Valve unit and vehicular air conditioner

Abstract

To provide a system configuration capable of effectively coping with refrigerant leakage if caused in a refrigeration cycle adopting natural refrigerant.SOLUTION: A valve unit 114 integrally includes an electric expansion valve 1 for applying decompression and expansion to refrigerant flowing from a first heat exchanger 104 to a second heat exchanger 106, and a relief valve 2 to be opened for releasing a low pressure passage on the downstream side of the electric expansion valve 1 to the atmosphere. When refrigerant leakage is detected by sensors 162, 164, the electric expansion valve 1 and the relief valve 2 are controlled in linkage with each other.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a valve unit used for countermeasures against refrigerant leakage in a refrigeration cycle.

Background Art

[0002] With the recent spread of electric vehicles, the development of their air conditioning systems has also been promoted. Since electric vehicles do not have an internal combustion engine as a heat source itself, a heat pump type air conditioning device that performs cycle operation using a refrigerant for both cooling and heating is adopted (see Patent Document 1). Such an air conditioning device is configured by arranging a compressor, an outdoor heat exchanger, an expansion device, an evaporator, an indoor heat exchanger, etc. in a refrigerant circulation passage. However, depending on the type of refrigerant used, the configuration of the optimal refrigerant circulation passage and the arrangement configuration of each device change.

[0003] In recent years, as part of measures against global warming, among fluorine-based refrigerants, those with a low ozone depletion potential and a low global warming potential are adopted, but the conversion to natural refrigerants with a smaller environmental load is also being considered. For example, propane, carbon dioxide, etc. are known as natural refrigerants with relatively high refrigeration effects.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, refrigerants mainly composed of hydrocarbons such as propane have high flammability (that is, they are highly flammable), and there is a risk of ignition if they leak under high temperature and high pressure. On the other hand, carbon dioxide is non-flammable, but at least leakage into the vehicle interior must be avoided.

[0006] One object of the present invention is to provide a system configuration that can effectively cope even if refrigerant leakage occurs in a refrigeration cycle employing a natural refrigerant.

Means for Solving the Problems

[0007] One aspect of the present invention is a valve unit applied to a refrigeration cycle. The refrigeration cycle includes a refrigerant circulation passage for circulating a natural refrigerant, a compressor disposed in the refrigerant circulation passage for compressing and discharging the refrigerant, a first heat exchanger disposed downstream of the compressor in the refrigerant circulation passage, a second heat exchanger disposed upstream of the compressor in the refrigerant circulation passage, and a sensor for detecting refrigerant leakage from the refrigerant circulation passage to the outside. This valve unit integrally includes an electric expansion valve for decompressing and expanding the refrigerant flowing from the first heat exchanger to the second heat exchanger, and a relief valve that is opened to open the low-pressure passage on the downstream side of the electric expansion valve to the atmosphere, and when refrigerant leakage is detected by the sensor, the electric expansion valve and the relief valve are controlled in conjunction with each other.

[0008] According to this aspect, a valve unit in which an electric expansion valve and a relief valve are integrated is provided. When refrigerant leakage from the refrigerant circulation passage is detected, the electric expansion valve and the relief valve operate in conjunction with each other, and the relief valve opens the low-pressure passage to the atmosphere to release the refrigerant. That is, even if refrigerant leakage occurs, the refrigerant can be safely released from the low-temperature and low-pressure region to the atmosphere, preventing leakage into the vehicle interior. Also, even if the natural refrigerant used is a highly flammable refrigerant, since it is released in a low-temperature and low-pressure state, there is no risk of ignition.

[0009] Another aspect of the present invention is a vehicle air conditioner. This vehicle air conditioner includes a refrigerant circulation passage for circulating a natural refrigerant, a compressor disposed in the refrigerant circulation passage for compressing and discharging the refrigerant, a first heat exchanger disposed downstream of the compressor in the refrigerant circulation passage, a second heat exchanger disposed upstream of the compressor in the refrigerant circulation passage, an electric expansion valve for decompressing and expanding the refrigerant flowing from the first heat exchanger to the second heat exchanger, a relief valve that is opened to release the low-pressure passage downstream of the electric expansion valve to the atmosphere, a sensor for detecting refrigerant leakage from the refrigerant circulation passage to the outside, and a control unit for controlling the compressor, the electric expansion valve, and the relief valve. The electric expansion valve and the relief valve are integrally provided. When the sensor detects refrigerant leakage, the control unit controls the electric expansion valve and the relief valve in conjunction with each other and stops the drive of the compressor.

[0010] According to this aspect, the electric expansion valve and the relief valve are integrated and controlled to open and close by the control unit. When refrigerant leakage from the refrigerant circulation passage is detected, the compressor is stopped, thereby reducing the momentum of the leakage. On the other hand, in the refrigerant circulation passage, although the refrigerant will flow for a while due to inertia even after the compressor stops, the electric expansion valve and the relief valve open in conjunction with each other, and the relief valve releases the low-pressure passage to the atmosphere, thereby promoting the relief of the refrigerant. That is, according to this aspect, even if refrigerant leakage occurs, the refrigerant can be safely relieved from the low-temperature and low-pressure region to the atmosphere, and leakage into the vehicle interior can be prevented. Also, even if the natural refrigerant used is a highly flammable refrigerant, since it is relieved in a low-temperature and low-pressure state, there is no risk of ignition.

