JP2006300371A - Air conditioner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an air conditioner capable of suppressing liquid back to a compressor and suppressing user discomfort due to generation of refrigerant sound.
An air conditioner 100 is an air conditioner including a refrigerant circuit including a compressor 10, an outdoor heat exchanger 14, a first indoor expansion valve 5a, and a first indoor heat exchanger 3a. A bypass circuit 13, a hot gas bypass circuit opening / closing unit 25, and a control unit are provided. The hot gas bypass circuit 13 is a circuit that connects the suction side and the discharge side of the compressor 10. The hot gas bypass circuit opening / closing unit 25 is provided on the hot gas bypass circuit 13 and opens and closes the hot gas bypass circuit 13. When the compressor 10 is started, the control unit opens the hot gas bypass circuit opening / closing unit 25, determines the wet state of the refrigerant on the suction side of the compressor 10, and determines the hot gas based on the determination result of the wet state of the refrigerant The bypass circuit opening / closing part 25 is closed.
[Selection] Figure 2

Description

  The present invention relates to an air conditioner.

In the air conditioner, in order to prevent liquid back at the time of starting the compressor, there is a case where control is performed to send a part of the high-pressure gas refrigerant on the discharge side of the compressor to the suction side via the hot gas bypass circuit. . The hot gas bypass circuit is a circuit that connects the discharge side and the suction side of the compressor, and the flow of the refrigerant is blocked and opened by a hot gas bypass opening / closing section provided on the hot gas bypass circuit. In this control, a hot gas bypass circuit opening / closing part that opens and closes the hot gas bypass circuit is opened when the compressor is started, and the hot gas bypass circuit opening / closing part is closed after a predetermined time has elapsed since the start (see Patent Document 1).
JP-A-6-341720 (paragraph [0020])

On the other hand, when the hot gas bypass circuit is opened, a refrigerant passing sound is often generated. In this case, as described above, when the closing timing of the hot gas bypass circuit opening / closing part is determined based on the time, the hot gas bypass circuit opening / closing part is opened for a longer time than necessary, There is a risk that the passing sound of the refrigerant will continue to be generated.
Moreover, if the time during which the hot gas bypass circuit opening / closing part is opened is shortened in order to shorten the generation time of the refrigerant sound, the prevention of liquid back becomes insufficient, and the compressor performance may be reduced.

  The subject of this invention is providing the air conditioner which can suppress the user's discomfort by generation | occurrence | production of a refrigerant | coolant sound while suppressing the liquid back to a compressor.

  An air conditioner according to a first aspect of the present invention is an air conditioner including a refrigerant circuit including a compressor, an outdoor heat exchanger, a first expansion valve, and a first indoor heat exchanger, and includes a hot gas bypass circuit and a hot gas. A bypass circuit opening / closing unit and a control unit are provided. The hot gas bypass circuit is a circuit that connects the suction side and the discharge side of the compressor. The hot gas bypass circuit opening / closing unit is provided on the hot gas bypass circuit and opens and closes the hot gas bypass circuit. The control unit opens the hot gas bypass circuit opening / closing unit at the time of starting the compressor, determines the wet state of the refrigerant on the suction side of the compressor, and opens / closes the hot gas bypass circuit based on the determination result of the wet state of the refrigerant Close the part.

  In this air conditioner, the hot gas bypass circuit opening / closing part opened when the compressor is started is closed based on the determination result of the wet state of the refrigerant on the suction side of the compressor. That is, the closing timing of the hot gas bypass circuit opening / closing unit, which has been conventionally determined by time, is determined based on the determination result of the wet state. For this reason, while suppressing liquid back | bag, the time which a hot gas bypass circuit opening-closing part is put into an open state can be suppressed short, As a result, the discomfort of the user by generation | occurrence | production of a refrigerant | coolant sound can be suppressed.

  An air conditioner according to a second aspect of the present invention is the air conditioner of the first aspect, comprising: a pressure equivalent saturation temperature detecting means for detecting a pressure equivalent saturation temperature of the suction side pressure of the compressor; and a first indoor heat exchanger. First room temperature detecting means for detecting the temperature of the room that receives air conditioning by the first indoor unit to be accommodated is further provided. Then, the control unit determines the wet state of the refrigerant on the suction side of the compressor based on the pressure equivalent saturation temperature of the suction side pressure and the indoor temperature.

In this air conditioner, the wet state of the refrigerant on the suction side of the compressor is determined based on the pressure equivalent saturation temperature of the suction side pressure and the indoor temperature. Thereby, the closing timing of a hot gas bypass circuit opening / closing part can be determined appropriately.
An air conditioner according to a third aspect of the invention is the air conditioner of the second aspect, wherein the control unit is hot when the pressure equivalent saturation temperature of the suction side pressure is lower than the room temperature or lower than the room temperature. Close the gas bypass circuit opening / closing part.

In this air conditioner, the hot gas bypass circuit opening / closing part is closed when the pressure-equivalent saturation temperature of the suction side pressure is lower than the room temperature or lower than the room temperature. Thereby, the liquid back | bag to a compressor can be suppressed appropriately.
An air conditioner according to a fourth aspect of the present invention includes a compressor, an outdoor heat exchanger, a plurality of indoor heat exchangers provided in parallel to each other, a plurality of expansion valves provided corresponding to the indoor heat exchanger, and a compression An air conditioner having a refrigerant circuit including a hot gas bypass circuit that connects a suction side and a discharge side of a machine, and a hot gas bypass circuit opening and closing unit that is provided on the hot gas bypass circuit and opens and closes the hot gas bypass circuit The pressure equivalent saturation temperature detection means, a plurality of indoor units, a plurality of temperature detection means, and a control unit are provided. The pressure equivalent saturation temperature detecting means detects the pressure equivalent saturation temperature of the suction side pressure of the compressor. Each of the plurality of indoor units accommodates an indoor heat exchanger and can be thermo-ON / OFF independently of each other. The plurality of temperature detection means respectively detect the temperatures of the plurality of rooms that receive air conditioning by the indoor unit. Then, the control unit opens the hot gas bypass circuit opening / closing unit at the time of starting the compressor, and then the pressure equivalent saturation temperature of the suction side pressure is set to a plurality of indoor temperatures subjected to air conditioning by the indoor unit in the thermo-on state. The hot gas bypass circuit opening / closing section is closed when the temperature is lower than the minimum indoor temperature or lower than the indoor temperature.

