| 摘要 |
A V-type internal combustion engine, having (2n+1) (n; natural number) cylinders, is provided with a crank shaft having n common crank pins Kc to which a pair of pistons in two banks are both connected and one stand-alone crank pin to which the remaining one piston only is connected. The common crank pins Kc are arranged at an equal phase, with a bank angle THETA set to satisfy the expression THETA = cos<-1>(1/(2n)). The stand-alone crank pin is disposed, when the remaining piston belongs to a bank on an advance side in a crank shaft rotation direction, on a lag side in a crank shaft rotation direction with an angle of (180- THETA ) degrees away from a common crank pin Kc, the masses M of reciprocating-motion portions such as pistons in all cylinders are set equal, and the crank shaft is provided with a balance weight WB that generates a balancing force having a magnitude of kMr omega <2> in a ( alpha +180)-degree direction, when k = 2ROOT {[1/2 2ROOT (1-1/4n<2>)]<2> + (n-1/4n)<2>} alpha =sin<-1>[1/2 2ROOT (1-1/4n<2>)/k], where alpha : rotation-direction angle from common crank pin Kc M: mass of each reciprocating-motion portion r: crank radius omega : angular speed of crank shaft. Accordingly, an odd-cylinder V-type internal combustion engine is provided that prevents a primary vibration generation to be caused by a primary inertia force without increases in weight and size of the internal combustion engine.
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