Advantages of the Invention

[0011] According to the present invention, it is possible to provide a system configuration that can effectively cope with refrigerant leakage even if it occurs in a refrigeration cycle that employs a natural refrigerant.

Brief Description of the Drawings

[0012]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Mode for Carrying Out the Invention

[0013] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the following description, for convenience, the positional relationship of each structure may be expressed based on the illustrated state. Also, for the following embodiments and their modifications, substantially the same components are denoted by the same reference numerals, and the description thereof will be omitted as appropriate.

[0014] In the present embodiment, a system capable of effectively coping even if refrigerant leakage occurs in a refrigeration cycle using a natural refrigerant is disclosed. This system includes a valve unit suitable for countermeasures against refrigerant leakage. First, a specific example of the system to which this valve unit is applied will be described below, and then the details of the valve unit will be described.

[0015] FIG. 1 is a system configuration diagram of a vehicle air conditioner according to an embodiment. The air conditioner 100 is a heat pump type air conditioner having a refrigerant circulation circuit 101 for circulating a natural refrigerant and a coolant circulation circuit 102 for circulating a coolant, and performing heat exchange between them. In the present embodiment, propane is adopted as the natural refrigerant. The coolant may be, for example, an aqueous solution (cooling water) mainly composed of ethylene glycol or propylene glycol.

[0016] In the air conditioner 100, in the process where the refrigerant circulates while changing its state in the refrigerant circulation circuit 101, the heat of the refrigerant is used to cool or heat the coolant in the coolant circulation circuit 102. By cooling or heating the air in the vehicle interior with the coolant, the air conditioning in the vehicle interior is performed. The air conditioner 100 also functions as a cooling device that appropriately cools the battery mounted on the vehicle. In a modified example, the coolant circulation circuit 101 may have a circuit for warming the battery.

[0017] The air conditioner 100 includes a water-refrigerant heat exchanger 104 and a water-refrigerant heat exchanger 106 for performing heat exchange between the refrigerant circulation circuit 101 and the coolant circulation circuit 102. The water-refrigerant heat exchanger 104 functions as the "first heat exchanger", and the water-refrigerant heat exchanger 106 functions as the "second heat exchanger".

[0018] The refrigerant circulation circuit 101 is configured by connecting a compressor 110, a water-refrigerant heat exchanger 104, a water-refrigerant heat exchanger 106, and an accumulator 112 with pipes. The water-refrigerant heat exchanger 104 is located on the downstream side of the compressor 110, and the water-refrigerant heat exchanger 106 is located on the upstream side of the compressor 110. A valve unit 114 is arranged on the upstream side of the water-refrigerant heat exchanger 106. The refrigerant circulation circuit 101 is provided outside the vehicle compartment.

[0019] The outlet (discharge chamber) of the compressor 110 is connected to the inlet of the water-refrigerant heat exchanger 104 via the first passage 201, and the outlet of the water-refrigerant heat exchanger 104 is connected to the inlet of the water-refrigerant heat exchanger 106 via the second passage 202. The outlet of the water-refrigerant heat exchanger 106 is connected to the inlet of the accumulator 112 via the third passage 203. The outlet of the accumulator 112 is connected to the inlet (suction chamber) of the compressor 110 via the fourth passage 204.

[0020] Since propane, which is the refrigerant, is highly flammable, the refrigerant filling amount in the refrigerant circulation circuit 101 is limited compared to the case of using a conventional fluorine-based refrigerant. For this reason, the volume of the pipes forming the refrigerant circulation circuit 101 is small, and the devices arranged in the circulation passage are also minimized.

[0021] The compressor 110 is configured as an electric compressor that houses a motor and a compression mechanism within a housing. The compressor 110 introduces refrigerant at the suction pressure Ps through its suction chamber, compresses it, and discharges it as refrigerant at the discharge pressure Pd. The compressor 110 is driven by a supply current from a battery, and the discharge capacity of the refrigerant changes according to the rotational speed of the motor. Since the electric compressor itself is well-known, its description is omitted.

[0022] The water-refrigerant heat exchanger 104 functions as a condenser that dissipates heat from the refrigerant passing through it. The valve unit 114 functions as an expansion device (expansion valve) capable of decompressing and expanding the refrigerant that has passed through the water-refrigerant heat exchanger 104. The water-refrigerant heat exchanger 106 functions as an evaporator that evaporates the refrigerant passing through it during the cooling operation.

[0023] On the other hand, the coolant circulation circuit 102 is configured by connecting the water-refrigerant heat exchanger 106, the cooler core 120, the heater core 122, and the water-refrigerant heat exchanger 104, the outdoor heat exchanger 108, etc. with pipes, and the first to fourth circulation passages (described later) are switched according to the operating state of the refrigeration cycle. Heat exchange occurs as the coolant circulates through the coolant circulation circuit 102. Outside the vehicle compartment, the outdoor heat exchanger 108 and the battery unit 140 are provided in the coolant circulation circuit 102. A fan 109 is arranged so as to face the outdoor heat exchanger 108. By driving the fan 109, outside air is introduced, and heat exchange is performed between the coolant flowing through the outdoor heat exchanger 108 and the outside air. The battery unit 140 includes a battery that is the power source of the vehicle and a heat exchanger for the battery.

