Battery unit mounting structure

A battery unit mounting structure includes a pair of right and left vehicle body frame members extending in a vehicle front-rear direction, a pair of right and left side members extending in the vehicle front-rear direction, a battery unit disposed between the right and left side members, and a reinforcement. The right and left vehicle body frame members are disposed respectively at right and left outer side portions of a vehicle body in a vehicle-width direction. The right and left side members are connected respectively to inner sides of the right and left vehicle body frame members in the vehicle-width direction. The reinforcement is disposed on a bottom or top surface of the battery unit, and disposed at a position at which the reinforcement overlaps with the battery unit in a plan view. The reinforcement extending in the vehicle-width direction is longer than the battery unit in the vehicle-width direction.

INCORPORATION BY REFERENCE

The disclosure of Japanese Patent Application No, 2015-045046 filed on Mar. 6, 2015 including the specification, drawings and abstract is incorporated herein by reference in its entirety.

BACKGROUND

1. Technical Field

The disclosure relates to battery unit mounting structures.

2. Description of Related Art

Structures for mounting storage battery packs in vehicles are known (for example, see Japanese Patent Application Publication No. 2007-253933 (JP 2007-253933 A)). Such structures can reduce damage of the storage battery packs when an impact is externally applied to the vehicles or the storage battery packs in the vehicle front-rear direction or vehicle-width direction.

However, there is still a need for improvement in structures for effective reductions in damage of battery units, such as storage battery packs, due to loads externally applied in the vehicle-width direction.

SUMMARY

The disclosed embodiments provide a battery unit mounting structure that effectively reduces damage of a battery unit due to a load externally applied in the vehicle-width direction.

According to one aspect, a battery unit mounting structure includes a pair of right and left vehicle body frame members, a pair of right and left side members, a battery unit, and a reinforcement. The right and left vehicle body frame members extend in a vehicle front-rear direction, and are disposed respectively at right and left outer side portions of a vehicle body in a vehicle-width direction. The right and left side members extend in the vehicle front-rear direction, and are connected respectively to inner sides of the right and left vehicle body frame members in the vehicle-width direction. The battery unit is disposed between the right and left side members. The reinforcement is disposed on a bottom surface or a top surface of the battery unit. The reinforcement is disposed at a position at which the reinforcement overlaps with the battery unit in a plan view. The reinforcement has a width in the vehicle-width direction that is longer than a width of the battery unit in the vehicle-width direction.

According to the above aspect, a load externally applied to one of the vehicle body frame members in the vehicle-width direction is transmitted from the one vehicle body frame member to the reinforcement and then transmitted from the reinforcement to the other vehicle body frame member. As a result, the load that could be applied to the battery unit is partially or completely absorbed, and damage of the battery unit is effectively reduced.

In addition, when a load is externally applied to one of the vehicle body frame members in the vehicle-width direction, at least part of the energy of the load is absorbed by one of the side members, resulting in a reduction in a load transmitted through the reinforcement to the other side member and the other vehicle body frame member. As a result, the load that could be applied to the battery unit is partially or completely absorbed more reliably, and damage of the battery unit is reduced more effectively.

In the above aspect, the reinforcement may be disposed at a position at which the reinforcement overlaps with the vehicle body frame members in a vehicle-height direction.

According to this aspect, a load externally applied to one of the vehicle body frame members in the vehicle-width direction is efficiently transmitted from the one vehicle body frame member to the reinforcement and then transmitted from the reinforcement to the other vehicle body frame member. As a result, the load that could be applied to the battery unit is partially or completely absorbed more reliably, and damage of the battery unit is reduced more effectively.

In the above aspect, the reinforcement may be fixed to the battery unit.

According to this aspect, when a load externally applied to one of the vehicle body frame members in the vehicle-width direction is transmitted from the one vehicle body frame member to the reinforcement, the battery unit moves toward the other vehicle body frame member together with the reinforcement. As a result, the load that could be applied to the battery unit is partially or completely absorbed more reliably, and damage of the battery unit is reduced more effectively.

In the above aspect, the battery unit mounting structure may further include a pair of right and left gussets, each of the gussets having an inner end portion in the vehicle-width direction connected to a corresponding one of outer end portions of the reinforcement in the vehicle-width direction, and each of the gussets having an outer end portion in the vehicle-width direction connected to a corresponding one of the side members.

According to this aspect, a load externally applied to one of the vehicle body frame members in the vehicle-width direction is promptly transmitted through one of the gussets to the reinforcement. The load transmitted to the reinforcement is then promptly transmitted through the other gusset to the side member on the other side. This effectively reduces damage of the battery unit.

