JPH10148407A - Air-conditioning apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve an enhancing of a heating capacity or the like by heating an excess of a refrigerant in an accumulator while satisfying the performance in the heating and cooling operations of a heat pump type air-conditioning apparatus and conserve the space and the cost by enabling reduction in the number of refrigerant containers preventing a wet vapor suction phenomenon. SOLUTION: In a heating/heating air-conditioning apparatus which has a compressor 20, a four-way valve 41, a room heat exchanger 42, an expansion valve 43 and an outdoor heat exchanger 44, an accumulator 45 is arranged on a suction side line 32 between the four-way valve and the compressor and a hot water heat exchanger 46 for heating an excess of refrigerant is provided in the accumulator 45 while a receiver tank 48 is interposed in a line between the outdoor heat exchanger 44 and the expansion valve 43. A liquid level within the receiver tank 48 is adjusted by a liquid level adjusting means 50 so that a part of the excess of refrigerant in a low pressure side circuit is stored into the receiver tank 48 on the upstream side of the accumulator 45 during the heating operation.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat pump type air conditioner capable of cooling and heating.

[0002]

2. Description of the Related Art A circuit for circulating a refrigerant is provided with a compressor, a condenser, an expansion valve and an evaporator. The refrigerant compressed by the compressor is condensed and liquefied while radiating heat in the condenser, and then expanded by the expansion valve. A heat pump is generally known in which heat is evaporated while absorbing heat in an evaporator and then returned to a compressor. The air conditioner using the function of the heat pump has a compressor, an indoor heat exchanger, an expansion valve, and an outdoor heat exchanger arranged in a refrigerant circuit and a four-way valve for switching a refrigerant circulation path. At the time of heating, the refrigerant circulates in the order of the compressor, the four-way valve, the indoor heat exchanger, the expansion valve, the outdoor heat exchanger, the four-way valve, and the compressor, so that the indoor heat exchanger becomes the condenser and the outdoor heat exchanger. The device becomes an evaporator, and heating is performed by heat radiation in the indoor heat exchanger.On the other hand, during cooling, the refrigerant is supplied to the compressor, four-way valve, outdoor heat exchanger, expansion valve, indoor heat exchanger, and four-way valve. By circulating in the order of the compressor, the outdoor heat exchanger functions as a condenser, the indoor heat exchanger functions as an evaporator, and the refrigerant circuit is configured to perform cooling by absorbing heat in the indoor heat exchanger. .

Conventionally, in this type of air conditioner, so-called subcool control is performed by controlling the expansion valve opening and the like so that the refrigerant temperature near the expansion valve on the high pressure side is lower than the saturated liquid temperature. Some of them are intended to improve COP (coefficient of performance) and performance as described in detail later. In such a device, a relatively large-capacity accumulator is arranged between the evaporator and the suction port of the compressor so that the surplus refrigerant stays in the accumulator.

[0004]

As described above, a comparatively large-capacity accumulator is arranged between the evaporator and the suction port of the compressor so that the surplus refrigerant stays in the accumulator. Further, a heating means comprising a heat exchanger is provided in the accumulator, and cooling water (warm water) after cooling the engine, for example, is guided to the heat exchanger to heat the refrigerant in the accumulator. . In this case, the heating capacity can be enhanced by utilizing the waste heat of the engine and the like.

[0005] However, if heating is performed with the entire amount of surplus refrigerant stored in the accumulator, droplets are discharged from the accumulator to a downstream circuit as the refrigerant boils,
This may be sucked into the compressor and cause a so-called liquid back phenomenon, which adversely affects the performance and reliability of the compressor. To avoid this situation,
It is necessary to divide the accumulator into a main accumulator and a sub-accumulator, and to increase the size, which leads to an increase in installation space and cost.

As a method of improving the COP and the performance of the heat pump, in addition to the above-described subcool control, expansion is performed so that the refrigerant temperature on the suction side of the compressor is higher than the saturated steam temperature. A so-called superheat control for controlling a valve or the like is known. When performing this superheat control, a receiver tank is arranged between the condenser and the expansion valve. And, as the load becomes smaller, the number of rotations of the compressor is reduced, and the degree of opening of the expansion valve is reduced, so that not only complete vaporization of the refrigerant in the evaporator but also superheat control that heats the refrigerant to the saturated vapor temperature or higher is performed. In this case, surplus refrigerant generated by a decrease in the circulation flow rate due to a decrease in the rotation speed of the compressor is stored as a liquid refrigerant that slowly circulates in the outdoor heat exchanger and the receiver tank.

If the superheat control and the subcool control are combined to perform, for example, the subcool control during heating and the superheat control during cooling as described later in detail, it is effective for improving the performance.

However, in such a case, an accumulator and a receiver tank are required, and in particular, when an excess refrigerant in the accumulator is heated as described above, a plurality of accumulators are required to prevent a liquid back phenomenon. When divided, three or more large refrigerant containers are required, which is very disadvantageous in terms of space, cost, and the like.

In view of the above circumstances, the present invention satisfies the performance at the time of heating and at the time of cooling, enhances the heating capacity by heating the excess refrigerant in the accumulator, and achieves the liquid back phenomenon. It is an object of the present invention to provide an air conditioner capable of reducing the number of refrigerant containers while saving space and cost.

[0010]

In order to achieve the above object, the present invention provides a compressor, an indoor heat exchanger serving as a condenser during heating and an evaporator during cooling, an expansion valve, and an evaporator during heating. An outdoor heat exchanger serving as a condenser during cooling and a means for switching a refrigerant circulation path are provided in the refrigerant circuit, and the refrigerant passes from the compressor through the indoor heat exchanger, the expansion valve, and the outdoor heat exchanger in this order during heating. In the air conditioner, the refrigerant circuit is configured such that the refrigerant passes through the outdoor heat exchanger, the expansion valve, and the indoor heat exchanger and returns to the compressor in this order during cooling. Place an accumulator in the path returning from the evaporator to the compressor, and in this accumulator, while providing heating means for heating the excess refrigerant in the liquid phase stored in the accumulator, during cooling between the condenser and the expansion valve during cooling High A receiver tank is provided at a position to be a side circuit, and at a position to be a low pressure side circuit between the expansion valve and the accumulator at the time of heating, and in this receiver tank, the liquid level in the receiver tank is set at the time of heating and at the time of cooling. Liquid level adjusting means for adjusting the liquid level in accordance with the condition.

