CN115244283B

CN115244283B - Catalyst degradation diagnosis device

Info

Publication number: CN115244283B
Application number: CN202080097947.2A
Authority: CN
Inventors: 藤田晋二
Original assignee: Honda Motor Co Ltd
Current assignee: Honda Motor Co Ltd
Priority date: 2020-03-05
Filing date: 2020-03-05
Publication date: 2023-08-08
Anticipated expiration: 2040-03-05
Also published as: WO2021176671A1; JPWO2021176671A1; JP7372440B2; BR112022017146A2; CN115244283A

Abstract

Provided is a catalyst degradation diagnosis device capable of detecting the degree of degradation of a catalyst device with 1 oxygen concentration sensor. The catalyst degradation diagnosis device includes: an oxygen concentration sensor (90) provided on the downstream side of a catalyst (C) provided in an exhaust pipe (19) of an engine (E); and a control unit (100) for diagnosing the degree of deterioration of the catalyst (C) on the basis of the output signal of the oxygen concentration sensor (90), wherein the catalyst deterioration diagnosis device is provided with a perturbation means (105), and wherein the perturbation means (105) performs a perturbation process for alternately shifting the air-fuel ratio of the mixture gas supplied to the engine (E) to a target air-fuel ratio, wherein the target air-fuel ratio is set to the rich side and the lean side of the stoichiometric air-fuel ratio. A 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) during the perturbation process.

Description

Catalyst degradation diagnosis device

Technical Field

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

Background

Conventionally, a catalyst degradation diagnosis device that detects the degree of degradation of a catalyst device provided in an exhaust pipe of an engine is known.

Patent document 1 discloses the following constitution: oxygen concentration sensors are disposed on the upstream side and the downstream side of the catalyst device, respectively, and the degree of deterioration of the catalyst device is detected based on a change in the output signal of the oxygen concentration sensor when the air-fuel ratio is switched to the rich side and the lean side.

Prior art literature

Patent literature

Patent document 1: japanese patent laid-open No. 2007-285288

Disclosure of Invention

Problems to be solved by the invention

However, in the configuration of patent document 1, since 2 oxygen concentration sensors are required and costs are incurred, a configuration in which the catalyst degradation degree is performed with 1 oxygen concentration sensor is sought.

The present invention aims to solve the problems of the prior art and to provide a catalyst degradation diagnosis device capable of detecting the degradation degree of a catalyst device by 1 oxygen concentration sensor.

Means for solving the problems

In order to achieve the above object, the 1 st aspect of the present invention is a catalyst degradation diagnosis device comprising: an oxygen concentration sensor (90) provided on the downstream side of a catalyst (C) provided in an exhaust pipe (19) of an engine (E); and a control unit (100) for diagnosing the degree of deterioration of the catalyst (C) based on the output signal of the oxygen concentration sensor (90), wherein the catalyst deterioration diagnosis device is provided with a perturbation means (105), wherein the perturbation means (105) performs a perturbation process for shifting the air-fuel ratio of the mixture gas supplied to the engine (E) alternately to a target air-fuel ratio, which is set to the rich side and the lean side of the stoichiometric air-fuel ratio, and wherein 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) during the perturbation process.

In claim 2, when the stoichiometric air-fuel ratio is set to 14.5, a coefficient indicating a degree of transition to the rich side or the lean side in the perturbation process for detecting the degree of degradation is set to K, and a correction coefficient determined from the target air-fuel ratio and the output signal of the oxygen concentration sensor (90) is set to H, AFR, which is the air-fuel ratio on the upstream side of the catalyst (C), is obtained by the following expression: afr=14.5++k×h.

In addition, in claim 3, the correction coefficient is calculated by PID control for a deviation of the target air-fuel ratio from an output signal of the oxygen concentration sensor (90).

