WO2008049675A1

WO2008049675A1 - Injector with an axial pressure-compensating control valve

Info

Publication number: WO2008049675A1
Application number: PCT/EP2007/059080
Authority: WO
Inventors: Francois Rossignol; Friedrich Howey; Olivier Charvet; Tony Dumont
Original assignee: Robert Bosch Gmbh
Priority date: 2006-10-27
Filing date: 2007-08-31
Publication date: 2008-05-02
Also published as: EP2084390A1; DE102006050811A1

Abstract

The invention relates to an injector (1) for injecting fuel into combustion chambers of combustion engines. According to the invention, a fuel channel (51) is provided in a valve element (3) of a control valve (28), wherein fuel can flow from a control chamber (18) to a compensating chamber (48) delimited by a seat element (44) and the valve element (30) when the control valve (28) is closed. Inside the compensating chamber, a compensating surface (47) is provided on the valve element (30), wherein which fuel pressure can be applied to the surface in the opening direction of the valve element (30), making it possible for a fuel pressure force acting on the valve element (30) in the closing direction to be compensated for.

Description

description

title

Injector with axial-pressure compensated control valve

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. The control chamber is supplied via a pressure channel with fuel from a high-pressure fuel storage. By varying the fuel pressure within the control chamber, a nozzle needle is moved between an open position and a closed position, wherein the nozzle needle in its open position releases the fuel flow into the combustion chamber of an internal combustion engine.

In Fig. 2 of EP 1 612 403 Al an injector is shown, the control valve has an adjustable in the axial direction by means of an electromagnetic actuator valve sleeve, which cooperates sealingly with a stationary conical valve seat surface. During its closing movement, the valve sleeve is moved in the axial direction away from the control valve towards the stationary seat element. Within the valve sleeve, a bolt is arranged, at the free, the control chamber facing away from the end of the seat member is formed. Through the bolt passes a connecting channel, which is part of the fuel drain path and which connects the control chamber to an annulus within the valve sleeve. Of the fuel within the annular space, a fuel pressure is exerted on the valve sleeve (valve element) only in the radial direction, so that the valve sleeve is pressure-balanced in the axial direction. The construction of the known injector is comparatively expensive due to the intended axially displaceable sleeve.

Technical task

The invention is therefore based on the object to propose an injector with a control valve, which is on the one hand pressure balanced in the axial direction and on the other hand manages without a displaceable in the axial direction of the valve sleeve.

Disclosure of Invention Technical Problem

This object is achieved with the features of claim 1; the dependent claims indicate favorable developments. 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 to introduce directly into the axially displaceable valve element a Kraftstoffka- channel, which is part of the fuel drainage path from the control chamber to a low pressure chamber. By this, preferably centrally disposed within the valve element fuel passage of the fuel from the control chamber to a compensation chamber at the Steuerkam- mer remote side of the valve element flow. This compensation chamber is bounded on the one hand by the valve element and on the other hand, with the control valve closed, by the seat element. Within the compensation chamber, a compensation surface is provided according to the invention on the valve element, which is acted upon by fuel pressure in the axial direction, ie in the opening direction or in the direction of the needle tip of the nozzle needle. In this case, the compensation surface is dimensioned such that an acting on the valve element in the opening direction hydraulic pressure force arises, which compensates for an opposing direction, ie in the closing direction and thus in the direction of the seat member acting on the valve element pressure force or repeals. In this case, the pressure force acting in the closing direction is caused by the axial fuel pressure on the valve element in the closing direction. The inventive design provides an injector with a control valve, which combines the advantages of a pressure-balanced in the axial direction valve with the simple structure of a conventional ball / cone valve.

Preferably, the valve element is moved by an electromagnetic actuator in the opening direction against the force of a biasing spring acting on the valve element. It can be provided according to an advantageous embodiment of the invention to arrange the actuator axially between the control chamber and the seat member. The arrangement of the electromagnetic actuator axially between the control chamber and the seat member has the advantage that the control amount (fuel) can be dissipated from the low pressure chamber surrounding the seat element in a simple manner, since a corresponding return bore can be drilled directly from above into the low pressure chamber. The placement of this Return bore is not hindered by the advantageous development of the invention by the arrangement of the actuator. Instead of an electromagnetic actuator, a piezoelectric actuator can also be used. Additionally or alternatively, it is conceivable to arrange the actuator such that it applies force to the valve element in the closing direction when energized.

In a further development of the invention is advantageously provided that the seat element is a ball or a cone. Preferably, it is a separate component which is arranged supportingly on a component of the injector, preferably on the injector body. The formation of the seat element as a ball has the advantage that it is available as a mass product and thus only the - in particular conical - counter surface must be ground on the valve element.

