JP2001056156A - Air conditioning apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve a heating efficiency when an outside air temperature is low, and to improve a heating capability. SOLUTION: An outdoor unit 20 having a low stage side compressing mechanism 21 and an outdoor heat exchanger 25 and an indoor unit 40 having an indoor heat exchanger 42 are provided. A power-up unit 30 having a high stage side compressor 31 to two-stage compress a refrigerant is provided between the unit 20 and the unit 40. The unit 30 is switched to a two-stage compressing operation for two-stage compressing the refrigerant by the mechanism 21 and a single-stage compressing operation for single-stage compressing the refrigerant only by the mechanism 21. Further, an intermediate cooler 50 for holding the refrigerant at an intermediate pressure is provided on the way of a liquid line 3L of the unit 30. A discharged refrigerant of the mechanism 21 is sucked to the compressor 31 through the cooler 50.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an air conditioner for performing a two-stage compression operation.

[0002]

2. Description of the Related Art Conventionally, air conditioners have been disclosed in
As disclosed in Japanese Unexamined Patent Publication No. -272259, a plurality of indoor units are connected to one outdoor unit to perform a cooling / heating operation.

Specifically, as shown in FIG. 16, the outdoor unit (a) includes a compression mechanism (b) and a four-way switching valve (c).
And an outdoor heat exchanger (d), an outdoor expansion valve (e), and a liquid receiver (f). The compression mechanism (b), the four-way switching valve (c), and the like are connected by a refrigerant pipe (g).
The compression mechanism (b) includes a first compressor (h) and a second compressor (i).

On the other hand, the indoor unit (j) includes an indoor heat exchanger (k) and an indoor expansion valve (m). The indoor heat exchanger (k) and the indoor expansion valve (m) are connected to a refrigerant pipe (g).
Connected by

During the heating operation, the refrigerant discharged from the compression mechanism (b) condenses in the indoor heat exchanger (k), expands in the outdoor expansion valve (e), and expands in the outdoor heat exchanger (d). ), And circulates back to the compression mechanism (b).

During the cooling operation, the refrigerant discharged from the compression mechanism (b) condenses in the outdoor heat exchanger (d), expands in the indoor expansion valve (m), and expands in the indoor heat exchanger (k). ), And circulates back to the compression mechanism (b).

[0007]

Since the above-described air conditioner performs a single-stage compression operation, the cycle indicated by a broken line in FIG. 17 is performed during a normal heating operation. That is, the compression mechanism (b) sucks the refrigerant at the point A1 and the refrigerant
Compressed to one point. Subsequently, the refrigerant condenses in the indoor heat exchanger (k), changes to the point C1, and expands to the point D1 in the outdoor expansion valve (e). Thereafter, the refrigerant evaporates in the outdoor heat exchanger (d) and returns to the point A1.

If the outside air temperature decreases during this heating operation,
The cycle shown by the solid line in FIG. 17 (A2 → B2 → C2 → D
By performing 2), the condensation temperature of the refrigerant decreases and the evaporation temperature decreases.

As a result, the compression ratio E of the compression mechanism (b) is obtained.
And the efficiency decreases. Further, since the condensation temperature of the refrigerant decreases, the temperature difference G with respect to the room temperature F becomes smaller than the temperature difference H during the normal heating operation. For this reason, there was a problem that the performance was reduced.

The present invention has been made in view of the above points, and has as its object to improve the heating efficiency at a low outside air temperature and to improve the heating capacity.

[0011]

<Summary of the Invention> In the present invention, an intermediate unit (30) for two-stage compression is provided between a heat source unit (20) and a utilization unit (40). .

Means taken by the present invention to achieve the above object are a main compression mechanism (21) and a heat source side heat exchanger (2).
5) heat source unit (20) and use side heat exchanger (4
It is assumed that the air conditioner includes a utilization unit (40) having 2) and performs an air conditioning operation by circulating a refrigerant. An intermediate unit (30) that includes an auxiliary compression mechanism (31) and compresses the refrigerant in two stages is provided between the heat source unit (20) and the utilization unit (40).

The intermediate unit (30) may include a gas line (3G) to which the auxiliary compression mechanism (31) is connected and through which gas refrigerant flows, and a liquid line (3L) through which liquid refrigerant flows. . At this time, while the gas line (3G) of the intermediate unit (30) is connected between the gas line (2G) of the heat source unit (20) and the gas line (4G) of the utilization unit (40), The liquid line (3L) of the unit (30) is connected to the liquid line (2L) of the heat source unit (20) and the utilization unit (4
0) It is connected between the liquid line (4L).

The intermediate unit (30) has a two-stage compression operation in which the main compression mechanism (21) and the auxiliary compression mechanism (31) compress the refrigerant in two stages, and the intermediate unit (30) performs the refrigerant compression only by the main compression mechanism (21). It may be configured to switch to single-stage compression operation in which single-stage compression is performed.

The intermediate unit (30) includes a heat source unit (20) side of the gas line (3G) and an auxiliary compression mechanism (31).
And the discharge side of the auxiliary compression mechanism (31) communicates with the utilization unit side (40) of the gas line (3G).
The first communication state during the stage compression operation, the heat source unit (20) side of the gas line (3G) communicates with the use unit side (40), and the discharge side and suction side of the auxiliary compression mechanism (31) communicate. A four-way switching valve (37) that can be switched to the second communication state during the single-stage compression operation.

In the middle of the liquid line (3L) of the intermediate unit (30), an intermediate cooler (50) for maintaining the refrigerant at an intermediate pressure may be provided. At this time, the main compression mechanism (21) is so drawn that the refrigerant discharged from the main compression mechanism (21) is sucked into the auxiliary compression mechanism (31) via the intercooler (50).
And the suction side of the auxiliary compression mechanism (31) are connected to the intercooler (50).

When the intercooler (50) is provided, the discharge side of the main compression mechanism (21) in the gas line (3G) of the intermediate unit (30) is connected to the liquid line (3L) to the intercooler (50). ) May be connected to the intercooler (50) after being merged with the inflow side.

Further, an injection passage (3e) for supplying the intermediate-pressure refrigerant to the auxiliary compression mechanism (31) from the middle of the liquid line (3L) of the intermediate unit (30) may be provided. At this time, the liquid line (3
L) and an injection passage (3e), an intermediate heat exchanger (60) for exchanging heat between the high-pressure liquid refrigerant and the intermediate-pressure refrigerant.
Is provided.

When the injection passage (3e) is provided, a pressure reducing mechanism (3k) for reducing the pressure of the high-pressure liquid refrigerant to an intermediate pressure may be provided instead of the intermediate heat exchanger (60).

The discharge side and the suction side of the auxiliary compression mechanism (31) may be provided with blocking valves (3c, 3d) for preventing the refrigerant from flowing into the stopped auxiliary compression mechanism (31). .

The liquid refrigerant stored in the stopped auxiliary compression mechanism (31) is transferred from the auxiliary compression mechanism (31) to the liquid line (3L).
A liquid return passage (3f) may be provided for returning the liquid.

The lubricating oil stored in the stopped auxiliary compression mechanism (31) is transferred from the auxiliary compression mechanism (31) to the liquid line (3L).
An oil return passage (3h) may be provided for returning the oil to the tank.

The intermediate unit (30) may be configured to perform a two-stage compression operation at a high load during the heating operation and a single-stage compression operation at a low load during the heating operation.

<Function> In the present invention, for example, in the heating operation, when the heating load is large, the two-stage compression operation is performed by driving both the main compression mechanism (21) and the auxiliary compression mechanism (31). First, the refrigerant that has been one-stage compressed by the main compression mechanism (21) in the heat source unit (20) flows to the intermediate unit (30). The refrigerant flows into the auxiliary compression mechanism (31) and is compressed in two stages.

The two-stage compressed refrigerant flows to the use unit (40), and exchanges heat with air in the use side heat exchanger (42) to condense. The condensed liquid refrigerant flows through the intermediate unit (30) to the heat source unit (20), where the heat source-side heat exchanger (25)
And evaporates. Thereafter, the evaporated gas refrigerant returns to the main compression mechanism (21). This circulation operation is repeated.

In the case where the intermediate unit (30) is provided with a four-way switching valve (37) capable of switching between a first communication state during the two-stage compression operation and a second communication state during the single-stage compression operation, The intermediate unit (30) performs a two-stage compression operation of compressing the refrigerant in two stages by the main compression mechanism (21) and the auxiliary compression mechanism (31) simply by switching the four-way switching valve (37). The operation is switched to the single-stage compression operation in which the refrigerant is single-stage compressed only by (21).

In the case where the intercooler (50) is provided, the intermediate-pressure liquid refrigerant flows into the intercooler (50), and the gas refrigerant flowing from the main compression mechanism (21) to the auxiliary compression mechanism (31). Cooled.

