GB2567931A

GB2567931A - Vehicle body structure

Info

Publication number: GB2567931A
Application number: GB1813938.6A
Authority: GB
Inventors: Nakamura Hideyuki; Yamamoto Hisatoshi; Kawasaki Takeshi
Original assignee: Hitachi Ltd
Current assignee: Hitachi Ltd
Priority date: 2012-09-20
Filing date: 2012-09-20
Publication date: 2019-05-01
Anticipated expiration: 2032-09-20
Also published as: GB2567931B; GB201813938D0

Abstract

A railway vehicle body structure 1 having a roof structure 10, side structures 20, and an underframe 40 and provided with bolsters for coupling running devices to the lower surface of the underframe 40. Each bolster comprises a first bolster 47 located at the center of the underframe, and second bolsters 48 located at ends of the underframe in the width direction 110 to abut air springs of the running gear. The bolsters are constructed from hollow extruded shapes each obtained by forming two opposed plates and multiple ribs connecting the plates by hollow extrusion molding. The bolster is so arranged that the extrusion direction of the center bolster 47 corresponds to the widthwise direction 110, and the extrusion direction of the end bolsters 48, corresponds to the longitudinal direction 120. This enables modularized wires and pipes to pass through between multiple ribs formed inside the end bolsters 48 along the longitudinal direction, so that the steps of manufacturing the car body can be reduced while improving the rigidity of the bolster.

Description

DESCRIPTION

Title of the Invention

VEHICLE BODY STRUCTURE

Technical Field [0001]

The present invention relates to a vehicle body structure for a monorail car, a railway car, or the like, which has a roof structure that forms an upper surface, side structures that form side surfaces, and an underframe that forms a lower surface, and is provided with bolsters for coupling running devices to the lower surface of the underframe.

Background Art [0002]

With the goal of achieving light weight and high rigidity, and further enhancing productivity, a construction method for constructing a vehicle body structure as the structure of a monorail car or a railway car has recently been becoming popular, in which high-rigidity hollow extruded aluminum alloy shapes, each composed of two opposed plates and multiple ribs for connecting these plates, are manufactured by hollow extrusion molding, and these are used as respective structures that form the vehicle body structure.

The vehicle body structure is generally constructed from a roof structure that forms the upper surface, side structures that form the side surfaces, an underframe that forms the lower surface, and end structures that form longitudinal end faces. Among them, center sills equipped with a coupler for mutually connecting cars, and bolsters for supporting the weight of the car body on a running device (hereinafter called a bogie) are provided on an end underframe that forms each end side of the lower surface near the end of the lower surface of the underframe in the longitudinal direction.

[0003]

In general, a structure having strength capable of bearing major load applying on the vehicle body structure through the coupler and the bogie by crossing and combining these center sills and bolsters is employed. An extruded aluminum alloy shape is applied to the center sills, and the above-mentioned hollow extruded aluminum alloy shapes are applied to the bolsters because of the need for a reasonable area to support the load acting through the bogie with high rigidity.

[0004]

On the lower surface of the underframe reinforced by the center sills and the bolsters, many devices such as a power supply system, a control system, and a highpressure air system that constitute a driving device, a braking device, and the like

-2need to be fitted in a limited space, and wires and pipes connecting these devices need to be arranged.

However, a center pin support of the bogie needs to be formed in the bolsters at the center and air spring supports for suspensions also need to be formed on both sides of the center pin support, respectively, and this accounts for the majority of the underframe in the width direction. Thus, the space for the wires and pipes mentioned above cannot be secured sufficiently.

[0005]

Therefore, FIGS. 14 and 15 of Patent Document 1 mentioned below show that penetration pipes are provided in a bolster located above the bogie to achieve wires and pipes therethrough in order to secure the space for wires and pipes.

However, since the placement of the penetration pipes increases the steps of manufacturing a car body, Patent Document 1 proposes a vehicle body structure for making use of a space in a center sill for wires and pipes to prevent the increase in the steps of manufacturing the car body associated with the placement of the penetration pipes.

