JPH07190508A - Freezer - Google Patents

Abstract

PURPOSE:To provide a freezer which is capable of improving the follow-up property to a load and preventing the start of a compressor from being frequently initerrupted by measuring pressure at an inlet of the compressor and automatically altering a time interval till the time the operation number of the compressors when the pressure value exceeds a preset range. CONSTITUTION:There are inputted into a control board 7 for controlling capacity a defrosting completion signal and a pressure signal detected by a pressure detector 6. After the defrosting, a load is increased together with an increase of variations thereof. Accordingly, once the defrosting completion signal is inputted, a certain predetermined time after the defrosting, i.e., a time interval till the capacity control is again performed is reduced. Hereby, the follow-up property with larger pressure variations is ensured, and reversely with smaller variations of pressure frequency of starting or interruption of each of compressors 1a, 1b, 1c can be restricted. As a result, the load of the compressor is reduced to avoid an increase of the power cost, overheating of a motor, and the shortening of the life of the motor.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a refrigeration system, and more particularly to operation control of a refrigeration system in which a plurality of compressors are connected in parallel and capacity control is performed.

[0002]

2. Description of the Related Art In a conventional refrigeration system, when the capacity is controlled by changing the number of operating compressors, the time interval until the number of operating compressors is changed is either fixed or fixed by manual setting. The method of choice is taken.

A related device of this type is, for example, Japanese Utility Model Publication No. 2-20058.

[0004]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
In a refrigeration system with a constant time interval until the number of operating compressors is changed during capacity control by changing the number of operating compressors, if the time interval is short, start / stop of the compressor due to a sudden increase / decrease in load. Becomes more frequent. Therefore, there is a problem that the compressor is burdened. Further, the electric motor of the compressor has a large current at the time of starting, and frequent starting has a problem of increasing the electricity bill, overheating of the motor, and shortening of the life of the motor.

Contrary to the above, when the time interval until the number of operating compressors is changed is long, the followability to the load fluctuation becomes poor and the time required to reach the required capacity increases. there were.

An object of the present invention is to obtain a refrigeration system in which the frequency of starting and stopping the compressor is minimized without impairing the followability to load fluctuations.

[0007]

In order to achieve the above-mentioned object, the structure of the present invention comprises a plurality of compressors connected in parallel,
In a refrigeration system including a control device that performs capacity control by changing the number of operating compressors according to load, the control device inputs a function of performing capacity control at predetermined step time intervals and a predetermined signal. At this time, a step time interval prior to the step time interval is set, and the capacity control is performed based on the set step time interval.

[0008]

[Operation] The pressure value at the inlet of the compressor is measured, and when the pressure value exceeds the preset range, the time interval until the number of operating pressure compressors is changed is automatically changed. As a result, load following performance can be improved and frequent start and stop of the compressor can be prevented.

Further, by automatically changing the time interval until the number of operating compressors is changed by a signal that detects time, temperature, etc., load followability is improved and frequent start / stop of the compressor is performed. It can be prevented.

In the refrigeration system, since the load is high and the load changes rapidly after defrosting, the time interval until the number of operating compressors is changed after defrosting is changed to be short to improve load followability. And Further, during normal operation, the load fluctuation is small, so the time interval until the number of operating compressors is changed is returned to the original long state, and frequent start / stop of the compressor is prevented.

[0011]

Embodiments of the present invention will be described below with reference to FIGS.
This will be described with reference to FIG.

As shown in FIG. 1, compressors 1a, 1b, 1
A refrigeration cycle is formed by the main components of c, the condenser 2, the liquid receiver 3, the expansion valve 4, and the evaporator 5. A pressure detector 6 is attached to the pipe on the suction side of the compressor. The capacity is controlled by the pressure value detected by the pressure detector 6.