In addition, in the 4 th aspect, when the air amount per 1 cycle is GAIR, O2, which is the inflow oxygen amount on the upstream side of the catalyst (C), is obtained by the following expression: O2=GAIR× (1-14.5. AFR).

Further, in the 5 th aspect, the control portion (100) calculates the oxygen adsorption capacity of the catalyst (C) by accumulating the inflow oxygen amount, and diagnoses the deterioration state of the catalyst (C).

ADVANTAGEOUS EFFECTS OF INVENTION

According to the 1 st aspect, the catalyst degradation diagnosis device has: an oxygen concentration sensor (90) provided on the downstream side of a catalyst (C) provided in an exhaust pipe (19) of an engine (E); and a control unit (100) for diagnosing the degree of deterioration of the catalyst (C) based on the output signal of the oxygen concentration sensor (90), wherein the catalyst deterioration diagnosis device is provided with a perturbation means (105), wherein the perturbation means (105) performs a perturbation process for shifting the air-fuel ratio of the mixture gas supplied to the engine (E) alternately to a target air-fuel ratio, which is set to the rich side and the lean side of the stoichiometric air-fuel ratio, and wherein the control unit (100) can estimate and detect 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) during the perturbation process, whereby the degree of deterioration of the catalyst can be detected by only 1 oxygen concentration sensor provided on the downstream side of the catalyst.

According to claim 2, when the stoichiometric air-fuel ratio is set to 14.5, a coefficient indicating a degree of transition to the rich side or the lean side in the perturbation process for detecting the degree of deterioration is set to K, and a correction coefficient determined by the target air-fuel ratio and the output signal of the oxygen concentration sensor (90) is set to H, AFR, which is the air-fuel ratio on the upstream side of the catalyst (C), is obtained by the following equation: afr=14.5++kxh, whereby the air-fuel ratio on the upstream side of the catalyst can be calculated with a simple expression.

According to claim 3, the correction coefficient is calculated by PID control for the deviation of the target air-fuel ratio from the output signal of the oxygen concentration sensor (90), whereby the correction coefficient can be calculated using normal feedback processing.

According to claim 4, when the air amount per 1 cycle is GAIR, O2, which is the inflow oxygen amount on the upstream side of the catalyst (C), is obtained by the following expression: o2=gair× (1-14.5 ≡afr), whereby the inflow oxygen amount on the upstream side of the catalyst can be calculated by a simple equation.

According to the 5 th aspect, the control section (100) calculates the oxygen adsorption capacity of the catalyst (C) by accumulating the amount of inflow oxygen and diagnoses the deterioration state of the catalyst (C), whereby the degree of deterioration of the catalyst can be detected by only 1 oxygen concentration sensor provided on the downstream side of the catalyst.

Drawings

Fig. 1 is a left side view of a motorcycle as a saddle-ride type vehicle according to an embodiment of the present invention.

Fig. 2 is a cross-sectional view of an expanded diameter portion provided midway in the exhaust pipe.

Fig. 3 is a schematic diagram showing a relationship between an engine and an oxygen concentration sensor.

Fig. 4 is a block diagram showing the configuration of a control unit that performs degradation diagnosis of the catalyst device.

Fig. 5 is a graph illustrating the responsiveness of the catalyst device before and after degradation.

Fig. 6 is a timing chart when degradation diagnosis is performed on the catalyst device after degradation.

Fig. 7 is a timing chart when degradation diagnosis is performed on the catalyst device before degradation.

Detailed Description

Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. Fig. 1 is a left side view of a motorcycle 1 as a saddle-ride type vehicle according to an embodiment of the present invention. A head pipe 12 rotatably supporting a steering system 10 is attached to a front end of a body frame 2 of a motorcycle 1 as a saddle-ride type vehicle. A steering handle 6 is attached to the upper end of the steering system 10 via a roof rail, not shown. The top beam that rotates integrally with the steering system 10 supports a pair of left and right front forks 16 together with a bottom beam, not shown, that is fixed to the steering system 10 at the lower portion of the head pipe 12. The front wheel WF including the brake disc 35 is rotatably journaled at the lower end of the front fork 16.

