JPH0532660B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Objective of the Invention) (Industrial Application Field) The present invention relates to a method for controlling an air conditioner in which a compressor motor that drives a compressor in a refrigeration cycle is operated by a power source with variable frequency output.

(Prior Art) An example of a general configuration of a refrigeration cycle of this type of air conditioner is shown in FIG.

FIG. 3 shows a refrigeration cycle that is equipped with a four-way switching valve 22 and is capable of both heating operation (solid line arrow) and cooling operation (broken line arrow). During heating operation, the refrigerant is transferred to compressor 2.
1 to four-way switching valve 22, indoor heat exchanger 23, expansion valve 24, outdoor heat exchanger 25, and four-way switching valve 22
The flow passes through the compressor 21 in the direction of reflux. For heating and cooling operation, the refrigerant is compressor 21.
From the four-way switching valve 221, the outdoor heat exchanger 25, the expansion valve 24, the indoor heat exchanger 23, and the four-way switching valve 22
The flow passes through the compressor 21 in the direction of reflux. In the apparatus shown in FIG. 3, the compressor 21 is connected to a compressor motor 26 which is operated at variable speeds, resulting in a variable capacity configuration. The indoor heat exchanger 23 is equipped with an indoor fan 23a, and the outdoor heat exchanger 25 is equipped with an outdoor fan 25a. The indoor heat exchanger 23 functions as a radiator during heating operation, and functions as a heat absorber (cooler) during cooling operation. Correspondingly, the outdoor heat exchanger 25 functions as a heat absorber during heating operation, and functions as a radiator during cooling operation.

Indoor fan 23a is stopped - Breeze operation (breeze) -
Switching operation such as strong wind operation (strong wind) is possible, and the switching is performed by the indoor control device 30 in FIG. 4 according to the temperature of the indoor heat exchanger 23 detected by a temperature detector (not shown). controlled. Outdoor fan 25a and compressor motor 26 are controlled by outdoor control device 31. The compressor motor 26 operates so that the motor current detected by a current transformer 33 and a current detection circuit 34 is within a predetermined range shown below via an inverter circuit 32 provided as an AC power source with variable frequency output. is controlled to take the value of .

That is, the compressor motor 26 has a second
As shown in figure a, the upper limit value UL for the operating current i
and a lower limit value LL are set, and the area below the lower limit value LL performs accelerated operation as a compressor speed increase zone (that is, compressor motor speed increase zone), and the area above the upper limit value UL performs deceleration operation as a compressor deceleration zone. Let's do it. The region between the lower limit value LL and the upper limit value UL is the compressor stability holding zone, and constant speed holding operation is performed.

The above operation mode is shown in a flowchart as shown in FIG. 5. Upon start of operation, the step
While detecting the current of the compressor motor 26 in step S1, the compressor motor 26 is detected in step S2.
1 (that is, compressor motor 26). It continues unless i>UL. When i>UL, the compressor 21 is decelerated in step S4. In step S3, it is determined whether or not i>UL. The reduction in motor current i resulting from the compressor deceleration in step S4 is monitored in step S5;
If i≧LL, proceed to step S6 and maintain the compressor speed at that time; if i<LL, proceed to step S2.
Return to When i>UL, the process returns to step S4 and deceleration is performed.

(Problems to be Solved by the Invention) As already mentioned, the speed of the indoor fan 23a is changed according to the temperature of the indoor heat exchanger 23,
In particular, when the heating starts immediately after the heating operation starts, the indoor heat exchanger 23 is in a low temperature state, so the indoor fan 2
If the compressor 3a is stopped or operated in a light breeze (low speed), the load on the compressor 21 increases.
1 is decelerated, even if the indoor fan 23a is switched to strong wind operation due to the temperature rise of the indoor heat exchanger 23 and the load on the compressor 21 is reduced, LL≦
As long as i≦LU, constant speed operation is maintained, and the motor current i may continue to operate at a current value just below the lower limit value LL. This tendency is particularly noticeable when heating operation is started when the indoor temperature is relatively high.

This situation results in the air conditioner being operated below its maximum capacity, slowing down the room temperature rise time, even though it is desirable to operate the air conditioner at its maximum capacity to achieve a rapid rise in room temperature. A similar situation can be said about the fall in room temperature during cooling operation.

Therefore, it is an object of the present invention to control an air conditioner that achieves performance improvement and shortens room temperature rise time or fall time under the condition that the compressor motor is operated within the limited current range. The purpose is to provide a method.

(Structure of the Invention) (Means for Solving the Problems) The control method of the present invention detects the current flowing through the compressor motor, and when the detected current value exceeds a first set value, the power supply is turned off. When the frequency is lowered and the detected current value falls below the second set value, which is lower than the first set value, the frequency of the power supply is increased, and the detected current value becomes lower than the first set value. When the current value changes from a large value to the first set value and the second set value lower than that, the power supply frequency at that time is maintained, and the detected current value continues for the set time. The present invention is characterized in that the frequency of the power source is increased when the value is between the first set value and the second set value.

(Function) According to the above method, the current of the compressor motor is detected, and the compressor motor can be operated at almost maximum capacity within the limited current range according to the detected current value and its change mode. It is possible to shorten the start-up or fall time of air conditioning immediately after the start of operation while maintaining stable operation.

