EP2959155A1

EP2959155A1 - Fuel injector

Info

Publication number: EP2959155A1
Application number: EP13818660.6A
Authority: EP
Inventors: Markus Kalenborn; Michael Willmann; Horst Ressel
Original assignee: LOrange GmbH
Current assignee: Woodward LOrange GmbH
Priority date: 2013-02-22
Filing date: 2013-12-13
Publication date: 2015-12-30
Also published as: DE102013002969B3; KR20150120360A; US20160003204A1; US9765737B2; WO2014127794A1; HK1216550A1; CN104995395A

Abstract

Disclosed is a fuel injector (10) for a fuel injection device, wherein the injector (10) has a control chamber (28), which can be selectively relieved of pressure by means of a pilot valve (54) of the injector (10) in order to control the nozzle needle stroke of an axially displaceable nozzle needle (12) of the injector (10), wherein the fuel injector (10) has at least one nozzle (20) on a first end (12a) of the nozzle needle (12) and has the control chamber (28) on a second end (12b) of the nozzle needle (12), wherein the control chamber (28) is sub-divided by a throttle plate (38) accommodated therein into a first chamber (40), which is further away from the nozzle, and a second chamber (42), which is closer to the nozzle, said chambers communicating with each other via the throttle plate (38), wherein a first resilient element (46) and a second resilient element (48) are each accommodated in a pre-stressed manner against the throttle plate (38) in the first chamber (40) and in the second chamber (42) respectively, which resilient elements (46, 48) axially displaceably bear the throttle plate (38), and wherein a high-pressure inflow line (50) into the control chamber (28) and a relief outflow line (52) out of the control chamber (28) lead into and out of the first chamber (40) respectively.

Description

Kraftstoffiniektor

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

It is in fuel injectors, particularly conventional pilot-valve controlled injectors, which are mostly for use with diesel fuel, e.g. Heavy fuel oil or biofuel, are provided regularly only with considerable structural complexity possible to produce a stepped opening ramp in Dü- sennennhubverlauf, in particular with an initially steeper opening ramp section and a subsequent flatter opening ramp section. However, this is desirable for an emission-optimized combustion characteristic when using a fuel injector on a combustion chamber of an internal combustion engine, in particular a reciprocating piston engine.

Proceeding from this, the present invention seeks to propose a generic fuel injector, which advantageously unobstrusively allows a stepped opening stroke in particular of the above type.

This object is achieved by the features of claim 1.

Advantageous developments and embodiments of the invention are specified in the dependent claims.

According to the invention, a fuel injector for a fuel injector is proposed. The injector may preferably be provided for use in a common rail system, wherein the fuel injector is generally intended for use with internal combustion engines in the form of gasoline or diesel engines, in particular large diesel engines and further in particular vehicle engines, for example in off-road or marine applications. also in stationary applications, for example combined heat and power plants.

The fuel injector has a control chamber which can be selectively relieved of pressure via a pilot valve (servo or control valve) of the injector for controlling the nozzle needle stroke of an axially displaceable nozzle needle of the injector (indirectly controlled injector). Here, at the first end of the nozzle needle at least one nozzle and at a second end of the nozzle needle of the control chamber depending on the fuel injector is formed.

The fuel injector is characterized in that a first, nozzle-remote and a second nozzle-closer chamber is divided in the control chamber, which communicate with each other via the throttle plate, wherein in the first chamber, a first resilient element and in the second chamber, a second resilient Element is received biased against the throttle plate, which resilient elements axially support the throttle plate, and wherein a high-pressure inlet to the control chamber and a discharge process from the control chamber each open into and out of the first chamber. In this embodiment, the throttle plate is arranged between the first and the second resilient element and insofar preferably in a sandwich arrangement.

The proposed injector is inexpensive and easy to produce and suitable with little structural complexity, the intended grading in the opening ramp at the beginning of an injection process, i. before the nozzle needle goes to the stop to achieve reliable, in particular with the intended steep initial ramp portion immediately after the start of the opening and the subsequent flatter opening ramp portion before the nozzle needle is in the stop. Furthermore, a fast closing ramp can also be generated here.

