1The Mazda Speed Sensing Computerised 4-Wheel Steering System. Three and a half decades ago, two young Mazda designers arrived at a far-sighted and well-calculated conclusion that was quite revolutionary for the time. In their technical presentation at the October 26, 1962 Japanese Automotive Engineers' Society Technical Conference, Dr Tadashi Okada and engineer Toshiaki summarised their arduous research concerning vehicle dynamics as follows. 1. The basic difference in the characteristics of oversteer and understeer lies in the magnitude of time delay and response. 2. a vehicle that is stable under high speed must possess understeer characteristics 3. the rear wheel tyre reflects heavily on the stability 4. a major improvement on control and stability may be anticipated by means of the automatic rear wheel steering system. The conclusions and formulations presented by these two engineers established the foundation for Mazda's present-day reputed suspension technology. Over years of dedicated research and development expertise, their original discoveries and theories have contributed to some of the most significant achievements within the recent history of automotive chassis engineering, incorporated by Mazda within its series production products. These developments include the twin trapezoidal link rear suspension, first employed in the original front-wheel drive Mazda 323 (1980) and the Mazda 626 (1982), and then perfected within the updated Mazda 626; the award winning Dynamic Tracking Suspension System of the second generation Mazda RX-7 (1985); and the elaborate E-link rear suspension of the new Mazda 929 (1987). While various external forces and loads are exerted to the rear wheels of a vehicle as it combats the elements of the law of motion as defined by Sir Isaac Newton, these new suspension systems convert those forces into “4WS effects“ which positively aid in vehicle stability and agility. The Mazda designers' and engineers' ultimate goal was still a positive measure to generate forces for positive controls; a Four-Wheel Steering system. 2In 1983, Mazda astonished the automotive world with the introduction of an engineering concept car, the MX-02, exhibited at the Tokyo Motor Show. This four-door Sedan, with generous passenger accommodation on an unusually long wheelbase, incorporated among its numerous advanced features a true 4WS system that aided high-speed stability as well as its low-speed manoeuvring. The degree of rear wheel steering was determined by the measurement of both front wheel steering angle and vehicle speed, by means of a central computer unit. The MX-02 was followed by another exciting concept car; the MX-03, first exhibited at the Frankfurt Motor Show in September 1985. This sleek four seat futuristic coupe of the 1990s combined a refined electronically-controlled 4WS system with a continually varying torque-split, four-wheel drive system and a powerful three-rotary engine. Mazda Electronically -Controlled Four-Wheel Steering System: A Beneficial Technology Mazda's electronically-controlled, vehicle-speed-sensing Four-Wheel Steering System (4WS) steers the rear wheels in a direction and to a degree most suited to a corresponding vehicle speed range. The system is mechanically and hydraulically actuated, producing greatly enhanced stability, and within certain parameters, agility. The driver of a Mazda 4WS-equipped car derives five strategic benefits, over and above the conventional vehicle chassis. Superior cornering stability 1.Improved steering responsiveness and precision 2.High-speed straightline stability 3.Notable improvement in rapid lane-changing manoeuvres 4.Smaller turning radius and tight-space manoeuvrability at low vehicle speed range The most outstanding advantage of the Mazda 4WS is that it contributes to a notable reduction in driver fatigue over high-speed and extended travelling. This is achieved by optimally: 31.reducing the response delay to steering input and action and 2.eliminating the vehicle's excessive reaction to steering input In essence, by providing the optimum solution to the phenomena researched by the two young Mazda engineers in the early sixties - by the method advocated by them - the 4WS system has emerged as a fully beneficial technology. Strategic Construction The Mazda 4WS consists of a rack-and-pinion front steering system that is hydraulically assisted by a twin-tandem pump main power source, with an overall steering ratio of 14.2:1. The rear wheel steering mechanism is also hydraulically assisted by the main pump and electronically