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畢 業(yè) 設 計(論 文)
題目 實用微型客車設計—車架、制動系設計
畢業(yè)設計(論文)開題報告
(學生填表)
院系:車輛與動力工程學院
課題名稱
實用微型客車設計------------車架設計、制動系統(tǒng)設計
學生姓名
專業(yè)班級
課題類型
指導教師
職稱
課題來源
1. 設計(或研究)的依據(jù)與意義
近年來,我國客車市場相繼出現(xiàn)了高速增長、平緩調整、全面回升的發(fā)展景象:2003-2004年高速發(fā)展;2005年,隨著國家宏觀調控政策的全面施行,客車市場受到一定的抑制,銷量下滑,2007年國民經(jīng)濟穩(wěn)定快速發(fā)展,汽車行業(yè)蓬勃向上,汽車市場也走出了2005年的低迷狀態(tài),表現(xiàn)出良好的回升勢頭。,
當然,隨著汽車技術的進步和汽車行駛速度的提高,車架及車輛制動系統(tǒng)在車輛的安全方面占著重要的地位,車架作為汽車的承載基體,為貨車,中型及以下的客車,中高級轎車所采用;支撐著發(fā)動機,離合器,變速器,轉向器,非承載式車身和貨箱等所有簧上質量的有關機件,承受著傳給它的各種力和力矩。本設計采用邊梁式車架。要保證微型客車的良性發(fā)展必須采用低成本戰(zhàn)略。采用傳統(tǒng)技術,以低的投入實現(xiàn)高的效益的增長,發(fā)展廉價的中低檔車,以適應市場的需求,本設計采用液力制動器,由于降低成本,采用人力制動系統(tǒng),行車制動系統(tǒng)采用液力式,駐車制動采用機械式。在制動傳動機構方面,為適應各國和各地區(qū)制動法規(guī)的要求,制動管路必須采用雙回路傳能型式。
為保證汽車行駛的安全性,進行車架和制動系的設計是很有必要的。
2. 國內外同類設計(或同類研究)的概況綜述
車架有邊梁式,鋼管式等多種形式,目前國內外采用最多的是邊梁式,而汽車制動器的種類很多,形式多樣。伴隨著汽車的研究開發(fā),汽車動力系統(tǒng)發(fā)生了很大的改變,出現(xiàn)了很多新的結構型式和功能形式。新型動力系統(tǒng)的出現(xiàn)也要求制動系統(tǒng)結構形式和功能形式發(fā)生相應的改變。
(1)供能裝置的發(fā)展
氣壓制動是發(fā)展最早的一種動力制動系統(tǒng)。液壓制動是目前得到廣泛應用的一種制動系統(tǒng),技術已經(jīng)非常成熟。目前正在發(fā)展的電液復合制動以及電子制動中使用了電機作為制動能源,人力踩制動踏板作為控制來源。
(2)控制裝置的發(fā)展
隨著清潔能源汽車和電動汽車的研究應用,以及電子技術在汽車上面的廣泛應用,制動系統(tǒng)的控制裝置也出現(xiàn)了電子化的趨勢,其中電制動完全改變了制動系統(tǒng)的控制和管理,會使汽車制動系統(tǒng)發(fā)生革命性的變化,它采用電子控制,可以更加準確、更高效率地實現(xiàn)制動。
(3)傳動裝置的發(fā)展
電子制動是利用制動電機產(chǎn)生制動力直接作用到制動器,它的控制信號來自控制單元,用信號線傳遞制動信號和制動力信息。
(4)制動器的發(fā)展
目前汽車制動器基本都是摩擦式制動器,由于盤式制動器熱和水穩(wěn)定性以及抗衰減性能較鼓式制動器好,可靠性和安全性也好,而得到廣泛應用。普遍應用的液壓制動現(xiàn)在已經(jīng)是非常成熟的技術,隨著人們對制動性能要求的提高,防抱死制動系統(tǒng)、驅動防滑轉控制系統(tǒng)、電子穩(wěn)定性控制程序、主動避撞技術等功能逐漸融人到制動系統(tǒng)中,需要在制動系統(tǒng)上添加很多附加裝置來實現(xiàn)這些功能,使得制動系統(tǒng)結構復雜化,增加了液壓回路泄漏的可能以及裝配、維修的難度,制動系統(tǒng)要求結構更加簡潔,功能更加全面和可靠,制動系統(tǒng)的管理也成為必須要面對的問題,電子技術的應用是大勢所趨。
