Exhaust gas purification device

Abstract

To provide an exhaust emission control device that enables enhancement of frequency for detecting an abnormality of an exhaust sensor.SOLUTION: An exhaust emission control device 1 includes: a three-way catalyst 31 for purifying exhaust gas to be discharged from an internal combustion engine 10; a particulate filter 32 for collecting particulate matters in exhaust gas; an exhaust sensor 33 for detecting a state value related to an air-fuel ratio of exhaust gas; and a control section that executes filter regeneration control for burning the collected particulate matters by controlling the air-fuel ratio in the exhaust passage and on the upstream side of the three-way catalyst 31 to a value larger than a theoretical air-fuel ratio when the accumulation amount of the particulate matters is specified amount or larger. The control section prohibits the filter regeneration control when an abnormality diagnosis prerequisite of the exhaust sensor 33 is satisfied, and determines an abnormality of the exhaust sensor 33 on the basis of a response time of the exhaust sensor 33 from start of fuel cut control until the state value reaches a specified value on the lean side from a specified air-fuel ratio that is equal to or smaller than the theoretical air-fuel ratio in a period when the filter regeneration control is prohibited.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an exhaust gas purification device, and more particularly to an exhaust gas purification device that purifies exhaust gas discharged from an internal combustion engine.

Background Art

[0002] In an internal combustion engine, feedback control of the air-fuel ratio is performed based on the output of an exhaust gas sensor that detects the state of exhaust gas discharged from the internal combustion engine. When an abnormality occurs in this exhaust gas sensor, it is necessary to perform an abnormality diagnosis of the exhaust gas sensor because the accuracy of the air-fuel ratio feedback control may decrease.

[0003] Patent Document 1 discloses an air-fuel ratio detection sensor abnormality diagnosis device including a reaction delay determination unit that determines that a reaction delay abnormality has occurred in an air-fuel ratio sensor when a reaction delay condition is satisfied a predetermined number of times, and a sensor abnormality diagnosis unit that diagnoses an abnormality of the air-fuel ratio sensor based on the determination result of the reaction delay determination unit. According to the technique described in Patent Document 1, it is described that it is possible to accurately determine that an abnormality has occurred in an air-fuel ratio detection sensor that detects the air-fuel ratio of exhaust gas.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] By the way, in the exhaust passage of an internal combustion engine, a three-way catalyst that purifies exhaust gas discharged from the internal combustion engine or a particulate filter that collects particulate matter in the exhaust gas may be provided. Since the particulate filter accumulates particulate matter inside during use and the passage resistance increases, filter regeneration control is performed to remove the particulate matter collected in the particulate filter by varying the air-fuel ratio.

[0006] In such particulate filter regeneration control, by supplying oxygen to the particulate filter, particulate matter collected in the particulate filter can be combusted and removed. Therefore, during filter regeneration control, the air-fuel ratio of the exhaust gas flowing into the particulate filter becomes an oxidizing atmosphere (lean).

[0007] On the other hand, when the exhaust gas is controlled to the lean side due to filter regeneration control, if an abnormality diagnosis of an exhaust gas sensor that detects the state value of the exhaust gas flowing into the particulate filter is performed, there is a risk of misdiagnosing an abnormality of the exhaust gas sensor. In order to prevent such misdiagnosis of the abnormality of the exhaust gas sensor, it may be considered to not perform the abnormality diagnosis of the exhaust gas sensor during filter regeneration control. However, in this case, there is a problem that the frequency of detecting an abnormality of the exhaust gas sensor decreases.

[0008] The present invention has been made to solve such problems, and an object thereof is to provide an exhaust gas purification device that increases the frequency of detecting an abnormality of an exhaust gas sensor.

