Ballnut Lubrication Reservoirs for Ballscrew Leakage Control

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Solution Overview

Problem

Ballscrew actuators experience lubricant leakage, leading to reduced efficiency and increased maintenance frequency due to inefficient lubrication distribution and retention within the helical raceway.

Innovation Solution

Incorporating lubricant reservoirs and seals at the ends of the nut, along with a lubricant passage and ports, and a track wiper to redirect and distribute lubricant back into the helical raceway, combined with a lubricant injection assembly to optimize lubricant levels.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If traditional lubrication without reservoirs is used, then the structure is simple, but lubricant leakage occurs and lubrication efficiency decreases

Engineering Contradiction:

Improvelubrication efficiencyVSAvoidstructure complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The lubricant reservoirs are integrated within the nut body structure, with passages connecting the reservoirs to the helical groove. This nesting approach allows the lubrication system to be embedded within the existing nut geometry, improving lubrication efficiency while minimizing additional structural complexity.

Inventive Principle:

Principle #7Nested doll (Nesting)

Solution Approach 2:

Lubricant is pre-stored in the lubricant reservoirs formed in the nut body before operation begins. This preliminary storage ensures that lubricant is readily available at the start of operation and during intervals between external reapplications, maintaining reliable lubrication without requiring continuous external supply.

Inventive Principle:

Principle #10Preliminary action

2Loss of substance

If lubricant reservoirs and passages are added, then lubricant retention improves, but manufacturing complexity increases

Engineering Contradiction:

Improvelubricant lossVSAvoidmanufacturing ease

Core Design Contradiction:

Loss of substanceVSEase of manufacture

Solution Approach 1:

The lubricant reservoirs, passages, and end seals are combined into an integrated lubrication system within the nut. This merging of functions reduces the number of separate components and assembly steps, improving lubricant retention while keeping manufacturing complexity manageable through consolidation rather than proliferation of parts.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

Lubricant reservoirs are strategically formed at specific locations within the nut body, and seals are positioned at axial ends where lubricant leakage occurs. This localized approach addresses lubricant loss at critical points without requiring modifications throughout the entire structure, balancing improved retention with manufacturing feasibility.

Inventive Principle:

Principle #3Local quality

3Reliability

If seals are added at axial ends, then lubricant leakage is reduced, but device complexity increases

Engineering Contradiction:

Improvesealing effectivenessVSAvoidcomponent count

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The sealing function is segmented and distributed to multiple seals positioned at different axial ends of the nut, rather than relying on a single sealing mechanism. This segmentation provides comprehensive sealing coverage to prevent lubricant leakage at multiple potential escape points while keeping each individual seal component relatively simple.

Inventive Principle:

Principle #1Segmentation

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

Significantly reduces lubricant loss and ensures consistent lubrication throughout the ballscrew assembly, enhancing operational efficiency and extending the interval between lubricant reapplications.

Implementation Method 1

at least one lubricant reservoir formed in the nut body at or adjacent to an end of the helical raceway

Methodology Applied

Scientific EffectFluid containment: Physical Containment

Implementation Method 2

a lubricant passage extending through the nut body and fluidly coupled to the at least one lubricant reservoir; wherein the lubricant reservoir is fluidly linked to the helical groove of the nut via the lubricant passage

Methodology Applied

Scientific EffectFluid flow through passage: Convection

Implementation Method 3

at least one seal disposed between the at least one lubricant reservoir and an axial end of the nut, the seal sealingly engaging the nut and the screw shaft

Methodology Applied

Scientific EffectSealing: Physical Containment

Data Source

PatentUS11236815B2Ballnut lubrication

Publication Date: 2022.02.01 GOODRICH ACTUATION SYST

AI summary

A ballscrew assembly comprises: a nut having a nut body with a radially inner surface and a helical groove formed on the radially inner surface; a screw shaft disposed within the nut, the screw shaft comprising a radially outer surface and a groove formed on the outer surface, the groove on the screw shaft cooperating with the groove on the nut to define a helical raceway for a plurality of balls; at least one lubricant reservoir formed in the nut body at or adjacent to an end of the helical raceway; and a lubricant passage extending through the nut body and fluidly coupled to the at least one lubricant reservoir; wherein the lubricant reservoir is fluidly linked to the helical groove of the nut via the lubricant passage.