Battery

BACKGROUND OF THE INVENTION

FIELD OF INVENTION

0001The present invention relates to a battery, and more particularly, to a battery having a coolant passage for better cooling efficiency.

DESCRIPTION OF RELATED ART

0002In recent years, growing environmental consciousness has led to a movement to shift the power sources of vehicles from engines using fossil fuels to motors using electrical energy.

0003The technologies of batteries and cells, which are the power sources of the motors, have also been developed and advanced rapidly.

0004A battery to be mounted on a hybrid vehicle is required to be compact and lightweight as well as capable of charging and discharging high power frequently. The battery is also required to have excellent shock-proofness and heat radiation characteristics.

0005A battery disclosed in the <patcit id="pcit0001" dnum="JP2000195480A"><text>Japanese Patent Application Laid-open Publication No. 2000-195480</text></patcit> is one in which a plurality of flat cells are arranged in an outer frame member. Given spaces are provided between each cell by interposing spacers therebetween, so that each cell has good heat radiation characteristics, thus improving the cycle characteristics and the rate characteristics (discharge characteristics) of the battery.

0006The use of a flat unit cell in the above-mentioned battery makes energy density higher as compared with a battery composed of non-flat cells (for example, cells in a cylindrical or a rectangular shape), contributing to downsizing the battery. This means that the battery of flat unit cells will be suited for the battery mounted on vehicles because of its compactness and high energy density.

0007<patcit id="pcit0002" dnum="US6479185B1"><text>US 6,479,185 B1</text></patcit> discloses a module for retaining and cooling a group of electrochemical cells, which may include stacking of two decks of modules. Air as a cooling medium is introduced through each module to reduce cell temperatures.

0008<patcit id="pcit0003" dnum="US20020028375A1"><text>US 2002/0028375 A1</text></patcit> relates to a method for cooling assembled rechargeable batteries comprising an array of modular batteries which are banded by means of aluminium plates and iron bands.

SUMMARY OF THE INVENTION

0009However, it is difficult for the above-mentioned battery to be further downsized and to have an increased energy density, since the battery requires the spaces between the unit cells thereof for keeping its radiation characteristic. The necessity of the spaces makes it difficult to keep the stiffness of the battery and improve the shock-proofness thereof. One solution for this problem would be flat unit cells stacked on one another in their thickness direction with heat sinks inserted between certain layers. However, the heat radiation of the battery in this configuration relies on the indirect heat transfer through the stacked unit cells to the heat sinks, resulting in an uneven three-dimensional temperature distribution in the battery. Particularly in a flat unit cell, an excessively uneven temperature distribution leads to decrease in lifetime of the cell.

0010The present invention has been made in the light of the problems and an object of the present invention is to provide a compact and lightweight high-energy density battery which is excellent in heat radiation and shock-proofness.

0011Said objective is achieved by a battery according to claim 1 and a method of claim 10.

BRIEF DESCRIPTION OF THE DRAWINGS

0012The invention will now be described with reference to the accompanying drawings wherein: <ul id="ul0001" list-style="none" compact="compact"><li><figref idref="f0001">FIG. 1</figref> is a perspective view showing the appearance of a battery related to the present invention;</li><li><figref idref="f0002">FIG. 2</figref> shows the appearance of a cooling system for cooling the battery shown in <figref idref="f0001">FIG. 1</figref>;</li><li><figref idref="f0003">FIG. 3</figref> shows the structure of a frame member in a first embodiment of the present invention;</li><li><figref idref="f0004">FIG. 4</figref> shows the structure of the frame member in the first embodiment;</li><li><figref idref="f0005">FIG. 5</figref> shows the structure of the frame member in the first embodiment;</li><li><figref idref="f0006">FIG. 6</figref> shows the structure of the frame member in the first embodiment;</li><li><figref idref="f0007">FIG. 7</figref> shows the structure of another example of a frame member in the first embodiment;</li><li><figref idref="f0008">FIG. 8</figref> shows the structure of the frame member of <figref idref="f0007">FIG. 7</figref>;</li><li><figref idref="f0009">FIG. 9</figref> shows the structure of a frame member in a second embodiment of the present invention;</li><li><figref idref="f0010">FIG. 10</figref> shows the structure of the frame member in the second embodiment;</li><li><figref idref="f0011">FIG. 11</figref> shows the structure of the frame member in the second embodiment;</li><li><figref idref="f0012">FIG. 12</figref> shows the structure of a frame member in a third embodiment of the present invention not covered by the present invention.</li><li><figref idref="f0013">FIG. 13</figref> shows the structure of the frame member in the third embodiment;</li><li><figref idref="f0014">FIG. 14</figref> shows the structure of the frame member in the third embodiment;</li><li><figref idref="f0015">FIG. 15</figref> shows the structure of a frame member in a fourth embodiment of the present invention;</li><li><figref idref="f0016">FIG. 16</figref> shows the structure of the frame member in the fourth embodiment;</li><li><figref idref="f0017">FIG. 17</figref> shows the structure of the frame member in the fourth embodiment;</li><li><figref idref="f0018">FIG. 18A</figref> shows a profile of air flows in the battery;</li><li><figref idref="f0018">FIG. 18B</figref> shows another profile of air flows in the battery;</li><li><figref idref="f0018">FIG. 18C</figref> shows another profile of air flows in the battery;</li><li><figref idref="f0018">FIG. 18D</figref> shows another profile of air flows in the battery;</li><li><figref idref="f0019">FIG. 19A</figref> is a graph showing the relationship between positions of unit cells in the battery and air flow velocity;</li><li><figref idref="f0020">FIG. 19B</figref> is a graph showing the relationship between positions of the unit cells in the battery and temperature increase thereof;</li><li><figref idref="f0021">FIG. 20</figref> shows the structure of a frame member and a heat sink in a fifth embodiment of the present invention;</li><li><figref idref="f0022">FIG. 21</figref> shows the structure of the frame member and the heat sink in the fifth embodiment;</li><li><figref idref="f0022">FIG. 22A</figref> is a sectional view taken along line A-A in <figref idref="f0022">FIG. 21</figref>;</li><li><figref idref="f0022">FIG. 22B</figref> is a sectional view taken along line B-B in <figref idref="f0022">FIG. 21</figref>;</li><li><figref idref="f0022">FIG. 22C</figref> is a sectional view taken along line C-C in <figref idref="f0022">FIG. 21</figref>;</li><li><figref idref="f0023">FIG. 23</figref> shows the structure of the frame member and the heat sink in the fifth embodiment;</li></ul>

