JPH0413844B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a self-holding solenoid, and more particularly to an excitation current control device for a self-holding solenoid driven by a small-capacity power source such as a dry battery.

[Conventional technology]

In general, a self-holding solenoid attracts the movable iron core by passing an exciting current through the coil, and after the attraction, the movable iron core is attracted and held by a permanent magnet, so it is suitable for power saving.

[Problem that the invention seeks to solve]

However, the excitation current control circuit for the conventional self-holding solenoid cannot cut off the excitation current when the movable iron core is completely attracted, resulting in wasteful power consumption.

For this reason, various methods have been proposed for detecting the point in time when the adsorption operation of the movable iron core is completed. Namely, limit switch methods, timer methods, current detection methods, electric quantity setting methods, reed switch methods, and the like are known.

However, although the limit switch method is inexpensive, it requires a contact point, so it has poor durability and has the drawbacks of being bulky. Furthermore, the timer method has the disadvantage that the excitation current is cut off even before the suction operation is completed.
In addition, the current detection method requires a complicated and expensive determination circuit, and further has the drawback that if the power supply fluctuates during operation, the excitation current may be cut off even if the suction operation is not completed. Also,
The electric quantity detection method has the disadvantage that if there is a load fluctuation (surge load), the excitation current is cut off even if the suction operation is not completed. In addition, the reed switch system requires contacts and is poor in durability, and furthermore, it is difficult to adjust the setting position and has the disadvantage that it cannot handle large fluctuations in the input power supply.

[Means for solving problems]

The present invention improves this point, and provides a self-holding solenoid that does not have a complicated circuit configuration, has good durability, and can accurately detect the point at which the suction operation is completed and turn off the excitation current. The purpose is to

In the present invention, a magnetic sensing element is arranged at a position where leakage magnetic flux from a self-holding permanent magnet and leakage magnetic flux from an excitation coil interfere with each other in opposite directions, and the output of this magnetic sensing element is sent to an excitation current control circuit. It is characterized by being connected.

[Effect]

Focusing on the fact that when the movable iron core enters a stable adsorption state, which has been experimentally proven, the leakage magnetic flux of the self-holding permanent magnet and the leakage magnetic flux from the excitation coil caused by the excitation current cancel each other out, and the output of the magnetic sensing element is determined by The point in time when becomes zero is detected, and the excitation current control circuit is controlled based on this detection output so that the movable core is self-held by the permanent magnet.

〔Example〕

The present invention will be explained below based on the drawings.

Figures 1a and 1b are experimental data illustrating the principle of the invention.

That is, as shown in FIG. 2, in FIGS. 1a and 1b, magnetic flux is generated at a position where the leakage magnetic flux of the self-holding permanent magnet 2 of the self-holding solenoid 1 and the leakage magnetic flux of the excitation coil 3 interfere with each other in opposite directions. This is experimental data obtained by arranging the sensor 5. FIG. 1a shows experimental data on the excitation current of the exciting coil 3, and FIG. 1b shows experimental data on the output waveform of the magnetic sensor 5 at this time.

Excitation current A in FIG. 1a will be explained. This exciting current waveform itself is a known waveform, and attraction of the movable iron core 6 starts a little before the peak, and along with this, the reactance of the L component of the exciting coil 3 increases, and the exciting current A then decreases, and the exciting current A decreases. The adsorption of the movable iron core 6 ends when the current I becomes the minimum, and then the excitation current I increases.

The output of the magnetic sensor 5 at this time is shown in Figure 1b.
The waveform will be as shown in . That is, the magnetic sensor 5
detects the leakage magnetic flux φm generated in the magnetic path between the fixed iron core 7 and the yoke 8 of the permanent magnet 2, and the leakage magnetic flux φc generated in the magnetic path between the fixed iron core 7, the movable iron core 6, and the yoke 8 of the excitation coil 3. . In this case, the magnetic flux φm is constant, but the magnetic flux φc changes due to changes in the excitation current A, so after a short period of time has elapsed since the movable core 6 was attracted (shown as point α in FIGS. 1 a and b) At this time, the output A' of the magnetic sensor 5 becomes zero and is reversed.
That is, when the movable iron core 6 is attracted and the repulsive force is overcome and the attraction becomes stable (above point α), the output of the magnetic sensor 5 is reversed.

Here, in Fig. 1a, experimental data is shown for other excitation currents B and C, and similar magnetic sensor outputs B' and C' are obtained, and the magnetic sensor outputs at points β and γ are respectively Invert.

The present invention focuses on this point, and detects the point in time when the output of the magnetic sensor 5 is reversed, and controls the excitation current control circuit based on this detected output.

An embodiment of the present invention will be described below based on the drawings.

