JPH074727A - Control device for air conditioner - Google Patents

Abstract

PURPOSE:To provide a control device for an air conditioner, which can prevent the freezing of an evaporator from happening without stopping a compressor. CONSTITUTION:A control device for an air conditioner is equipped with a capacity control unit which variable-controls the operation capability of a compressor 3 in response to the load of a room to be air conditioned, sensors 8a-8c to detect the temperatures of evaporators 2a-2c, and a control unit 9 which provides a signal to decrease the operation capacity of the compressor 3 to the capacity control unit when the detected temperatures of these sensors 8a-8c are lower than a first value to be previously set, and provides a signal to prohibit the increase of the operation capacity of the compressor 3 to the capacity control unit during a period from when the detected temperatures of the sensors 8a-8c exceed the first value after the above-mentioned signal is provided to when the detected temperatures exceed a second value.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to
The present invention relates to a control device for an air conditioner that prevents freezing of an evaporator.

[0002]

2. Description of the Related Art Generally, variable capacity compressors, evaporators,
An air conditioner including a refrigeration cycle configured by using a pressure reducing device and a condenser is known.

In this type, in order to prevent the evaporator from freezing during the cooling operation, the temperature of the evaporator is a predetermined temperature (for example,
When the temperature falls below 0.8 ° C, the compressor is stopped to recover the temperature. In this case, once the compressor is stopped, it cannot be restarted for several minutes.

[0004]

By the way, in recent years,
A multi-type air conditioner has been proposed in which a plurality of indoor units are connected to an outdoor unit to air-condition a plurality of rooms.

However, when the conventional control is applied to this multi-type air conditioner, when the temperature of even one of the evaporators falls below a predetermined temperature, the compressor immediately stops and the operation of other evaporators stops. Therefore, there is a problem that it is not possible to realize proper cooling according to the situation.

[0006] Therefore, an object of the present invention is to solve the above-mentioned problems of the prior art and to provide an air conditioner control device capable of preventing freezing of an evaporator without stopping the compressor as much as possible. To provide.

[0007]

In order to solve the above-mentioned problems, the present invention provides an air conditioner having a refrigeration cycle constituted by a variable capacity compressor, an evaporator, a pressure reducing device, and a condenser. In the control device, the capacity control unit that variably controls the operating capacity of the compressor according to the load of the room to be conditioned, the sensor that detects the temperature of the evaporator, and the detected temperature of this sensor have a preset first value. When the temperature falls below the value, the capacity control unit is given a signal to reduce the operating capacity of the compressor, and after this signal, the temperature detected by the sensor exceeds the first value until it exceeds the second value which is higher than the first value. And a control section for giving a signal for prohibiting an increase in the operating capacity of the compressor to the capacity control section.

[0008]

According to the present invention, the first value and the second value higher than the first value are provided. Then, when the temperature of the evaporator falls below the first value, the drive frequency of the compressor is first lowered to recover the temperature of the evaporator. To stop.
When the temperature of the evaporator is recovered by lowering the drive frequency of the compressor, the drive frequency is changed to increase. However, according to the present invention, even if the temperature is recovered, the temperature of the evaporator is set to the second value.
Keep the drive frequency down until the value of is reached.
According to this, the temperature of the evaporator can be recovered without stopping the compressor.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

In FIG. 1, reference numeral 3 indicates a compressor.
A condenser 1 and an electric expansion valve (pressure reducing device) 5 are connected to the compressor 3, and three opening / closing valves 6a to 6c are connected in parallel to the electric expansion valve 5. Electric expansion valves (pressure reducing devices) 7a to 7c and evaporators 2a to 2c are connected in series to each on-off valve 6, and these are connected to a compressor 3 via a refrigerant pipe 4.

Further, temperature sensors 8a to 8c are attached to the respective evaporators 2a to 2c, and these temperature sensors 8 are connected to a controller 9.

According to this embodiment, however, the controller 9 controls the drive frequency of the compressor 3 as follows according to the temperature of each evaporator 2 detected by the above-mentioned temperature sensors 8a-8c. To do.

That is, referring to FIG. 2, when the temperature of the evaporator 2 falls and enters the range of 4.0 ° C. to 0.8 ° C., first, the driving frequency of the compressor 3 is lowered by Hz, and then Hz. Even if it goes down, the temperature of the evaporator 2 continues to drop, and
If it seems to be 8 ° C or lower, stop the compressor 3.

If the driving frequency of the compressor 3 is lowered by Hz and the temperature of the evaporator 2 seems to rise, the driving frequency of the compressor 3 is turned up again. However, even if the temperature of the evaporator 2 rises, if it is in the range of 4.0 ° C. to 6.0 ° C.
The drive frequency of the compressor 3 is prohibited from increasing so as to prevent the temperature of 1 from decreasing.

