JP3039941B2 - Refrigeration equipment - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a refrigeration system, and more particularly to a refrigeration system suitable for performing stable refrigerant flow control over a wide operating range.

[Conventional technology]

As described in JP-A-56-44569, a conventional apparatus controls the degree of superheat of refrigerant in an evaporator of a refrigeration cycle by PI control (proportional + integral operation) of a valve opening of an electric expansion valve. Configuration.

[Problems to be solved by the invention]

In recent years, the introduction speed of the computerization technology in the refrigerating apparatus has been remarkable, and the operation range of the refrigerating apparatus has been greatly expanded by adopting an inverter control compressor, an electric expansion valve and the like. In particular, refrigerant control by an electric expansion valve is important for preventing liquid return, preventing excessive refrigerant overheating, and improving performance.

However, as a conventional expansion valve control method, as represented by a temperature expansion valve, a proportional control based only on a current evaporator superheat degree signal or a superheat degree of an evaporator And the degree of superheat over time
PI control, PID control (control based on proportional + integral + differential operation)
Was used. In these control methods, since control is performed using mathematical formulas, accurate information on the dynamic characteristics of the target superheat degree of the refrigerant is required, and whether the control can be properly performed based on the accuracy of this information is required. Will be decided. When the operation of the refrigeration system is performed over a wide range, the dynamic characteristics of the refrigerant superheat greatly change.Therefore, in order to perform good control with the conventional technology, the control constant of PI control must be adjusted to various operating conditions. It is necessary to switch accordingly. Actually, since the control becomes very complicated, the above-mentioned conventional technology is not practical, and in reality, the present situation recognizes that controllability is insufficient.

An object of the present invention is to control an electric expansion valve based on information indicating a state of a refrigerant superheat degree and a control rule obtained from an empirical rule regarding this information, and over a wide operating range,
An object of the present invention is to provide a refrigeration apparatus capable of performing stable refrigerant flow control.

[Means for solving the problem]

In order to achieve the above object, the present invention provides a detecting means for detecting a refrigerant temperature difference during a refrigeration cycle, and a control rule relating to the opening degree operation amount of the electric expansion valve based on an empirical rule corresponding to the information of the refrigerant temperature difference. A memory device, and a fuzzy inference processor that fetches information about a refrigerant temperature difference from the detection unit, fetches a control rule corresponding to the information from the memory device, calculates and outputs an operation amount of opening of an electric expansion valve. A control device having the following is provided.

[Action]

In the present invention, the refrigerant temperature difference detecting means detects the refrigerant temperature difference in the refrigeration cycle.

On the other hand, in the memory device of the control device, a control rule relating to the opening degree operation amount of the electric expansion valve is stored in advance based on an empirical rule in association with the information of the refrigerant temperature difference.

Therefore, the fuzzy inference processor of the control device fetches information on the refrigerant temperature difference from the detection means and fetches a control rule corresponding to the information from the memory device. Is calculated and output.

Therefore, according to the present invention, it is possible to calculate the opening operation amount of the electric expansion valve based on the control rule obtained from the empirical rule according to the change state of the refrigerant superheat degree, and therefore, over a wide operating range. Stable refrigerant flow control is possible.

〔Example〕

 Hereinafter, embodiments of the present invention will be described with reference to the drawings.

1 is a system diagram showing a first embodiment of the present invention, FIGS. 2 and 3 are control rule and control situation assumption diagrams in fuzzy inference, and FIGS. 4 (a) to 4 (c) are fuzzy inferences. FIG. 6 is a diagram showing a membership function in FIG.

The refrigerating apparatus of the first embodiment shown in FIG. 1 comprises a compressor 1, a condenser 2, a condenser blower 2 ', an electric expansion valve 3, an evaporator 4, and an evaporator blower 4'. , Control device 5
And a sensor 6 for detecting the evaporator outlet refrigerant temperature, and a sensor 7 for detecting the evaporator inlet refrigerant temperature.

