KR101886106B1 - Exhaust gas purification apparatus and method for controlling the same - Google Patents

Abstract

A method of controlling an exhaust gas purifying apparatus according to an embodiment of the present invention is a method of controlling exhaust gas purifying conditions to improve the performance of a three way catalyst (TWC) for purifying exhaust gas discharged from an engine, Calculating an oxygen storage capacity (OSC) of the three-way catalyst according to the thermal load, determining an inflection point using the variation of the OSC, And controlling the control variables related to the performance of the three-way catalyst differently around the inflection point.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to an exhaust gas purifying apparatus,

More particularly, the present invention relates to an exhaust gas purifying apparatus and a control method thereof, and more particularly, to an exhaust gas purifying apparatus and a control method thereof, And a method of controlling the gas purifier.

Recently, as the use of automobiles has increased and traffic volume has increased, the problem of air pollution due to exhaust gas has become a serious social problem.

Accordingly, governments in each country have set emission standards for pollutants in exhaust gases such as carbon monoxide (CO), hydrocarbons (HC), and nitrogen oxides (NOx) to regulate exhaust gas. have.

In addition, each automobile manufacturer is putting a lot of effort into effectively coping with the exhaust gas regulation which is being strengthened, and the new vehicle is produced in accordance with the exhaust gas emission standard.

In particular, in automobiles, a three-way catalyst converter carrying a precious metal is mounted on the exhaust system to meet the exhaust emission standards, thereby promoting the decomposition of hydrocarbons, the oxidation of carbon monoxide, and the reduction of nitrogen oxides.

The three-way catalyst means a catalyst which reacts with hydrocarbon compounds, carbon monoxide and nitrogen oxides (NOx) which are harmful components of exhaust gas to remove these compounds, and mainly Pt / Rh, Pd / Rh or Pt / Pd / Rh- .

The three-way catalyst performs a function of reducing carbon monoxide and hydrocarbons and reducing nitrogen oxides in accordance with lean (rich) and rich (rich) states based on the air-fuel ratio of the exhaust gas.

However, the catalytic performance of such a three-way catalyst deteriorates as the catalyst deteriorates. However, three - way catalyst control has not been achieved due to changes in catalyst performance. In the case of controlling the three-way catalyst in the region where the amount of oxygen storage capacity (OSC) is less than a certain value, it is difficult to control the catalytic performance due to the change of the OSC, There was a difficulty to occur.

Accordingly, it is an object of the present invention to provide an apparatus and method for determining the inflection point using the amount of change in OSC according to the thermal load of a three-way catalyst, and to control the control variable related to the performance of the three- And to provide a method for controlling the exhaust gas purifying apparatus.

A method for controlling an exhaust gas purifying apparatus according to an embodiment of the present invention is a method for controlling an exhaust gas purifying state so as to improve performance of a three way catalyst (TWC) for purifying exhaust gas discharged from an engine, Calculating an oxygen storage capacity (OSC) of the three-way catalyst according to the thermal load, determining an inflection point using the amount of change of the OSC, calculating a thermal load of the three-way catalyst using a temperature sensor, And controlling the control variables related to the performance of the three-way catalyst differently before and after the inflection point.

The inflection point may include a point at which the rate of decrease of the variation of the OSC varies.

Wherein the step of determining the inflection point includes calculating a thermal load by accumulating temperatures at a front end of the three-way catalyst, calculating an OSC reduction rate by measuring an OSC amount according to the thermal load, and if the absolute value of the OSC reduction rate is less than a predetermined value, It can be determined that the inflection point has passed.

Wherein the control variable includes at least one of a catalytic heating period, an oxygen (O ₂ ) purge period after fuel cut, a lambda rich control period during deceleration, a high rpm holding period of the engine, . ≪ / RTI >

Controlling the control variable to sequentially increase or decrease the control variable according to the aging of the three-way catalyst when the amount of change of the OSC is before the inflection point; , It is possible to control the control variable to have a predetermined set value.

