JPS6130176B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Technical Field> The present invention relates to a control circuit for an air conditioner having a refrigerant compression cycle, and particularly to a control circuit for a variable capacity air conditioner controlled by an inverter.

<Prior art> Electric compressor, refrigerant flow switching valve, outdoor heat exchanger,
In an air conditioner that is equipped with a refrigerant compression cycle in which a pressure reducer and an indoor heat exchanger are sequentially connected, and a blower is installed in the outdoor heat exchanger and the indoor heat exchanger, the outdoor heat exchanger is As frost forms on the equipment, the heating capacity decreases and the operating efficiency decreases, so when the frost reaches a certain value, it is necessary to perform a defrosting operation to remove the frost. This defrosting operation is performed by stopping the indoor and outdoor blowers and switching the refrigerant compression cycle to the refrigerant flow path switching valve, which reverses the heating cycle and flows high-temperature refrigerant to the outdoor heat exchanger. It is something. However, if you suddenly switch the switching valve when switching from heating operation to defrosting operation, the flow of refrigerant will reverse.
Because the pressures of the high-pressure and low-pressure parts of the refrigerant eventually reach balance, a rather loud gas noise was produced, which was unpleasant to the ears.

Furthermore, since defrosting operation is essentially refrigerant operation, the difference between high pressure and low pressure becomes large during defrosting operation. Since this defrosting operation is performed in a reverse (that is, cooling) cycle, the blower is in a stopped state. At this time,
Since heating operation has been stopped, when defrosting operation is started, the compressor is generally driven at full power to complete defrosting in a short time, thereby shortening the heating stop time.

Therefore, even after defrosting is completed, there is a considerable difference in the high and low pressures of the refrigerant, and if the switching valve is suddenly switched at this point, the pressures of the high-pressure part and the low-pressure part of the refrigerant will eventually balance, producing gas noise.

<Purpose> In view of the above, the present invention was provided for the purpose of reducing the gas noise generated when switching the switching valve from heating operation to defrosting operation and from defrosting operation to heating operation. .

<Embodiment> The present invention will be described in detail below with reference to the illustrated embodiment. In FIG. 1, 1 is a compressor, 2 is a compressor motor that drives this compressor 1, and these constitute an electric compressor. Ru. 3 is an outdoor heat exchanger, 4 is a pressure reducer such as a capillary tube, 5 is an indoor heat exchanger, 1a is a four-way valve as an example of a switching valve for switching the flow of refrigerant, and these are connected to the compressor 1 and a closed circuit. are connected to form a refrigerant compression cycle. In this refrigerant compression cycle, heating operation is performed when the four-way valve 1a is on, and cooling operation is performed when it is off. 6 is an outdoor blower provided corresponding to the outdoor heat exchanger 3, and 7 is an indoor blower provided corresponding to the indoor heat exchanger 5.

8 is a general one-chip microcomputer (hereinafter referred to as microcomputer), which has input terminals IN1 to IN.
5 and output terminals OUT1 to OUT6, as well as internal program ROM, data RAM, and ALU.
, and is driven by a reference clock oscillator 9. 10 is a thermistor as a room temperature detector, 1
1 is an A/D converter which converts the room temperature detected by the thermistor 10 into a digital value and inputs it to the input terminal IN1 of the microcomputer 8. 12 is a variable resistor as a room temperature setting device, 13 is an A/D converter, and variable resistor 1
Convert the room temperature set in step 2 into a digital value and input it to the input terminal IN2 of the microcomputer 8. 14 is an inverter section, which rectifies the AC power input from power supply terminals 15 and 15' with diodes D ₁ to D ₄ and smoothes it with a capacitor C ₁₀ , and then outputs it to transistors Tr 1 and Tr.
1' is W phase, transistors Tr2 and Tr2' are V phase,
The three phases of the U phase are controlled by transistors Tr3 and Tr3' to generate three-phase alternating current, thereby operating the three-phase compressor motor 2. 16 is a run/stop switch,
Connected to input terminal IN4 of microcomputer 8. 17
is a cooling/heating selector switch for switching the four-way valve 1a, and is connected to the input terminal IN3 of the microcomputer 8. The microcomputer 8 reads the room temperature from the input terminal IN1 and the room temperature set value from the input terminal IN2, and controls the frequency and voltage of the three-phase voltages U, V, and W that are energized to the compressor motor 2 via the inverter section 14 based on these values. Output the signal to output terminal OUT1~
It outputs from OUT3, and thereby controls the rotation speed of the compressor motor 2 via the transistor drive circuit 18, thereby making the cooling (heating) capacity variable. 19 is a thermistor as a frost detector, 20
is an A/D converter that converts the room temperature detected by the thermistor 19 into a digital value and inputs it to the input terminal IN5 of the microcomputer 8. The microcomputer 8 generates a three-phase voltage U, which energizes the compressor motor 2 according to the signal.
Output terminal for signals that control the frequency and voltage of V and W
Output from OUT1 to OUT3 and four-way valve 1a
Outputs a signal to switch to the off state (cooling side). In this way, the microcomputer 8 and the inverter section 14
This constitutes a so-called pulse width modulation type inverter control section.

