JP2010255582A - Exhaust emission control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exhaust emission control device for an internal combustion engine capable of restricting thermal decomposition of ozone in regeneration of a particulate filter using ozone as an oxidizer. <P>SOLUTION: This emission control device for an internal combustion engine includes: a filter 30 for collecting particulate materials contained in exhaust gas; an ozone generator 41 provided upstream of the filter to generate ozone for supply; an exhaust temperature sensor 31 for obtaining the temperature of the filter 30; a low-pressure EGR passage 20 communicating an exhaust passage 15 provided downstream of the filter 30 with an intake passage 16 provided upstream of the filter 30; a high-pressure EGR passage 23 communicating the intake passage 16 with a manifold 12; and an EGR pump 22 provided in the low-pressure EGR passage 20. In the case wherein the floor temperature of the filter 30 is a predetermined temperature, at which thermal decomposition of ozone is possible to occur, or more, the EGR pump 22 is driven to circulate the exhaust to the filter 30 through each EGR passage so as to lower the floor temperature of the filter 30, and thereafter, ozone is supplied to the filter 30, circulating the exhaust. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an exhaust gas purification apparatus for an internal combustion engine, and more particularly to an exhaust gas purification apparatus for an internal combustion engine that collects particulate matter in exhaust gas discharged from the internal combustion engine and purifies it by oxidation.

In general, exhaust gas from an internal combustion engine, particularly a diesel engine, is known to contain particulate matter containing carbon as a main component (hereinafter referred to as PM) and cause air pollution. Therefore, a technique for collecting and removing PM in the exhaust gas by providing a particulate filter (hereinafter referred to as a filter) in the exhaust passage is well known.
When the amount of PM trapped in the filter increases, the filter is clogged, and the resistance of the exhaust gas passing through the filter increases, resulting in deterioration of fuel consumption. For this reason, it is necessary to perform a so-called filter regeneration process for removing the PM collected by the filter, and various methods for oxidizing and removing the PM collected by the filter are conventionally known.

By the way, when the PM is accumulated on the filter when the internal combustion engine is stopped, the PM changes to a state in which it is difficult to oxidize as time passes. Therefore, it is conceivable that the filter regeneration process is performed before the internal combustion engine is stopped. However, when the filter regeneration process is performed during operation of the internal combustion engine, it is difficult to maintain the filter temperature depending on changes in the operating state. Since the reproduction process cannot be continued and is interrupted, it is difficult to cope with it. Therefore, it is desirable to remove PM while the internal combustion engine is stopped. Therefore, for example, in the technique described in Patent Document 1, the amount of PM accumulated on the filter is calculated while the internal combustion engine is stopped, and fuel is added to the filter when the amount of PM is a predetermined amount or more. The deposited PM is removed by oxidation by raising the temperature of the filter. Further, Patent Document 2 discloses a technique for oxidizing and removing PM by supplying ozone O ₃ having a strong oxidizing power to a filter while the fuel supply of an internal combustion engine is stopped. For example, Patent Document 3 discloses a filter regeneration process performed while the internal combustion engine is stopped.

JP 2007-187006 A JP 2008-14219 A JP 2001-50031 A

In the technique described in Patent Document 1, while the internal combustion engine is stopped, the fuel is added to the filter and the temperature of the filter is raised to oxidize and remove PM accumulated on the filter. Therefore, there was a risk of fuel consumption deterioration. In addition, in the technique described in Patent Document 2, during the fuel supply stop to the internal combustion engine, the ozone is removed by oxidizing ozone by supplying ozone to the filter using an ozone supplier that generates ozone by electric power. Although there is no risk of fuel consumption deterioration, depending on the flow rate of the exhaust gas exhausted from the internal combustion engine, there is a risk that the supplied ozone may be released from the filter before causing sufficient oxidation reaction with PM in the filter.
The present invention has been made in view of the above-described problems, and is an exhaust of an internal combustion engine that can efficiently use ozone when oxidizing and removing PM using ozone while the internal combustion engine is stopped. It aims to provide a purification device.

