WO2021176671A1

WO2021176671A1 - Catalyst deterioration diagnostic device

Info

Publication number: WO2021176671A1
Application number: PCT/JP2020/009530
Authority: WO
Inventors: 晋二藤田
Original assignee: 本田技研工業株式会社
Priority date: 2020-03-05
Filing date: 2020-03-05
Publication date: 2021-09-10
Also published as: BR112022017146A2; CN115244283B; CN115244283A; JPWO2021176671A1; JP7372440B2

Abstract

Provided is a catalyst deterioration diagnostic device that is capable of detecting the degree of deterioration of a catalyst device with use of a single oxygen concentration sensor.　The catalyst deterioration diagnostic device has: an oxygen concentration sensor (90) that is provided downstream of a catalyst (C) provided to an exhaust pipe (19) of an engine (E); and a control unit (100) that diagnoses the degree of deterioration of the catalyst (C) on the basis of an output signal of the oxygen concentration sensor (90). The catalyst deterioration diagnostic device is provided with: a perturbation means (105) for carrying out a perturbation process in which the air-fuel ratio of an air-fuel mixture fed to the engine (E) is alternately shifted toward target air-fuel ratios that are set on richer and leaner sides compared to a theoretical air-fuel ratio. During the perturbation process, the control unit (100) infers and detects the air-fuel ratio upstream of the catalyst (C) on the basis of the target air-fuel ratios and of the output signal of the oxygen concentration sensor (90).

Description

Catalyst deterioration diagnostic equipment

The present invention relates to a catalyst deterioration diagnostic device, and more particularly to a catalyst deterioration diagnostic device that detects the degree of deterioration of the catalyst device provided in the exhaust pipe of an engine.

Conventionally, a catalyst deterioration diagnostic device that detects the degree of deterioration of the catalyst device provided in the exhaust pipe of an engine has been known.

In Patent Document 1, oxygen concentration sensors are arranged on the upstream side and the downstream side of the catalyst device, respectively, and the catalyst device is based on the change in the output signal of the oxygen concentration sensor when the air-fuel ratio is switched between the rich side and the lean side. The configuration for detecting the degree of deterioration of the above is disclosed.

Japanese Unexamined Patent Publication No. 2007-285288

However, in the configuration of Patent Document 1, two oxygen concentration sensors are required and it is costly, so a configuration in which the degree of deterioration of the catalyst is executed by one oxygen concentration sensor has been sought.

An object of the present invention is to solve the above-mentioned problems of the prior art and to provide a catalyst deterioration diagnostic device capable of detecting the degree of deterioration of the catalyst device with one oxygen concentration sensor.

In order to achieve the above object, the present invention comprises an oxygen concentration sensor (90) provided on the downstream side of the catalyst (C) provided in the exhaust pipe (19) of the engine (E) and the oxygen concentration sensor (90). In a catalyst deterioration diagnosis device having a control unit (100) for diagnosing the degree of deterioration of the catalyst (C) based on the output signal of the above, the air-fuel ratio of the air-fuel mixture supplied to the engine (E) is calculated from the stoichiometric air-fuel ratio. The control unit (100) is provided with a catalyst means (105) for performing a catalyst process that alternately shifts toward the target air-fuel ratio set on the rich side and the lean side, and the control unit (100) is said to be in the middle of the pattern processing. The first feature is that the air-fuel ratio on the upstream side of the catalyst (C) is estimated and detected based on the target air-fuel ratio and the output signal of the oxygen concentration sensor (90).

Further, the AFR as the air-fuel ratio on the upstream side of the catalyst (C) has a theoretical air-fuel ratio of 14.5, and is a coefficient indicating the degree of transition to the rich side or the lean side in the perturbation treatment for detecting the degree of deterioration. Is K, and the correction coefficient determined by the target air-fuel ratio and the output signal of the oxygen concentration sensor (90) is H. There is a second feature.

The third feature is that the correction coefficient is calculated by performing PID control on the deviation between the target air-fuel ratio and the output signal of the oxygen concentration sensor (90).

Further, O2 as the amount of inflow oxygen on the upstream side of the catalyst (C) is calculated by the following formula O2 = GAIR × (1-14.5 ÷ AFR) when the amount of air per cycle is GAIR. There is a fourth feature in what is required.

