JPH0760023B2 - Refrigeration equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a refrigeration system used in a plurality of refrigerating / freezing showcase groups installed in the same place such as a supermarket, that is, load fluctuations. The present invention relates to a refrigerating device which can be always operated in an optimal state in a large refrigerating device.

[Prior Art] As a conventional refrigerating apparatus of this type, there is one shown in FIG. In FIG. 2, 1 is a parallel compression type refrigeration system,
A cooling device 2 is composed of a combination of a plurality of coolers 2a, 2b, 2c such as showcases.

In the parallel compression refrigeration system 1, the rated capacity ratio of the compressor is set to approximately 2: 1 on the receiver connected downstream of the water-cooled condenser 1a or the air-cooled condenser (not shown). The large capacity compressor 1b and the small capacity compressor 1c are mounted in parallel, and the refrigerant discharge pipe 1d and the suction pipe 1e of each compressor 1b and 1c are connected in parallel.

Note that 1f is a pressure equalizing and equalizing pipe that connects the crank chambers of the compressors 1b and 1c to each other.

Further, 5 is according to the pressure difference between the output signal of the pressure detection unit 3 for detecting the low pressure side refrigerant pressure and the refrigerant pressure set by the pressure setting unit 4 for setting the low pressure side refrigerant pressure to be converged. This is a control unit that controls the operation and stop of the compressors 1b and 1c individually.

Further, as shown in FIG. 3, the normal pressure region has a capacity in the parallel compression refrigeration system 1 depending on three values of the capacity increasing pressure value, the capacity decreasing pressure value, and the low pressure cut value set by the pressure setting unit 4. In parallel with the area D above the capacity up pressure value that outputs an up signal, and the area c below the capacity down pressure value that is neither the capacity down signal nor the capacity up signal to the parallel compression refrigeration system 1 and less than the capacity up pressure value. It is divided into four areas, i.e., an area b below the capacity down pressure value for outputting the capacity down signal to the compression type refrigeration apparatus 1 and an area a below the low pressure cut value for outputting a stop signal to the parallel compression type refrigeration apparatus 1.

Next, the operation will be described. For example, the required power for obtaining the maximum refrigerating capacity for the refrigerating load of the cooling device 2 is
If it is 15HP, the rated capacity of the compressor 1b is 10HP, the compressor
The rated capacity of 1c is 5HP.

On the other hand, in the cooling device 2 including a plurality of coolers 2a, 2b, 2c, the cooling load is 0 to 10 depending on the usage of each showcase.
It fluctuates significantly up to 0%.

Here, when the refrigerating load decreases, the refrigerant pressure on the low pressure side of the refrigerating cycle decreases, and with this, the pressure detecting unit 3
The level of the pressure detection signal output from the control unit 5 also decreases.

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), when the pressure detection signal is lower than the capacity down pressure value, that is, In the case of area B, the control unit 5
Controls to reduce the capacity of the parallel compression type refrigeration system 1 and lowers the cooling capacity.

In this way, when the cooling capacity is lowered, the refrigerant pressure on the low pressure side of the refrigeration cycle rises, converges to the region C, and the operation becomes stable.

Further, when the cooling load is high, the refrigerant pressure on the low pressure side of the refrigeration cycle rises, and with this, the pressure detection unit 3
The level of the pressure detection signal output from the control unit 5 to the control unit 5 increases.

As a result, when the pressure detection signal is higher than the capacity increase pressure value, that is, in the area D, the control unit 5 controls so that the capacity of the parallel compression refrigerator 1 is increased, and the cooling capacity is increased. .

In this way, when the cooling capacity is increased, the refrigerant pressure on the low pressure side of the refrigeration cycle is reduced, converges to the area C, and the operation is stabilized.

The time from when the pressure detector 3 detects the pressure in the area D or the area B until the capacity up signal or the capacity down signal output from the controller 5 is the same.

When the pressure of the refrigerant on the low pressure side of the refrigeration cycle is equal to or lower than the low pressure cut value, that is, when the region B is reached, the compressors 1b and 1c are immediately stopped.

Therefore, the refrigeration load is 33
Only the compressor 1c with a rated capacity of 5HP operates independently when the partial load is less than%.

Further, when the refrigeration load is in the range of 33 to 66%, only the compressor 1b having a rated capacity of 10 HP is operated independently.

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

That is, as shown in FIG. 4, the refrigeration load is reduced to 0, by selectively operating and stopping the large and small compressors whose rated capacity ratio is selected to be about 2: 1.
Capacity control operation can be performed in three stages of 33,66%.

[Problems to be Solved by the Invention] Since the conventional refrigeration system is configured as described above, when the lowest capacity compressor is operating independently, the refrigerant pressure is compared with the refrigerant pressure which is about to converge. When the pressure is low, that is, in the range b below the capacity down pressure set value, it was not judged how much the pressure value is decreasing even if the cooling load is drastically decreased after the pressure is detected. The operation time until the compressor is stopped by generating the output signal for changing the capacity of the machine is set to 3 minutes or more in order to suppress the pressure fluctuation due to the capacity change as much as possible. That was a waste of electricity.

The present invention has been made to solve the above problems, and when the cooling load sharply decreases, it is possible to obtain a refrigerating apparatus in which the compressor can be quickly stopped by judging by the pressure value to save energy. With the goal.

