Vehicle battery unit

In a battery unit 10 in which plural high-voltage batteries 31a to 33a are accommodated in a battery case 50, the battery case 50 includes: a bottom plate 51A on which the batteries 31a to 33a are mounted; and a cover 52 covering the batteries 31a to 33a from above. The bottom plate 51A includes a tray 54 having a plate shape, lengthwise reinforcing members 55, and brackets 53. The lengthwise reinforcing members 55 are disposed so as to connect at least adjacent brackets 53. The lengthwise reinforcing members 55 and the brackets 53 are disposed in a lattice shape with the tray 54 interposed therebetween. The batteries 31a to 33a are fixed to the lengthwise reinforcing members 55 such that a longitudinal direction thereof faces the vehicle width direction. The battery case 50 is fixed under a floor of a vehicle V by the brackets 53.

CROSS REFERENCE TO PRIOR APPLICATION

This application is a National Stage Patent Application of PCT International Patent Application No. PCT/JP2016/065214 (filed on May 23, 2016) under 35 U.S.C. § 371, which claims priority to Japanese Patent Application No. 2015-113855 (filed on Jun. 4, 2015), which are all hereby incorporated by reference in their entirety.

TECHNICAL FIELD

The present invention relates to a vehicle battery unit mounted on a vehicle.

BACKGROUND ART

In a vehicle such as a hybrid vehicle, an electric vehicle, or a fuel cell vehicle, a battery unit in which a plurality of batteries are accommodated in a battery case is provided. In a battery unit described in Patent Literature 1, a battery case includes: a tray on which batteries are mounted; and a cover that covers the batteries from above, and a plurality of beam members that extend in a vehicle width direction are fixed to a lower surface of the tray. The battery unit is fixed to left and right side members through fastening portions of the beam members exposed from the tray in the vehicle width direction. In addition, in a battery accommodation portion of the tray, front-rear-direction partitions and width-direction partitions are provided in a lattice shape to be integrated with the tray. As a result, battery accommodation chambers that accommodate the batteries are divided, and the rigidity of the tray is secured.

PRIOR ART LITERATURE

Patent Literature

SUMMARY OF THE INVENTION

Problem that the Invention is to Solve

However, in the battery unit described in Patent Literature 1, the rigidity in the front-rear-direction is secured by the front-rear-direction partitions that are formed to be integrated with the tray. Therefore, a shape of the tray becomes complicated, and a manufacturing step may become complicated.

The present invention provides a battery unit that can reliably hold batteries and can realize structural simplification and weight reduction of a tray.

Means for Solving the Problem

The present invention provides the following aspects.

According to a first aspect, there is provided a vehicle battery unit (for example, a battery unit10in an embodiment described below) including:

a plurality of batteries (for example, high-voltage batteries31ato33ain the embodiment described below); and

a battery case (for example, a battery case50in the embodiment described below) that accommodates the batteries,

wherein the battery case includes a bottom plate (a bottom plate51A or51B in the embodiment described below) on which the batteries are mounted and a cover (for example, a cover52in the embodiment described below) that covers the batteries from above,

the bottom plate includes a tray (for example, a tray54or64in the embodiment described below) that has a plate shape, a plurality of lengthwise reinforcing members (for example, lengthwise reinforcing members55or65in the embodiment described below) that are provided on an upper surface of the tray and that extend in a front-rear-direction of a vehicle, and a plurality of lateral reinforcing members (for example, brackets53or63in the embodiment described below) that are provided on a lower surface of the tray and that extend in a vehicle width direction of the vehicle,

the lengthwise reinforcing members are disposed so as to connect at least adjacent lateral reinforcing members,

the lengthwise reinforcing members and the lateral reinforcing member are disposed in a lattice shape with the tray interposed therebetween,

the batteries are fixed to the lengthwise reinforcing members such that a longitudinal direction of the batteries faces the vehicle width direction, and

the battery case is fixed under a floor of the vehicle by the lateral reinforcing members.

