GB2574449A

GB2574449A - Valve for an internal combustion engine

Info

Publication number: GB2574449A
Application number: GB1809344.3A
Authority: GB
Inventors: Guisasola Inigo
Original assignee: Caterpillar Energy Solutions GmbH
Current assignee: Caterpillar Energy Solutions GmbH
Priority date: 2018-06-07
Filing date: 2018-06-07
Publication date: 2019-12-11
Anticipated expiration: 2038-06-07
Also published as: GB2574449B; DE102019115200A1; GB201809344D0

Abstract

A valve 1 for an internal combustion engine includes a valve head 12 to abut against a valve seat 22 of a cylinder head 2 comprises a valve stem 10 to be slidably received in a valve guide 3 of the cylinder head. The valve stem includes a transport pocket 5 for transporting lubrication fluid beyond a gasket 4 of the valve guide. The transport pocket may be a bore, indentation, milling or embossing within the material of the valve stem. Preferably, the transport pocket has a main extension between an opening 50 and an end section provided at an angle with respect to the longitudinal extension of the valve stem. Multiple pockets may be included in the valve stem preferably at an even distribution, which may be arrange at different horizontal planes. An embossing tool is also claimed.

Description

Valve for an internal combustion engine

Technical Field [0001] The present invention relates to a valve for an internal combustion engine, for example to be used in a natural gas internal combustion engine with a high specific output.

Technological Background [0002] Valves for combustion engines are well known. Such a valve for an internal combustion engine usually includes a valve head which is to abut against a corresponding valve seat of a cylinder head of the internal combustion engine in order to open and close an inflow or outflow port of a cylinder cavity during operation. The valve usually comprises a valve stem which is at least partially received in a valve guide situated at the cylinder head. By means of the valve guide, the valve is enabled to conduct a reciprocating movement for opening and closing the respective port of the cylinder cavity.

[0003] The valve stem typically extends between a distal end and the valve head, wherein the valve stem as well as the valve head may be made integrally from a single piece of material or the valve may comprise more than one material in order to accommodate different requirements.

[0004] The reciprocating movement of the valve is typically induced by a cam of a revolving cam shaft wherein the cam is in direct or indirect contact with the distal end of the valve stem. In other arrangements, the valve may also be moved by one or several intermediate elements which transfer the reciprocating movement of the cam to the valve.

-2[0005] The valve guide in the cylinder head typically includes some means for lubricating the valve stem at least in the area where it is received in the valve guide in order to provide lubrication.

[0006] US 4,022,294 discloses a device for lubricating the guiding system of an internal combustion engine valve mounted with its valve stem in a guide. [0007] US 5,904,125 discloses an exhaust valve for internal combustion engines having a solid lubricant coating at the valve stem.

[0008] The valve seat situated in the cylinder head abuts against the valve head in order to close the respective inlet port or outlet port of the cylinder cavity. In order to reduce wear of the valve head as well as wear of the valve seat, there is a need of also lubricating the valve seat and the valve head during operation.

Summary of the invention [0009] Starting from the prior art, it is an objective to improve the lubrication of a valve head of a valve for an internal combustion engine, in particular for a natural gas internal combustion engine of high specific output.

[0010] This objective is solved by means of the valve for an internal combustion engine with the features of claim 1. Preferred embodiments are set forth in the present specification, the Figures as well as the dependent claims.

[0011] Accordingly, a valve for an internal combustion engine, preferably for a natural gas internal combustion engine, is proposed wherein the valve includes a valve head to abut against a valve seat of a cylinder head and wherein the valve includes a valve stem to be slidably received in a valve guide of the cylinder head. The provision of a transport pocket in the valve stem for transporting lubrication fluid beyond a gasket of the valve guide is proposed.

