BATTERY PACK OF AN ELECTRIC VEHICLE

Abstract

Battery pack of an electric vehicle comprising a plurality of battery modules (34) which are enclosed within a battery housing (18) manufactured by die casting of metal, wherein the battery housing (18) has a drain hole (31i) for releasing water inside to the outside and a water detection means (37) which is arranged near the drain hole (31i), at least a part of the upper surface of a housing bottom wall (31a) of the battery housing (18) is inclined downwards towards the drain hole (31i), a recessed section (31h) is formed at the lowest position of the housing bottom wall (31a) of the battery housing (18), and the drain hole (31i) is formed in a lower part of a wall (31b, 31c) of the battery housing (18) extending in an upward and downward direction, which points towards the recessed section (31h).

Description

BACKGROUND OF THE INVENTION AREA OF THE INVENTION

[0001] The present invention relates to a battery pack of an electric vehicle comprising a plurality of battery modules which are contained within a battery housing made of die-cast metal.

[0002] JP 2011-195069 A discloses an arrangement in which a recessed section formed in a bottom wall of a battery housing is provided with a water sensor and a drain opening which is opened and closed by an opening / closing valve, and when the water sensor detects the entry of water into the interior of the battery housing, the drain opening is opened by the opening / closing valve in order to drain water out of the battery housing. DESCRIPTION OF RELATED TECHNOLOGY

[0003] Since in the conventional arrangement above the battery housing is formed by press forming a sheet of steel, the number of components increases and the structure of the press mold becomes more complicated when attempting to shape the battery housing to guide water to the drain opening or water sensor, increasing the possibility of increased costs.

[0004] DE 10 2013 018 416 A1 discloses a battery housing for accommodating a plurality of battery cells, which has a drain opening for discharging water and a water detection device that can be arranged near the drain opening. The drain opening is located in the bottom of a recessed section, with part of the base of the battery housing inclined downwards towards the drain opening.

[0005] EP 2 749 444 A1 and DE 10 2013 011 894 A1 show a battery housing made of die-cast metal. SUMMARY OF THE INVENTION

[0006] The present invention has been achieved in light of the above circumstances, and its object is to enable the simple design of a battery housing with water detection and water drainage functions without increasing the number of components.

[0007] To solve the problem, a battery pack for an electric vehicle according to claim 1 is specified according to a first aspect of the present invention.

[0008] According to the first aspect, the battery pack of the electric vehicle houses the majority of battery modules within a die-cast metal battery casing. Since the battery casing has a drain hole for discharging water to the outside, as well as a water detection device located near the drain hole, and since at least part of the top of the casing's bottom wall slopes downwards towards the drain hole, it is not only easy to form this downward slope during die-casting without increasing the number of components, but it is also possible to smoothly guide any water that has entered the battery casing to the drain hole, reliably detect it with the water detection device, and quickly discharge it through the drain hole.

[0009] According to a second aspect of the present invention, a battery pack for an electric vehicle is specified according to claim 2.

[0010] According to the second aspect, the battery pack of the electric vehicle houses the majority of battery modules within a die-cast metal battery casing. Since the battery casing has a drain hole for discharging water to the outside, as well as a water detection device located near the drain hole, and since the drain hole is provided in the downward-facing recessed section formed in the top of the casing's bottom wall, it is not only easy to form the recessed section in the top of the casing's bottom wall during die-casting without increasing the number of components, but it is also possible to smoothly guide any water that has entered the battery casing to the recessed section, reliably detect it with the water detection device, and quickly discharge it through the drain hole.

[0011] According to a third aspect of the present invention, in addition to the first or second aspect, the interior of the battery housing is divided into two battery chambers by a beam section formed integrally with the battery housing, and the drain hole and the water detection means are provided in each of the battery chambers.

[0012] Since, according to the third aspect, the interior of the battery housing is divided into two battery chambers by the beam section integrated with it, and the drain hole and water detection device are provided in each of the battery chambers, it is possible to carry out the detection of the ingress of water and the discharge of water in both battery chambers without problems.

[0013] According to a fourth aspect of the present invention, in addition to the third aspect, the beam section extends in the vehicle width direction, and the drain hole and the water detection means are arranged in a part of the battery housing that is central in the vehicle width direction.

