JP2936961B2 - Air conditioner - Google Patents

Abstract

PURPOSE:To perform a stable cooling operation by minimizing a lowering of the pressure on a low pressure side when a compressor is started in the cooling operation and by maintaining the refrigerant on an inlet side of a flow amount control device on room interior side at a predetermined supercooling degree in a rapid manner. CONSTITUTION:An operation control part 18a of an air conditioning device sets a bypass flow amount control device 7 at the initial opening degree at which a relatively warm air is produced to such an extent as to avoid the overheating of the refrigerant in a bypass circuit 5 on the outlet side of a heat exchanging part 6 and, in this condition, a compressor 1 is started. The opening degree of the bypass flow amount control device 7 is then changed from the initial opening degree to the closing direction. When the overheating degree of the refrigerant detected by an overheating degree detecting means 8 reaches at least a predetermined degree, a change is first made to the opening direction to bring the refrigerant in the bypass circuit 5 close to a predetermined overheating degree. When the compressor 1 is started, this method permits the refrigerant flowing into a flow amount control device 3a on room interior side, etc., to rapidly become a predetermined supercooling condition without an extreme lowering of the refrigerant pressure on the low pressure side.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention suppresses a decrease in low-pressure side refrigerant pressure at the time of starting a compressor in a cooling operation, and reduces a refrigerant in a main refrigerant circuit from a heat source side heat exchanger to an indoor side heat exchanger. The present invention relates to an air conditioner capable of performing a stable cooling operation by quickly maintaining a predetermined cooling degree suitable for operation.

[0002]

2. Description of the Related Art FIG. 15 shows a refrigerant circuit diagram of a refrigerant circuit used in a conventional air conditioner. In FIG. 15, 1 is a compressor having a variable refrigerant discharge capacity, 2 is a heat source device side heat exchanger, 3a, 3b, 3c and 3d are indoor flow control devices for adjusting the refrigerant flow control valve opening by an electric signal, 4a. , 4
b, 4c, 4d are indoor heat exchangers, 5 is a bypass circuit connected to a discharge pipe from the heat source unit side heat exchanger 2 and a suction pipe of the compressor 1, and 6 is a bypass circuit in the bypass circuit 5. From the refrigerant and the heat source unit side heat exchanger 2 to the indoor side flow control devices 3 a to 3
a heat exchange unit for exchanging heat with the refrigerant in the main refrigerant circuit up to d; a throttle control for reducing a bypass flow rate of the refrigerant provided upstream of the heat exchange unit in the refrigerant flow direction in the middle of the bypass circuit; Is a bypass flow rate control device, 8 is a device for detecting the degree of superheat of the refrigerant in the bypass circuit 5 on the exit side of the heat exchange section 6 (an example of superheat degree detection means), and 9 is the refrigerant of the main refrigerant circuit on the exit side of the heat exchange section 6. A subcooling degree detecting device, 10 is a branch portion of the refrigerant from the main refrigerant circuit to the bypass circuit 5, 11 is a junction of the refrigerant from the bypass circuit 5 to the main refrigerant circuit, and 12 is a heat source device side for exchanging heat with the refrigerant. 13a, 13 a fluid flow control device for a heat exchange fluid such as outdoor air sent to the heat exchanger 2.
b, 13c, 13d are the indoor side flow control devices 3a, 3
b, 3c, 3d and indoor heat exchangers 4a, 4b, 4c, 4
d, four indoor units respectively having 14 d, a means for detecting a fluid temperature of a heat exchange fluid sent to the heat source unit side heat exchanger 2,
15 means for detecting the refrigerant discharge temperature on the discharge side of the compressor 1;
Is a means for detecting the low pressure of the refrigerant on the suction side of the compressor 1, and 17 is a means for detecting the degree of supercooling of the refrigerant on the exit side of the heat exchanger 2 on the heat source unit side. In the drawing, solid arrows indicate the flow direction of the refrigerant.

FIG. 16 is a control block diagram of the refrigerant circuit shown in FIG. 15, FIGS. 17A to 17D are electric circuit diagrams showing a drive circuit for driving the indoor side flow control device, and FIG. FIG. 19 is an electric circuit diagram showing an operation circuit for operating the compressor, and FIG. 20 is an electric circuit diagram showing an operation circuit of the fluid flow control device. In FIG. 16, reference numeral 18 denotes an operation control unit mainly constituted by, for example, a microcomputer (CPU), and reference numerals 19a, 19b, 19c, and 19d denote operation / operation of the indoor units 13a, 13b, 13c, and 13d, respectively.
Operation detection means for detecting a stop. 17A to 17D, reference numerals 20a, 20b, 20c, and 20d denote driving means for driving the indoor-side flow control devices 3a to 3d. In FIG. 18, reference numeral 21 denotes a bypass flow control device 7.
Is driving means for driving. In FIG. 19, reference numeral 22 denotes a power source, and reference numeral 23 denotes a capacity control unit of the compressor 1. In FIG. 20, reference numeral 24 denotes a driving unit of the fluid flow control device 12.

First, the operation of each electric circuit component will be described. Now, it is assumed that the indoor unit 13a has started operation.
When the operation control unit 18 detects the start of operation of the indoor unit 13a based on a signal from the operation detection unit 19a, the operation control unit 18
Sends a signal to the capacity control device 23, the driving unit 24, the driving unit 21, and the driving unit 20a related to the indoor unit 13a that has started operation. Then, the compressor 1 is started, the fluid flow control device 12 sends the heat exchange fluid to the heat source device side heat exchanger 2, and the valves of the bypass flow control device 7 and the indoor flow control device 3a are respectively opened. Thus, the refrigerant shown in FIG.
5 flows in the main refrigerant circuit in the direction indicated by the solid arrow. Thereafter, when any of the indoor units 13b to 13d starts operation, the operation detection means 19b to 1 corresponding to the operation starts.
Based on the signal of 9d, the operation control unit 18 sends a signal to any of the driving devices 20b to 20d corresponding to the indoor unit that has started operation, and the corresponding indoor-side flow control devices 3b to 3d.
Open the valve.

Next, the operation of the refrigerant during the cooling operation will be described. In order to facilitate understanding, it is assumed that only the indoor unit 13a is operating. The high-temperature and high-pressure gas refrigerant discharged from the compressor 1 flows into the heat source device side heat exchanger 2.
Here, the heat exchange fluid such as outdoor air is sent into the heat source unit side heat exchanger 2 by the drive of the fluid flow control device 12, and the refrigerant in the heat source unit side heat exchanger 2 exchanges heat with this heat exchange fluid. As a result, heat is dissipated and condensed to become a high-temperature and high-pressure liquid refrigerant.
A part of the liquid refrigerant branches off at the branch part 10, passes through the bypass flow control device 7, and most of the rest flows toward the indoor unit 13a. The liquid refrigerant that has flowed into the bypass flow control device 7 is decompressed here, becomes a gas-liquid two-phase refrigerant at a low temperature, and flows through the bypass circuit 5. In the heat exchange unit 6, heat is exchanged between the low-temperature gas-liquid two-phase refrigerant in the bypass circuit 5 and the high-temperature liquid refrigerant that has flowed out of the heat source unit side heat exchanger 2,
The gas-liquid two-phase refrigerant in the bypass circuit 5 evaporates, and at that time, the liquid refrigerant from the heat source unit side heat exchanger 2 is cooled to be a supercooled liquid refrigerant. For this reason, the branch section 1 on the exit side of the heat exchange section 6
The liquid refrigerant in the main refrigerant circuit at 0 is lower in temperature than the liquid refrigerant on the exit side of the heat source unit side heat exchanger 2. This liquid refrigerant is decompressed by the indoor flow controller 3a and flows into the indoor heat exchanger 4a as a low-pressure gas-liquid two-phase refrigerant. Here, by absorbing heat from the indoor air, the liquid refrigerant portion evaporates to become a low-temperature gas refrigerant, and merges with the refrigerant from the bypass circuit 5 at the junction 11 and returns to the compressor 1.

The reason that the liquid refrigerant from the heat source unit side heat exchanger 2 is turned into supercooled liquid in the main refrigerant circuit on the exit side of the heat exchange unit 6 by the bypass circuit 5 and the bypass flow rate control device 7 is as follows. by. From the heat exchange unit 6 to the indoor side flow control devices 3a to 3a to
When the pipe length up to 3d is long and the heat exchange unit 6 is located at a position lower than the indoor side flow control devices 3a to 3d, a kind of pressure loss due to friction in the pipe and a pressure drop due to the liquid head are caused. A squeezing action occurs. Due to this throttle action, the degree of supercooling of the liquid refrigerant is reduced, and the liquid refrigerant is likely to be in a gas-liquid two-phase state. If the state of the refrigerant at the inlet of the indoor-side flow control device 3a is a liquid single-phase state, relatively high-precision flow control is easy, but if the refrigerant is in a gas-liquid two-phase state, flow control becomes difficult, And the pressure loss becomes very large. for that reason,
Even if the pressure drops as described above, for example, in order to maintain a liquid state in the main refrigerant circuit on the inlet side of the indoor side flow control device 3a, the refrigerant needs to be sufficiently supercooled by the heat exchange unit 6. is there.

