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.

Description

FIELD OF THE INVENTION

This application relates generally to valves used in internal combustion engines. More specifically, this application describes a coolant-free hollow valve with a vacuum cavity.

BACKGROUND OF THE INVENTION

Valves are essential components of internal combustion engines to regulate the intake of fuel and air as well as the exhaust of the combustion products. An alternative name for the valves for internal combustion engines is poppet valves. As shown in FIG. 1A, a typical valve consists of a long valve stem 200 and a broad valve head 100. Combustion inside an engine produces heat and the hot gas reaches a high temperature to produce useful work such as propelling an automobile or rotating a generator to produce electricity. A surface 110 of the valve comes into contact with the combustion chamber and is exposed to high temperatures. In addition to the solid (cavity-free) valve schematically illustrated in FIG. 1A, there are hollow valves with cavities that are filled with a coolant having a low-melting metal such as sodium to conduct the heat away from the head of the valves in order to prevent the valve head 100 from heat damage and to prolong the lifetime of the valve by reducing the temperature of the valve head 100. U.S. Pat. Nos. 1,670,965 and 9,611,953 and the patents cited within the '953 patent disclose prior art hollow valves.

These various hollow valves described above and schematically illustrated in FIG. 1B all purposely use a cavity filled with a coolant 1000, a low-melting point metal, and most predominantly sodium, to conduct heat away from the valve head 100 to prolong the lifetime of the valve. Because part of the heat inside the engine is extracted away by the valves instead of being used to do useful work, these valves have the negative effect of reducing the efficiency of the engine.

Solid valves without a coolant filled cavity are also widely used in engines. Even for these solid valves, the heat conduction from them amounts to a significant part of the heat loss of the engine and thus leads to reduced efficiency. Some of the solid valves also have an internal cavity 2000 that is used primarily to reduce the weight of the valve, as schematically shown in FIG. 1C. An example of such a valve is disclosed in U.S. Pat. No. 5,413,073. The internal cavity in such a valve is not evacuated.

U.S. Pat. No. 9,790,822 discloses a two-cavity poppet valve, as schematically shown in FIG. 1D. A small cavity within the valve stem 200 is partially filled with a coolant (sodium) 1000 with the remaining space in the cavity being filled with an inert gas 3000. A large cavity 4000 inside the valve head 100 is filled with insulation with examples such as an inert gas, partial vacuum, vacuum, and heat-resistant metal or carbon as a filter. Even though the '822 patent recognized the benefits of insulation, the solutions are very complex and require several manufacturing steps to make the two-cavity valve, which may lead to prohibitive cost. The valve in FIG. 1D also requires a cap 120 made up of a low conductivity heat resistant material to be welded onto an opening (necessary for manufacturing access) at location 130 at the combustion-facing surface 110 of the valve head 100. Because the surface 110 of the valve head 100 comes into contact with the combustion chamber of the engine, it is exposed to the harsh, high-temperature environment; welding of two different materials (one for the cap 120 and one for the valve head 100) at this surface may lead to accelerated degradation due to the mismatch of the coefficients of thermal expansion of the two materials and reduction of properties at the weld joint.

SUMMARY OF THE INVENTION

Accordingly, the above-identified shortcomings of prior art valves are overcome by embodiments of the present invention. Embodiments of this invention comprise of a coolant-free hollow valve in an engine wherein a vacuum is enclosed in a cavity, thereby providing better insulating property to the valve. By removing the coolant altogether and the associated manufacturing steps, the present invention will lead to better insulation and more manufacturing flexibility and lower cost for the valve. The removal of the coolant cavity also allows the entire combustion-facing surface 110 of the valve head 100 to be made of one heat-resistant material without any welding on that surface, thus shifting the welding-induced vulnerability to less critical and easier to manufacture locations.

The vacuum is broadly defined in the present invention as from reduced or partial vacuum such as one hundredth of an atmospheric pressure to high vacuum conditions. The vacuum definition in this invention comprises vacuum achieved through simple mechanical pumping to more advanced vacuum technologies that are all known in the art. The present invention discloses a coolant-free hollow valve in an engine, the valve including a cavity in the valve and a vacuum being enclosed in the cavity.

In one embodiment of the present invention, a thermal barrier coating 6000 is deposited onto the combustion-facing surface 110 of the valve head 100 to further improve the thermal insulation property of the valve.

BRIEF DESCRIPTION OF THE DRAWINGS

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

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

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

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

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.

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.

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.

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.

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

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.

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.

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.

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.

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).

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.

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.

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.

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.

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.

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.

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.

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.

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.