In preferred embodiments of the invention, it is provided that the second spring-elastic element has a spring stiffness greater than or equal to equal to the spring stiffness of the first spring-elastic element. In particular, when the spring stiffnesses are the same (preferred), preload displacement tolerances have only insignificant influence on the relative rest position of the throttle plate after installation.

Besides, the spring stiffnesses can be e.g. be selected such that the stiffness of the second resilient member is 1 to 4 times the stiffness of the first resilient member. This can help to avoid too close approach of the nozzle needle to the throttle plate in the steep first opening ramp section.

In order to keep the length of the initial opening ramp phase short in the injection rate curve, the spring length of the first elastic element may be shorter than that of the second elastic element. The same applies to the reverse case.

Preferably, the throttle plate, in particular as a plate element, formed with or by means of at least one throttle bore, which extends as a passage opening axially through the throttle plate. For example, a throttle bore extends centrally through the throttle plate. In general, the throttle plate may be disc-shaped (extending radially in a planar manner), wherein the throttle plate preferably - but not necessarily - H-shaped cross-section.

In the case of an H-shaped embodiment, the transverse web of the H-shape extends in particular radially. The throttle plate formed in this way allows the circumference optimized guidance, ie on the wall of the control chamber (eg, providing a sliding seal) woneben the throttle plate also an overuse of the recorded springs in the compression of the same can advantageously avoid the fact that the throttle plate at the same time as a distancing Stop element acts. Preferably, at least one axial throttle bore extends through the transverse web of the H-shape, in particular also all of the throttle plate formed in cross-section H-shaped.

It is generally desirable in the context of the invention that fluid communication between the first and the second chamber (in the control chamber) can take place exclusively via the throttle plate, in particular via the at least one throttle bore thereof.

The orifice characteristic is preferably set at the fuel injector such that the relief drain has a drainage flow area which is greater than the throttle area of the throttle plate, i.e. the throttle bore (s) of the same. Preferably, based on Qioo flow values (at 100 bar), the ratio throttle cross-section of throttle plate to outlet throttle in the range of 0.12 to 0.4 and / or, based on Qioo flow values (at 100bar), the ratio inlet throttle cross-section (ZDr) of the high-pressure inlet to the outlet throttle section (ADr) in the range of 0.5 to 0.9.

The proposed fuel injector is advantageously usable with a fuel injection device, for example, in a common rail system. In that regard, a fuel injection device is proposed which has at least one fuel injector as described above.

Further features and advantages of the invention will become apparent from the following description of embodiments of the invention, with reference to the figures of the drawings, which show details essential to the invention, and from the claims. The individual features can be realized individually for themselves or for several in any combination in a variant of the invention.

Exemplary embodiments of the invention are explained below with reference to the accompanying drawings. Show it: 1 shows an example and schematically a achievable with the fuel injector Nadelhubverlauf during an injection process;

2 shows by way of example and schematically a simplified structural diagram of the fuel injector with fuel paths guided thereon according to a possible embodiment of the present invention; and

3 shows an example and schematically a simplified view to illustrate the functionality of the injector according to the invention.

In the following description and the drawings, the same reference numerals correspond to elements of the same or comparable function.

FIG. 1 shows, schematically and by way of example, an intended needle stroke progression over time, as it can be achieved advantageously simply with the proposed fuel injector 10. The Nadelhubverlauf has a steep opening ramp section 1 immediately after the start of the injection process and an adjoining flatter opening ramp section 2. The following section 3 in Nadelhubverlauf adjusts itself, as soon as the nozzle needle 12 reaches the stop (Vollhubstellung), the closing ramp 4 in a subsequent closing movement of the nozzle needle 12th

Fig. 2 illustrates in more detail (simplified) the fuel injector 10 according to the invention, which is intended for use with a fuel injector. The fuel injector 10 may preferably be used with diesel fuel, for example in a common rail system.

The injector 10 has an axially displaceable nozzle needle 12, which is received in an axial bore 14, which is formed in a nozzle body 16 of the fuel injector 10. For example, the nozzle body 16 forms part of an injector housing 18.

