Patent Application
20190277169
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.
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
These various hollow valves described above and schematically illustrated in
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
U.S. Pat. No. 9,790,822 discloses a two-cavity poppet valve, as schematically shown in
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.
The features and embodiments of the present invention will become more apparent from the following descriptions of the accompanying drawings.
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.
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
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 (
One further embodiment of this invention is shown schematically in
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
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.
