CN219163519U

CN219163519U - Battery pack

Info

Publication number: CN219163519U
Application number: CN202223598890.XU
Authority: CN
Inventors: 何亚飞
Original assignee: Envision Power Technology Jiangsu Co Ltd; Envision Ruitai Power Technology Shanghai Co Ltd
Current assignee: Envision Power Technology Jiangsu Co Ltd; Envision Ruitai Power Technology Shanghai Co Ltd
Priority date: 2022-12-29
Filing date: 2022-12-29
Publication date: 2023-06-09
Anticipated expiration: 2032-12-29

Abstract

The utility model discloses a battery pack. The battery pack includes: the box body comprises a bottom guard plate and edge beams surrounding the bottom guard plate; the battery cell assembly is accommodated in the box body and comprises a plurality of battery cells, and a bus bar and an insulating bracket which are used for electrically connecting the battery cells, wherein the top surface of the battery cells is provided with a pole which is arranged towards the bottom guard plate, and the bus bar is connected to the pole; the insulating piece is arranged between the bottom guard plate and the bus piece; the first cooling channel is arranged in the bottom guard plate and corresponds to the converging sheet. The heat conductivity coefficient of the converging sheet is higher than that of the battery cell, the first cooling channel is arranged at the position corresponding to the converging sheet, the converging sheet can be cooled, and meanwhile, the battery cell can be cooled, so that the cooling effect is good. In addition, through setting up first cooling channel in the below of electric core, need not to set up comparatively complicated connecting line in the inside of box, be favorable to simplifying the structure of battery package, simultaneously, also can reduce the weeping or prevent taking place the weeping.

Description

Battery pack

Technical Field

The utility model relates to the field of battery packs, in particular to a battery pack.

Background

The battery pack is an important component of the electric automobile, generally comprises a box body and a plurality of electric cells arranged in the box body, and can emit a large amount of heat energy under the working state, the existing battery pack is cooled by introducing water, and the water is used for taking away the redundant heat generated in the charging and discharging process of the battery, so that the battery pack is at a proper working temperature, and the temperature of each part of the battery pack is controlled within a smaller range.

In the prior art, for a square-case battery with an inverted battery cell (i.e., a battery cell with a pole downward), the following problems mainly exist:

(1) The cooling position is mainly the large surface of the battery cells, but does not cool the bus plates for realizing the electric connection between the battery cells, and the cooling effect is limited;

(2) In order to realize the flow of water, the inside of battery package needs to set up connecting tube way, and the inner structure of battery package is comparatively complicated, and also produces the weeping in the inside of battery package easily, influences the normal use of battery package.

Disclosure of Invention

The utility model aims to overcome the defects that in the prior art, a battery with an inverted battery core is limited in cooling effect, the internal structure of a battery pack is complex and liquid leakage is easy to occur.

The utility model solves the technical problems by the following technical scheme:

a battery pack, the battery pack comprising:

the box body comprises a bottom guard plate and edge beams arranged around the bottom guard plate;

the battery cell assembly is accommodated in the box body and comprises a plurality of battery cells, and a bus piece and an insulating bracket which are used for electrically connecting the battery cells, wherein a pole is arranged on the top surface of the battery cells and faces to the bottom guard plate, and the bus piece is connected to the pole;

an avoidance window is formed in the insulating support, and the confluence sheet is accommodated in the avoidance window; the insulating piece is arranged between the bottom guard plate and the bus plate; a kind of electronic device with high-pressure air-conditioning system

The first cooling channel is arranged in the bottom guard plate and corresponds to the confluence sheet.

In this scheme, the coefficient of heat conductivity of converging the piece is higher than the electric core, and first cooling channel sets up in the position department that corresponds with converging the piece, can cool off converging the piece, can also cool off the electric core simultaneously, and the cooling effect is better. In addition, through setting up first cooling channel in the below of electric core, need not to set up comparatively complicated connecting line in the inside of box, be favorable to simplifying the structure of battery package, simultaneously, also can reduce the weeping or prevent taking place the weeping. Wherein, the setting of insulating part separates the piece that converges with end backplate, can protect the piece that converges, is favorable to guaranteeing the security of battery package.

Preferably, the battery pack further includes a first heat conductive member disposed between the bus bar and the insulating member.

