JP2001330331A - Refrigerant circuit of air conditioner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce costs by performing reliable control without causing pressure fluctuation to prevent temperature increase at a high-pressure part in heating operation and temperature decrease at a low-pressure part in cooling operation when capacity is higher in the rated operation of a compressor than that of an indoor heat exchanger. SOLUTION: In the refrigerant circuit of the air conditioner where an outdoor machine side refrigerant circuit including an accumulator 105 that is arranged in an outdoor machine 100, a compressor 101, a four-way switching valve 102, and an outdoor heat exchanger 103, is connected to an indoor heat exchanger 201 that is arranged in the indoor machine 200 are connected by liquid pipe side piping and gas pipe side piping, a discharge bypass circuit 194 that is provided with a discharge-suction electric motor operated valve 142 having a pressure reduction function and an opening/closing function is provided between the discharge pipe of the compressor 101 and the suction pipe of the accumulator 105.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a refrigerant circuit for an air conditioner, and more particularly to an outdoor unit-side refrigerant circuit including an accumulator, a compressor, a four-way switching valve, and an outdoor heat exchanger disposed in the outdoor unit. The present invention relates to a refrigerant circuit of an air conditioner that connects an indoor heat exchanger disposed in an indoor unit by a liquid pipe side pipe and a gas pipe side pipe.

[0002]

2. Description of the Related Art In a refrigerant circuit of an air conditioner, an accumulator, a compressor, a four-way switching valve, an outdoor heat exchanger disposed in an outdoor unit and an indoor heat exchanger disposed in an indoor unit are connected by refrigerant piping. Are connected and form a circulation path for the refrigerant. In such a refrigerant circuit of an air conditioner, the refrigerant circulation direction is controlled by a four-way switching valve so that the outdoor heat exchanger functions as a condenser during cooling and the indoor heat exchanger functions as an evaporator. In addition, at the time of heating, the refrigerant circulation direction is controlled by the four-way switching valve so that the outdoor heat exchanger functions as an evaporator and the indoor heat exchanger functions as a condenser.

[0003] In the case of a multi-type air conditioner in which a plurality of indoor units are connected to one outdoor unit, only one of the connected indoor units is operated, or an indoor unit in operation is operated. If the capacity of the compressor is small, the capacity of the compressor will be larger than that of the connected indoor heat exchanger, and there will be problems such as a pressure increase during heating in the high pressure section and freezing during cooling in the indoor heat exchanger. Becomes

In order to suppress the pressure rise in the high pressure section,
It is conceivable to provide a discharge bypass circuit between the discharge pipe of the compressor and the suction side of the accumulator. This discharge bypass circuit can be constituted by a solenoid valve and a capillary for capacity control. In this case, when the capacity of the indoor unit during operation is small, the capacity control can be performed by returning a part of the refrigerant discharged from the compressor to the accumulator side via the electromagnetic valve and the capillary.

[0005]

In the case where the displacement control is performed by the discharge pipe bypass circuit having the above-mentioned solenoid valve, the opening of the solenoid valve cannot be adjusted, and the pressure is adjusted to an arbitrary value. It is difficult to make it converge, and it is inevitable that pressure fluctuations occur when opening and closing the solenoid valve. In order to prevent such pressure fluctuation, a method as described in Japanese Patent Publication No. 9-2685463 has been proposed. Here, if the refrigerant discharge pressure or the compressor input current exceeds a predetermined value during the heating operation, the compressor operation frequency is reduced to the predetermined value, and the solenoid valve of the discharge bypass circuit is opened, so that the compressor input current or the refrigerant If the compressor operating frequency is lower than the predetermined value when the discharge pressure exceeds the predetermined value, the solenoid valve of the discharge bypass circuit is opened even after the compressor input current or the refrigerant discharge pressure returns to the normal value. It is configured to keep the state and continue control.

In the case of such a method, it is necessary to set each parameter in advance for each model and perform complicated control. Further, even if such control is performed, pressure fluctuations caused by opening and closing of the solenoid valve cannot be completely eliminated. Further, the problem that it is difficult to reduce the cost because the electromagnetic valve is used has not been solved at all. The present invention, in order to prevent the temperature rise of the high pressure section during the heating operation when the capacity at the time of the compressor rated operation is larger than the capacity of the indoor heat exchanger, to prevent the temperature decrease of the low pressure section during the cooling operation,
An object of the present invention is to enable reliable control without causing pressure fluctuation and reduce costs.

[0007]

A refrigerant circuit for an air conditioner according to the present invention includes an accumulator disposed in an outdoor unit.
An air conditioner that connects an outdoor unit-side refrigerant circuit including a compressor, a four-way switching valve, and an outdoor heat exchanger, and an indoor heat exchanger disposed in the indoor unit by a liquid pipe side pipe and a gas pipe side pipe. A discharge circuit including a discharge-suction electric valve having a pressure reducing function and an opening / closing function between a discharge pipe of a compressor and a suction pipe of an accumulator in order to control a capacity of the compressor. Is provided.

Here, a discharge bypass heat exchanger can be provided between the discharge pipe of the compressor and the discharge-suction electric valve of the discharge bypass circuit. This discharge bypass heat exchanger can be provided inside the accumulator, and can be a discharge bypass pipe inserted inside the accumulator. Further, the discharge bypass heat exchanger can be provided at the bottom of the accumulator.

