WO2014183902A1

WO2014183902A1 - Fuel injection valve for internal combustion engines

Info

Publication number: WO2014183902A1
Application number: PCT/EP2014/054928
Authority: WO
Inventors: Katja Grothe; Christian Berg
Original assignee: Robert Bosch Gmbh
Priority date: 2013-05-17
Filing date: 2014-03-13
Publication date: 2014-11-20
Also published as: DE102013209251A1

Abstract

A fuel injection valve (1) for internal combustion engines for injecting fuel at high pressure, having a pressure chamber (10) in which a nozzle needle (5) is arranged in longitudinally displaceable fashion, wherein the nozzle needle (5) interacts, by way of its longitudinal movement, with a nozzle needle seat (3) and thereby opens and closes at least one injection opening (4), and wherein the nozzle needle (5) is subjected, by the pressure in a control chamber (12), to a closing force in the direction of the nozzle needle seat (3), and having a feed bore (22) via which the pressure chamber (10) can be supplied with fuel at high pressure and which forms a flow cross section at the pressure chamber-side end thereof, wherein the nozzle needle (5), by way of its stroke movement, varies the opened-up flow cross section of the feed bore (22).

Description

Description title

Fuel injection valve for internal combustion engines

The invention relates to a fuel injection valve for internal combustion engines, as it is used for fuel injection into the combustion chamber of an internal combustion engine.

State of the art

From the published patent application DE 10 2007 032 741 AI is a

A fuel injection valve is known which comprises a holding body in which a pressure chamber is formed with a longitudinally displaceably arranged nozzle needle, which with a nozzle needle seat of the holding body

interacts. The nozzle needle seat limits the pressure chamber, wherein a fuel flow to at least one injection port is made possible or interrupted by the interaction of the nozzle needle with the nozzle needle seat. Between holding body and nozzle needle hub-independent gap reactor is formed. The gap throttle accelerates the closing operation of the nozzle needle in such a way that during the closing operation in the pressure chamber upstream of the

Gap throttle is a higher pressure than downstream of the gap choke; the resulting hydraulic forces on the nozzle needle in the direction of its longitudinal axis are then greater than without gap choke.

Furthermore, from the published patent EP 2 280 160 A2 a

interacts. The nozzle needle seat limits the pressure chamber, whereby a fuel flow through the interaction of the nozzle needle with the nozzle needle seat at least one injection opening is enabled or interrupted. The fuel flow to the injection openings flows between the nozzle needle and the wall of the pressure chamber, wherein between the nozzle needle and the wall of the pressure chamber in the vicinity of the nozzle needle seat a throttle point is formed to pressure fluctuations in the pressure chamber, due to the opening and

Closing operations of the nozzle needle arise to dampen.

Due to the known throttle but only higher frequency

Pressure fluctuations in the area of the nozzle needle seat are damped, but not or only insufficiently low-frequency pressure fluctuations. On the one hand, this results in instabilities and fluctuations in the injection rate, and on the other hand, the overshoots of the high pressure in the pressure chamber at the end of the closing process reduce the service life of the nozzle body. Another disadvantage of the known throttle point is the strong dependence of the throttle effect of manufacturing tolerances.

Disclosure of the invention

The fuel injection valve according to the invention has more constant injection rates and achieves a better multiple injection capability. In addition, a better Kleinstmengenfähigkeit the fuel injection valve is achieved by a slower opening of the nozzle needle. Furthermore, the life of the nozzle body is increased and the throttling effect more robust

Manufacturing tolerances.

For this purpose, the fuel injection valve to a pressure chamber, in which a

Nozzle needle is arranged longitudinally displaceable, wherein the nozzle needle by their

Longitudinal movement cooperates with a nozzle needle seat and thereby at least one injection opening opens and closes, and wherein the nozzle needle undergoes a directed in the direction of the nozzle needle seat closing force by the pressure in a control room. In addition, the fuel injection valve has a feed bore, via which the pressure chamber can be supplied with fuel under high pressure and at its pressure-chamber-side end

Flow cross section forms. Due to its stroke movement, the nozzle needle changes the released flow cross-section of the feed bore and thus also the associated throttling effect. The fuel injection valve according to the invention is a more robust

Throttling achieved, since the throttle body is no longer designed radially circumferentially between the nozzle needle and the wall of the pressure chamber, but it results from the (partial) opening and closing a