DETAILED DESCRIPTION OF EMBODIMENTS

Example embodiments will now be described in detail with reference to the attached drawings. For convenience of the description, an arrow UP indicates the upward direction with respect to a vehicle body, an arrow FR indicates the forward direction with respect to the vehicle body, and an arrow OUT indicates the outward direction along the vehicle-width direction, in the drawings. In the following description, the terms “upper and lower”, “front and rear”, and “right and left” indicate “upper and lower” in the vehicle-height direction, “front and rear” in the vehicle front-rear direction, and “right and left” in the vehicle lateral direction (vehicle-width direction), respectively, unless otherwise specified. InFIGS. 2 and 5, illustration of a battery unit40, which will be described later, is omitted.

Hereinafter, a first embodiment will be described. A battery unit mounting structure10in accordance with the first embodiment will now be described. As illustrated inFIGS. 1 and 2, a vehicle12, such as a hybrid vehicle or an electric vehicle, provided with the battery unit mounting structure10includes a metal floor panel14that constitutes a floor of a vehicle cabin. As illustrated inFIG. 3, the floor panel14has outer portions in the vehicle-width direction. The outer portions of the floor panel14bend upward in the vehicle-height direction and then bend outward in the vehicle-width direction. Outer end portions of the floor panel14in the vehicle-width direction that bend outward in the vehicle-width direction define flanges14A.

As illustrated inFIGS. 1 to 3, metal rockers20are disposed outside the floor panel14(flanges14A) in the vehicle-width direction. The rockers20may function as a pair of right and left vehicle body frame members extending in the vehicle front-rear direction. The rockers20each include an outer panel22having a substantially hat-shaped cross section and an inner panel26having a substantially hat-shaped cross section. Flanges24of the outer panel22and flanges28of the inner panel26are joined to each other by, for example, welding, to form a closed space in a cross-sectional view.

Rear side members30having a substantially C-shaped cross section are connected to the inner sides (inner panels26) of the rockers20in the vehicle-width direction. The rear side members30may function as a pair of side members extending in the vehicle front-rear direction. The rear side members30each include an upper panel32and a lower panel34. An outer end portion32A of the upper panel32in the vehicle-width direction is joined to a top wall26A of the inner panel26by, for example, welding. An outer end portion34A of the lower panel34in the vehicle-width direction is joined to a bottom wall26B of the inner panel26by, for example, welding.

The upper panel32has an integrated flange33, at its inner end portion in the vehicle-width direction. The lower panel34has an integrated flange35, at its upper portion. The flange35is an inner end portion of the lower panel34in the vehicle-width direction. The flange33and the flange35are joined to each other with the flange14A of the floor panel14disposed therebetween. With this configuration, a closed space is defined by the rear side member30and the inner panel26of the rocker20in a sectional view, and the flange14A of the floor panel14is fixed to the rocker20via the rear side member30.

As illustrated inFIGS. 1 and 2, the floor panel14has a tunnel portion16that is disposed at the center in the vehicle-width direction. The tunnel portion16protrudes upward in the vehicle-height direction, and extends in the vehicle front-rear direction. A rear cross member36having a substantially hat-shaped cross section is joined to the top surface of the floor panel14, at a position forward of the rear side members30in the vehicle front-rear direction. The rear cross member36extends in the vehicle-width direction and connects the right and left rockers20(inner panels26) to each other.

The battery unit40is disposed between the right and left rear side members30(and the rockers20) and above the top surface of the floor panel14. The battery unit40is disposed at a position rearward of the rear cross member36in the vehicle front-rear direction. The battery unit40, which is called a storage battery pack, a battery pack, or a hybrid (HV) battery, and has a substantially rectangular parallelepiped shape having a lengthwise direction that coincides with the vehicle-width direction.

The floor panel14has a recess18on its top surface, at a position rearward of the rear cross member36in the vehicle front-rear direction. The recess18is shaped so as to substantially conform to the lower portion of the battery unit40. The lower portion of the battery unit40is fitted into the recess18of the floor panel14so as to prevent, for example, misalignment of the battery unit40from the given position. A rear seat38(seeFIG. 3) supported by the rear side members30is disposed above the battery unit40in the vehicle-height direction.

As illustrated inFIGS. 1 to 3, a rod50is fitted to a bottom surface42of the battery unit40. The rod50may function as a reinforcement extending in the vehicle-width direction. The rod50is a circular pipe. The rod50is connected and fixed, with several, for example, two brackets48, at a position at which the rod50overlaps with the battery unit40in a plan view (bottom view). For example, the rod50is connected and fixed at or near the center of the bottom surface42in the vehicle front-rear direction.

The brackets48each have a substantially U-shaped cross section. The rod50is fixed to the bottom surface42of the battery unit40by fitting and joining the brackets48to the outer peripheral surface of the rod50from below the rod50with a predetermined pressure and by fastening the flanges48A extending in the vehicle front-rear direction, to the bottom surface42of the battery unit40with bolts. This prevents the rod50from moving in the vehicle-width direction relatively to the battery unit40.