3. 課題設計(或研究)的內容
微型客車的基本參數(shù)為:發(fā)動機選用JL462Q,最高車速為95km/h,最小轉彎半徑≤4.5m,乘員人數(shù)6-8人,檔位數(shù)4+1。
參照長安牌SC6331A微型客車的整體布局參數(shù)(網(wǎng)上可以查到)、亞洲牌微型客車底盤實物(車輛實驗室整車陳列室內)、長劍牌微型轎車實物(車輛實驗室整車拆裝室內)和有關的其他車型(查閱有關資料),完成微型客車的車架、制動系設計任務。
4. 設計(或研究)方法
(1)進行制動系統(tǒng)的總成設計
1,制動系的結構類型及選擇
2,制動系參數(shù)選擇及計算
3,駐車制動和應急制動的計算
4,制動器主要零件的結構設計
5,制動驅動機構的選擇及計算
(2)進行車架的總成設計
5. 實施計劃
(5-6周) 進行調研,搜集,分析資料,完成開題報告。
(6-7周) 全組集體討論,確定總體方案。每個學生確定自己的設計內容與繪圖數(shù)量。
(8-9周) 整理本設計內容相關的數(shù)據(jù)資料,進行必要的理論計算,擬說明書 草稿,搜集相關外文資料并翻譯。
(10-11周) 完成總圖設計。
(12-13周) 完成零部件圖設計,并完成機繪圖。
(14-15周) 按要求整理,編寫設計說明書。
(16-17周) 審閱,評閱設計資料,答辯,評定成績。
指導教師意見
指導教師簽字: 年 月 日
研究所(教研室)意見
研究所所長(教研室主任)簽字: 年 月 日
車輛與動力工程學院畢業(yè)設計說明書
實用微型客車設計—車架、制動系設計
摘要
汽車制動系是保證汽車及駕駛者生命安全的重要部分,制動系是使行進中的汽車減慢速度或者停止運動。
這次我的畢業(yè)設計題目是微型客車設計---車架和制動系設計。在第二章我主要介紹了制動系的概況和設計時應滿足的基本要求。第三章主要是制動系的類型及最后確定的方案,其中列出了幾種可供選擇的類型并進行了分析、比較最后確定的方案如下:行車制動器:前盤后鼓,盤式制動器為通風型浮動鉗盤式制動器,鼓式制動器為領從蹄式制動器。第四章主要介紹了制動系主要結構參數(shù)的選擇并進行了簡單的計算,是本設計說明書的核心部分,其中包括鼓式和盤式制動器主要結構參數(shù)的選擇,例如:制動鼓內徑、摩擦襯片寬度和包角、摩擦襯片起始角、制動盤直徑和厚度等,同時對制動力和制動力矩分配系數(shù)進行了計算。第五章主要對駐車制動和應急制動進行了簡單的計算。第六章介紹的是制動器主要零件的結構設計,如制動鼓、制動蹄、制動底板和制動輪缸等。第七章包括制動驅動機構的選擇和計算,制動管路的分路系統(tǒng)和液壓驅動機構的設計和計算。第八章列出了車架的幾種類型,分析比較之后,最后確定選用前窄后寬的邊梁式車架,并且在這一章中對車架的彎曲強度進行了計算,對車架的剛度進行了校核。通過這一系列的分析、計算、校核等,這套設計方案是可行的。 THE DESIGN OF PRARECTICAL MINIATURE
CAR’S —THE DESIGN OF FRAME AND BRAKE SYSTEM
ABSTRACT
The brake system is an important part to keep safety for automobile, the purpose of the braking system is to slow down and stop the moving automobile.
