JP2564605Y2 - Over-current prevention device for always-on solenoid - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for preventing over-current of a solenoid that is always energized and is used, for example, for stopping an engine.

[0002]

2. Description of the Related Art As an overcurrent preventing device for a constantly energized solenoid, there is a prior art device as shown in FIG. That is, a normally energized solenoid 4 that opens a normally closed contact 3 for energizing the attraction coil 2 by the operating force of the holding coil 1 and maintains the operating state of the load, and a normally open contact that connects a power source 5 to the solenoid 4 A control device 8 for controlling the on / off of a relay 7 having a solenoid 6 and a means 9 for preventing overcurrent of the solenoid 4 are provided. The solenoid 4 includes a holding coil 1 and a suction coil 2 on the same core. The holding coil 1 has a relatively thin winding wound many times, and its DC resistance and inductance are relatively large. However, the attracting coil 2 has a relatively small number of thick windings so that its DC resistance is also small. The inductance is also relatively small. When the controller 8 closes the normally open contact 6 of the relay 7 at the current start time To, the current Ih flows through the holding coil 1 and the current Ip flows through the attraction coil 2 of the normally energized solenoid 4. As shown in FIG. 3, the current Ip becomes a large current Ipm that increases in a short time, generates a strong suction force, and operates a load such as an engine stop lever. On the other hand, the current Ih increases relatively slowly and stops at the small current Ihs, and at time Th, the normally closed contact 3 for energizing the attraction coil 2 is opened. Since the normally closed contact 3 is opened, the current Ip of the attracting coil 2 is cut off, but the load is maintained in operation by the attracting force of the current Ihs of the holding coil 1. If, for some reason, the current Ip of the suction coil 2 is not interrupted and continues to be energized for a long time, the temperature of the winding of the suction coil 2 increases, the DC resistance increases, and the current gradually decreases from the current Ipm to Ips. However, since the value is still large, the suction coil 2 may be overheated and burned out. In order to prevent the suction coil 2 from burning, a method of inserting a low resistance in series with the suction coil 2 and detecting a voltage drop occurring in the low resistance to cut off the current can be considered. Since the resistance value is small, the resistance value that does not impede the current becomes very small, and the feasibility is low. Therefore, instead of inserting a low resistance in series with the attraction coil 2 as the over-current preventing means 9, the voltage Vp between the contacts of the normally open contact 6 of the relay 7 is detected by the voltage detection circuit 20 between the contacts, The reference voltage Vs set by the reference voltage generation circuit 21 is compared with the voltage comparator 22 and the voltage Vp between the contacts is compared with the reference voltage Vs.
When the time exceeds s, the power supply to the solenoid 4 is cut off, or the fuse 10 is simply inserted between the solenoid 4 and the power supply 5.

[0003]

The above prior art has the following problems. The inter-contact voltage Vp of the normally open contact 6 of the relay 7 is detected and compared with a preset reference voltage Vs,
When the voltage between the contacts Vp exceeds the reference voltage Vs, the power supply to the solenoid 4 is cut off. Since Vp also fluctuates,
It becomes difficult to compare with the reference voltage Vs. In the case where the fuse 10 is simply inserted, the capacity of the fuse 10 can withstand the current Ipm of the suction coil 2 in a short time, and the current Ihs of the holding coil 1 and the current of the suction coil 2 in a long time. It is necessary to set so as to be cut in the middle of Ips. However, it is very difficult to ensure the reliability of the cutoff characteristics of the fuse 10 such that the cutoff can be surely interrupted between the current Ihs and the current Ips while enduring the current Ipm. SUMMARY OF THE INVENTION It is an object of the present invention to secure the reliability of an overcurrent prevention device for a constantly energized solenoid by reliably operating the device.

