JPH0927421A - Detection circuit of operation of solenoid - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect operation of a solenoid and prevent malfunction of the solenoid by providing a circuit for detecting operation of a solenoid with a current detection circuit connected to a driving coil of a solenoid. SOLUTION: A pulse current flows through a coil 7 of a solenoid when a pulse voltage V is applied to both ends of the coil 7 of a solenoid. This current is current of a series circuit which depends on a d.c. resistance (r) of the coil 7 and an inductance L. Although the d.c. resistance (r) is proper to a coil, an inductance L changes as a movable core moves. A current of the coil 7 of a solenoid is detected and operation of a solenoid is detected by a value of the current or change of a current with time. Operation of a solenoid is detected and malfunction of the solenoid is prevented by measuring a current of the coil 7 of a solenoid in this way.

Description

Detailed Description of the Invention

[0001]

INDUSTRIAL APPLICABILITY The present invention can be used in all fields where it is necessary to confirm the drive of a solenoid.

[0002]

2. Description of the Related Art In a conventional solenoid, a micro switch or an optical sensor is installed near a solenoid or a mechanism driven by the solenoid to detect its operation.

[0003]

The conventional solenoid requires a mechanical space for installing a sensor for detecting its operation, and the detection mechanism becomes complicated. Also, the cost of this sensor is required, so it is quite difficult to detect the operation of the solenoid.

The present invention does not require such a sensor or micro switch, but detects the operation of the solenoid by measuring the current of the solenoid coil.

[0005]

In order to achieve the above object, the present invention detects the current of a solenoid coil and detects the operation of the solenoid based on the value of the current or the time change of the current.

In FIG. 1, when the pulse voltage V shown in FIG. 2 is applied to both ends of the solenoid coil, the pulse current shown in FIG. 3 flows through the solenoid coil. This current is a series circuit current due to the DC resistance R and the inductance L of the coil.
This DC resistance is unique to the coil, but the inductance changes as the movable iron core of the solenoid moves. In FIG. 4, the position of the push rod 16 of the solenoid is A
The inductance of the solenoid at the position is La and the inductance at the position of the push rod is B is Lb. This change in the inductance of the solenoid can be detected from the change in current over time.

In FIG. 4, it is assumed that the push rod of the solenoid is initially in the A position, and the push rod of the solenoid driven by the pulse voltage of the time width T is moved to the B position and stopped. The pulse current begins to rise with a time constant T1 calculated by La / R, but the coil current of the solenoid stopped at the B position falls gently with a time constant T2 calculated by Lb / R. Even if the solenoid is driven for some reason, it is still in the B position and A
If it stays in position, the current quickly drops to the time constant T1.

In FIG. 3, the solenoid is operated with a pulse voltage V
The current is measured after a lapse of time t from immediately after driving with. If this current is i1, it can be detected that the push rod remains at the A position, and if it is i2, it can be detected that the push rod is driven to the B position and stopped. When the pulse voltage is constant, it is only necessary to measure the current once after a certain time has passed, but when the pulse voltage is not stable, the time constant of the change in current may be measured. This time constant can be calculated by measuring the current twice after the passage of t1 and the passage of t2.

To summarize the concrete method, the coil current is measured once after a certain time has elapsed after the completion of the pulse voltage driving, or the current is measured twice after the completion of the pulse driving to measure the time constant of the current decrease. The stop position of the solenoid can be detected by measuring and calculating.

[0010]

[Example] When the position of the push rod of the solenoid constituted by the circuit of FIG. 1 is the position A of FIG. 4, the time width is 40 ms.
A pulse voltage of 24 V was applied. The current was measured 5 milliseconds after the application of the pulse voltage, and when the value was 0.5 A or more, the push rod remained stopped at the A position. When the current value was 0.3 A or less, the position of the movable core moved to the position B and stopped. The current value 5 milliseconds after the application of the pulse voltage is taken out as the voltage across the shunt 8, and is held in the voltage holder 6 to be used as the reverse phase input of the voltage comparator 5. When the value of the shunt r is 1 ohm and 0.4 V is applied to the positive phase input of the voltage comparator, the output terminal 3 of the comparator
Is high, the negative-phase input voltage of the voltage comparator is 0.4
Since it is lower than V, the push rod is stopped at the position B in FIG. In this way, the position of the push rod could be detected by the output of the voltage comparator.

[Brief description of drawings]

FIG. 1 is a diagram showing a solenoid and an operation detection circuit for the solenoid.

FIG. 2 is a pulse voltage waveform for driving a solenoid.

FIG. 3 is a pulse current waveform flowing in a solenoid.

FIG. 4 is a sectional view of a solenoid.

[Explanation of symbols]

 1 Anode terminal of solenoid circuit 2 Cathode terminal of solenoid circuit 3 Output terminal of voltage comparator 4 Positive phase input terminal of voltage comparator 5 Voltage comparator 6 Sampling hold circuit 7 Solenoid coil 8 Shunt 9 Reverse surge absorption diode 10 Movable iron core 11 Frame 12 Magnet 13 Coil 1 14 Coil 2 15 Stopper 16 Push rod

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[Procedure amendment]

[Submission date] November 23, 1995

[Procedure amendment 1]

[Document name to be amended] Drawing

[Correction target item name] All figures

[Correction method] Change

[Correction contents]

FIG.

[Fig. 2]

[Figure 3]

FIG. 4

Claims (3)

[Claims] 1. A circuit for detecting the operation of a solenoid having a current detection circuit connected to a drive coil of the solenoid. 2. Utilizing the fact that the inductance of a solenoid coil changes before and after the operation of the solenoid,
A circuit that detects the operation of the solenoid. 3. A solenoid drive circuit having the detection circuit according to any one of claims 1 and 2.