Note that the capacitor C ₁ of the inverter section 14,
C ₁ '~C ₃ , C ₃ ' are transistors Tr1, Tr1'~
This is to prevent Tr3 and Tr3' from malfunctioning due to noise. Also, resistor R ₁ and capacitor C ₄ , R ₄ and C ₇ , R ₂ and C ₅ , R ₅ and C ₈ , R ₃ and C ₆ , R ₆
Each RC series circuit consisting of C ₉ connects compressor motor 2
Transistor due to back electromotive force after energization is turned off
This is a discharge circuit to prevent damage to Tr1, Tr1' to Tr3, Tr3'. Microcomputer output terminal OUT4,
Control outputs of the outdoor blower 6, indoor blower 7, and four-way valve 1a are generated at OUT5 and OUT6, respectively.

That is, the control circuit controls the inverter section 14
, a frost detector 19 , a rotation speed detection means for detecting the rotation speed of the electric compressor 2 , and an output signal from the rotation speed detection means and the frost formation detector 19 to control the inverter section 14 and the switching valve 1 a. It is equipped with 8 microcontrollers.

Next, the various functions (means) of the microcomputer 8 will be explained based on the functional block diagram of FIG.
compares the room temperature storage means that stores the temperature signal from the room temperature detector 10, the set temperature storage means that stores the setting signal from the room temperature setting device 12, and the signals from the room temperature storage means and the set temperature storage means. It is provided with a room temperature comparison and determination function for determining and outputting a compressor control signal to the rotation speed control means.

Further, the microcomputer 8 compares the signals from the frosting state storage means for storing the defrosting signal from the frosting detector 19 and the defrosting level set value storage means for setting the defrosting level in advance. A frosting comparison/determination means is provided for making a determination and outputting a determination signal to the rotation speed control means, the switching valve switching means, and the indoor/outdoor blower control means.

Furthermore, the microcomputer 8 includes a rotation speed storage means for storing the detection signal of the rotation speed detection means, and an electric compressor 2.
minimum rotational speed storage means for storing the minimum rotational speed of the
The rotation speed comparison and judgment means compares the signals from both means and outputs a judgment signal to the rotation speed control means, and also outputs a judgment signal to the switching valve switching means and the indoor/outdoor blower control means based on the signal from the timer means. I'm being forced to do it.

In particular, the microcomputer 8 includes a rotation speed control means for lowering the rotation speed of the electric compressor based on a defrost start signal and a defrost end signal from the frost detector;
Switching the switching valve from the heating cycle to the defrosting cycle based on the compressor minimum rotation speed detection signal of the rotation speed detection means after the defrosting start signal of the frost detector is output, and the defrosting end signal of the frost detector. A switching means is provided for switching the switching valve from a defrosting cycle to a heating cycle based on a compressor minimum rotational speed detection signal of the rotational speed detection means after output.