According to this structure, during cooling, the receiver tank fulfills the original function of retaining the excess refrigerant in the high-pressure side circuit upstream of the expansion valve, while at the time of heating, the receiver tank has a low pressure upstream of the accumulator in the low-pressure side circuit. By preliminarily storing a part of the surplus refrigerant in the side circuit, the function of reducing the refrigerant storage amount in the accumulator is achieved. And by reducing the refrigerant storage amount in the accumulator during heating in this way, even if the refrigerant in the accumulator is heated by the heating means and boils, it is avoided that the droplets are discharged downstream of the accumulator, The liquid back phenomenon to the compressor is prevented.

In the apparatus of the present invention, the receiver tank may be provided, for example, in a circuit between the outdoor heat exchanger and the expansion valve.

[0013] Also, during cooling, subcool control is performed by adjusting the opening degree of the expansion valve so that the refrigerant temperature near the expansion valve on the high-pressure side is lower than the saturated liquid temperature. If a control means for performing super heat control for setting the refrigerant temperature on the suction side to a temperature higher than the saturated vapor temperature is provided, CO2 can be effectively used during heating and cooling.
P is improved, and the refrigerant in the accumulator is heated by the heating means, so that the heating performance and the like are improved.
Then, in this case, the surplus refrigerant in the low-pressure side circuit tends to increase during heating in which the subcool control is performed, but a part of the surplus refrigerant in the low-pressure side circuit is stored in the receiver tank as described above. This can prevent an increase in the amount of stored refrigerant in the accumulator.

In this device, when a non-azeotropic refrigerant is used as the refrigerant, when the amount of surplus refrigerant in the liquid layer stored in the accumulator increases during heating in which subcool control is performed, the composition ratio of the refrigerant sucked into the compressor is increased. However, since the refrigerant in the accumulator is heated by the heating means, an effect of correcting a change in the composition ratio can be obtained.
Then, while such an operation is effectively exerted, an increase in the refrigerant storage amount in the accumulator is avoided by the above-described operation of the receiver tank, and the liquid back phenomenon is prevented.

Further, in the apparatus of the present invention, if the liquid level adjusting means is configured so that the liquid level in the receiver tank is higher during heating than during cooling, the amount of refrigerant stored in the accumulator during heating can be reduced. The effect of reducing is favorably obtained.

Further, the liquid level adjusting means has switching means for switching the liquid level in the receiver tank in a plurality of stages, and the switching means is operated according to the liquid level in the accumulator. , The amount of refrigerant stored in the accumulator is appropriately controlled.

[0017]

Embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a circuit diagram schematically showing an air conditioner of the present invention. As shown in FIG.
A water-cooled engine 2, a refrigerant circuit 30 for circulating a refrigerant by a compressor 20 driven by the engine 2, and a cooling water circuit 80 for cooling the engine 2 are provided. As the refrigerant, a non-azeotropic refrigerant in which a plurality of types of refrigerants having different boiling points are mixed is used. For example, R32 and R125 which are relatively low-boiling refrigerants and R134a which is a relatively high-boiling refrigerant are mixed. Refrigerant is used.

The refrigerant circuit 30 includes the compressor 20 and
Indoor heat exchanger 4 that becomes a condenser during heating and an evaporator during cooling
2, an expansion valve 43, an outdoor heat exchanger 44 serving as an evaporator during heating and a condenser during cooling, and a four-way valve 41 as means for switching a refrigerant circulation path.

A discharge line 31 is provided between the discharge port of the compressor 20 and the first port 41a of the four-way valve 41, and between the fourth port 41d of the four-way valve 41 and the suction port of the compressor 20. Is provided with a suction side line 32. On the other hand, an indoor heat exchanger 42 is connected to the second port 41b of the four-way valve 41 via a line 33, and an expansion valve 43 is connected to the indoor heat exchanger 42, and the expansion valve 43 is connected to the outdoor heat exchanger. 44 is connected via lines 34 and 35, and the outdoor heat exchanger 44 and the third port 41 c of the four-way valve 41 are connected via line 36.

The refrigerant flows from the evaporator (the outdoor heat exchanger 44 during heating and the indoor heat exchanger 42 during cooling) from the compressor 2.
The accumulator 45 is disposed in the path returning to 0, and in the illustrated example, the accumulator 45 is disposed in the middle of the suction side line 32 between the four-way valve 41 and the suction port of the compressor 20. In the accumulator 45, a hot water heat exchanger 46 is provided as a heating means for heating the excess refrigerant in the liquid phase stored in the accumulator 45. As will be described in detail later, the hot water heat exchanger 46 includes a cooling water circuit. From 80, hot water after engine cooling is guided through a linear three-way valve 86.

A liquid-gas heat exchanger 47 is interposed in the suction line 32 between the four-way valve 41 and the accumulator 45.

In addition, at the position of the high pressure side circuit between the condenser and the expansion valve 43 at the time of cooling, and at the position of the expansion valve 4 at the time of heating.
A receiver tank 48 is provided at a position on the low-pressure side circuit from the position 3 to the accumulator 45. In the illustrated refrigerant circuit 30, the receiver tank 48 is interposed in a circuit between the expansion valve 43 and the outdoor heat exchanger 44. A line 34 extending from the expansion valve 43 through the liquid / gas heat exchanger 47 reaches the receiver tank 48, and a line 35 from the outdoor heat exchanger 44 reaches the receiver tank 48.

The receiver tank 48 is provided with a liquid level adjusting means 50. As shown in FIG. 3, the liquid level adjusting means 50 includes first and second pipes 50a and 50b connected to a line 35 on the outdoor heat exchanger side.
And a third pipe 5 connected to the line 34 on the expansion valve side.
0c and a liquid level control valve 50 for opening and closing the second pipe 50b.
d, the pipes 50a, 50b, and 50c protrude into the receiver tank 48 from below, the upper end of the first pipe 50a opens to a predetermined high-level position L1, the upper end of the second pipe 50b and the second pipe 50b. The upper end of the third pipe 50c opens at a predetermined low level position L2.

Then, as shown in a flowchart to be described later, the liquid level in the receiver tank 48 is adjusted by opening and closing the liquid level control valve 50d according to the time of heating and the time of cooling. ing.

The detailed structure of the air conditioner 1 will be specifically described with reference to FIG.

The engine 2 shown in FIG. 2 is a water-cooled gas engine, and an air cleaner 4 is provided in an intake pipe 3 of the engine 2.
And a mixer 5 are connected. A fuel supply pipe 6 connected to a fuel gas supply source (not shown) is connected to the mixer 5, and a flow control valve 7, a governor 8, and an electromagnetic valve 9 are interposed in the fuel supply pipe 6. . In the mixer 5, the supply amount of fuel gas and air to the engine is adjusted by the operation of the throttle by the pulse motor 5a. In the engine 2 oil pan,
An oil tank 11 is connected via an oil supply pipe 10, and an electromagnetic valve 12 for adjusting the oil supply amount is provided in the oil pipe 10.

