DE19623211A1 - Fuel injection valve for internal combustion engines - Google Patents

Abstract

The valve has a valve element 11, which is guided axially in a bore 9 of a valve body 1. The combustion chamber end of the valve element 11 has at least two injection openings (25, fig.2) which lie one above the other in an axial direction of the valve element 11 and are connected by inlet channels to a pressure chamber formed between the valve element 11 and the bore 9. In the course of the outwardly directed opening stroke of the valve element 11 the injection openings (25) are successively uncovered by the wall of the bore 9. The stop 37 which delimits the maximum opening stroke of the valve element 11 is provided on a hydraulically displaceable piston 39. One face of the piston 39 forms the stop 37 while the other face delimits a hydraulic working chamber 43.

Description

State of the art

The invention relates to a fuel injection valve for Internal combustion engines according to the preamble of claim 1 out. Such a known from DE-OS 43 40 883 A1 Fuel injection valve has a valve body with a axial bore in which a piston-shaped valve member is led to control an injection cross section by the high fuel pressure against the force of one Closing spring can be moved outwards. The valve member has one at the end of the combustion chamber Bore of the valve body protruding closing head, the one Forms valve closing member and the valve body thereof facing a valve sealing surface is arranged with the closing head with one on the combustion chamber side End face of the valve body arranged valve seat surface cooperates. There is still at least one Injection opening on the valve member at the level of the closing head provided by a between the valve member and the Bore formed pressure chamber. The exit opening the injection opening is in the closed position of the Valve member covered by the valve body and is only in Course of the outward opening stroke of the Valve member released by dipping out of the hole.  

With its end facing away from the closing head and away from the combustion chamber the valve member protrudes into a spring chamber which is axially aligned is formed with the valve body clamped holding body. The valve member points to its distant combustion chamber Shaft a spring plate between, and one on Valve body attached to the housing-fixed stop Closing spring is clamped.

The fuel injection takes place at the beginning of the High pressure fuel supply in the pressure chamber of the Injector, the high pressure fuel that Valve member acted in the opening direction and counter the restoring force of the closing spring from the valve seat stands out on the outside. After a short Opening stroke of the valve member the injection opening turned on so that the fuel in the combustion chamber too supplying internal combustion engine is injected. The maximum opening stroke movement of the valve member is thereby by creating a shoulder on the valve member limited to a housing-fixed stop, over the protrusion the maximum opening stroke can be set.

For optimal fuel injection, known fuel injection valve several, preferably two lying one above the other in the axial direction of the valve member Injection orifices may be provided during the after outward opening stroke of the valve member are controllable one after the other. It is special advantageous, in certain operating conditions only the lower one Open row of injection ports so that only 50% of the opening cross-section for fuel injection be used, which in the partial load range Internal combustion engine with the same injection quantity  Injection duration can be extended.

Such a partial However, the injection cross section can be controlled due to the fixed stroke stop of the valve member only inadequate and difficult to reproduce on reach known injection valve. It is special disadvantageous that the stroke stop in the known Injector is not accessible from the outside without it Disassemble the injector.

From DE-OS 43 32 124 is a fuel injection valve the outward opening type is known, in which the maximum opening stroke of the valve member by a variable Opening stroke stop is controllable, this adjustable The stroke stop is very expensive to construct by one Piezo actuator is formed. Such piezo actuators are included in addition to the high manufacturing and assembly costs Disadvantage that they have a large space and a relative need complex power supply and control. In addition Piezo actuators are very sensitive to heat, so that they are only through the heat-stressed fuel injectors additional thermal expansion compensation devices too are what the effort and therefore the costs such stroke stops increased again.

Advantages of the invention

The fuel injector according to the invention for Internal combustion engines with the characteristic features of the Claim 1 has the advantage that with structurally simple means an adjustable stop for the maximum opening stroke of the valve member is formed, which also the hard striking of the valve member on  Stroke stop dampens. The adjustable stop is as hydraulically displaceable piston formed, one of which End face that cooperating with the valve member Stroke stop surface forms and the other end face one Working space limited. This work space is over one Pressure line can be filled with a hydraulic fluid and relieved, preferably by the fuel of the Internal combustion engine is formed. The pressure in the work space is relatively low (about 5-10 bar), but is sufficient out to the piston with its stroke stop surface at one to hold the upper stop. This upper stop has one certain distance from the stop surface on the valve member in Closed position, this distance a first Opening stroke of the valve member defined, the Immerse the lower row of spray holes on the combustion chamber side corresponds to the bore of the valve body at which preferably 50% of the total injection cross section are released. The degree of open Injection cross section at half valve link stroke can thereby by the number of injection openings one Spray hole row vary.

