JPH11142001A - Air conditioner - Google Patents

Abstract

(57) [Summary] [PROBLEMS] The reliability of a compressor accompanying the mixing of liquid refrigerant into gas refrigerant returned from a gas-liquid separator interposed in a liquid pipe to a compressor through a gas injection bypass pipe To prevent the deterioration of the gas injection and to make more effective use of gas injection. SOLUTION: A float switch 17L, 17M, 17 for detecting a liquid level of a liquid refrigerant inside a gas-liquid separator 10 is provided.
U, and according to the liquid level detected by these,
The opening degree of a bypass valve 15 composed of an electric valve provided on the bypass pipe 14 is controlled. When the liquid level is high, the bypass valve 15 is set at the intermediate opening to weaken the suction force from the compressor 1, so that the liquid level can be increased over a wider range within the fluctuation range of the liquid level in the gas-liquid separator. It is possible to continue gas injection in a state where no refrigerant is mixed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas pipe for connecting an outdoor heat exchanger and an indoor heat exchanger with a gas-liquid separator interposed therebetween. TECHNICAL FIELD The present invention relates to an air conditioner provided with a bypass pipe for returning air to an air conditioner.

[0002]

2. Description of the Related Art For example, a heating operation in an air conditioner is performed as follows.
This is performed by circulating the refrigerant gas discharged from the compressor from the indoor heat exchanger to the outdoor heat exchanger. At this time,
If the outside temperature is low, it becomes difficult to obtain sufficient heating capacity. In such a case, the gas refrigerant condensed in the indoor heat exchanger and mixed into the liquid refrigerant flowing to the outdoor heat exchanger is separated, and gas injection is performed to return the gas refrigerant to the compressor. The refrigerant is two-stage compressed by the compressor and supplied again to the indoor heat exchanger, thereby improving the overall heating capacity.

In order to perform such gas injection, conventionally, in an air conditioner provided with a compressor having a constant compression capacity, gas-liquid separation is provided in a liquid pipe between an indoor heat exchanger and an outdoor heat exchanger. It is known that a bypass pipe is provided between the gas-liquid separator and the suction side of the compressor, with a bypass valve including an on-off valve interposed between the gas-liquid separator and the suction side of the compressor. In the gas-liquid separator, the gas refrigerant and the liquid refrigerant are separated vertically, and when the bypass valve is opened, the suction force from the compressor acts on the gas-liquid separator and opens near the upper wall of the gas-liquid separator. The gas refrigerant on the upper side is sucked out through the bypass pipe which flows and returned to the compressor.

[0004] In recent years, an air conditioner equipped with a compressor whose compression capacity is variable by inverter control has become mainstream. Also in such an air conditioner, the gas-liquid separator as described above is interposed in the liquid pipe, and the gas refrigerant is returned from the gas-liquid separator to the compressor through a gas injection bypass pipe. Thus, it becomes possible to perform a heating operation or a cooling operation with increased capacity.

[0005]

However, in particular, in an air conditioner having a compressor having a variable compression capacity controlled by an inverter, when the gas injection is performed by providing the above-described gas-liquid separator and the bypass pipe, the gas-liquid There is a problem that a liquid refrigerant is likely to be mixed in a gas refrigerant (hereinafter, referred to as an injection gas) returned from the separator to the compressor.

That is, in such an air conditioner, a large amount of refrigerant is charged into the refrigerant circulation circuit in anticipation of the required amount of refrigerant circulation at the maximum load. Then, the actual amount of refrigerant circulating greatly fluctuates according to the change in load, and accordingly, the amount of liquid refrigerant in the gas-liquid separator also fluctuates greatly. For this reason, if the liquid level of the liquid refrigerant is high in the gas-liquid separator and this is near the opening end of the bypass pipe, and gas injection is performed, the liquid refrigerant is also sucked out according to the suction force from the compressor. As a result, the liquid refrigerant is mixed into the injection gas. When this liquid refrigerant is sucked into the compressor, liquid compression occurs, and if this continues, the reliability of the compressor decreases.

