JPS6340757Y2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to an operation control system for a refrigerator that employs a multi-type compressor unit consisting of a plurality of compressors.

Open shovel cases and other refrigeration and freezing equipment are
The refrigeration load fluctuates greatly throughout the year. From this perspective, the above-mentioned multi-type compressor unit is now being used as the refrigeration unit for the above-mentioned equipment.
Systems that control capacity in response to fluctuations in refrigeration load and achieve efficient operation with high power saving effects are widely used.

Figure 1 shows an open show case facility that employs such a multi-type compressor unit. In the figure, 1 indicates three compressors 2,
2, 2, and a liquid receiver 3, 4 is a remote condenser, 5 is an open case with a built-in evaporator 6, and an expansion valve 7, and these are connected by refrigerant piping. They are tied together to form a refrigeration circuit.
As is well known in such a refrigeration circuit, the low pressure side pressure, that is, the suction pressure of the compressor unit, is proportional to the refrigeration load; when the refrigeration load increases, the suction pressure increases, and conversely, when the refrigeration load decreases, the suction pressure decreases. decreases. Utilizing this characteristic, the suction pressure is detected to determine the size of the refrigeration load, and based on this suction pressure detection value, compressors 2 to 2 are selectively stopped one by one according to the decrease in suction pressure. Conventionally, an operation control method has been implemented that performs operation and stop control, and performs capacity control within a range of fluctuations in refrigeration load. In this case, conventional machines use a mechanical pressure switch as a means of controlling operation, but in the case where one pressure switch is installed for each compressor, the mechanical pressure switch has poor operating characteristics. Because there are many variations and the differential cannot be made sufficiently small, it is difficult to set close step differences between each compressor, and it is difficult to perform fine-grained capacity control with high power-saving effects. Ta. In response to this, an electronic pressure switch that combines an electronically controlled CPU (Central Processing Unit) such as a microprocessor, which has been rapidly developed in recent years, with an electronic pressure sensor with high resolution and precision is being adopted in place of the conventional mechanical pressure switch. This makes it possible to uniformly and easily set multi-stage step differences within a range of fluctuations in refrigeration load, and to perform fine capacity control. The electronic pressure switch and its electronic pressure sensor are designated 8 and 9 in FIG. 1, respectively. The electronic pressure switch 8 inputs the suction pressure detection value obtained by the pressure sensor 9 and sets the pressure of each compressor 2 to 1 in advance.
A step difference is given between the cut-out and cut-in setting values so as to change them for each machine, and the operation control signals 8, Give 8,8. Next, actual operation control will be described with reference to the operation pattern of the electronic power switch shown in FIG. 2 and the operation chart of the refrigerator shown in FIG. First, in Figure 2, P ₁ , P ₃ ,
P ₅ is the cut-in setting value for compressor 2, 2, 2, which is set based on the refrigeration load fluctuation range, P ₂ , P ₄ , P ₆ is the cut-out setting value,
Pd is the differential between the cut-in and cut-out pressure settings, and Ps is the step difference.
An example of specific numerical values for actual cooling operation is P ₁ = 2Kg/cm ²・G, P ₆ ... 1Kg/cm ²・G, Pd
= 0.2Kg/ ^cm2・G, Ps=0.4/ ^cm2・G, and the differential and step difference can be set smaller than when using a conventional mechanical pressure switch. This allows for finer capacity control within the range of refrigeration load fluctuations. Moreover, by using a microprocessor or the like, each set value can be easily set and changed over a wide range. Furthermore, the operation chart of the refrigerating machine under the above-mentioned capacity control is as shown in Fig. 3, and the operation of the compressors 2 to 2 is selectively controlled according to fluctuations in the suction pressure of the compressor unit, thereby reducing the load. From time to time, some compressors can be shut down to reduce excess power consumption and achieve high power savings.

