Cooling device

Abstract

To correctly determine the propriety of replacement of a cooling liquid even when the detection accuracy of a conductivity sensor is lowered.SOLUTION: A cooling device 125 includes a sensor 210 and a control device 250. The sensor 210 detects the conductivity of a cooling liquid that cools a battery. The control device 250 controls the cooling device 125 . When the cooling liquid is replaced, in a case in which a value obtained by subtracting a second conductivity V2 which is the conductivity after the cooling liquid replacement from a first conductivity V1 which is the conductivity before the cooling liquid replacement is a threshold value or more, the control device 250 allows activation of the cooling device 125.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present disclosure relates to a cooling device, and more particularly, to a cooling device for cooling a battery. [Background technology]

[0002] Generally, in a system that uses a coolant to cool a battery, it is preferable that the conductivity of the coolant is low, but it is known that the conductivity of the coolant increases. JP 2020-107444 A (Patent Document 1) discloses a battery cooling system for suppressing an increase in the conductivity of the coolant. This battery cooling system includes a coolant that cools a battery, a battery cooling circuit through which the coolant flows, and a control unit. The battery cooling circuit has a conductivity sensor that detects the conductivity of the coolant. The control unit controls the battery cooling circuit based on the detection value of the conductivity sensor. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2020-107444 A Summary of the Invention [Problem to be solved by the invention]

[0004] When the conductivity of the coolant increases, it is preferable to replace the coolant. Here, when a conductivity sensor detects the conductivity of the coolant as in Patent Document 1, if the detection accuracy of the sensor decreases due to aging or the like, the control unit may not be able to obtain accurate values ​​of the conductivity of the coolant before and after replacement based on the detection value of the sensor. Therefore, in this case, even if an inappropriate coolant (e.g., one with an increased conductivity) is mistakenly injected into the cooling device when the coolant is replaced, the control unit may not be able to accurately determine that the coolant has not been replaced appropriately.

[0005] The present disclosure has been made in consideration of the above-described background, and its purpose is to correctly determine whether or not to replace the coolant even if the detection accuracy of the conductivity sensor has decreased. [Means for solving the problem]

[0006] The cooling device of the present disclosure includes a sensor and a control device. The sensor detects the conductivity of a coolant that cools a battery. The control device controls the cooling device. When the coolant is replaced, the control device allows the cooling device to start when a value obtained by subtracting a second conductivity, which is a conductivity after the coolant is replaced, from a first conductivity, which is a conductivity before the coolant is replaced, is equal to or greater than a threshold value.

[0007] With the above configuration, the control device can obtain a value indicating the difference between the detection values ​​of the conductivity sensor under the condition that the detection accuracy of the conductivity sensor is the same before and after replacement of the coolant. Therefore, unlike a case where the appropriateness of replacing the coolant is determined using only the absolute value of the detection value of the conductivity of the replaced coolant, even if the detection accuracy of the conductivity sensor has decreased, the appropriateness of replacing the coolant can be correctly determined according to the difference that does not depend on the detection accuracy. As a result, it is possible to avoid a situation where an inappropriate coolant (for example, a coolant having a higher conductivity than the coolant before replacement) is mistakenly injected into the cooling device, causing the cooling device to start up. Effect of the Invention

[0008] Even if the detection accuracy of the conductivity sensor is degraded, the appropriateness of replacing the coolant can be correctly determined. [Brief description of the drawings]

[0009] [Figure 1] 1 is a diagram showing an overall configuration of a vehicle according to an embodiment of the present invention; [Diagram 2] 2 is a diagram showing a detailed configuration of a cooling device and a battery pack. FIG. [Diagram 3] FIG. 2 is a diagram showing a more detailed configuration of a conductivity sensor. [Figure 4]10A and 10B are diagrams for explaining how the electrical conductivity of the coolant changes before and after replacement of the coolant. [Diagram 5] 5 is a flowchart showing an example of a procedure of a process associated with replacement of a coolant. [Figure 6] 5 is a flowchart showing an example of a procedure of a process associated with replacement of a coolant. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, the present embodiment will be described with reference to the drawings. Note that the same or corresponding parts in the drawings are given the same reference numerals, and the description thereof will not be repeated. In the following embodiment, the configuration of a vehicle shown as an application example of the cooling device will be described, but the cooling device of the present disclosure is not limited to use in vehicles, and may be applied to stationary battery systems, etc.

