外文翻譯--內(nèi)燃機(jī)連續(xù)可變氣門正時齒輪傳動機(jī)構(gòu)【中英文文獻(xiàn)譯文】

外文翻譯--內(nèi)燃機(jī)連續(xù)可變氣門正時齒輪傳動機(jī)構(gòu)【中英文文獻(xiàn)譯文】,中英文文獻(xiàn)譯文,外文,翻譯,內(nèi)燃機(jī),連續(xù),可變,氣門,正時,齒輪,傳動,機(jī)構(gòu),中英文,文獻(xiàn),譯文 工程,2013,5,245 - 250 DOI：10.4236/eng.2013.53035在線發(fā)布2013年3月(http://www.scirp. org/journal/eng) 內(nèi)燃機(jī)連續(xù)可變氣門正時齒輪傳動機(jī)構(gòu) 奧薩馬·本·M.河1 ， 穆罕默德·H.墻裙2 機(jī)械工程系，應(yīng)用科學(xué)大學(xué)，安曼，喬丹 機(jī)械工程系，約旦大學(xué)，約旦，安曼 電子郵件：hamzy211@yahoo.com，dado@ju.edu.jo 2012年12月18日收到；2013年1月15日修訂；2013年1月23日被接受 摘要 連續(xù)可變氣門驅(qū)動（CVVA）技術(shù)提供了高的潛力，實現(xiàn)高性能，低燃料消耗和污染物減排 。從中得到充分的好處（CVVT）各種類型的機(jī)制已經(jīng)提出并設(shè)計。這些機(jī)制的一部分機(jī)制進(jìn)行生產(chǎn)，對改善發(fā)動機(jī)的性能表現(xiàn)出顯著的好處。本研究設(shè)計一個新的齒輪傳動機(jī)構(gòu)，從控制LS的進(jìn)氣閥打開（Ivo）和關(guān)閉（IVC）的角度進(jìn)行了研究。 該控制方案的基礎(chǔ)上最大限度地發(fā)揮發(fā)動機(jī)制動功率（P）和燃油消耗（BSFC）在任何轉(zhuǎn)速連續(xù)變化的凸輪軸角度和曲軸轉(zhuǎn)角之間的相。 單缸發(fā)動機(jī)是由“蓮花”軟件模擬，找出最佳在給定的發(fā)動機(jī)轉(zhuǎn)速下的最大功率和最小燃料消耗的相位角。該機(jī)構(gòu)是一個平面的齒輪傳動設(shè)計的精確和連續(xù)控制。 這種機(jī)制在一個簡單的設(shè)計和操作條件下，它可以沒有限制的改變相位角。 關(guān)鍵詞：結(jié)構(gòu)設(shè)計；行星齒輪；可變氣門定時；火花點火發(fā)動機(jī)；性能 1. 介紹 在內(nèi)燃機(jī)中，可變氣門正時（VVT），也被稱為變閥致動器（VVA），是一個廣義的術(shù)語，是一個用來描述任何機(jī)構(gòu)或廣義方法，可以改變在一個內(nèi)燃機(jī)[1-6]氣門升程的形狀或定時事件的。（VVT）系統(tǒng)允許提升，持續(xù)時間或時間（在各種的組合）的攝入和/或排氣閥應(yīng)轉(zhuǎn)變而發(fā)動機(jī)在運轉(zhuǎn)，這對發(fā)動機(jī)性能和排放有重要影響。在一個標(biāo)準(zhǔn)的發(fā)動機(jī)，氣門的事件是固定的，所以每次在不同的負(fù)載和速度性能一直是一個COM的承諾之間的駕駛性能（功率和扭矩），燃油經(jīng)濟(jì)性和排放。發(fā)動機(jī)配備可變氣門驅(qū)動系統(tǒng)是從這個條件約束中解放出來，使性能得到了發(fā)動機(jī)的工作范圍[7-10]改進(jìn)。 某些類型的可變氣門控制系統(tǒng)優(yōu)化功率和扭矩，通過改變閥門開度的時間和/或持續(xù)時間。這些閥門控制系統(tǒng)優(yōu)化性能，在低中檔的發(fā)動機(jī)轉(zhuǎn)速。其他重點加強高轉(zhuǎn)速功率。還有的系統(tǒng)同時提供這些好處，通過控制氣門正時。這可以實現(xiàn)的方法有很多，范圍從機(jī)械設(shè)備的液壓，氣動和無凸輪系統(tǒng)[11-14]。液壓系統(tǒng)遭受許多問題，包括由于溫度變化，液體趨向于像一個堅實的高速行駛時，液壓系統(tǒng)的液壓介質(zhì)的粘度變化，必須仔細(xì)地控制，需要使用功能強大的計算機(jī)和非常精確的傳感器。利用氣動驅(qū)動發(fā)動機(jī)閥將在所有的可能性中不可行，因為它們的復(fù)雜性和壓縮的空氣所需的能量的量非常大。無凸輪系統(tǒng)（或免費使用的電磁閥發(fā)動機(jī)），液壓或氣動執(zhí)行器，打開錐閥代替。常見的問題包括高功耗，高速的準(zhǔn)確性，溫度敏感性，重量和包裝的問題，噪音高，成本高，不安全的情況下操作的電氣問題。Multiair系統(tǒng)（或UniAir）是一個電液可變氣門技術(shù)進(jìn)氣控制（無節(jié)流閥）在汽油或柴油發(fā)動機(jī)。該系統(tǒng)允許最佳進(jìn)氣閥開啟的時間表，它可以完全控制氣門升程和時間。 2.連續(xù)可變氣門正時(CVVT) 首先，（CVVT）系統(tǒng)提供了一個獨特的能力，有獨立的進(jìn)氣和排氣閥門控制內(nèi)燃機(jī)[15-17]。對于任何發(fā)動機(jī)負(fù)荷標(biāo)準(zhǔn)，進(jìn)氣和排氣的時機(jī)可以獨立地編程，并在所有情況下，可以優(yōu)化發(fā)動機(jī)的性能。然而，如果氣門正時可以獨立控制的曲柄軸的旋轉(zhuǎn)，然后接近無限的閥定時的情況下，可容納這將大大提高汽車的燃油經(jīng)濟(jì)性和排放水平。這些系統(tǒng)用于汽油發(fā)動機(jī)，如豐田，日產(chǎn)，本田，和其他幾個汽車比爾斯。在2010年，三菱開發(fā)，并開始批量生產(chǎn)4N13的1.8 L DOHC I4世界第一乘用車柴油發(fā)動機(jī)，采用了可變氣門正時系統(tǒng)。 一個高效的機(jī)制，提出了控制可變氣門正時是行星齒輪機(jī)構(gòu)。行星變速箱裝置的工程設(shè)計，提供了許多優(yōu)點。一個優(yōu)勢是其獨特的緊湊性和卓越的動力傳輸效率的組合。一個典型的行星齒輪箱安排的效率損失是每級只有3％。這種類型的效率，保證了能量輸入的高比例是通過變速器傳輸，而不是浪費在機(jī)械損失在變速箱。行星齒輪箱的布置的另一個優(yōu)點是負(fù)載分布。因為傳輸?shù)呢?fù)載之間的多個行星的共享，扭矩能力大大提高。更多的行星系統(tǒng)有更大的負(fù)載能力和更高的轉(zhuǎn)矩密度。行星變速箱的布置也會創(chuàng)造出更大的穩(wěn)定性，由于均勻分布的質(zhì)量和增加的轉(zhuǎn)動剛度。因此，在這項工作中我們將提出一個新的連續(xù)可變氣門正時的內(nèi)燃機(jī)的行星齒輪傳動機(jī)構(gòu)的設(shè)計。 3. 齒輪傳動機(jī)構(gòu)的設(shè)計 修改后的文本已經(jīng)完成，該文件是為模板準(zhǔn)備。通過使用“另存為”命令復(fù)制模板文件，并使用命名約定的規(guī)定你的雜志你論文的名稱。