Battery protection structure

Abstract

This battery protection structure comprises: a battery pack in which a battery is accommodated inside a battery case; a main frame that is disposed so as to be separated in the left-right direction of a vehicle and in which the battery pack is fastened by a plurality of fastening portions; and a bumper beam that is connected to the rear end of the main frame. The most rearward-side fastening portion is provided on the rear side of a bent portion of the main frame.

Description

Battery Protection Structure

[0001] The present invention relates to a battery protection structure.

[0002] 2. Description of the Related Art In vehicles such as hybrid vehicles and electric vehicles, a battery pack for supplying electricity to a motor that serves as a drive source is provided under the luggage compartment behind the rear seats (see, for example, Patent Document 1).

[0003] JP 2018-167640 A

[0004] In the above-mentioned vehicle, it is required to protect the battery, high-voltage unit, and other components housed inside the battery pack in the event of a rear-end collision.

[0005] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide suitable protection for components provided inside a battery pack.

[0006] A battery protection structure according to one embodiment of the present invention comprises a battery pack in which a battery is housed inside a battery case, a main frame arranged at a distance in the left-right direction of the vehicle and to which the battery pack is fastened by a plurality of fastening portions, and a bumper beam connected to the rear end of the main frame, and is located rearward of the bent portion of the main frame.

[0007] According to the present invention, it is possible to suitably protect components provided inside the battery pack.

[0008] 13 is a diagram showing an outline of the configuration of a vehicle. FIG. 13 is a diagram showing an example of how a battery pack is installed. FIG. 13 is a diagram showing the configuration of a battery pack. A top view of a lower case. A diagram showing a battery and a high-voltage unit housed in the lower case. A bottom view of the lower case. An exploded view of a battery cover. A cross-sectional view taken along VIII-VIII in FIG. 3. A cross-sectional view taken along IX-IX in FIG. 3. FIG. 13 is a diagram showing the configuration of a vehicle body. A diagram showing a vehicle body with a battery pack installed. A diagram showing a vehicle body with a battery pack installed with the cover removed. A diagram showing the state of a fastening portion during a rear-end collision. A partially enlarged view of the area surrounded by the dashed dotted line in FIG. 13.

[0009] 1. General Configuration of Vehicle> Fig. 1 is a diagram showing the general configuration of a vehicle 1. As shown in Fig. 1, the vehicle 1 is an electric vehicle or a hybrid vehicle equipped with a motor generator 2 (denoted as "M / G" in the figure) as a power source. The vehicle 1 includes the motor generator 2, a battery pack 3, an inverter 4, and a power transmission cable 5. The battery pack 3 includes a battery 11 and a high-voltage unit 12.

[0010] The motor generator 2 is a power source, such as a three-phase AC motor, that drives the vehicle 1. The motor generator 2 generates driving force using electricity (power) supplied from the battery 11 via the high-voltage unit 12, the inverter 4, and the power transmission cable 5, and transmits the driving force to the drive wheels to drive the vehicle 1. If the vehicle 1 is a hybrid vehicle, it will also be equipped with an engine as a power source.

[0011] The motor generator 2 is capable of generating electricity (power) by performing regenerative operation. The electricity generated by the regenerative operation of the motor generator 2 is supplied to the battery 11 via the inverter 4, the power transmission cable 5, and the high-voltage unit 12.

[0012] The inverter 4 converts the DC current supplied from the battery 11 into three-phase AC current and supplies it to the motor generator 2 via the power transmission cable 5. When the motor generator 2 performs regenerative operation, the inverter 4 converts the AC current supplied from the motor generator 2 into DC current and supplies it to the battery 11 via the power transmission cable 5.

[0013] The battery 11 is a so-called high-voltage secondary battery that stores electricity to be supplied to the motor generator 2. The battery 11 can be charged by regenerative operation of the motor generator 2. The battery 11 may also be charged by electricity supplied from an external device (not shown).

[0014] The high-voltage unit 12 includes a junction box and a monitoring unit. The junction box is provided with electronic components such as relays, fuses, and connectors. The monitoring unit is provided with electronic components such as sensors for monitoring the state of the battery 11. In the vehicle 1, a BCU (Battery Control Unit), which is a computer for controlling the operation of the battery 11, is provided separately from the battery pack 3, but the BCU may be included in the high-voltage unit 12.

[0015] The high voltage unit 12 is connected to the battery 11 via a cable (not shown). Therefore, the high voltage from the battery 11 is applied to the high voltage unit 12.

[0016] Fig. 2 is a diagram showing an example of installation of the battery pack 3. As shown in Fig. 2, the vehicle 1 is provided with a luggage compartment 7 behind the rear seats 6. The luggage compartment 7 can be opened and closed by a back door 8.

