GB2335007A

GB2335007A - Fuel-injection device for internal combustion engines

Info

Publication number: GB2335007A
Application number: GB9904313A
Authority: GB
Inventors: Manfred Mack; Anton Brandstaetter
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1998-03-06
Filing date: 1999-02-26
Publication date: 1999-09-08
Anticipated expiration: 2019-02-26
Also published as: FR2775737B1; GB2335007B; FR2775737A1; JPH11294297A; DE19809627A1; GB9904313D0

Abstract

A unit fuel-injector for an internal combustion engine comprises a high pressure fuel pump 1 which is connected on its intake side to a low pressure fuel supply system and is connected on its high pressure side to a fuel-injection valve 13 which protrudes into the combustion chamber of the internal combustion engine. Pressure relief from a high pressure duct 11 provided between the high pressure fuel pump 1 and the fuel-injection valve 13 is controlled by means of an electric control valve 15 which comprises an electrically operable, displaceable valve member 21 having a valve sealing surface 35 which cooperates with a positionally-fixed valve seat surface 29 on a valve seat sleeve 25, which guides the valve member 21, to form a sealing cross-section. In order to improve the adjustment times and the incidence of wear in the control valve, the control valve member 21 is formed from ceramic material. The valve seat sleeve 25 may also consist of a ceramic material.

Description

2335007 1

DESCRIPTION FUEL-INJECTION DEVICE FOR INTERNAL COMBUSTION ENGINES

The invention relates to fuel-injection devices for internal combustion engines and is concerned in particular with such devices of the type having a high pressure fuel pump which is connected on the intake side to a low pressure fuel supply system and is connected on the high pressure side at least indirectly to a fuel-injection valve which protrudes into the combustion chamber of the internal combustion engine, wherein the high pressure delivery into a high pressure duct, which is provided between the high pressure fuel pump and the fuel-injection valve, can be controlled by means of an electric control valve which comprises an electrically operable, displaceable valve member having a valve sealing surface, with which said valve member cooperates with a positionally- fixed valve seat to form a sealing cross-section.

In the case of this type of fuel-injection device which is disclosed in EP 0 178 427 B1 a high pressure fuel pump is connected on the intake side to a low pressure fuel supply system and is connected on the high pressure side at least indirectly to a fuel-injection valve which protrudes into the combustion chamber of the internal combustion engine. Between the pump working chamber, which is defined by the pump piston, of the high pressure fuel pump and the injection valve there is provided a high pressure duct from which in the case of the known fuel-injection device a relief line branches off which issues into the low pressure fuel system and which can be closed by means of an electric control valve. The high pressure fuel delivery is controlled in the pump working chamber of the high pressure fuel pump by virtue of the fact that the relief line which is connected to the high pressure duct is closed by means of the electric control valve. Owing to the fact that the relief line is closed, high fuel 2 pressure is built up during the delivery stroke movement of the pump piston of the high pressure fuel pump in the pump working chamber and said pressure is guided by way of the high pressure duct to the injection valve where it causes the injection valve to open in a known manner. The high pressure fuel delivery or the high pressure fuel-injection is terminated at the known fuel-injection device by opening the relief line by means of the electric control valve and subsequently the high pressure fuel located in the pump working chamber and in the high pressure duct is relieved by way of the control valve into the low pressure line system.

The electric control valve which controls the high pressure delivery of the high pressure pump is formed as a solenoid valve whose displaceable armature is connected to a piston-shaped valve member of the control valve on the peripheral surface of which there is provided a valve sealing surface. By means of this valve sealing surface the control valve member cooperates with a positionally-fixed valve seat on the control valve body, wherein between the valve sealing surface and the valve seat surface there is formed a sealing cross-section which closes the relief duct. The control valve member of the known fuel-injection device has the disadvantage that it comprises a relatively large mass moment of inertia and thus requires extremely large adjusting forces in order for the control valve to achieve rapid control times. However, these large adjusting forces can only be achieved in a costly manner by virtue of large operating magnets, so that currently available operating magnets are not able to satisfy the high demands with respect to the rapid control times. A further disadvantage of the known control valve is seat wear which occurs on the valve seat surface and which arises because of the high impact speeds of the valve member or because of erosion wear due to fuel impurities and said seat wear can cause failures in the seal at the sealing cross-section and consequently can destroy same.