Here, the valve opening degree control of the bypass flow control device 7 will be described. When the opening degree of the bypass flow rate control device 7 is increased, the bypass flow rate of the refrigerant flowing through the bypass circuit 5 increases. However, if the opening degree is too large, the bypass flow rate becomes too large, so that the flow rate of the refrigerant flowing toward the indoor unit decreases, and the heat exchange capacity of the indoor unit decreases. Further, the throttle effect of the bypass flow control device 7 as a throttle device is reduced, and the temperature of the refrigerant in the bypass circuit 5 is increased, so that the temperature difference between the high-temperature liquid refrigerant flowing out of the heat source unit side heat exchanger 2 is reduced. Therefore, since the cooling effect is reduced, the refrigerant flowing out of the heat source device side heat exchanger 2 is not sufficiently supercooled. If the bypass flow rate is excessive as described above, the refrigerant flowing through the bypass circuit 5 does not sufficiently evaporate.
The refrigerant passing near the superheat degree detecting means 8 is in a gas-liquid two-phase state, and merges with the refrigerant in the main refrigerant circuit at the junction 11 as it is.

Conversely, when the opening of the bypass flow rate control device 7 is reduced, the bypass flow rate is reduced. At this time, although the temperature at the inlet of the bypass circuit 5 decreases due to the large throttle effect, the refrigerant evaporates immediately due to the small bypass flow rate, and the superheated gas is already passed from the bypass circuit 5 to the junction 11. State. Therefore, the amount of heat exchange in the heat exchange unit 6 is also small, and the degree of supercooling of the refrigerant in the main refrigerant circuit on the exit side of the heat exchange unit 6 is also small. For this reason, the state of the refrigerant in the bypass circuit 5 on the exit side of the heat exchange section 6 is detected by the superheat degree detecting means 8, and the degree of supercooling of the refrigerant in the main refrigerant circuit on the exit side of the heat exchange section 6 is subcooled. The opening / closing control of the opening degree of the bypass flow rate control device 7 is performed so that the degree of supercooling becomes a predetermined value or more while detecting the degree by the degree detecting means 9. The relationship between the opening degree of the bypass flow rate control device 7 and the degree of superheating of the refrigerant in the bypass circuit 5 on the exit side of the heat exchange section 6 and the degree of supercooling of the refrigerant in the main refrigerant circuit on the exit side of the heat exchange section 6 are shown. FIG. 21 shows the result. As shown in FIG. 21, when the degree of superheat of the refrigerant in the bypass circuit 5 on the exit side of the heat exchange unit 6 is less than a certain value (point A in FIG. 21), , The degree of supercooling of the refrigerant is small, and reaches a maximum at the certain value.

During the cooling operation, when the high-pressure side refrigerant pressure in the heat source unit side heat exchanger 2 decreases, the indoor side heat exchangers 4a to 4a
The low-pressure side refrigerant pressure such as the refrigerant pressure in d and the suction pressure of the compressor 1 also tends to decrease. In this case, if the pressure of the low-pressure side refrigerant is reduced more than necessary, frost is formed on the surfaces of the indoor side heat exchangers 4a to 4d, and the discharge temperature increases as a general characteristic of the compressor 1. Therefore, when the temperature of the heat exchange fluid is low, the fluid flow rate is reduced by the fluid flow rate control device 12 so that the low-pressure side refrigerant pressure does not decrease more than necessary.

[0010]

In the conventional air conditioner, the initial opening of the bypass flow control device 7 is always set to a constant value when the compressor 1 is started, and the opening / closing operation is performed as required after a predetermined time has elapsed. It had been. However, in general, at the time of startup, the low-pressure side refrigerant pressure tends to decrease. If the low-pressure side refrigerant pressure excessively decreases, it takes time to increase the pressure to a level suitable for operation. Then, there arises a problem that the discharge temperature of the compressor 1 rises due to a decrease in the low-pressure side refrigerant pressure, or that frost forms due to a decrease in the refrigerant pipe temperature of the indoor heat exchangers 4a to 4d. In such a case, in the conventional air conditioner, the discharge temperature detecting means 15 for detecting the discharge temperature or the suction pressure or the low pressure
When the discharge temperature rises above a predetermined discharge temperature or when the low-pressure side refrigerant pressure falls below a predetermined pressure, the capacity of the compressor 1 is reduced to thereby damage the compressor 1 and heat exchange inside the room. The frost on the vessel 2 is prevented.

At this time, the operating capacity of the compressor 1 is maintained until the discharge temperature of the refrigerant falls below the predetermined discharge temperature or the low-pressure side refrigerant pressure exceeds the predetermined pressure, even if the required indoor load is large. Cannot increase. Further, when the capacity of the compressor 1 is reduced when the low-pressure side refrigerant pressure is reduced more than necessary, it takes time to increase the low-pressure side refrigerant pressure. However, if the state in which the capacity of the compressor 1 is suppressed continues for a long time, the state in which the required capacity of the indoor unit cannot be achieved continues because the circulation amount of the refrigerant is small. Such a decrease in the low-pressure side refrigerant pressure at the time of startup becomes more remarkable as the throttle in the bypass circuit 5 becomes tighter, that is, as the opening degree of the bypass flow rate control device 7 becomes smaller. In addition, the capacity of the indoor unit for driving is small,
As the heat exchange capacity of the indoor unit is smaller than the heat exchange capacity of the heat source unit side heat exchanger 2, the heat exchange capacity becomes more remarkable. Similarly, when the temperature of the fluid that exchanges heat with the refrigerant in the heat source unit-side heat exchanger 2 is low, the fluid flow rate of the fluid sent to the heat source unit-side heat exchanger 2 by the fluid flow control device 12 is reduced to lower the low-pressure side refrigerant pressure. Is to prevent. However, in an extreme case, when the fluid flow rate reaches the controllable lower limit value and the fluid temperature further decreases, the low-pressure side refrigerant pressure decreases as the fluid temperature further decreases.

Since the branch 10 from the main refrigerant circuit to the bypass circuit 5 is provided on the refrigerant outlet side of the heat exchange unit 6, after the compressor 1 is started, the main refrigerant circuit on the heat exchange unit 6 outlet side is provided. When the degree of supercooling of the refrigerant in the state is small, the bypass flow rate control device 7 adjusts the bypass flow rate to maintain a predetermined degree of supercooling.
Since the degree of subcooling of the refrigerant on the inlet side is small, the refrigerant hardly flows through the bypass flow control device 7, and the flow control may not be performed properly even if the opening and closing operation of the bypass flow control device 7 is performed. As a result, the degree of supercooling of the refrigerant in the main refrigerant circuit on the exit side of the heat exchange section 6 does not increase forever, and control for maintaining a predetermined degree of supercooling may not be performed well.

On the other hand, in the case where the unstable operation at the start-up is somewhat eliminated and the operation is approaching a stable operation, if the opening degree of the indoor side flow control device is larger than necessary, the throttling action of the entire refrigerant circuit is reduced. The heat source unit side heat exchanger 2
, The liquid portion of the refrigerant in the main refrigerant circuit from the air conditioner to the indoor units 13a to 13d easily moves to the low pressure side refrigerant pressure side. Therefore, the liquid portion of the refrigerant in the main refrigerant circuit from the heat source unit side heat exchanger 2 to the indoor unit is reduced, and the liquid subcooling action is also reduced.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and it is possible to minimize a decrease in the low-pressure side refrigerant pressure at the time of starting the compressor in the cooling operation, and to reduce the pressure on the inlet side of the indoor flow control device. It is an object of the present invention to provide an air conditioner capable of performing a stable cooling operation by rapidly maintaining a refrigerant at a predetermined degree of subcooling.

[0015]

An air conditioner according to the present invention comprises a main refrigerant circuit connecting a compressor, a heat source unit side heat exchanger, an indoor side flow control device and an indoor side heat exchanger, and a heat source. Branch of refrigerant provided in the main refrigerant circuit between the machine side heat exchanger and the indoor side flow control device, and merging of refrigerant provided in the main refrigerant circuit between the compressor and the indoor side heat exchanger Part, a bypass circuit connected to the branch part and the junction part, and a bypass circuit for bypassing the refrigerant from the branch part to the junction part, and a bypass flow control device provided in the bypass circuit to throttle and control the flow rate of the refrigerant in the bypass circuit. A heat exchange unit that performs heat exchange between the refrigerant in the bypass circuit from the bypass flow control device to the junction and the refrigerant in the main refrigerant circuit from the heat source unit side heat exchanger to the branch unit; and a heat exchange unit. Superheat that detects the degree of superheat of the refrigerant in the outlet bypass circuit Detecting means and first initial opening setting means for setting a first initial opening of the bypass flow rate control device in which the degree of superheat of the refrigerant in the bypass circuit on the heat exchange section outlet side is equal to or less than a predetermined degree of superheat. And starting the compressor in a state where the opening degree of the bypass flow control device is set to the first initial opening degree,
After the compressor is started, the degree of opening of the bypass flow control device is changed from the first initial degree of opening to the closing direction so that the degree of superheat of the refrigerant in the bypass circuit on the outlet side of the heat exchange unit approaches the predetermined degree of superheat.
And control means.