An exhaust pipe 13 extends from the engine 2, and an exhaust gas heat exchanger 14, an exhaust silencer 15, and a mist separator 16 are interposed in the exhaust pipe 13. Reference numeral 17 denotes a heater for adjusting the oil temperature in the oil pan of the engine 2, and reference numeral 18 denotes an exhaust gas heat exchanger 14.
And a drain treatment device for treating drain water from the exhaust silencer 15 and the mist separator 16.

The compressor 20 is a multi-type compressor having two unit compressors 20a and 20b in the illustrated example, and each of the unit compressors 20a and 20b is an electromagnetic clutch 2a.
1 is connected to the output shaft 22 of the engine. 2
Reference numeral 3 denotes a heater for adjusting the oil temperature in the compressor 20.

The refrigerant circuit 30 is configured to be capable of cooling and heating a plurality of rooms.
3, 34, a plurality of indoor heat exchangers 42a to 42n
And expansion valves 43a to 43n respectively provided therein.
Are connected in parallel, and two outdoor heat exchangers 44a and 44b are connected in parallel between the lines 35 and 36.

The discharge line 31 of the refrigerant circuit 30 is led out of the discharge part of the compressor 20 and is connected to the first port 41a of the four-way valve 41 via an oil separator 52. The oil return line 53 is connected to the suction side line 3 via a capillary tube 53a.
2 is connected to a downstream line 32d.

On the other hand, the suction side line 32 is
And the liquid-gas heat exchanger 4
7, a line 32a extending to the accumulator 45, a line 32b derived from the accumulator 45, and a line 32d connected to the line 32b via a U-shaped line 32c and a capillary tube 54.
Is connected to a suction port of the compressor 20 via a check valve 55. The portion of the discharge-side line 31 near the downstream is a line 32 in the suction-side line 32.
a, a line 5 having a strainer 57 and an on-off valve 58;
The on-off valve 58 is opened when the pressure is abnormally high or the like.

The accumulator 45 is provided with the hot water heat exchanger 46, and the accumulator 45
A composition ratio detector 101 for detecting a composition ratio of a liquid-phase refrigerant stored therein is provided. The accumulator 45
Is connected to the line 32c by a passage 60 having a strainer 61 and a capillary tube 62, and a temperature sensor 102 is provided for the passage 60, and the liquid level in the accumulator 45 increases in accordance with the rise in the liquid level. When the phase refrigerant is led out to the passage 60, a temperature change accompanying the phase refrigerant is detected by the temperature sensor 102, so that the temperature sensor 102 functions as a liquid level sensor of the accumulator 45.

Further, when the operation is stopped, the accumulator 4
5 so that the liquid refrigerant in the accumulator 4 can be extracted.
5 is connected to the lower end of the U-shaped line 32c via a passage 63 having a strainer 64 and an on-off valve 65.

The compressor 20 has a compressor temperature sensor 1
The discharge side line 31 is provided with the compressor 2
A high pressure side pressure sensor 104 for detecting the pressure of the refrigerant discharged from 0 is provided. On the other hand, a low pressure side for detecting the pressure of the refrigerant sucked into the compressor 20 is provided on a downstream line 32 d of the suction side line 32. A pressure sensor 105 and a suction refrigerant temperature sensor 106 for detecting the temperature of the refrigerant are provided.

The four-way valve 41 and the indoor heat exchanger 42
In the line 33 between a to 42n, an on-off valve 66, a joint 67 connecting the outdoor side and the indoor side, and a composition ratio detector 107 for detecting a composition ratio of the circulating refrigerant are provided. .

Each of the indoor units provided with the indoor heat exchangers 42a to 42n and the expansion valves 43a to 43n has expansion valve upstream temperature sensors 110a to 110n for detecting the refrigerant temperature of the expansion valve upstream portion during heating. Indoor temperature sensor 1
11a to 111n are provided.

Expansion valves 43a to 43n and receiver tank 4
A joint 68 connecting the outdoor side and the indoor side, an on-off valve 69, a dryer 70, a filter 71, and the like are provided in the line 34 between the outside and the inside 8 and the liquid-gas heat exchanger 47 is interposed. ing. The line 35 between the receiver tank 48 and the outdoor heat exchangers 44a and 44b is connected to the upstream line 32a of the suction line 32 via a line 72 having a control valve 73 and a strainer 74. . Opening / closing valves 76 and 77 are provided on both sides of the outdoor heat exchanger 44b.

The cooling water circuit 80 includes a pump 82
A cooling water line 81a is led out from the discharge side of the exhaust gas heat exchanger 14, and the cooling water line 81a is
3 and connected to the cooling water inlet of the water jacket 84 of the engine 2.
A cooling water line 81b is led out of the cooling water outlet through a thermostat 85, and is connected to a linear three-way valve 86.

From the linear three-way valve 86, cooling water lines 81c and 81e are respectively led. The cooling water line 81c is connected to a radiator 87, and a cooling water line 81d derived from the radiator 87 is connected to the suction side of the pump 82. On the other hand, the cooling water line 81e reaches a hot water heat exchanger 46 provided in the accumulator 45, and is connected to the cooling water line 81d via the heat exchanger 46.

The linear three-way valve 86 controls the flow rate of the cooling water to the cooling water lines 81c and 81e. Specifically, as shown in FIG. 4, according to the operating position of the three-way valve 86, 100% of the cooling water guided to the three-way valve 86 flows to the cooling water line 81c, and 100% of the cooling water flows to the cooling water line 81e. The ratio of the amount of cooling water in both cooling water lines 81c and 81e can be changed linearly. Then, in the cooling water circuit 80, the cooling water that has received heat from the exhaust gas heat exchanger 14 and the water jacket 84 is guided to the linear three-way valve 86, and further, the cooling water by an amount corresponding to the operating position of the linear three-way valve 86. By being led to the hot water heat exchanger 46 via the line 81e, heat is supplied to the refrigerant in the accumulator 45 by the heat exchanger 46, and the supplied heat amount is adjusted by the linear three-way valve 86. I have.

Reference numeral 112 denotes a water temperature sensor for detecting the temperature of the hot water after cooling the engine, and 113 denotes an outside air temperature sensor. Reference numeral 81g denotes a cooling water supply line connected to the cooling water line 81d, reference numeral 88 denotes a water tank connected to the cooling water supply line 81g, and reference numeral 89 denotes a fan for cooling the radiator 87.

