GB2130648A

GB2130648A - Accumulator fuel injection device

Info

Publication number: GB2130648A
Application number: GB08330992A
Authority: GB
Inventors: Takeo Funada
Original assignee: Diesel Kiki Co Ltd
Current assignee: Bosch Corp
Priority date: 1982-11-26
Filing date: 1983-11-21
Publication date: 1984-06-06
Also published as: JPS5999061A; DE3342759A1; GB8330992D0

Abstract

The pressure in an accumulator chamber 28, supplied with a metered fuel quantity by a pump and discharging through an engine nozzle 30 when an electromagnetic valve 16 is energised, is controlled by adjustment of the abutment 52 of the accumulator plunger biasing springs 24. The abutment position is detected by a sensor 60 providing a feed back signal to a controller providing an engine speed and load dependent accumulator pressure. The abutment piston 52 may be adjusted by fuel or engine oil supplied to the chamber 58 or the abutment (54, Fig. 2) may be adjusted by a screw (70) rotated by a stepping motor via a gear mechanism (72) or by a lever (74) linked to an accelerator pedal. Accumulator plunger movement may be detected, and provide a feed back signal to control metering by the fuel pump. <IMAGE>

Description

SPECIFICATION Accumulator fuel injection device Background of the Invention The present invention relates to an accumulator fuel injection device and, more particularly, to one which controls injection pressure by varying a biasing force of a spring installed in an accumulator thereof.

In an accumulator fuel injection device heretofore proposed for a diesel engine, a fuel pump or a metering pump delivers an accurately metered (adjusted) volume of fuel under pressure to an accumulator. Injection of the fuel accumulated in the accumulator begins at a timing which is controlled by an electromagnetic valve.

An example of such a type of fuel injection device is disclosed in Japanese Patent Publication No.

48-3765/1973. In the art of accumulator fuel injection, there is an increasing demand, both socially and individually, for a fuel injection control which controls fuel injection using engine exhaust, fuel consumption, knocking and the like as parameters, so that optimum combustion of fuel may be attained in accordance with the varying engine load and speed. In other words, it is required to control the injection pressure of the device in response to a change in a shift of the engine speed and load range, thereby setting up desirable conditions for fuel atomization. The need for such injection pressure control is particularly pronounced in the case where the use of lowgrade fuel is unavoidable.

Summary of the Invention It is therefore an object of the present invention to provide an accumulator fuel injection device which controls a fuel injection pressure always to an optimum value.

It is another object of the present invention to provide an accumulator fuel injection device which additionally improves conditions for fuel atomization.

It is another object of the present invention to provide an accumulator fuel injection device which cuts down smoke emission and knocking to improve engine exhaust and fuel economy.

It is another object of the present invention to provide an accumulator fuel injection device which is capable of compensating for a leak of fuel to be injected.

It is another object of the present invention to provide a generally improved accumulator fuel injection device.

An accumulator fuel injection device which injects fuel from an injection nozzle by applying a pressure thereto of the present invention comprises accumulator means for accumulating fuel fed thereto, said accumulator means comprising a spring which exerts a force predetermined for applying a pressure to the fuel, valve means for controlling communication of the accumulated fuel to the injection nozzle, said valve means comprising an electromagnetic valve made up of an electromagnet and a valve member, pressure adjuster means for adjusting the force of the spring in order to adjust the pressure to be applied to the fuel which is accumulated in the accumulator means, and sensor means for sensing an amount of pressure adjustment performed by the pressure adjuster means, whereby injection of the fuel is adjusted.

In accordance with the present invention, an accumulator fuel injection device includes an accumulator for accumulating fuel which is metered and fed under pressure by a fuel pump, and an electromagnetic valve for controlling the timing to deliver the accumulated fuel to an injection nozzle. The accumulator is provided with a spring which is loaded in an accumulation chamber for compressing the fuel. A pressure adjusting mechanism is associated with the accumulator in order to adjust the force of the spring and, thereby, the pressure of fuel injection.

The pressure adjusting mechanism comprises a piston which is movable within the accumulation chamber to vary the force of the spring, a passageway for introducing a hydraulic control pressure adapted to move the piston, and a coil for sensing a displacement of the piston. The control pressure is controlled by an output signal of the coil in accordance with a predetermined program.

