EP2232044A1

EP2232044A1 - Fuel injector

Info

Publication number: EP2232044A1
Application number: EP08870365A
Authority: EP
Inventors: Bernd Streicher; Ralf Nussbaumer; Rudolf Heinz; Michael Mennicken; Holger Rapp; Christian Faltin; Nadja Eisenmenger
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2008-01-07
Filing date: 2008-12-03
Publication date: 2010-09-29
Anticipated expiration: 2028-12-03
Also published as: EP2232044B1; JP2011508853A; CN101910606B; WO2009086996A1; ATE512298T1; JP5010035B2; DE102008003348A1; CN101910606A

Abstract

The invention relates to a fuel injector, comprising an injector nozzle arrangement for injecting fuel into an internal combustion engine, a control piston moving back and forth inside a piston working space for the actuation of a closing element of an injector nozzle arrangement, a seat-controlled servo-valve arrangement which permits the connection of the piston working space of the control piston, said piston working space communicating with a high-pressure fuel source via an intake throttle, to a relatively pressure-less discharge space in such a way that the control piston, which is biased upon pressure application by the high-pressure fuel source in the direction of the end position associated with the closed position of the closing element of the injector nozzle arrangement, makes a stroke motion which moves the closing element to the open position thereof, wherein the servo-valve arrangement, which is located in an injector body, comprises a valve seat body and a sleeve-like closing body that can be shifted to the open position thereof by an electromagnet against a closing force, said closing body cooperating with an annular seat at the valve seat body and being slideably movable on an axial projection located at the valve seat body centrally with respect to the annular seat.

Description

20/12/2007

ROBERT BOSCH GMBH, 70442 Stuttgart

fuel injector

Technical area

Current motor vehicles regularly have internal combustion engines

Fuel injection. In engines, in particular diesel engines, with direct injection, each cylinder or combustion chamber of the engine is assigned a fuel injector with an injector nozzle arrangement for injecting fuel into the respective combustion chamber. These fuel injectors each have a liftable in a piston working chamber control piston for

Actuation of a closure element of the injector nozzle arrangement and a seat-controlled servo valve arrangement, which allows the communicating via an inlet throttle with a high-pressure source piston working space of the control piston with a relatively pressureless outflow space, so that when pressure is applied by the high pressure source in the direction of

Closing position of the closure element of the injector nozzle assembly associated Schließendlage acted control piston executes a closure element leading to its open position stroke in the direction of its open end, said arranged in an injector servo valve assembly a valve seat body and a through a

Electromagnet against a closing force in its open position adjustable sleeve-shaped closing body which cooperates with an annular seat on the valve seat body and is displaceably guided on a valve seat body arranged centrally to the annular seat axial extension, and wherein in the open position of the sleeve-shaped closing body within the Closing body formed on the axial extension and communicating with the piston working chamber of the control piston valve space is connected under pressure relief to the outflow chamber.

Such a fuel injector is described by way of example in EP 1612403 A1.

In this known fuel injector disposed on the valve seat body axial extension passes through the entire interior of the sleeve-shaped closing body of the servo valve assembly, wherein at a valve seat remote end of the sleeve-shaped closing body outstanding part of the axial extension a stop for limiting the Axialhubes of the sleeve-shaped

Valve-closing body is arranged. Near the valve seat, a ringnutförmige recess is formed on the axial extension, so that within the valve closing body of the corresponding ring-shaped valve space is created, which is provided via a provided with an outlet throttle bore, which is arranged in the valve seat body, with the piston working space of

Control piston communicates and is connected to the outside of the sleeve-shaped closing body arranged outflow space as soon as the sleeve-shaped closing body lifts off from its seat on the valve seat body.

The sealing of the annular gap between the inner circumference of the sleeve-shaped

The closing body and the outer circumference of the axial extension on the side remote from the valve seat side of the annular valve space within the sleeve-shaped closing body is effected by high pressure resistant seals.

This known fuel injector has a manufacturing-consuming

Construction. For the hydraulic connection of the piston working chamber of the control piston with the valve chamber within the sleeve-shaped closing body of the servo valve assembly, an axial blind bore is provided within the axial extension, which forms in the region of the aforementioned valve space annular groove constriction of the axial extension of

Radial holes is penetrated with leading into the valve chamber mouths. According to the cycle of the opening or closing strokes of the servo valve arrangement, these bores are subjected to extreme pressure pulsations, so that the valve seat body and the axial extension are subjected to this high-quality plastic materials have to be made in order to ensure the stability of the known fuel injector.

