JPH04347337A - Engine fuel cutoff device - Google Patents

Abstract

PURPOSE:To miniaturize a solenoid with a simple combination of a relay and a thermal relay in the fuel interrupting solenoid of a diesel engine. CONSTITUTION:A contact 13 of a thermal relay 12 is connected to a contact 16 of a relay 15 in series with a suction coil 14, and an exciting coil 19 of the relay 15 is connected thereto in surrounding both these contacts. Accordingly, since current-energization to the suction coil of a solenoid available for a fuel cutoff is limited to a short time, the solenoid is miniaturized and, what is more, large attraction can be outputted.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a diesel engine fuel cutoff system using a solenoid equipped with a suction coil and a holding coil.

0002

[Prior Art] Conventionally, solenoids used to shut off fuel in diesel engines require a large suction force when operating, so they are used separately from a holding coil to keep the fuel valve open during driving. A coil is provided and the attraction coil is energized for only a short period of time, and a similar idea is shown in, for example, Japanese Patent Laid-Open No. 56-110207.

0003

[Problems to be Solved by the Invention] In the above-mentioned conventional technology, the suction coil of the solenoid is continuously energized until the startup of the starter is completed. It was difficult to do so. Furthermore, a large voltage drop occurs due to the large current flowing through the solenoid, which lowers the voltage effectively applied to the starter.
In some cases, starting problems may occur. SUMMARY OF THE INVENTION An object of the present invention is to provide a fuel cutoff device for an engine that is small and has a large suction force by suppressing the heat generation of a solenoid suction coil and further installing a device that applies maximum voltage to the starter.

0004

[Means for solving the problem] In order to achieve the above object, a thermal relay contact that operates based on current value and energization time and a contact of a normally closed contact type relay are connected in series, and a normally closed contact type relay excitation coil is connected in series. This can be handled by connecting in parallel.

[0005]

[Operation] In the present invention, the attraction coil of the solenoid is energized by the running terminal of the key switch to operate the plunger and open the fuel valve. The thermal relay contacts open due to the current flowing through the attraction coil and the energization time, and the normally closed contact type relay continues to operate, so the attraction coil is only energized for a short period of time, which can suppress heat generation.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is an overall wiring diagram including the engine fuel cutoff device, FIG. 2 is a detailed wiring diagram of the solenoid section, and FIGS. 3 and 4 are operating waveforms.

In the figure, reference numeral 1 denotes an in-vehicle battery, which is connected to a B terminal 3 of a key switch 2. The key switch 2
The running terminal 4 is connected to a solenoid 6 via a time selection circuit 5. A diesel engine 7 is equipped with an injection pump 8 that supplies fuel to each cylinder. A rod 9 opens and closes the fuel passage of the injection pump, and the plunger 10 of the solenoid 6 contacts this rod. 11 is a starter for starting the engine. Inside the time selection circuit 5, one side of the contact 13 of the heat-sensitive thermal relay 12 is connected to the attraction coil 14 of the solenoid 6, and the other side is connected to the contact 16 of the normally closed contact type relay 15. The excitation coil 19 of the relay 15 is connected to surround the contacts 13 and 14. A holding coil 16 is connected to the running terminal 4 of the key switch 2.

Reference numeral 18 denotes a coil spring that pushes out force on the plunger 10 in the P direction.

Next, the operation of the embodiment having the above structure will be explained. Turn on key switch 2, that is, drive terminal 4
When closed, the holding coil 17 in the solenoid 6 is energized. In this state, the suction force is very weak, so plunger 1
0 does not work. Thermal relay 1 is installed in the attraction coil 14.
2 and the contact 16 of the normally closed contact type relay 15. Since this coil 14 flows a large current and obtains a large attractive force, the plunger 10 of the solenoid 6 overcomes the coil spring 18 and moves to the left. In other words, the rod 9 in the injection pump 8 is freed and the fuel is opened, and preparations for starting are completed. When the starter 11 is operated from this state, the engine 7 is started. However, since the attraction coil 14 passes a large current, it generates a lot of heat and cannot be run for a long time. Further, since the gap L of the solenoid 6 becomes shorter as the plunger 10 moves to the left, the holding coil 17 alone can sufficiently hold the plunger 10 at the operation completion position. Therefore, as described above, current flows through the attraction coil 14, that is, the contacts 13,
Since the relay 16 is closed, both terminals of the excitation coil 19 of the normally closed contact type relay 15 are at the same potential, and the relay 15 does not operate. However, when a large current flows for a long time, the characteristics of the thermal relay 12 are as shown in FIG. 3, so the thermal relay 12 operates and the contacts 13 are opened. For this reason, until now, one side of the excitation coil 19 of the relay 15 is grounded via the attraction coil 14, so the relay 15 operates, that is, contact 1
6 is opened and this state continues. Therefore, even if the temperature of thermal relay 12 decreases and the contacts restart, contact 1
6 is open, the attraction coil 14 will never be energized again. This relationship is shown in FIG.

0010

According to the present invention, the energization of the suction coil of a solenoid using a fuel cutoff device can be limited to a short period of time, so that the heat generation of the coil can be suppressed, thereby increasing the suction force of the solenoid. Therefore, it is possible to downsize the device.

[Brief explanation of drawings]

FIG. 1 is an overall wiring diagram showing an engine fuel cutoff mechanism according to an embodiment of the present invention.

FIG. 2 is a detailed wiring diagram of FIG. 1;

FIG. 3 is a thermal relay characteristic diagram.

FIG. 4 is an operation explanatory diagram.

[Explanation of symbols]

1...Battery, 2...Key switch, 5...Time selection circuit,
6...Solenoid, 8...Injection pump, 10...
Plunger, 12...thermal relay, 15...normally closed contact type relay.

Claims (3)

[Claims] Claim 1: A fuel cutoff device for an engine that operates a plunger using electromagnetic force to open and close a fuel valve, wherein a solenoid equipped with the plunger is used to maintain the fuel valve in an "open" state. An engine fuel cutoff device comprising a solenoid using a holding coil and a suction coil used during operation, and a time selection device connected through a switch between the suction coil and a power source. 2. The engine fuel cutoff device according to claim 1, wherein said time selection device uses a normally open contact type relay and a thermal relay that is turned on and off depending on current value and time. 3. The thermal relay and the normally closed contact type relay have the contact of the normally closed contact type relay connected to the power supply side, the normally closed thermal relay contact connected in series to the solenoid suction coil side, and the contact of the normally closed contact type relay connected in series to the solenoid suction coil side. 2. The engine fuel cutoff device according to claim 1, further comprising an excitation coil of a normally closed contact type relay connected in parallel with both of the contacts.