Patent Publication Number: US-2021180842-A1

Title: Air conditioner

Description:
TECHNICAL FIELD 
     The present invention relates to air conditioners. 
     BACKGROUND ART 
     Air conditioners that reduce refrigerant consumption with the use of low global warming potential (GWP) refrigerant are desired in consideration of global environment. Used as the refrigerant enabling such air conditioners that reduce refrigerant consumption with the use of low GWP refrigerant is R32. R32 is refrigerant which has a small politropic exponent and whose temperature easily increases when discharged from a compressor. The use of R32 as refrigerant thus easily increases the temperature of the refrigerant discharged from the compressor at high outside temperature and at high condensation temperature. Since an increase in the temperature of the refrigerant discharged from the compressor may lead to a failure of the compressor, the temperature of the refrigerant discharged from the compressor is desired not to exceed a set temperature in order to prevent a failure of the compressor. 
     In a conventional air conditioner using R32 as refrigerant, thus, a linear expansion valve (LEV) is used to adjust the temperature of the refrigerant discharged from a compressor. Specifically, a microcomputer controls the degree of opening of the LEV based on a signal from a thermistor that has detected the temperature of the refrigerant discharged from the compressor to adjust the temperature of the refrigerant discharged from the compressor not to exceed the set temperature. 
     For example, Japanese Patent Laying-Open No. 2016-109356 (PTL 1) discloses an air conditioner that uses R32 as refrigerant and includes an LEV. 
     CITATION LIST 
     Patent Literature 
     PTL 1: Japanese Patent Laying-Open No. 2016-109356 
     SUMMARY OF INVENTION 
     Technical Problem 
     The air conditioner disclosed in the above literature has a long response time of the temperature of the refrigerant discharged from the compressor with respect to the adjustment of the degree of opening of the LEV. Consequently, the adjustment of the degree of opening of the LEV may not keep up with an increase in the temperature of the refrigerant discharged from the compressor, allowing the temperature of the refrigerant discharged from the compressor to exceed the set temperature. A reduced amount of refrigerant may lead to a shorter response time of the temperature of the refrigerant discharged from the compressor with respect to the adjustment of the degree of opening of the LEV. As a result, even when the degree of opening of the LEV is adjusted to allow the temperature of the refrigerant discharged from the compressor to be equal to the set temperature, a phenomenon (hunting) occurs in which the temperature of the refrigerant discharged from the compressor exceeds or falls below the set temperature. 
     The present invention has been made in view of the above problem and has an object to provide an air conditioner that can suppress an increase in the temperature of refrigerant discharged from a compressor and reduce refrigerant consumption with the use of low GWP refrigerant. 
     Solution to Problem 
     An air conditioner of the present invention includes a refrigerant circuit and refrigerant. The refrigerant circuit has a compressor, a condenser, a pressure-regulating valve, and an evaporator. The refrigerant flows through the refrigerant circuit in the order of the compressor, the condenser, the pressure-regulating valve, and the evaporator. The refrigerant is R32. The pressure-regulating valve includes a flow path causing the refrigerant flowing from the condenser to flow to the evaporator, a pressure reference chamber partitioned from the flow path and tilled with inert gas, and a valve portion disposed in the flow path. The pressure-regulating valve is configured to adjust a degree of opening of the valve portion to adjust a flow rate of the refrigerant flowing through the flow path. The valve portion is configured to increase the degree of opening when a pressure in the flow path is higher than a pressure in the pressure reference chamber and reduce the degree of opening when the pressure in the flow path is lower than the pressure in the pressure reference chamber. 
     Advantageous Effects of Invention 
     The air conditioner of the present invention sets the pressure in the pressure reference chamber to the pressure in the flow path where the temperature of the refrigerant discharged from the compressor is a set temperature, and accordingly can increase the degree of opening of the valve portion when the pressure in the flow path is higher than the pressure in the pressure reference chamber, thus suppressing the temperature of the refrigerant discharged from the compressor exceeding the set temperature. Also, the degree of opening of the valve portion is adjusted before the temperature of the refrigerant discharged from the compressor exceeds the set temperature, thus suppressing the generation of hunting. R32 is low GWP refrigerant. Therefore, an air conditioner that reduces refrigerant consumption with the use of low GWP refrigerant can be achieved. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  schematically shows the structure of a refrigerant circuit of an air conditioner in Embodiment 1 of the present invention. 
