JP3056832B2 - Latch type electromagnet protection circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a protection circuit for a latch-type electromagnet which retains a position after the armature is displaced even after the energization is stopped when the armature is displaced by energizing an exciting coil.

[0002]

2. Description of the Related Art Conventionally, there has been provided a latch-type electromagnet constituted by using an exciting coil and an armature having a permanent magnet. Such a latch type electromagnet is, for example,
It is used for solenoids, relays, and the like, and has a function of holding the position after the displacement of the armature when the armature is displaced when the excitation coil is energized, even after the energization is stopped. Therefore, in order to displace the armature, a pulse current of about several tens of milliseconds may be applied to the exciting coil, and a small capacity having a rated value set for the instantaneous current can be used as the exciting coil. Because
Compared to an electromagnet of a type in which an armature is held at a displaced position by continuous energization, it has the advantage that a large output can be obtained for a small size. Further, since there is no need to continuously supply a current to the drive circuit for supplying a current to the exciting coil, there is an advantage that the power supply capacity and the capacity of circuit components can be reduced.

That is, a conventional drive circuit is configured as shown in FIG. Excitation coil SOL of solenoid
The emitter transistor Q ₁ is a switching element - are connected in series to the collector. This series circuit includes a bridge rectifier R for rectifying an AC power supply (for example, 24 V).
The output of the e are connected across capacitor C ₁ for smoothing. The voltage between both ends of the capacitor C ₁ is stabilized by a stabilizing circuit 3 composed of an integrated circuit and a smoothing capacitor C _2, and is supplied to the control circuit 1 by a DC power supply (for example, 5 V).
V). The output of the control circuit 1 includes resistors R ₁ and R ₂
And is input to the drive circuit 2 consisting of transistors Q _1, the transistor Q ₁ on and off control. That is, the control circuit 1 outputs a pulsed control signal as shown in FIG. 5, the excitation current to the exciting coil SOL transistor Q ₁ is momentarily conductive will flow quickly. The armature is displaced by this exciting current.
The exciting coil SOL has a diode D ₁ for blocking back electromotive force.
Are connected in parallel.

[0004]

As described above, since the latch type electromagnet has a rated value set for the instantaneous current, an abnormality occurs in the control circuit 1 and the drive circuit 2, and As shown by the broken line in FIG.
If a state occurs in which the OL is continuously energized, a problem arises in that the exciting coil SOL is overheated. Further, even if the ON time of the control signal generated from the control circuit 1 is long or the control signal is repeatedly generated and the on-duty exceeds a predetermined value, the excitation coil SOL is not necessarily in the continuous energized state. Will overheat.

[0005] If the overheating state of the exciting coil SOL continues for a long time, a rare short circuit may occur in the exciting coil or the burnout may occur. In addition, in such a state, an excessive current flows to the circuit side, so that the circuit may be damaged and the entire device may even be damaged.
Further, the abnormality of the current supplied to the exciting coil SOL is not only caused by the circuit side, but also sometimes caused by a rare short circuit or incorrect connection of the exciting coil SOL.

Therefore, in order to prevent damage due to abnormal current flowing through the exciting coil SOL, the exciting coil SO
L is designed to be a rated value corresponding to the continuous current so as to allow a margin for abnormalities in the energizing current, or to configure a latch-type electromagnet having a built-in thermal fuse disposed close to the exciting coil SOL, or For the circuit side, it is conceivable to cope with the problem by designing the power supply capacity and the circuit components so that continuous energization is possible.

However, if the excitation coil SOL is given a margin or a thermal fuse is provided, the size of the latch-type electromagnet is increased, and the mounting space is restricted. Further, since the thermal fuse has a slow response, rare short circuit due to overheating of the exciting coil SOL cannot be sufficiently prevented. On the other hand, if a circuit is designed with a margin, circuit components with a large current capacity are required, and costs are significantly higher than when a new circuit is added using circuit components with the same current capacity. Will increase.

