JPH09138021A - Air-conditioning device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve operation performance through effective improvement of COP and to prevent lowering of heating capacity, in a heat pump type air- conditioning device using a non-azeotropic refrigerant. SOLUTION: In an air-conditioning device formed in such a manner that a refrigerant circuit 30 is provided with a compressor 20, a four-way valve 41, indoor heat-exchangers 68a-68n, expansion valves 70a-70n, and outdoor heat- exchangers 75a and 75b, and a non-azeotropic refrigerant is used as a refrigerant, an accumulator 45 is arranged in a route through which a refrigerant returns from a vaporizer to a compressor 20. Further, a control means is provided to effect sub-cool control through which the number of revolutions of a compressor is controlled according to a load and meanwhile, at least during heating, a refrigerant temperature in the vicinity of an expansion valve on the high pressure side is reduced to a value lower than a saturated liquid temperature through regulation of the opening of the expansion valve. Moreover, the accumulator 45 is provided with a heatexchanger 51 to heat a surplus refrigerant in a liquid phase stored in the accumulator 45 during heating operation wherein the sub-cool control is executed.

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, and more particularly to an air conditioner using a non-azeotropic refrigerant as a working refrigerant.

[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. When cooling, the refrigerant circulates in the order of the compressor, the four-way valve, the outdoor heat exchanger, the expansion valve, the indoor heat exchanger, the four-way valve, and the compressor, so that the outdoor heat exchanger is the condenser and the indoor heat exchange. The evaporator serves as an evaporator to cool the indoor heat exchanger by absorbing heat.On the other hand, during heating, the refrigerant is compressed by the compressor, four-way valve, indoor heat exchanger, expansion valve, outdoor heat exchanger, four-way valve. By circulating in the order of the compressor, the indoor heat exchanger serves as a condenser and the outdoor heat exchanger serves as an evaporator, and the refrigerant circuit is configured to perform heating by radiating heat in the indoor heat exchanger. .

Conventionally, in this type of air conditioner, so-called superheat control is performed to control the expansion valve and the like so that the refrigerant temperature on the compressor suction side becomes higher than the saturated vapor temperature during cooling and heating. By doing so, there are some which are intended to improve COP (coefficient of performance) and performance as will be described later in detail.

This device incorporates a receiver tank in the refrigerant circuit so that the receiver tank is located between the condenser and the expansion valve, that is, between the outdoor heat exchanger and the expansion valve during heating. At this time, the refrigerant circuit is configured to be located between the indoor heat exchanger and the expansion valve, and a small capacity accumulator is provided between the four-way valve and the compressor suction port. Then, both during cooling and during heating, as the load decreases, the rotation speed of the compressor is reduced and the opening of the expansion valve is reduced, so that the evaporator (indoor heat exchanger during cooling, outdoor heat during heating) In the (exchanger), not only complete vaporization of the refrigerant but also superheat control for heating above the saturated vapor temperature is performed, and a large amount of excess refrigerant ( A refrigerant corresponding to the difference between the amount of filled refrigerant and the amount of circulating refrigerant required for the heat pump function) is stored in the outdoor heat exchanger and the receiver tank as a slowly circulating liquid refrigerant.

The accumulator is provided in order to prevent the liquid refrigerant from being sucked into the compressor when the liquid refrigerant that cannot be completely evaporated in the evaporator is temporarily stored during a transition. ing.

As another example of the conventional heat pump type air conditioner, the expansion valve opening degree is set so that the refrigerant temperature near the expansion valve on the high pressure side is lower than the saturated liquid temperature both during cooling and during heating. There is a device for improving the COP by performing so-called subcool control for controlling the above.

In this device, while the capacity of the accumulator is increased, the receiver tank is abolished. Then, both during cooling and during heating, the rotation speed of the compressor is reduced as the load becomes smaller, and the expansion valve opening is set to a larger value than in the case of the above superheat control, thereby expanding the high pressure side. Subcool control is performed to reduce the temperature of the refrigerant near the valve to a temperature equal to or lower than the saturated liquid temperature, and excess refrigerant is retained in the accumulator.

[0008]

By the way, recently, as a refrigerant in this type of air conditioner, a plurality of kinds of refrigerants having different boiling points are mixed in order to satisfy requirements such as prevention of ozone layer destruction and improvement of refrigerant capacity. Although a non-azeotropic refrigerant has been developed, the conventional apparatus has the following problems when using this non-azeotropic refrigerant.

In a device that performs the above superheat control during cooling and heating, if the outdoor air temperature is low during heating, the outdoor heat exchanger absorbs heat sufficiently to heat the refrigerant temperature at the outlet to a saturated vapor temperature or higher. Therefore, the heating capacity is lowered, the COP is also lowered, and the low boiling point component is vaporized due to the characteristic of the non-azeotropic refrigerant, so that there is a problem that frost is easily formed on the outdoor heat exchanger.

Further, in the device for performing the sub-cool control, since the surplus liquid refrigerant is accumulated in the accumulator,
Due to the characteristics of the non-azeotropic refrigerant, the proportion of low-boiling components in the refrigerant sucked into the compressor during steady operation increases relative to the composition ratio at the time of initial filling.

As a result, the capacity is increased because the low boiling point component has a small specific volume, but the discharge pressure rises, the compression work increases, and the COP decreases.

However, since the capacity increase rate is high during heating, the COP can be improved by setting it lower than the compressor rotational speed when the circulation composition ratio becomes equal to the initial filling composition ratio, which is not a problem. Since the capacity increase rate is small during cooling, it is not possible to take measures against the COP decrease by setting the compressor rotation speed.

