DE102005059163A1 - Fuel injection device for an internal combustion engine - Google Patents

Abstract

A fuel injection device (10) is used to inject fuel into a combustion chamber of an internal combustion engine. It comprises at least two coaxial valve elements (34, 36) and a switching valve (24, 26) for controlling the stroke of the valve elements (34, 36). It is proposed that a hydraulic delay element (71) be arranged between the switching valve (26) and at least one valve element (34).

Description

State of technology

The The invention relates to a fuel injection device for an internal combustion engine according to the preamble of claim 1.

Known are stroke-controlled common-rail injectors with at least one as Solenoid valve formed switching valve and an injection nozzle with Sitzloch- or blind hole geometry for distribution of a defined amount of fuel in the combustion chamber. By controlling the switching valve is a pressure lowered in a control chamber, whereby the valve element from the valve seat, the upstream from the actual fuel outlet openings, lifts off.

For a favorable emission behavior of the internal combustion engine, it is important in some operating situations that the fuel, in particular when using diesel fuel, is distributed as homogeneously as possible in the combustion chamber. So that this is just as possible with small quantities of injected fuel as with large quantities of fuel, so-called coaxial vario nozzles are used. These have two mutually coaxial valve elements, by the actuation of different fuel outlet openings are released, which may also be oriented differently. It is advantageous if the two valve elements can be actuated completely independently. Such a fuel injection device is for example from the EP 1 069 308 A2 known.

task The present invention is a fuel injection device provide at the very different amounts of fuel reliable can be injected.

These Task is by a fuel injection device with the features of claim 1. Advantageous developments of the invention are specified in subclaims.

Advantages of invention

The Use of a delay element allowed it also with a slow-switching switching valve, for example a solenoid valve, a short opening time of the valve element to realize. The period during which has lifted the valve element from the valve seat, so is shorter than the period while whose switching valve is in the corresponding switching position.

The Embodiment of the delay element as hydraulic delay element elevated to a considerable extent the degrees of freedom in the interpretation of the Switching behavior of the thus controlled valve element. Also the Degrees of freedom in constructional terms are due to the hydraulic Configuration of the delay element elevated, because of the hydraulic delay element also "crooked" routes are bridged can. This is especially cheap for the Control of the axially outside lying valve element.

at the fuel injection device according to the invention is an independent Control of the two valve elements with simultaneous consideration hydraulic and mechanical requirements and of the disposal standing space available. Furthermore, can thanks to the hydraulic delay element the electrical, hydraulic and mechanical controls, the for an operation the valve elements are required, housed in a compact housing become. As a result, the fuel injection device according to the invention in previous internal combustion engines without additional space adaptations be used. Thus could the fuel injection device according to the invention against known pressure-controlled or stroke-controlled injection systems, like common rail, pump pipe nozzle or pressure-boosted Common rail systems, easily exchanged.

A particularly advantageous embodiment of the hydraulic delay element is that it includes a pilot space whose length is one Multiple of its diameter is, the pilot space at one end region with the switching valve and at another end region with a control room and a high-pressure connection is connected. One such pilot space acts similarly like a hydraulic spring, thus providing the desired deceleration function ready. The advantage of such a pilot space is mainly in its easy realization. Furthermore, by such Pilot control room a big one Distance between control room and switching valve are bridged, at the same time small and therefore precise acting control room.

there the use of a pilot control room offers the possibility of hydraulic delay so that it forms in the opening direction of the associated Valve element stronger as in the closing direction delayed. This can be a late opening, however an early one Shut down the associated valve element be realized, what for the emission behavior of the internal combustion engine, in which the fuel injection device according to the invention used is, again improved.

A directional dependence of the filling and emptying of the control chamber can be realized that the hydraulic delay element comprises a throttle check valve which is arranged between the pilot control chamber and control chamber and opens to the control chamber. Such a throttle check valve comprises, for example, a valve element into which a flow throttle is integrated.

A sees further preferred embodiment of the fuel injection device according to the invention before that the hydraulic delay element a first flow restrictor between pilot control room and control room, a second flow restrictor between pilot control room and a high-pressure connection, and a third flow throttle between pilot chamber and the switching valve comprises. In this way can the opening and closing behavior the valve element can be adjusted, allowing for optimal adaptation the fuel injection device to the requirements of the internal combustion engine thus ultimately optimizing emission behavior.

