EP2235356B1 - Fuel injector - Google Patents

Description

State of the art

The invention relates to an injector for injecting fuel into a combustion chamber of an internal combustion engine, in particular a common rail injector, according to the preamble of claim 1.

From the EP 1 612 403 A1 is a common rail injector with a pressure balanced in the axial direction control valve known. By means of the control valve, the fuel pressure can be influenced within a limited by an injection valve element control chamber. By varying the fuel pressure within the control chamber, the injection valve element is adjusted between an open position and a closed position, wherein the injection valve element releases the fuel flow into the combustion chamber of an internal combustion engine in its open position. In order to realize the axial pressure balance of the control valve, this comprises a sleeve-shaped control valve element which can be adjusted by means of an electromagnetic actuator and whose end-face sealing line interacts with a control valve seat. The annular sealing line is formed directly on the inner guide diameter of the control valve sleeve. The guide diameter of the sleeve-shaped control valve element corresponds to the outer diameter of an axially projecting into the control valve element bolt plus a minimum clearance. When the injector is new, the sealing line has a minimum width extension. This leads to extremely high surface pressures, which in turn leads to a strong flattening of the sealing edge by the high-momentum forces and by the friction between the control valve element and the control valve seat. This results in a decrease in the surface pressure, which in turn can lead to leaks in the control valve.

From the WO 2009/071472 A1 a switching valve for injectors is known in which the control valve member is in the form of a sleeve. The sleeve-shaped control valve member may have on its inside a conical annular surface which limits the sealing edge of the control valve member.

Disclosure of the invention Technical task

The invention has for its object to propose an improved injector, in the leaks between the control valve element and the control valve seat, at least largely avoided.

Technical solution

This object is achieved with an injector having the features of claim 1. Advantageous developments of the invention are specified in the subclaims. All combinations of at least two features disclosed in the description, the claims and / or the figures fall within the scope of the invention.

The invention is based on the idea that the particular annular sealing line (sealing edge) of the injector with an (inner) diameter form, which is greater than the inner guide diameter. In other words, in the case of an injector designed according to the concept of the invention, the sealing line is not located directly on the inner bore of the control valve element, but is at a radial distance therefrom to the outside staggered. Preferably, the sealing line is located at the radially outer edge of a seat boundary of the control valve element. The proposal to form the sealing line with a diameter which is greater than the inner guide diameter of the control valve element, initially surprising, since this is an axial pressure balance is dispensed with - there is an internal pressure stage, attack on the flow of fuel from a control chamber and thus the Control valve element can act on a force in the opening direction. The described effect is accepted because, in the case of an injector designed according to the concept of the invention, wear phenomena in the region of the sealing edge are advantageously minimized, which consequently considerably reduces the risk of leaks. During operation of the injector, the originally very sharp-edged sealing line will widen in the radial direction (plates), but preferably maximally to a radial extent between about 50μm and 150μm (depending on the actual acting pressures, diameter and forces). It is particularly advantageous that this widening takes place in contrast to the prior art in a trained according to the concept of the invention injector in the radial direction inwardly to the high pressure region, so that in the sequence reduces the pressure level during operation.

In order to form as small as possible from the arrangement of the sealing line with radial distance to the guide diameter pressure level on the control valve element, the sealing line is not directly adjacent to the boundary to the outer diameter of the control valve in the invention, but is relative to this with radial distance, ie radially offset inside, arranged. Especially preferred is an embodiment in which the radial distance between the inner guide diameter and the sealing line in the new state of the injector is only about 20 microns to 120 microns, preferably about 30μm to 100 microns.

As mentioned above, a sealing line arranged on the inner circumference of the control valve element leads to plastic deformations, in particular at the control valve seat, and thereby reduces the strength values. This is the case, in particular, in the case of control valve seats formed as a flat seat and in the case of conical control valve angles with a flat cone angle of approximately 120 ° and less than 180 °. However, since precisely designed control valve seats have significantly less slippage between the control valve element and the control valve seat, they are characterized by a low Reibverschleiß. Therefore, the arrangement of the sealing line with radial distance to the inner guide diameter is particularly advantageous in combination with designed as a flat seat or a conical seat with a small cone angle control valve seats. A cone angle is understood to be the angle between two diametrically opposite inclined sections of the cone, that is to say twice the angle between the conical surface and the longitudinal central axis of the control valve element.

