Operation

OPERATION

LOW LIFT
When the low lift arm and the high lift arm are pushed up by the camshaft rotation, the locking pin is in the unlock position. Therefore, the high lift arm is separated from the low lift rocker arm and can operate freely. The valve lift may be small in this condition because the valve is opened or closed being linked with the low lift cam via the low lift arm.

At this time, the high lift arm is pushed against the high lift cam with the torsion spring.

In the cylinder at intake air process, the swirl occurs because the flow velocity is sped up by the air- fuel mixture sucked from one side valve. The flow velocity of air-fuel mixture in the combustion chamber is further sped up around TDC on its compression stroke because of the piston head and the squish area of the combustion chamber.




Then, the rich A/F area is made around the ignition area of spark plug and the combustion of the air-fuel mixture is improved. As a result, the generated torque improves, and at the same time it is possible to drive with the lean NF, and toxic substances in exhaust gas are decreased.




- Operation change from low lift to high lift
When the oil pressure provided from OSV to the oil chamber increases, the locking pin is pushed against the high lift arm side. Then, the return spring of small cylinder is compressed, and then the locking pin of low lift arm is pressed into the locking hole of high lift arm. By a series of these operations, the low lift arm is integrated to the high lift arm.

HIGH LIFT
As the valve is pushed up to the high lift cam by the high lift arm and low lift arm that were integrated, the valve lift becomes larger.

When the low lift arm operates upward or downward, the connecting position between the locking pin of low lift arm and the locking pin of support may change. But the low lift arm keeps integrating with the high lift arm because the locking pin of the low lift arm keeps being pushed.




By opening the 2 intake valves, the air flow resistance of valves is decreased and the valve overlap in TDC on its exhaust stroke is increased (because the valve opening angle of high lift cam is wider than the fixed lift cam). Then, in the high-speed area that the throttle valve opens greatly, the intake and exhaust inertia effect can be used. As a result, a lot of air is sucked in the cylinder and the engine output may be improved.




- Operation change from high lift to low lift
When the oil pressure from OSV to oil chamber is decreased, the return spring of small cylinder pushes back the locking pin of low lift arm and the locking pin of rocker shaft holder to the unlock position.
As a result, the low lift arm separates from the high lift arm, and then the variable valve lift mechanism becomes the low lift operation.