Summary
A starter motor is an electric motor that turns the engine on when you switch the ignition. It is a device that rotates (cranks) an internal combustion engine so that the engine can operate under its power.
The primary function of a starter motor in an automobile engine is to start the engine so it can work on its power. This is achieved due to the high torque rotation from the starter motor, which is used to turn the engine at fast speeds. The starter motor gives the engine the first or second rotation it needs to start working on its own.
A car starter motor’s major parts include ammature, commulator, brushes, solenoid, plunger, lever fork, pinion, and field coils.
Types of starter motors are direct drive starter motor, planetary gear, permanent magnet gear reduction, permanent magnet direct drive, offset-gear reduction, and initial starter. These are suitable for specific engine power loads.
In the working, the starter motor is powered by the solenoid, which helps to push the starter gear forward to mesh with the engine flywheel.
This flywheel is mounted on the engine crankshaft, so as the starter motor spins, it turns the flywheel as well as the crankshaft. As soon as the engine starts, the system disengages from the flywheel. Learn about the reason why starter not engaging here!
Car Starter not engaging: Causes and How to Diagnose the issue
Now, let’s go deep to explain what a starter motor is, its function, parts, diagram, types, and working principle!
Contents
What is a Car Starter?
A starter or starter motor is an electrical device that is used to rotate (crank) internal combustion engines so as to initiate the engine’s operation under its own power.
As soon as the engine begins to run, it gets disconnected from the engine, which now relies on the combustion process. The component is mounted on the engine’s gearbox housing, and the starter motor gear meets the flywheel’s teeth.
Being an electrical component, a starter consists of a powerful DC (Direct Current) electric motor and a solenoid. The solenoid receives positive power directly from the battery and heart current from the engine body.
In order to turn the engine, a 12-volt battery must be used to run the starter. This means the battery has to be sufficient to power the device. In most situations where the starter motor clicks but won’t start, the issue is either from the battery or the starter itself.
Function
The starter motor has only one function, which is the first and second rotations the engine needs. Apart from that, the device is just an extra load on the vehicle. There should be another means of starting vehicles without starter motors, right? I think the component is too big for one function.
Parts of the Starter Motor
Below are the starter motor parts and their functions:
Armature:
An armature is an electromagnet component that is mounted on the driveshaft or bearings for a guide. It is made of a laminated soft iron core which is wrapped with numerous conductor loops or windings.
Commutator:
A commutator is a section of the shaft at the rear of the housing on which brushes run to conduct electricity. It is made of two plates mounted to the axle of the armature, the plates provide connections for the coil of the electromagnet.
Brushes:
Brushes are parts that run on a section of the commutator at the rear of the housing. it rubs the commutator and conducts electricity.
Solenoid:
The solenoid features two coils of wire that are wrapped around the core. This solenoid serves as a switch that connects and closes the electrical connection between the starter motor and the vehicle’s battery.
Plunger:
The function of a plunger in a starter motor is to push forward so the pinion can be engaged.
Lever Fork:
The lever fork is connected to the plunger which makes them push forward together to engage the pinion.
Pinion:
A pinion is a small mechanism containing gear and springs. It engages immediately after the engine starts, by extending the gear to the flywheel teeth. The flywheel is the source of engine rotation.
Field Coils:
The field coils are held in housing with screws as it consists of two or more coils connected in series. These coils receive power from the battery that converts them into an electromagnet that turns the armature. This creates a magnetic field around the armature.
Diagram of a starter motor:
Types of Starter Motor
Below are the five types of starter and their difference:
Direct Drive Starter Motor DD
Direct drive is the most common and older type of starter motor available out there. it comes with different applications and construction designs but it’s a solenoid-operated unit. Well, its working remains plain like other types.
The solenoid is energized by the car battery when the ignition switch or key is pressed. This pushes the plunger to shift the lever that directs the pinion gear. The pinion gear then meshes with the engine flywheel. So, as the starter motor spin, the flywheel spins along, which then causes the engine’s combustion to run on its own.
Planetary Gear (PLGR)
The existence of these types of starter motors has vastly replaced direct-drive types. It is a permanent magnet that transmits power between the pinion shaft and the armature. The armature spins with more speed and torque. The essence of planetary gear is to reduce gear, which further reduces the requirement of high current.
There is a sun gear located at the end of the armature and three plenary carrier gears inside the ring gear, held stationary. Planetary gears are able to attain a great amount of gear reduction as the ring gear is held and the sun gear is input while outputting the carrier.
Permanent Magnet Gear Reduction (PMGR)
The permanent magnet gear reduction is designed to offer less weight, easy construction, and less heat generation. It features four to six magnet field assemblies rather than field coil starters. It has three terminals on the 12V solenoid and is also heavy-duty, making it require less current. Because there are no field coils, the commutator and brushes transfer current directly to the armature.
Permanent Magnet Direct Drive PMDD
The PMDD types of starter motors are similar to direct drive in several ways. Their difference is that the field coil is replaced with permanent magnets in the permanent magnet direct drive type.
Off-Set Gear Reduction OSGR
These starter motor types work at high speeds at low currents. They are lighter and more compact, which makes them easy to assemble. Off-set gear reduction starters are common among four-wheel-drive vehicles as they increase cranking torque.
Inertial Starter
Inertial starters are the electric types that achieve the features of all types of starter motors. It works perfectly fine during cranking and even ensures the motor part’s safety. It starts the engine strong and very fast, making it the best option for cracking speed. The amount of weight associated with the torque capacity of the starter is extremely minimal. Learn about the symptoms of a bad starter here!
Working Principle
The working of a starter is quite easy and interesting, but most drivers really don’t know the secret behind motor cranking. When the ignition key or bottom is pressed, the transmission should be in the park or neutral state. The battery voltage goes through the starter control circuit to activate the solenoid.
The starter motor is powered by the solenoid, which helps push the starter gear forward to mesh with the engine flywheel. This flywheel is mounted on the engine crankshaft, so as the starter motor spins, it turns the flywheel as well as the crankshaft. As soon as the engine starts, the system disengages from the flywheel.
Note that in an automatic transmission, starter motors can only be operated when the vehicle is in a park or neutral position. In manual transmission, the clutch pedal must be depressed.
Working inside the starter motor, there are four field windings attached to the housing from inside. The armature (rotating parts) is connected through the carbon brushes in series with the field coils. However, in some starters, field coils are replaced with magnet fields. There is a small gear at the front of the armature attached with an overrunning clutch. Watch the video to have more understanding of how a starter motor works:
That is all for this article, where i explained what a starter motor is, its function, parts, diagram, types, and working principle. I hope it was helpful, if so, kindly share with others. Thanks for reading, see you around!
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