According to the invention, an inner annular surface adjoins the sealing line radially inward, which is designed to be in the form of an inner cone, that is to say at an angle to the control valve seat, more precisely to the control valve seat surface. Such a trained inner annular surface forms a seat boundary, whose radially outer boundary is formed by the sealing line. Preferably, the angle at which the inner annular surface of the control valve seat (Control valve seat surface) extends away, between about 0.1 ° and about 50 °. Particularly preferably, the angle is selected from a range between about 0.5 ° and about 5 °.

An advantage is an embodiment in which the inner annular surface, starting from the sealing line, extends radially as far as the inner guide diameter and does not adjoin an additionally innermost annular surface, which would run at an angle to the inner annular surface. In a radially extending to the inner guide diameter inner annular surface, the seat boundary is formed radially inward of the edge between the inner annular surface and the guide portion of the control valve element, wherein the inner diameter of the edge corresponds to the guide diameter of the control valve element.

In order to further minimize the loads occurring in the region of the sealing line and thus plastic deformation, it is advantageously provided in a further development of the invention that the angle which is spanned by the radially inner annular surface and an outer annular surface adjoining radially outside the sealing line is greater as 90 °. Preferably, the angle is greater than 100 ° selected. Particularly preferred is an embodiment with an angle of about 120 °. It is also inverse cone shapes (inner cone), preferably with a corresponding angle of up to about - 120 °, realized.

In particular, when the control valve seat is designed as a flat seat or as a conical seat with a flat cone angle, an embodiment is preferred in which the radially outside of the sealing line adjacent outer annular surface to the control valve seat, more precisely to the control valve seat surface, is inclined. The angle should be such that on the one hand a sufficient seat limitation is ensured and on the other hand a support function for the sealing line is ensured. Particularly preferably, the angle is between about 10 ° and about 50 °, in particular between about 20 ° and about 45 °. Particularly preferably, the angle is about 30 °.

Particularly preferred is an embodiment in which the angularly arranged to the control valve seat outer annular surface in the radial direction does not reach to the outer periphery of the control valve member, but in which the outer annular surface merges with radial distance to the sealing line in an outer annular surface. Preferably, this outer ring surface (outermost ring surface) lies in a plane perpendicular to the longitudinal central axis of the control valve element plane. Preferably, the radial extent of the outer, immediately adjacent to the sealing line, annular surface is selected so that the sealing line has a greater axial distance to the radially outermost edge of the outer annular surface than the radially innermost edge of the inner annular surface.

It is also an embodiment feasible, in which the outer annular surface is not inclined to the control valve seat (control valve seat surface), but lies in such a plane. In this case, the outer annular surface may preferably extend in the radial direction to the outer diameter of the control valve element in this design. The non-oblique arrangement of the outer annular surface is particularly advantageous for designed as a conical seat control valve seats. Particularly preferably, the angle between the outside of the sealing line adjacent annular surface and the control valve seat is greater than the angle between the radially inner adjacent to the sealing surface annular surface and the control valve seat.

In a further development of the invention is advantageously provided that the sealing line of the injector, especially after a certain period, at most a radial extent of 150 .mu.m, preferably less than 50 .mu.m. Preferably, the radial extent of the sealing edge immediately after the new production of the injector (substantially) smaller than 50 microns.

Brief description of the drawings

Fig. 1:

eine schematische Darstellung eines als Common-Rail-Injektor ausgebildeten Injektors mit einem hülsenförmigen Steuerventilelement,

Fig. 2:

eine vergrößerte Darstellung eines Details aus Fig. 1

Fig. 3:

eine vergrößerte Darstellung eines Details aus Fig. 1

Further advantages, features and details of the invention will become apparent from the following description of preferred embodiments and from the drawings. These show in:

Fig. 1:

a schematic representation of a common rail injector designed as an injector with a sleeve-shaped control valve element,

Fig. 2:

an enlarged view of a detail Fig. 1

3:

an enlarged view of a detail Fig. 1

Embodiments of the invention

In the figures, the same components and components with the same function with the same reference numerals.