[0007] Even when the ratio of the liquid refrigerant in the gas-liquid separator is maximized, if a large-capacity gas-liquid separator is provided so that a sufficient gas refrigerant phase is present on the upper side, the compression is achieved. It is possible to prevent the liquid refrigerant from returning to the machine. However, providing such a large-capacity gas-liquid separator increases the size of the apparatus and increases the cost of the apparatus.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to suppress a decrease in the reliability of a compressor due to gas injection without providing a large-capacity gas-liquid separator. Another object of the present invention is to provide an air conditioner that can improve air-conditioning comfort by effectively utilizing gas injection.

[0009]

The air conditioner according to the first aspect of the present invention includes a liquid pipe 9/11 between the outdoor heat exchanger 8 and the indoor heat exchanger which are connected to the compressor 1 so that the refrigerant can circulate. A gas-liquid separator 10 is interposed, and between the gas-liquid separator 10 and the suction side of the compressor 1, the gas refrigerant separated from the liquid refrigerant in the upper part of the gas-liquid separator 10 is supplied to the compressor 1. A bypass pipe 14 for gas injection to be returned, and the bypass pipe 14
Air conditioner provided with a bypass valve 15 that opens and closes a flow path through the fluid passage, and liquid level detecting means 17L, 17M, and 17 for detecting the liquid level of the liquid refrigerant in the gas-liquid separator 10.
U and the bypass valve 15 when the liquid level detected by the liquid level detecting means 17L / 17M / 17U exceeds the reference level.
Injection control means 1 for operating the valve in the valve closing direction
6 is provided.

In the air conditioner having the above structure, when the liquid level in the gas-liquid separator 10 detected by the liquid level detecting means 17L, 17M, 17U exceeds the reference height, the bypass valve 1
5 is operated in the valve closing direction, whereby the bypass valve 15
When the valve is closed, gas injection stops.
If the bypass valve 15 can be set at an intermediate opening between the fully open state and the fully closed state, as described later,
In the above-described operation in the valve closing direction, it is also possible to perform control so as to reduce the opening to an intermediate opening, for example. In this case, the flow path through the bypass pipe 14 is narrowed, and the suction force acting on the inside of the gas-liquid separator 10 from the compressor 1 is reduced, so that the suction of the liquid refrigerant hardly occurs.

Therefore, for example, when gas injection is performed with the bypass valve 15 fully opened, the height at which the risk of liquid refrigerant being mixed into the injection gas is determined in advance and set as the reference height. When the liquid level exceeds this reference height, the gas injection is automatically stopped or switched to the gas injection state in which mixing of the liquid refrigerant is suppressed, so that a gas-liquid separator with an excessive capacity is provided. At least, the occurrence of liquid compression in the compressor is suppressed, and the reliability of the compressor is ensured.

The air conditioner according to claim 2 is characterized in that the bypass valve 15 can be set to an intermediate opening between a fully closed state and a fully open state, and is provided with such a bypass valve 15. In the air conditioner described above, when the liquid level detected by the liquid level detecting means 17L, 17M, 17U is lower than the reference level, for example,
5 is fully opened, while the bypass valve 15 is operated in the valve closing direction to set the intermediate opening until the upper limit is reached beyond the reference height. 1
It is possible to adopt a configuration in which the above-mentioned gas injection control means 16 performs control for bringing the 5 into a fully closed state.

As described above, even if the liquid level exceeds the reference level, by setting the bypass valve 15 to the intermediate opening degree until the liquid level reaches the upper limit level, as described above, the air from the compressor 1 is discharged from the compressor 1. Due to a decrease in the suction force acting in the liquid separator 10, gas injection can be performed in which mixing of the liquid refrigerant into the injection gas is suppressed. Therefore, it is possible to perform the operation with improved performance over a wider range.