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

0013Embodiments of the present invention will be explained below with reference to the drawings, wherein like members are designated by like reference characters.

0014The battery in each embodiment basically comprises a cell unit consisting of twenty-four (24) unit-cell layers and heat sinks pressing the cell unit from outside in the direction in which the unit-cell layers are stacked (i.e. , in the thickness direction of the layer) to hold the cell unit. The cell unit also has intermediate heat sinks inserted every six unit-cell layers. Each of the unit-cell layers comprises a frame member and four flat unit cells (hereinafter referred to as unit cell) which are held with and housed in the frame member with those arrayed in the longitudinal direction of the battery.

0015The cell unit has ninety-six (96) unit cells in total. All unit cells are connected in series by electrical connecting means provided on the frame members and heat sinks.

[First Embodiment]

0016As shown in <figref idref="f0001">FIG. 1</figref>, a battery 100 related to this application is structured in such a manner that a cell unit 200 composed of a plurality of plate-shaped frame members 210 stacked in their thickness direction is put between heat sinks 300 and 340, and both end faces of the cell unit is pressed in the stacking direction to hold it integrally.

0017Each frame member 210 is formed to have thereon four holding sections, not shown, for holding four unit cells in parallel arrangement therein. The cell unit 200 has a stack of twenty-four frame members 210 and three intermediate heat sinks 310, 320, and 330 inserted every six layers of the frame members. The cell unit 200 thus has ninety-six (96) unit cells in total, with twenty-four unit cells in total between each two heat sinks.

0018Both sides of each frame member 210 (here, the side of the frame member refers to a side constituting the lateral side of the cell unit 200 when the unit-cell layers are stacked.) opposite to each other are formed to have a coolant inlet 230 for introducing air as a coolant into the cell unit 200 and a coolant outlet 250 for discharging the coolant circulated through the cell unit 200. In the cell unit 200, a coolant passage having the inlet 230 and the outlet 250 at both upstream and downstream ends thereof is defined by the inner surface of the frame member 210 and the outer surface of each unit cell housed in the frame member 210. That is, the air introduced from the inlet 230 circulates inside the unit through defined spaces between the frame members 210 and unit cells 200 and then discharged from the outlet 250.

0019The heat sinks 300 and 340 are fixed by fastening six pressing units connected thereto with nuts 400A to 400F. The pressing unit has a shaft attached to both ends of an extension coil spring with the nuts 400A and 400F. The provision of the pressing units between the heat sinks 300 and 340 gives all unit cells in the cell unit 200 a proper surface pressure in the stacking direction.

0020In the heat sinks 300 and 340 and the intermediate heat sinks 310, 320 and 330 are provided with a plurality of coolant passages 300A, 340A, 310A, 320A, and 330A therein through which the coolant flows from one lateral side to another lateral side thereof. (Here, the lateral side of the heat sink refers to a side constituting the lateral side of the cell unit 200 when the unit-cell layers are stacked.)

0021The battery 100 is cooled with a vehicle-mounted cooling system 500, shown in <figref idref="f0002">FIG. 2</figref>, when mounted on a vehicle.

0022The cooling system 500 is equipped with a housing 600 for housing the battery 100, a coolant introducing duct 700 for introducing air into the housing 600, and a coolant discharging duct 800 for discharging air from the housing 600.

0023The battery 100 is set in the housing 600 so that the inlets 230 thereof are directed upstream and the outlets 250 thereof downstream. More specifically, the inlets 230 of the battery 100 are oriented toward the coolant introducing duct 700 and the outlets 250 of the battery 100 toward the coolant discharging duct 800. A single or a plurality of batteries 100 are arranged in the housing 600.

0024A ventilator fan 850 is provided on the coolant discharging duct 800 on the side of the housing 600. The ventilator fan 850 is equipped with a sensor for detecting temperature of air discharged from the housing 600. The rotating speed of the ventilator fan 850 (ventilation flow rate) is controlled by a controller (not shown) according to a temperature detected by the sensor.

0025In the battery 100 arranged in the housing 600, the air introduced from the inlet 230 is circulated through the coolant passage in the battery 100 and discharged from the outlet 250, cooling the unit cells in direct contact therewith. The air flowing through the coolant passages 300A, 340A, 310A, 320A and 330A of the heat sinks 300 and 340 and the intermediate heat sinks 310, 320, and 330 also cools the unit cells indirectly.

0026As shown in <figref idref="f0003">FIG. 3</figref>, the frame member 210 is composed of a rectangular outer frame portion 212 and three cross member portions 214A, 214B, and 214C crossing over to two opposing sides of the outer frame portion 212 in the shape of a ladder. A U-shaped notch (opening or groove) 216A is formed on one side of the outer frame portion 212, a U-shaped notch 216B on the cross member portion 214A, a U-shaped notch 216C on the cross member portion 214B, a U-shaped notch 216D on the cross member portion 214C, and a U-shaped notch 216E on the other side of the outer frame portion 212. The frame member may be integrally formed, or, it may be formed by assembling two components symmetric with respect to a center line of the direction in which the unit cells are arranged.

