JP2007170363A - Engine control - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To diagnose whether engine control is made according to the command irrespective of manipulated variables in the catalyst control for early warming up an engine. <P>SOLUTION: If an actual ignition time lag disagrees with the command value making ignition time lag due to abnormal conditions (if no ignition time angle lag occurs at all against a lag command or if the lag speed is slow compared with such as commanded), ignition timing is faster and engine torque can be less reduced, as that engine revolutions become much higher than the target revolution during usual engine idling time. For this reason, the value when engine is abnormal is larger than that when it is normal due to its more increased revolutions, as shown in the ratio of engine revolutions NE to suction air volume Qa (NE/Qa). Accordingly the use of the ratio of engine revolutions to suction air volume (NE/Qa) as a diagnostic value makes it possible to diagnose the abnormality of an engine without being affected by the size of ignition time lag angle. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an engine control device for diagnosing abnormality in early catalyst warm-up control that promotes warm-up of a catalyst by increasing the amount of exhaust heat of the engine.

  In general, a catalyst interposed in an exhaust system for purifying engine exhaust gas cannot obtain sufficient exhaust gas purification performance if the temperature is low. For this reason, conventionally, at the time of cold start of the engine, control (catalyst early warm-up control) that retards the ignition timing from the normal ignition timing is performed in order to activate the catalyst early in order to reduce exhaust emission. It has been broken.

  If this early catalyst warm-up control is not performed normally, exhaust emissions will deteriorate, so conventionally, whether or not the catalyst early warm-up control has been performed normally, that is, the ignition timing is set according to the command from the controller. Various techniques for diagnosing whether the retard control or the like is being executed have been proposed.

  For example, in Patent Document 1, when the catalyst temperature raising means is in operation, the engine speed NE is equal to or less than the value obtained by subtracting the predetermined deviation amount DNEFIRE from the target speed NOBJ (NE ≦ NOBJ−DNEFIRE), or the ignition timing. A technique for determining that a failure has occurred in the catalyst temperature raising means when IGLOG is equal to or greater than a determination threshold value DIGJUD (IGLOG ≧ DIGJUD) is disclosed.

Further, in Patent Document 2, an estimated exhaust temperature is calculated based on an estimated air-fuel ratio (air-fuel ratio parameter), an ignition timing retardation amount, and an engine speed, and the estimated exhaust temperature and intake air amount (intake air amount). A technique for diagnosing the presence or absence of abnormality by calculating an estimated exhaust heat quantity of an engine based on a parameter) and comparing an estimated exhaust heat quantity integrated value QSUM obtained by integrating the calculated exhaust heat quantity with a predetermined value Qmin is disclosed.
JP 2001-132526 A JP 2003-201906 A

  However, since the ignition timing retardation amount in the catalyst early warm-up control is determined based on the engine water temperature or the like, in the technology that makes a diagnosis based on the engine speed or the ignition timing as in the technology disclosed in Patent Document 1. When the ignition timing retardation amount is small, the difference between the diagnosis value and the determination threshold value becomes small, and when the ignition timing retardation amount is small, it is difficult to perform the diagnosis strictly.

  Further, as in the technique disclosed in Patent Document 2, the exhaust heat amount is calculated to perform abnormality diagnosis of the catalyst early warming-up system. Although it is possible to diagnose whether or not the catalyst is warmed up, the intake air amount It is difficult to diagnose whether each control such as an increase in the amount of ignition and retard of the ignition timing is performed as instructed from the control device.

  The present invention has been made in view of the above circumstances, and controls an engine that can diagnose whether or not control according to a command is being executed without being affected by the magnitude of the control amount in the early catalyst warm-up control. The object is to provide a device.

  In order to achieve the above object, an engine control apparatus according to the present invention is a catalyst that executes catalyst early warm-up control that promotes warm-up of a catalyst interposed in an exhaust system of the engine by increasing the amount of exhaust heat of the engine. An abnormality for diagnosing the presence or absence of an abnormality in the catalyst early warm-up control means based on a ratio between the engine warm-up control means and the engine load and the engine speed during idle operation that changes with the execution of the catalyst early warm-up control A diagnostic means is provided.

  The engine control apparatus according to the present invention can diagnose whether or not the control according to the command is executed without being affected by the magnitude of the control amount in the catalyst early warm-up control, and reliably detect an abnormality. It becomes possible.