At a first end 12a of the nozzle needle 12, a nozzle (nanordnung) 20 is formed (one or more injection holes), which is needle-dependent flowed through by hochdruckbeaufschlagtem fuel. In an axial displacement 2, in which the nozzle needle 12 sealingly abuts the first end 12a against a valve seat 22, a fuel flow path is formed from a volume 24 (axial bore 14) upstream of the nozzle needle 12 and the valve seat 22 formed nozzle valve toward the nozzle 18 turned on.

In the volume 24 can be promoted auszubringender hochdruckbeaufschlagter fuel via a high pressure feed line 26 of the fuel injector 10 in an injection process. The volume 24 can - as shown in Fig. 2 - be formed by the axial bore 14 into which the high-pressure feed line 24 opens, alternatively, for example in the form of a separate high-pressure chamber upstream of the nozzle 20, which communicates with the nozzle 20 after opening the nozzle needle.

When the nozzle needle 12 returns to the closed position (zero stroke position), the flow path to the nozzle 20 is closed.

The fuel injector 10 further has a control chamber 28, which is provided at the upper or nozzle-distal end 12b of the nozzle needle 12. The control chamber 28 is formed by means of a needle guide sleeve 30, in which the nozzle needle 12 with its nozzle-distal end 12b circumferentially (leakage-prone) dipping immersed. Furthermore, the fuel injector 10 to form the control chamber 28, a lidding element 32 at the nozzle distal end of the guide sleeve 30, which is provided for example as a valve plate 32, in particular in the injector 18th

Between the nozzle-near end 30a of the guide sleeve 30 and a collar 34 on the nozzle needle 12, a nozzle spring 36 is still caught, which urges the nozzle needle 12 in the closed position.

According to the invention, a throttling element or throttle plate 38 is received in the control chamber 28 in this way, see FIGS. 2 and 3, that in the control chamber 28, a first, more remote chamber 40 and a second nozzle nearer Chamber 42 are divided. Via the throttle plate 38, the chambers 40, 42 communicate with each other (wherein the first 40 and the second chamber 42 in particular have volumes which vary in dependence on an axial displacement position of the throttle plate 38).

The present (circular) disc-shaped and corresponding to the cross-section of the control chamber 28 throttle plate 38 extends - preferably with H-shaped cross section - radially between the end portion 12b of the nozzle needle 12 and the lidding element 32 (wherein the transverse web of the H-shape in the radial Direction extends), in particular plane-parallel with the same. On the circumference, the throttle plate 38 is preferably guided over the webs of an H-shaped cross-section on the wall 28 a of the control chamber 28 (slide-sealed), generally over the circumferential wall of the throttle plate 38.

In the throttle plate 38, an axially passing throttle bore 44 is formed, e.g. centrally, (alternatively, for example, a plurality of throttle holes 44) forming a throttle with a cross-section D, s. e.g. Fig. 2 or 3. In the preferred H-shape solution, a respective such throttle bore 44 preferably each extends through the disc-shaped crosspiece of the H-shape, in particular all.

Preferably, the fuel injector 10 is further configured such that fluid communication between the chambers 40, 42 exclusively via the throttle plate 38, i.e. via the at least one throttle bore 44 or the cross-section D thereof can take place.

In the first chamber 40 according to the invention is a first resilient element 46, in particular in the form of a helical compression spring (alternatively, for example, in the form of a wave washer spring or a plate spring), and in the second chamber 42, a second resilient element 48, in particular in the form of a helical compression spring ( Alternatively, for example, in turn, in the form of a wave washer spring or eg a plate spring), each received biased against the throttle plate 38. The first helical compression spring 46 is at the other end pushed against the lidding member 32, the second helical compression spring 48 against the end 12 b of the nozzle needle 12th

By the resilient elements 46, 48, the throttle plate 38 is mounted axially displaceable in the control chamber 28, it is held so far in the balance.

