EP2156048A1

EP2156048A1 - Injector

Info

Publication number: EP2156048A1
Application number: EP08759584A
Authority: EP
Inventors: Bernhard Arnold; Thomas Sommer; Friedmar Dresig
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2007-06-01
Filing date: 2008-05-14
Publication date: 2010-02-24
Also published as: CN101680407A; DE102007025615A1; BRPI0810792A2; WO2008145517A1

Abstract

The invention relates to an injector (1) for injecting fuel into a combustion chamber of an internal combustion machine, particularly a common rail injector, having a valve element adjustable between a closed position and an open position allowing fuel to flow into the combustion chamber as a function of the pressure in a control chamber (23), and having a control valve (24) by means of which the pressure in the control chamber, which is hydraulically connected to a high-pressure region of the injector (1) via an inlet throttle (19), can be influenced. According to the invention, it is provided that the inlet throttle is introduced into the valve element (4).

Description

description

Title Injector

State of the art

The invention relates to an injector for injecting fuel into a combustion chamber of an internal combustion engine, in particular a common rail injector, according to the preamble of claim 1.

From DE 198 27 267 Al a designed as a common-rail injector injector for injecting fuel into a combustion chamber of an internal combustion engine is known. The known injector comprises a two-part valve element consisting of a control rod and a nozzle needle. In this case, the control rod is longitudinally displaceable in an injector body (part of the injector). With its end face, the control rod delimits a control chamber arranged in a valve element accommodated in the injector body, which is supplied with high-pressure fuel from an annular space (high-pressure region) within the injector body with fuel under high pressure via an inlet throttle. With the control valve open, fuel flows from the control chamber into a low-pressure region of the injector and from there to an injector return, the flow cross sections of the outlet throttle and the inlet throttle are coordinated so that a net outflow from the control chamber results, whereby the valve element is lifted from its valve seat and thus fuel from a nozzle hole arrangement in the combustion chamber of the internal combustion machine can flow. The guide function for the axially displaceable guidance of the control rod is taken over by the valve piece accommodated in the injector body into which the inlet throttle for supplying the control chamber with fuel under high pressure is introduced. The well-known injector has proven itself. However, there are efforts to simplify the structure of the injector while increasing the strength of the injector body.

DISCLOSURE OF THE INVENTION Technical Problem

The invention is therefore based on the object to propose an injector with a simplified structure and preferably an increased pressure resistance.

Technical solution

This object is achieved with the features of claim 1. Advantageous developments of the invention are specified in the subclaims. All combinations of at least two features specified in the description, the claims and / or the figures also fall within the scope of the invention.

The invention is based on the idea of not integrating the inlet throttle for supplying the control chamber with high-pressure fuel as in the prior art in a sleeve-shaped portion of a valve piece or in a valve fitting on the sleeve, but the inlet throttle directly in the one-piece or multi-part Provide valve element. The concept of the invention makes it possible according to the subclaims to realize advantageously further developed injector. In particular, due to the invention can be dispensed with a sleeve-shaped portion of the valve piece or a replacement this separate sleeve for receiving the inlet throttle. Therefore, it is possible to reduce the diameter of the injector body (housing part of the injector) and / or to increase the pressure resistance of the injector body, since the wall thickness of the injector can be increased with a constant or even smaller injector diameter. A diameter reduction of the injector advantageously has a material and thus a weight saving result. The inlet throttle is preferably a throttle bore introduced radially into the valve body. Advantageously, the throttle bore is associated with a radially outwardly widening recess in the valve element in order to equalize the flow through the inlet throttle.

In an embodiment of the invention is advantageously provided that the control chamber is at least partially radially outwardly bounded directly by the injector body of the injector. It is therefore deliberately dispensed with a separate component to the radially outer boundary of the control chamber. In particular, a sleeve-shaped section of a valve piece or a control chamber limiting in the prior art, the valve piece fitting sleeve is omitted, whereby the injector body can be made narrower than in the prior art and possibly the compressive strength of the injector with the same or even smaller diameter can be increased. In the context of the development, it is that the axial portion of the control chamber, which is bounded radially outside of the injector, is only temporarily limited by the injector body or only occasionally, in particular when the valve element is closed, even exists, in particular because the axial section is completely occupied by the valve element when the valve element is open.

It is particularly advantageous if the valve element, which delimits the control chamber in the axial direction, is guided directly on the injector body, that is to say on a housing part of the injector enclosing at least one pressure chamber and a valve element section. The provision of a guide sleeve for axially displaceable guidance of the valve element is superfluous due to the development of the invention. The circumferential gap between the valve element and the injector body simultaneously forms a sealing gap for sealing the control chamber in the direction of the injector tip.