Wherein the controlling of the control variable controls the catalytic heating (CH) period to linearly increase when the amount of change of the OSC is before the inflection point, and when the amount of change of the OSC is after the inflection point, It is possible to control the catalyst heating period to have a predetermined set value.

Controlling the control variable, when the change amount of the OSC of the inflection point before the fuel cut off (Fuel cut) after the oxygen (O _2), and control so as to reduce the purge period linearly, the amount of change in the OSC the In the case of the inflection point or later, it is possible to control the oxygen purge period to have a predetermined set value.

Wherein the controlling of the control variable controls the lambda-rich control period during deceleration to be linearly reduced when the amount of change of the OSC is before the inflection point, and when the amount of change of the OSC is after the inflection point, The control period can be controlled to have a predetermined set value.

Wherein the controlling of the control parameter controls to increase the high rpm holding period of the engine linearly when the variation amount of the OSC is before the inflection point and when the variation amount of the OSC is after the inflection point, It is possible to control the sustain period to have a predetermined set value.

Wherein the controlling of the control parameter controls the ignition timing maintaining period to be linearly increased when the amount of change of the OSC is before the inflection point and when the amount of change of the OSC is beyond the inflection point, It is possible to control to have the predetermined set value.

An exhaust gas purifying apparatus according to an embodiment of the present invention is an exhaust gas purifying apparatus provided to purify an exhaust gas of an engine. The exhaust purifying apparatus is disposed in an exhaust line through which exhaust gas discharged from the engine passes, A three way catalyst (TWC) for converting harmful substances including carbon monoxide, hydrocarbons and nitrogen oxides into harmless components by oxidation-reduction reaction, an oxygen storage capacity (OSC ), And a controller for calculating a thermal load of the three-way catalyst and controlling a control parameter related to the performance of the three-way catalyst using the change amount of the OSC according to the thermal load.

Wherein the control variable includes at least one of a catalytic heating period, an oxygen (O ₂ ) purge period after fuel cut, a lambda rich control period during deceleration, a high rpm holding period of the engine, . ≪ / RTI >

The control unit may determine an inflection point at which the rate of decrease of the variation of the OSC varies and control the control variable related to the performance of the three-way catalyst differently around the inflection point.

Wherein the control unit controls the control variable to be sequentially increased or decreased in accordance with the aging of the three-way catalyst when the change amount of the OSC is before the inflection point, and when the change amount of the OSC is after the inflection point, Can have a predetermined set value.

As described above, according to the present invention, the inflection point is determined by using the amount of change of OSC according to the thermal load of the three-way catalyst, and the control accuracy of various control parameters is improved by controlling the control variable related to the performance of the three- Thereby improving the performance of the three-way catalyst and improving the purification performance of the exhaust gas.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic view showing a structure of an exhaust gas purifying apparatus for improving performance of a three-way catalyst according to an embodiment of the present invention; FIG.
2 is a flowchart briefly illustrating a process of controlling an exhaust gas purifying apparatus according to an embodiment of the present invention to control the control parameters to improve the performance of the three-way catalyst.
3 is a graph showing changes in OCS due to aging of a three-way catalyst according to an embodiment of the present invention.
4 is a graph showing an example of control variables of each control region according to the inflection point of FIG.
5 is a graph showing the correlation between the OCS change and the EM of the three-way catalyst.
6 is a graph comparing the exhaust gas purifying performance according to the OCS change of the three-way catalyst.
7 is a graph showing changes in OCS according to aging time of a three-way catalyst according to an embodiment of the present invention.
8 is a graph showing the effect of the OCS change on the exhaust gas purifying performance for each control region according to an embodiment of the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

The exhaust gas purifying apparatus according to the embodiment of the present invention can be applied not only to a vehicle but also to various devices for obtaining energy by burning fossil fuel and discharging gas generated in the process to the atmosphere. In this specification, the exhaust gas purifying apparatus is applied to a vehicle, but it should not be construed as being applied only to a vehicle.

