Ball Screw Retaining Structure for Reset Spring Axial Stability
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Solution Overview
Problem
The end portion of a reset spring in ball screws is unrestrained axially, leading to displacement and failure, especially at higher actuation speeds, resulting in the failure of the reset spring and subsequently the ball screw.
Innovation Solution
A retaining device is directly connected to the ball nut, positioned to limit the axial displacement of the end portion of the reset spring, ensuring it remains engaged and preventing unwanted movement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the end portion of the reset spring is left unrestrained axially to allow dynamic operation, then the actuation speed can be increased, but the reset spring may axially displace and fail
Solution Approach 1:
A retaining device is introduced as an intermediary component between the reset spring and the ball nut. This retaining device axially engages with the end portion of the reset spring to prevent excessive axial displacement while allowing the reset spring to function dynamically. The retaining device transfers and limits the axial forces acting on the reset spring, thereby preventing failure without restricting normal dynamic operation.
2Reliability
If a retaining device is added to constrain the reset spring, then the reliability is improved, but the device complexity increases
Solution Approach 1:
The retaining device is merged with the existing ball nut structure. The retaining device is directly connected to the ball nut and integrates seamlessly with it, forming a unified component assembly. This merging approach allows the retaining function to be added without requiring a completely separate, complex retaining mechanism, thereby minimizing the increase in overall device complexity.
3Stability of the object's composition
If the retaining device is positioned to fully constrain the reset spring, then the reset spring stability is improved, but the actuation dynamics are restricted
Solution Approach 1:
The retaining device applies constraint only at the specific location of the end portion of the reset spring, rather than constraining the entire spring. This localized constraint approach maintains the dynamic characteristics and flexibility of the reset spring body while preventing failure at the critical end portion. The retaining device allows sufficient axial movement for dynamic operation but prevents excessive displacement that would cause failure.
Data Source
AI summary
A ball screw, including: a spindle supported for rotation around an axis of rotation; a ball nut radially disposed around the spindle, axially displaceable with respect to the spindle, and including a helical protrusion, the helical protrusion defining a helical groove; a plurality of balls disposed in the helical groove and in contact with the spindle; a reset spring including a portion located in the helical groove and an end portion extending past the helical groove in a circumferential direction around the axis of rotation; and a retaining device directly connected to the ball nut and arranged to limit displacement of the end portion of the reset spring in a first axial direction parallel to the axis of rotation. For a first circumferential position of the spindle around the axis of rotation, the reset spring urges the plurality of balls in a second axial direction, opposite the first axial direction.