JP2001304700A - Air conditioner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To contrive the enhancement of COP (energy consumption efficiency), achievement of a reference value which is a target prescribed by New Energy Saving Law to be achieved by the year 2007, and the reduction of yearly power consumption, by reducing the power consumption of an air conditioner more. SOLUTION: In an air conditioner where a compressor 81, whose capacity is variably controlled, a condenser 11, an expansion valve 22, and an evaporator 12 are connected in circular form by pipe, the temperature of gas discharged from the compressor 81 is controlled by the opening of the expansion valve 22, and the opening of the expansion valve 22 is controlled, so that the temperature of discharged gas at compressor 81 operation with its lowest capacity is lower than the temperature of the discharged gas at the compressor 81 which is operated with its rated capacity.

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 controlling a refrigeration cycle, and is particularly suitable for power saving of an air conditioner.

[0002]

2. Description of the Related Art Conventionally, in order to save power in an air conditioner,
It is known to search for the minimum value of the power consumption by slightly adjusting the operating capacity of the compressor and the opening of the expansion valve, and is described in, for example, JP-A-7-110165.

[0003]

In the above prior art, since the minimum value of the power consumption is searched for by constantly changing the operating capacity of the compressor and the opening of the expansion valve, the operating state of the refrigeration cycle becomes unstable. Or a sensor for detecting power consumption is required, which may increase the cost.

[0004] It is an object of the present invention to further reduce the power consumption of an air conditioner, improve the COP (energy consumption efficiency), achieve the new energy saving law 2007 standard value, and reduce the annual power consumption. It is in. Another object of the present invention is not only to reduce power consumption, but also to stabilize a refrigeration cycle and improve comfort.

[0005]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a compressor, a condenser and a compressor whose capacity is variably controlled.
In an air conditioner in which an expansion valve and an evaporator are connected in a ring by piping, the discharge gas temperature of the compressor is controlled by the degree of opening of the expansion valve, and the discharge gas temperature when the compressor is operated at the minimum capacity is: The opening of the expansion valve is controlled so as to be lower than the discharge gas temperature when the compressor is operated at the rated capacity.

In the above, the discharge gas temperature is made proportional to the discharge pressure of the compressor until the discharge pressure reaches a predetermined value, and is controlled so as to be a constant target temperature above the predetermined value. It is desirable that the target temperature when the compressor is operated be lower than the target temperature when the compressor is operated at the rated capacity.

Further, according to the present invention, a compressor, a condenser, an expansion valve, and an evaporator whose capacity is variably controlled is connected in a ring shape by piping, and the degree of superheating of the refrigerant at the suction or discharge of the compressor is determined by the opening degree of the expansion valve. In the air conditioner controlled by the above, the degree of superheat of the refrigerant when the compressor is operated at the minimum capacity is such that the opening degree of the expansion valve is lower than the degree of superheat of the refrigerant when the compressor is operated at the rated capacity. Is controlled.

In the above, the degree of superheat of the refrigerant is set to a fixed target value when the compressor is operated at a rated capacity or more, and is set to be lower than the fixed target value when the compressor is less than the rated capacity. Is desirable.

Further, the present invention includes an outdoor unit having a compressor, an outdoor heat exchanger, and an outdoor fan having a variable operating frequency, and an indoor unit having an indoor heat exchanger and an indoor expansion valve. In an air conditioner in which the degree of superheat of refrigerant at the suction or discharge of the air is controlled by the degree of opening of an expansion valve, the outdoor unit has a throttle mechanism of a fixed throttle, and the operating frequency is reduced when the compressor is lower than a predetermined operating frequency. , The degree of superheat of the refrigerant is reduced.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIGS. FIG. 1 shows a refrigeration cycle according to one embodiment. An outdoor unit 1 has a compressor 81 whose operating frequency is variable and whose capacity is variably controlled.
Discharge temperature sensor 13 for detecting the refrigerant temperature at the compressor outlet
1. Discharge pressure sensor 1 for detecting refrigerant pressure at compressor outlet
41, four-way valve 61, outdoor heat exchanger 11, outdoor fan 3
1, throttle mechanism 21, liquid tank 101, gas blocking valve 41,
It has a liquid blocking valve 51. During cooling, the four-way valve 61 communicates with the discharge side of the compressor 81 and the outdoor heat exchanger 11, and communicates with the low-pressure side of the compressor 81 and the gas blocking valve 41.
During heating, the discharge side of the compressor 81 communicates with the gas blocking valve 41, and the low-pressure side of the compressor 81 communicates with the outdoor heat exchanger 11.

