KD1060型貨車設(shè)計(jì)(轉(zhuǎn)向及前橋設(shè)計(jì))【含3張CAD圖紙】
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外文資料及翻譯
Steering system
Motor steering system: On the automobile uses for to change or restores its travel direction to suppose the organization to be called the motor turning system specially. Automobile's steering system is uses for to change the automobile travel direction and to maintain the automobile straight line travel organization
Composes
(1)To change the control mechanism basically mainly by the steering wheel, the steering axle, the steering tube column and so on to be composed.
(2) Diverter becomes steering wheel's rotation steering arm's swinging or the rack axis straight reciprocating motion, and to changes the control force to carry on the enlargement the organization. The diverter fixes generally on the automobile frame or the automobile body, changes the control force after the diverter generally will also change the transmission direction.
(3) Steering transmission system the strength which and the movement outputs the diverter passes to the wheel (knuckle), about and causes the wheel to carry on the deflection according to certain relations the organization.
Type
Crooked to energy difference, the steering system may divide into the machinery steering system and the power steering system two broad headings crooked.
Mechanical steering system: And changes the transmission system by the diverter to be composed.
Diverter: By the steering wheel, the steering wheel steering axle, changes meshing to pay (diverter) to be composed.
Steering transmission system: By drop arm (drop arm), drag link, drag link arm, about trapezoidal arm, steering knuckle tie rod, if a dry bulb joint composes.
Power steering system: Changes the augmenter constitution by mechanical steering system Canada.
1.Mechanical steering system The mechanical steering system changes the energy by pilot's physical strength achievement, all power transmission are the machinery. The mechanical steering system by changes the control mechanism, the diverter and changes the transmission system three major part to be composed.
(1) steering control mechanism
Changes the control mechanism by the steering wheel, the steering axle, the steering tube column and so on to be composed, its function is rotates the pilot steering wheel's control force to pass to the divertor.
(2) Divertor
The diverter (also often is called steering unit) is completes from the rotary motion to the translation (or approximate straightline motion) a group of gear mechanism, simultaneously is also in the steering system speed reducer drive. At present the commonly used toothed wheel rack type, follows round the world the crank to refer to sells the type, the worm bearing adjuster crank to refer to sells the type, to follow round the world - the tooth rack tooth fan type, the worm bearing adjuster hoop type and so on. We mainly introduce the first several kinds.
1) Gear rack type divertor
The gear rack type diverter divides the both sides output type and among (or single end) the output type two kinds .The both sides output's gear rack type diverter, changes the gear shaft as the transmission vice-host moving parts and installs through the bearing in the diverter shell, its upper extreme through spline and universal joint sliding yoke and steering axle connection. With the steering gear meshing steering rack level arrangement, the both sides with change the steering knuckle tie rod through a ball place to be connected. The spring presses through the briquetting the rack depending in the gear, guarantees ceaseless meshing.
Spring's pretightening up force available adjustment thread plug adjustment. When rotates the steering wheel, the diverter gear-driven, causes with it meshing rack along the end motion, thus about causes the steering knuckle tie rod to lead about the knuckle to rotate, causes to change the wheel deflection, thus realizes motor turning.
Middle output gear rack type diverter, its structure and principle of work and both sides output gear rack type diverter basic same, the difference lies in it to change the steering knuckle tie rod in steering rack's middle with the bolt with about to be connected. On single-ended output's gear rack type diverter, a rack's end with changes the steering knuckle tie rod through the inside and outside bracket to be connected.
2) Follows round the world-like the divertor
Follows round the world-like the diverter is one of present domestic and foreign application most widespread structure patterns, generally has two-stage drive, the first level is screw rod nut transmission, the second level is tooth rack tooth fan transmission.
In order to reduce between the steering screw steering nut's friction, the two's thread immediate contact, during is loaded with many steel balls, realizes the rolling friction. On the steering screw and the nut processes the profiled outline is two section or three section of not concentric circular arc composition approximate semicircle spiral groove. The two's spiral groove can coordinate to form the approximate circular cross section the spiral tubular channel.
The nut side has two pair of through holes, may henceforth the vent plug enter the steel ball in the helix channel. Outside the steering nut has two steel ball drive pipes, each drive pipe's both sides insert the nut side separately in a pair of through hole. In the drive pipe has also packed the steel ball. Thus, in two drive pipes and nut's spiral tubular channels combine two respectively independent seals the steel ball " the flow channel ".
When the steering screw rotates, passes to the steering nut through the steel ball the strength, the nut namely along the end motion. At the same time, friction couple function between the screw rod and the nut and under the steel ball, all steel balls then rolls in the spiral tubular channel, formation " ball class ". When the diverter works, two rows steel balls are only in the respective seal flow channel internal recycling, will leave.
3) The worm bearing adjuster crank refers to sells the type diverter
The worm bearing adjuster crank refers to sells the type diverter's transmissionvice-(by the steering worm primarily moving parts, it is installs from the moving parts in the rocker arm shaft crank nose refers to sells. When the steering worm rotates, refers to with it meshing sells namely circles the rocker arm shaft spool thread along the circular, and leads the rocker arm shaft rotation.
(3) Steering transmission system
Steering transmission system the function is the strength which and the movement outputs the diverter passes to the steering axle both sides the knuckle, causes the both sides wheering wheel deflection, and causes two wheering wheel deflection angles according to certain relational change, guarantees when motor turning the wheel and the ground relative sliding is as far as possible small.
1) Uses for parts with the non-independent suspension fork changes the transmission system mainly to include the steering arm, to change the drag link, the steering, and the steering trapezium. In the front axle is only in the steering axle situation, by changes the steering trapezium general arrangement which the steering knuckle tie rod and the left and right trapezoidal arm are composed after the front axle, when the wheering wheel is in with the automobile straight line travel corresponding neutral point, trapezoidal arm and steering knuckle tie rod in and path parallel plane (horizontal plane) in angle of intersection >90.In the engine position is low or in the steering axle concurrently sufficient driving axle's situation, to avoid the movement interference, often steering trapezium arrangement before the front axle, this time above angle of intersection <90, if the steering arm is not around swings in the automobile fore-and-aft plane, but is shaking right toward left with the path parallel plane, then may change the drag link horizontal, and sells taking advantage of ball leads directly changes the steering knuckle tie rod, thus pushes somebody into doing something the both sides trapezoidal arm rotation.
2) Uses for parts with the independent suspension fork changes the transmission systemWhen wheering wheel independent suspension, each wheering wheel needs to be opposite in the frame makes the independence movement, thus the steering axle must be the separation type. With this corresponding, changes in the transmission system the steering trapezium also to be the separation type.
3) Steering drag link.Changes drag link's function is the strength which and the movement transmits the steering arm passes to the steering trapezium arm (or steering). It receives the strength already has the pulling force, also to have the pressure, therefore the drag link is uses the high quality special steel products manufacture, guarantees the operation reliable. In wheering wheel deflection or because of suspension fork elastic deformation when is opposite beats in the frame, changes the drag link and the steering arm and the steering relative motion is the space motion, for does not have the movement interference, the above three connection uses the pin ball.
轉(zhuǎn)向系統(tǒng)
汽車轉(zhuǎn)向系統(tǒng):汽車上用來(lái)改變或恢復(fù)其行駛方向的專設(shè)機(jī)構(gòu)稱為汽車轉(zhuǎn)向系統(tǒng)。汽車的轉(zhuǎn)向系統(tǒng)是用來(lái)改變汽車行駛方向和保持汽車直線行駛的機(jī)構(gòu)
基本組成
(1)轉(zhuǎn)向操縱機(jī)構(gòu)主要由轉(zhuǎn)向盤、轉(zhuǎn)向軸、轉(zhuǎn)向管柱等組成。
(2)轉(zhuǎn)向器將轉(zhuǎn)向盤的轉(zhuǎn)動(dòng)變?yōu)檗D(zhuǎn)向搖臂的擺動(dòng)或齒條軸的直線往復(fù)運(yùn)動(dòng),并對(duì)轉(zhuǎn)向操縱力進(jìn)行放大的機(jī)構(gòu)。轉(zhuǎn)向器一般固定在汽車車架或車身上,轉(zhuǎn)向操縱力通過轉(zhuǎn)向器后一般還會(huì)改變傳動(dòng)方向。
(3)轉(zhuǎn)向傳動(dòng)機(jī)構(gòu)將轉(zhuǎn)向器輸出的力和運(yùn)動(dòng)傳給車輪(轉(zhuǎn)向節(jié)),并使左右車輪按一定關(guān)系進(jìn)行偏轉(zhuǎn)的機(jī)構(gòu)。
類型
按轉(zhuǎn)向能源的不同,轉(zhuǎn)向系統(tǒng)可分為機(jī)械轉(zhuǎn)向系統(tǒng)和動(dòng)力轉(zhuǎn)向系統(tǒng)兩大類。
機(jī)械轉(zhuǎn)向系:由轉(zhuǎn)向器和轉(zhuǎn)向傳動(dòng)機(jī)構(gòu)組成.
轉(zhuǎn)向器:由方向盤,方向盤轉(zhuǎn)向軸,轉(zhuǎn)向嚙合付(轉(zhuǎn)向器)組成.