My topic in this graduation design is the design of frame and the brake system.In second chapter we mainly introduced something about the brake system and some requests which the brake system should satisfied. The third chapter mainly introduced the type of the brake system and finally determined the plan, in this chapter we listed several kinds to choose, at last we determined the plan through analysis and compare with as follows: In traveling brake system, the former wheels are disc brake and the rear wheels are drum brake. The disc brake for ventilating fluctuation pliers disc brake, and the drum type brake for collar from foot brake. The fourth chapter mainly introduced the main design parameter’s choice and has carried on the simple computation, and this chapter is the most important part. Including drum type and disc brake main design parameter choice, For example: The brake drum inside diameter, the width, the angle and the outset angle, the diameter and thickness of the brake plate and so on, simultaneously have carried on the computation to the brake strength and the braking moment distribution coefficient. The fifth chapter mainly said the vehicle to brake on stopping and momentary through simple computation. The brake major parts structural design, like brake drum, brake shield plate or disc and brake wheel cylinder and so on were designed in the sixth chapter. Seventh chapter including applies the brake the driving mechanism choice and the computation, the brake line by-pass system and the hydraulic pressure driving mechanism design and the computation. Eighth chapter has listed the frame several kind of types, after the analysis comparison, after finally front determined selects the narrow width side beam plate frame, And has carried on the computation in this chapter to the frame bending strength, has carried on the examination to the frame rigidity. Through this a series of analysis, computation, examination and so on, this set of design proposal is feasible
KEY WORDS: brake system, drum brake, disk brake, frame
目 錄
第一章 前言…………………………………………………………......1
§1.1 汽車的誕生與世界汽車工業(yè)的發(fā)展……..…….……….…....1
§1.2 我國汽車工業(yè)的發(fā)展………….………….……………..…....2
第二章 制動系概況………………………………………………..…....4
第三章 制動系的結構類型及選擇………………………………..…....6
§3.1 后輪鼓式制動器的選擇…………………………………........6
§3.2 前輪盤式制動器的選擇…………………………………...….9
§3.3 盤式制動器的優(yōu)缺點及確定的方案………………………..10
第四章 制動系參數(shù)選擇及計算…………………………………........11
§4.1 制動器主要結構參數(shù)的選擇………………………….….....11
§4.2 制動力與制動力矩分配系數(shù)………………………………..14
第五章 駐車制動和應急制動計算…………………………………....18
§5.1 駐車制動計算………………………………………………..18
§5.2 應急制動計算…………………………………………..…....19
第六章 制動器主要零件的結構設計………………………………....20
第七章 制動驅動機構的選擇及計算………………………………....22
第八章 車架…………………………………………………………....26
第九章 總結……………………………………………………….…...33
參考文獻………………………………………………………….….....34
致謝………………………………………………………………...…...35
III
Brake System Service and Maintenance
The types of trouble that may develop in drum-type hydraulic braking systems include the following.
(1) Brake pedal goes to floorboard. When this happens, it means that there is no pedal reserve, since full pedal movement does not provide adequate braking. This would be a very unlikely situation with a dual-brake system. One section might fail (front or rear) but it would be rare for both to fail at the same time. If this happens, chances are the driver has been driving for some time with one section out .
(2) One brake drags. This means that the brake shoes are not moving away from the brake drum when the brakes are released.
(3) All brake drag. When all brakes drag, it may be that the brake pedal does not have sufficient play, so that the piston in the master cylinder does not fully retract.
(4) Car pulls to one side. If the car pulls to one side when the brakes are applied, this means that more braking pressure is being applied to one side than to the other.
(5) Soft, or spongy, pedal. If the pedal action is soft, or spongy, the chances are that there I is air in the system, although out-of adjustment brake shoes could cause this.