  In this air conditioner, the hot gas bypass circuit opening / closing part is opened when the compressor is started, and the saturation temperature corresponding to the pressure of the suction side pressure is within the temperature of a plurality of rooms subjected to air conditioning by the indoor unit in the thermo-on state. Closed when the temperature is below the minimum indoor temperature or below the indoor temperature. For this reason, while suppressing liquid back | bag, the time which a hot gas bypass circuit opening-closing part is put into an open state can be suppressed short, As a result, the discomfort of the user by generation | occurrence | production of a refrigerant | coolant sound can be suppressed.

  According to a fifth aspect of the present invention, there is provided a control method for an air conditioner comprising a compressor, an outdoor heat exchanger, a first expansion valve, a first indoor heat exchanger, and a hot that connects a suction side and a discharge side of the compressor. A control method for an air conditioner comprising a refrigerant circuit including a gas bypass circuit and a hot gas bypass circuit opening / closing unit provided on the hot gas bypass circuit to open and close the hot gas bypass circuit, the hot gas bypass circuit opening step; A wet state determination step and a hot gas bypass circuit closing step. In the hot gas bypass circuit opening step, the hot gas bypass circuit opening / closing section is opened when the compressor is started. In the wet state determination step, the wet state of the refrigerant on the suction side of the compressor is determined. In the hot gas bypass circuit closing step, the hot gas bypass circuit opening / closing unit is closed based on the determination result of the wet state of the refrigerant.

  In this air conditioner control method, the hot gas bypass circuit opening / closing section that is opened when the compressor is started is closed based on the determination result of the wet state of the refrigerant on the suction side of the compressor. That is, the closing timing of the hot gas bypass circuit opening / closing unit, which has been conventionally determined by time, is determined based on the determination result of the wet state. For this reason, while suppressing liquid back | bag, the time which a hot gas bypass circuit opening-closing part is put into an open state can be suppressed short, As a result, the discomfort of the user by generation | occurrence | production of a refrigerant | coolant sound can be suppressed.

In the air conditioner according to the first aspect of the invention, it is possible to suppress the liquid back and to shorten the time for which the hot gas bypass circuit opening / closing part is kept open. As a result, the user feels uncomfortable due to the generation of refrigerant sound. Can be suppressed.
In the air conditioner according to the second aspect of the invention, the wet state of the refrigerant on the suction side of the compressor is determined based on the pressure equivalent saturation temperature of the suction side pressure and the indoor temperature. Thereby, the closing timing of a hot gas bypass circuit opening / closing part can be determined appropriately.

In the air conditioner according to the third aspect of the present invention, the hot gas bypass circuit opening / closing part is closed when the pressure equivalent saturation temperature of the suction side pressure is lower than the room temperature or lower than the room temperature. Thereby, the liquid back | bag to a compressor can be suppressed appropriately.
In the air conditioner according to the fourth aspect of the invention, the liquid back can be suppressed, and the time for which the hot gas bypass circuit opening / closing part is kept open can be shortened. Can be suppressed.

  In the control method of the air conditioner according to the fifth aspect of the invention, it is possible to suppress the liquid back and to shorten the time for which the hot gas bypass circuit opening / closing part is kept open. Discomfort can be suppressed.

<Configuration>
FIG. 1 is a block diagram showing a configuration of an air conditioner 100 according to an embodiment of the present invention. The air conditioner 100 is an air conditioner that cools and heats a house, and is a so-called multi-type air conditioner in which a plurality of indoor units 2 a-2 i are connected to one outdoor unit 1. The indoor units 2a-2i are connected to the outdoor unit 1 via branch units BP1-BP3. In the present embodiment, a plurality of branch units BP1-BP3 are connected to one outdoor unit 1, and three branch units BP1-BP3 from the first branch unit BP1 to the third branch unit BP3 are connected. ing. A plurality of indoor units are connected to each branch unit BP1-BP3. Three indoor units 2a-2c from the first indoor unit 2a to the third indoor unit 2c are connected to the first branch unit. Three indoor units 2d-2f from the fourth indoor unit 2d to the sixth indoor unit 2f are connected to the second branch unit BP2. Three indoor units 2g-2i from the seventh indoor unit 2g to the ninth indoor unit 2i are connected to the third branch unit BP3. A refrigerant circuit diagram showing the configuration of the air conditioner 100 is shown in FIG.

<Configuration of outdoor unit>
The refrigerant circuit on the outdoor unit 1 side includes a compressor 10, a switching mechanism 11, an oil separator 12, a hot gas bypass circuit 13, an outdoor heat exchanger 14, an outdoor expansion valve 15, a receiver 16, a bridge circuit 17, a cooler 18, A supercooling bypass circuit 19, a gas vent circuit 20, a pressure equalizing circuit 21 and the like are included.

The compressor 10 is an electric motor-driven scroll compressor, and is a device for compressing the sucked gas refrigerant. The compressor 10 can variably control the operation frequency by an inverter.
The switching mechanism 11 is a mechanism that switches the direction of the refrigerant flow when switching between the operation by the cooling cycle and the operation by the heating cycle, and the gas side of the discharge pipe 22, the suction pipe 23, and the outdoor heat exchanger 14 of the compressor 10. And a four-way switching valve connected to the gas side of the indoor heat exchanger 3a-3c. The switching mechanism 11 connects the discharge side of the compressor 10 and the gas side of the outdoor heat exchanger 14 and connects the suction side of the compressor 10 and the gas shut-off valve 24 during operation in the cooling cycle (switching in FIG. 1). (Refer to the solid line of the mechanism 11. Hereinafter, this state is referred to as “cooling cycle side state”.) Moreover, the switching mechanism 11 can connect the discharge side of the compressor 10 and the gas shut-off valve 24 and can connect the suction side of the compressor 10 and the gas side of the outdoor heat exchanger 14 during operation by the heating cycle. (Refer to the broken line of the switching mechanism 11 in FIG. 1. Hereinafter, this state is referred to as a “heating cycle side state”).