0027Stacking and bringing the frame members 210 into intimate contact with one another causes the notch 216A to function as a coolant inlet and the notch 216E as a coolant outlet. The notches 216B, 216C and 216D function as a part of a coolant passage.

0028Both notches 216A and 216E are formed to be different in size from each other so that the cross-sectional area (an opening area) of the notch 216A functioning as the coolant inlet in the coolant flow direction is larger than that of the notch 216E functioning as the coolant outlet in the coolant flow direction.

0029The notches 216B, 216C and 216D functioning as a part of the coolant passage gradually decrease in cross-sectional area in the coolant flow direction from the upstream to downstream in the coolant flow direction so that the coolant flowing therethrough can be gradually increased in flow velocity from the upstream to downstream in the coolant flow direction. That is, the notch 216B is formed to be larger in cross-sectional area than the notch 216C, and the notch 216C also larger than the notch 216D; the notches 216B, 216C and 216D are different in cross-sectional area from one another. In this embodiment, all notches 216A to 216E are formed at center portions in the width direction of the frame member 210. The notch 216A is the largest in cross-sectional area than the others. The notches 216B, 216C, 216D, and 216E are so formed to be reduced in cross-sectional area in that order.

0030Unit cells 220A, 220B, 220C and 220D are lithium-ion cells each having a power generating element covered with a laminate film, and the power-generating portion is formed in a stool shape having a trapezoidal cross section as shown in the figure. The unit cells 220A, 220B, 220C and 220D are so arranged that their stool-shaped portions are inserted upward from under the frame member into compartment spaces defined by the outer frame portion 212 and the cross member portions 214A, 214B and 214C of the frame member 210 as shown in <figref idref="f0004">FIG. 4</figref>. Thereby the unit cells 220A, 220B, 220C and 220D are held flat with the outer frame portion 212 and the cross member portions 214A, 214B and 214C of the frame member 210 respectively.

0031The frame member 210 is formed to be slightly thicker than the unit cells 220 so that all unit cells 220 can be subjected to a predetermined surface pressure and all frame members 210 can be compressed with some deformation.

0032In the above description, a part of the coolant passage is formed by the notches 216B, 216C, and 216D. In addition, a groove 210A is formed in the outer frame portion 212 and the cross member portions 214A, 214B and 214C of the frame member 210 so as to circulate air on the surface thereof where the peripheral flange portions 222A, 222B, 222C and 222D of the unit cells 220A, 220B, 220C and 220D come into contact therewith, as shown in <figref idref="f0004">FIG. 4</figref>. The circulation of air through the groove will remove heat of the unit cells 220A, 220B, 220C and 220D through the peripheral flange portions 222A, 222B, 222C and 222D.

0033Six frame members 210, each holding the unit cells 220A, 220B, 220C and 220D in the abovementioned manner, are stacked on one another as illustrated in <figref idref="f0005">FIGS. 5</figref> and <figref idref="f0008">8</figref>. This stack arrangement brings the unit cells into direct contact or coherence with each other, and the frame members into direct contact with each other in the stacking direction. A coolant passage from the inlet 230 to outlet 250 is formed by interstices or spaces defined between the frame members 210 and the unit cells 220, the grooves 210A formed in the frame member 210, and the notches 216B to 216D.

0034The stack so built in the above manner is further stacked while inserting the intermediate heat sinks 310, 320, and 330 therebetween as shown in <figref idref="f0001">FIG. 1</figref>. The stack is placed between the heat sinks 300 and 340 and fastened with the nuts 400A to 400F to form the battery. The operation of the ventilator fan 850 of the cooling system 500 with the battery 100 is set in will produce the following air flow within the frame members 210 of the battery 100.

0035Cohesion or close contact of the frame members 210 with one another in the stacking direction permits air to be introduced only from the inlet 230 shown in <figref idref="f0005">FIGS. 5</figref> and <figref idref="f0008">8</figref>. The introduced air reaches the notch 216B of the cross member portion 214A through the interstices between the outer surface of the unit cell 220A and the inner surface of the frame member 210, and through the groove 210A of the frame member 210 formed in a position where the frame member comes into contact with the peripheral flange portion of the unit cell 220A. The air introduced from the notch 216B then reaches the notch 216C of the cross member portion 214B through the interstices between the outer surface of the unit cell 220B and the inner surface of the frame member 210, and through the groove 210A of the frame member 210 formed in a position where the frame member comes into contact with the peripheral flange portion of the unit cell 220B. The air introduced from the notch 216C then reaches the notch 216D of the cross member portion 214C through the interstices between the outer surface of the unit cell 220C and the inner surface of the frame member 210 , and through the groove 210A of the frame member 210 formed in a position where the frame member comes into contact with the peripheral flange portion of the unit cell 220C. Finally the air introduced from the notch 216D is discharged from the outlet 250 through the interstices between the outer surface of the unit cell 220D and the inner surface of the frame member 210 and the groove 210A of the frame member 210 formed in a position where the member comes into contact with the peripheral flange portion of the unit cell 220C. In this manner the unit cells 220A to 220D are directly cooled by the air flowing on the outer surfaces thereof and the peripheral flange portions thereof.

0036The notch 216A forming the inlet 230, the notches 216B to 216D forming the coolant passage, and the notch 216E forming the outlet 250 are formed to be gradually reduced in cross-sectional area from the inlet 230 to the outlet 250, while the air velocity gradually increases as air flows from the inlet 230 to the outlet 250. This allows the air introduced from the inlet 230 to flow through spaces defined between the inner surface of the frame member 210 and the outer surface of each unit cell 220, to converge at the center portion of each cross member portion to increase its velocity toward the downstream, and to be discharged from the outlet 250. Although the air introduced from the inlet 230 gradually increases in temperature as the air flows downstream, the air gradually increases in flow velocity toward the outlet 250. This makes a cooling efficiency even at the upstream and at the downstream, equally cooling all unit cells 220A to 220D wherever they are. The frame member 210 may be formed so that the interstices forming a part of the coolant passage between the unit cells 220A, 220B, 220C and 220D and the frame member 210 are gradually decreased in width or size of flow passage toward the downstream from the upstream.