According to an advantageous embodiment of the invention it is provided that the fuel channel is formed within the valve element as a throttle-free through hole. It is thereby achieved that the fuel pressure in the compensation chamber and immediately adjacent to an opposite end face of the compensating surface of the valve element is at least approximately the same, whereby it is possible, by an equal design of the axial projection surface of the compensation surface and an axial projection surface of the compensation surface opposite end side of the Valve element to create a pressure force compensation in the axial direction.

A simple way, the axial projection surfaces of the compensation surface and the opposite end face form the same size, in a further development of the invention is to match the diameter of the contact surface of the valve element on the valve seat surface of the diameter of the valve element in the region of the end face within the valve element guide. In this way, the surfaces which can be acted upon with pressure in the axial direction are the same size on both sides of the valve element, which leads to a pressure force compensation in the axial direction at at least approximately the same pressure on both sides of the valve element.

In a purely conical configuration of the counter-surface (contact surface) of the valve element opposite the seat element, the seat element, in particular the ball, can engage in the counter-surface on the valve element by often repeated closing operations in long-term operation, resulting in a change in the valve seat diameter and thus can lead to a change in the compensation area. In order to avoid this, it is provided in an embodiment of the invention that the valve element has a cylindrical depression in its end region facing the seat element, wherein the seat element adjoins the inner edge, i. abuts the inner diameter of this cylindrical opening. Even if the seat element is incorporated into the valve element during long-term operation, the compensation surface which is effective in the axial direction remains the same size. Preferably, the bottom of the cylindrical opening within the valve member is tapered toward the mouth of the fuel passage within the valve member.

Expediently, a fuel chamber is provided on the end face of the valve element which is opposite to the compensation chamber, said fuel chamber communicating with the outlet via the connection channel. is connected. This chamber is connected via a fuel channel with outlet throttle with the control chamber. In this case, the outlet throttle is matched to the inlet throttle arranged within the pressure chamber which supplies the control chamber with high-pressure fuel, so that when the control valve is open, a net fuel discharge into the low-pressure chamber results.

It is advantageously provided that the valve element (valve piston) is guided in a bore within a component accommodated in the injector body. The longer the bore is carried out, the better the armature and the electromagnet of an electromagnetic drive are aligned concentrically with each other, resulting in a symmetrical magnetic force and thus smaller lateral forces on the valve needle, which in turn reduces the friction between the valve element and guide bore.

In a further development of the invention is advantageously provided that the guide bore for the valve element is formed as a through hole, which means that the outlet throttle is not part of this hole. The outlet throttle and possibly also the chamber on the end face of the valve element are for this purpose introduced into a throttle plate arranged adjacent to the component with a through bore. This development of the invention simplifies the production of the outlet throttle, since it can now be produced perpendicular to a surface. In addition, the production of the guide hole for the valve element is simplified because a through hole is easier to grind than a bore with variable bore cross section. 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 drawing; this shows in:

1 shows a partially sectioned view of an injector with a pressure-compensated valve element in the axial direction;

Fig. 2 is an illustration of a possible embodiment of the valve element and the associated seat element and

Fig. 3: a partial view of another embodiment of an injector.

Embodiments of the invention

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

In Figs. 1 and 3, the essential components of a common rail injector 1 are shown. The injector 1 has an injector body 2, a nozzle body 3 and a nozzle clamping nut 4, which is screwed to the injector body 2 and thus clamps the nozzle body 3 against the injector body 2. As indicated schematically in Fig. 3, the nozzle body 3 passes through a through hole 5 of the nozzle lock nut 4 in the axial direction.

Within the nozzle body 3, a guide bore 6 is formed, in which an elongated nozzle needle 7 is guided. At a needle point 8, the nozzle needle 7 has a closing surface 9 with which it can be brought into tight contact with a needle seat 10 formed inside the nozzle body 3.

When the nozzle needle is in contact with the needle seat 10, i. is in a closed position, the fuel outlet from a nozzle hole assembly 11 is locked. If, on the other hand, it is raised by the needle seat 10, fuel can flow from an annular space 12 formed between the nozzle needle 7 and the circumferential jacket of the guide bore 6 past the needle tip 8 to the nozzle hole arrangement 11 and there substantially under the high pressure (rail pressure) into a combustion chamber be sprayed.

The nozzle needle 7 is biased by an only partially indicated in Fig. 3 biasing spring 13 in the direction of its closed position. The biasing spring 13 is arranged within a pressure chamber 14 and is supported at one end on a lower end face of a sleeve-shaped component 15 and at its other end on the nozzle needle 7 (not shown).

In the embodiment according to FIG. 1, the sleeve-shaped component is braced with the biasing spring, not shown in FIG. 1, against a throttle plate 16 in the axial direction. In the embodiment of FIG. 3 is no separate throttle plate provided. Here, the sleeve-shaped component 15 is clamped by the pretensioning spring 13 against a (valve) component 17.

