JPH1062026A - Air conditioner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an air conditioner in which refrigerant is prevented from staying in a compressor at a stop side and in its suction pipe during a heating operation of refrigerant or. SOLUTION: In the case that only a first compressor 21 is being operated when a refrigerant is heated, a shut-off valve 39 at an outdoor device ECU 35 is closed for every predetermined time and then a refrigerant circuit ranging from a refrigerant pipe 56 to the first compressor 21 is made to be a closed circuit. With such an arrangement as above, as gaseous refrigerant is discharged from the first compressor 21 to a refrigerant pipe 51, the refrigerant circuit which is a closed circuit is pumped down to cause a pressure within the circuit to be decreased and as this pressure is decreased, liquid refrigerant within a second compressor 23 or within a suction pipe 64 is rapidly gasified so as to eliminate a staying of the refrigerant. In addition, the outdoor device ECU 35 closes the shut-off valve 39 also when the second compressor 23 is energized again and its pump-down operation is carried out, thereafter the second compressor 23 is energized again.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an air conditioner provided with a plurality of compressors and refrigerant heating means, and more particularly, to a method for stagnation of refrigerant in a stop compressor and its suction pipe during refrigerant heating operation. Related to the technology to be eliminated.

[0002]

2. Description of the Related Art In recent years, a heat pump type air conditioner for heating using air as a heat source has been increasing in place of a conventional cooling only device. However, in the heat pump type air conditioner, when the outside air temperature is extremely low, the difference between the evaporation temperature of the refrigerant in the outdoor heat exchanger and the outside air temperature becomes very small, and there is a problem that the heating can hardly be performed. Therefore, by providing a refrigerant heater in the outdoor unit in addition to a normal outdoor heat exchanger (air heat exchanger), and performing heat exchange between hot water or the like and the refrigerant (that is, refrigerant heating), Some have supplied relatively hot refrigerant to the compressor. In this type of air conditioner, the latent heat of condensation in the indoor heat exchanger can be ensured irrespective of the outside air temperature, so that sufficient heating is possible even in severe winter.

On the other hand, a large-sized air conditioner is known in which a plurality of compressors are installed in an outdoor unit, and the capacity and the number of operating compressors are changed according to an increase or decrease in an air conditioning load.
For example, some of the compressors provided with two compressors combine a constant speed compressor with a variable compressor having a maximum capacity equal to that of the constant speed compressor, and perform capacity control over a wide range. In this air conditioner, when the capacity of 50% or less is required, only the variable compressor is driven, and when the capacity of 50% or more is required, both compressors are driven together. Thereby, if the capacity can be switched in five stages by the variable compressor, the capacity can be switched in ten stages as a whole.

[0004]

In a heat pump type air conditioner provided with a plurality of compressors and a refrigerant heater, when operating while heating the refrigerant, a part of the compressor is controlled for controlling the capacity. When the compressor is stopped, the liquid refrigerant may accumulate inside the stopped compressor or the suction pipe to the compressor (the refrigerant may stagnate). This is because the saturation temperature of the refrigerant is increased by being heated, and the refrigerant is condensed by contacting the compressor or the suction pipe which has been exposed to the outside air and has a low temperature without the flow of the refrigerant. It progresses gradually while continuing driving.

[0005] When the refrigerant stagnates in the compressor or the suction pipe, a large amount of liquid refrigerant flows into the compression mechanism at the time of restart, and the compressor may break down due to liquid compression. Further, if a large amount of refrigerant is stagnated in the stopped compressor or its suction pipe, the refrigerant flowing through the operating compressor or the refrigerant circuit becomes insufficient, and air conditioning may not be performed smoothly. Further, when the amount of refrigerant stagnation in the compressor increases, the winding of the electric motor may be broken down by being immersed in the liquid refrigerant. A crankcase heater is provided at the lower part of the compressor to prevent the refrigerant from dissolving in the lubricating oil sealed when the compressor is stopped. No ability to vaporize refrigerant
Further, there was almost no effect on the liquid refrigerant stored in the suction pipe.

