JPH05291032A - DC electromagnet device - Google Patents

Abstract

(57) [Summary] [Purpose] To prevent unnecessary energization of the coil current that occurs in the operating coil due to changes in the power supply voltage. [Structure] An operating coil 1, a switching element 7 and a current detecting resistor 8 connected in series to the operating coil 1.
And a one-shot pulse generation circuit 6 that generates a one-shot pulse having a pulse width inversely proportional to the power supply voltage and corresponding to the energization period of the closing coil current of the operation coil 1, and the operation coil 1 during the one-shot pulse output period. The comparator 3 which outputs a control signal for controlling the closing coil current to a constant set current to the switching element 7.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a DC electromagnet device used for driving an electromagnetic contactor or the like.

[0002]

2. Description of the Related Art Generally, an electromagnet device comprises a fixed iron core around which an operating coil is wound and a movable iron core facing the fixed iron core through a gap. When the operating coil is excited, the movable iron core is attracted to the fixed iron core and the gap Just move and be adsorbed. At this time, the movable iron core overcomes the load to be driven and the repulsive force of the spring and moves. In this case, a large suction force is required in the initial stage of suction with a large iron core gap,
After the adsorption is completed, it can be maintained with a small suction force.

As a device corresponding to such a characteristic, there is an electromagnet device using a drive circuit as described in, for example, Japanese Patent Laid-Open No. 59-168607. FIG. 6 shows the conventional circuit. In FIG. 6, the operating coil 1 of the electromagnet is connected to the DC power supply terminals P and N in series with the switch element 5d, for example, a transistor.
The switch element 5d is controlled by the control power supply circuit 6, the voltage detection circuit 7, the timer circuit 8 and the oscillation circuit 9, and the signals of the voltage detection circuit 7 and the timer circuit 8 and the signal of the oscillation circuit 9 are the OR circuit 10, It is adapted to be input to the switch element 5d via the resistor 11. Further, an operation switch 4 for opening and closing the power supply circuit is provided.

Next, the operation of the circuit of FIG. 6 will be described. When the operation switch 4 is turned on, the power supply voltage is supplied from the terminals P and N, and the power supply voltage exceeds a certain value, the voltage detection circuit 7 outputs an output signal. This signal gives a closing signal to the switch element 5d via the OR circuit 10 and the resistor 11, the switch element 5d is turned on (at time t _{1 in} FIG. 7), and a large current necessary to turn on the electromagnet is supplied to the operation coil 1. Supply. The electric current causes the electromagnet to perform the closing operation and enters the closing state (at time t _{2 in} FIG. 7). At this time, the switch element 5d remains on and a large current flows through the operation coil 1.
The output signal of the voltage detection circuit 7 also starts the timer circuit 8, and after a predetermined time, the timer circuit 8 outputs to stop the signal from the voltage detection circuit 7 and the switch element 5d is turned off. At the same time, the output of the timer circuit 8 is also applied to the oscillating circuit 9, and the oscillating circuit 9 starts operating and outputs an intermittent output signal (at time t _{3 in} FIG. 7). This intermittent signal is applied to the switch element 5d via the OR circuit 10 and the resistor 11, and the switch element 5d repeats on and off. As a result, the operation coil 1
The intermittent voltage (the current actually flowing through the operating coil 1 is smoothed by the flywheel diode 14) is applied to the electromagnet, and by appropriately selecting the on / off time, the electromagnet can generate a small current. Continue to hold.

[0005]

The above-mentioned DC electromagnet device has the following problems. This problem is shown in FIG.
Will be explained. In the case of the circuit of FIG. 6, since the power supply voltage is applied as it is when the circuit is turned on, the attraction force of the electromagnet largely changes depending on the power supply voltage. Currently, the working voltage range of the electromagnetic contactor is defined by the standard as 85 to 110% of the rated voltage,
Therefore, the electromagnet section must be designed so as to have a sufficient attraction force necessary for the closing operation even at a voltage of 85% of the rated value. However, since the attractive force of the electromagnet is proportional to the square of the applied voltage, as shown in FIG. 8, an excessively large attractive force is generated as the applied voltage increases, and a large impact is applied to the iron core of the electromagnet and its value. There are drawbacks such as a short mechanical life and chattering of the main contact portion, resulting in a short contact life.

