Bicycle Drive Apparatus Gear Shift Detection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing bicycle control systems for electrically assisted bicycles require complex structures and sensors to confirm gear shifting operations, which can be difficult to implement, especially when the type of transmission is variable.
Innovation Solution
A bicycle drive apparatus that uses a crank variation determining sensor and a microcomputer to limit and cancel the output of the drive assistance electric motor based on measured rotation or pedaling force variations, eliminating the need for a shift position sensor and simplifying the structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a sensor is added to detect shift position to confirm gear shifting completion, then the reliability of gear shift detection is improved, but the device complexity increases
Solution Approach 1:
The system uses the existing crank rotational speed sensor to detect gear shift completion by monitoring changes in rotational speed that occur during gear transitions. The control unit analyzes the rotational speed data to determine when gear shifting is complete, eliminating the need for a separate shift position sensor. This self-service approach uses existing components to perform the additional detection function.
Solution Approach 2:
The crank rotational speed sensor serves dual purposes: it monitors pedaling speed for motor control and simultaneously detects gear shift completion by identifying characteristic speed changes during gear transitions. This multi-functionality allows one sensor to perform multiple detection tasks, reducing overall system complexity while maintaining detection reliability.
2Measurement precision
If a shift position sensor is installed to confirm gear shifting operation, then the accuracy of shift completion detection is improved, but the manufacturing cost increases
Solution Approach 1:
The system repurposes the existing crank rotational speed sensor to detect gear shift completion through characteristic speed changes, eliminating the need to manufacture and install additional shift position sensors. This approach maintains detection accuracy while avoiding the additional manufacturing costs associated with extra sensors and their integration.
Solution Approach 2:
The control unit acts as an intermediary that processes rotational speed data to infer gear shift completion status. Instead of directly measuring shift position with a dedicated sensor, the system uses the rotational speed as an intermediate parameter that reflects gear state changes, providing accurate detection without the cost of direct position sensing.
3Adaptability or versatility
If the transmission type is made variable to accommodate different bicycle configurations, then the adaptability is improved, but the difficulty of detecting and measuring gear shift completion increases
Solution Approach 1:
The control unit implements a universal detection method that works across different transmission types (derailleur, internal gear hub, belt drive) by monitoring characteristic rotational speed changes during gear transitions. This approach provides transmission-type-agnostic gear shift detection, maintaining adaptability to various bicycle configurations while avoiding the complexity of transmission-specific detection mechanisms.
Solution Approach 2:
The system detects gear shift completion by identifying characteristic changes in rotational speed parameters that occur during gear transitions. By focusing on dynamic parameter changes rather than static position measurements, the system achieves detection capability that is independent of transmission type, accommodating variable configurations without increasing detection difficulty.
Data Source
AI summary
A bicycle drive apparatus comprises a bicycle crankset, a bicycle transmission, a drive assistance electric motor, a crank variation determining sensor and a microcomputer. The crank variation determining sensor is arranged to determine a variation value related to rotation of the bicycle crankset. The microcomputer includes a shift command section, a limiting section, a determining section and a limitation cancelling section. The shift command section issues a shift command commanding the bicycle transmission to change gears. The limiting section limits an output of the drive assistance electric motor upon issuance of the shift command. The determining section determines completion of a gear shift operation upon the variation value being within a prescribed range. The limitation cancelling section cancels the limitation of the output of the drive assistance motor upon the determining section determining the completion of the gear shift operation.