JP5386141B2 - Heat pump device control method, heat pump device outdoor unit and heat pump device - Google Patents

Description

  The present invention relates to a heat pump device control method suitable for use in a hot water supply system or a heat pump device used in an air conditioning system, an outdoor unit of the heat pump device, and a heat pump device.

  Usually, an outdoor unit used in an air conditioning system (that is, an air conditioner (heat pump device) for business use) or an outdoor unit of a hot water supply system or heat pump device includes a compressor, a heat exchanger, a four-way valve, an expansion valve, A low-pressure sensor is provided.

  In a heat pump apparatus having such an outdoor unit, the expansion valve is generally controlled based on the suction superheat degree. That is, control is performed to adjust the suction superheat degree to the target suction superheat degree by changing the opening of the expansion valve and adjusting the flow rate of the refrigerant passing through the expansion valve.

  Here, the suction superheat degree is obtained from the difference between the suction pipe temperature and the suction pressure saturation temperature. The suction pipe is a conduit through which the refrigerant sucked into the compressor flows, and the temperature of the sucked refrigerant is measured by measuring the temperature of the suction pipe. The suction pressure saturation temperature is a temperature calculated from the pressure of the sucked refrigerant measured by the low pressure sensor.

  However, when the heating operation is performed in the cooling / heating system or when the hot water supply is performed in the hot water supply system, if the outside air temperature decreases, the heating capacity decreases, or the temperature of the motor that drives the compressor increases, resulting in a predetermined There was a problem that the ability could not be demonstrated.

  When the outside air temperature decreases, the pressure of the refrigerant sucked into the compressor, that is, the low pressure decreases. When the low pressure is lowered, the load on the motor driving the compressor is increased, so that the motor coil temperature is increased. In other words, the compression ratio in the compressor increases, and the temperature of the refrigerant discharged from the compressor increases. Then, the temperature of the compressor itself for compressing the refrigerant and the motor for driving the compressor also increased, and as a result, the temperature of the motor coil also increased.

  Generally, a motor has a temperature range suitable for use, and when the temperature range is exceeded, the capacity of the motor decreases. Therefore, as described above, when the temperature of the motor rises, there is a problem that the motor cannot exhibit a predetermined ability.

  Conventionally, in order to prevent the temperature of the motor coil from increasing, the number of rotations of the compressor is controlled to reduce the refrigerant flow rate. For this reason, there is a problem that the heating capacity is lowered.

  Therefore, in order to solve the above-described problem, a technique for controlling the expansion valve based on the discharge superheat degree instead of the control of the expansion valve based on the suction superheat degree has been proposed (for example, see Patent Document 1). .

Here, the discharge superheat degree is a difference between the temperature of the refrigerant discharged from the compressor and the discharge pressure saturation temperature calculated from the pressure of the refrigerant discharged from the compressor.
JP-A-6-288654

  However, the technique described in Patent Document 1 described above has a problem that it is difficult to suppress an increase in the temperature of the motor coil even though the ability in heating operation can be exhibited. In other words, there is a problem that it is difficult for the motor to exhibit a predetermined ability and it is difficult to perform a stable heating operation.

  The present invention has been made to solve the above-described problem, and is a method for controlling a heat pump device that can expand the range of the outside air temperature at which stable operation can be performed to the low temperature side, and the outdoor of the heat pump device. It aims at providing a machine and a heat pump device.

In order to achieve the above object, the present invention provides the following means.
The control method of the heat pump device of the present invention includes a first control step of controlling the opening degree of the expansion valve based on the suction superheat degree of the refrigerant sucked into the compressor, and at least the discharge refrigerant discharged from the compressor. In a second control step of controlling the opening of the expansion valve based on the temperature and sucking the refrigerant in a gas-liquid two-phase state into the compressor, and in the first control step, the temperature of the discharged refrigerant and the first switching When the temperature of the discharged refrigerant is higher than the first switching temperature by comparing the temperature, the temperature of the discharged refrigerant in the first switching step and the second control step for switching to the second control step And a second switching temperature, and a second switching step for switching to the first control step when the temperature of the discharged refrigerant is lower than the second switching temperature.

  According to the present invention, for example, when the temperature of the discharged refrigerant becomes higher than the first switching temperature due to a decrease in the outside air temperature or the like, the refrigerant in the gas-liquid two-phase state is sucked into the compressor, and the liquid phase Since the refrigerant absorbs heat and evaporates, the temperature of the discharged refrigerant, the compressor, the motor driving the compressor, the motor coil, and the like can be lowered.

  Further, since the opening degree of the expansion valve is controlled based on at least the temperature of the discharged refrigerant, the opening degree of the expansion valve is appropriately controlled even when the gas-liquid two-phase refrigerant flows into the compressor. Can do.

  On the other hand, when the temperature of the discharged refrigerant becomes lower than the second switching temperature, that is, when the temperature of the discharged refrigerant, the compressor, or the motor that drives the compressor decreases, the above-described second The control method is changed from the control related to the control step, that is, the opening control of the expansion valve based on at least the temperature of the discharged refrigerant, to the control related to the first control step, that is, the control of the expansion valve based on the intake superheat degree. For this reason, the temperature of the motor coil or the like is controlled within a predetermined range.

In the above invention, in the second control step, the control according to the second control step, the third control step for performing the control for reducing the flow rate of the refrigerant discharged from the compressor based on the temperature of the discharged refrigerant, and the second control step. A third switching step of comparing the temperature of the discharged refrigerant with a third switching temperature and switching to the third control step when the temperature of the discharged refrigerant is higher than the third switching temperature. It is desirable.

  According to the present invention, when the temperature of the discharged refrigerant becomes higher than the third switching temperature during the control in the second control step, the flow rate of the refrigerant discharged from the compressor is further increased. Control to reduce is added. That is, since the amount of work in the compressor is reduced, the temperature of the motor driving the compressor, the motor coil, etc. can be lowered.

  Examples of the control for reducing the flow rate of the refrigerant discharged from the compressor include control for reducing the drive rotational speed of the compressor.

  In the above invention, it is desirable that in the second control step, the opening degree of the expansion valve is controlled based on a temperature of the discharged refrigerant and a discharge pressure saturation temperature determined from the pressure of the discharged refrigerant.

  According to the present invention, the opening degree of the expansion valve is controlled based on the discharge refrigerant temperature and the discharge pressure saturation temperature, in other words, based on the discharge superheat degree which is the difference between the discharge refrigerant temperature and the discharge pressure saturation temperature. Therefore, compared with the method of controlling the opening degree of the expansion valve based only on the temperature of the discharged refrigerant, the outdoor unit can be controlled more stably.

  In the above invention, in the second control step, there is also a method of controlling the opening degree of the expansion valve based only on the temperature of the discharged refrigerant.

  According to the present invention, since the opening degree of the expansion valve is controlled based only on the temperature of the discharge refrigerant, the opening degree of the expansion valve is based on the degree of discharge superheat that is the difference between the temperature of the discharge refrigerant and the discharge pressure saturation temperature. Compared with the method of controlling the above, it is possible to perform control that follows changes in the discharged refrigerant temperature or the like in a short time.

