WO2020218008A1

WO2020218008A1 - Cooling system

Info

Publication number: WO2020218008A1
Application number: PCT/JP2020/015945
Authority: WO
Inventors: 清水　肇; 義則　毅; 康光大見; 功嗣三浦
Original assignee: 株式会社デンソー
Priority date: 2019-04-26
Filing date: 2020-04-09
Publication date: 2020-10-29
Also published as: JP2020183815A

Abstract

A cooling system (1) is provided with a looped thermosiphon (10) including a cooler (11) and a condenser (12), wherein a refrigerant naturally circulates between the cooler (11) and the condenser (12). The cooling system (1) is provided with a shut-off valve (15) for closing a liquid pipe (14), an ECU (20) for controlling opening and closing of the shut-off valve (15), and a pressure sensor (33) for detecting the pressure of the gas refrigerant. The ECU (20) closes the shut-off valve (15) in a state in which there is a temperature difference between a refrigerant temperature in the cooler (11) and a refrigerant temperature in the condenser (12). When the pressure detected by the pressure sensor (33) has increased to a predetermined value or above, the ECU (20) determines that the refrigerant is normally circulating in the looped thermosiphon (10). If the pressure detected by the pressure sensor (33) does not increase to the predetermined value when the shut-off valve (15) is closed, the ECU (20) determines that the looped thermosiphon (10) has abnormality.

Description

Cooling system

Cross-reference of related applications

This application is based on Patent Application No. 2019-086770 filed in Japan on April 26, 2019, the contents of which are incorporated herein by reference.

The disclosure in this specification relates to a cooling system.

Patent Document 1 includes a loop-type thermosiphon having an evaporator (cooler) that evaporates the liquid phase refrigerant and a condenser that condenses the gas phase refrigerant, and phase changes between the liquid phase and the gas phase. A cooling system is disclosed in which heat is transported by using a refrigerant to be used, and the refrigerant naturally circulates between the cooler and the condenser. In the configuration described in Patent Document 1, an on-off valve is provided in the liquid pipe between the condenser and the cooler, and the control unit controls the opening and closing of the on-off valve for the purpose of preventing supercooling of the battery cell.

International Publication No. 2018/047531

Examples of the cooling device in which the refrigerant circulates include a configuration in which the refrigerant is forcibly circulated and a configuration in which the refrigerant circulates naturally. In the case of forced circulation, for example, in a configuration in which the refrigerant is circulated by an electric pump, it is possible to determine whether or not the refrigerant is normally circulated by monitoring the pump rotation speed and the drive current. That is, it is possible to detect a refrigerant circulation abnormality based on the pump rotation speed and the drive current. On the other hand, in the case of natural circulation, for example, in a configuration provided with a loop type thermosiphon, since the electric pump does not exist, the state cannot be determined based on the pump rotation speed and the drive current. Therefore, it is desired that the loop type thermosiphon in which the refrigerant naturally circulates can be accurately determined that the internal refrigerant circulates normally.

The present disclosure has been made in view of the above circumstances, and it is possible to determine the circulation state of the refrigerant with a simple configuration for a loop type thermosiphon in which the refrigerant that changes phase between the liquid phase and the gas phase naturally circulates. The purpose is to provide a cooling system that can.

The present disclosure is a cooler that absorbs the heat of a heating element to evaporate a liquid refrigerant, a condenser that is arranged above the cooler and condenses a gaseous refrigerant vaporized by the cooler, and is vaporized by the cooler. It is provided with a loop type thermosiphon having a gas pipe for circulating the gas refrigerant to the condenser and a liquid pipe for circulating the liquid refrigerant liquefied by the condenser to the cooler, and the refrigerant is provided between the cooler and the condenser. Is a cooling system that circulates naturally. It is installed in a gas pipe or a liquid pipe and is provided in a shut valve that closes the pipe, a control unit that controls the opening and closing of the shut valve, and a gas pipe that detects the pressure of the gaseous refrigerant. The control unit closes the shut valve when there is a temperature difference between the refrigerant temperature in the cooler and the refrigerant temperature in the condenser, and the pressure detected by the pressure sensor reaches a predetermined value or higher. When it rises, it has a first determination unit that determines that the liquid is normally circulating in the loop type thermosiphon, and the first determination unit has a first determination unit even if the shut valve is closed with a temperature difference. If the pressure detected by the pressure sensor does not rise to a predetermined value, it is determined that the loop type thermosiphon is abnormal.