The vehicle is equipped with an engine for generating power. The engine combusts a mixture of fuel and air to convert chemical energy into mechanical energy. The engine is connected to an intake manifold to introduce air into the combustion chamber, and is connected to an exhaust manifold so that the exhaust gas generated in the combustion process is collected in the exhaust manifold and discharged to the outside of the vehicle. An injector is mounted on the combustion chamber or the intake manifold to inject fuel into the combustion chamber or the intake manifold.

The exhaust gas generated in the engine is discharged to the outside of the vehicle through the exhaust gas. The exhaust device may include an exhaust pipe and an exhaust gas recirculation (EGR) device.

The exhaust pipe is connected to the exhaust manifold to exhaust the exhaust gas to the outside of the vehicle.

The exhaust gas recirculation device is mounted on the exhaust pipe, and the exhaust gas discharged from the engine passes through the exhaust gas recirculation device. The exhaust gas recirculation device is connected to the intake manifold to mix a part of the exhaust gas with the air to control the combustion temperature. Such a combustion temperature can be adjusted by controlling ON / OFF of an EGR valve (not shown) provided in the exhaust gas recirculation device. That is, the amount of exhaust gas supplied to the intake manifold is regulated by controlling ON / OFF of the EGR valve.

The exhaust device may further include a soot filter mounted on the exhaust pipe and collecting particulate matter contained in the exhaust gas. The particulate filter may be an exhaust gas purifying apparatus according to an embodiment of the present invention for purifying harmful substances other than the particulate matter contained in the exhaust gas.

Hereinafter, an exhaust gas purifying apparatus and an exhaust gas purifying apparatus control method according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic view showing a structure of an exhaust gas purifying apparatus for improving performance of a three-way catalyst according to an embodiment of the present invention; FIG. At this time, the exhaust gas purifying apparatus shows only the schematic configuration necessary for the explanation according to the embodiment of the present invention, but the present invention is not limited to this configuration.

1, an exhaust gas purifying apparatus according to an embodiment of the present invention includes an engine 100, a combustion chamber 102, an injector 104, an exhaust line 110, a three way catalyst (TWC) 120 A lambda sensor 130, a temperature sensor 140, an oxygen sensor 150, and a controller 160.

Outside air is supplied to the combustion chamber 102 of the engine 100 and the injector 104 injects a predetermined amount of fuel into the combustion chamber 102 and the exhausted combustion gas is exhausted to the exhaust line 110 And is discharged to the outside through the three-way catalyst 120 of FIG.

The three-way catalyst 120 is disposed in an exhaust line 110 through which exhaust gas discharged from the engine 100 passes, and a harmful substance including carbon monoxide, hydrocarbon, and nitrogen oxide contained in the exhaust gas is subjected to oxidation- To harmless components.

The lambda sensor 130 senses the lambda value of the exhaust gas passing through the exhaust line 110 and transmits the signal to the control unit 160. The control unit 160 controls the injector 104 And it is possible to determine the fuel cut-off state of the injector 104 or the like.

The temperature sensor 140 is disposed at a front end or a rear end of the three-way catalyst 120. The temperature sensor 140 measures the temperature of the exhaust gas, the intake air flow rate, or the catalyst temperature of the three- .

Also, the oxygen sensor 150 measures the oxygen storage capacity (OSC) of the three-way catalyst 120 and provides the measured oxygen storage capacity information to the controller 160. Although the oxygen sensor 150 is described as being disposed in the three-way catalyst 120, the oxygen sensor 150 may be disposed at the front end or the rear end of the three-way catalyst 120, no.

The control unit 160 calculates the thermal load of the three-way catalyst 120 using the temperature information measured by the temperature sensor 140 or the intake air flow rate and calculates the performance of the three way catalyst 120 using the change amount of the OSC according to the heat load. Lt; / RTI > Here, the control variable includes at least one of a catalytic heating period, an oxygen (O2) purge period after fuel cut, a lambda rich control period during deceleration, a high rpm holding period of the engine, .

The control unit 160 determines an inflection point using the variation amount of the OSC according to the thermal load and controls the control variable related to the performance of the three-way catalyst 120 differently around the inflection point. Here, the inflection point includes a point at which the rate of decrease of the variation of the OSC changes. In addition, the inflection point may include a point indicating a tendency that the decreasing tendency of the amount of OSC decreases rapidly with the aging time of the catalyst and gradually decreases.

