Steering Actuator Gear Backlash Adjustment With Eccentric Holder
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Solution Overview
Problem
Steer-by-wire type steering apparatuses in small vehicles require a significant reduction ratio and initial free play adjustment for smooth engagement between reducer gears, which is challenging due to the small driving range of the output shaft and mechanical structure limitations.
Innovation Solution
A steering actuator with a two-stage reduction structure and an initial free play adjustment method that includes a holder with an eccentric rotational center axis to adjust the axial distance between the pinion shaft and output shaft, using free play adjustment protrusions and grooves to adjust backlash between gears, and a fixing device to restrict axial movement and absorb tolerance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a two-stage reduction structure is used to provide a significant reduction ratio, then the reduction ratio is improved, but the device complexity increases
Solution Approach 1:
The steering actuator is divided into two separate reduction stages: a worm gear reducer and a planetary gear reducer. Each reducer handles a portion of the total reduction ratio, allowing the system to achieve high overall reduction (e.g., 20:1 or higher) while keeping each individual stage manageable in size and complexity. This segmentation enables the use of standard, off-the-shelf components for each stage.
Solution Approach 2:
The planetary gear set is positioned within the housing structure of the worm gear reducer, and the output shaft of the first reducer serves as the input for the second reducer. This nested arrangement allows both reduction stages to be compactly integrated into a single housing, reducing overall device footprint and simplifying the mechanical connection between stages.
2Reliability
If initial free play adjustment is implemented for smooth engagement between reducer gears, then the reliability is improved, but the ease of manufacture decreases
Solution Approach 1:
The patent incorporates adjustable mounting brackets or shims between the worm gear reducer and planetary gear reducer that allow for pre-adjustment of the axial position of one reducer relative to the other. This preliminary adjustment ensures proper gear mesh clearance (backlash) and smooth engagement before the steering actuator is installed in the vehicle, eliminating the need for field adjustments.
Solution Approach 2:
The design includes adjustable parameters such as axial positioning of the planetary gear input shaft or the mounting position of the worm gear output shaft. By changing these positional parameters during assembly, the gear mesh clearance can be optimized for smooth engagement while maintaining ease of manufacture through simple mechanical adjustments rather than complex machining.
3Adaptability or versatility
If the holder has an eccentric rotational center axis to adjust axial distance between pinion shaft and output shaft, then the adaptability is improved, but the manufacturing precision requirements increase
Solution Approach 1:
The holder acts as an intermediary component between the planetary gear reducer and the pitman arm mounting. By making the holder rotatable about an eccentric axis, it provides a mechanical means to adjust the axial distance between the pinion shaft and output shaft without requiring precision machining of the main reducer housings. The eccentricity of the holder is a fixed, pre-manufactured feature that simplifies the adjustment mechanism.
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 solution provides a significant reduction ratio and easy adjustment of backlash between reducer gears, ensuring stable steering and preventing noise issues from gear disengagement, thereby enhancing the quality and reliability of the steering system in small vehicles.
Implementation Method 1
a holder configured to rotatably support the pinion shaft and having a rotational center axis eccentric with respect to a central axis of the pinion shaft to adjust an axial distance between the pinion shaft and the output shaft
Implementation Method 2
a first reducer including a worm configured to rotate by receiving a rotational force of a motor and a worm wheel configured to rotate in engagement with the worm
Implementation Method 3
a second reducer including a first gear formed on the pinion shaft, and an output shaft configured to operate a pitman arm while rotating by receiving a rotational force through a second gear engaged with the first gear
Data Source
AI summary
Disclosed herein is a steer-by-wire type steering actuator. In accordance with one aspect of the present disclosure, a steering actuator may include: a first reducer including a worm configured to rotate by receiving a rotational force of a motor and a worm wheel configured to rotate in engagement with the worm; a pinion shaft coupled to a center of the worm wheel and configured to rotate together with the worm wheel; a second reducer including a first gear formed on the pinion shaft, and an output shaft configured to operate a pitman arm while rotating by receiving a rotational force through a second gear engaged with the first gear; a first gear housing configured to receive the worm and coupled to the motor; a second gear housing provided with a first mounter for receiving and mounting the pinion shaft and a second mounter formed apart to communicate with the first mounter and configured to receive and mount the output shaft, and coupled to the first gear housing; and a holder configured to rotatably support the pinion shaft and having a rotational center axis eccentric with respect to a central axis of the pinion shaft to adjust an axial distance between the pinion shaft and the output shaft.