JPH065139B2 - Refrigeration equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention is, for example, a refrigerating apparatus used in a plurality of refrigerating / freezing showcase groups installed in the same place such as a market, that is, a load variation is large. The present invention relates to a refrigerating device that can be always operated in an optimum state.

[Conventional technology]

As a conventional refrigerating apparatus of this type, there is one shown in FIG. In FIG. 3, 1 is a parallel compression type refrigeration system,
2 is a plurality of coolers 2a, 2b, 2 such as showcases
It is a cooling device configured by a combination of c.

The parallel compression refrigeration system 1 has a rated capacity ratio of approximately 2 to 1 selected on a receiver connected downstream of a water-cooled condenser 1a or an 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 with each other.

In addition, 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. 4, the normal pressure region has a capacity in the parallel compression refrigeration system 1 which is set by 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, when the required power for obtaining the required refrigerating capacity for the refrigerating load of the cooling device 2 is 15, the rated capacity of one compressor 1b is set to 10, and the rated capacity of the other compressor 1c is set to 5. ing.

On the other hand, in the cooling device 2 composed of a plurality of coolers 2a, 2b, 2c, the cooling load greatly changes from 0 to 100% depending on the usage status of each showcase.

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 case of region D, the control unit 5 controls the capacity of the parallel compression refrigeration unit 1 to increase, and increases the cooling capacity.

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.

After the pressure detection unit 3 detects the pressure in the area D or the area B, the time until the capacity up signal or the capacity down signal output from the control unit 5 is the same, and the stability of operation is taken into consideration. Then it is set to 3 minutes.

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
Is supposed to stop immediately.

Therefore, the refrigeration load is 3 when the above refrigeration load changes.
Compressor 1c with a rated capacity of 5 when the partial load is 3% or less
Only is operated alone.

When the refrigeration load is 33 to 66%, the rated capacity is 1
Only the compressor 1b of 0 operates independently.

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

That is, as shown in FIG. 5, 0, 33, 6 is controlled by selectively operating and stopping the large and small compressors whose rated capacity ratio is selected to be about 2: 1.
It is possible to perform 4 steps of capacity control operation of 6%.

[Problems to be solved by the invention]

Since the conventional refrigeration system is configured as described above, stable operation is performed when the load fluctuation is gentle, but it takes 3 minutes until a capacity up or capacity down signal is output, so the load fluctuation is rapid. In this case, there is a problem in that the internal temperature rises because the change in capacity is delayed, and as a result, the freshness of the coolant is impaired and the operation becomes inefficient. Also,
Since the capacity change time is the same when the capacity is increased and when the capacity is decreased, overcurrent flows when the capacity is increased and the high pressure side refrigerant pressure rises sharply, so the capacity change time can be shortened, but the capacity change There was also a problem that the time could not be shortened too much.

The present invention has been made in order to solve the above problems, and an efficient refrigeration apparatus capable of rapidly changing the capacity according to the changing speed of the load, to obtain a refrigeration apparatus capable of energy-saving operation. To aim.

[Means for solving problems]

The refrigeration apparatus according to the present invention, the time to change the compressor capacity, the length according to the difference between the pressure set on the low pressure side of the refrigeration cycle detected by the pressure detection unit and the pressure setting unit,
In addition, a time setting unit is provided to always set the capacity to be longer when the capacity is increased than when the capacity is decreased.

[Action]

In the present invention, the time setting unit sets the length according to the pressure difference between the pressure detection signal and the convergent pressure value, and the time for changing the compressor capacity so that the capacity increase is always longer than the capacity decrease time. Therefore, it works so as to quickly reach a predetermined pressure without being accompanied by an overcurrent at the time of increasing the capacity or a rapid increase in high voltage.

〔Example〕

 An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of a refrigerating apparatus, and the same parts as those of the conventional apparatus shown in FIG.
In FIG. 1, reference numerals 1 to 5 are the same as those in FIG. 3, and a time setting unit indicated by reference numeral 6 is newly added to the apparatus of FIG.