轉(zhuǎn)向傳動(dòng)機(jī)構(gòu):由轉(zhuǎn)向臂(轉(zhuǎn)向垂臂),直拉桿,直拉桿臂,左右梯形臂,橫拉桿,若干球頭關(guān)節(jié)組成.
動(dòng)力轉(zhuǎn)向系:由機(jī)械轉(zhuǎn)向系加轉(zhuǎn)向加力裝置構(gòu)成.
1.機(jī)械轉(zhuǎn)向系
機(jī)械轉(zhuǎn)向系以駕駛員的體力作為轉(zhuǎn)向能源,其中所有傳力件都是機(jī)械的。機(jī)械轉(zhuǎn)向系由轉(zhuǎn)向操縱機(jī)構(gòu)、轉(zhuǎn)向器和轉(zhuǎn)向傳動(dòng)機(jī)構(gòu)三大部分組成。
(1)轉(zhuǎn)向操縱機(jī)構(gòu)
轉(zhuǎn)向操縱機(jī)構(gòu)由方向盤、轉(zhuǎn)向軸、轉(zhuǎn)向管柱等組成,它的作用是將駕駛員轉(zhuǎn)動(dòng)轉(zhuǎn)向盤的操縱力傳給轉(zhuǎn)向器。
(2 )轉(zhuǎn)向器
轉(zhuǎn)向器(也常稱為轉(zhuǎn)向機(jī))是完成由旋轉(zhuǎn)運(yùn)動(dòng)到直線運(yùn)動(dòng)(或近似直線運(yùn)動(dòng))的一組齒輪機(jī)構(gòu),同時(shí)也是轉(zhuǎn)向系中的減速傳動(dòng)裝置。
目前較常用的有齒輪齒條式、循環(huán)球曲柄指銷式、蝸桿曲柄指銷式、循環(huán)球-齒條齒扇式、蝸桿滾輪式等。我們主要介紹前幾種。
1)齒輪齒條式轉(zhuǎn)向器
齒輪齒條式轉(zhuǎn)向器分兩端輸出式和中間(或單端)輸出式兩種。
兩端輸出的齒輪齒條式轉(zhuǎn)向器,作為傳動(dòng)副主動(dòng)件的轉(zhuǎn)向齒輪軸通過軸承和安裝在轉(zhuǎn)向器殼體中,其上端通過花鍵與萬(wàn)向節(jié)叉和轉(zhuǎn)向軸連接。與轉(zhuǎn)向齒輪嚙合的轉(zhuǎn)向齒條水平布置,兩端通過球頭座與轉(zhuǎn)向橫拉桿相連。彈簧通過壓塊將齒條壓靠在齒輪上,保證無(wú)間隙嚙合。
彈簧的預(yù)緊力可用調(diào)整螺塞調(diào)整。當(dāng)轉(zhuǎn)動(dòng)轉(zhuǎn)向盤時(shí),轉(zhuǎn)向器齒輪轉(zhuǎn)動(dòng),使與之嚙合的齒條沿軸向移動(dòng),從而使左右橫拉桿帶動(dòng)轉(zhuǎn)向節(jié)左右轉(zhuǎn)動(dòng),使轉(zhuǎn)向車輪偏轉(zhuǎn),從而實(shí)現(xiàn)汽車轉(zhuǎn)向。
中間輸出的齒輪齒條式轉(zhuǎn)向器,其結(jié)構(gòu)及工作原理與兩端輸出的齒輪齒條式轉(zhuǎn)向器基本相同,不同之處在于它在轉(zhuǎn)向齒條的中部用螺栓與左右轉(zhuǎn)向橫拉桿相連。在單端輸出的齒輪齒條式轉(zhuǎn)向器上,齒條的一端通過內(nèi)外托架與轉(zhuǎn)向橫拉桿相連。
2)循環(huán)球式轉(zhuǎn)向器
循環(huán)球式轉(zhuǎn)向器是目前國(guó)內(nèi)外應(yīng)用最廣泛的結(jié)構(gòu)型式之一, 一般有兩級(jí)傳動(dòng)副,第一級(jí)是螺桿螺母?jìng)鲃?dòng)副,第二級(jí)是齒條齒扇傳動(dòng)副。
為了減少轉(zhuǎn)向螺桿轉(zhuǎn)向螺母之間的摩擦,二者的螺紋并不直接接觸,其間裝有多個(gè)鋼球,以實(shí)現(xiàn)滾動(dòng)摩擦。轉(zhuǎn)向螺桿和螺母上都加工出斷面輪廓為兩段或三段不同心圓弧組成的近似半圓的螺旋槽。二者的螺旋槽能配合形成近似圓形斷面的螺旋管狀通道。
螺母?jìng)?cè)面有兩對(duì)通孔,可將鋼球從此孔塞入螺旋形通道內(nèi)。轉(zhuǎn)向螺母外有兩根鋼球?qū)Ч?,每根?dǎo)管的兩端分別插入螺母?jìng)?cè)面的一對(duì)通孔中。導(dǎo)管內(nèi)也裝滿了鋼球。這樣,兩根導(dǎo)管和螺母內(nèi)的螺旋管狀通道組合成兩條各自獨(dú)立的封閉的鋼球"流道"。
轉(zhuǎn)向螺桿轉(zhuǎn)動(dòng)時(shí),通過鋼球?qū)⒘鹘o轉(zhuǎn)向螺母,螺母即沿軸向移動(dòng)。同時(shí),在螺桿及螺母與鋼球間的摩擦力偶作用下,所有鋼球便在螺旋管狀通道內(nèi)滾動(dòng),形成"球流"。在轉(zhuǎn)向器工作時(shí),兩列鋼球只是在各自的封閉流道內(nèi)循環(huán),不會(huì)脫出。
3)蝸桿曲柄指銷式轉(zhuǎn)向器
蝸桿曲柄指銷式轉(zhuǎn)向器的傳動(dòng)副(以轉(zhuǎn)向蝸桿為主動(dòng)件,其從動(dòng)件是裝在搖臂軸曲柄端部的指銷。轉(zhuǎn)向蝸桿轉(zhuǎn)動(dòng)時(shí),與之嚙合的指銷即繞搖臂軸軸線沿圓弧運(yùn)動(dòng),并帶動(dòng)搖臂軸轉(zhuǎn)動(dòng)。
(3)轉(zhuǎn)向傳動(dòng)機(jī)構(gòu)
轉(zhuǎn)向傳動(dòng)機(jī)構(gòu)的功用是將轉(zhuǎn)向器輸出的力和運(yùn)動(dòng)傳到轉(zhuǎn)向橋兩側(cè)的轉(zhuǎn)向節(jié),使兩側(cè)轉(zhuǎn)向輪偏轉(zhuǎn),且使二轉(zhuǎn)向輪偏轉(zhuǎn)角按一定關(guān)系變化,以保證汽車轉(zhuǎn)向時(shí)車輪與地面的相對(duì)滑動(dòng)盡可能小。
1)與非獨(dú)立懸架配用的轉(zhuǎn)向傳動(dòng)機(jī)構(gòu)
與非獨(dú)立懸架配用的轉(zhuǎn)向傳動(dòng)機(jī)構(gòu)主要包括轉(zhuǎn)向搖臂、轉(zhuǎn)向直拉桿、轉(zhuǎn)向節(jié)臂、和轉(zhuǎn)向梯形。在前橋僅為轉(zhuǎn)向橋的情況下,由轉(zhuǎn)向橫拉桿和左、右梯形臂組成的轉(zhuǎn)向梯形一般布置在前橋之后,當(dāng)轉(zhuǎn)向輪處于與汽車直線行駛相應(yīng)的中立位置時(shí),梯形臂與橫拉桿在與道路平行的平面(水平面)內(nèi)的交角>90。
在發(fā)動(dòng)機(jī)位置較低或轉(zhuǎn)向橋兼充驅(qū)動(dòng)橋的情況下,為避免運(yùn)動(dòng)干涉,往往將轉(zhuǎn)向梯形布置在前橋之前,此時(shí)上述交角<90,若轉(zhuǎn)向搖臂不是在汽車縱向平面內(nèi)前后擺動(dòng),而是在與道路平行的平面向左右搖動(dòng),則可將轉(zhuǎn)向直拉桿橫置,并借球頭銷直接帶動(dòng)轉(zhuǎn)向橫拉桿,從而推使兩側(cè)梯形臂轉(zhuǎn)動(dòng)。
2)與獨(dú)立懸架配用的轉(zhuǎn)向傳動(dòng)機(jī)構(gòu)
當(dāng)轉(zhuǎn)向輪獨(dú)立懸掛時(shí),每個(gè)轉(zhuǎn)向輪都需要相對(duì)于車架作獨(dú)立運(yùn)動(dòng),因而轉(zhuǎn)向橋必須是斷開式的。與此相應(yīng),轉(zhuǎn)向傳動(dòng)機(jī)構(gòu)中的轉(zhuǎn)向梯形也必須是斷開式的。
3)轉(zhuǎn)向直拉桿
轉(zhuǎn)向直拉桿的作用是將轉(zhuǎn)向搖臂傳來(lái)的力和運(yùn)動(dòng)傳給轉(zhuǎn)向梯形臂(或轉(zhuǎn)向節(jié)臂)。它所受的力既有拉力、也有壓力,因此直拉桿都是采用優(yōu)質(zhì)特種鋼材制造的,以保證工作可靠。在轉(zhuǎn)向輪偏轉(zhuǎn)或因懸架彈性變形而相對(duì)于車架跳動(dòng)時(shí),轉(zhuǎn)向直拉桿與轉(zhuǎn)向搖臂及轉(zhuǎn)向節(jié)臂的相對(duì)運(yùn)動(dòng)都是空間運(yùn)動(dòng),為了不發(fā)生運(yùn)動(dòng)干涉,上述三者間的連接都采用球銷。
9
KD1060型貨車設(shè)計(jì)(轉(zhuǎn)向及前橋設(shè)計(jì))
摘 要
