EP3074623A1

EP3074623A1 - Fuel injector

Info

Publication number: EP3074623A1
Application number: EP14781567.4A
Authority: EP
Inventors: Florian Hoffmann
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2013-11-28
Filing date: 2014-10-09
Publication date: 2016-10-05
Anticipated expiration: 2034-10-09
Also published as: DE102013224404A1; WO2015078629A1; EP3074623B1

Abstract

The invention relates to a fuel injector (10) comprising an injector housing (11) in which at least one injection port (17) is designed for injecting fuel into the combustion chamber of an internal combustion engine, wherein the through flow through the at least one injection port (17) can be controlled by means of an injection member (15), in particular a nozzle needle, reciprocatingly moveable in a longitudinal axis (12), wherein the injection member (15) is arranged in a high pressure chamber (18) and has an end region, sunk into an element (25; 25a) delimiting a control chamber (45) facing away from the at least one injection port (17), and wherein the high pressure chamber (18) is hydraulically connected to the control chamber (45) via at least one inflow channel (48, 49; 51; 55) and can be depressurized into a low pressure region (50) via an outflow channel (46). According to the invention the at least one inflow channel (48, 49; 51; 55) is designed to form a laminar through flow of the fuel.

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 2006 049 830 A1

Applicant known. The well-known fuel! The injector has, within an injector housing, a control chamber in which the end of a nozzle needle opposite an injection opening is inserted. The control chamber is formed via an inlet channel designed as an inflow bore with a

High-pressure region of the injector connected via which the control chamber is supplied with fuel under high pressure. The control chamber is used in a known manner to the opening and closing movement of the

To influence nozzle needle via a fuel drain to a low pressure region by means of a Abiaufbohrung which can be opened or closed by means of a valve member.

The injection amount during the opening and closing of the

Nozzle needle is injected into the combustion chamber of the internal combustion engine depends inter alia on different fuel properties. The

Fuel properties in turn depend on the type of fuel and the environmental conditions. For example, the viscosity of both the type of fuel (winter diesel, summer diesel, mixtures of various

Fuels etc.) and within the respective fuel grade also from the

Temperature dependent. Although there are already ways to detect the viscosity of the fuel in common rail injection systems by means of a fuel detection function during the closing of the fuel injection valve, but the quality of the detection depends on the settings the fuel injector, such as the magnetic force, the armature stroke and other factors.

During a cold start of an internal combustion engine, the viscosity of the fuel is usually higher than when the engine is at operating temperature. This has the consequence that, without influencing the injection parameters during the cold start, too little fuel is usually injected into the combustion chamber. It is therefore necessary or desirable, during the warm-up phase of the engine or the internal combustion engine, the fuel quantity during an injection process of a relatively high value due to the low

To reduce fuel temperature or its high viscosity gradually until the engine has reached its operating temperature or the fuel within a certain viscosity lying viscosity. As explained above, although there are already methods or approaches for detecting the viscosity of

Fuel, but the aforementioned measures usually mean an increased design or control engineering effort. In addition, it is essential that in the above-mentioned document

Although inlet bore into the control chamber is shown as an elongated bore, in practice, however, within the diameter / length ratio of approximately 1: 2.5 having inlet bore to influence the flow rate, a flow constriction in the form of a diaphragm is formed. This diaphragm causes the fuel flowing out of the high-pressure chamber into the control chamber to continue to flow turbulently after passing through the diaphragm. From the

Flow technology, it is known that the flow through a diaphragm is independent of viscosity, so that conventional inlet holes have a temperarturunabhängigen flow.

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 during a Einspritztaktes a

Injector valve member (nozzle needle), in particular during the warm-up phase of the internal combustion engine, a target injection amount despite different Viscosities of the fuel at different temperatures in the

Combustion chamber of the internal combustion engine can be achieved with the least possible effort. In particular, it should be achieved that even at a relatively high viscosity, i. at a relatively low temperature of the fuel, the desired injection quantity is achieved.

