One-Way Isolator for High Torque Alternator-Starters
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Solution Overview
Problem
Conventional isolators and overrunning decouplers are inadequate for BAS systems and other flexible drive devices that require high torque transfer in one direction and some degree of isolation in the opposite direction, due to the high inertia of devices like alternator-starters.
Innovation Solution
A one-way isolator with a hub and sheave mechanism, where stop members on the hub and sheave engage to transfer torque through solid contact when high torque is applied in one direction, and the spring provides isolation when torque is transferred in the opposite direction, allowing the sheave to rotate relative to the hub.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional isolators or overrunning decouplers are used, then torque isolation is provided, but high torque transfer capability is lost
Solution Approach 1:
The isolator pulley incorporates a one-way locking mechanism that dynamically switches between two states: a locked state for high torque transfer and an unlocked state for torque isolation. The locking mechanism engages when high torque is applied in the reverse direction, providing solid pulley functionality, and disengages during normal operation, allowing the spring to provide isolation. This dynamic state change resolves the contradiction by making the isolator adaptive to different operational requirements.
Solution Approach 2:
The system changes the mechanical coupling parameter between the flexible drive and the driven device based on torque direction and magnitude. During normal operation, the spring provides elastic coupling for isolation. When reverse torque exceeds a threshold, the one-way locking mechanism engages to provide rigid coupling for high torque transfer. This parameter change allows the system to optimize performance for different operational phases.
2Force
If solid pulleys are used, then high torque transfer is enabled, but torque isolation and vibration damping are lost
Solution Approach 1:
The isolator pulley incorporates a one-way locking mechanism that dynamically switches between two states: a locked state for high torque transfer and an unlocked state for torque isolation. The locking mechanism engages when high torque is applied in the reverse direction, providing solid pulley functionality, and disengages during normal operation, allowing the spring to provide isolation. This dynamic state change resolves the contradiction by making the isolator adaptive to different operational requirements.
3Reliability
If conventional isolators are used with high inertia devices, then vibration damping is provided, but the device cannot drive the flexible drive when the engine decelerates
Solution Approach 1:
The one-way locking mechanism dynamically controls the coupling between the isolator pulley and the driven device. During engine deceleration, the mechanism allows the device to overrun the pulley by disengaging the lock, providing overrun capability. During normal operation, the spring provides vibration damping. The mechanism adapts to different operational modes based on torque direction, resolving the contradiction between vibration damping and overrun capability.
Solution Approach 2:
The isolator pulley is segmented into distinct functional components: the locking mechanism for directional control, the spring for vibration damping, and the bearing for rotational support. This segmentation allows each component to specialize in its function, with the locking mechanism specifically enabling overrun capability while the spring handles vibration damping, resolving the contradiction through functional separation.
4Force
If the sheave is rigidly mounted to the hub, then solid pulley functionality is achieved, but torque isolation is lost
Solution Approach 1:
The mounting arrangement between the sheave and hub is made dynamic through the one-way locking mechanism. During normal operation, the spring allows relative movement between the sheave and hub, providing torque isolation. When reverse torque is applied, the locking mechanism engages to rigidly connect the sheave and hub, providing solid pulley functionality. This dynamic mounting resolves the contradiction by adapting the connection rigidity based on torque direction.
Solution Approach 2:
The one-way locking mechanism acts as an intermediary between the sheave and hub, controlling their relative movement. It allows the spring to provide isolation during normal operation by permitting relative movement, but engages to provide rigid connection when high reverse torque is applied. This intermediary component resolves the contradiction by mediating the interaction between the sheave and hub based on operational conditions.
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
Enables efficient torque transfer as a solid pulley when high torque is required and provides isolation when torque variations occur, extending the operational longevity of flexible drive systems in hybrid vehicle applications.
Implementation Method 1
a spring having a first end engaging the hub and a second end engaging the sheave to elastically couple the hub and sheave
Implementation Method 2
the sheave is rotatably mounted to the hub by at least one bearing
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
A one way isolator for high torque devices, such as alternator-starters, driven by a flexible drive means includes a hub and a sheave each of which includes at least one stop member. The hub and sheave are linked by a isolating spring and, via a bearing and/or bushing, can rotate with respect to each other to provide isolation, through the spring, from torque variations when torque is transferred from the flexible drive means to the device. When substantial amounts of torque are transferred from the device to the flexible drive means, the sheave rotates with respect to the hub to bring the stop members into contact such that the isolator then acts like a solid pulley to facilitate the transfer of the torque from the device.