Seat Linear Actuator With Phase-Offset Teeth for Backlash-Free Motion
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Solution Overview
Problem
Existing linear actuators for seat adjustment in vehicles face challenges in achieving backlash-free movement, adapting to varying loads, and ensuring high adjustment speed, with complex manufacturing processes.
Innovation Solution
A linear drive mechanism with drive teeth and a rack system, where the drive teeth engage and disengage from the rack with a phase offset during the drive shaft's rotation, utilizing asymmetric tooth distances and friction surfaces for propulsion, and incorporating guide means and roller contacts for smooth operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a spindle mechanism is used for linear adjustment, then the structure is simple and easy to manufacture, but backlash-free movement cannot be achieved
Solution Approach 1:
The linear drive is segmented into multiple drive teeth (at least two) that engage with the rack in sequence. Each drive tooth can be moved independently to engage or disengage from the rack, allowing the system to achieve backlash-free movement through coordinated segmentation of the driving elements rather than relying on a single complex spindle mechanism.
Solution Approach 2:
The drive teeth perform cyclical lifting movements with a phase offset during rotation of the drive shaft. This periodic engagement and disengagement from the rack creates a continuous propulsion effect while eliminating backlash, as each drive tooth repeatedly enters and exits the rack in a controlled periodic sequence.
2Productivity
If multiple drive teeth with phase offset are used, then backlash-free high-speed movement is achieved, but the manufacturing process becomes more complex
Solution Approach 1:
The drive system uses multiple independent drive teeth that can be manufactured as separate components. Each drive tooth is a discrete element that can be produced using standard manufacturing processes, then assembled onto the drive shaft. This segmentation allows for simpler individual part manufacturing while achieving high-speed backlash-free operation through the coordinated action of multiple teeth.
Solution Approach 2:
The drive teeth are designed to be movable and adjustable on the drive shaft, allowing dynamic positioning and phase offset control. This dynamic capability enables high-speed adjustment while maintaining manufacturing simplicity, as the teeth can be positioned and phased during assembly or operation without requiring complex fixed mechanisms.
3Power
If friction surfaces with wedge shape are used for propulsion, then power transmission is improved, but friction losses increase
Solution Approach 1:
The friction surfaces of the drive teeth and rack teeth are designed with asymmetric wedge shapes. The wedge angle and surface geometry are optimized to provide strong propulsion forces during engagement while minimizing the contact area and duration of frictional interaction. This asymmetric design allows the surfaces to generate effective propulsive force while reducing overall energy loss to friction.
Solution Approach 2:
The cyclical engagement and disengagement of drive teeth with the rack creates periodic friction contact rather than continuous contact. During each engagement phase, the wedge-shaped friction surfaces provide strong propulsive force; during the disengagement phase, friction losses are eliminated. This periodic action pattern allows high power transmission during active phases while minimizing average friction losses over the complete cycle.
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
Enables virtually backlash-free, high-speed, and adjustable linear movement with variable breaking loads, improving power transmission and reducing friction losses.
Implementation Method 1
the drive tooth and the rack tooth coming into operative contact at so-called friction surfaces, resulting in propulsion
Data Source
Figure 1~2
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Figure 5~6
AI summary
The present invention relates to a linear drive (1) having a drive shaft (10) along a longitudinal axis (X), at least two propelling teeth (20), and at least one gear rack (30) comprising a plurality of teeth (31), the propelling teeth (20) being reciprocatingly movable perpendicularly to the longitudinal axis (X) and being drivingly connected to the drive shaft (10) such that said at least two propelling teeth (20) carry out at least one cyclical reciprocating movement (21) during the course of one revolution (φ) of the drive shaft (10), dipping into and out of the at least one gear rack (30) in order to produce propelling motion along the longitudinal axis (X), the cyclical reciprocating movement (21) of the at least two propelling teeth (20) having offset phases (Δφ). The present invention also relates to a longitudinal-adjustment unit and to a motor vehicle comprising a longitudinal-adjustment unit of this type.