FIG. 8 is a general attraction force characteristic diagram of an electromagnet.
The applied voltage v is plotted on the horizontal axis and the attractive force f is plotted on the vertical axis. F is the attractive force of the electromagnet, and f ₀ is the attractive force required for the operation of the electromagnet. It can be seen that the attraction force f increases rapidly as the applied voltage v increases, as compared with the attraction force at the lowest operating voltage of the electromagnet. In order to solve the above-mentioned problems, Japanese Patent Laid-Open No. 61-
A DC electromagnet device described in Japanese Patent No. 187304 has been proposed. FIG. 9 shows the circuit, and FIG. 10 is an operation waveform diagram showing the output relation of the constant current circuit 16 with respect to the current change of the coil 1 in FIG. Although the description of this content is omitted, the point is that the current i flowing through the operating coil 1 is detected, and when the level is lower than the set level V ₁ of the constant current circuit 16 when the electromagnet is turned on, an output is output to apply a voltage to the operating coil 1. The coil current i is thereby increased. When the coil current i becomes larger than the set level V ₁ , the constant current circuit 16
Stops the output, which reduces the coil current i. When the coil current i becomes smaller than the set level V ₁ ,
The constant current circuit 16 outputs again to increase the coil current i, and the above operation is repeated to keep the coil current i constant. Further, when the electromagnet is held, control is performed with respect to the set level V ₂ that is lower than the set level V ₁ , and similarly, the coil current i is maintained at the low value required for holding the electromagnet.

However, this DC electromagnet device also has the following problems. FIG. 11 is a waveform diagram showing the operation of the electromagnet when the power supply voltage v is a low value v ₁ and a high value v ₂ , and when the power supply voltage is applied at time t ₀ in FIG. 11, {FIG. 11 (1)}. , the current i of the operation coil when the power supply voltage v is low v ₁ is increased in a low rise as i ₁ indicated by the solid line, when the power supply voltage v is higher v ₂ is as high as i ₂ indicated by a broken line Rises at the start (Fig. 11
(2)}. Be suppressed magnitude of the current i in the coil because the set value V _1, electromagnet low supply voltage v short operating time when the long operating time high supply voltage v ₂ after TM ₁ when the ₁ TM ₂ After that, they are input at times t ₁ and t ₂ , respectively. It should be noted that in FIG. 11 (2), the point where the current i of the operating coil 1 temporarily drops after increasing is that the electromagnet is turned on. This current decrease occurs because the inductance of the operating coil 1 increases because the electromagnet is turned on. It is a thing. In this way, when the power supply voltage v is high v ₂ , the time t covering the closing operation time TM ₁ when the power supply voltage v is low is v ₁ even though the closing is completed in the closing operation time TM _{2. It} is necessary to energize the operation coil during the period TC up to _3, and an unnecessary current flows during the period of T ₂ -T ₁ , which makes it difficult to reduce the impact at the time of closing.

It is an object of the present invention to provide a DC electromagnet device which prevents unnecessary energization of an energizing coil current generated in an operating coil due to a change in power supply voltage.

[0009]

In order to achieve the above-mentioned object, a DC electromagnet device of the present invention comprises a fixed iron core around which an operating coil is wound, a movable iron core facing the fixed iron core through a gap, and the operation described above. A switching element and a current detection resistor connected in series to the coil, a voltage detection circuit that detects the power supply voltage and outputs a detection signal when this voltage is above a set value, and the detection output from this voltage detection circuit A one-shot pulse generation circuit that starts with a signal and outputs a one-shot pulse that is inversely proportional to the power supply voltage and has a pulse width corresponding to the energization period of the closing coil current of the operating coil, and this one-shot pulse generation circuit at its base. The one-shot pulse output from the circuit is input to the emitter of the detection signal output from the voltage detection circuit. The control transistor and one of its input terminals are respectively supplied with the divided voltage of the collector voltage of the control transistor and the detection signal output from the voltage detection circuit via the first resistor, and the other terminal is supplied with the current detection signal. The voltage drop of the resistor for input is input through the integrating circuit, and when the magnitude of the signal input to the one input terminal is larger than the magnitude of the signal input to the other input terminal, the control signal of the ON state is turned on. It consists of a comparator that outputs to the control terminal. Then, for example, in the voltage detection circuit, the voltage component of the power supply voltage is input to its positive input terminal, and the voltage component of the output voltage of the constant voltage circuit is input to its negative input terminal. The one-shot pulse generation circuit consists of an operational amplifier that outputs a detection signal from its output terminal when the voltage is larger than the output voltage of the circuit. The one-shot pulse generation circuit has a capacitor and a resistor in series to which the detection signal output from the voltage detection circuit is input. A voltage corresponding to the power supply voltage is input to the connected charging circuit and its positive input terminal, and a voltage drop of the resistance of the charging circuit is input to its negative input terminal, and the voltage drop of this resistance corresponds to the power supply voltage. An operational amplifier that outputs a signal voltage from its output terminal while the voltage exceeds the voltage is used.

