Abnormality diagnostic device for catalytic converter

Abstract

To detect an abnormality of a catalyst carrier holding material.SOLUTION: An abnormality diagnostic device detects an abnormality of a catalytic converter 50 that includes: a catalyst carrier 51 for purifying exhaust gas discharged from an internal combustion engine of a vehicle; a converter case 52 that accommodates the catalyst carrier 51; and a catalyst carrier holding material that holds the catalyst carrier 51 in the converter case 52 by covering an outer peripheral surface of the catalyst carrier 51. The abnormality diagnostic device includes: an exhaust pressure sensor 45 disposed downstream of the catalytic converter 50 to detect exhaust pressure of exhaust gas; and a control device 12 that detects an abnormality of the catalyst carrier holding material when a value detected by the exhaust pressure sensor 45 during traveling of the vehicle is less than a predetermined value.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to an abnormal diagnosis device for a catalytic converter.

Background Art

[0002] Conventionally, vehicles have used catalytic converters to purify harmful components contained in exhaust gas. A catalytic converter is configured by holding a catalyst carrier of a vehicle exhaust gas purification catalyst in a converter case using a holding mat as a catalyst carrier holding material. The holding mat is configured by combining a cylindrical shape or a plurality of plate-like members, and holds the catalyst carrier by covering the outer peripheral surface of the catalyst carrier.

[0003] Patent Document 1 discloses a catalytic converter configured by winding a holding mat around the outer peripheral surface of a honeycomb structure body and press-fitting and fixing it to a cylindrical case as a converter case. In addition to the role of preventing displacement of the catalyst carrier due to vibrations during vehicle travel or thermal expansion of the converter case, the holding mat also plays a role of preventing leakage of unpurified exhaust gas from the outer periphery of the catalyst carrier.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Here, when assembling the holding mat to the converter case, there is a possibility that the holding mat may be curled or the like in part due to poor assembly. In such a case, the exhaust gas flow collides locally with a part of the holding mat, and the holding mat may be damaged over a long period of driving.

[0006] The present invention has been made in view of the above-described problems, and an object thereof is to enable detection of an abnormality in a catalyst carrier holding member when an abnormality such as a defect occurs in the catalyst carrier holding member.

Means for Solving the Problems

[0007] The present invention is an abnormality diagnosis device for detecting an abnormality in a catalytic converter including a catalyst carrier that purifies exhaust gas discharged from an internal combustion engine of a vehicle, a converter case that houses the catalyst carrier, and a catalyst carrier holding member that holds the catalyst carrier in the converter case by covering an outer peripheral surface of the catalyst carrier, the abnormality diagnosis device being disposed downstream of the catalytic converter and including pressure detection means for detecting an exhaust pressure of the exhaust gas, and control means for detecting an abnormality in the catalyst carrier holding member when a value detected by the pressure detection means is less than a threshold value during travel of the vehicle.

Effects of the Invention

[0008] According to the present invention, when an abnormality such as a defect occurs in the catalyst carrier holding member, the abnormality in the catalyst carrier holding member can be detected.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Embodiments for Carrying Out the Invention

[0010] An embodiment according to the present invention is an abnormality diagnosis device that detects an abnormality in a catalytic converter 50 including a catalyst carrier 51 that purifies exhaust gas discharged from an internal combustion engine of a vehicle, a converter case 52 that houses the catalyst carrier 51, and a catalyst carrier holding member that holds the catalyst carrier 51 in the converter case 52 by covering the outer peripheral surface of the catalyst carrier 51. The abnormality diagnosis device is disposed downstream of the catalytic converter 50 and includes an exhaust pressure sensor 45 that detects the exhaust pressure of the exhaust gas, and a control device 12 that detects an abnormality in the catalyst carrier holding member when a value detected by the exhaust pressure sensor 45 is less than a predetermined value during vehicle travel. When an abnormality such as a defect occurs in the catalyst carrier holding member, the value detected by the exhaust pressure sensor 45 becomes low, so that an abnormality in the catalyst carrier holding member can be detected based on the value detected by the exhaust pressure sensor 45.

Example

[0011] Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a diagram showing a schematic configuration of a vehicle 10 that functions as an abnormality diagnosis device for a catalytic converter according to the present embodiment. Note that FIG. 1 is simplified for the sake of explanation to describe the present embodiment, and it is assumed that the vehicle has components that are not shown but are normally provided.

