Cooling system

Abstract

The invention provides a cooling system for cooling electrical equipment more appropriately. The cooling system includes a cooling device that circularly supplies cooling water to an object to be cooled including an electrical device, and a control device that controls the cooling device. The control device sets a temperature threshold value on the basis of seasons or outside air temperature, estimates the temperature of the electrical equipment on the basis of the amount of heat generated by the object to be cooled, and increases the flow rate of the cooling water when the temperature of the electrical equipment is higher than the temperature threshold value than when the temperature of the electrical equipment is equal to or lower than the temperature threshold value.

Description

Technical Field

[0001] This disclosure relates to cooling systems. Background Technology

[0002] Conventionally, fuel cell systems have been proposed that include a fuel cell stack, a voltage converter that steps down the output voltage of the fuel cell stack via a circuit with switching elements (i.e., a voltage converter that supplies power to multiple electrical devices), a cooler for cooling the voltage converter with refrigerant, and a controller for controlling the voltage converter (for example, see Patent Document 1). In this fuel cell system, the controller determines the upper limit of the voltage converter's output based on the temperature of the switching elements and the temperature of the refrigerant.

[0003] Existing technical documents

[0004] Patent Document 1: Japanese Patent Application Publication No. 2024-71120

[0005] In a cooling system that circulates cooling water to an object containing electrical equipment, the temperature of the electrical equipment is affected by the season (outdoor temperature), thus requiring more appropriate cooling of the electrical equipment. The main objective of the cooling system disclosed herein is to more appropriately cool electrical equipment. Summary of the Invention

[0006] To achieve the aforementioned main objectives, the cooling system of this disclosure employs the following means. The cooling system of this disclosure comprises: a cooling device that circulates cooling water to a cooling object containing electrical equipment; and a control device that controls the cooling device, the main purpose of which is that the control device sets a temperature threshold based on the season or external temperature, estimates the temperature of the electrical equipment based on the heat generated by the cooling object, and increases the flow rate of the cooling water when the temperature of the electrical equipment is higher than the temperature threshold compared to when the temperature of the electrical equipment is lower than the temperature threshold.

[0007] In the cooling system disclosed herein, a temperature threshold is set based on the season or external temperature, and the temperature of the electrical equipment is estimated based on the heat generated by the object being cooled. When the temperature of the electrical equipment is higher than the temperature threshold, the flow rate of cooling water is increased compared to when the temperature of the electrical equipment is lower than the temperature threshold. Therefore, the electrical equipment can be cooled more appropriately based on the season and external temperature. For example, by lowering the temperature threshold in winter compared to summer, or by lowering the temperature threshold as the external temperature decreases, the temperature of the electrical equipment can be reduced in winter and when the external temperature is low, thereby extending the lifespan of the electrical equipment. Attached Figure Description

[0008] Figure 1 This is a schematic structural diagram of a fuel cell vehicle equipped with a cooling system according to the implementation method.

[0009] Figure 2 This is a schematic diagram of the electronic control unit in a fuel cell vehicle.

[0010] Figure 3 This is a flowchart illustrating an example of a processing routine.

[0011] The annotations in the attached figures are explained as follows:

[0012] 10 Fuel cell vehicle, 12 Power control unit, 14, 23, 25, 54 Inverter, 16 Power line, 20 Power module, 21 Fuel cell stack, 22 Hydrogen pump, 24 Air compressor, 26, 30, 34 DC / DC converter, 32 High voltage battery, 36 Auxiliary battery, 50 Cooling device, 51 Circulation path, 52 Storage tank, 53 Water pump, 54 Inverter, 55 Oil cooler, 56 Radiator, 60 Electronic control unit, 62 CPU, 64 Power circuit, 65, 67, 69, L0~L3 Power lines, 66, 68, 70 Capacitor, 72 Power control unit. Detailed Implementation

[0013] The embodiments (implementations) for carrying out this disclosure will be described with reference to the accompanying drawings. Figure 1 This is a schematic structural diagram of a fuel cell vehicle 10 equipped with a cooling system according to an embodiment of the present disclosure. As shown, the fuel cell vehicle 10 includes a motor MG, an inverter 14, a fuel cell stack (FC stack) 21, a hydrogen pump (HP) 22, an inverter 23, an air compressor (ACP) 24, an inverter 25, and a DC / DC inverter 26. Furthermore, the fuel cell vehicle 10 includes a DC / DC converter 30, a high-voltage battery 32, a DC / DC converter 34, an auxiliary battery 36, a cooling device 50, and an electronic control unit (ECU) 60. Here, the fuel cell stack 21 and the DC / DC converter 26 are housed in the same housing or arranged close to each other, forming a power module 20. The inverter 14, inverter 25, DC / DC converter 30, DC / DC converter 34, and electronic control unit 60 are housed in the same housing or arranged close to each other, forming a power control unit (PCU) 12. Additionally, the inverter 23 and / or the inverter 54 of the cooling device 50 may also be part of the power control unit 12. The cooling system implemented in this way mainly consists of a cooling device 50 and an electronic control unit 60.