[0010]

In the DC electromagnet device of the present invention, the one-shot pulse generation circuit outputs a one-shot pulse having a pulse width inversely proportional to the power supply voltage, and the one-shot pulse turns on the closing control transistor, and the one-shot pulse is generated. During the pulse, one input terminal of the comparator receives the divided voltage of the collector voltage of the closing control transistor, that is, the divided voltage of the detection signal output from the voltage detection circuit divided by the resistors 16 and 17 shown in FIG. , Since the voltage proportional to the coil current of the operating coil (which becomes the closing coil current) is input to the other input terminal through the current detection resistor, the switching element is controlled by this comparator when the electromagnet is closed. A current proportional to the input coil current of the operating coil depending on the signal output from the voltage detection circuit To control the constant current. Since the pulse width of the one-shot pulse output from the one-shot pulse generation circuit is inversely proportional to the power supply voltage, this input coil current is short when the power supply voltage is high and short when the power supply voltage is low. It is controlled for a long energization period.
Further, the closing operation time is a long closing operation time when the power supply voltage is high, and is a short closing operation time when the power supply voltage is low, so that the closing coil current energization period of the operation coil is almost matched to this closing operation time. As a result, it is possible to prevent unnecessary energization of the making coil current.

[0011]

1 is a circuit diagram showing an embodiment of a DC electromagnet device of the present invention. In FIG. 1, the DC electromagnet device is
A fixed iron core (not shown) around which the operating coil 1 is wound, a movable iron core (not shown) facing the fixed iron core through a gap, a switching element 7 and a current detecting resistor 8 which are connected in series to the operating coil 1, respectively. The voltage detection circuit 5 which detects the power supply voltage v and outputs a detection signal when this voltage is equal to or higher than a set value, and the detection coil which is started by the detection signal output from the voltage detection circuit 5 and is inversely proportional to the power supply voltage v The one-shot pulse generation circuit 6 that outputs a one-shot pulse having a pulse width corresponding to the energization time of the input coil current of No. 1, and the one-shot pulse output from the one-shot pulse generation circuit to the base thereof has The closing control transistor 22 to which the detection signals output from the detection circuit are respectively input, and the resistor 16 at one of the input terminals a Divided voltage and detection signal outputted from the voltage detection circuit 5 via the first resistor 15 of the divided collector voltage of the control transistor 22 by 17 is input, respectively, and the other current detecting resistor to the terminal b of 8
Voltage drop of diode 10, capacitor 11, resistance 1
The magnitude of the signal input through the integrator circuit 13 composed of 2 and input to one of the input terminals a is equal to that of the other input terminal b.
And a comparator 3 for outputting a control signal which is turned on to the control terminal of the switching element 7 via the gate resistor 9 when the magnitude of the signal input to the switch is larger than that of the comparator 3. In addition,
P and N are power supply terminals, and 14 is a flywheel diode connected in parallel to the operation coil 1 in reverse polarity.

