JPH0621716B2 - Refrigeration equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to, for example, a refrigerating device used in a plurality of refrigerating / freezing canister cases installed in the same place such as a market, that is, a refrigerating machine having a large load fluctuation. 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. 2, 1 is a parallel compression type refrigeration system,
Reference numeral 2 denotes a plurality of coolers 2a, 2b, 2 such as a case
It is a cooling device configured by a combination of c.

In the parallel compression refrigeration system 1, the rated capacity ratio of the compressor is selected to be about 2: 1 on the liquid receiver connected to the downstream side 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.

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. 3, the normal pressure range is determined by the parallel compression refrigeration system by three of the capacity up pressure value, the capacity down pressure value, and the low pressure cut value set by the pressure setting unit 4. Region D of a capacity up pressure value or more for outputting a capacity up signal to the device 1, and region of a capacity down pressure value or more for which the capacity down signal or the capacity up signal is not output to the parallel compression refrigeration device 1 and less than the capacity up pressure value. C, a region b below the capacity down pressure value for outputting the capacity down signal to the parallel compression type refrigeration system 1 and a region a below the low pressure cut value for outputting the stop signal to the parallel compression type refrigeration system 1. That is, by the above capacity up signal and capacity down signal,
As shown later in FIG. 4, operation control is performed in which the capacity is changed step by step.

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
Selected as 10.

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

Here, when the refrigeration load decreases, the refrigerant pressure on the low pressure side of the refrigeration cycle decreases, and along with this, the pressure detection 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 for comparing 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 along 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-up pressure value, that is, in the area D, the control unit 5 controls so that the capacity of the parallel compression type refrigeration 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 detection unit 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 control unit 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, 1
c is set to stop immediately.

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

Also, when the refrigeration load is in the range of 33 to 66%, the rated fixed amount is 1
Only the compressor 1b of 0 operates independently.

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

That is, as shown in FIG. 4, by selectively operating and stopping the large and small compressors whose rated capacity ratio is selected to be approximately 2 to 1, , 6
It is possible to perform capacity control operation in four stages of 6,100%.

[Problems to be solved by the invention]

Since the conventional refrigeration system is configured as described above, when the pressure of the refrigerant is higher than the pressure of the refrigerant which is about to be converged when the compressor is restarted after the two compressors are stopped, that is, the capacity up pressure is increased. In the area d equal to or larger than the set value, the time from the detection of the pressure to the generation of the output signal for changing the capacity of the compressor must be 3 minutes or more in order to suppress the pressure change due to the capacity change as much as possible. Therefore, the compressor 2
It takes 3 minutes to operate the small-capacity compressor and 3 minutes to switch the small-capacity compressor to the large-capacity compressor until the two compressors operate from the standstill condition. Therefore, it takes 3 minutes to switch to the operation of two compressors by adding a small-capacity compressor, and it takes 9 minutes or more in total, so it takes a long time to reach the target refrigerant pressure, and the freshness of the object to be refrigerant is not maintained. There was a drawback.

The present invention has been made to solve such a problem, and even when the compressor is restarted after two compressors are stopped,
An object of the present invention is to obtain a refrigerating apparatus which can quickly reach a predetermined pressure and keep the freshness of an object to be cooled.

[Means for Solving Problems] A refrigerating apparatus according to the present invention includes a plurality of compressors each having a suction pipe and a discharge pipe connected in parallel, and a condenser for condensing refrigerant discharged from the compressor. And a refrigerating section sequentially connected to form a closed circuit by a cooler that evaporates and vaporizes the refrigerant sent from the condenser, and the refrigerant pressure on the low pressure side of the refrigerating section is detected to the refrigerant pressure. A pressure detection unit that outputs a pressure detection signal according to the pressure detection unit, a pressure setting unit that sets a converged pressure value of the low-pressure side refrigerant pressure that is to be converged, and whether the pressure detection signal is the converged pressure value or more or less. A means for performing a stepwise operation suppression for increasing or decreasing the capacity of the refrigerating section step by step by individually controlling the operation and stop of each of the compressors based on the result of the determination, Capacity control A capacity control output signal is output from the control section when the pressure detection section outputs a capacity control output signal for a predetermined time after the pressure detection section detects that the plurality of compressors are stopped. The means for switching the stepwise operation to the non-stepwise operation at the restarted time, in order to obtain a compressor capacity suitable for the pressure difference between the pressure detection signal and the converged pressure value immediately after the restart, And a compressor capacity setting unit that determines a compressor to be operated from among the plurality of compressors according to the difference.

