JP7480658B2 - Battery unit - Google Patents

Description

The present invention relates to a battery unit.

Patent Document 1 describes a battery pack made up of multiple batteries. Each battery in the battery pack is rectangular plate-shaped. The batteries are stacked vertically with a gap between them. Metal heat dissipation members are provided on the surfaces of the batteries to dissipate heat from the batteries. In addition, a heat insulating member is provided between adjacent batteries so as to come into contact with the heat dissipation members provided on both batteries.

The heat dissipation member provided on the battery in this battery pack is connected to the heat dissipation member provided on the other non-adjacent batteries by a heat-conductive member. Heat generated by the battery is transferred to the heat dissipation member provided on the other non-adjacent batteries via this heat dissipation member. In addition, a heat insulating member is provided between adjacent batteries. This heat insulating member prevents the heat generated by the battery from being transferred to the adjacent battery. Therefore, when a battery generates heat, the heat is prevented from building up around the heated battery, and the temperature rise of the battery pack is suppressed.

JP 2011-238374 A

However, in the battery pack described in Patent Document 1, two heat dissipation members and one heat insulating member are placed between each battery. This causes a problem that the battery pack becomes large. In addition, each battery cell is always insulated from the other battery cells by the heat insulating member.

The present invention was made in consideration of these points, and its purpose is to provide a battery unit equipped with a compact and efficient cooling system by providing the cooling system that cools the battery unit with a heat insulating function for each battery cell that operates only when necessary.

Specifically, the battery unit disclosed here is a battery unit including a plurality of battery cells arranged in parallel and a cooling system for cooling these battery cells, and the cooling system is characterized by having a refrigerant, a circulation path for circulating the refrigerant that is provided in contact with the battery cells, a circulator for circulating the refrigerant that is provided in the circulation path, a heat exchanger for dissipating heat from the refrigerant that is provided in the circulation path, an insulating material feeder that is provided in the circulation path for feeding an insulating material having thermal cohesive properties into the refrigerant, a means for feeding the battery cells, and a controller that operates the insulating material feeder so that the insulating material is fed into the circulation path when overheating is detected.

With this configuration, heat generated by each battery cell during use of the battery unit is absorbed by the refrigerant circulating through a circulation path provided in these battery cells. This refrigerant is circulated through this circulation path by a circulator. This refrigerant dissipates heat by a heat exchanger provided in this circulation path. By repeatedly absorbing and dissipating heat by this refrigerant, the temperature rise of these battery cells is suppressed.

In addition, when a malfunction occurs in a battery cell, the battery cell may overheat (generate abnormal heat). When this happens, a large amount of heat is transferred from the overheated battery cell to the refrigerant. This causes the temperature of the refrigerant to rise sharply locally around the overheated battery cell.

When overheating of a battery cell is detected, the controller causes the insulation material injector to inject thermally cohesive insulation material into the refrigerant. This insulation material flows with the refrigerant as the refrigerant circulates. The flowing insulation material is carried to the area around the overheated battery cell. When the temperature of the insulation material around the overheated battery cell rises above its thermal cohesive temperature, an insulation layer is formed around the battery cell where the insulation material coagulates.

Therefore, the heat insulating layer prevents heat from being transferred from an overheated battery cell to other battery cells, which would cause the temperature of these other battery cells to rise. Furthermore, this insulating layer is formed inside the circulation path through which a refrigerant circulates to cool the battery cells. This eliminates the need to provide insulation material separate from the circulation path, making the battery unit more compact in configuration.

On the other hand, if overheating of the battery cells is not detected, the insulating material is not introduced into the refrigerant. Therefore, when the battery cells are not overheated, the flow rate of the refrigerant is reduced by the insulating material, and the efficiency of the heat absorption and dissipation of the refrigerant is prevented from decreasing.

In the battery unit, the circulation path may be provided with a collector for collecting the insulating material that has been introduced into the refrigerant.

In this way, after an insulating layer is formed in the circulation path that comes into contact with the overheated battery cell, the insulating material that did not form the insulating layer is collected by the collector. This prevents the cooling performance of the refrigerant from deteriorating due to the insulating material that does not form an insulating layer remaining in the refrigerant.

In the battery unit, the cooling system further includes a voltage detection means for detecting the voltage of each battery cell, a cell temperature sensor for detecting the temperature of each battery cell, and a refrigerant temperature sensor for detecting the temperature of the refrigerant flowing into the heat exchanger. The controller identifies battery cells that are not adjacent to the overheated battery cell based on the voltage of each battery cell detected by the voltage detection means or the temperature of each battery cell detected by the cell temperature sensor, and can be configured to collect the insulating material using a collector when a predetermined time has elapsed since the operation of the insulating material inserter, the temperature of the refrigerant flowing into the heat exchanger is less than a predetermined value, and the temperature of the identified battery cell is equal to or greater than a predetermined value.

In this way, the completion of insulation of the overheated battery cell is determined based on the temperature of the refrigerant flowing into the heat exchanger confirmed after a predetermined time has elapsed since the introduction of the insulating material. This makes it possible to prevent erroneous determination of the completion of insulation of the overheated battery cell.