Further, even when the outside air temperature is low during heating, the low boiling point component is vaporized due to the characteristics of the non-azeotropic refrigerant, so that the outdoor heat exchanger is frosted unless an auxiliary heat source is used. We cannot take measures against the points.

In view of the above circumstances, the present invention is an air conditioner capable of effectively improving COP to improve operating performance and preventing a decrease in heating capacity when a non-azeotropic refrigerant is used. The purpose is to provide.

[0015]

In order to achieve the above object, the present invention provides a compressor, an indoor heat exchanger that serves as a condenser during heating and an evaporator during cooling, an expansion valve, and an evaporator during heating. An indoor heat exchanger that serves as a condenser during cooling and a means for switching the refrigerant circulation path are provided in the refrigerant circuit, and during heating, the refrigerant passes from the compressor through the indoor heat exchanger, the expansion valve, and the outdoor heat exchanger in this order. Is returned to the compressor, and at the time of cooling, the refrigerant circuit is configured such that the refrigerant passes from the compressor through the outdoor heat exchanger, the expansion valve, and the indoor heat exchanger in this order and is returned to the compressor. An air conditioner using an azeotropic refrigerant, the accumulator is arranged in the route in which the refrigerant returns from the evaporator to the compressor, while controlling the rotation speed of the compressor according to the load, at least during heating operation. For adjusting the opening of the expansion valve The control means for performing subcool control to make the temperature of the refrigerant near the expansion valve on the high pressure side lower than the saturated liquid temperature is provided, and the accumulator is provided in the accumulator during heating operation in which the subcool control is performed. The heating means for heating the excess liquid-phase refrigerant to be stored is provided.

According to this device, the subcool control is performed during the heating operation, so that the capacity and COP are increased,
At the same time, it also serves as a measure against frost formation in the outdoor heat exchanger. Further, during the heating operation in which the subcool control is performed, the liquid-phase excess refrigerant stays in the accumulator, and in particular, the high-boiling point component of the non-azeotropic refrigerant tends to stay at a high rate. By being heated by the heating means provided in the accumulator, the high boiling point component in the accumulator is easily liquefied, and the component ratio of the refrigerant sucked into the compressor and circulated becomes close to the initial filling ratio. Therefore, it is possible to avoid a decrease in COP due to a change in the component ratio of the circulating refrigerant.

Further, since the heat is absorbed in the accumulator, the heating capacity can be enhanced when the outside air temperature is low.

In this air conditioner, the control means is
During cooling, superheat control is performed by adjusting the opening of the expansion valve to make the refrigerant temperature on the compressor intake side higher than the saturated steam temperature, and the amount of excess refrigerant stored in the accumulator is maintained in the steady operating state during cooling. It is preferably configured to be zero.

In this way, in addition to the above operation, COP is improved by superheat control during cooling operation. Moreover, since the amount of excess refrigerant stored in the accumulator is made zero by the superheat control in the steady operation state during cooling, the high boiling point component does not stay in the accumulator, and the component ratio of the circulating refrigerant changes. C
It does not cause a drop in OP.

The control of the rotation speed of the compressor in accordance with the load during both the cooling and heating operations means that the refrigerant discharge amount of the compressor is increased as the load increases. The refrigerant discharge amount of the compressor is controlled if the discharge amount can be increased or decreased even if the number is constant.

[0021]

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

FIG. 1 is a circuit diagram showing an air conditioner of the present invention. As shown in this figure, in the air conditioner 1, a water-cooled gas engine 2 (hereinafter abbreviated as engine 2), a compressor 20 driven by this, a refrigerant circuit 30 for circulating a refrigerant, and the engine 2 described above. And a cooling water circuit 80 for cooling the. As the refrigerant, a non-azeotropic refrigerant in which a plurality of kinds of refrigerants having different boiling points are mixed is used, and for example, R32 and R which are relatively low boiling point refrigerants.
A refrigerant in which 125 and R134a, which is a refrigerant having a relatively high boiling point, are mixed is used.

An intake pipe 3 is connected to the engine 2,
An air cleaner 4 and a mixer 5 are connected to the intake pipe 3. 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. An oil tank 11 is connected to an oil pan of the engine 2 via an oil supply pipe 10.
Is provided with a solenoid valve 12 for adjusting the oil supply amount.

An exhaust pipe 13 is led out from the engine 2 and an exhaust gas heat exchanger 14, an exhaust silencer 15 and a mist separator 16 are provided 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.
This is a drain treatment device for treating drain water from the exhaust silencer 15 and the mist separator 16.

In the illustrated example, the compressor 20 is a multi-type compressor having two unit compressors 20a and 20b, and each unit compressor 20a and 20b is an electromagnetic clutch 2.
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 passes the refrigerant discharged from the compressor 20 through the condenser, the expansion valve and the evaporator to the compressor 2
A closed circuit for circulation to return to 0 is configured.

In this embodiment, a plurality of indoor heat exchangers 6 are used.
8a to 68n and the expansion valves 7 respectively provided therein
0a to 70n, two outdoor heat exchangers 75a and 75b, etc. are incorporated in the refrigerant circuit 30, and a four-way valve 41 as a means for switching the refrigerant circulation path is provided. Then, during heating, the refrigerant flows from the compressor 20 to the indoor heat exchanger 6
8a to 68n, expansion valves 70a to 70n, outdoor heat exchanger 7
By returning to the compressor 20 through 5a and 75b in this order, the indoor heat exchangers 68a to 68n serve as condensers, and the outdoor heat exchangers 75a and 75b serve as evaporators. To outdoor heat exchangers 75a, 75
b, expansion valves 70a to 70n, indoor heat exchangers 68a to 68
By being returned to the compressor 20 through n in this order,
The indoor heat exchangers are evaporators 68a to 68n and the outdoor heat exchanger 7
5a and 75b are configured as condensers.

