JP2756750B2 - 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-energization of a solenoid which 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 energizing 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. 4, the current Ip becomes a large current Ipm which 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, a fuse 10 is inserted between the solenoid 4 and the power supply 5 as the over-current preventing means 9.

[0003]

The above prior art has the following problems. The fuse 10 for preventing the suction coil 2 from overheating and burning out has a capacity that withstands the current Ipm of the suction coil 2 for a short time and the current Ihs of the holding coil 1 for a long time. It is necessary to set so as to be cut in the middle of the current Ips of the attraction coil 2. 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 An object of the present invention is to ensure the reliability of an overcurrent prevention device for a constantly energized solenoid by ensuring its operation.

[0004]

In order to solve the above-mentioned problems, the present invention is configured as follows, for example, as shown in FIGS. The invention of claim 1 (see FIG. 1) The normally closed contact 3 for energizing the attraction coil 2 is opened by the operating force of the holding coil 1 and the operating state of the load is maintained.
A normally energized solenoid 4 and a power supply 5 to the solenoid 4
A controller 8 for controlling the on / off of a relay 7 having a normally open contact 6 for connecting the power supply and a means 9 for preventing overcurrent of the solenoid 4. By detecting the voltage Vp between the contacts of the normally open contact 6 of the relay 7 and comparing it with the reference voltage Vs, the energization start time To of the solenoid 4 is detected, and the elapsed time Tx from the energization start time To is set in advance. When the elapsed time Tx exceeds the reference time Ts as compared with the reference time Ts, the normally open contact 6 of the relay 7 is opened via the controller 8 to cut off the power supply to the solenoid 4. It is configured as follows. The invention of claim 2 (see FIG. 2) The normally closed contact 3 for energizing the attraction coil 2 is opened by the operating force of the holding coil 1, and the operating state of the load is maintained.
A normally energized solenoid 4 and a power supply 5 to the solenoid 4
A controller 8 for controlling the on / off of a relay 7 having a normally open contact 6 for connecting the power supply and a means 9 for preventing overcurrent of the solenoid 4. The energization start time To of the solenoid 4 is detected by detecting the inter-contact voltage Vp of the normally open contact 6 of the relay 7 and comparing it with a preset reference voltage value Vs. After the lapse of the time Ts, the voltage Vp between the contacts becomes the reference time T
The voltage generated between the contacts of the normally open contact 6 due to the current Ihs flowing to the holding coil 1 after the lapse of s, and the current Ips flowing through the suction coil 2 when the energized state continues for a long time, the contact between the normally open contacts 6 If the voltage exceeds a preset voltage value which is an intermediate value with respect to the voltage generated at
The normally open contact 6 of the relay 7 is opened via the
The power supply to the power supply is cut off.

[0005]

