JP3317170B2 - Refrigeration equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a refrigerating apparatus having a gas injection circuit, and more particularly to an intermediate pressure control.

[0002]

2. Description of the Related Art Conventionally, various types of air conditioners as refrigeration systems have been proposed. For example, as disclosed in Japanese Patent Publication No. 1-15786, a compressor and a four-way switching system are disclosed. Some include a refrigerant circuit in which a valve, an outdoor heat exchanger, a first expansion mechanism, a gas-liquid separator, a second expansion mechanism, and an indoor heat exchanger are sequentially connected.

An injection circuit is provided between the gas-liquid separator and the compressor to supply the intermediate-pressure gas refrigerant of the gas-liquid separator to the compressor, thereby improving the air-conditioning capacity.

[0004]

In the above-described air conditioner, since both the first expansion mechanism and the second expansion mechanism are constructed by combining a capillary tube, the amount of reduced pressure is fixed, and the capacity of the compressor is reduced. When it increases, there is a problem that the intermediate-pressure gas refrigerant to be injected cannot be maintained at an appropriate amount.

Therefore, it is conceivable that the first expansion mechanism and the second expansion mechanism are constituted by expansion valves whose opening degree is variable. However, since both of the above-mentioned expansion mechanisms are conventionally configured by combining a capillary tube, no consideration is given to the adjustment of the intermediate pressure. Although the injection amount of the gas refrigerant is changed, there is no guarantee that the pressure is maintained at the optimum intermediate pressure, and there is a problem that the injection effect cannot be said to be maximized.

[0006] The present invention has been made in view of such a point, and it is an object of the present invention to maintain the intermediate pressure at an appropriate value so as to exhibit the maximum injection effect.

[0007]

Means for Solving the Problems-Summary of the Invention- The present invention provides an injection circuit (30) in a main refrigerant circuit (2M), while corresponding to a maximum flow rate of an intermediate-pressure gas refrigerant flowing through the injection circuit (30). The target pressure of the intermediate-pressure refrigerant is set for each refrigerant state in the main refrigerant circuit (2M), and the opening degree of the downstream expansion valve (EV) is controlled so that the intermediate pressure of the intermediate-pressure refrigerant becomes the target pressure. . In particular, the opening degree of the downstream expansion valve (EV) is controlled at a point where the amount of decrease in the discharge temperature of the compressor (21) corresponding to the maximum flow rate of the intermediate-pressure gas refrigerant suddenly changes.

-Solution Means- Specifically, as shown in FIG. 1, means taken by the invention according to claim 1 includes a compressor (21) and a heat source side heat exchanger (2).
3) Variable opening degree first expansion valve (EV-1) and gas-liquid separator (2
There is provided a main refrigerant circuit (2M) in which a fourth expansion valve (EV-2) having a variable opening and a use-side heat exchanger (25) are connected in order. Further, the intermediate-pressure gas refrigerant of the intermediate-pressure refrigerant at an intermediate pressure between the condensing pressure and the evaporating pressure in the main refrigerant circuit (2M) is transferred from the gas-liquid separator (24) to the compressor (2M).
An injection circuit (30) for supplying to 1) is provided. And the upstream expansion valve of the main refrigerant circuit (2M)
(EV) is the user-side heat exchanger (25) or heat source that will be the evaporator
Superheat degree at the outlet side of the side heat exchanger (23) reaches a predetermined value
Is controlled in such a manner. In addition, the opening of the intermediate-pressure gas refrigerant flowing through the Injection <br/> down circuit (30) adjusts the degree of opening of the downstream-side expansion valve of the main refrigerant circuit (2M) so that the maximum flow rate (EV) Adjusting means (52) is provided.

The means adopted by the invention according to claim 2 is the invention according to claim 1, wherein the opening adjustment means (52) is
The target pressure of the intermediate-pressure refrigerant corresponding to the maximum flow rate of the intermediate-pressure gas refrigerant is set for each refrigerant state in the main refrigerant circuit (2M), and the downstream expansion is performed so that the intermediate pressure of the intermediate-pressure refrigerant becomes the target pressure. It is configured to control the opening of the valve (EV).

The means adopted by the third aspect of the present invention is the discharge temperature detecting means (Th) for detecting the discharge temperature of the refrigerant discharged from the compressor (21) and outputting a detection signal in the first aspect of the present invention. -d) is provided. Further, in response to the detection signal of the discharge temperature detecting means (Th-d), the opening degree adjusting means (52) expands the downstream side to a sudden change point in the discharge temperature decrease amount corresponding to the maximum flow rate of the intermediate-pressure gas refrigerant. It is designed to control the opening of the valve (EV).