According to older, not previously published patent applications (R.316364, R.314516) can be provided that the formed in the tubular closing body valve space is closed at the valve seat remote end of the closing body by a projecting into the closing body in the manner of a plunger guide rod, the pressure in the valve chamber pressed against a bottom surface of the injector body and thus urged into a vertical position to the bottom surface and aligns the closing body accordingly. The closing body cooperates with a flat seat parallel to the bottom surface, which annularly encloses an opening of a channel connecting the piston working space with the valve space in the valve seat body and leading into the valve space. Such injectors offer the advantage of a very high compressive strength. However, the longitudinal axis of the closing body may shift slightly in the sideways direction, because the guide rod has a corresponding mobility. This has the consequence that the closing body has to cooperate sealingly with a correspondingly offset annular zone of the seat. This can result in a critical closing behavior of the servo valve arrangement. This applies in principle even if the valve seat according to an older not previously published

Patent application has the shape of the surface of a spherical section.

The object of the invention is now, fuel injectors with respect to pressure pulsations in principle comparatively insensitive construction and with ease of manufacture and good closing behavior of

Servo valve arrangement to create.

This object is achieved in a fuel injector of the type specified by the characterizing features of claim 1.

The invention is based on the general idea of providing a separate part from the valve seat body for the closure of the end remote from the valve seat body of the sleeve-shaped closing body of the servo valve. As a result, the design and manufacture of the valve seat body is simplified, furthermore, the need for the arrangement of a strong compared Interference stresses sensitive zone avoided on the axial extension of the valve seat body.

In addition, the invention provides to guide the closing body valve seat side, so that the valve seat side ring zone, with which the closing body sealingly cooperates, has a fixed position in principle unchangeable. In the invention, on the one hand, a valve seat-side guide of the closing body and on the other hand a separate valve seat for sealing the valve seat facing away from the end of the closing body is provided, a high stability of the injector against pressure pulsations and an excellent

Realize closing behavior of the servo valve assembly of the injector. At the same time a simple manufacturability is ensured because the channel connecting the valve chamber with the piston working space is formed as an axial passage in the axial extension.

According to an advantageous embodiment of the invention, the valve seat body facing away from the end of the plunger rod with a fixed disc-shaped foot rest flat on a bottom of the injector body, which may be useful additionally provided that the foot piece is arranged on the floor with radial play and the sleeve-shaped Closing body is guided at least limited wobble on the axial extension of the valve seat body. During operation of the fuel injector, the plunger rod is tensioned with its foot piece by the hydraulic pressure in the valve chamber within the sleeve-shaped closing element of the servo valve against the bottom of the injector body. Thus, the plunger rod assumes a position orthogonal to the bottom and guides the sleeve-shaped closing body in the direction orthogonal to the ground. The centering of the closing body relative to the seat on the valve seat body is taken over in this embodiment of the axial extension of the valve seat body. As a result, therefore, a self-aligning arrangement is achieved.

According to an alternative embodiment, the plunger rod with its end facing away from the valve seat body end also supported radially movable and wobble on a facing bottom of the injector body and the sleeve-shaped closing body untaumelbar on the axial extension of the Be guided valve seat body hubbeweglich. Here, therefore, the exact stroke direction of the sleeve-shaped closing body and its radial orientation by the valve seat body or guide elements arranged thereon are given, while the plunger rod essentially takes on the task of closing the valve seat body facing away from the end of the sleeve-shaped closing body.

The annular gap between the inner circumference of the sleeve-shaped closing body and the outer circumference of the plunger rod can in basically conventional manner by high-pressure-resistant seals, for example by in annular grooves on

Outer circumference of the plunger rod used sealing rings. This applies to all embodiments of the invention. Instead, it is also possible and advantageous to form said annular gap as a high-pressure-tight throttle gap, i. The radial dimension of the annular gap is so small and the axial dimension so large that even in the operating phases, in which

Valve space within the sleeve-shaped closing body maximum high pressure is present, only a vanishing leakage current is expected. Such an embodiment has the advantage that the sleeve-shaped closing body is mounted hydraulically on the plunger rod during operation of the fuel injector and thus no direct contact between the inner circumference of

Closing body and the outer periphery of the plunger rod can occur. Furthermore, the assembly is simplified because separate sealing elements omitted.