controlled - according to the front steering angle and vehicle speed. The rear steering shaft extends from the rack bar of the front steering gear assembly to the rear steering-phase control unit. The rear steering system is comprised of the input end of the rear steering shaft, vehicle speed sensors, a steering-phase control unit (determining direction and degree), a power cylinder and an output rod. A centering lock spring is incorporated, which locks the rear system in a neutral (straightforward) position in the event of hydraulic failure. Additionally, a solenoid valve that disengages hydraulic assist (thereby activating the centering lock spring) in case of an electrical failure is included. The 4WS system varies the phase and ratio of the rear-wheel steering to the front wheels, according to the vehicle speed. It steers the rear wheels toward the opposite phase (direction) of the front wheel during speeds less than 35km/h (22mph) for a tighter turn and “neutralizes“ them (to a straightforward direction, as in a conventional two-wheel steering principle) at 35km/h (22mph). Above that speed, the system steers toward the same phase-direction as the front wheels, thereby generating an increased cornering force for stability. The maximun steering angle of the rear wheels extends 5 degrees to either left or right, a measurement that Mazda has determined to be optimally effective and natural to human sensitivity. 4Primary Components 1. Vehicle speed sensors Interpret speedometer shelf revolutions and send signal to the electronic computer unit. two sensors, one within the speedometer and the other at the transmission output, are used to crosscheck the other for accuracy and failsafe measures. 2. Steering phase control unit* Conveys to the power steering cylinder booster valve thedirection and stroke of rear wheel steering by the combined movement of the control yoke angle and bevel gear revolutions. 3. Electric stepper motor Performs altering of the yoke angle and bevel gear phasing 4. Rear steering shaft Transmits front wheel steering angle by turning the small bevel gear in the steering phase control unit, which rotates the main bevel gear in the assembly. 5. Control valve Feeds hydraulic pressure to the steering actuator, according to the phase and stroke required for appropriate rear wheel steering. 56. Hydraulic power cylinder Operates the output rod by hydraulic pressure and steers the rear wheels. It locks the rear wheels in a “neutral“ (straightforward) position with the centering lock spring, which is activated by a solenoid valve in case of failure to ensure a normal 2WS function for the vehicle. 7. Hydraulic pump. Provides hydraulic pressure to both the front and rear steering systems. Details of Steering Phase Control Unit The steering phase control unit alters the direction and degree of rear wheel steering. It consists of a stepper motor that controls the rear steering ratio, a control yoke, a swing arm, a main bevel gear engaged to the rear steering shaft via a small bevel gear, and a control rod connected to the control valve. It operates: a. Opposite phase (direction) steering under 35km/h (22mph) 1. Control Yoke is at an angle activated by the stepper motor 2. Front wheels are steered to the right. The small bevel gear is rotated in direction X by the rotation of the rear steering shaft. The small bevel gear, in turn, rotates the main bevel gear. 3. Rotation of the main bevel gear causes movement of the control rod toward the control valve. 4. Input rod of the control valve is pushed to the right, according to the degree of the control rod's movement (determined by the disposition of the swing arm), which is 6positioned to move in an upward direction, to the right. The rear wheels are thus steered to the left, in an opposite direction to the front wheels. 5. As the angle of the control yoke is increased in direction A as vehicle speed decreases, the rear-to-front steering ratio proportionately increases and the vehicle's steering lock tightens. b. Same phase (direction) over 35km/h (22mph) The operation of this phase is the reverse of the opposite phase one, because the control yoke is angled toward “positive“ in this vehicle speed range, as illustrated. The phasing of the swing arm, yoke rod and bevel gear steers the rear wheels toward the right-the same direction as the front wheels. c. Neutral phase, at 35km/h (22mph) The control yoke's angle is horizontal (neutral). Thus, the input rod is not affected, even if the control rod is moved with the rotation of the bevel gear unit. As a result, the