Refrigerant reduction detection device

Abstract

To detect reduction of coolant for cooling a motor as soon as possible.SOLUTION: A coolant reduction detection device comprises: a motor 10 with a stator coil 14 and a rotor 13 in a casing 15; a cooling circuit 1 placed for removing heat of the motor 10 and an inverter 3; a capacitor tank 20 which stores coolant circulating in the cooling circuit 1; a thermistor 17 which detects temperature of the stator coil 14; and a coolant temperature sensor 30 which detects temperature of the coolant in the capacitor tank 20. The thermistor 17 is connected with the coolant temperature sensor 30 by a metal material, a prediction area B and a prediction area A of output of the coolant temperature sensor 30 to output from the thermistor 17 are prepared under each of liquid environment in which the coolant temperature sensor 30 is below a liquid level of the coolant and air environment in which the coolant temperature sensor 30 is above the liquid level of the coolant, and the coolant reduction detection device certifies reduction of the coolant on the basis of the output from the coolant temperature sensor 30, the prediction area B under the liquid environment and the prediction area A under the air environment when temperature rise information of the thermistor 17 is output.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] This invention relates to a refrigerant reduction detection device for detecting a decrease in a refrigerant for cooling a motor.

Background Art

[0002] Generally, electric vehicles and hybrid vehicles are equipped with a motor that supplies driving force for running and an inverter that controls AC power for driving the motor. A cooling circuit is provided for the motor and the inverter, and a liquid (cooling water) is supplied as a refrigerant for cooling the motor and the inverter to the cooling circuit. Hereinafter, a motor using cooling water as the refrigerant flowing in the cooling circuit is referred to as a water-cooled motor.

[0003] In a water-cooled motor, the cooling water flowing in the cooling circuit is stored in a capacitor tank (reservoir tank). The capacitor tank is provided with a pressure valve for setting the internal pressure to a pressure within a predetermined range. When the water-cooled motor is used over a long period of time, the cooling water may significantly decrease due to evaporation generated when the pressure valve opens or leakage due to damage to the cooling circuit. When the cooling water significantly decreases, when the pump sucks in the cooling water, the probability of sucking in air increases, air begins to mix into the cooling water, the actual flow rate decreases, and the motor and inverter may overheat. Depending on the type of pump used, there is concern about an adverse effect on the pump. In such a case, for protecting the components, a warning is issued to notify that the cooling water has decreased, or the motor output is suppressed to limit acceleration and vehicle speed to prevent overheating of the motor and inverter. However, depending on the operating state, damage to the components may occur. In particular, in the bearing of an impeller (rotor) that rotates in an electric water pump to circulate water, when using a bearing that supports the rotation of the impeller using cooling water, if air mixes into the cooling water, it will lead to abnormal wear and shortened life of the bearing provided in the electric water pump. Therefore, it is required to detect the decrease in the cooling water as early as possible.

[0004] Patent Document 1 discloses a technique for estimating the remaining amount of cooling water stored in a condenser tank based on the power supply status of the drive motor, the temperature of the inverter, and the rate of temperature rise of the cooling water calculated from the control status of the electric water pump. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2014-121999 [Overview of the project] [Problems that the invention aims to solve]

[0006] However, conventional technology detects the decrease in coolant based on the rise in the coolant temperature. Therefore, a certain amount of time is required between the time the coolant decreases and the actual rise in the coolant temperature to detect the decrease. In the technology described in Patent Document 1, the remaining amount of coolant stored in the condenser tank is estimated based on the rate of rise in the coolant temperature, which may delay the detection of the decrease in coolant and the initiation of corresponding control measures.

[0007] Therefore, the objective of this invention is to detect a decrease in the refrigerant used to cool the motor as quickly as possible. [Means for solving the problem]

[0008] To solve the above problems, this invention provides a motor comprising a stator coil and rotor housed in a metal casing, a cooling circuit arranged to remove heat from the motor, a metal condenser tank for storing a refrigerant flowing through the cooling circuit, a thermistor for detecting the temperature of the stator coil, and a refrigerant temperature sensor for detecting the temperature of the refrigerant in the condenser tank, wherein the thermistor and the refrigerant temperature sensor are connected by a metal material, and a prediction range for the output of the refrigerant temperature sensor relative to the output from the thermistor is provided for both the liquid environment where the refrigerant temperature sensor is below the liquid surface of the refrigerant and the air environment where the refrigerant temperature sensor is above the liquid surface of the refrigerant, and a refrigerant decrease detection device is employed that, when temperature rise information of the thermistor is output, determines the decrease in the refrigerant based on the output from the refrigerant temperature sensor, the prediction range in the liquid environment, and the prediction range in the air environment (Configuration 1).