Further, an oil separator is further provided between the discharge pipe of the compressor and the four-way switching valve, so that the oil return pipe of the oil separator and a part of the discharge bypass circuit can be shared.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS [Summary of the Invention] Embodiments considered from various viewpoints to achieve the object of the present invention will be described below. <First Embodiment: Providing Electric Valve in Discharge Bypass Circuit>
As shown in FIG. 1, the branch unit 30 is attached to the outdoor unit 100.
0A, 300B, and a plurality of indoor units 200A, 200B.
Consider the case where B ... are connected.

The outdoor unit 100 includes a compressor 101, a four-way switching valve 102, an outdoor heat exchanger 103, and an accumulator 105.
And so on. The discharge side of the compressor 101 is provided with a discharge side pressure protection switch 108 for detecting an abnormal rise in discharge pressure and a discharge pipe thermistor 109 for detecting discharge pipe temperature. A suction side pressure sensor 11 for detecting a suction pressure is provided on a suction side of the compressor 101.
0 is provided.

The outdoor unit 100 has an outdoor air thermistor 111 for detecting the outdoor air temperature and an outdoor heat exchange thermistor 11 for detecting the temperature of the outdoor heat exchanger 103.
2 are provided. Further, a fan 106 for sucking outside air and performing heat exchange between the sucked outside air and the refrigerant flowing inside the outdoor heat exchanger 103, and a fan motor 104 for rotating the fan 106 are provided. ing.

Refrigerant pipes leading from the outdoor unit 100 to the indoor unit include a liquid pipe connection port 114 leading out of the outdoor heat exchanger 103 and a gas pipe connection port 115 leading out through the four-way switching valve 102. And a liquid pipe closing valve 116 and a gas pipe closing valve 117 provided inside each connection port. Further, in the outdoor unit 100,
The refrigerant pipe located between the outdoor heat exchanger 103 and the liquid pipe closing valve 116 is referred to as a liquid pipe side pipe section 131, and the four-way switching valve 10
Assuming that the refrigerant pipe located between the gas pipe closing valve 117 and the gas pipe closing valve 117 is a gas pipe side pipe section 132, the liquid pipe side pipe section 131
Is provided with a receiver 121 for temporarily storing excess refrigerant. The receiver 121 includes a gas venting circuit 191 connected between the four-way switching valve 102 and the accumulator 105. The degassing circuit 191 includes a degassing solenoid valve 192 and a degassing capillary 193. The receiver 121 may be provided with a bypass circuit that bypasses the liquid shutoff valve 116 and the gas shutoff valve 117, and may be configured on this bypass circuit.

The discharge side of the compressor 101 and the accumulator 1
A discharge bypass circuit 194 is provided between the discharge bypass circuit 505 and the suction side. The discharge bypass circuit 194 is provided with a discharge-suction electric valve 142 having a pressure reducing function and an opening / closing function. When the discharge pressure of the compressor 101 becomes high, the displacement control is performed by controlling the opening degree of the discharge-suction electric valve 142.

The liquid pipe connection port 114 and the gas pipe connection port 115 of the outdoor unit 100 have branch units 300A and 3B, respectively.
00B is connected. Branch unit 300A, 30
OB have the same configuration, and only one branch unit 300A will be described. The outdoor liquid pipe connection port 30 connected to the liquid pipe connection port 114 of the outdoor unit 100
1 and an outdoor gas pipe connection port 303 connected to the gas pipe connection port 115 of the outdoor unit 100. The branching unit 300A includes a liquid pipe side branch path that branches inside the outdoor liquid pipe connection port 301, and the distal end thereof is connected to the indoor liquid pipe connection port 302 of the number of indoor units to be connected.
Is composed. Also, the outdoor side gas pipe connection port 303
The gas pipe side branch path which branches in the inside of the inside, the tip is connected to the indoor side gas pipe connection port 3 of the number of indoor units to be connected
04. Here, the indoor units to be connected are 3
And a liquid pipe connection port 302A, 302B, 3
02C and indoor side gas pipe connection ports 304A, 304
B, 304C.

Each of the indoor liquid pipe connection ports 302A to 302A-3 is connected to the outdoor liquid pipe connection port 301 in the branching unit 300A.
In the branch path to 02C, there are electrically operated valves 305A to 305C for reducing the pressure of the refrigerant passing therethrough, and a liquid tube thermistor 306 for detecting the temperature of the refrigerant passing therethrough.
A to 306C are provided. In the branch path from the outdoor-side gas pipe connection port 303 in the branch unit 300A to each of the indoor-side gas pipe connection ports 304A to 304C, gas pipe thermistors 307A to 307C for detecting the temperature of the refrigerant passing therethrough are provided, respectively. Is provided.

Each branch unit 300A, 300B has
A plurality of indoor units 200 are connected. Here, the number of indoor units that can be connected to the branch unit 300 is three, indoor units 200A to 200C are connected to the branch unit 300A, and indoor units 200D to 200C are connected to the branch unit 300B.
F is connected. Each indoor unit 200A-200
Each of F can use both the indoor unit for the multi-unit and the indoor unit for the pair unit. Here, the case where the indoor unit for the pair unit is used will be described.