One end of the outdoor heat exchanger 11 is connected to the four-way valve 61 as described above, and the other end of the outdoor heat exchanger 11 is connected to the liquid tank 101 via the throttle mechanism 21. Further, the liquid tank 101 is connected to the liquid blocking valve 51. The other end of the liquid blocking valve 51 is connected to a liquid pipe 111, and the other end of the gas blocking valve 41 is connected to a gas pipe 121. The other ends of the liquid pipe 111 and the gas pipe 121 are connected to the indoor unit 2. The indoor unit 2 includes an indoor heat exchanger 12,
It has the indoor expansion valve 22 and the indoor fan 32 that can adjust the flow rate, and although one is shown in the figure, a plurality of them are often connected. One end of the indoor heat exchanger 12 is connected to the gas pipe 121, and the other end is connected to the indoor expansion valve 22.
The other end of 2 is connected to liquid pipe 111.

Looking at the annual air conditioner load condition of the air conditioner, the frequency of occurrence of a load corresponding to the rated capacity of the air conditioner is extremely low, and the frequency of occurrence of the load corresponding to the minimum capacity or less of the air conditioner is high. . Therefore, to reduce the power consumption of the air conditioner, it is effective to improve the efficiency at the time of the minimum capacity operation. Since the minimum capacity operation is an operation that requires less air conditioning function, it is necessary to lower the discharge pressure in heating in order to reduce power consumption.

Next, the operation will be described. The dashed arrow in FIG. 1 indicates the cooling operation and the solid arrow indicates the refrigerant flow in the heating operation. First,
The case where the indoor unit 2 performs the cooling operation will be described.
The four-way valve 61 is in the cooling mode. The high-pressure gas refrigerant discharged from the compressor 81 flows to the outdoor heat exchanger 11 through the four-way valve 61. The high-pressure gas refrigerant that has entered the outdoor heat exchanger 11 undergoes heat exchange with the outdoor air blown by the outdoor fan 31 to be condensed into a liquid refrigerant. The refrigerant is first depressurized by the throttle mechanism 21 that is a fixed throttle, and then enters the liquid tank 101. .
The liquid refrigerant in the liquid tank 101 is supplied to the liquid blocking valve 51 and the liquid pipe 111.
Through the indoor unit 2, is subjected to secondary pressure reduction by the indoor expansion valve 22, enters the indoor heat exchanger 12, and
The heat is exchanged with the room air blown by 2 to evaporate to become a gas refrigerant. At this time, the room is cooled. The gas refrigerant that has exited the indoor heat exchanger 12 enters the outdoor unit 1 through the gas pipe 121, and is drawn into the compressor 81 through the gas blocking valve 41 and the four-way valve 61.

Next, a case where the indoor unit 2 is operated for heating will be described. The four-way valve 61 is in the heating mode. The high-pressure gas refrigerant discharged from the compressor 81 is supplied to the four-way valve 6.
1. The gas flows through the gas check valve 41 to the gas pipe 121. The high-pressure gas refrigerant that has passed through the gas pipe 121 enters the indoor heat exchanger 12 of the indoor unit 2 and exchanges heat with the indoor air blown by the indoor fan 32 to condense into a liquid refrigerant. At this time, the room is heated. The liquid refrigerant is the indoor expansion valve 2
After the primary pressure reduction in step 2, the liquid enters the liquid tank 101 through the liquid pipe 111 and the liquid blocking valve 51. The liquid refrigerant in the liquid tank 111 is secondarily decompressed by the throttle mechanism 21 and enters the outdoor heat exchanger 11, where it exchanges heat with the outdoor air blown by the outdoor fan 31 and evaporates to become a low-pressure gaseous refrigerant. 61
Through the compressor 81.

