JPH0563701B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is applicable to refrigeration equipment used in a group of multiple refrigeration and freezing show cases installed in the same place, such as a supermarket, that is, refrigeration equipment with large load fluctuations. This invention relates to a refrigeration system that can be operated in an optimal state at all times.

[Conventional technology]

Conventionally, there has been a device of this type as shown in FIG. In FIG. 3, 1 is a parallel compression type refrigeration system, and 2 is a plurality of show cases 2a, 2b, 2.
This is a cooling device composed of a combination of c. The parallel compression type refrigeration system 1 has a compressor with a rated capacity ratio of approximately 2:1 selected above a liquid receiver connected to the downstream side of a water-cooled condenser 1a or an air-cooled condenser (not shown). Two large-capacity compressors 1b and small-capacity compressors 1c are installed in parallel, and the refrigerant discharge pipes 1d and suction pipes 1 of each compressor 1b and 1c are installed in parallel.
e are connected in parallel with each other. Note that 1f is a pressure-equalizing oil pipe that connects the crank chambers of the compressors 1b and 1c with each other.

Further, 5 corresponds to the pressure difference between the output signal of the pressure detection unit 3 that detects the refrigerant pressure on the low pressure side and the refrigerant pressure set in the pressure setting unit 4 that sets the refrigerant pressure on the low pressure side to be converged. The above compressors 1b and 1
This is a control unit that individually controls the operation and stopping of the controllers c.

Also, as shown in Figure 4, the normal pressure region is
A region above the capacity up pressure value in which a capacity up signal is sent to the parallel compression refrigeration system 1 based on the capacity up pressure value, capacity down pressure value, and low pressure cut value set by the pressure setting section 4. (2) In a region where the pressure is above the capacity down pressure value and below the capacity up pressure value in which neither a capacity down signal nor a capacity up signal is issued to the parallel compression refrigeration system 1, a capacity down signal is issued to the parallel compression refrigeration system 1. It is divided into four regions: region (b) below the capacity down pressure value, and region (b) below the low pressure cut value that issues a stop signal to the parallel compression type refrigeration system 1.

Next, the operation will be explained. For example, if the required capacity to obtain the required refrigerating capacity for the refrigerating load of the cooling device 2 is 15, the rated capacity of one compressor 1b is selected to be 10, and the rated capacity of the other compressor 1c is selected to be 5. ing.

On the other hand, multiple show cases 2a, 2b, 2c
In the cooling device 2, the refrigeration load varies greatly from 0 to 100% depending on the usage status of each case.

Here, when the refrigeration load decreases, the refrigerant pressure on the low pressure side of the refrigeration cycle decreases, and the level of the pressure detection signal output from the pressure detection section 3 to the control section 5 also decreases accordingly.

Since the control unit 5 has a comparison circuit that compares the pressure detection signal with a reference value (capacity up pressure value or capacity down pressure value), if the pressure detection signal is lower than the capacity down pressure value, that is,
In the case of region B, the control unit 5 controls the capacity of the parallel compression type refrigeration device 1 to decrease, thereby lowering the cooling capacity. When the cooling capacity is reduced in this way, the refrigerant pressure on the low pressure side of the refrigeration cycle increases,
It converges to region C, and operation becomes stable.

Further, when the cooling load is high, the refrigerant pressure on the low pressure side of the refrigeration cycle increases, and the level of the pressure detection signal output from the pressure detection section 3 to the control section 5 increases accordingly. As a result, when the pressure detection signal is higher than the capacity up pressure value, that is, in the case of region 2, the control unit 5 controls the capacity of the parallel compression refrigeration system 1 to increase, thereby increasing the cooling capacity. . When the cooling capacity increases in this way, the refrigerant pressure on the low pressure side of the refrigeration cycle decreases,
It converges to region C, and operation becomes stable. It should be noted that the time from when the pressure detection section 3 detects the pressure in the region N or the region L until the capacity up signal or capacity down signal output from the control section 5 is generated is the same.

Note that when the refrigerant pressure on the low-pressure side of the refrigeration cycle falls below the low-pressure cut value, that is, falls into region A, the compressors 1b and 1c are designed to immediately stop.