Means taken by the invention described in claim 4 is shown in FIG.
As described in the first aspect of the present invention, the condensation temperature detecting means (Th) for detecting the condensation temperature of the refrigerant in the main refrigerant circuit (2M), and the evaporation temperature detection means (Th for detecting the evaporation temperature of the refrigerant. ) And an intermediate pressure temperature detecting means (Th-m) for detecting an intermediate pressure temperature of the intermediate pressure refrigerant. Further, the opening degree adjusting means (52) sets the target temperature of the intermediate-pressure refrigerant corresponding to the maximum flow rate of the intermediate-pressure gas refrigerant in advance for each condensation temperature and each evaporation temperature of the main refrigerant circuit (2M), Upon receiving the detection signals from the condensing temperature detecting means (Th), the evaporating temperature detecting means (Th) and the intermediate pressure temperature detecting means (Th-m), the intermediate pressure temperature of the intermediate pressure refrigerant is changed to the detected condensing temperature and the detected evaporating temperature. The opening degree of the downstream expansion valve (EV) is controlled so that the corresponding target temperature is reached.

Means taken by the invention described in claim 5 is shown in FIG.
As shown in (1), in the first aspect of the present invention, a flow rate detecting means (60) for detecting a flow rate of the intermediate-pressure gas refrigerant flowing through the injection circuit (30) is provided. The opening degree adjusting means (52) is configured to control the opening degree of the downstream expansion valve (EV) so that the flow rate detected by the flow rate detecting means (60) is maximized .

-Operation- According to the above-mentioned invention specifying matter, in the invention described in claim 1,
During the refrigeration operation, the high-pressure refrigerant flows through the first expansion valve (EV-1)
And the second expansion valve (EV-2), the main pressure reduction is performed by the upstream expansion valve (EV). For example, the first expansion valve (EV-1) at the time of the cooling operation and the second expansion valve (EV-2) at the time of the heating operation include the use-side heat exchanger (25) or the heat-source-side heat exchanger ( The degree of opening is controlled so that the degree of superheat of the refrigerant at the outlet side of ( 23) becomes a predetermined value.

On the other hand, the pressure reduction for the injection of the intermediate-pressure gas refrigerant is performed by a downstream expansion valve (EV). For example, the second expansion valve (EV-2) during the cooling operation and the first expansion valve (EV-1) during the heating operation reduce the pressure.

The downstream pressure reducing operation is performed by the opening degree adjusting means (52), and the downstream side expansion of the main refrigerant circuit (2M) is performed so that the intermediate pressure gas refrigerant flowing through the injection circuit (30) has the maximum flow rate. Adjust the opening of the valve (EV).

More specifically, in the present invention, the target pressure of the intermediate-pressure refrigerant corresponding to the maximum flow rate of the intermediate-pressure gas refrigerant is set for each refrigerant state in the main refrigerant circuit (2M), The opening degree of the downstream expansion valve (EV) is controlled so that the intermediate pressure of the compressed refrigerant becomes the target pressure.

According to the third aspect of the present invention, the opening degree of the downstream expansion valve (EV) is maintained such that the intermediate-pressure refrigerant is maintained at the intermediate pressure at the sudden change point where the discharge temperature of the compressor (21) suddenly decreases. To adjust. That is, as the intermediate pressure of the gas-liquid separator (24) increases, the flow rate of the intermediate-pressure gas refrigerant, that is, the injection amount increases, but the dryness X of the gas-liquid separator (24) decreases. Become. As a result, the amount of the intermediate-pressure gas refrigerant in the gas-liquid separator (24) decreases, and when the pressure exceeds a predetermined pressure, the actual injection amount of the intermediate-pressure gas refrigerant decreases.

When the injection amount becomes maximum,
Since the intermediate-pressure gas refrigerant of the gas-liquid separator (24) is small, the intermediate-pressure liquid refrigerant of the gas-liquid separator (24) is supplied to the compressor (21) through the injection circuit (30). As a result,
Due to the evaporation of the liquid refrigerant, the refrigerant in the compressor (21) is rapidly cooled, and the discharge temperature is rapidly lowered. Therefore, the opening degree of the downstream expansion valve (EV) is adjusted so that the intermediate pressure refrigerant becomes the intermediate pressure at the point where the amount of decrease in the discharge temperature of the compressor (21) changes abruptly, and the intermediate pressure gas refrigerant is injected. Maximize volume.

According to the fourth aspect of the present invention, the opening degree adjusting means (52) sets the target temperature of the optimum intermediate pressure temperature at which the injection amount of the intermediate pressure gas refrigerant becomes maximum at each condensation temperature and each evaporation temperature in advance. For example, the target temperatures are tabulated and set. The opening degree adjusting means (52) derives an optimum intermediate pressure target temperature based on the condensing temperature and the evaporating temperature of the condensing temperature detecting means (Th) and the evaporating temperature detecting means (Th). Adjust the opening of the downstream expansion valve (EV) so that the temperature reaches the target temperature.

