Exhaust purification system of internal combustion engine

Patent metadata

Field	Value
Publication number	US-9427704-B2
Application number	US-201214429508-A
Country	US
Kind code	B2
Filing date	Sep 25, 2012
Priority date	Sep 25, 2012
Publication date	Aug 30, 2016
Grant date	Aug 30, 2016

Abstract

In an internal combustion engine, an exhaust purification catalyst: ( 13 ), particulate filter ( 14 ), and hydrocarbon feed valve ( 15 ) are arranged in an engine exhaust passage. A low pressure exhaust gas recirculation system (LPL) is provided for making the exhaust gas downstream of the particulate filter ( 14 ) recirculate. If hydrocarbons are injected from the hydrocarbon feed valve ( 15 ), the carbon dioxide which is produced in the exhaust purification catalyst ( 13 ) is recirculated and the air-fuel ratio of the exhaust gas which flows into the exhaust purification catalyst ( 13 ) temporarily drops. At the time of regeneration of the particulate filter ( 14 ), hydrocarbons are injected from, the hydrocarbon feed valve ( 15 ) so as not to overlap with this temporary drop of the air-fuel ratio.

First claim

The invention claimed is:

1. An exhaust purification system of an internal combustion engine, comprising:
a hydrocarbon feed valve arranged in an engine exhaust passage;
an exhaust purification catalyst and a particulate filter arranged downstream of the hydrocarbon feed valve in the engine exhaust passage;
a precious metal catalyst carried on an exhaust gas flow surface of the exhaust purification catalyst;
a basic exhaust gas flow surface part formed around the precious metal catalyst; and
an electronic control unit configured to control the hydrocarbon feed valve such that a concentration of hydrocarbons flowing into the exhaust purification catalyst vibrates within a predetermined range of amplitude and within a predetermined range of period,
wherein the exhaust purification catalyst has a property of reducing NO X contained in an exhaust gas, when the electronic control unit controls the hydrocarbon feed valve such that the concentration of hydrocarbons flowing into the exhaust purification catalyst vibrates within the predetermined range of amplitude and within the predetermined range of period, and
wherein the exhaust purification catalyst has a property of increasing an amount of NO X contained in the exhaust gas when the electronic control unit causes the concentration of hydrocarbons to vibrate for a period longer than the predetermined range of period,
wherein the electronic control unit is further configured to control the hydrocarbon feed valve to inject the hydrocarbons within the predetermined range of period at the time of engine operation to thereby remove NO X contained in the exhaust gas,
wherein the exhaust purification system comprises a low pressure exhaust gas recirculation system that makes the exhaust gas in the engine exhaust passage downstream of the exhaust purification catalyst and the particulate filter recirculate to an inside of an intake passage,
wherein when the electronic control unit controls the hydrocarbon feed valve to inject the hydrocarbons while an exhaust gas recirculation action is performed by the low pressure exhaust gas recirculation system, carbon dioxide produced in the exhaust purification catalyst is recirculated, and after the injection of the hydrocarbons, each time when a time required for recirculation of the carbon dioxide elapses, a temporary drop is repeatedly caused in an air-fuel ratio of an inflowing exhaust gas that flows into the exhaust purification catalyst and the particulate filter,
wherein the electronic control unit is further configured to allow an injection of the hydrocarbons from the hydrocarbon feed valve that is synchronized with the temporary drop in air-fuel ratio of the inflowing exhaust gas, when the hydrocarbons are injected from the hydrocarbon feed valve within the predetermined range of period for removing NO x contained in the exhaust gas, and
wherein the electronic control unit is further configured to control the hydrocarbon feed valve to inject the hydrocarbons so as not to overlap with the temporary drop in the air-fuel ratio of the inflowing exhaust gas when the hydrocarbons are periodically injected from the hydrocarbon feed valve for temperature elevation control of at least one of the particulate filter and the exhaust purification catalyst.

