JP5910061B2 - Catalyst deterioration determination device for internal combustion engine - Google Patents

Description

  The present invention relates to a catalyst deterioration determination device for an internal combustion engine, and more particularly to a catalyst deterioration determination device for an internal combustion engine that can determine deterioration of a catalyst that purifies exhaust gas at an early stage.

Degradation determination of the catalyst that purifies the exhaust gas of the internal combustion engine is performed by detecting the OSC capability of the OSC material (oxygen storage component) included in the catalyst with exhaust detectors arranged on the upstream side and the downstream side of the catalyst. By doing that. There is a correlation between the deterioration of the catalyst and the decrease in the OSC capacity of the catalyst, and it is determined that the OSC capacity is decreased = catalyst deterioration.
2. Description of the Related Art Conventionally, in a catalyst deterioration determination device for an internal combustion engine, for example, as disclosed in Patent Document 1, air-fuel ratio sensors (exhaust detectors) are arranged on the upstream side and the downstream side of a catalyst provided in an exhaust passage. There is known a catalyst deterioration detection device that compares a detection signal corresponding to an air-fuel ratio of exhaust flowing into a catalyst and a detection signal corresponding to an air-fuel ratio of exhaust flowing out of the catalyst, and determines catalyst deterioration based on the comparison result. ing.

JP-A-5-321642

By the way, as shown in FIG. 8, the catalyst used for the exhaust system of the internal combustion engine is gradually deteriorated at the initial stage of use of the catalyst (the increase in NOx emission amount is moderated with respect to the decrease in the catalyst deterioration index), and then a certain amount of catalyst is used. Then, there is a characteristic that the deterioration rapidly progresses (NOx emission increases rapidly with respect to the decrease in the catalyst deterioration index). The catalyst deterioration index is the amount of catalyst used (oxygen passage amount), and is obtained by integrating the voltage output value of the downstream air-fuel ratio sensor with time.
However, in the enhanced regulations such as EURO5 + and EURO6, the judgment level is lowered than before, the exhaust component regulation value such as HC and NOx is low, and the catalyst is not deteriorated more than before, the catalyst is degraded. Therefore, there is a problem that the conventional catalyst deterioration judging method cannot diagnose the catalyst deterioration. Even if a diagnosis can be made, the difference between normal and abnormal OSC determination levels is very small, and the risk of erroneous determination becomes extremely high. (Refer to the judgment zone in FIG. 8)

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a catalyst deterioration determination device for an internal combustion engine that can reliably determine deterioration even at the initial use stage of the catalyst. To do.

The present invention determines the deterioration of the catalyst based on the catalyst disposed in the exhaust passage of the internal combustion engine, the exhaust detectors disposed on the upstream side and the downstream side of the catalyst, and the output value of the exhaust detector. The catalyst is divided into an early deterioration portion where deterioration starts early and a non-early deterioration portion where deterioration starts later than the early deterioration portion, and the downstream exhaust detector The detection unit is arranged to detect exhaust gas flowing out from the early deterioration unit , and the exhaust passage is connected to a catalyst holding unit that holds the catalyst and to an upstream side of the catalyst holding unit in a direction in which exhaust flows. Between the upstream exhaust passage portion, the downstream exhaust passage portion having a smaller diameter than the catalyst holding portion and connected to the downstream side of the catalyst holding portion, and the catalyst holding portion and the downstream exhaust passage portion. Gradually reduce diameter toward exhaust downstream A virtual boundary surface drawn by extending the boundary surface between the non-early deterioration portion and the early deterioration portion of the catalyst until it contacts the downstream exhaust passage portion, and A virtual inner peripheral surface depicted by extending an inner peripheral surface portion of the downstream exhaust passage portion located downstream of the early deterioration portion until it contacts the rear end of the early deterioration portion, and downstream of the early deterioration portion The virtual boundary surface of the reduced diameter portion located on the side and the inner peripheral surface of the reduced diameter portion facing the virtual inner peripheral surface, the virtual boundary surface of the catalyst holding portion located downstream of the early deterioration portion, and the A holding portion inner peripheral surface facing the virtual inner peripheral surface, a rear end section screen which is a rear end of the early deterioration portion and is partitioned by the virtual boundary surface, the virtual inner peripheral surface and the holding portion inner peripheral surface; It is arranged in a detection space surrounded by .

