DE10046829C2 - Control valve for injection injectors of internal combustion engines - Google Patents

Abstract

According to the invention, a control plunger (9) is provided for a control valve (8) of fuel injectors (1) for internal combustion engines. Said control plunger is provided with a support plunger (25), which is guided in an axially displaceable manner inside the control plunger (9), in order to achieve a pressure compensation in an opened and closed state and in both stroke directions. The support plunger forms a spool valve, which is located inside the connection of two channel ports, in order to configure the control valve (8) as a three/two-way directional control valve.

Description

The invention relates to a control valve for injection injectors of internal combustion engines, especially those with storage pressure spraying, operated with diesel or heavy oil Internal combustion engines, according to the preamble of claim 1.

Control valves for injection injectors are of diverse construction known forms, for example via EP 0 657 642 A2 in the function as a 3/2-way valve, the connection connections to the Pressure accumulator, assigned to the injector and to the return are and depending on the switch position the injector with the Pressure accumulator or the return as well, in a transition phase between these two switch positions, injector, pressure memory and return link. The injection nozzle needle Nozzle is exposed to the injection medium on the pressure side towards their opening position and through the return side loading impacted towards their closed position, and they opens when the connection between the print memory is switched cher and injector. When applied on the return side over the pressure given on the return side the one over Closing spring exerts pressure on the closing force exerted on the nozzle needle depending, and thereby the nozzle needle in its closing location as long as it is not by the when the Connection of the pressure accumulator to the injection nozzle, and thus off controlled connection to the return, through the pressure side loading impact against the closing force of the spring in the Seat lifted open position is pressed. The control valve is in this known solution with regard to the Druckangriffsflä Chen dimensioned so that it is open in both directions  and closed state, is pressure balanced, so that about the forces to be applied by the actuator only the the spool towards its the connection between Closing position blocking the pressure accumulator and the injector are overcome.

In terms of construction, the opening to the pressure chamber of the nozzle needle Channel from one of the receiving bore for the control piston ringing space on which along the control piston Open the fender, high-pressure and return-side ring channels which, depending on the stroke position of the control piston to cover and lock it over a ring collar are, with the return-side ring channel in one through channel formed from a central bore of the control piston cut continues. In connection with the desired printout the same applies to such a solution for the tax piston a relatively complex design.

Control valves for injection are also practical ejectors known, the control piston the through connection between two duct connections in the sense of a 2/2-way valve controls and with a view to pressure equalization in both strokes directions, in open and closed condition, with one Support piston is provided, which is in a koaxia to the control piston len mounting hole is located and supported against a stop against which the control piston is displaceable. In the The support piston forms part of the recesses one to the through connection of the channel connections closed room, so that the ruling in this room Pressure the control piston and the support piston into each other opposed directions and across the cross cutting surfaces of the support piston or the receiving bore Un differences in the pressure attack on the control piston side areas can be compensated.  

Analogous to EP 0 657 642 A2, US 5 311 850 also shows one pressure-controlled injection injector, in which the control valve acted upon by an actuator, the high-pressure side pressure memory connects to the pressure chamber of the nozzle needle and there by lifting the latter in its open position. Will the Pressure chamber above the control piston against the high pressure side locked, then another lock is activated via the control piston piston acted upon in its open position a Querver binding of the controlled part opening onto the pressure chamber les the high pressure side supply to the spring chamber of the Dü sennadel and releases them on the return. All in all this requires a rather complex construction.

Further stroke-controlled are known from JP 07 332 200 AA Injection injectors, the control valve of which is a 3/2-way valve a control piston works, which is supported by a fixed position pressure piston is balanced. The control piston and the Support pistons determine a sealing limit in the connection a pressure chamber on the back of the nozzle needle with the High pressure side is. The connection of the pressure chamber with the low pressure side return leads over a sealing limit between control piston and housing-side mounting hole, which in the Area of the sealing limit is extended to an annulus, from which runs out a return-side channel connection. The supporting col ben only has a function as an area compensation element with regard to the pressure compensation aimed for by the control valve ches as well as a slide-like, bearing as a sealing surface Locking element to that in its relative position to the control piston depending on the stroke, the connection to the back of the nozzle needle releasing or blocking the pressure space in question, being in the blocked position by the corresponding position of the spool on the back pressure chamber of the nozzle needle is connected to the return.