When the amount of change of the OSC is before the inflection point, the control unit 160 may control the control variable to sequentially increase or decrease the control variable according to the aging of the three-way catalyst 120. [ The control unit 160 may control the control variable to have a preset value when the amount of change of the OSC is beyond the inflection point. Here, the predetermined set value includes a value set to maintain the performance of the catalyst based on the distance value corresponding to the guaranteed period of the catalyst.

For example, the control unit 160 controls the catalytic heating (CH) period to linearly increase when the amount of change of the OSC is before the inflection point. The control unit 160 may control the catalyst heating period to have a predetermined set value when the amount of change of the OSC is the inflection point or more.

In addition, when the amount of change of the OSC is before the inflection point, the control unit 160 controls the oxygen (O ₂ ) purge period to be linearly reduced after the fuel cut. The control unit 160 may control the oxygen purge period to have a predetermined set value when the amount of change of the OSC is the inflection point or more.

The control unit 160 controls the lambda-rich control period during deceleration to be linearly reduced when the amount of change of the OSC is before the inflection point. The control unit 160 may control the lambda-rich control period to have a predetermined set value when the variation amount of the OSC is beyond the inflection point.

The control unit 160 controls to increase the high rpm holding period of the engine linearly when the variation amount of the OSC is before the inflection point. Further, when the amount of change of the OSC is equal to or greater than the inflection point, the control unit 160 may control the high rpm holding period to have a predetermined set value.

The control unit 160 controls the ignition timing maintaining period to be linearly increased when the amount of change of the OSC is before the inflection point. The control unit 160 may control the ignition timing maintaining period to have a predetermined set value when the amount of change of the OSC is beyond the inflection point.

For this purpose, the control unit 160 may be implemented with one or more processors operated by the set program, and the set program may be programmed to perform each step of the control method of the exhaust gas purifying apparatus according to the embodiment of the present invention. .

2 is a flowchart briefly illustrating a process of controlling an exhaust gas purifying apparatus according to an embodiment of the present invention to control the control parameters to improve the performance of the three-way catalyst. The following flowchart will be described using the same reference numerals in conjunction with the configuration of Fig.

Referring to FIG. 2, the exhaust gas purifying apparatus according to an embodiment of the present invention calculates the thermal load of the three-way catalyst 120 using the temperature value of the temperature sensor and the intake air flow rate (S102).

Then, the exhaust gas purifier measures the oxygen storage capacity (OSC) according to the thermal load (S104).

The exhaust gas purifier determines the inflection point using the amount of change of the OSC (S106). Here, the inflection point includes a point at which the rate of decrease of the variation of the OSC changes. The inflection point may include a point indicating a tendency that the decreasing tendency of the amount of OSC depending on the aging time of the catalyst is rapidly decreased and gradually decreases.

The exhaust gas purifying apparatus calculates the heat load by accumulating the temperature at the front end of the three-way catalyst 120, and calculates the OSC reduction rate by measuring the amount of OSC according to the heat load. If the absolute value of the OSC reduction rate is less than a predetermined value, the exhaust gas purifier may determine that the inflection point has passed.

If the OCS value of the exhaust gas is greater than the OCS value of the inflection point, the exhaust gas purifying apparatus may control the control parameters to be sequentially increased or decreased according to the aging of the three-way catalyst (S108, S110). Here, the control variable includes at least one of a catalytic heating period, an oxygen (O2) purge period after fuel cut, a lambda rich control period during deceleration, a high rpm holding period of the engine, .

If the OCS value is smaller than the OCS value of the inflection point, the exhaust gas purifier may control the control parameter to have a predetermined set value (S112). Here, the predetermined set value includes a value set to maintain the performance of the catalyst based on the distance value corresponding to the guaranteed period of the catalyst.

FIG. 3 is a graph showing changes in OCS due to aging of the three-way catalyst according to an embodiment of the present invention, and FIG. 4 is a graph showing an example of control variables of each control region according to the inflection point of FIG.