The oil separator 12 is a mechanism for separating the lubricating oil contained in the refrigerant on the discharge side of the compressor 10 and returning it to the suction side of the compressor 10, and is provided in the middle of the discharge pipe 22.
The hot gas bypass circuit 13 is a circuit that connects the discharge pipe 22 and the suction pipe 23 of the compressor 10, and connects the suction side and the discharge side of the compressor 10. The hot gas bypass circuit 13 has one end connected to the oil separator 12 and the other end connected to the suction pipe 23. Accordingly, the hot gas bypass circuit 13 functions as an oil recovery circuit for returning the refrigerant discharged from the compressor 10 to the suction side and returning the oil component separated by the oil separator 12 to the suction side of the compressor 10. can do. Further, on the hot gas bypass circuit 13, a hot gas bypass circuit opening / closing part 25 and a capillary 26 for reducing the pressure of the refrigerant passing therethrough are provided. The hot gas bypass circuit opening / closing unit 25 is an electromagnetic valve that opens and closes the hot gas bypass circuit 13, and can close and open the flow of the refrigerant flowing through the hot gas bypass circuit 13.

  The outdoor heat exchanger 14 is a cross fin tube type heat exchanger, and is a device for exchanging heat with a refrigerant using air as a heat source. The outdoor unit 1 includes an outdoor blower 27 that generates an air flow through the outdoor heat exchanger 14 in order to take in outdoor air into the outdoor unit 1 and send it out. The outdoor fan 27 exchanges heat between outdoor air and the refrigerant flowing through the outdoor heat exchanger 14 by passing air through the outdoor heat exchanger 14.

The outdoor expansion valve 15 is connected to the liquid side of the outdoor heat exchanger 14 and is positioned between a bridge circuit 17 described later and the outdoor heat exchanger 14. The outdoor expansion valve 15 is a motor-operated valve that can depressurize the refrigerant passing therethrough, and can control the flow rate of the refrigerant passing therethrough by controlling the opening of the valve.
The receiver 16 is a container for temporarily storing the refrigerant flowing between the outdoor heat exchanger 14 and the indoor heat exchangers 3a to 3c, and can store the liquid refrigerant. The receiver 16 has an inlet at the top of the container and an outlet at the bottom of the container. The inlet of the receiver 16 is connected to the outdoor expansion valve 15 and the liquid closing valve 28 via the bridge circuit 17. The outlet of the receiver 16 is connected to the outdoor expansion valve 15 and the liquid closing valve 28 via the cooler 18 and the bridge circuit 17. The receiver 16 is located between the outdoor heat exchanger 14 and the indoor heat exchanger 3a-3c and on the opposite side of the compressor 10, and is connected between the indoor expansion valve 5a-5c and the outdoor heat exchanger 14. Located between. The receiver 16 is located upstream of the indoor expansion valves 5a-5c and downstream of the outdoor heat exchanger 14 in the refrigerant flow direction in the cooling cycle.

  The bridge circuit 17 is a circuit composed of four check valves 17a-17d connected between the outdoor expansion valve 15 and the receiver 16, and includes an outdoor heat exchanger 14 and an indoor heat exchanger 3a-3c. The refrigerant flowing between them flows into the receiver 16 from the inlet of the receiver 16 in both cases of flowing into the receiver 16 from the outdoor heat exchanger 14 side and flowing into the receiver 16 from the indoor heat exchanger 3a-3c side. The refrigerant flows in and has a function of returning the refrigerant between the outdoor heat exchanger 14 and the indoor heat exchangers 3a-3c from the outlet of the receiver 16. Specifically, the check valve 17a is connected so as to guide the refrigerant flowing from the indoor heat exchanger 3a-3c toward the outdoor heat exchanger 14 to the inlet of the receiver 16. The check valve 17b is connected to guide the refrigerant flowing from the outdoor heat exchanger 14 toward the indoor heat exchanger 3a-3c to the inlet of the receiver 16. The check valve 17c is connected so that the refrigerant flowing from the outlet of the receiver 16 through the cooler 18 can flow to the indoor heat exchanger 3a-3c side. The check valve 17d is connected so that the refrigerant flowing from the outlet of the receiver 16 through the cooler 18 can flow to the outdoor heat exchanger 14 side. Thereby, the refrigerant flowing between the outdoor heat exchanger 14 and the indoor heat exchangers 3a-3c always flows in from the inlet of the receiver 16 and flows out of the outlet of the receiver 16, and flows out of the outdoor heat exchanger 14 and the indoor heat. It is returned to the exchanges 3a-3c.

The cooler 18 is a double-pipe heat exchanger, and is provided to cool the refrigerant condensed in the outdoor heat exchanger 14 and sent to the indoor heat exchangers 3a to 3c. The cooler 18 is connected between the receiver 16 and the bridge circuit 17.
The subcooling bypass circuit 19 is provided so as to branch a part of the refrigerant sent from the outdoor heat exchanger 14 to the indoor heat exchanger 3a-3c and return it to the suction side of the compressor 10. Specifically, the supercooling bypass circuit 19 is branched from a circuit portion that connects the outlet of the receiver 16 and the check valve 17d of the bridge circuit 17, passes through the cooler 18, and joins the suction pipe 23 of the compressor 10. So connected. The supercooling bypass circuit 19 is provided with a supercooling bypass expansion valve 29 for adjusting the flow rate of the refrigerant flowing through the supercooling bypass circuit 19. The subcooling bypass expansion valve 29 is an electric valve for adjusting the flow rate of the refrigerant flowing through the cooler 18. Thereby, the refrigerant flowing through the refrigerant circuit 10 is cooled by the refrigerant returned from the outlet of the supercooling bypass expansion valve 29 to the suction pipe 23 of the compressor 10 in the cooler 18.

  One end of the gas vent circuit 20 is connected to the upper end of the receiver 16, and the other end is connected to the supercooling bypass circuit 19, and merges with the suction pipe 23 of the compressor 10. The degassing circuit 20 is a circuit for sending the gaseous refrigerant in the receiver 16 to the suction side of the compressor 10. In addition, a degas circuit opening / closing section 30 is provided on the degas circuit 20. The degassing circuit opening / closing unit 30 is an electromagnetic valve that opens and closes the degassing circuit 20, and can close and open the flow of the refrigerant flowing through the degassing circuit 20.

  One end of the pressure equalizing circuit 21 is connected between the gas vent circuit opening / closing part 30 and the receiver 16 in the gas vent circuit 20, and the other end is connected to the discharge pipe 22. Further, the pressure equalizing circuit 21 is provided with a pressure equalizing check valve 31 that allows only the refrigerant to flow from one end to the other end. This pressure equalization circuit 21 is used to prevent the receiver 16 from bursting by allowing the gas refrigerant to escape when the outside air temperature rises abnormally while the air conditioner 100 is stopped and the pressure of the receiver 16 becomes too high. Is.