A main refrigerant circuit comprising a compressor having a variable refrigerant discharge amount, a heat source unit side heat exchanger, an indoor flow control device and an indoor heat exchanger having a variable heat exchange capacity, and a heat source side heat exchanger. A branch portion of the refrigerant provided in the main refrigerant circuit between the exchanger and the indoor-side flow control device, and a merging portion of the refrigerant provided in the main refrigerant circuit between the compressor and the indoor heat exchanger, A bypass circuit provided in connection with the branch portion and the junction portion to bypass the refrigerant from the branch portion to the junction portion; a bypass flow control device provided in the bypass circuit to throttle and control the flow rate of the refrigerant in the bypass circuit; A heat exchange unit that performs heat exchange between the refrigerant in the bypass circuit from the flow control device to the junction and the refrigerant in the main refrigerant circuit from the heat source unit side heat exchanger to the branch unit, and a heat exchange unit outlet side. Superheat degree detection means to detect superheat degree of refrigerant in bypass circuit A heat exchange capacity setting means for externally setting a heat exchange capacity of the indoor heat exchanger; and a bypass flow rate control in which the degree of superheat of the refrigerant in the bypass circuit on the outlet side of the heat exchange section is equal to or less than a predetermined degree of superheat. A second initial opening setting means for setting the second initial opening of the device in accordance with the heat exchange capacity of the indoor heat exchanger set by the heat exchange capacity setting means; The compressor is started in a state where the opening is set to the second initial opening, and after starting the compressor, the opening of the bypass flow rate control device is changed from the second initial opening to the closing direction to change the heat exchange unit. And a second control means for bringing the degree of superheating of the refrigerant in the outlet side bypass circuit close to a predetermined degree of superheating.

Further, a main refrigerant circuit comprising a compressor, a heat source unit side heat exchanger, an indoor side flow control device and an indoor side heat exchanger connected to a variable refrigerant discharge amount, a heat source unit side heat exchanger and an indoor side heat exchanger. A branch portion of the refrigerant provided in the main refrigerant circuit between the flow control device, a junction of the refrigerant provided in the main refrigerant circuit between the compressor and the indoor heat exchanger, a branch portion and a junction portion A bypass circuit that is connected to the bypass section and bypasses the refrigerant from the branch section to the junction section; a bypass flow rate control apparatus that is provided in the bypass circuit to throttle and control the flow rate of the refrigerant in the bypass circuit; A heat exchange unit that exchanges heat between the refrigerant in the bypass circuit up to the heat exchanger and the refrigerant in the main refrigerant circuit from the heat source unit side heat exchanger to the branch unit, and a refrigerant in the bypass circuit on the heat exchange unit outlet side Superheat degree detection means for detecting the degree of superheat of the heat source side And the fluid temperature detecting means for detecting the fluid temperature of the heat exchange fluid heat exchange between the refrigerant fed to the exchanger, the fluid temperature detected by the fluid temperature detecting means
When below the Jo Tokoro temperature, a third bypass flow control device
The initial opening is set in the opening direction according to the decrease in the fluid temperature from the predetermined initial opening set in correspondence with the predetermined temperature, and when the detected fluid temperature exceeds the predetermined temperature,
Third initial opening setting means for setting the third initial opening from a predetermined initial opening to a constant or an opening direction in accordance with an increase in fluid temperature, and an opening of the bypass flow control device to a third initial opening. The compressor is started with the initial opening set, and after the compressor is started, the opening of the bypass flow control device is changed from the third initial opening to the closing direction to change the opening in the bypass circuit on the heat exchange unit outlet side. Third control means for bringing the degree of superheat of the refrigerant closer to a predetermined degree of superheat.

[0018] The main refrigerant circuit connecting the compressor, the heat source unit side heat exchanger, the indoor side flow control device and the indoor side heat exchanger, and the main refrigerant circuit between the heat source unit side heat exchanger and the indoor side flow control device. The branch portion of the refrigerant provided in the main refrigerant circuit between, the junction of the refrigerant provided in the main refrigerant circuit between the compressor and the indoor heat exchanger, and connected to the branch and the junction A bypass circuit provided to bypass the refrigerant from the branch to the junction; a bypass flow controller provided in the bypass circuit to throttle and control the flow rate of the refrigerant in the bypass circuit; and a bypass circuit from the bypass flow controller to the junction. A heat exchange section that exchanges heat between the refrigerant in the main refrigerant circuit and the refrigerant in the main refrigerant circuit from the heat source device side heat exchanger to the branch section, and the refrigerant in the bypass circuit on the heat exchange section outlet side has a predetermined degree of superheat. The first initial opening of the bypass flow control device becomes First initial opening degree setting means for setting, first supercooling degree detecting means for detecting a first degree of supercooling of the refrigerant in the main refrigerant circuit on the heat exchange section outlet side, and heat exchange section input means. Second supercooling degree detecting means for detecting a second supercooling degree of the refrigerant in the main refrigerant circuit on the side, and a first supercooling degree detected by the first supercooling degree detecting means. The supercooling degree difference from the second supercooling degree detected by the supercooling degree detecting means is:
Maintaining the opening of the bypass flow rate control device at the set first initial opening until a predetermined supercooling difference is reached, in which the refrigerant in the main refrigerant circuit on the outlet side of the heat exchange section is converted into liquid refrigerant. And control means.

A main refrigerant circuit connecting the compressor, the heat source unit side heat exchanger, the indoor side flow control device and the indoor side heat exchanger, and a main refrigerant circuit comprising the heat source unit side heat exchanger and the indoor side flow control device The branch portion of the refrigerant provided in the main refrigerant circuit between, the junction of the refrigerant provided in the main refrigerant circuit between the compressor and the indoor heat exchanger, and connected to the branch and the junction A bypass circuit provided to bypass the refrigerant from the branch to the junction; a bypass flow controller provided in the bypass circuit to throttle and control the flow rate of the refrigerant in the bypass circuit; and a bypass circuit from the bypass flow controller to the junction. A heat exchange unit that exchanges heat between the refrigerant in the main refrigerant circuit and the refrigerant in the main refrigerant circuit from the heat source unit side heat exchanger to the branch unit, and a first refrigerant in the main refrigerant circuit on the heat exchange unit outlet side. First subcooling degree detecting means for detecting the degree of subcooling, and first subcooling The first degree of subcooling detected by the detecting means is lower than a predetermined degree of subcooling in which the refrigerant in the main refrigerant circuit between the heat source unit side heat exchanger and the indoor side flow control device becomes a liquid refrigerant. And a fifth control means for changing the opening of the indoor-side flow control device in the closing direction.

[0020]

In the air conditioner according to the present invention, the first
Initial opening setting means of the opening of the bypass flow control device,
The first initial opening degree is set to be relatively gentle so that the refrigerant in the bypass circuit on the heat exchange section outlet side is not overheated. After starting the compressor in that state, the first control means always changes the opening of the bypass flow control device from the first initial opening to the closing direction when changing the opening next. When the refrigerant in the bypass circuit on the outlet side of the heat exchanger detected by the superheat degree detection means has a predetermined degree of superheat or more, the first control means first operates the bypass flow rate control device. Is changed in the opening direction so that the refrigerant in the bypass circuit approaches a predetermined degree of superheat. This prevents the low-pressure side refrigerant pressure at the time of starting the compressor from being too low.

When the heat exchange capacity of the indoor heat exchanger is externally set by the heat exchange capacity setting means, the second initial opening degree setting means sets the indoor side heat exchanger set by the heat exchange capacity setting means. The second initial opening of the bypass flow control device is set according to the heat exchange capacity of the heat exchanger. The second initial opening degree is an opening degree at which the degree of superheat of the refrigerant in the bypass circuit on the heat exchange part outlet side is equal to or less than a predetermined degree of superheat so that the low-pressure side refrigerant pressure does not excessively decrease. In this case, the initial opening of the bypass flow control device is set to be equal to or larger than the second initial opening as the heat exchange capacity of the indoor heat exchanger increases. After starting the compressor in this state, the second control means changes the opening degree of the bypass flow control device from the second initial opening degree to the closing direction when changing the opening degree. The second control means opens the opening of the bypass flow control device for the first time when the refrigerant in the bypass circuit on the outlet side of the heat exchange part detected by the superheat degree detection means has a predetermined superheat degree or more. The refrigerant in the bypass circuit is made to approach a predetermined degree of superheat by changing the direction. Accordingly, even when the refrigerant discharge amount of the compressor at the time of startup is increased in accordance with the heat exchange capacity of the indoor heat exchanger, it is possible to prevent the low-pressure side refrigerant pressure from dropping too much.