A parallel two-cylinder engine E in which a lower portion of a cylinder head 18 is supported by a hanger 17 extending downward from the rear of a head pipe 12 is arranged at the lower portion of a 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 of engine cooling water is disposed in front of the hanger 17.

The vehicle body frame 2 supports the engine E at the upper and rear portions of the engine E, and pivotally supports the swing arm 24 by a pivot 21 so as to be swingable. A pair of foot pedals 23 for the driver are provided below the pivot plate 21a for pivotally supporting the pivot shaft 21, and a folding type step 21b for the fellow passenger is disposed on the foot support 21c above and behind the foot pedals. A main support 22 for automatically standing the rear wheel WR of the motorcycle 1 while standing on the air and a side support 140 for automatically standing the vehicle body obliquely to the left are attached below the step plate 23. The main bracket 22 and the side brackets 140 are swung substantially 90 degrees to the vehicle body rear side to be in the housed state.

An exhaust device 20 for purifying and silencing exhaust gas from the engine E and discharging the same rearward is attached to a lower portion of the body of the motorcycle 1. The exhaust device 20 includes an exhaust pipe 19 connected to an exhaust port of the cylinder block and guiding exhaust gas rearward, and a muffler 26 connected to a rear end of the exhaust pipe 19. An exhaust pipe cover 5a is disposed below and in front of the cylinder head 18 to cover the front and side of the exhaust pipe 19. The swing arm 24 pivotally supported by the pivot shaft 21 is suspended from the vehicle body frame 2 by a rear cushion portion, not shown. The driving force of the engine E is transmitted to a rear wheel WR rotatably journaled at the rear end portion of the swing arm 24 via a drive chain 25.

A storage box 4 is provided above the engine E and at a position covered by a side cowl 5 as an exterior member, the storage box being inserted from the large-sized opening/closing cover 3. A headlight 13 is disposed in front of the side cowl 5, and a pair of left and right flash lamps 11 and a windshield 9 are disposed above the headlight 13. The left and right steering handles 6 are respectively provided with a joint cover 8 and a rearview mirror 7. A pair of left and right fog lamps 14 are mounted at positions on the outer sides of the front fork 16 in the vehicle width direction under the side cowl 5, and a front fender 36 for preventing splash mud of the vehicle body is mounted above the front wheel WF.

A rear frame 29 supporting a fuel tank 28 and the like is mounted behind the vehicle body frame 2. The rear frame 29 is covered on the left and right by a seat cover 31, and a driver seat 27 and a passenger seat 30 are disposed on the upper portion thereof. A tail lamp device 32 is attached to the rear end of the seat cover 31, and a rear fender 34 extending rearward and downward from the seat cover 31 supports a rear flasher lamp 33.

Fig. 2 is a cross-sectional view of the expanded portion 61 provided in the middle of the exhaust pipe 19. The catalyst device C is accommodated in the enlarged diameter portion 61, and the oxygen concentration sensor 90 is disposed behind the catalyst device C. The diameter-enlarged portion 61 is configured such that the catalyst device C is held inside the front outer tube 76 via the spacer 75, and the rear end portions of the catalyst device C and the front outer tube 76 are welded and fixed to the outer peripheral surface of the funnel-shaped rear outer tube 78 by the weld bead B. The oxygen concentration sensor 90 is held by screwing to a base 86 as a mounting table, and the base 86 is welded to the rear outer tube 78.

The oxygen concentration sensor 90 can employ an LAF sensor that can linearly detect a change in oxygen concentration or an O2 sensor that detects only a case at the stoichiometric air-fuel ratio by inverting the output value with the stoichiometric air-fuel ratio as a boundary. The oxygen concentration sensor 90 may be a sensor with a heater, and the sensor may realize optimal temperature control by using the heater controlled by the control unit 100.

