JP2005147456A - Air conditioner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To secure sufficient heating ability even at low outside air temperatures. <P>SOLUTION: This air conditioner comprises a refrigerant circuit 20 of a refrigerating cycle, and the refrigerant circuit 20 has a compressor 21, an outdoor heat exchanger 25, a receiver 23, a first expansion valve 24, and an indoor heat exchanger 22. The compressor 21 is constituted so as to compress refrigerant in two stages. A second expansion valve 3a for compressing the refrigerant to a middle pressure is provided between the indoor heat exchanger 22 and the receiver 23, and an injection pipe 31 wherein the middle pressure liquid refrigerant flows into between the lower stage side compressor and the higher stage side compressor from the receiver 23 is connected between the receiver 23 and the compressor 21 and comprises a heater 32 heating the middle pressure liquid refrigerant in the injection pipe 31. Thereby, since the middle pressure refrigerant with increased enthalpy by heating by the heater 32 is added to the indoor heat exchanger 22, the heating ability can be improved. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an air conditioner, and particularly relates to an air conditioner including a refrigerant circuit that performs a refrigeration cycle by compressing refrigerant in two stages.

  2. Description of the Related Art Conventionally, some air conditioners include a refrigerant circuit that performs a refrigeration cycle by compressing a refrigerant in two stages and performs indoor heating (see, for example, Patent Document 1).

  Specifically, in the air conditioner disclosed in Patent Document 1, a compression mechanism, an outdoor heat exchanger, a first expansion valve, a gas-liquid separator (receiver), a second expansion valve, and an indoor heat exchanger are connected by piping in order. A refrigerant circuit. This air conditioner is configured to switch between heating operation and cooling operation by reversibly switching the refrigerant circulation in the refrigerant circuit. And the said compression mechanism is comprised so that a low stage side compressor and a high stage side compressor may be accommodated in a casing, and a refrigerant | coolant may be compressed 2 steps | paragraphs. The refrigerant circuit is provided with an injection pipe connected between the compression mechanism and the gas-liquid separator. The injection pipe is configured to supply an intermediate-pressure gas refrigerant from the gas-liquid separator between the low-stage compressor and the high-stage compressor of the compression mechanism.

In the heating operation of the air conditioner, the high-pressure gas refrigerant discharged from the compression mechanism is condensed by exchanging heat with the room air in the room heat exchanger, and the room air is heated to heat the room. The condensed high-pressure liquid refrigerant is depressurized by the second expansion valve to become an intermediate-pressure refrigerant and stored in the gas-liquid separator. Of the intermediate pressure refrigerant in the gas-liquid separator, the intermediate pressure liquid refrigerant is depressurized by the first expansion valve to become a low pressure refrigerant, exchanges heat with outdoor air in the outdoor heat exchanger, evaporates, and then is compressed again. Return to. On the other hand, intermediate-pressure gas refrigerant among the intermediate-pressure refrigerant in the gas-liquid separator is injected into the compressor. Thereby, in the said indoor heat exchanger, since the refrigerant | coolant circulation amount increases by adding the injected intermediate pressure gas refrigerant | coolant, heating capability improves.
JP 2000-73974 A

  However, in the conventional air conditioner described above, since heating operation is performed using only outdoor air as a heat source, there is a limit to the increase in heating capacity due to the injection of intermediate pressure gas refrigerant. There was a problem that sufficient heating capacity could not be ensured when there was a large.

  This invention is made | formed in view of such a point, The place made into the objective is ensuring sufficient heating capability also at the time of the low external air, without reducing the operating efficiency of a compressor.

  Specifically, the first invention is a vapor compression refrigeration cycle in which a compression mechanism (21), a heat source side heat exchanger (25), an expansion mechanism (24), and a use side heat exchanger (22) are connected by piping. On the assumption that the compression mechanism (21) includes a low-stage compressor and a high-stage compressor to compress the refrigerant in two stages. Yes. Then, the liquid refrigerant is divided from between the use side heat exchanger (22) and the expansion mechanism (24), and the divided liquid refrigerant is connected between the low stage compressor and the high stage compressor in an intermediate pressure state. In addition to an injection pipe (31) supplied in between, heating means (32) for heating the intermediate-pressure liquid refrigerant flowing through the injection pipe (31) during a predetermined heating operation is provided.

  In the above invention, the intermediate pressure refrigerant whose enthalpy is increased by being heated by the heating means (32) is added to the compression mechanism (21). Thereby, since the calorie | heat amount of the refrigerant | coolant condensed in an indoor heat exchanger (22) increases, heating capability improves.

