EP2171257B1 - Control valve for a fuel injector and fuel injector - Google Patents

Abstract

The invention relates to a control valve (25) for a fuel injector having a control sleeve (24) delimiting a pressure chamber (23) and being movably supported in the longitudinal direction, wherein the control sleeve (24) has a sealing surface (36) at the face thereof, the sleeve using the surface to interact with a control valve seat (27) having an outside truncated cone shape and being configured on a valve body (28). The invention provides that the cone angle of the control valve seat (27) is selected from a value range between 120° and 170°. The invention further relates to a fuel injector.

Description

State of the art

The invention relates to a control valve for a fuel injector according to the preamble of claim 1 and a fuel injector according to claim 10.

From the EP 1 612 403 A1 is a fuel injector with a pressure-balanced in the axial direction control valve known. The control valve has an adjustable by means of an electromagnetic actuator in the axial direction between a closed position and an open position control sleeve which is guided on a, passing through the control sleeve guide pin. In this case, the guide pin is formed integrally with a valve body on which the control valve seat is arranged for the control sleeve. A disadvantage of the known control valve is that the control valve seat is expensive to manufacture due to its poor accessibility and that a comparatively large minimum diameter of the guide pin must not be exceeded for reasons of strength, since the supply of fuel from a control chamber via a valve body provided in the flow channel which is cut perpendicularly inside the guide pin by transverse bores.

As an in-house state of the art of the applicant, an optimized control valve is known. This, in the axial direction likewise pressure-balanced valve has a control sleeve which encloses a pressure pin, which seals the pressure chamber arranged inside the control sleeve and connected to the control chamber in the axial direction. The pressure pin is not formed integrally with the valve body on which the control valve seat is arranged, but as a separate component of the valve body, which is supported in the axial direction at a spaced from the control valve seat injector component, in particular spring assisted. This allows improved accessibility of the control valve seat and thus a simplified manufacturability. In addition, strength problems are avoided. In experiments with the in-house control valve has been found that there is a relative movement of the valve sleeve transversely in both a designed as a conical seat valve seat with a cone angle of 90 ° and a flat seat (cone angle = 180 °) control valve seat when striking the control sleeve on the control valve seat comes to its longitudinal extent relative to the control valve seat. It was observed that in a control valve seat formed as a conical seat with a cone angle of 90 ° of the sealing surface of the control sleeve having portion of the control sleeve elastically radially outwardly adjusted, ie expanded, whereas it comes in a flat seat to a radial adjustment inwards. This slip between the control sleeve and control valve seat leads to increased wear on the control sleeve and the control valve seat and thus to form a pressure step on the control sleeve, which causes an undesirable force acting in the opening direction of the control sleeve force on the control sleeve.

Disclosure of the invention Technical task

The invention has for its object to provide a control valve (servo valve) are minimized in the wear phenomena. Furthermore, the object is to propose a correspondingly optimized fuel injector.

Technical solution

This object is achieved in terms of the control valve with the features of claim 1 and with respect to the fuel injector with the features of claim 10. 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 also fall within the scope of the invention.

The invention is based on the idea of selecting the cone angle of the external truncated-cone-shaped control valve seat so that the stop slip of the sealing surface region of the control sleeve is minimized relative to the control valve seat or, in the optimum case, completely avoided. It has surprisingly been found that when the cone angle of the control valve seat is selected from a value range between about 120 ° and about 170 °, a positive effect with regard to minimizing the stop slip across the length of the control sleeve results. This effect can be attributed to the fact that by a cone angle from a value range between about 120 ° and about 170 °, depending on the dimensions and geometric design of the sealing surface having sealing area the control sleeve must be selected, a radially outwardly acting force component is induced in the sealing region of the control sleeve, which counteracts the Nachinnengleiten the sealing area, as this is observed in a flat seat. The fact that a cone angle of 120 ° is not exceeded, it is achieved that the induced, radially outwardly acting force component is lower than in a conical control valve seat with a cone angle of 90 °, whereby, a (too large) radially outwardly acting, elastic deformation or movement of the control sleeve in its sealing area relative to the control valve seat is surprisingly avoided. For the purposes of the invention, the term "cone angle" is understood to mean the angle that two lateral surface sections (oblique sections) of the control valve seat enclose in a plane receiving the longitudinal central axis of the control valve seat. In other words, the cone angle is the doubled angle between the lateral surface of the outer truncated cone-shaped control valve seat and the longitudinal center axis of the control valve seat.