Furthermore, after it is determined that insulation of the overheated battery cell has been completed, if the temperature of the battery cell distant from the overheated battery cell is still high, the insulating material is collected. This makes it possible to collect the insulating material while avoiding poor insulation of the overheated battery cell. As a result, after insulation of the overheated battery cell has been completed, the decrease in the flow rate of the refrigerant caused by the insulating material is suppressed, and the rise in temperature of the distant battery cell is suppressed, preventing its deterioration.

Furthermore, after it is determined that insulation of the overheated battery cell has been completed, the temperature of a battery cell distant from the overheated battery cell is checked, rather than the battery cell adjacent to the overheated battery cell. This is because this adjacent battery cell typically deteriorates due to the heat of the overheated battery cell. Although the distant battery cell is also affected by the heat of the overheated battery cell, the effect is smaller than that of the adjacent battery cell. Therefore, by measuring the temperature of a non-adjacent battery cell, this battery cell can be protected from thermal deterioration as much as possible.

In the battery unit, each of the battery cells has corresponding surfaces that are opposite to each other in the juxtaposition direction of the battery cells, and side surfaces that connect the corresponding surfaces at their peripheries. The circulation path has a first side path portion that is connected to the refrigerant discharge portion of the circulator and extends continuously in the juxtaposition direction along one side of each of the battery cells, a second side path portion that is connected to the refrigerant suction portion of the circulator and extends continuously in the juxtaposition direction along the other side of each of the battery cells, and a corresponding surface path portion that extends along the corresponding surface in the juxtaposition direction and connects the first side path portion and the second side path portion, and the length that each of the first side path portion and the second side path portion extends along the side of each of the battery cells is shorter than the length that the corresponding surface path portion extends along the corresponding surface of each of the battery cells.

With this configuration, the battery cells may overheat due to an abnormality occurring in the battery unit. The battery cells have corresponding surfaces that face each other in the direction in which the battery cells are arranged side by side, and side surfaces that connect the corresponding surfaces at their periphery. The lengths of the first and second side path sections that extend along these side surfaces are shorter than the corresponding surface path sections that extend along these corresponding surfaces. The amount of heat that the refrigerant receives from one overheated battery cell in the first and second side path sections that are shorter is less than the amount of heat that the refrigerant receives from one overheated battery cell in the corresponding surface path section that is longer. The amount of aggregation of the thermally cohesive insulating particles in the first and second side path sections that receive less heat is less than the amount of aggregation in the corresponding surface path sections.

In this way, the amount of agglomeration of thermally cohesive insulating particles in the first side path section and the second side path section is small. Because the amount of agglomeration is small, clogging of the first side path section and the second side path section with agglomerated thermally cohesive insulating particles is suppressed. In other words, even if the corresponding side path sections on both sides of an overheated battery cell are blocked by agglomeration of thermally cohesive insulating particles, the flow of refrigerant in both the first and second side path sections that are continuous in the direction in which the battery cells are arranged side by side is likely to be maintained. Therefore, it becomes easy to maintain circulation of refrigerant throughout the entire battery cells even after the battery cells overheat.

The present invention makes it possible to realize a compact and efficient battery unit that combines a cooling system that cools the entire battery unit with a thermal insulation function for the battery cells that operates only when necessary.

1 is a schematic diagram of a battery unit 1 according to a first embodiment of the present invention. FIG. FIG. 2 is a perspective view showing the internal structure of a battery cell. FIG. 4 is a side view showing a circulation path provided in the battery cell. 1 is a cross-sectional view of a heat insulating member according to the present invention. FIG. 2 is a block diagram showing the configuration of a control system of the cooling system. FIG. 2 is a view corresponding to FIG. 1 when the battery cell is overheated. 4 is a flowchart showing a flow of control processing of the cooling system. 11 is a schematic diagram of a battery unit according to a second embodiment of the present invention when a battery cell is overheated. FIG. FIG. 5 is a view corresponding to FIG. 4 according to another embodiment. FIG. 5 is a view corresponding to FIG. 4 according to another embodiment.

The following describes in detail the embodiments of the present invention with reference to the drawings. The following description of the preferred embodiment is merely exemplary in nature and is in no way intended to limit the present invention, its applications, or its uses.

(Embodiment 1)
FIG. 1 shows a configuration of a battery unit 1 according to a first embodiment of the present invention. The battery unit 1 includes a plurality of battery cells 2 arranged in parallel (only three battery cells 2 are shown in FIG. 1) and a cooling system for cooling the battery unit 1. The battery unit 1 is used in an electric vehicle or the like. The plurality of battery cells 2 have corresponding outer surfaces 211 that are opposite to each other in the juxtaposition direction of the battery cells 2, and side surfaces 212 that connect the peripheral portions of the corresponding surfaces 211. The battery cells 2 are arranged so that the corresponding surfaces 211 face each other. In addition, each of the battery cells 2 is provided with a voltage detection circuit VD as a voltage detection means via a voltage line. Furthermore, each of the battery cells 2 is provided with a cell temperature sensor SN1 that measures the temperature of each battery cell 2. Examples of the cell temperature sensor SN1 include an NTC thermistor and a thermocouple. The temperature of each battery cell 2 is measured by detecting a signal from the cell temperature sensor SN1 using a temperature detection circuit.