[Operation] In the present invention, the control unit performs stepwise operation control for increasing or decreasing the capacity of the refrigeration unit step by step, and outputs the capacity control output signal after the pressure detection unit detects the pressure.
Output after a lapse of a predetermined time. Therefore, during normal operation, smooth operation can be realized, and stable operation can be realized without the number of operating machines repeatedly increasing and decreasing.

On the other hand, when restarting the compressor, the compressor capacity setting unit
A predetermined compressor is selected according to the pressure difference between the pressure detection signal and the converged pressure value. Therefore, upon restarting, a capacity suitable for the pressure difference can be obtained immediately after restarting, and the predetermined pressure can be reached quickly.

〔Example〕

Embodiments 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 in 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, the compressor capacity setting unit 6 uses the capacity control output signal generated by the control unit 5 to output the plurality of compressors 1
When b and 1c are all stopped, it has a function of determining the capacity at the time of restarting the compressor according to the pressure difference between the pressure detection signal and the converged pressure value.

Next, the operation of the refrigerating apparatus of the present invention will be described. When the refrigerant pressure is higher than the refrigerant pressure to be converged while the compressors 1b and 1c are stopped by the output signal for capacity control generated from the control unit 5, that is, the area of the capacity up pressure set value or more. In D, the compressor capacity setting unit 6
When the pressure difference between the pressure detection signal and the converged pressure value is very large, for example, when the pressure difference is 4 kg / cm ² or more and the compressor is restarted, the plurality of compressors 1b and 1c are operated simultaneously. It has become.

Also, the pressure difference is medium, for example, 2 kg / cm ² or more and 4 k.
When the pressure is less than g / cm ² , the compressor 1b operates when restarting the compressor, and when the pressure difference is less than 2 kg / cm ² , the compressor 1c operates when restarting the compressor. Therefore, the predetermined pressure can be reached quickly. That is, in the present embodiment, although the control unit 5 outputs the capacity control output signal after a predetermined time has elapsed after the pressure detection unit detects the pressure, it does not differ between the normal operation and the restart operation, but at the time of restart, Normal stepwise operation can be switched to non-step operation only for restart, and optimum capacity can be obtained immediately after restart.

〔The invention's effect〕

As described above, in the present invention, when the control unit performs the stepwise operation control, the capacity control output signal is generated after a predetermined time has elapsed after the pressure detection unit detected the pressure. Therefore,
During normal operation, stable control can be performed without frequently repeating the start / stop of the compressor and the increase / decrease of the operating number. On the other hand, when the compressor is restarted, the compressor capacity setting unit determines the compressor suitable for the pressure difference between the pressure detection signal and the converged pressure value, and the capacity control output signal is output once to provide an appropriate capacity. Obtained immediately after restart. Therefore, even when the load is rapidly increased and the compressor is restarted from the stop state, it is possible to quickly reach the predetermined pressure while maintaining the stability of the control during the normal operation. As a result, for example, the temperature of the uncooled object can be kept constant, and the freshness of the object to be cooled can be effectively maintained.

[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 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 detector, 4 ... Pressure setting unit, 5 ...
... control unit, 6 ... compressor capacity setting unit. 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 refrigerant discharged from the compressor, and a refrigerant discharged from the condenser. A refrigerating section in which a cooler to be vaporized is sequentially connected so as to form a closed circuit, and a pressure detecting section that detects a refrigerant pressure on the low pressure side of the refrigerating section and outputs a pressure detection signal corresponding to the refrigerant pressure, A pressure setting unit that sets the convergent pressure value of the refrigerant pressure on the low pressure side that is to be converged, and determines whether the pressure detection signal is equal to or greater than or equal to the convergent pressure value, and based on the determination result, each compression A capacity control output signal for performing capacity control of the refrigeration unit, which is a means for performing stepwise operation control to increase or decrease the capacity of the refrigeration unit step by step by individually controlling the operation / stop of the refrigeration unit. The pressure detector is After the force is detected, the control unit that outputs after a predetermined time has elapsed, and at the time of restart when the output signal for capacity control is output from the control unit in a state where all of the plurality of compressors are stopped, the stepwise operation is not performed. Means for switching to a stepwise operation, in order to obtain a compressor capacity suitable for the pressure difference between the pressure detection signal and the converged pressure value immediately after restarting, among the plurality of compressors according to the pressure difference. A refrigerating apparatus comprising: a compressor capacity setting unit that determines a compressor to be operated from.