The present invention, since the catalyst is divided into a premature aging section and the non-premature aging unit, early deterioration part early deterioration thermal durability rather low begins, after the early deterioration unit heat durability rather high Compared with the non-early deterioration part where deterioration starts from, the time during which the high temperature state is maintained becomes longer, so the oxidation rate becomes faster and the deterioration occurs earlier. Therefore, according to the present invention, even if the non-early deteriorated part does not emit harmful substances, the early deteriorated part already begins to discharge harmful substances at the time of deterioration, so the exhaust detector reliably detects this harmful substance. Therefore, it is possible to reliably determine deterioration at an early stage from the start of use of the catalyst. Since the main exhaust gas passes through the non-early deterioration part , the harmful component value of the exhaust gas discharged into the atmosphere does not exceed the reference value.

FIG. 1 is a system diagram of a catalyst deterioration determination device for an internal combustion engine. Example 1 FIG. 2 is a graph of catalyst deterioration determination showing a determination zone of a catalyst deterioration index based on the NOx emission amount. Example 1 FIG. 3 is a cross-sectional view of the catalyst holding unit in which the exhaust detector is disposed in the front detection space. Example 1 FIG. 4 is a perspective view of a catalyst holding unit in which a catalyst having a high heat resistant part and a low heat resistant part is arranged. Example 1 FIG. 5 is an enlarged cross-sectional view of the catalyst holding unit in which the exhaust detector is disposed in the rear detection space. (Example 2) FIG. 6 is a cross-sectional view of the catalyst holding unit in which the exhaust detector is disposed in the rear detection space. (Example 2) FIG. 7 is a cross-sectional view of a catalyst holding unit using an oxygen storage material in a portion upstream of the low heat resistant unit. (Modification) FIG. 8 is a graph of catalyst deterioration determination showing a determination zone of a catalyst deterioration index based on the NOx emission amount. (Conventional example)

  Embodiments of the present invention will be described below with reference to the drawings.

1 to 4 show the first embodiment. In FIG. 1, 1 is an internal combustion engine, 2 is an exhaust manifold, 3 is a catalytic converter, and 4 is an exhaust pipe. While exhaust gas discharged from the internal combustion engine 1 flows through the exhaust passage 5 formed by the exhaust manifold 2, the catalytic converter 3, and the exhaust pipe 4, harmful components are removed by the catalyst 6 disposed in the catalytic converter 3, and the exhaust pipe 4 to the outside.
In the catalyst deterioration determination device 7 for determining the deterioration of the catalyst 6, exhaust detectors 8 and 9 are disposed on the upstream side and the downstream side of the catalyst 6 disposed in the exhaust passage 5, respectively. The upstream exhaust detector 8 includes a detection unit 10 and outputs a detection signal corresponding to the air-fuel ratio of the exhaust flowing into the catalyst 6. The downstream exhaust detector 9 includes a detection unit 11 and outputs a detection signal corresponding to the air-fuel ratio of the exhaust gas flowing out from the catalyst 6. The upstream side exhaust detector 8 and the downstream side exhaust detector 9 are connected to the deterioration determining means 12. The deterioration determination means 12 compares the detection signal output from the upstream exhaust detector 8 with the detection signal output from the downstream exhaust detector 9, and determines the deterioration of the catalyst 6 based on the comparison result.
The catalyst 6 includes a high heat resistant portion 13 having high heat durability and a low heat resistant portion 14 having lower heat durability than the high heat resistant portion 13. The high heat resistance portion 13 includes an OSC material (oxygen storage material) having high heat resistance. The low heat resistance portion 14 includes an OSC material having low heat resistance. The high heat resistant part 13 and the low heat resistant part 14 are partitioned in the radial direction so as to follow the direction in which the exhaust flows, and the cross sectional area of the high heat resistant part 13 is set larger than that of the low heat resistant part 14. The high heat resistance part 13 passes most main exhaust gas and removes harmful substances. The downstream exhaust detector 9 is disposed downstream of the low heat resistant portion 14.
Thus, in the catalyst deterioration determination device 7 of the internal combustion engine 1, since the catalyst 6 includes the high heat resistant portion 13 and the low heat resistant portion 14, the low heat resistant portion 14 having low heat durability has high heat durability. Compared with the high heat resistant portion 13, the time for maintaining the high temperature state becomes longer, so that the oxidation rate becomes faster and deteriorates earlier.
Therefore, in the catalyst deterioration determination device 7, even if the high heat resistant portion 13 does not discharge harmful substances, the low heat resistant portion 14 has already started to discharge harmful substances at the time of deterioration, so the low heat resistant portion 14 The exhaust detector 9 arranged on the downstream side of this can reliably detect this harmful substance. For this reason, the catalyst deterioration determination device 7 can reliably determine the deterioration of the catalyst 6 at an early stage from the start of use of the catalyst 6, and as shown in FIG. %), The deterioration of the catalyst 6 can be determined at the determination level after the tightening of regulations, which is lower than before. Since the main exhaust gas passes through the high heat resistance part 13, the harmful component value of the exhaust gas discharged into the atmosphere does not exceed the reference value.

