| 摘要 |
PURPOSE:To control the break-down and the like of mechanical parts by a structure wherein a shut-off valve is provided in a relief passage in order to shift the stopper of a directional control valve by raising the delivery pressure of an oil pump in a device which changes valve characteristics by means of oil pressure controlled by the directional control valve. CONSTITUTION:The oil pressure developed by an oil pump 2 driven by a camshaft 1 is stored in an accumulator 5. Said stored pressure is supplied to an actuator 12 or 13 by shifting a directional control valve 9 by means of the actuation of a solenoid valve 18 in accordance with engine conditions so as to shift rocker arms 10 and 11 relative to cams in order to change the action characteristics of a valve. A shut-off valve 21 is provided in the relief passage of the oil pump 2. The shut-off valve 21 is closed by being operated by a pilot valve 19 when the change of the valve characteristics is intended, resulting in causing to raise the delivery pressure of the oil pump 2 and consequently shifting a piston 24 and releasing the engagement of the stopper 23 of the directional control valve 9. As a result, no excessive mechanical contact surface pressure is applied to the stopper, resulting in preventing the parts from being broken down, worn and the like. |
