A
hydraulic motor transforms hydraulic energy into rotary mechanical
energy applied to a resisting object by means of a shaft connected with
the motor. They closely resemble hydraulic pumps in construction and
size. The difference being, instead of pushing the fluid as the pump
does, in a hydraulic motor the rotating elements (i.e. vanes, gears,
pistons, etc.) are pushed by the oil pressure to enable the motor shaft
to rotate and thus develop the necessary turning torque and continuous
rotating motion.
Types of Motors:
Hydraulic motors are classified as:
1.Uni-directional, or
2.Bi-directional.
As per their construction, hydraulic motors are of:
1.Gear type
This is generally a fixed capacity imbalanced motor. The hydraulic
imbalance in a gear motor is caused by gear teeth unmeshing. Meaning all
teeth subjected to system pressure are hydraulically balanced except for
one side of one tooth on one gear. This is the point where the torque is
developed. The larger the gear tooth or higher the pressure, more is the
torque produced.
2.Vane type
This is a positive displacement motor that develops an output torque at
its shaft by allowing hydraulic pressure to act in the vanes that are
extended. The vane motor includes: vanes, rotor, cam-ring, shaft and
port plates. In vane motors the imbalance is caused by the difference in
vane area exposed to hydraulic energy which is due to the eccentric
position of the rotor to the housing. When pressure oil enters the inlet
port, the unequal area of the vanes results in development of a torque
in the motor shaft. The larger the exposed area of the vane, or higher
the pressure, more is the torque that is developed. This makes the shaft
rotate.
3. Piston type
In general three types of piston motors exist. These include: These are
positive displacement motors that can develop an output torque at the
shaft by allowing oil pressure to act on the pistons. The piston type
motors include: in-line piston, axial piston and radial piston. The
axial piston motors are used for medium to high pressure and moderately
high power ranges whereas, radial piston motors are used for very high
pressure ranges.
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