On the other hand, pump-down operation cannot be performed using the conventional control method described above. In other words, for pump down, the liquid solenoid valve 10 is inserted into the high pressure liquid line in the refrigeration circuit shown in Fig. 1, and when the compressors 2 to 2 are completely stopped, such as during defrosting or maintenance inspection, the liquid solenoid valve 10 is turned on. This is a control method in which the compressor is taken over for a while after closing, and the refrigerant remaining in the evaporator 6 and the low-pressure side circuit is collected and stored in the liquid receiver 3 etc. through the compressor.
This is an extremely effective operating method in terms of compressor unit operation control, as it prevents liquid back up when the compressor is restarted, and reduces the heat capacity of the evaporator during defrosting, thereby shortening the defrosting time. By the way, in order to perform the above-mentioned pump down, it is necessary that the compressor does not come to a complete stop until the suction pressure reaches a pump down pressure close to the vacuum of zero gauge pressure. However, in the conventional operation control method described in Figures 2 and 3, the set values P1 to P6 are set within the range of fluctuations in the refrigeration load during cooling operation, and if this continues, the pump down pressure will not reach the pump down pressure. Since the compressor will completely stop, pump-down operation control cannot be performed.

This idea was developed in consideration of the above points, and its purpose was to enable pump-down operation control while utilizing the electronic pressure switch that controls the capacity of the multi-compressor unit based on the suction pressure detection value mentioned above. The purpose of this invention is to obtain an operation control device for a refrigerator.

The operation control device of this invention will be described in detail below with reference to FIGS. 3 to 8. FIG. 6 is a circuit diagram of a part of the sequence for controlling the open show case equipment shown in FIG. 1. In the figure, T is a defrost timer which switches the internal switch S to the fixed contact N side during cooling operation and to the fixed contact D side during defrosting operation. When the cooling operation is switched to the defrosting operation by this timer, the relay X is energized, the relay contact X1 is turned on, and the solenoid valve 10 is operated to close the valve. At the same time, contact X2 turns ON and gives a pump down signal to CPU8. Furthermore, the defrost heater H is turned on when relay contact X3 is turned ON and when compressor 2
It is energized by its contact 8b via a relay (not shown) so that it is energized when it is OFF.
That is, during defrosting operation, the solenoid valve 10 is energized, the valve is closed, and pump-down mode begins, and when the pump-down is completed, the defrost heater H is energized after the compressor 2 is stopped.

As shown in FIG. 7, an electronic pressure switch 8, which is a combination of a pressure sensor 9 and a CPU, uses a signal input through the pressure sensor 9 and a contact X2 of a relay Control 2.

When explaining this program, first contact X2 is
It is determined whether it is ON, and if X2 is ON, the pressure setting value is changed from P6 to P6', and further the compressors 2 to 2 are turned OFF according to the program.

In other words, when the input value Px of the pressure sensor 9 is greater than or equal to _P5 , the compressor 2 is operated and the input value
When Px becomes _P3 or more, compressor 2 is operated, when input value Px becomes _P1 or more, compressor 2 is operated, and when Px becomes _P2 or less, compressor 2 is stopped (2, 2 motion)
When Px is _P4 or less, compressor 2 is stopped (2 operations), and when Px is _P6 or less, compressor 2 is stopped.
control to stop. During cooling operation, _P6 performs control with the initial settings.

With this invention, the minimum cutout setting value for completely stopping the compressor unit in FIG.
Changed to ¹ . Note that this setting value can be easily changed by applying a signal from the outside to the electronic pressure switch 8 in FIG. 1 and processing the signal. Note that the cut-in setting value P5 of compressor 2 is the same as in ^FIG .
is larger than the differential Pd for Therefore, in the conventional system shown in Fig. 2, compressors 2 to 2 come to a complete stop at a gauge pressure of 1 kg/cm ² G, whereas according to the operation pattern shown in Fig. 4, only compressor 2 stops suction. It will continue to operate until the pressure drops to the pump down pressure of set value _P6 . In this way, the operating chart of the refrigerator becomes as shown in Figure 5. That is, when the liquid electromagnetic valve 10 is closed at a time To prior to defrosting the open shower case 5 in FIG. 1, the suction pressure rapidly drops due to the operation of the compressor.
Even if the current minimum cutout setting value P ₆ is exceeded, the compressor 2 continues to operate and performs pump-down operation until the gauge pressure reaches zero setting value P 6 ¹
It will start and stop when it drops to this point. Therefore, pump-down operation is performed from T ₁ to T ₂ in terms of time, and the refrigerant remaining on the low pressure side of the evaporator or the like can be recovered. Therefore, defrosting performed after pumping down can be performed efficiently in a short time. When defrosting starts, the temperature of the residual gas in the evaporator rises, so the gas pressure on the suction side rises somewhat from the middle, but as shown in Figure 4, the compressor 2 cut-in setting P5 remains the same as during cooling operation. By fixing it, you can prevent the compressor from restarting unexpectedly.