[0017] A battery pack 3 is mounted below the luggage compartment 7. A luggage compartment board 9 is provided above the battery pack 3, and luggage and the like can be placed on the luggage compartment board 9.

[0018] 2. Battery Pack Configuration Fig. 3 is a diagram showing the configuration of the battery pack 3. Fig. 4 is a top view of the lower case 14. Fig. 5 is a diagram showing the battery 11 and high-voltage unit 12 housed in the lower case 14. Fig. 6 is a bottom view of the lower case 14. Fig. 7 is an exploded view of the battery case cover 15. Fig. 8 is a cross-sectional view taken along line VIII-VIII in Fig. 3. Fig. 9 is a cross-sectional view taken along line IX-IX in Fig. 3.

[0019] In the following description, the forward direction of the vehicle 1 will be referred to as the forward direction, the backward direction of the vehicle 1 as the backward direction, the direction facing right with respect to the forward direction of the vehicle 1 as the right direction, the direction facing left with respect to the forward direction of the vehicle 1 as the left direction, the vertically upward direction as the upward direction, and the vertically downward direction as the downward direction. The left-right direction may also be referred to as the width direction of the vehicle 1 or simply as the width direction.

[0020] 3 , the battery pack 3 includes a battery case 13. The battery 11 and the high-voltage unit 12 are housed inside the battery case 13. The battery case 13 is composed of a lower case 14 that is recessed and opens upward, and a battery case cover 15 that closes the opening of the lower case 14.

[0021] As shown in Figures 3 to 6, the lower case 14 includes a front frame 21, a rear frame 22, a left frame 23, a right frame 24, a battery case pan 25, a center frame 26, a stay 27, a left front bracket 28, a right front bracket 29, a left side bracket 30, a right side bracket 31, a center frame lower 32, a left side frame lower 33, a right side frame lower 34, a crash box 35, a front frame lower 36, and a rear frame lower 37.

[0022] The front frame 21 extends in the left-right direction. As shown in Figure 8, the front frame 21 is formed so that the cross section perpendicular to the longitudinal direction is generally in an inverted U shape, opening downward. In other words, the cross section of the front frame 21 is hat-shaped. The front frame 21 is formed with fastening holes 38a, 38b, 38c, and 38d for fixing the battery pack 3 to the vehicle body.

[0023] A front bracket 17 is fastened to the front surface of the front frame 21. The front bracket 17 is attached so as to extend downward and forward from the front wall surface of the front frame 21. Two through holes are formed on the front side of the front bracket 17, and when the battery pack 3 is attached to the vehicle body 100 (see FIG. 10 ), the front bracket 17 is fastened to the front cross member 103 by fastening parts (e.g., bolts and nuts) via the through holes.

[0024] The rear frame 22 is located rearward of the front frame 21 and is arranged parallel to and spaced apart from the front frame 21 in the front-to-rear direction. Note that "parallel" includes not only completely parallel but also approximately parallel, and this also applies hereinafter. Like the front frame 21, the rear frame 22 extends in the left-to-right direction and has a cross section perpendicular to the longitudinal direction that is approximately inverted U-shaped (hat-shaped). Fastening holes 38e, 38f, 38g, and 38h are formed in the rear frame 22 for fixing the battery pack 3 to the vehicle body.

[0025] The left frame 23 extends in the front-to-rear direction. As shown in Figure 9, the left frame 23 is formed so that a cross section perpendicular to the longitudinal direction is generally in an inverted U shape, opening downward. In other words, the left frame 23 has a hat-shaped cross section. A fastening hole 39a is formed in the left frame 23 rearward of the center in the front-to-rear direction. The fastening hole 39a is formed in a position facing a fastening hole 45a of a left bracket 45 (described later), and the fastening hole 39a and the fastening hole 45a are fastened together by a fastening portion 47a.

[0026] The right frame 24 is disposed to the right of the left frame 23 and is spaced apart from and parallel to the left frame 23 in the left-right direction. Like the left frame 23, the right frame 24 extends in the front-to-rear direction and has a generally inverted U-shaped (hat-shaped) cross section. A fastening hole 39b is formed in the right frame 24 rearward of the center in the front-to-rear direction. The fastening hole 39b is formed in a position facing a fastening hole 46a of a right bracket 46 (described later), and the fastening hole 39b and the fastening hole 46a are fastened together by a fastening portion 48a. The fastening portions 47a, 48a are, for example, bolts and nuts.