Further, when the fluid temperature of the heat exchange fluid that exchanges heat with the refrigerant sent to the indoor side heat exchanger is detected by the fluid temperature detecting means, the third initial opening degree setting means is provided. When the fluid temperature falls below a predetermined temperature at which the heat exchange fluid delivery amount changed in accordance with the fluid temperature approaches the control lower limit value, the third flow rate control device of the bypass flow control device
Is changed from the predetermined initial opening set corresponding to the predetermined temperature to the opening direction in accordance with the decrease in the fluid temperature. On the other hand, when the detected fluid temperature is higher than the predetermined temperature, the third initial opening setting means keeps the third initial opening at the predetermined initial opening, The third initial opening is changed from a predetermined initial opening to the opening direction in accordance with the rise. Therefore, the third control means starts the compressor in a state where the opening of the bypass flow control device is set to the third initial opening, and after the start, sets the opening of the bypass flow control device to the third initial opening. The degree of superheating of the refrigerant in the bypass circuit on the outlet side of the heat exchange section is made closer to a predetermined degree of superheating by changing the temperature from the degree to the closing direction. Thus, even when the compressor is started in a state where the fluid temperature is low, it is possible to prevent the low-pressure side refrigerant pressure from dropping too much.

The first initial opening of the bypass flow control device for reducing the refrigerant in the bypass circuit on the outlet side of the heat exchange section to a predetermined degree of superheat is set by the first initial opening setting means. The first degree of subcooling of the refrigerant in the main refrigerant circuit on the outlet side is detected by first subcooling degree detection means, and the second degree of subcooling of the refrigerant in the main refrigerant circuit on the side of the heat exchange section is further detected. Is detected by the second degree of supercooling detection means, the fourth control means determines that the difference between the detected first degree of supercooling and the detected second degree of supercooling is a thermal difference. The opening degree of the bypass flow control device is maintained at the first initial opening degree until the predetermined supercooling difference is reached in which the refrigerant in the main refrigerant circuit on the outlet side of the exchange section is changed to the liquid refrigerant. This makes it easier for the liquid refrigerant to accumulate in the main refrigerant circuit between the outlet side of the heat exchange section and the indoor flow control device. Therefore, the flow rate control of the bypass flow rate control device can be started from a state of the refrigerant whose flow rate is easily controlled such as a supercooled state.

When the first degree of supercooling of the refrigerant in the main refrigerant circuit on the outlet side of the heat exchange section is detected by the first degree of supercooling detecting means, the fifth control means controls the first degree of supercooling. The first degree of supercooling detected by the degree of cooling detection means falls below a predetermined degree of supercooling in which the refrigerant in the main refrigerant circuit between the heat source unit side heat exchanger and the indoor side flow control device becomes a liquid refrigerant. When it is determined that the control is performed, that is, when the control cannot be performed by the bypass flow control device, the opening degree of the indoor flow control device is changed in the closing direction. Thus, the liquid refrigerant can be easily stored in the main refrigerant circuit between the heat source unit side heat exchanger and the indoor side flow control device.

[0025]

【Example】

Embodiment 1 FIG. FIG. 1 is a configuration diagram illustrating a refrigerant circuit and an operation control unit of an air-conditioning apparatus according to an embodiment of the present invention.
Reference numeral 17 is exactly the same as the above-mentioned conventional device. 18
a has a characteristic function as shown in a control flowchart of each embodiment described later, and similarly to the conventional operation control unit 18 shown in FIG. 16, each of the devices 8, 9, 15 to 17, and
19a to 21, 23, and 24 are connected. The operation of the refrigerant circuit and the flow of the refrigerant in FIG. 1 are the same as those of the conventional device, and thus the description thereof is omitted here. FIG. 2 is a control flowchart showing a first embodiment of the control operation by the operation control unit of the air conditioner.

Here, the control flowchart shown in FIG. 2 will be described. First, at step 31, the compressor 1 is started. Then, at step 32, a control signal is sent from the operation control unit 18a to the bypass flow control device 7, and the opening based on the control signal is referred to as an initial opening (hereinafter, referred to as Sj ₀ ). I do. The current opening degree Sj ^* of the bypass flow rate control device 7 and the degree of superheat of the refrigerant in the bypass circuit 5 on the exit side of the heat exchange section 6 (hereinafter referred to as S
HB) is shown in FIG. As shown in the figure, Sj ₀ is an opening degree at which SHB becomes smaller than a predetermined value a. That is, Step 3 is performed by the operation control unit 18a.
2, the initial opening degree Sj at which the SHB becomes equal to or less than the predetermined value a.
Means for realizing the function of setting ₀ (an example of the first initial opening) is an example of the first initial opening setting means. Note that the relationship between Sj ^* and SHB was empirically determined by experiments or the like. The predetermined value a is a value of the degree of superheat at which the refrigerant in the bypass circuit 5 on the exit side of the heat exchange section 6 does not become overheated, and is an example of the predetermined degree of superheat according to the present invention. Referring again to FIG. 2, in step 33, the current SH
The change width ΔSj ₁ (SHB) is determined according to B, and a signal related to the opening Sj smaller by ΔSj ₁ (SHB) than the current opening Sj ^* is output. Next, in step 34, the magnitude of the current SHB is compared with the predetermined value a. If this SHB is larger than the predetermined value a (that is, when the refrigerant in the bypass circuit 5 is in an overheated state), the process proceeds to step 35, SH
The change width ΔSj ₂ (SHB) is determined according to B, and the opening Sj that is larger than the current opening Sj ^* by ΔSj ₂ (SHB).
Is output. Conversely, if SHB is smaller than the predetermined value a, the process returns to step 33, and the change width Δ
Sj ₁ (SHB) is determined, and a signal relating to the valve opening degree smaller by ΔSj ₁ than the current opening degree Sj ^* of the bypass flow rate control device 7 is output. That is, in step 33 to 35 by the operation control unit 18a, closer to SHB the opening degree of the bypass flow control device 7 from the initial opening Sj ₀ to SHB is equal to or less than a predetermined value a is varied in the closing direction to a predetermined value a functional Is an example of a first control unit.

Thus, SHB is brought close to the predetermined value a. Finally, the opening and closing of the valve opening of the bypass flow control device 7 is repeated when the SHB is near the predetermined value a,
When SHB is extremely close to the predetermined value a, ΔSj ₁ or ΔSj
By very small size of the j _2, SHB is apparently stable, even the degree of subcooling of the refrigerant in the subcooling degree detecting means detected the heat exchange section 6 outlet side in the main refrigerant circuit by 9 Stabilizes in relatively large areas. in this way,
When the compressor 1 is started, the initial opening degree Sj of the bypass flow rate control device 7 is set so that the SHB becomes slightly smaller than the predetermined value a.
_{Since 0} is set and the operation is started at Sj _0, it is possible to prevent the low-pressure-side refrigerant pressure at the time of startup from unnecessarily lowering due to the relatively gentle throttle effect of the bypass flow control device 7. Thereafter, the opening degree Sj output to the bypass flow control device 7 is changed in the closing direction. Thus,
By changing the opening degree Sj in the closing direction until the SHB exceeds the predetermined value a, and changing the opening direction only when the SHB exceeds the predetermined value a, the main refrigerant is quickly changed from a state in which the low-pressure side refrigerant pressure does not decrease. Control can be performed in a direction to increase the degree of supercooling of the refrigerant in the circuit. Thereby, the flow rate control of the refrigerant by the indoor side flow control devices 3a to 3d can be performed successfully. As a result, the heat exchange capacity of the indoor heat exchangers 4a to 4d can be quickly brought out, so that the reliability of the air conditioner can be significantly improved.

Embodiment 2 FIG. FIG. 4 is a control flowchart showing a second embodiment of the control operation by the operation control unit of the air conditioner. Since the operation of the refrigerant circuit and the flow of the refrigerant in the second embodiment are the same as those of the conventional device, the description thereof is omitted here. In FIG. 4, in step 41, the compressor 1
Starts. Then, in step 42, the operation control unit 18a outputs a control signal to the bypass flow rate control device 7,
The opening degree Sj to the bypass flow control device 7 is set to the initial opening degree Sj _0.
Set to. Here, FIG. 5 shows the current relationship between the opening degree Sj ^* of the bypass flow rate control device 7 and the degree of superheat SHB of the refrigerant in the bypass circuit 5 on the exit side of the heat exchange section 6. As shown in the figure, Sj ₀ is set to such an opening that SHB becomes smaller than a predetermined value a. The relationship between Sj ^* and SHB and Sj ₀ are empirically obtained by experiments and the like.

