Vane Motor | Diagram , Construction , Working , Application
Vane motors work on the same principle as vane pumps in reverse. In these motors, the pressurised fluid acting on the vanes cause them to rotate and thus developing the torque output. They are suitable for low speed applications than gear motors.
Vane Motor Parts :
- Slotted Rotor : It is the rotating element of the vane moor. It is mounted on a drive shaft. It has slots to accommodate the freely sliding vanes.
- Vanes : These are usually rectangular. Vanes help maintain air columns inside the motor housing. Due to the difference in the forces acting on the vane surfaces the motor rotates.
- Motor Housing : It is hollow cylinder in which the rotor and vanes are kept. The center of rotor is offset with the housing. It has ports for inlet and outlet of air. The inlet port is at the place where the rotor is nearest to the housing. Outlet port is usually diametrically opposite.
Like vane pumps, vane motors can be classified as unbalanced or balanced vane motors.
But most vane motors used universally are of the balanced-rotor type. Because hydraulic unbalance causes large radial bearing loads which limit the use of unbalanced vane motors to low pressure operation. Therefore most vane motors have a mechanical configuration similar to that of the balanced vane pump. Also balanced vane motors are fixed-displacement units.
Fig. illustrates the construction and operation of a balanced-type vane motor. The vane motor produces torque by the hydraulic pressure that acts , on the exposed surfaces of the vanes, which slide in and out of the rotor connected to the driver shaft. To accommodate starting and low-speed operation, it is usually necessary to provide a force, in addition to the centrifugal force, to move the vane radially outward/Springs are commonly used for this purpose. The larger the exposed area of the vane, or higher the pressure, more is the torque developed. Also, as the inlet connects to two opposing pressure passages, the side loads on the rotor are balanced with each other (Fig.6.10(h)).
Advantages of Vane Motors
The vane motors have relatively less internal leakage than gear motors. Also the balanced vane motors eliminate the side and bearing loads.
Disadvantages of Vane Motors
Vane type motors, like gear motors, do not generate maximum torque at very low speeds, due to internal leakage. So both gear and vane type motors are not suitable for vehicle drive applications.
Vane motors are available at pressure ratings to about 175 bars, with rated capacities upto 15 Lps, and at speeds up to 4000 rpm.
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