HST Control Lever Vibration Reduction via Nested Rod
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Vibrations from engine and mowing blade rotations are transmitted to control levers in zero-turn riding lawnmowers, causing operator fatigue and discomfort due to sympathetic resonance, which existing designs fail to adequately mitigate.
Innovation Solution
The control lever is designed with a distinct natural frequency lower than the engine's operating frequency, incorporating a rod with specific mass and length within a tube to reduce resonance and vibration, particularly in the vertical direction from 20 Hz to 200 Hz, using a solid member with high Young's modulus and density, and fixed at one or both ends, often via welding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the control lever uses a conventional design with simple tube structure, then the device complexity is low and ease of manufacture is high, but the natural frequency matches the engine operating frequency causing resonance and increased vibration transmission to the operator
Solution Approach 1:
The control lever incorporates a rod nested inside the tubular structure, creating a composite configuration where the rod is positioned within the lumen of the tube and fixed at predetermined positions. This nested arrangement modifies the natural frequency of the control lever to differ from the engine operating frequency, thereby reducing resonance and vibration transmission to the operator while maintaining a compact design.
Solution Approach 2:
The control lever combines two different structural elements (tube and rod) with different mechanical properties to create a composite structure. The rod has a predetermined mass and is made of material with specific density and Young's modulus, while the tube provides the outer structure. This composite configuration allows tuning of the natural frequency to avoid resonance with the engine, reducing harmful vibrations without significantly complicating the manufacturing process.
2Ease of operation
If a spongy hand grip is provided at the free end of the control lever, then the comfort of the handle is improved, but the vibration of the hand grip is not suppressed favorably and discomfort to the operator persists
Solution Approach 1:
The rod nested within the tube structure acts as an internal vibration damping element. By positioning the rod at predetermined locations within the lumen and securing it with stoppers or welding, the composite structure reduces vibrations propagating through the control lever, including those transmitted to the hand grip area, while the spongy material maintains its comfort function.
Solution Approach 2:
The invention changes the physical parameters of the control lever by adding mass (through the rod) and modifying the structural stiffness distribution. This alters the natural frequency and vibration characteristics of the entire control lever assembly, reducing the amplitude of vibrations at the hand grip frequency range (20-200 Hz) while preserving the cushioning effect of the spongy material.
3Object-affected harmful factors
If the control lever natural frequency is made different from engine operating frequency, then resonance is reduced and vibration is minimized, but the control lever structure becomes more complex requiring rod, tube, stoppers, and welding
Solution Approach 1:
The nested configuration of the rod within the tube allows for modular assembly. The rod can be inserted into the tube and positioned using stoppers that engage with the tube wall, enabling straightforward assembly without complex machining. The nested structure also simplifies the overall manufacturing process compared to creating a completely new complex geometry, as it uses standard tubular and rod components.
Solution Approach 2:
The stoppers act as intermediary elements that facilitate the connection between the rod and tube. These stoppers are inserted through holes in the tube wall and engage with the rod, providing a simple mechanical means to secure the rod at predetermined positions without requiring complex welding or interference fits, thereby easing the manufacturing process.
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 configuration effectively reduces unwanted vibrations at the control lever, enhancing operator comfort by avoiding resonance with the engine's operating frequency, as demonstrated in experimental tests with varying rod lengths and configurations.
Implementation Method 1
If sympathetic vibration (resonance) occurs in a control lever due to vibration of the other parts of the working machine (e.g., the engine), this can lead to increase of vibration of the lever which is transmitted to the operator.
Implementation Method 2
The control lever is configured to have a different (e.g., lower) natural frequency than an operating frequency (i.e., main operating frequency) of the engine of the mower. By differentiating the natural frequency of the control lever from the main operating frequency of the engine, resonance at the control lever can be reduced or avoided
Data Source
AI summary
A control lever of a working machine having a main operating frequency includes, a tube having a mass and a length extending from a first end to a second end. The tube defines a lumen extending from the second open end towards the first end of the tube. The control lever includes a rod having a predetermined mass and a length extending from a first end to a second end. The rod is fixed to the tube and is disposed in the lumen at a predetermined position with respect to the second end of the tube. In embodiments, the mass of the rod is determined based at least on the mass of the tube and the main operating frequency of the working machine, and the control lever has a natural frequency that is less than the main operating frequency of the working machine.