JP2012117512A - After-treatment method for exhaust gas - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an after-treatment method for exhaust gas which has a self-diagnosis function for determining whether rapid heat up logic for quickly raising the temperature of the exhaust gas can be executed without errors or not when executing the rapid heat up logic.SOLUTION: This after-treatment method for exhaust gas includes: a step to determine whether or not present operation is included in an operation region, in which the rapid heat up (RHU) logic for quickly raising the temperature of the exhaust gas discharged from an engine and passing in an exhaust line is monitored; a step to sense ON/OFF signals for executing and interrupting the rapid heat up logic; a step to determine whether an injection signal for executing the rapid heat up logic is activated or not; a step to sense errors of a part for executing the rapid heat up logic; and a step to sense the temperature of the exhaust gas during the time when the rapid heat up logic is being executed.

Description

    The present invention relates to an exhaust gas aftertreatment method, and more particularly, rapid heat up (RHU) that rapidly increases the temperature of exhaust gas in order to activate a catalyst that reduces harmful substances contained in the exhaust gas. heat up) relates to an exhaust gas aftertreatment method including logic.

According to the conventional exhaust gas purification device, a smoke oxidation catalyst (DOC), a diesel smoke filter (DPF), and a selective catalytic reduction (SCR) device are attached to the exhaust pipe in this order.
Exhaust gas generated from the engine passes through a diesel oxidation catalyst, a diesel smoke filter, and a selective catalytic reduction device in this order to remove harmful substances contained in the exhaust gas.
That is, the diesel smoke filter collects particulate matter (PM) contained in the exhaust gas, and the diesel oxidation catalyst oxidizes carbon monoxide and hydrocarbons contained in the exhaust gas. The catalytic catalytic reduction device reduces nitrogen oxides contained in the exhaust gas to nitrogen gas.

On the other hand, in order for nitrogen oxides to react with the reducing agent, the temperature of the exhaust gas at the front end of the selective catalytic reduction device needs to be 200 ° C. or higher. However, since the selective catalytic reduction device is attached to the rear end of the exhaust pipe, it takes a long time for the exhaust gas temperature at the front end of the selective catalytic reduction device to reach 200 ° C. or higher. Before the temperature of the exhaust gas reaches 200 ° C. or higher, there is a problem that nitrogen oxides contained in the exhaust gas are hardly reduced and discharged to the outside.
As a solution to the above problem, rapid heat-up (RHU) logic that rapidly raises the temperature of exhaust gas is gradually applied in order to quickly raise the temperature of the catalyst, and such rapid heat-up is performed. Therefore, there is an eagerly desired method for determining an operation region for accurately determining the error.

Japanese Patent Laid-Open No. 05-202735

  The present invention provides an exhaust gas having a self-diagnostic (OBD) function for determining whether or not this is performed without error when performing rapid heat-up logic for rapidly increasing the temperature of the exhaust gas. An object is to provide a post-processing method.

  The exhaust gas aftertreatment method according to the present invention is included in an operating region for monitoring rapid heat up (RHU) logic for rapidly increasing the temperature of exhaust gas discharged from an engine and passing through an exhaust line. Determining whether or not an on / off signal for performing or interrupting the rapid heat-up logic is activated, and whether or not an injection signal for performing the rapid heat-up logic is activated. Determining, detecting a component error for performing the rapid heat-up logic, sensing an exhaust gas temperature during the rapid heat-up logic, and comparing the detected temperature with a model value. It is characterized by including.

  The method may further include outputting an error signal when the temperature of the exhaust gas raised by the rapid heat-up logic deviates from the model value.

  Accumulating the error signal; storing the accumulated value; and, if the accumulated value exceeds a set value, activating a rapid heat-up logic warning lamp (MIL). It is further characterized by including.

  The driving region for performing the rapid heat-up logic needs to satisfy the conditions for entering the rapid heat-up logic, and the conditions for entering the rapid heat-up logic include atmospheric pressure, vehicle speed, engine It is determined based on the rotational speed, the intake air temperature, the coolant temperature, the number of gears, and the fuel injection amount.

  If the conditions for entering the rapid heat-up logic are satisfied, the post-injection amount for performing the rapid heat-up is determined based on the engine speed and the fuel injection amount, and the fuel injection amount is increased. It is characterized by.

  In the step of sensing an error of the component, the component is an injector for injecting fuel and a temperature sensor for sensing the temperature of exhaust gas.

