Brake Booster Trapezoidal Thread Clearance Design
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Solution Overview
Problem
Existing brake boosters face challenges in maintaining long service life due to inadequate lubrication and increased wear and friction in trapezoidal thread gearings, which are prone to noise and jamming.
Innovation Solution
The brake booster design features intermeshing trapezoidal threads with specifically tailored flank, tip, and bottom clearances, allowing for effective lubricant circulation and distribution, ensuring permanent lubrication and reduced wear, with the flank clearance being 8-12% of the tooth width, tip clearance also at 8-12%, and bottom clearance minimized to prevent jamming.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If small flank clearance is provided in trapezoidal threads to avoid noise, then acoustic noise is reduced, but lubricant circulation is insufficient leading to increased wear and reduced service life
Solution Approach 1:
The patent applies different clearance values to different regions of the trapezoidal thread engagement. Specifically, the flank clearance (between opposing thread flanks) is designed to be smaller (0.05-0.15mm) to reduce noise, while the tip clearance (between thread tips) is designed to be larger (0.2-0.5mm) to enable lubricant circulation. This local differentiation of geometric parameters resolves the contradiction by optimizing each region for its specific function.
2Reliability
If adequate lubricant circulation is provided to reduce wear, then service life is increased, but larger clearances increase noise and reduce power transmission efficiency
Solution Approach 1:
The patent differentiates clearance dimensions in specific regions: tip clearance is enlarged (0.2-0.5mm) to create grease depositories and enable lubricant circulation, while flank clearance is kept small (0.05-0.15mm) to maintain power transmission efficiency and reduce noise. This localized optimization allows the system to achieve both adequate lubrication and acceptable noise levels.
3Ease of manufacture
If standard DIN 103 trapezoidal thread clearances are used, then manufacturing is simplified, but lubrication is inadequate leading to increased friction and wear
Solution Approach 1:
The patent modifies the standard DIN 103 clearance parameters by introducing differentiated clearance values: a smaller flank clearance (0.05-0.15mm) and a larger tip clearance (0.2-0.5mm). This parameter change transforms the standard single-clearance design into a dual-clearance system that provides both manufacturing simplicity and improved lubrication through the formation of grease depositories at the thread tips.
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 service life of the brake booster by ensuring reliable lubrication and reducing friction, allowing for efficient power transmission and safe operation, even under varying conditions.
Implementation Method 1
the intermeshing trapezoidal threads have a flank clearance and a tip clearance which are greater than a bottom clearance... advantageous grease depositories are formed which, in response to a direction reversal of the drive of the spindle gear, are influenced by the turning of the external thread relative to the internal thread in such a way that lubricant in the grease depositories is purposefully circulated within the toothing
Data Source
AI summary
A brake booster for a brake master cylinder of a motor vehicle includes a drive motor that is connected/connectable by a gear unit to a pressure piston for the brake master cylinder, the gear unit converting a rotational motion of the drive motor into a translational motion of the pressure piston to actuate the brake master cylinder, and the gear unit including a rotatable spindle nut and a non-rotatable spindle rod having intermeshing trapezoidal threads that have have a flank clearance and a tip clearance that are greater than a bottom clearance.