Engine-Cooling Fan Hub Isolation for NVH Reduction
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Solution Overview
Problem
Automotive engine-cooling fan assemblies often suffer from excessive noise, vibration, and harshness (NVH) due to motor cogging torque, axial cogging forces, and torque ripple, which excite resonant modes in the fan structure.
Innovation Solution
The fan assembly incorporates a dual hub structure with a central inner hub portion and an outer hub portion, connected by radially and axially extending vibration isolation members, such as L-shaped ribs, that function as centrifugal fans to maintain airflow while reducing torsional and axial vibration modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If radial ribs are attached to the interior surface of the hub to stiffen the fan structure and generate centrifugal cooling airflow, then structural integrity and motor cooling are improved, but torsional and axial vibration modes are excited due to motor cogging torque and torque ripple
Solution Approach 1:
The hub is divided into two separate portions: an inner hub portion that rotates with the driveshaft and an outer hub portion that remains stationary. The radial ribs are attached only to the inner hub portion, allowing them to provide structural support and generate centrifugal cooling airflow without being directly connected to the rotating fan blades. This segmentation isolates the vibration-generating ribs from the rotating assembly, reducing noise and vibration while maintaining structural integrity and cooling performance.
2Volume of moving object
If the motor is positioned on the concave side of the hub to conserve axial space, then axial space utilization is improved, but the hub must withstand higher centrifugal forces and deformation
Solution Approach 1:
By separating the hub into inner and outer portions, the structural load-bearing function is assigned to the stationary outer hub portion while the inner hub portion rotates with the driveshaft. This allows the hub to maintain structural rigidity to resist centrifugal forces while accommodating the motor in the concave space, effectively resolving the conflict between space utilization and structural strength.
3Temperature
If radial ribs extend toward the motor to generate centrifugal cooling airflow, then motor cooling performance is improved, but the ribs may interfere with motor operation and increase complexity
Solution Approach 1:
The ribs are attached only to the inner hub portion and do not extend into the motor's running clearance, eliminating potential interference with motor operation. The inner hub portion with attached ribs rotates to generate centrifugal cooling airflow through the motor, while the outer hub portion remains stationary to provide structural support. This segmentation allows effective motor cooling without rib-motor interference or increased complexity.
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 effectively decreases noise and vibration by isolating the outer hub and fan blades from the inner hub, maintaining air-moving performance and structural integrity while reducing resonant mode excitation and costs.
Implementation Method 1
The ribs may also help cool the motor. The region between the face of the motor and the face of the hub, including the ribs, acts like a centrifugal fan to pull cooling air through the motor.
Implementation Method 2
The present invention provides, in one aspect, an automotive engine-cooling fan assembly including a motor having a driveshaft defining a central axis, and a fan driven by the motor. The fan includes an inner hub portion coupled to the driveshaft, and an outer hub portion coupled to the inner hub portion. The outer hub portion is coupled to a plurality of radially-extending blades. The fan also includes a plurality of vibration isolation members interconnecting the inner hub portion and the outer hub portion.
Data Source
AI summary
The present invention provides an automotive engine-cooling fan assembly including a motor having a driveshaft defining a central axis, and a fan driven by the motor. The fan includes an inner hub portion coupled to the driveshaft, and an outer hub portion coupled to the inner hub portion. The outer hub portion is coupled to a plurality of radially-extending blades. The fan also includes a plurality of vibration isolation members interconnecting the inner hub portion and the outer hub portion.