In particular, the discharge side of the main compression mechanism (21) in the gas line (3G) is merged with the inflow side of the liquid line (3L) to the intercooler (50), and then the intercooler (50) When connected to, gas-liquid mixing will be performed reliably,
The gas refrigerant flowing from the main compression mechanism (21) to the auxiliary compression mechanism (31) is more reliably cooled.

When an intermediate heat exchanger (60) is provided,
The intermediate-pressure liquid refrigerant is supplied to the auxiliary compression mechanism (31) via the intermediate heat exchanger (60). At that time, the intermediate-pressure liquid refrigerant exchanges heat with the high-pressure liquid refrigerant, and the high-pressure liquid refrigerant is cooled to a supercooled state.

Further, when the injection passage (3e) is provided, the amount of circulating refrigerant increases.

When the load is small during the heating operation, the refrigerant discharged from the main compression mechanism (21) bypasses the auxiliary compression mechanism (31), and the single-stage compression operation is performed.

When the auxiliary compression mechanism (31) is stopped, the blocking valves (3c, 3d) are closed to prevent accumulation of liquid refrigerant in the auxiliary compression mechanism (31).

When the liquid return passage (3f) is provided, the liquid refrigerant of the auxiliary compression mechanism (31) is sucked into the liquid line (3L).

When the oil return passage (3h) is provided, the lubricating oil accumulated in the auxiliary compression mechanism (31) is sucked into the liquid line (3L) and returns to the main compression mechanism (21).

[0035]

Therefore, according to the present invention, the two-stage compression operation is performed by the main compression mechanism (21) and the auxiliary compression mechanism (31), so that the input of the main compression mechanism (21) is reduced. Can be. As a result, the efficiency can be improved as compared with the case where the operation at a high compression ratio is performed by the single-stage compression operation.

Further, since the condensing temperature during the heating operation can be kept high, the heating capacity can be improved.

Also, since the intermediate unit (30) is formed as a single component, it can be easily added to an existing air conditioner. As a result, it is possible to easily increase the heating capacity and the like.

Since the single-stage compression operation and the two-stage compression operation can be switched, a normal heating operation can be performed even when the intermediate unit (30) fails. As a result, the reliability can be improved.

When the single-stage compression operation and the two-stage compression operation are switched by the four-way switching valve (37), the circuit configuration can be simplified since a plurality of closing valves (electromagnetic valves) need not be used. In addition, opening and closing control can be easily performed. Moreover, in this case, since all the passages connected to the four-way switching valve (37) are not closed due to malfunction, the switching reliability can be improved.

When an intercooler (50) and an injection passage (3e) are provided, an intermediate-pressure refrigerant can be supplied to the auxiliary compression mechanism (31). As a result, the refrigerant circulation amount can be increased, and the heating capacity can be further improved.

In particular, the discharge side of the main compression mechanism (21) in the gas line (3G) is merged with the inflow side of the liquid line (3L) to the intercooler (50), and then the intercooler (50) When connected to the main compression mechanism (21) to the auxiliary compression mechanism (31)
Therefore, it is possible to avoid a problem that the discharge temperature of the auxiliary compression mechanism (31) is excessively increased and the lubricating oil is deteriorated or the refrigerant is decomposed.

Further, when the blocking valves (3c, 3d) for blocking the refrigerant from flowing into the auxiliary compression mechanism (31) are provided, the accumulation of the liquid refrigerant in the auxiliary compression mechanism (31) can be reliably prevented. In addition, shortage of the refrigerant can be reliably prevented.

If a liquid return passage (3f) for returning the liquid refrigerant of the auxiliary compression mechanism (31) to the liquid line (3L) is provided, shortage of the refrigerant can be more reliably prevented.

Further, since the oil return passageway (3h) for returning the lubricating oil of the auxiliary compression mechanism (31) to the liquid line (3L) is provided, it is possible to reliably prevent shortage of the lubricating oil.

[0045]

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) of the present embodiment is configured as an air conditioner capable of performing a cooling / heating operation and a two-stage compression operation.

The air conditioner (10) includes one outdoor unit (20) as a heat source unit, one power-up unit (30) as an intermediate unit, and a plurality of utilization units as plural units. Indoor unit (40),
It is configured as a so-called multi-type.

A closed-circuit refrigerant circuit (11) having a reversible refrigerant circulation is formed between the outdoor unit (20), the power-up unit (30), and the indoor unit (40).

The outdoor unit (20) includes a low-stage compression mechanism (21) as a main compression mechanism, a four-way switching valve (22), a receiver (23), an outdoor expansion valve (24), and a heat source side heat source. An outdoor heat exchanger (25) as an exchanger is provided. These low-stage compression mechanism (21) and outdoor heat exchanger (25) are connected to refrigerant pipe (12)
Are connected in order.

The low-stage compression mechanism (21) is configured by connecting two compressors (26, 27) in parallel. Said 2
The compressors (26, 27) are, for example, an inverter-controlled variable-capacity compressor (26) and a constant-capacity compressor (2
7).

An oil separator (2a) is connected to the discharge side of the variable capacity compressor (26), and a check valve (2b) is connected to the discharge side of the constant capacity type compressor (27). Have been. On the other hand, a gas-liquid separator (2c) is connected to the suction sides of the two compressors (26, 27).

An oil return pipe (2e) having a capillary tube (2d) is connected to the oil separator (2a). The oil return pipe (2e) is connected to the suction side of a variable capacity compressor (26). An oil equalizing pipe (2g) having a capillary tube (2f) is connected between the two compressors (26, 27).

The discharge side and the suction side of both compressors (26, 27) are connected to two ports of a four-way switching valve (22). The other two ports of the four-way switching valve (22) are connected to the power-up unit (30) and the outdoor heat exchanger (25).

The outdoor heat exchanger (25) is connected to the outdoor expansion valve (2).
4) and the liquid receiver (23) are connected to the power-up unit (30) in order.

A line from one end of the outdoor heat exchanger (25) to the power-up unit (30) including the outdoor expansion valve (24) is a liquid line (2L). A line from the other end of the outdoor heat exchanger (25) to the power-up unit (30) including the low-stage compression mechanism (21) is a gas line (2).
G).

The plurality of indoor units (40) are connected in parallel with each other, and the power-up unit (30)
It is connected to the. Each of the indoor units (40) is configured such that an indoor expansion valve (41) and an indoor heat exchanger (42) as a use side heat exchanger are connected in series by a refrigerant pipe (12).

The line from one end of the indoor heat exchanger (42) to the power-up unit (30) including the indoor expansion valve (41) is a liquid line (4L). A line from the other end of the indoor heat exchanger (42) to the power-up unit (30) is a gas line (4G).

The power-up unit (30) is mainly for increasing the heating capacity by performing the two-stage compression operation, and is constituted by one single component. The power-up unit (30) is connected at four points to a gas line (2G, 4G) and a liquid line (2L, 4L) between the outdoor unit (20) and the indoor unit (40). .

The power-up unit (30) is
It may be added to an existing air conditioner having an outdoor unit (20) and an indoor unit (40).

The power-up unit (30) includes a high-stage compressor (31) as an auxiliary compression mechanism, and includes a gas line (3G) and a liquid line (3L).

Both ends of the liquid line (3L) are connected to the liquid line (2L) of the outdoor unit (20) and the liquid line (4L) of the indoor unit (40). A liquid expansion valve (32) and an intercooler (50) are provided in the middle of the liquid line (3L). The liquid expansion valve (32) maintains the refrigerant pressure of the intercooler (50) at the intermediate pressure.

Both ends of the gas line (3G) are connected to the gas line (2G) of the outdoor unit (20) and the gas line (4G) of the indoor unit (40). The high-stage compressor (31) is provided in the middle of the gas line (3G). The high-stage compressor (31) is an outdoor unit (20)
The two-stage compression of the refrigerant discharged from the low-stage compression mechanism (21). The suction side of the high-stage compressor (31) is connected to the outdoor unit (20) via the gas expansion valve (33), the intercooler (50), and the gas-liquid separator (34). The discharge side of the high-stage compressor (31) is connected to the indoor unit (40).

The gas line (3G) is connected to a gas bypass passage (3a). The gas bypass passage (3a)
Is connected between the outdoor unit (20) and the gas expansion valve (33). The other end of the gas bypass passage (3a) is connected to the discharge side of the high-stage compressor (31) and the indoor unit (40).
Is connected between. The gas bypass passage (3a) is provided with a closing valve (3b).

The gas bypass passage (3a) is configured to communicate when performing a single-stage compression operation and to be shut off during a two-stage compression operation. That is, the power-up unit (30) is configured to switch between the single-stage compression operation and the two-stage compression operation. In the single-stage compression operation, the refrigerant of the low-stage compression mechanism (21) flows through the gas bypass passage (3a), and the refrigerant bypasses the high-stage compressor (31).

<Operation> Next, the air conditioner (1
The cooling / heating operation 0) will be described. Therefore, first, a case where the heating load is large in the heating operation will be described with reference to FIG.