Further, the control unit (100) has a fifth feature in that it calculates the oxygen adsorption capacity of the catalyst (C) by integrating the amount of inflow oxygen and diagnoses the deteriorated state of the catalyst (C). ..

According to the first feature, the output signals of the oxygen concentration sensor (90) provided on the downstream side of the catalyst (C) provided in the exhaust pipe (19) of the engine (E) and the oxygen concentration sensor (90). In the catalyst deterioration diagnosis apparatus having a control unit (100) for diagnosing the degree of deterioration of the catalyst (C) based on the above, the air-fuel ratio of the air-fuel mixture supplied to the engine (E) is set to be richer and leaner than the stoichiometric air-fuel ratio. The control unit (100) is provided with a catalyst means (105) that performs a catalyst processing that alternately shifts toward a target air-fuel ratio set on the side, and the control unit (100) is capable of performing the target air-fuel ratio and the target air-fuel ratio during the catalyst processing. Since the air-fuel ratio on the upstream side of the catalyst (C) is estimated and detected based on the output signal of the oxygen concentration sensor (90), the degree of deterioration of the catalyst is determined by only one oxygen concentration sensor provided on the downstream side of the catalyst. Can be detected.

According to the second feature, the AFR as the air-fuel ratio on the upstream side of the catalyst (C) has a theoretical air-fuel ratio of 14.5, and the perturbation treatment for detecting the degree of deterioration has a rich side or a lean side. When the coefficient indicating the degree of transition is K and the correction coefficient determined by the target air-fuel ratio and the output signal of the oxygen concentration sensor (90) is H, the following calculation formula AFR = 14.5 ÷ K × Since it is obtained by H, it is possible to calculate the air-fuel ratio on the upstream side of the catalyst by a simple calculation formula.

According to the third feature, the correction coefficient is calculated by performing PID control on the deviation between the target air-fuel ratio and the output signal of the oxygen concentration sensor (90), and thus is a general feedback process. It is possible to calculate the correction coefficient using.

According to the fourth feature, O2 as the amount of inflow oxygen on the upstream side of the catalyst (C) is calculated by the following formula O2 = GAIR × (1-14) when the amount of air per cycle is GAIR. Since it is calculated by (5.5 ÷ AFR), it is possible to calculate the amount of inflow oxygen on the upstream side of the catalyst by a simple calculation formula.

According to the fifth feature, the control unit (100) calculates the oxygen adsorption capacity of the catalyst (C) by integrating the amount of inflow oxygen, and diagnoses the deteriorated state of the catalyst (C). It is possible to detect the degree of deterioration of the catalyst with only one oxygen concentration sensor provided on the downstream side of the catalyst.

It is a left side view of the motorcycle as a saddle-type vehicle which concerns on one Embodiment of this invention. It is sectional drawing of the diameter expansion part provided in the middle of an exhaust pipe. It is a schematic diagram which shows the relationship between an engine and an oxygen concentration sensor. It is a block diagram which shows the structure of the control part which performs the deterioration diagnosis of a catalyst device. It is a figure explaining the responsiveness before and after deterioration of a catalyst apparatus. It is a timing chart when the deterioration diagnosis of the catalyst device after deterioration is made. It is a timing chart when the deterioration diagnosis of the catalyst device before deterioration is made.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a left side view of a motorcycle 1 as a saddle-type vehicle according to an embodiment of the present invention. A head pipe 12 that rotatably supports the steering stem 10 is attached to the front end of the vehicle body frame 2 of the motorcycle 1 which is a saddle-mounted vehicle. A steering handle 6 is attached to the upper end of the steering stem 10 via a top bridge (not shown). The top bridge that rotates integrally with the steering stem 10 supports a pair of left and right front forks 16 together with a bottom bridge (not shown) that is fixed to the steering stem 10 at the lower part of the head pipe 12. A front wheel WF provided with a brake disc 35 is rotatably supported at the lower end of the front fork 16.

A parallel two-cylinder engine E in which the lower part of the cylinder head 18 is supported by a hanger frame 17 extending downward from the rear of the head pipe 12 is arranged in the lower part of the vehicle body frame 2. A generator cover Ea and a drive sprocket cover Eb are attached to the left side of the engine E in the vehicle width direction. A radiator 15 for engine cooling water is arranged in front of the hanger frame 17.

