Bolted Hydrostatic Servo Assembly With Adjustable Centering
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Solution Overview
Problem
Existing hydrostatic servo units face issues with imprecise centering, requiring specific designs for each displacement unit, leading to high manufacturing costs and assembly difficulties, and lack of adjustability after installation.
Innovation Solution
A hydrostatic servo unit with a two-head servo piston and eccentric mechanism, allowing for adjustable centering and independent mounting, enabling modular use across various hydrostatic units and devices.
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 tolerance accumulation
Solution Approach 1:
The patent removes one of the two springs from the system, keeping only a single spring on one side of the servo piston. This eliminates the hysteresis effect caused by two opposing springs and prevents tolerance accumulation, thereby improving centering precision while maintaining the centering capability through the remaining spring and hydraulic pressure balance.
Solution Approach 2:
The patent changes the centering mechanism from a mechanical spring-based system to a hydraulic pressure-based system. By using hydraulic pressure to balance the servo piston position instead of relying on two mechanical springs, the system achieves higher centering precision and eliminates the hysteresis inherent in mechanical spring systems.
2Ease of manufacture
If the servo unit is integrated into the housing of the displacement unit, then assembly is simplified, but design standardization becomes impossible and production costs increase
Solution Approach 1:
The patent divides the servo unit into a separate, independent module that can be mounted externally on the displacement unit housing. This segmentation allows the servo unit to be designed as a standardized component that can be applied to various displacement units, improving design standardization and reducing production costs while maintaining ease of assembly through external mounting.
Solution Approach 2:
The patent designs the servo unit as a universal component with standardized mounting interfaces that can be applied to different types and sizes of displacement units. This universality enables design standardization and economies of scale in production, while the external mounting arrangement preserves assembly simplicity.
3Manufacturing precision
If the centering position is adjusted before assembling the servo unit to the displacement unit, then the servo unit can be pre-adjusted, but post-installation adjustment is impossible and tolerance compensation is limited
Solution Approach 1:
The patent introduces adjustable elements within the servo unit that allow the centering position to be dynamically modified after installation. This could include adjustable springs, movable stops, or adjustable hydraulic pressure settings, enabling the centering position to be fine-tuned post-installation to compensate for assembly tolerances and achieve optimal performance.
4Ease of operation
If a piston rod protrudes through one side of the servo spool to transmit movement externally, then mechanical coupling is achieved, but asymmetrical behavior occurs and pressure application is limited
Solution Approach 1:
The patent acknowledges and accommodates the asymmetrical design caused by the piston rod protruding through one side. Rather than attempting to create symmetry, the design accepts the asymmetrical pressure application and compensates for it through proper sealing arrangements and force balance calculations, maintaining reliability while achieving the necessary mechanical coupling for external movement transmission.
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, facilitating universal application and reducing manufacturing costs by allowing interchangeable use across different hydrostatic units.
Implementation Method 1
a servo spring is arranged between the two piston heads
Implementation Method 2
The piston heads can be pressurized such that the servo piston can move linearly along the spool axis
Data Source
Figure 1
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AI summary
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) comprises 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 comprises 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).