JPS624618B2 - - 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> In an air conditioner that is equipped with a refrigerant compression cycle in which an electric compressor, a condenser, a pressure reducer, and an evaporator are connected in sequence, and a blower is provided in the condenser and evaporator, the power supply to the electric compressor is There is an inverter control method that controls the frequency and voltage of the motor.This method allows stepless control of the rotation speed and is very effective in keeping room temperature fluctuations small.

However, in this type of air conditioner, when the operation of the air conditioner is stopped, a back electromotive force is generated in the compressor when the power is turned off, which may adversely affect the inverter section. 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, conventionally, as shown in the time chart in Figure 7, if a stop operation is performed at point A, the rotation speed of the compressor at that point is sequentially decreased at a fixed ratio, and the compressor is stopped after reaching the minimum rotation speed. He adopted the method of letting people know.

However, in this case, for example, when operating at the maximum rotation speed, it will stop at point C after ₂ hours, and when operating at 65% rotation speed, it will stop at point B after ₁ hour, and at the minimum rotation speed of 30%. When the compressor is in operation, it will stop at point A, so the time from when the stop switch is operated to when the compressor stops will vary depending on the operating state at the time of the stop, causing a sense of uneasiness to the user. It was hot.

<Purpose> In order to solve these problems, the present invention has the following objectives:
The purpose of this invention is to provide a control circuit that can stop an electric compressor by delaying the operation stop operation by a certain period of time.

<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 a condenser, 4 is a pressure reducer such as a capillary tube, and 5 is an evaporator, which are connected to the compressor 1 in a closed circuit to form a refrigerant compression cycle. 6 is an outdoor blower provided corresponding to the condenser 3, and 7 is an indoor blower provided corresponding to the evaporator 5.

8 is a general one-chip microcomputer (hereinafter referred to as microcomputer), which has input terminals IN1 to IN.
3 and output terminals OUT1 to OUT5, 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 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 uses the values to set the three-phase voltage U, which energizes the compressor motor 2 via the inverter section 14.
Output terminal for signals that control the frequency and voltage of V and W
The output is output from OUT1 to OUT3, thereby controlling the rotation speed of the compressor motor 2 and making the cooling capacity variable. Microcomputer 8 and 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'.

Control outputs for the outdoor fan 6 and indoor fan 7 are generated at output terminals OUT4 and OUT5 of the microcomputer, respectively.

Next, the various functions (means) of the microcomputer 8 will be explained based on the functional block diagram in Figure 2.
a compressor rotation speed reducing means for outputting a signal to the inverter section to reduce the rotation speed of the electric compressor at a predetermined rotation speed reduction rate in response to a stop signal from the stop switch; Compressor rotation speed detection means detects and outputs a substantially minimum rotation speed detection signal when the compressor reaches a substantially minimum rotation speed; a timer means for outputting a count-up signal when the delay time has elapsed; and a compressor stop means for outputting an electric compressor stop signal to the inverter section based on an AND condition of the count-up signal and the substantially minimum rotational speed detection signal. and are forced to have it.

Further, the compressor rotation speed lowering means stores a rotation speed reduction rate for lowering the maximum rotation speed of the compressor to the minimum rotation speed within the delay time T, and is configured to reduce the rotation speed by outputting a stop signal from the stop switch 16. The rotation speed is reduced at a fixed rotation speed reduction rate that is stored.

The compressor rotation speed detection means recognizes a rotation speed reduction command output from the compressor rotation speed reduction means to the inverter section, and also detects a compressor stop means when the rotation speed reduction command becomes a minimum rotation speed reduction command. This outputs a minimum rotation speed detection signal.

The timer means counts time by inputting a clock signal, and outputs a count-up signal when a predetermined delay time has elapsed.
That is, the delay time T stored in the ROM and the time counted by clock input are compared at any time, and a signal is output when the count reaches a set value (stored value).

Note that the microcomputer 8 has functions for performing various controls in addition to the above-mentioned functions, but these functions are not directly related to the present invention and will therefore be omitted.

