JPS58115238A - Control circuit of air conditioner - Google Patents

Abstract

PURPOSE:To reduce gas sound generated when the changeover valve is switched by carrying out at least one switching operation among operations of switching the changeover valve from the heating mode operation to the defrosting operation and vice versa, after decreasing the electrically driven compressor to the minimum rotational speed. CONSTITUTION:During the heating mode operation, the coolant discharged from the compressor 1 flows in the sequence of four way valve 1a, indoor heat- exchanger 5, pressure reducing device 4 and outdoor heat exchanger 3, and the heating mode operation is carried out by a blast from an indoor blower 7. Then, a defrosting condition is satisfied during the heating mode operation, the rotational speed of the compressor motor 2 is gradually lowered to the minimum rotational speed while the heating mode operation is continued. After the compressor motor 2 has reached a state of the minimum rotational speed, the four- way valve 1a is changed over to a defrosting operation, and thereafter the rotational speed of the compressor motor 2 is gradually increased, and the freezing cycle is shifted to a full-scale defrosting mode operation.

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.

It is equipped with a refrigerant compression cycle in which an electric compressor, a refrigerant flow switching valve, an outdoor heat exchanger, a 1-pressure machine, 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. In air conditioners, frost forms on the outdoor heat exchanger during low temperature and high humidity during heating operation, reducing heating capacity and operation efficiency. It is necessary 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 be reversed, and the high-pressure part and low-pressure part of the refrigerant will eventually reach a pressure balance, resulting in quite loud gas noise. It was around the ear.

In view of the above, the present invention has been provided for the purpose of reducing gas noise generated when a switching valve is switched from heating operation to defrosting operation and from defrosting operation to heating operation.

2- Hereinafter, the present invention will be described in detail with respect to the illustrated embodiment.
In the figure, 1 is a compressor, 2 is a compressor motor that drives this compression +f9.1, 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, and 1a is a four-way valve as an example of a switching valve for switching the flow of refrigerant! ], these are connected to the compressor 1 in a closed circuit 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.

Reference numeral 8 denotes a general one-chip microcomputer (hereinafter referred to as MyFun), which has input terminals IN1 to ■N5 and output terminals OUT1 to OUT6, and internally includes a program RO and a data RAM.

A L Ll, and is driven by the reference clock oscillation section 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 inputs it to the input terminal IN1 of the microcomputer 8. 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 microcomputer 80 input terminal TN2. 14 is an inverter section, which rectifies the AC power input from the power terminals 15 and 15' with diodes D1 to D4, and connects the capacitor C4.
After smoothing at ゜), the run star Tr1. W at Tr1'
phase, transistor Tr2. Tr2' is V phase, transistor Tr3. The three phases of the U phase are each phase-controlled by Tr3' to generate three-phase alternating current, and the three-phase compressor motor 2 is operated. 1
6 is a run/stop switch, which is the input terminal IN of microcomputer 8.
Connected to 4. 17 is a cooling/heating selector switch for switching the four-way valve 1a, and is connected to the input terminal I of the microcomputer 8.
Connected to NS. The microcomputer 8 reads the room temperature from the input terminal INI and the room temperature set value from the input terminal IN2, and uses these values to control the frequency and voltage of the three-phase voltages U, V, and W that are energized to the compressor motor 2 via the impark section 14. A control signal is outputted from the output terminals 0UT1 to 0UT3-3=, thereby controlling the rotation speed of the compressor motor 2 via the transistor drive circuit 18 and making the cooling capacity variable. One is a thermistor for frost detection, and 20 is an A/D converter that converts the room temperature detected by the thermistor 19 into a digital value and sends it to the input terminal I of the microcomputer 8.
Input to NS.

The microcomputer 8 generates three-phase voltages U, \1, . A signal for controlling the frequency and voltage of W is output from the output terminals 0UT1 to 0UT3, and a signal for switching the four-way valve 1a to the OFF state (cooling side) is output. In this way, 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,'~c,,c3' are transistors Tri, T
r1. '-Tr3. This is to prevent Tr3' from malfunctioning due to noise. Also, resistor R1 and capacitor C, , R4 and C, , R2 and C5, R, , and C8,
Each RC series circuit consisting of R, and Cb, Rs and C5,
Tiger 5 due to back electromotive force after energization to compressor motor 2 is turned off
- 4- Register Trl, Trl'-Tr3. This is a discharge circuit to prevent damage to Tr3'. Microcomputer output terminal 0UT4
．． ○UT5,0UT6+: are outdoor blower 6 and indoor blower respectively? , a control output of the four-way valve 1a is generated.