(6) Poor braking action requiring excessive pedal pressure. If the brake lining is soaked with oil or brake fluid, they will not hold well, and excessive pedal pressure is required for braking action. Improper brake-shoe adjustment or the use of the wrong brake lining could cause the same trouble.
(7) Brakes too sensitive or grab. When the brakes are too sensitive and brake hard or grab with slight brake –pedal pressure, it may be that the linings have become greasy , that the brake shoes are out of adjustment , that the wrong lining is being used and that drums are scored or rough .
(8) Noisy brakes. Brakes will become noisy if the brake linings wear so much that rivets come into contact with the brake drum, if the shoes become warped so that pressure on the drum is not uniform ,if shoe rivets become loose so that they contact the drum , or if the drum becomes rough or worn .
(9)Air in system. If air gets into the hydraulic system, poor braking and a spongy pedal will result. It is possible accidentally to plug the vent (by wrench action ) when the filler plug is removed .
(10) Loss of brake fluid. Brake fluid can be lost if the master cylinder leaks, if the wheel cylinder leaks, if the wheel cylinder leaks, if the line connections are loose, or if the line is damaged.
(11) Warning light comes on when braking (dual system). This is a signal that one of the two braking systems has failed. Both systems (rear and front) should be checked so that the trouble can be found and eliminated. It is dangerous to drive with this condition, even though braking can be achieved, because only half the wheels are being broken.
Many of the troubles on the disk in the disk type of brake system are similar to those that may be found in the drum type.
Whenever you encounter a complaint of faulty braking action, always try to analyze it and determine its cause. Sometimes, all that is necessary (in earlier drum-type brakes) is a minor brake with the self-adjuster; the brakes automatically adjust themselves to compensate for lining wear. Other brake services include addition of brake fluid, bleeding the hydraulic system to remove air, repair or replacement of master cylinder and wheel cylinders, replacement of master cylinder and wheel cylinders, replacement of brake linings, and refinishing of brake drums.
Tire service and maintenance includes periodic inflation to make sure that the tire is kept at the proper pressure, periodic tire inspection so that small damages can be detected and repaired before they develop into major defects, and tire removal, repair, and replacement.
Incorrect tire inflation can cause many types of steering and braking difficulty. Low pressure will cause hard steering, front wheel shimmy, steering kickback, and tire squeal on turns. Uneven tire pressure will tend to make the car pull to one side. For these reason, it is very important to maintain proper pressure in the tires. There are a few points you should remember when inflating tires:
(1) Don’t inflate a tire when it is hot, as, for instance, after hard driving on the highway.
(2) Always replace the cap (where used) after checking air pressure or inflating a tire.
The removal and replacement of tires are not difficult on smaller vehicles, but on large, heavy-duty applications special tools are required to remove and handle them. Air must be released from the center of the rim. A tire tool or flat stock can be used to pry one part of the bead up over the rim flange (start near the valve stem). Care must be exercised to avoid damaging the tire bead or inner tube. After the bead is started over the rim flange with the tool, the remainder of the bead can be worked out over the flange with the hands. The other bead of the tire is removed from over the same side of the rim flange in a similar manner.
In tire shops where many tires are being changed daily, special tire-changing machines are used. In these, the wheel is put into place and air pressure is used to force the tire bead away from the rim. This machine will remove a tire from a wheel rim in a few seconds. Further, it can be used to quickly install a tire on the rim.
The following cautions should be carefully observed in tire service and maintenance work:
(1) On tubeless tires, do not use tire irons to force the beads away from the rim flanges; this could damage the rim seals on the beads and cause an air leak. Instead, use a bead breaker tool.
(2) If a tire has been deflated, never inflate it while the car weight is on the tire. Always jack up the car before inflating the tire so that the tube can distribute itself around the tire evenly. If this is not done, some parts of the tube will be stretched more than other parts, and this puts a strain on the tube that might cause it to blow out.
A number of repairs can be made on tires and tubes, ranging from the patching of nail holes, punctures, or cuts to vulcanizing new tread material to the tire casing. This latter operation is known as recapping, since a new cap, or tread, is placed on the tire. Repair procedures vary according to whether the tire is or is not of the tubeless type.
