JP2757900B2 - Air conditioner - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a means for preventing supercooling of an air conditioner during a low-humidity dry operation.

[0002]

2. Description of the Related Art Refrigeration cycle (refrigerant circuit) of an air conditioner
Is basically a pipe connection of a compressor, a four-way valve, an outdoor heat exchanger, a throttle means (expansion valve), and an indoor heat exchanger.
In an air conditioner equipped with such a refrigeration cycle,
For example, the refrigerant in the refrigeration cycle during cooling operation becomes a high-temperature and high-pressure gas at the inlet side of the outdoor heat exchanger, a high-temperature and high-pressure liquid at the outlet side, and a low-temperature and low-pressure liquid at the inlet side of the indoor heat exchanger, and at the outlet side. The return of liquid to the compressor is eliminated by controlling the number of revolutions of the compressor so as to be in a low-temperature low-pressure gas state, or by controlling the expansion and contraction of an expansion valve. In addition,
The air conditioner has a function of low-humidity dry operation that lowers the indoor humidity.In this low-humidity dry operation, the operating frequency of the compressor is reduced from that in normal cooling operation,
Control for reducing the number of revolutions of the indoor blower is performed.

[0003]

However, in the above-described low-humidity dry operation, the number of revolutions of the indoor blower becomes small, so that the amount of air passing through the indoor heat exchanger becomes small. Then, there is a problem that the evaporation temperature of the indoor heat exchanger becomes too low and the temperature of the air blown from the indoor unit becomes too low. In addition, if the expansion valve is not properly throttled and the amount of refrigerant flowing into the indoor heat exchanger is too large, the amount of heat exchange in the indoor heat exchanger is reduced, dehumidifying capacity is reduced, and liquid flowing to the compressor is reduced. There is a problem that the return cannot be eliminated and the life of the compressor is adversely affected. Therefore, an object of the present invention is to provide an air conditioner that solves these problems.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above-mentioned problems, and has a refrigeration cycle including a compressor, a four-way valve, an outdoor heat exchanger, a throttle means, an indoor heat exchanger, and the like. In the air conditioner provided, a temperature sensor is provided on each of a pipe on the leeward side and a pipe on the leeward side of the indoor heat exchanger, and the expansion means is provided with an expansion valve capable of performing throttle control in at least several stages. The temperature difference obtained from the outputs of the two temperature sensors during the low-humidity dry operation in which the compressor and the indoor blower are operated at a low speed is the indoor temperature difference.
The expansion valve is controlled so as to fall within a predetermined temperature range in which the leeward side of the heat exchanger is in a superheat state .

[0005]

According to the above configuration and control method, the temperature sensors are provided in the pipeline on the windward side of the indoor heat exchanger and the pipeline on the leeward river. Can be obtained, it is possible to determine from this temperature difference whether the amount of refrigerant flowing into the indoor heat exchanger is an appropriate amount, if the amount of refrigerant is not an appropriate amount,
If the temperature difference between the leeward side and the leeward side of the indoor heat exchanger is not within a predetermined temperature range, the expansion valve can be controlled to fall within the temperature range, so that the compressor and the indoor blower are operated at a low speed. It is possible to prevent the indoor heat exchanger from being excessively cooled, which often occurs during the low-humidity dry operation, and to prevent the refrigerant from returning to the compressor in a liquid state.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIGS. FIG. 1 schematically shows a refrigeration cycle of an air conditioner and a control system thereof. 1 is a compressor, 1a is an accumulator, and 2 is a refrigerant flow discharged from the compressor 1 for cooling operation, heating operation, and the like. Four-way valve, 3
Is an outdoor heat exchanger, 4 is an expansion valve provided as a throttling means for controlling the flow of the refrigerant, 5 is an indoor heat exchanger, and 6 is a temperature of a pipe (hairpin) on the windward side of the indoor heat exchange 5. A temperature sensor, 7 is a temperature sensor for detecting the temperature of a pipe (hairpin) on the lee side of the indoor heat exchanger 5, 8 is an indoor unit control unit, 9 is an outdoor unit control unit, and 10 is an indoor blower. The indoor unit control unit 8 and the outdoor unit control unit 9 are connected by a signal line and a power line, and the indoor unit control unit 8 controls an indoor blower 10 and a wind direction control device (not shown) and the like to control the outdoor unit. The unit 9 controls the compressor 1, the four-way valve 2, the expansion valve 4, and an outdoor blower (not shown). The expansion valve 4 is provided with a pulse motor and can finely control the flow of the refrigerant in multiple stages.

