【正文】 12 Road springs 。這也是采用了最優(yōu)化設(shè)計(jì)方法選用了轉(zhuǎn)向梯形結(jié)構(gòu)這樣得到最佳的設(shè)計(jì)效果。在設(shè)計(jì)中首先是要確定轉(zhuǎn)向梯形機(jī)構(gòu)的幾何尺寸參數(shù)。因汽車行駛時(shí)要不停踩油門踏板，所以踩下時(shí)要輕便。后板簧的布置應(yīng)做到前低后高，亦可獲得不足轉(zhuǎn)向?？拓泝捎密嚥捎靡粋€(gè)萬向節(jié)。特別是驅(qū)動(dòng)橋的傳動(dòng)軸與油底殼或附近的橫梁等零件的間隙也應(yīng)如此。當(dāng)車架和地面平行時(shí)，前輪垂直線和前輪中心線重合。所以要滿足以下要求：有足夠的負(fù)荷能力和速度能力；較小的滾動(dòng)阻力和行駛噪聲；良好的均勻性和質(zhì)量平衡性；耐磨損、耐老化、抗刺扎和良好的氣密性；質(zhì)量小、價(jià)格低、拆裝方便、互換性好。客貨兩用車通常采用前輪為獨(dú)立懸架，后輪采用非獨(dú)立懸架設(shè)計(jì)，這種懸架設(shè)計(jì)時(shí)注意到了，懸架上載荷變化時(shí)，保證輪距變化不超過177。8）作用滯后性應(yīng)盡可能好。10）進(jìn)行運(yùn)動(dòng)校核，保證轉(zhuǎn)向輪與轉(zhuǎn)向盤轉(zhuǎn)動(dòng)方向一致。（2）主減速器的選擇主減速器的齒輪有弧齒錐齒輪、雙曲面齒輪、圓柱齒輪和蝸輪蝸桿等形式。圖24 雙十字軸萬向節(jié)的等速傳動(dòng)條件十字軸萬向節(jié)兩軸的夾角a不宜過大，當(dāng)a由4176。4）設(shè)置動(dòng)力輸出裝置，需要時(shí)能進(jìn)行功率輸出。5）應(yīng)有足夠的吸熱能力和良好的通風(fēng)散熱效果，以保證工作溫度不致過高，延長使用壽命。（4） 防止部件的疲勞、損壞或誤操作，如散熱器、儀表等。于是可根據(jù)（2－6）得：其相應(yīng)轉(zhuǎn)數(shù)為：在實(shí)際工作中，還利用現(xiàn)有汽車統(tǒng)計(jì)數(shù)據(jù)初步估計(jì)汽車比功率來確定發(fā)動(dòng)機(jī)應(yīng)有功率。4）比功率和比轉(zhuǎn)矩比功率是評(píng)價(jià)汽車動(dòng)力性能如速度性能和加速性能的綜合指標(biāo)，比轉(zhuǎn)矩則反映了汽車的比牽引力或牽引能力。在汽車設(shè)計(jì)時(shí)一般希望汽車具有適度的不足轉(zhuǎn)向特性。其中，乘員和駕駛員每人質(zhì)量按計(jì)，于是有： （2－1）式中，為包括駕駛員及隨行人員數(shù)在內(nèi)的人數(shù)，應(yīng)等于座位數(shù)。為此，輪距寬度應(yīng)在規(guī)定的輪距之間，這里取前輪距，后輪距。為解決此矛盾，一般采用增加汽車軸數(shù)的辦法來減少單軸的負(fù)荷采用增加軸數(shù)的辦法，可以提高載重量而不增加單軸負(fù)荷，同時(shí)還不會(huì)增加車箱底板的離地高度，提高通用化、系列化水平，便于生產(chǎn)、降低生產(chǎn)成本等。對(duì)于轉(zhuǎn)向系統(tǒng)，采用了循環(huán)球式的轉(zhuǎn)向器。為了提高安全性和舒適性在行車制動(dòng)方面應(yīng)采用氣壓式的行車制動(dòng)系統(tǒng)并且為了提高其制動(dòng)效能應(yīng)采用分路系統(tǒng)。最后參考了同類車型的底盤總布置方案來對(duì)黃?？拓泝捎密囘M(jìn)行底盤總布置，并繪制了底盤的總布置圖。前懸采用扭桿彈簧獨(dú)立懸架,增加汽車行駛的平順性和舒適性,使車身底板空載與滿載時(shí)保持平衡。（7）試制、試驗(yàn)、定型。三、各部件及總成總體位置的確定對(duì)于各部件及總成在車架上安裝位置的問題，主要考慮到它們之間的工作關(guān)系、運(yùn)動(dòng)關(guān)系、安全因素和對(duì)軸荷分配的影響來完成的。綜上所述，汽車的型式如圖2－1所示。V，人均整備質(zhì)量值在人，這里取人均整備質(zhì)量值為人。為了使其磨損均勻，對(duì)后輪裝單胎的雙軸汽車，要求其滿載時(shí)的前后軸荷分配均為50％，而對(duì)后輪為雙胎的雙軸汽車，則前后軸荷可大致按1／3和2／3的比例處理。發(fā)動(dòng)機(jī)排量小些的乘用車為。（3）通過性幾何參數(shù)底盤設(shè)計(jì)要確定的通過性幾何參數(shù)有：最小離地間隙、接近角、離去角等。發(fā)動(dòng)機(jī)就是振源之一。圖23汽車發(fā)動(dòng)機(jī)的彈性懸置離合器在機(jī)械傳動(dòng)中是作為一個(gè)獨(dú)立的總成而存在的，它是汽車傳動(dòng)系中直接與發(fā)動(dòng)機(jī)連接的總成。則由（2－11）可算出：故查汽車設(shè)計(jì)手冊，取 ，取 。最低擋傳動(dòng)比則要考慮汽車的最大爬坡度、驅(qū)動(dòng)輪與路面間的附著力、主減速比和驅(qū)動(dòng)輪的半徑及所要達(dá)到的最低穩(wěn)定行駛車速等。3）齒輪及其他傳動(dòng)件工作平穩(wěn)，噪聲小。3）汽車在任何行駛狀態(tài)下，轉(zhuǎn)向輪都不得產(chǎn)生自振，轉(zhuǎn)向盤沒有擺動(dòng)。確定制動(dòng)系時(shí)應(yīng)滿足以下要求：1）具有足夠的制動(dòng)效能。確定懸架時(shí)應(yīng)滿足以下要求：1）保證汽車有良好的行駛平順性。車架主要作用是搭載汽車各總成與部件，是整個(gè)汽車的基體。