DE102018221086A1 - Valve for metering a fluid, in particular fuel injection valve - Google Patents

Abstract

The valve according to the invention, in particular the fuel injection valve, is distinguished by the fact that it can be used for higher fluid pressures despite the reduced geometrical dimensioning. The fuel injection valve (1) comprises an excitable actuator (15) for actuating a valve closing section (21), which forms a sealing seat together with a valve seat surface (14) formed on a valve seat body (13), and spray orifices (4) which are located downstream of the valve seat surface ( 14), and an axially movable valve needle (11) which has a valve needle shaft (19) with which a guide section (30) and the valve closing section (21) are formed in one piece. According to the invention, the guide section (30) is formed with a cylindrical outer contour between the cylindrical valve needle shaft (19) and the valve closing section (21), the center point M of an imaginary ball with the diameter D3, which the spherically shaped sealing seat surface (28) has on the The central axis of the valve needle shaft (19) lies in the axially short guide section (30).

Description

State of the art

The invention is based on a valve for metering a fluid, in particular a fuel injection valve according to the preamble of the main claim.

In the 1 shows, by way of example, a fuel injection device known from the prior art, in which a fuel injection valve is provided in a receiving bore in a cylinder head of an internal combustion engine. The fuel injection device is particularly suitable for use in fuel injection systems of mixed-compression spark-ignition internal combustion engines. The valve has a valve housing, which includes, among other things, a valve seat support which receives a valve seat body and is fixedly connected to the valve seat body. A valve closing body interacts with the valve seat body to form a sealing seat. The valve seat body is typically a ball, for example a ball bearing ball, which is attached to a solid valve needle shaft, for example by welding. Together, the valve seat body and the valve needle shaft form an axially movable valve needle, which has its lower guide in the area of the spherical valve closing body (e.g. DE 10 2005 052 255 A1 or DE 100 55 513 A1 ).

It is also known from the DE 101 08 945 A1 to provide a valve needle in a fuel injection valve for a fuel injection system of mixed-compression spark-ignition internal combustion engines, in which a ball is fastened to a hollow valve needle shaft as a valve closing body.

It is also from the DE 10116 186 A1 Already known to form a valve needle as a solid rod-shaped, largely circular cross-section valve needle, which has a valve closing section at its downstream end, which emerges directly from the rod. This, for example spherical or partially spherical or rounded, or tapered valve closing section interacts in a known manner with the valve seat surface provided in the valve seat element. The lower guidance of the valve needle is realized in the area of a cylinder section of the rod-shaped valve needle.

Advantages of the invention

The valve according to the invention for metering a fluid with the characterizing features of claim 1 has the advantage that it can be used for higher fluid pressures despite reduced geometrical dimensions. The geometry of the valve needle is advantageously optimized at its downstream end in such a way that a small guide diameter of the valve needle is achieved, hydraulic loads in the sealing seat area are reduced or a larger wall thickness of the valve seat body is permitted in the area of the guide and no additional joining steps are required during its manufacture will.

In order to achieve these advantages, according to the invention the guide section with a cylindrical outer contour of a very short axial length is integrally formed together with the valve needle shaft and the valve closing section between the cylindrical valve needle shaft and the valve closing section.

This geometric design reduces the Hertzian pressure of the valve needle on the valve seat surface compared to known spherical valve closing body solutions. In this way, higher injection pressures can be realized. For example, Customer requirements for the direct injection of mixture-compressing spark-ignition internal combustion engines with fluid pressures of> 350 bar up to 500 - 600 bar can be implemented. Valve seat bodies with a smaller outside diameter can advantageously be used, so that the diameter of the cylinder head bores for the valves can also be reduced. Alternatively, however, valve seat bodies with greater radial wall thickness can also be realized for a given outer diameter, which increase the pressure stability and the robustness against corrosion.

Due to the center of the imaginary sphere placed on a pivot point M, the diameter advantageously lies D3 , which the spherically shaped sealing seat has, on the central axis of the valve needle shaft in the middle in the axially short guide section.

Advantageous further developments and improvements of the valve specified in claim 1 are possible through the measures listed in the subclaims.

Due to its design, the valve closing section gimbally seals against the valve seat surface. Because the diameter D2 of the guide section regardless of the size of the diameter D3 of the sealing seat surface, the guide diameter corresponding to D2 can advantageously be made smaller than in known solutions. Tolerance-related oblique positions of the valve needle can be compensated for by slightly turning or tilting the valve needle around the above-mentioned pivot point M. When the valve needle is tilted, there is advantageously no change in the Sealing diameter D4 , and the valve closing section seals over the entire circumference on the valve seat surface.

