JPS6252225B2 - - Google Patents

Description

Detailed Description of the Invention The present invention provides a refrigerator having a refrigerant circuit that connects a compressor whose compression capacity can be switched into multiple stages, a condenser, a pressure reducing device, and a user-side heat exchanger that performs evaporation. The present invention relates to a control method.

Generally, as shown in Fig. 1, this type of refrigerator is equipped with a compressor 1 that is equipped with a capacity adjustment mechanism and whose compression capacity can be switched to multiple stages, a condenser 2, a pressure reducing device 3, and a user side that performs evaporation. It has a refrigerant circuit 5 connected to a heat exchanger 4, and cold water as a secondary refrigerant cooled by the user-side heat exchanger 4 is circulated by a pump 7 via a water pipe 6 and supplied to a fan coil 8. ing.

Then, in the fan coil 8, heat exchange is performed between the cold water and the indoor air, and indoor cooling operation is performed.
It constitutes a so-called chiller type air conditioner.

A conventional refrigerator control device incorporates a drive device for an unloader mechanism, so that an appropriate compression capacity of the compressor 1 can be selected depending on the load. However, when the outside temperature is low, such as in the middle of spring and autumn, the compressor 1 may be operated at a large capacity, and in this case, the refrigerant pressure on the low pressure side of the refrigerant circuit 5 becomes low.
As the refrigerant temperature drops, water freezes in the water circuit inside the heat exchanger 4 on the user side and the water pipe 6 on the outlet side, and there is a risk that the water circuit and the water pipe will burst. Furthermore, even when the outside temperature was high, the low pressure could drop suddenly due to temporary disturbances.

For this reason, a conventional refrigerator control device is provided with a pressure switch that detects an abnormal decrease in refrigerant pressure on the low-pressure side of the refrigerant circuit 5, and when the detected value becomes lower than a set value, the compressor is stopped. However, if the compressor is stopped frequently during operation, the life of the compressor will be shortened, so the set value will inevitably be kept low, causing gas shortage in the refrigerant circuit 5 and depressurization. The pressure switch is activated only when there is a continuous abnormality such as clogging in the device 3 or insufficient water volume in the water circuit 6. It was not able to cope with pressure drops caused by external disturbances, nor was it able to prevent water circuits and water pipes from freezing.

The present invention has been made in view of the above-mentioned fact, and detects the refrigerant pressure or temperature on the low pressure side of the refrigerant circuit or the temperature of the medium that exchanged heat with the user side heat exchanger, and this detected value is set as the first setting. After the detected value has decreased to the second set value, the compression capacity is sequentially lowered at a predetermined cycle until it rises to the second set value, and when the minimum capacity operation continues for a certain period of time and the detected value does not rise to the second set value, the compressor is turned off. When there is a risk that the heat exchanger on the user side may freeze, the compressor is operated at a small capacity for a predetermined period of time without stopping, thereby sufficiently increasing the low pressure to prevent freezing. It is an object of the present invention to provide a method for controlling a refrigerator that can prevent wear of a capacity adjustment mechanism and damage to equipment due to frequent repetition of large capacity and small capacity.

Hereinafter, an embodiment in which the present invention is applied to the refrigerator shown in FIG. 1 will be described based on the drawings. In FIG. 2, reference numeral 9 denotes a microcomputer, and a power supply terminal B is connected to a bus line l to which a constant DC voltage is supplied.

Further, 10 is an oscillator which determines the free running time of the microcomputer, and is connected between clock terminals CL ₁ and CL ₂ . Reference numeral 11 denotes a compressor capacity adjustment switch, the switching contact S ₀ is connected to the bus line l ₁ and the fixed contacts S ₁ to S ₅ are connected to the input ports I ₁ to I ₅ . 12 is a pressure switch that detects the refrigerant pressure on the low-pressure side of the refrigerant circuit 5, for example, the outlet side of the utilization side heat exchanger 4; it closes when the detected value is 3.9 kg/cm ² or less, and closes when the detected value is 4.1 kg/cm ² It is set to open circuit and is connected between bus l and input port _I6 . 13 is supplied with a constant DC voltage from the bus l,
It is a reference pulse generator that generates reference pulses of a predetermined frequency, and its output end is connected to the input port _I7 . 14 is a drive motor for the compressor 1 (not shown)
This is a capacity adjustment relay circuit that controls the energization and capacity adjustment mechanism, and is composed of relays 15 to 18, one end of each relay is connected to the bus line l, and the other end is outputted via a driver 19 having a reversing function. Connected to ports P ₁ to P ₄ .
20 is a warning lamp, which connects bus line l and output port _P5
A driver 21 having a reversing function is connected therebetween.