         FIG. 2  is a sectional view schematically showing the structure of a pressure-regulating valve of the air conditioner in Embodiment 1 of the present invention. 
         FIG. 3  is a sectional view for illustrating an operation of a valve portion of the air conditioner in Embodiment 1 of the present invention. 
         FIG. 4  schematically shows the structure of a refrigerant circuit of an air conditioner in a comparative example. 
         FIG. 5  schematically shows the structure of a refrigerant circuit of an air conditioner in Embodiment 2 of the present invention, 
         FIG. 6  schematically shows the structure of a refrigerant circuit of an air conditioner in Embodiment 3 of the present invention. 
         FIG. 7  is a sectional view schematically showing the structure of a pressure-regulating valve of a modification of the air conditioner in Embodiment 3 of the present invention. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Embodiments of the present invention will be described below with reference to the drawings. 
     Embodiment 1 
     A configuration of an air conditioner  10  in Embodiment 1 of the present invention will be described with reference to  FIG. 1 . Air conditioner  10  of the present embodiment is a device dedicated to cooling. That is to say, air conditioner  10  of the present embodiment has a cooling function and does not have a heating function. 
     Air conditioner  10  of the present embodiment mainly includes a compressor  1 , a condenser  2 , a pressure-regulating valve  3 , an evaporator  4 , a blower for condenser  5 , a blower for evaporator  6 , pipes PI 1  to PI 4 , and refrigerant. Compressor  1 , condenser  2 , pressure-regulating valve  3 , and blower for condenser  5  are accommodated in an outdoor unit  11 . Evaporator  4  and blower for evaporator  6  are accommodated in an indoor unit  12 . 
     Refrigerant circuit  13  has compressor  1 , condenser  2 , pressure-regulating valve  3 , and evaporator  4 . Compressor  1 , condenser  2 , pressure-regulating valve  3 , and evaporator  4  communicated with each other through pipes PI 1  to PI 4  constitute refrigerant circuit  13 . Specifically, compressor  1  and condenser  2  are connected to each other by pipe PI 1 . Condenser  2  and pressure-regulating valve  3  are connected to each other by pipe PI 2 . Pressure-regulating valve  3  and evaporator  4  are connected to each other by pipe PI 3 . Evaporator  4  and compressor  1  are connected to each other by pipe PI 4 . 
     Refrigerant circuit  13  is configured to allow refrigerant to circulate therethrough in the order of compressor  1 , pipe PI 1 , condenser  2 , pipe PI 2 , pressure-regulating valve  3 , pipe PI 3 , evaporator  4 , and pipe PI 4 . That is to say, refrigerant flows through refrigerant circuit  13  in the order of compressor  1 , condenser  2 , pressure-regulating valve  3 , and evaporator  4 . Refrigerant is R32. The amount of the refrigerant flowing through refrigerant circuit  13  is preferably 300 g or more and 500 g or less. 
     Compressor  1  is configured to compress refrigerant. Compressor  1  is also configured to compress the sucked refrigerant and discharge the compressed refrigerant. Compressor  1  is configured to have a variable capacity. Compressor  1  of the present embodiment is configured to variably control the number of rotations. Specifically, the drive frequency of compressor  1  is changed based on an instruction from a controller (not shown), so that the number of rotations of compressor  1  is adjusted. This changes the capacity of compressor  1 . The capacity of compressor  1  is an amount by which refrigerant is fed per unit time. That is to say, compressor  1  can perform a high-capacity operation and a low-capacity operation. In the high-capacity operation, an operation is performed by setting the drive frequency of compressor  1  high to increase the flow rate of refrigerant circulating through refrigerant circuit  13 . In the low-capacity operation, an operation is performed by setting the drive frequency of compressor  1  low to reduce the flow rate of refrigerant circulating through refrigerant circuit  13 . 
     Condenser  2  is configured to condense the refrigerant compressed by compressor  1 . Condenser  2  is an air-heat exchanger formed of a pipe and a fin. Pressure-regulating valve  3  is configured to decompress the refrigerant condensed by condenser  2 . Pressure-regulating valve  3  has the function as an expansion valve. Pressure-regulating valve  3  is also a mechanical pressure control valve. Pressure-regulating valve  3  is also configured to adjust the flow rate of the refrigerant flowing through pressure-regulating valve  3 . The flow rate of the refrigerant flowing through pressure-regulating valve  3  is a flow rate per unit time. Evaporator  4  is configured to evaporate the refrigerant decompressed by pressure-regulating valve  3 . Evaporator  4  is an air-heat exchanger formed of a pipe and a fin. 