Next, a method of controlling the indoor expansion valve 22 will be described with reference to FIG. Assuming that the compressor frequency at which the rated capacity of the air conditioner is obtained is the rated frequency, as shown in the table of FIG. 2, when the compressor frequency is equal to or higher than the rated frequency, the target discharge gas temperature is set to the target temperature 1, and the compressor frequency is set to When the frequency is lower than the rated frequency, the target discharge gas temperature is set to be lower than the target temperature 1 as the compressor frequency decreases. The graph of FIG. 2 shows the relationship between the target temperature 1 where the compressor frequency is equal to or higher than the rated frequency and the target temperature 2 when the compressor frequency is the lowest frequency. The target temperature is proportional to the discharge pressure in both cases, and when the discharge pressure exceeds a certain pressure, the target temperature becomes constant.
The target temperature is set to a temperature higher than the saturation temperature of the discharge pressure. By setting the target discharge gas temperature at the time when the operating frequency of the compressor is the lowest frequency lower than the target discharge gas temperature at the rated frequency, the opening degree of the indoor expansion valve 22 is increased and the discharge pressure during heating is reduced. Can be.

The discharge pressure is detected by a discharge pressure sensor 141, the discharge gas temperature is detected by a discharge temperature sensor 131, and the opening degree of the expansion valve is such that the discharge gas temperature or superheat at the time of the minimum capacity operation is lower than at the time of the rated capacity operation. Control so that This makes it difficult for the liquid refrigerant to accumulate in the condenser, increases the effective heat transfer area, and lowers the discharge pressure.

Next, another embodiment of the control method of the indoor expansion valve 22 will be described with reference to FIG. As shown in the table of FIG. 3, when the compressor frequency is equal to or higher than the rated frequency, the target discharge gas superheat degree is set to S.
Hoo, when the compressor frequency is lower than the rated frequency, the target discharge gas superheat degree is set to S as the compressor frequency decreases.
Set to be lower than Hoo. The relationship between the compressor frequency and the target discharge gas superheat degree is shown in the graph of FIG. The target discharge gas superheat degree is S when the compressor frequency is higher than the rated frequency.
Ho is constant, and when the compressor frequency is less than the rated frequency, the target discharge gas superheat degree is reduced in proportion to the frequency. As described above, when the compressor frequency is lower than the rated frequency, by reducing the target discharge gas superheat degree, the opening degree of the indoor expansion valve 22 when the compressor frequency is the lowest frequency increases, and the discharge pressure during heating increases. Can be lowered. Also,
The superheat degree of the discharge gas is calculated based on the detection values of the discharge pressure sensor 141 and the discharge temperature sensor 131.

In the refrigeration cycle shown in FIG. 1, the order of the expansion valve 22 and the throttle mechanism 21 is switched between during cooling and during heating, and the discharge pressure is reduced during heating by lowering the degree of discharge superheat, and the suction pressure is reduced during cooling. Goes up. Therefore, the power input decreases during heating, and the capacity increases during cooling.

Next, another embodiment of the present invention is shown in FIG.
The refrigeration cycle of FIG. 4 is different from the refrigeration cycle of FIG. 1 in that the liquid tank 101 and the throttle mechanism 21 are removed, and an accumulator 91 is provided between the suction side of the compressor 81 and the four-way valve 61. The operation is the same as in FIG.

