JPH0238867B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION TECHNICAL FIELD The present invention relates to an air conditioner that has a refrigerant compression cycle and whose capacity is variable through frequency conversion control.

Conventional technology A conventional air conditioner has an outdoor heat exchanger installed outdoors, an indoor heat exchanger installed indoors, and a connection between the outdoor heat exchanger and the indoor heat exchanger. It includes a pressure reducer that reduces the pressure of the refrigerant gas, and a switching valve that compresses the refrigerant gas and sends the compressed refrigerant gas to the outdoor heat exchanger during cooling and to the indoor heat exchanger during heating. It has a refrigerant compression cycle consisting of an electric compressor.

When operating an air conditioner in an ordinary home, there is a regulation that requires the use of a circuit breaker with an electrical wiring capacity of 20A. If the load current exceeds 20A while the air conditioner is in operation, the circuit breaker will trip and the power will be cut off, or the air conditioner's protection circuit will trip and stop the operation. In order to protect the indoor heat exchanger from heat, a protection circuit is activated to stop the electric compressor when the temperature exceeds a predetermined value. Therefore, conventional air conditioners have a structure that cuts off the power to the electric compressor if an abnormal temperature rise occurs in the indoor heat exchanger during heating or if the rated current of the air conditioner is exceeded. The air conditioner stops operating due to the temperature. To restart a stopped air conditioner,
It is troublesome to have to turn the air conditioner on again or press the reset button.

Purpose The purpose of the present invention is to solve the above-mentioned technical problem and to solve the problem when an abnormal temperature rise occurs in the indoor heat exchanger of an air conditioner or when the load current of the air conditioner exceeds the rating. To provide an air conditioner capable of returning to the original normal operation without stopping the operation of the air conditioner even in the event of a failure.

The present invention provides: an electric compressor that compresses refrigerant gas; an outdoor heat exchanger installed outdoors; an indoor heat exchanger installed indoors; an outdoor heat exchanger and an indoor heat exchanger. A pressure reducer that reduces the pressure of refrigerant gas, and a switching valve that switches between sending refrigerant gas from the electric compressor to the outdoor heat exchanger and sending it to the indoor heat exchanger. In an air conditioner having a refrigerant compression cycle, the current detection means detects the load current of the electric compressor, the temperature detection means detects the temperature of the indoor heat exchanger, and the outputs of the current detection means and the temperature detection means In response, (a) when the load current detected by the current detection means exceeds a predetermined first value, the operation of lowering the drive frequency of the electric compressor by one predetermined step is repeated to lower the detected load current to the first value; 1 or less, and when the detected load current is less than a predetermined second value that is less than the first value, the operation of increasing the drive frequency by one step is repeated to make the detected load current equal to or greater than the second value, (b) When the temperature detected by the temperature detection means exceeds a predetermined third value, the drive frequency is lowered by one step and the operation lasting for a predetermined time is repeated to bring the detected temperature below the third value. , and when the detected temperature is less than a predetermined fourth value, which is less than a third value, means for increasing the driving frequency by one step and repeating an operation that lasts for a predetermined time to make the detected temperature equal to or higher than the fourth value. An air conditioner characterized by comprising:

Embodiment FIG. 1 shows the configuration of an embodiment of the present invention. The refrigerant compression cycle of the air conditioner includes an electric compressor 1, an outdoor heat exchanger 3, an indoor heat exchanger 5, a pressure reducer 4,
and a four-way switching valve 2. The electric compressor 1 includes a compressor 1b and an electric motor 1a that rotates the compressor 1b. The outdoor heat exchanger 3 is installed outdoors. The indoor heat exchanger 5 is installed indoors. The pressure reducer 4 connected between the outdoor heat exchanger 3 and the indoor heat exchanger 5 is for reducing the pressure of the refrigerant gas. Regarding the structure of the four-way switching valve 2, during heating operation, refrigerant gas is compressed by the compressor 1b and sent to the line 26, and then sent to the line 29 through the four-way switching valve 2. Further, the refrigerant gas sent from the line 28 is sent to the line 27 through the four-way switching valve 2, and returns to the compressor 1b. On the other hand, during cooling operation, the refrigerant gas is compressed by the compressor 1b and sent to the line 26,
It is sent to line 28 through four-way switching valve 2. Further, the refrigerant gas sent from the line 29 is sent to the line 27 through the four-way switching valve 2, and returns to the compressor 1b.

