EP1115974A1

EP1115974A1 - Fuel injection system for an internal combustion engine

Info

Publication number: EP1115974A1
Application number: EP00960307A
Authority: EP
Inventors: Friedrich Boecking
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1999-07-22
Filing date: 2000-07-22
Publication date: 2001-07-18
Also published as: JP2003505646A; DE19934354C1; US6532937B1; WO2001007778A1

Abstract

A fuel injection system for an internal combustion engine comprising a high-pressure store (10) for said fuel, whereby an injection line for the fuel which is to be injected and a drive line (16; 16') for the fuel depart therefrom and said fuel is used as a working medium. The aim of the invention is to use the fuel in a simple manner, whereby a high pressure working medium is provided and used for additional functions. At least one converter (18; 18') is connected to the drive line (16; 16'), enabling a volume flow of the pressurized fuel to be converted into a volume flow of a pressurized working medium..

Description

Fuel injection system for an internal combustion engine

State of the art

The invention relates to a fuel injection system for an internal combustion engine, with a high-pressure fuel accumulator, from which an injection line for the fuel to be injected and a drive line for fuel branch off, which is used as the drive medium.

Such a fuel injection system is already known from DE 44 07 585 AI and is based on an injection system that is known under the name "Co mon Rail". This injection system uses a cylindrical pressure tank, to which fuel is supplied by a high-pressure pump. The high-pressure accumulator essentially serves as a buffer that dampens pressure fluctuations that result from the supply of fuel by the high-pressure pump and the withdrawal of fuel through the injection nozzles.

From the aforementioned publication it is known to use the fuel present in the high-pressure accumulator for a hydraulic valve control. For this purpose, the fuel is first supplied to a hydraulic chamber which is assigned to an outlet valve and is controlled by two control valves, and then to a hydraulic chamber which is assigned to an inlet valve and is likewise controlled by two control valves. Through Suitable switching of the control valves, the inlet valve and the outlet valve are opened against the action of a conventional valve spring or closed again by means of the valve spring.

Advantages of the invention

The fuel injection system according to the invention with the features of the characterizing part of claim 1 has the advantage that an external consumer can be connected to the high-pressure accumulator, which is not operated with the fuel itself, but with any other working medium. The converter makes it possible to put the working medium under a pressure that deviates from the fuel pressure.

Advantageous further developments and improvements of the fuel injection system specified in claim 1 are possible through the measures listed in the further claims.

According to an advantageous embodiment of the invention, it is provided that the converter has a translationally displaceable input piston and an actuator by means of which the pressurized fuel can be periodically applied to the input piston. In this way it is possible with little design effort, which in the under

Pressurized fuel to convert stored potential energy into a reciprocating movement of the input piston, which in turn can then be converted into a volume flow of a working medium under pressure.

It is preferably provided that the actuator is a 3/2-way valve. Such valves are available as reliable series components, so that the effort for controlling the input piston is minimal.

According to a preferred embodiment of the invention, it is further provided that the converter has a translationally displaceable output piston which is connected to the input piston. >> tt t- * »- ^■

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The invention is described below with reference to two embodiments which are illustrated in the accompanying drawings. In these show:

1 shows a schematic view of an inventive fuel injection system according to a first embodiment; and

Fig. 2 is a schematic view of an inventive fuel injection system according to a second embodiment.

Description of the embodiments

1 schematically shows a fuel injection system according to a first embodiment of the invention. This contains a high-pressure accumulator 10 for fuel, which is used to operate an internal combustion engine, not shown. The fuel is supplied to the high-pressure accumulator 10 through a supply line 12, which is connected to a high-pressure pump, not shown. An injection line 14 for the fuel branches off from the high-pressure accumulator 10 and leads to the individual injection nozzles of the injection system.

A drive line 16 branches off from the high-pressure fuel reservoir 10 and can be used to remove fuel from the high-pressure reservoir, which fuel is used as the drive medium.

A converter 18 is connected to the drive line 16 and consists of an actuator 20 and a piston pump 22.

The actuator 20 is a 3/2-way valve which has an inlet 24 which is connected to the drive line 16, an outlet 26 which is connected to the piston pump 22 and an outlet 28 which returns to a fuel accumulator. leads. The actuator 20 also has a valve drive 30, which can adjust a valve slide 32 in translation.

The piston pump 22 has a translationally displaceable input piston 34, which is connected to the output 26 of the actuator 20, and a translationally displaceable output piston 36, which is fixedly connected to the input piston 34. A discharge line 37 for a leakage current branches off from a space between the input piston 34 and the output piston 36. A compression spring 38 is supported on the output piston 36 and acts on the input piston and the output piston in a position in which the volume of the piston pump assigned to the input piston 34 and connected to the output 26 is minimal.

A working volume is assigned to the output piston 36, into which a supply line 39 for a working medium opens. A check valve 40 is arranged in the feed line 39. An output line 41, in which a check valve 42 is arranged, extends from the working volume assigned to the output piston 36. The outlet line 41 leads to a high-pressure accumulator 44 for the working medium. The working medium can be fed from a high-pressure accumulator 44 to a consumer through an extraction line 46.

A sensor 43 is attached to the piston pump 22 and measures the path of the input and output pistons and the pressure. This data is made available to the valve drive 30.

The described injection system with the converter 18 works in the following way: The valve drive 30 controls the valve slide 32 so that the input piston 34 is periodically acted upon by the pressurized fuel from the high-pressure accumulator 10. The output piston 36 is adjusted downward with respect to FIG. 1, whereby the working medium from the supply line 39 into the output line in N a tr Z ö P- -3 tn s tn?: φ in c α Φ rt <3 P- 3 P ß φ tr a er <rt ö ß a er * -

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Claims

Expectations

1. Fuel injection system for an internal combustion engine, with a high-pressure fuel reservoir (10), from which an injection line (14) for the fuel to be injected and a drive line (16; 16 ') for fuel branch off, which is used as the drive medium, characterized in that at least one converter (18; 18) is provided, which is connected to the drive line (16 16 _'?) and in which a volume flow of the pressurized fuel is converted into a volume flow of a pressurized working medium.

2. Fuel injection system according to claim 1, characterized in that the converter (18; 18 ') has a translationally displaceable input piston (34; 34') and an actuator (20; 20 ') through which the input piston periodically with under Fuel under pressure can be applied.

3. Fuel injection system according to claim 2, characterized in that the actuator is a 3/2-way valve (20; 20 ').

4. Fuel injection system according to one of claims 2 and 3, characterized in that the converter (18; 18 ') has a translationally displaceable output piston (36; 36') which is connected to the input piston (34; 34 '), and two check valves (40, 42; 40 ', 42') assigned to the output piston.

5. Fuel injection system according to claim 4, characterized in that the cross section of the input piston

(34; 34 ') differs from the cross section of the output piston (36; 36').

6. Fuel injection system according to one of the preceding claims, characterized in that a high pressure accumulator

(44) is provided for the working medium.

7. Fuel injection system according to one of the preceding claims, characterized in that two converters (18; 18 ') are provided which operate alternately.