JPH0661043A - Apparatus for driving electromagnetic - Google Patents

Abstract

PURPOSE:To provide an apparatus for driving an electromagnet, consumes minimum energy and minimizes the initial shock by ensuring magnetic attraction depending on the repulsion in the position of the armature when power is switched on. CONSTITUTION:An apparatus for driving an electromagnet comprises a position sensor 9 for detecting the position of the armature of an electromagnet 4; a current setting circuit 10 for setting the current flowing through the coil of the electromagnet that produces an attractive force depending on the repulsion in the position of the armature; a pulse output circuit 7 for controlling the current to the magnetizing coil according to the coil current of the electromagnet as well as to the value set by the circuit 10; and a switching device 5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coil driving device for an electromagnet such as an electromagnetic contactor.

[0002]

2. Description of the Related Art FIG. 6 is a circuit diagram of a conventional coil driving device for an electromagnet. In FIG. 6, a DC voltage is supplied to the circuit by a rectifier circuit 3 connected to a power source 1 via a switch 2. An electromagnet coil 4 and a switching element 5 are connected in series in parallel to the rectifier circuit 3, and a flywheel diode 6 is connected in parallel with the electromagnet coil 4. Further, a voltage detection circuit 12 and a constant voltage circuit 13 are connected in parallel to the rectifier circuit 3, and the constant voltage circuit 13 includes a first timer circuit 20, a second timer circuit 21, a gain circuit 19, a pulse generation circuit 9, and a comparison circuit. A voltage is supplied to the circuit 8 and the pulse output circuit 7. The signal from the voltage detection circuit 12 is input to the switching element 5 via these circuits.

Although a description of this operation is omitted, the point is that when the electromagnet is turned on, the coil current is sequentially decreased with the lapse of time so as to obtain an attractive force corresponding to the reaction force at each position of the movable iron core. To minimize the impact at the time of charging.

[0004]

In the coil drive device for the electromagnet described above, the coil current is gradually decreased with the passage of time when the electromagnet is turned on to obtain the attraction force corresponding to the reaction force at each position of the movable iron core. However, since the operating time of an electromagnet generally changes depending on the mounting angle of the electromagnet, in order to cover these, it is necessary to reduce the rate of decrease of the coil current at the time of turning on. For this reason, the actual current is such that an input current flows more than necessary, the coil loss increases, and the impact reducing effect is reduced.

An object of the present invention is to solve the above-mentioned problems and to provide a coil driving device for an electromagnet which surely obtains a suction force corresponding to a reaction force at each position of the movable iron core when the electromagnet is turned on. is there.

[0006]

In order to achieve the above-mentioned object, a coil drive device for an electromagnet according to the present invention detects a power supply voltage and a switching element and a current detection circuit which are respectively connected in series to the coil of the electromagnet. A voltage detection circuit that outputs a closing signal when the voltage is a predetermined value or more, a position sensor that detects the position of the movable iron core of the electromagnet, a closing signal from the voltage detection circuit, and a position detection signal from the position sensor. Is input and a current setting circuit that sets a coil current of an electromagnet that generates an attraction force corresponding to a reaction force at each position of the movable iron core, a detected current value of the current detection circuit and a set current value of the current setting circuit are input. And a pulse output circuit for outputting an opening / closing pulse signal for controlling the coil current of the electromagnet to the set current value to the switching element. That. The position sensor is composed of, for example, a fixed coil provided in a fixed portion of an electromagnet and a magnetic body which is connected to a movable iron core and is movable in the fixed coil in the axial direction. The body moves to the outside of the fixed coil when the electromagnet starts to be turned on, and moves to the inside when the turning is completed, and the current setting circuit oscillates by the closing signal from the voltage detection circuit. When applied, the set current value having a magnitude proportional to the current flowing through the fixed coil is output.