In this scheme, the setting of first heat-conducting piece makes to have certain clearance between backplate and the insulating part at the bottom, more is favorable to the heat dissipation, and then more is favorable to realizing the cooling to the electric core, is favorable to guaranteeing the life of battery package.

Preferably, the size of the first heat conducting piece is not smaller than the corresponding size of the bus piece along the length direction of the bus piece;

and/or, along the width direction of the bus sheet, the size of the first heat conduction piece is not smaller than the corresponding size of the bus sheet.

In this scheme, adopt above-mentioned structure setting, along the length and/or the width direction of converging the piece on, first heat conduction spare is not less than the converging piece for all there is first heat conduction spare in the extension scope of converging the piece, thereby is favorable to realizing the reliable heat dissipation to converging the piece.

Preferably, the insulating part is of an integral structure or comprises a plurality of insulating units which are arranged in a split mode, and the insulating units are arranged in one-to-one correspondence with the bus plates of the battery cells;

and/or the first heat conduction piece is of an integrated structure or the battery pack comprises a plurality of first heat conduction pieces which are arranged in a split mode, and the plurality of first heat conduction pieces and the plurality of bus plates of the battery cells are arranged in one-to-one correspondence.

In this scheme, the insulating piece and/or the first heat conducting piece can be set to a split structure or an integral structure according to actual needs, wherein when the insulating piece and/or the first heat conducting piece is set to the integral structure, the extension range of the insulating piece and/or the first heat conducting piece can correspond to the bus plates of a plurality of electric cores; when the structure is in a split structure, any one insulating piece and/or the first heat conducting piece are arranged corresponding to the bus piece of the corresponding battery cell.

Preferably, the bus plates of the plurality of electric cores are arranged side by side, each row of bus plates is arranged along the length direction of the battery pack, the first cooling channel comprises a plurality of sub-channels arranged side by side, and the sub-channels extend along the length direction of the battery pack;

each row of the bus plates comprises a plurality of bus plates which are arranged at intervals along the length direction of the battery pack, and a first heat conduction piece is arranged between the insulating piece at each bus plate and the bottom guard plate at the corresponding sub-channel.

In this scheme, the subchannel extends along the length direction of battery package, and the extension scope of subchannel is wider, also wider to the scope of electric core effect to be favorable to guaranteeing the reliable cooling to the top of converging piece and electric core. The plurality of first heat conducting pieces on each sub-channel are arranged in a scattered manner, rather than being arranged into an integral structure, so that the compression unevenness and poor heat conducting effect caused by the virtual contact between the first heat conducting pieces and the sub-channels can be prevented due to the structural limitation of the insulating bracket for mounting the bus bar.

Preferably, the first heat conducting piece is a heat conducting glue or a heat conducting pad;

and/or the first heat conduction piece is connected with the first cooling channel in an adhesive mode.

Preferably, the first cooling channel is integrated on the bottom guard plate, and a groove is further formed in the top of the bottom guard plate;

the grooves are arranged at intervals with the first cooling channels, and the grooves are arranged corresponding to the pressure release valves of the battery cells.

In this scheme, first cooling channel integration need not to set up in addition and is used for setting up the carrier of first cooling channel on the backplate at the bottom, is favorable to simplifying the overall structure of battery package, is favorable to lightweight design and reduce cost. The arrangement of the exhaust channel is beneficial to ensuring the normal use of the pressure release valve, and further beneficial to ensuring the use safety and the service life of the battery pack.

Preferably, the box body further comprises an upper cover arranged opposite to the bottom guard plate, and the upper cover is integrated with a second cooling channel.

In this scheme, the cooling of the bottom of electric core can be realized to the second cooling channel, and second cooling channel and first cooling channel cooperate, can cool off respectively from the bottom and the top of electric core, and the cooling effect is better, more is favorable to guaranteeing the life of battery package. In addition, the second cooling channel is integrated on the upper cover, and a carrier for arranging the second cooling channel is not required to be additionally arranged, so that the integral structure of the battery pack is simplified, and the design of light weight and the cost are reduced.

Preferably, the battery pack further includes a second heat conductive member disposed between the upper cover and the battery cell.

In this scheme, the setting of second heat-conducting piece makes to have certain clearance between upper cover and the electric core, more is favorable to the heat dissipation, and then more is favorable to realizing the cooling to the electric core, is favorable to guaranteeing the life of battery package.