Therefore, in the refrigerant circuit 30, during heating, from the discharge portion of the compressor 20 to the expansion valves 70a to 70n via the indoor heat exchangers 68a to 68n, after passing through the high pressure circuit and the expansion valves 70a to 70n. Outdoor heat exchangers 75a, 75
From b to the suction part of the compressor 20 is a low pressure circuit, while during cooling, the discharge part of the compressor 20 is a high pressure circuit from the outdoor heat exchangers 75a and 75b to the expansion valves 70a to 70n. A low-pressure circuit extends from the expansion valves 70a to 70n to the suction portions of the compressor 20 via the indoor heat exchangers 68a to 68d.

Further, in the refrigerant circuit 30, an accumulator is arranged in the path through which the refrigerant returns from the evaporator to the compressor 20, and in this embodiment, the four-way valve 41 to the compressor 2 are arranged.
A main accumulator 45 and a sub accumulator 46 are arranged in the path leading to the suction unit of 0.
Further, inside the main accumulator 45, there is provided a heat exchanger 51 as a heating means for heating the excess refrigerant in the accumulator 45.

Explaining the structure of the refrigerant circuit 30 in detail, a discharge side line 31 and a suction side line 32 are provided between the compressor 20 and the four-way valve 41, and the discharge side line 31 is , Is discharged from the discharge portion of the compressor 20 and is connected to the first port 41 a of the four-way valve 41 via the oil separator 42. The oil separator 42
The oil return line 43 derived from the
Downstream side line 32c in the suction side line 32 via
It is connected to the.

On the other hand, the suction side line 32 is connected to the four-way valve 4 described above.
And the liquid-gas heat exchanger 4
Line 32 from 4 to main accumulator 45
a, a line 32b derived from the main accumulator 45 to reach the sub accumulator 46, and a downstream branch portion derived from the sub accumulator 46 and a check valve 47.
And a line 32c reaching the suction portion of the compressor 20 through the. A portion of the discharge side line 31 near the downstream side is a line 32a in the suction side line 32.
In line 33 with strainer 48 and on-off valve 49
The open / close valve 49 is opened when the pressure is abnormally high.

The main accumulator 45 is provided with a heat exchanger 51, and the accumulator 4 is provided.
A composition ratio detector 101 for detecting the composition ratio of the liquid-phase refrigerant stored in 5 is provided, and a site 52 for checking the filling amount is additionally provided. Further, the predetermined high-level position and the predetermined low-level position of the main accumulator 45 and the strainer 5 and the passage having the strainer 53 and the capillary tube 54.
5 and a passage having a capillary tube 56 respectively connected to the line 32b, temperature sensors 102 and 103 are provided for these passages, and the liquid-phase refrigerant is generated in accordance with the rise of the liquid level in the main accumulator 45. The temperature sensor 102, 103 has a function of detecting the liquid level in the main accumulator 45 by being guided to the passage and the temperature change caused by the temperature change being detected by the temperature sensor 102, 103.

Further, the lower end portion of the main accumulator 45 has a strainer 57 and an opening / closing valve 5 so that the liquid-phase refrigerant in the main accumulator 45 can be discharged when the operation is stopped.
8 is connected to the line 32b via a passage 59. A capillary tube 60 is provided on the line 32b.

The sub-accumulator 46 is provided therein with a U-shaped tube 61 which is continuous with the line 32c and whose lower end communicates with the bottom of the sub-accumulator 46 through a capillary tube 61a.
A heater 62 for adjusting the temperature of 6 is attached. Further, a predetermined level position of the sub accumulator 46 is connected to the line 32c by a passage having a strainer 63 and a capillary tube 64, and a temperature sensor 104 having a liquid level detecting function is provided for this passage.

The compressor 20 has a compressor temperature sensor 1
05 is provided, and the compressor 2 is provided in the discharge side line 31.
A high pressure side pressure sensor 106 for detecting the pressure of the refrigerant discharged from 0 is provided, while a low pressure side for detecting the pressure of the refrigerant sucked into the compressor 20 is provided in the downstream side line 32c of the suction side line 32. A pressure sensor 107 and a suction refrigerant temperature sensor 108 for detecting the temperature of this refrigerant are provided.

The second port 41b of the four-way valve 41
From which the line 34 is led out, and this line 34 reaches each of the indoor heat exchangers 68a to 68n via the on-off valve 65 and the joint 66. The line 34 is provided with a composition ratio detector 109 that detects the composition ratio of the circulating refrigerant.

The indoor heat exchangers 68a to 68n are arranged in parallel with each other as shown in the figure, and the input / output portions on one side (lower side in the figure) are connected to the line 34, and The input / output portions on the other side (upper side in the figure) are connected to the line 35 via expansion valves 70a to 70n, respectively. Note that 110a to 110n are expansion valve upstream temperature sensors that detect the refrigerant temperature of the expansion valve upstream portion during heating, and 111a to 111n are indoor temperature sensors.