[0007]

In the coil driving device for the electromagnet of the present invention,
For example, it is connected to a fixed coil provided in the fixed part of the electromagnet and is movable in the axial direction inside the fixed coil. When the electromagnet is turned on, it is outside the fixed coil, and when it is completed, it moves inside. The position of the movable iron core is determined by the position sensor consisting of the body and the size of the inductance of this fixed coil (small at the start of charging and large at the completion of charging).
The current setting circuit applies the oscillating voltage oscillated by the input signal from the voltage detection circuit to the fixed coil of this position sensor, and outputs the set current value proportional to the current flowing through the fixed coil. The set current value is the reciprocal of the inductance of the fixed coil and is large at the start of charging,
The value will be small when the charging is completed. Since the coil current of the electromagnet is controlled to this set current value, the electromagnet can obtain the attraction force according to each position of the movable iron core.

[0008]

1 is a circuit diagram showing an embodiment of a coil driving device for an electromagnet according to the present invention. In FIG. 1, a coil driving device for an electromagnet includes a switch 2 and a rectifying circuit 3 which are connected in series to a power source 1, and a coil 4A of an electromagnet 4 which is connected in series to the rectifying circuit 3 in series, for example, a MOSFET. A voltage detection circuit 11 that is connected in parallel to the switching element 5 and the current detection circuit 8 and the rectification circuit 3 and detects the current voltage of the power supply ₁ and outputs an "L" level closing signal P ₁ when this voltage is above a predetermined value. (When the power supply voltage is equal to or lower than a predetermined value, a non-closed signal P ₀ of “H” level is output) and a fixed coil 9A provided in a fixed portion (not shown) of the electromagnet 4 and a movable iron core (not shown). The position sensor 9 is composed of a magnetic body 9B that is movable in the axial direction and that moves to the outside of the fixed coil at the start of charging of the electromagnet, and moves to the inside of the fixed coil at the completion of charging, and the electromagnetic sensor 9B. The input signal P ₁ from the pressure detection circuit 11 and the position detection signal P ₂ from the position sensor 9 are input, and the coil current of the electromagnet 4 that produces an attractive force corresponding to the reaction force at each position of the movable iron core of the driven electromagnet 4 a current setting circuit 10 for setting a set current value P ₃ of the detected current values P ₄ and a current setting circuit 10 of the current detecting circuit 8 is input, closing pulse to control the coil current of the electromagnet 4 to the set current value P ₃ The pulse output circuit 7 outputs the signal P ₅ to the switching element 5. Reference numeral 6 is a flywheel diode connected in parallel to the coil 4A of the electromagnet 4, and the current detection circuit 8 is composed of a current detection resistor 8A and a detection output smoothing capacitor 8B connected in parallel with the current detection resistor 8A. ing.

FIG. 2 shows an example of the circuit of the current setting circuit 10 of FIG.
Here is an example: FIG. 3 is a waveform diagram of the operation, refer to FIG.
Explain. In FIG. 2, the operational amplifier OP₁， Conden
SA C ₁, Resistance R₁, R_Five, R₆, R₇, R₈Is the oscillator circuit
And a capacitor C₁, Resistance R₁At the frequency determined by
Oscillates, operational amplifier OP₁The output terminal of is shown in Fig. 3 (1)
Oscillation voltage v₀Cause 9A is a fixed sensor for the position sensor 9.
The fixed coil 9A has an oscillation voltage v₀Mark
Added capacitor C connected in series₂, Resistance R₂To
A current I close to the sine wave shown in FIG._SFlows,
Resistance R₂A voltage with a similar waveform is generated between the two terminals. this
Voltage is diode D₁Is rectified by capacitor C₃Charge
Power, capacitor C₃Between both terminals of is shown in Figure 3 (3)
Such resistance R₂The voltage between both terminals of the
Generated voltage. Therefore, the magnitude of this voltage is fixed coil
Current I flowing to 9A_SIndicates the size of.