During the heating operation, the low-stage compression mechanism (21)
And the high-stage compressor (31) are driven together to perform a two-stage compression operation. In this case, the four-way switching valve (22) switches to the solid line side in FIG.

The closing valve (3b) of the gas bypass passage (3a) in the power-up unit (30) is closed, and the gas expansion valve (33) is open. Further, the liquid expansion valve (32)
The opening degree is set to a predetermined value so as to generate the intermediate-pressure refrigerant.

In this state, as shown in FIG.
The three low-pressure refrigerants are one-stage compressed to point B3 by both compressors (26, 27) of the low-stage compression mechanism (21) in the outdoor unit (20). The one-stage compressed refrigerant flows to the power-up unit (30) via the four-way switching valve (22). This refrigerant flows into the intercooler (50) via the gas expansion valve (33). In the intercooler (50), the refrigerant is cooled to a point C3 by a liquid refrigerant described later, and then flows into the high-stage compressor (31).

The refrigerant that has been two-stage compressed to point D3 in the high-stage compressor (31) flows to the indoor unit (40),
The heat is exchanged with the indoor air in the indoor heat exchanger (42) to condense (see point E3). The condensed liquid refrigerant flows to the power-up unit (30), is depressurized to the intermediate pressure F3 by the liquid expansion valve (32), and flows into the intercooler (50). In the intercooler (50), as described above, the refrigerant flowing from the low-stage compression mechanism (21) to the high-stage compressor (31) is cooled.

At this time, assuming that the flow rate of the liquid refrigerant is 1.2 G, the flow rate of the gas refrigerant supplied from the intercooler (50) to the high-stage compressor (31) is 0.2 G.

On the other hand, the liquid refrigerant (H
3) flows into the outdoor unit (20), and the receiver (2
After 3), the pressure is reduced to the point I3 by the outdoor expansion valve (24).
The liquid refrigerant flows into the outdoor heat exchanger (25) and evaporates to A3
Transform into a point. The flow rate of this liquid refrigerant is 1 G.

Thereafter, the evaporated gas refrigerant returns to the low-stage compression mechanism (21) via the four-way switching valve (22). This circulation operation is repeated to heat the room.

Next, a case where the heating load is small in the above-described heating operation will be described with reference to FIG.

During the heating operation, the low-stage compression mechanism (21)
And the high-stage compressor (31) is stopped to perform single-stage compression operation. In this case, the four-way switching valve (22) switches to the solid line side in FIG. Also, the closing valve (3b) of the gas bypass passage (3a) in the power-up unit (30) opens,
While the gas expansion valve (33) is closed, the liquid expansion valve (32) of the power-up unit (30) is fully open.

In this state, the refrigerant compressed by the low-stage compression mechanism (21) of the outdoor unit (20) flows to the power-up unit (30) via the four-way switching valve (22). The refrigerant flows through the gas bypass passage (3a) and bypasses the high-stage compressor (31).

Thereafter, the refrigerant is supplied to the indoor unit (40).
And condensed in the indoor heat exchanger (42). The condensed liquid refrigerant flows to the power-up unit (30), passes through the liquid expansion valve (32) and the intercooler (50), and is supplied to the outdoor unit (2).
Flow to 0). Further, the liquid refrigerant passes through the liquid receiver (23) and is decompressed by the outdoor expansion valve (24), flows into the outdoor heat exchanger (25), and evaporates.

Thereafter, the evaporated gas refrigerant returns to the low-stage compression mechanism (21) through the four-way switching valve (22), and repeats this circulation operation to heat the room.

The cooling operation of the air conditioner (10) will be described with reference to FIG.

During the cooling operation, the low-stage compression mechanism (21)
And the high-stage compressor (31) is stopped to perform single-stage compression operation. In this case, the four-way switching valve (22) switches to the broken line side in FIG. Also, the closing valve (3b) of the gas bypass passage (3a) in the power-up unit (30) opens,
While the gas expansion valve (33) is closed, the liquid expansion valve (32) of the power-up unit (30) is fully open.

In this state, the refrigerant compressed by the low-stage compression mechanism (21) of the outdoor unit (20) flows through the four-way switching valve (22) to the outdoor heat exchanger (25) and condenses. The condensed liquid refrigerant flows to the power-up unit (30) via the liquid receiver (23), and flows to the indoor unit (40) via the intercooler (50) and the liquid expansion valve (32). Further, the liquid refrigerant is reduced in pressure by the indoor expansion valve (41), flows into the indoor heat exchanger (42), and evaporates.

Thereafter, the evaporated gas refrigerant flows to the power-up unit (30), flows through the gas bypass passage (3a), and bypasses the high-stage compressor (31). The gas refrigerant flows to the outdoor unit (20), and returns to the low-stage compression mechanism (21) via the four-way switching valve (22). This circulation operation is repeated to cool the room.

<Effects of First Embodiment> As described above, according to this embodiment, the two-stage compression operation is performed by the low-stage compression mechanism (21) and the high-stage compressor (31). ,
The input of the low-stage compression mechanism (21) can be reduced. As a result, the efficiency can be improved as compared with the case where the operation at a high compression ratio is performed by the single-stage compression operation.

Further, since the condensing temperature during the heating operation can be kept high, the heating capacity can be improved.

The intermediate-pressure refrigerant is supplied to the high-stage compressor (31).
, The amount of circulating refrigerant can be increased, and the heating capacity can be further improved.

Since the power-up unit (30) is formed as a single component, it can be easily added to an existing air conditioner. As a result, it is possible to easily increase the heating capacity and the like.

Since the single-stage compression operation and the two-stage compression operation can be switched, the normal heating operation can be performed even when the power-up unit (30) fails. As a result, the reliability can be improved.

[0087]

Second Embodiment Next, a second embodiment of the present invention will be described in detail with reference to the drawings.

As shown in FIG. 5, in this embodiment, the power-up unit (30) of the first embodiment is provided with two closing valves (3).
c, 3d).

Specifically, the power-up unit (3
In (0), closing valves (3c, 3d) are provided on the discharge side and the suction side of the high-stage compressor (31), respectively. The shut-off valves (3c, 3d) are blocking valves for preventing the refrigerant from flowing into the high-stage compressor (31). The shut-off valves (3c, 3d) are closed during single-stage compression operation to prevent liquid refrigerant from accumulating in the stopped high-stage compressor (31). Conversely, the closing valve (3c,
3d) is opened during the two-stage compression operation.

Therefore, according to the present embodiment, the accumulation of the liquid refrigerant in the high-stage compressor (31) can be reliably prevented by the closing valves (3c, 3d), and the shortage of the refrigerant is surely prevented. be able to. Other configurations, operations and effects are the same as those of the first embodiment.

Incidentally, the closing valve (3c) on the discharge side of the high-stage compressor (31) may be a check valve.

[0092]

Third Embodiment Next, a third embodiment of the present invention will be described in detail with reference to the drawings.

As shown in FIG. 6, in this embodiment, an intermediate heat exchanger (60) is provided in place of the intercooler (50) of the first embodiment.

The intermediate heat exchanger (60) has a casing (6
The heat exchange coil (62) is housed in 1). The casing (61) is provided in the middle of the liquid line (3L) of the power-up unit (30).
The heat exchange coil (62) is connected to the injection passage (3
e). The injection passage (3e)
One end of the intermediate heat exchanger (60) through the liquid expansion valve (32)
Is connected to the liquid line (3L) between the casing (61) and the indoor unit (40), and the other end is connected to the connection between the suction side of the high-stage compressor (31) and the gas bypass passage (3a). It is connected.

The suction side of the high-stage compressor (31) is directly connected to the outdoor unit (20), and the gas expansion valve (33) in the first embodiment is not provided.

[0096] A case where the heating load is large in the heating operation of the air conditioner (10) will be described.

At the time of this heating operation, as in the first embodiment,
A stage compression operation is performed. In this case, the four-way switching valve (22) switches to the solid line side in FIG. In addition, the closing valve (3) of the gas bypass passage (3a) in the power-up unit (30)
b) is closed and the liquid expansion valve (32) is controlled to a predetermined opening.

In this state, as shown in FIG.
The four low-pressure refrigerants are one-stage compressed to point B4 by both compressors (26, 27) of the low-stage compression mechanism (21) in the outdoor unit (20). The one-stage compressed refrigerant flows to the power-up unit (30) via the four-way switching valve (22). This refrigerant flows into the high-stage compressor (31). At that time, as described later, the intermediate-pressure refrigerant is supplied to the high-stage compressor (31) from the injection passage (3e), and the refrigerant is cooled to the C4 point.

The refrigerant that has been two-stage compressed to point D4 in the high stage compressor (31) flows to the indoor unit (40),
Heat is exchanged with indoor air in the indoor heat exchanger (42) to condense (see point E4). The condensed liquid refrigerant flows to the power-up unit (30), and a part of the liquid refrigerant flows to the injection passage (3e).

