EP2347115B1 - Injector for injecting high-pressure fuel into the combustion chamber of an internal combustion engine - Google Patents

Description

State of the art

In injectors for injecting high-pressure fuel into a combustion chamber of an internal combustion engine, as are known from the field of storage injection systems, the control of the injection process in dependence on the position of a control valve, which is associated with a control chamber of a valve spool. The control chamber is in this case connected via an inlet bore in terms of flow with a high-pressure line via which the injector is supplied with the high-pressure fuel. For pressure relief, the control chamber of the valve spool is connected via a drain hole with a pressure compensation chamber, wherein the drain hole is closed by the pressure-compensating control valve. With an opening of the control valve, the high-pressure fuel flows through the drain hole from the control chamber into the pressure compensation chamber of the injector, whereby the valve spool is released. The release of the valve control piston opens a nozzle needle valve, via which the fuel is injected into the combustion chamber of the internal combustion engine. The dynamic opening and closing behavior of the nozzle needle valve, which is dependent on the change in the control volume in the control chamber of the valve spool, can be determined by the design of an inlet throttle provided in the inlet bore and an outlet bore provided in the drain hole.

When opening the control valve, the high-pressure fuel from the control chamber flows at a high flow rate through the drain hole in the direction of the pressure equalization chamber of the injector, resulting in a reduction of the cross section in the region of the drain hole and the drain throttle local changes in fuel pressure. Since in storage injection systems of the fuel with a pressure of about 100 MPa or 1000 bar is applied, it may come due to the highly dynamic fluid movement to a local pressure drop, which leads to the local formation of vapor bubbles. In the adjoining the cross-sectional reduction Überden Overpressure phases implode these vapor bubbles, which is also called cavitation. With an implosion of the vapor bubbles in the region of the control valve, the resulting high local energy density over time leads to a hollowing on the surface of the delimiting wall and thus to an undesired removal of material and wear on the valve seat of the control valve. As a result of the occurrence of cavitation erosion, the surface on the valve seat and in the seating area of the valve body is thus damaged, which can result in a leakage of the control valve and thus an injector malfunction.

Out DE 198 59 592 C1 For example, a high pressure injection fuel injection valve is known from a central high pressure accumulator used in internal combustion engines. The high-pressure accumulator is connected via an inlet throttle bore with a control chamber in operative connection and controls an opening and closing of an injection nozzle. In this case, the control chamber communicates via an outlet throttle bore with a switching valve. The inlet throttle bore is also eccentrically aligned with respect to the control chamber.

Disclosure of the invention

The invention is therefore based on the object to provide an injector for the injection of high-pressure fuel into the combustion chamber of an internal combustion engine, in which caused by Kavitationserosion damage to the valve seat of a pressure-compensating control valve, which closes the drain hole of a control chamber is avoided.

According to the invention, the injector for injecting high-pressure fuel into the combustion chamber of an internal combustion engine comprises an at least approximately rotationally symmetrical control chamber to which a valve control piston is assigned. The control chamber is connected via an inlet bore hydraulically connected to the high pressure side of an injection system. The inlet bore comprises an inlet throttle, which limits the flow of high-pressure fuel into the control chamber. The control chamber is further connected via a drain hole with a low pressure side of the injector, wherein the drain hole is closed by a control valve. For injecting high-pressure fuel into the combustion chamber of the internal combustion engine, the control valve can be opened, wherein the high-pressure fuel from the control chamber via the drain hole and one in the drain hole provided drain throttle flows and as a result, the valve spool is released to open an injector.

According to the invention, the high-pressure fuel is introduced eccentrically via the inlet bore into the control chamber, so that the inflowing fuel generates a swirl flow within the control chamber, which has a rotational and a translational component. The rotating within the control chamber flow has an axis of rotation which is coaxial with the axis of the drain hole.

The rotating fuel flow, which is generated by the off-center supply of high-pressure fuel into the control chamber, continues in the form of a swirl into the drain hole. Due to the swirl and the resulting flow creates a vortex filament, which extends along the axis of rotation of the rotating flow and in the vortex core forms a Totwassergebiet. The Totwassergebiet is no longer available to transport the fuel, so that the fuel can flow only on the walls of the control chamber and the drain hole along. The vapor bubbles that result in an open control valve due to the high flow rate of the fuel and the change in fuel pressure in the region of the drain hole are in the center of the rotating flow, d. H. pushed into the vortex core, where the implosion of the vapor bubbles takes place. In this way it is prevented that the vapor bubbles implode in the vicinity of the wall limiting the drain hole or in the region of the valve seat of the control valve, so that material removal and thus damage by cavitation is avoided. By using the principle underlying the invention, there is the possibility to provide injectors with a long service life, which are suitable for multiple injection and highest load.

