JPH08162325A - Controller for electromagnetic actuator - Google Patents

Abstract

PURPOSE: To provide a controller for electromagnetic actuator capable of definitely preventing burning of an electromagnetic coil, of performing automatic reset after a drop in temperature and also of not affected by disturbance. CONSTITUTION: This controller comprises a resistor RG connected in series to an electromagnetic coil 1, a comparator 19 for comparing whether a voltage drop by the resistor RG is larger or smaller than the allowable voltage drop during allowable maximum temperature of the electromagnetic coil 1, and a switching transistor 16 which turns off the current to the electromagnetic coil 1 when the voltage drop is larger than the allowable voltage drop by means of the comparator 19 and continues the current to the electromagnetic coil 1 when the voltage drop is smaller than allowable voltage drop.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for an electromagnetic actuator, and more particularly to a fail safe circuit for preventing burning of an electromagnetic coil.

[0002]

2. Description of the Related Art As a fail-safe circuit for preventing a conventional electromagnetic actuator of this type from being burnt out, a temperature fuse as shown in FIG. 2 is generally used.

That is, the temperature fuse 101 is attached to the electromagnetic coil 100, and heat is generated by the current flowing through the electromagnetic coil 100. When the temperature reaches the rated temperature of the temperature fuse 101, the temperature fuse 101 is melted and the current flowing through the electromagnetic coil 100 is changed. By stopping, the burning of the electromagnetic coil 100 was prevented.

[0004]

However, in the above-described conventional electromagnetic actuator control device, there is a problem that the melted temperature fuse 101 cannot be restored unless replaced and the device stops. .

Further, the temperature at which the temperature fuse 101 melts may vary depending on the mounting position of the temperature fuse 101 and the heat radiation state, and the electromagnetic coil 100 may be burned in some cases.

The present invention has been made in order to solve the above-mentioned problems of the prior art. The purpose of the present invention is to reliably prevent the electromagnetic coil from being burnt out and to automatically recover it when the temperature drops. Another object of the present invention is to provide a control device for an electromagnetic actuator that is not affected by disturbance.

[0007]

In order to achieve the above object, the present invention provides an electromagnetic actuator including an electromagnetic actuator having an electromagnetic coil and a DC power supply for supplying electric power to the electromagnetic coil. In the control device of
Resistance means connected in series to the electromagnetic coil, comparison means for comparing whether the voltage drop due to the resistance means is larger or smaller than the allowable voltage drop at the maximum allowable temperature of the electromagnetic coil, and the voltage drop by the comparing means. Is larger than the permissible voltage drop, the electromagnetic coil is deenergized, and when the voltage drop is smaller than the permissible voltage drop, the energization is continued to the electromagnetic coil.

[0008]

According to the present invention, the value of the current flowing through the electromagnetic coil changes as the temperature rises when the electromagnetic coil is energized. Due to this change in current value, the voltage drop of the resistance means connected in series to the electromagnetic coil changes, and this change in voltage drop depends on the temperature change of the electromagnetic coil.

Therefore, the comparison means compares whether the voltage drop of the resistance means is larger or smaller than the allowable voltage drop of the electromagnetic coil at the maximum allowable temperature. Then, when the voltage drop is larger than the allowable voltage drop, the energization to the electromagnetic coil is cut off by the switch means, and when the voltage drop is smaller than the allowable voltage drop, the electromagnetic coil is continuously energized.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the illustrated embodiments.

FIG. 1A shows a block diagram of a control device for an electromagnetic actuator according to an embodiment of the present invention.
Here, as an electromagnetic actuator, as shown in FIG. 1B, a case where a pull coil 1 having a different coil resistance and a solenoid 3 having a hold coil 2 are controlled will be described as an example.

The solenoid 3 includes a fixed iron core 4, a movable iron core 6 having a rod 5 arranged coaxially with the fixed iron core 4, and a coil portion arranged so as to surround the fixed iron core 4 and the movable iron core 6. 7 and a yoke member 8 for forming a magnetic circuit between the fixed iron core 4 and the movable iron core 6.