According to a second aspect,

in the vehicle battery unit according to the first aspect,

in the battery case, a first battery module (for example, a front battery module31in the embodiment described below) and a second battery module (for example, a lower rear battery module32in the embodiment described below) that include the batteries are disposed apart from each other in the front-rear-direction with a space portion (for example, a space portion34in the embodiment described below) interposed therebetween,

a front seat (for example, a front seat4in the embodiment described below) is disposed above the first battery module,

a rear seat (for example, a rear seat5in the embodiment described below) is disposed above the second battery module, and

each of the first battery module and the second battery module is disposed between a pair of the lateral reinforcing members.

According to a third aspect,

in the vehicle battery unit according to the second aspect,

a high-voltage device (for example, a DC-DC converter22in the embodiment described below) is disposed in the space portion, and

the high-voltage device is fixed to the lengthwise reinforcing member (for example, first and second middle lengthwise reinforcing members55E and55F or a second lengthwise reinforcing member65B in the embodiment described below).

According to a fourth aspect,

in the vehicle battery unit according to the third aspect,

a pair of the lateral reinforcing members (for example, a second bracket53B and a third bracket53C, or a second bracket63B and a third bracket63C in the embodiment described below) are provided in a front-rear-direction of the high-voltage device,

at least one cross member (for example, a front cross member56A and a rear cross member56B, or a cross member68in the embodiment described below) is provided along the lateral reinforcing member on the upper surface of the tray, and

the lengthwise reinforcing member that hold the high-voltage device is fixed to the cross member.

According to a fifth aspect,

in the vehicle battery unit according to the fourth aspect,

the at least one cross member is disposed so as to overlap with one of the pair of the lateral reinforcing members, which interpose the high-voltage device therebetween, in a top view, and

a closed space is formed by the cross member and the one of the pair of the lateral reinforcing members.

Advantage of the Invention

According to the first aspect, the lengthwise reinforcing members and the lateral reinforcing members are disposed in a lattice shape with the tray interposed therebetween. As a result, the rigidity of the bottom plate can be improved without increasing the thickness of the tray or without imparting rigidity to the tray, and thus the structural simplification and weight reduction of the tray can be realized. In addition, the batteries can be reliably held by the lengthwise reinforcing members that connect the lateral reinforcing members. Further, the lateral reinforcing members not only function as reinforcing members but also function as a fastening member. As a result, the battery unit can be fixed under the floor of the vehicle through the lateral reinforcing members, the number of components can be reduced, and the assembly can be easily performed, as compared to a case where a fastening member is separately provided.

According to the second aspect, each of the first battery module and the second battery module is disposed between the pair of lateral reinforcing members. As a result, the batteries can be held in a lattice-shaped space with high rigidity.

In addition, in the vehicle battery unit, the space portion is formed between the front seat and the rear seat. Therefore, an influence on the interior space can be avoided. As a result, an operation of a passenger of the rear seat putting a foot into or out from under the front seat is not interrupted, and the passenger comfort can be secured.

According to the third aspect, the high-voltage device that is fixed to the lengthwise reinforcing member is interposed between the first battery module and the second battery module in the front-rear-direction. Therefore, the high-voltage device can be effectively protected from impact during collision or the like.

According to the fourth aspect, the high-voltage device can be more reliably protected by the cross member that is disposed on the upper surface of the tray. In addition, the rigidity of the bottom plate can be further improved by the cross member.

According to the fifth aspect, a closed space is formed by the cross member and the one of the pair of the lateral reinforcing members between which the high-voltage device is interposed. As a result, the batteries and the high-voltage device can be more reliably held with high rigidity.

MODE FOR CARRYING OUT THE INVENTION

Hereinafter, an embodiment of a vehicle battery unit according to the present invention will be described with reference to the accompanying drawings. It should be noted that the drawings are seen such that reference numerals look properly oriented.

