JP2009030498A - Exhaust emission control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide technology reducing noise when an exhaust throttle valve operates and inhibiting emission of particulate matter in an exhaust emission control device for an internal combustion engine. <P>SOLUTION: This device is provided with a DPF 3 provided in an exhaust passage 2 of the internal combustion engine 1 and collecting particulate matter in exhaust gas, the exhaust throttle valve 4 provided in the exhaust gas passage at a downstream side of the DPF 3, adjusting exhaust gas flow rate, and a sub DPF 5 provided in the exhaust passage at a downstream side of the exhaust throttle valve 4, reducing noise when the exhaust throttle valve 4 operates and collecting particulate matter which can not be collected by the DPF 3 filter. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an exhaust emission control device for an internal combustion engine.

  The particulate matter deposited on the filter is oxidized and removed while the opening of the exhaust throttle valve is controlled to the closed side, the filter is regenerated, and when the regeneration of the filter is completed, the EGR valve is opened first and then the exhaust throttle valve is opened. To fully open. As a result, the pressure of the exhaust system is reduced by opening the EGR valve, and a technique that can significantly reduce noise generated when the exhaust throttle valve is opened is disclosed (for example, Patent Document 1). reference).

Moreover, in order to raise the temperature of the filter, a technique is disclosed in which the engine speed of the internal combustion engine is increased and the exhaust flow rate is reduced by an exhaust brake disposed in the exhaust passage upstream of the filter (for example, Patent Document 2). reference).
JP 2005-315189 A JP 2005-155534 A

  By the way, when the particulate matter deposited on the filter is oxidized and removed to regenerate the filter, the opening degree of the exhaust throttle valve provided in the exhaust passage downstream of the filter is controlled to the closed side, and the upstream side of the exhaust throttle valve. By increasing the exhaust pressure, the exhaust temperature is increased to promote the combustion of particulate matter deposited on the filter.

  However, noise is generated when the opening of the exhaust throttle valve is controlled to close to increase the exhaust pressure when the filter is regenerated. Further, when the opening of the exhaust throttle valve is controlled to the open side when the regeneration of the filter is completed, noise is generated and particulate matter attached to the exhaust passage downstream of the filter is released into the exhaust.

  The present invention has been made in view of the above problems, and an object of the present invention is to reduce noise and suppress emission of particulate matter when an exhaust throttle valve is operated in an exhaust purification device of an internal combustion engine. To provide technology.

In the present invention, the following configuration is adopted. That is,
A filter provided in an exhaust passage of the internal combustion engine for collecting particulate matter in the exhaust;
An exhaust throttle valve that is provided in the exhaust passage downstream of the filter and adjusts an exhaust flow rate;
A sub-filter that is provided in the exhaust passage downstream of the exhaust throttle valve, reduces noise when the exhaust throttle valve is activated, and collects particulate matter that was not collected by the filter;
An exhaust emission control device for an internal combustion engine, comprising:

According to the present invention, the sub-filter is provided in the exhaust passage downstream of the filter and the exhaust throttle valve. Therefore, even if the noise when the exhaust throttle valve is actuated is transmitted to the exhaust passage downstream of the exhaust throttle valve, the sub-filter can reduce the noise and suppress the noise from being transmitted to the outside. Moreover, even if the particulate matter that has not been collected by the filter flows out to the exhaust passage downstream of the filter, the particulate matter can be collected by the sub-filter, and the particulate matter can be prevented from being discharged to the outside.

  The sub-filter may be smaller than the filter.

  According to the present invention, the exhaust pressure in the exhaust passage immediately upstream of the sub-filter is slightly increased, and the exhaust temperature immediately upstream of the sub-filter is increased. Therefore, it is possible to easily regenerate the subfilter by raising the exhaust temperature and removing the particulate matter deposited on the subfilter by oxidation. Further, when the sub filter is small, the manufacturing cost can be reduced. Furthermore, even if the sub-filter is small, the particulate matter collected by the sub-filter is a very small amount of particulate matter that was not collected by the filter. There is little concern about the increase.

  The sub-filter reduces the noise when controlling the opening of the exhaust throttle valve to the closed side to oxidize and remove particulate matter deposited on the filter and regenerate the filter. Before the opening of the exhaust throttle valve is controlled to the opening side, noise is reduced, and before the opening of the exhaust throttle valve is controlled to the opening side, the particulate matter is attached to the exhaust passage, and the exhaust throttle The particulate matter released into the exhaust when the valve opening is controlled to the open side may be collected.

  According to the present invention, it is possible to reduce noise when the exhaust throttle valve operates in the above case, and to suppress discharge of particulate matter.

  According to the present invention, in the exhaust gas purification apparatus for an internal combustion engine, noise when the exhaust throttle valve is actuated can be reduced and discharge of particulate matter can be suppressed.