(Example) FIG. 1 is a flowchart showing an example of the present invention. This flowchart differs from that shown in FIG. 5 in that step S7 and step S8 are added after step S6. In step S7, for example, a time TA approximately equal to the heating start-up time at the start of heating operation is set, and the time t from the start of operation is compared with the time TA, and t<
If it is TA, proceed to step S8. By the way, time
TA may be about several tens of minutes during heating, and about half that during cooling. When t≧TA, jump to step S5.
In step S8, it is determined whether the YES condition in step S5, that is, the state LL≦i≦UL, has continued for a preset time TB (<TA) or more. If it has continued, the process jumps to step S2 and the compressor 21 is , the speed is increased until the motor current i reaches the upper limit value UL. If the judgment result in step S8 is NO, the process jumps to step S5. Time TB
For example, it may take several minutes.

In steps S7 and S8 described above, the current of the compressor motor 26 is continuously increased within the operation start time TA to exceed the shorter predetermined time TB LL≦
When I≦UL, the speed of the compressor motor 26 is increased so that the current i of the compressor motor 26 takes the upper limit value UL, and the condition of step S8 is not satisfied or the time TA after the start of operation is increased.
When t≧TA has passed, the operation mode is exactly the same as that shown in FIG. 5, which has already been described.

Figure 2 shows (a) motor current i, (b) compressor motor speed, and indoor fan operation when heating is performed according to the control method of the present invention and when heating is performed according to the conventional method. A typical example of the mode is schematically shown. When the compressor motor 26 is started at time t=0, the motor current i and motor speed gradually increase, and at time _t1 , the motor current i
When reaches the upper limit value UL, compressor motor 2
6 is decelerated by one step, and the motor current i is decreased. Up to this point, the temperature of the indoor heat exchanger 23 has been low, so
The indoor fan 23a remains stopped. However, in this state, the load on the compressor 21 is large, so the current i in the compressor motor 26 starts to increase again, and exceeds the upper limit value UL again at time _t2 , so the compressor motor 26 is decelerated by one more step, and the motor current Try to reduce i. If the temperature of the indoor heat exchanger 23 reaches a predetermined value around this point, the indoor fan 23a will be operated with a gentle breeze. As a result, the load on the compressor 21 is slightly reduced, and the motor current i changes to the constant speed holding zone (LL≦i≦
UL). The compressor motor 26 is
It operates at constant speed as long as LL≦I≦UL. Time t ₃
Assume that the indoor fan 23a is switched to strong wind operation due to a further rise in the temperature of the indoor heat exchanger 23. As a result, the load on the compressor 21 is further reduced, and the motor current i is reduced at an even greater rate. However, when the continuous operation time in the constant speed holding zone reaches a preset time TB at time _t4 , the speed increase control of the compressor motor 26 is performed according to the present invention, and the motor current i is operated at approximately the upper limit value UL. Do it like this. In the illustrated example, the motor current i reaches the upper limit value UL at time _t5 , and thereafter the motor is operated at a constant speed. By operating the compressor motor 26 at almost the upper limit value UL of the motor current i, the compressor 21 operates at the highest speed within the limit of the motor current, that is, the highest operation of the refrigeration cycle, and the heating starts quickly. can do.

Incidentally, if the control method of the present invention is not adopted, after time _t4 , LL≦i≦UL, as shown by the broken line.
As long as the motor current i remains close to the lower limit value LL, the compressor motor 26
Speed increase control will not be performed. Therefore, unlike the present invention, the maximum capacity operation of the refrigeration cycle is not necessarily performed under restricted conditions, and the heating start-up speed may become slow.

Although the present invention has been described above with respect to the case where the air conditioner is operated for heating, the present invention can also be applied to the case where the air conditioner is operated for heating. In that case, when the temperature of the indoor heat exchanger, which functions as a heat absorber or cooler, is high, the indoor fan is stopped, and as the temperature of the indoor heat exchanger becomes low, the indoor fan is switched between operating with a light breeze and strong wind. It turns out.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to improve performance and shorten the rise time or fall time of room temperature, provided that the compressor motor is operated within the limited current range. .

[Brief explanation of the drawing]

Fig. 1 is a flowchart for explaining an embodiment of the present invention, Fig. 2 is a time chart for comparing and explaining the control method of the present invention and a conventional control method, and Fig. 3 is a flowchart for explaining an embodiment of the present invention. Fig. 4 is a block diagram of a control device that controls the refrigeration cycle of Fig. 3, and Fig. 5 is a flowchart for explaining the conventional control method. It's a chat. 21...Compressor, 23...Indoor heat exchanger, 23a...Indoor fan, 25...Outdoor heat exchanger, 25a...Outdoor fan, 26...Compressor motor, 30...Indoor control device, 31... Outdoor control device, 32... Inverter circuit, 33... Current transformer, 34... Current detection circuit, UL... Current upper limit value, LL... Current lower limit value.

Claims (1)

[Claims] 1. In a method for controlling an air conditioner in which a compressor motor that drives a compressor in a refrigeration cycle is operated by a variable frequency output power source, a current flowing through the compressor motor is detected, and the detected current value is set as a first set value. When the detected current value exceeds the second set value, the frequency of the power supply is increased, and when the detected current value falls below the second set value, which is lower than the first set value, the power supply frequency is increased. changes from a value larger than the first set value to a second set value lower than that, the frequency of the power supply at that time is maintained, and the detected current value is A method for controlling an air conditioner, characterized in that the frequency of the power source is increased when the frequency is between the first set value and the second set value for a continuous set time.