In the above configuration, when the compressor 1 is driven by the compressor motor 2 during cooling operation, the refrigerant compressed by the compressor 1 is cooled and condensed by the air from the outdoor blower 6 in the outdoor heat exchanger 3, and then decompressed. The pressure is reduced in the chamber 4, evaporated in the indoor heat exchanger 5 to perform a cooling effect, and the indoor blower 7 blows air to cool the room. On the other hand, during heating operation, the four-way valve 1a is switched on as shown in Figure 2, and the flow of refrigerant is reversed so that the compressor 1 → four-way valve 1a → indoor heat exchanger 5 → pressure reducer 4 → outdoor heat exchange Heating operation is performed by air flowing through the indoor air blower 7.

Next, the defrosting operation of the outdoor heat exchanger during heating will be explained based on the time chart of FIG. First, the defrosting conditions (sensing the temperature drop of the outdoor heat exchanger (approximately -
When 2.5)) is satisfied, the rotation speed of the electric compressor is controlled via the microcomputer 8 and the inverter section 14. For example, when the defrosting signal L is input from the defrosting thermostat etc. at point A, the microcomputer 8 and the inverter 1
4 works, compressor motor 2 continues heating operation.
Gradually reduce the rotation speed to the minimum rotation speed. After the rotation speed of the compressor motor 2 reaches the minimum rotation speed, the operation continues until the amount of circulating refrigerant in the refrigerant compression cycle decreases, and at point B, the four-way valve 1a is switched and defrosting operation begins. and compressor motor 2
Gradually increase the rotation speed to perform a full-scale defrosting operation. At the end of the defrosting operation, when the defrosting end signal H is input at point C, the microcomputer 8 and inverter section 14 operate in the same way as above to gradually reduce the rotation speed of the compressor motor 2 to the minimum rotation speed. After that, the compressor motor 2 is operated at the minimum rotational speed for a while, and then the four-way valve 1a is switched to return to heating operation.

The control operation by the microcomputer 8 as described above will be explained based on the flowchart of FIG. If there is
Branch towards YES and take the route in the 2nd to 4th rows from the left in Figure 4, but if not, take the route in the 1st row. That is, if the ``defrost flag H'' is NO, then it is determined whether the ``defrost signal is L'', that is, the defrost start signal, and if it is the start signal, the rotational speed of the electric compressor is lowered by one step. Thereafter, it is determined whether the compressor is at the minimum rotation speed, and if it is the minimum rotation speed, the defrost flag is set to H and the process returns to the beginning of the defrost loop.
Also, if the electric compressor does not rotate at the minimum speed, it will jump and return to the beginning of the loop. In addition, "Defrost signal L
If the answer is NO, normal heating operation will be performed.

If the "defrost flag H" branches to YES, it is determined here whether the "defrost signal is H", that is, whether it is a defrost end signal, and if it is an end signal, columns 3 and 4 in Figure 4 go through the route of If not, the second route is entered and it is determined whether the amount of circulating refrigerant in the refrigerant compression cycle has decreased to a predetermined value. This corresponds to "WAIT OK?" in the diagram. If the amount of refrigerant is decreasing, the four-way valve is switched to the defrosting side and the indoor and outdoor blowers are commanded to stop. Thereafter, it is determined whether the compressor is at the maximum rotation speed, and if the maximum rotation speed has not been reached, a command is given to increase the compressor rotation speed by one step. Note that if "WAIT OK" is NO and "Is the compressor at maximum rotation speed" is YES, the process returns to the beginning of the defrosting loop again.

Also, if the "defrost signal H" is YES, it is determined whether "the compressor is at the minimum rotation speed", and if it is the minimum rotation speed, it enters the fourth column in Figure 4, where the refrigerant compression cycle is circulated. It is determined whether the refrigerant amount has decreased to a predetermined value, and if it has not reached the predetermined value, it returns to the beginning of the loop, and if it has reached the predetermined value,
After "setting the defrosting flag to L", that is, setting the defrosting flag to the end of defrosting, the four-way valve is switched to the heating side and the indoor and outdoor blowers are commanded to operate, and heating operation begins. In addition, “Is the compressor at the minimum rotation speed?”
If NO, the rotation speed of the electric compressor is lowered by one step and the process returns to the beginning of the defrosting loop. Gas noise can be reduced by controlling the air conditioner using the microcomputer 8 in this way.