A directionality the delay effect is achieved by the first and second flow restrictors are close to each other.

there might in most cases a very cheap Result can be achieved when the throttling action of the first flow restrictor the strongest is, and when the throttle effect of the second flow restrictor is about the same that of the third flow restrictor is.

at two valve elements can one with the above-mentioned hydraulic delay element, a but otherwise be equipped with a mechanical delay element. This will make it possible the control rooms the individual valve elements to place relatively far away from each other, what the risk of mutual interference due to leaks reduced. Furthermore can by such a delay element, which is designed for example as a control rod, a whole certain deceleration behavior will be realized.

Advantageous is further, when the mechanical delay member is a control rod includes, for example, limits a control room that has at least a flow restrictor connected to the switching valve. Such a classic stroke control allows thanks to the flow restrictor a desired opening and closing behavior.

there it is particularly preferred if a high pressure port with a between the at least one flow restrictor and the switching valve lying area over connected to an inflow throttle is. In between the flow restrictor and Switching valve lying area can be a very open switch valve low pressure can be realized, which is a safe opening of the Valve element allows, through the inflow throttle too large flow losses be avoided from the high pressure connection ago.

Especially advantageous is that embodiment in which between switching valve and control chamber a throttle check valve and preferably for this purpose an additional flow restrictor are arranged serially. By such a check throttle valve can have a different characteristic when emptying and filling the Control space of the valve element can be realized, ultimately to a different opening and closing behavior can lead. By an additional serial flow restrictor can do the filling of the control room delayed a bit be too hard closing the Valve element to avoid. Furthermore thus becomes the necessary control chamber volume and thus the valve opening speed or a valve or control chamber pressure fluctuation minimized.

At the can be simplest two independent switching valves for the independent activity the valve elements are then housed when a switching valve for the inner valve element at an axial end portion of a housing and a switching valve for the outer valve element on the side of the housing are arranged. Alternatively, it is also conceivable that both Switching valves arranged side by side on an axial end portion of the housing and preferably encapsulated there. This allows a special slim design of fuel injector.

drawings

following become particularly preferred embodiments the present invention with reference to the accompanying Drawing closer explained.

there It should be noted at this point that in the description, the drawing and the claims mentioned features in very different Combinations for the invention may be essential without this being mentioned separately becomes. In the drawing show:

1 a perspective view of a first embodiment of a fuel injection device;

2 a partially sectioned and partially schematic representation of areas of the fuel injection device of 1 ; and

3 a perspective view of an alternative embodiment of a fuel injection device.

description the embodiments

In 1 a fuel injection device collectively bears the reference numeral 10 , Via a high pressure connection 12 For example, it can be connected to a high-pressure fuel tank 14 ("Rail") or an external booster can be connected. A return connection 16 connects the fuel injector 10 with a low pressure area 17 , For example, a fuel tank.

This in 1 lower end of the fuel injector 10 is with two axially spaced rows of fuel outlet openings 18 respectively. 20 Mistake. These can be released independently, allowing fuel through them into a combustion chamber 22 is injected. For this purpose are at the in 1 upper axial end two solenoid valves 24 and 26 provided, which in on 1 non-visible valve elements act. The solenoid valves 24 and 26 are at the top of the fuel injector 10 capsuled.

Further inside the fuel injection device 10 arranged functional elements will now be with reference to 2 explains: The fuel injector 10 includes a housing 28 with a central body 30 and a nozzle body 32 , In the case 28 are an outer valve element 34 and in this at least partially coaxially received inner valve element 36 arranged. The outer valve element 34 includes a sleeve-like nozzle needle 38 in the nozzle body 32 is arranged and with a sealing surface 40 with a housing-side valve seat (no reference numeral) in the region of the upper fuel outlet openings 18 cooperates.

That of the fuel outlets 18 opposite end of the nozzle needle 38 works with an outer sleeve-like coupler piston 42 together, a radially projecting annular collar 44 has, on which a spring 46 supported, in turn, with her from the ring collar 44 opposite end on the central body 30 supported. In this way, the coupler piston 42 and over this again the nozzle needle 38 acted upon in the closing direction. nozzle needle 38 and coupler pistons 42 in this case have the same diameter, but in principle also versions with different diameters are possible. This in 1 upper end of the coupler piston 42 forms an annular control surface 48 , which an annular disk-shaped control room 50 limited.

About a channel 52 is the control room 50 with a valve chamber 54 a throttle check valve 56 connected. This includes a valve body 58 that of a spring 60 is acted upon against a valve seat (without reference numeral). The valve body 58 is penetrated by a flow channel (without reference numeral), which is a flow restrictor 62 having.

