WO2017108298A1

WO2017108298A1 - Fuel injector

Info

Publication number: WO2017108298A1
Application number: PCT/EP2016/078379
Authority: WO
Inventors: Andreas Gruenberger; Hans-Christoph Magel
Original assignee: Robert Bosch Gmbh
Priority date: 2015-12-21
Filing date: 2016-11-22
Publication date: 2017-06-29
Also published as: DE102015226350A1

Abstract

The invention relates to a fuel injector for injecting fuel under high pressure, comprising a housing (2) in which a pressure chamber (10) is formed which can be filled with fuel under high pressure, and in which a nozzle needle (12) interacts with a nozzle seat (13) to open and close at least one injection opening (15). In this regard, the end of the nozzle needle (12) facing away from the nozzle seat (13) is guided in a guide sleeve (20), which delimits a control chamber (25) together with the end face (16) of the nozzle needle (12) facing away from the nozzle seat, which control chamber can be filled via an inlet throttle (31) with fuel under high pressure. A control chamber sleeve (26) is arranged in a longitudinally movable manner in the control chamber (25), which sleeve opens and closes a connection of the inlet throttle (31) to the control chamber (25) via its longitudinal movement, wherein the control chamber sleeve (26) has a longitudinal bore (36), in which a guide pin (33) is arranged.

Description

description

title

fuel injector

The invention relates to a fuel injector, as it is preferably used for the injection of fuel under high pressure in the combustion chamber of an internal combustion engine.

State of the art

Fuel injectors for injecting fuel under high pressure into a combustion chamber of an internal combustion engine are known in various variants from the prior art. Thus, from DE 10 2012 220 025 AI a fuel injector is known which has a longitudinally movable in a pressure chamber nozzle needle, which cooperates for opening and closing an injection port with a nozzle seat. The nozzle needle is guided with its end facing away from the nozzle seat in a sleeve which defines a control chamber together with the nozzle needle. Within the control chamber, a longitudinally movable control in the form of a control piston is arranged, which has the function of keeping the return flow rate as low as possible, ie the proportion of the compressed fuel, which is fed back into the return of the fuel injector. For this purpose, the control piston hydraulically closes the inlet throttle when a control valve is opened, via which the control chamber can be connected to a low-pressure chamber. As a result, during this opening phase, in which the control chamber is connected to the low-pressure space, no compressed fuel flows into the control space and from there directly into the low-pressure space.

In the known fuel injector, the placement of this control piston within the control chamber is structurally complex and requires in the components in which the control piston is guided, a high processing cost with the necessary precision. This increases the cost of the fuel injectors and makes them sensitive to disturbances, for example due to manufacturing tolerances.

Advantages of the invention

In contrast, the fuel injector according to the invention has the advantage that the control element in the form of a control sleeve can be guided precisely within the control chamber, without the processing complexity being substantially increased thereby. For this purpose, the fuel injector to a fuel-filled under high pressure pressure chamber in which a nozzle needle for opening and closing at least one injection port with a nozzle seat cooperates, wherein the nozzle seat facing away from the end of the nozzle needle is guided in a guide sleeve. The guide sleeve, together with the end face of the nozzle needle facing away from the nozzle, defines a control chamber which can be filled with fuel at high pressure via an inlet throttle. In the control chamber, a control chamber sleeve is arranged to be longitudinally movable, which opens and closes a connection of the inlet throttle to the control chamber by their longitudinal movement, wherein the control chamber sleeve has a longitudinal bore in which a guide pin is arranged.

By guiding the control chamber sleeve on a guide pin, which engages in a longitudinal bore of the control chamber sleeve, a precise guidance of the control chamber sleeve is possible, the manufacturing cost is relatively low, since the longitudinal bore can be formed in the control chamber sleeve in a separate processing of the control chamber sleeve outside of the fuel injector and no elaborate processing of internal surfaces is necessary.