[0012] The vehicle 10 of the present embodiment includes an engine 11 as an internal combustion engine and a control device 12 that controls the engine 11 and related devices. The engine 11 will be described as a four-cylinder engine, but it may be a single-cylinder engine or a multi-cylinder engine other than four cylinders.

[0013] Vehicle 10 includes, as an intake system, an air cleaner 21, an intake pipe 22, an electronically controlled throttle valve 23, and an intake manifold 24. In the intake pipe 22, a MAF sensor 25 for detecting the intake air flow rate and a MAP sensor 26 for detecting the intake air pressure are disposed. The intake air purified by the air cleaner 21 flows through the intake pipe 22 into the intake manifold 24 and branches from the intake manifold 24 to flow into each cylinder of the engine 11. The control device 12 controls the electronically controlled throttle valve 23 based on the information detected by the MAF sensor 25 and the MAP sensor 26, so as to adjust the appropriate intake air amount to flow into each cylinder of the engine 11 according to the operating state of the vehicle 10 and the like.

[0014] Vehicle 10 includes, as a fuel supply system, fuel injectors 31a to 31d for injecting fuel. The fuel injectors 31a to 31d inject fuel toward the cylinders of the first cylinder to the fourth cylinder respectively. The fuel injected from the fuel injectors 31a to 31d is mixed with the intake air taken in from the intake system to generate an air-fuel mixture, and the generated air-fuel mixture flows into the cylinders of each cylinder of the engine 11.

[0015] In addition, the engine 11 is provided with ignition coils 32a to 32d corresponding to each cylinder. The ignition coils 32a to 32d apply a high voltage to the spark plugs provided in the combustion chambers communicating with the cylinders of each cylinder. When the spark plugs ignite, the air-fuel mixture in the combustion chamber ignites and burns. The control device 12 controls the ignition timing of the spark plugs by controlling the timing at which the ignition coils 32a to 32d apply a high voltage to the spark plugs. When the air-fuel mixture in the combustion chamber burns, the piston reciprocates in the cylinder of each cylinder of the engine 11, and the reciprocating motion of the piston is converted into the rotational motion of the crankshaft. The rotation of the crankshaft is transmitted to the drive shaft via the transmission, and the drive wheels connected to the drive shaft rotate, causing the vehicle 10 to travel. Further, the engine 11 is provided with a crank angle sensor 33 for detecting the rotational speed of the crankshaft and a coolant temperature sensor 34 for detecting the temperature of the coolant of the engine 11. The control device 12 controls the ignition timing of the spark plugs and calculates the engine speed based on the information detected by the crank angle sensor 33. In addition, the control device 12 determines whether the engine 11 is in a fully warmed-up state based on the temperature of the coolant detected by the coolant temperature sensor 34.

[0016] The vehicle 10 includes, as an exhaust system, an exhaust manifold 41, a catalytic converter 50, and a muffler 42. An AF sensor 43 for linearly detecting the oxygen concentration in the exhaust gas is disposed between the exhaust manifold 41 and the catalytic converter 50, and an O2 sensor 44 for detecting whether oxygen is contained in the exhaust gas is disposed between the catalytic converter 50 and the muffler 42. The control device 12 controls the electronic control throttle valve 23 and the fuel injectors 31a to 31d so that the air-fuel mixture becomes the stoichiometric air-fuel ratio based on the information detected by the AF sensor 43 and the O2 sensor 44. The exhaust gas generated by burning the air-fuel mixture in the combustion chamber of each cylinder flows into the exhaust manifold 41 and is purified by the catalytic converter 50. The exhaust gas purified by the catalytic converter 50 is discharged after being silenced by the muffler 42. Further, an exhaust pressure sensor 45 for detecting the exhaust pressure of the exhaust gas is disposed downstream of the catalytic converter 50.

[0017] The catalytic converter 50 includes a catalyst carrier 51, a converter case 52, and a holding mat 53 as a catalyst carrier holding member. The catalyst carrier 51 purifies the exhaust gas discharged from the engine 11 of the vehicle 10. The catalyst carrier 51 is, for example, a honeycomb structure in which a plurality of cells are formed inside, and ceramics are used as the material. The converter case 52 is cylindrical and houses the catalyst carrier 51 inside. The holding mat 53 holds the catalyst carrier 51 in the converter case 52 by covering the outer peripheral surface of the catalyst carrier 51. That is, the holding mat 53 is located between the inner peripheral surface of the converter case 52 and the outer peripheral surface of the catalyst carrier 51.