An object of the present invention is to solve the above-mentioned problems.
Another object of the present invention is to provide a latch-type electromagnet protection circuit that can reliably protect against an abnormal current flowing through an exciting coil while preventing the cost of circuit components from increasing significantly. It is.

[0009]

According to a first aspect of the present invention, there is provided a protection circuit for a latch-type electromagnet, wherein when an excitation coil is energized and an armature is displaced, the armature retains the displaced position even after the energization is stopped. The switch element inserted in the power supply path to the exciting coil and the current flowing through the exciting coil
Average voltage obtained by averaging the voltage across the
A comparison circuit for obtaining a binary output according to the magnitude relationship between the voltage and a predetermined reference value, and a switch drive circuit for turning off a switch element in response to the output of the comparison circuit when the average voltage exceeds the reference value Is provided.

According to the second aspect of the present invention, a normally closed contact of a relay is used for the switch element.

[0011]

According to the first aspect of the present invention, the average value of the current supplied to the exciting coil is detected, and when the average value of the supplied current is excessive, the switch element inserted in the power supply path to the exciting coil is turned off. Therefore, it is possible to prevent an excessive current from flowing through the exciting coil. As a result, overheating of the excitation coil can be prevented, and rare short circuit and burnout can be prevented. In particular, exciting carp
If the average voltage corresponding to the current flowing through the
Switch element inserted in the feed path to the excitation coil
Is turned off, so the energizing current to the exciting coil is continuously energized.
Or the current flowing through the exciting coil is
When the length is longer than necessary for displacement or when the
When the electric current is repeatedly generated within a short time,
Even if the switch element is turned off and the excitation coil overheats
Can be prevented. Also, since an excessive current does not flow to the circuit side, it is possible to use a circuit component having a small capacity according to the rated value of the exciting coil,
Although the number of parts increases as compared with the conventional configuration shown in FIG. 4, a significant increase in cost can be avoided. In addition, since the excitation coil is prevented from being overheated on the circuit side, the size of the latch-type electromagnet does not increase, and there is no restriction on the mounting space.

According to the second aspect of the present invention, since the normally closed contact of the relay is used as the switch element, the control current is supplied to the switch element only when the current supplied to the exciting coil is abnormal. The power consumption can be reduced as compared with the case where the normally open contact is used, and the characteristic of low power consumption when the latch type electromagnet is used can be utilized.

[0013]

[Embodiment] (Embodiment 1) In this embodiment, as shown in FIG. 1, insert the normally open contact ra of the relay Ry as switching element between the bridge rectifier Re and a capacitor C ₁ for smoothing the excitation The normally open contact ra of the relay Ry is opened and closed according to the magnitude of the current flowing through the coil SOL.

[0014] current supplied to the exciting coil SOL, the emitter of the transistor Q ₁ - is detected as a voltage across the resistor R ₃ for current detection connected in series with the collector, the magnitude relationship between the reference voltage from the comparator circuit 4 A corresponding binary output is obtained. That is, the voltage across the resistor R _3, the comparison circuit 4
After being averaged by the integrating circuit composed of a resistor R ₄ and the capacitor C ₃ Metropolitan provided in, it is input to the comparator CP and is compared with a reference voltage. The reference voltage is obtained by dividing the output voltage of the stabilizing circuit 3 by resistors R ₅ and R ₆ . Further, the capacitor C ₄ is connected in parallel to the resistor R _6. Comparator CP is connected feedback resistor R ₇ is between the inverting input terminal and the output terminal, configured to compare circuit 4 has a hysteresis. Further, the comparator C
The output terminal of the P pullup resistor R ₈ is connected.
In the comparison circuit 4, when the average voltage corresponding to the current supplied to the exciting coil SOL exceeds the reference voltage, the output becomes L level.

