JP2538694B2 - DC solenoid valve control circuit - Google Patents

Description

TECHNICAL FIELD The present invention relates to a DC solenoid valve control circuit for controlling an electromagnetic valve coil of a DC solenoid valve.

(B) Conventional technology In a conventional DC solenoid valve, when a rated voltage is normally applied to a movable iron core, suction of the movable iron core is completed in 10 to 50 msec. The movable iron core was suction-held by the rated voltage.

Further, in the conventional DC solenoid valve control circuit, a diode is connected between both ends of the solenoid valve coil in a direction in which a reverse bias is applied when the solenoid valve coil is energized. This diode discharges the electromotive force of L (di / dt) that is accumulated during energization of the solenoid valve coil and is generated when the coil is closed, and acts so that high voltage and noise are not applied to other circuits.

(C) Problem to be Solved by the Invention The above-described conventional DC solenoid valve attracts and holds the movable iron core at a voltage higher than necessary while maintaining the rated voltage applied at the start even after the completion of the movable iron core suction operation. Wasted and the coil temperature was raised, which adversely affected the valve control fluid and the surrounding components.

In addition, since the control circuit for the applied voltage is not provided, if the applied voltage sharply drops due to an abnormality in the circuit or the like, there is a fear that the valve may open or leak may occur.

Furthermore, when the solenoid valve coil is de-energized, the discharge current flows through the diode connected in parallel to this coil, so that even after the power is closed, the current in the same direction continues to flow while the energy stored in the coil is discharged. As a result, the solenoid valve does not return to its original position for a certain period of time after the power is closed.

The DC solenoid valve according to the present invention is used, for example, in a device for putting an equal amount of a reagent or the like in a blood test or the like.
It is required that the valve be opened (or closed) as soon as the solenoid valve coil is energized and that the valve be closed (or opened) as soon as the power is closed. However, due to the action of the accumulated energy emitting diode connected in parallel to the solenoid valve coil, the response of the solenoid valve coil after the power is closed becomes a problem, and it is possible to perform accurate valve control in a short time. There wasn't.

An object of the present invention is to provide a direct current solenoid valve control circuit that enhances the responsiveness of the solenoid valve coil after closing the electric power, suppresses unnecessary power consumption, and avoids adverse effects due to heat generation of the solenoid valve coil.

(D) Means for Solving the Problem In the present invention, the electromagnetic valve coil attracts the movable iron core by energization, and when the energization is cut off, the movable iron core returns to its original position to open and close the valve. In the DC solenoid valve control circuit, one end of the solenoid valve coil is connected to the reference potential line of the input power source, the rated voltage is applied to the solenoid valve coil at the time of starting suction of the movable iron core, and the applied voltage is applied to the movable iron core after suction. A voltage control circuit for controlling to a low voltage capable of attracting and holding is connected between the voltage supply line of the input power supply and the other end of the solenoid valve coil, and means for discharging accumulated energy between both ends of the solenoid valve coil. And a backflow prevention diode is provided between the voltage control circuit and the reference potential line without connecting.

(E) Operation When the input power is supplied, the voltage control circuit applies the rated voltage to the solenoid valve coil. As a result, suction start of the movable iron core is performed. The voltage control circuit reduces the voltage applied to the solenoid valve coil to a low voltage after the movable iron core is attracted, and maintains the reduced applied voltage. Therefore, the movable iron core remains sucked and held. After that, when the input power is cut off, an electromotive force of L (di / dt) is generated at both ends of the solenoid valve coil (the solenoid valve coil is not connected to a means such as a diode for discharging accumulated energy) Since the backflow prevention diode is provided between the control circuit and the reference potential line, the reverse high voltage is not applied to the voltage control circuit, and the circuit is protected.

(F) Embodiment FIG. 2 shows a solenoid valve of a two-way valve as an embodiment of the DC solenoid valve according to the present invention. Reference numeral 1 is a coil housing, and a fluororesin valve body 2 is provided under the coil housing. Are combined. Inside the coil housing 1, an electromagnetic valve coil 3, a plunger 4 as a movable iron core attracted by the electromagnetic valve coil 3, and a plunger spring 5 for urging the electromagnetic valve coil 3 downward are housed. A control unit 6 that controls the voltage applied to the solenoid valve coil 3 is provided above the coil housing 1.

Further, inflow and outflow ports 7, 7 are opened on both left and right sides of the valve body 2 (indicated to the left and right in FIG. 2), and a fluororesin diaphragm 9 is provided between the valve seat 8 and the plunger 4. It is provided. That diaphragm 9
Is configured so that the plunger 4 is pushed down by the plunger spring 5 to close the valve seat 8, and when the plunger 4 is attracted by the excitation of the solenoid, the valve seat 8 is lifted to open the valve seat 8.

The structure and operation of the control circuit provided in the control unit 6 will be described below.