The liquid refrigerant flowing through the injection passage (3e) is reduced to an intermediate pressure at point F4 by the liquid expansion valve (32) and flows to the intermediate heat exchanger (60). The intermediate heat exchanger (60)
In, the high-pressure liquid refrigerant condensed in the indoor heat exchanger (42) exchanges heat with the intermediate-pressure liquid refrigerant, and the intermediate-pressure refrigerant flows into the high-stage compressor (31) as described above.

At this time, assuming that the flow rate of the liquid refrigerant is 1.2 G, the flow rate of the gas refrigerant supplied from the intermediate heat exchanger (60) to the high-stage compressor (31) is 0.2G.

On the other hand, the high-pressure liquid refrigerant is cooled to a supercooled state up to point H4. The liquid refrigerant flows to the outdoor unit (20), and is decompressed to the point I4 by the outdoor expansion valve (24) via the liquid receiver (23). The liquid refrigerant is supplied to the outdoor heat exchanger (2
It flows to 5), evaporates and transforms to A4 point. The flow rate of this liquid refrigerant is 1 G.

Thereafter, the evaporated gas refrigerant returns to the low-stage compression mechanism (21) via the four-way switching valve (22). This circulation operation is repeated to heat the room.

The other structures, operations and effects are the same as those of the first embodiment, and the liquid expansion valve (32) is fully closed during the low-load heating operation and the cooling operation.

[0105]

Fourth Embodiment Next, a fourth embodiment of the present invention will be described in detail with reference to the drawings.

As shown in FIG. 8, in the present embodiment, two closing valves (3c, 3d) are added to the power-up unit (30) of the third embodiment, similarly to the second embodiment.

More specifically, the power-up unit (3
In (0), closing valves (3c, 3d) are provided on the discharge side and the suction side of the high-stage compressor (31), respectively. The shut-off valves (3c, 3d) are blocking valves for preventing the refrigerant from flowing into the high-stage compressor (31). The shut-off valves (3c, 3d) close during single-stage compression operation to prevent liquid refrigerant from accumulating in the stopped high-stage compression. Conversely, the closing valves (3c, 3d)
It opens during the two-stage compression operation.

Therefore, according to the present embodiment, accumulation of the liquid refrigerant in the high-stage compressor (31) can be reliably prevented by the closing valves (3c, 3d), and shortage of the refrigerant is surely prevented. be able to. Other configurations, operations and effects are the same as those of the third embodiment.

The discharge-side closing valve (3c) of the high-stage compressor (31) may be a check valve.

[0110]

Next, a fifth embodiment of the present invention will be described in detail with reference to the drawings.

As shown in FIG. 9, in the present embodiment, the liquid return passage (3f) is connected to the power-up unit (30) of the second embodiment.
Is added.

More specifically, one end of the liquid return passage (3f) is connected to the high-stage compressor (31), and the other end is connected to the intercooler (50). And the liquid return passage (3f)
Has a closing valve (3g).

The reason for providing the liquid return passage (3f) is as follows. In the second embodiment, the high-stage compressor (31)
Although the closing valves (3c, 3d) are provided on the discharge side and the suction side to prevent accumulation of the liquid refrigerant, the liquid refrigerant slightly accumulates because the valve itself has a leak.

Therefore, in the present embodiment, the liquid refrigerant of the high-stage compressor (31) is sucked into the intermediate-pressure intercooler (50). As a result, shortage of the refrigerant can be reliably prevented. Other configurations, operations and effects are the same as those of the second embodiment.

[0115]

Sixth Embodiment Next, a sixth embodiment of the present invention will be described in detail with reference to the drawings.

As shown in FIG. 10, in this embodiment, the oil return passage (3) is connected to the power-up unit (30) of the fourth embodiment.
h) is added.

More specifically, one end of the oil return passage (3h) is connected to the high-stage compressor (31), and the other end is connected between the intermediate heat exchanger (60) and the outdoor unit (20). Have been.
The oil return passage (3h) is provided with a closing valve (3i).

Further, the liquid line (3L) of the power-up unit (30) has a liquid receiver (35) between the intermediate heat exchanger (60) and the connection portion of the oil return passage (3h). Main expansion valve (3
6) is provided.

In other words, lubricating oil may accumulate in the stopped high-stage compressor (31). This lubricating oil is returned to the low-pressure side of the liquid line (3L), and the low-stage compression mechanism (21) I try to return to. For this purpose, a main expansion valve (36) is provided in the power-up unit (30), and an oil return passage (3h) is connected to a lower pressure side than the main expansion valve (36).

Further, during the single-stage compression operation of the heating operation, the pressure of the refrigerant is reduced by the main expansion valve (36), so that the liquid receiver (23) of the outdoor unit (20) cannot sufficiently store the liquid refrigerant. . Therefore, the power up unit (30)
A liquid receiver (35) is provided for storing the liquid refrigerant.

Therefore, according to the present embodiment, since the oil return passage (3h) is provided, shortage of lubricating oil can be reliably prevented. Other configurations, operations, and effects are the same as those of the fourth embodiment.

[0122]

Embodiment 7 Next, Embodiment 7 of the present invention will be described in detail with reference to the drawings.

As shown in FIG. 11, in the present embodiment, an injection passage (3e) is provided instead of the intermediate heat exchanger (60) of the third embodiment.

That is, the injection passage (3e)
Is a closing valve (3j) and a capillary tube (decompression mechanism)
(3k), when the heating load is large, the shut-off valve (3j)
To supply the intermediate-pressure liquid refrigerant to the high-stage compressor (31). Other configurations, operations and effects are the same as those of the third embodiment.

[0125]

Eighth Embodiment Next, an eighth embodiment of the present invention will be described in detail with reference to the drawings.

As shown in FIG. 12, in this embodiment, the power-up unit (30) has a different configuration from the above-described first to seventh embodiments, and switches between a single-stage compression operation and a two-stage compression operation. For this purpose, a second four-way switching valve (37) is provided in the gas line (3G) of the power-up unit (30). In the following description, the four-way switching valve (22) of the outdoor unit (20) is referred to as a first four-way switching valve because of the provision of the second four-way switching valve (37).

Power up unit (30) of the present embodiment
In the gas line (3G), two ports of the second four-way switching valve (37) are connected to the discharge side and the suction side of the high-stage compressor (31), and the other two ports are It is connected to the gas line (2G) side of the outdoor unit (20) and the gas line (4G) side of the indoor unit (40).

The second four-way switching valve (37) is connected between the outdoor unit (20) of the gas line (3G) and the high-stage compressor (3).
The first communication state in which the suction side of 1) communicates with the discharge side of the high-stage compressor (31) and the indoor unit (40) side of the gas line (3G), and the gas line (3G) The outdoor unit (20) and the indoor unit (40) communicate with each other, and can be set to a second communication state in which the discharge side and the suction side of the high-stage compressor (31) communicate with each other.

The gas line (3G) has an overpressure release connected to the suction side of the high-stage compressor (31) and the position of the second four-way switching valve (37) on the outdoor unit (20) side. The passage (3m)
It is provided as a one-way passage that bypasses the second four-way switching valve (37). In the overpressure release passage (3m), only refrigerant flows in the direction from the high-stage compressor (31) to the gas line (3G) between the second four-way switching valve (37) and the outdoor unit (20). Check valve (3n) is provided.

When the high-stage compressor (31) is stopped during the single-stage compression operation, the high-stage compressor (31) is cooled to prevent accumulation of liquid refrigerant. The stage-side compressor (31) is heated by heating means (not shown) such as a crankcase heater so that the gas refrigerant is discharged from the overpressure release passage (3m).

On the other hand, the liquid expansion valve (32) and the gas-liquid separator (70) are connected to the liquid line (3L) of the power up unit (30) from the indoor unit (40) side to the outdoor unit (20) side. Are connected in order. The gas-liquid separator (70) is connected to a gas line (3G) between the second four-way switching valve (37) and the outdoor unit (20) via a gas passage (3o). The gas passage (3o) is provided with a closing valve (3p) and a check valve (3q).

Further, the liquid expansion valve (32) and the indoor unit (4
0), and the liquid injection passage (3r) is connected to the gas line (3G) side of the check valve (3q) of the gas passage (3o) between the liquid line (3L). The liquid injection passage (3r) is provided with a closing valve (3s) and a check valve (3t).

As the second four-way switching valve (37), for example, a rotary four-way switching valve can be used.
The rotary four-way switching valve may be configured to switch the communication state by employing an electromagnetic drive system, a motor drive system, or the like.

<Operation> Next, the air conditioner (1
First, in the cooling / heating operation 0), the case where the heating load is large in the heating operation will be described.

During this heating operation, the low-stage compression mechanism (21)
And the high-stage compressor (31) are driven together to perform a two-stage compression operation. In this case, both four-way switching valves (22, 37) are
It switches to the solid line side of.

