1. Modern Automotive Technology PowerPoint for by Russell Krick
Publisher The Goodheart-Willcox Co., Inc. Tinley Park, Illinois

2. Chapter 30
Starting System
Fundamentals

3. Contents
Starting system principles
Starting motor construction

4. Starting System Principles
The starting system uses battery power and an electric motor to turn the engine crankshaft for engine starting

5. Basic Starting System
The ignition switch energizes the solenoid, which allows the battery to energize the starting motor, which turns the flywheel gear, starting the engine

6. Components Battery Ignition switch Solenoid Starting motor
source of energy
Ignition switch
allows the driver to control operation
Solenoid
high current relay (switch)
Starting motor
high-torque electric motor

7. Energizing the Starting System
Turning the ignition key to the “start” position allows current to flow through the solenoid coil
Magnetism closes the solenoid contacts, connecting the battery to the starting motor
The motor turns the flywheel ring gear until the engine runs on its own

8. De-energizing the Starting System
When the ignition key is released to the “run” position, no current flows to the solenoid coil
The solenoid contacts open, the starter stops turning, and the starter gear moves away from the flywheel

9. Starting Motor Fundamentals
Converts electrical energy from the battery to mechanical energy to crank the engine
Like other electric motors, the starting motor produces a turning force through the interaction of magnetic fields inside the motor assembly

10. Magnetic Field Action Made up of invisible lines of force
Since like charges (fields) repel each other and unlike charges (fields) attract each other, magnetic fields can be used to produce motion

11. Magnetic Field Action

12. Simple Electric Motor
If a current-carrying winding is placed inside a magnetic field, the winding rotates away from the pole shoes

13. Commutator and Brushes
Keep a motor turning by controlling the current through the windings
The commutator serves as a sliding connection between the motor windings and the brushes
The brushes ride on top of the commutator, carrying current to the spinning winding

14. Commutator and Brushes
The commutator reverses the electrical connection when the loop rotates around

15. Increasing Motor Power
Several windings (loops of wire) and a commutator with many segments are used to increase motor power
As the motor spins, many windings contribute to the motion, producing a smooth turning force

16. Armature Supports the windings
Increases the strength of each winding’s magnetic field

17. Field Windings Stationary insulated wire wrapped in a circular shape
When current flows through the field windings, the magnetic field between the pole shoes becomes very large
This field acts against the armature’s field, producing motion

18. Armature and Field Windings

19. Starter Pinion Gear Small gear on the armature shaft
Engages a large ring gear on the engine flywheel
Moves into and meshes with the flywheel ring gear

20. Starter Pinion Gear

21. Overrunning Clutch Locks in one direction
Releases in the other direction
Allows the pinion gear to turn the flywheel ring gear for starting
Lets the pinion gear freewheel when the engine starts

22. Overrunning Clutch
Locks the flange to the pinion gear in one direction and releases in the other direction

23. Overrunning Clutch Operation
Rollers jam and lock in one direction and release in the other direction

24. Pinion gear assembly slides on the shaft for engagement

25. Starter Solenoid An electromagnetic switch
Makes an electrical connection between the battery and the starting motor
Allows the low current ignition switch circuit to control the high current starting motor

26. Starter Solenoid
Plunger movement pulls the disc into contact with the battery terminal and the starter terminal to activate the starter motor

27. Solenoid Operation
Low current flows through the windings when the ignition is in the start position
The magnetic field pulls the solenoid plunger and disc toward the windings
The disc touches both of the high-current terminals
High current flows to the starter motor

28. Solenoid Operation

29. Solenoid Functions Closes the battery-to-starter circuit
Pushes the starter pinion gear into mesh with the flywheel ring gear
Bypasses the resistance wire in the ignition circuit

30. Starting Motor Construction
All starting motor construction is similar, but there are slight variations in design

31. Main Parts of a Starting Motor
Armature
windings, core, shaft, and commutator assembly that spins inside a stationary field
Pinion drive assembly
pinion gear, overrunning clutch, and sometimes a shift lever and solenoid
Commutator end frame
end housing for brushes, brush springs, and shaft bushing

32. Main Parts of a Starting Motor
Field frame
center housing that holds field coils and pole shoes
Drive end frame
end housing around pinion gear; has bushing for armature shaft

33. Starting Motor Types Classified by type of pinion gear engagement
There are two main types:
movable pole shoe starting motor
starter-mounted solenoid (starting motor with solenoid)

34. Movable Pole Shoe Starting Motor
Uses a drive yoke lever to move the pinion gear into contact with the flywheel gear

35. Movable Pole Shoe Starting Motor
A magnetic field pulls the pole shoe downward, forcing gear engagement as the armature starts to spin

36. Starter-Mounted Solenoid
Solenoid plunger moves a lever to engage the pinion gear

37. Starter-Mounted Solenoid
The solenoid not only operates the pinion gear but also completes the battery-to-starter circuit

38. Solenoid Operation

39. Permanent-Magnet Starter
Uses special high-strength magnets in place of conventional field windings

40. Starting Motor Torque A starting motor must produce high torque
Difference in gear size between the small pinion and large flywheel ring gear increases turning force

41. Extra gears further increase torque
Reduction Starter
Extra gears further increase torque

42. Internal Motor Circuits
Series-wound motor
Shunt-wound motor
Compound-wound motor

43. Series-Wound Motor
Develops maximum torque at initial start-up and decreases as motor speed increases

44. Shunt-Wound Motor
Produces less starting torque but more constant torque at varying speeds

45. Compound-Wound Motor
Has both series and shunt windings and produces good starting power and constant operating speed

46. Neutral Safety Switch
Prevents the engine from cranking unless the shift selector is in neutral or park
Mounted on the shift lever or on the transmission

47. Wired in series with the starter solenoid
Neutral Safety Switch
Wired in series with the starter solenoid

48. Starter Relay
Opens or closes one circuit by responding to an electrical signal from another circuit
Uses a small current from the ignition switch to control a larger current through the starter solenoid
Reduces the load on the ignition switch

49. Starter Relay Operation
Ignition switch is turned to “start”
Current flows through the relay windings
Magnetism closes the relay contacts
Contacts complete the circuit to the solenoid windings
Solenoid contacts close, which energizes the starting motor

50. Starting System Circuit