[0027] The upper end of the left frame 23 is joined to the left end of the front frame 21. The upper end of the right frame 24 is joined to the right end of the front frame 21. The lower end of the left frame 23 is joined to the left end of the rear frame 22. The lower end of the right frame 24 is joined to the right end of the rear frame 22. As a result, the front frame 21, rear frame 22, left frame 23, and right frame 24 are formed as a substantially rectangular frame as a whole. Furthermore, the front frame 21, rear frame 22, left frame 23, and right frame 24 have hat-shaped cross sections, which increases their rigidity.

[0028] 8 and 9, the battery case pan 25 is formed by bending a single plate material to form a bottom surface 25a, and a front wall 25b, a rear wall 25c, a left side wall 25d, and a right side wall 25e that surround the bottom surface 25a. The bottom surface 25a, the front wall 25b, the rear wall 25c, the left side wall 25d, and the right side wall 25e form the battery case pan 25 in a recessed shape that is open at the top.

[0029] The bottom portion 25a is formed in a generally rectangular shape and extends horizontally (front-to-back and left-to-right directions). A front wall 25b is formed continuously with the upper end of the bottom portion 25a. The front wall 25b is formed so as to extend in the up-down and left-to-right directions. A rear wall 25c is formed continuously with the lower end of the bottom portion 25a. The rear wall 25c is formed so as to extend in the up-down and left-to-right directions. A left side wall 25d is formed continuously with the left end of the bottom portion 25a. The left side wall 25d is formed so as to extend in the up-down and front-to-back directions. A right side wall 25e is formed continuously with the right end of the bottom portion 25a. The right side wall 25e is formed so as to extend in the up-down and front-to-back directions. The battery case pan 25 may be formed by combining the bottom portion 25a, front wall 25b, rear wall 25c, left side wall 25d, and right side wall 25e, each made of a different plate material, by welding or the like.

[0030] The front wall 25b, rear wall 25c, left side wall 25d, and right side wall 25e each have a flange 25f formed continuously at the upper end thereof so as to extend outward. That is, the battery case pan 25 has the flange 25f formed on its outer edge. The flange 25f extends horizontally (in the front-to-rear and left-to-right directions). The front frame 21, rear frame 22, left frame 23, and right frame 24 are joined to the flange 25f from above.

[0031] The center frame 26 is joined to the upper surface of the bottom surface 25a of the battery case pan 25 so as to be centered in the left-right direction of the battery case pan 25 and aligned along the front-rear direction. As shown in Fig. 8 , the rear end of the center frame 26 abuts against the rear side wall 25c, and the front end extends forward from the center in the front-rear direction of the bottom surface 25a. As shown in Fig. 9 , the cross section of the center frame 26 perpendicular to the longitudinal direction is formed in an inverted U-shape (hat-shape), thereby increasing the rigidity of the center frame 26.

[0032] The stay 27 is joined to the upper surface of the bottom portion 25a at the center in the left-right direction of the battery case pan 25 so as to overlap the front end of the center frame 26. The front end of the stay 27 abuts the front side wall 25b and extends obliquely upward from the rear to the front. The stay 27 has an inverted U-shape (hat shape) perpendicular to the longitudinal direction, which increases its rigidity.

[0033] The left front bracket 28 is joined to the left front of the upper surface of the bottom surface portion 25a. The left front bracket 28 is made of a bent plate material so that the center portion is positioned substantially horizontal and higher than the upper surface of the bottom surface portion 25a. As shown in FIG. 5, the high-voltage unit 12 is attached to the center portion of the left front bracket 28.

[0034] The right front bracket 29 is joined to the right front of the upper surface of the bottom surface portion 25a. The right front bracket 29 is made of a bent plate material so that its center is positioned substantially horizontal and higher than the upper surface of the bottom surface portion 25a. As shown in FIG. 5, the high-voltage unit 12 is attached to the center of the right front bracket 29.

[0035] In this way, the high-voltage unit 12 is attached separately to the left front bracket 28 and the right front bracket 29. However, the high-voltage unit 12 may be attached collectively to only one of the left front bracket 28 and the right front bracket 29.

[0036] The left side bracket 30 is joined to the left rear of the upper surface of the bottom portion 25a. The left side bracket 30 is arranged to extend in the front-to-rear direction, and is made of a bent plate material so that its central portion is higher than the upper surface of the bottom portion 25a and is generally horizontal. The right side bracket 31 is joined to the right rear of the upper surface of the bottom portion 25a. The right side bracket 31 is arranged to extend in the front-to-rear direction, and is made of a bent plate material so that its central portion is higher than the upper surface of the battery case pan 25 and is generally horizontal. As shown in FIG. 9 , the battery 11 is attached so as to span the center of the left side bracket 30 and the right side bracket 31. Note that the illustration shows an example in which two stacks of multiple cells are provided as the battery 11.

