JP2003156244A - Control method for air-conditioner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a control method for an air-conditioner allowing the operation for an always optimum refrigerating cycle, without additionally using sensors. SOLUTION: An exterior heat exchange temperature sensor 9, an interior heat exchange temperature sensor 9 and a discharge temperature sensor 8 are provided for detecting an evaporation temperature Te and a condensation temperature Tc. A degree of superheat SH corresponding thereto for the optimum refrigerating cycle is found from a Mollier chart, a discharge temperature Trd in a theoretical cycle is found from an evaporation temperature Te, a condensation temperature Tc and the degree of superheat SH, and the discharge temperature Trd in the theoretical cycle is corrected with compression efficiency determined by the unit performance of a compressor to calculate a target discharge temperature Tmd. The opening of an electronic expansion valve is controlled so that an actual discharge temperature Td approximates to the target discharge temperature Tmd. Thus, the degree of superheat is kept for the always optimum refrigerating cycle without additionally using conventional sensors for detecting an interior heat exchange inlet pipe temperature and a compressor suction pipe temperature.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control method for an air conditioner, and more particularly to a control method that enables operation while maintaining an optimum refrigeration cycle.

[0002]

2. Description of the Related Art Conventionally, a compressor, a four-way valve, an outdoor heat exchanger, an electric expansion valve, and an indoor heat exchanger are sequentially piped to form a refrigeration cycle. By switching the four-way valve, cooling is performed. During operation, the high-pressure refrigerant compressed by the compressor, the outdoor heat exchanger, the electric expansion valve, the indoor heat exchanger in this order,
During heating operation, the air conditioner that flows through the indoor heat exchanger, the electric expansion valve, and the outdoor heat exchanger in this order and operates while maintaining an optimal refrigeration cycle detects the evaporation temperature and compression suction pipe temperature of the refrigeration cycle. Then, the degree of superheat during operation is calculated, and the opening degree of the expansion valve is controlled so that the degree of superheat becomes the optimum degree of superheat. However, in this control method, it is necessary to detect an accurate superheat degree, and in order to detect an accurate superheat degree, in addition to the indoor heat exchange intermediate temperature sensor normally used for protection control and the outdoor heat exchange temperature sensor, A sensor to detect the indoor heat exchange inlet pipe temperature and the compressor suction pipe temperature is required,
There was a problem that it became a factor of cost increase. Also,
In order to solve the above problems, the reference temperature of the discharge pipe temperature of the compressor corresponding to each operation mode is obtained in advance, and the opening degree of the electronic expansion valve is adjusted so that the discharge pipe temperature becomes the reference temperature during operation. Methods of controlling to adjust are also used. However, in the case of this method, it is not possible to cope with changes in room temperature conditions, and there is a problem in that it is not possible to always maintain and operate an optimum refrigeration cycle, although it is possible under constant room temperature conditions.

[0003]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems and provides a method for controlling an air conditioner that enables operation that always maintains an optimum refrigeration cycle without adding a sensor. Is intended.

[0004]

In order to solve the above problems, the present invention constitutes a refrigeration cycle by sequentially connecting a compressor, a four-way valve, an outdoor heat exchanger, an electric expansion valve, and an indoor heat exchanger. By switching the four-way valve, the high-pressure refrigerant compressed by the compressor during the cooling operation is the outdoor heat exchanger, the electric expansion valve, the indoor heat exchanger in this order, and the indoor heat exchanger during the heating operation. , An electric expansion valve, an outdoor heat exchanger, and an air conditioner in which the degree of opening of the electronic expansion valve is adjusted so that an optimal refrigeration cycle is achieved, and an outdoor unit that detects an intermediate temperature of the outdoor heat exchanger. A heat exchange temperature sensor, an indoor heat exchange temperature sensor for detecting an intermediate temperature of the indoor heat exchanger, and a discharge temperature sensor for detecting a discharge temperature of the compressor are provided, and the compressor is operated at a predetermined rotation speed N. And then start cooling or heating operation Evaporation temperature Te and the condensation temperature Tc for detecting the outdoor heat exchanger temperature sensor and an indoor heat exchanger temperature sensor
And the superheat degree S set to be optimum on the Mollier diagram for the detected evaporation temperature Te and condensation temperature Tc.
The discharge temperature Trd during the theoretical cycle is calculated by multiplying H and the constant coefficients a, b, and c and adding them, and the discharge temperature Trd during the theoretical cycle is set as the target discharge temperature Tmd. The control method of the air conditioner is such that the opening degree of the electronic expansion valve is adjusted so that the discharge temperature Td of 1 approaches the target discharge temperature Tmd.