[0014] The rotor of motor MG is connected to the drive wheel. Inverter 14 is connected to power line L1. Inverter 14 is controlled by electronic control unit 60 and drives motor MG. Fuel cell stack 21 generates electricity through the electrochemical reaction of hydrogen supplied to the anode electrode and oxygen supplied to the cathode electrode. Hydrogen pump 22 supplies hydrogen from hydrogen tank to the anode electrode. Inverter 23 is connected to power line L2. Inverter 23 is controlled by electronic control unit 60 and drives hydrogen pump 22. Air compressor 24 supplies oxygen from the air to the cathode electrode. Inverter 25 is connected to power line L1. Inverter 25 is controlled by electronic control unit 60 and drives air compressor 24. DC / DC converter 26 is connected to power lines L0 and L1. DC / DC converter 26 is controlled by electronic control unit 60, boosts the power from power line L0 and supplies it to power line L1.

[0015] DC / DC converter 30 is connected to power lines L1 and L2.

[0016] The DC / DC converter 30, controlled by the electronic control unit 60, either boosts the power from power line L2 and supplies it to power line L1, or steps down the power from power line L1 and supplies it to power line L2. The high-voltage battery 32, with a rated voltage of several hundred volts, is connected to power line L2. The DC / DC converter 34 is connected to both power lines L2 and L3. Controlled by the electronic control unit 60, the DC / DC converter 34 steps down the power from power line L2 and supplies it to power line L3. The auxiliary battery 36, with a rated voltage of approximately 12V, is connected to power line L3.

[0017] The cooling device 50 includes a circulation path 51, a storage tank 52, a water pump 53, an inverter 54, an oil cooler 55, and a radiator 56. The circulation path 51 is configured to circulate cooling water sequentially through the power module 20, the power control unit 12, the storage tank 52, the water pump 53, the air compressor 24, the oil cooler 55, and the radiator 56. The water pump 53 circulates the cooling water in the circulation path 51. The inverter 54 is connected to the power line L2. This inverter 54 is controlled by an electronic control unit 60 and drives the water pump 53.

[0018] like Figure 1 , Figure 2As shown, the electronic control unit 60 includes a microcomputer with a CPU 62, a power supply circuit 64, various drive circuits, and various logic ICs. The power supply circuit 64 is connected to the power line 16, converting the power voltage of the power line 16 into a first voltage V1, a second voltage V2, and a third voltage V3, which are then output to power lines 65, 67, and 69, respectively. The first, second, and third voltages are, for example, 5.0V, 2.5V, and 1.5V, respectively. Capacitors 66, 68, and 70 are connected to power lines 65, 67, and 69, respectively. The voltages on power lines 65, 67, and 69 are essential for the operation of the CPU 62, the switching elements of inverters 14, 23, 25, and 54, the DC / DC converters 26, 30, and 34, and various sensors. Signals from various sensors are input to the electronic control unit 60. For example, the inputs also include the voltages VL0, VL1, VL2, and VL3 from the power lines L0, L1, L2, and L3 of each voltage sensor; the output voltage Vfc and output current Ifc of the fuel cell stack 21 from the voltage and current sensors; the rotational speed Nw of the water pump 53 from the speed sensor; the external gas temperature To from the external gas temperature sensor; and the switching signal from the power switch. The electronic control unit 60 calculates the generated power (output power) Pfc of the fuel cell stack 21 based on the output voltage Vfc and output current Ifc. Various control signals are output from the electronic control unit 60. For example, control signals are output to inverters 14, 23, 25, and 54, and DC / DC converters 26, 30, and 34.

[0019] Furthermore, at least a portion of the inverters 23 and 54 and the DC / DC converter 26 can also be controlled by an electronic control unit different from the electronic control unit 60.

