JP2951051B2 - Cooling device and cooling device control method based on fuzzy inference - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is applied to a refrigerating apparatus such as an air conditioner, a freezer / refrigerator, and a freezer / refrigerator case, and controls the degree of superheat by adjusting the opening of an expansion valve. The present invention relates to a cooling device and a control method thereof by fuzzy inference.

[0002]

2. Description of the Related Art Conventionally, in this type of cooling apparatus, as disclosed in Japanese Patent Application Laid-Open No. 60-196569, for example, a valve is driven by a pulse motor between a condenser and an evaporator in a refrigerant circuit to open a valve. An expansion valve whose degree is adjusted is interposed, the degree of superheat is obtained from the difference between the evaporation temperature of the refrigerant in the evaporator and the outlet temperature, and the degree of opening of the expansion valve is adjusted to maintain this degree of superheat constant. This prevents the liquid from returning to the compressor.

Here, as the control method in the above publication, so-called PID control is adopted. This PID control is based on a deviation between a set superheat degree and a measured superheat degree, and is controlled so as to eliminate this deviation from an output proportional thereto, and is controlled based on a change in the deviation, that is, a differential value to eliminate the deviation. D control, and I control, which performs control based on the steady-state deviation, that is, the integrated value, so as to eliminate it.

[0004]

In such a PID control, it is difficult to follow a transient fluctuation, especially after defrosting, and therefore, the phenomenon of liquid return to the compressor or an overheating state continues for a long time. There was also. In order to solve this problem, measures such as changing the proportionality constant have been taken, but this time there has been a problem that the sensitivity becomes too sensitive and the stability of the control deteriorates.

[0005] It is an object of the present invention to solve the above-mentioned problems, and to provide a cooling apparatus and a control method thereof capable of appropriately and quickly responding to a transient fluctuation and a steady deviation.

[0006]

According to the present invention, there is provided a refrigerant circuit comprising a compressor, a condenser, an expansion valve, and an evaporator connected in sequence,
Means for detecting the evaporation temperature of the refrigerant, means for detecting the outlet temperature of the evaporator, and control means for adjusting the opening of the expansion valve based on the evaporation temperature of the refrigerant and the outlet temperature of the evaporator. When the opening degree adjustment output is determined by the means, a fuzzy inference using a deviation of the degree of superheat of the refrigerant circuit, a steady state deviation of the deviation, and a change in the deviation as input variables is used.

In the present invention, the deviation of the degree of superheat of the refrigerant circuit is set as an input variable A, and the steady-state deviation of the deviation is set as an input variable B,
The change of the deviation is used as an input variable C to determine a membership value corresponding to each input variable from a membership function corresponding to each input variable of a plurality of inference rules, and then the output variable Y of the inference rule is fuzzy synthesized. This is a method of controlling a cooling device by fuzzy inference, in which an inference result is obtained by taking its center of gravity, and this is used as an output for adjusting the opening of an expansion valve connected to the inlet of the evaporator.

[0008]

According to the present invention, it is possible to quickly cope with fluctuations in the degree of superheat, and further to cope with steady-state deviations to accurately eliminate the liquid return state and the overheat state.

[0009]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. FIG. 1 shows a refrigerant circuit diagram of a cooling device 1. The cooling device 1 is configured by connecting a compressor 2, a condenser 3, an expansion valve 4, and an evaporator 5 in a ring shape with a pipe to compress the refrigerant. Liquefaction,
A well-known refrigeration cycle for reducing pressure (expansion) and evaporating is formed.

A space 6 surrounded by a dashed line is a space to be cooled which is cooled by the cold air heat-exchanged by the evaporator 5, and includes a cool air A1 supplied from the evaporator 5 and a return cool air A2 returning to the evaporator 5. Is provided.

Reference numeral 8 denotes a controller for controlling the opening / closing operation of the expansion valve 4. As shown in FIG. 2, the controller 8 compares a set superheat degree, which is a target value, with a feedback signal. 9, an internal algorithm unit 10 serving as an adjustment unit, a valve drive unit 11 serving as an operation unit, an evaporator temperature measuring unit 12 detecting the temperature of the evaporator 5, and a cooled unit detecting the temperature of the space 6 to be cooled. A space temperature measuring unit 13, a second comparing unit 14 for comparing the set temperature with the cooled space temperature, and a valve fully closed signal generating unit 1
5.

