Two-Stage Stiffness Driveshaft for Torsional Vibration Control
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Solution Overview
Problem
Conventional driveshafts face challenges in effectively managing torsional vibrations and inertia-induced loads, leading to inefficiencies in torque transmission and increased weight and inertia, particularly in motor vehicles where alignment and distance variations between drive-train components necessitate specialized mechanical joints.
Innovation Solution
A two-stage stiffness driveshaft design featuring a hollow cylinder and an inner shaft with a rotational clearance fit, along with damping elements such as elastomer or friction components, to control torque transmission and absorb vibrations, providing a smooth transition between two distinct stiffness stages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional driveshafts are constructed to withstand operating stresses, then strength and reliability are improved, but weight and inertia increase
Solution Approach 1:
The driveshaft is divided into an inner shaft and an outer tube, creating a nested structure where the inner shaft can twist independently within the outer tube. This segmentation allows the driveshaft to withstand torsional stresses while using less material, reducing weight while maintaining strength.
Solution Approach 2:
The inner shaft is nested within the outer tube, with the inner shaft's outer diameter less than the outer tube's inner diameter. This nesting arrangement allows both components to work together to handle operating stresses while minimizing material usage and weight.
2Adaptability or versatility
If mechanical joints are incorporated to permit variation in alignment and distance, then adaptability is improved, but device complexity increases
Solution Approach 1:
The inner shaft is designed to twist dynamically within the outer tube through a controlled rotational clearance fit, allowing the driveshaft to adapt to alignment variations and distance changes without requiring additional mechanical joints or universal joints.
Solution Approach 2:
A damping element is introduced as an intermediary between the inner shaft and outer tube to control the interaction during twisting motion. This damping element manages the clearance fit and provides controlled movement, reducing complexity compared to traditional mechanical joints.
3Stability of the object's composition
If the inner shaft is rigidly fixed at both ends, then stiffness is improved, but ability to absorb torsional vibrations decreases
Solution Approach 1:
The inner shaft is rigidly fixed at the second end but allowed to twist relative to the outer tube at the first end through a rotational clearance fit. This dynamic arrangement maintains stability where needed while providing the flexibility to absorb torsional vibrations through controlled twisting motion.
Solution Approach 2:
The damping element acts as an intermediary that controls the twisting motion of the inner shaft relative to the outer tube. It provides controlled clearance and damping to absorb torsional vibrations while maintaining the necessary stability for torque transmission.
4Device complexity
If a single-stage stiffness driveshaft is used, then structural simplicity is maintained, but ability to control torque transmission under varying conditions decreases
Solution Approach 1:
The driveshaft transitions from a single-stage stiffness design to a two-stage stiffness design where the inner shaft provides one level of compliance through twisting, and the outer tube provides a second level of stiffness. This dynamic two-stage system adapts to varying torque conditions while maintaining relative structural simplicity.
Solution Approach 2:
The nested configuration of the inner shaft within the outer tube creates a two-stage stiffness system where the inner shaft handles high-frequency torsional vibrations with its compliance, while the outer tube provides overall structural stiffness for torque transmission, achieving adaptive torque control without complex mechanisms.
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 driveshaft effectively filters and attenuates torque variations, reduces vibration, and optimizes compliance for both cruising and acceleration conditions, enhancing the efficiency and durability of the drive-train by managing torsional vibrations and inertia loads.
Implementation Method 1
The first damping element may be an elastomer component having an internal elastic hysteresis.
Implementation Method 2
The friction component may be one or more friction washers.
Data Source
AI summary
A two-stage stiffness driveshaft includes a hollow cylinder having first and second ends and a hollow cylinder stiffness. An inner shaft having first and second ends and an inner shaft stiffness extends through the hollow cylinder. The inner shaft's first end and the hollow cylinder's first end are engaged via a rotational clearance fit. The inner shaft's second end is rotationally fixed to the hollow cylinder's second end to permit the inner shaft's first end to twist through a predetermined angle relative to the inner shaft's second end. The inner shaft's stiffness defines the driveshaft's first-stage stiffness, while the combined stiffness of the inner shaft and the hollow cylinder defines the driveshaft's second-stage stiffness. A damping element positioned between the inner shaft and the hollow cylinder controls variation in torque transmitted by the driveshaft and generates gradual transition between the first-stage stiffness and the second-stage stiffness.