A correction value Thd calculated by multiplying the number of revolutions N of the compressor and the condensing temperature Tc by constant coefficients d and e and adding them is added to the discharge temperature Trd in the theoretical cycle. The value is set as the target discharge temperature Tmd in the control method of the air conditioner.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, a control method for an air conditioner according to the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic configuration diagram showing an embodiment of a control method for an air conditioner according to the present invention. In FIG. 1, 1 is a compressor for compressing a gas refrigerant, 2 is a four-way valve for switching the direction of the refrigerant, 3 is an outdoor heat exchanger for exchanging heat between the refrigerant and the outside air, and 4 is compressed by adjusting its opening degree. Electronic expansion valves 5 for reducing the pressure of the refrigerant are indoor heat exchangers for exchanging heat between the refrigerant and the indoor air, and these are sequentially piped to form a refrigeration cycle. Then, by switching the four-way valve 2, the cooling operation and the heating operation are switched, and the compressed refrigerant compressed by the compressor 1 is transferred to the outdoor heat exchanger 3, the electronic expansion valve 4, and the indoor heat during the cooling operation. Exchanger 5
In this order, during the heating operation, the indoor heat exchanger 5, the electronic expansion valve 4,
The outdoor heat exchanger 3 is circulated in this order and circulated to the compressor 1.

Further, 6 is an outdoor unit controller provided in the outdoor unit, 7 is an indoor unit controller provided in the indoor unit, 8 is a discharge temperature sensor for detecting the discharge temperature Td of the compressor 1, and 9 is outdoor heat exchange. Outdoor heat exchange temperature sensor to detect the intermediate temperature of the vessel, 1
Reference numeral 0 denotes an indoor heat exchange temperature sensor that detects an intermediate temperature of the indoor heat exchanger. The discharge temperature sensor 8 and the outdoor heat exchange temperature sensor 9 are directly connected to the outdoor unit control unit 6, and the indoor heat exchange temperature sensor 10 is connected. Is connected to the outdoor unit control unit 6 via the indoor unit control unit 7. The outdoor heat exchange temperature sensor 9 is
The condensing temperature Tc of the refrigerant is detected during the cooling operation, and the evaporation temperature Te is detected during the heating operation. Further, the indoor heat exchange temperature sensor 10 detects the evaporation temperature Te of the refrigerant during the cooling operation and the condensation temperature Tc during the heating operation.

FIG. 2 is a flow chart for explaining the control method of the air conditioner of the present invention, and FIG. 3 is a diagram showing theoretical cycles on the Mollier diagram. The control method will be described below with reference to FIGS. 2 and 3. When the cooling operation mode or the heating operation mode is designated, the four-way valve 2 is switched to the cooling side or the heating side, and the compressor 1 is operated at a predetermined rotation speed N determined by the set temperature, the room temperature, etc. The operation or heating operation is started. When the cooling operation or the heating operation is started, the rotation speed N of the compressor 1 and the evaporation temperature Te and the condensation temperature Tc detected by the outdoor heat exchange temperature sensor 9 and the indoor heat exchange temperature sensor 10 become the outdoor temperature. It is input to the machine control unit 6 (ST1). Next, based on the evaporation temperature Te and the condensation temperature Tc, the superheat degree SH that makes the refrigeration cycle optimum is input on the Mollier diagram shown in FIG. 3 (S
T2) The point A in FIG. 3 is obtained, the evaporation temperature Te, the condensation temperature Tc, and the superheat degree SH are multiplied by constant coefficients a, b, and c, respectively, and these are added to obtain the discharge temperature Trd in the theoretical cycle. Is calculated as Trd = a × Te + b × Tc + c × SH (a, b, and c are coefficients) ... Equation 1 (ST3). Further, the rotational speed N of the compressor 1 and the condensing temperature Tc are respectively multiplied by constant coefficients d and e, and these are added to obtain a correction value Thd: Thd = d × N + e × Tc (where d and e are Coefficient) ... Calculated as Equation 2 (ST4). Then, the correction value Thd is added to the discharge temperature Trd during the theoretical cycle, and
The target value Tmd of the discharge temperature shown in is calculated as Tmd = Trd + Thd (Equation 3) (ST5). Next, the discharge temperature Td detected by the discharge temperature sensor 8 is input to the outdoor unit control unit 6 so that the discharge temperature Td approaches the target value Tmd of the discharge temperature (ST6) to open the electronic expansion valve 4. Adjust the degree (ST7).

