Chassis Systems
Design
AUTE 4070U
Lecture 5
Yuping He
Ontario Tech University
September 19, 2023
Chapter 3: Brake System Design
1. Introduction
1) Design Requirements
2) Geometric Configurations of Brake
3) Performance Determination and Parameter Selection
4) Typical Component Design
5) Anti-Lock Brake Systems (ABS) and Electronic Stability
Control (ESC) Systems
2. Design Requirements
1) Functionality
In a braking operation, the kinetic energy is converted into heat
or electricity stored in battery (regenerative braking systems).
o Decelerate a vehicle including stopping
o Maintain vehicle speed during a downhill operation
1.1
o Hold a vehicle stationary on a grade
A Road Vehicle Brake System
1.2
1.3
1.4
1.5
Human-driver based or Automated braking system 1.6
2) Brake System Components
o Energy Source including driver muscular pedal effort and brake
boost assist components
o Energy Transmission System including brake lines, wheel
cylinder, pressure limiting valves, and energy accumulators.
o Wheel Brakes including disc and drum brakes.
o Electric Motor/Generator/Battery and Fluid Motor
/Pump/Accumulators.
3) Design Requirements
o Sufficient braking capability, e.g. deceleration, braking
distances, and maximum grade-holding capacity.
o High reliability, e.g. in service brakes, dual-circuit systems are
used to transmit braking energy to the wheel brakes.
o Braking directional stability, e.g. front and rear axle braking
force distributions.
o Light driver pedal efforts, considering human factors including
pedal forces (<500N) and strokes.
o Short brake system response time, for air brakes, application
and release time lag.
o Good thermal performance, such as maintaining braking
effectiveness during high temperature faded conditions.
o Low environment pollution, e.g. low level braking noise and
suitable friction lining materials (non-asbestos materials).
o ABS system, heavy braking or on slippery road, ABS working.
o Differential braking, in emergency scenarios (high-g in lateral
direction), differential braking taking the authority of driver to
control the vehicle.
4) Brake Safety Standards and Regulations
o Brake component and vehicle manufacturers are responsible
for the inherently sound design, manufacturing, and reliability
of the brakes.
o Users/customers are responsible for continued safety of their
brakes by ensuring proper maintenance and repair.
o Governmental agencies/departments are responsible for
meaningful and safety-oriented standards and regulations.
Typical Standards and Regulations:
a) FMVSS (federal motor vehicle safety standard) 135.
After September 1, 2000, FMVSS135 replaced FMVSS105 for
vehicles with a GVW (gross vehicle weight) of less than 4,500kg
b) FMVSS 121. Trucks, trailers, and buses equipped with air
brakes are regulated by FMVSS121.
c) FMVSS122. It specifies performance requirements for
motorcycle brake systems.
d) FMVSS126/136. It specifies performance requirements for ESC.
e) ECE R13. It is European safety standard and it is very similar
to FMVSS135. (ECE R13, Economic Commission for Europe
Regulation 13)
❑ CMVSS FMVSS
❑ Harmonization of Vehicle Regulations
❑ Self-Certification :CMVSS, FMVSS
❑ Type-Approval System: ECE 1.9
3. Geometric Configurations of Brakes
Friction brakes in automotive applications can be divided into
drum and disc brakes
1) Drum Brakes
Drum brakes can be further divided into: 1) Leading-Trailing
Shoe Brake; 2) Two-Leading Shoe Brake; 3) Two-Trailing Shoe
Brake; and 4) Duo-Servo Brake.
(1) Leading-Trailing Shoe Brake
o A single cylinder twin piston expander;
o Leading shoe forced along the drum in forward direction;
o Trailing shoe working against the rotation direction;
o The increase in shoe tip force above that of the original
expander force is called positive servo;
o The shoe that provides this self-energizing or servo
action is known as a leading shoe.
1.10
1.11
1.12
1.13
Leading Shoe
1.14
Trailing Shoe
1.15
Brake Shoe Self-Energization
o Frequently used in rear wheel brakes incorporating some
sort of hand brake mechanism.
1.16
o Equal braking effect in both forward and reverse motion.
1.17
(2) Two-Leading Shoe Brake
o Two single piston cylinders or cams arranged diametrically
opposite each other with their pistons/cams pointing in the
direction of drum rotation;
o Both shoes becoming self-energizing;
o In reverse, the braking force being reduced due to the drag
force opposing the piston tip forces and both shoes having a
trailing action;
o Used as front wheel brakes in light commercial vehicles.
1.18
1.19
(3) Two-Trailing Shoe Brake
o Two single cylinders counteracting the rotational forward
direction of the drum and a negative servo condition existing;
o Good lining stability achieved at the expense of low resultant
drag force;
o For the same brake effect as a two leading shoe brake, much
higher hydraulic line pressure required.
1.20
(4) Duo-Servo Shoe Brake
o Equipped with a single cylinder twin piston expander (double
action) and a floating adjuster link;
o The primary (servo) shoe being equivalent to a leading shoe;
o The secondary shoe producing larger friction drag than the
servo shoe;
o Offering large braking torque with a given wheel cylinder
actuating thrust, but very sensitive to changes in shoe lining
properties caused by heat and wetness.
1.21
1.22
1.23
2) Disc Brakes
The caliper disc brakes are often used in modern vehicles. The
rotor or disc rotates through a caliper. The wheel cylinder
pistons force the pads against the rotor and produce brake
torque.
1.24
1.25
1.26
(1) Fixed Caliper Disc Brake
o It comprises simply a mounting half and a rim half;
o One or more cylinders in each half of the caliper house
sealed and self-adjusting pistons;
o The friction pads are located in a recess within the caliper.
1.27
(2) Floating Caliper Disc Brake
o Only the inboard pad is directly operated by hydraulic means;
o The reaction force from this being transmitted to the outboard
pad by an abutment in the floating caliper;
o A floating action for the caliper is obtained by virtue of either a
pivoting or a sliding mounting system;
o Current developments of the disc brake seem to be
concentrated on the sliding mounting system for the caliper;
o The sole purpose of the sliding caliper is to clamp the pads on
to the disc.
1.28
1.29