  In the above invention, in the third control step, the temperature of the discharged refrigerant is compared with the fourth switching temperature and the fifth switching temperature, the temperature of the discharged refrigerant is lower than the fourth switching temperature, and When the temperature is higher than the fifth switching temperature, the third control step is continued, and when the temperature of the discharged refrigerant is lower than the fifth switching temperature, the fourth switching step is switched to the second control step. It is desirable to have.

According to the present invention, when the temperature of the discharged refrigerant is lower than the fourth switching temperature and higher than the fifth switching temperature, in other words, when the degree of temperature drop in the discharged refrigerant is small, the third control step. Thus, the supply of the gas-liquid two-phase refrigerant to the compressor is continued.

On the other hand, when the temperature of the discharged refrigerant is lower than the fifth switching temperature, in other words, when the degree of temperature drop in the discharged refrigerant is large, control related to the second control step is performed. For this reason, the temperature of the motor coil or the like is controlled within a predetermined range.

  In the above invention, in the liquid injection step for guiding a part of the liquid phase refrigerant before passing through the expansion valve to the compression step of the refrigerant in the compressor, and in the first control step, It is desirable to have a fifth switching step that switches to the liquid injection step when the temperature of the discharged refrigerant is higher than the sixth switching temperature.

  According to the present invention, when the temperature of the discharged refrigerant is higher than the sixth switching temperature, the liquid phase refrigerant is supplied to the refrigerant compression step, and the liquid phase refrigerant absorbs the heat of the adiabatic compressed refrigerant. Evaporate. In other words, the adiabatic-compressed refrigerant, the compressor, the motor that drives the compressor, the motor coil, and the like are cooled by the supplied liquid-phase refrigerant.

  The outdoor unit of the heat pump device according to the present invention includes a compressor that compresses refrigerant, a switching valve that switches an outlet of the refrigerant discharged from the compressor based on an operating state, and heat between the refrigerant and outside air. An outdoor heat exchanger that performs exchange, an expansion valve that reduces the pressure of the refrigerant, and a control unit that performs opening degree control of the expansion valve based on the control method of the present invention are provided. And

  According to this invention, since the control part which performs the control method of the outdoor unit of the said invention is provided, the range of the outside temperature which can operate | move stably can be extended to the low temperature side.

  The heat pump device of the present invention is characterized in that the outdoor unit of the present invention and an indoor unit having an indoor heat exchanger in which the refrigerant circulates between the outdoor unit and the outdoor unit are provided.

  According to the present invention, since the outdoor unit of the present invention is provided, the range of the outside air temperature at which stable operation can be performed can be expanded to the low temperature side.

According to the control method of the heat pump device, the outdoor unit of the heat pump device, and the heat pump device of the present invention, the opening degree of the expansion valve is controlled based on at least the temperature of the discharged refrigerant, and the refrigerant in the gas-liquid two-phase state is used as the compressor. Since it is inhaled, there is an effect that the range of the outside air temperature that can be stably operated can be expanded to the low temperature side.
Further, when the temperature of the discharged refrigerant becomes lower than the second switching temperature, the control method is changed from the opening degree control of the expansion valve based on at least the temperature of the discharged refrigerant to the opening degree control of the expansion valve based on the suction superheat degree. Since it changes, there exists an effect that the range of the outside temperature which can be drive | operated stably can be extended to the low temperature side.

[First Embodiment]
Hereinafter, a first embodiment of the present invention will be described with reference to FIGS.
In the present embodiment, the heat pump device of the present invention will be described by applying it to an air conditioner.
Drawing 1 is a mimetic diagram explaining the whole air conditioner composition concerning this embodiment.
The air conditioner (heat pump device) 1 performs temperature adjustment of indoor air, which is indoor air, by performing cooling operation or heating operation.
As shown in FIG. 1, the air conditioner 1 includes an outdoor unit 2 and an indoor unit 3.

In the present embodiment, description will be made by applying to an example in which one indoor unit 3 is connected to one outdoor unit 2, but a plurality of indoor units 3 are connected to one outdoor unit 2. There is no particular limitation.

FIG. 2 is a block diagram illustrating the configuration of the outdoor unit in FIG.
The outdoor unit 2 constitutes a refrigerant circuit in which the refrigerant circulates together with the indoor unit 3, and performs heat exchange between the outdoor air that is outdoor air and the refrigerant.
As shown in FIGS. 1 and 2, the outdoor unit 2 includes a compressor 21, an outdoor heat exchanger 22, an expansion valve 23, an accumulator 24, a four-way valve (switching valve) 25, and a connection valve 26. The low pressure sensor 27L, the high pressure sensor 27H, the suction temperature sensor 28L, the discharge temperature sensor 28H, and the control unit 29 are provided.

The compressor 21 is rotationally driven by an integrally configured electric motor, thereby sucking in and compressing low-pressure refrigerant and discharging high-pressure refrigerant.
Furthermore, the compressor 21 is arrange | positioned so that a refrigerant | coolant can distribute | circulate between the four-way valve 25 and the accumulator 24, as shown in FIG.

  The compressor 21 may be a known compressor such as a scroll compressor or a rotary compressor, and is not particularly limited.

  As shown in FIG. 1, the outdoor heat exchanger 22 performs heat exchange between the outside air and the refrigerant. Furthermore, the outdoor heat exchanger 22 is disposed between the four-way valve 25 and the expansion valve 23 so that the refrigerant can flow therethrough.

  In addition, as the outdoor heat exchanger 22, a well-known heat exchanger can be used and it does not specifically limit.

As shown in FIGS. 1 and 2, the expansion valve 23 decompresses the high-pressure refrigerant by adiabatically expanding it into a low-pressure refrigerant, and the opening degree is controlled by the control unit 29. . Furthermore, the expansion valve 23, between the connecting valve 26 and the chamber outer heat exchanger 22, the refrigerant is arranged to be distributed.

  In addition, as the expansion valve 23, a well-known thing can be used and it does not specifically limit.

  The accumulator 24 separates the liquid-phase refrigerant contained in the refrigerant flowing into the compressor 21 and supplies only the gas-phase refrigerant to the compressor 21. Furthermore, the accumulator 24 is arrange | positioned so that a refrigerant | coolant can distribute | circulate between the four-way valve 25 and the suction part in the compressor 21, as shown in FIG.

  The accumulator 24 may be a known one, and is not particularly limited.

The four-way valve 25 is a switching valve that controls the flow of the refrigerant based on the operating state of the air conditioner 1. For example, the high-temperature and high-pressure refrigerant discharged from the compressor 21 is transferred to the indoor heat exchanger 31 during the heating operation. The air is guided to the outdoor heat exchanger 22 during cooling operation.
Furthermore, the four-way valve 25 is connected to the compressor 21, the accumulator 24, the indoor heat exchanger 31, and the connection valve 26 so that the refrigerant can flow therethrough.

  Note that the four-way valve 25 may be used as the switching valve as described above, and a known switching method such as a combination of a plurality of on-off valves can be used, and is not particularly limited.

