DE102022213511A1 - Gas injector with improved needle guide - Google Patents

Abstract

The present invention relates to a gas injector for blowing in a gaseous medium, in particular hydrogen, comprising an actuatable closing element (6) which opens and closes a through-opening (20) on a sealing seat (5) of a valve body (21), wherein the closing element (6) is designed as part of a valve needle (4). The valve needle (4) has at least one guide element (25) for guiding the valve needle (4) in a valve housing (21) during its axial movement along an axial direction X-X. According to the invention, a particle deflector (28, 29) is fluidically connected upstream of the at least one guide element (25), which ensures that particles are kept away from the circumferential guide surface (26) of the guide element (25).

Description

State of the art

The present invention relates to a gas injector for injecting a gaseous fuel, e.g. hydrogen or methane or the like, directly into a combustion chamber of an internal combustion engine with an improved needle guide.

Gas injectors are known from the state of the art in various designs. Compared to fuel injectors for liquid fuels, the technical requirements for gas injectors are significantly different. In addition to a lack of lubrication from a liquid fuel, a significantly larger volume of the gaseous medium is particularly problematic. This can lead to problems with the exact metering for an injection process. Furthermore, high temperatures arise during operation, particularly in the area of a sealing area between a closing element and a valve seat of the gas injector. The combustion gases during operation, which reach up to the sealing area between the closing element and the valve seat, can result in increased temperatures in the sealing area, which leads to increased wear and possible increased distortion of the components. This can lead to leaks in the seat area in particular.

From the EN 10 2020 201 973 A1 For example, a gas metering valve for an internal combustion engine is known which has a housing in which a gas chamber is formed. A movable valve element is arranged in the gas chamber, which can be moved by an electric actuator against the force of a return spring and which interacts with a valve seat to open and close the valve. A valve needle, which is designed together with a closing member, has at least one guide area. The valve needle opens with the closing member towards the combustion chamber, so that it is an outward-opening gas metering valve.

The valve needle guides are designed with very small guide clearances due to their essential centering function of the sealing seat and to avoid bearing tilting with the associated tendency to wear. To ensure good centering of the valve needle and the largest possible contact surface to reduce wear, a guide surface is usually designed to be circumferential.

A disadvantage of this type of needle guide design can be that the circumferentially closed guide surface forces particles in the gaseous fuel that reach the guide area from upstream in the gas injector into the narrow guide gap and become jammed. The result can be mechanical jamming due to tilting and/or adhesive and abrasive wear phenomena up to the tendency to seize. This is particularly critical in dry-running guides.

Interrupted guides, in which surface grindings or recesses in the guide area create the flow, are known as an alternative to closed guides. This type of guide design does offer the possibility of particles in the gas flowing through flow pockets formed by the grindings, which is why jamming is largely ruled out. The disadvantage of such a solution, however, is that the surface area that remains to represent the guide properties is significantly reduced and tilting can occur.

Disclosure of the invention

The gas injector according to the invention for blowing in a gaseous medium, in particular for blowing in gaseous hydrogen, with the features of claim 1 has the advantage that, despite a large circumferential guide surface, it is still possible to transport particles in the gas away. The guide surface is advantageously protected from particles in the fluid flow. This is achieved according to the invention in that a particle deflector is fluidically connected upstream of the at least one guide element on the valve needle, which ensures that particles are kept away from the circumferential guide surface of the guide element.

The subclaims show preferred developments of the invention.

It is particularly advantageous that the particle deflector has an inner opening for the flow of the gaseous fuel, which tapers conically in the direction of flow. In this way, the fluid flow is directed radially inwards towards the valve axis and thus away from the guide area which is further radially outwards. Furthermore, the build-up of a radial pressure gradient as a result of the acceleration of the fluid through the nozzle-like constriction of the particle deflector tends to deflect the particles in the direction of the needle-side flow openings of the guide element, since a higher static pressure prevails in the guide area of the guide surface than in the main flow field (Bernoulli effect).

To further enhance this effect, it is advantageous to provide at least one very small pressure equalization path that is smaller than the particles to be held back with their corresponding particle sizes. This pressure equalization path is located radially further out than the inner opening of the particle deflector. The pressure equalization path can "tap" the higher static pressure above upstream of the particle deflector at the start of the flow of the particle deflector. In the area between the particle deflector and the guide element, there is then a higher pressure than in the radially inner area of the transition from the reduced-diameter opening of the particle deflector to the flow openings, so that particles can flow radially outwards to the guide area can be excluded.

Advantageously, the particle deflector and the guide element can be designed with thin-walled ring collars or extensions that dip into each other so that there is a stroke overlap that, in the manner of a labyrinth seal, protects the guide area particularly effectively against particles of the gas flow.

