Brake Ball-Nut Assembly Contact Geometry for Low Friction
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Solution Overview
Problem
Existing brake systems with ball and nut assemblies (BNAs) face issues of inconsistent operation, distortion, and increased friction, leading to premature wear and degradation, which affects the lifespan and efficiency of the brake system.
Innovation Solution
A BNA design featuring a nut and spindle with enhanced contact regions, including multiple line contacts and planar contacts, and the use of bearings to minimize direct contact, reducing friction and preventing unwanted tilting, along with anti-rotation features to ensure consistent operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a ball and nut assembly is used to convert rotary motion to linear motion in a brake system, then the actuator can drive a piston to create clamping force, but the movable components experience wear and distortion over time leading to inconsistent operation
Solution Approach 1:
The patent introduces a flange as an intermediary component between the ball and nut assembly and the end stop. This flange distributes the contact forces across multiple engagement surfaces rather than concentrating them at a single point, thereby reducing wear on individual components and preventing distortion. The intermediary flange absorbs and redistributes the mechanical stresses, maintaining operational consistency throughout the component's lifespan.
2Productivity
If the spindle rotates continuously to drive the piston, then linear motion is generated, but friction between the spindle and additional components increases, causing degradation
Solution Approach 1:
The patent transitions from a single-line contact interface to a multi-surface engagement geometry. By designing the flange with multiple engagement surfaces that contact the end stop at different locations and orientations, the force distribution is moved from a one-dimensional line contact to a two-dimensional area contact. This dimensional change reduces frictional losses by spreading the contact pressure across larger surface areas, thereby maintaining brake apply efficiency while reducing energy loss to friction.
3Ease of operation
If the contact area between the end stop and spindle is minimized to reduce friction, then rotation is easier, but the spindle may tilt or deflect under load
Solution Approach 1:
The patent segments the contact interface into multiple discrete engagement surfaces distributed around the spindle-flange-end stop assembly. Rather than a single large contact area, the contact is divided into multiple smaller surfaces at different angular positions. This segmentation allows the spindle to rotate with minimal friction at each individual contact point while the collective arrangement of segmented contacts provides sufficient support to prevent tilting and maintain alignment under operational loads.
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 design enhances the operational consistency and longevity of the BNA by reducing friction and preventing distortion, maintaining continuous contact and efficient load transfer, thereby improving the overall performance and lifespan of the brake system.
Implementation Method 1
a spindle having a threaded portion positioned at least partially within the nut so that the threaded portion of the spindle engages the threaded portion of the nut
Implementation Method 2
the contact region includes a circumferential area greater than a circumferential area of a single line contact between the end stop and the spindle
Data Source
AI summary
A ball and nut assembly adapted for a brake system of a vehicle, comprising: (a) a nut having a threaded portion; (b) a spindle having a threaded portion positioned at least partially within the nut so that the threaded portion of the spindle engages the threaded portion of the nut; and (c) an end stop positioned adjacent to the spindle, wherein a mating area is located between the end stop and the spindle, the mating area includes a contact region in which the end stop contacts the spindle directly or indirectly, and the contact region includes a circumferential area greater than a circumferential area of a single line contact between the end stop and the spindle.