它作為標(biāo)注縱向尺寸的基準(zhǔn)線，向前為“”，向后為“+”，該線標(biāo)記為x/0。發(fā)動(dòng)機(jī)罩與發(fā)動(dòng)機(jī)零件之間的間隙不得小于。越野車的傳動(dòng)夾角可達(dá)11176。在縱置板簧的布置中，轉(zhuǎn)向垂臂的球頭中心應(yīng)與板簧的跳動(dòng)中心重合或接近，上節(jié)臂的球頭中心應(yīng)與主片的高度相差，這樣可以減少車輪跳動(dòng)時(shí)的干涉量，緊急制動(dòng)時(shí)的干涉跑偏問題。布置制動(dòng)管時(shí)要注意安全可靠，整齊美觀，防止管子腐蝕。在此主要對(duì)轉(zhuǎn)向系的運(yùn)動(dòng)干涉問題進(jìn)行檢核。當(dāng)車輪轉(zhuǎn)向時(shí)U點(diǎn)將在垂直于主銷中心線EG的平面上畫弧。 4Engine 。 instead, they are locked together so that the front and rear wheels have to turn at the same average speed. This is why these vehicles are hard to turn on concrete when the fourwheeldrive system is engaged.Each wheel is provided with its own separate halfshaft connected by a differential gear and meeting at about the center of the wheels are free to rotate at different speeds although they are provided with equal by the differential gear.Bake SystemFor controlling the movement of the vehicles or to stop them,efficient braking system is a necessity for a attached to each of the four wheels are of two the initial type,a pair of shoes carried on a stationary plate is expanded in contact with a rotating drum mounted on the wheels to arrest the motion of the the modern type of brakes,one or more pairs of pads are carried in a caliper attached to the axle or wheel supporting sides of the disk mounted on the wheel are griped by these applying pressure on a pedal,the brakes are hand lever acting through a separate linkage and locked in the on position is used.For operating the brake,either mechanical or hydraulic system is system requiring gearing system for mechanical and hydraulic fluid for the hydraulic brakes are usedPropeller Shaft And Uniwersal JointFor connecting the output shaft of the gear box to the rear axle,a long shaft known as propeller shaft is shaft is either enclosed in a tubular casing or kept exposed or opened with a universal joint fitted at each end for allowing the changes in the shaft alignment with the rise and fall of the rear axle due to road surface joints cannot be eliminated even if the final drive gears are fixed to the frame with the wheel springing the misalignment resulting from the flexing of the vehicle structure over bumpy road surfaces can be avoided nor the precise alingnment of shaft can be ensured without them.For preventing the transmission of shock from uneven road surfaces to the vehicle,springs are used to support the vehicle on the axle.In order to allow for the vertical movements of the wheels relative to the