DE102007043540A1 - Leak-free fuel injector with long nozzle needle - Google Patents

Abstract

A fuel injector (1) for internal combustion engines comprises a longitudinally displaceable nozzle needle (7, 13), which controls the opening of at least one injection opening (5) by its longitudinal movement, a longitudinally high-pressure line which is inserted into a nozzle space (9) annularly surrounding the nozzle needle (7, 13) ), a control room (8) connected to a fuel high-pressure side (16), in which the nozzle needle (7, 13) acts in the closing direction 22), which blocks the connection of the control chamber (8) to a low-pressure side (25) or opens. According to the invention, the high-pressure line is formed by a high-pressure space (9b) surrounding the nozzle needle (7, 13) in an annular manner.

Description

State of the art

The The invention is based on a fuel injector of the type of claim 1

From the DE 101 46 743 A1 is such a fuel injector with a designed as a solenoid valve control valve known.

at Such solenoid injectors (MVI) is used for sealing between Low pressure chamber and high pressure chamber a sealing ring in combination with used a support ring. However, this combination is preparing significant problems that can even go so far that the MVI completely loses its functionality, because the seal moves away from the support ring and then the functionally necessary sealing of high and low pressure space no longer exists. The cause of the migrating sealing ring is until today not clarified with final certainty and is also still found in MVI developments. The on the nozzle needle acting control piston is in a valve piece guided, exposed to high deformation forces is because it is in both the low pressure room and in the high pressure room protrudes. This can lead to undesirable frictional forces between valve piece and control piston, with the result of uneven injection quantities, since These frictional forces on the one hand, the lifting and closing speed and on the other hand influence the stroke of the nozzle needle itself can. The deformation forces can also to misalignment of the control piston relative to the nozzle needle lead and therefore same negative friction conditions cause at the nozzle needle, d. H. too difficult manageable additional influence on the injection quantity to lead. To mitigate the danger, so far come specifically trained guides are used and are both selected highly stable materials for the valve piece as also close tolerances between the control piston and valve piece and between the nozzle needle and its guide required. For reasons of assembly and tightness, the outer contour must be the valve piece in the region of the sealing ring and the support ring be tight tolerated constructively, be relatively long and towards Nozzle leaving the pure cylindrical shape taper to have. In the area of the sealing ring is naturally also subject the holding body the tight tolerances. The high pressure must be over one almost over the entire length of the holding body fed to be produced inclined high-pressure bore become. The high pressure bore will have an additional supplied oblique hole in the holding body. The tight ones Space constraints lead to difficult compromises, to avoid bores with sufficient certainty can. The spool is in a low pressure hole arranged, also for the sake of needed Wall thickness is stepped. For derivation the leakage amounts will be an oblique hole (also with the problem of "bore intersection"), which ultimately leads to the outflow of the leakage quantity into the low-pressure space, from which also the tax amount led to the return system becomes.

Disclosure of the invention

• – keine Leckagemenge, da Düsen- und Steuerkolbenführungen keinem Druckgefälle ausgesetzt sind, und daher hoher hydraulischer Wirkungsgrad;
• – Reduzierung der Bauteilanzahl, da keine Dicht- und Stützringe erforderlich sind, und damit Kostenreduzierung;
• – einfachere Ausgestaltung des Steuerkolbens und damit Kostenreduzierung;
• – Reduzierung der Anzahl schräger und zum Teil langer Bohrungen (Leckagebohrungen und Hochdruckbohrung) im Haltekörper;
• – der für den Steuerkolben verwendete Raum kann durch eine einfache Durchgangsbohrung ohne Absätze gebildet werden und ist gleichzeitig Hochdruckbohrung, was Kosten reduziert;
• – problemloses Ersetzen (Nachrüstbarkeit) von bisherigen Injektoren durch den erfindungsgemäßen Injektor;
• – das Ventilstück ist praktisch druckausgeglichen, wodurch kritische Verformung verhindert werden;
• – extrem einfache und damit kostengünstige Ausbildung der Dichtkontur zwischen Haltekörper und Düsenkörper als reine Ringflächen;
• – Ventilstück kann mit Spiel eingebaut werden und dennoch den Steuerkolben korrekt führen, ohne dass schwer beherrschbare Reibungskräfte auftreten;
• – Anbindung des Hochdruckraumes an den Niederdruckraum erfolgt nur noch über die Ablaufdrossel.

