DE102005024871A1 - Injector for diesel fuel has a control chamber, which is subjected to fluid pressure whereby nozzle needle or tappet of nozzle needle of injector is coupled fluid mechanically with servo valve - Google Patents

Abstract

Injector e.g. servo hydraulically operated has a control chamber, which is subjected to fluid pressure. Nozzle needle (20) or tappet of nozzle needle of injector is coupled fluid mechanically with a servo valve (30). For reproducibly controlling injection of smaller amount of fuel, a servo valve on control chamber side is connected upstream to a separate throttle plate (100). A separate throttle plate is provided at or in a valve bore (38) of the servo valve. Independent claims are also included for the following: (A) Injection system; and (B) Internal combustion engine.

Description

The The invention relates to an injector, in particular a servohydraulic actuated Common rail injector, for injecting a fluid into a combustion chamber an internal combustion engine.

For a good Preparation of a fuel-air mixture must be a fuel depending on the combustion process, with pressures up to more than 2,000 bar in a combustion chamber an internal combustion engine are injected and thereby with the greatest possible accuracy be metered per injection. To make a compromise between one Low fuel consumption and compliance with legal limits for emissions (Exhaust gases and noise of the engine), it is necessary to start the injection process of the fuel injector precisely to control. Essential parameters are a respective start of injection (Pre-injection, main injection (s) and post-injection), an injection duration, a respective injection end and a dynamic behavior of a nozzle needle during the Injection.

It There are high demands on the dynamic behavior of the nozzle needle over a entire speed range of the internal combustion engine away. by virtue of the high injection pressures work great hydraulic forces, which in particular also act on a sealing element of a servo valve. This results in connection with the mechanical elasticities (stiffnesses) in the drive train of the servo valve (inter alia servo valve member, piezoelectric actuator, injector housing) bistable behavior (open / closed) the nozzle needle, with the nozzle needle due to the released by the servo valve flow cross section with very high speed from a closed position to an open position of the Injector moves. While closing of the servo valve are similar Conditions. Through this quasi-digital opening or Close the nozzle needle is a reproducible controlled injection of small amounts of fuel, especially for a pre / post injection and injections at speeds below the full load speed, considerably more difficult.

The Control of an injection amount of a fuel injector is good manageable, as long as the injection quantity is determined by that duration, while the nozzle needle of the fuel injector fully open in their position on a jet needle stop lingers and a movement phase of the nozzle needle only a negligible Contribution to the total injection quantity supplies. However, the problem is that in motor vehicles over Run 90% of the engine operation such that the required injection quantity is so small that the injection process has to be ended, before the nozzle needle hers Reached stop. The movement phase of the nozzle needle determines the injected one Fuel quantity almost completely.

The Movement phase of the nozzle needle is difficult to control because of the nozzle needle during the opening process of the servo valve is greatly accelerated. Furthermore, the opening process the servo valve of complex nature and many parameters - such. B. parasitic elasticities; a temperature distribution in the fuel injector; an electromechanical State of the actuator, which fluctuate due to hysteresis and aging can and therefore is at least not easily predictable; and from mechanical friction - dependent.

The EP 0 949 415 B1 teaches a servohydraulically actuated injector with piezoelectric actuator. The injection device has a nozzle needle and a plunger actuating the nozzle needle, which can be moved up and down in dependence on a fluid pressure in a control chamber and thus controls a movement of the nozzle needle. The control chamber can be filled by a feed with integrated fixed throttle with fuel under high pressure, and emptied through a drain with therein fixed throttle through a valve chamber of a servo valve. Here, the fixed throttle of the process is provided coaxially to the plunger upstream of the control chamber fixed in the injector. In the valve chamber of the servo valve opens a valve member with valve head, wherein the valve member, surrounded with a sleeve-shaped drag valve member cooperating with the valve head, can release two different fluid passage cross-sections for the injector.

By forming the drain throttle in a housing portion of the injector as well as the comparatively large one Space requirement of the two-part valve member in the valve chamber is the Dead volume of the servo valve of the injector comparatively large, what the dynamic behavior of the injector disadvantageous influenced and a comparatively long response time of the nozzle needle conditionally.