For an eccentric or tangential inflow of high-pressure fuel from the inlet bore into the control chamber, the inlet throttle of the inlet bore extends in a direction which is eccentric to the cross section of the control chamber. The axis of the inlet throttle and preferably also the axis of the entire inlet bore thus do not intersect the cross-sectional center of the control chamber. The generation of the rotating flow or the twist of the high-pressure fuel in the control chamber is thus realized by a simple structural measure, namely an eccentric arrangement of the inlet throttle in relation to the cross section of the control chamber.

In contrast to other known from the prior art centric arrangement of the inlet throttle, wherein the fuel is introduced into a radial direction to the cross section of the control chamber in the control chamber, there is the advantage that by the tangential inflow of fuel through the eccentric inlet throttle Vortex within the control room can be generated, which continues until the drain hole.

In addition or as an alternative to an eccentric arrangement of the inlet throttle, according to a further embodiment of the invention it may be provided that in the control chamber at least one section is provided with an impact surface, which deflects the high-pressure fuel, which flows into the control chamber via the inlet bore. As a result of the deflection of the inflowing fuel according to the invention via the impact surface, the fuel flow inside the control chamber is set into a rotation according to the invention, resulting in the advantages described above. The at least one baffle can be associated, for example, a portion of the wall which limits the control room.

In addition to an eccentric arrangement of the inlet throttle or the arrangement of baffles within the control chamber for deflecting the fuel flowing into the control chamber other design measures are of course conceivable, with which a rotating fuel flow can be generated within the control room.

For targeted control of the implosion of the vapor bubbles, it may be provided according to the invention that the drain hole comprises a diffuser which reduces the flow rate of the fuel and increases the fuel pressure. The diffuser is arranged on the control valve side facing the outlet throttle in the drain hole and thus in the flow direction of the fuel after the outlet throttle. As experimental studies have shown in an open control valve, the rotating flow continues as a vortex to the drain hole, the vortex is fully formed in the area of the outlet throttle and rotates at high speed. During the transition into the diffuser, the air venting area of the vortex widens conically, whereby the vapor bubbles present in the vortex core are purposefully brought to implosion. The inventive arrangement of the diffuser after the outlet throttle thus results in the advantage that the cavitation takes place in the region of the drain hole in which it does not cause erosion.

For a stable formation of the vortex in the region of the diffuser, it has been found to be particularly advantageous according to the invention, when the diffuser has an optimized opening angle in a range of less than 15 ° or is cylindrical.

According to a further embodiment of the invention, it may be provided that the drain hole has a control chamber side bore portion which is arranged coaxially to the outlet throttle and has a larger inner diameter than the outlet throttle. The cross-sectional transition from the bore section to the outlet throttle can in this case be stepped, conical or in a rounded shape. The control-chamber-side bore portion, which preferably has a cylindrical shape, stabilizes the vortex core, which results from the rotating in the control room flow. The vortex core continues as vortex filament into the outlet throttle, which adjoins the bore section.

According to an embodiment of the bore section according to the invention, it can be provided that the transition from the bore section to the outlet throttle has a conical shape, whereby flow turbulences in the transition region between the bore section and the outlet throttle are avoided.

In order to prevent the transition from the control chamber into the drain hole, a demolition of the rotating flow of the fuel, it may be provided according to the invention that the drain hole has at its end facing the control chamber an inlet rounding. For a targeted expansion of the Luftaufgasungsgebietes downstream of the outlet throttle, it may alternatively be provided that the drain hole at its end facing the control chamber has an inlet edge, which forms the transition between the control chamber and the drain hole.

To improve the pressure level in the seating area of the control valve, it can further be provided according to the invention that a further conical transition area is provided between the outlet throttle and the valve seat of the control valve. The further conical transition region, which is provided at the end of the drainage bore facing the control valve and thereby forms the transition from the drainage bore to the valve seat of the control valve, is in this case designed as a chamfer.