在這個新創(chuàng)建的文件，突出顯示的所有內(nèi)容，并導(dǎo)入準(zhǔn)備好的文本文件。 3.1.說明 該齒輪傳動機(jī)構(gòu)是由教授M.墻裙機(jī)械工程系在喬丹大學(xué)設(shè)計。該機(jī)制保證了精確的和連續(xù)的凸輪軸相位在內(nèi)燃機(jī)的進(jìn)氣和排氣閥。相位角之間的凸輪軸和曲軸在發(fā)動機(jī)的轉(zhuǎn)速關(guān)系的變化，從而提高發(fā)動機(jī)的性能和排放。 在圖1中所示的機(jī)構(gòu)是一個行星齒輪系由從外部的太陽齒輪（3）的系統(tǒng)中，行星齒輪（2）進(jìn)行了行星臂（1），和一個內(nèi)部的環(huán)形齒輪（4）嚙合的蝸桿齒與外部的蝸輪（5），其連接到一個步進(jìn)電機(jī)連接到發(fā)動機(jī)的計算機(jī)控制系統(tǒng)。當(dāng)步進(jìn)電機(jī)軸是固定的，在很普遍的情況下，環(huán)形齒輪也是靜止的。這將在曲柄軸和凸輪軸之間產(chǎn)生一個恒定的的速度比。一個旋轉(zhuǎn)的步進(jìn)電機(jī)軸使行星齒輪與太陽齒輪和凸輪軸的外部產(chǎn)生附加轉(zhuǎn)動齒圈旋轉(zhuǎn)。這種額外的旋轉(zhuǎn)的結(jié)果，在曲柄軸和凸輪軸之間的相位變化。 圖1.該機(jī)構(gòu)的組成。 3.2.機(jī)構(gòu)安裝 該機(jī)制的操作是由行星齒輪系連續(xù)和精確地改變凸輪軸和曲軸之間的相位角來實現(xiàn)的。內(nèi)齒圈的外齒可以像蝸輪。該機(jī)制通過行星輪系的操作，連續(xù)精確的改變凸輪軸和齒輪之間的相位角。四個相同的行星齒輪與環(huán)形齒輪和太陽齒輪嚙合，它們被兩個行星臂帶動。機(jī)構(gòu)（圖2）被安裝到所述內(nèi)燃機(jī)上，如下所示：在這種方式，凸輪軸（6）和所述太陽齒輪軸是同軸的，然后軸連接的花鍵結(jié)合（7）。一個的行星臂（1）是由鏈條或正時皮帶（8）與曲柄軸（9）連接。蝸輪軸與步進(jìn)電機(jī)是機(jī)械連接的。步進(jìn)電機(jī)配有傳感器和電源，這是連接到CPU控制蝸桿齒輪的運動。 圖2.該機(jī)構(gòu)的安裝 3.3.操作方法 該機(jī)構(gòu)的操作方法簡單，它的描述如下： 1） 當(dāng)步進(jìn)電機(jī)的軸是固定的，在通常情況下，環(huán)形齒輪也是靜止的。通過曲軸臂的轉(zhuǎn)動使旋轉(zhuǎn)一圈，根據(jù)公式： 其中： ω3的速度，在太陽齒輪（3），這也是所述凸輪軸的轉(zhuǎn)速; ω1-臂（1）的速度。 T1和T4的分別是太陽齒輪齒數(shù)和齒圈的內(nèi)齒數(shù)。 太陽齒輪，行星齒輪，內(nèi)齒圈的齒的數(shù)目之間的關(guān)系是： 其中： T2-行星齒輪（2）的齒的數(shù)目。 2） 當(dāng)步進(jìn)電機(jī)的有來自CPU的信號，它會導(dǎo)致蝸桿齒輪的旋轉(zhuǎn)所需要的位移角（5），這將導(dǎo)致環(huán)形齒輪的旋轉(zhuǎn)，因此需額外的旋轉(zhuǎn)的行星旋轉(zhuǎn)齒輪。 3） 旋轉(zhuǎn)產(chǎn)生的太陽齒輪附加轉(zhuǎn)動，這與凸輪軸連接，根據(jù)以下公式 其中： Δθ3位移角的凸輪軸; Δθ5蝸桿齒輪的旋轉(zhuǎn)角度; T5，T6分別表示齒蝸桿齒輪和環(huán)形齒輪的外齒的數(shù)量。 4） 行星臂不會被這旋轉(zhuǎn)影響，因為它是連接到曲軸的。 5） 連接到凸輪軸的太陽輪的附加轉(zhuǎn)動，引起了凸輪軸和曲柄軸之間 Δθ1的 相位變化。 3.4.該機(jī)構(gòu)的優(yōu)點 與其他機(jī)構(gòu)相比，上述機(jī)構(gòu)的主要優(yōu)點可以概括如下： 1） 步進(jìn)電機(jī)的運動限制了相位角的變化，它可以精確到1.8度，控制每一步的零超調(diào)。此值將取決于齒輪的齒數(shù)較小的凸輪軸。 2） 蝸輪，這是連接到步進(jìn)電機(jī)與齒圈嚙合，提供齒輪自鎖機(jī)構(gòu)。保證特定相位角的凸輪軸和曲軸之間的恒定速度比，這對于發(fā)動機(jī)的良好運行是非常必要的。 3） 在該機(jī)構(gòu)中，相位角改變值沒有限制，除了由發(fā)動機(jī)的性能包絡(luò)線所施加的限制。 4.凸輪相位優(yōu)化輸出功率最大化 在這項工作中，進(jìn)氣和排氣氣門正時的最佳值被計算出來，以最大限度地提高制動功率。這些值被用于計算并折衷為不同的發(fā)動機(jī)的速度和壓縮比的制動功率和燃料消耗。分析發(fā)動機(jī)特性的尺寸的目的用的是蓮花工程軟件。蓮花工程軟件里包括的蓮花引擎模擬和分析程序是由蓮花工程公司開發(fā)的20世紀(jì)80年代后期以來的一個內(nèi)部代碼。其中全球性能參數(shù)的功率，容積效率和燃料消耗的驗證，目前已進(jìn)行了廣泛的電流產(chǎn)引擎。 研發(fā)4缸發(fā)動機(jī)（圖3）的仿真模型用來找出最佳的相位角，最大功率。如表1，展示的是發(fā)動機(jī)的幾何數(shù)據(jù)和閥定時。輸入例如進(jìn)氣壓力、溫度、當(dāng)量比的數(shù)據(jù)也已經(jīng)引入到發(fā)動機(jī)的各種運行當(dāng)中。除此之外，還有定的出口數(shù)據(jù)，如背壓。在表2中對氣門正時的默認(rèn)最佳值進(jìn)行了計算。優(yōu)化引擎變量是為了找到最大制動功率輸出。發(fā)動機(jī)的速度是1000-6000r/min。最佳的閥門定時值和默認(rèn)值的制動功率和不同的壓縮率（ CR ）的影響在表3和圖4至6中呈現(xiàn)出來。 5.該機(jī)制的應(yīng)用（例） 表2中給出的數(shù)據(jù)被用來計算蝸輪減速機(jī)的位移角。為了說明上述機(jī)制的工作，我們作出如下設(shè)想： =20，=20，=2，=45 （4） 由方程（1）和（2） ，我們得到： =20×（2+20）=60 （5） 圖3 內(nèi)燃機(jī)的仿真模型 表1基本幾何引擎，燃料是汽油（C8H18） 表2氣門正時的最大功率和不同的速度的最佳值 圖6 制動功率（CR14）效果最佳的閥門值和默認(rèn)值 表3（a）制動功率的最佳氣門正時不同的速度和默認(rèn)值; （b）制動功率運算的最佳氣門正時不同的速度和默認(rèn)值。 表示一個轉(zhuǎn)動臂旋轉(zhuǎn)一周，將導(dǎo)致凸輪軸(和太陽齒輪)轉(zhuǎn)四周。此時需要重新保持曲柄軸和臂之間的速度比與凸輪軸和曲軸之間的速度比相等且等于2，即四沖程內(nèi)燃機(jī)此時的操作。 另一方面，步進(jìn)電機(jī)的角度和凸輪軸角度之間的關(guān)系獲得的公式（3 ） 這意味著當(dāng)步進(jìn)電機(jī)（蝸輪）旋轉(zhuǎn)7.5度，凸輪軸旋轉(zhuǎn)一個額外的程度。 