Creep-Mode Gearshift Control with Target Engine Speed Matching

Solution Overview

Problem

Current methods for gearshift in creep mode of heavy vehicles either require terminating the creep mode or result in uncomfortable and slower gearshifts, leading to increased clutch wear.

Innovation Solution

A method involving a control device that disconnects the combustion engine from the gearbox, shifts the gearbox to a target speed corresponding to a desired torque ramp, and reconnects it, allowing for comfortable and reduced-clutch-wear gearshifts during creep mode.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If the vehicle speed is automatically increased before the gearshift (first alternative), then the gearshift is faster, but the comfort is reduced and clutch wear is increased

Engineering Contradiction:

Improvegearshift speedVSAvoidgearshift comfort

Core Design Contradiction:

ProductivityVSEase of operation

Solution Approach 1:

The control device determines a target engine speed corresponding to the desired vehicle speed after gearshift before actually executing the gearshift. By preparing the engine speed in advance (increasing it slightly above idle speed), the system ensures that when the clutch is engaged, the speed mismatch is minimized, enabling faster and more comfortable gearshift without excessive clutch wear

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system dynamically adjusts the engine speed parameter during the gearshift process. Instead of maintaining constant idle speed, the control device increases the engine speed to a target value that corresponds to the higher vehicle speed after gearshift. This parameter change allows the clutch to engage with minimal speed difference, resolving the contradiction between fast gearshift and comfort

Inventive Principle:

Principle #35Parameter changes

2Ease of operation

If the vehicle speed is automatically increased to the new higher speed by reengagement of the clutch after gearbox shift (second alternative), then the gearshift is more comfortable, but the gearshift is slower and clutch wear is increased

Engineering Contradiction:

Improvegearshift comfortVSAvoidgearshift time

Core Design Contradiction:

Ease of operationVSLoss of time

Solution Approach 1:

The control device determines a target engine speed corresponding to the desired vehicle speed after gearshift before actually executing the gearshift. By preparing the engine speed in advance (increasing it slightly above idle speed), the system ensures that when the clutch is engaged, the speed mismatch is minimized, enabling faster and more comfortable gearshift without excessive clutch wear

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system dynamically adjusts the engine speed parameter during the gearshift process. Instead of maintaining constant idle speed, the control device increases the engine speed to a target value that corresponds to the higher vehicle speed after gearshift. This parameter change allows the clutch to engage with minimal speed difference, resolving the contradiction between fast gearshift and comfort

Inventive Principle:

Principle #35Parameter changes

3Loss of time

If the engine speed is controlled to a target speed corresponding to desired torque for completing torque ramp during clutch closing, then clutch wear is reduced and gearshift is faster, but the control complexity increases

Engineering Contradiction:

Improveclutch engagement timeVSAvoidcontrol system complexity

Core Design Contradiction:

Loss of timeVSDevice complexity

Solution Approach 1:

The control device continuously monitors the actual engine speed and compares it with the target engine speed. Based on this feedback, the control device adjusts the engine speed by controlling the fuel injection amount and ignition timing. This closed-loop feedback control ensures accurate speed regulation without requiring overly complex control logic

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The control device utilizes existing engine control capabilities (fuel injection and ignition timing control) to achieve speed regulation. By leveraging the engine's own control systems rather than introducing separate control mechanisms, the solution reduces overall system complexity while still achieving the desired torque ramp and reduced clutch wear

Inventive Principle:

Principle #25Self-service

Data Source

PatentUS12168444B2Control device, vehicle, computer program, computer readable medium and method for performing a gearshift during creep mode

Publication Date: 2024.12.17 SCANIA CV AB

AI summary

A method for, during creep mode, performing gearshift in a vehicle powertrain comprising a combustion engine, a gearbox, and a clutch is provided. The method comprises, in response to a request for gearshift, disconnecting the combustion engine from the gearbox by opening the clutch. The method further comprises, when the combustion engine is disconnected from the gearbox, shifting the gearbox and controlling the speed of the combustion engine to a target speed. Said target speed constitutes a combustion engine speed corresponding a desired combustion engine torque for completing a torque ramp during closing of the clutch. The method further comprises connecting the combustion engine to the gearbox by closing the clutch. A control device configured to perform the method and a vehicle comprising the control device are also provided.