  In order to achieve the above object, an exhaust gas purification apparatus for an internal combustion engine according to one aspect of the present invention includes a particulate filter that collects particulate matter in exhaust gas in an exhaust passage, and an upstream side of the particulate filter. An exhaust gas purification apparatus for an internal combustion engine, comprising: ozone supply means for supplying ozone; and an EGR passage communicating with an exhaust passage and an intake passage on a downstream side of the particulate filter. The particulate filter through the EGR passage. The exhaust gas is provided with a circulation means for circulating the exhaust gas, and ozone supply is executed by the ozone supply means in a state where the exhaust gas is circulated through the particulate filter by the circulation means while the internal combustion engine is stopped.

  According to the present invention, the exhaust gas is circulated through the EGR passage while the internal combustion engine is stopped, so that the ozone that has not passed through the filter without reacting with the PM passes from the EGR passage connected to the exhaust passage downstream of the filter to the intake passage. Since it can be reintroduced into the filter through the exhaust passage upstream of the filter, unreacted ozone can be used again for PM oxidation removal when passing through the filter.

Here, the apparatus further comprises temperature acquisition means for acquiring the temperature of the particulate filter, and when the temperature acquired by the temperature acquisition means is higher than a predetermined temperature, the temperature acquired by the temperature acquisition means is equal to or lower than the predetermined temperature. It is preferable that the ozone supply by the ozone supply means is performed after exhaust gas is circulated through the particulate filter by the circulation means until it becomes.
Ozone has an appropriate temperature window for oxidizing and removing PM. When the temperature is higher than this temperature window (for example, 200 ° C. or more), ozone is thermally decomposed and disappears. Thus, when the temperature of the filter is such that most of the ozone supplied to the filter is thermally decomposed while the internal combustion engine is stopped, the exhaust gas is discharged from the EGR passage, the intake passage, and By releasing heat when passing through the exhaust passage or the like, the temperature of the exhaust gas can be lowered quickly, and when the exhaust gas whose temperature has dropped flows into the filter, the temperature of the filter can be lowered quickly. After the temperature of the filter is lowered to a temperature range where ozone is hardly thermally decomposed, the ozone is supplied to the filter, so that the thermal decomposition of ozone can be suppressed and used for PM oxidation removal.

  More preferably, either an intake throttle valve in an intake passage upstream from a connection portion between the intake passage and the EGR passage, and an exhaust throttle valve in an exhaust passage downstream from a connection portion between the exhaust passage and the EGR passage. If either one or both are further provided and either one is provided, the ozone supply means supplies ozone through the opening direction of the intake throttle valve or the exhaust throttle valve in the closing direction. It is good to execute. If both are provided, ozone supply by the ozone supply means may be executed after controlling the opening degree of both the intake throttle valve and the exhaust throttle valve in the closing direction.

  When an intake throttle valve is provided in the intake passage upstream from the connection portion between the EGR passage and the intake passage, and an exhaust throttle valve is provided in the exhaust passage downstream from the connection portion between the EGR passage and the exhaust passage, the intake throttle valve and the exhaust throttle valve Since the exhaust gas circulated by the circulation means can be prevented from being released from the intake passage or the exhaust passage by executing the circulation means after closing the ozone, the release of ozone into the atmosphere is suppressed. can do. Even if it has either an intake throttle valve or an exhaust throttle valve, it is not as much as having both an intake throttle valve and an exhaust throttle valve by controlling the throttle valve opening in the closing direction. The effect can be expected.

  According to the present invention, when PM is oxidized and removed using ozone while the internal combustion engine is stopped, ozone that has not reacted with PM and passed through the filter is reintroduced into the filter and used for oxidizing and removing PM. In addition, it is possible to reduce the temperature of the filter by circulating the exhaust gas, and it is possible to suppress the thermal decomposition of ozone. Moreover, it is possible to suppress the ozone that has passed through the filter without being reacted from being released to the atmosphere.

1 is a diagram illustrating a schematic configuration of an internal combustion engine to which an exhaust gas purification apparatus for an internal combustion engine according to an embodiment of the present invention is applied, and an intake system and an exhaust system thereof. It is the flowchart which showed the flow of the filter reproduction | regeneration process after the internal combustion engine stop which concerns on the Example of this invention.

