WO2008046677A2 - Fuel injector comprising a sealing element - Google Patents

Abstract

The invention relates to a fuel injector (10) comprising an injector member (12) and a high-pressure chamber (68) that is subjected to system pressure (86). The high-pressure chamber (68) is sealed against a low-pressure zone (70) of the injector member (12) by means of a sealing element (64, 80) which has a U-shaped (84) cross section. The open end of the sealing element (64, 80) faces the high-pressure chamber (68).

Description

 description

title

Fuel injector with solenoid valve

State of the art

DE 196 50 865 A1 relates to a solenoid valve for controlling the fuel pressure in a control chamber of an injection valve, such as a common rail high-pressure accumulator injection system. Via the fuel pressure in the control chamber, a stroke movement of a valve piston is controlled, with which an injection opening of the injection valve is opened or closed. The solenoid valve comprises an electromagnet, a movable armature and a valve member which is moved with the armature and acted upon by a valve closing spring in the closing direction and which cooperates with the valve seat of the solenoid valve and thus controls the fuel drain from the control chamber.

There is known a common rail injector for use in high-pressure storage chambers comprehensive injection systems, wherein in an injector body in a Einspritzventilgliedfüh- tion guided injection valve member is received. The injection valve member is actuated by pressurization or pressure relief of a control chamber formed in the injection valve member guide. The control chamber communicates with a high-pressure chamber via a supply throttle element, so that it is always filled with a sufficient control volume. The pressure in the control chamber is relieved by the operation of a two-part armature, which is attracted by a solenoid valve. The armature exerts the closing force on a valve ball in the currentless case. When the electromagnet is energized, the armature moves upwards by the armature stroke, the closing force acting on the valve ball becomes zero, and an outflow valve opens. An armature guide, which is bolted firmly in the injector body of the fuel injector, receives the anchor bolt. On the anchor bolt, the anchor plate is guided, which in turn is attracted by the electromagnet.

In the common-rail injector, the high-pressure space, which is filled with pressurized fuel under system pressure, is sealed against an underlying low-pressure space, which is coaxial with the injection valve member between the injection valve guide and the injector body and acts as a leakage space. Conventionally, for this purpose, a Teflon sealing ring is used, which is stabilized by a support ring.

Disclosure of the invention

According to the invention, instead of the previously used combination of a sealing ring of Teflon and a support ring, which is used below the sealing ring made of Teflon, use a U-shaped profiled sealing ring made of a metallic material. For example, in the metallic material, a soft annealed steel having a carbon content in the range of 0.5% to 0.8% may be used.

Due to the geometry of the sealing ring in U-shape is achieved that this on its open side by the pressure prevailing in the high-pressure chamber system pressure, d. H. the high-pressure fuel, is applied and is pressed to its receiving surface within the fuel injector. As a result, a high migration of the sealing ring is prevented, since the z. B. in a high pressure accumulator body (common rail) prevailing system pressure in addition to the U-shaped profiled sealing ring presses against the formed in the injector body sealing surface and thus gives him a much higher permanent biasing force, as is the case with the previously used sealing rings made of Teflon. Due to the biasing force generated by the system pressure, the high migration of the sealing ring and thus the cancellation of the sealing effect of the sealing ring is effectively prevented, since the movement of the sealing ring on the valve member within the fuel injector is additionally inhibited upwards by self-locking.

The inventively proposed U-shaped profiled sealing ring can not hineinzuextrudieren in the gap between the axial bore of the injector body and embedded in this leadership of the injection valve member, since the metallic material does not tend to flow in the context of plastic deformation, compared to a sealing ring, the Teflon material is made. Furthermore, can be dispensed with by the inventively proposed solution to the previously used support ring, since the present invention proposed U-shaped profiled seal the required mechanical stability is already inherent. The inventively proposed profiled sealing ring may instead of a U-profile and a V-shaped profiling or a rectangular, stepped profiling have depending on the purpose and injector design.

drawing With reference to the drawing, the invention will be described below in more detail.

It shows:

Figure 1 shows a cross section through an actuatable by a solenoid valve fuel injector according to the prior art and

FIG. 2 shows a comparison of the sealing concept known from the prior art and the seal proposed according to the invention within the fuel injector.

variants

Figure 1 shows a cross section through a fuel injector according to the prior art, which is actuated by means of a solenoid valve.