As a general rule this affects the known solutions size hydraulic dead volume of the servo valve negative, which is by additional Integration of a fixed outlet throttle section in the form of a throttle plate over the gives complete cross section of the fuel injector away.

It is an object of the invention to provide an improved injector which can be used in the art Specially realized a dynamic response with short response time of the nozzle needle, so as to allow a controlled injection of partial and very small amounts with high reproducibility. Furthermore, an object of the invention is to integrate into an existing injector, in particular a servohydraulically actuated fuel injector, subsequently an outlet throttle without significant design changes of the fuel injector, while keeping the dead volume of the servo valve as low as possible.

The The object of the invention is achieved by means of an injector, in particular a servohydraulically operated Common rail fuel injector solved, one fluidically connected in series with a servo valve Outflow throttle, wherein the outlet throttle as a separate Component is provided directly on the servo valve. This provides the Invention provides an injector having a servo valve with therein integrated throttle includes.

through the inventive arrangement is it is possible with the outlet throttle as close as possible to a valve member or Approached sealing element of the servo valve and so the between a sealing surface the servo valve and the outlet throttle existing dead volume of the Servovalve as low as possible to keep. This inventive arrangement is particularly simple inwardly opening servo valves within a piezoelectric fuel injector to realize. Due to the small dead volume between outlet throttle and a servo valve seat is on the one hand a very short response time or realized a dynamic response of the nozzle needle, and on the other hand a reproducible controlled injection of smallest fuel quantities of the injector possible. It is according to the invention possible, the movement phase of the nozzle needle between its closed and fully open positions in the injector to influence without the nozzle needle digitally auf- or zurueuert, whereby the injection smallest Fuel quantities can be realized.

In a preferred embodiment the invention is the outlet throttle as an extra mounted throttle plate on a valve body provided the servo valve. Here, the throttle plate is preferred at a sealing portion of the servo valve opposite End of a valve bore arranged. On the one hand, this enables the low one Dead volume of the servo valve and on the other a subsequent attachment the throttle plate on the valve body, so that in the assembly process of the injector or the servo valve only slightly must be intervened, since first the sealing element of the servo valve is inserted into the valve bore, then attached to the throttle plate and then with the herkömmli chen Assembly process of the injector can be continued. In particular, the subsequent provision according to the invention Throttle plate in an existing fuel injector upgraded this to the effect that it reproducible even the smallest fuel quantities can inject without going into the concept of the existing injector to intervene. Ie. It is according to the invention possible an existing fuel injector with a drain throttle retrofit, without changing it constructively to have to.

According to the invention is a Valve plate of the servo valve preferably dimensioned so that they on the one hand, the sealing element of the servo valve including a guide (designed as an extension on the sealing element) can accommodate the sealing element, On the other hand, provision of the throttle plate is preferably at least partially within the valve bore of the valve plate allows. Furthermore, the valve plate is preferably designed such that the throttle plate in a recess within the valve plate located, which serves as a control room for controlling the nozzle needle.

By an at least partial provision of the throttle plate within the Valve bore is guaranteed that the dead volume of the servo valve as small as possible is and the fuel injector not by an additional Disc, in which the outlet throttle is provided is extended, which requires a partial redesign of the fuel injector would do.

to fluid-tight connection between throttle plate and valve plate can the throttle plate in the valve bore in the valve plate be pressed and / or with a around the edge of the valve bore circumferential weld be connected to the valve plate.

Further the invention relates to an injection system, in particular a common rail injection system, with a fuel injector according to the invention; such as an internal combustion engine, in particular a diesel engine, with a Fuel injector according to the invention.

Further preferred embodiments The invention results from the remaining dependent claims.

The Invention will be described below with reference to exemplary embodiments with reference closer to the drawing explained.

In show the drawing:

1 a sectional partial side view of an injector according to the prior art;

2 a sectional partial side view of a first embodiment of an injector according to the invention;

3 an enlarged sectional partial side view of a second embodiment of the injector according to the invention; and

4 a sectional partial side view of a third embodiment of the injector according to the invention.

