WO2010081576A1

WO2010081576A1 - Fuel injector

Info

Publication number: WO2010081576A1
Application number: PCT/EP2009/065436
Authority: WO
Inventors: Nadja Eisenmenger
Original assignee: Robert Bosch Gmbh
Priority date: 2009-01-19
Filing date: 2009-11-19
Publication date: 2010-07-22
Also published as: DE102009000300A1

Abstract

The invention relates to a fuel injector (1), in particular a common rail injector, for injecting fuel into a combustion chamber of an internal combustion engine, having an injector valve element (11) that can be adjusted between a closed position and an open position releasing the flow of fuel into the combustion chamber as a function of the fuel pressure in a control chamber (21), and having a control valve (28) associated with the control chamber (21) and comprising a control valve element (30) having a first sealing surface (39) disposed on a first end face (41) for interacting with a first control valve seat (40). According to the invention, the control valve (28) is configured as a 3/2 directional valve, and the control valve element (30) of the control valve (28) comprises a second sealing surface (31) on a second end face (18) facing away from the first end face (41) for interacting with a second control valve seat (32).

Description

description

Fuel injector

State of the art

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

For introducing fuel into direct injection diesel engines are the

Time increasingly used stroke-controlled common rail systems. The advantage here is that the injection pressure can be adapted to load and speed. Basically known are stroke-controlled common rail injectors with 2/2-way valves, in which the pressure in a control chamber (servo chamber) by means of a control valve (servo valve) can be switched. By establishing a hydraulic connection between the control chamber and a low-pressure region of the fuel injector, the fuel pressure in the control chamber is lowered, resulting in a hydraulic force oriented toward the injection valve element in the opening direction, which causes the injection valve element to lift from its injection valve element seat and so on releases the flow of fuel into the combustion chamber of the internal combustion engine. In order to reduce emissions and to achieve high specific power ever higher injection pressures are required, which change the requirements of known control valves. Since the control valves used today in practice are not pressure-balanced in the axial direction, their use is beyond

1800 bar problematic, especially because more and more Aktuatorkräfte must be realized.

From DE 10 2006 060 593 A1 a fuel injector with a control valve is known, which is designed as a pressure-balanced in the axial direction 2/2 way valve. The closing time of the known injector seems optimizable. Disclosure of the invention

The object of the invention is to propose a fuel injector with a control valve which is of simple design and with which short injection valve element closing times can be realized. The control valve should preferably be suitable for integration in common rail injectors in use.

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

The invention is based on the idea that the control valve element as 3/2

Directional valve form so as to fill in a switching position of the control valve element, the control chamber via an addition to the inlet throttle provided Rückfüllkanal back, thus accelerating the Rückfüllvorgang the control chamber and to achieve a shortened closing time of the one- or multi-part injection valve element. The control valve element of the

3/2-way valve trained control valve is characterized according to the invention by two sealing surfaces for cooperation with a respective control valve seat, wherein the sealing surfaces are arranged on two opposite end faces of the control valve element. Such an arrangement of the sealing surfaces makes it possible, if necessary, to realize a control valve which is axially compressible, at least approximately, preferably completely, pressure-balanced, and which can be used at fuel pressures of more than 1800 bar. In other words, a fuel injector is proposed with a control valve designed as a 3/2-way valve whose sealing faces are remote from each other for interaction with a control valve seat, thereby achieving shorter shift times and improved dynamics over standard fuel injectors.

As indicated at the outset, the control valve can-but does not necessarily have to-be designed as a control valve that is pressure-balanced in the axial direction, at least approximately, preferably completely. This means that up the control valve element act in its two switching positions substantially only in the radial direction oriented forces, whereas the pressure forces acting in axial directions, at least approximately, compensate. The advantage of, at least approximately, pressure balance in the axial direction is that overall the forces acting on the control valve element forces are minimized, whereby smaller closing springs and smaller actuators, in particular electromagnetic actuators, can be used, wherein an embodiment with piezoelectric actuator can be realized. The only approximately pressure balance in the axial direction can be realized, for example, that the diameter of the first sealing surface, at least approximately, the diameter of the second sealing surface corresponds or in that the diameter of the first control valve seat corresponds to the diameter of the second control valve seat, and it is particularly preferred is, if the sealing surface diameter additionally correspond to a guide diameter of the control valve element, with which the control valve element at its

Outside circumference is guided. Depending on how far at least one of the sealing surface diameters deviates from the guide diameter, an opening or closing, preferably small, compression stage occurs.