As the degradation proceeds, the amount of OSC decreases sharply at the beginning, and after a certain time, the amount of OSC decreases slowly. Accordingly, as shown in FIG. 3, there is an inflection point of the TWC in which the tendency of the OSC change varies, and it can be divided into a zone (Zone_1) in which the OSC rapidly decreases based on the inflection point and a zone (Zone_2) in which the OSC gently decreases.

In the case before the inflection point (Zone_1), since the OSC changes largely according to the aging time, the influence of the EM due to the change of the OSC is small, so that it is easy to control the control parameters related to the performance of the three-way catalyst.

However, in the case after the inflection point (Zone_2), the change of the OSC according to the aging time is small, but the influence of the EM due to the change of the OSC is sensitive, so that it is difficult to control the control parameters related to the performance of the three-way catalyst.

5 is a graph showing the correlation between the OCS change and the EM of the three-way catalyst.

Referring to FIG. 5, it can be seen that the OSC changes according to the aging time of the three-way catalyst cause many changes before and after the inflection point, and the EM change tendency increases with increasing aging time of the three- Lt; / RTI > Also, the EM trend is more sensitive to the inflection point (Zone_2) than to the inflection point (Zone_1).

6 is a graph comparing the exhaust gas purifying performance according to the OCS change of the three-way catalyst.

Referring to FIG. 6, a change in OSC according to the aging time of the three-way catalyst causes many changes before and after the inflection point, and the exhaust gas purifying performance decreases toward a direction in which the aging time of the three-way catalyst increases and a direction in which the OSC decreases. Therefore, it can be seen that the exhaust gas purifying performance varies based on the inflection point, and the purifying performance is lower in the zone after the inflection point (Zone_2) than in the zone before the inflection point (Zone_1).

FIG. 7 is a graph showing changes in OCS according to the aging time of the three-way catalyst according to an embodiment of the present invention. FIG. 8 is a graph showing changes in OCS according to control regions according to an embodiment of the present invention, As shown in FIG.

Referring to FIG. 7, the OSC decrease amount changes with reference to the inflection point, and the OSC change tendency differs between the case before the inflection point (Zone_1) and the case after the inflection point (Zone_2). In the case of the inflection point (Zone_1), the decrease rate of the OSC is large. In the case of the inflection point (Zone_2), the decrease rate of the OSC is small.

However, referring to FIG. 8, the influence of the OSC amount change on the EM change before the inflection point (Zone_1) is insensitive, but the influence of the OSC amount change on the EM change after the inflection point (Zone_2) is sensitive.

Therefore, as shown in FIG. 4, the exhaust gas purifying apparatus according to an embodiment of the present invention controls the control parameters related to the performance of the three-way catalyst differently based on the inflection point.

For example, in the case of Zone 1 before the inflection point, the control variable C is linearly decreased or increased in accordance with the amount of the OSC (A) depending on the thermal load of the catalyst. 4 shows an example in which the control variable linearly increases, the control variable may be controlled to decrease linearly, which may be applied differently depending on the type of the control variable.

In the case of the zone after the inflection point Zone_2, it is possible to control the control parameter value D to correspond to the OSC amount B according to the thermal load at the inflection point.

As described above, according to the exhaust gas purifying apparatus and the control method of the present invention, the inflection point is determined by using the amount of change in OSC according to the thermal load of the three-way catalyst, and the control variable related to the performance of the three- , The control accuracy of various control parameters is improved, and the performance of the three-way catalyst is improved to provide an environment capable of improving the purification performance of the exhaust gas.

While the present invention has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, And all changes to the scope that are deemed to be valid.

