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可变气门机构是进气门升程及配气正时可变的气门机构,如图1所示。采用VTEC的发动机,其凸轮轴除原有控制进、排气门的一对凸轮外,还增加了一个较高升程的凸轮C。此外,由凸轮推动的摇臂被分成三部分:主、中间和副摇臂。三根摇臂内部有一根液压控制的活塞锁栓,ECM控制液压系统,推动活塞使三根摇臂锁成一体时,则由高升程的凸轮进行驱动,从而可改变气门的开启程度,如图2所示。低速时,主与副摇臂未与中间摇臂相连,但分别由A、B两凸轮驱动,在不同时间与升程下驱动,副凸轮B升程较小,故只能使进气门的开度较小。此时虽然中摇臂也随中间凸轮运动,但在低速状态下对气门开启不起任何作用。高速时,如图3中箭头所示,正时活塞由于液压作用而移动。因此,主、副与中间摇臂就被两个同步活塞贯穿,使三个摇臂连成一体一起移动。在此情况下,所有的摇臂均由C凸轮驱动,使气门开启和关闭,并改变气门正时和升程,使之适应发动机的高速工况。
Variable valve mechanism is intake valve lift and valve timing variable valve mechanism, shown in Figure 1. The use of VTEC engine, the camshaft addition to the original control into the exhaust valve of a pair of cams, but also increased a higher lift cam C. In addition, the cam driven rocker arm is divided into three parts: the main, middle and secondary rocker arm. The three rocker arm has a hydraulically controlled piston lock bolt, ECM control of the hydraulic system, pushing the piston so that the three rocker lock into one, then by the high-lift cam drive, which can change the degree of opening of the valve, as shown in Figure 2 Show. At low speed, the main and auxiliary rocker arm is not connected to the middle rocker arm, but driven by A and B cams respectively, driven at different times and elevators, the sub-cam B has smaller lift, so only the inlet valve Opening smaller. At this point although the rocker arm with the middle cam movement, but at low speeds on the valve can not afford to open any role. At high speed, as shown by the arrow in FIG. 3, the timing piston is moved by the hydraulic pressure. Therefore, the main, deputy and middle rocker arm by two synchronous piston penetration, so that the three rocker arm together as a whole to move. In this case, all the rocker arms are driven by the C cam to open and close the valve and change the valve timing and lift to accommodate the engine’s high-speed operating conditions.