[0037] As shown in Fig. 6, the center frame lower 32 extends in the front-rear direction at the center of the battery case pan 25 in the left-right direction and is joined to the underside of the bottom surface 25a. The left side frame lower 33 and the right side frame lower 34 are arranged parallel to the left and right of the center frame lower 32, extend in the front-rear direction, and are joined to the underside of the bottom surface 25a. As shown in Fig. 9, the center frame lower 32, the left side frame lower 33, and the right side frame lower 34 have a U-shaped (inverted hat) cross section perpendicular to the longitudinal direction, which increases their rigidity.

[0038] In this way, the rigidity of the upper part of the lower case 14 is increased by the front frame 21, rear frame 22, left frame 23, and right frame 24. In addition, the rigidity of the lower part of the lower case 14 is increased by the center frame 26, stays 27, center frame lower 32, left side frame lower 33, and right side frame lower 34.

[0039] The lower case 14 also prevents the battery case pan 25 from being crushed by external forces from the left and right direction by the front frame 21 and rear frame 22. Furthermore, the lower case 14 also prevents the battery case pan 25 from being crushed by external forces from the front and rear direction by the left frame 23, right frame 24, center frame 26, stays 27, center frame lower 32, left side frame lower 33, and right side frame lower 34.

[0040] The crash boxes 35 are joined from below to the central rear end of the bottom surface 25a so as to overlap the rear ends of the center frame lower 32, left side frame lower 33, and right side frame lower 34. As shown in FIG. 8 , the crash boxes 35 are composed of two plates 35a, 35b, and a separator member 35c. The front end of the plate 35a is joined to the vertical center of the rear wall 25c and extends downward and rearward from its front end to its rear end. The tip of the plate 35b is joined to the bottom surface 25a and the rear end of the center frame lower 32 and extends upward and rearward from its front end to its rear end. The separator member 35c has a structure including two separators connecting the plate members 35a and 35b, which are spaced apart in the vertical direction. The crash box 35 is formed by plate members 35a and 35b so that the cross section perpendicular to the left-right direction has a closed cross section (approximately rectangular), and its interior is reinforced by a separator member 35c to increase its strength.

[0041] 8, the front frame lower 36 is joined from below to the front flange 25f of the battery case pan 25. As a result, the front flange 25f of the battery case pan 25 is sandwiched between the front frame 21 and the front frame lower 36, further increasing the rigidity of the front portion of the lower case 14.

[0042] The rear frame lower 37 is joined from below to the rear flange 25f of the battery case pan 25. As a result, in the battery case pan 25, the rear flange 25f is sandwiched between the rear frame 22 and the rear frame lower 37, further increasing the rigidity of the rear portion of the lower case 14.

[0043] As shown in FIGS. 3 and 7, the battery case cover 15 includes a main cover 41, a left front cover 42, a service plug cover 43, a right front cover 44, a left bracket 45, and a right bracket 46.

[0044] The main cover 41 includes a lower cover 51, a center frame upper 52, a first cover cross member 53, and a second cover cross member 54.

[0045] The lower cover 51 is formed in a shape such that the front left and front right portions are cut out of a substantially rectangular plate material. The length of the lower cover 51 in the front-to-rear direction is approximately the same as the distance between the front frame 21 and the rear frame 22 of the lower case 14, and the length of the lower cover 51 in the left-to-right direction is approximately the same as the distance between the left frame 23 and the right frame 24 of the lower case 14.

[0046] A through-hole 51a is formed in the lower cover 51 below the second cover cross member 54. A cooling duct (not shown) is connected to the through-hole 51a. The cooling duct is a duct for sending air from the vehicle interior into the battery case 13, and the air is sent into the battery case 13 by a fan (not shown).

[0047] A through hole 51b is formed in the lower cover 51 between the first cover cross member 53 and the second cover cross member 54. An exhaust duct 16 is connected to the through hole 51b. One end of the exhaust duct 16 is connected to the through hole 51b, and the other end is open to the outside of the vehicle. The exhaust duct 16 is provided to exhaust smoke outside the vehicle when the battery 11 emits smoke.

[0048] The upper center frame 52 is joined to the top surface of the lower cover 51 at the center in the left-right direction of the lower cover 51 so as to extend in the front-rear direction. The upper center frame 52 is formed so that its length in the front-rear direction is approximately the same as that of the lower cover 51. As shown in FIG. 8 , the upper center frame 52 spans between the front frame 21 and the rear frame 22.

[0049] The first cover cross member 53 is joined to the upper surface of the lower cover 51 so as to extend in the left-right direction near the center of the lower cover 51 in the front-rear direction. The first cover cross member 53 is formed so that its length in the left-right direction is approximately the same as that of the lower cover 51.