<Configuration of indoor unit>
The plurality of indoor units 2a-2c are respectively arranged on the wall surface of the room, the ceiling, etc., and blow out conditioned air into the room. The indoor units 2a-2c may be arranged in different rooms, or may be arranged at different positions in the same room. The indoor units 2a-2c can be thermo-ON / OFF and start / stop operation independently, and the operation state can be switched for each indoor unit 2a-2c. The plurality of indoor units 2a-2c are connected to the outdoor unit 1 via the first branch unit BP1, and the refrigerant sent from the outdoor unit 1 is branched in the first branch unit BP1, and each indoor heat exchanger 3a. -3c. In addition, the refrigerant that has flowed through each of the indoor heat exchangers 3a to 3c joins again in the first branch unit BP1 and is sent to the outdoor unit 1.

The first indoor unit 2a includes a first indoor heat exchanger 3a and a first indoor blower 4a. The first indoor heat exchanger 3a performs heat exchange between the refrigerant flowing inside and the air. The 1st indoor fan 4a produces | generates the flow of the air which blows off from the inside of the 1st indoor unit 2a, and sends the air which heat-exchanged with the refrigerant | coolant which flows through the 1st indoor heat exchanger 3a indoors.
The second indoor unit 2b includes a second indoor heat exchanger 3b and a second indoor blower 4b. The second indoor heat exchanger 3b performs heat exchange between the refrigerant flowing inside and the air. The 2nd indoor air blower 4b produces | generates the flow of the air blown out from the inside of the 2nd indoor unit 2b, and sends the air which heat-exchanged with the refrigerant | coolant which flows through the 2nd indoor heat exchanger 3b indoors.

The third indoor unit 2c includes a third indoor heat exchanger 3c and a third indoor fan 4c. The third indoor heat exchanger 3c performs heat exchange between the refrigerant flowing inside and the air. The 3rd indoor fan 4c produces | generates the flow of the air which blows off from the inside of the 3rd indoor unit 2c, and sends the air which heat-exchanged with the refrigerant | coolant which flows through the 3rd indoor heat exchanger 3c indoors.
The first indoor heat exchanger 3a, the second indoor heat exchanger 3b, and the third indoor heat exchanger 3c are provided in parallel in the refrigerant circuit, and are connected to the first branch unit BP1.

The other indoor units 2d-2i have the same configuration as described above.
<Branch unit configuration>
The first branch unit BP1 branches the refrigerant sent from one outdoor unit 1 and distributes the refrigerant to the plurality of indoor units 2a-2c, and merges the refrigerant sent from the plurality of indoor units 2a-2c, This unit is sent to the outdoor unit 1.

  The first branch unit BP1 has a liquid branch pipe 32 branched into three and a gas branch pipe 33 branched into three. The liquid branch pipe 32 connects the liquid closing valve 28 of the outdoor unit 1 to the liquid side of the first indoor heat exchanger 3a, the second indoor heat exchanger 3b, and the third indoor heat exchanger 3c. The gas branch pipe 33 connects the gas shut-off valve 24 of the outdoor unit 1 to the gas side of the first indoor heat exchanger 3a, the second indoor heat exchanger 3b, and the third indoor heat exchanger 3c. Between the branch point of the liquid branch pipe 32 and each indoor heat exchanger 3a-3c, a first indoor expansion valve 5a (first indoor expansion valve), a second indoor expansion valve 5b, and a third indoor expansion valve 5c are provided. The indoor expansion valves 5a-5c are provided in parallel in the refrigerant circuit. Therefore, a refrigerant circuit on the first indoor unit 2a side made up of the first indoor heat exchanger 3a and the first indoor expansion valve 5a, and a second room made up of the second indoor heat exchanger 3b and the second indoor expansion valve 5b. The refrigerant circuit on the side of the unit 2b and the refrigerant circuit on the side of the third indoor unit 2c composed of the third indoor heat exchanger 3c and the third indoor expansion valve 5c are parallel to each other via the first branch unit BP1. Is connected to the refrigerant circuit on the side. Each of the first indoor expansion valve 5a, the second indoor expansion valve 5b, and the third indoor expansion valve 5c is an electric valve that can depressurize the refrigerant that passes through the first indoor expansion valve 5a. Can be controlled. The first indoor expansion valve 5a, the second indoor expansion valve 5b, and the third indoor expansion valve 5c can be independently controlled.

An electric valve 6 for pressure adjustment is provided between the liquid branch pipe 32 and the first gas liquid branch pipe.
The other branch units BP2 and BP3 have the same configuration as described above.
<Various sensors>
The air conditioner 100 includes various sensors 40-51 such as a pressure sensor and a temperature sensor provided in each part. Hereinafter, the various sensors 40-51 will be described with reference to FIG.

  A suction side pressure sensor 40 (corresponding to pressure) for detecting a pressure of a low-pressure gas refrigerant flowing on the suction side of the compressor 10 (hereinafter referred to as “suction side pressure Pe”) is provided in the suction pipe 23 of the compressor 10. Saturation temperature detection means) is provided. The discharge pipe 22 of the compressor 10 is provided with a discharge side pressure sensor 41 for detecting the pressure of the high-pressure gas refrigerant flowing on the discharge side of the compressor 10 (hereinafter referred to as “discharge side pressure Pc”). ing. The discharge pipe 22 of the compressor 10 is provided with a high pressure switch 42 for detecting an excessive increase in the pressure of the high pressure gas refrigerant. The discharge pipe 22 of the compressor 10 is provided with a discharge side temperature sensor 43 for detecting the discharge side temperature Td of the refrigerant on the discharge side of the compressor 10. The suction pipe 23 of the compressor 10 is provided with a compressor. A suction side temperature sensor 44 for detecting the suction side temperature Ts of the ten suction side refrigerants is provided.