0037As shown in another example of the first embodiment in <figref idref="f0007">FIGS. 7</figref> and <figref idref="f0008">8</figref>, the inlet 230 and outlet 250 may be differentiated in cross-sectional area in the stacking direction of the frame member 210 according to a stack level (upward and downward position) thereof, in view of a cooling efficiency at unit cells 220 which are far from the heat sinks 300 and 340 or the intermediate heat sinks 310, 320 and 330. In the present embodiment, the inlet 230 gradually increases in cross-sectional area from the one end of stack (bottom side) of the frame member 210 to the intermediate position, and gradually decreases in cross-sectional area from the intermediate position to the other end of the stack (upper side) . On the other hand, the outlet 250 gradually decreases in cross-sectional area from one end of stack (bottom side) of the frame member 210 to the intermediate position, and gradually increases in cross-sectional area from the intermediate position to the other end of the stack (upper side). This achieves a uniform three-dimensional distribution in temperature all over the unit cells 100, since the unit cells 220 at a position far from the heat sinks (where heat of the cells is not easily removed thereby) can have an increased air flow rate with an increased air flow velocity as compared with those near the heat sinks (at a position where heat of the cells is easily removed thereby).

0038In the present embodiment, air as a coolant is exemplified, but it is not limited to this. Inactive gas such as nitrogen and liquid such as oil may be used according to the required cooling capacity.

[Second Embodiment]

0039The configuration of the frame member related to the second embodiment is described according to <figref idref="f0009 f0010 f0011">FIGS. 9 to 11</figref>.

0040Similarly to the first embodiment, the frame member 210 is composed of a rectangular outer frame portion 212 and three cross member portions 214A, 214B, and 214C crossing over to two opposing sides of the outer frame portion 212 in the shape of a ladder. U-shaped notches (openings or grooves) 216A1 and 216A2 are formed on one side of the outer frame portion 212 at both ends thereof, U-shaped notches 216B1 and 216B2 on the cross member portion 214A at both ends thereof, U-shaped notches 216C1 and 216C2 on the cross member portion 214B at both ends thereof, U-shaped notches 216D1 and 216D2 on the cross member portion 214C at both ends thereof, and U-shaped notches 216E1 and 216E2 on the other side of the outer frame portion 212 at both ends thereof. Further, there is formed in the frame member 210 a groove 210A similar to that of the first embodiment.

0041Stacking and bringing the frame members 210 into intimate contact with one another causes the notches 216A1 and 216A2 to function as coolant inlets 230 and the notches 216E1 and 216E2 as coolant outlets 250. Each of the notches 216B1, 216B2 , 216C1, 216C2, 216D1 and 216D2 functions as a part of a coolant passage.

0042The notches 216A1 and 216A2 functioning as the inlet 230 in the coolant circulation direction are the same in cross-sectional area, the notches 216B1 and 216B2, 216C1 and 216C2, 216D1 and 216D2 composing the coolant passage are also the same in cross-sectional area respectively, and the notches 216E1 and 216E2 functioning as the outlet 250 are the same in cross-sectional area as well.

0043In the present embodiment as with the first embodiment the notch 216A1 and 216A2 are the largest in cross section than the others at the both ends of the frame member 210 in the longitudinal direction. The notches 216B1 and 216B2, 216C1 and 216C2, 216D1 and 216D2, and 216E1 and 216E2 are formed to be gradually reduced in cross section in that order.

0044The unit cells 220A, 220B, 220C and 220D are so arranged that their stool-shaped portions are inserted upward from under the frame member into compartment spaces defined by the outer frame portion 212 and the cross member portions 214A, 214B and 214C of the frame member 210 as shown in <figref idref="f0010">FIG. 10</figref>.

0045Six frame members 210, each holding the unit cells 220A, 220B, 220C and 220D in the abovementioned manner, are stacked on one another as illustrated in <figref idref="f0011">FIG. 11</figref>. This stack arrangement brings the unit cells into direct contact or coherence with each other, and the frame members into direct contact with each other in the stacking direction. A coolant passage from the inlet 230 to outlet 250 is formed by interstices or spaces defined between the frame members 210 and the unit cells 220, the grooves 210A formed in the frame member 210, and the notches 216B1 to 216D2.

0046The stack so built in the above manner is further stacked while inserting the intermediate heat sinks 310, 320, and 330 therebetween as shown in <figref idref="f0001">FIG. 1</figref>. The stack is placed between the heat sinks 300 and 340 and fastened with the nuts 400A to 400F to form the battery. The operation of the ventilator fan 850 of the cooling system 500 with the battery 100 is set in will produce the following air flow within the frame members 210 of the battery 100.

