What are the flywheel and crankshaft in a gasoline engine?

Flywheel is a disc-shaped part, which has a large moment of inertia and plays the role of energy storage. For a four-stroke engine, work is done every four piston strokes, that is, only the power stroke does work, while the exhaust, intake and compression strokes all consume work.

2. Machine shaft

Crankshaft is the most important component in the engine. It bears the force from the connecting rod and converts it into torque, which is output through the crankshaft to drive other accessories on the engine to work. The crankshaft is subjected to the centrifugal force of rotating mass, periodically changing gas inertia force and reciprocating inertia force, which makes the crankshaft bear bending and torsion load. Therefore, the crankshaft is required to have sufficient strength and rigidity, and the journal surface should be wear-resistant, uniform and well balanced.

Functions of components:

1, flywheel:

The moment of inertia of flywheel is very large. Because the work of each cylinder of the engine is discontinuous, the engine speed also changes. When the engine speed increases, the kinetic energy of flywheel increases and energy is stored. When the engine speed decreases, the kinetic energy of the flywheel decreases and the energy is released. Flywheels can be used to reduce the speed fluctuation when the engine is running.

Installed at the rear end of the engine crankshaft, it has the moment of inertia, which is used to store the engine energy, overcome the resistance of other components and make the crankshaft rotate at a uniform speed; The engine is connected with the automobile transmission through the clutch installed on the flywheel; Engage the starter to facilitate engine starting. But also the integration of crankshaft position sensing and vehicle speed sensing.

In the power stroke, the energy transmitted by the engine to the crankshaft is not only output, but also absorbed by the flywheel, so that the rotation speed of the crankshaft will not increase much. In the three strokes of exhaust, intake and compression, the flywheel releases its stored energy to compensate the work consumed in these three strokes, so that the crankshaft speed will not be reduced too much.

In addition, the flywheel has the following functions: the flywheel is the driving part of the friction clutch; The flywheel rim is inlaid with a flywheel gear ring for starting the engine; The flywheel is also engraved with the top dead center mark, which is used to calibrate the ignition timing or fuel injection timing and adjust the valve clearance.

2. Crankshaft:

The most important part of the engine. It bears the force from the connecting rod and converts it into torque, which is output through the crankshaft to drive other accessories on the engine to work.

The crankshaft is subjected to the centrifugal force of rotating mass, periodically changing gas inertia force and reciprocating inertia force, which makes the crankshaft bear bending and torsion load. Therefore, the crankshaft is required to have sufficient strength and rigidity, and the journal surface should be wear-resistant, uniform and well balanced.

In order to reduce the mass of the crankshaft and the centrifugal force generated during movement, the crankshaft journal is usually made hollow. The surface of each journal is provided with oil holes, so that oil can be introduced or led out to lubricate the journal surface. In order to reduce stress concentration, the joints of the main journal, crank pin and crank arm are all connected by transitional arcs.

Crankshaft counterweight (also called counterweight) is used to balance the rotating centrifugal force and its torque, and sometimes it can also balance the reciprocating inertial force and its torque. When these forces and moments are balanced with each other, the counterweight can also be used to reduce the load of the main bearing.

The number, size and position of counterweight should be considered according to the number of cylinders, cylinder arrangement and crankshaft shape of the engine. The balance weight is generally cast or forged with the crankshaft as a whole. The balance weight of high-power diesel engine is manufactured separately from the crankshaft, and then connected together by bolts.