Battery installation structure for electric vehicles

1. Field of the Invention

The invention relates to a battery installation structure for electric vehicles, and more specifically, to a structure that prevents damages to the battery in the event of a side impact crash.

2. Description of the Related Art

According to conventional battery installation structures for electric vehicles, to prevent damages to a battery pack in the event of a collision against a vehicle, a battery case containing battery cells is fixed with bolts to a battery cross member having a closed section, and the battery cross member is also fixed with bolts to a pair of side members so that the battery pack is positioned between the side members fixed to the sides of the vehicle and extending in the vehicle's anteroposterior direction (Japanese Unexamined Patent Publication (Kokai) No. 2008-162497).

In the battery installation structure for electric vehicles which is disclosed in the above publication, since the battery case is fixed with bolts to the battery cross member having a closed section, for example, if the vehicle is hit by another vehicle or the like in the side at high speed, the structure fails to absorb the load produced by the collision. This leads to an unfavorable condition in which the battery cross member is moved towards the center of the vehicle and damages the battery pack, or even battery cells in the battery case, and electrical safety is degraded.

It is an object of the invention to provide a battery installation structure for electric vehicles, which is capable of reducing damages to a battery pack in the event of a side impact crash.

In order to achieve the above object, a battery installation structure for electric vehicles, comprising a battery pack located between a pair of side members fixed to both sides of a vehicle body and extending in an anteroposterior direction of the vehicle body, and a plurality of battery cross members extending in a width direction of the vehicle body and fixing the battery pack to the side members, wherein at least one of the battery cross members have deformable zones between the battery pack and the respective side members.

Because of the deformable zones located between the battery pack and the respective side members, the battery cross members are deformable in the deformable zones when being applied with load in a side impact crash. The deformation prevents the contact between the battery pack and the battery cross members, which is brought about by the battery cross members being moved in the crash, and thus reduces damages to the battery pack caused by the battery cross members.

The present invention will become more fully understood from the detailed description given hereinafter and the accompanying drawings which are given by way of illustration only, and thus, are not limitative of the present invention, and wherein:

FIG. 1 is a bottom view showing a central part of a vehicle body applied with a battery installation structure for electric vehicles according to a first embodiment of the invention;

FIG. 2 is a sectional view taken along line A-A of FIG. 1 ;

FIG. 3 is an enlarged view of an encircled part B shown in FIG. 2 ;

FIG. 4 is a sectional view taken along line C-C of FIG. 3 ;

FIG. 5 is an enlarged view of the encircled part B of FIG. 2 in the event of a side impact crash;

FIG. 6 is a bottom view showing a central part of a vehicle body applied with a battery installation structure for electric vehicles according to a second embodiment of the invention;

FIG. 7 is a sectional view taken along line of FIG. 6 ;

FIG. 8 is an enlarged view of an encircled part B′ shown in FIG. 7 ; and

FIG. 9 is an enlarged view of the encircled part B′ of FIG. 7 in the event of a side impact crash.

Embodiments of the invention will be described below with reference to the attached drawings.

Vehicles used in the embodiments are electric vehicles having a motor for moving a vehicle, which is supplied with power from a battery pack and is controlled by an inverter, as a device for moving the vehicles.

Firstly, a battery installation structure for electric vehicles according to a first embodiment of the invention will be described.

[First Embodiment]

FIG. 1 is a bottom view showing a central part of a vehicle body applied with a battery installation structure for electric vehicles according to the first embodiment of the invention. FIG. 2 is a sectional view taken along line

A-A of FIG. 1 . FIG. 3 is an enlarged view of an encircled part B shown in FIG. 2 . FIG. 4 is a sectional view taken along line C-C of FIG. 3 . In the drawings, “UP”, “FRONT” and “SIDE” arrows represent the upward, forward and width directions, respectively, of the vehicle body.

As illustrated in FIGS. 1 to 4 , a vehicle body 1 of the first embodiment is made up of a pair of side members 3 extending in an anteroposterior direction along right and left sides of the vehicle body 1 , and a front battery cross member lower 5 and a rear battery cross member lower 6 connected to a pair of side members 3 through battery cross member uppers 4 . A battery pack 2 is disposed on the front battery cross member lower 5 and the rear battery cross member lower 6 through a battery tray 7 that positions the battery pack 2 between the side members 3 located under a floor 11 in the center of the vehicle body.

