Seat Lifter Clutch with Axial Teeth Locking Against Reverse Torque

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Solution Overview

Problem

Conventional clutch units in automobile seat lifters experience seat height instability due to hysteresis and elastic deformation during vehicle vibrations on rough roads, causing the seat to lower due to alternating forward and reverse rotational torque inputs.

Innovation Solution

A clutch unit with a recess-projection fitting part between the stationary and clutch members, featuring teeth on axial end surfaces, which securely locks the output shaft by meshing in the rotation direction, minimizing axial movement and maintaining seat height by blocking reverse torque inputs.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If cylindrical rollers are used to control torque transmission through wedge gap engagement, then the clutch unit can transmit and block rotational torque, but hysteresis and elastic deformation occur during vehicle vibrations causing seat height instability

Engineering Contradiction:

Improveseat height stabilityVSAvoidhysteresis and elastic deformation

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent replaces the cylindrical roller wedge gap engagement mechanism with a recess-projection fitting part featuring teeth on axial end surfaces. This teeth-meshing mechanism eliminates hysteresis and elastic deformation by providing direct geometric locking between the clutch member and stationary member, ensuring stable seat height during vehicle vibrations.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

Instead of using cylindrical rollers that engage with wedge gaps (conventional approach), the patent inverts the approach by using recess-projection fitting parts with teeth that mesh directly in the rotation direction. This inversion provides positive mechanical locking without the elastic deformation issues of the roller-based system.

Inventive Principle:

Principle #13The other way round (Inversion)

2Reliability

If a recess-projection fitting part with teeth is provided between the clutch member and stationary member, then the output shaft can be securely locked during alternating torque inputs, but the axial movement distance of the clutch member increases

Engineering Contradiction:

Improvelocking reliability during alternating torque inputsVSAvoidaxial movement distance of clutch member

Core Design Contradiction:

ReliabilityVSLength of moving object

Solution Approach 1:

The patent forms teeth on the axial end surfaces of the clutch member and stationary member, utilizing the axial dimension for torque transmission and locking. This allows the teeth to mesh in the rotation direction while minimizing axial movement distance, as the locking action occurs primarily through rotational meshing rather than axial displacement.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

3Ease of operation

If the teeth part is formed on the axial end surface of the clutch member and stationary member, then the meshing is facilitated and axial movement is minimized, but the manufacturing complexity increases

Engineering Contradiction:

Improvemeshing facilitation and axial movement minimizationVSAvoidmanufacturing complexity of teeth parts

Core Design Contradiction:

Ease of operationVSEase of manufacture

Solution Approach 1:

The recess-projection fitting part with teeth on axial end surfaces serves multiple functions: it provides secure locking during alternating torque inputs, minimizes axial movement distance, and facilitates meshing in the rotation direction. By integrating these functions into a single structural feature, the patent reduces overall device complexity despite the added manufacturing step of forming teeth.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Data Source

PatentEP3686452B1Clutch unit

Publication Date: 2023.08.30 NTN CORP

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AI summary

A clutch unit includes a lever-side clutch part 11 that controls transmission and blocking of a rotational torque to be input, and a brake-side clutch part 12 that transmits the rotational torque from the lever-side clutch part 11 to an output side and blocks the rotational torque reversely input from the output side. The brake-side clutch part 12 includes an input shaft 15, an output shaft 31 that is arranged coaxially with and opposing to the input shaft 15, an outer ring 33 that rotatably supports the input shaft 15 and the output shaft 31, and an output gear 36 that is arranged between the input shaft 15 and the output shaft 31 so as to be axially movable. A recess-projection fitting part 54 that can be meshed in a rotation direction is provided between the output gear 36 and the outer ring 33. The recess-projection fitting part 54 is constituted of a teeth part 56 formed on an axial end surface of the outer ring 33, and a teeth part 55 formed on an axial end surface of the output gear 36 opposing to the axial end surface of the outer ring 33.