As illustrated inFIGS. 1 and 2, a battery unit10according to the embodiment of the present invention mainly includes: a plurality of battery modules31to33, a DC-DC converter22, a battery ECU40, and a battery case50that accommodates the above-described components, and is mounted on a vehicle V such as a hybrid vehicle, an electric vehicle, or a fuel cell vehicle. The battery unit10is disposed under a floor panel3forming a floor of a passenger compartment2.

The battery case50includes: a bottom plate51on which the plurality of battery modules31to33, the DC-DC converter22, and the battery ECU40are mounted; and a cover52that covers the bottom plate51from above. In the battery case50, a plurality of brackets53(in a second embodiment, brackets63) that form a part of the bottom plate51and that horizontally extend are fastened to floor frames (not illustrated) that are provided inside side sills disposed on opposite sides of the vehicle V. As a result, the battery unit10is attached to be suspended under the floor panel3. The detailed configuration of the bottom plate51will be described below.

The battery modules31to33include: a front battery module31that is accommodated in a front portion of the battery case50; and two rear battery modules32and33which are accommodated in a rear portion of the battery case50with a space portion34from the front battery module31. Each of the battery modules31to33includes a plurality of high-voltage batteries31ato33a. In the embodiment, the front battery module31includes six high-voltage batteries31ain total that are disposed in two lines in a left-right direction and in three lines in a front-rear-direction. Likewise, one rear battery module32(hereinafter, also called “lower rear battery module32”) includes six high-voltage batteries32ain total that are disposed in two lines in the left-right direction and in three lines in the front-rear-direction. The other rear battery module33(hereinafter, also called “upper rear battery module33”) includes two high-voltage batteries33athat are disposed in the left-right direction.

The battery modules31to33are disposed under a front seat4and a rear seat5of the vehicle V (refer toFIG. 1). Specifically, the front battery module31is disposed under the front seat4, and the lower rear battery module32and the upper rear battery module33are disposed under the rear seat5.

When the front battery module31is disposed under the front seat4, the front battery module31is placed flat without overlapping. When the lower rear battery module32and the upper rear battery module33are disposed under the rear seat5, the lower rear battery module32and the upper rear battery module33are vertically disposed in a front portion of a seating surface of the rear seat5. Specifically, the two high-voltage batteries33aconstituting the upper rear battery module33are disposed above two high-voltage batteries32awhich are disposed on the most front side among the six high-voltage batteries32aconstituting the lower rear battery module32.

The DC-DC converter22is a high-voltage device that converts a voltage of a direct, and is disposed at the center of the battery unit10in the width direction and in the space portion34between the front battery module31and the rear battery modules32and33. In addition, the battery ECU40is a battery controller that manages charging and discharging of the high-voltage batteries31ato33aand temperatures thereof, and is disposed above the lower rear battery module32and in rear of the upper rear battery module33.

Bottom Plate

First Embodiment

Next, a bottom plate51according to a first embodiment (hereinafter, also called a bottom plate51A) constituting the battery case50will be described in detail with reference toFIGS. 3 and 4.FIG. 3is a top view illustrating the bottom plate51A, andFIG. 4is a bottom view illustrating the bottom plate51A.

The bottom plate51A includes: a tray54that is disposed under the high-voltage batteries31ato33a; a plurality of lengthwise reinforcing members55that are fixed to an upper surface of the tray54and that extend in a front-rear-direction of the vehicle V; and a plurality of brackets53that are fixed to a lower surface of the tray and that extend in a vehicle width direction of the vehicle V. The brackets53reinforce the tray54as the lateral reinforcing members, and are fastened to the floor frame (not illustrated) as described above. A pair of front brackets57A and57B are fixed to the front of the tray54, and the front brackets57A and57B are fixed to a cross member (not illustrated) that connect left and right side sills.