The above and other objects, features and advantages of the present invention will become apparent from the following detailed description taken with the accompanying drawings.

Brief Description of the Drawings Figure 1 is a sectional side eievation of an accumulator fuel injection device embodying the present invention; Figure 2 is a section of a pressure adjusting mechanism in accordance with another embodiment of the present invention; and Figure 3 is a schematic representation of phenomena which are entailed by changes in the volume of fuel injection and engine speed.

Description of the Preferred Embodiments While the accumulator fuel injection device of the present invention is susceptible of numerous physical embodiments, depending upon the environment and requirements of use, substantial number of the herein shown and described embodiments have been made, tested and used, and all have performed in an eminently satisfactory manner.

Referring to Figure 1 of the drawings, a fuel injection device of the present invention is shown and generally designated by the reference numeral 10. A metered volume of fuel is fed under pressure from a fuel pump (not shown) to the fuel injection device 10 by a conduit 12. The hydraulic communication between the conduit 12 and the device 10 is provided by a tubular connector 14, which is located in an upper central portion of the device 1 0. An electromagnetic valve, generally 16, is located at one side of the connector 14 (to the left in the drawing) and comprises a valve member 18 which is operated by an electromagnet 20.

Located at the other side of the connector 14 (to the right in the drawing) is an accumulator 22 which has a spring 24, a plunger 26 constantly urged by the spring 24 and an accumulation chamber 28. Disposed below the connector 14 is an injection nozzle 30 which comprises a fuel passageway 32, a spring 34, and a nozzle needle 36 constantly biased by the spring 34. In this construction, fuel fed under pressure through the conduit 1 2 forces a check valve 38 to open to enter the chamber 28 via a fuel passageway 40.

The fuel is stored in the chamber 28 while urging the plunger 26 of the accumulator 22 against the action of the spring 24. When the valve member 1 8 of the valve 1 6 has opened the passageway 32, the fuel in the chamber 28 is injected from the nozzle 30 in a moment via a passageway 42, the passageway 32 and a passageway 44.

The accumulator 22 is furnished with an injection pressure adjusting mechanism generally designated by the reference numeral 50. The function assigned to the mechanism 50 is to control the injection pressure by adjusting the biasing force of the spring 24. As shown, the mechanism 50 includes a piston 52 which abuts against a spring seat 54 of the accumulator 22 while being slidably engaged with the inner periphery of the accumulator 22. A passageway 56 communicates a hydraulic control pressure to a pressure chamber 58 which is defined at the back of the piston 52. A displacement of the piston 52 is sensed by a sensor 60 which may be a coil, for example. The device 10 further comprises passageways 62 and 64 for returning leaks of fluid to a fuel reservoir (not shown), and a safety passageway 66.

In a device 10 having the above construction, when a control pressure is admitted into the pressure chamber 58 via the passageway 56, it urges the piston 52 downwardly against the action of the spring 24 thereby varying the back pressure which is acting on the plunger 26. On the change of the pressure acting on the plunger 26, the pressure of fuel inside the chamber 28, i.e., fuel injection pressure, is varied. Stated another way, the fuel injection pressure is controllable by varying the biasing force of the spring 24. In accordance with the present invention, the relationship between a biasing force of the spring 24 and an injection pressure is measured and stored in a storage which is built in a controller (not shown).The output of the sensor 60 indicative of a displacement of the piston 52 is compared with the measured relationship to adjust the control pressure such that the injection pressure is controlled based on a predetermined program to an optimum value which the controller calculates out employing engine load and speed as parameters. This allows the injection pressure to be controlled automatically.

The optimum injection pressure mentioned above depends upon the structure and operating conditions of an engine. For example, for a common nozzle hole area, an increase in injection pressure P reduces the diameter doffuel drops in a spray and shortens a time period of injection t.

Figure 3 represents phenomena which occur in different operation ranges (I, II, III and IV), the ordinate indicating a volume of fuel injection Q and the abscissa, an engine speed N. As shown in Figure 3, in a low speed, light load operation range I, the fuel drop diameter d is small so that the concentration of hydrocarbons (HC) in engine exhaust is small but, due to the short injection time t, noise is intensified. In the high speed, heavy load range Ill, although the emission of smoke is cut down, the injection pressure P is elevated to cause power loss and wear while degrading fuel economy.

