Technical field [001 ] The present invention relates to a gas exchange valve assembly for an internal combustion engine comprising a valve member including a head and a stem part, and a guide member, in which the guide member is provided with a substantially cylindrical hole to co-operate with the stem part, into which hole the valve member is arranged when installed for operation and wherein the guide member is arranged to guide the valve member, the cylindrical hole having a first end and second end, and the guide member is provided with an opening extending through a wall of the guide member at a location between the ends, guiding area between the surfaces of the stem part of the valve member and the guide member is provided with longitudinally flow path extend- ing between the opening in the guide member and the second end of the cylindrical hole in the guide member.

Background art

[002] It is known as such, that during the gas exchange, when exhaust gases are removed from a cylinder of an internal combustion piston engine and fresh combustion air is introduced into the cylinder, both the exhaust and intake valve(s) may be open concurrently causing a so called scavenging stage.

[003] In gas operated internal combustion piston engines, denoted here as gas engines, fuel gas is usually introduced to the cylinder i.e. combustion chamber of the engine during the intake stroke along with the combustion air, so that the gas has been introduced in to the intake air before entering the cylinder.

[004] Now in case a scavenging stage is desired, it poses a risk of unburned fuel conveying, i.e. so called fuel slip, directly to the exhaust system, which is an undesired phenomena. [005] In document JP 2003138917 A there is disclosed gas fuel inlet port in connection with an intake valve stem. It is mention that the timing of opening the valve is thus set so that the fuel gas injected from the valve does not blow through a cylinder during a valve overlap period of the intake and exhaust valve.

[006] Corresponding solution is shown also in publications WO2012131956 A1 .

[007] There is a demand of continuously improve the operation of a gas engines both in fuel economy and emission wise. The manner of introduction the fuel gas into the combustion air is of great importance.

[008] An object of the invention is to provide gas exchange valve assembly in which the introduction of the fuel gas into the combustion is taken place by improved manner.

Disclosure of the Invention

[009] The objects of the invention can be met substantially as is disclosed in the independent claim and in the other claims describing more details of different embodiments of the invention.

[0010] A gas exchange valve assembly for an internal combustion engine according to the invention comprises a valve member including a head and a stem part, and a guide member, in which the guide member is provided with a substantially cylindrical hole to co-operated with for the stem part, into which hole the valve member is arranged when installed for operation and wherein the guide member is arranged to guide the valve member, the cylindrical hole having a first end and second end, and the guide member is provided with an opening extending through a wall of the guide member at a location between the ends, guiding area between the surfaces of the stem part of the valve member and the guide member is provided with longitudinally flow path extending between the opening in the guide member and the second end of the cylindrical hole in the guide member. The assembly is provided with a sealing arrangement which is arranged such that a flow connection out from the flow path in the guiding area is closed when the head of the valve member is in closing connection with a seat surface of the valve assembly, and further such that the flow path in the guiding area is arranged to open at a predetermined position of the valve member where the head of the valve member is at the predetermined distance from the seat surface. The assembly is provided with an annular gas sealing element arranged to the inner surface of the hole of the guide member at the second end thereof and the stem part comprises outer surface having an even flat circular section at a region which is in contact with the sealing element at least when the head of the valve is in closing connection with the seat sur- face.

[001 1 ] By this kind of a valve arrangement it is possible to accomplish a scavenging operation of a combustion chamber in an internal combustion engine with minimized risk of fuel slip through the combustion chamber.

[0012] In the valve assembly the sealing arrangement is arranged at a first distance from a fixed point in the seat surface. Such a fixed point may be for example predetermined location in an inner edge of the seat surface. Respectively, an end of the longitudinally flow path of the stem part on the side of valve head is arranged at a second distance D2 from the same fixed point the seat surface. The second distance is greater than the first distance. This way it is possible to open the valve at least to some extent and still maintain the flow connection out from the flow path in the guiding area closed while. Thus a safe scavenging may be provided without a risk of fuel slip into the atmosphere. The difference between the first and the second distance is selected according to the needs of the application. In case only minimal scavenging is desired the difference of the distances is as small as possible and respective, the difference is increased according to the need of the extent of scavenging. [0013] According to an embodiment of the invention the longitudinal flow path in the guiding area between the surfaces of the stem part of the valve member comprises longitudinal grooves arranged to the stem part of the valve member.

[0014] According to an embodiment of the invention the grooves are arranged to a separate sleeve part releasably fitted to the stem part. [0015] According to an embodiment of the invention the longitudinal flow path in the guiding area between the surfaces of the stem part of the valve member comprises longitudinal grooves arranged to the guide member. [0016] According to an embodiment of the invention the longitudinal flow path in the guiding area between the surfaces of the stem part of the valve member comprises longitudinal grooves arranged to the guide member and/or the stem part. [0017] According to an embodiment of the invention the grooves are arranged to a separate sleeve part releasably fitted to the guide member.

