JPS621496B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION 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.

Electric compressors, refrigerant flow switching valves, outdoor heat exchangers,
In an air conditioner equipped with a refrigerant compression cycle in which a pressure reducer and an indoor heat exchanger are sequentially connected, and a blower is provided in the outdoor heat exchanger and the indoor heat exchanger, respectively, the frequency and voltage of the power supply to the electric compressor There is an inverter control method that calculates the rotation speed from the room temperature, room temperature set value, and other outside temperature, etc., and automatically controls the rotation speed according to load fluctuations, keeping the range of room temperature fluctuations small. It is effective on However, if the electric compressor is operated at a low rotational speed during heating operation and frost forms on the outdoor heat exchanger, it may be necessary to enter defrosting operation and continue defrosting at the same rotational speed. When you do it,
There was a problem that the defrosting time was long due to the low rotation speed.

In view of the above, the present invention controls the rotation speed of the electric compressor during and before and after defrosting operation, shortens the defrosting operation time, suppresses the drop in room temperature as much as possible, and further suppresses the rise in room temperature after defrosting. The purpose of this invention is to provide a control circuit that allows the process to be performed quickly.

Hereinafter, the present invention will be described in detail 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. 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 a defrosting timer (software timer), which are driven by the reference clock oscillator 9. 10 is a thermistor for detecting room temperature, 11 is A/
The D converter converts the room temperature detected by the thermistor 10 into a digital value and sends it to the input terminal IN of the microcomputer 8.
Enter 1. 12 is a variable resistor for setting the room temperature, 1
3 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, in which the AC power input from power supply terminals 15 and 15' is rectified by diodes _D1 to _D4 , smoothed by a capacitor _C10 , and then converted to W phase by transistors Tr1 and Tr1', and W phase by transistors Tr2 and Tr2. ′, V phase, transistor Tr
3. Tr 3' controls the three phases of the U phase to generate three-phase alternating current and operate 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.
Microcontroller 8 connects input terminal IN1 to room temperature, input terminal
The room temperature setting values are read from IN2, and signals for controlling the frequency and voltage of the three-phase voltages U, V, and W that energize the compressor motor 2 via the inverter section 14 are output from the output terminals OUT1 to OUT3 based on the values. , thereby controlling the rotation speed of the compressor motor 2 via the transistor drive circuit 18 and making the cooling (heating) capacity variable. 19 is a thermistor for frost detection, and 20 is an A/D converter, which 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 outputs signals for controlling the frequency and voltage of three-phase voltages U, V, and W that are energized to the compressor motor 2 from the output terminals OUT1 to OUT3 according to the signals, and also outputs a signal for switching the four-way valve 1a. do. In this way, the microcomputer 8 and the inverter section 14
This constitutes a so-called pulse width modulation type inverter control section. In addition, inverter section 1
The capacitors C ₁ , C ₁ ′ to C ₃ , C ₃ ′ are for preventing the transistors Tr1, Tr1′ to Tr3, 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
Each RC series circuit consisting of C ₈ , R ₃ and C ₆ , and R ₆ and C ₉ prevents damage to transistors Tr 1 , Tr 1 ′ to Tr 3 , Tr 3 ′ due to back electromotive force after the compressor motor 2 is turned off. This is a discharge circuit to prevent this. Control outputs for the outdoor blower 6, indoor blower 7, and four-way valve 1a are generated at output terminals OUT4, OUT5, and OUT6 of the microcomputer, respectively.

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. Third
In the figure, the defrost signal is based on a signal from a defrost timer that is built into the microcomputer 8 and operates at a certain time period, and a temperature data signal from a defrost thermostat, etc. that detects the temperature of the outdoor heat exchanger 3. This is the signal that is output when For example, the defrost timer operates in a 60-minute cycle to perform heating operation for 50 minutes and defrost operation for 10 minutes, and the defrost thermostat outputs a signal indicating the end of defrosting when the temperature exceeds 10°C.
Assuming that a frosting signal is output at -2.5°C or lower, the defrosting signal starts defrosting under the AND condition of the defrosting timer and the defrosting thermostat, and ends defrosting under the OR condition. That is, the defrosting time ends when the defrosting thermostat reaches 10°C or higher, or when 10 minutes have passed, and the heating operation returns. For example, when the defrosting timer reaches point A, the microcomputer 8 and inverter section 14 operate to increase the rotation speed of the compressor motor 2 to the maximum rotation speed while continuing the heating operation. Then, at point B, after T1 time has elapsed from point A, a defrosting signal for switching the four-way valve 1a to the OFF state (cooling side) is output, the four-way valve 1a is switched, and the defrosting operation is started. During the defrosting operation, the compressor motor 2 is rotated at the maximum rotation speed. At the end of the defrosting operation, when the defrosting end signal is input at point C, the microcomputer 8
operates, outputs a signal to switch the four-way valve 1a from the cooling side to the heating side, and switches the four-way valve 1a. However, the compressor motor 2 then operates at the maximum rotation speed for a time T2, returns to the normal set rotation speed at point D, and continues operating. Note that after point E in Figure 3, the defrost signal is not output because the defrost thermostat is 10°C or higher when the defrost timer operates, and therefore the defrost signal is not output at point E. The compressor continues to operate at maximum rotation speed for T3 hours,
After that, it returns to the set rotation speed.

