Patent Application
20090095247
The present invention relates to an internal combustion engine and more particularly provides an intake valve that lessens the accumulation within a valve guide of high boiling fraction materials of the fuel.
A gasoline-fueled spark-ignition combustion engine traditionally has the fuel introduced into the intake system either through a carburetor or a port fuel injector. Some fuels contain high boiling materials, or fractions, such as polymer fuel additives or gum, and some of the high boiling fractions have a high viscosity, which generally increases exponentially with a decrease in temperature. Consequently, after an engine cools down, an accumulation of high viscosity high boiling fraction on the intake valve surfaces may result. Accordingly, there is a need in the art for an intake system in a combustion engine that may lessen the accumulation of high boiling fraction on intake valve surfaces.
An intake valve for a combustion engine includes a valve guide having a bore and a lower end surface surrounding the bore, and a valve stem having an upper valve stem portion moving up and down within the bore of the valve guide and a valve at the lower end of the stem. A valve guide shield is carried by the valve stem below the upper valve stem portion that moves up and down within the bore to shield the upper valve stem portion from high boiling fraction material from the fuel to lessen the accumulation of high boiling fraction between the valve stem and the valve guide.
Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating exemplary embodiments of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.
The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein:
The following description of certain exemplary embodiments is exemplary in nature and is not intended to limit the invention, its application, or uses.
Referring to
An operational cycle of combustion system 100 begins with intake valve 200 being closed, that is, with seating surface 212 seated against valve seat 117, as shown in
During the combustion cycle, the outer surface 207 of the valve stem 205 is at an elevated temperature, which results in the evaporation of the low boiling fraction of the fuel and the adhesion to outer surface 207 of the high boiling fraction of the fuel. With an upper portion of valve stem 205 moving in and out of valve guide 230, over many combustion cycles some of the high boiling fraction on valve stem 205 may be pushed into the clearance space between the outer surface 207 of valve stem 205 and the bore 232 of the valve guide 230.
According to the invention, the accumulation of the high boiling fraction (also referred to as residue or gum) at the clearance space may be lessened by providing a valve stem shield 250 on the valve stem 205. As best seen in
As seen in
In view of the foregoing, it will be seen and understood that the valve stem shield 250 will reduce the accumulation of high boiling fraction at the clearance space between the valve stem 205 and the valve guide 230. In particular, the valve stem shield 250 will act as a shield to fend off the high boiling fraction material that might otherwise be deposited on that portion of the length of the valve stem 205 that will travel up and down in valve guide 230. The valve stem shield 250 is effective both during the injection of fuel while the intake valve 200 is closed, and during the opening of the intake valve 200, when there is blowback of high boiling fracture material onto the valve stem 205. Depending upon the dimensions and geometry of the arrangement, it may be desirable to have the valve stem shield 250 be of a diameter greater than the diameter of the valve guide lower face 232, particularly in fending off the blowback of combustion products.
While an embodiment of the invention has been described employing a fuel injection system for supplying fuel, it will be appreciated that the scope of the invention is not so limited, and that the invention may also apply to a carburetor fuel delivery system. Although the drawings herein depict a linear piston and cylinder arrangement as an exemplary combustion system for the combustion engine, it will be appreciated that the disclosed invention may also be applicable to other combustion systems, such as a rotary combustion system employed in a rotary combustion engine for example. And although the drawings show the example of a valve stem shield 250 that is a flat shape, the shield 250 can be either concave or convex.
