1、独立悬架概论 轿车底盘的发展应该比发动机发展得快。加速性能不断改善，最高车速和转弯车速愈来愈高以及行驶减速度愈来愈大，要求有更加安全的底盘，独立悬架正是适合于此要求。它的主要优点是： a 需用空间小； b 前束的运动学变化及弹性运动学变化产生不足转向趋势； c 易于实现驱动轮的转向； d 质量小； e 左右车轮互不影响。 后两个特点对于获取良好的地面附着性 特别是在起伏的路面作曲线行驶时 尤为重要。 Independent wheel suspensions-general The chassis of a passenger car must be able to handle the en
2、gine power installed. Ever-improving acceleration, higher peak and cornering speeds, and deceleration lead to significantly increased requirements for safer chassis. Independent wheel suspensions follow this trend. Their main advantages are: a. little space requirement b. a kinematic and/or elastoki
3、nematic toe-in change, tending towards under steering is possible(see Section 3.6) c. easier steerability with existing drive； d. low weight； e. no mutual wheel influence. The last two characteristics are important for good road-holding, especially on bends with an uneven road surface. 麦弗逊式悬架是双横臂式悬架
4、的发展，汽车翼子板上的铰链点代替了上横臂，减振器的活塞杆头和螺旋弹簧支承在这里。该铰点承受所有方向的力。这些力在活塞杆中引起弯曲变形。为了避免它引起的不利的外倾角变化和主销后倾变化，减振器活塞杆直径必须从 11mm 至少增大到 20mm。如果不改变活塞杆直径，则通常采用双筒式减振器。 麦弗逊式悬架的主要优点在于所有承担弹性元件功能和车轮导向功能的零件可组合在一个结构单元里。这些零件是： a 支承螺旋弹簧下端的托盘； b 辅助弹簧 11 或压缩行程限位块； c 拉伸行程限位块； d 与拉杆 5 连接的摆轴式横向稳定杆； e 车轮转向节。 这些零件可通过熔焊或硬钎焊，或者是用螺栓固接在外套管上。麦
5、弗逊式悬架的其他优点是： a 由于具有较大的有效距离 c，作用在车身连接点 E 和 D 处的力较小； b 点 G 和 N 之间只有很小的距离 b； c 弹簧行程大； d 省去了三处支承； e 易于构造前部车底板形状。 McPherson struts and strut dampers The McPherson strut is a further development of double wishbone suspension. The upper transverse link is replaced by a pivot point on the wheel house panel,
6、 which takes the end of the coil spring. Forces from all directions are concentrated at this point and these cause bending stress in the piston rod. To avoid detrimental elastic camber and caster changes, the normal rod diameter of 11 mm (in the shock absorber) must be increased to at least 18 mm. W
7、ith a piston diameter of usually 30 mm or 32 mm the damper works on the twin-tube system and can be non-pressurized or pressurized (see Section 5.8). The main advantage of the McPherson strut is that all the parts providing the suspension and wheel control can be combined into one assembly. As can b
8、e seen in Fig. 1.8, this includes: a. the spring seat 3 to take the underside pf the coil spring； b. the auxiliary spring 11 or a bump stop (see Fig.5.49)； c. the rebound-travel stop (Fig.5.54)； d. the underslung anti-roll bar(7) via rod 5； e. the steering knuckle. The steering knuckle can be welded
9、, brazed or bolted (Fig.5.53) firmly to the outer tube (Fig.1.56). Further advantages are: a. lower forces in the body-side mounting points E and D due to a large effective distance c(Fig.1.5)； b. short distance b between points G and N (Fig.3.30)； c. long spring travel； d. three beating positions n
10、o longer needed； e. better design options on the front crumple zone； 近 10 年来，麦弗逊式悬架大都是用于前桥。但它也经常在前轮驱动车辆中用作后悬架。由于空气动力学缘故，汽车后尾上翘，这就允许活塞导向杆和活塞杆之间的导向长度较大。在图 1.7 所示的后悬架上： a 省去了滚动轴承； b 可采用较长的横臂，它几乎可伸到汽车中心线位置，从这样做的缺点是会使主销偏移距 sr 变大并为正值而使得外倾角变化和轮距变化合理，并使得加载时汽车的侧倾中心有微小的下降 c 横臂外端点可深入车轮内，从而获得较小的距离 b； d 行李箱深度可增大
11、，并在采用减振器柱式还可加宽； e 然而 ，必须通过橡胶的硬度和恰当的横臂在转向节上固定点之间的距离来保证不产生不希望的弹性自转向现象。 McPherson struts have become widely used as front axles, but they are also fitted as the rear suspension on front -wheel drive vehicles (e.g. Ford Mondeo sedan). The vehicle tail, which has been raised for aerodynamic reasons, allows a larger bearing span between the piston rod guide and piston. On the rear axle(Fig.1.12).