  As shown in FIG. 1, the connection valve 26 is an on-off valve used when connecting or disconnecting the flow path through which the refrigerant flows between the outdoor unit 2 and the indoor unit 3. In other words, the opening / closing valve is used when the outdoor unit 2 and the indoor unit 3 are connected or disconnected.

  As shown in FIGS. 1 and 2, the low-pressure sensor 27 </ b> L measures the pressure of the refrigerant sucked into the compressor 21, and inputs information on the measured refrigerant pressure to the control unit 29. . Furthermore, the low pressure sensor 27L is arranged on a pipe connecting the four-way valve 25 and the accumulator 24 so that the pressure of the refrigerant flowing inside the pipe can be measured.

  As the low-pressure sensor 27L, a known sensor can be used and is not particularly limited.

  As shown in FIGS. 1 and 2, the high pressure sensor 27 </ b> H measures the pressure of the refrigerant discharged from the compressor 21, and inputs information on the measured refrigerant pressure to the control unit 29. . Further, the high pressure sensor 27H is arranged on a pipe connecting the discharge part of the compressor 21 and the four-way valve 25 so that the pressure of the refrigerant flowing inside the pipe can be measured.

  As the high-pressure sensor 27H, a known sensor can be used and is not particularly limited.

As shown in FIG. 2 , the suction temperature sensor 28 </ b> L measures the temperature of the refrigerant sucked into the compressor 21, and inputs information on the measured refrigerant temperature to the control unit 29.

  Note that a known arrangement position can be used as the arrangement position of the suction temperature sensor 28L, and is not particularly limited. Further, a known temperature sensor can be used as the suction temperature sensor 28L, and is not particularly limited.

As shown in FIG. 2 , the discharge temperature sensor 28 </ b> H measures the temperature of the refrigerant discharged from the compressor 21, and inputs information on the measured refrigerant temperature to the control unit 29.

  A known arrangement position can be used as the arrangement position of the discharge temperature sensor 28H, and is not particularly limited. Furthermore, as the discharge temperature sensor 28H, a known temperature sensor can be used and is not particularly limited.

The control part 29 controls the opening degree of the expansion valve 23 according to the driving | running state of the air conditioning apparatus 1, as shown in FIG. 1 and FIG.
The control unit 29 is connected to the low pressure sensor 27L, the high pressure sensor 27H, the suction temperature sensor 28L, and the discharge temperature sensor 28H so that information related to the refrigerant is input, and the control unit 29 is connected to the expansion valve 23. It is connected so that a signal for controlling the opening can be output.
The control of the opening degree of the expansion valve 23 by the control unit 29 will be described later.

As shown in FIG. 1, the indoor unit 3 constitutes a refrigerant circuit in which a refrigerant circulates together with the outdoor unit 2, and performs heat exchange between the inside air and the refrigerant.
The indoor unit 3 is provided with an indoor heat exchanger 31.

  The high-pressure sensor 27H may be provided in the outdoor unit 2 as described above, or may be provided in the vicinity of the refrigerant inflow portion or outflow portion in the indoor heat exchanger 31, which is particularly limited. is not.

Next, an operation method in the air conditioner 1 having the above configuration will be described.
First, the flow of the refrigerant when the air-conditioning apparatus 1 performs the heating operation and the cooling operation will be described, and then the opening degree control of the expansion valve 23 will be described.

  When heating operation is performed in the air conditioner 1, as shown in FIG. 1, the discharge part of the compressor 21 and the indoor heat exchanger 31 are connected, and the outdoor heat exchanger 22 and the accumulator 24 are connected. As a result, the four-way valve 25 is switched.

  In the above-described state, the high-temperature and high-pressure gas-phase refrigerant compressed by the compressor 21 is guided to the indoor heat exchanger 31 via the four-way valve 25. The refrigerant exchanges heat with the inside air in the indoor heat exchanger 31, that is, dissipates heat toward the inside air.

Therefore, the high-temperature and high-pressure gas-phase refrigerant is condensed inside the indoor heat exchanger 31 and becomes a high-pressure liquid-phase refrigerant.
On the other hand, the inside air absorbs the heat of the refrigerant in the indoor heat exchanger 31 and flows out into the room as warmed air.

  The refrigerant that has flowed out of the indoor heat exchanger 31 is guided to the expansion valve 23 and adiabatically expands when passing through the expansion valve 23 to become a low-temperature and low-pressure refrigerant. Thereafter, the refrigerant is guided to the outdoor heat exchanger 22 and exchanges heat with the outside air in the outdoor heat exchanger 22, that is, absorbs the heat of the outside air. Therefore, the low-temperature and low-pressure liquid-phase refrigerant evaporates inside the outdoor heat exchanger 22 and becomes a gas-phase refrigerant.

The refrigerant that has flowed out of the outdoor heat exchanger 22 flows into the accumulator 24 through the four-way valve 25. The refrigerant is separated in the accumulator 24 into a gas phase refrigerant and a liquid phase refrigerant, and the gas phase refrigerant is sucked into the compressor 21.
The sucked refrigerant is compressed by the compressor 21, and then discharged again toward the indoor heat exchanger 31, and the above-described process is repeated.

  When cooling operation is performed in the air conditioner 1, as shown in FIG. 1, the discharge part of the compressor 21 and the outdoor heat exchanger 22 are connected, and the indoor heat exchanger 31 and the accumulator 24 are connected. As a result, the four-way valve 25 is switched.

  In the above-described state, the high-temperature and high-pressure gas-phase refrigerant compressed by the compressor 21 is guided to the outdoor heat exchanger 22 via the four-way valve 25. The refrigerant radiates heat toward the outside air in the outdoor heat exchanger 22. Therefore, the high-temperature and high-pressure gas-phase refrigerant is condensed inside the outdoor heat exchanger 22 and becomes a high-pressure liquid-phase refrigerant.

  The refrigerant flowing out of the outdoor heat exchanger 22 is guided to the expansion valve 23 and adiabatically expands when passing through the expansion valve 23 to become a low-temperature and low-pressure refrigerant. Thereafter, the refrigerant is guided to the indoor heat exchanger 31 and absorbs the heat of the inside air in the indoor heat exchanger 31. Therefore, the low-temperature and low-pressure liquid-phase refrigerant evaporates inside the indoor heat exchanger 31 and becomes a gas-phase refrigerant.

  On the other hand, the inside air takes heat from the refrigerant in the indoor heat exchanger 31 and flows out into the room as cooled air.

The refrigerant that has flowed out of the indoor heat exchanger 31 flows into the accumulator 24 through the four-way valve 25. The refrigerant is separated in the accumulator 24 into a gas phase refrigerant and a liquid phase refrigerant, and the gas phase refrigerant is sucked into the compressor 21.
The sucked refrigerant is compressed by the compressor 21, and then discharged again toward the outdoor heat exchanger 22, and the above-described process is repeated.