FIG. 3 shows the internal system of the microcomputer 9. The microcomputer 9 includes a discriminating device 22 that sequentially and repeatedly detects the presence or absence of signals at input ports _I1 to _I7 , and a discriminating output of the discriminating device 22 and a pre-stored memory. Program (not shown)
The control signal generator 23 generates a control signal of "0" or "1" from the output ports P ₁ to P ₄ based on the pulse count from the reference pulse generator 13 based on the set signal from the control signal generator 23. The apparatus is provided with timer devices 24 to 25 for counting time of 5 seconds, 20 seconds, and 2 minutes, respectively.

Assuming that the adjustment switch 11 is now connected to the fixed contact _S5 , the microcomputer 9 determines this because the determination device 22 has a high level signal "1" at the input port _I5 . Therefore, based on this discrimination output, the control signal generator 23 generates a "1" signal from the output ports P ₁ to P ₄ to energize all the relays 15 to 18. For this reason, the compressor 1 performs 100% large capacity operation, and the refrigerant is transferred from the compressor 1 to the condenser 2 to the pressure reducing device 3 to the user-side heat exchanger 4.
→Flows in the order of compressor 1. When the refrigerant evaporates inside the user-side heat exchanger 4, the water that is the secondary refrigerant is cooled, and the cooling water is circulated in the water pipe 6 by the pump 7 and supplied to the fan coil 8. In the coil 8, heat exchange is performed between the water and the indoor air, thereby performing indoor cooling operation.

If the outside temperature becomes low during this operation, the refrigerant circuit 5
As the high pressure decreases, the low pressure decreases. As shown in FIG. 4a, when the pressure switch 12 senses a pressure of 3.9 kg/cm ² or less at time _T1 , the pressure switch 12 closes. At this time, the microcomputer 9 determines whether the pressure switch 12 is closed by the determination device 22 detecting the "1" signal at the input port _I6 . Furthermore, the control signal generator 2
3, based on the discrimination output of the pressure switch 12 of the discrimination device 22, first sets the control signal from the output port _P4 to a "0" signal to de-energize the relay 18 and issues a set command to the timer devices 24 and 26. Therefore, the compressor 1 operates at a small capacity of 75% as shown in FIG. 4b, and the low pressure in the refrigerant circuit 5 is increased. At time _T2 when the 75% small capacity operation continues for 5 seconds, the control signal generator 23 determines whether the determination device 22 continues to output the determination output from the pressure switch 12 based on the time-up signal from the timer device 24. If the refrigerant pressure has not reached 4.1Kg/ ^cm2 as shown in the figure, "0" is further output from output port _P3 and relay 1 is activated.
7, the compressor 1 is operated at a small capacity of 50%, and the timer device 24 is reset.
As a result, the refrigerant pressure increases, and the time when 5 seconds have passed.
If _T3 is 4.1Kg/ ^cm2 or more, the pressure switch 12 is open, so no further small capacity switching is performed, and the timer device 26 of the control signal generator 23 times out. from output port P ₁ to P ₄ to [1, 1, 0,
0] control signal is issued to continue the 50% small capacity operation of the compressor 1.

In this way, the low pressure is sufficiently increased to prevent the temperature of the refrigerant in the user-side heat exchanger 4 from decreasing, and to raise the temperature to a temperature at which the cold water does not freeze.

At time _T4, which is two minutes after time _T1 , the time-up signal of the timer device 26 is output to the control signal generator 2.
3, the generator 23 has output ports P ₃ , P ₄
Relays 17 and 18 with the control signal from
Turn on electricity and return compressor 1 to 100% capacity operation.

Thereafter, at time _T5 , when the low pressure in the refrigerant circuit 5 reaches 3.9 kg/cm ² , the pressure switch 12 closes again. Then, the control signal generator 23 sequentially issues small capacity operation commands of 75%, 50%, and 25% at a 5-second cycle until the pressure switch 12 returns to normal operation, similar to the operation described above. Also, the timer device 26
is set and a time count of 2 minutes is carried out.
At the same time as the compressor 1 is brought into operation at a minimum capacity of 25%, a timer device 25 is set in place of the timer device 24 to count time for 20 seconds.
If the low pressure still does not return to 4.1Kg/ ^cm2 even after performing the minimum capacity operation in this way, the refrigerant circuit 5
The control signal generator 2 is activated when the timer device 25 times up due to continuous abnormalities such as lack of gas, clogging of the pressure reducing device 3, and insufficient water amount in the water circuit 6.
3 emits control signals of all "0" from the output ports _P1 to _P4 to turn off the power to the drive motor and stop the compressor 1. At this point, the timer device 26 is reset, and the output port P _Five
The alarm lamp 20 is illuminated by emitting a signal of "1" from the alarm.