The gas injector is preferably an outward opening injector.

drawing

• 1 eine schematische Schnittansicht eines bekannten Gasinjektors im geschlossenen Zustand,
• 2 eine schematische Schnittansicht des brennraumseitigen Endes des Gasinjektors von 1 im geöffneten Zustand,
• 3 eine schematische Schnittansicht eines Führungselements der Ventilnadel mit einem strömungstechnisch vorgeschaltetem Partikelabweiser gemäß einem ersten und zweiten Ausführungsbeispiel der Erfindung in einer Darstellung mit geöffnetem und geschlossenem Ventil und
• 4 eine schematische Schnittansicht eines Führungselements der Ventilnadel mit einem strömungstechnisch vorgeschaltetem Partikelabweiser gemäß einem dritten und vierten Ausführungsbeispiel der Erfindung in einer Darstellung mit geöffnetem und geschlossenem Ventil.

Preferred embodiments of the invention are described in detail below with reference to the accompanying drawings. In the drawing:

• 1 a schematic sectional view of a known gas injector in the closed state,
• 2 a schematic sectional view of the combustion chamber end of the gas injector of 1 in the open state,
• 3 a schematic sectional view of a guide element of the valve needle with a particle deflector arranged upstream in terms of flow technology according to a first and second embodiment of the invention in a representation with the valve open and closed and
• 4 a schematic sectional view of a guide element of the valve needle with a particle deflector arranged upstream in terms of flow according to a third and fourth embodiment of the invention in a representation with the valve open and closed.

Preferred embodiments of the invention

The following is based on the 1 to 4 the invention is described in detail according to various embodiments.

1 shows, by way of example and in a highly simplified manner, a gas injector 1 with a magnetic actuator 10. The magnetic actuator 10 comprises a magnetic coil 3 for acting on an axially movable armature 2, whereby the magnetic actuator 10 generally serves to actuate a closing element 6. The armature 2 is operatively connected to a valve needle 4, i.e. can be brought into contact in any case. The valve needle 4 comprises the closing element 6 at its downstream end, which opens and closes a through-opening 20 on a sealing seat 5 of a valve body 21, whereby the closing element 6 is designed, for example, as a valve disk of the valve needle 4. An injection cross-section can thus be opened at the sealing seat 5. The reference number 8 designates a return element of the gas injector designed as a helical spring. The closing element 6 is, for example, by means of a valve spring 7 in the 1 shown, closed position on the sealing seat 5.

When the magnetic coil 3 is energized, a magnetic field is formed, the magnetic force of which moves the armature 2 in the direction of the closing element 6, which is marked with the arrow 11. In this case, an armature bolt 9 connected to the armature 2, for example, comes into contact with the valve needle 4, so that the closing element 6 can lift off the sealing seat 5 against the spring force of the valve spring 7 and the through opening 20 is opened. The armature 2 is moved, for example, up to a stroke stop 16 for the armature 2, which represents the fully open state of the gas injector.

To close the gas injector 1, the current supply to the magnetic coil 3 is stopped so that the reset element 8 returns the armature 2 to the 1 At the same time, the valve spring 7 also returns the closing element 6 to the position shown in 1 shown, closed position. Due to the direction of movement of the closing element 6, this valve type is an outward opening valve.

As an alternative to the magnetic actuator 10 described, the closing element 6 can also be actuated by means of a piezo actuator (not shown). The valve needle 4 can also perform its opening movement outwards using a hydraulic transmission in addition to a mechanical transmission. It is also conceivable to open the valve needle 4 purely hydraulically via a pressure increase of the medium to be introduced. In addition, embodiments with Indirect control of the valve needle 4 via a servo principle can be realized.

The gas injector 1 is supplied with a gaseous fuel to be blown in, in particular hydrogen, via a schematically indicated gas supply line 12. In the gas supply line 12, for example, a pressure sensor 13 is arranged, which is connected to a control unit 14. The direction of gas flow is indicated by the arrows 15.

To guide the valve needle 4 in a valve housing, in particular also in the valve body 21 belonging to the valve housing, during its axial movement along the axial direction X-X of the gas injector 1, the valve needle 4 has at least one guide element 25. In the simplified embodiment shown, the valve needle 4 has two guide elements 25.

In the 2 the downstream end region of the gas injector 1 is shown enlarged as a partial view for a better understanding of the invention. A lower, downstream guide element 25 can be seen, which is either formed in one piece with the valve needle 4 or is securely and firmly attached to its shaft. The precise guidance of the valve needle 4 in the valve body 21 during its axial movement takes place via a circumferential guide surface 26, which is precisely machined for jam-free guidance. At least one flow opening 27 is provided in the guide element 25; normally between three and ten flow openings 27 are formed.