In the refrigerant compression cycle during room cooling, refrigerant gas circulates in the direction of the dashed arrow in FIG. When the compressor 1b rotates, the high temperature and high pressure refrigerant gas is sent to the line 26, passes through the four-way switching valve 2, and is sent to the line 28. The high temperature and high pressure refrigerant gas enters the outdoor heat exchanger 3 via line 28. The high-temperature, high-pressure refrigerant gas that has entered the outdoor heat exchanger 3 is cooled by air from the outdoor fan 6 and enters the pressure reducer 4 . The pressure reducer 4 reduces the pressure of the high-pressure refrigerant gas to a low-temperature, low-pressure gas. The low-temperature, low-pressure refrigerant gas cools the indoor heat exchanger 5.
Indoor air is cooled by blowing air from the indoor fan 7 to the indoor heat exchanger 5. The refrigerant gas that has passed through the indoor heat exchanger 5 is heated and sent to the line 29. The refrigerant gas entering the four-way switching valve 2 via the line 29 is
7 and returns to the delivery compressor 1b.

Next, in the refrigerant compression cycle during room heating, refrigerant gas circulates in the direction of the solid arrow in FIG. When the compressor 1b rotates, the compressed refrigerant gas, which has become high temperature and high pressure, is sent to the line 26, passes through the four-way switching valve 2, and is sent to the line 29. The high temperature and high pressure refrigerant gas enters the indoor heat exchanger 5 via line 29. The high-temperature, high-pressure refrigerant gas that has entered the indoor heat exchanger 5 warms the indoor heat exchanger 5. By blowing air from the indoor blower 7, the indoor heat exchanger 5 is cooled, and the refrigerant gas is also cooled. The air is warmed by this blast of air, heating the room. The high-pressure refrigerant gas sent out from the indoor heat exchanger 5 is depressurized by the pressure reducer 4 and becomes a low-temperature, low-pressure refrigerant gas. The low-temperature, low-pressure refrigerant gas cools the outdoor heat exchanger 3. The refrigerant gas is warmed by the air blown from the outdoor side blower 6. The refrigerant gas sent out from the outdoor heat exchanger 3 passes through the four-way switching valve 2 via the line 28, is sent out to the line 27, and returns to the compressor 1b.

The processing circuit 8 realized by a microcomputer etc. has input terminals IN1 to IN3 and an output terminal.
It has OUT1 to OUT6. The processing circuit 8 also includes a read-only memory that stores programs, a random access memory that temporarily stores data, and an arithmetic circuit that performs arithmetic operations.
Clock oscillation circuit 9 is used to generate a reference clock pulse for operating processing circuit 8. Contact 13b of power switch 13 and reactor 1
2 is connected to the contact 13a of the power switch 13.
A reactor 12 to which a commercial AC power supply 20 is connected.
and the converter circuit 21 are connected by an electric wire 23. The reactor 12 is for improving the power factor. The converter circuit 21 includes an electric wire 23 from the reactor 12 and an electric wire 30 from the commercial AC power supply 20.
Power is supplied by the converter, which converts AC power into DC power. Current transformer 10 electromagnetically coupled to line 23 connecting reactor 12 and converter circuit 21
is a current transformer that detects the load current flowing through line 23. The output of the current transformer 10 is input to an analog/digital conversion circuit 11 that converts an analog signal into a digital signal. The analog signal of the current detected by the current transformer 10 is converted into a digital signal by the analog/digital conversion circuit 11, and the digital signal enters the input terminal IN1 of the processing circuit 8. A thermistor 16 that detects a temperature, such as the inlet temperature of the refrigerant of the indoor heat exchanger 5 or the temperature of air blown into the room, is connected to the analog/digital conversion circuit 15. The analog signal from the thermistor 16 is converted into a digital signal by the analog/digital circuit 15, and the digital signal is input to the input terminal IN2 of the processing circuit 8. An indoor temperature setting variable resistor 18 used to set the indoor temperature is connected to the analog/digital conversion circuit 17. The analog signal from the indoor temperature setting variable resistor 18 is converted into a digital signal by the analog/digital conversion circuit 17, and then sent to the input terminal IN3 of the processing circuit 8.
is input.