In Fig. 1 a designed as a common rail injector injector 1 for injecting fuel into a combustion chamber of an internal combustion engine (not shown) of a motor vehicle is shown. A high pressure pump 2 delivers fuel from a reservoir 3 in a high-pressure fuel storage 4 (Rail). In this fuel, especially diesel or gasoline, is stored under high pressure of about 2000 bar in this embodiment. To the high-pressure fuel accumulator 4, the injector 1 is connected to other, not shown, injectors via a respective supply line 5. The supply line 5 opens into a pressure chamber 6 of the injector 1. By means of a return line 7, a low-pressure region 8 of the injector 1 is connected to the reservoir 3. Via the return line 7, a later to be explained control amount of fuel from the injector 1 to the reservoir 3 flow.

Within an injector body 9, an injection valve element 10 is arranged axially adjustable in this embodiment. The injection valve element 10 is guided with a lower portion in a nozzle body 11, which is clamped by means of a union nut, not shown, against the injector body 9. With its upper section in the plane of the drawing, the injection valve element 10 is guided in an axially facing sleeve section 12 of a throttle plate 13.

The injection valve element 10 has at its tip 14 a closing surface 15 with which the injection valve element 10 can be brought into a tight contact with an injection valve element seat 16 formed inside the nozzle body 11. When the injection valve member 10 abuts against its injection valve member seat 16, d. H. is in a closed position, the fuel outlet from a nozzle hole arrangement 17 is locked. If, on the other hand, it is lifted off its injection valve element seat 16, fuel can flow directly from the pressure chamber 6 via axial channels 18 formed on the outer circumference of the injection valve element 10 and the annular space 19 between the lower section of the injection valve element 10 and the nozzle body 11 past the injection valve element seat 16 to the nozzle hole arrangement 17 flow and there are essentially injected under high pressure (rail pressure) standing in the combustion chamber, not shown.

From an upper end face 20 of the injection valve element 10, which in addition to the shown one-piece design can be formed in several parts, and in the drawing plane lower sleeve portion 12 of the throttle plate 13, a control chamber 21 is limited, the peripheral wall is bounded radially outwardly from the pressure chamber 6. The control chamber 21 is connected via a radially extending in the sleeve portion 12 inlet throttle 22 with the pressure chamber 6. About the inlet throttle 22, the control chamber 21 is supplied with high-pressure fuel from the pressure chamber 6. The control chamber 21 is connected via a, arranged in the upper, plate-shaped portion of the throttle plate 13, the drain passage 23 with outlet throttle 24 with a valve chamber 25, which is radially outwardly of a sleeve-shaped control valve element 26 of a control valve 27 (servo-valve) is limited. From the valve chamber 25, fuel can flow into the low-pressure region 8 of the injector when the control valve element 26 which can be actuated by an electromagnetic actuator 28 is lifted from its control valve seat 29, which is formed on the throttle plate 13, ie the control valve 27 is open. The flow cross-sections of the inlet throttle 22 and the outlet throttle 24 are matched to one another such that when the control valve 27 is open, a net outflow of fuel (control amount) from the control chamber 21 via the valve chamber 25 in the low pressure region 8 of the injector 1 and from there via the return line. 7 resulted in the reservoir 3.

Within the control valve element 26, a pressure pin 30 is received, which receives the pressure forces acting in the axial direction within the valve chamber 25 and the valve chamber 25 seals in the axial direction in the plane of the drawing upwards. The pressure pin 30 is supported on a closure lid 31, to which the pressure pin 30 passes through a holding body 32 for electromagnets 33 of the actuator 28 in the axial direction centric and with radial distance. When the internal combustion engine is switched off, the pressure pin 30 drops and lies on the top of the throttle plate 13 until the pressure builds up again. The outer diameter of the cylindrical pressure pin 30 corresponds to the inner guide diameter D _{i of} the control valve element 26 less a guide clearance. In addition, the control valve element 26 at its outer diameter D _a , with which it passes through a plate member 34 with axial distance to the throttle plate 13, out.