An outdoor air temperature sensor 45 for detecting the temperature Ta of the outdoor air is provided at the air inlet of the outdoor fan 27 of the outdoor unit 1. The outdoor heat exchanger 14 is provided with an outdoor heat exchanger temperature sensor 46 for detecting the refrigerant temperature Tb corresponding to the refrigerant condensation temperature during the cooling operation and corresponding to the refrigerant evaporation temperature during the heating operation. Yes.
Further, at the junction of the supercooling bypass circuit 19 with the suction side of the compressor 10, the temperature Tsh of the refrigerant flowing through the supercooling bypass circuit 19 on the outlet side of the cooler 18 is detected to detect the degree of superheat. A supercooling bypass circuit temperature sensor 47 is provided. The supercooling bypass circuit temperature sensor 47 can detect the degree of superheat on the suction side of the compressor 10.

  An indoor temperature sensor 48 (first indoor temperature detection means) for detecting the temperature Tr of the indoor air is provided at each of the air suction ports of the indoor fans 4a-4c of the indoor units 2a-2i. The indoor temperature sensor 48 can detect the temperature of the room that receives air conditioning by the indoor units 2a-2i. The indoor heat exchangers 3a to 3c are each provided with an indoor heat exchanger temperature sensor 49 for detecting a refrigerant temperature Tn corresponding to the evaporation temperature during the cooling operation and corresponding to the condensation temperature during the heating operation. ing.

  Each branch of the gas branch pipe 33 in the first branch unit BP1 is provided with a gas pipe temperature sensor 50 for detecting the temperature of the refrigerant passing through the inside. The gas pipe temperature sensor 50 is provided between the indoor expansion valves 5a-5c and the indoor heat exchangers 3a-3c. Each branch of the liquid branch pipe 32 is provided with a liquid pipe temperature sensor 51 for detecting the temperature of the refrigerant passing through the inside. The liquid pipe temperature sensor 51 is provided between the indoor heat exchangers 3a to 3c and the branch point of the liquid branch pipe.

In addition, about the various sensors 48-51 with which each indoor unit 2a-2c and 1st branch unit BP1 were equipped, the same code | symbol is attached | subjected to the sensor of the same function for the simplification.
In FIG. 2, the description of the second branch unit BP2 and the third branch unit BP3 and the indoor units 2d-2i connected to the branch units BP2 and BP3 is omitted, but the first branch unit BP1 is omitted. Various sensors similar to the indoor units 2a-2c connected to the first branch unit BP1 are provided.

<Control part>
As shown in FIG. 3, the air conditioner 100 controls each device such as the compressor 10 and the switching mechanism 11 on the basis of signals detected by the various sensors 40 to 51 and performs air conditioning such as cooling operation and heating operation. The control part 60 for performing a driving | operation is provided.
The control unit 60 is mainly composed of a microcomputer and a memory, is connected so as to receive the input signals of the various sensors 40-51 described above, and receives a command signal input to the operation terminal 61. it can. The controller 60 can control the various devices 4a-4c, 10, 11, 27, the valves 5a-5c, 15, 29, and the various opening / closing units 25, 30 based on these input signals and command signals. It is connected to the. And this control part 60 controls various apparatus 4a-4c, 10,11,27, valves 5a-5c, 15,29, various opening-and-closing parts 25 and 30, and performs air-conditioning operation, such as cooling operation and heating operation. It can be carried out. In FIG. 2, a plurality of components such as valves 5a-5c, various opening / closing sections 25 and 30, indoor blowers 4a-4c, and indoor expansion valves 5a-5c are collectively displayed as one block. Each component can be controlled individually.

Hereinafter, various controls performed by the control unit 60 will be described.
<Control performed by the control unit>
The control unit 60 can switch between the operation by the cooling cycle and the operation by the heating cycle. Examples of the operation by the cooling cycle include a cooling operation, a defrost operation, and an oil recovery operation. There is a heating operation as an operation by the heating cycle. Hereinafter, the refrigerant flow in the indoor units 2a-2i will be described only for the first indoor unit 2a to the third indoor unit 2c, but the same applies to the other indoor units 2d-2i.

(Heating operation control)
In the heating operation control, a heating operation is performed in which the indoor heat exchangers 3a to 3c serve as a condenser. In this heating operation control, the switching mechanism 11 is in a state indicated by a broken line in FIG. The outdoor expansion valve 15, the outdoor blower 27, the indoor expansion valves 5a-5c of the indoor units 2a-2c in the operating state, and the indoor blowers 4a-4c are controlled according to the operating conditions of the indoor units 2a-2c. The hot gas bypass circuit opening / closing part 25 is closed, and the supercooling bypass expansion valve 29 is appropriately opened and closed. The degassing circuit opening / closing part 30 is appropriately opened and closed. In this state, the refrigerant circulates through the refrigerant circuit, so that the indoor heat exchangers 3a-3c of the indoor units 2a-2c in the operating state function as a condenser and the outdoor heat exchanger 14 functions as an evaporator. Thereby, the heated air is blown out indoors and a heating operation is performed.

In the heating operation as described above, the refrigerant circulates through the refrigerant circuit as follows. Note that. Here, description will be made assuming that the first indoor unit 2a is in the thermo-on state, and the second indoor unit 2b and the third indoor unit 2c are in the thermo-off state or the operation stopped state.
First, the refrigerant discharged from the compressor 10 is sent from the switching mechanism 11 to the first indoor heat exchanger 3a through the gas closing valve 24 and the first branch unit BP1. In the first indoor heat exchanger 3a, the refrigerant radiates heat to the indoor air and condenses. The refrigerant condensed in the first indoor heat exchanger 3a flows into the receiver 16 through the first indoor expansion valve 5a, the liquid closing valve 28, and the bridge circuit 17. The refrigerant that has flowed out of the receiver 16 is depressurized by the outdoor expansion valve 15, passes through the bridge circuit 17, and is sent to the outdoor heat exchanger 14. In the outdoor heat exchanger 14, the refrigerant absorbs heat from the outdoor air and evaporates. The refrigerant evaporated in the outdoor heat exchanger 14 is sucked into the compressor 10 through the switching mechanism 11. The compressor 10 compresses the sucked refrigerant and discharges it again.

In the second indoor unit 2b and the third indoor unit 2c that are stopped among the indoor units 2a-2c, the corresponding second indoor expansion valve 5b and third indoor expansion valve 5c are opened with a slight opening. Inflow of refrigerant is restricted.
The control unit 60 performs capacity control by controlling the frequency of the compressor 10, the opening degree of the outdoor expansion valve 15, and the like according to the change in the operating state of each indoor unit 2a-2c.