The output from the output terminal OUT1 of the processing circuit 8 is
The signal is input to the drive circuit 14. The output from the drive circuit 14 turns the power switch 13 ON and OFF. Outputs from the output terminals OUT2 to OUT4 enter the inverter drive circuit 19 and are amplified. The output from the inverter drive circuit 19 is input to the inverter circuit 22, and the output of the inverter circuit 22 is U,
The electric motor 1a is driven by V and W. Inverter circuit 22 exchanges DC power from converter circuit 21 into three-phase AC power. The frequency of the three-phase AC power output from the inverter circuit 22 changes in response to signals from the output terminals OUT2 to OUT4 of the processing circuit 8. The rotation speed of the electric compressor 1 is thereby controlled. The output from the output terminal OUT5 is input to the drive circuit 24, and the output from the drive circuit 24 drives the indoor fan 7. Output terminal OUT6
The output from the drive circuit 25 is input to the drive circuit 25, and the output from the drive circuit 25 drives the outdoor fan 6.

Next, the operation of the processing circuit 8 will be explained based on the flowchart of FIG. 2 while referring to FIG. In step n1, when the air conditioner is turned on, the processing circuit 8 starts operating. step n2
At this point, the power switch 13 is turned on and the air conditioner starts operating. The processing circuit 8 enters an operational state in which it can respond to command signals from each circuit. step
At n3, it is determined whether the air conditioner should be placed in the operating mode or in the stop mode, and when the air conditioner is in the operating mode, the process moves to step n4, and when the air conditioner is in the stop mode, the process moves to step n10. The operating mode refers to a state in which the electric compressor 1 is operating when the indoor temperature is not equal to the preset temperature, and the stop mode refers to a state in which the electric compressor 1 is operating when the indoor temperature is equal to the preset temperature. This refers to the state in which the electric compressor 1 is stopped. In step n10, a stop mode process is performed to stop the electric compressor 1.

In step n4, it is determined whether the load current of the air conditioner in operation is less than a predetermined value, for example 20A, and if it is less than 20A, the process moves to step n5.
If it exceeds 20A, move to step n11. In step n11, in order to lower the load current, the frequency of the three-phase AC power output from the inverter circuit 22 is lowered by one step (ie, a predetermined value), and the rotational speed of the electric compressor 1 is lowered. By repeating steps n4 and n11 in this way, when the load current exceeds the predetermined set value of 20A, the driving frequency of the electric compressor is sequentially lowered by the predetermined value as described above. and set the load current to 20A or less.

In step n5, during heating, it is determined whether the temperature of the indoor heat exchanger 5 is below a predetermined value, for example, 55 degrees Celsius. When it is over, move on to step n12. 55 degrees Celsius is selected within a safe temperature range that will not cause damage due to the thermal stress of the materials that make up the indoor heat exchanger 5. step
At n12, in order to lower the temperature of the indoor heat exchanger 5, the operating frequency of the electric compressor 1 is lowered to lower the operating capacity. At step n13, the timer of the processing circuit 8 is set to a predetermined time of 5 minutes. During these 5 minutes, the temperature of the indoor heat exchanger 5 is
It is predetermined that the time required for the temperature to drop to a certain level is about 5 minutes. In step n14, it is determined whether a predetermined time of 5 minutes has elapsed, and if it has elapsed, a flag signal is set to cause the analog/digital conversion circuit 15 to detect the temperature of the indoor heat exchanger 5 again. Return to step n5. By repeating the series of steps n5, n12, n13, and n14 in this way, when the temperature of the indoor heat exchanger 5 exceeds the predetermined set value of 55°C, the electric compressor 1 The state in which the driving frequency of
The operation that lasts for 5 minutes (as determined by n13) is repeated, thereby bringing the temperature of the heat exchanger 5 indoors to a predetermined set value of 55° C. or lower.

At step n6, the load current of the air conditioner is 18A.
It is determined whether or not the current is greater than or equal to 18A, and if it is greater than or equal to 18A, the process moves to step n7, and if it is less than 18A, the process moves to step n15. In step n15, the operating frequency of the electric compressor 1 is increased to return the air conditioner to its original operating capacity. In step n7, it is determined whether the temperature of the indoor heat exchanger 5 is equal to or higher than a predetermined value of 50 degrees Celsius, and if the temperature is equal to or higher than 50 degrees Celsius, the process returns to step n3.
If the temperature is less than 50 degrees Celsius, move to step n16. In step n16, the operating frequency of the electric compressor 1 is increased. At step n8, the timer of the processing circuit 8 is set to 5 minutes. In step n9, a flag signal is set to detect the temperature of the indoor heat exchanger 5 again when the timer has elapsed for 5 minutes, and step n9 is started.
Return to n7. The operation frequency of the electric compressor 1 is controlled by the operation of the processing circuit 8 as described above.

