Vehicle Seat Reclining Device Hardness-Graded Pawl Cam Mechanism
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Solution Overview
Problem
Conventional vehicle seat reclining devices fail to maintain locking strength when subjected to large loads, such as those caused by collisions, due to the breakdown of the support structure of the pawls and ratchet engagement.
Innovation Solution
The vehicle seat reclining device incorporates engagement teeth members with higher hardness than the pressure cam, which are designed to press and plastically deform the cam when a large load is applied, maintaining engagement and increasing locking strength by deforming guide and pressure cam components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the pawls are spring biased radially outwardly to maintain locking engagement with the ratchet, then the locking strength is sufficient for normal operation, but the support structure breaks down when large loads are applied, causing the pawls to rotate with the ratchet instead of maintaining engagement
Solution Approach 1:
The patent changes the material parameter (hardness) of the engagement teeth members to be greater than the pressure cam. This parameter change allows the engagement teeth members to resist deformation and maintain their shape under large loads, preventing the support structure breakdown that occurs in conventional designs where the pawls rotate with the ratchet.
Solution Approach 2:
The patent employs different materials with different hardness properties for the engagement teeth members and the pressure cam. The engagement teeth members are made with higher hardness material to maintain structural integrity, while the pressure cam is made with lower hardness material to allow controlled plastic deformation. This composite material approach resolves the contradiction by ensuring the support structure remains stable under large loads.
2Strength
If the engagement teeth members have higher hardness than the pressure cam, then the engagement teeth members can plastically deform the pressure cam without buckling under large loads, but this requires precise control of the deformation to maintain locking strength
Solution Approach 1:
The patent converts the potentially harmful effect of plastic deformation into a beneficial mechanism. When large loads are applied, the engagement teeth members are designed to plastically deform the pressure cam in a controlled manner. This controlled deformation allows the engagement teeth members to absorb energy and maintain their engagement without buckling, thereby maintaining locking strength while accommodating extreme loads.
Solution Approach 2:
The patent designs the pressure cam with lower hardness to act as a cushioning element before the engagement teeth members are subjected to excessive stress. The pressure cam is intended to deform first, absorbing the impact and preventing the engagement teeth members from buckling. This beforehand cushioning mechanism ensures that the engagement teeth members maintain their structural integrity even under large loads.
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 design enhances the locking strength of the reclining device by allowing engagement teeth members to absorb and distribute large loads without buckling, ensuring the seat back remains securely positioned even under significant rotational displacement forces.
Implementation Method 1
the engagement teeth members are pressed by the other of the connecting elements in a radially inward direction in which the engagement teeth members are disengaged therefrom, so as to press the pressure cam with an increased buckling strength and plastically deform the same
Data Source
AI summary
Each of the pawls that are capable of rotationally locking a reclining device has a hardness greater than a slide cam that is capable of pressing the pawls to engage a ratchet. When a large load capable of forcibly rotationally displacing the ratchet is applied thereto while the pawls mesh with the ratchet, the pawls are pressed by the ratchet in a radially inward direction in which the pawls are disengaged therefrom, so as to press the slide cam with an increased buckling strength and plastically deform the same.