WO2008049666A1

WO2008049666A1 - Injector having a control valve which has a conical stroke stop face

Info

Publication number: WO2008049666A1
Application number: PCT/EP2007/058921
Authority: WO
Inventors: Hans-Christoph Magel
Original assignee: Robert Bosch Gmbh
Priority date: 2006-10-24
Filing date: 2007-08-28
Publication date: 2008-05-02
Also published as: DE102006050032A1

Abstract

The invention relates to an injector (1) for injecting fuel into combustion chambers of internal combustion engines, in particular a common-rail injector, having an actuator (30) which is arranged so as to axially actuate a valve piston (36) of an axial pressure-compensated control valve (31) between a valve seat face (40) and an opposite stroke stop face (47), wherein, by means of the control valve (31), the pressure in a control chamber (20) can be influenced and a nozzle needle (8) can thereby be adjusted between an open position, in which a fuel flow is enabled, and a closed position. It is provided according to the invention that the stroke stop face (47) is conically shaped.

Description

description

title

Injector with a control valve with a conical stroke stop surface

State of the art

The invention relates to an injector according to the preamble of claim 1.

EP 1 612 403 A1 describes a common-rail injector with a pressure-balanced control valve in the axial direction for blocking and opening a fuel discharge path from a control chamber. By means of the control valve, the fuel pressure can be influenced within the control chamber, wherein the control chamber is supplied via a pressure channel (throttle bore) with fuel from an annular chamber connected to a high-pressure fuel storage. By varying the fuel pressure within the control chamber, a nozzle needle is moved between an open position of a closed position, wherein the nozzle needle in its open position releases the fuel flow into the combustion chamber of an internal combustion engine. The axial travel of the valve sleeve is limited on the one hand by a stationary valve seat surface and on the other hand by a Hubanschlagsfläche. In the known injector, the Hubanschlagsfläche is formed by a flat annular surface of a locking ring which is received in a circumferential groove of a valve sleeve passing through the pin. The switching behavior of the control valve is affected by abutment bouncers of the valve sleeve on the flat Hubanschlagsfläche. For damping the abutment bounce, it is known, the anchor surfaces of a Valve sleeve actuated solenoid drive form as large as possible. In this case, however, there are large tolerance problems caused by the non-negligible influences of the fuel temperature, the air content and the return pressure. Furthermore, large-surface anchor surfaces cause a delay in the closing movement, which has a negative effect on the switching times and thus on the multiple injection capability of the injector.

DISCLOSURE OF THE INVENTION Technical Problem

The invention is therefore based on the object to propose an injector in which abutment bumpers of the valve sleeve on the lifting stop surface are damped in a simple manner with minimized negative effects on the switching time.

Technical solution

This object is achieved with the features of claim 1. The dependent claims indicate favorable developments of the invention. In addition, all combinations of at least two of the features disclosed in the description, the drawings and / or the claims fall within the scope of the invention.

The invention is based on the idea, instead of a flat Hubanschlagsfläche a conically shaped Huban- strike surface to provide, which cooperates with a corresponding counter-cone of the valve sleeve or a fixedly connected to the valve sleeve member. The provision of a conical stroke stop makes a good stop achieved damping and effectively prevents abutment bounce. In this case, only a small radial Hubanschlagsfläche is advantageously required to realize a large hydraulic and mechanical stop damping. As a result, negative effects of the impact damping on the closing and / or opening time of the control valve can be significantly reduced. The control valve is preferably a pressure-balanced valve in the axial direction. In a pressure-balanced control valve in the axial direction, no or only minimal pressure forces in the axial direction act on the valve piston when the control valve is closed. A realization of such an axially pressure compensated control valve can be realized in a simple manner by using a valve sleeve with a sleeve bore, wherein the sleeve bore has the same diameter as the valve seat. The valve sleeve is preferably with its inner diameter sealingly against the valve seat surface. By providing an axially-pressure compensated control valve only low spring forces and / or low actuator switching forces, in particular low magnetic forces for actuating and / or holding the control valve in its closed position are required. This in turn has advantageous effects on the stop behavior of the valve piston, in particular a valve sleeve, as well as on the maximum space required. Furthermore, smaller valve piston strokes and thus faster switching times can be realized, whereby the multiple injection capability is improved.