On the other hand, a bypass valve 1 that can be set to an intermediate opening degree
In the air conditioner provided with 5, as in claim 4,
While the bypass valve 15 is fully closed when the liquid level detected by the liquid level detecting means 17L, 17M, 17U exceeds the reference height, the reference height and a target height area lower than the reference height are set. The gas injection control means 1 controls the opening degree of the bypass valve 15 to decrease when the time is less than the target height and to increase the opening degree of the bypass valve 15 when the opening degree is lower than the target height region.
6, it is also possible to configure.

In this case, it is possible to obtain a control state in which the liquid level is maintained in the target height region lower than the reference height. That is, when the liquid level height is lower than the target height range, increasing the opening degree of the bypass valve 15 increases the injection gas flow rate, and accordingly, the liquid level height in the gas-liquid separator increases. Rise. On the other hand, when the opening of the bypass valve 15 is reduced between the reference height and the target height region, the flow rate of the injection gas is reduced, and the liquid level is reduced accordingly.

Therefore, by performing the above-described control for increasing / decreasing the opening with the target height region interposed therebetween, the liquid level is controlled to be maintained in the target height region. At this time,
Correspondingly, the opening of the bypass valve 15 and the flow rate of the injection gas are also kept substantially constant.
Since the fluctuation of the air conditioning capacity due to the change of the injection gas flow rate is suppressed, the air conditioning comfort is maintained.

The air conditioner according to claim 5 is the compressor 1
Is characterized by a compressor with a variable compression capacity by inverter control.In such an air conditioner, a large amount of refrigerant is charged into the refrigerant circulation circuit in anticipation of the required amount of refrigerant circulation at the maximum load. Since a gas-liquid separator having a smaller capacity than the amount of the refrigerant can be employed, more remarkable effects can be obtained in terms of downsizing of the apparatus and cost reduction.

[0018]

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

FIG. 1 is a refrigerant circuit diagram showing a configuration inside an outdoor unit in a separate type air conditioner. As shown
A compressor 1 is installed in the outdoor unit, and a discharge pipe 2 of the compressor 1 and a suction pipe 4 provided with accumulators 3, 3 are connected to a four-way switching valve 5, respectively. . The compressor 1 has an inverter 1a for controlling the rotation speed, that is, the compression capacity.

The four-way switching valve 5 is connected to a first gas pipe 6 at one switching port and a second gas pipe 7 to the other switching port. An outdoor heat exchanger 8 is connected to the second gas pipe 7.
First, the first liquid pipe 9, the gas-liquid separator 10, and the second liquid pipe 11
And are connected. The first liquid pipe 9 is provided with a first electric valve 12 that is driven when performing superheat control during a heating operation described later as a pressure reducing mechanism. Also,
The second liquid pipe 11 is provided with a second electric valve 13 that is driven during a cooling operation described later.

Although not shown, an indoor unit equipped with an indoor heat exchanger is connected between the end of the second liquid pipe 11 and the end of the first gas pipe 6 through a communication pipe. Thus, a refrigerant circulation circuit is formed in which the refrigerant discharged from the compressor 1 passes through the outdoor heat exchanger 8 and the indoor heat exchanger and is returned to the compressor 1.

That is, when the compressor 1 is operated with the four-way switching valve 5 positioned at the switching position as shown by the solid line in the figure, the refrigerant discharged from the compressor 1 circulates along the solid line arrow in the figure,
At this time, while the outdoor heat exchanger 8 functions as an evaporator and absorbs heat from the outside, the indoor heat exchanger functions as a condenser, and the heat is radiated to perform indoor heating.

On the other hand, by switching the four-way switching valve 5 from the above,
By circulating the refrigerant discharged from the compressor 1 along the dashed arrow in the drawing, a cooling operation is performed in which the outdoor heat exchanger 8 functions as a condenser and the indoor heat exchanger functions as an evaporator.