  Further, since the intermediate-pressure liquid refrigerant is heated, the enthalpy of the refrigerant is effectively increased and the amount of refrigerant after the heating (refrigerant density) compared to heating a gas refrigerant having a specific volume larger than that of the liquid refrigerant. ) Is suppressed. Thereby, the fall of the volumetric efficiency in a compression mechanism (21) is suppressed. Moreover, since the fall of the refrigerant | coolant circulation amount in the said utilization side heat exchanger (22) is also suppressed, the fall of heating capability is suppressed.

  Further, according to a second aspect, in the first aspect, a liquid receiver (23) is provided between the use side heat exchanger (22) and the expansion mechanism (24), and the injection pipe (31 ) Is connected to the liquid receiver (23), and the liquid refrigerant of the liquid receiver (23) flows. And at least any one between the use side heat exchanger (22) and the liquid receiver (23) and between the liquid receiver (23) and the heating means (32) in the injection pipe (31). Is provided with an intermediate pressure adjusting mechanism (30) for reducing the liquid refrigerant to an intermediate pressure.

  In the above invention, for example, when the intermediate pressure adjusting mechanism (30) is provided between the use side heat exchanger (22) and the liquid receiver (23), the intermediate pressure liquid refrigerant is injected from the liquid receiver (23). It flows into the pipe (31). On the other hand, when the intermediate pressure adjusting mechanism (30) is provided between the liquid receiver (23) and the heating means (32) in the injection pipe (31), the liquid receiver (23) is connected to the injection pipe (31). The flowing liquid refrigerant is depressurized by the intermediate pressure adjusting mechanism (30) to become an intermediate pressure liquid refrigerant. Further, when the intermediate pressure adjusting mechanism (30) is provided in both of the above, the high-pressure liquid refrigerant condensed in the use side heat exchanger (22) is reduced in pressure by the first intermediate pressure adjusting mechanism (30). The refrigerant in the pressure state between the high pressure and the intermediate pressure is accumulated in the liquid receiver (23), and the liquid refrigerant flowing from the liquid receiver (23) to the injection pipe (31) is adjusted for the second intermediate pressure. By being depressurized by the mechanism (30), it becomes an intermediate-pressure liquid refrigerant. Thereby, the refrigerant in the intermediate pressure state surely flows through the injection pipe (31) and is heated by the heating means (32).

  In a third aspect based on the second aspect, the expansion mechanism (24) comprises a first expansion valve (24). On the other hand, the intermediate pressure adjusting mechanism (30) includes a second expansion valve (3a) provided between the use side heat exchanger (22) and the liquid receiver (23).

  In the above invention, as shown in FIG. 1, the high-pressure liquid refrigerant condensed in the use side heat exchanger (22) is depressurized by the second expansion valve (3a) and becomes an intermediate-pressure refrigerant to receive the receiver (23 ). Part of the intermediate-pressure liquid refrigerant in the liquid receiver (23) is decompressed by the first expansion valve (24) to become a low-pressure two-phase refrigerant, and is evaporated by the heat source side heat exchanger (25). On the other hand, the intermediate-pressure liquid refrigerant in the liquid receiver (23) flows into the injection pipe (31), is heated by the heating means (32), and is supplied to the compression mechanism (21).

  In a fourth aspect based on the second aspect, the expansion mechanism (24) comprises a first expansion valve (24). On the other hand, the intermediate pressure adjusting mechanism (30) includes a capillary tube (3b) provided between the use side heat exchanger (22) and the liquid receiver (23), and a liquid receiver in the injection pipe (31). (23) and a second expansion valve (3a) provided between the heating means (32).

  In the above invention, as shown in FIG. 5, the high-pressure liquid refrigerant condensed in the use side heat exchanger (22) is depressurized in the capillary tube (3b), and the refrigerant in a pressure state between the high pressure and the intermediate pressure And accumulates in the receiver (23). A part of the liquid refrigerant in the liquid receiver (23) flows into the injection pipe (31), is decompressed by the second expansion valve (3a) to become an intermediate-pressure liquid refrigerant, and is then heated by the heating means (32). And supplied to the compression mechanism (21).