According to a further embodiment of the injector according to the invention, the control valve has a spherical valve body, which serves as a shut-off for the drain hole. The spherical valve body is in this case rotatably received in a corresponding guide of the control valve and can thus be offset by the swirl pulse of the fuel flow in rotation. The rotation of the valve ball has the advantage that the wear of the valve ball is reduced and extends the service life of the control valve.

In the same way, it can be provided according to a further embodiment of the invention that the valve control piston is received rotatably about its longitudinal axis in the injector. The valve control piston is in this case displaceable by the swirl flow in a rotation, which advantageously reduces the wear of the valve spool and increases its life.

Description of the drawings

The invention will be described below with reference to the drawings based on preferred embodiments.

Figur 1

einen schematischen Längsschnitt durch einen erfindungsgemäßen Injektor, in dessen Gehäuse ein Ventilstück mit einen Ventilsteuerkolben eingefügt ist;

Figur 2a

eine schematische Querschnittsansicht durch den Steuerraum eines Ventilstücks mit einer um einen Winkel exzentrisch verdrehten Zulaufbohrung, welche eine Zulaufdrossel umfasst;

Figur 2b

eine schematische Querschnittsansicht durch den Steuerraum eines Ventilstücks mit einer zentrisch angeordneten Ansenkung und einer gemäß der Erfmdung exzentrisch versetzten Zulaufdrossel;

Figur 3

eine schematische Darstellung der Kraftstoffströmung in einem Steuerraum eines Ventilstücks nach Figur 2a; sowie

Figur 4

eine schematische Darstellung eines Längsschnitts durch ein Ventilstück im Bereich der Ablaufbohrung mit einer die Ablaufbohrung verschließenden Ventilkugel eines Steuerventils.

In the drawings show:

FIG. 1

a schematic longitudinal section through an injector according to the invention, in the housing, a valve piece is inserted with a valve control piston;

FIG. 2a

a schematic cross-sectional view through the control chamber of a valve piece with an angularly eccentrically twisted inlet bore, which comprises an inlet throttle;

FIG. 2b

a schematic cross-sectional view through the control chamber of a valve piece with a centrally arranged countersink and an eccentrically offset according to the invention inlet throttle;

FIG. 3

a schematic representation of the fuel flow in a control chamber of a valve piece after FIG. 2a ; such as

FIG. 4

a schematic representation of a longitudinal section through a valve piece in the region of the drain hole with a drain hole closing valve ball of a control valve.

FIG. 1 shows a partial view of an axial section through an injector 1 with a valve piece 4, which is inserted into a housing 2 of the injector 1. The valve piece 4 is arranged in a multi-stepped axial recess 6 of the housing 2, in which a valve spool 8 centered and axially and rotationally movably received. At the bottom of the in FIG. 1 shown injector 2 includes a FIG. 1 not shown nozzle body, in which a coaxial with the valve control piston 8 arranged nozzle needle is provided which opens an injection nozzle for injecting high-pressure fuel in the combustion chamber of an internal combustion engine in phases.

In the provided in the injector 2 valve member 4, an axial bore 10 is provided, which extends in the axial direction of the valve member 4 therethrough and is divided into sections with different sized inner diameters. In a lower portion of the axial bore 10 of the valve member 4 while the valve control piston 8 is movably received with its upper end in the axial direction, resulting in a comparatively small-volume control chamber 12 in the valve piece 4 above the valve spool 8. Starting from the control chamber 12, the provided in the valve piece 4 axial bore 10 extends to a valve seat 16 of an in FIG. 1 not shown control valve. The portion of the axial bore 10 between the control chamber 12 and the valve seat 16 is in this case designed as a drain hole 14 and is characterized by a in FIG. 1 not further illustrated control valve with respect to the arranged above the valve member 4 cavity of the axial recess 6 of the injector housing 2, which serves as a pressure equalization chamber, closed. At the height of the control chamber 12, an inlet bore 20 is provided in the wall 18 of the valve member 4, which connects the control chamber 12 via an annular space 22 with a high pressure port 24. Via the high-pressure connection 24, the control chamber 12 is thus supplied with high-pressure fuel via the annular space 22 and the inlet bore 20, an inlet throttle 26 being provided in the inlet bore 20 for restricting the volume flow.