[0050] The second cover cross member 54 is joined to the upper surface of the lower cover 51 so as to be disposed parallel to and spaced apart from the first cover cross member 53 in the front-to-rear direction. The second cover cross member 54 is disposed rearward of the first cover cross member 53. Like the first cover cross member 53, the second cover cross member 54 is formed so that its length in the left-to-right direction is approximately the same as that of the lower cover 51.

[0051] As shown in Figure 9, the first cover cross member 53 and the second cover cross member 54 are bridged between the left frame 23 and the right frame 24. In addition, as shown in Figure 8, the first cover cross member 53 and the second cover cross member 54 are disposed directly above the battery 11.

[0052] The center frame upper 52, the first cover cross member 53 and the second cover cross member 54 have a cross section perpendicular to the longitudinal direction that is formed in a generally inverted U-shape (hat-shape), thereby increasing rigidity.

[0053] The first cover cross member 53 and the second cover cross member 54 have a thickness in the vertical direction greater than that of the center frame upper 52. Therefore, the first cover cross member 53 and the second cover cross member 54 are joined to the lower cover 51 so as to pass above the center frame upper 52.

[0054] The left front cover 42 is formed from a plate material in a generally rectangular shape so as to fit into the upper left notch of the lower cover 51. A through hole 42a is formed in the left front cover 42 at a position facing the service plug of the high-voltage unit 12 provided in the battery case 13. A service plug cover 43 is attached to cover the through hole 42a from above. The service plug cover 43 is formed from a plate material and is detachable from the left front cover 42.

[0055] The right front cover 44 is made of a plate material and is formed into a substantially rectangular shape so as to fit into the upper right notch of the lower cover 51 .

[0056] The left front cover 42 and the right front cover 44 are fastened to the lower cover 51 and the upper center frame 52 by fastening parts (e.g., bolts and nuts). This gives the battery case cover 15 a generally rectangular shape as a whole. The battery case cover 15 is then fastened to the front frame 21, rear frame 22, left frame 23, and right frame 24 of the lower case 14 by fastening parts.

[0057] The left bracket 45 and the right bracket 46 are made of plate material and are formed into a generally triangular shape in top view. Fastening holes 45a, 45b, and 45c are formed in the left bracket 45 at positions corresponding to the corners of the generally triangle. Fastening holes 46a, 46b, and 46c are formed in the right bracket 46 at positions corresponding to the corners of the generally triangle.

[0058] The main cover 41 has a fastening hole 41a formed in a position facing the fastening hole 45b, and a fastening hole 41b formed in a position facing the fastening hole 46b. The left bracket 45 has the fastening hole 45a fastened to the fastening hole 39a of the left frame 23 by the fastening portion 47a, and the fastening hole 45b fastened to the fastening hole 41a of the main cover 41 by the fastening portion 47b. This fixes the left bracket 45 to the left frame 23 and the main cover 41. The right bracket 46 has the fastening hole 46a fastened to the fastening hole 39b of the right frame 24 by the fastening portion 48a, and the fastening hole 46b fastened to the fastening hole 41b of the main cover 41 by the fastening portion 48b. This fixes the right bracket 46 to the right frame 24 and the main cover 41.

[0059] The left bracket 45 and the right bracket 46 are not essential components, and may not be provided.

[0060] 3. Vehicle Body Configuration Next, a description will be given of the configuration of a vehicle body on which the battery pack 3 is mounted. It is assumed that the battery pack 3 will be mounted on a plurality of different vehicle bodies. Therefore, an example of a vehicle body on which the battery pack 3 is mounted will be described here.

[0061] Fig. 10 is a diagram showing the configuration of a vehicle body 200. Fig. 11 is a diagram showing the vehicle body 200 on which a battery pack 3 is mounted. Fig. 12 is a diagram showing the vehicle body 200 on which a battery pack 3 is mounted with the battery case cover 15 removed.

[0062] 10, 11, and 12, the vehicle body 200 includes a left main frame 201 and a right main frame 202. The left main frame 201 and the right main frame 202 are spaced apart in the left-right direction and extend along the front-rear direction.

[0063] A front cross member 203 and a rear cross member 204 are spanned between the left main frame 201 and the right main frame 202. The front cross member 203 and the rear cross member 204 are joined to the left main frame 201 and the right main frame 202 so as to be spaced apart in the front-rear direction and extend in the left-right direction. The front cross member 203 is disposed near the boundary between the rear seat 6 and the luggage compartment 7 in the front-rear direction. The rear cross member 204 is disposed approximately in the center of the luggage compartment 7 in the front-rear direction. The front cross member 203 has a cross section perpendicular to the longitudinal direction that is formed as a hollow, approximately rectangular, closed cross section, thereby increasing its rigidity. The rear cross member 204 has a cross section perpendicular to the longitudinal direction that is formed as a hollow, approximately rectangular, closed cross section, thereby increasing its rigidity.

