How Starter Motors Work

The Engineering Mindset

19 Sept 202203:04

Summary

TLDRThis video explains the detailed process of how a car's starter motor system works. It describes how turning the ignition key sends a small electric current to the solenoid coil, activating both the pulling and holding coils to create a magnetic field. This field moves a piston, engaging the pinion gear with the flywheel, allowing the engine to start. Once the engine runs faster than the starter motor, the system disengages. The video also covers how the car battery recharges. Viewers are encouraged to check out related videos for more insights on automotive engineering.

Takeaways

🔑 Turning the ignition key sends a small electric current to the solenoid coil.
🔋 The solenoid is made up of two coils: the pulling coil and the holding coil.
🔌 The holding coil is connected to the starter motor casing, returning current to the battery via the car's frame.
⚡ Both coils are energized, creating a magnetic field that pulls the piston back, allowing the contactor plate to connect across the main terminals.
🚫 The pulling coil turns off once both ends become the same voltage, as no current flows through it.
📉 The holding coil continues running since it requires less energy to hold the piston in position.
🛠️ As the piston moves, it pulls a lever that rotates the pinion, locking it into the flywheel to start the engine.
🔄 The rotor spins rapidly due to the electromagnetic field produced by the coil, creating torque that turns the flywheel.
🌀 When the engine begins rotating faster than the starter motor, the overrunning clutch unlocks, allowing the pinion gear to spin freely.
🔋 Releasing the key cuts power to the solenoid, disengaging the pinion gear, while the alternator recharges the battery as the engine runs on its own.

Q & A

What happens when the ignition key is turned?
-When the ignition key is turned, a small current of electricity flows into the solenoid coil, which activates both the pulling and holding coils, creating a strong magnetic field.
What are the functions of the pulling coil and the holding coil?
-The pulling coil is responsible for pulling the piston back by creating a strong magnetic field, while the holding coil maintains the piston in position with far less energy after the pulling coil turns off.
How does the pulling coil turn off?
-The pulling coil turns off when both ends of the coil reach the same voltage, causing no voltage difference across it, so no current flows through the pulling coil.
What happens after the piston moves back?
-As the piston moves back, it pulls on a lever, which pivots and transfers motion to the drive sleeve. This pushes the pinion forward, slightly rotating it to lock the rollers in the clutch and slide the pinion into the flywheel.
What role does the contactor plate play?
-The contactor plate connects across the main terminals, allowing a large current to flow through it and into the starter motor, powering the motor to turn the flywheel.
How does the current flow through the starter motor?
-The current flows through the contactor plate, through the thick wire to the brushes, then to the commutator plates, through the coil, and back through another commutator plate and brush, which is grounded to the car's frame.
How does the rotor or armature rotate?
-The rotor rotates by the interaction between the electromagnetic field generated by the starter motor coil and the permanent magnet or field winding in the stator. This causes the rotor to rotate with high speed and torque.
What happens when the flywheel starts the combustion process?
-Once the flywheel starts the combustion process, the engine rotates the flywheel faster than the starter motor, unlocking the overrunning clutch so the pinion gear can spin freely.
What happens when the key is released after starting the engine?
-When the key is released, the power to the solenoid coil is cut off, releasing the piston. A spring pushes the lever back, removing the pinion gear from the flywheel, and the starter motor stops running.
How does the battery recharge after the engine starts?
-Once the engine is running, the alternator takes over and recharges the battery, allowing the combustion engine to continue running by itself.

Outlines

00:00

🔑 How the Ignition Key Powers the Starter Motor

When the ignition key is turned, a small electric current flows into the solenoid coil, which consists of two coils: the pulling coil and the holding coil. The holding coil connects to the starter motor casing, allowing current to return to the battery via the car’s frame. The pulling coil is connected to the main output terminal, and both coils generate a magnetic field to move the piston. As the contactor plate connects the main terminals, the pulling coil deactivates, while the holding coil continues to run with less energy to maintain the piston’s position. The piston movement pulls a lever, transferring motion to the drive sleeve, which pushes and slightly rotates the pinion to lock the clutch rollers and slide the pinion into the flywheel.

⚡ The Starter Motor Engages and Powers the Engine

Once the contactor plate connects the terminals, the pulling coil turns off, allowing a large current to flow through the contactor plate, thick wire, and into the brushes. This current moves through the commutator plates, the coil, and back through another commutator plate, grounding it to the car’s frame and returning it to the battery. The coil generates an electromagnetic field that interacts with the permanent magnet or stator windings. This interaction causes the rotor to rotate quickly and with high torque, transferring power through the shaft and clutch to the pinion gear, which turns the flywheel to initiate the engine's combustion process.

