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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 and 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 Mazdas 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 Mazdas 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. 1. Superior cornering stability 2. Improved steering responsiveness and precision 3. High-speed straightline stability 4. Notable improvement in rapid lane-changing manoeuvres 5. 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 vehicles 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 the direction 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 rods 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 vehicles 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 yokes 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 cylinders spool. The spools 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. 车辆与动力工程学院毕业设计说明书4座微型客货两用车设计（前悬架、转向系设计）摘 要在这次毕业设计中，我主要负责转向系统及前悬架系统的设计。经过收集各类型的悬架的资料，实车观测，老师的指导。在研究了各类型的独立，非独立悬架系统之后，总结了其各自特点，认识到了各自优劣，分析对比之后，最终确定本车悬架系统：麦弗逊前独立悬架。在前悬的设计中主要围绕麦弗逊独立悬架展开。前期的工作主要是收集相关资料，信息，在此过程中，其结构是研究的重点。计算主要集中在了弹性元件普通圆形螺旋弹簧的各个重要参数。如，弹簧刚度，中径，弹簧钢丝直径等等。随后对这些数据进行了必要的校核。最后对减振器和横向稳定器的结构以及它们在整个悬架系统中的作用进行了一些探讨。转向系统设计内容主要包括转向系统形式的选择、转向器的选择、转向梯形的选择及其布置。我们所设计的车型是小排量车，鉴于我国路面质量的逐步提高和作用于方向盘的作用力(144.865N-177.06N)不是很大，故在设计中考虑采用机械式转向系统。由于齿轮齿条式转向器与其他的转向器相比，虽然其逆效率很高，但其具有结构简单、紧凑、壳体采用铝合金或者镁合金压铸而成，转向器质量比较小、传动效率高达90以上，因此本设计选用齿轮齿条式转向器。由于我们设计的车前悬比较短，发动机占有的空间相对来说很大，且由于转向系统转向梯形最小传动角和转向器的安装距离有很大的关系，综合以上因素我采用后置式转向梯形。关键词：独立悬架，麦弗逊式，机械式转向系，齿轮齿条式转向器。THE DESIGN OF THE FRONT SUSPENSION AND STEERING SYSTEM OF THE MINIATURE MOTORCAR TO CARRY PERSONS AND GOODS WITH 4 SEATS ABSTRACTIn this graduation design, I am responsible for automobiles steering system and the front suspension system design of the miniature motorcar to carry persons and goods with 4 seats mainly.In weeks ,I work hard to get the more useful information to do my work better. With the helping of Mr Li and other teachers ,and observation on vehicle in laboratory .I got a conclusion : the front independent McPherson suspension is the best form for this automotive . All focus on elastic part .Because elastic is the most important part in them .And I have got some important data for my design work . If I cant get those data ,I could not do my work in the following days .I get many data ,but for front independent McPherson suspension the main thing is about spring , such as spring rate ,middle diameter ,spring wire diameter and so on .spring rate is the most important data for my independent suspension ,it do many influence about suspension. In the last I discussion shock absorber and anti-roll-bar a little,and involve the basic of them and