It is simple by controlling the Pressure line possible, the opening stroke in the amount of this limit the first upper stop, which is in The volume enclosed in the work area acts as an oil pressure spring works. So that the necessary oil pressure, the Holds the valve member in the partial stroke, even after a small one Compression stroke of the piston is a small one Total volume of the work area and in the pressure line necessary. Therefore, the piston is preferably as Stepped piston formed by the work area with its  Ring face limited. The pressure line is up to Control valve preferably as short as possible and with little Cross section formed.

Should the total opening stroke of the valve member be passed through, the pressure line remains open, so that compared to the working pressure of the one acting on the piston Pressure means much larger opening forces on Valve member this together with the piston to one move the lower stop. This preferably through the formed the piston facing away from the working space lower stop corresponds to one Valve link opening stroke position, in which the second upper Row of spray holes from the bore of the valve body is dipped, so that now 100% of the Opening cross-section on the injection valve are controlled. The operating point at which 50% or 100% of the Injection cross-section are controlled by appropriate control of the control valve in the Pressure line in the engine characteristic map freely selectable, whereby Control valve preferably as a 2/2-way solenoid valve is trained. The control of the valve member stroke stop is independent of the injection pressure, the load or the Speed possible. A single control valve can be used for all injectors are used, however it is also possible, each injector has its own control valve assign.

The working pressure of the hydraulic fluid can by a separate pump can be built, but it is also possible the feed pressure at the fuel injection pump to use. With the hydraulic stroke stop actuated for 50%  The control valve becomes the opening stroke or injection cross-section controlled between the injection cycles so that the The oil volume in the work area is completely replenished, to compensate for leakage losses and maintain a constant To ensure stroke stop.

The fuel injection valve according to the invention can in a pump-line-nozzle-injection system can be integrated into it but it is also possible with memory injection systems (Common rail) to use, which has the advantage of a free Injection selection in the entire map of the internal combustion engine exhibit.

The use of the hydraulically adjustable stroke stop also has the advantage of cushioned striking the Valve member at the stop, what the component stress decreased.

The fuel injector according to the invention with the adjustable stroke stop has the advantages that the installation space compared to conventional injectors not enlarged so that it is at existing Internal combustion engines can be retrofitted.

Further advantages and advantageous configurations of the The invention relates to the description of Drawing and the claims can be removed.

drawing

Two embodiments of the invention Fuel injection valves for internal combustion engines are in  of the drawing and are shown in the following Description explained in more detail.

They show: Fig. 1 is a longitudinal section through a first embodiment of the fuel injection valve which is installed in a pump-line-nozzle injection system, Fig. 2 shows an enlarged detail of FIG. 1 along the line II in the area of the injection openings Fig. 3 is a schematic representation of the control of the hydraulic flow into the working space on the stroke stop piston and Fig. 4 to 4B, a second embodiment in which the fuel injection valve is integrated in a memory injection system.

Description of the embodiments

The first exemplary embodiment of the fuel injection valve according to the invention shown in a longitudinal section in FIG. 1 has a valve body 1 which projects with its lower free end into the combustion chamber of the internal combustion engine to be supplied and which axially counteracts with its upper end surface 3 remote from the combustion chamber by means of a clamping nut 5 a valve holding body 7 is clamped. The valve body 1 has an axial through bore 9 , in which a piston-shaped valve member 11 is axially displaceably guided. The valve member 11 has at its lower end on the combustion chamber side a closing head 13 protruding from the bore 9 and forming a valve closing member, which, as shown enlarged in FIG. 2, has a valve sealing surface 15 on its side facing the valve body 1 , with which it engages with a on the combustion chamber end face of the valve body 1 arranged valve seat surface 17 cooperates. The resulting cross-section of a sealing valve sealing surface 15 and valve seat 17 are formed preferably conical, with the cone angles of the two contact surfaces 15, 17 slightly different from each other, so that a defined sealing edge is formed. Between the valve member 11 and the wall of the bore 9 , an annular pressure chamber 19 is formed, which is delimited on the combustion chamber side by an annular shoulder 21 of a piston slide 22 formed by a diameter expansion of the valve member 11 , which merges into the closing head 13 . In this case, 21 injection ports 23 of the annular shoulder from lead, which are formed initially as a longitudinal bore 23 A, of which then 13 dissipate transverse bores 23 B in the amount of the closing head. The outlet openings 25 of the injection openings 23 on the wall of the valve member 11 are arranged in such a way that they are covered by the bore wall 9 of the valve body 1 in the closed position of the valve member 11 and opened only when the valve member 11 is directed outward from the bore 9 by being pushed out will. In addition, two rows of rows of spray holes arranged one above the other in the axial direction of the valve member 11 are preferably provided, which can be opened one after the other.