The controller 8 includes a first sensor 16 for measuring the evaporator inlet temperature, a second sensor 17 for measuring the evaporator outlet temperature, a third sensor 18 for measuring the supply cool air temperature, and a feedback cool air. The fourth sensor 19 for measuring temperature and the expansion valve 4
They are connected via signal lines 20 to 24.

In the present invention, a pulse drive type expansion valve shown in FIG. 3 is used as the expansion valve 4. The valve 4 is a pulse motor comprising a coil 25, a rotor 26, a gear 27 and a drive shaft 28. A valve part 30, a bellows 31, a refrigerant inlet pipe 32, which is pressed by the drive shaft 28,
A valve body 34 comprising a refrigerant outlet pipe 33, and a pulse motor for maintaining an appropriate degree of superheat by a valve opening control signal (pulse signal) from the valve driving section.
Drive the motor 29; Further, the rotational force of the pulse motor 29 is converted into a vertical movement of the drive shaft 28 to adjust the valve opening.

Next, the opening and closing operation of the expansion valve 4 will be described.

In FIG. 2, SHS is a preset superheat degree, SH is an evaporator outlet temperature ST-refrigerant temperature from the inlet to the middle of the evaporator, that is, an evaporation temperature ET.
, DV is a deviation calculated from SH-SHS, HSS is an adjustment signal for correcting deviation according to fuzzy control described later, and BKC controls an operation amount based on the adjustment signal. Opening control signal giving the number of pulses for opening and closing the valve, GA is a refrigerant flow rate which is reduced by the expansion valve 4 and becomes a control amount, DT is a change in condensing pressure, a change in temperature and humidity of outside air, a supply cold air A1 and a return cold air A2. Is a disturbance to the evaporator 5 such as a temperature difference and an enthalpy difference.

First, a description will be given of the degree of superheat control that does not generate a so-called liquid back or overheat state, that is, a valve opening operation, in which the refrigerant liquid returns to the compressor 2.

When the set superheat degree SHS is set to 5 ° C., the set superheat degree SHS is compared with the superheat degree SH measured by the evaporator temperature measuring section 12 by the first comparing section 9 and the deviation DV is calculated. Is input to the internal algorithm unit 10.

The internal algorithm unit 10 determines the adjustment signal HSS using fuzzy inference.

As an input, that is, as a variable (fuzzy variable) of the condition part of the rule, the deviation DV is set as an input variable A, and an integral value obtained by integrating the deviation DV over a predetermined period;
That is, the steady-state error IDV is set as an input variable B, and the differential value of the error from before the predetermined sampling period to the present, that is, the change DDV of the error is set as an input variable C.

The output, ie the output variable Y at the conclusion of the rule, takes the control signal HSS.

Five fuzzy labels are used: PB (positive and large), PM (positive and medium), ZR (zero), NM (negative and medium), and NB (negative and large).
The following seven rules are used as inference rules. Furthermore, positive means a dry state and negative means a wet state.

The first rule is that if the input variable A is NBa
d input variable B is NMand input variable C is ZRthenY
Is NM "and the second rule is" if input variable A is NBand
Input variable B is ZRand input variable C is NMthenY is NB ", and the third rule is" if input variable A is NMand input variable B is NMand input variable C is ZRthenY is Z
R ", the fourth rule is" if input variable A is ZRand input variable B is ZRand input variable C is NMthenY is N
M ", the fifth rule is" if input variable A is PMand input variable B is ZRand input variable C is ZRthenY is P
M ", the sixth rule is" if input variable A is PBand input variable B is ZRand input variable C is PMthenY is P
B ", the seventh rule is" if input variable A is PBand input variable B is PMand input variable C is ZRthenY is P
M ”respectively.

Next, each rule will be described in detail.

The membership function of each rule is shown in FIG. 4, and the membership function at the left end of each rule indicates how close the measured superheat SH is to the set superheat SHS. It is for judging the degree of salinity,-is wet,
+ Indicates a thirst state, and the deviation DV is set as an input variable A. The second membership function from the left is for integrating the deviation DV for a predetermined period of time to determine the steady-state deviation of whether the wet state or the thirst state continues, and-indicates that the wet state continues. + Indicates that the thirst state continues, and the steady-state deviation IDV, which is the integral value of the deviation, is set as the input variable B. The second membership function from the right is for judging the degree of change whether the deviation DV changes in the wet direction, does not change, or changes in the dry direction. The change, +, indicates that the change is in the drying direction, and the change DDV, which is the differential value of the deviation, is used as the input variable C. The membership function at the right end is used to determine the degree of adjustment of the opening of the expansion valve 4 as a conclusion, and corresponds to the above-described HSS.
Indicates a valve closing direction, and + indicates a valve opening direction.