[0064] A floor pan 205 is mounted between the left main frame 201 and the right main frame 202. The floor pan 205 is formed by bending a plate material into a concave shape with an open top. A flange is formed on the outer edge of the floor pan 205, and the left main frame 201, right main frame 202, and front cross member 203 are joined to this flange. The rear cross member 204 is joined to the underside of the floor pan 205.

[0065] An accommodation space 205a is formed in the floor pan 205 rearward of the rear cross member 204. Therefore, the vehicle body 200 is longer rearward of the rear cross member 204 than if the accommodation space were not provided.

[0066] A left gusset 206 is joined to the joint between the left main frame 201 and the front cross member 203, reinforcing the joint between the left main frame 201 and the front cross member 203. Similarly, a right gusset 207 is joined to the joint between the right main frame 202 and the front cross member 203, reinforcing the joint between the right main frame 202 and the front cross member 203.

[0067] A suspension support member 208, to which a suspension abuts, is joined to the left main frame 201 forward of the rear cross member 204 in the front-to-rear direction. The suspension support member 208 is disposed so as to protrude leftward from the left main frame 201. The suspension support member 208 is also disposed so as to tilt upward as it extends leftward.

[0068] A suspension support member 209, to which the suspension abuts, is joined to the right main frame 202 forward of the rear cross member 204 in the front-to-rear direction. The suspension support member 209 is disposed so as to protrude to the right from the right main frame 202. The suspension support member 209 is also disposed so as to tilt upward as it extends to the right.

[0069] A rear skirt 210 is joined to the rear end of the floor pan 205. The rear skirt 210 is disposed so as to extend upward from the floor pan 205. A striker is attached to the center of the rear skirt 210 in the left-right direction, and the luggage compartment 7 is closed when the back door 8 engages with the striker.

[0070] A rear bumper beam 211 is joined to the rear ends of the left main frame 201 and the right main frame 202. The rear bumper beam 211 is arranged to extend in the left-right direction, with both ends joined to the left main frame 201 and the right main frame 202, respectively. Most of the rear bumper beam 211 is arranged rearward and spaced apart from the left main frame 201, the right main frame 202, the floor pan 205, and the rear skirt 210. The rear bumper beam 211 has greater strength than other components constituting the vehicle body 200, and reduces damage to the vehicle body 200 in a rear-end collision (including an offset collision).

[0071] In the vehicle body 200, the battery pack 3 is fastened to the left main frame 201, the right main frame 202, and the front cross member 203. The front cross member 203 (left gusset 206, right gusset 207) has fastening holes 212a and 212b spaced apart in the left-right direction on the left side and fastening holes 212c and 212d spaced apart in the left-right direction on the right side. The left main frame 201 has fastening holes 212e, 212f, and 212i spaced apart in the front-rear direction on the rear side. The right main frame 202 has fastening holes 212g, 212h, and 212j spaced apart in the front-rear direction on the rear side. These fastening holes 212a to 212h are located at positions corresponding to fastening holes 38a to 38h formed in the battery pack 3, respectively. Fastening hole 212i is located at a position corresponding to fastening hole 45c of the left bracket 45. The fastening hole 212j is provided at a position corresponding to the fastening hole 46c of the right bracket 46.

[0072] Fastening hole 212a and fastening hole 38a are fastened together by fastening portion 213a. Similarly, fastening hole 212b and fastening hole 212h and fastening hole 38b and fastening hole 38h are fastened together by fastening portion 213b and fastening portion 213h, respectively. Fastening hole 212i and fastening hole 45c are fastened together by fastening portion 213i. Fastening hole 212j and fastening hole 46c are fastened together by fastening portion 213j. Fastening portions 213e and 213g are formed by threads and nuts welded to extend upward from the top surfaces of left main frame 101 and right main frame 102. Fastening portions 213a, 213b, 213c, 213d, 213f, 213h, 213i, and 213j are formed by, for example, bolts and nuts. In the following description, when the fastening portions 213a to 213j are not to be distinguished from one another, they will be referred to as fastening portions 213.

[0073] 4. Battery Protection Structure Fig. 13 is a diagram showing the state of the fastening portion 213 during a rear-end collision. Fig. 14 is a partial enlarged view of the area surrounded by the dashed line in Fig. 13. Note that for ease of explanation, Figs. 13 and 14 omit part of the configuration of the vehicle body 200.