In this embodiment, among the temperature differences during the refrigeration cycle, the controller 5 controls the evaporator inlet / outlet temperature difference detected by the sensors 6 and 7, that is, the evaporator refrigerant superheat degree to be appropriate. The opening of the electric expansion valve 3 is controlled. As means for detecting the degree of superheat of the evaporator 4, there is also means for detecting the saturation temperature of the refrigerant by using a pressure sensor instead of the sensor 7 for the refrigerant temperature at the evaporator inlet to obtain the degree of superheat.

The controller 5 includes a refrigerant temperature difference setting device 8, a temperature difference calculator 9, a fuzzy inference processor 10, a control rule memory device 11, and an expansion valve controller 12.

In such a configuration, the detection signals from the sensors 6 and 7 are taken into the refrigerant temperature difference calculator 9 at regular intervals during the operation of the refrigeration system, and the evaporator refrigerant superheat degree is calculated and the refrigerant temperature is calculated. The deviation from the superheat degree set value input from the difference setting unit 8 and the time change of the deviation are calculated.
The fuzzy inference for obtaining the opening operation amount of the electric expansion valve 3 based on these pieces of information is executed based on the following control rules stored in the memory device 11. That is, R1: If the deviation e of the refrigerant superheat degree is negative and large and the time change Δe of the deviation is zero, the opening of the electric expansion valve is largely closed.

R2: If the deviation e of the refrigerant superheat degree is zero and the time change Δe of the deviation is positive and large, the opening of the electric expansion valve is greatly opened.

R3: If the deviation e of the refrigerant superheat degree is positive and large and the time change Δe of the deviation is zero, the opening of the electric expansion valve is greatly opened.

R4: ... and so on.

The control rule is a rule for controlling the degree of superheat of the refrigerant to a set value by changing the opening degree of the electric expansion valve obtained from an empirical rule, and is shown in a table as shown in FIG. Become.

In FIG. 2, the symbols are PB: positive and large, PM: positive and medium, P
S: Positive and small, ZO: Zero, NS: Negative and small, NM: Negative medium, N
B: Negative and large. Further, e indicates a deviation of the refrigerant superheat degree, and Δe indicates a time change of the deviation of the refrigerant superheat degree. For example, in the rule 1 (R1 :), e = NB and Δe
If e = ZO, it indicates that the change in the opening degree of the electric expansion valve is ΔU = NB.

FIG. 3 shows a state in which the deviation e of the refrigerant superheat degree is controlled to 0, and the numbers 1 to 13 shown in the figure show the numbers of the control rules applied in this state. It corresponds to the numbers in the figure.

Since the control rule defines the relationship between the refrigerant superheat degree deviation e, the time change Δe of the refrigerant superheat degree deviation and the opening degree change ΔU of the electric expansion valve stepwise as shown in FIG. 2, fine control is performed. When performing, the degree of the degree of satisfaction of the antecedent part (IF part) of the control rule is calculated by the intermediate value of the deviation e of the refrigerant superheat degree and the time change Δe of the deviation,
It is necessary to estimate the opening degree of the electric expansion valve according to the degree. Therefore, in the fuzzy inference processor 10,
The degree is calculated using a membership function of a fuzzy variable with respect to the deviation e of the refrigerant superheat degree, the time change Δe of the deviation, and the opening change ΔU of the electric expansion valve.

FIG. 4A shows the membership functions μEPB (e), μEPM (e), μEPS (e), μEZO of the fuzzy variables EPB, EPM, EPS, EZO, ENS, ENM, ENB with respect to the deviation e of the refrigerant superheat degree.
4 (e), μENS (e), μENM (e), μENB (e). FIG. 4 (b) shows a fuzzy variable E′PB, E ′ with respect to a time change Δe of the deviation of the refrigerant superheat degree. PM, E′PS,
Membership functions μE'PB of E'ZO, E'NS, E'NM, E'NB
(Δe), μE′PM (Δe), μE′PS (Δe), μ
E′ZO (Δe), μE′NS (Δe), μE′NM (Δ
e), μE′NB (Δe). FIG. 4 (c) shows the membership function μU of the fuzzy variables UPB, UPM, UPS, UZO, UNS, UNM and UNB with respect to the change ΔU of the opening of the electric expansion valve.
PB (ΔU), μUPM (ΔU), μUPS (ΔU), μUZO
(ΔU), μUNS (ΔU), μUNM (ΔU), μUNB (Δ
U).

