WO2013000618A1

WO2013000618A1 - Fuel injector

Info

Publication number: WO2013000618A1
Application number: PCT/EP2012/058808
Authority: WO
Inventors: Florian Schmid; Johannes UNRATH; Eike Kobes; Holger Rapp
Original assignee: Robert Bosch Gmbh
Priority date: 2011-06-30
Filing date: 2012-05-11
Publication date: 2013-01-03
Also published as: EP2726728B1; DE102011081643A1; EP2726728A1

Abstract

The invention relates to a fuel injector (100), having a holding body (2) and a nozzle body (8) which is clamped axially against the holding body (2) by means of a nozzle clamping nut (9) with a restrictor plate (6) and a valve plate (4) being arranged in between, wherein a control valve (30) which can be switched between at least two switching positions is arranged in the valve plate (4) in a control-valve chamber (31), which control valve (30) can be actuated by means of an actuator which is arranged in an actuator chamber (23) of the holding body (2) and is preferably configured as a piezoelectric actuator, wherein fuel can flow through the actuator chamber (23) which is coupled hydraulically to a return bore (65) via a connection (73), and wherein a return quantity of the fuel which escapes from the control-valve chamber (31) during the switching of the control valve (30) and/or a return quantity of the fuel which escapes from the control-valve chamber (31) in the switching pauses of the control valve (30) can be discharged at least indirectly into the return bore (65) via a further connection. According to the invention, it is provided that the further connection has a flow path which comprises the annular chamber (5) between the nozzle clamping nut (9) and the nozzle body (8) and/or the valve plate (4) and/or the restrictor plate (6).

Description

Description fuel injector

State of the art

The invention relates to a fuel injector according to the preamble of claim 1.

Such a fuel injector is known from DE 10 2008 001 330 A1 of the Applicant. In the known fuel injector, the movement of a nozzle needle arranged in a nozzle needle is generated via a control valve, which has a valve element, which in turn via a solenoid actuator or a piezoelectric actuator, at least indirectly, is controlled. In a movement of the valve element, which is required to allow lifting of the nozzle needle from its sealing seat, a control amount is derived in the receiving space of the Magnetaktors or the piezoelectric actuator, which in turn has a connection to a return port to the fuel injector. The outflow of the fuel via throttles and the valve seat of the valve element is associated with a strong pressure reduction of the originally high-pressure fuel. Such pressure reduction is physically associated with a temperature increase of the fuel.

Current fuel injection systems in auto-ignition internal combustion engines operate at a system pressure of about 1500 bar to a maximum of about 2000 bar. For future fuel efficiency reasons, it is planned to increase the system pressure to well over 2000bar. This means that in the mentioned outflow of the control amount in the region of the control valve, an even greater pressure reduction is associated with an associated even greater increase in the fuel temperature. Especially with piezo actuators there is a temperature upper limit up to which the piezo actuators work reliably, without the need for additional design measures or piezoelectric actuators made of more temperature-resistant materials are required. However, in the case of the aforementioned planned system pressure increase, a temperature range of the fuel is reached at which reliable operation is no longer guaranteed in conventional piezo actuators. For this reason, it is known, for example from the applicant's later published DE 10 2010 040381 A1, to cool the space in which the piezoactuator is located by means of an additional fuel flow with cooler or not previously flown through the high pressure circuit. However, such a measure is relatively expensive in terms of design and consequently produces undesirable additional costs.

Disclosure of the invention

Based on the illustrated prior art, the present invention seeks to further develop a fuel injector according to the preamble of claim 1 such that the flowing into the receiving space for the piezoelectric actuator as well as in the return bore fuel occurs with respect to the prior art reduced temperature, without the need for additional (external) fuel supply from an area outside the fuel injector. This object is achieved in a fuel injector with the features of claim 1 according to the invention that the outflowing when switching the control valve control amount passes through a flow path in an annular intermediate region between the nozzle retaining nut and the nozzle body and / or the valve plate and / or throttle plate. There, the fuel can be cooled before it enters the immediate vicinity of temperature-sensitive components.

