WO2008138743A1

WO2008138743A1 - Injector

Info

Publication number: WO2008138743A1
Application number: PCT/EP2008/055206
Authority: WO
Inventors: Bernd Streicher; Ralf Nussbaumer; Rudolf Heinz; Michael Mennicken; Holger Rapp; Wolfgang Stoecklein; Christian Faltin; Nadja Eisenmenger
Original assignee: Robert Bosch Gmbh
Priority date: 2007-05-14
Filing date: 2008-04-29
Publication date: 2008-11-20
Also published as: RU2469206C2; CN101680405B; DE502008001904D1; EP2156045A1; CN101680405A; RU2009146123A; DE102007022586A1; EP2156045B1; ATE489551T1

Abstract

The invention relates to an injector (1) for injecting fuel into a combustion chamber of an internal combustion engine, particularly a common rail injector, comprising a control valve (18) having an axially adjustable valve sleeve (17) that is guided on the outer circumference, the control valve being used to release and block the fuel flow through a discharge duct (14) introduced in a valve piece in the direction of a low-pressure region (12) of the injector (1) from a control chamber (5), which is operatively connected to an axially adjustable valve element (2). According to the invention, the valve sleeve (17) is guided on the outer circumference by a guide element (26), the element being formed as a component that is separate from the valve piece (6) and fixed to the valve piece (6).

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.

EP 1 612 403 A1 describes a common-rail injector with a control valve (servo-valve) pressure-balanced in the axial direction for blocking and opening a fuel outflow channel 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 permanently supplied via an inlet throttle with fuel under high pressure. By varying the fuel pressure within the control chamber, a valve element is moved between an open position and a closed position, the valve element releasing the fuel flow into the combustion chamber of an internal combustion engine in its open position. The control valve comprises an adjustable in the axial direction by means of an electromagnetic actuator valve sleeve which is guided on an integrally formed with a valve piece guide pin. The valve sleeve defines a valve chamber of the control valve formed by a reduced diameter portion of the guide pin only radially outward, so that no opening or closing forces of the high pressure Fuel within the valve chamber acting on the valve sleeve. Due to this characteristic, the control valve is suitable for switching very high pressures. Since the high-pressure fuel through the vertical drain channel and lateral, the drain channel intersecting transverse bores in the valve piece must flow into the valve chamber, the miniaturization of such control valves are limited. For fuel pressures above 2000 bar only comparatively large valve seat diameter can be realized for reasons of strength, otherwise there is a risk of breakage of the valve piece in the area of the existing bore intersections.

For this reason, in the applicant (so far) in-house state of the art has been developed in which the valve sleeve encloses a separate from the valve piece pressure pin, which only has the task to seal the valve located within the valve sleeve valve chamber in the axial direction upwards. The separation of the valve piece and pressure pin eliminates the need to produce complicated Bohrungsverschneidungen in the valve piece and it accounts thus in particular the high tensile stresses loaded areas of the previous valve piece. As a result, the valve seat diameter can be made significantly smaller than is the case with the prior art known from EP 1 612 403 A1. The disadvantage, however, is that for the valve sleeve a guide must be provided on its outer circumference in the valve piece. This has the consequence that the production of the valve piece is complicated by the outer, extending in the axial direction, circumferentially closed guide. In particular, the valve sleeve seat is no longer free on the surface of the Valve piece, but is sunk in the axial direction in the guide of the valve sleeve, so that it must be processed with a filigree grinding pin. Even in the event that a coating of the valve sleeve seat should be provided, this is very difficult to access for the coating process, which complicates the coating. In addition, located at the bottom of the guide valve sleeve seat for manufacturing reasons, only as a flat seat or concave conical seat, but not be designed as a convex conical seat.

DISCLOSURE OF THE INVENTION Technical Problem

The invention is therefore based on the object to propose an injector with an axially adjustable valve sleeve having control valve, which on the one hand is easy to manufacture and on the other hand, strength problems are avoided.

Technical solution

This object is achieved with the features of claim 1. Advantageous developments of the inventions are specified in the subclaims. In the context of

Inventions also fall all combinations of at least two of the features specified in the description, the claims and / or the figures. For specified value ranges, values lying within the stated limits should also be disclosed as limit values and be used as desired. The invention is based on the idea to guide the valve sleeve with its outer diameter axially displaceable in a guide element, which is formed as a separate component from the valve member, but fixed to this. This embodiment has the advantage that the guide element can be set only after production of the valve seat for the valve sleeve on the valve piece, whereby the valve seat in the usual way can be produced, since the valve piece, in particular the valve seat (from above) is freely accessible. It is also possible to form the valve seat in any, in particular also convex conical seat shape. Furthermore, the feasibility of an optional coating process is simplified. In addition, the guide element is easier to produce, as a grinding on the inner circumference guide bore for guiding the valve sleeve. Due to the provision of a separate, subsequently fixable on the valve member guide member for guiding the valve sleeve at its outer periphery can be dispensed with a guide of the valve sleeve by means of a guide pin on its inner circumference. This in turn means that it is possible to dispense with the necessary for a guidance of the valve sleeve on its inner circumference Bohrungsverschneidungen for discharging fuel, whereby the strength of the valve member is substantially improved.

