Pendulum Absorber System for Drivetrain Torsional Vibration Control
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Solution Overview
Problem
Existing methods for reducing torsional vibrations in vehicle drivelines, such as disabling lock-up clutches and using damping devices, are inefficient and lead to increased fuel consumption or limited effectiveness due to space constraints, especially at low engine speeds where torsional vibrations are most severe.
Innovation Solution
A pendulum absorber system is integrated into the drivetrain, featuring a pendulum weight that moves along a predetermined path to absorb and restore energy, using a limiter assembly to stop the weight's movement without applying turning moments, thereby mitigating torsional surging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If damping devices are attached to crankshafts within engine crankcases, then space utilization is maximized, but the devices cannot be radially spaced far enough from the crankshaft's axis of rotation to provide sufficient rotational inertia needed to correct strong drive train torsional vibrations
Solution Approach 1:
The pendulum weight moves in a circular path that is offset from the crankshaft axis, creating motion in a different dimensional plane. This allows the weight to achieve greater effective radius and rotational inertia without occupying more space within the crankcase, as the circular motion path extends the lever arm dynamically rather than requiring static radial space
Solution Approach 2:
The pendulum weight transitions from a static position to dynamic circular motion, allowing the system to achieve variable rotational inertia that increases with operating speed. The dynamic motion creates centrifugal forces that enhance the damping effect without requiring the device to be physically larger or positioned farther from the axis
2Object-affected harmful factors
If lock-up clutches of torque converters are disabled at low engine operating speeds, then torsional vibrations are reduced, but fuel economy deteriorates
Solution Approach 1:
The pendulum absorber system acts as an intermediary device that reduces torsional vibrations without requiring disengagement of the lock-up clutch. It provides a mechanical damping mechanism that operates independently of the torque converter control system, allowing the lock-up clutch to remain engaged for fuel efficiency while the pendulum absorbs harmful vibrations
Solution Approach 2:
The system converts the harmful torsional vibrations into useful centrifugal forces that drive the pendulum weight's circular motion. The vibrational energy that would otherwise be transmitted to the vehicle structure is captured and dissipated through the pendulum's inertial motion and friction in the guide tracks
3Use of energy by moving object
If engines operate at lower speeds with higher torque to improve fuel economy, then fuel efficiency increases, but torsional vibrations become more severe
Solution Approach 1:
The system uses mechanical vibration principles by allowing the pendulum weight to oscillate in circular paths that are tuned to counteract the dominant torsional vibration frequencies. The pendulum's natural frequency is designed to match the engine's torsional vibration order, creating a resonant damping effect that reduces vibration transmission
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 pendulum absorber system achieves a 60-70% reduction in torsional vibrations across a range of engine RPMs, improving NVH levels without amplifying other vibration orders, and is effective when torsional vibrations are most severe.
Implementation Method 1
The system includes a pendulum weight that dynamically moves along a predetermined path in response to torsional vibrations which can be realized as variations in rotational velocities of a housing of the system
Implementation Method 2
allowing a pendulum weight to freely move with respect to an engine's crankshaft, while restricting the pendulum weight to an epicycloidal travel path that takes advantage of angular inertia of the pendulum weight to resist rapid or near instantaneous increases in rotational velocity. The centrifugal force generated by the pendulum weight provides a rotational velocity restoring force
Implementation Method 3
A limiter assembly, which can include a single or multiple limiters, is provided within the system for stopping movement of the weight when it reaches certain positions along the movement path by mechanically impeding further movement at both of a first and second end of the weight
Data Source
AI summary
A pendulum absorber system attenuates torsional vibrations within a drive train of a vehicle. The system can be incorporated between an engine and an automatic transmission, for example, within a flex plate assembly attached to an engine's crankshaft, within a pump housing cover of a torque converter, or as a stand-alone unit between a flex plate assembly and a torque converter. The system includes at least one pendulum weight that dynamically moves along a predetermined path in response to variations in rotational velocities of a housing of the system and that is tuned to attenuate excitation of torsional vibrations within the drive train. A limiter assembly, which can include multiple limiters, is provided within the system for stopping movement of the weight when it reaches endpoints of the predetermined path, by mechanically impeding further movement at both of a first and second end of the weight.