Reclining Adjuster Lock Mechanism Backlash Reduction
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Solution Overview
Problem
Reclining adjusters face challenges in size reduction, increased strength, and backlash reduction, particularly in locking mechanisms for both normal use and emergency situations.
Innovation Solution
A reclining adjuster design featuring a lock mechanism with a first and second bracket, an engaging member, and an emergency lock actuation mechanism that securely locks the seatback relative to the seat cushion, utilizing a worm gear system with a lead angle greater than the friction angle to prevent rotation and eliminate backlash.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the worm and worm wheel are used with lead angle larger than friction angle for continuous variable adjustment, then the reclining angle can be adjusted continuously, but backlash occurs causing extraneous noise and reduced seating comfort
Solution Approach 1:
The worm gear is designed to dynamically switch between two states: during normal operation, the lead angle allows continuous variable adjustment; during locking, the worm is pressed against the worm wheel by spring force to eliminate backlash. This dynamic state change resolves the contradiction between adjustability and noise elimination.
2Object-generated harmful factors
If the worm is pressed toward the worm wheel side by spring force to reduce backlash, then extraneous noise is reduced, but the structure becomes more complex
Solution Approach 1:
The spring force mechanism is merged with the existing worm and worm wheel locking structure. The spring is integrated into the assembly to press the worm against the worm wheel, combining the backlash elimination function with the existing mechanical components rather than adding a separate complex system.
3Reliability
If the lock mechanism is designed for reliable locking, then seating comfort is improved, but the size of the mechanism increases
Solution Approach 1:
The worm gear parameters (lead angle, friction angle relationship) are optimized to achieve reliable locking with compact dimensions. By carefully selecting the lead angle to be larger than the friction angle for adjustment mode, and using spring force to press the worm against the wheel for locking mode, reliable locking is achieved without increasing overall mechanism size.
4Reliability
If the emergency lock mechanism uses inner teeth and outer teeth for preventing tilting, then collision protection is provided, but the overall structure becomes more complex
Solution Approach 1:
The inner teeth and outer teeth of the worm gear assembly serve multiple functions: they enable continuous variable adjustment during normal operation, provide backlash elimination through spring-pressed engagement, and act as an emergency lock mechanism for collision protection. This multi-functionality reduces overall structural complexity despite the added safety features.
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
The design effectively locks the seatback, reduces backlash, and enhances strength while maintaining a compact size, ensuring reliable locking and comfort by eliminating wobbling and extraneous noise.
Implementation Method 1
the lead angle is made larger than the friction angle, and in the unlocked state of the worm continuously variable adjustment of the reclining angle of the seatback relative to the seat cushion is permitted
Data Source
AI summary
A reclining adjuster has a lower bracket fixed to a seat cushion; an upper bracket fixed to a seatback and connected to the lower bracket so as to be rotatable about a shaft; a lock mechanism capable of having a locked state where rotation of the upper bracket relative to the lower bracket is locked and a released state where the lock is released; and an emergency lock mechanism for preventing relative rotation between the lock mechanism and the upper bracket when it occurs. In the emergency lock mechanism, when a cam projection of an outer toothed ring gear is pressed in the circumferential direction by a cam pin of a disk member by the relative rotation therebetween, the outer toothed ring gear meshes with both inner teeth of the lower bracket and inner teeth of the upper bracket.