Battery protection structure

Abstract

This battery protection structure comprises: a battery pack in which a battery is housed inside a battery case; a vehicle body to which the battery pack is fastened; and a rear seat provided on the vehicle body. The battery pack includes an upper frame provided above and extending in the front-rear direction, and a lower frame provided below and extending in the front-rear direction. The upper frame is provided at a height that allows the upper frame to face the rear seat in the vertical direction.

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 vehicle body to which the battery pack is fastened, and a rear seat provided in the vehicle body, wherein the battery pack comprises an upper frame provided above and extending in the fore-and-aft direction, and a lower frame provided below and extending in the fore-and-aft direction, the upper frame being provided at a height opposite the rear seat in the vertical direction.

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

[0008] 3 is a diagram showing an outline of the configuration of a vehicle. FIG. 3 is a diagram showing an example of how a battery pack is installed. FIG. 4 is a diagram showing the configuration of a battery pack. FIG. 4 is a top view of a lower case. FIG. 5 is a diagram showing a battery and a high-voltage unit housed in the lower case. FIG. 5 is a bottom view of the lower case. FIG. 6 is an exploded view of a battery cover. FIG. 7 is a cross-sectional view taken along line VIII-VIII in FIG. 3. FIG. 8 is a cross-sectional view taken along line IX-IX in FIG. 3. FIG. 6 is a diagram showing the configuration of a vehicle body. FIG. 7 is a diagram showing a vehicle body with a battery pack installed. FIG. 8 is a diagram showing a vehicle body with a battery pack installed with the cover removed. FIG. 9 is a diagram showing the transition over time around the battery pack during a rear-end collision. FIG. 10 is a diagram showing the transition over time around the battery pack during a rear-end collision. FIG. 11 is a diagram showing the transition over time around the battery pack during a rear-end collision.

[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 the vehicle body 100. Fig. 11 is a diagram showing the vehicle body 100 equipped with the battery pack 3. Fig. 12 is a diagram showing the vehicle body 100 equipped with the battery pack 3 with the battery case cover 15 removed.

[0062] 10, 11, and 12, the vehicle body 100 includes a left main frame 101 and a right main frame 102. The left main frame 101 and the right main frame 102 are spaced apart in the left-right direction and extend along the front-rear direction.

[0063] A front cross member 103 and a rear cross member 104 are spanned between the left main frame 101 and the right main frame 102. The front cross member 103 and the rear cross member 104 are joined to the left main frame 101 and the right main frame 102 so as to be spaced apart in the front-to-rear direction and extend in the left-to-right direction. The front cross member 103 is disposed near the boundary between the rear seat 6 and the luggage compartment 7 in the front-to-rear direction. The rear cross member 104 is disposed approximately in the center of the luggage compartment 7 in the front-to-rear direction. The front cross member 103 has a cross section perpendicular to the longitudinal direction that is formed as a hollow, approximately rectangular, closed cross section, thereby enhancing its rigidity. The rear cross member 104 has a cross section perpendicular to the longitudinal direction that is formed as a hollow, approximately rectangular, closed cross section, thereby enhancing its rigidity.

[0064] A floor pan 105 is mounted between the left main frame 101 and the right main frame 102. The floor pan 105 is formed by bending a plate material into a concave shape that opens upward. A flange is formed on the outer edge of the floor pan 105, and the left main frame 101, the right main frame 102, and the front cross member 103 are joined to this flange. The rear cross member 104 is joined to the underside of the floor pan 105.

[0065] A left gusset 106 is joined to the joint between the left main frame 101 and the front cross member 103, reinforcing the joint between the left main frame 101 and the front cross member 103. Similarly, a right gusset 107 is joined to the joint between the right main frame 102 and the front cross member 103, reinforcing the joint between the right main frame 102 and the front cross member 103.

