Patent Application
20170204752
This application claims priority to German Patent Application DE 10 2016 200 739.4, filed Jan. 20, 2016, the contents of which is hereby incorporated by reference in its entirety.
The invention relates to a metallic hollow valve for an internal combustion engine of a utility vehicle. The invention, furthermore, relates to an internal combustion engine of a utility vehicle with such a metallic hollow valve. The invention also relates to a utility vehicle with such an internal combustion engine.
Increasing thermal loads in internal combustion engines of utility vehicles make it increasingly necessary to cool central components such as valves for opening and closing air inlets and exhaust outlets of the internal combustion engine of these vehicles. From the passenger car sector it is known to design said valves as so-called metallic hollow valves which comprise a liquid cooling medium located inside. It is generally true for metallic hollow valves that these have a lower own weight than solid valves and because of said filling with a cooling medium allow an improved heat dissipation.
Since the requirements made on said valves in the utility vehicle sector with respect to wear resistance and lifespan are significantly higher than in the passenger car sector and could not be achieved to date by conventional hollow valves, conventional hollow valves are not employed in utility vehicles to date.
It is therefore an object of the present invention to create an improved embodiment for a metallic hollow valve which is also suitable in particular with respect to wear characteristics and lifespan for use in utility vehicles.
According to the invention, this object is solved through the subject of the independent claim(s). Advantageous embodiments are subject of the dependent claims.
A metallic hollow valve according to the invention for an internal combustion engine of a utility vehicle comprises a tubular valve stem, which merges into a valve head with an outer diameter that is enlarged with respect to the valve stem. Here, “metallic” is to mean that the material both of the valve stem and also of the valve head is or comprises a metal. The valve steam and the valve head according to the invention comprise a common hollow space. Said hollow space can be filled with a cooling medium in order to decisively improve the heat dissipation from the hollow valve. Experimental tests have now surprisingly shown that a metallic hollow valve is also capable of fulfilling the requirements that exist with respect to wear resistance and expected lifespan in a utility vehicle, when the valve stem has an outer diameter of more than 7 mm and an inner diameter delimiting the hollow space of at least 4.5 mm. Said dimensions of the valve stem which are substantial for the invention result in that by means of the cooling medium present in the hollow space heat can be particularly effectively dissipated from the hollow valve and evenly distributed.
To achieve a particularly high wear resistance and a particularly long lifespan, the valve stem can particularly preferably have an outer diameter between 8 mm and 11 mm. Alternatively or additionally, the valve stem can have an inner diameter between 5 mm and 7 mm.
In an advantageous further development, the valve head comprises a head base facing away from the valve stem, which has a base thickness between 2 mm and 4 mm. Such a delicate, i.e. comparatively thin-walled configuration of the base thickness results in a particularly even thermal coupling of the hollow valve to the combustion chamber of the internal combustion engine, in which the hollow valve is employed as part of a valve drive. In particular, the formation of undesirable cracks due to uneven heating of the hollow valve in the region of the head base can be counteracted by means of this measure.
In order to be able to achieve as efficient as possible a cooling of the metallic hollow valve, a wall thickness of the valve stem is designed delicate, i.e. comparatively thin-walled. With this version, the wall thickness of the valve stem therefore is between 1.5 mm and 5 mm.
In order to be able to achieve the desired cooling of the metallic hollow valve that is as efficient as possible, a wall thickness of the hollow valve in the region between valve stem and valve head, i.e. in the region of the so-called valve neck, can also be designed delicately. Particularly preferably, said wall thickness of the valve neck amounts to between 1.5 mm and 5 mm.
In a further preferred embodiment, the valve head is produced by means of forging or by means of electrochemical machining. In this way, a high wear resistance of the valve head which is exposed to particularly high thermal loads can be achieved.
In a preferred embodiment, the hollow space is partly filled with a fluid, preferentially with sodium. This allows a particularly effective dissipation of the heat from the combustion chamber of the internal combustion engine absorbed by the hollow valve in the region of the valve head.