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
After being cooled and condensed in the outdoor heat exchanger 3 by the air blown by the outdoor blower 6, the pressure is reduced in the pressure reducer 4, evaporated in the indoor heat exchanger 5 to perform a cooling effect, and the indoor blower 7 blows air to cool the room. do. 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. 3. First, when the defrosting condition (sensing the temperature drop of the outdoor heat exchanger (approximately -2° to 54° C.) is satisfied, the rotational speed of the electric compressor is controlled via the microcomputer 8 and impark unit 14.

-6= For example, when a defrost signal is input from a defrost thermostat etc. at point 1X, the microcomputer 8 and inverter unit 14 act to gradually reduce the rotation speed of the compressor motor 2 while continuing the heating operation. Reduce the rotation speed to the minimum. and compressor motor 2
After the rotational speed reaches the minimum rotational speed, 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 to enter defrosting operation. Then, the rotational speed of the compressor motor 2 is gradually increased by 1 to carry out a full-scale defrosting operation. At the end of the defrosting operation, when the defrosting end signal is input at the 0 point, the microcomputer 8 and inverter sections 1 and 1 operate in the same way as above, and the rotation speed of the compressor motor 2 is gradually reduced 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 in FIG. If so, branch to YES and take the route on the second to fourth side from the left in Figure 4, but if not, take the route on the first row. That is, if the "defrosting flag H" is NO, then it is determined whether the "defrosting signal -", that is, the defrosting 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 14 and the process returns to the beginning of the defrost loop. Also, if the electric compressor does not have the minimum rotation speed, it will jump and return to the beginning of the loop. In addition, if the "defrost signal -?" is NO, the heating operation is normally turned off.
Try to do E.

Also, if the "defrost flag H" branches to YES, it is determined here whether the "defrost signal H", that is, whether it is a signal for the end of defrosting, and if it is an end signal, then .

Take the four-sided route. If not, when entering the second route, it is determined whether the amount of circulating refrigerant in the refrigerant compression cycle has decreased to a predetermined value. This or rWArT in the figure
It corresponds to "Is it OK?" If the amount of refrigerant is decreasing, a command is given to switch the four-way valve to the defrosting side and stop the indoor and outdoor blowers.

Thereafter, it is determined whether the rotation speed of the compressor is the maximum rotation speed, and if the maximum rotation speed has not been reached, a command is given to lower the rotation speed of the compressor by one step. Please note that “WAJTOK?” is no.
If , and if "Compressor or maximum rotation speed" is YES, the process returns to the beginning of the defrosting loop again.

Also, if the "defrost signal 11" is YES, "compression (or minimum rotation speed - 1 or not) is set, and if the minimum rotation speed enters the fourth side of Figure 4, here. Determine whether the amount of circulating refrigerant in the refrigerant compression cycle has decreased to a predetermined value,
If the predetermined value has not been reached, return to the beginning of the loop, and if the predetermined value has been reached, "set the defrost flag to L", that is, set the defrost flag to the end of defrost, and then turn the four-way valve to the heating side. , and commands to operate the indoor and outdoor blowers to begin heating operation. Note that if "Is the compressor at the minimum rotation speed" is 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.

In addition, in the present invention, gas noise can be constantly reduced by controlling the compressor motor 2 before and after defrosting as in the above embodiment, but it is not always necessary to control before and after defrosting. It goes without saying that the gas noise can be reduced compared to the conventional method by only using either before or after defrosting, and it is also effective to do so.

As is clear from the above description, the present invention allows at least one of the switching operations of the switching valve from heating operation to defrosting operation and from defrosting operation to heating operation to be performed by changing the rotational speed of the electric compressor. According to the present invention, the rotation speed is lowered to approximately the minimum rotation speed and held there.
It is possible to reduce the gas noise generated when switching the switching valve, and there is an effect that 1) there is no generation of annoying noise even when sleeping.

[Brief explanation of drawings]

Fig. 1 is a control circuit diagram showing an 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, and Fig. 4 is a flow chart thereof. . 1: Compressor, 1a: West valve, 2: Compressor motor, 310
- 2 outdoor heat exchangers, 4: pressure reducer, 5: indoor heat exchanger, 6:
Outdoor blower, 7: Indoor air blower, 8: Microcomputer, 14: Inverter section, 16: Run/stop switch,
]7: Cooling/heating selector switch. Applicant Sharp Corporation Agent Tsunehisa Nakamura

Claims (1)

[Claims] Electric compressors, refrigerant flow switching valves, outdoor heat exchangers, pressure reducers,
It is equipped with a refrigerant compression cycle in which indoor heat exchangers are sequentially connected, and each of the outdoor heat exchanger and indoor heat exchanger is equipped with a blower, and an inverter control unit is installed to control the frequency and voltage of the power supply to the electric compressor. In the control circuit of the air conditioner, at least one of the switching operations of the switching valve from heating operation to defrosting operation and from defrosting operation to heating operation is performed so that the rotational speed of the electric compressor is set to approximately the minimum rotational speed. A control circuit for an air conditioner, characterized in that the operation is performed after being lowered and held.