Means for Solving the Problem

[0009] An exhaust gas purification device according to an embodiment is provided in an exhaust passage of an internal combustion engine, and includes a three-way catalyst that purifies exhaust gas discharged from the internal combustion engine, a particulate filter that is provided in the exhaust passage downstream of the three-way catalyst and collects particulate matter in the exhaust gas, an exhaust gas sensor that detects a state value related to the air-fuel ratio of the exhaust gas that has passed between the three-way catalyst and the particulate filter, and when the accumulation amount of the particulate matter collected by the particulate filter is equal to or greater than a predetermined amount, a control unit that executes filter regeneration control to burn the particulate matter collected by the particulate filter and regenerate the particulate filter by controlling the air-fuel ratio in the exhaust passage and upstream of the three-way catalyst to be greater than the theoretical air-fuel ratio. The control unit prohibits the filter regeneration control when the preconditions for the abnormality diagnosis of the exhaust gas sensor are satisfied, and based on the response time of the exhaust gas sensor from when the fuel cut control for stopping the fuel injection of the internal combustion engine is started until the state value reaches a predetermined value on the lean side from the specified air-fuel ratio that is equal to or less than the theoretical air-fuel ratio during the period when the filter regeneration control is prohibited, determines the abnormality of the exhaust gas sensor.

Effect of the Invention

[0010] According to the present invention, an exhaust gas purification device that increases the frequency of detecting an abnormality of an exhaust gas sensor can be provided.

Brief Description of the Drawings

[0011]

Figure 1

Figure 2

Mode for Carrying Out the Invention

[0012] Embodiment 1 Hereinafter, embodiments of the present invention will be described with reference to the drawings. Also, for clarity of explanation, the following description and drawings are appropriately simplified. What is shown in the drawings is a part of the whole, and many other configurations not shown are actually included. Further, in the following description, the same or equivalent elements are denoted by the same reference numerals, and redundant descriptions are omitted.

[0013] First, with reference to FIG. 1, the configuration of the exhaust gas purification device 1 according to the present embodiment will be described. FIG. 1 is a block diagram for explaining the configuration of the exhaust gas purification device according to Embodiment 1. FIG. 1 shows the main parts of the vehicle 100 related to the exhaust gas purification device 1. In the present embodiment, the case where the exhaust gas purification device 1 is applied to a vehicle 100 equipped with a gasoline engine will be described as an example.

[0014] The internal combustion engine 10 mounted on the vehicle 100 has a cylinder 11, a piston 12, an intake valve 13, an exhaust valve 14, a fuel injection valve 15, and a spark plug 16. Further, an intake passage 20 and an exhaust passage 30 communicate with the internal combustion engine 10.

[0015] The piston 12 moves up and down in the cylinder 11. The intake valve 13 is provided at the intake port of the intake passage 20 facing the cylinder 11. The exhaust valve 14 is provided at the exhaust port of the exhaust passage 30 facing the cylinder 11. The fuel injection valve 15 and the spark plug 16 are provided such that their tips face into the cylinder 11. The fuel injection valve 15 and the spark plug 16 are driven and controlled by a control unit (ECU 50). Further, the internal combustion engine 10 is provided with a water temperature sensor 17 that detects the temperature of the cooling water passing through the cooling water passage formed in the housing of the internal combustion engine 10. The water temperature sensor 17 outputs the detected temperature of the cooling water to the ECU 50 as the engine coolant temperature.

[0016] The intake passage 20 is provided with an air filter 21, an air flow meter 22, and a throttle valve 23. The air filter 21 is disposed at the upstream end of the intake passage 20. An intake air temperature sensor (not shown) for detecting the intake air temperature (i.e., the outside air temperature) is assembled to the air filter 21. Downstream of the air filter 21, the air flow meter 22 is disposed. The air flow meter 22 is a sensor that detects the amount of intake air flowing through the intake passage 20. The air flow meter 22 outputs the detected amount of intake air to the ECU 50. Downstream of the air flow meter 22, Throttle valve 23 is disposed. Near the throttle valve 23, a throttle sensor 24 for detecting the throttle opening is disposed. The throttle valve 23 is driven by the ECU 50 to adjust the amount of intake air supplied to the cylinder 11.