In a first advantageous embodiment, the guide pin is formed integrally with a throttle plate, which forms a part of the housing and which limits the pressure chamber. The guide pin can thus be manufactured in a simple manner, for example, by a turning process in the production of the throttle disk and allows a precise guidance of the control chamber sleeve on the journal. In the guide journal, a connection bore is preferably excluded. forms, via which the control chamber with a low-pressure space is connectable. Thus, a compact structure of the fuel injector can be achieved. In this case, the connection of the control chamber to the low-pressure chamber can preferably be opened or closed by means of a control valve, wherein the connection bore is a part of this connection.

In a further advantageous embodiment, the longitudinal bore is connected to the control chamber via an outlet throttle, which is formed in the control chamber sleeve, which allows a compact construction.

Furthermore, it can be provided in an advantageous manner that the control chamber sleeve facing away from the nozzle needle end face has a sealing edge with which the control chamber sleeve rests against the housing and thereby seals a trained between the guide pin and the control chamber sleeve annulus against the control chamber. A hydraulic and longitudinally effective force can be exerted on the control chamber sleeve via this annular space in order to move it in its longitudinal direction and thereby to ensure the function of the fuel injector.

In a further advantageous embodiment, a spring is arranged under prestress between the control chamber sleeve and the guide sleeve, which presses the control chamber sleeve against the housing. As a result, an accurate positioning of the control chamber sleeve is ensured, in particular when the hydraulic forces are eliminated or for establishing a clear starting position at the beginning of the working cycle.

In a further advantageous embodiment, a further inlet throttle is formed in the guide sleeve, which connects the control chamber with the high-pressure chamber. About the additional inlet throttle, the inlet can be accelerated into the control chamber, so that when closing the fuel injection valve, so the movement of the nozzle needle to the nozzle seat, the high pressure level can be reached again very quickly and thus a dripping of fuel from the injection ports is avoided which would adversely affect the hydrocarbon emissions of the corresponding internal combustion engine. Further advantages and advantageous embodiments of the invention are described in the description and the drawings.

drawing

In the drawing, an inventive fuel injection valve is shown in longitudinal section.

Description of the embodiment

In the single FIGURE of the drawing, a fuel injector according to the invention is shown schematically in longitudinal section. The fuel injector 1 has a housing 2, which comprises an injector body 3, a valve disk 4, a throttle disk 5 and a nozzle body 6, which are clamped in a liquid-tight manner against one another by means of a clamping nut 8. In the nozzle body 6, a pressure chamber 10 is formed, which can be filled with fuel under high pressure via a high-pressure passage 17 formed in the throttle disk 5, the valve disk 4 and the injector body 3. The fuel under high pressure is made available for example by a fuel high-pressure accumulator, which in turn is supplied via a high-pressure fuel pump, both of which is not shown in the drawing. In the high pressure chamber 10, a piston-shaped valve needle 12 is arranged longitudinally displaceable, which is guided with a guide portion 112 in the pressure chamber 10. The nozzle needle 12 has at its brennraumseiti- gen the end of a sealing surface 14, with which the nozzle needle 12 cooperates with a nozzle seat 13 and thereby one or more injection ports 15 can open and close. If the nozzle needle 12 is lifted from the nozzle seat 13, then fuel can flow from the pressure chamber 10 to the injection openings 15 and be ejected through it. If the nozzle needle 12 in contact with the nozzle seat 13, the injection openings 15 are sealed against the pressure chamber 10.

The nozzle needle 12 is guided with its end facing away from the nozzle seat 13 in a guide sleeve 20. The guide sleeve 20 is thereby replaced by a closing spring 22 pressed against the throttle plate 5, wherein the closing spring 22 is supported at its other end to a shoulder 23 on the nozzle needle 12. Through the guide sleeve 20 and the nozzle seat facing away from the end face 16 of the nozzle needle 12, a control chamber 25 is limited, which is completed by the control chamber sleeve 20 against the pressure chamber 10. Within the control chamber 25, a control chamber sleeve 26 is arranged, which is also pressed against the throttle plate 5 by a spring 34 which is arranged between the control chamber sleeve 26 and the guide sleeve 20 under bias. The control chamber sleeve 26 in this case has a longitudinal bore 36 into which a guide pin 33 protrudes and through which the control chamber sleeve 26 is guided during its longitudinal movement.

