Motorcycle Gearshift Device Miniaturization via Merged Shift Lever
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Solution Overview
Problem
Conventional gearshift devices for motorcycles are large in size and have a high number of parts, leading to increased manufacturing costs, due to the use of two shift levers to transmit rotation from the shift shaft to the transmission input member.
Innovation Solution
A gearshift device design that incorporates a shift shaft, a clutch release mechanism, and an engaging member which rotates between an initial position and a speed change position, allowing the clutch to be disconnected simultaneously with the gear shift operation, reducing the number of lever members and enabling miniaturization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If two shift levers are used to transmit rotation from the shift shaft to the transmission input member, then the gear shift operation is reliable, but the device size increases and the number of parts increases leading to higher manufacturing cost
Solution Approach 1:
The patent merges the functions of two separate shift levers into a single shift lever. The first shift lever is eliminated, and its gear shift transmission function is integrated into the second shift lever, which now directly transmits rotation from the shift shaft to the transmission input member. This consolidation reduces the number of parts while maintaining the reliability of gear shift operation through the engaging member that ensures proper engagement at the speed change position.
2Reliability
If two shift levers are used to transmit rotation from the shift shaft to the transmission input member, then the gear shift operation is reliable, but the device size increases
Solution Approach 1:
The patent merges the functions of two separate shift levers into a single shift lever. The first shift lever is eliminated, and its gear shift transmission function is integrated into the second shift lever, which now directly transmits rotation from the shift shaft to the transmission input member. This consolidation reduces the number of parts while maintaining the reliability of gear shift operation through the engaging member that ensures proper engagement at the speed change position.
3Reliability
If the shift lever floats for a period from the start of speed change operation to when clutch disconnection is completed, then the clutch can be disconnected properly, but the response time for gear shift is delayed
Solution Approach 1:
The patent implements preliminary action by designing the engaging member to be positioned in advance at the speed change position before the shift lever arrives. When the shift lever rotates, the engaging member is already in position to immediately engage with the transmission input member as soon as the clutch disconnection is completed, eliminating the floating period and reducing gear shift response time while ensuring proper clutch disconnection.
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
The design achieves miniaturization and reduces the number of parts, thereby lowering manufacturing costs while ensuring precise speed changes by disconnecting the clutch during the gear shift process, maintaining operational efficiency similar to conventional systems.
Implementation Method 1
The clutch release mechanism comprises a cam, which converts rotation of the shift shaft into axial movements, and is constructed that the cam pushes a release push rod of the clutch.
Data Source
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AI summary
A gearshift device (1) comprises a shift shaft (32), a clutch release mechanism (31), and a shift lever provided between the shift shaft (32) and a segment (21) of a transmission (3) to float by a distance corresponding to a release angle. The shift lever comprises a shift lever body (34), which rotates integrally with the shift shaft (32), and an engaging member (35) provided rotatably on the shift lever body (34). The engaging member (35) moves between an initial position spaced a distance corresponding to the release angle from the segment (21) and a speed change position, in which the segment (21) is rotated until the completion of speed change.