Motor Gear Case Board Cover Positioning Without Rattle
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Solution Overview
Problem
The existing motor device fixing structure for the board cover between the gear cover and gear case is prone to inaccurate positioning and rattles due to size variations and seal material repulsive forces, risking damage from excessive holding.
Innovation Solution
A motor device design featuring a board cover with a positioning protrusion part that press-fits into a recessed part on the gear case, combined with abutment parts on both the gear case and cover to ensure accurate positioning and prevent damage, using a polyacetal material for the board cover with a lower rigidity than the gear case.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the board cover is strongly held to avoid rattles, then the positioning accuracy and stability are improved, but the board cover may be damaged due to excessive holding force
Solution Approach 1:
The invention changes the physical state of the board cover by using a thermally expandable material. When heated, the material expands to fill the cavity, creating a secure fit without requiring excessive holding force. This parameter change (volume expansion with temperature) allows the board cover to be firmly positioned while avoiding damage to the cover itself.
Solution Approach 2:
The invention directly applies thermal expansion by heating the board cover made of thermally expandable material. The material expands when heated, increasing its volume to fill the cavity completely and create a tight fit. This thermal expansion mechanism achieves reliable positioning without needing strong mechanical holding forces that could damage the board cover.
2Ease of operation
If protrusion parts or support parts are used to fix the board cover, then the board cover can be held in place, but inaccurate positioning and rattles occur due to size variations and seal material repulsive forces
Solution Approach 1:
The invention uses a thermally expandable material that changes its physical parameters (volume and density) in response to temperature changes. This allows the board cover to adapt to size variations in the cavity and overcome repulsive forces from seal materials, achieving accurate positioning without requiring precise manufacturing tolerances for protrusion or support parts.
Solution Approach 2:
The invention transforms the static board cover into a dynamic system that can change its volume. The thermally expandable material allows the board cover to adjust its size dynamically, filling the cavity completely and eliminating gaps or rattles that would occur with fixed-size protrusion or support parts.
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 solution achieves accurate positioning of the board cover without rattles and minimizes the risk of damage, ensuring reliable operation and miniaturization of the motor device.
Implementation Method 1
The positioning protrusion part is press-fit into a positioning recess part
Implementation Method 2
at least a portion of the collapsed parts is collapsed by interference with an inner circumferential surface of the positioning recess part
Data Source
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AI summary
This motor device 1 includes: a motor part including an armature shaft; a speed reduction mechanism which includes a worm and a worm wheel and outputs the rotation of the armature shaft at a reduced speed; a gear case 40 which is provided with a bottom part and an opening part 42 and accommodates the worm and worm wheel in a rotatable manner; a gear cover 50 which covers the opening part 42 of the gear case 40; a circuit board 70 which is arranged between the speed reduction mechanism and the gear cover 50; and a board cover 80 which is arranged between the circuit board 70 and the speed reduction mechanism. The board cover 80 is provided with a positioning protrusion part 85 protruding toward the gear case 40, the gear case 40 is provided with a positioning recess part into which the positioning protrusion part 85 is press-fit, and the bottom surface of the positioning recess part and the tip surface of the positioning protrusion part 85 press-fit into the positioning recess part face each other with a gap therebetween.