chapter 4_starting systems

8/2/2019 CHAPTER 4_Starting Systems

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Chapter 4: STARTING

SYSTEMS


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Starting System

Introduction

Internal combustion engines are not capable of startingthemselves.

Therefore, its require external force to start them up.

Motors which provide this force are called starter.

This is a powerful electric motor that engages the car's

flywheel in order to spin the crankshaft

It converts electrical energy from the battery intomechanical energy that rotates the flywheel-crankshaft


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Starting System Principles

The major parts of a starting system include:

1. Battery (source of energy for starting system)2. Ignition switch (allows driver to control starting system

operation)3. Solenoid (high current relay (switch) for connecting battery to

starting motor)4. Starter motor (high torque electric motor for turning gear on

engine flywheel)


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Starting circuit

The starting system has two circuits.1. The low current control circuit2. The high current motor circuit

When the ignition key is started; Starter relay or solenoid switch close

High current flows from the battery insulated cable through starterrelay to starting motor A gear on starting motor shaft moves into mesh with the ring gear

around the engine flywheel causes the crankshaft spins fast enoughto start the engine


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Power Transmission

Power transmission takes place in two stages when the

starter switch is operated.

First, there is a power flow from the battery to the startermotor, causing the the motor armature to rotate.

Then, there is power flow from the armature to the vehicleengine.

This being accomplished by the engagement of a pinion gearon the armature shaft with a gear ring on the engineflywheel.


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Starter Motor

This is a powerful electric motor thatengages the car's flywheel in order to spinthe crankshaft.

The starter is composed of windings of wire

that form loops, ending at the commutatorsegments.

The armature coils are mounted on themotor's central shaft (supported withbearings.
http://en.wikipedia.org/wiki/File:Automobile_starter.JPGhttp://en.wikipedia.org/wiki/File:Automobile_starter_2.JPG


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Starter Motor Construction


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Starter Motor Construction

The starting motor has two basic parts;

1. A starter armature - the rotating assembly consists of anarmature shaft, armature core, commutator and armaturewindings

2. Field frame assembly - field windings produce strongmagnetic field around starter armature when battery current

flows through them


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Starting Motor Operation

Brushes are used to create electrical contact to

the commutator segments. When current is fed into brushes, it flows

through all the loops of the shoe windings andarmature and out the other brushes.

This creates a electromagnetic field around eachloop. As the armature turns, and spin the motor.

The greater the current flowing in the coils, thegreater the magnetic forces, and the greater thepower of the motor.

Since the coil draw heavy amounts of current, itmust not be operated on a continuous basis forlonger than 30 seconds.

After cranking for 30seconds it is wise to wait acouple of minutes to let the starter motordissipate some of its heat.


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Ammature & Commutator

Actual starting motor has multiple (several)commutator segments and windings to increasemotor power and smoothness.


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FLYWHEEL RING GEAR

-This is a toothed ring that is fitted to theoutside of the engine's flywheel.

Matching teeth on the starter motor mesh

with this gear in order to spin thecrankshaft.


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Solenoid Starter Switch Function :

1. As a relay switch to complete the battery-starter motor circuit.

2. To pull plunger and sleeve for pinion gear engagement to ring gear

on the flywheel.

Operation:

1. When the ignition key in start position, a small amount of current

flows through the solenoid windings. This produces a magnetic

field that pulls on the solenoid plunger. The plunger and disc are

pulled into the coil windings

2. The solenoid disc touches both of the terminals and completes the

battery-to-starter circuit. About 150 200 Amps current flows

through the solenoid and to the starter.

3. When the ignition key is released, current is disconnected from

the solenoid windings. The magnetic field collapsed and plunger

slide out of the windings and starter motor shuts off.


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Starting Motor Drive

A. Before ignition key start, no field coilsenergized so motor does not run. Contact Awill close before contact B

B. When ignition key is turned to start, theplunger pulling the sleeve and pinion

moves towards flywheel. Touches tooth-to-tooth abutment. Contact A Closes-motor turns slowly to allow pinion to slideinto engagement.

C. Pinion fully engaged, both contact (A & B)

are close, full power (current) to motor,armature and pinion starting spin (hightorque) and rotate ring gear flywheel.


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Movable-Pole-Shoe Starting Motor Instead of a solenoid mounted on the starting motor, some cars

have a movable-pole-shoe starting motor that uses a movablepole shoe to move the overrunning clutch shift lever.