Next, the opening degree control of the expansion valve 23 by the control unit 29 will be described.
First, the opening control of the expansion valve 23 in the cooling operation state in the air conditioner 1 and in the heating operation state when the outside air temperature is high will be described.
FIG. 3 is a Mollier diagram showing the state of the refrigerant during control based on the suction superheat degree in the air conditioner of FIG. 1.

In the cooling operation state and the heating operation state when the outside air temperature is high, the control unit 29 controls the opening degree of the expansion valve 23 so that the suction superheat degree SH1 becomes a predetermined value as shown in FIG.
By controlling in this way, the state of the refrigerant sucked into the compressor 21 is controlled.

Specifically, when the value of the suction superheat degree SH1 is smaller than a predetermined value, the control unit 29 performs control to close the opening of the expansion valve 23, and the value of the suction superheat degree SH1 is reduced to a predetermined value. It is increasing. On the other hand, if the value of the suction superheat degree SH 1 is larger than the predetermined value, the control unit 29 performs control to widen the opening of the expansion valve 23, the value of the suction superheat degree SH1 to a predetermined value It is lowered.

Here, a method of calculating the suction superheat degree SH1 in the control unit 29 will be described.
The suction superheat degree SH1 is a temperature difference between the temperature of the refrigerant sucked into the compressor 21 and the suction pressure saturation temperature of the suction refrigerant.

  As shown in FIG. 3, the control unit 29 calculates the above-described suction pressure saturation temperature from the information on the pressure of the suction refrigerant input from the low pressure sensor 27L. Therefore, the control unit 29 calculates the intake superheat degree SH1 from the intake refrigerant temperature input from the intake temperature sensor 28L and the calculated intake pressure saturation temperature.

Next, the opening degree control of the expansion valve 23 in the heating operation state when the outside air temperature is low, which is a feature of the present embodiment, will be described.
4 and 5 are flowcharts for explaining the opening degree control of the expansion valve in the control unit of FIG.

As shown in FIG. 4, in the heating operation state when the outside air temperature is low, first, control based on the suction superheat degree SH1 is performed (step S1 (first control step)).
That is, the control unit 29 controls the opening degree of the expansion valve 23 so that the suction superheat degree SH1 becomes a predetermined value.

  While the control based on the suction superheat degree SH1 is performed, the control unit 29 controls the temperature of the refrigerant discharged from the compressor 21 and the first predetermined temperature, which is about 100 ° C. (first switching temperature) in the present embodiment. Compare with.

When the temperature of the discharged refrigerant is lower than about 100 ° C. (first predetermined temperature), the control unit 29 continues to perform control based on the suction superheat degree SH1.
On the other hand, when the temperature of the discharged refrigerant is higher than about 100 ° C., the control unit 29 changes the control method of the opening degree of the expansion valve 23 from the control based on the suction superheat degree SH1 to the control based on the discharge superheat degree SH2. (Step S2 (first switching step)).

FIG. 6 is a Mollier diagram showing the state of the refrigerant during control based on the discharge superheat degree in the air conditioner of FIG. 1.
As described above, when the temperature of the discharged refrigerant becomes higher than about 100 ° C., control based on the discharge superheat degree SH2 is performed (step S3 (second control step)).
That is, as shown in FIG. 6, the control unit 29 controls the opening degree of the expansion valve 23 so that the discharge superheat degree SH2 becomes a predetermined value.

  Here, the predetermined value in the control based on the discharge superheat degree SH2 is a value at which the gas-liquid two-phase refrigerant flows into the compressor 21 as shown in FIG. Therefore, the opening degree of the expansion valve 23 is larger in the control based on the discharge superheat degree SH2 than in the control based on the suction superheat degree SH1.

On the other hand, the discharge superheat degree SH2 is a temperature difference between the temperature of the refrigerant discharged from the compressor 21 and the discharge pressure saturation temperature of the discharge refrigerant.

  As shown in FIG. 3, the control unit 29 calculates the discharge pressure saturation temperature from the information on the pressure of the discharge refrigerant input from the high pressure sensor 27H. Therefore, the control unit 29 calculates the discharge superheat degree SH2 from the temperature of the discharge refrigerant input from the discharge temperature sensor 28H and the calculated discharge pressure saturation temperature.

  By controlling the opening degree of the expansion valve 23 as described above, as shown in FIG. 6, the compression process moves in a direction in which the specific enthalpy is reduced (the left direction in FIG. 6). Thereby, the temperature of a discharge refrigerant | coolant, the temperature of the compressor 21, an electric motor, and a motor coil falls.

That is, the gas-liquid two-phase refrigerant is sucked into the compressor 21, and the liquid-phase refrigerant absorbs heat of the refrigerant to be compressed, the compressor 21, and the electric motor, and evaporates. In other words, the compressor 21 and the electric motor are cooled by the liquid phase refrigerant.
As a result, the temperature of the refrigerant discharged from the compressor 21 also decreases.

  While the control based on the discharge superheat degree SH2 is performed, the control unit 29 controls the temperature of the refrigerant discharged from the compressor 21 and the second predetermined temperature, which is about 80 ° C. (second switching temperature) in the present embodiment. Compare with.

When the temperature of the discharged refrigerant is lower than about 80 ° C., the control unit 29 switches the control method of the opening degree of the expansion valve 23 from control based on the discharge superheat degree SH2 to control based on the suction superheat degree SH1 (step) S4 (second switching step)).

  On the other hand, when the temperature of the discharged refrigerant is higher than about 80 ° C., the temperature of the discharged refrigerant is further compared with the third predetermined temperature, which is about 105 ° C. (third switching temperature) in the present embodiment. Do.

  When the temperature of the discharged refrigerant is lower than about 105 ° C., that is, when the temperature of the discharged refrigerant is between about 80 ° C. and about 105 ° C., the control based on the discharge superheat degree SH2 is continued. .

  On the other hand, as shown in FIG. 5, when the temperature of the discharged refrigerant is higher than about 105 ° C., the control unit 29 performs control based on the discharge superheat degree SH2 from control based on the discharge superheat degree SH2, and It switches to the rotation speed control of the compressor 21 (step S5 (3rd switching step)).

As described above, when the temperature of the discharged refrigerant is higher than about 105 ° C., the rotational speed control of the compressor 21 is added to the control based on the discharge superheat degree SH2 (step S6 (third control step)).
Specifically, the control unit 29 performs protection control of the rotational speed of the compressor 21 based on the temperature of the discharged refrigerant, and determines the upper limit of the rotational speed of the compressor 21 or defines the rotational speed of the compressor. Drop at speed.

  For this reason, an upper limit is set for the flow rate of the refrigerant discharged from the compressor 21, and the flow rate of the discharged refrigerant is generally reduced. In other words, the amount of work in the compressor 21 decreases, and the temperature of the electric motor, the motor coil, etc. that drives the compressor 21 decreases.

While the control based on the discharge superheat degree SH2 and the rotation speed control of the compressor 21 are being performed, the control unit 29 includes the temperature of the refrigerant discharged from the compressor 21, the fourth predetermined temperature, and the present embodiment. Then, comparison with about 115 ° C. (fourth switching temperature) is performed (step S7).
When the temperature of the discharged refrigerant is higher than about 115 ° C., the control unit 29 stops the operation of the compressor 21 and stops the operation of the outdoor unit 2 and the air conditioner 1.