In addition, in a fifth aspect based on any one of the first to fourth aspects, the heating means (32) is configured such that the compression mechanism (21) during a predetermined heating operation heats the refrigerant at the maximum frequency. According to the above-described invention, for example, when the outside air temperature is high, that is, when the heating load is small, the refrigerant circulation amount in the use side heat exchanger (22) is adjusted by the frequency control of the compression mechanism (21). By doing so, the heating capacity is adjusted. When the outside air temperature decreases and the heating load increases, and the compression mechanism (21) is driven at the maximum frequency (maximum capacity) and cannot cope with the heating load, the intermediate pressure liquid refrigerant in the injection pipe (31) Heated by the heating means (32). Thereby, the efficient driving | operation corresponding to heating load is performed.

  Further, a sixth aspect of the present invention is the method according to any one of the second to fourth aspects, wherein the intermediate pressure adjusting mechanism (30) is compressed with the intermediate pressure refrigerant of the injection pipe (31) heated by the heating means (32). The flow rate is controlled such that the intermediate pressure gas refrigerant in the mechanism (21) is mixed to become a gas refrigerant having a predetermined superheat degree.

  In the above invention, the intermediate-pressure gas refrigerant having a predetermined superheat is always sucked into the high-stage compressor. Thereby, since the rise in the discharge temperature of the compression mechanism (21) is suppressed, an operation friendly to the compression mechanism (21) is performed.

  Therefore, according to the first invention, the heating means (32) is provided to heat the intermediate pressure liquid refrigerant injected into the compression mechanism (21), so that the intermediate pressure with increased enthalpy is applied to the compression mechanism (21). A refrigerant can be supplied. Thereby, since the calorie | heat amount of the refrigerant | coolant condensed with a utilization side heat exchanger (22) can be increased, heating capability can be improved.

  Further, according to the above invention, since the intermediate-pressure liquid refrigerant is heated, the enthalpy of the refrigerant can be effectively increased as compared with the case of heating the gas refrigerant, and the amount of the refrigerant after the heating A decrease in (refrigerant density) can be suppressed. Thereby, while being able to aim at the improvement of heating capability effectively, the fall of the volumetric efficiency in a compression mechanism (21) can be suppressed, efficient heating operation can be performed. Moreover, since the fall of the refrigerant | coolant circulation amount in the said utilization side heat exchanger (22) can be suppressed, the fall of heating capability can be suppressed.

  Moreover, according to 2nd invention, between the utilization side heat exchanger (22) and liquid receiver (23), and the liquid receiver (23) and heating means (32) in an injection pipe (31), Since the intermediate pressure adjusting mechanism (30) for reducing the liquid refrigerant to the intermediate pressure is provided at at least one of the two, the intermediate pressure liquid refrigerant is surely flowed into the injection pipe (31) and the heating means (32) Can be heated. Thereby, heating capability can be improved reliably.

  Further, according to the third or fourth invention, the intermediate pressure adjusting mechanism (30) is constituted by only the second expansion valve (3a) or two of the second expansion valve (3a) and the capillary tube (3b). Since it did in this way, the effect of 2nd invention can be acquired concretely.

According to the fifth aspect of the invention, when the compression mechanism (21) is at the maximum frequency, that is, when the heating load is large, the intermediate pressure liquid refrigerant is heated by the heating means (32). Further, according to the sixth aspect of the invention, the intermediate pressure refrigerant in the injection pipe (31) heated by the heating means (32) and the intermediate pressure gas refrigerant in the compression mechanism (21) Since the flow rate is controlled by the intermediate pressure adjusting mechanism (30) so that the gas refrigerant is mixed and becomes a gas refrigerant with a predetermined superheat degree, the high-pressure side compressor always sucks the intermediate pressure gas refrigerant with the predetermined superheat degree. be able to. As a result, an increase in the discharge temperature of the compression mechanism (21) and a decrease in volumetric efficiency in the compression mechanism (21) can be suppressed, so that a gentle and efficient operation can be performed on the compression mechanism (21).

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

Embodiment 1 of the Invention
As shown in FIG. 1, the air-conditioning apparatus (10) of Embodiment 1 includes a refrigerant circuit (20) that performs a vapor compression refrigeration cycle by circulating refrigerant, and is configured as a dedicated heating unit that performs only heating operation. Has been.

  The refrigerant circuit (20) includes a compressor (21), an indoor heat exchanger (22) as a use side heat exchanger, a receiver (23) as a liquid receiver, and a first expansion valve (24) as an expansion mechanism. And an outdoor heat exchanger (25), which is a heat source side heat exchanger, are piped in order to form a closed circuit. The refrigerant circuit (20) is configured such that the refrigerant circulates in a heating cycle in which the indoor heat exchanger (22) functions as a condenser and the outdoor heat exchanger (25) functions as an evaporator. .