The line 35 includes a joint 71 and an opening / closing valve 7.
2, the dryer 73, the filter 74 and the like to reach the liquid gas heat exchanger 44, and the liquid gas heat exchanger 44 is connected to the outdoor heat exchanger 75a. Outdoor heat exchanger 7
A line 36 is derived from 5a, and this line 36 is connected to the fourth port 41d of the four-way valve 41. Further, the line 37 branched from the line 35 is connected to the outdoor heat exchanger 75b, and the outdoor heat exchanger 75b is also connected.
The line 38 derived from is connected to the line 36. The lines 37 and 38 are provided with open / close valves 76 and 77. The line 35 between the liquid gas heat exchanger 44 and the outdoor heat exchangers 75a and 75b is connected to the upstream line 32a of the suction side line 32 via a line 39 having a control valve 78 and a strainer 79. Has been done.

The cooling water circuit 80 includes a pump 82
A cooling water line 81a is led out from the discharge side of the cooling water line 81a, and the cooling water line 81a is connected to the cooling water introduction port of the water jacket 83 of the engine 2 via the exhaust gas heat exchanger 14 and the cooling of the water jacket 83 is performed. A cooling water line 81b is led out from the water outlet and is connected to the linear three-way valve 84.

Cooling water lines 81c and 81e are led out from the linear three-way valve 84, respectively. The cooling water line 81c is connected to the radiator 85, and the cooling water line 81d led out from the radiator 85 is connected to the suction side of the pump 82. On the other hand, the cooling water line 81e reaches the heat exchanger 51 provided in the main accumulator 45, and is connected to the cooling water line 81d via the heat exchanger 51.

The linear three-way valve 84 is adapted to adjust the flow rate of cooling water to the cooling water lines 81c and 81e. Specifically, as shown in FIG. 4, in accordance with the operating position of the three-way valve 84, 100% of the cooling water guided to the three-way valve 84 flows from the cooling water line 81c to the cooling water line 81e. The ratio of the amount of cooling water in both the cooling water lines 81c and 81e can be linearly changed. Then, in the cooling water circuit 80, the cooling water that has received heat from the exhaust gas heat exchanger 14 and the like is guided to the linear three-way valve 84, and the cooling water line 81e is further provided in an amount corresponding to the operating position of the linear three-way valve 84. By being guided to the heat exchanger 51 via the heat exchanger 51, heat is supplied to the refrigerant in the main accumulator 45 by the heat exchanger 51, and the amount of heat supplied is adjusted by the linear three-way valve 84.

81g is a cooling water replenishing line connected to the cooling water line 81d, and 86 is a cooling water replenishing line 81.
is a water tank connected to g.

Next, the control system of the air conditioner 1 will be described with reference to the block diagram of FIG. It should be noted that this figure mainly shows the configuration of the control system relating to the refrigerant circuit 30.

As shown in the figure, the control system of the air conditioner is
The indoor heat exchangers 68a to 68n and the expansion valves 70a to 7
The indoor units control devices 91a to 91n for individually controlling the indoor units 90a to 90n provided with 0n, the compressor 20, the outdoor heat exchangers 75a and 75b, the four-way valve 41, the accumulators 45 and 46, and the like are provided. And an outdoor unit control device 92 for controlling the outdoor unit being installed, and electrically connected so that each of the indoor unit control devices 91a to 91n and the outdoor unit control device 92 can perform control in association with each other. Has been done.

The indoor units 90a to 90n have fans 93a to 93n for blowing air and expansion valves 70a to 70n, respectively.
n, expansion valve upstream-side refrigerant temperature sensors 110a to 110n
And an operation unit 9 equipped with 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 an engine 2, a four-way valve 41, a linear three-way valve 84, an open / close valve 49,
58, 65, 72, 76, 77, the control target elements such as the outdoor unit fan 95, etc. are connected, and the suction refrigerant temperature sensor 108, the compressor temperature sensor 105, the temperature sensor 102 having the accumulator liquid level detection function, 1
03, high pressure side pressure sensor 106, low pressure side pressure sensor 10
7, outside air temperature sensor 112, composition ratio detector 101, 109
Control input elements such as are connected, and a storage device 96 for storing various data and programs for control is also connected.

The outdoor unit controller 92 controls each of the indoor units 90.
As described above, the four-way valve 41 is switch-controlled to switch the circulation direction of the refrigerant in the refrigerant circuit 30 in response to 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.

Further, each of the control devices 91a to 91n, 9 described above
No. 2 executes subcool control at least during heating, and in the present embodiment, as will be described later in detail, subcool control is performed during heating and superheat control is performed during cooling.
The expansion valves 70a to 70n are controlled. In addition to such control, during heating, the heat exchange amount of the heat exchanger 51 is adjusted according to the liquid level in the accumulator 45, etc.
During cooling, the three-way valve 84 is controlled so as to adjust the heat exchange amount of the heat exchanger 51 according to the outside air temperature and the like. further,
During heating with sub-cool control, control of compressor speed according to comparison of high pressure value and target value described later, and control of refrigerant heating amount in accumulator according to comparison of low pressure value and target value described later When cooling is performed by performing the superheat control, the compressor rotation speed and the refrigerant heating amount in the accumulator are controlled according to the comparison between a low pressure value described later and its target value.

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

In this control, it is first determined whether the indoor unit is in the cooling operation or the heating operation (step S1), and during cooling, the main routine processing of steps S2 to S11 and the step S4 in the main routine are started. The parallel routine processing of steps S12 to S14 is performed,
On the other hand, during heating, the main routine process of steps S15 to S24 and the parallel routine process of steps S25 to S27 started at step S17 in the main routine are performed.

