Engine control device

Abstract

The present invention provides an engine control device that can determine whether or not a filter has been removed, without being affected by the exhaust gas flow rate. [Solution] The engine 10 is equipped with a filter 11 on which a three-way catalytic converter is supported. The filter 11 is located in the exhaust passage 15. The engine 10 is equipped with an air-fuel ratio sensor 13 located upstream of the filter 11 in the exhaust passage 15 to measure the air-fuel ratio of the exhaust. The engine 10 is equipped with a nitrogen oxide sensor 14 located downstream of the filter 11 in the exhaust passage 15 to measure the concentration of nitrogen oxides contained in the exhaust. The control device 12 of the engine 10 determines whether the filter 11 has been removed based on the cumulative value of the intake air amount during the period from the time the output of the air-fuel ratio sensor 13 changes from rich to lean after the start of fuel cut until the time the output value of the nitrogen oxide sensor 14 becomes zero.

Description

【Technical Field】 【0005】 , , 【0001】 The present invention relates to an engine control device. 【Background Art】 【0002】 Patent Document 1 discloses an engine control device. The engine exhaust system includes a filter capable of collecting particulate matter (PM). The control device calculates an integrated value of the differential pressure before and after the filter when the engine is operating. When the integrated value is greater than or equal to a threshold value, the control device determines that there is no abnormality in the exhaust system. On the other hand, when the integrated value is less than the threshold value, the control device determines that there is an abnormality in the exhaust system. Note that the state where there is an abnormality in the exhaust system means a state where the filter is removed in the exhaust system. 【Prior Art Documents】 【Patent Documents】 【0003】 【Patent Document 1】 Japanese Unexamined Patent Application Publication No. 2020-112039 【Summary of the Invention】 【Problems to be Solved by the Invention】 【0004】 The differential pressure before and after the filter decreases when the exhaust gas flow rate is low. Therefore, even when there is an abnormality in the exhaust system, if the exhaust gas flow rate is low, the abnormality may not be detected. A control device that can detect an abnormality in the exhaust system even when the exhaust gas flow rate is low is desired. 【Means for Solving the Problems】 【0005】 The engine control device for solving the above problems controls the engine. The engine is equipped with a filter on which a three-way catalytic converter is supported. The filter is located in the exhaust passage. The engine is equipped with an air-fuel ratio sensor located upstream of the filter in the exhaust passage to measure the air-fuel ratio of the exhaust. The engine is equipped with a nitrogen oxide sensor located downstream of the filter in the exhaust passage to measure the concentration of nitrogen oxides contained in the exhaust. This control device determines whether the filter has been removed based on the cumulative value of the intake air amount during the period from the time the output of the air-fuel ratio sensor changes from rich to lean after the start of fuel cut until the time the output value of the nitrogen oxide sensor becomes zero. [Effects of the Invention] 【0006】 The engine control system can determine whether or not the filter has been removed, regardless of the exhaust flow rate. [Brief explanation of the drawing] 【0007】 [Figure 1] Figure 1 is a schematic diagram showing the configuration of an exhaust system equipped with a control device for an engine according to an embodiment. [Figure 2] Figure 2 is a flowchart showing the sequence of processes performed by the control device in Figure 1. [Modes for carrying out the invention] 【0008】 Hereinafter, one embodiment of the engine control device will be described with reference to Figures 1 and 2. <Configuration of exhaust system 100> As shown in Figure 1, the engine 10 is equipped with an exhaust system 100 for releasing exhaust gases outside the vehicle. The exhaust system 100 includes a filter 11, an air-fuel ratio sensor 13, a nitrogen oxide sensor 14, and an exhaust passage 15. 【0009】 The exhaust passage 15 is connected to the engine 10. The exhaust gas emitted by the engine 10 is discharged outside the vehicle through the exhaust passage 15. As shown in Figure 1, a filter 11 is installed in the middle of the exhaust passage 15. The filter 11 collects particulate matter (PM) contained in the exhaust. A three-way catalyst is supported on the filter 11. 【0010】 As shown in Figure 1, an air-fuel ratio sensor 13 is installed upstream of the filter 11 in the exhaust passage 15. The air-fuel ratio sensor 13 measures the air-fuel ratio of the exhaust gas. As shown in Figure 1, a nitrogen oxide sensor 14 is installed downstream of the filter 11 in the exhaust passage 15. The nitrogen oxide sensor 14 measures the concentration of nitrogen oxides (NOx) contained in the exhaust. 【0011】 The control device 12 controls the engine 10. The control device 12 controls the engine 10, for example, by controlling the amount of fuel injected by the injectors provided in the engine 10. 【0012】 The control device 12 is connected to the air-fuel ratio sensor 13 in a communication manner. The control device 12 obtains the output value of the air-fuel ratio sensor 13 by communicating with the air-fuel ratio sensor 13. The control device 12 is connected to the nitrogen oxide sensor 14 in a communication manner. The control device 12 obtains the output value of the nitrogen oxide sensor 14 by communicating with the nitrogen oxide sensor 14. 