The tray54has a substantially rectangular shape and is formed by press-forming a sheet material. The tray54protects the high-voltage batteries31ato33a, the DC-DC converter22, the battery ECU40, and the like, which are accommodated, together with the cover52from water or foreign materials. It is not necessary that the tray54itself have high rigidity.

Each of the brackets53includes: a bracket main body53pthat extends to a region below the tray54in the left-right direction and that is fixed to the tray54by spot welding or the like; and bracket fastening portions53qthat are horizontally exposed from the tray54to opposite left and right end portions of the bracket main body53p. The brackets53include four brackets in total including a first bracket53A, a second bracket53B, a third bracket53C, and a fourth bracket53D in order from the front. The bracket main body53pof the third bracket53C and the bracket main body53pof the fourth bracket53D are integrally formed. The bracket fastening portions53qof the first bracket53A to the fourth bracket53D are disposed at substantially regular intervals in the front-rear-direction so as to hold the tray54with a good balance.

Each of the first bracket53A, the third bracket53C, and the fourth bracket53D is formed such that the bracket main body53pis wider than that the bracket fastening portions53q. The second bracket53B is formed such that the bracket fastening portions53qand the bracket main body53phave substantially the same width. Accordingly, the width of the bracket main body53pof the second bracket53B is narrower than the widths of the bracket main bodies53pof the other brackets53A,53C, and53D.

The lengthwise reinforcing members55are provided above the tray54, that is, on a side opposite to the brackets53with the tray54interposed therebetween. Four first to fourth front lengthwise reinforcing members55A to55D are disposed so as to connect the first bracket53A and the second bracket53B. Two first and second middle lengthwise reinforcing members55E and55F are disposed so as to connect the second bracket53B and the third bracket53C. Further, four first to fourth rear lengthwise reinforcing members55G to55J are disposed so as to connect the third bracket53C and the fourth bracket53D.

The first front lengthwise reinforcing member55A and the first rear lengthwise reinforcing member55G are disposed at a left end of the tray54. The fourth front lengthwise reinforcing member55D and the fourth rear lengthwise reinforcing member55J are disposed at a right end of the tray54. The second front lengthwise reinforcing member55B and the second rear lengthwise reinforcing member55H are disposed at the left center of the tray54apart from the first front lengthwise reinforcing member55A and the first rear lengthwise reinforcing member55G. The third front lengthwise reinforcing member55C and the third rear lengthwise reinforcing member55I are disposed at the right center of the tray54apart from the fourth front lengthwise reinforcing member55D and the fourth rear lengthwise reinforcing member55J. Accordingly, in the front portion of the tray54, the second and third front lengthwise reinforcing members55B and55C are disposed adjacent to each other. In the rear portion of the tray54, the second and third rear lengthwise reinforcing members55H and55I are disposed adjacent to each other.

The first middle lengthwise reinforcing member55E is provided between the first front lengthwise reinforcing member55A and the first rear lengthwise reinforcing member55G, and the second front lengthwise reinforcing member55B and the second rear lengthwise reinforcing member55H in the vehicle width direction so as to be positioned near the second front lengthwise reinforcing member55B and the second rear lengthwise reinforcing member55H. The second middle lengthwise reinforcing member55F is provided between the fourth front lengthwise reinforcing member55D and the fourth rear lengthwise reinforcing member55J, and the third front lengthwise reinforcing member55C and the third rear lengthwise reinforcing member55I in the vehicle width direction so as to be positioned near the third front lengthwise reinforcing member55C and the third rear lengthwise reinforcing member55I.