In the FIG. 2a and the FIG. 2b two cross-sectional views of a control chamber 12 of a valve piece 4 are shown, which comprises an inlet bore 20 with an inlet throttle 26. The inlet bore 20 in this case connects the arranged within the valve member 4 control chamber 12 hydraulically with the in FIG. 1 shown annulus 22 of the injector 1. As from the FIG. 2a and the FIG. 2b shows, the inlet bore 20 in addition to the inlet throttle 26, which merges into the control chamber 12, moreover, a counterbore with a cylindrical portion 28 and a conical portion 30. Compared to a known from the prior art centrally arranged inlet throttle are in the Figure 2a and 2b shown inlet throttles 26 arranged eccentrically.

When in FIG. 2a shown cross-section of an eccentrically arranged inlet throttle 20, the axis of the inlet bore 20 and the inlet throttle 26 is rotated by an angle x relative to a radial orientation of the inlet bore. The cylindrical portion 28 of the inlet bore 20 is in this case arranged coaxially to the inlet throttle 26. Due to the conical portion 30 of the inlet bore 20, which may also be arranged coaxially to the inlet throttle 26, resulting from the inflow of high-pressure fuel from the annular space 22 into the inlet bore 20 hydrodynamically advantageous Flow conditions. The cross section of an injector according to the invention with an eccentrically arranged inlet bore 20 is in FIG. 2b shown. The conical portion 30 and the cylindrical portion 28 of the inlet bore 20 are arranged centrally, whereas the inlet throttle 26 is eccentrically offset from a radial alignment by an offset e.

Due to the eccentric arrangement of the inlet throttle 26 in the wall 18 of the valve member 4 of the high-pressure fuel flows from the in FIG. 1 shown annulus 22 tangentially into the control chamber 12, whereby a swirl flow with a translational and rotational component is formed. The arrows 34 in FIG. 3 indicated swirl flow rotates in the direction of the arrow 32 within the control chamber 12, wherein in the region of the axis 36 of the valve member 4, a vortex core and a vortex thread is formed in FIG. 3 are indicated in a schematic manner by the reference numeral 38. In this case, the vortex filament represents the center line of the vortex core 38 extending in the axial direction of the axial bore 10 of the valve piece 4, which propagates along the flow direction.

By the rotating in the direction of arrow 32 flow of the fuel, a centrifugal force which drives the fuel due to its high mass from the axis of rotation or the axis 36 of the valve member 4 to the outside. The lighter in relation to the mass of the fuel vapor bubbles, cavities or cavitation bubbles are thereby forced away from the wall 18 to the center of the rotating flow, ie in the direction of the axis of rotation. In the vortex core 38 creates a so-called dead water area, which is no longer available for transporting the fuel within the control chamber 12. The fuel can therefore flow only on the control chamber 12 facing the inner surface of the wall 18 of the valve member 4 along, with the rotating flow in the axial direction of the axial bore 10 of the valve member 4 into the in FIG. 1 shown drain hole 14 continues.

After the in FIG. 1 illustrated embodiment of the drain hole 14, this extends in several cross-sectional sections up to the conically shaped valve seat 16 of the control valve. Starting from the control chamber 12, following a cylindrical bore section 40, an outlet throttle 42 follows, followed by a diffuser 44. Between the diffuser 44 and the valve seat 16, a conical transition region 46 may be arranged, which has a smaller cone diameter than the adjoining valve seat 16. Furthermore, the different sections 40, 42, 44 differ-Nach the embodiment of the drain hole 14 after FIG. 1 the transition from the control chamber 12 to the cylindrical bore portion 40, the transition from the cylindrical bore portion 40 to the outlet throttle 42 and the transition from the outlet throttle 42 to the diffuser 44 are made step-shaped.

An alternative embodiment of the drain hole 14 is the FIG. 4 can be seen in which an axial longitudinal section through the valve member 4 in the region of the drain hole 14 is shown. Unlike the in FIG. 1 illustrated drain hole 14 made the transition from the control chamber 12 to the cylindrical bore portion 40 and the transition from the cylindrical bore portion 40 to the outlet throttle 42 is not in a stepped shape. Between the control chamber 12 and the cylindrical bore portion 40, a conical portion 48 of the drain hole 14 is arranged, which tapers from the control chamber 12 in the direction of the cylindrical bore portion 40 tapers. At the control chamber 12 facing the end of the conical portion 48 may be provided a circumferential chamfer 50, which has a larger cone diameter in the transition from the control chamber 12 to the drain hole 14 by the arrangement of the circumferential chamfer 50 and the conical sections 48 in front of the cylindrical bore portion 40, a break in the flow in the region of the change in cross section between the control chamber 12 and the cylindrical bore portion 40 is prevented, whereby the vortex core 38 of the rotating flow is stabilized.

