JPH11118263A - Air conditioner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the reduction of air-conditioning comfort by suppressing the fluctuation of ability when turning on and off a gas injection in air- conditioner where bypass piping for returning a gas refrigerant to a compressor from a vapor-liquid separator provided at a liquid pipe between outdoor and indoor heat exchangers and performing gas injection. SOLUTION: When a switching valve 14 provided at bypass piping 13 for gas injection is switched, the compression capability of a compressor 1 is changed depending on the increase or decrease in freezing capability according to the presence and absence of the gas injection due to the switching, thus suppressing the change of the entire freezing capability also on switching, maintaining an operation state corresponding to the change in a load, preventing the capability from being excessive or insufficient, and hence suppressing the reduction in air-conditioning comfort.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas for returning a gas refrigerant to a compressor from a gas-liquid separator interposed in a liquid pipe interconnecting an outdoor heat exchanger and an indoor heat exchanger. The present invention relates to an air conditioner provided with a bypass pipe for injection.

[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,
Heat is absorbed from outside air in the outdoor heat exchanger functioning as an evaporator, and indoor heating is performed by heat radiation in the indoor heat exchanger functioning as a condenser.

[0003] When the outside air temperature is low during the heating operation, it is difficult to obtain a sufficient heating capacity. In this case, the mixing ratio of the gas refrigerant into the liquid refrigerant that is condensed in the indoor heat exchanger and flows to the outdoor heat exchanger increases. Even if this gas refrigerant is supplied to the outdoor heat exchanger, it hardly contributes to the heat absorbing action from the outside air. Therefore, by performing an operation of separating this gas refrigerant and returning it to the compressor, so-called gas injection,
This gas refrigerant is two-stage compressed by the compressor and supplied to the indoor heat exchanger again, whereby the condensation in the indoor heat exchanger is easily caused and the overall heating capacity is improved.

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. There is known a device in which a bypass pipe is provided between the gas-liquid separator and the suction side of the compressor, with an on-off valve provided between the gas-liquid separator and the suction side of the compressor. In this case, as described above, during the heating operation in which the capacity is likely to be insufficient, the operation using the gas injection is also performed by opening the on-off valve, and during the cooling operation, the on-off valve is held in the closed state. Control for operating without gas injection is performed.

[0005] In recent years, air conditioners equipped with a compressor having a variable compression capacity by inverter control have become mainstream, and such an air conditioner is provided with a bypass pipe for gas injection as described above. In the case where the gas injection is provided, for example, it is not necessary to adopt a configuration in which the gas injection is uniformly performed during the heating operation. That is, while the load is small, the load can be accommodated with a margin within the variable compression capacity range, and in this case, the operation without gas injection can maintain the operation state with higher efficiency. . Therefore, when the operating frequency of the compressor reaches a predetermined frequency in response to the increase in the load, the on / off valve of the on-off valve provided in the bypass pipe is switched, whereby the high frequency range exceeding the above-mentioned frequency is performed. Thus, it is conceivable to control the operation so as to use gas injection together.

[0006]

However, as described above, when the operating frequency of the compressor reaches a predetermined frequency, the control that simply performs the open / close switching of the open / close valve provided in the bypass pipe is not performed. In addition, there is a problem that air conditioning comfort is easily impaired.

That is, if the gas injection is switched during the air-conditioning operation while changing the operation frequency in accordance with the change in the load, the refrigeration capacity is suddenly changed accordingly. Therefore, for example, when the operation is switched from the operation without gas injection to the operation with gas injection, the capacity tends to be excessive, and conversely, when the operation is switched from the operation with gas injection to the operation without gas injection, the capacity tends to be insufficient. As a result, the thermo-OFF after the indoor air-conditioning temperature exceeds the set temperature
The air-conditioning controllability is reduced, for example, the time becomes longer, or the time required to reach the set temperature becomes longer due to insufficient capacity, and the comfort is impaired.

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 air conditioning comfort when switching between gas injections, and to further improve economic efficiency. An object of the present invention is to provide an air conditioner.