The power-up unit (30) is set so that the closing valve (3p) of the gas passage (3o) and the closing valve (3s) of the liquid injection passage (3r) are open. Further, the liquid expansion valve (32) is set to a predetermined opening so as to generate the intermediate-pressure refrigerant.

In this state, the low-pressure refrigerant is supplied to both compressors (26, 2) of the low-stage compression mechanism (21) of the outdoor unit (20).
7) is compressed by one stage.
After 7), two-stage compression is performed by the high-stage compressor (31) of the power-up unit (30).

[0138] The refrigerant flows into the indoor unit (40), exchanges heat with the indoor air in the indoor heat exchanger (42), condenses and heats the indoor air, and then flows into the power-up unit (30). The liquid refrigerant is supplied to the power-up unit (3
In the liquid line (3L) of (0), the liquid is decompressed to an intermediate pressure by the liquid expansion valve (32) and flows into the gas-liquid separator (70) and flows into the liquid injection passage (3r).

In the gas-liquid separator (70), the intermediate-pressure two-phase refrigerant is separated into a liquid refrigerant and a gas refrigerant, and the liquid refrigerant flows to the outdoor unit (20), while the gas refrigerant flows into the gas passage (3o). Flows through. This gas refrigerant flows into the liquid injection passage (3r)
And then merges with the refrigerant discharged from the low-stage compression mechanism (21) to cool the discharged refrigerant.

Therefore, since the sufficiently cooled refrigerant is sucked into the high-stage compressor (31), for example, the deterioration of the lubricating oil due to the excessive rise of the discharge temperature of the high-stage compressor (31) and the refrigerant Can be prevented from decomposing, and the reliability can be improved. Also,
The COP (coefficient of performance) can be increased by improving the efficiency.

On the other hand, the liquid refrigerant of the gas-liquid separator (70)
After flowing to the outdoor unit (20), the pressure is reduced by the outdoor expansion valve (24) via the liquid receiver (23), and then evaporated by the outdoor heat exchanger (25), and then reduced through the first four-way switching valve (22). Stage side compression mechanism (21)
Return to By repeating the above-described circulation operation, the indoor heating operation under a high load is performed.

Next, when the heating load is small, the low-stage compression mechanism (21) is driven, the high-stage compressor (31) is stopped, and the single-stage compression operation is performed. In this case, the first four-way switching valve (22) switches to the solid line side in FIG. 12, and the second four-way switching valve (37) switches to the broken line side in FIG. Further, the liquid expansion valve (32) of the power-up unit (30) is fully opened, and the closing valve (3p) of the gas passage (3o) and the closing valve (3s) of the liquid injection passage (3r) are both closed. .

In this state, the refrigerant compressed by the low-stage compression mechanism (21) of the outdoor unit (20) passes through the two-way switching valves (22, 37) to the high-stage compressor (31). It bypasses and flows to the indoor unit (40), and is condensed in the indoor heat exchanger (42).

The condensed liquid refrigerant is supplied to the liquid expansion valve (32) and the gas-liquid separator (70) of the power-up unit (30).
Through the outdoor unit (20). Further, the liquid refrigerant passes through the liquid receiver (23) and is decompressed by the outdoor expansion valve (24).
It flows into the outdoor heat exchanger (25) and evaporates.

Thereafter, the evaporated gas refrigerant returns to the low-stage compression mechanism (21) via the first four-way switching valve (22), and repeats this circulation operation to heat the room.

Next, the cooling operation of the air conditioner (10) will be described.

During the cooling operation, the low-stage compression mechanism (21)
And the high-stage compressor (31) is stopped to perform single-stage compression operation. In this case, the two four-way switching valves (22, 37) are
It switches to the broken line side of No. 2. Further, the liquid expansion valve (32) of the power-up unit (30) is fully opened, and the closing valve (3p) of the gas passage (3o) and the closing valve (3s) of the liquid injection passage (3r) are both closed. . And the outdoor expansion valve (24)
Is fully opened, and the degree of opening of the indoor expansion valve (41) is set so as to reduce the high-pressure refrigerant to a predetermined low pressure.

In this state, the refrigerant compressed by the low-stage compression mechanism (21) of the outdoor unit (20) flows through the first four-way switching valve (22) to the outdoor heat exchanger (25) and condenses. I do. The condensed liquid refrigerant flows to the power-up unit (30) via the liquid receiver (23), and flows to the indoor unit (40) via the gas-liquid separator (70) and the liquid expansion valve (32). Further, the liquid refrigerant is reduced in pressure by the indoor expansion valve (41), flows into the indoor heat exchanger (42), and evaporates.

After that, the evaporated gas refrigerant flows to the power-up unit (30), flows through the second four-way switching valve (37), and bypasses the high-stage compressor (31). Then, the gas refrigerant flows to the outdoor unit (20), and returns to the low-stage compression mechanism (21) via the first four-way switching valve (22). This circulation operation is repeated to cool the room.

When a single-stage compression operation is performed in a heating operation or a cooling operation at a low load, the discharge side and the suction side of the high-stage compressor (31) are connected to the second stage with the high-stage compressor (31) stopped. The four-way switching valve (37) communicates, and the refrigerant of the low-stage compression mechanism (21) does not flow into the high-stage compressor (31). At this time, the high-stage compressor (31) is heated by a heating means (not shown) such as a crankcase heater to draw the gas refrigerant from the overpressure release passage (3m) to the gas line (3G). The liquid refrigerant is prevented from accumulating in the high-stage compressor (31). In addition, even when the liquid refrigerant accumulated in the high-stage compressor (31) evaporates due to a rise in ambient temperature, the refrigerant is transferred to the gas line (3G).
The pressure in the high-stage compressor (31) can be prevented from rising abnormally.

<Effect of Embodiment 8> As described above, according to the present embodiment, it is possible to prevent the refrigerant from flowing into the high-stage compressor (31) during the single-stage compression operation as in the present embodiment. In Embodiments 2, 4, 5 and 6, etc., a plurality of closing valves (3b, 3c, 3d) are used as a mechanism for switching between a single-stage compression operation and a two-stage compression operation. Second
Since the four-way switching valve (37) is used, the cost can be reduced and the circuit can be simplified. In addition, each of the above shut-off valves (3b, 3c,
Although an electromagnetic valve is generally used for 3d), even when an electromagnetic drive system is used for the second four-way switching valve (37), the number can be reduced as compared with a case where a plurality of electromagnetic valves are used. Even if it does, cost reduction can be achieved.

In the case where a plurality of closing valves (3b, 3c, 3d) are used, in order to avoid a situation in which these solenoid valves are all closed during operation due to malfunction,
When switching between the single-stage compression operation and the two-stage compression operation, it is necessary to open and close each solenoid valve (3b, 3c, 3d) at the same time, and it is necessary to ensure the reliability of the opening and closing control.
By using the four-way switching valve (37), it is possible to reliably prevent all the passages connected to the second four-way switching valve (37) from being simultaneously closed. Therefore, switching between the single-stage compression operation and the two-stage compression operation can be performed with simple control and with high reliability.

Further, an overpressure release passage (3 m) is provided to allow the refrigerant accumulated in the high-stage compressor (37) to pass through the gas line (3G).
To prevent the inside of the high-stage compressor (31) from becoming abnormally high in pressure due to the rise in ambient temperature, and to prevent the refrigerant of the high-stage compressor (31) from being discharged into the crankcase. The refrigerant can be sent out into the circuit by heating it occasionally as needed with a heater or the like, so that the amount of circulating refrigerant in the circuit can be prevented from being reduced.

The effect of enabling the two-stage compression operation using the power-up unit (30) is the same as in the first to seventh embodiments.

[0155]

Ninth Embodiment Next, a ninth embodiment of the present invention will be described in detail with reference to the drawings.

As shown in FIG. 13, the present embodiment is different from the first to eighth embodiments in that the power-up unit (30) is configured differently, and the power-up amount during the two-stage compression operation is increased. It is configured as follows.

Specifically, in the power-up unit (30) of this embodiment, the gas line (3G) is connected from the outdoor unit (20) side to the inlet pipe (51) of the intercooler (50). The gas outlet pipe (52) of the intercooler (50) is connected to the suction side of the high-stage compressor (31), and the discharge side of the high-stage compressor (31) is connected to the indoor unit (40). Connected and configured.

A gas bypass passage (3a) is connected to the suction side and the discharge side of the high-stage compressor (31), and a closing valve (3b) is provided in the gas bypass passage (3a). The gas line (3G) on the suction side of the high-stage compressor (31) is provided with a shut-off valve (3d), and the gas line (3G) on the discharge side
Is provided with a check valve (3u).

The gas line (3G) has an intercooler (50)
Oil separators (38) are provided on the inlet side to the compressor and on the discharge side of the high-stage compressor (31), respectively. Each oil separator (38)
Is connected to the suction side of the high-stage compressor (31) via an oil supply pipe (3w) provided with a closing valve (3v).