The guides of the valve needle 4 are generally designed with very small guide clearances due to their essential centering function of the sealing seat 5 and to avoid bearing tilting with the corresponding tendency to wear. To ensure good centering of the valve needle 4 and the largest possible contact surface to reduce wear, the guide surface 26 is usually designed to be circumferential.

A disadvantage of such a design of the needle guide can be that the circumferentially closed guide surface 26 forces particles in the gaseous fuel that reach the guide area from upstream in the gas injector 1 into the narrow guide gap and become jammed. The result can be mechanical jamming due to tilting and/or adhesive and abrasive wear phenomena up to the tendency to seize. This is particularly critical in the case of dry-running guides.

Interrupted guides, in which surface grindings or recesses in the guide area create the flow, are known as an alternative to closed guides. This type of guide design does offer the possibility of particles in the gas flowing through flow pockets formed by the grindings, which is why jamming is largely ruled out. The disadvantage of such a solution, however, is that the surface area that remains to represent the guide properties is significantly reduced and tilting can occur.

To prevent particles from entering the guide area in a guide with a circumferentially closed guide surface 26, as in 2 shown, a fluid mechanical design element is now proposed as the core of the invention, which keeps the flow away from the guide contact area and thus also the particles due to their mass inertia.

According to the invention, a design solution is therefore described which has a large circumferential guide surface 26 and which nevertheless enables the removal of particles. In a particularly advantageous manner, a particle deflector 28, 29, 30, 31 is arranged fluidically upstream of the at least one guide element 25 inside the gas injector 1, which ensures that particles are kept away from the circumferential guide surface 26 of the guide element 25.

In the 3 is a schematic sectional view of a guide element 25 of the valve needle 4 with a particle deflector 28, 29 arranged upstream of the valve in accordance with a first and second embodiment of the invention in a representation with the valve open and closed. The left side of the 3 the state of the valve needle 4 with the guide element 25 when the valve is closed, while on the right side the 3 the state of the valve needle 4 with the guide element 25 is shown when the valve is completely open. The double arrow 35 shows the dimension for the entire valve needle stroke.

In addition to the representation of the two maximum motion states of the valve needle 4 together in the 3 Furthermore, two different embodiments of the particle deflector according to the invention are shown. The 3 on the left side an embodiment of the particle deflector 28, which is formed in one piece together with the valve body 21 or another section of the valve housing. The particle deflector 28 is a component section which, for example, has an inner opening for the flow of the gaseous fuel with a slope running inwards towards the valve axis XX, which opening tapers conically. In this way, the fluid flow marked with arrows 32 is directed towards the valve axis XX and thus to the flow openings 27.

Furthermore, the build-up of a radial pressure gradient as a result of acceleration through the nozzle-like constriction of the particle deflector 28 causes the particles to be deflected in the direction of the needle-side flow openings 27, since a higher static pressure prevails in the guide area of the guide surface 26 than in the main flow field (Bernoulli effect). To further enhance this effect, a very small pressure equalization path 33, which is smaller than the particles to be held back with their corresponding particle sizes, can also be integrated. This pressure equalization path 33 can, for example, be a groove formed by a laser. The pressure equalization path 33 can "tap" the higher static pressure above upstream of the particle deflector 28 at the start of the flow of the particle deflector 28. In the area between the particle deflector 28 and the guide element 25, there is therefore a higher pressure than in the radially inner area of the transition from the reduced-diameter opening of the particle deflector 28 to the flow openings 27, so that a flow of particles radially outward to the guide area can be excluded. As an alternative to a single pressure equalization path 33, several pressure equalization paths 33 can also be provided distributed over the circumference.

Like in the 3 As shown on the right-hand side, the particle deflector 29 can also be an independent component, which can therefore optionally be inserted and fastened in a section of the valve body 21 specially designed for this purpose, e.g. with receiving shoulders, and has the same functionality as previously described.

The maximum outlet diameter of the inner opening of the particle deflector 28, 29 should not be larger than the maximum radial extent of the flow openings 27, so that an optimal flow transition is ensured.

In the 4 is a schematic sectional view of a guide element 25 of the valve needle 4 with a particle deflector 30, 31 arranged upstream of the valve in accordance with a third and fourth embodiment of the invention in a representation with the valve open and closed. The left side of the 4 the state of the valve needle 4 with the guide element 25 when the valve is closed, while on the right side the 4 the state of the valve needle 4 with the guide element 25 is shown when the valve is completely open. The double arrow 35 shows the dimension for the entire valve needle stroke.