A functionally corresponding design of a control valve of an injection injector is known from DE 196 05 277 A1, in particular FIG. 5, and is taken into account in the preamble of claim 1. The control piston has a central receiving bore for a support piston, which widens into an annular space and starts from the channel connections to the high-pressure and return-side connection and to a control chamber which receives a control piston which acts on the back of the nozzle needle. The connection between the high-pressure side and the control chamber on the one hand and the control chamber and return on the other hand is controlled via the sealing limit assigned between the control piston and the support piston, the latter control position corresponding to a position of the control piston in which it closes the sealing limit between the high-pressure connection and the control chamber , when a circumferential sealing limit is released between the control piston and the housing, via which the connection from the control chamber to the return is released. Here too, the support piston has only one function with regard to the pressure-balanced design of the control piston and as a blocking element in the corresponding position of the control valve.

The invention is based, with a Steuererven the task til the type mentioned the constructive design to expand possibilities and thereby also the requirement for functional expansions with essentially unchanged To create space and manufacturing effort.

This is achieved by the features of claim 1, accordingly follow the support piston in the course of the duct guide is included, so that over the support piston in the Ü overflow cross sections lying on the control piston give. The use of the support piston for channel guides enables light simplifications in this regard on the control piston itself and are additional options in the placement of the over flow cross sections and in the arrangement of further channels le.  

In a further embodiment of the inventive concept, the Stroke mobility of the control piston in relation to the support piston with appropriate placement and dimensioning of the over flow cross sections also a stroke-dependent variability of these Cross sections, so that throttling effects without additional effort let it be realized.

Such design options are particularly advantageous in connection with tax designed as 3/2-way valves valves for additional influencing of the closing behavior the nozzle needle by pressurizing the nozzles on the back needle.

Further details and features of the invention emerge from the claims. Furthermore, the invention is set forth below hand of an embodiment with further details tert. Show it:

Fig. 1 is a schematic sectional view showing the basic structure of Einspritzinjektors according to the invention,

Fig. 2 is a highly schematic sectional view of a section of the injection injector in the control piston area of the control valve, this section being indicated by A in Fig. 1, and

Fig. 3 is a further enlarged, now of the cutout B in Fig. 2.

In the figures, with 1 the Einspritzinjektor referred to, which, as the schematic representation shown in FIG. 1, an injection nozzle 2 with a nozzle needle 3 has that the arrangement in the direction of ih re closed position over an opening provided in a spring chamber 4 Fe 5 is loaded wherein the nozzle needle 3, a pressure chamber 6 connects with the spring chamber 4 in the opposite direction, in which a spring assembly 5 in the direction of the closed position of the nozzle needle 3 burdensome Niederhaltekol ben 7 is disposed in pressurization.

The injection injector 1 further comprises a control valve 8 with a control piston 9 . On the control valve 8 , the connections to the high and low pressure side are controlled, the injection injector 1 being connected on the high pressure side to a high pressure accumulator, not shown, as is known for accumulator pressure systems, for example in the form of common rail systems.

The control valve 8 is controlled via a magnetic actuator 10 , a servo control valve 11 being interposed in the exemplary embodiment for power amplification, as can be used in particular when the required control forces cannot be made available via magnetic actuator 10 and / or which Switching operations are too slow. If such a servo control valve 11 is used, then a separate pressure supply is preferably assigned to it, which is not discussed in more detail here.

The supply valve connections assigned to the control valve 8 and controlled via the control piston 9 are identified by 12 to 14 and are illustrated in particular in FIG. 2, the channel connection 12 standing for the high-pressure side inlet and establishing the connection to the high-pressure accumulator. The connection 13 is in the connection to the injection nozzle 2 , the associated channel 15 , as shown schematically in Fig. 1, opens onto the pressure chamber 16 , so that the pressure needle ter 17 of the nozzle needle 3 the latter with appropriate pressurization in the opening direction which is increased, inter alia, by the spring force 5 applied by the spring arrangement.

The return flow takes place via the channel connection 14 , the associated return channel 18 opening out via a pressure holding valve 19 onto a storage tank (not shown) and being connected to the pressure chamber 6 via a spur line 20 . From the pressure chamber 6 is also a leading to the low-pressure side throttle channel 21 , the low-pressure side at least up to the pressure chamber 6 dependent on the inflow on the channel 14 and / or, as a combined throttle valve, a predetermined minimum pressure.