With the tube type, puncture repair requires removal of the tire so that the puncture in the tube can be attached. This is done with a special kit. Patches require curing, or vulcanizing, at a temperature of around 150℃.
Tubeless-tire punctures can usually be repaired without taking the tire off the rim. One method uses a rubber plug, which is inserted, into the puncture hole along with special cement. After the cement dries and the plug is trimmed flush with the tread, the repair is complete.
Applying a patch on the inside can repair larger holes and cuts in tires. In addition, when treads have worn down, new treads can be vulcanized onto the casing provided the casing is in good condition.
Tires have two functions. First, they interpose a cushion between the road and the car wheels to absorb shocks resulting from irregularities in the road. The tires flex, or give, as bumps are encountered, thus reducing the shock effect to the passengers in the car. Second, the tires provide frictional contact between the wheels and the road so that good traction is secured. This permits the transmitting of power through the tires to the road for rapid accelerating, combats the tendency of the car to skid on turns, and allows quick stops when the brakes are applied.
Tires are of two basic types, solid and pneumatic (air filled). Solid tires have very limited usage, being confined largely to specialized industrial applications. Pneumatic tires are of two types, those using an inner tube and the tubeless type. The amount of air pressure used depends on the type of tire and operation. Passenger-car tires are inflated to about 275 to 413 KPa. Air is introduced into the tire (or inner tube) through a valve that opens when the chuck on the air hoses if applied. On the tire with an inner tube, the valve is mounted on the tube. On the tubeless tire, the valve is mounted on the wheel rim.
外文資料翻譯
翻 譯
Fig.3.5 裝備有獨立懸掛時,當車輪行駛在顛簸道路作上下的反復運動時,可以使軌跡改變,是輪胎在微小的α角度范圍內轉動。尤其是顛簸發(fā)生在一側時可以影響側向力、方向的穩(wěn)定性和滾動阻力。