Embodiments of the present invention will be described below with reference to the accompanying drawings.
FIG. 1 is a system diagram schematically showing an exhaust gas purification apparatus for an internal combustion engine according to an embodiment of the present invention. In the figure, reference numeral 10 denotes an internal combustion engine, which is a diesel engine in this embodiment. 11 is an intake manifold communicated with the intake port, 12 is an exhaust manifold communicated with the exhaust port, and 13 is a combustion chamber. The intake passage 16 is provided with an intercooler 29. In this embodiment, fuel supplied from a fuel tank (not shown) to the high pressure pump is pumped to the common rail by the high pressure pump and accumulated in a high pressure state, and the high pressure fuel in the common rail is directly fed into the combustion chamber 13 from the fuel injection valve. Be injected. Exhaust gas from the diesel engine 10 passes from the exhaust manifold 12 through the turbocharger 19 and then flows into the exhaust passage 15 downstream thereof, and after being purified as described later, is discharged to the atmosphere. In addition, as a form of a diesel engine, it is not restricted to the thing provided with such a common rail type fuel injection device.

A particulate filter (filter) 30 for collecting particulate matter (PM) in the exhaust gas is disposed in the exhaust passage 15. The ozone supply means for supplying ozone (O ₃₎ are provided from the upstream side to the filter 30. The ozone supply means includes an ozone supply nozzle 40 disposed in the exhaust passage 15 on the upstream side of the filter 30, and an ozone generator 41 as an ozone generation means connected to the ozone supply nozzle 40 via an ozone supply passage 42. Is provided. Ozone generated by the ozone generator 41 using electric power from a battery 43 (not shown) is supplied to the ozone supply nozzle via the ozone supply passage 42 and from the ozone supply nozzle 40 toward the downstream filter 30. Then, it is injected and supplied into the exhaust passage 15.

  As the ozone generator 41, for example, a form in which ozone is generated while flowing air or oxygen as a raw material in a discharge tube to which a high voltage can be applied, or any other type can be used. Here, as the raw material air or oxygen, the gas contained in the exhaust gas in the exhaust passage 15 is taken into the ozone generator 41 using an air pump (not shown), and a high voltage is directly applied to the exhaust in the exhaust passage 15. An application method may be used. In addition, the gas taken in from the outside of the exhaust passage 15, for example, the gas contained in the outside air may be used.

  An exhaust temperature sensor 31 that acquires the temperature of the exhaust gas flowing through the exhaust passage 15 is disposed in the exhaust passage 15 upstream of the filter 30. Based on the output signal of the exhaust temperature sensor 31, the temperature of the filter 30 is detected. In the present invention, the exhaust temperature sensor 31 corresponds to the temperature acquisition means in the present invention.

  Furthermore, one end of a low-pressure EGR passage 20 is connected to the exhaust passage 15 on the downstream side of the filter 30 for circulating a part of the exhaust gas into the combustion chamber 13 as EGR gas. The other end of the low pressure EGR passage 20 is connected to the intake passage 16 upstream of the turbocharger 19. An intake throttle valve 26 is provided upstream of the connection between the low pressure EGR passage 20 and the intake passage 16, and an exhaust throttle valve 28 is provided downstream of the connection between the low pressure EGR passage 20 and the exhaust passage 15. ing. An EGR cooler 21 for cooling the EGR gas and an EGR pump 22 for assisting the circulation of the EGR gas are arranged in the low pressure EGR passage 20, and this EGR pump 22 serves as a circulation means in the present invention. Equivalent to. Further, the exhaust manifold 12 and the intake manifold 11 communicate with each other by connecting a high-pressure EGR passage 23, and here, a part of the exhaust is circulated into the combustion chamber 13 as EGR gas and flows into the combustion chamber 13. A throttle valve 27 is provided upstream from the connection between the high pressure EGR passage 23 and the intake passage 16. In addition to the above, a low pressure EGR valve 24 and a high pressure EGR valve 25 for adjusting the flow rate of the circulated EGR gas are respectively provided at one end connected to the intake passage side of the low pressure EGR passage 20 and the high pressure EGR passage 23. Is provided.