  The exhaust line includes a diesel oxidation catalyst that oxidizes harmful substances contained in the exhaust gas, a diesel smoke filter that filters particulate matter contained in the exhaust gas, and a reduction to exhaust gas that passes through the exhaust line. A dosing module for injecting the agent, a selective catalytic reduction (SCR) unit for oxidizing / reducing nitrogen oxides contained in the exhaust gas using the reducing agent injected from the dosing module; Are arranged in this order.

  The temperature sensor senses temperatures of a rear end of the engine, a front end of the diesel oxidation catalyst, a front end of the diesel smoke filter, and a front end of the selective catalytic reduction unit.

  According to the present invention, the rapid heat-up logic can be prevented from malfunctioning and the rapid heat-up logic can be realized more stably, and the self-diagnosis function can be realized by notifying the user of malfunction caused by an error signal. There is an effect to improve.

1 is a schematic configuration diagram of an exhaust gas aftertreatment system according to an embodiment of the present invention. It is a schematic flowchart of the exhaust-gas post-processing method which concerns on embodiment of this invention. It is a detailed flowchart of the exhaust-gas aftertreatment method which concerns on embodiment of this invention. In the exhaust-gas post-processing method which concerns on embodiment of this invention, it is a graph which shows the temperature of the exhaust gas in the state in which rapid heat-up logic is performed, and its self-diagnosis function.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a schematic configuration diagram of an exhaust gas aftertreatment system according to an embodiment of the present invention.
As shown in FIG. 1, the exhaust gas aftertreatment system includes an engine 100, an injector 110, a control unit 120, an exhaust line 130, a diesel oxidation catalyst 140, a diesel smoke filter 150, a dosing module 160, and a mixer. 170, a selective catalytic reduction unit 180, and temperature sensors T3, T4, T5, T6, T6 and T7.
An injector 110 is disposed in the engine 100, and the injector 110 injects fuel into the cylinder and performs post-injection for rapid heat-up (RHU).

Exhaust gas discharged from the engine 100 passes through the diesel oxidation catalyst 140, the diesel smoke filter 150, the mixer 170, and the selective catalytic reduction unit 180 in this order in the exhaust line 130, and passes through a muffler (not shown). Discharged outside.
The temperature sensors T 6 and T 7 sense the temperature of the exhaust gas flowing into the diesel oxidation catalyst 140, the temperature of the exhaust gas flowing into the diesel smoke filter 150, and the temperature of the exhaust gas flowing into the selective catalytic reduction unit 180.

The control unit 120 determines whether to perform a rapid heat-up (RHU) logic using the operating state of the engine 100 and the temperature of the exhaust gas passing through the exhaust line 130, and the conditions for performing the rapid heat-up logic are determined. If satisfied, the injector 110 performs normal injection and further post-injection.
Further, the control unit 120 controls the start and interruption of the rapid heat-up logic using the operating state of the engine 100 and the temperature of the exhaust gas passing through the exhaust line 130.

FIG. 2 shows a schematic flowchart of the exhaust gas aftertreatment method according to the embodiment of the present invention, and FIG. 3 shows a detailed flowchart of the exhaust gas aftertreatment method according to the embodiment of the present invention.
As shown in FIG. 2, in S200, it is determined whether or not a rapid heat up (RHU) function monitoring condition is satisfied. That is, it is determined here whether or not it is a region for monitoring the rapid heat-up function.
The region where the rapid heat-up function is monitored is regarded as a state where the rapid heat-up function is performed.
More specifically, in (1) in FIG. 3, the control unit 120 senses atmospheric pressure, vehicle speed, engine speed, intake air temperature, cooling water temperature, gear stage number, fuel injection amount, and exhaust gas temperature T6 or T7. It is determined whether or not the rapid heat-up function is performed, and the state where the rapid heat-up function is performed is continuously monitored.

In S210 in FIG. 2, it is determined whether the rapid heat-up function is in an “on” state or an “off” state. In S220, whether or not an injection signal for rapid heat-up is activated. Judging.
The injection signal includes a drive signal that is applied from the control unit 120 and causes the injector 110 to perform post-injection.
In S230, an error of a part for performing rapid heat-up is determined.
As shown in (4) in FIG. 3, in order to perform rapid heat-up, the injector 110 and the temperature sensors T3 to T7 are used. When the injector 110 or the temperature sensors T3 to T7 malfunctions or fails, the control unit 120 Generates component error signals for rapid heat-up.