[0024] An in-vehicle air-conditioning unit 124 for performing heat exchange of air is provided inside the vehicle compartment. A blower 126, a cooler core 120, and a heater core 122 are arranged in the air flow direction upstream side in the duct constituting the in-vehicle air-conditioning unit 124. An air mix door 128 is rotatably provided upstream of the heater core 122, and the ratio of the air volume passing through the heater core 122 and the air volume bypassing the heater core 122 is adjusted.

[0025] The coolant circulation circuit 102 has a first passage 221 where the heater core 122 is disposed, a second passage 222 where the water-refrigerant heat exchanger 104 is disposed, a third passage 223 where the water-refrigerant heat exchanger 106 is disposed, and a fourth passage 224 where the outdoor heat exchanger 108 is disposed, and the connection of these passages is switched between the cooling operation and the heating operation. A first connection point with the first passage 221, the third passage 223, and the fourth passage 224 is provided at the upstream end of the second passage 222, and a switching valve 130 is provided at the first connection point. Also, a second connection point with the first passage 221, the third passage 223, and the fourth passage 224 is provided at the downstream end of the second passage 222, and a switching valve 132 is provided at the second connection point. The switching valves 130 and 132 are four-way valves. Pumps 134 and 136 for circulating the coolant are provided in the second passage 222 and the third passage 223, respectively.

[0026] A cooler core 120 is provided on the downstream side of the water-refrigerant heat exchanger 106 in the third passage 223. A branch point p1 is provided on the upstream side of the cooler core 120 in the third passage 223, and a confluence point p2 is provided on the downstream side. A bypass passage 226 is provided so as to connect these branch point p1 and confluence point p2, and an on-off valve 142 is provided in the bypass passage 226. The on-off valve 142 is a solenoid-driven electromagnetic valve in the present embodiment, but may be a motor-driven electric valve. By opening the on-off valve 142, the coolant can flow so as to substantially bypass the cooler core 120. Since the pressure loss on the cooler core 120 side is large, the flow rate of the coolant flowing through the cooler core 120 when the on-off valve 142 is opened is small and has no substantial influence on heat exchange. In a modification, a three-way valve may be provided at the branch point p1 instead of the on-off valve 142. By switching the flow path of the three-way valve, it is possible to completely bypass the cooler core 120.

[0027] In addition, a battery unit 140 is provided between the switching valve 130 and the water-refrigerant heat exchanger 106 in the third passage 223. A branch point p3 is provided on the upstream side of the battery unit 140, and a confluence point p4 is provided on the downstream side. A bypass passage 228 is provided so as to connect these branch point p3 and confluence point p4. An on-off valve 144 is provided between the branch point p3 and the battery unit 140 in the third passage 223. The on-off valve 144 is an electromagnetic valve in the present embodiment, but may be an electric valve. By closing the on-off valve 144, the coolant can flow around the battery unit 140.

[0028] The water-refrigerant heat exchanger 104 supplies the coolant heated by heat exchange with the refrigerant to the coolant circulation circuit 102. The water-refrigerant heat exchanger 106 supplies the coolant cooled by heat exchange with the refrigerant during the cooling operation to the coolant circulation circuit 102.

[0029] The cooler core 120 performs heat exchange between the coolant passing through the inside and the outside air during the cooling operation. The air introduced from the upstream side of the duct in the indoor air conditioning unit 124 is cooled by the coolant. The air cooled at this time is distributed to pass through the heater core 122 and to bypass the heater core 122 according to the opening degree of the air mix door 128. The air passing through the heater core 122 is heated during the passing process. The air that has passed through the heater core 122 and the bypassed air are mixed on the downstream side of the heater core 122 and adjusted to a target temperature, and then supplied into the vehicle interior from an air outlet (not shown).

[0030] The air conditioning device 100 configured as described above is controlled by the control unit 150. The control unit 150 calculates the control amount of the actuator of each device in order to realize the room temperature set by the vehicle occupant, and outputs a control signal to the drive circuit of each actuator. The control unit 150 determines the control amount (opening / closing state) of each control valve, the drive amount of the compressor 110, etc. based on predetermined external information detected by various sensors such as the temperature inside and outside the vehicle compartment and the blown air temperature of the cooler core 120, and outputs a control command or supplies a control current for driving them.

[0031] The control unit 150 may be a control device that comprehensively manages a plurality of electronic control units (hereinafter referred to as "ECUs") mounted on the vehicle and controlling each part, or it may be an air conditioner ECU which is one of the plurality of ECUs. The air conditioner ECU controls each device constituting the air conditioning device 100. Alternatively, it may be a lower-level control device that operates in response to a command from the air conditioner ECU.

[0032] FIG. 2 is a diagram showing the operation of the air conditioning device 100. FIG. 2(A) shows the cooling operation, and FIG. 2(B) shows the heating operation. The thick lines and arrows in the figure indicate the flow of the refrigerant, and "×" indicates that the flow of the refrigerant is blocked (the same applies hereinafter).

[0033] (Cooling operation) As shown in FIG. 2(A), during the cooling operation, the expansion valve (to be described in detail later) of the valve unit 114 is in an open valve state (control state) in the refrigerant circulation circuit 101. The refrigerant discharged from the compressor 110 is condensed by passing through the water-refrigerant heat exchanger 104. At this time, heat exchange occurs in the water-refrigerant heat exchanger 104. The refrigerant led out from the water-refrigerant heat exchanger 104 is throttled and expanded by the expansion valve of the valve unit 114 to become low temperature and low pressure, and is introduced into the water-refrigerant heat exchanger 106. At this time, heat exchange occurs in the water-refrigerant heat exchanger 106, and the coolant is cooled. The refrigerant led out from the water-refrigerant heat exchanger 106 is gas-liquid separated by the accumulator 112, and the gas-phase component thereof is returned to the compressor 110.

