JPH06100385B2 - Refrigerator control method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a refrigerator control method for controlling the capacity of a compressor forming a refrigeration cycle according to a load.

[Technical background of the invention and its problems]

It is considered that the refrigerator and the air conditioner basically have the same refrigeration cycle, and the control technology of the air conditioner that controls the capacity of the compressor according to the air conditioning load can be used for controlling the refrigerator. However, since the load of the air conditioner and the load of the refrigerator differ in measuring method, it takes a long time to reach the control target zone and the hunting is likely to occur. This will be described below.

First, the air conditioner is equipped with the refrigeration cycle shown in FIG. 7, and the gas refrigerant discharged from the compressor 1 during the cooling operation is made into a liquid refrigerant by the condenser (outdoor heat exchanger) 2, and then,
It is supplied to the evaporator (indoor heat exchanger) 5 installed in the room 4 through the expansion valve 3, is converted into the gas refrigerant again here, and is then sucked into the compressor 1. The air conditioning load in such a refrigeration cycle can be roughly known by measuring the difference between the room temperature and the temperature set value. Therefore, the indoor temperature is detected by the temperature sensor 6, and the temperature sensor 6
The inverter device 7 controls the capacity of the compressor 1 based on the output signal of

Here, the inverter device 7 includes a temperature setter for setting the room temperature, a microcomputer, and the like, and the stored data of the microcomputer is used to determine the variation range of the difference between the room temperature and the temperature set value by the eighth value. 7 as shown
Divide into two zones. In this case, the range where the room temperature decreases and the deviation from the temperature setting value T _s is +1 to +2 [° C] is C
When set as a zone, the temperature set value is set when the room temperature rises.
The range in which the deviation from T _s is +2 to +3 [° C] is defined as the C zone, and further, two zones centered on the temperature set value T _s in the falling gradient of room temperature and the temperature in the rising gradient of room temperature. Two zones centered on (T _s +1), that is, a D zone indicated by diagonal lines, are control target zones.

The inverter device 7 performs the processing shown in the flowchart of FIG. 9 in order to maintain the control target zone. That is,
When the room temperature decreases, the output frequency of the inverter device is reduced by 10 [Hz] every time the zone changes, and the system switches to low capacity operation (step 105). Conversely, when the room temperature rises, the output frequency of the inverter device changes every time the zone changes. Is increased by 10 [Hz] to switch to high-performance operation (step 106).

On the other hand, except when the difference between the room temperature and the temperature setting value belongs to the control target zone, when the operating time in the same zone exceeds the predetermined value, increase 5 [Hz] in the zone higher than the control target zone, On the contrary, in the zone lower than the control target zone, 5
[Hz] is being reduced (step 109).

As a result, the room temperature (or the difference from the set value) can be quickly matched to the control target zone according to the air conditioning load, and
As long as the room temperature is within the control target zone, the rotation speed of the compressor does not change, which enables highly efficient operation.

In order to apply such control technology to the control of the refrigerator, a refrigerating load instead of the air conditioning load must be obtained. Generally, it is appropriate to use the difference between the suction pressure of the compressor and the set pressure as the refrigerating load. is there.

FIG. 5 is a system diagram of an apparatus that performs such control. The refrigerant that has left the condenser 2 is sucked into the compressor 1 through the evaporators 5a to 5c provided for each showcase. Of these, an electromagnetic on-off valve 8a and an expansion valve 3a are provided in front of the evaporator 5a,
Similarly, an electromagnetic opening / closing valve 8b and an expansion valve 3b are provided in front of the evaporator 5b.
However, an electromagnetic opening / closing valve 8c and an expansion valve 3c are provided in front of the evaporator 5c. A pressure sensor 9 for measuring the suction pressure of the refrigerant is provided on the suction side of the compressor 1, and the output signal thereof is applied to the inverter device 7.

The inverter device 7 is capable of continuously changing the frequency of the AC voltage applied to the compressor 1 within a range of approximately 25 to 80 (Hz), and thus the rotation speed of the compressor 1 is 1400 to 4500 (rp).
It changes in the range of m).

Then, an appropriate pressure corresponding to the refrigeration load is set by a setting device (not shown) that constitutes the inverter device 7, and the deviation from the pressure sensor 9 is divided into a plurality of zones corresponding to FIG. If the same control as described above is performed, the suction pressure of the compressor 1 changes as shown in FIG.

