Intake valve for lessening accumulation of high boiling fraction from fuel

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 following description of certain exemplary embodiments is exemplary in nature and is not intended to limit the invention, its application, or uses.

FIG. 1 is an exemplary embodiment of a combustion system 100 for a combustion engine having a cylinder 105 and a piston 1 10 defining a combustion chamber 107, an intake port 115, an exhaust port 120, a fuel supply 125, such as a fuel injector for example, an intake valve 200, and an exhaust valve 300. Intake valve 200 includes a valve stem 205, and a valve head 210 (also referred to as a valve tulip) that has a seating surface 212 that seats against an intake valve seat 117 at intake port 115 during the opening and closing action of intake valve 200. Surrounding valve stem 205 is a valve guide 230 having a bore 232 that is dimensioned in close relationship with an outer surface 207 of the valve stem 205 for guiding the movement of valve stem 205 during the opening and closing action of intake valve 200. The valve guide 230 has a lower end surface 252 that extends into the intake port 115 as seen in FIG. 1.

Referring to FIG. 1, at the top of valve guide 230 is a valve seal 235 for controlling the flow of oil from an oil reservoir, generally depicted as 130 in the combustion engine, for providing lubrication of the valve stem 205 and valve guide 230. An upper end 208 of valve stem 205 is arranged in mechanical communication with a valve cam (not shown) of the combustion engine for driving intake valve 200 to an open position. Intake valve 200 is driven to a closed position by the action of a valve spring 215.

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 FIG. 1, and fuel injector 125 providing a supply of fuel to intake port 1 15 where it is mixed with air. As shown in FIG. 1, spray 135 of the fuel is directed toward valve stem 205 and valve tulip 210. In response to intake valve 200 being opened via the valve cam, the fuel and air mixture is permitted to enter combustion chamber 107. Thereafter valve spring 215 drives intake valve 200 to the closed position and timed combustion and exhaust take place.

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.