Axial Piston Pump Zero-Crossover Control Without Orifices
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Solution Overview
Problem
Existing pivotable axial piston pumps in hydrostatic traction drives for mobile working machines face challenges with dynamic control, particularly during zero crossover, due to the need for orifices which increase product variance, require additional installation space, restrict pivoting dynamics, and are optimized for only one operating point, making precise control difficult.
Innovation Solution
A method controlling a pivotable axial piston pump using a double-acting actuating cylinder with centering springs and pressure-reducing valves, where orifices are eliminated by detecting zero crossover time to implement a sudden change in actuating pressure, allowing continuous direction change without dynamics restriction, reduced variance, and lower costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If orifices are used in the adjustment device for actuating pressure medium flow, then the axial piston pump can pivot through the zero position, but the pivoting dynamics are reduced and precise control becomes difficult
Solution Approach 1:
The patent removes the orifices from the adjustment device entirely. Instead of using orifices to regulate actuating pressure medium flow, the system uses direct supply to the actuating chambers, eliminating the flow restriction and associated dynamics limitations while maintaining the ability to pivot through the zero position.
Solution Approach 2:
The patent changes the control parameter from orifice-based flow regulation to direct pressure supply with electronically controlled pressure-reducing valves. This allows dynamic adjustment of actuating pressure without the physical flow restrictions imposed by fixed orifices, improving pivoting dynamics and control precision.
2Reliability
If orifices are installed in the adjustment device, then actuating pressure can be regulated, but additional installation space is required and product variance increases
Solution Approach 1:
The patent integrates the pressure regulation function directly into the pressure-reducing valves without requiring separate orifices. The valves incorporate all necessary flow control and pressure regulation capabilities in a single component, reducing installation space and simplifying the overall adjustment device structure.
3Stress or pressure
If orifices are used for actuating pressure medium flow, then pressure can be built up, but the orifice diameter is only optimum for one operating point, restricting adaptability
Solution Approach 1:
The patent replaces fixed orifices with electronically controlled pressure-reducing valves that can dynamically adjust their opening degree and flow characteristics. This allows the system to adapt to different operating points and pivoting speeds, maintaining optimal performance across a wide range of conditions rather than being restricted to a single design point.
4Reliability
If orifices are installed in the adjustment device, then actuating pressure can be controlled, but manufacturing precision requirements increase product variance and costs
Solution Approach 1:
The patent replaces the mechanical orifice system with electronically controlled pressure-reducing valves. This substitution eliminates the need for precision-machined orifices with tight tolerance requirements, as the electronic control system can achieve the necessary pressure regulation through software-controlled valve actuation, thereby reducing manufacturing precision requirements and associated costs.
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 method enables continuous change of direction without restricting pump dynamics, reduces variance and costs, and improves controllability, especially during positioning, by eliminating the need for orifices and optimizing actuating pressure changes based on zero crossover detection.
Implementation Method 1
The actuating piston is prestressed into a central position by means of two centering springs which act in opposition to one another
Implementation Method 2
The actuating pressure in the two actuating chambers is respectively regulated by means of an electroproportional pressure-reducing valve
Implementation Method 3
a first actuating pressure medium supply line (22A) with a first pressure-reducing valve (18A) for supplying a first actuating pressure (pstA) to the first actuating chamber (8A) and a second actuating pressure medium supply line (22B) with a second pressure-reducing valve (18B) for supplying a second actuating pressure (pstB) to the second actuating chamber (8B)
Data Source
AI summary
In a drive unit which has an axial piston pump and an electronic control unit, the axial piston pump is pivoted with a method in which pressure-reducing valves which act in opposition to one another are suddenly energized. Since in this respect no orifices are provided in the adjustment device, a so-called initiation jump of the excited current gives rise to a sudden reduction in the assigned actuating pressure or the actuating pressure difference formed therefrom. Then, a zero crossover jump of the excited current or of the excited currents is carried out in order to overcome the centering spring and therefore ensure a continuous zero crossover of the axial piston pump. Furthermore, a hydrostatic traction drive includes such a drive unit.