The fuel injector according to the invention has the following advantages in comparison to the known fuel injector:

• No amount of leakage, since nozzle and control piston guides are not exposed to pressure gradient, and therefore high hydraulic efficiency;
• - Reduction of the number of components, as no sealing and support rings are required, and thus cost reduction;
• - simpler design of the control piston and thus cost reduction;
• - Reduction in the number of oblique and partially long holes (leakage holes and high-pressure bore) in the holding body;
• - The space used for the control piston can be formed by a simple through hole without paragraphs and is also high-pressure bore, which reduces costs;
• - Easy replacement (retrofitting) of previous injectors by the injector according to the invention;
• - The valve piece is practically pressure balanced, whereby critical deformation can be prevented;
• - Extremely simple and therefore cost-effective design of the sealing contour between the holding body and nozzle body as pure annular surfaces;
• - Valve piece can be installed with clearance and still lead the spool correctly, without difficult to control frictional forces occur;
• - Connection of the high-pressure chamber to the low-pressure chamber takes place only via the outlet throttle.

Further Advantages and advantageous embodiments of the subject invention are the description, the drawing and the claims removable.

Short description of the drawing

Of the Fuel injector according to the invention is in the Drawing shown and closer in the following description explained. The features shown in the drawing are purely schematic and not to scale.

The single figure shows a longitudinal section through the invention Fuel injector.

Embodiment of invention

The fuel injector (fuel injection valve) shown in the figure 1 is commonly used in an internal combustion engine having a plurality of cylinders, wherein each of these cylinders is associated with such an injector.

The injector 1 comprises in a conventional manner a holding body 2 and a nozzle body protruding into a cylinder combustion chamber of the internal combustion engine 3 passing through a clamping nut 4 be pressed against each other. At its projecting into the cylinder combustion chamber end of the nozzle body 3 several injection openings 5 up through one in a pilot hole 6 of the nozzle body 3 longitudinally displaceable guided nozzle needle (valve needle) 7 depending on the pressure in a control room 8th be opened or closed. The fuel becomes the injection ports 5 inside the nozzle body 3 over a nozzle space 9 fed to the nozzle needle 7 surrounds and can be filled with fuel under high pressure. Moves the nozzle needle 7 from the injection ports 5 and thus moves into its open position, fuel from the nozzle chamber 9 over the injection openings 5 injected into the cylinder combustion chamber. Is the nozzle needle located 7 however, in its closed position, ie with a sealing surface 10 in contact with one in the guide bore 6 provided valve seat 11 , so will the injection ports 5 through the nozzle needle 7 locked.

In the holding body 2 is a longitudinal bore 12 formed coaxially with the nozzle needle 7 runs and in which a control piston (push rod) 13 under formation of an annulus (high pressure room) 14 is arranged longitudinally displaceable. This high pressure room 14 opens into the annular nozzle space 9 and forms in the holding body 2 a high-pressure line, which has a high-pressure connection 15 to a high-pressure accumulator (common rail) 16 connected. The control room 8th is over the high pressure room 14 to the high pressure side 16 connected. The nozzle needle 7 and the control piston 13 are together by means of a bolt 17 rigidly connected to a "long nozzle needle." The bolt 17 is in the illustrated embodiment on the control piston 13 provided and in the nozzle needle 7 z. B. pressed or screwed. The bolt 17 but also on the nozzle needle 7 provided and in the control piston 13 be pressed or screwed or may also be a separate part, in both parts 7 . 13 pressed or screwed. Through the nozzle needle 7 is the control piston 13 in the longitudinal bore 12 coaxial with the nozzle needle 7 centered.

At its other end is the spool 13 in a guide hole 18 a valve piece 19 axially guided, which in the longitudinal bore 12 is used. The control piston 13 limited in the guide hole 18 with a closing direction of the nozzle needle 7 acting control surface 20 the control room 8th , which has an inlet throttle (Z throttle) 21 permanently to the high pressure side 16 connected. To control the injection process is a control valve 22 provided in the form of a 2/2-way valve whose sliding control valve member (valve ball) 23 the connection of the control room 8th via an outlet throttle (A-throttle) 24 with a low pressure side 25 opens or locks. The control valve 22 can as an actuator for the control valve member 23 a piezoelectric actuator or, as shown in the figure, have a magnetic drive. The control piston 13 is from a closing spring 26 surrounded on the one hand by a covenant 27 of the control piston 13 and on the other hand on the valve piece 19 supported, so by the force of the closing spring 26 the control piston 13 in the direction of the nozzle body 3 and thus the nozzle needle 7 is pressed into its closed position. About a shim 28 between closing spring 26 and valve piece 19 can the bias of the closing spring 26 be set.

The functioning of the injector 1 is as follows.

