JPS62155472A - Controller for air conditioner - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION What) Industrial Field of Application The present invention is a refrigeration cycle/I/? The present invention relates particularly to the protection of the compressor in an air conditioner configured such that the operating capacity of the compressor is changed by the frequency of the power supply applied to the compressor.

(b) Conventional technology Conventionally, when the compressor is started, the refrigerant trapped in the oil of the compressor enters a forming state, and a crankcase heater is provided to prevent the so-called oil forming, which occurs when the amount of oil in the compressor becomes insufficient. This was done to prevent the refrigerant from getting trapped in the oil.

Particularly when using a compressor whose capacity changes depending on the frequency applied to the refrigeration cycle, if there is refrigerant trapped in the oil, increasing the compressor's operating capacity will result in more oil foaming, and the capacity of the crankcase heater will need to be increased. Without this, oil forming could not be completely prevented.

In order to solve these problems, the method described in Japanese Patent Application Laid-Open No. 152187/1987 has been developed. This bulletin states that ``After the start of operation, the compressor is controlled to gradually increase the rotation speed, operate at a certain rotation speed for one hour, and then further increase the rotation speed.'' If you do this, even if you start the compressor with refrigerant stuck in the oil, it will run at a low rotation speed (medium to low speed) for a certain period of time, and during this time the refrigerant in the oil will come out and the compressor rotation speed will increase. This prevents oil forming when

? -1 Problems to be Solved by the Invention In the conventional technology as described above, when the air conditioner starts operating, it is always operated at a certain rotation speed for a certain period of time. In such an operation, for a compressor that uses a compressor whose capacity changes depending on the frequency (or rotational speed), it is difficult to output the maximum capacity particularly at the start of operation, resulting in control that has a slow start-up.

In other words, this hinders the "successful start-up operation" that is a characteristic of compressors using such compressors, and the larger the maximum capacity, the more problematic it becomes.

Furthermore, when the outside temperature is particularly low, such as in the winter, the outdoor heat exchanger is cooled down, so the refrigerant liquefies inside the heat exchanger. When the compressor is started in this state, a large amount of liquid refrigerant returns to the accumulator, and the liquid refrigerant that cannot be completely vaporized in the accumulator is sucked into the compressor, causing oil forming as described above. This oil foaming was more severe as the operating capacity of the compressor was increased, but as the compressor was operated at a lower operating capacity, such oil forming did not occur as much.

Therefore, in the conventional method, in order to prevent such oil foaming, it is necessary to set a sufficient period of time for operation at the intermediate frequency at startup, which further impairs the start-up of the air conditioner.

In view of these problems, the present invention provides a control device for an air conditioner that performs oil forming prevention operation based on the state of the refrigerant in the accumulator.

B) Means for Solving the Problems The present invention constructs a refrigeration cycle by sequentially connecting a compressor, a condenser, an expansion device, an evaporator, and an accumulator in an annular manner. In an air conditioner that changes the frequency of the power supply applied to the compressor, there is a detector that detects the gas-liquid separation state of the refrigerant in the accumulator, and a control that increases or decreases the frequency of the power supply applied to the compressor based on the output of this detector. It is equipped with a section.

(4) Effect When using the air conditioner control device configured as described above, oil forming prevention operation is performed based on the state of gas-liquid separation of the refrigerant in the accumulator.

(F) Embodiments Below, embodiments of the present invention will be described based on the drawings. First, FIG. 1 is a schematic diagram of an air conditioner using the apparatus of the present invention. 1 is a compressor whose capacity changes depending on the frequency of the power supply applied from the control unit 2, and a four-way valve 3, an indoor heat exchanger 4, an expansion device 5, an outdoor heat exchanger 6, and an accumulator 7 are connected in a ring. It consists of frozen buital. If the four-way valve 3 is in the state shown by the solid line in the figure, the refrigerant discharged from the compressor 1 is transferred to the four-way 9'P3 and the outdoor heat exchanger 6 (acts as a condenser).
, the expansion device 5, the indoor heat exchanger 4 (acts as an evaporator), the four-way valve 3, and the accumulator T, which can flow in the direction of the solid arrow in order to cool the room.
3 is in the state indicated by the dotted line in the figure, the refrigerant discharged from the compressor 1 passes through the four-way valve 3, the indoor heat exchanger 4 (acts as a condenser), the expansion device 5, and the outdoor heat exchanger 6 (evaporator). ), the four-way valve 3, and the accumulator 7 in order to flow in the direction of the dotted arrow to heat the room.

A detector 8 is provided inside the accumulator 7 and detects the gas-liquid separation state of the refrigerant inside the accumulator 7.

