《汽车理论》课程教学课件（英文讲稿）第4章 汽车制动性 Braking Performance 4.4 Braking Steering Stability（制动时的方向稳定性）

4-4 Braking Steering Stability>off-tracking（制动跑偏）：制动时汽车自动向左或向右偏向行驶。·Automobile direction turns to left or rightduring braking8B制动跑偏时轮胎在地面上留下的印迹

4-4 Braking Steering Stability off-tracking(制动跑偏) ：制动时汽车自动向 左或向右偏向行驶。 •Automobile direction turns to left or right during braking

>sideslip（侧滑）：指制动时汽车的某一轴或两轴发生横向移动Oneaxleortwoaxlesmovehorizontalduring braking.制动跑偏引起后轴轻微侧滑时轮胎留在地面上的印迹

sideslip(侧滑)：指制动时汽车的某一轴或两轴 发生横向移动。 •One axle or two axles move horizontal during braking

>losingthesteeringability（失去转向能力）：指弯道制动时，汽车不再按原来弯道行驶而沿弯道切线方向驶出以及直线行驶制动时转动方向盘汽车仍按直线方向行驶的现象。.Braking in a turn,the caris no longerrunningalongthe original curvedirection and turn the steering wheelwhen driving straight with braking carremaining on the direction of straight

 losing the steering ability (失去转向能力)： 指弯道制动时，汽车不再按原来弯道行驶而 沿弯道切线方向驶出以及直线行驶制动时转 动方向盘汽车仍按直线方向行驶的现象。 • Braking in a turn, the car is no longer running along the original curve direction and turn the steering wheel when driving straight with braking car remaining on the direction of straight

1.Off-tracking（制动跑偏）HHLulubAF×100%lurTwo reasons:FLub(1)Fxbi-left is not equal to Fxbl-right :汽车左、右轮，特别是前轴左、右车轮制动器制动力不相等。X2Rule :AFrm ≤20%AF≤24%ur2Fx21Fxil

1. Off-tracking(制动跑偏) Two reasons: (1)FXb1-left is not equal to FXb1-right . 汽车左、右轮，特别是前轴左、右车轮制动器制动力 不相等。 1 2 : 20% 24% r r Rule F F       FY1 FY2 100% b l r b F F F F        

There are three reasons which lead to braking force isnot equal between left and right.引起左右轮制动力不等的原因有三：)Technical condition of brakes制动器的技术状况2) Fzi-left is not equal to Fzl-right :左右轮荷重不等，出现制动力差。3Roadcondition

There are three reasons which lead to braking force is not equal between left and right. 引起左右轮制动力不等的原因有三： 1) Technical condition of brakes. 制动器的技术状况 2) FZ1-left is not equal to Fz1-right . 左右轮荷重不等，出现制动力差。 3)Road condition

(2)Suspensionguide arms are interfered with draglinks ofsteering system during braking制动时悬架导向杆系与转向系拉杆在运动学上的不协调。转向纵拉杆制动鼓转向节衬套轮毂主销轴承止推轴承前梁梯形臂转向横拉杆轮毂

(2)Suspension guide arms are interfered with drag links of steering system during braking 制动时悬架导向杆系与转向系拉杆在运动学上的不协调

（失去转向能力）2.Losing the steering abilityIn the case offront brakelocking firstlyFxb!FxblFy ~ 0AF: (centrifugalforce)CFxblFxhzUBFy2B0

FXb1 FXb1 uA A B FY2 0 FY1  uB O C Fj (centrifugal force) FXb2 FXb2  2. Losing the steering ability (失去转向能力) In the case of front brake locking firstly:

2.Losingthesteeringability（失去转向能力）The ability of vehicle to maintain its initial driving directionwhenusingbrake.It is related to the lock seguence of front and rear brakesInthe case of front brake locking firstly:Because of the relationship between Prs ,front wheels lost theabilitytobalance the sideforce dramatically at 10o%s.Side force→ one component of the speed ua→instantspeedcentercentrifugalforce→negativefeedback tothe sideforce→stable situation→losing the steering ability

 The ability of vehicle to maintain its initial driving direction when using brake. • It is related to the lock sequence of front and rear brakes. In the case of front brake locking firstly:  Because of the relationship between φl -s ,front wheels lost the ability to balance the side force dramatically at 100% s . Side force→ one component of the speed uA →instant speed center →centrifugal force →negative feedback to the side force →stable situation →losing the steering ability 2. Losing the steering ability (失去转向能力)

3.Sideslip（侧滑）In the case of rear brake locking firstlyFMXb1FyOAHFxbkXb2uBF~0B

o Fj A C B uA uB FY1 FY2≈0 FXb1 FXb1 FXb2 FXb2  3. Sideslip(侧滑) In the case of rear brake locking firstly:

3.Sideslip（侧滑）Inthecase of rearbrakelockingfirstly:Becauseofthe relationship between P-s,rear wheelslostthe ability tobalance the sideforce dramaticallyat100%s.Side force→ one component of the speed uBinstantspeed center→centrifugalforcepositivefeedback to the side force→unstable situation→swervingeffect（甩尾）In the case of front and rearlocking togetherIt is anidea and stable situation for traditional brakes

In the case of rear brake locking firstly:  Because of the relationship between φl -s ,rear wheels lost the ability to balance the side force dramatically at 100% s . Side force→ one component of the speed uB →instant speed center →centrifugal force →positive feedback to the side force →unstable situation →swerving effect （甩尾）  In the case of front and rear locking together It is an idea and stable situation for traditional brakes. 3. Sideslip(侧滑)