[0004]

According to the present invention, in order to achieve the above-mentioned object, the following improved structure is added to the above-mentioned prior art, for example, as shown in FIG. That is, the over-current preventing means 9 detects the voltage Vp between the contacts of the normally open contact 6 of the relay 7 and compares the voltage Vp with the first reference voltage Vs set in advance, so that the energization start time To of the solenoid 4 is determined. To detect. Further, a voltage drop value Vq of the inter-contact voltage Vp from the energization start time To to a preset reference time Ts is calculated. If the voltage drop value Vq does not exceed the preset second reference voltage Vr after the elapse of the reference time Ts, the normally open contact 6 of the relay 7 is turned off via the controller 8. Open it up,
The power supply to the solenoid 4 is shut off.

[0005]

The present invention operates as follows. The voltage Vp between the contacts of the normally open contact 6 of the relay 7 of the overcurrent preventing means 9 is equal to the voltage of the power source 5 when the normally open contact 6 is opened without the controller 8 being turned on. When the normally open contact 6 is closed by turning on the switch 8, as shown in FIG.
It appears as a voltage drop due to a slight contact resistance of the contact, which is proportional to the sum of the current Ih of the holding coil 1 of the solenoid 4 flowing therethrough and the current Ip of the suction coil 2. A voltage slightly higher than a voltage drop due to a slight contact resistance of the normally open contact 6 is set as a first reference voltage Vs, and a voltage Vp between the contacts when the normally open contact 6 is closed is detected. By comparing with the first reference voltage Vs, the time at Vpm when the inter-contact voltage Vp becomes lower than the first reference voltage Vs can be detected as the energization start time To of the solenoid 4. Since the DC resistance rises due to the temperature rise due to the self-heating of the attraction coil 2 and the current gradually decreases, the inter-contact voltage Vp also gradually decreases. On the other hand, the holding coil 1 opens the normally closed contact 3 for energizing the suction coil 2 at time Th. Since the normally-closed contact 3 is opened, the current Ip of the attraction coil 2 is cut off, and the inter-contact voltage Vp rapidly decreases at the time Th, and thereafter is maintained as the inter-contact voltage Vhs by the current of the holding coil 1. I do. Here, the contact point voltage Vp (the difference voltage between Vpm and Vhs) when the solenoid 4 operates normally is preset as a second reference voltage Vr. Further, the over-current prevention means 9
The time during which the attraction coil 2 of the solenoid 4 is not overheated and burned out is defined as a reference time Ts, and a voltage drop value Vq of the inter-contact voltage Vp from the energization start time To to the reference time Ts is calculated. I do. If the solenoid 4 does not operate normally and the current Ip of the attraction coil 2 is not interrupted and is kept energized for a long time, the attraction coil 2
The DC voltage rises due to the rise in the temperature of the winding and the current gradually decreases, so that the voltage Vp between the contacts gradually decreases from the voltage Vpm.
Is still large, the voltage drop value Vq is smaller than when the solenoid 4 operates normally. As described above, after the reference time Ts elapses, if the voltage drop value Vq of the inter-contact voltage Vp does not exceed the second reference voltage Vr, the relay via the controller 8 The normally open contact 6 of the solenoid 7 is opened, and the solenoid 4 is opened.
Cut off the power supply to the

[0006]

