Hybrid Engine Start Controller for Stall-Free Deceleration

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Solution Overview

Problem

In hybrid vehicles, existing engine start controllers struggle to activate the engine brake effectively during EV traveling states without stalling the engine, especially when shifting from a higher gear to a lower gear or when the engine speed is too low or too high, leading to inadequate deceleration and driver discomfort.

Innovation Solution

An engine start controller that detects the driver's intention for deceleration by engaging and disengaging the clutch, increasing the engine speed to a target rotational speed lower than the reference speed, and reengaging the clutch to activate the engine brake, while also adjusting the target rotational speed difference based on vehicle speed to ensure proper deceleration.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Force

If the engine brake is activated by reengaging the clutch after starting the engine, then deceleration force is improved, but the engine may stall if engine speed is too low

Engineering Contradiction:

Improvedeceleration forceVSAvoidengine stall prevention

Core Design Contradiction:

ForceVSReliability

Solution Approach 1:

The controller increases engine speed to a target rotational speed before reengaging the clutch to activate the engine brake. This preliminary speed increase ensures the engine operates at a safe speed threshold, preventing stall while enabling effective deceleration force when the clutch is reengaged.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system dynamically adjusts engine speed control based on real-time conditions. The controller monitors engine speed and implements conditional control: increasing speed when below threshold, maintaining at target speed during clutch reengagement, and adjusting accordingly to balance deceleration effectiveness with stall prevention.

Inventive Principle:

Principle #15Dynamics

2Reliability

If the engine speed is increased to a high target rotational speed to prevent stalling, then engine reliability is improved, but sufficient engine brake does not activate and driver comfort deteriorates

Engineering Contradiction:

Improveengine stall preventionVSAvoiddriver comfort

Core Design Contradiction:

ReliabilityVSEase of operation

Solution Approach 1:

The controller optimizes the target rotational speed parameter based on actual engine speed conditions. Rather than using a fixed high target speed, the system adjusts the target speed dynamically, setting it to a threshold value that is sufficient to prevent stall but not excessively high, thereby enabling timely clutch reengagement and adequate engine brake activation for driver comfort.

Inventive Principle:

Principle #35Parameter changes

3Adaptability or versatility

If the clutch is temporarily disengaged and then reengaged to perform gear shift after starting the engine, then gear shift capability is improved, but deceleration feeling is delayed and driver comfort worsens

Engineering Contradiction:

Improvegear shift capabilityVSAvoiddeceleration feeling

Core Design Contradiction:

Adaptability or versatilityVSEase of operation

Solution Approach 1:

The controller preliminarily increases engine speed to a target rotational speed before reengaging the clutch. This preliminary action ensures the engine is ready for immediate clutch reengagement, enabling timely engine brake activation and providing proper deceleration feeling without delaying for gear shift operations.

Inventive Principle:

Principle #10Preliminary action

4Ease of operation

If the clutch is reengaged earlier to provide deceleration feeling, then driver comfort is improved, but the engine may stall due to insufficient engine speed

Engineering Contradiction:

Improvedeceleration feelingVSAvoidengine stall prevention

Core Design Contradiction:

Ease of operationVSReliability

Solution Approach 1:

The controller performs preliminary engine speed increase to a target rotational speed before clutch reengagement. This ensures that when the clutch is reengaged earlier for deceleration, the engine already operates at a safe speed threshold, preventing stall while enabling timely deceleration for driver comfort.

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentUS9580069B2Engine start controller for hybrid vehicle

Publication Date: 2017.02.28 HONDA MOTOR CO LTD

AI summary

When driver's deceleration intention is detected during traveling by a motor generator with an engine being stopped, a clutch is engaged to start the engine, and thereafter disengaged. When an engine speed after engine start is lower than a reference rotational speed being an input shaft rotational speed produced by driving force reversely transmitted from drive wheels, the engine speed is increased to a target rotational speed lower than the reference rotational speed. When the engine speed reaches the target rotational speed, output from the engine is decreased and the clutch is reengaged. Thus, while engine stall when activating the engine brake, which is due to the engine speed too low after engine start, is avoided by increase in the engine speed, the clutch is reengaged earlier so as to activate the engine brake fully, generating deceleration feeling the driver expects.