Claims (14)

In a method for controlling the exhaust gas purifying conditions so as to improve the performance of a three way catalyst (TWC) for purifying the exhaust gas discharged from the engine,
Calculating a thermal load of the three-way catalyst using a temperature sensor,
Measuring an oxygen storage capacity (OSC) of the three-way catalyst according to the thermal load;
Determining an inflection point using the variation amount of the OSC, and
Controlling the control variables related to the performance of the three-way catalyst differently before and after the inflection point
And the exhaust gas purifying apparatus. The method according to claim 1,
The inflection point
Wherein the rate of change of the amount of change of the OSC varies. The method according to claim 1,
Wherein the step of determining the inflection point comprises:
Calculating an OSC reduction rate by measuring the amount of the OSC according to the thermal load, calculating a thermal load by accumulating the temperature at the front end of the three-way catalyst, calculating an OSC reduction rate according to the thermal load, and if the absolute value of the OSC reduction rate is less than a predetermined value, Device control method. The method according to claim 1,
Wherein the control variable comprises:
Including at least one of a catalytic heating period, an oxygen (O ₂ ) purge period after fuel cut, a lambda rich control period during deceleration, a high rpm maintenance period of the engine, or an ignition timing maintenance period A method of controlling a purifier. The method according to claim 1,
Wherein controlling the control variable comprises:
Controlling the control variable to increase or decrease in accordance with the aging of the three-way catalyst when the change amount of the OSC is before the inflection point,
And controls the control variable to have a predetermined set value when the amount of change of the OSC is equal to or greater than the inflection point. The method according to claim 1,
Wherein controlling the control variable comprises:
Wherein the control unit controls the catalytic heating (CH) period to linearly increase when the amount of change of the OSC is before the inflection point, and when the amount of change of the OSC is after the inflection point, To the exhaust gas purifying apparatus. The method according to claim 1,
Wherein controlling the control variable comprises:
If the amount of change in the OSC of the inflection point before the fuel cut off (Fuel cut) after the controls so as to reduce the purge period the oxygen (O ₂₎ linearly, when the amount of change in the OSC is after the inflection point, the oxygen purge period And the exhaust gas purifying device has a predetermined set value. The method according to claim 1,
Wherein controlling the control variable comprises:
And controlling the lambda-rich control period to be linearly decreased when the amount of change of the OSC is before the inflection point, and when the amount of change of the OSC is beyond the inflection point, Wherein the exhaust gas purifying apparatus is controlled by the exhaust gas purifying apparatus. The method according to claim 1,
Wherein controlling the control variable comprises:
Wherein when the amount of change of the OSC is before the inflection point, the controller controls the engine to maintain the high rpm maintaining period linearly, and when the change amount of the OSC is after the inflection point, Wherein the exhaust gas purifying apparatus is controlled by the exhaust gas purifying apparatus. The method according to claim 1,
Wherein controlling the control variable comprises:
Controlling the ignition timing maintaining period to be linearly increased when the amount of change of the OSC is before the inflection point and controlling the ignition timing maintaining period to have a predetermined set value when the variation amount of the OSC is beyond the inflection point A method for controlling an exhaust gas purifier. 1. An exhaust gas purifying apparatus for purifying exhaust gas of an engine, comprising:
A three-way catalyst which is disposed in an exhaust line through which exhaust gas discharged from the engine passes and which converts harmful substances including carbon monoxide, hydrocarbon, and nitrogen oxides contained in the exhaust gas into harmless components by an oxidation- catalyst, TWC),
An oxygen sensor for measuring the oxygen storage capacity (OSC) stored in the three-way catalyst, and
A control unit for controlling the control parameters related to the performance of the three-way catalyst by using the change amount of the OSC according to the thermal load,
/ RTI >
Wherein,
Wherein an inflection point at which the rate of decrease of the variation amount of the OSC changes is determined, and control variables related to the performance of the three-way catalyst are controlled differently around the inflection point. 12. The method of claim 11,
Wherein the control variable comprises:
Including at least one of a catalytic heating period, an oxygen (O ₂ ) purge period after fuel cut, a lambda rich control period during deceleration, a high rpm maintenance period of the engine, or an ignition timing maintenance period Purification device. delete 12. The method of claim 11,
Wherein,
Controlling the control variable to increase or decrease in accordance with the aging of the three-way catalyst when the change amount of the OSC is before the inflection point,
And controls the control variable to have a predetermined set value when the amount of change of the OSC is after the inflection point.

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