The brackets53and the lengthwise reinforcing members55disposed as described above form a lattice shape with the tray54interposed therebetween and secure the rigidity of the bottom plate51A. In addition, above the tray54, in order to further improve the rigidity, a front cross member56A is provided along the second bracket53B so as to be fixed to rear end portions of the first to fourth front lengthwise reinforcing members55A to55D and front end portions of the first and second middle lengthwise reinforcing members55E and55F and to overlap with the second bracket53B in a top view. A rear cross member56B is provided along the third bracket53C so as to be fixed to rear end portions of the first and second middle lengthwise reinforcing members55E and55F and front end portions of the first to fourth rear lengthwise reinforcing members55G to55J and to overlap with the third bracket53C in a top view. The second bracket53B and the third bracket53C are fastened to the front cross member56A and the rear cross member56B, respectively, by bolts penetrating the tray54and nuts to form closed sections. As a result, the rigidity of the bottom plate51A is further improved.

The high-voltage batteries31aconstituting the front battery module31are fixed between the first front lengthwise reinforcing member55A and the second front lengthwise reinforcing member55B and between the third front lengthwise reinforcing member55C and the fourth front lengthwise reinforcing member55D such that a longitudinal direction thereof faces the vehicle width direction. In addition, the high-voltage batteries32aconstituting the lower rear battery module32are fixed between the first rear lengthwise reinforcing member55G and the second rear lengthwise reinforcing member55H and between the third rear lengthwise reinforcing member55I and the fourth rear lengthwise reinforcing member55J such that a longitudinal direction thereof faces the vehicle width direction. Further, the DC-DC converter22is fixed between the first and second middle lengthwise reinforcing members55E and55F.

Regarding the respective high-voltage batteries31aand32a, a plurality of battery cells are held by a rectangular frame member although not illustrated in the drawing. Therefore, the lengthwise reinforcing members55are connected on the tray54through the frame member. Accordingly, substantially a pair of lateral reinforcing members are vertically formed on the tray54, and thus the high-voltage batteries31aand32a(battery cells) are held with a high strength.

On the bottom plate51A having the above-described configuration, three high-voltage batteries31aare disposed in the front-rear-direction between the first front lengthwise reinforcing member55A and the second front lengthwise reinforcing member55B that connect the first bracket53A and the second bracket53B, and three high-voltage batteries31aare also disposed in the front-rear-direction between the third front lengthwise reinforcing member55C and the fourth front lengthwise reinforcing member55D that connect the first bracket53A and the second bracket53B. As a result, the front battery module31is constituted by the six high-voltage batteries31ain total. In addition, three high-voltage batteries32aare disposed in the front-rear-direction between the first rear lengthwise reinforcing member55G and the second rear lengthwise reinforcing member55H that connect the third bracket53C and the fourth bracket53D, and three high-voltage batteries32aare also disposed in the front-rear-direction between the third rear lengthwise reinforcing member55I and the fourth rear lengthwise reinforcing member55J that connect the third bracket53C and the fourth bracket53D. As a result, the lower rear battery module32is constituted by the six high-voltage batteries32ain total. The high-voltage batteries33aconstituting the upper rear battery module33are disposed on the left and right high-voltage batteries32aof the most front portion of the lower rear battery module32.

In the space portion34between the front battery module31and the lower rear battery module32, the DC-DC converter22is disposed on the first and second middle lengthwise reinforcing members55E and55F that are fixed to the front cross member56A and the rear cross member56B.

As described above, according to the embodiment, the lengthwise reinforcing members55and the brackets53are disposed in a lattice shape with the tray54interposed therebetween. As a result, the rigidity of the bottom plate51A can be improved without increasing the thickness of the tray54or without imparting rigidity to the tray54, and thus the structural simplification and weight reduction of the tray54can be realized. In addition, the high-voltage batteries31ato33acan be reliably held by the lengthwise reinforcing members55that connect the brackets53. Further, the brackets53not only function as reinforcing members but also function as a fastening member. As a result, the battery unit10can be fixed under the floor of the vehicle V through the bracket53, the number of components can be reduced, and the assembly can be easily performed, as compared to a case where a fastening member is separately provided. In addition, the high-voltage batteries31ato33aare covered with the battery case50including the bottom plate51A and the cover52. As a result, the high-voltage batteries31ato33adisposed under the floor can be protected from water or foreign materials.