The operation of the coil drive circuit of the electromagnet is as follows.
It is Ri. First, if the power supply voltage is below a specified value, voltage detection
Non-input signal P of "H" level from circuit 11₀Is output
And the transistor T of this current setting circuit 10₁Oh
The set current value P to the pulse output circuit 7.₃Becomes zero
ing. When the power supply voltage exceeds the specified value, the voltage detection circuit 1
Input signal P from 1 to "L" level₁Is output
T₁Is turned off, and the pulse output circuit 7 is shown in FIG.
Capacitor C₃The voltage between both terminals is the current setting value P ₃As
Is output. Here, the position sensor 9 detects the position of the movable iron core.
Inductance L of fixed coil 9A of_SIndicated by the size of
Position detection signal P₂Is output. This position detection signal P₂,
That is, the inductance L of this fixed coil 9A_SIs a figure
As shown in the operating characteristic diagram of No. 4, when the electromagnet is turned on, it is magnetic.
Since the body 9B is outside the fixed coil 9A, it is small,
At the completion of charging, it will be larger because it is inside. And solid
Current I flowing in constant coil 9A_SIs almost this inductor
S L_SBecomes the reciprocal of the same as above, and as shown in FIG.
Value gradually decreases and becomes the smallest value at the completion of charging.
become.

FIG. 5 is a general operational characteristic diagram of an electromagnet showing a coil current required for a closing operation at each position of the movable iron core, that is, a coil current which produces an attractive force corresponding to a reaction force at each position of the movable iron core. Since the value becomes smaller from the large value at the start of making and becomes the smallest value at the completion of making, the set current value P ₃ (the capacitor C ₃ of the current setting circuit 10 of the current setting circuit 10 is proportional to the current I _S flowing through the fixed coil 9A. By controlling the coil current of the electromagnet 4 to the voltage between both terminals), it is possible to obtain an attractive force corresponding to the reaction force at each position of the movable iron core.

[0012]

The coil driving device for an electromagnet according to the present invention is adapted to obtain a large attraction force at the beginning of charging and a small attraction force at the completion of charging according to the reaction force of each position of the movable iron core at the time of charging the electromagnet. Therefore, the input energy can be minimized and the impact at the time of application can be minimized. For example, the reliability of an electromagnetic contactor using this electromagnet is improved and the life is extended.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of a coil driving device for an electromagnet according to the present invention.

FIG. 2 is a circuit diagram of a current setting circuit shown in FIG.

3 is an operation waveform diagram of the current setting circuit shown in FIG.

4 is an operation characteristic diagram of the position sensor of the movable core shown in FIG.

FIG. 5 is a general operating characteristic diagram of an electromagnet.

FIG. 6 is a circuit diagram showing an example of a conventional coil driving device for an electromagnet.

[Explanation of symbols]

 4 Electromagnet 4A Coil 5 Switching Element 7 Pulse Output Circuit 8 Current Detection Circuit 9 Position Sensor 9A Fixed Coil 9B Magnetic Material 10 Current Setting Circuit 11 Voltage Detection Circuit

Claims (3)

[Claims] 1. A switching element and a current detection circuit which are respectively connected in series to coils of an electromagnet, a voltage detection circuit which detects a power supply voltage and outputs a closing signal when the voltage is a predetermined value or more, and the electromagnet movable. A position sensor that detects the position of the iron core, and a coil current of an electromagnet that receives an input signal from the voltage detection circuit and a position detection signal from the position sensor to generate an attractive force corresponding to a reaction force at each position of the movable iron core. And a current setting circuit for setting the current detection circuit and the set current value of the current setting circuit are input, and an open / close pulse signal for controlling the coil current of the electromagnet to the set current value is output to the switching element. And a pulse output circuit for controlling the coil of the electromagnet. 2. The coil drive device for an electromagnet according to claim 1, wherein the position sensor is a fixed coil provided in a fixed portion of the electromagnet, and a magnetic body connected to a movable iron core and axially movable in the fixed coil. A coil drive device for an electromagnet, comprising: 3. The coil driving device for an electromagnet according to claim 2, wherein the magnetic material of the position sensor is outside the fixed coil when the electromagnet is turned on and moves inside the fixed coil when the turn is completed. It oscillates with a closing signal from the voltage detection circuit, applies this oscillating voltage to the fixed coil of the position sensor, and outputs a set current value having a magnitude proportional to the current flowing through the fixed coil. Coil drive.