Of particular advantage is an embodiment in which the guide element is designed as, in particular cylindrical, sleeve whose inner diameter corresponds at least in sections to the outer diameter of the valve sleeve plus a (minimum) guide clearance. Preferably, the end face of the cylindrical sleeve in the axial direction of one operatively connected to the valve sleeve, in particular integrally therewith trained, extending in the radial direction anchor plate spaced. For sealing a control chamber located radially inside the valve sleeve, a pressure pin is advantageously provided, which is pressurized in the axial direction upwards by the fuel flowing out of the control chamber. The outer diameter of the pressure pin corresponds to the inner diameter of the valve sleeve minus a minimum clearance. The pressure pin is supported in the axial direction upward on an injector component, in particular a holding body of an electromagnet arrangement. It is conceivable that the pressure pin, which preferably has no guiding function, is spring-loaded in the axial direction by means of a spring which is supported on the valve piece in the direction of the electromagnet arrangement.

In an embodiment of the invention is advantageously provided that the guide element is fixed to the valve piece by means of a press fit. This embodiment is advantageously without additional fasteners. This type of attachment is particularly suitable for a sleeve-shaped (tubular) formed guide element, which is pressed in the axial direction on the valve piece. It is advantageous if the guide element is elastically deformable in the radial direction, at least in the region of the press fit, in order to improve the clamping effect.

In order to ensure optimum hold of the guide element on the valve piece, it is provided in an embodiment of the invention that the guide element is fixed to a, in particular slightly conical portion of the valve piece. To achieve a press fit, it is of Advantage, when the cone angle of a corresponding inner cone of the guide element before its attachment to the conical portion, in particular slightly smaller than the cone angle of the conical portion of the valve piece. Preferably, the press fit as a so-called Morsekegelpassung, as it is known, for example, for the determination of tools on shafts, formed.

As already explained, the cone angle (angle between the axis of symmetry of the conical section and the oblique lateral surface of the conical section) of the conical section of the valve piece is small, in particular very small, preferably the cone angle is less than approximately

10 °, in particular less than about 5 °. Particularly preferably, the cone angle of the conical section lies in one

Range between about 0.5 ° and about 2.5 °. It is the

Angle (angle between the axis of symmetry of the inner cone and the oblique inner surface of the inner cone)

Inner cone of the guide element with advantage about 0.1 ° to about 1.5 °, preferably by about 0.25 ° to about 0.75 ° smaller than the cone angle of the conical portion of the

Valve piece.

In terms of production technology, an embodiment is advantageous in which the valve seat is arranged on the valve piece directly adjacent to the conical portion of the valve piece on which the guide element is fixed. Preferably, the

Valve seat designed as a convex conical seat, wherein the

Angle of the conical surface is substantially flatter than the angle of the conical section for fixing the

Valve piece. In addition, it is conceivable, the valve seat as

Flat seat, or even form as a concave cone seat. There are various possibilities for realizing the interference fit between the guide element and the valve piece. According to a first variant it is provided that the guide element rests with a continuous contact surface on the valve piece, in particular on the conical portion of the valve piece.

Alternatively, it is conceivable that the contact surface, in particular annularly interrupted, preferably by an exemption, so a non-contacting area on the guide element and / or on the valve piece. In this embodiment, two, in particular annular, in the axial direction by the clearance spaced contact areas between the guide member and the valve piece are formed, whereby the clamping action can be improved.

In order for the fuel quantity (control quantity) flowing out of the control chamber to be able to flow freely in the direction of the low-pressure region of the injector when the control valve is open, ie when the valve sleeve is raised, an outflow channel has to be provided from the fuel volume within the valve sleeve. For this purpose, it is advantageous to provide at least one transverse bore in the guide element. In this case, the transverse bore does not necessarily extend orthogonally to the longitudinal center axis of the valve sleeve, but may also be arranged obliquely. Additionally or alternatively, it is conceivable to equip the valve sleeve on its outer circumference and / or the guide element on its inner periphery with at least one Flächenanschliff to form an axial outflow channel. Likewise, it is possible to provide an outlet bore or a discharge channel on the valve piece, via which or the control quantity, in particular down, below the guide element can flow through the outside in the low pressure area.