In addition, the front battery module31is disposed between the first bracket53A and the second bracket53B, and the lower rear battery module32and the upper rear battery module33are disposed between the third bracket53C and the fourth bracket53D. As a result, the high-voltage batteries31ato33acan be held in a lattice-shaped space with high rigidity.

The third bracket53C and the fourth bracket53D that hold the lower rear battery module32and the upper rear battery module33having a larger capacity than the front battery module31are integrally formed. As a result, the lower rear battery module32and the upper rear battery module33having a large capacity can be reliably held.

In addition, in the battery unit10, the space portion34is formed between the front seat4and the rear seat5. Therefore, an influence on the passenger compartment2can be avoided. As a result, an operation of a passenger of the rear seat5putting a foot into or out from under the front seat4is not interrupted, and the passenger comfort can be secured.

In addition, the DC-DC converter22that is fixed to the first and second middle lengthwise reinforcing members55E and55F is interposed between the front battery module31and the lower rear battery module32in the front-rear-direction. Therefore, the DC-DC converter22can be effectively protected from impact during collision or the like.

In addition, the DC-DC converter22can be more reliably protected by the front cross member56A and the rear cross member56B that are disposed on the upper surface of the tray54. In addition, the rigidity of the bottom plate51A can be further improved by the front cross member56A and the rear cross member56B.

In addition, the front cross member56A and the second bracket53B form a closed space, and the rear cross member56B and the third bracket53C form a closed space. As a result, the high-voltage batteries31ato33aand the DC-DC converter22can be more reliably held with high rigidity.

Second Embodiment

Next, a bottom plate51according to a second embodiment (hereinafter, also called a bottom plate51B) constituting a battery case50will be described in detail with reference toFIGS. 5 and 7,FIG. 5is a top view illustrating the bottom plate51B,FIG. 6is a bottom view illustrating the bottom plate51B, andFIG. 7is an exploded perspective view illustrating the bottom plate51B.

The bottom plate51B mainly includes: a tray64that is disposed under high-voltage batteries31ato33a; a plurality of lengthwise reinforcing members65that are fixed to an upper surface of the tray64and that extend in a front-rear-direction of a vehicle V; and a plurality of brackets63that are fixed to a lower surface of the tray and that extend in a vehicle width direction of the vehicle V. The brackets63reinforce the tray64as the lateral reinforcing members, and are fastened to the floor frames (not illustrated) as described above.

The tray64has a substantially rectangular shape and is formed by press-forming a sheet material. The tray64protects the high-voltage batteries31ato33a, the DC-DC converter22, the battery ECU40, and the like, which are accommodated, together with the cover52from water or foreign materials. It is not necessary that the tray54itself have high rigidity.

Each of the brackets63includes: a bracket main body63pthat extends to a region below the tray64in the left-right direction and that is fixed to the tray64by spot welding or the like; and bracket fastening portions63qthat are horizontally exposed from the tray64to opposite left and right end portions of the bracket main body63p. The brackets63include four brackets in total including a first bracket63A, a second bracket63B, a third bracket63C, and a fourth bracket63D in order from the front. The bracket main body63pof the third bracket63C and the bracket main body63pof the fourth bracket63D are integrally formed. The bracket fastening portions63qof the first bracket63A to the fourth bracket63D are disposed at substantially regular intervals in the front-rear-direction so as to hold the tray64with a good balance. A pair of front brackets67A and67B are integrally formed to the front of the first bracket63A, and the front brackets67A and67B are fixed to a cross member (not illustrated) that connects left and right side sills.

Each of the first bracket63A, the third bracket63C, and the fourth bracket63D is formed such that the bracket main body63pis wider than the bracket fastening portions63q. The second bracket63B is formed such that the bracket fastening portions63qand the bracket main body63phave substantially the same width. Accordingly, the width of the bracket main body63pof the second bracket63B is narrower than the widths of the bracket main bodies63pof the other brackets63A,63C, and63D.