When the ignition key is turned to START;

1. Contacts closes in the relay and current flows to the startingmotor.

2. The magnetic field from the field windings around themovable-pole shoe pulls it down.

3. As the shoe moves down, the shift lever pivots and moves

the pinion into mesh with the ring-gear teeth


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Starting Motor Drive The pinion gear meshes with the ring gear on the flywheel.

The ring gear has about 15 times as many teeth as the

pinion. This means the armature must rotate 15 times to rotate the

ring gear (flywheel) and crankshaft once

When the starting motor operates, the armature spins about3000 rpm. This rotates the crankshaft about 200 rpm or

higher which is fast enough to start the engine After the engine starts, crankshaft speed may increase to

3000 rpm or more.

If the pinion remains in mesh with the ring gear, the pinionand armature will spin at 45 000 rpm because of the 15:1

gear ratio


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Overrunning Clutch

Thestarter overrunning clutchtransmits torque (turning power) inone direction and turns freely in theother direction. This allows the piniongear to turn the flywheel ring gear forstarting. It also lets the pinion gearfreewheel when the engine begins torun.

Without the overrunning clutch, thestarter could be driven by the engine

flywheel. The flywheel gear could spinthe starter too fast and causearmature damage
http://en.wikipedia.org/wiki/File:Freewheel_en.svg


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Overrunning Clutch Operation

The overrunning clutch consists of an outershell and a pinion-and-collar assembly. Theouter shell has five steel rollers fitted intofive notches. The notches are smaller at oneend.

When the armature and shell begin torotate, the rollers roll into the smaller ends ofthe notches.

There, they jammed between the shell andthe pinion collar. This forces the pinion to

turn with the sleeve, cranking the engine

When the engine starts, it drives the pinionfaster than the shell and armature. Therollers roll back into the larger ends of thenotches. This allows the pinion and collar to

spin faster than the shell and armature


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Gear Reduction Many starting motor have internal gear reduction to increase

cranking torque.

The small pinion gear on the armature shaft drives the larger gearon the clutch shaft.

There are two gear reductions

1) reduction gear set inside the starting motor

2) reduction gear between the overrunning clutch pinion and

the ring gear teeth


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Gear Reduction

Gear reduction 45:1 the armature turns 45 times to turn thecrankshaft

Many permanent magnets starting motor have planetary gear setof gear reduction. It provides a gear reduction of about 4.5 to 1.

Total gear reduction between the starting motor armature andcrankshaft is about 70 to 1


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Permanent Magnet Starting Motors Instead of electromagnets, some starting motors use four or six

permanent magnets to provide the stationary magnetic field so

that the size is smaller and lighter that starting motor with fieldcoils

This starter motor has 40% lighter than conventional equivalentand suitable for petrol engine.

Permanent magnet resulting a low torque compared to coilwinding, so its using the gear reduction (planetary gear drive) toincrease torque.


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Permanent Magnet Starting Motors


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Complete Starting System Circuit


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Starting System Testing & Repair

Starting System Trouble Diagnosis

The figure shows the most common starting system troubles. Ifany of these parts have high resistance, lower than normalresistance, damage or wear, the engine may not crank normally

Three basic starting system complaints are:

1. The engine does not crank2. The engine cranks slowly but does not start

3. The engine cranks normally but does not start


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Starting Headlight Test The test will make a quick check of the starting system. Turn ON the headlights and

try to start the engine. Note any sound and watch the brightness of the headlights (orthe inside dome-light)

1. No Cranking, Lights Stay Bright Current is not getting to the starting motor. Check the voltage at ignition key switch

and starting motor terminals with ignition key at START. If has voltage at starting motor terminal trouble at starting motor If no voltage at starting motor terminal trouble in the relay or solenoid

2. No Cranking, Lights Dim Heavily

The starting motor cannot crank the engine with low battery. Recharge or replace a discharged battery. Other possible causes are advanced spark timing, excessive starter draw and loose or

dirty connections

3. No Cranking, Lights Dim Slightly The drive pinion may not be engaging with the ring gear. If starting motor armature

spins, then the overrunning clutch is slipping. Other possible causes are highresistance or an open circuit in the starting motor

4. No Cranking, Lights Go Out Caused by poor connection at the battery. Wiggle cable connection, if tight, perform a

voltage drop test. If there is voltage, the connection has excessive resistance so cleanthe cable clamp and battery terminal. Install and tighten the clamp

5. No Cranking, No Lights Points to a dead battery or open in the electrical system. Possibilities include a loose

connection at the battery, relay or solenoid


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Starting Test

1. Engine Cranks Slowly but Does Not Start Engine crankshaft does not rotate properly with the ignition key at START. The

most common causes are a dead battery, poor electrical connection or faultysystem component