Brief description of the drawings [0012] The present disclosure will be more readily appreciated by reference to the following detailed description when being considered in connection with the accompanying drawings in which:

-3[0013] Figure 1 is a schematic cross-section through a valve and a cylinder head in a first position of the valve in which the valve head abuts against a cylinder seat and the port is closed;

[0014] Figure 2 shows the valve of Figure 1 in a second position of the valve with the port opened and the valve head lifted away from the valve seat;

[0015] Figure 3 shows further exemplary embodiments of a valve in a schematic cross-section;

[0016] Figure 4 shows a schematic cross-section through the valve stem viewed from the top;

[0017] Figure 5 is a schematic perspective partial view and a schematic cross-section of a valve stem according to another embodiment;

[0018] Figure 6 is a detailed schematic cross-sectional view of a transport pocket according to the embodiment of Figure 5;

[0019] Figure 7 schematically shows an embossing tool for providing transport pockets in a valve stem of a valve;

[0020] Figure 8 schematically shows different angles for using the embossing tool according to Figure 7; and [0021] Figure 9 schematically shows an embossing tool in another embodiment for providing transport pockets in a valve stem.

Detailed description of preferred embodiments [0022] In the following, the invention will be explained in more detail with reference to the accompanying figures. In the Figures, like elements are denoted by identical reference numerals and repeated description thereof may be omitted in order to avoid redundancies.

[0023] In Figure 1 a valve 1 is shown which is schematically sketched situated at least partially in a cylinder head 2 comprising an inlet port 20. The valve 1 includes a valve stem 10 and a valve head 12, wherein valve stem 10 and valve head 12 may be provided integrally made from a single piece of material.

-4However, in different embodiments the valve 1 may also be made from more than one material. The valve stem 10 may also be welded to the valve head 12. [0024] The valve head 12 has a front circular face 16 and a valve seat area 18, which is intended to abut against a valve seat 22 of the cylinder head 2 in order to close the port 20.

[0025] In operation, the valve 10 reciprocates in the direction indicated by the arrow X in Figure 1 in order to open and close the port 20 in the cylinder head 2. The port 20 may be an inlet port into the cylinder cavity in order to allow for an inflow of a gas mixture, for example a mixture of natural gas and air, into the cylinder cavity. The port 20 can alternatively also be an exhaust port through which the hot gases are expelled from the cylinder cavity after combustion.

[0026] The circular face 16 of the valve head 12 may have a diameter of about 52 mm in a large natural gas internal combustion engine. A typical diameter for most of the length of the valve stem is about 10.6 mm in a large natural gas internal combustion engine. The stem 10 is preferably made of 4140steel. The valve stem 10 may, in a different embodiment, also be welded to the valve head 12.

[0027] The valve stem 10 comprises a distal end 14 which is intended to extend beyond the cylinder head 2 through the port 20 and which may be in contact with a cam of a revolving cam shaft (not shown) to control the movements of the valve 1 and to induce a reciprocating movement of the valve 1 during operation. The valve stem 10 may alternatively be connected by different bars and rockers with a tappet roller which rolls on the cam of the cam shaft and transfers the rotating movement of the cam to a reciprocating movement.

[0028] When the valve 1 is in a position in which the port 20 is closed, as shown in Figure 1, the valve seat area 18 of the valve head 12 abuts against the valve seat 22 of the cylinder head 2. The valve seat area 18 is defined by the overlap between the valve head 12 and the valve seat 22 and provides for a sealing of the port 20 when the valve head 12 abuts against the valve seat 22. In the valve seat area 18 there may be full contact between the valve seat 22 and the

-5valve head 12 when the valve head 12 abuts against the valve seat 22. In alternative embodiments, the contact between the valve head 12 and the valve seat 22 in the valve seat area 18 may be partial, for example in the form of a ring or more than one ring.

[0029] In Figure 2, the valve 1 is shown in an open position in which the valve 1 is moved downwards such that port 20 is open. In this position, the valve seat area 18 of the valve head 12 is lifted away from the valve seat 22.

[0030] In an embodiment of a natural gas internal combustion engine, the displacement between the fully closed position as shown in Figure 1 and the fully opened position as shown in Figure 2 may be induced by a movement of the valve head 12 of about 16 mm from the fully closed position to the fully opened position.