After a not in FIG. 4 illustrated embodiment may be provided as an alternative or in addition to an adjacent to the control chamber 12 circumferential chamfer 50 that the drain hole 14 at its end facing the control chamber 12 has an outlet opening whose edge is rounded.

For further stabilization of the vortex core 38 of the swirl flow forming within the drainage bore 14, the cylindrical bore section 40 has a conical shape in the transitional region 52 to the outlet throttle 42.

In contrast to the transitions from the control chamber 12 to the cylindrical bore section 40 and from the cylindrical bore section 40 to the outlet throttle 42, the transition from the outlet throttle 42 to the diffuser 44 is step-shaped. The diffuser 44 may in this case have an optimized opening angle of preferably less than 15 °, whereby the speed level of the swirl flow is reduced and the pressure level is increased. The vapor bubbles formed in the vortex core 38 of the swirl flow are due the increase in the pressure level in the region of the diffuser 44 is deliberately brought to implosion, without any damage being caused by cavitation erosion at the wall bounding the drainage bore 14. In addition, the effect according to the invention that no damage to the conical valve seat 16 occurs.

In the flow direction after the diffuser 44, a conical transition region 46 connects, which merges into a conical valve seat 16. The conical transition region 46 has a smaller cone diameter than the conical valve seat 16.

The conical transition region 46 FIG. 1 and 4 represents a flow transition section, which can serve as a damage-relevant area for cavitation in front of the valve seat 16. As from the illustration in FIG. 4 can be seen, the drain hole 14 is closed by a spherical valve body 54, which by a in FIG. 1 and 4 not shown ball guide rotatably guided and actuated by an actuator, also not shown. The swirl impulse of the swirl flow allows the spherical valve body 54 to be set in rotation.

In addition to the above-described embodiments of the transitions between the sections with different inner diameter of the inlet bore 20 and the drain hole 14, it is provided for further not shown in the figures alternative embodiments that the inlet bore 20 and the drain hole 14 have a combination of differently shaped transitions. The transitions between the sections of different inner diameter preferably have a conical or conical shape, a step shape or a rounded shape.

Claims (8)

1. Injector for internal combustion engines, comprising a control chamber (12) of a valve control piston (8), to which control chamber there is assigned an inflow bore (20) which has an inflow throttle (26) and which serves for the supply of highly pressurised fuel, and an outflow bore (14) which has an outflow throttle (42) and which can be closed off by a control valve, wherein the inflow throttle (26) extends in a direction which is eccentric with respect to the control chamber (12) and in which the highly pressurised fuel flowing through the inflow bore (20) is introduced eccentrically into the control chamber (12), characterized in that the inflow bore (20) comprises a cylindrical portion (28) and a conical portion (30) in addition to the inflow throttle (26) which merges into the control chamber (12), and in that the conical portion (30) and the cylindrical portion (28) of the inflow bore (20) are arranged centrically, whereas the inflow throttle (26) is offset eccentrically with respect to a radial orientation by an offset e.
2. Injector according to Claim 1, characterized in that, in the control chamber (12), there is provided at least one portion which comprises an impingement surface, which portion diverts the fuel flowing into the control chamber (12).
3. Injector according to Claim 1, characterized in that the outflow bore (14) comprises a diffuser (44) which is arranged on that side of the outflow throttle (42) which faces toward the control valve.
4. Injector according to Claim 3, characterized in that the diffuser (44) has an opening angle in an optimized range of less than 15°.
5. Injector according to Claim 3 or 4, characterized in that the outflow bore (14) has a control-chamber-side bore portion (40) which has a larger inner diameter than the outflow throttle (42), wherein the cross-sectional transition from the bore portion (40) to the outflow throttle (42) is stepped, conical or rounded.
6. Injector according to one of Claims 3 to 5, characterized in that the outflow bore (14) has, at its end facing toward the control chamber (12), a rounded run-in portion.
7. Injector according to one of Claims 3 to 6, characterized in that the outflow bore (14) has, at its end facing toward the control chamber (12), a conical portion (48) which widens in the direction of the control chamber (12).
8. Injector according to one of Claims 3 to 7, characterized in that a conical transition region (46) is provided between the outflow throttle (42) and the valve seat (16).

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