The indoor unit 200A includes an indoor heat exchanger 201. Refrigerant piping connected to the indoor heat exchanger 201 is connected to the outdoor unit via a liquid pipe connection port 204 and a gas pipe connection port 205. Derived. The indoor unit 200A includes a room temperature thermistor 202 for detecting the indoor temperature and an indoor heat exchange thermistor 203 for detecting the temperature of the indoor heat exchanger 201.

When a multi-unit indoor unit is used as the indoor unit connected to the branch unit 300, a liquid tube thermistor for detecting the temperature of the refrigerant flowing inside the liquid tube side pipe portion is provided. In this case, the liquid tube thermistor in the branch unit 300 can be omitted. In this embodiment, the capacity of the indoor heat exchanger 201 during operation is smaller than the capacity of the compressor 101 during rated operation.
In the case where the capacity is small, by opening the discharge-suction electric valve 142, it is possible to prevent an increase in high pressure during heating and a decrease in low pressure during cooling. For example, compressor 1
If the discharge pressure is equal to or higher than the predetermined value even when the operating frequency of 01 becomes the lower limit frequency, the opening degree of the discharge-suction electric valve 142 is increased to increase the bypass circulation amount of the refrigerant. When the high pressure is reduced due to a change in environmental conditions, the opening of the discharge-suction electric valve 142 is reduced, and when the opening becomes equal to or less than a predetermined value, the discharge-suction electric valve 142 is set to the fully closed state. I do. If the high pressure is still low, the compressor 101
The required high pressure is controlled by increasing the operating frequency of
At this time, the discharge-suction electric valve 14 is controlled according to the values detected by the discharge pipe thermistor 109 and the suction-side pressure sensor 110.
2 can be adjusted, and control can be performed to maintain an arbitrary pressure.

<Second Embodiment: Provision of Heat Exchanger in Discharge Bypass Circuit> As shown in FIG.
At 94, the compressor 101 of the discharge-suction electric valve 142
It is conceivable to provide a discharge bypass heat exchanger 195 on the side. The discharge bypass heat exchanger 195 functions as a condenser for the refrigerant passing through the discharge bypass circuit 194, and lowers the temperature of the hot gas discharged from the compressor 101. Therefore, this discharge bypass heat exchanger 19
The refrigerant condensed to some extent by the accumulator 10
It will be returned to 5.

Since the refrigerant discharged from the compressor 101 has a high temperature, it is necessary to use a motor valve having a high heat-resistant temperature when directly flowing the refrigerant into the discharge-suction motor valve 142, which increases the cost and increases the cost. Problems with durability and reliability occur. As described above, the discharge-suction electric valve 142
By providing the discharge bypass heat exchanger 195 on the side of the compressor 101, the temperature of the refrigerant passing therethrough can be controlled by the discharge-suction electric valve 1.
42 or less. Therefore, an inexpensive electric valve can be used as the discharge-suction electric valve 142, and the problems of durability and reliability can be solved.

Third Embodiment: Discharge Bypass Heat Exchanger Provided in Accumulator As shown in FIG. 3, discharge bypass heat exchanger 1 provided in discharge bypass circuit 194
It is conceivable that 95 is provided inside the accumulator 105. In this case, the high-temperature refrigerant passing through the discharge bypass heat exchanger 195 exchanges heat with the low-temperature refrigerant in the accumulator 105, so that the condensation efficiency is increased and the capacity control can be performed efficiently.

When the liquid refrigerant is accumulated in the accumulator 105, the refrigerant in the refrigerant circuit may be insufficient and a so-called lack of gas state may occur. By exchanging heat with the high-temperature refrigerant in the discharge bypass heat exchanger 195, it is possible to quickly evaporate and return to the system. <Fourth embodiment: inserting discharge bypass pipe into accumulator> As shown in FIG.
A configuration in which a part of the pipe of No. 4 is inserted into the accumulator 105 can be considered. In the second embodiment and the third embodiment, a discharge bypass heat exchanger 195 having a large number of plate-like radiating fins attached to a pipe portion is used, whereas in the fourth embodiment, a pipe of a discharge bypass circuit 194 is used. Is bent and a heat exchange pipe section 196 introduced into the accumulator 105 is used as a discharge bypass heat exchanger.

In the fourth embodiment, although the efficiency is reduced as compared with the case of using a heat exchanger provided with a large number of radiating fins as in the third embodiment, the heat exchange piping section 196 is introduced into the accumulator 105. By doing so, it is possible to achieve the object of lowering the temperature of the refrigerant below the heat-resistant temperature of the discharge-suction electric valve 142. Further, it is possible to configure an inexpensive discharge bypass heat exchanger as compared with the case where a large number of heat radiation fins are provided, and it is possible to reduce the cost.

In the third and fourth embodiments, the discharge bypass heat exchanger 195 and the heat exchange pipe 196 are preferably provided so as to reach the bottom of the accumulator 105. In this case, heat exchange with the liquid refrigerant accumulated at the bottom in the accumulator 105 becomes possible, and the discharge bypass heat exchanger 195 or the heat exchange pipe 1
Condensation of high-temperature refrigerant passing through 96, accumulator 10
The evaporation efficiency of the low-temperature refrigerant in 5 is improved.

