Automotive Brake System

1
Brake System Fundamentals

• Konto Abba Pascal Technical Vocational Training
  Institute
• Automotive Technology
• 
  Compiled by Mesay D.

2
Purpose

• Reducing the speed of a vehicle
• To stop or
• Hold it stationary

3

• The principle of the brake is attained by causing
  a fixed object to be pressed against a rotating
  object.
• The braking effect is obtained from the friction
  that is generated between the two objects.
• The system converts mechanical energy in to heat
  energy.

4
Friction -is the resistance to motion between two
objects in contact with each other

• Dry friction (Brakes)
• Greasy Friction (Wheel bearings)
• Viscous (Crank main bearings)
• Friction varies with the roughness of the
  surfaces.
• Kinetic (Motion) Friction
• Static (Rest) Friction

5
Friction between Drums Shoes or Pads Rotors
slows the car.
Friction between TIRES and ROAD stops the car.
6
Construction

• The two categories are -
• The disc brake
• The drum brake

7
Application of brakes

• Service brakes Its the primary braking system
  using a the pedal connected to a hydraulic system
  causing it to operate.
• Parking brakes Its mechanically applied by a
  lever or pedal.

8
Classification of brakes

• Hydraulic brake
• Pneumatic brake
• Mechanical brake
• Electric brake
• Vacuum brake

9
Typical System (No ABS)
10
Typical Layout of System(with ABS)
11
Brake Pedal Design Advantage by Leverage

• First Mechanical Advantage is Drivers foot
• Length of Lever determines force applied
• Uses Fulcrum
• Pedal Ratio

10
51
2.5 inches
0.5 inch
2
5
12
Disc Brake
13
Types of disc brake

• Fixed caliper
• Floating caliper
• Sliding caliper type

14
Fixed caliper

• The fixed caliper disc brake has piston on
  both sides of disc. Some fixed-caliper disc
  brakes have two pistons, one on each side. Other
  has four pistons two on each side.
• The caliper is rigidly attached to the
  stationary car parts.

15
Fixed Caliper

• Applies two pistons to opposite sides of rotor
• Caliper stays stationary
• Disc Brakes require higher hydraulic pressure

16
Floating-Caliper

• The floating caliper, or swinging caliper can
  pivot, or swinging in or out. It is suspended
  from rubber bushings which give enough to permit.
  The caliper has either one or two piston.

17
Sliding-caliper

• The principle of operation of a sliding caliper
  is the same as that of a floating caliper. The
  difference is in the method of attaching the
  caliper to the mounting bracket. The grooves (or
  the sliding surfaces) in the caliper and mounting
  brackets are called ways.
• The caliper is held in the ways by a retaining
  key, a spring, and a lock screw. There is no
  sideward motion of the caliper when the brakes
  are applied.

18
Sliding Caliper

• Applies pressure to two pads on opposite sides of
  rotor
• Caliper
• Sliding
• Fixed
• Friction Material exposed to air

19
Caliper Pistons

• Caliper pistons have the piston seal mounted
  stationary in the housing and the piston in the
  seal. This design requires a good piston surfaces
  finish for maximum seal life.
• Mounting the seal in this way produces the force
  to pull the released piston and pad away from the
  rotor to reduce drag. This design provides
  "self-adjustment" to a automatically maintain the
  correct lining-to-rotor clearance.

20
BRAKES

• Air Brakes. (Pneumatic)

• Hydraulic Brakes use hydraulic fluid pressure to
  transmit power.
• (Incompressible)

• Two pistons of same size will travel the same
  distance, with the
• same force.

• If the small piston acts on a large piston,
• the large piston will travel with more
• force, but a shorter distance.

• If the larger piston acts on a small piston, the
  small piston will
• travel a longer distance, but with less force.

21
Drum Brake
22

• It is a brake in which curved brake shoes press
  against the inner surface of a rotating metal
  drum to produce the braking action applied for
  rear brake for most vehicles

23
Duo-servo Brake

• return springs hold the bottoms of the shoes
  against the adjusting screw while the tops of the
  shoes are held against the anchor pin.

24
Self-adjusters

• Drum brake systems have a self-adjust capability
  to compensate for wear on the brake shoes.
• Self-adjuster mechanism consists of a series of
  links, springs, retainers and a star wheel
  (screw) adjuster.

