- Describe, with the aid of a sketch, the operation of a variable delivery axial piston pump.
(10)
Operation of a Variable Delivery Axial Piston Pump
1. General Arrangement
- The pump consists of a cylinder block (barrel) mounted on and rotating with the drive shaft.
- Several pistons are arranged axially in the block, parallel to the shaft.
- A swash plate (tilting plate) is positioned at an adjustable angle to the shaft axis.
- A valve (port) plate controls fluid flow to suction and discharge ports.
2. Principle of Operation
- As the shaft rotates, the pistons slide against the angled swash plate.
- The angle of the swash plate causes the pistons to reciprocate in their cylinders.
- On piston retraction, the piston draws fluid into the cylinder (suction stroke).
- On piston extension, the piston forces fluid out into the delivery port (delivery stroke).
3. Variable Delivery Feature
- The stroke length of the pistons (and therefore the pump’s displacement) depends on the angle of the swash plate.
- Large angle → longer stroke → maximum delivery.
- Small angle → shorter stroke → reduced delivery.
- Zero angle (vertical swash plate) → no piston reciprocation → zero delivery.
- The swash plate angle is adjusted by a servo piston or control mechanism, which can respond to operator setting, system load, or pressure demand.
4. Advantages
- Flow can be matched to system demand without changing shaft speed.
- Reduces wasted power and heat, improving efficiency.
- Can also function as a motor if fluid flow is reversed.
Sketch (what to draw)
A simple labelled diagram should include:
- Drive shaft and rotating cylinder block.
- Pistons arranged axially.
- Swash plate at an angle (show with arrows how piston reciprocates).
- Suction port (inlet) and delivery port (outlet).
- Indication of how changing swash plate angle alters piston stroke length.