According to the fifth aspect of the invention, the flow rate detecting means (60) provided in the injection circuit (30) detects the flow rate of the intermediate-pressure gas refrigerant flowing through the injection circuit (30). In response to the flow rate detected by the flow rate detecting means (60), the opening degree adjusting means (52) sets the flow rate of the intermediate-pressure gas refrigerant,
Adjust the opening of the downstream expansion valve (EV) so that the injection amount is maximized .

[0021]

Therefore, according to the present invention, the downstream expansion valve (EV) is controlled so that the supply amount of the intermediate-pressure gas refrigerant is maximized.
The opening degree of the intermediate pressure gas refrigerant is controlled, so that the injection effect of the intermediate-pressure gas refrigerant can be reliably exhibited. That is, it is possible to surely improve the operation capacity by the injection of the intermediate-pressure gas refrigerant, and to improve the operation capacity. In other words, if the operating capacity is maintained as before, the input of the compressor (21) can be reduced, and energy saving can be reliably achieved.

In particular, according to the third aspect of the present invention, the opening degree of the downstream expansion valve (EV) is adjusted so that the discharge temperature of the compressor (21) changes abruptly. Two
Since the intermediate pressure refrigerant can be maintained at an appropriate intermediate pressure only by detecting the discharge temperature in 1), it is possible to surely improve the refrigeration capacity or save energy with a simple control configuration.

According to the fourth aspect of the present invention, since the intermediate-pressure refrigerant is maintained at the intermediate-pressure temperature at which the intermediate-pressure gas refrigerant is maximized, the injection effect of the intermediate-pressure gas refrigerant can be reliably exhibited. Since the optimal target temperature at each condensation temperature and each evaporation temperature is set in advance,
The supply amount of the intermediate-pressure gas refrigerant can be reliably adjusted to the maximum value.

According to the fifth aspect of the invention, since detecting the flow rate of intermediate-pressure gas refrigerant directly, as possible out to adjust the flow rate of intermediate-pressure gas refrigerant in exactly the maximum value.

[0025]

Embodiment 1 Hereinafter, Embodiment 1 of the present invention will be described in detail with reference to the drawings.

As shown in FIG. 1, the air conditioner (10)
Is a heat pump type air conditioner as a refrigerating device, which is configured to be freely operable by switching between a cooling operation and a heating operation.

The refrigerant circuit (20) of the air conditioner (10)
Is a compressor (21), a four-way switching valve (22), an outdoor heat exchanger (23) as a heat source side heat exchanger, a first electric expansion valve (EV-1), and a gas-liquid separator (24). The second electric expansion valve (EV-2), the indoor heat exchanger (25), which is a use side heat exchanger, and the accumulator (2
6) and a main refrigerant circuit (2M) connected in order by a refrigerant pipe (27).

The compressor (21) is connected to an inverter (40) to be supplied with control power, and a controller (50) is connected to the inverter (40) to control the inverter (4).
0) is controlled by the power control unit (51) of the controller (50). The power control unit (51) of the controller (50) controls the supply frequency of the compressor (21) according to the indoor thermal load, and adjusts the operating capacity of the compressor (21) in a stepless or multi-step manner. It constitutes frequency control means for controlling.

The four-way switching valve (22) is in a state where the discharge side of the compressor (21) is connected to the outdoor heat exchanger (23) and the suction side is connected to the indoor heat exchanger (25) (FIG. 1). And a state where the discharge side of the compressor (21) is connected to the indoor heat exchanger (25) and a suction side is connected to the outdoor heat exchanger (23) (the state shown by the broken line in FIG. 1). ). The switching operation of the four-way switching valve (22) changes the refrigerant circulation direction of the refrigerant circuit (20), and switches between the cooling operation and the heating operation of the air conditioner (10).

The refrigerant circuit (20) is provided with an injection circuit (30) as a feature of the present invention. The injection circuit (30) is a circuit for injecting the intermediate-pressure gas refrigerant into the compressor (21), one end of which is above the gas-liquid separator (24), and the other end of which is a compression stroke of the compressor (21). There is a solenoid valve (SV) on the way.
That is, the gas-liquid separator (24) stores an intermediate-pressure refrigerant at an intermediate pressure between the condensing pressure and the evaporating pressure, but the injection circuit (30) opens the solenoid valve (SV). Then, of the intermediate-pressure refrigerant of the gas-liquid separator (24), the gas-phase intermediate-pressure gas refrigerant is injected into the compressor (21).

The first motor-operated expansion valve (EV-1) and the second motor-operated expansion valve (EV-2) are characterized in that the opening degree is freely adjustable and the degree of pressure reduction (throttle ratio) is adjusted. Can be done. Then, the first electric expansion valve (EV-1) or the second
The intermediate-pressure refrigerant decompressed by the electric expansion valve (EV-2) is stored in the gas-liquid separator (24).