Fig. 3 is a schematic diagram showing a 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 as a fuel injection device is provided in an intake pipe 56 of the engine E, and an intake air amount sensor 55 is disposed upstream thereof. 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 based on signals from the air amount detection unit 58 and the control unit 100 based on information on the throttle operation and the engine speed, and performs combustion at an appropriate air-fuel ratio.

In general, the degradation diagnosis of the catalyst device C is performed by 2 sensors, that is, 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, the change associated with the deterioration of the catalyst device C is detected focusing on the relationship between the sensor output of the upstream-side oxygen concentration sensor and the sensor output of the downstream-side oxygen concentration sensor. For example, in the method focusing on the decrease in the adsorption rate of oxygen associated with the deterioration of the catalyst device C, when the air-fuel ratio is feedback-controlled based on the output of the downstream-side oxygen concentration sensor, the response time until the oxygen concentration in the exhaust gas changes due to the feedback control changes due to the influence of the deterioration, and therefore, it is possible to determine the deterioration state of the catalyst by determining whether or not the period of change in the output of the downstream-side oxygen concentration sensor corresponds to the preset catalyst deterioration condition. Specifically, a counting method of counting the number of times the downstream side oxygen concentration sensor makes a predetermined change in a predetermined time period can be used.

Such degradation diagnosis processing is accompanied by execution of a perturbation processing for alternately shifting the air-fuel ratio of the internal combustion engine to the rich side and the lean side. Specifically, the degradation of the catalyst device C is detected by repeating the following operations: an observation is made as to whether or not the accumulated oxygen amount exceeds a threshold value using the upstream side oxygen concentration sensor while the air-fuel ratio is switched to the lean side until the value of the downstream side oxygen concentration sensor reaches a predetermined value, and then an observation is made as to whether or not the accumulated oxygen amount exceeds the threshold value using the upstream side oxygen concentration sensor while the air-fuel ratio is switched to the rich side until the value of the downstream side oxygen concentration sensor reaches a predetermined value. In the case of the normal catalyst device C, the catalyst device C is able to accumulate during the perturbation process, but if the catalyst device C is deteriorated, the lean operation is performed so as to supply oxygen in an amount that cannot be accumulated, and then the rich operation is switched to the rich operation to perform the rich operation so as to release substantially all the accumulated oxygen. As described above, if the catalyst device C is not degraded, the output of the oxygen concentration sensor 90 is not substantially changed, but in the case of degradation, the output of the oxygen concentration sensor 90 is increased, so that degradation diagnosis can be realized.

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 side oxygen concentration sensor, and the degradation diagnosis of the catalyst device C is performed based on the estimated and detected value.

Fig. 4 is a block diagram showing the configuration of the control unit 100 for performing degradation diagnosis of the catalyst device C. The control unit 100 includes a perturbation mechanism 105, a pre-catalyst air-fuel ratio calculation unit 101, a pre-catalyst oxygen amount calculation unit 102, a pre-catalyst oxygen amount accumulation unit 103, and a catalyst diagnosis unit 104. The output signal of the oxygen concentration sensor 90 is input to the pre-catalyst air-fuel ratio calculation unit 101. The output signal of the air amount sensor 55 is input to the pre-catalyst oxygen amount calculation unit 102. The catalyst diagnosis unit 104 is configured to notify the occupant by an indicator 74 provided to a meter device or the like when it is determined that the catalyst device C is in a predetermined degradation state.

The perturbation mechanism 105 executes a perturbation process of shifting the air-fuel ratio of the internal combustion engine to the rich side and the lean side. The pre-catalyst air-fuel ratio calculation unit 101 obtains AFR, which is the air-fuel ratio on the upstream side of the catalyst device C, from an expression of afr=14.5++k×h.

