Reclining Device Cam-Driven Sequential Pawl Engagement
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Solution Overview
Problem
The existing reclining device structure experiences instability in lock strength due to variations in component accuracy, leading to incomplete engagement of sub-pawls with internal teeth, resulting in inconsistent lock performance under load.
Innovation Solution
The reclining device is designed such that the external tooth of the sub-pawl starts engaging with the internal tooth before the main pawl is fully engaged, ensuring stable lock strength by eliminating the state where only the main pawls engage without sub-pawls.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the main pawls and sub-pawls are designed to engage with internal teeth simultaneously, then the structure is simple, but variation in component accuracy causes incomplete engagement of sub-pawls, resulting in unstable lock strength
Solution Approach 1:
The cam is designed to push the sub-pawls into engagement with internal teeth before the main pawls are fully engaged. This preliminary action ensures that sub-pawls are already engaged when main pawls complete their engagement, preventing the unstable state where only main pawls are engaged. The sequential engagement is achieved through the cam's geometry and positioning, which contacts sub-pawls at a different radial distance than main pawls.
2Strength
If only main pawls are engaged with internal teeth, then the structure is simpler, but the lock strength becomes unstable under load
Solution Approach 1:
The cam has different local contact points for main pawls and sub-pawls. The distance from the cam's rotation axis to the contact point for sub-pawls is greater than that for main pawls, creating different engagement sequences. This local differentiation in the cam's geometry ensures that sub-pawls engage first, providing stable lock strength, while maintaining a unified cam structure.
3Device complexity
If the cam pushes all pawls equally, then the mechanism is simpler, but component accuracy variation causes inconsistent engagement timing
Solution Approach 1:
The cam's geometry is designed with different radial distances to contact points for sub-pawls versus main pawls. This parameter change in the cam's structure creates a built-in timing mechanism that ensures sub-pawls engage before main pawls, compensating for component accuracy variations without adding complex control systems.
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 ensures consistent and stable lock strength by ensuring all pawls engage properly, preventing relative rotation and enhancing the device's ability to restrict movement.
Implementation Method 1
a cam provided rotatably and coaxially with the first member and the second member between the first member and the second member and configured to push the main pawl and the sub-pawl in a lock position direction
Implementation Method 2
main pawls including external teeth engageable with the internal teeth, sub-pawls including external teeth engageable with the internal tooth... in a case where the main pawl and the sub-pawl are at the lock position, the external tooth of the main pawl and the internal tooth of the first member are in a fully-engaged state, the external tooth of the sub-pawl and the internal tooth of the first member are in a softly-engaged state, and relative rotation of the first member and the second member is restricted
Data Source
AI summary
A reclining device cylindrical first member including an internal tooth and an opening surface on one side; a main pawl including an external tooth engageable with the internal tooth; a sub-pawl including an external tooth engageable with the internal tooth; a second member stacked on an opening surface side of the first member and rotatable relative to the first member. The second member includes a pawl guide to guide the main pawl/sub-pawl between a lock position and an unlock position. A cam between the first and second members is configured to push the main pawl and sub-pawl in a lock direction; and a second cam between the cam and the main pawl is pushed by the cam at the lock position to contact the main pawl and the pawl guide.