  Although not shown, the compressor (21) includes a low-stage compressor and a high-stage compressor housed in a hermetic casing to form a compression mechanism. The compressor (21) is connected so that the suction side of the low-stage compressor communicates with the outdoor heat exchanger (25) and the discharge side of the high-stage compressor communicates with the indoor heat exchanger (22). Has been. The compressor (21) is configured to circulate in the refrigerant circuit (20) by compressing the refrigerant in two stages. The compressor (21) is configured such that the capacity is variable stepwise or continuously.

  The receiver (23) is configured as a gas-liquid separator in which the refrigerant flowing in is divided into a gas refrigerant and a liquid refrigerant and stored. The first expansion valve (24) is a motor-operated valve whose opening degree is adjustable.

  The refrigerant circuit (20) is provided with an intermediate pressure adjusting mechanism (30), an injection pipe (31), and a heater (32) as features of the present invention. The intermediate pressure adjusting mechanism (30) is constituted by a second expansion valve (3a) which is an expansion mechanism, and the second expansion valve (3a) is constituted by an electric valve whose opening degree is adjustable. The second expansion valve (3a) is provided between the indoor heat exchanger (22) and the receiver (23), and depressurizes the high-pressure liquid refrigerant condensed in the indoor heat exchanger (22) to provide an intermediate pressure refrigerant. And is configured to be stored in the receiver (23).

  The injection pipe (31) has one end connected to the receiver (23) and the other end connected to the compressor (21). The injection pipe (31) allows the intermediate-pressure liquid refrigerant of the intermediate-pressure refrigerant in the receiver (23) to flow between the low-stage compressor and the high-stage compressor in the compressor (21). It is configured. That is, in the injection pipe (31), the liquid refrigerant is divided from between the indoor heat exchanger (22) and the first expansion valve (24), and the low-stage compressor is in a state where the divided liquid refrigerant is at an intermediate pressure. And a high-stage compressor.

  The heater (32) is provided in the middle of the injection pipe (31). The heater (32) is configured as a heating unit that heats the intermediate-pressure liquid refrigerant flowing through the injection pipe (31) during a predetermined heating operation. The predetermined heating operation is a case where the heating load is increased and the compressor (21) is driven at the maximum frequency (maximum capacity).

-Driving action-
Next, the heating operation of the above-described air conditioner (10) will be described. The air conditioner (10) performs switching between “normal operation” performed when the heating load is small and “low outside air operation” performed when the heating load is large. Hereinafter, each operation will be described with reference to FIGS.

<Normal operation>
This normal operation is an operation in which the heater (32) is not energized, that is, the refrigerant flowing through the injection pipe (31) is supplied to the compressor (21) without being heated. In the following, the operation is described, and the refrigerant behavior is also described with reference to FIG. FIG. 4 shows the refrigerant behavior during the low outside air operation, but shows the refrigerant behavior during the normal operation except for point F in the figure.

  First, when the compressor (21) is driven, the high-pressure gas refrigerant (point C in FIG. 4) compressed by the compressor (21) exchanges heat with room air in the indoor heat exchanger (22). Condensation (point D in FIG. 4). At that time, the heated room air is supplied to the room and the room is heated. The high-pressure liquid refrigerant condensed in the indoor heat exchanger (22) is reduced in pressure by the second expansion valve (3a) to become a two-phase refrigerant having an intermediate pressure (point E in FIG. 4), and the intermediate pressure in the receiver (23). It separates into a gas refrigerant and an intermediate pressure liquid refrigerant and accumulates in an equilibrium state. Of the intermediate pressure refrigerant in the receiver (23), the intermediate pressure liquid refrigerant (point H in FIG. 4) is decompressed by the first expansion valve (24) to become a low-pressure two-phase refrigerant (point I in FIG. 4). . This low-pressure two-phase refrigerant evaporates by exchanging heat with outdoor air in the outdoor heat exchanger (25), and returns to the compressor (21) again as a low-pressure gas refrigerant having a predetermined superheat degree (see FIG. 4). A point). Thereafter, the low-pressure gas refrigerant is compressed by the low-stage compressor to become an intermediate-pressure gas refrigerant (point B in FIG. 4), and this refrigerant circulation is repeated.

