Securing Screw with Latching Levers for Play-Free Steering Gear Fixation
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Solution Overview
Problem
Existing securing mechanisms for units in motor vehicle steering gears, such as pinions, face issues with play and frictional wear due to different material coefficients of thermal expansion, leading to reduced securing effectiveness over time and increased complexity in assembly, particularly with zinc die-cast adjusting screws.
Innovation Solution
A securing screw with latching levers that engage with an internal thread in the housing, allowing for a tool-assisted release mechanism via radially inward movement of the latching levers, ensuring play-free fixation and easy assembly, even with different thermal expansion coefficients.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional securing screw is used, then assembly is simple, but play forms over service life due to thermal expansion differences
Solution Approach 1:
The securing screw is segmented into multiple functional components: the screw body, latching lever, and latching lug. This segmentation allows each component to perform its specific function - the screw body provides threading engagement, the latching lever provides radial movement capability, and the latching lug provides positive engagement with the housing, collectively preventing play while maintaining assembly simplicity
Solution Approach 2:
The latching lever is designed as a dynamic component that can move radially between engaged and disengaged positions. During assembly, the latching lever moves radially outward to engage the latching lug in the housing, creating a positive lock that prevents play. This dynamic capability allows the same structure to provide both secure fixation and easy release
2Ease of manufacture
If a zinc die-cast adjusting screw is used, then initial securing is achieved, but preload decreases over service life leading to play
Solution Approach 1:
The latching lever and latching lug are designed to create preliminary action during assembly - as the screw is tightened, the latching lever is forced radially outward by the tightening torque, causing the latching lug to engage positively with the housing before the screw reaches its final position. This preliminary engagement ensures that the screw maintains its preload and prevents play throughout service life
Solution Approach 2:
The invention converts the harmful effect of material thermal expansion differences into a beneficial feature. The latching mechanism is designed to accommodate thermal expansion and contraction of the screw and housing materials while maintaining positive engagement, transforming what would be a source of play into a feature that maintains securing effectiveness across temperature variations
3Reliability
If a latching mechanism is added, then play-free fixation is achieved, but assembly complexity increases
Solution Approach 1:
The latching mechanism is designed to be self-actuating during assembly. As the screw is tightened using conventional tools, the tightening torque automatically forces the latching lever radially outward, causing the latching lug to engage with the housing. No separate operation or special tool is needed to activate the latching mechanism - the assembly process itself activates it, maintaining ease of operation while achieving play-free fixation
Solution Approach 2:
The latching mechanism is merged with the screw structure itself rather than being a separate assembly. The latching lever is integrated into the screw body, and the latching lug is formed as part of the housing structure. This merging eliminates the need for separate latching components and operations, achieving play-free fixation without significantly increasing assembly complexity
4Object-affected harmful factors
If thread sealing agent is used, then sealing against external media is achieved, but manufacturing complexity increases
Solution Approach 1:
The invention extracts the sealing function from the thread sealing agent and relocates it to the latching mechanism. The latching lug and latching lever create a positive mechanical lock that inherently seals against external media by preventing relative movement between the screw and housing. This extraction eliminates the need for thread sealing agents while maintaining sealing performance, reducing manufacturing complexity
Data Source
AI summary
In a device for releasing a securing screw for a unit in a housing, in particular a pinion unit in a steering gear of a motor vehicle, the securing screw is connected via an external thread to an internal thread in the housing, wherein the securing screw is provided with a latching device, which has latching levers disposed distributed on the circumference of the securing screw, each of which said latching levers is provided with latching lugs disposed on the free ends of the latching levers. The latching lugs latch into teething gaps of a teething geometry of the housing. The latching devices can be connected to a tool in order to release the latching levers having the latching lugs from the latched position by means of a radially inwardly directed movement of the latching levers.