Fig. 5 is a graph illustrating the responsiveness of the catalyst device C before and after degradation. The catalyst device C after degradation has a lower purge rate and a lower oxygen storage capacity than the catalyst device C before degradation, and thus the response of the oxygen concentration sensor 90 provided downstream of the catalyst becomes faster. As described above, the perturbation process repeatedly performs the following operations: if the catalyst device C is normal, the oxygen can be stored, and if the catalyst device C is deteriorated, the lean operation is performed so as to supply oxygen in an amount that cannot be stored, and then the operation is switched to the rich operation, and the rich operation is performed so as to release substantially all of the stored oxygen. If this perturbation process is performed, the following differences occur: the output of the oxygen concentration sensor 90 is substantially unchanged before the catalyst device C is deteriorated, and the output of the oxygen concentration sensor 90 is increased after the catalyst device C is deteriorated.

Fig. 6 is a timing chart of degradation diagnosis of the catalyst device C after degradation. Fig. 7 is a timing chart of the degradation diagnosis of the catalyst device C before degradation. In the two timing charts, the estimated air-fuel ratio on the upstream side of the catalyst device C (solid line), the target air-fuel ratio (solid line), the air-fuel ratio on the downstream side of the catalyst based on the oxygen concentration sensor 90 (two-dot chain line), the coefficient indicating the degree of transition to the rich side or the lean side in the perturbation process for detecting the degree of degradation (solid line), the correction coefficient H (broken line) determined from the target air-fuel ratio and the output signal of the oxygen concentration sensor 90, the oxygen storage capacity at the time of rich indication (OSR), the oxygen storage capacity at the time of lean indication (OSL) (solid line), the O2 amount on the upstream side of the catalyst device C as the amount of inflow oxygen (one-dot chain line) are shown from top to bottom. In the present embodiment, the operation is performed based on 3 elements, that is, the deviation between the target air-fuel ratio and the air-fuel ratio on the downstream side of the catalyst obtained by the oxygen concentration sensor 90, and the integration and differentiation thereof. Since the air-fuel ratio on the downstream side of the catalyst obtained by the oxygen concentration sensor 90 before degradation greatly deviates from the target air-fuel ratio, if the correction coefficient H is increased in order to adjust the deviation, the air-fuel ratio on the downstream side of the catalyst obtained by the oxygen concentration sensor 90 overshoots. In the NG catalyst after degradation, the air-fuel ratio on the downstream side of the catalyst obtained by the oxygen concentration sensor 90 follows the target air-fuel ratio faster than the new catalyst before degradation and does not overshoot.

AFR, which is the air-fuel ratio on the upstream side of the catalyst device C, is obtained by an expression of afr=14.5++k×h. At this time, 14.5: theoretical air-fuel ratio, K: a coefficient indicating a degree of transition to the rich side or the lean side in the perturbation process for detecting the degree of deterioration, H: a correction coefficient determined from the output signal of the target air-fuel and oxygen concentration sensor 90.

Specifically, at t=a of fig. 6, at 2.5% rich indication of perturbation treatment, k=1.025, h=0.99. The correction coefficient H is calculated by PID control for deviation from the target air-fuel ratio. Thus, the correction coefficient can be calculated using a normal feedback process.

Thus, afr=14.5++1.025×0.99= 14.005.

On the other hand, at time B of fig. 6, at the 2.5% lean indication of the perturbation process, k=0.975, h=1.01. Thus, afr=14.5++0.975×1.01=15.02. Thus, the air-fuel ratio on the upstream side of the catalyst device C is calculated by the expression afr=14.5++kxh.

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 expression of o2=gair× (1-14.5/AFR). At this time, GAIR: air amount per 1 cycle.

Specifically, at time a of fig. 6, at AGAIR:1mg and 2.5% oil rich indication of perturbation treatment, at AFR:14.005, O2=1× (1-14.5++ 14.005) = -0.0353mg (reducing side in rich oil, hence negative).