The following versions relate to an injector, in particular a fuel injector, with an inward opening (Servo) valve, d. H. a against a flow direction of a working fluid opening Valve. However, the invention should not be limited to such valves - but equally outward opening Valves, d. H. valves opening in the direction of fluid flow; opening from the outside Valves, d. H. from the non-pressurized side actuated valves; and opening from the inside Valves, d. H. from the pressurized side actuated valves; or injectors with such (servo) valves. Furthermore, should the invention should not be limited to fuel injectors, but generally include injectors.

1 shows in a section of the structure of a servo-hydraulically actuated fuel injector of a common rail injection system for diesel vehicles according to the prior art with a digital switching, piezoelectrically actuated 2/2-servo valve 30 (2/2: two connections / two switching positions). Digital switching in this context means that the servo valve 30 having only two fixed valve member positions: fully open and fully closed; between these two positions the servo valve switches 30 abruptly back and forth.

Im in 1 illustrated embodiment of the fuel injector, the fuel injector has an actuator body 140 and an injector body 130 on, between which a valve plate 34 and a to these below (in relation to 1 ) subsequent intermediate plate 120 are clamped. The actuator body 140 has a high pressure hole 50 which supplies the fuel injector with high pressure fuel from a rail (not shown) which ensures a constant high pressure fuel flow. Furthermore, within the actuator body 140 a piezoelectric actuator constructed as a multilayer piezo stack 40 provided, which is the servo valve 30 up and headed. The construction of mainly from the valve plate 34 and a valve member 32 or sealing element 32 existing servo valve 30 will be explained in more detail below.

Between the valve plate 34 and the intermediate plate 120 is a tax room 10 formed, in which there is fuel, depending on the pressure conditions of the fuel in the control room 10 a nozzle needle 20 is movable up or down. The washer 120 on the one hand serves to guide the nozzle needle 20 or one the nozzle needle 20 actuated plunger, as well as on the other hand, a throttled fuel inlet of the control chamber 10 from an annulus 52 out, between the intermediate plate 120 and the injector body 130 is trained. A necessary throttling (see below) of the fuel inlet for the control room 10 takes place via the intake throttle designed as a fixed throttle 60 instead of. Furthermore, the annulus supplies 52 the nozzle needle 20 in a lower region with fuel, so that on the one hand, the nozzle needle (not shown) can be moved over her at the bottom provided pressure shoulder up and on the other hand via a lower nozzle needle seat (not shown) and provided there injector bores (not shown) fuel into a combustion chamber (not shown) is injectable. The fuel supply to the lower section of the nozzle needle 20 takes place via longitudinal recesses, between a downwardly drawn extension of the washer 120 and the injector body 130 are formed. This is the extension of the washer 120 Faceted in a lower area outside (not shown), resulting in an unthrottled fluidic connection between the annulus 52 and the seat of the nozzle needle 20 manufactures. To supply the annulus 52 over the high pressure bore 50 are both the valve plate 34 as well as the intermediate plate 120 provided with appropriate holes.

The function of the fuel injector is briefly outlined below:
In the in 1 illustrated position of the nozzle needle 20 the fuel injector is closed, ie there is no injection of fuel into the combustion chamber. About the high pressure bore 50 , the ring channel 52 and the inlet throttle 60 is in the control room 10 the injection pressure of typically 2,000 bar. Likewise, the full injection pressure is at the nozzle end of the nozzle needle 20 at. Ie. at a free end 22 the nozzle needle 20 or at the free end 22 one the nozzle needle 20 actuating ram and at the nozzle end of the nozzle needle 20 is equal pressure in the illustrated embodiment. Due to a larger pressure-effective area of the control room end 22 the nozzle needle 20 this is held in its valve seat. Supporting acts here a return spring 70 , which are on the extension of the intermediate plate 120 and the nozzle needle 20 supported. The return spring 70 Holds the nozzle needle 20 also in the pressureless state in its valve seat. The under the full injection pressure control room 10 is over the servo valve 30 with a little under pressure or Ambient pressure stagnant drain or low pressure range 90 (eg a tank). The servo valve 30 is from the sealing element 32 and one in the valve plate 34 trained servo valve sealing seat 36 formed, wherein the sealing element 32 on the one hand preferably with guide surfaces in a valve bore 38 the valve plate 34 for guiding the sealing element 32 hineinerstreckt, on the other hand, however, by means of longitudinal recesses or a faceting, z. B. a Flächenanschliff, the unthrottled passage of fuel from the control chamber 10 in the drain area 90 allowed. The recesses or Flächenanschliffe are with dashed lines on the sealing element 32 or on the extension of the sealing element 32 indicated in the figures.