  Specific examples of the present invention will be described below.

<Example 1>
FIG. 1 is a diagram showing a schematic configuration of an internal combustion engine to which the exhaust gas purification apparatus for an internal combustion engine according to this embodiment is applied and an exhaust system thereof.

  An internal combustion engine 1 shown in FIG. 1 is a water-cooled four-stroke cycle diesel engine having four cylinders that form a combustion chamber together with a piston. The internal combustion engine 1 is mounted on a vehicle.

  An exhaust passage 2 is connected to the internal combustion engine 1. In the middle of the exhaust passage 2, a DPF (diesel particulate filter) 3 is disposed. Here, the DPF 3 of this embodiment corresponds to the filter of the present invention.

  The DPF 3 forms a filter body by forming a porous ceramic such as cordierite or silicon carbide into a honeycomb shape, and sealing the inlet side or the outlet side of the flow path. Exhaust gas discharged from the internal combustion engine 1 to the exhaust passage 2 upstream of the DPF 3 flows into the flow path in the DPF 3 and flows to the downstream exhaust passage 2 while passing through the porous partition wall. At this time, the particulate matter contained in the exhaust gas is collected in the DPF 3 and accumulates as the operation time passes. The DPF 3 can also have a structure in which an oxidation catalyst mainly composed of a noble metal such as platinum or palladium is supported on the porous ceramic surface constituting the filter body, and the fine particles can be stably formed in a low temperature range of the DPF 3. Substances can be oxidized and burned.

  An exhaust throttle valve 4 is disposed in the exhaust passage 2 downstream of the DPF 3. The exhaust throttle valve 4 can adjust the flow rate of the exhaust gas flowing through the exhaust passage 2.

  A sub-DPF 5 is disposed in the exhaust passage 2 downstream of the exhaust throttle valve 4. Here, the sub-DPF 5 of the present embodiment corresponds to a sub-filter of the present invention.

  The sub DPF 5 has the same configuration as that of the DPF 3, but is small in size with half the capacity of the DPF 3.

  The internal combustion engine 1 configured as described above is provided with an ECU 6 that is an electronic control unit for controlling the internal combustion engine 1. The ECU 6 is a unit that controls the operation state of the internal combustion engine 1 in accordance with the operation conditions of the internal combustion engine 1 and the request of the driver.

  Various sensors are connected to the ECU 6 through electric wiring, and output signals of these various sensors are input to the ECU 6.

  On the other hand, the exhaust throttle valve 4 and the like are connected to the ECU 6 via electric wiring, and these devices are controlled by the ECU 6.

  The ECU 6 controls the regeneration of the DPF 3 by calculating the amount of particulate matter deposited on the DPF 3 based on the operating state of the internal combustion engine 1, the intake air amount, the differential pressure across the DPF 3, and the like. The regeneration of the DPF 3 is a so-called filter regeneration, and is a process of raising the temperature of the DPF 3 to, for example, 600 ° C. and oxidizing and removing (burning and removing) the particulate matter deposited on the DPF 3.

  During regeneration of the DPF 3, it is necessary to raise the temperature of the DPF 3. As a means for raising the temperature of the DPF 3 for this purpose, in this embodiment, a method of controlling the opening of the exhaust throttle valve 4 to the closed side is adopted. That is, the opening degree of the exhaust throttle valve 4 disposed in the exhaust passage 2 downstream of the DPF 3 is controlled to the closed side, and the exhaust pressure is increased by increasing the exhaust pressure upstream of the exhaust throttle valve 4 to increase the exhaust temperature. It promotes the combustion of particulate matter deposited on the surface.

  However, if the opening degree of the exhaust throttle valve 4 is controlled to close to increase the exhaust pressure when the DPF 3 is regenerated, noise is generated. The noise at the time of controlling the opening degree of the exhaust throttle valve 4 to the closed side has a significantly higher frequency than the pulsation of the exhaust, and the muffler for silencing the noise caused by the pulsation of the exhaust effectively uses sound pressure The level cannot be lowered.

  Further, if the opening of the exhaust throttle valve 4 is controlled to the open side when the regeneration of the DPF 3 is completed, noise is generated and particulate matter adhering to the inner wall surface of the exhaust passage 2 is released into the exhaust. The noise at the time of controlling the opening of the exhaust throttle valve 4 to the open side is also significantly higher than the exhaust pulsation, and the muffler for silencing the noise caused by the exhaust pulsation effectively produces sound pressure. The level cannot be lowered. Further, the particulate matter released when the opening degree of the exhaust throttle valve 4 is controlled to the open side remains attached to the inner wall surface of the exhaust passage 2 downstream of the DPF 3 in the normal exhaust pulsation, The exhaust throttle valve 4 is discharged from the inner wall surface of the exhaust passage 2 by an impact caused by a sudden pressure change when the opening degree of the exhaust throttle valve 4 is controlled to the open side.

