EP1519034A1 - Fuel injection valve - Google Patents

Abstract

Fuel pressure acts on at least one of the two coupler sections (23, 24) such that it becomes axially shortened, whilst the gap (27) increases with increasing fuel pressure. The first coupling surface (28) is larger than the second coupling surface (29). The casing includes components compensating gap variation as a result of temperature changes.

Description

State of the art

The invention is based on a fuel injection valve according to the preamble of the main claim.

For example, from DE 35 33 085 A1 a Fuel injector with a piezoelectric or magnetostrictive actuator known, which in operative connection with a valve needle is. The valve needle points to her discharge end on a valve closing body, which with a valve seat surface cooperates with a sealing seat. One Coupler, which compensates for changes in length of Components of the fuel injection valve, in particular of temperature-related changes in length of the actuator, serves, is arranged upstream of the actuator module.

A coupler in the form of an adaptive, mechanical Tolerance compensation with stroke ratio for the stroke of a piezoelectric actuator, is for example from EP 0 447 400 A1. The coupler described here has two against each other axially movable sections, the one Annular gap and a hydraulic volume form. The annular gap connects the hydraulic volume with a compensation chamber. To compensate for changes in length of the actuator is the Hydraulic medium between the hydraulic volume and the Replacement chamber replaced, with the annular gap as Throttle serves. Due to the different sizes Areas of the sections in the hydraulic volume is one Hub translation given.

A disadvantage of the above-mentioned prior art in particular, that it is due to longer lasting Injection phases or Aktorerregungen, for example, at a start of the associated internal combustion engine from hot as well as from cold condition are necessary, to oversized Loss of hydraulic fluid from the hydraulic volume can come. The consequence of this is that the Valve closing body prematurely closes the sealing seat and the required amount of fuel not in the combustion chamber can be delivered.

Advantages of the invention

The fuel injection valve according to the invention with the Features of the main claim has the advantage over that even with significantly extended injection phases or Aktorerregungen the valve closing body the actuator movements can follow exactly in the stroke direction, the flow rate in any operating state of the fuel injection valve is precisely controllable.

By the measures listed in the dependent claims are advantageous developments of the main claim specified fuel injector possible.

In a first embodiment of the invention Fuel injection valve, the fuel than Hydraulic medium used. The fuel injector This makes it easier to build up and the hydraulic volume Can be direct, without consuming and pressure-reducing Seals, are subjected to the fuel pressure.

It is also advantageous if the first coupler surface of first coupler section is larger than the second coupler area of the second section. This can be a Stroke ratio between actuator stroke and needle stroke reach, with the Ventilnadelhub increases.

In a further developments of the invention Fuel injector are the two coupler sections shaped like a piston and gripping from opposite sides in each case at least partially in one Coupler housing a. The coupler sections are in the Coupler housing with a first annular gap and a second Guided annular gap, these each throttle points for form the hydraulic medium.

Furthermore, it is advantageous if in the Coupler housing opposite end faces of the coupler sections the two coupler surfaces form over which the Hydraulic medium acts axially on the coupler sections. The Fuel injection valve can be particularly easy build up.

Is the hydraulic volume through the coupler housing and the limited to two coupler sections, the coupler can in be constructed in a particularly simple manner.

It is also advantageous if at least one of Coupler sections in part, especially in axial Subsections, made of a material, in particular of Aluminum, insists that under hydraulic pressure more deformed than the material from which the housing and / or the coupler housing.

It is also advantageous, the gap in an axial on the Coupler sections or coupler surfaces acting Fuel pressure of 0.3 to 0.7 MPa to 0 to 3 microns adjust, wherein the coupler surfaces at a gap of 0 microns only touch almost without pressure.

Advantageously, the housing has compensation elements, the temperature-related changes in the size of the gap compensate. The size of the gap is independent of temperature fluctuations of the fuel injection valve.

Furthermore, it is advantageous, the gap in a Fuel pressure of 10 MPa or higher to at least 100 Micrometer, more preferably at a fuel pressure from 60 Mpa or higher to at least 25 microns, too sized. The function of the coupler is added in this way ensured higher fuel pressures.

drawing

Fig. 1

eine vereinfachte schematische axiale Schnittdarstellung durch das Ausführungsbeispiel eines erfindungsgemäßen Brennstoffeinspritzventils.

An embodiment of the invention is shown in simplified form in the drawing and explained in more detail in the following description. It shows:

Fig. 1

a simplified schematic axial sectional view through the embodiment of a fuel injection valve according to the invention.

Description of the embodiment

Hereinafter will be an embodiment of the invention described by way of example.

One shown in Fig. 1 in an axial sectional view Inventive fuel injection valve 1 is used in particular for the direct injection of fuel into a combustion chamber of a mixture-compressing, spark-ignited Internal combustion engine.