The sleeve-shaped member 15 defines together with the nozzle needle 7 and the throttle plate 16 and the component 17 a control chamber 18. The control chamber 18 is supplied via a pressure channel 19 with inlet throttle 20 with fuel under high pressure. In the embodiment of FIG. 3, the pressure channel 19 connects the control chamber 18 via a pocket 54 with a supply line 21, which connects the pressure chamber 14 surrounding the control chamber 18 with a high-pressure fuel storage, not shown. In the embodiment according to FIG. 1, the pressure channel 19 is connected to the supply line 21 via a pocket 22. Via the supply line 21, the pressure chamber 14 (annulus) is supplied with high-pressure fuel from a high-pressure fuel storage also in the embodiment of FIG. 1. The fuel can flow from the pressure chamber in the axial direction as far as the nozzle hole arrangement 11.

Fuel can flow from the control chamber 18 to a low-pressure chamber 26 via a drain channel 24 equipped with an outlet throttle 23, which is part of a fuel drainage path 25, and from there flow away via a return line (not shown).

By means of an electromagnetic actuator 27, a pressure-balanced control valve 28 in the axial direction can block the fuel flow to the low-pressure chamber 26. By the biasing spring 13 and the action of the prevailing pressure in the control chamber 18 on a control chamber 18 delimiting end face 29 of the nozzle needle 7, an axially directed toward the combustion chamber closing force is exerted on the nozzle needle 7. This closing force counteracts an opening force which, as a result of the action of the fuel pressure, is exerted on a step surface (not shown) on the nozzle needle 7. If the control valve 28 is in a closed position and the fuel flow through the fuel drainage path 25 is blocked, the closing force in the stationary state is greater than the opening force, which is why the nozzle needle 7 then assumes its closed position. When the control valve 28 is then opened, the fuel flows from the control chamber 18.

The flow cross sections of the inlet throttle 20 and the outlet throttle 23 are matched to one another such that the inflow through the pressure channel 19 is smaller than the outflow through the outlet channel 24 and thus results in a net outflow of fuel when the control valve 28 is open. The resulting pressure drop in the control chamber 18 causes the amount of closing force falls below the amount of the opening force and the nozzle needle 7 lifts from the needle seat 10.

In the following, the embodiment of FIG. 1 will be explained in more detail. The control valve 28 has an axially displaceable valve element 30 which is guided within a component 32 in a guide bore 31 formed as a through-bore. The play between the bolt-shaped valve element 30 and the through-bore 31 is to be selected such that leakage losses from a plane below the component 32 (valve Body) arranged chamber 33 in the low pressure chamber 26 are low. The chamber 33 is hydraulically connected via the outlet channel 24 with the control chamber 18. The control chamber 18 facing end 34 with its end face 35 of the valve member 30 limits the chamber 33 in the plane of the drawing upwards. A pressure force in the closing direction acts on the end face 35 on the valve element 30. In addition, in the closing direction, a spring force acts on a helical spring 36 which is arranged radially inside a passage opening 37 of the actuator 27 and adjoins one shoulder surface 38 of the valve element 30 and the other end is supported on an adjusting ring 39, which in turn rests on the component 32. About the adjustment ring 39, the bias of the coil spring 36 and thus the closing force of the control valve 28 can be adjusted.

The electromagnetic actuator 27 is arranged in the plane of the drawing below the upper end of the valve element 30 and is pressed against an annular abutment surface 41 of the injector body 2 via a spring 40, which is supported on the component 32. With the electromagnetic actuator 27, an armature plate 42 cooperates, which is positively connected to the valve element 30. It is also conceivable to form the anchor plate 42 in one piece with the valve element 32. The electrical connection of the coil of the actuator 27 is guided via a housing part 43 from the lower side in the drawing plane to the upper end of the injector 1 for electrical contacting (not shown).

In the illustrated closed position of the control valve 28, the valve element 30 is supported by a spring-assisted on a sitting as a ball seat member 44, which in axia- Ler direction of the control chamber 18 away directly on the injector body 2 is supported. For sealing contact with the seat element 44, an inner cone 45 is provided on the plane of the drawing in the upper end of the valve element 30. The diameter D1 of the effective valve seat surface 46 of the seat element 44 corresponds to the outer diameter D1 of the valve element 30 in the guide bore 31. Thus, a compensation surface 47 is created within a compensation chamber 48, to which a fuel pressure in the axial direction acts on the valve element 30 in the opening direction. The resulting compressive force counteracts a pressure force in the closing direction, which results from the pressurization of the end face 35 of the valve element 30 from the chamber 33. Due to the same diameter Dl of the valve element within the valve seat surface 46 and the valve element 30 in its end, the chamber 33 facing end portion, the axial projection surfaces of the end face 35 and the compensation surface 47 are identical, which at the same pressure within the compensation chamber 48 and the chamber 33rd leads to a hydraulic force balance in the axial direction. Since the compensation chamber 48 and the chamber 33 are connected via a centrally guided by the valve element 30 fuel passage 51, an at least approximately equal pressure equalization between the expansion chamber 48 and chamber 33 is ensured.

