Catalyst deterioration diagnosis method and catalyst deterioration diagnosis device for internal combustion engine having exhaust turbocharger

Abstract

According to the present invention, an internal combustion engine having an exhaust turbocharger (3) comprises: a catalytic converter (13) disposed in an upstream-side exhaust pipe (8) connecting a cylinder (2) and an exhaust turbine (7) of the exhaust turbocharger (3); a bypass passage (14) for releasing a part of an exhaust gas flowing through the catalytic converter (13) to a downstream-side exhaust pipe (9); a waste gate valve (15) for adjusting the flow rate of the exhaust gas flowing through the bypass passage (14); a first exhaust sensor (16) disposed upstream of the catalytic converter (13) in the upstream-side exhaust pipe (8); and a second exhaust sensor (17) disposed downstream of a confluence portion (A) between the downstream-side exhaust pipe (9) and the bypass passage (14) in the downstream-side exhaust pipe (9). A control device diagnoses deterioration of the catalytic converter (13) on the basis of a comparison between a first signal from the first exhaust sensor (16) and a second signal from the second exhaust sensor (17).

Description

Method and device for diagnosing catalyst deterioration in an internal combustion engine with an exhaust turbocharger

[0001] The present invention relates to a catalyst deterioration diagnosis method and a catalyst deterioration diagnosis device for an internal combustion engine having an exhaust turbocharger.

[0002] In an internal combustion engine having an exhaust turbocharger described in Patent Document 1, an exhaust turbine of the exhaust turbocharger is disposed downstream of the cylinders of the internal combustion engine, and an exhaust purification catalyst is disposed downstream of this exhaust turbine. An upstream exhaust sensor is disposed upstream of the exhaust purification catalyst, detecting signals related to the components of the exhaust flowing into the exhaust purification catalyst, while a downstream exhaust sensor is disposed immediately downstream of the exhaust purification catalyst, detecting signals related to the components of the exhaust after passing through the exhaust purification catalyst. A control device provided in the internal combustion engine compares the waveforms of the signals from the upstream exhaust sensor and the downstream exhaust sensor, thereby diagnosing deterioration of the exhaust purification catalyst.

[0003] Furthermore, in recent years, an internal combustion engine has become known that has a configuration in which the positions of the exhaust turbine and exhaust purification catalyst of Patent Document 1 are reversed, that is, the exhaust purification catalyst is disposed downstream of the cylinder of the internal combustion engine, and the exhaust turbine is disposed downstream of this exhaust purification catalyst. In such internal combustion engines, the housing surrounding the exhaust purification catalyst and its surrounding structure tend to be complex, and there has been a problem in that there is no room to install a downstream exhaust sensor immediately downstream of the exhaust purification catalyst.

[0004] The present invention has been made with an eye on such problems, and one of its objects is to provide a catalyst deterioration diagnosis method and catalyst deterioration diagnosis device for an internal combustion engine that makes it possible to diagnose the deterioration of an exhaust purification catalyst without having to install an exhaust sensor immediately downstream of the exhaust purification catalyst.

[0005] JP 2014-5779 A

[0006] The present invention relates to a catalyst deterioration diagnosis method for an internal combustion engine including an exhaust gas purification catalyst arranged in an upstream exhaust pipe connecting a cylinder of the internal combustion engine having an exhaust turbocharger to an exhaust turbine of the exhaust turbocharger, a bypass passage for releasing a portion of the exhaust gas that has passed through the exhaust gas purification catalyst to a downstream exhaust pipe, a wastegate valve for adjusting the flow rate of the portion of the exhaust gas passing through the bypass passage, a first exhaust sensor arranged in the upstream exhaust pipe upstream of the exhaust gas purification catalyst, a second exhaust sensor arranged in the downstream exhaust pipe downstream of a junction of the downstream exhaust pipe and the bypass passage, and a control device having a deterioration diagnosis unit that performs deterioration diagnosis of the exhaust gas purification catalyst using a first signal and a second signal, in which the catalyst deterioration diagnosis method performs deterioration diagnosis of the exhaust gas purification catalyst based on a comparison of the waveform of the first signal with the waveform of the second signal.

