Everything you need about the engine flywheel
The flywheel refers to several engine systems at once and performs the following functions in them:
- reduction of uneven rotation of the crankshaft (flywheel – a structural element of the crank mechanism );
- transmission of torque from the engine to the gearbox (flywheel – drive clutch disc );
- transmission of torque from the starter to the crankshaft of the engine (flywheel – driven gear of the launch system gearbox ).
Smoothing of pulsations of the torque is carried out due to the periodic accumulation and return of kinetic energy by the flywheel. Energy is stored during the stroke of the piston and is consumed at other engine strokes, incl. to remove pistons from dead spots. The more cylinders in the engine, the longer the piston stroke in each of them takes longer, therefore, the torque of such an engine is more uniform, and the mass of the flywheel can be reduced.
The flywheel is mounted at the end of the crankshaft near the rear main bearing. This is, as a rule, the most powerful bearing in the engine, since it must withstand the weight of the flywheel and the loads associated with its operation.
The following types of flywheel design are distinguished:
The flywheel of a continuous design found the greatest distribution on cars . This is a massive cast-iron disk with a diameter of 30 to 40 centimeters. A steel gear rim is pressed onto the outer surface of the disk, which allows the crankshaft to rotate when the engine is started using the starter. On one side of the flywheel, a hub is made for attaching to the flange of the crankshaft, the other side plays the role of a clutch plate.
When the engine is running at different speeds, the crankshaft is constantly twisted and untwisted, i.e. subjected to torsional vibrations. The engine uses torsional vibration dampers of various designs. One of these devices is a dual-mass flywheel (another name is a damper flywheel ), which has been used on automobile engines since 1985.
Two-mass flywheel device
The flywheel includes two disks connected by means of a spring-damper system, which allows to completely isolate the transmission from torsional vibrations and to ensure uniform operation of its elements. With the use of a dual-mass flywheel, there is no need for a damping device in the clutch disc.
The advantages of the dual-mass flywheel are damping, vibration reduction, noise isolation, gear shifting convenience, reducing synchronizer wear, protecting the transmission from overload and even fuel economy. On the other hand, the intensive work of the two-mass flywheel leads to increased wear of the spring-damper system and even breakdown of its main element – the arc spring. All this restrains the mass use of a damper flywheel on engines.
Current trends in the development of automotive engines, such as downsizing (reducing engine volume and mass while maintaining power) and downsizing (expanding the engine torque range with the ability to work at low revs), have demanded a new level of damping. Since 2008, a two-mass flywheel with a pendulum damper has been used on engines .
To eliminate uneven rotation of the crankshaft in the low-speed range, a centrifugal pendulum is installed on the flywheel together with the arc spring. It creates its own vibrations, which in antiphase are superimposed on smoothed vibrations after the arc spring and completely dampens them.
The centrifugal pendulum is made in the form of goods located around the circumference of the flywheel. At low engine speeds, loads of the pendulum swing more strongly, because the centrifugal forces acting on them are small. With increasing speed, the amplitude of the oscillations of the cargo decreases and their role in damping the oscillations decreases.
A lightweight flywheel is used when tuning the engine. The redistribution of the mass of the flywheel to the edges of the disk allows to reduce its mass to 1.5 kg and in turn to reduce the moment of inertia. With the use of a lightweight flywheel, the engine reaches its maximum speed faster, accordingly, it has better acceleration dynamics, and an increase in power of up to 5% is also observed.
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