It is within the scope of the invention that the control sleeve is guided on its inner circumference and / or on its outer circumference. It can be provided to guide the control sleeve on its inner circumference with the control valve seat having the component piece guide pin, which passes through the control sleeve. Alternatively, it is conceivable that in the control sleeve, a pressure pin is arranged, which is designed as a separate part of the valve body having the control valve seat and which is positioned so that it can take over the leadership of the control sleeve. Preferred is an embodiment in which in the control sleeve only one at one, of which the control valve seat having valve body, spaced component abstützender pressure pin is provided and the control sleeve is guided on its outer periphery. Furthermore, it is within the scope of the invention, the control sleeve alternatively by means of a piezoelectric actuator or an electromagnetic actuator between its closed position in which it rests on the control valve seat and a spaced from the control valve seat opening position in which the control chamber is hydraulically connected to a low pressure region of the injector is adjustable ,

Depending on the geometric design of the control sleeve, in particular in its sealing surface having sealing area, an optimum for the specific application cone angle of the control valve seat must be selected from the value range between about 120 ° and about 170 °. It has been found that cone angles from a value range between 130 ° and 170 ° are to be preferred. Especially preferred are cone angles from a value range between 140 ° and 170 °. In tests, particularly good results were achieved in the combination of a seat diameter (sealing diameter) of 2.5 mm and a cone angle of 140 °. Particularly advantageous is the choice of a cone angle from a range of values between 150 ° and 170 °, preferably from a range of values between 155 ° and 160 ° has been found. In particular, for a seat diameter (sealing diameter) of 1.8 mm, a cone angle of the control valve seat of 160 ° is optimal.

Preferred is an embodiment in which the sealing surface, which cooperates with the outer cone-shaped control valve seat is formed on an inner cone-shaped end side portion of the control sleeve, the sealing surface so itself is internally cone-shaped. As a result, signs of wear can be further minimized.

To realize a sealing edge with a minimum radial extent, an embodiment is advantageous in which the inner cone angle of the inner surface of the sealing surface (something) is selected to be greater than the cone angle of the outer frustoconical control valve seat.

It has proved to be particularly advantageous if the angular difference between the inner cone angle and the portion of the control sleeve having the sealing surface is selected from a value range between approximately 1 ° and approximately 10 °. Particularly preferred is an inner cone angle greater by about 2 ° to 9 ° than the cone angle of the control valve seat. Particularly optimized results with regard to the wear and the tightness of the control valve in the closed state were achieved with an angle difference between inner cone angle and cone angle of the control valve seat from a value range between 3 ° and 6 °.

Particularly preferred is an embodiment of the control valve as a pressure balanced in the axial direction valve, ie a valve on the control sleeve act in the closed state no directed in the axial direction, resulting adjustment forces. This can be realized in particular by the fact that the sealing surface frontally adjacent to the inner peripheral wall of the control sleeve and extending from this in the radial direction outwards and in the axial direction, ie in the direction of the control valve seat. In other words, the seat line (sealing line) with which the control sleeve interacts with the outer truncated-cone-shaped control valve seat adjoins the inner circumference the control sleeve. The inner diameter of the sealing line corresponds to the inner diameter of the control sleeve.

In order to limit the maximum extension of the wear surface over time by increasing the sealing surface, an embodiment is preferred in which the sealing surface having sealing area in the radial direction connects an annular surface, preferably in an imaginary, arranged transversely to the longitudinal extent of the control sleeve level lies. It is within the scope of the development that this, the maximum extent of the sealing surface limiting annular surface with the transversely extending to the longitudinal extent of the control sleeve, imaginary plane includes an angle from a value range between about -20 ° and about + 20 °.

The invention also leads to a fuel injector for injecting fuel into a combustion chamber of an internal combustion engine. This has a designed according to the concept of the invention, preferably in the axial direction pressure compensated control valve with a control sleeve which cooperates with an outer truncated cone-shaped control valve seat having a cone angle from a value range between 120 ° and 170 °. By opening the control valve, ie by lifting the control sleeve of the control valve seat operatively connected to a one-piece or multi-part injection valve element control chamber is connected to an injector return, so that the fuel pressure in the control chamber drops rapidly and the injection valve element lifts from its valve seat and fuel through at least one Nozzle hole opening can flow into the combustion chamber of the internal combustion engine. In this case, an embodiment is preferred in which the control sleeve is operatively connected to an anchor plate, ie integrally with this is formed or, in particular form-fitting, connected thereto, wherein the armature plate cooperates for adjusting the control sleeve with an electromagnetic actuator.

Brief description of the drawings

Fig. 1:

eine unvollständige Darstellung eines Kraftstoffinjektors mit einem eine Steuerhülse aufweisenden Steuerventil und

Fig. 2:

eine vergrößerte Darstellung einer möglichen Ausbildung des Steuerventilsitzes.

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:

an incomplete illustration of a fuel injector with a control sleeve having a control valve and

Fig. 2:

an enlarged view of a possible embodiment of the control valve seat.