[0007] Therefore, the exhaust gas that has passed through the exhaust purification catalyst is led to the second exhaust gas sensor that is disposed downstream of the confluence portion.

[0008] Therefore, according to the present invention, even if an exhaust sensor is not provided immediately downstream of the exhaust purification catalyst, deterioration of the exhaust purification catalyst can be diagnosed by the second exhaust sensor.

[0009] While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments.

[0010] An embodiment of the present invention will be described below with reference to the drawings. In the embodiment, an internal combustion engine of the present invention is applied as an internal combustion engine used in a series hybrid vehicle. The internal combustion engine of the present invention is not limited to an internal combustion engine used in a series hybrid vehicle, but may also be used in other hybrid vehicles, such as a parallel hybrid vehicle, or other vehicles having an internal combustion engine.

[0011] 1 is an explanatory diagram of the configuration of an internal combustion engine according to one embodiment. This internal combustion engine is a power-generating internal combustion engine that drives a power-generating motor-generator (not shown) that operates primarily as a generator in response to a power generation request. Although not shown, a series hybrid vehicle equipped with this internal combustion engine further includes a traction motor-generator that operates primarily as a motor to drive a pair of drive wheels, a battery that temporarily stores the generated electric power, and an inverter device that converts electric power between the battery and the power-generating motor-generator and the traction motor-generator.

[0012] The internal combustion engine is configured as a direct injection internal combustion engine having four cylinders 2 provided in an engine body 1. The engine body 1 of the internal combustion engine is provided with a fuel injection valve (not shown) for injecting fuel into each cylinder 2 and a spark plug, both not shown. The injection amount and injection timing of the fuel injection valve and the ignition timing of the spark plug are controlled by control signals from a control device (not shown). The internal combustion engine is also provided with an exhaust supercharger 3, which is a turbocharger.

[0013] The engine body 1 has an intake passage 4 through which air drawn into each cylinder 2 flows (only the passage upstream of the compressor 5 is shown in FIG. 1), and an exhaust passage 6 through which exhaust gas discharged from each cylinder 2 flows.

[0014] A compressor 5 of the exhaust turbocharger 3 is disposed in the intake passage 4 .

[0015] The exhaust passage 6 has an upstream exhaust pipe 8 that connects each cylinder 2 of the engine body 1 of the internal combustion engine to an exhaust turbine 7 of the exhaust turbocharger 3, and a downstream exhaust pipe 9 that is connected downstream of the exhaust turbine 7 and through which exhaust gas that has passed through the exhaust turbine 7 flows. The upstream exhaust pipe 8 has exhaust ports 10 that communicate with each cylinder 2, an exhaust manifold 11 that communicates with the exhaust ports 10, and a pipe 12 that communicates with the exhaust manifold 11. The pipe 12 is connected to the exhaust manifold 11 and the exhaust turbine 7.

[0016] The exhaust turbocharger 3 has an exhaust turbine 7 and a compressor 5 connected to the exhaust turbine 7 via a shaft (not shown). In such an internal combustion engine, exhaust air from a pipe 12 rotates the exhaust turbine 7, compressing the air in the intake passage 4 downstream of the compressor 5, and this compressed air is supplied to an intake manifold (not shown) of the engine body 1.

[0017] A catalytic converter (exhaust purification catalyst) 13 made of a three-way catalyst is disposed in pipe 12 of the upstream exhaust pipe 8, and purifies the exhaust gas passing through this pipe 12. The part of pipe 12 downstream of the catalytic converter 13 is connected to one end of a bypass passage 14, which bypasses the exhaust turbine 7 and is connected to the downstream exhaust pipe 9 located downstream of the exhaust turbine 7. The bypass passage 14 allows a portion of the exhaust gas that has passed through the catalytic converter 13 to escape to the downstream exhaust pipe 9.