As shown in FIG. 2, each of the battery cells 2 has a substantially rectangular parallelepiped cell housing 21. The battery cells 2 are electrically connected in parallel or in series with the other battery cells 2. The battery cells 2 have a corresponding surface 211 with a large area and a side surface 212 with a small area. Two terminals 213 are provided on the upper side surface (upper side in the figure) of the battery cell 2. One of these terminals 213 is a positive pole, and the other is a negative pole. The internal structure of the battery cell 2 is shown in FIG. 3. The battery cell 2 has a substantially rectangular parallelepiped electrode body 22. The electrode body is formed into a substantially rectangular parallelepiped shape by winding or stacking a positive electrode sheet, a negative electrode sheet, and a separator. Resin fixing members 23 are provided on both ends of the side surface 212 side of the electrode body 22. Metal tab leads 24 are provided on the upper side surface (upper side in the figure) of the electrode body 22, extending from both ends of the side surface 212 side toward the center of the battery cell 2. One of the tab leads 24 is a positive pole, and the other is a negative pole. The tab lead 24 extends in a plate shape from both ends of the side surface 212 on the upper surface (upper side in the figure) of the electrode body 22 toward the lower side (lower side in the figure). The plate-shaped portion of the tab lead 24 that extends toward the lower side is connected to the current collector of the electrode body 22.

The cooling system has cooling water 3 as a refrigerant, a circulation path 4, a circulator 5, and a heat exchanger 6. This cooling water 3 is circulated through the multiple battery cells 2 of the battery unit 1. As a result, this cooling water 3 removes heat from these battery cells 2 and cools them. This cooling water 3 is circulated via the circulation path 4.

This circulation path 4 is provided so as to run along the multiple battery cells 2. The refrigerant discharge section 51 and the refrigerant suction section 52 of the circulator 5 are connected to this circulation path 4. This circulator 5 is a pump for circulating the cooling water 3 in the circulation path 4.

An insulating material reservoir 7a is connected to the circulator 5 via a valve 7b. The insulating material reservoir 7a contains an insulating material 70 that has thermal cohesiveness and insulating properties. The insulating material reservoir 7a, the valve 7b, and the circulator 5 constitute an insulating material input device 7 that inputs the insulating material 70 into the circulation path 4.

In addition, a heat exchanger 6 is connected in series to the circulator 5 in the circulation path 4. This heat exchanger 6 is a device that cools the cooling water 3, and has an air-cooling fan (not shown).

A collector 9 is provided in the circulation path 4. The collector 9 is a device for collecting the insulating material 70 in the cooling water 3. The collector 9 is connected to the circulation path 4 via a bypass path 91. A switching valve 92 for switching the flow direction of the cooling water 3 is provided at the branching point where the circulation path 4 branches into the bypass path 91 and at the merging point where the bypass path 91 merges with the circulation path 4.

A concentration sensor SN3 is provided between the collector 9 and the circulator 5 in the circulation path 4. This concentration sensor SN3 measures the concentration of the insulating material 70 that has been added to the cooling water 3. In addition, a refrigerant temperature sensor SN2 that detects the temperature of the cooling water 3 is provided between the circulator 5 and the heat exchanger 6 in the circulation path 4. This allows the temperature of the cooling water 3 before it flows into the heat exchanger 6 to be measured.

The circulation path 4 has a corresponding surface path portion 41 and a side path portion 42 provided along the battery cell 2. The corresponding surface path portion 41 is provided along the corresponding surface 211 of the battery cell 2. The corresponding surface path portion 41 is provided on both sides of the corresponding surface 211 of each battery cell 2 in the juxtaposition direction. The shape of the corresponding surface path portion 41 is shown in FIG. 4. The cell housing 21 is omitted in FIG. 4. The corresponding surface path portion 41 is provided so as to proceed in a zigzag manner from one side surface 212 to the other side surface 212. The side path portion 42 is provided along the side surface 212 of the battery cell 2. On one side of the adjacent battery cells 2, the side path portion 42 is provided along the side surface 212 of one side of the battery cell 2 and connected to the corresponding surface path portions 41 on both sides of the battery cell 2, and on the other side, the side path portion 42 is provided along the side surface 212 on the opposite side of the battery cell 2 and connected to the corresponding surface path portions 41 on both sides of the battery cell 2. As a result, the circulation path 4 is configured so that the cooling water 3 can circulate through the corresponding surface path portion 41 and the side path portion 42.

The heat insulating member 70 stored in the heat insulating member reservoir 7a is shown in FIG. 5. The heat insulating member 70 has hollow silica 71. The hollow silica 71 contains air 72 in the center. The air 72 gives the hollow silica 71 heat insulation. The surface of the hollow silica 71 is provided with polyacrylate sodium, which is a water-absorbent polymer. As a result, a polyacrylate sodium polymer layer 73 with high water absorption is formed on the surface of the hollow silica 71. The polyacrylate sodium polymer layer 73 is formed by directly adding polyacrylate sodium to the hollow silica 71 or by using a binder. Ultra-high molecular weight polyethylene oxide or the like is used as the binder. The outside of the polyacrylate sodium polymer layer 73 is covered with polystyrene, which is a heat-fusible polymer. As a result, a polystyrene polymer layer 74 is formed as a heat-fusible polymer layer with heat melting properties on the outside of the polyacrylate sodium polymer layer 73. The polystyrene polymer layer 74 is formed by a liquid drying method or the like.

