Hollow Valve For An Engine

Abstract

The embodiments of the present invention comprise a coolant-free hollow valve with a cavity and a vacuum being enclosed in the cavity. The valve is used for an engine and one example of an engine is an internal combustion engine. The valve comprises a coolant-free hollow vacuum cavity to reduce the heat conduction such that the combustion heat is used to perform useful work to improve the efficiency of the engine. One embodiment of the present invention is a coolant-free valve with a hollow vacuum cavity and a thermal barrier coating being deposited onto part of the external surface of the valve that comes into contact with the combustion chamber of the engine.

Claims

1. A coolant-free hollow valve for use in an engine having a combustion chamber, the valve comprising: a valve stem; a valve head having a weld-free, combustion-facing surface that is adapted to come in contact with the combustion chamber of the engine; a cavity in the valve head; and a vacuum being enclosed in the cavity.

2. The coolant-free hollow valve of claim 1, wherein the cavity is formed in the valve head and in at least part of the valve stem; and the vacuum being enclosed in the cavity.

3. The coolant-free hollow valve of claim 1, wherein the cavity is formed in the valve head and the valve stem; and the vacuum being enclosed in the cavity.

4. A coolant-free hollow valve for use in an engine having a combustion chamber, the valve comprising: a valve stem; a valve head having a weld-free, combustion-facing surface that is adapted to come in contact with the combustion chamber of the engine; a cavity in the valve head; and a vacuum being enclosed in the cavity; and a thermal barrier coating being deposited on at least part of the combustion-facing surface of the valve head.

5. The hollow valve of claim 4 wherein the engine is an internal combustion engine.

6. The coolant-free hollow valve of claim 4, wherein the cavity is formed in the valve head and in at least part of the valve stem and the vacuum being enclosed in the cavity.

7. The coolant-free hollow valve of claim 4, wherein the cavity is formed in the valve head and the valve stem and the vacuum being enclosed in the cavity.

8. The coolant-free hollow valve of claim 1, wherein the valve head and the combustion-facing surface are made of the same material.

9. The coolant-free hollow valve of claim 4, wherein the valve head and the combustion-facing surface are made of the same material.

10. The hollow valve of claim 1 wherein the engine is an internal combustion engine.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] The features and embodiments of the present invention will become more apparent from the following descriptions of the accompanying drawings.

[0010] FIG. 1A depicts a central longitudinal cross section of a prior art round, solid valve.

[0011] FIG. 1B depicts a central longitudinal cross section of another prior art round valve with a cavity partially filled with a coolant (sodium).

[0012] FIG. 1C depicts a central longitudinal cross section of yet another prior art valve with a hollow, unevacuated cavity.

[0013] FIG. 1D depicts a central longitudinal cross section of yet another prior art valve with a cavity partially filled with a coolant with the remaining space being filled with an inert gas, and a second cavity filled with insulation.

[0014] FIG. 2A depicts one embodiment of the present invention in a central longitudinal cross sectional view showing a coolant-free valve with a cavity in a state of vacuum.

[0015] FIG. 2B depicts another embodiment of the present invention in a central longitudinal cross sectional view showing a valve with a cavity in a state of vacuum.

[0016] FIG. 2C depicts yet another embodiment of the present invention in a central longitudinal cross sectional view showing a cavity in a state of vacuum, and a thermal barrier coating deposited onto a combustion-facing surface of the valve head.

[0017] These drawings are intended to facilitate the description of the present invention. They are by no means limiting the various embodiments and variants of the present invention. Further features, aspects, and advantages of the present invention will be more readily apparent to those skilled in the art during the course of the following detailed description.

DETAILED DESCRIPTION OF THE INVENTION

[0018] For the purposes of promoting an understanding of the invention, the terminology used herein is for the purpose of description, not limitation. Specific geometries, methods and processes disclosed herein are meant to be used as examples. Various variants or embodiments should be considered as part of this invention.

[0019] Prior art valves conduct heat through the metal or intentionally accelerate the heat conduction using a low-melting point metal coolant, predominantly sodium, to conduct heat away from the valve during operation. Even the most recent two-cavity valve disclosed in the '822 patent still uses sodium coolant to conduct heat away even though the '822 patent recognizes the need to have a separate insulation cavity. Such prior art valves conduct significant amount of heat away from the engine and thus lead to reduced efficiency. The present invention removes the coolant altogether and uses a vacuum cavity in the valve to achieve better insulation (instead of better heat conduction) so that more heat can be kept inside the engine to perform useful work such as propelling a vehicle or driving a generator to produce electricity.