[0017] In the internal combustion engine 10, when the piston 12 descends, the intake valve 13 opens and intake air is drawn from the intake passage 20 into the cylinder 11, and fuel is injected from the fuel injection valve 15 to form an air-fuel mixture in the cylinder 11 (intake stroke). When the piston 12 ascends next, the intake valve 13 is closed and the formed air-fuel mixture is compressed (compression stroke). The compressed air-fuel mixture is ignited by the spark plug 16 and expands to push down the piston 12 (expansion stroke). When the piston 12 ascends next, the exhaust valve 14 opens and combustion gas (exhaust) is discharged into the exhaust passage 30 (exhaust stroke).

[0018] The exhaust passage 30 is provided with a three-way catalyst 31 and a particulate filter (GPF) 32. The three-way catalyst 31 is a catalyst having oxygen storage and release performance, and oxidizes or reduces hydrocarbons (HC), carbon monoxide (CO), and nitrogen oxides (NO X ) in the exhaust discharged from the internal combustion engine 10 to purify the exhaust. For example, when the exhaust is in a rich state, the three-way catalyst 31 adsorbs oxygen in the exhaust, and when the exhaust is in a lean state, it releases the adsorbed oxygen to purify HC, CO, NO X etc. in the exhaust.

[0019] Downstream of the three-way catalyst 31, a particulate filter 32 is disposed. The particulate filter 32 collects particulate matter (PM) contained in the exhaust gas. The PM collected by the particulate filter 32 burns (oxidizes) when oxygen is supplied to the particulate filter 32 while the particulate filter 32 is in a high-temperature state.

[0020] Further, the particulate filter 32 may be, for example, a filter having a function of oxygen storage and release performance configured by supporting a catalyst component on the surface of a filter carrier. The particulate filter 32 having the catalyst component supported thereon also functions as a three-way catalyst 31, and oxidizes or reduces HC, CO, and NO in the exhaust gas X to purify the exhaust gas. By giving the particulate filter 32 not only the three-way catalyst 31 but also the function of a three-way catalyst, the purification efficiency of the exhaust gas is enhanced.

[0021] An exhaust gas sensor 33 is provided in the exhaust passage 30. The exhaust gas sensor 33 is disposed between the three-way catalyst 31 and the particulate filter 32, downstream of the three-way catalyst 31 and upstream of the particulate filter 32.

[0022] The exhaust gas sensor 33 is a sensor that detects a state value related to the air-fuel ratio of the exhaust gas passing between the three-way catalyst 31 and the particulate filter 32. The exhaust gas sensor 33 outputs the detected state value to the ECU 50. As the exhaust gas sensor 33, an air-fuel ratio sensor or an oxygen concentration sensor can be used. The air-fuel ratio sensor is a sensor that outputs a linear signal according to the air-fuel ratio of the exhaust gas and detects the air-fuel ratio (A / F) as the state value. The oxygen concentration sensor is a sensor that outputs a signal according to the oxygen concentration in the gas and detects the oxygen concentration as the state value.

[0023] An exhaust temperature sensor for measuring the temperature of the exhaust gas may be provided in the exhaust passage 30 downstream of the three-way catalyst 31 and upstream of the particulate filter 32. Based on the output of the exhaust temperature sensor, the temperature of the three-way catalyst 31 or the particulate filter 32 can be estimated. Even if the exhaust temperature sensor is not provided, the temperatures of the three-way catalyst 31 and the particulate filter 32 can also be estimated based on the operating state of the internal combustion engine 10.

[0024] The exhaust gas purification device 1 has an ECU (Electronic Control Unit) 50 as a control unit. The ECU 50 includes a CPU (Central Processing Unit), a RAM (Random Access Memory), a ROM (Read Only Memory), and a storage device, etc. The CPU expands various control programs stored in the ROM and data referred to when executing the various control programs in the RAM and executes arithmetic processing.

