JPS6151220B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application 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 connected in sequence, and that the outdoor heat exchanger and the indoor heat exchanger are each equipped with a blower, and that performs cooling and heating operations by switching a switching valve. There is an inverter control method that controls the frequency and voltage of the power supply to the electric compressor, and this method allows stepless control of the rotation speed and is very effective in keeping room temperature fluctuations small.

<Problems to be Solved by the Invention> However, in this type of device, when the operation (heating, cooling) of the air conditioner is stopped, a back electromotive voltage is generated in the compressor when the power is turned off, and the inverter section is May have side effects.

In other words, the magnitude of the back electromotive force generated in the compressor when the energization is off is approximately proportional to the energization frequency, that is, the rotational speed when the energization is off, and suddenly turning off at a high frequency causes damage to the transistors in the inverter. This will have a negative impact and is not very desirable.

Therefore, a method must be adopted in which the energization frequency is gradually lowered from the point of operation stop, and the energization to the compressor motor is stopped after reaching the lowest frequency.

However, in this case, the operation does not stop until, for example, several tens of seconds after the user presses the run/stop switch, which has the disadvantage of making the user feel uneasy.

The present invention aims to solve the above-mentioned problems and provide a control circuit for an air conditioner that does not cause the user to feel uneasy, especially when the heating operation is stopped.

<Means for Solving the Problems> In order to solve the above problems, the present invention has the following features:
As shown in the control circuit diagram shown in the figure, a refrigerant compression cycle is provided in which an electric compressor, an outdoor heat exchanger 3, a pressure reducer 4, and an indoor heat exchanger 5 are sequentially connected, and a refrigerant flow path is connected to the refrigerant compression cycle for heating. A refrigerant flow switching valve 1a is provided to switch the refrigerant flow path to one of the side and the cooling side, and the outdoor heat exchanger 3 and the indoor heat exchanger 5
and an inverter section 14 that controls the frequency and voltage of the power supply to the electric compressor.
, stop switch 16 and changeover valve changeover switch 1
A microcomputer 8 has an input terminal for inputting the signals of 7 and controls the inverter section 14, the switching valve 1a, the indoor blower 7, and the outdoor blower 6.
An inverter control section is constructed from these.

Then, the microcomputer 8
As shown in the functional block diagram shown in the figure, there is a valve switching means 8B that outputs a signal for switching the switching valve 1a from the heating side to the cooling side in response to a stop signal from the stop switch 16 during heating operation, and a valve switching means 8B that outputs a signal to switch the switching valve 1a from the heating side to the cooling side in response to a stop signal from the stop switch 16 during heating operation. indoor blower stopping means 8C for stopping the indoor blower 7; and compressor rotation speed reducing means 8D for outputting a compressor rotation speed reduction signal to the inverter section 14 in response to a stop signal from the stop switch 16.
and rotation speed determination means 8F for determining whether the reduction signal of the compressor rotation speed reduction means 8D has reached a predetermined value.
and a compressor stop means 8G that outputs a compressor stop signal to the inverter section 14 in response to a predetermined value attainment signal from the determination means 8F, and an outdoor blower that stops the outdoor blower 6 in response to a predetermined value attainment signal from the determination means 8F. A stop means 8H is provided.

<Function> In the above configuration, the indoor blower stopping means 8C stops the indoor blower 7 in response to an operation to stop the heating operation. Therefore, the indoor fan 7 is stopped at the same time as the stop operation, and the user's anxiety is alleviated.

The valve switching means 8B switches the switching valve 1a from the heating side to the cooling side in response to a stop signal from the stop switch 16 during heating operation. At this time, if the indoor fan 7 is stopped while the heating operation is continued without switching the switching valve 1a, the high temperature refrigerant is flowing through the indoor heat exchanger 5, so the refrigerant will not be cooled and the refrigerant pressure will rise abnormally. However, since it is controlled as described above, the refrigerant pressure does not rise abnormally and the refrigerant stops smoothly.

Then, in response to the stop signal from the stop switch 16, the compressor rotation speed reducing means 8D lowers the rotation speed of the electric compressor to a predetermined value, and then the rotation speed determining means 8D lowers the rotation speed of the electric compressor to a predetermined value.
The compressor stopping means 8 is activated by the minimum rotational speed reaching signal of F.
G and the outdoor blower stopping means 8H stop the electric compressor and the outdoor blower 8H. Therefore, an adverse effect on the transistors of the inverter section 14 is prevented.