As shown in FIG. 6, the battery unit 1 is equipped with a microcomputer-based control unit CU as a cooling control means for controlling the cooling system. This control unit CU has a CPU (Central Processing Unit) that executes computer programs, and a memory consisting of a RAM (Random Access Memory) and a ROM (Read Only Memory) that store computer programs and data.

Measurement information is sent from various sensors to this control unit CU via the bus. Specifically, the control unit CU is electrically connected to a voltage detection circuit VD, a cell temperature sensor SN1, a refrigerant temperature sensor SN2, and a concentration sensor SN3. The voltage of each battery cell 2, the temperature of each battery cell 2, the temperature of the cooling water 3, and the concentration of the insulating material 70 in the cooling water 3 detected by the voltage detection circuit VD and the various sensors SN1 to SN3 are each sent as a signal to the control unit CU.

The control unit CU also performs various judgments and controls each device in the cooling system based on input information from the voltage detection circuit VD and the various sensors SN1 to SN3. The control unit CU outputs control signals to each device via the bus. Specifically, the control unit CU is electrically connected to the circulator 5, heat exchanger 6, insulation material inserter 7, and switching valve 92.

The control unit CU is sent the voltage of the entire battery unit 1 and the voltage of each battery cell 2 measured via the voltage detection circuit VD. When there is a sudden drop in the voltage of the entire battery unit 1 or the voltage of each battery cell 2, the control unit CU determines that one of the battery cells 2 is overheating. In this way, the control unit CU and the voltage detection circuit VD function as a means for detecting overheating of the battery cell 2.

The memory of this control unit CU records the allowable limit temperature, which is the maximum allowable temperature of each battery cell 2. This control unit CU controls the output of the circulator 5 so that the temperature of each battery cell 2 does not exceed this allowable limit temperature. The control unit CU also controls the output of the heat exchanger 6 fan so that the temperature of the cooling water 3 does not exceed this allowable limit temperature.

Furthermore, when overheating of a battery cell is detected, the control unit CU causes the insulation material inserter 7 to open the valve 7b. This causes the insulation material 70 to be inserted into the cooling water 3.

After the insulating material 70 is introduced, the control unit CU determines whether to collect the insulating material 70 based on the temperature of each battery cell 2 or the cooling water 3 detected by the cell temperature sensor SN1 or the refrigerant temperature sensor SN2. When it is determined that the insulating material 70 should be collected, the control unit CU switches the switching valve 92 so that the cooling water 3 circulates via the collector 9. As a result, the insulating material 70 introduced into the cooling water 3 is collected in the collector 9. When the concentration of the insulating material 70 in the insulated cooling water 3 is collected to a predetermined value or less, the control unit CU determines that the collection of the insulating material 70 is complete. The control unit CU then switches the switching valve 92 so that the cooling water 3 circulates without passing through the collector 9.

Next, we will explain how the cooling system of the battery unit 1 suppresses temperature rise. When the battery unit 1 is used, each battery cell 2 generates heat. The heated battery cells 2 absorb heat into the cooling water 3 via the corresponding surface path section 41 and the side surface path section 42, which are provided on the corresponding surface 211 and side surface 212 of each battery cell 2, respectively. This heat absorption suppresses the temperature rise of the battery cells 2. When the cooling water 3, whose temperature has increased due to this heat absorption, passes through the heat exchanger 6, it is cooled by heat exchange with the outside air sent by the air-cooled fan.

Next, the function of the insulating member 70 that is put into the cooling water 3 when overheating of the battery cell 2 is detected will be described. This insulating member 70 is put into the cooling water 3 when the battery cell 2 overheats. Therefore, as the cooling water 3 circulates, the insulating member 70 flows inside the circulation path 4 together with the cooling water 3. FIG. 7 shows the state in which the battery cell 2 on the leftmost side in the figure is overheated. When the battery cell 2 overheats, the corresponding surface path portion 41 and the side path portion 42 that are in contact with the battery cell 2 are heated. When these corresponding surface path portion 41 and side path portion 42 are heated, the temperature of the cooling water 3 inside them is raised. The surface temperature of the insulating member 70 put into the cooling water 3 is raised by the rise in the temperature of the cooling water 3. The polystyrene polymer layer 74 that forms the surface of the insulating member 70 with the surface temperature raised is melted. As a result, the polyacrylate soda polymer layer 73 provided inside the polystyrene polymer layer 74 of the insulating member 70 is exposed. This water-absorbent polyacrylate sodium polymer layer 73 absorbs the cooling water 3 flowing through the circulation path 4 and expands. As a result, the hollow silica 71 bonds and aggregates through the swollen polyacrylate sodium polymer layer 73. The hollow silica 71 in the insulation member 70 also has insulating properties. Therefore, the aggregated insulation member 70 forms an insulating layer 8 around the overheated battery cell 2, in which the air 72 in the hollow silica 71 exerts an insulating effect.

Next, we will explain the operation of the cooling system when overheating of the battery cell 2 of the battery unit 1 is detected. Figure 8 shows the procedure for controlling the cooling system by the control unit CU.