Very particular preference is given to an embodiment of the fuel injector in which the first end face of the control valve element having the first sealing surface is arranged on a side facing the one- or multi-part injection valve element, pointing in the axial direction, and consequently avoids the second end face of the injection valve element is. As indicated, the injection valve element may alternatively be formed in one or more parts. In a multi-part design of the injection valve element, the combination of a control rod with a nozzle needle is preferred, wherein the control rod more preferably immediately frontally limits the control chamber in the axial direction.

The design of the control valve as a 3/2 way valve makes it possible to provide a backfilling channel in addition to the inlet valve supplying the control chamber permanently with fuel under high pressure, via which the control chamber can be backfilled in one of the two switch positions of the control valve element. Preferably flows through the backfilling channel in the direction

Control chamber flowing fuel through the outlet throttle, through which force substance can flow to the Injektorrücklaufanschluss in located in the other switching position control valve element.

Particularly preferred is an embodiment of the fuel injector in which the controllable between two switching positions control valve element in the first switching position with its first sealing surface on the first control valve seat and in the second switching position with its second, preferably facing away from the injection valve element, sealing surface on the second control valve seat.

In a further development of the invention is advantageously provided that the control valve element is penetrated by a flow channel through which fuel in the first switching position of the control valve can flow to an injector return port. The hydraulic connection to the injector return connection is preferably interrupted in the second switching position.

It is preferred if the control valve releases a hydraulic connection between the backfilling channel and the control chamber in the second switching position. For this purpose, the backfill channel preferably opens into a valve chamber, which in the first switch position is hydraulically separated from an outlet throttle that opens out of the control chamber, through which fuel in the second switch position can flow out of the valve chamber into the control chamber.

Particularly expedient is an embodiment in which the drainage channel is arranged centrally within the control valve in order to achieve a symmetrical loading of the control valve element.

It is particularly preferred if the flow channel located within the control valve element is aligned in the axial direction with the outlet throttle through which fuel, preferably in the first switching position of the control valve, can flow out of the control chamber into the drainage channel. Such an embodiment enables in a simple manner the integration of the control valve in known common rail injectors in series use, without it being necessary to completely change over the injector design.

Quite particularly preferred is an embodiment in which for adjusting the

Control valve element between its switching positions an electromagnetic Actuator is provided which preferably cooperates with a fixedly connected to the control valve member or integrally formed therewith anchor plate. Preferably, the electric actuator is arranged such that the control valve element when energized in the direction of the injection valve element, ie in the direction of a nozzle hole arrangement, by the fuel when open

Injection valve element can flow into the combustion chamber, is adjusted.

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 the only one

Fig. 1 is a schematic, sectional view of a fuel injector with a pressure-balanced in the axial direction, as

3/2-way valve trained control valve.

In Fig. 1, designed as a common rail injector fuel injector 1 is shown for injecting fuel into a combustion chamber, not shown, of a likewise not shown internal combustion engine of a motor vehicle. A high-pressure pump 2 delivers fuel from a reservoir 3 in a high-pressure fuel storage 4 (Rail). In this fuel, especially diesel or gasoline, under high pressure, of about 2000 bar in this embodiment, stored. To the high-pressure fuel accumulator 4, the fuel injector 1 is connected, among other injectors, not shown, via a supply line 5. The supply line 5 opens into a supply channel 6, which in turn opens into a pressure chamber 7 (high pressure area). The fuel flowing into the pressure chamber 7 flows in an injection process directly into the combustion chamber of the internal combustion engine. The fuel injector 1 is connected to a return line 9 via an injector return port 8.

Via the return line 9, a later to be explained control amount of fuel from the fuel injector 1 to flow to the reservoir 3 and fed from there from the high pressure circuit again.

Within an injector body 10, an injection valve element 1 1 is arranged.

This is formed in the embodiment shown in several parts and um- summarizes an upper in the drawing plane control rod 1 1 a and coupled with this nozzle needle 1 1 b. The nozzle needle 1 1 b is guided within an axially adjacent to the injector body 10 nozzle body 12 at its outer periphery. The only partially shown nozzle body 12 is clamped by means of a union nut, not shown, with the injector body 10.

The injection valve element 1 1 has at its tip 13 a closing surface 14 (sealing surface), with which the injection valve element 1 1 can be brought into a tight contact with an injection valve element seat 15 formed inside the nozzle body 12. When the injection valve element 1 1 is applied to its injection valve element seat 15, i. is in a closed position, the fuel outlet from a nozzle hole arrangement 16 is locked. If, on the other hand, it is lifted off its injection valve element seat 15, fuel can flow out of the pressure chamber 7 into an annular space 17 formed radially between the injection valve element 11 and the nozzle body 12, past the injection valve element seat 15 to the nozzle hole arrangement 16 and there substantially under high pressure (rail pressure). be sprayed standing in the combustion chamber.