On the other hand, the liquid line (3L) of the power-up unit (30) is connected to the liquid expansion valve (3) from the indoor unit (40) side.
2) is connected to the inlet pipe (51) of the intercooler (50), and the liquid outlet pipe (53) of the intercooler (50) is connected to the outdoor unit (20) through the check valve (3x). Side. This liquid line (3L) has a liquid expansion valve (32)
And a liquid bypass passage (3y) connected between the check valve (3x) and the outdoor unit (20). The liquid bypass passage (3y) has a shutoff valve (3 3z) is provided.

As described above, in the present embodiment, the liquid from the indoor heat exchanger (42) to the gas line (3G) connected from the discharge side of the low-stage compression mechanism (21) to the intercooler (50). Intercooler (50) in liquid line (3L) via expansion valve (32)
And the liquid outlet pipe (53) of the intercooler (50) is connected to the outdoor heat exchanger (25) by the gas outlet pipe (5).
2) is connected to the high-stage compressor (31).

With the above configuration, during the two-stage compression operation, the refrigerant discharged from the low-stage compression mechanism (21) and the refrigerant generated from the indoor heat exchanger (31) through the liquid expansion valve (32) are generated. The two-phase refrigerant at the intermediate pressure is combined and mixed and supplied to the intercooler (50), and the gas refrigerant separated by the intercooler (50) is supplied to the high-stage compressor (31). An economizer is configured to supply the refrigerant to the outdoor heat exchanger (25) of the outdoor unit (20).

<Operation> Next, the air conditioner (1
First, in the cooling / heating operation 0), the case where the heating load is large in the heating operation will be described.

In the heating operation, the low-stage compression mechanism (21)
And the high-stage compressor (31) are driven together to perform a two-stage compression operation. In this case, the four-way switching valve (22) is set to the state shown by the solid line in FIG. The indoor expansion valve (41) is set to a fully open state, the liquid expansion valve (32) is set to a predetermined opening so as to generate an intermediate-pressure refrigerant, and the outdoor expansion valve (24) controls an intermediate-pressure refrigerant to a predetermined degree. The opening is set so as to reduce the pressure to a low pressure.
Further, the closing valve (3d) on the suction side of the high-stage compressor (31) is opened, while the closing valve (3b) on the gas bypass passage (3a) is opened.
And the closing valve (3z) of the liquid bypass passage (3y) are closed. In addition, the shutoff valve (3v) of each refueling pipe (3w) is open.

In this state, the low-stage compression mechanism (21)
Is discharged into the high-stage compressor (31) through the oil separator (38) and the intercooler (50), and is compressed in two stages. The refrigerant discharged from the high-stage compressor (31) is an oil separator (38)
Flows into the indoor heat exchanger (42) functioning as a condenser through the, and exchanges heat with room air to heat the room air.
The heated indoor air is blown into the room by an indoor fan (not shown), and warm air is supplied to the room.

The refrigerant condensed by the heat exchange in the indoor heat exchanger (42) passes through the indoor expansion valve (41), and then partially expands in the liquid expansion valve (32) to form an intermediate-pressure two-phase refrigerant. And flows into the intercooler (50). At that time, the two-phase refrigerant flows into the intercooler (50) after being mixed with the refrigerant discharged from the low-stage compression mechanism (21). For this reason, a part of the two-phase refrigerant evaporates and the dryness is increased, and the low-stage discharge gas refrigerant is cooled by the two-phase refrigerant.

In this regard, in the configurations of the first, second, and fifth embodiments, the low-stage compression mechanism (2) is provided in the intercooler (50).
The refrigerant discharged in 1) and the two-phase refrigerant at the intermediate pressure generated by the liquid expansion valve (32) are caused to flow separately. Therefore, in the first, second, and fifth embodiments, the refrigerant discharged from the low-stage compression mechanism (21) flows into the gas-phase refrigerant separated from the two-phase refrigerant in the intercooler (50). In some cases, the refrigerant sucked into the high-stage compressor (31) may not be sufficiently cooled by the liquid refrigerant, but according to the present embodiment, the refrigerant is more reliably cooled.

Then, the liquid refrigerant in the intercooler (50) flows out of the intercooler (50), is decompressed by the outdoor expansion valve (24), and is sent to the outdoor heat exchanger (25) acting as an evaporator. Inflow. This refrigerant is heated by exchanging heat with outdoor air in the outdoor heat exchanger (25), changes its phase into a gas refrigerant, and changes into a four-way switching valve (2).
After passing through 2), it is sucked into the low-stage compression mechanism (21).

On the other hand, the gas refrigerant in the intercooler (50)
It is sucked into the high-stage compressor (31). At this time, as shown in the Mollier diagram of FIG. 2 described above, during the compression stroke,
The low-stage discharge gas refrigerant at the point B3 can be reliably cooled to the state of the saturated gas indicated by the point C3. Therefore, the temperature rise of the refrigerant discharged from the high-stage compressor (31) is suppressed. Further, by increasing the dryness of the two-phase refrigerant flowing into the intercooler (50), the amount of refrigerant flowing through the indoor heat exchanger (42) increases, so that a higher heating capacity can be obtained.

A part of the lubricating oil contained in the refrigerant discharged from the low-stage compression mechanism (21) and a part of the lubricating oil contained in the refrigerant discharged from the high-stage compressor (31) are separated from each other by oil separation. Since the oil is separated by the compressor (38) and supplied to the high-stage compressor, the shortage of lubricating oil does not occur in the high-stage compressor (31). Further, since the lubricating oil contained in the liquid refrigerant in the intercooler (50) returns to the low-stage compression mechanism (21), there is no shortage of lubricating oil in the low-stage compression mechanism (21).

Next, when the heating load is small, the high-stage compressor (31) is stopped to perform the single-stage compression operation. At this time, the liquid expansion valve (32) and the suction-side closing valve (3d) of the high-stage compressor (31) are closed, while the gas bypass passage (3a) is closed.
Closing valve (3b) and closing valve (3z) for liquid bypass passage (3y)
Is opened. In addition, a shutoff valve (3v) for each oil supply pipe (3w)
Is closed. The indoor expansion valve (41) is set to fully open, and the opening of the outdoor expansion valve (24) is controlled so as to reduce the high-pressure refrigerant to a predetermined low pressure.

In this state, the refrigerant discharged from the low-stage compression mechanism (21) flows to the indoor heat exchanger (42) via the intercooler (50), and exchanges heat with indoor air to condense. The condensed liquid refrigerant is supplied to the indoor expansion valve (41) and the liquid bypass passage (3).
y), the pressure is reduced by the outdoor expansion valve (24) through the liquid receiver (23), and further evaporated by the outdoor heat exchanger (25), and then returns to the low-stage compression mechanism (21).

In the cooling operation, the four-way switching valve (22) is switched to the broken line in FIG. 13 to flow the refrigerant in a direction opposite to the heating operation by single-stage compression, and the refrigerant is condensed by the outdoor heat exchanger. This can be done by a cycle of evaporation in a heat exchanger.

<Effects of the Ninth Embodiment> As described above, according to the present embodiment, during the two-stage compression operation, the refrigerant discharged from the low-stage compression mechanism (21) and the liquid expansion in the power-up unit (30) are expanded. Gas-liquid separation is performed after mixing with the intermediate-pressure refrigerant generated by the valve (32) in advance. Therefore, a sufficiently cooled gas refrigerant can be supplied to the high-stage compressor (31), so that the discharge temperature of the high-stage compressor during the two-stage compression operation can be reduced as compared with the first to eighth embodiments. Deterioration of the lubricating oil and decomposition of the refrigerant due to excessive rise can be reliably prevented, and reliability can be further improved.

Further, by mixing the refrigerant discharged from the low-stage compression mechanism (21) and the intermediate-pressure refrigerant generated by the liquid expansion valve (32) in advance, the dryness of the two-phase refrigerant is increased. The amount of suction gas of the side compressor (31) can be increased, and the capacity can be increased by improving efficiency.

The effect of enabling the two-stage compression operation using the power-up unit (30) is the same as in the first to eighth embodiments.

[0177]

Embodiment 10 Next, Embodiment 10 of the present invention will be described.
Will be described in detail with reference to the drawings.

As shown in FIG. 14, this embodiment is different from the ninth embodiment in that a closing valve (3b, 3d) and a check valve (3u) are used to switch between a single-stage compression operation and a two-stage compression operation.
Instead of the second four-way switching valve (37) as in the eighth embodiment.
Is used.

Specifically, the second four-way switching valve (37) is connected to the gas outlet pipe (52) of the intercooler (50) and the high-stage compressor (31).
And a first communication state in which the discharge side of the high-stage compressor (31) communicates with the indoor unit (40) side, and a gas outlet pipe (52) of the intercooler (50). Indoor unit (40)
And a second communication state in which the discharge side and the suction side of the high-stage compressor (31) communicate with each other.