Preferably, the side wall of the box body is provided with a water inlet joint and a water return joint which are communicated with the first cooling channel.

On the basis of conforming to the common knowledge in the field, the above preferred conditions can be arbitrarily combined to obtain the preferred examples of the utility model.

The utility model has the positive progress effects that:

in this battery package, first cooling channel sets up in the position department that corresponds with the confluence piece, can cool off the confluence piece, can also cool off the electric core simultaneously, and the cooling effect is better. In addition, through setting up first cooling channel in the below of electric core, need not to set up comparatively complicated connecting line in the inside of box, be favorable to simplifying the structure of battery package, simultaneously, also can reduce the weeping or prevent taking place the weeping. Wherein, the setting of insulating part separates the piece that converges with end backplate, can protect the piece that converges, is favorable to guaranteeing the security of battery package.

Drawings

Fig. 1 is an exploded view of a battery pack according to a preferred embodiment of the present utility model.

Fig. 2 is a schematic structural view of a battery pack according to a preferred embodiment of the present utility model.

Fig. 3 is a partial schematic structure of a battery pack according to a preferred embodiment of the present utility model.

Fig. 4 is a schematic view showing another part of the structure of a battery pack according to a preferred embodiment of the present utility model.

Fig. 5 is an enlarged schematic view of the portion a in fig. 1.

Fig. 6 is a schematic view of another part of the battery pack according to a preferred embodiment of the present utility model, showing the bottom plate and the first heat conductive member.

Reference numerals illustrate:

10 electric core

101 pole

102 pressure release valve

20 box body

201 boundary beam

30 bottom guard board

40 upper cover

50 confluence sheet

60 first heat conducting member

70 first cooling passage

701 subchannel

702 water inlet joint

703 backwater joint

80 second heat conducting member

90 second cooling channels

100 insulating support

110 back-off window

120 groove

130 insulating member

Detailed Description

The utility model is further illustrated by means of examples which follow, without thereby restricting the scope of the utility model thereto.

As shown in fig. 1 to 6, the present embodiment provides a battery pack including a case 20, a cell assembly, and an insulating member 130. Wherein the case 20 includes a bottom guard plate 30 and a side rail 201 disposed around the bottom guard plate 30. The battery cell assembly is accommodated in the box 20 and comprises a plurality of battery cells 10, a bus bar 50 and an insulating bracket 100, wherein the bus bar 50 and the insulating bracket 100 are used for electrically connecting the battery cells 10, a pole column 101 is arranged on the top surface of the battery cells 10, the pole column 101 is arranged towards the bottom guard plate 30, and the bus bar 50 is connected to the pole column 101. The insulating bracket 100 is provided with an avoidance window 110, and the busbar 50 is accommodated in the avoidance window 110. The insulator 130 is disposed between the bottom shield 30 and the bus bar 50 (as shown in fig. 1). The bottom guard plate 30 is provided with a first cooling passage 70 therein, and the first cooling passage 70 is provided in correspondence with the manifold 50.

Wherein the above-described disposition of the pole 101 toward the bottom shield 30 means that the battery is inverted.

As shown in fig. 1, 3 and 4, the bus bar 50 is connected with the corresponding pole 101 through the avoiding window 110, for example, bonding is performed by welding, so that the plurality of battery cells 10 in the battery pack are finally connected in series or in parallel through the plurality of bus bars 50.

In the present embodiment, the heat conductivity coefficient of the busbar 50 is higher than that of the battery cell 10, and the first cooling channel 70 is disposed at a position corresponding to the busbar 50, so that the busbar 50 can be cooled, and the battery cell 10 can be cooled, so that the cooling effect is better. In addition, by arranging the first cooling channel 70 below the battery cell 10, a relatively complex connecting pipeline is not required to be arranged in the box body 20, which is beneficial to simplifying the structure of the battery pack, and meanwhile, leakage can be reduced or prevented.

As shown in fig. 1, 2, 5 and 6, the side wall of the case 20 is provided with a water inlet joint 702 and a water return joint 703 that communicate with the first cooling passage 70. The positions of the water inlet joint 702 and the water return joint 703 are schematically shown in fig. 1, 2, 5 and 6, wherein the water inlet joint 702 is connected to a water source, and a circulation loop is formed among the water inlet joint 702, the water source, the first cooling passage 70 and the water return joint 703. It should be noted that the positions and structures of the water inlet joint 702 and the water return joint 703 are not limited to those shown in the drawings, and may be set according to actual requirements in other alternative embodiments. For example, the positions of water inlet joint 702 and water return joint 703 may be interchanged.