2. Engine Cranks at Normal Speed but Does Not Start The starting systems okay. The trouble is elsewhere (ignition system, fuel

system, engine defective or air leaks in intake manifold)

3. Relay or Solenoid Chatters (rattle on) If happens when the key at START,

a. Battery is probably low. Charge the battery b. Contact in the relay or solenoid may be burned replace the contact plate c. Defective solenoid hold-in winding replace solenoid

4. Pinion Disengages Slowly After Starting Caused by sticky solenoid plunger, overrunning clutch sticks on armature shaft,

overrunning clutch defective and shift-lever return spring weak

5. Unusual Noises Caused by too much or too little clearance between the overrunning clutch

pinion and the ring gear. Adjust according to manufacturers service manual


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Starting System Testing

1. Cranking-Voltage Test Measures the voltage for ignition while the starting motorcranks the engine1) Disable the ignition so the engine will not start2) Connect a voltmeter across the battery3) Crank the engine

If the starting motor cranks normally & voltage > 9,cranking voltage is normal

If slow cranking & voltage > 9, high resistance in motorcircuit or starting motor

If low cranking speed & low voltage, a discharged battery


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2. Voltage Drop Test To determine if there is excessive resistance across a cable,

component or connection while current flows through it.1) Disable ignition2) Connect the voltmeter leads to the terminal and cable clamp3) Turn the ignition key to start

The meter should show zero. Typical voltage drop should notexceed 0.2 volts across a wire or cable and 0.3 volts across aswitch. (Refer service manual).

Voltage drop from the starting motor ground to the battery groundterminal should not exceed 0.2 volt.


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3. Current-Draw Test / Starter-Draw Test To measure the current flow to the starting motor

while it cranks the engine1) Disable ignition

2) Connect the ammeter to the battery cable3) Turn the ignition key to START

A reading of 200 Amps is typical for someengines. If higher than specified, the trouble is in

starting motor or engine


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Starting System Testing4. Starting Motor Bench Test

After removing the starter motor from the engine, two test can be made

1) No-Load Test2) Stall test no longer used/ recommended

1) No-Load Test

It requires a voltmeter, ammeter and carbon pile or the volt-ampere tester.Connect a remote starter switch from the large solenoid battery (BAT) terminalto the smaller solenoid (S) terminal

1) Hold revolution counter/ rpm indicator against the end of thearmature shaft

2) Close the remote starter switch

3) Note armature speed (rpm), current and voltage


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Result of No-Load Test

The result indicate various electrical and mechanical problems inthe starting motor

1)Rated current draw speed indicate normal conditions2)Low no-load speed and high current draw indicates excessive

internal friction or a shorted armature. Excessive friction is due todirty, tight or worn bearings or by the armature dragging on thepole shoes

3)Failure to operate with a high current draw indicates groundedterminal or brush assembly or frozen bearings

4)Failure to operate with no current draw indicates open brush leadsor field circuit or open armature coils. Other causes include brokenbrush springs, worn brushes, glazed commutator or high insulationbetween the commutator bars

5)Low no-load speed with a low current draw indicates high internalresistance caused by poor connections, defective leads or a dirtycommutator

6) High no-load speed with high current draw indicates shorted fields.


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Starter Motor Service

Removing and Installing Starter MotorTo remove:1. Disconnect the ground cable from the battery. If necessary, raise

the car2. Remove any braces, shields or other parts that may be in the way3. Disconnect the wires and cables from the starting motor4. Support the starting motor5. Remove the starting motor mounting bolts ( watch for any shims

between the starting motor and its mounting pad for reinstallation)

To Install:1. Clean the mounting surfaces on the drive end and on the

engine for god electrical contact

2. Install the starting motor3. Reconnect the wiring and cable4. Start the engine5. Follow procedure to install data to ECM6. Check for normal cranking speed and starting system

operation


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Structure of starter motor


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Servicing Starter Motor

Permanent magnets in the starting motor increase its durabilitybecause failures caused by shorted or grounded field coils eliminated.1. To disassemble, remove the solenoid (if used) and through bolts.

Remove the housing. Inspect and service the components. Majorsteps in rebuilding starting motor:

2. Replace armature bushings or bearings3. Test the armature and field coils (if used)

4. Refinish the commutator5. Replace damaged field coils (if used)6. Replace brushes7. Wipe clean or replace overrunning clutch drive8. Replace contacts in the solenoid switch

9. Then, lubricate the shaft splines, bushings and bearings.10. Assemble the starting motor. If required, energized the solenoid and

check the clearance


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THE END

Any question?
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