[0018] The bypass passage 14 is also provided with an electric wastegate valve 15 that adjusts the flow rate of a portion of the exhaust gas flowing through the bypass passage 14. Generally, in a configuration in which an exhaust turbine of an exhaust turbocharger is arranged downstream of the cylinder and an exhaust purification catalyst is further arranged downstream of this exhaust turbine, the wastegate valve is provided integrally with a housing that accommodates the exhaust turbine of the exhaust turbocharger, but the wastegate valve 15 of this embodiment is provided separately from a housing (not shown) that accommodates the exhaust turbine 7 of the exhaust turbocharger 3, and is arranged in the bypass passage 14. The wastegate valve 15 is controlled by a control signal that is generated by a control device (not shown) based on the operating state of the vehicle.

[0019] A first exhaust sensor 16 is disposed in the upstream exhaust pipe 8 upstream of the catalytic converter 13 and downstream of the exhaust manifold 11. The first exhaust sensor 16 detects a first signal related to the components of the exhaust gas flowing into the catalytic converter 13. The first exhaust sensor 16 is an air-fuel ratio sensor that detects the air-fuel ratio of the exhaust gas flowing into the catalytic converter 13, or detects the amount of oxygen in the exhaust gas flowing into the catalytic converter 13. ２The first signal detected by the first exhaust sensor 16 is input to a control device (not shown).

[0020] Furthermore, a second exhaust sensor 17 is disposed in the downstream exhaust pipe 9 downstream of a junction A between the downstream exhaust pipe 9 and the bypass passage 14. The second exhaust sensor 17 detects a second signal related to the components of the exhaust passing through the downstream exhaust pipe 9. The second exhaust sensor 17 is an air-fuel ratio sensor that detects the air-fuel ratio of the exhaust passing through the downstream exhaust pipe 9, or an air-fuel ratio sensor that detects the amount of oxygen in the exhaust passing through the downstream exhaust pipe 9. ２ The second signal detected by the second exhaust sensor 17 is input to a control device (not shown).

[0021] In addition, a gasoline particulate filter (GPF) (not shown) that removes particulate matter (PM) from the exhaust gas is disposed downstream of the second exhaust sensor 17 in the downstream exhaust pipe 9 .

[0022] The reason why the second exhaust sensor 17 is arranged downstream of the junction A in the downstream exhaust pipe 9 is that when regenerating the GPF, it is necessary to increase the opening of the wastegate valve 15 to guide high-temperature exhaust gas into the GPF via the bypass passage 14, and the flow rate of this exhaust gas must be monitored.

[0023] For convenience of explanation, the following description will be given assuming that the first exhaust sensor 16 and the second exhaust sensor 17 are air-fuel ratio sensors.

[0024] The first exhaust sensor 16 and the second exhaust sensor 17 are used to diagnose the deterioration of the catalytic converter 13. This deterioration diagnosis is performed by a deterioration diagnosis unit provided in the control device (not shown) based on a comparison between the waveform of a first signal from the first exhaust sensor 16 and the waveform of a second signal from the second exhaust sensor 17. More specifically, when the catalytic converter 13 deteriorates, the oxygen storage function within the catalytic converter 13 ceases to function, and the oxidation-reduction reaction does not proceed normally. As a result, the waveform indicating the air-fuel ratio detected by the first exhaust sensor 16, i.e., a waveform alternating rich and lean, appears as a waveform with a smaller amplitude downstream of the catalytic converter 13. Therefore, if the waveform of the air-fuel ratio acquired by the second exhaust sensor 17 has a smaller amplitude than the waveform of the air-fuel ratio detected by the first exhaust sensor 16, the control device determines that the catalytic converter 13 may be deteriorated. Furthermore, a prerequisite for performing a highly accurate deterioration diagnosis is that the waveform of the air-fuel ratio detected by the upstream first exhaust sensor 16 during steady-state operation is a regular waveform with a substantially constant frequency and amplitude. Based on this premise, in this embodiment, whether or not there is a deviation in the average air-fuel ratio is monitored for the air-fuel ratio acquired from the first exhaust sensor 16. In order to determine whether or not there is a deviation in this average air-fuel ratio, if the average gas mode (exhaust mode) in the case of steady operation, that is, a state in which there is no transient exhaust flow during steady operation, is known in advance, then even if the deterioration diagnosis is delayed, it is possible to estimate whether or not there is a deviation in the average air-fuel ratio based on the average gas mode.