0047Cohesion or close contact of the frame members 210 with one another in the stacking direction permits air to be introduced only from the inlets 230 shown in <figref idref="f0011">FIG. 11</figref>. The introduced air reaches the notches 216B1 and 216B2 of the cross member portion 214A through the interstices between the outer surface of the unit cell 220A and the inner surface of the frame member 210, and through the groove 210A of the frame member 210 formed in a position where the frame member comes into contact with the peripheral flange portion of the unit cell 220A. The air introduced from the notches 216B1 and 216B2 then reaches the notches 216C1 and 216C2 of the cross member portion 214B through the interstices between the outer surface of the unit cell 220B and the inner surface of the frame member 210, and through the groove 210A of the frame member 210 formed in a position where the frame member comes into contact with the peripheral flange portion of the unit cell 220B. The air introduced from the notches 216C1 and 216C2 then reaches the notches 216D1 an 216D2 of the cross member portion 214C through the interstices between the outer surface of the unit cell 220C and the inner surface of the frame member 210, and through the groove 210A of the frame member 210 formed in a position where the frame member comes into contact with the peripheral flange portion of the unit cell 220C. Finally the air introduced from the notches 216D1 an 216D2 is discharged from the outlet 250 through the interstices between the outer surface of the unit cell 220D and the inner surface of the frame member 210 and the groove 210A of the frame member 210 formed in a position where the member comes into contact with the peripheral flange portion of the unit cell 220C. In this manner the unit cells 220A to 220D are directly cooled by the air flowing on the outer surfaces thereof and the peripheral flange portions thereof.

0048The notches 216A1 and 216A2 forming the inlet 230, the notches 216B1 to 216D2 each forming a part of the coolant passage, and the notches 216E1 and 216E2 forming the outlet 250 are formed to be gradually reduced in cross-sectional area from the inlet 230 to the outlet 250, while the air velocity gradually increases as air flows from the inlet 230 to the outlet 250. This allows the air introduced from the inlet 230 to flow through spaces defined between the inner surface of the frame member 210 and the outer surface of each unit cell 220, to increase its velocity when passing the cross member portions 214 toward the downstream, and to be discharged from the outlet 250. Although the air introduced from the inlet 230 gradually increases in temperature as the air flows downstream, the air gradually increases in flow velocity toward the outlet 250. This makes a cooling efficiency even at the upstream and at the downstream, equally cooling all unit cells 220A to 220D wherever they are.

[Third Embodiment]

0049The configuration of the frame member related to the third embodiment not belonging to the present invention is described according to <figref idref="f0012 f0013 f0014">FIGS. 12 to 14</figref>.

0050As shown in <figref idref="f0012">FIG. 12</figref>, the frame member 210, as with the first embodiment, is composed of a rectangular outer frame portion 212 and three cross member portions 214A, 214B, and 214C crossing over to two opposing sides of the outer frame portion 212 in the shape of a ladder. Notches 216A to 216H are formed at the front side of the outer frame portion 212 along the cross member portions 214A, 214B, and 214C. The notches 216I to 216P are formed at opposing positions of the notches 216A to 216H on the back side. As with the first embodiment, the groove 210A is formed in the frame member 210.

0051Stacking and bringing the frame members 210 into intimate contact with one another causes the notches 216A to 216H to function as coolant inlets and the notches 216I to 216P as coolant outlets. The size of the notches is made constant along the direction of the coolant flow in the same layer.

0052The unit cells 220A, 220B, 220C and 220D are so arranged that their stool-shaped portions are inserted upward from under the frame member into compartment spaces defined by the outer frame portion 212 and the cross member portions 214A, 214B and 214C of the frame member 210 as shown in <figref idref="f0013">FIG. 13</figref>.

0053Six frame members 210, each holding the unit cells 220A, 220B, 220C and 220D in the abovementioned manner, are stacked on one another as illustrated in <figref idref="f0014">FIG. 14</figref>. This stack arrangement brings the unit cells into direct contact or coherence with each other, and the frame members into direct contact with each other in the stacking direction. A coolant passage from the inlet 230 to outlet 250 is formed by interstices or spaces defined between the frame members 210 and the unit cells 220, the grooves 210A formed in the frame member 210, and the notches 216B to 216D.

0054The stack so built in the above manner is further stacked while inserting the intermediate heat sinks 310, 320, and 330 therebetween as shown in <figref idref="f0001">FIG. 1</figref>. The stack is placed between the heat sinks 300 and 340 and fastened with the nuts 400A to 400F to form the battery. The operation of the ventilator fan 850 of the cooling system 500 with the battery 100 is set in will produce the following air flow within the frame members 210 of the battery 100.

0055In the present embodiment, the battery 100 in the housing of the cooling system 500 is different by 90 degrees in arrangement direction from that in the first and second embodiments. This is because air needs to be circulated widthwise (i.e., in the vertical direction of the figure) in the present embodiment, whereas in the battery 100 in the first and second embodiments air is circulated in the longitudinal direction (in the horizontal direction of the figure) of the battery.

0056The frame members 210 cohere with one another in the stacking direction, causing air to be introduced only from the inlets 230 shown in <figref idref="f0014">FIG 14</figref>. The introduced air flows in parallel through the interstices between the unit cells 220A to 220D and the frame member 210 and the groove 210A of the frame member 210 formed at a place where the frame member touches the peripheral flange portion of the unit cells 220A to 220D to be discharged from the outlet 250. As a result, the unit cells 220A to 220D are directly cooled chiefly by air flowing on the surfaces of the side and the peripheral flange portions thereof.

0057In the present embodiment the air introduced from the inlet 230 is the same in velocity and that flowing over the unit cells 220A to 220D is also the same in temperature and quantity, allowing all unit cells to be cooled uniformly.

0058In the present embodiment also, as is the case with the first and second embodiments, the inlet 230 may be increased in cross-sectional area than the outlet 250.

[Fourth Embodiment]

0059The configuration of the frame member related to the fourth embodiment is described according to <figref idref="f0015 f0016 f0017">FIGS. 15 to 17</figref>.

0060As shown in <figref idref="f0015">FIG. 15</figref>, the frame member 210 is composed of a rectangular outer frame portion 212 and three cross member portions 214A, 214B, and 214C crossing over to two opposing sides of the outer frame portion 212 in the shape of a ladder. A U-shaped notch (opening or groove) 216A is formed on one side of the outer frame portion 212, a U-shaped notch 216B on the cross member portion 214A, a U-shaped notch 216C on the cross member portion 214B, a U-shaped notch 216D on the cross member portion 214C, and a U-shaped notch 216E on the other side of the outer frame portion 212.