Therefore, with respect to the above-mentioned refrigeration load fluctuation, only the compressor 1c with a rated capacity of 5 is operated independently when the refrigeration load is at a partial load of 33% or less. In addition, when the refrigeration load is in the range of 33% to 66%, compressor 1 with a rated capacity of 10
Only b is operated independently.

Furthermore, when the refrigeration load becomes 66 to 100%, compressors 1b and 1c are simultaneously operated in parallel. The transition of this capacity control operation is shown in FIG. 5.

That is, as shown in Fig. 5, by selectively operating and stopping large and small compressors whose rated capacity ratio is selected to be approximately 2:1, 0, 33, 66 , 100% capacity control operation can be performed in four stages.

[Problem that the invention seeks to solve]

However, in the conventional refrigeration equipment described above, when the refrigerant pressure fluctuates greatly, or when the refrigerant pressure at the start of operation and during pulldown after defrosting is higher than the refrigerant pressure to be converged, In region 2 above the capacity up pressure set value and region 2 below the capacity down pressure set value, the time from detection of the pressure until the output signal for changing the pressure is generated is the same, and moreover, the pressure fluctuation due to the change in capacity is the same. In order to suppress the refrigerant pressure as much as possible, it is necessary to make the time until the above output signal is generated at least 3 minutes. Therefore, it takes a long time to reach the target refrigerant pressure, and The drawback was that it did not retain its freshness.

In addition, in order to shorten the time until the target refrigerant pressure is reached, if the time until the output signal for changing the capacity is generated is shortened, the refrigeration capacity will fluctuate significantly, making it difficult to respond well to cooling load fluctuations. , there is a problem that the refrigerant pressure does not converge to the target refrigerant pressure.

This invention was made to solve the conventional problems as described above, and it is possible to quickly maintain a predetermined pressure even when there are large pressure fluctuations or when there is a large cooling load such as at the start of operation or after defrosting. It is an object of the present invention to provide a refrigeration system capable of achieving the above goals and reducing power consumption.

[Means for solving problems]

A refrigeration system according to the present invention includes a plurality of compressors each having a suction pipe and a discharge pipe connected in parallel, a condenser that condenses and liquefies refrigerant discharged from these compressors, and a refrigerant sent from the condenser. The system detects the refrigerant pressure on the low-pressure side of the refrigerant circuit and the refrigerant circuit in which condensers that evaporate refrigerant are connected in sequence to form a closed circuit, and generates a pressure detection signal according to the refrigerant pressure. a pressure detection section, a pressure setting section that sets a convergence pressure value of the refrigerant pressure on the low pressure side to be converged, and a pressure detection section that determines whether the pressure detection signal is greater than or equal to the convergence pressure value, and based on the determination result. In the area above the capacity up pressure value,
an area determination unit that generates an area determination signal for any of the following areas: an area where neither a capacity up signal nor a capacity down signal is issued; an area where the capacity down pressure is less than a low pressure cut value that issues an operation stop signal; Based on the area determination signal generated from the
A capacity control output signal for controlling the capacity of the refrigeration circuit is generated, and the time until the capacity control output signal is generated is determined by comparing the area determination signal and pressure detection signal with the convergence pressure value. an output control unit that controls based on the area determination signal that is successively changed according to the pressure difference and is just before finally outputting the capacity control output signal, and the pressure difference; , the time until the output signal for capacity control for changing the capacity in the area above the capacity up pressure value is generated; the output signal for controlling capacity for changing the capacity in the area below the capacity down pressure; The period of time required for the occurrence of the

[Effect]

The refrigeration system according to the present invention detects a low-pressure side refrigerant pressure, and when converging the low-pressure side refrigerant pressure to a convergence pressure value, determines whether the pressure detection signal is above or below the convergence pressure value to be converged. The determination unit makes a determination, and the output control unit generates an output signal for capacity control of the refrigerator in accordance with the area determination signal and the pressure difference between the pressure detection signal and the convergence pressure value, and the output control unit generates an output signal for capacity control of the refrigerator. The time until the capacity control output signal is generated is finally controlled by the area determination signal immediately before the capacity control output signal is output, and the pressure difference between the pressure detection signal and the convergence pressure value, Even when there are large pressure fluctuations or when the cooling load is large, such as at the start of operation or after defrosting, the predetermined pressure can be quickly reached, reducing power consumption. The time it takes to generate a capacity control output signal for capacity change in the area of less than the capacity down pressure is longer than the time it takes to generate a capacity control output signal for capacity change in the area of less than the capacity down pressure. Because of this, overcurrent may flow,
The detected refrigerant pressure until convergence does not change above or below the refrigerant pressure to be converged, and quickly reaches the predetermined pressure.