[0025] Furthermore, the deterioration diagnosis of the catalytic converter 13 in this embodiment includes a two-stage deterioration diagnosis. In this embodiment, this two-stage deterioration diagnosis is performed once per trip. However, the two-stage deterioration diagnosis may be performed at a frequency other than once per trip.

[0026] In the first stage of deterioration diagnosis, regardless of whether the wastegate valve 15 is open or closed, the possibility of deterioration of the catalytic converter 13 is determined based on a comparison between the waveform of the first signal from the first exhaust sensor 16 and the waveform of the second signal from the second exhaust sensor 17. When the wastegate valve 15 is closed, the air-fuel ratio acquired by the second exhaust sensor 17 is the air-fuel ratio related to the exhaust gas flowing from the catalytic converter 13 through the downstream exhaust pipe 9 via the pipe 12 and the exhaust turbine 7. Therefore, in this case, in the first stage of deterioration diagnosis, the possibility of deterioration of the catalytic converter 13 is determined based on a comparison between the waveform of the air-fuel ratio acquired by the first exhaust sensor 16 and the waveform of the air-fuel ratio acquired by the second exhaust sensor 17, which is the air-fuel ratio related to the exhaust gas flowing from the catalytic converter 13 through the downstream exhaust pipe 9 via the pipe 12 and the exhaust turbine 7. Furthermore, for example, when the wastegate valve 15 is opened to a relatively small degree for boost pressure control, the air-fuel ratio acquired by the second exhaust sensor 17 will be the air-fuel ratio for the exhaust gas flowing through the downstream exhaust pipe 9 via the pipe 12 and the bypass passage 14, and the air-fuel ratio for the exhaust gas flowing from the catalytic converter 13 through the pipe 12 and the exhaust turbine 7 into the downstream exhaust pipe 9, but the air-fuel ratio for the latter exhaust will account for the majority. Therefore, in this case, the first-stage deterioration diagnosis determines the possibility of deterioration of the catalytic converter 13 based essentially on a comparison between the air-fuel ratio waveform acquired by the first exhaust sensor 16 and the air-fuel ratio waveform acquired by the second exhaust sensor 17, which is the air-fuel ratio waveform for the exhaust gas flowing from the catalytic converter 13 through the pipe 12 and the exhaust turbine 7 into the downstream exhaust pipe 9.

[0027] Furthermore, if the wastegate valve 15 is opened to a relatively large degree and the amount of exhaust gas flowing through the downstream exhaust pipe 9 via the pipe 12 and the bypass passage 14 is greater than the amount of exhaust gas flowing through the downstream exhaust pipe 9 from the catalytic converter 13 via the pipe 12 and the exhaust turbine 7, a second-stage deterioration diagnosis, which will be described later, will be performed.

[0028] Then, if the waveform of the air-fuel ratio acquired by the second exhaust sensor 17 has an amplitude smaller than the amplitude of the waveform of the air-fuel ratio detected by the first exhaust sensor 16, it is determined that there is a possibility of deterioration of the catalytic converter 13. If there is a possibility of deterioration of the catalytic converter 13, a waveform with a smaller amplitude will be acquired downstream of the catalytic converter 13, but in the first-stage deterioration diagnosis, the waveform of the air-fuel ratio of the exhaust that has passed through the catalytic converter 13 is blunted by flowing through a relatively long and large-volume flow path that passes through the piping 12, the exhaust turbine 7, and the downstream exhaust pipe 9, so the accuracy of the deterioration diagnosis will be lower than the accuracy of the second-stage deterioration diagnosis.

