ENGINE UNIT


  1. CONSTRUCTION


    1. 2 balance shafts are used to reduce vibration.

    2. The crankshaft directly drives the No. 1 balance shaft.

    3. A scissors gear is used for the No. 1 balance shaft to reduce gear noise.

    4. The No. 2 balance shaft is driven by the No. 1 balance shaft.

      A00YYL4C01
      *1 Balance Shaft Drive Gear *2 No. 1 Balance Shaft
      *3 No. 2 Balance Shaft - -

  2. OPERATION


    1. In the in-line 4-cylinder engine, the crankshaft angle for No. 1 and No. 4 cylinders are at the exact opposite (180°) positions of No. 2 and No. 3 cylinders. Therefore, the inertial force of the pistons and the connecting rods of the former 2 cylinders and of the latter 2 cylinders almost cancel each other out. However, because the position at which the piston reaches its maximum speed is located toward the top dead center from the center of the stroke, the upward inertial force is greater than the downward inertial force. This unbalanced secondary inertial force is generated twice for each rotation of the crankshaft.

      A00YY8WE04
      A00YYG2E07

    2. To cancel the unbalanced secondary inertial force, 2 balance shafts are rotated twice for each rotation of the crankshaft and generate inertial force in the opposite direction. Also, in order to cancel the inertial force generated by the balance shaft itself, the balance shaft actually consists of 2 shafts rotating in opposite directions.

      A00YYS5E04