The refrigerant pipe on the discharge side of the compressor (21) is provided with a discharge pipe sensor (Th-d). The discharge pipe sensor (Th-d) constitutes a discharge temperature detecting means for detecting the discharge temperature of the refrigerant discharged from the compressor (21) and outputting the detected temperature to the controller (50).

The controller (50) is provided with an opening degree adjusting means (52) which is the most characteristic of the present invention. The opening degree adjusting means (52) is an intermediate-pressure gas refrigerant flowing through the injection circuit (30). The intermediate pressure is controlled by adjusting the opening of the downstream electric expansion valve (EV) so that the maximum flow rate is obtained. Specifically, the opening degree of the downstream expansion valve (EV) is controlled so that the intermediate-pressure refrigerant becomes the intermediate pressure at the point where the amount of decrease in the discharge pipe temperature detected by the discharge pipe sensor (Th-d) suddenly changes. I do.

-Basic Principle of Opening Adjustment- Therefore, a basic principle of controlling the above-described intermediate pressure based on the discharge temperature will be described.

First, the state change of the refrigerant in the main refrigerant circuit (2M) will be briefly described. As shown in FIG. 2, the refrigerant in the compressor (21) is compressed to a high pressure state from the point A to the point B. This high-pressure gas refrigerant is condensed and becomes a high-pressure liquid refrigerant at point C. This high-pressure liquid refrigerant is decompressed to an intermediate-pressure refrigerant to point D by the first electric expansion valve (EV-1) or the second electric expansion valve (EV-2), and is then discharged by the gas-liquid separator (24). And an intermediate-pressure gas refrigerant.

The separated intermediate-pressure gas refrigerant is supplied through the injection circuit (30) to the middle of the compression stroke (see point G) of the compressor (21), while the intermediate-pressure liquid refrigerant is supplied to the compressor E21.
From the point of view, the second electric expansion valve (EV-2) or the first electric expansion valve (EV
In -1), the pressure is reduced to the low-pressure two-phase refrigerant to point F. This low-pressure two-phase refrigerant evaporates and changes to point A, and returns to the compressor (21).

The flow rate of the intermediate-pressure gas refrigerant flowing through the injection circuit (30), that is, the injection amount is determined by the pressure difference between the low pressure and the intermediate pressure.

On the other hand, as shown in FIG.
When the injection amount of the intermediate-pressure gas refrigerant to be injected in 1) is increased, the operating capacity is improved. Specifically, when the injection amount is increased in the order of A2 and A3 from the case where the injection of A1 is not performed, the driving ability is improved.

That is, assuming that the supply power (compressor input) of the compressor (21) is constant, when the injection amount of the intermediate-pressure gas refrigerant is increased during the heating operation, the refrigerant circulation flowing through the indoor heat exchanger (25) As the amount increases, the heating capacity (operating capacity) improves, and during cooling operation, the enthalpy from point D to point E increases, so that the amount of heat of the evaporated refrigerant increases, and the cooling capacity (operating capacity) increases. Is improved.

In other words, assuming that the operating capacity is constant, the supply power (compressor input) of the compressor (21) decreases as the intermediate-pressure gas refrigerant increases from when no intermediate-pressure gas refrigerant is injected.

Therefore, when the injection amount of the intermediate-pressure gas refrigerant, that is, the flow rate of the intermediate-pressure gas refrigerant flowing through the injection circuit (30) is maximized, the operating capacity is maximized or the compressor input is minimized.

The injection amount of the intermediate-pressure gas refrigerant is the pressure between the low-pressure pressure (the suction pressure of the compressor (21)) which is the refrigerant pressure of the evaporator and the intermediate pressure which is the refrigerant pressure of the gas-liquid separator (24). Determined by the difference. Therefore, as shown in FIG. 4, as the pressure difference ΔP is increased, the injection amount Q1 of the intermediate-pressure gas refrigerant is increased to a predetermined pressure difference ΔP.
At the maximum Qmax. Further, when the pressure difference ΔP is increased,
Conversely, the injection amount Q1 of the intermediate-pressure gas refrigerant decreases.

The pressure difference ΔP and the injection amount Q1
When the characteristic of the discharge temperature Td is superimposed on the characteristic diagram of FIG. 5, the discharge temperature Td gradually decreases as the pressure difference ΔP increases, and the discharge temperature Td is increased at the point where the injection amount Q1 of the intermediate-pressure gas refrigerant becomes maximum. The temperature Td drops rapidly. The sudden change point C1 of the decrease amount of the discharge temperature Td substantially coincides with the maximum point Qmax of the injection amount Q1.

