Motor Layout for Compact Straddled Vehicle Transmission
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Solution Overview
Problem
Conventional straddled vehicle multistage transmission devices are unable to be further downsized while maintaining suitable environmental dispositions for each mechanism, due to spatial constraints and protrusion issues with gear-shifting motors and rotation angle detection sensors.
Innovation Solution
The multistage transmission device is redesigned with the shift motor positioned in a manner that increases the distance between the drive source and driven target, allowing for a compact arrangement and suitable environmental placement, including the shift motor being mounted to the crankcase's inner side and supported by a vibration and heat reduction member, and the clutch motor positioned to avoid overlapping with the shift motor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the gear-shifting motor is positioned near the shift spindle to downsize the transmission device, then the device size is reduced, but the motor protrudes outward and creates spatial constraints
Solution Approach 1:
The shift motor is repositioned from a lateral arrangement (protruding outward) to a longitudinal arrangement (behind the output shaft), utilizing the front-rear dimension of the vehicle. This dimensional change allows the motor to be accommodated within the existing spatial envelope without increasing lateral protrusion, effectively resolving the contradiction between compactness and spatial constraints.
2Length of moving object
If the shift motor is repositioned behind the output shaft to reduce protrusion, then the vehicle width is reduced, but the distance between drive source and driven target increases
Solution Approach 1:
A power transmission mechanism consisting of a gear and a long-axis direction converting mechanism is introduced as an intermediary between the shift motor and the shift cam. This intermediary system efficiently transmits power over the increased distance, overcoming the drawback of reduced drive proximity while maintaining the compact lateral profile achieved by repositioning the motor.
3Volume of moving object
If mechanisms are disposed close together to downsize the transmission device, then compactness is improved, but suitable environmental placement becomes difficult
Solution Approach 1:
The transmission device is segmented into distinct functional zones: the clutch mechanism remains in the oil-filled environment for lubrication, while the shift motor and its power transmission components are positioned in the air-filled environment. This spatial segmentation allows each mechanism to operate in its optimal environmental condition, maintaining reliability while achieving compact overall sizing through efficient space utilization.
Data Source
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AI summary
Provided is a straddled vehicle with which a multistage transmission device can be further downsized while mechanisms thereof are disposed in suitable environments. The straddled vehicle of the present teaching includes an engine, a multistage transmission device, and a driving wheel. The multistage transmission device includes an input shaft, an output shaft, a clutch, a clutch motor, a shift cam, and a shift motor. The shift motor includes a body part and a shaft part rotatably protruding therefrom and outputting operation power by rotation, causes the shift cam to rotate for up-shifting or down-shifting by causing the shaft part to rotate such that rotation directions for up-shifting and down-shifting are opposite to each other, and is disposed to satisfy all of (A) to (D) below: (A) the shaft part is in parallel with or substantially in parallel with the input shaft, the output shaft, and the shaft of the shift cam; (B) the body part is at least partially disposed inward of outside surfaces of crankcase covers in a vehicle width direction; (C) when seen in the vehicle width direction, the shaft part is located in the rear of the output shaft such that the output shaft is located between the shaft part and the shaft of the shift cam in a front-rear direction; and (D) the shift motor is mounted to the second inside surface of the crankcase.