The output of the comparison circuit 4 is a transistor Q ₂ ,
The current flowing to the relay Ry is turned on and off through the switch drive circuit 5 including the resistors R ₉ and R ₁₀ . That is, the switch driving circuit 5 comprises a transistor Q ₂ as a switching element, the emitter of the transistor Q ₂ - collector are connected in series to the relay Ry, compared to the base circuit 4
Output is input. Since energization current of the exciting coil SOL is the output when the normal comparator circuit 4 at H level, is energized the relay Ry transistor Q ₂ is an ON, the normally open contact ra as a result, the relay Ry is turned on Hold. On the other hand, when the current supplied to the exciting coil SOL becomes excessive, the output of the comparator circuit 4, the transistor Q ₂ is turned off to the L level, as a result of energization of the relay Ry is stopped, the normally open contact ra off The excitation coil SO
The energization to L stops. As a result, overheating of the exciting coil SOL is reliably prevented. The relay Ry diode D ₂ for the back EMF blocking are connected in parallel.

Incidentally, a relay Ry is used as a switch element.
When the power is turned on, it is necessary to energize the relay Ry to turn on the normally open contact ra so that power supply to each circuit is started. Therefore,
The timer circuit 6 is provided.
A pair of resistors R ₁₁ , which divide the output of the bridge rectifier Re,
R ₁₂ , a transistor Q ₃ having a base connected to a connection point of the two resistors R ₁₁ and R ₁₂ , a capacitor C ₅ connected in parallel with the resistor R _12, and a collector resistor R ₁₃ of the transistor Q ₃ ,
While the capacitor C ₅ via a resistor R ₁₁ at power-on is charged, by using the fact that the transistor Q ₃ is turned off, the resistor R _9, transistors Q ₂ to give a bias to the base of the transistor Q ₂ through R ₁₃ It is designed to be turned on. Thereby, the normally open contact r of the relay Ry
Since a is turned on, power is supplied to each circuit. Further, the feeding state of the voltage across the capacitor C ₅ is the respective circuits up transistor Q ₃ is turned on reaches a predetermined voltage is stabilized, subsequently, the transistor Q ₂ is controlled by only the output state of the comparator circuit 4 Become so.

According to the above configuration, if the current supplied to the exciting coil SOL is normal, as shown by the solid line in FIG.
The voltage across the capacitor C ₃ which constitutes the integration circuit, since kept lower than the reference voltage Vr of the comparator circuit 4,
The normally open contact ra of the relay Ry keeps the ON state. On the other hand, becomes excessive current supplied to the exciting coil SOL is, as indicated by a broken line in FIG. 2, when the voltage across the capacitor C ₃ is higher than the reference voltage Vr, the normally open contact ra is turned off, the excitation coil The energization to the SOL stops. When the normally open contact ra is turned off, the power supply to each circuit is stopped thereafter, so that the state in which the power supply to the excitation coil SOL is stopped continues. By releasing this state, to turn on the normally open contact ra again, once the power is turned off, after the charge of the capacitor C ₅ is discharged via the resistor R _12, may be re-powered on.

[0018] In the above embodiment, by the comparison voltage for the comparator CP and the output of the integrating circuit, but as compared to the baseline average value of current supplied to the exciting coil SOL, resistor R ₄ and a capacitor omitting the C _3, only allowing control to turn off the normally open contact ra when abnormally large current flows through the exciting coil SOL.

(Embodiment 2) In Embodiment 1, the normally open contact ra of the relay Ry is used as a switch element, but in this embodiment, the normally closed contact rb is used as a switch element. Therefore, the configuration of the switch driving circuit 5 is different from that of the first embodiment. That is, the switch driving circuit 5, the emitter to the relay Ry - includes transistors Q ₂ to which collectors are connected in series, the base of the transistor Q ₂ - The emitter, the emitter of the transistor Q ₄ - collector connected. The base of the transistor Q ₄ - resistor R ₁₄ is connected to the emitter. Since the base of the transistor Q ₄ are given the output of the comparator circuit 4, when the output of the comparator circuit 4 is at the H level, the transistor Q
₄ is turned on, the transistor Q ₂ is turned off. That is, the on transistor Q _2, the relationship between the output level of the comparator circuit 4 and the state of off, the reverse of the first embodiment. Therefore, when the current supplied to the exciting coil SOL is abnormal and the output of the comparison circuit 4 goes low, the transistor Q
₂ is turned on, the relay Ry is energized and the normally closed contact rb
Is turned off.