🔁 Overrunning Clutch Disengages as Engine Takes Over

As the flywheel starts the engine’s combustion process, the engine eventually rotates the flywheel faster than the starter motor, unlocking the overrunning clutch. This allows the pinion gear to spin freely. When the key is released, power to the solenoid coil is cut, releasing the piston, and a spring pushes the lever back, disengaging the pinion gear from the flywheel. The current to the starter motor is cut off, and the engine continues to run independently. Meanwhile, the alternator recharges the car battery.

🔗 Learn More About Car Batteries and Stay Connected

This video concludes with a reference to a previous video covering how car batteries work, providing a link for viewers to explore further. The narrator encourages viewers to check out additional videos on automotive engineering and stay connected through social media platforms such as Facebook, Twitter, Instagram, TikTok, LinkedIn, and their website, theengineeringmindset.com.

Mindmap

Keywords

💡Solenoid

A solenoid is a cylindrical coil of wire acting as a magnet when carrying electric current. In the video, the solenoid is used to activate the starter motor by creating a magnetic field when the ignition key is turned, which pulls a piston back to initiate the engine starting process.

💡Pulling Coil

The pulling coil is part of the solenoid and is responsible for pulling the piston back when energized. This coil is deactivated after the piston is pulled back since both ends of the coil become the same voltage, preventing any current from flowing through it.

💡Holding Coil

The holding coil works in conjunction with the pulling coil in the solenoid. It remains active to maintain the position of the piston with less energy after the pulling coil is turned off. This allows the starter motor to continue functioning until the engine starts.

💡Contactor Plate

The contactor plate is a crucial component that connects across the main terminals of the starter motor when the solenoid is activated. It allows a large current to flow through the system, powering the starter motor and engaging the engine’s flywheel.

💡Pinion Gear

The pinion gear is a small gear that engages with the flywheel of the engine. As the piston pulls the lever, the pinion moves forward, slightly rotating and locking into place, allowing it to transfer motion to the flywheel, which helps start the combustion process.

💡Flywheel

The flywheel is a large, heavy wheel connected to the engine, storing rotational energy. The pinion gear engages with the flywheel to start the engine, and once the engine begins to run faster than the starter motor, the flywheel disengages from the pinion.

💡Overrunning Clutch

The overrunning clutch is a mechanism that allows the pinion gear to disengage from the flywheel once the engine begins to rotate faster than the starter motor. This prevents the starter motor from being damaged as the engine takes over the motion.

💡Commutator

The commutator is a rotary switch in the starter motor that helps direct current through the motor's windings, allowing the motor to produce rotational movement. In the script, it directs the flow of current through the coil, enabling the rotor to rotate.

💡Rotor

The rotor is the rotating part of the motor that produces mechanical motion. In the video, the rotor interacts with the electromagnetic field created by the coil and stator magnets, rotating rapidly to transfer torque to the engine's flywheel via the pinion.

💡Alternator

The alternator is a device that recharges the car battery once the engine is running. After the starter motor disengages, the alternator ensures that the battery is replenished to provide electrical power for the vehicle's systems and future starts.

Highlights

The ignition key triggers a small current of electricity to flow into the solenoid coil, initiating the start process.

The solenoid consists of two coils: the pulling coil and the holding coil, both of which create a strong magnetic field.

The pulling coil connects to the main output terminal, while the holding coil is grounded through the car’s frame.

When both coils are energized, the piston is pulled back, connecting the contactor plate across the main terminals.

Once the contactor plate connects, the pulling coil turns off as no current flows through it due to equal voltage.

The holding coil uses less energy to maintain the piston’s position, continuing to operate while the pulling coil turns off.

The piston movement pulls a lever, which pivots and pushes the drive sleeve forward, slightly rotating the pinion.

The pinion locks with the rollers in the clutch, sliding into the flywheel to initiate engine rotation.

A large current flows through the contactor plate and the thick wire into the starter motor's brushes and commutator plates.

The rotor of the starter motor rotates rapidly due to electromagnetic interaction between the coil and permanent magnet.

The rotating rotor transfers motion through the clutch and pinion gear, turning the flywheel to start the combustion process.

As the engine surpasses the starter motor speed, the overrunning clutch unlocks, allowing the pinion gear to spin freely.

When the ignition key is released, power to the solenoid coil is cut, releasing the piston and retracting the pinion gear from the flywheel.

The starter motor stops, and the combustion engine runs independently, while the alternator recharges the battery.

Detailed explanation of how the car battery works, previously covered in another video.