During heating, the load on the indoor unit side (the number of indoor units used) and the temperature condition are detected. As the temperature condition, the indoor temperature is detected by the indoor temperature sensors 111a to 111n, and the desired temperature is operated by the operation units 94a to 94n. From the data, the outdoor temperature is detected by the outdoor air temperature sensor 112 (step S15). A preferable correspondence relationship during the heating operation such as the expansion valve opening degree of each indoor unit, the three-way valve opening degree, the compressor rotation speed, the target high pressure value, the target low pressure value, the target SC value, and the like corresponding to the load and temperature conditions is stored in advance in the storage device 96. The expansion valve opening of each indoor unit, the three-way valve opening, the compressor rotation speed, the target high pressure value, the target low pressure value and the target SC value, etc. Expansion valve 7
0a to 70n, the three-way valve 84, the compressor 20 are controlled so as to take their initial setting values, and the target high pressure value,
The target low pressure value, the target SC value, etc. are held in the storage device 96 (step S16).

Here, the target high pressure value is the 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 70a to 70n. Further, 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 70a to 70n to the suction port of the compressor 20 through the outdoor heat exchangers 75a and 75b which are evaporators. A target value.

Then, the parallel routine of steps S25 to S27, which is processed in parallel with the main routine, is started (step S17). Further, on the main routine side, the high pressure side pressure sensor 106 subsequently detects the high pressure side pressure (step S18), and the comparison with the target high pressure value set in step S16 and held in the storage device 96 is carried out. It is performed (step S19). If the detected value is lower than the target high pressure value by a predetermined value or more, the compressor 2
The rotational speed of 0 is increased and corrected, and when the detected value is higher than the target high pressure value by a predetermined value or more, the rotational speed of the compressor 20 is decreased and corrected (step S20). After the execution of this rotation speed correction, the high-pressure side pressure is detected again and the target high-pressure value is compared, and if the absolute value of the difference between the detected value and the target high-pressure value is still above the predetermined value, step S20. The correction of the compressor rotation speed is repeated.

When the absolute value of the difference between the detected value and the target high pressure value is less than or equal to the predetermined value, the low pressure side pressure sensor 107 detects the low pressure side pressure (step S21). A comparison with the value is made (step S22). Here, when the detected value is lower than the target low pressure value by a predetermined value or more, the opening amount of the three-way valve 84 is corrected to be increased to increase the heating amount to the low pressure side refrigerant. Is higher than the target low pressure value by a predetermined value or more,
By correcting the opening degree of the three-way valve 84 to be reduced, the amount of heat to the low pressure side refrigerant is reduced (step S23). 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 the predetermined value, step S
The process of 23 is repeated. If the absolute value of the difference between the detected value and the target low pressure value is less than or equal to the predetermined value in step S22, the parallel routine processing is terminated and step S1 is terminated.
(Step S24).

Further, in the parallel routine processing started in step S17, SC (supercooling degree) is first detected (step S25). Here, SC is the saturated liquid temperature calculated based on the high-pressure side pressure (detected by the high-pressure side pressure sensor 106) and the refrigerant composition (mainly detected by the composition ratio detector), and the expansion valves 70a to 70n. It refers to the difference with the refrigerant temperature near the upstream side (detected by the temperature sensors 110a to 110n). The SC detection value obtained by calculating the difference between the saturated liquid temperature and the refrigerant temperature near the expansion valve upstream side is compared with the target SC value set in step S16 (step S26). 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. Thereby, the indoor heat exchanger 68a, which is a condenser,
The amount of liquid refrigerant staying at ~ 68n increases, and the actual SC value rises. If the SC detected value is larger than the target SC value by the predetermined value or more, the expansion valve opening is corrected to be increased (step S27). Then, the SC detection value is obtained again, and this is compared with the target SC value. If the absolute value of the difference between the SC detection value and the target SC value is greater than or equal to the predetermined value, the process of step S27 is repeated, If the absolute value of the difference is equal to or smaller than the predetermined value, the processing of the parallel routine is ended, and the process returns to step S24 of the main routine.

On the other hand, during cooling, the load on the indoor unit side (the number of indoor units used) and the temperature condition are detected. As the temperature condition, the indoor temperature is detected by the indoor temperature sensors 111a to 111n, and the desired temperature is the operating portion 94a to 94n. The outdoor temperature is detected by the outside air temperature sensor 112 based on the operation data (step S2). Expansion valve opening of each indoor unit, three-way valve opening, compressor rotation speed for this load and temperature conditions,
A preferable correspondence relationship during the cooling operation such as the target high pressure value and the target SH value is stored in the storage device 96 in advance, and from this correspondence relationship, the expansion valve opening degree of each indoor unit according to the load and temperature conditions at that time, three-way The valve opening, the compressor rotation speed, the target low pressure value, the target SH value, etc. are obtained, and the expansion valves 70a to 70n, the three-way valve 84, and the compressor 20 are controlled so as to take their initial setting values, and the target The low pressure value, the target SH value, etc. are held in the storage device 96 as data (step S3).

Then, the parallel routine of steps S12 to S15, which is processed in parallel with the main routine, is started (step S4). On the main routine side, the low pressure side pressure sensor 107 subsequently detects the low pressure side pressure (step S5), and the comparison with the target low pressure value set in step S3 and held in the storage device 96 is carried out. It is performed (step S6). 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 increased and corrected. When the detected value is higher than the target low pressure value by a predetermined value or more, the rotation speed of the compressor 20 is increased. The number is reduced and corrected (step S7). After the execution of this rotation speed correction, the low pressure side pressure is detected again (step S8), and this detected value is compared with the target low pressure value (step S).
9).