The rod50fixed to the bottom surface42of the battery unit40and disposed in the recess18of the floor panel14is located at a position at which the rod50overlaps with the rear side members30and the rockers20(except the flanges24and28) in the vehicle-height direction when viewed from the front, rear, and sides of the vehicle body. That is, the rod50is disposed at a position at which the rod50is located neither above nor below the rear side members30and the rockers20(except the flanges24and28) in the vehicle-height direction when viewed from the front, rear, and sides of the vehicle body.

The rod50is longer than the battery unit40in the vehicle-width direction. That is, the rod50has right and left outer end portions52that protrude by the same length outward in the vehicle-width direction from side surfaces44(outer ends in the vehicle-width direction) of the battery unit40. This configuration forms right and left spaces S of the same size between the side surfaces44of the battery unit40and the outer portions of the floor panel14in the vehicle-width direction that bend upward in the vehicle-height direction.

The rod50illustrated in the drawings is a circular pipe. Alternatively, the rod50may have any shape, for example, the rod50may be a square pipe. The number of the brackets48used to join the rod50to the bottom surface42of the battery unit40may be any number other than two as illustrated in the drawings. Alternatively, the rod50may be directly joined and fixed to the bottom surface42of the battery unit40by, for example, welding.

Advantageous effects of the battery unit mounting structure10having the above-described configuration in the first embodiment will now be described. With reference toFIG. 4, description will be provided on advantageous effects in the event of a lateral collision of the vehicle12with, for example, a columnar or cylindrical metal pole (obstacle) P extending vertically.

As illustrated inFIG. 4, when the vehicle12collides with the pole P laterally, a significantly high collision load F headed inward in the vehicle-width direction is applied to the rocker20and the rear side member30on the collision side. The collision load F externally applied to the rocker20and the rear side member30in the vehicle-width direction plastically deforms and moves the rocker20and the rear side member30inward in the vehicle-width direction. Thus, part of the energy of the applied collision load F is absorbed and the remainder is transmitted to the rod50fixed to the battery unit40.

Since the rod50extends so as to be longer than the battery unit40in the vehicle-width direction (the rod50is longer than the battery unit40in the vehicle-width direction), a collision load is transmitted to the outer end portion52of the rod50in the vehicle-width direction before being transmitted to the side surface44of the battery unit40in the event of a lateral collision of the vehicle12. The rod50has high rigidity and strength in its axial direction due to its circular pipe shape.

Thus, the lateral collision load externally transmitted to the rod50in the vehicle-width direction is received by the rod50in its axial direction, and the rod50then moves in its axial direction (vehicle-width direction) and crushes, from the inside in the vehicle-width direction, the rear side member30located on the opposite side of the rod50from the collision side (hereinafter, simply referred to as “the opposite side”). Thus, the collision load applied to the rocker20and the rear side member30on the collision side is transmitted to the rear side member30and the rocker20on the opposite side and thus dispersed (energy is absorbed). As a result, the collision load that could be applied to the battery unit40is partially or completely absorbed.

That is, damage of the battery unit40due to the collision load externally applied in the vehicle-width direction can be effectively reduced (the battery unit40can be protected). Since the rod50is fixed to the battery unit40, movement of the rod50away from the collision side (in the vehicle-width direction) also moves the battery unit40away from the collision side. As a result, the collision load that could be applied to the battery unit40is partially or completely absorbed more reliably.

Since the rod50is disposed at a position at which the rod50overlaps with the rear side members30and the rockers20in the vehicle-height direction, the collision load applied to the rocker20and the rear side member30on the collision side is readily transmitted to the rear side member30and the rocker20on the opposite side. That is, this configuration can efficiently transmit the collision load applied to the rocker20and the rear side member30on the collision side to the rear side member30and the rocker20on the opposite side, thereby efficiently dispersing the collision load. This makes it possible to more effectively reduce damage of the battery unit40due to the collision load externally applied in the vehicle-width direction.

The battery unit mounting structure10in this embodiment can be easily formed just by fixing the rod50to the bottom surface42of the battery unit40. Further, the battery unit mounting structure10has a lighter weight than, for example, a battery unit mounting structure including a rear cross member36with an increased strength for reduction of damage of the battery unit40. This results in an improvement in fuel efficiency performance of the vehicle12. On disposition of the battery unit40on the floor panel14, the battery unit mounting structure10only requires the recess18to be shaped to have a space for the rod50, which does not limit the layout of the components on the top surface of the floor panel14.

Hereinafter, a second embodiment will be described. A battery unit mounting structure10in accordance with the second embodiment will now be described. Components equivalent to those in the first embodiment have the same reference characters, and detailed description (including common advantageous effects) thereof may be omitted.