[0034] On the other hand, in the coolant circulation circuit 102, the pumps 134 and 136 are driven, the on-off valve 142 is in a closed valve state, and the on-off valve 144 is in an open valve state. Further, the switching valves 130 and 132 are switched to a state where the first passage 221 and the third passage 223 are connected, and the second passage 222 and the fourth passage 224 are connected.

[0035] Therefore, a first circulation passage indicated by a two-dot chain line and a second circulation passage indicated by a dotted line are formed in the figure. The first circulation passage is a passage through which the coolant circulates as follows: water-refrigerant heat exchanger 106 → cooler core 120 → heater core 122 → battery unit 140 → water-refrigerant heat exchanger 106. The second circulation passage is a passage through which the coolant circulates as follows: water-refrigerant heat exchanger 104 → outdoor heat exchanger 108 → water-refrigerant heat exchanger 104.

[0036] At this time, the coolant cooled by passing through the water-refrigerant heat exchanger 106 is supplied to the cooler core 120 and exchanges heat with the air. Thereby, the air in the vehicle interior is cooled. The coolant is slightly warmed by passing through the cooler core 120, but is also supplied to the battery unit 140 via the heater core 122 to cool the battery. The coolant that has passed through the battery unit 140 is led back to the water-refrigerant heat exchanger 106 again.

[0037] On the other hand, the coolant heated by passing through the water-refrigerant heat exchanger 104 dissipates heat when passing through the outdoor heat exchanger 108 and is led back to the water-refrigerant heat exchanger 104 again. That is, the condensation heat of the water-refrigerant heat exchanger 104 is discharged to the atmosphere by the outdoor heat exchanger 108.

[0038] (Heating operation) As shown in Fig. 2(B), also during the heating operation, the expansion valve of the valve unit 114 in the refrigerant circulation circuit 101 is in an open valve state (control state) to exhibit an expansion function.

[0039] On the other hand, in the coolant circulation circuit 102, the pumps 134 and 136 are driven, the on-off valve 142 is in an open valve state, and the on-off valve 144 is in a closed valve state. Also, the switching valves 130 and 132 are switched to a state of connecting the first passage 221 and the second passage 222 and connecting the third passage 223 and the fourth passage 224.

[0040] Therefore, a third circulation passage indicated by a two-dot chain line and a fourth circulation passage indicated by a dotted line are formed in the figure. The third circulation passage is a passage through which the coolant circulates like water-refrigerant heat exchanger 104 → heater core 122 → water-refrigerant heat exchanger 104. The fourth circulation passage is a passage through which the coolant circulates like water-refrigerant heat exchanger 106 → outdoor heat exchanger 108 → water-refrigerant heat exchanger 106.

[0041] At this time, the coolant flowing through the third circulation passage is warmed when passing through the water-refrigerant heat exchanger 104 and supplied to the heater core 122. Thereby, the temperature of the heater core 122 rises, and the air supplied into the vehicle interior is warmed.

[0042] On the other hand, the coolant flowing through the fourth circulation passage sequentially passes through the water-refrigerant heat exchanger 106 and the outdoor heat exchanger 108, but substantially bypasses the cooler core 120 and also bypasses the battery unit 140. At this time, the water-refrigerant heat exchanger 106 absorbs heat from the coolant and evaporates the refrigerant. Conversely, the coolant is cooled by the evaporation of the refrigerant. The cooled coolant exchanges heat with the outside air and absorbs heat when passing through the outdoor heat exchanger 108, and then is guided back to the water-refrigerant heat exchanger 106 again. In addition, when the battery temperature rises, the on-off valve 144 may be opened to flow the coolant through the battery unit 140.

[0043] Next, the configuration of the refrigerant unit including the valve unit 114 will be described. In this embodiment, as described above, highly flammable propane is adopted as the natural refrigerant used in the refrigerant circulation circuit 101. Therefore, it is necessary to prevent refrigerant leakage not only into the vehicle interior but also at locations where high temperature and high pressure occur outside the vehicle. Even if refrigerant leakage occurs, it is desirable to have a system that can be safely and promptly released to the atmosphere.

[0044] Therefore, in the present embodiment, a relief valve is provided integrally with the valve unit 114, and a configuration is adopted in which when a refrigerant leak occurs in the refrigerant circulation circuit 101, the relief valve is opened to release the refrigerant to the atmosphere. As shown in FIG. 1, the devices constituting the refrigerant circulation circuit 101 are integrated as a refrigerant unit 160, and sensors 162 and 164 for detecting refrigerant leaks in the refrigerant unit 160 are provided.

[0045] The refrigerant unit 160 includes a housing 166 that houses each device and piping constituting the refrigerant circulation circuit 101, and a partition member 168 that partitions the inside of the housing 166 into a high-pressure corresponding region HA and a low-pressure corresponding region LA. The high-pressure corresponding region HA is a region where high-pressure refrigerant leaks when a refrigerant leak occurs, and specifically includes a piping portion that constitutes a region from near the discharge chamber of the compressor 110 to near the valve portion of the expansion valve. The low-pressure corresponding region LA is a region where low-pressure refrigerant leaks when a refrigerant leak occurs, and specifically includes a piping portion that constitutes a region from near the valve portion of the expansion valve to near the suction chamber of the compressor 110.

