Fuel injection device

Abstract

A fuel injection device comprising electricity-generating means generating electricity by rotation of an engine and outputting a predetermined signal, and a solenoid valve injecting fuel; the valve being opened as a result of a drive current applied to a coil, and the fuel being injected into an intake passage of the engine at a predetermined timing during the rotation of the engine; to ensure that the flow rate required during high-speed operation ca be adequately provided in a fuel injection device for injecting/supplying fuel to an engine. The electricity-generating means is an alternating current generation means attached to the engine in a crank angle position at which an output is generated in synchronization with the intake timing of the engine; the signal is an injection command signal applied to the solenoid valve as an alternating-current drive current; and the applied voltage increases with increased engine speed.

Claims

1. A method for injecting fuel comprising the steps of: generating a predetermined signal as a function of the rotation of an engine with an alternating-current generator, and injecting fuel from a solenoid valve into an intake passage of the engine at a predetermined timing during the rotation period of the engine in response to the predetermined signal.

2. The method of claim 1, wherein the predetermined signal is an injection command signal comprising an alternating-current drive current.

3. The method of claim 2, wherein the step of injecting fuel from the solenoid valve includes applying the drive current to a coil of the solenoid valve.

4. The method of claim 1, wherein the step of generating the predetermined signal includes generating the predetermined signal in synchronization with an intake timing of the engine.

5. The method of claim 3, wherein the step of applying the drive current to the coil includes applying the predetermined signal to the coil without modification.

6. The method of claim 1, wherein the alternating-current generator having an electromotive coil at a predetermined position on the external periphery of a flywheel disposed on an engine shaft and provided with a magnet in an area along the edge.

7. The method of claim 6, wherein the electromotive coil is disposed at a predetermined position along the external periphery of the flywheel in a crank angle position at which an output signal is generated in synchronization with the intake timing of the engine.

8. The method of claim 3, wherein an applied voltage increases with increased engine speed.

9. The method of claim 1, wherein per-cycle fuel injection rate increases with increased engine speed.

10. The method of claim 1, further comprising the step of adjusting the fuel flow rate through a fuel flow-rate adjustment valve in association with the operation of a throttle valve.

11. The method of claim 10, wherein the fuel flow-rate adjustment valve is provided to a fuel passage that extends to one of the solenoid valve or a fuel passage that extends from the solenoid valve to the intake passage, wherein the intake passage is configured as a through passage having the throttle valve positioned therein.

12. The method of claim 1, further comprising the step of pumping fuel to the solenoid valve by the introduction of a pulsating motion from the engine.

13. The method of claim 12, wherein the pressure of the fuel pumped to the solenoid valve increases as the engine speed increases.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a layout diagram of the fuel supply system for an engine provided with a fuel injection device as an embodiment of the present invention;

(2) FIG. 2 is a graph showing the changes in drive voltage brought about by the fuel injection device of FIG. 1; and

(3) FIG. 3 is a graph showing the relationship between the fuel flow rate produced by the solenoid and the flow rate required by the engine in a typical fuel injection device.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

(4) Embodiments of the invention are described below in reference to the drawings.

(5) FIG. 1 shows the configuration of the fuel supply system of an engine 1 provided with a fuel injection device 3 of the present embodiment. A fuel supply passage 20 that leads from a fuel tank 2 is connected to the fuel injection device 3 arranged so as to constitute a portion of the intake passage 10 of the engine 1, and fuel is injected and supplied by a solenoid valve 30 whose injection opening side is exposed to the intake passage 10.

(6) A fuel pump 32 having a fuel compression chamber that is partitioned with a diaphragm (not shown) is mounted on the fuel injection device 3. Fuel is pressurized by the introduction of a pulsating pressure from the engine 1 to the backpressure chamber, and is supplied to the solenoid valve 30 via a high-pressure fuel passage 34. This configuration is the same as the conventional example.

(7) A feature of the present invention is that an alternating-current generator 36 is used as electrical generation means operated by the rotation of the engine 1 and caused to output an injection command signal based on the injection period. The output signal is used as an injection command signal and is directly input as the drive current of the solenoid valve 30. There is no need to provide intermediately positioned parts such as an electronic controller, an injector trigger circuit, or a rectifier, and the flow rate required by the engine during high-speed operation can be achieved in a simple configuration and at a low cost.

(8) In the present embodiment, the alternating-current generator 36 comprises an ignition coil flywheel 11 in which a magnet 12 is disposed along part of the edge area in the engine 1, and an electromotive coil 31 provided at a predetermined location at the outer periphery of the flywheel. The electromotive coil 31 is positioned so as to match the engine used and to provide a crank angle position capable of generating an output in synchronization with the intake timing. The output signal is input directly to the solenoid valve 30, dispensing with the need to calculate the fuel injection period by the electronic controller.

(9) In addition, the alternating-current generator 36 has an electromotive coil at a predetermined location on the external periphery of the flywheel 11. The drive voltage of the alternating current output increases and the rise becomes more rapid with increased engine speed and a faster movement of the flywheel 11 past the magnet 12. For this reason, the angle (time) a based on the drive voltage during high-speed operation (indicated by the solid line) is smaller (shorter) than the angle (time) b from the start of input to the injection start voltage based on the drive voltage during low speeds (indicated by the dotted-dashed line), as shown in the graph of FIG. 2.

(10) The lift speed of the valve increases and the valve opening (stroke) becomes larger with increased drive voltage. The time during which the valve is open is therefore effectively determined not by the length of the drive current, but by the height of the peak voltage, and the fuel injection rate can be increased by increasing the valve opening time. Accordingly, the flow rate required by the engine during high-speed operation can be provided and the fuel injection time does not need to be computed using an electronic controller.

(11) Moreover, a throttle valve 33 is attached to the fuel injection device 3 in the present embodiment, and a needle-valve fuel-flow adjustment valve 35 is disposed in the high-pressure fuel passage 34 that extends from the fuel pump 32 to the solenoid valve 30. Thus, a link mechanism for lifting the needle valve is provided to the fuel-flow adjustment valve 35 so that the fuel flow rate increases in conjunction with the opening operation of the throttle valve 33, and the fuel rate increases in accordance with the increase in the flow rate required by the engine during high-speed operation.

(12) With the fuel pump 32 operated by the introduction of a pulsating pressure from the engine 1, it is recommended that the discharge pressure be increased with increased engine speed by varying the spring pressure of the diaphragm, the displacement width of the diaphragm, or the like in accordance with the throttle valve aperture. This allows the fuel injection rate to be increased with ease by increasing fuel pressure, even under conditions in which the engine speed is increases, the injection gap is reduced, and the effective injection time is less likely to be extended.

(13) The present embodiment was described with reference to a fuel-passage fuel injection device in which a fuel-flow adjustment valve is disposed in a fuel passage that extends to a solenoid valve, but the invention can be implemented in a similar manner with a fuel-passage fuel injection device in which the fuel-flow adjustment valve is disposed in the fuel passage that extends from the solenoid valve to the intake passage.

(14) As described above, the present invention, which has a simple configuration and only a small number of parts, is applied to a fuel injection device for injecting/supplying fuel to an engine, whereby the flow rate required during high-speed operation can be provided at a low cost.

KEY

(15) 1 Engine 2 Fuel tank 3 Fuel injection device 10 Intake passage 11 Fly wheel 30 Solenoid valve 31 Electromotive coil 32 Fuel pump 33 Throttle valve 34 High-pressure fuel passage 35 Fuel-flow adjustment valve 36 Alternating-current generator