In step St1, the control unit CU reads voltage information for the entire battery unit 1 and each battery cell 2 based on the input information from the voltage detection circuit VD.

In step St2, the control unit CU determines whether or not the voltage of the entire battery unit 1 or each battery cell 2 has suddenly dropped. When it is determined that there has been a sudden drop in voltage, the control unit CU detects overheating of the battery cell 2. If it is determined that there has been a sudden drop in voltage (YES), the control unit CU advances the process to step St3. If it is determined that there has not been a sudden drop in voltage (NO), the control unit CU returns the process to step St1.

In step St3, the control unit CU increases the output of the circulator 5 to its maximum. This causes the control unit CU to increase the flow rate of the cooling water 3 flowing through the circulation path 4.

In step St4, the control unit CU increases the output of the fan of the heat exchanger 6 to the maximum. This causes the control unit CU to increase the efficiency of the heat exchanger 6 in dissipating heat from the cooling water 3.

In step St5, the control unit CU instructs the insulation material inserter 7 to open the valve 7b and insert the insulation material 70 into the cooling water 3.

In step St6, the control unit CU identifies which battery cell 2 in the battery unit 1 is the overheated battery cell 2 based on the voltage or temperature of the battery cell 2. The control unit CU determines that the battery cell 2 whose voltage is extremely low or whose temperature is higher than the allowable limit temperature is overheated.

In step St7, the control unit CU searches for a battery cell 2 whose temperature is equal to or lower than the allowable limit temperature from among the battery cells 2 that are not adjacent to the overheated battery cell 2. From among the battery cells 2 whose temperatures are equal to or lower than the allowable limit temperature, the control unit CU identifies the second battery cell 2 in the juxtaposition direction from the overheated battery cell 2. The identified battery cell 2 is preferably the second battery cell 2 in the juxtaposition direction from the overheated battery cell 2, but it may be a battery cell 2 that is three or more cells away in the juxtaposition direction.

In step St8, the control unit CU waits for a predetermined time. After this predetermined time has elapsed, the control unit CU advances the process from step St8 to step St9.

In step St9, the control unit CU reads the temperature TB of the battery cell 2 identified in step St7 based on the input information from the cell temperature sensor SN1.

In step St10, the control unit CU reads the temperature TC of the cooling water 3 before it flows into the heat exchanger 6 based on the input information from the refrigerant temperature sensor SN2.

In step St11, the control unit CU compares the temperature TC of the cooling water 3 read in step St10 with the allowable limit temperature. If the temperature TC of the cooling water 3 is lower than the allowable limit temperature (YES), the control unit CU advances the process to step St12. If the temperature TC of the cooling water 3 is higher than the allowable limit temperature (NO), the control unit CU returns the process to step St10.

In step St12, the control unit CU compares the temperature TB of the battery cell 2 read in step St9 with the allowable limit temperature. If the temperature TB of the battery cell 2 is lower than the allowable limit temperature (YES), the control unit CU advances the process to step St19. If the temperature TC of the battery cell 2 is higher than the allowable limit temperature (NO), the control unit CU advances the process to step St13.

In step St13, the control unit CU switches the switching valve 92 so that the cooling water 3 passes through the collector 9. This causes the insulating material 70 in the cooling water 3 to be collected in the collector 9.

In step St14, the control unit CU reads the temperature TB of the battery cell 2 identified in step St7 based on the input information from the cell temperature sensor SN1.

In step St15, the control unit CU compares the temperature TB of the battery cell 2 read in step St14 with the allowable limit temperature. If the temperature TB of the battery cell 2 is lower than the allowable limit temperature (YES), the control unit CU advances the process to step St16. If the temperature TC of the battery cell 2 is higher than the allowable limit temperature (NO), the control unit CU returns the process to step St14.

In step St16, the control unit CU reads the concentration of the insulating material 70 added to the cooling water 3 based on the input information from the concentration sensor SN3.

In step St17, the control unit CU determines whether the concentration read in step St16 is equal to or less than a predetermined value. In this way, the control unit CU determines whether collection of the insulating material 70 in the cooling water 3 has been completed. If it is equal to or less than the predetermined value (YES), the control unit CU advances the process to step St18. If it is equal to or more than the predetermined value (NO), the control unit CU returns the process to step St16.

In step St18, the control unit CU switches the switching valve 92 so that the cooling water 3 circulates without passing through the collector 9.

In step St19, the control unit CU reduces the output of the fan of the heat exchanger 6 from maximum. This reduces the energy (electricity) consumed by the heat exchanger 6.

In step St20, the control unit CU reduces the output of the circulatory system 5 from maximum. This reduces the energy (electricity) consumed by the circulatory system 5.

Therefore, in this embodiment, when an overheated battery cell 2 is present, a heat insulating material 70 is introduced into the cooling water 3 of the cooling system, which suppresses the temperature rise of the battery unit 1. As a result, when a battery cell 2 overheats, a heat insulating layer 8 is formed inside the corresponding surface path portion 41 and the side path portion 42 of the circulation path 4 that contact the overheated battery cell 2. Therefore, the heat insulating layer 8 suppresses the influence of the heat generated by the overheated battery cell 2 on other battery cells 2. In addition, this heat insulating layer 8 is formed inside the circulation path 4 for cooling the battery unit 1. Therefore, there is no need to provide a heat insulating material separately from the circulation path 4, and the configuration of the battery unit 1 becomes compact.

