Clutch Torque Profile for Smooth Engine Start

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Solution Overview

Problem

Existing methods for starting an internal combustion engine using a controllable clutch result in a 'dead time' and abrupt torque buildup, leading to reduced comfort and delayed engine start, due to a non-monotonically increasing actual clutch torque curve.

Innovation Solution

The desired clutch torque is built up in a strictly monotonically increasing manner, with a steep initial gradient followed by a lower second gradient and then a flatter third gradient, ensuring the actual clutch torque reaches the application point quickly and transitions smoothly to a constant level, reducing 'dead time' and improving comfort.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of time

If the target clutch torque is built up in steps with a steep gradient to reach the engagement point quickly, then the engine start time is reduced, but the actual clutch torque becomes non-monotonically increasing causing abrupt torque buildup and reduced comfort

Engineering Contradiction:

Improveengine start timeVSAvoidabrupt torque buildup affecting comfort

Core Design Contradiction:

Loss of timeVSObject-affected harmful factors

Solution Approach 1:

The patent applies dynamics by continuously adapting the clutch torque buildup profile based on real-time feedback from engine speed, transmission input shaft speed, and clutch slip. The control method dynamically adjusts the torque gradient to maintain monotonic increase while reaching the engagement point efficiently, transforming the static stepwise approach into a dynamic continuous process that responds to actual system state.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent implements feedback control by continuously monitoring engine speed, transmission input shaft speed, and clutch slip, then using this information to adjust the target clutch torque profile. The feedback mechanism ensures the actual clutch torque follows a monotonically increasing curve by comparing the desired torque profile with actual system response and making real-time corrections.

Inventive Principle:

Principle #23Feedback

2Reliability

If the clutch torque increases linearly with strong gradient after engagement point, then the engagement is achieved, but the vehicle components experience abrupt displacement and increased reliance on rubber component mounts reducing comfort

Engineering Contradiction:

Improveclutch engagement reliabilityVSAvoidcomponent displacement and rubber mount stress

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent changes the torque profile parameters dynamically during the engagement process. Instead of using fixed linear gradients, the system adjusts the torque buildup rate based on actual clutch slip and system response, ensuring smooth transition through the engagement point and reducing abrupt displacements of vehicle components.

Inventive Principle:

Principle #35Parameter changes

3Reliability

If the clutch torque is built up in steps until engagement point then held constant, then the engagement point is reached, but a dead time occurs delaying the engine start

Engineering Contradiction:

Improveclutch engagement stabilityVSAvoidengine start delay

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The patent eliminates dead time by maintaining continuous monotonic increase of clutch torque through the engagement point. Instead of holding torque constant after reaching the engagement point, the system continues building torque smoothly, ensuring the engine starts without interruption. This continuous action principle removes the harmful pause in the torque transmission process.

Inventive Principle:

Principle #20Continuity of useful action

Data Source

PatentEP3380741B1Method for controlling the clutch of a motor vehicle

Publication Date: 2020.01.08 VOLKSWAGEN AG

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AI summary

The invention relates to a method for controlling the clutch of a motor vehicle, wherein the motor vehicle has an internal combustion engine, a transmission, and a clutch, wherein the clutch is operatively provided and/or arranged between the internal combustion engine and the transmission in order to transmit a torque and, by means of the clutch, an output shaft of the internal combustion engine can be coupled to a transmission input shaft of the transmission for transmission of the torque, wherein a transmission output shaft is operatively connected and/or coupled to drive wheels of the motor vehicle and wherein, in coasting operation of the motor vehicle, in which the motor vehicle rolls drive-free while the internal combustion engine switched off and while the clutch is at least partially, in particular completely open, the internal combustion engine is dragged along by closing the clutch in order to start the internal combustion engine, wherein a clutch target torque Ksoll and/or a progression of a clutch target torque Ksoll is specified and then a clutch actual torque Kist and/or a progression of a clutch actual torque Kist arises, and wherein the application point of the clutch to be closed is substantially determined and/or is substantially known as an application point accordingly ascertained and/or adapted in the case of one of the last closing operations. The internal combustion engine can be started earlier and the driving comfort is increased in that the progression of the clutch target torque Ksoll is constructed in such a way that the clutch actual torque Kist passes through the application point substantially in a strictly monotonically increasing manner.