<Fifth Embodiment: The oil return pipe of the oil separator is shared with a part of the pipe of the discharge bypass circuit> FIG.
As shown in the figure, the discharge pipe of the compressor 101 and the four-way switching valve 10
When the oil separator 107 is provided between the oil separator 2 and the oil separator 107, the oil return pipe 197 of the oil separator 107 and a part of the discharge bypass circuit 194 can be shared.

The oil return pipe 197 of the oil separator 107
Is branched from the heat exchange pipe section 196 of the discharge bypass circuit 194 and connected to the suction side of the accumulator 105.
A capillary 141 is provided on the way. With such a configuration, even if the refrigerant circuit is provided with the oil separator 107, the oil separator 10
The refrigerant separated from the oil via the accumulator 7
Heat exchange with the low-temperature refrigerant in 05 is possible.

[Preferred Examples] It is expected that a great effect can be obtained by appropriately combining the above-described first to fifth embodiments. A preferred example in which these embodiments are combined is described. Will be described below. FIG. 6 shows a preferred embodiment of the present invention.

The outdoor unit 100 includes a compressor 101, a four-way switching valve 102, an outdoor heat exchanger 103, and an accumulator 105.
And the like. Compressor 1
01 is provided with a discharge-side pressure protection switch 108 for detecting an abnormal rise in the discharge pressure.
A suction side pressure sensor 110 for detecting a suction pressure is provided on the suction side of the apparatus No. 01.

An oil separator 107 is provided on the discharge side of the compressor 101 for separating lubricating oil contained in the refrigerant and returning it to the accumulator 105 side. A discharge pipe thermistor 109 for detecting the temperature on the discharge side of the compressor 101 is attached to the oil separator 107. Oil return pipe 1 of oil separator 107
97 is provided with a discharge bypass circuit 194 branched from the oil return pipe 197 and connected to the inlet side of the accumulator 105. The discharge bypass circuit 194 includes a heat exchange pipe 196 introduced into the accumulator 105.
And a discharge-suction electric valve (EVP) 142 for controlling the displacement. A capillary 141 is provided in the oil return pipe 197 of the oil separator 107, and the other end of the capillary 141 is connected to the suction side of the accumulator 105.

The outdoor unit 100 has an outdoor air thermistor 111 for detecting the outdoor air temperature, and an outdoor heat exchanger 103.
And an outdoor heat exchange thermistor 112 for detecting the temperature of the air. Further, a fan 106 for sucking outside air and performing heat exchange between the sucked outside air and the refrigerant flowing inside the outdoor heat exchanger 103, and a fan motor 104 for rotating the fan 106 are provided. ing.

A refrigerant pipe extending from the outdoor unit 100 to the indoor unit has a liquid pipe connection port 114 extending from the outdoor heat exchanger 103 and a gas pipe connection port 115 extending through the four-way switching valve 102. And a liquid pipe closing valve 116 and a gas pipe closing valve 117 provided inside each connection port. The outdoor unit 100 is provided with a receiver 121 that temporarily stores excess refrigerant liquid from the outdoor heat exchanger 103 that functions as a condenser during a cooling operation. The receiver 121 includes a liquid pipe side connection pipe 122 and a gas pipe side connection pipe 123, and the liquid pipe side connection pipe 122 is a liquid pipe side pipe 131 between the outdoor heat exchanger 103 and the liquid pipe closing valve 116. , And the gas pipe side connection pipe 123 is connected to a gas pipe side pipe part 132 between the four-way switching valve 102 and the gas pipe closing valve 117.

A liquid pipe motor-operated valve (E) having a pressure reducing function and a refrigerant shutoff function is connected to the liquid pipe side connecting pipe 122 of the receiver 121.
VL) 128 is provided, and the gas pipe side connection pipe 123 is provided with a gas pipe motorized valve (EVG) 129. An auxiliary heat exchanger 133 is provided between the gas pipe motorized valve 129 and a connection to the gas pipe side pipe 132. A subcool heat exchanger 13 is provided at an outlet of the outdoor heat exchanger 103 on the liquid tube side.
4 are arranged.

The gas venting capillary 1 for recovering gaseous refrigerant from the receiver 121 is directed toward the gas pipe side pipe 132 between the four-way switching valve 102 and the gas shutoff valve 117.
30 are provided. Liquid pipe connection port 11 of outdoor unit 100
A plurality of branch units 300A, 300B,... Are connected to 4 and the gas pipe connection port 115. Since each of the branch units 300A, 300B,... Has the same configuration, only the branch unit 300A will be described, and description of the other units will be omitted.

