Coaxial Shift Drum Actuation to Simplify Motorcycle Transmission Linkage
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Solution Overview
Problem
In straddle vehicles like motorcycles, the existing linkage mechanisms between the actuator and shift drum are complex and prone to weight increase when reinforced, due to the need to avoid interference with the actuator, complicating the power transmission route.
Innovation Solution
A configuration where the shift drum is rotated by an actuator unit with a drive shaft having the same rotational axis, simplifying the power transmission route and eliminating the need for reinforcement, thereby preventing weight increase.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a linkage mechanism is disposed between the actuator and shift drum to avoid interference, then the actuator can operate without interference, but the linkage mechanism becomes complicated and may require reinforcement increasing vehicle weight
Solution Approach 1:
The drive shaft of the actuator is merged with the rotational axis of the shift drum, combining two previously separate components into a coaxial arrangement. This eliminates the need for complex linkage mechanisms while ensuring reliable power transmission from the actuator to the shift drum without interference issues
2Reliability
If reinforcement is provided to improve the durability of the linkage mechanism, then the durability is improved, but the weight of the vehicle is increased
Solution Approach 1:
The complex linkage mechanism is extracted and removed from the system. By directly connecting the actuator's drive shaft to the shift drum's rotational axis, the patent eliminates the need for intermediate linkage components that would require reinforcement and add weight to the vehicle
3Measurement precision
If the gear position sensor is disposed on the axis of the shift drum, then the sensor can detect the rotation angle accurately, but the shift lever must be disposed away from the axis complicating the linkage mechanism
Solution Approach 1:
The drive shaft and shift drum rotational axis are merged into a coaxial arrangement, allowing the gear position sensor to be disposed on the axis for accurate detection while the shift lever can be positioned optimally without complicating linkage mechanisms
Data Source
AI summary
A straddle vehicle includes: a shift drum that makes a shift change of a transmission including a plurality of gear trains; a transmission case enclosing the shift drum, the transmission case including a side wall portion provided with an insertion hole into which an end portion of the shift drum is inserted; and an actuator unit secured to an outer surface of the side wall portion, the actuator unit including a drive shaft that outputs drive power to rotate the shift drum, the drive shaft having the same rotational axis as the shift drum and being connected to the shift drum on the rotational axis.