The lengthwise reinforcing members65are provided above the tray64, that is, on a side opposite to the brackets63with the tray64interposed therebetween. Three first to third lengthwise reinforcing members65A to65C are disposed so as to connect the first bracket63A to the fourth bracket63D. The first lengthwise reinforcing member65A is disposed at a left end of the tray64, the second lengthwise reinforcing member65B is disposed at the center of the tray64, and the third lengthwise reinforcing member65C is disposed at a right end of the tray64.

The brackets63and the lengthwise reinforcing members65disposed as described above form a lattice shape with the tray64interposed therebetween and secure the rigidity of the bottom plate51B. In addition, above the tray64, in order to further improve the rigidity, a subsidiary lengthwise reinforcing ember66and a cross member68are provided.

The subsidiary lengthwise reinforcing member66includes two members, that is first and second subsidiary lengthwise reinforcing members66A and66B. The first and second subsidiary lengthwise reinforcing members66A and66B are disposed so as to connect the first bracket63A to the fourth bracket63D. The first subsidiary lengthwise reinforcing member66A is disposed between the first lengthwise reinforcing member65A and the second lengthwise reinforcing member65B, and the second subsidiary lengthwise reinforcing member66B is disposed between the second lengthwise reinforcing member65B and the third lengthwise reinforcing member65C.

The cross member68is provided so as to cross the first to third lengthwise reinforcing members65A to65C and the first and second subsidiary lengthwise reinforcing members66A and66B. In addition, the cross member68is provided along the second bracket63B so as to overlap with the second bracket63B in a top view. The second bracket63B and the cross member68are fastened through the tray64and form a closed section. As a result, the rigidity of the bottom plate51B is further improved. This way, the second bracket63B can secure the rigidity in cooperation with the cross member68. Therefore, the width of the bracket main body63pof the second bracket63B is narrower than those of the other brackets63A,63C, and63D. In other words, the brackets63A,63C, and63D that are not fastened to the cross member68improve the rigidity of the brackets themselves by setting the widths of the bracket main bodies63pto be wider.

The high-voltage batteries31aconstituting the front battery module31and the high-voltage batteries32aconstituting the lower rear battery module32are fixed between the first lengthwise reinforcing member65A and the second lengthwise reinforcing member65B and between the second lengthwise reinforcing member65B and the third lengthwise reinforcing member65C such that a longitudinal direction thereof faces the vehicle width direction. Further, the DC-DC converter22is fixed substantially at the center of the second lengthwise reinforcing member65B in the front-rear-direction.

Regarding the respective high-voltage batteries31aand32a, a plurality of battery cells are held by a rectangular frame member although not illustrated in the drawing. Therefore, the lengthwise reinforcing members65are connected on the tray64through the frame member. Accordingly, substantially a pair of lateral reinforcing members are vertically formed on the tray64, and thus the high-voltage batteries31aand32a(battery cells) are held with a high strength.

On the bottom plate51B having the above-described configuration, three high-voltage batteries31aare disposed in front of the cross member68in the front-rear-direction between the first lengthwise reinforcing member65A and the second lengthwise reinforcing member65B that connect the first bracket63A to the fourth bracket63D, and three high-voltage batteries31aare also disposed in the front-rear-direction between the second lengthwise reinforcing member65B and the third lengthwise reinforcing member65C that connect the first bracket63A to the fourth bracket63D. As a result, the front battery module31is constituted by the six high-voltage batteries31ain total. In addition, three high-voltage batteries32aare disposed in rear of and apart from the cross member68in the front-rear-direction between the first lengthwise reinforcing member65A and the second lengthwise reinforcing member65B that connect the first bracket63A to the fourth bracket63D, and three high-voltage batteries32aare also disposed in the front-rear-direction between the second lengthwise reinforcing member65B and the third lengthwise reinforcing member65C that connect the first bracket63A to the fourth bracket63D. As a result, the front battery module31is constituted by the six high-voltage batteries32ain total. The high-voltage batteries33aconstituting the upper rear battery module33are disposed on the left and right high-voltage batteries32aof the most front portion of the lower rear battery module32.