[0018] The vehicle 10 also includes an accelerator pedal 13 operated by the driver, an accelerator opening sensor 14 that detects the accelerator opening when the accelerator pedal 13 is operated, and a notification device 15. The accelerator opening sensor 14 detects the accelerator opening when the driver operates the accelerator pedal 13 and transmits the detected information to the control device 12. The notification device 15 notifies the driver of an abnormality in the catalytic converter 50 (or the holding mat 53) when an abnormality in the holding mat 53 is detected by the control device 12. The notification device 15 can use, for example, a display unit such as a display or a meter panel provided in the vehicle 10, a speaker, or the like.

[0019] The control device 12 controls the entire vehicle 10. The control device 12 can use, for example, an ECU (Electronic Control Unit). As a hardware configuration, the control device 12 includes a CPU, a ROM, a RAM, etc. Programs and predetermined information for controlling the vehicle 10, the engine 11, etc. are stored in advance in the ROM. The RAM is a work memory that temporarily stores programs and data. By the CPU reading out the programs stored in the ROM, expanding them in the RAM, and executing them, the vehicle 10, the engine 11, etc. are controlled. Further, the control device 12 of the present embodiment diagnoses an abnormality of the catalytic converter 50 by detecting an abnormality of the holding mat 53, more specifically. When the control device 12 detects an abnormality of the holding mat 53, it notifies the driver of the abnormality of the catalytic converter 50 (or the holding mat 53) via the notification device 15.

[0020] Next, the process of detecting an abnormality of the holding mat 53 by the control device 12 will be specifically described with reference to the flowcharts of FIGS. 2(a) and 2(b). The flowchart of FIG. 2(a) and the flowchart of FIG. 2(b) are realized by the ECU of the control device 12 executing a program.

[0021] When the engine 11 is started and the vehicle 10 is driven, the processes of the flowchart of FIG. 2(a) and the flowchart of FIG. 2(b) are started. First, in the flowchart of FIG. 2(a), in order not to erroneously detect an abnormality of the holding mat 53, before actually performing the detection process of the abnormality of the holding mat 53, it is determined whether the implementation conditions for performing the detection process are satisfied. The implementation conditions for performing the detection process are satisfied when the engine 11 is in a steady stable state rather than a transient state.

[0022] In S10, the control device 12 determines whether the engine 11 is in a fully warmed-up state, that is, whether warm-up is completed. Specifically, the control device 12 determines whether the temperature of the cooling water detected by the cooling water temperature sensor 34 is higher than a threshold value (predetermined temperature A). If the temperature of the cooling water is higher than the threshold value, the process proceeds to S11. On the other hand, if the temperature of the cooling water is equal to or lower than the threshold value, since the implementation conditions for performing the detection process are not satisfied, the process of the flowchart in Fig. 2(a) is terminated.

[0023] In S11, the control device 12 determines whether a certain engine load is generated in the engine 11. Specifically, the control device 12 determines whether the engine load is greater than a threshold value (predetermined load B). The control device 12 calculates the engine load based on the accelerator opening detected by the accelerator opening sensor 14. Note that the control device 12 may also calculate the engine load based on the ratio of the current intake air amount to the maximum intake air amount corresponding to the engine speed. If the engine load is greater than the threshold value, the process proceeds to S12. On the other hand, if the engine load is equal to or lower than the threshold value, since the implementation conditions for performing the detection process are not satisfied, the process of the flowchart in Fig. 2(a) is terminated.

[0024] In S12, the control device 12 determines whether a state where the change amount of the engine load remains constant continues. Specifically, the control device 12 determines whether a predetermined time Ta has elapsed in a state where the change amount of the engine load is smaller than a threshold value (predetermined range C). If the predetermined time Ta has elapsed in a state where the change amount of the engine load is smaller than the threshold value, the process proceeds to S13. On the other hand, if the change amount of the engine load becomes equal to or greater than the threshold value before the predetermined time Ta elapses, since the implementation conditions for performing the detection process are not satisfied, the process of the flowchart in Fig. 2(a) is terminated.

[0025] In S13, the control device 12 determines that the implementation conditions for performing the abnormality detection process of the holding mat 53 are satisfied. Specifically, the control device 12 turns on a flag indicating that the implementation conditions for performing the detection process are satisfied, and terminates the process of the flowchart in Fig. 2(a).