On the other hand, if the pressure switch 12 is open when the timer device 25 times up, the control signal generator 23 outputs signals from the output ports P ₁ to P ₄ until the timer device 26 times up.
0, 0] is issued to maintain the compressor 1 at 25% capacity operation. Therefore, 100% large-capacity operation of the compressor 1 will be resumed after the low pressure has risen sufficiently and there is no risk that the water, which is the secondary refrigerant, will freeze.

By repeating this process, each time the low pressure in the refrigerant circuit 5 decreases to a value that may cause water, which is the secondary refrigerant, to freeze, the operating capacity of the compressor 1 is increased. is adjusted to a smaller capacity in stages at a predetermined period (for example, 5 seconds), and this small capacity operation continues for a predetermined period of time (for example, 2 minutes), and when performing 100% large capacity operation in the middle of spring and autumn, etc. When a drop in low pressure occurs due to a temporary disturbance, the compressor 1 can be operated at a moderately small capacity for a predetermined period of time without stopping the compressor 1, and water, which is a secondary refrigerant, can be prevented from freezing. In addition, wear and tear caused by frequent operation of the capacity adjustment mechanism can be prevented, and cooling operation can be performed without interruption.
Also, if compressor 1 is switched to minimum capacity operation and the low pressure does not rise to the return pressure even if this continues for a certain period of time (for example, 20 seconds), there is a continuous abnormality, so stop compressor 1. can cause an alarm to be issued.

In the above-mentioned embodiment, the case where the compressor capacity adjustment switch 11 is connected to the contact _S5 has been explained, but the same applies to the case where the compressor capacity adjustment switch 11 is connected to the contacts _S4 , _S3 , and _S2 . Capacity operations of 75%, 50%, and 25% are carried out, and the low pressure switch 12 is operated to switch to a lower capacity operation. Further, the adjustment switch 11 is not limited to a manual one, but may also be a thermoswitch that detects the temperature of the water pipe on the inlet side of the heat exchanger 4 on the user side and switches the contact points.

Furthermore, each counting time of the timer devices 24, 25, and 26 is appropriately selected depending on the type of refrigerator used and the installation location.
4 and 25 are determined by the pressure balance time after capacity switching. Furthermore, although the refrigerant pressure on the low-pressure side of the refrigerant circuit 5 is detected as a factor for freezing the secondary refrigerant, the refrigerant temperature on the low-pressure side of the refrigerant circuit or the secondary refrigerant temperature on the outlet side of the user-side heat exchanger 4 is detected. In this case as well, the counting times of the timer devices 24, 25, and 26 are adjusted to appropriate times.

As described above, the present invention detects the refrigerant pressure or temperature on the low pressure side of the refrigerant circuit or the temperature of the medium that has exchanged heat with the user side heat exchanger, and when the detected value falls to a set value, the compressor is operated at a small capacity. In this way, when there is a risk that the heat exchanger on the user side may freeze, the compressor can be operated at a low capacity for a predetermined period of time without stopping the compressor to maintain low pressure. This prevents freezing and wear of the capacity adjustment mechanism caused by frequent repetition of large and small volumes. Moreover, after the detected value drops to the first setting value, the compression capacity is sequentially lowered at a predetermined cycle until it rises to the second setting value.
A small capacity operation is selected according to the magnitude of the freezing factor, and freezing prevention is performed accurately. Furthermore, if the compressor continues to operate at its minimum capacity for a certain period of time and the detected value does not rise to the second set value, the compressor will be stopped and an alarm will be issued, making it easier to perform maintenance and inspections when abnormalities occur continuously. This will also be done easily.

[Brief explanation of the drawing]

Fig. 1 is a refrigerant circuit diagram showing an example of a refrigerator to which the present invention is applicable, Fig. 2 is an electric circuit diagram showing an embodiment of the present invention, and Fig. 3 is an internal system of the microcomputer shown in Fig. 2. The block diagrams shown in FIGS. 4a and 4b are explanatory diagrams for explaining the operation of the present invention. 1... Compressor, 2... Condenser, 3... Pressure reducing device, 4...
Utilization side heat exchanger, 5... Refrigerant circuit, 6... Water pipe, 9...
Microcomputer, 12...Pressure switch, 2
3... Control signal generator, 24, 25, 26... Timer device.

Claims (1)

[Claims] 1. In a refrigerator that has a refrigerant circuit that connects a compressor with switchable compression capacity, a condenser, a pressure reduction device, and a user-side heat exchanger that performs evaporation, the refrigerant pressure on the low-pressure side of the refrigerant circuit Alternatively, the temperature or the temperature of the medium that has exchanged heat with the heat exchanger on the user side is detected, and after this detected value falls to the first set value, the compression capacity is sequentially increased at a predetermined period until it rises to the second set value. A method for controlling a refrigerator, characterized in that the compressor is stopped when the detected value does not rise to a second set value after the minimum capacity operation is continued for a certain period of time.