     Blower for condenser  5  is configured to adjust a heat exchange amount between the outdoor air and refrigerant in condenser  2 . Blower for condenser  5  is formed of a fan  5   a  and a motor  5   b . Motor Sb may be configured to rotate fan  5   a  such that the number of rotations of fan  5   a  is variable. Motor  5   b  may also be configured to rotate fan  5   a  such that the number of rotations of fan  5   a  is constant. Blower for evaporator  6  is configured to adjust a heat exchange amount between the indoor air and refrigerant in evaporator  4 . Blower for evaporator  6  is formed of a fan  6   a  and a motor  6   b . Motor  6   b  may be configured to rotate fan  6   a  such that the number of rotations of fan  6   a  is variable. Motor  6   b  may be configured to rotate fan  6   a  such that the number of rotations of fan  6   a  is constant. 
     With reference to  FIGS. 1 and 2 , the configuration of pressure-regulating valve  3  in the present embodiment will be described in detail. 
     Pressure-regulating valve  3  includes a case  31 , a diaphragm  32 , a flow path  33 , a valve portion  34 , a spring  35 , and a partition member  36 . Pressure-regulating valve  3  is configured to adjust the degree of opening of valve portion  34  to adjust the flow rate of the refrigerant flowing through flow path  33 . 
     Diaphragm  32  is attached to the inner side of case  31  to partition the interior of case  31 . Case  31  has a first chamber S 1  and a second chamber S 2  partitioned by diaphragm  32 . 
     First chamber S 1  has flow path  33  which causes the refrigerant flowing from condenser  2  to flow to evaporator  4 . Specifically, first chamber S 1  has a flow inlet portion  31   a  and a flow outlet portion  31   b . Flow inlet portion  31   a  is connected to pipe PI 2 . Flow outlet portion  31   b  is connected to pipe PI 3 . First chamber S 1  is configured to allow the refrigerant flowing through the refrigerant circuit to flow from pipe PI 2  through flow inlet portion  31   a  into first chamber S 1  and then flow through outlet portion  31   b  to pipe PI 3 . That is to say, the refrigerant flowing through the refrigerant circuit flows into first chamber S 1  from flow inlet portion  31   a  and flows out of flow outlet portion  31   b , as indicated by arrows A 1  in  FIG. 2 . In the present embodiment, the path from flow inlet portion  31   a  to flow outlet portion  31   b  forms flow path  33  for refrigerant. 
     The pressure of first chamber S 1  is a pressure of the refrigerant in flow path  33 . Since the pressure of first chamber S 1  is a pressure of the refrigerant flowing thereinto from condenser  2 , it is a pressure of high-pressure-side refrigerant flowing through refrigerant circuit  13 . Pressure-regulating valve  3  is accordingly a high-pressure pressure-regulating valve. 
     Second chamber S 2  forms a pressure reference chamber S 2 . Pressure reference chamber S 2  is partitioned from flow path  33 . Pressure reference chamber S 2  is filled with inert gas. Pressure reference chamber S 2  is hermetically sealed while being filled with inert gas. The pressure in pressure reference chamber S 2  is a pressure of the inert gas. The inert gas is, for example, nitrogen or helium. Nitrogen is advantageous in low cost. Helium is advantageous in high level of safety. The pressure in pressure reference chamber S 2  is, for example, 3 MPa or more and 4 MPa or less. 
     Diaphragm  32  is configured to deform in the direction indicated by a double-pointed arrow A 2  in  FIG. 2  due to a pressure difference between the pressure of first chamber S 1  and the pressure of second chamber S 2 , that is, a pressure difference between the pressure of the refrigerant in flow path  33  and the pressure of the inert gas in pressure reference chamber S 2 . Specifically, diaphragm  32  is configured to curve in a projecting manner toward pressure reference chamber S 2  when the pressure of the refrigerant in flow path  33  is higher than the pressure of the inert gas in pressure reference chamber S 2 . In contrast, diaphragm  32  is configured to be planar when the pressure of the refrigerant in flow path  33  is equal to or lower than the pressure of the inert gas in pressure reference chamber S 2 . That is to say, in this case, diaphragm  32  does not curve in a projecting manner toward pressure reference chamber S 2 . 