In the above configuration, the compressor 1 is driven by the compressor motor 2 during cooling operation. Then, the refrigerant compressed by the compressor 1 is cooled and condensed by the air from the outdoor blower 6 in the condenser 3, and then reduced in pressure by the pressure reducer 4, evaporated in the evaporator 5, performs a cooling effect, and then transferred to the indoor blower 7. blows air to cool the room.

Meanwhile, during this operation, the rotation speed of the compressor motor 2 is controlled via the microcomputer 8 and the inverter section 14 according to the room temperature, etc., and the cooling capacity is varied. In other words,
If the room temperature rises, 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 cooling capacity increases, and the room temperature is lowered to the set temperature. On the other hand, if the room temperature drops too much, the rotation speed of the compressor motor 2 will decrease.

To stop the cooling operation, the operation/stop switch 16 may be turned off. For example, the capacitance variable width = frequency variable width is MAX100Hz, MIN30Hz.
In this case, the magnitude of the back electromotive force generated from the compressor motor 2 when the operation is stopped will be approximately proportional to the energizing frequency, that is, the rotation speed when off, as stated at the beginning, and therefore, if the frequency is too high, It is not preferable for the transistors Tr1, Tr1' to Tr3, Tr3' of the inverter section 14 to be suddenly turned off. Therefore, the rotation speed of the compressor motor 2 is lowered before turning it off. However, simply lowering the rotation speed causes variations in the stop time, which makes the user feel uneasy. make it work.

In other words, as shown in the time chart in Figure 3,
The time from stop operation A of the run/stop switch 16 to complete stop E is made constant, and the time to reduce the compressor motor 2 from the maximum rotation speed to the minimum rotation speed is T.
For example, if you were driving at 65% speed,
T After reducing the rotation speed to the minimum rotation speed for ₃ hours, the compressor motor 2 is operated at the same minimum rotation speed until E, and then the compressor motor 2 is completely stopped.

Also, if you were driving at 30% speed, the E
Run it and then stop it. That is, the AND condition of whether the minimum rotation speed has been reached or time T has been reached is taken, and the compressor motor 2 is thereby stopped.

That is, when the stop switch 16 is operated,
The compressor rotation speed reducing means of the microcomputer 8 outputs a signal for controlling the transistors of the inverter section 14 so as to reduce the rotation speed of the compressor over time.
For example, lower the frequency by 1Hz every second.
Specifically, assume that the code signal that instructs the compressor to operate at the highest speed is "11111." Assuming that the compressor motor 2 is at the highest speed when the stop switch 16 is operated, the commands to the inverter section 14 decrease over time, such as "11110", "11101", and "11100" every second. If the command corresponding to the minimum rotation speed is "00010", when the command becomes "00010" in the microcomputer 8, the compressor rotation speed detection means recognizes the command and sends the minimum rotation speed detection signal to the compressor stop means. Make it output.

In this case, strictly speaking, the compressor is not at its lowest level when "00010" is commanded, but it outputs a signal indicating that it has reached its lowest level.

Further, the timer means counts time by inputting a clock signal, and outputs a count-up signal when a predetermined delay time comes. That is, the delay time T stored in the ROM and the time counted by the clock input are compared at any time, and a signal is output when the count reaches a set value (stored value). In the compressor stop means of the microcomputer 8, the count-up signal of the timer means and the minimum rotation speed detection signal from the compressor rotation speed detection means are combined.
According to the AND condition, when both match, a stop signal is output to the inverter section. As a method of stopping, the microcomputer 8 outputs a signal (for example, "00000") that turns off all transistors in the inverter section. FIG. 4 is a flowchart regarding the above control.

In this way, by making the time constant from the stop operation of the operation stop switch 16 until the compressor motor 2 is lowered to the minimum rotational speed and stopped, the adverse effect of the back electromotive force on the inverter section 14 can be prevented, and at the same time, This can eliminate the user's anxiety.

FIG. 5 shows another embodiment of the invention. This is to reduce the rotation speed of the compressor motor 2 at a rate of decrease corresponding to the rotation speed when the stop switch is operated, and to keep the time T until the rotation speed reaches the minimum rotation speed constant.

The compressor rotation speed lowering means of the microcomputer 8 lowers the compressor motor 2 when the stop switch 16 outputs the stop signal.
The rotation speed of the compressor is read by the compressor rotation speed detection means, and the rotation speed N is divided by the delay time T stored in the ROM to calculate the rate of decrease in the rotation speed. It outputs a signal that reduces the rotation of the compressor motor 2.