These controls are for preventing freezing of the evaporator 2 during the cooling operation.

However, the feature of this embodiment is that, especially when the temperature of the evaporator 2 falls below a predetermined temperature, the driving frequency of the compressor 3 is first lowered by Hz instead of stopping the compressor 3 suddenly. The point is to recover the temperature of the evaporator 2.

The processing flow of this drive frequency control will be described with reference to FIG.

First, the temperature sensor 8 attached to the evaporator 2
It is determined whether or not the temperature is less than or equal to 4.0 ° C. (first value) (step 1).

When the temperature is 4.0 ° C. or higher, normal operation is performed (step 2), and when the temperature is 4.0 ° C. or lower, the drive frequency of the compressor 3 is lowered (hereinafter, Hz down) (step 3). Then, the openings of the electric expansion valves 7a to 7c are narrowed (step 4).

At this time, Hz down is 1 Hz / 30 se
Perform at a rate of c. Further, the opening degree of the electric expansion valve 7 is in 500 stages from 0 (fully closed) to 500 (fully opened),
Especially when the temperature of the evaporator 2 is 0.8 to 4.0 ° C,
Squeeze at a rate of 50 steps / 30 sec.

Next, it is determined whether the temperature of the evaporator 2 is 0.8 ° C. or lower (step 5). Normally, if the frequency is lowered by Hz, the temperature of the evaporator 2 will be recovered, but even if it still does not recover, and if it further decreases to 0.8 ° C. or less, the compressor 3 is stopped. (Step 6).

If the temperature is not 0.8 ° C. or lower, it is judged whether the temperature of the evaporator 2 is 4.0 ° C. or lower (step 7), 4.0.
If the temperature is not higher than 0 ° C., the process proceeds to step 3, the Hz is lowered, and the electric expansion valves 7a to 7c are throttled (step 4).

If it is 4.0 ° C. or higher, it is judged whether or not the temperature of the evaporator 2 is 6.0 ° C. (second value) or lower (step 8). If it is 6.0 ° C. or lower, evaporation is performed. Even if the temperature of the evaporator 2 is recovered, the increase of the driving frequency is prohibited so that the temperature of the evaporator 2 does not start to decrease again (step 9).

In short, according to this embodiment, even if the temperature of the evaporator 2 decreases to near the freezing temperature during the cooling operation, the temperature of the evaporator 2 can be recovered without stopping the compressor 3. You can

Since the control described above relates to the frequency control of the compressor 3, the control affects all the evaporators 2.

Therefore, it is desirable that the above-mentioned control is operated only when the following three conditions are satisfied.

(A) When the temperature of the evaporator 2 is 4.0 ° C. or lower (B) 6 minutes When the timer is up (C) When cooling or dry operation is in progress (B) 6 minutes The timer is a timer that counts the time during which the drive frequency of the compressor 3 is not changed even when the temperature of the evaporator 2 becomes 4.0 ° C. or lower.

For example, referring to FIG. 2, when the temperature of the evaporator 2 exceeds 6.0 ° C., the control according to this embodiment is released, but the above timer counts when it is released. Start.

Then, for 6 minutes until the time is up, even if the temperature of the evaporator 2 becomes 4.0 ° C. or lower,
The compressor 3 is operated without changing the drive frequency. This is because if the drive frequency of the compressor 3 is controlled during this 6 minutes, the output of the other evaporators 2 will be affected.

When any of the above three conditions is not satisfied, it is desirable to cancel the control according to this embodiment and perform control so as to proceed to normal operation.

[0031]

As is apparent from the above description, according to the present invention, it is possible to avoid freezing of the evaporator without stopping the compressor.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of a control device for an air conditioner according to the present invention.

FIG. 2 is a diagram showing a temperature curve of an evaporator.

FIG. 3 is a chart showing a processing flow of a controller.

[Explanation of symbols]

 1 Condenser 2 Evaporator 3 Compressor 5 Electric expansion valve (pressure reducing device) 6 Open / close valve 7 Electric expansion valve (pressure reducing device) 8 Temperature sensor 9 Controller

Claims (1)

[Claims] 1. A controller for an air conditioner having a refrigeration cycle including a variable capacity compressor, an evaporator, a pressure reducing device, and a condenser, the compressor being controlled according to the load of a room to be conditioned. A capacity control unit that variably controls the operation capacity, a sensor that detects the temperature of the evaporator, and when the temperature detected by this sensor falls below a preset first value, the capacity control unit reduces the operation capacity of the compressor. A signal is given to the capacity control unit after the signal is supplied, and the signal is prohibited from increasing the operating capacity of the compressor until the temperature detected by the sensor exceeds the first value and exceeds the second value higher than the first value. A control device for an air conditioner, comprising: a control unit for giving.