[0009]

Therefore, an air conditioner according to a first aspect of the present invention provides a liquid pipe between an outdoor heat exchanger 8 and an indoor heat exchanger which are connected to a compressor 1 having a variable compression capacity so that refrigerant can circulate. 10
12 is provided with a gas-liquid separator 11 and the gas-liquid separator 11
A gas injection bypass pipe 13 for returning the gas refrigerant in the gas-liquid separator 11 to the compressor 1 between the compressor and the suction side of the compressor 1, and an opening and closing switch for opening and closing a flow path through the bypass pipe 13 An air conditioner provided with a valve 14, based on a change in the refrigeration capacity with or without gas injection so that the refrigeration capacity before and after the switching is substantially equal to each other when the open / close valve 14 is switched. A switching control means 15 for correcting the compression capacity of the compressor 1 is provided.

In the air conditioner having the above-described structure, for example, the operation without the gas injection starts with the on-off valve 14.
When the operation is switched to the operation with gas injection by opening the valve, the refrigerating capacity is increased by the switching,
The control for reducing the compression capacity of the compressor 1 is a switching control means 1
5 is performed. When switching from the operation with gas injection to the operation without gas injection by closing the on-off valve 14, control is performed to increase the compression capacity of the compressor 1 by the amount by which the refrigeration capacity is reduced by this switching. Will be

As a result, even when the gas injection is switched, fluctuations in the overall refrigeration capacity are suppressed, and an operation state corresponding to a change in load is maintained, thereby preventing the capacity from becoming excessive or insufficient. A decrease in air conditioning comfort is suppressed.

In the air conditioner of the second aspect, the compression capacity of the compressor 1 to be increased or decreased according to the load corresponds to the vicinity of the intersection of the efficiency curve with gas injection and the efficiency curve without gas injection. When the valve has reached
The switching control means 15 performs switching of the opening and closing of the compressor and correction of the compression capacity of the compressor 1.

With such a configuration, the economic efficiency can be further improved. That is, from the viewpoint of efficiency, when the compressor 1 is operated in a region where the compression capacity is high,
Efficiency is higher in the operation with gas injection than in the operation without gas injection. Conversely, when the compressor 1 is operated in a region where the compression capacity is low, the operation without gas injection is more efficient. Is common. Therefore, by switching between the operation without gas injection and the operation with gas injection near the intersection of the efficiency curve with gas injection and the efficiency curve without gas injection, the compression capacity of the compressor is improved. A more efficient operating state is maintained throughout the variable range, and the economy is improved.

[0014]

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. In this second gas pipe 7,
An outdoor heat exchanger 8 is connected, and a first liquid pipe 10 having a motor-operated expansion valve 9 as a pressure reducing mechanism, a gas-liquid separator 11, and a pressure reducing mechanism are sequentially connected to the outdoor heat exchanger 8. And a second liquid pipe 12 provided with an electric expansion valve 9 ′ as an intermediary.

Although not shown, an indoor unit in which an indoor heat exchanger is installed is connected between the end of the second liquid pipe 12 and the end of the first gas pipe 6 through a communication pipe. Thereby, a refrigerant circulation circuit is formed in which the refrigerant discharged from the compressor 1 is returned to the compressor 1 after passing through the outdoor heat exchanger 8 and the indoor heat exchanger.

That is, when the compressor 1 is operated with the four-way switching valve 5 positioned at the switching position 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 11 interposed in the liquid pipe comprising the first liquid pipe 10 and the second liquid pipe 12 (the position on the high pressure side in both cases of cooling and heating) further includes a bypass pipe 13 connects to an intermediate port of the compressor 1, and an on-off valve 14 composed of an electromagnetic valve is interposed in the bypass pipe 13.

In the closed vessel-shaped gas-liquid separator 11, the first liquid pipe 10 and the second liquid pipe 12 are connected to the gas-liquid separator 1.
1, while the bypass pipe 13 opens at a position near the upper wall of the gas-liquid separator 11. Thus, for example, the refrigerant that has flowed into the gas-liquid separator 11 from the second liquid pipe 12 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 up and down inside the first liquid pipe 10
Supplied to. Also, during the cooling operation, similarly, the refrigerant from the first liquid pipe 10 is vertically separated into a gas phase and a liquid phase in the gas-liquid separator 11, and the separated liquid refrigerant is in the second liquid pipe.
The liquid is supplied to the liquid pipe 12.

On the other hand, the gas refrigerant separated upward in the gas-liquid separator 11 is returned to the compressor 1 through the bypass pipe 13 if the above-mentioned on-off valve 14 is opened, and this gas refrigerant is The gas refrigerant returned from the accumulator 3 is compressed and discharged by the compressor 1 (hereinafter, the on-off valve 14 is opened and the gas in the gas-liquid separator 11 is passed through the bypass pipe 13). Compressor 1
The operation of returning gas to gas is called gas injection.)