汽車在行駛過程中,需要經(jīng)常改變行駛方向,這就需要有一套能夠按照司機(jī)意志來(lái)改變或恢復(fù)汽車行駛方向的專設(shè)機(jī)構(gòu),它將司機(jī)轉(zhuǎn)動(dòng)方向盤的動(dòng)作轉(zhuǎn)變?yōu)檐囕喌钠D(zhuǎn)動(dòng)作,這就是所謂的轉(zhuǎn)向系統(tǒng)。轉(zhuǎn)向性能是保證車輛安全,減輕駕駛員勞動(dòng)強(qiáng)度和提高作業(yè)效率的重要因素。由于轉(zhuǎn)向系統(tǒng)是汽車的重要組成部分,它直接與汽車的行駛穩(wěn)定性有重要的關(guān)系,與前懸架和車輪關(guān)系亦十分密切,故轉(zhuǎn)向系統(tǒng)的設(shè)計(jì)也是整車設(shè)計(jì)中的關(guān)鍵一環(huán)。
本設(shè)計(jì)為KD1060型載貨汽車的轉(zhuǎn)向系統(tǒng)設(shè)計(jì),轉(zhuǎn)向系統(tǒng)設(shè)計(jì)內(nèi)容主要包括轉(zhuǎn)向系統(tǒng)形式的選擇、轉(zhuǎn)向器的選擇、轉(zhuǎn)向梯形的選擇及其布置。
在本次設(shè)計(jì)中采用了機(jī)械式轉(zhuǎn)向系統(tǒng),機(jī)械式轉(zhuǎn)向系統(tǒng)的特點(diǎn)是重量輕,結(jié)構(gòu)緊湊,布置方便,維修容易,操縱輕便,穩(wěn)定性好,成本低廉,不易出現(xiàn)直線行駛時(shí)的蛇形現(xiàn)象。機(jī)械式轉(zhuǎn)向系統(tǒng)還具有維修方便,容易安裝調(diào)整的優(yōu)點(diǎn)。轉(zhuǎn)向系統(tǒng)的轉(zhuǎn)向器選用的是整體式循環(huán)球轉(zhuǎn)向器, 整體式循環(huán)球轉(zhuǎn)向器的特點(diǎn)是可以將傳遞力矩機(jī)構(gòu)之間的滑動(dòng)摩擦轉(zhuǎn)變?yōu)闈L動(dòng)摩擦,這就使得轉(zhuǎn)向傳動(dòng)效率提高,使用壽命增長(zhǎng),傳動(dòng)比可以改變,轉(zhuǎn)向工作平穩(wěn)可靠。轉(zhuǎn)向傳動(dòng)機(jī)構(gòu)選用整體式梯形,這樣有利于保證KD1060型汽車在車輪轉(zhuǎn)動(dòng)時(shí)作無(wú)滑動(dòng)的純滾動(dòng)運(yùn)動(dòng),并且機(jī)構(gòu)簡(jiǎn)單, 容易調(diào)整前輪前束。
在說(shuō)明書的計(jì)算部分,對(duì)轉(zhuǎn)向器和轉(zhuǎn)向梯形主要參數(shù)選擇進(jìn)行了計(jì)算。此外,還校核了主要零件的強(qiáng)度。
關(guān)鍵詞:轉(zhuǎn)向系統(tǒng),機(jī)械轉(zhuǎn)向,前橋,轉(zhuǎn)向器
KD1060 GOODS VEHICLE DESIGN
(STEERING SYSTEM AND THE FRONT AXLE)
ABSTRACT
The automobiles often need to change the direction in driving, then a particular set of device which can change or recover the automobile’s running route according to the driver’s will is needed.
The device changing the action that the driver turns to move the steering wheel to the action of deflection of carriage wheels is called as steering system. The function of changing direction is to guarantee the vehicle’s safety, relieve the intension of labor and raise working efficiency. The steering system is important component of an automobile. It plays an important role on the driving stability of the automobile. And it also has close relationship with the front suspension and wheel tire components, so the design of the steering system is a key link in designing automobile.
The aim of this project is to design the steering system for KD1060 goods vehicle. The main job of designing steering system includes determining the kind of steering system, steering gear and the steering trapezoid and figure out how to fix them.
Manual steering system is adopted in this project. Manual steering system’s features are: weight light, tightly packed structure, convenient arrangements, easy manipulation, stabile quality, low cost. And the s form phenomenon seldom emerges in straightaway traveling.
It has other advantages: convenient maintenance. Integral circulating ball steering gears is working as steering gear in this design of medium freight steering system. Integral circulating ball steering gears can change slide friction between devices of carry-over momentums into rolling friction. This feature is propitious to better transfer motion efficiency; prolong application life, change transmission ratio and better degree of reliability of steering. Integrality trapezoid is adopted as Steering drive linkage, to guarantee automobile’s front wheel exercise of pure rolling without sliding. The structure is simple. And it is easy to adjust the toe-in.
The calculation section of this paper is mainly concerning about steering trapezoid and steering gear .In addition, the life of the main components are also calculated in this section.
KEY WORDS: The steering system, Manual steering, Front axle, Steering device
目 錄
前言..........................................................1
第一章 概述...........................................2
第二章 從動(dòng)橋的方案確定.............................4
第三章 轉(zhuǎn)向系的方案確定...............................6
