What is an alternator overrunning clutch?
An overrunning clutch is a component of an automotive alternator that allows the alternator rotor to rotate freely when the engine slows down or stops. It reduces the load on the alternator belt and prevents belt slippage and wear. To understand why the generator overrunning clutch is needed, let's first understand the principle of its operation.
How does the generator work?
The main task of the generator is to convert mechanical energy from the crankshaft of the engine into electrical energy and feed it into the onboard network of the car.
The car generator consists of such components:
- Rotor;
- Stator;
- Diode bridge;
- Voltage regulator;
- Pulleytator;
- Diode bridge;
- Voltage regulator;
- Pulley.
When the engine is running, it drives a belt that runs on a pulley attached to the alternator. The pulley rotates the alternator rotor shaft, which in turn rotates the magnets inside the coil. These rotating magnets generate alternating current in the stator, which is then sent to the generator's rectifier. The rectifier converts the alternating current into direct current. You can read more about how an alternator works here.
Why do you need an overrunning clutch?
Overrunning clutch Toyota 27415-0W131
For a long time, the pulley was a single piece attached to the alternator shaft. And such a rigid connection caused jerks in the motor operation and increased the load on the belt transmission. The fact is that the car engine works unevenly - torque is transmitted through the shaft by pulses that correspond to the combustion of fuel in the cylinders. And the speed of the car is constantly changing during acceleration and braking. As a result, the alternator belt stretched and tore, with a maximum resource of no more than 30,000 km.
Then there were new engines - even more powerful, and there was an increase in the number of devices and equipment that consumed even more energy. They required large generators, and their rotors have considerable inertia. And the problem was getting worse.
The solution was the introduction of an overrunning clutch in the generator design, which provided a balance between the speed of rotation of the drive shaft and the generator shaft.
How the generator overrunning clutch is arranged
The principle of operation of the clutch you can easily understand if you have ridden a bicycle at least once in your life. When you stop pedaling - the rear wheel of the bicycle is not blocked, but continues to rotate. The same mechanism is found in the generator overrunning clutch.
Advantages of a pulley with overrunning clutch
Apart from the factors we have already mentioned, other advantages of using an overrunning clutch are:
- Greater driving comfort and improved noise levels
- Reduced stress on the belt drive
- Reduced fuel consumption
- Increased service life of all components
Signs of malfunction of the overrunning clutch
The overrunning clutch has a service life of approx. 100,000 km. After this time, the risk of bearing failure increases. Other signs that indicate possible problems are:
- Dim car headlights and/or a burning battery indicator light on the dashboard, indicating that the battery is not getting enough charge
- Noise at low and high speeds
- Vibration at low speeds
- Whistling, squeaking and other extraneous sounds indicating problems with the tension rollers and bearings
If such signs appear, it is necessary to make a diagnosis at the service station. It is not recommended to examine the system on your own.