The embodiment shown in FIG. 1 has the advantage that the outlet channel 24 with outlet throttle 23 are introduced in a separate throttle plate, which rests against the separate component 32, which essentially serves to guide the valve element 30. In this way, the guide bore 31 can be performed as a continuous, easy to be ground through-bore. In the embodiment shown in FIG. 3, the throttle plate 16 and the component 32 are united in the component 17, wherein the pressure channel 19 is connected to inlet throttle 20 for connecting the control chamber in a plane other than the cutting plane via a pocket 22 with the supply line 21. Otherwise, the embodiment according to FIG. 3 essentially corresponds to the embodiment according to FIG. 1.

In order to avoid that the compensation surface 47 changes during the long-term operation of the injector 1 by incorporating the spherical seat element 44 into the valve element 30, in particular increases, the valve element 30 has a cylinder bore 49 at its end facing the seat element 44 (see FIG. 4). The valve element 44 abuts against the upper peripheral edge 50 of this cylinder bore 49. Even if the seat member 44 is incorporated into the valve member 30, in this way the compensating surface 47 and especially their axially effective axial projection surface 53 remains unchanged. The compensation surface 47 (bottom surface of the cylinder bore 49) extends conically toward the fuel channel 51 introduced centrally into the valve element 30. In the region of the seat element 44 facing the end of the cylinder bore 49, the valve element is conically chamfered. It can be seen that the diameter D1 of the circumferential edge 50, that is to say the diameter of the effective valve seat surface 46, corresponds to the outer diameter D1 of the valve element 30 in the guide section or the approximately identical inner diameter of the guide bore 31.

Claims

claims

An injector for injecting fuel into combustion chambers of internal combustion engines, in particular common rail injector (1), with a control valve (28) comprising a valve element (30) in the axial direction relative to a seat member (44) with valve seat surface (46) is adjustable, whereby a from a control chamber (18) in a low-pressure chamber (26) leading Kraftstoffablaufweg (25) is releasable or lockable, wherein the valve element (30) for locking the Kraftstoffablaufweges (25) axially from the control chamber (10) away in the closing direction on the seat member (44) is movable, and wherein by opening and locking the Kraftstoffablaufweges (25) of the pressure in the control chamber (18), which is supplied via a pressure channel (19) can be influenced, whereby a with the control chamber (18) operatively connected nozzle needle (7) between a fuel flow releasing opening position and a closed position is adjustable, characterized in that in d a fuel channel (51) is introduced through the valve element (30) through which fuel can flow from the control chamber (18) to a compensation chamber (48) delimited by the seat element (44) and the valve element (30) when the control valve (28) is closed; and that within the compensation chamber (48) in the opening direction of the valve element (30) acted upon by fuel pressure equalization surface (47) on the valve element (30) is provided, by a in the closing direction to the valve element (30) acting fuel pressure can be compensated.

2. An injector according to claim 1, characterized in that for adjusting the valve element (30) an actuator (27), in particular an electromagnetic actuator (27) is provided which is arranged axially between the seat member (44) and the control chamber (18) ,

3. Injector according to one of claims 1 or 2, characterized in that the seat element (44) is a ball or a cone.

4. Injector according to one of claims 1 to 3, characterized in that the fuel channel (51) within the valve element (30) is designed as a largely throttle-free through hole.

5. Injector according to one of claims 1 to 4, characterized in that an axial projection surface (53) of the compensating surface (47) and an axial projection surface of the compensating surface (47) opposite end face (35) of the valve element (30) are equal.

6. Injector according to one of claims 1 to 5, characterized in that the diameter (Dl) of the valve element (30) within the valve seat surface (46) corresponds to the diameter (Dl) of the valve element (30) within the guide bore (31).

7. Injector according to one of claims 1 to 6, characterized in that on a valve seat surface (46) can be applied abutment edge (50) of the valve element (30) of a ne axially extending circular cylindrical inner wall of the expansion chamber (48) connects.

8. Injector according to one of claims 1 to 7, characterized in that the compensating surface (47) opposite the end face (35) of the valve element (30) via the fuel passage (51) connected to the compensation chamber chamber (33) bounded over a flow channel (24) with outlet throttle (23) is connected to the control chamber (18).

9. Injector according to one of claims 1 to 8, characterized in that the valve element (30) in a guide bore (31) within a in the injector body (2) received component (32, 17) is guided.

10. An injector according to claim 9, characterized in that the guide bore (31) is formed as a through hole and that the outlet throttle (23) and the chamber (33) in a adjacent to the component (32) arranged throttle plate (16) are formed.