Furthermore, in the above method, a method was described in which the cutout setting value ^P61 of the compressor 2 is fixedly set, but during normal cooling operation without pump down, the minimum cutout setting value for complete stop of the compressor unit is set to P6. It is more effective to save energy if it is retained. As a method for this purpose, the cutout setting value of compressor 2 is set to P6 during normal cooling operation, and when pump down is required for defrosting etc., the minimum cutout setting value for complete stop of the compressor is set from P6 based on the pump down command. The method of changing to P6 ¹ is extremely effective, and this control method allows capacity control to respond to fluctuations in refrigeration load during cooling operation, and also enables pump-down operation when necessary.

In addition, the required refrigerating capacity of the housing case changes depending on the environment in which the housing case is placed, that is, summer, winter, and day and night.
By controlling 2, a significant energy saving effect can be obtained. For this reason, the range of variation in the required refrigerating capacity is predicted in advance, and the set values P ₁ to P ₆ set in the electronic pressure switch using a microprocessor etc. are adjusted based on changes in the environment so that the compressors 2 to 2 operate efficiently. Change it accordingly.

As mentioned above, this idea is designed to control capacity by selectively applying operation control signals to each of the multiple compressors that make up a multi-type compressor unit through an electronic pressure switch based on the detected suction pressure value. In the operation control device, the minimum cutout setting value when the compressor is completely stopped is set to the pressure equivalent to the pump down pressure when pump down operation is required, so capacity control is performed in response to refrigeration load fluctuations. It is possible to provide a pump-down function while making use of an electronic pressure switch for controlling the pump, which has the advantage of further expanding the control function.

[Brief explanation of the drawing]

Figure 1 is a system diagram of an open show case facility that employs a multi-compressor unit that controls capacity with an electronic pressure switch, Figure 2 is a control operation pattern diagram showing the output characteristics of a conventional electronic pressure switch, and Figure 3 is FIG. 2 is an operating chart of a refrigerator, FIGS. 4 and 5 are control operation pattern diagrams of an electronic pressure switch showing an embodiment of this invention, and an operation chart of a refrigerator, and FIG. 6 is an open shutter diagram of this invention. A circuit diagram for controlling the case equipment, FIG. 7 is a circuit diagram for explaining the operation of the electronic pressure switch of this invention, and FIG. 8 is a flowchart showing an operation program of the refrigerator operation control device of this invention. . 1...Multi compressor unit, 2-2
...Compressor, 9...Pressure sensor, 8...
CPU as an electronic pressure switch, P6...Cutout setting value for all compressor stops during cooling operation, P6 ¹ ...Cutout setting value for all compressor stops during pump down.

Claims (1)

[Claims for Utility Model Registration] 1. A multi-type compressor unit consisting of a plurality of compressors connected in parallel with each other, which is equipped with an electronic pressure switch consisting of a central processing unit that inputs the output signal of the pressure switch; In a refrigerator operation control device, capacity control is performed within a range of fluctuations in refrigeration load by selectively applying an operation control signal to each compressor through the electronic pressure switch during cooling operation using a pressure detection value as an input value, Refrigeration characterized in that the electronic pressure switch is provided with means for setting the minimum cutout setting value of the electronic pressure switch for completely stopping the compressor unit to a pressure corresponding to the pump-down pressure at least when pump-down operation is necessary. Machine operation control device. 2. Scope of Utility Model Registration In the operation control device set forth in claim 1, the minimum cutout setting value of the electronic pressure switch is set in accordance with the variation range of the required refrigerating capacity during normal cooling operation, and is set based on the pump down command. A refrigerator operation control device that changes the setting from the setting value during cooling operation to the pressure corresponding to the pump down pressure.