CVVT English Continue Variable Valve Timing acronym, translated into Chinese is continuously variable valve timing mechanism, it is one of many in recent years, variable valve timing on modern cars are increasingly used in a technique of timing. For example: BMW is called Vanos, Toyota called the VVTI, called the Honda VTEC, but no matter what is their purpose is to work under different conditions of the engine matches the best valve overlap angle (valve timing), but implemented the method is different.
Hyundai car developed CVVT a camshaft opens the intake valve is changed sooner or later by the electro-hydraulic control system to control a desired valve overlap angle. This technology focuses on the first letter C (Continue continuous), stressed continuously varied according to the operating condition of the engine, always control the size of the valve overlap angle, thereby changing the cylinder intake air quantity. When the engine low speed low load operation (idling state), this time should be delayed intake valve opening time, the valve overlap angle is reduced, a stable combustion state; when the low speed and high engine load operation (start, acceleration, climbing), should the intake valve opening time is advanced, the valve overlap angle is increased to obtain a greater torque; high speed and large when the engine load operation (high speed), and the intake valve opening time should be delayed, the valve overlap angle is reduced, thereby improving engine efficiency; when the engine operating condition is in the middle (with uniform speed), will be relatively CVVT intake valve opening delay time, reducing the valve overlap angle, in this case the aim of reducing fuel consumption and pollution.
CVVT system includes the following components: oil pressure control valve, the intake cam teeth plate, until the crankshaft sensor, cam position sensor, an oil pump, the engine electronic control unit (ECU).
The intake cam tooth plate comprising: an outer gear by the Timing Belt driven, the internal gear connected to the intake cam can be controlled with a piston movable between the inner and outer gears. When the piston moves the piston of the helical gear position of the external gear change, thereby changing the positive effect. The displacement of the piston by the hydraulic pressure control valve is determined, the hydraulic control valve is an electronically controlled valve which is controlled by the oil pressure pump. When the computer (ECU) receives input signals, such as the engine speed, the intake air amount, throttle position, engine temperature, etc. to determine the hydraulic controlOperation of the valve. The computer will use the cam position sensor and the crankshaft position sensor to determine the actual timing of the intake valve cam.
When the engine is started or closed position by changing the hydraulic control valve, so that the intake cam timing for delay state. When the engine is idling or low load, the timing is also delayed position than the engine promote stable operation. When the intake cam that meet at an advanced position, which when the low speed high load at an increased torque output advanced angle position. In line with the high-speed position in order to facilitate high speed operation delay. When the engine temperature is low in the retarded position of the cam position, stable idle reduce fuel consumption.