The battery pack 2 is formed by setting a plurality of battery cells 2 c in space created by a case 2 a and a cover 2 b.

The side members 3 are each formed into a bar-like shape having an inverted substantially hat-shaped section.

The battery cross member uppers 4 are each formed into a bar-like shape having an inverted substantially U-shaped section.

The front battery cross member lower 5 is made of a thin metal plate in a shape of a substantial pound sign (cross-hatched symbol). Projections of the front battery cross member lower 5 , which extend in rightward and leftward directions of the vehicle body, are provided with attachment portions 5 a to be connected to the side members 3 . In the attachment portions 5 a , there are formed bolt holes 5 b into which bolts are inserted. In the front battery cross member lower 5 , there are formed a plurality of bolt holes 5 c for fixing the battery pack 2 with bolts.

The rear battery cross member lower 6 is made of a thin metal plate in a shape of a substantial pound sign (cross-hatched symbol) whose pair of projections projecting rearwards are cut off. These rear projections of the front battery cross member lower 5 are connected to front projections of the rear battery cross member lower 6 . In this manner, the front battery cross member lower 5 and the rear battery cross member lower 6 support a lower face of the battery pack 2 as a unit. Projections of the rear battery cross member lower 6 , which extend in the rightward and leftward directions of the vehicle body, are provided with attachment portions 6 a to be connected to the side members 3 . In the attachment portions 6 a , there are formed bolt holes 6 b into which bolts are inserted. In the rear battery cross member lower 6 , there are formed a plurality of bolt holes 6 c for fixing the battery pack 2 with bolts.

The battery tray 7 is formed in a substantially Z-like shape in section as shown in FIG. 3 , and is made up of a thin metal plate expanding along the form of the case 2 a of the battery pack 2 in a bottom view. In the battery tray 7 , there is formed a deformable portion 7 a with which the end of the battery cross member upper 4 comes into contact, and which has relatively low rigidity.

The battery cross member upper 4 is welded to an upper face of the corresponding attachment portion 5 a of the front battery cross member lower 5 and an upper face of the corresponding attachment portion 6 a of the rear battery cross member lower 6 . The end face of the battery cross member upper 4 is welded and fixed to the deformable portion 7 a.

The front battery cross member lower 5 and the rear battery cross member lower 6 are fixed to the side members 3 through the battery cross member uppers 4 with bolts, not shown.

The battery pack 2 is mounted on and fixed to the battery tray 7 with bolts, not shown.

According to the first embodiment, the battery tray 7 is formed so as to curve in an outward direction of the vehicle in the deformable portion 7 a as mentioned, so that there is space created between a side wall of the case 2 a and the deformable portion 7 a of the battery tray 7 . In the battery tray 7 , there is formed a deformable zone 7 b between the battery pack 2 and the battery cross member upper 4 , which has relatively low rigidity.

The following description is about operation and advantages of the battery installation structure for electric vehicles according to the first embodiment of the invention thus configured.

FIG. 5 is an enlarged view of the encircled part B of FIG. 2 after a side impact crash. The thick arrow in the drawing shows a load-applied direction in the crash. In the drawing, “UP” and “SIDE” arrows represent the upward and width directions, respectively, of the vehicle body.

As illustrated in FIG. 5 , when load is applied to the side member 3 or the battery cross member upper 4 in a crash against the side of the vehicle body 1 , the load is transmitted from the battery cross member upper 4 to the front battery cross member lower 5 or the rear battery cross member lower 6 and the battery tray 7 . In the first embodiment, the battery cross member upper 4 is not fixed directly to the side wall of the case 2 a , and there is space between the battery pack 2 and the battery cross member upper 4 . Moreover, the rigidity of the deformable portion 7 a of the battery tray 7 is relatively low. For these reasons, in the event of a side impact crash, the deformable portion 7 a of the battery tray 7 is deformed toward the deformable zone 7 b located nearer the center of the vehicle body 1 , to thereby absorb the load produced in the crash.

In this manner, the deformable portion 7 a is designed to be deformable in the event of a crash against the side of the vehicle body 1 . Because of the deformable zone 7 b between the battery cross member upper 4 and the battery pack 2 , the deformation of the deformable portion 7 a of the battery tray 7 leads to deformation of the battery cross member upper 4 and prevents the load from being applied directly to the battery pack 2 . This eases the contact between the battery cross member upper 4 and the battery pack 2 , for example, if the battery cross member upper 4 is moved in the inward direction of the vehicle body 1 . It is therefore possible to reduce damages to the battery pack 2 .