Moreover, in terms of preferred features of the invention on the

Claims and the following explanation of the drawing referenced.

Protection is claimed not only for expressly given or illustrated combinations of features but also for any combination of the stated or illustrated features.

In the drawing shows

Fig. 1 is an axial section of a first embodiment of a

Fuel injector and Fig. 2 is an axial section of another embodiment.

According to FIG. 1, the fuel injector shown there in axial section has an injector body 1 with a stepped axial bore 2. On a lower stage of the axial bore 2 in FIG. 1, a valve seat body 3 with a molded-on body part 3 is formed on it

Collar 3 'mounted axially. For fixing the valve seat body 3 in the axial bore 2 is an external threaded ring 4, which is screwed into an internally threaded portion of the axial bore 2 and by screw adjustment against the facing end face of the collar 3 'is stretched. Through the valve seat body 3 and the collar 3 'is within the

Axial bore 2 a high pressure area 2 ', which communicates by non-illustrated lines constantly with a high pressure fuel source, from a downstream or low pressure area 2 "separated, which is connected via non-illustrated return lines with a relatively pressureless fuel reservoir.

In the lower end of the valve seat body 3 serving as a piston working space 5 for a control piston 6 blind bore is arranged.

The control piston 6 is connected to a nozzle needle or another

Closing element connected to the injector nozzle arrangement of the fuel injector, not shown. In the illustrated lower end position of the control piston 6, the injector nozzle arrangement is closed. If the control piston 6 is moved upward in FIG. 1, the injector nozzle arrangement is opened, so that fuel in the assigned

Combustion chamber of an internal combustion engine is injected.

About a designed as a radial bore of the valve seat body 3 inlet throttle 7 communicates the piston working chamber 5 with the high-pressure region 2 'of the axial bore 2. About a coaxial to the piston working space 5 axial bore

8, which is arranged in the valve seat body 3 and provided with an outlet throttle 9, the piston working chamber 5 communicates with a valve chamber 10 which is arranged axially in front of the front end of the valve seat body 3 arranged axial extension 11 within a sleeve-shaped closing body 12 of a servo valve assembly 13 and on the of Valve seat body 3 opposite end of the sleeve-shaped closing body 12 is closed by a protruding into the sleeve-shaped closing body 12 plunger rod 14. Against the possibly occurring in the valve chamber 10 hydraulic pressure plunger rod 14 by means of a fixed at its in Fig. 1 upper end disk-shaped foot piece 15 on a bottom 16 of the

Injector body 1 comparatively large area supported. The foot 15 serves as an abutment for a trained as a helical compression spring closing spring 17, which seeks to clamp the sleeve-shaped closing body 12 with its in Fig. 1 lower end against a formed on the valve seat body 3, to the axis of the axial extension 11 conical conical valve seat 18. Against the

Closing force of the closing spring 17, the sleeve-shaped closing body 12 can be excavated from the closed position shown in Fig. 1 by means of an annular electromagnet 19 which cooperates with the closing body 12 radially arranged radial armature webs 20. In the open position of the closing body 12 of the servo valve assembly 13 communicates the

Valve chamber 10 with the downstream or low pressure region 2 "of the axial bore 2. Here, a largely throttle-free connection between the valve chamber 10 and the low pressure region 2" of the axial bore 2 is given because the cross section of the axial extension 11 of the valve seat body 3 is formed substantially star-shaped in such a way that the axial extension 11 slidably rests on the inner circumference of the sleeve-shaped closing body with star-shaped axial webs. In the circumferential direction between the axial webs remain larger open spaces over which the valve chamber 10 communicates with lifted off from the seat 18 closing body 12 with the low pressure region 2 "of the axial bore 2.

Instead of the axial extension 11 provided with star-shaped axial webs, it is also possible to provide an axial extension designed as a triflane, four-flattened or multi-flattened one.

