Engine configured to drive a diaphragm fuel pump using pressure fluctuation in a crank chamber of the engine

摘要

An engine includes a crank chamber in which pressure fluctuation occurs and a carburetor including a diaphragm fuel pump. The diaphragm fuel pump includes a pump chamber configured to suck in and eject fuel and a diaphragm chamber to which a pressure that drives the pump chamber is supplied. The diaphragm chamber and the crank chamber communicate with one another in a state in which a negative pressure is created in the crank chamber.

主权项

1. An engine having a structure of a four-stroke engine, the engine comprising:
a piston configured to reciprocally move; a crank chamber in which pressure fluctuation occurs by the piston moving reciprocally in the crank chamber; a carburetor including a diaphragm fuel pump, the diaphragm fuel pump including:
a pump chamber configured to suck in and eject fuel; anda diaphragm chamber to which a pressure that drives the pump chamber is supplied; a single communicating path configured to allow communication between the diaphragm chamber and the crank chamber; and an opening of the communicating path in the crank chamber side, the opening being formed near a position in which a termination portion of a skirt part of the piston is located when the piston is located at a top dead center such that the piston opens and closes the opening, wherein the piston closes the opening of the communicating path when a positive pressure is created in the crank chamber and opens the opening to supply substantially only a negative pressure from the crank chamber to the diaphragm chamber via the communicating path, and the opening is not open in a combustion chamber formed by a cylinder part and an upper portion of the piston.