[0066] A suspension support member 108, to which a suspension abuts, is joined to the left main frame 101 forward of the rear cross member 104 in the front-to-rear direction. The suspension support member 108 is disposed so as to protrude leftward from the left main frame 101. The suspension support member 108 is also disposed so as to tilt upward as it extends leftward.

[0067] A suspension support member 109, to which the suspension abuts, is joined to the right main frame 102 forward of the rear cross member 104 in the front-to-rear direction. The suspension support member 109 is disposed so as to protrude to the right from the right main frame 102. The suspension support member 109 is also disposed so as to tilt upward as it extends to the right.

[0068] A rear skirt 110 is joined to the rear end of the floor pan 105. The rear skirt 110 is disposed so as to extend upward from the floor pan 105. A striker is attached to the center of the rear skirt 110 in the left-right direction, and the luggage compartment 7 is closed when the back door 8 engages with the striker.

[0069] A rear bumper beam 111 is joined to the rear ends of the left main frame 101 and the right main frame 102. The rear bumper beam 111 is arranged to extend in the left-right direction, with both ends joined to the left main frame 101 and the right main frame 102, respectively. Most of the rear bumper beam 111 is arranged rearward and spaced apart from the left main frame 101, the right main frame 102, the floor pan 105, and the rear skirt 110. The rear bumper beam 111 has greater strength than other components constituting the vehicle body 100, and reduces damage to the vehicle body 100 in a rear-end collision (including an offset collision).

[0070] In the vehicle body 100, the battery pack 3 is fastened to the left main frame 101, the right main frame 102, and the front cross member 103. When the battery pack 3 is fastened to the vehicle body 100, the left bracket 45 and the right bracket 46 are not provided on the battery pack 3 (they are removed).

[0071] The front cross member 103 (left gusset 106, right gusset 107) has fastening holes 112a, 112b spaced apart in the left-right direction on the left side and fastening holes 112c, 112d spaced apart in the left-right direction on the right side. The left main frame 101 has fastening holes 112e, 112f spaced apart in the front-rear direction on the rear side. The right main frame 102 has fastening holes 112g, 112h spaced apart in the front-rear direction on the rear side. These fastening holes 112a to 112h are located at positions corresponding to the fastening holes 38a to 38h formed in the battery pack 3, respectively.

[0072] Fastening hole 112a and fastening hole 38a are fastened together by fastening portion 113a. Similarly, fastening hole 112b and fastening hole 112h and fastening hole 38b and fastening hole 38h are fastened together by fastening portions 113b and 113h, respectively. Fastening portions 113e and 113g 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 113a, 113b, 113c, 113d, 113f, and 113h are formed by bolts and nuts, for example. Note that hereinafter, when fastening portions 113a to 113h are described without distinction, they will be referred to as fastening portions 113.

[0073] 13 to 15 are diagrams showing the transition over time around the battery pack 3 during a rear-end collision. Note that Fig. 13 to Fig. 15 show cross-sectional views passing through the up-down and front-rear directions of the vehicle 1 when a relatively thin impact object 300 such as a utility pole collides with the vehicle 1 near the center in the left-right direction, and parts that are not relevant to the explanation are omitted from the illustrations.

[0074] Before the collision of the object 300 with the rear end, the battery pack 3 is fastened to the left main frame 101 and the right main frame 102 as described above, and as shown in the upper part of Figure 13, most of the battery pack 3 is located below the upper surfaces of the left main frame 101 and the right main frame 102. More specifically, the stay 27 is provided at a height that faces the front cross member 103 in the vertical direction. At this time, the battery pack 3 is positioned so as to be spaced a predetermined distance up and down from the floor pan 105 and is not in contact with the floor pan 105.

[0075] In the vehicle 1, the rear seat 6 is disposed in front of the battery pack 3, and the front cross member 103 is disposed below and behind the rear seat 6. The battery pack 3 is provided at a height such that the battery case cover 15 faces the rear seat 6 (more precisely, the framework of the rear seat 6) in the vertical direction. Therefore, the center frame upper 52 constituting the battery case cover 15 is also provided at a height such that it faces the rear seat 6 in the vertical direction. The distance between the rear seat 6 and the center frame upper 52 in the front-to-rear direction is arranged to be shorter than the distance between the front cross member 103 and the stay 27.

