Title of Invention

FUEL INJECTION DEVICE FOR AN INTERNAL COMBUSTION ENGINE

Abstract

The invention relates to a fuel injection device for an internal combustion engine, having a common high-pressure collecting space (common rail) which is filled via a high-pressure pump. The high-pressure collecting space is connected to injection valves which each contion a control surfaces (5, 6; 19) which connect a high-pressure supply line (4), the control part (2) is activated by a controlled discharge line (23). the control part (2) contains a throttling element (10) which is connected to a cavity (7) via an orifice (11).

Full Text

Technical Field The invention relates to a fuel injection device for an internal combustion engine. In a fuel injection device having high-pressure collecting spaces (common rail) which can be filled, use is made of injectors which may be subjected continuously to the extremely high system pressure, which, on the one hand, permits largely delay-free injection of fuel, but, on the other hand, necessitates prevention of extremely small after injections after the end of injection by means of needle closure which is to be brought about rapidly at the end of the injection. Prior art EP 0 657 642 A2 relates to a fuel injection device for intemal combustion engines. A high-pressure collecting space is connected continuously to the injection valves. In order to avoid the high system pressure being continuously present at the injection valves, the control valve is designed in such a manner that during the intervals between the injection at the injection component it closes the connection thereof to the pressure storage space and opens up a connection between the injection valve and a relief space. As a result, the closing forces which are to be apphed and which are applied by spring forces can be reduced. Ever greater demands imposed on the system pressure level require greater closing forces which require springs of different dimensions. However, the construction space available for the movable springs is limited. DE 197 01 879 Al likewise relates to a fuel injection device for intemal combustion engines. By means of a solenoid valve which can be actuated, a relief channel which opens into a working space which is under pressure can be opened up in such a manner that the control valve can be moved into an open position or into a closed position. Summary of the invention With the throttling element provided on the control part it is possible, without additionally required components or having to fall back upon helical springs which produce relatively large closing forces, to obtain an increase in the closing force acting on the control part. This ensures more rapid closing of the injection needle at the end of the injection and tighter sealing of the high- pressure collecting container against the high-pressure supply line. The increase in the closing force at the control part prevents the occurrence of after injections of even extremely small quantities of fuel by increasing the pressure on the spring space. During the injection procedure, the spring space, in which a spring element is fitted, is acted upon by the fuel which is under high injection pressure. During the injection procedure, the pressure relief line which is provided next to the control part is closed by th,e control ramps of the control part, with the result that the high fuel pressure is also present at the spring space during the injection, so that a fuel pressure which assists the resetting procedure of the control part, which procedure is initiated after the end of the injection, is built up at the spring space as a function of the opening time of the control part. A further throttling element which is provided in the pressure-free release line is located opposite the control part, in its sleeve which surrounds it. After the end of the injection procedure, the throttle in the relief line prevents cavitation phenomena from occurring in the injection nozzle. With appropriate dimensioning of the cross section of the throttling element the spring space can, on the one hand, be completely relieved from pressure; on the other hand, complete pressure relief of the spring space can be prevented in that suitable dimensioning of the cross section of the throttling element enables an increased residual pressure to be preset and maintained in the spring space. An advantage which can further be obtained by the solution according to the invention resides in the fact that the throttling element on the control part of the 3/2-port directional control valve enables air to be evacuated from the internal combustion engine prior to the internal combustion engine being first started up. The significant effect of the solution according to the invention for the functional reliability of injection valves resides in a