Next, the control system of the air conditioner 1 will be described with reference to the block diagram of FIG.

As shown in the figure, the control system of the air conditioner
The indoor heat exchangers 42a-42n and expansion valves 43a-4
Indoor unit controllers 91a to 91n for individually controlling the indoor units 90a to 90n provided with 3n and the like, the compressor 20, the outdoor heat exchangers 44a and 44b, the four-way valve 41, the accumulator 45, and the like are provided. An outdoor unit control device 92 for controlling the outdoor unit unit is provided, and each of the indoor unit control devices 91a to 91n and the outdoor unit control device 92 are electrically connected so as to perform control in association with each other. I have.

The indoor units 90a to 90n have fans 93a to 93n for blowing air and expansion valves 43a to 43n, respectively.
n, expansion valve upstream-side refrigerant temperature sensors 110a to 110n
And an operation unit 9 having an on / off switch and a temperature setting key
4a to 94n, and indoor temperature sensors 111a to 111n for detecting each indoor temperature are provided. For example, when a desired temperature is input to the indoor unit 90a via the operation unit 94a, the indoor unit controller 91a calculates the indoor temperature with the indoor temperature sensor 111a, and calculates the difference between this temperature and the desired temperature. The output of the fan 93a is controlled to reduce the temperature difference.

On the other hand, the outdoor unit controller 92 includes the engine 2, the four-way valve 41, the linear three-way valve 86, the on-off valve 58,
Control target elements such as 65, 66, 69, 76, 77, outdoor unit side fan 88, etc. are connected, suction refrigerant temperature sensor 106, compressor temperature sensor 103, accumulator liquid level sensor (temperature sensor) 102, high pressure Side and low pressure side pressure sensors 104, 105, water temperature sensor 112, outside air temperature sensor 113, composition ratio detectors 101, 1
And a storage device 96 for storing various data and programs for control.
Is connected.

The outdoor unit controller 92 controls each of the indoor units 90.
The four-way valve 41 is controlled to switch the direction of circulation of the refrigerant in the refrigerant circuit 30 in accordance with the cooling / heating switching of a to 90n.
Further, the outdoor unit control device 92 checks a load that changes depending on, for example, the number of operating indoor units and other operation states during cooling and heating, and controls the driving of the engine 2 according to the load, thereby controlling the compressor 20. The number of revolutions is adjusted, and control is performed so that the number of revolutions of the compressor 20 decreases as the load decreases.

Each of the control units 91a to 91n, 9
2 controls the expansion valves 43a to 43n and the like so as to execute subcool control during heating and superheat control during cooling, and controls the heat exchanger 46 in accordance with the liquid level in the accumulator 45 during heating. The three-way valve 86 is controlled so that the amount of heat exchange is adjusted, and during cooling, the amount of heat exchange of the heat exchanger 46 is adjusted according to the outside air temperature or the like. Further, at the time of heating to perform subcool control, control of the compressor rotation speed according to a comparison between a high pressure value described below and a target value thereof, and a refrigerant heating amount in an accumulator according to comparison between a low pressure value described below and a target value thereof During the cooling operation in which the superheat control is performed, the compressor rotation speed and the amount of the refrigerant heated in the accumulator are controlled in accordance with a comparison between a low pressure value described later and its target value.

Further, the outdoor unit controller 92 controls the liquid level control valve 50d so as to change the liquid level in the receiver tank 48 according to the time of heating and the time of cooling.

The control by the control devices 91a to 91n and 92 according to the time of heating and the time of cooling is specifically performed as shown in FIGS.

In this control, first, it is determined whether the indoor unit is in the heating operation or the cooling operation (step S1). During heating, the main routine processing in steps S2 to S11 is performed, and in step S5 in the main routine. Steps S13 to S13 as the parallel routine process started when
The processing of S15 and the processing of steps S16 and S17 are performed. On the other hand, at the time of cooling, steps S21 to S30
Is performed, and the processes of steps S32 to S34 and the processes of steps S35 and S36 are performed as the parallel routine process started at step S24 in the main routine.

At the time of heating, the load on the indoor unit (the number of indoor units used) and temperature conditions are detected. As the temperature conditions, the indoor temperature is determined by the indoor temperature sensors 111a to 111n, and the desired temperature is controlled by operating the operation units 94a to 94n. Based on the data, the outdoor temperature is detected by the outdoor air temperature sensor 113 (step S2). The storage device 96 stores in advance a preferable correspondence between the expansion valve opening degree, the three-way valve opening degree, the compressor rotation speed, the target high pressure value, the target low pressure value, and the target SC value of the indoor unit to the load and temperature conditions during the heating operation. The expansion valve opening, the three-way valve opening, the compressor rotation speed, the target high pressure value, the target low pressure value, the target SC value, etc. of each indoor unit according to the load and temperature conditions at that time are stored from this correspondence. Is required, and the expansion valve 4
3a to 43n, the three-way valve 86, and the compressor 20 are controlled to take their initial set values, and the target high pressure value,
The target low pressure value, the target SC value, and the like are stored in the storage device 96 (step S3).

Here, the target high-pressure value refers to a target value of the high-pressure side pressure which is the pressure in the high-pressure side circuit from the compression chamber outlet of the compressor 20 to the expansion valves 43a to 43n. The target low pressure value is a low pressure side pressure which is a pressure in the low pressure side refrigerant circuit from the expansion valves 43a to 43n to the suction port of the compressor 20 through the outdoor heat exchangers 44a and 44b as evaporators. Refers to the target value.

Next, in order to set the liquid level in the receiver tank 48 to a height position corresponding to the time of heating, the liquid level control valve 50 is used.
d is closed (step S4).

Subsequently, the routines of steps S13 to S15 and the routines of steps S16 and S17, which are processed simultaneously in parallel with the main routine, are started (step S15).
5). Further, on the main routine side, the high pressure side pressure is subsequently detected by the high pressure side pressure sensor 104 (step S6), set in the above step S3, and stored in the storage device 96.
Is compared with the target high pressure value stored in the memory (step S7).

When the detected value is lower than the target high pressure value by a predetermined value or more, the rotational speed of the compressor 20 is corrected to increase. When the detected value is higher than the target high pressure value by a predetermined value or more, the compressor 2 is turned off.
The rotation number of 0 is corrected to decrease (step S8). After the execution of the rotation speed correction, the high-pressure side pressure is detected again and compared with the target high-pressure value. If the absolute value of the difference between the detected value and the target high-pressure value is still equal to or larger than the predetermined value, the process proceeds to step S
8 is repeated.

