ABS Sensor Ring Clip Retention for Thermal Expansion Mismatch
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Solution Overview
Problem
Existing disc brake systems face challenges with corrosion susceptibility of gray cast iron rotors, especially under transient heating and exposure to water, salt, and debris, which affects the accuracy of anti-lock braking system (ABS) sensors due to dimensional changes and potential disconnection of the exciter ring from the rotor.
Innovation Solution
An anti-lock sensor ring with cantilever spring retention clips and two surfaces - a retention surface and a support surface - is designed to provide a tool-less, fastener-less assembly, allowing for secure attachment to the brake band without interfering with ventilation channels, and accommodating differences in thermal expansion coefficients between materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an exciter ring is made from a material more corrosion-resistant than gray cast iron (e.g., low carbon steel), then corrosion resistance is improved, but thermal expansion mismatch with the rotor causes loss of tight fit and angular position accuracy
Solution Approach 1:
The exciter ring is segmented into multiple identical arc-shaped segments that can be independently mounted on the rotor. This segmentation allows each segment to accommodate thermal expansion independently while maintaining the overall circular geometry and angular position accuracy relative to the sensor.
Solution Approach 2:
The invention changes the geometric parameters of the exciter ring by introducing a circumferential gap between segments. This gap parameter allows the ring to expand thermally without constraining the segments, preventing distortion of the tooth geometry and maintaining angular position accuracy despite thermal expansion mismatch between the steel ring and iron rotor.
2Ease of operation
If the exciter ring is pressed onto the rotor hub, then assembly is simplified, but thermal expansion causes the ring to lose tight fit and rotate on the rotor
Solution Approach 1:
The exciter ring is divided into multiple segments that are pressed onto the rotor hub separately. Each segment maintains its own tight fit independently, and the cumulative effect of multiple segments provides overall secure attachment. This segmentation allows the ring to accommodate thermal expansion without losing the tight fit, as each segment can expand independently within its mounting location.
3Ease of manufacture
If the exciter ring is made as a single pressed piece, then manufacturing is simplified, but corrosion affects tooth uniformity and pulse train quality
Solution Approach 1:
The exciter ring is manufactured as separate segments rather than a single pressed piece. Each segment can be precisely manufactured with uniform teeth and then assembled onto the rotor. This approach protects the tooth geometry from corrosion that would affect a single continuous ring, as the segments can be individually protected or replaced, while maintaining manufacturing simplicity through modular production.
4Measurement precision
If the exciter ring is positioned to be easy to read by the sensor, then detection accuracy is improved, but it may interfere with ventilation channel airflow
Solution Approach 1:
The invention resolves the spatial conflict between sensor reading position and ventilation channel location by utilizing the axial dimension. The exciter ring is positioned axially at a location where it does not obstruct the radial airflow through the ventilation channels, while still maintaining the required radial proximity to the sensor for accurate detection. This dimensional separation allows both functions to coexist without interference.
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 solution ensures a secure, tool-free attachment of the anti-lock sensor ring to the disc brake rotor, maintaining accurate rotational speed detection and preventing disconnection due to thermal expansion, thereby enhancing the reliability and accuracy of ABS systems.
Implementation Method 1
said retention mechanism comprises cantilever spring retention clips (8) elastically deformable to snap on a disc brake band retention seat (27)
Implementation Method 2
One type of sensor used is a variable reluctance sensor that generates a train of electrical pulses as a function of the dispersion of the variable magnetic flux between the sensor head and the exciter ring
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
An anti-lock sensor ring (1) comprises a flattened exciting portion (3) having a retention mechanism (7) projecting from a ring radial edge (6); said retention mechanism (7) comprises cantilever spring retention clips (8) elastically deformable to snap on a disc brake band retention seat (27), and comprises a cantilever support portion (9) disposed side by side to and spaced apart from said cantilever spring retention clips (8); each of said cantilever spring retention clips (8) comprising a retention surface (11) and said cantilever support portion (9) comprising a support surface (12); wherein when said anti-lock sensor ring (1) is dismounted from a disc brake band (17), the plane defined by said retention surface (11) and the plane defined by said support surface (12) are facing each other in order to create opposing gripping elements.