The reason is as follows. First, assuming that the intermediate pressure is sufficiently stored in the gas-liquid separator (24), as shown in FIG.
The injection amount Q2 of the intermediate-pressure gas refrigerant increases. When the characteristics of the dryness X of the gas-liquid separator (24) are superimposed on the characteristic diagram of the pressure difference ΔP and the injection amount Q2, they intersect at a predetermined pressure difference ΔP, and the intersection point C2 corresponds to the actual injection amount Q1. It almost coincides with the maximum point Qmax.

That is, as the pressure difference ΔP increases, the injection amount Q2 of the intermediate-pressure gas refrigerant increases. However, when the intermediate pressure increases, the dryness X of the gas-liquid separator (24) decreases. Become smaller. As a result, the amount of the intermediate-pressure gas refrigerant present in the gas-liquid separator (24) is reduced. Therefore, when the pressure difference becomes equal to or more than the predetermined pressure difference ΔP, the actual injection amount Q1 of the intermediate-pressure gas refrigerant decreases, and the injection amount Q1 becomes the maximum. Is present.

Further, when the injection amount Q1 is maximized, the intermediate-pressure liquid refrigerant of the gas-liquid separator (24) is small because the intermediate-pressure gas refrigerant of the gas-liquid separator (24) is small as described above. It is supplied to the compressor (21) through 30). As a result, the refrigerant in the compressor (21) is rapidly cooled by the evaporation of the liquid refrigerant, and as shown in FIG. 4 , the discharge temperature Td is rapidly lowered at the point C1.

As described above, in the first embodiment, the intermediate-pressure refrigerant is set so that the intermediate-pressure refrigerant becomes the intermediate pressure at the point C1 at which the amount of decrease in the discharge temperature Td detected by the discharge pipe sensor (Th-d) suddenly changes. The opening of the expansion valve (EV) is adjusted so that the injection amount Q1 of the intermediate-pressure gas refrigerant is maximized.

-Air Conditioning Operation- Next, the air conditioning operation of the above-described air conditioner (10) will be described.

First, during the indoor cooling operation, the four-way switching valve (22) is switched to the solid line side in FIG. In this state, the refrigerant discharged from the compressor (21) is supplied to the four-way switching valve (2
After flowing through 2), it flows to the outdoor heat exchanger (23), where it exchanges heat with outside air and condenses. Thereafter, the liquid refrigerant is reduced in pressure by the first electric expansion valve (EV-1), becomes an intermediate-pressure refrigerant having an intermediate pressure between the condensing pressure and the evaporation pressure, flows into the gas-liquid separator (24), and Collect in the separator (24).

The intermediate-pressure liquid refrigerant among the intermediate-pressure refrigerant accumulated in the gas-liquid separator (24) is depressurized by the second electric expansion valve (EV-2), and then depressurized in the indoor heat exchanger (25). It exchanges heat with room air and evaporates to cool the room air. Thereafter, the gas refrigerant is supplied to the four-way switching valve (22) and the accumulator (26).
And returns to the compressor (21). By performing such a circulation operation of the refrigerant, indoor cooling is performed.

On the other hand, during the heating operation, the four-way switching valve (22)
Is switched to the broken line side in FIG. In this state, the refrigerant discharged from the compressor (21) flows through the four-way switching valve (22) to the indoor heat exchanger (25), and exchanges heat with indoor air in the indoor heat exchanger (25). Condenses while heating room air. Then, the liquid refrigerant is supplied to the second electric expansion valve (EV-2)
, And flows into the gas-liquid separator (24) as an intermediate-pressure refrigerant and accumulates in the gas-liquid separator (24).

Among the intermediate-pressure refrigerants stored in the gas-liquid separator (24), the intermediate-pressure liquid refrigerant is decompressed by the first electric expansion valve (EV-1), and then is decompressed in the outdoor heat exchanger (23). It evaporates by heat exchange with the outside air. Thereafter, the gas refrigerant returns to the compressor (21) via the four-way switching valve (22) and the accumulator (26). The indoor heating is performed by performing such a circulation operation of the refrigerant.

In the above-described air conditioning operation, when the solenoid valve (SV) of the injection circuit (30) is opened, the intermediate-pressure gas refrigerant of the gas-liquid separator (24) is injected into the compressor (21).

The state change of the refrigerant in the refrigerant circuit (20) is as shown in FIG.

First, the refrigerant in the compressor (21) is compressed from a low pressure state at the point A to a high pressure state at the condensation pressure at the point B. This high-pressure gas refrigerant is condensed in the outdoor heat exchanger (23) or the indoor heat exchanger (25) and becomes a high-pressure liquid refrigerant at point C. The high-pressure liquid refrigerant is reduced to an intermediate-pressure refrigerant at point D by the first electric expansion valve (EV-1) or the second electric expansion valve (EV-2), and stored in the gas-liquid separator (24). The gas-liquid separator (24) separates the intermediate-pressure liquid refrigerant and the intermediate-pressure gas refrigerant.