Fig.3.6 對路面的側向力Fy.w是由于軌跡的改變而產(chǎn)生的。圖中所示的是型號為175/65R 14 82 H的輪胎在充氣至1.9巴、負荷為380千克及時速80km時輪距的變化與橫向力的關系。
Fig.3.7 由畫出的輪胎軌跡的改變和外連接桿的軌跡在雙叉骨懸掛上的U點交匯可以進行計算,如Fig.3.8中的圖形所示。
Fig.3.8 為方便計算出軌跡的改變的圖形可以用于雙叉骨懸掛和縱連接軸系統(tǒng)。
正如水平線先前表明的那樣,在圖中沿著C、D點周圍的弧直到顛簸的最高點W上下行程為S1和S2。然后用鉛筆一步步記錄下點W、U的運動軌跡。由這種方法而畫出的連接各點的線可以顯示軌跡的改變和連接桿的運動,但沒有考慮懸掛控制臂所產(chǎn)生的彈力。(參見Fig.3.18)
若是在縱向臂狀控制軸情況下,必須在D點的下端畫一個弧,同時必須在旋轉的懸掛控制臂狀軸上畫一條過點1的垂線。同時,一個如Fig.3.8中的模形沿著弧和垂線運動以決定輪距的變化。
麥克佛森支撐桿在輪槽里有個最高點E(Fig1.7),當車輪行駛在顛簸道路上時較低的圓形連接點2 到C點的距離變短,當輪胎反彈時則變長。這個模型必須考慮像這種長度的變化,它在支撐減震器中線EE方向上有個槽。經(jīng)常且必須出現(xiàn)在模型中的點2在D點周圍的弧上運動,同時開口向上越過點C。應該在畫板上做個小標記。
若在P點周圍畫弧,那么雙重連接擺動軸軌跡的改變可以容易的畫出。Figure 3.12同時說明了這個和降低車尾的好處。例如,完成一較小的弧度角和較高的側面弧形力。
在全獨立懸掛情況下,P的位置決定了輪距的瞬間改變量±⊿b。如果P處在水平面上,當雙叉骨懸掛的懸掛控制臂的長度固定不變使`該點在車輪受擠壓或反彈時從一邊到另一邊作水平運動時(Fig.3.13),輪距的改變可以完全得到避免。這可以用計算、畫圖或者考慮任何彈力的模型來表明車輪運動距離s=±70mm之間(Fig.3.18)。
Fig.3.9確定縱向連接軸軌跡的改變和外連接桿交匯于U的軌跡在Fig.3.8中表示。對于此懸掛系統(tǒng)的說明參見參考文獻[2]中的Fig3.32、3.157 和9.4 Fig.3.10用畫圖的方法計算麥克佛森減震器輪距的改變,減振器中心線E方向必須有個槽。
在研究兩輪一軸的汽車時,輪距的改變量可以看作一個由兩平行車輪單側改變時引起車輪往復運動距離的方程。車輪的平行運行是必要的,因為在車輪顛簸在最高點或最低點時,運動軌跡的微小改變會使測量數(shù)據(jù)失真。
用圖形表示,車輪的改變應標在y軸上,
Fig.3.11 Fig.3.10顯示的是麥克佛森支撐桿減震器的單輪軌跡改變和U 點的變化。C點是麥克佛森支撐桿上部的槽的中心;這個點在Figs 1.8和 3.139中被標為E。
Fig.3.12降低懸掛的控制臂支點P可以減少雙擺動軸軌跡的改變,使車身的重心從RO1降到RO2且需要一個更寬的輪距。若車上有兩名乘客時,輪胎上會產(chǎn)生負曲面效應,盡管這樣做的優(yōu)點是吸收更多的側面力,但缺點是不利于減少顛簸。
Fig.3.13 要使輪距不改變就要求車的滾動中心位于水平面上。同時還會取得較好的運動性能。
要與軸的運動方向一致,即上彈為正下彈為負。原點應與設計重量一致,換句話說有兩個或三個體重68千克的人的重量。空車是不符合實際的。
兩個輪子軌跡的改變量⊿b標在x軸,向右表示增加,向左表示減少。需要指出的是目前軌跡處在原點位置。輪距在滿載或空車時的改變量⊿b可以由彈簧的彈性來界定。彈簧在彈性范圍內從原點運動距離⊿S1,從而得出一個⊿b關于⊿s的方程的曲線。
圖5.9中顯示的是一輛前輪驅動汽車的前輪彈簧的情況,用115毫米減掉80毫米就得到了反彈距離,到原點的距離⊿s=35mm。汽車在允許的負重范圍內,在顛簸路況行駛距離為⊿s1=92-50=42毫米。路線被顯示在Fig.3.14中;⊿s1減⊿b1=+4mm, ⊿s2-⊿b2=-8mm.在規(guī)定重量下的軌跡為:bf=1286mm.
Fig.3.14獨立懸掛系統(tǒng)中的輪距b取決于負荷。
圖3.7、3.15 和3.18 顯示的是雙叉骨懸掛系統(tǒng)和麥克佛森支撐桿系統(tǒng)輪距的改變,圖中顯而易見的是較低的改變值。正如在3.4.1章細節(jié)描述的那樣,曲線的形狀取決于重心的高低。在三座位的車型中,Rof在地面以上,當滿載時會靈敏的下降。
若汽車制造商設計較低的重心作為標準,那么重心隨后再下降則會走向反面。Rof在地面以下時,方向的穩(wěn)定性會受損,尤其是寬輪胎時。
在雙叉骨懸掛系統(tǒng)中,彈簧位于控制臂的上方或下方,無論哪種情況,猛然一下的提升會使輪距變化曲線發(fā)生輕微變動。同時引起重心的輕微變化(Fig3.18)。曲線的形狀取決于裝有彈簧的汽車上的測量量。在任何情況下曲線的變化表明了正確的高度。
典型的后輪懸掛輪距的變化……..
