Worm Speed Reducer Gap Compensation for Low-Noise Steering
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Solution Overview
Problem
Existing worm speed reducers in electric power steering systems for vehicles suffer from noise and vibration issues due to backlash, require complex machining, and have a large size and high part count, which affects their service life and efficiency.
Innovation Solution
A speed reducer design featuring a spring with elastic blades fixed in a cylindrical housing, reducing friction and wear by eliminating side gaps and allowing for non-through machining, which simplifies manufacturing and improves coaxial alignment of bearings, while the spring's shape and curvature help in reducing noise and vibrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a gap compensation spring with elastic blades is used to compensate the gap between worm and worm wheel, then the noise and vibrations are reduced, but the machining complexity and manufacturing time increase due to the complex oblong housing shape
Solution Approach 1:
Instead of fixing the spring in a complex oblong housing cavity, the invention inverts the approach by fixing the spring in a simple cylindrical portion of the housing and allowing the distal bearing to move within the spring's elastic blades. This reverses which component is stationary and which moves, simplifying the housing geometry while maintaining gap compensation functionality.
Solution Approach 2:
The invention changes the geometric parameters of the housing by replacing the complex oblong shape with a simple cylindrical portion. This parameter change simplifies the machining operations from complex contouring to basic cylindrical boring, while the spring's elastic blades provide the necessary gap compensation through their inherent flexibility and force characteristics.
2Duration of action of stationary object
If the spring is fixed in the housing and the distal bearing moves in the spring, then friction and wear are reduced, but the spring design complexity increases
Solution Approach 1:
The spring acts as an intermediary element between the fixed housing and the moving distal bearing. By positioning the spring in the cylindrical housing portion and allowing the bearing to move within it, the spring mediates the relative motion while maintaining favorable friction conditions between steel components, thereby extending service life without requiring complex external mechanisms.
3Manufacturing precision
If the housing is machined with a complex oblong shape to accommodate the spring, then the spring can be fixed to compensate gap, but the manufacturing time and precision requirements increase
Solution Approach 1:
The invention inverts the traditional approach by not machining a complex cavity in the housing to fix the spring. Instead, it uses a simple cylindrical portion of the housing to hold the spring, allowing the distal bearing to move within the spring's elastic blades. This inversion dramatically reduces machining time and precision requirements while maintaining effective gap compensation.
Solution Approach 2:
The housing geometry parameters are changed from a complex oblong shape requiring high-precision contouring to a simple cylindrical portion requiring only basic boring operations. This parameter change reduces manufacturing time and precision requirements, while the spring's elastic blades provide the necessary gap compensation through their inherent flexibility and force characteristics.
4Force
If the spring and distal bearing are made of steel, then friction is reduced compared to aluminum, but the coefficient of friction is still present causing wear
Solution Approach 1:
The spring acts as an intermediary that allows the distal bearing to move within it, creating a controlled interface between steel components. This intermediary arrangement minimizes friction and wear by allowing relative motion within the elastic blades rather than against the housing, thereby extending service life while maintaining low friction characteristics of steel-on-steel contact.
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 design effectively reduces noise and vibrations, simplifies manufacturing, and increases the service life of the speed reducer by minimizing friction and wear, and eliminating the need for complex machining operations.
Implementation Method 1
a spring held fixed in the distal portion of the housing around the distal bearing, the spring comprising at least one elastic blade disposed and shaped to rest on the case and to exert forces on the distal bearing in a direction towards the worm wheel
Data Source
AI summary
A speed reducer includes: a case, a worm disposed in a housing of the case and including a proximal portion coupled to an input shaft, a worm wheel coupled to an output shaft and arranged so as to be driven in rotation by the worm, a proximal bearing holding the proximal portion of the worm in the housing, a distal bearing holding a distal portion of the worm, the distal bearing being disposed in a cylindrical distal portion of the housing, a spring held fixed in the distal portion of the housing around the distal bearing, the spring including at least one elastic blade disposed and shaped to bear on the case and to exert forces on the distal bearing in a direction towards the worm wheel.