The internal combustion engine 10 configured as described above is provided with an ECU 50 that is an electronic control unit for controlling the internal combustion engine 10. The ECU 50 is a unit that controls the operation state of the internal combustion engine 10 in accordance with the operation conditions of the internal combustion engine 10 and the request of the driver. The exhaust temperature sensor 31 and other various sensors are connected to the ECU 10 via electrical wiring, and output signals from various sensors including the exhaust temperature sensor 31 are input. The generator 41, the low-pressure EGR valve 24, the high-pressure EGR valve 25, and other valves, the fuel injection valve, the high-pressure pump, and the like are controlled.
Next, FIG. 2 is a flowchart showing a flow of filter regeneration control while the internal combustion engine is stopped according to the embodiment of the present invention. The procedure of filter regeneration control in the present invention will be described based on FIG. This routine is executed while the internal combustion engine is stopped. For example, it is executed when the driver turns off the ignition key to stop the internal combustion engine 10 or when the internal combustion engine 10 is automatically stopped when the vehicle is stopped to improve fuel efficiency. In the case of a hybrid vehicle, the internal combustion engine may be stopped and executed during EV travel driven by a motor.
In step S101, it is determined whether the amount of PM deposited on the filter 30 has reached a predetermined amount that needs to be regenerated. Here, whether or not the PM accumulated on the filter has reached a predetermined amount is determined based on, for example, the distance traveled after the time when the filter regeneration process was performed or the travel time, and the travel distance, travel time. The amount of PM deposited according to the above is obtained in advance through experiments or the like. In addition, if there is a differential pressure sensor or the like that detects the pressure of the exhaust on the upstream side and downstream side of the filter 30, the amount of PM accumulated on the filter is estimated by calculating the differential pressure before and after the filter. It is good also as a judgment standard.

If an affirmative determination is made in step S101 that the amount of accumulated PM is determined to require filter regeneration processing, the routine proceeds to step S102, whereas if a negative determination is made, this routine is terminated.
In step S <b> 102, it is determined whether or not the charged amount of power stored in the battery 43 is sufficient. Further, external power supply means such as a plug-in or a vehicle-mounted solar battery may be provided. In this case, it is determined whether the amount of power supplied from the outside is sufficient. Specifically, in addition to the power consumption for generating ozone consumed by the ozone generator 41 and the power consumed by the EGR pump 22, even if there is power consumption in a load that requires another power supply Then, it is determined whether the amount of power does not cause a shortage of supply. If an affirmative determination is made in step S102, the process proceeds to step S103, and if a negative determination is made, this routine is terminated.
In step 103, the intake throttle valve 26 and the exhaust throttle valve 28 are closed, and the throttle valve 27, the high pressure EGR valve 25, and the low pressure EGR valve 24 are opened. By controlling each valve in this way, a circulation closed circuit for circulating the exhaust from the downstream of the filter 30 through the low pressure EGR passage 20, the intake passage 16, the high pressure EGR passage 23, and the exhaust passage 15 can be formed. It is possible to suppress the exhaust of the circulated exhaust to the atmosphere. When this control is completed, the process proceeds to step S104.

  In step S104, it is determined whether the temperature of the filter 30 detected by the exhaust temperature sensor 31 is equal to or lower than a predetermined temperature (for example, 200 ° C.). If an affirmative determination is made in step S104, the process proceeds to step S106, whereas if a negative determination is made, the process proceeds to step S105.

  In step S105, the EGR pump 22 is driven using the electric power from the battery 43. As a result, the exhaust gas passing through the filter 30 can be circulated again to the filter 30 through the low pressure EGR passage 20, the intake passage, the high pressure EGR passage 23, and the exhaust passage 15. At this time, since the exhaust gas circulated is cooled by heat exchange with the EGR cooler 21 and the intercooler 29 in addition to heat radiation in each passage, the exhaust gas temperature can be quickly lowered. As a result, when the temperature of the filter 30 detected by the temperature acquisition unit becomes equal to or lower than the predetermined temperature, the process proceeds to step S106.

  In step S106, exhaust gas is circulated through the filter 30 by driving the EGR pump 22 in the same procedure as in step S105, and ozone is generated by the ozone generator 41 using the power of the battery 43 to supply ozone. Ozone is supplied to the filter 30 by spraying from the ozone supply nozzle 40 through the passage 42. Thus, by supplying ozone to the filter 30, PM deposited on the filter 30 can be removed by oxidizing reaction with ozone, and ozone released from the filter 30 without reacting with PM can be removed by the above procedure. Therefore, the generated ozone can be efficiently used for the PM oxidation removal. In addition, soot, soot, and HC may adhere to the passages where exhaust has flowed since normal operation, such as the EGR passages and EGR pumps 22 in the circulation closed circuit, but the present invention is used. Thus, it can be removed by oxidizing these with ozone.