rear wheels are not steered in this mode. Power Cylinder The movement of the input rod of the control valve unit is transmitted to the power cylinder's spool. The spool's displacement to the sleeve causes a pressure difference between the right and left side chambers in the hydraulic power cylinder. The pressure difference overcomes the output shaft load and initiates sleeve movement. The sleeve-power rod assembly is moved in the direction of the input rod by a proportionate degree. The output rod transmits steering action to the tie rod on either end of the rear wheel steering control-mechanism unit, thereby steering the rear wheels. Fail-Safe Measures 7The system automatically counteracts possible causes of failure, both electronic and hydraulic. In either case, the centering lock spring housed in the steering system unit returns the output rods in the “neutral“ straightforward position, essentially alternating the entire steering system to a conventional 2WS principle. Specifically, if a hydraulic defect should render a reduction in pressure level (by a movement malfunction or a broken driving belt), the rear wheel steering mechanism is automatically locked in a neutral position, activating a low-level warning light. In the event of an electrical failure, such would be detected by a self-diagnostic circuit integrated within the 4WS control unit, which stimulates a solenoid valve and then neutralizes hydraulic pressure and return lines, thereby alternating the system again to that of a 2WS principle. Henceforth, the warning light referencing the 4WS system within the main instrument display is activated, indicating a system failure. 8翻譯馬自達(dá)公司的速度感應(yīng)四輪轉(zhuǎn)向系統(tǒng)三十五年前,兩個(gè)馬自達(dá)設(shè)計(jì)師提出了一個(gè)遠(yuǎn)見的、有計(jì)算認(rèn)為是相當(dāng)革命性的結(jié)論。他們?cè)?1962 年 10 月 26 日日本汽車工程師學(xué)會(huì)技術(shù)會(huì)議上 Tadashi Okada 博士和 Toshiaki 工程師總結(jié)了他們關(guān)于車輛動(dòng)力學(xué)的辛勤研究如下:1.基本特性差別在于過度轉(zhuǎn)向與不足轉(zhuǎn)向的量和時(shí)間上的延遲和響應(yīng)。2.汽車在高速狀態(tài)下應(yīng)具備不足轉(zhuǎn)向特點(diǎn)。3.后方的穩(wěn)定很大程度上反映出車輪和輪胎。4.控制與穩(wěn)定的一大進(jìn)步,可預(yù)期的方式自動(dòng)引導(dǎo)系統(tǒng)后車輪. 這種結(jié)論和提法被這兩個(gè)工程師提出并為良好懸架技術(shù)的研制成立了基金會(huì)多年來致力于研究和開發(fā),原有的理論有一定的作用,一些最重要的成就在近代歷史上汽車底盤工程,將在馬自達(dá)的系列產(chǎn)品的生產(chǎn). 這些發(fā)展包括雙斜后方的聯(lián)系中斷,首先采用原第一輪驅(qū)動(dòng) 323K(1980)、馬自達(dá) 626(1982),然后在更新完善馬自達(dá) 626. 獲獎(jiǎng)的動(dòng)態(tài)跟蹤系統(tǒng)中斷的第二代發(fā)票 RC7(1985); 并制定電子后方聯(lián)系中斷新馬自達(dá) 929(1987). 而與此同時(shí)各種外部壓力和負(fù)荷作用與汽車后方的車輪,因?yàn)樗`背牛頓的運(yùn)動(dòng)學(xué)原理,這些新系統(tǒng)中斷將這些力量納入“4ws 效應(yīng)“,積極幫助穩(wěn)定車輛和機(jī)敏. 馬自達(dá)的設(shè)計(jì)師和工程師們的最終目標(biāo)仍是積極的方法產(chǎn)生積極的控制措施; 四輪轉(zhuǎn)向體系。1983 年馬自達(dá)將舉世震驚的概念引入工程車 MX-02 中,并在東京會(huì)展上亮相。這輛四門私家轎車在不尋常的長(zhǎng)軸距上布置了寬敞的乘客空間,它匯聚許多先進(jìn)的特點(diǎn)具有高速穩(wěn)定和低速操控性能的真正意義的 4WS 系統(tǒng)。后方車輪的量取決于前方雙輪的角度和汽車的速度,而這些是由中央計(jì)算機(jī)單元控制的。MX-02 之后另一個(gè)令人振奮的概念車;MX-03 于 1985 年 9 月第一次在法蘭克福展出。這輛豪華的四座雙門未來派轎車裝配了 90 年代精確電子控制的 4WS 系統(tǒng)和不同扭矩均分系統(tǒng),四輪驅(qū)動(dòng)和強(qiáng)勁的三旋輪發(fā)動(dòng)機(jī)。馬自達(dá)電子控制四輪轉(zhuǎn)向系統(tǒng): 有利的技術(shù)9馬自達(dá)的電子控制、汽車速度感應(yīng)四輪轉(zhuǎn)向系統(tǒng)(4ws)驅(qū)動(dòng)雙后輪在一定方向和量上是最適合汽車的速度范圍的。這種系統(tǒng)是機(jī)械和液壓系統(tǒng)驅(qū)動(dòng),伴隨著生產(chǎn)穩(wěn)定提高,并在某些參數(shù)上反應(yīng)敏捷。馬自達(dá) 4WS 裝備車來自五個(gè)戰(zhàn)略利益的驅(qū)動(dòng),超過了傳統(tǒng)的底盤。1.優(yōu)秀的轉(zhuǎn)彎穩(wěn)定性。2.改良的駕駛響應(yīng)時(shí)間和精度控制。3.高速直線穩(wěn)定性。4.急速換道的機(jī)動(dòng)性大大改觀。5.更小的轉(zhuǎn)彎半徑和低速范圍狹小空間的可操縱性。馬自達(dá)最顯著的優(yōu)勢(shì)在于 4WS 系統(tǒng)能顯著降低高速疲勞駕駛和長(zhǎng)期駕駛,這是最優(yōu)化后取得的。1.降低對(duì)駕駛輸入和動(dòng)作的反應(yīng)延遲。2.消除汽車對(duì)駕駛輸入的過度響應(yīng)。從根本上說,在60 年代初兩位年輕的馬自達(dá)工程師通過提供這個(gè)最佳解決現(xiàn)象的方法,- 以這種方法他們提倡 -4WS系統(tǒng)已經(jīng)作為一項(xiàng)完全有利的技術(shù)出現(xiàn)。 戰(zhàn)略性建設(shè)馬自達(dá) 4WS 系統(tǒng)由兩個(gè)串聯(lián)泵來提供主要的動(dòng)力來源的液壓輔助的前置式齒輪齒條副轉(zhuǎn)向系統(tǒng),該轉(zhuǎn)向系的總的傳動(dòng)比為 14.2:1。后面的車輪的轉(zhuǎn)向依然是靠主泵提供動(dòng)力的液壓輔助驅(qū)動(dòng)和根據(jù)前輪轉(zhuǎn)角和汽車行駛速度來實(shí)現(xiàn)電子控制的裝置。后輪的轉(zhuǎn)向軸從前轉(zhuǎn)向器的轉(zhuǎn)向齒條延伸到轉(zhuǎn)向控制單元。后面的轉(zhuǎn)向系統(tǒng)包括轉(zhuǎn)向軸后的輸入端,車輛速度傳感器,轉(zhuǎn)向控制單元(確定方向和角度) ,一個(gè)動(dòng)力氣缸和一個(gè)輸入軸。為了以防液壓故障轉(zhuǎn)向系統(tǒng)上面裝了一個(gè)中央鎖彈簧,它將系統(tǒng)鎖止在中間位置,另外一旦發(fā)生電類的故障作用在螺旋管閥液體壓力將消失(因此此時(shí)將中央鎖彈簧將被開啟) 。依據(jù)車速的不同變化“4WS”系統(tǒng)因應(yīng)前輪的變化不斷改變后輪的狀態(tài)和比率。當(dāng)汽車在急轉(zhuǎn)彎時(shí)如果速度小于 ( )將使汽車的后輪與前輪的狀態(tài)相反hkm/35p2且在 ( )使它們失效(直到筆直向前,按照傳統(tǒng)的兩輪轉(zhuǎn)向原理) 。hkm/35p2當(dāng)速度高于 ( )時(shí)系統(tǒng)將于前輪保持同相轉(zhuǎn)動(dòng),因此增加了轉(zhuǎn)彎/時(shí)的穩(wěn)定力。將轉(zhuǎn)向后車輪的最大轉(zhuǎn)角無論向左或是向右都增加了 。馬自達(dá)已05經(jīng)確定了使人感覺到自然和保持人類靈敏性的測(cè)量方法。10主要組成部分 1. 車輛速度傳感器解析速度計(jì)架子的旋轉(zhuǎn)并把這種信號(hào)傳遞到打字計(jì)算機(jī)單元。有兩個(gè)傳感器,一個(gè)在速度計(jì)內(nèi)部另一個(gè)在傳輸?shù)妮敵龆?,用這樣兩個(gè)傳感器是為了使它們兩個(gè)相互求證和失效保險(xiǎn)。