The above-described opening / closing control of the on-off valve 14 monitors the entire air conditioner, and performs a heating operation or a cooling operation while performing frequency control for determining the compression capacity of the compressor 1, that is, the rotation speed according to the load. The operation is performed by an air conditioning control device (switching control means) 15 for controlling the operation. Less than,
The control contents will be described.

FIG. 2B shows the relationship between the operating frequency of the compressor 1 by the inverter 1a and the heating capacity or the cooling capacity (hereinafter, these are collectively referred to as refrigeration capacity). (A) shows the operating frequency and coefficient of performance (C
OP). The curves shown by broken lines in the figure are the performance curve and the coefficient of performance curve (hereinafter, referred to as the efficiency curve) when the on-off valve 14 is turned off, that is, when the valve is operated without performing the gas injection (hereinafter, referred to as gas injection OFF). The curves shown by solid lines in the figure are a performance curve and an efficiency curve when the on-off valve 14 is turned on, that is, when the on-off valve 14 is opened and gas injection is used together (hereinafter, referred to as gas injection ON).

The refrigeration capacity increases as the operating frequency increases, and when the gas injection is ON, the refrigeration capacity increases.
A larger refrigeration capacity than at F is obtained.

On the other hand, the efficiency curve is generally an upwardly convex curve having a maximum value at a specific operation frequency. When the gas injection is ON, the operating frequency when the efficiency is maximized is shifted to a higher frequency side than when the gas injection is OFF, and therefore, the efficiency curves when the gas injection is ON and when the gas injection is OFF cross each other. If the operating frequency at this intersection is Fp, this F
Gas injection OFF at frequencies lower than p
The operation at is more efficient than at ON, while
At frequencies above Fp, higher efficiency is obtained with gas injection ON operation.

Therefore, in this embodiment, the operating frequency F corresponding to the above-mentioned intersection is controlled by the air-conditioning controller 15.
gas injection ON / OF
As the switching area of F, the on / off control of the on-off valve 14 is performed. That is, in FIG. 6B, of the combinations of operating frequencies at which the refrigerating capacity in each operation of gas injection ON and OFF is equal to each other, a combination of frequencies substantially centered on the frequency Fp corresponding to the intersection described above. F ₁ and F ₂ are obtained, and these are stored in advance in the air-conditioning control device 15 as a lower limit frequency F ₁ and an upper limit frequency F _{2 at the} time of switching. Assuming that the frequency range of F _{1 to} F ₂ is a switching range Sc, the gas injection ON / OF is performed in this range Sc as shown in FIG.
Even if F is switched, there is almost no difference in efficiency.

The lower limit frequency F ₁ of the switching range Sc described above.
Air conditioning control apparatus 15 of the upper limit frequency F ₂ is stored,
First, while performing the operation with gas injection OFF is less than the lower limit frequencies F ₁ holds the on-off valve 14 in a closed state, in a range exceeding the upper limit frequency F ₂ is a gas injection ON by opening the on-off valve 14 Drive.

In the switching range Sc, for example, the operating frequency that is gradually increased in accordance with the load from the lower side of the switching range Sc sequentially exceeds F ₁ and Fp and becomes higher than F ₁ .
_When the number reaches ₂ , the on-off valve 14 is opened to switch the operation from the gas injection OFF to the ON operation. At the same time, performs control once reduced to F ₁ the operating frequency from F _2. Thereafter, the open state of the on-off valve 14 is maintained, and the frequency is gradually increased to a higher frequency side according to the load.

With this control, the increase in capacity due to switching from gas injection OFF to ON is reduced by the compressor 1
, The overall refrigeration capacity does not fluctuate, and a more efficient operating condition is maintained.

On the other hand, in the state where the gas injection is ON, when the operating frequency gradually decreased from the higher side than the switching range Sc reaches the switching range Sc, the operating frequency further passes through F ₂ and Fp sequentially. when it reaches F _1, to close the on-off valve 14. At the same time, the operating frequency is once increased to F ₂ from F _1, then hold the closed state of the opening and closing valve 14 performs control to gradually decrease to the low frequency side in accordance with the frequency to the load. As a result, similarly to the above, fluctuations in capacity due to switching of the on-off valve 14 are suppressed, and higher operating efficiency is maintained.