[0006] The present invention has been made in view of the above situation,
It is an object of the present invention to provide an air conditioner that eliminates refrigerant stagnation in a compressor on a stop side and a suction pipe thereof during a refrigerant heating operation.

[0007]

According to one aspect of the present invention, there is provided an air conditioner having a refrigerant circuit having a plurality of compressors and refrigerant heating means, wherein the low pressure side refrigerant circuit is provided. And a shut-off valve for shutting off the second compressor every first predetermined time when some of the compressors are stopped during the refrigerant heating operation.
It is proposed to provide a shut-off valve drive control means for driving the shut-off valve for a predetermined time to shut off the low-pressure side refrigerant circuit.

According to the present invention, for example, when one of the plurality of compressors is stopped during the refrigerant heating operation,
At a certain interval, the low-pressure side refrigerant circuit is shut off for several minutes by the shut-off valve. As a result, the refrigerant circuit between the shut-off valve and the compressor is pumped down, the pressure in the refrigerant circuit drops below the saturation pressure of the outside air temperature, and the refrigerant in the stopped compressor and its suction pipe is stopped. Sleep is resolved.

According to a second aspect of the present invention, in an air conditioner provided with a refrigerant circuit having a plurality of compressors and refrigerant heating means, a shut-off valve for shutting off a low pressure side refrigerant circuit, and a stop valve during a refrigerant heating operation. When the compressor which has been restarted is provided with a shut-off valve drive control means for driving the shut-off valve for a predetermined time to shut off the low-pressure side refrigerant circuit, prior to the restart.

According to the present invention, for example, when it is necessary to restart one of the plurality of compressors during the refrigerant heating operation, first, the low-pressure side refrigerant circuit is shut off for several minutes by the shutoff valve. Later, the stopped compressor is restarted.
As a result, the refrigerant circuit between the shut-off valve and the compressor is pumped down, and the pressure in the refrigerant circuit drops below the saturation pressure of the outside air temperature. The stagnation of the refrigerant inside is eliminated.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below in detail with reference to the drawings.

FIG. 1 shows a refrigerant circuit (shown by a solid line) and an electric circuit (shown by an alternate long and short dash line) of an air conditioner including an indoor unit 1 and an outdoor unit 3. The indoor unit 1 houses an indoor heat exchanger 5, an electric fan 7, an electric expansion valve 9, and the like, and an indoor ECU 11 that drives and controls the electric fan 7, the electric expansion valve 9, and the like. In the outdoor unit 3, the first and second compressors 21 and 23 arranged in parallel, the electromagnetic four-way valve 25, the outdoor heat exchanger 27 and the refrigerant heater 29 arranged in parallel, the accumulator 31 , Electric fan 33 and the like, and both compressors 2
An outdoor ECU 35 for controlling the driving of the 1, 23, the four-way valve 25, the electric fan 33 and the like is housed.

In the case of the present embodiment, the first compressor 21 is of a variable type and is driven preferentially during an air-conditioning operation. Also,
The second compressor 23 is of a constant speed type and is driven only when a capacity of 50% or more is required. The outdoor heat exchanger 27 is a normal air heat exchanger, while the refrigerant heater 29 is a water heat exchanger that performs heat exchange between hot water at a predetermined temperature (50 ° C. in the present embodiment) and the refrigerant. is there.

The equipment in the indoor unit 1 and the equipment in the outdoor unit 3 are connected by refrigerant pipes 51 to 64. During heating (during a refrigerant heating operation), the refrigerant circulates in the direction shown by the solid line arrow, and the air conditioner cools. During operation, the refrigerant circulates in the direction indicated by the dashed arrow. In the figure, reference numerals 37 and 39 denote the outdoor ECU 3
This is an electromagnetic shut-off valve that is opened and closed by 5 and shuts off refrigerant pipes 58 and 56 to the outdoor heat exchanger 27 or the refrigerant heater 29 during cooling or heating. Also, 4
1, 43, and 45 are check valves that allow the refrigerant to flow in only one direction, and are interposed in the refrigerant pipes 51, 52, and 60.