尺寸的機(jī)制中，可以發(fā)現(xiàn)，作以下述操作：我們假定，行星齒輪，太陽齒輪和環(huán)形齒輪都是螺旋齒輪而且螺旋角ψ = 30 °，模數(shù)m = 1 [毫米]和表面寬度F = 20 [毫米] 。此外，蝸桿齒的導(dǎo)程角χ = 10 °和軸向間距p = 2 [毫米]。從這些假設(shè)，我們發(fā)現(xiàn)，該機(jī)制的直徑不超過150 × 150 × 50毫米，因此它可以被較輕松安裝在發(fā)動機(jī)室之間。 6、結(jié)論 行星齒輪驅(qū)動機(jī)構(gòu)的設(shè)計實現(xiàn)了對四沖程單缸發(fā)動機(jī)性能的優(yōu)化。該機(jī)制連續(xù)精確地改變了凸輪軸和曲軸角之間的相位角。優(yōu)化的相位角在給定的速度下制動功率的效果是明顯的。制動功率范圍是在21％和35％ 之間，如表3中所示是根據(jù)發(fā)動機(jī)轉(zhuǎn)速和壓縮比增加的。這種增長是在發(fā)動機(jī)低轉(zhuǎn)速大的情況下，并且隨著發(fā)動機(jī)轉(zhuǎn)速的增加而下降。從而可以得出結(jié)論，建議在四沖程發(fā)動機(jī)實施該機(jī)制來證明發(fā)動機(jī)的性能和效率。 Engineering, 2013, 5, 245-250 doi:10.4236/eng.2013.53035 Published Online March 2013 (http://www.scirp.org/journal/eng) Gear Drive Mechanism for Continuous Variable Valve Timing of IC Engines Osama H. M. Ghazal 1 , Mohamad S. H. Dado 2 1 Mechanical Engineering Department, Applied Science Private University, Amman, Jordan 2 Mechanical Engineering Department, The University of Jordan, Amman, Jordan Email: hamzy211@, dado@ju.edu.jo Received December 18, 2012; revised January 15, 2013; accepted January 23, 2013 ABSTRACT Continuous variable valve actuating (CVVA) technology provides high potential in achieving high performance, low fuel consumption and pollutant reduction. To get full benefits from (CVVT) various types of mechanisms have been proposed and designed. Some of these mechanisms are in production and have shown significant benefits in improving engine performance. In this investigation a newly designed gear drive mechanism that controls the intake valve opening (IVO) and closing (IVC) angles is studied. The control scheme is based on maximizing the engine brake power (P) and specific fuel consumption (BSFC) at any engine speed by continuously varying the phase between the cam shaft angle and the crank shaft angle. A single-cylinder engine is simulated by the “LOTUS” software to find out the optimum phase angle for maximum power and minimum fuel consumption at a given engine speed. The mechanism is a plane- tary gear drive designed for precise and continuous control. This mechanism has a simple design and operation condi- tions which can change the phase angle without limitation. Keywords: Mechanism Design; Planetary Gear; Variable Valve Timing; Spark Ignition Engines; Performance 1. Introduction In internal combustion engines, variable valve timing (VVT), also known as Variable valve actuation (VVA), is a generalized term used to describe any mechanism or method that can alter the shape or timing of a valve lift event within an internal combustion engine [1-6]. The (VVT) system allows the lift, duration or timing (in vari- ous combinations) of the intake and/or exhaust valves to be changed while the engine is in operation, which have a significant impact on engine performance and emissions. In a standard engine, the valve events are fixed, so per- formance at different loads and speeds is always a com- promise between drivability (power and torque), fuel economy and emissions. An engine equipped with a variable valve actuation system is freed from this con- straint, allowing