[0046] The sensor 162 detects a refrigerant leak in the high-pressure corresponding region HA, and the sensor 164 detects a refrigerant leak in the low-pressure corresponding region LA. That is, the sensor 162 functions as the "first sensor", and the sensor 164 functions as the "second sensor". When the sensors 162 and 164 detect a refrigerant leak from the refrigerant circulation circuit 101 to the outside, they output a detection signal indicating that fact to the control unit 150.

[0047] FIG. 3 is a perspective view showing the configuration of the refrigerant unit 160. FIG. 3(A) shows the internal structure with the housing 166 removed, and FIG. 3(B) shows the external structure including the housing 166. As shown in FIG. 3(A), the refrigerant unit 160 is configured by arranging the water-refrigerant heat exchanger 104 and the water-refrigerant heat exchanger 106 side by side, assembling the compressor 110 to the water-refrigerant heat exchanger 104, and assembling the valve unit 114 to the water-refrigerant heat exchanger 106.

[0048] An accumulator 112 is integrally provided in the compressor 110. The valve unit 114 includes an expansion valve 1 and a relief valve 2, and is provided with a common body 200 in which these are integrally assembled. Although details will be described later, a first refrigerant passage and a second refrigerant passage are formed to penetrate the body 200. Further, a relief passage communicating with the middle of the second refrigerant passage is formed. The valve portion of the expansion valve 1 is provided in the first refrigerant passage. The second refrigerant passage forms a "low-pressure passage". The valve portion of the relief valve 2 is provided in the relief passage. By opening and closing the relief valve 2, the low-pressure passage is opened or blocked with respect to the atmosphere.

[0049] A pipe 230 connected to the discharge chamber of the compressor 110 is connected to the inlet of the water-refrigerant heat exchanger 104. A pipe 232 connected to the outlet of the water-refrigerant heat exchanger 104 is connected to the inlet of the first refrigerant passage. The outlet of the first refrigerant passage is connected to the inlet of the water-refrigerant heat exchanger 106. The outlet of the water-refrigerant heat exchanger 106 is connected to the inlet of the second refrigerant passage. A pipe 234 connected to the outlet of the second refrigerant passage is connected to the inlet of the accumulator 112. The outlet of the accumulator 112 is connected to the inlet (suction chamber) of the compressor 110 (not shown). A tube 236 (pipe) connected to the relief passage extends from the valve unit 114 (details will be described later).

[0050] These devices and pipes constituting the refrigerant circulation circuit 101 are housed in the housing 166 as shown in FIG. 3(B). Sensors 162 and 164 are disposed in a space sealed within the housing 166. This space is partitioned into a high-pressure corresponding region HA and a low-pressure corresponding region LA by a partition member 168 (not shown), and the sensor 162 is disposed in the high-pressure corresponding region HA, and the sensor 164 is disposed in the low-pressure corresponding region LA (see FIG. 1).

[0051] Pipes 240 and 242 extend airtightly from the water-refrigerant heat exchanger 104 and penetrate the housing 166. These pipes constitute the second passage 222. Pipes 244 and 246 extend airtightly from the water-refrigerant heat exchanger 106 and penetrate the housing 166. These pipes constitute the third passage 223.

[0052] Also, the tube 236 penetrates the housing 166 and extends downward toward the body 200, and the discharge port at its tip opens to the atmosphere. With such a configuration, the refrigerant relieved by the opening of the relief valve 2 is led out of the refrigerant unit 160 through the tube 236 and discharged to the atmosphere. Since propane, which is the refrigerant, is heavier than the atmosphere, the downward orientation of the tube 236 promotes its discharge.

[0053] Note that a pressure sensor (not shown) for detecting the refrigerant pressure in the low-pressure region is provided at a predetermined position on the downstream side of the expansion valve 1 in the refrigerant circulation circuit 101. The detection information by this pressure sensor is output to the control unit 150 and used for the processing when refrigerant leakage occurs, which will be described later.

[0054] FIG. 4 is a cross-sectional view showing the configuration of the valve unit 114. The valve unit 114 is configured by integrally assembling the expansion valve 1 and the relief valve 2 on a common body 200. The body 200 is made of a metal such as an aluminum alloy and is a block having a substantially prismatic shape. The expansion valve 1 is assembled on the upper surface of the body 200, and the relief valve 2 is assembled on the lower surface of the body 200.

[0055] On the side portion of the body 200, an introduction port 252, a lead-out port 254, an introduction port 256, and a lead-out port 258 are provided. A pipe extending from the water-refrigerant heat exchanger 104 side is connected to the introduction port 252, and a pipe leading to the inlet of the water-refrigerant heat exchanger 106 is connected to the lead-out port 254. A pipe leading to the outlet of the water-refrigerant heat exchanger 106 is connected to the introduction port 256, and a pipe extending toward the accumulator 112 side is connected to the lead-out port 258.