FIG. 3 is a diagram showing the main part of an embodiment of the present invention. A power source 11 is connected to the excitation coil 3 of the self-holding solenoid 1 via an excitation current control circuit 12. That is, the excitation current control circuit 12 is provided with a timer circuit 15 consisting of a variable resistor R ₀ , resistors R ₁ , R ₂ , R ₃ , a capacitor C, and an operational amplifier 13 , and the output of the operational amplifier 13 is connected to an AND circuit 16 . has been done. Further, 5 in FIG. 3 indicates the magnetic sensor such as a Hall element, and the output of this magnetic sensor 5 is connected to the + terminal of the operational amplifier 17. Further, the voltage of the power source 11 is divided and connected to the negative terminal of the operational amplifier 17 by a variable resistor R ₅ and a resistor R ₆ . This operational amplifier 17
The output of is connected to the AND circuit 16.

The output of this AND circuit 16 is the transistor 18
is connected through a resistor _R7 to the base terminal of.
The excitation coil 3 of the self-holding solenoid is connected to the collector terminal of this transistor 18, and the emitter terminal is grounded. A diode 19 is connected in parallel to the excitation coil 3 of the self-holding solenoid. Further, in FIG. 3, reference numeral 20 indicates a one-shot type switch circuit, and the excitation coil 3 is omitted.

FIG. 4 shows an operating waveform diagram at each point indicated by an x mark in FIG. 3.

〔motion〕

The characteristic operation of one embodiment of the present invention configured in this way will be explained.

When the one-shot switch circuit 20 is closed, the power supply voltage E is applied (FIG. 4a), which causes the timer circuit 15 to output for a predetermined time (the fourth
Figure b) is sent out. As a result, an excitation current (FIG. 4f) flows through the self-holding solenoid, and the magnetic sensor 5 outputs the output (FIG. 4f) as explained in FIG.
Figure c) is sent. If the output d is not inverted, the operational amplifier 17 continues to output and the transistor 18 is also turned on.

In this state, the operation that is a feature of the present invention is performed. That is, when the leakage flux of the permanent magnet and the leakage flux of the excitation coil cancel each other out and the magnetic sensor 5 detects this and its output becomes zero, the output of the operational amplifier 17 also becomes zero, the AND circuit 16 is closed, and the transistor 18 is turned off, and the excitation current to the excitation coil 3 is cut off. In this state, the movable iron core 6 is self-held only by the permanent magnet 2.
After this, the excitation current f is attenuated via the diode 19.

Here, the timer circuit 15 controls the excitation current control circuit 12 when the movable iron core 6 is not attracted.
This is a protection circuit that protects the self-holding solenoid by turning it off.

Furthermore, in the above embodiment, the magnetic sensor detects the point at which the leakage fluxes cancel each other out (for example, point α in FIG. 1), but when the leakage fluxes are reversed,
That is, the magnetic fluxes in the portions before and after point α shown as point α ₁ and point α ₂ in FIG. 1b may be detected respectively.

〔effect〕

As explained above, according to the present invention, the magnetic sensing element is arranged at a position where the leakage magnetic flux from the self-holding permanent magnet and the leakage magnetic flux from the excitation coil interfere with each other in opposite directions, and the magnetic sensing element The output was connected to the excitation current control circuit.

Therefore, it is possible to accurately detect from the output of the magnetic sensing element the point in time when the leakage magnetic flux of the self-holding permanent magnet and the leakage magnetic flux from the excitation coil due to the excitation current cancel each other out, when the movable core reaches a stable adsorption state. Based on this detection output, the movable core can be self-held by a permanent magnet without wasting power.

[Brief explanation of drawings]

FIGS. 1a and 1b are diagrams showing experimental data for explaining the principle of the present invention. FIG. 2 is an explanatory diagram of the arrangement position of the magnetic sensor. FIG. 3 is a diagram showing the main circuit configuration of an embodiment of the present invention. FIG. 4 is an operation waveform diagram of FIG. 3. 1... Self-holding solenoid, 2... Permanent magnet,
3... Excitation coil, 5... Magnetic sensor, 6... Movable iron core, 7... Fixed iron core, 8... Yoke, 11...
Power supply, 12... Excitation current control circuit, 13, 17...
... operational amplifier, 15 ... timer circuit, 16 ... AND circuit, 18 ... transistor, 19 ... diode, 20 ... one shot type switch circuit.

Claims (1)

[Scope of Claims] 1. A self-holding solenoid circuit comprising a movable iron core, an excitation coil, means for applying an excitation current to the excitation coil, and a permanent magnet for self-holding the movable iron core, wherein the permanent magnet a magnetic sensing element arranged at a position where leakage magnetic flux from the excitation coil and leakage magnetic flux from the excitation coil interfere with each other in opposite directions; and detecting a point in time when the output of the magnetic sensing element is reversed, and based on this detection output. A self-holding solenoid circuit comprising: an excitation current control circuit that controls supply of the excitation current to the excitation coil.