To explain this control operation using the flowchart in Fig. 5, first, it is determined by flag F (maximum rotation speed after defrosting) whether or not it is between C and D immediately after defrosting, and if it is not C to D, it is set to NO. Branch, then use the defrost flag (set during defrosting) to determine whether defrosting is in progress, and if NO, use the defrost timer to turn on the defrost time before the defrost time (3rd time).
(after point A in the figure). If NO, the system goes straight to OUT, and if YES, the compressor rotation speed is increased one step at a time to the maximum rotation speed in preparation for defrosting. Next, wait until the defrost timer reaches point B or above, and if it reaches point B or above, determine whether the defrost thermostat is below -2.5°C, and if it is below, set the defrost flag and exit to OUT. Then IN
Return to , and if YES is selected for ``Set defrost flag,'' switch the four-way valve to the cooling side, turn off the indoor and outdoor blowers, and start defrosting operation. And the defrost timer is C
Wait until the temperature reaches 10 degrees or the defrost thermostat reaches 10°C or higher, then finish defrosting and reset the defrost flag, switch the four-way valve to the heating side, and turn on the indoor and outdoor blowers. , completes the defrosting operation, sets flag F, and exits to OUT. Next, return to IN and check YES for "Set flag F"
If it branches to , the rotation speed of the compressor will be lowered one step at a time to the set rotation speed. Then, when the set rotation speed is reached, flag F is reset, the defrost timer is cleared, and the engine exits to OUT.

Here, the reason for operating at the maximum rotation speed between A → B and C → D is established based on Figure 4. Figure 4 a shows the room temperature change when operating at the maximum rotation speed only during defrosting operation. FIG. 4b shows the change in room temperature when A to B and C to D are also operated at the maximum rotational speed as in this embodiment. In the case of this a,
The room temperature begins to drop gradually from the start of defrosting operation, reaches its lowest level immediately after defrosting, and then returns to the original room temperature. However, in case b showing this embodiment, the room temperature rises a little before defrosting, that is, between A and B in FIG. Since the temperature increases with heating operation, the absolute value of the minimum room temperature is higher than in case a, that is, the difference from a is expressed as J. Furthermore, the temperature rise time T4 at the end of defrosting
With T5, T4>T5, and the temperature returns to the original room temperature faster in this example.

In the time chart of FIG. 3, the rotational speeds A to D are set to the maximum, but in the present invention, the rotational speed may not be the maximum, but may be around the maximum. Further, in the present invention, in addition to the control operation as in the above embodiment, a control operation as shown in the flowchart of FIG. 6 may be used. That is, it enters from IN and determines the defrost flag (set during defrosting), and if NO, then determines the frosting signal, and if it is OFF (no frosting), it goes directly to OUT.
If it is on (frosting), increase the rotation speed of the compressor one step at a time until it reaches the maximum rotation speed. Thereafter, it is determined whether the time T1 has elapsed, and if it has, the defrost flag is set, the four-way valve is switched to the cooling side, and the indoor and outdoor blowers are turned off to begin defrosting operation. Next, if it goes into IN and branches to YES based on the defrost flag judgment, it will judge whether the frosting signal is off, and if it is frosted, it will remain OUT and no frosting will occur (defrosting has finished).
If so, branch to YES, switch the four-way valve to the heating side, turn on the indoor and outdoor blowers, end the defrosting operation, and start the heating operation. Then, after T2 time has elapsed, the compressor rotation speed is lowered one step at a time, and when the set rotation speed is reached, the defrost flag is reset and the output goes out.

As is clear from the above description, in the present invention, the microcomputer switches the switching valve from the heating side to the cooling side at the start of the defrosting operation during heating, and switches the switching valve from the cooling side to the cooling side at the end of the defrosting operation. During the defrosting operation during heating and for a certain period of time before and after the defrosting operation during heating, a signal is sent to make the rotation speed of the electric compressor higher than the set rotation speed calculated based on the room temperature and the room temperature set value. Compressor control means for outputting to the inverter section is provided.

Therefore, according to the present invention, in particular, the temperature of the refrigerant in the refrigerant compression cycle is increased by operating at a rotation speed higher than the set rotation speed before switching the switching valve during defrosting operation during heating. By subsequently switching the switching valve, the high-temperature refrigerant is sent to the outdoor heat exchanger, allowing immediate defrosting, shortening the defrosting operation time, and suppressing the drop in room temperature as much as possible.

Further, by operating at a rotation speed higher than the set rotation speed after defrosting operation, the heat exchange temperature can be raised quickly, and the room temperature can be raised quickly after defrosting.

Further, by switching the refrigerant compression cycle, the high and low pressure sides are reversed, but by operating at a rotation speed higher than the set rotation speed after the defrosting operation, the refrigerant compression cycle can be stabilized at an early stage.

[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 a and b are time charts compared to the conventional control circuit, and FIG. 5 is a flow chart. FIG. 6 is a flowchart showing another embodiment of the present invention. 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 Equipped with a refrigerant compression cycle in which an electric compressor, a refrigerant flow switching valve, an outdoor heat exchanger, a pressure reducer, and an indoor heat exchanger are connected in sequence, and each of the outdoor heat exchanger and indoor heat exchanger is equipped with a blower. The air conditioner is provided with a room temperature detector that detects the room temperature, a room temperature setter that sets the room temperature, an inverter section that controls the frequency and voltage of the power supply to the electric compressor, and the inverter section and the switching valve. An inverter control unit is constituted by a microcomputer that controls the switching valve, and the microcomputer switches the switching valve from the heating side to the cooling side at the start of the defrosting operation during heating, and switches the switching valve from the cooling side to the cooling side at the end of the defrosting operation. and a switching means for switching from to the heating side, and during defrosting operation during heating and for a certain period of time before and after, the rotation speed of the electric compressor is set higher than the set rotation speed calculated based on the room temperature and the room temperature set value. A control circuit for an air conditioner, comprising compressor control means for outputting a signal to the inverter section.