Embodiments of the invention

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

In Fig. 1 is a common rail injector trained fuel injector with the fuel supply components shown schematically in longitudinal section. The fuel injector comprises a holding body 1 and a nozzle body 2, which are clamped together by a clamping nut 3. Within the holding body 1 and the nozzle body 2, a two-part injection valve element 3 is mounted longitudinally displaceable. The injection valve element 3 consists of a Nozzle needle 4, which is arranged longitudinally displaceably in the nozzle body 2 and a control rod 5, which is arranged longitudinally displaceable within the holding body 1.

The nozzle needle 4 controls the opening of at least one injection opening 6 by its longitudinal movement. The fuel is supplied to the injection openings 6 from the nozzle chamber 7, which surrounds the nozzle needle 4 and which can be filled with fuel at high pressure via an inlet channel 8. If the nozzle needle 10 moves away from the injection openings 6 and thus moves into its open position, fuel, essentially under rail pressure, is injected from the nozzle chamber 7 via the injection openings 6 into a combustion chamber, not shown in the drawing, of an internal combustion engine. If, however, the nozzle needle 10 is in its closed position, i. in contact with a valve seat, the openings 6 are closed by the nozzle needle 4.

The control rod 5 is received in a longitudinal bore 9 within the holder body 1. The control rod 5 is connected via a pressure piece 10 to the nozzle needle 4 within a low pressure chamber 11 which is connected via a channel, not shown, to the injector return, so that the control rod 5 moves synchronously with the nozzle needle 4 in the longitudinal direction. At the end facing the nozzle body 2, the control rod 5 is surrounded by a closing spring 12, which is supported on the one hand in a paragraph on the holding body 1 and on the other hand on the pressure piece 10, so that by the force of the closing spring 12, the pressure piece 10 in the direction of the nozzle needle 4 and so that the nozzle needle 4 is subjected to force in its closed position.

For supplying the fuel under high pressure, a high-pressure pump 13 is provided, which compresses the fuel from a reservoir 14 and a high-pressure accumulator 15 (Rail) supplies, in which the fuel is kept under high pressure. Via a high-pressure line 16 and a high-pressure connection 17, which is formed on the fuel injector, the high-pressure fuel is supplied to the fuel injector and injected in the manner described via the injection openings 6 into the combustion chamber of the internal combustion engine.

With its end facing away from the nozzle needle 4, the control rod 5 defines a control chamber 18, which is connected via an inlet bore 19 with inlet throttle 20 to the inlet channel 8. The control chamber 18 is connected via a drain passage 21 with outlet throttle 22 to a pressure chamber 23. The pressure chamber 23 is arranged radially within an adjustable in the axial direction of the control sleeve 24 of a control valve 25 (servo valve). The control sleeve 24 acts with an outer truncated cone-shaped control valve seat 27 which is formed on a valve body 28. Within the control sleeve 24, a pressure pin 29 is arranged, which is designed as a separate component from the valve body 28 and which is supported in the axial direction in the drawing plane upwards on a component, not shown. The pressure pin 29 is used in the embodiment shown to guide the control sleeve 24 in the axial direction. Additionally or alternatively, a guide for the control sleeve 24 may be provided on its outer periphery.

In the embodiment shown, the control sleeve 24 is integrally formed with an anchor plate 30 which cooperates with an electromagnetic actuator 31, in such a way in that the armature plate 30 and thus the control sleeve 24 are moved upwards in the drawing plane when the electromagnetic actuator 31 is energized so that fuel can flow from the pressure chamber 23 into a low-pressure region 32 of the fuel injector and from there to a return 33, via which one later yet to be explained control amount of fuel is returned to the reservoir 14. To close the control valve 25, the energization of the electromagnetic actuator 31 is interrupted and a control closing spring 34 pushes the control sleeve 24 in the axial direction in the drawing plane down to the control valve seat 27th

In order to initiate an injection process, the electromagnetic actuator 31 of the control valve 35 is energized. As a result, the control sleeve 24 lifts from its outer frustoconical control valve seat 27, whereby fuel from the control chamber 18 through the drain passage 21 with outlet throttle 22 and the pressure chamber 23 radially between the lower end of the control sleeve 24 and the control valve seat over in the low pressure region 32 and thus to the return 33rd can flow. In this case, the flow cross sections of the outlet throttle 22 and the inlet throttle 20, via which continues to flow fuel into the control chamber 18, so matched to each other that a net outflow (control amount) of fuel in the low pressure region 32 and from there into the return 33 results. As a result, the pressure within the control chamber 18 decreases rapidly, whereby the injection valve element 3, supported by the high-pressure fuel in the nozzle chamber 7 in the axial direction in the plane moves upward and the fuel flow through the injection openings 6 in the combustion chamber of the internal combustion engine releases.

