Crankshaft for a v-type internal combustion engine

A crankshaft ( 1 ) includes a first to a sixth crank pin ( 41 - 46 ), a first to a fourth main journal ( 21 - 24 ) and a first to a ninth crank arm ( 61 - 69 ). At least the first, the second, the eighth and the ninth crank arms ( 61, 62, 68, 69 ) have respective integral counterweights ( 61', 62', 68', 69' ) for balancing the crankshaft ( 1 ). In order to reduce bending stress on the areas where the second and the eighth crank arms ( 62, 68 ) are connected to the respective pairs of adjacent crank pins ( 41 - 42, 45 - 46 ), the axial dimensions of the first and the ninth crank arms ( 61, 69 ) are reduced, being substantially the same as those of the adjacent crank arms ( 62, 68 ) in order that the axial length of the two end spans of the crankshaft is the same as that of the intermediate span. In order to balance the crankshaft ( 1 ), two additional counterweights ( 71, 72 ) are arranged outwardly of the end journals ( 21, 24 ) and their axial dimensions are comparable to those of the end crank arms ( 61, 69 ).