Further, a temperature sensor for detecting the temperature of the refrigerant in the loop type thermo siphon is further provided, and the control unit detects the pressure detected by the pressure sensor and the temperature sensor when it is determined to be normal by the first determination unit. By comparing the actual refrigerant characteristics determined by the determined temperature with the theoretical characteristics determined by the saturation pressure and saturation temperature obtained from the physical property values of the refrigerant, whether or not the actual refrigerant characteristics deviate from the theoretical characteristics by a predetermined value or more. The second determination unit has a second determination unit that determines that the refrigerant characteristics are abnormal when the actual refrigerant characteristics deviate from the theoretical characteristics by a predetermined value or more, and the actual refrigerant characteristics are determined. If it does not deviate from the theoretical characteristics by a predetermined value or more, it may be determined that the refrigerant characteristics are normal.

According to this configuration, it is possible to detect an abnormality in the characteristics of the refrigerant by comparing the actual refrigerant characteristics inside the loop type thermosiphon with the theoretical characteristics obtained from the physical property values of the refrigerant.

Further, the heating element is a battery mounted on the vehicle, and the control unit may perform a determination process by the first determination unit when executing control for switching the open / closed state of the shut valve during soaking of the vehicle. ..

According to this configuration, it is possible to perform abnormality detection control of the loop type thermosiphon in parallel with the control executed during the soaking of the vehicle.

Further, the control unit may perform a determination process by the first determination unit when closing the shut valve by executing control for suppressing the temperature variation of the battery during soaking of the vehicle.

According to this configuration, it is possible to control the abnormality detection of the loop type thermosiphon in parallel with the control of suppressing the temperature variation executed during the soaking of the vehicle.

In addition, the control unit performs a determination process by the first determination unit when the shut valve is closed by executing control for suppressing supercooling of the battery due to the low outside air temperature of the vehicle during soaking of the vehicle. You may.

According to this configuration, it is possible to perform abnormality detection control of the loop type thermosiphon in parallel with suppression control of supercooling executed during soaking of the vehicle.

In the present disclosure, in a cooling system in which a refrigerant that changes phase between a gas phase and a liquid phase naturally circulates, the circulation state of the refrigerant in the loop type thermosiphon is monitored by monitoring the pressure change according to the opening and closing of the shut valve. It can be determined accurately.

It is a schematic diagram which shows the schematic structure of the cooling system in an embodiment. It is a schematic diagram which shows the state which the refrigerant naturally circulates between a cooler and a condenser. It is a figure for demonstrating the operation principle of a loop type thermosiphon. It is a figure which shows an example of the pressure change before and after opening and closing of a shut valve. It is a figure which shows the relationship between the temperature and pressure according to the open / closed state of a shut valve. It is a flowchart which shows an example of an abnormality detection control flow.

Hereinafter, the cooling system in the embodiment will be specifically described with reference to the drawings. The present disclosure is not limited to the embodiments described below.

FIG. 1 is a schematic diagram showing a schematic configuration of a cooling system according to an embodiment. FIG. 2 is a schematic view showing a state in which the refrigerant naturally circulates between the cooler and the condenser. FIG. 3 is a diagram for explaining the operating principle of the loop type thermosiphon. In FIG. 2, the flow when the refrigerant circulates is indicated by an arrow.

The cooling system 1 targets the battery cell 2 for cooling. The cooling system 1 includes a loop-type thermosiphon 10 that transports heat by using a working fluid (refrigerant) that changes phase between a liquid phase and a gas phase. The refrigerant is a heat transport medium that absorbs or dissipates heat by utilizing latent heat when gas-liquid changes occur. Here, the "liquid phase working fluid" is referred to as "liquid refrigerant", and the "gas phase working fluid" is referred to as "gas refrigerant".

The battery cell 2 has a square shape. The battery cell 2 constitutes a battery pack. The battery pack is composed of a plurality of battery modules. This battery module has a structure in which a plurality of battery cells 2 are arranged so as to be stacked. As described above, in the battery module composed of the plurality of battery cells 2, the temperature varies between the battery cells 2.

For example, the battery cell 2 is an in-vehicle battery mounted on an electric vehicle or a plug-in hybrid vehicle. In this case, the battery cell 2 stores electric power for supplying the traveling motor. Then, when the vehicle travels, electric power is supplied from the battery cell 2 to the traveling motor. Further, when charging from an external power source such as a charging stand, power is supplied from the external power source to the battery cell 2 in the vehicle. As described above, during discharging and charging, heat is generated in the battery cell 2 with energization. The heat of the battery cell 2 is transported by the loop type thermosiphon 10 and dissipated.

