Rack-Driven Steering Apparatus with Integrated Ball Nut Support
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Solution Overview
Problem
Rack-driven auxiliary power steering systems face issues with accurate transmission of steering force due to resilient deformation of the rack bar, leading to the need for a separate supporting unit, which can cause noise and damage from wear and impact loads.
Innovation Solution
A rack-driven steering apparatus utilizing a ball nut with a second gear and screw grooves on both the inner and outer surfaces to transmit steering force to the rack bar, eliminating the need for a support yoke and yoke plug, and incorporating a motor for auxiliary steering power.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a separate rack bar supporting unit (support yoke and yoke plug) is used to support the rack bar, then the rack bar can be supported and engaged with the pinion gear, but noise is generated due to gap increase caused by wear of the support yoke after long-term vehicle operation
Solution Approach 1:
The invention extracts and eliminates the separate rack bar supporting unit (support yoke and yoke plug) from the steering apparatus. By integrating the rack bar support function directly into the rack bar structure through protrusions and recesses, the patent removes the source of noise generation while maintaining the necessary support and engagement functions.
Solution Approach 2:
The invention merges the rack bar support function with the rack bar structure itself. The rack bar is designed with protrusions that directly engage with recesses in the housing, eliminating the need for a separate support yoke. This integration ensures that the support structure wears together with the rack bar, preventing relative motion and noise.
2Reliability
If a separate rack bar supporting unit is used, then the rack bar can be supported, but the unit is damaged by impact loads reversely input from the road surface
Solution Approach 1:
By integrating the support function into the rack bar structure itself through protrusions and recesses, the invention creates a unified load-bearing path. Impact loads from the road surface are directly transmitted through the rack bar to the housing without passing through a separate support yoke, eliminating the vulnerability of isolated support components.
Solution Approach 2:
The rack bar is segmented with protrusions at its ends that engage with corresponding recesses in the housing. This segmentation creates direct structural connection points that can effectively handle impact loads, distributing the stress along the rack bar structure rather than concentrating it in a separate support component.
3Productivity
If a pinion gear and rack gear are engaged to convert rotation to linear movement, then steering force can be transmitted, but the transmission is inaccurate due to resilient deformation of the rack bar
Solution Approach 1:
The rack bar is pre-formed with protrusions and the housing has pre-formed recesses that create a preliminary mechanical constraint. This preliminary structural arrangement prevents resilient deformation during operation by establishing fixed engagement points before the steering force is applied, ensuring accurate transmission from the pinion gear to the linear movement of the rack bar.
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
Enhances power transmission accuracy and comfort by preventing noise and damage from wear and impact, while providing a reliable steering experience without additional supporting units.
Implementation Method 1
a ball nut having one end provided with a second gear engaged with the first gear and having a screw groove on an inner periphery surface thereof to transmit a steering force of the steering shaft to a rack bar
Implementation Method 2
a first gear provided at a lower end of a steering shaft; a ball nut having one end provided with a second gear engaged with the first gear
Implementation Method 3
a rack bar coupled to an inner side of the ball nut and having a second screw groove corresponding to the first screw groove on an outer peripheral surface thereof to be slid during rotation of the ball nut
Data Source
AI summary
Disclosed are a rack-driven steering apparatus and a rack-driven auxiliary power steering apparatus including the same. The present invention can protect peripheral parts such as a motor for driving a nut pulley and an electronic control unit to improve durability when an excessive load reversely input from the outside is transmitted during an operation of a belt by the motor, and prevent a steering disabling state during a high speed travel of the vehicle, thereby providing a driver with a stable steering condition.