[0031] The valve stem 10 is guided in a valve guide 3, which is schematically shown in Figure 1. The valve stem 10 is mounted slidably within the valve guide 3 such that the valve 1 can move in a reciprocating movement during operation of the engine.

[0032] The valve guide 3 may be made out of a cast iron or a powered metal.

[0033] The valve guide 3 has an internal bore 36 that laterally supports the valve stem 10. The clearance between the surface of the bore 36 and the valve stem 10 may be around 10 pm, which his sufficient to maintain an oil film given manufacturing tolerances and thermal expansion, yet tight enough to allow for only little wobble of the valve 1.

[0034] The valve guide 3 shown in the embodiment of Figure 1 includes an upper valve guide section 30 and a lower valve guide section 32. Between the upper valve guide section 30 and the lower valve guide section 32 a lubricating area 34 is situated.

[0035] The lubricating area 34 is supplied with a lubricating fluid, usually oil under pressure. The lubricating fluid provided in the lubricating area 34 is in direct contact with the section of the valve stem 10 received in the valve guide 3. The lubricating fluid is intended to lubricate the valve stem 10 with respect to the

-6valve guide 3 in order to ensure smooth movement of the valve stem 10 in the valve guide 3 and in order to reduce wear.

[0036] In the lower valve guide section 32 a gasket 4 is provided for example in the form of an elastomeric O-ring as a sealing element. Other types of sealing elements may also be used as the gasket 4. The gasket 4 is intended to seal the lubricating area 34 of the valve guide 3 against the valve stem 10 in a direction towards the valve head 12. Even though only a single O-ring is shown in the Figures, the sealing element forming the gasket 4 may also include more than one sealing element.

[0037] The lubrication area 34 of the valve guide 3 may be constantly provided with lubrication fluid under pressure, for example with oil under pressure. Accordingly, an oil film is present at least between the surface of the bore 36 of the valve guide 3 and the outer surface of the valve stem 10 in the areas distal from the gasket 4. The gasket 4 is intended to seal the lubricating area 34 such that the lubricating fluid can be provided under pressure.

[0038] The gasket 4 may be provided such that small quantities of oil may pass between the gasket 4 and the valve stem 10 such that oil may flow in a film along the valve stem towards the valve head 12. The oil film provided may reach the valve seat area 18 and may serve to lubricate the valve seat area 18 and also the valve seat 22 of the cylinder head 2.

[0039] However, in engines of high specific output, and in particular large natural gas internal combustion engines, the pressure at the port 20 may be so high that lubricating fluid from the lubricating area 34 is not inclined to flow past the gasket 4 and towards the cylinder head 12 anymore and in particular does not flow towards the valve seat area 18 of the valve 1. Accordingly, appropriate amounts of lubrication fluid from the lubrication area 34 cannot make their way towards the valve seat area 18 of the valve head 12 such that the valve seat area 18 as well as the valve seat 22 may not be lubricated sufficiently.

[0040] In order to improve this situation, Figure 1 shows transport pockets 5 in the valve stem 10 which are intended to transport lubrication fluid from the

-7lubrication fluid area 34 beyond the gasket 4 in normal operation of the valve 1. Due to the provision of the transport pockets 5, the transport of the lubrication fluid takes place irrespective of the pressures of the lubricating fluid in the lubricating area 34 and the pressure at the port 20. Accordingly, the valve seat area 18 of the valve head 12 as well as the valve seat 22 can be lubricated sufficiently despite the high pressures at the port 20 and/or despite the high specific output of the engine.

[0041] Each of the transport pockets 5 has an opening 50 at the surface of the valve stem 10 and extend towards the inside of the valve stem 10. The transport pockets 5 terminate inside of the valve stem 10 at an end section 52 of the transport pockets 5. The end section 52 of the transport pocket 5 is situated inside the valve stem 10.

[0042] The gasket 4 divides the valve stem 10 in a first section which is situated towards the distal end 14 of the valve stem 10 and a second section which is situated towards the valve head 16. Accordingly, in the following reference will be made to a “distal section 42” of the valve stem 10 which spans between the distal end 14 and the gasket 4. Reference will also be made to a “valve head section 44” of the valve stem 10 which spans between the gasket 4 and the valve head 16. The dimensions of the two sections 42, 44 vary depending on the current opening status of the valve 1.