The branch unit 300A includes an outdoor liquid pipe connection port 301 connected to the liquid pipe connection port 114 of the outdoor unit 100, and an outdoor gas pipe connection port 303 connected to the gas pipe connection port 115 of the outdoor unit 100. And The branch unit 300A is connected to the outdoor liquid pipe connection port 3
01 is provided with a liquid pipe side branching path that branches inside the inside liquid pipe connection port 3 of the number of indoor units to be connected.
02. In addition, outdoor gas pipe connection port 3
A gas pipe-side branch path is provided which branches inside the inside of the fuel cell 03, and the distal end thereof constitutes the indoor-side gas pipe connection ports 304 of the number of connected indoor units. Here, three indoor units are connected, and the indoor liquid pipe connection ports 302A and 302A are connected.
B, 302C and the indoor gas pipe connection port 304A,
It is assumed that 304B and 304C are provided. Also,
An electric valve 308 for pressure adjustment is provided between the outdoor liquid pipe connection port 301 and the outdoor gas pipe connection port 303.

From the outdoor liquid pipe connection port 301 in the branching unit 300A to the indoor liquid pipe connection ports 302A to 302A-3.
In the branch path to 02C, there are electrically operated valves 305A to 305C for reducing the pressure of the refrigerant passing therethrough, and a liquid tube thermistor 306 for detecting the temperature of the refrigerant passing therethrough.
A to 306C are provided. In the branch path from the outdoor-side gas pipe connection port 303 in the branch unit 300A to each of the indoor-side gas pipe connection ports 304A to 304C, gas pipe thermistors 307A to 307C for detecting the temperature of the refrigerant passing therethrough are provided, respectively. Is provided.

A plurality of indoor units 200 are connected to each of the branch units 300A, 300B,. In the drawing, the number of indoor units that can be connected to each of the branch units 300A, 300B,.
A is connected to indoor units 200A to 200C, and branch unit 300B is connected to indoor units 200D to 200F. Each of the indoor units 200A to 200F can use either a multi-unit indoor unit or a pair-unit indoor unit. Here, a case where a pair-unit indoor unit is used as the indoor unit 200A will be described.

The indoor unit 200A has an indoor heat exchanger 201. Refrigerant piping connected to the indoor heat exchanger 201 is connected to the outdoor unit via a liquid pipe connection port 204 and a gas pipe connection port 205. Derived. The indoor unit 200A includes a room temperature thermistor 202 for detecting the indoor temperature and an indoor heat exchange thermistor 203 for detecting the temperature of the indoor heat exchanger 201.

When a multi-unit indoor unit is used as the indoor unit connected to the branch units 300A and 300B, a liquid pipe thermistor for detecting the temperature of the refrigerant flowing inside the liquid pipe side piping section is provided. In some cases, a liquid tube thermistor in the branch units 300A and 300B may be omitted. [Control Method of Refrigerant Circuit] In the above-described refrigerant circuit, the discharge-suction bypass motor-operated valve 142 operates when the refrigerant capacity on the indoor unit side is small (when the number of operating units is small or when the indoor heat exchanger of the operating indoor unit is used). The opening is increased when the capacity is small, for example, to prevent the discharge pressure from increasing during the heating operation, and to prevent the low-pressure pipe from freezing during the cooling operation.

During the heating operation, the liquid tube motorized valve 128 is operated while the gas tube motorized valve 129 is open.
When the excess refrigerant is present in 21, control of the entire system is performed by performing opening / closing control, and at the time of cooling operation, the presence or absence of the excess refrigerant is determined to control the excess refrigerant in the outdoor unit SC control. Further, the gas pipe electric valve 129 stores the excess refrigerant in the receiver 121 by opening at a predetermined opening when the surplus refrigerant processing is necessary during the heating operation, and the liquid pipe electric valve 128 is open during the cooling operation. Receiver 1 in state
When there is surplus refrigerant in 21, the whole system is controlled by opening and closing control.

<Control During Heating Operation> FIG. 7 shows an operation example during the heating operation. In FIG. 7, in step S1, it is determined whether or not there is no excess refrigerant in the refrigerant circuit and there is no need to perform capacity control. If it is determined that there is no excess refrigerant in the refrigerant circuit and that it is not necessary to perform capacity control, the process proceeds to step S2. In step S2,
The discharge-suction bypass electric valve 142 is fully closed, the liquid pipe electric valve 128 is fully open, and the gas pipe electric valve 129 is fully closed.

There is no excess refrigerant on such a refrigerant circuit,
A state where there is no need for capacity control may be a case where all the connected indoor units 200A to 200F are operating, as shown in FIG. In this case, the outdoor heat exchanger 103 functions as an evaporator, and the indoor heat exchanger 201 of each indoor unit is used.
Functions as a condenser. Branch unit 300A,
Motorized valves 305A-305C, 305D in 300B
To 305F are each controlled by an opening degree according to the setting of each indoor unit, and configured to distribute refrigerant to each indoor heat exchanger 201. The electric valve 305 for pressure adjustment is in a fully closed state here.

Therefore, the branch units 300A, 30
Electric valves 305A to 305C, 3 arranged in
With 05D to 305F, refrigerant distribution to each indoor heat exchanger 201 is appropriately performed. Further, since no excess refrigerant is generated on the circuit, the receiver 121 is in a non-functional state, and the discharge-suction bypass electric valve 142, the liquid pipe electric valve 128, and the gas pipe electric valve 129 are all controlled. Not used.