[0009] In configuration 1, when the thermistor outputs temperature rise information, a configuration (configuration 2) can be adopted in which a decrease in the refrigerant is recognized when the output from the refrigerant temperature sensor does not belong to the predicted region of the liquid environment but belongs to the predicted region of the air environment for a predetermined period of time or longer.

[0010] Furthermore, in configuration 1, the condenser tank may be provided with at least an inlet, and a wall portion extending from the top of the inside of the condenser tank to the lower end of the refrigerant temperature sensor may be provided between the refrigerant temperature sensor and the inlet, extending from the inner surface of the condenser tank so that the refrigerant from the inlet does not directly come into contact with the refrigerant temperature sensor (configuration 3).

[0011] In configuration 1, the condenser tank can be configured to have an intake valve located above the refrigerant temperature sensor (configuration 4).

[0012] Furthermore, in configuration 1, a configuration (configuration 5) can be adopted in which the casing and the condenser tank are made of a single integrally formed member.

[0013] Multiple elements selected from configurations 2 to 5 can be added to configuration 1. That is, in addition to the above-mentioned configurations in which only configuration 2, only configuration 3, or only configuration 4 is added to configuration 1, configurations in which configurations 2 and 3, configurations 2 and 4, configurations 2 and 5, configurations 2, 3 and 4, configurations 2, 3 and 5, configurations 2, 4 and 5, and all of configurations 2 to 5 can be added to configuration 1.

[0014] Furthermore, in each embodiment comprising configuration 5, a configuration (configuration 6) can be adopted in which the refrigerant temperature sensor is located above the thermistor. [Effects of the Invention]

[0015] This invention makes it possible to quickly detect a decrease in the refrigerant used to cool the motor. [Brief explanation of the drawing]

[0016] [Figure 1] Schematic diagram of the cooling circuit and refrigerant reduction detection device. [Figure 2] A schematic cross-sectional view showing a motor and a capacitor tank according to the first embodiment of this invention. [Figure 3] Schematic diagram of Figure 2 as viewed from the side. [Figure 4] Graphs showing the temperature changes of thermistor output, estimated water temperature sensor output (with coolant), and estimated water temperature sensor output (without coolant). [Figure 5] A graph illustrating the control of this invention. [Figure 6A] A graph illustrating the control of this invention. [Figure 6B] A graph illustrating the control of this invention. [Figure 7] A schematic cross-sectional view showing the positional relationship between the stator coil and thermistor, and the condenser tank and water temperature sensor. [Figure 8] A schematic cross-sectional view showing a motor and capacitor tank according to a second embodiment of this invention. [Figure 9] Schematic diagram of Figure 8 viewed from the side. [Modes for carrying out the invention]

[0017] The refrigerant reduction detection device according to an embodiment of the present invention will be described based on the drawings. This embodiment is a refrigerant reduction detection device that detects a reduction in a refrigerant (cooling water) for cooling a motor (electric motor) 10 as a driving source for traveling in an electric vehicle. Examples of the electric vehicle include a hybrid vehicle equipped with a traveling motor and an engine, and an EV vehicle equipped with a traveling motor and not equipped with an engine. Hereinafter, this electric vehicle is referred to as a vehicle.

[0018] FIG. 1 shows a schematic diagram of the device. A direct current from a battery 41 is converted into an alternating current by an inverter 3 and supplied to a motor 10. Further, regenerative power generated by the motor 10 is charged into the battery 41 via the inverter 3.

[0019] The first embodiment is shown in FIGS. 1 to 3. As shown in FIG. 2, the motor 10 is provided with a rotor 13 having an output shaft 12 of the motor 10 rotatably supported therein within a metal casing 15, and an annular stator coil 14 disposed in a non-contact state with the rotor 13 is provided around the rotor 13. The stator coil 14 includes a coil 14a and a stator coil iron core 14b (see FIG. 7) and is fixed within the casing 15. By switching the direction of the current supplied to the coil 14a by the inverter 3, the direction of the magnetic force generated in the stator coil 14 is controlled, and the output shaft 12, which is the axis of the rotor 13, is rotated to generate a driving force.

[0020] Since the motor 10 consumes a large amount of power, the current flowing through the switching element included in the inverter 3 is large, and the heat generation amount of the switching element is large. Further, the stator coil 14 of the motor 3 generates heat due to energization of the coil 14a. Therefore, a cooling circuit 1 is provided to lower the temperatures of these motor 10 and inverter 3.