2. 轉(zhuǎn)向狀態(tài)控制單元*通過控制軛角度和錐形齒輪的配合運(yùn)動(dòng)將方向和行程傳遞給轉(zhuǎn)向后輪3. 步進(jìn)電機(jī)執(zhí)行軛角度的改變和錐形齒輪定相。4. 后輪驅(qū)動(dòng)軸通過控制那些小錐形齒輪來傳遞前輪轉(zhuǎn)向角,旋轉(zhuǎn)在組件里的主要錐形齒輪。 5. 控制閥將液壓傳遞給轉(zhuǎn)向執(zhí)行機(jī)構(gòu),根據(jù)狀態(tài)和行程要求引導(dǎo)合適的后輪轉(zhuǎn)向。6. 液壓動(dòng)力氣缸以液壓驅(qū)動(dòng)輸出軸和后輪轉(zhuǎn)向,它用一個(gè)中央鎖止彈簧將后轉(zhuǎn)向輪鎖在中間位置,如果在不能確保其對(duì)一正常的2WS車輛起作用時(shí)該鎖將被開啟。液壓泵,給前面兩個(gè)提供液壓和后驅(qū)動(dòng)輪。轉(zhuǎn)向狀態(tài)控制的細(xì)節(jié)轉(zhuǎn)向控制單元改變轉(zhuǎn)向后輪的度和方向。它有控制轉(zhuǎn)向后輪轉(zhuǎn)向系傳動(dòng)比的步進(jìn)電機(jī),一個(gè)控制軛, 一只擺動(dòng)臂,一個(gè)通過小錐齒輪連接在后輪轉(zhuǎn)向軸上的錐齒輪,和一個(gè)操縱桿連接控制閥。 它操作: a.轉(zhuǎn)向狀態(tài)(方向)少于 ( )的轉(zhuǎn)向。35/kmh2p1. 控制軛在步進(jìn)電機(jī)作用下有一個(gè)角度。2. 前輪被轉(zhuǎn)向右邊。小的錐形齒輪由于轉(zhuǎn)向后輪軸的旋轉(zhuǎn)而沿X方向旋轉(zhuǎn),小的錐形齒輪依次旋轉(zhuǎn)主要的錐形齒輪。3. 主要錐形齒輪的旋轉(zhuǎn)引起控制閥操縱桿的運(yùn)動(dòng)。4. 控制閥的輸入桿被推到右邊, 根據(jù)操縱桿的運(yùn)動(dòng)的度(通過擺動(dòng)臂的安排確定),被確定位置進(jìn)入一個(gè)向上方向,朝右邊。 后車輪在左側(cè)被如此使得轉(zhuǎn)向后輪對(duì)轉(zhuǎn)向前輪有個(gè)相反的轉(zhuǎn)向。5. 隨著車輛速度的減少控制軛的角度增加,由后到前的轉(zhuǎn)向系傳動(dòng)比也要成比例增加而轉(zhuǎn)向鎖收緊。b.這個(gè)階段的操縱與第一個(gè)階段的操作相反,這是因?yàn)樵谝欢ǖ乃俣确秶刂栖椀霓D(zhuǎn)動(dòng)角度趨向明顯,如同說明的那樣。擺動(dòng)臂,軛桿和錐形齒輪與前轉(zhuǎn)向輪保11持相同的狀態(tài)。c.中間狀態(tài),以 ( )控制軛的角度是水平的(中間位置) 。因此,35/kmh2p這根輸入桿沒有被影響,即使這個(gè)操縱桿為錐形齒輪單元所帶動(dòng)。因此后轉(zhuǎn)向輪沒有被這種方式所驅(qū)動(dòng)。動(dòng)力氣缸控制閥單元的輸入軸的運(yùn)動(dòng)被傳遞給氣缸線軸。由于線軸相對(duì)與套管的位移使得液壓動(dòng)力氣缸的左右壁室的形成一個(gè)壓力差。壓力差克服輸出軸的負(fù)荷并使軸套運(yùn)動(dòng)。軸套動(dòng)力軸總成被以相同的比例傳遞到輸入。輸出軸將轉(zhuǎn)向運(yùn)動(dòng)傳遞到后輪的任一轉(zhuǎn)向控制單元。由此驅(qū)動(dòng)后轉(zhuǎn)向輪。故障安全保障 系統(tǒng)能自動(dòng)消除電子和液壓可能存在的問題, 無論發(fā)生哪種情況,封裝在轉(zhuǎn)向系統(tǒng)里面的中央鎖止彈簧返回給輸出軸并確保其在中間的位置。本質(zhì)上是使整個(gè)轉(zhuǎn)向系統(tǒng)符合一個(gè)傳統(tǒng)的 2WS 準(zhǔn)則。尤其是一個(gè)液壓的缺陷使得壓力水平的降低(一個(gè)錯(cuò)誤的操作或者是安全帶的斷裂) ,后輪轉(zhuǎn)向裝置被鎖止在中間位置,并氣動(dòng)一盞低級(jí)的警告燈,如果是一個(gè)電子元件的錯(cuò)誤,那么這個(gè)錯(cuò)誤將被集成在 4WS 控制單元里面的自診斷回路所探測(cè)到,這將促使一個(gè)螺線管閥門的開啟然后使液壓無效并且返回到回路里面,因此再次使該系統(tǒng)符合 2WS 準(zhǔn)則。 從今以后,4WS 系統(tǒng)在主要儀器內(nèi)展示的警告燈開動(dòng),就表明一個(gè)系統(tǒng)故障。I摘要本文主要研究了四輪轉(zhuǎn)向傳動(dòng)系統(tǒng)的基本結(jié)構(gòu)和工作原理,并對(duì)四輪轉(zhuǎn)向傳動(dòng)路線進(jìn)行了簡(jiǎn)要分析。以此為理論基礎(chǔ),以某汽車的相關(guān)參數(shù)設(shè)計(jì)了四輪轉(zhuǎn)向轉(zhuǎn)向器。包括前輪轉(zhuǎn)向器的設(shè)計(jì)計(jì)算,后輪轉(zhuǎn)向執(zhí)行器的設(shè)計(jì),齒條等強(qiáng)度的計(jì)算。四輪轉(zhuǎn)向傳動(dòng)系主要是通過車速傳感器、前輪轉(zhuǎn)角傳感器、前輪轉(zhuǎn)速傳感器、方向盤轉(zhuǎn)角傳感器、后輪轉(zhuǎn)角傳感器、后輪轉(zhuǎn)速傳感器,發(fā)送信號(hào)到四輪轉(zhuǎn)向控制器內(nèi),信號(hào)經(jīng)過處理,得出后輪所需的轉(zhuǎn)角大小及方向,控制執(zhí)行器完成轉(zhuǎn)向。此系統(tǒng)可以改善車輛低速的轉(zhuǎn)向靈活性和高速時(shí)的操縱穩(wěn)定性,使汽車在轉(zhuǎn)向時(shí)響應(yīng)快,轉(zhuǎn)向能力強(qiáng),直線行駛穩(wěn)定。前輪轉(zhuǎn)向器是四輪轉(zhuǎn)向的基礎(chǔ)部件,是電機(jī)助力的齒輪齒條轉(zhuǎn)向器。后輪執(zhí)行器是驅(qū)動(dòng)后輪轉(zhuǎn)向的主要部件。通過對(duì)前輪轉(zhuǎn)向器和后輪執(zhí)行器的設(shè)計(jì),為四輪轉(zhuǎn)向技術(shù)整體設(shè)計(jì)提供了基礎(chǔ)。關(guān)鍵詞 四輪轉(zhuǎn)向,齒輪齒條電動(dòng)助力轉(zhuǎn)向器,后輪轉(zhuǎn)向執(zhí)行器IIAbstractThis paper mainly studies is the four-wheel steering transmission system the basic structure and working principle, and the four-wheel steering transmission routes are briefly analyzed. This theory, with a car related parameters of the four-wheel steering transmission system was designed. Including front wheel steering gear design calculation, rear wheel actuator design strength calculation, rack .Four-wheel steering transmission system is primarily through speed sensor, front wheel Angle sensor, front wheel speed sensor, steering wheel Angle sensor, rear Angle sensor, rear Lord Angle sensor, rear vice, rotational speed sensor sends a signal to the four-wheel steering controller inside, signal through processing, draw the rear required corner size and direction, control actuator finish turning. This system can improve vehicle speed steering flexibility and high speed control stability of, make cars in steering response quickly, steering capability is strong, run straight stability. Front wheel steering gear is the basic components, four-wheel steering motor hydraulically rack-and pinion steering gear Rear actuators are drive rear wheel steering the major components. Through the front wheel steering gear and rear actuator is designed for four-wheel steering technology integral design provides the basis.Key words Four-wheel steering gear rack of electric power steering gear, rear wheel actuatorsIII目錄摘要 IAbstract.II目錄 III第一章 緒論 .1 第二章 設(shè)計(jì)方案選擇 72.1 各傳感器位置確定 7 2.2 轉(zhuǎn)向機(jī)構(gòu)的設(shè)計(jì)要求 8 2.3 轉(zhuǎn)向梯形設(shè)計(jì) 9 2.4 本章小結(jié) .10 第三章 齒輪齒條電動(dòng)助力轉(zhuǎn)向器設(shè)計(jì)計(jì)算 11 3.1 轉(zhuǎn)向器的效率 .11 3.2 轉(zhuǎn)向器正效率 η + 11 3.3 轉(zhuǎn)向器逆效率 η- 12 3.4 傳動(dòng)比的變化特性 .13 3.4.1 力傳動(dòng)比與角傳動(dòng)比的關(guān)系 .14 3.5 參數(shù)選擇 