[0011] [Embodiment] 1 is a diagram showing the overall configuration of a vehicle according to this embodiment. The vehicle 100 is an electric vehicle that runs using electric power from a battery. In this embodiment, the vehicle 100 is described as an electric vehicle, but the vehicle 100 may be a hybrid vehicle further equipped with an internal combustion engine, or a fuel cell vehicle further equipped with a fuel cell.

[0012] With reference to FIG. 1, a vehicle 100 includes an ECU (Electrical Control Unit) 105, a battery pack 110, a PCU (Power Control Unit) 115, a motor 120, and a cooling device 125.

[0013] The battery pack 110 is electrically connected to the PCU 115 and supplies the PCU 115 with electric power for generating a driving force for the motor 120 .

[0014] The PCU 115 includes a converter and an inverter (neither of which are shown). The converter boosts the voltage of the power from the battery pack 110. The inverter converts the DC power supplied from the converter into AC power to drive the motor 120.

[0015] The motor 120 is an AC rotating electric machine, for example a permanent magnet type synchronous motor equipped with a rotor in which a permanent magnet is embedded. The motor 120 drives the wheels (not shown) of the vehicle 100 by rotating using the electric power supplied from the PCU 115. This causes the vehicle 100 to run.

[0016] The cooling device 125 operates by receiving electric power from the battery pack 110. The cooling device 125 cools the battery pack 110 and the PCU 115.

[0017] The ECU 105 controls the entire vehicle 100. The ECU 105 controls the PCU 115, for example.

[0018] Fig. 2 is a diagram showing detailed configurations of the cooling device 125 and the battery pack 110. Referring to Fig. 2, the cooling device 125 includes a cooling path 205, a conductivity sensor 210, a temperature sensor 215, a heat sink 220, a pump 225, a liquid injection valve 240, a liquid drainage valve 245, and a control device 250. The battery pack 110 includes a battery 230 and a heater 235.

[0019] The cooling path 205 is a pipe that constitutes a path of coolant for cooling the battery pack 110. The arrows in the cooling path 205 indicate the direction in which the coolant circulates. The coolant is, for example, an insulating LLC (Long Life Coolant).

[0020] In the cooling path 205, when the pump 225 is operated, the cooling liquid supplied from the pump 225 passes through the battery pack 110 and the heat radiator 220, and then returns to the pump 225. In this way, the cooling liquid circulates in the cooling path 205.

[0021] Pump 225 is an electric water pump that is provided in cooling passage 205 and circulates the coolant within cooling passage 205 in accordance with a control signal from control device 250.

[0022] The conductivity sensor 210 detects the conductivity of the cooling liquid circulating in the cooling path 205. The temperature sensor 215 detects the temperature of the cooling liquid. The conductivity sensor 210 and the temperature sensor 215 are provided in the cooling path 205. The detected values ​​are output to the control device 250. The conductivity sensor 210 will be described in more detail with reference to FIG. 3.

[0023] Heat radiator 220 is provided in cooling path 205, and cools the coolant by exchanging heat between the coolant and the air outside vehicle 100. More specifically, a fan (not shown) of heat radiator 220 rotates to generate air, thereby accelerating heat exchange in heat radiator 220.

[0024] The liquid injection valve 240 is a valve that is opened when the cooling liquid is injected into the cooling path 205. The liquid drainage valve 245 is a valve that is opened when the cooling liquid is discharged from the cooling path 205. The liquid injection valve 240 and the liquid drainage valve 245 are configured so that they cannot be opened when they are locked. On the other hand, these valves are configured so that they can be opened when they are unlocked. In the example of FIG. 2, one liquid injection valve 240 and one liquid drainage valve 245 are shown for the sake of simplicity of explanation, but the cooling device 125 may include a plurality of liquid injection valves 240 and a plurality of liquid drainage valves 245.