The radially adjoining the axial bore of the closing body 12 end edge is formed as an inner cone whose opening angle is greater than the cone angle of the conical valve seat 18. Thus, on the one hand, a ring-shaped contact between the closing body 12 and valve seat 18 is ensured in the closed position closing body 12. On the other hand, at provided in the open position closing body 12, an annular opening gap, the axial cross-section increases radially outward.

The fuel injector of Fig. 1 functions as follows:

As long as the closing body 12 of the servo valve 13 assumes the illustrated closed position, the pressure prevailing in the high-pressure region 2 'of the axial bore 2 of the high-pressure fuel source communicating therewith is present in the piston working space 5 of the control piston 6. By energizing the electric coil 19 'of the electromagnet 19, the electromagnet 19 can now be activated, so that the magnetically cooperating armature webs 20 attracted and the closing body 12 is lifted against the force of the closing spring 17 from the closed position shown in Fig. 1. Thus, the piston working space 5 of the control piston 6 via the valve chamber 10 with the connected to the relatively pressureless fuel reservoir downstream or

Low pressure range 2 "of the axial bore 2 connected so that the pressure in the piston working chamber 5 drops accordingly, the time course of the pressure drop essentially by the dimensions of the inlet throttle 7 and the outlet throttle 9, the throttle resistance is lower than the throttle resistance of the inlet throttle 7, is specified. Due to this pressure drop, the

Control piston 6 raised by hydraulic forces acting on the connected to the control piston 6, usually needle-shaped closure element of the injector nozzle assembly, not shown, in the opening direction. This also has the consequence that the high-pressure region 2 'of the axial bore via the now open injector nozzle arrangement with the associated

Combustion chamber of the internal combustion engine connected and fuel is injected into the combustion chamber.

During its strokes, the closing body 12 is held radially centered relative to the conical valve seat 18 by the axial extension 11 or its axial extension, which is slidable on the inner circumference of the closing body 12. The Plungerstange 14 takes a correspondingly centered, ie the axial extension 11 equiaxial position, because the circular disk-shaped foot piece 15 is disposed within the annular electromagnet 19 with sufficient radial clearance and surface on the axis of the axial extension 11 vertical bottom 16 rests. To keep unwanted constraining forces acting on the closing body 12 as low as possible, it can be provided according to a preferred embodiment that the closing body 12 is guided in a tumble on the axial extension 11 and the stroke direction of the closing body 12 is predetermined solely by the plunger rod 14, which by means of the

Footpiece 15, which rests flat on the floor 16 is held in a direction orthogonal to the bottom 16.

The embodiment shown in Fig. 2 differs from the embodiment of Fig. 1, first in that the plunger rod 14 is supported wobble on the bottom 16 of the injector body 1, wherein the supported end of the plunger rod 14 within an annular disc 21 or the annular disc 21 within the annular electromagnet 19 are arranged with a certain radial clearance, so that the support point of the plunger rod 14 can move on the floor 16 radially to the rod axis.

In addition, the closing body 12 is guided in Fig. 2 untaumelbar axially displaceable on the axial extension 11 of the valve seat body 3, i. the position of the closing body 12 radially to the axis of the valve seat body 3 and the stroke direction of the closing body 12 are determined exclusively by the axial extension 11, which has a sufficient axial length and a sufficient axial overlap with the closing body 12. The position of the plunger rod 14 and its axial orientation are then determined by the closing body 12 and, accordingly, indirectly by the axial extension 11. In addition, in the embodiment of FIG. 2, an annular disc-shaped, flat valve seat 18 is provided, on which the closing body 12 in his

Closed position with ring-shaped contact is seated. For this purpose, the valve seat 18 facing the end face of the closing body 12 is slightly conical, so that at the transition between the valve seat side end face of the closing body 12 and the axial bore an acute-angled annular edge, which cooperates with the valve seat 18 is formed.

Functionally, the embodiment of FIG. 2 corresponds to the embodiment of FIG. 1, so that reference may be made to the corresponding above statements. Both in the embodiment of Fig. 1 and in the embodiment of Fig. 2, the annular gap between the outer periphery of the plunger rod 14 and the inner periphery of the closing body 12 can be sealed high pressure resistant by sealing rings, which are similar to the sealing rings 22 of the control piston 6 in the manner of piston rings may be arranged in circumferential grooves of the plunger rod 14.

