Torque Converter Clutch Slip Control via Target Torque

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Solution Overview

Problem

Existing methods for operating motor vehicles with hybrid drives face challenges in decoupling the prime mover from the driven end while maintaining torque transmission, leading to potential backward rolling on inclines due to reduced power transmission capacity when the torque converter lockup clutch or master clutch is brought into a slip operation.

Innovation Solution

The method involves bringing the torque converter lockup clutch or master clutch into a slip state by specifying a target rotational speed or torque that exceeds the clutch's power transmission capacity, allowing slip to build up without affecting torque transmission to the driven end, and then reducing slip through controlled pressure changes, ensuring neutral impact on wheel torque and preventing unexpected acceleration.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Speed

If the pressure control of the torque converter lockup clutch or master clutch is reduced to decouple the prime mover from the driven end, then the prime mover rotational speed can be increased, but the power transmission capacity is reduced causing noticeable slip and potential backward rolling on inclines

Engineering Contradiction:

Improveprime mover rotational speedVSAvoidtorque transmission stability

Core Design Contradiction:

SpeedVSReliability

Solution Approach 1:

The patent changes the control parameter from pressure reduction to torque demand increase. By specifying a target rotational speed that creates a torque demand exceeding the clutch's power transmission capacity, slip is induced without reducing pressure control, thereby maintaining torque transmission stability while achieving prime mover decoupling and speed increase.

Inventive Principle:

Principle #35Parameter changes

2Adaptability or versatility

If the torque converter lockup clutch or master clutch is brought into slip operation by reducing pressure control, then the prime mover can be decoupled from the driven end, but less torque can be transmitted in the direction of the driven end affecting vehicle dynamics

Engineering Contradiction:

Improverotational speed decoupling capabilityVSAvoidtorque transmission to driven end

Core Design Contradiction:

Adaptability or versatilityVSForce

Solution Approach 1:

Instead of reducing pressure control to induce slip (conventional approach), the patent inverts the approach by maintaining non-reduced pressure control and inducing slip through increased torque demand via target rotational speed specification. This inversion allows slip operation while preserving torque transmission capacity.

Inventive Principle:

Principle #13The other way round (Inversion)

3Speed

If the pressure control is reduced to bring the clutch into slip operation, then the prime mover rotational speed can be increased, but the process is noticeable at the driven end affecting comfort and safety

Engineering Contradiction:

Improveprime mover rotational speedVSAvoidvehicle operation smoothness

Core Design Contradiction:

SpeedVSEase of operation

Solution Approach 1:

Inventive Principle:

Principle #35Parameter changes

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

This approach maintains torque transmission to the driven end while allowing prime mover rotational speed increase, enhancing comfort, safety, and vehicle dynamics by avoiding torque reduction and ensuring controlled slip management.

Implementation Method 1

the transmission is friction-locking, i.e., when the prime-mover rotational speed is coupled to the driven-end rotational speed via the transmission ratio

Methodology Applied

Scientific EffectFriction: Friction

Implementation Method 2

the torque converter lockup clutch or the master clutch is subsequently brought into a slip operation in order to thereby decouple the prime-mover rotational speed from the driven-end rotational speed

Methodology Applied

Scientific EffectFriction: Friction

Data Source

PatentUS10293814B2Method and control unit for a motor vehicle

Publication Date: 2019.05.21 ZF FRIEDRICHSHAFEN AG

AI summary

A method for operating a motor vehicle originates from a condition in which a torque converter lockup clutch (6) or a master clutch (13) is engaged and the transmission (2) is friction-locking. The torque converter lockup clutch (6) or the master clutch (13) is then brought into a slip condition on a control side, and a prime-mover rotational speed is decoupled from a driven-end rotational speed. The torque converter lockup clutch (6) or the master clutch (13) is brought into the slip condition without reducing a pressure control of the torque converter lockup clutch (6) or the master clutch (13) and by specifying a target rotational speed or a target torque for the prime mover (1) such that a torque or a target torque is greater than a power transmission capacity of the torque converter lockup clutch (6) or the master clutch (13) and slip is built up.