The invention, furthermore, relates to an internal combustion engine for a utility vehicle with at least one cylinder, which comprises a combustion chamber. On the combustion chamber, an air inlet and an exhaust outlet are provided. The internal combustion engine, furthermore, comprises a valve drive which for opening and closing the air inlet and/or the exhaust outlet comprises a metallic hollow valve introduced above. The advantages of the metallic hollow valve explained above are therefore transferred to the internal combustion engine according to the invention.
In a preferred embodiment of the internal combustion engine according to the invention, the air inlet and/or the exhaust outlet are surrounded by a valve seat, against which the hollow valve in a closing position lies with a contact section. In the closing position, the hollow valve closes the air inlet and the exhaust outlet respectively. The hollow valve is hard-faced at least in the region of the contact section. This measure results in an improved wear resistance of the hollow valve.
Preferably, the hard facing of the contact section can be produced by means of plasma powder deposit welding, particularly preferably using iron (Fe) or Cobalt (Co) as filler material. A hard facing produced in this way has a particularly long lifespan.
The invention furthermore relates to a utility vehicle with an internal combustion engine introduced above. The advantages of the internal combustion engine according to the invention mentioned above are therefore also transferred to the utility vehicle according to the invention.
Further important features and advantages of the invention are obtained from the subclaims, from the drawing and from the associated FIGURE description by way of the drawing.
It is to be understood that the features mentioned above and still to be explained in the following cannot only be used in the respective combination stated but also in other combinations or by themselves without leaving the scope of the present invention.
Preferred exemplary embodiments of the invention are shown in the drawing and are explained in more detail in the following description, wherein same reference characters relate to same or similar or functionally same components.
The FIGURE shows a cross-sectional view of an exemplary metallic hollow valve according to the disclosure.
The only FIGURE shows an example of a metallic hollow valve 1 according to the invention in a longitudinal section along a centre longitudinal axis M of the valve stem 2 of the hollow valve. By way of the centre longitudinal axis M, an axial direction A is defined. Along the axial direction A, the valve stem 2 merges into a valve head 3, which compared with the valve stem 2 has an enlarged outer diameter dA. The valve stem 2 and the valve head 3 are integrally moulded onto one another. The valve head 3 can be produced by means of forging or by means of electrochemical machining.
As is evident from the FIGURE, the valve steam 2 and the valve head 3—known also as valve disc to the person skilled in the art—have a common hollow space 4. This hollow space 4 is partly filled with a fluid, preferentially with sodium, which for the sake of clarity is not shown in the FIGURE. The valve stem 2 has an outer diameter dA of more than 7 mm. Preferably, the value for the outer diameter dA is between 8 mm and 11 mm. Furthermore, the valve stem has an inner diameter dI of at least 4.5 mm. Preferably, the value for the inner diameter dI is between 5 mm and 7 mm. Particularly preferably, the valve stem has a wall thickness d between 1.5 mm and 5 mm. Here, said wall thickness d is defined by the difference between the outer diameter dA and the inner diameter dI.
As is further evident from the representation of the FIGURE, the valve head 3 has a head base 5 facing away from the valve stem 2, which has a base thickness dB between 2 mm and 5 mm. Furthermore, the wall thickness dK of a valve neck 6 formed between the valve stem 2 and the valve head 3 can be between 1.5 mm and 5 mm.
The hollow valve 1 shown in the FIGURE can be employed as part of a valve drive in an internal combustion engine (not shown in the FIGURE) of a utility vehicle in order to open and close air inlets and/or exhaust outlets. Said air inlet or exhaust outlet can be surrounded by a valve seat, against which the hollow valve 1 lies with a contact section 7 in a closing position, in which it closes the air inlet and the exhaust outlet respectively. Said contact section 7, which is merely schematically indicated in the FIGURE, is exposed to particular mechanical and thermal loads during the operation of the valve drive in the internal combustion engine. For this reason, the hollow valve 1 can be designed hard-faced at least in the region of the contact section 7. Such hard facing of the contact section 7 can be produced in particular by means of plasma powder deposit welding, particularly preferably using Iron (Fe) or Cobalt (Co) as filler material.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2016 200 739.4 | Jan 2016 | DE | national |