From an upper end face 18 of the injection valve element 1 1, more precisely, the control rod 1 1 a, and a lower in the plane of the drawing, sleeve-shaped

Section 19 of a throttle plate 20, a control chamber 21 is limited, which is supplied via a radially extending into the sleeve-shaped portion 19 of the throttle plate 20 inlet throttle 22 with fuel under high pressure from the pressure chamber 7. The sleeve-shaped section 19 with the control chamber 21 enclosed therein is located radially outward from under high pressure

Fuel enclosed, so that an annular guide gap 23 between the sleeve-shaped portion 19 and the injection valve element 1 1 is relatively fuel-tight.

The control chamber 21 is concentric with the longitudinal central axis 24 of the

Fuel injector 1 extending, a drain throttle 25 having channel 26 connected to a valve chamber 27. The valve chamber 27 is a valve chamber 27 of a control valve 28, by means of which the control chamber 21 can be hydraulically connected to the injector return port 8. In the valve chamber 27 also opens a Rückfüllkanal 29, which connects the pressure chamber 7 hydraulically with the valve chamber 27.

As is further apparent from FIG. 1, the control valve 28 is a 3/2-way valve whose sleeve-shaped control valve element 30 is axially adjustable between a lower, first switching position and an upper, second switching position shown. In the second switching position shown, the control valve element 30 abuts with a second sealing surface 31 against a second control valve seat 32. The second sealing surface 31 is arranged on a second end face 33, remote from the injection valve element 11, of the control valve element 30. The second control valve seat 32 is located on a cover surface 34 of a trough-shaped insert member 35, which is clamped by a clamping nut 36 in the axial direction in the drawing plane down against a guide member 37, which in turn is clamped against the throttle plate 20, on an inner annular shoulder 38th the injector body 10 rests. As mentioned, a hydraulic connection between the control chamber 21 and the injector return port 8 is interrupted in the second switching position shown. At the same time a hydraulic connection between the Rückfüllkanal 29 and the control chamber 21 is released so that fuel can flow through the Rückfüllkanal 29, the valve chamber 27 and the channel 26 with outlet throttle 25 in the control chamber 21 and thus can provide for faster refilling.

In the first, not shown, lower switching position, the control valve member 30 abuts with a first, lower sealing surface 39 at a first Steuerven- tilsitz 40, which is formed on the throttle plate 20 and within the

Valve chamber 27 is located. As is readily apparent from Fig. 1, the first sealing surface 39 is located on a first end face 41 of the control valve element 30, which faces the injection valve element 1 1. When the control valve element 30 is in the first switching position, fuel can flow (centric) around the valve chamber 27 directly into a flow channel 42 extending axially within the control valve element 30, which is arranged coaxially to the longitudinal central axis 24 and is aligned with the channel 26 in the axial direction , flow to the second control valve seat 32 and between the second sealing surface 31 and the second control valve seat 32 in an armature plate chamber 43 (low pressure area) and from there via an axial passage 44 to the injector return port 8. As is apparent from Fig. 1, the discharge channel 42 opens in a trained within the control valve element 30 chamber 45, whose upper diameter corresponds to the diameter of the second sealing surface 31.

In the illustrated embodiment, the diameter of the first sealing surface 39 corresponds to the diameter of the second sealing surface 31, wherein the sealing surface diameter again correspond to the diameter of the control valve element 30 in a guide portion 46, in which the control valve member 30 is guided at its outer periphery in a central bore 47 of the guide member 37 is. As a result, the control valve 28 is pressure-balanced in both switching positions in the axial direction. If the sealing surface diameters deviate slightly from one another, the control valve element 30 is only approximately pressure balanced and has a closing or opening pressure step. In the event that the sealing surface diameters differ greatly, it can not be said that there is an axial pressure balance.

As is further apparent from FIG. 1, an electromagnetic actuator 48 with coil 52 is provided for adjusting the control valve element 30. The electromagnetic actuator 48 is located in a region axially between an integrally formed with the control valve element 30 armature plate 49 and the injection valve element 1 1. At the armature plate 49 is a closing spring 50 is supported, extending in the axial direction into a region radially between the actuator 48 and a bore 47 having extension 51 of the guide member 37 continues. The closing spring 50 is supported on the guide part 37 on the side facing away from the armature plate 49 and acts on the control valve element 30 with a spring force in a direction away from the injection valve element 11 on the second control valve seat 32. To adjust the control valve element 30 on its the first control valve seat 40, the coil 52 of the actuator 48 is energized, whereby the control valve member 30 is adjusted towards the injection valve element 1 1.