[0020] Next, the operation of the cooling system provided by the fuel cell vehicle 10 according to the embodiment will be explained. Figure 3 This is a flowchart illustrating an example of a processing routine repeatedly executed by the CPU 62 of the electronic control unit 60 at predetermined intervals (e.g., a few seconds to tens of seconds) Δt.

[0021] When this routine is executed, CPU 62 determines whether it is the first execution of this routine after the power switch is turned on and the system starts up (step S100). If it is determined to be the first execution of this routine, a threshold Taref is set based on the temperature Ta around capacitors 66, 68, and 70 at system startup, i.e., the initial temperature Ta0 (step S110), and the counter C is set to 0 (step S120), proceeding to step S140. The initial temperature Ta0 can be, for example, the external temperature To at system startup, i.e., the initial external temperature To0. The threshold Taref can be set, for example, by applying the initial temperature Ta0 to a threshold mapping predetermined based on the relationship between the initial temperature Ta0 and the threshold Taref according to experiments or analysis, and deriving the corresponding threshold Taref. In the embodiment, the threshold Taref is set to be lower the lower the initial temperature Ta0. The reason for this will be explained later. If it is determined in step S100 that this routine is executed for the second time or later, the counter C is incremented by 1 to update it (step S130), proceeding to step S140.

[0022] Next, the heat generation Qfcm of the power generation Pfc of the fuel cell stack 21 is estimated (step S140). Based on the estimated heat generation Qfcm, the inlet water temperature Twi of the power control unit 12 is estimated (step S150). Based on the estimated inlet water temperature Twi, the outlet water temperature Two of the power control unit 12 is estimated (step S160). The heat generation Qfcm can be estimated, for example, by applying the power generation Pfc to a heat generation mapping predetermined based on experiments or analysis, which is the relationship between the power generation Pfc and the heat generation Qfcm, and deriving the corresponding heat generation Qfc. The inlet water temperature Twi can be estimated, for example, by applying the heat generation Qfcm to an inlet water temperature mapping predetermined based on experiments or analysis, which is the relationship between the heat generation Qfcm and the inlet water temperature Twi, and deriving the corresponding inlet water temperature Twi. The outlet water temperature Two can be estimated, for example, by applying the inlet water temperature Twi to a predetermined outlet water temperature mapping based on the relationship between the inlet water temperature Twi and the outlet water temperature Two, and deriving the corresponding outlet water temperature Two.

[0023] Then, based on the inlet water temperature Twi and the outlet water temperature Two, the base temperature Tatmp, which serves as the baseline value of the temperature Ta around capacitors 66, 68, and 70, is estimated (step S170). The estimated base temperature Tatmp is then multiplied by the counter C and the coefficient kt to estimate the temperature Ta (step S180). The base temperature Tatmp can be estimated, for example, by applying the inlet water temperature Twi and the outlet water temperature Two to a base temperature mapping predetermined based on experiments or analysis, which is the relationship between the inlet water temperature Twi, the outlet water temperature Two, and the base temperature Tatmp, and deriving the corresponding base temperature Tatmp. The coefficient kt, representing the increase in temperature Ta over a specified time Δt, is predetermined through experiments, analysis, etc.

[0024] When the estimated temperature Ta is determined in this way, it is determined whether the estimated temperature Ta is below the aforementioned threshold Taref (step S190). If it is determined that the temperature Ta is below the threshold Taref, the target rotational speed Nf* of the water pump 53 is set to a normal value Nw1 (step S200), and the target voltage VL3* of the power line L3 is set to a normal value VL31 (step S210), and the routine ends. If the target rotational speed Nw* and the target voltage VL3* are set, the inverter 54 is controlled so that the water pump 53 rotates at the target rotational speed Nw*, and the DC / DC converter 34 is controlled so that the voltage VL3 of the power line L3 becomes the target voltage VL3*.

[0025] In step S190, when the temperature Ta is higher than the threshold Taref, the target rotational speed Nf* of the water pump 53 is set to a value Nw2 higher than Nw1 (step S220), and the target voltage VL3* of the power line L3 is set to a value VL32 lower than VL31 (step S230), thus ending the routine. When the temperature Ta is higher than the threshold Taref, compared to when the temperature Ta is below the threshold Taref, increasing the rotational speed Nw of the water pump 53 increases the flow rate of the cooling water in the circulation path 51, thereby improving the cooling performance of the power control unit 12 and suppressing the rise in temperature Ta. Furthermore, when the temperature Ta is higher than the threshold Taref, compared to when the temperature Ta is below the threshold Taref, decreasing the voltage VL3 of the power line L3 reduces the voltage difference before and after the voltage drop in the power circuit 64, thereby suppressing the heat generation of the power circuit 64 and suppressing the rise in temperature Ta.