The vehicle body frame 2 supports the engine E at the upper and rear parts of the engine E, and the swing arm 24 is swingably supported by the pivot 21. A pair of left and right foot-resting steps 23 for the driver are provided below the pivot plate 21a that pivotally supports the pivot 21, and a foldable passenger step 21b is provided on the step bracket 21c on the rear upper side thereof. ing. Further, below the footrest step 23, a main stand 22 that floats the rear wheel WR of the motorcycle 1 to stand on its own when the vehicle is stopped, and a side stand 140 that tilts the vehicle body to the left to stand on its own are attached. The main stand 22 and the side stand 140 are retracted by swinging about 90 degrees toward the rear side of the vehicle body.

An exhaust device 20 that purifies and silences the exhaust gas of the engine E and discharges it to the rear is attached to the lower part of the vehicle body of the motorcycle 1. The exhaust device 20 has an exhaust pipe 19 connected to an exhaust port of a cylinder to guide exhaust gas to the rear, and a muffler 26 connected to the rear end of the exhaust pipe 19. An exhaust pipe cover 5a that covers the front and sides of the exhaust pipe 19 is arranged below the front of the cylinder head 18. The swing arm 24 pivotally supported by the pivot 21 is suspended from the vehicle body frame 2 by a rear cushion (not shown). The driving force of the engine E is transmitted to the rear wheel WR, which is rotatably supported by the rear end of the swing arm 24, via the drive chain 25.

Above the engine E, a storage box 4 accessed from the large opening / closing lid 3 is provided at a position covered by the side cowl 5, which is an exterior part. A headlight 13 is arranged in front of the side cowl 5, and a pair of left and right flasher lamps 11 and a windscreen 9 are arranged above the headlight 13. A knuckle guard 8 and a rearview mirror 7 are attached to the left and right steering handles 6, respectively. Further, a pair of left and right fog lamps 14 are attached to the lower part of the side cowl 15 at a position outside the front fork 16 in the vehicle width direction, and above the front wheel WF, a front that prevents mud splashing on the vehicle body and the like. A fender 36 is attached.

A rear frame 29 that supports the fuel tank 28 and the like is attached to the rear of the vehicle body frame 2. The left and right sides of the rear frame 29 are covered with seat cowls 31, and a driver's seat 27 and a passenger's seat 30 are arranged above the seat cowl 31. A taillight device 32 is attached to the rear end of the seat cowl 31, and a rear flasher lamp 33 is supported by a rear fender 34 extending rearward and downward from the seat cowl 31.

FIG. 2 is a cross-sectional view of the enlarged diameter portion 61 provided in the middle of the exhaust pipe 19. The catalyst device C is housed in the enlarged diameter portion 61, and the air-fuel ratio sensor 80 is arranged behind the catalyst device C. The enlarged diameter portion 61 holds the catalyst device C inside the front outer cylinder 76 via the packing 75, and the rear end portion of the catalyst device C and the front outer cylinder 76 is formed on the outer periphery of the funnel-shaped rear outer cylinder 78. It is configured by welding and fixing with a welding bead B to the surface. The air-fuel ratio sensor 90 is held by being screwed into a pedestal 86 as a mounting boss welded and fixed to the rear outer cylinder 78.

The air-fuel ratio sensor 90 may be a LAF sensor that can linearly detect changes in oxygen concentration, or an O2 sensor that can only detect that the air-fuel ratio is at the theoretical air-fuel ratio by reversing the output value at the boundary of the theoretical air-fuel ratio. can. Further, the oxygen concentration sensor 90 can be a sensor with a heater whose temperature is optimally controlled by a heater controlled by the control unit 100.

FIG. 3 is a schematic diagram showing the relationship between the engine E and the oxygen concentration sensor 90. The exhaust device 20 has an oxygen concentration sensor 90 located on the downstream side of the catalyst device C. An injector 57, which is a fuel injection device, is provided in the intake pipe 56 of the engine E, and an intake air amount sensor 55 is arranged upstream of the injector 57. The sensor signal of the intake air amount sensor 55 is input to the air amount detection unit 58. The injector control unit 59 controls the injector 57 so that combustion is performed at an appropriate air-fuel ratio based on signals from the air amount detection unit 58 and the control unit 100 in addition to information on throttle operation and engine speed.