163.5.1 轉(zhuǎn)向輪側(cè)偏角計(jì)算 .17 3.6 轉(zhuǎn)向系載荷確定 .18 3.7 轉(zhuǎn)向器的主要元件設(shè)計(jì) .19 3.7.1 選擇齒輪齒條材料 .19 3.7.2 齒輪齒條基本參數(shù) .21 3.7.3 轉(zhuǎn)向橫拉桿及其端部 .22 3.7.4 齒條調(diào)整 .23 3.8 齒輪齒條轉(zhuǎn)向器轉(zhuǎn)向橫拉桿的運(yùn)動(dòng)分析 .24 3.9 齒輪齒條傳動(dòng)受力分析 .25 3.10 彈簧的設(shè)計(jì)計(jì)算 29 3.11 齒輪軸軸承的校核 32 IV3.12 電機(jī)選擇 33 3.12.1 助力轉(zhuǎn)矩的計(jì)算 33 3.12.2 電動(dòng)機(jī)參數(shù)的選擇和計(jì)算 34 3.13 本章小結(jié) 34 第四章 后輪轉(zhuǎn)向執(zhí)行器設(shè)計(jì)計(jì)算 35 4.1 執(zhí)行器結(jié)構(gòu)設(shè)計(jì) .35 4.2 齒條設(shè)計(jì)計(jì)算 .35 4.3 回位彈簧的設(shè)計(jì)計(jì)算 .35 4.4 電機(jī)選擇 .37 4.4.1 助力轉(zhuǎn)矩的計(jì)算 .37 4.4.2 電動(dòng)機(jī)參數(shù)的選擇和計(jì)算 .37 4.5 本章小結(jié) .37 結(jié)論 39 致謝 40 參考文獻(xiàn) 41 附錄 42 - 1 -第一章 緒論四輪轉(zhuǎn)向(Four Wheel Steer)控制技術(shù)就是在汽車行駛轉(zhuǎn)向時(shí)通過引入一定的后輪轉(zhuǎn)向來增強(qiáng)汽車在高速行駛或在側(cè)向風(fēng)力作用時(shí)的操縱穩(wěn)定性、行駛安全性及改善低速時(shí)汽車的機(jī)動(dòng)靈活性。我們知道普通汽車的轉(zhuǎn)向是靠駕駛員轉(zhuǎn)動(dòng)方向盤,從而帶動(dòng)前輪的轉(zhuǎn)動(dòng)來實(shí)現(xiàn)的,前輪為轉(zhuǎn)向輪。前輪轉(zhuǎn)動(dòng)后,車身方向跟著改變,無轉(zhuǎn)向的后輪與車身的行進(jìn)方向產(chǎn)生差距,產(chǎn)生偏離角,從而發(fā)生彎力,產(chǎn)生轉(zhuǎn)向。由此可見,傳統(tǒng)的前輪轉(zhuǎn)向汽車有低速時(shí)轉(zhuǎn)向響應(yīng)慢,回轉(zhuǎn)半徑大,轉(zhuǎn)向不靈活;高速時(shí)方向穩(wěn)定性差等缺點(diǎn)。經(jīng)過二十余年的研究,4WS 技術(shù)已趨于成熟,日本的日產(chǎn)公司、馬自達(dá)公司、豐田公司,美國的福特公司、通用公司的汽車產(chǎn)品上都有裝用 4WS 系統(tǒng)。我國開展汽車四輪轉(zhuǎn)向技術(shù)研究相對(duì)較晚,80 年代末和 90 年代初開始有文章探討 4WS 問題,90 年代末,上海交通大學(xué)、浙江大學(xué)開始進(jìn)行 4WS 控制方法的研究。近年來,由于電子控制技術(shù)的快速發(fā)展,以及國內(nèi)愈趨緊張的交通狀況,四輪轉(zhuǎn)向控制技術(shù)越來越被汽車廠商及各高校重視,在 2003 年和 2005 年海峽連桿機(jī)構(gòu)學(xué)術(shù)研討會(huì)上臺(tái)北科技大學(xué)代表分享了后輪轉(zhuǎn)向機(jī)構(gòu)設(shè)計(jì)以及四輪轉(zhuǎn)向控制防側(cè)滑等理論成果。通過對(duì)目前四輪轉(zhuǎn)向技術(shù)的研究,我參照已有車型的參數(shù)設(shè)計(jì)了四輪轉(zhuǎn)向的前輪轉(zhuǎn)向器和后輪轉(zhuǎn)向執(zhí)行器,為國內(nèi)四輪轉(zhuǎn)向技術(shù)的發(fā)展提供基礎(chǔ)?!炯夹g(shù)說明】后輪轉(zhuǎn)向與前輪主要有兩個(gè)不同的相位轉(zhuǎn)角,當(dāng)車速較低時(shí)后輪與前輪轉(zhuǎn)向相反稱為逆向位轉(zhuǎn)角如圖(1-1) ,當(dāng)車速較高時(shí)后輪與前輪轉(zhuǎn)向相同稱為同相位轉(zhuǎn)角如圖(1-2) 。 - 2 -(a)2WS (b)4WS圖(1-1) 4WS 低速時(shí)逆向位轉(zhuǎn)向(a)2WS (b)4WS圖(1-2)4WS 高速時(shí)同向位轉(zhuǎn)向四輪轉(zhuǎn)向系統(tǒng)的控制目標(biāo)主要包括:1.減小側(cè)向加速度響應(yīng)和橫擺角速度響應(yīng)的滯后;2.減小汽車的側(cè)偏角;3.增強(qiáng)汽車的行進(jìn)穩(wěn)定性;4.改善低速范圍汽車的操縱性;- 3 -5.改善汽車的轉(zhuǎn)向響應(yīng)性能;6.抵制由汽車自身參數(shù)變化因素對(duì)汽車轉(zhuǎn)向響應(yīng)特性的影響,并保持所期望的汽車轉(zhuǎn)向響應(yīng)特性;后輪主動(dòng)轉(zhuǎn)向主要采用以下幾種控制模式:1.定前后輪轉(zhuǎn)向比轉(zhuǎn)向系統(tǒng);2.前輪參數(shù)控制后輪轉(zhuǎn)向(前饋型)3.前后輪轉(zhuǎn)向比是前輪轉(zhuǎn)角函數(shù)的四輪轉(zhuǎn)向系統(tǒng);4.前后輪轉(zhuǎn)向比是車速函數(shù)的四輪轉(zhuǎn)向系統(tǒng);5.具有反相特性的四輪轉(zhuǎn)向系統(tǒng);6.具有最優(yōu)來控制的四輪轉(zhuǎn)向系統(tǒng);7.具有自學(xué)習(xí)、自適應(yīng)能力的四輪轉(zhuǎn)向系統(tǒng)。四輪轉(zhuǎn)向系統(tǒng)的控制方法:前饋加反饋控制即前輪轉(zhuǎn)向角比例前饋加橫擺角速度比例反饋控制,控制后輪轉(zhuǎn)向,并且使汽車質(zhì)心處的側(cè)偏角始終為零。本設(shè)計(jì)采用具有自學(xué)習(xí)、自適應(yīng)能力的控制策略,的四輪轉(zhuǎn)向技術(shù)。主要工作形式是四輪轉(zhuǎn)向控制器收集各傳感器輸入的信號(hào),通過處理信號(hào),確定后輪所需的轉(zhuǎn)角大小及方向,將蓄電池電壓輸送到后輪轉(zhuǎn)向執(zhí)行器完成轉(zhuǎn)向如圖(1-3) 。1- 車速傳感器 2-方向盤轉(zhuǎn)角傳感器 3-后輪轉(zhuǎn)速傳感器 4-執(zhí)行器電源輸入端 5-后輪轉(zhuǎn)向執(zhí)行器 6-后輪轉(zhuǎn)角傳感器 7-四輪轉(zhuǎn)向控制單元 8-前輪轉(zhuǎn)角傳感器 圖(1-3)四輪轉(zhuǎn)向示意圖- 4 -四輪轉(zhuǎn)向的工作特性:當(dāng)車速低于 29km/h 時(shí),如果轉(zhuǎn)向盤轉(zhuǎn)動(dòng),后輪會(huì)立即開始向與前輪相反的方向轉(zhuǎn)動(dòng),在車速為零時(shí),后輪最大轉(zhuǎn)角是 6 度。后輪轉(zhuǎn)角減小程度隨車速變化,在車速為 29km/h 時(shí)后輪轉(zhuǎn)角幾乎是零。當(dāng)車速為29km/h 時(shí),轉(zhuǎn)向盤在最初 200°轉(zhuǎn)角內(nèi)后輪轉(zhuǎn)向與前輪方向一致。在這個(gè)車速范圍內(nèi),轉(zhuǎn)向盤轉(zhuǎn)角大于 200°時(shí)后輪會(huì)轉(zhuǎn)向相反的方向。當(dāng)車速提高到96km/h,并且轉(zhuǎn)向盤轉(zhuǎn)角是 100°時(shí),那么后輪將會(huì)向前輪的方向轉(zhuǎn)動(dòng)約 1°。在這個(gè)車速下,如果轉(zhuǎn)向盤轉(zhuǎn)動(dòng) 500°,后輪將會(huì)向前輪相反方向轉(zhuǎn)動(dòng)大約1°【設(shè)計(jì)說明】由于本項(xiàng)技術(shù)的特殊性,和時(shí)間關(guān)系,只對(duì)前輪電動(dòng)助力轉(zhuǎn)向轉(zhuǎn)向器,和后輪轉(zhuǎn)向執(zhí)行器進(jìn)行了設(shè)計(jì)。對(duì)于懸架系統(tǒng)和和后輪轉(zhuǎn)向梯形只是提出了設(shè)計(jì)方向。 (前懸架可以采用雙叉臂式懸架,后懸架系統(tǒng)可以采用多連桿式懸架,現(xiàn)有車型-寶馬七系,后輪轉(zhuǎn)向梯形可采用雙梯形,使用兩套機(jī)構(gòu)進(jìn)行切換。 )前輪齒輪齒條轉(zhuǎn)向器采用空心電機(jī)驅(qū)動(dòng)螺桿助力系統(tǒng),此系統(tǒng)具有節(jié)能、環(huán)保、高效、安全等諸多優(yōu)點(diǎn),其整體結(jié)構(gòu)如圖(1-4)所示。圖(1-4)前輪轉(zhuǎn)向器由電子控制單元(Electric Control Unit,簡(jiǎn)稱 ECU)轉(zhuǎn)矩傳感器( Torque Sensor) ,前輪角度傳感器( Rotation Speed sensor)電動(dòng)機(jī)(Motor) 、轉(zhuǎn)向盤(Steering Wheel)等組成。當(dāng)駕駛員轉(zhuǎn)動(dòng)方向盤時(shí),電動(dòng)助力轉(zhuǎn)向系統(tǒng)開始工作,轉(zhuǎn)向盤角度和扭矩傳感器把方向盤的輸入信號(hào)(轉(zhuǎn)向力矩和旋轉(zhuǎn)角度) ,以電壓信號(hào)的形式送至 ECU。與此同時(shí) ECU 讀取汽車的車的車速信號(hào)以及車輛發(fā)動(dòng)機(jī)的轉(zhuǎn)速信號(hào)。ECU 根據(jù)轉(zhuǎn)向力矩大小和方向、發(fā)動(dòng)機(jī)或電動(dòng)機(jī)轉(zhuǎn)速、車速、方向盤轉(zhuǎn)角、方向盤轉(zhuǎn)速等信號(hào),判斷是否需要助力及助力的大小和方向。若需要助力,則依據(jù)預(yù)先設(shè)計(jì)的助力特性曲線計(jì)算出必要的助力力矩,并- 5 -按照一定的控制策略和算法,輸出相應(yīng)的控制信號(hào)給驅(qū)動(dòng)電路,由驅(qū)動(dòng)電路提供相應(yīng)的電流給助力電機(jī),助力電機(jī)輸出的轉(zhuǎn)矩,由減速機(jī)構(gòu)放大后再傳送給轉(zhuǎn)向軸起助力轉(zhuǎn)向的作用,從而完成轉(zhuǎn)向助力的功能。