§3.1 轉(zhuǎn)向系整體方案確定..............................6
§3.2 轉(zhuǎn)向系結(jié)構(gòu)形式及選擇............................6
§3.3 循環(huán)球式轉(zhuǎn)向器結(jié)構(gòu)及選擇........................7
第四章 從動(dòng)橋的設(shè)計(jì)計(jì)算...............................8
§4.1從動(dòng)橋主要零件尺寸的確定.........................8
§4.2 從動(dòng)橋主要零件工作應(yīng)力的計(jì)算....................8
§4.3 在最大側(cè)向力(側(cè)滑)工況下的前梁應(yīng)力計(jì)算.........10
§4.4 轉(zhuǎn)向節(jié)在制動(dòng)和側(cè)滑工況下的應(yīng)力計(jì)算.............11
§4.5 主銷與轉(zhuǎn)向節(jié)襯套在制動(dòng)和側(cè)滑工況下的應(yīng)力計(jì)算...13
§4.6轉(zhuǎn)向節(jié)推力軸承的計(jì)算............................15
第五章 轉(zhuǎn)向系統(tǒng)的設(shè)計(jì)計(jì)算............................17
§5.1 轉(zhuǎn)向系主要性能參數(shù).............................17
§5.2 主要參數(shù)的確定.................................18
§5.3 轉(zhuǎn)向梯形的選擇設(shè)計(jì).............................20
§5.4 循環(huán)球式轉(zhuǎn)向器的設(shè)計(jì)...........................21
§5.5 轉(zhuǎn)向系主要性能參數(shù)確定.........................24
§5.6 轉(zhuǎn)向系其他元件的選擇及材料的確定...............25
第六章 轉(zhuǎn)向系主要零件的強(qiáng)度計(jì)算......................26
§6.1 計(jì)算載荷的確定.................................26 §6.2 主要零件的強(qiáng)度計(jì)算..............................26 第七章 結(jié)論..........................................28
參考文獻(xiàn)..............................................29致謝..................................................30外文資料及翻譯........................................31
前言
在目前金融危機(jī)的大環(huán)境下,伴隨著汽車行業(yè)的發(fā)展,輕型貨運(yùn)汽車在國(guó)民生產(chǎn)中扮演著更重要的角色。
輕型載貨汽車各個(gè)領(lǐng)域得到了廣泛應(yīng)用,對(duì)于它的設(shè)計(jì)是依據(jù)以往理論知識(shí)及實(shí)踐經(jīng)驗(yàn),在滿足其功用的前提下來(lái)進(jìn)行的。轉(zhuǎn)向系統(tǒng)是用來(lái)保持或改變汽車行駛方向的機(jī)構(gòu),它在整體設(shè)計(jì)中亦有其重要地位,對(duì)轉(zhuǎn)向時(shí)車輪正確運(yùn)動(dòng)和汽車的安全行駛有重大影響,這就要求其工作可靠、操縱輕便。
在目前的設(shè)計(jì)和使用方面,轉(zhuǎn)向系統(tǒng)由機(jī)械式和動(dòng)力式兩類,由于動(dòng)力式轉(zhuǎn)向系統(tǒng)能減輕駕駛員的負(fù)擔(dān),而且操作方便,所以到廣泛使用。機(jī)械式轉(zhuǎn)向系統(tǒng)由于造價(jià)低廉,而且能夠滿足輕型貨車等一大部分汽車的轉(zhuǎn)向需要,固也得到了廣泛的使用。機(jī)械式轉(zhuǎn)向系由操縱機(jī)構(gòu)、轉(zhuǎn)向器和轉(zhuǎn)向傳動(dòng)機(jī)構(gòu)組成,其重點(diǎn)是轉(zhuǎn)向器和傳動(dòng)機(jī)構(gòu)的設(shè)計(jì)?,F(xiàn)今國(guó)內(nèi)輕型汽車多才用整體式循環(huán)球式轉(zhuǎn)向器,整體式后置梯形。
本畢業(yè)設(shè)計(jì)說(shuō)明書,主要講述了前橋和轉(zhuǎn)向系統(tǒng)的選擇設(shè)計(jì)和方案分析。對(duì)前橋和轉(zhuǎn)向系統(tǒng)的分類和工作原理進(jìn)行了深入的對(duì)比和分析,選出最優(yōu)方案來(lái)進(jìn)行設(shè)計(jì);對(duì)于轉(zhuǎn)向系統(tǒng)的重要組成部分轉(zhuǎn)向器和轉(zhuǎn)向傳動(dòng)機(jī)構(gòu)進(jìn)行分析設(shè)計(jì),選擇合適的機(jī)構(gòu)和零件。
第一章 概述
從動(dòng)橋通過懸架與車架相聯(lián),兩側(cè)安裝著從動(dòng)車輪,用以在車架與車輪之間傳遞鉛垂力、縱向力和橫向力。從動(dòng)橋還要承受和傳遞制動(dòng)力矩。
根據(jù)從動(dòng)車輪能否轉(zhuǎn)向,從動(dòng)橋分為轉(zhuǎn)向橋與非轉(zhuǎn)向橋。一般汽車多以前橋?yàn)檗D(zhuǎn)向橋。為提高操縱穩(wěn)定性和機(jī)動(dòng)性,有些轎車采用全四輪轉(zhuǎn)向。多軸汽車除前輪轉(zhuǎn)向外,根據(jù)對(duì)機(jī)動(dòng)性的要求,有時(shí)采用兩根以上的轉(zhuǎn)向橋直至全輪轉(zhuǎn)向。
一般載貨汽車采用前置發(fā)動(dòng)機(jī)后橋驅(qū)動(dòng)的布置形式,故其前橋?yàn)檗D(zhuǎn)向從動(dòng)橋。轎車多采用前置發(fā)動(dòng)機(jī)前橋驅(qū)動(dòng),越野汽車均為全輪驅(qū)動(dòng),故它們的前橋既是轉(zhuǎn)向橋又是驅(qū)動(dòng)橋,稱為轉(zhuǎn)向驅(qū)動(dòng)橋。
從動(dòng)橋按與其匹配的懸架結(jié)構(gòu)的不同,也可分為非斷開式與斷開式兩種。與非獨(dú)立懸架相匹配的非斷開式從動(dòng)橋是一根支承于左、右從動(dòng)車輪上的剛性整體橫梁,當(dāng)又是轉(zhuǎn)向橋時(shí),則其兩端經(jīng)轉(zhuǎn)向主銷與轉(zhuǎn)向節(jié)相聯(lián)。斷開式從動(dòng)橋與獨(dú)立懸架相匹配。
為了保持汽車直線行駛的穩(wěn)定性、轉(zhuǎn)向輕便性及汽車轉(zhuǎn)向后使前輪具有自動(dòng)回正的性能,轉(zhuǎn)向橋的主銷在汽車的縱向和橫向平而內(nèi)都有一定傾角。在縱向平面內(nèi),主銷上部向后傾斜一個(gè)角,稱為主銷后傾角。在橫向平面內(nèi),主銷上部向內(nèi)傾斜一個(gè)β角,稱為主銷內(nèi)傾角。還有車輪外傾角及前束。