The operation of this embodiment will be described below.

When the outside air temperature falls below a predetermined value and heating using air as a heat source cannot be performed, the outdoor ECU 35 switches from a normal heating operation to a refrigerant heating operation. That is, while closing the shut-off valve 37, the shut-off valve 39 is opened,
The supply destination of the refrigerant is changed from the outdoor heat exchanger 27 to the refrigerant heater 29. Then, the electric fan 33 is stopped and hot water from a hot water source (not shown) is supplied to the refrigerant heater 29.

As a result, the liquid refrigerant from the indoor heat exchanger 5 flows into the refrigerant heater 29 through the refrigerant pipes 55 and 56, and has a relatively high temperature (for example, 20 to 20) due to heat exchange with hot water inside the liquid heater 29. (40 ° C.). The gas refrigerant flows into the accumulator 31 through the refrigerant pipes 57 and 61, and is sucked into the first and second compressors 21 and 23 through the refrigerant pipes 62 to 64. At this time, since the check valve 45 is provided in the refrigerant pipe 60, the gas refrigerant is prevented from flowing into the outdoor heat exchanger 27 side. First and second compressors 2
The gas refrigerant sucked into 1, 23 is compressed inside to become high temperature and high pressure, and flows into the indoor heat exchanger 5 via the refrigerant pipes 51-54. The high-temperature gas refrigerant emits thermal energy to the indoor air blown to the electric fan 7 to perform heating, and gradually condenses in the indoor heat exchanger 5 to become a liquid refrigerant again.

The outdoor ECU 35 controls the capacity of the first compressor 21 and stops the second compressor 23 when the required capacity of the outdoor unit 3 decreases.
Then, the gas refrigerant from the accumulator 31 is sucked into only the first compressor 21 via the refrigerant pipes 62 and 63,
After being compressed inside, it flows into the indoor heat exchanger 5 via the refrigerant pipes 51, 53 to 54. On this occasion,
Since the check valve 43 is provided in the refrigerant pipe 52, the first
The gas refrigerant discharged from the compressor 21 is prevented from flowing into the second compressor 23 side.

Next, the second compressor 23 and the suction pipe 64
The procedure for preventing the refrigerant from stagnation in the above will be described.

When the second compressor 23 is stopped during the refrigerant heating operation, there is a possibility that the refrigerant may stagnate in the suction pipe 64 or inside the second compressor 23. That is, when the suction pipe 64 or the second compressor 23 which is exposed to the outside air and has a low temperature without the flow of the refrigerant touches, the gas refrigerant which has been heated and has a high saturation temperature is easily condensed and becomes a liquid refrigerant. They may collect inside these. In the present embodiment, the following method is employed in order to prevent such stagnation of the refrigerant.

When the operation of the air conditioner is started, the outdoor ECU 35 operates at predetermined control intervals, as shown in FIGS.
Is repeatedly executed. When starting this subroutine, the outdoor ECU 35 first reads the operation information from the various subroutines that have been subjected to the parallel processing in step S1 of FIG. 2, and then determines in step S3 whether the second compressor 23 is stopped. Is determined. If this determination is No, the outdoor ECU 3
No. 5 returns to the start without performing any processing.

If the determination in step S3 is Yes, that is, if the second compressor 23 is stopped, the outdoor ECU 3
5 determines whether or not a drive command for the second compressor has been input in step S5. The drive command for the second compressor is output from a compressor drive control subroutine or the like when the capacity requirement for the outdoor unit 3 increases.

If the determination in step S5 is No,
The outdoor ECU 35 determines whether or not the compressor stop flag FSTOP is 1 in step S7. The compressor stop flag FSTOP is a flag indicating that the second compressor 23 is stopped, and its initial value is set to 0. If it is immediately after the second compressor 23 stops, step S5
Is determined as No, the outdoor ECU 35 activates the first timer T1 in step S9, and then proceeds to step S1.
At 1 the compressor stop flag FSTOP is set to 1 and the process returns to start.