若出現(xiàn)故障或車速超出設(shè)定值則控制助力電機(jī)停止輸出,系統(tǒng)不提供助力,系統(tǒng)轉(zhuǎn)為人工手動(dòng)轉(zhuǎn)向。由于電控單元可以采集車速、方向盤的轉(zhuǎn)矩和轉(zhuǎn)角信號(hào),所以 EPS 提供的助力大小可以根據(jù)控制策略調(diào)整。后輪轉(zhuǎn)向執(zhí)行器如圖(1-5)所示 1- 轉(zhuǎn)向軸螺桿 2-后輪轉(zhuǎn)角傳感器 3-定子 4-執(zhí)行器殼體 5-回位彈簧 6-換向器 7-電刷8-轉(zhuǎn)子 9-循環(huán)球螺桿圖(1-5)后輪執(zhí)行器執(zhí)行器包含一個(gè)通過循環(huán)球螺桿機(jī)構(gòu)驅(qū)動(dòng)轉(zhuǎn)向齒條的電動(dòng)機(jī)。轉(zhuǎn)向橫拉桿是從轉(zhuǎn)向執(zhí)行器連接到后輪轉(zhuǎn)向節(jié)臂和轉(zhuǎn)向節(jié)處,執(zhí)行器內(nèi)的回位彈簧在點(diǎn)火開關(guān)斷開,或四輪轉(zhuǎn)向系統(tǒng)失效時(shí)將后輪推回直線行駛位置。一個(gè)后輪轉(zhuǎn)角傳感器安裝在后輪轉(zhuǎn)向執(zhí)行器內(nèi)。通過對(duì)前輪轉(zhuǎn)向器和后輪轉(zhuǎn)向執(zhí)行器的設(shè)計(jì),為四輪轉(zhuǎn)向整體設(shè)計(jì)提供了基礎(chǔ)。- 6 -- 7 -第二章 設(shè)計(jì)方案選擇2.1 各傳感器位置確定1.車速傳感器:安裝在變速內(nèi)。車速傳感器將與車速相關(guān)的電壓信號(hào)送到四輪轉(zhuǎn)向系統(tǒng)電子控制模塊,這個(gè)車速信號(hào)也被送到自動(dòng)變速器內(nèi)的電子控制模塊。2.前/后輪轉(zhuǎn)速傳感器:安裝在車輪輪轂上,前/后輪轉(zhuǎn)速傳感器將前/后輪轉(zhuǎn)速電壓信號(hào)送到四輪轉(zhuǎn)向系統(tǒng)電子控制模塊,這個(gè)車輪轉(zhuǎn)速信號(hào)也被送到 ABS電子控制模塊。3.前輪轉(zhuǎn)角傳感器:前輪轉(zhuǎn)角傳感器安裝在前輪電機(jī)內(nèi)這個(gè)傳感器含有一個(gè)隨循環(huán)球螺桿旋轉(zhuǎn)的脈沖環(huán),電子霍爾傳感元件直接安裝在脈沖環(huán)上部,如圖(2-1)圖(2-1)當(dāng)安裝在轉(zhuǎn)子上的“轉(zhuǎn)角傳感器檢測(cè)凸臺(tái)”隨轉(zhuǎn)子旋轉(zhuǎn)時(shí),套在轉(zhuǎn)子上的轉(zhuǎn)角傳感器的霍爾傳感元件向電子控制模塊發(fā)出脈沖數(shù)字電壓信號(hào),顯示轉(zhuǎn)角。- 8 -4.后輪轉(zhuǎn)角傳感器:后輪轉(zhuǎn)角傳感器安裝后輪執(zhí)行器電機(jī)內(nèi),此傳感器與前輪轉(zhuǎn)角傳感器相似,如上圖,當(dāng)安裝在轉(zhuǎn)子上的“轉(zhuǎn)角傳感器檢測(cè)凸臺(tái)”隨轉(zhuǎn)子旋轉(zhuǎn)時(shí),套在轉(zhuǎn)子上的轉(zhuǎn)角傳感器的霍爾傳感元件向電子控制模塊發(fā)出脈沖數(shù)字電壓信號(hào),顯示后輪轉(zhuǎn)角。5.方向盤轉(zhuǎn)角傳感器:安裝在組合開關(guān)下方的轉(zhuǎn)向柱上。轉(zhuǎn)角傳感器采用霍爾效應(yīng)原理結(jié)構(gòu),轉(zhuǎn)角傳感器檢測(cè)轉(zhuǎn)向盤的轉(zhuǎn)動(dòng)方向、轉(zhuǎn)動(dòng)速度和轉(zhuǎn)動(dòng)角度。轉(zhuǎn)向盤轉(zhuǎn)動(dòng)時(shí),轉(zhuǎn)角傳感器向電子控制模塊傳送前輪轉(zhuǎn)動(dòng)的信號(hào)。6.轉(zhuǎn)向力矩傳感器:安裝在小齒輪內(nèi),轉(zhuǎn)向力矩傳感器根據(jù)小齒輪桿的旋轉(zhuǎn)情況,檢測(cè)出轉(zhuǎn)向力的大小并輸送至控制單元。如圖(2-2) 圖(2-2)2.2 轉(zhuǎn)向機(jī)構(gòu)的設(shè)計(jì)要求1.運(yùn)動(dòng)學(xué)上應(yīng)保持轉(zhuǎn)向輪轉(zhuǎn)角和駕駛員轉(zhuǎn)動(dòng)方向盤的轉(zhuǎn)角之間保持一定的比例關(guān)系。2.隨著轉(zhuǎn)向輪阻力增大(或減?。?,作用在轉(zhuǎn)向盤上的手力必須增大(或減?。Q之為“路感”3.當(dāng)作用在轉(zhuǎn)向盤上的切向力 0.025 0.190KN 時(shí),動(dòng)力轉(zhuǎn)向器就應(yīng)開始???≥ ~工作。4.轉(zhuǎn)向后,轉(zhuǎn)向盤應(yīng)自動(dòng)回正,并使汽車保持在穩(wěn)定的直線行駛狀態(tài)。- 9 -5.工作靈敏,即轉(zhuǎn)向盤轉(zhuǎn)動(dòng)后,系統(tǒng)內(nèi)壓力能很快增長(zhǎng)到最大值。6.轉(zhuǎn)向失靈時(shí),仍能用機(jī)械系統(tǒng)操縱車輪轉(zhuǎn)向。2.3 轉(zhuǎn)向梯形設(shè)計(jì)阿克曼原理:汽車在行駛(直線行駛和轉(zhuǎn)彎行駛)過程中,每個(gè)車輪的運(yùn)動(dòng)軌跡,都必須完全符合它的自然運(yùn)動(dòng)軌跡,從而保證輪胎與地面間處于純滾動(dòng)而無滑移現(xiàn)象。兩輪轉(zhuǎn)向汽車阿克曼原理如圖(2-3) 轉(zhuǎn)角關(guān)系 = 1?????????????????????(2.1)圖(2-3)L:前后輪軸距 K:兩輪轉(zhuǎn)向主銷距離但實(shí)際上的轉(zhuǎn)向中心 O 不再后輪延長(zhǎng)線上,這時(shí)汽車將產(chǎn)生側(cè)傾力,將導(dǎo)致重心偏移即重心測(cè)偏角。通過四輪轉(zhuǎn)向技術(shù),后輪微小的轉(zhuǎn)角(±3°)來控制車輛轉(zhuǎn)彎時(shí)的側(cè)傾角,使重心側(cè)偏角減小為零。這樣車輛在高速行駛時(shí)能迅速改變車道,車身又不致產(chǎn)生大的擺動(dòng),減少了產(chǎn)生擺尾的可能性,同時(shí)也改善了前輪轉(zhuǎn)向不足的問題。- 10 -四輪轉(zhuǎn)向汽車阿克曼原理如圖(2-4) 轉(zhuǎn)角關(guān)系圖(2-4)前輪與后輪同向轉(zhuǎn)向轉(zhuǎn)角關(guān)系: - = 1????????1-????????1 1????????2-????????2 ????(2.2)前輪與后輪反向轉(zhuǎn)向轉(zhuǎn)角關(guān)系:+ = 1????????1-????????1 1????????2-????????2 ????(2.3)2.4 本章小結(jié)本章對(duì)四輪轉(zhuǎn)向的具體結(jié)構(gòu)做了詳細(xì)介紹,并且對(duì)此結(jié)構(gòu)的轉(zhuǎn)向梯形進(jìn)行分析,對(duì)前輪轉(zhuǎn)向器和后輪執(zhí)行器的設(shè)計(jì)提供了基- 11 -第三章 齒輪齒條電動(dòng)助力轉(zhuǎn)向器設(shè)計(jì)計(jì)算3.1 轉(zhuǎn)向器的效率功率P 1從轉(zhuǎn)向軸輸入,經(jīng)轉(zhuǎn)向軸輸出所求得的效率稱為正效率,用符號(hào)η +表示,η +=(P1—P2)/P l;反之稱為逆效率,用符號(hào)η -表示,η - =(P3—P2)/P 3。式中,P 2為轉(zhuǎn)向器中的摩擦功率;P 3為作用在轉(zhuǎn)向軸上的功率。為了保證轉(zhuǎn)向時(shí)駕駛員轉(zhuǎn)動(dòng)轉(zhuǎn)向盤輕便,要求轉(zhuǎn)向器傳遞正效率高。為了保證汽車轉(zhuǎn)向后轉(zhuǎn)向輪和轉(zhuǎn)向盤能自動(dòng)返回到直線行駛位置,又需要有一定的逆效率。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轉(zhuǎn)向盤上要盡可能小,防止打手又要求逆效率盡可能低。3.2 轉(zhuǎn)向器正效率 η +影響轉(zhuǎn)向器正效率的因素有:轉(zhuǎn)向器的類型、結(jié)構(gòu)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 在前述四種轉(zhuǎn)向器中,齒輪齒條式、循環(huán)球式轉(zhuǎn)向器的正效率比較高,而蝸桿指銷式的固定銷和蝸桿滾輪式轉(zhuǎn)向器的正效率要明顯的低些。同一類型轉(zhuǎn)向器,因結(jié)構(gòu)不同效率也不一樣。如蝸桿滾輪式轉(zhuǎn)向器的滾輪與支撐軸之間的軸承可以選用滾針軸承、圓錐滾子軸承和球軸承等三種結(jié)構(gòu)之一。第一種結(jié)構(gòu)除滾輪與滾針之間有摩擦損失外,滾輪側(cè)翼與墊片之間還存在滑動(dòng)- 12 -摩擦損失,故這種轉(zhuǎn)向器的效率僅有54%。另外兩種結(jié)構(gòu)的轉(zhuǎn)向器效率,根據(jù)試驗(yàn)結(jié)果分別為70%和75%。轉(zhuǎn)向軸承的形式對(duì)效率也有影響,用滾針軸承比用滑動(dòng)軸承可使正或逆效率提高約10%。轉(zhuǎn)向器的結(jié)構(gòu)參數(shù)與效率 如果忽略軸承和其它地方的摩擦損失,只考慮嚙合副的摩擦損失,對(duì)于螺桿類轉(zhuǎn)向器,其效率可用下式計(jì)算(3.1))tan(0??????式中, 為螺桿的螺線導(dǎo)程角; 為摩擦角, ;f為摩擦因數(shù)。??0 ?? ??=??????????????3.3 轉(zhuǎn)向器逆效率 η-根據(jù)逆效率大小不同,轉(zhuǎn)向器又有可逆式、極限可逆式和不可逆式之分。路面作用在車輪上的力,經(jīng)過轉(zhuǎn)向系可大部分傳遞到轉(zhuǎn)向盤,這種逆效率較高的轉(zhuǎn)向器屬于可逆式。