  In this way, when the internal combustion engine is stopped, the PM is oxidized and removed using the electric power stored in the battery 43 or the electric power supplied from the outside, so that the filter regeneration process can be performed without using fuel. Since it can be performed, deterioration of fuel consumption can be suppressed. In addition, while the internal combustion engine is stopped, ozone can be efficiently used for oxidizing and removing PM by supplying ozone after the temperature of the filter is lowered to a temperature at which ozone is not thermally decomposed.

  In the present embodiment, the EGR pump is used as the circulation means. However, it is sufficient that the exhaust gas in the circulation closed circuit can be supplied. For example, when the provided turbocharger is an electric motor assist turbocharger, the electric motor is driven. By doing so, the exhaust gas may be circulated.

  Moreover, in the said embodiment, although control was performed by estimating and acquiring the filter bed temperature from the temperature of the exhaust gas flowing into the filter, the control may be performed by directly acquiring the filter bed temperature.

  In addition, depending on the configuration of the exhaust gas purification apparatus of the internal combustion engine, there may be another catalyst such as a NOx reduction catalyst, a NOx adsorption catalyst, or an oxidation catalyst provided downstream of the filter. In that case, ozone is also passed through the catalyst. Thus, soot, soot, and HC adhering to the catalyst can be removed.

  The present invention can be applied to all internal combustion engines that may generate PM, in addition to a diesel engine as a compression self-ignition internal combustion engine. For example, a direct injection spark ignition internal combustion engine. In this engine, fuel is directly injected into the in-cylinder combustion chamber. However, in a high load region where the fuel injection amount is large, the fuel does not completely burn and PM may be generated. Even if the present invention is applied to such an engine, similar effects can be expected.

DESCRIPTION OF SYMBOLS 10 Internal combustion engine 11 Intake manifold 12 Exhaust manifold 13 Combustion chamber 15 Exhaust passage 16 Intake passage 19 Turbocharger 19a Compressor 19b Turbine 20 Low pressure EGR passage 21 EGR cooler 22 EGR pump 23 High pressure EGR passage 24 Low pressure EGR valve 25 High pressure EGR valve 26 Intake throttle Valve 27 Throttle valve 28 Exhaust throttle valve 29 Intercooler 30 Particulate filter 31 Exhaust temperature sensor 40 Ozone supply nozzle 41 Ozone generator 42 Ozone supply passage 50 ECU
51 accelerator

Claims (4)

A particulate filter that collects particulate matter in the exhaust gas in the exhaust passage;
Ozone supply means for supplying ozone from the upstream side of the particulate filter;
An EGR passage communicating the exhaust passage and the intake passage on the downstream side of the particulate filter;
An exhaust gas purification apparatus for an internal combustion engine comprising:
Circulating means for circulating exhaust gas through the particulate filter through the EGR passage, and ozone supply by the ozone supplying means in a state where exhaust gas is circulated through the particulate filter by the circulating means while the internal combustion engine is stopped. An exhaust emission control device for an internal combustion engine characterized by being executed. A temperature acquisition means for acquiring the temperature of the particulate filter;
When the temperature acquired by the temperature acquisition means is higher than a predetermined temperature, the exhaust gas is circulated through the particulate filter by the circulation means until the temperature acquired by the temperature acquisition means is equal to or lower than the predetermined temperature. 2. The exhaust gas purification apparatus for an internal combustion engine according to claim 1, wherein ozone supply by the ozone supply means is executed. An intake throttle valve in an intake passage upstream of a connection portion between the intake passage and the EGR passage;
An exhaust throttle valve is further provided in the exhaust passage downstream of the connection portion between the exhaust passage and the EGR passage,
3. The exhaust gas purification apparatus for an internal combustion engine according to claim 1, wherein ozone supply by the ozone supply means is executed after controlling the opening degree of the intake throttle valve or the exhaust throttle valve in a closing direction. An intake throttle valve in an intake passage upstream of a connection portion between the intake passage and the EGR passage;
An exhaust throttle valve in an exhaust passage downstream of a connection portion between the exhaust passage and the EGR passage,
The exhaust purification device for an internal combustion engine according to claim 1 or 2, wherein ozone supply by the ozone supply means is executed after the intake throttle valve and the exhaust throttle valve opening are controlled in a closing direction.