Referring again to FIG. 4, in step 43, the change width ΔSj ₁ (SHB) is determined according to the current SHB.
A control signal related to the opening degree smaller than the current opening degree Sj ^* by ΔSj ₁ (SHB) is output to the bypass flow control device 7. Next, in step 44, the magnitude of the SHB value is compared with a value smaller than the predetermined value a by a stable width Δa ₁ , and a−Δa
If it is ₁ or more, the process proceeds to step 45; otherwise, the process returns to step 43. In step 45, the magnitude of the SHB value is compared with a value larger than the predetermined value a by a stable width Δa ₂ ,
If it is larger than a + Δa _{2, the} process proceeds to step 47; otherwise, the process proceeds to step 46. In step 47, the change width ΔSj ₂ (SHB) is determined according to the current SHB, a signal related to the opening Sj that is larger than the current opening Sj ^* by ΔSj ₂ (SHB) is output, and the process returns to step 44.
In step 46, the output opening Sj is the current opening S
The process returns to step 44 while keeping j ^* .

Thus, a certain stable width Δa with respect to the predetermined value a is obtained.
By setting ₁ and Δa ₂ , even when the current SHB reaches the vicinity of the predetermined value a, the valve opening of the bypass flow rate control device 7 can be minimized from opening and closing fluctuations. Control becomes more stable. Therefore, the degree of superheat of the refrigerant in the bypass circuit 5 on the exit side of the heat exchange unit 6 can be easily stabilized at a value close to the predetermined value a. If the behavior of the refrigerant in the main refrigerant circuit is likely to be unstable due to a change in the valve opening of the bypass flow control device 7, the stable width Δa is thus determined with respect to the predetermined value a.
₁ and Δa ₂ are set so that a stable operation is performed and the degree of supercooling of the refrigerant in the main refrigerant circuit on the exit side of the heat exchange unit 6 is increased, so that the same operation and effect as in the first embodiment are exhibited.

Embodiment 3 FIG. FIG. 6 is a control flowchart showing a third embodiment of the control operation by the operation control unit of the air conditioner. The operation of the refrigerant circuit and the flow of the refrigerant in the third embodiment are the same as those of the conventional device, and thus the description thereof is omitted here. In FIG. 6, in step 51, the compressor 1
Are activated to change the refrigerant discharge amount. Then, for example, the operation control unit 18a specifies the indoor unit that has started operation by setting an operation signal from the outside by a user using a remote controller or the like based on signals from the operation detection units 19a to 19d in step 52. Then, the operation control unit 18a calculates and sets the total capacity ΣQj of the specified heat exchange capacity (Qj: j = a to d) of the indoor unit, and further initializes the bypass flow control device 7 according to the total capacity ΣQj. An opening Sj ₀ (an example of a second initial opening) is set. That is, in step 52, the means for calculating and setting the total capacity 実 現 Qj of the heat exchange capacities of the indoor heat exchangers 4a to 4d by the operation control unit 18a is an example of the heat exchange capacity setting means according to the present invention. It is. At this time, Sj ₀ is set in advance so that the opening degree increases as ΔQj increases (see FIG. 7), and the superheat degree SHB of the refrigerant in the bypass circuit 5 on the exit side of the heat exchange unit 6
Is set to be equal to or less than the predetermined value a. That is, the means for realizing the function of setting the initial opening degree Sj ₀ of the bypass flow rate control device 7 in step 52 by the operation control unit 18a according to the specified total capacity ΣQj of the indoor units is the second means according to the present invention. Is an example of the initial opening setting means.

[0032] Then, the opening Sj outputted to the bypass flow control device 7 in step 53, the initial opening Sj _0, which is set as described above. In step 54, the supercooling degree difference (hereinafter, ΔSC) of the supercooling degree of the refrigerant detected by the supercooling degree detecting means 9 and the supercooling degree detecting means 17, respectively.
Is calculated, and the value of ΔSC is compared with a predetermined temperature difference (hereinafter, referred to as SC1). And ΔS
If C is equal to or greater than SC1, the process proceeds to step 55,
If smaller than ΔSC, the process returns to step 53, and ΔSC becomes SC
To greater than 1 is left not change holds leave Sj of initial opening Sj _0. In step 55 SHB detected by the superheat degree detecting means 8, is greater than the predetermined value a, at a predetermined opening degree DerutaSj ₁ than the opening Sj current opening Sj ^* to the bypass flow control device 7 Step 56 If the opening is increased and if SHB is smaller than the predetermined value a, in step 57, the predetermined opening ΔSj is larger than the current opening Sj ^*.
Repeat the control to make it smaller by ₂ . That is, in step 55 to 57 by the operation control unit 18a, closer to SHB to a predetermined value a to the valve opening degree of the bypass flow control device 7 from the initial opening Sj ₀ to SHB is equal to or less than a predetermined value a is varied in the closing direction Means for realizing the function is an example of the second control means in the present invention.

As the required heat exchange capacity on the indoor side is larger, it is necessary to increase the operating capacity of the compressor 1 sooner after the compressor 1 is started. By increasing the initial opening degree Sj ₀ of the bypass flow control device 7 according to ΣQj,
Since the suction of the low-pressure side refrigerant pressure into the compressor 1 is reduced, there is no concern about an increase in the discharge temperature of the compressor 1 and frost formation on the indoor unit side. Further, in step 53, the bypass flow rate control device 7 leave briefly held in a state of initial opening Sj _0, closing the regulation of the bypass flow control device 7 after the refrigerant at the branch portion 10 becomes supercooled state Thus, the flow rate control of the refrigerant in the bypass circuit 5 can be performed successfully. Therefore, the degree of supercooling of the refrigerant in the main refrigerant circuit from the heat source unit side heat exchanger 2 to the indoor flow control devices 3a to 3d can be quickly increased, and the indoor flow control device 3
Since the heat exchange capacity of the indoor unit is quickly brought out by adjusting the flow rate of the refrigerant in a to 3d, the reliability of the air conditioner can be significantly improved.

Embodiment 4 FIG. FIG. 8 is a control flowchart showing Example 4 of the control operation by the operation control unit of the air conditioner. The operation of the refrigerant circuit and the flow of the refrigerant in the fourth embodiment are the same as those of the conventional device, and thus the description thereof is omitted here. In FIG. 8, here, the indoor units 13a,
The control flowchart of FIG. 8 will be described assuming that only 13b is operating. First, step 61
As a result, the compressor 1 is started to change the refrigerant discharge amount. Then, in step 62, the operation control unit 18a calculates the total capacity ΣQj of the heat exchange capacity Qj (here, j = a, b) of the indoor unit whose operation has started based on the signals from the operation detection means 19a to 19d. , The initial opening S according to the total capacity ΣQj
j ₀ (= f (ΣQj)) is determined. At this time, Sj ₀
Is set in advance so as to have an opening that is changed stepwise in a range of a certain ΔQj according to the number of operating indoor units (see FIG. 9). Then, the initial opening Sj ₀ the opening Sj to the bypass flow control apparatus 7 in step 63. In step 64, if less than the target value a-.DELTA.a ₁ there is detected degree of superheat SHB by superheating degree detecting means 8, the opening Sj of the bypass flow control device 7 at step 66 the current opening Sj ^* ΔSj ₂ . When the target value a-.DELTA.a ₁ or more which has SHB at step 64, the process proceeds to step 65. If SHB is greater than the target value a + Δa ₂ in step 65, the process proceeds to step 67, where the opening Sj to the bypass flow control device 7 is increased by ΔSj ₁ from the current opening Sj ^* .

In the judgment at steps 64 and 65, SH
If B is within the range from a-.DELTA.a ₁ to a + .DELTA.a _2, the process proceeds to step 68, heat exchange is detected at that time by the subcooling degree detection means 9 (an example of the first degree of subcooling detecting means) The supercooling degree SC (an example of a first supercooling degree) of the refrigerant in the main refrigerant circuit on the outlet side of the unit 6 is compared with a certain predetermined supercooling degree SC2. The predetermined degree of supercooling SC2 is the degree of supercooling when the refrigerant in the main refrigerant circuit between the heat source unit side heat exchanger 2 and the indoor side flow controllers 3a to 3d becomes liquid refrigerant. If the supercooling degree SC is equal to a predetermined supercooling degree SC2
If the degree of supercooling is greater than the above, step 64
And the control of the same steps as before is repeated. On the other hand, if the degree of supercooling SC is smaller than the predetermined degree of supercooling SC2, it is determined that the opening of the bypass flow control device 7 is appropriate, but the opening of the indoor flow controllers 3a to 3d is loose. Then, in step 69, the openings of these indoor-side flow controllers 3a to 3d are made smaller by ΔICSj (j) than the current opening ICSj (j) *. Here, j means a suffix of a code indicating an operating indoor unit, and in this case, j
= A, b. That is, when the subcooling degree SC detected by the supercooling degree detecting means 9 is lower than the predetermined supercooling degree SC2 in steps 68 to 69 by the operation control unit 18a, the indoor side flow control devices 3a to 3d Means for realizing the function of changing the opening degree of the lens in the closing direction is an example of the fifth control means according to the present invention.

