1. Starting System Fundamentals
Chapter 28

2. Objectives Explain electric motor principles Describe starter parts
Understand the operation of a solenoid
Discuss starter drive operation

3. Introduction Starter system Without a starter
Important part of the automotive electrical system
Without a starter
Car would have to be push started
Henry Ford's Model T had a hand crank for the engine

4. Starter Motor Starter circuit includes: Starter operates at a high rpm
Starter drive
Battery
Ignition switch
Solenoid
Starter operates at a high rpm
Has a small pinion gear on end of starter drive
Meshes with a large gear on the flywheel

5. Starter Motor (cont'd.) Gear ratio
Provides starter with leverage needed
Gear ratio between the two gears is about 18:1
Crank engine at normal cranking speed
Starter motor must be turned 3,600 rpm

7. Starter Motor Fundamentals
Starters use electromagnetism to convert electrical energy to mechanical power
Two separate magnetic fields
Produced by horseshoe
Resulting from current flowing through the conductor
Push-pull effect on armature
Causes conductor to move from stronger to weaker magnetic field

9. Starter Motor Fundamentals (cont'd.)
Conductor is formed into a loop
Loop wire is placed between two electromagnetic pole shoes
Ends of the wires have commutator bars
Multiple loops make up an armature
Armature has a soft iron core
Field coils made of heavy copper ribbons
Wound around soft iron cores called pole shoes

11. Starter Motor Fundamentals (cont'd.)
Some starter motors don't have field coils
Have permanent magnets instead
Simpler
Weigh less
Create less heat
Brushes, usually made of carbon, are lightly held against the commutator by springs
Usually four brushes, which are together in pairs

13. Starter Drives Have an overrunning, or one-way clutch
Transmits motion from starter to flywheel
Disengages from the engine at startup
Teeth on the starter drive gear are tapered

14. Starter Electrical Circuit
Starter motor requires a large amount of current
Battery must be in good enough condition to provide sufficient current
Starter switched on by ignition switch and key
Most cars use a solenoid
Engages starter drive pinion with flywheel ring gear
When a coil in the solenoid is energized, a magnetic field draws the piston into the coil

16. Starter Electrical Circuit (cont'd.)
Ignition switch: opens and closes the circuit to the starter
Electricity can take two paths in the starter
Safety switches
Circuit on newer cars with automatic transmissions has a neutral safety switch
Late-model vehicles with manual transmissions have a starter/clutch interlock switch

19. Gear Reduction Starters
Some manufacturers use gear reduction starters
Lighter
Use less current
Small in size
Lower gear ratio gives them enough torque
Smaller battery cables can also be used

21. Brushless DC Motors Hybrid vehicles use brushless motors
No commutator or brushes
Arcing cannot occur
Permanent magnets are part of the rotor
Electromagnets are part of the stator
Electronic circuitry
Takes the place of brushes and commutator bars

23. Brushless DC Motors (cont'd.)
Rotor position
Sensed either by:
Hall switch
Magnetic field strength in unexcited field windings
Magnetic strength in windings
Varies with changes in the duty cycle
Pulse-width modulation
With longer pulses, the motor turns faster