As described above, in the present embodiment, when switching the gas injection ON / OFF, the control for changing the compression capacity of the compressor 1 at the same time so that the refrigerating capacity does not fluctuate before and after this switching is performed. Done. Thereby, good air conditioning comfort can be maintained. In addition, the above switching is performed in the vicinity area where the efficiency curves at the time of gas injection ON / OFF cross each other, and the operation state with higher efficiency is respectively set on the low band side and the high band side across this region. As a result, the power consumption is reduced overall and the economy is improved.

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, a separate type air conditioner in which one indoor unit is connected to an outdoor unit has been described as an example, but a multi-type air conditioner configured by connecting a plurality of indoor units to an outdoor unit is described. It is possible to apply the present invention also to the present invention.

In the above description, the gas injection O
To the operating frequency Fp corresponding to the intersection of the efficiency curve at N / OFF, determines the switching range Sc centering on this, the lower limit frequencies F ₁ and an upper frequency limit F ₂ of this range Sc, gas injection ON / Although the configuration is such that the switching of the OFF is performed, for example, in any of the processes of increasing and decreasing the operating frequency, the switching may be performed when the above-described Fp is reached.

However, in this case, as shown by the two-dot chain line in FIG. 2, when the operating frequency reaches Fp in the process of increasing, it is necessary to reduce the operating frequency from Fp to F ₁ ′. When the operating frequency reaches Fp in the process of decreasing, it is necessary to increase from Fp to F ₂ ′. The switching range F ₁ ′ to F ₂ ′ is wider than the switching range Sc in the above-described embodiment, so that the efficiency immediately after switching is lower. Therefore, as in the above-described embodiment, the switching range is substantially centered on Fp. in a lower frequency limit which is set respectively on both sides F ₁ and the upper limit frequency F _2, it is desirable to perform the switching of gas injection oN / OFF.

Further, in the scope of the first aspect of the present invention, the on / off switching of the on-off valve 14 is performed in another specific frequency region other than the vicinity of the frequency Fp corresponding to the intersection of the above-mentioned efficiency curves. Is also possible.

[0037]

As described above, in the air conditioner according to the first aspect of the present invention, the gas injection is turned on.
When switching between / OFF, the compression capacity of the compressor is corrected so as to compensate for the change in the refrigeration capacity accompanying the switching.
As a result, fluctuations in the overall refrigeration capacity are suppressed, and an operating state corresponding to a change in load is maintained, thereby preventing excessive capacity or insufficient capacity, thereby maintaining air conditioning comfort.

In the air conditioner of the second aspect, when the compression capacity of the compressor, which is increased or decreased in accordance with the load, reaches the compression capacity corresponding to the vicinity of the intersection of each efficiency curve at the time of gas injection ON / OFF. Injection ON /
Since the switching of the OFF state is performed, a more efficient operation state is maintained throughout the variable compression capacity range of the compressor, and the economy is improved.

[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 in an air conditioner according to an embodiment of the present invention.

FIG. 2 is a graph showing a relationship between an operating frequency of a compressor, a refrigerating capacity, and a coefficient of performance in the air conditioner.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Compressor 8 Outdoor heat exchanger 10 1st liquid pipe 11 Gas-liquid separator 12 2nd liquid pipe 13 Bypass piping 14 On-off valve 15 Air conditioning control device (switch control means)

Claims (2)

[Claims] A gas-liquid separator is provided in a liquid pipe (10) (12) between an outdoor heat exchanger (8) and an indoor heat exchanger connected to a compressor (1) having a variable compression capacity so as to circulate a refrigerant. (11) is interposed, and the gas refrigerant in the gas-liquid separator (11) is returned to the compressor (1) between the gas-liquid separator (11) and the suction side of the compressor (1). An air conditioner provided with a bypass pipe (13) for gas injection to be made and an on-off valve (14) for opening and closing a flow path through the bypass pipe (13), wherein the on-off switching of the on-off valve (14) is performed. In some cases, a switching control means (15) for correcting the compression capacity of the compressor (1) based on a change in the refrigeration capacity due to the presence or absence of gas injection is provided so that the refrigeration capacity before and after the switching is substantially equal to each other. An air conditioner characterized in that: 2. When the compression capacity of the compressor (1) to be increased or decreased according to the load reaches a compression capacity corresponding to the vicinity of the intersection between the efficiency curve with gas injection and the efficiency curve without gas injection, The air conditioner according to claim 1, wherein the switching control means (15) switches between opening and closing the on-off valve (14) and correcting the compression capacity of the compressor (1).