As described above, the initial opening degree Sj ₀ of the bypass flow control device 7 is gradually increased in accordance with the total capacity ΣQj of the indoor units operating when the compressor 1 is started, so that the compressor 1 is started from the start. In the process of increasing the capacity, it is possible to prevent the low-pressure side refrigerant pressure from dropping excessively. In addition, the throttle of the indoor side flow controllers 3a to 3d is not so loose that the degree of supercooling of the refrigerant on the exit side of the heat exchange unit 6 does not decrease. Therefore, the degree of supercooling on the entrance side of the indoor side flow controllers 3a to 3d. Does not occur due to the extremely small flow control. Therefore, the heat exchange capacity of the indoor heat exchangers 4a to 4d can be quickly brought out, and the reliability of the air conditioner can be significantly improved.

Embodiment 5 FIG. FIG. 10 is a control flowchart showing Example 5 of the control operation by the operation control unit of the air conditioner. Since the operation of the refrigerant circuit and the flow of the refrigerant in the fifth embodiment are the same as those of the conventional device, the description is omitted here. In FIG. 10, in step 71,
The compressor 1 is started to change the refrigerant discharge amount. Then, in step 72, the operation control unit 18a sets the initial opening degree Sj ₀ (an example of a third initial opening degree) in accordance with, for example, the fluid temperature T6 of the outdoor air (heat exchange fluid) detected by the fluid temperature detecting means 14. Set. At this time, T6 =
Sj ₀ (= Sj ₄ ) of t is minimized, and when T6> t, the opening degree of Sj ₀ is set to a predetermined temperature t as the fluid temperature T6 increases.
Is larger than the predetermined initial opening degree Sj _{4 at} the time of
In the case of (1), the relationship is set in advance so that the opening degree of Sj ₀ becomes larger than the predetermined initial opening degree Sj ₄ as the fluid temperature T6 decreases (FIG. 11). Assuming that the heat exchange amount of the heat source unit side heat exchanger 2 is the same, the sending amount of the heat exchange fluid by the fluid flow control device 12 also decreases with the decrease of the fluid temperature T6. This is the temperature when the amount of feed of the fluid flow control device 12 at the time reaches the mechanical limit lower limit value (for example, the control lower limit air flow rate).

That is, step 7 is performed by the operation control unit 18a.
In steps 2 to 73, when the fluid temperature T6 detected by the fluid temperature detecting means 14 falls below a predetermined temperature t at which the heat exchange fluid delivery amount changed in accordance with the fluid temperature T6 approaches a control lower limit value. The initial opening degree Sj ₀ of the bypass flow control device 7 is set in the opening direction from a predetermined initial opening degree Sj ₄ set corresponding to the predetermined temperature t in accordance with a decrease in the fluid temperature T6. when the fluid temperature T6 exceeds a predetermined temperature t, either set in the opening direction in accordance with initial opening Sj ₀ from a predetermined initial opening Sj ₁ to increase the fluid temperature T6, or constant (in the figure, indicated by y Means for realizing the function of setting the initial opening degree (as indicated by a broken line) is an example of the third initial opening degree setting means according to the present invention. The reason why the opening degree of Sj ₀ is increased as the fluid temperature T6 increases when T6> t is as follows. It is necessary to increase the cooling capacity of the indoor unit with an increase in the fluid temperature T6, thereby increasing the refrigerant discharge capacity of the compressor 1 and increasing the refrigerant circulation amount. However, when the opening degree of the bypass flow control device 7 is the same, the throttle is tight. Therefore, the bypass flow control device 7 is opened.

[0039] Then, the opening Sj to the bypass flow control device 7 and the initial opening Sj ₀ in step 73. In step 74, each of the supercooling levels detected by the supercooling level detecting means 9 (an example of the first supercooling level detecting means) and the supercooling level detecting means 17 (an example of the second supercooling level detecting means), The degree of supercooling difference ΔSC is calculated, and ΔSC
Is compared with a predetermined temperature difference SC1. And ΔS
If C is equal to or greater than SC1, the process proceeds to step 75, but ΔSC
If is SC1 less than Prefer not change holds the opening Sj to the bypass flow control device 7 returns to the step 73 remains in the initial opening Sj _0. In step 75, if the degree of superheat SHB detected by the degree of superheat detection means 8 is larger than the predetermined value a, the degree of opening Sj to the bypass flow rate control device 7 is set to be more than the current degree of opening Sj ^* in step 76. is increased by degrees ΔSj _1, SHB repeats control such as small as a predetermined opening degree DerutaSj ₂ than the current opening Sj ^* at step 77 is smaller than the predetermined value a. That is, means for realizing the functions of steps 73 and 75 to 77 by the operation control 18a is an example of the third control means of the present invention, and means for realizing the functions of steps 73 to 77 is the fourth control means of the present invention. It is an example of the means.

[0040] Thus, fluid temperature T6 in step 72 is higher than the predetermined temperature t, a larger initial opening Sj ₀ than the predetermined initial opening Sj ₄ at a predetermined temperature t as T6 increases but by the fluid temperature T6 to increase the initial opening Sj ₀ of the bypass flow control device 7 as T6 is also lowered to be lower than the predetermined temperature t, the compressor 1 of a refrigerant discharge amount variable is after startup, the fluid Even when the temperature T6 is low and the high-pressure side refrigerant pressure is low and the low-pressure side refrigerant pressure is likely to decrease, the suction of the low-pressure side refrigerant pressure into the compressor 1 becomes small, so that the discharge temperature rises and the indoor unit side becomes frosted. No worries. Further, in steps 73 and 74, the bypass flow rate control device 7 is held in the state of the initial opening degree Sj ₀ , and the opening and closing of the bypass flow rate control device 7 is adjusted after the refrigerant in the branch portion 10 is in a supercooled state. Thus, the flow rate of the refrigerant in the bypass circuit 5 can be controlled successfully. Thereby, the indoor side flow control device 3a
3d, the degree of supercooling of the refrigerant on the inlet side can be quickly increased, and then the capacity can be quickly obtained by adjusting the flow rate of the refrigerant by the indoor flow controllers 3a to 3d. As a result, the reliability of the air conditioner can be significantly improved. For example, when a compressor having a variable refrigerant discharge amount is used, the initial opening degree Sj ₀ and the fluid temperature T
6, as indicated by the broken line y in FIG.
The initial opening degree Sj ₀ when T6> t is changed to a predetermined initial opening degree Sj
₄ may be fixed.

Embodiment 6 FIG. In Example 6, as shown in FIG. 12, even when the pre-set so as to the initial opening Sj ₀ of the bypass flow control device 7 stepwisely changed with respect to the fluid temperature T6 of Example 5 The same operation and effect as those of the fifth embodiment are exhibited.

Embodiment 7 FIG. The refrigerant circuit shown in FIG.
This is a partial modification of the configuration of the refrigerant circuit of the conventional device shown in FIG. 1, and an accumulator 80, a high pressure sensor 81, a low pressure saturation temperature sensor 82, a four-way switching valve 83, and a low pressure saturation temperature generation circuit 84 are newly added. I have. The piping of the low-pressure saturation temperature generating circuit 84 has a very small inner diameter. Therefore, the flow rate of the flowing refrigerant is relatively small. 8a is a bypass circuit outlet refrigerant temperature sensor,
9a is a heat exchanger outlet refrigerant temperature sensor, and 17a is a heat source device side heat exchanger outlet refrigerant temperature sensor. FIG. 14 is a control block diagram of the refrigerant circuit according to the seventh embodiment, and reference numeral 18b denotes an operation control unit that controls the refrigerant circuit. Here, a description will be given of a part of the movement of the refrigerant at the time of cooling, which is different from that of the conventional apparatus, that is, the low-pressure saturation temperature generation circuit 84 and the accumulator 80. Note that the four-way switching valve 83 does not affect the movement of the refrigerant at all during the cooling operation as compared with the conventional device, and therefore the description is omitted here. First, the low-pressure saturation temperature generation circuit 84 will be described. Part of the high-pressure liquid refrigerant in the main refrigerant circuit on the exit side of the heat exchange section 6 flows through the low-pressure saturation temperature generation circuit 84. When the liquid refrigerant flows in the narrow pipe of the low-pressure saturation temperature generation circuit 84, the refrigerant immediately becomes a gas-liquid two-phase refrigerant due to a large pressure loss. Then, the gas-liquid two-phase refrigerant near the outlet has almost the saturation temperature at the outlet pressure. By detecting the saturation temperature by the low-pressure saturation temperature sensor 82 and converting it into pressure, the low-pressure side refrigerant pressure can be determined without using an expensive pressure sensor.

