Patent ID: 8707928

Claim:
A lubrication apparatus for a four-stroke engine configured to circulate oil accumulated in an oil reservoir provided separately from a crank chamber while lubricating each part of a valve operating mechanism for intake and exhaust, by supplying the oil to the crank chamber and a valve operating chamber accommodating the valve operating mechanism, using pressure fluctuation in the crank chamber, the pressure fluctuation being caused by reciprocating motion of a piston, and discharge blowby gas contained in a circulation route through which the oil circulates, from the valve operating chamber to a combustion chamber, the lubrication apparatus comprising: an intake part configured to be positioned below a level of the oil even when an oil reservoir is tilted so that the level of the oil changes, the oil being accumulated in the oil reservoir within a prescribed amount; an oil feeding passageway configured to allow communication between the oil reservoir and the crank chamber when a negative pressure is created in the crank chamber to suck up the oil in the oil reservoir from the intake part and supply the oil to the crank chamber; an open end part of the oil feeding passageway configured to be open in the crank chamber, the open end part opening while the piston moves from a position near a top dead center to the top dead center, and closing while the piston moves from the position near the top dead center to a bottom dead center; a communicating passageway configured to allow communication between the crank chamber and the oil reservoir when a positive pressure is created in the crank chamber and supply oil mist produced in the crank chamber to the oil reservoir; a supply passageway configured to supply the oil mist from the oil reservoir to the valve operating chamber; a direct passageway configured to allow communication between the valve operating chamber and the crank chamber when a negative pressure is created in the crank chamber; an open end part of the direct passageway configured to be open in the crank chamber, the open end part opening when the piston moves from the position near the top dead center to the top dead center, and closing when the piston moves from the position near the top dead center to the bottom dead center; and a flow rate control passageway configured to allow communication between the oil feeding passageway and the oil supply passageway, wherein the oil feeding passageway sucks air in the supply passageway via the flow rate control passageway, so that a flow rate of the oil which flows through the oil feeding passageway and is supplied to the crank chamber, is controlled.