【0013】 <Processing methods by the control device 12> The control device 12 determines whether or not the filter 11 has been removed from the exhaust system 100. Figure 2 shows the sequence of processes that the control device 12 performs when making this determination. The control device 12 performs the sequence of processes shown in Figure 2 when it initiates fuel cut in the engine 10. If the vehicle equipped with the engine 10 is a hybrid vehicle, the control device 12 can initiate fuel cut regardless of the vehicle's driving conditions. Therefore, if the vehicle equipped with the engine 10 is a hybrid vehicle, the frequency of performing the sequence of processes shown in Figure 2 can be increased. 【0014】 As shown in Figure 2, when the control device 12 starts this series of processes, it first executes the process in step S11. In the process in step S11, the control device 12 determines whether or not the preconditions are met. 【0015】 In step S11, the control device 12 checks whether both conditions A and B are met. Condition A is that the air-fuel ratio sensor 13 outputs that the air-fuel ratio is rich. Condition B is that the nitrogen oxide sensor 14 outputs a value greater than zero. 【0016】 The control device 12 determines that the precondition is met if both condition A and condition B are met. If the control device 12 determines that the precondition is met in the process of step S11 (step S11: YES), it proceeds to step S12. On the other hand, if the control device 12 determines that the precondition is not met in the process of step S11 (step S11: NO), it terminates the series of processes shown in Figure 2. 【0017】 When fuel cut is initiated, the air-fuel ratio gradually increases. In step S12, the control device 12 determines whether the output of the air-fuel ratio sensor 13 has changed from rich to lean. 【0018】 In the process of step S12, when the control device 12 determines that the output of the air-fuel ratio sensor 13 has not changed from rich to lean (step S12: NO), the process of step S12 is executed again. In the process of step S12, when the control device 12 determines that the output of the air-fuel ratio sensor 13 has changed from rich to lean (step S12: YES), the process proceeds to step S13. That is, the control device 12 repeatedly executes the process of step S12 until it determines that the output of the air-fuel ratio sensor 13 has changed from rich to lean. 【0019】 In the process of step S13, the control device 12 executes an estimation process. The estimation process is a process of estimating the oxygen input amount. The three-way catalyst releases oxygen when the air-fuel ratio is rich, while it stores oxygen when the air-fuel ratio is lean. Therefore, after the air-fuel ratio changes from rich to lean, the filter 11 stores the oxygen contained in the exhaust gas. The oxygen input amount refers to the amount of oxygen input into the filter 11 after the output of the air-fuel ratio sensor 13 changes from rich to lean. 【0020】 The control device 12 receives information indicating the intake air amount from an air flow meter or the like provided in the vehicle. The control device 12 measures the oxygen input amount as a value obtained by multiplying the intake air amount after the output of the air-fuel ratio sensor 13 changes from rich to lean by 0.2 and integrating the result. 【0021】 The estimation process ends when either the completion condition or the interruption condition is satisfied. The completion condition is a condition for the estimation process to complete. Specifically, the completion condition is that the output value of the nitrogen oxide sensor 14 becomes zero. 【0022】 The nitrogen oxide sensor 14 reacts to components such as NOx and moisture contained in the exhaust gas and outputs a value. The nitrogen oxide sensor 14 is a sensor that measures the concentration of NOx contained in the exhaust gas. Therefore, when the proportion of oxygen in the exhaust gas increases, the NOx concentration decreases, and even if NOx and other substances are present in the exhaust gas, the output value of the nitrogen oxide sensor 14 becomes zero. 【0023】 The control device 12 determines that the estimation process is complete when the output value of the nitrogen oxide sensor 14 becomes zero, and terminates the estimation process. In this way, the control device 12 calculates the cumulative amount of oxygen input during the period from the time the output of the air-fuel ratio sensor 13 changes from rich to lean until the time the output value of the nitrogen oxide sensor 14 becomes zero. 【0024】 An interruption condition is a condition that interrupts the estimation process before the completion condition is met. There are two types of interruption conditions: condition C and condition D. Condition C is that the fuel cut has finished in the engine 10. Condition D is that the air-fuel ratio sensor 13 has output a rich signal. The control device 12 terminates the estimation process if either condition C or condition D is met, even if the completion condition has not been met. 【0025】 After the estimation process is completed, the control device 12 executes the process in step S14. In the process in step S14, the control device 12 determines whether or not the estimation process has been interrupted. The control device 12 determines that the estimation process has been interrupted if the estimation process had ended due to the fulfillment of the interruption condition. If the control device 12 determines that the estimation process has been interrupted (step S14: YES), it terminates the series of processes shown in Figure 2. In this way, if the interruption condition is fulfilled, the control device 12 terminates the series of processes shown in Figure 2 without determining whether or not the filter 11 has been removed. If the control device 12 terminates the series of processes shown in Figure 2 after determining that the measurement process has been interrupted, it discards the oxygen input amount output in step S13. 