  Therefore, in this embodiment, a sub DPF 5 smaller than the DPF 3 is arranged in the exhaust passage 2 downstream from the DPF 3 and the exhaust throttle valve 4.

According to this, even when the noise when the exhaust throttle valve 4 is actuated is transmitted to the exhaust passage 2 downstream of the exhaust throttle valve 4, the noise is passed through the porous filter body when passing through the sub DPF 5. The noise can be reduced by attenuating the sound pressure of the noise, and transmission of the noise to the outside can be suppressed.

  The sub-DPF 5 allows noise to pass through the porous filter body and attenuates the sound pressure of the noise, so that the sound pressure level can be lowered regardless of the noise frequency. Therefore, noise such as noise when the opening degree of the exhaust throttle valve 4 is controlled to the closed side and noise when controlling the opening degree of the exhaust throttle valve 4 to the open side is different from the noise generated by the pulsation of the exhaust gas. Even for high frequency noise, the sound pressure level can be lowered.

  Moreover, even if the particulate matter not collected by the DPF 3 flows out to the exhaust passage 2 downstream of the DPF 3, the particulate matter can be collected by the sub DPF 5, and the particulate matter can be prevented from being discharged to the outside. . In particular, even in the case of particulate matter that is released from the inner wall surface of the exhaust passage 2 due to an impact caused by a sudden pressure change when the opening of the exhaust throttle valve 4 is controlled to the open side, the sub-DPF 5 The particulate matter can be collected, and the particulate matter can be prevented from being discharged to the outside.

  Here, since the sub DPF 5 is smaller and has a half capacity compared to the DPF 3, the exhaust pressure in the exhaust passage 2 immediately upstream of the sub DPF 5 slightly increases, and the exhaust temperature immediately upstream of the sub DPF 5 increases. Therefore, it is possible to easily regenerate the sub DPF 5 by raising the exhaust gas temperature and oxidizing and removing the particulate matter deposited on the sub DPF 5. Further, when the sub DPF 5 is small, the manufacturing cost can be reduced. Furthermore, even if the sub DPF 5 is small, the particulate matter collected by the sub DPF 5 is a very small amount of particulate matter that was not collected by the DPF 3, so that the pressure loss caused by collecting the particulate matter by the sub DPF 5 is reduced. There is little concern about the increase.

The sub-DPF 5 may have a structure in which an oxidation catalyst mainly composed of a noble metal such as platinum or palladium is supported on the porous ceramic surface constituting the filter body. When the catalyst is supported in this way, the sub-DPF 5 is oxidized by active species such as N ₂ O contained in the exhaust gas, and constantly oxidizes the particulate matter stably in a low temperature range (eg, about 200 ° C.). Can be burned. In this case, the regeneration of the sub-DPF 5 is always performed and the particulate matter deposited on the sub-DPF 5 is oxidized and removed, so that special regeneration means for regenerating the sub-DPF 5 by raising the temperature of the sub-DPF 5 to about 600 ° C., for example. Therefore, an increase in pressure loss due to the collection of the particulate matter by the sub-DPF 5 does not occur.

  The exhaust gas purification apparatus for an internal combustion engine according to the present invention is not limited to the above-described embodiments, and various modifications may be made without departing from the gist of the present invention.

1 is a diagram illustrating a schematic configuration of an internal combustion engine and an exhaust system thereof according to a first embodiment.

Explanation of symbols

1 Internal combustion engine 2 Exhaust passage 3 DPF
4 Exhaust throttle valve 5 Sub DPF
6 ECU

Claims (3)

A filter provided in an exhaust passage of the internal combustion engine for collecting particulate matter in the exhaust;
An exhaust throttle valve that is provided in the exhaust passage downstream of the filter and adjusts an exhaust flow rate;
A sub-filter that is provided in the exhaust passage downstream of the exhaust throttle valve, reduces noise when the exhaust throttle valve is activated, and collects particulate matter that was not collected by the filter;
An exhaust emission control device for an internal combustion engine, comprising:   The exhaust purification device for an internal combustion engine according to claim 1, wherein the sub-filter is smaller than the filter. The sub-filter reduces the noise when controlling the opening of the exhaust throttle valve to the closed side to oxidize and remove particulate matter deposited on the filter and regenerate the filter. Before the opening of the exhaust throttle valve is controlled to the opening side, noise is reduced, and before the opening of the exhaust throttle valve is controlled to the opening side, the particulate matter is attached to the exhaust passage, and the exhaust throttle The exhaust emission control device for an internal combustion engine according to claim 1 or 2, wherein the particulate matter released into the exhaust gas when the valve opening is controlled to the open side is collected.

Images