[0029] Furthermore, if the first-stage deterioration diagnosis determines that there is a possibility of deterioration of the catalytic converter 13, the system proceeds to a second-stage deterioration diagnosis, in which the opening of the wastegate valve 15 is increased, and the presence or absence of deterioration of the catalytic converter 13 is determined based on a comparison between the waveform of a first signal from the first exhaust sensor 16 and the waveform of a second signal from the second exhaust sensor 17. More specifically, the presence or absence of deterioration of the catalytic converter 13 is determined based on a comparison between the waveform of the air-fuel ratio acquired by the first exhaust sensor 16 and the waveform of the air-fuel ratio acquired by the second exhaust sensor 17, which is the air-fuel ratio of exhaust gas that flows from the catalytic converter 13 through the pipe 12 and the bypass passage 14 and into the downstream exhaust pipe 9. Here, the air-fuel ratio detected by the second exhaust sensor 17 actually includes the air-fuel ratio of the exhaust gas that has flowed through a relatively long flow path including the upstream exhaust pipe 8, the exhaust turbine 7, and the downstream exhaust pipe 9, but this air-fuel ratio is much smaller than the air-fuel ratio of a large amount of exhaust gas that is quickly guided through a relatively short flow path including the downstream exhaust pipe 9 via the pipe 12 and the bypass passage 14. Furthermore, in the second stage deterioration diagnosis, the exhaust gas is quickly guided to the second exhaust sensor 17 side through such a relatively short flow path, so the waveform of the air-fuel ratio of the exhaust gas that has passed through the catalytic converter 13 is less likely to be rounded, thereby improving the diagnostic accuracy compared to the first stage deterioration diagnosis. Then, if the waveform of the air-fuel ratio acquired by the second exhaust sensor 17 has a waveform with a smaller amplitude than the amplitude of the waveform of the air-fuel ratio detected by the first exhaust sensor 16, it is determined that the catalytic converter 13 has deteriorated.

[0030] Next, a catalyst deterioration diagnosis method using the catalyst deterioration diagnosis device for an internal combustion engine according to one embodiment will be described with reference to FIG.

[0031] First, in step S1 , the first exhaust sensor 16 acquires a first signal relating to the air-fuel ratio of the exhaust gas upstream of the catalytic converter 13 .

[0032] Next, in step S2, the second exhaust sensor 17 acquires a second signal relating to the air-fuel ratio of the exhaust downstream of the catalytic converter 13 and downstream of the confluence A of the downstream exhaust pipe 9 and the bypass passage 14.

[0033] Then, the process proceeds to the first stage of deterioration diagnosis of the catalytic converter 13 shown in step S3, and in step S4 it is determined whether there is a possibility of deterioration of the catalytic converter 13. In this determination, it is determined whether the waveform of the air-fuel ratio acquired by the second exhaust sensor 17 has a smaller amplitude than the amplitude of the waveform of the air-fuel ratio detected by the first exhaust sensor 16. If it is determined that the waveform does not have such a small amplitude, it is determined that there is no possibility of deterioration of the catalytic converter 13, and the flow ends.

[0034] Furthermore, if it is determined in step S4 that the waveform has the above-mentioned small amplitude, it is assumed that there is a possibility of deterioration of the catalytic converter 13, and the process proceeds to the second stage of deterioration diagnosis shown in step S5, and in step S6, the opening of the wastegate valve 15 is increased.

[0035] Next, in step S7, it is determined whether or not there is deterioration of the catalytic converter 13. In this determination, it is determined whether or not the waveform of the air-fuel ratio acquired by the second exhaust sensor 17 has a smaller amplitude than the amplitude of the waveform of the air-fuel ratio detected by the first exhaust sensor 16. If the waveform does not have such a small amplitude, it is determined that there is no deterioration of the catalytic converter 13, and the flow ends.

[0036] If it is determined in step S7 that the waveform has the small amplitude, deterioration of the catalytic converter 13 is confirmed in step S8.