This detector 8 consists of, for example, a thermistor. At this time, the boomister does not measure the temperature inside the accumulator 7, but detects changes in the self-heating of the boomister. Generally, the internal resistance of a thermistor changes based on temperature, and at the same time self-heating occurs when a voltage is applied, and this self-heating further changes the internal resistance.

For example, if a voltage is applied to the boomister while it is immersed in liquid refrigerant, the resistance value of the thermistor will first change to the temperature of the liquid refrigerant (in the accumulator T, gas and liquid are almost the same - g).
It is against A. ), and then the thermistor self-heats due to the applied voltage, but since the liquid refrigerant has a large heat capacity, it absorbs this heat, and the resistance value of the thermistor hardly changes. In other words, the temperature rise of the thermistor is almost undetectable.

Furthermore, when the Boomister is in the gas, the heat capacity of the gas refrigerant is small, so the gas cannot sufficiently absorb the heat generated by the Boomister's self-heating, and the resistance value changes. In other words, the temperature of the thermistor increases.

Therefore, the state of the refrigerant in the accumulator 7 can be determined by the temperature rise due to self-heating of the thermistor.

Furthermore, the mounting of this detector 8 allows the amount of liquid refrigerant to be determined based on its position.

FIG. 2 is an explanatory diagram of the inside of the accumulator 7 shown in FIG. 1, and has an inlet pipe 9 into which a refrigerant enters and a U-shaped outlet pipe 10. An oil return hole 11 is provided at the bottom of this outlet pipe 10. Note that 12 is the liquid level of the liquid refrigerant.

FIG. 3 is a main part flowchart showing the main operations of the control section 2 shown in FIG. 1. In this figure, first, when the compressor is started, operation is started at an intermediate frequency (60 Hz) at which the influence of oil forming is not so great. At the same time, the timer (Nx) (time count: 1 minute) starts counting. When this timer (N,) times out, it is determined whether the temperature increase rate of the detector during this period (1 minute) is greater than or equal to f. That is, if the temperature increase rate is f or more, the detector 8 is in the gas, and if the temperature increase rate is less than f, the detector 8 is in the liquid. Therefore, if the detector 8 is in the gas, it starts counting the timer (Nt), and this timer (Nt) starts counting the time.
The intermediate frequency (60H) continues until the time increases.
z) to maintain operation. by this,
This is to elute the refrigerant trapped in the oil in the accumulator 7. Since the amount of oil in the refrigeration cycle is determined, the time measured by the timer <, Nt) can be set according to the amount of oil in the refrigeration cycle.

When using the control device configured as described above, when starting the compressor 1, the compressor 1 is operated at an intermediate frequency ( 60Hz) to prevent the compressor 1 from forming. As a result of this operation, the liquid level of the liquid refrigerant in the accumulator 7 becomes lower than that of the detector 8, and then the rotation speed of the compressor 10 is increased to perform normal operation based on the load.

Furthermore, when there is a lot of liquid refrigerant in the accumulator 7, the expansion device 5 is opened to lower the expansion rate, and when there is less liquid refrigerant, the expansion device is closed to increase the expansion rate. increases.

(G) Effects of the Invention The present invention constructs a refrigeration cycle by sequentially connecting a compressor, a condenser, an expansion device, an evaporator, and an accumulator in a ring, and also provides a power supply that applies the operating capacity of the compressor to the compressor. An air conditioner that changes the frequency at a frequency of Therefore, the capacity of the compressor can be limited based on the gas-liquid separation state of the refrigerant in the accumulator. In other words, the capacity of the compressor can be limited only for the minimum amount of time necessary, and air conditioning operation with a smooth start-up can be performed using a variable capacity compressor.

[Brief explanation of drawings]

Fig. 1 is a schematic diagram of an air conditioner using the device of the present invention, Fig. 2 is an internal explanatory diagram of the accumulator shown in Fig. 1, and Fig. 3 is the main operation of the control section shown in Fig. 1. It is a main part flowchart which shows. DESCRIPTION OF SYMBOLS 1... Compressor, 2... Control part, 3... Four-way valve, 4... Indoor heat exchanger, 5... Expansion device,
6... Indoor heat exchanger, 7... Accumulator,
8...Detector.

Claims (1)

[Claims] (1) A refrigeration cycle is constructed by sequentially connecting a compressor, condenser, expansion device, evaporator, and accumulator in a ring, and the operating capacity of the compressor is changed by the frequency of the power supply applied to the compressor. The air conditioner is characterized by comprising: a detector for detecting the gas-liquid separation state of the refrigerant in the accumulator; and a control unit for increasing or decreasing the frequency of the power supply applied to the compressor based on the output of the detector. Air conditioner control device.