[0043] For example, when the valve 1 is in its fully closed position in which the valve head 16 abuts against the valve seat 22 - as it is shown in Figure 1 - the valve head section 44 is shorter than in a situation in which the valve 1 is its fully opened position where the valve head 16 is lifted away from the valve seat 22 as shown in Figure 2. Vice versa, the distal section 42 is longer in a situation when the valve 1 is in its fully closed position in which the valve head 16 abuts against the valve seat 22 - as it is shown in Figure 1 - and the distal section 42 is shorter in a situation in which the valve 1 is its fully opened position where the valve head 16 is lifted away from the valve seat 22 as shown in Figure 2.

-8[0044] The transport pockets 5 and, in particular, their openings 50, are provided in the valve stem 10 in a manner such that at least the openings 50 of the transport pockets 5 are situated in the distal section 42 in an fully closed end position of the valve 1, which is shown, for example, in Figure 1. In other words, in a fully closed end position of the valve 1, the openings 50 of the transport pockets 5 are arranged at the valve stem 10 such that they are positioned distal to the gasket 4 with respect to the cylinder head 2 and are in fluid connection with the lubrication fluid in the lubricating area 34.

[0045] In a fully opened end position of the valve 1, which is shown, for example, in Figure 2, the openings 50 of the transport pockets 5 are situated in the valve head section 44. In other words, in the fully opened end position of the valve 1, the openings 50 of the transport pockets 5 are situated at a position between the gasket 4 and the cylinder head 2 such that lubrication fluid may flow freely from the transport pockets 5 towards the valve head 12 and towards the valve seat area 18.

[0046] Accordingly, by means of the reciprocating movement of the valve 1 during operation, the openings 50 of the transport pockets 5 move between a position in which they are situated in the distal section 42 and thus are in fluid connection with the lubricating area 34 and a position in which they are situated in the valve head section 44 and thus outside of the lubricating area 34. Between the extreme end positions, the openings 50 of the transport pockets 5 pass the gasket 4. When the openings 50 of the transport pockets 5 are situated in the valve head section 44, they are also situated between the gasket 4 and the valve head 12.

[0047] By this movement of the openings 50 of the transport pockets 5 from the lubricating area 34 beyond the gasket 4, the transport pockets 4 may transport lubricating fluid from the lubricating area 34 beyond the gasket 4 such that the lubricating fluid may provide a film around valve stem 10 as well as around valve head 12 and in particular flow towards the valve seat section 18 of the valve head

-912 in order to lubricate the valve seat section 18 of the valve head 12 as well as the valve seat 22.

[0048] The transport pockets 5 are shown in Figures 1 and 2 to be formed in the form of bores which are provided in an angled manner in the valve stem 10 such that the opening 50 of the bore forming the transport pocket 5 is in a position closer to the valve head 16 than its end section 52. In other words, the main extension direction of the transport pockets, here the drilling axis of the bores, encloses an angle smaller than 90° with the longitudinal extension of the valve stem 10, wherein the angle opens towards the valve head 16.

[0049] As shown in Figure 4, the transport pocket 5 may have a main extension between an opening 50 and an end section 52 of the transport pocket 5 and the projection of the main extension of the transport pocket 5 onto a plane perpendicular to the main extension of the valve stem 12 is radial to the main extension of the valve stem 10.

[0050] A transport pocket 5 extending radially in this plane may still be inclined in the manner described above such that the radial extension is intended to refer to the extension of the transport pockets in plane perpendicular to the extension of the valve stem 10 only.

[0051] As can be seen in Figures 1 and 2, the position of the opening 50 of the transport pocket 5 in the valve stem 10 is arranged such that the distance between the opening 50 and the gasket 4 may be same in the fully closed position of the valve 1 as shown in Figure 1 and the fully opened position of the valve 1 as shown in Figure 2.

