Combined Thrust Bearing Strain Sensor Integration
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Solution Overview
Problem
Existing electromechanical brake systems face inaccuracies in force measurement due to bending and hoop stresses experienced by load cells, which increase weight and space requirements in circular actuators.
Innovation Solution
Implementing strain sensors on the inner race of a multiple row rotary thrust bearing within the electric brake actuator, eliminating the need for a separate load cell by positioning them in slots cut out of the thrust bearing to measure axial compression, reducing bending and hoop stresses and minimizing weight and size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a separate load cell is used to measure axial compression force, then force measurement capability is provided, but weight and axial length of the actuator increase
Solution Approach 1:
The patent combines the load cell function with the thrust bearing by integrating strain sensors directly into the bearing structure. The thrust bearing serves dual purposes: supporting axial loads and measuring compression forces through strain sensors embedded in its inner race, eliminating the need for a separate load cell component.
Solution Approach 2:
The thrust bearing is designed to perform multiple functions simultaneously: it provides mechanical support for axial loads during brake actuation and serves as the sensing element for force measurement. This multi-functional design reduces overall actuator weight by consolidating components.
2Measurement precision
If a separate load cell is used to measure axial compression force, then force measurement capability is provided, but axial length of the actuator increases
Solution Approach 1:
The load cell function is merged with the thrust bearing structure. The strain sensors are positioned within the bearing's inner race, allowing force measurement without requiring additional axial space that would be needed for a separate load cell component.
Solution Approach 2:
The strain sensing elements are nested within the thrust bearing structure itself. The strain sensors are embedded in the inner race of the bearing, utilizing the existing structural space rather than adding external measurement components that would increase axial length.
3Measurement precision
If strain sensors are positioned on a circular load cell, then force measurement is achieved, but bending and hoop stresses cause measurement inaccuracies
Solution Approach 1:
The strain sensors are strategically positioned on the flat surfaces of the thrust bearing's inner race where stress conditions are more favorable for accurate measurement. This local positioning avoids areas subject to bending and hoop stresses that would occur on a circular load cell, improving measurement reliability.
Solution Approach 2:
The patent converts the potential harm of stress-induced measurement errors into a benefit by using the thrust bearing's structural design. The bearing's geometry and the strategic placement of strain sensors on flat surfaces transform the stress distribution into a favorable condition for accurate force measurement, eliminating the bending and hoop stress problems associated with circular load cells.
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 configuration enhances measurement accuracy, reduces the axial length, and lowers the weight of the actuator by eliminating the need for a separate load cell, while maintaining precise force measurement capabilities.
Implementation Method 1
strain sensors positioned on the first flat wall of the first axial groove to measure compression in an axial direction
Data Source
Figure 1
Figure 2
Figure 3A
AI summary
A ring-shaped thrust bearing extending in an axial direction has an inner surface (50) which includes a first axial groove (54a) in the inner surface (50). The groove (54a) has a first flat wall (70) and a second flat wall (72); and a first principal strain sensor (56a) positioned on the first flat wall (70) of the first axial groove (54a) to measure compression in the axial direction.