25
Leading-trailing Brake

• Leading-trailing systems have the anchor pin
  mounted at the bottom of the backing plated
  rather than at the top.
• Leading-trailing drum brakes are automatically
  adjusted when the parking brake is applied and
  released.

26
Brake components
27
Brake Action

• Brake Pedal is connected to the Master Cylinder.

• Each wheel has a Wheel cylinder
• (Rear)

Or Caliper (Front)

• Each wheel has a brake Drum
• (Rear)

Or Disk (Front)

• Each wheel has Shoes
• (Rear)

Or Pads (Front)
28
Master Cylinder

• Type
• Single type master cylinder
• Tandem type master
• cylinder (tandem?
• one behind the other)

29
Function

• it converts the motion of brake pedal into
  hydraulic pressure.

30
Drum Brake System
31
Disc Brake Caliper Assembly
32
Brake Plumbing

• Rigid steel brake lines are double wall
• Flexible hoses connect rigid lines on vehicle to
  each wheel
• Transmits hydraulic fluid to each wheel

33
Pressure Control Valves
All systems use one or more valves
34
Pressure Differential Valve
Warning light (Dash mounted) will light up, in
case difference of pressure is detected in either
system due to a leak.
35
Metering Valve

• On vehicles with front disk and rear
• drum brakes.

• In hydraulic line to front brakes.

• During light brake application, metering valve
  prevents
• front brakes from applying until after the rear
  brakes
• shoes are in contact with the drums.

36
Combination Valve
Pressure Differential Switch, Proportioning Valve
Metering Valve are all combined in one.
37
(No Transcript)
38
Wheel Cylinder

• Wheel cylinder or caliper pistons are slave
  cylinders
• Change hydraulic pressure back into mechanical
  force
• Can use one or two cylinders at each wheel

39
Power AssistIncreases force of drivers foot
40

• Power Brakes assists in braking when the pedal is
  pressed.

Hydraulic booster hydraulic pressure is applied
by power-steering pump
Vacuum Booster works with the vacuum from the
vehicles manifold.
To Check press on the brake pedal and start the
vehicle, if working properly the pedal should
go down.
41
Cable Parking Brake
Parking or Emergency Brake
42
Parking Brake Systems

• Foot or Hand Brake
• Are cable controlled
• Several Styles
• As shown Drum in hat Driveline

43
Brake System Energy
44
Brake System Principles

• Kinetic Energy
• Mass
• Weight
• Speed
• Inertia and Momentum

45
Friction Principles

• Kinetic and Static Friction
• Friction and Pressure
• Friction and Surface Area
• Coefficient of Friction
• Brake Fade

Friction changes kinetic energy into heat
(thermal) energy.
46
Brake Friction Materials

• Five Characteristics
• Resist Fading with increased temp
• Resist fading when wet
• Recover quickly
• Wear gradually
• Quiet

Bonded or Riveted
47
Braking Dynamics

• Weight Transfer
• Weight Distribution
• Braking Power
• Friction Efficiency
• Brake to Wheel
• Wheel to Road Surface
• Traction Efficiency
• Skidding

48
Hydraulic Principles

• Fluids cannot be compressed
• Fluids can transmit Movement
• Acts Like a steel rod in a closed container
• Master cylinder transmits fluid to wheel cylinder
  or caliper piston bore.
• Fluids can transmit and increase force

49
The amount force is calculated by multiplying
the pressure times the area
Force
Pressure
3.14 X R2
Area
M X A Force
50
Hydraulics - its how the pressure is multiplied
and transferred
51
Hydraulic pressure is distributed equally in all
directions
52
The pressure that is applied at piston A is the
same as what is applied to piston B
53
The hydraulic pressure is the same, but the
applied force can be changed by changing the
piston size.
54
You cant have something for nothing
55
The caliper piston needs more applied force for
multiple reasons

56
Brake Fluid
Brake Fluid

• Use the one recommended by the manufacturer.
• DOT3
• DOT4
• DOT5

Brake parts can be cleaned with brake fluid.
Properties

• High Boiling point

• Water Tolerance

• Low Freezing Point

• Non-corrosive (rubber, plastic, metal).

• Lid should be always covered in order to prevent
• moisture in the system.

57
Have a nice time