[0025] In addition to the above-described sensors, various sensors for detecting the operating state of the internal combustion engine 10, including an accelerator opening sensor and a crank position sensor, are connected to the ECU 50. The ECU 50 receives a signal corresponding to the accelerator opening from the accelerator opening sensor, and calculates an accelerator operation amount, an engine load required for the internal combustion engine 10, etc. according to this signal. Further, the ECU 50 receives a signal corresponding to the rotation angle of the output shaft of the internal combustion engine 10 from the crank position sensor, and calculates the engine speed of the internal combustion engine 10. In addition, various actuators such as a throttle valve 23, a fuel injection valve 15, and a spark plug 16 are connected to the ECU 50.

[0026] Then, the ECU 50 executes various controls of the internal combustion engine 10 including fuel injection amount control of the fuel injection valve 15, ignition timing control of the spark plug 16, and throttle opening (intake air amount) control of the throttle valve 23 based on the signals input from the various sensors.

[0027] During normal operation of the vehicle 100, when a predetermined air-fuel ratio feedback control execution condition is satisfied, the ECU 50 performs air-fuel ratio feedback control to control the air-fuel ratio of the air-fuel mixture (fuel injection amount and intake air amount) so that the air-fuel ratio of the exhaust gas matches the stoichiometric air-fuel ratio, which is the target air-fuel ratio, based on the state value of the exhaust gas sensor 33.

[0028] Also, in fuel injection amount control, during deceleration or coasting of the vehicle 100, etc., the ECU 50 performs fuel cut control to stop the fuel injection of the internal combustion engine 10. During fuel cut control, the ECU 50 supplies air into the cylinder 11 while stopping the fuel injection by the fuel injection valve 15. For example, during the running of the vehicle 100, when the engine rotational speed is equal to or higher than a predetermined rotational speed and the accelerator operation amount becomes zero, the fuel cut control is started. By the fuel cut control, the fuel consumption is reduced, and the oxygen concentration in the exhaust gas increases, enabling the PM trapped in the particulate filter 32 to be burned.

[0029] Further, the ECU 50 estimates the deposition amount of PM trapped in the particulate filter 32 (hereinafter referred to as PM deposition amount). When the ECU 50 estimates the PM deposition amount, it may be estimated based on the past engine rotational speed and engine load, or based on the difference between the pressure of the exhaust gas upstream of the particulate filter 32 and downstream of the three-way catalyst 31 and the pressure of the exhaust gas downstream of the particulate filter 32 (hereinafter referred to as filter differential pressure), and the exhaust gas flow rate.

[0030] Here, since the engine speed and engine load are related to the amount of PM discharged from the internal combustion engine 10, the amount of PM discharged from the internal combustion engine 10 can be obtained based on the engine speed and engine load. By integrating the amount of PM discharged from this internal combustion engine 10, the PM deposition amount can be obtained. On the other hand, the greater the PM deposition amount, the greater the filter differential pressure. This filter differential pressure also varies depending on the exhaust gas flow rate. Therefore, if the relationship between the PM deposition amount, the filter differential pressure, and the exhaust gas flow rate is obtained in advance through experiments, simulations, etc., the PM deposition amount can be obtained from the filter differential pressure and the exhaust gas flow rate. Furthermore, since the PM deposition amount increases according to the operating time of the internal combustion engine 10 or the driving distance of the vehicle 100, the PM deposition amount can also be simply estimated based on these values.

[0031] And when the PM deposition amount is equal to or greater than a predetermined amount, the ECU 50 executes filter regeneration control to burn the PM in order to regenerate the particulate filter 32. Specifically, the ECU 50 appropriately adjusts the fuel injection amount, injection timing, or injection frequency by the fuel injection valve 15, the ignition timing or ignition frequency of the ignition plug 16, etc., to control the air-fuel ratio in the exhaust passage 30 and upstream of the three-way catalyst 31 to be a value greater than the stoichiometric air-fuel ratio (lean control). By controlling in this way, oxygen can be supplied to the particulate filter 32, and the PM collected in the particulate filter 32 can be burned to regenerate the particulate filter 32. Note that the predetermined amount is the PM deposition amount at which it is desirable to perform regeneration of the particulate filter 32. If the predetermined amount is too small, regeneration of the particulate filter 32 will be frequently performed, so there is concern about deterioration of fuel consumption, etc. On the other hand, if the predetermined amount is too large, there is concern about a decrease in the output of the internal combustion engine 10 due to an increase in the exhaust pressure, etc. Considering these, the predetermined amount is obtained in advance through experiments, simulations, etc.

