vane motors

VANE MOTORS

1. What are Vane Motors?

• Vane motors work on the same principle as vane pumps in reverse.

• In these motors, the pressurised fluid acting on the vanes causes them to rotate and thus developing the torque output.

• They are suitable for low speed applications than gear motors.

2. Construction and Operation

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.5.12 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.5.12(b)).

3. 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.

4. 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.

5. Ranges

Vane motors are available at pressure ratings to about 175 bars, with rated capacities upto 15 Lps, and at speeds up to 4000 rpm.