The other structure is the same as that of the ninth embodiment.
Switching of the operation is performed by the closing valve (3b, 3
The control can be performed by controlling the second four-way switching valve (37) instead of controlling d).

According to the present embodiment, the low-stage compression mechanism (2
The pre-mixing of the refrigerant discharged in 1) and the intermediate-pressure refrigerant generated in the liquid expansion valve (32) before gas-liquid separation allows reliability due to an excessive rise in the discharge temperature of the high-stage compressor (31). In addition to increasing the capacity while preventing a decrease in the pressure, the circuit configuration and the switching control can be simplified by using the second four-way switching valve (37).

[0182]

Eleventh Embodiment Next, an eleventh embodiment of the present invention will be described.
Will be described in detail with reference to the drawings.

As shown in FIG. 15, in this embodiment, the power-up unit (30) is different from the above-described embodiments 1 to 10 in that the two-stage compression operation is performed similarly to the ninth embodiment. It is configured to increase the power-up amount.

Specifically, in the power-up unit (30) of this embodiment, the gas line (3G) is connected to the inlet of the intercooler (50) from the outdoor unit (20) via the oil separator (38). A pipe (51), a gas outlet pipe (52) of the intercooler (50) is connected to a suction side of the high-stage compressor (31), and a gas outlet pipe of the high-stage compressor (31) is connected. The discharge side is connected to the indoor unit (40).

A gas bypass passage (3a) is connected between the outdoor unit (20) and the discharge side of the high-stage compressor (31), and a closing valve (3b) is connected to the gas bypass passage (3a). Is provided. A check valve (3u) is provided in the gas line (3G) on the discharge side of the high-stage compressor (31).

The gas line (3G) has an intercooler (50)
A closing valve (3v) and the oil separator (38) are provided in this order from the outdoor unit (20) side on the inflow side to the outside. The oil separator (38) is connected to the high-stage compressor (3
1) Connected to the suction side.

On the other hand, the liquid line (3L) of the power-up unit (30) is connected to the liquid expansion valve (3) from the indoor unit (40) side.
2) is connected to the inlet pipe (51) of the intercooler (50), and the liquid outlet pipe (53) of the intercooler (50) is connected to the outdoor unit (20) through the closing valve (3x). It is configured to be connected to. This liquid line (3L) has a liquid expansion valve (32)
And a liquid bypass passage (3y) connected between the shut-off valve (3x) and the outdoor unit (20), and a shut-off valve (3z) is provided in the liquid bypass passage (3y). ) Is provided.

As described above, in this embodiment, the liquid from the indoor heat exchanger (42) to the gas line (3G) connected to the intercooler (50) from the discharge side of the low-stage compression mechanism (21). Intercooler (50) in liquid line (3L) via expansion valve (32)
And the liquid outlet pipe (53) of the intercooler (50) is connected to the outdoor heat exchanger (25) by the gas outlet pipe (5).
2) is connected to the high-stage compressor (31).

With the above configuration, during the two-stage compression operation, the refrigerant discharged from the low-stage compression mechanism (21) and the refrigerant generated from the indoor heat exchanger (42) through the liquid expansion valve (32) are generated. The two-phase refrigerant at the intermediate pressure is combined and mixed and supplied to the intercooler (50), and the gas refrigerant separated by the intercooler (50) is supplied to the high-stage compressor (31). An economizer is configured to supply the refrigerant to the outdoor heat exchanger (25) of the outdoor unit (20).

<Operation> Next, the air conditioner (1
First, in the cooling / heating operation 0), the case where the heating load is large in the heating operation will be described.

In the heating operation, the low-stage compression mechanism (21)
And the high-stage compressor (31) are driven together to perform a two-stage compression operation. In this case, the four-way switching valve (22) is set to the state shown by the solid line in FIG. The indoor expansion valve (41) is set to a fully open state, the liquid expansion valve (32) is set to a predetermined opening so as to generate an intermediate-pressure refrigerant, and the outdoor expansion valve (24) controls an intermediate-pressure refrigerant to a predetermined degree. The opening is set so as to reduce the pressure to a low pressure.
In addition, a closing valve (3v) on the inlet side to the intercooler (50)
And the closing valve (3x) on the liquid outflow side from the intercooler (50) is opened, while the closing valve (3x) in the gas bypass passage (3a) is opened.
b) and the closing valve (3z) of the liquid bypass passage (3y) are closed.

In this state, the low-stage compression mechanism (21)
Is discharged into the high-stage compressor (31) through the oil separator (38) and the intercooler (50), and is compressed in two stages. The refrigerant discharged from the high-stage compressor (31) flows into the indoor heat exchanger (42) acting as a condenser, and exchanges heat with room air to heat the room air. The heated indoor air is blown into the room by an indoor fan (not shown), and warm air is supplied to the room.

The refrigerant condensed by the heat exchange in the indoor heat exchanger (42) passes through the indoor expansion valve (41), and partially expands in the liquid expansion valve (32) to produce an intermediate-pressure two-phase refrigerant. And flows into the intercooler (50). At that time, the two-phase refrigerant flows into the intercooler (50) after being mixed with the refrigerant discharged from the low-stage compression mechanism (21). For this reason, a part of the two-phase refrigerant evaporates and the dryness is increased, and the low-stage discharge gas refrigerant is cooled by the two-phase refrigerant.

In this regard, in the configurations of the first, second, and fifth embodiments, the low-stage-side compression mechanism (2) is provided in the intercooler (50).
The refrigerant discharged in 1) and the two-phase refrigerant at the intermediate pressure generated by the liquid expansion valve (32) are caused to flow separately. Therefore, in the first, second, and fifth embodiments, the refrigerant discharged from the low-stage compression mechanism (21) flows into the gas-phase refrigerant separated from the two-phase refrigerant in the intercooler (50). Although it is conceivable that the refrigerant sucked into the high-stage compressor (31) may not be sufficiently cooled by the liquid refrigerant, according to the present embodiment, the refrigerant is more reliably cooled as in the ninth embodiment.

The liquid refrigerant in the intercooler (50) flows out of the intercooler (50), is depressurized by the outdoor expansion valve (24), and is sent to the outdoor heat exchanger (25) acting as an evaporator. Inflow. This refrigerant is heated by exchanging heat with outdoor air in the outdoor heat exchanger (25), changes its phase into a gas refrigerant, and changes into a four-way switching valve (2).
After passing through 2), it is sucked into the low-stage compression mechanism (21).

On the other hand, the gas refrigerant in the intercooler (50)
It is sucked into the high-stage compressor (31). At this time, as shown in the Mollier diagram of FIG. 2 described above, during the compression stroke,
The low-stage discharge gas refrigerant at the point B3 can be reliably cooled to the state of the saturated gas indicated by the point C3. Therefore, the temperature rise of the refrigerant discharged from the high-stage compressor (31) is suppressed. Further, by increasing the dryness of the two-phase refrigerant flowing into the intercooler (50), the amount of refrigerant flowing through the indoor heat exchanger (42) increases, so that a higher heating capacity can be obtained.

A part of the lubricating oil contained in the refrigerant discharged from the low-stage compression mechanism (21) is separated by the oil separator (38) and supplied to the high-stage compressor. In other words, when the oil separator (38) is not provided, the lubricating oil contained in the refrigerant flowing in the circuit almost returns to the lower stage from the intercooler (50), and the lubricating oil runs short However, according to the above configuration, lubricating oil shortage does not occur in the high-stage compressor (31). The low-stage compression mechanism (21) has an intercooler (5
Since the lubricating oil contained in the liquid refrigerant in 0) returns, there is no shortage of lubricating oil in the low-stage compression mechanism (21).

Next, when the heating load is small, the high-stage compressor (31) is stopped to perform the single-stage compression operation. At this time, the liquid expansion valve (32) and the closing valve (3v) on the inflow side of the intercooler (50) are closed, while the closing valve (3b) of the gas bypass passage (3a) and the liquid bypass passage (3y) are closed. The closing valve (3z) is opened. The indoor expansion valve (41) is set to fully open, and the opening of the outdoor expansion valve (24) is controlled so as to reduce the high-pressure refrigerant to a predetermined low pressure.

In this state, the refrigerant discharged from the low-stage compression mechanism (21) flows to the indoor heat exchanger (42) through the gas bypass passage (3a) without passing through the intercooler (50), and Exchanges heat with air and condenses. The condensed liquid refrigerant passes through the indoor expansion valve (41), the liquid bypass passage (3y), and is decompressed by the outdoor expansion valve (24) via the receiver (23), and is further evaporated by the outdoor heat exchanger (25). After that, the process returns to the low-stage compression mechanism (21).

In the cooling operation, the four-way switching valve (22) is switched to the dashed line in FIG. 15 to flow the refrigerant in the direction opposite to the heating operation by single-stage compression, and the refrigerant is condensed by the outdoor heat exchanger. This can be done by a cycle of evaporation in a heat exchanger.