Advantageous developments of the fuel injector according to the invention are specified in the subclaims. All combinations of at least two of the features disclosed in the claims, the description and / or the figures fall within the scope of the invention. In a constructive preferred implementation of the connection to or from the annular intermediate region is proposed that the further connection a discharge channel into the annulus and a return channel from the annulus comprises, wherein the return channel opens at least indirectly in the return bore.

Most preferably, it is provided that the diversion channel and the return channel are formed at least substantially as arranged radially to the longitudinal axis of the valve plate channels.

In order to allow the longest possible flow path or the longest possible residence time of the hot fuel in the annular intermediate area, it is provided in a further variant of the invention that the discharge and the return channel on opposite sides of the from the valve plate, the throttle plate and the nozzle body existing composite are arranged.

In addition, it may further be provided that a part of the control quantity flows out of the control valve chamber into the actuator chamber. In other words, this means that only a part of the control amount is passed over the annular intermediate area, while another part of the control amount is discharged directly into the actuator space.

From the aforementioned DE 10 2008 001 330 A1 it is known to form the control valve with a sealing sleeve, in which the control bolt is arranged longitudinally displaceable. About the annular gap between the valve pin and the

Sealing sleeve passes under high pressure fuel in a leakage or low pressure chamber or a Abiaufbohrung. Since the fuel flowing into the annular gap has previously been heated, if necessary, by the flow through the throttles and then compressed again by the closing of the control valve, a particularly high fuel temperature can be produced here by reheating the already heated fuel. Therefore, it is proposed in a further variant that an additional connection between the leakage or low-pressure chamber and the return bore is provided, which is connected to the annulus.

In a variant of the last-mentioned embodiment, it is possible that the connection has a drain, which opens into a discharge channel. In addition, it may be be hen that the diversion channel opens via the annulus and a return channel in a riser, which is connected to the return line. An embodiment described so far can be structurally relatively simple and compact form.

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 partial region of a fuel injector according to the prior art in a longitudinal section,

Fig. 2 shows a detail of a fuel injector according to the invention, in

a control amount of fuel from a control chamber according to the invention led over an annular space, as well as again in the composite of the concrete case between a holding body and a nozzle clamping nut tensioned plates is introduced, the control amount can be discharged via a return path from the injector, in a kinked longitudinal section and

Fig. 3

and

4 shows a fuel injector according to the invention, in which a leakage quantity from a low-pressure space in an annular space is cooled, likewise in kinked longitudinal sections.

The same components or components with the same function are provided in the figures with the same reference numerals.

In Fig. 1, a fuel injector 1 according to the prior art is shown in longitudinal section. The fuel injector 1 has a holding body 2, a valve plate 4, a throttle plate 6 and a nozzle body 8 which abut each other in this order. The components are pressed against each other by a (nozzle) clamping nut 9, which is supported on a shoulder of the nozzle body 8 and is held by a thread on the holding body 2. Between the Clamping nut 9 and a portion of the nozzle body 8 and over the entire height of the valve plate 4 and the throttle plate 6, an annular space 5 is formed, in the area at least the valve plate 4 and the throttle plate 6 spaced from the clamping nut 9 are arranged. In the nozzle body 8, a pressure chamber 14 is formed, in which a piston-shaped nozzle needle 10 is arranged longitudinally displaceable. The nozzle needle 10 has at its end facing the combustion chamber on a sealing surface 11, with which it cooperates with a nozzle seat 13 which is formed at the combustion chamber end of the pressure chamber 14. From the nozzle seat 13 go from one or more injection ports 12, which open in installation position of the fuel injector 1 directly into a combustion chamber of the internal combustion engine. The nozzle needle 10 is guided in a middle section in the pressure chamber 14, wherein the fuel is passed through several slits 15 to the injection openings 12.