As illustrated inFIGS. 5 and 6, the battery unit mounting structure10in the second embodiment includes a pair of right and left gussets54connecting upper panels32of right and left rear side members30and outer end portions52of a rod50in the vehicle-width direction, which is the only difference from the first embodiment.

Each gusset54is bent to have a substantially Z-shaped cross section. The gusset54has an outer end portion54A in the vehicle-width direction, at its upper portion. The outer end portion54A is fastened to the top surface of the upper panel32of the rear side member30, for example, with bolts. The gusset54has an inner end portion54B in the vehicle-width direction, at its lower portion. The inner end portion54B is joined at its rear side portion in the vehicle front-rear direction, to the top surface of the outer end portion52of the rod50in the vehicle-width direction by, for example, welding.

When the vehicle12collides with the pole P laterally as illustrated inFIG. 4, a collision load is transmitted from the rear side member30on the collision side through the gusset54to the rod50promptly (in the early stage of the collision). The collision load transmitted to the rod50is then promptly transmitted through the gusset54on the opposite side of the rod50from the collision side, to the rear side member30on the opposite side, and thus dispersed

That is, provision of the gussets54makes it possible to promptly transmit the collision load applied to the rocker20and the rear side member30on the collision side, to the rear side member30and the rocker20on the opposite side, thereby dispersing the collision load, resulting in an improvement in energy absorption efficiency. As a result, the collision load that could be applied to the battery unit40is partially or completely absorbed more reliably, and the damage of the battery unit40due to the collision load externally applied in the vehicle-width direction is more effectively reduced.

As illustrated inFIG. 5, the inner end portion54B of each gusset54is fastened at its front side portion in the vehicle front-rear direction, to a top wall36A of a rear cross member36with bolts. Thus, the collision load is transmitted from the rear side member30on the collision side through the gusset54to the rear cross member36promptly (in the early stage of the collision) and thus dispersed. The gussets54hold right and left end portions of the bottom surface42of the battery unit40in the vehicle-width direction.

Hereinafter, a third embodiment will be described. A battery unit mounting structure10in accordance with the third embodiment will now be described. Components equivalent to those in the first and second embodiments have the same reference characters, and detailed description (including common advantageous effects) thereof may be omitted.

As illustrated inFIG. 7, the battery unit mounting structure10in the third embodiment includes a rod50connected and fixed to a top surface46of a battery unit40, with several, for example, two brackets48, at a position at which the rod50overlaps with the battery unit40, for example, at or near the center of the top surface46in the vehicle front-rear direction, in a plan view, which is the only difference from the second embodiment.

When the vehicle12collides with the pole P laterally as illustrated inFIG. 4, a collision load applied to the rocker20and the rear side member30on the collision side is transmitted to the rear side member30and the rocker20on the opposite side promptly (in the early stage of the collision) and thus dispersed, as in the second embodiment, resulting in an improvement in energy absorption efficiency.

As a result, the collision load that could be applied to the battery unit40is partially or completely absorbed more reliably, and the damage of the battery unit40due to the lateral collision load external applied in the vehicle-width direction is more effectively reduced. In the third embodiment, a rear seat38can be disposed lower than that in the first and second embodiments.

The battery unit mounting structures10in accordance with the embodiments have been described with reference to the attached drawings but should not be limited to those illustrated in the drawings. The design may be appropriately modified. For example, the number of the rod50may be any number other than one as illustrated in the drawings. Several, for example, two rods50may be arranged adjacent to each other in the vehicle front-rear direction.

The rod50may be attached to the battery unit40so as to be movable in the vehicle-width direction, instead of being fixed to the bottom surface42or the top surface46of the battery unit40. The right and left spaces S defined between the side surfaces44of the battery unit40and the outer portions of the floor panel14in the vehicle-width direction that bend upward in the vehicle-height direction may have different sizes.

In the first embodiment, which does not include the pair of right and left gussets54, a connector (not shown) may connect the substantial lengthwise center of the rod50with the substantial lengthwise center of the rear cross member36to transmit a collision load transmitted to the rod50to the rear cross member36, thereby dispersing the collision load.

The embodiments may exclude the rear side members30on the inner sides of the rockers20in the vehicle-width direction. In this case, the configuration only requires the flanges14A of the floor panel14to be joined to the top walls26A of the inner panels26of the rockers20, or the outer end portions54A of the gussets54in the vehicle-width direction to be connected to the top walls26A of the inner panels26of the rockers20.

It should be noted that the rear side members30provided on the inner sides of the rockers20in the vehicle-width direction have the advantage in that the rear side members30absorb energy of a collision load externally applied in the vehicle-width direction. The battery unit mounting structure10in the embodiments achieves the same advantageous effects in the event of, for example, a lateral collision of the vehicle12with a planar obstacle at high speed as in the event of a lateral collision of the vehicle12with an obstacle that may cause local deformation, such as the pole P.