The separated intermediate-pressure gas refrigerant is injected through the injection circuit (30) during the compression stroke of the compressor (21) (see point G), while the intermediate-pressure liquid refrigerant is injected from point E to point The pressure is reduced to the low-pressure two-phase refrigerant to point F by the second electric expansion valve (EV-2) or the first electric expansion valve (EV-1). This low-pressure two-phase refrigerant evaporates in the indoor heat exchanger (25) or the outdoor heat exchanger (23), changes to the point A, and the compressor (21)
Return to

As a result, during the heating operation, the refrigerant flowing through the indoor heat exchanger (25) serving as the condenser is added with the intermediate-pressure gas refrigerant, so that the refrigerant circulation amount increases, and the heating capacity is improved. .

On the other hand, during the cooling operation, the low-pressure two-phase refrigerant at the point F has an increased enthalpy from the point D to the point E, so that the amount of heat of the refrigerant evaporated in the indoor heat exchanger (25) increases. The cooling capacity is improved.

During the air-conditioning operation, the high-pressure refrigerant is reduced in pressure by the first electric expansion valve (EV-1) and the second electric expansion valve (EV-2). It is performed by the upstream electric expansion valve (EV). That is, the first electric expansion valve (EV-1) during the cooling operation and the second electric expansion valve (EV-2) during the heating operation are connected to the indoor heat exchanger (25) or the outdoor heat exchanger ( The opening degree is controlled so that the degree of superheat of the refrigerant at the outlet side of 23) becomes a predetermined value, and the pressure in CD in FIG. 2 is reduced.

On the other hand, the pressure reduction for the injection of the intermediate-pressure gas refrigerant is performed by the downstream electric expansion valve (EV).
That is, the second motor-operated expansion valve (EV-2) during the cooling operation and the first motor-operated expansion valve (EV-1) during the heating operation correspond to E-E in FIG.
The pressure of F is reduced.

As a feature of the present invention, this downstream pressure reduction operation is performed by the opening degree adjusting means (52). As shown in FIG. 4, the discharge temperature Td of the compressor (21) suddenly drops. The opening of the downstream electric expansion valve (EV) is adjusted so that the intermediate-pressure refrigerant is maintained at the intermediate pressure at the change point C1.

Specifically, the discharge pipe temperature sensor is connected to the compressor (2
The discharge temperature Td, which is the temperature of the discharged refrigerant in 1), is detected. When the opening degree of the downstream electric expansion valve (EV) is reduced and the intermediate pressure is increased as described above, the discharge temperature Td becomes a predetermined value. Drops sharply at intermediate pressures. The downstream electric expansion valve (EV), that is, the second electric expansion valve (EV-2) during the cooling operation, and the heating so that the intermediate-pressure refrigerant is maintained at the intermediate pressure at the point where the discharge temperature Td rapidly decreases. The opening degree of the first electric expansion valve (EV-1) during operation is controlled to maximize the injection amount Q1 of the intermediate-pressure gas refrigerant.

-Effects of First Embodiment- As described above, according to the present embodiment, the downstream-side electric expansion valve (EV) is set in a state where the discharge temperature Td of the compressor (21) changes rapidly.
The intermediate pressure refrigerant can be maintained at the intermediate pressure at which the injection amount Q1 of the intermediate pressure gas refrigerant is maximized. As a result, the injection amount Q1 of the intermediate-pressure gas refrigerant can be kept at the maximum, so that the injection effect of the intermediate-pressure gas refrigerant can be reliably exhibited. That is, it is possible to reliably improve the operation capacity by the injection of the intermediate-pressure gas refrigerant, and to improve the cooling capacity and the heating capacity.
In other words, if the operating capacity is maintained as before, the compressor input can be reduced, and energy saving can be reliably achieved.

In particular, since the intermediate-pressure refrigerant can be maintained at an appropriate intermediate pressure only by detecting the discharge temperature Td of the compressor (21), the cooling capacity and the heating capacity can be reliably improved by a simple control configuration. Alternatively, energy saving can be reliably achieved.

[0065]

Second Embodiment FIG. 6 shows a second embodiment of the present invention, in which an opening degree adjusting means (52) is provided with a downstream electric expansion valve (EV) based on a condensation temperature, an evaporation temperature and an intermediate pressure temperature. ) Is adjusted.

Specifically, the outdoor heat exchanger (23) is provided with an outdoor heat exchange sensor (Th-o) for detecting the refrigerant temperature of the outdoor heat exchanger (23). ) Is provided with an indoor heat exchange sensor (Th-i) for detecting the refrigerant temperature of the indoor heat exchanger (25), while the gas-liquid separator (24)
An intermediate pressure temperature sensor (Th-m) for detecting the refrigerant temperature of the gas-liquid separator (24) is provided.