The nozzle needle 10 is guided at its end remote from the combustion chamber of the internal combustion engine in a sleeve 22, wherein the sleeve 22 by a closing spring 18 which surrounds the nozzle needle 10 and the sleeve 22 facing away indirectly supported on a shoulder 16, presses against the throttle plate 6 , Through the sleeve 22, facing away from the combustion chamber end face of the nozzle needle 10 and the throttle plate 6, a control chamber 20 is limited, which is filled with fuel, so that exerted by the pressure in the control chamber 20, a hydraulic force on the side remote from the combustion chamber end face of the nozzle needle 10 and exerts a force in the direction of the nozzle seat 13 on the nozzle needle 10.

In the holding body 2, the valve plate 4 and the throttle plate 6, an inlet channel 25 is formed, is passed through the compressed fuel under high pressure from a high-pressure fuel source in the pressure chamber 14. The inlet channel 25 is connected to the control chamber 20 via an inlet throttle 40 extending in the throttle plate 6. With a certain time delay is thus always the same fuel pressure in the inlet channel 25 and the control chamber 20 when the control valve 30 is closed.

For controlling the fuel pressure in the control chamber 20, the switchable between two switching positions control valve 30 is provided in the valve plate 4, wherein the control valve 30 has a control valve chamber 31 which is formed as a cavity in the valve plate 4. The control valve chamber 31 is connected via a drain throttle 42, which is formed in the throttle plate 6, connected to the control chamber 20 in the nozzle body 8. In the control valve chamber 31, a control valve member 34 is arranged longitudinally displaceable, wherein the control valve member 34 has a piston-shaped shape and at its end facing away from the throttle plate 6 has a mushroom-shaped extension on which a sealing surface 52 is formed, with which the control valve member 34 cooperates with a control valve seat 37, which is formed on the inside of the control valve chamber 31.

The control valve member 34 is guided at its end remote from the control valve seat 37 in a sleeve 36 which is supported at one end to the throttle plate 6, and between the and the control valve member 34, a spring 38 is arranged under compressive prestress. By the force of the spring 38, the control valve member 34 is pressed against the control valve seat 37 on the one hand, and the sleeve 36 against the throttle plate 6 on the other hand. The movement of the control valve member 34 in the control valve chamber 31 occurs via a in a coupler housing

33 guided piston 32 which is arranged in the holding body 2, and which is movable by an electric actuator in its longitudinal direction, in particular by a single piezoelectric actuator, not shown. In this case, the piston 32 with the coupler housing 33 is located in an actuator chamber 23, which is always in the form of an actuator receiving space and is always under low pressure, which is always depressurized.

Through the sleeve 36, the control valve member 34 and the throttle plate 6, a leakage chamber 54 is limited, in which a low pressure is present, and is relieved of pressure via a drain 45 drain. The leakage oil drain 45 may in this case have, for example, a connection to the actuator chamber 23.

With regard to the mode of operation of such a fuel injector 1 known from the prior art, reference is made to DE 10 2008 001 330 A1 of the Applicant, which is to be part of this application to that extent.

During operation of the fuel injector 1, when the control valve 30 is opened, fuel passes via the control valve seat 37 and through outflow bores 35 in the coupler housing 33 into the actuator chamber 23, in which the piezoactuator is also arranged. As a result of the pressure reduction of the fuel, the fuel has a relatively high temperature. In this case, the more the fuel heats up, the higher the system pressure or the operating pressure of the fuel injector 1 is, since In this case, a particularly large pressure reduction associated with a particularly large increase in temperature of the fuel associated.

In order to keep the component load on the piezo actuator in the actuator chamber 23 as low as possible, it is provided in a fuel injector 100 according to the invention that the fuel flowing via the control valve seat 37 in the direction of the coupler body 33 at least partially, but preferably completely via one or more Outlet channels 60 is guided or discharged into the annular space 5. In this case, only a single diversion channel 60 is shown in FIG. 2, which is arranged radially to the longitudinal axis of the valve plate 4. The diversion channel 60 is located in an upper end region of the valve plate 4 with respect to the fuel injector 100.