[0076] For example, when a collision object 300 collides with the vehicle 1 from behind at the center in the left-right direction, as shown in the middle of Figure 13, the center of the rear bumper beam 111 bends forward, causing the collision object 300 to penetrate into the inside of the vehicle body 100. At this time, cracks occur around the fastening portions 113e, 113f, 113g, and 113h, making them prone to breakage.

[0077] Thereafter, when the colliding object 300 penetrates further forward, the colliding object 300 comes into contact with the battery pack 3, as shown in the lower part of Figure 13. Since the rear flange of the rear frame 22 of the battery pack 3 is located at the rearmost position, the rear flange of the rear frame 22 comes into contact with the colliding object 300 first, and the flange is crushed.

[0078] 14, the rear frame 22 begins to crush on the rear side of the battery pack 3, and the collision object 300 comes into contact with the rear end of the center frame upper 52 and the crash box 35. As the collision object 300 continues to penetrate forward, the fastening portions 113e, 113f, 113g, and 113h are broken by the load of the collision object 300, allowing the rear side of the battery pack 3 to move. As a result, the battery pack 3 is moved forward by the load of the collision object 300. Note that the front side of the battery pack 3 is allowed to move forward because part of the front frame 21 is crushed.

[0079] Additionally, the lower front portion of the center frame lower 32 comes into contact with the front wall 105a of the floor pan 105. At this time, the tip of the center frame upper 52 has not yet come into contact with the rear seat 6. Here, because the front wall 105a of the floor pan 105 has low strength, it is unable to stop the forward movement of the battery pack 3.

[0080] 14, the battery pack 3 is pushed forward, causing the front end of the upper center frame 52 to come into contact with the rear seat 6. In this state, the upper center frame 52 is sandwiched between the rear seat 6 and the object 300, and a load is applied to the upper center frame 52.

[0081] If the colliding object 300 then penetrates further forward, the upper center frame 52 presses the rear seat 6 forward, causing the battery pack 3 to move forward as a whole. As a result, as shown in the lower part of Figure 14, the front wall 105a of the floor pan 105 is further crushed, causing the battery pack 3 to come into contact with the front cross member 103. In this state, the lower parts of the center frame 26, stays 27, lower center frame 32, lower left side frame 33, and lower right side frame 34 are sandwiched between the front cross member 103 and the colliding object 300 and are subjected to a load (collision force).

[0082] 15, the center portion of the upper center frame 52 begins to bend upward so as to prevent an excessive load from being applied to the rear seat 6. The upper center frame 52 is designed to bend upward when a compressive force is applied in the fore-and-aft direction.

[0083] Thereafter, when the colliding object 300 penetrates further forward, the center frame upper 52 begins to break, reducing the load on the center frame upper 52 while increasing the load on the lower part. As a result, the increased load crushes the crash boxes 35, as shown in the middle of Figure 15.

[0084] 15, the center frame upper 52 is deformed upward, the crash boxes 35 are crushed, and the load on the center frame upper 52 (upper part) is released, with the lower part now supporting the load. Also, at this point, the vehicle 1 has started to move forward, so the load on the entire vehicle 1 has begun to decrease, and the lower part is the last to support the load from the time the vehicle 1 starts to move until the load is released.

[0085] 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.

[0086] The above description has been given with reference to an example in which the object 300 collides with the vehicle from behind at the center in the left-right direction. However, even if the object 300 collides with the vehicle from behind at a position offset in the left-right direction, the battery pack 3 can be protected in the same way.