In the example of FIG. 4, the discharge gas temperature or the degree of superheat of the discharge gas is controlled by controlling the indoor expansion valve 22 as shown in FIG. 2 or 3, so that the discharge pressure is reduced when the compressor frequency in the heating operation is the lowest frequency. Can be lowered. FIG.
Since the expansion mechanism is only the indoor expansion valve 22, the opening pressure of the indoor expansion valve 22 is opened when the compressor frequency is the lowest frequency even in the cooling operation by the same control as the heating, so that the discharge pressure can be reduced. it can. In addition, since power can be saved without detecting an electric input, a sensor for detecting an electric input is not required, and cost can be reduced.

[0021]

According to the present invention, the indoor expansion valve 22 is set by setting the target discharge gas temperature or superheat degree when the compressor frequency is the lowest frequency lower than the target discharge gas temperature or superheat degree when the compressor frequency is the rated frequency. The opening of
The discharge pressure can be reduced. Thereby, the work of the compressor is reduced, the electric input can be reduced, and the effect of power saving of the air conditioner can be obtained.

[Brief description of the drawings]

FIG. 1 is a cycle configuration diagram showing one embodiment of the present invention.

FIG. 2 is an explanatory view showing a method of controlling an indoor expansion valve according to the present invention.

FIG. 3 is an explanatory diagram showing a method for controlling an indoor expansion valve according to another embodiment of the present invention.

FIG. 4 is a cycle configuration diagram showing another embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Outdoor unit, 2 ... Indoor unit, 11 ... Outdoor heat exchanger, 12 ... Indoor heat exchanger, 21 ... Throttle mechanism, 2
2 ... indoor expansion valve, 31 ... outdoor fan, 32 ... indoor fan, 41, 51 ... blocking valve, 61 ... four-way valve, 81 ...
Compressor, 91: accumulator, 111: liquid pipe,
121 ... gas pipe 131 ... discharge temperature sensor, 141 ...
Discharge pressure sensor

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Hiroaki Tsuboe 390 Muramatsu, Shimizu-shi, Shizuoka Pref.Hitachi Air Conditioning Systems Co., Ltd. F term in Shimizu Production Headquarters (reference) 3L060 CC04 CC16 CC19 DD08 EE09

Claims (5)

[Claims] 1. An air conditioner in which a compressor, a condenser, an expansion valve, and an evaporator whose capacity is variably controlled is connected in a ring shape with a pipe, the discharge gas temperature of the compressor depends on the degree of opening of the expansion valve. The opening degree of the expansion valve is controlled such that the discharge gas temperature when the compressor is operated at the minimum capacity is lower than the discharge gas temperature when the compressor is operated at the rated capacity. An air conditioner characterized by that: 2. The method according to claim 1, wherein the discharge gas temperature is controlled so as to be proportional until the discharge pressure of the compressor reaches a predetermined value, and to be a constant target temperature above the predetermined value. The air conditioner is characterized in that the target temperature when the compressor is operated at the minimum capacity is lower than the target temperature when the compressor is operated at the rated capacity. 3. A compressor, a condenser, an expansion valve, and an evaporator, whose capacity is variably controlled, are connected in a ring shape by piping, and the degree of superheat of refrigerant at the suction or discharge of the compressor is controlled by the opening degree of the expansion valve. In the air conditioner, the refrigerant superheat degree when the compressor is operated at the minimum capacity is lower than the refrigerant superheat degree when the compressor is operated at the rated capacity. An air conditioner characterized in that the opening is controlled. 4. The refrigerant superheat degree according to claim 3, wherein the refrigerant superheat degree is a constant target value when the compressor is operated at a rated capacity or more, and the refrigerant superheat degree is a constant target value when the compressor is less than the rated capacity. An air conditioner characterized in that it is made lower. 5. An outdoor unit having a compressor, an outdoor heat exchanger, and an outdoor fan having a variable operating frequency, and an indoor unit having an indoor heat exchanger and an indoor expansion valve. In the air conditioner in which the degree of superheat of the refrigerant discharged is controlled by the degree of opening of the expansion valve, the outdoor unit includes a throttle mechanism of a fixed throttle, and the operating frequency decreases when the compressor is lower than a predetermined operating frequency. , The degree of superheat of the refrigerant is reduced.