Of particular advantage of an embodiment, according to which the inlet throttle is hydraulically connected via a bore, preferably an axial bore, more preferably via a central axial bore in the valve element with the radially outwardly of the injector limited axial portion of the control chamber. In this case, the bore is part of the control chamber, that is, of the fuel in it acts in closed in the direction of the low pressure region of the injector control chamber, a closing force on the valve element. The diameter of this bore is advantageously chosen so that the expansion of the valve element in its guide section leads to a favorable gap formation of the circumferential gap in the valve element and injector body in terms of tightness and wear. Preferred is an embodiment in which the control chamber on the opposite side of the valve member by a valve piece, in particular a throttle plate is limited, wherein in the valve piece an outlet throttle is introduced, through which the fuel from the control chamber with the control valve open in the low pressure region of the injector and from there to the injector return can flow. The flow cross sections of the outlet throttle and the inlet throttle are matched to one another in such a way that when the control valve is open, a net outflow of fuel (control quantity) from the control chamber into the low pressure region of the injector results.

Preferably, the valve piece additionally has the function of a sealing seat for the control valve. The control valve may be either a valve driven by means of an electromagnetic actuator or by means of a piezoelectric actuator. Preferably, the control valve is designed as a pressure balanced in the axial direction valve to reliably switch pressures above 2000 bar can.

In order to absorb the forces acting on the valve member from the control chamber forces, is provided in a further development of the invention advantageously that the valve member is supported in the axial direction of an inner annular shoulder of the injector against which it is preferably pressed by means of another Injektorbauteils.

It is expedient if a high-pressure supply channel, via which the injector is under high pressure fuel, in particular from a high-pressure fuel storage (Rail) is supplied, in an annular space (part of the high-pressure region) opens, which is bounded radially outwardly from the injector body and penetrated by the valve element. The inlet throttle introduced into the valve element connects this annular space hydraulically to the control chamber, so that a subsequent flow of high-pressure fuel into the control chamber is ensured. Preferred is an embodiment in which the high-pressure supply channel supplying the annular space is the only high-pressure supply channel in the injector body, that is, the fuel flowing into the annular space can flow axially through the annular space to a nozzle hole arrangement of the injector. Preferably, the injector is without a low-pressure stage, so leak-free, formed.

In a development of the invention, it is advantageously provided that the annular space into which the high-pressure supply channel of the injector discharges is sealed off from the control chamber via a guide gap between the valve element and the injector body. In order to minimize possible leakage losses from the annular space into the control chamber when the control valve is open, it is advantageous to design the guide section of the valve element guided on the injector body as long as possible.

In particular, the provision of only one high-pressure supply channel in the injector, preferably in the injector, makes it possible according to an advantageous embodiment of the invention, a high-pressure connection for connecting the injector to a high pressure supply line either directly on the injector set, in particular, or preferably integrally form with the injector body. Brief description of the drawings

Further advantages, features and details of the invention will become apparent from the following description of the preferred embodiment and from the drawings, which shows in the only Fig. 1 is a partial schematic representation of an injector.

Embodiment of the invention

In Fig. 1, designed as a common rail injector injector 1 for injecting fuel into a combustion chamber, not shown, of an internal combustion engine is shown. The injector 1 has a housing as an injector body 2 and an end nozzle body 3, which are braced against each other with a union nut, not shown in the usual way. In this case, the nozzle body 3 passes through the nozzle retaining nut in the axial direction.

Within the injector body 2 and within the nozzle body 3 a one-piece in this embodiment, valve element 4 is received axially displaceable. The valve element 4 has at its lower end in the drawing plane a tip 5 with a closing surface 6, with which it can be brought into tight contact with a formed within the nozzle body 3 valve seat 7.

When the valve element 2 rests against the valve seat 7, ie is in a closed position, the fuel outlet from a nozzle hole arrangement 8 is blocked. If, on the other hand, it is raised by the valve seat 7, fuel can flow from a pressure chamber 9 (high-pressure region) between the valve element 4 and the inside of the nozzle body 3 pass through and past the tip 5 to the nozzle hole arrangement 8, where they are sprayed into the combustion chamber substantially under high pressure (rail pressure).

The injector 1, or the annular pressure chamber 9, which is formed between the outer circumference of the valve element 4 and the inner peripheral wall of a stepped bore 10 within the injector body 2 and within the nozzle body 3 is supplied with fuel under high pressure from a high-pressure fuel reservoir 11 (Rail) , The fuel flows from the high-pressure fuel accumulator 11 via a feed line 12, through a high-pressure connection formed integrally with the injector body 2, into a high-pressure supply passage 13 within the injector body 2 formed as an oblique bore. The high-pressure supply passage 13 opens into a bulge 14 within the injector body 2 The high-pressure fuel accumulator 11 is supplied with fuel from a low-pressure reservoir 16 by a high-pressure pump 15 designed in particular as a radial piston pump.

Via a return line 17, a control quantity of fuel to be explained later flows from a low-pressure region 18 of the injector 1 to the reservoir 16 and is returned to the high-pressure circuit via the high-pressure pump 15.