Although not shown or described, the hydraulic fluid pressure source and the like may consist of conventional ones. If desired, the fuel or the engine oil may be employed as a source of pressure supply through a booster.

Referring to Figure 2, another possible form of the injection pressure adjusting mechanism in accordance with the present invention is shown.

This embodiment is distinguishable from the first embodiment in that it lacks the piston 52 which has been employed to govern the force of the spring 24. As shown in Figure 2, a bolt 70 is threaded into the top wall of the accumulation chamber 58 to abut against the spring seat 54.

The bolt 70 is rotated either by a gear transmission mechanism 72 or by a lever 74 to shift the spring seat 54 to a desired position.

It will be seen that the embodiment of Figure 2 allows the force of the spring 24 to be varied by a value which corresponds to the product of an angle of rotation and a pitch of the bolt 70, thereby varying the fluid pressure within the accumulation chamber 28. Various different designs are available for the drive of the lever 74 such as interlocking it to a hydraulic cylinder, a pressure receiving cylinder or an accelerator pedal.

The gear transmission mechanism 72, on the other hand, may be controlled by a stepping motor or like motor.

With any one of the constructions shown and described, the present invention achieves various outstanding advantages as enumerated below: (1) The volume of fuel injection can be controlled by means of pressure control.

(2) Suitable choice of a program suffices for the control over the injection pressure in order to improve the smoke, exhaust, fuel economy, knocking and other problematic situations.

(3) When the accumulated fuel has been lost due to leakage before the start of a fuel injection, the leak can be measured in terms of the resulting displacement of the plunger or the spring seat and, therefore, a volume of fuel allowing for the leak can be measured for the injection by adjusting a metering mechanism associated with the pump.

Various modifications will become possible for those skilled in the art after receiving the teachings of the present disclosure without departing from the scope thereof.

Claims

1. An accumulator fuel injection device which injects fuel from an injection nozzle by applying a pressure thereto, comprising: accumulator means for accumulating fuel fed thereto, said accumulator means comprising a spring which exerts a force predetermined for applying a pressure to the fuel; valve means for controlling communication of the accumulated fuel to the injection nozzle, said valve means comprising an electromagnetic valve made up of an electromagnet and a valve member; pressure adjuster means for adjusting the force of the spring in order to adjust the pressure to be applied to the fuel which is accumulated in the accumulator means; and sensor means for sensing an amount of pressure adjustment performed by the pressure adjuster means, whereby injection of the fuel is adjusted.

2. An accumulator fuel injection device as claimed in claim 1, in which the accumulator means comprises an accumulator chamber for accumulating the fuel, a plunger defining part of said accumulator chamber and movable to vary a volume of the accumulation chamber, a spring engaged at one end thereof with said plunger to bias the plunger in a direction for reducing the volume of the accumulation chamber, and a housing for accommodating said spring, the pressure adjuster means comprising a piston member engaged at one end thereof with the other end of the spring and movable within the housing to vary a force of the spring, and a passageway for communicating a hydraulic control fluid to a pressure chamber which is defined by the other end of the piston member and the housing, the sensor means comprising a coil responsive to a displacement of the piston member.

3. An accumulator fuel injection device as claimed in claim 1, in which the accumulator means comprises an accumulation chamber for accumulating the fuel, a plunger defining part of said accumulation chamber and movable to vary a volume of the accumulation chamber, a spring engaged at one end thereof with said plunger to bias the plunger in a direction for reducing a volume of the accumulation chamber, and a housing for accommodating said spring, the pressure adjuster means comprising a spring seat engaged at one end thereof with the other end of said spring and movable within the housing to vary a force of the spring, a bolt member threaded into the housing to abut against the other end of said spring seat, and a bolt rotating mechanism for rotating said bolt member to move the spring seat.

4. An accumulator fuel injection device as claimed in claim 3, in which the bolt rotating mechanism comprises a gear transmission mechanism.

5. An accumulator fuel injection device as claimed in claim 3, in which the bolt rotating means comprises a lever.

6. An accumulator fuel injection device substantially as herein described with reference to Figures 1 or 2 and Figure 3 of the accompanying drawings.