Worm Gear Motor Unit Grease Tuning for Reverse Rotation Resistance
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Solution Overview
Problem
Speed reducer-equipped motor units with high reverse rotation resistance tend to increase starting voltage excessively, which is undesirable.
Innovation Solution
A speed reducer-equipped motor unit that includes grease with a solid additive, such as acrylic resin powder, to adjust the friction coefficient between the worm gear and worm wheel, ensuring appropriate reverse rotation resistance while minimizing excessive starting voltage by setting the addition amount of the additive within specific threshold values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If reverse rotation resistance is increased, then self-lock function is improved, but starting voltage becomes excessively increased
Solution Approach 1:
The invention changes the friction coefficient parameter by adding solid additives (acrylic resin powder, polyethylene powder, or polypropylene powder) to the grease at controlled concentrations (0.1-10 wt%, 0.01-5 wt%, or 0.1-5 wt% respectively). This parameter adjustment increases reverse rotation resistance while controlling starting voltage within acceptable limits (not exceeding 1.5 times the rated voltage).
Solution Approach 2:
The invention uses composite grease materials combining base oil, thickener, and solid additives. The composite structure integrates the lubricating properties of base oil, the structural properties of thickener, and the friction-increasing properties of solid additives, achieving both reliable self-lock function and controlled starting voltage characteristics.
2Reliability
If friction coefficient between worm gear and worm wheel is increased, then reverse rotation resistance is improved, but transmission efficiency decreases
Solution Approach 1:
The invention precisely controls the friction coefficient parameter by adjusting solid additive concentration within specific ranges. This optimization ensures the friction coefficient is sufficient for reverse rotation resistance (preventing motor reverse rotation when window is fully closed) but not excessively high to maintain acceptable transmission efficiency.
Solution Approach 2:
The solid additives are applied locally at the contact interface between worm gear and worm wheel through grease. This localized friction enhancement occurs only where needed for self-locking, while other transmission paths maintain efficient energy transfer.
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 motor unit effectively suppresses excessive starting voltage while maintaining reverse rotation resistance, ensuring reliable operation of mechanisms like power windows even under varying battery conditions.
Implementation Method 1
a solid additive that is dispersed in the base oil and increases a friction coefficient between the worm gear and the worm wheel as its addition amount increases
Implementation Method 2
a thickener that is dispersed in the base oil and forms a three-dimensional structure
Implementation Method 3
includes grease that lubricates the worm gear and the worm wheel
Data Source
AI summary
A motor unit for transmitting a driving force of a motor driven by a battery to an opening and closing mechanism through a worm gear and a worm wheel includes lubricating grease. The grease includes a solid additive that increases a friction coefficient between the worm gear and the worm wheel as its addition amount increases. The addition amount is not less than a first threshold and is not more than a second threshold. The first threshold is an addition amount for realizing a friction coefficient at which transmission efficiency from the worm wheel to the worm gear becomes 0 [%]. The second threshold is an addition amount for realizing a friction coefficient at which a starting voltage of the motor to move the opening and closing mechanism in an opening direction becomes a minimum guaranteed voltage of the battery after the opening and closing mechanism is restrained fully closed.