It is particularly advantageous if the outflow bores 35 shown in FIG. 1 are omitted. In this case, the complete amount of fuel flowing out via the open valve seat 37 is led via the diversion channel 60 into the annular space 5.

Furthermore, it can be seen in Fig. 2 in the central region of the throttle plate 6 on the side opposite the discharge channel a return channel 61 which projects radially inwardly from the edge of the throttle plate 6, and 62 has a vertically arranged Rückleitkanalabschnitt connection with a circumferential annular groove 63 , which is formed on the throttle plate 6 facing the end face of the valve plate 4, and preferably on the return channel portion 62 opposite side hydraulically with a recognizable in particular in FIG. 4 riser 64 connection, which is formed in the region of the valve plate 6. The riser 64 in turn has hydraulic connection with a retaining body 2 formed in the return bore 65 which is connected to a return port, not shown, of the fuel injector 100. Furthermore, it can still be seen from FIG. 2 that the leakage chamber 54 is connected to the return channel 61 via a leakage oil outlet 45a.

During operation of the fuel injector 100 via the control valve seat 37 in the direction of the coupler body 33 escaping fuel first via the discharge channel 60 into the annular space 5 and from there via the return channel 61 and the return channel section 62 into the annular groove 63, from where the fuel on the Riser 64 and the return bore 65 is discharged from the fuel injector 100. Due to the fact that the fuel flows in particular through the annular space 5, cooling or temperature reduction of the fuel takes place before it reaches the area of the holding body 2. The same also applies to the fuel flowing out of the leakage chamber 54, which mixes in particular with the fuel already flowing in the annular space 5 or through the annular space 5.

In addition, it is mentioned that instead of the leakage oil outlet 45a, the leakage chamber 54 can also have a leakage oil outlet 45 in accordance with the prior art (compare FIG.

FIG. 3 shows an alternative flow guide for removing fuel from the leakage chamber 54.

In this case, the flow guide according to FIG. 2 has a leakage oil drain 45a which has a connection to the annular space 5 via a discharge channel 71 arranged radially in the throttle plate 6. In the valve plate 4, a radially arranged Rückleitkanal 72 is formed in an upper axial region, which also has connection with the annular space 5, and which opens into the riser 64. Thus, existing in the leakage chamber 54, due to the pressure reduction, a relatively high temperature having fuel via the discharge channel 71 and the annular space 5 in the return passage 72, wherein the flow control in the annulus 5, a cooling of the fuel takes place. About the return passage 72 of the fuel then passes through the return bore 65 in the fuel return of the engine.

In addition, it is mentioned that in FIG. 3, in the region of the holding body 2, there is still an area exposed area 73 which forms a hydraulic connection between the actuator space 23 and the return bore 65.

FIG. 4 shows a flow guide for the fuel from the leakage chamber 54 that has been modified with respect to FIG. 3. In this case, the fuel also passes through the leakage oil drain 45a and the discharge channel 71 into the annulus 5. In contrast to FIG. 3, in FIG. 4, the return channel 75, consisting of the partial channel sections 76, 77, is formed in the throttle plate 6, as well Has connection with the annular space 5, and which opens into the riser 64. It may be provided that the vertical part of the channel section 76 of the return channel 75 is not concentric with the riser 64, but is arranged in a certain offset to this. In the region of the annular groove 63, a separating web (not shown) may be present in the preferably shorter distance between the vertical partial channel section 76 and the riser 64, so that the fuel has as long a flow path as possible until it enters the riser 64.