[0052] This is also schematically shown in Figures 1 and 2 by means of an upper lift plane UL and a lower lift plane LL which are approximately symmetrical with respect to a plane G defined by the gasket 4.

[0053] The distance between the upper lift plane UL and the lower lift plane LL corresponds to the maximum valve lift.

[0054] This also implies that the opening 50 of the valve pocket 5 passes the gasket 4 approximately in the middle of the valve lift where also the velocity of

-10the valve stem 10 vis-a-vis the gasket 4 may be the highest. Accordingly, at the position of maximum valve speed an oil film is already present between the valve stem 10 and the gasket 4 such that no damage or wear of the gasket 4 may occur even though the opening 50 of the transport pocket 5 is sliding past the gasket 4. [0055] Figure 3 schematically shows alternative embodiments of the transport pockets 5 in the form of short bores or less steeply angled bores.

[0056] The transport pockets 5 may generated in the valve stem 10 by means of drilling, stamping, striking, laser structuring, embossing, pressing etc.

[0057] Figure 5 shows yet another embodiment of transport pockets 5, in a schematic perspective partial view of the valve stem 10 and also in a schematic cross-section. In this embodiment, the valve stem 10 comprises three rings of openings 50 of transport pockets 5 which are evenly distributed along the circumference of the valve stem 10. The transport pockets 5 may extend from an opening 50 towards an end section 52 such that they have a defined extension in the valve stem 10.

[0058] The openings 50 of the transport pockets 5 in the embodiment shown may be distributed evenly around the circumference of the valve stem 10.

[0059] The openings 50 of the transport pockets 5 in the embodiment shown may also be arranged in three parallel planes spaced apart from another along the valve stem 10.

[0060] Figure 6 is a detailed cross-sectional view of an individual transport pocket 5 according to another embodiment. According to this embodiment, the transport pocket 5 comprises a tapered form, in particular the form of an oblique cone, wherein the main axis of the cone is inclined towards the distal end 14 of the valve stem 10. Transport pockets 5 in this shape can be embossed in the valve stem 10 by means of an embossing needle which is guided along an inclined path towards the valve stem 10.

[0061] Figure 7 schematically shows an embossing tool 6 for providing the valve stem 10 of the valve 1 with the transport pockets 5.

-11[0062] The tool 6 comprises a receptacle 60 which receives the valve head

12. The receptacle 60 is coupled via a joint 63 with a C-shaped embossing die 62, which includes an embossing edge 64 which is intended to emboss the transport pocket into the valve stem 10.

[0063] By exerting a force in the direction of the arrow F, the embossing edge 64 is pressed into the valve stem 10 due to the joint 63 and the contact of a pivot point 66 of the embossing die 62 against a table 68. Accordingly, the embossing die 62 produces with its embossing edge 64 an indentation or embossing in the valve stem 10.

[0064] Figure 8 shows different angles which are intended to be used for embossing with the embossing edge 64 against the valve stem 10. Embossing edge 64 preferably is a needle-shaped point.

[0065] Alternatively, the embossing tool 6 may comprise a plurality of Cshaped embossing dies, indicated at reference sign 62’, each coupled to the receptacle 60 via a respective joint 62. Thus, a plurality of transport pockets 5 can be embossed into the valve stem 10 in a single embossing step.

[0066] In Figure 9 a different embossing tool 6 is shown, which uses the same principle as that shown in Figure 7, but in which the valve 1 is arranged in an upside-down manner respective to Figure 7.

[0067] Accordingly, the distal end 19 of the valve stem 10 is received in the receptacle 60. The joints 63 are provided to hold the embossing dies 62 which are arranged symmetrically. An embossing edge 64 is present again on both sides and by pressing down the valve 1 in the direction of the arrow F, a pivoting movement about the contact pivot point 66 with the table 68 is achieved such that the embossing edges 64 press against the valve stem 10.

[0068] By applying a predetermined impact force on the surface of the valve face 16 of the valve 1, the embossing edges 64 are protruded into the valve stem 10 with a predetermined force, thus inducing transport pockets 5 of a predetermined depth, here about 10 pm, as shown in Figure 6.

