Control device for an internal combustion engine

Patent metadata

Field	Value
Publication number	US-9650972-B2
Application number	US-201514628474-A
Country	US
Kind code	B2
Filing date	Feb 23, 2015
Priority date	Sep 3, 2014
Publication date	May 16, 2017
Grant date	May 16, 2017

Abstract

Provided is a control device for an internal combustion engine, which is capable of suppressing occurrence of knocking due to pre-ignition and occurrence of misfire even when an operating state in a previous cycle changes in a subsequent cycle. When a ratio of change in heat of air-fuel mixture, which is an index indicating how a heat of air-fuel mixture in the previous cycle changes in the subsequent cycle, does not fall within an allowable range, a variable valve control mechanism capable of changing a valve-closing timing of an exhaust valve for adjusting an internal EGR gas amount is controlled by using an optimum value of exhaust valve close (EVC) timing derived by correcting a set valve-closing timing of the exhaust valve so that the ratio of change in heat of air-fuel mixture falls within the allowable range.

First claim

What is claimed is:

1. A control device for an internal combustion engine, which is configured to control a variable valve control mechanism capable of changing a valve-closing timing of an exhaust valve and controlling the variable valve control mechanism so that the exhaust valve is closed at an optimum value of exhaust valve close (EVC) timing derived by optimizing a set valve-closing timing of the exhaust valve for each cycle, the control device comprising:
a parameter acquiring section configured to acquire an exhaust gas temperature, an exhaust pressure, an intake-air temperature, and an amount of intake-air of the internal combustion engine;
a heat of air-fuel mixture calculating section configured to execute first processing of calculating a heat of an air-fuel mixture as a heat of air-fuel mixture based on a relationship between an internal EGR gas heat and an intake-air heat,
the internal EGR gas heat being calculated by calculating a combustion-chamber volume in accordance with a current set valve-closing timing, and calculating a heat of an internal EGR gas present in a combustion chamber based on a relationship between the calculated combustion-chamber volume, and the exhaust gas temperature and the exhaust pressure acquired by the parameter acquiring section,
the intake-air heat being calculated by calculating a heat of intake air based on a relationship between the intake-air temperature and the amount of intake-air acquired by the parameter acquiring section;

a ratio of change in heat of air-fuel mixture calculating section configured to execute second processing of calculating a ratio of change in heat of air-fuel mixture, the ratio of change in heat of air-fuel mixture being an index indicating how the heat of air-fuel mixture that is calculated by the heat of air-fuel mixture calculating section so as to correspond to the current set valve-closing timing in a current cycle changes from a heat of air-fuel mixture corresponding to an optimum value of exhaust valve close (EVC) timing derived in a previous cycle; and
an optimum value of exhaust valve close (EVC) timing deriving section configured to execute third processing of determining whether or not the ratio of change in heat of air-fuel mixture falls within a preset allowable range, and execute fourth processing of deriving the current set valve-closing timing as the optimum value of exhaust valve close (EVC) timing in the current cycle when it is determined that the ratio of change in heat of air-fuel mixture falls within the allowable range, and deriving a corrected set valve-closing timing by correcting the current set valve-closing timing so that the ratio of change in heat of air-fuel mixture falls within the allowable range to update the current set valve-closing timing as the corrected set valve-closing timing when it is determined that the ratio of change in heat of air-fuel mixture does not fall within the allowable range,
wherein the first processing executed by the heat of air-fuel mixture calculating section, the second processing executed by the ratio of change in heat of air-fuel mixture calculating section, and the third processing and the fourth processing executed by the optimum value of exhaust valve close (EVC) timing deriving section are repeatedly executed until it is determined that the ratio of change in heat of air-fuel mixture falls within the allowable range by using the updated current set valve-closing timing.

2. A control device for an internal combustion engine according to claim 1 , wherein the optimum value of exhaust valve close (EVC) timing deriving section executes the third processing and the fourth processing by:
determining that the ratio of change in heat of air-fuel mixture falls within the allowable range when an absolute value of the ratio of change in heat of air-fuel mixture is equal to or smaller than a preset reference value that is equal to or larger than 0%;
determining that the ratio of change in heat of air-fuel mixture does not fall within the allowable range when the absolute value of the ratio of change in heat of air-fuel mixture is larger than the reference value and the ratio of change in heat of air-fuel mixture is positive, followed by correcting the current set valve-closing timing to a retard side; and
determining that the ratio of change in heat of air-fuel mixture does not fall within the allowable range when the absolute value of the ratio of change in heat of air-fuel mixture is larger than the reference value and the ratio of change in heat of air-fuel mixture is negative, followed by correcting the current set valve-closing timing to an advance side.

3. A control device for an internal combustion engine according to claim 1 ,
wherein the parameter acquiring section further acquires a load of the internal combustion engine, and
wherein, in a case where the load acquired in the current cycle is equal to or larger than the load acquired in the previous cycle, the optimum value of exhaust valve close (EVC) timing deriving section executes the third processing and the fourth processing by:
determining that the ratio of change in heat of air-fuel mixture falls within the allowable range when the ratio of change in heat of air-fuel mixture is equal to or larger than 0% and an absolute value of the ratio of change in heat of air-fuel mixture is equal to or smaller than a preset reference value that is equal to or larger than 0%;
determining that the ratio of change in heat of air-fuel mixture does not fall within the allowable range when the ratio of change in heat of air-fuel mixture is equal to or larger than 0% and the absolute value of the ratio of change in heat of air-fuel mixture is larger than the reference value, followed by correcting the current set valve-closing timing to a retard side; and
determining that the ratio of change in heat of air-fuel mixture does not fall within the allowable range when the ratio of change in heat of air-fuel mixture is smaller than 0%, followed by correcting the current set valve-closing timing to an advance side.

4. A control device for an internal combustion engine according to claim 1 ,
wherein the parameter acquiring section further acquires a load of the internal combustion engine, and
wherein, in a case where the load acquired in the current cycle is smaller than the load acquired in the previous cycle, the optimum value of exhaust valve close (EVC) timing deriving section executes the third processing and the fourth processing by:
determining that the ratio of change in heat of air-fuel mixture falls within the allowable range when the ratio of change in heat of air-fuel mixture is equal to or smaller than 0% and an absolute value of the ratio of change in heat of air-fuel mixture is equal to or smaller than a preset reference value that is equal to or larger than 0%;
determining that the ratio of change in heat of air-fuel mixture does not fall within the allowable range when the ratio of change in heat of air-fuel mixture is equal to or smaller than 0% and the absolute value of the ratio of change in heat of air-fuel mixture is larger than the reference value, followed by correcting the current set valve-closing timing to an advance side; and
determining that the ratio of change in heat of air-fuel mixture does not fall within the allowable range when the ratio of change in heat of air-fuel mixture is larger than 0%, followed by correcting the current set valve-closing timing to a retard side.

5. A control device for an internal combustion engine according to claim 1 ,
wherein the parameter acquiring section further acquires an amount of radiation from the air-fuel mixture, and
wherein the heat of air-fuel mixture calculating section executes the first processing by calculating the heat of air-fuel mixture based on a relatio

Assignees

• Mitsubishi Electric Corp
• Mistubishi Electric Corp

Inventors

• Honda Tetsuya

Classifications

• F02D41/0062

  Estimating, calculating or determining the internal EGR rate, amount or flow · CPC title

• F02D2041/001

  for engines with variable valve actuation · CPC title

• F02D41/0097

  using means for generating speed signals · CPC title

• F02D2041/007

  by estimation · CPC title

• F02D41/1498

  measuring engine roughness · CPC title