Brief description of the drawings

Further advantages, features and details of the invention will become apparent from the following description of preferred embodiments and from the drawings; these show in:

Fig. 1: a highly schematic partial view of a

Common rail injector trained injector and

Fig. 2: an alternative embodiment of an injector in a likewise highly schematic partial view.

Embodiments of the invention

In the figures, the same components and components with the same function with the same reference numerals.

In Fig. 1, a section of a trained as a common rail injector injector 1 for injecting fuel into a combustion chamber, not shown, of an internal combustion engine is shown very schematically. Fig. 1 is intended to explain only the operation of the injector, wherein the size ratios shown do not correspond to the real size ratios. The injector 1 comprises a single-part or multi-part valve element 2 which is shown only in sections and which is adjustable between an open position and a closed position. In its open position (adjusted upward in the plane of the drawing), the valve element 2 releases the fuel flow from a pressure chamber 3 through a nozzle hole arrangement, not shown, into the combustion chamber of an internal combustion engine.

With an upper end face 4, the valve element 2 delimits a control chamber 5. The latter is arranged radially inside a sleeve-shaped section of a valve piece 6 projecting into the pressure space 3.

In the control chamber 5 opens a introduced into the sleeve-shaped portion of the valve piece 6 inlet throttle 7, via which the control chamber 5 is supplied with fuel from the pressure chamber 3. The pressure chamber 3 is in turn supplied by a fuel supply line 8 under high pressure fuel from a high-pressure fuel storage 9 (Rail). This is powered by a, in particular designed as a radial piston pump high-pressure pump 10 with fuel from a low-pressure reservoir 11. In the reservoir 11 also flows later to be explained control amount of fuel from a low pressure region 12 of the injector via an injector return 13th

From the control chamber 5 opens an inserted in the axial direction in the valve piece 6 drain channel 14. This is provided with an outlet throttle 15, or designed as such. The drainage channel 14 spreads in his in the plane of the drawing upper portion and terminates in a valve chamber 16, which is bounded radially outwardly by the valve piece 6 and by an axially adjacent thereto valve sleeve 17 of a control valve 18 (servo valve). In the axial upward direction, the valve chamber 16 of the control valve 18 is delimited by an axially displaceably mounted pressure pin 19, which is pressed by befindlichem within the valve chamber 16 fuel in the axial direction in the plane up against a drain pipe 36. For this purpose, the pressure pin 19 passes through a bore 37 in a holding body 20 of an electromagnet assembly 21. In its upper plane in the drawing area of the pressure pin 19 is guided by a sleeve 22, by a closing spring 23 which is formed on an integrally formed with the valve sleeve 17 anchor plate 24 is supported, is spring-loaded against the outlet nozzle 36. The closing spring 23 acts simultaneously on the armature plate 24 and thus the valve sleeve with a spring force in the axial direction in the plane down to a formed on the valve piece 6, formed as a conical seat valve seat 25 of the control valve 18. Alternatively, the closing spring is supported on an annular shoulder of the holding body 20th the solenoid assembly 21 from.

Due to the fact that the valve sleeve 17 has no axially acting pressure application surface for fuel within the valve chamber, the control valve 18 is a servo-pressure-balanced in the axial direction servo valve.

To guide the valve sleeve 17 on its outer periphery is a hollow cylindrical, sleeve-shaped guide member 26th intended. The guide member 26 is fixed by means of a press fit to a conical portion 27 of the valve piece 6, wherein an outer cone angle OC of the conical portion 27 is shown for reasons of illustration much larger than this is preferably formed in reality. In reality, the cone angle CC between a conical surface 28 and an axis parallel to the longitudinal central axis L of the control valve 18 is approximately 1 ° in this exemplary embodiment.

The conical portion 27 facing away from end face 29 of the guide member 26 is arranged at an axial distance to the underside of the anchor plate 24. As can be seen from Fig. 1, the valve seat 25 is disposed radially within the conical portion 27 and the conical surface 28 (conical surface).

The guide element 26 is fixed by means of a press fit to the conical portion 27 of the valve piece 26. A cone angle ß of an inner cone 30 is like the cone angle CC of the conical portion 27 of the valve member 6 in the assembled state also 1 °. Before assembly, however, the cone angle β of the inner cone 30 is slightly smaller than the cone angle CC. When the guide element 26 is pressed onto the conical section 27, the inner cone is expanded elastically outward in the radial direction in order to improve the clamping effect. In the illustrated non-positive connection between the guide member 26 and the conical portion 27 of the valve member 6 is a kind Morsekegelpassung. In the guide member 26 has two opposite arranged at the level of the valve seat 25, slightly inclined transverse bores 31, 32 introduced by the fuel from the valve chamber 16 at the valve seat 25 lifted valve sleeve 17 of the control valve 18 in the guide member 26 surrounding the low pressure region 12 of the Injector can flow. From the low-pressure region 12, the fuel can flow through the injector return 13 to the reservoir 11.