In a step down in the direction of injection tapered hollow cylindrical housing 5 are a Valve needle 8, an actuator 2 and a hydraulic coupler. 3 each arranged coaxially with each other. The inflow side is the Housing 5 hermetically sealed by a housing cover 4 locked. On the housing cover 4 is based on the Inside the actuator 2 with its inflow end from.

Downstream, the actuator 2 has a disc-shaped Actuator head 10 on. The actuator head 10 is in one hollow cylindrical actuator housing 9 guided axially movable. The actuator housing 9 has a downstream at the downstream end inside third flange 16 and is on the inflow side hermetically attached tightly to the housing cover 4. A third Spring element 22 is between the actuator head 10 and the third flange 22 clamped with a bias and keeps the actuator head 10 in constant contact with the actuator 2.

In the illustrated embodiment, the hydraulic Coupler 3 between the actuator 2 and the valve needle. 8 arranged, wherein in a coupler housing 25, a first Coupler section 23 upstream and a second coupler section 24 partially intervene downstream. The first Coupler section 23 has a rod-shaped on the inflow side, made of aluminum spacer 34 and downstream a cup-shaped end piece 35. The intermediate piece 34 reaches downstream to the bottom of the cup-shaped End piece, is there, for example, cohesive fixed and accesses on the inflow side partially in the Actuator 9, where it is fixed to the actuator head 10 connected is.

A flexible section 26, for example corrugated pipe or hole disc-shaped, seals the actuator housing 9 against fuel. The flexible one Section 26 has one end in the area of downstream end of the actuator housing 9 and with the other end on the intermediate piece 34 hermetically sealed. The second coupler section 24 is piston-shaped educated. The first coupler section 23 has a first one Coupler face 28 and the second coupler section 24 has a second coupler face 29, the coupler faces 28, 29 at the opposite ends of the Coupler sections 23, 24 are arranged.

Because the second coupler portion 24 is smaller in diameter is as the first coupler section 23, is also the first Coupler face 28 larger than the second coupler face 29th The two coupler sections 23, 24 are through a gap 27 spaced. The size of the gap 27 is defined by the axial Displaceability of the coupler sections between 0 and for example, 50 microns variable.

Im also in the flow direction stepwise Tapered coupler housing 25 is a hydraulic volume 17 arranged, which through the coupler housing 25 and the both coupler sections 23, 24 is limited, wherein in This embodiment, the hydraulic volume 17 via a first generated by a first annular gap 32 first Throttle 30 and a through a second annular gap 33 generated second throttle body 31 with the fuel-filled interior of the housing 5 in conjunction stands.

In the region of the downstream end of the second coupler section 24, a second flange 15 is arranged. One second spring element 21 is between the second flange 15th and the downstream thickened edge of the coupler housing 25th clamped and biases the second coupler section 24 easy in spray direction. Outflow side of the second Coupler section 24, the valve needle 8 is arranged.

Abspritzseitig, the valve needle 8 has a Valve-closing body 7 and engages through an am ejection-side end of the housing 5 is arranged Valve seat body 6. The valve seat body 6 has a centered ejection opening 12 and a Valve seat surface 13, which communicates with the valve closing body. 7 cooperates to a sealing seat. On the inflow side, the Valve needle 8 to a first flange 14. Between the First flange 14 and the valve seat body 6 is a first Clamped spring element 20, which the valve closing body. 7 pulls in the sealing seat and how the second spring element 21st and the third spring element 22 is formed spirally. The fuel injection valve 1 opens to the outside.

In the idle state of the fuel injection valve 1 or the associated parked internal combustion engine is the size of gap 27 at pressures below 0.7 MPa ideally at 0 microns, with the two coupler faces 28, 29 only touch almost without pressure. In the valve housing introduced compensation elements 36, which, for example made of Invar steel, compensate for the Temperature - related changes in length, which are the size of the Crevices could affect, so that the size of the gap 27th just before a start of the engine from hot and cold state at 0 microns. At a start of the Internal combustion engine, the fuel pressure is usually at 0.5 MPa, as a mechanical drive of a pump through the internal combustion engine is not possible. Instead, it will the fuel pressure usually by an electric driven pump generates, without much effort To operate, only about 0.3 to 0.7 MPa applies.

In start-up phases, both hotter and cooler Internal combustion engine, usually a multiple of the Full load fuel injected. This is going through extended valve opening times or longer Actors excited reached. In conventional Fuel injection valves, in particular in Hot start phases, escapes from the hydraulic coupler in These starting phases so much hydraulic medium that the Valve-closing body 7 is no longer sufficient by the actuator 2 can be operated. The seal closes too soon and the required amount of fuel can not be injected. In the inventive Fuel injector 1 is in startup phases the Valve needle 8 and the valve closing body 7 directly, without Intermediate layer of a hydraulic cushion, actuated.