The injection openings 5 are closed when in the control room 8th High pressure (rail pressure) prevails, ie when the A-throttle 24 by means of the control valve 22 is closed and the control room 8th via the inlet throttle 21 with the high pressure side 16 communicates. For an injection, the control valve 22 opened and thereby the control room 8th over the A-throttle 24 with the low pressure side 25 connected and thus relieved of pressure, wherein the Z-throttle 21 prevents complete pressure equalization. The A / Z ratio determines the opening speed of the nozzle needle 7 , The nozzle needle 7 , on the sealing surface 10 in the nozzle room 9 prevailing fuel pressure acts in the opening direction, lifts from the valve seat 11 and gives the injection openings 5 free. The control piston 13 can reach its upper stop and there remain on a fuel cushion (hydraulic stop). The nozzle needle 7 is then fully opened, as the pressure in the control room 8th smaller than the pressure under the nozzle needle 7 , The nozzle room 9 is always under rail pressure.

To complete the injection, the control valve 22 closed, and the pressure in the control room 8th rises by means of the inlet throttle 21 whose flow rate is the closing speed of the nozzle needle 7 certainly. If that due to the pressure in the control room 8th on the nozzle needle 7 acting hydraulic closing force and the force of the closing spring 26 are larger than those on the nozzle needle 7 in the opening direction acting force, closes the nozzle needle 7 ,

As long as the drain throttle 24 is open, a fuel "control amount" flows to the low pressure space 25 , ie in the fuel return from. The low pressure room 25 and the high pressure room 14 are about the demand-opening and closing flow restrictor 24 connected and thus in principle leak-free. The valve piece 19 is not subject to any particular deformation forces, as it is subjected to comprehensive only with rail pressure, given the slightly lower pressure in the control room 8th initially ignored during the injection process because of the small areas. For the valve piece 19 Therefore, because of the pressure balance, there are no high material requirements. The low frictional forces are manageable and thus also the injection quantity quality. The control piston 13 leading guide part of the valve piece 19 can also be simply cylindrical on the outside and be provided with large tolerances in terms of geometry and surface. Also, the lead part does not have to be that long anymore. The high pressure room 14 in which the control piston 13 runs, at the same time forms the high-pressure line to the nozzle chamber 9 , so no separate high pressure holes in the nozzle body 3 and in the holding body 2 required are. Because the injector 1 is leak-free, are in the holding body 2 no drainage holes required. Consequently, in the holding body 2 and in the nozzle body 3 Also no Bohrverschneidungen available, which in addition to a cost-effective material selection for the holding body 2 contributes.

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - DE 10146743 A1 [0002]

Claims (9)

Fuel injector ( 1 ) for internal combustion engines, with a longitudinally displaceable nozzle needle ( 7 . 13 ), which by their longitudinal movement, the opening of at least one injection port ( 5 ), with a longitudinal high-pressure line, which into a the nozzle needle ( 7 . 13 ) annularly surrounding nozzle chamber ( 9 ), with one to a high-pressure fuel side ( 16 ) connected control room ( 8th ), in which the nozzle needle ( 7 . 13 ) a control surface acting in the closing direction ( 20 ), and with a control valve ( 22 ), the connection of the control room ( 8th ) to a low pressure side ( 25 ) either locks or opens, characterized in that the high pressure line through a nozzle needle ( 7 . 13 ) surrounding high-pressure space ( 14 ) is formed. Fuel injector according to claim 1, characterized in that the annular high pressure space ( 14 ) through a longitudinal bore ( 12 ) is formed, in which the nozzle needle ( 7 . 13 ) is arranged. Fuel injector according to claim 1 or 2, characterized in that the nozzle chamber ( 9 ) in a nozzle body ( 3 ) and the high-pressure chamber ( 14 ) in a holding body ( 2 ) of the nozzle body ( 3 ) are provided. Fuel injector according to one of the preceding claims, characterized in that the nozzle needle is formed in two parts, wherein the one part ( 7 ) in a nozzle body ( 3 ) and the other part ( 13 ) in a holding body ( 2 ) of the nozzle body ( 3 ) are arranged and rigidly interconnected. Fuel injector according to one of the preceding claims, characterized in that the control chamber ( 8th ) over the high-pressure chamber ( 14 ) to the high pressure side ( 16 ) connected. Fuel injector according to one of the preceding claims, characterized in that the control chamber ( 8th ) via an outlet throttle ( 24 ) with the low pressure side ( 25 ) is connectable. Fuel injector according to claim 5, characterized in that the high pressure space ( 14 ) exclusively via the control room ( 8th ) and the outlet throttle ( 24 ) with the low-pressure space ( 25 ) is connected or connectable. Fuel injector according to one of the preceding claims, characterized in that the nozzle needle ( 7 . 13 ) at its at least one injection opening ( 5 ) facing away in a valve piece ( 19 ) of the control valve ( 22 ) with formation of the control room ( 8th ) is guided. Fuel injector according to claim 8, characterized in that the nozzle needle ( 7 . 13 ) by a valve piece ( 19 ) supported closing spring ( 26 ) is tensioned in its closed position.