Cranking system - PowerPoint PPT Presentation

1 / 24
About This Presentation
Title:

Cranking system

Description:

Pinion gear ratio is usually 18:1 (9 teeth to 166 teeth) ... Low voltage drop= low resistance. High voltage drop= high resistance ... – PowerPoint PPT presentation

Number of Views:56
Avg rating:3.0/5.0
Slides: 25
Provided by: Greg374
Category:
Tags: cranking | system

less

Transcript and Presenter's Notes

Title: Cranking system


1
Cranking system
  • Cranking circuit
  • The starter motor
  • Starter drives
  • Starter solenoids
  • Testing and diagnosis

2
Cranking circuit
  • Starter motor
  • Battery
  • Starter solenoid and/ or relay
  • Starter drive
  • Ignition switch and safety control switches
  • Neutral safety switch
  • Clutch switch

3
(No Transcript)
4
Starter motor
  • Electromagnetism basics
  • A magnetic field surrounds every conductor
    carrying a current
  • The strength of the magnetic field is increased
    as current flow is increased

5
Starter motor
  • Electric motor that converts electrical energy
    (up to 500 amps) to mechanical energy (up to 8
    hp) to crank engine
  • Housing contains 4 positive electromagnets
  • Current is controlled by a solenoid or relay
  • Electromagnets are wired around an iron core
    called a pole shoe

6
(No Transcript)
7
Starter motor
  • The two pairs of shoes are wired in opposite
    directions to provide north and south magnetic
    fields and referred to as field coils
  • A shaft called an armature rotates in the center
    of the field coils
  • Brushes transfer the current from the field coils
    to the armature
  • Current travels from the field coils to the
    armature magnifying the magnetic fields that
    rotate the armature

8
(No Transcript)
9
Starter motor
  • The torque output of the starter is determined by
    the strength of the magnetic fields inside the
    starter
  • The torque of the starter decreases as the
    starter speed increases
  • Some starters use permanent magnets in place of
    electromagnets
  • PM starters are advantageous because of smaller
    size and lighter weight
  • Disadvantage is lower torque

10
Starter motor
  • PM starters do not produce as much torque and
    therefore require gear reduction to multiply
    torque

11
Starter motor
  • PM starters have a higher armature speed
  • Use a planetary gear drive for gear reduction
  • Consume less current and therefore allow
    manufacturers to install smaller battery cables
  • PMs are more susceptible to damage from impacts

12
(No Transcript)
13
Starter motor
  • Starter drives
  • Starter incorporates a pinion gear to drive ring
    gear on flywheel
  • Pinion gear ratio is usually 181 (9 teeth to 166
    teeth)
  • Normal engine cranking speed is 200-250 rpm
  • Starters must have a one-way clutch on pinion
    drive to prevent engine from turning starter

14
(No Transcript)
15
Starter motor
  • Starter solenoid
  • Electromagnetic switch
  • Contains two windings
  • Windings are of two different gauge sizes
  • Heavy winding is called the pull in winding
  • Purpose is to draw the plunger into solenoid
    which moves the starter drive pinion into mesh
    with the ring gear

16
  • The smaller winding is called the hold in winding
    and produces enough magnetic force to keep the
    plunger in position

17
  • As the plunger is drawn into the solenoid, the
    plunger makes contact with a metal contact that
    connects the positive battery cable with the
    motor terminal to operate the starter motor
  • The contact bypasses the pull in winding

18
Testing and diagnosis
  • Voltage drop testing
  • Low voltage drop low resistance
  • High voltage drop high resistance
  • Voltage drop is the drop in voltage that occurs
    when current is flowing through a resistance
  • Voltage drop is the difference between voltage at
    the source and voltage at the electrical device
    to which it is flowing

19
Testing and diagnosis
  • Before voltage drop testing can be done, current
    must be flowing through the circuit
  • Resistance is not effective unless current is
    flowing
  • A voltmeter tells you the difference in voltage
    from one test lead to another

20
(No Transcript)
21
Testing and diagnosis
  • Starter current draw tests
  • 4 cylinder engines 150 to 185 amps
  • 6 cylinder engines 160 to 200 amps
  • 8 cylinder engines 185 to 250 amps
  • Excessive draw may indicate
  • Starter motor worn
  • Internal engine problems
  • High resistance in starter motor
  • Starter motor internally shorted

22
(No Transcript)
23
Testing and diagnosis
  • Control circuit
  • Battery
  • Ignition switch
  • Security system
  • Neutral safety or clutch switch
  • Starter solenoid

24
(No Transcript)
Write a Comment
User Comments (0)
About PowerShow.com