[0056] The body 200 is formed with a first refrigerant passage 260 that connects the introduction port 252 and the discharge port 254, and a second refrigerant passage 262 (low-pressure passage) that connects the introduction port 256 and the discharge port 258. The first refrigerant passage 260 and the second refrigerant passage 262 are vertically separated by a partition wall 264. Further, a discharge port 270 is provided at the lower side portion of the body 200, and a relief passage 272 is provided so as to communicate the discharge port 270 and the second refrigerant passage 262. A tube 236 is connected to the discharge port 270.

[0057] The expansion valve 1 is a motor-driven electric expansion valve, and its valve portion is disposed in the middle of the first refrigerant passage 260. The expansion valve 1 functions as an on-off valve by opening and closing the valve portion, and functions as an expansion valve by adjusting the opening degree of the valve portion. The expansion valve 1 is configured by coaxially assembling a rotor unit 10 and a stator unit 12. The rotor unit 10 has a valve body 5, and the valve body 5 is assembled to the body 200. A seal ring 8 is provided at the tip of the valve body 5. The seal ring 8 seals between the upstream passage 280 and the downstream passage 282 of the valve portion in the first refrigerant passage 260.

[0058] A circuit board 152 is provided inside the stator unit 12. Mounted on the circuit board 152 are a drive circuit for driving the motor, a control circuit (microcomputer) that outputs a control signal to the drive circuit, a communication circuit for the control circuit to communicate with an external device, a power supply circuit for supplying power to each circuit and the motor (coil), and the like.

[0059] A valve hole 14 is provided at the tip of the valve body 5, and a valve seat 16 is provided at the opening end thereof. An operating rod 22 extending from the rotor 20 of the rotor unit 10 is inserted inside the valve body 5. A needle-shaped valve body 24 is integrally provided at the lower end of the operating rod 22. The valve body 24 attaches to and detaches from the valve seat 16 to open and close the valve portion. Note that for the specific configuration of such an electric expansion valve, for example, the structure described in Japanese Unexamined Patent Application Publication No. 2022-93842 can be adopted, and thus the details thereof will be omitted.

[0060] The relief valve 2 is a so-called pilot-operated solenoid valve, and its valve portion is disposed in the middle of the relief passage 272. The relief valve 2 is configured by assembling a valve body 30 and a solenoid 32. The valve body 30 is assembled to the body 200. A valve seat 34 is provided in the middle of the relief passage 272.

[0061] The relief valve 2 includes a valve body 36 that can be attached to and detached from the valve seat 34 to open and close the valve portion, a pilot valve hole 38 formed in the valve body 36, and a pilot valve body 40 that drives the valve body 36 by changing the back pressure of the valve body 36 by opening and closing the pilot valve hole 38. The pilot valve body 40 is driven by the solenoid 32. The relief valve 2 is a normally closed solenoid valve and is opened by energization. For the specific configuration of such a solenoid valve, for example, the structure described in Japanese Patent Application Laid-Open No. 2014-156921 can be adopted, and thus the details thereof will be omitted.

[0062] FIG. 5 is a flowchart showing an outline of the process executed when refrigerant leakage occurs. When refrigerant leakage in the refrigerant unit 160 is detected by the sensor 162 or 164 (S10), the air conditioner 100 executes different processes depending on whether it is a high-pressure side leak or a low-pressure side leak. When refrigerant leakage is detected by the sensor 162, it can be determined as a high-pressure side leak, and when refrigerant leakage is detected by the sensor 164, it can be determined as a low-pressure side leak.

[0063] In the case of a high-pressure side leak (Y in S12), the control unit 150 stops the operation of the refrigeration cycle by stopping the drive of the compressor 110 (S14). Then, the expansion valve 1 is fully opened (S16), and the relief valve 2 is opened (S18). At this time, the control unit 150 outputs a control command to the circuit board 152 of the expansion valve 1 and energizes the solenoid 32 of the relief valve 2.

[0064] At this time, even if the compressor 110 is stopped, the refrigerant will flow through the refrigerant circulation circuit 101 for a while due to inertia. By setting the expansion valve 1 to the fully open state and opening the relief valve 2, the pressure on the high-pressure side can be rapidly reduced, and leakage of the high-pressure refrigerant on the high-pressure side can be suppressed. On the other hand, although the pressure of the refrigerant released via the relief valve 2 will be slightly higher when the expansion valve 1 is set to the fully open state, it is guided to a safe space by the tube 236 and discharged to the atmosphere, so there is no risk of ignition or the like.

[0065] When there is a leak on the low-pressure side rather than the high-pressure side (N in S12), the control unit 150 first opens the relief valve 2 (S20). Then, until the refrigerant pressure in the low-pressure region detected by the pressure sensor becomes equal to or lower than the set pressure (N in S22), the control state (slightly open state) of the expansion valve 1 is maintained. In this embodiment, this set pressure is set to a value near atmospheric pressure. When the refrigerant pressure on the low-pressure side becomes equal to or lower than the set pressure (Y in S22), the control unit 150 stops the operation of the refrigeration cycle by stopping the drive of the compressor 110 (S24).

[0066] In this way, until the refrigerant pressure on the low-pressure side drops to a certain extent, the expansion valve 1 is set to a very small opening degree, and the refrigerant flow rate is suppressed, so that the refrigerant is slowly released little by little. Thereby, the refrigerant concentration when the refrigerant is discharged from the tube 236 to the atmosphere can be reduced to at least below the stoichiometric combustion concentration, and safety can be maintained at a higher level. There is also no risk of the refrigerant igniting due to refrigerant leakage on the low-pressure side.