As shown in FIG. 3, the exhaust passage 5 of the internal combustion engine 1 includes a catalyst holding unit 15 that holds the catalyst 6 and an upstream side of the catalyst holding unit 15 in a direction smaller than the catalyst holding unit 15 and flowing in the exhaust gas. An upstream exhaust passage portion 16 connected to the catalyst, a diameter-expanding portion 17 that gradually expands in the downstream direction of exhaust between the catalyst holding portion 15 and the upstream exhaust passage portion 16, and the catalyst holding portion. The downstream exhaust passage portion 18 having a diameter smaller than 15 and connected to the downstream side of the catalyst holding portion 15 and gradually between the catalyst holding portion 15 and the downstream exhaust passage portion 18 in the downstream direction of the exhaust gas. And a reduced diameter portion 19 that is reduced in diameter.
As shown in FIG. 4, the detection unit 11 of the downstream exhaust detector 9 is disposed in the detection space 20. The detection space 20 is surrounded by a virtual boundary surface 21, a virtual inner peripheral surface 22, a reduced diameter inner peripheral surface 23, a holding portion inner peripheral surface 24, and a rear end section screen 25.
The virtual boundary surface 21 is depicted by extending the boundary surface 26 between the high heat resistant portion 13 and the low heat resistant portion 14 of the catalyst 6 until it contacts the downstream exhaust passage portion 18. The virtual inner peripheral surface 22 is in contact with the rear end of the low heat resistant portion 14 at the inner peripheral surface portion 27 of the downstream exhaust passage portion 18 located downstream of the low heat resistant portion 14 defined by the virtual boundary surface 21. It is drawn by extending to.
The reduced diameter portion inner peripheral surface 23 is a portion of the reduced diameter portion 17 located on the downstream side of the low heat resistant portion 14 and facing the virtual boundary surface 21 and the virtual inner peripheral surface 22. The holding portion inner peripheral surface 24 is a portion facing the virtual boundary surface 21 and the virtual inner peripheral surface 22 of the catalyst holding portion 15 located on the downstream side of the low heat resistant portion 14. The rear end section screen 24 is a rear end of the low heat resistant portion 14 and is a portion defined by the virtual boundary surface 21, the virtual inner peripheral surface 22, and the holding portion inner peripheral surface 24.
This catalyst deterioration determination device 7 is a rear portion of the catalyst holding portion 15 and extends rearward from the rear end of the low heat resistant portion 14 of the catalyst 6 to form a detection space 20 having a substantially semi-cylindrical tapered shape. . Therefore, since the detection space 20 is formed to have the same diameter as the inner diameter of the catalyst holding unit 15, the exhaust discharged from the high heat-resistant part 13 and the low heat-resistant part 14 of the catalyst 6 flows backward without being mixed. .
Therefore, the catalyst deterioration determination device 7 discharges from the low heat resistance part 14 by disposing the downstream exhaust detector 9 in the detection space 20 formed to extend backward from the rear end of the low heat resistance part 14 of the catalyst 6. Only the component value of the exhausted gas can be reliably detected. As a result, the catalyst deterioration determination device 7 can reliably determine deterioration.

