JPS603980Y2 - Fuel cutoff device for distributed fuel injection pump - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement of a fuel cutoff device for a distributed fuel injection pump.

In general, in a distribution type fuel injection pump, as shown in Fig. 1, fuel in a fuel reservoir chamber 2 in an injection pump main body 1 flows into a fuel pumping chamber 4 through an oil passage 3, and is pumped into the engine by a plunger 5 that reciprocates while rotating. The fuel is distributed and pressure-fed from the discharge valves 6 provided for the number of cylinders, and the oil passage 3 leading from the fuel reservoir chamber 2 to the fuel pressure-feeding chamber 4 is further provided with a fuel cutoff electromagnetic valve 7.
In this electromagnetic valve 7, a valve body 7a protruding into the oil passage 3 is activated by a spring 7c according to the excitation state of the electromagnetic coil 7b.
By reciprocating against the force of , the oil passage 3 is opened and closed to start and stop the supply of fuel to the fuel pumping chamber 4 .

Conventionally, in order to save power consumption and prevent overheating of the electromagnetic coil, the control of the fuel cutoff electromagnetic valve 7 was carried out after the valve body 7a was attracted by the electromagnetic coil 7b via a resistor.
limits the current supplied to the

In other words, a circuit as shown in Fig. 2 is used to control the current supplied to the solenoid valve 7 by operating the vehicle's operation switch 8, and when starting the engine, the operation switch 8 is turned from the OFF position to the ON position and then back to the starting position. When the valve is in the ST position (hereinafter referred to as ST position), voltage from the power source 9 is applied directly to the electromagnetic coil 7b of the electromagnetic valve 7 via the conductor 10, thereby causing the valve body 7a to compress the spring 7c. The oil passage 3 opens.

Next, when the operation switch 8 is returned to the ON position after starting the engine, the voltage from the power source 9 is applied to the electromagnetic coil 7b via the resistor 11.
Since the current flowing through the electromagnetic coil 7b is limited, the valve body 7a is held in the attracted position.

When the engine is stopped, if the operation switch 8 is changed from the ON position to the OFF position, the current supply to the electromagnetic coil 7b is stopped, and the valve body 7a is pushed back by the spring 7c to cut off the oil passage 3.

However, in such a conventional current control mechanism, the operation switch 8 is manually operated by the operator, so the S
If the timing of switching from the T position to the ON position is delayed or it takes time to start the engine, especially in winter, the electromagnetic coil 7b
A current flows directly through the coil for a long period of time, which has the disadvantage that power is wasted and the electromagnetic coil 7b is overheated and burnt out.

In view of the above-mentioned reasons, the present invention applies current directly to the electromagnetic coil 7b when the operation switch changes from the OFF position to the ON position, and after a predetermined period of time has elapsed, conducts pulsed current to reduce the average current. The present invention provides a fuel cutoff device that automatically limits current to an electromagnetic coil without manual operation by an operator, thereby preventing wasteful consumption of power and overheating of the electromagnetic coil.

Embodiments of the present invention will be described in detail below.

FIG. 3 shows an electrical circuit diagram of the fuel cutoff device of the present invention, in which the movable contact of the operation switch 8 is connected to the power supply 9, and the S-point is connected in parallel to the ON contact of this operation switch 8. There is.

A variable resistor 14 is connected to the positive conductor 12 from the ON contact, and a capacitor 15 is connected in series between the variable resistor 14 and the negative conductor 13.
is connected.

The connection point between the variable resistor 14 and the capacitor 15 is the comparator 16.
The tenth input terminal of the comparator 16 is connected to a connection point between a resistor 17 and a resistor 18 connected in series between the positive conductor 12 and the negative conductor 13.

The variable resistor 14, capacitor 15, comparator 16, and resistors 17 and 18 constitute a timer circuit A.

In addition, the positive conductor 12 has a resistor 19. 20. 21. 22
is connected, the collector of the transistor 23 is connected to the resistor 19, and the emitter of the transistor 23 is connected to the negative conductor 13.
is connected to.

A capacitor 24 is connected to the connection point between the resistor 19 and the collector of the transistor 23, the other end of the capacitor 24 is connected to the resistor 20, and the base of the transistor 25 is connected to the connection point between the resistor 20 and the capacitor 24. There is.

The resistor 21 is connected to the base of the transistor 23. A capacitor 26 is connected to the connection point between the resistor 21 and the base of the transistor 23, and the other end of the capacitor 26 is connected to the connection point between the resistor 22 and the collector of the transistor 25. The emitter of the transistor 25 is connected to the negative conductor 13.

The above resistors 19, 20, 21, 22, transistor 23
, 25, and capacitors 24 and 26 constitute an oscillation circuit (unstable oscillation circuit) B.

The output of the oscillation circuit B, that is, the connection point between the resistor 22 and the collector of the transistor 25 is the resistor 27 and the diode 2.
The output of the timer circuit A, that is, the output terminal a of the comparator 16, is connected to the base of the transistor 29 via a resistor 30 and a diode 31.

The collector of the transistor 29 is connected to the positive conductor 12 via a resistor 32, and the emitter is directly connected to the negative conductor 13.

Resistors 27, 30, 32, diodes 2B, 31,
The transistor 29 is included in the OR circuit.

OR circuit internal output, that is, resistor 32 and transistor 29
The connection point with the collector is connected to the output section.

