JP2009074425A - Exhaust gas purification device for internal combustion engine - Google Patents

Abstract

The present invention relates to an exhaust gas purification device for an internal combustion engine, and in an internal combustion engine having a particulate filter and an exhaust gas sensor in order from the upstream side in an exhaust passage, it is possible to satisfactorily suppress the occurrence of element cracks in the exhaust gas sensor due to water. For the purpose.
A particulate filter (PM filter) 18 for collecting particulate matter PM is provided in an exhaust passage 12 of an internal combustion engine 10. The PM filter 18 includes a plurality of internal passages 28 and 30 formed in the exhaust gas flow direction by partition walls 26 having pores on the surface and inside. The PM filter 18 also includes a clogging member 32 that closes the downstream end of the internal passage 28 and a clogging member 34 that closes the upstream end of the internal passage 30. The volume of the downstream clogging member 32 is made larger than the volume of the upstream clogging member 34.
[Selection] Figure 2

Description

  The present invention relates to an exhaust gas purifying device for an internal combustion engine, and more particularly to an exhaust gas purifying device for an internal combustion engine including a particulate filter for collecting particulate matter PM contained in the exhaust gas.

  Conventionally, for example, Patent Document 1 discloses an exhaust gas purifying device for a diesel engine including a particulate filter (PM filter) for collecting particulate matter PM in an exhaust passage. In this conventional apparatus, an upstream filter and a downstream filter are arranged along the flow of exhaust gas. In the conventional apparatus, the pore diameter of the upstream filter is set larger than the pore diameter of the downstream filter in order to improve the durability against the destruction of the filter due to a rapid temperature change (thermal shock).

  Further, for example, Patent Document 2 discloses a diesel engine exhaust gas purification device including an O2 sensor that detects an oxygen concentration in exhaust gas in an exhaust passage downstream of a PM filter.

Japanese Utility Model Publication No. 5-57311 Japanese Utility Model Publication No. 64-3017 JP 2004-162537 A JP 2004-251245 A

  The exhaust gas of the internal combustion engine contains moisture. At the cold start, the water vapor discharged from the cylinder is condensed by touching the cooled exhaust pipe to become condensed water. Since a porous material such as cordierite is usually used for the PM filter, the PM filter has a property of easily absorbing and holding condensed water contained in the exhaust gas. For this reason, at the time of starting, if the amount of exhaust gas supplied to the PM filter holding a large amount of condensed water increases, a large amount of condensed water may be released from the PM filter.

  On the other hand, the system disclosed in Patent Document 2 includes an O2 sensor on the downstream side of the PM filter as described above. The sensor element of such an O2 sensor is heated by a built-in heater so that exhaust gas can be detected immediately even during cold start by being activated early. For this reason, at the time of starting, if a large amount of condensed water held in the PM filter flows out toward the heated sensor element, a large amount of condensed water is applied to the sensor element in a high temperature state. End up. As a result, the sensor element may be cracked.

  The present invention has been made to solve the above-described problems, and in an internal combustion engine having a particulate filter and an exhaust gas sensor in order from the upstream side in the exhaust passage, the occurrence of element cracking of the exhaust gas sensor due to moisture is favorable. It is an object of the present invention to provide an exhaust gas purification device for an internal combustion engine that can be suppressed to a low level.

A first invention is a particulate filter that is disposed in an exhaust passage of an internal combustion engine and collects particulate matter contained in exhaust gas;
An exhaust gas sensor disposed in an exhaust passage downstream of the particulate filter,
The flow resistance of the condensed water flowing inside the particulate filter is higher in the downstream portion of the filter than in the upstream portion of the filter.

Further, the second invention is a particulate filter disposed in the exhaust passage of the internal combustion engine and collecting particulate matter contained in the exhaust gas,
An exhaust gas sensor disposed in an exhaust passage downstream of the particulate filter,
The resistance of the condensed water flowing through the particulate filter is compared to the resistance of the condensed water flowing out of the filter toward the exhaust gas sensor compared to the resistance of the condensed water flowing out toward other parts. So that the vicinity of the exhaust gas sensor is different from the vicinity of the vicinity of the exhaust gas sensor.

