Fluid Controlled Swash Plate for Axial Piston Pump

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Solution Overview

Problem

Conventional axial piston pumps in traction drive systems of skid steer construction vehicles lack the ability to efficiently vary displacement without mechanical control pistons, limiting flexibility and efficiency in fluid flow management.

Innovation Solution

A variable displacement axial piston pump design featuring a pivotally supported swash plate that tilts in response to fluid pressure changes in control chambers, allowing for independent control of piston stroke and fluid flow direction without mechanical control pistons, utilizing fluid passages and ports to manage fluid flow and displacement.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If mechanical control pistons are used to tilt the swash plate, then the pump displacement can be controlled, but the device complexity increases and the efficiency of fluid flow management decreases

Engineering Contradiction:

Improvedisplacement control capabilityVSAvoidmechanical control structure

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent removes the mechanical control piston from the system entirely. Instead of using a mechanical piston to tilt the swash plate, the invention uses fluid pressure directly applied to the swash plate through fluid passages in the port block to achieve displacement control, thereby simplifying the mechanical structure.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent replaces the mechanical control system with a hydraulic control system. Fluid pressure is used to directly tilt the swash plate instead of mechanical linkages, and the same fluid is used for both control and pumping functions, eliminating the need for separate mechanical control components.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Ease of operation

If separate control systems are used for piston stroke and fluid flow direction, then precise control is achieved, but the device complexity increases

Engineering Contradiction:

Improvecontrol precisionVSAvoidcontrol system structure

Core Design Contradiction:

Ease of operationVSDevice complexity

Solution Approach 1:

The patent combines the control of piston stroke and fluid flow direction into a single integrated system. The swash plate angle simultaneously controls both the piston stroke length and the fluid flow direction through the port block passages, eliminating the need for separate control mechanisms.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The swash plate serves multiple functions: it controls piston stroke length, directs fluid flow through the port block, and its position is controlled by fluid pressure from the same system. This multi-functionality reduces the number of separate control systems needed while maintaining precise control.

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Adaptability or versatility

If mechanical control pistons are used, then displacement control is achieved, but the mechanical complexity and space requirements increase

Engineering Contradiction:

Improvedisplacement variation capabilityVSAvoidcontrol chamber space

Core Design Contradiction:

Adaptability or versatilityVSVolume of moving object

Solution Approach 1:

The patent eliminates the mechanical control piston and its associated control chamber. The swash plate is tilted directly by fluid pressure applied through passages in the port block, removing the need for a separate mechanical control piston volume and reducing the overall space required for control mechanisms.

Inventive Principle:

Principle #2Taking out (Extraction)

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

Enables flexible and efficient control of piston displacement and fluid flow, enhancing operational efficiency and adaptability in hydrostatic traction drive systems by directly using hydraulic pressure to adjust the swash plate angle, thus optimizing fluid management and reducing mechanical complexity.

Implementation Method 1

the swash plate is operable to tilt with respect to the port block, for varying a stroke length of the plurality of pistons, in response to a fluid pressure change in the at least one control chamber

Methodology Applied

Scientific EffectFluid pressure: Pressure Increase

Implementation Method 2

utilizing fluid passages and ports to manage fluid flow and displacement

Methodology Applied

Scientific EffectHydraulic pressure: Pressure Increase

Data Source

PatentUS10247178B2Variable displacement axial piston pump with fluid controlled swash plate

Publication Date: 2019.04.02 BOSCH REXROTH CORP

AI summary

A variable displacement axial piston pump including a cylinder block defining a plurality of cylinder bores, each receiving a piston. A swash plate having a piston-supporting surface is pivotally supported relative to the cylinder block. A port block defines first and second pumping ports arranged in fluid communication with the plurality of cylinder bores such that, during operation of the pump, one of the first and second pumping ports is configured to supply fluid to the cylinder bores for pumping, and the other of the first and second pumping ports is configured to receive fluid pumped from the plurality of cylinder bores. The swash plate partially defines at least one variable volume control chamber, and the swash plate is operable to tilt with respect to the port block in response to a fluid pressure change in the at least one control chamber.