| 摘要 |
PROBLEM TO BE SOLVED: To avoid that an intake valve and an exhaust valve are turned into a state where they can not be driven by a suitable cam as an oil pressure supplied to the intake valve and the exhaust valve becomes insufficient. SOLUTION: While hydraulic pressure is supplied from an oil pump 31 whose supply pressure increases with the increase of the number of engine revolutions to an intake valve 1, it is driven by a high cam for intake valve 12, and when the hydraulic pressure is not supplied from the oil pump 31 to the intake valve 1, it is driven by a hydraulic low cam for intake valve 13, and while the hydraulic pressure is supplied from the oil pump 31 to the exhaust valve 2, it is driven by a low cam for exhaust valve 23, and when the hydraulic pressure is not supplied from the oil pump 31 to the exhaust valve 2, it is driven by a high cam for exhaust valve 22, and the simultaneous supply of the hydraulic pressure from the oil pump 31 to both the intake valve 1 and the exhaust valve 2 is prohibited during the low speed rotation of the engine.
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