Further, in a third invention according to the second invention, the particulate filter has a plurality of internal passages formed in a flow direction of the exhaust gas by partition walls having pores on the surface and inside,
The partition wall is characterized in that a porosity in a vicinity of the exhaust gas sensor is higher than a porosity of a part other than the vicinity.

Further, in a fourth aspect based on the second aspect, the particulate filter has a plurality of internal passages formed in the flow direction of the exhaust gas by partition walls having pores on the surface and inside,
The partition wall is characterized in that the thickness in the vicinity of the exhaust gas sensor is larger than the thickness of the part other than the vicinity.

The fifth invention is the second invention, wherein the particulate filter has a plurality of internal passages formed in the flow direction of the exhaust gas by partition walls having pores on the surface and inside, and A clogging member that closes a downstream end of a part of the plurality of passages;
The clogging member arranged in the vicinity of the exhaust gas sensor has a larger volume than the clogging members arranged in other parts.

Further, in a sixth aspect based on the second aspect, the particulate filter has a plurality of internal passages formed in a flow direction of the exhaust gas by partition walls having pores on the surface and inside, and A clogging member that closes a downstream end of a part of the plurality of passages;
The clogging member is provided so as to cover the plurality of internal passages located in the vicinity of the exhaust gas sensor.

  According to the first aspect of the present invention, the water retention function is enhanced at the downstream portion of the particulate filter (PM filter), thereby making it difficult for condensed water discharged from the internal combustion engine during cold start to escape downstream of the PM filter. It is possible to prevent a large amount of droplets from flowing out downstream of the PM filter at one time. For this reason, it can suppress that the condensed water which arises in an exhaust passage at the time of the cold start of an internal combustion engine starts to the exhaust-gas sensor arrange | positioned downstream from PM filter. As a result, it is possible to satisfactorily reduce the risk that the sensor element of the exhaust gas sensor that is normally heated by the heater breaks due to the exposure of condensed water.

  According to the second invention, it is possible to satisfactorily prevent the condensed water from flowing out from the PM filter toward the exhaust gas sensor. For this reason, according to this invention, it can suppress suitably that the condensed water which arises in an exhaust passage at the time of the cold start of an internal combustion engine starts to the exhaust gas sensor arrange | positioned downstream from PM filter. As a result, it is possible to satisfactorily reduce the risk that the sensor element of the exhaust gas sensor that is normally heated by the heater breaks due to the exposure of condensed water.

  According to the third to sixth inventions, the resistance of condensed water flowing through the inside of the PM filter and the resistance of the condensed water flowing out from the filter toward the exhaust gas sensor are reduced in the other parts. The vicinity of the exhaust gas sensor and other parts can be made different so as to be larger than the resistance flowing out. Thereby, generation | occurrence | production of the element crack of the exhaust gas sensor by flooding can be suppressed favorably.

Embodiment 1 FIG.
[Description of system configuration]
FIG. 1 is a schematic diagram for explaining an internal combustion engine system according to Embodiment 1 of the present invention. The system shown in FIG. 1 includes an internal combustion engine 10. The internal combustion engine 10 is a stoichiometric burn engine that performs combustion based on air-fuel ratio control that is performed so as to achieve a stoichiometric air-fuel ratio (stoichiometric). Here, the internal combustion engine 10 is an internal combustion engine that performs such stoichiometric burn operation. An example of the engine is a gasoline engine.

  The internal combustion engine 10 is provided with an exhaust passage 12. A main linear A / F sensor (hereinafter simply referred to as “A / F sensor”) 14 for detecting an air-fuel ratio of exhaust gas discharged from the cylinder is disposed in the exhaust passage 12. The A / F sensor 14 is a sensor that emits a substantially linear output with respect to the air-fuel ratio of the exhaust gas.

  An upstream three-way catalyst 16 capable of purifying the three-way components ((NOx, HC, CO) contained in the exhaust gas is disposed in the exhaust passage 12 downstream of the A / F sensor 14. A particulate filter (hereinafter referred to as “PM filter”) 18 capable of collecting and removing particulate matter PM contained in the exhaust gas is disposed in the exhaust passage 12 downstream of the side three-way catalyst 16. The specific structure of the PM filter 18 is a characteristic part of the present embodiment, and will be described in detail later with reference to FIG.

