JPH10141784A - Refrigerator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform energy conservation operation and to reduce a change of interior temperature of a display case by automatically changing a pressure set value of a microcomputer controller according to load change and hence executing optimum operation control in response to a largely varying load, and reducing ON/OFF control of a refrigerator. SOLUTION: In the case of an operation stopping state, when number of times of stops is integrated to reach a set number, a pressure set value is slightly slid upward. In this case, only a capacity down value may be slid upward, and a capacity up value and operation stop value may simultaneously slid. The number of times of stops is different depending upon size of a facility, indoor temperature and load change. Since it is repeatedly controlled, about 4 to 6 times/hour may be sufficient. Sliding width of the pressure set value may be slightly about 0.01MPa. Thus, number of times of ON/OFF of a refrigerator is reduced, operating pressure is enhanced, and energy conservation can be more enhanced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a refrigeration system for a store, and more particularly to a refrigeration system having a plurality of showcases connected thereto and having a large load variation.

[0002]

2. Description of the Related Art Conventionally, as this kind of refrigerating apparatus, there are a multi refrigerating machine in which a plurality of compressors are combined and an inverter refrigerating machine. An example of controlling the capacity of a refrigerator is disclosed in
No. 175970 and JP-A-63-140254, one embodiment of the prior art will be described with reference to FIGS. FIG. 2 shows a cycle system diagram in the case of a multi refrigerator. Refrigerator 1 combines three compressors 2-a, 2-b and 2-c, forms a refrigerating cycle with condenser 3 and liquid receiver 4, and shows showcases 7-a, 7-b and 7-b. .. Are connected to a plurality of 7-x units. Each showcase has an evaporator 8, an expansion valve 9, and a solenoid valve 1.
0 is built in. Each showcase independently controls the supply of refrigerant by opening and closing the electromagnetic valve 10 by the temperature controller 11 to control the temperature in the showcase.
The low pressure of the refrigerator varies depending on the number of showcases to which the refrigerant is supplied. The microcomputer controller 6 changes the capacity of the refrigerator (the number or frequency of the refrigerators) so as to approach the preset pressure via the pressure sensor 5 attached to the low-pressure pipe of the refrigerator 1. FIG. 3 shows the relationship between the low pressure and the operating capacity, and this flowchart of FIG. 4 is shown. The contents of the control will be described with reference to FIGS. The capacity up value, capacity down value, and operation stop value are set in the microcomputer controller. The shutdown value may use a mechanical pressure switch. The operating pressure (low pressure) is read periodically and compared with the set pressure to control the operating capacity. In the case of the zone (A) higher than the capacity increase value, the load on the showcase side is large, and the capacity of the refrigerator is increased. The zone (B) between the capacity up value and the capacity down value is a case where the capacity of the load and the capacity of the refrigerator match, and the operation capacity is maintained without being changed. In the case of the zone (C) lower than the capacity down value, the refrigerator capacity is too large, and the operating capacity is reduced. The operating capacity is controlled so that the low pressure is always between the capacity up value and the capacity down value. The operation of the refrigerator is stopped when the low-pressure pressure is reduced even with the minimum capacity and the operation stop pressure is reached. The operation capacity is controlled by changing the number of rotations by the number of compressors to be operated or the frequency of the compressor drive by an inverter.

[0003]

SUMMARY OF THE INVENTION In a conventional refrigeration system,
Since the pressure set value was fixed, there were the following problems.

(1) Since the load on the low pressure side fluctuates greatly in daytime, nighttime, and summer and winter, the operation capacity is frequently controlled, and the optimum operation control cannot always be performed throughout the year.

(2) When the load greatly fluctuates and decreases, the follow-up ability to the minimum operation capacity is slow, and the on / off control of the operation is performed even in a multi refrigerator or an inverter refrigerator having a capacity control function. Sometimes it was repeated.

(3) When a large number of low-pressure-side devices are connected, the number of devices requiring cooling decreases and the low-pressure pressure decreases, or when the connection piping is long, the low-pressure pressure is reduced due to the pressure loss due to the piping length. Therefore, the pressure set value had to be set lower. Setting the pressure set value lower delays the timing at which the minimum operation capacity is reached, and promotes the above operation. The present invention has been made to solve these problems. The present invention implements optimal operation control according to a load that fluctuates greatly, reduces on / off control of a refrigerator as much as possible, and achieves more energy-saving operation and a temperature in a cabinet such as a showcase. It is an object of the present invention to obtain a refrigeration system for reducing fluctuations in the temperature.

[0007]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention is to automatically change a pressure set value of a microcomputer controller according to a load change. Judgment and slide the pressure set value upward little by little to extend the operation time with the required minimum operation capacity, thereby reducing the number of times the refrigerator is turned on and off, and increasing the operation pressure to achieve more energy-saving operation. It is intended.

In the case of long continuous operation with the minimum operation capacity, the pressure is periodically returned to the initial pressure setting or the maximum operation capacity is set so that low-pressure equipment with insufficient cooling is not generated. I have.