In step S3, it is determined whether or not there is surplus refrigerant in the refrigerant circuit and it is not necessary to perform capacity control. If it is determined that there is surplus refrigerant on the refrigerant circuit and it is not necessary to perform capacity control,
Move to step S4. In step S4, the discharge-suction bypass electric valve 142 is fully closed and the gas pipe electric valve 12
9 is a fixed opening, and the liquid tube electric valve 128 is controlled in accordance with the target discharge tube temperature.

For example, as shown in FIG. 9, indoor units 200A to 200C connected to branch unit 300A
When only the operation is performed, the excess refrigerant may be generated due to the capacity of the outdoor unit 100. In this case, the refrigerant condensed in the auxiliary heat exchanger 133 is opened by opening the gas pipe motor-operated valve 129 at a fixed opening to the receiver 121.
Can be introduced and stored. Since the refrigerant passing through the gas pipe motor-operated valve 129 is condensed in the auxiliary heat exchanger 133, its temperature does not exceed the heat-resistant temperature of a general motor-operated valve. It becomes possible to select. Further, by controlling the degree of opening of the liquid pipe electric valve 128 in accordance with the target discharge pipe temperature, the excess refrigerant in the receiver 121 is adjusted and the degree of superheat of the suction is controlled, whereby the entire system can be controlled. .

In step S5, it is determined whether or not there is surplus refrigerant in the refrigerant circuit and it is necessary to perform capacity control. For example, if there is excess refrigerant on the refrigerant circuit and the peak cut control is in the drooping zone even when the operating frequency of the compressor 101 is at the lower limit frequency, it is necessary to perform excess volume control and volume control. Then, the process proceeds to step S6.

In step S6, while the discharge-suction bypass motor-operated valve 142 remains fully closed, the opening control of the gas pipe motor-operated valve 129 is performed so as to be stable in a non-change range in the peak cut control. Further, the opening degree of the liquid pipe electric valve 128 is controlled in accordance with the target discharge pipe temperature. For example, as shown in FIG. 10, when only the indoor unit 200C is operated among the indoor units 200 connected to the branch units 300A and 300B, and the indoor unit 200C is a large-capacity indoor unit. In addition, there is a possibility that such an operation state will occur.

In this case, by opening the gas pipe motorized valve 129, the condensing capacity of the auxiliary heat exchanger 133 is increased, and the opening control of the gas pipe motorized valve 129 is performed so as to be stable in a range where the peak cut control is not changed. . As a result, the refrigerant condensed through the auxiliary heat exchanger 133 is introduced into the receiver 121, and the excess refrigerant is stored in the receiver 121.
By stabilizing the refrigerant capacity on the high pressure side, the frequency control of the compressor 101 is stabilized in the non-change range of the peak cut control. In addition, since the gas pipe motorized valve 129 is open, control of the entire system (intake superheat control) is performed by controlling the opening of the liquid pipe motorized valve 128 to correspond to the target discharge pipe temperature. This is done by adjusting the excess refrigerant.

In step S7, it is determined whether or not the gas pipe motor-operated valve 129 is in the droop zone of the peak cut control even when it is fully opened. When the peak cut control is in the drooping zone even when the operating frequency of the compressor 101 is at the lower limit frequency, and when the gas pipe motor-operated valve 129 is fully open, it is still in the drooping zone of peak cut control. Move to S8.

In step S8, the frequency control of the compressor 101 is stabilized in the non-change range of the peak cut control.
The opening of the discharge-suction bypass electric valve 142 is controlled. At this time, the gas pipe motorized valve 129 is in the fully opened state, and the liquid pipe motorized valve 128 performs opening control in accordance with the target discharge pipe temperature. For example, as shown in FIG.
Of the indoor units 200 connected to 0A and 300B,
Only the indoor unit 200C is operated, and the indoor unit 2
In the case where the capacity of 00C is small, there is a possibility that an operating condition such as a drooping zone of the peak cut control may occur even though the gas pipe motorized valve 129 is fully opened.
In this case, the displacement control is performed by controlling the electric discharge-suction bypass electric valve 142, and the frequency control of the compressor 101 is stabilized in a non-change range of the peak cut control. Also,
Since the gas pipe motorized valve 129 is open, the control of the entire system (suction superheat control) is performed by controlling the opening of the liquid pipe motorized valve 128 in accordance with the target discharge pipe temperature, thereby making the surplus refrigerant in the receiver 121 available. This is done by adjusting.

<Control During Cooling Operation> FIG. 12 shows an operation example during the cooling operation. In FIG. 12, step S1
At 1, it is determined whether or not there is excess refrigerant on the refrigerant circuit and the volume control is not required. When it is determined that there is no surplus refrigerant in the refrigerant circuit and that it is not necessary to perform capacity control, the process proceeds to step S12. In step S12, the discharge-suction bypass electric valve 142 is fully closed, the gas pipe electric valve 129 is fully opened, and the liquid pipe electric valve 128 is fully closed for SC control by the subcool heat exchanger 134.

There is no excess refrigerant in such a refrigerant circuit,
As shown in FIG. 13, the state where there is no need for capacity control may be a case where all of the connected indoor units 200A to 200F are operating. In this case, the outdoor heat exchanger 103 functions as a condenser, and the indoor heat exchanger 20 of each indoor unit is used.
1 functions as an evaporator. Branch unit 300
A, electric valves 305A to 305C, 30 in 300B
5D to 305F are each controlled by an opening according to the setting of each indoor unit, and configured to distribute refrigerant to each indoor heat exchanger 201. The electric valve 305 for pressure adjustment is in a fully closed state here.