(Cooling operation control)
During the cooling operation control, a cooling operation is performed in which the indoor heat exchangers 3a to 3c serve as an evaporator. During the cooling operation control, the switching mechanism 11 is in a state indicated by a solid line in FIG. The outdoor expansion valve 15 is fully opened, and the outdoor blower 27, the indoor expansion valves 5a-5c and the indoor blowers 4a-4c of the indoor units 2a-2c in the operating state are controlled according to the operating conditions of the indoor units 2a-2c, and the like. The The hot gas bypass circuit opening / closing part 25 and the supercooling bypass expansion valve 29 are appropriately opened and closed. The degassing circuit opening / closing part 30 is appropriately opened and closed. In this state, the refrigerant circulates through the refrigerant circuit, so that the indoor heat exchangers 3a-3c of the indoor units 2a-2c in the operating state function as an evaporator and the outdoor heat exchanger 14 functions as a condenser. Thereby, the cooled air is blown out into the room, and the cooling operation is performed.

In the cooling operation as described above, the refrigerant circulates through the refrigerant circuit as follows. Note that. Here, description will be made assuming that the first indoor unit 2a is in the thermo-on state, and the second indoor unit 2b and the third indoor unit 2c are in the thermo-off state or the operation stopped state.
First, the refrigerant discharged from the compressor 10 is sent from the switching mechanism 11 to the outdoor heat exchanger 14. In the outdoor heat exchanger 14, the refrigerant dissipates heat to the outdoor air and condenses. The refrigerant condensed in the outdoor heat exchanger 14 flows into the receiver 16 through the outdoor expansion valve 15 and the bridge circuit 17. The refrigerant flowing out from the receiver 16 passes through the liquid closing valve 28, is depressurized by the first indoor expansion valve 5a in the first branch unit BP1, and is sent to the first indoor heat exchanger 3a. In the first indoor heat exchanger 3a, the refrigerant absorbs heat from the indoor air and evaporates. The refrigerant evaporated in the first indoor heat exchanger 3a is sucked into the compressor 10 through the gas closing valve 24 and the switching mechanism 11. The compressor 10 compresses the sucked refrigerant and discharges it again.

In the second indoor unit 2b and the third indoor unit 2c that are stopped among the indoor units 2a-2c, the corresponding second indoor expansion valve 5b and third indoor expansion valve 5c are fully closed, and the refrigerant Inflow is restricted.
The control unit 60 performs capacity control by controlling the frequency of the compressor 10, the opening degree of the outdoor expansion valve 15, and the like according to the change in the operating state of each indoor unit 2a-2c.

(Compressor frequency control)
Next, frequency control of the compressor 10 will be described.
In the start-up control of the compressor 10, the control unit 60 increases the frequency of the compressor 10 stepwise until the difference between the discharge side pressure Pc and the suction side pressure Pe exceeds a predetermined value. In addition, when changing the frequency of the compressor 10, the control part 60 changes in steps for every predetermined interval. For example, if the minimum operating frequency of the compressor 10 is 52 Hz and this is the first level, the frequency of each level is a predetermined interval such that the second level = 57 Hz, the third level = 62 Hz, and the fourth level = 68 Hz. The frequency of the compressor 10 increases or decreases in units of this level. The difference in frequency set for each level is not necessarily limited to the same value, but is an approximate value. A higher frequency is set for a higher level.

  When the difference between the discharge side pressure Pc and the suction side pressure Pe exceeds a predetermined value, the normal control of the compressor 10 is performed. In this normal control, the control unit 60 determines the magnitude of the capacity request, and calculates the frequency change amount according to the capacity demand and the frequency of the compressor 10 at that time. As shown in FIG. 3, the control unit 60 includes a total ability value acquisition unit 62, a change amount determination unit 63, a frequency change unit 64, and the like. Hereinafter, the normal control of the compressor 10 will be described based on the control flow shown in FIG.

  First, in the first step S1 (total capacity value acquisition step), the total capacity value acquisition means 62 acquires the total capacity value of the indoor units 2a-2i in the thermo-on state among the plurality of indoor units 2a-2i. The indoor units 2a-2i store respective capability values, and the total capability value acquisition unit 62 calculates the capability values of the indoor units in the thermo-on state based on the capability values stored in the indoor units 2a-2i. Add the total ability value.

  Next, in the second step S2 (change amount determination step), the change amount determination means 63 determines the change amount of the frequency of the compressor 10 according to the total capacity value and the current frequency of the compressor 10, and the third step Proceed to S3 (frequency change step). As shown in FIG. 5 and FIG. 6, the change amount determining means 63 includes a capability value category in which the total capability value of the indoor units 2a-2i is divided into a plurality of ranges, and a change determined for each capability value category and the current frequency. The change amount determination table including the amount value is stored, and the change amount of the frequency of the compressor 10 is determined by the change amount determination table. In the present embodiment, the total capacity value division has four ranges from the first range to the fourth range. Note that the value of the change amount on the change amount determination table is described by the change width of the number of levels. For example, in the case of “+2”, the frequency of the compressor 10 is changed to a frequency that is two steps higher. In the change amount determination table, a larger change amount is set for a capability value category having a larger total capability value, and a smaller change amount is set for a larger current frequency. Therefore, the change amount is determined to be larger as the total capacity value is larger, and the change amount is determined to be smaller as the current frequency is larger. 5 is a change amount determination table during cooling operation, and FIG. 6 is a change amount determination table during heating operation. In the air conditioner 100, different change amount determination tables are used for the cooling operation and the heating operation.

In 3rd step S3, the frequency change means 64 changes the frequency of the compressor 10 for every change amount determined by the change amount determination means 63 at the time of starting of the air conditioner 100, and progresses to 4th step S4. The frequency change amount at this time is the change amount determined by the change amount determining means 63 described above.
Hereinafter, in the normal control of the compressor 10 during the cooling operation of the air conditioner 100, the first indoor unit 2a, the second indoor unit 2b, and the third indoor unit 2c are in the thermo-on state, and the other indoor units 2d-2i are stopped. A specific example will be described. The capacity values of the first indoor unit 2a, the second indoor unit 2b, and the third indoor unit 2c are 28, 30, and 40, respectively. Further, it is assumed that the compressor 10 is driven at a minimum operating frequency of 77 Hz.

