the portion 50 to be bent (the discontinuous portion 42 of the bead 40 ) of the front side member 12 . More specifically, bracket 32 connects the upper surface of MC cross member 20 and upper surface 12 t of front side member 12 . Therefore, the bracket 32 has a surface extending substantially horizontally along the upper surface 20 t of the MC cross member 20 and the upper surface 12 t of the front side member 12 . The bracket 32 also has an extension portion 32a that extends greatly outward so that it can be fastened to another member (for example, a suspension tower, etc.). The bracket 32 is formed with a plurality of (five in the illustrated example) fastening holes 54 , and the bracket 32 is secured to the MC cross member 20 and the front side member by fastening bolts 56 inserted through the fastening holes 54 . 12.

Next, a case where a vehicle having this vehicle front structure 10 undergoes a frontal collision will be described. Frontal collisions include full-wrap collisions in which the entire width of the front of the vehicle collides with the colliding object, offset collisions in which about half of the width of the front of the vehicle collides with the colliding object, and edges of the front of the vehicle (for example, the outer 25% of the front of the vehicle). ), and an oblique collision in which a high-speed collision object collides obliquely with the front of the vehicle.

First, the case of a minute wrap collision or an oblique collision will be described with reference to FIG. In this case, the collision object collides with the vehicle outside the front side member 12 in the vehicle width direction. Therefore, the impact load in this case is applied directly to the gusset 18 via the bumper RF 14 or not via the bumper RF 14 . A collision load applied to the gusset 18 is transmitted to the outer surface of the front side member 12 via the gusset 18 . Upon receiving this collision load, the front side member 12 bends inward in the vicinity of the rear end of the gusset 18 and enters inward in the vehicle width direction, as shown in FIG. As a result, the front side member 12 comes into contact with the side portion of the MC cross member 20 , and the collision load is further transmitted to the MC cross member 20 . The MC cross member 20 receives this collision load, moves in the vehicle width direction, and comes into contact with the front side member 12 on the opposite side (right side of the vehicle in the illustrated example).

That is, the collision load at the time of a small wrap collision or an oblique collision is sequentially transmitted to the gusset 18 on one side, the front side member 12 on one side, the MC cross member 20, and the front side member 12 on the opposite side. In the course of this transmission, the collision load is absorbed and dispersed. In addition, the collision load is finally transmitted to the front side member 12 on the opposite side, making it easier for the entire vehicle body to move in the direction of escaping from the collision load, reducing deformation and damage to each part of the vehicle due to the collision load. can.

By the way, in a small wrap collision or an oblique collision, not only bending of the front side member 12 but also movement of the front side member 12 to the rear of the vehicle occurs. When the front side member 12 freely moves rearward, the collision load is less likely to be transmitted to the MC cross member 20. - 特許庁In this example, in order to suppress such rearward movement of the front side member 12, a stepped portion 62 is provided on the side portion of the MC cross member 20 on the outer side in the vehicle width direction. With such a configuration, the front side member 12 that is about to move rearward comes into contact with the stepped portion 62, and further rearward movement of the front side member 12 is restricted. As a result, the collision load at the time of a minute wrap collision or oblique collision can be transmitted to the MC cross member 20 more reliably.

Next, a full wrap collision or an offset collision will be described with reference to FIG. In the event of a full wrap collision or an offset collision, the collision load is input to a pair of left and right crash boxes 16 via bumpers RF14. Upon receiving this collision load, the crash box 16 is compressed and deformed to absorb part of the collision load. The load that cannot be absorbed by the crash box 16 is further transmitted to the pair of left and right front side members 12. - 特許庁The front side member 12 transmits the collision load further rearward and absorbs the collision energy by bending inward in the vehicle width direction. At this time, the front side member 12 is likely to break at the interrupted portion 42 of the bead 40 which is one of the portions 50 to be broken.