The loop type thermosiphon 10 includes a cooler 11, a condenser 12, a gas pipe 13 through which a gas refrigerant flows, and a liquid pipe 14 through which a liquid refrigerant flows. In the loop type thermosiphon 10, the refrigerant is sealed in the closed loop circuit, and the refrigerant can be naturally circulated between the cooler 11 and the condenser 12. A gas pipe 13 is laid so as to connect the steam outlet of the cooler 11 and the steam inlet of the condenser 12. A liquid pipe 14 is piped so as to connect the liquid outlet of the condenser 12 and the liquid inlet of the cooler 11.

The cooler 11 absorbs the heat generated in the battery cell 2 to evaporate the liquid refrigerant. That is, the cooler 11 functions as an evaporator in the loop type thermosiphon 10. A liquid refrigerant is supplied to the inside of the cooler 11. The outer surface of the cooler 11 is in contact with the surface of the battery cell 2. The liquid refrigerant supplied to the inside of the cooler 11 receives the heat of the battery cell 2 and boils to evaporate. As shown in FIG. 3, when the liquid refrigerant evaporates in the cooler 11, heat is transferred from the battery cell 2 to the cooler 11 due to the transfer of latent heat accompanying the evaporation. In this way, the cooler 11 absorbs the heat of the battery cell 2 to cool the battery cell 2.

The steam (gas refrigerant) vaporized inside the cooler 11 flows out from the steam outlet to the gas pipe 13. Then, the heat generated in the battery cell 2 is transported to the condenser 12 by the gas refrigerant. The heat of the battery cell 2 is dissipated by the condenser 12.

The condenser 12 is arranged above the cooler 11 and condenses the gaseous refrigerant vaporized by the cooler 11. For example, the condenser 12 is composed of a radiator which is an air-cooled radiator. As shown in FIG. 3, the condenser 12 composed of a radiator exchanges heat between the gaseous refrigerant and the outside air of the vehicle. For example, since the running wind hits the radiator while the vehicle is running, the gaseous refrigerant can dissipate heat.

The gas pipe 13 and the liquid pipe 14 are formed in an annular shape as a refrigerant pipe. The gas pipe 13 is a pipe that circulates the gas refrigerant vaporized by the cooler 11 to the condenser 12. The liquid pipe 14 is a pipe for circulating the liquid refrigerant liquefied by the condenser 12 to the cooler 11.

The lower end of the gas pipe 13 is connected to the steam outlet of the cooler 11, and extends upward in the vertical direction. The upper end of the gas pipe 13 is connected to the steam inlet of the condenser 12. The gaseous refrigerant flowing in the gas pipe 13 toward the condenser 12 flows upward in the vertical direction and then reaches the condenser 12.

The upper end of the liquid pipe 14 is connected to the liquid outlet of the condenser 12. As shown in FIG. 3, the liquid pipe 14 is lowered along the vertical direction from the upper end so that the liquid refrigerant liquefied by the condenser 12 flows downward in the vertical direction by its own weight (gravity). It is extended to. Further, the lower end of the liquid pipe 14 is connected to the liquid inlet of the cooler 11. The liquid refrigerant that has flowed downward in the vertical direction due to its own weight in the liquid pipe 14 flows into the cooler 11 from the liquid inlet.

Further, the liquid pipe 14 is provided with a shut valve 15 for closing the liquid pipe 14. The shut valve 15 is an on-off valve that switches between an open state and a closed state. When the shut valve 15 is open, the liquid refrigerant can flow through the liquid pipe 14, so that the refrigerant can circulate between the cooler 11 and the condenser 12. On the other hand, when the shut valve 15 is closed, the liquid refrigerant cannot flow through the liquid pipe 14, so that the refrigerant cannot circulate between the cooler 11 and the condenser 12. The shut valve 15 is composed of an electromagnetic valve, and is controlled by an electronic control device (hereinafter, referred to as ECU) 20. The open state of the shut valve 15 may be described as "OPEN", and the closed state of the shut valve 15 may be described as "CLOSE".