The gas-liquid separator 10 interposed between the first liquid pipe 9 and the second liquid pipe 11 is further connected to an intermediate port of the compressor 1 by a bypass pipe 14. A bypass valve 15 composed of a motor-operated valve is interposed in 14.

In the closed vessel-shaped gas-liquid separator 10, the first liquid pipe 9 and the second liquid pipe 11 are connected to the gas-liquid separator 10.
Opening at a position close to the bottom of the
Reference numeral 4 denotes an opening at a position near the upper wall of the gas-liquid separator 10. Thus, for example, the refrigerant that has flowed into the gas-liquid separator 10 from the second liquid pipe 11 during the heating operation, if a gas component is mixed therein, is converted into a gas phase and a liquid phase. The liquid refrigerant separated vertically is supplied to the first liquid pipe 9. Also, during the cooling operation, similarly, the refrigerant from the first liquid pipe 9 is vertically separated into a gas phase and a liquid phase in the gas-liquid separator 10, and the separated liquid refrigerant is supplied to the second liquid pipe. 11 is supplied.

On the other hand, the gas refrigerant separated upward in the gas-liquid separator 10 is returned to the compressor 1 through the bypass pipe 14 if the above-mentioned bypass valve 15 is opened.
The gas refrigerant is compressed and discharged by the compressor 1 together with the gas refrigerant returned through the accumulator 3 (hereinafter, the gas refrigerant in the gas-liquid separator 10 is returned to the compressor 1 through the bypass pipe 14). Driving is called gas injection.)

By performing gas injection as described above, a heating operation or a cooling operation with an increased refrigerating capacity can be performed as described above. However, in the operation using such gas injection, when the amount of the liquid refrigerant in the gas-liquid separator 10 increases and the liquid level approaches the opening end of the bypass pipe 14, the bypass pipe 14 The liquid refrigerant easily mixes into a gas refrigerant (hereinafter, referred to as an injection gas) returned to the compressor 1 through the compressor.

Therefore, in the present embodiment, the entire air conditioner is monitored, and while the compression capacity of the compressor 1, that is, the rotation speed thereof, is controlled in accordance with the load, the frequency control is performed.
In addition to an air-conditioning control device (not shown) for controlling the heating operation or the cooling operation, the open / close state of the bypass valve 15 composed of a motor-operated valve is controlled so as to prevent the liquid refrigerant from being mixed into the injection gas. A gas injection control device (gas injection control means) 16 is further provided.

The gas-liquid separator 10 has a plurality of, in the case shown, three float switches (liquid level detecting means) 17L.
17M and 17U are attached so that their positions in the height direction are different from each other (hereinafter, from the lower side, the first float switch 17L, the second float switch 17M, the third float switch 17M)
Float switch 17U). Each of these switches 1
When the liquid level of the liquid refrigerant separated in the gas-liquid separator 10 exceeds the set height corresponding to each mounting position, an ON signal is output from each of the 7L, 17M, and 17U. You.

The opening / closing control of the bypass valve 15 by the gas injection control device 16 is performed based on the ON / OFF signals from the float switches 17L, 17M, and 17U described above. Hereinafter, the control procedure will be described with reference to FIG.

When the cooling or heating operation is started by the air-conditioning control device, the control by the gas injection control device 16 starts at the same time. First, in step S1, an operation mode in which the air-conditioning control device also uses gas injection. That is, it is determined whether or not the operation mode of the gas injection ON is selected.

If the gas injection ON mode is selected, then, at step S2, the liquid level of the liquid refrigerant in the gas-liquid separator 10 is determined by the ON / OFF signal from the first float switch 17L. It is determined whether or not H is equal to or less than a reference height H _L described later. H is H _L
If not, in step S3, the bypass valve 15
Is fully opened, and then the process returns to step S1. Accordingly, if there is no change in the determination results in S1 and S2, the processing of steps S1 to S3 is repeated, and as a result, gas injection is performed with the bypass valve 15 fully opened.