In a preferred embodiment, as will be understood with reference to fig. 1, 2, 4 and 6, in order to enhance the heat dissipation effect, a first heat conductive member 60 is provided between the bus bar 50 and the insulating member 130.

The first heat conducting member 60 is disposed such that a certain gap is formed between the bus plate 50 and the insulating member 130, and between the bottom protecting plate 30 and the battery cell 10, which is more conducive to heat dissipation, and further is more conducive to cooling the battery cell 10, thereby being beneficial to ensuring the service life of the battery pack.

Further, in the present embodiment, the size of the first heat conductive member 60 is not smaller than the corresponding size of the bus bar 50 in the length direction of the bus bar 50, and at the same time, the size of the first heat conductive member 60 is not smaller than the corresponding size of the bus bar 50 in the width direction of the bus bar 50.

The size or specification of the first heat conducting piece 60 is not smaller than that of the bus bar 50, and the first heat conducting piece 60 is arranged in the extending range of the bus bar 50, so that reliable heat dissipation of the bus bar 50 is facilitated. In addition, even if there is an installation error such that the position of the bus bar 50 with respect to the battery cell 10 is slightly shifted, with the above arrangement, it is possible to ensure that the first heat conductive member 60 functions normally, and thus to ensure reliable heat dissipation to the bus bar 50.

In particular, in the present embodiment, the size of the first heat conductive member 60 is the same as that of the bus bar 50.

In other alternative embodiments, only the dimensional relationship of the first heat conductive member 60 of the bus bar 50 may be set as: the size of the first heat conductive member 60 is not smaller than the corresponding size of the bus bar 50 only along the length direction of the bus bar 50; or, the size of the first heat conductive member 60 is not smaller than the corresponding size of the bus bar 50 in the width direction of the bus bar 50.

As will be understood with reference to fig. 1 and 3 to 5, in the present embodiment, the insulating member 130 includes a plurality of insulating units that are separately disposed, and the plurality of insulating units may be disposed in a one-to-one correspondence with the bus bars 50 of the plurality of battery cells 10. The battery pack comprises a plurality of first heat conducting members 60 which are arranged in a split mode, and the plurality of first heat conducting members 60 are arranged in a one-to-one correspondence with the bus plates 50 of the plurality of battery cells 10.

In an alternative embodiment, the insulating member 130 may be provided as a unitary structure, and accordingly, the first heat conductive member 60 may be provided as a unitary structure. Of course, in another alternative embodiment, only the insulating member 130 or the plurality of first heat conductive members 60 may be provided as a unitary structure, or only the insulating member 130 or the first heat conductive members 60 may be provided as a separate structure.

In addition, it should be noted that, in other alternative embodiments, when the insulating member 130 or the first heat conducting member 60 is configured as a separate structure, it may be one insulating unit or one first heat conducting member 60 corresponding to the bus bar 50 of the plurality of battery cells 10.

As will be further understood with reference to fig. 1, 3 to 5, the plurality of bus plates 50 are arranged side by side, each row of bus plates 50 is arranged along the length direction of the battery pack, and the first cooling passage 70 includes a plurality of sub-passages 701 arranged side by side, and the sub-passages 701 extend along the length direction of the battery pack. The sub-channels 701 extend along the length direction of the battery pack, and the extension range of the sub-channels 701 is wider, and the range of the sub-channels 701 acting on the battery cells 10 is also wider, so that the reliable cooling of the bus bar 50 and the top of the battery cells 10 is ensured.

It should be noted that, the top of the battery cell 10 refers to an end of the battery cell 10 where the pole 101 is disposed, and correspondingly, the bottom of the battery cell 10 refers to an end of the battery cell 10 where the pole 101 is not disposed, i.e., an end far from the pole 101.