When the absolute value of the difference between the detected value and the target high pressure value becomes equal to or less than a predetermined value, the low pressure side pressure sensor 105 detects the low pressure side pressure (step S9), and this detected value and the target low pressure value are detected. The comparison with the value is performed (step S
10). Here, when the detected value is lower than the target low pressure value by a predetermined value or more, the amount of heating to the low pressure side refrigerant is increased by increasing and correcting the opening of the three-way valve 86. Is higher than the target low pressure value by a predetermined value or more, the opening of the three-way valve 86 is corrected to be reduced, so that the amount of heating to the low pressure side refrigerant is reduced (step S11). And
If the low pressure side pressure is detected again and the absolute value of the difference between the detected value and the target low pressure value is not less than the predetermined value, step S11
Is repeated. If the absolute value of the difference between the detected value and the target low pressure value is equal to or less than the predetermined value in step S10, the parallel routine ends and the process returns to step S1 (step S12).

In one of the parallel routines started in step S5, first, SC (degree of supercooling) is detected (step S13). Here, SC is the saturated liquid temperature calculated based on the high pressure side pressure (detected by the high pressure side pressure sensor 104) and the refrigerant composition (mainly detected by the composition ratio detector), and the expansion valves 43a to 43n. Of the refrigerant near the upstream side (detected by the temperature sensors 110a to 110n). This SC detection value is compared with the target SC value set in step S3 (step S14). If the SC detection value is smaller than the target SC value by a predetermined value or more, a correction for reducing the expansion valve opening is performed. As a result, the amount of liquid refrigerant staying in the indoor heat exchangers 42a to 42n, which are condensers, increases, and the actual SC value increases. If the SC detection value is larger than the target SC value by a predetermined value or more, a correction for increasing the expansion valve opening is performed (step S15).

Then, the SC detection value is obtained again, and this is compared with the target SC value.
If the absolute value of the difference from the C value is equal to or greater than a predetermined value, step S1
Step 5 is repeated, and when the absolute value of the difference becomes equal to or smaller than the predetermined value, the processing of the parallel routine ends, and the process returns to step S12 of the main routine.

In another parallel routine started in step S5, the liquid level is detected by a signal from the accumulator liquid level sensor (temperature sensor) 102 (step S16). In this case, when there is a signal indicating that the liquid level in the accumulator 45 has exceeded a predetermined level from the sensor 102, it is determined to be abnormal, and when there is no such signal, it is determined to be normal. When the liquid level in the accumulator 45 exceeds a predetermined level, a warning is displayed by a lamp or a buzzer (not shown) (step S17).

On the other hand, during cooling, the load on the indoor unit (the number of indoor units used) and temperature conditions are detected. As the temperature conditions, the indoor temperature is determined by the indoor temperature sensors 111a to 111n, and the desired temperature is controlled by the operation units 94a to 94n. , The outdoor temperature is detected by the outside air temperature sensor 113 (step S21). Preferable correspondences between the load and the temperature conditions in the cooling operation such as the expansion valve opening degree, the three-way valve opening degree, the compressor rotation speed, the target low pressure value, and the target SH value of each indoor unit are stored in the storage device 96 in advance. From this correspondence, the expansion valve opening, the three-way valve opening, the compressor rotation speed, the target low pressure value, the target SH value, etc., of each indoor unit according to the load and temperature conditions at that time are obtained, and the expansion valves 43a to 43a are obtained. 43n, the three-way valve 86, the compressor 20 are controlled to take their initial set values, and the target low pressure value, the target SH value, and the like are stored in the storage device 96 (step S22).

Next, in order to set the liquid level in the receiver tank 48 to a height position corresponding to the time of cooling, a liquid level control valve 50 is provided.
d is opened (step S23).

Subsequently, the routines of steps S32 to S34 and the routines of steps S35 and S36, which are processed simultaneously in parallel with the main routine, are started (step S2).
4). On the main routine side, the low pressure side pressure sensor 105 continuously detects the low pressure side pressure (step S25), and compares the low pressure side pressure with the target low pressure value set in step S22 and held in the storage device 96 as data. This is performed (step S26). When the detected value is lower than the target low pressure value by a predetermined value or more, the rotation speed of the compressor 20 is corrected to increase. When the detected value is higher than the target low pressure value by a predetermined value or more, the rotation of the compressor 20 is stopped. The number is reduced and corrected (step S27). After the execution of the rotation speed correction, the low pressure side pressure is detected again (step S28), and the detected value is compared with the target low pressure value (step S29).

If the detected value is still lower than the target low pressure value by a predetermined value or more, the amount of heating of the low pressure side refrigerant is increased by correcting the opening of the three-way valve 86 to increase. If the value is higher than the target low-pressure value by a predetermined amount or more, the opening of the three-way valve 86 is corrected to decrease, so that the amount of heating to the low-pressure side refrigerant is reduced (step S30).
Then, the low pressure side pressure is detected again, and if the absolute value of the difference between the detected value and the target low pressure value is not less than or equal to the predetermined value, the process of step S30 is repeated. Step S26, S2
If the absolute value of the difference between the detected value and the target low pressure value becomes equal to or smaller than the predetermined value in step 9, the parallel routine process ends, and the process returns to step S1 (step S31).

In one of the parallel routines started in step S24, first, SH (degree of heating) is detected (step S32). Here, SH is the compressor inlet temperature (detected by the suction refrigerant temperature sensor 106), the low pressure side pressure (detected by the low pressure side pressure sensor 105), and the refrigerant composition (mainly detected by the composition ratio detector). Means the difference from the saturated steam temperature calculated based on The SH detection value is compared with the target SH value set in step S22 (step S33). If the SH detection value is smaller than the target SH value by a predetermined value or more, a correction for reducing the opening degree of the expansion valve is performed. As a result, the amount of refrigerant flowing into the evaporator decreases, and accordingly, the amount of heat received per unit refrigerant amount increases, and the actual SH value increases. If the SH detection value is larger than the target SH value by a predetermined value or more, a correction to increase the expansion valve opening is performed (step S34). Then, the SH detection value is obtained again, and this is compared with the target SH value. If the absolute value of the difference between the SH detection value and the target SH value is equal to or more than a predetermined value, the process of step S34 is repeated. When the absolute value of the difference becomes equal to or less than the predetermined value, the processing of the parallel routine is terminated, and the process returns to step S31 of the main routine.