Therefore, the branch units 300A, 30
Electric valves 305A to 305C, 3 arranged in
With 05D to 305F, refrigerant distribution to each indoor heat exchanger 201 can be appropriately performed. Further, since no excess refrigerant is generated on the circuit, the receiver 121 is in a non-functional state, and the discharge-suction bypass electric valve 14
2. Neither the liquid pipe motorized valve 128 nor the gas pipe motorized valve 129 is used for control.

In step S13, it is determined whether or not there is excess refrigerant in the refrigerant circuit and it is not necessary to perform capacity control. If it is determined that there is surplus refrigerant and that it is not necessary to perform capacity control, the process proceeds to step S14. In step S14, the discharge-suction bypass electric valve 1
42 is fully closed and the subcool heat exchanger 134
The liquid tube motorized valve 128 is opened (not fully opened) to the extent that SC control is possible. Further, the opening degree of the gas pipe motor-operated valve 129 is controlled so that the discharge pipe temperature of the compressor 101 becomes the target temperature, and control of the entire system (intake superheat control) is performed.

For example, as shown in FIG. 14, indoor units 200A-200 connected to branch unit 300A
When only C is operated, excess refrigerant may be generated due to the capacity of the outdoor unit 100. In this case, the liquid refrigerant can be introduced and stored in the receiver 121 by opening the liquid tube electric valve 128. In addition, by controlling the degree of opening of the gas pipe motorized valve 129 in accordance with the target discharge pipe temperature, the excess refrigerant in the receiver 121 is adjusted and the degree of superheat of the suction is controlled, whereby the entire system can be controlled. .

As shown in FIG. 15, among the connected indoor units 200, only the indoor unit 200C connected to the branch unit 300A is in the operating state.
It is conceivable that the same operation state is obtained when 0C is a large capacity. Also in this case, by performing the same control as in the case of FIG. 14, it is possible to perform appropriate surplus refrigerant processing and system control.

In step S15, it is determined whether or not there is surplus refrigerant in the refrigerant circuit and it is necessary to perform capacity control. If it is determined that there is excess refrigerant and that it is necessary to perform capacity control, the process proceeds to step S16. For example, in a state where the number of operating indoor units is small and there is excess refrigerant, when the anti-freezing control is in the drooping zone even when the operating frequency of the compressor 101 becomes the lower limit frequency, it is necessary to perform capacity control. And the process moves to step S16.

In step S16, in the frequency control of the compressor 101, the opening control of the electric discharge-suction bypass motor-operated valve 142 is performed so as to be stable in the non-change range of the freeze prevention control. At this time, the opening degree of the liquid tube motorized valve 128 is controlled (not fully opened) in order to process the excess refrigerant from the liquid tube piping section 131, and the liquid refrigerant is stored in the receiver 121. In addition, since the liquid pipe electric valve 128 is open, the gas pipe electric valve 129 is opened.
By controlling the degree of opening in accordance with the target discharge pipe temperature, the amount of refrigerant in the receiver 121 is adjusted, and the entire system is controlled.

Such an operating state is, for example, as shown in FIG.
As shown in FIG. 7, only the indoor unit 200C among the connected indoor units 200 is in the operating state, and
This may occur when 0C is a small capacity. The electric valve 305C corresponding to the indoor heat exchanger 201 of the operating indoor unit
The opening degree control according to the indoor temperature setting and the like is performed, and the other electric valves 305A and 305B and the branch unit 300B
The motorized valves 305D to 305F are in a closed state. In this state, the discharge-suction bypass electric valve 14
2, the frequency control of the compressor 101 is stabilized, the opening degree of the liquid pipe electric valve 128 is adjusted, the excess refrigerant processing is performed, and the opening degree of the gas pipe electric valve 129 is further adjusted. Can control the entire system.

In step S17, it is determined whether or not the outside air temperature is lower than a predetermined temperature. If the liquid pipe electric valve 128 is fully closed when the outside air temperature is equal to or lower than the predetermined temperature, the pressure in the receiver 121 becomes lower than the suction side pressure of the compressor 101, and the liquid accumulated in the receiver 121 is reduced. The refrigerant may not escape. In this case, there is a possibility that a shortage of the refrigerant in the refrigerant circuit may occur. Therefore, when it is determined that the outside air temperature is lower than the predetermined temperature assumed to be in such a state, the process proceeds to step S18.

In step S18, the pressure in the receiver 121 is made higher than the pressure in the gas pipe piping section 132 by opening the liquid pipe motorized valve 128 by a predetermined opening.
The liquid refrigerant in 1 is discharged to the auxiliary heat exchanger 133 side. In addition, since the liquid tube electric valve 128 is open, by controlling the opening of the gas tube electric valve 129, it is possible to control the target discharge pipe temperature and control the entire system. Further, by controlling the opening of the discharge-suction bypass electric valve 142 to prevent freezing, the liquid refrigerant in the accumulator 105 is evaporated, and the suction temperature of the compressor 101 can be increased.