[Means for Solving the Problems] A refrigerating apparatus according to the present invention condenses a plurality of compressors each having a suction pipe and a discharge pipe connected in parallel and having different capacities, and refrigerant discharged from these compressors. A refrigeration circuit in which a condenser and a cooler that evaporates and vaporizes the refrigerant sent from the condenser are sequentially connected to form a closed circuit, and the refrigerant pressure on the low-pressure side of the refrigeration circuit is detected. A pressure detection unit that generates a pressure detection signal according to the refrigerant pressure, a capacity up pressure value that is the upper limit and a capacity down pressure value that is the lower limit of the converged pressure value of the refrigerant pressure on the low pressure side to be converged, and all compressors. A pressure setting unit that sets a low pressure cut value, which is the pressure value that should output a stop signal immediately, determines whether the pressure detection signal is higher than the capacity up pressure value or lower than the capacity down pressure value, and the judgment result In a refrigeration system equipped with a control unit that generates a capacity control output signal for performing capacity control of a plurality of compressors based on, a predetermined pressure value is set between the capacity down pressure value and the low pressure cut value. , If the lowest capacity compressor among multiple compressors is operating independently, the compressor continues to operate even if the pressure detection signal becomes lower than the capacity down pressure value, and the pressure detection signal reaches the specified pressure value. It is provided with a compressor capacity setting unit that generates an output signal forcibly stopping the compressor only after reaching the limit.

[Operation] In the refrigerating apparatus of the present invention, when a predetermined pressure value is set between the capacity down pressure value and the low pressure cut value, and the compressor having the lowest capacity among the plurality of compressors operates independently, The compressor continues to operate even if the detection signal becomes lower than the capacity down value, and the output signal for forcibly stopping the compressor is generated only when the pressure detection signal reaches the predetermined pressure value, and the compressor stops quickly. Therefore, energy saving can be achieved.

[Embodiment] An embodiment of the refrigerating apparatus of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing the configuration of one embodiment of the present invention. The same parts as those of FIG. 2 are designated by the same reference numerals, and the description thereof will be omitted. The parts different from those of FIG. 2 will be mainly described.

In FIG. 1, the portions indicated by reference numerals 1 to 5 are the same as those in FIG. 2, and a compressor capacity setting unit indicated by reference numeral 6 is newly added to the configuration of FIG.

That is, this compressor capacity setting unit 6 uses the output signal for capacity control generated from the control unit 5 to set the pressure detection signal to a predetermined pressure value equal to or lower than the converged pressure value when the compressor 1c having the lowest capacity is operating independently. When it reaches, an output signal for forcibly stopping the compressor is generated, and the compressor can be stopped.

Next, the operation of the refrigerating apparatus of the present invention will be described. According to the capacity control output signal generated from the control unit 5, when only the compressor 1c is operating independently, when the refrigerant pressure is lower than the refrigerant pressure to be converged, that is,
In the region B below the capacity down pressure set value, the pressure detection signal is below the convergent pressure value by the function of the compressor capacity setting unit 6 and the predetermined pressure value above the low pressure cut value 0 kg / cm ² G for pump down, for example, Compressor 1 if 0.4kg / cm ² G is reached
c is supposed to stop.

In the embodiment, the case where the capacity control of the compressor is performed by the pressure detection signal has been described, but the same operation as above can be obtained when the capacity control is performed by other frequency converters.

[Effects of the Invention] As described above, according to the present invention, when the lowest capacity compressor is operating independently, the compressor continues to operate even if the pressure detection signal becomes lower than the capacity down pressure value, and the pressure detection signal indicates the predetermined pressure. Since it has a compressor capacity setting unit that generates an output signal that forcibly stops the compressor only when the value reaches the specified value, it will continue to operate even if the compressor with the lowest capacity in island operation becomes lower than the capacity down pressure value. Since the compressor with the minimum capacity is forcibly stopped when the predetermined pressure value is reached, it is possible to prevent the temperature inside the refrigerator from rising and to prevent frequent start and stop of the compressor due to a sudden load change. It is possible to save energy.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of an embodiment of a refrigeration system of the present invention, FIG. 2 is a diagram showing a configuration of a conventional refrigeration system, and FIG. 3 is a refrigerant pressure on a low pressure side in the refrigeration system of FIG. FIG. 4 is a diagram showing a region, and FIG. 4 is an explanatory diagram of capacity control operation of the refrigerating apparatus of FIG. 1a ... condenser, 1b, 1c ... compressor, 2a-2c ... cooler,
3 ... Pressure detection unit, 4 ... Pressure setting unit, 5 ... Control unit,
6 ... Compressor capacity setting section. The same reference numerals in the drawings indicate the same or corresponding parts.

Claims (1)

[Claims] 1. A plurality of compressors each having a suction pipe and a discharge pipe connected in parallel and having different capacities, a condenser for condensing and liquefying refrigerant discharged from these compressors, and a condenser for delivering the refrigerant. A refrigerating circuit in which pipes are sequentially connected to form a closed circuit with a cooler that evaporates the refrigerant to be evaporated,
A pressure detection unit 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 an increase in capacity that is the upper limit of the converged pressure value of the refrigerant pressure on the low-pressure side that is to be converged. A pressure setting unit for setting a pressure value and a capacity down pressure value which is a lower limit and a low pressure cut value which is a pressure value at which a stop signal should be immediately output to all compressors, and whether the pressure detection signal is higher than the capacity up pressure value. Capacity down In the refrigerating apparatus including a control unit that determines whether the pressure is lower than the pressure value and outputs a capacity control output signal for performing capacity control of the plurality of compressors based on the determination result, the capacity down When a predetermined pressure value is set between the pressure value and the low pressure cut value, and the compressor with the lowest capacity of the plurality of compressors is operating independently, the pressure detection signal is the capacity down pressure. A compressor capacity setting unit that continuously operates the compressor even when the pressure becomes lower than a value and generates an output signal for forcibly stopping the compressor only when the pressure detection signal reaches the predetermined pressure value is provided. Refrigerating device characterized by.