The present invention operates as follows. The invention of claim 1 (see FIG. 1) The voltage Vp between the contacts of the normally open contact 6 of the relay 7 of the over-current preventing means 9 is in a state where the normally open contact 6 is opened without the controller 8 being turned on. When the controller 8 is turned on and the normally open contact 6 is closed, only the voltage drop due to a slight contact resistance of the contact becomes almost equal to zero. Then, a voltage slightly higher than the voltage drop due to the slight contact resistance of the normally open contact 6 is set as the reference voltage Vs, and the inter-contact voltage Vp of the normally open contact 6 is detected and the reference voltage Vs
Is compared with the reference voltage Vs.
The time when the current becomes lower than the time when the energization of the solenoid 4 is started T
It can be detected as o. Further, the time during which the attraction coil 2 of the solenoid 4 is not overheated and burned out is set as a reference time Ts, and the elapsed time Tx from the energization start time To is compared with the reference time Ts. Exceeds the reference time Ts,
The controller 8 opens the normally open contact 6 of the relay 7 to cut off the power supply to the solenoid 4. The invention according to claim 2 (see FIG. 2) When the normally open contact 6 of the relay 7 of the overcurrent prevention means 9 is closed by the controller 8, a voltage slightly higher than the voltage drop due to a slight contact resistance is set to the reference voltage. Vs, the inter-contact voltage Vp of the normally open contact 6 is detected and compared with the reference voltage Vs, whereby the inter-contact voltage Vp is changed to the reference voltage Vs.
The time when the current becomes lower than the time when the energization of the solenoid 4 is started T
o can be detected. A time during which the suction coil 2 does not overheat and burn out, for example, a time slightly longer than the time Th, is set as a reference time Ts, and the energization start time To
After a lapse of the reference time Ts, the voltage Vp between the contacts changes between the voltage generated between the contacts of the normally open contact 6 due to the current Ihs flowing to the holding coil 1 after the lapse of the reference time Ts, Suction coil 2 in case of continuing
When the voltage exceeds an intermediate value with the voltage generated between the contacts of the normally open contact 6 due to the current Ips flowing through the controller 4, the controller 8 opens the normally open contact 6 to the solenoid 4, Cut off the power supply of the. That is, as shown in FIG. 4, after the normally closed contact 3 of the solenoid 4 is opened at the time Th, the suction coil 2 is cut off and no current flows, while the small current Ihs flows through the holding coil 1. Flows.
Therefore, the value of the inter-contact voltage Vp after the opening of the normally closed contact 3 becomes a voltage drop value due to the current Ihs to the holding coil 1. However, when the normally closed contact 3 is not opened for some reason, the large current Ips continues to flow through the attraction coil 2 even after the elapse of the time Th (see the broken line diagram in FIG. 4). The value is the large current Ips to the suction coil 2 (> the small current Ih to the holding coil 1).
s). Therefore, when the inter-contact voltage Vp exceeds the above-mentioned intermediate value after the elapse of the reference time Ts, the normally closed contact 3 is not opened for some reason, and the large current Ips continues to flow through the attraction coil 2. It can be determined that it is in the state of being. Then, at this time, the normally open contact 6 is opened to cut off the power supply to the solenoid 4. In order to detect the inter-contact voltage Vp after the elapse of the reference time Ts, the large current Ipm flowing through the attraction coil 2 immediately after the start of energization to the solenoid 4 is defined as the large current Ips when the normally closed contact 3 is not opened. There is no misjudgment. As a result, the current Ip of the attraction coil 2 which increases to the current Ipm in a short time after the start of energization and then stops flowing in a short time, which is the content described in the above-mentioned section 4 does not interrupt the power supply to the coil 4 and the current Ih flowing through the holding coil 1 flows through the holding coil 1 even if a long time has elapsed since the start of energization.
If the current value exceeds an intermediate value between the current s and the current Ips flowing to the attraction coil 2 because the normally open contact 6 is not opened, the power supply to the solenoid 4 is cut off. Obtainable. And fuse 1
0, it was difficult to stably obtain the cutoff characteristics. On the other hand, according to the second aspect of the present invention, the reference time Ts and the voltage value to be compared with the inter-contact voltage Vp after the elapse of the reference time Ts. The above-described blocking characteristics can be reliably obtained only by setting in advance.

[0006]

The present invention is constructed and operated as described above, and has the following effects. The invention of claim 1 (see FIG. 1) When the elapsed time from the energization start time exceeds the reference time, the controller cuts off the power supply to the solenoid. Therefore, it is possible to reliably prevent the suction coil from overheating and burning out due to the current flowing to the suction coil because the normally open contact is not opened. ○ The invention of claim 2 (see FIG. 2) With a large current flowing through the attraction coil immediately after the start of energization, the power supply to the solenoid is not interrupted, and the current to the solenoid is maintained even after a long time has elapsed from the start of energization. If the current flowing through the coil exceeds the current between the current that flows to the suction coil because the normally open contact of the relay is not opened, the power supply to the solenoid is cut off. It can be obtained more reliably than with a fuse. That is, the interruption characteristic can be obtained only by presetting the reference time or the voltage value to be compared with the voltage between the contacts after the elapse of the reference time, and the reliability can be reliably ensured. In addition, since the current to the solenoid is detected by effectively utilizing the contact resistance of the normally open contact,
There is no need to provide a current detection resistor separately from the normally open contact in the wiring from the power supply to the solenoid. Therefore, it is possible to prevent power from being wasted by the current detection resistor.

[0007]