In the area of the bulge 14, an inlet throttle 19 is introduced into the valve element 4. The inlet throttle 19 is formed in the embodiment shown as a radial bore. The inlet throttle 19 is at least approximately conical in the direction of the inlet throttle. jungende recess 20 upstream in the valve element 4. Through the inlet throttle 19 high-pressure fuel from the pressure chamber 9 flows into an axial bore formed as a blind hole 21 within the valve element 4. The axial bore 21 is arranged centrally within the valve element 4 and starts from an upper end face 22 of the valve element 4. The axial bore 21 is part of a control chamber 23, which is connectable by means of a control valve 24, shown schematically with the low pressure region 18 of the injector 1. If electromagnets 25 of an electromagnetic actuator 26 are energized, acts on an anchor plate 27, an opening force in the plane of the drawing upwards, whereby an integrally formed with the armature plate 27 control valve piston 28 is moved in the drawing plane upwards. As a result, a control valve ball 29 held by the control valve piston 28 lifts from its valve seat 30 on a valve piece 31, which is braced against an inner annular shoulder 40 of the injector body 2 and thus held stationary within the injector body 2, whereby the fuel from the control chamber 23 through a cavitating outlet throttle 32 can flow within the valve member 31 into the low-pressure region 18 and thus to the return 17. The flow cross-sections of the inlet throttle 19 and the outlet throttle 32 are matched to one another such that when the control valve 24 is open, a net outflow of fuel from the control chamber 23 results. Since the control chamber 23 is bounded in the axial direction by the valve element 4, this results in a force acting in the opening direction on the valve element 4, whereby this lifts off from its valve seat 7 and the fuel flow from the pressure chamber 9 through the Nozzle hole arrangement 8 releases into the combustion chamber of the internal combustion engine.

If the injection process is terminated, the energization of the electromagnets 25 is interrupted, whereby the control valve 24 closes and the pressure (control pressure) increases rapidly in the control chamber 23 due to the inflowing through the inlet throttle 19, under high pressure fuel, whereby the closing direction in the Valve elements 4 acting forces predominate and the valve member 4 comes with its closing surface 6 in tight contact with the valve seat 7 on the nozzle body 3. A closing spring 41, which is supported in the axial direction on an annular shoulder 42 within the injector body 2 and the other end on a retaining ring 43 held on the valve element 4, the closing movement of the valve element 4 is supported.

As explained, the axial bore 21 is part of the control chamber 23. The axial bore 21 opens into an axial section 33 of the control chamber 23, which is delimited radially on the outside by the injector body 2. In the axial direction, this axial portion 33 is bounded by the upper end face 22 of the valve element 4 and by a lower end face 34 of an extending into a bore portion 35 within the injector body 2 end portion 36 formed as a throttle plate valve piece 31. In the open state of the valve element 4 is the valve element 36 on the lower end face 34 of the end portion 36 of the valve piece 31, which serves as a stop for limiting the opening movement of the valve element 4. In the open state of the valve element 4, that is, during the injection process, the control chamber 23 is thus substantially exclusively of the peripheral walls of the Axial bore 21 and a running in the opposite direction blind hole 37 in the valve member 31 is limited, since the axial portion 33 is completely occupied by the valve element 4.

The axial portion 33 of the control chamber 23 is in the drawing plane down, ie in the direction of the pressure chamber 9, sealed via a guide gap (circumferential gap) radially between a guide portion 39 of the valve element 4 and the bore portion 35 (guide portion) of the injector body 2. The valve element is with its guide portion 39 axially displaceably guided directly from the injector body 2. By an appropriate choice of the diameter of the axial bore 21, the widening of the guide portion 39 can be determined and thus influence on the width of the guide gap 38 are taken.

Claims

claims

1. injector for injecting fuel into a combustion chamber of an internal combustion engine, in particular common rail Inj ector, with a function of the pressure in a control chamber (23) between a closed position and a fuel flow in the Bennraum releasing open position adjustable valve element (4) and with a control valve (24) with which the pressure in the control chamber (23), which is connected via an inlet throttle (19) hydraulically connected to a high-pressure region of the injector (1), can be influenced,

characterized,

the inlet throttle (19) is introduced into the valve element (4).

2. An injector according to claim 1, characterized in that an axial portion (33) of the control chamber (23), at least temporarily, radially outwardly of an injector body (2) is limited.

3. Injector according to 2, characterized in that the valve element (4), in particular directly, adjacent to the axial portion (33) of the control chamber (23) on the injector body (2) is guided axially displaceably.

4. Injector according to one of claims 2 or 3, characterized in that, from the inlet throttle (19), a bore, preferably an axial bore (21), in the valve element (4) leads to the axial section (33).

5. Injector according to one of the preceding claims, characterized in that the control chamber (23) on the valve element (4) opposite side of a valve piece (31) with outlet throttle (32) is limited.

6. An injector according to claim 5, characterized in that a valve seat (7) of the control valve (24) on the valve piece (31) is formed.

7. Injector according to one of claims 5 or 6, characterized in that the valve piece (31) on an inner annular shoulder (40) of the injector body (2) is supported.

8. An injector according to one of the preceding claims, characterized in that a high-pressure supply channel (13) of the injector (1) opens into one of the valve element (4) interspersed annulus, which is hydraulically connected via the inlet throttle with the control chamber (23).

9. An injector according to claim 8, characterized in that the annular space relative to the control chamber (23) via a guide gap between the valve element (4) and the injector body (2) is sealed.

10. Injector according to one of the preceding claims, characterized in that a high-pressure connection of the injector (1) on the injector body (2) fixed, in particular welded, or is integrally formed with the injector body (2).