From the valve seat to which the valve body 58 cooperates, extends an elongated pilot space 64 to the in 1 upper area of the central body 30 , The relation of the length of the pilot control room 64 opposite the entire fuel injection device 10 and its diameter / aspect ratio also goes out 1 in which the pilot control room 64 indicated by dashed lines. At its to throttle check valve 56 adjacent end is the pilot control room 64 via an inflow throttle 66 with a high pressure channel 68 connected, in turn, with the high pressure connection 12 connected is. From the throttle check valve 56 opposite end of the pilot control room 64 leads a discharge channel (without reference numeral) with a flow restrictor 70 to the designed as 2/2-way solenoid valve 26 , For the cross sections of the flow restrictors 62 . 66 and 70 applies: 62 < 66 ≈ 70 ,

The central or inner valve element 36 includes an inner nozzle needle 72 that with a sealing surface 74 in the area of the fuel outlet openings 20 with a housing-side sealing seat (no reference) cooperates. At her from the fuel outlets 20 opposite end works the inner nozzle needle 72 with an inner guide piston 76 together, in the outer coupler piston 42 is guided. Its in 2 the upper end cooperates again with an inner coupler piston 78 which has a radially extending annular collar 80 has, on which a spring 82 supported. Their from the ring collar 80 opposite end in turn is supported on the central body 30 which causes the inner coupler piston 78 , the inner guide piston 76 , and ultimately the inner nozzle needle 72 be acted upon in the closing direction.

In the 2 upper end face of the inner coupler piston 78 forms a control surface 84 that have a control room 86 limited. This is via a channel (without reference numeral) and an outflow throttle 88 with a valve chamber 90 a throttle check valve 92 connected. This includes, analogous to the throttle check valve 56 , a valve body 94 that of a spring 96 against one from the control room 86 facing away valve seat (without reference numeral) is acted upon. In the valve body 94 is a channel (not numbered) with a flow restrictor 97 available. From the valve seat extends a pilot control room 98 which, however, is one order of magnitude smaller than the pilot control room 64 , The pilot control room 98 is about an influx choke 100 with the high pressure channel 68 and thus with the high pressure connection 12 connected. There is also a connection from the pilot control room 98 to the solenoid valve 24 available, which is also designed as a 2/2-valve.

The in the 1 and 2 illustrated fuel injection device 10 works as follows: If no fuel is to be injected, both are solenoid valves 24 and 26 closed. At the high pressure connection 12 is the high pressure of the rail 14 at. This also prevails in the pilot control room 64 , the valve chamber 54 and the control room 50 as well as the pilot control room 98 , the valve chamber 90 , and the control room 86 this high fuel pressure. This causes the two valve elements 34 and 36 with their sealing surfaces 40 and 74 be pressed against the associated housing-side valve seats and no fuel from the fuel outlet openings 18 and 20 can escape.

When an injection through the fuel outlet 18 should be done, the solenoid valve 26 open. Thus, the pressure in the pilot chamber drops 64 , because fuel over the outflow throttle 70 to the low pressure area 17 can flow out. At the same time, fuel flows via the inflow throttle 66 in the pilot control room 64 to. It turns in the pilot control room 64 a stationary pressure level, which is due to the pressure at the high pressure port 12 and the ratio of the flow rate of the inflow throttle 66 and the outflow throttle 70 is determined.

Due to the large length / diameter ratio of the pilot control room 64 there will be a delay in the pressure reduction in the area of the closed throttle check valve 56 reached. As a result, the pressure in the control room reacts 50 delayed compared to the pressure in the pilot control room 64 , When in the opening direction on the outer valve element 34 attacking forces at the control surface 48 acting and by the spring 46 applied and acting in the closing direction forces exceed, lift the nozzle needle 38 with the sealing surface 40 from the housing-side valve seat. The opening speed is through the flow restrictor 62 limited. This reduces the volume of the control room 50 , The corresponding fuel volume is from the coupler piston 42 over the canal 52 , the valve room 54 and the flow restrictor 62 steamed in the pilot control room 64 pushed until the coupler piston 42 its stroke stop (the upper limit of the control room 50 ) reached.

To stop an injection, the solenoid valve 26 closed and so the outflow of fuel from the pilot chamber 64 completed. Due to the over the inflow throttle 66 nachströmenden fuel increases the pressure in the pilot chamber 64 , Now lift the valve body 58 from its housing-side valve seat, leaving fuel essentially unthrottled from the pilot chamber 64 over the valve space 54 and the channel 52 in the control room 50 can flow and there can lead to a corresponding pressure increase.

When the at the control surface 48 In closing direction acting forces reach a sufficient height, moves the coupler piston 42 together with the nozzle needle 38 again in the direction of the housing-side valve seat. The closing speed is determined by the inflow throttle 66 and the spring 46 certainly. If the sealing surface 40 the nozzle needle 38 rests again on the housing-side valve seat, adjusts pressure balance, ie, that in the control room 50 , in the valve room 54 , and in the pilot room 64 the same pressure, namely at the high pressure port 12 prevailing high fuel pressure, prevails.