[0006]

On the other hand, it is considered that modularized wires and pipes is fabricated in another process and attached to the car body as a method of preventing the increase in the steps of manufacturing the car body associated with the placement of wires and pipes.

However, in the structure shown in FIGS. 1 and 2 of Patent Document 1, it is difficult to provide a space to pass modularized wires and pipes in the center sill. Further, since the modularized wires and pipes needs to be bent front and rear of the bolster to fit the space in the center sill, the steps of manufacturing the car body may be rather increased.

Citation List

Patent Document [0007]

Patent Document 1: Japanese Patent Application Laid-Open No. 201 ΟΙ 73628

Summary of the Invention Problem to be Solved by the Invention [0008]

Therefore, it is an object of the present invention to achieve both the elimination of penetration pipes and the modularization of wires and pipes in a vehicle body structure having a roof structure that forms an upper surface, side structures that form side surfaces, and an underframe that forms a lower surface, and provided with bolsters for coupling running devices to the lower surface of the

-3underframe in order to reduce the steps of manufacturing a car body.

Means for Solving the Problems [0009]

In order to solve the above problems, a vehicle body structure according to the present invention is a vehicle body structure having a roof structure, side structures, and an underframe, and provided with bolsters for coupling running devices to the lower surface of the underframe, wherein each of the bolsters is composed of a first bolster located at the center of the underframe in a width direction and equipped with a center pin for coupling with each of the running devices, and second bolsters located at the ends of the underframe in the width direction to abut against air springs of the running device.

Then, the first bolster and the second bolsters are constructed from hollow extruded shapes each formed by hollow extrusion molding from two opposed face plates and multiple ribs connecting the face plates, and the extrusion direction of the hollow extruded shape that form the first bolster lies in the width direction of the underframe, and the extrusion direction of the hollow extruded shapes that form the second bolsters lies in a longitudinal direction of the underframe.

Advantageous Effect of the Invention [0010]

According to the vehicle body structure, modularized wires and pipes can be passed through inside the second bolsters, where the extrusion direction of the underframe lies in the longitudinal direction and the multiple ribs are formed in this direction, without placing penetration pipes, thereby enabling a reduction in the steps of manufacturing a car body. In addition, since the extrusion direction of the first bolster lies in the width direction of the underframe and the multiple ribs are formed in this direction, high rigidity can be obtained across the entire bolster in collaboration with the ribs of the second bolsters formed along the longitudinal direction of the underframe. Therefore, the entire bolster can bear load applied from the bogie and the coupler, and this enables a reduction in the weight of an end underframe as well.

Brief Description of the Drawings [0011]

FIG. 1 is a bottom perspective view showing one embodiment of a vehicle body structure according to the present invention.

FIG. 2 is an A-A cross-section view of the vehicle body structure shown in FIG. 1.

FIG. 3 is a B-B cross-section view of the vehicle body structure shown in FIG. 1.

FIG. 4 is a C-C cross-section view of the vehicle body structure shown in

-4FIG. 1.

FIG. 5 is a D-D cross-section view of the vehicle body structure shown in FIG. 1.

Modes for carrying out the Invention [0012]

An example of a vehicle body structure according to the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a bottom perspective view (a perspective view of a car body as viewed from a bogie side) showing one embodiment of a vehicle body structure according to the present invention. Note that in each diagram the vertical direction of a vehicle body structure 1 is referred to as a height direction 100, the width direction of the vehicle body structure 1 perpendicular to the height direction 100 is referred to as a width direction 110, and the longitudinal direction of the vehicle body structure 1 perpendicular to the height direction 100 and the width direction 110 is referred to as a longitudinal direction 120.