pressure compensation, which takes place via the throttling element and arises gradually, at the nozzle needle, on the one hand, and, by means of the throttling element and the orifice, at the spring space, on the other hand, when malfunctions arise at the injection valve, for example because of a solenoid valve which does not close or because of jamming or rubbing of the control part against the seat. The pressure compensation arises within a period of time. The period of time which is available via the cross section of the throttling element for the pressure compensation determines the maximum injection quantity at maximum system pressure. The maximum injection quantity, which exceeds the nominal injection quantity, can be deflected by suitable dimensioning of the cross section of the throttling element in the control part in such a manner that, if an injection procedure with maximum injection quantity in the engine occurs, the latter does not suffer any damage. With the maximum injection quantity controlled mechanically in this manner electronic malfunctions, in the form of activation signals which fail to materialize or are excessively long, can also be brought under control. Accordingly, the present invention provides a fuel injection device for an internal combustion engine, having a common high-pressure collecting space which is filled via a high-pressure pump and is connected to the injection valves which contain a control part which is designed as a 3/2 -port directional control valve and contains control surfaces which connect a high-pressure supply line to the injection line or to a relief line, the control part is capable of being activated by a controlled discharge line, characterized in that the control part contains a throttling element which is connected to a cavity via an orifice. Drawing : The invention is explained in greater detail below with reference to the graphical illustration, in which: Figure 1 shows an injector which is acted upon via a high-pressure collecting space (common rail), and Figure 2 shows the control part, illustrated on an enlarged scale, of the 3/2- port directional control valve between solenoid valve and spring space. Design variants The illustration according to Figure 1 reveals an injector which is acted upon via a high-pressure collecting space (common rail) Located at that end of the injector which is opposite the injection valve is a 2/2-port directional control valve which is preferably designed as an electrically actuable solenoid valve. The 2/2-port directional control valve 1 has the task of relieving a control chamber provided above the control part 2 - which is preferably designed as a control slide valve - from the high pressure which is present by a relief channel being opened. This causes fuel which is under high pressure in the supply line 18 to come into contact with the high-pressure line 9, 9' which leads to the nozzle needle 8 of the injection nozzle 13. By means of the injection nozzle 13, the fuel which is present and is under high pressure is injected at the beginning of the injection in a quantity proportioned in a defined manner into the combustion chamber of the internal combustion engine. The control part 2, which is illustrated on an enlarged scale and in more detail in Figure 2, is surrounded by a sleeve which is provided with inlet and outlet orifices for the fuel lines 4, 18 and for the- high-pressure line 9. The sleeve 12 for its part is fitted in a housing 21. A spring space 7, in which a helical spring 24 is fitted, is located in the housing 21. The helical spring 24 is supported at one end on a pair of plates 26 while it bears at the other end against an annular insert which accommodates a nozzle needle 8 with which the injection nozzle 13 can be opened and, after the end of the injection, closed again. The injector which is illustrated in Figure 1 is connected to the high-pressure collecting space (common rail) via a high-pressure line 18. The high- pressure collecting space is not illustrated in greater detail in Figure 1. The unpressurized relief line 4 conveys superfluous fuel into a fuel tank (likewise not illustrated). In comparison to the injector housing 21 which can be manufactured from a relatively inexpensive material, the sleeve 12 surrounding the control part 2 and the control part 2 itself are produced from high- quality material. In order to minimize leakage losses which arise during the relative movement between the control part 2 and sleeve 12 which surrounds it, the control part 2 and the sleeve 12 are designed with extremely exacting tolerances with regard to each other. Figure 2 shows, in a detailed illustration, the control part 2 which is fitted in the housing 21 and is surrounded by a sleeve 12. The 2/2-port directional control valve 1 which is accommodated in the injector housing 21 