在汽車的設(shè)計(jì)、制造、裝配調(diào)整和使用中必須注意防止可能引起的轉(zhuǎn)向車輪的擺振,它是指汽車行駛時(shí)轉(zhuǎn)向輪繞主銷不斷擺動(dòng)的現(xiàn)象,它將破壞汽車的正常行駛。轉(zhuǎn)向車輪的擺振有自激振動(dòng)與受迫振動(dòng)兩種類型。前者是由于輪胎側(cè)向變形中的遲滯特性的影響,使系統(tǒng)在一個(gè)振動(dòng)周期中路面作用于輪胎的力對(duì)系統(tǒng)作正功,即外界對(duì)系統(tǒng)輸入能量。如果后者的值大于系統(tǒng)內(nèi)阻尼消耗的能量,則系統(tǒng)將作增幅振動(dòng)直至能量達(dá)到動(dòng)平衡狀態(tài)。這時(shí)系統(tǒng)將在某一振幅下持續(xù)振動(dòng),形成擺振。其振動(dòng)頻率大致接近系統(tǒng)的固有頻率而與車輪轉(zhuǎn)速并不一致,且會(huì)在較寬的車速范圍內(nèi)發(fā)生。通常在低速行駛時(shí)發(fā)生的擺振往往屬于自攝振動(dòng)型。當(dāng)轉(zhuǎn)向車輪及轉(zhuǎn)向系統(tǒng)受到周期性擾動(dòng)的激勵(lì),例如車輪失衡、端面跳動(dòng)、輪胎的幾何和機(jī)械特性不均勻以及運(yùn)動(dòng)學(xué)上的干涉等,在車輪轉(zhuǎn)動(dòng)下都會(huì)構(gòu)成周期性的擾動(dòng)。在擾動(dòng)力周期性的持續(xù)作用下,便會(huì)發(fā)生受迫振動(dòng)。當(dāng)擾動(dòng)的激勵(lì)頻率與系統(tǒng)的固有頻率一致時(shí)便發(fā)生共振。其特點(diǎn)是轉(zhuǎn)向輪擺振頻率與車輪轉(zhuǎn)速一致,而且一般都有明顯的共振車速,共振范圍較窄(3~5km/h)。通常在高速行駛時(shí)發(fā)生的擺振往往屬于受迫振動(dòng)型。
轉(zhuǎn)向輪擺振的發(fā)生原因及影響因素復(fù)雜,既有結(jié)構(gòu)設(shè)計(jì)的原因和制造方面的因素.如車輪失衡、輪胎的機(jī)械特性、系統(tǒng)的剛度與阻尼、轉(zhuǎn)向輪的定位角以及陀螺效應(yīng)的強(qiáng)弱等;又有裝配調(diào)整方面的影響,如前橋轉(zhuǎn)向系統(tǒng)各個(gè)環(huán)節(jié)間的間隙(影響系統(tǒng)的剛度)和摩擦系數(shù)(影響阻尼)等。合理地選擇這些有關(guān)參數(shù)、優(yōu)化它們之間的匹配,精心地制造和裝配調(diào)整,就能有效地控制前輪擺振的發(fā)生。在設(shè)計(jì)中提高轉(zhuǎn)向器總成與轉(zhuǎn)向拉桿系統(tǒng)的剛度及懸架的縱向剛度,提高輪胎的側(cè)向剛度,在轉(zhuǎn)向拉桿系中設(shè)置橫向減震器以增加阻尼等,都是控制前輪擺振發(fā)生的一些有效措施。
第二章 從動(dòng)橋的方案確定
§2.1 從動(dòng)橋總體方案確定
轉(zhuǎn)向從動(dòng)橋的主要零件有前梁,轉(zhuǎn)向節(jié),主銷,注銷上下軸承及轉(zhuǎn)向節(jié)襯套,轉(zhuǎn)向節(jié)推力軸承,輪轂等。
轉(zhuǎn)向前橋有斷開式和非斷開式兩種。斷開式前橋與獨(dú)立懸架相配合,結(jié)構(gòu)比較復(fù)雜但性能比較好,多用于轎車等以載人為主的高級(jí)車輛。非斷開式又稱整體式,它與非獨(dú)立懸架配合。它的結(jié)構(gòu)簡(jiǎn)單,承載能力大,這種形式再現(xiàn)在汽車上得到廣泛應(yīng)用。因此本次設(shè)計(jì)就采用了非斷開式從動(dòng)橋。
作為主要零件的前梁是用中碳鋼或中碳合金鋼的,其兩端各有一呈拳形的加粗部分為安裝主銷的前梁拳部;為提高其抗彎強(qiáng)度,其較長(zhǎng)的中間部分采用工字形斷面并相對(duì)兩端向下偏移一定距離,以降低發(fā)動(dòng)機(jī)從而降低傳動(dòng)系的安裝位置以及傳動(dòng)軸萬(wàn)向節(jié)的夾角。為提高其抗扭強(qiáng)度,兩端與拳部相接的部分采用方形斷面,而靠近兩端使拳部與中間部分相聯(lián)接的向下彎曲部分則采用兩種斷面逐漸過渡的形狀。中間部分的兩側(cè)還要鍛造出鋼板彈簧支座的加寬文承面。
轉(zhuǎn)向節(jié)用中碳合金鋼模級(jí)成整體式結(jié)構(gòu)。轉(zhuǎn)向節(jié)通過主銷與前梁的拳部相連,使前輪可以繞主銷偏轉(zhuǎn)一定的角度使汽車轉(zhuǎn)向。為減小磨損,轉(zhuǎn)向節(jié)銷孔內(nèi)設(shè)計(jì)時(shí)壓入青銅襯套,襯套上的潤(rùn)滑油槽在上面端部是切通的,用裝在轉(zhuǎn)向節(jié)上的油嘴注入潤(rùn)滑脂潤(rùn)滑,為使轉(zhuǎn)向輕便,在轉(zhuǎn)向節(jié)和前梁拳部設(shè)有圓錐推力滾子軸承。
主銷的幾種結(jié)構(gòu)型式如下圖所示,本次設(shè)計(jì)用(a)。
(a) (b) (c) (d)
圖2-1主銷結(jié)構(gòu)形式
(a)圓柱實(shí)心型 (b) 圓柱空心型 (c) 上,下端為直徑不等的圓柱,中間為錐體的主銷 (d)下部圓柱比上部細(xì)的主銷
車輪輪轂通過兩個(gè)圓錐滾子軸承支撐在轉(zhuǎn)向節(jié)外端的軸頸上,軸承的松緊度可通過調(diào)整螺母進(jìn)行調(diào)整。輪轂外端用沖壓的金屬外罩罩住。輪轂內(nèi)側(cè)有油封,以防潤(rùn)滑油進(jìn)入制動(dòng)器內(nèi)。
第三章 轉(zhuǎn)向系的方案確定
§3.1 轉(zhuǎn)向系整體方案確定
用來(lái)改變或恢復(fù)汽車行駛方向的專設(shè)機(jī)構(gòu)即稱作汽車的轉(zhuǎn)向系。
轉(zhuǎn)向系可按轉(zhuǎn)向能源的不同分為機(jī)械轉(zhuǎn)向系和動(dòng)力轉(zhuǎn)向系兩大類。在現(xiàn)代汽車結(jié)構(gòu)中,常用機(jī)械式轉(zhuǎn)向系。機(jī)械式轉(zhuǎn)向系依靠駕駛員的手力轉(zhuǎn)動(dòng)方向盤,經(jīng)過轉(zhuǎn)向器和轉(zhuǎn)向傳動(dòng)機(jī)構(gòu)使轉(zhuǎn)向輪偏轉(zhuǎn)。有些汽車裝有防傷機(jī)構(gòu)和轉(zhuǎn)向減振裝置。還有一些汽車的專門裝有動(dòng)力轉(zhuǎn)向機(jī)構(gòu),并借助此機(jī)構(gòu)來(lái)減輕駕駛員的手力,以降低駕駛員的勞累程度。
本次設(shè)計(jì)采用機(jī)械式轉(zhuǎn)向器。
對(duì)轉(zhuǎn)向系的主要要求有:
一、操縱輕便。轉(zhuǎn)向時(shí)加在方向盤上的力對(duì)轎車不超過200N,對(duì)輕型貨車不超過360N,對(duì)中型貨車不超過450N,方向盤的回轉(zhuǎn)圈數(shù)要少。
二、工作安全可靠。
三、在轉(zhuǎn)向后,方向盤有自動(dòng)回正能力,能保持汽車有穩(wěn)定的直線行駛能力。
四、在前輪受到?jīng)_擊時(shí),轉(zhuǎn)向系傳遞反向沖擊到方向盤上要小。
五、應(yīng)盡量減小轉(zhuǎn)向系統(tǒng)連接處的間隙,間隙應(yīng)能自動(dòng)補(bǔ)償即調(diào)整,除了設(shè)計(jì)應(yīng)正確的選擇導(dǎo)向輪的定位角外,轉(zhuǎn)向盤在中間式的自由行程應(yīng)當(dāng)保證直線行駛的穩(wěn)定性和轉(zhuǎn)向盤相對(duì)導(dǎo)向輪偏轉(zhuǎn)角的靈敏度。
§3. 2轉(zhuǎn)向器結(jié)構(gòu)形式及選擇
根據(jù)轉(zhuǎn)向器所用傳動(dòng)副的不同,轉(zhuǎn)向器有多種。常見的有循環(huán)球式球面蝸桿蝸輪式、蝸桿曲柄銷式和齒輪齒條式等。
轉(zhuǎn)向器的結(jié)構(gòu)形式,決定了其效率特性以及對(duì)角傳動(dòng)比變化特性的要求。選用那種效率特性的轉(zhuǎn)向器應(yīng)有汽車用途來(lái)決定,并和轉(zhuǎn)向系方案有關(guān)。經(jīng)常行駛在好路面上的轎車和市內(nèi)用客車,可以采用正效率較高的、可逆程度大的轉(zhuǎn)向器。
效率高、工作可靠、平穩(wěn),蝸桿和螺母上的螺旋槽在淬火后經(jīng)過磨削加工,所以耐磨且壽命較長(zhǎng)。齒扇和齒條嚙合間隙的調(diào)整工作容易進(jìn)行。和其它形式轉(zhuǎn)向器比較,其結(jié)構(gòu)復(fù)雜,對(duì)主要零件加工精度要求較高。
蝸桿曲柄銷式轉(zhuǎn)向器角傳動(dòng)比的變化特性和嚙合間隙特性變化受限制,不能完全滿足設(shè)計(jì)者的意圖。
齒輪齒條式轉(zhuǎn)向器的結(jié)構(gòu)簡(jiǎn)單,因此制造容易,成本低,正、逆效率都高。為了防止和緩和反向沖擊傳給方向盤,必須選擇較大的傳動(dòng)比,或裝有吸振裝置的減振器。