performance to be improved over the engine operating range [7-10]. Some types of variable valve control systems optimize power and torque by varying valve opening times and/or duration. Some of these valve control systems optimize performance at low and mid-range engine speeds. Others focus on enhancing only high-rpm power. Other systems provide both of these benefits by controlling valve timing and lift. There are many ways in which this can be achieved, ranging from mechanical devices to hydraulic, pneumatic and camless systems [11-14]. Hydraulic sys- tem suffer from many problems including viscosity change of the hydraulic medium due to the temperatures change, the liquid tends to act like a solid at high speed, and hydraulic systems must be carefully controlled, which require the use of powerful computers and very precise sensors. Pneumatic system utilizing pneumatics to drive the engine valves would in all probability not be feasible because of their complexity and the very large amount of energy required for compressing the air. Camless system (or, free valve engine) uses electromagnetic, hydraulic, or pneumatic actuators to open the poppet valves instead. Common problems include high power consumption, accuracy at high speed, temperature sensitivity, weight and packaging issues, high noise, high cost, and unsafe operation in case of electrical problems. Multiair system (or Uniair) is an electro-hydraulic variable valve actuation technology controlling air intake (without a throttle valve) in petrol or diesel engines. The system allows optimum intake valve opening schedules, which gives full control over valve lift and timing. 2. Continuous Variable Valve Timing (CVVT) First, The (CVVT) system offers a unique ability to have C op yrigh t ? 20 13 S ciRes . ENG O. H. M. GHAZAL, M. S. H. DADO 246 independent control of the intake and exhaust valves in an internal combustion engine [15-17]. For any engine load criteria, the timing of intake and exhaust can be inde- pendently programmed and the engine’s performance could be optimized under all conditions. However, if valve timing could be controlled independent of crank- shaft rotation, then a near infinite number of valve timing scenarios could be accommodated which would dra- matically improve fuel economy and emission levels of an automobile. These systems are used in several automo- biles with gasoline engine like Toyota, Nissan, Honda, and others. In 2010, Mitsubishi developed and started mass production of its 4N13 1.8 L DOHC I4 world’s first passenger car diesel engine that features a variable valve timing system. One of the high effective mechanisms proposed for controlling variable valve timing is planetary gear me- chanism. The planetary gearbox arrangement is an eng- ineering design that offers many advantages. One ad- vantage is its unique combination of both compactness and outstanding power transmission efficiencies. A ty- pical efficiency loss in a planetary gearbox arrangement is only 3% per stage. This type of efficiency ensures that a