[0087] 6. Summary As described above, the battery protection structure of the embodiment includes the battery pack 3 in which the battery 11 is housed inside the battery case 13, the vehicle body 100 to which the battery pack 3 is fastened, and the rear seat 6 provided in the vehicle body 100. The battery pack 3 also includes an upper frame (corresponding to the upper center frame 52) provided above and extending in the front-to-rear direction, and a lower frame (corresponding to the center frame 26, stays 27, lower center frame 32, lower left side frame 33, and lower right side frame 34) provided below and extending in the front-to-rear direction. The upper frame is provided at a height that faces the rear seat 6 in the vertical direction. As a result, when a colliding object 300 collides from behind and moves the battery pack 3 forward, the upper center frame 52 comes into contact with the rear seat 6. Therefore, the upper center frame 52 is able to absorb a load by being sandwiched between the rear seat 6 and the colliding object 300. Thus, the battery protection structure can effectively protect the battery 11 and the high-voltage unit 12 provided inside the battery pack 3.

[0088] The lower frame is also positioned at a height that faces the cross member (front cross member 103) of the vehicle body 100 in the vertical direction. As a result, when a collision object 300 collides from behind and moves the battery pack 3 forward, the upper center frame upper 52 is sandwiched between the rear seat 6 and the collision object 300 to absorb the load. The lower center frame 26, stays 27, lower center frame 32, lower left side frame 33, and lower right side frame 34 are sandwiched between the front cross member 103 and the collision object 300 to absorb the load. Therefore, the battery pack 3 can absorb the load from both the upper and lower parts, further preventing the battery case 13 from colliding. Thus, the battery protection structure can effectively protect the battery 11 and high-voltage unit 12 provided inside the battery pack 3.

[0089] Furthermore, the distance between the rear seat 6 and the upper frame in the longitudinal direction is shorter than the distance between the cross member of the vehicle body and the lower frame. As a result, when a collision object 300 collides from behind and moves the battery pack 3 forward, the battery pack 3 can absorb the load first at its upper part and then, after a certain time, at its lower part. In this way, by distributing the load between the upper and lower frames with a time lag, the battery 11 and high-voltage unit 12 can be protected from the load caused by a rear-end collision.

[0090] The upper frame is formed so that when the vehicle collides with an obstacle 300 from behind and the upper frame is pinched between the rear seat 6 and the obstacle 300, the center portion of the upper frame is bent upward. This prevents the center frame upper 52 from coming into contact with the battery 11 and the high-voltage unit 12.

[0091] Crash boxes 35 are provided at the rear end of the lower frame, and are positioned so that they will be crushed when the upper frame bends. As a result, when a collision object 300 collides from behind and the battery pack 3 is moved forward, the load is received by the upper part, and the crash boxes 35 are crushed to absorb the load, thereby distributing the load more efficiently.

[0092] REFERENCE SIGNS LIST 1 vehicle 3 battery pack 11 battery 26 center frame 27 stay 28 center frame lower 33 left side frame lower 34 right side frame lower 52 center frame upper

Claims

1. A battery protection structure comprising: a battery pack in which a battery is housed inside a battery case; a vehicle body to which the battery pack is fastened; and a rear seat provided in the vehicle body, wherein the battery pack comprises an upper frame provided above and extending in the fore-and-aft direction, and a lower frame provided below and extending in the fore-and-aft direction, the upper frame being provided at a height facing the rear seat in the up-and-down direction.

2. The battery protection structure according to claim 1, wherein the lower frame is provided at a height that faces a cross member of the vehicle body in the vertical direction.

3. A battery protection structure according to claim 1 or 2, wherein the distance between the rear seat and the upper frame in the longitudinal direction is shorter than the distance between the cross member of the vehicle body and the lower frame in the longitudinal direction.

4. A battery protection structure as described in claim 1 or claim 2, wherein the upper frame is configured so that when the vehicle collides with an object from behind and the upper frame is pinched between the rear seat and the object, the center of the upper frame bends upward.

5. The battery protection structure according to claim 4, wherein a crash box is provided at the rear end of the lower frame, and the crash box is positioned so that it will be crushed when the upper frame is bent.

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