<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.
4 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 for detecting room temperature, and 11 is an A/D converter that converts the room temperature detected by the thermistor 10 into a digital value and sends it to the input terminal of the microcomputer 8.
Input to IN1. 12 is a variable resistor for setting the room temperature, and 13 is an A/D converter, which converts the room temperature set by the variable resistor 12 into a digital value and inputs 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, 15' with diodes D ₁ to D ₄ and connects a capacitor C ₁₀
After smoothing with W, transistors Tr1 and Tr1'
The three phases, V phase by transistors Tr2 and Tr2', and U phase by transistors Tr3 and Tr3', are controlled respectively to generate three-phase alternating current, thereby operating the three-phase compressor motor 2. 16 is a run/stop switch, which is connected to the input terminal IN4 of the microcomputer 8. Reference numeral 17 denotes a cooling/heating selector switch for switching the four-way valve 1a, and is connected to an 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.
The transistor drive circuit 18
The rotation speed of the compressor motor 2 is controlled through the compressor motor 2, thereby making the cooling (heating) capacity variable. The microcomputer 8 and the inverter section 14 constitute a so-called pulse width modulation type inverter control section. Note that the capacitor C 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.

As shown in FIG. 5, the microcomputer 8 has a heating/cooling determining means 8A that determines whether a heating operation instruction or a cooling operation instruction is given based on the switching signal of the changeover switch 17.
Then, the switching valve 1a is switched to the heating side or the cooling side by the signal from the heating/cooling determining means 8A, and a signal is output to switch the switching valve 1a from the heating side to the cooling side by the stop signal from the stop switch 16 during heating operation. Valve switching means 8B outputs a signal to maintain the switching valve on the cooling side in response to a stop signal from the stop switch 16 during operation, and indoor blower stopping means 8C causes the indoor blower 7 to be stopped by a stop signal from the stop switch during heating operation. Compressor rotation speed reducing means 8D for outputting a compressor rotation speed reduction signal to the inverter section 14 in response to a stop signal from the stop switch 16;
and a rotation speed determining means 8F for determining whether the reduction signal of the compressor rotation speed reducing means 8D has reached a predetermined value (minimum rotation speed) set by the predetermined rotation speed setting means 8E, and the determining means 8F. A compressor stop means 8G outputs a compressor stop signal to the inverter unit 14 in response to a signal that a predetermined value (minimum rotation speed) has been reached, and a compressor stop means 8G outputs a compressor stop signal to the inverter section 14 in response to a signal that the determination means 8F has reached a predetermined value (minimum rotation speed). An outdoor blower stopping means 8H is provided to stop the outdoor blower.

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. It is depressurized in the chamber 4, evaporated in the indoor heat exchanger 5, and performs a cooling action.
The indoor blower 7 blows air to cool the room. on the other hand,
During heating operation, the four-way valve 1a is switched to the on state as shown in Fig. 2, and the refrigerant reverses its flow to the compressor 1 -> the four-way valve 1a -> the indoor heat exchanger 5 -> the pressure reducer 4 ->
The air flows through the outdoor heat exchanger 3 and air is blown by the indoor blower 7 to perform heating operation. During this operation, the compressor motor 2 is
Controls the rotation speed according to the room temperature, etc., for heating (cooling)
Change ability. For example, during heating operation, if the room temperature drops, the microcomputer 8 determines this and increases the frequency and voltage of the three-phase voltage energized to the compressor motor 2 by the output from the inverter section 14. Therefore, the rotation speed of the compressor motor 2 increases, the heating capacity increases, and the room temperature rises to the set temperature. Moreover, if the room temperature rises too much, the rotation speed of the compressor motor 2 will decrease.

To stop the heating (cooling) operation, the operation/stop switch 16 may be turned off. Where,
For example, capacitance variable width = frequency variable width is MAX100Hz,
If MIN30Hz is used, the magnitude of the back electromotive force generated from the compressor motor 2 when the operation is stopped will be approximately proportional to the energization frequency, that is, the rotation speed when off, as stated at the beginning, and therefore it will not be too high. If the frequency suddenly turns off, the inverter section 14
This is not preferable since it will have an adverse effect on the transistors Tr1, Tr1' to Tr3, Tr3'.

