JPH09152198A - Parallel compression type multi-freezer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To restrict an increasing of low pressure value caused by a variation in thermal load and to reduce a consumption power by a method wherein a history of a deviation between a detected pressure value and a target value is calculated, and any one of a plurality of compressors is stepped down in response to the calculated value. SOLUTION: A micro-computer 10 samples a pressure value obtained from a low pressure sensor 9 which is changed into a digital signal by an A/D converter 11 and calculated a deviation P between a target value of 2.5kg/cm<2> and the detected pressure value. It is discriminated whether or not the deviation P is within a specified range and if the deviation is out of the specified range, the microcomputer calculates a sum Q of deviations of last five times, for example. Then, the microcomputer 10 calculates the equation of X=αB+βQ (where, α and β are constants calculated by experiment and they are a value such as 10). The microcomputer 10 reads out a time of energy saving mode and a step width from a table in the memory 12 in reference to the value of X. If the value X is larger then 25, any one of the compressors 1 to 3 is stepped down by one only for a time of one minute.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a parallel compression multi-refrigeration system, and more particularly to a parallel compression multi refrigeration system in which a plurality of compressors are mounted so as to be arranged in parallel to the same suction pipe and discharge pipe. Refrigeration equipment.

[0002]

2. Description of the Related Art FIG. 5 is a schematic block diagram of a conventional parallel compression type multi-refrigerating apparatus. In FIG. 5, the compressors (compressors) 1 to 3 have, for example, capacities of 3 kW, 4 kW,
The high pressure refrigerant gas discharged from the compressors 1 to 3 is liquefied by the condenser 4 and is stored in the receiver tank 5 and is stored in the receiver tank 5 by the pressure reducing solenoid valve 6. After the pressure is reduced, the pressure is applied to the evaporator 7 to perform the refrigerating action. An accumulator 8 is provided in association with the evaporator 7, and the compressor 1
3, a low pressure sensor 9 is provided on the suction pipe side of 3,
Low pressure is detected.

FIG. 6 shows a capacity control pattern of each compressor shown in FIG. 5, and FIG. 7 is a diagram for explaining an energy-saving operation method in a conventional parallel compression type multi-refrigerating apparatus.

By operating any of the compressors 1 to 3 shown in FIG. 5, the capacity control step shown in FIG. 6 is performed. That is, if all the compressors 1 to 3 are turned off, the capacity control step becomes 0, and if only the compressor 1 is operated, the capacity control step becomes 3.
When all the compressors 1 to 3 are operated, the capacity control step becomes 12. When operating in a capacity control step of maximum 12 kW, in order to perform energy-saving operation, as shown in FIG. 7, after operating for 30 minutes, for example, all compressors 1 to 3 are forced to operate for only 5 minutes. Duty operation is performed to stop at. In the example shown in FIG. 7, the average power consumption is 12 kW when continuously operated for 35 minutes, whereas 12 × 30 ÷ 35 = 10.3 when operating for 30 minutes and then stopped for 5 minutes.
It becomes kW, which means that energy is saved by 1.7 kW.

[0005]

However, in the conventional energy-saving operation, since all the compressors 1 to 3 are stopped for a fixed time, the low-pressure pressure value is likely to rise due to fluctuations in heat load. There was a drawback.

Therefore, a main object of the present invention is to suppress an increase in low-pressure pressure due to fluctuations in heat load and the like, and also to reduce power consumption, without temporarily stopping all the compressors. It is to provide such a parallel compression type multi-refrigerating device.

[0007]

The invention according to claim 1 is
In a parallel compression multi-refrigeration system in which a plurality of compressors are connected in parallel to the same suction pipe and discharge pipe, pressure detection means for detecting the pressure on the suction piping side and pressure detection means for each predetermined time are detected by the pressure detection means. Comprising a calculation means for calculating the history of the deviation between the pressure value and a predetermined target value, and a driving means for stepping down any one of the plurality of compressors based on the calculated history value. .

Therefore, according to the present invention, based on the value of the history of the deviation from the target value for energy saving operation,
By stepping down any one of the compressors, it is not necessary to stop all the compressors, and it is possible to suppress an increase in low-pressure pressure due to a change in heat load and the like, and further reduce power consumption.

The invention according to claim 2 further includes a table for storing the number of steps according to the history value, and the driving means responds by referring to the table based on the history value calculated by the calculation means. Read the number of steps to
One of the plurality of compressors is stepped down by the number of steps.

Therefore, by changing the number of steps stored in the table, any energy-saving operation can be performed.

According to the third aspect of the present invention, the sum of the deviation value detected as the deviation history value and the total deviation value of the past several times is calculated.

[0012]

1 is a schematic block diagram showing an embodiment of the present invention, and FIG. 2 is a diagram showing a table of the number of steps stored in the memory of FIG.

In this embodiment, the microcomputer 1
0 is used to perform capacity control for energy saving operation. Therefore, the microcomputer 10 is connected to the A / D converter 11, the memory 12, and the switch driver 13. The A / D converter 11 converts the low pressure detected by the low pressure sensor 9 into a digital signal and gives it to the microcomputer 10. The memory 12 stores X as shown in FIG. 2, the number of steps to step down or step up, and the time as a table. Here, X will be described in detail with reference to FIG. The switch driver 13 controls any of the magnet switches 14 to 16 to operate the corresponding compressors 1 to 3 according to a command from the microcomputer 10.