A fuel injector 10 as shown in Figure 1 comprises an injector body 12 in which a solenoid valve 14 is received. From the solenoid valve 14, a magnetic core 20 and the magnetic core 20 enclosed by the magnetic coil 22 are shown in the Dar position according to FIG. The solenoid coil 22 of the solenoid valve 14 is energized via not shown in Figure 1 electrical connections. In the injector body 12 of the fuel injector 10, an armature assembly 16 is arranged, which comprises an armature guide 30, an anchor bolt 32 and an anchor plate 34 and is formed in several parts. An armature spring 36, which biases the armature plate 34 against the anchor bolt 32, is located between the anchor plate 34 displaceably mounted on the anchor bolt 32 and a lower stop on the armature guide 30. Above the armature assembly 16 is located in a passage opening 24 of the magnetic core 20, a closing spring 18. A dial 26 is enclosed by a hat-shaped locking sleeve 28.

The armature guide 30 of the armature assembly 16 as shown in Figure 1 is attached via a clamping screw 38 in the injector body 12 of the fuel injector 10 and biased against an injection valve member guide 58 with an intermediate classified shim 42.

In the armature guide 30 are bores 40, via which flows from a control chamber 52 of the fuel injector 10 controlled amount of a low-pressure side return 62 flows. On the underside of the anchor bolt 32 there is a closing element guide 44 which partially encloses a closing element 46 which is shown spherically in FIG. About the anchor bolt 32 of the armature assembly 16, the here formed spherical locking element 46 is placed in its closing seat 48 and closes an outlet throttle 50 of the control chamber 52. The control chamber 52 is acted upon via an inlet throttle 54 with fuel under system pressure via a high-pressure chamber 68. The fuel under system pressure flows to the injector body 12 of the fuel injector 10 via a high-pressure port, via which the fuel injector 10 as shown in Figure 1 with a high pressure storage space of a high-pressure injection system such. B. is connected to a common rail injection system for self-igniting internal combustion engines.

In the illustration according to FIG. 1, the ball-shaped closing element 46 is placed in its closing seat 48. As a result, no control quantity can flow out of the control chamber 52 of the fuel injector 10, the control chamber 52 is subjected to system pressure, so that the injection needle member 56, which is shown only in part in FIG. 1 and is preferably needle-shaped, remains seated, ie. H. At the combustion chamber end of the fuel injector 10 formed injection openings for injecting fuel into the combustion chamber of the internal combustion engine remain closed.

The illustration according to FIG. 1 shows that the high-pressure chamber 68 is sealed against a low-pressure space 70, which extends substantially coaxially with the injection-valve element guide 58, via a Teflon sealing ring 64 and a support ring 66 arranged underneath.

Due to the material properties of the sealing ring 64, it tends to migrate into a gap resulting between the injection valve member guide 58 and the injector body 12. Furthermore, the sealing ring 64, which is made of Teflon, has the property to migrate on the outside of the injection valve member guide 58, so that this from the point to be sealed between the high-pressure chamber 68 and the low-pressure side gap between the injection valve member guide 58 and the inner wall of the Injector body 12 removed, which on the one hand leads to pressure loss in the high pressure chamber 68 and on the other hand, an undesirable leakage entails and can lead to total injector failure.

2, the sealing concept according to the prior art set forth in FIG. 1 is compared with the seal proposed according to the invention. represents, in each case on a greatly enlarged scale, wherein the proposed sealing concept is not shown to scale as a functional example.

From the representation according to FIG. 2 it can be seen that a low-pressure space 70 is formed between the outer circumference of the injection valve member guide 58 and the bore of the injector body 12, into which the injection valve member guide 58 is embedded. The high-pressure chamber 68, into which fuel that is under system pressure via a connecting piece, is sealed in accordance with the prior art by means of the Teflon sealing ring 64 and the support ring 66 arranged underneath, as illustrated on the left side of the illustration of FIG is.

As a result of the system pressure prevailing in the high-pressure chamber 68, the control chamber 52 is filled via the inlet throttle 54 with fuel under system pressure, so that it is ensured that the control chamber 52 is always under system pressure.

Following the proposed solution according to the invention, a U-shaped sealing ring 80 is used instead of the previously used components sealing ring 64 and support plate 66. The U-shaped sealing ring 80 includes an abutment surface 82 from which a first, vertically tapered flank 88 abuts with its outer surface on the periphery of the Einspritzventilgliedführung 58, and a second, also in the vertical direction tapered Flank 90, which rests with its outer surface on a surface of the injector 12, extend from. The ring-shaped bottom of the sealing ring 80 in a U-shape forming abutment surface 82 rests on a shoulder which is formed in the injector body 12 of the fuel injector 10 on. The sealing ring 80 formed in a U-shape is open at its end opposite the contact surface 82 and exposed to the system pressure prevailing in the high pressure chamber 68, indicated by the arrows shown in FIG.

