Vehicle Door Latch Over-Center Spring Axial Positioning
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Solution Overview
Problem
Conventional vehicle door latch devices with over-center springs face issues such as unstable spring elastic force, difficult assembly, interference with other parts, and compromised smooth rotation due to strong axial spring pressure, as well as potential deviations and instability caused by vehicle vibrations.
Innovation Solution
A vehicle door latch device design featuring a lock lever pivotably secured to a housing case with a lock shaft, an abutting pin, and an over-center spring with coil parts loosely inserted on a spring support shaft, where the spring leg parts are paired to elastically hold the abutting pin, and a spring support shaft with ribs to restrict movement, ensuring stable positioning and reduced backlash.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the coil part is merely loosely wound around the spring support shaft, then assembly is easier, but the coil part axially deviates with respect to the spring support shaft due to vehicle vibration, impairing stable switching operation
Solution Approach 1:
The patent changes the parameter of spring positioning by introducing spring positioning ribs that protrude from the spring support shaft. These ribs engage with grooves or flat surfaces on the coil part, converting the loose winding state into a positioned state that prevents axial deviation while maintaining ease of assembly through simple geometric features.
2Force
If long spring leg parts are used to extend in the radial direction, then the spring can effectively hold the lock lever, but interference with other parts needs to be avoided and dead space is likely to be generated
Solution Approach 1:
The patent repositions the spring leg parts from extending in the radial direction to extending in the axial direction of the spring support shaft. This dimensional change allows the spring to maintain its holding force while reducing radial footprint and eliminating dead space that would be created by long radial extensions.
3Ease of manufacture
If engaging end parts extending parallel to the axial direction are formed on the coil part, then the spring can be engaged with the lock lever, but strong action is caused by unnecessary spring pressure along the axial direction, compromising smooth rotation
Solution Approach 1:
The patent extracts the unnecessary axial spring pressure by changing the orientation of the engaging end parts from axial extension to radial extension. This removes the harmful axial force component while preserving the essential engagement function between the spring and lock lever.
4Ease of operation
If the spring leg parts extend long in the radial direction, then the spring can abut against the lock lever, but interference with other parts needs to be avoided
Solution Approach 1:
The patent changes the extension direction of spring leg parts from radial to axial, allowing the abutment function to be achieved without long radial extensions that would interfere with other door latch components.
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 achieves rational space usage, improved ease of operation, reduced spring force instability, and enhanced maintenance by allowing the lock lever and spring support shaft to be superposed, reducing axial backlash and maintaining strength, while also supporting a child lever for childproof functionality.
Implementation Method 1
the lock lever is elastically held on any one side of the lock position and the unlock position with a spring dead point as a boundary by elastic force of the over-center spring
Implementation Method 2
In the conventional over-center spring, a torsion coil spring is used
Data Source
AI summary
An over-center spring of a vehicle door latch device has a coil part that is loosely inserted on a spring support shaft, and a base end side spring leg part. A leading end side spring leg part elastically holds an abutting pin and is paired with the base end side spring leg part. A lock lever is provided with a slot through which the spring support shaft passes. The lock lever and the spring support shaft are disposed to be superposed on each other in an axial direction of the spring support shaft.