When the pressure value detected by the pressure detector 6 exceeds the pressure value A shown in FIG. 3, the capacity is increased, and conversely, the pressure value B shown in FIG.
If it falls below the range, control is performed to reduce the capacity. The capacity control here means starting or stopping of the compressor. After the capacity control is once performed (that is, after the compressor is started or stopped), if the capacity cannot be followed, the capacity control is performed again, but a certain time interval is provided until the capacity control is performed again. (This is called the step time interval).

In FIG. 2, the defrosting end signal and the pressure value signal detected by the pressure detector 6 are input to the control panel 7 for capacity control (in the case of FIG. 3, the pressure value signal is the pressure value). There are two values, A and above, and B and below, but not above C.) After defrosting, the load is large and the load fluctuates greatly. Therefore, when the defrosting end signal is input, the time interval (step time interval) until the capacity control is performed again is shortened for a certain period of time after defrosting. As a result, it is possible to ensure the followability when the pressure fluctuation is large, and conversely, when the pressure fluctuation is small, the frequency of starting or stopping the compressor can be suppressed.

The type of the control panel 7 shown here does not matter. For example, any device such as a microcomputer, a programmable controller, and a relay may be used.

As another method, in FIG. 4, a pressure value C is further provided on the high pressure side of the pressure value A, and when the pressure value detected by the pressure detector 6 exceeds the pressure value C (after defrosting, After defrosting, the load is high and the load fluctuates abruptly.) Time interval (step time interval) until capacity control is performed again
Shorten. As a result, when the pressure value detected by the pressure detector 6 is less than or equal to the pressure value C and the fluctuation is small, the frequency of starting or stopping the compressor is suppressed, and the followability at high load and large load fluctuation is secured. be able to. (In the case of FIG. 4,
There are three signals that enter the control panel 7 of FIG. 2 that are the pressure value A or higher, the pressure value B or lower, and the pressure value C or higher, and do not include the defrosting end signal). Although the case of shortening is described, the present invention is also applicable to the case of lengthening the step time interval.

[0017]

Since the present invention is constructed as described above, it has the following effects.

(1) There is an effect that the followability to the load fluctuation is improved and the time required to reach the required capacity is shortened.

(2) There is an effect that the frequency of starting and stopping the compressor is reduced. As a result, the load on the compressor is further reduced. Further, although the electric current of the electric motor at the time of starting is large, frequent starting is reduced, so that there is an effect that it is possible to avoid problems such as an increase in electricity bill, overheating of the electric motor, and shortening of the life of the electric motor.

[Brief description of drawings]

FIG. 1 is a refrigeration cycle according to an embodiment of the present invention.

FIG. 2 shows a control device according to an embodiment of the present invention.

FIG. 3 is a graph showing the relationship between the pressure fluctuation in the cooling circuit and the capacity control instruction pressure value according to the embodiment of the present invention.

FIG. 4 is a graph showing a relationship among pressure fluctuations in a cooling circuit, a capacity control instruction pressure value, and a step time interval change instruction pressure value according to an embodiment of the present invention.

[Explanation of symbols]

 1a, 1b, 1c ... Compressor, 2 ... Condenser 3 ... Liquid receiver, 4 ... Expansion valve 5 ... Evaporator, 6 ... Pressure detector 7 ... Control panel

Claims (5)

[Claims] 1. A refrigerating apparatus comprising a controller for connecting a plurality of compressors in parallel and changing the number of operating compressors according to a load for capacity control. It has a function of performing capacity control at time intervals and a function of setting a step time interval prior to the step time interval when a predetermined signal is input and performing capacity control based on the step time interval. Refrigeration equipment. 2. The refrigerating apparatus according to claim 1, wherein the predetermined signal is a signal indicating that the pressure value of the cooling circuit has exceeded a predetermined range. 3. The refrigerating apparatus according to claim 1, wherein the predetermined signal is a signal indicating completion of defrosting or the like. 4. The refrigerating apparatus according to claim 1, 2 or 3, wherein a step time interval set when the predetermined signal is input is shorter than the predetermined step time interval. 5. The refrigerating apparatus according to claim 1, 2 or 3, wherein a step time interval set when the predetermined signal is input is longer than the predetermined step time interval.