The ECU 20 includes a CPU, a storage unit that stores data such as various programs, and an arithmetic processing unit that performs various operations for controlling the temperature of the battery cell 2. Signals from various sensors are input to the ECU 20. As shown in FIG. 1, the cooling system 1 includes a first temperature sensor 31 that detects the temperature of the refrigerant in the cooler 11, a second temperature sensor 32 that detects the temperature of the refrigerant in the condenser 12, and the like. It is provided with a pressure sensor 33 that detects the pressure of the gas refrigerant in the gas pipe 13. Signals from the first temperature sensor 31, the second temperature sensor 32, and the pressure sensor 33 are input to the ECU 20. The first temperature sensor 31 is provided in a place where the representative temperature of the refrigerant (whether liquid or gas) in the cooler 11 can be measured. The second temperature sensor 32 is provided at a place where the representative temperature of the refrigerant (whether liquid or gas) in the condenser 12 can be measured. Further, signals from a battery temperature sensor (not shown) for detecting the temperature of the battery cell 2, an outside air temperature sensor (not shown) for detecting the temperature of the outside air, and the like may be input to the ECU 20. The battery temperature sensor is attached to the surface of the battery cell 2 and detects the battery temperature. In this description, the temperature of the battery cell 2 may be described as "battery temperature".

The ECU 20 executes abnormality detection control, which is a control for detecting an abnormality in the cooling system 1, based on input signals from the first temperature sensor 31, the second temperature sensor 32, and the pressure sensor 33. As abnormality detection control, the ECU 20 controls for detecting that the refrigerant is not normally circulated (circulation state determination control) and control for detecting that an abnormality has occurred in the refrigerant itself (refrigerant state). Discrimination control) and is executed.

In the circulation state discrimination control, the loop type thermosiphon uses the refrigerant temperature detected by the first temperature sensor 31, the refrigerant temperature detected by the second temperature sensor 32, and the refrigerant pressure detected by the pressure sensor 33. It is determined whether or not the refrigerant is normally circulated inside the 10. The circulation state discrimination control is a control focusing on the characteristics of the loop type thermosiphon 10. First, as a characteristic of the loop type thermosiphon 10, when there is a difference between the refrigerant temperature in the cooler 11 and the refrigerant temperature in the condenser 12, the pressure difference according to the temperature difference is the loop type thermosiphon 10. Occurs within. In this case, when the shut valve 15 is open, the refrigerant naturally circulates due to the pressure difference caused by this temperature difference. The internal pressure of the loop type thermosiphon 10 in the state where the refrigerant is naturally circulated is the same as the internal pressure of the loop type thermosiphon 10 in the state where the shut valve 15 is closed to correspond to a closed space (the liquid pipe 14 is closed). Will be different values.

Therefore, the shut valve 15 is switched from the open state to the closed state, and the pressure change generated at that time is detected by the pressure sensor 33. Then, when the detected pressure rises to a predetermined value or more, it is determined that the refrigerant is normally circulated in the loop type thermosiphon 10. On the other hand, when the detected pressure is lower than the predetermined value, it is determined that the refrigerant is not normally circulated in the loop type thermosiphon 10 (circulation abnormality).

As shown in FIG. 4, when compared at the same temperature, the refrigerant pressure when the shut valve 15 is open is lower than the refrigerant pressure when the shut valve 15 is closed. For example, the pressure difference at the same temperature is several tens of kPa. This means that in the loop type thermosiphon 10, the internal pressure when the shut valve 15 is closed to correspond to a closed space is higher than the internal pressure when the refrigerant is circulating. Therefore, as shown in FIG. 5, when the shut valve 15 is switched from the closed state to the open state (time t1), the pressure in the gas pipe 13 located in front of the condenser 12, that is, the pressure of the gas refrigerant becomes , It drops sharply before and after opening and closing the shut valve 15. Then, when the shut valve 15 is open, the pressure becomes lower than the theoretical saturation state. Although not shown in FIG. 4, the relationship between the pressure (theoretical saturation pressure) and the temperature (theoretical saturation temperature) in the theoretical saturation state is proportional. In theoretical saturation, the pressure rises proportionally (linearly) as the temperature rises. Further, the refrigerant pressure when the shut valve 15 is closed is closer to the theoretical saturation state than the refrigerant pressure when the shut valve 15 is open. Further, since the refrigerant flows when the shut valve 15 is open, the refrigerant pressure when the shut valve 15 is open is more turbulent than the refrigerant pressure when the shut valve 15 is closed (the deviation from the proportional change is large). Become).

