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2

History

Both Otto cycle and Diesel cycle internal-combustionengines require the pistons to be moving before the ignitionphase of the cycle. Originally, a hand crank was used tostart engines, but it was inconvenient and rather hard workto crank the engine up to speed. It was also highlydangerous.

Even though cranks had an overrun mechanism to preventit, when the engine started, the crank could begin to spinalong with the crankshaft. The engine could kick back (run

in reverse), pulling the crank with it, because the overrunsafety mechanism works in one direction only.

Even a simple backfire could result in a broken thumb; itwas possible to end up with a broken wrist, or worse

Moreover, increasingly larger engines with highercompression ratios made hand cranking a more physicallydemanding endeavor.

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3

Electric starter

Electric motor needed to turn over the internal-combustionengines to start.

Charles F. Kettering of Dayton Electric Laboratories (DELCO)invented the first useful electric starter.

 The starter motor is a small but powerful electric DC motorthat delivers a high degree of power for a short period of 

time.

 These starters were first installed by Cadillac on Productionmodels in 1912.

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Gear-reduction starters

In 1962, Chrysler introduced a starter incorporating ageartrain between the motor and the driveshaft.

 The motor shaft has integrally-cut gear teeth forming adrive gear which mesh with a larger adjacent driven gear toprovide a gear reduction ratio.. This permits the use of ahigher-speed, lower-current, lighter and more compactmotor assembly

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Principle of Operation

 The basic principle that drives the starter motor, which is aDC motor, is Faraday’s Law;

which states that electrical current is produced when thereis relative motion between a conductor and magnetic field.Of course the law is stated for a generator, however theopposite is also true, motion is produced when a currentcarrying wire is in the presence of magnetic field.

 The motion is determined by two factors, the direction of the current and the direction of the magnetic field.

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Basic requirements to be met by Startermotor

It should deliver the following requirements

Must meet the engine torque requirement (MaximumCranking Torque)

Must meet minimum engine starting temperature (ColdCrank)

Must meet minimum Engine RPM Requirement. (CrankSpeed)

Must adapt the vehicle battery rating. 

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DC motor

A DC electric motor converts electrical power(voltage and current) into mechanical power

(speed and torque) by passing a currentthrough a conductor suspended in a magneticfield.

When current passed through a conductor held

perpendicular to a magnetic field, a torque isgenerated which is proportional to the amountof current and the strength of the magneticfield.

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Starter motor - subassembly

Modern starters assemblies are usually made up of thebelow sub assemblies.

Solenoid assembly Armature Assembly Brush holder assembly Frame Assembly

Output Drive assembly End Housing

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Solenoid

 The solenoid assembly servers two function. It provides thenecessary force to pull the drive assembly into engagementwith the ring gear. It also provides a high current switch to

energies the starter motor with 12 volts from the batterycable.

A solenoid is a coil is wound on a cylindrical, hollow, plastic orphenolic form, and with a movable, rod-shaped form madeof solid ferromagnetic iron, solid steel, or powdered iron.

which can travel in and out of the coil along its axis.

When the key is turned in the ignition switch to the startposition, electricity flows from the batteries to the startersolenoid and coils inside the solenoid are energized byelectricity, they create a magnetic field which attracts and

pulls a plunger. This causes the starter solenoid to relay alarge electric current to the starter motor, which in turn sets

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Solenoid

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Armature Assembly

 The armature assembly is the heart of the starter.

It consists of a steel lamination stack pressed onto ashaft, armature copper windings inserted intolaminations core slots, the ends twisted to the properlocation and then welded into commutator bars.

commutator change or swap the direction of the current in thecoil twice each rotation (four pole).

 The conductors and commutator bars must be electricallyinsulated from each other and the steel core and shaft.

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Armature

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Brush Holder Assembly

 The brush holder assembly provides the electricalconnection to the armature and in conjunction withthe commutator assembly, switches the conductor

current directions as each commutator passes underit.

 The brush holder also must insulate the positive brushesfrom ground potential and locate the brushes at the

correct position for optimum output performance(good commutation) and brush life.

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Brush Holder Assembly

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Frame assembly

 The frame assembly consists of Permanent magnet &magnet clips which provides the main supportstructure for the starter subassemblies and also

servers to complete the flux path required for themagnetic circuit.

Size control is important in order to maintain tight air gaptolerance to maximize the starter output and

efficiency.

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Frame assembly

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Drive assembly

Drive assembly is made up of output shaft, Planetarygear assembly and with Over running roll clutch pinionassembly.

When the armature assembly is inserted in the driveassembly, the armature shaft gear teeth mesh withthe Epicycle planetary gear assembly.

As the armature shaft rotates inside the planet gears, the

planet gear are in mesh with the internal teeth of stationary gear internal. which is locked in place byfeature in the motor end housing, the output shaft alsorotated because the planet gear are spinning

 The drive assembly also transmitting the torque from the

starter output shaft to ring gear in order to crankengine.

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Drive assembly

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Planetary gear assembly

Example

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End Housing

 The drive end housing is normally a machined castingdesigned for attachment of the starter to the engine &transmission powertrain application. The casting also

supports all the other sub assemblies.