For receiving the pressure forces acting in the axial direction, a bolt is advantageously provided, which is received in the axial direction within the valve sleeve. This bolt transmits the pressure forces to an injector body. For this purpose, the bolt can either be firmly connected to the injector body or formed integrally therewith. It is also conceivable that the bolt has no fixed connection to the injector body, but is supported only on this. In this case, the bolt is pressed against the injector body, for example, by the fuel pressure acting on it.

It is particularly advantageous if the conical stroke stop surface is integrally formed on the bolt. As a result, the concentricity of Hubanschlagsfläche is significantly increased to the adjustment of the valve sleeve.

Any angular errors between the valve sleeve and Hubanschlags- surface can be reduced according to an advantageous development of the invention characterized in that the valve sleeve, preferably high pressure-tight, is guided with its inner circumferential surface on the outer surface of the bolt.

An additional damping of the stop of the valve sleeve on the Hubanschlagsfläche can be achieved according to an advantageous embodiment of the invention, that within the valve sleeve, a damping chamber is provided which is bounded on the one hand by the valve sleeve and on the other hand, by the end face of the bolt. To achieve the damping property of the damping chamber is advantageously connected hydraulically via at least one throttle with a valve seat chamber, wherein the valve seat chamber is in turn connected hydraulically to the control chamber. Via the valve seat chamber, fuel can flow out of the control chamber with the control valve open in a region with low fuel pressure. In a further development of the invention is advantageously provided that the actuator is designed as an electromagnetic drive, wherein at least one anchor plate is provided which is fixed to the valve piston, in particular the valve sleeve, connected or formed integrally therewith, to the valve piston when energized Electromagnetic actuator to adjust in the axial direction. Of course, it is conceivable to provide, for example, a piezoelectric actuator instead of an electromagnetic drive.

Preferably, the valve piston, in particular on its upper, the valve seat surface facing away from an inner cone, which cooperates with an outer cone (Hubanschlagsfläche). In this case, inner cone and outer cone are formed congruent with each other. Alternatively, it is conceivable that the valve piston has an outer cone and cooperates with a shape-congruent inner cone-shaped Hubanschlagsfläche, for example, on the injector body or on a component connected thereto, in particular a bolt.

Brief description of the drawings

Further advantages, features and details of the invention will become apparent from the following description of a preferred embodiment and from the drawing; 1 shows a highly schematized injector with a control valve, the valve sleeve of which is provided with an inner cone which cooperates with a cone-shaped lifting stop surface. Embodiment of the invention

In the only Fig. 1, an injector 1 is shown. The injector 1 has an injector body 2, a nozzle body 3 and a throttle plate 4 accommodated between the nozzle body 3 and the injector body 2. A nozzle retaining nut 5 is screwed to the injector body 2 and thus clamps the nozzle body 3 and the throttle plate 4 against the injector body 2.

The nozzle retaining nut 5 coaxially surrounds the throttle plate 4 and partially the injector body 2 and the nozzle body 3. The nozzle body 3 passes in the axial direction through a through hole 6 of the nozzle retaining nut fifth

Within the nozzle body 3, a guide bore 7 is formed, in which an elongated, in this embodiment, one-piece nozzle needle 8 is guided axially movable. Instead of a one-piece nozzle needle 8, a multi-part nozzle needle can be used, wherein the individual parts are operatively connected to each other. At a needle point 9, the nozzle needle 8 has a closing surface 10 with which it can be brought into tight contact with a needle seat 11 formed inside the nozzle body 3.

