JPH0526519A - Method of controlling reversible proportional type expansion valve - Google Patents

Abstract

PURPOSE:To increase the life of an expansion valve by constructing control rules for steady state and unsteady state separately and controlling by treating those control rules in parallel and, at the same time, adding a rule regarding time in order to control in the steady state for a longer period and control in the unsteady state for a shorter period. CONSTITUTION:A microcomputer 5 calculates the degree of overheating of the coolant from the detected values of a temperature sensor 6 that detects the temperature of evaporation of the coolant on the outlet side of an evaporator and a pressure sensor 7 that detects the evaporation pressure of the coolant and drives an expansion valve drive section 65 and regulates the degree of opening of a reversible proportional type expansion valve 3 by an electrical signal so as to place the degree of overheating in a set unsensitivity zone. During steady operation the deviation of the degrees of overheating in the coolant and the variation in the evaporation temperatures of the coolant age calculated by fuzzy theory to seek the first operating value and the deviation in the evaporation pressures of the coolant is calculated by fuzzy theory to seek 2 second operating value, and from the first operating value and second operating value a third operating value is sought. If the value of the third operating value is large, the period of control for the expansion valve 3 is shortened and if it is small, the control period is lengthened.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is a reversible proportional type device provided in a refrigerant passage of a refrigerating device or a heat pump device and utilizing an electromagnetic force for adjusting a refrigerant flow rate or a rotating force of a pulse motor. A method for controlling an expansion valve.

[0002]

2. Description of the Related Art As a conventional refrigeration system (for example, Japanese Patent Publication No. 60-45779 filed by the applicant of the present application), a structure shown in FIG. 18 is known. In the figure, 1 is a compressor, 2 is a condenser, 3 is a reversible proportional expansion valve, 4 is a drive source such as an electromagnet for adjusting the opening of the expansion valve 3 according to an input signal, a pulse motor, and 5 is an evaporator. Reference numerals 6 and 7 denote temperature sensors and pressure sensors that detect the temperature and pressure on the outlet side of the evaporator 5, and reference numeral 8 denotes a controller that controls the drive source based on the outputs of the temperature sensors 6 and 7.

In the case of the heat pump device, a four-way valve is connected between the inlet side and the outlet side of the compressor 1, the condenser 2 is used as an outdoor heat exchanger, and the evaporator 5 is used indoors. Since it has the same configuration as the refrigeration system except that it is used as a heat exchanger, the operation of the refrigeration system will be described below.

Then, the difference between the detected values from the temperature sensor 6 and the pressure sensor 7 is regarded as the degree of superheat, and the control circuit 8 calculates the difference between the degree of superheat and the set degree of superheat by PI calculation or PID calculation. The operation amount of the drive source 4 is calculated by applying the calculated electric signal to the drive source 4 to control the opening degree of the expansion valve 3 and adjust the refrigerant flow rate of the refrigeration system.

[0005]

By the way, in the control by the control circuit 8 described above, the steady state (following the target value)
It is required that the control response characteristics of both the unsteady state and the unsteady state (disturbance suppression) are the best, but in the conventional PID control described above, only one kind of parameter can be set in one functional expression. In addition, if the parameters are set so that the control response characteristic in the steady state is the best, the settling time becomes long in the non-steady state.

On the contrary, if the parameters are set so that the control response characteristic in the unsteady state becomes the best, the overshoot becomes large in the steady state, which is a contradictory characteristic (see curves A and B in FIG. 19). There is a problem that stable control cannot be performed in both the steady state and the unsteady state.

The present invention is intended to solve the above-mentioned problems, and an object thereof is to create a control rule by dividing it into a steady state and a non-steady state, and handle them in parallel to perform control. Therefore, it is an object of the present invention to provide a control method for a reversible proportional expansion valve capable of obtaining the best control response characteristics in both steady state and unsteady state.

Another object of the present invention is to:
Another object of the present invention is to provide a control method for a reversible proportional expansion valve in which control is performed with a cycle as long as possible in a steady state and control with a cycle as short as possible in a non-steady state by adding a control regulation regarding time.

[0009]

The method for controlling a reversible proportional expansion valve according to the present invention is intended to achieve the above-mentioned object. The means is a deviation of the degree of superheat of the refrigerant during steady operation,
The first operation amount is calculated by calculating the change amount of the evaporation temperature of the refrigerant, and the second operation amount is calculated by calculating the change amount of the evaporation pressure of the refrigerant during unsteady operation, and the first operation is further performed. The third operation amount is obtained from the amount and the second operation amount, the larger the value of the third operation amount, the shorter the control cycle of the expansion valve, and the smaller the value of the operation amount, the smaller the operation amount. That is, the control cycle of the expansion valve is lengthened.