Effects As described above, according to the present invention, the load current of the electric compressor is detected by the current detection means 10, the temperature of the indoor heat exchanger is detected by the temperature detection means 16, and (a ) When the detected load current exceeds a predetermined first value (for example, 20A in the above embodiment), the operation of lowering the driving frequency of the electric compressor by one predetermined step is repeated, thereby increasing the detected load current to the first value. , and when the detected load current is less than a predetermined second value (for example, 18 A) that is less than the first value, the operation of increasing the driving frequency by one step is repeated, thereby increasing the detected load current to the above value. The second value shall be greater than or equal to the second value. In this way, it is possible to continue operating the air conditioner at the highest possible capacity within a range where the load current does not become excessive. Furthermore, (b) when the detected temperature exceeds a predetermined third value (for example, 55°C), lower the driving frequency by one step for a predetermined time (for example, 5 minutes);
The sustained operation is repeated, whereby the detected temperature is lower than or equal to the third value, and the detected temperature is lowered to a predetermined fourth value (for example, 50
℃), the drive frequency is increased by one step and the operation is repeated for a predetermined period of time (for example, 5 minutes), allowing the air conditioner to continue operating at its highest possible capacity during heating. becomes possible.

In this way, the load current of the electric compressor installed in the air conditioner will not become excessive and the operation will stop, and the temperature of the indoor heat exchanger will not rise abnormally and be damaged. be able to continue to operate at the highest possible capacity at all times without any
Comfortable air conditioning operation can be performed.

In addition, in the present invention, as described above, the drive frequency of the electric compressor is changed step by step, so the change in operation is smooth, and the noise does not change suddenly. It is possible to prevent excessive current from flowing through power transistors and the like included in inverter circuits and the like.

Furthermore, according to the present invention, when the detected temperature of the indoor heat exchanger exceeds the third value or is less than the fourth value, the driving frequency is changed by one step and then maintained for a predetermined time. By changing the driving frequency, the temperature of the indoor heat exchanger changes, and then the driving frequency is changed by one step again according to the detected temperature, so the driving frequency can be changed over a large range of fluctuations. The air conditioner can continue to operate stably without being changed.

[Brief explanation of drawings]

FIG. 1 is a block diagram of one embodiment of the present invention, and FIG.
The figure is a flowchart for explaining the operation of the processing circuit 8. 1...Electric compressor, 2...Four-way switching valve, 3...
Outdoor heat exchanger, 4... Pressure reducer, 5... Indoor heat exchanger, 6... Outdoor blower, 7... Indoor blower, 8... Processing circuit, 9... Clock oscillation circuit,
10... Current transformer, 11, 15, 17... Analog/digital conversion circuit, 12... Reactor, 13
... Power switch, 14, 24, 25 ... Drive circuit, 16 ... Thermistor, 18 ... Indoor temperature setting variable resistor, 19 ... Inverter drive circuit, 2
0...Commercial AC power supply, 21...Converter circuit,
22... Inverter circuit, 23, 30... Electric wire,
26, 27, 28, 29... line.

Claims (1)

[Claims] 1. An electric compressor that compresses refrigerant gas, an outdoor heat exchanger installed outdoors, an indoor heat exchanger installed indoors, an outdoor heat exchanger and an indoor heat exchanger. A pressure reducer that is connected between the electric compressor and the refrigerant gas to reduce the pressure of the refrigerant gas, and a switching valve that switches between sending the refrigerant gas from the electric compressor to the outdoor heat exchanger and sending it to the indoor heat exchanger. In an air conditioner having a refrigerant compression cycle, the air conditioner includes: a current detection means for detecting a load current of an electric compressor; a temperature detection means for detecting a temperature of an indoor heat exchanger; a current detection means and a temperature detection means; (a) When the load current detected by the current detection means exceeds a predetermined first value, the operation of lowering the drive frequency of the electric compressor by one predetermined step is repeated to detect the detected load current. is equal to or less than the first value, and when the detected load current is less than a predetermined second value that is less than the first value, the operation of increasing the drive frequency by one step is repeated to bring the detected load current to the second value. (b) When the temperature detected by the temperature detection means exceeds a predetermined third value, the drive frequency is lowered by one step and the operation is repeated for a predetermined period of time to lower the detected temperature to the third predetermined value.
and the detected temperature is less than a predetermined fourth value, which is less than the third value, the driving frequency is set to 1.
An air conditioner comprising means for increasing the detected temperature by a step and repeating an operation that lasts for a predetermined period of time to make the detected temperature equal to or higher than the fourth value.