The geometry of the U-shaped profiled sealing ring 80 proposed according to the invention ensures that the system pressure 86 prevailing in the high pressure chamber 68 assists the sealing effect of the sealing ring 80. By prevailing in the high-pressure chamber 68 system pressure 86 on the one hand, the U-shaped cavity of the sealing ring 80 is subjected to system pressure and both the bottom of the sealing ring 80 forming abutment surface 82 is pressed into the shoulder of the injector 12, and the first, in the vertical direction to the open end tapered edge 88 and the second, also in the vertical direction tapered flank 90 of the sealing ring 80 expanded and pressed against their respective contact surfaces. This meant that by the system pressure 86, the first, in the vertical direction tapered edge 88 against a plant surface surface 94 of the injection valve member guide 58 and the second, also in the vertical direction to the open end of the sealing ring 80 tapered flank 90 are pressed against a contact surface 96 on the inside of the high-pressure chamber 68 in the injector body 12.

Due to the geometry of the preferably made of metallic material, U-shaped profiled sealing ring 80 of the system pressure 86, which is to be sealed against the low pressure chamber 70, used to increase the sealing force to improve the sealing effect of the U-shaped sealing ring 80. Due to the U-shaped design of the sealing ring 80, the tapered flanks 88, 90 are pressed at their respective upper ends by the system pressure 86 with a larger contact force against their corresponding contact surfaces than at the base of the flanks 88, 90 of the sealing ring 80. This will an underflow of the sealing ring 80 by fuel under high pressure along the contact surfaces 94, 96 avoided.

The flanks 88 and 90, which extend parallel to the longitudinal axis 60 of the fuel injector 10, starting from the contact surface 82 of the annular sealing element 80, taper continuously or discontinuously in the vertical direction towards the open end of the sealing element 80 - The cross section, so that the sealing member 80 is arranged self-locking. The self-locking of the sealing element 80 is further increased by the system system 86 still reinforced conditioning of the outer sides of the two flanks 88, 90 on the corresponding sealing surfaces 94 and 96 of the injection valve member guide 58 and the injector body 12. The U-shape 84 of the sealing element 80 is preferably produced by material-removing laser processing, which is a high-precision production of vertically tapering, parallel to the longitudinal axis 60 of the fuel injector 10 extending, tapered flanks 88, 90 of preferably a metallic material or a Ensured alloy of several metallic materials made sealing member 80.

In addition to the continuously tapered first flank 88 shown in FIG. 2 and the continuously tapered second flank 90, there is also the possibility of forming the flanks 88, 90 discontinuously. A discontinuous configuration of the profiling 84 formed in the sealing ring 80 can be given for example by a rectangular-shaped profiling, which is stepped. In this exemplary embodiment, a first rectangular groove formed below the end face of the sealing ring 80, wherein extending a likewise rectangular shaped, partially annular groove formed below the first formed in the material of the sealing ring 80 profiling. In addition to the formation of the flanks 88 and 90 in connection with the illustration of FIG. 2 For example, the U-shape 84 in the sealing ring 80 can also be V-shaped or have a rectangular shape.

Embodiments in which the assembly of the Einspritzventilgliedführung 58 pulls a twisting of the sealing ring 80 by itself, the injection valve member guide 58 assigning flank of the sealing ring 80 is made thicker. The profile formed in the material of the sealing ring 80, preferably in U-shape, is produced in all its variants, preferably by way of laser technology.

Claims

claims A fuel injector (10) having an injector body (12) and a high-pressure space (68) under system pressure (86), which is sealed by means of a sealing element (64, 80) against a low-pressure region (70) of the injector body (12) in that the sealing element (80) has a substantially U-shaped cross-section (84) and assigns its open end to the high pressure space (68). 2. Fuel injector (10) according to claim 1, characterized in that the sealing element (80) is annular and has a bottom forming Anlagefiäche (82). 3. Fuel injector (10) according to claim 1, characterized in that the sealing element (80) has at least one, in the vertical direction tapered flank (88, 90). 4. fuel injector (10) according to claim 3, characterized in that the sealing element (80) is preferably two in the vertical direction extending, tapered Flanks (88, 90). 5. Fuel injector (10) according to claim 1, characterized in that the sealing element (80) is made of a metallic material or an alloy of metallic materials. 6. Fuel injector according to claim 4, characterized in that the system pressure (86) the two in the vertical direction extending, tapered flanks (88, 90) on sealing surfaces (94, 96) hires. 7. Fuel injector according to claim 2, characterized in that the bottom of the sealing element (80) forming abutment surface (82) rests directly on a shoulder in the injector body (12). 8. Fuel injector according to claim 1, characterized in that in U-shape (84) formed cross-section in the sealing element (80) is made by laser machining. 9. Kraftstoffϊnjektor according to claim 4, characterized in that the material thickness of the two flanks (88, 90) decreases from the contact surface (82) of the sealing element (80), starting from the open end continuously or discontinuously. 10. Fuel injector according to claim 4, characterized in that the sealing element (80) is received with self-locking between an injection valve member guide (58) and the high-pressure chamber (68) of the injector body (12).