If the detected value is still lower than the target low pressure value by a predetermined value or more, the opening amount of the three-way valve 84 is corrected to be increased to increase the heating amount to the low pressure side refrigerant, and the detected value is increased. If the value is higher than the target low pressure value by a predetermined amount or more, the opening amount of the three-way valve 84 is corrected to be decreased, and the heating amount to the low pressure side refrigerant is decreased (step S10).
Then, the low-pressure side pressure is detected again, and when 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 S10 is repeated. When the absolute value of the difference between the detected value and the target low pressure value is equal to or smaller than the predetermined value in steps S6 and S9, the parallel routine process is terminated and the process returns to step S1 (step S11).

In the parallel routine process started in step S4, SH (heating degree) is first detected (step S12). Here, SH means the inlet temperature of the compressor 20 (detected by the suction refrigerant temperature sensor 108), the low pressure side pressure (detected by the low pressure side pressure sensor 107), and the refrigerant composition (mainly detected by the composition ratio detector). The difference from the saturated steam temperature calculated based on SH obtained by calculating the difference between the compressor 20 inlet temperature and the saturated steam temperature
The detected value is compared with the target SH value set in step S3 (step S13). 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 the predetermined value or more, the expansion valve opening is corrected (step S14). 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 greater than or equal to the predetermined value, the process of step S14 is repeated, If the absolute value of the difference is equal to or less than the predetermined value, the process of the parallel routine is ended, and the process returns to step S11 of the main routine.

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 with each other and the third port 41c and the fourth port 41d.
Is communicated with In this state, as shown by the solid arrow in FIG. 1, the refrigerant discharged from the compressor 20 is the four-way valve 41, the indoor heat exchangers 68a to 68n, and the expansion valve 70.
a to 70n, liquid gas heat exchanger 44, outdoor heat exchanger 75
a, 75b, the four-way valve 41, the liquid gas heat exchanger 44, the main accumulator 45, and the sub accumulator 46 are circulated to the compressor 20 in this order. The indoor heat exchangers 68a to 68n function as condensers to radiate heat, thereby heating the interior of the room, and the outdoor heat exchangers 75a and 75b function as evaporators to absorb heat.

In this case, the main routine process during heating in the flowchart of FIG. 3 (steps S15 to S23)
In addition, in addition to the control of the compressor rotation speed based on the comparison between the detected value of the high pressure side pressure and the target high pressure value, the opening degree of the three-way valve 84 based on the comparison between the detected value of the low pressure side pressure and the target low pressure value. Due to the control, the main accumulator 4
The amount of heat supplied from the heat exchanger 51 to the refrigerant in 5 is controlled.

Thus, the refrigerant in the main accumulator 45 is heated on the basis of the detection of the pressure on the low pressure side, whereby the pressure on the low pressure side becomes high, and the outdoor heat exchanger 75 serving as an evaporator is formed.
The pressure on the inlet side of a and 75b exceeds a specified value,
The refrigerant temperature at the inlets of the outdoor heat exchangers 75a and 75b rises, and condensation of water vapor in the atmosphere passing through the outdoor heat exchangers 75a and 75b, freezing of water, and frost formation are prevented.

Further, conventionally, when the outside air temperature is low, the amount of heat absorbed in the outdoor heat exchangers 75a, 75b decreases or becomes impossible to absorb, and the refrigerant temperature at the outlets of the outdoor heat exchangers 75a, 75b is the saturated vapor temperature at that pressure. The liquid refrigerant remains at a lower level, and the liquid refrigerant stays in the low-voltage side circuit. Further, the target SC value is set to 0 in order to reduce the heat radiation amount corresponding to the decrease in the heat absorption amount, and further, the expansion valve 70 is set at a temperature equal to or higher than the saturated liquid temperature.
The expansion valve opening is reduced to allow passage of a to 70n.
Even if the refrigerant is retained on the upstream side of 0a to 70n, the refrigerant temperature at the outlets of the outdoor heat exchangers 75a and 75b remains lower than the saturated steam temperature at that pressure, and heating may be disabled. there were. However, in the device of the present embodiment, since the refrigerant in the main accumulator 51 is heated based on the low pressure side pressure as described above, it is possible to prevent inability to perform heating due to insufficient heat absorption amount, and heating operation can be performed.

Further, as described above, the high pressure control (the steps S17 to S22) based on the target high pressure value is performed, the compressor rotation speed is controlled according to the load and the like, and as shown in FIG.
The sub-cool (supercooling) control operation is performed by correcting the expansion valve opening degree in the parallel routine process (steps S25 to S27) during heating in the flowchart of FIG. Here, the subcool control is a control for cooling the refrigerant temperature near 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. In this sub-cool control state, excess refrigerant is accumulated between the outdoor heat exchangers 75a and 75b and the compressor 20 in the accumulator 4.
Stay at 5,46.

According to this subcool control, the Ph diagram of the refrigeration cycle is as shown in FIG. 6 (a). 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 68a
The refrigerant changes from the gas phase to the liquid phase (b1 → c1) as the enthalpy is reduced by condensing and releasing heat at ~ 68n (b1 → c1). Control is performed. Next, the liquid-phase refrigerant is expanded by the expansion valves 70a to 70n to a low pressure (c1 → d).
1), and further, the enthalpy h rises due to evaporation in the outdoor heat exchangers 75a and 75b (d2 → a2). In addition, SC
i is the enthalpy change due to supercooling.