[0037] As described above, in this embodiment, the catalytic converter 13 is arranged in the upstream exhaust pipe 8 connecting the cylinder 2 of the internal combustion engine and the exhaust turbine 7 of the exhaust turbocharger 3, that is, the catalytic converter 13 is arranged downstream of the cylinder 2, and the exhaust turbine 7 of the exhaust turbocharger 3 is arranged downstream of this catalytic converter 13. In this configuration, a bypass passage 14 is provided to release a portion of the exhaust gas that has passed through the catalytic converter 13 to the downstream exhaust pipe 9, and a wastegate valve 15 is also provided in this bypass passage 14. In addition, a first exhaust sensor 16 and a second exhaust sensor 17 are provided so that they can be used for diagnosing deterioration of the catalytic converter 13. The first exhaust sensor 16 is arranged in the upstream exhaust pipe 8 upstream of the catalytic converter 13, while the second exhaust sensor 17 is arranged in the downstream exhaust pipe 9 downstream of the junction A of the downstream exhaust pipe 9 and the bypass passage 14. This second exhaust sensor 17 is an essential component for managing exhaust gas when the wastegate valve 15 is opened to guide high-temperature exhaust gas to the GPF via the pipe 12, the bypass passage 14, and the downstream exhaust pipe 9 in order to regenerate the GPF, which is located downstream of the second exhaust sensor 17. Furthermore, while it is generally necessary to place exhaust sensors upstream and immediately downstream of the catalytic converter to diagnose deterioration of the catalytic converter, this embodiment uses the second exhaust sensor 17, which is an essential component downstream of the junction A, so that deterioration of the catalytic converter 13 can be diagnosed without having to place an exhaust sensor immediately downstream of the catalytic converter 13.

[0038] Furthermore, if the second exhaust sensor 17, which is an essential component as in this embodiment, is provided in addition to the two exhaust sensors typically installed upstream and immediately downstream of a catalytic converter, three exhaust sensors would be required. However, in this embodiment, only two exhaust sensors, the first exhaust sensor 16 and the second exhaust sensor 17, are required, so the manufacturing cost of the internal combustion engine can be reduced by the cost of one exhaust sensor.

[0039] Furthermore, in this embodiment, when it is determined in the deterioration diagnosis of the catalytic converter 13 that there is a possibility of deterioration of the catalytic converter 13, the opening degree of the wastegate valve 15 is increased. As a result, an air-fuel ratio waveform that is not excessively smoothed is detected by the second exhaust sensor 17 through a relatively short flow path that passes through the pipe 12, the bypass passage 14, and the downstream exhaust pipe 9. Therefore, by comparing the air-fuel ratio waveform from the first exhaust sensor 16 with the air-fuel ratio waveform from the second exhaust sensor 17, deterioration diagnosis of the catalytic converter 13 can be performed quickly and accurately.

[0040] Furthermore, in this embodiment, the deterioration diagnosis of the catalytic converter 13 is performed in two stages. In the first stage, the possibility of deterioration of the catalytic converter 13 is determined mainly based on a comparison between the waveform of the air-fuel ratio from the first exhaust sensor 16 and the waveform of the air-fuel ratio from the second exhaust sensor 17, which is a second signal related to exhaust gas that has flowed a relatively long path from the catalytic converter 13 through the pipe 12 and the exhaust turbine 7 into the downstream exhaust pipe 9. In the second stage, the presence or absence of deterioration of the catalytic converter 13 is determined based on a comparison between the waveform of the air-fuel ratio from the first exhaust sensor 16 and the waveform of the air-fuel ratio from the second exhaust sensor 17, which is the air-fuel ratio waveform of exhaust gas that has flowed a relatively short path through the pipe 12, the bypass passage 14, and the downstream exhaust pipe 9. As described above, the accuracy of the second stage deterioration diagnosis is higher than that of the first stage deterioration diagnosis. Therefore, only when it is determined in the first stage of deterioration diagnosis that there is a possibility of deterioration of the catalytic converter 13, the deterioration diagnosis of the catalytic converter 13 can be performed with high accuracy in the second stage of deterioration diagnosis, thereby improving the efficiency of the deterioration diagnosis.

[0041] Furthermore, since the boost pressure of the exhaust turbocharger 3 only needs to be reduced when there is a possibility of deterioration of the catalytic converter 13 in the first stage deterioration diagnosis, the exhaust turbocharger 3 can be operated efficiently and fuel consumption can be reduced.

