Spring-Loaded Rack-and-Slide Linear Drive for Backlash-Free Seat Adjustment
Solution Overview
Problem
Existing linear drives for seat adjustment in vehicles face challenges in achieving backlash-free motion, managing breaking loads, and accommodating novel seating concepts, with wear leading to loss of smooth operation.
Innovation Solution
A linear drive design featuring a rack and slides with spring-loaded compensating means, allowing for operative contact that compensates for tolerances and wear, ensuring smooth, virtually backlash-free movement with adjustable breaking loads.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional linear drives with spindles are used, then the structure is simple and manufacturing is easier, but backlash-free operation cannot be achieved and wear leads to loss of smooth operation
Solution Approach 1:
The invention employs dynamic elements including spring-loaded slides that can move axially to compensate for wear and tolerances, and a drive shaft with variable eccentricity that can be adjusted during operation. These dynamic components enable the system to maintain backlash-free operation while adapting to wear over time, resolving the contradiction between reliability and complexity.
Solution Approach 2:
The invention changes key parameters including the eccentricity of the drive shaft (which can be varied to adjust the amplitude of slide movement), the spring preload forces on the slides, and the clearance between slides and rack. By dynamically adjusting these parameters, the system maintains optimal performance without backlash while managing the complexity through controlled parameter variation.
2Strength
If breaking loads are increased to ensure safety, then accident safety is improved, but the adjustment speed decreases and the drive becomes less responsive
Solution Approach 1:
The invention segments the load-bearing function across multiple slides (typically three or more) distributed around the drive shaft circumference. Each slide carries a portion of the total load, allowing the system to achieve high breaking load capacity while maintaining light individual slide weights and fast response times. This segmentation resolves the contradiction between strength and speed.
Solution Approach 2:
The drive shaft rotates periodically, causing the slides to move in a cyclic manner with each slide experiencing alternating periods of engagement and disengagement with the rack. This periodic action allows the system to build up high instantaneous forces during engagement (providing high breaking load) while maintaining fast cyclic movement (providing high adjustment speed).
3Manufacturing precision
If precision manufacturing is used to eliminate tolerances, then backlash-free operation is achieved, but manufacturing cost and complexity increase significantly
Solution Approach 1:
The invention incorporates spring-loaded slides that provide beforehand cushioning against the effects of manufacturing tolerances and wear. The springs are pre-loaded to compensate for expected tolerance variations, allowing the use of standard manufacturing tolerances while still achieving backlash-free operation. This approach resolves the contradiction by providing compensation in advance rather than requiring ultra-precise manufacturing.
Solution Approach 2:
The spring elements act as intermediaries between the slides and the rack, absorbing the effects of manufacturing tolerances and wear. Instead of requiring precise direct contact between slides and rack, the spring intermediaries provide a compliant interface that compensates for dimensional variations, making manufacturing easier while maintaining precision operation.
4Duration of action of stationary object
If the linear drive is designed for long service life, then wear resistance is improved, but the initial complexity and manufacturing difficulty increase
Solution Approach 1:
The invention employs self-service mechanisms where the spring-loaded slides automatically compensate for wear as it occurs, without requiring external intervention or complex monitoring systems. The springs continuously apply preload to maintain contact between slides and rack, and the variable eccentricity mechanism automatically adjusts to accommodate wear-induced clearance changes. This self-service approach extends service life while keeping the compensating mechanisms relatively simple.
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 provides a compact, high-speed, and durable linear drive with improved wear characteristics, maintaining smooth operation and reducing noise, suitable for various seating concepts.
Implementation Method 1
the at least one compensating means provides spring action, in particular preload, to at least one of the at least two slides and/or the at least one rack
Implementation Method 2
the operative contact between at least one of the at least two slides and the at least one rack is spring-loaded or pre-tensioned
Implementation Method 3
the slides, through operative contact with the at least one rack, are pushed along the rack to generate a thrust in a direction along the longitudinal axis
Data Source
Figure 1~2
Figure 3~5
Figure 6a~7b
AI summary
The present invention relates to a linear drive (1) comprising at least one rack (20) oriented along a longitudinal axis (L) and at least two slides (30) movable transversely to the longitudinal axis (L), and a drive shaft (60), wherein the at least two slides (30) are coupled to the drive shaft (60) such that the at least two slides (30) each perform at least one cyclic and mutually phase-shifted movement during one revolution of the drive shaft (60) and thereby slide off the at least one rack (20) by means of an operative contact to generate a thrust in a direction of the longitudinal axis (L), wherein the linear drive (1) comprises at least one compensating means (15) by which the operative contact between at least one of the at least two slides (30) and the at least one rack (20) is biased.