EPS Worm Reducer Bearing Support for Low-Torque Quiet Assembly
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Solution Overview
Problem
Conventional electric power steering reducers face challenges in accurately assembling the worm shaft with constant rotational torque and experience noise due to friction between the worm shaft and worm wheel, primarily because the bearings supporting the worm shaft are not fixed to the housing, leading to difficulties in precise assembly and increased load on the damper.
Innovation Solution
The reducer design includes bearings supported by the housing at the opposite ends of the worm shaft, with a damper axially supported on the outer race of one bearing and a damper support member that buffers axial and radial movements, reducing the load on the worm shaft and minimizing friction-induced noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the bearings supporting the worm shaft are not fixed to the housing, then the assembly structure is simpler and easier to manufacture, but it becomes difficult to accurately set the assembly position and assemble the worm shaft with constant rotational torque
Solution Approach 1:
The housing is pre-formed with bearing support portions that precisely position the bearings before worm shaft assembly. This preliminary structuring of the housing ensures accurate assembly position and constant rotational torque without complicating the manufacturing process
Solution Approach 2:
The patent uses simple, easily manufacturable bearing support portions integrated into the housing structure rather than complex adjustable mechanisms. This approach prioritizes ease of manufacture while achieving sufficient precision through clever structural design
2Device complexity
If the damper supports the worm shaft alone, then the structure is simpler, but the load applied to the damper when the worm shaft moves radially generates rotational torque and noise due to friction between the worm shaft and worm wheel
Solution Approach 1:
The support function is segmented between the housing (which provides rigid support through bearing support portions) and the damper (which handles vibration and radial movements). This segmentation allows the damper to be simpler in structure while the housing bears the load of reducing friction-induced noise
Solution Approach 2:
The bearing support portions act as intermediaries between the housing and the damper, transferring radial movement loads to the housing structure. This intermediary structure reduces the load on the damper and consequently reduces friction-induced noise between the worm shaft and worm wheel
3Ease of operation
If the bearing on the side opposite the motor needs to be mounted to be slidable to compensate for clearance, then clearance compensation is smooth, but the bearings supporting the worm shaft rotation are not fixed to the housing, making accurate assembly difficult
Solution Approach 1:
The bearing support portions are designed to allow controlled sliding movement for clearance compensation while maintaining precise positioning. This dynamic design enables the bearings to move smoothly for compensation while the housing structure ensures accurate assembly position is maintained
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 precise assembly of the worm shaft with constant rotational torque and significantly reduces rotational torque and noise generated by friction, enhancing the steering experience.
Implementation Method 1
the damper is provided in order to buffer the axial and radial movements of the worm shaft
Data Source
AI summary
A reducer of an electric power steering apparatus includes: a worm shaft having a first end thereof supported by a first bearing coupled to a housing and a second end supported by a second bearing coupled to the housing; a damper axially supported on an outer race of the second bearing; and a damper support member having a first side axially supported on the damper and a second side supported on an inner face of the housing. The worm shaft can be assembled with constant rotational torque at an accurate position with respect to the centers of the bearings at the opposite ends. And, the axial and radial movements of the worm shaft can be buffered and the load applied to the worm shaft in the direction in which the worm shaft is engaged with the worm wheel can be reduced.