[0014] Since, according to the fourth aspect, the beam section extends in the vehicle width direction, and the drain hole and the water detection device are located in the central part of the battery housing in the vehicle width direction, it is possible to detect the ingress of water even more reliably and to discharge water even more smoothly by collecting water from opposite sides in the vehicle width direction to the central part in the vehicle width direction, while the side collision resistance of the battery pack is improved by the beam section.

[0015] According to a fifth aspect of the present invention, in addition to one of the first to fourth aspects, the battery housing comprises a water jacket formed between the battery housing and a lid element attached to an underside of the housing bottom wall, and the drain hole is arranged in a position where, when viewed from above, the drain hole does not overlap the water jacket.

[0016] Since, according to the fifth aspect, the battery housing has the water jacket formed between the battery housing and the cover element attached to the underside of the housing bottom wall, and the drain hole is located in a position where, when viewed from above, it does not overlap the water jacket, the drain hole can be easily formed without interfering with the water jacket.

[0017] According to a sixth aspect of the present invention, in addition to the fifth aspect, the battery housing comprises a groove section formed in an upper part of the housing bottom wall, wherein the groove section is recessed downwards along part of a circumference of the water jacket, and the groove section extends towards the drain hole.

[0018] Since, according to the sixth aspect, the top of the housing bottom wall of the battery housing has the groove section, the groove section is recessed downwards along part of the circumference of the water jacket, and the groove section extends towards the drain hole, it is possible to guide water that has built up on the top of the housing bottom wall of the battery housing along the groove section and discharge it even more smoothly from the drain hole.

[0019] According to a seventh aspect of the present invention, in addition to one of the first to sixth aspects, an electrical current conductor extending from the plurality of battery modules is arranged in the front and rear direction in a space formed between the battery modules on the left and right in the central part of the battery housing in the vehicle width direction, and a connecting cable connecting the water detection means to an electrical component is bundled with the electrical current conductor in the space.

[0020] Since, according to the seventh aspect, the electrical power line extending from the majority of battery modules is arranged in the front-and-back direction in the space formed between the left and right battery modules in the central part of the battery housing in the direction of the vehicle width, and the connecting cable linking the water detection device to the electrical component is bundled with the electrical power line in this space, it is possible to arrange the electrical power line and the connecting cable in a compact manner by efficiently utilizing the space between the left and right battery modules.

[0021] Incidentally, a transverse element 31e of an embodiment corresponds to the beam section of the present invention, a front battery chamber 31f and a rear battery chamber 31g of the embodiment correspond to the battery chambers of the present invention, and a mass fault detection connector 37 of the embodiment corresponds to the water detection means of the present invention.

[0022] The above and other objectives, characteristics and advantages of the present invention will become clear from the detailed description of the preferred embodiment given below with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS Fig. Figure 1 is a side view of the body of a plug-in hybrid vehicle. Fig. 2 is a view in the direction of arrow 2 in Fig. 1. Fig. 3 is a section view along line 3-3 in Fig. 2. Fig. 4 is a view from the arrow line 4-4 in Fig. 3. Fig. 5 is a section view along line 5-5 in Fig. 4. Fig. 6 is a section view along line 6-6 in Fig. 4. Fig. Figure 7 is an exploded view of a battery pack. DESCRIPTION OF THE PREFERRED VERSION

[0023] An embodiment of the present invention with regard to is described below. Fig. 1 to Fig. 7 explained. In the following description, reference numerals corresponding to components of the exemplary embodiment are included only for ease of understanding, but the applicant's claims are not limited to the exemplary embodiment or to specific components of the exemplary embodiment. In the present description, the front and rear directions, the left and right directions (vehicle width direction), and the up and down directions are defined with respect to an occupant sitting in a driver's seat.

[0024] As in Fig. 1 and Fig. Figure 2 shows the following components mounted on the front of the body of a front-wheel-drive plug-in hybrid vehicle: an electric motor 11 for driving a front wheel, an internal combustion engine 12 for driving a generator that charges a battery, and a power driver unit 13 equipped with an inverter to control the operation of the electric motor 11. On the underside of the floor plate 14 are arranged a pair of left and right floor frames 15 extending forward and rearward, as well as a floor cross member 16 connecting the left and right floor frames 15 in the width direction of the vehicle. A battery housing 18, forming the outline of a battery pack 17 for powering the electric motor 11, is attached to the undersides of the floor frames 15 and the floor cross member 16.