In the catalyst deterioration determination device 7, the detection space 20 is formed behind the front detection space 28 provided between the rear end of the low heat resistant portion 14 and the front end of the reduced diameter portion 19 and the front end of the reduced diameter portion 19. The rear side detection space 29 is configured. In the downstream exhaust detector 9, the detection unit 11 is arranged in the front detection space 28.
Thus, the catalyst deterioration determination device 7 extends rearward from the rear end of the low heat resistant portion 14 of the catalyst 6 at the rear portion of the catalyst holding portion 15 to form the front detection space 28. Accordingly, the front detection space 28 has a structure in which impurities (for example, soot) contained in the exhaust gas are unlikely to be rolled up, unlike the reduced diameter portion 19 and the narrow downstream exhaust passage portion 18.
Therefore, the exhaust detector 9 on the downstream side of the catalyst deterioration determination device 7 is difficult to attach impurities such as soot and can prevent the detection accuracy from deteriorating. For this reason, the catalyst deterioration determination device 7 can reliably determine the deterioration of the catalyst 6.

5 and 6 show the second embodiment. As in the first embodiment, the catalyst deterioration determination device 7 according to the second embodiment includes the catalyst holding portion 15, the upstream exhaust passage portion 16, the enlarged diameter portion 17, the downstream exhaust passage portion 18, and the reduced diameter portion 19. An exhaust passage 5 is formed, and exhaust detectors 8 and 9 are disposed on the upstream side and the downstream side of the catalyst 6 disposed in the exhaust passage 5, respectively. The catalyst 6 includes a high heat resistant portion 13 having high heat durability and a low heat resistant portion 14 having lower heat durability than the high heat resistant portion 13.
The detection unit 11 of the exhaust detector 9 on the downstream side is surrounded by a virtual boundary surface 21, a virtual inner peripheral surface 22, a reduced diameter inner peripheral surface 23, a holding unit inner peripheral surface 24, and a rear end section screen 25. The detection space 20 is arranged. The detection space 20 includes a front detection space 28 provided between the rear end of the low heat resistant portion 14 and the front end of the reduced diameter portion 19, and a rear detection space 29 formed behind the front end of the reduced diameter portion 19. Consists of.
As shown in FIG. 5, the catalyst deterioration determination device 7 according to the second embodiment includes a downstream exhaust detector in a rear detection space 29 including a front detection space 28 and a rear detection space 29. Nine detection units 11 are arranged.
As shown in FIG. 6, when the exhaust A1 exhausted from the low heat resistant portion 14 flows into the rear detection space 29, the catalyst deterioration determining device 7 collides with the reduced diameter portion inner peripheral surface 23 of the reduced diameter portion 19. Then, the direction A2 is changed to the center side (radially inside) of the exhaust passage 5. At this time, the exhaust A2 discharged from the low heat resistant portion 14 and changed its direction pushes back the exhaust B1 discharged from the high heat resistant portion 13 to the center side B2, so that the rear detection space 29 is discharged from the low heat resistant portion 14. Only kept in the exhaust.
Therefore, the exhaust detector 9 on the downstream side of the catalyst deterioration determination device 7 can reliably detect only the exhaust discharged from the low heat resistant portion 14. For this reason, the catalyst deterioration determination device 7 can reliably determine the deterioration of the catalyst 6.