As shown in FIG. 17, the connected indoor unit 2
Even when only the small-capacity indoor unit 200C is operated out of 00, if the outside air temperature is low, surplus refrigerant may not be generated. In such a case,
It is conceivable to adopt a configuration in which the liquid pipe electric valve 128 is fully closed so that the liquid refrigerant is not introduced into the receiver 121. However, if the liquid pipe electric valve 128 is fully closed, the liquid refrigerant once accumulated may be drained. Can not be done. Therefore, the auxiliary heat exchanger 1 is opened by opening the electric valve 128 of the liquid pipe at a predetermined opening and controlling the opening of the electric valve 129 of the gas pipe.
It can be configured to discharge the liquid refrigerant to the 33 side and to control the entire system.

As for the anti-freezing control, by controlling the opening degree of the discharge-suction bypass electric valve 142, the liquid refrigerant in the accumulator 105 is evaporated, and the compressor 10
1 is configured to perform stable control in a non-change range of the frequency control.

[0064]

In the refrigerant circuit of the air conditioner according to the present invention, when the capacity during the rated operation of the compressor is larger than the capacity of the indoor heat exchanger, the temperature rise of the high pressure section during the heating operation and the cooling operation during the cooling operation are performed. In order to prevent the temperature of the low pressure part from dropping,
It is possible to perform reliable control without causing pressure fluctuation, and it is possible to reduce costs.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a first embodiment of the present invention.

FIG. 2 is a schematic configuration diagram of a second embodiment of the present invention.

FIG. 3 is a schematic configuration diagram of a third embodiment of the present invention.

FIG. 4 is a schematic configuration diagram of a fourth embodiment of the present invention.

FIG. 5 is a schematic configuration diagram of a fifth embodiment of the present invention.

FIG. 6 is a configuration diagram of an embodiment.

FIG. 7 is a control flowchart during a heating operation.

FIG. 8 is an explanatory diagram showing an operation example during a heating operation.

FIG. 9 is an explanatory diagram showing an operation example during a heating operation.

FIG. 10 is an explanatory diagram showing an operation example during a heating operation.

FIG. 11 is an explanatory diagram showing an operation example during a heating operation.

FIG. 12 is a control flowchart during a cooling operation.

FIG. 13 is an explanatory diagram showing an operation example during cooling operation.

FIG. 14 is an explanatory diagram showing an operation example during cooling operation.

FIG. 15 is an explanatory diagram showing an operation example during cooling operation.

FIG. 16 is an explanatory diagram showing an operation example during cooling operation.

FIG. 17 is an explanatory diagram showing an operation example during cooling operation.

DESCRIPTION OF SYMBOLS 100 outdoor unit 101 compressor 102 four-way switching valve 103 outdoor heat exchanger 105 accumulator 121 receiver 128 liquid pipe motorized valve 129 gas pipe motorized valve 130 gas release capillary 131 liquid pipe piping 132 gas pipe piping 133 Auxiliary heat exchanger 134 Subcool heat exchanger 141 Capillary 142 Discharge-suction bypass electric valve 194 Discharge bypass circuit 195 Discharge bypass heat exchanger 196 Heat exchange piping section 197 Oil return pipe

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 3L092 AA13 BA05 BA23 BA27 DA17 EA02 EA10 FA23 FA27 GA03 HA07 HA10 JA07 JA13 KA02 KA09 LA03

Claims (6)

[Claims] An accumulator (105), a compressor (101), and a four-way switching valve (1) arranged in an outdoor unit (100).
02), an outdoor unit-side refrigerant circuit including an outdoor heat exchanger (103), and an indoor heat exchanger (201) arranged in the indoor unit (200) by a liquid pipe side pipe and a gas pipe side pipe. A refrigerant circuit of an air conditioner to be connected, wherein a discharge pipe of the compressor (101) and the accumulator (10) are provided to control the capacity of the compressor (101).
5) A refrigerant circuit of an air conditioner provided with a discharge bypass circuit (194) including a discharge-suction electric valve (142) having a decompression function and an opening / closing function between the suction pipe and the suction pipe. 2. A discharge pipe of the compressor (101) and a discharge-suction electric valve (142) of the discharge bypass circuit (194).
The refrigerant circuit for an air conditioner according to claim 1, wherein a discharge bypass heat exchanger (195) is provided between the air conditioner and the discharge bypass heat exchanger. 3. The refrigerant circuit of an air conditioner according to claim 2, wherein said discharge bypass heat exchanger (195) is provided inside said accumulator (105). 4. The refrigerant circuit of an air conditioner according to claim 3, wherein the discharge bypass heat exchanger is a discharge bypass pipe (196) inserted inside the accumulator (105). 5. The discharge bypass heat exchanger (195, 19).
The refrigerant circuit of an air conditioner according to claim 3 or 4, wherein 6) is provided at a bottom of the accumulator (105). 6. An oil separator (107) between a discharge pipe of the compressor (101) and the four-way switching valve (102).
And an oil return pipe (197) of the oil separator (107) and the discharge bypass circuit (194).
The refrigerant circuit of an air conditioner according to any one of claims 1 to 5, wherein a part of the refrigerant circuit is common.