Hydrostatic Yoke Position Control via Magnetic Coupling

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Solution Overview

Problem

Existing hydrostatic module adjusting devices suffer from imprecision in yoke position control due to unavoidable play and progressive gear ratio issues in the control connection between the adjusting piston and the yoke, leading to increased imprecision with larger pivoting angles.

Innovation Solution

A control arrangement featuring an electromagnetically controllable hydraulic proportional valve with a non-positive locking mechanical return device, including an axially movable sensing piston and a helical return spring, is disposed axially parallel to the adjusting cylinder and radially spaced from the yoke's pivot axis, allowing direct transfer of the yoke's pivoting position to the control piston, with a convex feedback surface for precise control characteristics.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If a mechanical return device is used to transfer the control position of the adjusting piston to the control piston of the position regulating valve, then the control connection is established, but play in the control connection causes imprecision in yoke position control

Engineering Contradiction:

Improveyoke position control precisionVSAvoidcontrol connection reliability

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The patent replaces the mechanical return device with a magnetic coupling system. The magnetic coupling transfers the control position from the adjusting piston to the control piston without mechanical contact, eliminating play and improving precision while maintaining reliable force transmission.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Adaptability or versatility

If the adjusting piston is connected to the yoke by a pivot lever, then the yoke can be pivoted to adjust displacement volume, but progressive gear ratio causes increased imprecision with larger pivoting angles

Engineering Contradiction:

Improvedisplacement volume adjustment rangeVSAvoidyoke position control precision

Core Design Contradiction:

Adaptability or versatilityVSMeasurement precision

Solution Approach 1:

The patent eliminates the pivot lever mechanical connection and uses magnetic coupling instead. This direct magnetic coupling between the adjusting piston and control piston removes the progressive gear ratio effect, maintaining consistent control precision across the full displacement volume adjustment range.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Measurement precision

If an electromagnetically controllable hydraulic proportional valve is used, then precise control of adjusting pressure difference is achieved, but device complexity increases

Engineering Contradiction:

Improveadjusting pressure difference control precisionVSAvoidcontrol arrangement complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent combines the position sensing and force transmission functions into a single magnetic coupling system. The magnet assembly serves both as the sensing element for position feedback and as the force transmission medium, eliminating the need for separate mechanical return devices and simplifying the overall control arrangement.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The magnetic coupling system performs multiple functions simultaneously: it provides position feedback, transmits control force, and eliminates mechanical play. This multi-functionality reduces the number of separate components needed and simplifies the control arrangement while maintaining precise pressure difference control.

Inventive Principle:

Principle #6Universality (Multi-functionality)

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 solution provides increased precision in yoke position control by eliminating imprecision caused by return device play and adapting control characteristics for specific applications, ensuring accurate and progressive linear or degressive control of the yoke's pivoting position.

Implementation Method 1

position regulating valve in the form of an electromagnetically controllable hydraulic proportional valve

Methodology Applied

Scientific EffectElectromagnetic force: Electromagnet

Implementation Method 2

acting on the adjusting piston with an adjusting pressure difference of a hydraulic pressure medium

Methodology Applied

Scientific EffectHydraulic pressure: Hydraulic Press

Implementation Method 3

return device comprises an axially movable, guided sensing piston and a return spring in the form of a helical spring

Methodology Applied

Scientific EffectElastic potential energy: Spring

Data Source

PatentUS9518567B2Adjusting device of a hydrostatic module

Publication Date: 2016.12.13 ZF FRIEDRICHSHAFEN AG

AI summary

An adjusting device of an axial piston machine having a displacement volume that is adjusted by a pivoting yoke. The adjusting device has a cylinder, which is radially spaced from and tangential to the yoke pivot axis. A piston communicates with the yoke and is adjusted by hydraulic pressure change. A control arrangement has a position regulating valve with a control piston which can set the hydraulic pressure acting on the piston. A mechanical return can transfer the yoke pivoting position to the control piston. The valve is axially parallel to the cylinder and radially spaced from the yoke pivot axis. The return comprises an axially movable sensing piston and coaxial return spring which are axially adjacent to the valve. The sensing piston abuts a yoke surface that is eccentric with respect to the pivot axis and connected to the control piston by the return spring.