The first rule is that the state of the refrigerant circuit is a wet state in which the liquid refrigerant returns to the compressor 2 considerably, the steady state deviation is a little wet, and if there is no change in the superheat degree deviation, the expansion valve 4 is slightly closed ".

That is, the left end is a mountain-shaped membership function that has a maximum value (1) when the superheat degree deviation DV is considerably wet (−6). Obtains the membership value M11. The second from the left is a mountain-shaped membership function that has a maximum value (0.75) when the steady-state error IDV is slightly wet (−3). -The ship value M12 is obtained. The second from the right is a mountain-shaped membership function that has a maximum value (1) when there is no change in deviation DDV (= 0). By substituting the input variable C into this, the membership value M13 is obtained. I get it. The minimum membership value of each of the membership values M11, M12 and M13 is the degree of establishment M1 of the first rule.
Is selected as The right end of the conclusion is a mountain-shaped membership function with the maximum value (1) in the direction (-3) in which the valve 4 is slightly closed, and the area below the satisfaction degree M1 (the hatched portion in the figure) is the first. It is output as an adjustment signal HSS1 according to the rule.

The second rule is that the refrigerant circuit state is a wet state in which the liquid refrigerant returns to the compressor 2 considerably, there is no steady state deviation,
If the deviation of the degree of superheat slightly changes in the wet direction, the expansion valve 4 is considerably closed. "

That is, at the left end, the deviation DV of the superheat degree is similarly-
This is a mountain-shaped membership function that has a local maximum value (1) when it is 6, and the membership value M21 is obtained by substituting the input variable A into this function. The second from the left is a mountain-shaped membership function that has a maximum value (0.75) when there is no steady-state error IDV (0), and the input variable B
Is substituted to obtain the membership value M22. The second from the right is a mountain-shaped membership function that has a maximum value (1) when the deviation change DDV is slightly wet (-3), and the membership function is obtained by substituting the input variable C into this function. The value M23 is obtained. Similarly, the minimum value among the membership values M21, M22, M23 is selected as the degree of establishment M2 of the second rule. The right end of the conclusion is a mountain-shaped membership function with the maximum value (1) in the direction (-6) in which the valve 4 is substantially closed, and the area below the degree of establishment M2 (the hatched portion in the figure) is the second. Adjustment signal HSS with rules
Output as 2.

The third rule is that the refrigerant circuit state is a wet state in which the liquid refrigerant returns to the compressor 2 a little, the steady state deviation is a little wet, and if there is no deviation in the degree of superheat, the expansion valve 4 is changed. Is not satisfied. "

That is, the left end is a mountain-shaped membership function having a maximum value (1) when the superheat degree deviation DV is slightly wet (-3), and the input variable A is substituted into this. Obtains the membership value M31. 2 from left
The third is a mountain-shaped membership function that has a maximum value (0.75) when the steady-state deviation IDV is slightly wet (−3).
The ship value M32 is obtained. The second from the right is the change in deviation D
This is a mountain-shaped membership function that has a local maximum value (1) when there is no DV (0), and a membership value M33 is obtained by substituting an input variable C into this function. Similarly, the minimum value of the membership values M31, M32, and M33 is selected as the degree of establishment M3 of the third rule. The right end of the conclusion part is a mountain-shaped membership function having a maximum value (1) when the opening degree of the valve 4 is not changed (0), and the area below the satisfaction degree M3 (shaded area in the figure) is It is output as the adjustment signal HSS3 in the third rule.

A fourth rule is that the expansion valve 4 is slightly closed if the superheat degree of the refrigerant circuit is a set value, there is no steady-state deviation, and the deviation of the superheat degree slightly changes in the wet direction. Indicates the degree of establishment.