For the supply of the fuel under high pressure, an injection line 27 , which penetrates axially through the valve holding body 7 and the valve body 1, opens into the pressure chamber 19 , which on the other hand is connected to a high-pressure fuel pump in a manner not shown in the first exemplary embodiment.

The valve member 11 protrudes with its shaft facing away from the combustion chamber into a spring chamber 29 which is provided in the preferably two-part holding body 7 and in which a closing spring 31 which is fixedly supported with respect to the housing is arranged and which engages in the closing direction on the valve member 11 via a spring plate 33 fastened to the valve member and engages with the latter presses its valve sealing surface 15 against the valve seat 17 .

To limit the outward opening stroke movement of the valve member 11 , an annular shoulder 35 in the form of an annular web is further provided on the valve member shaft 11 , the combustion chamber-facing annular surface of which forms a stop surface which interacts with an adjustable stroke stop surface 37 . This stroke stop surface 37 is advantageously formed by the end surface of a hydraulically displaceable piston 39 facing away from the combustion chamber. This piston 39, which is designed as a stepped piston in the exemplary embodiment, is guided axially displaceably on the valve member 11 and, with its annular end face 41 facing away from the stroke stop face 37, delimits a hydraulic working space 43 at the diameter transition. At its end opposite the annular end face 41 of the piston 39 , the working space 43 is delimited by the wall of a bore shoulder 45 , which at the same time limits the maximum opening stroke of the valve member 11 . The fits between the lateral surfaces of the piston 39 and the wall of the bore leading this are designed so that the leakage flow is reduced to a minimum with good sliding ability. In its initial position, the piston 39 rests with its stroke stop surface 37 on a fixed shoulder, which in the exemplary embodiment is formed by an intermediate plate 47 clamped between the two parts of the valve holding body 7 , the axial extent of which extends the dimension of the first stroke stage of the valve member 11 to System on piston 39 can be adjusted.

The hydraulic stroke stop piston 39 is controlled by filling and relieving the work space 43 , for which purpose a pressure line 49 opens into the work space 43 , which, as shown in FIG. 3, is connected to a feed pump 50 which supplies the pressure medium from a pressure medium reservoir, preferably promotes the fuel tank 51 . The pressure line 49 can be opened or closed by a control valve designed as a 2/2 way solenoid valve, a common control valve 53 being provided for all the injection valves in the exemplary embodiment described
The first exemplary embodiment of the fuel injection valve according to the invention shown in FIG. 1 operates in the following manner.

In the closed position of the injection valve, the closing spring 31 holds the valve member 11 with its valve sealing surface 15 in contact with the valve seat 17 , the outlet openings 25 of the injection openings 23 are closed and the hydraulically adjustable stroke stop piston 39 is in contact with the stroke chamber 37 due to the pressure in the working space 43 Intermediate disc 47 moved.

At the start of the injection, the fuel under high pressure, which is periodically delivered by a high-pressure fuel pump, reaches the pressure chamber 19 via the injection line 27 , where it acts on the valve member 11 on the annular shoulder 21 in the opening direction. When a certain injection pressure in the pressure chamber 19 is reached , the pressure force of the fuel acting on the valve member 11 in the opening direction exceeds the restoring force of the closing spring 31 and the valve member 11 lifts outward from the valve seat 17 . After a short idle stroke of the valve member 11 in the opening direction, the outlet openings 25 of the lower row of spray holes near the combustion chamber are released, so that the fuel reaches the combustion chamber unthrottled for injection. After passing through this first opening stroke phase h1, which corresponds to the opening of the lower row of spray holes, the valve member 11 comes into contact with the ring shoulder 35 on the stroke stop surface 37 on the piston 39 . A further valve member opening stroke movement can now only take place by also displacing the piston 39 . If the upper row of spray holes is also to be opened, the pressure line 49 is opened by the control valve 53 , so that the high pressure forces acting on the valve member 11 move the valve member 11 and the piston 39 further until the piston 39 with its annular end face 41 in contact with the Hole paragraph 45 arrives. This second stroke h2 corresponds to the complete opening of the upper row of outlet openings 25 of the injection openings 23 from the contact of the valve member shoulder 35 on the piston 39 to its contact with the shoulder 45 .

If only a part (preferably 50%) of the injection cross section is to be opened at the injection valve, the pressure line 49 is closed by the electrically operated control valve 53 , so that the pressure medium in the working space 43 cannot be displaced. As a result, the enclosed volume acts like an oil spring and blocks the valve member 11 via the piston 39 in an intermediate position in which only the lower row of the outlet openings 25 of the injection openings 23 is opened.