  On the other hand, when the temperature of the discharged refrigerant is lower than about 115 ° C., the temperature of the discharged refrigerant is further compared with a fifth predetermined temperature, which is about 100 ° C. (the fifth switching temperature) in the present embodiment.

  When the temperature of the discharged refrigerant is higher than about 100 ° C. (the fifth predetermined temperature), that is, when the temperature of the discharged refrigerant is between about 100 ° C. and about 115 ° C., the control unit 29 Control based on the superheat degree SH2 and rotation speed control of the compressor 21 are continued.

  On the other hand, when the temperature of the discharged refrigerant is lower than about 100 ° C. (fifth predetermined temperature), the control unit 29 controls the control method of the opening degree of the expansion valve 23 based on the discharge superheat degree SH2. Then, the rotation speed control of the compressor 21 is switched to the control based on the discharge superheat degree SH2 (step S8 (fourth switching step)).

  According to the above configuration, when the temperature of the discharged refrigerant becomes higher than the first predetermined temperature due to a decrease in the outside air temperature or the like, the gas-liquid two-phase refrigerant is sucked into the compressor 21 and the liquid Since the phase refrigerant absorbs heat and evaporates, the temperature of the discharged refrigerant, the compressor 21, the electric motor, the motor coil, and the like can be lowered. Therefore, the range of the outside air temperature at which the air conditioner 1 and the outdoor unit 2 can be stably operated can be expanded to the low temperature side.

Furthermore, since the opening degree of the expansion valve 23 is controlled based on the discharge refrigerant temperature and the discharge pressure saturation temperature, that is, based on the discharge superheat degree SH2, the refrigerant in the gas-liquid two-phase state flows into the compressor 21. Even if it exists, unlike the case where it controls based on the suction superheat degree SH1, the opening degree of the expansion valve 23 can be controlled appropriately.

  At the same time, since the opening degree of the expansion valve 23 is controlled based on the discharge superheat degree SH2, which is the difference between the temperature of the discharge refrigerant and the discharge pressure saturation temperature, the opening degree of the expansion valve 23 is set based only on the temperature of the discharge refrigerant. Compared with the method of controlling, the outdoor unit can be controlled more stably.

  On the other hand, when the temperature of the discharged refrigerant is lower than the second predetermined temperature, that is, when the temperature of the discharged refrigerant, the compressor 21, or the electric motor is decreased, the discharge superheat degree SH2 is used. The control method is changed from opening degree control of the expansion valve 23 to opening degree control of the expansion valve 23 based on the suction superheat degree SH1. Therefore, the temperature of the motor coil or the like can be controlled within a predetermined range.

  When the opening degree control of the expansion valve 23 based on the discharge superheat degree SH2 is being performed, if the temperature of the discharged refrigerant becomes higher than the third predetermined temperature, the refrigerant discharged from the compressor 21 is further reduced. Control for reducing the flow rate, that is, control for reducing the drive rotational speed of the compressor 21, is additionally performed. That is, since the work amount in the compressor 21 is reduced, the temperature of the electric motor, the motor coil, etc. can be lowered.

When the temperature of the discharged refrigerant is lower than the fourth predetermined temperature and higher than the fifth predetermined temperature, in other words, when the degree of temperature drop in the discharged refrigerant is small, the expansion valve based on the discharge superheat degree SH2 23 is controlled, and the supply of the gas-liquid two-phase refrigerant to the compressor 21 is continued.
On the other hand, when the temperature of the discharged refrigerant is lower than the fifth predetermined temperature, in other words, when the degree of temperature decrease in the discharged refrigerant is large, the opening degree control of the expansion valve 23 based on the intake superheat degree SH1 is performed. Is called. Therefore, the temperature of the motor coil or the like can be controlled within a predetermined range.

[Modification of First Embodiment]
Next, a modification of the first embodiment of the present invention will be described with reference to FIGS.
The basic configuration of the air conditioner of the present modification is the same as that of the first embodiment, but differs from the first embodiment in the method for controlling the expansion valve opening. Therefore, in this embodiment, only the control method of the expansion valve opening degree will be described using FIG. 7 to FIG. 10, and description of other components and the like will be omitted.
FIG. 7 is a block diagram illustrating the control of the expansion valve opening degree in the air conditioner according to the present modification.
In addition, the same code | symbol is attached | subjected to the component same as 1st Embodiment, and the description is abbreviate | omitted.

As shown in FIG. 7, the control unit 129 in the outdoor unit 102 of the air conditioner 101 is connected to the low-pressure sensor 27L, the suction temperature sensor 28L, and the discharge temperature sensor 28H so that information about the refrigerant is input. In addition, the control unit 129 is connected to the expansion valve 23 so that a signal for controlling the opening degree can be output.
The control of the opening degree of the expansion valve 23 by the control unit 129 will be described later.

Next, the opening degree control of the expansion valve 23, which is a feature of the present embodiment, will be described.
In addition, about the opening control of the expansion valve 23 in the air_conditioning | cooling operation state in the air conditioning apparatus 101, and the heating operation state when external temperature is high, since it is the same as that of 1st Embodiment, the description is abbreviate | omitted.

From here, the opening degree control of the expansion valve 23 in the heating operation state when the outside air temperature is low, which is a feature of the present embodiment, will be described.
8 and 9 are flowcharts for explaining the opening degree control of the expansion valve in the control unit of FIG.

As shown in FIG. 8, in the heating operation state when the outside air temperature is low, control based on the suction superheat degree SH1 is first performed (step S1).
That is, the control unit 129 controls the opening degree of the expansion valve 23 so that the suction superheat degree SH1 becomes a predetermined value.

  While the control based on the suction superheat degree SH1 is performed, the control unit 129 controls the temperature T2 of the refrigerant discharged from the compressor 21 and the first predetermined temperature, which is about 100 ° C. (first switching temperature in this embodiment). ).

When the temperature T2 of the discharged refrigerant is lower than about 100 ° C. (first predetermined temperature), the control unit 129 continues to perform control based on the suction superheat degree SH1.
On the other hand, when the temperature T2 of the discharged refrigerant is higher than about 100 ° C., the control unit 129 changes the control method of the opening degree of the expansion valve 23 from the control based on the suction superheat degree SH1 to the temperature T2 of the discharged refrigerant. The control is switched to based control (step S2 (first switching step)).

FIG. 10 is a Mollier diagram showing the state of the refrigerant during control based on the discharge superheat degree in the air conditioner of FIG.
As described above, when the temperature T2 of the discharged refrigerant becomes higher than about 100 ° C., control based on the temperature T2 of the discharged refrigerant is performed (step S13 (second control step)).
That is, the control unit 129 controls the opening degree of the expansion valve 23 so that the temperature T2 of the discharged refrigerant becomes a predetermined value as shown in FIG.