Further, each of the bus plates 50 includes a plurality of bus plates 50 disposed at intervals along the length direction of the battery pack, and the first heat conductive member 60 is disposed between the insulating member 130 at each bus plate 50 and the corresponding sub-channel 701. That is, the plurality of first heat conductive members 60 on each sub-channel 701 are disposed in a dispersed manner, rather than being disposed as a unitary structure. Thus, it is possible to prevent uneven compression and poor heat conduction effect due to the structural limitation of the insulating holder 100 for mounting the bus bar 50, which is caused by the virtual contact of the first heat conductive member 60 with the sub-channel 701.

It should be noted that, as shown in fig. 1 and fig. 5, the number of the sub-channels 701 is related to the number of the cells 10 in the battery pack and the arrangement of the bus bars 50, in this embodiment, the cells 10 of the battery pack are arranged side by side, and specifically, two rows are each 27 cells 10, the bus bars 50 have three rows, two rows of bus bars 50 on two sides respectively correspond to the outer poles 101 (which may be positive poles or negative poles according to the arrangement of the cells 10) of the two rows of cells 10, one row of bus bars 50 on the middle corresponds to the pole 101 (which may be positive poles or negative poles according to the arrangement of the cells 10) near the middle of the two rows of cells 10, and one row of bus bars 50 on the middle may be regarded as two groups of bus bars 50 as a whole, and each group of bus bars 50 extends along the length direction of the battery pack as a whole. On this basis, the number of the sub-channels 701 corresponds to four, wherein two sub-channels 701 on both sides correspond to the two rows of bus plates 50 on both sides described above, and the two sub-channels 701 in the middle correspond to the two groups of bus plates 50 on the middle.

In addition, the structure and the specification of each sub-channel 701 are not particularly limited, and each sub-channel 701 may be the same, may not be completely the same or completely different, and is particularly determined according to actual design requirements.

In the present embodiment, the case 20 includes the bottom guard plate 30, and the first cooling passage 70 is integrated with the bottom guard plate 30, that is, the first cooling passage 70 is integrally formed with the bottom guard plate 30. The first cooling channel 70 is integrated on the bottom guard plate 30, and no carrier for setting the first cooling channel 70 is needed, which is beneficial to simplifying the overall structure of the battery pack, and reducing the design and cost.

Of course, in other alternative embodiments, the first cooling channel 70 may also be disposed between the bottom guard plate 30 and the battery cells 10, i.e., the first cooling channel 70 may be disposed separately from the bottom guard plate 30.

As shown in at least fig. 5, the sub-channel 701 is implemented by providing flow holes on the bottom plate (corresponding to the bottom guard plate 30 described below) of the case 20, so as to ensure the strength of the case 20 and facilitate the arrangement of the flow holes, the structure of the bottom guard plate 30 with the flow holes is protruded compared with other structures, that is, the flow holes are arranged on the protruded structure.

In the present embodiment, the first heat conductive member 60 is provided as a heat conductive paste. Further, the first heat conductive member 60 is adhesively connected to the first cooling passage 70. The bonding connection between the first heat conducting member 60 and the first cooling channel 70 herein is specifically bonding connection between the first heat conducting member 60 and the top of the protruding structure.

In other alternative embodiments, the first heat conducting member 60 is not limited to the above-mentioned heat conducting glue, but may be provided as a heat conducting pad, and of course, the heat conducting glue and the heat conducting pad may be mixed in the plurality of first heat conducting members 60, that is, some of the first heat conducting members 60 are heat conducting glue, and other of the first heat conducting members 60 are heat conducting pads.

As shown in fig. 1 and 5, a groove 120 is further formed in the top of the bottom guard plate 30, the groove 120 is spaced from the first cooling channel 70, and the groove 120 is disposed corresponding to the pressure release valve 102 of the battery cell 10. Specifically, in the present embodiment, one groove 120 is provided between two adjacent sub-channels 701, and the groove 120 extends along the length direction of the battery pack. Wherein fig. 3 and 4 only schematically show the pressure relief valve 102.

The groove 120 is beneficial to ensuring normal use of the pressure release valve 102, and the groove 120 acts as an exhaust channel, so that safety and service life of the battery pack are guaranteed.

As shown in fig. 1 and 2, the case 20 further includes an upper cover 40 disposed opposite the bottom guard plate 30, and a second cooling passage 90 is integrated in the upper cover 40. The second cooling channel 90 can realize the cooling of the bottom of the battery cell 10, the second cooling channel 90 and the first cooling channel 70 are matched, and the battery cell 10 can be cooled from the bottom and the top of the battery cell respectively, so that the cooling effect is better, and the service life of the battery pack is more beneficial to being ensured. In addition, the second cooling channel 90 is integrated on the upper cover 40, and a carrier for arranging the second cooling channel 90 is not required to be additionally arranged, so that the integral structure of the battery pack is simplified, and the design and the cost are reduced.

