Valve Spool Notch Geometry for Linear Hydraulic Flow Gain
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Solution Overview
Problem
Hydraulic valve spools often exhibit non-linear flow gain characteristics, making the movement of hydraulic actuators unpredictable and requiring complex machining techniques like EDM, which are costly.
Innovation Solution
A spool design featuring annular metering lands with a combination of sine notches and additional notches, such as square or triangular notches, to achieve substantially-linear flow gain, allowing for predictable actuator movement without expensive manufacturing processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional spool designs are used, then manufacturing is simpler, but flow gain characteristics become non-linear making actuator movement unpredictable
Solution Approach 1:
The spool is segmented into multiple lands (first land, second land, third land) with distinct notch patterns. Each land segment contributes differently to the overall flow characteristic, allowing the combination to achieve linear flow gain while each individual segment can be manufactured using standard techniques.
Solution Approach 2:
Different regions of the spool (different lands) have different local geometries with specific notch patterns. The first land has a first pattern of notches, the second land has a second pattern, and the third land has a third pattern. This local differentiation allows optimization of flow characteristics in specific zones while maintaining manufacturability.
2Manufacturing precision
If complex machining techniques like EDM are used, then linear flow gain can be achieved, but manufacturing cost increases
Solution Approach 1:
By dividing the spool into multiple lands with different notch patterns, the complex linear flow characteristic is achieved through combination of simpler individual segments. This segmentation allows each land to be manufactured with standard machining techniques rather than requiring expensive EDM for the entire spool geometry.
Solution Approach 2:
The invention changes the geometric parameters (notch patterns, land positions, diameters) of multiple spool regions to collectively achieve linear flow gain. By adjusting these parameters across different lands, the overall system achieves the desired flow characteristic without requiring complex manufacturing processes for any single region.
3Ease of operation
If the spool moves axially to control fluid flow, then valve function is achieved, but non-linear flow gain makes actuator movement unpredictable
Solution Approach 1:
The spool geometry is segmented into multiple lands with different notch patterns that collectively produce linear flow gain during axial movement. This segmentation allows the spool to maintain a relatively simple overall structure while achieving predictable actuator movement through the combined effect of its segments.
Solution Approach 2:
The different lands have asymmetric and different notch patterns relative to each other. The first land has a first pattern of notches, the second land has a second pattern, and the third land has a third pattern. This asymmetric design across multiple lands creates the linear flow characteristic that makes actuator movement predictable.
Data Source
Figure 1A
Figure 1B
Figure 2A~2C
AI summary
An example spool includes a shaft varying in diameter along a length of the shaft, and a plurality of annular lands formed on the shaft and spaced-apart by respective reduced diameter annular neck portions. The plurality of annular lands comprise at least one annular metering land, and wherein the at least one annular metering land comprises: one or more sine notches formed as a portion of a sine wave, and one or more additional notches having a different shape from the one or more sine notches.