That is, the left end is a mountain-shaped membership function which has a maximum value (1) when there is no superheat degree deviation DV (0). M41 is obtained. The second from the left is a mountain-shaped membership function that has a local maximum value (0.75) when there is no steady-state error IDV (0). By substituting the input variable B into this, the membership value M42 is obtained. I get it.
The second from the right is a mountain-shaped membership function that has a maximum value (1) when the deviation change DDV is slightly wet (-3), and the membership function is obtained by substituting the input variable C into this function. The value M43 is obtained. Similarly, the minimum value of the membership values M41, M42, and M43 is selected as the degree of establishment M4 of the fourth rule. The right end of the conclusion is a mountain-shaped membership function with the maximum value (1) in the direction (-3) in which the valve 4 is slightly closed, and the area below the degree of establishment M4 (the hatched portion in the figure) is the fourth. It is output as the regulation signal HSS4 in the rule.

The fifth rule is the degree of satisfaction of the condition that "the refrigerant valve is slightly dried, the expansion valve 4 is slightly opened if there is no steady-state error and there is no change in the superheat error". Show.

That is, the left end is a mountain-shaped membership function that has a maximum value (1) when the superheat degree deviation DV is slightly in the drying direction (+3). The membership value M51 is obtained. 2 from left
The maximum is the local maximum value (0. 0) when there is no steady-state error IDV (0).
75) is a mountain-shaped membership function. By substituting the input variable B into the function, the membership value M5 is obtained.
2 is found. The second from the right is a mountain-shaped membership function which becomes a local maximum value (1) when there is no change in the variation DDV of the deviation (0). By substituting the input variable C into this, the membership value M53 is obtained. Is found. Similarly, the minimum value of the membership values M51, M52, and M53 is selected as the degree of establishment M5 of the fifth rule. The right end of the conclusion is a mountain-shaped membership function having a maximum value (1) in the direction (+3) in which the valve 4 is slightly opened, and the area below the satisfaction degree M5 (the hatched portion in the figure) is the fifth rule. Is output as the adjustment signal HSS5.

The sixth rule states that "if the degree of superheat of the refrigerant circuit is considerably dry, there is no steady-state error, and if the deviation of the degree of superheat slightly changes in the drying direction, the expansion valve 4 is considerably opened." Indicates the degree of satisfaction of the condition.

That is, the left end is a chevron-shaped membership function that has a maximum value (1) when the superheat degree deviation DV is considerably dry (+6), and the input variable A is substituted into this. The membership value M61 is obtained. The second from the left is a mountain-shaped membership function that has a maximum value (0.75) when there is no steady-state error IDV (0),
By substituting the input variable B into this, the membership value M62 is obtained. The second from the right is a chevron-shaped membership function that reaches a local maximum value (1) when the change in deviation DDV changes slightly in the drying direction (+3).
Is substituted to obtain the membership value M63. Similarly, the minimum value of the membership values M61, M62, and M63 is selected as the degree of establishment M6 of the sixth rule. The right end of the conclusion is a mountain-shaped membership function having the maximum value (1) in the direction (+6) in which the valve 4 is considerably opened, and the area below the satisfaction degree M6 (the hatched portion in the figure) is the sixth rule. As the adjustment signal HSS6.

The seventh rule is that the condition is that the superheat degree of the refrigerant circuit is considerably dry, the steady-state deviation is a little dry, and if there is no change in the superheat degree, the expansion valve 4 is slightly opened. Is shown.

That is, the left end is a mountain-shaped membership function which has a maximum value when the deviation DV of the superheat degree is considerably in the drying direction (+6). The membership function is obtained by substituting the input variable A into this function. The value M71 is obtained. The second from the left is a mountain-shaped membership function that has a maximum value (0.75) when the steady state error IDV is a little thirst (+3), and the membership is obtained by substituting the input variable B into this function. The value M72 is obtained. The second from the right is the change in deviation DD
This is a mountain-shaped membership function that becomes a local maximum value (1) when V does not change (0), and a membership value M73 is obtained by substituting an input variable C into this function. Similarly, the minimum value of the membership values M71, M72, M73 is selected as the degree of establishment M7 of the seventh rule. The right end of the conclusion is a mountain-shaped membership function having the maximum value (1) in the direction (+3) in which the valve 4 is slightly opened, and the area below the degree of establishment M7 (shaded area in the figure) is the seventh rule. Adjustment signal H at
Output as SS7.

The control signal HS obtained by the above-described rules
The control signals HSS are obtained by fuzzy combining S1 to S7 by weighted averaging and obtaining the center of gravity. here,
The maximum value of the membership function of the input variable A and the input variable C is 1, whereas the maximum value of the membership function of the input variable B is as small as 0.75. As a result, the steady-state deviation IDV becomes the deviation DV and the variation of the deviation DDV.
The weight is heavier than that, and the factor of the integral value is made to work better.

