Axially Offset Isolator Spring for BAS Torque Management
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Solution Overview
Problem
Traditional isolators fail to effectively manage torsional vibrations and torque transmission in vehicles equipped with Belt-Assisted Start (BAS) drive systems, where an electric motor drives the crankshaft for starting the engine, leading to inefficiencies and potential damage.
Innovation Solution
An isolator design featuring a shaft adapter, rotary drive member, and an isolation spring arrangement with axially offset springs and a damping structure that generates frictional torque to resist relative rotation, effectively isolating torsional vibrations and managing torque transfer between the engine and motor-generator unit (MGU) shaft.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a traditional isolator is used in a BAS drive system, then torsional vibrations can be reduced, but the isolator cannot effectively manage torque transmission when the belt transmits torque to the crankshaft for engine starting
Solution Approach 1:
The isolator employs a dynamic design where the isolation spring arrangement can accommodate bidirectional torque transmission. The spring arrangement allows the isolator to adapt its stiffness characteristics based on the direction and magnitude of applied torque, enabling effective operation both during engine-driven belt rotation and during motor-generator assisted starting operations
Solution Approach 2:
The isolator utilizes parameter changes in the spring arrangement to adapt to different operating conditions. The spring configuration allows variation in effective spring rate and engagement characteristics depending on whether torque is being transmitted from the engine to the belt or from the belt to the crankshaft during BAS operation, thereby resolving the contradiction between vibration isolation and torque management
2Productivity
If the isolation spring is positioned close to the endless drive member engagement surface, then torque transmission efficiency is improved, but the spring may solidify under high torque loads
Solution Approach 1:
The patent positions the isolation spring axially offset from the endless drive member engagement surface, utilizing the axial dimension to resolve the contradiction. This axial offset creates sufficient clearance to prevent spring solidification under high torque loads while the spring's radial outer edge extends to maintain effective torque transmission. The spring arrangement thus operates in a different dimensional space than the engagement surface, avoiding interference while preserving functionality
3Force
If the isolator is designed for high torque capacity, then it can handle BAS operations, but torsional vibration isolation may be compromised
Solution Approach 1:
The isolator segments the torque transmission and vibration isolation functions through the shaft adapter, isolation spring arrangement, and rotary drive member. This segmentation allows each component to be optimized independently - the spring arrangement for vibration isolation and the overall assembly for torque capacity - thereby resolving the contradiction between handling high BAS torque loads and maintaining effective torsional vibration isolation
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 isolator efficiently isolates torsional vibrations and manages torque transfer in BAS systems, preventing damage and ensuring smooth engine starting, while maintaining low kinetic energies and preventing spring solidification, thus enhancing the longevity of the isolator.
Implementation Method 1
The isolation spring arrangement is positioned to transfer torque between the shaft adapter and the rotary drive member. The isolation spring arrangement has at least one isolation spring that is axially offset from the endless drive member engagement surface.
Implementation Method 2
a damping structure that includes a first damping surface that is rotationally fixed relative to one of the shaft adapter and the rotary drive member, a second damping surface that is rotationally fixed relative to the other of the shaft adapter and the rotary drive member, and a damping structure biasing member that urges the first and second damping surfaces into engagement with one another to generate a frictional torque to resist relative rotation between the shaft adapter and the rotary drive member
Data Source
AI summary
An isolator for isolating a device driven by an engine via an endless drive member is described. The isolator comprises a shaft adapter that is connectable with a shaft of the device, defining a shaft adapter axis, a rotary drive member that is rotatable relative to the shaft adapter and has an endless drive member engagement surface that is engageable with the endless drive member, and an isolation spring arrangement positioned to transfer torque between the shaft adapter and the rotary drive member. The isolation spring arrangement has at least one isolation spring that is axially offset from the endless drive member engagement surface. The at least one isolation spring has an outer edge that is radially outside the endless drive member engagement surface.