  In the normal operation, while the refrigerant circulation described above is repeated, the intermediate-pressure liquid refrigerant (point H in FIG. 4) of the receiver (23) flows to the compressor (21) through the injection pipe (31). In this compressor (21), the intermediate-pressure liquid refrigerant and the intermediate-pressure gas refrigerant compressed by the low-stage compressor are mixed to become an intermediate-pressure gas refrigerant having a predetermined superheat degree (point G in FIG. 4). Thereafter, the intermediate-pressure gas refrigerant is compressed by the high-stage compressor, becomes high-pressure gas refrigerant, and is discharged from the compressor (21) (point C in FIG. 4). As a result, in the indoor heat exchanger (22), the intermediate pressure liquid refrigerant is injected and added to increase the refrigerant circulation amount, so that the heating capacity is improved.

  Next, the control of the heating capacity during the normal operation will be described with reference to FIG. First, when the heating load varies, the compressor (21) is adjusted to a frequency corresponding to the heating load in step ST1. Subsequently, in step ST2, the opening of the first expansion valve (24) is adjusted so that the refrigerant evaporates in the outdoor heat exchanger (25) and becomes a low-pressure gas refrigerant having a predetermined degree of superheat (point A in FIG. 4). Adjusted. In step ST3, the intermediate-pressure gas refrigerant having a predetermined superheat (point G in FIG. 4) is mixed by mixing the intermediate-pressure liquid refrigerant in the injection pipe (31) and the intermediate-pressure gas refrigerant compressed by the low-stage compressor. The opening degree of the second expansion valve (3a) is adjusted so as to become a refrigerant.

  Specifically, for example, when the outside air temperature decreases and the heating load increases, the frequency of the compressor (21) is increased. Thereby, since the amount of high-pressure gas refrigerant discharged from the compressor (21) increases, the amount of refrigerant circulation in the indoor heat exchanger (22) increases and the heating capacity is improved.

  That is, during the normal operation, the heating capacity is improved by increasing the frequency (capacity) of the compressor (21) as the heating load increases. Further, the first expansion valve (24) and the second expansion valve (3a) are respectively provided with a predetermined degree of superheat (A in FIG. 4) in the low-stage compressor and the high-stage compressor in the constant compressor (21). The opening degree is controlled to be constant so that the gas refrigerant at the point and the point G) is sucked. Thereby, in the said compressor (21), while being able to prevent what is called a liquid back | bag, the raise of the discharge temperature (C point of FIG. 4) of gas refrigerant can be suppressed. The normal operation is switched to the low outside air operation when the heating load increases and the frequency of the compressor (21) reaches the maximum frequency (maximum capacity).

<Low outside air operation>
This low outside air operation is an operation in which the heater (32) is energized while the compressor (21) is driven at the maximum frequency, and the refrigerant flowing through the injection pipe (31) is heated and supplied to the compressor (21). is there. Here, only the operation operation and refrigerant behavior different from those in the normal operation described above will be described.

  In this low outside air operation, the intermediate-pressure liquid refrigerant (point H in FIG. 4) that has flowed from the receiver (23) to the injection pipe (31) is heated by the heater (32) to become a two-phase refrigerant of intermediate pressure (FIG. 4). F point). This intermediate-pressure two-phase refrigerant is mixed with the intermediate-pressure gas refrigerant (point H in FIG. 4) compressed by the low-stage compressor in the compressor (21) in the same manner as during normal operation, and has a predetermined degree of superheat. Intermediate pressure gas refrigerant (G point in FIG. 4). Thereafter, the intermediate-pressure gas refrigerant is compressed by the high-stage compressor, becomes high-pressure gas refrigerant, and is discharged from the compressor (21) (point C in FIG. 4). As a result, in the indoor heat exchanger (22), the intermediate pressure refrigerant whose enthalpy has been increased by being heated by the heater (32) is added to the refrigerant flowing through the indoor heat exchanger (22). The amount of heat increases. Therefore, the heating capacity is further improved.

  Next, the control of the heating capacity during the low outside air operation will be described with reference to FIG. First, when this control starts, in step ST4, the compressor (21) is driven at the maximum frequency. If the heating load fluctuates in this state, in step ST5, the first expansion is performed so that the refrigerant evaporates in the outdoor heat exchanger (25) and becomes a low-pressure gas refrigerant having a predetermined degree of superheat (point A in FIG. 4). The opening of the valve (24) is adjusted. Next, in step ST6, the heating amount of the heater (32) is adjusted so that the high-pressure gas refrigerant is condensed at a predetermined pressure (point D in FIG. 4) in the indoor heat exchanger (22). Finally, in step ST7, the intermediate pressure refrigerant of the injection pipe (31) heated by the heater (32) and the intermediate pressure gas refrigerant compressed by the low-stage compressor are mixed to obtain a predetermined superheat degree (FIG. 4). The opening of the second expansion valve (3a) is adjusted so that the intermediate-pressure gas refrigerant at point G) is adjusted to control the flow rate.

