Compact Marine Steering Actuator with Nested Roller Screw
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Marine steering systems face challenges in achieving a small spatial footprint while meeting durability and performance requirements due to limited spacing between the engine cowling and the hull of a marine vessel.
Innovation Solution
A marine steering system incorporating an electric actuator with a roller screw assembly, where a central screw is fixedly coupled with the output shaft, and a nut tube is translatable along the axis in response to motor rotation, allowing for axial movement and steering of the marine propulsion unit via a steering tiller, with multiple motors and output shafts for enhanced functionality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a compact electric actuator design is used to reduce spatial footprint, then the available space is reduced, but it becomes difficult to meet durability and performance requirements
Solution Approach 1:
The motor is positioned inside the housing that contains the roller screw assembly, creating a nested configuration where the motor (24) is housed within the same structural envelope as the driven components. This nesting arrangement minimizes the overall spatial footprint while maintaining all necessary functional components for reliable operation.
Solution Approach 2:
The housing (48) serves multiple functions simultaneously: it encloses the roller screw assembly (40), provides structural support, and acts as a mounting structure for the motor (24). By merging these functions into a single integrated housing component, the design reduces the number of separate parts and minimizes the overall spatial requirements while maintaining durability.
2Volume of moving object
If the motor is positioned inside the housing to save space, then the spatial footprint is reduced, but cable movement and wear increase
Solution Approach 1:
A cable management structure is introduced as an intermediary element between the motor (24) and the external environment. This structure guides and constrains the motor cables, preventing excessive movement and wear while allowing the motor to remain positioned inside the housing (48) for compactness.
3Device complexity
If a single motor is used to simplify the system, then the device complexity is reduced, but the reliability decreases due to single point of failure
Solution Approach 1:
The system employs two motors (24A, 24B) positioned at different locations within the housing (48), each capable of independently driving the output shaft (22). This distribution of functional capability to multiple locations provides redundancy, ensuring that if one motor fails, the other can continue to operate, thereby maintaining system reliability without excessive complexity.
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 compact, durable, and high-performance steering system that maintains operational reliability and reduces the spatial footprint, allowing for effective steering and reduced motor cable movement, while ensuring continued operation even if one motor fails.
Implementation Method 1
a roller screw assembly that includes the central screw fixedly coupled with the output shaft, the nut tube that receives the central screw therein, and a plurality of rollers disposed radially between the central screw and the nut tube and configured to engage the central screw and the nut tube
Implementation Method 2
a plurality of rollers disposed radially between the central screw and the nut tube and configured to engage the central screw and the nut tube
Data Source
AI summary
A marine steering system includes a marine propulsion unit, a steering tiller having a first end and a second end opposite the first end and being pivotably coupled to the marine propulsion unit proximate the second end, and an electric actuator. The electric actuator includes an output shaft, a motor that drives rotation of the output shaft about an axis, and a driven assembly pivotably coupled with the steering tiller proximate the first end and operably coupled with the output shaft, such that rotation of the output shaft by the motor drives axial movement of the driven assembly relative to the output shaft and the motor to steer the marine propulsion unit via the steering tiller.