[0013]

In the vehicle body structure shown in FIG. 1, the vehicle body structure 1 is constructed from an underframe 40, side structures 20, 20 (only one of them is shown) vertically arranged in both end portions of the underframe 40 in the width direction 110, end structures 30, 30 (only one of them is shown) vertically arranged in both end portions of the underframe 40 in the longitudinal direction 120, and a roof structure 10 provided on the top edges of the side structures 20, 20 and the end structures 30, 30. Side sills 41,41 are joined to both ends of the underframe 40 in the width direction 110 to extend in the longitudinal direction 120 to make joints with the side structures 20, 20, and end sills 42, 42 are joined to both ends of the underframe 40 in the longitudinal direction 120 to extend in the width direction 110 in order to make joints with the end structures 30, 30.

[0014]

Both ends of the side sills 41,41 are joined to end portions of the end sills 42, 42. Window openings 21,21,21,21,21, 21 (only one side of them is shown) for allowing passengers to watch the scenery outside the vehicle and letting light in, and door openings 22, 22, 22, 22 (only one side of them is shown) for passengers to get on or off are provided in the side structures 20, 20. Gangway openings 31, 31 (only one of them is shown) for allowing passengers to move to a front or back car are provided in the end structures 30, 30.

[0015]

The roof structure 10, the side structure 20, and the underframe 40 are constructed by arranging multiple hollow extruded aluminum alloy shapes along the longitudinal direction 120 and joining end portions of adjacent hollow extruded shapes in the width direction 110. Note that the side near the end of the underframe in the longitudinal direction 120 may be formed by joining plate-like extruded aluminum alloy shapes depending on the space on the lower surface of the underframe 40.

[0016]

The end structure 30 is formed by joining together a plate-like extruded shape and a beam-like extruded shape, both of which are made of aluminum alloy.

Then, the side sill 41 and the end sill 42 are hollow extruded aluminum alloy shapes. The side sill 41 and the side structure 20, the side structure 20 and the roof structure 10, the end sill 42 and the end structure 30, the end structure 30 and the side structure 20, and the end structure 30 and the roof structure 10 are joined by welding, friction stir welding, or the like, or by mechanical fastening means, such as bolts, rivets, or the like.

[0017]

The following will describe a detailed structure of an end underframe. Since the end underframe has a same structure between the front and back ends, the structure of one end will be described.

In the end underframe, center sills 43, 43 are joined on the lower surface of the underframe 40 near the center in the width direction 110 in parallel with the side sills 41,41. In the end underframe, a central transverse sill 44 as a first transverse sill and an end transverse sill 45 as a second transverse sill near the center and end in the longitudinal direction 120 are joined on the lower surface of the underframe 40 in parallel with the end sill 42. Both ends of the center sills 43, 43 are joined on the side surfaces of the end sill 42 and the central transverse sill 44.

[0018]

Both ends of the central transverse sill 44 are joined on the side surfaces of the side sills 41,41. Ends of the end transverse sill 45 divided by the center sills 43, 43 are joined on the side surfaces of the side sills 41,41 or the center sills 43, 43. A coupler support 46 is provided between the end sill 42 and the end transverse sill 45 to combine a coupler (not shown) for connecting the vehicle body structure 1 with the front or back vehicle body structure, and joined to the center sills 43, 43.

[0019]

A center bolster 47 is provided as a first bolster between the central transverse sill 44 and the end transverse sill 45 near the center in the width direction 110, and end bolsters 48, 48 are provided as second bolsters near both ends in the width direction 110. The center bolster 47 is joined on the side surfaces of the center sills 43, 43, and provided with a center pin support 49 for coupling a center pin (not shown) of a bogie to the lower surface.

[0020]

The end bolsters 48, 48 are joined on the side surfaces of the side sills 41, and the center sills 43, 43, and on the lower surface of the underframe 40, and provided with air spring supports 50, 50 for coupling air springs (not shown) of the bogie to the lower surface. In the case of being applied to the vehicle body structure for a monorail car, areas surrounded by the center sills 43, 43, the central transverse sill 44, the end transverse sill 45, and the center bolster 47 become wheel recesses 51, 51 in which wheels are inserted, and box-like members (not shown) protruding upward toward the underframe 40 are joined to or fastened by mechanical fastening means to the center sills 43, 43, the central transverse sill 44, and the end transverse sill 45. In order to prevent interference with the wheels and secure the area of contact with air springs, the length of the center bolster 47 in the longitudinal direction 120 is made shorter than the length of the end bolster 48 in the longitudinal direction 120.

