Engine Coolant Temperature Threshold Control for Idling-Stop Systems

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Solution Overview

Problem

Vehicles with idling-stop control systems face frequent engine restarts and stops due to temperature fluctuations of the engine coolant, leading to reduced fuel efficiency, increased noise, and discomfort for occupants, as the existing systems lack an effective method to maintain heating capacity while minimizing engine operation.

Innovation Solution

A control apparatus for internal combustion engines that includes coolant-temperature detection, stop prohibition, and movement determination means, allowing for the selection of different threshold values based on vehicle movement to maintain heating capacity and reduce engine start frequency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Temperature

If the engine is started to maintain the temperature of the engine coolant, then the heating capacity of the air conditioner is maintained, but the fuel efficiency is reduced and emission gas increases

Engineering Contradiction:

Improveengine coolant temperatureVSAvoidfuel efficiency

Core Design Contradiction:

TemperatureVSUse of energy by moving object

Solution Approach 1:

The system performs preliminary heating of the engine coolant by operating the engine before the vehicle stops. The control unit determines whether to stop the engine based on whether the coolant temperature has reached a predetermined threshold before stopping, ensuring the coolant is sufficiently heated in advance. This preliminary action allows the engine to be stopped without immediately compromising heating capacity, thereby improving fuel efficiency while maintaining thermal comfort.

Inventive Principle:

Principle #10Preliminary action

2Temperature

If the engine is repeatedly driven and stopped due to changes in the temperature of the engine coolant, then the heating capacity is maintained, but the occupants are discomforted by the vibration and noise

Engineering Contradiction:

Improveengine coolant temperatureVSAvoidvibration and noise

Core Design Contradiction:

TemperatureVSObject-affected harmful factors

Solution Approach 1:

The control unit determines whether to stop the engine based on whether the coolant temperature has reached a predetermined threshold before stopping. This preliminary heating action ensures that the engine can be stopped for longer periods without immediately compromising heating capacity, thereby reducing the frequency of restarts and suppressing vibration and noise that discomfort occupants.

Inventive Principle:

Principle #10Preliminary action

3Ease of operation

If the threshold value difference between engine restart and stop is increased to reduce frequent stops and restarts, then the engine operates for a long period of time, but the fuel efficiency improvement is less significant

Engineering Contradiction:

Improveengine operation stabilityVSAvoidfuel efficiency

Core Design Contradiction:

Ease of operationVSUse of energy by moving object

Solution Approach 1:

Inventive Principle:

Principle #10Preliminary action

4Use of energy by moving object

If the engine stops when the vehicle is stopped to improve fuel efficiency, then fuel consumption is reduced, but the heating capacity decreases when the air conditioner is heating the vehicle cabin

Engineering Contradiction:

Improvefuel consumptionVSAvoidheating capacity

Core Design Contradiction:

Use of energy by moving objectVSTemperature

Solution Approach 1:

The control unit determines whether to stop the engine based on whether the coolant temperature has reached a predetermined threshold before stopping. This preliminary heating action ensures that the engine can be stopped without immediately compromising heating capacity. Additionally, when the air conditioner is heating the vehicle cabin and the coolant temperature is below the threshold, the engine is prohibited from stopping, thereby maintaining heating capacity while still allowing fuel efficiency improvements when conditions permit.

Inventive Principle:

Principle #10Preliminary action

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

The solution effectively decreases the frequency of engine starts and stops, maintaining the required heating capacity of the air conditioning system while minimizing engine operation, thus improving fuel efficiency and reducing occupant discomfort.

Implementation Method 1

a vehicular air conditioning device that heats a vehicle cabin using a coolant for the internal combustion engine

Methodology Applied

Scientific EffectHeat transfer: Conduction (thermal)

Implementation Method 2

The coolant-temperature detection means detects the temperature of the coolant for the internal combustion engine

Methodology Applied

Scientific EffectTemperature detection: Thermocouple

Data Source

PatentUS7826961B2Control apparatus for internal combustion engine and method of controlling internal combustion engine

Publication Date: 2010.11.02 TOYOTA JIDOSHA KK

AI summary

In an engine ECU (60), a threshold line LS1 and a threshold line LS2 are set as threshold lines used when stopping of an engine is prohibited based on a coolant temperature Tw. The threshold line LS1 is set to ensure a predetermined heating capacity. The threshold value on the threshold line LS2 is higher than the threshold value on the threshold line LS1. When the vehicle is moving, the threshold line LS2 is selected to prohibit/permit stopping of the engine. This increases the amount of heat stored in an engine coolant. When the vehicle is stopped, the threshold line LS1 is selected to prohibit/permit stopping of the engine. This decreases the frequency of starting the engine in the stopped vehicle, while maintaining the predetermined heating capacity.