-12[0069] A coating, for example a hard chrome coating, may be provided on the valve 1. The coating may have a thickness of about 10-20 pm.

[0070] It is intended that the transport pockets 5 are provided in the valve stem 10 in a depth of about 5-15 pm, preferably about 10 pm such that the transport pockets 5 may be defined by the coating.

[0071] During final polishing the gratings and irregularities which may have been provided by inserting the pockets may be smoothened out. The roughness of the valve stem 10 of the valve 1 after final polishing may be about 0.8 pm.

[0072] Twelve transport pockets 5 may be situated around the circumference of the valve stem 10, i.e. one transport pocket 5 every 30°.

[0073] It will be obvious for a person skilled in the art that these embodiments and items only depict examples of a plurality of possibilities. Hence, the embodiments shown here should not be understood to form a limitation of these features and configurations. Any possible combination and configuration of the described features can be chosen according to the scope of the invention.

[0074] This is particular the case with respect to the following optional features which may be combined with some or all embodiments, items and/or features mentioned before in any technically feasible combination.

[0075] For example, a valve for an internal combustion engine is proposed, preferably for a natural gas internal combustion engine, including a valve head to abut against a valve seat of a cylinder head and including a valve stem to be slidably received in a valve guide of the cylinder head, wherein the valve stem includes a transport pocket for transporting lubrication fluid beyond a gasket of the valve guide.

[0076] By means of providing the valve stem with at least one transport pocket for transporting lubrication fluid beyond the gasket of the valve guide, lubrication fluid may be transported from the valve guide or its lubrication area towards the valve seat area.

-13[0077] The transport pocket in the valve stem may be arranged in such a way that it may transport the lubrication fluid from a lubrication area in the valve guide beyond the valve guide and its gasket(s) towards the valve seat during the reciprocating movement of the valve. The reciprocating movement of the valve may then transport lubrication fluid, which may be provided in the form of oil, from the valve guide area beyond the gasket which seals the lubrication area. The lubrication fluid may then flow along the valve stem towards the valve head such that it may distribute itself in the area of the valve seat as well. The lubrication fluid transported by the transport pockets, thus, may serve to lubricate parts of the surface of the valve seat of the cylinder head and the valve seat area of the valve head.

[0078] By means of this arrangement, the transport pockets may receive and release lubrication fluid such that it may flow towards the valve head for lubricating the valve seat area and the valve seat.

[0079] The transport pockets may be provided by means of bores, embossings, indentations, millings, or other defined structures which have dimensions fit to receive the lubrication fluid while in the lubrication area of the valve guide and also fit to release the lubrication fluid once they have passed the gasket restricting the lubrication area. In other words, the dimensions of the transport pockets are such that - bearing in mind the viscosity of the lubrication fluid - they may receive and release the lubrication fluid in an efficient manner. [0080] The transport pockets in the valve stem may be generated by operations like stamping, striking, embossing, laser structuring, pressing, drilling, milling etc.

[0081] The transport pocket may have an opening in the valve stem and the opening may be positioned in the valve stem such that in a fully closed end position of the valve, the opening may be positioned between the gasket and a distal end of the valve stem and in a fully opened end position of the valve, the opening may be positioned between the gasket and the valve head.

-14[0082] The opening of the transport pocket may be spaced apart from the gasket in the fully closed end position of the valve by the same distance as in the fully opened end position of the valve. In other words, the opening of the transport pocket may be positioned in the valve stem such that it travels the same distance with respect to the gasket while opening and while closing the valve.

[0083] Due to this arrangement, the opening of the transport pocket may pass the gasket at a high valve velocity as it may be typically the middle of the opening or closing stroke. At this high velocity a lubrication fluid film may be present between the valve stem and the gasket such that additional wear of the gasket due to the reciprocating movement of the openings can be reduced or even avoided.

