汽車四輪轉(zhuǎn)向傳動系統(tǒng)設(shè)計
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The 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.
In 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:
1.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.
Primary 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.
6. 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 positioned 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
The 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.
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翻譯馬自達公司的速度感應(yīng)四輪轉(zhuǎn)向系統(tǒng)
三十五年前，兩個馬自達設(shè)計師提出了一個遠見的、有計算認為是相當革命性的結(jié)論。他們在1962年10月26日日本汽車工程師學會技術(shù)會議上 Tadashi Okada博士和Toshiaki工程師總結(jié)了他們關(guān)于車輛動力學的辛勤研究如下：
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。
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)定的一大進步,可預(yù)期的方式自動引導(dǎo)系統(tǒng)后車輪.
這種結(jié)論和提法被這兩個工程師提出并為良好懸架技術(shù)的研制成立了基金會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323K(1980)、馬自達626(1982),然后在更新完善馬自達626. 獲獎的動態(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929(1987).
而與此同時各種外部壓力和負荷作用與汽車后方的車輪，因為它違背牛頓的運動學原理，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)定車輛和機敏.
馬自達的設(shè)計師和工程師們的最終目標仍是積極的方法產(chǎn)生積極的控制措施; 四輪轉(zhuǎn)向體系。
1983年馬自達將舉世震驚的概念引入工程車MX－02中，并在東京會展上亮相。這輛四門私家轎車在不尋常的長軸距上布置了寬敞的乘客空間，它匯聚許多先進的特點具有高速穩(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，而這些是由中央計算機單元控制的。
MX-02之后另一個令人振奮的概念車;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)動和強勁的三旋輪發(fā)動機。
馬自達電子控制四輪轉(zhuǎn)向系統(tǒng):
有利的技術(shù)
馬自達的電子控制、汽車速度感應(yīng)四輪轉(zhuǎn)向系統(tǒng)(4ws)驅(qū)動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)是機械和液壓系統(tǒng)驅(qū)動，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4WS裝備車來自五個戰(zhàn)略利益的驅(qū)動，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)時間和精度控制。
3.高速直線穩(wěn)定性。
4.急速換道的機動性大大改觀。
5.更小的轉(zhuǎn)彎半徑和低速范圍狹小空間的可操縱性。
馬自達最顯著的優(yōu)勢在于4WS系統(tǒng)能顯著降低高速疲勞駕駛和長期駕駛，這是最優(yōu)化后取得的。
1.降低對駕駛輸入和動作的反應(yīng)延遲。
2.消除汽車對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工程師通過提供這個最佳解決現(xiàn)象的方法，- 以這種方法他們提倡 -4WS系統(tǒng)已經(jīng)作為一項完全有利的技術(shù)出現(xiàn)。
戰(zhàn)略性建設(shè)
馬自達4WS系統(tǒng)由兩個串聯(lián)泵來提供主要的動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)向系的總的傳動比為14.2：1。后面的車輪的轉(zhuǎn)向依然是靠主泵提供動力的液壓輔助驅(qū)動和根據(jù)前輪轉(zhuǎn)角和汽車行駛速度來實現(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），一個動力氣缸和一個輸入軸。為了以防液壓故障轉(zhuǎn)向系統(tǒng)上面裝了一個中央鎖彈簧，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。當汽車在急轉(zhuǎn)彎時如果速度小于（）將使汽車的后輪與前輪的狀態(tài)相反且在()使它們失效（直到筆直向前，按照傳統(tǒng)的兩輪轉(zhuǎn)向原理）。當速度高于（）時系統(tǒng)將于前輪保持同相轉(zhuǎn)動，因此增加了轉(zhuǎn)彎時的穩(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。馬自達已經(jīng)確定了使人感覺到自然和保持人類靈敏性的測量方法。
主要組成部分
1. 車輛速度傳感器解析速度計架子的旋轉(zhuǎn)并把這種信號傳遞到打字計算機單元。有兩個傳感器，一個在速度計內(nèi)部另一個在傳輸?shù)妮敵龆?，用這樣兩個傳感器是為了使它們兩個相互求證和失效保險。
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動將方向和行程傳遞給轉(zhuǎn)向后輪
3. 步進電機執(zhí)行軛角度的改變和錐形齒輪定相。
4. 后輪驅(qū)動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. 液壓動力氣缸以液壓驅(qū)動輸出軸和后輪轉(zhuǎn)向，它用一個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一正常的２ＷＳ車輛起作用時該鎖將被開啟。
液壓泵，給前面兩個提供液壓和后驅(qū)動輪。
轉(zhuǎn)向狀態(tài)控制的細節(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)向系傳動比的步進電機，一個控制軛， 一只擺動臂，一個通過小錐齒輪連接在后輪轉(zhuǎn)向軸上的錐齒輪，和一個操縱桿連接控制閥。 它操作：
a. 轉(zhuǎn)向狀態(tài)（方向）少于（）的轉(zhuǎn)向。
1. 控制軛在步進電機作用下有一個角度。
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動。
4. 控制閥的輸入桿被推到右邊， 根據(jù)操縱桿的運動的度(通過擺動臂的安排確定)，被確定位置進入一個向上方向，朝右邊。 后車輪在左側(cè)被如此使得轉(zhuǎn)向后輪對轉(zhuǎn)向前輪有個相反的轉(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)向系傳動比也要成比例增加而轉(zhuǎn)向鎖收緊。
b.這個階段的操縱與第一個階段的操作相反，這是因為在一定的速度范圍控制軛的轉(zhuǎn)動角度趨向明顯，如同說明的那樣。擺動臂，軛桿和錐形齒輪與前轉(zhuǎn)向輪保持相同的狀態(tài)。
c.中間狀態(tài)，以（）控制軛的角度是水平的（中間位置）。因此，這根輸入桿沒有被影響，即使這個操縱桿為錐形齒輪單元所帶動。因此后轉(zhuǎn)向輪沒有被這種方式所驅(qū)動。
動力氣缸
控制閥單元的輸入軸的運動被傳遞給氣缸線軸。由于線軸相對與套管的位移使得液壓動力氣缸的左右壁室的形成一個壓力差。壓力差克服輸出軸的負荷并使軸套運動。軸套動力軸總成被以相同的比例傳遞到輸入。輸出軸將轉(zhuǎn)向運動傳遞到后輪的任一轉(zhuǎn)向控制單元。由此驅(qū)動后轉(zhuǎn)向輪。
故障安全保障
系統(tǒng)能自動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)上是使整個轉(zhuǎn)向系統(tǒng)符合一個傳統(tǒng)的2WS準則。尤其是一個液壓的缺陷使得壓力水平的降低（一個錯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，并氣動一盞低級的警告燈，如果是一個電子元件的錯誤，那么這個錯誤將被集成在4WS控制單元里面的自診斷回路所探測到，這將促使一個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準則。 從今以后，4WS系統(tǒng)在主要儀器內(nèi)展示的警告燈開動，就表明一個系統(tǒng)故障。
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