The spool 9 has concentrically to the piston axis 22 a extending from its end face 23 engaging hole 24 in which a support piston 25 is guided axially displaceably, which is supported against a housing-fixed, the receiving bore 24 überbrü-bridging support beams 26 which in turn fingers of support 27 of the Actuating piston 28 of the servo control valve 11 is reached, which are supported against the end face 23 of the control piston 9 . The support beam 26 lies in the transition between egg nem lower housing part 29 , which forms the receptacle for the control piston 9 , and an upper housing part 30 . The housing parts 29 , 30 are braced against each other over a flat surface.

The channel connection 12 in the control piston 9 is assigned a reduced-diameter annular space 31 , which is delimited against the valve chamber 32 assigned to the channel connection 13 via a sealing surface 33 of the control piston 9 , which, as a sealing edge with a corresponding valve seat on the housing, the sealing limit between the channel connections 12 and 13 forms which, when the control piston 9 is raised in the direction of the upper housing part 30 , releases the connection between the channel connections 12 and 13 and thereby supplies injection medium via the channel 15 to the pressure chamber 16 , so that the nozzle needle 3 against the force of the spring arrangement 5 in the opening direction is raised.

According to the stroke of the control piston 9 , there is an axial offset between the control piston 9 and the support piston 25 arranged in the receiving bore 24 , which is designed as a control slide and controls the connection between the valve chamber 32 and the return-side channel connection 14 . For this purpose, the support chamber 34 , which is delimited via the support piston 25 opposite the support beam 26 in the receiving bore 24 and is connected to the valve chamber 32 via a transverse channel 35 , is controllably connected to the return-side channel connection 14 , for which purpose the support piston 25 as a control slide is one in execution approximately example conical sealing surface 36 is assigned, which in the transition to the transverse channel 35 on the part of the receiving bore 24 a sealing surface 37 corresponds to the seat surface, so that when the control piston 9 in the direction of the seat surface 37 of the on receiving bore 24 retracted support piston 25, the Durchflussver bond between the Valve chamber 32 and the channel connection 14 is blocked. The support chamber 34 is connected with an open, formed by the sealing surfaces 36 and 37 sealing border via connecting channels 38 with an annular channel 39 which is arranged in the circumference of the support piston 25 and which is in the axial overlap area to radial, on the channel connections 14 connecting holes 40 ,

Relative to the stroke of the support piston 25 as a control slide ge compared to the control piston 9 can in the solution described, the opening cross-section 41 in the area of the sealing surface formed by the sealing surfaces 36 , 37 and the overlap cross-section 42 of the annular channel 39 to the connecting bores 40 both with regard to their maximum Size as well as the stroke-dependent cross-section vary, so that the connection from the valve chamber 32 to the return-side connection 14 can not only be throttled, but can also be controlled with respect to the degree of throttling, which means that the opening and closing behavior of the nozzle needle 3 when switching the Control valves 8 can be influenced, but in particular also influence on the opening and closing behavior of the nozzle needle 3 can be taken in the switching phase if both the connection between the connections 12 and 13 and between the connections 13 and 14's released is so that a short circuit condition is given.

It can be assumed here that when an injection of the control piston 9 is initiated, an increasingly larger flow cross-section is released via the sealing edge 33 , so that the pressure in the channel 13 or 15 increases rapidly. The flow connection to the low-pressure side connection 14 is also still open, but via the pressure holding valve 19 and the Drosselka channel 21 it is ensured that the hold-down piston 7 is pressurized accordingly and thus, in addition to the arrangement 5 , the nozzle needle 3 still holds in its closed position. This also applies to other operating conditions with corresponding pressurization of the hold-down piston 7 , even if the function of the quantity-limiting valve mentioned below has not yet been activated, that is to say it has not yet shut off, but instead only assumes a reversible intermediate position upstream of the shut-off position.

With a further stroke of the control piston 9 , the flow cross-section between the channel connections 12 and 13 increases , but at the same time the connection between the channel connections 13 and 14 is increasingly controlled by the support piston 25 acting as a control slide. The return-side pressure drops accordingly and the closing force-pressure component applied via the hold-down piston 7 decreases. Since the pressure in the duct 15 rises at the same time, the nozzle needle 3 can lift off and the injection can begin.

