Variable Helix Bi-Helical Gear for Hydraulic Apparatus
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Solution Overview
Problem
Hydraulic gear apparatuses with traditional straight teeth experience mechanical and hydraulic noise due to load variations and fluid encapsulation, while bi-helical teeth with opposite helices face manufacturing limitations and axial thrust issues.
Innovation Solution
A bi-helical toothed wheel with a variable helix angle along the axial direction, featuring a continuous cross-sectional shape without encapsulation, split into initial, central, and terminal zones with varying helix angles, ensuring axial balance and seamless fluid transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If traditional straight teeth are used, then the gear structure is simple and easy to manufacture, but mechanical vibrations and noises occur due to load variation and access/return shocks
Solution Approach 1:
The patent applies helical teeth with variable helix angle along the axial direction, transforming the static straight tooth structure into a dynamic configuration. This allows the teeth to gradually mesh and unmesh during rotation, dynamically distributing the load and eliminating the sudden access/return shocks characteristic of straight teeth, thereby reducing mechanical vibrations and noises while maintaining manufacturing feasibility
2Object-affected harmful factors
If helical teeth with opposite helices are used, then mechanical noise is reduced through gradual meshing, but axial thrust forces are generated that require thrust bearings
Solution Approach 1:
The patent changes the helix angle parameter along the axial direction of the teeth, using variable helix angle instead of constant opposite helices. This parameter variation allows the axial thrust forces generated by one helix to be compensated by the opposite helix at different axial positions, eliminating the need for separate thrust bearings while maintaining the noise-reducing gradual meshing characteristic
3Object-affected harmful factors
If herringbone gears with opposite helices are used, then axial thrust is suppressed, but manufacturing precision is limited due to delicate cusp machining
Solution Approach 1:
The patent introduces variable helix angle along the axial direction, which dynamically adjusts the tooth geometry to eliminate the cusp region. This dynamic configuration allows the teeth to mesh gradually without creating sharp cusps, thereby enabling high-precision machining while maintaining the axial thrust suppression characteristic of herringbone gears
4Strength
If thermal nitridation treatment is applied to herringbone gears, then tooth hardness is increased, but tooth twisting occurs that requires wider tolerances and reduces efficiency
Solution Approach 1:
The patent changes the helix angle parameter along the axial direction, which modifies the stress distribution during thermal nitridation treatment. This variable helix angle configuration prevents the tooth twisting that occurs in conventional herringbone gears, allowing high hardness treatment while maintaining tight tolerances and high efficiency
Data Source
AI summary
The invention relates to a bi-helical toothed wheel (1) with non-encapsulating profile for a hydraulic gear apparatus, of the type bound to a support shaft (5) to form a driving or driven wheel of the hydraulic apparatus and comprising a plurality of teeth (6) extended with variable helix angle with continuous function in the longitudinal direction, wherein the teeth profile keeps a shape continuity in each cross section thereof. More particularly, each tooth of the toothed wheel is longitudinally split in three zones: initial (A), central (B) and terminal (C) zones, and the central zone (B) has a variable helix angle, while the initial (A) and terminal (c) zones have a constant helix angle. The invention allows to manufacture contra-rotating rotors, having a non-encapsulating profile and a helix shape such as to suppress the angular point at the center of the rotors themselves and therefore all the problems related to their machining.