How out Fig. 1 can be seen, an anchor plate 35 of the electromagnetic actuator 28 is integrally formed with the control valve element 26 in the illustrated embodiment. When the electromagnet 33 of the electromagnetic actuator 28 is energized, the sleeve-shaped control valve member 26 lifts from its control valve seat 29, whereby the pressure within the control chamber 21 drops rapidly and the injection valve member 16 moves in the axial direction in the drawing plane up into the control chamber 21, whereby the nozzle hole assembly 17 is released and fuel can flow into the combustion chamber.

To end the injection process, the energization of the electromagnet 33 of the actuator 28 is interrupted. A control closing spring 36, which is supported on the closure lid 31, moves the control valve element 26 back to its control valve seat 29. By flowing through the inlet throttle 22 fuel, the pressure in the control chamber 21 increases rapidly, whereby the injection valve element 10, supported by the spring force of a closing spring 37, which at one end is supported on a peripheral collar 38 of the control valve element 26 and the other end on the lower end side of the sleeve portion 12, is moved in the direction of the injection valve member seat 16, which in turn the fuel flow from the nozzle hole assembly 17 is interrupted in the combustion chamber.

In the closed state of the control valve 27, the control valve member 26 is located at an end face, annular contoured sealing line 39 on the control valve seat 29. The sealing line 39 is, as in the following with reference to FIGS. 2 and 3 will be explained, not immediately adjacent to the inner guide diameter D _{i of} the control valve element 26, but arranged at a radial distance to this offset outwards. The very sharp-edged sealing edge after production widens due to the load occurring during operation to a radial extent of between about 50 μm and about 150 μm. Due to the compressive forces acting during operation, the sealing line 39 is infiltrated to some extent by fuel under high pressure in the radial direction to the outside.

In Fig. 2 is a possible education of a detail Fig. 1 shown enlarged. For reasons of clarity, only the left half of the control valve element 26 is shown. The control valve element 26 with the inner guide diameter D _i is shown in its closed position, in which it bears against the control valve seat 29 with its frontal, annular contoured sealing line. The control valve seat 29 is formed in the embodiment shown as a flat seat. It can be seen that the sealing line 39 is not directly adjacent to the inner guide diameter D _i , but is arranged at a radial distance a to this. The radial distance a is 100μm in the embodiment shown. The radial distance a from the inner guide diameter D _i , ie from the inner guide bore of the control valve element 26 to the sealing line 39, is bridged by a single inner annular surface 40, which in the embodiment shown at an angle α to the control valve seat 29 (control valve seat surface). The angle α is in the illustrated embodiment about 5 ° (exaggerated), wherein the inner annular surface 40, starting from the sealing line 39, both axially and radially from the control valve seat 29 extends away. The inner annular surface 40 forms a seat boundary and is bounded radially outwardly by the sealing line 39 and radially inwardly by a peripheral edge 41 at the transition to the inner guide diameter D _i .

Radially outwardly, the sealing line 39 is adjoined by an outer annular surface 42 which also extends away from the control valve seat 29 in the axial and in the radial direction. The angle β between the control valve seat 29 and the outer annular surface 42 is in the illustrated embodiment about 30 ° and thus (significantly) greater than the angle α. As a result, an angle γ between the outer ring surface and the inner ring surface 40 of about 145 ° results. As can be seen from point two, the axial distance between the sealing line 39 and the radially outer edge 43 of the outer annular surface 42 is greater than the axial distance between the sealing line 39 and the inner edge 41 of the inner annular surface 40th

At the radially outer edge 43 of the outer annular surface 42 adjoins an outer annular surface 44 (outermost annular surface) which lies in a direction perpendicular to the longitudinal central axis L extending plane and extending to the outer diameter D _{a of} the control valve member 26. The radial extension of the outer ring surface 44 (or of its axial projection surface) corresponds to a multiple of the radial extent a (radial distance of the sealing line to the inner guide circumference) of the inner annular surface 40 (or of its axial projection surface).