0061The notches 216A to 216E in the first embodiment are formed at the center in the longitudinal direction of the frame member 210. In the present embodiment, however, the notches 216A to 216E are displaced from the center in position and placed along the diagonal of the frame member 210. The groove 210A is provided in the frame member 210 as with the first embodiment.

0062Stacking and bringing the frame members 210 into intimate contact with one another causes the notch 216A to function as a coolant inlet and the notch 216E as a coolant outlet. The notches 216B, 216C and 216D function as a part of a coolant passage.

0063Both notches 216A and 216E are formed to be different in size from each other so that the cross-sectional area (an opening area) of the notch 216A functioning as the coolant inlet in the coolant flow direction is larger than that of the notch 216E functioning as the coolant outlet in the coolant flow direction.

0064The notches 216B, 216C and 216D functioning as a part of the coolant passage gradually decrease in cross-sectional area in the coolant flow direction from the upstream to downstream in the coolant flow direction so that the coolant flowing therethrough can be gradually increased in flow velocity from the upstream to downstream in the coolant flow direction.

0065The unit cells 220A, 220B, 220C and 220D are so arranged that their stool-shaped portions are inserted upward from under the frame member into compartment spaces defined by the outer frame portion 212 and the cross member portions 214A, 214B and 214C of the frame member 210 as shown in <figref idref="f0016">FIG. 16</figref>.

0066Six frame members 210, each holding the unit cells 220A, 220B, 220C and 220D in the abovementioned manner, are stacked on one another as illustrated in <figref idref="f0017">FIG. 17</figref>. This stack arrangement brings the unit cells into direct contact or coherence with each other, and the frame members into direct contact with each other in the stacking direction. A coolant passage from the inlet 230 to outlet 250 is formed by interstices or spaces defined between the frame members 210 and the unit cells 220, the grooves 210A formed in the frame member 210, and the notches 216B to 216D.

0067The stack so built in the above manner is further stacked while inserting the intermediate heat sinks 310, 320, and 330 therebetween as shown in <figref idref="f0001">FIG. 1</figref>. The stack is placed between the heat sinks 300 and 340 and fastened with the nuts 400A to 400F to form the battery. The operation of the ventilator fan 850 of the cooling system 500 with the battery 100 is set in will produce the following air flow within the frame members 210 of the battery 100.

0068Cohesion or close contact of the frame members 210 with one another in the stacking direction permits air to be introduced only from the inlet 230 shown in <figref idref="f0017">FIG. 17</figref>. The introduced air reaches the notch 216B of the cross member portion 214A through the interstices between the outer surface of the unit cell 220A and the inner surface of the frame member 210, and through the groove 210A of the frame member 210 formed in a position where the frame member comes into contact with the peripheral flange portion of the unit cell 220A. The air introduced from the notch 216B then reaches the notch 216C of the cross member portion 214B through the interstices between the outer surface of the unit cell 220B and the inner surface of the frame member 210, and through the groove 210A of the frame member 210 formed in a position where the frame member comes into contact with the peripheral flange portion of the unit cell 220B. The air introduced from the notch 216C then reaches the notch 216D of the cross member portion 214C through the interstices between the outer surface of the unit cell 220C and the inner surface of the frame member 210, and through the groove 210A of the frame member 210 formed in a position where the frame member comes into contact with the peripheral flange portion of the unit cell 220C. Finally the air introduced from the notch 216D is discharged from the outlet 250 through the interstices between the outer surface of the unit cell 220D and the inner surface of the frame member 210 and the groove 210A of the frame member 210 formed in a position where the member comes into contact with the peripheral flange portion of the unit cell 220C. In this manner the unit cells 220A to 220D are directly cooled by the air flowing on the outer surfaces thereof and the peripheral flange portions thereof.

0069The notch 216A forming the inlet 230, the notches 216B to 216D forming the coolant passage, and the notch 216E forming the outlet 250 are formed to be gradually reduced in cross-sectional area from the inlet 230 to the outlet 250, while the air velocity gradually increases as air flows from the inlet 230 to the outlet 250.

0070This permits the air introduced from the inlet 230 to flow along the interstices between the inner surface of the frame member 210 and the periphery of each unit cell 220 and gradually increase in air velocity toward the downstream to be discharged from the outlet 250. In the present embodiment, the air flows obliquely from the inlet 230 toward the outlet 250, touching the four sides on the periphery of each unit cell 220, which further increases the cooling efficiency.

0071Although the air introduced from the inlet 230 gradually increases in temperature as the air flows downstream, the air gradually increases in flow velocity toward the outlet 250. This makes a cooling efficiency even at the upstream and at the downstream, equally cooling all unit cells 220A to 220D wherever they are.

[Evaluation of the embodiments]

0072<figref idref="f0018">FIGS. 18A to 18D</figref> show how air circulates in the battery 100. <figref idref="f0019">FIG. 19A</figref> and <figref idref="f0020">19B</figref> show the relationship between the positions of unit cells composing the battery 100 and cooling air velocity and between the positions of unit cells and temperature increase of unit cells respectively.

0073As illustrated in <figref idref="f0018">FIG. 18A</figref> the air follows the same route as that in the first embodiment. That is, the air introduced into the room of the unit cell 220A from the inlet 230 splits outward in the width direction W of the battery 100, flows along the periphery of the unit cell 220A, and converges at the center of the width direction W of the battery 100 to then increase in velocity, and flows into the room of the adjacent unit cell 220B. The same is repeated for the unit cells 220B to 220D to discharge the air from the outlet 250.

