Publisher The Goodheart-Willcox Co., Inc. Tinley Park, Illinois

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

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 • 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 andField 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 theother direction

24. Pinion Gear Assembly 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 thebattery-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. 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. 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