[0032] Furthermore, when the abnormal diagnosis prerequisite conditions (exhaust sensor OBD prerequisite conditions) of the exhaust sensor 33, which will be described later, are satisfied, the ECU 50 prohibits the filter regeneration control, and during the period when the filter regeneration control is prohibited, based on the response time of the exhaust sensor 33 from when the fuel cut control is started until the state value reaches a predetermined value on the lean side from the specified air-fuel ratio equal to or lower than the theoretical air-fuel ratio (stoichiometry), the ECU 50 determines the abnormality (response degradation) of the exhaust sensor 33.

[0033] Therefore, with reference to FIG. 2, the processing flow of the abnormality diagnosis (exhaust sensor OBD) of the exhaust sensor 33 executed by the ECU 50 will be described. FIG. 2 is a flowchart showing the flow of the exhaust sensor OBD processing executed by the ECU. Hereinafter, the case where the exhaust sensor 33 is an air-fuel ratio sensor will be described as an example. Also, in the present embodiment, the case where the above-described specified air-fuel ratio is stoichiometry will be described, but the specified air-fuel ratio is not limited to stoichiometry and may be a rich-side air-fuel ratio.

[0034] The processing flow shown in FIG. 2 is realized by repeatedly executing a program preliminarily stored in the ECU 50 at a predetermined cycle during the power-on period of the ECU 50 (during the on period of the ignition switch). Alternatively, it is also possible to realize the processing by constructing a part or all of the steps of the program using dedicated hardware.

[0035] When the processing shown in FIG. 2 is started during the execution of the filter regeneration control, the ECU 50 determines whether the exhaust sensor OBD prerequisite conditions for executing the exhaust sensor OBD are satisfied (step S1). Specifically, when the ECU 50 satisfies all of the following conditions (1) to (3), it determines that the exhaust sensor OBD prerequisite conditions are satisfied (step S1: YES), and proceeds to step S2 for processing.

[0036] Condition (1): The engine coolant temperature detected by the water temperature sensor 17 is equal to or higher than a predetermined value (for example, 75°C). Condition (2): The state value detected by the exhaust sensor 33 is stoichiometry (for example, 16). Condition (3): The three-way catalyst 31 is in an active state.

[0037] Note that whether the three-way catalyst 31 is in an active state can be determined based on the temperature of the three-way catalyst 31.

[0038] On the other hand, when at least one of the conditions for the exhaust sensor OBD preconditions is not satisfied, the ECU 50 determines that the exhaust sensor OBD preconditions are not met (step S1: NO), and returns the process to step S1 (return).

[0039] When the exhaust sensor OBD preconditions are satisfied in step S1, the ECU 50 prohibits the filter regeneration control (step S2). The ECU 50 sets the regeneration control prohibition request flag to ON. The regeneration control prohibition request flag is a flag that is set to ON when the filter regeneration control is prohibited and set to OFF when it is not prohibited. When the regeneration control prohibition request flag is set to ON, the control of the air-fuel ratio associated with the filter regeneration control is stopped.

[0040] Next, the ECU 50 determines whether the fuel cut control is being executed (step S3). This determination is made based on the state of the fuel cut flag. The fuel cut flag is a flag that is set to ON when the fuel cut control is being executed and set to OFF when the fuel cut control is not being executed. Here, the EUC 50 executes the fuel cut control when the accelerator operation amount becomes zero while the engine speed is equal to or higher than a predetermined speed during the running of the vehicle 100. On the other hand, the EUC 50 stops the fuel cut control and resumes fuel injection when the accelerator operation amount increases during the execution of the fuel cut control.

