| 摘要 |
A V-type internal-combustion engine comprises first and second cylinders arranged so as to form a V shape on a vehicle body frame, a piston slidably and reciprocally engaged in each of the first and second cylinders, and a crank shaft connected to the pistons by connecting rods. The crank shaft comprises a central web, side webs arranged on both sides of the central web, and two crank pins carried by the central and each of the side webs and connected to the connecting rods. The crank pins are arranged so that the rotary phases thereof with respect to the central axis of the crank shaft are offset by an angle alpha from each other. The side webs each carry a balancer weight of a mass W/2 corresponding to half the sum of half the mass of the reciprocating part and the mass of the rotating parts of one cylinder in such a manner that the center of gravity of each balancer weight is positioned at the crank radius r (the distance from the central axis to the crank pin center) from the central axis of the crank shaft on the side opposite to the crank pin across the central axis of the crank shaft. The central web carries a balancer weight of a mass of Wxcos ( alpha /2) in such a manner that its center of gravity is positioned at a distance of the crank radius r along a line bisecting the angle between the crank pins, on the side opposite to the crank pins across the central axis of the crank shaft. Engine vibrations caused by the masses of the reciprocating and rotating parts can be reduced markedly with this construction. |