[0025] As in Fig. As shown in Figure 7, the battery housing 18 is formed by connecting a housing main body 31, made of die-cast metal (aluminum) and open at the top, to a cover 32, also made of die-cast metal (aluminum) and open at the bottom, via their outer circumferential parts by means of a plurality of bolts 33 in the top-bottom direction. Eight battery modules 34 are mounted on a base part of the housing main body 31, and an electrical component 35, such as a battery control device, a connecting board, or a cell voltage sensor, is arranged above the battery modules 34.

[0026] The main housing body 31 has a shallow container shape and includes a substantially flat base wall 31a, a front wall 31b, a rear wall 31c, and left and right side walls 31d extending from the outer circumference of the base wall 31a, as well as a transverse element 31e connecting the left and right side walls 31d in the vehicle width direction. The transverse element 31e, which forms a beam section of the present invention, is an arrangement of a large number of ribs extending from the base wall 31a, but any other structure can also be used. The interior of the main housing body 31 is divided by the transverse element 31e into a front battery 31f and a rear battery 31g, with four battery modules 34 arranged in the front battery compartment 31f and four battery modules 34 arranged in the rear battery compartment 31g.

[0027] As in Fig. 3 and Fig. As shown in Figure 4, with respect to the vehicle body centerline L, the left half of the housing bottom wall 31a of the main housing body 31 is inclined downwards to the right, and the right half is inclined downwards to the left. That is, the cross-section of the housing bottom wall 31a of the main housing body 31 is V-shaped in the vehicle width direction, so that the position of the vehicle body centerline L is lowest (see Figure 4). Fig. 3) The angle of inclination of the housing bottom wall 31a is a small angle required to collect water that has accumulated on the housing bottom wall 31a towards the vehicle body centerline L-side, and in this embodiment is, for example, 1.08°. Therefore, the front battery compartment 31f and the rear battery compartment 31g of the main housing body 31 each have a recessed section 31h at a position where the housing bottom wall 31a is lowest on the vehicle body centerline L.

[0028] A drain hole 31i for draining water that has accumulated in the front battery chamber 31f and the rear battery chamber 31g is formed in a lower part of the housing front wall 31b and the housing rear wall 31c, respectively, facing towards the recessed section 31h, and these drain holes 31e are closed by means of a drain bolt 36. A ground fault detection connector or plug 37, which constitutes a water detection means of the present invention, is provided on the housing bottom wall 31a near the drain hole 31e.

[0029] The ground fault detection connector 37 detects an electrical short circuit (ground fault) between the positive terminal of the battery module 34 and the main housing body 31, to which the negative terminal of the battery module 34 is grounded, and issues an alarm. It detects a ground fault by applying a square-wave pulse voltage between a high-voltage section and a low-voltage section of the battery pack 17 and measuring an impedance change based on the amplitude of a reflected waveform. The reason the ground fault detection connector 37 can detect the ingress of water into the battery housing 18 is that a ground fault condition occurs when the high-voltage and low-voltage sections of the battery pack 17 become electrically connected due to the ingress of water.

[0030] As in Fig. As shown in Figure 5, electrical power lines 38 extending from the respective battery modules 34 are bundled together, and the electrical power line 38 runs between the left and right battery modules 34, which are arranged on opposite sides of the vehicle body centerline L, and is connected to an electrical component 35 (connection board) located above the battery module 34. Two connecting cables 40 extending from the front and rear ground fault detection connectors 37 are bundled with the electrical power line 38 and are connected to the electrical component 35 (battery control unit).

[0031] As in Fig. 4 to Fig. As shown in Figure 7, an upwardly recessed zigzag-shaped water jacket upper wall 31j is formed on the housing bottom wall 31a of the main housing body 31, a cooling water supply opening 31k is formed at the front end of the water jacket upper wall 31j, a cooling water discharge opening 31m is formed at the rear end of the water jacket upper wall 31j, and three connecting sections 31n are formed at opposite ends of the recessed section 31a in the direction of the vehicle width (see Figure 7). Fig. 4) Attaching a cover element 41 to an underside of the housing bottom wall 31a by means of a plurality of bolts 47 forms four rows of water jackets 42, which extend in the vehicle width direction between an underside of the water jacket top wall 31j and an upper side of the cover element 41. The drain hole 31i is formed in a position where, when viewed in the top-bottom direction, the drain hole 31i does not overlap with the water jacket 43.