[Second Embodiment]

The battery installation structure for electric vehicles according to a second embodiment of the invention will be described below.

The second embodiment is different from the first in terms of the form of a battery cross member upper 4 ′ and a battery tray 7 ′. The following description is about matters modified from the first embodiment.

FIG. 6 is a bottom view showing a central part of a vehicle body applied with the battery installation structure for electric vehicles according to the second embodiment of the invention. FIG. 7 is a sectional view taken along line A′-A′ of FIG. 6 . FIG. 8 is an enlarged view of an encircled part B′ shown in FIG. 7 . In the drawings, “UP”, “FRONT” and “SIDE” arrows represent the upward, forward and width directions, respectively, of the vehicle body.

As illustrated in FIGS. 6 to 8 , the battery cross member uppers 4 ′ are each formed into a bar-like shape having an inverted substantially U-shaped section. An attachment portion 4 a′ is formed in an upper surface of the battery cross member upper 4 ′ to be situated nearer the outside of the vehicle body when the battery cross member upper 4 ′ is attached to the side member 3 . A deformable zone 4 b′ , which is lower in height and smaller in cross-sectional area than the attachment portion 4 a′ , is formed in the battery cross member upper 4 ′ to be situated nearer the center of the vehicle body when the battery cross member upper 4 ′ is attached to the side member 3 . The attachment portion 4 a′ and the deformable zone 4 b′ are connected to each other with a slope 4 c ′ intervening therebetween in the center of the battery cross member upper 4 ′.

The battery tray 7 ′ is formed in a substantially Z-like shape in section, and is made up of a thin metal plate expanding along the form of the case 2 a of the battery pack 2 in a bottom view. In the battery tray 7 ′, there is formed a connecting portion 7 a′ with which an end of the battery cross member upper 4 ′ comes into contact.

The battery cross member upper 4 ′ is welded to an upper face of the corresponding attachment portion 5 a of the front battery cross member lower 5 and an upper face of the corresponding attachment portion 6 a of the rear battery cross member lower 6 . The end face of the battery cross member upper 4 ′ is welded and fixed to the connecting portion 7 a′ of the battery tray 7 ′.

The front battery cross member lower 5 and the rear battery cross member lower 6 are fixed to the side members 3 with bolts, not shown, through the battery cross member uppers 4 ′.

The battery tray 7 ′ is mounted on the front battery cross member lower 5 and the rear battery cross member lower 6 . The battery pack 2 is mounted on the battery tray 7 ′ to be fixed with bolts, not shown.

The following description is about operation and advantages of the battery installation structure for electric vehicles according to the second embodiment of the invention thus configured.

FIG. 9 is an enlarged view of the encircled part B′ of FIG. 7 after a side impact crash. The thick arrow in the drawing shows a load-applied direction in the crash. In the drawing, “UP” and “SIDE” arrows represent the upward and width directions, respectively, of the vehicle body.

As illustrated in FIG. 9 , because the deformable zone 4 b′ of the battery cross member upper 4 ′ has smaller sectional area than the attachment portion 4 a′ , when load is applied to the side member 3 or the battery cross member upper 4 ′ in a crash against the side of a vehicle body 1 ′, the battery cross member upper 4 ′ is deformed in the deformable zone 4 b′ that is small in section in the inward direction of the vehicle body 1 ′ and thus absorbs the load produced in the crash.

Since the battery cross member upper 4 ′ is designed so that deformation occurs in the deformable zone 4 b′ in the event of a crash against the side of the vehicle body 1 ′, load is not applied directly to the battery pack 2 . This softens the contact between the battery cross member upper 4 ′ and the battery pack 2 , for example, even if the battery cross member upper 4 ′ is moved in the inward direction of the vehicle body. This makes it possible to reduce damages to the battery pack 2 .

This is the end of descriptions of the embodiments of the invention. However, the invention is not limited to the above-described embodiments.

The first embodiment leaves space between the battery cross member upper 4 and the battery pack 2 and uses the space as a deformable zone. The second embodiment reduces the sectional area of the battery cross member upper 4 ′ and uses the portion reduced in sectional area as a deformable zone. This way, the first and second embodiments allow deformation to take place in the deformable zones. Instead of this, a deformable zone may be formed to have lower strength in section than other portions so that deformation occurs in the deformable zone. In this case, the same advantages as in the embodiments can be provided.