[0074] When a relatively thin object 300, such as a utility pole, collides from behind near the center in the lateral direction, the rear bumper beam 211 may break, as shown in Figure 13 . If the object 300 then continues to move forward in the vehicle body 200, it may come into contact with the battery pack 3. In such a case, if the battery pack 3 is firmly fixed to the vehicle body 200 by the fastening portion 213, the load (collision force) caused by the collision with the object 300 will be absorbed by the battery pack 3. This may result in, for example, a large force being applied to the rear frame 22, causing the center of the rear frame 22 to bend forward, potentially damaging the battery 11 and the high-voltage unit 12 and causing a current leak.

[0075] Therefore, the rear fastening portions 213e, 213f, 213g, and 213h are made to break easily (to come off easily) when the collision object 300 collides with the vehicle 1 from behind. As a result, even when a load due to a collision with the collision object 300 is applied to the battery pack 3, the fastening portions 213e, 213f, 213g, and 213h break, allowing the battery pack 3 to move forward, thereby reducing the load applied to the battery pack 3.

[0076] 13, the colliding object 300 collides from behind near the center in the left-right direction, bending the rear bumper beam 211 forward. At this time, because the rear bumper beam 211 is fixed to the rear ends of the left main frame 201 and the right main frame 202, when the rear bumper beam 211 bends forward, the left main frame 201 and the right main frame 202 are consequently bent so that their rear ends approach each other (move toward the center) as indicated by the arrows in the figure.

[0077] 10, floor pan 205 has a bead 205b on its left side wall that contacts left main frame 201. Bead 205b is formed between fastening portions 213e and 213f in the front-to-rear direction. Bead 205b has an uneven surface on the left side surface of floor pan 205. Therefore, when left main frame 201 bends, a load is likely to be concentrated on bead 205b.

[0078] As a result, when the rear bumper beam 211 is bent forward and a force is applied toward the center, the left main frame 201 bends at a position where a bead 205b provided on the left wall of the floor pan 205 is located.

[0079] Similarly, floor pan 205 has a bead 205c on the right side wall that contacts right main frame 202. When rear bumper beam 211 bends forward and a force is applied toward the center, right main frame 202 bends at the position of bead 205c on the right side wall of floor pan 205.

[0080] Therefore, the bent portion 301, which is the portion of the left main frame 201 that bends during a rear-end collision, is located at the position where the bead 205b is located in the front-rear direction. Also, the bent portion 302, which is the portion of the right main frame 202 that bends during a rear-end collision, is located at the position where the bead 205c is located in the front-rear direction.

[0081] When the rear side of the left main frame 201 is bent inward at the bent portion 301, a large force is applied around the fastening portion 213e (fastening hole 212e) in the left main frame 201 because the fastening portion 213e is located rearward of the bent portion 301, causing a crack 303. Similarly, when the rear side of the right main frame 202 is bent inward at the bent portion 302, a large force is applied around the fastening portion 213g (fastening hole 212g) in the right main frame 202 because the fastening portion 213g is located rearward of the bent portion 302, causing a crack 303.

[0082] Furthermore, since the fastening portion 213f is disposed in front of the bending portion 301 but close to the bending portion 301, when the left main frame 201 bends at the bending portion 301, force is also applied to the periphery of the fastening portion 213f on the left main frame 201. As a result, a crack 303 also occurs around the fastening portion 213f (fastening hole 212f) on the left main frame 201. Similarly, a crack 303 occurs around the fastening portion 213h (fastening hole 212h) on the right main frame 202.

[0083] In this way, when the left main frame 201 and the right main frame 202 bend inward due to the load caused by the collision of the collision object 300, cracks 303 occur around the fastening portions 213e, 213f, 213g, and 213h that fasten the rear frame 22 to the left main frame 201 and the right main frame 202, respectively.

[0084] Thereafter, when the colliding object 300 further penetrates forward into the vehicle body 200, the colliding object 300 hits the battery pack 3 and pushes the battery pack 3 forward. Then, due to the load caused by the collision with the colliding object 300, the fastening portions 213e, 213f, 213g, and 213h are broken at the cracks 303, or the surrounding area is destroyed, causing the fastening portions 213e, 213f, 213g, and 213h to come off.

[0085] This allows the rear side of the battery pack 3 to move freely. Therefore, when the battery pack 3 is further pushed into the collision object 300, it moves forward, reducing the possibility of bending the rear frame 22. This makes it difficult for the battery case 13 to be crushed, thereby providing optimal protection for the battery 11 and the high-voltage unit 12.

[0086] 5. Modifications The above embodiment is merely an example of how the present invention can be implemented, and the implementation of the present invention is not limited to the above example, and various modifications are possible.

[0087] For example, when the left main frame 201 and the right main frame 202 bend at the bending portions 301, 302, cracks 303 are generated around the fastening portions 213e, 213f, 213g, and 213h, but this force may also cause the fastening portions 213e, 213f, 213g, and 213h to break or come off.