In the above-described embodiment, the catalyst 6 is composed of the high heat resistant portion 13 including the OSC material having high heat resistance and the low heat resistant portion 14 including the OSC material having low heat resistance. By using the material and reducing the amount of use of the OSC material only in the part corresponding to the upstream side of the exhaust detector 9 (for example, 70% reduction), the high heat resistant part 13 and the low heat resistant part 14 are configured. You can also.
Further, since the deterioration of the catalyst 6 is mainly correlated with the temperature at which the catalyst 6 has a history, as shown in FIG. 7, the portion of the catalyst 6 corresponding to the upstream side of the downstream exhaust detector 9 (low The heat-resistant portion 14) is an upstream portion 14-1 that uses an OSC material in the upstream portion 14-1 where the catalyst 6 is likely to become high temperature (for example, within 30 mm and within 60 mm from the inlet). By using no OSC material for the downstream portion 14-2 other than 1, deterioration of the catalyst 6 can be detected with higher sensitivity. In addition, about the part (high heat resistant part 13) other than the part (low heat resistant part 14) corresponding to the upstream side of the downstream exhaust gas detector 9, by using a normal amount of OSC material, the catalyst 6 as a whole. High exhaust purification performance can be maintained.

  The present invention is a technique applied to a three-way catalyst of an internal combustion engine using gasoline as a fuel. However, even in an oxidation catalyst (DOC) for a diesel internal combustion engine, it is diverted when detecting catalyst deterioration by OSC capability. be able to.

DESCRIPTION OF SYMBOLS 1 Internal combustion engine 5 Exhaust passage 6 Catalyst 7 Catalyst deterioration determination apparatus 8 Upstream exhaust detector 9 Downstream exhaust detector 12 Degradation determination means 13 High heat resistant portion 14 Low heat resistant portion 15 Catalyst holding portion 16 Upstream exhaust passage portion 17 Expanded portion 18 Downstream exhaust passage portion 19 Reduced diameter portion 20 Detection space 21 Virtual boundary surface 22 Virtual inner peripheral surface 23 Reduced diameter portion inner peripheral surface 24 Holding portion inner peripheral surface 25 Rear end section screen 28 Front detection space 29 Rear detection space

Claims (3)