[0084] Thus, the small amount of additional lubrication fluid which may be transported by means of the transport pockets from the lubrication area beyond the gasket is transported such that additional wear, which would extend beyond the typical wear of the gasket, may be reduced or even avoided.

[0085] The transport pocket may have a main extension between an opening and an end section and the main extension may be provided at an angle with respect to the longitudinal extension of the valve stem.

[0086] The transport pocket may further be angled such that the opening of the transport pocket is closer to the valve head than the end section of the transport pocket.

[0087] The main extension of the transport pocket may further enclose an angle smaller than 90° with the longitudinal extension of the valve stem, preferably an angle between 20° and 80° or between 30° and 70° or between 40° and 60°.

[0088] In other words, the individual transport pockets may be inclined towards the valve head such that a lubrication fluid transported in the transport pockets may be pressed into the transport pockets while the valve stem is accelerated at the beginning of the opening movement and the lubrication fluid

-15may be expelled from the inclined pockets at the end of the opening movement when the speed of the valve is decelerated.

[0089] The transport pocket may have a depth of about 5-15 pm, preferably a depth of up to about 10 pm. These measures may allow for transportation of a sufficient and adequate amount of lubrication fluid via the transport pockets while any weakening of the integrity of the valve stem can be neglected.

[0090] The transport pocket may have a main extension between an opening and an end section and the projection of the main extension onto a plane perpendicular to the main extension of the valve stem may be radial to the main extension of the valve stem.

[0091] More than one transport pocket may be provided in the valve stem in order to evenly distribute the lubrication fluid.

[0092] The openings of the transport pockets may be distributed evenly around the circumference of the valve stem. The openings of the transport pockets may also be arranged in different horizontal planes in the valve stem.

[0093] Furthermore, an embossing tool for embossing a transport pocket into a valve stem of a valve may be provided, the tool may comprise a receptacle for receiving a valve head or a distal end of the valve, a substantially C-shaped embossing die comprising an embossing edge for embossing the transport pocket into the valve, wherein the embossing die is coupled to the receptacle via a joint.

[0094] By means of this arrangement, the transport pockets may be embossed into the valve stem in an easy, reproducible and reliable manner. Furthermore, there may be no need for an additional treatment in a high cost tooling machine.

[0095] If a plurality of embossing dies each coupled to the receptacle via a respective joint are provided, a plurality of transport pockets may be induced into the valve stem within one step.

[0096] The transport pockets may be embossed into the valve stem via applying a predetermined impact force on the valve received in the receptacle, such that the embossing edges are protruded into the valve stem with a predetermined force, thus inducing transport pockets of a predetermined depth.

-16Industrial applicability [0097] By means of providing the valve stem 10 with at least one transport pocket 5 for transporting a lubrication fluid beyond the gasket 4 of the valve guide 3, lubrication fluid may be transported from the valve guide 3 or its lubrication area 34 towards the valve seat area 18.

[0098] By means of the provision of the transport pockets 5 in the valve stem 10, lubrication fluid may pass beyond the gasket 4 such that the lubrication fluid may flow along the surface of the valve stem 10 and towards the valve head 12 even if higher cylinder pressures are present in an internal combustion engine with higher specific outputs. Thus, the valve 1 as described above may have improved characteristics in terms of the lubrication of the valve head 12 as well as the lubrication of the valve seat area 18, leading to reduced wear.

[0099] By providing the individual transport pockets 5 in an angled and/or inclined manner, further preferred characteristics may be obtained during movement of the valve 1. During acceleration of the valve 1 downwards, the lubrication fluid 34 may be pressed into the transport pocket 5 as it may act against the inertia of the fluid. At the lower position, the valve 1 may be decelerated such that the inertia of the lubrication fluid in the transport pocket 5 expels the lubrication fluid out of the transport pockets 5 again.

[00100] Accordingly, an efficient transport of lubrication fluid from the lubrication area 34 beyond the gasket 4 may be achieved which may be provided with every reciprocating movement of the valve 1.

[00101] By means of the transport pockets 5, the wear of the valve seat area 18 of the valve head 12 as well as the valve seat 22 may be reduced even in larger natural gas internal combustion engines of high specific output.