FIG. 1 is a circuit diagram of the entire control circuit. When switch SW is closed, diode D3, resistor R4 and solenoid valve coil 3
A base current flows through the transistor Q1 through. This turns on the transistor Q1. At the same time, the capacitors R1 and R2 start charging the capacitor C1. When the charging voltage of the capacitor C1 exceeds the Zener voltage of the Zener diode ZD1, a base current flows through the transistor Q2 through the resistor R1 and the Zener diode ZD1 and the transistor Q2 turns on. When the transistor Q2 is turned on, the base potential of the transistor Q1 changes from the zener diode ZD2 to the transistor Q1.
The collector-emitter voltage of 2 and the forward voltage drop of the diode D4 are reduced to the total voltage, and the emitter voltage of the transistor Q1, that is, the voltage applied to the solenoid valve coil 3, is (base potential of the transistor Q1−base of the transistor Q1).・ Voltage between emitters).

The rated voltage application time to the solenoid valve coil 3 is resistance R
1, R2, the value of capacitor C1 and Zener diode ZD1
Is determined by the Zener voltage of the Zener diode ZD2.

The diode D3 is a reverse connection protection diode and protects the circuit when a voltage with an incorrect polarity is applied to the input power supply line. In order to reduce diode loss during normal use, a Schottky diode with a low forward drop voltage is effective as this diode D3.

If the switch SW1 is turned off after the solenoid valve coil 3 is energized, an electromotive force of L (di / dt) is generated in the direction indicated by the arrow in the figure. However, since this voltage is applied as a reverse bias voltage to the diode D4, the voltage control circuit is protected from a high voltage. Immediately after the switch SW1 is turned off, the current flowing through the solenoid valve coil 3 is attenuated, the plunger 4 shown in FIG. 2 moves downward due to the bias of the plunger spring 5, and the diaphragm 9 closes the valve seat 8.

The resistor R5 shown in FIG. 1 is intended to disperse the temperature rise of the transistor Q1. That is, if the Zener diode ZD1 and the transistor Q2 are off, the collector-emitter voltage of the transistor Q1 is 0.
Since it is 1 to 0.5V, most of the current flows through the transistor Q1, but the Zener diode ZD1 and transistor Q2
Is turned on, the on-resistance of the transistor Q1 increases, and the current to the solenoid valve coil 3 shunts the resistor R5. For example, the emitter voltage of transistor Q1 is Zener diode
From the sum of the Zener voltage of ZD2, the collector-emitter voltage of transistor Q2 (0.1 to 0.4V) and the forward drop voltage of diode D4 (0.5 to 1.5V), the base-emitter voltage of transistor Q1 (0.5 to 0.7V). V) is subtracted. For example, when the input power supply voltage is 12V and the rated voltage of the solenoid valve coil 3 is 6V, the rated voltage of about 3V is output after a lapse of time. In this case, the resistor R5 has about 12V-diode D3
Forward voltage (about 0.5V) -voltage of solenoid valve coil 3 (about 3V
V) = 8.5V is applied, and by appropriately selecting the value of the resistor R5, the current flowing through the transistor Q1 can be shunted. As a result, a relatively small capacity element can be used as the transistor Q1.

The capacitor C2 in FIG. 1 is for preventing abnormal oscillation.

Although the transistor Q1 is used in the dropper method in the above-described embodiments, the control circuit may be configured in a chopper method such as pulse width control.

Further, in this embodiment, the present invention is applied to a two-way valve DC solenoid valve, but it can be applied to a three-way valve or four-way valve DC solenoid valve in the same manner.

(G) Effect of the Invention According to the present invention, after the attraction of the movable iron core of the solenoid valve coil is completed, the applied voltage is reduced to a low voltage at which the movable iron core can be attracted and held, thus saving power consumption. Also, it is possible to prevent the fluid and other peripheral components from being adversely affected by the rise in the coil temperature. Also, since the current flowing through the solenoid valve coil is attenuated immediately after the solenoid valve coil is closed, the response characteristics when the solenoid valve coil is closed are improved, and the solenoid valve can be controlled to open and close accurately in a short time. it can.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a DC solenoid valve control circuit according to an embodiment of the present invention, and FIG. 2 is a longitudinal sectional view of a main part of a DC solenoid valve controlled by the circuit. 1 ... Coil housing, 2 ... Valve body, 3 ... Solenoid valve coil, 4 ... Plunger, 5 ... Plunger spring, 6 ... Control part, 7 ... Inflow / outflow port, 8 ... Valve seat, 9 …… Diaphragm, D4 …… Backflow prevention diode.

Claims (1)

(57) [Claims] 1. A direct current solenoid valve control circuit for opening and closing a valve by energizing an electromagnetic valve coil to attract a movable iron core and returning the movable iron core to its original position when the electricity is cut off. The one end of the solenoid valve coil is connected to the reference potential line of, the rated voltage is applied to the solenoid valve coil at the time of starting the suction of the movable iron core, and after the suction, the applied voltage is controlled to a low voltage capable of attracting and holding the movable iron core. The voltage control circuit for connecting the voltage supply line of the input power source and the other end of the solenoid valve coil, and the voltage control circuit without connecting means for discharging stored energy between both ends of the solenoid valve coil. A DC solenoid valve control circuit comprising a backflow prevention diode provided between the circuit and a reference potential line.