Furthermore, when the cells 2 do not overheat, the insulating member 70 is not introduced into the circulation path 4. Therefore, the introduction of the insulating member 70 reduces the flow rate of the cooling water 3, and the efficiency of the heat absorption and dissipation of the cooling water 3 is prevented from decreasing. This allows the cooling system of the battery unit 1 to efficiently cool the battery unit 1.

In addition, after the temperature of the refrigerant before flowing into the heat exchanger 6 has decreased, when the temperature of the battery cells 2 away from the overheated battery cells 2 is higher than the allowable limit temperature, the heat insulating material 70 introduced into the cooling water 3 is collected by the collector 9. That is, after the insulation of the overheated battery cells 2 is completed by the formation of the insulating layer 8, the heat insulating material 70 flowing together with the cooling water 3 is collected. As a result, after the temperature of the refrigerant before flowing into the heat exchanger 6 has decreased, the flow rate of the cooling water 3 due to the heat insulating material 70 flowing together with the cooling water 3 decreases, and the efficiency of heat absorption and heat dissipation of the cooling water 3 is prevented from decreasing. Therefore, the temperature rise of the battery cells 2 away from the overheated battery cells 2 is suppressed, and deterioration of the battery cells 2 can be prevented.

Furthermore, the temperature rise of battery cells 2 that are not adjacent to the overheated battery cell 2 due to the occurrence of an overheated battery cell 2 is suppressed by the formation of the insulating layer 8. At this time, even if a battery cell 2 overheats, the vehicle cannot be stopped immediately and must continue running for a while. During this running, the energy (power) consumed by the heat exchanger 6 and the circulator 5 is suppressed in steps St19 and St20, thereby suppressing the energy (power) consumed by the battery unit 1.

(Embodiment 2)
9 shows the configuration of a battery unit 1 according to embodiment 2 of the present invention. The configuration of the circulation path 4 provided along the battery cells 2 differs from that of embodiment 1, but the other configurations are the same as those of embodiment 1.

In the second embodiment, as in the first embodiment, the battery unit 1 includes a plurality of battery cells 2 arranged in parallel (only three battery cells 2 are shown in FIG. 9). FIG. 9 shows the battery unit 1 when the battery cell on the far left in the figure has overheated. The structure of this battery cell 2 is the same as in the first embodiment.

As shown in FIG. 9, the battery unit 1 includes a plurality of battery cells 2 (only three battery cells 2 are shown in FIG. 9). These battery cells 2 are arranged with their corresponding surfaces 211 facing each other.

The battery unit 1 is equipped with a cooling system for cooling the entire battery unit. This cooling system cools each battery cell using cooling water 3 as a refrigerant. As in the first embodiment, the battery unit 1 is cooled by circulating the cooling water 3 through a circulation path 4. Furthermore, the operation of this cooling system in the second embodiment is controlled by the control unit CU in the same manner as in the first embodiment.

The circulation path 4 has a first side path section 421, a second side path section 422, and a corresponding surface path section 41. The first side path section 421 is provided continuously along the upper side surface 212 of each battery cell 2 in the figure in the direction in which the battery cells 2 are arranged side by side (left and right direction in the figure). The first side path section 421 is connected to the refrigerant discharge section 51 of the circulator 5. The second side path section 422 is connected along the lower side surface 212 of each battery cell 2 in the figure in the direction in which the battery cells 2 are arranged side by side (left and right direction in the figure). The second side path section 422 is connected to the refrigerant suction section 52 of the circulator 5. The corresponding surface path section 41 is provided along the corresponding surface 211 of the battery cell. One end of the corresponding surface path section 41 is connected to the first side path section 421 and the other end is connected to the second side path section 422.

The length of the side surface 212 of each battery cell 2 is shorter than the length of the corresponding surface 211. Therefore, the length of the first side surface path portion 421 and the second side surface path portion 422 along the side surface 212 of each battery cell 2 is shorter than the length of the corresponding surface path portion 41 along the corresponding surface 211.

Next, the action of the insulating member 70 when the battery cell 2 of the battery unit 1 in the second embodiment overheats will be described. When the battery cell 2 overheats, heat is transferred from the battery cell 2 to the corresponding surface path portion 41, the first side surface path portion 421, and the second side surface path portion 422. The length extending along the overheated battery cell 2 of the first side surface path portion 421 and the second side surface path portion 422 is shorter than that of the corresponding surface path portion 41. Therefore, the amount of heat transferred to the first side surface path portion 421 and the second side surface path portion 422 is smaller than the amount of heat transferred to the corresponding surface path portion 41.

In addition, when the electrode body 22 of the battery cell 2 overheats, the heat generated by the electrode body 22 is transferred to the cell casing 21. This heat is transferred directly to the cell casing 21 on the corresponding surface 211 side. On the other hand, this heat is transferred to the cell casing 21 via the tab lead 24 and the fixing member 23 on the side surface 212 side. As a result, the temperature of the corresponding surface 211 of the cell casing 21 of the battery cell 2 is more likely to rise, and the temperature of the side surface 212 is less likely to rise.