In the illustrated initial state of the closed fuel injector, the servo valve sealing element 32 through a mechanical reset element 31 , z. B. in the form of a bending or leaf spring, tight in the valve seat 36 held. The servo valve 30 is thus closed. At applied high pressure in the control room 10 acts according to the seat diameter of the servo valve 30 an additional hydraulic force on the sealing element 32 , bringing the servo valve 30 is safely closed even at pressures of 2,000 bar. The actuation of the servo valve 30 via the mechanically or hydraulically pressure-biased piezoactuator 40 that attaches itself to an injector housing 110 supported (not shown) and the free end of the sealing element 32 of the servo valve 30 acts.

In an electrical activation of the piezoelectric actuator 40 by charging or energizing, the piezoelectric actuator expands 40 longitudinally and displaces the sealing element 32 from the valve seat 36 away, creating an unthrottled fluidic connection between the control room 10 and the drain area 90 will be produced. By limiting the inflow volume flow into the control room 10 through the inlet throttle 60 the pressure falls in the control room 10 abruptly. Since the injection-side end of the nozzle needle 20 However, the full injection pressure of about 2,000 bar is still pending, at the control room end 22 the nozzle needle 20 but only a much lower pressure prevails (typically some 100 bar), the nozzle needle 20 against the force of the return spring 70 in the direction of the control room 10 moved and the injector holes are released; the injection begins.

The injection is terminated in the reverse order, ie after contraction (discharge) of the piezo actuator 40 , the servo valve closes 30 , whereupon the pressure in the control room 10 increased again to 2,000 bar and the nozzle needle 20 is moved back into its valve seat, the Injektorbohrungen be closed; the injection is finished.

When opening the servo valve 30 turns in the control room 10 abruptly a lower pressure than at the pressure shoulder of the nozzle needle 20 one. When re-closing the servo valve 30 happens similar, but not so violent, since the excess power is provided by the comparatively weak return spring. This causes the nozzle needle to move 20 almost digitally between its open and closed position back and forth.

In an internal combustion engine, more than 90% of the engine operation is such that the injection quantity required is so small that the injection process should be terminated before the nozzle needle reaches its upper stop on the valve plate 34 reached. Ie. the movement phase of the nozzle needle 20 determines the amount of fuel injected completely. Due to the jarring movement of the nozzle needle 20 is a reproducible controlled injection of these amounts of fuel significantly more difficult.

According to the invention, an adjustment of a defined opening characteristic of the nozzle needle 20 through one with the servo valve 30 fluidically connected in series throttle plate 100 possible. 2 shows an inventive embodiment of the fuel injector with the throttle plate 100 , In the illustrated embodiment, the servo valve 30 and the throttle plate 100 arranged directly adjacent to each other so that the dead volume between the servo valve seat 36 and throttle plate 110 arises as low as possible. The servo valve 30 is according to the invention by the throttle plate 100 added.

The assembly of the servo valve according to the invention 30 is easy and is by providing the throttle plate 100 not hindered, since the mounting of the throttle plate 100 in time to a pre-assembly of the servo valve 30 followed. The servo valve 30 is first as before, ie without an assembly of the throttle plate 100 , assembled. For this purpose, the sealing element 32 with its sealing surface coming up from below (everything related to 2 ) into the valve bore 38 the valve plate 34 used and then by means of the return element 31 recorded. In a subsequent step, the throttle plate 100 on the valve plate 34 attached. This can be z. B. by pressing and / or welding, z. B. laser welding, done. This can be a weld 104 completely around the throttle plate 100 be configured circumferentially, whereby by means of the weld 104 a fluid-tight connection between throttle plate 100 and valve plate 34 is realized. Furthermore, the throttle plate 100 at least partially into the valve bore 38 be pressed, which is also a fluid-tight connection between the throttle plate 100 and valve plate 34 realized. Furthermore, this interference fit can be additionally welded, which also only occasionally ge can happen.

