Vehicle Seat Longitudinal Adjuster With Resilient Spindle-Worm Drive
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Solution Overview
Problem
Existing longitudinal adjusters for vehicle seats lack increased load-carrying capacity and effective force transmission, particularly in crash scenarios.
Innovation Solution
A longitudinal adjuster with a spindle connected to a worm wheel via a fixing element, allowing resilient power transmission in the longitudinal direction, and featuring a trapezoidal thread design for enhanced torque transmission and force distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the spindle is connected to the worm wheel via a fixing element, then load-carrying capacity is enhanced, but device complexity increases
Solution Approach 1:
The fixing element integrates the spindle and worm wheel into a unified rotational connection, merging two previously separate functional components. This combination enhances load-carrying capacity by creating a rigid torque transmission path while maintaining manageable device complexity through a single integrated fixing mechanism rather than multiple separate connections.
Solution Approach 2:
The fixing element is pre-installed on the spindle before assembly with the worm wheel, establishing a predetermined rotational connection. This preliminary action ensures proper alignment and reduces assembly complexity, while the pre-established connection immediately provides the enhanced load-carrying capacity when the components are engaged.
2Power
If the spindle is rotationally fixed to the worm gear, then torque transmission is improved, but ease of manufacture deteriorates
Solution Approach 1:
The fixing element is designed as a separate, modular component that can be manufactured independently from both the spindle and worm wheel. This segmentation allows each component to be produced using optimized manufacturing processes, improving ease of manufacture while the assembled combination delivers effective torque transmission through the integrated rotational connection.
Solution Approach 2:
The fixing element acts as an intermediary component between the spindle and worm wheel, providing the rotational fixation function without requiring direct integration of the spindle and worm wheel. This intermediary approach simplifies manufacturing by allowing standardization of the fixing element across different configurations while ensuring reliable torque transmission.
3Force
If the spindle has a threadless section pressed between components, then force transmission is enhanced, but device complexity increases
Solution Approach 1:
The spindle features a localized threadless section specifically positioned between the fixing element and worm wheel, creating a focused area for force transmission. This local modification enhances force transmission at the critical interface without requiring the entire spindle to be redesigned, thereby limiting the increase in device complexity to a specific functional zone.
Solution Approach 2:
The threadless section on the spindle introduces a dimensional variation in the spindle's structural properties along its length. This dimensional change creates a distinct zone for force transmission that complements the rotational connection, enhancing overall force transmission capability while maintaining the spindle's fundamental cylindrical geometry and limiting complexity increases.
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 solution enhances load-carrying capacity and ensures efficient force transmission during crashes by providing a resilient connection between the spindle and worm wheel, enabling effective power distribution and torque transmission.
Implementation Method 1
The spindle is screwed into an internal thread of a worm gear of the gearbox by means of an external thread of the spindle
Implementation Method 2
a fixing element which is arranged coaxially to a spindle axis of the spindle and which is pressed between a threadless section at the front end section of the spindle and the worm wheel
Data Source
Figure 1~2
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AI summary
The invention relates to a longitudinal adjustment mechanism (10), more particularly for a vehicle seat (1), the longitudinal adjustment mechanism (10) having at least one rail pair, which is formed of a first rail (12) and a second rail (14) that can be displaced relative to the first rail (12) in the longitudinal direction (x), wherein: the rails (12, 14) engage about one another to form an inner channel (16); a spindle nut (30) connected to the second rail (14) and a spindle (20) operationally connected to the spindle nut (30) are arranged in the inner channel (16); on one end of the first rail (12) a transmission (50) driven by a motor and interacting with the spindle (20) is arranged; the spindle (20) is screwed, by means of an outer thread (22) of the spindle (20), into an internal thread (56) of a worm gear (54) of the transmission (50), and the spindle (20) is conjointly connected by means of a fixing element (58) to the worm gear (54); the fixing element (58) is arranged coaxially to a spindle axle (A) of the spindle (20) and is pressed between an end portion (20a, 20b), more particularly a front end portion (20a), of the spindle (20) and the worm gear (54). The invention further relates to a vehicle seat (1) having such a longitudinal adjustment mechanism (10).