     Valve portion  34 , spring  35 , and partition member  36  are disposed in first chamber S 1 . Partition member  36  is configured to partition first chamber S 1  into a first region on the flow inlet portion  31   a  side arid a second region on the flow outlet portion  31   b  side. That is to say, partition member  36  is disposed between flow inlet portion  31   a  and flow outlet portion  31   b  in flow path  33  extending from flow inlet portion  31   a  to flow outlet portion  31   b.    
     Valve portion  34  has a valve body  34   a  and a valve seat  34   b . Valve portion  34  is configured to adjust the degree of opening by the gap between valve body  34   a  and valve seat  34   b . Valve body  34   a  is formed in a shaft shape. One end (first end) of valve body  34   a  is connected to diaphragm  32 . The other end (second end) of valve body  34   a  is connected to spring  35 . Valve body  34   a  is configured to move in the direction indicated by a double-pointed arrow A 3  in  FIG. 2  due to the deformation of diaphragm  32 . That is to say, valve body  34   a  is configured to move in the axial direction of valve body  34   a  due to the deformation of diaphragm  32 . Valve body  34   a  has a tapered shape with a cross-section continuously decreasing from the one end to the other end. Valve body  34   a  is formed in a truncated cone shape and is formed with a diameter continuously decreasing in the axial direction toward valve seat  34   b.    
     Valve seat  34   b  is provided in partition member  36 . Valve seat  34   b  is disposed between flow inlet portion  31   a  and flow outlet portion  31   b  in flow path  33  extending from flow inlet portion  31   a  to flow outlet portion  31   b . Valve seat  34   b  is provided around a valve hole  37  passing through valve seat  34   b . Valve body  34   a  moves in the axial direction of valve body  34   a  clue to the deformation of diaphragm  32  and accordingly leaves valve seat  34   b , thereby opening valve hole  37 . Specifically, when the pressure of the refrigerant in flow path  33  exceeds the pressure of the inert gas in pressure reference chamber S 2 , diaphragm  32  curves in a projecting manner toward pressure reference chamber S 2 . This causes valve body  34   a  connected to diaphragm  32  to move toward pressure reference chamber S 2  in the axial direction of valve body  34   a . The other end of valve body  34   a  accordingly leaves valve seat  34   b  to expose valve hole  37  from valve body  34   a , thereby opening valve hole  37 . 
     Valve seat  34   b  is configured such that each of the surface (upper surface) on the first region side of first chamber S 1  and the surface (lower surface) on the second region side of first chamber S 1  becomes dented. That is to say, valve seat  34   b  has a dent on each of the first region side and the second region side of first chamber S 1 . In valve seat  34   b , the bottom of the dent on the first region side of first chamber S 1  and the bottom of the dent on the second region side of first chamber S 1  are communicated with each other. The bottom of the dent on the first region side of first chamber S 1  and the bottom of the dent on the second region side of first chamber S 1  which are communicated with each other define valve hole  37 . 
     Specifically, valve seat  34   b  is formed such that each of the surface on the first region side of first chamber S 1  and the surface on the second region side of first chamber S 1  is formed in a cone shape. Valve seat  34   b  is formed in a cone shape such that the surface on the first region side of first chamber S 1  has a diameter continuously decreasing toward the second region of first chamber S 1 . The surface of valve seat  34   b  on the first region side of first chamber S 1  is formed in a cone shape to have a diameter continuously decreasing toward second region of first chamber S 1 . 
     Valve portion  34  is configured to increase the degree of opening when the pressure in flow path  33  is higher than the pressure in pressure reference chamber S 1 . That is to say, valve portion  34  is configured as follows. When the pressure in flow path  33  is higher than the pressure in pressure reference chamber S 2 , valve body  34   a  moves toward diaphragm  32  in the axial direction of valve body  34   a  to increase the gap between valve body  34   a  arid valve seat  34   b , thereby increasing the degree of opening. Valve portion  34  is also configured to reduce the degree of opening when the pressure in flow path  35  is lower than the pressure in pressure reference chamber S 2 . That is to say, valve portion  34  is configured as follows. When the pressure in flow path  35  is lower than the pressure in pressure reference chamber S 2 , valve body  34   a  moves toward spring  35  in the axial direction of valve body  34   a  to reduce the gap between valve body  34   a  and valve seat  34   b , thereby reducing the degree of opening. 