[0021]

FIG. 2 shows an A-A cross-section view in FIG. 1 when the internal structure of the center bolster 47 in the vehicle body structure 1 is viewed from the width direction 110. The center bolster 47 is constructed from one hollow extruded aluminum alloy shape, composed of an upper face plate 61, a lower face plate 62, diagonal ribs 63, and longitudinal ribs 64, and a flat plank 65. The center bolster 47 is so arranged that the extrusion direction of the hollow extruded shape corresponds to the width direction 110 and the diagonal ribs 63 and the longitudinal ribs 64 extend in this direction, and joined on the side surfaces of the center sills 43 (see FIG. 1) in both end portions of the upper face plate 61, the lower face plate 62, and the longitudinal ribs 64 in the width direction 110. The plank 65 for supporting the center pin of the bogie with high rigidity is joined on the lower surface of the lower face plate 62 in joint 66. A center pin inserting port 67 is provided at the center of the center bolster 47 to insert the center pin, and screw seat inserting ports 69 are provided at the center of the longitudinal ribs 64 to insert screw seats 68 into which bolts (not shown) for coupling the center pin to the lower surface of the plank 65 are fastened.

[0022]

FIG. 3 shows a B-B cross-section view in FIG. 1 when the internal structure of the end bolster 48 in the vehicle body structure 1 is viewed from the longitudinal direction 120. The end bolster 48 is constructed from two hollow extruded aluminum alloy shapes, the extrusion direction of which corresponds to the longitudinal direction 120 and each of which is composed of horizontal upper face plate 71 and lower face plate 72, and diagonal ribs 73 extending in the extrusion direction, and a flat closing plate 74. The end of the upper face plate 71 near the center of the end bolster 48 in the width direction 110 more protrudes toward the center of the end bolster 48 in the width direction 110 than the end of the lower face plate 72 in the width direction 110 of the end bolster 48. After the end bolster 48 is inverted to the height direction 100 and the ends of the upper face plates 71 near the center of the end bolster 48 in the width direction 110 are joined in a joint 75 from the side of the closing plate 74 in such a state that the closing plate 74 is not placed, the closing plate 74 is placed between the two hollow extruded shapes, and the ends of the

-7lower face plates 72 near the center of the end bolster 48 in the width direction 110 and the ends of the closing plate 74 in the width direction 110 are joined in joint 76.

[0023]

The surfaces of the joint parts 76 attaching to the air spring are finished smoothly together with the surfaces of the lower face plates 72. As shown in FIG. 1, the end bolster 48 is joined on the side surfaces of the side sill 41 and the center sill 43 at both ends of the upper face plate 71 and the lower face plate 72 in the width direction 110. An air intake seat mounting surface 77 for mounting an air intake seat of the air spring, and an air intake seat inserting port 78 are provided at the center of the end bolster 48.

[0024]

FIG. 4 shows a C-C cross-section view in FIG. 1 when the internal structure of the center sill 43 in the vehicle body structure 1 is viewed from the longitudinal direction 120. The center sill 43 is constructed an extruded aluminum alloy shape composed of an upper horizontal rib 81, a lower horizontal rib 82, a longitudinal rib 83, and a box support 84. The center bolster 47 (see FIG. 1) is joined on a side surface (the right side in FIG. 4) of the longitudinal rib 83 near the center in the width direction 110. The end bolster 48 (see FIG. 1) is joined to an end of the upper horizontal rib 81 near the end in the width direction 110 and on a side surface (the left side in FIG. 4) of the longitudinal rib 83 near the end in the width direction 110. The position of the upper horizontal rib 81 in the height direction 100 is equivalent to the position of the upper face plate 61 of the center bolster 47 shown in FIG. 2 and the position of the upper face plate 71 of the end bolster 48 in the height direction 100 shown in FIG. 3.

