Force-Balanced Drivetrain Assembly for Low-Handle Vibration
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Solution Overview
Problem
Existing personal care devices with force unbalanced mechanical resonators experience mechanical stress and failures due to unwanted vibrations transferred from the resonator to the handle, often resulting from improper fixation of the nodal point, leading to stress and failure.
Innovation Solution
A drivetrain assembly with a force balanced mechanical resonator design, comprising a load mass connected to a fixed point by a spring, a balance mass connected to the same fixed point by a second spring, and a coupling spring connecting the load and balance masses, with an actuator exerting force on both masses to minimize stress and vibrations, utilizing a configuration that balances forces to reduce net reaction forces on the handle.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a nodal point is rigidly fixed to the housing in a force balanced mechanical resonator, then vibrations are eliminated, but high local stresses cause resonator failure
Solution Approach 1:
The nodal point is selectively suspended only at its specific location rather than rigidly fixing the entire resonator housing interface. This localized compliance allows vibrations to be eliminated at the critical nodal point while avoiding high stresses that would occur with rigid fixation of the entire structure.
Solution Approach 2:
A counterbalancing mass is introduced to create a force-balanced system where the centrifugal force of the counterweight offsets the reactive forces from the primary resonator. This force balancing eliminates the need for rigid fixation and reduces stress on the resonator structure while maintaining vibration elimination.
2Reliability
If the nodal point fixation is not exactly at the nodal point of the eigenmode, then force balancing is achieved, but unwanted vibrations occur
Solution Approach 1:
The system incorporates feedback through the suspended nodal point configuration that automatically adjusts to maintain proper force balancing. The suspension allows the nodal point to find its correct position dynamically, providing self-correction capability that eliminates sensitivity to initial positioning errors while maintaining vibration elimination.
3Device complexity
If a force unbalanced resonator is used, then device complexity is reduced, but mechanical stress and failures increase due to vibrations transferred to the handle
Solution Approach 1:
A counterbalancing mass is introduced to create a force-balanced system where the centrifugal force of the counterweight offsets the reactive forces from the primary resonator. This force balancing eliminates the need for rigid fixation and reduces stress on the resonator structure while maintaining vibration elimination.
Solution Approach 2:
The nodal point is selectively suspended only at its specific location rather than rigidly fixing the entire resonator housing interface. This localized compliance allows vibrations to be eliminated at the critical nodal point while avoiding high stresses that would occur with rigid fixation of the entire structure.
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 force balanced drivetrain assembly reduces mechanical stress and failures by minimizing vibrations transferred to the handle, ensuring efficient operation and extended device lifespan by maintaining low net forces on the housing, even when minor tolerances or external factors affect the resonator frequencies.
Implementation Method 1
a first spring member connected at a first end to the primary resonator and at a second end to the fixed member; a second spring member connected at a first end to the secondary resonator and at a second end to the fixed member
Implementation Method 2
The actuator force excites the resonance of the system, which ensures high rotational amplitude at low input power
Implementation Method 3
an actuator configured to exert force on at least the secondary resonator
Data Source
Figure 1
Figure 2~3
Figure 4~5
AI summary
A drivetrain assembly (100) for a personal care device (10), the drivetrain assembly including a primary resonator (110); a secondary resonator (140) configured to reduce vibrations transmitted from the motor to a body (12) of the personal care device; a fixed point (130) positioned between the primary resonator and the secondary resonator; a first spring member (120) connected at a first end to the primary resonator and at a second end to the fixed point; a second spring member (150) connected at a first end to the secondary resonator and at a second end to the fixed point; a coupling spring (160) connected at a first end to the primary resonator and at a second end to the secondary resonator; and an actuator (170) configured to exert force on at least one of the primary resonator and the secondary resonator.