To start an injection process, the electromagnetic actuator 48 is energized, so that the control valve element 30 is on the first control valve seat 40, ie in the first switching position, adjusted. As a result, fuel can flow via the channel 26, through the outlet throttle 25 and the central outlet channel 42 to the injector return port 8. The cross sections of the outlet throttle 25 and the inlet throttle 22 are matched to one another in such a way that a net Outflow of fuel (control amount) from the control chamber 21 results, with the result that the injection valve element 1 1 lifts from its injection valve element seat 15 and fuel can flow into the combustion chamber. To end the injection process, the energization of the electromagnetic actuator 48 is interrupted. The control valve element 30 is adjusted by the spring force of the closing spring 50 in the second switching position, ie to the second control valve seat 32, so that the fuel through the drain passage 42 only into the chamber 45, but not on to the injector return port 8 can flow. At the same time, the hydraulic connection between the backfill channel 29 via the valve chamber 27 and the channel 26 is released into the control chamber 21, so that it is simultaneously refilled via the inlet throttle 22 and the Rückfüllkanal 29, with the result that the fuel pressure in the control chamber 21 rapidly rises and the injection valve element 1 1 is moved back on its injection valve element seat 15, whereby the nozzle hole assembly 16 is closed.

In the fuel-injector design shown in Fig. 1 is a so-called coaxial structure. An embodiment is also conceivable in which the control valve 28 is displaced, i. is not arranged coaxially to the longitudinal central axis 24.

In the embodiment of FIG. 1, both control valve seats 40, 32 are designed as flat seats. Of course, as control valve seats 40, 32, other known per se seat shapes, such as ball seats, inner cone or outer conical seats can be realized.

Claims

claims

1 . A fuel injector, in particular a common rail injector, for injecting fuel into a combustion chamber of an internal combustion engine, having an injection valve element which is adjustable as a function of the fuel pressure in a control chamber (21) between a closed position and an open position releasing a fuel flow into the combustion chamber ( 1) and with a control valve (28) assigned to a control chamber (21) and having a control valve element (30), wherein on the control valve element (30) on a first end face (41) a first sealing surface (39) for interacting with a first control erventilsitz (40) is formed,

characterized,

in that the control valve (28) is designed as a 3/2-way valve and that the control valve element (30) of the control valve (28) on a second end face (33) remote from the first end side (41) has a second sealing surface (31) for interacting with a second control valve seat (32).

2. Fuel injector according to claim 1, characterized in that the control valve (28) in the axial direction, at least approximately, is pressure balanced.

3. Fuel injector according to one of claims 1 or 2, characterized in that the first end face (41) of the control valve element (30) facing the one- or multi-part injection valve element (1 1) and the second end face (33) of the injection valve element ( 1 1) facing away.

4. Fuel injector according to one of the preceding claims, characterized in that the control chamber (21) is permanently refillable via an inlet throttle (22) and in a switching position of the control valve element (30) via a Rückfüllkanal (29) with fuel under high pressure.

5. Fuel injector according to one of the preceding claims, characterized in that the control valve element (30) abuts in a first switching position with its first sealing surface (39) on the first control valve seat (40) and in a second

Switching position with its second sealing surface (31) on the second control valve seat (32).

6. Fuel injector according to claim 5, characterized in that an axially through the control valve element (30) extending flow channel (42) is provided, through the fuel at befindlichem in the first switching position control valve element (30) to an injector return port (8) can.

7. Fuel injector according to one of claims 5 or 6, characterized in that in the second switching position, a hydraulic connection between the Rückfüllkanal (29) and the control chamber (21), preferably via a valve chamber (27) is released.

8. Fuel injector according to one of claims 6 or 7, characterized in that the flow channel (42) centrally within the control valve (28), preferably coaxially to a longitudinal central axis (24) of the fuel injector (1) runs.

9. Fuel injector according to one of claims 6 to 8, characterized in that the outlet channel (42) is aligned in the axial direction with an outlet throttle (25) through which fuel can flow out of the control chamber (21).

10. Fuel injector according to one of the preceding claims, characterized in that for adjusting the control valve element (30), preferably in the direction of the injection valve element (1 1), an electromagnetic actuator (48) is provided.