On the other hand, at time B of fig. 6, at 2.5% lean indication of the perturbation process and AFR: in the case of 15.02, o2=1× (1-14.5≡15.02) = 0.0346mg. Thus, the amount of oxygen flowing in upstream of the catalyst device C is calculated by the equation of o2=gair× (1-14.5++afr).

The pre-catalyst oxygen amount accumulating unit 103 accumulates the calculated inflow oxygen amount to determine an oxygen storage capacity (OSR) at the time of the rich instruction and an oxygen storage capacity (OSL) at the time of the lean instruction, thereby performing degradation diagnosis of the catalyst device C.

As described above, the catalyst degradation diagnosis device according to the present invention has: an oxygen concentration sensor 90 provided on the downstream side of a catalyst device C provided in the exhaust pipe 19 of the engine E; and a control unit 100 for diagnosing the degree of deterioration of the catalyst device C based on the output signal of the oxygen concentration sensor 90, wherein the catalyst deterioration diagnosis device includes a perturbation means 105, wherein the perturbation means 105 performs perturbation processing for shifting the air-fuel ratio of the mixture gas supplied to the engine E alternately to a target air-fuel ratio set to the rich side and the lean side of the stoichiometric air-fuel ratio, and wherein the control unit 100 estimates and detects the air-fuel ratio 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 processing, so that the degree of deterioration of the catalyst device C can be detected using only 1 oxygen concentration sensor 90 provided on the downstream side of the catalyst device.

The mode 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 perturbation process, and the like are not limited to the above embodiment, and various modifications are possible. The catalyst degradation diagnosis device of the present invention can be applied to various internal combustion engines having a catalyst device and an oxygen concentration sensor.

Description of the reference numerals

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 accumulation unit, 104 … catalyst diagnosis unit, 105 … perturbation mechanism, E … engine, C … catalyst device, air-fuel ratio on the upstream side of AFR … catalyst device, coefficient K … indicating transition degree to rich side or lean side in perturbation treatment, correction coefficient of H … determined by target air-fuel ratio and output signal of oxygen concentration sensor, inflow oxygen amount on the upstream side of O2 … catalyst device, air amount per 1 cycle of GAIR …

Claims

1. A catalyst degradation diagnosis device is provided with:

an oxygen concentration sensor (90) provided on the downstream side of a catalyst (C) provided in an exhaust pipe (19) of an engine (E); and a control unit (100) for diagnosing the degree of deterioration of the catalyst (C) based on the output signal of the oxygen concentration sensor (90), wherein the catalyst deterioration diagnosis device is characterized in that,

a perturbation means (105) is provided, wherein the perturbation means (105) performs a perturbation process of alternately shifting the air-fuel ratio of the mixture gas supplied to the engine (E) to a target air-fuel ratio set to a rich side and a lean side of a stoichiometric air-fuel ratio,

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) during the perturbation process,

assuming that the theoretical air-fuel ratio is 14.5, a coefficient indicating the degree of transition to the rich side or the lean side in the perturbation process for detecting the degree of degradation is K, and a correction coefficient determined by the target air-fuel ratio and the output signal of the oxygen concentration sensor (90) is H, AFR, which is the air-fuel ratio on the upstream side of the catalyst (C), is obtained by the following equation:

AFR＝14.5÷K×H，

when the air amount per 1 cycle is GAIR, O2, which is the inflow oxygen amount upstream of the catalyst (C), is obtained by the following equation:

O2＝GAIR×(1-14.5÷AFR)。

2. the catalyst degradation diagnosis device according to claim 1, wherein,

the correction coefficient is calculated by PID control for the deviation of the target air-fuel ratio from the output signal of the oxygen concentration sensor (90).

3. The catalyst degradation diagnosis device according to claim 1 or 2, characterized in that,

the control unit (100) calculates the oxygen adsorption capacity of the catalyst (C) by accumulating the amount of inflow oxygen, and diagnoses the deterioration state of the catalyst (C).