As mentioned above, due to the elongated shape of the pilot control room 64 and the specific arrangement of the inflow throttle 66 to the outlet throttle 70 a pressure reduction in the pilot control room 64 only delayed to the valve chamber 54 and thus to the control room 50 forwarded. Therefore, pilot room 64 (together with the specific arrangement of inflow throttle 66 and outflow throttle 70 ) and throttle check valve 56 also as a delay element 71 designated. The delay effect is direction-dependent, because a pressure increase in the pilot control room 64 is through the then opened throttle check valve 56 very fast or directly to the control room 50 forwarded.

By the realization of the delay element 71 can very short opening or closing times on the valve element 34 are shown, although the solenoid valve 26 only switches relatively slowly. Or, in other words: the opening time of the valve element 34 is shorter than the opening time of the solenoid valve 26 , Due to the directionality, the valve element reacts 34 relatively earlier on the closing of the solenoid valve 26 as at its opening. This is favorable for the controllability of very small injection quantities or for the depictability of certain operating points of the internal combustion engine, and thus at least indirectly for the emission behavior of the internal combustion engine.

When fuel injection through the fuel outlet 20 The procedure is as follows: here, too, is the solenoid valve in the initial state 24 closed, so in the pilot control room 98 , in the valve room 90 and in the control room 86 the at the high pressure connection 12 high fuel pressure prevails. By the at the control surface 84 and because of the spring 82 in the closing direction acting forces is the nozzle del 72 with the sealing surface 74 pressed against the housing-side valve seat, so that fuel can not escape.

For an injection, the solenoid valve 24 open. Because the pilot room 98 with the solenoid valve 24 is connected directly, ie without the interposition of a throttle, the pressure drops in the pilot chamber 98 close to the level in the low pressure range 16 off (a certain amount of fuel flows over the inflow throttle 100 in the pilot control room 98 to). As the valve body 94 of the throttle check valve 92 abuts on its housing-side valve seat, fuel flows from the control room 86 only slowly over the outflow throttle 88 and in the valve body 94 existing flow restrictor 97 from. Since the throttle effect of the flow restrictor 97 stronger than the outflow throttle 88 , In this case, the outflow velocity through the flow restrictor 97 in the valve body 94 certainly.

The pressure in the control room 86 So slowly, until, analogously to the outer valve element decreases 34 , below the opening pressure of the valve element 36 , The coupler piston 78 , the guiding piston 76 and the nozzle needle 72 then move in 2 up, leaving the sealing surface 74 lifts off the associated valve seat and fuel via the fuel outlet openings 20 can escape.

To close the inner valve element 36 becomes the solenoid valve 24 closed. This fills the pilot control room 98 via the inflow throttle 100 , due to the small volume of the pilot control room 98 comparatively fast. Due to the pressure difference between pilot control room 98 and valve room 90 raises the valve body 94 of the throttle check valve 92 from the valve seat, so that the pressure in the valve chamber 90 and, over the outflow throttle 88 somewhat muffled, also the pressure in the control room 86 rises again.

Analogous to the valve element 34 closes the valve element 36 as soon as the pressure in the control room 86 and the resulting force acting in the closing direction on the control surface 84 exceeds a certain amount. The closing speed is determined by the inflow throttle 100 and the outflow throttle 88 certainly. The outflow throttle 88 Above all, it has the effect of pressure oscillations between the control room 86 , Valve room 90 and pilot room 98 prevent and the controllability of valve element 34 to improve.

Also for the control of the valve element 36 a delay element is provided, which does not, however, like the delay element 71 , hydraulically acting, but mechanically in the form of a control rod 102 of the coupler piston 78 , Like also out 1 is apparent, is also this control rod 102 comparatively long. Their cross-section, length and material show a specific elastic behavior. This causes that when the control surface 84 moved in the opening direction, first the control rod 102 lengthens and thus the sealing surface 74 only delayed by the associated housing-side valve seat lifts.

Will at this time the solenoid valve 24 closed again, the nozzle needle 72 with the sealing surface 74 pressed against the housing-side sealing seat, hardly that she has lifted. This can also be done on the valve element 36 a very short opening time can be realized despite slowly switching solenoid valve 24 , Due to the throttle check valve 92 can also, analogous to the valve element 34 , a directional opening or closing behavior can be realized.