In addition to the representation of the two maximum motion states of the valve needle 4 together in the 4 Furthermore, two different embodiments of the particle deflector according to the invention are shown. The 4 on the left side, an embodiment of the particle deflector 30, which is formed in one piece together with the valve body 21 or another section of the valve housing. The particle deflector 30 is a component section which, for example, has an inner opening for the flow of the gaseous fuel with a slope running inwards towards the valve axis XX, which tapers conically. In this way, the fluid flow marked with arrows 32 is directed towards the valve axis XX and thus towards the flow openings 27. The fluid mechanical effect also arises at the two in 4 illustrated embodiments as before to the first two embodiments according to 3 described.

To further enhance the Bernoulli effect achieved due to the geometric design, a very small pressure equalization path 33, which is smaller than the particles to be held back with their corresponding particle sizes, or several such pressure equalization paths 33 can be integrated. On the left side of the 4 this is indicated.

The two versions of the 4 are characterized in particular by the fact that the particle deflector 30, 31 has a downstream thin-walled ring collar 36. This ring collar 36, which is directed towards the guide element 25, represents a circular-cylindrical stroke overlap attachment which dips into a likewise thin-walled, upstream-directed, ring-collar-shaped extension 37 of the guide element 25 and thus the axially movable valve needle 4. The ring collar 36 of the particle deflector 30, 31 and the extension 37 of the guide element 25 have a large axial overlap length. In particular with large needle strokes, the penetration of particles into the guide area is thus very effectively prevented. This advantageous design has the structure of a labyrinth seal.

Like in the 4 As shown on the right-hand side, the particle deflector 31 can also be an independent component, which can therefore optionally be inserted and fastened in a section of the valve body 21 specially designed for this purpose, e.g. with receiving shoulders, and has the same functionality as previously described.

The maximum outlet diameter of the inner opening of the particle deflector 30, 31 in the area of the ring collar 36 should not be larger than the maximum radial extent of the flow openings 27 so that an optimal flow transition is ensured.

For all described embodiments, it should be noted that any combination of the features shown in the embodiments is possible.

QUOTES INCLUDED IN THE DESCRIPTION

This list of documents listed by the applicant was generated automatically and is included solely to provide the reader with better information. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions.

Cited patent literature

• DE 102020201973 A1 [0003]

Claims (11)

Gas injector for blowing in a gaseous medium, in particular hydrogen, comprising: - an actuatable closing element (6) which opens and closes a through-opening (20) on a sealing seat (5) of a valve body (21), wherein the closing element (6) is designed as part of a valve needle (4), - at least one guide element (25) for guiding the valve needle (4) in a valve housing (21) during its axial movement along an axial direction XX, characterized in that a particle deflector (28, 29, 30, 31) is fluidically connected upstream of the at least one guide element (25), which ensures that particles are kept away from the circumferential guide surface (26) of the guide element (25). Gas injector according to Claim 1 , characterized in that the particle deflector (28, 30) is formed in one piece together with the valve housing (21). Gas injector according to Claim 1 , characterized in that the particle deflector (29, 31) represents an independent component and can be inserted into a section of the valve housing (21) designed for this purpose and can be fastened there. Gas injector according to one of the preceding claims, characterized in that the particle deflector (28, 29, 30, 31) has an inner opening for the flow of the gaseous fuel, which tapers conically in the direction of flow. Gas injector according to Claim 4 , characterized in that at least one pressure equalization path (33) is provided, which is radially formed on a larger diameter than the opening width of the inner opening of the particle deflector (28, 29, 30, 31). Gas injector according to Claim 4 , characterized in that the at least one pressure equalization path (33) is arranged such that in a flow connection in the region between the particle deflector (28) and the guide element (25) a higher fluid pressure prevails than in the outlet region of the inner opening of the particle deflector (28, 29, 30, 31). Gas injector according to Claim 5 or 6 , characterized in that the opening width of the pressure equalization paths (33) is smaller than the particles to be kept out with their corresponding particle sizes. Gas injector according to Claim 5 , 6 or 7 , characterized in that the at least one pressure equalization path (33) is a groove formed by means of a laser. Gas injector according to one of the preceding claims, characterized in that the particle deflector (30, 31) has a downstream thin-walled annular collar (36) and the guide element (25) of the valve needle (4) has a thin-walled, upstream-directed, annular collar-shaped extension (37) of the guide element (25), wherein the annular collar (36) dips radially inside the extension (37). Gas injector according to one of the preceding claims, characterized in that the maximum outlet diameter of an inner opening of the particle deflector (28, 29, 30, 31) is not greater than the maximum radial extent of flow openings (27) which are introduced into the guide element (25). Gas injector according to one of the preceding claims, characterized in that the closing element (6) is an outward-opening closing element (6).

Images