In the operation of the internal combustion engine, not shown, after longer term or usually short after the start of the engine adjusting Fuel pressure of 10 MPa or more, the size of the Gaps 27 ideally between 25 and 100 microns. Of the increased fuel pressure, which axially in each case opposite directions on the two coupler sections 23, 24 over the two coupler surfaces 28, 29th acts, causes a compression in the axial direction of the For example, made of aluminum intermediate piece 34, whereby during operation of the coupler 3, the functions, Stroke ratio and / or compensation of temperature-related Length changes of the actuator 2, can take over.

If after the start phase of the actuator 2 via a not When the electric wire is energized, it stretches fast. Because the hydraulic medium is not fast enough through the throttle bodies 30, 31 from the hydraulic volume 17th can flow off, the coupler 3 behaves very stiff, whereby the longitudinal extent of the actuator 2 almost completely acts on the valve needle 8. The valve needle 8 is opposed the biasing force of the first spring element 20 axially in Abspritzrichtung moves. This opens the sealing seat and the pressurized fuel is supplied via the Spray opening 12 in the combustion chamber, not shown hosed. Slow changes in length of the actuator 2 become by exchanging hydraulic medium between the Hydraulic volume 17 and the fuel-filled interior of the Housing 5 balanced.

The invention is not limited to those shown Embodiments limited and z. B. also for internal opening fuel injectors are used.

Claims (11)

Fuel injection valve (1), in particular for the direct injection of fuel into a combustion chamber of an internal combustion engine, with a housing (5), a piezoelectric, electrostrictive or magnetostrictive actuator (2), a valve closing body (7) operatively connected to the actuator (2), which cooperates with a valve seat surface (13) to a sealing seat, and a coupler (3) having a first coupler portion (23) with a first coupler surface (28) and a second coupler portion (24) with a second coupler Surface (29), wherein the two coupler sections (23, 24) are mutually movable and with each other in a hydraulic volume (17) are in operative connection, and wherein the hydraulic volume (17) with hydraulic medium, the at least a throttle point (30, 31) is supplied or discharged, is filled and is pressurized by the fuel, and wherein between the coupler portions (23, 24), a gap (27) is arranged over d the hydraulic medium acts in each case axially on the coupler surfaces (28, 29) or coupler sections (23, 24),
characterized in that the fuel pressure acts on at least one of the two coupler portions (23, 24) so as to be shortened axially, the gap (27) increasing with increasing fuel pressure. Fuel injection valve according to claim 1,
characterized in that the hydraulic medium is the fuel. Fuel injection valve according to claim 1 or 2,
characterized in that the first coupler surface (28) is larger than the second coupler surface (29). Fuel injection valve according to one of the preceding claims,
characterized in that the two coupler portions (23, 24) in the region of their in a coupler housing (25) from opposite sides at least partially engaging ends are each shaped like a piston and so in the coupler housing (25) engage, that the first coupler section (23) in a first annular gap (32) which forms a first throttle point (30), is guided and that the second coupler portion (24) in a second annular gap (33), which forms a second throttle point (31) out is. Fuel injection valve according to claim 4,
characterized
in that the two coupler surfaces (28, 29) of the coupler sections (23, 24) are formed from the end faces of the coupler sections (23, 24) which are opposite in the coupler housing (25). Fuel injection valve according to claim 4 or 5,
characterized in that the hydraulic volume (17) through the coupler housing (25) and the two coupler sections (23, 24) is limited. Fuel injection valve according to one of claims 4 to 6,
characterized
the at least one of the coupler sections (23, 24) is at least partially made of a material that deforms more under hydraulic pressure than the material of which the housing (5) and / or the coupler housing (25) is made. Fuel injection valve according to one of the preceding claims,
characterized
the at least one of the coupler sections (23, 24) consists at least partially of aluminum. Fuel injection valve according to one of the preceding claims,
characterized in that at a axially on the coupler sections (23, 24) or coupler surfaces (28, 29) acting fuel pressure of 0.3 to 0.7 MPa, a gap (27) from 0 to 3 microns adjusts , wherein at a gap (25) of 0 microns, the coupler surfaces (28, 29) only touch almost without pressure. Fuel injection valve according to claim 9,
characterized in that the housing (5) compensating elements (36) which compensate for temperature-induced changes in the size of the gap (27). Fuel injection valve according to one of the preceding claims,
characterized in that at a fuel pressure of 10 MPa or higher acting axially on the coupler sections (23, 24) or coupler surfaces (28, 29), a gap (27) of between 25 microns and 100 microns or preferably of at least 50 microns.

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