Figure list

• 1 einen schematischen Schnitt durch ein Brennstoffeinspritzventil in einer bekannten Ausgestaltung mit einem Abspritzöffnungen aufweisenden Ventilsitzkörper am stromabwärtigen Ventilende und
• 2 das abströmseitige Ventilende in einer erfindungsgemäßen Ausgestaltung der Ventilnadel im Bereich von unterer Führung und Ventilschließabschnitt als Ausschnitt II von 1 in einer vergrößerten Darstellung.

Embodiments of the invention are shown in simplified form in the drawing and explained in more detail in the following description. Show it

• 1 a schematic section through a fuel injector in a known embodiment with a spray orifice having valve seat body at the downstream valve end and
• 2nd the downstream valve end in an embodiment of the valve needle according to the invention in the region of the lower guide and valve closing section as a cutout II from 1 in an enlarged view.

Description of the embodiments

An in 1 illustrated known example of a fuel injector 1 is in the form of a fuel injector 1 designed for fuel injection systems of mixture-compressing, spark-ignited internal combustion engines. The fuel injector 1 is particularly suitable for injecting fuel directly into a combustion chamber (not shown in detail) 25th an internal combustion engine. In general, the invention is applicable to valves for metering a fluid.

With a downstream end is the fuel injector 1 in a mounting hole 20th a cylinder head 9 built-in. A sealing ring 2nd , especially made of PTFE or PTFE with fillers, ensures an optimal seal of the fuel injector 1 opposite the wall of the location hole 20th of the cylinder head 9 .

The fuel injector 1 points at its inlet end 3rd a connector to a fuel rail, not shown, through a sealing ring 5 between a connection piece of the fuel distribution line and an inlet piece 7 of the fuel injector 1 is sealed. The fuel injector 1 has an electrical connector 8th for the electrical contact to actuate the fuel injector 1 .

Between a valve housing 22 and one, for example, at right angles to the longitudinal extent of the receiving bore 20th trending shoulder 23 the mounting hole 20th is for example a decoupling element 24th inserted, which serves to compensate for manufacturing and assembly tolerances and a shear-free bearing even with slight misalignment of the fuel injector 1 ensures. This also results in optimized noise decoupling. The decoupling element 24th is, for example, using a lock washer 39 secured.

The valve housing 22 of the fuel injector 1 is inter alia through the inlet connection 7 , but also from a nozzle body 10th formed in which a valve needle 11 is arranged. The valve needle 11 stands in such a typical and usual design with a spherical valve closing body 12 in operative connection by being attached to a rod-shaped valve needle shaft 19th is firmly connected by welding. The valve closing body 12 works with one on a valve seat body 13 arranged valve seat surface 14 to form a sealing seat. At the fuel injector 1 in the exemplary embodiment, it is an inward opening fuel injector 1 which has at least one spray orifice 4th has, but typically at least two spray orifices 4th having. The fuel injector 1 is ideally designed as a multi-hole injection valve and therefore has between four and thirty spray orifices 4th .

An electromagnetic circuit, for example a magnetic coil, serves as the drive 15 comprises as an actuator, which is encapsulated in a coil housing and wound on a coil carrier, which has an inner pole 16 surrounds. An armature also belongs to the electro-magnetic circuit 17th that on the valve pin 11 is arranged. In the idle state of the fuel injector 1 becomes the anchor 17th from a return spring 18th acted against its stroke direction so that the valve closing body 12 on the valve seat 14 is kept in a sealing system. When the solenoid is excited 15 this builds up a magnetic field, which is the anchor 17th against the spring force of the return spring 18th moved in the stroke direction. The anchor 17th takes the valve needle 11 also in the stroke direction. The one with the valve pin 11 related valve closing body 12 lifts from the valve seat 14 and the fuel is discharged through the orifices 4th hosed.

If the coil current is switched off, the armature drops 17th after sufficient reduction of the magnetic field by the pressure of the return spring 18th from the inner pole 16 off, causing the valve needle 11 moved against the stroke direction. This sets the valve closing body 12 on the valve seat 14 on, and the fuel injector 1 will be closed.

