Control device for internal combustion engines

Abstract

To detect when the PM collection device has been removed from the exhaust passage using a common determination method, regardless of the operating range of the internal combustion engine. [Solution] A control device is applied to an internal combustion engine equipped with an exhaust system comprising a PM collection device and an air-fuel ratio sensor located in the exhaust passage. The exhaust system includes a NOx sensor located downstream of the PM collection device in the exhaust passage. During lean active control, the control device calculates the cumulative value of the amount of oxygen supplied to the PM collection device based on the oxygen surplus rate in the lean gas, as an integrated value from the time the output of the air-fuel ratio sensor changes from rich to lean until the output of the NOx sensor exceeds a predetermined value. Based on the amount of oxygen stored in the PM collection device calculated from the amount of oxygen supplied, it is determined whether or not the PM collection device has been removed from the exhaust passage.

Description

Technical Field

[0001] The present invention relates to a control device for an internal combustion engine.

Background Art

[0002] Patent Document 1 discloses that a control device for an internal combustion engine determines whether or not a PM collection device is in a state (tampering) of being removed from an exhaust passage based on a differential pressure before and after the PM collection device.

Prior Art Document

Patent Document

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the configuration described in Patent Document 1, due to the influence of exhaust pulsation, it is not possible to determine tampering based on the differential pressure before and after the PM collection device unless the intake air amount of the internal combustion engine (or the exhaust flow rate in the exhaust passage) is large. The configuration described in Patent Document 1 determines tampering based on the difference between the time change rate of the exhaust temperature flowing into the PM collection device and the time change rate of the exhaust temperature flowing out of the PM collection device when the intake air amount (exhaust flow rate) is small. In the configuration described in Patent Document 1, since tampering is determined by different methods depending on whether the intake air amount is large or small, both a temperature sensor and a pressure sensor are required.

[0005] The present invention has been made in view of the above circumstances, and an object thereof is to provide a control device for an internal combustion engine that can detect a state in which a PM collection device is removed from an exhaust passage by a common determination method regardless of the operating region of the internal combustion engine.

Means for Solving the Problems

[0006] The present invention is applicable to an internal combustion engine equipped with an exhaust system comprising a PM collection device having a PM collection function and an exhaust gas purification function by a three-way catalyst, and an air-fuel ratio sensor provided upstream of the PM collection device in the exhaust passage, and is a control device for an internal combustion engine that performs lean active control as active control of the air-fuel ratio, changing the target air-fuel ratio of the air-fuel mixture supplied to the internal combustion engine from an air-fuel ratio richer than the stoichiometric air-fuel ratio to an air-fuel ratio leaner than the stoichiometric air-fuel ratio, wherein the exhaust system comprises a NOx sensor provided downstream of the PM collection device in the exhaust passage, and during the execution of the lean active control, the cumulative value of the amount of oxygen input to the PM collection device is calculated based on the oxygen excess rate in the lean gas as the cumulative value during the period from the time when the output of the air-fuel ratio sensor changes from rich to lean until the output of the NOx sensor exceeds a predetermined value, and it is determined whether or not the PM collection device has been removed from the exhaust passage based on the oxygen storage amount of the PM collection device calculated from the amount of oxygen input. [Effects of the Invention]

[0007] In this invention, it is possible to detect the state in which the PM collection device has been removed from the exhaust passage using a common determination method, regardless of the operating range of the internal combustion engine. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 is a schematic diagram showing the exhaust system in the embodiment. [Figure 2] Figure 2 is a flowchart illustrating the tampering detection process of a PM collection device. [Modes for carrying out the invention]

[0009] The control device for an internal combustion engine in an embodiment of the present invention will be described in detail below. However, the present invention is not limited to the embodiments described below.

[0010] Figure 1 is a schematic diagram of the exhaust system in an embodiment. The exhaust system 1 is a device that purifies the exhaust gas produced in the combustion chamber of the engine 2 and discharges it into the outside air. The exhaust system 1 is mounted on the vehicle. The engine 2 is an internal combustion engine that functions as the power source of the vehicle and is composed of a gasoline engine. The engine 2's fuel injection and ignition timing are electrically controlled by the control device 3. The control device 3 outputs command signals to the engine 2 to control the engine 2's output, starting, and stopping.