[0026] In this implementation, the threshold value Tarf is set based on the initial temperature Ta0 (initial external air temperature To0) around capacitors 66, 68, and 70, thus enabling more appropriate cooling of capacitors 66, 68, and 70 based on the initial temperature Ta0. Specifically, the threshold value Tarf is set so that the lower the initial temperature Ta0, the lower the temperature rise of capacitors 66, 68, and 70 when the initial temperature Ta0 is low, thereby extending the lifespan of capacitors 66, 68, and 70. When the initial temperature Ta0 is high, the increased power consumption of water pump 53 can be suppressed.

[0027] In the cooling system of the embodiment described above, the threshold Tarf is set so that the lower the initial temperature Ta0 (initial external air temperature To0), the higher the threshold Tarf. Then, when the temperature Ta is higher than the threshold Tarf, the speed Nw of the water pump 53 is increased to increase the flow rate of cooling water compared to when the temperature Ta is lower than the threshold Tarf. Therefore, when the initial temperature Ta0 is low, the temperature rise of capacitors 66, 68, and 70 (the objects being cooled) can be further suppressed, thus extending the lifespan of capacitors 66, 68, and 70. When the initial temperature Ta0 is high, the increased power consumption of the water pump 53 can be suppressed.

[0028] In the above implementation, the threshold Taref is set as lower as the initial temperature Ta0 (initial external temperature To0) is. However, this is not a limitation. For example, a year can be divided into two periods, with the threshold Taref lowered for winter (e.g., November to April) compared to summer (May to October). Alternatively, a year can be divided into four periods, with the threshold Taref set from low to high as winter, spring, autumn, and summer.

[0029] In the above embodiment, the inlet water temperature Twi of the power control unit 12 is estimated based on the heat output Qfcm of the power module 20, and the outlet water temperature Two of the power control unit 12 is estimated based on the estimated inlet water temperature Twi, but it is not limited to this. For example, a temperature sensor can be installed near the inlet of the power control unit 12 in the circulation path 51 to detect the inlet water temperature Twi. Alternatively, a temperature sensor can be installed near the outlet of the power control unit 12 in the circulation path 51 to detect the outlet water temperature Two.

[0030] In the above-described embodiment, when the temperature Ta is higher than the threshold Taref, compared to when the temperature Ta is below the threshold Taref, the rotational speed Nw of the water pump 53 is increased to increase the flow rate of cooling water, and the voltage VL3 of the power line L3 is decreased, but this is not the only limitation. For example, the flow rate of cooling water may be increased simply by increasing the rotational speed Nw of the water pump 53.

[0031] In the above embodiment, the cooling system is designed to be installed in a fuel cell vehicle 10 that includes a motor MG, a fuel cell stack 21, a hydrogen pump 22, an air compressor 24, a DC / DC converter 26, and a high-voltage battery 32, but it is not limited to this. For example, it could be installed in the cooling system of an electric vehicle that includes a motor and a high-voltage battery, or it could be installed in the cooling system of a hybrid vehicle that includes an engine in addition to a motor and a high-voltage battery. Otherwise, any cooling system that includes a cooling device for circulating cooling water to objects containing electrical equipment and a control device for controlling the cooling device is acceptable.

[0032] The correspondence between the main elements of the implementation method and the main elements of the invention listed in the means for solving the problem section will be explained. In the implementation method, capacitors 66, 68, 70, etc. correspond to "cooling objects", cooling device 50 corresponds to "cooling device", and electronic control unit 60 corresponds to "control device".

[0033] The above describes the methods for implementing this disclosure using various embodiments, but this disclosure is not limited to such embodiments. Of course, it can be implemented in various ways without departing from the spirit of this disclosure.

[0034] Industrial availability

[0035] This disclosure can be used in industries such as the manufacturing of cooling systems.

Claims

1. A cooling system comprising: a cooling device for circulating cooling water to an object including electrical equipment; and a control device for controlling the cooling device. in, The control device sets a temperature threshold based on the season or external temperature, estimates the temperature of the electrical equipment based on the heat generated by the object being cooled, and increases the flow rate of cooling water when the temperature of the electrical equipment is higher than the temperature threshold compared to when the temperature of the electrical equipment is lower than the temperature threshold.

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