     Valve portion  34  is configured to continuously change the size of the gap between valve body  34   a  and valve seat  34   b  by valve body  34   a  moving in the axial direction of valve body  34   a  due to the deformation of diaphragm  32 . That is to say, valve portion  34  is configured to increase or reduce the degree of opening of valve portion  34  in proportional to the amount of movement in the axial direction of valve body  34   a.    
     Spring  35  is connected to the other end of valve body  34   a  and the bottom of case  31 . Spring  35  is configured to bias valve body  34   a  toward the bottom of case  31  by elastic force. 
     A small hole  38  is provided in partition member  36 . Small hole  38  is provided to pass through partition member  36 . Small hole  38  defines a part of flow path  33 . Since small hole  38  is not closed by valve body  34   a  and is open constantly, refrigerant can constantly flow through small hole  38  front the first region to the second region in first chamber S 1 . In the present embodiment, small hole  38  has the function as a capillary. That is to say, the refrigerant is decompressed by flowing through small hole  38 . 
     A flow of refrigerant in the refrigerant circuit of air conditioner  10  of the present embodiment will now he described. 
     With reference to  FIG. 1 , the refrigerant that has flowed into compressor  1  is compressed by compressor  1  to turn into high-temperature, high-pressure gas refrigerant. The high-temperature, high-pressure gas refrigerant discharged from compressor  1  flows through pipe PI 1  into condenser  2 . The refrigerant that has flowed into condenser  2  is subjected to heat exchange with the air in condenser  2 . Specifically, in condenser  2 , the refrigerant is condensed by heat dissipation to the air, and the air is heated by the refrigerant. High-pressure liquid refrigerant condensed by condenser  2  flows through pipe PI 2  into pressure-regulating valve  3 . 
     The refrigerant that has flowed into pressure-regulating valve  3  is decompressed by pressure-regulating valve  3  to turn into low-pressure gas-liquid two-phase refrigerant. The refrigerant decompressed by pressure-regulating valve  3  flows through pipe PI 3  into evaporator  4 . The refrigerant that has flowed into evaporator  4  is subjected to heat exchange with the air in evaporator  4 . Specifically, in evaporator  4 , the air is cooled by the refrigerant, and the refrigerant turns into low-pressure gas refrigerant. The refrigerant decompressed by evaporator  4  to turn into low-pressure gas flows through pipe PI 4  into compressor  1 . The refrigerant flowing into compressor  1  is compressed and pressurized again and subsequently discharged from compressor  1 . 
     With reference to  FIGS. 2 and 3 , the operation of pressure-regulating valve  3  in the present embodiment will now be described in detail. 
     When the pressure of the refrigerant in flow path  33  is equal to or lower than the pressure of the inert gas in pressure reference chamber S 2 , diaphragm  32  is maintained in a planar manner, so that valve body  34   a  is in contact with valve seat  34   b . This maintains the state in which valve hole  37  is closed by valve body  34   a . Valve portion  34  is closed in this state. 
     When the pressure of the refrigerant in flow path  33  is higher than the pressure of the inert gas in pressure reference chamber S 2 , diaphragm  32  deforms in a projecting manner toward pressure reference chamber S 2 . The deformation of diaphragm  32  causes valve body  34   a  to move toward pressure reference chamber S 2  in the axial direction of valve body  34   a . Consequently, valve body  34   a  leaves valve seat  34   b . In this state, valve portion  34  is opened. Further, when valve body  34   a  moves toward pressure reference chamber S 2  in the axial direction of valve body  34   a  due to the deformation of diaphragm  32 , the gap between valve body  34   a  and valve seat  34   b  increases. That is to say, the degree of opening of valve portion  34  increases. This increases the amount of refrigerant flowing through pressure-regulating valve  3 , thus increasing the amount of refrigerant flowing into evaporator  4 . The degree of superheat (SH) accordingly decreases. As a result, an increase in the temperature of the refrigerant discharged from compressor  1  can he suppressed. 