high proportion of the energy being input is transmitted through the gearbox, rather than being wasted on me- chanical losses inside the gearbox. Another advantage of the planetary gearbox arrangement is load distribution. Because the load being transmitted is shared between multiple planets, torque capability is greatly increased. The more planets in the system the greater load ability and the higher the torque density. The planetary gearbox arrangement also creates greater stability due to the even distribution of mass and increased rotational stiffness. Hence, in this work we will present a new design of planetary gear drive mechanism for Continuous variable valve timing IC engine. 3. The Gear Drive Mechanism Design After the text edit has been completed, the paper is ready for the template. Duplicate the template file by using the save as command, and use the naming convention pre- scribed by your journal for the name of your paper. In this newly created file, highlight all of the contents and import your prepared text file. You are now ready to style your paper. 3.1. A Description The proposed gear drive mechanism is designed by Prof. M. Dado from mechanical engineering department at the University of Jordan. This mechanism guarantees a pre- cise and continuous camshaft phasing for intake and ex- haust valves in internal combustion engine. The phase angle between the camshaft and crankshaft changes re- lated to engine’s speed, which improve engine’s per- formance and emissions. The mechanism shown in Figure 1 is a planetary gear train system consisting from an external sun gear (3), planetary gears (2) carried by two planet arms (1), and an internal ring gear (4) with external worm teeth meshing with a worm gear (5) which is connected to a stepper motor interfaced to the engine computer control system. When the stepper motor shaft is stationary, which is the prevailing case, the ring gear is also stationary. This yields a constant speed ratio between the crank shaft and the camshaft. A rotation of the stepper motor shaft leads to the rotation of the ring gear resulting in additional rotation for the planetary gears and the external sun gear and the camshaft. This additional rotation results in phase change between the crank shaft and the cam shaft. 3.2. Mechanism Installation The mechanism is operated by planetary gear train to continuously and precisely change the phase angle be- tween camshaft and crank shaft. The internal ring gear has an external worm tooth so it can acts like a worm wheel. It trains with the worm. The mechanism is operated by planetary gear train to continuously and precisely change the phase angle between camshaft and gear. The four identically planetary gears are meshing with the ring gear and the sun gear and they are carried by the two arms. The mechanism (Figure 2) is installed to the internal combustion engine as follows: The mechanism is carried by bearing in such way that the camshaft (6) and the sun gear shaft are coaxial and then shafts are connected by the Figure 1. The components of the mechanism. Cop yrigh t ? 