  In the exhaust passage 12 downstream of the PM filter 18, a sub O2 sensor 20 that emits a signal corresponding to whether the air-fuel ratio at that position is rich or lean is disposed. Further, a downstream side three-way catalyst 22 capable of purifying the three-way component contained in the exhaust gas is disposed in the exhaust passage 12 downstream of the sub O2 sensor 20. Further, the sensor elements of the A / F sensor 14 and the sub O2 sensor 20 are heated to appropriate temperatures by heaters incorporated therein in order to enable early detection of exhaust gas even in a cold state. . The exhaust gas sensor disposed on the upstream side of the upstream side three-way catalyst 16 may not be the main linear A / F sensor 14 but may be an oxygen sensor having the same configuration as the sub O2 sensor 20.

  The system shown in FIG. 1 includes an ECU (Electronic Control Unit) 24. In the ECU 24, various information for controlling the internal combustion engine 10 together with the A / F sensor 14 and the sub-O2 sensor 20 (engine coolant temperature, intake air amount, engine speed, throttle opening, accelerator opening, etc.). Various sensors (not shown in the figure) for measuring are connected. The ECU 24 is connected to various actuators (not shown) such as a throttle valve, a fuel injection valve, and a spark plug.

[PM Filter Structure of Embodiment 1]
FIG. 2 is a diagram for explaining the detailed structure of the PM filter 18 according to Embodiment 1 of the present invention. More specifically, FIG. 2A shows a longitudinal sectional view of the PM filter 18 shown in FIG. 1, and FIG. 2B shows the PM filter 18 on the outlet side (that is, downstream of the exhaust gas flow). It is the figure seen from the side.
As shown in FIG. 2, the PM filter 18 is configured in a honeycomb shape, and has a plurality of internal passages 28 and 30 formed by partition walls 26 in the exhaust gas flow direction. The partition wall 26 is made of a porous material such as cordierite, and has pores on the surface and inside.

  In the internal passage 28, the downstream end of the PM filter 18 is closed by a clogging member 32. The clogging member 32 is made of a porous sintered body that does not allow exhaust gas to pass through. The internal passage 30 is closed at the upstream end of the PM filter 18 by a clogging member 34 having the same configuration. More specifically, in the PM filter 18, as shown in FIG. 2, the internal passages 28 and the internal passages 30 are alternately and adjacently arranged.

  According to the PM filter 18 having the above-described configuration, the exhaust gas that has flowed into the internal passage 28 passes through the pores of the partition wall 26 except for the portion where the clogging member 32 is packed, and passes through the internal passage 28. To the internal passage 30. Then, when the exhaust gas passes through the partition wall 26 through the pores, PM contained in the exhaust gas is collected.

  The PM filter 18 of the present embodiment is characterized by the configuration of the clogging member 32 disposed at the downstream end of the PM filter 18 as described below. That is, as shown in FIG. 2A, the clogging member 32 has a larger volume than the clogging member 34 disposed at the upstream end. Since the clogging member 32 is made of a porous material as described above, it can absorb and hold the condensed water contained in the exhaust gas.

  That is, in the PM filter 18 of the present embodiment, the flow resistance of the condensed water flowing inside the filter is lower than the upstream portion of the filter 18 due to the configuration of the clogging member 32 as described above. Is higher.

  When the internal combustion engine 10 is cold-started, moisture contained in the exhaust gas discharged from the cylinder is condensed by the cooled exhaust passage 12 to become condensed water. According to the PM filter 18 of the present embodiment described above, the condensed water discharged from the internal combustion engine 10 at the time of cold start is reduced downstream of the PM filter 18 by enhancing the water retention function at the downstream side of the PM filter 18. It is possible to prevent a large amount of droplets from flowing out downstream of the PM filter 18 at a time. When a certain amount of time elapses after the internal combustion engine 10 is started, the exhaust passage 12 is warmed, so that condensation of moisture discharged from the cylinder does not occur. In addition, the condensed water stored in the PM filter 18 is discharged downstream of the PM filter 18 after being vaporized by the exhaust gas warmed after the start.