Here, the broken front side member 12 is, of course, brought into contact with the side portion of the MC cross member 20 . At this time, if the side portion of the MC cross member 20 has high strength, further bending of the front side member 12 is inhibited, and collision energy cannot be absorbed sufficiently. In this example, as described above, the side portion of the MC cross member 20 is provided with the weakened portion 44 into which the collided front side member 12 bites in the width direction, more specifically, the notch 46 . In a full wrap collision or an offset collision, even if the front side member 12 tries to bend inward in the vehicle width direction, the bent portion does not interfere with the MC cross member 20, or even if it interferes, the MC cross member 20 can be easily bent. transform. As a result, the front side member 12 more reliably folds inward in the vehicle width direction, thereby effectively absorbing the collision energy.

As is clear from the above description, in a full wrap collision or an offset collision, the MC cross member 20 is required to be able to bend greatly inward in the vehicle width direction. The member 20 is required to abut against the MC cross member 20 .

Here, if it is only to allow the front side member 12 to bend, the width direction dimension of the MC cross member 20 is reduced instead of providing the fragile portion 44 so that the front side member 12 and the MC cross member 20 are separated from each other. You can widen the gap. However, when the gap between the front side member 12 and the MC cross member 20 is widened, the front side member 12 is less likely to collide with the MC cross member 20 in the event of a small wrap collision or an oblique collision. The collision load cannot be transmitted/distributed to the member 12 . On the other hand, as in this example, while keeping the gap between the MC cross member 20 and the front side member 12 small, by providing the fragile portion 44 on the side portion of the MC cross member 20, the transmission of the load according to the collision mode, Absorption becomes possible.

The configuration described so far is only an example, and a portion of the side portion of the MC cross member 20 has a weaker strength than other portions and is a weak portion into which the front side member 12 that is bent inward in the vehicle width direction can enter. 44, other configurations may be changed as appropriate. For example, in the above description, the side notch portion of the MC cross member 20 is the weakened portion 44, but the weakened portion 44 may have other forms as long as the strength thereof is lower than that of other portions. For example, the weakened portion 44 may be configured by providing a plurality of small holes that reduce strength in the side portion of the MC cross member. As another form, a bead and a discontinuous portion may be provided on the side portion of the MC cross member 20 in the same manner as the portions 48 and 50 to be bent of the front side member 12 , and the discontinuous portion may be used as the weakened portion 44 . . Furthermore, as another form, the weakened portion 44 may be configured by partially changing the cross-sectional shape of the MC cross member 20 . For example, the thickness of only the portion of the side portion of the MC cross member 20 that functions as the weakened portion 44 may be reduced.

Further, in the above description, the MC cross member 20 is provided with the stepped portion 62 in addition to the weakened portion 44, but this may be omitted. Further, the weakened portion 44 and the stepped portion 62 may be provided only on the left and right sides of the MC cross member 20 .

Further, the portions to be broken 48, 50 provided in the front side member 12 may be of other forms as long as they induce the bending at the time of the corresponding collision. For example, the portions to be folded 48 and 50 may be configured with a notch that triggers folding, a shape of bending, or the like.

10 vehicle front structure, 11 power unit chamber, 12 front side member, 16 crash box, 18 gusset, 20 MC cross member, 22 rotating electric machine unit, 26 charger, 28 motor mount, 32 bracket, 34 opening, 36 upper member , 38 lower member, 40 bead, 42 discontinuous portion, 44 fragile portion, 46 notch, 48, 50 portion to be broken, 62 stepped portion, MG rotary electric machine, 14 bumper RF.

Claims (1)

a pair of front side members spaced apart in the width direction of the vehicle, each extending in the front-rear direction of the vehicle;
an MC cross member that is substantially rectangular in plan view and that is disposed between the pair of front side members and supports a driving motor;
with
A part of the side portion of the MC cross member is provided with a weakened portion that is lower in strength than other portions and into which the front side member that is bent inward in the vehicle width direction can enter ,
The front side member has a portion to be bent which is set to be bent inward in the vehicle width direction by receiving a collision load at the time of a frontal collision,
The fragile portion is provided at a position facing the portion to be bent in the vehicle width direction,
A vehicle front structure characterized by:

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