Next, the above operation will be executed assuming an actual situation.

As a first example, a wet state with a deviation DV = -4 (that is, an input variable A = -4) and a steady-state deviation IDV =-
2 (ie, the input variable B = −
2), change in deviation If the wet state changes slightly in the direction of wetness of DDV = -2 and the wet state tends to expand (that is, the input variable C = -2), the membership function at the left end as shown in FIG. Only the first to third rules are hit, the second membership function from the left hits all functions except the seventh rule, and the second membership function from the right is other than the sixth rule Hits all functions. That is, the membership values M11 = 0.5, M12 = 0.5, M13 = 0.5, M21 = 0.5, M22 = 0.25, M23 =
0.75, M31 = 0.75, M32 = 0.5,
M33 = 0.5, M41 = 0, M42 = 0.2
5, M43 = 0.75, M51 = 0, M52 =
0.25, M53 = 0.5, M61 = M63 =
0, M62 = 0.25, M71 = M72 = 0, M
73 = 0.5.

The rules obtained from these membership values as the conclusion of each rule are only the first to third rules. In the first rule, the membership values M11 = M12 =
M13 = 0.5 is selected, and the area below M1 = 0.5 is set to HSS1. In the second rule, the membership value M
22 = 0.25 is selected, and the area below M2 = 0.25 is taken as HSS2. In the third rule, the membership value M32 = M33 = 0.5 is selected, and the area below M3 = 0.5 is set to HSS3.

FIG. 5 shows a value obtained by superimposing these HSS1 to HSS3.
= -1.38 (direction for slightly closing the valve 4).

The control signal HSS obtained by the fuzzy inference as described above is input to the valve driving unit 11 and the valve driving unit 1
1 is based on the control signal HSS, and provides a valve opening control signal BKC for closing the expansion valve 4 for a step corresponding to -1.38 to the expansion valve 4 to reduce the refrigerant flow rate GA by reducing the valve opening, Eliminate liquid return. In particular, in the above example, in the second rule, the members of the membership function of the steady-state deviation IDV
The ship value M22 is selected as the establishment degree M2, and the degree of closing the valve 4 is smaller than when the input variable B is not taken. That is, when the wet state is slightly continued (input variable B = −2), the degree of closing the valve 4 is slightly reduced, and the fluctuation of the superheat degree is reduced as much as possible. This valve opening / closing step is performed by changing the output variable of FIG.
6 is determined by a factor of 200/256 or 256 times the resolution.

Next, as a second example, in a dry state where the deviation DV = + 1 (that is, the input variable A = + 1), the steady-state deviation IDV
= + 2 and the thirst continues a little (that is, the input variable B
= + 2) and a change in deviation DDV = 0 and no change (ie, input variable C = 0), as shown in FIG. 6, the membership function at the left end has only the fourth and fifth rules. Hit, the second membership function from the left is the fourth to seventh
The rule hits, and the second membership function from the right hits. That is, the membership value M11 = M
12 = 0, M13 = 1, M21 = M22 = 0, M
23 = 0.25, M31 = M32 = 0, M33 =
1, M41 = 0.75, M42 = M43 = 0.2
5, M51 = 0.5, M52 = 0.25, M53
= 1, M61 = 0, M62 = M63 = 0.25, and M71 = 0, M72 = 0.5, and M73 = 1.

The rules obtained as the conclusion of each rule from these membership values are only the fourth and fifth rules. In the fourth rule, the membership values M42 = M43 =
0.25 is selected, and the area under M4 = 0.25 is HS
S4 is set. In the fifth rule, the membership value M52
= 0.25, and the area below M5 = 0.25 is H
SS5.

FIG. 7 shows a value obtained by superimposing these HSSs 4 and 5, and the center of gravity becomes 0, and HSS = 0 (valve 4).
Is not changed). Also in this case, the fifth
In the rule, the membership value M52 of the membership function of the steady-state error IDV is selected as the satisfaction degree M5,
The degree to which the valve 4 opens is smaller than when the input variable B is not taken (it does not actually open). . In other words, when the thirst state continues only a little (input variable B = + 2), the degree of opening of the valve 4 is slightly reduced, and the fluctuation of the degree of superheat is minimized.