This embodiment of the fuel injection device is a system for direct gasoline injection with fuel injection valves 1 which, as shown, with an electromagnetic actuator, but also with piezo actuators operated and used, for example, in a constant pressure system.

The axially movable valve needle 11 has its lower guide area in the area of the spherical valve closing body 12 along a cylindrical wall of the central opening of the valve seat body 13 . The guide diameter is comparatively large because of the spherical valve closing body 12 has a larger diameter than that of the solid valve needle shaft 19th . This dimensioning in turn requires a comparatively large diameter of the sealing seat and the outside diameter of the valve seat body 13 , so that there is a high hydraulic load on the sealing seat. With such a known solution, it is also particularly important to ensure that the valve needle shaft 19th and the valve closing body 12 are welded exactly coaxially to each other. This dimensioning also requires a comparatively small wall thickness of the valve seat body 13 in the area of the guide for a given outer diameter of the valve housing or nozzle body 10th .

The object of the invention is therefore to provide a valve needle that is optimized in its geometry at its downstream end 11 to provide for a valve for metering a fluid, in particular a fuel injection valve, which allows smaller guide diameters and the reduced hydraulic loads in the sealing seat area or a larger wall thickness on the valve seat body 13 allow and which does not require additional joining steps in their manufacture.

2nd shows the downstream valve end in a configuration according to the invention as a section II from 1 in an enlarged view. It can be seen that the valve needle shaft 19th integrally into a valve closing section at its downstream end 21st passes, wherein between the cylindrical valve needle shaft formed with a constant diameter 19th and the valve closing section 21st an axially short guide section having a cylindrical outer contour 30th is formed.

The 2nd illustrates the shape of, for example, one to five, in particular three, recesses serving as flow pockets 31 , the groove-shaped, axially extending in the inner opening of the valve seat body 13 are formed to the unimpeded flow of the fluid to be dispensed to the valve seat 14 to guarantee. The recesses 31 are extensive, ideally evenly distributed over the circumference of the inner opening of the valve seat body 13 arranged. Between the recesses 31 there are guide regions of the valve seat body each having cylindrical wall regions, viewed over the circumference 13 on which the valve needle 11 during its axial movement at the level of the short cylindrical guide section 30th to be led.

Also shows 2nd the valve needle designed according to the invention 11 in the area of the lower guide with the guide section 30th and valve closing section 21st . From the anchor 17th the cylindrical valve needle shaft starts out 19th the valve needle 11 towards the valve closing section 21st largely with a constant diameter D1 . At the end of the needle, this constant-cylindrical section is followed by a slight taper, which begins with a conical bevel, for example has a cylindrical taper section subsequently, and which then continues to widen conically. The cylindrical guide section immediately adjoins this 30th which is followed in the downstream direction by a conically tapered stem region and in turn by the integral valve closing section 21st connects, which is cylindrical, for example.

The leadership section 30th has a cylindrical outer contour with a small axial length which is only between 0.02 mm and 0.3 mm, in particular approximately 0.05 mm to 0.1 mm. The valve needle shaft 19th has in the area of the management section 30th a diameter D2 . The leadership section 30th serves the lower guidance of the valve needle 11 in the valve seat body 13 .

The one-piece molded valve closing section 21st has an outer diameter D5 . In one section to the valve seat 14 is the valve closing section 21st with a constant outside diameter D5 provided so that this section is cylindrical. Between the cylindrical area with the diameter D5 and the seating area of the valve closing section 21st may be a transition in the form of a chamfer or a radius. With the tapered valve seat 14 acts as a sealing seat 28 of the valve closing section 21st to the sealing seat, which is spherical, with a diameter D3 . According to the invention, the center M of the imaginary sphere is located with the diameter D3 at a point on the central axis of the valve needle shaft 19th at least approximately in the axially short guide section 30th , ideally in the middle of the axially short guide section 30th . The sealing seat line between the valve seat surface 14 and sealing seat 28 runs on a diameter D4 .