20 13 S ciRes . ENG O. H. M. GHAZAL, M. S. H. DADO 247 Figure 2. The mechanism installation. spline coupling (7). One of the planet arms (1) is con- nected with the crank shaft (9) by chain or timing belt (8). The worm gear shaft is connected mechanically with a stepper motor. The stepper motor is equipped with sensors and power supply, which are connected to the CPU to control the motion of the worm gear. 3.3. The Method of Operation The method of the mechanism operation is easy and sim- ple and it’s described below: 1) When the stepper motor shaft is stationary, which is the prevailing case, the ring gear is also stationary. The rotation of the arm by the crank shaft causes the rotation of the ring according to the equation: 4 3 1 1 T T 1 ? ? ?? ?? ?? ?? (1) where: ω 3 —the speed of the sun gear (3), which is also the speed of the camshaft; ω 1 —the speed of the arm (1). T 1 and T 4 are the number of teeth of the sun gear and the number of internal teeth for the ring gear, respectively. The relationship between the number of teeth for the sun gear, planetary gears, and internal ring gear is: 43 2 TTT ?? 2 (2) where: T 2 —the number of teeth for the planetary gears (2). 2) When the stepper motor have a signal from the CPU it will rotate according to the required shift angle resulting in the rotation of the worm gear (5), which will cause the rotation of the ring gear and consequently an additional rotation of the planetary gears. 3) This rotation resulting in additional rotation for the sun gear, which is connected with the camshaft, according to the following equation 35 3 46 TT TT 5 ? ? ? ?? ? (3) where: Δ θ 3 —the shift angle for the camshaft; Δ θ 5 —the angle of rotation for the worm gear; T 5 , T 6 —the number of teeth for worm gear and external teeth for the ring gear, respectively. 4) The arm will not be affected by this rotation, because it is coupled to the crankshaft. 5) The additional rotation for the sun gear which is connected to the camshaft results in phase change between camshaft and crank shaft of value Δ θ 1 . 3.4. The Advantages of the Mechanism The main advantages of the above mechanism over other mechanisms can be summarized as follows: 1) The change in the phase angle is constrained to the motion of the stepper motor, which can be controlled with accuracy up to 1.8 degrees for each step with zero over- shoot. This value will be smaller for the camshaft de- pending on the gear teeth numbers. 2) The worm gear, which is connected to the stepper motor and meshing with ring gear, offers a self-locking mechanism for ring gear. That will guarantee a constant speed ratio between the camshaft and crank shaft for specific phase angle, which is necessary for good engine operation. 3) In this mechanism there is no limitation for phase angle changing value, except the limitation imposed by the engine’s performance envelop. 