  First, the total capacity value acquisition unit 62 calculates the total capacity value of the first indoor unit 2a, the second indoor unit 2b, and the third indoor unit 2c. Here, ΣS = 98 is calculated. ΣS is the total ability value. Based on this total capacity value, the change amount determination means 63 refers to the change amount determination table during cooling operation in FIG. 5 to determine the frequency change amount. Here, since the current frequency is 77 Hz and the total capability value is 98, the change amount is determined to be “+2”. The frequency changing unit 64 increases the frequency of the compressor 10 from the sixth level by two steps based on the change amount to the eighth level. Specifically, the frequency of the compressor 10 increases from 77 Hz to 88 Hz. The frequency change is repeated every predetermined time until the evaporation pressure or the condensation pressure reaches the target value.

When the number of indoor units in the thermo-on state changes during the process, the amount of frequency change is determined according to the total capacity value after the change.
(Start-up control of outdoor expansion valve)
With the change in the frequency of the compressor 10 as described above, the opening degree of the outdoor expansion valve 15 is also adjusted. Hereinafter, activation control of the outdoor expansion valve 15 when the air conditioner 100 is activated will be described.

As shown in FIG. 3, the control unit 60 has an expansion valve opening degree determining means 65 and an expansion valve opening degree changing means 66.
The expansion valve opening determining means 65 calculates the opening of the outdoor expansion valve 15 by the following calculation formula.
EV = EV ₀ + w (SH) × f (Ft ′ / Ft)
EV is an outdoor expansion valve opening degree, and EV ₀ is a predetermined initial opening degree. w (SH) is a weighting function determined by the suction superheat degree SH, and f (Ft ′ / Ft) is an opening change amount function determined by the frequency change rate Ft ′ / Ft. Ft is a value determined by the frequency of the compressor 10 before the change, and Ft ′ is a value determined by the frequency of the compressor 10 after the change. Further, the suction superheat degree SH is calculated from SH = Ts−Teg, where Teg is the equivalent saturated gas temperature of the suction side gas refrigerant. Therefore, the expansion valve opening degree determining means 65 determines the opening degree of the outdoor expansion valve 15 based on the frequency change rate Ft ′ / Ft of the compressor 10 and the suction superheat degree SH on the suction side of the compressor 10.

The weight function w (SH) for increasing the opening of the outdoor expansion valve 15 is determined as follows.
When SH ≦ b, w (SH) = 1.0
When SH> b w (SH) = c (c> 1)
b and c are predetermined constants.

Therefore, when the opening degree of the outdoor expansion valve 15 is increased during the start control of the heating operation, if the suction superheat degree exceeds a predetermined value, the weight function becomes a value larger than 1, and the outdoor expansion valve 15 is opened. The degree of change increases more than when the suction superheat degree is small. In addition, not only at the time of starting control of heating operation, but also at the time of starting control of cooling operation, a weight function may be set similarly to the above.
The expansion valve opening changing means 66 changes the opening of the outdoor expansion valve 15 to the above opening determined by the expansion valve opening determining means 65.

As described above, the activation control of the outdoor expansion valve 15 is performed.
Note that the controller 60 can also calculate the opening degree by the same calculation formula as described above in the startup control of the supercooling bypass expansion valve 29 at the startup of the cooling operation of the air conditioner 100.
(Start-up control of hot gas bypass circuit opening / closing part)
Next, startup control of the hot gas bypass circuit opening / closing unit 25 when the air conditioner 100 is started will be described. The control unit 60 opens the hot gas bypass circuit opening / closing unit 25 when the compressor 10 is started up, determines the wet state of the refrigerant on the suction side of the compressor 10, and determines the hot gas based on the determination result of the wet state of the refrigerant The bypass circuit opening / closing part 25 is closed. Hereinafter, a description will be given with reference to FIG.

First, the compressor 10 is started in 11th step S11. The compressor 10 is controlled by the activation control as described above.
In addition, the hot gas bypass circuit opening / closing section 25 is opened in the twelfth step S12 (hot gas bypass circuit opening step) when the compressor 10 is started. Thereby, a part of the refrigerant discharged from the compressor 10 is returned to the suction side, and liquid back in the compressor 10 can be prevented.

  Next, in a thirteenth step S13 (wet state determination step), determination of a wet state is performed. Here, the wet state of the refrigerant on the suction side of the compressor 10 is determined based on the pressure equivalent saturation temperature Te of the suction side pressure Pe of the compressor 10 and the indoor temperature Tmin. That is, it is determined whether Te <Tmin is satisfied. The room temperature Tmin is the minimum value among the room temperatures detected by the indoor unit in the thermo-on state. When Te <Tmin is satisfied, the process proceeds to the 14th step S14. If Te <Tmin is not satisfied, the thirteenth step S13 is repeated.

In the fourteenth step S14 (hot gas bypass circuit closing step), the hot gas bypass circuit opening / closing unit 25 is closed, and then the normal control is performed.
<Features>
(1)
In this air conditioner 100, the frequency control of the compressor 10 as described above is performed, and the amount of increase in the frequency of the compressor 10 is increased as the required supply capacity is increased. Conversely, the smaller the required supply capacity, the smaller the increase in frequency of the compressor 10. For this reason, frequency overshoot can be prevented and frequency hunting can be prevented. Thereby, the compressor 10 can be stably controlled when the compressor 10 is started. Moreover, the start-up performance of the air conditioner 100 is improved, and the comfort is improved. Furthermore, it is possible to supply capacity according to the load, and the follow-up performance of the control system to fluctuations in the number of indoor units to be operated is improved.

(2)
In the air conditioner 100, the activation control of the outdoor expansion valve 15 as described above is performed, and when the suction superheat degree is large, the increase amount of the opening degree of the outdoor expansion valve 15 is increased. Thereby, the followability of the opening degree control of the outdoor expansion valve 15 with respect to the increase in the frequency of the compressor 10 is improved, and the startup performance of the air conditioner 100 is improved.

(3)
In the air conditioner 100, the activation control of the hot gas bypass circuit opening / closing unit 25 as described above is performed. For this reason, compared with the case where it is judged only that the timing which closes the hot gas bypass circuit opening / closing part 25 has passed predetermined time, the time which has opened the hot gas bypass circuit opening / closing part 25 can be shortened. In addition, since suction overheating is grasped, the reliability of preventing liquid back can be improved.