[0025] The control device 250 includes a CPU (Central Processing Unit) (not shown) and a memory 255. The memory 255 includes a ROM (Read Only Memory) and a RAM (Random Access Memory) (neither of which are shown). The ROM stores programs executed by the CPU, etc. The RAM temporarily stores data referenced by the CPU, etc. The memory 255 stores, for example, the conductivity of the coolant detected by the conductivity sensor 210.

[0026] The control device 250 controls the cooling device 125 based on information stored in the memory 255, etc. The control device 250 adjusts the temperature of the coolant in the cooling path 205 by controlling the heater 235 and the radiator 220 based on a value detected by the temperature sensor 215, for example. The control of the control device 250 is realized by software processing, but may also be realized by hardware created in the control device 250.

[0027] When the conductivity of the coolant in the cooling path 205 has increased due to deterioration or the like, and the coolant is to be replaced, the control device 250 receives a trigger TR for determining whether or not the coolant has been replaced in error, in order to determine whether or not the coolant should be replaced. The trigger TR is, for example, a signal indicating that the vehicle 100 has transitioned to a maintenance mode. In response to receiving the trigger TR, the control device 250 determines whether or not the coolant has been mistakenly injected (i.e., determines whether or not an inappropriate coolant that should not be injected has been injected into the cooling path 205). Note that the transition to the maintenance mode is a procedure that is performed before an operator such as a mechanic maintains the vehicle 100, and this transition is basically performed when the coolant is replaced.

[0028] Battery 230 is a power storage element configured to be capable of charging and discharging. Battery 230 is, for example, a lithium ion battery, or a secondary battery such as a nickel-metal hydride battery or a lead storage battery. Instead of battery 230, a power storage device configured with a power storage element such as an electric double layer capacitor may be used.

[0029] The heater 235 is used to adjust the temperature of the cooling liquid circulating through the cooling path 205. The heater 235 operates according to a control signal from the control device 250.

[0030] The reason why the detection accuracy of the conductivity sensor 210 decreases will be described with reference to Fig. 3. Fig. 3 is a diagram showing a more detailed configuration of the conductivity sensor 210. The conductivity sensor 210 includes a detection unit 302 and electrodes 305A and 305B.

[0031] The detection unit 302 detects the conductivity of the coolant 310 circulating through the cooling path 205. As an example, the detection unit 302 includes an ammeter and a power source (neither is shown). When a voltage is applied between the electrodes 305A and 305B by the power source, a current flows between these electrodes in the coolant 310 containing anions and cations. As a result, this current also flows in the detection unit 302. The ammeter detects this current, and a resistance value between the electrodes 305A and 305B in the coolant 310 is obtained based on the detected value and the voltage of the power source. Here, since the conductivity is the reciprocal of the resistance value, the conductivity sensor 210 detects the conductivity of the coolant 310 by obtaining the conductivity based on the obtained resistance value.

[0032] When the conductivity sensor 210 detects the conductivity of the coolant 310 in this manner, a current flows through the electrodes 305A and 305B. Due to this current flow, the electrodes 305A and 305B deteriorate over time. Furthermore, the electrodes 305A and 305B deteriorate by gradually corroding while immersed in the coolant 310. Due to the deterioration of the electrodes 305A and 305B as described above, the detection accuracy of the conductivity sensor 210 decreases over time.

[0033] Here, the conductivity of the coolant 310 may increase due to deterioration of the coolant 310. In this case, it is preferable to replace the coolant 310. However, when the detection accuracy of the conductivity sensor 210 is reduced as described above, it may not be possible to obtain an accurate value of the conductivity of the replaced coolant based on the detection value of the conductivity sensor. Therefore, in this case, even if an inappropriate coolant (e.g., a coolant having a higher conductivity than the coolant 310 before replacement; details will be described later) is mistakenly injected when the coolant 310 is replaced, it may not be possible to accurately determine that the coolant 310 has not been replaced appropriately based on the detection value.

