Accumulating fuel injection apparatus

Abstract

This accumulating fuel injection apparatus is provided with a needle valve 6 adapted to open and close an injection nozzle 11 having injection ports 14 in a lower end portion thereof, a balancing chamber 5 formed in a casing 2 so as to apply a fuel pressure to a head portion of the needle valve 6, a supply passage including a slit 10 and used for supplying a fuel from a fuel supply port 19 to the balancing chamber 5, a discharge passage 20 comprising an orifice for discharging the fuel from the balancing chamber 5, and a solenoid valve 22 adapted to open and close the discharge passage 20, the lift of a valve disc 26 of the solenoid valve 22 is controlled by a lift control means comprising a stopper 28 the position of which is controlled by a lift control mechanism 23. The opening area of the discharge passage 20 comprising an orifice increases and decreases in accordance with the lift of the valve disc 26, and the lift of the needle valve 6 is determined so that the opening area of the slit 10 facing the interior of the balancing chamber 5 increases and decreases correspondingly to the flow rate of the fuel passing through the discharge passage 20, the degree of opening of the injection nozzle 11 increasing and decreasing accordingly.

Description

TECHNICAL FIELDThis invention relates to an accumulator fuel injection apparatus applied to internal combustion engines, such as a diesel engine.BACKGROUND ARTThe conventional fuel injection apparatuses for multi-cylinder engines include an apparatus of a fuel injection system (electronically controlled fuel injection system) in which the controlling of an injection rate and injection time is done by an electronic circuit, an apparatus of a common injection system (common-rail injection system) in which a fuel is distributed from an injection pump to combustion chambers through a common passage, and an apparatus of a pressure storage type injection system (accumulator injection system) in which a fuel is distributed from an injection pump to combustion chambers through a common passage and an accumulator. Since the fuel injection apparatuses themselves of these systems are not provided with an accumulator in which the fuel from an injection pump is temporarily stored, the supplying ...

AI Technical Summary

Benefits of technology

In this accumulating fuel injection apparatus, the lift of the solenoid valve can be controlled, so that an opening area of the discharge passage, i.e. an amount of discharge per unit time of the fuel from the balancing chamber can also be controlled in a stepped manner. This enables the controlling of an amount of the fuel flowing into the balancing chamber through the supply passage of a predetermined opening area to be done so that this amount corresponds to the mentioned amount of discharge, i.e., the controlling of the lift of the needle valve which determines the opening area of the supply passage to be done as well. Accordingly, the degree of opening of the injection nozzle opened and closed with the needle valve, i.e. the injection rate of the fuel from the injection nozzle can be controlled with a high accuracy. Moreover, the half lifted condition of the needle valve can be retained by an operation of the solenoid valve, and the controlling of the fuel injection time can also be done easily.

The lift control means is adapted to deenergize or energize the solenoid, whereby the control means can be used as a stopper limiting the motion of the valve disc of the solenoid valve in at least two positions. In this case, the stopper limits the motion of the valve disc of the solenoid valve in at least two positions by a simple method, i.e., the deenergization or energization of the solenoid, and the fuel injection rate can thereby be controlled in at least two stages, i.e., at higher and lower levels.

When a groove type passage formed between the needle valve and a valve casing, which is adapted to guide the needle valve slidingly, is included in the supply passage, the opening area of an orifice at which the groove type passage faces the balancing chamber increases and decreases in accordance with the lift of the needle valve, so that the lift of the needle valve can be controlled accurately and stably.

When the lift of the needle valve in the accumulating fuel injection apparatus and an engine load are set correlative, the fuel injection rate in a low-load condition can be set low by reducing the opening area of the discharge passage, and that in a high-load condition can be set high by increasing the opening area of the discharge passage.

When the fuel passage, which extends to the injection ports formed at a lower end portion of the injection nozzle, in the accumulator fuel injection apparatus has a flow passage resistance high enough to lower the fuel pressure when a fuel flow exists, a force working on the needle at the lower end portion of the needle valve to lift the needle valve can be reduced at such time that equal fuel pressure is applied to the balancing chamber and injection nozzle by closing the discharge port with the solenoid valve deenergized. This enables the closing of the needle valve to be done reliably.

When a return spring urging the needle valve in the closing direction thereof is provided between the needle valve and casing in this accumulating fuel injection apparatus, the needle valve receives, when the discharge port is closed by deenergizing the solenoid valve, a high fuel pressure occurring momentarily in the balancing chamber, a fuel pressure in the fuel storage chamber and a fuel pressure occurring on the seat in accordance with the respective pressure receiving surface area. Even when a difference between a force based on a fuel pressure and working in the valve closing direction and a force based on the fuel pressure and working in the valve opening direction is small, so that a sufficiently large valve closing force cannot be obtained, the needle valve can be closed reliably since the return spring urges the needle valve constantly in the valve closing direction. When the discharge passage is opened by energizing the solenoid valve, the fuel is discharged from the balancing chamber whether the needle valve is half lifted or fully lifted. Therefore, the pressure in the balancing chamber lowers, and the injection ports are opened by the needle valve. Owing to the positive urging force in the valve closing direction of the return spring, a speedy valve closing action of the needle valve can be obtained, and the after-dripping of the fuel can be prevented.

Problems solved by technology

When an initial injection rate is high, combustion noise and NOx occur.

Consequently, the atomization of the fuel is not attained, and smoke increases.

Therefore, it is impossible to use this injector in combination with the injectors of the first and second conventional examples in which the half lift condition of the needle valve cannot be controlled.

However, in the fourth and fifth conventional examples, the half lifted state of the needle valve cannot be retained, though the half lifted state can be temporarily obtained.

Moreover, when such a half lifting means is used, the lift of the needle valve scatters due to the influence of the actual fuel pressure, so that it is difficult to precisely control the half lifted state of the needle valve.

Therefore, a high-performance solenoid magnetic valve is required, and this causes the manufacturing cost to increase.

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