Normally, the deterioration diagnosis of the catalyst device C is performed by two sensors, an oxygen concentration sensor provided on the upstream side of the catalyst device C and an oxygen concentration sensor provided on the downstream side of the catalyst device C. Specifically, attention is paid to the relationship between the sensor output of the upstream oxygen concentration sensor and the sensor output of the downstream oxygen concentration sensor, and the change due to the deterioration of the catalyst device C is detected. For example, in the method focusing on the decrease in the oxygen adsorption rate due to the deterioration of the catalyst device C, when the air-fuel ratio is feedback-controlled based on the output of the downstream oxygen concentration sensor, the oxygen concentration in the exhaust gas changes due to the feedback control. Since the response time until the reaction changes due to the influence of deterioration, the deterioration state of the catalyst is determined by determining whether or not the change cycle of the output of the downstream oxygen concentration sensor corresponds to the predetermined catalyst deterioration conditions. Can be determined. Specifically, a counting method can be used in which the number of times the downstream oxygen concentration sensor makes a predetermined fluctuation within a predetermined time is counted.

Such deterioration diagnosis processing is executed with a patrol processing in which the air-fuel ratio of the internal combustion engine is alternately changed to the rich side and the lean side. Specifically, whether or not the amount of oxygen accumulated using the upstream oxygen concentration sensor exceeds the threshold value until the value of the downstream oxygen concentration sensor reaches a predetermined value by switching the air fuel ratio to the lean side. Then, the air-fuel ratio is switched to the rich side, and the amount of oxygen accumulated using the upstream oxygen concentration sensor exceeds the threshold value until the value of the downstream oxygen concentration sensor reaches a predetermined value. Deterioration of the catalyst device C is detected by repeating the operation of observing whether or not. When such a perturbation treatment is performed, a lean operation is executed so as to supply an amount of oxygen that can be accumulated in the normal catalyst device C but cannot be accumulated in the deteriorated catalyst device C, and then the lean operation is executed. Switch to the rich operation and execute the rich operation so as to release almost all the accumulated oxygen. Then, if the catalyst device C is not deteriorated, the output of the oxygen concentration sensor 90 hardly changes, but if it is deteriorated, the output of the oxygen concentration sensor 90 changes significantly, so that the deterioration diagnosis becomes possible. ..

In the present embodiment, since the oxygen concentration sensor is not provided on the upstream side of the catalyst device C, the oxygen concentration on the upstream side of the catalyst device C is estimated and detected based on the output of the downstream oxygen concentration sensor, and the estimated detected value is used. It is characterized in that deterioration diagnosis of the catalyst device C is performed based on the above.

FIG. 4 is a block diagram showing a configuration of a control unit 100 that diagnoses deterioration of the catalyst device C. The control unit 100 includes a perturbation means 105, a catalyst pre-catalyst air-fuel ratio calculation unit 101, a pre-catalyst oxygen amount calculation unit, a pre-catalyst oxygen amount integration unit 103, and a catalyst diagnosis unit 104. The output signal of the oxygen concentration sensor 90 is input to the air-fuel ratio calculation unit 101 before the catalyst. Further, the output signal of the air amount sensor 58 is input to the oxygen amount calculation unit 102 before the catalyst. When the catalyst diagnosis unit 104 determines that the catalyst device C is in a predetermined deteriorated state, the catalyst diagnosis unit 104 is configured to notify the occupant by an indicator 74 provided in a meter device or the like.

The perturbation means 105 executes a patrol process for shifting the air-fuel ratio of the internal combustion engine to the rich side and the lean side. The catalyst front air-fuel ratio calculation unit 101 obtains the AFR as the air-fuel ratio on the upstream side of the catalyst device C by the calculation formula of AFR = 14.5 ÷ K × H.

FIG. 5 is a diagram for explaining the responsiveness of the catalyst device C before and after deterioration. The catalyst device C after deterioration has a lower purification rate and a lower oxygen storage capacity than the catalyst device C before deterioration, whereby the response of the oxygen concentration sensor 90 provided downstream of the catalyst becomes faster. .. As described above, in the perturbation treatment, a lean operation is executed so as to supply an amount of oxygen that can be accumulated in the normal catalyst device C but cannot be accumulated in the deteriorated catalyst device C, and then a rich operation is performed. The rich operation is repeated so as to switch to and release almost all the accumulated oxygen. When this perturbation process is executed, the output of the oxygen concentration sensor 90 hardly changes before the catalyst device C deteriorates, but the output of the oxygen concentration sensor 90 changes significantly after the deterioration. It becomes.