本設(shè)計(jì)采用循環(huán)球式轉(zhuǎn)向器。
§3.3 循環(huán)球式轉(zhuǎn)向器結(jié)構(gòu)及工作原理
循環(huán)球式轉(zhuǎn)向器中一般有兩級(jí)傳動(dòng)副。第一級(jí)是螺桿螺母?jìng)鲃?dòng)副,第二級(jí)是齒條齒扇傳動(dòng)副。
轉(zhuǎn)向螺桿的軸頸支撐在兩個(gè)圓錐滾子軸承上。軸承緊度可用調(diào)整墊片調(diào)整。轉(zhuǎn)向螺母的下平面上加工成齒條,與齒扇軸內(nèi)的齒扇部分相嚙合。通過轉(zhuǎn)向盤轉(zhuǎn)動(dòng)轉(zhuǎn)向螺桿時(shí),轉(zhuǎn)向螺母不轉(zhuǎn)動(dòng),只能軸向移動(dòng),并驅(qū)使齒扇軸轉(zhuǎn)動(dòng)。為了減小轉(zhuǎn)向螺桿和轉(zhuǎn)向螺母之間的摩擦,其間裝有小鋼球以實(shí)現(xiàn)滾動(dòng)摩擦。二者的螺旋槽能配合形成近似圓形斷面輪廓的螺旋管狀通道。轉(zhuǎn)向螺母外有兩根導(dǎo)管,兩端分別插入螺母的一對(duì)通孔。導(dǎo)管內(nèi)裝滿了鋼球。兩根導(dǎo)管和螺母內(nèi)的螺旋管狀通道組合成兩條各自獨(dú)立的封閉的鋼球流道。轉(zhuǎn)向器工作是兩列鋼球只是在各自封閉的流道內(nèi)循環(huán),而不脫出。
轉(zhuǎn)向螺母上的齒條式傾斜的,因此與之嚙合的齒應(yīng)當(dāng)是分度圓上的齒厚沿齒扇軸線按線性關(guān)系變化的變厚齒扇。因?yàn)檠h(huán)球轉(zhuǎn)向器的正傳動(dòng)效率很高,操作輕便,使用壽命長(zhǎng)。經(jīng)常用于各種汽車。
綜上最后本次設(shè)計(jì)選定循環(huán)球式轉(zhuǎn)向器。
第四章 從動(dòng)橋的設(shè)計(jì)計(jì)算
§4.1從動(dòng)橋主要零件尺寸的確定
轉(zhuǎn)向從動(dòng)橋采用工字形斷面的前梁,可保證其質(zhì)量最小而在垂向平面內(nèi)的剛度大,強(qiáng)度高。工字形斷面尺寸的推薦值,見圖4-1,圖中虛線繪出的是其當(dāng)量斷面。該斷面的垂向彎曲截面系數(shù)和水平彎曲截面系數(shù)(單位為)可近似取為
} (4-1)
式中 a----工字形斷面的中部尺寸。
由經(jīng)驗(yàn)公式:
式中 m---作用于前梁上的簧上質(zhì)量;
l---車輪中線至板簧中線的距離。
求得
§4.2 從動(dòng)橋主要零件工作應(yīng)力的計(jì)算
主要是計(jì)算前梁、轉(zhuǎn)向節(jié)、主銷、主銷上下軸承(即轉(zhuǎn)向節(jié)襯套)、轉(zhuǎn)向節(jié)推力軸承或止推墊片等在制動(dòng)和側(cè)滑兩種工況下的工作應(yīng)力。繪制計(jì)算用簡(jiǎn)圖時(shí)可忽略車輪的定位角,即認(rèn)為主銷內(nèi)傾角、主銷后傾角,車輪外傾角均為零,而左右轉(zhuǎn)向節(jié)軸線重合且與主銷軸線位于同一側(cè)向垂直平面內(nèi)。如下所示:
圖 4—2轉(zhuǎn)向從動(dòng)橋在制動(dòng)和側(cè)滑工況下的受力分析簡(jiǎn)圖
1-制動(dòng)工況下的彎矩圖 2-側(cè)滑工況下的彎矩圖
制動(dòng)工況下的前梁應(yīng)力計(jì)算:
制動(dòng)時(shí)前輪承受的制動(dòng)力和垂直力傳給前梁,使前梁承受彎矩和轉(zhuǎn)矩??紤]到制動(dòng)時(shí)汽車質(zhì)量向前,轉(zhuǎn)向橋轉(zhuǎn)移,則前輪所承受的地面垂直反力為:
式中:——汽車滿載靜止于水平路面時(shí)前橋給地面的載荷,N;
——汽車制動(dòng)時(shí)對(duì)前橋的質(zhì)量轉(zhuǎn)移系數(shù),對(duì)轎車和載貨汽車的前橋可取1.5;質(zhì)量分配給前橋35%;
=15550.76N
前輪所承受的制動(dòng)力
式中:——輪胎與路面的附著系數(shù)取為0.6;
=15550.760.6=9330.45 N
由于和對(duì)前梁引起的垂向彎矩和水平方向的彎矩在兩鋼板彈簧座之間達(dá)最大值,分別為:
N·mm
式中:—見圖3—1,取=397 mm
—車輪(包括輪毅、制動(dòng)器等)所受的重力,N;取=980N;
—前輪輪距取B=1567 mm;
S—前梁上兩鋼板彈簧座中心間的距離取為767 mm
則
N·mm
制動(dòng)力還使前梁在主銷孔至鋼板彈簧座之間承受轉(zhuǎn)矩T:
T= N·mm
式中:—輪胎的滾動(dòng)半徑取410 mm
則有 T=9330410=3825300 N·mm
前梁在鋼板彈簧座附近危險(xiǎn)斷面處的彎曲應(yīng)力(單位為MPa)為:
式中: ,,T——見式(4-1)
前梁應(yīng)力的許用值為=300~500 MPa,當(dāng)a=15mm時(shí),
= 236.48N·mm
得:
故a=15mm滿足使用條件。
§4.3 在最大側(cè)向力(側(cè)滑)工況下的前梁應(yīng)力計(jì)算
當(dāng)汽車承受最大側(cè)向力時(shí)無(wú)縱向力作用,左、右前輪承受的地面垂向反力和 與側(cè)向反力,各不相等,前輪的地面反力(單位都為N)分別為:
式中:—汽車質(zhì)心高度取為1100 mm;—車輪與地面附著系數(shù)取為0.42;
此時(shí),向右作用。則有:
側(cè)滑時(shí)左、右鋼板彈簧對(duì)前梁的垂直作用力為:
式中: —滿載時(shí)車廂分配給前橋的垂向總載荷
=1232.989.8=12069.2N;
則有
§4.4 轉(zhuǎn)向節(jié)在制動(dòng)和側(cè)滑工況下的應(yīng)力計(jì)算
如圖4—2所示,轉(zhuǎn)向節(jié)的危險(xiǎn)斷面在軸徑為的輪軸根部即III-III剖面處。
圖4—2 轉(zhuǎn)向節(jié),主銷及轉(zhuǎn)向節(jié)襯套的計(jì)算用圖
一、在制動(dòng)工況下
III—III剖面處的軸徑僅受垂向彎矩和水平方向的彎矩而不受轉(zhuǎn)矩,因制動(dòng)力矩不經(jīng)轉(zhuǎn)向節(jié)的輪軸傳遞而直接由制動(dòng)底板傳給在轉(zhuǎn)向節(jié)上的安裝平面。這時(shí)的,及III—III剖面處的合成彎矩應(yīng)力(MPa)為:
=
式中:—轉(zhuǎn)向節(jié)的輪軸根部軸徑取為50mm,=30 mm,=550 MPa,
則 ==81.099MPa
得:
故50mm的軸頸滿足要求。
轉(zhuǎn)向節(jié)采用30Cr,40Cr等中碳合金鋼制造,心部硬度HRC241~285,高頻淬火后表面硬度HRC57~65,硬化層深1.5~2.0mm。輪軸根部的圓角液壓處理。
二、在側(cè)滑工況下
在側(cè)滑時(shí)左、右轉(zhuǎn)向節(jié)在危險(xiǎn)斷面III—III處的彎矩是不等的,可分別下式求得:
許用彎矩
因此左右轉(zhuǎn)向節(jié)都符合要求。
§4.5 主銷與轉(zhuǎn)向節(jié)襯套在制動(dòng)和側(cè)滑工況下的應(yīng)力計(jì)算
在制動(dòng)和側(cè)滑工況下,在轉(zhuǎn)向節(jié)上、下襯套的中心,即與輪軸中心線相距分別為c,d的兩點(diǎn)處,在側(cè)向平面(圖4—2(c))和縱向平面(圖4—2(d))內(nèi),對(duì)主銷作用有垂直其軸線方向的力。
一、在制動(dòng)工況下
地面對(duì)前輪的垂向支承反力所引起的力矩,由位于通過主銷軸線的側(cè)向平面內(nèi)并在轉(zhuǎn)向節(jié)上下襯套中點(diǎn)處垂直地作用于主銷的力所形成的力偶矩(c+d)所平衡(見圖4—2(b)),故有
N 式中取150,c取91,d取98 mm;
制動(dòng)力矩由位于縱向平面內(nèi)并作用于主銷的力所形成的力偶
(c+d)所平衡(見圖4—2(c))。故有
而作用于主銷的制動(dòng)力,則由在轉(zhuǎn)向節(jié)上下襯套中點(diǎn)處作用于主銷的力,平衡(見圖4—2(c)),且有:
由轉(zhuǎn)向橋的俯視圖(圖4—2(d)的下圖)可知,制動(dòng)時(shí)轉(zhuǎn)向橫拉桿的作用力N為:
N=