When the nozzle needle 8 abuts the needle seat 11, ie, is in a closed position, the fuel outlet from a nozzle hole arrangement 12 is blocked. If, on the other hand, it is raised by the needle seat 11, fuel can flow from a high-pressure space 13 formed between the nozzle needle 8 and the peripheral jacket of the guide bore 7 and an annular space 14 arranged below it in the direction of flow to the needle. delsitz 11 flow to the nozzle hole assembly 12 and there are injected substantially under the high pressure (rail pressure) standing in a combustion chamber. The high-pressure chamber 13 is hydraulically connected via a supply line 15 to a high-pressure fuel accumulator 16, which is supplied with fuel, for example via a radial piston pump, not shown.

The nozzle needle 8 is biased by a biasing spring 17 in the direction of its closed position. For this purpose, the biasing spring 17 is supported at one end on a held on the outer circumference of the nozzle needle 8 retaining ring 18 and the other end on a sleeve-shaped member 19, which in turn is supported on the throttle plate 4. The component 19 and the throttle plate 4 may also be integrally formed.

Within the component 19, a control chamber 20 is arranged, which is supplied via a pressure channel 21 with inlet throttle 22 with fuel under high pressure. The pressure channel 21 connects the control chamber 20 with an annular space 23 within the nozzle body 3, wherein the annular space 23 is connected via a supply line 24 to the high-pressure fuel reservoir 16.

The nozzle needle 8 projects through a bore 25 in the component 19 with its upper end face 26 into the control chamber 20, so that the fuel pressure within the control chamber 20 acts on the nozzle needle 8 in the axial direction.

The control chamber 20 is provided with a flow restrictor 27 equipped with a drain hole 28, which is both the component 19 as well as the throttle plate 4 passes through, connected to a Kraftstoffabflussweg 29.

By means of an electromagnetic actuator 30, a pressure-balanced control valve 31 in the axial direction can block the fuel flow to the outflow line 29.

By the biasing spring 17 and the action of the pressure prevailing in the control chamber 20 pressure on the end face 26 an axially directed toward the combustion chamber closing force is exerted on the nozzle needle 8. This closing force acts axially against an opening force, which is exerted on the nozzle needle 8 as a result of the action of the pressure prevailing in the high-pressure chamber 13 on a cone surface 32 formed on the nozzle needle 8. If the control valve 31 is in a closed position and the fuel drain is blocked by the drainage bore 28, the closing force is greater than the opening force in the stationary state, for which reason the nozzle needle 8 then assumes its closed position. If the control valve 31 is then opened, fuel flows from the control chamber 15 into a low-pressure chamber 33 and from there through the discharge path 29. Depending on the operating state, the fuel pressure in the low-pressure space 33 is approximately between 0 and 10 bar. By contrast, the fuel pressure in the annular space 23 and in the high-pressure space 13 is approximately 1800 to 2000 bar.

The flow cross-sections of the inlet throttle 22 and the outlet throttle 27 are coordinated so that the inflow through the pressure channel 21 is weaker than the outflow through the drain hole 28 and thus results in open control valve 31, a net outflow of fuel. The resulting pressure drop in the control chamber Mer 15 causes the amount of closing force drops below the amount of the opening force and the nozzle needle 8 lifts from the needle seat 11.

The low-pressure space 33 is bounded radially on the outside by an armature stroke adjusting ring 34, via which the actuator 30 is supported on the throttle plate 4.

The control valve 31 comprises a valve sleeve 36 (valve piston) which can be displaced in the axial direction and which is firmly connected to an anchor plate 37 or formed integrally therewith. The armature plate 37 cooperates with an electromagnet 38 of the electromagnetic actuator 30 and is received radially within the Ankerhubeinstellrings 34.

The valve sleeve 31 is supported on the injector body 2 by a coil spring 39 and is urged by the coil spring 39 in the direction of its closed position, i. Federkraftbeaufschlagt in the direction of a valve seat surface 40.

The coil spring 39 is received in a through hole 41 within the actuator 30. Radially within the coil spring 39, a bolt 42 is arranged, which is supported with its upper surface 43 in the plane of the drawing on the injector 2. With a lower portion 44 of the bolt 42 is received within the valve sleeve 36, wherein the valve sleeve 36 is guided high pressure-tight in the axial direction at the lower portion 44.

