What is the function of the car flywheel?
A disc-shaped part with a high rotational inertia acts like an energy storage device. For a four-stroke engine, each four piston strokes generate power, meaning only the power strokes do the work, while the exhaust, intake, and compression strokes all consume power. At the power output end of the crankshaft, that is, the side connected to the transmission and the working equipment. The main function of the flywheel is to store the energy and inertia outside the power strokes of the engine. For a four-stroke engine, only the power stroke absorbs the energy from the flywheel stored energy.
The flywheel has a large rotational inertia. Due to the discontinuous power generation of each cylinder in the engine, the engine speed is also variable. When the engine speed increases, the kinetic energy of the flywheel increases and the energy is stored; when the engine speed decreases, the kinetic energy of the flywheel decreases and the energy is released. The main function of the flywheel is to reduce the speed fluctuations during the engine's operation.
Installed at the rear end of the engine crankshaft, with rotational inertia, its function is to store the engine's energy, overcome the resistance of other components, and make the crankshaft rotate uniformly; through the clutch installed on the flywheel, the engine is connected to the car transmission; it engages with the starter to facilitate engine starting. And it is the integration point for crankshaft position sensing and speed sensing.
During the power stroke, the energy transmitted by the engine to the crankshaft, apart from being output externally, also has a part absorbed by the flywheel, so that the crankshaft's rotational speed does not increase much. In the exhaust, intake, and compression strokes, the flywheel releases its stored energy to compensate for the work consumed by these three strokes, so that the crankshaft's rotational speed does not decrease too much.
In addition, the flywheel has the following functions: The flywheel is the active part of the friction clutch; on the rim of the flywheel, there is a flywheel ring gear for starting the engine; on the flywheel, there is also an upper stop mark for calibrating ignition timing or fuel injection timing, and adjusting valve clearance.
The main symptoms of a damaged flywheel in a car are engine shaking, abnormal noise, difficulty starting, transmission imbalance, difficulty shifting gears, clutch slipping or incomplete disengagement, and abnormal noise or shaking of the clutch.
Difficulty starting and idling abnormality:
Abnormal noise and metal friction sound during ignition, or a severe metallic impact sound, and multiple attempts to start still fail. This is usually caused by the wear or deformation of the flywheel ring gear, resulting in the starter small gear not being able to mesh normally; when the damage to the ring gear exceeds 4 teeth, the flywheel must be replaced.
Shaking during idling: Continuous tremors in the steering wheel or vehicle body during idling, and the tremors reduce when the clutch is depressed. This is a typical characteristic of failed flywheel dynamic balance, which will disrupt the smooth rotation of the crankshaft and cause vehicle resonance.
Abnormal power transmission: During acceleration, the engine speed increases but the vehicle speed rises slowly, feeling like "shaking but not moving", and the fuel consumption may increase by 10%-30%. The vibration of the double mass flywheel's shock absorber spring fracture or the flywheel transmission imbalance will cause unstable energy storage and release, resulting in power delay.
Significant performance decline: The maximum speed may decrease by 15-20 km/h, the climbing ability may decrease by 40%, and there may be abnormal noise in the transmission shaft. Long-term neglect may cause secondary damage such as wear of the input shaft of the transmission.
Abnormal clutch and transmission system faults:
Abnormal clutch operation:
Clutch slipping: Difficulty starting at low speed, weak acceleration, and severe cases may emit a burnt smell or smoke.
Incomplete clutch disengagement: The clutch pedal cannot be fully depressed to cut off the power, resulting in difficulty shifting gears, teething, or inability to stop the vehicle.
Noise and shaking: Shaking is emitted in the semi-engaged state, and during starting or disengagement, there is also shaking. These symptoms are often caused by excessive end face runout of the flywheel ( > 0.2mm) or wear of the contact plane, affecting the normal operation of the clutch. Transmission system disorder: During gear shifting, there is a stuck feeling, difficulty in shifting gears, or even imbalance in the transmission of the gearbox. Damage to the flywheel will directly interfere with the linkage between the clutch and the gearbox, resulting in poor gear shifting performance.
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