Structure and working principle of valve timing regulator? Great gods, help!

Take CVVT as an example. CVVT system includes the following parts: oil pressure control valve, intake cam gear, crankshaft sensor, cam position sensor, oil pump and engine electronic control unit (ECU). The toothed disc of the air intake cam comprises an external gear driven by a timing belt, an internal gear connected with the air intake cam and a control piston which can move between the internal gear and the external gear. When the piston moves, the spiral gear on the piston will change the position of the external gear, thus changing the timing effect. The displacement of the piston is determined by the oil pressure control valve, which is an electronic control valve, and its oil pressure is controlled by the oil pump. When the computer (ECU) receives input signals such as engine speed, air intake, throttle position and engine temperature, it will determine the operation of the oil pressure control valve. The computer will also use the cam position sensor and crankshaft position sensor to determine the actual valve timing of the intake cam. When the engine is started or shut down, the position of the oil pressure control valve changes, so that the intake cam timing is in a delayed state. When the engine is idling or loading at low speed, the timing is also in the delayed position, which improves the stable working state of the engine. The intake cam is in the advanced position when it is in the middle position, and it is in the advanced angle position to increase the torque output when it is in the middle, low speed and high load. When at high speed, it is in a delayed position to facilitate high-speed operation. When the engine temperature is low, the cam position is in the delayed position, which stabilizes the idle speed and reduces the fuel consumption.

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