Dual Spring Isolator Torque Management
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Solution Overview
Problem
Existing isolators between engine crankshafts and belt-driven accessories, such as MGUs or alternators, often generate perceivable noise and struggle to effectively seal against dirt and contaminants, affecting vehicle quality and interior cleanliness.
Innovation Solution
The isolator design incorporates a hub, pulley, isolation springs, and transition springs with distinct spring rates, where the transition springs act in series with the isolation springs to manage torque transfer, and a seal member with lips to prevent contamination, ensuring effective noise reduction and sealing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single spring isolator is used, then the structure is simple, but noise is perceivable and quality perception is negative
Solution Approach 1:
The isolator is segmented into two distinct spring systems: isolation springs (first spring rate) and transition springs (second spring rate). This segmentation allows each spring type to perform its specific function - isolation springs handle primary vibration isolation while transition springs manage noise during transition phases, thereby reducing perceivable noise without requiring a completely complex overall structure.
Solution Approach 2:
The patent applies parameter changes by using springs with different spring rates (k1 for isolation springs, k2 for transition springs where k2 < k1). This parameter differentiation enables the system to optimize performance across different operating conditions - the softer transition springs reduce noise during transitions while the stiffer isolation springs maintain isolation effectiveness, resolving the noise quality issue.
2Reliability
If the isolator interior is sealed to prevent contaminant migration, then sealing effectiveness improves, but device complexity increases
Solution Approach 1:
The patent employs flexible seal lips (first seal lip and second seal lip) that extend into the interior chamber from the pulley and hub respectively. These flexible sealing elements create an effective seal against contaminant migration without requiring complex rigid sealing structures, maintaining reliability while minimizing added complexity.
Solution Approach 2:
The seal lips are positioned and configured to work with the natural pressure differentials and movement of the isolator components during operation. The sealing action is self-regulating, where the relative movement between hub and pulley maintains seal contact, eliminating the need for additional actuation mechanisms or complex control systems.
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 design reduces noise perception by smoothing torque transfer and prevents dirt ingress, enhancing the vehicle's interior quality and reliability by minimizing resonance and contamination.
Implementation Method 1
The isolation spring and transition spring act in series in a torque path between the pulley and the hub. The isolation spring has a first spring rate. The transition spring has a second spring rate that is lower than the first spring rate.
Data Source
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AI summary
It is provided a method for executing a movement between a hub (22) and a pulley (28) of an isolator (20), wherein the hub (22) defines an axis, the pulley (28) is rotatably mounted to the hub (22) through an isolation spring (24) and a transmission spring (26) connected together via a rotatable intermediate member (25), wherein the isolation spring (24) has a first spring rate and the transition spring (26) has a second spring rate. The method comprising: executing a relative movement in a first rotational direction between the hub (22) and the pulley (24) away from a home position throughout a first range, and executing a relative movement beyond the first range and between the hub (22) and the pulley (24) away from the home position throughout a second range, wherein during the relative movement throughout the first range the effective spring rate of the isolator (20) is the series sum of the first and second spring rates, and wherein during the relative movement throughout the second range the effective spring rate of the isolator (120) is the first spring rate; and executing a relative movement in a second, opposite, rotational direction between the hub (22) and the pulley (24) away from a home position throughout a third range, wherein during the relative movement throughout the third range the effective spring rate of the isolator (120) is the first spring rate.