On the other hand, in step S2, the liquid level H
Is determined to be greater than the reference height H _L by outputting the ON signal from the first float switch 17L, then, in step S4, the ON / OFF signal from the second float switch 17M is output. By
Liquid level height H of whether below mid-height H _M to be described later is determined. If H is equal to or less than H _M , in step S5,
A process for setting the bypass valve 15 to the first intermediate opening degree smaller than the fully opened state is performed. Thereafter, by returning to step S1, the bypass valve 15
Is set to the first intermediate opening, gas injection is performed.

Further, in step S4, if it is judged that the liquid level height H is also beyond mid-height H _M further in step S6, ON / OFF of the third float switch 17U the signal, liquid level height H is whether less than the upper limit height H _U to be described later is determined. H
Is less than or equal to H _U , in step S7, a process of setting the bypass valve 15 to a second intermediate opening smaller than the first intermediate opening is performed. Thereafter, by returning to step S1, the bypass valve 15
Is set to the second intermediate opening, gas injection is performed.

On the other hand, in step S6, when it is discriminated that the liquid level height H is greater than the upper limit height H _U, the process of fully closed the bypass valve 15 in step S8 is performed, therefore Even if the operation mode of gas injection ON is selected by the air conditioning control device, at this time, control for forcibly stopping gas injection is performed by the gas injection control device 16.

If the operation mode of the gas injection ON is not selected in the air conditioning control device, or
When the operation mode is switched from the gas injection ON to the OFF, the process proceeds from step S1 to step S8, and a process of completely closing the bypass valve 15 is performed.

With the above-described control, the gas injection is continued while the open / close state of the bypass valve 15 is switched at any time according to the liquid level H in the gas-liquid separator 10 as shown in the following. Stopped. H ≦ H _L → bypass valve fully opened (gas injection _{ON) H L <H ≦ H} M → first intermediate opening (gas injection _{ON) H M <H ≦ H} U → second intermediate opening (gas injection ON) H > H _U → Bypass valve fully closed (gas injection OFF)

Here, the reference height H _L will be described first.

Gas injection is performed by the bypass pipe 1
4 is generated by the suction force from the compressor 1 acting through the compressor 4. When the bypass valve 15 is fully opened, for example, when the compressor 1 is operated at a high operation frequency, a large value corresponding to the frequency is used. The suction force acts from the compressor 1 into the gas-liquid separator 10. At this time, the gas-liquid separator 10
Even if the liquid level in the inside and the open end of the bypass pipe 14 are separated, when the liquid level height H approaches the open end,
The liquid refrigerant is also easily sucked out according to the above-mentioned suction force, and the liquid refrigerant is mixed into the injection gas.

Therefore, in the gas injection when the compressor 1 is operated at the maximum frequency and the bypass valve 15 is fully opened, the maximum liquid level height at which the liquid refrigerant is not mixed into the injection gas is obtained in advance. This is set as the reference height _HL . The mounting position of the first float switch 17L is determined according to the height.

Further, in the present embodiment, the bypass valve 15
Is constituted by a motor-operated valve that can be set to an intermediate opening between the fully closed state and the fully opened state. In this case, the opening degree of the bypass valve 15 is reduced, and the flow path through the bypass pipe 14 is reduced. Thereby, the suction force from the compressor 1 acting in the gas-liquid separator 10 is reduced. Accordingly, even if the liquid level height H exceeds the above-described reference height _HL , gas injection can be performed without causing liquid refrigerant to be mixed into the injection gas.

From such a viewpoint, the above-mentioned intermediate height H _M and upper limit height H _U , and the first intermediate opening and the second intermediate opening are set. That is, when the gas injection is performed with the opening of the bypass valve 15 set to the first intermediate opening that is appropriately smaller than the fully opened state, the maximum liquid level at which the liquid refrigerant is not mixed into the injection gas. the height is set as an intermediate height H _M, further, when performing a gas injection by setting the bypass valve 15 to a smaller second intermediate opening than the first intermediate opening, the liquid refrigerant to the injection gas maximum liquid level is set as the upper limit height H _U that does not cause contamination.