0074As illustrated in <figref idref="f0018">FIG. 18B</figref> the air follows the same route as that in the second embodiment. That is, the air introduced into the room of the unit cell 220A from the inlet 230 flows along two outsides of the battery 100 in the width direction W at the periphery of the unit cell 220A, and increases in velocity when moving from the room of the unit cell 220A to that of the adjacent unit cell 220B . The same is repeated for the unit cells 220B to 220D to discharge the air from the outlet 250.

0075As illustrated in <figref idref="f0018">FIG. 18C</figref> the air follows the same route as that in the third embodiment. That is, the air introduced into the rooms of the unit cells 220A to 220D from the inlets 230 arranged in parallel on the outer sides in the width direction W of the battery 100 flows along two sides parallel with the width direction W of the battery 100 at the periphery of the unit cells 220A to 220D, and is discharged from the outlet 250 arranged in parallel on the opposite side in the width direction W of the battery 100.

0076As illustrated in <figref idref="f0018">FIG. 18D</figref> the air follows the same route as that in the fourth embodiment. That is, the air introduced into the room of the unit cell 220A from the inlet 230 splits outward in the width direction W of the battery 100, flows along the periphery of the unit cell 220A, and then flows together to increase in air velocity, flowing into the room of the adjacent unit cell 220B . The air will part and meet repeatedly as with the first embodiment. When the air moves from the room of one unit cell to that of an adjacent unit cell, it flows together at a point along the diagonal in each unit-cell layer of the battery 100. Consequently, as compared with the first embodiment is further suppressed the loss in pressure caused when the air introduced into the room of the unit cell 220A from the inlet 230 first splits expansively and when the air finally flows together contractively before discharged from the outlet 250 through the room of the unit cell 220D.

0077<figref idref="f0019">FIG. 19A</figref> is graphic presentation of experimental results on the relationship between positions of unit cells and air velocity, obtained when air flows along the routes shown in <figref idref="f0018">FIGS. 18A to 18D</figref>. <figref idref="f0020">FIG. 19B</figref> is graphic presentation of experimental results on the relationship between positions of unit cells and temperature increase, obtained when air flows along the routes shown in <figref idref="f0018">FIGS. 18A to 18D</figref>. A comparative art shown in these figures refer to a battery comprising only heat sinks 300 and 340, and intermediate heat sinks 310, 320, and 330 as cooling means in the battery 100 shown in <figref idref="f0001">FIG. 1</figref>.

0078From these graphs, it is shown that, in comparison with the comparative art, air velocities are gradually faster from the inlet 230 to the outlet 250 in all the above routes which the air follows and increase in temperature of the unit cell is also moderated.

0079The third embodiment shows that dispersion in temperature of the unit cell is the smallest in the graph. The fourth embodiment follows after the third.

0080In the third embodiment, more coolant inlets in number enable supplying an air capacity equally to each unit cell, but requiring the use of an exhaust fan with large power consumption. On the other hand, in the fourth embodiment, the air velocity is about 2.0 m/s in the vicinity of the sides of the unit cell 220A, and about 12.0 m/s in that of the unit cell 220D when the air capacity of, for example, 1.9 m³/min is given. With an initial cooling air temperature set at 35°C the temperature on the unit cell 220A is about 38°C, and that on the unit cell 220D is about 42°C. The fourth embodiment gets an advantage over the third in manufacturing a small battery with a moderate power consumption.

0081In the battery shown as a comparative art, the air capacity flowing on the heat sinks does not change regardless of positions when the air capacity of 1.9 m³/min is given as with the fourth embodiment. With an initial cooling air temperature set at 35°C, the temperature on the unit cell 220A is about 38 °C, but the temperature on the unit cell 220D is high as 48 _°C.

0082From the above graphs it is shown how greatly the present invention will contribute to improve the disproportion in three-dimensional temperature distribution of the battery 100.

[Fifth Embodiment]

0083The configuration of the frame member related to the fifth embodiment is described according to <figref idref="f0021 f0022 f0023">FIGS. 20 to 23</figref>.

0084As shown in <figref idref="f0021">FIG. 20</figref>, the frame member 210 is composed of a rectangular outer frame portion 212 and three cross member portions 214A, 214B, and 214C crossing over to two opposing sides of the outer frame portion 212 in the shape of a ladder. A U-shaped notch (opening or groove) 216A is formed on one side of the outer frame portion 212, a U-shaped notch 216B on the cross member portion 214A, a U-shaped notch 216C on the cross member portion 214B, a U-shaped notch 216D on the cross member portion 214C, and a U-shaped notch 216E on the other side of the outer frame portion 212.

0085In the present embodiment all notches 216A to 216E are the same in cross-sectional area in the direction of the coolant circulation.

0086While, on the intermediate heat sink 330 to be stacked on the frame member 210 are provided projections 332A to 332C at the positions corresponding to the notches 216B to 216D provided on the cross member portions 214A to 216C of the frame member 210. As shown in <figref idref="f0022">FIG. 21</figref>, the length La of the projection 332A is shorter than the length Lb of the projection 332B. The length Lb of the projection 332B is shorter than the length Lc of the projection 332C. In other words, each projection is gradually increased in length from the upstream to downstream in the direction of air circulation.

0087The projections 332A to 332C have U-shaped notches 332A1 to 332C2 being of a section-channel type as shown in <figref idref="f0021">FIGS. 20</figref> and <figref idref="f0022">22A to 22C</figref>. As <figref idref="f0022">FIGS. 22A to 22C</figref> show, the width of the notch 332A1 is equal to the width Wa of the notch 332A2, the width of the notch 332B1 equal to the width Wb of the notch 332B2, and the width of the notch 332C1 equal to the width Wc of the notch 332C2. The width Wa of the notches 332A1 and 332A2 is larger than the width Wb of the notches 332B1 and 332B2, and the width Wb of the notches 332B1 and 332B2 is larger than the width Wc of the notches 332C1 and 332C2. That is, the width of each notch 332 is gradually reduced from the upstream to downstream in the direction of air circulation.