That is, if the output frequency of the inverter device 7 increases or decreases by 10 [Hz] due to a change in the zone, or if the output frequency of the inverter device 7 increases or decreases by 5 [Hz] because the operating time in the same zone exceeds a predetermined value. The suction pressure also fluctuates greatly following this.

By the way, in the refrigerator, because the suction pressure of the compressor is closer to the refrigeration load than the temperature in the showcase,
Although the pressure sensor 9 is provided in the preceding stage of the compressor 1, since the rotational speed of the compressor 1 and the suction pressure are directly related to each other, the variation of the suction pressure with respect to the set value is large, and as a result, It takes a long time to reach the control target zone,
Moreover, there is a problem that hunting is likely to occur.

[Object of the Invention]

The present invention has been made to solve the above problems, and a method of controlling a refrigerator that can quickly reach the control target zone and that can suppress hunting by suppressing the pressure fluctuation on the suction side of the compressor. For the purpose of providing.

[Outline of Invention]

In order to achieve this object, the present invention divides the variation range of the difference between the suction pressure of the compressor and the set pressure into a plurality of zones,
The compressor is operated by changing the rotation speed of the compressor in response to the change of the zone, and the operating time in the same zone is controlled except when the difference between the suction pressure and the set pressure belongs to the control target zone. The compressor is operated by changing the rotation speed so that the difference between the suction pressure and the set pressure becomes smaller when the set value is set larger as it gets closer to the zone.

Example of Invention

FIG. 2 is a structural example of an apparatus for carrying out the present invention. Since the installation positions of the refrigeration cycle and the pressure sensor are all equal to those in FIG. 5, the detailed structure of the inverter device 7a different from that in FIG. 5 will be described. It is shown.

In FIG. 2, the inverter device 7a includes an A / D converter 11 for converting the output of the pressure sensor 9 into a digital signal, and a digital signal corresponding to the set value when the suction pressure of the compressor 1 to be held constant is set. Pressure setting device 12 that outputs a signal
And input the output signals of the pressure setter 12 and the A / D converter 11 and calculate the frequency for driving the compressor by executing a predetermined calculation process, and generate a pulse signal corresponding to this frequency. Output microcomputer 18
And a waveform synthesizing circuit 16 for synthesizing the outputs of the microcomputer 18 and outputting, for example, a three-phase pulse signal,
It is composed of a large-capacity transistor etc. connected by Graetz, and is composed of an inverter main body 17 which converts direct current of a power source (not shown) into alternating current and adds it to the compressor by controlling the conduction angle by the output of the waveform synthesizing circuit 16. Has been done.

Further, among them, when focusing on its function, the microcomputer 18 compares the output of the A / D converter 11 with the output of the pressure setting device 12 to calculate a deviation, and the comparing means 13 Of the output level of the above, and the frequency determining means 14 for determining the frequency by determining how long the operating time in the same zone, and the pulse signal corresponding to the output of this frequency determining means 14 And a signal output means 15 for generating the signal.

FIG. 1 is an explanatory diagram for explaining the outline of frequency determination, and the variation range of the difference between the suction pressure and the set pressure of the compressor is divided into seven zones A to G. In this case, a difference of 0.1 (kg / cm ² ) was found between the downward slope and the upward slope of the suction pressure, as in the case where the temperature was set differently between the downward slope and the upward slope at room temperature in the air conditioner. Have it and set the zone. Further, the D zone indicated by the diagonal lines is the control target zone.

Since the suction pressure is considerably high immediately after the start of operation of the compressor, the output frequency of the inverter device is increased until the zone A is reached, while the suction pressure is reduced and the zones A, B, C, The output frequency of the inverter device is decreased by 5 [Hz] each time it changes. When the suction pressure becomes lower than that in the G zone because the refrigeration load becomes extremely small, the output frequency of the inverter device is continuously decreased, and the suction pressure rises, and the zones become G, F. , E,
Each time it changes ...
Increase in increments of [Hz].

On the other hand, when the operating time in the A, B, C zones exceeds the time set in the microcomputer 5, 20, 30 seconds respectively, the output frequency of the inverter device is increased by 5 Hz to reach the control target zone. Match. Further, when the operating time in the G, F, and E zones exceeds 5, 20, 30 seconds, respectively, the output frequency of the inverter device is reduced by 5 Hz so as to match the control target zone.