     The amount of movement in the axial direction of valve body  34   a  can be adjusted by the pressure of the refrigerant in flow path  33 , the pressure of the inert gas in pressure reference chamber S 2 , and the biasing force of spring  35  connected to valve body  34   a . The degree of opening of valve portion  34  can be adjusted by the gap between valve body  34   a  and valve seat  34   b . The amount of the refrigerant flowing through pressure-regulating valve  3  can thus be adjusted by adjusting the amount of movement in the axial direction of valve body  34   a  and the degree of opening of valve portion  34 . 
     The function and effect of the present embodiment will now be described in comparison with those of a comparative example. The same components as those of Embodiment 1 will he denoted by the same reference signs, and description thereof will not be repeated, unless otherwise noted. 
     With reference to  FIG. 4 , air conditioner  10  of the comparative example differs from air conditioner  10  of the present embodiment in that it includes a linear expansion valve (LEV)  30 , a thermistor  7 , and a microcomputer  8 . In air conditioner  10  of the comparative example, microcomputer  8  controls the degree of opening of LEV  30  based on a signal from thermistor  7  that has detected the temperature of the refrigerant discharged from compressor  1 , so that the temperature of the refrigerant discharged from compressor  1  is adjusted not to exceed a set temperature (a temperature set to prevent a failure of compressor  1 ). 
     In air conditioner  10  of the present embodiment, refrigerant is R32. R32 is refrigerant which has a small politropic exponent and whose temperature easily increases when discharged from compressor  1 . Thus, when R32 is used as refrigerant, the temperature of the refrigerant discharged from compressor  1  increases easily at high outside air (high outside air temperature) and at high condensation temperature. 
     Air conditioner  10  of the present embodiment sets the pressure in pressure reference chamber S 2  to the pressure in flow path  33  where the temperature of the refrigerant discharged from compressor  1  is the set temperature (the temperature set to prevent a failure of compressor  1 ), thereby increasing the degree of opening of valve portion  34  when the pressure in flow path  33  is higher than the pressure in pressure reference chamber S 2 . This can suppress the temperature of the refrigerant discharged from compressor  1  exceeding the set temperature. The amount of the refrigerant flowing into evaporator  4  can also be increased by increasing the amount of the refrigerant flowing through pressure-regulating valve  3 , thus reducing the degree of superheat. An increase in the temperature of the refrigerant discharged from compressor  1  can thus be suppressed. Also, the generation of hunting can be suppressed by adjusting the degree of opening of valve portion  34  before the temperature of the refrigerant discharged from compressor  1  exceeds the set temperature. R32 is low GWP refrigerant. Consequently, air conditioner  10  that reduces refrigerant consumption with the use of low GWP refrigerant can be achieved. 
     Air conditioner  10  of the comparative example needs LEV  30 , thermistor  7 , and microcomputer  8  to adjust the temperature of the refrigerant discharged from compressor  1 , leading to a complex configuration of air conditioner  10 . Also, the cost of manufacturing air conditioner  10  is increased. Contrastingly, in air conditioner  10  of the present embodiment, pressure-regulating valve  3  can adjust the temperature of the refrigerant discharged from compressor  1 , leading to a simple configuration of air conditioner  10 . Also, the cost of manufacturing air conditioner  10  is reduced. 
     In air conditioner  10  of the present embodiment, pressure-regulating valve  3  can adjust the flow rate of the refrigerant flowing: through flow path  33  by adjusting the degree of opening of valve portion  34 . Thus, the generation of hunting can be suppressed more than in the case where valve portion . 34  is merely opened/closed (ON/OFF). Also, the controllability of the flow rate of refrigerant can be improved. 
     In air conditioner  10  of the present embodiment, the amount of refrigerant flowing through refrigerant circuit  13  is 300 g or more and 500 g or less. According to the documents provided by the Ministry of Economy, Trade and Industry (documents related to a method of estimating emissions outside notification, 2003), the average refrigerant chlorofluorocarbon (CFC) charge amount of a room air conditioner is 800 g. Air conditioner  10  of the present embodiment can thus reduce the amount of refrigerant to about a half of 800 g that is the average refrigerant CFC charge amount of a room air conditioner. If the amount of refrigerant is 400 g±100 g, where 400 g is a half of the average refrigerant CFC charge amount of a room air conditioner, the refrigerant consumption can be reduced while maintaining the cooling capacity. 