Fig.3.15 奧迪A6、歐寶阿斯特拉、和本田雅閣的前輪距的變化曲線。其中本田是唯一裝備雙叉骨懸掛的乘用車;行使方面的優(yōu)勢顯而易見。
汽車重心高見下表,單位是mm
制動系的保養(yǎng)和維修
鼓式液壓制動系統(tǒng)所發(fā)生的故障有以下幾種類型:
(1)制動踏板移至汽車底板:發(fā)生這種情況時,由于整個踏板位移,不能提供滿意的制動,意味著沒有踏板行程余量。這對于裝有雙管路的制動系統(tǒng)來說,是極不可能發(fā)生的事,(前部或后部的)一套管路可能損壞,但兩套管路同時損壞是極少見的。如果發(fā)生這種情況,駕駛員很可能在一套管路失靈的情況下已經(jīng)行駛了一段時間。
(2)一邊制動器咬死:這意味著解除制動時,制動蹄片不能從制動鼓上分開。
(3)全部制動器咬死:如果所有的制動器都咬死,可能是由于踏板未能充分地起作用,致使制動總泵中的活塞不能完全返回。
(4)汽車跑偏:如果制動時發(fā)生汽車跑偏,即意味著提供的制動力一邊比另一邊要大。
(5)制動踏板發(fā)軟或如踏在海綿上:如果踩踏板時,感覺發(fā)軟或像踏在海綿上,可能是系統(tǒng)中進了空氣。不過,調整不當?shù)闹苿犹闫矔l(fā)生這種現(xiàn)象。
(6)制動作用不佳,需加大踏板壓力:如果制動襯片被油或制動液浸漬,就會失去作用。調整不當?shù)闹苿右r片或是使用的制動襯片有毛病均會引起同樣的問題。
(7)制動器反應過于靈敏或猛烈:制動器過于靈敏,或輕輕踏下制動踏板,即猛然剎車,可能是襯片被油浸漬、制動片脫出、使用的是有毛病的襯片、以及制動鼓工作面擦傷或凹凸不平所至。
(8)制動噪音:制動器襯片磨損嚴重,致使鉚釘直接與制動鼓接觸;制動蹄翹曲,使其直接觸及制動鼓上的壓力不均;制動蹄上的鉚釘松動,使其直接觸及制動鼓;制動鼓凹凸不平或磨損;這些情況都會使制動器產(chǎn)生噪音。
(9)空氣進入系統(tǒng):如果空氣進入系統(tǒng),就會產(chǎn)生制動不良和踩下踏板不能產(chǎn)生制動力。也可能是拆卸加注口螺栓時,(用扳手不當)偶然堵住排氣口所至。
(10)制動液流失:如果制動總泵滲漏,連接管松動或破損,均會使制動液流失。
(11)制動時(雙管路系統(tǒng))警示燈亮:這是兩路制動系統(tǒng)之一發(fā)生故障的信號,檢查(前后)兩個系統(tǒng)以便發(fā)現(xiàn)并排除故障。帶著這類故障行車是非常危險的,即使還可實現(xiàn)制動,也僅僅是因為半數(shù)車輪還能夠實現(xiàn)制動。
在盤式制動系統(tǒng)中制動盤與鼓式制動系統(tǒng)所發(fā)生的大部分故障相類似。
無論何時制動出故障,總要盡力去分析并確定其原因。有時,所要做的僅僅是對制動器稍做調整,以減少襯片磨損。目前帶有自動調校裝置的制動器,可自動調整以減少襯片的磨損。制動器的其它維修工作還包括:添加制動液,排出液壓系統(tǒng)的空氣,修理或更換制動總泵和分泵,更換制動襯片和整修制動鼓工作表面。