FIG. 3 is a flowchart showing an example of the processing procedure of the inverter device 7a that executes such control.
Then, the deviation between the suction pressure of the compressor and the set pressure is obtained.

Next, at step 205, this pressure deviation is divided by the unit pressure to be zoned to determine the zone to which it belongs first and the output frequency. Then step 206
In Nos. 207 to 207, in-zone control is performed to increase or decrease the operating time in the same zone by 5 [Hz] each time the set time is exceeded. Further, in steps 209 to 211, so-called zone change control is performed in which the zone is increased or decreased by 5 [Hz] each time the zone changes.

FIGS. 4 (a) and 4 (b) are diagrams showing changes in pressure and frequency when these controls are performed. In the drawing, the suction pressure of the compressor drops, and the output frequency decreases by 5 [Hz] each time it reaches the A, B, and C zones at times t ₁ , t ₂ , and t ₃ , respectively.

Although the pressure gradually rises and falls, when it stays in the C zone for a long time, the output frequency increases by 5 [Hz] at times t ₄ , t ₅ and t ₆ when 30 [sec] has passed.

Next, at time t ₇ , the difference between the suction pressure and the set pressure is 0.1 (kg /
cm ² ] or less, and when reaching the control target zone, the output frequency also decreases by 5 [Hz], but as long as it remains in the control target zone thereafter, the output frequency does not change.

Then, the suction pressure decreased due to the sudden decrease in the refrigeration load.
When entering the E zone at t ₈ , the output frequency is 5 [Hz] at this point.
It decreases, and when it enters the F zone at time t ₉ , it becomes 5 [H
z] decrease. The operating time of the F zone of the output frequency at time t ₁₀ of more than 20 seconds 5 Hz and decreases when you Chikazukeyo control target zone.

After that, the time to reach the E zone as the suction pressure rises
At time t ₁₁ and time t ₁₂ when reaching the D zone, the output frequency increases by 5 [Hz].

Thus, when the operating time in the same zone exceeds the set value that is set larger toward the control target zone, the rotation is such that the difference between the suction pressure and the set pressure becomes small, except when it belongs to the control target zone. The compressor can be operated at different speeds.

In the above embodiment, the output frequency of the inverter device is changed to change the rotation speed of the compressor. However, even if a device that changes the rotation speed of the compressor while changing the voltage by tap switching is used, it is the same as described above. Various controls can be performed.

〔The invention's effect〕

As is clear from the above description, according to the present invention, the closer the control target zone is, the longer the time interval of speed change in the same zone is, so that the suction pressure fluctuation of the compressor can be suppressed low and the speed can be increased quickly. The effect is that the control target zone can be reached.

[Brief description of drawings]

FIG. 1 is an explanatory diagram for explaining the outline of the present invention, FIG. 2 is a block diagram showing a configuration example of an apparatus for carrying out the present invention, and FIG. 3 is a flowchart for explaining the operation of the apparatus,
FIGS. 4 (a) and 4 (b) are time charts for explaining the operation of the apparatus, FIG. 5 is a cycle system diagram of a refrigerator to which the present invention is applied, and FIG. 6 is an operation of this cycle system. 7 is a time chart for explaining, FIG. 7 is a cycle system diagram for explaining control of a general air conditioner, FIG. 8 is an explanatory diagram for explaining the outline of the limitation, and FIG. 9 is its control. It is a flowchart which shows the procedure of. 1 ... Compressor, 2 ... Condenser, 5a, 5b, 5c ... Evaporator, 7a
...... Inverter device, 9 ...... Pressure sensor, 12 ...... Pressure setting device, 17 …… Inverter body, 18 …… Microcomputer.

Claims (1)

[Claims] 1. A method of controlling a refrigerator in which a rotation speed of a compressor forming a refrigeration cycle is changed according to a load, a variation range of a difference between a suction pressure of the compressor and a set pressure is divided into a plurality of zones. The operation time in the same zone is controlled unless the rotational speed of the compressor is changed according to the change of the zone and the difference between the suction pressure and the set pressure belongs to the control target zone. A method of controlling a refrigerator, wherein the compressor is operated by changing the rotation speed so that the difference between the suction pressure and the set pressure becomes smaller when the set value is set larger as the target zone gets closer. .