Worm Reducer Coil Spring Preload Against Stick-Slip Sound
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Solution Overview
Problem
Worm reducers with coil springs often generate an abnormal stick-slip sound due to the interaction between the coil spring and the bearing, which existing designs fail to effectively mitigate without increasing complexity or part count.
Innovation Solution
A worm reducer design featuring a coil spring with a specific winding direction opposite to that of the preload member, where the coil spring contacts the bearing's outer surface, and a preload member is screwed into the housing to apply pressure, ensuring the coil spring's distal end is positioned within a predetermined range to minimize stick-slip sound generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a coil spring is used to urge the worm shaft toward the worm wheel, then backlash is prevented and collision sounds are restrained, but a stick-slip sound is generated between the coil spring and the bearing
Solution Approach 1:
The invention changes the winding direction parameter of the coil spring to be opposite to the winding direction of the preload member thread. This parameter change modifies the interaction between the coil spring and preload member, preventing the coil spring from rotating during assembly and eliminating the stick-slip sound between the coil spring and bearing while maintaining the backlash prevention function
Solution Approach 2:
The invention introduces a preload member as an intermediary component between the housing and the coil spring. The preload member transfers the pressing force to the coil spring while its thread winding direction is designed to oppose the coil spring's winding direction, creating friction that prevents rotation and eliminates the harmful stick-slip sound
2Force
If the coil spring is positioned to contact the bearing, then the worm shaft is properly urged toward the worm wheel, but the stick-slip sound between the coil spring and bearing occurs
Solution Approach 1:
The invention changes the friction parameter between the coil spring and preload member by designing opposite winding directions, creating sufficient friction to prevent rotation. This allows the coil spring to maintain proper contact with the bearing for force transmission while eliminating the rotational movement that causes stick-slip sound
3Manufacturing precision
If the preload member is screwed into the housing, then the coil spring is pressurized to maintain inter-shaft distance, but the coil spring may rotate and generate abnormal sound
Solution Approach 1:
The invention changes the winding direction parameter of the coil spring to be opposite to the thread winding direction of the preload member. This creates a frictional lock during the screwing process that prevents the coil spring from rotating, ensuring precise inter-shaft distance maintenance without generating abnormal stick-slip sounds
Solution Approach 2:
The invention designs the winding directions in advance so that when the preload member is screwed into the housing, the friction between the oppositely wound coil spring and preload member automatically prevents rotation. This preliminary design feature ensures proper positioning is maintained throughout the assembly process without requiring additional anti-rotation mechanisms
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
This configuration significantly reduces the likelihood of stick-slip sound occurrence between the coil spring and the bearing, maintaining optimal inter-shaft distance and preventing collision sounds even under vibration or sudden torque conditions.
Implementation Method 1
a coil spring that contacts an outer peripheral surface of the bearing and applies an urging force toward the worm wheel
Implementation Method 2
contact resistance between the coil spring and the preload member is greater than contact resistance between the coil spring and the bearing
Data Source
AI summary
A worm reducer includes a worm shaft; a worm wheel; a housing that houses the worm shaft and the worm wheel; a bearing that holds the worm shaft inside the housing; a coil spring that contacts an outer peripheral surface of the bearing and applies an urging force toward the worm wheel; and a preload member that is screwed into and fixed to the housing and pressurizes the coil spring. A winding direction of the coil spring is different from a winding direction of a thread of the preload member, and contact resistance between the coil spring and the preload member is greater than contact resistance between the coil spring and the bearing.