  According to the PM filter 18 of the present embodiment described above, the condensed water generated in the exhaust passage 12 when the internal combustion engine 10 is cold started is applied to the sub O2 sensor 20 disposed on the downstream side of the PM filter 18. Can be suppressed. As a result, it is possible to satisfactorily reduce the risk that the sensor element of the sub O2 sensor 20 heated by the heater will be broken due to the exposure to condensed water.

  By the way, in Embodiment 1 mentioned above, the volume of the clogging member 32 arrange | positioned at the downstream end part of PM filter 18 is made into the volume of the clogging member 34 arrange | positioned at the upstream end part of the said filter 18. It is supposed to be larger than that. However, in the present invention, the method for configuring the PM filter so that the flow resistance of the condensed water flowing through the filter in the downstream portion is higher than the upstream portion is limited to such a method. Is not to be done. That is, for example, by increasing the porosity of the downstream part of the partition wall 26 of the PM filter 18 to the porosity of the upstream part, the downstream part flows in the filter more than the upstream part. You may comprise PM filter so that the water flow resistance of condensed water may be raised.

Embodiment 2. FIG.
Next, a second embodiment of the present invention will be described with reference to FIG.
FIG. 3 is a diagram for explaining a detailed structure of the PM filter 40 according to Embodiment 2 of the present invention. More specifically, FIG. 3A shows a longitudinal sectional view of the PM filter 40, and FIG. 3B shows the PM filter 40 viewed from the outlet side (that is, the downstream side of the exhaust gas flow). It is a figure. The PM filter 40 of the present embodiment is configured in the same manner as in the first embodiment described above except that the configuration of the partition wall 42 is different from the configuration of the partition wall 26. For this reason, in FIG. 3, the same components as those shown in FIG. 2 are denoted by the same reference numerals, and the description thereof is omitted or simplified.

  As shown in FIG. 3A, the partition wall 42 of the PM filter 40 of the present embodiment has a downstream portion of the PM filter 40 and a thickness of other portions (more specifically, upstream portions). The thick part 42a comprised so that it may become thick is provided. According to such a structure, the water retention function of the condensed water in the site | part of the downstream of PM filter 40 can be improved favorably. That is, also in the PM filter 40 of the present embodiment, the flow resistance of the condensed water flowing through the filter in the downstream portion is higher than that in the upstream portion.

  For this reason, even with the PM filter 40 of the present embodiment, it is possible to prevent a large amount of liquid droplets from flowing out to the downstream side of the PM filter 40 at a time, and this is generated in the exhaust passage 12 when the internal combustion engine 10 is cold started. It is possible to suppress the condensed water from being applied to the sub O2 sensor 20 disposed on the downstream side of the PM filter 40. As a result, it is possible to reduce the risk that the sensor element of the sub O2 sensor 20 heated by the heater will break due to exposure to condensed water.

  By the way, in Embodiment 2 mentioned above, the thick part 42a comprised so that it might become thicker than the thickness of the upstream site | part is provided in the downstream site | part of the partition 42. As shown in FIG. However, in the present invention, the method for configuring the PM filter so that the flow resistance of the condensed water flowing through the filter in the downstream portion is higher than the upstream portion is limited to such a method. Is not to be done. That is, for example, by increasing the porosity of the downstream part of the partition wall 42 of the PM filter 40 to the porosity of the upstream part, the downstream part flows in the filter more than the upstream part. You may comprise PM filter so that the water flow resistance of condensed water may be raised.

Embodiment 3 FIG.
Next, Embodiment 3 of the present invention will be described with reference to FIG.
FIG. 4 is a diagram for explaining a detailed structure of the PM filter 50 according to Embodiment 3 of the present invention. More specifically, FIG. 4A shows a longitudinal sectional view of the PM filter 50, and FIG. 4B shows the PM filter 50 viewed from the outlet side (that is, the downstream side of the exhaust gas flow). It is a figure. The PM filter 50 according to the present embodiment is configured in the same manner as in the first embodiment described above except that the configuration of the downstream portion is different from that of the PM filter 18. Therefore, in FIG. 4, the same components as those shown in FIG. 2 are given the same reference numerals and the description thereof is omitted or simplified.

