Although engine mounts are relatively small, they are important in controlling NVH.
They link the vehicle body to the engine, the largest source of vibration. It is through these mounts that the engine vibration is transmitted to the body. The vibration from the tires are also transmitted to the engine, causing the engine to resonate with them. The three characteristics required for engine mounts are: a large dampening great ability to dampen vibrations, a small spring constant, and a suitable natural frequency. These characteristics are defined as follows:
A great ability to dampen vibrations reduces the vibration from the engine itself.
A small spring constant reduces the engine vibration transmitted to the body.
A suitable natural frequency is a frequency which falls outside of normal operating vibration range, determined by the engine weight and the engine mount spring constant.
There are various design configurations of engine mounts to comply with vibration- and sound-proofing requirements.
Mounts for Linearly-mounted Engines
This type of engine is usually supported at the following three locations: the right and the left side of the engine block, and the rear mount for the transmission.
Mounts for Transversely-mounted Engines
The right and left mounts are located linearly over the crankshaft, and the front and rear mounts serve to prevent the engine from “rolling”. The center mount also helps to control engine roll.
This type of engine mount utilizes the spring force of the rubber insulator to absorb vertical vibrations.
This type utilizes the rubber insulator’s spring force to absorb transverse vibrations.
A bushing type mount in which a rubber insulator is sandwiched between an inner and an outer cylinder.
Slit Cylinder Type
A cylindrical mount with a slit in it, satisfying spring constants in various directions. This type is currently in wide use.
Fluid Type (Liquid-Filled Compound)