enables the opening of a closing body 15 which, when non-operative and acted upon via a spring element 16, closes a relief orifice 23 provided in a stop 17. The relief orifice 23 is designed with a small flow cross-sectional surface, as a result of which the relief orifice 23 acts as a throttle. Illustrated opening into the injector housing 21 is a high-pressure supply line 18 via which the injector is supplied with fuel which is under high pressure. The high-pressure supply line 18 from the high-pressure collecting space (common rail) opens into an orifice of the sleeve 12. On activation of the 2/2-port directional control valve 1, the control part 2, which is preferably designed as a control slide valve, releases the relief orifice 23 which opens into a control chamber 22, as a result of which the pressure in the control chamber 22 decreases. This causes a movement of the control slide valve towards the stop surface 17, which restricts the orifice 20 of the sleeve 12, which orifice accommodates the control part 2. As pressure in the control chamber 22 decreases, the control part opens at the valve seat 3 and fuel which is under high pressure shoots along the control step 19 into the high-pressure lines 9, 9\ which lead to the injection nozzle 13. The course of the injection procedure can be decisively influenced by the shaping of the control step 19. The fuel which is under high pressure acts not only on the high-pressure channels 9, 9' of the lines leading to the injector nozzle, but also on a throttling element 10, which is arranged in the control part 2 upstream of the control ramps 5, 6. This throttling element 10 - designed, for example, as a cost effective orifice in the control part 2 -opens into an axial orifice 11 of the control part 2 which, in tum, opens into a clearance 7. A [sic] plates 26 are fitted in this cavity of the injector housing 21 and the spring element 24 is supported against them. The other end of the spring element 24 is assigned to that end of the cavity 7 which faces the nozzle needle 8. During the injection procedure, the pressure in the spring space 7 is raised as a function of the opening time of the control valve 2. The pressure is built up in the cavity 7 on the side which faces away from the nozzle needle 8 (Figure 1). Towards the end of the injection, i.e. the 2/2-port directional control valve 1 is closed, the pressure in the control chamber 22 rises as a consequence and the control part 2 moves towards the valve seat 3 in the control housing 21, pressure is removed from the injection nozzle 13 by the relief line 4 being released by the control ramps 5, 6 formed on the control part 2. Likewise formed as an orifice in the sleeve 12 surrounding the control part 2 is a further throttling element 14 which is provided in the relief line 4. The further throttling element 14 prevents an abrupt dropping of the fuel pressure below the corresponding vapor pressure, with the result that cavitation is prevented by the further throttling element 14. Since a continuous pressure increase - corresponding to the opening time of the control part 2 - has taken place in the spring space 7 during the injection procedure, an increase in the rise in closing pressure for the control part 2 is obtained by the closing movement of the control part 2 towards the spring space 7. As a result, any leakages which arise between the valve seat 3 and the control step 19 and which may lead to extremely undesirable fuel after injections can be effectively avoided. Between the individual injection procedures, the spring space 7 can be relieved from pressure by the opening cross section of the throttling element 10. The control ramps 5, 6 enable fuel to flow back via the relief line 4 into the storage tank (not illustrated in greater detail). The spring space 7 may be completely relieved from pressure, depending on the cross section selected for the throttling element 10. Given appropriate dimensioning of the throttle cross section for the throttling element 10 in the control part 2, a residual pressure which depends on the engine speed can also be maintained in the spring space 7, as a result of which the nozzle-opening pressure can be raised at higher speeds. When the internal combustion engine is first started up, air can be evacuated from the combustion chambers of the intemal combustion engine in an advantageous manner, as a result of which easier starting up of the engine can be obtained. With the solution according to the invention, disadvantageous effects of mechanical or electronic mal functions can advantageously be avoided. If, for example, a leak has occurred at the 2/2-port directional control valve 1 or the spring 16 is broken or wedging of the control part 2 in the sleeve 12 has occurred, the nozzle needle 8 is acted upon at its seat by the same pressure as on the