0088The unit cells 220A, 220B, 220C and 220D are so arranged that their stool-shaped portions are inserted upward from under the frame member into compartment spaces defined by the outer frame portion 212 and the cross member portions 214A, 214B and 214C of the frame member 210 as shown in <figref idref="f0021">FIG. 20</figref>.

0089Cohesion of the intermediate heat sink 330 on the frame members 210 allows the notch 216A to function as the inlet 230 and the notch 216E as the outlet 250. That also permits the notches 216B, 216C and 216D, the projections 332A, 332B, and 332C, and the notches 332A1 to 332C2 to function as a coolant passage.

0090The six frame members 210, each holding the unit cells 220A, 220B, 220C, and 220D therein, are coherently stacked one by one upward from the bottom and sandwiched between the heat sink 340 and the intermediate heat sink 330 from both sides in the stacking direction. Laminating the heat sinks 330 and 340 and the frame members 210 in this manner permits the unit cells 220 situated at both ends in the stacking direction to cohere directly with the heat sinks 330 and 340, the unit cells situated elsewhere to cohere directly with one another, the frame members 210 situated at both ends in the stacking direction to cohere directly with the heat sinks 330 and 340, and the frame members 210 situated elsewhere to cohere directly with one another.

0091Providing any form of the notches in the first to fourth embodiments to the frame members 210 that do not cohere with the heat sinks 330 and 340 and lie at an intermediate position allows a coolant passage from the inlet 230 to the outlet 250 to be formed between the frame members 210 by interstices between the frame member 210 and the unit cells 220, the groove formed in the frame member 210, and the notches 216B to 216D. Also among the frame members 210 and the heat sinks 330 and 340 from the inlet 230 to the outlet 250 is formed a coolant passage by interstices among the frame member 210, the heat sinks 330 and 340, and unit cells 220, by the notches 216B to 216D formed in the frame members 210, by the projections 332A to 332C formed on the heat sinks 330 and 340, and by the notches 332A1 to 332C2 formed in the projections 332A to 332C.

0092The stack so built in the above manner is further stacked while inserting the intermediate heat sinks 310, 320, and 330 therebetween as shown in <figref idref="f0001">FIG. 1</figref>. The stack is placed between the heat sinks 300 and 340 and fastened with the nuts 400A to 400F to form the battery. The operation of the ventilator fan 850 of the cooling system 500 with the battery 100 is set in will produce the following air flow within the frame members 210 of the battery 100.

0093The air flow between frame members 210 in the present embodiment is the same as the above first to fourth embodiments, description is therefore omitted. In the following is described the air flow between the heat sinks 330 and 340, and the frame members 210.

0094The cohesion of the heat sinks 330 and 340 to the frame members 210 in the stacking direction causes air to be introduced only from the inlet 230 shown in <figref idref="f0021">FIG. 20</figref>. The introduced air reaches the notch 216B of the cross member portion 214A through interstices among the unit cell 220A, the frame member 210, and the intermediate heat sink 330. As shown in <figref idref="f0022">FIGS. 21, 22A to 22C</figref>, in the notch 216B the projection 332A of the heat sink 330 gets in, and notches 332A1 and 332A2 are formed in the projection 332A, which causes the air to circulate via interstices formed by the notch 216B, projection 332A, and notches 332A1 and 332A2. Then the air introduced from the notch 216B reaches the notch 216C through interstices among the unit cell 220B, frame member 210, and intermediate heat sink 330. The air introduced from the notch 216C through the notch 216C, projection 332B, and notches 332B1 and 332B2 reaches the notch 216D of the cross member 214C through interstices among the unit cell 220C, frame member 210 and intermediate heat sink 330. Finally, the air introduced from the notch 216D through interstices formed by the notch 216D, projection 332C, and notches 332C1 and 332C2 is discharged from the outlet 250 through the interstices among the unit cell 220D, frame member 210, and intermediate heat sink 330.

0095In the present embodiment the areas of interstices formed by the notches 216B to 216D, projections 332A to 332C, and notches 332A1 to 332C2 are formed to be gradually decreased from the upstream to the downstream. Consequently air gradually increases in velocity from the unit cell 220A to the unit cell 220D.

0096For this reason, the air introduced from the inlet 230 flows along interstices between the inner surfaces of the frame member 210 and the intermediate heat sink 330 and the peripheries of the unit cells 220, converges at the center of each cross member portion 214 to gradually increase in velocity toward the downstream, and is discharged from the outlet 250. The air introduced from the inlet 230 gradually increases its temperature as it flows downstream, but the velocity thereof increases as it flows to the outlet 250, making the cooling capacity almost equal both at the upstream and at the downstream, which results in cooling all unit cells 220A to 220D uniformly.

0097The present embodiment treats how to form the projection 332 only on the intermediate heat sink 330, but it may be formed on the heat sinks 300 and 340 instead of on the intermediate heat sink 330.

0098In the above embodiment an air velocity is increased by changing the sizes of the projections 332 and notches formed in the intermediate heat sink 330 without changing those of the notches 216 formed in the cross member portions 214 of the frame member 210. Contrary to that, however, an air velocity may be increased by changing the sizes of the notches 216 formed in the cross member portions 214 of the frame member 210 without changing those of the projections 332 and notches formed in the intermediate heat sink 330.

0099The preferred embodiments described herein are illustrative and not restrictive, and the invention may be practiced or embodied in other ways without departing from the spirit or essential character thereof. The scope of the invention being indicated by the claims, and all variations which come within the meaning of claims are intended to be embraced herein.