The position of the throttle plate 100 on the valve plate 34 or on or in the valve bore 38 is selected such that in a later operation of the fuel injector, the sealing element 32 of the servo valve 30 the throttle plate 100 not affected or impaired in their function (pressure waves due to the opening or closing sealing element 32 ). On the other hand, the throttle plate 100 as close as possible to the sealing element 32 placed or so on or in the valve bore 38 provided that the servo valve 30 has the lowest possible dead volume.

In the embodiment of 2 forms the throttle plate 100 a limitation in the longitudinal direction of the valve bore 38 , where the throttle plate 100 in a recess 35 the valve plate 34 at the valve bore 38 is provided. This recess 35 has the dimensions of the throttle plate 100 , where the throttle plate 100 in this recess 35 can be pressed and / or welded. Preferred is a surface of the throttle plate 100 in a plane with a surface of the valve plate 34 or that portion of the valve plate 34 which the control room 10 limited. This has the advantage of increasing the volume of the control room 10 through the throttle plate 100 not or only slightly changes (weld 104 is in the 2 exaggerated).

In this embodiment, only inside the valve plate 34 of the servo valve 30 the additional recess 35 be provided to the servo valve 30 or the fuel injector with a drain throttle 100 retrofit. A redesign of neither the fuel injector nor the servo valve 30 is needed.

In the above invention, the throttle plate 100 a simple plate or disc, the only one throttling function by means of a throttle bore 102 realized. The throttle plate 100 otherwise takes no further tasks, the z. B. by drilling fluid transport or the like.

The throttle bore 102 the throttle plate 100 is Favor coaxial with the valve bore 38 aligned. Other positions of throttle bore 102 are also possible; z. B. with regard to the fuel transport along the sealing element 32 provided longitudinal recesses or Flächenanschliffe can the throttle bore 102 or a plurality of throttle bores 102 lie to these "coaxial" to a quick response of the servo valve 30 and thus also a fast response of the nozzle needle 20 to ensure. Furthermore, the throttle bore 102 Preferably we coaxial with the nozzle needle 20 still coaxial with the inlet throttle 60 intended. However, embodiments are also possible in which the throttle bore 102 coaxial with respect to the inlet throttle 60 or coaxial with respect to the nozzle needle 20 is arranged.

3 shows a second embodiment of an inventive arrangement of the throttle plate 100 in the servo valve 30 or the servo valve according to the invention 30 , In this embodiment, the throttle plate 100 completely in the valve hole 38 intended. The throttle plate 100 can also be welded or pressed in this case.

In such an embodiment eliminates all measures that a kind of any kind of reconstruction of the injector or the servo valve 30 or the valve plate 34 of the servo valve 34 necessary, because only in the valve bore 38 the throttle plate 100 is attached.

In the two embodiments of the fuel injector according to the 2 and 3 is the reset element 31 a bending or leaf spring 31 that attach to one of the valve bore 38 protruding portion of the sealing element 31 and on the valve plate 31 supported. Preference is given to the bending or leaf spring 31 in a groove of the sealing element 32 held. Also in the valve plate 31 may be formed a corresponding annular groove, which is the return element 31 holds in position.

4 shows a third embodiment of the fuel injector according to the invention, the differently constructed sealing element 32 , as well as another reset element 31 and another arrangement of the return element 31 in the servo valve 30 having. In this embodiment, the return element 31 a coil spring 31 and the sealing element 32 of the servo valve 30 is a so-called mushroom valve member, preferably completely in the valve bore 38 is arranged. The spiral spring 31 holding the servo valve 30 holds closed ge also in the pressureless state, in this case provides a mechanically resilient connection between the throttle plate 100 and the sealing element 32 ago; the sealing element 32 So it supports resiliently on the throttle plate 100 from.