Pressure chamber filling feed bore, by the stroke of the nozzle needle and the nozzle needle geometry. The nozzle needle geometry is designed so that at the end of the opening process results in a small throttle effect, which is preferably defined only by the diameter of the feed bore. At the end of the closing process, however, results from the partial closing of the flow cross-section, a stronger throttle effect, which is defined by the shared flow cross-section of the feed bore. Upon completion of the closing process, it comes due to the kinetic energy of the in the

Pressure chamber nachströmenden and high pressure fuel to pressure oscillations; The resulting maximum pressures are also referred to as high pressure overshoot. The stronger throttling action at the end of the closing operation reduces the amount or momentum of the fuel flowing into the pressure chamber and thereby leads to maximum damping, to reduced high-pressure overshoots and to more constant injection rates. In a first advantageous embodiment of the invention, the

Nozzle needle below its guide section at the level of the feed bore on a conical section. Due to the conical geometry is changed by the Düsennadelhub the shared flow cross-section of the feed bore and with him the throttle effect. The angle of the cone can be used to define the extent to which the released flow cross-section of the feed bore changes with the nozzle needle stroke.

In a further embodiment, the nozzle needle has a shoulder below its guide section instead of the conical section. in the

closed state of the nozzle needle, this paragraph partially covers the opening of the feed hole. In the opened state of the nozzle needle, the released flow cross-section of the feed bore is increased or the opening of the feed bore completely released. As a result, the released flow cross-section changing with the nozzle needle stroke and thus the throttling action become more robust with respect to manufacturing tolerances. In a further embodiment of the invention, the guide section of the nozzle needle has at least one bevel on the shoulder. As a result, the gradient of the throttling effect changing with the nozzle needle stroke can be increased. By using at least one bevel, it is also possible to position the shoulder at the end of the guide portion of the nozzle needle so that it completely covers the opening of the feed bore in the closed state of the nozzle needle. The released flow cross section is then defined by the geometry of the bevel.

In a further embodiment of the invention, the nozzle needle is guided at its end facing away from the nozzle needle seat in a valve piece.

Feed bore, inlet bore and control chamber are also formed here in the valve piece. A compact design with as few individual parts can be realized. In addition, the fuel volume between the throttle point and nozzle needle seat is increased, since the throttle point is so at the nozzle needle seat facing away from the end of the pressure chamber; the increased fuel volume can better dampen pressure surge occurring in the pressure chamber. Particularly preferably, the feed bore opens into the pressure chamber side in a circumferential annular groove, which is formed in the valve piece. The filling of the pressure chamber with high-pressure fuel is thus uniform and any cuts on the shoulder of the nozzle needle must not be fixed against rotation to the feed bore.

In a further embodiment of the invention, the valve piece is surrounded in an annular space on the outside by high pressure. The pressure chamber facing away from the end of the feed hole opens into this annulus. Furthermore, the inlet bore for the control chamber can be designed so that it also opens into the annulus. The connection of feed bore and control chamber with the high-pressure channel is easily feasible by the use of an annular space manufacturing technology, complex holes can be avoided.

drawings Fig.l shows a longitudinal section through a fuel injection valve according to the invention in a schematic representation, wherein only the essential areas are shown.

Fig.2 shows the designated II section of Fig.l another

Embodiment and

3 shows a longitudinal section of a further embodiment in the same representation as in Figure 2.

description

Fig.l schematically shows an inventive fuel injection valve 1 in longitudinal section. The fuel injection valve 1 has a holding body 6 and a nozzle body 2 which are mutually opposed by a not shown

Clamping device are braced. Holding body 6 and nozzle body 2 form in their interior a pressure chamber 10, in which a piston-shaped nozzle needle 5 is arranged longitudinally displaceable. At the nozzle needle 5, a shoulder 50 is arranged, which together with the holding body 6, a feed gap 51st

forms, which achieves a throttle effect, which is independent of the stroke of the nozzle needle 5. The nozzle needle 5 acts at its the combustion chamber

facing end with a nozzle needle seat 3 of the nozzle body 2 together and can thereby open or close one or more injection openings 4 in the nozzle body 2 via the fuel in the combustion chamber a

Internal combustion engine can be injected. At the opposite end of the combustion chamber of the nozzle needle 5, a control chamber 12 is arranged, via the pressure of the opening and closing movement of the nozzle needle 5 is controlled in such a way that at pressure reduction in the control chamber 12, the nozzle needle 5 lifts from the nozzle needle seat 3 and so the at least one Injection opening 4 releases and upon pressure increase in the control chamber 12 the

