Control device for an internal combustion engine preventing condensation of intake gas in an intercooler

Patent metadata

Field	Value
Publication number	US-2016265458-A1
Application number	US-201415036070-A
Country	US
Kind code	A1
Filing date	Nov 7, 2014
Priority date	Nov 12, 2013
Publication date	Sep 15, 2016
Grant date	—

Abstract

A control device for an internal combustion engine includes an intake gas compressor, a cooling water circuit, an intercooler and an EGR device. An ECU is configured to: (a) control the temperature, of the cooling water of the intercooler to a target temperature in a specified external air state in which an external air temperature and an external air humidity are a specified temperature and a specified humidity, the target temperature being the temperature of the cooling water of the intercooler required for ensuring a specified performance in the specified external air state; and (b) control the EGR device based on an EGR rate mapping of the EGR rate. The EGR rate mapping being set so that a dew point of gas flowing into the intercooler does not exceed the target temperature.

First claim

What is claimed is:

1 . A control device for an internal combustion engine, the control device comprising:
a compressor arranged in an intake passage of the internal combustion engine, the compressor configured to supercharge gas flowing in the intake passage; a first cooling water circuit configured to circulate cooling water; an intercooler arranged in the intake passage closer to a downstream side as compared with the compressor, the intercooler configured to exchange heat between the gas flowing in the intake passage and the cooling water circulated in the first cooling water circuit; an EGR device configured to adjust an EGR rate of EGR gas for supplying a portion of exhaust gas flowing in an exhaust passage of the internal combustion engine to the intake passage closer to an upstream side as compared with the intercooler, an ECU configured to: (a) control the temperature of the cooling water of the intercooler to a target temperature in a specified external air state in which an external air temperature and an external air humidity are a specified temperature and a specified humidity, the target temperature being the temperature of the cooling water of the intercooler required for ensuring a specified performance in the specified external air state; and (b) control the EGR device based on an EGR rate mapping in which the EGR rate is set according to a relationship with parameters for determining an operating state of the internal combustion engine, the EGR rate mapping configured to set the EGR rate so that a dew point of cooler inflow gas flowing into the intercooler does not exceed the target temperature when the EGR gas is introduced by using the EGR device.

2 . The control device according to claim 1 , wherein,
the parameters used in the EGR rate mapping are engine load and engine speed; the EGR rate mapping is configured to set the EGR rate with which the dew point of the cooler inflow gas is limited not to exceed the target temperature in a high load and high revolution speed operating region as a value of the EGR rate mapping.

3 . The control device according to claim 1 , wherein,
the specified external air state is a high-temperature state or humid state or high-temperature and humid state in which condensed water tends to be provided in the intercooler.

4 . The control device according to claim 1 , further comprising:
an external air temperature detector configured to detect or estimate the external air temperature; and an external air humidity detector configured to detect or estimate the external air humidity, wherein the ECU corrects the target temperature based on the dew point of the cooler inflow gas corresponding to the current external air temperature and the current external air humidity when the external air temperature and the external air humidity are different from the external air temperature and the external air humidity in the specified external air state.

5 . The control device according to claim 4 , wherein,
the ECU controls the EGR device to the EGR rate lower than the EGR rate obtained from the EGR rate mapping when the external air temperature and the external air humidity are within a temperature and humidity region of external air where the dew point of the cooler inflow gas is above a specified temperature upper limit.

6 . The control device according claim 1 , further comprising:
a second cooling water circuit arranged separately from the first cooling water circuit and configured to cool the internal combustion engine by using a circulation water of the second cooling water circuit; a heat exchanger configured to exchange heat between the second cooling water circulated in the second cooling water circuit and the cooling water circulated in the first cooling water circuit; wherein the first cooling water circuit includes a radiator, a first cooling water bypass and a first flow path switcher, the radiator is configured to cool the cooling water, the first cooling water bypass is configured to bypass the radiator, and the first flow path switcher is configured to switch a flow path pattern of the cooling water between the flow path pattern in which the cooling water is introduced into the radiator and the flow path pattern in which the cooling water flows through the first cooling water bypass rather than the radiator.

7 . The control device according to claim 1 , further comprising:
a second cooling water circuit arranged separately from the first cooling water circuit and configured to cool the internal combustion engine by using a circulation water of the second cooling water circuit; and a heat exchanger configured to exchange heat between the second cooling water circulated in the second cooling water circuit and the cooling water circulated in the first cooling water circuit; wherein the first cooling water circuit comprises a second cooling water bypass and a second flow path switcher, the second cooling water bypass is configured to bypass the heat exchanger, and the second flow path switcher is configured to switch the flow path pattern of the cooling water between a flow path pattern in which the cooling water is introduced into the heat exchanger and a flow path pattern in which the cooling water flows through the second cooling water bypass rather than the heat exchanger.

8 . The control device according to claim 1 , further comprising:
a second cooling water circuit arranged separately from the first cooling water circuit and configured to cool the internal combustion engine by using a circulation water of the second cooling water circuit; a heat exchanger configured to exchange heat between the second cooling water circulated in the second cooling water circuit and the cooling water circulated in the first cooling water circuit; wherein, the second cooling water circuit comprises a water amount adjustor, the water amount adjuster adjusts an amount of the circulating water of the second cooling water circuit.

9 . The control device according to claim 1 , further comprising an adsorptive reduction type NOx catalyst provided in the exhaust passage of the internal combustion engine;
wherein, the ECU is configured to: (c) execute a rich spike control in which an air-fuel ratio of gas flowing into the NOx catalyst is temporarily enriched during operation; and (d) control the EGR device to the EGR rate lower than the EGR rate obtained from the EGR rate mapping when the rich spike control is executed and the EGR gas is supplied to the intake passage by the EGR device.

10 . The control device according to claim 1 , further comprising:
an exhaust gas heat exchanger configured to exchange heat between the exhaust gas flowing in the exhaust passage and the cooling water circulated in the first cooling water circuit; and an exhaust gas purification catalyst provided in the exhaust passage closer to a downstream side as compared with the exhaust gas heat exchanger; wherein the first cooling water circuit comprises a third cooling water bypass and a third flow path switcher, wherein the third cooling water bypass is configured to bypass the exhaust gas heat exchanger, the third flow path switcher is configured to switch the flow path pattern of the cooling water between the flow path pattern in which the cooling water is introduced into the exhaust gas heat exchanger and the flow path pattern in which the cooling water flows through the third cooling water bypass rather than the exhaust gas heat exchanger, and the ECU is configured to control the third flow path switcher so that the cooling water is prohibited to be introduced into the exhaust gas heat exchanger in the case where the temperature of the exhaust gas purification c

Assignees

• Toyota Motor Co Ltd

Inventors

• Okada Yoshihiro
• Kobayashi Shu

Classifications

• F02B29/0462

  Liquid cooled heat exchangers · CPC title

• F02M35/10393

  for characterising a multi-component mixture, e.g. for the composition such as humidity, density or viscosity · CPC title

• F02D41/26

  using computer, e.g. microprocessor · CPC title

• F01N3/0842

  Nitrogen oxides · CPC title

• F02M35/1038

  for temperature or pressure · CPC title