FIG. 2 shows the operation waveform. In FIG. 2, FIG. 2A shows the power supply voltage v, which is applied to the power supply terminals P and N at time t ₀ and gradually increases with time. This is an example of a case where, for example, when the induction motor is started, immediately after the switch is turned on, the induction motor is close to a short-circuited state and the power supply voltage drops significantly, and the induction motor recovers to the normal power supply voltage as the rotation speed increases. Usually, in such a case, the electromagnet device is apt to cause a malfunction, so that the power supply voltage is shown especially under such a bad condition. When the power supply voltage v becomes equal to or higher than the set value at time t ₁ , the voltage detection circuit 5 outputs a detection signal {FIG. 2 (2)}. This detection signal is input to the one-shot pulse generation circuit 6, and is inversely proportional to the power supply voltage from the one-shot pulse generation circuit 6, and a one-shot pulse having a pulse width TC corresponding to the energization period of the closing coil current of the operating coil 1 is generated. It is output {(2) in FIG. 2}. This one-shot pulse turns on the closing control transistor 22, and the voltage dividing resistor 16,
The divided voltage of the voltage detection circuit 5 divided by 17 is input {(4) in FIG. 2}. On the other hand, the coil current i flows through the operating coil 1 and a voltage drop occurs in the current detecting resistor 8 (see FIG. 2).
(5)}, this voltage drop is smoothed by the integrating circuit 13 and input to the other input terminal b of the comparator 3 (FIG. 2).
(6)}. The comparator 3 outputs an ON control signal to the control terminal of the switching element 7 when the magnitude of the signal input to the one input terminal a is larger than the magnitude of the signal input to the other input terminal b. The current i is divided by the voltage dividing resistors 16 and 17 into the voltage detection circuit 5
The current value is controlled to be constant in proportion to the divided voltage of the detection signal output from. And the one-shot pulse generation circuit 6
Since the pulse width of the one-shot pulse output from is inversely proportional to the power supply voltage v, this coil current (which becomes the making coil current) is short when the power supply voltage is high, and when the power supply voltage is low. Is controlled for a long energization period, and the coil current i smoothed by the flywheel diode 14 flows through the operating coil 1 (FIG. 2 (7)). Next, at time t ₃ , when the output period of the one-shot pulse ends (FIG. 2 (3)), the closing control transistor 22 is turned off, and one terminal a of the comparator 3 has a voltage dividing resistor 15,
The voltage is switched to the divided voltage of the detection signal output from the voltage detection circuit 5 divided by 17, and the magnitude of this divided voltage is set smaller than the divided voltage by the resistors 16 and 17, so that the operating coil 1 A coil current with a low current value (which becomes the holding coil current) flows through the current {Fig. 2 (4),
(5), (6), (7)}.

FIG. 3 shows that the input coil current is controlled to be constant.
Shows how the closing operation time TM changes (this figure
11 (2)), and the closing operation time TM is an example.
For example, the power supply voltage v is v₁And low input operation time TM₁And long
Or the power supply voltage v is v ₂Higher loading time T
M₂When these are short, these input operation time TM₁, TM ₂
, For example, the power supply voltage v is₁Long when low
Energization period TC₁, And the power supply voltage v is v₂When high
Short energization period TC₂Unnecessary by adjusting to
It is possible to prevent energization of the closing coil current.

FIG. 4 shows an example of the voltage detection circuit 5 and the one-shot pulse generation circuit 6. In FIG. 4, the voltage detection circuit 5 has voltage dividing resistors 51 and 52 at its positive input terminal.
The divided voltage of the power supply voltage v divided by is input to the negative side input terminal of the divided voltage of the output voltage v _S of the constant voltage circuit 2 divided by the voltage dividing resistors 53 and 54, respectively. when divided voltage is higher than the divided voltage of the output voltage v _S of the constant voltage circuit 2 consists of an operational amplifier 55 for outputting a detection signal from its output terminal. Therefore, when the power supply voltage v is equal to or higher than the set value determined by the divided voltage of the output voltage v _S of the constant voltage circuit 2, the detection signal is output.

In FIG. 4, the one-shot pulse generation circuit 6 includes a charging circuit in which a capacitor 61 to which the detection signal output from the voltage detection circuit 5 is input and a resistor 62 are connected in series, and its positive side input terminal. Voltage dividing resistors 64 and 65
The power supply voltage v divided by is divided by the operational amplifier 66 into which the voltage drop of the resistor 62 of the charging circuit is input to the negative side input terminal thereof. FIG. 5 shows the operation, and when the detection output of the voltage detection circuit 5 is input {FIG. 5 (11)}, the charging circuit 63 is charged, and the resistor 62 receives a current falling from the initial current with the time constant. Flow, causing the voltage drop shown in FIG. When this voltage drop is larger than the voltage corresponding to the power supply voltage v, a signal voltage, that is, a one-shot pulse is output from the output terminal of the operational amplifier 66 as shown in FIG. 5C. In this case, the power supply voltage v is low. Figure 5 is when the ₁ (3), a long pulse width TC ₁ as shown in (b), the power supply voltage v is high v ₂
In this case, the pulse width TC ₂ becomes short as shown in FIGS. 5 (3) and 5 (b). Then, as described above, the pulse widths TC ₁ and TC ₂ of the one-shot pulse are made to approximately match the closing operation times TM ₁ and TM ₂ of the electromagnet, respectively.