FIG. 2 shows a schematic configuration of the indoor heat exchanger 5 and mounting positions of the temperature sensors 6 and 7. Pipelines (hereinafter referred to as hairpins) 11 constituting the indoor heat exchanger 5 are arranged on the windward and leeward sides with respect to the flow of air indicated by arrows, and the refrigerant in the low-humidity dry operation is in the cooling operation. Similarly, after flowing in from the inlet a, it goes up and down and goes out from the two outlets b and c toward the four-way valve 2 shown in FIG. By the way, the temperature sensor 6 is fixed to a hairpin projecting on the windward side surface, and the other temperature sensor 7 is fixed to a hairpin projecting on the leeward side surface. These two temperature sensors 6 and 7 each detect the surface temperature of the hairpin, and the output signal is input to the indoor unit control unit 8 so that the internal microcomputer determines the temperature difference between the windward side and the leeward side. Has become. It is determined whether or not the temperature difference is within a preset temperature range. If the temperature difference is outside the predetermined temperature range, the expansion valve 4 is finely controlled so that the temperature difference falls within the predetermined temperature range. Has become.

Hereinafter, an example of the control method will be described with reference to the flowchart of FIG. When the low-humidity dry operation is started, the process proceeds to step ST1, and the operation is performed for 10 minutes until the temperature of the indoor heat exchanger 5 is substantially stabilized.
When 10 minutes have elapsed, the process proceeds to step ST2, where the temperature sensors 6 and 7 detect the temperature Tc1 of the hairpin on the leeward side of the indoor heat exchanger 5 and the temperature Tc2 of the hairpin on the leeward side, and compare Tc1 and Tc2. You. When the temperature Tc1 on the leeward side is higher than the temperature Tc2 on the leeward side, the process proceeds to step ST3. After the expansion valve 4 is throttled by two stages, the process proceeds to step ST4, and the temperature of the indoor heat exchanger 5 is reduced. Hold for 2 minutes until almost stable. After two minutes have passed, the process proceeds to step ST5, where the temperature Tc1 of the hairpin on the leeward side of the indoor heat exchanger 5 and the temperature Tc2 of the hairpin on the leeward side are detected again, and the temperature difference obtained by subtracting Tc1 from Tc2 is 5 ° C. or more. , That is, whether the leeward side of the indoor heat exchanger 5 is superheated.

If the temperature difference when the temperature Tc1 on the leeward side is subtracted from the temperature Tc2 on the leeward side exceeds 5 ° C., it is determined that the temperature difference is too large, and the process proceeds to step ST6. After the aperture is loosened by one step, the process proceeds to step ST7, and after a hold for 2 minutes until the aperture effect is obtained, the process proceeds to step ST8. If the temperature difference obtained by subtracting the leeward temperature Tc1 from the leeward temperature Tc2 from the leeward temperature Tc2 in the determination in the step ST5 is 5 ° C. or less, the process immediately proceeds to the step ST8.
Proceed to In this step ST8, the indoor heat exchanger 5
It is determined whether or not the temperature difference (Tc2−Tc1) between the windward side and the leeward side is 3 ° C. or less. It is controlled to return to ST3.

As can be understood from the above description, in this embodiment, the throttle of the expansion valve 4 is adjusted so that the temperature Tc2 on the leeward side of the indoor heat exchanger 5 becomes higher than the temperature Tc1 on the leeward side by 3 to 5 ° C. In addition, the circulation amount of the refrigerant is controlled. That is, during the low-humidity dry operation, the rear part of the indoor heat exchanger 5 is placed in a superheat state, and only the front part performs a predetermined function. The result is similar to that when the size is reduced by about half. Note that the indoor heat exchanger 5 of FIG. 2 is configured so that the refrigerant flowing in from the substantially central inlet a on the leeward side is separated into upper and lower parts and is taken out from the two outlets b and c on the leeward side. The present invention is not limited to such a configuration, and the mounting positions of the temperature sensors 6 and 7 are not limited to the positions shown in FIG.

[0011]

According to the air conditioner described above, the circulation amount of the refrigerant is controlled so that the leeward side of the indoor heat exchanger is in a superheat state in the low-humidity dry operation. This helps to prevent the room from getting too cold, which can occur during low-humidity dry operation in which the air conditioner and indoor blower are operated at low speeds, improves comfort, and prevents the refrigerant returning to the compressor from remaining liquid. Since there is no compressor, there is no danger of adversely affecting the compressor.

[Brief description of the drawings]

FIG. 1 is a block diagram schematically illustrating a refrigeration cycle and a control system thereof according to the present invention.

FIG. 2 is a side view of the indoor heat exchanger according to the present invention.

FIG. 3 is a flowchart showing one embodiment of the control of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Compressor 2 Four-way valve 3 Outdoor heat exchanger 4 Expansion valve (throttle means) 5 Indoor heat exchanger 6 Temperature sensor 7 Temperature sensor 8 Indoor unit control unit 9 Outdoor unit control unit 10 Indoor blower 11 Pipe

Claims (1)

(57) [Claims] 1. An air conditioner provided with a refrigeration cycle including a compressor, a four-way valve, an outdoor heat exchanger, a throttling means, an indoor heat exchanger, and the like. A temperature sensor is provided in each of the side pipes, and an expansion valve capable of controlling the throttle in at least several stages is used as the throttle means, and the two compressors and the indoor blower are operated at a low speed in a low-humidity dry operation. The temperature difference obtained from the output of the temperature sensor is on the leeward side of the indoor heat exchanger.
An air conditioner configured to control the expansion valve so that the temperature falls within a predetermined temperature range in which a superheat state is set.