To open the valve element 2, the pressure in the control chamber 5 must be lowered. For this purpose, the valve sleeve 17 is moved from the position shown in Fig. 1 by energizing the solenoid assembly 21 in the plane up, so that fuel introduced via the introduced into the conical section 27, central drain passage 14 into the valve chamber 16 and from there below the Valve sleeve in the radial direction and through the transverse bores 31, 32 can flow into the low pressure region 12 and from there to the injector return 13.

In addition or as an alternative to the formation of a discharge throttle 15 in the discharge channel 14, the transverse bores 31, 32 themselves can be formed as discharge throttles.

Since the flow cross section of the outlet throttle 15 is greater than the flow cross section of the inlet throttle 7 results in open control valve 18, a net outflow of fuel from the control chamber 5, whereby the force acting on the valve element 2 closing force is reduced and the valve element 2 lifts from its valve seat, not shown, and the Fuel flow releases. To close the Valve element 2, the energization of the solenoid assembly 21 is interrupted, whereby the valve sleeve 17 is spring assisted by the closing spring 23 in the axial direction down to its valve seat 25 is moved, so that no more fuel can flow out of the valve chamber 16 in the low pressure region. By continuing to flow through the inlet throttle 7 in the control chamber 5 fuel increases the pressure in the control chamber 5 and thus acting on the valve element 2 closing force.

The embodiment of an injector 1 shown in FIG. 2 essentially corresponds to the embodiment according to FIG. 1, so that only the differences will be discussed below in order to avoid repetition. With regard to the similarities, reference is made to the preceding description of the figures.

The only difference to the embodiment of FIG. 1 is that the interference fit between the guide member 26 and the conical portion 27 of the valve member 6 is realized differently. In the inner cone 30 of the guide member 26, an annular release position 33 is introduced, so that the guide element rests against two axially spaced contact surfaces 34, 35 to the conical portion 27 of the valve member 6. Thereby, the clamping action between the guide member 26 and the valve member 6 can be further improved.

Instead of the illustrated transverse bores 31, 32 in the guide element 26, for discharging fuel from the valve chamber 16 when the control valve 18 is open, Preferably in the axial direction extending Flächenanschliffe be provided on the outer circumference of the valve sleeve 17 and / or on the inner circumference of the guide member 26.

Claims

claims

1. injector for injecting fuel into a combustion chamber of an internal combustion engine, in particular common rail Inj ector, with an axially adjustable, guided on its outer circumference

Valve sleeve (17) having control valve (18), by means of which the fuel flow through a in

Valve piece (6) introduced flow channel (14) in the direction of a low pressure region (12) of the injector

(1) one with an axially adjustable

Valve element (2) operatively connected control chamber (5) is releasable and lockable,

characterized,

the valve sleeve (17) is guided on its outer circumference by a guide element (26) which is designed as a separate component from the valve piece (6) and fixed to the valve piece (6).

2. An injector according to claim 1, characterized in that the guide element (26) as, in particular cylindrical, sleeve is formed whose inner diameter corresponds to the outer diameter of the valve sleeve (17) plus a guide clearance.

3. Injector according to one of claims 1 or 2, characterized in that the guide element (26) on the valve piece (6) is fixed by means of a press fit.

4. Injector according to one of the preceding claims, characterized in that the guide element (26) is fixed to a conical portion (27) of the valve piece (6).

5. An injector according to claim 4, characterized in that a cone angle (ß) of an inner cone (30) of the guide element (26), in particular slightly smaller than the cone angle (OC) of the conical portion (27) of the valve piece.

6. Injector according to one of claim 4 or 5, characterized in that the conical portion (27) of the valve piece (6) has a cone angle (OC) from a range between about 0.5 ° and about 10 °, preferably less than 7 °, preferably of less than 5 °, in particular of less than 3 °, more preferably of less than 2 °, particularly preferably of about 1 °.

7. Injector according to one of claims 4 to 6, characterized in that a valve seat (25) of the valve sleeve (17) is formed radially within the conical portion (27).

8. Injector according to one of the preceding claims, characterized in that the guide element (26) in the contact region to the valve piece (6) rests flat against this.

9. Injector according to one of claims 1 to 7, characterized in that in the contact region between the guide element (26) and the valve piece (6) there is provided an in particular annular release (33) on the guide element (26) and / or on the valve piece (6).

10. Injector according to one of the preceding claims, characterized in that in the guide element (26) has a transverse bore (31, 32) for discharging fuel from the flow channel (14) in the low pressure region (12) is introduced.