[0032] A lower plate 43, forming a bottom wall of each battery module 34, is attached via a thermally conductive element 48 to an upper surface of the water jacket top wall 31j of the main housing body 31 defining the water jacket 42, and its four corners are fastened by means of four bolts 44. A front edge portion and a rear edge portion of the water jacket top wall 31j, forming the edge of each water jacket 42, are designed as a thick section, and an intermittent groove section 31o is formed in an upper surface of the thick section, extending in the vehicle width direction with a downward slope towards the recessed section 31h of the housing bottom wall 31a.

[0033] As in Fig. 1 and Fig.As shown in Figure 2, the battery housing 20 thus formed is attached to an underside of the floor cross element 16 by means of two bolts 45, which extend from bottom to top through its central part in a state in which a recessed section 32a, which is formed in the cover 32 and extends in the vehicle width direction, is placed on the floor cross element 16 from below, and is attached to an underside of the floor frame 15 by means of two bolts 46, which extend from bottom to top through each of its left and right side parts.

[0034] The operation of the embodiment of the present invention with the above arrangement will now be explained.

[0035] When water enters the interior of the battery housing 18, the bottom wall 31a of the main housing body 31 slopes downwards from the outside towards the center in the vehicle width direction. This causes the water to collect along the slope of the recessed section 31h in the central part of the main housing body 31 in the vehicle width direction. The water is then detected by the ground fault detection connector 37, triggering an alarm to indicate the occurrence of a ground fault. As a result, the drain bolt 36 of the main housing body 31 is released, the drain hole 31i opens, and any accumulated water can be rapidly discharged to the outside of the main housing body 31.

[0036] Since the main housing body 31 is made of die-cast metal, the downward slope of the housing bottom wall 31a of the main housing body 31 can be easily formed during casting without increasing the number of components.Furthermore, to improve side-impact resistance, the transverse element 31e, extending in the vehicle width direction, is formed on the main housing body 31. Since the interior of the main housing body 31 is divided into the front battery chamber 31f and the rear battery chamber 31g, if only one battery chamber below the front battery chamber 31f and the rear battery chamber 31g were provided with the ground fault detection connector 37, there would be a possibility that water ingress into the other battery chamber would not be detected. However, because, according to the present embodiment, the ground fault detection connector 37 and the drain hole 31i are provided in both the front battery chamber 31f and the rear battery chamber 31g, water detection and drainage can be easily carried out.

[0037] Because in this arrangement the intermittent groove section 31o, which extends in the vehicle width direction so that it follows the top of the thick part of the front and rear edges of the water jacket 42, is formed in the top of the housing bottom wall 31a of the main housing body 31, it is possible to effectively direct water that has built up on the housing bottom wall 31a along the groove section 31o to the drain hole 31i, which is formed in the recess section 31h in the middle in the vehicle width direction.

[0038] Furthermore, because the transverse element 31e extends in the vehicle width direction, and the mass fault detection connector 37 and the drain hole 31i are arranged in the central part of the main housing body 31 in the vehicle width direction, water that has accumulated on the top of the housing bottom wall 31a of the main housing body 31 can be collected in the recessed section 31h via the shortest path, water can be detected more reliably and water can be drained more smoothly.

[0039] Furthermore, because the water jacket 42 is provided on the bottom part of the main housing body 31, there is a possibility that the drain hole 31i would interfere with the water jacket 42 if one were to attempt to position the downwardly extending drain hole 31i above the water jacket 42. However, since, according to the present embodiment, the drain hole 31i is arranged in a position where, when viewed from above, it does not overlap the water jacket 42, the drain hole 31i can easily be formed without interfering with the water jacket 42.