  Here, the predetermined value in the control based on the temperature T2 of the discharged refrigerant is a value at which the gas-liquid two-phase refrigerant flows into the compressor 21, as shown in FIG. Therefore, the opening degree of the expansion valve 23 is larger in the control based on the discharge refrigerant temperature T2 than in the control based on the suction superheat degree SH1.

  By controlling the opening degree of the expansion valve 23 as described above, as shown in FIG. 10, the compression process moves in a direction in which the specific enthalpy decreases (the left direction in FIG. 10). Thereby, the temperature of a discharge refrigerant | coolant, the temperature of the compressor 21, an electric motor, and a motor coil falls.

That is, the gas-liquid two-phase refrigerant is sucked into the compressor 21, and the liquid-phase refrigerant absorbs heat of the refrigerant to be compressed, the compressor 21, and the electric motor, and evaporates. In other words, the compressor 21 and the electric motor are cooled by the liquid phase refrigerant.
As a result, the temperature of the refrigerant discharged from the compressor 21 also decreases.

  While the control based on the temperature T2 of the discharged refrigerant is performed, the control unit 129 controls the temperature T2 of the refrigerant discharged from the compressor 21 and the second predetermined temperature, which is about 80 ° C. in the present embodiment (second switching). Temperature).

  When the temperature T2 of the discharged refrigerant is lower than about 80 ° C., the control unit 129 switches the control method of the opening degree of the expansion valve 23 from the control based on the temperature T2 of the discharged refrigerant to the control based on the suction superheat degree SH1. (Step S4).

  On the other hand, when the temperature T2 of the discharged refrigerant is higher than about 80 ° C., the temperature T2 of the discharged refrigerant is further set to the third predetermined temperature, which is about 105 ° C. (third switching temperature) in the present embodiment. Make a comparison.

  When the temperature T2 of the discharged refrigerant is lower than about 105 ° C., that is, when the temperature T2 of the discharged refrigerant is a temperature between about 80 ° C. and about 105 ° C., the control based on the temperature T2 of the discharged refrigerant is performed. Will continue.

  On the other hand, as shown in FIG. 9, when the temperature T2 of the discharged refrigerant is higher than about 105 ° C., the control unit 129 performs control based on the temperature T2 of the discharged refrigerant from the control based on the temperature T2 of the discharged refrigerant. And switching to the rotation speed control of the compressor 21 (step S5).

As described above, when the temperature T2 of the discharged refrigerant is higher than about 105 ° C., the rotational speed control of the compressor 21 is added to the control based on the temperature T2 of the discharged refrigerant (step S16 (third control step)). .
Specifically, the control unit 129 performs protection control of the rotational speed of the compressor 21 based on the temperature T2 of the discharged refrigerant, and determines the upper limit of the rotational speed of the compressor 21.

While the control based on the temperature T2 of the discharged refrigerant and the rotation speed control of the compressor 21 are being performed, the control unit 129 includes the temperature T2 of the refrigerant discharged from the compressor 21, the fourth predetermined temperature, In the embodiment, a comparison with about 115 ° C. (fourth switching temperature) is performed (step S7).
When the temperature T2 of the discharged refrigerant is higher than about 115 ° C., the control unit 129 stops the operation of the compressor 21 and stops the operation of the outdoor unit 2 and the air conditioner 1.

  On the other hand, when the temperature T2 of the discharged refrigerant is lower than about 115 ° C., the temperature T2 of the discharged refrigerant is further compared with the fifth predetermined temperature, which is about 100 ° C. (the fifth switching temperature) in this embodiment. Do.

When the temperature T2 of the discharged refrigerant is higher than about 100 ° C. (the fifth predetermined temperature), that is, when the temperature T2 of the discharged refrigerant is a temperature between about 100 ° C. and about 115 ° C., the control unit 129 Then, the control based on the temperature T2 of the discharged refrigerant and the rotation speed control of the compressor 21 are continued.

  On the other hand, when the temperature T2 of the discharged refrigerant is lower than about 100 ° C. (fifth predetermined temperature), the control unit 29 uses a method for controlling the opening degree of the expansion valve 23 based on the temperature T2 of the discharged refrigerant. The control and the rotation speed control of the compressor 21 are switched to the control based on the temperature T2 of the discharged refrigerant (step S8).

  According to the above configuration, since the opening degree of the expansion valve 23 is controlled based only on the temperature T2 of the discharge refrigerant, the discharge superheat degree SH2 that is the difference between the temperature T2 of the discharge refrigerant and the discharge pressure saturation temperature is used. Compared with the method of controlling the expansion valve 23, it is possible to perform control that follows changes in the discharged refrigerant temperature T2 in a short time.

[Second Embodiment]
Next, a second embodiment of the present invention will be described with reference to FIGS.
The basic configuration of the air conditioner of this embodiment is the same as that of the first embodiment, but differs from the first embodiment in that an injection circuit is provided. Therefore, in the present embodiment, only the injection circuit and its control method will be described with reference to FIGS. 11 to 14, and description of other components will be omitted.
FIG. 11 is a schematic diagram illustrating the configuration of the outdoor unit of the air-conditioning apparatus according to the present embodiment. FIG. 12 is a block diagram illustrating the configuration of the outdoor unit in FIG. 11.
In addition, the same code | symbol is attached | subjected to the component same as 1st Embodiment, and the description is abbreviate | omitted.

As shown in FIGS. 11 and 12 , the outdoor unit 202 of the air conditioner 201 includes a compressor 21, an outdoor heat exchanger 22, an expansion valve 23, an accumulator 24, a four-way valve 25, and a connection valve 26. A low pressure sensor 27L, a high pressure sensor 27H, a suction temperature sensor 28L, a discharge temperature sensor 28H, a control unit 229, an injection circuit 231, and a solenoid valve 232.

As shown in FIG. 11, the injection circuit 231 is a circuit that connects between the expansion valve 23 and the connection valve 26 and the compressor 21, and is a circuit that supplies liquid refrigerant to the compressor 21.
The injection circuit 231 includes an electromagnetic valve 232, and the supply of the liquid-phase refrigerant to the compressor 21 is controlled by the electromagnetic valve 232.

  As shown in FIGS. 11 and 12, the electromagnetic valve 232 is a valve whose opening / closing is controlled by the control unit 229, and is a valve that controls the liquid-phase refrigerant flow in the injection circuit 231.

  In the present embodiment, description will be made by applying to an example in which an electromagnetic valve 232 that performs an opening / closing operation is arranged in the injection circuit 231, but a flow rate adjustment valve capable of adjusting the opening degree may be arranged in the injection circuit 231. There is no particular limitation.

As shown in FIG. 12 , the control unit 229 is connected to the low pressure sensor 27L, the high pressure sensor 27H, the suction temperature sensor 28L, and the discharge temperature sensor 28H so that information related to the refrigerant is input. Further, the control unit 229 is connected so that a signal for controlling the opening degree can be output to the expansion valve 23 and a signal for controlling opening and closing can be output to the electromagnetic valve 232.

  The control of the opening degree of the expansion valve 23 by the control unit 229 and the control of opening / closing the electromagnetic valve 232 will be described later.