As described above, the number of revolutions N of the compressor relating to the indoor temperature conditions, the evaporation temperature Te, the outside air temperature, and the condensing temperature Tc relating to the performance of the compressor so that the discharge temperature Td becomes the optimum refrigeration cycle. Also, since the opening of the electronic expansion valve 4 is adjusted so as to approach the target value Tmd of the discharge temperature calculated based on the correction value related to the performance peculiar to the compressor, the indoor temperature condition, the outside air temperature condition, and the performance of the compressor. It is possible to provide a control method for an air conditioner that can operate in an optimum refrigeration cycle even if conditions change.

[0010]

As described above, according to the control method of the air conditioner of the present invention, the evaporation temperature Te and the condensation temperature T
c is detected, and the corresponding superheat degree SH that optimizes the refrigeration cycle is obtained from the Mollier diagram, and the discharge temperature Trd at the theoretical cycle is obtained from the evaporation temperature Te, the condensation temperature Tc, and the superheat degree SH. The target discharge temperature Tmd is calculated by correcting the discharge temperature Trd during this theoretical cycle with the compression efficiency determined by the performance of the compressor alone, and the electronic discharge valve of the electronic expansion valve is adjusted so that the actual discharge temperature Td approaches the target discharge temperature Tmd. Since the opening degree is adjusted, it is possible to always maintain the superheat degree that is an optimum refrigeration cycle without adding a sensor for detecting the indoor heat exchange inlet pipe temperature and the compressor suction pipe temperature as in the conventional case.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an embodiment of a control method for an air conditioner according to the present invention.

FIG. 2 is a flowchart illustrating the operation of the control method for an air conditioner according to the present invention.

FIG. 3 is a Mollier diagram for explaining the operation of the control method for an air conditioner according to the present invention.

FIG. 4 is a schematic configuration diagram showing a control method for a conventional air conditioner.

[Explanation of symbols]

1 compressor 2 four-way valve 3 outdoor heat exchanger 4 Electronic expansion valve 5 Indoor heat exchanger 6 Outdoor unit control unit 7 Indoor unit controller 8 Discharge temperature sensor 9 Outdoor heat exchange temperature sensor 10 Indoor heat exchange temperature sensor

Claims (2)

[Claims] 1. A refrigeration cycle is constructed by sequentially connecting a compressor, a four-way valve, an outdoor heat exchanger, an electric expansion valve, and an indoor heat exchanger, and by switching the four-way valve, a cooling operation is performed. The high-pressure refrigerant compressed by the compressor flows in the order of the outdoor heat exchanger, the electric expansion valve, and the indoor heat exchanger, and during the heating operation, the indoor heat exchanger, the electric expansion valve, and the outdoor heat exchanger in that order. In an air conditioner that adjusts the opening degree of the electronic expansion valve so as to be a refrigeration cycle, an outdoor heat exchange temperature sensor that detects an intermediate temperature of the outdoor heat exchanger, and an intermediate temperature of the indoor heat exchanger An indoor heat exchange temperature sensor for detecting and a discharge temperature sensor for detecting the discharge temperature of the compressor are provided, and when the compressor is operated at a predetermined rotation speed N to start cooling or heating operation, the outdoor heat exchange temperature is detected. Sensor and indoor heat exchange temperature sensor The evaporating temperature Te and the condensing temperature Tc, and the superheat degree SH set to be optimum on the Mollier diagram with respect to the detected evaporating temperature Te and condensing temperature Tc, have constant coefficients a, b, and The discharge temperature Trd in the theoretical cycle is calculated by multiplying and adding c, and the discharge temperature Td in the theoretical cycle is set as the target discharge temperature Tmd, and the discharge temperature Td of the compressor is the target discharge temperature Tm.
An air conditioner control method, wherein the opening of the electronic expansion valve is adjusted so as to approach d. 2. A correction value Thd calculated by multiplying the number of revolutions N of the compressor and the condensing temperature Tc by constant coefficients d and e, and adding them, is used as the discharge temperature Trd in the theoretical cycle. The method for controlling an air conditioner according to claim 1, wherein the added value is used as the target discharge temperature Tmd.