Further, during steady operation, a fuzzy theoretical operation is performed based on a control rule from the value of the deviation between the calculated superheat degree and the preset superheat degree and the value of the change amount of the evaporation temperature of the refrigerant. Determine the operation amount of the expansion valve, and also change the amount of change in the evaporation pressure of the refrigerant during unsteady operation such as starting, stopping, changing capacity of the compressor, defrosting operation, changing condition of the condenser, changing condition of the evaporator, etc. Fuzzy theoretical calculation based on the control rule from the value, the operation amount of the expansion valve is obtained, the operation amount during the steady operation, and the operation amount during the unsteady operation is calculated to obtain the operation amount, The value of the control cycle of the expansion valve, which is set to a value larger than the dead time of the refrigerant flow path system of the refrigerating apparatus or the heat pump apparatus, is set to a positive large value of the membership function (P
As a point B), fuzzy theoretical calculation is performed based on a control rule from the value of the elapsed time from when the expansion valve was operated last time until the next operation of the expansion valve and the value of the calculated operation amount. , The opening of the expansion valve is controlled according to the flow rate of the refrigerant required by the device by obtaining the value of the operation amount of the expansion valve and sending an electric signal to the drive unit of the expansion valve. That's what I did.

[0011]

The operation of the above configuration will be described below. Figure 1
6 shows the characteristic of the flow rate Q with respect to the opening degree O of the expansion valve 3.
Let Q _{0 be} the flow rate when fully closed O ₀ , Q _{100 be} the flow rate when fully open O ₁₀₀ , L be the low opening region, M be the medium opening region, and H be the high opening region.

FIG. 17 is a timing chart for operating the expansion valve 3. The dead time TL of the refrigerant passage system peculiar to the refrigeration system, the control cycle of the expansion valve 3 set to a value larger than the dead time TL, Ts, and the elapsed time from the previous operation of the expansion valve 3 Tm. During steady operation,
The opening of the valve is controlled within each of the above-mentioned regions, and the timing is controlled so that Tm ≈Ts.

On the other hand, during unsteady operation, the current area is changed to another area, and the timing is Tm <Ts, so that the opening degree is quickly changed.

Particularly, at the time of starting the compressor, since it is necessary to change rapidly from the fully closed O ₀ to the high opening region H, fuzzy theoretical calculation is performed so that Tm ≈0. Thus, in order to allow the degree of superheat to exist within the preset dead zone, the opening of the expansion valve is controlled according to the flow rate of the refrigerant in a short settling time regardless of the magnitude of the disturbance.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG. The same reference numerals as those in FIG. 18 described above indicate the same parts, and the description thereof will be omitted. Further, in this embodiment, the expansion valve 3 is an expansion valve using a pulse motor as the drive source 4.

61 receives the signal from the evaporation temperature sensor 6,
A temperature-voltage signal converter 62 for performing calculation and amplification so that the signal level is suitable for input to the A / D converter 63 in the subsequent stage.
Receives the signal from the evaporation pressure sensor 7, and receives the A / D converter 63.
, A pressure-voltage signal converter that performs calculation and amplification to obtain a signal level suitable for input, 63 is controlled by a microcomputer 64 to select input data, convert analog data to digital data, output digital data It is an A / D converter for performing the above.

Reference numeral 64 is a single-chip microcomputer incorporating a ROM, a RAM, an I / O port, etc., which controls the A / D converter 63 according to a program stored in advance, inputs its digital data, and executes a program. And outputs the calculation result to the pulse motor drive unit 65. 65 is a pulse motor drive type expansion valve 3 based on the output signal from the microcomputer 64.
It is a motor drive unit that sends a pulse signal to and rotates the motor.

Next, to explain the operation based on the above configuration, the flow rate of the refrigerant is controlled by increasing or decreasing the number of pulses.
If the number of pulses is stored, the operation pulse amount ΔU at any opening L can be calculated as needed.

In this case, it is necessary to detect the reference position, but when the power source of the microcomputer 64 is established,
The expansion valve 3 is operated so that the fully closed position O ₀ becomes the reference position. The method of this operation is already known. After performing this operation in the microcomputer 64, the actual control is started. The operation will be described below with reference to the flowcharts of FIGS. 2 and 3.

The evaporation temperature TEn at an arbitrary time n on the outlet side of the evaporator 4 is converted into a digital signal by the A / D converter 63, and this digital data is read and stored by the microcomputer 64 (step S1). On the other hand, the evaporation pressure PEn at the arbitrary time n on the outlet side of the evaporator 4 is similarly stored (step S2). Next, it is possible to obtain the vaporization pressure equivalent temperature TPn from the stored vaporization pressure PEn from the saturated vapor pressure diagram of the refrigerant used.

