Integrated Power Shaft Structure for EV Drive NVH Stability
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Solution Overview
Problem
Existing electric drive assemblies face complications in torque transmission due to separate design of motor and reducer shafts, leading to increased axial size, poor concentricity, and poor NVH performance, with high manufacturing costs for improved precision.
Innovation Solution
A power shaft structure integrating the motor and reducer shafts as a single main shaft with axially extending flanges and bushings for radial positioning, along with bearings and splines or keys for fixation, ensuring concentricity and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the motor shaft and reducer input shaft are independently designed and connected through splines or couplings, then the torque transmission between motor and reducer is achieved, but the structure becomes complicated and the axial size increases
Solution Approach 1:
The patent merges the motor shaft and reducer input shaft into a single integrated power shaft structure. The power shaft serves dual functions as both the motor shaft and the reducer input shaft, eliminating the need for separate shafts and coupling components. This integration directly reduces structural complexity while maintaining torque transmission capability between the motor and reducer.
2Power
If the motor shaft and reducer input shaft are independently designed and connected through splines or couplings, then the torque transmission between motor and reducer is achieved, but the axial size between reducer and motor increases
Solution Approach 1:
By integrating the motor shaft and reducer input shaft into one continuous power shaft, the patent eliminates the axial gap that would otherwise exist between separate shafts and their coupling components. The power shaft extends continuously from the motor rotor through the reducer input, minimizing the axial dimension of the electric drive assembly and optimizing vehicle layout space.
3Ease of manufacture
If the parking gear and input shaft of reducer are assembled with clearance fit, then the assembly is easy to manufacture, but the concentricity between them deteriorates
Solution Approach 1:
The patent introduces a bushing as an intermediary component between the parking gear and the power shaft. The bushing serves as a precision reference element that mediates the connection between the clearance-fit assembled parking gear and the power shaft. This intermediary component ensures accurate concentricity and radial positioning without requiring tight tolerance assembly, thus maintaining ease of manufacture while achieving high precision.
4Manufacturing precision
If the concentricity when parking gear and input shaft of reducer are assembled is improved by improving the machining precision of the parking gear, then the concentricity is improved, but the manufacturing cost of the parking gear will be greatly increased
Solution Approach 1:
The bushing acts as a precision intermediary that transfers the concentricity requirement from the difficult-to-machine parking gear to the easier-to-machine bushing itself. By making the bushing the precision reference element rather than the parking gear, the patent achieves high concentricity while significantly reducing the machining cost and complexity of the parking gear.
Solution Approach 2:
The patent changes the functional parameter assignment by making the bushing (a simpler, smaller component) the precision reference element rather than the parking gear (a larger, more complex component). This parameter change allows the precision requirement to be applied to a component that is more economical to manufacture with tight tolerances, thereby reducing overall manufacturing cost while achieving the required concentricity.
Data Source
AI summary
A power shaft structure of an electric drive assembly is disclosed. The power shaft structure comprises a main shaft, a right end of the main shaft is located inside a motor and fixedly connected to a rotor of the motor, and a left end of the main shaft is located inside a reducer and fixedly connected to a driving gear and a parking gear of the reducer. At least one side of the driving gear is provided with an axially extending flange, and at least one side of the parking gear is provided with an axially extending flange. A bushing is provided between an inner hole of one flange at one side of the driving gear and the main shaft as well as between an inner hole of one flange at one side of the parking gear and the main shaft for radial positioning of the driving gear and the parking gear, so that the driving gear, the parking gear, and the main shaft are on the same axis, thereby improving the stability and NVH performance of the electric drive assembly.