3 In accordance with the present invention, the valve member of the electric control valve is formed from ceramic material.

In contrast to the prior art, a fuel-injection device for internal combustion engines in accordance with the present invention has the advantage that the mass inertia of the control valve member can be reduced considerably by forming the control valve from ceramic material. In the case of comparable valve member geometry, it is possible to reduce the mass by up to 60% with respect to conventional steel valve members. This mass reduction renders it possible to achieve extremely short switching sequences and extremely rapid control times in the control valves without, for this purpose, having to increase the size of the operating magnets used for actuation. Furthermore, the wear on the sealing surfaces of the valve members can be reduced considerably by using ceramic material. In so doing, it is particularly advantageous, in addition to forming the valve member and thus the valve sealing surface from ceramic material, also to form the valve sealing surface, which cooperates therewith, from ceramic material which once again reduces considerably the wear on the valve sealing seat. In order to make this possible structurally, the piston-shaped valve member is guided advantageously in a slide-displaceable manner in a ceramic sleeve which for its part is inserted into a receiving bore of the valve body. Furthermore, it is particularly advantageous to provide the electric control valve, which controls the high pressure delivery of the high pressure pump, directly in the high pressure duct between the high pressure pump and the injection valve. A further advantage of using ceramic control valve members andlor seat sleeves is achieved by the simplified manufacture thereof by means of a compression moulding process.

4 In addition to being used in a pump-line-nozzle described in the exemplified embodiment the design, in accordance with the invention, of the control valve member and a valve seat sleeve in ceramic material is also possible in different fuel-injection systems, such as pump nozzles and all solenoid valve-controlled injection systems, wherein the control valve member and the valve seat surface can be manufactured in pairs or also individually from ceramic material.

An exemplified embodiment of the fuel-injection device for internal combustion engines in accordance with the invention is explained in detail in the description hereinunder and illustrated in the drawing, in which i 1 i Figure 1 shows a simplified longitudinal sectional view through the fuel- injection device in the region of the electric control valve inserted into the high pressure duct.

The exemplified embodiment illustrated in Figure 1 of the fuelinjection device for internal combustion engines in accordance with the invention is formed as a so-called pump-line-nozzle. A high pressure fuel pump 1 comprises a pump piston 7 which can be displaced in an axial manner in a guide bore 3 of a pump housing 5 and which is driven axially in a reciprocating manner by a cam drive [not illustrated in detail] of the internal combustion engine. The pump piston 7 defines in the guide bore 3 a pump working chamber 9, into which issues a closeable fuel supply line [not illustrated in detail] of a low pressure fuel supply system, by way of which fuel supply line the pump working chamber 9 can be filled with fuel from a fuel storage tank during the downwardly directed intake stroke movement of the pump piston 7. Furthermore, a high pressure duct 11 leads off from the pump working chamber 9 and issues on the other side at a fuel-injection valve 13 which protrudes with its injection orifices in a manner not illustrated in detail into the combustion chamber of the internal combustion engine which is to be supplied.

In order to control the high pressure delivery at the high pressure fuel pump 1, an electrically operable control valve 15 is inserted into the high pressure duct 11 between the pump working chamber 9 and the injection valve 13.

