Hybrid Vehicle Torque Control for Smooth Acceleration

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Solution Overview

Problem

Hybrid vehicles experience unexpectedly slow acceleration due to the delay in engine torque output during sudden acceleration events, causing discomfort for drivers as the motor's torque decreases with increasing rotation speed, leading to a mismatch in torque demand between the motor and engine.

Innovation Solution

Implementing a control method that restricts motor operation until a predetermined condition is met, ensuring a smooth transition from motor-only to engine-motor output mode by imposing a wait time or torque restriction, thereby ensuring equivalent driving force output and preventing slow acceleration.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Speed

If the motor outputs large torque at low rotation speed for sudden acceleration, then the jackrabbit start capability is improved, but the acceleration becomes unexpectedly slow when the engine starts because the motor torque decreases with increasing rotation speed and the engine start takes time

Engineering Contradiction:

Improveacceleration speedVSAvoidengine start delay time

Core Design Contradiction:

SpeedVSLoss of time

Solution Approach 1:

The control device starts the engine in advance before the driver operates the accelerator pedal, so that the engine is already running and ready to output torque immediately when acceleration is demanded, eliminating the engine start delay during sudden acceleration

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The control device dynamically adjusts the motor torque output based on the engine start status. When the engine is starting, the motor torque is restricted to prevent a sudden drop in total torque output, ensuring smooth acceleration throughout the transition period

Inventive Principle:

Principle #15Dynamics

2Productivity

If the motor operates without restriction during engine start, then the response to acceleration demand is improved, but the total driving force becomes insufficient causing unexpectedly slow acceleration

Engineering Contradiction:

Improveacceleration responseVSAvoidtotal driving force

Core Design Contradiction:

ProductivityVSForce

Solution Approach 1:

The control device continuously monitors the engine start status and adjusts the motor torque restriction accordingly. When the engine is starting, the motor torque is restricted to maintain smooth total torque output. When the engine is running stably, the motor torque restriction is released to maximize acceleration response

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The control device changes the motor torque parameter dynamically based on engine operation status. During engine start, the motor torque is limited to a restricted value. After engine start completion, the motor torque returns to its full demanded value, ensuring optimal acceleration performance

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentEP1885589B1Hybrid vehicle and control method of hybrid vehicle

Publication Date: 2010.03.24 TOYOTA JIDOSHA KK

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AI summary

When the driver heavily depresses an accelerator pedal (83) to start a hybrid vehicle in an engine stop condition, the control of the invention waits until elapse of a preset wait time and then starts outputting a torque equivalent to a preset torque demand to a ring gear shaft (32a) or a driveshaft. The preset wait time is determined not to make the driver feel uncomfortable with a poor response. This arrangement desirably shortens a time period when the vehicle acceleration is restricted due to insufficient power output until the engine starts to output sufficient power and make significant contribution to the vehicle acceleration. The control of the invention thus desirably prevents the driver from feeling the unexpectedly slow acceleration.