To end the injection process, the energization of the electromagnetic actuator 31 is interrupted, so that the control sleeve 24 is moved by the control closing spring 34 to its control valve seat 27. As a result of the fuel flowing in through the inlet throttle 20 into the control chamber 18, the pressure in the control chamber 18 increases rapidly, so that the injection valve element 3 moves downwards onto its valve seat in the drawing plane and thus interrupts the fuel flow through the injection openings 6.

In Fig. 6, a possible embodiment of the seat portion of the control valve 25 is shown enlarged. Evident is the control sleeve 24, in which the pressure pin 29 is received and thus the radially outwardly limited by the control sleeve 24 pressure chamber 23 in the axial direction in the plane of the drawing seals and absorbs the pressure forces. Evident is also the frontal sealing portion 35 of the control sleeve 24 with its annular sealing surface 36 which cooperates with the outer truncated cone-shaped control valve seat 27.

Evident is also the flow channel 21, can flow from the fuel from the control chamber into the pressure chamber 23. The cone angle α of the control valve seat 27 is about 120 ° in the embodiment shown. Preference is given to an even greater design of the cone angle, in particular of about 160 °. The cone angle is formed by the lateral surface 37 of the control valve seat 27, more precisely by two sections of the lateral surface 37 accommodating in a plane receiving the longitudinal central axis L of the control valve seat. By selecting the cone angle α, a slip occurs when striking the control sleeve 24 in the radial direction relative to the control valve seat 27 at least largely avoided.

As is also apparent Fig. 2 results, the sealing surface 36, which cooperates with the lateral surface 37 on an inner cone-shaped portion 26 with an inner cone angle β of about 125 ° in this embodiment. It is essential that the inner cone angle β of the annular sealing surface 36 having portion 26 which is arranged on the axial extension 38, (something) is greater than the cone angle α of the outer frustoconical control valve seat 27th

It can also be seen that the sealing surface 36 is arranged on an annular axial extension 38 on the end face of the control sleeve 24, wherein the sealing surface 36 extends directly from the inner circumference of the control sleeve 24 both in the radial and in the axial direction. The axial extension 38 with the sealing surface 36 having inner cone-shaped portion 26 is radially outwardly slightly concave curved in an end face annular surface 39 of the control sleeve, wherein the annular surface 39 is located in a plane perpendicular to the longitudinal central axis L level. As a result, the maximum extent, which is limited by wear increasing sealing surface 36.

Claims (10)

1. Control valve for a fuel injector having a control sleeve (24) which delimits a pressure space (23) and which is mounted such that it can be moved in the longitudinal direction, the control sleeve (24) having, on its end side, a sealing face (36), by way of which it interacts with an outwardly frustoconical control-valve seat (27) which is formed on a valve body (28), characterized in that the cone angle of the control-valve seat (27) is selected from a value range between 120° and 170°.
2. Control valve according to Claim 1, characterized in that the cone angle of the control-valve seat (27) is selected from a value range between 130° and 170°, in particular from a value range between 140° and 170°, preferably from a value range between 150° and 170°, particularly preferably between 155° and 165°.
3. Control valve according to either of Claims 1 and 2, characterized in that the cone angle is approximately 160°.
4. Control valve according to one of Claims 1 to 3, characterized in that the sealing face (36) is formed on an inner cone-shaped section (26) of the control sleeve (24).
5. Control valve according to Claim 4, characterized in that the inner cone angle of the section (26) which has the sealing face (36) is greater than the cone angle of the control-valve seat (27).
6. Control valve according to Claim 5, characterized in that the inner cone angle is greater than the cone angle of the control-valve seat (27) by an angle from a value range between 1° and 10°, in particular between 2° and 9°, preferably between 3° and 6°.
7. Control valve according to one of Claims 4 to 6, characterized in that the sealing face (36) adjoins the inner circumferential wall of the control sleeve (24) and extends from this radially to the outside and in the axial direction.
8. Control valve according to one of Claims 4 to 7, characterized in that the sealing face (36) is arranged on an end-side, annular axial projection (38) of the control sleeve (24) and is adjoined radially on the outside by an annular face (39) which extends transversely with respect to the longitudinal extent of the control sleeve (24) or, with an imaginary plane which is arranged transversely with respect to the longitudinal extent of the control sleeve (24), encloses an angle in a range between -20° and +20°.
9. Control valve according to one of the preceding claims, characterized in that, when it bears against the control-valve seat (27), the control sleeve (24) is pressure-equalized in the axial direction.
10. Fuel injector for the injection of fuel into a combustion chamber of an internal combustion engine, in particular common-rail injector, having a control valve (25) according to one of Claims 1 to 9, by way of which the fuel pressure in a control chamber (18) which is operatively connected to an injection-valve element (3) can be influenced, it being possible for the injection-valve element (3) to be adjusted as a function of the fuel pressure in the control chamber (18) between a closed position and an open position which releases the fuel flow into the combustion chamber.

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