ENGINE UNIT


  1. CONSTRUCTION


    1. A 4-blade vane type VVT-i controller (camshaft timing exhaust gear assembly) is used on the exhaust side.

    2. When the engine is stopped, a lock pin locks the exhaust camshaft (No. 2 camshaft and No. 4 Camshaft Sub-assembly) at the most advanced position in order to enhance startability.

    3. An advance assist spring is provided in the VVT-i controller (camshaft timing exhaust gear assembly) to assist the necessary torque in the advanced direction to keep the lock pin securely connected when the engine is stopped.

    4. An oil control valve is built into the camshaft timing gear bolt, which secures the vane to the exhaust camshaft (No. 2 camshaft and No. 4 Camshaft Sub-assembly). As a result, the controlled oil passage is shortened to improve response performance and operation at low temperatures. The oil control valve switches the oil passage when pressed by the cam timing oil control solenoid assembly. Oil passage switching is controlled to continuously change the exhaust camshaft (No. 2 camshaft and No. 4 Camshaft Sub-assembly) phase.

      Figure 1. VVT-i Controller (Camshaft Timing Exhaust Gear Assembly)

      A0025UMC01
      *1 Camshaft Timing Gear Bolt *2 Advance Assist Spring
      *3 Camshaft Timing Gear Cover FR *4 Housing
      *5 Lock Pin *6 Vane (Fixed on Exhaust Camshaft (No. 2 Camshaft and No. 4 Camshaft Sub-assembly))
      *7 Camshaft Timing Gear Cover RR (Sprocket) *8 Exhaust Camshaft (No. 2 Camshaft and No. 4 Camshaft Sub-assembly)
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      *a At a Stop *b In Operation
      B003YU9 Oil Pressure - -

      Figure 2. Camshaft Timing Gear Bolt (Built into Oil Control Valve)

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      *1 Oil Control Valve - -
      *a To Advance Side Vane Chamber *b To Retard Side Vane Chamber
      *c Engine Oil - -
  2. OPERATION


    1. Advance


      1. The cam timing oil control solenoid assembly operates according to the advance signal from the ECM. When the oil control valve reaches the position shown in the following illustration, the advance side vane chamber of the VVT-i controller (camshaft timing exhaust gear assembly) is affected by oil pressure and the vane inside the VVT-i controller (camshaft timing exhaust gear assembly) rotates in the advanced direction. The exhaust camshaft (No. 2 camshaft and No. 4 Camshaft Sub-assembly) fixed to the vane also rotates to the advanced side.

        A0025QBC01
        *1 Vane *2 ECM
        *3 Cam Timing Oil Control Solenoid Assembly - -
        *a Rotation Direction *b Retard Side Vane Chamber
        *c Advance Side Vane Chamber *d To Advance Side Vane Chamber
        *e From Retard Side Vane Chamber *f Drain
    2. Retard


      1. The cam timing oil control solenoid assembly operates according to the retard signal from the ECM. When the oil control valve reaches the position shown in the following illustration, the retard side vane chamber of the VVT-i controller (camshaft timing exhaust gear assembly) is affected by oil pressure and the vane inside the VVT-i controller (camshaft timing exhaust gear assembly) rotates in the retarded direction. The exhaust camshaft (No. 2 camshaft and No. 4 Camshaft Sub-assembly) fixed to the vane also rotates to the retarded side.

        A0025NIC01
        *1 Vane *2 ECM
        *3 Cam Timing Oil Control Solenoid Assembly - -
        *a Rotation Direction *b Retard Side Vane Chamber
        *c Advance Side Vane Chamber *d From Advance Side Vane Chamber
        *e To Retard Side Vane Chamber *f Drain
    3. Hold


      1. The ECM calculates the target advanced angle according to driving conditions and performs control. After setting the target timing, timings are maintained by the neutral camshaft timing oil control valve assembly as long as driving conditions do not change. As a result, unnecessary engine oil discharge is suppressed while valve timings are aligned to the desired target position.