In the above-described embodiment, the first to seventh rules are set as inference rules based on experimental results, but the present invention is not limited thereto, and more or fewer rules may be set.

The control signal HSS obtained by the fuzzy inference as described above is similarly input to the valve drive section 11, and the valve drive section 11 opens the expansion valve 4 for a step corresponding to +3 based on the control signal HSS. Degree control signal BKC to the expansion valve 4 to increase the valve opening degree ~ opening area ~ refrigerant flow rate G
The superheat degree SHS is set to 5 by the mechanical action of increasing A.
The valve opening is adjusted to maintain the refrigerant flow rate GA at ° C.

Here, the temperature control of the space 6 to be cooled, which is generally called a thermocycle, will be described. In FIG. 2, the measured temperature TM is a value obtained by processing the average value of the temperatures of both the supply cool air A1 and the return cool air A2. Is calculated by the second comparison unit 14 with the set temperature TS. In the second comparison unit 14,
When the temperature signal of TM> TS is output, that is, when the measured temperature TM is higher than the set temperature TS, the superheat control is performed, and when the temperature signal of TM ≦ TS is output, that is, the measured temperature TM Is lower than or equal to the set temperature TS, the temperature of the cooled space 6 is controlled.

That is, when the measured temperature TM of the space to be cooled 6 reaches the set temperature TS, the second comparator 14 outputs TM ≦ TS
Is input to the valve fully-closed signal generator 15, the valve-closed signal BP is output from the valve fully-closed signal generator 15 to the valve driver 11, the expansion valve 4 is fully closed, and the Is stopped.

This fully closed state continues until the upper limit temperature higher than the set temperature TS is reached. When the temperature reaches the upper limit, the expansion valve 4
Is opened again, and the opening / closing operation based on the above-described fuzzy inference is performed. With the above operation, the temperature control of the cooled space 6 and the superheat degree control of the refrigerant circuit are performed.

[0053]

As described above, according to the present invention, by using fuzzy inference for adjusting the opening degree of the expansion valve of the cooling device, it is possible to quickly respond to transient fluctuations in the refrigerant circuit, , And the variation in the degree of superheat can be accurately suppressed. Therefore, the state of liquid return to the compressor and the state of overheating are smoothly eliminated, and the reliability can be improved.

In particular, since the fuzzy inference is performed based on the deviation of the superheat degree, the steady-state deviation, and the change of the deviation, the superheat degree control can be performed quickly and stably, and based on the rules determined experimentally. Therefore, only a qualitative relationship needs to be determined, and there is an advantage that a mathematical model is not required, and there is little restriction on determination of an operation amount, and control is hardly saturated.

[Brief description of the drawings]

FIG. 1 is a refrigerant circuit diagram.

FIG. 2 is a block diagram of a controller.

FIG. 3 is a longitudinal sectional view of an expansion valve.

FIG. 4 is an explanatory diagram of rules (inference rules).

FIG. 5 is an explanatory diagram of synthesis of rule conclusions.

FIG. 6 is an explanatory diagram of rules (inference rules).

FIG. 7 is an explanatory diagram of synthesis of rule conclusions.

[Explanation of symbols]

 2 Compressor 4 Expansion valve 5 Evaporator 8 Controller 16 First sensor 17 Second sensor

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁶ , DB name) F25B 1/00

Claims (2)

(57) [Claims] 1. A refrigerant circuit in which a compressor, a condenser, an expansion valve, and an evaporator are sequentially connected, a unit for detecting a refrigerant evaporation temperature, a unit for detecting an outlet temperature of the evaporator, and the refrigerant Control means for adjusting the degree of opening of the expansion valve based on the evaporation temperature of the evaporator and the outlet temperature of the evaporator. A cooling device characterized by using fuzzy inference using a deviation and a change in the deviation as input variables. 2. A membership corresponding to each input variable of a plurality of inference rules, wherein a deviation of the degree of superheat of the refrigerant circuit is an input variable A, the steady-state deviation is an input variable B, and a change of the deviation is an input variable C. Member according to each input variable from function
After obtaining the ship value, the output variable Y of the inference rule is fuzzy-synthesized, and the center of gravity is obtained to obtain an inference result, which is used to adjust the opening of an expansion valve connected to the inlet of the evaporator. A method of controlling a cooling device by fuzzy inference, wherein the method is used for output.