[0025]

Further, in FIG. 4, the position of the lower horizontal rib 82 in the height direction 100 is equivalent to the position of the lower face plate 62 of the center bolster 47 shown in FIG. 2 and the position of the lower face plate 72 of the end bolster 48 in the height direction 100 shown in FIG. 3.

In other words, the lower horizontal rib 82 is cut out in a range where the end bolster 48 is joined. The box support 84 protruding above the upper horizontal rib 81 is provided as an extension of the longitudinal rib 83 in the height direction 100. The box-like member protruding upward toward the underframe 40 to form the wheel recess 51 is coupled to this box support 84.

[0026]

FIG. 5 shows a D-D cross-section view in FIG. 1 when the internal structure of the central transverse sill 44 in the vehicle body structure 1 is viewed from the width direction 110. The central transverse sill 44 is constructed from an extruded aluminum alloy shape composed of an upper horizontal rib 91, a lower horizontal rib 92, a longitudinal rib 93, and a box support 94. The end transverse sill 45 shown in FIG. 1 also has a similar structure.

-8Further, in FIG. 5, the center sill 43 in FIG. 4 is joined on a side surface (the right side in FIG. 5) of the longitudinal rib 93 near the end in the longitudinal direction 120. The position of the upper horizontal rib 91 in the height direction 100 is equivalent to the position of the upper horizontal rib 81 of the center sill 43 in the height direction 100 shown in FIG. 4. The position of the lower horizontal rib 92 in the height direction 100 is equivalent to the position of the lower face plate 82 of the center sill 43 in the height direction 100 shown in FIG. 4. The box support 94 protruding above the upper horizontal rib 91 is provided as an extension of the longitudinal rib 93 in the height direction 100. The box-like member protruding upward toward the underframe 40 to form the wheel recess 51 is coupled to this box support 94.

[0027]

In such a structure, since a triangular wide space extending in the longitudinal direction 120 within the end bolster 48 can be used to pass wires and pipes therethrough in the longitudinal direction 120, modularized wires and pipes can be passed through without installing penetration pipes, thereby enabling a reduction in the working steps of the car body.

[0028]

Further, the diagonal ribs 63 in the center bolster 47 extend in the width direction 110 as shown in FIG. 2, and the diagonal ribs 73 in the end bolster 48 extend in the longitudinal direction 120 as shown in FIG. 3 to bear the shear load applied from the bogie through the air spring effectively. Furthermore, since the center bolster 47 on which the load from the bogie directly applied is joined to the high-rigidity center sill 43 in the entire circumference and jointed to the plank 65 on the lower surface, adequate strength can be secured even by the combination of the small-sized center bolster 47 and the end bolster 48 with only the upper face plate 71 and the lower face plate 72 joined to the side sill 41 and the center sill 43. According to this structure, even if the size of the center bolster 47 in the longitudinal direction 120 is made smaller than the size of the end transverse sill 48 in the longitudinal direction 120 not to interfere with the wheels, required strength can be obtained. In addition, the end bolster 48 can be joined by working from one side (the side of the lower face plate 72), and this enables a further reduction in the working steps of the car body.

[0029]

Further, the outer edges of an end underframe (a lower surface part of the underframe 40 near the end in the longitudinal direction 120) is made up of the side sill 41, the end sill 42, and the central transverse sill 44, and the end bolster 48, the center sill 43, the center bolster 47, the center sill 43, and the end bolster 48 are joined in this order from one side sill 41 to the other side sill 41 along the width direction 110 to form an integrated bolster. Furthermore, both ends of the center sill 43 in the longitudinal direction 120 are joined to the end sill 42 and the central

-9transverse sill 44, respectively, to form an integral structure in which all of side sills 41, the end sill 42, the center sills 43, the central transverse sill 44, the end transverse sill 45, the coupler support 46, center bolster 47, and the end bolsters 48 are joined and rigidly connected. Therefore, load applied from the bogie and the coupler can be borne by the overall end underframe, and this enables a reduction in the weight of the end underframe as well. Further, since the center sills 43, the central transverse sill 44, and the end transverse sill 45, which form the wheel recesses 51, integrally have the box supports 84 (see FIG. 4), 94 (see FIG. 5) for coupling the box-like members protruding upward toward the underframe 40, there is no need to provide box supports separately, and this enables a further reduction in the working steps of the car body.