Note that the other configurations are the same as those in the above embodiment.

In the above configuration, as shown in the time chart in FIG. 5 and the flowchart in FIG. The rotation speed of the compressor motor 2 is lowered by the above-mentioned embodiment, and the compressor is stopped based on the AND condition of the minimum rotation speed detection signal of the compressor rotation speed detection means and the count-up signal from the timer means. .

It should be noted that the present invention is not limited to the above embodiments, and it goes without saying that many modifications and changes can be made to the above embodiments within the scope of the present invention.

For example, the rotational speed of the compressor motor 2 when it is stopped does not necessarily have to be the minimum rotational speed, and can be close to the minimum rotational speed.

Further, the outdoor blower 6 and the indoor blower 7 may be stopped at the same time as the compressor motor 2 is stopped, or may be stopped before that.

<Effects> As is clear from the above description, the present invention provides an air conditioner equipped with a refrigerant compression cycle in which an electric compressor, a condenser, a pressure reducer, and an evaporator are sequentially connected. An inverter control section is composed of an inverter section that controls the frequency and voltage, and a microcomputer that has an input terminal that inputs a stop switch signal and an output terminal that outputs a control signal to the inverter section. a compressor rotation speed reducing means for outputting a signal to the inverter section to reduce the rotation speed of the electric compressor at a predetermined rotation speed reduction rate in response to a stop signal from the stop switch; Compressor rotation speed detection means detects and outputs a substantially minimum rotation speed detection signal when the compressor reaches a substantially minimum rotation speed; a timer means for outputting a count-up signal when the delay time has elapsed; and a compressor stop means for outputting an electric compressor stop signal to the inverter section based on an AND condition of the count-up signal and the substantially minimum rotational speed detection signal. The present invention relates to a control circuit for an air conditioner, characterized in that it has the following features:

Therefore, according to the present invention, the rotational speed of the electric compressor when it is stopped is reduced to approximately the minimum rotational speed, so that the back electromotive force generated in the electric compressor when it is stopped does not adversely affect the inverter section. Furthermore, regardless of the rotational speed of the electric compressor when the stop switch is operated to stop it, it is delayed by a certain delay time and then stopped, reducing user anxiety due to variations in the time it takes to stop. It can also relieve feelings.

[Brief explanation of the drawing]

FIG. 1 is a control circuit diagram showing one embodiment of the present invention;
Fig. 2 is a functional block diagram of the microcomputer, Fig. 3 is a time chart showing its stopping operation, Fig. 4 is a control flowchart of the same, and Fig. 5 is a time chart showing the stopping operation of another embodiment of the present invention. Chart, Figure 6 is its control flowchart, Figure 7
The figure is a time chart showing a conventional example. 1: Compressor, 2: Compressor motor, 3: Condenser,
4: Pressure reducer, 5: Evaporator, 6: Outdoor blower, 7:
Indoor blower, 8: Microcomputer, 14:
Inverter section, 16: Run/stop switch.

Claims (1)

[Claims] 1 In an air conditioner equipped with a refrigerant compression cycle in which an electric compressor, condenser, pressure reducer, and evaporator are connected in sequence, an inverter unit that controls the frequency and voltage of the power supply to the electric compressor, and a stop switch signal An inverter control section is constituted by a microcomputer having an input terminal for inputting a control signal and an output terminal for outputting a control signal to the inverter section. Compressor rotation speed reducing means outputs a signal to reduce the rotation speed of the compressor at a predetermined rotation speed reduction rate; and detecting the rotation speed of the electric compressor and detecting the rotation speed of the electric compressor when the rotation speed of the compressor reaches a substantially minimum rotation speed. Compressor rotation speed detection means for outputting a substantially minimum rotation speed detection signal, and timer means for counting a certain delay time from the input of the stop signal of the stop switch and outputting a count-up signal when the delay time has elapsed. and AND of the count-up signal and the substantially minimum rotation speed detection signal.
1. A control circuit for an air conditioner, comprising compressor stop means for outputting an electric compressor stop signal to the inverter section depending on conditions.