The fuzzy inference executed by the fuzzy inference processor 10 shown in FIG. 1 is performed by performing a fuzzy inference operation using the control rules R1 to R13 and the membership functions of FIGS. 4 (a), (b) and (c). Then, the operation amount of the opening degree of the electric expansion valve is calculated.

 The procedure of inference is shown below.

Step 1: Using the membership function for the deviation e of the refrigerant superheat degree and the time change Δe of the deviation of the refrigerant superheat degree, the detected membership e of the deviation e of the refrigerant superheat degree and the temporal change Δe of the deviation are calculated.

Step 2: The degree to which the membership values of the deviation e of the refrigerant superheat degree and the time change Δe of the deviation obtained in Step 1 satisfy the antecedents of the above-mentioned 13 control rules is as follows. Calculate with AND.

R1: W ₁ = μENB (e) ∧μE'ZO (Δe) = MIN ｛μNB (e), μE'ZO (Δe)｝ ... (1) R2: W ₂ = μEZO (e) ∧μE'PB (Δe ) = MIN {μEZO (e), μE′PB (Δe)} (2) Equation (1) shows that the ratio of the deviation e of the refrigerant superheat degree into the ENB and the time change Δe of the deviation become E′ZO. This indicates that the ratio is satisfied as a small value among the ratios included. That is,
When the deviation of the refrigerant superheat degree is e and the time change of the deviation is Δe,
Antecedent of control rules R1 shows that established at a rate of W _1.

Similarly, the equation (2) shows that the control rule R2 is established in a ratio of W _2.

Step 3: if satisfied with the antecedents proportion W _n of one control rule, therefore established at a rate of execution unit (THEN part) is also W _n of the control rules, established antecedent of each control rule Fuaji variable in the execution unit the ratio W _n to (UPB, UPM, UPS, UZO , UNS, UNM, UN
The membership function of the execution unit is modified by multiplying the membership function of B) as follows.

R1: μUNB * (C) = W 1 × μUNB (C) R2: μUPB * (C) = W 2 × μUPB (C) ...... step 4: Menbashitsupu function executing unit of the modified control rules in step 3 Thus, the deviation e of the detected superheat degree of the refrigerant,
The total membership function of the opening degree operation amount of the electric expansion valve with respect to the time change Δe of the deviation is obtained in the form of a logical sum as follows.

μ * (C) = μUNB * (C) UμNM * (C) U... UμPB * (C) (3) Equation (3) shows the degree of occurrence for each opening of the electric expansion valve. It is expressed as a function of the opening.

Step 5: The degree of opening of the electric expansion valve, which is a fuzzy variable of the total membership function, is weighted and averaged based on the degree of belonging to the total membership function, thereby obtaining the opening operation amount C * of the electric expansion valve.

C * = ΔC × μ * (C) dC / Δμ * (C) dC As described above, the opening operation amount of the electric expansion valve obtained by the fuzzy inference from step 1 to step 5 is determined by the expansion valve control. Is output to the electric expansion valve 3 through the device 12.

In the first embodiment, the control of the degree of superheat of the refrigerant is performed using a redundant membership function as shown in FIGS. 4 (a) to 4 (c) and a control rule obtained based on empirical rules. As a result, even if the operating conditions change, the control result does not change, and stable refrigerant flow rate control can be performed over a wide operating range, thereby improving the performance and reliability of the refrigerant device. There is a plausible effect.

Next, FIG. 5 is a system diagram showing a second embodiment of the present invention.