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21

Performance Curve

  E

  x a  m  p  l

 e

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Direct Drive Starter motor

1 Drive shaft

2 Stop ring

3 Pinion

4 Roller-type

overrunning clutch

5 Pinion-engaging

lever 

6 Solenoid switch

7 Electrical connection

8 Commutator bearing

9 Brush holder 

10 Commutator 

11 Armature

12 Magnet

13 Stator housing

14 Meshing spring

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Gear-reduction starter motor

1 Drive shaft

2 Stop ring

3 Pinion

4 Roller-type

overrunning clutch

5 Meshing spring6 Pinion-engaging

lever 

7 Solenoid switch

8 Hold-in winding

9 Pull-in winding

10 Return spring11 Switch contact

12 Switch contact

13 Electrical connection 14 Commutator end Shield

15 Commutator 16 Brush holder 17 Armature18 Magnet 19 Stator housing 20 Planetary gear 

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1.8 kW starter motor

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Alternator - Charging

Nothing can function without electric power in a vehicle.

 The battery represents the vehicle’s energy store tosupply power to all current consuming loads (ignition,lighting, starter motor etc…). But we need somethingto keep the battery charged or it will lose its chargeand die.

In order to supply the power required for the electricalsystem. The alternator is the onboard “electricity-generating plant” when engine is operation. The taskis to supply power all current consuming loads andmaintains battery a full charge at all times. 

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Basic requirements to be met byalternator

Supplying all connected loads with direct current Additional power reserves for fast charging of battery –

even when continuous loads are switched on and when

engine is only idling Keeping the alternator voltage constant over the entire

engine speed range As maintenance-free as possible in operation Rugged construction to withstand external influences such

as vibration, change in temperature, dirt, damp.

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Magnetic Induction Principles

Michael Faraday discovered in 1831 that if a electricconductor cut across the lines of magnetic force of amagnet, an electric charge is induced in the

conductor. It is immaterial whether the whether themagnetic field remains stationary while the conductormoves, or vise versa.

 This is the basic principle by which practically all our

present day electric current is generated .

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Alternator

Alternator are driven directly by the vehicle engine. Driveis usually by means of V-belt.

 The four main parts of the alternator are

A rotating field winding called the rotor. A stationary induction winding called the stator.

A diode assembly called the rectifier bridge. A control device called the voltage regulator.

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Rotor

A rotor consists of a iron core, coilwinding, two slip rings, and twoclaw-shaped finger pole pieces.some models include support

bearings and two internalcooling fans. The assembly isthen machined and balanced tocontrol tight air gap to the stator& insures quite operation at highspeed.

When ignition is switched on the

current flows via warning lampto the rotor field winding andfrom their via the regulator toground. Which creates the perexcitation magnetic field.

When magnetic field saturates . Onefinger pole becomes a northpole and the other a south pole.that induces voltage into the

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Stator

Stator Designs

Delta wound stators can

be identified by havingonly three stator leads,and each lead will havethe same number of wires attached.

Wye style has four statorleads. One of the leadsis called the Neutral Junction. The Neutral Junction is common toall the other leads.

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Star or Wye connection

Wye wound stators have three windings with a commonneutral junction. They can be identified because they have4 stator lead ends (3 phase). Wye wound stators are used in

alternators that require high voltage output at lowalternator speeds. Two windings are in series at any onetime during charge output.

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Delta connection

Delta wound stators can be identified because they have onlythree stator lead ends (3 phase). Delta stators allow forhigher current flow being delivered at low RPM. The

windings are in parallel rather than series as like the Wyedesign

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Stator

 The stator winding hasthree sets of windings.Each is formed into a

number of evenlyspaced coils around thestator core.

 The result is threeoverlapping singlephase AC sine wavecurrent signatures, A,B, C.

Adding these wavestogether make up thetotal AC output of thestator. This is calledthree phase current.

 Three phase current

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Rectifier

 The Diode Rectifier Bridge is responsible for theconversion or rectification of the AC voltage into DCvoltage.

 Two diodes are connected to each stator lead. Onepositive the other negative.

When three or six phase alternator current is applied

across a rectifier diode, the diode allows current topass only one direction.

Diodes used in this configuration will redirect both thepositive and negative polarity signals of the AC

voltage to produce DC voltage. This process is called'Full - Wave Rectification'.

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Rectification circuit

Diodes are used as one-way electrical check valves. Passingcurrent in only one direction, never in reverse.

In red you can see B+ current pass through to the rectifier as itgoes to the battery. In green you can see the return path.

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Rectification circuit

Diodes are mounted in a heat sink to dissipate the heatgenerated by the diodes.

Diodes redirect the AC voltage into DC voltage so the battery

receives the correct polarity

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Regulator

 The regulator will attempt to maintain a pre-determinedcharging system voltage level. If the voltage producedby the alternator goes above 13.5 - 14.5 volts, the

battery will be ruined very quickly. It's the job of thevoltage regulator to keep the output voltage betweenthe 13.5 - 14.5 volt range.

When charging system voltage falls below the set point,

the regulator will increase the field current, thusstrengthening the magnetic field, which results in anincrease of alternator output.

When charging system voltage raises above the set point,the regulator will decrease field current , thus

weakening the magnetic field, and results in a

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Regulator

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  The regulator monitors battery voltage.

 The regulator controls current flow to the rotor assembly.

 The rotor produces a magnetic field.

Voltage is induced into the stator.

 The rectifier bridge converts AC stator voltage to DC outputfor use by the vehicle.

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Performance Curve

  E  x a  m

  p  l e

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Alternator

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Although the individual components “Alternator withvoltage regulator” and “Starter motor" are subject totheir own operating conditions, they are highly

dependent on each other.