This object is achieved in a fuel injector with the features of claim 1, characterized in that the at least one

Inflow channel, via which a post-flow of fuel from the high-pressure chamber takes place in the control chamber of the fuel injector, is formed to form a laminar flow. The invention is based on the finding that in the presence of a laminar flow the

Flow rate through the inflow channel is viscosity-dependent. In particular, at a relatively high viscosity, a flow which is reduced compared to a lower viscosity is made possible. This has the consequence that the pressure in the control chamber when opening the Abiaufbohrung falls faster or faster, since the inflowing over the inflow channel fuel with less

Flow rate (per unit time) flows through the inflow channel.

Furthermore, when introducing the closing movement of the nozzle needle by closing the drainage channel, the pressure in the control chamber later or

time-delayed. Both properties result in that

Dynamics of the movement of the injection valve member (nozzle needle) is changed such that during an injection cycle, an increased amount of fuel is injected via the injection port into the combustion chamber of the internal combustion engine. Since the viscosity is temperature dependent, the effects decrease

increasing fuel temperature. Thus, a desired viscosity or temperature-dependent injection quantity of the fuel is achieved in the combustion chamber of the internal combustion engine.

Advantageous developments of the fuel injector according to the invention are given in the dependent claims. All combinations of at least two of the features disclosed in the claims, the description or the drawings fall within the scope of the invention. In structurally particularly preferred embodiment of the invention, it is provided that the at least one inflow channel at least two, preferably a constant diameter having first

Includes throttle bores in the element, wherein the diameter / length ratio of the at least two throttle bores is less than 1: 5, preferably about 1:10. In addition, it is mentioned that, for example, with three throttle bores, the diameter / length ratio should be about 1: 15.

As a background to this, it should be noted that the control chamber is usually formed by an annular circumferential wall portion of a valve piece, or by a voltage applied to a throttle plate in the axial direction control chamber sleeve. Both the minimum wall thickness of the control chamber sleeve and the valve piece is given for pressure or strength reasons and is usually chosen as small as possible. Now to the desired

It is this that it is possible to adjust the throttle function of the inflow channel via the diameter / length ratio so that in particular enough fuel can flow into the control chamber even under extreme conditions (full load)

According to the invention provided that not only a single throttle bore, but at least two throttle bores are provided. This makes it possible on the one hand by the choice of a correspondingly small diameter, even with relatively small wall thicknesses of the valve piece or the

Control chamber sleeve to effect the desired throttle function, and on the other hand, for example, in full load operation to take into account that enough fuel can flow into the control chamber, that is, the fuel! Njektor has a desired high dynamics.

In particular, for flow-related reasons, it is advantageous if the at least two throttle bores are arranged at regular angular intervals from one another.

In an alternative embodiment of the invention, it may also be provided that the at least one inflow channel comprises at least one groove formed in the injection member between the control chamber and the high-pressure chamber on the lateral surface of the injection member whose width / depth ratio is smaller 1: 10, preferably about 1: 20. In this idea, in contrast to a trained in a control chamber sleeve or a valve piece

Throttle bore dispensed with these and instead of a targeted

Leakage in the leadership of the injection member in the form of a formed on the circumferential or lateral surface of the injection member groove the inflow of the

Fuel causes from the high-pressure chamber in the control room. This solution has a constructive extent in that the strength of the valve piece or the control chamber sleeve is not weakened by throttle bores, and that on the other hand by the usually relatively long in the axial direction of the injection member formed guide a single groove is sufficient to the viscosity-dependent throttling effect of To realize inflow channels.

In particular, for fluidic reasons, it may be advantageous to provide a plurality of grooves, which are then arranged at equal angular intervals to each other.

In order to mechanically process the injection valve member only over a portion of its length, it is advantageous if, when using at least one groove, a first portion of the injection member immersed in the element on the side facing the high-pressure chamber into a second

Section passes, which has a smaller diameter compared to the first section.

