In the procurement process of the hydraulic industry, some customers will have such questions when they see the technical parameters of the piston pump: "Why do most hydraulic axial piston pumps or radial piston pumps have an odd number of pistons, such as 7, 9, or 11?"
This seemingly simple question actually contains the deep principles of hydraulic design and mechanical dynamic balance. Today, Poocca Hydraulic Manufacturer will take you to understand why the piston pump has an odd number of pistons, and help you better maintain your piston pump.
Behind the design of odd number of pistons: structure and balance
Main reason: avoid dynamic imbalance and reduce vibration
When the piston pump is working, the piston reciprocates continuously in the cylinder body. If the number of pistons is an even number, it often causes two symmetrical pistons to absorb or discharge oil at the same time. This will produce instantaneous torque fluctuations and uneven flow pulsations, resulting in greater vibration of the whole machine.
The use of odd number of pistons can make each piston evenly distributed on the circumference, staggered working angles, and achieve a balance between hydraulic and mechanical loads, thereby greatly reducing pump vibration and noise and improving the stability of the whole machine.
Poocca technology example:
Our Kawasaki K3V/K5V series and Rexroth A10VSO series all use 7-plunger, 9-plunger or 11-plunger structures, which are more stable and have a lifespan of more than 5,000 hours.
Structural matching: the angle of the swash plate or the slanted shaft and the design of the oil distribution plate
Hydraulic piston pumps (especially axial piston pumps) usually work with swash plates or slanted shaft structures. In order to achieve the oil suction and oil discharge actions of each piston at different angles in turn during the rotation process, the pistons need to be distributed on the circumference of the cylinder in an asymmetric manner.
The odd-number structure can just avoid the symmetrical overlap of the oil inlet and outlet holes on the oil distribution plate, prevent oil from being tangled or impacted, and is conducive to a more reasonable oil distribution path design.
More balanced dynamic torque
When the pump shaft rotates, each piston generates an alternating torque on the pump shaft. If the number of pistons is an even number, it may cause the alternating torque to be superimposed, causing uneven load on the main shaft. The odd-number structure can be staggered between multiple piston actions to disperse the impact force, which is beneficial to reduce bearing wear and extend the life of the pump.
Most models manufactured by Poocca Hydraulics are in stock and support OEM/ODM and technical selection services.
Why do you need to know this?
For you as an intermediary customer, understanding the design logic of "odd-number pistons" will help you explain the advantages of Poocca products to customers more professionally during sales and enhance trust.
For you as an end customer, choosing pump products with reasonable structure and smooth operation can avoid high-frequency maintenance, reduce downtime, and improve the economy of the overall equipment.
Poocca Hydraulic Manufacturer-Your Trustworthy Supply Partner
As a professional hydraulic manufacturer, Poocca has its own factory, professional R&D team and strict quality control system. We focus on:
Hydraulic piston pumps (full range of axial and radial)
Gear pumps, vane pumps, hydraulic motors, hydraulic valves
Support global export, can provide prototype testing and customization services
Poocca piston pumps all adopt odd-number piston design, strictly pass the factory dynamic balance test, stable performance and fast delivery.
Technology determines quality, structure affects efficiency
The core of hydraulic pumps is not only pressure and flow, but also "rationality of structure". Odd number of pistons is one of the secrets of stable operation of Poocca hydraulic pumps. We understand the importance of every detail of the hydraulic system to customers, and are committed to providing professional, efficient and reliable hydraulic solutions to customers around the world.
Welcome to contact Poocca sales engineers for selection suggestions and accurate quotations!
