Closed-Loop Torque Phase Control for Automatic Transmission Shifting

Solution Overview

Problem

Conventional automatic transmission shift control methods rely on open-loop approaches based on speed measurements, leading to inconsistent shift feel and undesirable shift shock due to premature or delayed release of friction elements, and sensitivity to slip conditions.

Innovation Solution

A closed-loop shift control system that estimates friction element load levels to predict optimal release timing and engage on-coming friction elements, ensuring consistent shift feel by maintaining torque capacity until the off-going friction element's load drops below a predetermined level.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If open-loop control based on pre-calibrated timing is used to release the off-going friction element, then the control system is simple, but the shift feel is inconsistent and shift shock occurs

Engineering Contradiction:

Improvecontrol system complexityVSAvoidshift feel consistency

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The patent implements closed-loop feedback control by continuously monitoring the actual torque phase duration and comparing it to a target value. The controller adjusts the off-going friction element release timing based on the difference between actual and target torque phase durations, ensuring consistent shift feel across varying operating conditions while maintaining reasonable system complexity.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent uses speed measurements of powertrain components (engine, transmission input shaft) to predict and prepare for the optimal release timing of the off-going friction element before the torque phase begins. This preliminary action allows the controller to anticipate the correct release moment, improving shift consistency without requiring complex real-time adjustments.

Inventive Principle:

Principle #10Preliminary action

2Ease of operation

If speed-based control is used to gauge off-going friction element release timing, then the control method is simple, but engine speed flare and hunting behavior occur leading to inconsistent shift feel

Engineering Contradiction:

Improvecontrol method simplicityVSAvoidshift feel consistency

Core Design Contradiction:

Ease of operationVSReliability

Solution Approach 1:

The patent implements closed-loop feedback control by continuously monitoring the actual torque phase duration and comparing it to a target value. The controller adjusts the off-going friction element release timing based on the difference between actual and target torque phase durations, ensuring consistent shift feel across varying operating conditions while maintaining reasonable system complexity.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent replaces direct speed-based control with torque phase duration-based control. Instead of reacting to speed changes (engine flare detection), the system proactively controls the release timing based on measured torque phase characteristics, eliminating the hunting behavior between gear tie-up and engine flare.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Speed

If the off-going friction element is released prematurely, then the shift response is fast, but engine speed flare and torque hole deepen causing perceptible shift shock

Engineering Contradiction:

Improveshift response speedVSAvoidengine speed flare and shift shock

Core Design Contradiction:

SpeedVSObject-affected harmful factors

Solution Approach 1:

The patent uses speed measurements of powertrain components (engine, transmission input shaft) to predict and prepare for the optimal release timing of the off-going friction element before the torque phase begins. This preliminary action allows the controller to anticipate the correct release moment, improving shift consistency without requiring complex real-time adjustments.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent implements closed-loop feedback control by continuously monitoring the actual torque phase duration and comparing it to a target value. The controller adjusts the off-going friction element release timing based on the difference between actual and target torque phase durations, ensuring consistent shift feel across varying operating conditions while maintaining reasonable system complexity.

Inventive Principle:

Principle #23Feedback

4Object-affected harmful factors

If the off-going friction element is released delayed, then engine speed flare is reduced, but gear elements tie-up causing deep and wide torque hole for inconsistent shift feel

Engineering Contradiction:

Improveengine speed flareVSAvoidshift feel consistency

Core Design Contradiction:

Object-affected harmful factorsVSReliability

Solution Approach 1:

The patent uses speed measurements of powertrain components (engine, transmission input shaft) to predict and prepare for the optimal release timing of the off-going friction element before the torque phase begins. This preliminary action allows the controller to anticipate the correct release moment, improving shift consistency without requiring complex real-time adjustments.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent implements closed-loop feedback control by continuously monitoring the actual torque phase duration and comparing it to a target value. The controller adjusts the off-going friction element release timing based on the difference between actual and target torque phase durations, ensuring consistent shift feel across varying operating conditions while maintaining reasonable system complexity.

Inventive Principle:

Principle #23Feedback

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 reduces engine flare and shift shock, providing a consistent and seamless shifting experience by accurately controlling torque flow and minimizing the effects of friction element variability.

Implementation Method 1

A step-ratio automatic transmission system in a vehicle utilizes multiple friction elements for automatic gear ratio shifting. These friction elements function to establish power flow paths from an internal combustion engine to vehicle traction wheels.

Methodology Applied

Scientific EffectFriction: Friction

Data Source

PatentUS8706369B2Closed-loop torque phase control for shifting automatic transmission gear ratios based on friction element load estimation

Publication Date: 2014.04.22 FORD GLOBAL TECH LLC

AI summary

A closed loop shift control apparatus and method based on estimated torque in friction elements controls a torque transfer phase when shifting from a low gear configuration to a high gear configuration for an automatic transmission system. When pressure actuated friction elements are selectively engaged and released to establish torque flow paths in the transmission, estimates of torsional load exerted on the off-going friction element are used to predict the optimal off-going friction element release timing for achieving a consistent shift feel. The estimated torque is preferably calculated by using estimated torque signals generated as a function of speed measurements represented either the engine speed and turbine output speed or transmission output speed and wheel speed under dynamically changing conditions.