[0067] As described above, according to this embodiment, when a refrigerant leak occurs in the refrigerant circulation circuit 101, the expansion valve 1 and the relief valve 2 are interlocked and controlled according to the location of the refrigerant leak. Thereby, even if a leak occurs on either the high-pressure side or the low-pressure side, the refrigerant can be safely released from the low-temperature and low-pressure region to the atmosphere, and leakage into the vehicle interior can be prevented. Also, although the natural refrigerant used is highly flammable propane, since it is released in a low-temperature and low-pressure state, there is no risk of ignition.

[0068] In addition, since the expansion valve 1 and the relief valve 2 are integrated via a common body 200, they are more compact as a whole than when these control valves are provided individually. As a result, simplification and reduction in size and weight of the air conditioner can be achieved. By providing the relief valve 2 in the body 200, it is also possible to move it away from the compressor 110 that becomes high-temperature and high-pressure and its surroundings, and it is easy to ensure safety when releasing the refrigerant. Since the compressor 110 becomes hot during operation and also includes lubricating oil, it is preferable that the refrigerant release location be moved away.

[0069] As described above, the preferred embodiments of the present invention have been explained. However, it goes without saying that the present invention is not limited to the specific embodiments, and various modifications are possible within the scope of the technical idea of the present invention.

[0070] [Modification Example] FIG. 6 is a cross-sectional view showing the configuration of a valve unit according to a modification example. The valve unit 214 of this modification example is common to the above-described embodiment in that it has a common body 290 for the expansion valve 1 and the relief valve 2, but is different from the above-described embodiment in that it does not have a second refrigerant passage 262. The body 290 is provided with a relief passage 292 that connects the downstream passage 282 of the refrigerant passage 260 and the discharge port 270. The downstream passage 282 corresponds to the "low-pressure passage". On the other hand, although not shown, a pipe connecting the outlet of the water-refrigerant heat exchanger 106 and the inlet of the accumulator 112 is separately provided. The valve unit 214 is controlled by the control unit 150.

[0071] Also in this modification example, by opening the relief valve 2, the low-pressure passage is opened to the atmosphere and the refrigerant can be released, so the same effects as in the above-described embodiment can be obtained. Further, since the expansion valve 1 and the relief valve 2 are close to each other, the effects when both control valves are interlocked can be obtained promptly.

[0072] [Other Modification Examples] In the above-described embodiment, an example in which propane is adopted as a natural refrigerant was shown. In a modification, a natural refrigerant mainly composed of butane or other hydrocarbons may be adopted. Even if a flammable natural refrigerant is adopted, by adopting the system configuration of the above-described embodiment, the same effects as those of the above-described embodiment can be obtained. Alternatively, carbon dioxide may be adopted as the natural refrigerant. When carbon dioxide is adopted, there is no risk of ignition, but at least leakage into the passenger compartment needs to be avoided. By adopting the system configuration of the above-described embodiment, when refrigerant leakage occurs, it can be quickly relieved to the atmosphere, so safety can be ensured.

[0073] In the above-described embodiment, an example in which the inside of the housing 166 in the refrigerant unit 160 is partitioned into a high-pressure corresponding region HA and a low-pressure corresponding region LA, and refrigerant leakage is detected in each region was shown. In a modification, a configuration in which these regions are not partitioned may be adopted. In that case, it is sufficient to provide a single sensor for detecting refrigerant leakage. However, since it is unknown whether leakage is occurring on the high-pressure side or the low-pressure side, it is preferable to execute more safety-oriented control. For example, regardless of the location of the refrigerant leakage, the processing (S12 to S18) when leakage on the high-pressure side is detected in FIG. 5 may be performed.

[0074] In the above-described embodiment, an example of the structure of the electric expansion valve and the relief valve was shown (see FIG. 4), but it goes without saying that the specific structure of each control valve is not limited to this. The relief valve may be an electric valve instead of a solenoid valve, and may be controlled to open and close by a control unit. The relief valve may be a direct-acting type in which the main valve is directly driven by a solenoid instead of a pilot-operated type.

[0075] In the above-described embodiment, as shown in FIG. 4, an example of a configuration in which the valve unit 114 includes a single body 200 shared by the expansion valve 1 and the relief valve 2 was illustrated. In a modification, the electric expansion valve and the relief valve may each have an individual block-shaped body, and those bodies may be directly connected and integrated.

[0076] In the above embodiment, an example in which the on-off valve 142 for opening or closing the bypass passage 226 is configured as a solenoid valve has been shown, but it may be configured as an electric valve. Similarly, an example in which the on-off valve 144 for opening or closing the bypass passage 228 is configured as a solenoid valve has been shown, but it may be configured as an electric valve.

[0077] In the above embodiment, as shown in FIG. 1, an example in which an accumulator 112 is provided upstream of the compressor 110 in the refrigerant circulation circuit 101 has been shown. In a modified example, instead of the accumulator 112, a liquid receiver (liquid tank) may be provided upstream of the water-refrigerant heat exchanger 106 (second heat exchanger).

[0078] In the above embodiment, as shown in FIG. 3, a configuration in which each device constituting the refrigerant unit 160 is connected by piping has been illustrated. In a modified example, independent devices may be configured in a block shape, and by directly connecting each device, a configuration in which piping is substantially eliminated may be adopted.

