Engine Torque Control for Automatic Transmission Downshift Shock

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Solution Overview

Problem

Existing engine torque control devices during downshifting in automatic transmissions can lead to excessive engine output torque, causing shift shock and potentially damaging friction engagement elements, especially in manual shift modes where synchronizing target torque is computed inaccurately.

Innovation Solution

An engine torque control device with an automatic transmission control section and an engine output torque control section that increases engine output torque during downshifting while setting an allowable time for torque increase, forcibly halting the control if the increase exceeds a specific amount to prevent excessive torque and reduce shift shock.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If engine output torque is increased during downshifting to synchronize engine speed with target speed, then shift shock is reduced, but excessive torque may be applied causing damage to friction engagement elements

Engineering Contradiction:

Improvedurability of friction engagement elementsVSAvoidshift shock

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The control device computes the synchronizing target torque in advance before the downshift occurs, and prepares the torque increase schedule. This preliminary computation allows the system to have a planned torque increase strategy ready, ensuring that torque is increased appropriately to reduce shift shock while staying within safe limits to protect friction engagement elements.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The control device dynamically adjusts the engine output torque during the downshift process based on real-time conditions. It monitors the actual torque increase and compares it with the computed synchronizing target torque, continuously adapting the torque control to achieve the desired engine speed synchronization while preventing excessive torque that could damage friction engagement elements.

Inventive Principle:

Principle #15Dynamics

2Device complexity

If synchronizing target torque is computed without considering manual shift mode, then torque control is simplified, but excessively high engine speed may result causing unnecessary torque increase

Engineering Contradiction:

Improvetorque control mechanismVSAvoidengine output torque

Core Design Contradiction:

Device complexityVSPower

Solution Approach 1:

The control device applies different torque control strategies for different shift modes. It specifically addresses manual shift mode by detecting when this mode is active and applying a modified torque increase control that prevents excessive torque. This localized approach to different operating conditions allows the system to maintain simplicity while addressing the specific problem of excessive torque in manual shift mode.

Inventive Principle:

Principle #3Local quality

3Speed

If torque increasing control continues without time limitation, then engine speed synchronization is achieved, but excessive torque duration adversely affects friction engagement elements

Engineering Contradiction:

Improveengine speed synchronizationVSAvoidtorque application duration

Core Design Contradiction:

SpeedVSDuration of action of stationary object

Solution Approach 1:

The control device sets an allowable time for torque increasing control in advance, before the downshift process begins. This predetermined time limit ensures that torque is increased only for the necessary duration to achieve engine speed synchronization, preventing prolonged excessive torque application that would damage friction engagement elements.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The control device rushes through the torque increasing phase by imposing a strict time limit. It increases torque quickly to achieve the necessary engine speed synchronization within the allowable time, then immediately halts further torque increase. This approach achieves the synchronization goal while minimizing the duration of excessive torque application.

Inventive Principle:

Principle #21Skipping (Rushing through)

Data Source

PatentUS7282010B2Engine torque control device

Publication Date: 2007.10.16 NISSAN MOTOR CO LTD

AI summary

An engine torque control device is configured to provide increase engine output torque during shifting, with excessive engine output torque being prevented while shift shock is reduced. The engine torque control device has an automatic transmission control section that controls an automatic transmission and an engine output torque control section that performs a torque increasing control of an engine output torque to increase the engine output torque during a downshifting so that an actual engine speed will substantially approach a target speed. The allowable time for torque increasing control is set according to the amount of torque increase. If the increase in engine output torque is below a specified value at the point when the allowable time has elapsed, the torque increasing control is continued, but if the torque increase is at or above the specified value when the allowable time has elapsed, the torque increasing control is forcibly halted.