  Embodiments of the present invention will be described below with reference to the drawings. 1 to 3 relate to a first embodiment of the present invention, FIG. 1 is a schematic configuration diagram of an engine system, and FIG. 2 is a graph showing changes in engine speed and intake air amount by ignition timing retardation control and diagnostic values. FIG. 3 is a flowchart of the diagnostic routine.

  First, the schematic configuration of the engine and the engine control system will be described with reference to FIG. In the figure, reference numeral 1 denotes a multi-cylinder engine having a plurality of cylinders, and an intake manifold 2 is communicated with an intake port 1b of each cylinder formed in a cylinder block 1a of the engine 1. An intake pipe 4 is communicated with a collecting portion of the intake manifold 2 via an air chamber 3, and an air cleaner 5 is interposed at an air intake port upstream of the intake pipe 4.

  Further, a muffler 8 is communicated with an aggregate portion of the exhaust manifold 6 communicating with the exhaust port 1 c of each cylinder of the engine 1 through an exhaust pipe 7, and a catalyst 9 is interposed in the middle of the exhaust pipe 7. A spark plug 10 faces the combustion chamber of each cylinder, and an injector 11 faces just upstream of the intake port 1b of the intake manifold 2 communicating with each cylinder. An ignition coil 10a is connected to the spark plug 10, and an igniter 12 is connected to the ignition coil 10a.

  Further, as sensors for detecting the operating state of the engine 1, an intake air amount sensor 13 is provided immediately downstream of the air cleaner 5 of the intake pipe 4, and a throttle valve 14 interposed in the middle of the intake pipe 4 A throttle opening sensor 15 is continuously provided. Further, a water temperature sensor 16 faces a cooling water passage (not shown) formed in the cylinder block 1a.

  An air-fuel ratio sensor 18 such as an O2 sensor is provided on the upstream side of the exhaust pipe 7, and a crank angle sensor 20 is provided opposite to a crank rotor 19 that rotates synchronously with the crankshaft. The crank rotor 19 is formed with a projection or the like for detecting the crank angle for each predetermined crank angle.

  On the other hand, reference numeral 50 denotes an electronic control unit (ECU) that controls the engine 1 and is formed around a microcomputer. The ECU 50 processes signals from sensors and switches in accordance with a control program stored in a memory (ROM), and executes engine control via an actuator. This engine control is based on fuel injection control via the injector 11 and ignition timing control via the igniter 12 of the ignition coil 10a connected to the spark plug 10.

  In such engine control by the ECU 50, the ECU 50 promotes the early warm-up of the catalyst 9 by increasing the exhaust heat amount of the engine by the function as the early catalyst warm-up control means at the time of cold start of the engine. More specifically, this early catalyst warm-up control is a control in which ignition timing is retarded and combustion is performed at a stage close to the exhaust stroke, and exhaust gas having a high temperature is led to the catalyst to promote catalyst activation. If the ignition timing retardation control for early catalyst warm-up (catalyst early warm-up retard control) does not function normally, exhaust emission may be deteriorated.

  For this reason, the ECU 50 makes a self-diagnosis as to whether or not the catalyst early warm-up / retard angle control is functioning normally by the function as the abnormality diagnosis means. The diagnosis for the early catalyst warm-up / retard angle control is performed by monitoring the engine load (for example, intake air amount, intake pipe pressure, fuel injection amount, etc.) and the engine speed which change as the ignition timing is retarded. By comparing the ratio as a diagnostic value with a determination threshold value, it is determined whether or not the catalyst early warm-up / retard angle control is functioning normally.

  In the present embodiment, the intake air amount Qa is used as the engine load that changes with the retarded ignition timing, and the ratio (NE / Qa) that uses the intake air amount Qa as the denominator and the engine speed NE is the numerator. By calculating and comparing this diagnostic value (NE / Qa) with a preset determination threshold value, it is determined whether or not the catalyst early warm-up / retarding angle control is normal.

  That is, when the catalyst early warm-up / retard angle control is executed after the engine is started, the ignition timing is retarded according to the engine water temperature, the engine torque is decreased, and the engine speed is decreased. In response to this decrease in engine torque, the intake air amount and the fuel injection amount are increased at the same time to stabilize the engine speed, and the engine speed is increased. Since the timing is late, there is a tendency that it is difficult to increase with an increase in air volume. Accordingly, as shown by the solid line in FIG. 2, when the catalyst early warm-up / retarding angle control is normally executed, the engine speed is temporarily slightly higher than the target speed during normal idle control. Number.