By 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, where A is the amount of increase in enthalpy due to compression in the compressor 20, and B is the amount of increase in enthalpy due to evaporation in the evaporator (see FIG. 6). ), And during heating and cooling respectively.

(At the time of heating) COP = (A + B) / A (at the time of cooling) COP = B / A ... Then, when the subcool control is performed, the value of B in the above equation is changed by the enthalpy change SCi due to supercooling. Since it becomes large, COP will be improved.

When the sub-cool control is performed in the air conditioner using the non-azeotropic refrigerant, the liquid-phase refrigerant stays in the accumulators 45 and 46 and is particularly liquefied among the non-azeotropic refrigerants. Easy high boiling point components (eg R1
Since 34a) stays at a high rate over time, the rate of low-boiling components (for example, R32 and R125) in the gas-phase refrigerant that is sucked into the compressor 20 tends to be higher than the initial filling rate.

This will be described with reference to FIG. In this figure, the horizontal axis shows the composition ratio of the low boiling point component in the non-azeotropic refrigerant, and the vertical axis shows the temperature, showing the saturated vapor line and the saturated liquid line under a constant pressure, as shown in the same figure. In addition, when the temperature of the refrigerant introduced into the accumulator by the subcool control becomes relatively low, the composition ratio of the low boiling point component in the liquid non-azeotropic refrigerant staying in the accumulator becomes a low value X1 (high boiling point component). On the other hand, from the accumulator to the compressor 2
The composition ratio of the low boiling point component of the vapor phase non-azeotropic refrigerant sent to 0 becomes a high value X2 (the ratio of the low boiling point component increases).

However, since the main accumulator 45 is provided with the heat exchanger 51, and the liquid-phase refrigerant that stays in the main accumulator 45 during heating is heated by the heat exchanger 51, the high boiling point component that stays in the main accumulator 45. Is easily vaporized, the above tendency is corrected, and the component ratio of the refrigerant sucked and circulated in the compressor 20 approaches the initial filling ratio. In particular, when a large amount of high boiling point components tend to accumulate in the main accumulator 45, the vaporization thereof is promoted. 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.

Moreover, since heat is applied to the refrigerant by the heat exchanger 51 in the main accumulator 45, even if the outdoor air heat exchangers 75a and 75b are less likely to absorb heat sufficiently, the above heat Heat absorption is promoted by the exchanger 51, and the heating capacity is improved.

On the other hand, when the air conditioner is in the cooling operation, the four-way valve 41 has the first port 41a and the fourth port 4a.
1d and the second port 41b and the third port 41c are in communication with each other. In this state, the refrigerant discharged from the compressor 20 is the four-way valve 41, the outdoor heat exchangers 75a and 75b, the liquid-gas heat exchanger 44, the expansion valves 70a to 70n, and the indoor chamber, as shown by the dashed arrows in FIG. Heat exchangers 68a to 68n, four-way valve 41, liquid gas heat exchanger 44,
It is circulated to the compressor 20 through the main accumulator 45 and the sub accumulator 46 in this order. The outdoor heat exchangers 75a and 75b function as condensers to radiate heat, while the indoor heat exchangers 68a to 68n function as evaporators to absorb heat and cool the room.

In this case, in the main routine process (steps S2 to S10) during cooling in the flow chart of FIG. 3, based on the comparison between the detected value of the low-pressure side pressure and the target low-pressure value, the compressor rotation speed is controlled, By controlling the opening degree of the three-way valve 84, the amount of heat supplied from the heat exchanger 51 to the refrigerant in the main accumulator 45 is controlled, and the refrigerant in the low pressure side circuit is heated.

By thus heating the refrigerant based on the detection of the low pressure side pressure, the low pressure side pressure becomes high and the inlet side pressure of the indoor heat exchangers 68a to 68n, which are evaporators, becomes a predetermined value or more. , That much, indoor heat exchanger 68a
The temperature of the refrigerant at the inlet of ~ 68n rises and the indoor heat exchanger 6
Condensation of water vapor in the atmosphere passing through 8a to 68n, freezing of water, and frost formation are prevented.

Further, conventionally, when the outside air temperature is low, the amount of heat radiation in the outdoor heat exchangers 75a and 75b becomes excessive, and the refrigerant temperature at the outlets of the outdoor heat exchangers 75a and 75b is lower than the saturated liquid temperature at that pressure. However, even if the pressure on the high-pressure side decreases and the expansion valve opening increase is corrected, the refrigerant circulation amount may decrease and the cooling operation may become impossible, but according to the device of the present embodiment, By heating the refrigerant on the low pressure side, the pressure on the low pressure side rises, and the pressure on the high pressure side rises accordingly.Therefore, the refrigerant circulation amount can be increased by correcting the expansion valve opening increase, and cooling operation is possible. Becomes

Further, by the parallel routine processing (steps S12 to S14) during cooling in the flowchart of FIG.
Superheat (heating) control operation is performed.

Here, the superheat control is control for heating the refrigerant temperature in the compressor suction section 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 this superheat control, the Ph diagram of the refrigeration cycle is as shown in FIG. 6 (b). That is, after the gas-phase refrigerant is compressed by the compressor 20 to increase the pressure P and the enthalpy h (a2 → b2), the outdoor heat exchanger 7
The refrigerant changes from a gas phase to a gas-liquid mixture or a liquid phase as the enthalpy h is reduced by being condensed at 5a and 75b (b2
→ c2), then the liquid-phase refrigerant is expanded by the expansion valves 70a to 70n to a low pressure (c2 → d2), and the enthalpy h rises due to evaporation and heat absorption in the indoor heat exchangers 68a to 68n (d2 → a2 ), At this time, the refrigerant is excessively heated so as to greatly exceed the saturated vapor temperature, and superheat control is performed. SHi is an enthalpy change due to excessive heating.