[0011] The exhaust system 1 comprises an exhaust manifold 11, an exhaust pipe 12, a catalytic converter 13, and a PM collection device 14.

[0012] The exhaust manifold 11 is connected to the engine 2 and the exhaust pipe 12, and collects the exhaust gases discharged from each combustion chamber of the engine 2 and discharges them into the exhaust pipe 12. The exhaust pipe 12 forms an exhaust path through which the exhaust gases from the engine 2 flow. The exhaust pipe 12 is equipped with a catalytic converter 13 and a PM collection device 14. The catalytic converter 13 is located upstream of the PM collection device 14.

[0013] The catalyst device 13 comprises a honeycomb structured carrier made of ceramic (cordilley). The carrier has multiple through-holes. Each through-hole extends linearly, forming a flow path for exhaust gas. A three-way catalyst is supported on the wall surface of each pore. The three-way catalyst has oxygen storage capacity. The three-way catalyst has the function of removing hydrocarbons, carbon monoxide, and nitrogen oxides from the exhaust gas.

[0014] The PM collection device 14 is equipped with a wall-flow type filter. This filter is made of porous ceramic and collects PM from the exhaust gas that flows into the PM collection device 14, and supports a three-way catalyst. In addition to its PM collection function, the PM collection device 14 also has an exhaust gas purification function using the three-way catalyst. Since engine 2 is a gasoline engine, the PM collection device 14 is a GPF (Gasoline Particulate Filter). Unburned gases and NOx contained in the exhaust gas discharged from the catalytic converter 13 are purified by the PM collection device 14.

[0015] The exhaust system 1 includes a first air-fuel ratio sensor 21, a second air-fuel ratio sensor 22, and a NOx sensor 23. The first air-fuel ratio sensor 21, the second air-fuel ratio sensor 22, and the NOx sensor 23 are all located in the exhaust pipe 12. In this description, the air-fuel ratio may be referred to as A / F.

[0016] The first air-fuel ratio sensor 21 is positioned upstream of the catalytic converter 13 and detects the air-fuel ratio of the exhaust gas flowing into the catalytic converter 13. The first air-fuel ratio sensor 21 is located in the exhaust path between the exhaust manifold 11 and the catalytic converter 13. The first air-fuel ratio sensor 21 outputs a signal indicating the detected air-fuel ratio to the control device 3.

[0017] The second air-fuel ratio sensor 22 is located downstream of the catalytic converter 13 and upstream of the PM collection device 14, and detects the air-fuel ratio of the exhaust gas flowing into the PM collection device 14. The second air-fuel ratio sensor 22 is installed in the exhaust path between the catalytic converter 13 and the PM collection device 14. The second air-fuel ratio sensor 22 outputs a signal indicating the detected air-fuel ratio to the control device 3.

[0018] The NOx sensor 23 is positioned downstream of the PM collection device 14 and detects NOx in the exhaust gas flowing out of the PM collection device 14. The NOx sensor 23 outputs a signal indicating the detection of NOx to the control device 3.

[0019] The control device 3 is an electronic control device that controls the engine 2. The control device 3 consists of a microcomputer equipped with a CPU, RAM, ROM, and input / output interface. Signals from various sensors mounted on the vehicle are input to the control device 3. The vehicle is equipped with an airflow meter 24 that detects the amount of intake air drawn into the engine 2, an accelerator position sensor 25 that detects the accelerator opening, which is the amount the accelerator pedal is operated, and a crank angle sensor 26 that detects the crank angle of the crankshaft of the engine 2. The control device 3 performs various controls based on the signals input from the various sensors.

