Bicycle Bottom Bracket Unit with Phase-Shifted Optical Sensors
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing bottom bracket units for bicycles, particularly e-bikes, can detect rotational speed but not the direction of rotation, which is necessary for accurate power control and electric auxiliary drive management.
Innovation Solution
Incorporating two optical sensors with a fixed phase difference, such as 90°, to determine the direction of rotation by analyzing the chronological arrival of signals from a common signaling device, which can be a marking on the bottom bracket axle or a disk locked in rotation, allowing for efficient use of installation space and detection of both speed and direction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single optical sensor is used to detect rotational speed, then the rotational speed can be detected, but the direction of rotation cannot be determined
Solution Approach 1:
The single optical sensor is segmented into two optical sensors arranged at different positions around the bottom bracket axle. Each sensor detects the passage of the signaling device at its specific location, generating separate signals that can be compared to determine rotation direction. This segmentation allows the system to capture both speed and directional information.
Solution Approach 2:
The two optical sensors are positioned asymmetrically relative to each other around the bottom bracket axle, creating a fixed phase difference in their detection signals. This asymmetric arrangement ensures that the signals arrive at different times during rotation, enabling direction determination through phase comparison while maintaining compact installation space.
2Loss of information
If two optical sensors are arranged offset in the circumferential direction to detect rotation direction, then direction of rotation can be determined, but installation space is increased in the axial direction
Solution Approach 1:
Instead of arranging the two optical sensors along the circumferential direction (which would increase axial space), the invention positions them in the radial direction around the bottom bracket axle. This dimensional change allows both sensors to be mounted on the same axial plane, eliminating the need for additional axial space while still achieving the required phase difference for direction detection.
3Area of stationary object
If two optical sensors are arranged offset in the axial direction, then installation space in the radial direction is spared, but the phase difference between sensors is reduced
Solution Approach 1:
The invention optimizes the positioning parameters of the two optical sensors by arranging them at specific angular positions around the bottom bracket axle in the radial direction. This parameter optimization ensures a substantial phase difference (ideally 90 degrees) between the sensor signals, maximizing measurement precision for rotation direction detection while maintaining compact radial installation space.
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
Enables the detection of the direction of rotation, allowing for precise control of electric auxiliary drives and power management in e-bikes, while optimizing installation space usage by employing a phase-shifted optical detection system.
Implementation Method 1
the optical detection unit measures at least one signaling device locked in rotation on the bottom bracket axle
Implementation Method 2
a permanent magnetic field is impressed in a magnetic field section of the body of the bottom bracket unit so that, if there is a torque in the bottom bracket axle, a magnetic field that can be detected outside of the body is generated due to the magnetostrictive effect
Data Source
AI summary
A bottom bracket unit including a bottom bracket axle (1), at least one bearing (2, 3) that receives the bottom bracket axle (1) in a rotatable manner, and an optical detection unit (11), by which a rotational speed of the bottom bracket axle (1) can be detected. The optical detection unit (11) measures at least one signaling device (12) that is rotationally fixed to the bottom bracket axle (1). The aim of the invention is to provide a bottom bracket unit that can also detect the rotational direction of the bottom bracket axle in addition to the rotational speed of the axle. This is achieved in that the optical detection unit (11) has two optical sensors (17), with one of these sensors (17) providing a signal that is phase-shifted with respect to the other sensor (24) having a fixed phase difference, in particular with a phase difference of 90°.