Hydrostatic Axial Piston Liner Recess Design
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Solution Overview
Problem
Hydrostatic axial piston machines face challenges in handling varying operating conditions, where liners either crack under high pressures or experience piston seizure at low pressures due to inadequate clearance and heat dissipation, leading to additional costs and complexity in managing different operational states.
Innovation Solution
The liners are designed with an axially delimited, circumferential recess region where the depth increases and decreases multiple times, creating protrusions that do not reach the outer diameter, providing permanent support and sufficient clearance to prevent cracking and piston seizure, while the base contour is curved without edges or straight portions to reduce the risk of cracking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If liners are designed as intact hollow cylinders without recesses, then they can withstand high operating pressures without cracking, but they experience piston seizure at high rotation speeds and low pressures due to insufficient clearance and heat dissipation
Solution Approach 1:
The liner is designed with a circumferential recess region in its outer half, creating local structural variation. This recess region provides clearance for thermal expansion and improved heat dissipation at the loaded outer surface, while the inner half remains intact to maintain overall structural strength. The localized modification allows the liner to handle both high pressure and high rotation speed conditions effectively.
2Reliability
If liners are equipped with circumferential recess regions to prevent piston seizure, then they can withstand high rotation speeds and low pressures, but they may break prematurely under high operating pressures
Solution Approach 1:
The recess region is specifically located in the outer half of the liner where the greatest forces and heat loads occur, while the inner half remains intact. This localized design provides clearance and heat dissipation where needed without compromising the overall structural integrity of the liner under high pressure conditions.
3Reliability
If different liner variants (intact vs. compensated) are used for different application cases, then optimal performance for specific operating conditions is achieved, but additional costs and complexity arise in planning, procurement, stockholding, and assembly
Solution Approach 1:
The liner design combines features of both intact liners and compensated liners into a single universal variant. The circumferential recess region in the outer half provides the benefits of compensated liners (clearance for expansion, heat dissipation) while the intact inner half maintains the strength of original liners. This multi-functional design allows a single liner type to handle both high pressure and high rotation speed conditions, eliminating the need for multiple liner variants.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration enhances the strength and durability of the liners, reducing the risk of breakage and piston seizure across different operating conditions, allowing for broader application without the need for multiple liner variants, thus simplifying and cost-reducing the design and maintenance of hydrostatic axial piston machines.
Implementation Method 1
The circumferential groove creates a clearance between the liner and the wall of the cylinder bore, into which the liner can expand
Implementation Method 2
the leakage through the gap between the liners and the displacement pistons moving to and fro in the liners is so high that the guide faces between the displacement pistons and the liners are well lubricated
Implementation Method 3
the leakage through the gap between the liners and the displacement pistons moving to and fro in the liners is so high that the guide faces between the displacement pistons and the liners are well lubricated and the generated heat is dissipated well
Data Source
AI summary
A hydrostatic axial piston machine includes a cylinder drum having a substantially hollow cylindrical base body, and liners. The body includes cylinder bores located around a central axis. The liners have an outer diameter press-fitted into the bores such that an outer end face of each liner is positioned in a region of an opening of a respective bore, and such that an inner end face of each liner is positioned deep within the respective bore. An outer half of each liner, starting from the outer end face, includes an axially delimited circumferential recess in an outer casing surface of the liner. The machine is configured to operate with great forces acting between the liners and displacement pistons. The recess in each liner is shaped such that, in an axial section through the liner enclosing an axis of the liner, a depth of the recess increases more than once and decreases more than once.