<Other embodiments>
(1)
In the above embodiment, nine indoor units 2a-2i are connected to one outdoor unit 1, but the number of indoor units connected to one outdoor unit 1 is not limited to the above, More indoor units may be connected. Further, the number of branch units and the number of indoor units connected to one branch unit are not limited to the above.

(2)
In the above embodiment, the indoor units 2a-2i and the outdoor unit 1 are connected via the branch units BP1-BP3. However, the branch units BP1-BP3 are not provided and the indoor expansion valves 5a-5c are incorporated. The indoor units 2a-2i may be directly connected to the outdoor unit 1.
(3)
The total capacity value calculated in the start-up control of the compressor 10 only needs to indicate a load change accompanying a change in the number of indoor units in the thermo-on state. For example, even if it is the total number of indoor units in the thermo-on state Good.

(4)
In the above embodiment, the change amount determination table is referred to when determining the frequency change amount. However, the frequency change amount may be calculated by a predetermined calculation formula.
(5)
In the above embodiment, the condition for setting the weighting function w (SH) to the constant c is when SH> b is satisfied, but even if a conditional expression of SH ≧ b is used instead of this conditional expression. Good.

(6)
In the above embodiment, it is determined whether or not Te <Tmin is satisfied in the determination of the wet state, but a conditional expression of Te ≦ Tmin may be used instead of this condition. Also, other conditions may be used as long as the refrigerant flowing through the suction pipe 23 can be regarded as being superheated by suction.

(7)
In the above embodiment, a plurality of indoor units 2 a-2 i are connected to one outdoor unit 1. However, regarding the startup control of the outdoor expansion valve 15 and the startup control of the hot gas bypass circuit opening / closing unit 25, 1 This is also effective in an air conditioner in which only one indoor unit is connected to one outdoor unit.

  INDUSTRIAL APPLICABILITY The present invention has an effect of suppressing liquid back to the compressor and suppressing user discomfort due to generation of refrigerant sound, and is useful as an air conditioner.

The block diagram which shows the structure of an air conditioner. The refrigerant circuit diagram which shows the structure of an air conditioner. The control block diagram of an air conditioner. The flowchart of the starting control of a compressor. Change amount determination table during cooling operation. Change amount determination table during heating operation. The flowchart of starting control of a hot gas bypass circuit opening / closing part.

Explanation of symbols

2a First indoor unit 3a First indoor heat exchanger 5a First expansion valve (first indoor expansion valve)
DESCRIPTION OF SYMBOLS 10 Compressor 13 Hot gas bypass circuit 14 Outdoor heat exchanger 25 Hot gas bypass circuit opening / closing part 40 Suction side pressure sensor (pressure equivalent saturation temperature detection means)
48 Indoor temperature sensor (first indoor temperature detection means)
60 Control Unit 100 Air Conditioner

Claims (5)

An air conditioner including a refrigerant circuit including a compressor (10), an outdoor heat exchanger (14), a first expansion valve (5a), and a first indoor heat exchanger (3a),
A hot gas bypass circuit (13) connecting the suction side and the discharge side of the compressor (10);
A hot gas bypass circuit opening / closing section (25) provided on the hot gas bypass circuit (13) for opening and closing the hot gas bypass circuit (13);
When the compressor (10) is started, the hot gas bypass circuit opening / closing part (25) is opened, and then the wet state of the refrigerant on the suction side of the compressor (10) is determined, and the wet state of the refrigerant is determined. A control unit (60) for closing the hot gas bypass circuit opening and closing unit (25) based on the result;
An air conditioner (100) comprising: Pressure equivalent saturation temperature detecting means (40) for detecting the pressure equivalent saturation temperature of the suction side pressure of the compressor (10);
First indoor temperature detection means (48) for detecting the temperature of the room subject to air conditioning by the first indoor unit (2a) that houses the first indoor heat exchanger (3a);
Further comprising
The control unit (60) determines the wet state of the refrigerant on the suction side of the compressor (10) based on the pressure equivalent saturation temperature and the indoor temperature.
The air conditioner (100) according to claim 1. The control unit (60) closes the hot gas bypass circuit opening / closing unit (25) when the pressure equivalent saturation temperature is lower than the indoor temperature or lower than the indoor temperature.
The air conditioner (100) according to claim 2. A compressor (10), an outdoor heat exchanger (14), a plurality of indoor heat exchangers (3a-3c) provided in parallel to each other, and the indoor heat exchangers (3a-3c) are provided. A plurality of expansion valves (5a-5c), a hot gas bypass circuit (13) connecting the suction side and the discharge side of the compressor (10), and the hot gas bypass circuit (13) provided on the hot gas bypass circuit (13) An air conditioner (100) comprising a refrigerant circuit including a hot gas bypass circuit opening / closing part (25) for opening and closing a gas bypass circuit (13),
Pressure equivalent saturation temperature detecting means (40) for detecting the pressure equivalent saturation temperature of the suction side pressure of the compressor (10);
A plurality of indoor units (3a-3c) that house the indoor heat exchanger (3a-3c) and can be thermo-on / off independently of each other, and a plurality of indoors that receive air conditioning by the indoor units (3a-3c) A plurality of temperature detection means (48) for detecting the temperature of each,
When the compressor (10) is started, the hot gas bypass circuit opening / closing part (25) is opened, and then the pressure equivalent saturation temperature is subjected to air conditioning by the indoor units (2a-2c) in a thermo-on state. A control unit (60) for closing the hot gas bypass circuit opening / closing unit (25) when the temperature is lower than or lower than the minimum indoor temperature among the indoor temperatures;
An air conditioner (100) comprising: A compressor (10), an outdoor heat exchanger (14), a first expansion valve (5a), a first indoor heat exchanger (3a), and a suction side and a discharge side of the compressor (10); A refrigerant circuit including a hot gas bypass circuit (13) to be connected and a hot gas bypass circuit opening / closing part (25) provided on the hot gas bypass circuit (13) to open and close the hot gas bypass circuit (13) is provided. A control method for an air conditioner (100), comprising:
A hot gas bypass circuit opening step (S12) in which the hot gas bypass circuit opening and closing unit (25) is opened when the compressor (10) is started;
A wetting state determination step (S13) in which the wetting state of the refrigerant on the suction side of the compressor (10) is determined;
A hot gas bypass circuit closing step (14) in which the hot gas bypass circuit opening / closing part (25) is closed based on the determination result of the wet state of the refrigerant;
The control method of an air conditioner (100) provided with.

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