[0016]

In the DC electromagnet device of the present invention, control is performed so that the closing operation time and the closing coil current energization period of the operating coil are matched to changes in the power supply voltage to prevent unnecessary application of the closing coil current. Therefore, the impact when the electromagnet is turned on is reduced. Furthermore, since the closing operation time and the energization period of the closing coil current of the operating coil are controlled to match the change of the power supply voltage, the power supply voltage range used is, for example, 100 V
It can be expanded to the range of up to 200V.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of a DC electromagnet device of the present invention.

FIG. 2 is an operation waveform diagram of the DC electromagnet device of the present invention shown in FIG.

FIG. 3 shows the DC electromagnet device of the present invention shown in FIG.
Waveform diagram showing how the closing operation time changes with changes in the power supply voltage

FIG. 4 is a circuit diagram of a voltage detection circuit and a one-shot pulse generation circuit of the DC electromagnet device of the present invention shown in FIG.

5 is an operation waveform diagram of the one-shot pulse generation circuit shown in FIG.

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

7 is an operation waveform diagram of the conventional electromagnet device shown in FIG.

FIG. 8 is a general attraction force characteristic diagram of an electromagnet.

FIG. 9 is a circuit diagram showing a different example of a conventional electromagnet device.

10 is an operation waveform diagram of the conventional electromagnet device shown in FIG.

11 is an operation waveform diagram of the conventional electromagnet device shown in FIG.

[Explanation of symbols]

 1 Operation Coil 2 Constant Voltage Circuit 3 Comparator 5 Voltage Detection Circuit 6 One-shot Pulse Generation Circuit 7 Switching Element 8 Current Detection Resistor 13 Integration Circuit 22 Injection Control Transistor 51 Op Amp 61 Capacitor (of Charging Circuit 63) 62 Resistance (Charging Circuit 63) 63) 63 charging circuit 66 operational amplifier

Claims (3)

[Claims] 1. A fixed iron core around which an operating coil is wound, a movable iron core facing the fixed iron core through a gap, a switching element and a current detection resistor connected in series to the operating coil, and a power supply voltage. Voltage detection circuit that outputs a detection signal when this voltage is equal to or higher than a set value, and the detection signal output from this voltage detection circuit is used to start, which is inversely proportional to the power supply voltage. A one-shot pulse generation circuit that outputs a one-shot pulse with a pulse width corresponding to the current-carrying period, and a one-shot pulse output from this one-shot pulse generation circuit to its base, and the one-shot pulse output to the emitter from the voltage detection circuit Input control transistor to which each of the detected signals is input, and one of the input terminals of the control transistor Divided voltage of the collector voltage and the first
The detection signal output from the voltage detection circuit is input via the resistance of the input signal, the voltage drop of the current detection resistor is input to the other terminal via the integration circuit, and the signal input to one of the input terminals. Is a magnitude greater than the magnitude of the signal input to the other input terminal, the comparator outputs a control signal that is turned on to the control terminal of the switching element. 2. The DC electromagnet device according to claim 1,
The voltage detection circuit receives the power supply voltage divided voltage at its positive input terminal and the output voltage divided by the constant voltage circuit at its negative input terminal. The power supply divided voltage is output by the constant voltage circuit. A DC electromagnet device comprising an operational amplifier that outputs a detection signal from its output terminal when the voltage is larger than the voltage. 3. The DC electromagnet device according to claim 1,
The one-shot pulse generation circuit is a charging circuit in which a capacitor and a resistor to which the detection signal output from the voltage detection circuit is input are connected in series, and a voltage corresponding to the power supply voltage at its positive input terminal and its negative input. A voltage drop across the resistance of the charging circuit is input to each terminal, and the operational amplifier outputs a signal voltage from its output terminal while the voltage drop across the resistance exceeds the voltage corresponding to the power supply voltage. DC electromagnet device.