[0021] The cooling circuit 1 includes a refrigerant passage 6 that connects a radiator 4 equipped with a cooling fan 5, a condenser tank 20 for temporarily storing circulating coolant, a motor 10, an electric pump 2, and an inverter 3 in a ring shape. By circulating coolant as a refrigerant within the refrigerant passage 6, heat is removed from the switching elements of the inverter 3 and the stator coil 14 of the motor 10. Long Life Coolant (LLC) is commonly used as the coolant.

[0022] The electric pump 2 uses a built-in motor (not shown) to rotate an internal impeller, and the pressure generated by this rotation pumps the internal cooling water. The built-in motor is powered by electricity supplied from the battery 41.

[0023] The radiator 4 has a core with a passage through which coolant flows. As the coolant flows through the core, it exchanges heat with the outside air in contact with the core. Normally, the temperature of the outside air is lower than the temperature of the coolant, which has become hot due to the heat generated by the motor, etc., so the temperature of the coolant decreases. In addition, by operating the attached electric cooling fan 5 as needed, the amount of air hitting the core can be increased, thereby improving the cooling effect.

[0024] The control of the driving force provided by the motor 10, as well as the control of each component of the cooling circuit 1, such as the electric pump 2, inverter 3, and cooling fan 5, is performed by the control unit 40 of the vehicle's electronic control unit (see Figure 1). The electronic control unit controls all the components of the vehicle. The control unit 40 also acquires information from various sensors in the vehicle and uses it for control.

[0025] As shown in Figures 2 and 3, the condenser tank 20 is composed of a container 22 having a hollow storage section inside. The condenser tank 20 is equipped with a refrigerant temperature sensor 30 (referred to as a water temperature sensor 30) for detecting the temperature of the cooling water inside. The water temperature sensor 30 comprises a temperature sensing element 31, a metal cover 32 that covers the temperature sensing element 31, and a metal case 33 integrated with the cover 32, which has a screw portion for fixing the water temperature sensor 30 to the container 22. The case 33 is fixed in a position that is in direct contact with the cooling water, and the heat of the cooling water is conducted to the temperature sensing element 31. The case 33 is also fixed in contact with the metal container 22 by its screw portion.

[0026] The container 22 has an opening above the water temperature sensor 30, and this opening is sealed by a removable cap. The cap is also equipped with at least an intake valve 21 of the pressure valves. When the cap is attached to seal the opening of the container 22, the intake valve 21 is normally closed. If the air pressure inside the container 22 drops, the intake valve 21 automatically opens to take in outside air. If an exhaust valve is also present among the pressure valves, it adjusts the pressure inside the cooling circuit 1 by exhausting the air from the top of the container 22 when the pressure inside the cooling circuit 1 becomes high. The condenser tank 20 is also provided with an inlet 24 for supplying cooling water into the container 22. In Figure 3, the display window 25 on the container 22 shows only the minimum water level line (indicated as "Low" in Figure 3) below which the cooling water must not fall, but the display window 25 also has a maximum water level line (Full) above which the cooling water must not exceed.

[0027] If the uppermost part of the water inlet 24 is located above the metal cover 32 that covers the temperature sensing part (temperature sensing element 31) of the water temperature sensor 30, a wall portion 23 is provided between the water temperature sensor 30 and the water inlet 24, extending from the inner surface of the condenser tank 20 to the lower end of the water temperature sensor 30 (the lower end of the temperature sensing element 31). That is, the lower end 23a of the wall portion 23 must reach at least the same height as the lower end of the temperature sensing element 31 of the water temperature sensor 30, and preferably, it should reach the same height as the lower end of the metal cover 32 that covers the temperature sensing element 31 of the water temperature sensor 30. Furthermore, it is desirable that it be even lower by a predetermined distance (for example, 5 mm to account for manufacturing variations and variations in the flow of cooling water) than the lower end of the cover 32.

[0028] The stator coil 14 of the motor 10 is equipped with a thermistor 17 that detects the temperature of the stator coil 14 (particularly the copper wire of coil 14a). The thermistor 17 is a temperature sensor that utilizes the change in resistance value when heat is detected. Generally, the thermistor 17 can detect temperature based on the resistance value, as a higher resistance value in the electrical circuit surrounding the thermistor 17 indicates a lower temperature, and a lower resistance value indicates a higher temperature. The aforementioned water temperature sensor 30 also employs this mechanism. The cooling water flowing through the cooling circuit 1 passes through a refrigerant jacket 16 provided inside the casing 15, as shown in Figure 2.