The valve 1 described above may also be used as a replacement or retrofit part for replacing valves in existing internal combustion engines in order to improve the lubrication of the valve seat area 18.

-17List of reference numerals valve valve stem valve head distal end valve face valve seat area cylinder head port valve seat valve guide upper valve guide section lower valve guide section lubrication area bore gasket distal section valve head section transport pocket opening end portion tool receptacle embossing die joint embossing edge pivot point table

UL upper lift plane

-18LL lower lift plane

G plane of gasket

Claims

Claims What is claimed is:

1. Valve (1) for an internal combustion engine, preferably for a natural gas internal combustion engine, including a valve head (12) to abut against a valve seat (22) of a cylinder head (2) and including a valve stem (10) to be slidably received in a valve guide (3) of the cylinder head (2), wherein the valve stem (10) includes a transport pocket (5) for transporting lubrication fluid beyond a gasket (4) of the valve guide (3).

2. Valve (1) according to claim 1, wherein the transport pocket (5) is a bore or an indentation or a milling or an embossing provided in the material of the valve stem (10).

3. Valve (1) according to claim 1 or 2, wherein the transport pocket (5) has an opening (50) in the valve stem (10) and the opening (50) is positioned in the valve stem (10) such that in a fully closed end position of the valve (1), the opening (50) is positioned between the gasket (4) and a distal end (14) of the valve stem (10) and in a fully opened end position of the valve (1), the opening (50) is positioned between the gasket (4) and the valve head (12).

4. Valve (1) according to claim 3, wherein the opening (50) of the transport pocket (5) is spaced apart from the gasket (4) in the fully closed end position of the valve (1) by the same distance as in the fully opened end position of the valve (1).

5. Valve (1) according to any one of the preceding claims, wherein the transport pocket (5) has a depth of about 5-15 pm, preferably a depth of up to about 10 pm.

6. Valve (1) according to any one of the preceding claims, wherein the transport pocket (5) has a main extension between an opening (50) and an end section (52) and the main extension is provided at an angle with respect to the longitudinal extension of the valve stem (10).

7. Valve (1) according to claim 6, wherein the transport pocket (5) is angled such that the opening (50) of the transport pocket (5) is closer to the valve head (12) than the end section (52) of the transport pocket (5).

8. Valve (1) according to claim 6 or 7, wherein the main extension of the transport pocket (5) encloses an angle smaller than 90° with the longitudinal extension of the valve stem (10), preferably an angle between 20° and 80° or between 30° and 70° or between 40° and 60°.

9. Valve (1) according to any one of the preceding claims, wherein the transport pocket (5) has a main extension between an opening (50) and an end section (52) and the projection of the main extension onto a plane perpendicular to the main extension of the valve stem (12) is radial to the main extension of the valve stem (10).

10. Valve (1) according to any one of the preceding claims, wherein more than one transport pockets (5) are provided in the valve stem (10).

11. Valve (1) according to claim 10, wherein the openings (50) of the transport pockets (5) are distributed evenly around the circumference of the valve stem (10).

12. Valve (1) according to claim 10 or 11, wherein the openings (50) of the transport pockets (5) are arranged in different horizontal planes in the valve stem (10).

13. Embossing tool (6) for embossing a transport pocket (5) into a valve stem (10) of a valve (1), comprising a receptacle (60) for receiving a valve head (12) or a distal end (19) of the valve (1), a substantially C-shaped embossing die (62) comprising an embossing edge (64) for embossing the transport pocket (5) into the valve (1), wherein the embossing die (62) is coupled to the receptacle (60) via a joint (63).

14. Embossing tool (6) according to claim 13, further comprising a plurality of embossing dies (62), each coupled to the receptacle (60) via a respective joint (63).

15. Embossing tool (6) according to claim 13 or 14, configured such that by means of providing a predetermined impact force on the valve (1) received in the receptacle (60), the embossing edges (64) are protruded into the valve stem (10) with a predetermined force, thus embossing transport pockets (5) of a predetermined depth.