Balancing Machine Bearing Stand Spring Rods
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Solution Overview
Problem
Existing cardan shaft balancing machines face limitations in measuring imbalance due to tilting resonances caused by leaf spring support systems, which result in higher natural frequencies above measuring speeds, limiting the maximum speed for imbalance measurement and risking component failure.
Innovation Solution
The upper part of the bearing stand is oscillatingly supported by spring rods arranged in two parallel, vertical planes with elongated, slender shapes, providing at least 100 times greater axial stiffness than radial bending stiffness, thereby lowering the first natural frequency below measuring speeds and increasing tilting resonance to create a large resonance-free measurement range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If leaf springs are used to support the oscillating upper part of the bearing stand, then the natural frequencies are reduced, but the springs warp or bulge under load causing higher natural frequencies that exceed measuring speeds
Solution Approach 1:
The patent changes the geometric parameters of the spring rods by making them elongated and slender with specific length-to-diameter ratios. This parameter change creates a stiffness differential where axial stiffness is at least 100 times greater than radial bending stiffness, fundamentally altering the natural frequency characteristics to separate the first natural mode below measuring speeds from the tilting resonance mode above measuring speeds.
Solution Approach 2:
The spring rods are designed with non-uniform cross-sections along their length, creating local quality variations. The rods have different diameters at different positions, with the thinnest section having a diameter of 2-5 mm while other sections are thicker. This local quality variation optimizes the stress distribution and maintains the desired stiffness characteristics throughout the structure.
2Strength
If the spring support is made stiffer to prevent warping, then structural integrity improves, but natural frequencies rise above measuring speeds limiting the measurement range
Solution Approach 1:
The patent implements parameter changes by creating spring rods with elongated dimensions and specific cross-sectional variations. The length-to-diameter ratio is optimized to achieve at least 100:1 stiffness ratio between axial and radial directions. This allows the structure to maintain high strength where needed while keeping natural frequencies in the desired range for productivity.
3Speed
If the upper part of the bearing stand is made lighter, then the natural frequencies decrease, but the mass is needed to simulate dynamic properties of engine block and differential gear
Solution Approach 1:
The patent resolves this contradiction by changing the stiffness parameters of the spring support system rather than the mass of the upper part. By making the spring rods elongated and slender with optimized cross-sections, the natural frequencies are reduced below measuring speeds while the mass of the upper part remains sufficient to simulate the dynamic properties of the engine block and differential gear.
4Reliability
If spring rods with high axial stiffness are used, then tilting resonance increases, but the rods must maintain adequate radial flexibility for oscillation
Solution Approach 1:
The patent achieves the desired stiffness differential through parameter changes in the spring rod geometry. The elongated shape with length-to-diameter ratios of 15:1 to 30:1 creates inherent stiffness anisotropy where axial stiffness is at least 100 times greater than radial bending stiffness. This geometric parameter optimization simultaneously achieves high tilting resonance control and adequate radial flexibility.
Solution Approach 2:
The spring rods feature local quality variations with non-uniform cross-sections. The rods have thinnest sections with diameters of 2-5 mm positioned strategically along their length, while other sections are thicker. This local quality variation optimizes both the axial stiffness for tilting resistance and radial flexibility for oscillation, reducing device complexity through geometric optimization rather than additional components.
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 allows for supercritical unbalance measurements within a broad, resonance-free speed range, enhancing the machine's operational safety and accuracy by maintaining isotropic rigidity in all radial directions and preventing excessive stress on components.
Implementation Method 1
spring rods arranged in two parallel, vertical planes with elongated, slender shapes, providing at least 100 times greater axial stiffness than radial bending stiffness
Implementation Method 2
lowering the first natural frequency below measuring speeds and increasing tilting resonance to create a large resonance-free measurement range
Data Source
Figure 1~2
Figure 3~4
AI summary
The device has stand upper part (4) that is supported by three torsion bars (3) at a bearing stand (1). The torsion bars are arranged at a distance from the axis of rotation of a rotor bearing (5) and in a distance from each other. The longitudinal axes of the torsion bars are aligned parallel to the axis of rotation of the rotor bearing. The torsion bars has such an elongated, slim form that their rigidity in axial direction is 100 times, particularly 300 times, larger is than their radial flexural rigidity.