Visible, for example, Fig. 2, the fuel injector 10 according to the invention further configured such that a (fuel) high-pressure inlet 50, in particular with an inlet throttle ZDr to the control chamber 28 and a discharge process 52, in particular with an outlet throttle ADr, from the control chamber 28th into and out of the first chamber 40.

To control the needle lift via a selective pressure relief of the control chamber 28, the fuel injector 10 further comprises a pilot valve (control valve) 54, which is preferably provided as a magnetaktuiertes valve, alternatively, for example as a piezoelectric valve. The pilot valve 54 may be a simple and preferably quick-acting 2/2-way valve, besides e.g. also a 3/2-way valve. The relief valve 52 can be selectively blocked or released at the injector 10 via the pilot valve 54 toward the low-pressure side (leakage; LP).

With the inventive fuel injector 10, in which the first resilient element 46 preferably has a smaller or a spring stiffness equal to the second spring-elastic element 48 and / or in which the outlet throttle cross-section ADr (substantially) is greater than the throttle cross section D of the throttle bore (en ) 44, the intended Nadelhubverlauf can be realized as part of an injection process. This will be described below with reference to FIGS. 3 explained in more detail.

In a first operating state (before the beginning of an injection, zero stroke position of the nozzle needle 12) of the fuel injector 10, illustrated under a) in FIG. 3, the relief flow 52 from the control chamber 28 to the low-pressure side ND, which is guided via the throttle ADr, blocked via the pilot valve 54 connected in the blocking position. About the hochdruckbeaufschlagten fuel from the high pressure inlet 50 to the control chamber 28 of the control chamber 28 is loaded. In this closed position, the throttle plate 38 is held at an axial distance both to the valve plate 32 and the nozzle needle end 12a between the resilient elements 46, 48, in particular held in suspension. For covering element 32, a distance is set towards the end 12a of the nozzle needle 12, a distance Ah2.

If the control chamber 28 is now relieved by opening the pilot valve 54, s. b) in Fig. 3, so that the closing force balance on the needle 12 is dissolved, the nozzle needle 12 moves together with the throttle plate 38 toward the nozzle distal end of the control chamber 28 axially with the same (or only slightly smaller) speed until the Throttle plate 38 on the lidding element 32 comes into abutment (whereby the opening phase 1 is terminated). The spring-elastic element 48 is not compressed during the opening phase 1 (or only slightly in comparison with the elastic element 46). During this opening _phase 1, the distance h _1i0 above the throttle plate 38 is consumed.

After the first opening phase 1 (steep needle lift opening ramp section 1 in FIG. 1), the slower opening phase 2 follows (flatter Nadelhubrampenabschnitt 2 in Fig. 1), in which the volume of the second chamber 42, the (smaller than ADR) throttle (D ) flows through in the throttle plate 38, wherein an increased resistance prevails. The second opening phase 2 ends when the nozzle needle 12 with the end portion 12a after compression of the second resilient element 48 against the nozzle near end 38a of the throttle plate 38 comes into abutment (full stroke position of the nozzle needle 12). During this opening phase 2, the further distance Ah2 is consumed.

When closing the nozzle needle 12, shown at d) in Fig. 3, first the pilot valve 54 is closed, whereupon the pressure in the control chamber 28th rises again. The needle 12 begins to move down again. Due to the high pressure in the first chamber 40, the throttle plate 38 initially remains at the nozzle needle 12 (12 a), ie sticks to the same. The throttle plate 38 moves away only slowly from the nozzle needle 12, insofar as the fuel flows only slowly through the throttle 44 (D) of the throttle plate 38. During this phase, the resilient element 46 can also relax.

As soon as the nozzle needle 12 has come to rest against the valve seat 22, the throttle plate 38 returns to its initial position shown under a) in FIG. 3. About the height hi, ₀ in the idle state, the duration of the opening ramp 1 is set to the fuel injector 10.

Preferably, based on Q-100 values at 100 bar, the ratio throttle cross-section D of the throttle plate 38 to outlet throttle ADr in the range of 0.12 to 0.4 and / or, based on Q ₁₀ o values at 100 bar, the ratio throttle cross-section Inlet restrictor ZDr to outlet throttle cross section ADr in the range of 0.5 to 0.9.