[0041] When the fuel cut control is being executed (step S3: YES), the process proceeds to step S4. When the fuel cut control is not being executed (step S3: NO), the process returns to step S1 (return).

[0042] If fuel cut control is in execution, the ECU 50 determines whether the state value of the exhaust gas sensor 33 before the start of fuel cut control is stoichiometric (the specified air-fuel ratio) (step S4). If the state value of the exhaust gas sensor 33 before the start of fuel cut control is stoichiometric (step S4: YES), the process proceeds to step S5. If the state value of the exhaust gas sensor 33 before the start of fuel cut control is not stoichiometric (step S4: NO), the processes of steps S5 and S6 are skipped and the processing flow shown in FIG. 2 is ended.

[0043] If the state value of the exhaust gas sensor 33 before the start of fuel cut control is stoichiometric, the ECU 50 measures the response time of the exhaust gas sensor 33 (step S5). Specifically, when fuel cut control is started, due to the stop of fuel injection, the state value of the exhaust gas sensor 33 fluctuates toward the lean side. Therefore, the ECU 50 measures, as the response time of the exhaust gas sensor 33, the time required for the state value of the exhaust gas sensor 33 to change from stoichiometric to a lean state value (for example, 18) which is a predetermined value on the lean side of this stoichiometric. Note that the stoichiometric and the lean state value are to be appropriately set according to the internal combustion engine 10 and the properties of the fuel.

[0044] Then, the ECU 50 performs a process of determining whether the exhaust gas sensor 33 is normal / abnormal (step S6). Specifically, when the response time measured in step S5 is less than or equal to a preset reference response time, it is determined that the exhaust gas sensor 33 is normal (normal determination), and the abnormality flag is maintained OFF. On the other hand, when the measured response time exceeds the preset reference response time, it is determined that an abnormality has occurred in the exhaust gas sensor 33 (abnormal determination), and the abnormality flag is set ON.

[0045] Note that the reference response time is to be appropriately set according to the exhaust gas sensor 33 subject to abnormality diagnosis. Also, when an abnormality has occurred in the exhaust gas sensor 33, a failure flag may be internally held as necessary, or an abnormality lamp may be lit to notify the driver.

[0046] The ECU 50 stores the results of the abnormality diagnosis in the memory of the ECU 50 as necessary. In this way, a series of processing flows of the exhaust gas sensor OBD are carried out. And if there is a history of normal / abnormal determination, the next processing cycle is not executed.

[0047] In this way, in the configuration where the three-way catalyst 31 and the particulate filter 32 are provided in the exhaust passage 30 and the exhaust gas sensor 33 is provided between the three-way catalyst 31 and the particulate filter 32, when the PM deposition amount increases, filter regeneration control is performed.

[0048] During the filter regeneration control, the temperature of the particulate filter 32 is equal to or higher than the temperature at which the particulate matter collected by the particulate filter 32 can be burned, and the air-fuel ratio of the exhaust gas flowing into the particulate filter 32 is controlled to the lean side. Therefore, when the filter regeneration control and the abnormality diagnosis of the exhaust gas sensor 33 are executed simultaneously, even if the exhaust gas sensor 33 is operating normally, if the state value indicates a lean state due to the filter regeneration control, there is a risk of misdiagnosing the abnormality of the exhaust gas sensor 33. In order to prevent such misdiagnosis of the abnormality of the exhaust gas sensor 33, it is conceivable to not execute the abnormality diagnosis of the exhaust gas sensor 33 during the filter regeneration control. However, in this case, the frequency of detecting the abnormality of the exhaust gas sensor 33 will decrease.