[0020] For example, the control device 3 executes active control of the air-fuel ratio based on the signal input from the NOx sensor 23. The active control of the air-fuel ratio is control that actively switches the air-fuel ratio of the air-fuel mixture supplied to the engine 2 between the rich side and the lean side with respect to the stoichiometric air-fuel ratio. The control device 3 executes active control and sets the target air-fuel ratio of the air-fuel mixture supplied to the engine 2 to an air-fuel ratio richer than the stoichiometric air-fuel ratio. When the target air-fuel ratio of the air-fuel mixture is set to an air-fuel ratio richer than the stoichiometric air-fuel ratio, the amount of unburned fuel contained in the exhaust from the engine 2 increases. Further, the control device 3 executes active control and sets the target air-fuel ratio of the air-fuel mixture to an air-fuel ratio leaner than the stoichiometric air-fuel ratio. When the target air-fuel ratio of the air-fuel mixture is set to an air-fuel ratio leaner than the stoichiometric air-fuel ratio, the amount of unburned fuel contained in the exhaust from the engine 2 decreases. As the active control of the air-fuel ratio, the control device 3 executes lean active control that changes the target air-fuel ratio of the air-fuel mixture supplied to the engine 2 from an air-fuel ratio richer than the stoichiometric air-fuel ratio to an air-fuel ratio leaner than the stoichiometric air-fuel ratio.

[0021] The exhaust device 1 and the control device 3 are configured to be able to detect a state (tampering) in which the PM collection device 14 is removed from the exhaust passage. In that case, it is desirable that the tampering of the PM collection device 14 can be detected by the same determination method whether the vehicle speed is high and the load is high, whether the vehicle speed is high and the load is low, whether the vehicle speed is low and the load is high, or whether the vehicle speed is low and the load is low. Therefore, the control device 3 is configured to determine whether or not the PM collection device 14 is in a state of being removed from the exhaust passage by a common determination method regardless of the operating region of the engine 2. Specifically, the control device 3 actively swings the air-fuel ratio between the rich side and the lean side based on the signal of the NOx sensor 23, and uses up the oxygen storage amount of the PM collection device 14, thereby confirming the presence of the PM collection device 14 by the NOx sensor 23 and detecting tampering.

[0022] FIG. 2 is a flowchart showing the tampering detection process of the PM collection device. The control shown in FIG. 2 is implemented by the control device 3.

[0023] The control device 3 starts the engine 2 (step S1). When the control device 3 detects that the engine start button of the vehicle has been turned on, the engine 2 is started.

[0024] After the engine is started, the control device 3 determines whether the A / F preprocessing is completed (step S2). In order to determine that the A / F preprocessing is completed, the control device 3 determines whether all the conditions from the first condition to the third condition are satisfied. The first condition is that the control device 3 is setting the target air-fuel ratio of the air-fuel mixture to 13.5. The second condition is that the second air-fuel ratio sensor 22 is outputting a signal indicating that the air-fuel ratio of the exhaust is richer than the stoichiometric air-fuel ratio. The third condition is that the output of the NOx sensor 23 is detecting NOx within a predetermined range. The predetermined range is 0 to 5 ppm. When it is determined that all of the first to third conditions are satisfied, it is determined that the A / F preprocessing is completed. When it is determined that the A / F preprocessing is not completed (step S2: No), this control routine ends.

[0025] When it is determined that the A / F preprocessing is completed (step S2: Yes), the control device 3 determines whether the prerequisite conditions are satisfied (step S3). In order to determine that the prerequisite conditions are satisfied, the control device 3 determines whether all the conditions from the fourth condition to the sixth condition are satisfied. The fourth condition is that the A / F preprocessing is in progress. The fifth condition is that the change in the intake air amount is within a predetermined value. The sixth condition is that the intake air amount is below a predetermined value. When it is determined that all of the fourth to sixth conditions are satisfied, it is determined that the prerequisite conditions are satisfied. The control device 3 sets the target air-fuel ratio of the air-fuel mixture to 15.1 when the prerequisite conditions are satisfied. The control device 3 leans the target air-fuel ratio. When it is determined that the prerequisite conditions are not satisfied (step S3: No), this control routine ends.

[0026] If it is determined that the preconditions are met (Step S3: Yes), the control device 3 calculates the amount of oxygen supplied to the PM collection device 14 (Step S4). The control device 3 calculates and integrates the amount of oxygen supplied to the PM collection device 14 based on the oxygen excess rate in the lean gas after the signal from the second air-fuel ratio sensor 22 changes from rich to lean. The control device 3 can detect whether the exhaust flowing into the PM collection device 14 is lean or rich based on the signal input from the second air-fuel ratio sensor 22. If the NOx sensor 23 outputs a detection value below a predetermined value, the control device 3 continues to integrate the amount of oxygen supplied to the PM collection device 14. The predetermined value is 5 ppm. When the NOx sensor 23 outputs a detection signal of 5 ppm or more, the control device 3 ends the integration of the amount of oxygen supplied to the PM collection device 14 and sets the target air-fuel ratio to the stoichiometric ratio. The control device 3 stoichiometricizes the target air-fuel ratio. While the control device 3 is performing active control from rich to lean, it calculates the cumulative amount of oxygen input to the PM collection device 14 based on the oxygen excess rate in the lean gas, as the cumulative value during the period from when the output of the second air-fuel ratio sensor 22 changes from rich to lean until the output of the NOx sensor 23 exceeds a predetermined value.