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”,使之精神狀態(tài)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。屬于可逆式的轉(zhuǎn)向器有齒輪齒條式和循環(huán)球式轉(zhuǎn)向器。不可逆式轉(zhuǎn)向器,是指車輪受到的沖擊力不能傳到轉(zhuǎn)向盤的轉(zhuǎn)向器。該沖擊力由轉(zhuǎn)向傳動(dòng)機(jī)構(gòu)的零件承受,因而這些零件容易損壞。同時(shí),它既不能保證車輪自動(dòng)回正,駕駛員又缺乏路面感覺;因此,現(xiàn)代汽車不采用這種轉(zhuǎn)向器。極限可逆式轉(zhuǎn)向器介于上述兩者之間。在車輪受到?jīng)_擊力作用時(shí),此力只有較小一部分傳至轉(zhuǎn)向盤。它的逆效率較低,在不平路面上行駛時(shí),駕駛員并不十分緊張,同時(shí)轉(zhuǎn)向傳動(dòng)機(jī)構(gòu)的零件所承受的沖擊力也比不可逆式轉(zhuǎn)向器要小。如果忽略軸承和其它地方的摩擦損失,只考慮嚙合副的摩擦損失,則逆效率可用下式計(jì)算- 13 -(3.2) 0tan???)( ???式(3.1)和式(3.2)表明:增加導(dǎo)程角 ,正、逆效率均增大。受 η -增大的影??0響 不宜取得過大。當(dāng)導(dǎo)程角小于或等于摩擦角時(shí),逆效率為負(fù)值或者為零,??0此時(shí)表明該轉(zhuǎn)向器是不可逆式轉(zhuǎn)向器。為此,導(dǎo)程角必須大于摩擦角。通常螺線導(dǎo)程角選在8°~10°之間。3.4 傳動(dòng)比的變化特性轉(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 從輪胎接地woi pi面中心作用在兩個(gè)轉(zhuǎn)向輪上的合力2Fw與作用在轉(zhuǎn)向盤上的手力 之比,稱為???力傳動(dòng)比,即 =2Fw/ (3.3)???? ???轉(zhuǎn)向盤轉(zhuǎn)動(dòng)角速度 與同側(cè)轉(zhuǎn)向節(jié)偏轉(zhuǎn)角速度 之比,稱為轉(zhuǎn)向系角傳動(dòng)???? ????比 ,即; 式中, 為轉(zhuǎn)向盤轉(zhuǎn)角增量; 為轉(zhuǎn)向woi kkkwodti ???????? ??????節(jié)轉(zhuǎn)角增量; 為時(shí)間增量。它又由轉(zhuǎn)向器角傳動(dòng)比 和轉(zhuǎn)向傳動(dòng)機(jī)構(gòu)角傳動(dòng)???? ????比 所組成,即 = 。????' ????0????????'轉(zhuǎn)向盤角速度 與搖臂軸轉(zhuǎn)動(dòng)角速度 之比,稱為轉(zhuǎn)向器角傳動(dòng)比 , ???? ???? ????'即 。ppwdti ?????式中, 為搖臂軸轉(zhuǎn)角增量。此定義適用于除齒輪齒條式之外的轉(zhuǎn)向器。??????搖臂軸轉(zhuǎn)動(dòng)角速度 與同側(cè)轉(zhuǎn)向節(jié)偏轉(zhuǎn)角速度 之比,稱為轉(zhuǎn)向傳動(dòng)機(jī)構(gòu)的角???? ????傳動(dòng)比 ,即 。????' kkpkwdti ????’- 14 -3.4.1 力傳動(dòng)比與角傳動(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 之間有如???? ????下關(guān)系(3.4)aMFrW?式中,α為主銷偏移距,指從轉(zhuǎn)向節(jié)主銷軸線的延長(zhǎng)線與支承平面的交點(diǎn)至車輪中心平面與支承平面交線間的距離。作用在轉(zhuǎn)向盤上的手力 可用下式表示???(3.5)SWhDF2?式中, ——作用在轉(zhuǎn)向盤上的力矩;???——為轉(zhuǎn)向盤直徑。??????將式(3.4)、式(3.5)代入式(3.3)得到(3.6)aMDihswrP?分析式(3.6)可知,當(dāng)主銷偏移距a小時(shí),力傳動(dòng)比 應(yīng)取大些才能保證轉(zhuǎn)向????輕便。通常轎車的 a 值在0.4~0.6倍輪胎的胎面寬度尺寸范圍內(nèi)選取,而貨車的d值在40~60mm范圍內(nèi)選取。轉(zhuǎn)向盤直徑 根據(jù)車型不同在JB4505—??????86轉(zhuǎn)向盤尺寸標(biāo)準(zhǔn)中規(guī)定的系列內(nèi)選取。如果忽略摩擦損失,根據(jù)能量守恒原理,2 / 可用下式表示???? ???(3.7)wokhridM???2將式(3.7)代人式(3.6)后得到(3.8)aDiswoP2當(dāng) 和 不變時(shí),力傳動(dòng)比 越大,雖然轉(zhuǎn)向越輕,但 也越大,?? ?????? ???? ??????- 15 -表明轉(zhuǎn)向不靈敏。根據(jù)相互嚙合齒輪的基圓齒距必須相等, 即 = 。其中齒輪基圓齒距????1????2,齒條基圓齒距 。由上述兩式可知:當(dāng)齒輪????1=????1????????1 ????2=????2????????2具有標(biāo)準(zhǔn)模數(shù) 和標(biāo)準(zhǔn)壓力角 與一個(gè)具有變模數(shù) 、變壓力角 的齒條相??1 ??1 ??2 ??2嚙合,并始終保持 時(shí),它們就可以嚙合運(yùn)轉(zhuǎn)。如果齒條中??1????????1=??2????????2部(相當(dāng)汽車直線行駛位置)齒的壓力角最大,向兩端逐漸減小(模數(shù)也隨之減小),則主動(dòng)齒輪嚙合半徑也減小,致使轉(zhuǎn)向盤轉(zhuǎn)動(dòng)某同一角度時(shí),齒條行程也隨之減小。因此,轉(zhuǎn)向器的傳動(dòng)比是變化的。隨轉(zhuǎn)向盤轉(zhuǎn)角變化,轉(zhuǎn)向器角傳動(dòng)比可以設(shè)計(jì)成減小、增大或保持不變的。影響選取角傳動(dòng)比變化規(guī)律的因素,主要是轉(zhuǎn)向軸負(fù)荷大小和對(duì)汽車機(jī)動(dòng)能力的要求。若轉(zhuǎn)向軸負(fù)荷小,在轉(zhuǎn)向盤全轉(zhuǎn)角范圍內(nèi),駕駛員不存在轉(zhuǎn)向沉重問題。裝用動(dòng)力轉(zhuǎn)向的汽車,因轉(zhuǎn)向阻力矩由動(dòng)力裝置克服,所以在上述兩種情況下,均應(yīng)取較小的轉(zhuǎn)向器角傳動(dòng)比并能減少轉(zhuǎn)向盤轉(zhuǎn)動(dòng)的總?cè)?shù),以提高汽車的機(jī)動(dòng)能力。轉(zhuǎn)向盤在中間位置的轉(zhuǎn)向器角傳動(dòng)比不宜過小。過小則在汽車高速直線行駛時(shí),對(duì)轉(zhuǎn)向盤轉(zhuǎn)角過分敏感和使反沖效應(yīng)加大,使駕駛員精確控制轉(zhuǎn)向輪的運(yùn)動(dòng)有困難。直行位置的轉(zhuǎn)向器角傳動(dòng)比不宜低于15~16。- 16 -3.5 參數(shù)選擇1.本系統(tǒng)車型為前置前驅(qū) 2.部分參數(shù)選取國內(nèi)已有車型前/后輪距 K 1540/1540(mm) 軸距 L 2578(mm)輪胎型號(hào) 205/55 R16整備質(zhì)量 1405(kg)允許總質(zhì)量 M 800(kg)前/后軸載荷 1000/1000(kg)方形盤直徑 400(mm)??????齒條有效行程 150(mm)??1最小轉(zhuǎn)彎半徑 R 6000(mm)齒輪齒條轉(zhuǎn)向器正效率 90 %表 3.1項(xiàng)目 轉(zhuǎn)向小齒輪 轉(zhuǎn)向齒條模數(shù) ???? 2.5 2.5齒數(shù) /??1??2 6 28法相壓力角 ?? 20 20螺旋角/齒傾角 ??1/??2 140 80變位系數(shù) Xn 0 0齒頂高系數(shù) h﹡???? 1 1 頂隙系數(shù) c﹡ ?? 0.25 0.253.5.1 轉(zhuǎn)向輪側(cè)偏角計(jì)算說明:此四輪轉(zhuǎn)向技術(shù)為主動(dòng)轉(zhuǎn)向技術(shù),后輪微小轉(zhuǎn)角( )考慮當(dāng)后輪執(zhí)±3°行器失靈時(shí),汽車按二輪轉(zhuǎn)向技術(shù)行駛,所以轉(zhuǎn)向輪側(cè)偏角按二輪轉(zhuǎn)向汽車方法計(jì)算如圖(3-1)- 17 -。Sin 0.43 ??=????=25786000=(3.9) 25.470??=tan 0.665 ??=????????????????= 25786000×??????25.47?1540=(3.10) 33.620 ??=3.6 轉(zhuǎn)向系載荷確定為了保證行駛安全,組成轉(zhuǎn)向系的各零件應(yīng)有足夠的強(qiáng)度。欲驗(yàn)算轉(zhuǎn)向系零- 18 -件強(qiáng)度,需首先確定作用在各零件上的力。線角傳動(dòng)比 i i= 47.58 π????????1??????β2 =3.14×2.5×6??????8° =(3.11)方向盤轉(zhuǎn)動(dòng)圈數(shù) n n= 3.15 (3.12)??1?? =15047.58=角傳動(dòng)比 = 19.19 ???? ????????????=??×360??+?? = 3.15×36025.47+33.62=(3.13)原地轉(zhuǎn)向阻力距 的計(jì)算: ????455557.72N.mm ????=f3G3P=0.73 (9.8×900)30.18 =(3.14)f ——輪胎和路面間的滑動(dòng)摩擦因數(shù)G ——轉(zhuǎn)向前輪負(fù)荷。單位為 NP ——輪胎氣壓,單位為 MPa作用在轉(zhuǎn)向盤上的手力 ???= 131.89N ???2?MR?????????????=2×455557.719400×19.19×90%=(3.15)——原地轉(zhuǎn)向阻力矩MR——轉(zhuǎn)向盤直徑??????- 19 -——轉(zhuǎn)向器角傳動(dòng)比????——轉(zhuǎn)向器正效率??