     In air conditioner  10  of the comparative example, a reduced amount of refrigerant results in a shorter response time of the temperature of the refrigerant discharged from compressor  1  with respect to the adjustment of the degree of opening of LEV  30 , so hunting may occur at the set temperature. Contrastingly, air conditioner  10  of the present embodiment increases the degree of opening of valve portion  34  with reference to the pressure in pressure reference chamber S 2 , thereby suppressing the generation of hunting with respect to the set temperature even when the amount of refrigerant decreases. Controllability can thus be improved. 
     In air conditioner  10  of the present embodiment, compressor  1  can variably control the number of rotations. Power consumption can thus be reduced by variably controlling the number of rotations of compressor  1 . Also, even when the temperature of the refrigerant discharged from compressor  1  increases due to an increase in the number of rotations of compressor  1 , an increase in the temperature of the refrigerant discharged from compressor  1  can be suppressed by increasing the degree of opening of valve portion  34  with reference to the pressure in pressure reference chamber S 2 . 
     Embodiment 2 
     The same components as those of Embodiment 1 will be denoted by the same reference signs in Embodiment 2, and description thereof will not be repeated, unless otherwise noted. 
     With reference to  FIG. 5 , air conditioner  10  of Embodiment 2 of the present invention differs from air conditioner  10  of Embodiment 1 in the configuration of pressure-regulating valve  3 . 
     In air conditioner  10  of the present embodiment, pressure-regulating valve  3  includes a capillary  39 . Capillary  39  is connected to case  31  of pressure-regulating valve  3  and evaporator  4 . The configuration in case  31  of pressure-regulating valve  3  is identical to the configuration of Embodiment 1. Capillary  39  is disposed between valve portion  34  and evaporator  4  in refrigerant circuit  13 . Capillary  39  can thus decompress the refrigerant. 
     The present embodiment can adjust the decompression of refrigerant by capillary  39 . This leads to easier adjustment of the decompression of the refrigerant. 
     Embodiment 3 
     The same components as those of Embodiment 1 will be denoted by the same reference signs in Embodiment 3, and description thereof will not be repeated, unless otherwise noted. 
     With reference to  FIG. 6 , air conditioner  10  of Embodiment 3 of the present invention differs from air conditioner  10  of Embodiment 1 in the configuration of pressure-regulating valve  3 . 
     In air conditioner  10  of the present embodiment, pressure-regulating valve  3  includes capillary  39 . Capillary  39  is connected in parallel with case  31  of pressure-regulating valve  3  in refrigerant circuit  13 . The configuration in case  31  of pressure-regulating valve  3  is identical to the configuration of Embodiment 1. Capillary  39  is disposed in parallel with valve portion  34  in refrigerant circuit  13 . Capillary  39  can thus decompress the refrigerant. 
     The present embodiment can accordingly adjust the decompression of refrigerant by capillary  39 . The adjustment of the decompression of refrigerant can thus be simplified. 
     With reference to  FIG. 7 , a modification of air conditioner  10  of Embodiment 3 will now be described. This modification differs from Embodiment 1 in that small hole  38  is not provided. In this modification, capillary  39  is disposed in parallel with valve portion  34  in refrigerant circuit  13 , and accordingly, capillary  39  can cause refrigerant to constantly flow through refrigerant circuit  13  even when small hole  38  of Embodiment 1 is not provided. 
     Capillary  39  can adjust the decompression of refrigerant more easily than small hole  38  of Embodiment 1. In the modification of air conditioner  10  of the present embodiment, thus, capillary  39  can adjust the decompression of refrigerant easily. 
     It is to be understood that the embodiments disclosed herein have been presented for the purpose of illustration and non-restrictive in every respect. It is therefore intended that the scope of the present invention is defined by claims, not only by the embodiments described above, and encompasses all modifications and variations equivalent in meaning and scope to the claims. 
     REFERENCE S 1 GNS LIST 
       1  compressor,  2  condenser,  3  pressure-regulating valve,  4  evaporator,  5  blower for condenser,  6  blower for evaporator,  7  thermistor,  8  microcomputer,  9  capillary,  10  air conditioner,  11  outdoor unit,  12  indoor unit,  13  refrigerant circuit,  31  case,  31   a  flow inlet portion,  31   b  flow outlet portion,  32  diaphragm,  33  flow path,  34   a  valve body,  34   b  valve seat,  35  spring,  36  partition member,  37  valve hole,  38  small hole,  39  capillary, S 1  first chamber, S 2  second chamber (pressure reference chamber).