[0026] Next, in the flowchart of FIG. 2(b), the detection process for the abnormality of the holding mat 53 is actually performed. In S20, the control device 12 determines whether or not the implementation conditions for performing the detection process are satisfied. Specifically, when the flag indicating that the implementation conditions for performing the detection process are established is on, the control device 12 determines that the implementation conditions for performing the detection process are satisfied. If the implementation conditions for performing the detection process are satisfied, the process proceeds to S21. On the other hand, if the implementation conditions for performing the detection process are not satisfied, since there is a possibility of false detection of the abnormality of the holding mat 53, the process of the flowchart in FIG. 2(b) is terminated.

[0027] In S21, the control device 12 determines whether or not the negative pressure value of the exhaust pressure of the exhaust gas downstream of the catalytic converter 50 is smaller than the threshold value (predetermined pressure value D), that is, whether or not it is less than the threshold value. Here, if the holding mat 53 is missing due to running with the holding mat 53 assembled to the converter case 52 due to improper assembly, the unpurified exhaust gas flows out downstream of the catalytic converter 50 from the gap between the outer peripheral surface of the catalyst carrier 51 and the inner wall surface of the converter case 52. In this case, since the exhaust gas flows more easily than normal, the negative pressure value of the exhaust pressure decreases more than normal. Thus, if the negative pressure value of the exhaust pressure is less than the threshold value, there is a possibility that the holding mat 53 is abnormal. Therefore, if the negative pressure value of the exhaust pressure is less than the threshold value, the process proceeds to S22. On the other hand, if the negative pressure value of the exhaust pressure is equal to or greater than the threshold value, the process of the flowchart in FIG. 2(b) is terminated. The threshold value can be set, for example, based on the exhaust pressure measured when the holding mat 53 is actually missing, or based on the exhaust pressure when simulated to cause the holding mat 53 to be missing.

[0028] In S22, the control device 12 determines whether or not a predetermined time Tb has elapsed while the negative pressure value of the exhaust pressure of the exhaust gas downstream of the catalytic converter 50 is less than the threshold value. If the predetermined time Tb has elapsed while the negative pressure value of the exhaust pressure is less than the threshold value, the process proceeds to S23. On the other hand, if the negative pressure value of the exhaust pressure becomes equal to or greater than the threshold value before the predetermined time Tb elapses, the process of the flowchart in Fig. 2(b) ends. Depending on the driving situation, even when the holding mat 53 is not abnormal, a situation may occur where the negative pressure value of the exhaust pressure temporarily decreases. Therefore, by determining whether or not the predetermined time Tb has elapsed while the negative pressure value of the exhaust pressure is less than the threshold value, it is possible to prevent misdetection of an abnormality in the holding mat 53. Note that the predetermined time Tb can be set to a time longer than the time during which the negative pressure value of the exhaust pressure becomes less than the threshold value when the holding mat 53 is not missing, for example.

[0029] In S23, the control device 12 determines that the holding mat 53 is abnormal. Specifically, the control device 12 determines that an abnormality has occurred due to the holding mat 53 being missing. In this way, the control device 12 can detect an abnormality in the holding mat 53. In addition, the control device 12 notifies the driver of an abnormality in the catalytic converter 50 (or the holding mat 53) via the notification device 15. Therefore, the driver can recognize an abnormality in the catalytic converter 50 (or the holding mat 53).

[0030] When the process of S23 ends, the flowchart in Fig. 2(b) ends. Note that the control device 12 can sequentially detect an abnormality in the holding mat 53 by periodically executing the flowchart in Fig. 2(a) and the flowchart in Fig. 2(b).

[0031] Fig. 3 is a timing chart at each timing when the control device 12 performs the abnormality detection process of the holding mat 53. Here, it will be described assuming that the holding mat 53 is missing. Figure 3(a) shows the change in the temperature of the cooling water of the engine 11. Figure 3(b) shows the change in the engine load. Figure 3(c) shows the change in the negative pressure value in the exhaust pipe, that is, the negative pressure value of the exhaust gas pressure downstream of the catalytic converter 50. Figure 3(d) shows the determination of the fully warmed-up state. Figure 3(e) shows the determination of the establishment of the implementation conditions for performing the detection process. Figure 3(f) shows the determination of an abnormality in the holding mat 53.

[0032] First, in response to the engine 11 starting and the vehicle 10 traveling, the temperature of the cooling water of the engine 11 shown in Figure 3(a) gradually rises. When the temperature of the cooling water of the engine 11 becomes higher than the threshold value (predetermined temperature A) at time T0, it is determined that the engine 11 is in the fully warmed-up state as shown in Figure 3(d). Also, as shown in Figure 3(b), the engine load is gradually increasing. At time T1, when the engine load becomes larger than the threshold value (predetermined load B) and a predetermined time (T2 - T1) elapses in a state where the change amount of the engine load is smaller than the threshold value (predetermined range C), at time T2, it is determined that the implementation conditions for performing the detection process are satisfied as shown in Figure 3(e).