The end of the injection is initiated by the termination of the high-pressure fuel supply to the high-pressure pump, as a result of which the pressure in the pressure chamber 19 drops again below the injection pressure and the closing spring 31 again moves the valve member 11 into contact with the valve seat 17 . It is ensured by the one-sided contact of the piston 39 on the valve member 11 that the closing stroke movement of the valve member 11 takes place quickly and is not delayed by a possible negative pressure in the working space 43 . The time between two injections is sufficient to completely fill the working space 43 with fuel.

The second exemplary embodiment of the fuel injection valve according to the invention shown in FIGS. 4, 4a and 4B differs from the first exemplary embodiment in the type of injection system, which is now designed as a storage injection system (common rail).

In the second exemplary embodiment, the pressure chamber 19 is constantly supplied with high pressure from a high-pressure fuel reservoir 61 via the injection line 27 , from which all the injection lines of the individual injection valves lead away. Furthermore, a control line 63 leading away from the injection line 27 is provided, which is connected to a resetting space 65 on the valve member 11 via an annular gap between the piston 39 and the valve member 11 . This resetting space 65 is delimited by the annular end face of a sleeve 67 , which on the other hand is supported on the ring shoulder 35 of the valve member 11 formed here by a snap ring, so that the high pressure in the resetting space 65 acts on the valve member 11 in the closing direction and blocks it hydraulically. In addition, a relief line 69 branches off from the control line 63 into a relief space, not shown, via which the reset space 65 can be relieved. To control the pressure relief of the reset space 65 , a control valve 71 is inserted into the relief line 69 , which is preferably designed as an electrically controlled 2/2 way valve. Furthermore, throttle points 73 are provided in the branch lines of the control line 63 to the injection line 27 and to the relief line 69 .

The hydraulic control of the stroke stop piston 39 takes place as in the first exemplary embodiment, the confluence of the pressure line 49 into the working space 43 being shown in sectional views in FIGS . 4A and 4B. The second embodiment shown in Fig. 4 operates in the following manner.

In the closed state of the injection valve, the control valve 71 in the relief line 69, as shown in FIG. 4, is switched so that the drain is closed in the low-pressure chamber. As a result, the restoring space 65 acting on the valve member 11 in the closing direction is filled with the high-pressure fuel of the high-pressure accumulator 61 and, together with the closing spring 31 , holds the valve member 11 in contact with the valve seat 17 against the opening pressure force present in the pressure chamber 19 .

The injection at the injection valve is carried out by switching the control valve 71 to passage, so that the high pressure in the reset space 65 can now relax via the control line 63 and the relief line 69 in the low-pressure space, not shown, for example the fuel tank. As a result of the pressure drop in the reset chamber 65 , the closing force on the valve member 11 drops below the opening pressure acting in the pressure chamber 19 on the valve member 11 in the opening direction, and the valve member 11 is displaced outward from the valve seat 17 , so that the injection openings 23 are released analogously to FIG. 2 . The course of the opening stroke movement of the valve member 11 can be adjusted via the throttle 73 in the relief line 69 .

As in the first exemplary embodiment, the maximum opening stroke of the valve member 11 can be set by hydraulically blocking or relieving the work space 43 , the control of the work space 43 taking place analogously to the first exemplary embodiment via the control valve 53 in the pressure line 49 . In the second exemplary embodiment, two stroke stop positions can also be set for the valve member 11 , of which only the lower spray hole row (50% injection cross-section) is opened in a first stop position, while in the second stop position all spray hole rows are swapped out of the overlap with the valve body 1 ( 100% injection cross section).

The high-pressure injection at the injection valve is initiated by the renewed switching of the control valve 71 in the relief line 69 , with the closing of the relief line 69 again creating a high pressure in the reset space 65 , which together with the force of the closing spring 31, the valve member 11 with its valve sealing surface 15 moved back into contact with valve seat 17 .

The second exemplary embodiment described in FIG. 4 has the advantage of a completely free choice of injection timing, duration and quantity in the map of the internal combustion engine to be supplied with a variable injection cross section at the injection valve.