力N位于側(cè)向平面內(nèi)且與輪軸中心線的垂直距離為(取為100 mm)如將N的著力點(diǎn)移至主銷中心線與輪鈾中心線的交點(diǎn)處.則需對(duì)主銷作用一側(cè)向力矩N (見圖4—2(b))。力矩N由位于側(cè)向平面內(nèi)并作用于主銷的力偶矩所平(c+d)衡,故有
而力N則內(nèi)存整向節(jié)上下襯套中點(diǎn)處作用于主銷的力,所平衡,且有:=
=
由圖4—2(b)可知,在轉(zhuǎn)向節(jié)上襯套的中點(diǎn)作用于主銷的合力和下襯套的中心作用于主銷的合力分別為:
=20440.3N
=31708.2N
由上兩式可見,在汽車制動(dòng)時(shí),主銷的最大載荷發(fā)生在轉(zhuǎn)向節(jié)下襯套的中點(diǎn)處,其值為=31708.2N。
二、在側(cè)滑工況下
僅有在側(cè)向平面內(nèi)起作用的力和力矩,且作用于左右轉(zhuǎn)向節(jié)主銷的力是不相等的,它們可分別按下式求得:
取中最大的作為主銷的計(jì)算載荷,計(jì)算主銷在前梁拳部下端面應(yīng)力和剪切應(yīng)力:
MPa ; MPa;
式中:—主銷直徑取為32 mm;
h —轉(zhuǎn)向節(jié)下襯套中點(diǎn)至前梁拳部下端面的距離,見圖4—2(a),取h=36mm;
;
<;
其中=500MPa;=100MPa。
主銷采用20cr,20CrNi,20crMnTi等低碳合金鋼制造,滲碳淬火,滲碳層深1.0~1.5mm,HRC56~62。
轉(zhuǎn)向節(jié)襯套的擠壓應(yīng)力為:
式中:—襯套長(zhǎng)為36mm。
在靜載荷下,上式的計(jì)算載荷取
N
。
§4.6轉(zhuǎn)向節(jié)推力軸承的計(jì)算
對(duì)轉(zhuǎn)向節(jié)推力軸承,取汽車以等速=40km/h,沿半徑R=50m的圓周行駛的工況作為計(jì)算工況。如果汽車向右轉(zhuǎn)彎,外輪即左前左輪的地面垂向反力增大。
,將上述計(jì)算工況的有關(guān)數(shù)據(jù)代入上式,并設(shè)
=0.5,
則有: ,
可近似地認(rèn)為推力軸承的軸向載荷等于上述前外輪的地面垂向外力,即:
。
鑒于轉(zhuǎn)向節(jié)推力軸承在工作中的相對(duì)轉(zhuǎn)角不大及軸承滾輪使圓周破壞帶來(lái)的危險(xiǎn)性,軸承的選擇按其靜承載容量進(jìn)行,且取當(dāng)量靜載荷 》,故此推力軸承滿足要求。
第五章 轉(zhuǎn)向系統(tǒng)的設(shè)計(jì)計(jì)算
§5.1 轉(zhuǎn)向系主要性能參數(shù)
§5.1.1轉(zhuǎn)向器的效率
功率從轉(zhuǎn)向軸輸入,經(jīng)轉(zhuǎn)向器輸出所求得的效率稱為正效率,用符號(hào)表示,;反之稱為逆效率,用符號(hào)表示,。
其中,為轉(zhuǎn)向器中的摩擦功率;為作用在齒條軸上的功率。為了保證轉(zhuǎn)向時(shí)駕駛員轉(zhuǎn)動(dòng)方向盤輕便,要求正效率高;為了保證汽車轉(zhuǎn)向后轉(zhuǎn)向輪和轉(zhuǎn)向盤能自動(dòng)回正,又需要一定的逆效率。為了減輕在不平路面上行駛時(shí)駕駛員的疲勞,車輪與路面之間的作用力傳至方向盤時(shí)應(yīng)盡可能小,防止打手,這又要求此逆效率盡可能低。
轉(zhuǎn)向器的正效率:
影響轉(zhuǎn)向器正效率的因素有:轉(zhuǎn)向器的類型、結(jié)果特點(diǎn)、結(jié)構(gòu)參數(shù)和制造質(zhì)量等。轉(zhuǎn)向器類型、結(jié)構(gòu)特點(diǎn)與效率 在前述的幾種轉(zhuǎn)向器中,齒輪齒條式、循環(huán)球式的正效率比較高。同一類型的轉(zhuǎn)向器,因結(jié)構(gòu)不同效率也不一樣。
轉(zhuǎn)向器逆效率:
根據(jù)逆效率大小的不同,轉(zhuǎn)向器又分為可逆式、極限可逆式、和不可逆式三種。
齒輪齒條式轉(zhuǎn)向器屬于可逆式轉(zhuǎn)向器,其逆效率相當(dāng)高,它能保證轉(zhuǎn)向后,轉(zhuǎn)向輪和轉(zhuǎn)向盤自動(dòng)回正。這既減輕了駕駛員的疲勞,又提高了行駛的安全性。但是,在不平路面上行駛時(shí),車輪受到的沖擊力能大部分傳至轉(zhuǎn)向盤,造成駕駛員“打手”,使之精神緊張;如果長(zhǎng)時(shí)間在不平路面上行駛,易使駕駛員疲勞,影響安全駕駛。
§5.1.2傳動(dòng)比的變化特性
1. 轉(zhuǎn)向系傳動(dòng)比
轉(zhuǎn)向系的傳動(dòng)比包括轉(zhuǎn)向系的角傳動(dòng)比和轉(zhuǎn)向系的力傳動(dòng)比。
2. 力傳動(dòng)比與轉(zhuǎn)向系角傳動(dòng)比的關(guān)系
輪胎與地面之間的轉(zhuǎn)向阻力和作用在轉(zhuǎn)向節(jié)上的轉(zhuǎn)向阻力矩之間的關(guān)系
(4-1)
式中,a為主銷偏移距此處,指從轉(zhuǎn)向節(jié)主銷軸線的延長(zhǎng)線與支撐平面的交點(diǎn)至車輪中心平面與支撐平面交線間的距離。作用在方向盤上的手力為為
(4-2)
式中,為作用在方向盤上的力矩;為方向盤的直徑。
將式(4-1)、 (4-2)代入后得到
(4-3)
有 (4-3)知,當(dāng)主銷偏移矩a小時(shí),力傳動(dòng)比應(yīng)取大些才能保持轉(zhuǎn)向輕便。
§5.2 主要參數(shù)的確定
§5.2.1 給定的主要計(jì)算參數(shù)
軸距 L=3308mm
輪距 前輪1567mm 后輪1485mm
輪胎 70.00-20 D=508mm B=293mm
最小轉(zhuǎn)彎半徑小于等于7.5m
§5.2.2 選擇主要轉(zhuǎn)向參數(shù)
汽車在轉(zhuǎn)向時(shí)需要有自動(dòng)回正能力,這需要轉(zhuǎn)向主銷在汽車的縱向和橫向平面內(nèi)各有一定的傾角。所以選定主銷后傾角γ為2°30′,主銷內(nèi)傾角β為7°,車輪外傾角α為1°,前輪前束為10mm。
轉(zhuǎn)向盤由輪轂、輪緣和輪輻構(gòu)成,方向盤的直徑D有一系列尺寸(如下表)
汽車類型
方向盤直徑D,mm
轎車、小型客車、小載重量貨車
400
中型大客車、中等載重量貨車
450、500
大型客車、大載重量貨車
550
可選擇方向盤直徑400mm , 轉(zhuǎn)向軸是用雙萬(wàn)向節(jié),軸與萬(wàn)向節(jié)的連接用花鍵來(lái)實(shí)現(xiàn)。
§5.2.3 車輪的左右最大轉(zhuǎn)角確定
為了避免在汽車轉(zhuǎn)向時(shí)產(chǎn)生路面對(duì)汽車行駛的附加阻力和輪胎的過快磨損,要求轉(zhuǎn)向系統(tǒng)能保證汽車轉(zhuǎn)向時(shí)所有車輪均做純滾動(dòng),這就需要所有車輪的軸線都交于一點(diǎn)才能實(shí)現(xiàn)。此輕型貨車應(yīng)滿足轉(zhuǎn)向時(shí)候最小轉(zhuǎn)彎半徑小于7.5米,而理想的車輪轉(zhuǎn)角α與β應(yīng)滿足理想關(guān)系式:
(4-6)
式中為車輪外轉(zhuǎn)角,β為車輪內(nèi)轉(zhuǎn)角,K為兩側(cè)主銷軸線與地面相交點(diǎn)之間的距離 (K=1567-2100=1367mm),為3308mm ,前輪轉(zhuǎn)臂a=120mm。
又因?yàn)槔硐肭闆r下,最小轉(zhuǎn)彎半徑與外轉(zhuǎn)向輪最大偏轉(zhuǎn)角的關(guān)系為:
(4-7)
聯(lián)立(4-6)(4-7)式得到:
=26.17°, =31.66°
圖3-1 理想內(nèi)外輪轉(zhuǎn)角關(guān)系簡(jiǎn)圖
§5.3 轉(zhuǎn)向梯形的選擇設(shè)計(jì)
圖3-2 整體式轉(zhuǎn)向梯形
1- 轉(zhuǎn)向橫拉桿 2-轉(zhuǎn)向梯形臂 3-前軸
轉(zhuǎn)向梯形選擇的是整體式后置梯形(如圖),圖視為把三軸式汽車假想為兩軸式時(shí)的圖形,L為假想的軸線距離,即是上圖的l,γ為轉(zhuǎn)向梯形的底角,S為兩個(gè)梯形臂延長(zhǎng)線與汽車中心線的交點(diǎn)與前軸的距離,一般為2/3l.