That is, it is connected to the base of a transistor 34 via a resistor 33 , the collector of the transistor 34 is connected to the positive conductor 12 via a resistor 35 , and the emitter is connected to the negative conductor 13 .

The base of an output transistor 36 is connected to the connection point C between the resistor 35 and the collector of the transistor 34, the collector of the output transistor 36 is connected to the positive conductor 12, the emitter is connected to the negative conductor 13 via the electromagnetic coil 7b, A diode 37 is connected in parallel to the electromagnetic coil 7b.

To explain the operation of the above circuit, when the operator turns the operation switch 8 to the ON position, the capacitor 15 of the timer circuit A
A current is supplied from the positive conducting wire 12 through the variable resistor 14 to start charging.

The voltage at the connection point between the capacitor 15 and the variable resistor 14 is applied to one input terminal of the comparator 16;
While the voltage VC applied to the negative input terminal is lower than the input terminal voltage VR of the comparator 16 to which the divided voltage of 8 is applied, that is, during the charging period of the capacitor 15, the output of the comparator 16 remains at the H level. , when the charging voltage of the capacitor 15, that is, the voltage VC of one input terminal of the comparator 16, becomes the same level as the voltage VR of the ten input terminals of the comparator 16, the voltage of the comparator 16
The output becomes L level, and this state does not change even if the operation switch 8 is subsequently moved to the ST or other position.

Changes in the voltage at one input terminal of the comparator 16 over time and the related output of the comparator 16, that is, the voltage at point a, are shown in FIGS. 4a and 4.

Here, the charging time of the capacitor 15 can be changed by the variable resistor 14.

On the other hand, the oscillation circuit B is a well-known astable oscillation circuit that oscillates pulses at a set constant cycle whether the operation switch 8 is in the ON position or in the ST position.

The output of this oscillation circuit B, that is, the voltage at point b, is shown in FIG. 4C.

The output of timer circuit A and the output of oscillation circuit B described above are applied to the base of transistor 29 via OR circuit power diodes 31 and 28, respectively.

OR circuit power As is well known, this circuit operates when either or both of the output of timer circuit A and the output of oscillation circuit B are at H level, so the output of timer circuit A is continuously at H level. During this period, the transistor 29 is continuously turned on, and thereafter the output of the timer circuit A becomes L level, and only the output of the oscillation circuit B is input, so that the transistor 29 is periodically turned on and off.

This OR circuit output is inverted by transistor 34, and the output of transistor 34 is as shown in FIG. 4d.

Therefore, the transistor 36 is driven and the electromagnetic coil 7b is energized in the state shown in FIG. ) is integrated, so that, for example, when the applied voltage has a duty ratio of 50%, a continuous excitation state is maintained at an average voltage of about 1/2.

That is, the valve body 7a of the solenoid valve 7 is strongly attracted by the electromagnetic coil 7b from when the operation switch 8 is turned to the ON position until VC=VR, but once the valve body 7 is attracted,
Holding a does not require large energy such as at the moment of adsorption, and after VC≧VR, sufficient holding force can be obtained by simply supplying pulsed power to the electromagnetic coil 7b.

When the operation switch 8 is turned from the ON position to the OFF position, the power supply from the positive conductor 12 to each circuit is cut off, so the electromagnetic coil 7b is de-energized, and the valve body 7a is pushed back by the spring 7c and is connected to the oil path 3. The fuel pumping chamber 4 is cut off.

That is, the engine can be stopped simply by operating the operation switch 8.

As described above, according to the present invention, the electromagnetic coil 7b of the electromagnetic valve 7
It is possible to automatically change the excitation state of the engine regardless of the operation of the operation switch 8, and if this invention is applied to an engine equipped with a distributed fuel injection pump, it will prevent errors in operation switch operation and long periods of time in winter. It is possible to prevent wasteful power consumption due to direct excitation and burnout due to overheating of the electromagnetic coil, and because it generates little heat, it is possible to downsize the electromagnetic valve, making it an extremely effective idea in practice.

In this example, the oscillation circuit and timer circuit are explained using a general useless stable oscillation circuit and a capacitor charging/discharging timer circuit, but it goes without saying that the same effect can be obtained by using other oscillation circuits and timer circuits. It is.

[Brief explanation of the drawing]

Fig. 1 is a cutaway view of the main parts of a distribution type fuel injection pump according to the present invention, Fig. 2 is an electric circuit diagram of a conventional fuel cutoff device, Fig. 3 is an electric circuit diagram of a fuel cutoff device of the present invention, and Fig. 4 The figure shows a time chart in the circuit of FIG. 1: Fuel injection pump, 3: Oil passage, 4: Fuel pressure chamber, 7:
Solenoid valve, 8: Operation switch, 15: Capacitor, A: Timer circuit, B: Oscillator circuit, C: OR circuit.

Claims (1)

[Scope of utility model registration request] In a distribution type fuel injection pump equipped with a solenoid valve that shuts off fuel flowing into the fuel injection chamber of the fuel injection pump, a timer that starts operating when the vehicle operation switch is turned to the ON position and reverses the output after a predetermined period of time has elapsed. an oscillation circuit that generates a pulse train having a repetition period shorter than the response time of the solenoid valve when the operation switch is in the ON position or the start position; and an OR input circuit that inputs the output of the timer circuit and the output of the oscillation circuit. 1. A fuel cutoff device for a distribution type fuel injection pump, characterized in that the solenoid valve is controlled by the output of the OR circuit.