Electric Parking Brake Spindle Thread for High-Force Rolling
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Solution Overview
Problem
Existing electric parking brake spindle drives with sawtooth thread profiles are difficult to produce efficiently due to their asymmetric design, leading to low thread closure and high manufacturing costs, and do not meet requirements for high clamping force and rapid adjustability.
Innovation Solution
A spindle drive with a symmetrical thread profile, featuring rounded profile troughs and flanks, which allows for better stress absorption and production reliability, including a specific geometry with a 28° flank angle and 1.25 mm pitch, and a method involving rolling after heat treatment for enhanced strength and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If an asymmetrical sawtooth thread profile is used, then the spindle drive can absorb loads in one direction with high efficiency, but the production complexity and manufacturing difficulty increase significantly
Solution Approach 1:
The patent applies asymmetry in reverse by using a symmetrical thread profile instead of the conventional asymmetrical sawtooth profile. This symmetrical design with rounded profile troughs eliminates the manufacturing difficulties associated with asymmetrical forming while maintaining load-bearing capabilities through optimized geometry and material flow during the rolling process.
Solution Approach 2:
The patent introduces curvature by rounding the profile troughs of the thread instead of using sharp corners. This rounded geometry facilitates material flow during forming operations, reduces stress concentrations, and enables reliable production through rolling processes while maintaining the structural integrity and load-bearing properties of the thread.
2Productivity
If forming methods are used to produce sawtooth profiles, then production can be achieved, but the thread closure is insufficient and cycle times are extended
Solution Approach 1:
The patent changes the geometric parameters of the thread profile from asymmetrical sawtooth to symmetrical with rounded troughs. This parameter change enables the use of rolling forming methods that achieve complete thread closure with overlapping material flow, significantly reducing cycle times while ensuring precise thread geometry and high manufacturing quality.
3Reliability
If a symmetrical thread profile with rounded profile troughs is used, then production reliability and strength are enhanced, but the thread geometry becomes more complex
Solution Approach 1:
The patent applies local quality by rounding only the profile troughs while maintaining straight profile flanks. This localized curvature application provides the stress-absorbing benefits and production reliability of rounded geometry at the critical stress points, while keeping the overall thread geometry simple and manufacturable through standard rolling processes.
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 symmetrical thread profile design enhances the strength and reliability of the spindle drive, enabling high clamping force and rapid adjustability while reducing production complexity and costs, and the method ensures a high-strength, compact, and cost-efficient electric parking brake.
Implementation Method 1
the profile troughs are rounded, in order for it to be possible for the stresses which are introduced into the thread under loading to be absorbed and therefore for a thread fracture to be avoided
Implementation Method 2
it can be produced with less complexity and more reliably with high quality by way of forming, in particular by way of rolling
Implementation Method 3
a method involving rolling after heat treatment for enhanced strength and efficiency
Data Source
AI summary
An electric parking brake (100) has a spindle drive (28) which is electrically actuable and self-locking. The spindle drive (28) comprise a spindle (34) with an external thread and a spindle nut (30) with an internal thread which is in engagement with the external thread. Here, the external thread and the internal thread have a symmetrical thread profile. Furthermore, the profile edges of adjacent profile crests of the external thread merge directly into one another via a rounded portion in the profile trough which lies in between. Furthermore, a method for producing a parking brake (100) of this type is provided.