<Effects> As is clear from the above description, the present invention includes a refrigerant compression cycle in which an electric compressor, a refrigerant flow path switching valve, an outdoor heat exchanger, a pressure reducer, and an indoor heat exchanger are connected in sequence, and In an air conditioner in which an outdoor heat exchanger and an indoor heat exchanger are each equipped with a blower, frost formation is detected in an inverter unit that controls the frequency and voltage of a power supply to the electric compressor and the outdoor heat exchanger. A frosting detector, a rotational speed detection means for detecting the rotational speed of the electric compressor, and a microcomputer that controls the inverter section and the switching valve based on output signals from the rotational speed detection means and the frosting detector. The microcomputer is provided with a rotation speed control means for reducing the rotation speed of the electric compressor according to a defrost start signal and a defrost end signal from the frost detector, and a rotation speed control means that lowers the rotation speed of the electric compressor according to a defrost start signal and a defrost end signal from the frost detector. The switching valve is switched from the heating cycle to the defrosting cycle by the compressor minimum rotational speed detection signal of the rotational speed detection means after output, and the compression of the rotational speed detection means is performed after the defrosting end signal of the frosting detector is output. The present invention relates to a control circuit for an air conditioner, characterized in that it includes a switching means for switching the switching valve from a defrosting cycle to a heating cycle in response to a machine minimum rotational speed detection signal.

Therefore, according to the present invention, the switching operation of the switching valve from heating operation to defrosting operation and from defrosting operation to heating operation is performed after the rotational speed of the electric compressor is reduced to approximately the minimum rotational speed and maintained. By doing so, it is possible to reduce the gas noise generated when the switching valve is switched, and there is an effect that the noise is not so harsh that it is generated even when the user is sleeping.

[Brief explanation of the drawing]

FIG. 1 is a control circuit diagram showing one embodiment of the present invention;
FIG. 2 is a diagram showing the switching state of the four-way valve, FIG. 3 is a time chart of the control circuit, FIG. 4 is a flowchart thereof, and FIG. 5 is a functional block diagram of the control circuit. 1... Compressor, 1a... Four-way valve, 2... Compressor motor, 3... Outdoor heat exchanger, 4... Pressure reducer, 5
...Indoor heat exchanger, 6...Outdoor blower, 7...Indoor blower, 8...Microcomputer, 10...
... Room temperature detector, 12 ... Room temperature setting device, 14 ... Inverter section, 16 ... Run/stop switch, 17
...Cooling/heating selector switch, 19...Frost formation detector.

Claims (1)

[Claims] 1.Equipped with a refrigerant compression cycle in which an electric compressor, refrigerant flow switching valve, outdoor heat exchanger, pressure reducer, and indoor heat exchanger are connected in sequence, and an air blower equipped with the outdoor heat exchanger and indoor heat exchanger. In the harmonizer, an inverter section that controls the frequency and voltage of the power supply to the electric compressor, a frost detector that detects frost formation on the outdoor heat exchanger, and a rotation speed that detects the rotation speed of the electric compressor. and a microcomputer that controls the inverter section and the switching valve based on the output signals from the rotation speed detection means and the frosting detector, and the microcomputer controls the speed at which the frosting detector starts defrosting. A rotation speed control means for lowering the rotation speed of the electric compressor according to a signal and a defrosting end signal, and a compressor minimum rotation speed detection signal of the rotation speed detection means after the defrosting start signal is output from the frost detector. The switching valve is switched from the heating cycle to the defrosting cycle, and the switching valve is switched from the defrosting cycle to the heating cycle by the compressor minimum rotation speed detection signal of the rotation speed detection means after the defrosting end signal is output from the frost detector. 1. A control circuit for an air conditioner, comprising a switching means for switching to.