In another parallel routine started in step S24, the liquid level is detected based on a signal from the accumulator liquid level sensor (temperature sensor) 102 (step S35). When the liquid level in the nozzle 45 exceeds an abnormal level, a warning is displayed by a lamp, a buzzer or the like (not shown) (step S36).

The operation of the air conditioner of this embodiment as described above will be described below.

When the air conditioner is operated for heating, the four-way valve 41 connects the first port 41a and the second port 41b, and the third port 41c and the fourth port 41d.
Is communicated with In this state, the refrigerant discharged from the compressor 20 is supplied to the four-way valve 41, the indoor heat exchangers 42a to 42n, and the expansion valve 43 as indicated by solid arrows in FIG.
a to 43n, liquid-gas heat exchanger 47, receiver tank 4
8. The outdoor heat exchangers 44a and 44b, the four-way valve 41, the liquid / gas heat exchanger 47, and the accumulator 45 are circulated to the compressor 20 in this order. And the indoor heat exchangers 42a-
42n functions as a condenser and radiates heat here, thereby heating the room, and furthermore, the outdoor heat exchangers 44a, 44a.
4b acts as an evaporator, where heat is absorbed.

In this case, the compressor speed is controlled based on the comparison between the target high pressure value and the detected value in steps S6 to S8 in the main routine in the flowchart of FIG. 6, and the parallel routine of steps S13 to S15 is performed. The sub-cool (supercooling) control is performed by correcting the expansion valve opening based on the comparison between the target SC value and the SC detection value. Here, the subcool control is
This is control for cooling the refrigerant temperature in the vicinity of the expansion valve on the high pressure side so as to be equal to or lower than the condensation temperature. Specifically, it refers to correcting the expansion valve opening in a direction to increase the expansion valve opening so as to reduce the temperature to a predetermined value equal to or lower than the condensation temperature in accordance with the detected value of the expansion valve upstream-side refrigerant temperature.

According to the subcool control, the Ph diagram of the refrigeration cycle is as shown in FIG. That is,
After the gas phase refrigerant is compressed by the compressor 20 and the pressure P and the enthalpy h rise (a1 → b1), the indoor heat exchanger 42a
The refrigerant changes from a gas phase to a liquid phase as the enthalpy h decreases due to condensation and heat radiation at 42 n (b1 → c1). At this time, the refrigerant is supercooled so as to be significantly lower than the saturated liquid temperature, and the subcooling is performed. Control is performed. Next, the liquid-phase refrigerant is expanded by the expansion valves 43a to 43n to have a low pressure (c1 → d
1) Further, the enthalpy h rises due to evaporation in the outdoor heat exchangers 44a and 44b (d1 → a1). Note that SC
i is the enthalpy change due to supercooling.

With this subcool control, the COP (coefficient of performance) is increased, and the performance of the air conditioner is enhanced.

That is, the COP represents the efficiency of the refrigeration cycle, and the amount of increase in enthalpy due to compression in the compressor 20 is A, and the amount of increase in enthalpy due to evaporation in the evaporator is B (see FIG. 8). ), During heating and during cooling, respectively.

(At the time of heating) COP = (A + B) / A (at the time of cooling) COP = B / A When the subcool control is performed, the value of B in the above equation is changed by the enthalpy change SCi due to supercooling. As a result, the COP is improved.

In the subcool control state, the expansion valve 43
A large amount of excess refrigerant is generated in the low pressure side circuit between the compressors 20 to 43n and the excess refrigerant in the liquid phase stays in the accumulator 45. In particular, when subcool control is performed in an air conditioner using a non-azeotropic refrigerant, a high boiling point component (for example, R134a) of the non-azeotropic refrigerant that is easily liquefied stays in the accumulator 45 at a high rate over time. By doing so, the ratio of low-boiling components (for example, R32 and R125) in the gas-phase refrigerant sucked into the compressor 20 tends to be higher than the initial charging ratio.

However, since the accumulator 45 is provided with the hot water heat exchanger 46, and the liquid-phase refrigerant staying in the accumulator 45 during heating is heated by the heat exchanger 46, the high boiling point component staying in the accumulator 45 is vaporized. The above tendency is corrected, and the component ratio of the refrigerant sucked into and circulated into the compressor 20 approaches the initial charging ratio. Therefore, a decrease in the COP due to a change in the composition ratio of the circulating refrigerant (an increase in the low boiling point component) is suppressed.

In addition, since heat is given to the refrigerant by the heat exchanger 46 in the accumulator 45, even when the outside air temperature is low and the heat absorption in the outdoor heat exchangers 44a and 44b is difficult to be sufficiently performed, the heat is not affected. The heat absorption is promoted by the exchanger 46, and the heating capacity is improved.

Further, by controlling the opening of the three-way valve 86 based on the comparison between the detected value of the low pressure side pressure and the target low pressure value, the amount of heat supplied from the heat exchanger 46 to the refrigerant in the accumulator 45 is reduced. If the low-pressure side pressure is controlled, the refrigerant is heated to increase the low-pressure side pressure, so that the outdoor heat exchanger 44 serving as an evaporator is increased.
a, 44b the inlet side pressure exceeds a predetermined value,
The refrigerant temperature at the inlet of the outdoor heat exchangers 44a, 44b rises. Accordingly, an effect of preventing dew condensation of water vapor in the atmosphere passing through the outdoor heat exchangers 44a and 44b, freezing of water, and formation of frost can be obtained.

During heating in which the subcool control is performed, the amount of surplus refrigerant generated in the low pressure side circuit between the expansion valves 43a to 43n and the compressor 20 increases, and a large amount of surplus refrigerant is stored in the accumulator 45. When the liquid level rises and the liquid level rises, a phenomenon (liquid back phenomenon) in which droplets are discharged to a downstream circuit and sucked into the compressor 20 due to the boiling of the refrigerant when heated in the heat exchanger 46 is caused. May occur.

On the other hand, in the device of this embodiment, the accumulator 45
The receiver tank 48 is disposed further upstream, and a part of the surplus refrigerant in the low-pressure side circuit is stored in the receiver tank 48, so that the amount of surplus refrigerant stored in the accumulator 45 is reduced. When the liquid level control valve 50d of the liquid level adjusting means 50 provided in the receiver tank 48 is closed, the amount of surplus refrigerant stored in the accumulator 45 is sufficiently reduced, and the liquid back phenomenon is prevented. .