Next, the accumulator 80 will be described. Most of the refrigerant returning from the indoor units 13a, 13b, 13c, and 13d to the compressor 1 via the four-way switching valve 83, or the refrigerant returning to the compressor 1 through the bypass circuit 5 and the junction 11 is gaseous. However, some refrigerants do not evaporate,
That is, it returns to the compressor 1 in a liquid state. Since the liquid refrigerant is almost an incompressible fluid, when the compressor 1 performs the compression operation by sucking the liquid refrigerant, the inside of the compressor 1 may be damaged. In order to avoid such a problem, an accumulator 80 is provided as a gas-liquid separator on the suction side of the compressor 1 so as to prevent the liquid refrigerant from being sucked into the compressor 1. This allows the refrigerant in the main refrigerant circuit to perform the same movement as in the conventional device.

Next, the operation of the high pressure sensor 81 and the various temperature sensors 8a, 9a, 17a, 82 will be described. In the refrigerant circuit of FIG. 13, the degree of supercooling of the refrigerant at the outlet side of the heat source unit side heat exchanger 2 is determined by the saturation temperature TC of the refrigerant converted from the pressure detected by the high pressure sensor 81 and the heat source unit side heat exchanger outlet refrigerant temperature sensor 17a. Is easily obtained from the temperature difference (= TC−T17) from the refrigerant temperature T17 detected by the above equation. Further, the degree of supercooling of the refrigerant in the main refrigerant circuit on the exit side of the heat exchange unit 6 is simplified by the temperature difference (= TC−T9) between the saturation temperature TC and the temperature T9 detected by the heat exchange unit outlet refrigerant temperature sensor 9a. Required. The degree of superheat of the refrigerant in the bypass circuit 5 on the exit side of the heat exchange section 6 is determined by the bypass circuit outlet refrigerant temperature sensor 8a.
And the temperature difference (= T8−T82) between the refrigerant temperatures detected by the low-pressure saturation temperature sensor 82 and the low-pressure saturation temperature sensor 82, respectively.

Since the refrigerant circuit of FIG. 13 functions similarly to the refrigerant circuit of the conventional apparatus, the refrigerant circuits of the first, second, third, fourth, fifth, and sixth embodiments are used. In the case where the refrigerant circuit of FIG. 13 is used, the same operation and effect as those of the respective embodiments are exhibited.

[0046]

Since the present invention is configured as described above, it has the following effects.

By preventing the refrigerant from being overheated in the bypass circuit on the heat exchange section outlet side when the compressor is started, it is possible to prevent the low-pressure side refrigerant pressure at the time of start-up from dropping more than necessary. Therefore, it is possible to prevent adverse effects caused by an unnecessary decrease in the low-pressure side refrigerant pressure. And the refrigerant | coolant to an indoor side flow control apparatus can be made into a predetermined | prescribed supercooled state promptly, in the state where the low pressure side refrigerant pressure does not fall more than needed. As a result, the flow rate control by the bypass flow rate control device can be performed successfully, and the heat exchange capacity can be quickly extracted from the indoor heat exchanger, so that the reliability of the air conditioner can be significantly improved. it can.

Also, when changing the refrigerant discharge capacity of the compressor in accordance with the heat exchange capacity of the indoor heat exchanger (for example, when there are a plurality of indoor heat exchangers, it corresponds to the operating number of the heat exchangers). Since the initial opening degree of the bypass flow control device is not set to be small, the low-pressure side refrigerant pressure is unlikely to drop sharply. Therefore, it is possible to prevent the temperature of the refrigerant discharged from the compressor from increasing when the pressure of the low-pressure side refrigerant is suddenly reduced, thereby significantly improving the reliability of the air conditioner.

Further, even when the compressor is started when the temperature of the heat exchange fluid flowing into the heat exchanger on the heat source unit side to exchange heat with the refrigerant is relatively low, the pressure of the low pressure side refrigerant drops extremely. Can be prevented. Therefore, it is possible to prevent an increase in the temperature of the refrigerant discharged from the compressor caused by a decrease in the pressure of the low-pressure side refrigerant, to operate the compressor successfully, and to significantly improve the reliability of the air conditioner.

When the flow rate of the refrigerant is controlled by the bypass flow rate control device for the first time, the bypass flow rate control is performed from the supercooled state of the refrigerant at the branch between the heat source unit side heat exchanger and the indoor side flow rate control device. The flow control of the device can be started. Therefore, the flow rate of the refrigerant in the bypass circuit can be accurately controlled and the reliability of the air conditioner can be significantly improved.

When the degree of supercooling of the refrigerant in the main refrigerant circuit between the heat exchanger on the heat source unit side and the indoor-side flow control device does not reach a predetermined level, ie, the bypass flow control device controls the refrigerant. Even in the case where it cannot be completed, the degree of supercooling of the refrigerant at the branch portion can be increased, and the main refrigerant circuit can be easily filled with the liquid refrigerant. For this reason, the flow rate control by the bypass flow rate control device is successfully performed, and the heat exchange capacity can be quickly controlled also in the indoor heat exchanger, so that the reliability of the air conditioner can be significantly improved.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing a refrigerant circuit and an operation control unit of an air conditioner according to an embodiment of the present invention.

FIG. 2 is a control flowchart showing Example 1 of a control operation by an operation control unit of the air conditioner.

FIG. 3 is a graph showing a relationship between a current valve opening degree of the bypass flow control device and a refrigerant and a superheat degree in a bypass circuit on a heat exchange unit outlet side in the first embodiment.

FIG. 4 is a control flowchart showing Example 2 of a control operation by an operation control unit of the air conditioner.

FIG. 5 is a graph showing the relationship between the current valve opening of the bypass flow control device and the degree of superheat of the refrigerant in the bypass circuit on the heat exchange unit outlet side in the second embodiment.

FIG. 6 is a control flowchart illustrating Example 3 of a control operation by an operation control unit of the air-conditioning apparatus.

FIG. 7 is a graph illustrating a relationship between an initial opening degree of the bypass flow control device and a total capacity of the indoor units that have started operation in the third embodiment.

FIG. 8 is a control flowchart illustrating Example 4 of a control operation by an operation control unit of the air-conditioning apparatus.

FIG. 9 is a graph showing a stepwise relationship between the initial opening degree of the bypass flow control device and the total capacity of the indoor units that have started operation in the fourth embodiment.

FIG. 10 is a control flowchart showing a fifth embodiment of the control operation by the operation control unit of the air conditioner.

FIG. 11 is a graph showing the relationship between the initial opening degree of the bypass flow control device and the fluid temperature of the heat exchange fluid in the fifth embodiment.

FIG. 12 is a graph showing a stepwise relationship between the initial opening degree of the bypass flow rate control device and the fluid temperature of the heat exchange fluid in the sixth embodiment.

FIG. 13 is a refrigerant circuit diagram illustrating a cooling / heating switching type refrigerant circuit according to a seventh embodiment.

FIG. 14 is a control block diagram of a refrigerant circuit according to a seventh embodiment.

FIG. 15 is a refrigerant circuit diagram of a refrigerant circuit used in a conventional air conditioner.

FIG. 16 is a control block diagram of the refrigerant circuit of FIG.

FIG. 17A is an electric circuit diagram showing a drive circuit for driving the indoor flow control device 3a. (B) is an electric circuit diagram showing a drive circuit for driving the indoor-side flow control device 3b. (C) is an electric circuit diagram showing a drive circuit for driving the indoor flow control device 3c. (D) is an electric circuit diagram showing a drive circuit for driving the indoor-side flow control device 3d.

FIG. 18 is an electric circuit diagram showing a drive circuit for driving a bypass flow control device.

FIG. 19 is an electric circuit diagram showing an operation circuit for operating the compressor.

FIG. 20 is an electric circuit diagram showing an operation circuit of the fluid flow control device.

FIG. 21 shows a relationship between the valve opening degree of the bypass flow rate control device, the degree of superheating of the refrigerant in the bypass circuit on the heat exchange section outlet side, and the degree of supercooling of the refrigerant in the main refrigerant circuit on the heat exchange section exit side. FIG.