As will be appreciated with reference to fig. 1 and 2, the second cooling passage 90 is realized by providing a runner hole in the upper cover 40.

Further, as shown in fig. 1, the battery pack further includes a second heat conductive member 80 disposed between the upper cover 40 and the battery cell 10. The second heat conducting member 80 is disposed such that a certain gap is formed between the upper cover 40 and the battery cell 10, which is more conducive to heat dissipation, and further is more conducive to cooling the battery cell 10, thereby being beneficial to ensuring the service life of the battery pack.

It should be noted that, in the present embodiment, since a structure similar to the insulating bracket 100 described above is not required between the bottom of the battery cell 10 and the upper cover 40, the second heat conducting member 80 may be formed into a unitary plate structure, and the connection between the second heat conducting member 80 and the bottom of the battery cell 10 is more convenient than a plurality of scattered structures.

Similar to the first heat conductive member 60, the second heat conductive member 80 may be provided as a heat conductive adhesive or a heat conductive pad, and in this embodiment, the second heat conductive member 80 is preferably adhesively connected between the bottom of the battery cell 10 and the upper cover 40.

The cooling process of the battery pack is briefly described below:

(1) When the top of the battery cell 10 and the confluence sheet 50 need to be cooled, cooling liquid is introduced from the water inlet joint 702, so that water flows out from the water return joint 703 after flowing through each sub-channel 701 of the first cooling channel 70;

(2) When it is desired to cool the bottom of the cell 10, the cooling fluid is correspondingly caused to flow through the second cooling channel 90.

The battery pack of the present application can reliably realize cooling of the top of the battery cell 10, the bus bar 50, and the bottom of the battery cell 10 by the dual functions of the first cooling passage 70 and the second cooling passage. And, the cooling of battery package need not to add comparatively complicated connecting tube way in the inside of the box 20 of battery package, is favorable to simplifying the structure of battery package, simultaneously, also can reduce the weeping or prevent taking place the weeping.

While specific embodiments of the utility model have been described above, it will be appreciated by those skilled in the art that this is by way of example only, and the scope of the utility model is defined by the appended claims. Various changes and modifications to these embodiments may be made by those skilled in the art without departing from the principles and spirit of the utility model, but such changes and modifications fall within the scope of the utility model.

Claims

1. A battery pack, the battery pack comprising:

an avoidance window is formed in the insulating support, and the confluence sheet is accommodated in the avoidance window;

the insulating piece is arranged between the bottom guard plate and the bus plate; a kind of electronic device with high-pressure air-conditioning system

2. The battery pack of claim 1, further comprising a first thermally conductive member disposed between the bus bar and the insulating member.

3. The battery pack according to claim 2, wherein the first heat conductive member has a size not smaller than a corresponding size of the bus bar along a length direction of the bus bar;

4. The battery pack according to claim 2, wherein the insulating member is of an integral structure or comprises a plurality of insulating units which are arranged in a split manner, and the insulating units are arranged in one-to-one correspondence with the bus plates of the battery cells;

5. The battery pack of claim 2, wherein a plurality of said battery cells are arranged side-by-side with each row of said bus bars being arranged along the length of the battery pack, said first cooling channel comprising a plurality of side-by-side sub-channels extending along the length of said battery pack;

6. The battery pack of claim 2, wherein the first thermally conductive member is a thermally conductive adhesive or a thermally conductive pad;

and/or the first heat conduction piece is connected with the bottom guard plate in an adhesive mode.

7. The battery pack of claim 2, wherein the first cooling channel is integrated on the bottom guard plate, the top of the bottom guard plate further provided with a groove;

8. The battery pack of claim 1, wherein the case further comprises an upper cover disposed opposite the bottom guard plate, the upper cover having a second cooling channel integrated therein.

9. The battery pack of claim 8, further comprising a second thermally conductive member disposed between the upper cover and the electrical cell.

10. The battery pack of any one of claims 1-9, wherein a side wall of the case is provided with a water inlet joint and a water return joint in communication with the first cooling passage.