That is, at the time of heating, the receiver tank 48
, The refrigerant flows in from the expansion valve side line 34 and flows out to the outdoor heat exchanger side line 35. In this case, the second pipe 50 out of the pipes leading to the line 35
When the liquid level control valve 50d provided in the b is closed, the refrigerant flows out from the first pipe 50a which opens at a high position, and the upper end position of the pipe 50a is set at the liquid level in the receiver tank 48 during heating. It becomes the lowest level L1 of the surface (see FIG. 3). Therefore, when the liquid level control valve 50d is opened or when the liquid level is lower than the liquid level minimum level L2 (the position corresponding to the upper ends of the pipes 50b and 50c) when the refrigerant flows out of the pipe 50c, the level in the receiver tank 48 is reduced. The amount of stored refrigerant increases, and the amount of surplus refrigerant stored in the accumulator 45 decreases by that amount, so that even when the refrigerant is heated in the heat exchanger 46 and boiled, discharge of droplets to the downstream circuit is prevented. It will be.

Although the amount of surplus refrigerant stored in the accumulator 45 is reduced by storing the refrigerant in the receiver tank 48 as described above, the surplus refrigerant is still too large and the liquid level in the accumulator 45 rises. If an abnormality that exceeds a predetermined level occurs, the process proceeds to step S16,
A warning is displayed by the processing of S17.

On the other hand, when the air conditioner is operated for cooling, the four-way valve 41 is connected to the first port 41a and the third port 4a.
1c and the second port 41b and the fourth port 41d. In this state, the refrigerant discharged from the compressor 20 is supplied to the four-way valve 41, the outdoor heat exchangers 44a and 44b, the receiver tank 48, the liquid-gas heat exchanger 47, and the expansion valve 43a, as indicated by the broken arrows in FIG.
To 43n, indoor heat exchangers 42a to 42n, four-way valve 41,
The liquid-gas heat exchanger 47 and the accumulator 45 are circulated through the compressor 20 in this order. And the outdoor heat exchanger 4
4a and 44b work as condensers to radiate heat, while indoor heat exchangers 42a to 42n work as evaporators to absorb heat here, thereby cooling the room.

In this case, the compressor speed is controlled based on the comparison between the detected value of the low pressure side pressure and the target low pressure value in steps S25 to S27 in the main routine in the flowchart of FIG. S
The expansion valve opening is corrected based on the comparison between the target SH value and the SH detection value by the parallel routine of 34,
Superheat (heating) control is performed. Here, the superheat control is control for heating the refrigerant temperature of the compressor suction part to the saturated vapor temperature or higher. Specifically, it refers to correcting the expansion valve opening in a direction to reduce the expansion valve opening so as to increase the temperature to a predetermined high temperature in accordance with the suction refrigerant temperature or the compressor temperature.

According to the superheat control, the Ph diagram of the refrigeration cycle is as shown in FIG. That is, after the gas phase refrigerant is compressed by the compressor 20 and the pressure P and the enthalpy h rise (a2 → b2), the outdoor heat exchanger 4
As the enthalpy h is reduced by being condensed at 4a and 44b, the refrigerant changes from a gaseous phase to a gas-liquid mixture or a liquid phase (b2
→ c2) Then, the liquid-phase refrigerant is expanded by the expansion valves 43a to 43n to a low pressure (c2 → d2), and the enthalpy h rises due to evaporation and heat absorption in the indoor heat exchangers 42a to 42n (d2 → a2). At this time, the refrigerant is excessively heated so as to greatly exceed the saturated steam temperature, and superheat control is performed. SHi is an enthalpy change due to excessive heating.

By this superheat control, the amount of enthalpy change SHi due to excessive heating can be obtained by calculating B
Is increased, so that the COP is improved.

In addition, the amount of surplus refrigerant stored in the accumulator 45 is reduced to zero in the steady operation state during cooling by this control, so that the high boiling point component does not stay in the accumulator 45, so that the compressor 20 It does not occur that the proportion of the low-boiling component in the gas-phase refrigerant sucked into the air increases and the COP decreases.

When the load decreases, the excess refrigerant stays in the receiver tank 48 on the upstream side of the expansion valve, but unlike the accumulator that separates gas and liquid, both the low-boiling component and the high-boiling component after condensation are mixed. Since the refrigerant stays and sequentially passes through the expansion valve, the residence does not change the composition ratio of the circulating refrigerant, so that the COP does not decrease.

Further, in this superheat control state, in steps S28 to S30 during the main routine processing, the opening of the three-way valve 86 is controlled based on the comparison between the detected value of the low pressure side pressure and the target low pressure value. The amount of heat supplied from the heat exchanger 46 to the refrigerant in the accumulator 45 is controlled, and the refrigerant in the low-pressure side circuit is heated. This effectively assists superheat control. In addition, the heating increases the low-pressure side pressure, and the inlet-side pressures of the indoor heat exchangers 42a to 42n serving as evaporators become equal to or higher than a predetermined value.
Since the refrigerant temperature at the inlets of the 2a to 42n rises, it is also effective in preventing condensation of water vapor in the atmosphere passing through the indoor heat exchangers 42a to 42n, freezing of water, and prevention of frost formation.

During the cooling operation in which the superheat control is performed, the receiver tank 48 is located in the high pressure side circuit upstream of the expansion valve, and the refrigerant is supplied to the receiver tank 48 from the line 35 on the outdoor heat exchanger side. It flows in and flows out to the line 34 on the expansion valve side. As described above, the surplus refrigerant stays in the receiver tank 48 when the load decreases, but the amount of the staying refrigerant is relatively small. Therefore, the upper end of the pipe 50c is set so that the liquid level minimum level L2 is lower than that during the heating. The opening position is set. During cooling, the liquid level control valve 5
0d is opened (step S23).

As described above, during cooling, the amount of surplus refrigerant stored in the accumulator 45 becomes zero in a steady operation state. However, during transition, liquid-phase refrigerant may accumulate in the accumulator 45. Also steps S35 and S36
When an abnormality occurs such that the liquid level exceeds a predetermined level based on the detection of the liquid level in the accumulator 45, a warning is displayed.

Note that, in the apparatus of the present invention, the liquid level adjusting means provided in the receiver tank 48 is not limited to the above-described embodiment. For example, the structure shown in FIG.
The structure shown in FIG.

The example shown in FIG. 9 is the simplest structure for enabling the liquid level in the receiver tank 48 to be changed between a predetermined high level and a predetermined low level in accordance with the time of heating and the time of cooling. Pipe 120 leading to line 35 on the exchanger side
a is at a predetermined high level position L in the receiver tank 48
1, and the upper end of the pipe 120b communicating with the line 34 on the expansion valve side opens at a predetermined low level position L2 in the receiver tank 48. According to this structure, the liquid level is adjusted by the opening position of the upper end of the pipe 120a on the refrigerant outflow side during heating when the refrigerant flows as indicated by the solid line arrow, and the refrigerant outflow side during cooling when the refrigerant flows as indicated by the broken line arrow. The liquid level is adjusted according to the opening position of the upper end of the pipe 120b.