the important usefully in modern cars suspension.Because the motortcar we design is a kind of small output volume, seeing that the gradual improvement of the road surface quality of our country and effort of acting on the steering wheel are not very large, so I choose the manual steering system. Compared with others steering gear, though the negative efficiency of the rack and pinion steering gear is high, but it have of simple structure, compactness, shell adopt aluminum alloy or magnesium alloy die casting, the weight of the rack and pinion steering system is much smaller than others, transmission efficiency is up to more than 90%, so in this design I choose the rack and pinion steering system.Because the front overhang of the car is very short and the engine occupied comparatively very big space, what is more, the minimum transmission angle of the Ackerman steering has a very close relation with installation distance of the steering gear, so I choose fit the Ackerman steering in the back of the car conceding all those factor above.KEY WORDS : independent suspension,MacPherson，the manual steering system, the rack and pinion steering gear目 录第一章 前言1第二章 汽车转向系设计32.1 概述32.2 转向系的设计要求7 第三章 转向器、转向传动操纵机构、转向传动机构93.1 转向器93.2 转向操纵机构93.3 转向传动机构和布置10第四章 转向系有关的计算及校核114.1 转向系主要性能参数114.2 转向器有关参数的设计计算及校核144.3 转向传动机构的设计计算与强度校核15第五章 悬架结构方案分析195.1 悬架的功用195.2 悬架系统的组成195.3 悬架的类型及其特点21第六章 前悬架的设计计算256.1 弹簧形式的选择256.2 弹簧参数的计算256.3 弹簧的校验27第七章 减震器的结构原理及其功用287.1 减震器的作用287.2 减震器的结构297.3 减震器的工作原理297.4 减振器主要尺寸的确定29第八章 横向稳定器的作用32第九章 结论34 参考文献35致谢 36 V外文资料译文翻译马自达公司的速度感应四轮转向系统三十五年前，两个马自达设计师提出了一个远见的、有计算认为是相当革命性的结论。他们在1962年10月26日日本汽车工程师学会技术会议上 Tadashi Okada博士和Toshiaki工程师总结了他们关于车辆动力学的辛勤研究如下：1.基本特性差别在于过度转向与不足转向的量和时间上的延迟和响应。2.汽车在高速状态下应具备不足转向特点。3.后方的稳定很大程度上反映出车轮和轮胎。4.控制与稳定的一大进步,可预期的方式自动引导系统后车轮. 这种结论和提法被这两个工程师提出并为良好悬架技术的研制成立了基金会多年来致力于研究和开发,原有的理论有一定的作用,一些最重要的成就在近代历史上汽车底盘工程,将在马自达的系列产品的生产. 这些发展包括双斜后方的联系中断,首先采用原第一轮驱动323K(1980)、马自达626(1982),然后在更新完善马自达626. 获奖的动态跟踪系统中断的第二代发票RC7(1985); 并制定电子后方联系中断新马自达929(1987). 而与此同时各种外部压力和负荷作用与汽车后方的车轮，因为它违背牛顿的运动学原理，这些新系统中断将这些力量纳入4ws效应,积极帮助稳定车辆和机敏. 马自达的设计师和工程师们的最终目标仍是积极的方法产生积极的控制措施; 四轮转向体系。1983年马自达将举世震惊的概念引入工程车MX02中，并在东京会展上亮相。这辆四门私家轿车在不寻常的长轴距上布置了宽敞的乘客空间，它汇聚许多先进的特点具有高速稳定和低速操控性能的真正意义的4WS系统。后方车轮的量取决于前方双轮的角度和汽车的速度，而这些是由中央计算机单元控制的。MX-02之后另一个令人振奋的概念车;MX-03于1985年9月第一次在法兰克福展出。这辆豪华的四座双门未来派轿车装配了90年代精确电子控制的4WS系统和不同扭矩均分系统，四轮驱动和强劲的三旋轮发动机。马自达电子控制四轮转向系统: 有利的技术马自达的电子控制、汽车速度感应四轮转向系统(4ws)驱动双后轮在一定方向和量上是最适合汽车的速度范围的。这种系统是机械和液压系统驱动，伴随着生产稳定提高,并在某些参数上反应敏捷。马自达4WS装备车来自五个战略利益的驱动，超过了传统的底盘。1.优秀的转弯稳定性。2.改良的驾驶响应时间和精度控制。3.高速直线稳定性。4.急速换道的机动性大大改观。5.更小的转弯半径和低速范围狭小空间的可操纵性。马自达最显著的优势在于4WS系统能显著降低高速疲劳驾驶和长期驾驶，这是最优化后取得的。1.降低对驾驶输入和动作的反应延迟。2.消除汽车对驾驶输入的过度响应。从根本上说，在60 年代初两位年轻的马自达工程师通过提供这个最佳解决现象的方法，- 以这种方法他们提倡 -4WS系统已经作为一项完全有利的技术出现。 战