FIG. 6 is a timing chart when the deterioration diagnosis of the catalyst device C after deterioration is made. Further, FIG. 7 is a timing chart when the deterioration diagnosis of the catalyst device C before deterioration is made. In both time charts, in order from the top, the estimated air-fuel ratio (solid line) on the upstream side of the catalyst device C, the target air-fuel ratio (solid line), and the air-fuel ratio on the downstream side of the catalyst by the oxygen concentration sensor 90 (two-point chain line). A coefficient (solid line) indicating the degree of transition to the rich side or lean side in the perturbation process for detecting the degree of deterioration, and a correction coefficient H (broken line) determined by the target air-fuel ratio and the output signal of the oxygen concentration sensor 90. , Oxygen storage capacity (OSR) at the time of rich instruction, oxygen storage capacity (OSL) (solid line) at the time of rich instruction, and O2 amount (single point chain line) as the inflow oxygen amount on the upstream side of the catalyst device C are shown. .. In the present embodiment, the correction coefficient H is controlled by three elements: the deviation between the target air-fuel ratio and the air-fuel ratio on the downstream side of the catalyst by the oxygen concentration sensor 90, and its integration and differentiation. Before deterioration, the difference between the air-fuel ratio on the downstream side of the catalyst by the oxygen concentration sensor 90 and the target air-fuel ratio is relatively large. Therefore, if the correction coefficient H is increased to adjust it, the downstream side of the catalyst by the oxygen concentration sensor 90 The air-fuel ratio on the side overshoots. In the deteriorated NG catalyst, the air-fuel ratio on the downstream side of the catalyst by the oxygen concentration sensor 90 follows the target air-fuel ratio faster than that of the new catalyst before deterioration, and overshoot does not occur.

The AFR as the air-fuel ratio on the upstream side of the catalyst device C is calculated by the formula of AFR = 14.5 ÷ K × H. At this time, 14.5: theoretical air-fuel ratio, K: coefficient indicating the degree of transition to the rich side or lean side in the perturbation process for detecting the degree of deterioration, H: target air-fuel ratio and output of the oxygen concentration sensor 90. It is a correction coefficient determined by the signal.

Specifically, at t = A in FIG. 6, K = 1.025 and H = 0.99 at the time of the 2.5% rich instruction of the perturbation process. The correction coefficient H is calculated by performing PID control with respect to the deviation from the target air-fuel ratio. This makes it possible to calculate the correction coefficient using general feedback processing.
From the above, AFR = 14.5 ÷ 1.025 × 0.99 = 14.005.

On the other hand, at the time point B in FIG. 6, K = 0.975 and H = 1.01 when the 2.5% lean instruction of the perturbation process is performed. From the above, AFR = 14.5 ÷ 0.975 × 1.01 = 15.02. From the above, the air-fuel ratio on the upstream side of the catalyst device C is calculated by the formula of AFR = 14.5 ÷ K × H.

Next, the pre-catalyst oxygen amount calculation unit 102 obtains O2 as the inflow oxygen amount on the upstream side of the catalyst device C by the formula of O2 = GAIR × (1-14.5 ÷ AFR). At this time, GAIR: the amount of air per cycle.

Specifically, at the time point A in FIG. 6, AGAIR: 1 mg, and when the 2.5% rich instruction of the perturbation treatment is given, when AFR: 14.005, O2 = 1 × (1-14.5 ÷). 14.005) = -0.0353 mg (when rich, it is negative because it is on the reducing side).

On the other hand, at time point B in FIG. 6, when the 2.5% lean instruction of the perturbation treatment is given, in the case of AFR: 15.02, O2 = 1 × (1-14.5 ÷ 15.02) = 0.0346 mg. Will be. From the above, the amount of inflow oxygen on the upstream side of the catalyst device C is calculated by the calculation formula of O2 = GAIR × (1-14.5 ÷ AFR).

The pre-catalyst oxygen amount integrating unit 103 obtains the oxygen storage capacity (OSR) at the time of rich instruction and the oxygen storage capacity (OSL) at the time of rich instruction by integrating the calculated inflow oxygen amount, and obtains the oxygen storage capacity (OSL) at the time of rich instruction. Perform deterioration diagnosis.