In S240, during the rapid heat-up, the temperature of the exhaust gas is sensed and compared with the modeled temperature range to determine whether the temperature of the exhaust gas is included in the set temperature range. .
In S250, when the rapid heat-up is completed, the monitoring operation is terminated and the result is output.
As shown in (5) and (6) in FIG. 3, a rapid heat-up strategy is evaluated by sensing the temperature of the exhaust gas using a temperature sensor.
More specifically, if the exhaust gas temperature exceeds the set temperature range during the monitoring period, an error signal is generated, and the generated error signal is counted (accumulated). Save.
Also, if the counted number exceeds the set numerical value, it is determined that the rapid heat up (RHU) logic operates abnormally, and a warning light (MIL: malfunction indicator lamp) is displayed.

FIG. 4 is a graph showing the exhaust gas temperature and the self-diagnosis function in a state where rapid heat-up logic is performed in the exhaust gas aftertreatment method according to the embodiment of the present invention.
As shown in FIG. 4, the horizontal axis represents time, and the vertical axis represents the temperature of the exhaust gas flowing into the selective catalytic reduction unit 180.
As shown in the figure, the range of the RHU model temperature 400 is set by the set map data, and a graph of the exhaust temperature 410 actually flowing into the selective catalytic reduction unit 180 is formed while the RHU is performed (ON). Is done. Note that a graph of the exhaust temperature 420 is also set while RUH is not performed (OFF).
Further, a modeled exhaust gas temperature 430 by engine operating conditions and rapid heat-up (RHU) logic is also formed, and an error signal 440 is generated at a portion exceeding the modeled temperature 430 and the set temperature range 400.
The controller 120 counts the error signal, stores the counted number, and displays a warning light (MIL) if the counted number deviates from the set value.

    As mentioned above, although preferred embodiment regarding this invention was described, this invention is not limited to the said embodiment, All the changes in the range which does not deviate from the technical scope to which this invention belongs are included.

100 Engine 110 Injector 120 Control unit 130 Exhaust line 140 Diesel oxidation catalyst (DOC)
150 Diesel smoke filter (DPF)
160 Dosing module 170 Mixer 180 Selective catalytic reduction (SCR) unit T3, T4, T5, T6, T7 Temperature sensor

Claims (8)

Determining whether a rapid heat up (RHU) logic for rapidly raising the temperature of the exhaust gas exhausted from the engine and passing through the exhaust line is included in an operating region for monitoring;
Sensing an on / off signal to perform or interrupt the rapid heat-up logic;
Determining whether an injection signal for performing the rapid heat-up logic is activated; and
Sensing an error in a component for performing the rapid heat-up logic;
Sensing the temperature of the exhaust gas during the rapid heat-up logic and comparing it to a model value;
An exhaust gas aftertreatment method comprising:   The exhaust gas post-processing method according to claim 1, further comprising a step of outputting an error signal when the temperature of the exhaust gas raised by the rapid heat-up logic deviates from a model value. Accumulating the error signal;
Storing the accumulated value and, if the accumulated value exceeds a set value, activating a rapid heat-up logic warning light (MIL);
The exhaust gas aftertreatment method according to claim 2, further comprising: The operation region for performing the rapid heat-up logic needs to satisfy the conditions for entering the rapid heat-up logic,
The condition for entering the rapid heat-up logic is determined based on atmospheric pressure, vehicle speed, engine speed, intake air temperature, cooling water temperature, gear stage number, and fuel injection amount. Exhaust gas aftertreatment method.   If the conditions for entering the rapid heat-up logic are satisfied, the post-injection amount for performing the rapid heat-up is determined based on the engine speed and the fuel injection amount, and the fuel injection amount is increased. The exhaust gas aftertreatment method according to claim 4. In the step of sensing an error of the part,
The exhaust gas after-treatment method according to claim 1, wherein the components are an injector for injecting fuel and a temperature sensor for sensing the temperature of exhaust gas. In the exhaust line,
A diesel oxidation catalyst that oxidizes harmful substances contained in exhaust gas;
A diesel smoke filter that filters particulate matter contained in the exhaust gas; and
A dosing module for injecting a reducing agent into the exhaust gas passing through the exhaust line;
A selective catalytic reduction (SCR) unit that oxidizes / reduces nitrogen oxides contained in exhaust gas using a reducing agent injected from the dosing module;
2. The exhaust gas aftertreatment method according to claim 1, wherein the exhaust gas is disposed in this order.   The temperature sensor senses temperatures of a rear end of the engine, a front end of the diesel oxidation catalyst, a front end of the diesel smoke filter, and a front end of the selective catalytic reduction unit. The exhaust gas aftertreatment method according to claim 7.

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