In yet another alternative constructive embodiment of the invention, it can be provided that the at least one inflow channel has one in the

Injection member formed second throttle bore comprises, wherein the

Diameter / length ratio of the throttle bore is less than 1: 5, preferably about 1:10. This variant supplies the fuel via a throttle bore formed, for example, in the longitudinal axis of the injection member (nozzle needle), which is then connected to the high-pressure chamber, for example via a transverse bore. Such a design has the advantage that, for example, compared to the second embodiment of the invention, the injection valve member may have a substantially constant diameter or that no mechanical processing is required on the peripheral surface of the injection valve. To form the throttle bores, it is advantageous if the at least two first throttle bores, the second throttle bore or the at least one groove are produced by a laser processing system. By such a method can be used in large-scale deployment the required

Making throttle bores easy and reliable with the required accuracy.

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:

Fig. 1 shows a portion of a fuel injector according to the invention in

Longitudinal section and

Fig. 2

and

Fig. 3 each have a comparison with FIG. 1 modified injection member

(Nozzle needle) with differently shaped inflow channels for the fuel in the control room.

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

In Fig. 1 is a portion of a fuel according to the invention! shown ejector 10, as it is used as part of a common rail injection system in self-igniting internal combustion engines.

The fuel injector 10 has an injector 1 1, in which in an axis 12, an injection member in the form of a nozzle needle 15 is arranged up and down movable. In the illustrated in Fig. 1, lowered position of the nozzle needle 15, the nozzle needle 15 is seated with a seating area on an inner wall of the injector 1 1 to form a sealing seat sixteenth on, at least one, formed in the injector 1 1

Close injection port 17. In the raised position of the nozzle needle 15, however, the at least one injection port 17 is released for injecting fuel into a combustion chamber of the internal combustion engine by 1 befindlicher fuel in a high-pressure chamber 18 of the injector 1 1 fuel can be injected via the at least one injection port 17 into the combustion chamber.

The high-pressure chamber 18 is connected via a supply bore 19 with a

Fuel connection 21 is connected, which in turn is connected via a connection, not shown, in particular with a high-pressure accumulator (rail) for the fuel.

Within the injector 1 1 a stepped bore 22 is formed, which has two bore sections 23, 24 substantially. In the first bore portion 23 projects in the axial direction, a portion of a valve piece 25 into it, which in turn in the transition region between the two bore sections 23, 24 axially on an end face 26 of the Stepped bore 22 is applied. Within the second bore portion 24, in addition to a second portion of the valve member 25 viewed in the axial direction, an annular shield member 27, a likewise annular housing part 28 and a clamping ring 29 is arranged, which is formed by means of a threaded connection 30, the

addressed components axially against the end face 26 of the stepped bore 22 to brace.

Within the housing part 28, an actuator 32 for at least indirect actuation of the nozzle needle 15 is arranged, which has a magnet armature 33. The armature 33 cooperates with a magnetic coil 34 which is inserted in an annular recess of a magnetic core 35. The magnetic core 35 is again arranged with the interposition of a support plate 36 between a step 37 on the housing part 28 and the clamping ring 29. The armature 33 has aligned to the longitudinal axis 12 has a through hole 38 in which a guide pin 39 is arranged. The guide pin 39 serves the axial guidance of the armature 33 and is supported on the side facing away from the valve piece 25 axially against the support plate 36 from. The armature 33 is by means of a compression spring 41 in the direction of an end face

42 of the valve member 25 is subjected to force and forms in the illustrated in Fig. 1 lowered position of the armature 33 with a sealing surface

43 of the armature 33 from a sealing seat. The in the first bore portion 23 of the stepped bore 22 protruding

Section of the valve piece 25 has in the longitudinal axis 12 a formed of a plurality of bore portions through hole, which forms a guide portion 44 on the nozzle needle 15 side facing.

