Split-Mass Gear Assembly With Resilient Coupling for Rattle Mitigation
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Solution Overview
Problem
Gear rattle in gear-trains is caused by dynamic behavior of gears due to excitation forces and tooth profile errors, leading to repeated impacts and rebounds of meshed gear teeth, which results in an acoustic disturbance.
Innovation Solution
A gear rattle mitigation assembly is introduced, comprising a rotatable shaft with a gear element that includes a primary mass and a secondary mass connected by a resilient member. The resilient member, comprising spring elements, absorbs torque variations and decouples the inertias of the masses, thereby mitigating gear rattle.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If gear teeth are designed with standard profiles for smooth motion transmission, then motion transmission quality is improved, but gear rattle occurs due to tooth profile errors and increased gear lash
Solution Approach 1:
The gear element is divided into two separate masses: a primary mass that rotates with the shaft and a secondary mass that carries the gear teeth. This segmentation allows the primary mass to provide rotational inertia for smooth operation while the secondary mass can be isolated from rattle-inducing forces through the resilient member connection.
Solution Approach 2:
A resilient member (spring element) is introduced as an intermediary between the primary mass and secondary mass. This resilient member acts as a mediator that decouples the two masses, allowing the secondary mass to absorb rattle forces while the primary mass maintains steady rotational motion, thereby reducing gear rattle transmission.
2Object-generated harmful factors
If tooth profile errors are reduced through improved manufacturing, then gear rattle is reduced, but manufacturing cost and complexity increase
Solution Approach 1:
The gear teeth are extracted from the primary rotating mass and placed on a separate secondary mass. This extraction allows the majority of the gear element (primary mass) to be manufactured as a simple rotating component, while the toothed secondary mass can be separately manufactured and connected via the resilient member, potentially simplifying overall manufacturing while addressing rattle issues.
Solution Approach 2:
The invention changes the dynamic parameters of the gear element by introducing a resilient member with specific stiffness characteristics. This parameter change allows the system to tolerate certain tooth profile errors while maintaining acceptable vibration levels, reducing the stringency of manufacturing tolerances required.
3Ease of manufacture
If gear lash is increased to accommodate manufacturing tolerances, then ease of assembly is improved, but gear rattle increases due to repeated impacts and rebounds
Solution Approach 1:
The resilient member (spring element) provides beforehand cushioning by being pre-loaded or designed to absorb impact forces before they can propagate through the gear system. This cushioning effect occurs during normal operation, absorbing the repeated impacts and rebounds that would otherwise cause gear rattle while accommodating the increased gear lash.
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 gear rattle mitigation assembly effectively absorbs torque variations and reduces the excitation force that causes gear rattle, resulting in a significant reduction of acoustic disturbances generated by the gear-train.
Implementation Method 1
a resilient member arranged between the secondary mass and the primary mass and configured to absorb variation in torque applied to the secondary mass and mitigate gear rattle
Data Source
AI summary
A gear rattle mitigation assembly includes a rotatable shaft and a gear element mounted to the rotatable shaft. The gear element includes a primary mass rotatably fixed to the rotatable shaft and a secondary mass operatively connected to the primary mass. The gear element also includes a resilient member arranged between the secondary mass and the primary mass and configured to absorb variation in torque applied to the secondary mass and mitigate gear rattle when the gear element is in mesh with another gear. A gear-train assembly employing the gear rattle mitigation assembly and a motor vehicle having such a gear-train assembly are also included.