[0030]

While the technical scope of the present invention is defined based on the description of Claims or the description of Means for Solving the Problems, the present invention will cover a scope that can easily be replaced therefrom by those skilled in the art.

Description of Reference Numerals [0031]

... vehicle body structure

... roof structure

... side structure

... window opening

... door opening

... end structure

... gangway opening

... underframe

... side sill

... end sill

... center sill

... central transverse sill

... end transverse sill

... coupler support

... center bolster

... end bolster

... center pin support

... air spring support

... wheel recess

... upper face plate

... lower face plate

... diagonal rib

... longitudinal rib

... plank

... joint

... center pin inserting port

... screw seat

... screw seat inserting port

... upper face plate

... lower face plate

... diagonal rib

... closing plate

75, 76 ... joint

... air intake seat mounting surface

... air intake seat inserting port

... upper horizontal rib

... lower horizontal rib

... longitudinal rib

... box support

... upper horizontal rib

... lower horizontal rib

... longitudinal rib

... box support

100 ... height direction of vehicle body structure 1

110 ... width direction of vehicle body structure 1

120 ... longitudinal direction of vehicle body structure 1

-11 NUMBERED CLAUSES RELATING TO THE INVENTION

1. A vehicle body structure having a roof structure, side structures, and an underframe, and provided with bolsters for coupling running devices to a lower surface of the underframe, wherein each of the bolsters is composed of a first bolster located at a center of the underframe in a width direction and equipped with a center pin for coupling with each of the running devices, and second bolsters located at ends of the underframe in the width direction to abut against air springs of the running device, the first bolster and the second bolsters are constructed from hollow extruded shapes each formed by hollow extrusion molding from two opposed face plates and a plurality of ribs connecting the face plates, and an extrusion direction of the hollow extruded shape that form the first bolster lies in the width direction of the underframe, and an extrusion direction of the hollow extruded shapes that form the second bolsters lies in a longitudinal direction of the underframe.

2. The vehicle body structure according to clause 1, wherein at least one of the ribs is inclined from a normal direction of the face plate.

3. The vehicle body structure according to clause 1, wherein a length of the first bolster in the longitudinal direction of the underframe is made shorter than a length of the second bolsters in the longitudinal direction of the underframe.

4. The vehicle body structure according to clause 1, wherein the first bolster is constructed from one of the hollow extruded shapes and a flat plank joined on a lower surface thereof.

5. The vehicle body structure according to clause 1, wherein each of the second bolsters is constructed from two of the hollow extruded shapes and a flat closing plate joined therebetween, and side ends of one side of the face plates that form the hollow extruded shapes on a center side in the width direction of the second bolster protrude nearer the center in the width direction of the second bolster than side ends of the other side of the face plates that form the hollow extruded shapes on the center side in the width direction of the second bolster, and ends of the one side of the face plates near the center in the width direction of the second bolster are joined to each other, and ends of the other side of the face plates on a center side in the width direction of the second bolster are joined through the closing plate located between the other side of the face plates.

6. The vehicle body structure according to clause 1, wherein both ends of the first bolster in the width direction of the underframe, and side ends of the second bolsters on a center side in the width direction of the underframe are joined to center sill located between the first bolster and the second bolsters to extend in the longitudinal direction of the underframe, and

- 12side ends of the second bolsters on end sides in the width direction of the underframe are joined to side sills located at both ends in the width direction of the underframe to extend in the longitudinal direction of the underframe.