That is, the time setting unit 6 converges the time from the pressure detection unit 3 detecting the pressure in the area D or the area B to the generation of the capacity up or capacity down signal output from the control unit 5 with the pressure detection signal. It has a function of determining according to the pressure difference between the pressure values, and the relationship is as shown in FIG.

Next, the operation of the present invention will be described. When the cooling load increases due to the output signal for capacity control generated from the control unit 5 when the compressor 1b is operating in the area C, and the detected pressure starts increasing and becomes 1.6 kg / cm ^{2 accordingly.} ,
The difference between the detected pressure (1.6kg / cm ² ) and the set pressure (1.3kg / cm ² ) is 0.3k.
Since it is g / cm ² , the detected pressure is 1.3 kg / c as shown in Fig. 2.
After 105 seconds from when m ² is exceeded, a capacity increase signal is output from the control unit 5, and the operation of the compressors 1b and 1c is started to cope with an increase in load. Conversely, if the load decreases and the detected pressure drops to 0.6 kg / cm ² while the compressor 1b is operating in the area C, the pressure difference becomes 0.2 kg / cm ² , so as shown in Fig. 2. 23 seconds after the detected pressure falls below 0.8 kg / cm ² , the control unit 5 outputs a capacity down signal, and the compressor 1c only operates. Further, when both the compressors 1b and 1c are stopped, when moving to the area D, the compressor 1c is started after a time determined by A, and the time measurement to the next mode starts from that time. If the load is large and the area is in the area D as it is, the operation of the compressor 1b is started with the characteristic of A.

〔The invention's effect〕

As described above, according to the present invention, the pressure detection section detects the refrigerant pressure on the low pressure side of the refrigeration cycle to generate a pressure detection signal, and the refrigerant pressure to be converged is set by the pressure setting section, A control unit that generates a capacity control output signal for controlling the capacity of the refrigerator by judging whether the pressure detection signal is above or below the refrigerant pressure to be converged, and the compressor capacity based on this capacity control output signal. Since a time setting unit that sets the time for changing the time according to the difference between the pressure detection signal and the convergent pressure value and always sets the capacity up time longer than the capacity down time, It is possible to change the capacity at different times depending on the changing direction and speed of the. Therefore, stable operation can be performed without causing overcurrent and sudden rise in high pressure due to sudden capacity increase, and a predetermined pressure can be reached quickly, so that the temperature of the cooling object is constant and freshness can be maintained. In addition, energy saving and efficient operation can be performed.

[Brief description of drawings]

FIG. 1 is a block diagram of a refrigerating apparatus according to an embodiment of the present invention,
FIG. 2 is a characteristic diagram showing the relationship between the difference between the detected pressure and the set pressure and the compressor capacity change time, FIG. 3 is a configuration diagram of a conventional refrigeration system, and FIG. 4 is the pressure-side refrigerant in FIG. FIG. 5 is a diagram showing the region of pressure, and FIG. 5 is an explanatory diagram of the same capacity control operation. 1a ... condenser, 1b, 1c ... compressor, 2a-2c ... cooling device, 3 ... pressure detection part, 4 ... pressure setting part, 5 ... control part,
6 ... Time 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, a condenser for condensing and liquefying the refrigerant discharged from these compressors, and a refrigerant discharged from this condenser. A refrigeration circuit sequentially connected to form a closed circuit with a cooler that evaporates and detects the refrigerant pressure on the low pressure side of this refrigeration circuit, and a pressure detection that generates a pressure detection signal according to this refrigerant pressure. Section, a pressure setting section for setting a convergent pressure value of the low-pressure side refrigerant pressure to be converged, it is determined whether the pressure detection signal is equal to or more than the convergent pressure value, the output signal based on the determination result. A controller that generates a capacity control output signal for performing up / down control of the capacity of the refrigerator based on the output signal, and a compressor capacity is changed by the capacity control output signal. Is provided with a time setting unit for setting the length according to the difference between the pressure detection signal and the converged pressure value and always setting the capacity up time longer than the capacity down time. Refrigeration equipment.