〔Example〕

FIG. 1 is a block diagram showing one embodiment of a refrigeration system according to the present invention, and the same parts as in FIG. 3 are indicated using the same symbols. In the figure, reference numeral 6 denotes a region determining section, which determines whether the pressure detection signal generated by the pressure detecting section 3 is above or below the refrigerant pressure to be converged. Further, 7 generates an output signal for capacity control of the parallel compression type refrigeration apparatus 1 according to the area determined by the area determining section 6, and the time period until this output signal is generated is as described above. The area determination signal and the area determination signal and the above are sequentially changed according to the pressure difference between the area determination signal and the pressure detection signal and the convergence pressure value to be converged, and are finally outputted immediately before the output signal for capacity control. Based on the pressure difference, it is determined which region B or D belongs to, and a region determination signal is generated based on the determination result. The output control section 7 calculates the time period from when the area determination signal is supplied until generating a capacity control output signal for capacity control of the parallel compression refrigeration apparatus 1 based on the area determination signal and the above. It can be freely changed according to the pressure difference between the pressure detection signal and the convergence pressure value of the refrigerant pressure to be converged. That is, the time from pressure detection to capacity change operation can be freely changed. For example, as shown in FIG. 2, the capacity change time can be changed depending on the pressure difference. That is, if the pressure detection signal output from the pressure detection unit 3 belongs to region B and the pressure difference between the pressure detection signal and the refrigerant pressure to be converged is large, an output signal for changing the capacity is generated. If the pressure difference between the pressure detection signal and the refrigerant pressure to be converged is small, the time until the output signal for changing the capacity is generated is set to 20 seconds. can do.

Moreover, the refrigerant pressure in the operating state is constantly detected and compared with the refrigerant pressure to be converged.
Depending on the pressure difference, the output time changes, for example, from 10 seconds to 11 seconds to 20 seconds, converging the refrigerant pressure. Until this convergence, the pressure detection signal does not change more than the refrigerant pressure to be converged, and quickly reaches the predetermined pressure. After reaching the predetermined pressure, parallel compression refrigeration equipment 1
Continue driving.

In addition, if the pressure detection signal output from the pressure detection unit 3 belongs to region 2 and the pressure difference between the pressure detection signal and the refrigerant pressure to be converged is large, an output signal for changing the capacity is generated. If the pressure difference between the pressure detection signal and the refrigerant pressure to be converged is small, the time until the output signal for capacity change is generated is set to 60 seconds. can do.

Moreover, the refrigerant pressure in the operating state is constantly detected and compared with the refrigerant pressure to be converged.
Depending on the pressure difference, the output time changes, for example, from 30 seconds to 31 seconds to 60 seconds, converging the refrigerant pressure. Until this convergence, the pressure detection signal does not change below the refrigerant pressure to be converged, and quickly reaches the predetermined pressure. After reaching the predetermined pressure, parallel compression refrigeration equipment 1
Continue driving.

In other words, when the refrigeration load fluctuates greatly, the refrigerant pressure on the low-pressure side of the refrigeration cycle fluctuates greatly, and the level of the pressure detection signal output from the pressure detection unit 3 also fluctuates accordingly. The refrigerant pressure is constantly detected and compared with the refrigerant pressure to be converged, and the output signal is generated to change the capacity on the capacity down side. Because it is longer than the time it takes to
The predetermined pressure is quickly reached without causing an overcurrent to flow through the parallel compression type refrigeration device 1, and without causing the detected refrigerant pressure to change above or below the refrigerant pressure to be converged until convergence.