The guide pin 33 may be integrally formed with the throttle plate 5 or manufactured as a separate component, which is then connected to the throttle plate 5. The longitudinal bore 36 of the control chamber sleeve 26 is connected via an outlet throttle 30 with the control chamber 25. The fuel from the control chamber 25 can so on the outlet throttle 30 and in the

Guide pin 33 and the throttle disk 5 formed connecting bore 35, which opens into a further connecting bore 37, are connected to a low-pressure chamber 48, in which there is always a low fuel pressure due to a connected to a return system Abiaufbohrung 50. In this case, the connection, consisting of the connection bore 35 and the further connection bore 37, can be opened or closed by means of a control valve 40.

The control valve 40 is arranged in the low-pressure chamber 48 and comprises an electromagnet 42, which is arranged within a magnetic core 43. Furthermore, in the low-pressure chamber 48, a magnet armature 45 is movably arranged with a closing element 47, which is movable by the electromagnet 42 against the force of an armature spring 49. If the solenoid 42 is energized, the armature 45 is pulled away from the mouth of the further communication bore 37, so that fuel from the control chamber 25 through the outlet throttle

30 and the connecting bores 35, 37 can flow into the low pressure chamber 48. If the energization of the electromagnet 42 is terminated, then the armature spring 49 presses the closing element 47 against the mouth of the further connecting bore 37 and interrupts the connection of the control chamber 25 with the low-pressure chamber 48. The control chamber sleeve 26 has at its outer edge a sealing edge 32, which is annularly circumferential and comes to rest on the throttle plate 5. Characterized an annular space 38 is limited between the control chamber sleeve 26 and the guide pin 33, which is filled via a formed in the throttle disk 5 inlet throttle 31 with fuel at high pressure.

The operation of the fuel injector is as follows: At the beginning, in all spaces of the fuel injection valve, apart from the low-pressure chamber 48, the high fuel pressure prevails, as provided by the high-pressure line 17 in the fuel injector. Due to the pressure in the control chamber 25, the nozzle needle 12 is pressed against the nozzle seat 13 and thus closes the injection openings 15. Since a part of the sealing surface 14 of the nozzle needle 12 is not acted upon by high fuel pressure in the pressure chamber 10, the hydraulic force on the end face 16 of the nozzle needle 12 sufficient to push them into their closed position. If injection is to take place, the electromagnet 42 is supplied with current and pulls the magnet armature 45 and thus the closing element 47 away from the mouth of the further drain bore 37 against the force of the armature spring 49 and opens a hydraulic connection between the low-pressure chamber 48 and the control chamber 25. Due to the high pressure difference between the control chamber 25 and the low-pressure chamber 48 instantaneously fuel flows through the outlet throttle 30 and thus reduces the pressure in the control chamber 25 and thus also the hydraulic closing force on the end face 16 of the nozzle needle 12. Once acting in the longitudinal direction hydraulic Force on the nozzle needle 12 within the pressure chamber 10 is sufficient to overcome the hydraulic force within the control chamber 25 and the force of the closing spring 22, lifts the nozzle needle 12 from the nozzle seat 13 and releases the injection openings 15. As a result, fuel flows between the sealing surface 14 and the nozzle seat 13 to the injection openings 15 and is injected through this into a combustion chamber of the internal combustion engine. Since the inlet throttle 31 is sealed at this time by the control chamber sleeve 26 against the control chamber 25, no fuel flows from the high pressure passage 17 into the control chamber 25, so that the amount of fuel that enters the low pressure chamber 48 is relatively low. If the injection is terminated, the solenoid 42 is no longer energized and the armature spring 49 presses the closing element 47 again against the opening of the further communication bore 37 and thus interrupts the connection of the control chamber 25 with the low-pressure chamber 48th Die Druck in der Längsbohrung 36 der Control chamber sleeve 26 was significantly lower during the open control valve 40 than in the control chamber 25 due to the outlet throttle 30, which causes a pressure drop. This is sufficient to press the control chamber sleeve 26 against the throttle disk 5 and seal the annular space 38, which is under high pressure, against the control chamber 25. Now closes the control valve 40, the pressure within the longitudinal bore 36 quickly equalizes against the pressure in the control chamber 25, so now an excess force in the direction of the nozzle seat on the control chamber sleeve 26 acts due to the high pressure in the annular space 38, so that the control chamber sleeve 26 of the throttle plate 5 lifts and releases a hydraulic connection between the annular space 38 and the control chamber 25. As a result, again fuel flows under high pressure in the control chamber 25 and there again builds up the high fuel pressure, which leads to the closing of the nozzle needle 12. As soon as the pressure in the control chamber 25 is equal to the pressure in the annular space 38, the closing spring 22 pushes the control chamber sleeve 26 back into contact with the throttle disk 5.