[0088] The bent portions 301 and 302 may be located forward of the fastening portions 213e, 213f, 213g, and 213h that fasten the rear frame 22 to the left main frame 201 and the right main frame 202, respectively. However, it is preferable that the bent portions 301 and 302 be located rearward of the fastening portion 213i that fastens the left bracket 45 to the left main frame 201 and the fastening portion 213j that fastens the right bracket 46 to the right main frame 202.

[0089] Furthermore, the battery pack 3 is provided with the left bracket 45 and the right bracket 46. However, the battery pack 3 does not have to be provided with the left bracket 45 and the right bracket 46. Even in this case, the same effects as when the left bracket 45 and the right bracket 46 are provided can be achieved.

[0090] 6. Summary As described above, the battery protection structure of this embodiment includes the battery pack 3 in which the battery 11 is housed inside the battery case 13, the main frames (left main frame 201, right main frame 202) that are spaced apart in the left-right direction of the vehicle 1 and to which the battery pack 3 is fastened by a plurality of fastening portions 213, and the rear bumper beam 211 connected to the rear ends of the main frames, with at least the rearmost fastening portions 213e, 213g being located rearward of the bent portions 301, 302 of the main frames. As a result, when the rear sides of the left main frame 201 and the right main frame 202 are bent toward the center, cracks 303 are generated around the fastening portions 213e, 213g. When a colliding object 300 comes into contact with the battery pack 3, the cracks 303 trigger the fastening portions 213e, 213g to become disengaged. This allows the rear side of the battery pack 3 to move more easily, and when the battery pack 3 is pushed into the colliding object 300, it moves forward, thereby enabling the load caused by the collision to be released from the battery pack 3. Thus, with this battery protection structure, the battery case 13 is less likely to be crushed, and the battery 11 and high-voltage unit 12 can be suitably protected.

[0091] The battery pack 3 also includes a front frame 21 and a rear frame 22 that are spaced apart in the front-to-rear direction, and the front frame 21 and the rear frame 22 are fastened together by fastening portions 213. The fastening portions 213e, 213f, 213g, and 213h that fasten the rear frame 22 are provided rearward of the bent portions 301 and 302, and the fastening portions 213a, 213b, 213c, and 213d that fasten the front frame 21 are provided forward of the bent portions 301 and 302. This makes it easier for the fastening portions 213e, 213f, 213g, and 213h that fasten the rear frame 22 to come loose when the collision object 300 collides from behind, thereby making it easier for the rear side of the battery pack 3 to move. This allows the battery 11 and the high-voltage unit 12 to be more effectively protected.

[0092] The vehicle also includes a floor pan 205 supported by the main frame and having beads 205b and 205c formed thereon, and bent portions 301 and 302 are formed near beads 205b and 205c when the center of bumper beam 311 is hit from behind. By forming bent portions 301 and 302 at the positions where beads 205b and 205c are located in the fore-and-aft direction, it is possible to position bent portions 301 and 302 at any desired positions. This makes it possible to adjust the timing and amount of breakage (disengagement) of fastening portions 213e and 213g.

[0093] The fastening portions 213e and 213g are provided at positions offset from the center of the main frames in the left-right direction. As shown in Fig. 11 , the fastening portion 213e is provided at a position offset inward from the center X1 of the left main frame 201 in the left-right direction. Similarly, the fastening portion 213g is provided at a position offset inward from the center X2 of the right main frame 202 in the left-right direction. This makes it possible to adjust the timing and amount of breakage (detachment) of the fastening portions 213e and 213g.

[0094] REFERENCE SIGNS LIST 1 vehicle 3 battery pack 11 battery 201 left main frame 202 right main frame 301 bending portion 302 bending portion

Claims

1. A battery protection structure comprising: a battery pack in which a battery is housed inside a battery case; main frames arranged at intervals in the left-right direction of the vehicle and to which the battery pack is fastened by a plurality of fastening portions; and a rear bumper beam connected to the rear end of the main frame, wherein at least the rearmost fastening portion is provided rearward of the bent portion of the main frame.

2. The battery protection structure according to claim 1, wherein the battery pack comprises a front frame and a rear frame arranged at a distance in the front-to-rear direction, the front frame and the rear frame are fastened together by the fastening parts, the fastening parts fastening the rear frame are provided rearward of the bent part, and the fastening parts fastening the front frame are provided forward of the bent part.

3. The battery protection structure according to claim 1 or claim 2, further comprising a floor pan supported by the main frame and having a bead formed thereon, wherein the bent portion is formed near the bead when the center portion of the rear bumper beam is hit from behind.

4. A battery protection structure according to claim 1 or 2, wherein the fastening portion is provided at a position offset from the center of the main frame in the left-right direction.

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