In the refrigeration apparatus according to the present invention, when the load on the low pressure side is reduced and the on / off operation of the refrigerator is increased, the pressure set value is automatically slid upward. The operation time at the operation capacity of, also increases, the number of times the refrigerator is turned on / off is reduced, and more energy-saving operation can be achieved. Decreasing the number of times the refrigerator is turned on / off reduces fluctuations in the temperature of the inside of the refrigerator such as a showcase and the like, resulting in high freshness operation. In addition, by periodically returning to the initial pressure setting or maximizing the operation capacity, there is no fear of generating low-pressure side equipment with insufficient cooling.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described. FIG. 1 is a flowchart of the operation control of the present invention,
The basic parts of the refrigeration cycle and operation control are the same as those of the prior art shown in FIGS. The control added after the operation stop state in the flowchart of FIG. 1 is a part of the present invention. In the case of the operation state after taking in Ps (low pressure), the capacity is increased, the capacity is maintained, or the capacity is reduced as before, but in the case of the operation stop state, the stop times are accumulated and the set number is reached. If so, slightly slide the pressure setting upward. In order to achieve the object of the present invention, only the capacity down value needs to be slid upward, but the capacity up value and the operation stop value may also be slid simultaneously. The number of stops varies depending on the size of the equipment, the internal temperature, and the load fluctuation. However, since the number of stops is repeatedly controlled, it may be about 4 to 6 times / hour, and the slide width of the pressure set value may be as small as about 0.01 MPa. .

Next, when the number of stop times is small and the set number is not reached, the capacity of the refrigerator matches the cooling load on the low pressure side, and it can be said that it is not necessary to change the pressure set value. Connect a large number of low-pressure devices and reduce the low-pressure pressure due to a decrease in the number of devices that require cooling. In the case of setting, it is conceivable that continuous operation is performed with a small number of stops and a small operation capacity. In this case, in order to eliminate insufficient cooling of the low-pressure side device, if a predetermined operation time has elapsed, it is possible to periodically return to the initial pressure set value and solve the problem. Instead of returning to the initial pressure set value, the same effect can be exhibited by operating the refrigerator once at the maximum capacity and then returning to the normal capacity operation. When the number of stops is small and the set number of times has not been reached, control for temporarily increasing the operation capacity of the refrigerator has been described.However, in many cases, it is not necessary to consider the above-described problem. The control may be returned to the capacity control.

The general number of stops is 4 to 6 times / hour. However, if the number of stops can be selected depending on the operation status of the refrigeration facility, the versatility can be further expanded. This setting can be easily performed by a dip switch (not shown) on the microcomputer board. It is also effective to periodically return to the initial pressure set value, or to set a predetermined time for operating the refrigerator at the maximum capacity once, so that it can be similarly selected.

[0013]

According to the present invention, the cooling load is reduced by automatically changing the pressure set value of the capacity control of the multi refrigerator or the inverter refrigerator according to the change in the number of times the refrigerator is stopped due to the load fluctuation. However, the operation time of the refrigerator at the minimum capacity can be prolonged, the number of stop times can be reduced as much as possible, and the operation pressure can always be operated at a high level, so that significant energy saving operation can be achieved.

[0014] Reducing the on / off operation of the refrigerator reduces fluctuations in the internal temperature of the refrigerator such as a showcase.
High freshness operation is also possible. In addition, since the refrigerator is subjected to the most stress at the time of starting, reducing the on / off operation is also effective in terms of reliability.

Operating at a higher operating pressure means that the evaporating temperature becomes higher, so that frost formation on the evaporator is reduced, the number of times of defrosting can be reduced, energy saving is achieved, and cooling is performed more efficiently. Can reduce the adverse effect on the contents caused by a remarkable rise in the internal temperature. As described above, the present invention has many effects.

[Brief description of the drawings]

FIG. 1 is a flowchart of operation control showing one embodiment of the present invention.

FIG. 2 is a system diagram of a refrigeration cycle of a conventional store refrigeration apparatus.

FIG. 3 is an explanatory diagram of a conventional relationship between operating pressure and operating capacity.

FIG. 4 is a flowchart of the operation control of FIG. 3;

[Explanation of symbols]

1: Refrigerator, 2-a to 2-c: Compressor, 3: Condenser, 4
... a liquid receiver, 5 ... a pressure sensor, 6 ... a microcomputer controller.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kazumasa Ota 390 Muramatsu, Shimizu-shi, Shizuoka Prefecture Air Conditioning Systems Division, Hitachi, Ltd.

Claims (1)

[Claims] 1. A refrigerating cycle comprising a multi-refrigerator combining a plurality of compressors or an inverter refrigerating machine for controlling the number of revolutions of the compressor by an inverter, a showcase or a unit cooler, and a capacity-increasing pressure value and capacity. In a refrigeration system whose operation is controlled by a down pressure value and an operation stop pressure value,
A refrigeration system characterized by automatically changing the capacity up pressure value and the capacity down pressure value.