[0042] Furthermore, in this embodiment, the internal combustion engine is an internal combustion engine used in a series hybrid vehicle, and by increasing the opening of the wastegate valve 15 only when highly accurate deterioration diagnosis is required as described above, it is possible to reduce the frequency of deterioration diagnosis of the catalytic converter 13 in situations where the amount of power generation is low and the operating point of the internal combustion engine is off the optimum fuel efficiency point.

Claims

1. A catalyst deterioration diagnosis method for an internal combustion engine, comprising: an exhaust purification catalyst that is arranged in an upstream exhaust pipe connecting a cylinder of an internal combustion engine having an exhaust turbocharger to an exhaust turbine of the exhaust turbocharger and purifies exhaust; a bypass passage that bypasses the exhaust turbine and releases a portion of the exhaust that has passed through the exhaust purification catalyst to a downstream exhaust pipe located downstream of the exhaust turbine; a wastegate valve that adjusts the flow rate of the portion of the exhaust that passes through the bypass passage; a first exhaust sensor that is arranged in the upstream exhaust pipe upstream of the exhaust purification catalyst and detects a first signal related to components of the exhaust that flow into the exhaust purification catalyst; a second exhaust sensor that is arranged in the downstream exhaust pipe downstream of a junction of the downstream exhaust pipe and the bypass passage and detects a second signal related to components of the exhaust that pass through the downstream exhaust pipe; and a control device having a deterioration diagnosis unit that performs deterioration diagnosis of the exhaust purification catalyst using the first signal and the second signal, a catalyst deterioration diagnosis method for an internal combustion engine having an exhaust turbocharger, wherein deterioration diagnosis of the exhaust purification catalyst is performed based on a comparison between a waveform of the first signal and a waveform of the second signal.

2. A catalyst deterioration diagnosis method for an internal combustion engine having an exhaust turbocharger according to claim 1, wherein when diagnosing the deterioration of the exhaust purification catalyst, the opening of the wastegate valve is made larger than the opening immediately before.

3. A catalyst deterioration diagnosis method for an internal combustion engine having an exhaust turbocharger as set forth in claim 1, wherein the deterioration diagnosis of the exhaust purification catalyst has a two-stage deterioration diagnosis, and in a first-stage deterioration diagnosis, regardless of whether the wastegate valve is open or closed, a determination is made as to the possibility of deterioration of the exhaust purification catalyst based on a comparison between the waveform of the first signal and the waveform of the second signal, and if it is determined that there is a possibility of deterioration of the exhaust purification catalyst, in a second-stage deterioration diagnosis, the opening of the wastegate valve is made larger than the opening immediately before, and the presence or absence of deterioration of the exhaust purification catalyst is determined based on a comparison between the waveform of the first signal and the waveform of the second signal.

4. A catalyst deterioration diagnosis device for an internal combustion engine having an exhaust turbocharger, comprising: an exhaust purification catalyst that is arranged in an upstream exhaust pipe connecting a cylinder of the internal combustion engine and an exhaust turbine of the exhaust turbocharger and purifies exhaust gas; a bypass passage that bypasses the exhaust turbine and releases a portion of the exhaust that has passed through the exhaust purification catalyst to a downstream exhaust pipe located downstream of the exhaust turbine; a wastegate valve that adjusts the flow rate of the portion of the exhaust that passes through the bypass passage; a first exhaust sensor that is arranged in the upstream exhaust pipe upstream of the exhaust purification catalyst and detects a first signal related to components of the exhaust that flow into the exhaust purification catalyst; a second exhaust sensor that is arranged in the downstream exhaust pipe downstream of a junction of the downstream exhaust pipe and the bypass passage and detects a second signal related to components of the exhaust that pass through the downstream exhaust pipe; and a control device having a deterioration diagnosis unit that performs deterioration diagnosis of the exhaust purification catalyst using the first signal and the second signal, wherein the control device performs deterioration diagnosis of the exhaust purification catalyst based on a comparison between the waveform of the first signal and the waveform of the second signal. A catalyst deterioration diagnosis device for an internal combustion engine equipped with an exhaust turbocharger.

Images