<Effect of Embodiment 11> As described above, according to the present embodiment, during the two-stage compression operation, the refrigerant discharged from the low-stage compression mechanism (21) and the liquid expansion in the power-up unit (30) are expanded. The intermediate-pressure refrigerant generated by the valve (32) is mixed in advance, and then gas-liquid separated by the intermediate cooler (50). Therefore, the sufficiently cooled gas refrigerant is transferred to the high-stage compressor (31).
, As in the ninth embodiment.
During the stage compression operation, it is possible to reliably prevent the deterioration of the lubricating oil and the decomposition of the refrigerant due to the excessive rise of the discharge temperature of the high stage side compressor (31), and the reliability can be further improved.

Further, by mixing the refrigerant discharged from the low-stage compression mechanism (21) and the intermediate-pressure refrigerant generated by the liquid expansion valve (32) in advance, the dryness of the two-phase refrigerant is increased. As in the ninth embodiment, it is possible to increase the amount of suction gas of the side compressor (31) and increase the capacity by improving efficiency.

The effect of enabling the two-stage compression operation using the power-up unit (30) is the same as in the first to tenth embodiments. Also, in the present embodiment, similarly to the eighth and tenth embodiments, the second four-way switching valve (37) may be used to switch between the single-stage compression operation and the two-stage compression operation.

[0204]

Other embodiments of the present invention In the above embodiments,
Although the air conditioner (10) performing the cooling / heating operation has been described, the present invention may perform only the heating operation.

The low stage compression mechanism (21) may have one compressor.

It is needless to say that the number of the indoor units (40) may be one.

[Brief description of the drawings]

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

FIG. 2 is a Mollier chart showing a refrigerant state during a high-load heating operation.

FIG. 3 is a refrigerant circuit diagram illustrating a low-load heating operation in the first embodiment.

FIG. 4 is a refrigerant circuit diagram illustrating a cooling operation according to the first embodiment.

FIG. 5 is a refrigerant circuit diagram showing Embodiment 2 of the present invention.

FIG. 6 is a refrigerant circuit diagram showing Embodiment 3 of the present invention.

FIG. 7 is a Mollier chart showing a refrigerant state during a high-load heating operation.

FIG. 8 is a refrigerant circuit diagram showing Embodiment 4 of the present invention.

FIG. 9 is a refrigerant circuit diagram showing Embodiment 5 of the present invention.

FIG. 10 is a refrigerant circuit diagram showing Embodiment 6 of the present invention.

FIG. 11 is a refrigerant circuit diagram showing Embodiment 7 of the present invention.

FIG. 12 is a refrigerant circuit diagram showing Embodiment 8 of the present invention.

FIG. 13 is a refrigerant circuit diagram showing Embodiment 9 of the present invention.

FIG. 14 is a refrigerant circuit diagram showing Embodiment 10 of the present invention.

FIG. 15 is a refrigerant circuit diagram showing an eleventh embodiment of the present invention.

FIG. 16 is a refrigerant circuit diagram showing a conventional air conditioner.

FIG. 17 is a Mollier chart showing a refrigerant state during a conventional heating operation.

[Explanation of symbols]

 10 Air conditioner 20 Outdoor unit (heat source unit) 21 Low stage compression mechanism (main compression mechanism) 25 Outdoor heat exchanger (heat source side heat exchanger) 26,27 Compressor 30 Power up unit (intermediate unit) 31 High stage Side compressor (auxiliary compression mechanism) 32 Liquid expansion valve 3a Gas bypass passage 3c, 3d Shut-off valve (blocking valve) 3e Injection passage 3f Liquid return passage 3h Oil return passage 3k Capillary tube (decompression mechanism) 40 Indoor unit (use unit) 42 Indoor heat exchanger (use side heat exchanger) 50 Intercooler 60 Intermediate heat exchanger 2G, 3G, 4G Gas line 2L, 3L, 4L Liquid line

 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Yoshikazu Sato 1304 Kanaokacho, Sakai-shi, Osaka Daikin Industries Inside the Kanaoka Plant of Sakai Seisakusho Co., Ltd. (72) Inventor Toru Inazuka 1304 Kanaokacho, Sakai-shi, Osaka Daikin Industries Inside the Sakai Plant Kanaoka Plant (72) Takahiro Yamaguchi 1304 Kanaokacho, Sakai City, Osaka Daikin Industries F-term in the Sakai Plant Kanaoka Plant (reference) 3L092 AA01 AA02 BA05 BA06 BA08 BA16 BA26

Claims (12)

[Claims] 1. A heat source unit (20) having a main compression mechanism (21) and a heat source side heat exchanger (25), and a use unit (40) having a use side heat exchanger (42). In an air conditioner that circulates and performs air conditioning operation, an intermediate unit (30) that includes an auxiliary compression mechanism (31) and compresses refrigerant in two stages between the heat source unit (20) and the utilization unit (40). An air conditioner provided with. 2. The intermediate unit (30) according to claim 1, wherein the intermediate unit (30) includes a gas line (3G) to which the auxiliary compression mechanism (31) is connected and through which gas refrigerant flows, and a liquid line (3L) through which liquid refrigerant flows. The gas line (3G) of the intermediate unit (30) is connected between the gas line (2G) of the heat source unit (20) and the gas line (4G) of the utilization unit (40), while the intermediate unit (3 The liquid line (3L) of 30) is the liquid line (2L) of the heat source unit (20) and the liquid line (4L) of the utilization unit (40)
Air conditioner connected between. 3. The intermediate unit (30) according to claim 1, wherein the intermediate unit (30) is a two-stage compression operation in which the main compression mechanism (21) and the auxiliary compression mechanism (31) compress the refrigerant in two stages, and only the main compression mechanism (21). An air conditioner configured to switch to a single-stage compression operation in which a single-stage compression of a refrigerant is performed. 4. The intermediate unit (30) communicates with the heat source unit (20) side of the gas line (3G) and the suction side of the auxiliary compression mechanism (31), and the auxiliary compression mechanism (31). ) And the use unit side (40) of the gas line (3G) communicate with the first communication state during the two-stage compression operation, and the heat source unit (20) of the gas line (3G)
Four-way switching valve (37) capable of switching to a second communication state in a single-stage compression operation in which the communication side communicates with the use unit side (40) and the discharge side and the suction side of the auxiliary compression mechanism (31) communicate with each other. ) Is provided. 5. An intermediate cooler (50) for holding a refrigerant at an intermediate pressure in the middle of a liquid line (3L) of an intermediate unit (30) according to any one of claims 1 to 4. The discharge side of the main compression mechanism (21) and the auxiliary compression mechanism (31) so that the refrigerant discharged from the main compression mechanism (21) is sucked into the auxiliary compression mechanism (31) via the intercooler (50). An air conditioner wherein the suction side of the air conditioner is connected to the intercooler (50). 6. The discharge side of the main compression mechanism (21) in the gas line (3G) of the intermediate unit (30) is connected to the inlet side of the liquid line (3L) to the intermediate cooler (50). An air conditioner that is joined and then connected to the intercooler (50). 7. The injection passage (3e) according to claim 1, wherein intermediate pressure refrigerant is supplied to the auxiliary compression mechanism (31) from the middle of the liquid line (3L) of the intermediate unit (30). An intermediate heat exchanger (60) for exchanging heat between the high-pressure liquid refrigerant and the intermediate-pressure refrigerant is provided between the liquid line (3L) of the intermediate unit (30) and the injection passage (3e). Air conditioner. 8. The injection passage (3e) according to any one of claims 1 to 4, wherein intermediate pressure refrigerant is supplied to the auxiliary compression mechanism (31) from the middle of the liquid line (3L) of the intermediate unit (30). ) Is provided, and a pressure reducing mechanism (3k) for reducing the pressure of the high-pressure liquid refrigerant to an intermediate pressure is provided in the injection passage (3e). 9. The blocking valve according to claim 1, wherein a discharge valve and a suction valve of the auxiliary compression mechanism (31) prevent a refrigerant from flowing into the stopped auxiliary compression mechanism (31). Air conditioner equipped with (3c, 3d). 10. The liquid return according to claim 1, wherein the liquid refrigerant stored in the stopped auxiliary compression mechanism (31) is returned from the auxiliary compression mechanism (31) to the liquid line (3L). An air conditioner with a passage (3f). 11. The oil return according to claim 1, wherein the lubricating oil stored in the stopped auxiliary compression mechanism (31) is returned from the auxiliary compression mechanism (31) to the liquid line (3L). An air conditioner with a passage (3h). 12. The intermediate unit (30) according to any one of claims 1 to 4, wherein the intermediate unit (30) performs a two-stage compression operation at a high load during the heating operation and a single-stage compression operation at a low load during the heating operation. An air conditioner configured to perform.