Refrigerant state determination control includes a refrigerant abnormality (foreign matter mixed) in which foreign matter is mixed in the loop type thermosiphon 10 and a refrigerant abnormality (refrigerant) in which the refrigerant sealed in the loop type thermosiphon 10 leaks to the outside. This is a control for detecting omission). In this refrigerant state discrimination control, in a state where the shut valve 15 is closed and the inside of the loop type thermosiphon 10 is equivalent to a closed space, the actual refrigerant characteristics based on the measured values measured by the sensor and the physical property values of the refrigerant are used. Abnormality of the refrigerant characteristics is detected by comparing with the theoretical characteristics which are the theoretical values. The theoretical values are the theoretical saturation pressure and the theoretical saturation temperature obtained from the physical property values of the refrigerant. That is, the theoretical value is the physical property value of the refrigerant. The saturation pressure and saturation temperature theoretically obtained from the physical property values are the pressures when the refrigerant is filled in the closed space in a saturated state, and therefore correspond to the case where the shut valve 15 is closed and the refrigerant pipe is closed.

Therefore, the ECU 20 compares the measured value and the theoretical value (physical property value) with respect to the characteristics of the refrigerant indicating the relationship between pressure and temperature, and if the measured value deviates significantly from the theoretical value, the loop type thermosiphon. At 10, it is determined that an abnormality of the refrigerant has occurred.

Further, the ECU 20 controls the opening and closing of the shut valve 15 based on the temperature of the battery cell 2 detected by the battery temperature sensor, and adjusts the battery temperature to the optimum temperature. The ECU 20 executes temperature control for adjusting the temperature of the battery module to an optimum temperature by the loop type thermosiphon 10. The temperature control is for controlling the temperature variation among a plurality of battery cells 2 during the soaking of the vehicle and for suppressing the supercooling of the battery cells 2 due to the low outside air temperature during the soaking of the vehicle. Includes control of.

The vehicle equipped with the cooling system 1 is equipped with an ignition switch. The ignition switch accepts a user's start operation of the vehicle drive system (ignition on operation) and stop operation of the drive system (ignition off operation). In this description, the ignition on operation may be described as "IG-ON" and the ignition off operation may be described as "IG-OFF". When IG-ON is turned on, an IG-ON signal is output from the ignition switch to the ECU 20. When the IG-OFF signal is turned off, the IG-OFF signal is output from the ignition switch to the ECU 20. The ignition switch may be either a start switch or an ignition key.

When the IG-OFF signal is input from the ignition switch, the ECU 20 determines that the vehicle is soaking. The soaking of the vehicle means a state in which the electric power for the vehicle to travel is output from the battery cell 2 in a discharged state, and a state in which the vehicle is not charged from an external power source while the vehicle is stopped. The state in which electric power is not exchanged with respect to the battery cell 2 can be expressed as during soaking of the vehicle.

FIG. 6 is a flowchart showing an abnormality detection control flow. The control shown in FIG. 6 is executed by the ECU 20.

The ECU 20 determines whether or not it is the usage time of the battery pack, which is the time for detecting an abnormality in the cooling system 1 (step S1). In the storage unit of the ECU 20, abnormality detection timing information, which is a timing for detecting whether or not an abnormality has occurred in the loop type thermosiphon 10 of the cooling system 1, is stored. The abnormality detection time information includes the usage time of the battery pack, the mileage of the vehicle, and the like. In step S1, it is determined whether or not it is time to detect an abnormality in the cooling system 1.

If it is not the time to detect an abnormality in the cooling system 1 (step S1: No), this control routine ends.

When it is the time for detecting an abnormality in the cooling system 1 (step S1: Yes), the ECU 20 determines whether or not there is a temperature difference between the refrigerant temperature in the condenser 12 and the refrigerant temperature in the cooler 11 (step S2). ). In step S2, the temperature difference is calculated between the refrigerant temperature in the cooler 11 detected by the first temperature sensor 31 and the refrigerant temperature in the condenser 12 detected by the second temperature sensor 32. In this case, the refrigerant temperature in the condenser 12 is lower than the refrigerant temperature in the cooler 11. The refrigerant temperature detected by the first temperature sensor 31 is a representative temperature of the refrigerant in the cooler 11. Similarly, the refrigerant temperature detected by the second temperature sensor 32 is a representative temperature of the refrigerant in the condenser 12.