The electrically adjustable control valve 15 is formed as a solenoid valve, wherein an operating magnet 17 which can be controlled electrically comprises an axially displaceable armature plate 19 which is connected to a piston-shaped, hollow-cylindrical valve member 21. This valve member 21 which forms the actuator of the electric control valve 15 is inserted in a transverse manner with respect to the high pressure duct 11 into the pump housing 5 to which the operating magnet 17 is flanged protruding radially thereto. The valve member 21 is disposed in a receiving bore 23 in the pump housing 5, which receiving bore extends in a transverse manner with respect to the high pressure duct 11 and a valve seat sleeve 25 is pressed into the said receiving bore at its outer periphery. At the level of the inlet orifices of the high pressure duct 11 into the receiving bore 23 this valve seat sleeve 25 comprises radial through-going bores 27, by way of which the fuel flows out of the pump working chamber 9 by way of the high pressure duct 11 through the valve seat sleeve 25 to the injection valve 13. On its right-hand end remote from the operating magnet 17, the valve seat sleeve 25 forms a valve seat surface 25 on its end face. The valve seat sleeve 25 comprises a stepped inner diameter, wherein starting from the opposite end faces the different diameter regions each lead to as far as the through-going bores 27. An inner wall region, which has a smaller diameter, of the valve seat sleeve 25 is disposed on the side of the valve seat sleeve 25 facing the operating 6 magnet 17. This inner wall region having the smaller diameter forms a guide surface 31 for the valve member 21 which with a part of its peripheral wall is guided in a slide-displaceable manner on the guide surface 31 within the sleeve 25. The piston-shaped valve member 21 comprises on its end remote from the operating magnet 17 an annular collar 33 which on its transitional surface with respect to the cylindrical peripheral wall of the valve member 21 forms a valve sealing surface 35, with which the valve member 21 cooperates with the valve seat surface 29 on the sleeve 25 to form a sealing cross-section. The opening stroke movement, which is directed to the right in the direction remote from the operating magnet 17, of the valve member 21 of the control valve 15 is defined by virtue of a cylindrical stroke stop body 37 which by means of a sealing flange part 39 is inserted into the orifice of the receiving bore 23 which is remote from the operating magnet 17. In the region of the stroke stop body 37 a return line 41 leads off from the receiving bore 23 and issues in a manner not illustrated in detail into the low pressure fuel supply system of the internal combustion engine. The valve member 21 of the control valve 15 is influenced in the opening direction by means of a valve spring 43, so that when the operating magnet 17 is switched to currentless the valve member 21 is raised with its valve sealing surface 35 from the valve seat 29 and the fuel can flow off from the high pressure duct 11 by way of the sleeve 25, the opened sealing cross-section between the surfaces 29 and 35 into the annular region of the receiving bore 23, which surrounds the stroke stop body 37, and said fuel can flow off further by way of the return line 41 into the low pressure system. If an injection procedure is to take place at the fuel-injection valve 13, the operating magnet 17 of the electric control valve 15 is supplied with current during the high pressure delivery stroke of the pump piston 7, so that the valve member 21 is pulled with its valve sealing surface 35 in a sealing manner into position against the valve seat surface 29. Therefore, the flow-off 7 cross-section into the return line 41 is closed so that the fuel which is delivered at high pressure is delivered from the pump working chamber 9 by way of the high pressure duct 11 to the injection valve 13 where it is injected in a known manner. The high pressure fuel-injection procedure is terminated when the operating magnet 17 is switched to currentless again, so that the valve spring 43 displaces the valve member 21 once again to the open position and subsequently the high pressure fuel in the pump working chamber 9 and in the high pressure duct 11 is relieved once again into the return line 41, so that the fuel-injection valve 13 closes.

In order to achieve the most rapid possible adjustment times in the electric control valve 15 for the purpose of modulating the injection progression and in order to achieve the lowest possible wear on the sealing seat, the valve seat sleeve 25 and the valve member 21 of the control valve 15 are produced from a ceramic material.

8

Claims

1 1. A fuel-injection device for internal combustion engines having a high pressure fuel pump which is connected on the intake side to a low pressure fuel supply system and is connected on the high pressure side at least indirectly to a fuel-injection valve which protrudes into the combustion chamber of the internal combustion engine, wherein the high pressure delivery into a high pressure duct, which is provided between the high pressure fuel pump and the fuel-injection valve, can be controlled by means of an electric control valve which comprises an electrically operable, displaceable valve member having a valve sealing surface, with which said valve member cooperates with a positionally- fixed valve seat to form a sealing cross-section, the valve member of the electric control valve being formed from ceramic material.

2. A fuel-injection device according to claim 1, wherein the electric control valve is disposed in the high pressure duct.

3. A fuel-injection device according to claim 1, wherein the valve member is formed as a hollow-cylindrical piston which is guided in a slidedisplaceable manner in a sleeve on one end face of which the positionallyfixed valve seat is formed.

4. A fuel-injection device according to claim 1, wherein a component which comprises the valve seat consists of ceramic material.

5. A fuel-injection device according to claim 1, wherein the valve sealing surface is formed on the valve member as an annular collar.

6. A fuel-injection device according to claim 1, wherein the electric P (0 W Z:5 &P 9 control valve is formed as a solenoid valve whose moveable armature plate is connected to the valve member.

7. A fuel-injection device according to claim 1, wherein the fuelinjection device is formed as a pump-line-nozzle unit.

8. A fuel-injection device substantially as hereinbefore described, with reference to and as illustrated in the accompanying drawing.