〔Effect of the invention〕

As explained above, the refrigeration system of the present invention is
A plurality of compressors each having a suction pipe and a discharge pipe connected in parallel, a condenser that condenses and liquefies the refrigerant discharged from these compressors, and a cooler that evaporates and vaporizes the refrigerant sent out from the condenser. Detects the refrigeration circuit that is connected to the piping in order to form a closed circuit, and the refrigerant pressure on the low pressure side of this refrigeration circuit.
a pressure detection section that generates a pressure detection signal according to the refrigerant pressure; a pressure setting section that sets a convergence pressure value of the refrigerant pressure on the low pressure side to be converged; Based on the judgment result, the following areas are determined: the area above the capacity up pressure value, the area where neither the capacity up signal nor the capacity down signal is issued, the area below the capacity down pressure, and the area below the low pressure cut value where the operation stop signal is issued. an area determination unit that generates an area determination signal for which area of the area; and a capacity control output signal for controlling the capacity of the refrigeration circuit based on the area determination signal generated from the area determination unit. Then, the time until the capacity control output signal is generated is successively changed according to the area determination signal and the pressure difference between the pressure detection signal and the convergence pressure value, and finally the capacity control output signal is generated. an output control unit that performs control based on the area determination signal immediately before outputting the output signal and the pressure difference; Since the configuration is such that the time until the output signal for capacity control is generated is longer than the time until the output signal for capacity control is generated for changing the capacity in the region below the capacity down pressure, the pressure Even when there are large fluctuations or when the cooling load is large, such as at the start of operation or after defrosting, the specified pressure can be quickly reached, reducing power consumption and keeping the temperature of the cooled object constant to maintain freshness. be done. Further, the predetermined pressure is quickly reached without causing an overcurrent to flow or causing the detected refrigerant pressure until the refrigerant pressure to converge to change above or below the refrigerant pressure to be converged.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram showing an embodiment of a refrigeration system according to the present invention, FIG. 2 is a characteristic diagram showing an example of capacity change time with respect to the pressure difference between the low pressure side refrigerant pressure and the convergence pressure value, and FIG. A configuration diagram showing a conventional refrigeration system, FIG. 4 is a diagram showing a region of refrigerant pressure on the low pressure side,
FIG. 5 is an explanatory diagram of the capacity control operation of the refrigeration system shown in FIG. 3. In these figures, 1a is the condenser, 1b, 1
2a to 2c are coolers, 9 is a refrigeration circuit, 3 is a pressure detection section, 4 is a pressure setting section, 6 is a region determination section, and 7 is an output control section. Note that the same reference numerals in each figure indicate the same or corresponding parts.

Claims (1)

[Claims] 1 Multiple compressors each having a suction pipe and a discharge pipe connected in parallel, a condenser that condenses and liquefies the refrigerant discharged from these compressors, and a cooling system that evaporates and vaporizes the refrigerant sent out from the condenser. A refrigeration circuit in which the pipes are connected in sequence to form a closed circuit, a pressure detection section that detects the refrigerant pressure on the low pressure side of this refrigeration circuit and generates a pressure detection signal according to this refrigerant pressure, and A pressure setting unit that sets a convergence pressure value of the refrigerant pressure on the low pressure side to be used; and a pressure setting unit that determines whether the pressure detection signal is greater than or equal to the convergence pressure value, and based on the determination result, the capacity increase pressure value is determined to be greater than or equal to the capacity increase pressure value. an area determination unit that generates an area determination signal for any of the following areas: an area where neither a capacity up signal nor a capacity down signal is issued, an area where the capacity down pressure is below, and an area below a low pressure cut value where an operation stop signal is issued; A capacity control output signal for controlling the capacity of the refrigeration circuit is generated based on the area determination signal generated from the area determination section, and the time taken until the capacity control output signal is generated;
The area determination signal and the pressure difference are sequentially changed according to the pressure difference between the pressure detection signal and the convergence pressure value, and the area determination signal and the pressure difference immediately before the output signal for capacity control is finally output. , and an output control unit for controlling the capacity up pressure value, and the output control unit is configured to control the capacity down pressure for a period of time until the capacity control output signal is generated for changing the capacity in a region equal to or higher than the capacity up pressure value. A refrigeration system characterized in that the time is set to be longer than the time until the capacity control output signal for changing the capacity in a region of less than or equal to the above is generated.