[0033] On the other hand, the negative pressure value of the exhaust pressure shown in Figure 3(c) is gradually decreasing because the holding mat 53 is missing. At time T2 when the implementation conditions for performing the detection process are satisfied, the negative pressure value of the exhaust pressure is already less than the threshold value (predetermined D) which is smaller than the threshold value (predetermined pressure value D). Here, when a predetermined time (T3 - T2) elapses in a state where the negative pressure value of the exhaust pressure is smaller than the threshold value (predetermined pressure value D), at time T3, as shown in Figure 3(f), it is determined that an abnormality has occurred due to the missing of the holding mat 53.

[0034] As described above, when an abnormality such as a defect occurs in the holding mat 53, a gap is formed between the outer peripheral surface of the catalyst carrier 51 and the inner wall surface of the converter case 52. At this time, the negative pressure value of the exhaust pressure detected by the exhaust pressure sensor 45 disposed downstream of the catalytic converter 50 due to the blow-by of the exhaust gas becomes low. Therefore, according to the present embodiment, the control device 12 can detect an abnormality in the holding mat 53 when the value detected by the exhaust pressure sensor 45 disposed downstream of the catalytic converter 50 is less than the threshold value during the running of the vehicle 10.

[0035] In addition, when the catalyst carrier 51 itself has a blockage of the carrier pores due to melting or the like, the negative pressure value of the exhaust pressure increases more than usual, unlike the case where the holding mat 53 is missing because the exhaust gas is less likely to flow than usual. Therefore, the case where the negative pressure value of the exhaust pressure decreases downstream of the catalytic converter 50 is due to the blow-by of the exhaust gas caused by the defect of the holding mat 53 of the catalyst carrier 51, and it can be estimated that there is an abnormality in the holding mat 53.

[0036] Further, according to the present embodiment, the control device 12 detects an abnormality in the holding mat 53 when the state where the value detected by the exhaust pressure sensor 45 is less than the predetermined value continues for a predetermined time during the running of the vehicle 10. By detecting an abnormality in the holding mat 53 when the state where the negative pressure value of the exhaust pressure is less than the threshold value continues for a predetermined time, false detection can be prevented.

[0037] In addition, according to this embodiment, when the engine 11 is in a steady-state stable condition, that is, when the engine 11 is in a fully warmed-up state and a predetermined time has elapsed in a state where the engine load is within a predetermined value ± a predetermined error, a detection process for detecting an abnormality of the holding mat 53 is performed. In a state where the engine load is too small, etc., the operating state of the engine 11 is unstable, and there are disturbances in intake and exhaust, etc., so it may not be possible to appropriately detect an abnormality of the holding mat 53. By performing the detection process for detecting an abnormality of the holding mat 53 in a steady-state stable condition as in this embodiment, the accuracy of detecting an abnormality of the holding mat 53 can be improved.

[0038] As described above, the embodiments according to the present invention have been described. However, the present invention is not limited to the above-described embodiments, and changes and the like are possible within the scope of the present invention.

Explanation of Reference Numerals

[0039] 10: Vehicle 11: Engine 12: Control device 15: Notification device 41: Exhaust manifold 45: Exhaust pressure sensor 50: Catalytic converter 51: Catalyst carrier 52: Converter case 53: Holding mat (catalyst carrier holding material)

Claims

1. A catalyst carrier for purifying exhaust gas discharged from an internal combustion engine of a vehicle, a converter case for housing the catalyst carrier, and a catalyst carrier holding member that holds the catalyst carrier in the converter case by covering an outer peripheral surface of the catalyst carrier, and an abnormality diagnosis device for detecting an abnormality of the catalytic converter, a pressure detection means disposed downstream of the catalytic converter for detecting an exhaust pressure of the exhaust gas, and a control means for detecting an abnormality of the catalyst carrier holding member when a value detected by the pressure detection means during running of the vehicle is less than a threshold value. An abnormality diagnosis device for a catalytic converter, characterized by comprising:

2. The control means, when a state in which a value detected by the pressure detection means during running of the vehicle is less than a predetermined value continues for a predetermined time, detects an abnormality of the catalyst carrier holding member. The abnormality diagnosis device for a catalytic converter according to claim 1, characterized by:

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