Claims (14)

1.Fuel injection valve for internal combustion engines with a valve member ( 11 ) guided axially displaceably in a bore ( 9 ) of a valve body ( 1 ), at the combustion chamber-side end of which at least two injection openings ( 23 ) lying one above the other in the axial direction of the valve member ( 11 ) are provided Inlet channels are connected to a pressure chamber ( 19 ) formed between the valve member ( 11 ) and the bore ( 9 ) and whose outlet openings ( 25 ) are covered by the wall of the bore ( 9 ) in the closed position of the valve member ( 11 ) and when directed outwards Opening stroke of the valve member ( 11 ) are released one after the other into the combustion chamber of the internal combustion engine and with a stop limiting the maximum opening stroke of the valve member ( 11 ), characterized in that the stop limiting the maximum opening stroke of the valve member ( 11 ) is adjustable and on a displaceable piston ( 39 ) is provided, one e end face forms a stroke stop face ( 37 ) for the valve member ( 11 ) and its other end face ( 41 ) facing away from the stroke stop face ( 37 ) is designed as a pressure face which delimits a controllable hydraulic working space ( 43 ). 2. Fuel injection valve according to claim 1, characterized in that the piston ( 39 ) is arranged coaxially to the valve member ( 11 ), preferably axially on this sliding. 3. Fuel injection valve according to claim 1, characterized in that the piston ( 39 ) is designed as a stepped piston, the larger end face of which the stroke stop face ( 37 ) and the annular end face ( 41 ) formed at the cross-sectional transition form the pressure area ( 41 ) delimiting the working space ( 43 ) , The piston ( 39 ) with its peripheral surfaces sealingly slides in a guide bore in the housing. 4. Fuel injection valve according to claim 1, characterized in that an annular web ( 35 ) is provided on the stem of the valve member ( 11 ), the combustion chamber-facing annular end face forms a stop surface with which the valve member ( 11 ) with the stroke stop surface ( 37 ) on the piston ( 39 ) interacts. 5. Fuel injection valve according to claim 1, characterized in that a stationary upper stop ( 47 ) is provided, on which the piston ( 39 ) bears in the starting position with its stroke stop surface ( 37 ) and via its design the opening stroke of the valve member ( 11 ) up to whose system on the stroke stop surface ( 37 ) of the piston ( 39 ) is adjustable and that a stationary lower stop ( 45 ) is provided which limits the maximum possible stroke of the piston ( 39 ). 6. Fuel injection valve according to claim 1, characterized in that the working space ( 43 ) by means of a pressure line ( 49 ) with a hydraulic pressure medium, preferably fuel can be filled and relieved, the pressure line ( 49 ) being connected to a pressure medium reservoir ( 51 ) and by means of a Control valve ( 53 ) can be closed. 7. Fuel injection valve according to claim 6, characterized in that the control valve ( 53 ) is designed as a 2/2-way valve. 8. Fuel injection valve according to claim 1, characterized in that a plurality of outlet openings ( 25 ) of the injection openings ( 23 ) are provided in a common radial plane of the valve member ( 11 ), each of which form one of preferably two axially superimposed rows of spray holes, each being controlled Spray hole row is assigned a defined stroke stop position of the piston ( 39 ). 9. Fuel injection valve according to claim 1, characterized in that the valve member ( 11 ) at its combustion chamber end has a sealingly guided in the bore ( 9 ) piston spool ( 22 ) with the combustion chamber facing away from the annular face ( 21 ), the pressure chamber ( 19 ) in the Bore ( 9 ) is limited, the inlet channels of the injection openings ( 23 ) being designed as axial blind bores in the piston slide valve ( 22 ) starting from the annular end face ( 21 ), from which radial bores lead to the lateral surface thereof and which open out at the outlet openings ( 25 ). 10. Fuel injection valve according to claim 9, characterized in that a combustion valve-side a projecting from the bore ( 9 ), a valve closing member forming the closing head ( 13 ) connects to the piston valve ( 22 ) which on its side facing the valve body ( 1 ) has a valve sealing surface ( 15 ) with which it interacts with a valve seat surface ( 17 ) arranged on the combustion chamber end face of the valve body ( 1 ). 11. Fuel injection valve according to claim 1, characterized in that the pressure chamber ( 19 ) in the valve body ( 1 ) via an injection line ( 27 ) with a high-pressure fuel reservoir ( 61 ) is connected. 12. A fuel injection valve according to claim 11, characterized in that a resetting space ( 65 ) is provided which acts on the valve member ( 11 ) at least indirectly in the closing direction and can be filled and relieved of high pressure fuel via a control line ( 63 ) leading away from the injection line ( 27 ), wherein a relief line ( 69 ) leads away from the control line ( 63 ) and can be opened or closed by means of a control valve ( 71 ). 13. Fuel injection valve according to claim 12, characterized in that the control valve ( 71 ) is designed as a 2/2 way valve. 14. Fuel injection valve according to claim 12, characterized in that the control line ( 63 ) each has a throttle point ( 73 ) in your connection to the injection line ( 27 ) and to the relief line ( 69 ).