  The PM filter 50 of the present embodiment incorporates the features of the first and second embodiments described above only in the vicinity of the sub O2 sensor 20. More specifically, as shown in FIG. 4, in the PM filter 50, the clogging member 52 disposed at the downstream end near the sub O2 sensor 20 is disposed at another part at the downstream end. The volume is increased as compared with the clogging member 54 and the clogging member 34 disposed at the upstream end. Further, the partition wall 56 of the PM filter 50 shown in FIG. 4 is provided only at the downstream side near the sub O2 sensor 20, other than the part (that is, the downstream side away from the sub O2 sensor 20 and the filter 50. A thick portion 56a configured to be thicker than the thickness of the upstream portion). According to such a structure, the water retention function of the condensed water in the downstream part near the sub O2 sensor 20 can be improved satisfactorily.

  That is, in the PM filter 50 of the present embodiment, the resistance at which the condensed water flows out from the filter 50 toward the sub O2 sensor 20 is larger than the resistance at which the condensed water flows out to other parts. As described above, the water flow resistance inside the filter 50 in the vicinity of the sub O2 sensor 20 is higher than that in the vicinity of the vicinity.

  For this reason, according to the PM filter 50 of the present embodiment, it is possible to satisfactorily prevent the condensed water from flowing out from the PM filter 50 toward the sub O2 sensor 20. Furthermore, in the present embodiment, with the above-described configuration, the flow resistance inside the filter 50 in the vicinity of the sub O2 sensor 20 is increased in the downstream portion instead of the upstream portion of the PM filter 50. The following effects can be obtained in the upstream portion of the filter 50 as compared with the case where such consideration is taken.

  That is, the amount of water supplied to the PM filter 50 as condensate at the time of cold start is limited, and when the condensate is supplied to the PM filter 50, the amount of water retained in each part of the filter 50 is The filter 50 is saturated toward the downstream side in order from the upstream side portion of the filter 50. For this reason, unlike the configuration of the present embodiment, when the water retention function is enhanced in the upstream portion of the PM filter 50 where the water retention amount is saturated first, the water retention amount is increased in the upstream portion. The distribution of the condensed water flowing out downstream of the filter 50 is uniform in the radial direction of the filter 50 after the saturation and the condensed water is still being supplied. On the other hand, according to the configuration of the present embodiment, the water retention function is enhanced at a site downstream of the PM filter 50 where the water retention amount will be saturated at the end and close to the sub O2 sensor 20. Therefore, the distribution of the condensed water flowing out from the filter 50 can be stably biased so that the condensed water is not applied to the sub O2 sensor 20.

  As described above, even with the configuration of the PM filter 50 of the present embodiment, the condensed O2 sensor 20 in which the condensed water generated in the exhaust passage 12 when the internal combustion engine 10 is cold-started is disposed downstream of the PM filter 50. It can suppress suitably. As a result, it is possible to satisfactorily reduce the risk that the sensor element of the sub O2 sensor 20 heated by the heater will be broken due to the exposure to condensed water.

  By the way, in Embodiment 3 mentioned above, the volume of the clogging member 52 is made larger than the other part in the vicinity of the sub O2 sensor 20 in the PM filter 50, and the partition wall 56 in the vicinity is thick. The portion 56a is configured. However, instead of these methods, as already described in the first and second embodiments, the porosity of the clogging member 52 arranged in the vicinity of the sub O2 sensor 20 is changed to the clogging member 54 arranged in another part. Alternatively, the porosity of the partition wall 56 in the vicinity of the sub O2 sensor 20 may be higher than the porosity of the partition wall 56 in other parts.

Embodiment 4 FIG.
Next, a fourth embodiment of the present invention will be described with reference to FIG.
FIG. 5 is a diagram for explaining a detailed structure of the PM filter 60 according to the fourth embodiment of the present invention. More specifically, FIG. 5A shows a longitudinal sectional view of the PM filter 60, and FIG. 5B shows the PM filter 60 viewed from the outlet side (that is, the downstream side of the exhaust gas flow). It is a figure. The PM filter 60 of the present embodiment is configured in the same manner as in the third embodiment described above except that the configuration of the downstream portion is different from that of the PM filter 50. Therefore, in FIG. 5, the same components as those shown in FIG. 4 are given the same reference numerals, and the description thereof is omitted or simplified.