[0018] According to an embodiment of the invention that the grooves arranged to directly to the guide member.

[0019] According to an embodiment of the invention the longitudinal grooves are evenly distributed around the guiding area.

[0020] According to an embodiment of the invention radial depth of the groove is non-constant in longitudinal direction.

[0021 ] According to an embodiment of the invention the longitudinal flow path in the guiding area between the surfaces of the stem part of the valve member comprises first spiral grooves arranged to the stem part of the valve member and second spiral grooves arranged to the guide member, and the first and the second spiral grooves are contra-directed.

[0022] According to an embodiment of the invention the assembly is provided with the annular gas sealing element arranged to an annular recess on the in- ner surface of the hole of the guide member.

[0023] Gas injection may be controlled by inlet gas exchange valve. When valve is open, gas injection is open. In this kind of system gas supply may be controlled also with exhaust gas valve such that while exhaust gas valve is open, it will close gas supply ensuring that no fuel slip is going to take place during the scavenging. Implementation could be fully mechanic or electric or combination thereof. Brief Description of Drawings [0024] In the following, the invention will be described with reference to the accompanying exemplary, schematic drawings, in which

Figure 1 illustrates a gas exchange valve arrangement according to the first embodiment of the invention,

Figure 2 illustrates a gas exchange valve arrangement according to another embodiment of the invention,

Figure 3 illustrates a gas exchange valve arrangement according to another embodiment of the invention,

Figure 4 illustrates a gas exchange valve arrangement according to another embodiment of the invention,

Figure 5 illustrates different embodiments of the structure of the valve stem part and the guide member according to the invention, and

Figure 6 illustrates a gas exchange valve arrangement according to another embodiment of the invention.

Detailed Description of Drawings

[0025] Figure 1 depicts schematically a cut out of a cylinder head 10 suitable in an internal combustion engine. In order to make the presentation more easily understandable there are also schematically shown upper part a piston and a cylinder liner.

[0026] The cylinder head 10 is provided with at least one inlet valve assembly 12 and at least one exhaust valve assembly 14. It should be understood that both of the valve assemblies are provided with mechanism for opening the valve, even if not shown here. Such a mechanism is apparent to a skilled person in the art, as such.

[0027] The cylinder head is specifically intended for gas engine, where the used fuel is introduced in gaseous manner. The inlet valve assembly 12 is provided with an integrated gas admission valve system. The inlet valve assembly 12 comprises a valve member 18. The valve member includes a head 20 and a stem part 22. The inlet valve assembly comprises also a guide member 24 which is a sleeve-like part arranged between the stem part and cylinder head to guide the valve's stem part 22. The guide member 24 is provided with a gener- ally cylindrical hole 24 for the stem part. The stem part is advantageously of circular cross section and the hole is advantageously arranged at its central axis e.g. by boring. The guide member 24 may be attached to the cylinder head for example by shrink fitting method. [0028] The hole 26, as well as the guide member 24, has a first 24' end and a second end 24", and the guide member 24 is provided with at least one opening 28, which extends radially in respect to the longitudinal axis of the guide member through the wall of the guide member 24. The opening is located between the first and the second end and it is a part of the gas admission valve system. The guide member 24 is provided with a recess 29 circumscribing the outer surface of the guide member at the same location as the opening 28. Advantageously there are more than one openings 28 evenly space around the guide member 24. There is also a gaseous fuel feed channel 13 arranged to the cylinder head 10 connectable to a source of gaseous fuel. The feed channel 13 arranged open into the recess 29 of the guide member 24.

[0029] The guiding area between the surfaces of the stem part 22 of the valve member and the guide member 24 is provided with longitudinal flow path 30 extending between the opening 28 in the guide member 24 and the second end 24" of the cylindrical hole 26 in the guide member 24. The flow path allows the gaseous fuel passage from the opening 28 into an inlet channel 1 1 of the cylinder head 10.

[0030] At the second end 24" of the guide member 24 there is arranged a sealing arrangement 32. The sealing arrangement 32 is arranged such that a flow connection between the inlet channel 1 1 and the flow path 30 in the guiding area is closed when the head 20 of the valve member is in closing connection with a seat surface 21 of the valve assembly 12, and further such that the flow path 30 in the guiding area is arranged to open at a predetermined position of the valve member where the head 20 of the valve member is at the prede- termined distance from the seat surface 21 . The sealing arrangement 32 com- prises an ring formed sealing element 34 arranged to an annular recess 36 on the inner surface of the hole of the guide member 24 at the second end 24" thereof and that the stem part comprises outer surface even flat circular section at a region which is in contact with the sealing element at least when the head of the valve is in closing connection with the seat surface. The sealing element is constantly pressed against the surface of the stem 22.