The movable iron core 6 makes a stroke from a first position a which is separated from the fixed iron core 4 by a predetermined distance to a second position b which is attracted to the fixed iron core 4. When pulling the movable iron core 6 from the first position a to the second position b, a large magnetic force is required, so that both the pull coil 1 and the hold coil 2 are energized, and the pulling end is moved to the second position b. In order to hold the iron core 6, it is controlled so that only the hold coil 2 is energized.

FIG. 1A shows a control circuit for the solenoid 1.

To briefly explain the control circuit, a pull coil 1 and a hold coil 2 are connected to a DC power source, and power transistors 11 and 12 are connected to the pull coil 1 and the hold coil 2, respectively. That is, the collector terminals 11c and 12c of the power transistors 11 and 12, respectively.
Is connected to the pull coil 1 and the hold coil 2, a DC power supply 14 is connected to the base terminals 11b and 12b via the start switch 13, and the emitter terminals 11e and 12e are grounded.

The circuit on the pull coil 1 side is provided with a timer 15 which turns off the power when the start switch 13 is turned on for a predetermined time. The timer 15 is connected to the power transistors 11 and 12 via a transistor 16 as a switching means. That is, the output terminal of the timer 15 is connected to the base terminal 16b of the transistor 16, and the collector terminal 16c of the transistor 16 is connected to the power transistor 1.
1 is connected to the base terminal 11b, and the emitter terminal 16e of the transistor 16 is grounded.

When the start switch 13 is turned on, the power transistors 11 and 12 are turned on, and the pull coil 1
A direct current flows through both the holding coil 2 and the holding coil 2, and the movable iron core 6 moves from the first position a to the second position b. Then, after a lapse of a predetermined time, the timer 15 times out and outputs an output signal, and the transistor 16 is turned on. As a result, the power transistor 11 for driving the pull coil is turned off, the power supply to the pull coil 1 is cut off, and the movable core 6 is adsorbed and held by the fixed core 4 only by the hold coil 2.

On the other hand, when the start switch 13 is turned off, the power transistor 12 is turned off and the hold coil 2 is also turned off.

Since a large current flows through the pull coil 1 even for a short time during the stroke, there is a risk of burnout during continuous energization or repeated frequent operations. Therefore, the pull coil 1 is configured so that a failsafe for preventing burnout works.

That is, a resistor RG is connected in series to the pull coil 1, and a voltage drop Vc due to the resistor RG is amplified by an amplifier 17 and corrected by a voltage fluctuation compensator 18 to a comparator 19 as a comparison means. Connected. The power supply VE for correction of the voltage fluctuation corrector 18 is obtained by dividing the power supply voltage VS of the DC power supply 14 by the resistors 19a and 19b.

The comparator 19 is for comparing whether the voltage drop is larger or smaller than the allowable voltage drop of the pull coil 1 at the maximum allowable temperature.
Base terminal 1 of transistor 16 as switch means
6b.

Here, the resistance (Rc0) of the pull coil 1
Is R20, temperature coefficient is α, and pull coil temperature is t at 20 [° C], Rc0 = R20 [1 + α (t-20)] as shown in FIG. 1 (c). , As described above, the resistor RG is inserted in series in the pull coil circuit, and the current (IP) is generated by the voltage drop (VG) of this resistor.
Seeking.

If the resistance of the pull coil of 20 ° C. is RC, then IP = VG / RG≈VS / RC. This is because the resistance RG of FIG. 1A and the 0N resistance of the power transistor 11 are small and do not affect IP.

At this time, the current (IP) is heated by energization, so that the pull coil 1 is heated and changes to the following equation (Iph).

Iph = VGh / RG≈VS / RC [1 + α (th−20)] It is common sense that th is the temperature of the pull coil 1 when heated.