4. Cam Phasing Optimization—Maximizing Power Output In this work, the optimum values for intake and exhaust valve timing have been calculated to maximize brake power. These values were used to calculate and compro- mise the brake power and fuel consumption for different engine’s speeds and compression ratios. For the purpose of analyzing the engine characteristics the dimensions were considered with Lotus Engineering Software. The Lotus Engine Simulation and analysis program is an in-house code developed by LOTUS ENGINEERING Company since the late 1980’s. Validation of global per- Cop yrigh t ? 20 13 S ciRes . ENG O. H. M. GHAZAL, M. S. H. DADO Cop yrigh t ? 20 13 S ciRes . ENG 248 which means that one revolution of the arm results in 4 revolutions of the camshaft (and the sun gear). This re- quires keeping the velocity ratio between crankshaft and the arm equals two to obtain the velocity ratio between the camshaft and the crankshaft equals two, which is neces- sary for four stroke IC engine operation. formance parameters of power, volumetric efficiency and fuel consumption has been performed on a wide range of current production engines. The simulation model of 4-cylinder engine (Figure 3) has been built to find out the optimum phase angle for maximum power. The engine geometry data and valve timings are as shown in Table 1. Input data such as inlet pressure, temperature, equivalence ratio are also intro- duced for all runs. Also the required exit data such as the back pressure are given. The calculations were carried out for the default and optimum values of valve timing which are given in Table 2. The optimization engine variable is to find the maximum brake power output. The speed is varied from 1000 - 6000 rpm. The effects of optimum valve timings values and default values on the brake power and for different compression ratio (CR) are illus- trated in Table 3 and Figure 4 through 6. On the other hand, the relationship between the stepper motor angle and camshaft angle is obtain from Equation (3) 35 5 35 3 46 7.5 NN NN ? ?? ? ? ?? ? ?? ?? ? ( 6) That mean when the stepper motor (and worm gear) rotates 7.5 degrees, the camshaft rotates one additional degree. The dimensions of the mechanism can be found as fol- lowing: we assume that planetary gear, sun gear, and ring gear are helical gears with helical angle ψ = 30? and module m = 1 [mm] and the face width f = 20 [mm]. In addition, the worm teeth has lead angle χ = 10? and axial pitch p = 2 [mm]. From these assumptions we find out that the diameter of the mechanism are not more than 150 × 150 × 50 [mm], so it can be installed in engine room eas- ily. 5. The Application of the Mechanism (Example) The data given in Table 2 were used to calculate the re- quired values of shift angle for worm gear. To illustrate the work of the above mentioned mechanism we have made the following assumptions: 6. Conclusion 3256 20, 20, 2, 45 TTTT ???? (4 ) A planetary gear drive mechanism is designed and im- plemented to optimize the performance of a four stroke single-cylinder engine. The mechanism precisely and continuously changes the phase angle between the cam shaft and crank shaft angles. The effect of optimizing the phase angle at a given speed on the brake power is From Equations (1) and (2) we get: ?? 