The outdoor heat exchange sensor (Th-o) detects the condensation temperature of the refrigerant during the cooling operation and the evaporation temperature of the refrigerant during the heating operation, and the indoor heat exchange sensor (Th-i)
The outdoor heat exchange sensor (Th-o) and the indoor heat exchange sensor (Th-i) detect the evaporation temperature of the refrigerant during the cooling operation and the condensation temperature of the refrigerant during the heating operation. It constitutes evaporating temperature detecting means (Th).

The intermediate pressure temperature sensor (Th-m) constitutes an intermediate pressure temperature detecting means for detecting an intermediate pressure temperature which is a saturation temperature of the intermediate pressure refrigerant in the gas-liquid separator (24).

On the other hand, in the controller (50), as shown in FIG. 7, a target temperature Tm of the optimum intermediate pressure temperature at each condensation temperature Tc and each evaporation temperature Te is stored in advance. That is, as shown in the Mollier diagram of FIG. 2 in the first embodiment, when the condensation temperature Tc and each evaporation temperature Te in the main refrigerant circuit (2M) are determined, the optimum intermediate pressure at this condensation temperature Tc and each evaporation temperature Te is determined. Temperature target temperature Tm
Can be determined experimentally.

Therefore, the opening degree adjusting means (52) of the controller (50) determines the target temperature of the optimum intermediate pressure temperature at which the injection amount of the intermediate pressure gas refrigerant becomes maximum at each condensation temperature Tc and each evaporation temperature Te. Tm is tabulated in advance and set, and the target temperature Tm of the optimum intermediate pressure temperature is derived based on the detected condensation temperature and detected evaporation temperature of the outdoor heat exchange sensor (Th-o) and the indoor heat exchange sensor (Th-i). I do. Furthermore,
The opening degree adjusting means (52) receives the detected intermediate pressure temperature from the intermediate pressure temperature sensor (Th-m) and changes the intermediate pressure temperature to the target temperature T.
The opening degree of the downstream electric expansion valve (EV) is adjusted to be m.

Therefore, according to the present embodiment, similarly to the first embodiment, the intermediate-pressure refrigerant can be maintained at the intermediate-pressure temperature at which the injection amount Q1 of the intermediate-pressure gas refrigerant is maximized. The injection effect of the refrigerant can be reliably exhibited. In addition, the optimum target temperature Tm at each condensation temperature Tc and each evaporation temperature Te
Is set in advance, the injection amount Q1 of the intermediate-pressure gas refrigerant can be reliably adjusted to the maximum value.

[0072]

Third Embodiment FIG. 8 shows a third embodiment of the present invention, in which a flow meter (60) is provided in an injection circuit (30).

Specifically, the flow meter (60) constitutes flow rate detecting means for detecting the flow rate of the intermediate-pressure gas refrigerant flowing through the injection circuit (30), and directly detects the injection amount Q1 of the intermediate-pressure gas refrigerant. Detected.

On the other hand, the opening degree adjusting means (52) of the controller (50) receives the detected flow rate of the intermediate-pressure gas refrigerant from the flow meter (60) so that the injection amount Q1 of the intermediate-pressure gas refrigerant is maximized. Adjust the opening of the side electric expansion valve (EV).

Therefore, according to the present embodiment, similarly to the first embodiment, the injection amount Q1 of the intermediate-pressure gas refrigerant can be maximized, so that the injection effect of the intermediate-pressure gas refrigerant can be reliably exhibited. Can be. In addition, the injection amount Q1 of the intermediate-pressure gas refrigerant
Since the detection directly, Ki out to adjust the injection amount Q1 of the intermediate-pressure gas refrigerant in exactly the maximum value
You.

[0076]

Other Embodiments In this embodiment, an air conditioner reversible between a cooling operation and a heating operation has been described. However, the present invention is not limited to an air conditioner for a cooling only device or a heating only device. Various refrigeration devices may be used.

Further, as an embodiment of the invention according to claim 2, the intermediate pressure of the intermediate-pressure gas refrigerant may be detected by a pressure sensor other than the intermediate-pressure temperature sensor (Th-m). The intermediate pressure temperature may be an intermediate pressure equivalent saturation temperature based on the intermediate pressure obtained by the pressure sensor.

[Brief description of the drawings]

FIG. 1 is a refrigerant circuit diagram showing Embodiment 1 of the present invention.

FIG. 2 is a Mollier diagram showing a refrigerant state of a refrigerant circuit.

FIG. 3 is a characteristic diagram of an operation capacity and a compressor input with respect to an injection amount.

FIG. 4 is a characteristic diagram of an injection amount and a discharge temperature with respect to a pressure difference between an intermediate pressure and a low pressure.

FIG. 5 is a characteristic diagram of an injection amount and a dryness with respect to a pressure difference between an intermediate pressure and a low pressure.