[Effects of the Invention] The present invention has the following effects since it is constructed and operates as described above. If the voltage drop value Vq of the inter-contact voltage Vp does not exceed the second reference voltage Vr after the elapse of the reference time Ts from the energization start time To, the controller 8 cuts off the power supply to the solenoid 4. . As a result, the overcurrent preventing means of the overcurrent preventing device for the constantly energized solenoid operates reliably, so that its reliability can be ensured.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1A is a configuration system diagram of an overcurrent prevention device for a constantly energized solenoid, and FIG. 1B is a diagram showing a voltage time characteristic between contacts. In the figure, for example, an over-current preventing device for an always-on type solenoid used for stopping an engine or the like is provided with a normally closed contact 3 for energizing a suction coil 2 by an operating force of a holding coil 1.
And a controller 8 for turning on and off a normally energized solenoid 4 for maintaining the operating state of the load, a relay 7 having a normally open contact 6 for connecting a power supply 5 to the solenoid 4, and an operation of the solenoid 4 And a power supply preventing means 9. The over-current preventing means 9 includes a contact voltage detecting circuit 20, a reference voltage generating circuit 21, and a voltage comparator 2.
2. Elapsed time timer 23, reference time timer 24, time comparator 25, etc. The inter-contact voltage detection circuit 20 detects the inter-contact voltage Vp of the normally open contact 6, the reference voltage generation circuit 21 generates a reference voltage Vs, and the voltage comparator 22 uses the inter-contact voltage Vp and the first voltage. And outputs the energization start signal So when the inter-contact voltage Vp becomes lower than the first reference voltage Vs. The first reference voltage Vs is preferably a voltage slightly higher than a voltage drop due to a slight contact resistance of the normally open contact 6, for example. The reference time timer 24 sets a time during which the attraction coil 2 of the solenoid 4 does not overheat and burn out, for example, a time slightly longer than the time during which the current Ip flowing through the attraction coil 2 increases to the maximum value Ipm, It is set in advance as the reference time Ts. In addition, solenoid 4
Is normally set as the second reference voltage Vr. Further, the elapsed time timer 23 receives the energization start signal So to measure an elapsed time Tx from the energization start time To, the reference time timer 24 measures the reference time Ts, and the time comparator 25 When the elapsed time Tx exceeds the reference time Ts, an energization stop signal Ss is output to the controller 8. On the other hand, the voltage comparator 22 calculates a voltage drop value Vq of the inter-contact voltage Vp from the energization start time To to a preset reference time Ts.
If the voltage drop value Vq does not exceed the preset second reference voltage Vr after the elapse of the reference time Ts, the controller 8 receiving the energization stop signal Ss
Is configured to open the normally open contact 6 of the relay 7 and cut off the power supply to the solenoid 4. still,
The elapsed time timer 23 and the reference time timer 24 are automatically reset with a certain time constant at the same time as the power supply to the solenoid 4 is cut off.

[Brief description of the drawings]

FIG. 1 shows an embodiment of the present invention, and FIG. 1 (A) is a configuration system diagram of an overcurrent prevention device for a constantly energized solenoid, and FIG. 1 (B).
FIG. 3 is a diagram showing a voltage-time characteristic between contacts.

FIG. 2 shows a conventional example and is a diagram corresponding to FIG.

FIG. 3 is a diagram showing a coil current time characteristic of a constantly energized solenoid.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Holding coil, 2 ... Suction coil, 3 ... Normally closed contact, 4 ...
Normally energized solenoid, 5 ... Power supply, 6 ... Normally open contact, 7 ...
Relay, 8: controller, 9: over-current prevention means, To: power supply start time, Ts: reference time, Vp: voltage between contacts, Vq ...
Voltage drop value, Vr: second reference voltage, Vs: first reference voltage.

Claims (1)

(57) [Scope of request for utility model registration] 1. A normally energizing solenoid (4) for opening a normally closed contact (3) for energizing and energizing a load by an operating force of a holding coil (1) and maintaining an operating state of a load; Normally open contact (6) connecting power supply (5) to solenoid (4)
A controller (8) for controlling the ON / OFF of a relay (7) having a relay and a means (9) for preventing overcurrent of the solenoid (4). (9) is a normally open contact of the relay (7).
By detecting the voltage (Vp) between the contacts (6) and comparing it with the first reference voltage (Vs) set in advance, the energization start time (To) of the solenoid (4) is detected. A preset reference time (T) from the energization start time (To)
s), the voltage drop value (Vq) of the inter-contact voltage (Vp) is calculated, and after the reference time (Ts) has elapsed, the voltage drop value is calculated.
If (Vq) does not exceed the second reference voltage (Vr) set in advance, the normally open contact (6) of the relay (7) is opened via the controller (8), and the solenoid is opened. (4) An over-current preventing device for a constantly energizing solenoid, characterized in that the power supply to the (4) is cut off.