[0043] Then, only when the liquid level height H exceeds the upper height H _U, the bypass valve 15 is fully closed to stop the gas injection.

Therefore, in the present embodiment, by controlling the opening / closing state of the bypass valve 15 in accordance with the liquid level H as described above, the injection can be performed without providing a gas-liquid separator having an excessive capacity. It is possible to perform gas injection without mixing liquid refrigerant into gas, and therefore, liquid compression in the compressor is avoided, and reliability can be maintained and improved.

Further, even if the liquid level H exceeds the reference height H _U , the opening of the bypass valve 15 is set to a first intermediate opening or a second intermediate opening smaller than the fully opened state, Since gas injection can be continued without causing liquid refrigerant to be mixed into the injection gas, air-conditioning operation with improved capacity through more effective use of gas injection can be performed over a wider range. ing.

Although the specific embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and can be implemented with various modifications within the scope of the present invention.

For example, in the above embodiment, control is performed such that gas injection is performed by setting the bypass valve 15 to a predetermined first intermediate opening or a second intermediate opening between the fully open state and the fully closed state. An example was given, but for example, the reference height H
_L below the float switch for detecting the float switch for detecting respectively the upper and lower limits of the target height region provided, the bypass valve when the liquid level height H is greater than the reference height H _L 15 is fully closed while the reference height H _L
It is also possible to configure the gas injection control device 16 so that the opening of the bypass valve 15 is gradually reduced between the target height region and the opening degree is gradually increased when the opening is lower than the target height region. is there.

According to such a control configuration, a large capacity fluctuation is suppressed even during gas injection, and a stable air-conditioning operation can be performed. In other words, as the opening degree of the bypass valve 15 increases, the injection gas flow rate increases. On the other hand, if the gas component mixed in the liquid refrigerant flowing into the gas-liquid separator 10 is small, the gas-liquid separator 10
The amount of gas refrigerant in the inside decreases, and the amount of liquid refrigerant increases accordingly.

Therefore, when the opening of the bypass valve 15 is gradually increased when the liquid level H is lower than the target height range, the liquid level in the gas-liquid separator 10 increases, and conversely, the target level increases. When the opening degree of the bypass valve 15 is gradually reduced when exceeding the height range, the liquid level becomes lower.

Therefore, by such control, in the gas-liquid separator 10, a control state is established in which the liquid level of the liquid refrigerant is maintained in the target height region. Since the opening of the bypass valve 15 at this time is also maintained at an opening corresponding to the liquid level, the flow rate of the injection gas returned to the compressor 1 is also substantially constant. This suppresses a large change in the refrigerating capacity that increases in accordance with the injection gas flow rate, and thus enables a stable air-conditioning operation to be continued even during gas injection.

It is also possible to configure the target height area as described above at a plurality of locations. In this case, when controlling the opening of the bypass valve 15 so as to maintain the liquid level of the liquid refrigerant at a lower level, the injection gas flow rate increases, and the increase in the refrigerating capacity increases, and the liquid level height increases. Is controlled at a higher level, the injection gas flow rate becomes smaller and the increase in the refrigerating capacity becomes smaller. Therefore, it is possible to control the amount of increase in the refrigeration capacity due to gas injection.

In such a control, particularly when the flow rate of the injection gas is increased, for example, the first liquid pipe 9 and the second liquid pipe 13 shown in FIG. First motor-operated valve 12 and second motor-operated valve 13
By linking with each of the opening degree controls, a more stable control state can be obtained.