[Description of Signs] 1 Compressor 2 Heat source-side heat exchanger 3a Indoor-side flow control device 3b Indoor-side flow control device 3c Indoor-side flow control device 3d Indoor-side flow control device 4a Indoor heat exchanger 4b Indoor heat exchange Unit 4c Indoor heat exchanger 4d Indoor heat exchanger 5 Bypass circuit 6 Heat exchange unit 7 Bypass flow control device 8 Superheat degree detecting means 9 Supercooling degree detecting means 10 Branch unit 11 Merging unit 13a Indoor unit 13b Indoor unit 13c Indoor unit Unit 13d Indoor unit 14 Fluid temperature detection means 17 Subcooling degree detection means 18a Operation control unit 18b Operation control unit 19a Operation detection means 19b Operation detection means 19c Operation detection means 19d Operation detection means

Claims (5)

(57) [Claims] 1. A main refrigerant circuit connecting a compressor, a heat source unit side heat exchanger, an indoor side flow control device and an indoor side heat exchanger, the heat source unit side heat exchanger and the indoor side flow control device A branching portion of the refrigerant provided in the main refrigerant circuit between the compressor, the junction of the refrigerant provided in the main refrigerant circuit between the compressor and the indoor heat exchanger, and the junction with the branching portion. A bypass circuit that is provided in connection with the section and bypasses the refrigerant from the branch section to the merge section; a bypass flow rate control device that is provided in the bypass circuit and controls the flow rate of the refrigerant in the bypass circuit; A heat exchange unit that performs heat exchange between a refrigerant in a bypass circuit from a bypass flow control device to the junction and a refrigerant in a main refrigerant circuit from the heat source unit side heat exchanger to the branch unit; Superheat degree of refrigerant in the bypass circuit at the outlet of the exchange section Degree of superheat detecting means for detecting a degree of superheat, and a first degree of opening of the bypass flow control device for setting the first degree of opening of the bypass flow rate control device in which the degree of superheat of the refrigerant in the bypass circuit on the heat exchange unit outlet side is equal to or less than a predetermined degree of superheat The first opening degree setting means, and the compressor is started in a state where the opening degree of the bypass flow rate control device is set to the first initial opening degree. First control means for changing the opening degree from the first initial opening degree to the closing direction so as to make the degree of superheat of the refrigerant in the bypass circuit on the outlet side of the heat exchange section close to the predetermined degree of superheat. An air conditioner characterized by the following. 2. A main refrigerant circuit comprising a compressor having a variable refrigerant discharge amount, a heat source unit-side heat exchanger, an indoor flow control device, and an indoor heat exchanger having a variable heat exchange capacity; A branch portion of the refrigerant provided in the main refrigerant circuit between the heat exchanger and the indoor flow control device, and a branch of the refrigerant provided in the main refrigerant circuit between the compressor and the indoor heat exchanger. A merging portion, a bypass circuit provided to be connected to the branch portion and the merging portion to bypass the refrigerant from the branch portion to the merging portion, and a flow rate of the refrigerant in the bypass circuit provided in the bypass circuit. A bypass flow control device for controlling the throttle;
A heat exchange unit that performs heat exchange between a refrigerant in a bypass circuit from the bypass flow rate control device to the junction and a refrigerant in a main refrigerant circuit from the heat source unit side heat exchanger to the branch unit; Superheat degree detection means for detecting the degree of superheat of the refrigerant in the bypass circuit on the heat exchange section outlet side; heat exchange capacity setting means for externally setting the heat exchange capacity of the indoor heat exchanger; The second initial opening degree of the bypass flow rate control device in which the degree of superheat of the refrigerant in the outlet side bypass circuit is equal to or less than a predetermined degree of superheat is determined by the heat exchange capacity setting means. Second initial opening setting means for setting according to the heat exchange capacity, and starting the compressor in a state where the opening of the bypass flow control device is set to the second initial opening, After the compressor is started, the bypass flow control device Second control means for changing the degree of superheat of the refrigerant in the bypass circuit on the outlet side of the heat exchange section closer to the predetermined degree of superheat by changing the degree from the second initial opening degree to the closing direction. An air conditioner characterized by: 3. A main refrigerant circuit connecting a compressor having a variable refrigerant discharge amount, a heat source unit side heat exchanger, an indoor side flow control device and an indoor side heat exchanger, and the heat source unit side heat exchanger and the main heat exchanger. A branch portion of the refrigerant provided in the main refrigerant circuit between the indoor side flow control device, and a merging portion of the refrigerant provided in the main refrigerant circuit between the compressor and the indoor heat exchanger, A bypass circuit provided in connection with the branch portion and the junction portion for bypassing the refrigerant from the branch portion to the junction portion; and a bypass flow amount provided in the bypass circuit to throttle and control the flow rate of the refrigerant in the bypass circuit. Heat exchange for performing heat exchange between a control device and a refrigerant in a bypass circuit from the bypass flow control device to the junction and a refrigerant in a main refrigerant circuit from the heat source device side heat exchanger to the branch portion. Part and a bypass circuit on the heat exchange part outlet side Superheat degree detection means for detecting the degree of superheat of the refrigerant in the fluid, fluid temperature detection means for detecting the temperature of the heat exchange fluid which is sent to the heat source unit side heat exchanger and exchanges heat with the refrigerant, and the fluid when the fluid temperature detected by the temperature detecting means falls below the Jo Tokoro temperature, the from the bypass flow control device third predetermined initial opening the initial opening is set corresponding to the predetermined temperature of the fluid temperature When the detected fluid temperature exceeds the predetermined temperature, the third initial opening is set from the predetermined initial opening in accordance with the rise of the fluid temperature. A third initial opening setting means for setting the opening to a constant or an opening direction; and starting the compressor with the opening of the bypass flow control device set to the third initial opening. After the startup of the bypass flow control device And third control means for changing the opening degree of the refrigerant from the third initial opening degree to the closing direction to bring the degree of superheat of the refrigerant in the bypass circuit on the outlet side of the heat exchange section closer to the predetermined degree of superheat. An air conditioner characterized by the above-mentioned. 4. A main refrigerant circuit connecting a compressor, a heat source unit side heat exchanger, an indoor side flow control device and an indoor side heat exchanger, the heat source unit side heat exchanger and the indoor side flow control device A branching portion of the refrigerant provided in the main refrigerant circuit between the compressor, the junction of the refrigerant provided in the main refrigerant circuit between the compressor and the indoor heat exchanger, and the junction with the branching portion. A bypass circuit that is provided in connection with the section and bypasses the refrigerant from the branch section to the merge section; a bypass flow rate control device that is provided in the bypass circuit and controls the flow rate of the refrigerant in the bypass circuit; A heat exchange unit that performs heat exchange between a refrigerant in a bypass circuit from a bypass flow control device to the junction and a refrigerant in a main refrigerant circuit from the heat source unit side heat exchanger to the branch unit; The refrigerant in the bypass circuit on the outlet side of the exchange First initial opening setting means for setting a first initial opening of the bypass flow rate control device to be equal to or lower than a superheat degree, and a first superheat of refrigerant in the main refrigerant circuit on the outlet side of the heat exchange section. First supercooling degree detecting means for detecting a degree of cooling, second supercooling degree detecting means for detecting a second degree of supercooling of the refrigerant in the main refrigerant circuit on the heat exchange unit entrance side, 1
The difference between the first degree of supercooling detected by the second degree of supercooling detected by the second degree of supercooling and the degree of supercooling detected by the second degree of supercooling is determined by the heat exchange unit outlet side. A fourth control means for holding the opening of the bypass flow control device at the set first initial opening until a predetermined degree of supercooling of the refrigerant in the main refrigerant circuit into the liquid refrigerant is reached. An air conditioner comprising: 5. A main refrigerant circuit which connects a compressor, a heat source unit side heat exchanger, an indoor side flow control device and an indoor side heat exchanger, the heat source unit side heat exchanger and the indoor side flow control device. A branching portion of the refrigerant provided in the main refrigerant circuit between the compressor, the junction of the refrigerant provided in the main refrigerant circuit between the compressor and the indoor heat exchanger, and the junction with the branching portion. A bypass circuit that is provided in connection with the section and bypasses the refrigerant from the branch section to the merge section; a bypass flow rate control device that is provided in the bypass circuit and controls the flow rate of the refrigerant in the bypass circuit; A heat exchange unit that performs heat exchange between a refrigerant in a bypass circuit from a bypass flow control device to the junction and a refrigerant in a main refrigerant circuit from the heat source unit side heat exchanger to the branch unit; The first excess refrigerant in the main refrigerant circuit on the outlet side of the exchange section A first degree of subcooling detecting means for detecting a degree of cooling; and a first degree of supercooling detected by the first degree of subcooling detecting means, wherein the heat source unit side heat exchanger and the indoor side flow control device are provided. And a fifth control means for changing an opening degree of the indoor side flow control device in a closing direction when a degree of supercooling of the refrigerant in the main refrigerant circuit between the main refrigerant circuit and the liquid refrigerant is lower than a predetermined degree. An air conditioner characterized by the above-mentioned.