The base of the transistor Q ₂ has a pair of resistors R ₁₁ and R connected between the output terminals of the bridge rectifier Re.
Is connected to the connection point of the series circuit _12, the capacitor C ₅ is connected in parallel to the resistor R _12. After the power supply is turned until the voltage across the capacitor C ₅ is sufficiently high, since the transistor Q ₂ is not able to turn on, to each circuit from power will be able to operate stably, This prevents the normally closed contact rb of the relay Ry from being turned off. Further, the relay Ry capacitor C ₆ for preventing chattering is connected in parallel. Other configurations and operations are the same as those of the first embodiment.

[0021]

According to the first aspect of the present invention, the average value of the current supplied to the exciting coil is detected, and when the average value of the supplied current is excessive, the switch element inserted into the power supply path to the exciting coil is detected. Since it is turned off, it is possible to prevent an excessive current from flowing through the exciting coil. As a result, overheating of the excitation coil can be prevented, and rare short circuit and burnout can be prevented. In particular,
The average voltage corresponding to the current flowing through the exciting coil
If it exceeds, the switch inserted in the feed path to the excitation coil
Switch element is turned off, so that the current
If continuous energization occurs, or if the energizing current
If it is longer than necessary for the displacement of the
Such that the current flowing through the
If the switch element is turned off, the excitation coil
This has the advantage that overheating of the substrate can be prevented. Also, since an excessive current does not flow to the circuit side, a circuit component having a small capacity corresponding to the rated value of the exciting coil can be used, and although the number of components is increased as compared with the conventional configuration, This has the effect that a significant increase in cost can be avoided. Moreover, since the excitation coil is prevented from being overheated on the circuit side, there is an advantage that the size of the latch-type electromagnet does not increase and there is no restriction on the mounting space.

According to the second aspect of the present invention, since the normally closed contact of the relay is used as the switch element, the control current is applied to the switch element only when the current supplied to the exciting coil is abnormal. The power consumption can be reduced as compared with the case where the normally open contact is used, and there is an advantage that the characteristic of low power consumption when the latch type electromagnet is used can be utilized.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a first embodiment.

FIG. 2 is an operation explanatory diagram of the embodiment.

FIG. 3 is a circuit diagram showing a second embodiment.

FIG. 4 is a circuit diagram showing a conventional example.

FIG. 5 is an operation explanatory diagram of the control circuit.

[Explanation of symbols]

 1 control circuit 2 drive circuit 4 comparison circuit 5 switch drive circuit Ry relay ra normally open contact rb normally closed contact SOL exciting coil

──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Masaki Chikazawa 1048 Odakadoma, Kadoma City, Osaka Prefecture Matsushita Electric Works, Ltd. JP, U) (58) Field surveyed (Int. Cl. ⁷ , DB name) H01F 7/18

Claims (2)

(57) [Claims] 1. A protection circuit for a latch-type electromagnet, in which when an excitation coil is energized and an armature is displaced, the armature retains its displaced position even after the energization is stopped, and is inserted into a power supply path to the excitation coil. The voltage across the switch element and the resistor through which the current flowing through the exciting coil flows is integrated by the integrating circuit.
A comparison circuit that obtains a binary output according to the magnitude relationship between the averaged average voltage and a predetermined reference value; and a switch element that is turned off in response to the output of the comparison circuit when the average voltage exceeds the reference value. A protection circuit for a latch-type electromagnet, comprising: 2. The protection circuit according to claim 1 , wherein the switch element is a normally closed contact of a relay.