Vehicle Seat Slide Lock Mechanism Backlash Reduction
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Solution Overview
Problem
Existing seat slide apparatuses for vehicles face issues with backlash and stability under load, particularly during vehicle collisions, due to pin deformation and stress concentration at locking protrusions, leading to uncomfortable seating and potential unlocking of the seat.
Innovation Solution
A seat slide apparatus with a lock member and biasing mechanism that includes a flat plate portion with lock portions, which engages with locking protrusions to restrict movement, and a support shaft with a wedging portion to maintain stability under varying loads, ensuring secure locking and reduced backlash.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a pin connects the lock member to the upper rail for rotation, then the lock member can rotate to engage and disengage locking protrusions, but the pin deforms under load during vehicle collisions causing instability and potential unlocking
Solution Approach 1:
The support shaft is divided into a fixed portion (inserted in the upper rail) and a movable portion (projecting from the fixed portion). This segmentation allows the movable portion to absorb collision loads through relative movement, preventing deformation of the connection between lock member and upper rail, thus maintaining locking stability under load.
2Reliability
If the lock member is biased to move upward by a lock spring for automatic locking, then the locking protrusions engage with lock portions, but stress concentrates at the locking protrusions causing potential failure
Solution Approach 1:
The movable portion of the support shaft acts as an intermediary between the lock member and the upper rail. Under collision load, this intermediary absorbs stress through relative movement along the elongated hole, preventing stress concentration at the locking protrusions while maintaining the automatic locking function provided by the lock spring.
3Reliability
If the support shaft is fixed rigidly to prevent movement, then stability under load is improved, but backlash occurs during normal operation reducing seating comfort
Solution Approach 1:
The support shaft design transitions from a static fixed connection to a dynamic system where the movable portion can shift position. During normal operation, the movable portion remains fixed relative to the upper rail ensuring stability. During collision, it moves dynamically to absorb load, eliminating backlash while maintaining stability under varying conditions.
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 solution effectively reduces backlash and maintains stability under both normal and collision loads, providing a comfortable and secure seating experience by ensuring the seat remains locked relative to the rail.
Implementation Method 1
a lock spring (50) serving as a biasing member biasing the lock lever (30) to rotate about the support shaft (22) in a direction in which the flat plate portion (125) restricts the relative movement
Implementation Method 2
a support shaft biasing member biasing the support shaft to move in a direction orthogonal to the first and second directions of the relative movement between the first rail and the second rail
Implementation Method 3
a wedging portion formed at at least one of the elongated hole and the support shaft biasing member to make pressure-contact with the support shaft, the wedging portion restricting the support shaft from moving in the front/rear direction of the vehicle within the elongated hole
Data Source
AI summary
A seat slide apparatus for a vehicle includes a first rail, a second rail, a lock member, a biasing member, the lock member being rotatably connected to the second rail in a state where a support shaft fixed to one of the second rail and the lock member is positioned within an elongated hole formed at the other of the second rail and the lock member to be movable in first and second directions of the relative movement and is biased by a support shaft biasing member in a direction orthogonal to the first and second directions, and a restriction portion restricting the support shaft from moving within the elongated hole in the first and second directions in a case where a load applied in one of the first and second directions is smaller than a predetermined value.