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 • 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 motor • 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