Furthermore, the corresponding surface 211, which is closer to the cell casing 21 and the electrode body 22, is more susceptible to the heat generated by the electrode body 22 than the side surface 212, and the surface temperature is more likely to rise. As a result, the cell casing 21 of the battery cell 2 is more likely to have a high temperature at the corresponding surface 211 and less likely to have a high temperature at the side surface 212.

In this way, the temperature of the cooling water 3 in the first side path portion 421 and the second side path portion 422 provided on the side surface 212 where the amount of heat transmitted is small and the temperature is difficult to increase is lower than the temperature of the cooling water 3 in the corresponding surface path portion 41 provided on the corresponding surface where the amount of heat transmitted is large and the temperature is easy to increase. First, the temperature of the cooling water 3 in the corresponding surface path portion 41 is raised to a temperature at which the polystyrene polymer layer 74 of the insulating member 70 melts due to the heat of the overheated battery cell 2. As in the first embodiment, the insulating member 70 with the polystyrene polymer layer 74 melted forms an insulating layer 8 in the corresponding surface path portion 41. On the other hand, the temperature of the cooling water 3 in the first side path portion 421 and the second side path portion 422 is lower than the temperature of the cooling water 3 in the corresponding surface path portion 41. In the first side path portion 421 and the second side path portion 422 where the temperature is low, the polystyrene polymer layer 74 of the insulating member 70 is difficult to melt, and the amount of aggregation is reduced.

Therefore, in this embodiment, when the battery cell 2 overheats, the amount of agglomerated insulating material 70 is smaller in the first side path portion 421 and the second side path portion 422 than in the corresponding surface path portion 41. This suppresses clogging of the first side path portion 421 and the second side path portion 422 by the agglomerated insulating material 70. Therefore, the flow rate of the cooling water 3 flowing through these first side path portion 421 and the second side path portion 422 is sufficiently ensured. Furthermore, these first side path portion 421 and the second side path portion 422 are continuous in the arrangement direction of the battery cell 2. Therefore, when the insulating layer 8 is formed in the corresponding surface path portion 41, even if the corresponding surface path portion 41 is clogged by the insulating layer 8, the cooling water 3 can be circulated through the first side path portion 421 and the second side path portion 422.

In this way, this battery unit 1 is configured so that when the insulating layer 8 is formed on the corresponding surface path portion 41, the cooling water 3 can circulate through the first side surface path portion 421 and the second side surface path portion 422. This allows the cooling of the battery unit 1 by the circulation of the cooling water 3 and the insulation of the overheated battery cells 2 to be performed simultaneously.

As shown in FIG. 9, the battery cells 2 are arranged with their corresponding surfaces 211 facing each other. Since a heat insulating layer 8 is easily formed in the corresponding surface path portion 41 provided between these corresponding surfaces 211, the influence of the heat of an overheated battery cell 2 on other battery cells 2 can be sufficiently suppressed.

(Other embodiments)
In the above embodiment, only three battery cells 2 are described, but the number of battery cells 2 is not limited to three. It is sufficient that there are a plurality of battery cells 2.

In the above embodiment, the corresponding surface path portion 41 of the circulation path 4 is provided in a zigzag pattern on the corresponding surface 211. However, as shown in FIG. 10, three corresponding surface path portions 41 may be provided in parallel in the vertical direction (vertical direction in the figure) on the corresponding surface 211. In this case, one circulation path 4 continuing to the refrigerant discharge portion 51 of the circulator 5 is branched into three side path portions 42, and the branched side path portion 42 is connected to the three corresponding surface path portions 41. The three downstream side path portions 42 continuing to the three corresponding surface path portions 41 may be collected into one and connected to the refrigerant suction portion 52 of the circulator 5. Alternatively, the side path portion 42 provided on each of the upstream and downstream sides of the corresponding surface path portion 41 may be one, and may be branched into three corresponding surface path portions 41. Alternatively, three circulation paths 4 may be provided in parallel, and a circulator 5 and a heat exchanger 6 may be provided on each.

Furthermore, as shown in FIG. 11, the corresponding surface path section 41 may be configured as two zigzag corresponding surface path sections 41 arranged in parallel. Also, these two corresponding surface path sections 41 may be arranged with their vertices corresponding to each other in the vertical direction (vertical direction in the figure). In this case, one circulation path 4 continuing to the refrigerant discharge section 51 of the circulator 5 is branched into two side path sections 42, and the branched side path section 42 and the two corresponding surface path sections 41 are connected. Then, the two downstream side path sections 42 continuing to the two corresponding surface path sections 41 may be collected into one and connected to the refrigerant suction section 52 of the circulator 5. Alternatively, the side path section 42 provided on each of the upstream and downstream sides of the corresponding surface path section 41 may be one, and may be branched into two corresponding surface path sections 41. Alternatively, two circulation paths 4 may be provided in parallel, and each may be provided with a circulator 5 and a heat exchanger 6.