[0027] The control device 3 determines whether the detection termination condition has been met (step S5). To determine whether the detection termination condition has been met, the control device 3 determines whether both the 7th condition and the 8th condition have been met. The 7th condition is that the target air-fuel ratio is stoichiometric. The 8th condition is that the second air-fuel ratio sensor 22 is outputting a signal indicating that the exhaust air-fuel ratio is richer than the stoichiometric air-fuel ratio. If it is determined that the detection termination condition has not been met (step S5: No), this control routine terminates.

[0028] If it is determined that the detection termination condition has been met (Step S5: Yes), the control device 3 determines the oxygen storage capacity of the PM collection device 14 (Step S6).

[0029] The control device 3 determines whether the oxygen storage capacity of the PM collection device 14 is above a predetermined value (step S7). This predetermined value is set in advance.

[0030] If it is determined that the oxygen storage capacity of the PM collection device 14 is equal to or greater than a predetermined value (Step S7: Yes), the control device 3 confirms that it is functioning normally (Step S8). In Step S8, it is confirmed that the PM collection device 14 is properly installed in the exhaust passage.

[0031] If it is determined that the oxygen storage capacity of the PM collection device 14 is not above a predetermined value (Step S7: No), the control device 3 confirms that there is an abnormality (Step S9). In Step S9, it is confirmed that the PM collection device 14 is in a state where it has been removed from the exhaust passage, that is, an abnormal state in which tampering of the PM collection device 14 has been detected.

[0032] As described above, according to the embodiment, it is possible to determine whether or not the PM collection device 14 has been removed from the exhaust passage using a common determination method that does not depend on the operating range of the engine 2. As a result, the control device 3 can detect that the PM collection device 14 has been removed when the amount of oxygen stored in the catalyst is small during lean active control.

[0033] The vehicle may also be a hybrid vehicle. If the vehicle is a two-motor hybrid vehicle, it is possible to arbitrarily increase the intake air volume (shorten monitoring time) and improve the signal-to-noise ratio in a steady state by coordinating with the motor. The electric device of the hybrid vehicle may be used to keep the intake air volume below a predetermined value and to keep the change in intake air volume below a predetermined value. [Explanation of symbols]

[0034] 1. Exhaust system 2. Engine (internal combustion engine) 3. Control device 12. Exhaust pipe (exhaust passage) 14 PM collection device 22. Second air-fuel ratio sensor 23 NOx Sensors

Claims

[Claim 1] This invention is applied to an internal combustion engine equipped with an exhaust system comprising a PM collection device having a PM collection function and an exhaust purification function using a three-way catalytic converter, and an air-fuel ratio sensor provided upstream of the PM collection device in the exhaust passage. A control device for an internal combustion engine that performs lean active control as an active control of the air-fuel ratio, which changes the target air-fuel ratio of the air-fuel mixture supplied to the internal combustion engine from an air-fuel ratio richer than the stoichiometric air-fuel ratio to an air-fuel ratio leaner than the stoichiometric air-fuel ratio, The exhaust system includes a NOx sensor located downstream of the PM collection device in the exhaust passage. While the lean active control is being executed, the cumulative value of the amount of oxygen supplied to the PM collection device is calculated based on the oxygen excess rate in the lean gas, as the cumulative value during the period from when the output of the air-fuel ratio sensor changes from rich to lean until the output of the NOx sensor exceeds a predetermined value. Based on the amount of oxygen stored in the PM collection device calculated from the amount of oxygen input, it is determined whether or not the PM collection device has been removed from the exhaust passage. A control device for an internal combustion engine, characterized by the following features.

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