In particular, when the spring stiffnesses of the first 46 and second 48 resilient members are chosen to be the same, the ratio of the spring lengths after installation is independent of the sum of the spring lengths, thereby facilitating the equalization of a plurality of fuel injectors 10 of an injection system.

LIST OF REFERENCE NUMBERS

First ramp section opening ramp

Second ramp section opening ramp

Third section of needle stroke course

closing ramp

fuel injector

nozzle needle

a nozzle near end 12

b Nozzle end 12

axial bore

nozzle body

injector

jet

valve seat

volume

High pressure supply line

control room

a wall 28

needle sleeve

a nozzle near end 30

Covering element

collar

nozzle spring

throttle plate

a nozzle near end 38

First chamber

Second Chamber

Throttle bore 38 (D)

First elastic element

Second spring-elastic element

High pressure feed HD

Discharge process ND

pilot valve

Claims

claims

A fuel injector (10) for a fuel injection device, wherein the injector (10) comprises a control valve (54) of the injector (10) for controlling the nozzle needle stroke of an axially displaceable nozzle needle (12) of the injector (10 ) is selectively depressurable, wherein the fuel injector (10) at a first end (12a) of the nozzle needle (12) at least one nozzle (20) and at a second end (12b) of the nozzle needle (12) the control chamber (28), characterized characterized in that in the control chamber (28) by a throttle plate (38) received therein a first, nozzle-remote (40) and a second nozzle-closer (42) chamber is divided, which communicate with each other via the throttle plate (38), wherein in the first chamber ( 40) a first spring-elastic element (46) and in the second chamber (42) a second spring-elastic element (48) each biased against the throttle plate (38) is added, which spring-elastic elements (46, 48) Support throttle plate (38) axially displaceable, and wherein a high-pressure inlet (50) to the control chamber (28) and a discharge outlet (52) from the control chamber (28) opens into and out of the first chamber (40).

2. Fuel injector (1) according to claim 1, characterized in that the second resilient element (48) has a spring stiffness greater than or equal to that of the first resilient element (46).

3. fuel injector (1) according to any one of the preceding claims, characterized in that the throttle plate (38) has at least one throttle bore (44), which as a passage opening in communication with the first (40) and second (42) chamber axially through the Throttle plate (38) extends.

4. fuel injector (1) according to any one of the preceding claims, characterized in that the throttle plate (38) is peripherally guided on the wall (28 a) of the control chamber (28), in particular circumferentially slidingly sealed to the wall (28 a) of the control chamber (28) is applied.

5. Fuel injector (1) according to one of the preceding claims, characterized in that the throttle plate (38) has H-shaped cross-section.

6. Fuel injector (1) according to any one of the preceding claims, characterized in that the throttle plate (38) has H-shaped cross-section, wherein at least one axial throttle bore (44) in the throttle plate (38) through the crosspiece of the H-shape extends , in particular all.

7. Fuel injector (1) according to one of the preceding claims, characterized in that a fluid communication between the chambers (40, 42) exclusively via the throttle plate (38), in particular via the at least one throttle bore (44) thereof, can take place.

8. Fuel injector (1) according to one of the preceding claims, characterized in that by means of the first (46) and the second (48) resilient element and the throttle plate (38) a Nadelhubverlauf is set during operation of the injector (10), which has two-stage opening ramp.

9. fuel injector (1) according to any one of the preceding claims, characterized in that the discharge process (52) has a flow restrictor cross-section (ADr), which is greater than the throttle cross-section (D) of the throttle plate (38).

10. Fuel injector (1) according to one of the preceding claims, characterized in that, based on Qioo values, a ratio of throttle cross section (D) of the throttle plate (38) to a flow restrictor cross section (ADr) in the discharge process (52) in the range of 0 , 12 to 0.4 and / or, based on Qioo values, a ratio inlet throttle cross-section (ZDr) of the high pressure inlet (59) to the outlet throttle cross section (ADr) in the range of 0.5 to 0.9.

11. Fuel injection device, characterized by at least one fuel injector (10) according to one of the preceding claims.