When there is no temperature difference between the refrigerant temperature in the condenser 12 and the refrigerant temperature in the cooler 11 (step S2: No), this control routine ends.

When there is a temperature difference between the refrigerant temperature in the condenser 12 and the refrigerant temperature in the cooler 11 (step S2: Yes), the ECU 20 determines whether or not there is a drive request for the shut valve 15 by another control. (Step S3). The drive request for the shut valve 15 may be either when the shut valve 15 is switched from the open state to the closed state or when the shut valve 15 is switched from the closed state to the open state.

The other control in step S3 is a control executed for a purpose different from the abnormality detection. For example, as another control, there is a control for switching the opening and closing of the shut valve 15 for the purpose of suppressing the variation in the battery temperature during soaking of the vehicle or for the purpose of lowering the temperature of the entire battery. Another control includes a control for switching the shut valve 15 from an open state to a closed state for the purpose of preventing supercooling of the battery when the outside air temperature is low.

If there is no drive request for the shut valve 15 by another control (step S3: No), this control routine ends.

When there is a drive request for the shut valve 15 by another control (step S3: Yes), the ECU 20 executes a control for switching the open / closed state of the shut valve 15 and drives the shut valve 15 (step S4). If the shut valve 15 is closed, in step S4, control for opening the shut valve 15 is executed. When the shut valve 15 is open, the control for closing the shut valve 15 is executed in step S4. At this time, a command signal for switching the open / closed state is output from the ECU 20 to the shut valve 15 composed of the solenoid valve.

The ECU 20 determines whether or not the internal pressure (refrigerant pressure) of the loop type thermosiphon 10 has changed before and after opening and closing the shut valve 15 (step S5). When the shut valve 15 is switched from the open state to the closed state, in step S5, it is determined whether or not the internal pressure of the loop type thermosiphon 10 has increased. When the shut valve 15 is switched from the closed state to the open state, in step S5, it is determined whether or not the internal pressure (refrigerant pressure) of the loop type thermosiphon 10 has decreased. The internal pressure used in step S5 is the pressure of the gas refrigerant measured by the pressure sensor 33 provided in the gas pipe 13. In addition, "internal pressure of loop type thermosiphon 10" may be described as "refrigerant pressure in loop type thermosiphon 10." Further, the ECU 20 has a first determination unit that executes the determination process of step S5.

Further, in step S5, not only the presence / absence of the pressure change but also the determination process based on the refrigerant pressure after the shut valve 15 is driven can be performed. For example, when the shut valve 15 is switched from the open state to the closed state, in step S5, it is determined whether or not the refrigerant pressure after closing the shut valve 15 has risen to a first predetermined value or more. When the refrigerant pressure is equal to or higher than the first predetermined value, a positive determination is made in step S5. On the other hand, when the shut valve 15 is switched from the closed state to the open state, in step S5, it is determined whether or not the refrigerant pressure after closing the shut valve 15 has dropped to the second predetermined value or less. When the refrigerant pressure is equal to or less than the second predetermined value, a positive determination is made in step S5.

When the refrigerant pressure in the loop type thermosiphon 10 does not change before and after opening and closing the shut valve 15 (step S5: No), the ECU 20 determines that the cooling system 1 is abnormal (step S6). In step S6, it is determined that the refrigerant in the loop type thermosiphon 10 is not normally circulated, that is, a circulation abnormality. By executing step S6, the ECU 20 can detect that the circulation state in the loop type thermosiphon 10 is abnormal. When step S6 is performed, this control routine ends.

On the other hand, when the refrigerant pressure in the loop type thermosiphon 10 changes before and after opening and closing the shut valve 15 (step S5: Yes), the ECU 20 determines that the refrigerant in the loop type thermosiphon 10 is normally circulating. (Step S7). By executing step S7, the ECU 20 can detect that the circulation state in the loop type thermosiphon 10 is normal. The processes of steps S1 to S7 described above are included in the control for detecting the circulation abnormality in the loop type thermosiphon 10 (circulation state determination control).

Further, the ECU 20 determines whether or not the shut valve 15 is currently closed (step S8).

If the shut valve 15 is currently open (step S8: No), this control routine ends.

When the shut valve 15 is currently closed (step S8: Yes), the ECU 20 determines the actual characteristics determined by the refrigerant pressure and the refrigerant temperature in the loop type thermosiphon 10 by the theoretical saturation pressure and the theoretical saturation temperature. Compare with the characteristic (step S9). In step S9, the actual refrigerant characteristics (characteristics of pressure and temperature) obtained from the sensor values and the theoretical characteristics (characteristics of pressure and temperature) obtained from the physical property values of the refrigerant are compared.