Nozzle needle 5 is pressed against the nozzle needle seat 3 and thus closes the at least one injection opening 4. In the embodiment shown in Fig.l the control chamber 12 is arranged in a valve member 7 which limits the pressure chamber 10 facing away from the combustion chamber. A closing spring 8, which biases the nozzle needle 5 against the nozzle needle seat 3, is arranged in the control chamber 12 and acts on the end face of the nozzle needle 5 opposite the combustion chamber. A guide section 17 of the nozzle needle 5, which is formed on the end of the nozzle needle 5 opposite the combustion chamber , is guided radially in the valve piece 7. This guide portion 17 limits at its upper end the control chamber 12 and at its lower end the pressure chamber 10th

The control chamber 12 is connected through an inlet bore 20, which with a

High-pressure passage 15 is connected and is also formed in the valve piece 7, supplied with fuel under high pressure, which is provided for example by a common rail, not shown. From the control chamber 12 a Abiaufbohrung 21, which passes through a valve disc 13, leads into a low-pressure space 11. The opening of the Abiaufbohrung 21 in the low-pressure space 11 can from a control valve 9, the e. is electromagnetically controlled, opened or closed.

A feed bore 22 connects the pressure chamber 10 with the high pressure passage 15. The pressure chamber 10 facing opening of the feed bore 22 is in the closed position of the nozzle needle 5 partially and in the

Opening position of the nozzle needle 5 completely released.

In the embodiment shown in Fig.l an at least partially dependent on the stroke of the nozzle needle 5 throttling of the fuel flowing into the pressure chamber 10 fuel at the opening of the feed bore 22 through a conical section 18 of the nozzle needle 5. Furthermore Fig.l shows an annular space 28, which surrounds the valve member 7 at high pressure and both feed bore 22 and inlet bore 20 with the high-pressure passage 15 and thus with a high-pressure fuel source, eg a common rail, connects.

At the beginning of the injection process is in both the pressure chamber 10 and in the control chamber 12 high pressure. To open the nozzle needle 5 is the

Control valve 9 the Abiaufbohrung 21 free and thus connects the control chamber 12 with the low-pressure chamber 11. The pressure in the control chamber 12 drops off and with him the acting on the nozzle needle 5 closing force, whereupon the nozzle needle 5 opens and the injection port 4 is free. At the beginning of the opening process, the nozzle needle 5 opens relatively slowly due to the hydraulic power ratios and thus achieves a better Kleinstmengenfähigkeit. In the open nozzle needle position, the nozzle needle 5 releases the entire flow cross section of the feed bore 22. The inflow of high-pressure fuel into the pressure chamber 10 is determined only by the geometry of the feed bore 22 and can flow freely. During the injection process, the pressure in the pressure chamber 10 decreases.

To complete the injection, the control valve 9 closes the

Abiaufbohrung 21 and thus separates the control chamber 12 from the low-pressure chamber 11. About the inlet bore 20 of the control chamber 12 is filled with high-pressure fuel. The force acting on the nozzle needle 5 closing force increases and the nozzle needle 5 is thereby pressed against the nozzle needle seat 3 and closes the injection port 4. During this

Closing reduces the nozzle needle 5 by their lifting movement the shared flow cross-section of the feed bore 22, so that with the progress of the closing movement of the nozzle needle 5, the throttling effect of the gap between the conical portion 18 and the mouth of the

Feeding bore 22 is increased. This leads to a faster closing of the nozzle needle 5. With the closing of the nozzle needle 5, the pressure rises in the

Due to the strong throttling effect at the mouth of the feed bore 22 at the end of the closing process, the fuel under high pressure can flow only throttled into the pressure chamber 10, and the Hochdrucküberschwinger in the pressure chamber 10 is thereby reduced.

Fig.2 shows the designated II section of Fig.l another

Embodiment of the fuel injection valve 1 according to the invention, in which the guide portion 17 of the nozzle needle 5 is guided in the valve piece 7 and the nozzle needle 5 below its guide portion 17 in the region of

Feeding bore 22 has a shoulder 30 which during the stroke of

Nozzle needle 5 along the cross section of the pressure chamber 10 facing Opening the feed bore 22 is moved and so the released

Flow cross section of the feed bore 22 changed. Preferably, in the closed position of the nozzle needle 5, the opening of the feed bore 22 partially and in the open position of the nozzle needle 5, the opening of the

Feed bore 22 completely released. This embodiment has a comparatively simple geometry.