[0034] Fig. 4 is a diagram for explaining how the conductivity of the coolant changes before and after replacement of the coolant. In the example of Fig. 4, a case is shown in which a deteriorated coolant is normally replaced with unused coolant. With reference to Fig. 4, the vertical axis represents the conductivity, and the horizontal axis represents the time.

[0035] The conductivity V1 is the conductivity (first conductivity) of the deteriorated coolant before replacement. The conductivity V2 is the conductivity (second conductivity) of the coolant after replacement. The initial value V0 will be described later.

[0036] Before and after the coolant is replaced at time t1, the conductivity detected by the conductivity sensor 210 changes from V1 to V2 (V1>V2). The difference between the conductivity V1 and the conductivity V2 before and after the replacement of the coolant (before and after time t1) is ΔV. In the example of FIG. 4, the difference ΔV is shown to be equal to or greater than a predetermined value ΔTH. Here, the value ΔTH is, for example, a threshold value that can be used to determine whether or not a deteriorated coolant has been replaced with an appropriate coolant (e.g., unused coolant; details will be described later), and is set to a suitable value through experiments or the like. In the above case, under the following assumptions, the conductivity V1 has increased by a value ΔTH or more from the initial value V0.

[0037] The conductivity of the coolant may vary depending on the characteristics of the coolant, but if the coolant before and after replacement have similar characteristics, it can be assumed that the conductivity of both coolants when they are unused (or were unused) will be the same initial value V0.

[0038] In the cooling device 125, when the coolant deteriorates and its conductivity increases, it is not preferable that the conductivity of the coolant increases, since current easily flows through the coolant in the cooling device 125. Therefore, in this case, it is preferable that the coolant with the increased conductivity is replaced with a coolant with no increased conductivity (for example, unused). Under the above assumption that the conductivity of the coolant before and after replacement is the initial value V0 when the coolant is unused (or was unused), if the conductivity V2 of the replaced coolant is the initial value V0 (i.e., if the replaced coolant is unused), it is considered that the replacement of the coolant has been performed appropriately. Hereinafter, the replaced coolant with the conductivity of the initial value V0 will be referred to as an "appropriate coolant", and the replaced coolant with the conductivity higher than the initial value V0 will be referred to as an "inappropriate coolant".

[0039] Therefore, when an appropriate coolant is used as the replacement coolant, i.e., when an inappropriate coolant has not been mistakenly injected into the cooling device 125 (cooling path 205), the difference ΔV between the conductivity V1 that has increased due to deterioration of the coolant and the conductivity V2 that has not increased from the initial value V0 (i.e., is equal to the initial value V0) is considered to be greater than or equal to the value ΔTH.

[0040] The control device 250 according to this embodiment compares the electrical conductivity V1 with the electrical conductivity V2 when the coolant is replaced. Then, for example, when the electrical conductivity V1 changes to the electrical conductivity V2 while the vehicle 100 is in the maintenance mode (around time t1 in the example of FIG. 4), the control device 250 determines whether the difference ΔV between the electrical conductivity V1 and the electrical conductivity V2 is equal to or greater than a value ΔTH.

[0041] If the difference ΔV is greater than or equal to the value ΔTH, the controller 250 allows the start of the cooling device 125 since the replaced coolant is considered to be an appropriate coolant.

[0042] On the other hand, if the difference ΔV is not equal to or greater than the value ΔTH, it is considered that the electrical conductivity V2 has increased from the initial value V0, and therefore it is possible that an inappropriate coolant has been mistakenly injected into the cooling device 125 as the coolant after replacement. In particular, if the electrical conductivity V2 is high enough to exceed the predetermined value PV, it is undesirable because a current is particularly likely to flow through the cooling device 125 via the replaced coolant. Therefore, in this case, the control device 250 may output, for example, a signal to the ECU 105 indicating that an inappropriate coolant may have been mistakenly injected into the cooling device 125. At that time, the ECU 105 notifies a mechanic or the like of the possibility. Then, the control device 250 does not permit the start of the cooling device 125.