[0029] In this embodiment, the casing 15 of the motor 10 and the container 22 of the condenser tank 20 are made of a single, integrally formed metal member. That is, the casing 15 and the container 22 are made of a continuous metal material, and the outer surfaces 11 of the container 22 and the casing 15 are in contact with the outside air. Therefore, the thermistor 17 and the water temperature sensor 30 are connected by a metal material.

[0030] In this invention, the output of the thermistor 17 and the output of the water temperature sensor 30 are compared, and the cooling water By quickly detecting the decrease, the motor 10 and inverter 3 are prevented from being exposed to abnormal overheating.

[0031] When the coolant level in the condenser tank 20 decreases, the pressure inside the container 22 decreases, allowing outside air to enter through the intake valve 21. However, if the decrease in coolant is significant, and the liquid level falls below the metal cover 32 covering the temperature sensing element 31 of the water temperature sensor, which is installed below the minimum water level line, then outside air may enter up to the height of the metal cover 32 covering the temperature sensing element 31 of the water temperature sensor 30, creating an air phase around the temperature sensing element. In this case, if the temperature of the air phase differs significantly from the temperature of the coolant, it may be possible to immediately detect an abnormality. However, if the temperature of the air phase is similar to that of the coolant, the output of the water temperature sensor 30 alone cannot detect an abnormality. Therefore, the difference in the degree of heat transfer from the stator coil 14 to the temperature sensing element of the water temperature sensor 30 is utilized, and the decrease in coolant is detected based on this difference in the degree of heat transfer.

[0032] Figure 4 is a graph comparing the output of the water temperature sensor 30 with that of the thermistor 17. As indicated by the symbol p, when the temperature of the thermistor 17 rises, the temperature of the water temperature sensor 30 also starts to rise with a slight delay. Here, the temperature change of the coolant when the water temperature sensor 30 is below the liquid surface of the coolant (referred to as a liquid environment) is indicated by the symbol r. The temperature change of the coolant when the water temperature sensor 30 is above the liquid surface of the coolant (referred to as an air environment) is indicated by the symbol q. The temperature increase of symbol q in the air environment is clearly larger than the temperature increase of symbol r in the liquid environment.

[0033] In a liquid environment, the water temperature sensor 30 outputs the result of heat conduction from the cooling water through the metal cover 32 and metal case 33 that cover the temperature sensing element 31. Therefore, the output of the water temperature sensor 30 asymptotically approaches the temperature of the cooling water. However, in an air environment, the effect of heat conduction between the metal cover 32 and metal case 33 and the metal container 22 (condenser tank 20) ​​in contact with the metal cover 32 and metal case 33 outweighs the effect of heat transfer between the metal cover 32 and metal case 33 and the surrounding air. Therefore, by making a metal connection between the metallic cover 32 and metal case 33 and the stator coil 14 of the motor 10 (metal casing 15 that fixes the stator coil 14), the heat generated by the stator 14 is directly transmitted to the water temperature sensor 30, clearly detecting that the area around the water temperature sensor 30 is air.

[0034] Here, even if the cooling water level falls below the minimum water level line, the heat removal function of the cooling circuit 1, which is the purpose of removing heat from the motor 10 and inverter 3, is not immediately lost. In conventional technology, the decrease in cooling water is only detected after the amount of cooling water has decreased considerably and the heat removal function has deteriorated. In contrast, with this invention, the decrease in cooling water can be detected early, even when the heat removal function has not deteriorated (when the cooling water level is only slightly below the minimum water level line), so it is possible to take appropriate measures early. For this reason, it is preferable to set the temperature sensing part of the water temperature sensor 30 just below the minimum water level line of the container 22.

[0035] Here, the relationship between the output of the thermistor 17 and its changes, and the output of the water temperature sensor 30 and its changes, is measured in advance for many anticipated temperature conditions and many cooling water volume conditions (water level conditions), so that transient temperature phenomena (temperature changes) in a liquid environment and transient temperature phenomena (temperature changes) in an air environment can be estimated. Estimating transient temperature phenomena means modeling how the output of the water temperature sensor 30 increases when the temperature of the thermistor 17 rises. This modeled temperature change is called the prediction region. Specifically, a prediction region for the output of the water temperature sensor 30 in relation to the output from the thermistor 17 is prepared for both the liquid environment and the air environment. The necessary data is stored in the control unit 40 so that the prediction region can be predicted by the control unit 40. Then, when information on the temperature rise of the thermistor 17 is output, the decrease in cooling water is determined (detected) based on the actual output from the water temperature sensor 30, the prediction region B in the liquid environment, and the prediction region A in the air environment. This determination is also performed by the control unit 40.