[0020] Three example embodiments of this invention are schematically shown in FIG. 2A, FIG. 2B, and FIG. 2C. These drawings are for illustration purposes and various variants and modifications should be considered part of this invention to those who are skilled in the art.

[0021] FIG. 2A is one embodiment of the current invention where a coolant-free hollow vacuum cavity 5000 extends to near a stem tip 400 for better insulation as well as reduction of the weight of the valve. Various manufacturing methods known in the art can be employed to make the valve. One embodiment of the manufacturing methods is to use additive manufacturing (AM) to make both a valve head 100 and majority of a stem 200, from the bottom up to location 1 in FIG. 2A. AM is also termed 3D printing and other alternative names. AM apparatus melts powders layer by layer or wires to build structures and components and it is a manufacturing method that is known in the art. The stem tip 400 can then be attached at location 1. An example of the joining process is welding and another example is brazing, both are known in the art. Both welding and brazing can be performed inside a vacuum chamber such that during and after joining, the coolant-free hollow cavity 5000 inside the valve is in a state of vacuum. An alternative embodiment of the manufacturing method is to perform the joining in air or under a protective gas such as argon environment, but leave a small evacuation hole 500 in the stem tip 400 to allow evacuation after the joining and then seal off to retain the vacuum inside. Such evacuation scheme is known in the art. The location of the joining can be selected, for instance from location 1 to location 2 to location 3, based on the relative ease and cost of manufacturing. These locations can vary depending on the valve design and manufacturing process and are put on FIG. 2A for illustration purpose only.

[0022] One embodiment of the invention is to use electron beam (EB) welding that is known in the art. The EB welding is usually performed inside a vacuum, thus there is no need for an additional evacuation step. Another embodiment of this invention is to use friction welding which is again known in the art. During the friction welding process, one piece is rubbed against another piece at high speed until they are joined together. Most friction welding is performed in air; and in this case, an extra evacuation step is needed similar to the process explained heretofore. Alternatively, the friction welding can be performed inside a vacuum chamber, and in this case, the welded cavity will be automatically in a state of vacuum. The friction welding motion can be rotational instead of linear for the joint 220 (FIG. 2B).

[0023] One further embodiment of this invention is shown schematically in FIG. 2B. Part of the stem 200 (above point 4) remains solid without a hollow cavity, which facilitates the friction welding process. The cost of the solid stem can be lower than that of another stem with a cavity. Location 4 can vary depending on the requirement of the engine with consideration of the cost of manufacturing the entire valve.

[0024] Yet another embodiment of the present invention entails a thermal barrier coating 6000 being deposited onto the combustion-facing surface 110 of the valve head 100, as schematically illustrated in FIG. 2C. Thermal barrier coatings are known in the art to those skillful in engine technologies.

[0025] The valve disclosed in the current invention is made up of heat resistant materials such as high-temperature alloys that are known in the art. In one embodiment of this invention, the valve head 100 and the valve stem 200 are made up of different heat-resistant materials. Because the stem 200 is exposed to much lower temperatures, it can be made up of a low cost material.

[0026] In addition to AM, other manufacturing processes can be used to make the valve of the present invention and its various components. Technologies known in the art to make sodium-filled hollow valves can be used to make the valve of the present invention. Instead of filling the cavity with sodium, a vacuum can be created in a cavity 5000.

[0027] One embodiment of the present invention employs casting to make the valve head 100 and the stem 200. Casting is a cost-effective technology widely used to make components, especially metal components.

[0028] Another embodiment of the present invention employs forging to make the valve head 100 and the stem 200. Forging is already widely used to make valves.

[0029] When AM is used to make the valve components such as the valve head 100, various structural features can be introduced into the valve head cavity to improve its mechanical performance.

[0030] Various embodiments of the present invention have been described in fulfillment of the various needs that the invention meets. It should be recognized that these embodiments are merely illustrative of the principles of various embodiments of the present invention. Numerous modifications and adaptations thereof will be apparent to those skilled in the art without departing from the spirit and scope of the present invention. It is intended that the present invention cover all suitable modifications and variations as come within the scope of the appended claims and their equivalents.