Embodiments of the present invention will be described below with reference to the drawings. 1st invention (refer to FIG. 1) FIG. 1 is a configuration system diagram of an overcurrent prevention device for a constantly energized solenoid. In the figure, for example, an over-current prevention device for an always-on solenoid that is used for stopping the engine, etc.
The normally closed contact 3 for energizing the attraction coil 2 is opened by the operating force of the holding coil 1 and the operating state of the load is maintained.
A normally energized solenoid 4 and a power supply 5 to the solenoid 4
A controller 8 for controlling on / off of a relay 7 having a normally open contact 6 for connecting the solenoid 4 and a means 9 for preventing overcurrent of the solenoid 4
And The over-current prevention means 9 comprises a voltage detection circuit 20 between contacts, a reference voltage generation circuit 21, a voltage comparator 22, an elapsed time timer 23, a reference time timer 24, a time comparator 25, and the like. 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 determines the inter-contact voltage Vp and the reference voltage. Compared with the reference voltage Vs, when the inter-contact voltage Vp becomes lower than the reference voltage Vs, an energization start signal So is output.
The 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.
Further, the elapsed time timer 23 is provided with the power supply start signal S
o, the elapsed time Tx from the energization start time To is measured, and the reference time timer 24 sets the reference time T set in advance.
When the elapsed time Tx exceeds the reference time Ts, the time comparator 25 outputs an overcurrent prevention signal Ss to the controller 8. This preset reference time Ts
Is preferably set to a time during which the suction coil 2 of the solenoid 4 is not overheated and burned out, for example, a time slightly longer than a time Th at which the suction coil 2 is shut off when the suction coil 2 operates normally. The controller 8 receives the overcurrent prevention signal Ss and opens the normally open contact 6 of the relay 7 to cut off the power supply to the solenoid 4.

FIG. 2 is a diagram corresponding to FIG. In the present invention, the over-current preventing means 9 detects the inter-contact voltage Vp of the normally open contact 6 of the relay 7 by the inter-contact voltage detection circuit 20, and compares the reference voltage Vs generated by the reference voltage generation circuit 21 with the voltage comparator. By comparing at 22, the energization start time To of the solenoid 4 is detected. Further, the voltage comparator 22 sets a voltage drop between the contacts of the normally open contact 6 due to an overcurrent flowing through the suction coil 2 as a second reference voltage Vr, and compares the second reference voltage Vr with the contact voltage Vp. Compare. Also, the solenoid 4
The time during which the suction coil 2 does not overheat and burn out,
For example, a time slightly longer than the time Th when the suction coil 2 is normally operated and shut off is set as the reference time Ts by the reference time timer 24 in advance. After the elapsed time timer 23 counts from the energization start time To and the reference time Ts elapses, when the inter-contact voltage Vp exceeds the second reference voltage Vr, the controller 8 is turned off. The normally open contact 6 of the relay 7 is opened via the relay 7 to cut off the power supply to the solenoid 4. The elapsed time timer 23 and the reference time timer 24 in the first and second inventions 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 a first embodiment of the present invention, and is a configuration system diagram of an overcurrent prevention device for a constantly energized solenoid.

FIG. 2 shows a second embodiment of the invention and is a view corresponding to FIG.

FIG. 3 is a view showing a conventional example and corresponding to FIG. 1;

FIG. 4 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, Tx: elapsed time, Vp: voltage between contacts, Vr: second reference voltage, Vs: reference voltage.

Claims (2)

(57) [Claims] 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 the normally open contact of the relay (7).
By detecting the voltage (Vp) between the contacts (6) and comparing it with the reference voltage (Vs), the energization start time of the solenoid (4) is obtained.
(To) is detected, the elapsed time (Tx) from the energization start time (To) is compared with a preset reference time (Ts), and the elapsed time (Tx) is detected.
Exceeds the reference time (Ts), the controller
(8) The normally open contact (6) of the relay (7) is opened through (8) to cut off the power supply to the solenoid (4). Prevention device. 2. A normally energizing solenoid (4) which opens a normally closed contact (3) for energizing by an operating force of a holding coil (1) and maintains an operating state of a load; A controller (8) for turning on and off a relay (7) having a normally open contact (6) for connecting a power supply (5) to the solenoid (4), and a means (9) for preventing overcurrent of the solenoid (4). An over-current prevention device for a normally-conductive solenoid provided with the over-current prevention means (9), the normally open contact of the relay (7)
By detecting the voltage (Vp) between the contacts (6) and comparing it with a preset reference voltage value (Vs), the solenoid (4)
Of detecting the energization start time (To), its energization start time (To) reference time set in advance from (T
s) after a lapse of, said contact voltage (Vp) is the group
Current flowing to holding coil (1) after elapse of quasi-time (Ts)
(Ihs) is generated between the normally open contacts (6).
Voltage and suction coil when energized for a long time
The current (Ips) flowing through (2) causes the normally open contact (6) to
A preset voltage that is an intermediate value with the voltage generated between the contacts
If exceeds the pressure value is via the controller (8) to open the normally open contact (6) of the relay (7) the solenoid
(4) An over-current preventing device for a constantly energizing solenoid, wherein the power supply to the solenoid is shut off.