Crown Gear Speed Reduction Mechanism Backlash Prevention
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Solution Overview
Problem
Existing reduction gears, such as harmonic drive and oscillating bevel reduction gears, face challenges in achieving a high reduction ratio while preventing backlash, maintaining smooth rotation, and compacting the mechanism to save weight, making them unsuitable for applications like robot hands.
Innovation Solution
A modified crown reduction gear with a pressing mechanism that rotates, a fixed crown gear, and a movable crown gear with a one-tooth difference, where the movable gear engages with the fixed gear at a slant, dispersing contact locations to prevent backlash and allow for compact design, using a flexible material for enhanced smoothness and strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If harmonic drive reduction gear uses circular spline and Flexspline with even number difference in teeth, then rotation smoothness is improved and backlash is prevented, but reduction ratio is limited to 2/N and mechanism size and weight increase
Solution Approach 1:
The patent applies asymmetry by using crown gears with an odd number difference in teeth (specifically 1 tooth difference) between the fixed crown gear and movable crown gear, rather than the conventional even number difference. This asymmetric tooth difference enables engagement at two locations while achieving a reduction ratio of 1/N, resolving the contradiction between smooth rotation and compact size.
2Productivity
If oscillating bevel reduction gear uses fixed bevel gear and movable bevel gear with one tooth difference, then high reduction ratio is achieved, but rotation smoothness is reduced and backlash occurs
Solution Approach 1:
The patent employs curved tooth surfaces on the crown gears, where the tooth surfaces are formed with specific curvature radii (R1 for fixed crown gear, R2 for movable crown gear). This curvature enables simultaneous engagement at two locations, achieving both high reduction ratio and smooth rotation without backlash.
3Productivity
If bevel gears are combined in oscillating bevel reduction gear, then high reduction ratio is achieved, but axial direction size increases and mechanism becomes larger and heavier
Solution Approach 1:
The patent transitions from the conventional oscillating bevel gear's single-point contact to two-location engagement by utilizing the radial dimension of crown gears. The movable crown gear engages the fixed crown gear at two symmetric locations, achieving high reduction ratio without increasing axial length.
Data Source
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AI summary
A reduction gear capable of satisfying, at high level, each of: realizing a high reduction ratio; preventing backlash by securing rotation smoothness; and carrying out compactification and weight saving of entire mechanism is provided. The reduction gear of the invention is a modified crown reduction gear, comprising: a pressing mechanism 16 operated to rotate; a fixed crown gear 2 fixed to an external member 15; a movable crown gear 1, wherein the difference in the number of teeth between the gears is one; and an output axis 3 flexibly attached to the gear 1. The gear 1 engages with the gear 2 at a slant by pressing-force provided from the mechanism 16. In this instance, contact locations of teeth of the gears 1 and 2 are dispersed at two places existing at both sides between which a gradient center line intervenes.