Specifically, the ECU 20 loops based on the refrigerant pressure (gas refrigerant pressure) in the gas pipe 13 measured by the pressure sensor 33 and the refrigerant temperature in the cooler 11 measured by the first temperature sensor 31. The actual refrigerant characteristics of the type thermo siphon 10 are obtained. The ECU 20 is configured to plot the refrigerant pressure and the refrigerant temperature measured in several states to create characteristic data (actual characteristics) based on the actual saturation pressure and saturation temperature. The created characteristic data can be used for comparison processing as actual characteristics. On the other hand, the theoretical characteristic is a value determined by the physical property value of the refrigerant. The refrigerant in the cooler 11 is basically saturated. Therefore, the saturation pressure and the saturation temperature, which are determined as the physical property values of the refrigerant, are uniquely determined.

Further, in step S9, it is possible to determine not only whether or not there is a deviation from the theoretical characteristics, but also whether or not the actual refrigerant characteristics (measured value) deviates from the theoretical characteristics (theoretical value) by a predetermined value or more. The predetermined value used here is a preset value. Further, as shown in FIG. 3 described above, the principle that the refrigerant naturally circulates in the loop type thermosiphon 10 is condensed in addition to the pressure difference of the refrigerant due to the temperature difference of the refrigerant between the cooler 11 and the condenser 12. This includes the liquid refrigerant flowing downward in the vertical direction due to its own weight (gravity) in the liquid pipe 14. Therefore, the internal pressure of the loop type thermosiphon 10 in the state where the refrigerant is circulated converges to a value slightly different from the theoretical saturation pressure and the theoretical saturation temperature obtained from the physical property values. In consideration of this, the ECU 20 determines whether or not the amount of deviation from the theoretical characteristics is large with respect to the characteristics of the actual refrigerant.

The ECU 20 determines whether or not the actual refrigerant characteristics determined by the measured refrigerant pressure and the refrigerant temperature deviate from the theoretical characteristics by a predetermined value or more (step S10). Further, the ECU 20 has a second determination unit that executes the determination process of step S10.

For example, if a foreign substance is mixed in the loop type thermosiphon 10, the flow path of the refrigerant becomes narrow and the internal pressure in the state where the refrigerant is circulating becomes higher than in the normal state. Therefore, in an abnormal state due to foreign matter contamination, when the shut valve 15 is switched from the closed state to the open state, the amount of pressure drop becomes smaller than in the normal state. In this way, a pressure change that deviates from the theoretical characteristics at the normal time occurs. In step S10, such a deviation (deviation) from the normal state is determined.

Also, if the refrigerant leaks from the loop type thermosiphon 10 to the outside, and if all the refrigerant leaks to the outside, the refrigerant does not circulate in the first place. Therefore, in an abnormal state due to the outflow of the refrigerant, no pressure change occurs when the shut valve 15 is switched from the closed state to the open state. In this way, a pressure change that deviates from the theoretical characteristics at the normal time occurs. In step S10, such a deviation (deviation) from the normal state is determined.

When the actual refrigerant characteristics determined by the measured refrigerant pressure and the refrigerant temperature deviate from the theoretical characteristics by a predetermined value or more (step S10: Yes), the ECU 20 determines that the refrigerant characteristics in the loop type thermosiphon 10 are abnormal. (Step S11). By executing step S11, the ECU 20 can detect that an abnormality in the refrigerant characteristics has occurred in the loop type thermosiphon 10. When step S11 is performed, this control routine ends.

When the actual refrigerant characteristics determined by the measured refrigerant pressure and the refrigerant temperature do not deviate from the theoretical characteristics by a predetermined value or more (step S10: No), the ECU 20 determines that the refrigerant characteristics in the loop type thermosiphon 10 are normal. (Step S12). By carrying out step S12, the ECU 20 can detect that the refrigerant characteristics in the loop type thermosiphon 10 are normal. When step S12 is performed, this control routine ends.