【0026】 The control device 12 determines that the estimation process was not interrupted if the estimation process had ended due to the fulfillment of the completion condition. If the control device 12 determines that the estimation process was not interrupted (step S14: NO), it proceeds to step S15. 【0027】 As mentioned earlier, after the air-fuel ratio changes from rich to lean, filter 11 absorbs oxygen contained in the exhaust. Therefore, if filter 11 is not removed, after the air-fuel ratio changes from rich to lean, the proportion of oxygen in the exhaust flowing downstream of filter 11 will remain low until filter 11 has absorbed all the oxygen it can absorb. 【0028】 As mentioned earlier, the output value of the nitrogen oxide sensor 14 becomes zero when the proportion of oxygen in the exhaust increases. In other words, when the filter 11 is not removed, the amount of oxygen added after the air-fuel ratio changes from rich to lean until the output value of the nitrogen oxide sensor 14 becomes zero is greater than when the filter 11 is removed. 【0029】 In step S15, the control device 12 determines whether the amount of oxygen input estimated by the estimation process is equal to or greater than a default value. The magnitude of the default value is set to a size that allows the control device to determine that the filter 11 has not been removed based on whether the amount of oxygen input estimated by the estimation process is equal to or greater than a default value. 【0030】 If the control device 12 determines in step S15 that the oxygen input amount is greater than or equal to a predetermined value (step S15: YES), it proceeds to step S16. A oxygen input amount greater than or equal to a predetermined value indicates that a large amount of oxygen is being input after the air-fuel ratio changes from rich to lean, until the output value of the nitrogen oxide sensor 14 becomes zero. In other words, this indicates that oxygen is being absorbed by the filter 11. In step S16, the control device 12 determines that the exhaust system 100 is in a normal state, with the filter 11 still in place. After that, the control device 12 completes the series of processes shown in Figure 2. 【0031】 If the control device 12 determines in step S15 that the oxygen input amount is less than a predetermined value (step S15: NO), it proceeds to step S17. An oxygen input amount less than a predetermined value indicates that the amount of oxygen input is insufficient from the time the air-fuel ratio changes from rich to lean until the output value of the nitrogen oxide sensor 14 becomes zero. In other words, this indicates that oxygen is not being absorbed by the filter 11. In step S17, the control device 12 determines that the exhaust system 100 is in an abnormal state, with the filter 11 removed. Subsequently, the control device 12 terminates the series of processes shown in Figure 2. 【0032】 As shown in Figure 2, the control device 12 determines whether the filter 11 has been removed based on the oxygen input amount, which is the cumulative value of the intake air amount multiplied by 0.2. Note that even if the control device 12 uses the cumulative value of the intake air amount instead of the oxygen input amount, it can make the same determination by adjusting the default value. 【0033】 <Operation of this embodiment> The nitrogen oxide sensor 14's output value becomes zero when the proportion of oxygen in the exhaust increases after fuel cut-off is initiated. If filter 11 is installed, after fuel cut-off is initiated, the oxygen in the exhaust is first absorbed by filter 11. Therefore, when filter 11 is installed, the cumulative amount of intake air until the output value of nitrogen oxide sensor 14 becomes zero is larger compared to when filter 11 is removed. 【0034】 The control device 12 determines whether the filter 11 has been removed based on the cumulative amount of intake air from the time the fuel cut is initiated until the output value of the nitrogen oxide sensor 14 becomes zero. 【0035】 <Effects of this embodiment> (1) The control device 12 can determine whether or not the filter 11 has been removed, without being affected by the exhaust flow rate. [Explanation of Symbols] 【0036】 10…Engine, 11…Filter, 12…Control unit, 13…Air-fuel ratio sensor, 14…Nitrogen oxide sensor, 15…Exhaust passage, 100…Exhaust system

Claims

[Claim 1] A filter is installed in the exhaust passage and supports a three-way catalytic converter, An air-fuel ratio sensor is disposed upstream of the filter in the exhaust passage and measures the air-fuel ratio of the exhaust gas. A nitrogen oxide sensor is disposed downstream of the filter in the exhaust passage and measures the concentration of nitrogen oxides contained in the exhaust. This is an engine control device that controls an engine equipped with the following: Whether or not the filter has been removed is determined based on the cumulative value of the intake air volume during the period from the point when the output of the air-fuel ratio sensor changes from rich to lean after the fuel cut is initiated, until the point when the output value of the nitrogen oxide sensor becomes zero. Engine control device.

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