Nested Screw Actuator Structure for Compact Nut Stroke
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Solution Overview
Problem
Conventional actuators and suspensions with screw mechanisms require long screw shafts to achieve sufficient nut stroke, resulting in increased total length, which is a challenge in compact space applications.
Innovation Solution
The design incorporates a hollow shaft with a screw shaft and nut that moves axially, allowing the nut to enter between the hollow and screw shafts, and an anti-rotation mechanism to prevent nut rotation, reducing the overall length while maintaining stroke.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If the screw shaft is made long to ensure the stroke of the nut, then the nut stroke is sufficient, but the total length of the actuator increases
Solution Approach 1:
The nut is configured to enter between the hollow shaft and the screw shaft during actuator operation. This nested arrangement allows the nut to utilize the annular space between the two shafts, enabling sufficient nut stroke without increasing the overall length of the actuator. The hollow shaft provides an internal cavity that accommodates the nut's movement path.
Solution Approach 2:
The invention transitions from a conventional linear arrangement where the nut moves along the external surface of the screw shaft to a two-dimensional annular space between the hollow shaft and screw shaft. This dimensional change allows the nut to achieve sufficient stroke length without proportionally increasing the actuator's external dimensions.
2Length of moving object
If the screw shaft is made long to ensure the stroke of the nut, then the nut stroke is sufficient, but the total length of the suspension increases
Solution Approach 1:
The nut enters between the hollow shaft and the screw shaft, utilizing the annular space for its stroke. This nested configuration ensures that the suspension mechanism achieves the necessary stroke length while maintaining a compact overall length suitable for vehicle suspension applications.
Solution Approach 2:
By utilizing the annular dimension between the hollow shaft and screw shaft, the invention achieves sufficient nut stroke without extending the suspension's external length, thereby resolving the contradiction between stroke requirement and compact installation space.
3Device complexity
If the nut is allowed to rotate freely, then the mechanism is simpler, but the nut may disengage from the screw shaft
Solution Approach 1:
The anti-rotation member is nested within the nut structure, providing a constraint mechanism that prevents nut rotation while maintaining the overall compact nested arrangement of the actuator. This integrated approach adds minimal complexity to the existing nested configuration.
Solution Approach 2:
The anti-rotation member acts as an intermediary element between the nut and the hollow shaft or casing, preventing unwanted nut rotation that could lead to disengagement. This intermediary component ensures reliable nut engagement without significantly complicating the overall 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
This configuration effectively reduces the total length of the actuator and suspension while ensuring the necessary nut stroke, addressing the space constraints and preventing nut disengagement.
Implementation Method 1
a hollow shaft rotatably supported by the casing via a bearing
Implementation Method 2
a screw shaft coupled to the bottom portion of the hollow shaft, the screw shaft sharing a common center line with the hollow shaft; and a nut threadedly connected to the screw shaft
Data Source
AI summary
An actuator whose total length can be reduced is provided. An actuator (2) includes: a casing (7); a hollow shaft (8) rotatably supported by the casing (7) via a bearing (9a, 9b), the hollow shaft (8) including a bottom portion (8b); a screw shaft (14) coupled to the bottom portion (8b) of the hollow shaft (8), the screw shaft (14) sharing a common center line with the hollow shaft (8); and a nut (15) threadedly connected to the screw shaft (14). The nut (15) is capable of moving in an axial direction of the screw shaft (14) to enter between the hollow shaft (8) and the screw shaft (14).