  Specifically, in the state where the compressor (21) is driven at the maximum frequency, for example, when the outside air temperature decreases and the heating load increases, the opening of the first expansion valve (24) is decreased and the refrigerant is reduced. The pressure is further reduced. Next, the heating amount of the heater (32) is increased, and the condensation pressure of the refrigerant in the indoor heat exchanger (22) is increased. Finally, the opening degree of the second expansion valve (3a) is increased, and the amount of liquid refrigerant flowing through the injection pipe (31) is increased. Thereby, since the circulation amount of the intermediate pressure refrigerant injected into the compressor (21) is increased, the heat of condensation of the refrigerant in the indoor heat exchanger (22) is increased and the heating capacity is improved.

  That is, during the low outside air operation, the heating amount of the heater (32) is increased as the heating load is increased, and the opening of the second expansion valve (3a) is increased, thereby circulating the intermediate pressure refrigerant. The amount is increased to improve the heating capacity.

  Further, the opening degree of the first expansion valve (24) and the second expansion valve (3a) is set to a predetermined degree of superheat (see FIG. 2) for the low-stage compressor and the high-stage compressor in the constant compressor (21). 4 is controlled so that the gas refrigerant at points A and G) is sucked. Thus, in the compressor (21), so-called liquid back can be prevented and an increase in the discharge temperature of gas refrigerant (point C in FIG. 4) can be suppressed. You can do gentle driving.

  Further, since the gas refrigerant having a predetermined superheat degree is sucked into the low-stage compressor and the high-stage compressor in the compressor (21), the refrigerant density is lowered, that is, the refrigerant specific volume is increased. The accompanying reduction in volumetric efficiency in the compressor (21) can be suppressed.

-Effect of the embodiment-
As described above, according to the first embodiment, the intermediate-pressure liquid refrigerant is heated by the heater (32) and injected between the low-stage compressor and the high-stage compressor in the compressor (21). As the heating load is increased, the heating amount of the heater (32) and the opening of the second expansion valve (3a) are increased to increase the injection pipe without causing the compressor (21) to liquid-back. The circulation amount of the intermediate pressure refrigerant in 31) can be increased. Thereby, the amount of heat of condensation of the refrigerant in the indoor heat exchanger (22) can be increased, and the heating capacity can be improved.

  In addition, since the intermediate-pressure liquid refrigerant is heated, the enthalpy of the refrigerant can be effectively increased as compared with the case of heating the gas refrigerant having a larger specific volume than the liquid refrigerant, and the refrigerant after the heating A decrease in the amount (refrigerant density) can be suppressed. Thereby, while being able to aim at the improvement of heating capability effectively and the fall of the volumetric efficiency in a compressor (21) can be suppressed, an efficient driving | operation can be performed. Moreover, since the fall of the refrigerant | coolant circulation amount in the said utilization side heat exchanger (22) can be suppressed, the fall of heating capability can be suppressed.

  In addition, since the second expansion valve (3a), which is an intermediate pressure adjusting mechanism (30), is provided between the indoor heat exchanger (22) and the receiver (23), the intermediate pressure liquid is added to the injection pipe (31). Refrigerant can be reliably flowed. Thereby, heating capability can be improved reliably.

In addition, when the compressor (21) is at the maximum frequency, that is, when the heating load is large, the intermediate pressure liquid refrigerant is heated by the heating means (32), so that an efficient operation corresponding to the heating load is performed. Further, the intermediate pressure refrigerant in the injection pipe (31) heated by the heater (32) and the intermediate pressure gas refrigerant in the compressor (21) are mixed to become a gas refrigerant having a predetermined superheat degree. Since the opening degree of the second expansion valve (3a) is adjusted, the intermediate pressure gas refrigerant having a predetermined superheat degree can always be sucked into the high stage compressor. Thereby, since the raise of the discharge temperature of a compressor (21) and the fall of the volumetric efficiency in a compressor (21) can be suppressed, a friendly and efficient driving | operation can be performed to a compressor (21).

<< Embodiment 2 of the Invention >>
In the air conditioner (10) of the second embodiment, as shown in FIG. 5, the above-described first embodiment is configured such that the intermediate pressure adjusting mechanism (30) is configured only by the second expansion valve (3a). Instead, the intermediate pressure adjusting mechanism (30) is configured by two of the second expansion valve (3a) and the capillary tube (3b).