[0036] Figure 5 shows an example of the predicted region B in a liquid environment and the predicted region A in an air environment.

[0037] The prediction range B in a liquid environment is set by providing a fixed upper and lower approximation range relative to the output of the water temperature sensor 30 (water temperature sensor output e / with cooling water) obtained from actual experiments and simulations. In Figure 5, this fixed range is set to ±3 degrees relative to the water temperature sensor output e, but this value can be freely increased or decreased. Furthermore, the width of the positive approximation range and the negative approximation range may be different. That is, the upper limit of prediction range B set with a positive approximation range relative to the water temperature sensor output e is the upper limit d with water in the figure. The lower limit of prediction range B set with a negative approximation range relative to the water temperature sensor output e is the lower limit f with water in the figure.

[0038] Similarly, the prediction region A in an air-filled environment is set by providing a certain range of approximations above and below the output of the water temperature sensor 30 (water temperature sensor output b / no cooling water) obtained from actual experiments and simulations. The width of the approximation range can be set arbitrarily, as in the case of prediction region B. That is, the upper limit of prediction region A, when the approximation range on the positive side is set with respect to the water temperature sensor output b, is the waterless upper limit a in the figure. The lower limit of prediction region A, when the approximation range on the negative side is set with respect to the water temperature sensor output b, is the waterless lower limit c in the figure.

[0039] If the actual output of the water temperature sensor 30 does not fall within prediction range B for an underwater environment (when there is cooling water around the water temperature sensor 30), but falls within prediction range A for an air environment (when there is no cooling water around the water temperature sensor 30), it can be determined that the cooling water level is decreasing.

[0040] Here, even if it is determined that the environment does not belong to predicted region B of the liquid environment and belongs to predicted region A of the air environment, the accuracy of detection will be further improved if the decrease in cooling water is not immediately recognized, but rather after a short period of time has been observed to confirm that the condition persists. In other words, the decrease in the refrigerant is recognized when the condition that does not belong to predicted region B of the liquid environment and belongs to predicted region A of the air environment persists for a predetermined time t or longer. This predetermined time t can be freely increased or decreased according to the specifications, but for example it can be 10 seconds (10 sec), 20 seconds (20 sec), 30 seconds (10 sec), etc.

[0041] Examples of control for determining the decrease in cooling water are shown in Figures 6A and 6B. Figure 6B is an enlarged view of the main part of Figure 6A. The predicted region A for the air environment and the predicted region B for the liquid environment are in accordance with Figure 5. The output example indicated by the symbol g in the figure is an example of the output assumed for the actual water temperature sensor 30. Initially, the output example g is in the predicted region B for the liquid environment, but at position x around 10 minutes (10 min), it leaves the predicted region B for the liquid environment. At position x around 10 minutes (time x'), the output example g continues to be in the predicted region A for the air environment. The position y (time y') at which the state in which the output example g is not in the predicted region B for the liquid environment and is in the predicted region A for the air environment continues for a predetermined time t is the timing at which it can be definitively determined that the cooling water is decreasing.

[0042] Note that at position z (time z'), after the decrease in cooling water is confirmed at position y (time y'), the output example g has left the predicted region A of the air environment. However, once the decrease in cooling water is confirmed, the confirmation is not reset until the prescribed countermeasures are taken. The symbol e' in the figure is a flag indicating departure from the predicted region B of the liquid environment, and the symbol b' is a flag indicating departure from the predicted region A of the air environment.

[0043] Here, the shorter the distance between the water temperature sensor 30 fixed to the condenser tank 20 and the stator coil 14 of the motor 10, the more smoothly the heat from the stator coil 14 can be transferred to the water temperature sensor 30.

[0044] Figure 7 shows the positional relationship between the stator coil 14 and thermistor 17, and the condenser tank 20 and water temperature sensor 30. The distance between the coil 14a of the stator coil 14, which is a heat source, and the metal cover 32 covering the temperature sensing element 31 of the water temperature sensor 30 is calculated as the sum of the distance Ls, which corresponds to the width from the coil 14a to the outside of the stator coil core 14b in the stator coil 14 shown in the figure, the distance Lh, which corresponds to the material thickness of the casing 15 of the motor 10 and the container 22 of the condenser tank 20, and the distance Lw, which corresponds to the thickness of the case 33 of the water temperature sensor 30. It is desirable that the sum of these distances, Ls + Lh + Lw, be as small as possible.

