Automatic Transmission Clutch Slip Control for Coasting Fuel Efficiency

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Solution Overview

Problem

Current fuel-cut control methods in automatic transmissions lead to rapid vehicle deceleration when coasting, necessitating premature accelerator re-engagement, resulting in only slight improvements in fuel efficiency.

Innovation Solution

Implementing clutch slip logic in automatic transmissions to determine coasting conditions and adjust clutch slip control time and torque, reducing engine brake torque and allowing vehicles to decelerate at a desired speed without rapid loss of momentum.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If fuel-cut control is used to improve fuel efficiency during coasting, then fuel consumption is reduced, but vehicle deceleration becomes too rapid causing driver discomfort and premature accelerator re-engagement

Engineering Contradiction:

Improvefuel efficiencyVSAvoidvehicle deceleration rate

Core Design Contradiction:

Use of energy by moving objectVSSpeed

Solution Approach 1:

The patent changes the control parameter from binary fuel-cut on/off to continuous clutch slip ratio control. By adjusting the clutch slip ratio dynamically during coasting, the system modulates engine brake torque to achieve a balanced deceleration rate that maintains both fuel efficiency and driving comfort, preventing premature accelerator re-engagement.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The system transitions from static fuel-cut control to dynamic clutch slip control. The clutch slip ratio is continuously adjusted based on vehicle speed, deceleration rate, and driver intent, enabling real-time optimization of the balance between fuel efficiency and acceptable deceleration characteristics.

Inventive Principle:

Principle #15Dynamics

2Loss of energy

If engine brake is activated during coasting to reduce fuel consumption, then fuel efficiency improves slightly, but vehicle momentum is lost rapidly requiring accelerator re-engagement

Engineering Contradiction:

Improvefuel consumption during coastingVSAvoidcoasting duration

Core Design Contradiction:

Loss of energyVSDuration of action of moving object

Solution Approach 1:

The system performs preliminary determination of coasting conditions and pre-calculates optimal clutch slip control parameters before actual coasting begins. This allows the engine to remain in a ready state for fuel injection while the clutch slip control prepares to modulate power transmission, enabling smoother transition and extended coasting duration without momentum loss.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent maintains continuous clutch slip control throughout the coasting phase, ensuring uninterrupted modulation of engine brake torque. This continuous control prevents abrupt momentum loss and extends the duration of effective coasting by smoothly managing the transition between engine power and vehicle inertia.

Inventive Principle:

Principle #20Continuity of useful action

Data Source

PatentUS8938341B2Method for controlling clutch of automatic transmission for improvement of fuel efficiency

Publication Date: 2015.01.20 HYUNDAI MOTOR CO LTD

AI summary

A method for controlling a clutch of an automatic transmission for improvement of fuel efficiency may include determining whether external driving conditions of a vehicle meets coasting conditions, determining a clutch slip control time and an amount of clutch slip torque according to internal driving conditions of the vehicle, performing slip control on a clutch that works at each step of the automatic transmission using the determined clutch slip control time and torque, wherein an engine brake torque transmitted to a final output shaft of the automatic transmission may be reduced.