Due to its design, the valve closing section seals 21st gimbal against the valve seat 14 from. Because the diameter D2 regardless of the size of the diameter D3 , the guide diameter corresponding to D2 can be in advantageously be carried out smaller than in known solutions. Tolerance-related oblique positions of the valve needle 11 can by slightly twisting or tilting the valve needle 11 around the pivot point M mentioned above. When the valve needle is tilted 11 there is advantageously no change in the sealing diameter D4 , and the valve needle lies with its valve closing section 21st nevertheless extensive on the diameter D4 on the valve seat body 13 on. For manufacturing and assembly reasons as well as for an optimized sealing in the sealing seat, the following should apply: D1> = D2; especially also D1> = D2> D5. In particular, the guide section can be so 30th better process in its cylindrical shape by, for example, continuous grinding. Practical size information should be mentioned below as an example: D1 = 1.9 mm; D2 = 1.9 mm; D3 = 3 mm; D4 = 1.5 mm; D5 = 1.7 mm. These sizes are only intended to roughly indicate the relationships to one another; Deviations from the concrete dimensions are conceivable. These dimensions do not limit the invention in any way.

This geometric design allows the wall thickness of the valve seat body 13 be made larger in the area of leadership. In this way, higher injection pressures can in turn be achieved, and there is increased stability against corrosion, which is otherwise from the outside and from the inside of the valve seat body 13 could attack. For example, customer requirements can also be met for the direct injection of mixed-compression spark-ignition internal combustion engines with fluid pressures of> 350 bar to 500 - 600 bar. Valve seat bodies can advantageously 13 with a smaller outer diameter, so that the diameter of the cylinder head bores for the valves 1 can be reduced.

QUOTES INCLUDE IN THE DESCRIPTION

This list of documents listed by the applicant has been generated automatically and is only included for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent literature cited

• DE 102005052255 A1 [0002]
• DE 10055513 A1 [0002]
• DE 10108945 A1 [0003]
• DE 10116186 A1 [0004]

Claims (10)

Valve for metering a fluid, in particular fuel injection valve (1), in particular for injecting fuel directly into a combustion chamber, for fuel injection systems of internal combustion engines, with an excitable actuator (15) for actuating a valve closing body (12) which, together with a valve seat body ( 13) formed valve seat surface (14) forms a sealing seat, and at least one spray opening (4), which is formed downstream of the valve seat surface (14), and with a valve needle (11), which has a valve needle shaft (19), together with the one piece Guide section (30) and a valve closing section (21) are formed, characterized in that on the valve closing section (21) of the valve needle (11) a sealing seat surface (28) is formed, which is designed spherically with a diameter D3 and with the conical valve seat surface ( 14) cooperates with the sealing seat and between the cylindrical valve needle shaver ft (19) and the valve closing section (21) of the guide section (30) is cylindrical, the center M of an imaginary ball with the diameter D3 on the central axis of the valve needle shaft (19) being approximately in the axially short guide section (30). Valve after Claim 1 , characterized in that the valve needle shaft (19) is formed with a diameter D1, the guide section (30) with a diameter D2 and the valve closing section (21) with an outer diameter D5, D1> = D2, in particular D1> = D2> D5. Valve after Claim 2 , characterized in that D3> D2 applies. Valve according to one of the preceding claims, characterized in that the valve needle (11) runs with a largely cylindrical valve needle shaft (19) over its axial length, which is followed by a slight taper which continues to widen conically and on which the cylindrical guide section (30) which is followed by a conically tapering stem region in the downstream direction and in turn is followed by the valve closing section (21) which is formed in one piece. Valve according to one of the preceding claims, characterized in that the valve closing section (21) is provided in a section up to the valve seat surface (14) with a constant outer diameter D5, so that this section is cylindrical. Valve after Claim 5 , characterized in that between the cylindrical section with the diameter D5 and the spherical sealing seat surface (28) of the valve closing section (21) the transition is in the form of a chamfer or a radius. Valve according to one of the preceding claims, characterized in that the cylindrical guide section (30) has a small axial length which is between 0.02 mm and 0.3 mm, in particular approximately 0.05 mm to 0.1 mm. Valve according to one of the preceding claims, characterized in that the guide section (30) with its cylindrical outer contour can be shaped by means of continuous grinding. Valve according to one of the preceding claims, characterized in that the sealing seat line between the valve seat surface (14) and the sealing seat surface (28) runs on a diameter D4, where D4 <D5 <D2. Valve according to one of the preceding claims, characterized in that the valve seat body (13) has in its inner opening one to five recesses (31) serving as flow pockets, which run in a groove-shaped manner and between which guide regions of the valve seat body (viewed over the circumference) each have cylindrical wall regions. 13) are formed, on which the valve needle (11) is guided during its axial movement at the level of the cylindrical guide section (30).

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