PURPOSE: To reduce the sliding friction loss of a crank shaft with a number of V type or opposed-type cylinders on both its sides and reduce its size by improving the length between the cylinders of each side and the axial position of the crank shaft.
CONSTITUTION: When applied to a 4-cylinder V type engine, the length in the axial direction of a crank shaft 1 between both central lines of the cylinders 51 and 53 on one side of the crank shaft 1 and the cylinders 52 and 54 on the other side is specified below half the inner diameter (d) of the respective cylinders 51W54. Each pair of crank pins 21W24 which corresponds to the cylinders 51W54 on each side is formed on the crank shaft 1 and journals 41W43 are formed only on both sides of each pair of crank pins 21W24. Besides, the axis of the crank shaft 1 is located at the position where a piston 6 is offset toward the side force R which pushes the piston 6 on the inner surface of the cylinder for the length (a) of 10% or more to less than 45% of the piston stroke S during the expanded stroke time of each cylinders 51W54.
KATAOKA MASAO
NODA TAKU