This point in time (start of injection) is selected and the corresponding cross-sections are coordinated such that if the control piston 9 remains in a corresponding stroke position due to a malfunction, or in an intermediate stroke position that goes beyond it, and the consequent continuous injection, the fuel quantity flowing through, preferably, finally, the portion still flowing out via the return flow is greater than the amount of fuel that would result from the functionally timed injection of the maximum permissible injection amount, so that a flow control valve (not shown), which is located on the high-pressure side inlet, would respond and shut off the high-pressure side inlet. A particularly sensitive control is possible by taking into account the portion flowing off via the return.

At the end of the injection, the control piston 9 is spring loaded, indicated in Fig. 2 by the spring 43 , and by the pressure applied by the servo control valve 11 again in the direction of its starting position shown in the drawings, in which the connection between the channel connections 12 and 13 is driven off via the sealing surface 33 . This also moves the support piston 25 relative to the control piston 9 , so that the hold-down piston 7 is acted upon by the pressure build-up in the pressure chamber 6 and superimposed on the force of the spring arrangement 5, the nozzle needle 3 is loaded in the closing direction, thus controlling the injection.

In the invention, the support piston 25 used as a control slide to compensate for differently sized pressurized surfaces of the control piston and the resulting actuating forces, so that pressure balance is achieved via the support piston 25 not only in both stroke directions, in the open and in the closed position , but at the same time additional control functions are performed, which leads to a simplified overall construction.

Claims (8)

1. Control valve for injection injectors of Brennkraftmaschi NEN, in particular of working with storage pressure injection, operated with diesel or heavy oil internal combustion engines, comprising a displaceable control piston in a housing bore, a coaxial in the control piston receptacle, a positionally fixed to the housing, in the receiving bore orderly support piston and housing-side channel connections and channel guides running over the control piston in the connections of the channel connections, in which sealing surfaces formed by sealing surfaces between the receiving bore and the control piston and flowable in the direction of the supporting piston between the control piston and the supporting piston formed sealing limits, which are opened and closed depending on the stroke position of the control piston, characterized in that one of the channel guides (guide channels 38 ) is connected downstream to the sealing limit (sealing surfaces 36 , 37 ) z wipe control piston (9) and the support piston (25) piston (25) to the supporting piston (25) and between the support and extends the control piston (9) lying overflow cross. 2. Control valve according to claim 1, characterized in that the support piston ( 25 ) in the sealing limit (sealing surfaces 36 , 37 ) to the control piston ( 9 ) associated sealing surface ( 37 ) of the control piston ( 9 ) by a seat in the receiving bore ( 24 ) is formed. 3. Control valve according to claim 2, characterized in that the receiving bore ( 24 ) in the area on the seat as Dichtflä surface ( 37 ) for the support piston ( 25 ) tapering area is expanded to a support chamber ( 34 ). 4. Control valve according to one of the preceding claims, characterized in that in the transition between the support piston ( 25 ) and control piston ( 9 ) lying in axial overlap, the support piston ben ( 25 ) and the control piston ( 9 ) assigned overflow cross sections of the channel guide ( Channels 38 ) one of the stroke of the control piston ( 9 ) relative to the support piston ( 25 ) depending on the variable cross-section ( 42 ) determine as a throttle cross-section. 5. Control valve according to claim 4, characterized in that the stroke-dependent variable throttle cross-section lies axially spaced from the support chamber ( 34 ) widening the receiving bore. 6. Control valve according to claim 4 or 5, characterized in that in the direction of the support piston ( 25 ) overflowable sealing boundary (sealing surfaces 36 , 37 ) between the receiving bore ( 24 ) expanding support chamber ( 34 ) and the nozzle for injection ( 2nd ) of the injection injector ( 1 ) leading duct connection ( 13 ) and that the duct connection ( 14 ) which can be flowed in via the duct guide (ducts 38 ) downstream of the sealing boundary (sealing surfaces 36 , 37 ) forms a return connection. 7. Control valve according to claim 6, characterized in that the leading to the injection nozzle ( 2 ) channel connection ( 13 ) over a sealing surface ( 33 ) of the control piston ( 9 ) comprehensive sealing boundary between the control piston ( 9 ) and housing (housing part 29 ) is formed , 8. Control valve according to claim 6 or 7, characterized in that the return-side channel connection ( 14 ) is connected to a pressure chamber ( 6 ) which is assigned to the rear of the nozzle needle ( 3 ) of the injection nozzle ( 2 ), such that that in the pressure chamber ( 6 ) pending pressure loads the nozzle needle ( 3 ) in the closing direction.