The lower portion 44 is in its upper end in the drawing plane via a conically shaped shoulder 45 in an upper portion 46 with a larger Diameter over. In other words, the two cylindrical sections 44, 46 are connected to one another via the conical shoulder 45 that tapers in the direction of the needle point 9, preferably in one piece. The outer surface of the conical shoulder 45 forms a Hubanschlagsfläche 47 for abutment of an inner cone 48 which is provided on the plane of the drawing in the upper portion of the valve sleeve 36. The inner cone 48 is made by chamfering the sleeve bore 49. Inner cone 48 and paragraph 45 (outer cone) are formed congruent with each other and are in the open position of the control valve 31, so lifted at the valve seat surface 40 valve sleeve 36 to each other and thus dampen Auflaufpreller between the valve sleeve 36 and bolt 42nd

The lower end face 50 of the bolt 42 delimits a damping chamber 51 within the valve sleeve 36. The damping chamber 51 is connected to a valve seat chamber 54 via a throttle bore 52 within the throttle chamber bottom 53. Upon movement of the valve sleeve 36 from the valve seat surface 40 in the direction of the stroke stop surface 47, fuel is displaced through the throttle bore 52 in the valve seat chamber 54 and flows from there into the low-pressure chamber 33 and from there via the passage opening 41 to the discharge path 29. that the fuel must flow through the throttle bore 52, the closing movement and thus the impact of the inner cone 48 is damped at the Hubanschlagsfläche 47.

The control valve 31 is, as mentioned, a pressure balanced in the axial direction valve. For this purpose, the valve sleeve 36 abuts with its inner contour 35 on the annular valve seat surface 40. The diameter The lower portion 44 of the bolt 42 corresponds to the inner diameter of the valve seat chamber 54 and the inner diameter of the damping chamber 51. To optimize the valve design of the lower portion 44 of the bolt 42 may also have a slightly smaller diameter than the valve seat surface 40th

Claims

claims

1. injector for injecting fuel into combustion chambers of internal combustion engines, in particular common rail injector (1), with an actuator (30) having a valve piston (36) of a particular axially pressure-balanced control valve (31) between a valve seat surface ( 40) and an opposite Hubanschlagsfläche (47) is axially actuated, wherein by means of the control valve (30) the pressure in a control chamber (20) influenced and thereby a nozzle needle (8) between the fuel flow releasing open position and a closed position is adjustable , characterized in that the Hubanschlagsfläche (47) is conically shaped.

2. Injector according to one of the preceding claims, characterized in that the valve piston (36) is designed as a valve sleeve (36).

3. An injector according to claim 2, characterized in that in the valve sleeve (36) integral with an injector body (2) connected, or integrally formed therewith or is supported on this bolt (42) is added.

4. An injector according to claim 3, characterized in that the conical Hubanschlagsfläche (47) on the bolt (42) is formed

5. Injector according to one of claims 3 or 4, characterized in that the valve sleeve (36) is guided high pressure-tight on the bolt (42).

6. Injector according to one of claims 3 to 5, characterized in that within the valve sleeve (36) of the bolt (42) limited damping space (51) is arranged.

7. An injector according to claim 6, characterized in that the damping chamber (51) via at least one throttle bore (52) is hydraulically connected to a valve seat chamber (54).

8. Injector according to one of the preceding claims, characterized in that the actuator (30) is designed as an electromagnetic drive and cooperates with at least one armature plate (37) which is fixedly connected to the valve piston (36) or formed integrally therewith.

9. Injector according to one of the preceding claims, characterized in that the valve piston (36) or a component connected to it an inner cone (48) for abutment against the outer cone-shaped Hubanschlagsfläche (47) has up.

10. Injector according to one of claims 1 to 8, characterized that the valve piston (36) or a component connected to it has an outer cone for abutment with the inner cone-shaped Hubanschlagsfläche (47).