A catalyst disposed in the exhaust passage of the internal combustion engine, an exhaust detector disposed upstream and downstream of the catalyst, and a deterioration determining means for determining deterioration of the catalyst based on an output value of the exhaust detector The catalyst is divided into an early deterioration portion where deterioration starts early and a non-early deterioration portion where deterioration starts later than the early deterioration portion, and the detection unit of the downstream exhaust detector is, The exhaust passage is arranged to detect exhaust gas flowing out from the early deterioration portion , and the exhaust passage includes a catalyst holding portion for holding the catalyst, and an upstream exhaust gas connected to the upstream side of the catalyst holding portion in the exhaust flow direction. A downstream direction of exhaust gas between the passage portion, a downstream exhaust passage portion having a smaller diameter than the catalyst holding portion and connected to the downstream side of the catalyst holding portion, and the catalyst holding portion and the downstream exhaust passage portion A diameter-reducing portion that gradually decreases toward Formed by extending the boundary surface between the non-early deterioration portion and the early deterioration portion of the catalyst until it contacts the downstream exhaust passage portion, and the early deterioration portion. A virtual inner peripheral surface depicted by extending an inner peripheral surface portion of the downstream exhaust passage portion positioned on the downstream side until it contacts the rear end of the early deterioration portion, and the downstream surface of the early deterioration portion. The virtual boundary surface of the reduced diameter portion and the inner peripheral surface of the reduced diameter portion facing the virtual inner peripheral surface, and the virtual boundary surface and the virtual inner peripheral surface of the catalyst holding portion located on the downstream side of the early deterioration portion Detection surrounded by the opposing holding portion inner peripheral surface and the rear end section screen which is the rear end of the early deteriorated portion and is partitioned by the virtual boundary surface, the virtual inner peripheral surface, and the holding portion inner peripheral surface catalyst deterioration determination device for an internal combustion engine, characterized in that it is arranged in a space A catalyst disposed in the exhaust passage of the internal combustion engine, an exhaust detector disposed upstream and downstream of the catalyst, and a deterioration determining means for determining deterioration of the catalyst based on an output value of the exhaust detector The catalyst is divided into an early deterioration portion where deterioration starts early and a non-early deterioration portion where deterioration starts later than the early deterioration portion, and the detection unit of the downstream exhaust detector is, The exhaust passage is arranged to detect exhaust gas flowing out from the early deterioration portion, and the exhaust passage includes a catalyst holding portion for holding the catalyst, and an upstream exhaust gas connected to the upstream side of the catalyst holding portion in the exhaust flow direction. A downstream direction of exhaust gas between the passage portion, a downstream exhaust passage portion having a smaller diameter than the catalyst holding portion and connected to the downstream side of the catalyst holding portion, and the catalyst holding portion and the downstream exhaust passage portion A diameter-reducing portion that gradually decreases toward Formed by extending the boundary surface between the non-early deterioration portion and the early deterioration portion of the catalyst until it contacts the downstream exhaust passage portion, and the early deterioration portion. A virtual inner peripheral surface depicted by extending an inner peripheral surface portion of the downstream exhaust passage portion positioned on the downstream side until it contacts the rear end of the early deterioration portion, and the downstream surface of the early deterioration portion. The virtual boundary surface of the reduced diameter portion and the inner peripheral surface of the reduced diameter portion facing the virtual inner peripheral surface, and the virtual boundary surface and the virtual inner peripheral surface of the catalyst holding portion located on the downstream side of the early deterioration portion Detection surrounded by the opposing holding portion inner peripheral surface and the rear end section screen which is the rear end of the early deteriorated portion and is partitioned by the virtual boundary surface, the virtual inner peripheral surface, and the holding portion inner peripheral surface It is arranged in a space, the detection space, the rear end of the early deterioration section A front detection space provided between the front end of diameter, the consists of a front end of the reduced diameter portion and the side detection space after being formed in the rear, the detection portion of the exhaust detector of the downstream, the A catalyst deterioration determination device for an internal combustion engine, which is disposed in a front detection space. A catalyst disposed in the exhaust passage of the internal combustion engine, an exhaust detector disposed upstream and downstream of the catalyst, and a deterioration determining means for determining deterioration of the catalyst based on an output value of the exhaust detector The catalyst is divided into an early deterioration portion where deterioration starts early and a non-early deterioration portion where deterioration starts later than the early deterioration portion, and the detection unit of the downstream exhaust detector is, The exhaust passage is arranged to detect exhaust gas flowing out from the early deterioration portion, and the exhaust passage includes a catalyst holding portion for holding the catalyst, and an upstream exhaust gas connected to the upstream side of the catalyst holding portion in the exhaust flow direction. A downstream direction of exhaust gas between the passage portion, a downstream exhaust passage portion having a smaller diameter than the catalyst holding portion and connected to the downstream side of the catalyst holding portion, and the catalyst holding portion and the downstream exhaust passage portion A diameter-reducing portion that gradually decreases toward Formed by extending the boundary surface between the non-early deterioration portion and the early deterioration portion of the catalyst until it contacts the downstream exhaust passage portion, and the early deterioration portion. A virtual inner peripheral surface depicted by extending an inner peripheral surface portion of the downstream exhaust passage portion positioned on the downstream side until it contacts the rear end of the early deterioration portion, and the downstream surface of the early deterioration portion. The virtual boundary surface of the reduced diameter portion and the inner peripheral surface of the reduced diameter portion facing the virtual inner peripheral surface, and the virtual boundary surface and the virtual inner peripheral surface of the catalyst holding portion located on the downstream side of the early deterioration portion Detection surrounded by the opposing holding portion inner peripheral surface and the rear end section screen which is the rear end of the early deteriorated portion and is partitioned by the virtual boundary surface, the virtual inner peripheral surface, and the holding portion inner peripheral surface It is arranged in a space, the detection space, the rear end of the early deterioration section A front detection space provided between the front end of diameter, the consists of a front end of the reduced diameter portion and the side detection space after being formed in the rear, the detection portion of the exhaust detector of the downstream, the A catalyst deterioration determination device for an internal combustion engine, which is disposed in a rear detection space.

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