Shift Cam Neutral Position Control for Reliable Shifting
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Solution Overview
Problem
Conventional manually controlled transmissions, such as the return-type transmission in motorcycles, face challenges in reliably shifting to a neutral position due to the lack of distinct rotational angles between gear positions, leading to potential errors in gear selection and inefficient shifting mechanisms.
Innovation Solution
An electronically controlled transmission system with a shift cam having specific grooves and a control device that sets distinct rotation angles for shift steps, including a neutral position below the lowest gear speed, allowing precise control and reliable shifting to the neutral position, utilizing a clutch actuator and shift actuator connected to an Electronic Control Unit (ECU) for automated gear changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the neutral position is disposed between the first speed position and the second speed position in a conventional return-type transmission, then the shift pattern is compact, but the shifting to neutral position becomes unreliable due to complex gear engagement and precise rotation angle requirements
Solution Approach 1:
The shift cam is segmented into distinct grooves: a first groove for engaging the neutral position and a second groove for engaging speed positions. This segmentation separates the neutral position engagement from the speed position engagement, allowing each to be optimized independently and reducing the complexity of simultaneous engagement requirements.
Solution Approach 2:
The neutral position engagement is extracted as a separate function from the speed position engagement. The shift cam includes a dedicated first groove for neutral position that is structurally distinct from the second groove used for speed positions, simplifying the engagement mechanism for each function.
2Measurement precision
If the shift cam uses uniform rotation angles for all shift positions, then the control mechanism is simple, but the neutral position cannot be reliably distinguished from other gear speeds
Solution Approach 1:
The shift cam employs asymmetric groove designs: the first groove for neutral position has a different shape and engagement characteristic from the second groove for speed positions. This asymmetry allows the neutral position to be precisely distinguished from other positions while maintaining a relatively simple control mechanism through the electronic actuator.
Solution Approach 2:
Different portions of the shift cam have different groove characteristics tailored to their specific functions. The first groove for neutral position engagement has local quality differences (shape, depth, engagement angle) compared to the second groove, enabling precise neutral position detection without complicating the overall control system.
3Reliability
If the transmission uses a manual shifting mechanism, then the structure is simple, but the shifting accuracy and reliability are compromised due to human error
Solution Approach 1:
The manual mechanical shifting operation is replaced with an electronically controlled shift actuator that automatically rotates the shift cam to precise positions. This substitution eliminates human error in shift execution while the mechanical gear engagement structure remains relatively simple through the use of standardized grooves and shift forks.
Data Source
AI summary
A vehicle transmission can comprise a plurality of gears, and a shift cam coupled to the gears to at least partly control shifting of the gears. The shift cam comprise a plurality of grooves each with respective positions corresponding to gear speeds, and further including a neutral position, wherein the neutral position is below a position corresponding to a lowest gear speed in a view of at least a portion of the shift cam. A rotation angle of the shift cam between the neutral position and a lowest step corresponding to the lowest gear speed can be different from that between any adjacent shift steps, respectively corresponding to other gear speeds.