Drum Brake Expansion Mechanism With Idle-Rotation Wear Readjustment
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Solution Overview
Problem
Existing drum brake spreading devices with integrated adjustment devices require high spreading force, leading to increased frictional forces and inefficiencies during adjustment and wear compensation.
Innovation Solution
A spreading device with an elastically prestressed locking member and a coaxial drive mechanism, featuring a locking toothing system and idling rotation design, decouples the adjustment process from the spreading force, allowing for efficient and force-reduced readjustment and initial adjustment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a stiff ball ramp arrangement is used for converting rotary drive movement into translatory spreading movement, then the spreading device can be driven robustly in rotation, but the adjustment process requires high spreading force resulting in increased frictional forces
Solution Approach 1:
The invention segments the functions of the spreading device into two independent parts: a stiff ball ramp arrangement for spreading movement and a separate coaxial adjustment mechanism for wear compensation. This segmentation allows the adjustment function to be decoupled from the spreading force, enabling robust spreading while reducing adjustment force requirements.
Solution Approach 2:
The invention introduces a ball ramp arrangement as an intermediary mechanism between the rotary drive and the adjustment screw. This intermediary converts the rotary adjustment movement into translatory movement with reduced force requirements, mediating between the stiff spreading mechanism and the adjustment function.
2Adaptability or versatility
If a separate threaded adjustment screw is used for wear compensation, then the adjustment function can be implemented, but the adjustment process generates high internal force levels affecting efficiency and component wear
Solution Approach 1:
The invention replaces the conventional threaded adjustment screw mechanism with a ball ramp-based adjustment mechanism. This substitution changes the mechanical principle from thread friction to ball rolling contact, significantly reducing frictional losses and energy consumption during the adjustment process.
Solution Approach 2:
The invention changes the mechanical parameters of the adjustment mechanism by using balls with specific diameters and ramp geometries optimized for low-friction operation. This parameter optimization reduces the force levels and energy loss during wear compensation while maintaining the adaptability function.
3Volume of moving object
If the locking member is arranged elastically prestressed axially against the adjustment screw, then the coaxial drive can be implemented in a space-saving manner, but the locking device requires precise toothing engagement
Solution Approach 1:
The invention uses elastic prestressing of the locking member to create a controlled preload force that ensures reliable toothing engagement. By optimizing the prestress parameter, the system achieves secure locking without requiring excessive manufacturing precision, as the elastic force compensates for minor dimensional variations.
Solution Approach 2:
The elastic prestressing of the locking member beforehand provides a cushioning effect that absorbs dimensional tolerances and ensures reliable toothing engagement. This pre-applied elastic force acts as a buffer, reducing the impact of manufacturing variations on the locking mechanism's performance.
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 provides a robust, space-saving, and efficient adjustment mechanism that reduces frictional forces and improves control consistency, enabling reliable wear compensation with lower operational force levels.
Implementation Method 1
at least one ball ramp arrangement for converting a rotary drive movement into a translatory spreading movement
Implementation Method 2
locking member which is arranged elastically prestressed axially against the adjusting screw
Data Source
AI summary
The invention relates to an improved expansion device (1) for a drum brake (4) having an integrated readjustment device (8) having a readjusting screw (9) therein that can be blocked by means of a spring-biased latching unit (12) which, for a reliable readjustment function, provides for the latching unit (9) to permit a defined idle rotation (L) of the readjusting screw (9), which is defined constructionally by a first stop (13) acting in a first direction of revolution and a second stop (14) acting in the opposite direction of revolution.