[0079] In the above embodiment, the heat exchanger that exchanges heat with the air supplied into the vehicle interior is the cooler core 120 and is provided in the coolant circulation circuit 102. This is because the refrigerant filling amount of the refrigerant circulation circuit 101 is limited due to the use of highly flammable propane as the refrigerant. That is, since the piping length of the refrigerant circulation circuit 101 cannot be made sufficiently large due to the limited refrigerant filling amount, it is difficult to install the evaporator of the refrigerant circulation circuit 101 in the vehicle interior. When a natural refrigerant that is not thus limited in refrigerant filling amount is adopted, the evaporator of the refrigerant circulation circuit 101 may be provided in the vehicle interior. Thereby, the cooling function can be enhanced.

[0080] Note that the present invention is not limited to the above embodiment and modified examples, and components can be modified and embodied without departing from the gist. Various inventions may be formed by appropriately combining a plurality of components disclosed in the above embodiment and modified examples. Also, some components may be deleted from all the components shown in the above embodiment and modified examples.

Explanation of Reference Numerals

[0081] 1 Expansion valve, 2 Relief valve, 5 Valve body, 10 Rotor unit, 12 Stator unit, 14 Valve hole, 16 Valve seat, 20 Rotor, 24 Valve body, 30 Valve body, 32 Solenoid, 34 Valve seat, 36 Valve body, 38 Pilot valve hole, 40 Pilot valve body, 100 Heating and cooling device, 101 Refrigerant circulation circuit, 102 Coolant circulation circuit, 104 Water-refrigerant heat exchanger, 106 Water-refrigerant heat exchanger, 108 Outdoor heat exchanger, 110 Compressor, 112 Accumulator, 114 Valve unit, 120 Cooler core, 122 Heater core, 130 Changeover valve, 132 Changeover valve, 134 Pump, 140 Battery unit, 142 On-off valve, 144 On-off valve, 150 Control unit, 160 Refrigerant unit, 162 Sensor, 164 Sensor, 166 Housing, 168 Partition member, 200 Body, 214 Valve unit, 230 Pipe, 232 Pipe, 234 Pipe, 236 Tube, 260 First refrigerant passage, 260 Refrigerant passage, 262 Second refrigerant passage, 270 Discharge port, 272 Relief passage, 280 Upstream passage, 282 Downstream passage, 290 Body, 292 Relief passage, HA High-pressure corresponding region, LA Low-pressure corresponding region.

Claims

1. A refrigerant circulation passage for circulating a natural refrigerant, a compressor disposed in the refrigerant circulation passage for compressing and discharging the refrigerant, a first heat exchanger disposed downstream of the compressor in the refrigerant circulation passage, a second heat exchanger disposed upstream of the compressor in the refrigerant circulation passage, a sensor for detecting refrigerant leakage from the refrigerant circulation passage to the outside, A valve unit applied to a refrigeration cycle comprising: An electric expansion valve for decompressing and expanding the refrigerant flowing from the first heat exchanger to the second heat exchanger, and a relief valve that is opened to release the low-pressure passage on the downstream side of the electric expansion valve to the atmosphere, and when refrigerant leakage is detected by the sensor, the electric expansion valve and the relief valve are controlled in conjunction with each other. A valve unit characterized by this.

2. The valve unit according to claim 1, wherein the natural refrigerant is a flammable refrigerant mainly composed of hydrocarbon.

3. A body shared by the electric expansion valve and the relief valve, A pipe connected to the body and communicating with the low-pressure passage when the relief valve is opened, Comprising, The valve unit according to claim 2, wherein the pipe extends downward from the body.

4. A refrigerant circulation passage for circulating a natural refrigerant, a compressor disposed in the refrigerant circulation passage for compressing and discharging the refrigerant, a first heat exchanger disposed downstream of the compressor in the refrigerant circulation passage, a second heat exchanger disposed upstream of the compressor in the refrigerant circulation passage, An electric expansion valve for decompressing and expanding the refrigerant flowing from the first heat exchanger to the second heat exchanger, A relief valve that is opened to release the low-pressure passage on the downstream side of the electric expansion valve to the atmosphere, a sensor for detecting refrigerant leakage from the refrigerant circulation passage to the outside, A control unit for controlling the compressor, the electric expansion valve, and the relief valve, Comprising, The electric expansion valve and the relief valve are integrally provided, The control unit controls the electric expansion valve and the relief valve in conjunction with each other and stops driving the compressor when refrigerant leakage is detected by the sensor. A vehicle air conditioner characterized by this.

5. The vehicle air conditioner according to claim 4, wherein the natural refrigerant is a flammable refrigerant mainly composed of hydrocarbon.

6. As the sensor, a first sensor for detecting refrigerant leakage upstream of the electric expansion valve, A second sensor that detects refrigerant leakage downstream of the electric expansion valve as the sensor; A pressure sensor that detects the pressure of the refrigerant downstream of the electric expansion valve; Comprising; The control unit; When refrigerant leakage is detected by the first sensor, the driving of the compressor is stopped, the electric expansion valve is fully opened, and the relief valve is opened; When refrigerant leakage is detected by the second sensor instead of the first sensor, the relief valve is opened while the electric expansion valve is maintained at a small opening degree, and the driving of the compressor is stopped when the pressure detected by the pressure sensor becomes equal to or lower than the set pressure. The vehicle air conditioning apparatus according to claim 4 or 5, characterized in that.

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