FIG. 6 is a refrigerant circuit diagram showing Embodiment 2 of the present invention.

FIG. 7 is an explanatory diagram showing stored contents of an optimum intermediate pressure temperature.

FIG. 8 is a refrigerant circuit diagram showing Embodiment 3 of the present invention .

[Explanation of symbols]

10 Air conditioner 20 Refrigerant circuit 21 Compressor 23 Outdoor heat exchanger (heat source side heat exchanger) 24 Gas-liquid separator 25 Indoor heat exchanger (use side heat exchanger) 2M Main refrigerant circuit EV-1 1st electric expansion Valve EV-2 2nd electric expansion valve 30 Injection circuit 40 Inverter 50 Controller 51 Power control unit (Frequency control means) 52 Opening adjustment means 60 Flow meter (Flow rate detection means) Th-d Discharge pipe temperature sensor (Discharge temperature detection means) Th-m Intermediate pressure temperature sensor (Intermediate pressure temperature detection means) Th-o Outdoor heat exchange sensor (Temperature detection means) Th-i Indoor heat exchange sensor (Temperature detection means)

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-5-302767 (JP, A) JP-A-6-11205 (JP, A) JP-A-60-111849 (JP, A) 33910 (JP, B2) (58) Fields investigated (Int. Cl. ⁷ , DB name) F25B 13/00

Claims (5)

(57) [Claims] 1. A compressor (21), a heat source side heat exchanger (23), a first expansion valve (EV-1) having a variable opening, a gas-liquid separator (24), and a second opening having a variable opening. Expansion valve (EV-2) and use side heat exchanger (2
5) are connected in order, and the intermediate-pressure gas refrigerant of the intermediate-pressure refrigerant at an intermediate pressure between the condensing pressure and the evaporation pressure in the main refrigerant circuit (2M) is vaporized. liquid separator and a injection circuit (30) to the compressor (21) from (24), the upstream side expansion valve of the main refrigerant circuit (2M) (EV) is an evaporator
User side heat exchanger (25) or heat source side heat exchanger (23)
Opening is controlled so that the superheat of the refrigerant at the outlet
While the downstream-side expansion valve of the main refrigerant circuit (2M) as intermediate-pressure gas refrigerant flowing through the injection circuit (30) becomes the maximum flow opening adjustment means for adjusting the opening degree of the (EV) (52) Provided
A refrigeration apparatus characterized by being used. 2. The refrigeration apparatus according to claim 1, wherein the opening degree adjusting means (52) is configured to set the target pressure of the intermediate-pressure refrigerant corresponding to the maximum flow rate of the intermediate-pressure gas refrigerant in each refrigerant state in the main refrigerant circuit (2M). And the opening degree of the downstream expansion valve (EV) is controlled so that the intermediate pressure of the intermediate-pressure refrigerant becomes the target pressure. 3. The refrigeration apparatus according to claim 1, further comprising a discharge temperature detecting means (Th-d) for detecting a discharge temperature of a refrigerant discharged from the compressor and outputting a detection signal. The adjusting means (52) receives the detection signal from the discharge temperature detecting means (Th-d), and sets a downstream expansion valve (EV) at a point where the discharge temperature decreases rapidly corresponding to the maximum flow rate of the intermediate-pressure gas refrigerant. A refrigeration apparatus characterized by controlling the opening degree of the refrigeration system. 4. The refrigerating apparatus according to claim 1, wherein a condensing temperature detecting means (Th) for detecting a condensing temperature of the refrigerant in the main refrigerant circuit (2M), and an evaporating temperature detecting means (Th) for detecting an evaporating temperature of the refrigerant. ) And an intermediate-pressure temperature detecting means (Th-m) for detecting the intermediate-pressure temperature of the intermediate-pressure refrigerant, while the opening degree adjusting means (52) provides an intermediate-pressure refrigerant corresponding to the maximum flow rate of the intermediate-pressure gas refrigerant. Is preset for each condensing temperature and each evaporating temperature of the main refrigerant circuit (2M), and the condensing temperature detecting means (Th), the evaporating temperature detecting means (Th), and the intermediate pressure temperature detecting means (Th- m), the opening degree of the downstream expansion valve (EV) is controlled so that the intermediate pressure temperature of the intermediate pressure refrigerant reaches the target temperature corresponding to the detected condensation temperature and the detected evaporation temperature in response to the detection signal of (m). And refrigeration equipment. 5. The refrigeration apparatus according to claim 1, wherein a flow rate detecting means (60) for detecting a flow rate of the intermediate-pressure gas refrigerant flowing through the injection circuit (30) is provided, while the opening degree adjusting means (52) comprises: A refrigeration system characterized by controlling the opening of a downstream expansion valve (EV) so that the flow rate detected by the flow rate detection means (60) is maximized.