To accelerate the closing process, a further inlet throttle 41 may be provided, which is arranged, for example, within the guide sleeve 20. Although the return flow amount entering the low-pressure space 48 during the opening phase of the fuel injector is increased by this additional intake throttle 41, the closing operation of the nozzle needle 12 is accelerated because the fuel is not only filled via the opened sealing edge 32 of the control chamber sleeve 26. In addition, via the further inlet throttle 41. Due to the now rapidly building up fuel pressure within the control chamber 25, the nozzle needle 12 is closed quickly, so there is no dripping fuel through the injection ports 15, which is unfavorable to the hydrocarbon emissions of the engine the fuel injector supplies, affects.

Claims

claims

A fuel injector for injecting fuel under high pressure with a housing (2) in which a high pressure fuelable pressure chamber (10) is formed, in which a nozzle needle (12) for opening and closing at least one injection port (15) cooperates with a nozzle seat (13), wherein the nozzle seat (13) facing away from the end of the nozzle needle (12) in a guide sleeve (20) is guided, which together with the nozzle seat facing away from end face (16) of the nozzle needle (12) has a control chamber (25). limited, which is fillable via an inlet throttle (31) with fuel at high pressure, characterized in that in the control chamber (25) a control chamber sleeve (26) is longitudinally movably arranged, the connection of the inlet throttle (31) to the control chamber (25) by their Longitudinal movement opens and closes, wherein the control chamber sleeve (26) has a longitudinal bore (36) in which a guide pin (33) is arranged.

2. Fuel injector according to claim 1, characterized in that the guide pin (33) is formed integrally with a throttle disc (5) which forms part of the housing (2) and which limits the pressure chamber (10).

3. Fuel injector according to claim 1 or 2, characterized in that in the guide pin (33) has a connecting bore (35) is formed, via which the control chamber with a low-pressure chamber (48) is connectable.

4. Fuel injector according to claim 3, characterized in that the connection (38, 37) of the control chamber (25) with the low-pressure chamber (48) by means of a control valve (40) can be opened and closed.

5. Fuel injector according to one of claims 1 to 4, characterized in that the longitudinal bore (36) with the control chamber (25) via an outlet throttle (30) is connected, which is formed in the control chamber sleeve (20).

6. Fuel injector according to one of claims 1 to 5, characterized in that the control chamber sleeve (26) facing away from the nozzle needle (12) end face has a sealing edge (32) with which the control chamber sleeve (26) rests against the housing (2) and thereby a between the guide pin (33) and the control chamber sleeve (26) formed annular space (38) can seal against the control chamber (25).

7. Fuel injector according to one of claims 1 to 6, characterized in that between the control chamber sleeve (26) and the guide sleeve (20) a spring (34) is arranged under bias, which presses the control chamber sleeve (26) against the housing (2) ,

8. Fuel injector according to one of claims 1 to 7, characterized in that in the guide sleeve (20), a further inlet throttle (41) is formed, which connects the control chamber (25) with the high-pressure chamber (10).