As described above, according to the embodiment, when there is a difference between the refrigerant temperature in the cooler 11 and the refrigerant temperature in the condenser 12, the open / closed state of the shut valve 15 is switched, and the refrigerant pressure at that time is changed. By monitoring the change, the abnormality of the loop type thermosiphon 10 can be detected. Thereby, with a simple configuration, it is possible to determine whether the circulation state in the loop type thermosiphon 10 and the refrigerant characteristics are in a normal state or an abnormal state.

As a modification of the above-described embodiment, the shut valve 15 may be provided in the gas pipe 13. That is, in the loop type thermosiphon 10, the shut valve 15 may be provided in the gas pipe 13 or the liquid pipe 14.

Further, in the control shown in FIG. 6 described above, it is determined whether or not there is a drive request for the shut valve 15 by another control, but the processes of steps S3 and S4 may not be performed. That is, if a positive determination is made in step S2 (step S2: Yes), the control routine may be configured to proceed to step S5. That is, the control may be an abnormality detection control executed independently of the other controls, instead of the control parallel to the drive request of the shut valve 15 by the other controls.

Further, when steps S3 and S4 are not performed, it may be configured to determine in step S1 whether or not the vehicle is soaking. That is, the soaking of the vehicle can be included in the abnormality detection time of step S1.

Further, in step S5, it is possible to determine not only whether or not there is a pressure change, but also whether or not the amount of pressure change before and after opening and closing the shut valve 15 is equal to or greater than a predetermined value. For example, when the shut valve 15 is switched from the open state to the closed state, in step S5, it is determined whether or not the amount of increase in the refrigerant pressure is equal to or greater than a predetermined value. When the shut valve 15 is switched from the closed state to the open state, in step S5, it is determined whether or not the amount of decrease in the refrigerant pressure is equal to or greater than a predetermined value. The rising amount, the falling amount, and the predetermined value described here represent absolute values.

Claims

A cooler that absorbs the heat of the heating element and evaporates the liquid refrigerant,
A condenser that is placed above the cooler and condenses the gaseous refrigerant vaporized by the cooler.
A gas pipe that distributes the gaseous refrigerant vaporized by the cooler to the condenser, and
A liquid pipe that distributes the liquid refrigerant liquefied by the condenser to the cooler, and
A cooling system comprising a loop type thermosiphon having a structure in which a refrigerant naturally circulates between the cooler and the condenser.
A shut valve provided on the gas pipe or the liquid pipe to close the pipe,
A control unit that controls the opening and closing of the shut valve,
A pressure sensor provided in the gas pipe to detect the pressure of the gaseous refrigerant,
With
When the control unit closes the shut valve in a state where there is a temperature difference between the refrigerant temperature in the cooler and the refrigerant temperature in the condenser, and the pressure detected by the pressure sensor rises to a predetermined value or more. Has a first determination unit that determines that the refrigerant is normally circulating in the loop type thermosiphon.
If the pressure detected by the pressure sensor does not rise to a predetermined value even if the shut valve is closed in a state where there is a temperature difference, the first determination unit determines that the loop type thermosiphon is abnormal. Cooling system.
A temperature sensor for detecting the temperature of the refrigerant in the loop type thermosiphon is further provided.
When the control unit is determined to be normal by the first determination unit, the control unit is based on the actual refrigerant characteristics determined by the pressure detected by the pressure sensor and the temperature detected by the temperature sensor, and the physical property value of the refrigerant. It has a second determination unit that compares the obtained saturation pressure with the theoretical characteristics determined by the saturation temperature and determines whether or not the actual refrigerant characteristics deviate from the theoretical characteristics by a predetermined value or more.
The second determination unit
If the actual refrigerant characteristics deviate from the theoretical characteristics by a predetermined value or more, it is determined that the refrigerant characteristics are abnormal.
The cooling system according to claim 1, wherein when the actual refrigerant characteristics do not deviate from the theoretical characteristics by a predetermined value or more, the refrigerant characteristics are determined to be normal.
The heating element is a battery mounted on a vehicle.
The cooling system according to claim 1 or 2, wherein the control unit performs a determination process by the first determination unit when executing control for switching the open / closed state of the shut valve during soaking of the vehicle.
According to claim 3, the control unit executes a control for suppressing temperature variation of the battery during the soaking of the vehicle, and when the shut valve is closed, the determination process by the first determination unit is performed. The cooling system described.
When the control unit executes control for suppressing supercooling of the battery due to the low outside air temperature of the vehicle during soaking of the vehicle and closes the shut valve, the first determination unit determines the control unit. The cooling system according to claim 3 or 4, wherein the determination process is performed.