JPH0627558B2 - Motorized valve control method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a method for controlling a thermoelectric expansion valve, a reversible solenoid proportional valve, or other motor-operated valve with a decompression mechanism used in air conditioners, refrigerators, and other refrigeration and air conditioning equipment. Regarding

(B) Prior Art This type of motor-operated valve is introduced in Japanese Patent Publication No. 58-7869 as a "bimetal type thermo-responsive valve having an electric heating means". There are two types of this motor-operated valve, an energizing valve closing type and an energizing valve opening type, and the operating characteristics thereof are described in the above publication and the publication "Freezing", Vol. 56, No. 641 (March 1981).
Monthly issue, pp. 60-64.

The basic characteristic of the operating characteristics of the motor-operated valve is the relationship between the voltage applied to the heater serving as the energizing portion and the refrigerant flow rate. FIG. 2 on page 61 of the above publication shows the flow characteristics of the energizing valve closing type and the energizing valve opening type, both of which theoretically can control a wide range from fully closed to fully opened. The straight line portion of the flow rate characteristic is used so that the control method can be simplified.

That is, in such a control method, since the applied voltage of the current-carrying portion is an analog voltage, the flow rate characteristic becomes a curve as a whole, and as a result, only a narrow range of the linear portion of this curve can be controlled. It was

Therefore, the inventor of the present application has found that the electric valve closing type electric valve (thermoelectric expansion valve) SQX-22012D (differential pressure 1) manufactured by Sagikan Seisakusho Co., Ltd.
An experiment was conducted to confirm the above flow rate characteristics using 0 kg).

The experimental results are shown in FIG. In such an experiment, in consideration of the fact that both the flow rate of the refrigerant and the flow rate of the air have a unique relationship with the fluid, even if the flow rate of the refrigerant is replaced with the air flow rate, the characteristic is not deteriorated. Airflow was used as the fluid passing through the valve.

According to the experimental results, there is almost no linear relationship between the analog voltage (applied voltage) E that is the control amount and the air flow rate GA that is the operation amount, and the air flow rate characteristic becomes a curve. That is, if the load on the cooled side of the refrigeration system, for example, in a refrigerator, the load on the refrigerator is increased or decreased, the flow rate of the refrigerant entering the motor-operated valve is changed. A change amount ΔE of the same control amount, for example, a change amount of the manipulated variable ΔGA with respect to 0.5 V is displayed by the analog voltage E at each time as shown in FIG. 1 and the table below.

In this way, even if the change amount ΔE of the control amount of the analog voltage E applied to the current-carrying portion is the same, the value of the operation amount ΔGA changes, and therefore, when the same change amount ΔGA of the operation amount is obtained, the control is performed. It was difficult to determine the amount ΔGA (adjustment of the opening of the valve), that is, it was difficult to control the curve portion of the flow rate characteristic, and the drawbacks described in the above publication were confirmed.

(C) Purpose of the invention The present invention solves the drawbacks of the prior art and represents the relationship between the controlled variable (applied voltage = number of pulses) and the manipulated variable (air flow rate = opening area) in a straight line to control the motor-operated valve. The purpose is to make it easy to do.

(D) Structure of the Invention The present invention has a characteristic that the change of the opening area is proportional to the square of the applied voltage, and the opening area can be variably controlled from fully open to fully closed or vice versa. When a rectangular shock wave, which is a kind of distorted wave, is applied to the energization part of the expansion valve at time intervals, the effective value of the rectangular shock wave is proportional to the 1/2 power of the ratio of the HIGH time to the first cycle. In addition, the first cycle is divided into a second cycle shorter than the first cycle to form a quasi-pulse, and the HIGH time is controlled by applying a rectangular shock wave as a group of a plurality of reference pulses. This is a method for controlling a motor-operated valve in which the relationship between the quantity and the manipulated value is substantially linear over a wide range.

(E) Embodiment of the Invention FIG. 2 is a control circuit of a refrigerating apparatus, showing a refrigerant circuit (A) and an electric circuit (B). The refrigerant circuit comprises a refrigerant electric compressor (1), a condenser (2), a motorized valve with a known decompression mechanism described above (3), an evaporator (4) and the like, which are connected in an annular shape by piping. Then, a predetermined refrigeration cycle is formed to cool the load (5) to be cooled. Further, the electric circuit includes a control center portion (6) including a microprocessor and the like, a primary side (7A) and a control center portion (2).
An interface section (7) equipped with a photo-curbler (8), PNP transistors (9) and (10), fixed resistors (11), (12) and (13) straddling the secondary side (7B), and an output section (14). ) And the output part (1
From 4), the effective value of the square shock wave is applied voltage, and the motor-operated valve (3)
To the energized part of.

In order to improve the controllability of the motor-operated valve, it suffices if the relationship between the controlled variable (applied voltage E) and the manipulated variable (air flow rate G _A ) can be expressed in a linear relationship. For example, Linear equation is obtainedゝif that can solve the situation where variation △ G _A of the operation amount depends on the size and position of the control amount E.

In order to obtain the value equivalent to the applied voltage, the waveform HIGH
It is necessary to use the value corresponding to the DC voltage of the effective value depending on the length of time, that is, the effective value voltage of the rectangular shock wave.