That is, since the temperature TPn corresponding to the evaporation pressure is a function of the evaporation pressure PEn, if this is expressed by an equation, TPn = f (PEn). Since PEn is digital data, the pressure-temperature conversion can be easily converted by the microcomputer 64 by programming the value of TPn corresponding to each data (step S3).

At an arbitrary time n on the outlet side of the evaporator 4,
, Where SHn is the superheat degree of the refrigerant, the difference between the evaporation temperature TEn and the evaporation pressure equivalent temperature TPn is obtained in the microcomputer 64 to obtain the superheat degree SHn of the refrigerant at an arbitrary time n (step S4), SHn = TEn-TPn The value of this superheat degree SHn is stored.

Next, the microcomputer 64 obtains the deviation En of the superheat degree. If the center of the dead zone shown in FIG. 3 is a preset superheat degree SHs, the deviation En is calculated by the following equation. (Step S5), this value is stored. En = SHn-SHs

Next, a time (n-
The evaporation temperature in 1) is TEn-1, and the evaporation pressure is PEn-1.
, Change of evaporation temperature is △ SHn, change of evaporation pressure is △
PEn is calculated by ΔSHn = TEn-TEn-1ΔPEn = PEn-PEn-1 (steps S6 and S7), and this value is stored.

For the deviation En, the corresponding fuzzy variable grade is calculated by the membership function shown in FIG. 5 (step S8). In FIG. 5, NB is Negative Big,
Negative large, NS is Negative Small, that is, negative small, ZO is Zero, that is, neutral, PS is Positive Small, that is, positive small, and PB is Positive Big, that is, positive large. The symbols have the same meanings below.

The amount of change in evaporation temperature ΔSHn is also shown in FIG.
The corresponding fuzzy variable grade is calculated by the membership function shown in (step S81). In the above,
Using the two calculated fuzzy variable grades, FIG.
The manipulated variable ΔU ₁ is obtained by the Min-Max centroid method according to the fuzzy control rule shown in. Operation amount △ U ₁ is the membership function shown in FIG. 8, the corresponding fuzzy variable grade is calculated (step S82).

Next, the amount of change in evaporation pressure ΔPEn is shown in FIG.
The corresponding fuzzy variable grade is calculated by the membership function shown in (step S83), and the manipulated variable ΔU ₂ is obtained by the Min-Max centroid method according to the fuzzy control rule shown in FIG. 10 (step S84).

Here, there is a rule in which the expansion valve is not operated when the change amount of the evaporation pressure is small and the operation amount of the expansion valve is increased when the change amount is large. When the amount of change is +, the valve is a closing operation, and when it is −, it is an opening operation. Operation amount △ U ₂ is a membership function shown in FIG. 11, corresponding fuzzy variable grade is calculated.

Next, the operation amount is ΔU₃As below
Calculation △ U₃= △ U₁+ △ U₂ The calculation operation amount by ΔU₃(Step S8)
5). Here, by taking the absolute value of the operation amount, | ΔU
₃| The absolute value | △ U ₃| Means the men shown in FIG.
Corresponding fuzzy variable grade by barship function
Is calculated.

Further, rather than the dead time TL of the refrigerant flow path system,
The control cycle Ts of the expansion valve set to a large value is set to the positive large (PB) point of the membership function, and the elapsed time Tm from the previous operation of the expansion valve is the member shown in FIG. The corresponding fuzzy variable grade is calculated by the ship function (step S86).

Using the two fuzzy variable grades calculated above, the manipulated variable multiplying factor R is determined by the Min-Max centroid method according to the fuzzy control rule shown in FIG. As for the manipulated variable magnification R, the corresponding fuzzy variable grade is calculated by the membership function shown in FIG. 15 (step S87).

Next, the final control as .DELTA.U _4, the following calculation △ U ₄ = △ by the U ₃ × R, obtaining the final control .DELTA.U ₄ (step S8
8).

Here, the obtained final manipulated variable ΔU ₄ is
It is sent to the expansion valve 3 by an electric signal (step S8).
9), the opening degree of the expansion valve 3 is controlled according to the flow rate of the refrigerant (step S9).

When the sign of the operation amount ΔU ₃ is +, the opening operation for the final operation amount ΔU ₄ is performed, and when the sign of ΔU ₃ is −, the closing operation for ΔU ₄ is performed. Is being done.

Next, the microcomputer 64 calculates the previous opening of the expansion valve 3 and the final manipulated variable ΔU ₄ as follows, and stores it as a new opening (step S10). O = O + ΔU ₄

Further, the microcomputer 64 resets the elapsed time T _m (step S11) and newly starts counting the elapsed time T _m in preparation for the next operation of the expansion valve 3 (step S12).

[0037]

As described above, according to the present invention, the control rule is created separately for the steady state and the non-steady state, and the control rules are handled in parallel to perform the control, so that the steady state as shown by the curve C in FIG. 19 is obtained. It is possible to obtain the best control response characteristics in both the steady state and the non-steady state, and by adding the control regulation related to time, the steady state controls the cycle as long as possible, and the non-steady state controls the cycle as short as possible. In addition, the expansion valve has a long service life and is less likely to malfunction.

[Brief description of drawings]

FIG. 1 is a block diagram showing an example of the inside of a controller.

FIG. 2 is a characteristic diagram of an operation pulse amount with respect to a deviation En.

FIG. 3 is a flowchart of a part of arithmetic processing of a microcomputer.

FIG. 4 is a flowchart of a routine of a fuzzy calculation unit.

FIG. 5 is a membership function of the deviation En.

FIG. 6 is a membership function of the variation ΔSHn of the evaporation temperature.

FIG. 7 is a table of fuzzy control rules for obtaining a manipulated variable ΔU ₁ .

FIG. 8 is a membership function of the manipulated variable ΔU ₁ .

FIG. 9 is a membership function of a change amount ΔPEn of evaporation pressure.

FIG. 10 is a table of fuzzy control rules for obtaining a manipulated variable ΔU ₂ .

FIG. 11 is a membership function of the manipulated variable ΔU ₂ .

[12] the absolute value of the operation amount △ U ₃ | △ U ₃ | is a membership function of.

FIG. 13 is a membership function of elapsed time Tm.

FIG. 14 is a table of fuzzy control rules for obtaining a manipulated variable ΔU ₄ .

FIG. 15 is a membership function of the manipulated variable ΔU ₄ .

FIG. 16 is a characteristic diagram of the flow rate with respect to the opening degree of the expansion valve.

FIG. 17 is a timing diagram for controlling the expansion valve.

FIG. 18 is a block diagram showing an example of control of a conventional expansion valve.

FIG. 19 is a diagram showing control response characteristics.

[Explanation of symbols]

1 compressor 2 condenser 3 expansion valve 4 drive source 5 evaporator 6 Temperature sensor 7 Pressure sensor 8 controller 61 Temperature-voltage signal converter 62 Pressure-voltage signal converter 63 A / D converter 64 microcomputer 65 Expansion valve drive

Claims (2)

[Claims] 1. A refrigerant having a temperature sensor for detecting the evaporation temperature of the refrigerant at the outlet side of the evaporator of the refrigerating apparatus or the heat pump apparatus and a pressure sensor for detecting the evaporation pressure of the refrigerant, the refrigerant being detected from the both sensors. In a reversible proportional expansion valve that calculates the degree of superheat of, adjusts the opening by being driven by an electric signal so that the degree of superheat exists within a preset dead zone, and controls the flow rate of the refrigerant by the degree of opening. , During the steady operation, the deviation of the superheat of the refrigerant and the amount of change in the evaporation temperature of the refrigerant are fuzzy theoretically calculated to obtain the first manipulated variable, and during the unsteady operation, the amount of change in the evaporation pressure of the refrigerant is fuzzy theoretically calculated. Then, a second manipulated variable is obtained, and a third manipulated variable is obtained from the first manipulated variable and the second manipulated variable. The larger the value of the third manipulated variable, the larger the control of the expansion valve. The cycle is shortened and the operation amount The method of reversible proportional expansion valve, characterized in that the control cycle of small enough expansion valve smaller value longer. 2. During the steady operation, a fuzzy theoretical operation is performed based on a control rule from a value of a deviation between the calculated superheat degree and a preset superheat degree and a value of a change amount of a refrigerant evaporation temperature. , The operation amount of the expansion valve is calculated, and when the compressor is started, stopped, the capacity is changed, the defrosting operation is performed, the condition of the condenser is changed, or the condition of the evaporator is changed, the evaporation pressure of the refrigerant changes. A fuzzy theoretical calculation is performed from the value of the amount based on a control rule to obtain the operation amount of the expansion valve, and the operation amount in the steady operation and the operation amount in the unsteady operation are calculated to calculate the operation amount. Then, the value of the control cycle of the expansion valve set to a value larger than the dead time of the refrigerant flow system of the refrigeration system or the heat pump system is used as the positive large (PB) point of the membership function, From the time when the expansion valve is operated, the next time the expansion valve From the value of the elapsed time until operating the and the value of the operation amount, fuzzy theoretical operation based on the control rule,
By determining the value of the manipulated variable of the expansion valve and sending an electric signal to the drive unit of the expansion valve, the opening degree of the expansion valve is controlled according to the flow rate of the refrigerant required by the device. A method for controlling a reversible proportional expansion valve, characterized in that