In the above embodiment, the refrigerant discharge section 51 and the refrigerant suction section 52 of the circulator 5 are connected to the circulator 5 so that the cooling water 3 circulates counterclockwise in Figures 1, 7, and 9. However, the refrigerant discharge section 51 and the refrigerant suction section 52 may be connected in the opposite direction so that the cooling water 3 circulates clockwise. In this case, the location of the concentration sensor SN3 may be changed to between the collector 9 and the heat exchanger 6. The point is that the concentration sensor SN3 must be able to measure the concentration of the cooling water 3 flowing out of the collector 9. Furthermore, the refrigerant temperature sensor SN2 may be installed between the heat exchanger 6 and the switching valve 92. The point is that the refrigerant temperature sensor SN2 must be able to measure the temperature of the cooling water 3 flowing into the heat exchanger 6.

In the above embodiment, the battery cell 2 is a rectangular parallelepiped battery having a corresponding surface 211 and a side surface 212. However, the shape of the battery cell 2 may be any shape, including a cylindrical battery. For example, when cylindrical batteries are used and the cylindrical batteries are arranged side by side in a direction perpendicular to the axial direction, the side surfaces of the cylindrical batteries may be the corresponding surfaces 211 and both bottom surfaces may be the side surfaces 212. On the other hand, when the cylindrical batteries are arranged side by side in the axial direction, both bottom surfaces of the cylindrical batteries may be the corresponding surfaces 211 and the side surfaces may be the side surfaces 212.

In the above embodiment, hollow silica 71, which is a hollow particle, is used as the core material of the insulating member 70, but foam particles, etc. may also be used. The particles used as the core material need only have insulating properties. For example, alternatives to hollow silica 71 include porous silica, porous polyimide, organic-inorganic hybrid porous, etc.

In the above embodiment, the surface of the hollow silica 71 is provided with sodium polyacrylate, which is a water-absorbent polymer, but sodium polyacrylate is not essential as long as the polymer has water-absorbent properties. For example, alternatives to sodium polyacrylate include polyacrylates, starch-acrylate graft polymers, vinyl acetate copolymers, maleic anhydride copolymers, polyvinyl alcohols, CMCs, etc.

In the above embodiment, the outside of the polysodium acrylate polymer layer 73 is covered with polystyrene, which is a heat-fusible polymer, but it does not have to be polystyrene as long as it is heat-fusible. For example, alternatives to polystyrene include ABS (acrylonitrile-butadiene-styrene copolymer) and AS (acrylonitrile-styrene copolymer).

In the above embodiment, the heat insulating member 70 has a three-layer structure in which a core material, a water-absorbent polymer layer, and a heat-fusible polymer layer are laminated. However, the structure of the heat insulating member 70 is not limited to a three-layer structure. For example, a two-layer structure may be formed by forming a layer of a resin that exhibits adhesiveness when heated on the outside of the core material, or a layer of a resin that exhibits water absorption when heated.

The present invention is extremely useful in that it allows the battery unit 1 to have a compact configuration and be cooled efficiently.

1 Battery unit
2 Battery cells
3. Cooling water
4. Circulation route
5. Circulatory system
6. Heat exchanger
7. Heat insulating material inserter
8. Thermal insulation layer
9 Collector
92 Switching valve

Claims (4)

A battery unit including a plurality of battery cells arranged in parallel and a cooling system for cooling the battery cells,
The cooling system comprises:
A refrigerant;
a circulation path for circulating the coolant, the circulation path being provided in contact with the battery cell;
a circulator for circulating the refrigerant provided in the circulation path;
a heat exchanger provided in the circulation path for dissipating heat of the refrigerant;
An insulating material feeder provided in the circulation path for feeding an insulating material having thermal coagulation properties into the refrigerant;
means for detecting overheating of the battery cell;
a controller that operates the insulating material inserter to insert the insulating material into the circulation path when the overheating is detected. The battery unit according to claim 1 ,
The battery unit according to claim 1, wherein the circulation path is provided with a collector for collecting the heat insulating material that has been put into the refrigerant. The battery unit according to claim 2,
the cooling system further includes a voltage detection means for detecting a voltage of each of the battery cells, a cell temperature sensor for detecting a temperature of each of the battery cells, and a refrigerant temperature sensor for detecting a temperature of the refrigerant flowing into the heat exchanger;
The controller identifies a battery cell that is not adjacent to an overheated battery cell based on the voltage of each battery cell detected by the voltage detection means or the temperature of each battery cell detected by the cell temperature sensor, and when a predetermined time has elapsed since the operation of the insulation material inserter, the temperature of the refrigerant flowing into the heat exchanger is less than a predetermined value, and the temperature of the identified battery cell is equal to or higher than a predetermined value, the controller performs collection of the insulation material using the collector. The battery unit according to any one of claims 1 to 3,
each of the plurality of battery cells has corresponding surfaces that are outer surfaces facing opposite directions in a direction in which the battery cells are arranged side by side, and side surfaces that connect the corresponding surfaces to each other at their peripheries;
The circulation path is
a first side path portion connected to a refrigerant discharge portion of the circulator and extending continuously in the arrangement direction along one of the side surfaces of each of the battery cells;
a second side path portion connected to the refrigerant suction portion of the circulator and extending continuously in the juxtaposition direction along the other side surface of each of the battery cells;
a corresponding surface path portion that connects the first side surface path portion and the second side surface path portion and that extends along the corresponding surface in the juxtaposition direction,
a length over which each of the first side path portion and the second side path portion extends along the side surface of each of the battery cells is shorter than a length over which the corresponding surface path portion extends along the corresponding surface of each of the battery cells.

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