In the example shown in FIG. 10, the first and second pipes 130 connected to the line 35 on the side of the outdoor heat exchanger 44 are connected.
a, 130b, a third pipe 130c connected to the line 34 on the side of the expansion valve 43, and a liquid level control valve 130d for opening and closing the second pipe 130b.
0a opens at a predetermined high level position L1 in the receiver tank 48, the upper end of the third pipe 130c opens at a predetermined low level position L2 in the receiver tank 48, and the upper end of the second pipe 130b An intermediate height position L between the predetermined high level position L1 and the predetermined low level position L2
11 is open.

In the case of this structure, for example, a sensor (not shown) for detecting the liquid level lower limit level is provided in the accumulator 45, and the liquid level control valve 130 is usually provided during heating.
By closing d, the liquid level in the receiver tank 48 is kept high, but the refrigerant is stored to such an extent that the liquid level in the accumulator 45 becomes lower than the liquid level lower limit level and the heat exchanger 46 is not immersed. When the amount decreases too much,
By opening the liquid level control valve 130d, the liquid level in the receiver tank 48 is lowered to the intermediate height position L2, and the amount of refrigerant stored in the accumulator 45 is increased. The amount can be controlled in a feedback manner.

In addition to this, the specific structure of each part in the apparatus of the present invention can be variously changed. For example, in the above embodiment, a plurality of indoor heat exchangers 42a to 42n are provided, and the outdoor heat exchangers 44a and 44b are provided. Although two are provided,
One indoor heat exchanger and one outdoor heat exchanger may be used.

[0096]

As described above, according to the present invention, in a heat pump type air conditioner capable of cooling and heating, an accumulator is arranged in a path in which a refrigerant returns from an evaporator to a compressor, and a heating means is provided in the accumulator. The receiver tank is provided at a position that becomes a high-pressure side circuit during cooling, and at a position that becomes a low-pressure side circuit upstream of the accumulator during heating, and the receiver tank is provided with a liquid level adjusting means. Surplus refrigerant is stored during heating and cooling, and
The heating means can improve the heating performance and the like. The receiver tank stores a part of the excess refrigerant in the low-pressure side circuit upstream of the accumulator during heating, thereby reducing the amount of refrigerant stored in the accumulator, so that the capacity of the accumulator does not increase and the sub-accumulator does not increase. However, even if the refrigerant in the accumulator is heated and boiled, the liquid droplets are prevented from being discharged downstream of the accumulator, and the phenomenon of liquid back to the compressor can be prevented.

In the present invention, in particular, when the subcool control is performed during heating and the superheat control is performed during cooling in order to improve the COP, the receiver tank is designed to perform the subcool control during cooling when superheat control is performed. On the other hand, during heating, when the subcool control is performed and the surplus refrigerant is likely to increase, by storing a part of the surplus refrigerant in the low pressure side circuit upstream of the accumulator, the amount of refrigerant stored in the accumulator can be effectively increased. Can be prevented.

[Brief description of the drawings]

FIG. 1 is a schematic circuit diagram showing a basic structure of an air conditioner according to an embodiment of the present invention.

FIG. 2 is a detailed circuit diagram showing a specific structure of the air conditioner.

FIG. 3 is a structural explanatory view showing a receiver tank and a liquid level adjusting means.

FIG. 4 is a view showing operating characteristics of a three-way valve incorporated in a cooling water circuit of the air conditioner.

FIG. 5 is a diagram showing a control system of the air conditioner.

FIG. 6 is a part of a flowchart showing an example of control.

FIG. 7 is the remaining part of the above flowchart.

FIG. 8A is a graph showing the P of the refrigeration cycle during subcool control.
It is a -h diagram, and (b) is a Ph diagram of the refrigeration cycle at the time of superheat control.

FIG. 9 is a structural explanatory view showing another embodiment of the receiver tank and the liquid level adjusting means.

FIG. 10 is a structural explanatory view showing still another embodiment of the receiver tank and the liquid level adjusting means.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Air conditioner 20 Compressor 30 Refrigerant circuit 41 Four-way valve 42 Indoor heat exchanger 43 Expansion valve 44 Outdoor heat exchanger 45 Accumulator 46 Hot water heat exchanger 48 Receiver tank 50 Liquid level adjusting means

Claims (6)

[Claims] 1. A compressor, an indoor heat exchanger serving as a condenser during heating and an evaporator during cooling, an expansion valve, an outdoor heat exchanger serving as an evaporator during heating and a condenser during cooling, and a refrigerant circulation path. Means is provided in the refrigerant circuit, the refrigerant is returned from the compressor to the compressor through the indoor heat exchanger, the expansion valve, and the outdoor heat exchanger in this order during heating, and the refrigerant is discharged from the compressor during outdoor cooling. In an air conditioner in which a refrigerant circuit is configured to be returned to the compressor through the exchanger, the expansion valve, and the indoor heat exchanger in this order, an accumulator is arranged in a path in which the refrigerant returns from the evaporator to the compressor, The accumulator is provided with heating means for heating the excess refrigerant in the liquid phase stored in the accumulator. A receiver tank is provided at a position that is a low-pressure side circuit between the evaporator and the evaporator, and the receiver tank is provided with a liquid level adjusting means for adjusting a liquid level in the receiver tank according to heating and cooling. Air conditioner characterized by the above-mentioned. 2. The air conditioner according to claim 1, wherein the receiver tank is provided in a circuit between the outdoor heat exchanger and the expansion valve. 3. Subcool control for adjusting the opening of the expansion valve during heating to make the refrigerant temperature near the expansion valve on the high-pressure side lower than the saturated liquid temperature, and adjusting the opening of the expansion valve during cooling to control the compressor. 3. The air conditioner according to claim 1, further comprising control means for performing superheat control for setting the temperature of the refrigerant on the suction side to a temperature higher than the saturated vapor temperature. 4. The air conditioner according to claim 3, wherein a non-azeotropic refrigerant is used as the refrigerant. 5. The air conditioner according to claim 3, wherein the liquid level adjusting means is configured to make the liquid level in the receiver tank higher during heating than during cooling. 6. The liquid level adjusting means includes switching means for switching the liquid level in the receiver tank to a plurality of levels, and the switching means is operated according to the liquid level in the accumulator. The air conditioner according to any one of claims 1 to 5, wherein: