Ball Nut Bearing Support for Rack Assist Steering Vibration
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Solution Overview
Problem
Conventional rack assist type electric power steering apparatuses experience noise and vibration issues due to axial and radial vibrations generated during the sliding of the rack bar and ball nut, which deteriorate the steering feeling for the driver.
Innovation Solution
A rack assist type electric power steering apparatus is designed with a bearing mounted on the outer peripheral surface of the ball nut to support its rotation, and a support member is coupled to the bearing to dampen vibrations and noise by being elastically supported between the bearing's outer race and the housing, preventing the bearing from rotating or releasing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a ball nut is rotated to slide the rack bar, then steering assistance is provided, but axial and radial vibrations are generated causing noise and deteriorating steering feeling
Solution Approach 1:
A bearing is introduced as an intermediary component between the ball nut and the rack housing. The bearing mediates the interaction by providing a controlled rotation interface that reduces direct contact and friction, thereby minimizing the generation and transmission of axial and radial vibrations while maintaining the steering assistance function
Solution Approach 2:
The invention converts the harmful vibrations into beneficial controlled motion through the bearing. The bearing transforms the uncontrolled axial and radial vibrations generated during ball nut rotation into smooth, controlled rotational motion, turning the harmful vibration energy into useful rotational assistance for steering
2Ease of operation
If the bearing is mounted on the ball nut without support, then rotation is enabled, but the bearing becomes loose and rotates due to vibration
Solution Approach 1:
A support member is pre-installed on the ball nut before operation. This support member preliminarily positions and secures the bearing in the correct location, preventing it from becoming loose or rotating during operation. The support member is prepared in advance to counteract the effects of vibration before they occur
Solution Approach 2:
The support member provides preliminary anti-action against the forces that would cause the bearing to become loose or rotate. By being pre-installed and positioned, the support member creates opposing forces that counteract the vibrational forces and prevent the bearing from shifting or rotating during ball nut operation
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 configuration effectively reduces vibrations and noise transmitted through the ball nut and rack bar, enhancing the comfort of the steering experience for the driver by minimizing axial and radial vibrations.
Implementation Method 1
a bearing mounted on an outer peripheral surface of the ball nut so as to support rotation of the ball nut
Implementation Method 2
a support member coupled to the bearing so as to support the bearing, that is, coupled to at least one of a space between one side of an outer race of the bearing and a housing and a space between the other side of the outer race and the housing
Data Source
AI summary
The present invention provides a rack assist type electric power steering apparatus. The power steering apparatus includes: a ball nut coupled to a rack bar via balls to be rotated, and configured to cause the rack bar to slide; a bearing mounted on an outer peripheral surface of the ball nut so as to support rotation of the ball nut; and a support member coupled to at least one of a space between one side of an outer race of the bearing and a housing and a space between the other side of the outer race of the bearing and the housing so as to support the bearing.