Servo Valve Neutral Setting Mechanism for Hydraulic Machines
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Solution Overview
Problem
Hydraulic servo valves face challenges in achieving symmetrical volumetric deliveries due to manufacturing tolerances, leading to asymmetrical neutral positions and inefficient shutdowns of hydraulic machines, as the control piston's position deviates from the geometric center, causing uneven flow rates in both delivery directions.
Innovation Solution
A neutral setting apparatus with a rotatable input shaft, eccentric cylindrical extension, and an adjustable control piston, along with a sliding part and guide element, ensures symmetrical deflection and maintains the neutral position, allowing for identical volumetric deliveries in both directions by aligning the input shaft, sliding part, and control piston simultaneously, thus compensating for manufacturing tolerances and ensuring the hydraulic machine remains at a standstill.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the control piston is centered geometrically in the control cylinder, then the neutral position is predefined structurally, but manufacturing tolerances cause the control piston to deviate from the geometric center, resulting in asymmetrical volumetric deliveries
Solution Approach 1:
The neutral setting apparatus performs preliminary adjustment of the control piston position before operation. By pre-centering the control piston using the adjustable mechanism (comprising adjustment screw, thrust bearing, and spring), the system compensates for manufacturing tolerances in advance, ensuring symmetrical volumetric deliveries without requiring extremely precise manufacturing of individual components.
Solution Approach 2:
The spring-loaded adjustment mechanism allows the control piston to self-center automatically. The spring applies continuous force to push the control piston toward the geometric center of the control cylinder, and the adjustable thrust bearing provides fine-tuning capability. This self-adjusting system compensates for tolerance variations without requiring complex external positioning equipment.
2Reliability
If the control piston position deviates from the geometric center due to tolerances, then the neutral position is not exactly set, but adding a neutral setting mechanism increases device complexity
Solution Approach 1:
The neutral setting apparatus integrates multiple functions into a compact assembly. The adjustment screw serves both as a positioning mechanism and a locking mechanism; the thrust bearing provides both adjustment capability and mechanical support; the spring provides both centering force and compensation for position variations. This multi-functional design achieves reliable neutral positioning without adding excessive complexity.
Solution Approach 2:
The thrust bearing acts as an intermediary element between the adjustment screw and the control piston. It translates the rotational adjustment of the screw into precise linear positioning of the control piston, while the spring acts as an intermediary force element that maintains continuous contact and provides automatic centering. These intermediary components simplify the overall control mechanism while ensuring reliable neutral positioning.
3Measurement precision
If the control edges of the control piston and control cylinder have tolerances, then the control edge overlaps are affected, but adjusting the neutral position requires simultaneous alignment of multiple components
Solution Approach 1:
The adjustment mechanism replaces complex mechanical alignment procedures with a simple threaded adjustment system. Instead of requiring precise mechanical positioning of multiple components simultaneously, the adjustment screw provides a single-point control that automatically aligns the control piston with the control cylinder center through the spring force and thrust bearing interface, simplifying the alignment operation.
Solution Approach 2:
The neutral setting apparatus changes the position parameter of the control piston continuously through the adjustment screw mechanism. By rotating the screw, the position of the control piston can be fine-tuned incrementally until the optimal neutral position is achieved, allowing operators to compensate for control edge tolerance variations without requiring precise pre-alignment of all components.
Data Source
AI summary
The invention relates to a neutral setting apparatus for adjustable hydraulic machines, in particular the adjustment of the neutral position of a servo valve. In particular, the invention relates to servo adjustment devices with mechanically adjustable control pistons, wherein the forces necessary for this can be applied mechanically, electro-magnetically, pneumatically or hydraulically. The invention relates to a neutral setting apparatus of an adjustable hydraulic machine, with a housing in which a mounted input shaft is arranged, to one end of which a torque can be applied for rotating the input shaft about an axis. Thus providing a robust and cost-effective setting mechanism for the neutral position of a servo valve.