Next, the opening degree control of the expansion valve 23, which is a feature of the present embodiment, will be described.
In addition, about the air_conditioning | cooling operation state in the air conditioning apparatus 201, and the opening degree control of the expansion valve 23 in the heating operation state when external temperature is high, since it is the same as that of 1st Embodiment, the description is abbreviate | omitted.

From here, the opening degree control of the expansion valve 23 in the heating operation state when the outside air temperature is low, which is a feature of the present embodiment, will be described.
13 and 14 are flowcharts for explaining the opening control of the expansion valve in the control unit of FIG.

As shown in FIG. 13, in the heating operation state when the outside air temperature is low, first, control based on the intake superheat degree SH1 is performed (step S1).
That is, the control unit 229 controls the opening degree of the expansion valve 23 so that the suction superheat degree SH1 becomes a predetermined value.

  While the control based on the suction superheat degree SH1 is performed, the control unit 229 controls the temperature of the refrigerant discharged from the compressor 21 and the sixth predetermined temperature, which is about 100 ° C. (sixth switching temperature) in the present embodiment. Compare with.

When the temperature of the discharged refrigerant is lower than about 100 ° C. (sixth predetermined temperature), the control unit 229 continues to perform control based on the suction superheat degree SH1.
On the other hand, when the temperature of the discharged refrigerant is higher than about 100 ° C., the control unit 229 switches to control for opening the electromagnetic valve 232 in addition to control based on the suction superheat degree SH1 (step S21 (fifth switching). Step)).

  As described above, when the control in the control unit 229 is switched, that is, when the electromagnetic valve 232 is opened (step S22), the liquid-phase refrigerant is supplied to the compressor 21 via the injection circuit 231.

  The liquid-phase refrigerant is supplied to the refrigerant compression process in the compressor 21, absorbs heat of the refrigerant that is adiabatically compressed and the temperature is rising, and evaporates. In other words, the refrigerant in the compression process is cooled. Therefore, the temperature of the refrigerant discharged from the compressor 21 is lower than that in the state where the electromagnetic valve 232 is closed.

  While the control based on the suction superheat degree SH1 and the control to open the solenoid valve 232 are being performed, the control unit 229 controls the temperature of the refrigerant discharged from the compressor 21 and the first predetermined temperature, in this embodiment. Comparison with about 100 ° C. (first switching temperature) is performed.

  When the temperature of the discharged refrigerant is higher than about 100 ° C. (first predetermined temperature), the control method of the opening degree of the expansion valve 23 is controlled from the control based on the suction superheat degree SH1 and the control to open the electromagnetic valve 232. The control is switched to the control based on the discharge superheat degree SH2 (step S2).

  On the other hand, when the temperature of the discharged refrigerant is lower than about 100 ° C. (first predetermined temperature), the control unit 229 further determines that the temperature of the discharged refrigerant is the seventh predetermined temperature, which is about 80 in this embodiment. Comparison with ° C. (seventh switching temperature) is performed (step S23 (sixth switching step)).

When the temperature of the discharged refrigerant is higher than about 80 ° C. (seventh predetermined temperature), that is, when the temperature of the discharged refrigerant is included in the range of about 80 ° C. to about 100 ° C., the controller 229 The control based on the suction superheat degree SH1 is continuously performed with 232 open.
On the other hand, when the temperature of the discharged refrigerant is lower than about 80 ° C., the control unit 229 outputs a control signal for closing the electromagnetic valve 232 (step S24).

  Since the control by the control unit 229 after switching to the control based on the discharge superheat degree SH2 is the same as in the first embodiment, the control flowchart is shown in FIGS. 13 and 14, and the description thereof is omitted.

  According to the above configuration, when the temperature of the discharged refrigerant is higher than the sixth predetermined temperature, the liquid phase refrigerant is supplied to the refrigerant compression step, and the liquid phase refrigerant absorbs the heat of the adiabatic compressed refrigerant. Then evaporate. In other words, the adiabatic-compressed refrigerant, the compressor 21, the electric motor, the motor coil, and the like can be cooled by the supplied liquid-phase refrigerant.

[Modification of Second Embodiment]
Next, a modification of the second embodiment of the present invention will be described with reference to FIGS.
The basic configuration of the air conditioner of the present modification is the same as that of the second embodiment, but differs from the second embodiment in the method for controlling the expansion valve opening. Therefore, in this embodiment, only the control method of the expansion valve opening degree will be described using FIGS. 15 to 17, and description of other components and the like will be omitted.
FIG. 15 is a block diagram illustrating the control of the expansion valve opening degree in the air conditioner according to the present modification.
In addition, the same code | symbol is attached | subjected to the component same as 2nd Embodiment etc., and the description is abbreviate | omitted.

As shown in FIG. 15, the control unit 329 in the outdoor unit 302 of the air conditioner 301 is connected to the low pressure sensor 27L, the suction temperature sensor 28L, and the discharge temperature sensor 28H so that information related to the refrigerant is input. Yes. Further, the control unit 329 is connected so that a signal for controlling the opening degree can be output to the expansion valve 23 and a signal for controlling opening and closing can be output to the electromagnetic valve 232.
Note that control of the opening degree of the expansion valve 23 and opening / closing control of the electromagnetic valve 232 by the control unit 329 will be described later.

Next, the opening degree control of the expansion valve 23 and the opening / closing control of the electromagnetic valve 232, which are features of the present embodiment, will be described.
In addition, about the air_conditioning | cooling operation state in the air conditioning apparatus 301, and the opening degree control of the expansion valve 23 in the heating operation state when external temperature is high, since it is the same as that of 1st Embodiment, the description is abbreviate | omitted.

From here, the opening degree control of the expansion valve 23 and the opening / closing control of the electromagnetic valve 232 in the heating operation state when the outside air temperature is low, which is a feature of the present embodiment, will be described.
16 and 17 are flowcharts for explaining the opening control of the expansion valve in the control unit of FIG.

As shown in FIG. 16, in the heating operation state when the outside air temperature is low, first, control based on the suction superheat degree SH1 is performed (step S1).
That is, the control unit 329 controls the opening degree of the expansion valve 23 so that the suction superheat degree SH1 becomes a predetermined value.

  While the control based on the suction superheat degree SH1 is performed, the control unit 329 controls the temperature of the refrigerant discharged from the compressor 21 and the sixth predetermined temperature, which is about 100 ° C. (sixth switching temperature) in the present embodiment. Compare with.

When the temperature of the discharged refrigerant is lower than about 100 ° C. (sixth predetermined temperature), the control unit 329 continues to perform control based on the suction superheat degree SH1.
On the other hand, when the temperature of the discharged refrigerant is higher than about 100 ° C., the control unit 329 switches to the control for opening the electromagnetic valve 232 in addition to the control based on the suction superheat degree SH1 (step S21).

  While the control based on the suction superheat degree SH1 and the control for opening the electromagnetic valve 232 are being performed (step S22), the control unit 329 includes the temperature T2 of the refrigerant discharged from the compressor 21 and the first predetermined temperature. In this embodiment, a comparison with about 100 ° C. (first switching temperature) is performed.