[0043] Figures 5 and 6 are flow charts showing an example of a procedure of a process associated with replacement of a coolant. Referring to Figure 5, in step S105, the control device 250 judges whether the vehicle 100 has transitioned to a maintenance mode according to whether the trigger TR in Figure 2 has been received. Note that the control device 250 may judge whether another procedure that is always performed when the coolant is replaced has been performed, instead of whether the vehicle 100 has transitioned to the maintenance mode.

[0044] If the vehicle 100 has not transitioned to the maintenance mode (NO in step S105), the valves for replacing the coolant (i.e., the liquid inlet valve 240 and the liquid drainage valve 245) are locked (step S110) until the vehicle 100 transitions to the maintenance mode (until the YES branch is followed in step S105). On the other hand, if the vehicle 100 has transitioned to the maintenance mode (YES in step S105), the control device 250 advances the process to step S115.

[0045] In step S115, the control device 250 operates the pump 225 and the heater 235 to average the concentration of the coolant before replacement in the cooling path 205 and adjust the temperature of the coolant. The conductivity of the coolant may change depending on the concentration and temperature of the coolant. Therefore, the concentration of the coolant before replacement is averaged so that the conductivity sensor 210 can accurately detect the conductivity V1 of the coolant before replacement in step S120. In addition, the control device 250 controls the heater 235 based on the detection value of the temperature sensor 215 so that the temperature of the coolant when the conductivity sensor 210 detects the conductivity V1 and the conductivity V2 in the subsequent steps S120 and S185 is the same. In this way, the control device 250 adjusts the temperature of the coolant before replacement to a predetermined temperature. The predetermined temperature is, for example, a temperature at which the conductivity sensor 210 can most accurately detect the conductivity of the coolant, and is determined by experiments or the like.

[0046] In step S120, the control device 250 acquires the conductivity V1 before replacement of the coolant from the conductivity sensor 210. Then, the control device 250 stores the conductivity V1 in the memory 255 (step S122).

[0047] In step S125, the drain valve 245 is released (that is, the valve is unlocked).

[0048] In step S130, the control device 250 judges whether the drainage valve 245 has been removed within a certain period of time. This certain period of time is provided to prevent the drainage valve 245 from being left unlocked. If the drainage valve 245 has not been removed within the certain period of time (NO in step S130), the drainage valve 245 is locked again (step S135). Thereafter, the control device 250 returns the process to step S115. On the other hand, if the drainage valve 245 has been removed within the certain period of time (YES in step S130), the cooling liquid before replacement within the cooling device 125 is discharged (step S140).

[0049] When the draining of the cooling liquid is completed, in step S145, the control device 250 judges whether or not a valve other than the liquid injection valve 240 (including the liquid drainage valve 245) is installed. If a valve other than the liquid injection valve 240 is not installed (NO in step S145), the control device 250 cannot start the cooling device 125 as it is, and the ECU 105 cannot start the vehicle 100 either. Therefore, when an instruction to start the vehicle 100 is output, the ECU 105 prohibits the start of the vehicle 100 and outputs an alarm to the effect that the start of the vehicle 100 is not permitted (step S150). The alarm is output to a display (not shown) of the vehicle 100 or the like. After the alarm is output, the process returns to step S145. On the other hand, if a valve other than the liquid injection valve 240 is installed (YES in step S145), the control device 250 advances the process to step S155 in FIG. 6.

[0050] 6, in step S155, the valves (including the drain valve 245) other than the liquid injection valve 240 are locked. After that, a mechanic or the like injects new cooling liquid into the cooling device 125 (step S160).

[0051] When the injection of the cooling liquid is completed, in step S165, the control device 250 judges whether or not the liquid injection valve 240 is attached. If the liquid injection valve 240 is not attached (NO in step S165), the control device 250 cannot start the cooling device 125 as it is, and the ECU 105 cannot start the vehicle 100 either. Therefore, when an instruction to start the vehicle 100 is output, the ECU 105 prohibits the start of the vehicle 100 and outputs an alarm to the effect that the start of the vehicle 100 is not permitted (step S170). After the alarm is output, the process returns to step S165. On the other hand, if the liquid injection valve 240 is attached (YES in step S165), the liquid injection valve 240 is then locked (step S175).

