Starter Motor & Control Circuits
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What consist of the low-current control circuit ?
Ignition Switch, Control Module, Netural Safety Switch or clutch switch, relays and the solenoid windings.
What consist of the high-current control circuit ?
Battery, the contacts in the solenoid (or relay) and the starter motor.
Armature - describe construction & function.
Splined shaft that allows the drive mechanism to slide along the shaft & engage with the ring gear.
To magnetically produce a voltage or electromotive force (EMF) there must be 3 factors
- - A conductor
- - A magnetic field
- - relative motion between the two
conduct current through the armature when it is being rotated in operation.
Anytime a conductor is moved in a magnetic field, a ________ is produced.
What is the purpose of the starting system ?
purpose is to crank the engine at starting speed while providing smooth, clash-free engagement of the starter drive.
Counter Electromotive Force (CEMF)
acts as the opposition to the applied EMF of the circuit (battery voltage)
Definition of Magnetism
is a measurable characteristic of a moving electrical charge.
form of energy that is caused by the motion of electrons in some materials
ex. current flowing through a conductor is a moving electrical charge and both produce a magnetic field.
The strength of an electromagnet is determined by ?
the number of turns of wire and the amount of current flowing through it.
Electromagnetism - name 2 points
the magnetic field strength around a conductor may be controlled by changing the current.
if the amount of current in the conductor increases, then the number of lines of force around the conductor also increases.
Whenever there is current in a conductor, there must be a magnetic field around the conductor.
wrapping a conductor around a permeable core to form a coil creates an electromagnetic.
The Magnetic Strength of a coil depends on two things:
the number of turns and and the current.
changing either of these also changes the strength.
a coil of wire that when a current flows through it, acts like a magnet and draws a moveable core in to coil.
change electrical energy into linear motion.
What does the Armature contain ?
many conductors inside an iron frame or has permanent magnets attached to it. The armature can rotate inside the field frame.
Induced Voltage occurs ?
when a conductor moves through a magnetic field OR when a magnetic field moves across a conductor and cuts across the lines of force. An electromotive force (EMF) will develop in the conductor.
The quicker the conductor moves through the field the greater the __________.
Starter Motors are designed as ?
are designed as low duty-cycle motors, meaning - they are not meant to be run continuously and will overheat if engaged for an extended period of cranking.
Starter motor should not be cranked for more than _______ before starter damage can occur.
While performing a starter motor current draw test, the cranking voltage should not drop below ____ volts.
As battery voltage drops during the cranking, current flow _______.
A starter that has been cranking for more than 30 seconds should be allowed _________ to cool down before cranking the engine again.
The central portion of the starter motor is called _______.
the frame or yoke.
Construction of the housing ? 1 point
is made of heavy gauge steel to concentrate the magnetic field of the field magnets.
A set of brushes is positioned in the housing where they can contact the commutator on the armature, which are usually at the back end of the housing.
Pole Shoes are used for ?
is used to mount the field windings into the starter frame and to concentrate the magnetic field generated by the windings.
Field Magnets are either ?
strong permanent magnets or powerful electromagnets (called field windings)
A very strong field is needed to generate the amount of mechanical power needed to crank an engine.
Permanent Magnet Fields (on PM motors)
Are mounted in the frame. They are arranged w/ alternating north & south poles facing the inside of the frame.
Brushes - 3 points
One pair of brushes is Grounded to the frame and the other pair is Insulated & connected to the motor terminal. (total of 4 brushes in most starters)
The brushes are positioned at regular intervals around the commutator (every 90 degrees for 4 brushes)
A heavy braided wire, commonly called Pigtail provides the electrical connection.
Solenoid (Starter Motor application)
Solenoid operation moves the operating fork and pinion to mesh with the ring gear and causes the plunger contacts to bridge the main starter terminals.
The ________ of the solenoid operates the _______ that engages the drive mechanism.
Plunger, shift fork
Solenoid Connection - There are 3 terminals on the end cover of the solenoid.
A battery terminal connects directly to the battery to supply the operating current of the starter.
The motor terminal is connected to the starter motor itself and receives battery power when the solenoid is energized.
The solenoid terminal is connected to the ignition switch or starter relay and energizes the solenoid when the current is supplied to it.
Solenoid has 2 separate windings called the _________ ?
Pull-in and Hold-in
What are the windings grounded to ?
The hold-in winding is grounded to the solenoid case while the pull-in winding is grounded through the armature of the starter motor.
Process of windings during Engagement
Both coils work together in parallel to engage the starter.
Process of the windings during Cranking
the hold-in winding works alone to hold the plunger engaged.
Process of the windings during Disengagement
Both coils oppose each other in SERIES to cancel the magnetic field allowing the plunger spring to disengage the starter.
Operation of the Shift Fork.
A shift fork operated by the solenoid slides the drive into mesh w/ the ring gear when the starter is Engaged.
The Shift Fork is returned to its rest position by the return spring on the solenoid plunger, which Disengages the drive.
Purpose of the Overrunning Clutch
allows the starter motor to drive the ring gear, but prevents the starter from being driven by ring gear once the engine starts.
prevents Overspinning of the armature.
Neutral Safety Switch or Clutch Switch
This switch disables the starter motor unless the transmission range selector is placed in either park or neutral.
Usually mounted on the transmission.
Engine Running Lockout
Some vehicles open the starter-enable relay when the Powertrain Control Module (PCM) detects an engine rpm signal above a certain point.
This prevents the stater from engaging when engine is already running.
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