由公式
cotγ=0.75 (4-8)
得轉(zhuǎn)向梯形的底角 γ=72.78°
轉(zhuǎn)向梯形臂的長(zhǎng)度m,是參考現(xiàn)有汽車梯形臂長(zhǎng)度與主銷中心距K之比的統(tǒng)計(jì)數(shù)據(jù)后進(jìn)行選擇,一般范圍是:m=(0.11~0.15)K。由于是輕型載重汽車,固可取梯形臂長(zhǎng)度 m=150mm 。
由圖形可知,轉(zhuǎn)向橫拉桿的長(zhǎng)度跟K和γ有關(guān),其關(guān)系式為:
=K-2×m×cosγ (4-9)
=1262mm
則橫拉桿長(zhǎng)度為 1262mm。
§5.4 循環(huán)球式轉(zhuǎn)向器的設(shè)計(jì)
§5.4.1 轉(zhuǎn)向器(循環(huán)球式)的效率
為保證轉(zhuǎn)向時(shí)駕駛員轉(zhuǎn)動(dòng)轉(zhuǎn)向盤的輕便,要求正效率高;為了保證汽車轉(zhuǎn)向后轉(zhuǎn)向輪和轉(zhuǎn)向盤能自動(dòng)回正,又需要一定的逆效率;為減輕駕駛員在不平路面上的疲勞,防止打手,又要求逆效率盡可能低。
正效率的計(jì)算公式:
(4-10)
其中為螺桿的螺線導(dǎo)程角,選6°;為摩擦角,=?;?為摩擦因數(shù),選0.04,則=2.29°。
數(shù)據(jù)代入(4-10)解得 =72.1%。
逆效率的計(jì)算公式:
(4-11)
=71.3%。
§5.4.2 主要參數(shù)的選擇
主要參數(shù)參考《汽車設(shè)計(jì)》表7-1
齒扇模數(shù)m=6mm,搖臂軸直徑D=40mm,鋼球中心距=35mm,螺桿外徑=34mm,鋼球直徑d=8mm,螺距P=10mm,工作圈數(shù)W=2.5,環(huán)流行數(shù)b=2,齒扇齒數(shù)=5,齒扇整圓齒數(shù)Z=13,齒扇壓力角為27°30′,切削角=6°30′,齒扇寬B=34mm。
§5.4.3 螺桿、鋼球和螺母?jìng)鲃?dòng)副
螺母內(nèi)徑=+8%=36mm
每個(gè)環(huán)路中鋼球的數(shù)量為:
=35
其中為螺桿的螺線導(dǎo)程角,選6°。
接觸角θ是鋼球與螺桿滾道接觸點(diǎn)的正壓力方向與螺桿滾道法向截面軸線間的夾角,一般取45°,以使軸向力和徑向力分配均勻。
圖3-3 螺桿,鋼球,螺母?jìng)鲃?dòng)副
轉(zhuǎn)向盤轉(zhuǎn)動(dòng)角,對(duì)應(yīng)螺母移動(dòng)距離s為:
(4-12)
與此同時(shí)齒扇節(jié)圓轉(zhuǎn)過的弧長(zhǎng)等與s,相應(yīng)搖臂軸轉(zhuǎn)過角,其關(guān)系:
S=r (4-13)
其中r為齒扇節(jié)圓半徑。
聯(lián)立(4-12)(4-13)得= ,將對(duì)求導(dǎo),得轉(zhuǎn)向器角傳動(dòng)比為:
=24.492
§5.4.4 齒條、齒扇傳動(dòng)副設(shè)計(jì)
循環(huán)球式轉(zhuǎn)向器的齒扇為變厚齒扇,它的齒頂和齒根的輪廓是圓錐的一部分,分度圓上的齒厚是變化的,所以此傳動(dòng)副的設(shè)計(jì)主要是變厚齒扇的設(shè)計(jì)。
基準(zhǔn)剖面(1-1剖面)的齒形計(jì)算:
名稱
公式
結(jié)果(mm)
分度圓直徑
D=90
齒頂高
=6
齒根高
=1.5
齒全高
h=7.5
齒頂圓直徑
=102
分度圓齒厚
=9.42
頂圓壓力角
=39.75°
頂圓齒厚
=6
最大變位系數(shù)剖面(2-2剖面)齒頂變尖核算:
名稱
公式
結(jié)果(mm)
最大變位系數(shù)
=0.3608
齒頂圓半徑
=50.1648
齒頂圓壓力角
=40.642°
分度圓齒厚
=11.4389
齒頂圓齒厚
=1.698
圖3-4 變厚齒扇齒形計(jì)算簡(jiǎn)圖
§5.5 轉(zhuǎn)向系主要性能參數(shù)確定
§5.5.1 轉(zhuǎn)向系的角傳動(dòng)比
= (4-14)
式中為轉(zhuǎn)向器的角傳動(dòng)比,=24.492;為轉(zhuǎn)向傳動(dòng)機(jī)構(gòu)的角傳動(dòng)比,一般選擇=1。代入(9) 得 =24.492
其中 式中為轉(zhuǎn)向搖臂長(zhǎng)(mm),所以==137mm。
§5.5.2 轉(zhuǎn)向盤旋轉(zhuǎn)圈數(shù)n
(4-15)
式中為轉(zhuǎn)向盤從一個(gè)極限位置到另一個(gè)極限位置所轉(zhuǎn)過的角度,且:
=24.492(26.17°+31.66°)
=1416.37°
所以 n=1416.37÷360°=3.9 (圈)
§5.6 轉(zhuǎn)向系其他元件的選擇及材料的確定
轉(zhuǎn)向主銷選用圓柱實(shí)心型,D=40mm;一般選用20Cr。轉(zhuǎn)向節(jié)臂和梯形臂有中碳鋼或中合金鋼如35Cr,40,40Cr等模鍛加工而成,一般選用40Cr。轉(zhuǎn)向縱、橫拉桿應(yīng)選用質(zhì)量較輕剛性較好的20,30或40無(wú)縫鋼管制造,選用40鋼。球頭銷用合金結(jié)構(gòu)鋼12CrNiB、15CrMo、20CrMnTi或液體碳氮共滲鋼35Cr、35CrNi等制造(如下圖所示結(jié)構(gòu)),一般選用20CrMnTi。
圖3-5 轉(zhuǎn)向主銷
1-球頭銷 2-球頭碗 3-壓緊彈簧
第六章 轉(zhuǎn)向系主要零件的強(qiáng)度計(jì)算
§6.1 計(jì)算載荷的確定
轉(zhuǎn)向系全部零件的強(qiáng)度,是根據(jù)作用在零部件上的力來(lái)確定的。一般來(lái)說(shuō)汽車在瀝青或混凝土路面上的園地轉(zhuǎn)向阻力,用經(jīng)驗(yàn)公式計(jì)算:
,N.mm (5-1)
載重
前軸負(fù)荷(N)
質(zhì)心高度(mm)
空載
9775.5
1100
滿載
21324.8
852
數(shù)據(jù)代入(5-1)得 = N.mm
由于力矩平衡,所以轉(zhuǎn)向上節(jié)臂受反方向力矩M==8.69 N.mm,所受到的拉力P==8.69/1376343N。
§6.2 主要零件的強(qiáng)度計(jì)算
圖4-1 轉(zhuǎn)向搖臂受力圖
轉(zhuǎn)向搖臂(45鋼)的受力及形狀如上圖,尺寸如下:F=P=2292N,c==137mm,e=50mm,d=90mm,b=50mm,a=27mm
通過計(jì)算比較確定斷面A-A為危險(xiǎn)截面。
斷面A-A處的彎曲應(yīng)力:
= (5-2)
W==6623=6.623
=2.655Pa=265.5
斷面A-A處的扭轉(zhuǎn)剪應(yīng)力:
(5-3)
=7.15
= 76.85
斷面A-A處的最大合成正應(yīng)力:
=306.78〈[]=353
斷面處的最大切線應(yīng)力:
=153.39=230
故此轉(zhuǎn)向搖臂滿足使用條件。
第七章 結(jié)論
通過對(duì)前橋及轉(zhuǎn)向的設(shè)計(jì),我得出結(jié)論,此設(shè)計(jì)滿足設(shè)計(jì)要求。第二章列出了前橋的設(shè)計(jì)方案,第三章列出了轉(zhuǎn)向系的設(shè)計(jì)方案,第四章主要對(duì)前橋的主要零件進(jìn)行了強(qiáng)度校核,經(jīng)校核滿足要求。第五章主要對(duì)轉(zhuǎn)向系的方案進(jìn)行了論證,并詳細(xì)計(jì)算了循環(huán)球式轉(zhuǎn)向器的各個(gè)參數(shù),這說(shuō)明也是可行的。故此設(shè)計(jì)我比較滿意,真誠(chéng)接受各評(píng)委老師的批評(píng)指教!
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17. 閻蔭棠.幾何量精度設(shè)計(jì)與檢測(cè).北京:機(jī)械工業(yè)出版社,1996
致 謝
畢業(yè)設(shè)計(jì)的完成首先要感謝曹青梅老師,曹老師在繁忙的工作中為我們的畢業(yè)設(shè)計(jì)提供了大量資料,并在設(shè)計(jì)過程中對(duì)我們進(jìn)行了耐心的開導(dǎo),給我們提了好多中肯的建議和方法。再次對(duì)曹老師表示衷心的感謝!
其次感謝許銳良老師和同做畢業(yè)設(shè)計(jì)的各位同學(xué),他們可謂是我的良師益友,許多問題我們?cè)诨ハ嗵接懼泄餐砷L(zhǎng),三人行,必有我?guī)?,每個(gè)人都有自己的長(zhǎng)處和優(yōu)點(diǎn)。
還有本系的領(lǐng)導(dǎo),系辦,車輛研究所,車輛實(shí)驗(yàn)室老師的關(guān)心和支持!在此一并表示感謝!
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外文資料及翻譯
Steering system
Motor steering system: On the automobile uses for to change or restores its travel direction to suppose the organization to be called the motor turning system specially. Automobile's steering system is uses for to change the automobile travel direction and to maintain the automobile straight line travel organization
Composes
(1)To change the control mechanism basically mainly by the steering wheel, the steering axle, the steering tube column and so on to be composed.
(2) Diverter becomes steering wheel's rotation steering arm's swinging or the rack axis straight reciprocating motion, and to changes the control force to carry on the enlargement the organization. The diverter fixes generally on the automobile frame or the automobile body, changes the control force after the diverter generally will also change the transmission direction.
(3) Steering transmission system the strength which and the movement outputs the diverter passes to the wheel (knuckle), about and causes the wheel to carry on the deflection according to certain relations the organization.
Type
Crooked to energy difference, the steering system may divide into the machinery steering system and the power steering system two broad headings crooked.
Mechanical steering system: And changes the transmission system by the diverter to be composed.
Diverter: By the steering wheel, the steering wheel steering axle, changes meshing to pay (diverter) to be composed.
Steering transmission system: By drop arm (drop arm), drag link, drag link arm, about trapezoidal arm, steering knuckle tie rod, if a dry bulb joint composes.
Power steering system: Changes the augmenter constitution by mechanical steering system Canada.
1.Mechanical steering system The mechanical steering system changes the energy by pilot's physical strength achievement, all power transmission are the machinery. The mechanical steering system by changes the control mechanism, the diverter and changes the transmission system three major part to be composed.
(1) steering control mechanism
Changes the control mechanism by the steering wheel, the steering axle, the steering tube column and so on to be composed, its function is rotates the pilot steering wheel's control force to pass to the divertor.
(2) Divertor
The diverter (also often is called steering unit) is completes from the rotary motion to the translation (or approximate straightline motion) a group of gear mechanism, simultaneously is also in the steering system speed reducer drive. At present the commonly used toothed
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