2. The exhaust purification system of an internal combustion engine as claimed in claim 1 , wherein when the electronic control unit controls the hydrocarbon feed valve to periodically inject the hydrocarbons for temperature elevation control of at least one of the particulate filter and the exhaust purification catalyst, after a first injection of the hydrocarbons, a second injection of the hydrocarbons from the hydrocarbon feed valve is performed in an interval between two temporary drops in the air-fuel ratio of the inflowing exhaust gas that are caused after the first injection of the hydrocarbons.

3. The exhaust purification system of an internal combustion engine as claimed in claim 2 , wherein when the electronic control unit controls the hydrocarbon feed valve to periodically inject the hydrocarbons for temperature elevation control of at least one of the particulate filter and the exhaust purification catalyst, an injection timing of the hydrocarbons, at which the second injection of the hydrocarbons from the hydrocarbon feed valve is performed after the first injection of the hydrocarbons, is calculated from a recirculation rate of the exhaust gas and an intake air amount.

4. The exhaust purification system of an internal combustion engine as claimed in claim 2 , wherein when the electronic control unit controls the hydrocarbon feed valve to periodically inject the hydrocarbons for temperature elevation control of at least one of the particulate filter and the exhaust purification catalyst, after the first injection of hydrocarbons, the second injection action of the hydrocarbons from the hydrocarbon feed valve is performed after the temporary drop in the air-fuel ratio of the inflowing exhaust gas is first caused due to the first injection of the hydrocarbons.

5. The exhaust purification system of an internal combustion engine as claimed in claim 1 , wherein the electronic control unit controls the hydrocarbon feed valve to inject the hydrocarbons for the temperature elevation control of the particulate filter to regenerate the particulate filter.

6. The exhaust purification system of an internal combustion engine as claimed in claim 1 , wherein the electronic control unit controls the hydrocarbon feed valve to inject the hydrocarbons for the temperature elevation control of the exhaust purification catalyst to release SO x from the exhaust purification catalyst.

7. The exhaust purification system of an internal combustion engine as claimed in claim 6 , wherein when SO x should be released from the exhaust purification catalyst, the electronic control unit is further configured to control the hydrocarbon feed valve to alternately perform rich control for making the air-fuel ratio of the inflowing exhaust gas into the exhaust purification catalyst temporarily rich and temperature elevation control for releasing SO x from the exhaust purification catalyst, and wherein when the rich control is being performed, the exhaust gas recirculation action by the low pressure exhaust gas recirculation system is suspended.

8. The exhaust purification system of an internal combustion engine as claimed in claim 1 , further comprising:
a cooling device arranged in an exhaust gas recirculation passage of the low pressure exhaust gas recirculation system for cooling the exhaust gas flowing within the exhaust gas recirculation passage;
a bypass passage that bypasses the cooling device and that is connected to the exhaust gas recirculation passage;
a flow path switching valve configured for selectively feeding exhaust gas to the inside of the cooling device or the inside of the bypass passage, wherein the flow path switching valve is provided so that exhaust gas is normally fed into the cooling system, and the flow path switching valve is switched so that the exhaust gas does not flow into the cooling device, but flows into the bypass passage when the exhaust gas recirculation action by the low pressure exhaust gas recirculation system is performed and when an amount of hydrocarbons flowing into the exhaust gas recirculation passage exceeds a predetermined allowable amount.

9. The exhaust purification system of an internal combustion engine as claimed in claim 8 , wherein the flow path switching valve is switched so that the exhaust gas does not flow into the cooling device, but flows into the bypass passage when hydrocarbons are injected from the hydrocarbon feed valve within said predetermined period so as to re

Assignees

• Toyota Motor Co Ltd

Inventors

• Bisaiji Yuki
• Yoshida Kohei
• Inoue Mikio

Classifications

• B01D53/9495 Primary

  Controlling the catalytic process · CPC title

• B01D53/9431

  Processes characterised by a specific device · CPC title

• F02D41/0055 Primary

  Special engine operating conditions, e.g. for regeneration of exhaust gas treatment apparatus · CPC title

• F01N2260/04

  for regeneration or reactivation, e.g. of catalyst · CPC title

• F01N2610/03

  the substance being hydrocarbons, e.g. engine fuel · CPC title