If the second compressor 23 is already stopped, the determination in step S7 becomes Yes, so that the outdoor EC
U35 determines in step S13 whether the value of the first timer T1 has reached a predetermined standby time T1X (one hour in this embodiment). If the determination in step S13 is No, the outdoor ECU 35 returns to the start without performing any processing.

The standby time T from the time when the second compressor 23 is stopped
When 1X has elapsed and the determination in step S13 is Yes, the outdoor ECU 35 determines whether the pump down flag FPD is 1 in step S15 in FIG. The pump down flag FPD is a flag indicating that the refrigerant circuit is being pumped down, and its initial value is set to 0.

Immediately after the determination in step S13 becomes Yes, the determination in step S15 becomes No. Therefore, the outdoor ECU 35 first activates the second timer T2 in step S17, and in step S19, the pump down flag FPD Is set to 1. Thereafter, the outdoor ECU 35 proceeds to step S.
At 21, the shut-off valve 39 is closed, and the refrigerant circuit from the refrigerant pipe 56 to the first compressor 21 is closed to return to the start.
As a result, as the gas refrigerant is discharged from the first compressor 21 to the refrigerant pipe 51 side, the low-pressure side refrigerant circuit that has been closed is pumped down, and the pressure in the circuit is reduced.

When the pump down is started, the gas refrigerant in the refrigerant heater 29 and the accumulator 31 is supplied to the refrigerant pipe 51.
On the other hand, the liquid refrigerant in the second compressor 23 and the suction pipe 64 evaporates rapidly as the pressure in the circuit decreases, and the stagnation of the refrigerant starts to be eliminated. At this time, since the check valve 43 is provided in the refrigerant pipe 52, the backflow of the gas refrigerant from the refrigerant pipe 53 to the second compressor 23 is prevented.

After the start of pump down, step S15
Is determined as Yes, the outdoor ECU 35 determines in step S23 that the value of the second timer T2 is equal to the predetermined duration T2X.
It is determined whether or not (in the present embodiment, one minute) has been reached. If this determination is No, the pump-down is continued and the process returns to the start.

When the value of the second timer T2 reaches the duration time T2X and the determination in step S23 becomes Yes, the outdoor ECU
35 resets the compressor stop flag FSTOP and the pump down flag FPD to 0 in step S25, and then opens the shutoff valve 39 in step S27. As a result, the pump down ends and the operation returns to the normal refrigerant heating operation.
At this point, stagnation of the refrigerant in the second compressor 23 and the suction pipe 64 has been completely eliminated. Then, in the next processing, since the determination in step S7 is No, the control including starting the first timer T1 is newly started. That is, in the present embodiment, the duration T
Pumping down is performed over 2X, which prevents air conditioning failure due to insufficient refrigerant flowing through the refrigerant circuit and stagnation of refrigerant that causes dielectric breakdown of the electric motor winding due to liquid refrigerant.

On the other hand, if a drive command for the second compressor 23 is input during the refrigerant heating operation, the determination in step S5 becomes Yes, so that the outdoor ECU 35 sets the pump down flag FPD to 1 in step S31 in FIG. It is determined whether or not there is.
If the determination is No, that is, if the pump is not currently down, the second timer T2 is started in step S33, and the pump down flag FPD is set to 1 in step S35.
And Thereafter, the outdoor ECU 35 proceeds to step S3.
At 7, the shutoff valve 39 is closed, and the refrigerant circuit from the refrigerant pipe 56 to the first compressor 21 is closed to return to the start. Thus, the pump-down of the low-pressure side refrigerant circuit is started as described above, and the stagnation of the refrigerant in the second compressor 23 and the suction pipe 64 is started to be eliminated.

After the pump down is started, since the determination in step S31 is Yes, the outdoor ECU 35
In step S39, it is determined whether or not the value of the second timer T2 has reached the continuation time T2X. As long as this determination is No, the pump-down is continued and the process returns to the start.