[0045] Furthermore, the fewer the number of contact surfaces between the water temperature sensor 30 fixed to the container 22 of the condenser tank 20 and the stator coil 14 of the motor 10, the more smoothly the heat from the stator coil 14 can be transferred to the water temperature sensor 30. For this reason, as in this embodiment, composing the container 22 of the condenser tank 20 and the casing 15 of the motor 10 as a single integrated component is effective in improving detection accuracy. When composing as a single integrated component, in order to bring air in and out using the pressure valve (equipped with at least an intake valve 21) located at the top of the condenser tank 20, it is necessary for the outside and inside of the pressure valve to be filled with air, so the water temperature sensor 30 needs to be located above the thermistor 17. Moreover, it is desirable that the refrigerant jacket 16 through which the cooling water flows is not interposed in the shortest heat transfer path connecting the casing 15 of the motor 10 and the container 22.

[0046] A second embodiment is shown in Figures 8 and 9. In the first embodiment, the casing 15 of the motor 10 and the container 22 of the condenser tank 20 were made of a single, integrally formed member. However, in the second embodiment, this is changed so that the casing 15 of the motor 10 and the container 22 of the condenser tank 20 are made of separately molded metal members and are assembled together with bolts or the like to form a single unit. The metal casing 15 and the metal container 22 have a metal-to-metal contact structure where the metal members are in direct contact with each other. Various methods can be used to fix the casing 15 and the container 22, including using fasteners such as bolts, or by tightening them together with a predetermined bracket.

[0047] In the embodiments described above, the motor 10 is assumed to function as a drive source for the vehicle to move, but the embodiment is not limited to this, and for example, it may be an electric motor (generator) that functions as a generator. Also, while cooling water is generally used as a refrigerant, it is also conceivable that lubricating oil or other liquids may be used as a refrigerant instead of cooling water. [Explanation of symbols]

[0048] 1 Cooling circuit 2 Electric pump 3 Inverter 4. Radiator 5 Cooling fan 6 Refrigerant passage 10 motors 13 Rotors 14 Stator Coil 15 Casing 17 Thermistor 20 Condenser Tanks 21 Intake valve 22 Container 23 Wall 23a Lower end of wall 24 Water Inlet 25 Display window 30. Refrigerant temperature sensor (water temperature sensor) 31 Temperature sensing element 32 Cover 33 cases 40 Control Unit

Claims

1. A motor comprising a stator coil and rotor within a metal casing, A cooling circuit is provided to remove heat from the motor, A metal condenser tank for storing the refrigerant flowing through the aforementioned cooling circuit, A thermistor for detecting the temperature of the stator coil, A refrigerant temperature sensor for detecting the temperature of the refrigerant in the condenser tank, Equipped with, The thermistor and the refrigerant temperature sensor are connected by a metal material. In both the liquid environment where the refrigerant temperature sensor is below the liquid surface of the refrigerant and the air environment where the refrigerant temperature sensor is above the liquid surface of the refrigerant, a prediction range for the output of the refrigerant temperature sensor relative to the output from the thermistor is provided. A refrigerant reduction detection device that, when the thermistor is output with rising temperature information, determines a decrease in the refrigerant based on the output from the refrigerant temperature sensor, the predicted region in the liquid environment, and the predicted region in the air environment.

2. The refrigerant reduction detection device according to claim 1, wherein when the thermistor outputs temperature rise information, the output from the refrigerant temperature sensor does not belong to the predicted region of the liquid environment but belongs to the predicted region of the air environment, and this condition continues for a predetermined period of time or longer, thereby determining a reduction in the refrigerant.

3. The refrigerant reduction detection device according to claim 1, wherein the condenser tank is provided with at least an inlet, and a wall portion is provided between the refrigerant temperature sensor and the inlet, extending from the inner surface of the condenser tank to the top surface inside the condenser tank and to the lower end of the refrigerant temperature sensor.

4. The refrigerant reduction detection device according to claim 1, wherein the condenser tank is provided with an intake valve located above the refrigerant temperature sensor.

5. The refrigerant reduction detection device according to claim 1, wherein the casing and the condenser tank are composed of a single integrally formed member.

6. The refrigerant reduction detection device according to claim 5, wherein the refrigerant temperature sensor is located above the thermistor.

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