In the space portion34between the front battery module31and the lower rear battery module32, the DC-DC converter22is disposed on the second lengthwise reinforcing member65B that is fixed to the cross member68. In the second lengthwise reinforcing member65B, a hole portion69is provided in a part of a region where the DC-DC converter22is disposed, and a space that is formed by the lengthwise reinforcing members65and the tray64is connected to the DC-DC converter22through the hole portion69. As a result, a harness (not illustrated) that is routed in the space is connected to the DC-DC converter22through the hole portion69. By providing the hole portion69in the second lengthwise reinforcing member65B as described above, the space formed by the lengthwise reinforcing members65and the tray64can be effectively used as a harness accommodation space, and the DC-DC converter22can be disposed compactly in the height direction.

As described above, according to the embodiment, the lengthwise reinforcing members65and the brackets63are disposed in a lattice shape with the tray64interposed therebetween. As a result, the rigidity of the bottom plate51B can be improved without increasing the thickness of the tray64or without imparting rigidity to the tray64, and thus the structural simplification and weight reduction of the tray64can be realized. In addition, the high-voltage batteries31ato33acan be reliably held by the lengthwise reinforcing members65that connect the brackets63. Further, the brackets63not only function as reinforcing members but also function as a fastening member. As a result, the battery unit10can be fixed under the floor of the vehicle V through the bracket53, the number of components can be reduced, and the assembly can be easily performed, as compared to a case where a fastening member is separately provided.

In addition, the front battery module31is disposed between the first bracket63A and the second bracket63B, and the lower rear battery module32and the upper rear battery module33are disposed between the third bracket63C and the fourth bracket63D. As a result, the high-voltage batteries31ato33acan be held in a lattice-shaped space with high rigidity.

The third bracket63C and the fourth bracket63D that hold the lower rear battery module32and the upper rear battery module33having a larger capacity than the front battery module31are integrally formed. As a result, the lower rear battery module32and the upper rear battery module33having a large capacity can be reliably held.

In addition, in the battery unit10, the space portion34is formed between the front seat4and the rear seat5. Therefore, an influence on the passenger compartment2can be avoided. As a result, an operation of a passenger of the rear seat5putting a foot into or out from under the front seat4is not interrupted, and the passenger comfort can be secured.

In addition, the DC-DC converter22that is fixed to the second lengthwise reinforcing member65B is interposed between the front battery module31and the lower rear battery module32in the front-rear-direction. Therefore, the DC-DC converter22can be effectively protected from impact during collision or the like.

In addition, the DC-DC converter22can be more reliably protected by the cross member68that is disposed on the upper surface of the tray54. In addition, the rigidity of the bottom plate51B can be further improved by the cross member68.

In addition, the closed space is formed between the cross member68and the second bracket53B. As a result, the high-voltage batteries31ato33aand the DC-DC converter22can be more reliably held with high rigidity.

The present invention is not limited to the above-described embodiments, and modifications, improvements, and the like can be appropriately made.

For example, the shapes, numbers, and the like of the lengthwise reinforcing members55(65) and the brackets53(63) can be appropriately changed as long as the lengthwise reinforcing members55(65) and the brackets53(63) are disposed in a lattice shape with the tray54(64) interposed therebetween.

In addition, the DC-DC converter22is used as the example of the high-voltage device. However, it is not necessary that the battery unit10include a high-voltage device. In addition, another high-voltage device may be provided instead of or in addition to the DC-DC converter22.

DESCRIPTION OF REFERENCE NUMERALS AND CHARACTERS