In this second embodiment, the sensor 6 'is attached to the discharge pipe at the outlet of the compressor 1, and the other sensor 7' is attached to the outlet of the condenser 2 to determine the degree of superheat of the discharged gas refrigerant. It is configured to control to the set value.

In the second embodiment, other configurations such as fuzzy inference are exactly the same as those in the first embodiment. In order to more accurately detect the degree of superheat of the discharged gas refrigerant, the sensor 7 '
May be used as a pressure sensor, the pressure on the high pressure side may be detected and converted to the saturation temperature, and then the superheat degree of the discharged gas refrigerant may be calculated.

In the case of the second embodiment, since the superheat degree of the discharge gas refrigerant can be controlled to the set value, there is an effect that the reliability of the refrigerating apparatus can be particularly improved.

FIG. 6 is a system diagram showing a third embodiment of the present invention.

In the third embodiment, the sensor 6 "is provided at an intermediate portion of the condenser 2 to detect the condensing temperature. On the other hand, the sensor 7" is provided at the outlet of the condenser 2. Thus, the temperature of the supercooled liquid refrigerant is detected. From the temperatures detected by these two sensors 6 ", 7", the degree of subcooling of the refrigerant in the condenser 2 is obtained, and in the third embodiment, the degree of subcooling of the refrigerant is maintained at a set value.

As in the second embodiment, if a pressure sensor is used as the sensor 6 ", the degree of subcooling of the refrigerant can be detected more accurately.

In the third embodiment, since the degree of supercooling of the condenser 2 is controlled, it is possible to prevent an excessive increase in the high pressure of the refrigerating apparatus, and to always keep the upstream side of the electric expansion valve 3 in a liquid refrigerant state. Since stable refrigerant supply to the constant pressure side can be secured,
The effects of better reliability and performance can be expected.

In each of the embodiments described above, the refrigerant temperature difference is controlled as a set value. However, the set value may not be a constant value, and may be changed in conjunction with a signal of another refrigeration apparatus. Good.

Next, FIG. 7 is a system diagram showing a fourth embodiment of the present invention, and FIG. 8 is an explanatory diagram showing the contents of a control rule memory device in the fourth embodiment.

In the fourth embodiment, the third embodiment shown in FIGS.
1, the same parts as those in the second embodiment are denoted by the same reference numerals.

In the fourth embodiment, in addition to the control device 5, another control device 5 'is provided.

The controller 5 'includes a refrigerant temperature difference setting device 8', a temperature difference calculator 9 ', a fuzzy inference processor 10', a control rule memory device 11 ', and a control rule memory device 11'.
And an expansion valve controller 12 '. The temperature difference calculator 9 ′ is connected to a sensor 6 ′ attached to the discharge pipe at the outlet of the compressor 1 and a sensor 7 ′ attached to the outlet of the condenser 2.

Further, the expansion valve controllers 12, 12 'of the control devices 5, 5'
It is connected to a separately installed fuzzy inference processor 16.
Further, the fuzzy inference processor 16 is connected to the sensor 6 ', a memory device 15 for separately installed control rules, and an expansion valve controller 17. The expansion valve controller 17 is connected to the electric expansion valve 3.

In the fourth embodiment, the control device 5 is a control unit for controlling the degree of superheat of the evaporator, and receives the detection signals of the sensors 6 and 7 for detecting the inlet and outlet temperatures of the evaporator, as in the first embodiment. The expansion valve operation signal 13 is output from the expansion valve controller 12 by fuzzy inference. The control device 5 'is a controller for the degree of superheat of the discharge gas. The control device 5' receives a detection signal from a sensor 6 'for detecting the discharge gas temperature and a sensor 7' for detecting the condensate temperature, and receives a fuzzy inference processor 10 '. The same operation as that of the fuzzy inference processor 10 of the control device 5 is performed, and an expansion valve operation signal 13 'is output from the expansion valve controller 12'.

A fuzzy inference processor 16 newly incorporated in the fourth embodiment is connected to a memory device 15 for control rules whose contents are shown in FIG.
And 5 'and the detection signal 14 from the discharge gas temperature sensor 6'.

