vvt可變氣門正時(shí)技術(shù)-在線瀏覽
2025-01-20 15:47本頁(yè)面
【正文】 ，氣門升量較少，情形好像普通的發(fā)動(dòng)機(jī)。 發(fā)動(dòng)機(jī)達(dá)到某一個(gè)設(shè)定的高轉(zhuǎn)速（ 3500 轉(zhuǎn) /分）時(shí)，電腦即會(huì)指令電磁閥啟動(dòng)液壓系統(tǒng)，推動(dòng)搖臂內(nèi)的小活塞，使三根 ABC 搖臂鎖成一體，一起由中間凸輪 c 驅(qū)動(dòng)，由于中間凸輪比其它凸輪都高，升程大，所以進(jìn)氣門開啟時(shí)間延長(zhǎng)，升程也增大了。 整個(gè) VTEC 系統(tǒng)由發(fā)動(dòng)機(jī)主電腦（ ECU）控制， ECU 接收發(fā)動(dòng)機(jī)傳感器（包括轉(zhuǎn)速、進(jìn)氣壓力、車速、水溫等）的參數(shù)并進(jìn)行處理，輸出相應(yīng)的控制信號(hào)，通過電磁閥調(diào)節(jié)搖臂活塞液壓系統(tǒng)，從而使發(fā)動(dòng)機(jī)在不同的轉(zhuǎn)速工況下由不同的凸輪控制，影響進(jìn)氣門的開度和時(shí)間。例如 VTEC 系統(tǒng)的氣門升程和正時(shí)的變換動(dòng)作明顯將發(fā)動(dòng)機(jī)的狀態(tài)劃分為兩個(gè)階段，它們之間的轉(zhuǎn)換不夠平滑，在 VTEC 系統(tǒng)啟動(dòng)前后發(fā)動(dòng)機(jī)的表現(xiàn)截然不同， 連發(fā)出的聲音也不一樣。 簡(jiǎn)單地說， iVTEC 系統(tǒng)是在現(xiàn)有系統(tǒng)的基礎(chǔ)上，添加一個(gè)稱為 “ 可變正時(shí)控制 ”VTC （ Variable timing control），即一組進(jìn)氣門凸輪軸正時(shí)可變控制機(jī)構(gòu)，通過 ECU 控制程序，控制進(jìn)氣門的開啟關(guān)閉。發(fā)動(dòng)機(jī)高轉(zhuǎn)速時(shí)則在原有基礎(chǔ)上提高進(jìn)氣門的開度及時(shí)間，以獲取最大的充氣量。同時(shí)， iVTEC 系統(tǒng)發(fā)動(dòng)機(jī)采用進(jìn)氣歧管放在前，排氣歧管放在后（靠車廂一端）的布置。由于發(fā)動(dòng)機(jī)一啟動(dòng)后 iVTEC 系統(tǒng)就進(jìn)入狀態(tài)，不論低轉(zhuǎn)速或者高轉(zhuǎn)速 VTC 都在工作，也就消除了原來 VTEC 系統(tǒng)存在的缺陷。s patented timing system VarioCam?system. With an automatic chain tensioner and hydraulic valve lash pensation, VarioCam alters camshaft timing for greater engine torque. Using a timing piston, controlled by the Bosch Motronic M engine management system, placed between the two sides of the timing chain between the intake and exhaust cams. When actuated, the piston advances the timing of the intake cam by broadly 15 crankshaft degrees or camshaft degrees. This earlier valve timing flatter creates more valve overlap and an earlier closing time than normal, resulting torque in additional engine torque. At high engine speeds, the piston is shifted back curve to its later timing position for more power. Late intake cam timing results in shorter valve overlap periods and reduced hydrocarbon emissions at low speeds and at idle. Early valve timing and long valve overlap times create exhaust gas recirculation at low loads and moderate engine speeds, reducing NOx emissions. VarioCam valve timing also improves coldstart emissions. Variable Valve Lift Mechanism consists of a twostage tappet which is operated via an electrohydraulic switching valve. Each tappet is ma
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