Webbing Take-Up Device Gear Axial Movement Suppression
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Solution Overview
Problem
Existing webbing take-up devices face issues with slight axial movement of gears, which can lead to rattling and instability in the transmission of rotation force, affecting the efficiency and reliability of the overload release mechanism.
Innovation Solution
A webbing take-up device design that includes a spool, motor, first and second gears, a retaining member, and a clutch member, where the first gear is sandwiched between the second gear and the retaining member, with a restriction portion to prevent axial movement of the retaining member, and a rotation stopper to prevent relative rotation, ensuring smooth operation and stabilization of the gear system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a small diameter gear and a large diameter gear are respectively supported on a support shaft of a clutch housing, then the overload release mechanism can function, but slight axial movement of the gear occurs causing rattling and instability
Solution Approach 1:
A retaining member is introduced as an intermediary component between the first gear and the second gear. This retaining member has a restriction portion that prevents axial movement of the first gear, thereby eliminating the slight axial movement and rattling while maintaining the overload release mechanism's functionality.
Solution Approach 2:
The retaining member is pre-installed on the support shaft before assembling the gears. The restriction portion of the retaining member is positioned in advance to restrict axial movement of the first gear, preventing instability before it occurs during operation.
2Reliability
If the first gear is sandwiched between the second gear and the retaining member, then axial movement is restricted, but the structure becomes more complex
Solution Approach 1:
The retaining member serves multiple functions: it retains the first gear on the support shaft, restricts axial movement through its restriction portion, and provides a mounting surface for the clutch member. By combining multiple functions into a single component, the overall structural complexity is minimized while achieving the desired stability.
3Reliability
If a rotation stopper is added to prevent relative rotation of the retaining member with respect to the second gear, then gear stability is improved, but manufacturing complexity increases
Solution Approach 1:
The rotation stopper function is merged with the retaining member by forming a projection on the retaining member that fits into a corresponding groove on the second gear. This integration eliminates the need for a separate rotation stopper component, simplifying manufacturing while preventing relative rotation between the retaining member and the second gear.
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 suppresses slight axial movement of the first gear, stabilizes the gear engagement, and enhances the transmission performance by preventing rattling, thus ensuring reliable operation of the overload release mechanism.
Implementation Method 1
a clutch member that is attached to the retaining member and transmits rotation between the first gear and the second gear by frictional engagement with the retaining member
Data Source
AI summary
A webbing take-up device is obtained capable of suppressing slight axial direction movement of a gear configuring a mechanism to release overload. A large gear portion of a two-step gear configuring an overload release mechanism of the webbing take-up device is sandwiched between a small gear portion end face of a small gear portion and a bottom portion of a rotor. This thereby enables rattling which is slight axial direction movement of the large gear portion to be suppressed.