The fuel injector 100 according to the invention thus far described can be modified or modified in many ways without departing from the spirit of the invention. This consists, at least partially, but preferably completely over a particular between the valve plate 4, the throttle plate 6, the nozzle body 8 and the Clamping nut 9 trained annular space 5 to lead, so that the fuel is cooled there. Conceivable modifications of the fuel injector 100 may be e.g. be such that only the fuel in the leakage chamber 54 is passed through the annulus 5. It is also conceivable that only the fuel flowing out via the control valve seat 37 is guided via the annular space 5 or that part of the fuel flowing out through the control valve seat 37 passes directly into the actuator chamber 23, and from there via the surface exposure region 73 into the return bore 65 , Likewise, any combination of the described solutions for guiding the fuel flowing out of the valve seat 37 and / or the fuel flowing out of the leakage chamber 54 via the annular space 5 to the actuator space 23 or to the return bore 65 is part of this invention. Finally, it is also conceivable to form the discharge of the fuel from the annular space 5 via a formed in the holding body 2 radial bore or formed in an end face of the holding body 2, radially extending groove directly into the return bore 65.

Claims

claims

1 . Fuel injector (100), with a holding body (2) and a nozzle body (8) by means of a nozzle retaining nut (9) with the interposition of a throttle plate (6) and a valve plate (4) axially braced against the holding body (2), wherein in the valve plate (4) a switchable between at least two switching positions control valve (30) is arranged in a control valve chamber (31) which is actuated by means of an actuator in an area (23) of the holding body (2), preferably designed as a piezoactuator actuator, wherein the Fuel is flowed through the actuator space (23), which is hydraulically coupled via a connection (73) with a return bore (65), and one in the switching of the control valve (30) and / or one in the switching pauses of the control valve (30) from the Control valve chamber (31) emerging return amount of fuel via a further connection at least indirectly in the return bore (65) can be derived, characterized in that the we iter connection has a flow path which comprises the annular space (5) between the nozzle retaining nut (9) and the nozzle body (8) and / or the valve plate (4) and / or the throttle plate (6).

2. Fuel injector according to claim 1,

characterized,

the further connection comprises a discharge channel (60) into the annular space (5) and a return channel (61) from the annular space (5), wherein the return channel (61) opens at least indirectly into the return bore (65).

3. Fuel injector according to claim 2,

characterized,

in that the diversion channel (60) and the return channel (61) are formed at least substantially as channels arranged radially to the longitudinal axis of the valve plate (4).

Fuel injector according to claim 2 or 3,

characterized,

in that the discharge channel (60) and the return channel (61) are arranged on opposite sides of the composite, consisting of valve plate (4), throttle plate (6) and nozzle body (8).

Fuel injector according to one of claims 1 to 4,

characterized,

the further flow path comprises an annular groove (63) formed on an end face of the valve plate (4) and / or the throttle plate (6).

Fuel injector according to claim 5,

characterized,

in that a separating element, in particular in the form of a separating web, is arranged in the annular groove (63).

Fuel injector according to one of claims 1 to 6,

characterized,

a part of the control quantity flows out of the control valve chamber (31) into the actuator chamber (23).

Fuel injector according to one of claims 1 to 7,

characterized,

the control valve (30) comprises a control valve member (34) arranged longitudinally displaceably in a sleeve (26) such that the annular region between the sleeve (26) and the control valve member (34) opens into a leakage space (54) which at least indirectly communicates with the Return passage (65) is connected, and that an additional connection between the leakage space (54) and the return bore (65) is provided which is connected to the annular space (5).

9. Fuel injector according to claim 8,

characterized,

in that the connection has a drain (45a) which opens into a discharge channel (71).

10. Fuel injector according to claim 9,

characterized,

that the diversion channel (71) opens via the annular space (5) and a return channel (72, 75) into a riser (64) which is connected to the return line (65) or in that the annular space (5) via a in the holding body (2) formed flow path is connected to the return line (65).

11. Fuel injector according to one of claims 1 to 10,

characterized,

the maximum system pressure in the fuel injector (100) is more than 2000 bar.