  Specifically, the second expansion valve (3a) is provided between the receiver (23) and the heater (32) in the injection pipe (31). On the other hand, the capillary tube (3b) is provided between the indoor heat exchanger (22) and the receiver (23). The capillary tube (3b) is configured as an expansion mechanism that depressurizes the refrigerant at a constant rate at all times.

  In the above case, the high-pressure liquid refrigerant condensed in the indoor heat exchanger (22) is depressurized by the capillary tube (3b) and accumulated in the receiver (23). Thereafter, the liquid refrigerant flowing from the receiver (23) to the injection pipe (31) is depressurized by the second expansion valve (3a) to become an intermediate pressure liquid refrigerant. That is, the refrigerant in the receiver (23) is in a pressure state between a high pressure and an intermediate pressure. Other structures, operations, and effects are the same as those in the first embodiment.

<< Embodiment 3 of the Invention >>
As shown in FIG. 6, the air conditioner (10) of the third embodiment is obtained by replacing the connection positions of the second expansion valve (3a) and the capillary tube (3b) in the second embodiment described above. That is, the second expansion valve (3a) is provided between the indoor heat exchanger (22) and the receiver (23), and the capillary tube (3b) is connected to the receiver (23) and the heater (32 in the injection pipe (31)). ).

  In the above case, the high-pressure liquid refrigerant condensed in the indoor heat exchanger (22) is depressurized by the second expansion valve (3a) and accumulated in the receiver (23). Thereafter, the liquid refrigerant flowing from the receiver (23) to the injection pipe (31) is depressurized by the capillary tube (3b) to become an intermediate pressure liquid refrigerant. Other structures, operations, and effects are the same as those of the second embodiment.

<< Embodiment 4 of the Invention >>
As shown in FIG. 7, the air conditioner (10) of Embodiment 4 is obtained by changing the capillary tube (3b) in Embodiment 3 described above to a third expansion valve (3c) that is an expansion mechanism. The third expansion valve (3c) is configured as a motor-operated valve whose opening degree can be adjusted, like the second expansion valve (3a). That is, the intermediate pressure adjusting mechanism (30) is constituted by two expansion valves, the second expansion valve (3a) and the third expansion valve (3c).

  In the above case, the high-pressure liquid refrigerant condensed in the indoor heat exchanger (22) is depressurized by the second expansion valve (3a) and accumulated in the receiver (23). Thereafter, the liquid refrigerant flowing from the receiver (23) to the injection pipe (31) is depressurized by the third expansion valve (3c) to become an intermediate pressure liquid refrigerant.

  During normal operation in the present embodiment, the intermediate pressure gas refrigerant in the injection pipe (31) and the intermediate pressure gas refrigerant in the compressor (21) are mixed to have a predetermined degree of superheat (point G in FIG. 4). Thus, the opening degrees of both the second expansion valve (3a) and the third expansion valve (3c) are adjusted. On the other hand, during the low outside air operation, the intermediate pressure refrigerant in the injection pipe (31) heated by the heater (32) and the intermediate pressure gas refrigerant in the compressor (21) are mixed to obtain a predetermined superheat degree (see FIG. 4). The opening degrees of both the second expansion valve (3a) and the third expansion valve (3c) are adjusted so that the intermediate pressure gas refrigerant at point G) is obtained. Other structures, operations, and effects are the same as those in the third embodiment.

<< Embodiment 5 of the Invention >>
As shown in FIG. 8, the air conditioner (10) of the fifth embodiment is obtained by omitting the receiver (23) and the capillary tube (3b) in the second embodiment described above. That is, the intermediate pressure adjusting mechanism (30) is configured only by the second expansion valve (3a).

  Specifically, the injection pipe (31) is directly connected to a liquid pipe between the indoor heat exchanger (22) and the first expansion valve (24). In this case, part of the high-pressure liquid refrigerant condensed in the indoor heat exchanger (22) is diverted from the liquid pipe to the injection pipe (31), and is depressurized by the second expansion valve (3a) to become an intermediate-pressure liquid refrigerant. . That is, the injection pipe (31) diverts the liquid refrigerant from between the indoor heat exchanger (22) and the first expansion valve (24), and the diverted liquid refrigerant in the intermediate pressure state is a low-stage compressor. And a high-stage compressor. Other structures, operations, and effects are the same as those of the second embodiment.

<< Other Embodiments >>
The present invention may be configured as follows with respect to the above embodiment.