7. The vehicle body structure according to clause 6, wherein both ends of the side sills in the longitudinal direction are joined to end sills located at both ends in the longitudinal direction of the underframe to extend in the width direction of the underframe, both ends of the center sill in the longitudinal direction are joined to the end sills and first transverse sills located nearer the center than the bolster in the longitudinal direction of the underframe to extend in the width direction of the underframe, both ends of the first transverse sills in the longitudinal direction are joined to the side sills, ends of second transverse sills located between the end sills and the bolster to extend in the width direction of the underframe are joined to the side sills and the center sills, and coupler supports located between the end sills and the second transverse sills to support load acting from couplers are joined to the center sill.

8. The vehicle body structure according to clause 7, wherein the center sill, the first transverse sills, and the second transverse sills are each constructed from an extruded shape having two horizontally-extending ribs with a certain distance therebetween in a height direction of the underframe, and positions of the ribs that form each of the center sill, the first transverse sills, and the second transverse sills in the height direction of the underframe are equivalent to positions of the two face plates that form each of the first bolster and the second bolsters in the height direction of the underframe.

9. The vehicle body structure according to clause 7, wherein area surrounded by the first bolster, the center sill, the first transverse sills, and the second transverse sills is wheel recess in which wheels of the running devices are inserted.

10. The vehicle body structure according to clause 9, wherein the center sill, the first transverse sills, and the second transverse sills are each constructed from an extruded shape extruded integrally with a box support for coupling a box-like member protruding upward toward the underframe to form the wheel recess.

Claims

1. A vehicle body structure having a roof structure, side structures, and an underframe, and provided with bolsters for coupling running devices to a lower surface of the underframe, wherein each of the bolsters is composed of a first bolster located at a center of the underframe in a width direction and equipped with a center pin for coupling with each of the running devices, and second bolsters located at ends of the underframe in the width direction to abut against air springs of the running device, the first bolster and the second bolsters are constructed from hollow extruded shapes each formed by hollow extrusion molding from two opposed face plates and a plurality of ribs connecting the face plates, an extrusion direction of the hollow extruded shape that form the first bolster lies in the width direction of the underframe, and an extrusion direction of the hollow extruded shapes that form the second bolsters lies in a longitudinal direction of the underframe, both ends of the first bolster in the width direction of the underframe, and side ends of the second bolsters on a center side in the width direction of the underframe are joined to center sill located between the first bolster and the second bolsters to extend in the longitudinal direction of the underframe, and side ends of the second bolsters on end sides in the width direction of the underframe are joined to side sills located at both ends in the width direction of the underframe to extend in the longitudinal direction of the underframe.

2. The vehicle body structure according to claim 1, wherein both ends of the side sills in the longitudinal direction are joined to end sills located at both ends in the longitudinal direction of the underframe to extend in the width direction of the underframe, both ends of the center sill in the longitudinal direction are joined to the end sills and first transverse sills located nearer the center than the bolster in the longitudinal direction of the underframe to extend in the width direction of the underframe, both ends of the first transverse sills in the longitudinal direction are joined to the side sills, ends of second transverse sills located between the end sills and the bolster to extend in the width direction of the underframe are joined to the side sills and the center sills, and coupler supports located between the end sills and the second transverse sills to support load acting from couplers are joined to the center sill.

3. The vehicle body structure according to claim 2, wherein the center sill, the first transverse sills, and the second transverse sills are each constructed from an extruded shape having two horizontally-extending ribs with a certain distance therebetween in a height direction of the underframe, and

-14positions of the ribs that form each of the center sill, the first transverse sills, and the second transverse sills in the height direction of the underframe are equivalent to positions of the two face plates that form each of the first bolster and the second bolsters in the height direction of the underframe.

4. The vehicle body structure according to claim 2, wherein area surrounded by the first bolster, the center sill, the first transverse sills, and the second transverse sills is wheel recess in which wheels of the running devices are inserted.

5. The vehicle body structure according to claim 4, wherein the center sill, the first transverse sills, and the second transverse sills are each constructed from an extruded shape extruded integrally with a box support for coupling a box-like member protruding upward toward the underframe to form the wheel recess.