frame as well as to allow the parts of the shaft to operate at different angle,another increasingly used arrangement is consists of mounting the finaldrive gears and the differential gear in a casing attached to the frame with independently sprung wheels attached to them by means of shafts through devices called universal joints.WheelsThe wheels which are four in number are fitted below the car chassis to support the load of the vehicle and passengers as well as to run the arefitted with hollow rubber tyres filled with air in rubber tubes under sufficient pressure necessary for carrying the caused by road irregularities are absorbed by fitting springs between the wheels and the vehicle allowing the vertical movement of wheels in relation to vehicle,greater part of unevenness of road surfaces is taken care of.When going round a curve,the inner wheel has to travel a smaller distance in parison to the ou。 2Wheels 。上述的是在前輪未轉(zhuǎn)向的情況下確定的橫拉桿鉸接點(diǎn)的圖解法，同時(shí)也適用于對(duì)前輪向左、向右轉(zhuǎn)向后的不同位置進(jìn)行校核。油箱應(yīng)遠(yuǎn)離消聲器和排氣管，更不能布置在發(fā)動(dòng)機(jī)艙內(nèi)。整車設(shè)計(jì)人員要與總成設(shè)計(jì)人員共同商定，選擇行車和駐車制動(dòng)器的方案、制動(dòng)操縱方式及驅(qū)動(dòng)機(jī)構(gòu)的型式、結(jié)構(gòu)和布置。在系列車型設(shè)計(jì)當(dāng)中，由于軸距的變化會(huì)影響梯形底角的變化，在實(shí)際生產(chǎn)中，這種細(xì)小的變動(dòng)很難處理，管理上容易出現(xiàn)誤裝或錯(cuò)裝，生產(chǎn)也不好安排，為此就應(yīng)在設(shè)計(jì)時(shí)回避這一誤區(qū)。目的是能使汽車在滿載狀態(tài)時(shí)，傳動(dòng)系的軸線互相之間夾角最小，甚至從前至后成為一條直線，以提高萬向節(jié)的傳動(dòng)效率和減少磨損；（5）滿載時(shí)傳動(dòng)軸的正常夾角在4176。發(fā)動(dòng)機(jī)高度位置初步確定之后，風(fēng)扇和散熱器的高度也隨之而定，要求風(fēng)扇中心與散熱器幾何中心相重合。它作為標(biāo)注垂直尺寸的基準(zhǔn)線，向上為“+”、向下為“”，該線標(biāo)記為z/0。一般將后懸架縱置鋼板彈簧的前部吊耳位置布置的比后部吊耳低，于是懸架的瞬時(shí)運(yùn)動(dòng)中心位置降低，結(jié)果后橋軸線的偏離不再使汽車具有過多轉(zhuǎn)向的趨勢。懸架是現(xiàn)代汽車上的重要總成之一，它把懸架與車軸彈性地連接起來。制動(dòng)系的功用是使汽車以適當(dāng)?shù)臏p速度降速行駛直至停車；在下坡時(shí)，使汽車保持適當(dāng)?shù)姆€(wěn)定車速；使汽車可靠地停留在原地或坡道上。確定轉(zhuǎn)向系時(shí)應(yīng)滿足以下要求：1)汽車轉(zhuǎn)彎行駛時(shí)，全部車輪應(yīng)繞瞬時(shí)轉(zhuǎn)向中心旋轉(zhuǎn)，任何車輪不應(yīng)有側(cè)滑。驅(qū)動(dòng)橋地選擇應(yīng)滿足一下要求：1）選擇適當(dāng)?shù)闹鳒p速比，保證給定條件下的動(dòng)力性和經(jīng)濟(jì)性。一般乘用車變速器多采用個(gè)擋，這里采用五擋變速器。所以由（2－9）可確定離合器的摩擦力矩為離合器的靜摩擦力矩為： （2－10）式中，為摩擦面的靜摩擦因數(shù)，一般取，這里取；為壓盤施加在摩擦面上的工作壓力；為摩擦片的平均摩擦半徑；為摩擦片面數(shù)，單片離合器的。在變速器端放置一個(gè)支點(diǎn)，傳動(dòng)系前方承載質(zhì)量較大，所以前方放置兩個(gè)支點(diǎn)?？紤]到整車的動(dòng)力性、經(jīng)濟(jì)性、環(huán)保性等因素及國內(nèi)發(fā)動(dòng)機(jī)制造廠現(xiàn)生產(chǎn)的發(fā)動(dòng)機(jī)種類和型式，選用大連道依茨柴油發(fā)動(dòng)機(jī)，型號(hào)為CA4DC210E3，直列四缸四沖程、水冷式柴油發(fā)動(dòng)機(jī)，其最大功率/3600r/min，最大扭矩/2000r/min。（2）汽車最小轉(zhuǎn)彎直徑轉(zhuǎn)向盤轉(zhuǎn)至極限位