other side, where the same pressure is gradually buih up via the throttling element 10, the orifice 11 and the spring space 7. The period of time in which the gradual built-up of the pressure equilibrium takes place is determined by the throttling cross section at the throttling element 10. The period of time which the pressure compensation needs at maximum system pressure at the nozzle needle 8 determines the maximum injection quantity. The maximum injection quantity, which exceeds the nominal injection quantity, can be determined, by specifying the throttling cross section of the throttling element 10, in such a manner that, when the maximum injection quantity is injected into the combustion chamber of the intemal combustion engine, the latter does not suffer any damage. If an electronic malfunction should occur in the form of an excessively long activation signal at the solenoid valve 1, this functional error can be brought under control by the [sic] in a mechanical manner by appropriate dimensioning of the cross-sectional surface of the throttling element 10, since the maximum injection quantity has been predetermined in a mechanical manner. List of reference numbers 1 2/2 - port directional solenoid control valve 2 3/2 - port directional control valve 3 Valve seat (stop) 4 Relief line 5 Control ramp 6 Control ramp 7 Spring space 8 Nozzle needle 9 Nozzle feed 9' Channel 10 Throttling element 11 Orifice 12 Sleeve 13 Injection nozzle 14 Further throttling element 15 Valve seat 16 Spring 17 Stop 18 Fuel supply line 19 Control step 20 Orifice 21 Injector housing 22 Control chamber 23 Pressure-removal orifice 24 Spring 25 Orifice 26 Plates WE CLAIM : 1. Fuel injection device for an internal combustion engine, having a common high-pressure collecting space which can be filled via a high-pressure pump and is connected to the injection valves which contain a control valve (2) which is designed as a 3/2 -port directional control valve and contains control surfaces (5, 6, 19) which connect a high-pressure supply line (18) to the injection line (9, 9') or to a rehef line (4), in which case the control part (2) is capable of being activated by a controlled discharge line (23), characterized in that the control part (2) contains a throttling element (10) which is connected to a cavity (7) via an orifice (11) 2. Fuel injection device as claimed in claim 1, wherein the orifice (11) is connected to the nozzle feed (9) via the throttling element (10). 3. Fuel injection device as claimed in claim 1, wherein the relief line (4) contains a further throttling element (14) which avoids cavitation when the injection nozzle (13) is relieved from pressure. 4. Fuel injection device as claimed in claim 1, wherein the control ramps (5, 6) of the control part (2) closes the relief line (4) and thus the closing pressure exerted at the control part is increased. 5. Fuel injection device as claimed in claim 1, wherein the cavity (7) is completely pressure-relieved by means of the dimension of the cross section of the throttle element (10). 6. Fuel injection device as claimed in claim 1, wherein a residual pressure in the cavity (7) that increases the opening pressure of the injection nozzle (13) is capable of being set by the dimension of the cross section of the throttle element (10). 7. Fuel injection device as claimed in claim 1, wherein the cavity (7) is capable of being vented when the internal combustion engine is first started by means of the throttle element (10). 8. Fuel injection device as claimed in claim 1, wherein the throttle element (10) establishes a pressure difference between the nozzle needle (8) and the cavity (7) at the control part (2) in the event of malfunctions of the control part (2). 9. Fuel injection device as claimed in claim 8, wherein by means of the cross section of the throttle element (10) when the maximum system pressure is applied, the time difference in the pressure equalization that is established at the nozzle needle (8) is capable of being predetermined, and thus the maximum injection quantity is defined. 10. Fuel injection device for an internal combustion engine, substantially as hereinabove described and illustrated with reference to the accompanying drawings. Dated this 25 day of June 2001

Documents:

in-pct-2001-886-che-abstract.pdf

in-pct-2001-886-che-claims filed.pdf

in-pct-2001-886-che-claims granted.pdf

in-pct-2001-886-che-correspondnece-others.pdf

in-pct-2001-886-che-correspondnece-po.pdf

in-pct-2001-886-che-description(complete)filed.pdf

in-pct-2001-886-che-description(complete)granted.pdf

in-pct-2001-886-che-drawings.pdf

in-pct-2001-886-che-form 1.pdf

in-pct-2001-886-che-form 19.pdf

in-pct-2001-886-che-form 26.pdf

in-pct-2001-886-che-form 3.pdf

in-pct-2001-886-che-form 5.pdf

in-pct-2001-886-che-other document.pdf

in-pct-2001-886-che-pct.pdf