Fuel Cutoff Apparatus for Engine-Driven Vehicle

The present invention relates to a fuel cutoff apparatus used in an engine-driven vehicle to control the fuel supply means in such a way that the supply of fuel to the engine is cut off.

Conventional engine-driven forklift trucks have been equipped with oil pressure switches to monitor the amount of the engine oil. When the truck is in operation, if the amount of the engine oil decreases below a certain level, the oil pressure switch is turned on. This causes a warning lamp to light up, informing the human operator of lack of the oil.

However, the operator can continue the operation even after the warning lamp has lit up. Accordingly, the operator might continue to run the vehicle while neglecting the warning. In this case, the engine may be burned out or other trouble may take place.

It is an object of the present invention to provide a fuel cutoff apparatus which is installed in an engine-driven vehicle to bring the engine to a stop when the amount of the engine oil decreases below a certain level during the operation of the vehicle, in order to prevent the occurrence of troubles such as burnout of the engine.

Other objects of the invention will become obvious upon an understanding of the illustrative embodiment about to be described or will be indicated in the appended claims, and various advantages not referred to herein will occur to one skilled in the art upon employment of the invention in practice.

FIG. 1 is an electric circuit diagram of a fuel cutoff apparatus installed in an engine-driven vehicle, the apparatus being fabricated in accordance with the invention; and

FIG. 2 is an electric circuit diagram of a modification of the fuel cutoff apparatus shown in FIG. 1.

Referring to FIG. 1, there is shown a fuel cutoff apparatus embodying the concept of the invention. An ignition switch 1 has AM, ST, and IG terminals. When the engine, indicated by numeral 5, is started, all the terminals are connected with the circuitry. When the engine is in operation, the AM and IG terminals are connected with the circuitry to energize various devices (described later). At this time, the ST terminal is not connected. A starter relay 2 consists of a normally open contact 2a and a driver coil 2b. One end of the contact 2a is connected to the positive terminal of the battery, indicated by numeral 4. One end of the coil 2b is connected to the ST terminal. The other end of the contact 2a is tied to the starter, indicated by numeral 3. When the coil 2b of the relay 2 is energized, the normally open contact 2a is closed. Then, the starter 3 is driven from the battery 4, so that the starter 3 starts the engine 5. Another relay 6 for starting the engine acts as a means for supplying fuel to the engine upon the start of the engine. The relay 6 consists of a normally open contact 6a and a driver coil 6b, one end of the contact 6a being connected with the IG terminal. The coil 6b is connected to the ST terminal. The other end of the contact 6a is connected to a solenoid 7 that controls the supply of fuel. When the coil 6b of the engine-starting relay 6 is energized, the normally open contact 6a is closed, energizing the solenoid 7. Then, fuel is supplied to the engine 5. A further relay 8 for controlling the cutoff of the supply of fuel consists of a normally closed contact 8a and a driver coil 8b. One end of the contact 8a and one end of the coil 8b are connected to the IG terminal. The other end of the contact 8a is connected to the solenoid 7. The other end of the coil 8b is hooked up to an oil pressure switch 9 that is actuated in response to the hydraulic pressure of the engine oil. In particular, when the pressure is below a preset level, the switch is closed. When the pressure is in excess of the preset level, the switch is open. When the switch 9 is closed, the coil 8b of the relay 8 is energized to open the contact 8a. A warning lamp 10 is connected between the IG terminal of the ignition switch 1 and the pressure switch 9. When the switch 9 is closed, the lamp 10 is energized through the ignition switch 1 and caused to light up.

In the operation of the fuel cutoff apparatus constructed as described above, when the AM, IG, and ST terminals are excited by operating the ignition switch 1 to start the engine 5, the driver coil 2b of the starter relay 2 is energized. This causes the normally open contact 2a to close. As a result, the starter 3 starts the engine 5. At the same time, the driver coil 6b of the engine-starting relay 6 is energized, closing the normally open contact 6a. Then, fuel is supplied to the engine 5.

At the time of this start of the engine the pressure of the engine oil is below the preset value. Under this condition, the pressure switch 9 is closed. Therefore, the coil 8b of the relay 8 is kept energized, so the contact 8a is open. The pressure of the engine oil increases with the operation of the engine 5 until the preset level is reached, whereupon the pressure switch 9 is opened. Then, the normally closed contact 8a of the relay 8 is closed, followed by energization of the solenoid 7.

When the engine 5 shifts to its normal operation after being started by the starter 3, the ignition switch 1 automatically returns to its original state, where the IG and AM terminals are excited. The contact 2a of the relay 2 and the contact 6a of the relay 6 are then opened. Consequently, the starter 3 ceases to operate. Simultaneously, the relay 6 ceases to energize the solenoid 7, but the supply of fuel to the engine 5 is not stopped, because the contact 8a of the relay 8 has been already closed, resulting in energization of the solenoid 7.

When the pressure of the engine oil decreases below the preset level during the operation of the engine, the fuel cutoff apparatus operates in the manner described below. When the amount of the engine oil is reduced to such a value that the oil pressure decreases below the preset level, the pressure switch 9 is closed. The driver coil 8b of the relay 8 is then energized to thereby open the normally closed contact 8a. This deenergizes the solenoid 7, cutting off the supply of fuel to the engine 5. As a result, the engine 5 stops. The closure of the pressure switch 9 also causes the warning light 10 to light up, which informs the driver that the amount of engine oil has decreased below the preset level.

In the present example, the reduction in the amount of the engine oil is detected by the pressure switch 9, which then actuates the relay 8 to deenergize the solenoid 7. Then, the supply of fuel to the engine 5 is halted, stopping the engine 5. Since it is impossible to continue the operation of the vehicle while the engine oil is deficient in amount, burnout of the engine or other trouble can be prevented.

Also in the present example, when the engine is started, the oil pressure might be low in spite of the normal state of the engine oil. In this case, the solenoid 7 is energized via the engine-starting relay 6 until the contact 8a of the relay 8 is closed to open the pressure switch 9. Therefore, it is unlikely that the supply of fuel is cut off, disabling the start of the engine 5. Thus, the starting operation can be performed with certainty.

It is to be understood that the invention is not limited to the above example. A modification of this example is shown in FIG. 2, where the pressure switch 9 has three terminals, and the normally closed contact 8a of the relay 8 has been replaced by a normally open contact 8c. When the oil pressure is below the preset level, the pressure switch 9 may be connected to the warning lamp 10. When the pressure is in excess of the preset level, the switch 9 may be connected to the driver coil 8b of the relay 8. In this case, the supply of fuel to the engine 5 can be cut off in the same manner as in the above example.

It is also possible to discontinue the supply of fuel to the engine 5 after the warning lamp 10 is lit for a given period to warn the driver. In this case, a timer is provided which begins to operate in response to the actuation of the pressure switch 9. The elapse of the given period is timed by the timer, which then actuates the relay 8.

As described in detail thus far, in accordance with the present invention, when the quantity of the engine oil decreases below the given level during the operation of the vehicle, the operation is stopped. Consequently, the occurrence of burnout of the engine or other trouble can be prevented.

As many apparently widely different embodiments of the invention may be made without departing from the spirit and scope thereof, it is to be understood that the invention is not limited to the specific embodiments thereof except as defined in the appended claims.