4 31 20 2 20 60 and 4 T ?? ???? ? (5) Figure 3. The simulation model of IC engine. O. H. M. GHAZAL, M. S. H. DADO 249 Table 1. Base engine geometry, fuel is gasoline (C 8 H 18 ). Type of engine 4-stroke Bore 82 mm Stroke 80 mm No. of cylinders 4 Compression ratio 8 - 14 Inlet throat dia. 26.5 mm Exhaust throat dia. 22.5 mm Max. valve lift 8 mm IVO angle bTDC 10 deg IVC angle aBDC 66 deg EVO angle bBDC 38 deg EVC angle bTDC 38 deg Speed 1000 - 6000 rpm Table 2. Optimum values of valve timing for maximum power and different speeds. Valve timings Inlet valve timing Exhaust valve timing Speed, rpm Open, bTDC Close, aBDC Open, bBDC Close, aTDC 1000 25? 30? 55? 32? 2000 33? 37? 65? 39? 3000 44? 43? 70? 45? 4000 49? 47? 70? 51? 5000 51? 50? 70? 53? 6000 57? 60? 70? 57? Table 3. (a) Brake power for optimum and default values of valve timing for different speeds; (b) Brake power for op- timum and default values of valve timing for different speeds. (a) CR 8 CR 10 Speed rpm Opti Def % incre Opti Def % incre 1000 3.73 2.78 34 4.1 2.98 37 2000 7.8 6.09 28 8.35 6.52 28 3000 11.7 9.37 25 12.56 10.05 25 4000 15.31 12.4 23 16.47 13.38 23 5000 18.56 15.2 22 20.07 16.43 22 6000 21.39 17.7 21 23.22 19.13 21 (b) CR 12 CR 14 Speed, rpm Opti Def % incre Opti Def % incre 1000 4.21 3.11 35 4.3 3.24 33 2000 8.76 6.8 29 9.07 7.06 28 3000 13.1 10.5 25 13.69 10.91 25 4000 17.3 14.0 23 18.01 14.58 24 5000 21.1 17.3 22 22.02 17.97 23 6000 24.5 20.2 22 25.62 21.03 22 Figure 4. The effect of optimum valve values and default values on brake power (CR 8). (a) (b) Figure 5. (a) The effect of optimum valve values and default values on brake power (CR 10); (b) The effect of optimum valve values and default values on brake power (CR 12). Figure 6. The effect of optimum valve values and default values on brake power (CR 14). Cop yrigh t ? 20 13 S ciRes . ENG O. H. M. GHAZAL, M. S. H. DADO 250 appreciable. The increase of the brake power ranges be- tween 21% and 35% depending on the engine speed and compression ratio as indicated in Table 3. This increase is large at low engine speed and drops as the engine speed increases. It could be concluded that the implementation of the proposed mechanism in four stroke engines im- proves the engine performance and efficiency. REFERENCES [1] S. Bohac and D. Assanis, “Effects of Exhaust Valve Tim- ing on Gasoline Engine Performance and Hydrocarbon Emissions,” SAE Technical Paper No. 2004-01-058, 2004. [2] T. H. Ma, “Effect of Variable Engine Valve Timing on Fuel Economy,” SAE Technical Paper No. 880390, 1988. [3] C. Gray, “A Review of Variable Engine Valve Timing,” SAE Technical Paper No. 880386, 1988. [4] T. Ahmad and M. A. Theobald, “A Survey of Variable Valve-Actuation Technology,” SAE Technical Paper No. 891674, 1989. [5] T. Dresner and P. Barkan, “A Review and Classification of Variable Valve Timing Mechanisms,” SAE Paper, No. 890667, 1989. 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