Within the guide portion 44 of the immersed at least one

Injection opening 17 facing away from the end portion of the nozzle needle 15 in the

Guide portion 44 and is guided by this radially and axially. Within the valve piece 25, a control chamber 45 is formed, which has a

Abiaufbohrung 46 with integrated Abströmdrossel 47 in a low pressure chamber 50 can be relieved of pressure. For this purpose, the Abiaufbohrung 46 opens into the end face 42 of the valve member 25 and is radially surrounded by the sealing surface 43 of the armature 33.

According to the invention, the control chamber 45 is hydraulically connected to the high-pressure chamber 18 via at least two inflow channels arranged at regular angular intervals in the form of first throttle bores 48, which are formed in the radially encircling wall of the valve member 25 and perpendicular to the longitudinal axis 12. According to the invention, it is essential that the first throttle bores 48, 49, which are preferably produced by a laser-beam device, are designed in such a way that, when fuel flows from the high-pressure chamber 18 into the control chamber 45, a laminar flow is achieved

Flow prevails. For this purpose, it is provided according to the invention that the diameter / length ratio of the two, preferably identical

formed first throttle bores 48, 49 is less than 1: 5, preferably about 1:10. Such a design causes a dependent of the viscosity of the fuel in the high-pressure chamber 18 flow rate of the fuel in the Control room 45. If instead of two throttle holes 48, 49 three

Throttle holes are used, so is a preferential

Diameter / length ratio of the three throttle bores about 1:15. For injecting fuel into the combustion chamber (not shown)

Internal combustion engine, the actuator 32 by energizing the

Magnetic coil 34 is actuated. This raises the armature 33 with his

Sealing surface 43 from the end face 42 of the valve member 25, whereby a flow of fuel from the control chamber 45 via the Abiaufbohrung 46 in the low pressure chamber 50 of the injector 1 1 is made possible, in which the actuator 32 is arranged. The low-pressure chamber 50 is in turn known per se, and therefore not shown manner with a fuel return of the fuel! njektors 10 hydraulically connected. The pressure drop in the control chamber 45 causes the nozzle needle 15 lifts from its sealing seat 16 and the at least one injection port 17 releases. When cold, i. a relatively high one

Viscosity-containing fuel, the fuel flows from the high-pressure chamber 18 via the first two throttle bores 48, 49 as a result of

Viscosity-dependent flow rate decelerates towards lower viscosity fuel, resulting in a particularly rapid pressure drop in the air

Control chamber 45 is achieved, and thus a particularly rapid lifting of the

Nozzle needle 15 from the sealing seat 16.

To stop the injection process, the solenoid 34 of the

Voltage source disconnected, so that the armature 33 is pressed by the spring force of the compression spring 42 against the end face 42 of the valve member 25 to a further outflow of fuel from the control chamber 45 in the

Low pressure chamber 50 to prevent. Due to the inflowing fuel from the high-pressure chamber 18 into the control chamber 45, the hydraulic pressure on the one end face of the nozzle needle 15 increases, so that they again toward their sealing seat 16 (in particular by supporting a in the

Fig. 1, not shown, operatively connected to the nozzle needle 15 arranged closing spring) is moved. Due to the delayed at high viscosity of the fuel afterflow of the fuel from the high-pressure chamber 18 into the control chamber 45, the pressure in the control chamber 45 is relatively slow

constructed so that the closing of the nozzle needle 15 is delayed. FIG. 2 shows a modified embodiment of the invention in which no first throttle bores 48, 49 are formed in the valve piece 25a. The two first throttle bores 48, 49 are in uniform by at least one, preferably more, preferably more than three

Replaced angular intervals to each other grooves 51 which are formed on the peripheral or lateral surface of the nozzle needle 15 and preferably parallel to the longitudinal axis 12 extend. For this purpose, the nozzle needle 15 in the illustrated embodiment, a first, disposed substantially within the valve piece 25a portion 52 and a second, disposed substantially within the high-pressure chamber 18 section 53. It is essential that the second section 53 has a smaller diameter than the first section 52, so that the at least one groove 51 only in the first