Instead, it is also possible and provided according to an advantageous embodiment of the invention to form this annular gap as a high pressure-tight throttle gap, such that virtually only vanishing leakage currents can occur even at high hydraulic pressure differences between the axial ends of said annular gap. This can be ensured by an extremely narrow radial gap and a sufficiently large axial overlap between closing body 12 and plunger rod 14. The particular advantage of such training is that at

Hubbewegungen the closing body 12 relative to the plunger rod 14 no mechanical contact or friction between these parts occurs, but the closing body 12 is mounted hydrodynamically on the plunger rod with the interposition of a hydraulic layer.

Possibly. can also be the control piston 6 arranged in the piston working space 5 forming axial bore of the valve seat body 3 with high pressure-tight throttle gap.

Such a throttle gap offers the further advantage that account for their assembly carefully handled sealing rings.

Notwithstanding the illustrated in Fig. 2 embodiment shown supported on the bottom 16 spherical end of the plunger rod 14 may be formed with the omission of the annular disc 21 as a mushroom head, which is supported with its convex side on the floor 16 and its from the bottom 16 opposite side forms an abutment surface for the closing spring 17. The diameter of the mushroom head is expediently dimensioned so that within the annular electromagnet 19 still a certain amount of radial play for a force-free alignment of the plunger rod 14 remains, ie the Plunger rod 14 can zwangskraftfrei take their equiaxial to the closing body 12 position.

Claims

claims

1. A fuel injector with an injector nozzle arrangement for injecting fuel into an internal combustion engine, a piston in a piston working space (5) liftable control piston (6) for actuating a closure element of the injector nozzle assembly, a seat-operated servo valve assembly (13) which via an inlet throttle (8) with a Fuel pressure source communicating piston working space of the control piston with a relatively pressureless Abstromraum (2 ") to connect, such that the pressure applied by the high-pressure fuel source in the direction of the closing position of the closure element of the injector nozzle arrangement associated end position acted upon

Control piston (6) executes a the closing element in its open position stroke, wherein in an injector body (1) arranged servo valve assembly (13) has a valve seat body (3) and one by an actuator or electromagnet (19) against a closing force (17) in its open position adjustable sleeve-shaped

Closing body (12) which cooperates with an annular seat (18) on the valve seat body (3) and on a valve seat body (3) centrally to the annular seat (18) arranged axial extension (11) with deviating from the inner cross section of the sleeve-shaped closing body or non-circular Cross-section is slidably guided, and wherein in the open position of the

Closing body (12) within the sleeve-shaped closing body (12) on the axial extension (11) formed and with the piston working space (5) of the control piston (6) communicating valve space (10) is connected under pressure relief to the Abstromraum (2 "), characterized that of the axial extension (11) of the valve seat body (3) facing away from the end of the valve chamber (10) or the interior of the sleeve-shaped closing body (12) is closed by an axially projecting into the closing body plunger rod (14) whose axial extension of the (11) facing away from the axial end is supported axially on a bottom (16) of the injector body (1), and that the valve space (10) with the piston working space (5) via a

Axialfortsatz axially passing, with a throttle (9) provided channel (8) communicates.

2. Fuel injector according to claim 1, characterized in that the valve seat body (3) facing away from the end of the plunger rod (14) with a fixed thereto disc-shaped foot piece (15) rests flat on the floor (16).

3. Fuel injector according to claim 1 or 2, characterized in that the foot piece (15) or the plunger rod (14) on the bottom (16) with radial

Game are arranged.

4. Fuel injector according to one of claims 1 to 3, characterized in that the sleeve-shaped closing body (12) on the axial extension (11) is guided wobble.

5. Fuel injector according to one of claims 1 to 4, characterized in that the Plungerstange (14) with its valve seat from the body (3) facing away from the end radially movable and wobble on the floor (16) is supported.

6. Fuel injector according to claim 5, characterized in that on the bottom (16) supported end of the plunger rod (14) is formed with spherical end side.

7. Fuel injector according to one of claims 1 to 6, characterized in that the sleeve-shaped closing body (12) on the axial extension (11) is guided untaumelbar.

8. Fuel injector according to one of claims 1 to 7, characterized in that between the inner periphery of the sleeve-shaped closing body (12) and the outer circumference of the plunger rod (14) existing annular gap is designed as a high-pressure-tight throttle gap.