Ball-Engagement Clutch with Spring Preload for High Torque Transfer

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Solution Overview

Problem

Existing drive train systems face challenges in efficiently transmitting high torques due to limitations in friction clutches, which can lead to premature wear and damage when exceeding torque limits, and require innovative solutions for reliable and durable torque transmission.

Innovation Solution

A positive-locking clutch system with axially displaceable balls and a spring device for axial prestressing, allowing for uniform support and high torque transmission, combined with a friction clutch for initial synchronization, enabling efficient transmission of high torques without excessive wear or damage.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If a friction clutch is used to transmit torque in a drive train, then the torque transmission is smooth and wear is controlled, but the maximum transmittable torque is limited and wear increases over time

Engineering Contradiction:
Improvemaximum transmittable torqueVSAvoidclutch durability
Core Design Contradiction:
StrengthVSReliability

Solution Approach 1:

The clutch system is divided into two separate clutch units: a friction clutch for smooth torque transmission and a positive-locking clutch for high torque transmission. Each clutch is optimized for its specific function, allowing the system to handle both normal and peak torque conditions reliably without excessive wear on either component.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The system changes the torque transmission mechanism parameter from friction-based to form-fitting-based when high torque conditions are detected. The positive-locking clutch engages to transmit torques above the friction clutch's limit torque, fundamentally changing how torque is transmitted to prevent wear and damage.

Inventive Principle:
Principle #35Parameter changes

2Strength

If multiple balls are used for positive-locking coupling, then high torque transmission is enabled, but uniform load distribution among balls becomes difficult to achieve

Engineering Contradiction:
Improvetorque transmission capacityVSAvoidball position uniformity
Core Design Contradiction:
StrengthVSManufacturing precision

Solution Approach 1:

A spring device is introduced that preliminarily pre-stresses each ball in the axial direction before torque transmission begins. This preliminary action ensures that all balls are positioned uniformly and are pre-loaded, so when torque is applied, the load is evenly distributed across all balls from the start, preventing individual ball overload.

Inventive Principle:
Principle #10Preliminary action

Solution Approach 2:

The spring device acts as an intermediary between the actuating element and the balls. It mediates the force transmission by applying uniform axial pre-stress to each ball, ensuring that variations in ball positioning due to manufacturing tolerances do not lead to uneven load distribution during operation.

Inventive Principle:
Principle #24Intermediary (Mediator)

3Ease of manufacture

If balls are inserted with play in the receiving recess, then ease of assembly is improved, but load distribution among balls becomes uneven leading to premature wear

Engineering Contradiction:
Improveassembly easeVSAvoidball load distribution
Core Design Contradiction:
Ease of manufactureVSReliability

Solution Approach 1:

The spring device applies axial pre-stress to each ball before torque transmission begins, compensating for the play in the receiving recess. This preliminary action ensures that even though balls can move axially during assembly, they are pre-positioned and pre-loaded uniformly, eliminating the negative effects of assembly play during operation.

Inventive Principle:
Principle #10Preliminary action

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 system ensures reliable and efficient transmission of high torques by maintaining even ball contact and load distribution, preventing premature wear and damage, while allowing for seamless transition beyond friction clutch limits, thus enhancing drive train performance.

Implementation Method 1

a spring device attached to the actuating element for axial prestressing of each ball within the receiving recess towards the axial toothing

Methodology Applied
Scientific EffectSpring force: Spring

Implementation Method 2

the rotational speed of the output element is synchronized with the input element when the friction clutch is in slipping operation

Methodology Applied
Scientific EffectFriction: Friction

Data Source

PatentEP3976985B1Positive coupling and method for coupling a motor shaft to a transmission input shaft and/or to an intermediate shaft
Publication Date: 2023.03.08 SCHAEFFLER TECHNOLOGIES AG & CO KG
  • EP3976985B1 patent drawingFigure 1
  • EP3976985B1 patent drawingFigure 2~3

AI summary

A positive-engagement clutch (14) is provided with an input element (10), which can be directly or indirectly coupled to the motor shaft in order to introduce a torque, an output element (12), which can be rotated relative to the input element (10) in order to output the torque, multiple axially movable balls (18) for coupling the output element (12) to the input element (10) in positive engagement, and an actuation element (20) for axially moving the balls (18) between a closed position, in which they are inserted into an axial toothing and an open position, in which they are axially offset relative to the axial toothing. The balls are inserted into a radial toothing (24) between the closed position and the open position, and the actuation element (20) has a receiving depression (22) for partly receiving each ball (18). The clutch also comprises a spring device (26) which is secured to the actuation element (20) in order to axially bias each ball (18) within the receiving depression (22) onto the axial toothing. The spring device (26) ensures the uniform support of the balls (18), allowing effective transmission of high torques in a powertrain.