That is, for example, during the heating operation, the second motorized valve 13
Is fully opened, and the first motor-operated valve 12 is connected to the outdoor heat exchanger 8.
Is controlled so as to keep the degree of superheat of the refrigerant after passing through. At this time, the supercooled high-temperature and high-pressure liquid refrigerant that is condensed in the indoor heat exchanger and flows from the second liquid pipe 11 to the first liquid pipe 9 through the gas-liquid separator 12 passes through the first motor-operated valve 12. Is converted into a low-temperature and low-pressure liquid refrigerant due to the throttle action.

On the other hand, first, a certain degree of throttling action is given by the second motor-operated valve 13 to reduce the supercooled high-temperature and high-pressure liquid refrigerant to an intermediate pressure.
When the opening control is performed to maintain the degree of superheat constant, a throttling action on the liquid refrigerant is given to some extent before flowing into the gas-liquid separator 10, so that the vapor in the liquid refrigerant depends on the throttling action at this time. Is generated, whereby the gas-liquid separator 10
It is possible to increase the amount of the gas component separated in the inside.

Therefore, by interlocking with the opening control of the first and second electric valves 12 and 13 as described above, it is possible to stably maintain the control state in which the injection gas flow rate is increased.

Further, in the air conditioner having a bypass valve which can be set to an intermediate opening degree according to the second aspect, in addition to the above-mentioned respective control structures, for example, the liquid level H is set to the above-mentioned reference level H _L The opening degree of the bypass valve 15 in the following cases may be set to a fully open state during the heating operation, and may be set to an intermediate opening degree during the cooling operation. In other words, when switching between operation using gas injection and operation not using gas injection, the refrigeration capacity may fluctuate greatly and air conditioning comfort may be impaired. At the time of the cooling operation in which the gas injection is fully opened but the capacity does not need to be increased so much, the above-mentioned decrease in the air conditioning comfort can be suppressed by setting the bypass valve to the intermediate opening degree.

On the other hand, in the above embodiment, the gas-liquid separator 10
3 has been given an example in which to attach a float switch 17L · 17M · 17U are not to be limited to the number, for example, in the scope of the claims 1, corresponding to the reference height H _U described above 1st float switch 17L
It is also possible to provide a bypass valve composed of an electromagnetic valve to switch between a fully open state and a fully closed state based on the ON / OFF signal. Also,
Instead of the float switch, any detecting means that outputs a signal corresponding to a change in the liquid level in the gas-liquid separator 10 can be employed.

In the above-described embodiment, the separate type air conditioner in which one indoor unit is connected to the outdoor unit is described as an example. However, a multi-type air conditioner configured by connecting a plurality of indoor units to the outdoor unit is described. The present invention can also be applied to an air conditioner, and in the above, an air conditioner including the compressor 1 having a variable compression capacity by an inverter has been described as an example. The present invention can also be applied to an air conditioner provided with a compressor having a constant compression capacity. However, in an air conditioner equipped with a compressor whose compression capacity is variable by inverter control, a large amount of refrigerant is charged into the refrigerant circulation circuit in anticipation of the required amount of refrigerant circulation at the maximum load. By applying the present invention, a gas-liquid separator having a smaller capacity than the amount of refrigerant can be employed, so that more remarkable effects can be obtained in terms of downsizing and cost reduction of the apparatus.

[0059]

As described above, in the air conditioner according to the first aspect of the present invention, the liquid level in the gas-liquid separator detected by the liquid level detecting means exceeds the reference level. At this time, since the control for operating the bypass valve in the valve closing direction is performed, it is possible to maintain the operation state in which the liquid refrigerant is prevented from being mixed into the injection gas, and thereby, the gas-liquid separation having an excessive capacity is performed. Even without providing a compressor, the occurrence of liquid compression in the compressor is suppressed, and the reliability of the compressor is ensured.