[0031 ] According to the embodiment shown in figure 1 the longitudinal flow path 30 is accomplished such that the outer surface of the stem part 22 is provided with one, or preferably more longitudinally extending grooves 30 while the inner surface of the guide member 24 even. The longitudinal path extends in one direction to the flat circular section in the stem part i.e. the flat circular section start where the grooves end. Figure 1 shows also an alternative embodiment of the invention according to which the grooves are arranged to a separate sleeve part 22' releasably fitted to the stem part 22. This provides an effect of making it possible to easily change the sleeve with different kinds of grooves if needed.

[0032] Figure 1 discloses also an optional embodiment of the invention where the gas supply is dependent on the position of the exhaust valve arrangement 14 such that the gas flow is allowed only when the exhaust gas is closed. This embodiment comprises an additional valve system 13' in series with the gas admission valve system in the inlet valve assembly. Here the valve system 13' in integrated to the exhaust valve mechanically but it may also be realized by a computer controlled valve which has access to the position information of the exhaust valve and which includes instructions to is arranged to allow the gas flow only when the exhaust gas is at closed position.

[0033] In figure 2 there are shown two positions of the valve member as well as the integrated gas admission valve system. In the figure a there is shown a position where the sealing arrangement 32 is arranged such that the flow connection out from the flow path 30 in the guiding area is closed while the head 20 of the valve member is slightly opened and combustion air flow (arrow A _a ) into the combustion chamber is allowed to take place. After moving a predetermined distance from the seat surface 21 the flow path 30 in the guiding area is arranged to open, which is shown in figure b. At this position the gas admis- sion valve system is open and gas flow is indicated with arrows A _g . Now the valve member being also open allows a mixture of combustion air (arrow A _m ) and fuel gas to flow into the combustion chamber. In the valve assembly 12 the sealing arrangement 32 is arranged at a first distance D1 from a fixed point in the seat surface 21 , Respectively, an end of the longitudinally flow path 30 of the stem part, on the side of the second end 24" of the guide member 24 is arranged a second distance D2 from the same fixed point the seat surface 21 . The second distance D2 is greater than the first distance D1 and therefore it is possible to open i.e. move the valve and maintain the flow connection out from the flow path 30 in the guiding area closed while the head 20 of the valve member is slightly opened and combustion air flow (arrow A _a ) into the combustion chamber is allowed to take place. Even if shown only in connection with the figure 2 a) the difference of the first distance and the second distance is applicable to all embodiments of the invention. [0034] In figure 3 there is shown an embodiment of the invention where the longitudinal flow path 30 in the guiding area between the surfaces of the stem part of the valve member comprises longitudinal grooves 30' arranged directly to the guide member 24 and the outer surface of the stem part is substantially even. Figure 3 also shows a location of a cross sectional view V-V, which refers to figure 5.

[0035] In figure 4 there is shown an embodiment of the invention where the longitudinal flow path 30 in the guiding area between the surfaces of the stem part of the valve member comprises longitudinal grooves 30' arranged to a separate sleeve part 25 releasably fitted to the guide member 24 and the outer surface of the stem part is substantially even.

[0036] In figure 5 there are shown different embodiments of the structure of the valve stem part 22 and the guide member 24 as the view V-V. Figure a) shows an embodiment where the valve member comprises longitudinal grooves 30' arranged to the stem part and the inner surface of the guide member 24 is substantially even. The grooves are substantially wide and cover a major part of the outer surface of the stem, and are evenly spaced around the stem part. In figure b) the grooves cover about a half of the outer surface of the stem 22. In figure c) there is shown an embodiment where the valve member comprises longitudinal grooves 30' arranged directly to the guide member 24 and the outer surface of the stem part is substantially even. In figure d) there is shown an embodiment where the guiding area between the surfaces of the stem part 22 of the valve member comprises first spiral grooves 30.1 arranged to the stem part of the valve member and second spiral grooves 30.2 arranged to the guide member, the first and the second spiral grooves are contra-directed.

[0037] Figure 6 depicts an embodiment of the invention where the radial depth of the groove 30 is non-constant in longitudinal direction. This way gas flow may be more dependent on the valve stem position.

[0038] While the invention has been described herein by way of examples in connection with what are, at present, considered to be the most preferred embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but is intended to cover various combinations or modifica- tions of its features, and several other applications included within the scope of the invention, as defined in the appended claims. The details mentioned in connection with any embodiment above may be used in connection with another embodiment when such combination is technically feasible.