As described above, according to the catalyst deterioration diagnostic apparatus according to the present invention, it is based on the oxygen concentration sensor 90 provided on the downstream side of the catalyst device C provided in the exhaust pipe 19 of the engine E and the output signals of the oxygen concentration sensor 90. In the control unit 100 for diagnosing the degree of deterioration of the catalyst device C, the air-fuel ratio of the air-fuel mixture supplied to the engine E is alternately set toward the target air-fuel ratio set on the rich side and the lean side from the stoichiometric air-fuel ratio. The control unit 100 includes a patrol means 105 that performs a transitional patrol process, and the control unit 100 is in the air on the upstream side of the catalyst device C based on the target air-fuel ratio and the output signal of the oxygen concentration sensor 90 during the perturbation process. Since the fuel ratio is estimated and detected, it is possible to detect the degree of deterioration of the catalyst device C with only one oxygen concentration sensor 90 provided on the downstream side of the catalyst device.

The form of the motorcycle, the shape and structure of the catalyst device and the oxygen concentration sensor, the configuration of the control unit, the transition concentration in the patrol processing, etc. are not limited to the above embodiment and can be changed in various ways. The catalyst deterioration diagnostic apparatus according to the present invention can be applied to various internal combustion engines having a catalyst apparatus and an oxygen concentration sensor.

1 ... Motorcycle, 19 ... Exhaust pipe, 74 ... Indicator, 90 ... Oxygen concentration sensor, 100 ... Control unit, 101 ... Pre-catalyst air-fuel ratio calculation unit, 102 ... Pre-catalyst oxygen amount calculation unit, 103 ... Pre-catalyst oxygen amount integration Part, 104 ... Catalyst diagnosis unit, 105 ... Perturbation means, E ... Engine, C ... Catalyst device, AFR ... Air-fuel ratio on the upstream side of the catalyst device, K ... Degree of transition to the rich side or lean side in the perturbation process. Factor indicating, H ... Correction coefficient determined by the target air-fuel ratio and the output signal of the oxygen concentration sensor, O2 ... Amount of inflow oxygen on the upstream side of the catalyst device, GAIR ... Amount of air per cycle

Claims

The oxygen concentration sensor (90) provided on the downstream side of the catalyst (C) provided in the exhaust pipe (19) of the engine (E) and the catalyst (C) based on the output signals of the oxygen concentration sensor (90). In a catalyst deterioration diagnostic apparatus having a control unit (100) for diagnosing the degree of deterioration,
The engine (E) is provided with a patrol means (105) for performing a patrol process in which the air-fuel ratio of the air-fuel mixture supplied to the engine (E) is alternately changed toward the target air-fuel ratio set on the rich side and the lean side from the stoichiometric air-fuel ratio. ,
During the perturbation process, the control unit (100) estimates and detects the air-fuel ratio on the upstream side of the catalyst (C) based on the target air-fuel ratio and the output signal of the oxygen concentration sensor (90). A catalyst deterioration diagnostic device characterized by
The AFR as the air-fuel ratio on the upstream side of the catalyst (C) has a theoretical air-fuel ratio of 14.5 and a coefficient indicating the degree of transition to the rich side or lean side in the perturbation treatment for detecting the degree of deterioration. When the correction coefficient determined by the target air-fuel ratio and the output signal of the oxygen concentration sensor (90) is H, the following calculation formula AFR = 14.5 ÷ K × H
The catalyst deterioration diagnostic apparatus according to claim 1, wherein the catalyst deterioration diagnostic apparatus is required.
The catalyst deterioration diagnostic apparatus according to claim 2, wherein the correction coefficient is calculated by performing PID control on a deviation between the target air-fuel ratio and the output signal of the oxygen concentration sensor (90). ..
O2 as the amount of inflow oxygen on the upstream side of the catalyst (C) is calculated by the following formula O2 = GAIR × (1-14.5 ÷ AFR) when the amount of air per cycle is GAIR.
The catalyst deterioration diagnostic apparatus according to claim 2 or 3, wherein the catalyst deterioration diagnostic apparatus is obtained.
The fourth aspect of claim 4, wherein the control unit (100) calculates the oxygen adsorption capacity of the catalyst (C) by integrating the amount of inflow oxygen and diagnoses the deteriorated state of the catalyst (C). Catalyst deterioration diagnostic equipment.