According to the air conditioner of the second aspect, the bypass valve can be set to an intermediate opening degree between the fully closed state and the fully opened state,
In an air conditioner equipped with such a bypass valve,
For example, even if the liquid level in the gas-liquid separator exceeds the reference level, the bypass valve is set at an intermediate opening degree until the upper limit is reached, so that the injection gas is not discharged. Gas injection without mixing of the liquid refrigerant into the gas injection can be continued, so that the operation whose capacity is improved by the gas injection can be continued over a wider range.

In an air conditioner having a bypass valve that can be set to an intermediate opening degree, the liquid level height is set between the reference height and a target height region lower than the reference height. In the meantime, while reducing the opening of the bypass valve,
It is also possible to perform control to increase the opening of the bypass valve when it is lower than the target height region. In this case, a control state in which the liquid level is maintained in the target height range is obtained, and in response to this, the opening degree of the bypass valve and the injection gas flow rate are also maintained substantially constant. Since the fluctuation of the air conditioning capacity due to the change of the injection gas flow rate is suppressed, the comfort of the air conditioning is maintained.

Further, when the compressor is a compressor whose compression capacity is variable by inverter control as in the air conditioner of claim 5, the capacity of the compressor is smaller than the amount of refrigerant charged in the refrigerant circuit. Since a liquid separator can be employed, more remarkable effects can be obtained in terms of downsizing of the apparatus and cost reduction.

[Brief description of the drawings]

FIG. 1 is a refrigerant circuit diagram additionally showing a control block diagram of a configuration inside an outdoor unit of an air conditioner according to an embodiment of the present invention.

FIG. 2 is a flowchart showing a gas injection control procedure in the air conditioner.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Compressor 8 Outdoor heat exchanger 9 1st liquid pipe 10 Gas-liquid separator 11 2nd liquid pipe 14 Bypass piping 15 Bypass valve 16 Gas injection control device (gas injection control means) 17L 1st float switch (liquid level detection means) 17M 2nd float switch (liquid level detecting means) 17U 3rd float switch (liquid level detecting means) _HL reference height H _M intermediate height H _U upper limit height

Claims (5)

[Claims] 1. A liquid pipe (9) between an outdoor heat exchanger (8) and an indoor heat exchanger connected to a compressor (1) so as to circulate a refrigerant.
A gas-liquid separator (10) is interposed in (11), and between the gas-liquid separator (10) and the suction side of the compressor (1), an upper side inside the gas-liquid separator (10) is provided. A gas injection bypass pipe (14) for returning gas refrigerant separated from the liquid refrigerant to the compressor (1), and a bypass valve (15) for opening and closing a flow path through the bypass pipe (14) are provided. An air conditioner, a liquid level detecting means (17L) (17) for detecting a liquid level of a liquid refrigerant in a gas-liquid separator (10).
M) (17U) and the liquid level detection means (17L) (17
M) Gas injection control means (16) for operating the bypass valve (15) in the valve closing direction when the liquid level detected at (17U) exceeds the reference level. Air conditioner. 2. The air conditioner according to claim 1, wherein the bypass valve (15) can be set to an intermediate opening between a fully closed state and a fully opened state. 3. A liquid level detecting means (17L) (17M) (1
7U), the bypass valve (15) is fully opened when the liquid level detected below the reference level is lower than the reference level.
Is operated in the valve closing direction to set the intermediate opening, and when the gas exceeds the upper limit height, the bypass valve (15) is fully closed by the gas injection control means (16). The air conditioner according to claim 2, wherein 4. A liquid level detecting means (17L) (17M) (1
7U), the bypass valve (15) is fully closed when the liquid level detected above the reference height exceeds the reference height, while the bypass valve (15) is between the reference height and a target height region lower than the reference height. The gas injection control means (16) performs control to decrease the opening of the bypass valve (15) and increase the opening of the bypass valve (15) when the opening is lower than the target height region. The air conditioner according to claim 2. 5. The compressor according to claim 1, wherein the compressor is a compressor having a variable compression capacity controlled by an inverter.
5. The air conditioner according to any one of items 1 to 4.