To disturbing shear forces between the central body 30 and the coupler piston 42 and between the coupler piston 42 and the guide piston 76 to prevent which due to a geometric offset between the axes of the coupler piston 78 to the guide piston 76 could occur, the coupler piston 78 or its control rod 102 over a leadership alliance 104 relative to the guide piston 76 centered. Then, if necessary, between the central body 30 and coupler pistons 78 in the area of the control room 86 Trapping occurring transverse forces is the coupler piston 78 designed accordingly stiff.

An alternative embodiment of a fuel injection device 10 is in 3 shown. It applies to this figure that such elements and areas that have equivalent functions to elements and areas that already in connection with the 1 and 2 have been explained, bear the same reference numerals and are not explained again in detail. The main difference of in 3 shown fuel injector 10 to that of the 1 and 2 consists in the arrangement of the two solenoid valves 24 and 26 : at the in 3 shown fuel injector 10 is the solenoid valve 26 , with which the outer valve element 34 is actuated, laterally on the housing 28 attached, whereas the solenoid valve 24 , with which the inner valve element 36 is pressed, on in 3 upper axial end of the housing 28 is appropriate.

Claims (13)

Fuel injection device ( 10 ) for an internal combustion engine, with at least two coaxial valve elements ( 34 . 36 ) and with at least one switching valve ( 24 . 26 ) for the stroke control of the valve elements ( 34 . 36 ), characterized in that zwi the switching valve ( 26 ) and at least one valve element ( 34 ) a hydraulic delay element ( 71 ) is arranged. Fuel injection device ( 10 ) according to claim 1, characterized in that the hydraulic delay element ( 71 ) a pilot control room ( 64 ) whose length is a multiple of its diameter, the pilot space ( 64 ) at an end region with the switching valve ( 26 ) and at another end area with a high-pressure connection ( 12 ) and a control room ( 50 ) connected is. Fuel injection device ( 10 ) according to claim 2, characterized in that the hydraulic delay element ( 71 ) is designed so that it in the opening direction of the valve element ( 34 ) acts stronger than in the closing direction. Fuel injection device ( 10 ) according to claim 3, characterized in that the hydraulic delay element ( 71 ) a throttle check valve ( 56 ), which between pilot control room ( 64 ) and control room ( 50 ) and to the control room ( 50 ) opens. Fuel injection device ( 10 ) according to one of claims 2 to 4, characterized in that the hydraulic delay element ( 71 ) a first flow restrictor ( 62 ) between pilot control room ( 64 ) and control room ( 50 ), a second flow restrictor ( 66 ) between pilot control room ( 64 ) and a high-pressure connection ( 12 ), and a third flow restrictor ( 70 ) between pilot control room ( 64 ) and the switching valve ( 26 ). Fuel injection device ( 10 ) according to claim 5, characterized in that the first flow restrictor ( 62 ) and the second flow restrictor ( 66 ) are arranged close to each other. Fuel injection device ( 10 ) according to claim 5 or 6, characterized in that the throttling action of the first flow restrictor ( 62 ) is the strongest, and that the throttle effect of the second flow restrictor ( 66 ) is approximately equal to that of the third flow restrictor ( 70 ). Fuel injection device ( 10 ) according to one of the preceding claims, characterized in that it comprises at least one mechanical delay element ( 102 ). Fuel injection device ( 10 ) according to claim 8, characterized in that the mechanical delay element is a control rod ( 102 ). Fuel injection device ( 10 ) according to claim 9, characterized in that the control rod ( 102 ) or a part coupled to it, a control room ( 86 ), which via at least one flow restrictor ( 88 . 97 ) with the switching valve ( 24 ) and that a high pressure port ( 12 ) with one between the at least one flow restrictor ( 88 . 97 ) and the switching valve ( 24 ) area ( 98 ) via an inflow throttle ( 100 ) connected is. Fuel injection device ( 10 ) according to one of claims 9 or 10, characterized in that between switching valve ( 24 ) and control room ( 86 ) a throttle check valve ( 92 ) and preferably for this purpose an additional flow restrictor ( 88 ) are arranged. Fuel injection device ( 10 ) according to one of the preceding claims, characterized in that a switching valve ( 24 ) for the inner valve element ( 36 ) at an axial end portion of a housing ( 28 ) and a switching valve ( 26 ) for the outer valve element ( 34 ) on the side of the housing ( 28 ) are arranged. Fuel injection device ( 10 ) according to one of claims 1 to 11, characterized in that a switching valve ( 24 ) for the inner valve element ( 36 ) and a switching valve ( 26 ) for the outer valve element ( 34 ) preferably adjacent to each other at an axial end portion of the housing ( 28 ) are arranged.