  For example, in each of the above embodiments, the air conditioner (10) is a dedicated heating unit, but the present invention can also be applied to an air conditioner that is also used for cooling and heating. For example, the refrigerant circuit (20) is provided with a four-way switching valve which is a flow path switching means, and refrigerant circulation in the refrigerant circuit (20) is configured reversibly. In this case, the cooling operation is performed without energizing the heater (32), and the refrigerant is circulated so as to be condensed in the outdoor heat exchanger (25) and evaporated in the indoor heat exchanger (22). During this cooling operation, the enthalpy of the refrigerant (point I in FIG. 4) flowing through the indoor heat exchanger (22) increases (point H from point E in FIG. 4), so the refrigerant in the indoor heat exchanger (22) The amount of heat of evaporation increases and the cooling capacity improves.

  As described above, the present invention is useful as an air conditioner that performs a refrigeration cycle by compressing a refrigerant in two stages.

1 is a refrigerant circuit diagram of an air conditioner according to Embodiment 1. FIG. It is a flowchart figure which shows the normal operation control of the air conditioning apparatus which concerns on Embodiment 1. FIG. It is a flowchart figure which shows the operation control at the time of the low outside air of the air conditioning apparatus which concerns on Embodiment 1. FIG. It is a Mollier diagram which shows the refrigerant | coolant behavior at the time of the low outdoor air driving | running of the air conditioning apparatus which concerns on Embodiment 1. FIG. 6 is a refrigerant circuit diagram of an air conditioner according to Embodiment 2. FIG. FIG. 6 is a refrigerant circuit diagram of an air conditioner according to Embodiment 3. FIG. 6 is a refrigerant circuit diagram of an air conditioner according to Embodiment 4. FIG. 6 is a refrigerant circuit diagram of an air conditioner according to Embodiment 5.

Explanation of symbols

10 Air conditioner
20 Refrigerant circuit
21 Compressor (compression mechanism)
22 Indoor heat exchanger (use side heat exchanger)
23 Receiver
24 First expansion valve (expansion mechanism)
25 Outdoor heat exchanger (heat source side heat exchanger)
30 Intermediate pressure adjustment mechanism
3a Second expansion valve
3b capillary tube
31 Injection tube
32 Heater (heating means)

Claims (6)

A refrigerant circuit (20) of a vapor compression refrigeration cycle in which a compression mechanism (21), a heat source side heat exchanger (25), an expansion mechanism (24), and a use side heat exchanger (22) are connected by piping;
The compression mechanism (21) is an air conditioner that includes a low-stage compressor and a high-stage compressor, and is configured to compress the refrigerant in two stages,
The liquid refrigerant is divided from between the use side heat exchanger (22) and the expansion mechanism (24), and the divided liquid refrigerant is interposed between the low stage compressor and the high stage compressor in an intermediate pressure state. An injection pipe (31) to be supplied;
An air conditioner comprising heating means (32) for heating the intermediate-pressure liquid refrigerant flowing through the injection pipe (31) during a predetermined heating operation. In claim 1,
Between the use side heat exchanger (22) and the expansion mechanism (24), a liquid receiver (23) is provided,
The injection pipe (31) is connected to the liquid receiver (23), and is configured to allow the liquid refrigerant in the liquid receiver (23) to flow.
Between at least one of the use side heat exchanger (22) and the liquid receiver (23) and between the liquid receiver (23) and the heating means (32) in the injection pipe (31) An air conditioner comprising an intermediate pressure adjusting mechanism (30) for reducing the liquid refrigerant to an intermediate pressure. In claim 2,
The expansion mechanism (24) includes a first expansion valve (24), and the intermediate pressure adjustment mechanism (30) is provided between the use side heat exchanger (22) and the liquid receiver (23). An air conditioner comprising the second expansion valve (3a). In claim 2,
The expansion mechanism (24) includes a first expansion valve (24), and the intermediate pressure adjustment mechanism (30) is provided between the use side heat exchanger (22) and the liquid receiver (23). It is constituted by a capillary tube (3b) and a second expansion valve (3a) provided between the liquid receiver (23) and the heating means (32) in the injection pipe (31). Air conditioner. In any one of Claims 1-4,
The air conditioner characterized in that the heating means (32) is configured such that the compression mechanism (21) during a predetermined heating operation heats the refrigerant at the maximum frequency. In any one of Claims 2-4,
The intermediate pressure adjusting mechanism (30) is a gas having a predetermined superheat degree by mixing the intermediate pressure refrigerant in the injection pipe (31) heated by the heating means (32) and the intermediate pressure gas refrigerant in the compression mechanism (21). An air conditioner that controls a flow rate so as to be a refrigerant.

Images