  The control method of the opening degree of the expansion valve 23 is switched from control based on the suction superheat degree SH1 and control based on the opening of the electromagnetic valve 232 to control based on the temperature T2 of the discharged refrigerant (step S2).

  On the other hand, when the temperature T2 of the discharged refrigerant is lower than about 100 ° C. (first predetermined temperature), the control unit 329 further determines that the temperature T2 of the discharged refrigerant is the seventh predetermined temperature, which is the present embodiment. Comparison with about 80 ° C. (seventh switching temperature) is performed (step S23).

When the temperature T2 of the discharged refrigerant is higher than about 80 ° C. (seventh predetermined temperature), that is, when the temperature T2 of the discharged refrigerant is included in the range of about 80 ° C. to about 100 ° C., the control unit 329 The control based on the suction superheat degree SH1 is continued while the solenoid valve 232 is kept open.
On the other hand, when the temperature T2 of the discharged refrigerant is lower than about 80 ° C., the control unit 329 outputs a control signal for closing the electromagnetic valve 232 (step S24).

  Since the control by the control unit 329 after switching to the control based on the temperature T2 of the discharged refrigerant is the same as the modification of the first embodiment, the control flowchart is shown in FIGS. 16 and 17 and the description thereof is omitted. To do.

  According to the above configuration, when the temperature of the discharged refrigerant is higher than the sixth predetermined temperature, the liquid phase refrigerant is supplied to the refrigerant compression step, and the liquid phase refrigerant absorbs the heat of the adiabatic compressed refrigerant. Then evaporate. In other words, the adiabatic-compressed refrigerant, the compressor 21, the electric motor, the motor coil, and the like can be cooled by the supplied liquid-phase refrigerant.

The technical scope of the present invention is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention.
For example, in the above embodiment, the present invention has been described by applying it to an air conditioner. However, the present invention is not limited to an air conditioner and may be applied to hot water supply equipment, and is not particularly limited. Absent.

It is a mimetic diagram explaining the whole air conditioner composition concerning a 1st embodiment of the present invention. It is a block diagram explaining the structure in the outdoor unit of FIG. It is a Mollier diagram which shows the state of the refrigerant | coolant at the time of control based on the suction superheat degree in the air conditioner of FIG. It is a flowchart explaining the opening degree control of the expansion valve in the control part of FIG. It is a flowchart explaining the opening degree control of the expansion valve in the control part of FIG. It is a Mollier diagram which shows the state of the refrigerant | coolant at the time of control based on the discharge superheat degree in the air conditioner of FIG. It is a block diagram explaining control of the expansion valve opening degree in the air conditioning apparatus which concerns on the modification of the 1st Embodiment of this invention. It is a flowchart explaining the opening degree control of the expansion valve in the control part of FIG. It is a flowchart explaining the opening degree control of the expansion valve in the control part of FIG. It is a Mollier diagram which shows the state of the refrigerant | coolant at the time of control based on the discharge superheat degree in the air conditioner of FIG. It is a schematic diagram explaining the structure of the outdoor unit of the air conditioning apparatus in the 2nd Embodiment of this invention. It is a block diagram explaining the structure of the outdoor unit of FIG. It is a flowchart explaining the opening degree control of the expansion valve in the control part of FIG. It is a flowchart explaining the opening degree control of the expansion valve in the control part of FIG. It is a block diagram explaining control of the expansion valve opening degree in the air conditioning apparatus which concerns on the modification of the 2nd Embodiment of this invention. It is a flowchart explaining the opening degree control of the expansion valve in the control part of FIG. It is a flowchart explaining the opening degree control of the expansion valve in the control part of FIG.

Explanation of symbols

1, 101, 201, 301 Air conditioner (heat pump device)
2,102,202,302 Outdoor unit 21 Compressor 22 Outdoor heat exchanger 23 Expansion valve 25 Four-way valve (switching valve)
29,129,229,329 Control part S1 1st control step S2 1st switching step S3, S13 2nd control step S4 2nd switching step S5 3rd switching step S6, S16 3rd control step S8 4th switching step S21 2nd 5 switching step S23 6th switching step

Claims (8)

A first control step for controlling the opening of the expansion valve based on the suction superheat degree of the refrigerant sucked into the compressor;
A second control step of controlling the opening of the expansion valve based on at least the temperature of the discharged refrigerant discharged from the compressor, and causing the compressor to suck in a refrigerant in a gas-liquid two-phase state;
In the first control step, the temperature of the discharged refrigerant is compared with the first switching temperature, and when the temperature of the discharged refrigerant is higher than the first switching temperature, the first control step is switched to the second control step. A switching step;
In the second control step, the temperature of the discharged refrigerant is compared with a second switching temperature, and when the temperature of the discharged refrigerant is lower than the second switching temperature, the second control step switches to the first control step. A switching step;
A method for controlling a heat pump apparatus, comprising: A third control step for performing control according to the second control step and control for reducing the flow rate of the refrigerant discharged from the compressor based on the temperature of the discharged refrigerant;
In the second control step, the temperature of the discharged refrigerant is compared with a third switching temperature, and when the temperature of the discharged refrigerant is higher than the third switching temperature, the third control step is switched to the third control step. A switching step;
The method for controlling a heat pump apparatus according to claim 1, wherein:   3. The opening degree of the expansion valve is controlled in the second control step based on a discharge pressure saturation temperature determined from a temperature of the discharge refrigerant and a pressure of the discharge refrigerant. 4. Method for controlling the heat pump apparatus.   3. The method of controlling a heat pump device according to claim 1, wherein, in the second control step, the opening degree of the expansion valve is controlled based only on the temperature of the discharged refrigerant. 4. In the third control step, the temperature of the discharged refrigerant is compared with the fourth switching temperature and the fifth switching temperature,
When the temperature of the discharged refrigerant is lower than the fourth switching temperature and higher than the fifth switching temperature, the third control step is continued.
A fourth switching step for switching to the second control step when the temperature of the discharged refrigerant is lower than the fifth switching temperature;
The method of controlling a heat pump apparatus according to claim 2, wherein A liquid injection step for guiding a part of the liquid phase refrigerant before passing through the expansion valve to the refrigerant compression step in the compressor;
In the first control step, the temperature of the discharged refrigerant is compared with a sixth switching temperature, and when the temperature of the discharged refrigerant is higher than the sixth switching temperature, the fifth switching is switched to the liquid injection step. Steps,
The method for controlling a heat pump apparatus according to claim 1, wherein: A compressor for compressing the refrigerant;
A switching valve for switching the flow destination of the refrigerant discharged from the compressor based on the operating state;
An outdoor heat exchanger that exchanges heat between the refrigerant and outside air;
An expansion valve for reducing the pressure of the refrigerant;
A control unit that performs opening degree control of the expansion valve based on the control method according to any one of claims 1 to 6,
An outdoor unit for a heat pump device, wherein: An outdoor unit according to claim 7;
An indoor unit having an indoor heat exchanger through which the refrigerant circulates with the outdoor unit;
A heat pump device characterized in that is provided.

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