Therefore, when stopping heating operation, turn on/off switch 16 at point A as shown in the time chart in Figure 3.
If you operate and stop it, microcomputer 8 will work,
Switching means 8B turns off the four-way valve 1a (cooling side)
At the same time, the indoor blower 7 is stopped by the indoor blower stopping means 8C, and at the same time, the frequency of the compressor motor 2 is gradually lowered by the operation of the inverter section 14 in response to a signal from the compressor rotation speed lowering means 8D. Then, when the frequency of the compressor motor 2 reaches the minimum frequency after T hours from this stop operation, the compressor motor 2 and the outdoor blower 6 are stopped by the compressor stop means 8G and the outdoor blower stop means 8H. Therefore, heating operation is completely stopped at point B.

To explain the control operation of the microcomputer 8 using the flowchart shown in Fig. 4, it first determines whether the run/stop switch is off, and if it is not off, it goes into the operation loop, and if it is off, it stops the indoor fan and Switch the valve to the cooling side. After lowering the rotation speed of the compressor by one step, it is determined whether "the compressor rotation speed is at the minimum rotation speed." While the determination is NO, the rotation speed of the compressor is lowered by one step and the determination as to whether the rotation speed is the minimum is repeated. When the compressor reaches the minimum rotation speed, a command is given to stop the outdoor blower and compressor. Then wait until the run/stop switch is turned on.

Here, we will discuss the reason why the four-way valve 1a is turned off at the same time as the stop operation and the refrigerant compression cycle is switched to the cooling side. This is because high-temperature refrigerant is flowing through the exchanger 5, so the refrigerant is no longer cooled, and the refrigerant pressure increases abnormally, which is dangerous.

Note that when stopping the cooling operation, the indoor blower 7 is stopped in response to the operation of the run/stop switch 16, and after the rotation speed of the compressor motor 2 is reduced to a predetermined value, the compressor motor 2 and The outdoor blower 6 is stopped. At this time, there is no need to switch the four-way valve 1a as when stopping the heating operation.

By doing so, if the air conditioner is a separate type, when the operation/stop switch 16 is operated to stop the indoor blower 7, the indoor blower 7 will immediately stop, so the user can operate the outdoor compressor 1, the outdoor blower 6 is operating, so you don't have to feel anxious as mentioned above.

<Effects of the Invention> As is clear from the above description, according to the present invention, the indoor blower stopping means stops the indoor blower in response to the heating operation stop operation, so the indoor blower stops at the same time as the stop operation, and the indoor blower is stopped when the heating operation is stopped. Furthermore, since the heating/cooling determining means and the valve switching means switch the switching valve from the heating side to the cooling side in response to a stop signal from the stop switch during heating operation, the refrigerant pressure does not rise abnormally. Furthermore, after the compressor rotation speed reducing means lowers the rotation speed of the electric compressor to a predetermined value based on the stop signal from the stop switch, the compressor is stopped by the minimum rotation speed reaching signal from the rotation speed determination means. Since the electric compressor and the outdoor blower are stopped by the means and the outdoor blower stopping means, it is possible to prevent an adverse effect on the transistors of the inverter section.

[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 microcomputer. 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, 14: Inverter section, 1
6: Run/stop switch, 17: Cooling/heating switch.

Claims (1)

[Claims] 1. A refrigerant comprising a refrigerant compression cycle in which an electric compressor, an outdoor heat exchanger, a pressure reducer, and an indoor heat exchanger are sequentially connected, and in which the refrigerant flow path is switched to one of the heating side and the cooling side. A flow path switching valve is provided, each of the outdoor heat exchanger and the indoor heat exchanger is provided with a blower, an inverter section that controls the frequency and voltage of the power supply to the electric compressor, and a stop switch and a switching valve selector switch. The inverter control section is composed of a microcomputer that has an input terminal for inputting the information and controls the inverter section, the switching valve, the indoor blower, and the outdoor blower, and the microcomputer is switched by a stop signal from a stop switch during heating operation. a valve switching means for outputting a signal to switch the valve from the heating side to the cooling side; an indoor blower stopping means for stopping the indoor blower in response to a stop signal from a stop switch during heating operation; Compressor rotation speed reduction means for outputting a compressor rotation speed reduction signal, rotation speed determination means for determining whether the reduction signal of the compressor rotation speed reduction means has reached a predetermined value, and a predetermined value for the determination means. Compressor stopping means outputs a compressor stop signal to the inverter section in response to an arrival signal, and outdoor blower stopping means stops the outdoor blower in response to a predetermined value arrival signal from the determining means. air conditioner control circuit.