Even with this superheat control, only the enthalpy change SHi due to excessive heating by B in the above equation
Is increased, so that the COP is improved.

Moreover, by this control, the storage amount of the excess refrigerant in the accumulators 45, 46 is made zero in the steady operation state during cooling, so that the accumulators 45, 4
No high boiling point component stays in the compressor 6, and thus the compressor 2
There is no possibility that the proportion of low-boiling components in the gas-phase refrigerant sucked to 0 will increase and cause a decrease in COP.

Further, when the load decreases, the excess refrigerant stays on the upstream side of the expansion valve, but unlike the accumulator that separates gas and liquid, the low boiling point component and the high boiling point component after condensation both stay, and sequentially. Since it passes through the expansion valve, the composition ratio of the circulating refrigerant does not change due to the retention here, and therefore the COP does not decrease.

Further, in this superheat control state, the amount of heat supplied by the heat exchanger 51 is controlled, so that the refrigerant temperature is appropriately raised by the main accumulator 45, and the superheat control is effectively assisted.

In the above embodiment, the indoor heat exchanger 68 is used.
A plurality of a to 68n are provided, and the outdoor heat exchanger 75 is provided.
Although two a and 75b are provided, one indoor heat exchanger and one outdoor heat exchanger may be provided. Further, although the main accumulator 45 and the sub accumulator 46 are provided as the accumulators in the above embodiment, the number of accumulators may be one. The specific structure of each of the other parts may be changed in design without departing from the gist of the present invention.

[0086]

As described above, according to the present invention, the compressor, the indoor heat exchanger, the expansion valve, the outdoor heat exchanger, and the means for switching the refrigerant circulation path are provided in the refrigerant circuit, so that the refrigerant is not blocked. In a heat pump type air conditioner capable of heating and cooling using an azeotropic refrigerant, an accumulator is arranged in the path in which the refrigerant returns from the evaporator to the compressor, and at least subcool control is performed during heating operation. Therefore, the COP can be increased during the heating operation to improve the heating operation performance. Moreover, since the accumulator is provided with a heating means for heating the excess refrigerant in the liquid phase stored in the accumulator during the heating operation in which the subcool control is performed, the liquid accumulated in the accumulator when the subcool control is performed. The high boiling point component contained in the non-azeotropic refrigerant of the phase becomes easy to liquefy, and the component ratio of the refrigerant that is sucked and circulated in the compressor is brought close to the initial filling ratio, which is caused by the fluctuation of the component ratio of the circulating refrigerant. The decrease in COP can be suppressed.

In addition to the above construction, during cooling, superheat control is performed by adjusting the opening degree of the expansion valve so that the refrigerant temperature on the compressor suction side becomes higher than the saturated vapor temperature, and the excess refrigerant in the accumulator is removed. If the storage amount is configured to be zero in the steady operation state during cooling, it is possible to improve the heating operation performance by increasing the COP while avoiding fluctuation of the circulating refrigerant composition by superheat control during cooling. You can

[Brief description of the drawings]

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

FIG. 2 is a diagram showing a control system of the air conditioner.

FIG. 3 is a flowchart showing an example of control according to heating and cooling.

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 relationship between a composition ratio of a non-azeotropic refrigerant and a temperature.

FIG. 6 (a) is a refrigeration cycle P during subcool control.
It is a -h diagram, and (b) is a Ph diagram of the refrigeration cycle at the time of superheat control.

[Explanation of symbols]

 1 Refrigerant circuit 20 Compressor 30 Refrigerant circuit 41 Four-way valve 45 Main accumulator 46 Sub accumulator 51 Heat exchanger 68a-68n Indoor heat exchanger 70a-70n Expansion valve 75a, 75b Outdoor heat exchanger

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location F25B 1/00 395 F25B 1/00 395A 43/00 43/00 G

Claims (2)

[Claims] 1. A compressor, a condenser during heating, an indoor heat exchanger serving as an evaporator during cooling, an expansion valve, an evaporator during heating, an indoor heat exchanger serving as a condenser during cooling, and a refrigerant circulation path. Is provided in the refrigerant circuit, and during heating, the refrigerant is returned from the compressor through the indoor heat exchanger, the expansion valve, and the outdoor heat exchanger to the compressor in this order, and during cooling, the refrigerant flows from the compressor to the outdoor heat. The refrigerant circuit is configured to return to the compressor through the exchanger, the expansion valve, and the indoor heat exchanger in this order, and is an air conditioner that uses a non-azeotropic refrigerant as the refrigerant. An accumulator is placed in the route from the compressor to the compressor, and while controlling the rotation speed of the compressor according to the load, the refrigerant temperature near the expansion valve on the high pressure side is adjusted at least during heating operation by adjusting the opening of the expansion valve. Below the saturated liquid temperature A control means is provided for performing subcool control to maintain a high temperature, and a heating means is provided in the accumulator for heating the excess refrigerant in the liquid phase stored in the accumulator during the heating operation in which the subcool control is performed. An air conditioner characterized by being 2. The air conditioner according to claim 1, wherein the control means performs superheat control for making the refrigerant temperature on the compressor suction side higher than the saturated vapor temperature by adjusting the opening degree of the expansion valve during cooling. In addition, the air conditioner is configured so that the storage amount of the excess refrigerant in the accumulator becomes zero in a steady operation state during cooling.