In this embodiment, based on the control rule shown in FIG. 8, when the absolute value of the discharge gas temperature of the refrigeration cycle is high, the weight of the discharge gas superheat degree control is increased among the two control rules, If the discharge gas temperature is not high, the inference result is output from the expansion valve controller 17 to the electric expansion valve 3 in order to perform the evaporator superheat control. These weightings are performed by the fuzzy inference processor 16.

According to the fourth embodiment, when the absolute value of the discharge gas temperature is likely to be high, discharge gas superheat control is performed with an emphasis on reliability, and otherwise, performance improvement is emphasized. ,
The superheat degree of the evaporator 4 can be controlled.

〔The invention's effect〕

As described above, according to the present invention, the refrigeration cycle is operated by controlling the opening degree of the electric expansion valve by fuzzy inference based on a redundant membership relationship and a control rule obtained based on empirical rules. The refrigerant temperature difference inside is controlled, so that even if the operating conditions change, there is an effect that stable refrigerant flow control can be performed over a wide operating range, and as a result, the performance of the refrigeration system is improved and reliability is improved. This has the effect of improving the performance.

[Brief description of the drawings]

1 is a system diagram showing a first embodiment of the present invention, FIGS. 2 and 3 are control rule and control situation assumption diagrams in fuzzy inference, and FIGS. 4 (a) to 4 (c) are diagrams in fuzzy inference. FIGS. 5, 6, and 7 are diagrams showing the membership functions, FIGS. 5, 6, and 7 are system diagrams showing the second, third, and fourth embodiments of the present invention, and FIG. 8 is a diagram showing control rules in the fourth embodiment. FIG. 3 is an explanatory diagram of the contents of a memory device. 1 ... Compressor, 2 ... Condenser, 3 ... Electric expansion valve, 4 ...
... Evaporator, 5,5 '... Control device, 6,7; 6', 7 '; 6 ", 7" ...
... Sensor, 8,8 '... Refrigerant temperature difference setting device, 9,9' ... Temperature difference calculator, 10,10 '... Fuzzy inference processor, 11,1
1 ': Control rule memory device, 12, 12': Expansion valve controller, 15: Control rule memory device, 16: Fuzzy inference processor, 17: Expansion valve controller.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Susumu Nakayama 502 Kandate-cho, Tsuchiura-shi, Ibaraki Pref. Machinery Research Laboratory, Hitachi, Ltd. (72) Inventor Rumi 502-Kandate-cho, Tsuchiura-City, Ibaraki Hitachi, Ltd. In-house (72) Inventor Takao Chiaki 390 Muramatsu, Shimizu-shi, Shizuoka Prefecture Inside Shimizu Plant, Hitachi Ltd. (72) Inventor Yoshiaki Taga 390 Muramatsu, Shimizu-shi, Shizuoka Prefecture Inside Shimizu Plant, Hitachi Ltd. (72) Inventor Keishi Takagi 390 Muramatsu, Shimizu-shi, Shizuoka Prefecture Inside the Shimizu Plant of Hitachi Ltd. (56) References JP-A-62-158953 (JP, A) JP-A-2-85960 (JP, U) JP-A-3-34564 (JP, U) (58) Field surveyed (Int. Cl. ⁷ , DB name) F25B 1/00

Claims (1)

(57) [Claims] In a refrigeration cycle including a compressor, a condenser, an evaporator, and an electric expansion valve, a detecting means for detecting a refrigerant temperature difference in the refrigeration cycle, and corresponding to information on the refrigerant temperature difference. Then, a memory device storing a control rule regarding the opening degree operation amount of the electric expansion valve based on an empirical rule, and information regarding the refrigerant temperature difference are fetched from the detection unit, and a control rule corresponding to the information is fetched from the memory device. A refrigeration system comprising a controller having a fuzzy inference processor for calculating and outputting a disclosed operation amount of the electric expansion valve.