FIG. 3 is a flow chart for explaining the operation of the embodiment of the present invention. Next, the energy saving operation of the parallel compression type multi-refrigerating apparatus shown in FIG. 1 will be described with reference to FIG. The microcomputer 10 converts the low pressure value from the low pressure sensor 9 converted into a digital signal by the A / D converter 11 into, for example, 10
It is sampled every second, and the target value is 2.5, for example.
The deviation P between kG / cm ² and the detected low pressure value is calculated. This target value is preset according to the application. Then, the microcomputer 10 determines whether the calculated deviation P is within the range of P> 2.0 or P <-1.0, for example. If it is within the range, the energy saving mode is canceled and the normal capacity control mode is entered. However,
If the deviation P is larger than 2 or smaller than -1.0, the calculated deviation P is included, and the sum Q of the deviations of the past five times is calculated. Next, the microcomputer 1
0 calculates X = αB + βQ. Here, α and β are constants that are experimentally recognized in advance, and are values such as 10. Then, the time and the step width of the energy saving mode are read from the table of the memory 12 and set from the obtained value of X. For example, if the value of X is larger than 25, one of the compressors 1 to 3 is stepped down by 1 minute, and if X is larger than 5, the step is down by 3 minutes. Thereafter, similarly, one of the compressors is stepped down according to the table shown in FIG.

FIG. 4 is a diagram showing an energy-saving operation cycle in this embodiment. In the example shown in FIG. 4,
Operate at 12 kW for the first 5 minutes, then for each 5 minutes thereafter
8kW, 12kW, 9kW, 12kW, 7kW, 12k
The capacity is controlled in steps of W to perform energy saving operation, and the average power consumption in this case is {12 × 20 +
(7 + 8 + 9) × 5} ÷ 35 = 10.3 kW, which is similar to the energy saving operation of the conventional example shown in FIG.
Energy will be saved by 7 kW. Moreover, in this example, since the operation of all the compressors 1 to 3 is not stopped, even if the heat load changes, the energy saving operation can be immediately stopped and the normal capacity control mode can be entered. It is possible to suppress an increase in low-pressure pressure due to load fluctuations as much as possible.

[0016]

As described above, according to the present invention, the history of the deviation between the pressure value detected at each predetermined time and the predetermined target value is calculated, and a plurality of compressions are performed based on the history values. Energy saving operation is performed by stepping down one of the machines, so that the heat load changes suddenly and the energy saving operation can be immediately stopped to resume normal operation. The power consumption can be reduced while suppressing the rise of the low pressure value as much as possible.

[Brief description of the drawings]

FIG. 1 is a schematic block diagram showing one embodiment of the present invention.

FIG. 2 is a diagram showing contents of a table stored in a memory shown in FIG.

FIG. 3 is a flowchart for explaining the operation of the embodiment of the present invention.

FIG. 4 is a diagram showing an energy-saving operation cycle performed in an embodiment of the present invention.

FIG. 5 is a schematic block diagram of a conventional parallel compression type multi-refrigerating apparatus.

6 is a diagram showing a capacity control pattern of the compressor shown in FIG.

FIG. 7 is a diagram for explaining a conventional energy-saving operation cycle.

[Explanation of symbols]

 1-3 Compressor 9 Low pressure sensor 10 Microcomputer 11 A / D converter 12 Memory 13 Switch driver 14-16 Magnet switch

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[Procedure amendment]

[Submission date] February 5, 1996

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0014

[Correction method] Change

[Correction contents]

FIG. 3 is a flow chart for explaining the operation of the embodiment of the present invention. Next, the energy saving operation of the parallel compression type multi-refrigerating apparatus shown in FIG. 1 will be described with reference to FIG. The microcomputer 10 converts the low pressure value from the low pressure sensor 9 converted into a digital signal by the A / D converter 11 into, for example, 10
It is sampled every second, and the target value is 2.5, for example.
The deviation P between kG / cm ² and the detected low pressure value is calculated. This target value is preset according to the application. Then, the microcomputer 10 determines whether the calculated deviation P is within the range of P> 2.0 or P <-1.0, for example. If it is within the range, the energy saving mode is canceled and the normal capacity control mode is entered. However,
If the deviation P is smaller than 2 and larger than -1.0, the sum Q of the deviations of the past five times is calculated, including the calculated deviation P. Next, the microcomputer 10
Calculates X = αB + βQ. Here, α and β are constants that are experimentally recognized in advance, and are values such as 10. Then, the time and the step width of the energy saving mode are read from the table of the memory 12 and set from the obtained value of X. For example, if the value of X is larger than 25, one of the compressors 1 to 3 is stepped down by 1 minute, and if X is larger than 5, the step is down by 3 minutes. Thereafter, similarly, one of the compressors is stepped down according to the table shown in FIG.

Claims (3)

[Claims] 1. A parallel compression type multi-refrigerating apparatus in which a plurality of compressors are connected in parallel to the same suction pipe and discharge pipe, pressure detection means for detecting the pressure on the suction pipe side, and the pressure for each predetermined time. Based on the history value calculated by the calculation means for calculating the history of the deviation between the pressure value detected by the detection means and the predetermined target value, and one of the plurality of compressors, A parallel compression type multi-refrigerating machine provided with a driving means for stepping down. 2. A table including a table for storing the number of steps according to the value of the history, wherein the driving unit responds by referring to the table based on the value of the history calculated by the calculating unit. The number of steps is read, and one of the plurality of compressors is stepped down by the number of steps.
The parallel compression type multi-refrigerating apparatus according to claim 1. 3. The calculation means refers to the sum of the deviation value detected by the pressure detection means and the total deviation value of the past several times as the deviation history value. The parallel compression type multi-refrigerating apparatus according to claim 1.