Bolted Servo Assembly With Eccentric Centering for Hydrostatic Units
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Solution Overview
Problem
Existing hydrostatic servo units face issues with imprecise centering due to manufacturing and assembly tolerances, leading to hysteresis and the need for specific designs for each displacement unit, limiting standardization and assembly flexibility.
Innovation Solution
A hydraulic servo assembly unit with a servo piston that can be pressurized for linear movement, featuring a movable output element and an eccentric mechanism, allowing for adjustable centering and compatibility with various hydrostatic units, and enabling separate installation inside or outside the unit casing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If two springs are arranged on both sides of the servo piston to provide centering force, then the servo piston can be centered, but the centering precision deteriorates due to hysteresis and cumulative tolerances
Solution Approach 1:
The patent removes one of the two springs from the conventional design, leaving a single spring on one side of the servo piston. This extraction eliminates the hysteresis caused by two opposing springs and reduces the cumulative effect of manufacturing tolerances, thereby improving centering precision while maintaining sufficient centering reliability through the remaining spring and hydraulic pressure balance.
Solution Approach 2:
The patent introduces an asymmetric design by placing only one spring on one side of the servo piston rather than symmetric springs on both sides. This asymmetry allows for more precise control of the centering force and eliminates the hysteresis loop that occurs with symmetric spring arrangements, directly addressing the centering precision problem.
2Ease of manufacture
If the servo unit is integrated into the housing of the displacement unit, then assembly is simplified, but design standardization and adaptability deteriorate
Solution Approach 1:
The patent divides the servo unit into a separate, modular component that can be independently manufactured and then assembled to the displacement unit. This segmentation allows the servo unit to be standardized as a separate module while maintaining adaptability to different displacement unit models through standardized mounting interfaces and adjustable components.
Solution Approach 2:
The patent designs the servo unit with universal mounting capabilities that allow it to be adapted to different displacement unit models. The adjustable centering mechanism and standardized interfaces enable a single servo unit design to serve multiple applications, achieving both manufacturing efficiency and design versatility.
3Measurement precision
If the centering position is adjusted before assembly into the displacement unit, then the servo unit can be calibrated, but post-installation adjustment capability is lost
Solution Approach 1:
The patent incorporates an adjustable centering mechanism that allows preliminary adjustment of the servo piston centering position during assembly, while also enabling post-installation fine-tuning. This dual-stage adjustment capability ensures precise centering accuracy during initial assembly while maintaining operational flexibility for future adjustments if needed.
Solution Approach 2:
The patent implements a dynamic adjustment mechanism that allows the centering position to be modified both during assembly and after installation. This dynamic capability transforms the previously static centering system into one that adapts to actual operating conditions, combining preliminary calibration with post-installation flexibility.
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
Provides a robust, reliable, and economically viable centering mechanism that can be adjusted post-installation, enhancing design flexibility and reducing manufacturing costs by allowing universal use across different hydrostatic units.
Implementation Method 1
A piston head of the servo piston can be pressurized such that the servo piston can move linear relative to a servo cylinder formed in the servo housing
Implementation Method 2
A first end of an eccentric mechanism can be attached to a central part of the piston rod such that a second end of the eccentric mechanism rotates when the servo piston is moving
Data Source
AI summary
A hydrostatic servo assembly unit (1) for being arranged inside, outside or distant from a variable displacement hydrostatic unit (100) and for controlling the displacement of the variable displacement hydrostatic unit (100). The servo assembly unit (1) includes a servo housing (10) in which at least one servo piston (40) is arranged. The piston head (42) of the servo piston (40) can be pressurized such that the servo piston (40) can move linear relative to a servo cylinder (12) formed in the servo housing (10). The servo assembly unit (100) further includes a movable output element (49) protruding outside of the servo housing (10), which can be mechanically coupled to a displacement element (102) of a variable displacement hydrostatic unit (100).