FIG. 3 shows, in the same representation as FIG. 2, a further embodiment of the fuel injection valve 1 according to the invention in the closed position of the nozzle needle 5, in which the guide section 17 of the nozzle needle 5 is provided with at least one bevel 31 on the shoulder 30. The feed bore 22 opens pressure chamber side in a circumferential annular groove 35 which is formed in the valve member 7, so that in the closed position of the nozzle needle 5 shown always a connection of the feed bore 22 is ensured with the pressure chamber 10 via the bevels 31; a filling of the pressure chamber 10 is always ensured by the bevels 31 and the annular groove 35 in the closed state of the nozzle needle 5. This embodiment is comparatively robust with respect to manufacturing tolerances.

Through the use of bevels 31 and the annular groove 35, a constant throttling action in the first part of the opening operation of the nozzle needle 5 can first be achieved via a defined nozzle needle stroke. If the shoulder 30 is moved during the second part of the opening process of the nozzle needle 5 along the cross section of the pressure chamber 10 facing opening of the feed bore 22, the throttle effect is reduced with increasing stroke of

Nozzle needle 5, until the feed bore 22 in the third part of the

Opening operation of the nozzle needle 5 is completely released from paragraph 30; From this point on, the throttle effect is only determined by the cross section of the feed bore 22.

During the closing of the nozzle needle 5 changes the

Throttle action correspondingly in reverse order: first constant minimum throttle effect, defined by the cross section of the feed bore 22, then linearly increasing throttling effect as long as the shoulder 30 along the cross section of the pressure chamber 10 facing opening of the Feeding bore 22 is moved and in the final phase of the closing operation of the nozzle needle 5 is a constant throttling action, defined by the bevels 31st

Claims

claims

1. Fuel injection valve (1) for internal combustion engines for the injection of fuel under high pressure with a pressure chamber (10) in which a nozzle needle (5) is longitudinally displaceable, wherein the nozzle needle (5) by their longitudinal movement with a nozzle needle seat (3) cooperates and thereby opening and closing at least one injection opening (4), and wherein the

Nozzle needle (5) by the pressure in a control chamber (12) in the direction of the nozzle needle seat (3) directed closing force undergoes, and with a

Feed bore (22) through which the pressure chamber (10) can be supplied with fuel under high pressure and forms a flow cross-section at its pressure-chamber-side end, characterized in that the nozzle needle (5) released by their stroke movement

Flow cross section of the feed bore (22) changed.

2. Fuel injection valve (1) according to claim 1, characterized in that the nozzle needle (5) at the height of the flow cross section has a conical portion (18) and thereby changed during the stroke of the shared flow cross section of the feed bore (22).

3. Fuel injection valve (1) according to claim 1, characterized in that the nozzle needle (5) at the height of the flow cross-section has a shoulder (30) and thereby during the stroke, wherein the shoulder (30) along the diameter of the feed bore (22). is running, the shared

Flow cross section of the feed bore (22) changed.

4. Fuel injection valve (1) according to claim 3, characterized in that a guide portion (17) of the nozzle needle (5) on the shoulder (30) has at least one bevel (31).

5. Fuel injection valve (1) according to claim 3 or 4, characterized

characterized in that the shoulder (30) in the closed state of the nozzle needle (5) partially covers the opening of the feed bore (22).

6. Fuel injection valve (1) according to one of claims 1 to 5, characterized in that the control chamber (12) in a valve piece (7) is formed and that the valve piece (7), the guide portion (17) of the nozzle needle (5) radially ,

7. Fuel injection valve (1) according to one of claims 1 to 6, characterized in that the feed bore (22) in the valve piece (7) is formed.

8. Fuel injection valve (1) according to claim 7, characterized in that the feed bore (22) pressure chamber-side in an annular groove (35) opens, which is formed in the valve piece (7).

9. Fuel injection valve (1) according to one of claims 6 to 8, characterized in that the valve piece (7) in an annular space (28) is surrounded by high pressure and the feed bore (22) this annular space (28) with the

Pressure chamber (10) connects.

10. Fuel injection valve (1) according to claim 9, characterized in that an inlet bore (20) connects the annular space (28) with the control chamber (12).