As typical examples of vibrating force in a vehicle, there are the following: combustion pressure or torque fluctuation in the engine, unbalanced tires, rough road, imbalance or joint angle in the propeller shaft, engagement of the gears in transmission or the differential component, and fluctuations of friction in the clutch or the brakes. If all these causes could be reduced to zero, vibration and noise would not occur. However, it is impossible to fully remove some of the causes such as the combustion pressure in the engine, or the external force from a rough road. The following explanation is about the generation mechanism for typical vibrating forces in vehicles and how the vehicle responds to them.
The cause of vehicle vibration/noise generation is the vibrating force. A typical portion which generates the vibrating force is the engine.
In engines, since the fuel is burned in the combustion chamber and many components are moving, many types of vibrating forces is generated. They cause the engine to vibrate, making itself a vibrator. They are transmitted to the drive train and the body.There are a number of factors linked to the generation of the vibrating force in engines, but among them, the following two factors are especially important. One is the combustion pressure of the fuel in the combustion chamber. The other is the inertia force caused by the reciprocating movement of the piston and rotary movement of the crankshaft.
These two factors generate vibration and torque fluctuation in the engine. Factors other than these two are caused by the mechanical movement of the components, which cause engine noise.