主銷偏移距 a a﹦0.5×205﹦102.5mm作用在轉(zhuǎn)向盤上的力矩 ???﹦ 26378N.mm?????????????2 =131.89×4002 =力轉(zhuǎn)動(dòng)比 =6.9???? ????=??????????????? =455557.72×40026378×100輪輞直徑 16in﹦16×25.4﹦406.4mm?????? ??????=梯形臂長(zhǎng)度 ×(0.8/2)??2 ??2= ??????﹦162.56mm 取 162mm輪胎直徑 55%×2×205???? ????=??????+﹦631.9mm 取 632mm 齒寬系數(shù) =1.2 15.46mm???? ??1=??????1????????=2.5×6??????14°=齒條寬度 . 1.2×15.46﹦18.55mm??2 ??2=???? ??1=圓整取 ﹦20mm 則取齒輪齒寬 +10=20+10=30mm??2 ??1=??23.7 轉(zhuǎn)向器的主要元件設(shè)計(jì)3.7.1 選擇齒輪齒條材料小齒輪:齒輪通常選用國內(nèi)常用、性能優(yōu)良的 20CrMnTi 合金鋼,熱處理采- 20 -用表面滲碳淬火工藝,齒面硬度為 HRc58 63/。齒輪是一只切有齒形的軸。它~安裝在轉(zhuǎn)向器殼體上并使其齒與齒條上的齒相嚙合。齒輪齒條上的齒選用斜齒。斜齒的彎曲增加了一對(duì)嚙合齒輪參與嚙合的齒數(shù)。相對(duì)直齒而言,斜齒的運(yùn)轉(zhuǎn)趨于平穩(wěn),并能傳遞更大的動(dòng)力齒輪軸上端與轉(zhuǎn)向柱內(nèi)的轉(zhuǎn)向軸相連。因此,轉(zhuǎn)向盤的旋轉(zhuǎn)使齒條橫向移動(dòng)以操縱前輪。齒輪軸由安裝在轉(zhuǎn)向器殼體上的球軸承支承。表(3-2)齒輪軸的設(shè)計(jì)參數(shù)項(xiàng)目 符號(hào) 尺寸參數(shù)(mm)總長(zhǎng) ??1 165齒寬 ??1 30齒數(shù) ??1 6法向模數(shù) Mn 2.5螺旋角 ??1 140旋向 左旋齒條:選用與 20CrMnTi 具有較好匹配性的 40Cr 作為嚙合副,齒條熱處理采用高頻淬火工藝,表面硬度 HRc50 56。齒條是在金屬殼體內(nèi)來回滑動(dòng)的,加工有~齒形的金屬條。轉(zhuǎn)向器殼體是安裝在前橫梁或前圍板的固定位置上的。齒條代替梯形轉(zhuǎn)向桿系的搖桿和轉(zhuǎn)向搖臂,并保證轉(zhuǎn)向橫拉桿在適當(dāng)?shù)母叨纫允顾麄兣c懸架下擺臂平行。齒條可以比作是梯形轉(zhuǎn)向桿系的轉(zhuǎn)向直拉桿。導(dǎo)向座將齒條支撐在轉(zhuǎn)向器殼體上。齒條的橫向運(yùn)動(dòng)拉動(dòng)或推動(dòng)轉(zhuǎn)向橫拉桿,使前輪轉(zhuǎn)向 (圖 3.4.1)- 21 -(圖 3.1)表(3-3)齒條尺寸設(shè)計(jì)參數(shù)項(xiàng)目 符號(hào) 尺寸參數(shù)(mm)總長(zhǎng) ??2 763直徑 ? 30齒數(shù) ??2 283.7.2 齒輪齒條基本參數(shù)齒輪:分度圓直徑 15.46mm ??1=??????1????????=2.5×6??????14°=齒頂高 ???=????(??????+????)﹦1.2×15.46﹦18.55mm 齒頂圓直徑 ????1=??+2???- 22 -﹦15.46+2×2.5﹦20.46mm齒根高 ???=????(???????????+?????)﹦2.5×(1-0+0.25)﹦3.125mm齒根圓直徑 ????=??1?2???=15.46?2×????(???????????+?????)=15.46-2×2.5(1-0+0.25)﹦9.21mm齒條:齒頂高 ???=????(??????+????)﹦2.5×(1=0)﹦2.5mm 齒根高 ???=????(???????????+?????)﹦ 2.5×(1-0+0.25)﹦3.125mm——齒頂高系數(shù)取 1??????——頂隙系數(shù)取 0.25?????3.7.3 轉(zhuǎn)向橫拉桿及其端部 轉(zhuǎn)向橫拉桿與梯形轉(zhuǎn)向桿系的相似。球頭銷通過螺紋與齒條連接。當(dāng)這些球頭銷按制造廠的規(guī)范擰緊時(shí),在球頭銷上產(chǎn)生了一個(gè)預(yù)載荷。防塵套夾在轉(zhuǎn)向器兩側(cè)的殼體和轉(zhuǎn)向橫拉桿上,防塵套阻止雜物進(jìn)入球銷及齒條中。轉(zhuǎn)向橫拉桿端部與外端用螺紋聯(lián)接。這些端部與梯形轉(zhuǎn)向桿系的相似。側(cè)面螺母將橫拉桿外端與橫拉桿鎖緊如圖(3-2) 。- 23 -1—橫拉桿 2—鎖緊螺母 3—外接頭殼體 4—球頭銷 5—六角開槽螺母 6—球碗 7—端蓋 8—梯形臂 9—開口槽圖(3-2)表(3-4)橫拉桿尺寸項(xiàng)目 符號(hào) 尺寸參數(shù)(mm)橫拉桿總長(zhǎng) ???? 376螺紋長(zhǎng)度 ???? 62外接球頭總長(zhǎng) ?????? 68外接頭螺紋公稱直徑 ???? M12 ×1.5橫拉桿直徑 ????? 183.7.4 齒條調(diào)整一個(gè)齒條導(dǎo)向座安裝在齒條光滑的一面。齒條導(dǎo)向座和與殼體螺紋連接的調(diào)節(jié)螺塞之間連有一個(gè)彈簧。調(diào)節(jié)螺塞由鎖緊螺母固定。齒條導(dǎo)向座的調(diào)節(jié)使齒輪、齒條間有一定預(yù)緊力,預(yù)緊力會(huì)影響轉(zhuǎn)向沖擊、噪聲及反饋。表(3-5)導(dǎo)向座項(xiàng)目 符號(hào) 尺寸參數(shù)(mm)導(dǎo)向座外徑 ??3 38導(dǎo)向座高度 ??1 40- 24 -彈簧總高度 ???? 19彈簧外徑 ???? 26螺塞螺紋公稱直徑 ??4 8螺塞高度 ???? 28轉(zhuǎn)向傳動(dòng)比:當(dāng)轉(zhuǎn)向盤從鎖點(diǎn)向鎖點(diǎn)轉(zhuǎn)動(dòng),每只前輪大約從其正前方開始轉(zhuǎn)動(dòng)30°,因而前輪從左到右總共轉(zhuǎn)動(dòng)大約 60°。若傳動(dòng)比是 1:1,轉(zhuǎn)向盤旋轉(zhuǎn) 1°,前輪將轉(zhuǎn)向 1°,轉(zhuǎn)向盤向任一方向轉(zhuǎn)動(dòng) 30°將使前輪從鎖點(diǎn)轉(zhuǎn)向鎖點(diǎn)。這種傳動(dòng)比過于小,因?yàn)檗D(zhuǎn)向盤最輕微的運(yùn)動(dòng)將會(huì)使車輛突然改變方向。轉(zhuǎn)向角傳動(dòng)比必須使前輪轉(zhuǎn)動(dòng)同樣角度時(shí)需要更大的轉(zhuǎn)向盤轉(zhuǎn)角。19.19:1 的傳動(dòng)比較為合理。在這樣的傳動(dòng)比下,轉(zhuǎn)向盤每轉(zhuǎn)動(dòng) 19.19°,前輪轉(zhuǎn)向 1°。為了計(jì)算傳動(dòng)比,可將鎖點(diǎn)到鎖點(diǎn)過程中轉(zhuǎn)向盤轉(zhuǎn)角的度數(shù)除以此時(shí)轉(zhuǎn)向輪轉(zhuǎn)角的度數(shù)。3.8 齒輪齒條轉(zhuǎn)向器轉(zhuǎn)向橫拉桿的運(yùn)動(dòng)分析- 25 -圖(3-3)當(dāng)轉(zhuǎn)向盤從鎖點(diǎn)向鎖點(diǎn)轉(zhuǎn)動(dòng),每只前輪大約從其正前方開始轉(zhuǎn)動(dòng) ,因而前30°輪從左到右總共轉(zhuǎn)動(dòng)約 60°。當(dāng)轉(zhuǎn)向輪右轉(zhuǎn) 30°,即梯形臂或轉(zhuǎn)向節(jié)由 OC 繞圓心 O 轉(zhuǎn)至?xí)r OA,齒條左端點(diǎn) E 移至 EA 的距離為 ??1OD = OACOS 16230°= ×??????25°=146.8????DC = OC ?????=162?146.8=15.2????齒輪齒條嚙合長(zhǎng)度應(yīng)大于 ??1+??2=??????????25°+??????????33°=163.8????A A ??'=???? ????=????=??????=200??????'??=??????'??= ????2???????'2= 2002?15.22=199.4????C A????= ???????'??=200?95.3=104.7??????1=?????C????=200?104.7=95.3????同理計(jì)算轉(zhuǎn)向輪左轉(zhuǎn) 35°,轉(zhuǎn)向節(jié)由 OC 繞圓心 O 轉(zhuǎn)至 OB 時(shí),齒條左端點(diǎn) E 移至 的距離為?????? ??2DB=DA=68.46mm DC=B??'B’????= ????2???????'2= 2002?15.22=199.4??????2=??????=????'+??'?????????=95.34+199.4?200=94.74????即 L =95.3+94.74=190.04 取 L=200mm??1+??2 m- 26 -3.9 齒輪齒條傳動(dòng)受力分析軸的受力分析:若略去齒面間的摩擦力,則作用于節(jié)點(diǎn) P 的法向力 可分解為????徑向力 和分力 F,分力 F 又可分解為圓周力 和軸向力 。???? ???? ????????=2??1??1=2×3916821.64=3619.96??????=??????????????????????=3619.98??????20°/??????14°=1357.90??????=????????????=3619.98??????14°=937.84計(jì)算支承反力在垂直面上????????=??2????1+????1??2??1+??2 =39×1357.9+902.56×10.8278=804.15??????????=????1?????????=1357.9?804.15=553.75??在水平面上????????=????????=????12=3619.982 =1809.98??畫彎矩圖在水平面上,a-a 剖面左側(cè)、右側(cè)??????=??'????=???????????1=1809.98×39=70589.22????