Shift Fork Actuation With Cam Linkage for Low-Backlash Gear Engagement
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Solution Overview
Problem
Existing driveline shifting systems face issues with accuracy and wear due to the use of parallel axle gear trains, which result in potential backlash and reduced accuracy, especially in commercial vehicle transmissions where small rotational actuations are required.
Innovation Solution
A low rotation angle actuation system is implemented, featuring a motor coupled to a lever arm via a parallel axis gear train and a shaft connected to a driveline shifting member, with a rolling element housed within a slot in the lever arm and an eccentric pin on the final gear to create a cam effect, allowing for precise and efficient gear engagement with increased torque.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If parallel axle gear trains are used to actuate the shift fork, then the gear engagement can be achieved, but backlash and reduced accuracy occur due to small number of teeth engagement
Solution Approach 1:
A cam-based linkage connector is introduced as an intermediary mechanism between the gear train and the shift fork. The cam profile is specifically designed to convert rotational motion into precise linear motion, eliminating backlash and improving engagement accuracy by providing a controlled interaction surface that maintains constant contact between components.
Solution Approach 2:
The cam mechanism utilizes curved surfaces and profiles to achieve smooth, accurate motion transfer. The cam's curved geometry ensures continuous contact and eliminates the tooth engagement discontinuities inherent in standard gear trains, thereby reducing backlash and improving positioning precision.
2Duration of action of stationary object
If parallel axle gear trains are used for shift fork actuation, then gear engagement is achieved, but increased wear of working surfaces occurs due to changes in gear clearance
Solution Approach 1:
The cam-based linkage connector serves as a mediator that distributes and smooths the contact forces during gear engagement. By providing a larger, more evenly distributed contact surface through the cam profile, the mechanism reduces localized stress and wear on the gear teeth and shift fork surfaces, thereby extending component service life.
Solution Approach 2:
The cam mechanism is designed to preliminarily position and pre-load the shift fork before final engagement occurs. This preliminary action ensures proper alignment and minimizes impact forces during engagement, reducing wear on working surfaces and extending the duration of component operation.
3Measurement precision
If a cam based linkage connector is used in the shift fork actuator, then small movements are achieved with increased accuracy, but device complexity increases
Solution Approach 1:
The cam-based linkage connector is integrated directly into the existing gear train structure, merging the cam mechanism with the gear teeth and shaft assembly. This integration approach achieves precise positioning functionality while minimizing the addition of separate components, thereby limiting the increase in overall device complexity.
4Force
If a cam based linkage connector is used to achieve small rotational movements, then torque benefit is attained, but manufacturing complexity increases
Solution Approach 1:
The cam profile is formed as an integral feature of the existing gear components rather than as a separate part. This merging of the cam function into the gear teeth and shaft assembly maintains torque multiplication benefits while simplifying manufacturing by eliminating the need for separate cam component fabrication and assembly.
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
This solution enables accurate and efficient small rotational movements of the shift fork, reducing wear and improving engagement speed, while maintaining a cost-effective arrangement for multiple driveline members.
Implementation Method 1
A cam is established by using an eccentric pin on a final gear of the gear train in which the rolling element is mounted
Implementation Method 2
The dowel pin is eccentric to the final gear to generate a cam effect
Implementation Method 3
the lever arm driven via a rolling element housed within a slot in the lever arm
Data Source
AI summary
Methods and systems are provided for an actuation system for a driveline shifting member in a transmission system of a vehicle. In one example, a system may include an actuator coupled to a lever arm via one or more parallel axis gears, and a shaft connecting the lever arm to a driveline shifting member, the lever arm driven via a rolling element housed within a slot in the lever arm aligned with a center of a parallel axis gear of the one or more parallel axis gears.