[0049] On the other hand, the exhaust gas purification device 1 according to the present embodiment is provided in the exhaust passage 30 of the internal combustion engine 10, and includes a three-way catalyst 31 that purifies the exhaust gas discharged from the internal combustion engine 10, and a particulate filter 32 that is provided in the exhaust passage 30 downstream of the three-way catalyst 31 and collects particulate matter in the exhaust gas. An exhaust gas sensor 33 that detects a state value related to the air-fuel ratio of the exhaust gas passing between the three-way catalyst 31 and the particulate filter 32, and when the deposition amount of the particulate matter collected by the particulate filter 32 is equal to or greater than a predetermined amount, the air-fuel ratio in the exhaust passage 30 and upstream of the three-way catalyst 31 is controlled to be greater than the stoichiometric air-fuel ratio. And a control unit that executes filter regeneration control to burn the particulate matter collected by the particulate filter 32 and regenerate the particulate filter 32. Then, when the preconditions for the abnormality diagnosis of the exhaust gas sensor 33 are satisfied, the control unit prohibits the filter regeneration control, and during the period when the filter regeneration control is prohibited, the fuel injection of the internal combustion engine 10 is stopped. The abnormality of the exhaust gas sensor 33 is determined based on the response time of the exhaust gas sensor 33 from the start of the fuel cut control until the state value reaches a predetermined value on the lean side from the specified air-fuel ratio equal to or less than the stoichiometric air-fuel ratio.

[0050] In the exhaust gas purification device 1 configured as described above, when the preconditions for performing the abnormality diagnosis of the exhaust gas sensor 33 are satisfied, the filter regeneration control is stopped. As a result, since the abnormality diagnosis of the exhaust gas sensor 33 is performed from the state where the filter regeneration control is stopped, it is possible to increase the frequency of detecting the abnormality of the exhaust gas sensor 33 while suppressing the misdiagnosis of the abnormality of the exhaust gas sensor 33.

[0051] As described above, according to the exhaust gas purification device 1 according to the present embodiment, the frequency of detecting the abnormality of the exhaust gas sensor 33 can be increased. As a result, the accuracy of the abnormality diagnosis of the exhaust gas sensor 33 is improved.

Explanation of symbols

[0052] 1 Exhaust gas purification device 10 Internal combustion engine 11 Cylinder 12 Piston 13 Intake valve 14 Exhaust valve 15 Fuel injection valve 16 Spark plug 17 Water temperature sensor 20 Intake passage 21 Air filter 22 Airflow meter 23 Throttle valve 24 Throttle sensor 30 Exhaust passage 31 Three-way catalyst 32 Particulate filter 33 Exhaust sensor 50 ECU 100 Vehicle

Claims

【Claim 1】 A three-way catalyst provided in an exhaust passage of an internal combustion engine for purifying exhaust discharged from the internal combustion engine; A particulate filter provided in the exhaust passage downstream of the three-way catalyst for collecting particulate matter in the exhaust; An exhaust gas sensor for detecting a state value related to the air-fuel ratio of the exhaust gas that has passed between the three-way catalyst and the particulate filter; When the accumulation amount of the particulate matter collected in the particulate filter is equal to or greater than a predetermined amount, by controlling the air-fuel ratio upstream of the three-way catalyst in the exhaust passage to be greater than the stoichiometric air-fuel ratio, the particulate matter collected in the particulate filter is burned to regenerate the particulate filter, a control unit that executes filter regeneration control; having; the control unit; when the preconditions for abnormality diagnosis of the exhaust gas sensor are satisfied, prohibits the filter regeneration control; during the execution of fuel cut control for stopping the fuel injection of the internal combustion engine, if the state value of the exhaust gas sensor before the start of the fuel cut control is a specified air-fuel ratio equal to or less than the stoichiometric air-fuel ratio, during the period in which the filter regeneration control is prohibited, based on the response time of the exhaust gas sensor from the start of the fuel cut control until the state value reaches a predetermined value on the lean side from the specified air-fuel ratio, determines the abnormality of the exhaust gas sensor; An exhaust gas purification device.

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