When the value of the second timer T2 reaches the duration T2X and the determination in step S39 becomes Yes, the outdoor ECU
35 resets the compressor stop flag FSTOP and the pump down flag FPD to 0 in step S41, and then opens the shutoff valve 39 in step S43. The second compressor 2
If the pump down has already been started when the drive command of No. 3 is input, the outdoor ECU 35 performs the pump down until the remaining time of the duration T2X is consumed.

The outdoor ECU 35 that has finished pumping down
Outputs the drive start flag FSTART to 1 in step S45 to the compressor drive control subroutine, and then returns to the start. Then, in the compressor drive control subroutine, the outdoor ECU 35 starts driving the second compressor 23 when the drive start flag FSTART is input. Thereby, at the time of the restart, the refrigerant stagnation in the second compressor 23 and the suction pipe 64 is completely eliminated, and the failure of the second compressor 23 due to the inflow of the liquid refrigerant does not occur. After this point, the determination in step S3 is No until the second compressor 21 stops again, so the outdoor ECU 35 does not perform any substantial processing in the pump-down control subroutine.

As described above, in the present embodiment, while the pump is down at regular intervals, when the second compressor 21 is restarted, the pump down is performed prior to the restart. Trouble can be prevented beforehand, and smooth air-conditioning operation has been realized.

The description of the specific embodiment has been completed.
The present invention is not limited to the embodiments described above.
For example, in the above-described embodiment, the pump down and the pump down at the time of restart are performed at regular intervals, but the pump down at the time of startup may be omitted by shortening the standby time. Further, in the above embodiment, the present invention is applied to an air conditioner including one variable compressor and one constant speed compressor, but one variable compressor and two or more compressors. You may apply to the air conditioner provided with the constant speed compressor. Further, the present invention may be applied to an air conditioner having only a plurality of constant speed compressors and operating them alternately. Further, the above embodiment is applied to an air conditioner having an electric compressor, but may be applied to a gas heat pump type air conditioner or the like, or to a device having a plurality of indoor units and outdoor units. May be applied. Further, the specific configuration of the apparatus, the control procedure, and the like can be appropriately changed without departing from the spirit of the present invention.

[0036]

As described above, according to the refrigerator of the present invention, when there is a compressor that is stopped during the refrigerant heating operation,
Pump down at predetermined time intervals, or pump down at restart, prevents stagnation of refrigerant in the compressor and suction pipe, and prevents compressor failure due to liquid compression or shortage of refrigerant. Problems such as poor air conditioning and insulation breakdown of electric motor windings can be eliminated.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an air conditioner according to an embodiment of the present invention.

FIG. 2 is a flowchart showing a procedure of a pump down control subroutine.

FIG. 3 is a flowchart showing a procedure of a pump down control subroutine.

FIG. 4 is a flowchart showing a procedure of a pump down control subroutine.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Indoor unit 3 Outdoor unit 21 1st compressor 23 2nd compressor 27 Outdoor heat exchanger 29 Refrigerant heater 35 Outdoor ECU 37,39 Shutoff valve 63,64 Suction piping

Claims (2)

[Claims] An air conditioner provided with a refrigerant circuit having a plurality of compressors and refrigerant heating means, a shut-off valve for shutting off a low-pressure side refrigerant circuit, and a part of the compressor being stopped during refrigerant heating operation. And a shut-off valve drive control means for driving the shut-off valve at every first predetermined time for a second predetermined time to shut off the low-pressure side refrigerant circuit. 2. An air conditioner provided with a refrigerant circuit having a plurality of compressors and refrigerant heating means, wherein a shut-off valve for shutting off a low-pressure side refrigerant circuit and a compressor stopped during a refrigerant heating operation are reactivated. An air conditioner, comprising: a shut-off valve drive control means for driving the shut-off valve for a predetermined time to shut off the low-pressure side refrigerant circuit before the restart.