輪胎的維修包括定期充氣,保證輪胎氣壓正常;定期檢查輪胎可以及時發(fā)現(xiàn)和修理較小的損壞,以免發(fā)展為大故障。維修還包括拆卸、修理和更換輪胎。
不適當?shù)妮喬コ錃鈺鸲喾N類型的轉向和制動障礙。壓力低會使轉向沉重,前輪擺振,轉向回跳以及轉動時輪胎發(fā)出噪音;各輪胎壓力不均勻將增加汽車跑偏的傾向。由于這些原因,保持輪胎的正常氣壓是非常重要的。在給輪胎充氣時,應注意以下幾點:
(1)輪胎在熱狀態(tài)下時不要充氣。例如,在高速公路上長途行駛之后。
(2)檢查氣壓或充氣后,應該把輪胎氣門蓋放回原處。
在小型車輛上更換和拆卸輪胎并不困難。但是在重型車輛上,需使用專門的工具進行拆卸和操作。開始拆卸輪胎時,首先應從內胎中排除空氣,輪胎的輪緣一側應推向輪輞的中心,可用輪胎工具或扁平的翹棒把輪緣的一端從輪輞輞圈上翹起。要當心不要損壞輪胎輪緣或內胎。當用工具使輪緣從輪輞輞圈中脫出后,輪緣的剩余部分可用手將其扒過輞圈。再用類似的方法拆卸另一邊的輪緣。
輪胎商店每天都更換很多輪胎,所使用的是專門的輪胎更換設備。使用這種設備時,只要把輪胎安裝到位,氣壓裝置就把輪緣從輞圈中壓出,這種裝置在幾秒鐘的時間內即可將輪胎從輞圈中拆下來。此外,還可以很快地把輪胎裝入輞圈內。維修輪胎時,應該認真遵守下列注意事項:
(1)維修無內胎輪胎時,不能使用撬棒強行把輪緣從輪輞上拆卸下來。這樣容易損壞輪緣上的輪輞止口,并造成空氣泄漏。應該使用專門工具。
(2)如果輪胎已經(jīng)沒氣了,不要在汽車負載時給輪胎充氣。在充氣前,通常應該用千斤頂頂起汽車,使內胎能夠均勻地沿著輪胎的每一處擴充起來。如果不這樣做,內胎的某一部分就比其它部分膨脹的更多,這一部分內胎可能就會因拉的過緊而引起爆裂。
輪胎和內胎的維修范圍為修補釘子劃破的口子、破洞、或切口,以及用新的胎冠材料熱補外胎。后者就是大家都知道的輪胎翻新,因為是在輪胎上加了一層胎紋。維修過程要依據(jù)是無內胎輪胎,還是有內胎輪胎而定。
修補內胎的破口,需拆下輪胎,粘補內胎破口。需用專門工具。硫化或熱補的溫度大約為150℃。
通常修補無內胎輪胎的破口時,無需將輪胎從輪輞上取下。一種方法是橡皮塞修整的與胎冠一樣高,修理工作就完成了。較大的輪胎破口和切口可用補胎片在內側進行修補。另外,輪胎磨損后,可在外胎上熱補新的胎面,使外胎翻舊如新。
輪胎有兩種功能。首先,輪胎吸收路面的沖擊。輪胎具有可彎性,也就是彈性。在遇到顛簸路面時,可以減少對車上乘員的沖擊。其次,輪胎提供了車輪與路面的摩擦接觸,保證汽車穩(wěn)定行駛。輪胎的這些功能可以使汽車在突然加速時傳遞驅動力,在汽車轉彎時避免打滑,在汽車剎車時快速停車。
輪胎有兩種基本形式,實心輪胎和充氣輪胎。實心輪胎的使用范圍極為有限,僅在某些特定的工業(yè)方面應用。充氣輪胎又分為有內胎式和無內胎式兩種。輪胎的充氣量取決于輪胎的種類和用途。載人轎車的輪胎充氣量為275千帕到413千帕。把導入空氣的橡膠軟管夾在氣門上,空氣就被打入輪胎(或內胎)。
有內胎式輪胎氣門是直接做在內胎上的,無內胎式輪胎的氣門安裝在輪轂上。
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