[0052] In step S180, similar to step S115, the control device 250 operates the pump 225 and the heater 235 to average the concentration of the replaced coolant in the cooling path 205 and adjust the temperature of the coolant to the predetermined temperature.

[0053] In step S185, the control device 250 acquires the conductivity V2 from the conductivity sensor 210.

[0054] In step S190, the control device 250 compares the conductivity V1 with the conductivity V2, and determines whether the value obtained by subtracting the conductivity V2 from the conductivity V1, i.e., the difference ΔV (ΔV=V1-V2), is greater than or equal to the value ΔTH.

[0055] If the difference ΔV is smaller than the value ΔTH (NO in step S190), there is a possibility that an inappropriate coolant for use after replacement has been mistakenly injected into the cooling device 125, and therefore the control device 250 does not permit the start of the cooling device 125. Therefore, the ECU 105 prohibits the start of the vehicle 100, and outputs a notification urging a mechanic or the like to replace the erroneously injected coolant (with an appropriate coolant) again (step S195). The notification is output to a display or the like of the vehicle 100. Thereafter, the process returns to step S125.

[0056] On the other hand, if the difference ΔV is greater than or equal to the value ΔTH (YES in step S190), it is considered that an appropriate coolant has been injected into the cooling device 125 as the coolant after replacement (i.e., an inappropriate coolant has not been mistakenly injected into the cooling device 125), so the control device 250 proceeds to step S198.

[0057] In step S198, the control device 250 permits the start-up of the cooling device 125. Accordingly, after the ECU 105 permits the start-up of the vehicle 100, the series of processes ends.

[0058] As described above, in this embodiment, the control device 250 compares the conductivity V1 of the coolant before replacement with the conductivity V2 of the coolant after replacement, and determines whether the value obtained by subtracting the conductivity V1 of the coolant before replacement from the conductivity V2 of the coolant after replacement (i.e., the difference ΔV) is greater than or equal to the value ΔTH.

[0059] Here, as described above, the detection accuracy of the conductivity sensor 210 deteriorates over time, but the detection accuracy does not change in a short period such as before and after the coolant is replaced. Therefore, the difference ΔV according to the conductivity V1 and the conductivity V2 is obtained under the condition that the detection accuracy of the conductivity sensor 210 is the same before and after the coolant is replaced. Therefore, even if the detection accuracy has decreased, the difference ΔV does not change depending on the detection accuracy.

[0060] Therefore, unlike a case where the appropriateness of replacing the coolant is determined using only the absolute value of the detected value of the conductivity V2 of the replaced coolant, the control device 250 according to the embodiment can correctly determine the appropriateness of replacing the coolant according to the difference ΔV even if the detection accuracy of the conductivity sensor 210 is reduced. As a result, it is possible to prevent the cooling device 125 from starting up due to erroneous injection of an inappropriate coolant (for example, a coolant having a higher conductivity than that of the coolant before replacement) into the cooling device 125.

[0061] The embodiments disclosed herein should be considered to be illustrative and not restrictive in all respects. The scope of the present invention is defined by the claims, not by the description of the embodiments described above, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0062] 100 vehicle, 110 battery pack, 125 cooling device, 250 control device, 205 cooling path, 210 conductivity sensor, 230 battery, 255 memory, 305A, 305B electrodes, 310 coolant.

Claims

[Claim 1] A cooling device for cooling a battery, comprising: A sensor for detecting the conductivity of a cooling fluid that cools the battery; A control device for controlling the cooling device, When the coolant is replaced, the control device A cooling device that allows the cooling device to start up when a value obtained by subtracting a second conductivity, which is the conductivity after the cooling liquid is replaced, from a first conductivity, which is the conductivity before the cooling liquid is replaced, is greater than or equal to a threshold value.

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