Section 52 must be formed to the control chamber 45 with the

High pressure chamber 18 to connect hydraulically. According to the invention, the width / depth ratio of the at least one groove 51 is less than 1:10, preferably about 1:20, wherein the cross-sectional shape of the groove 51 is preferably rectangular or semicircular (not shown). For example, (with a rectangular cross-section) at a width of 1000μηι the groove 51, the depth of the groove 51 is about δθμηη, with an overall length of the groove 51 of about 12mm. In the embodiment of the invention shown in FIG. 2 thus finds the

Supply of the control chamber 45 with fuel via the at least one groove 51 instead. Finally, in Fig. 3 is a further modified embodiment of

Invention, in which, in contrast to FIG. 2, a formed in the longitudinal axis 12 second throttle bore 55 is formed, which has a

Cross hole 56 connection with the high-pressure chamber 18 has. The second throttle bore 55 has a diameter / length ratio of less than 1: 5, preferably about 1:10.

The fuel injector 10 described so far can be modified or modified in many ways, without departing from the spirit of the invention

departing. In particular, it can also be provided that the

Control chamber 45 formed by a so-called control room sleeve or is limited, which is arranged in analogy to the arranged in the first bore portion 23 portion of the valve member 25, 25 a and then the first throttle bores 48, 49 may have.

Claims

claims

1 . A fuel injector (10) having an injector housing (11) in which at least one injection opening (17) is formed for injecting fuel into the combustion chamber of an internal combustion engine, the flow through the at least one injection opening (17) being realized by means of a longitudinal axis ( 12) up and down movable injection member (15), in particular a

Nozzle needle, is controllable, wherein the injection member (15) in one

High pressure chamber (18) is arranged and with one of the at least one injection opening (17) facing away from the end region in a control chamber (45) delimiting element (25; 25a) immersed, and wherein the high-pressure chamber (18) via at least one inflow channel (48, 49; 51, 55) with the

High pressure chamber (18) hydraulically connected and via a discharge channel (46) in a low pressure region (50) is pressure relieved, characterized in that the at least one inflow channel (48, 49; 51; 55) is formed to form a laminar flow through the fuel.

2. Fuel injector according to claim 1,

characterized,

in that the at least one inflow channel comprises at least two, preferably constant diameter, first throttle bores (48, 49) in the element (25), the diameter / length ratio of the at least two throttle bores (48, 49) being less than 1: 5, preferably approximately 1: 10.

3. Fuel injector according to claim 2,

characterized,

that the at least two first throttle bores (48, 49) in

uniform angular intervals are arranged to each other. Fuel injector according to claim 1,

characterized,

that the at least one inflow channel at least one in the

Injection member (15) between the control chamber (45) and the high-pressure chamber (18) formed on the lateral surface of the injection member (15) formed groove (51) whose width / depth ratio is less than 1:10, preferably about 1: 20.

Fuel injector according to claim 4,

characterized,

that in the presence of a plurality of grooves (51), the plurality of grooves (51) are arranged at equal angular distances from each other.

Fuel injector according to one of claims 4 or 5,

characterized,

in that when at least one groove (51) is used, a first section (52) of the injection member (15) immersed in the element (25a) merges on the side facing the high-pressure chamber (18) into a second section (53) which is opposite to the one first portion (52) has a smaller diameter.

Fuel injector according to claim 1,

characterized,

in that the at least one inflow channel comprises a second throttle bore (55) formed in the injection member (15), wherein the diameter / length ratio of the second throttle bore (55) is less than 1: 5,

preferably about 1:10.

Fuel injector according to one of claims 2 to 7,

characterized,

in that the at least two first throttle bores (48, 49), the second throttle bore (55) or the at least one groove (51) pass through a

Laser processing system are generated. Fuel injector according to one of claims 1 to 8,

characterized,

the element is a valve piece (25; 25a) insertable into the injector housing or a control chamber sleeve.