Patent Application
20200166001
This invention relates generally to cylinder liners for internal combustion engines, and methods of manufacturing the cylinder liners.
Engine blocks of internal combustion engines include cylindrical shaped openings for receiving cylinder liners. Each cylinder liner presents an inner surface surrounding the cylindrical opening for receiving a piston. The rings of the piston slide along the inner surface of the cylinder liner during operation of the engine.
One aspect of the invention provides an insert for a cylinder liner of an internal combustion engine. The insert includes an insert body extending circumferentially around a center axis and longitudinally from an upper end to a lower end. The insert body includes an inner portion presenting an inner surface facing the center axis, and the inner surface presents an opening. The insert body also includes an outer portion presenting an outer surface facing away from the center axis. The inner portion is formed of an iron-based material, and the outer portion is formed of a material having a thermal conductivity of not greater than 3.5 W/mK.
Another aspect of the invention provides a cylinder liner for an internal combustion engine. The cylinder liner includes a liner body extending circumferentially around a center axis and longitudinally from a top end to a bottom end. The liner body presents an interior surface facing the center axis. The cylinder liner also includes an insert body disposed along the interior surface of the liner body. The insert body extends circumferentially around the center axis and longitudinally from an upper end to a lower end. The insert body includes an inner portion presenting an inner surface facing the center axis, and the inner surface presents an opening. The insert body also includes an outer portion presenting an outer surface facing away from the center axis. The outer surface of the outer portion engages the interior surface of the liner body. The inner portion of the insert body is formed of an iron-based material, and the outer portion of the insert body is formed of a material having a thermal conductivity of not greater than 3.5 W/mK.
Yet another aspect of the invention provides a method of manufacturing an insert for a cylinder liner of an internal combustion engine. The method comprises the steps of forming an insert body by providing an inner portion formed of an iron-based material and presenting an inner surface facing and extending circumferentially around a center axis and presenting an opening, and applying a material having a thermal conductivity of not greater than 3.5 W/mK to an exterior surface of the inner portion to form an outer portion presenting an outer surface facing away from the center axis.
Another aspect of the invention provides a method of manufacturing a cylinder liner for an internal combustion engine. The method comprises the steps of providing a liner body extending circumferentially around a center axis and longitudinally from a top end to a bottom end, the liner body presenting an interior surface facing the center axis; and disposing an insert body along the interior surface of the liner body. The insert body extends circumferentially around the center axis and longitudinally from an upper end to a lower end. The insert body includes an inner portion presenting an inner surface facing the center axis, and the inner surface presents an opening. The insert body also includes an outer portion presenting an outer surface facing away from the center axis. The outer surface of the outer portion engages the interior surface of the liner body. The inner portion is formed of an iron-based material, and the outer portion is formed of a material having a thermal conductivity of not greater than 3.5 W/mK.
Other advantages of the present invention will be readily appreciated, as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:
The invention provides an insert 10 for a cylinder liner of an internal combustion engine, and a cylinder liner 12 which includes the insert 10. An example of the insert 10 for the cylinder liner 12 is shown in
As shown in
The insert body also includes an outer portion 24 presenting an outer surface 26 facing away from the center axis A. The outer portion 24 includes an interior surface 28 facing toward the center axis A, and the interior surface 28 of the outer portion 24 engages the exterior surface 22 of the inner portion 18. The outer portion 24 is formed of a material having a thermal conductivity of not greater than 3.5 W/mK. For example, the outer portion 24 can be formed of a material including ceria and/or zirconia. According to one embodiment, the outer portion 24 is formed of ceria stabilized zirconia.
The outer portion 24 and the inner portion 18 each have a thickness, and the thicknesses can vary between the upper end 14 to the lower end 16. For example, the thicknesses could present a gradient between the upper end 14 and the lower end 16. According to one embodiment, the thickness of the outer portion 24 formed of the material having a thermal conductivity of not greater than 3.5 W/mK is greater at the upper end 14 than the bottom end 16. For example, the thickness of the outer portion 14 decreases from the upper end 14 to the lower end 16.
The insert body can optionally include a bonding layer applied to the outer portion 24 for bonding to the engine block, which is typically a block casting. According to this embodiment, the outer portion 24 formed of the material having a thermal conductivity of not greater than 3.5 W/mK is actually a middle layer of the insert 10.
Another aspect of the invention provides the cylinder liner for an internal combustion engine including the insert. The cylinder liner includes a liner body 30 extending circumferentially around the center axis and longitudinally from a top end 32 to a bottom end 34. The liner body is typically formed of a metal material, such as steel. The liner body presents an interior surface 36 facing the center axis. The liner body is formed of a metal, such as steel. The insert body is disposed along the interior surface of the liner body. The outer surface of the outer portion of the insert is disposed along and engages the interior surface of the liner body.
Another aspect of the invention provides a method of manufacturing the insert for the cylinder liner of the internal combustion engine. The method includes forming the insert body by providing the inner portion formed of the iron-based material, and then applying the material having a thermal conductivity of not greater than 3.5 W/mK to the exterior surface of the inner portion to form the outer portion.
According to an example embodiment, the inner portion and the outer portion are formed by spraying. For example, the method can first include surface activation of a mandrel, and then spraying the iron-based material onto the mandrel to form the inner portion. Next, the method includes removing the inner portion from the mandrel. The method further includes spraying the material having a thermal conductivity of not greater than 3.5 W/mK, for example ceria stabilized zirconia, to the exterior surface of the inner portion to form the outer portion. The method also includes machining the outer portion.
Yet another aspect of the invention provides a method of manufacturing the cylinder liner for the internal combustion engine. The method comprises the steps of providing the liner body, and disposing the insert body along the interior surface of the liner body. The method can include machining the liner body.
The insert provides the advantage of trapping heat in the combustion chamber of the cylindrical opening during operation of the internal combustion engine, like a thermal barrier coating on a piston or on the outer diameter of the liner would do. However, when the thermal barrier coating is disposed on the outer diameter of the cylinder liner, there are challenging tolerances after the coating process and dimensions on the outer diameter of the liner which are difficult to deal with.
Another advantage is that the inner portion of the insert formed of steel provides a normal surface for the piston rings and piston to interact with, while the outer portion of the insert acts as a thermal barrier coating to interrupt the heat flow out of the combustion chamber.
Obviously, many modifications and variations of the present invention are possible in light of the above teachings and may be practiced otherwise than as specifically described while within the scope of the claims. It is contemplated that all features described and of all embodiments can be combined with each other, so long as such combinations would not contradict one another.