[0040] Furthermore, because the electrical current line 38, which extends from the majority of battery modules 34, is arranged in the front and rear direction in the space formed between the left and right battery modules 34 in the central part of the battery housing 18 in the vehicle width direction, and the connecting cable 40, which connects the ground fault detection connector 37 to the electrical component 35, is bundled with the electrical current line 38 in the space, it is possible to arrange the electrical current line 38 and the connecting cable 40 in a compact manner by effectively utilizing the space between the left and right battery modules 34.

[0041] Above, one embodiment of the present invention is described, but the present invention can be modified in numerous ways, as long as the modifications do not deviate from the idea of ​​the present invention.

[0042] For example, in the design of the mass fault detection connector 37, water detection means is used, but detection means exclusively intended for this purpose can also be provided.

[0043] Furthermore, in this embodiment the entire upper surface of the housing bottom wall 31a is inclined downwards towards the drain hole 31i or the recessed section 31h, but only a part of the upper surface of the housing bottom wall 31 needs to be inclined downwards around the drain hole 31i or the recessed section 31h.

[0044] The battery housing of an electric vehicle includes a drain hole for discharging internal water to the outside, as well as a water detection device located near the drain hole. At least part of the upper surface of the battery housing's bottom wall slopes downwards towards the drain hole. Accordingly, it is not only easy to mold the downward slope of the upper surface of the battery housing's bottom wall during die casting without increasing the number of components, but it is also possible to smoothly guide any water that has entered the battery housing to the drain hole, reliably detect it with the water detection device, and rapidly discharge it through the drain hole 31i.

Claims

[1] Battery pack of an electric vehicle comprising a plurality of battery modules (34) which are enclosed within a battery housing (18) produced by metal die casting, wherein the battery housing (18) has a drain hole (31i) for releasing water inside to the outside and a water detection means (37) which is arranged near the drain hole (31i), at least a part of the upper surface of a housing bottom wall (31a) of the battery housing (18) is inclined downwards towards the drain hole (31i), a recessed section (31h) is formed at the lowest position of the housing bottom wall (31a) of the battery housing (18), and the drain hole (31i) is formed in a lower part of a wall (31b, 31c) of the battery housing (18) extending in an upward and downward direction, which points towards the recessed section (31h). [2] Battery pack of an electric vehicle comprising a plurality of battery modules (34) which are enclosed within a battery housing (18) produced by metal die casting, wherein the battery housing (18) has a drain hole (31i) for releasing water inside to the outside and a water detection means (37) which is arranged near the drain hole (31i), a downwardly recessed recessed section (31h) is formed at the lowest position in an upper surface of a housing bottom wall (31a) of the battery housing (18), and the drain hole (31i) is formed in a lower part of a wall (31b, 31c) of the battery housing (18) extending in an upward and downward direction, which points towards the recessed section (31h). [3] The battery pack of an electric vehicle according to claim 1 or 2, wherein the interior of the battery housing (18) is divided into two battery chambers (31f, 31g) by a beam section (31e) integrated with the battery housing (18), and the drain hole (31i) and the water detection means (37) are provided in each of the battery chambers (31f, 31g). [4] The battery pack of an electric vehicle according to claim 3, wherein the beam section (31e) extends in the direction of the vehicle width, and the drain hole (31i) and the water detection means (37) are arranged in a central part of the battery housing (18) in the direction of the width of the vehicle. [5] The battery pack of an electric vehicle according to any one of claims 1 to 4, wherein the battery housing (18) has a water jacket (42) formed between the battery housing (18) and a cover element (41) attached to an underside of the housing bottom wall (31a), and the drain hole (31i) is located in a position where, when viewed from above, the drain hole (31i) does not overlap the water jacket (42). [6] The battery pack of an electric vehicle according to claim 5, wherein the battery housing (18) has a groove section (31o) formed in an upper surface of the housing bottom wall (31a), the groove section (31o) being recessed downwards along part of a circumference of the water jacket (42), and the groove section (31o) extends towards the drain hole (31i). [7] The battery pack of an electric vehicle according to any one of claims 1 to 6, wherein an electrical current line (38) extending from the majority of battery modules (34) in the front and rear direction is arranged in a space formed between the battery modules (34) on the left and right in the central part of the battery housing (18) in the direction of the vehicle width, and a connecting cable (40) that connects the water detection device (37) to an electrical component (35) is bundled with the electrical power line (38) in the room.

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