The waveform and effective value of the above rectangular shock wave are shown in FIG. From such drawings, the applied voltage equivalent value Ee [V] is Therefore, the value corresponding to the applied voltage, that is, the effective value is proportional to the 1/2 power of the ratio of HIGH time τ to the period T.

Next, the applied voltage E [V] vs. air flow rate G _A [M ³ / H] is analyzed.

When the curve of FIG. 1 is approximated by a curve, the following equation is obtained.

G _A = G _A [MAX] −k ₁ E ² − That is, it can be seen that the flow rate changes with the square of the applied voltage. Furthermore, if the above equation is differentiated by the applied voltage E, Therefore, the ratio of the flow rate depending on the magnitude of the voltage is well understood. Concretely speaking, when the applied voltage is small, the air flow rate changes only slightly, but as the applied voltage increases, the air flow rate changes more and control of the motor-operated valve (3) becomes difficult.

Next, the applied voltage versus the air flow rate given by the effective value of the rectangular shock wave will be explained. Substituting the above equation into the equation The equation [k ₃ = k ₁ EH ² / T] can be obtained, or according to such an equation, the air flow rate G _A can be obtained as a linear equation of the HIGH time τ of the rectangular shock wave, which is difficult in the above equation. Can be solved and controllability is improved.

Next, the composition of the square shock wave is expressed by specific values, However, τ _s : reference pulse: period (second period) is set to 5 msec, and the HIGH time τ can be treated as a group of the number of reference pulses. As a result, 0 ≦ N ≦ 200 [pieces / second]
Then, 0 ≦ Ee ≦ 11.4 [V].

The waveform in this state is as shown in Fig. 4, and its effective value Ee is And as shown in FIGS. 4 and 5.

Further, when the relationship between the number of pulses of the rectangular shock wave and the air flow rate G _A is examined from the above formula, G _A = G _A [MAX] −k ₃ τ = G _A [MAX] −k ₃ × (N τ _s ) = G _A [MAX] −k ₄ N [k ₄ = k ₃ τ _s ]. This relationship is the air flow rate characteristic shown in FIG.
A straight line descending to the right can represent the air flow rate characteristic, that is, the change in the opening area with the change in the number of pulses.

Therefore, the motorized valve (3) can be controlled from fully closed to fully open,
Linear control is achieved at any part of the flow rate characteristic.

(F) Effects The present invention makes the effective value of the rectangular shock wave proportional to the 1/2 power of the ratio of the time of HIGH to the first cycle when applying the rectangular shock wave to the thermoelectric expansion valve, and Is divided by a second period shorter than the first period to form a reference pulse, and a rectangular shock wave is applied with the HIGH time as a group of a plurality of reference pulses. Play.

The effective value of the voltage applied to the thermoelectric expansion valve changes due to the relationship between the control amount and the operation amount, that is, the change in the time ratio of the reference pulse group, and the control accuracy of the opening area of the thermoelectric expansion valve can be improved. At the same time, the flow rate characteristic of the thermoelectric expansion valve that changes based on the effective value becomes linear over a wide range, and the opening area can be variably controlled at any position until the thermoelectric expansion valve is fully opened and fully closed, or vice versa. Since it is a straight line regardless of which part of the flow rate characteristic is taken, it is easy to control within a predetermined range, and even if there is a load fluctuation on the cooled side, it is possible to reduce the pressure of the refrigerant while changing the opening area and to easily converge it. Therefore, a stable cooling effect can be obtained as a whole.

Even if the controlled variable varies in various ways according to the fluctuation of the load on the cooled side, the amount of change in the manipulated variable is substantially constant, so that the degree of superheat can be maintained in an optimum state and the heat exchange efficiency of the evaporator can be improved.

Even if the load on the cooled side fluctuates, the degree of superheat can be maintained at a substantially constant level, reducing the amount of liquid returning to the refrigerant electric compressor,
The safety of the refrigeration system is improved.

Since the waveform generation is suitable for digital processing, the configuration of the electric circuit is easy to handle.

[Brief description of drawings]

FIG. 1 is a flow rate characteristic diagram according to a control method of the prior art, FIG. 2 is a control circuit diagram of a refrigerating device equipped with an electric valve according to the present invention, FIG. 3 is a basic waveform diagram of a rectangular shock wave, and FIG. Is a block diagram of a rectangular shock wave according to the present invention, FIG. 5 is a reference pulse diagram of FIG. 4, and FIG. 6 is a flow rate characteristic diagram by the control method of the present invention.

Claims (1)

[Claims] 1. A thermoelectric expansion valve having a characteristic that the change of the opening area is proportional to the square of the applied voltage and capable of variably controlling the opening area at any position from fully open to fully closed or vice versa. When a rectangular shock wave, which is a kind of distorted wave, is applied to the current-carrying part at a time interval, the effective value of the square shock wave is proportional to the 1/2 power of the ratio of the HIGH time to the first cycle, and The first cycle is divided by a second cycle shorter than the first cycle to form a reference pulse,
A method for controlling an electric expansion valve, characterized in that a time period of H is used as a group of a plurality of reference pulses and a rectangular shock wave is applied to make a relationship between a control amount and an operation amount substantially linear over a wide range.