  In the PM filter 60 of the present embodiment, as shown in FIG. 5, the downstream ends of all the internal passages 28 and 30 located in the vicinity of the sub O2 sensor 20 are closed by the clogging member 54. In other words, in this embodiment, with such a configuration, the resistance of the condensed water flowing out from the filter 50 toward the sub O2 sensor 20 is compared with the resistance of the condensed water flowing out toward other parts. In order to increase, the water flow resistance inside the filter 50 in the vicinity of the sub O2 sensor 20 is higher than that in the vicinity of the vicinity.

  Even with the configuration of the PM filter 60 of the present embodiment described above, the condensed water generated in the exhaust passage 12 when the internal combustion engine 10 is cold-started is applied to the sub O2 sensor 20 disposed on the downstream side of the PM filter 60. Can be suitably suppressed. As a result, it is possible to satisfactorily reduce the risk that the sensor element of the sub O2 sensor 20 heated by the heater will be broken due to the exposure to condensed water.

It is the schematic for demonstrating the internal combustion engine system in Embodiment 1 of this invention. It is a figure for demonstrating the detailed structure of PM filter in Embodiment 1 of this invention. It is a figure for demonstrating the detailed structure of PM filter in Embodiment 2 of this invention. It is a figure for demonstrating the detailed structure of PM filter in Embodiment 3 of this invention. It is a figure for demonstrating the detailed structure of PM filter in Embodiment 4 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Internal combustion engine 12 Exhaust passage 14 Main linear A / F sensor 16 Upstream side three-way catalyst 18, 40, 50, 60 Particulate filter (PM filter)
20 Sub O2 sensor 22 Downstream three-way catalyst 24 ECU (Electronic Control Unit)
26, 42, 56 Bulkhead 28 Internal passage 30 Internal passages 32, 34, 52, 54 Clogging member 34 Clogging members 42a, 56a Thick part

Claims (6)

A particulate filter disposed in the exhaust passage of the internal combustion engine for collecting particulate matter contained in the exhaust gas;
An exhaust gas sensor disposed in an exhaust passage downstream of the particulate filter,
Exhaust gas purification of an internal combustion engine, wherein the resistance to water flow of condensed water flowing inside the particulate filter is higher in the downstream portion of the filter than in the upstream portion of the filter apparatus. A particulate filter disposed in the exhaust passage of the internal combustion engine for collecting particulate matter contained in the exhaust gas;
An exhaust gas sensor disposed in an exhaust passage downstream of the particulate filter,
The resistance of the condensed water flowing through the particulate filter is compared to the resistance of the condensed water flowing out of the filter toward the exhaust gas sensor compared to the resistance of the condensed water flowing out toward other parts. An exhaust gas purifying apparatus for an internal combustion engine, wherein the exhaust gas sensor is made different between a vicinity of the exhaust gas sensor and a part other than the vicinity. The particulate filter has a plurality of internal passages formed in the exhaust gas flow direction by partition walls having pores on the surface and inside,
The exhaust gas purifying device for an internal combustion engine according to claim 2, wherein the partition wall has a porosity in a vicinity of the exhaust gas sensor higher than a porosity of a part other than the vicinity. The particulate filter has a plurality of internal passages formed in the exhaust gas flow direction by partition walls having pores on the surface and inside,
The exhaust gas purifying apparatus for an internal combustion engine according to claim 2, wherein the partition wall has a thickness in a vicinity of the exhaust gas sensor larger than a thickness of a part other than the vicinity. The particulate filter has a plurality of internal passages formed in the flow direction of the exhaust gas by partition walls having pores on the surface and inside, and closes a downstream end portion of a part of the plurality of passages. Having a clogging member,
3. The internal combustion engine according to claim 2, wherein the clogging member disposed in the vicinity of the exhaust gas sensor has a larger volume than the clogging member disposed in another portion. Exhaust gas purification device. The particulate filter has a plurality of internal passages formed in the flow direction of the exhaust gas by partition walls having pores on the surface and inside, and closes a downstream end portion of a part of the plurality of passages. Having a clogging member,
The exhaust gas purification apparatus for an internal combustion engine according to claim 2, wherein the clogging member is provided so as to cover the plurality of internal passages located in the vicinity of the exhaust gas sensor.

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