In Fig. 3 an alternative embodiment is shown. In the embodiment shown, the control valve seat 29 is not formed as a flat seat, but as a conical conical seat, wherein the cone angle δ in the shown Embodiment is about 160 °. Evident is the sealing line 39 (sealing edge), which is arranged with a radial distance a to the inner guide diameter D _i , ie the guide bore in the control valve element 26. The angle α between the lateral surface of the control valve seat 29 and the radially adjacent to the sealing line 39 arranged inner annular surface 40 is in the illustrated embodiment about 4 ° (exaggerated drawn).

Radially outwardly adjacent to the sealing line 39, the outer annular surface 42 which lies in a direction perpendicular to the longitudinal central axis L extending plane and extending to the outer diameter D _{a of} the control valve member 26. The angle β between the outer annular surface 42 and the control valve seat 29 is in the illustrated embodiment about 22 °, so that in the sequence of the angle γ between the outer annular surface 42 and the inner annular surface 40 is about 154 °.

Claims (10)

1. Injector for injecting fuel into a combustion chamber of an internal combustion engine, in particular a common rail injector, having an injection valve element (10) which can be adjusted between a closed position and an open position and can be actuated by means of a control valve (27) which has a sleeve-shaped control valve element (26) with an inner guide diameter (D_i), a circumferential sealing line (39) bearing against a control valve seat (29) when the control valve (27) is closed, the sealing line (39) being arranged at a radial spacing (a) from the inner guide diameter (D_i), an inner annular face (40) which adjoins the sealing line (39) radially on the inside being angled away with respect to the control valve seat (29), characterized in that the control valve seat (29) is configured as a conical seat.
2. Injector according to Claim 1, characterized in that the sealing line (39) is arranged at a radial spacing (a) from the outer diameter (D_a) of the control valve element (26).
3. Injector according to either of the preceding claims, characterized in that the radial spacing (a) between the guide diameter (D_i) and the sealing line (39) is from approximately 20 µm to approximately 120 µm.
4. Injector according to Claim 1, characterized in that the inner annular face (40) which adjoins the sealing line (39) radially on the inside is angled away with respect to the control valve seat (29) at an angle (α) between approximately 0.1° and approximately 50°, in particular between approximately 0.5° and approximately 5°.
5. Injector according to Claim 1, characterized in that the inner annular face (40) extends radially as far as the inner guide diameter (D_i).
6. Injector according to either of Claims 1 and 5, characterized in that an outer annular face (42) which adjoins the sealing line (39) radially on the outside and the radially inner annular face (40) define an angle (γ) of greater than 90°, by preference greater than 100°, preferably greater than 110°, particularly preferably greater than 120°, in particular preferably greater than 140°.
7. Injector according to Claim 6, characterized in that the outer annular face (42) is inclined with respect to the control valve seat (29), by preference at an angle (β) between approximately 10° and approximately 50°, in particular at an angle between approximately 20° and approximately 45°, particularly preferably at an angle of approximately 30°.
8. Injector according to either of Claims 6 and 7, characterized in that the outer annular face (42) merges into an outer annular face (44) which is arranged radially outside the former, encloses an angle with the outer annular face (42) and preferably lies in a plane which runs perpendicularly with respect to the longitudinal centre axis (L) of the control valve element (26).
9. Injector according to Claim 6 or 7, characterized in that the outer annular face (42) lies in a plane which runs perpendicularly with respect to the longitudinal centre axis (L) of the control valve element (26) and preferably extends radially as far as the outer diameter (D_a) of the control valve element (26).
10. Injector according to one of Claims 7 to 9, characterized in that the angle (α) between the inner annular face (40) and the control valve seat (29) is smaller than the angle (β) between the outer annular face (42) and the control valve seat (29).

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