Therefore, focusing on the voltage drop of the resistor RG, VG = RG.multidot.VS / RC VGh = RG.multidot.VS / RC [1 + .alpha. (Th-20)] VG / VGh = [RG.multidot.VS / RC] / [RG.multidot. VS / RC {1
+ Α (th−20)}] = 1 + α (th−20) From this, the change in the voltage drop of the resistor RG depends only on the temperature of the pull coil 1, and the change in resistance due to the temperature of the pull coil 1 is known. .

Therefore, the voltage drop VG of the resistor RG is compared with the voltage drop VGMAX (supplied to the comparator as a constant voltage) at the maximum allowable temperature of the pull coil, and when the condition of VG> VGMAX, the comparator 19 outputs an output. Transistor 1
6 is turned on to turn off the power transistor 11 which supplies a current to the pull coil 1 to stop the current flowing through the pull coil 1.

The pull coil 1 is cooled, the temperature is lowered,
When the condition of VG <VGMAX is satisfied, the automatic recovery is performed, and the current can be supplied to the pull coil 1 again.

Further, the timer 15 is the start switch 1
It is controlled so that the current flows through the pull coil 1 only while the rod 5 is retracted after 3 has entered.

The current flowing through the hold coil 2 is small and does not contribute much to heat generation. That is, since the hold coil 2 is in the state of being attracted to the fixed iron core 4, a small current is sufficient, and there is no risk of burning even if it is energized for a long time. Therefore, although the fail-safe circuit is not formed in this embodiment, the fail-safe circuit may be formed similarly to the pull coil 1.

In this embodiment, the example in which the coil portion is divided into the hold coil and the pull coil has been described, but the same can be applied to a single coil solenoid.
The invention is not limited to solenoids, and can be similarly applied to other electromagnetic actuators including electromagnetic coils.

[0032]

As described above, according to the present invention,
The resistance change of the electromagnetic coil due to the temperature rise is detected as a voltage drop due to the resistance means connected in series with the electromagnetic coil, and the voltage drop is compared to determine whether the voltage drop is larger or smaller than the allowable voltage drop at the allowable maximum temperature of the electromagnetic coil. Since the energization to the electromagnetic coil is controlled, it is possible to prevent the electromagnetic coil from being burned, and to automatically recover when the temperature of the electromagnetic coil is lowered to start energizing the electromagnetic coil.

Further, since the temperature change of the electromagnetic coil itself is handled by utilizing the voltage drop of the resistance means, it is possible to surely protect the electromagnetic coil without disturbance.

[Brief description of drawings]

FIG. 1 (a) is a block diagram of a control device for an electromagnetic actuator of the present invention, FIG. 1 (b) is a diagram showing an example of an electromagnetic actuator, and FIG. 1 (c) is a resistance change of an electromagnetic coil due to temperature. FIG.

FIG. 2 is a control circuit diagram of a conventional electromagnetic actuator.

[Explanation of symbols]

 1 Pull coil 2 Hold coil 3 Solenoid 4 Fixed iron core 5 Rod 6 Movable iron core 7 Coil part 8 Yoke member a 1st position b 2nd position 11,12 Power transistor 11c, 12c Collector terminal 11b, 12b Base terminal 11e, 12e Emitter terminal 13 Start switch 14 DC power supply 15 Timer 16 Transistor (switch means) 16c Collector terminal 16b Base terminal 16e Emitter terminal RG resistor 17 Amplifier 18 Voltage fluctuation compensator 19 Comparator

Claims (1)

[Claims] 1. A control device for an electromagnetic actuator, comprising: an electromagnetic actuator having an electromagnetic coil; and a DC power supply for supplying electric power to the electromagnetic coil, comprising: resistance means connected in series to the electromagnetic coil; Comparing means for comparing whether the voltage drop by the means is larger or smaller than the allowable voltage drop at the maximum allowable temperature of the electromagnetic coil; and when the voltage drop is larger than the allowable voltage drop by the comparing means, A control device for an electromagnetic actuator, comprising: switch means for turning off the power supply and continuing to supply power to the electromagnetic coil when the voltage drop is smaller than the allowable voltage drop.