STRUCTURE AND OPERATION 8. Mitsubishi 4M50 Balance Shafts
• The balance shaft RH and balance shaft LH are mounted in the upper crankcase on the right and left sides of the crankshaft. The balance shafts reduce the vibration of the engine caused by the rotation of the crankshaft. • The balance shaft RH and balance shaft LH are both driven by timing gears. Each balance shaft is held in the upper crankcase by way of three balance shaft bushings. • The balance shaft LH has a locating hole to enable correct installation.
8.1 Reduction of vertical vibration (secondary vibration element)
Mitsubishi 4M50 Engine Parts contact email: EngineParts@HeavyEquipmentRestorationParts.com Phone: 269 673 1638
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• When the piston moves up and down, vertical vibrations are generated at the top dead center (TDC) and bottom dead center (BDC) due to inertia. • The balance shaft LH and the balance shaft RH rotate so that their weight portions are at the bottom positions when a piston is at TDC and at the top positions when the piston is at BDC, i.e., the weight portions are always on the opposite side to the piston head. • This creates centrifugal forces in the balance shaft RH and balance shaft LH, the total of which is equal in amount to the inertia force that the piston creates when it is at TDC or BDC. These centrifugal forces in the balance shafts cancel out the inertia forces resulting from piston’s movements and reduce the amount of vertical vibration. • The balance shafts also reduce the moment created around the crankshaft (which constitutes secondary vibration elements) when the engine is running in the middle-to-high speed range.