An advantage of this embodiment is that the inventive arrangement of the throttle plate 100 fully compatible with a mushroom-shaped servo valve sealing element 32 is. Such mushroom valves are in fuel injectors for years in mass production, so all the questions about the maturity and life (= 10 ⁹ cycles) of such a servo valve 30 answered positively. The same applies to the coil spring. Also with this embodiment it is ensured that an already existing fuel injector easily with the throttle plate according to the invention 100 can be retrofitted.

According to the invention, a servo valve 30 with upstream throttle bore 102 provided with all fluid passing through the servo valve 30 the throttle body flows 102 must happen.

Claims (16)

Injector, in particular servohydraulically actuated common-rail injector for diesel fuel, with a control chamber subjected to fluid pressure (US Pat. 10 ), which has a nozzle needle ( 20 ) or a plunger of the nozzle needle ( 20 ) of the injector fluid mechanically with a servo valve ( 30 ), wherein for the reproducible controlled injection of smallest amounts of fuel the servo valve ( 30 ) control room side a separate throttle plate ( 100 ) which is connected to or in a valve bore ( 38 ) of the servo valve ( 30 ) is provided. Injector according to claim 1, wherein the throttle plate ( 100 ) a sealing element ( 32 ) of the servo valve ( 30 ) upstream upstream. Injector according to claim 1 or 2, wherein the sealing element ( 32 ) of the servo valve ( 30 ) and the throttle plate ( 100 ) are arranged directly adjacent to each other. Injector according to one of claims 1 to 3, wherein the sealing element ( 32 ) into a first end ( 39 ) of the valve bore ( 38 ) a valve plate ( 34 ) and the throttle plate ( 100 ) on the valve bore ( 38 ) on one side of the valve plate ( 34 ) provided to the first end ( 39 ) of the valve bore ( 38 ) is opposite. Injector according to one of claims 1 to 4, wherein the throttle plate ( 100 ) partially into the valve bore ( 38 ) or within the valve bore ( 38 ) is provided. Injector according to one of claims 1 to 5, wherein a throttle bore ( 102 ) of the throttle plate ( 100 ) coaxial with the valve bore ( 38 ) lies. Injector according to one of claims 1 to 6, wherein the throttle bore ( 102 ) of the throttle plate ( 100 ) and the nozzle needle ( 20 ) are not arranged coaxially with each other. Injector according to one of claims 1 to 7, wherein the throttle bore ( 102 ) of the throttle plate ( 100 ) and an inlet throttle ( 60 ) of the control room ( 10 ) are not arranged coaxially with each other. Injector according to one of claims 1 to 8, wherein the throttle plate ( 100 ) in the valve plate ( 34 ) and / or with the valve plate ( 34 ) is welded. Injector according to one of claims 1 to 9, wherein the sealing element ( 32 ) by means of a return element ( 31 ) can be brought into a closed position, in which the servo valve ( 30 ) is fluid-tight. Injector according to claim 10, wherein the return element ( 31 ) a bending or leaf spring ( 31 ), which is on the one hand at one of the first end ( 39 ) of the valve bore ( 38 ) protruding portion of the sealing element ( 32 ) is supported, and on the other hand on the valve plate ( 34 ) is supported. Injector according to claim 10, wherein the return element ( 31 ) a coil spring ( 31 ), which on the one hand at the in the valve bore ( 38 ) sealing element ( 32 ) is supported, and on the other hand on the throttle plate ( 100 ) is supported. Injector according to one of claims 1 to 12, wherein the servo valve ( 30 ) an inwardly opening servo valve ( 30 ). Injector according to one of claims 1 to 13, wherein after insertion of the sealing element ( 32 ) into the valve bore ( 38 ) the throttle plate ( 100 ) is mountable on the valve plate. Injection system, in particular common-rail injection system, with an injector according to one of claims 1 to 14. Internal combustion engine, in particular diesel engine, with An injection system according to claim 15.