  On the other hand, when the actual ignition timing is not retarded according to the command value due to the occurrence of an abnormality with respect to the control command for retarding the ignition timing, for example, as shown by a rough broken line in FIG. If the engine is not retarded at all, or if the retarding speed is slow relative to the ignition timing retarding control command as shown by the thin broken line in FIG. The engine speed becomes higher than the engine speed when the catalyst early warm-up / retard angle control is normally executed.

  That is, when the actual ignition timing is not retarded according to the control command, the amount of air and fuel increase is small, the balance of ignition with respect to the air amount and fuel amount is lost, and the engine speed increases more than normal. End up. For this reason, when the ratio (NE / Qa) between the engine speed NE and the intake air amount Qa is taken, the value at the time of abnormality becomes larger than the normal value due to the increase in the engine speed NE.

  Therefore, by using the ratio (NE / Qa) between the engine speed NE and the intake air amount Qa as a diagnostic value, it is possible to diagnose whether there is an abnormality without being affected by the magnitude of the ignition timing retard amount. Thus, the presence or absence of abnormality is diagnosed by comparing the diagnosis value (NE / Qa) with a preset determination threshold. The determination threshold is determined in advance by simulation or experiment with respect to the ignition timing retard amount in the catalyst early warm-up retard control that is set depending on the engine characteristics, the capacity of the exhaust system, etc. This is a threshold value for determination.

  Specifically, the above diagnosis processing is executed by a diagnosis routine shown in the flowchart of FIG. Next, this diagnosis routine will be described with reference to the flowchart of FIG.

  This diagnosis routine is executed immediately after the engine is started. First, in the first step S1, it is checked whether or not the conditions for executing the catalyst early warm-up / retard angle control are satisfied. That is, the catalyst early delay warm-up control is control for early warm-up of the catalyst when the engine is cold. Therefore, when the engine water temperature is higher than the set value and the catalyst warm-up has already been completed, step S1 is performed. The routine is exited from this step, and this processing is terminated, and the diagnosis is not actually executed.

  On the other hand, when the engine water temperature is in the cold state below the set value, the execution condition of the catalyst early warm-up / retarding angle control is satisfied, so that the process proceeds from step S1 to step S2 to determine whether or not the idling operation is being performed. When the engine is not idling, the process exits the routine from step S2 and ends the present process. When the engine is idling, the process proceeds to step S3 to check whether a diagnosis start condition with an ignition timing equal to or greater than a set value is satisfied. .

  The catalyst early warm-up / retard angle control is started immediately after the engine water temperature is started below the set value, and the retard amount of the ignition timing is gradually increased. The retard amount command value is determined based on the engine water temperature, and is decreased as the engine water temperature increases. Therefore, in order to perform the diagnosis reliably, it is desirable to perform the diagnosis after the retard amount of the ignition timing is increased to some extent. On the other hand, as shown in FIG. Regardless of whether the early warm-up control is normal or abnormal, it will converge to a predetermined target speed after the failure detection interval, so it is better to make a diagnosis as soon as possible after the catalyst scavenging warm-up delay control is executed. good.

  In this diagnostic routine, the diagnosis start condition is satisfied when the ignition timing fluctuation amount (retard amount) by the ignition timing retard control command is greater than or equal to the set value (ignition timing is greater than or equal to the set value) in step S3. . When the ignition timing retard amount is less than the set value and the diagnosis start condition is not satisfied, the process returns from step S3 to step S1, and when the ignition timing retard amount is equal to or greater than the set value and the diagnosis start condition is satisfied, step S3 to step S1. Proceed to S4. For the same reason, the diagnosis is ended when the set time has elapsed after the engine is started (determination in step S7 described later).

  In step S4, the current engine speed NE based on the signal from the crank angle sensor 20 and the current intake air amount Qa based on the signal from the intake air amount sensor 13 are read, and the ratio (NE / Qa) is calculated. Calculated as a diagnostic value. And it progresses to step S5 and it is investigated whether a diagnostic value (NE / Qa) is more than a determination threshold value.

  As a result, if the diagnosis value (NE / Qa) is less than the determination threshold, the catalyst early warm-up / retarding control functions normally in step S6, and the actual ignition timing is retarded according to the command value. In step S7, the diagnosis end condition is determined. This diagnosis end condition is determined by whether or not the elapsed time after engine start has reached the set time. If the elapsed time after engine start reaches the set time, it is determined that the diagnosis has ended and the routine exits. If the elapsed time after engine startup has not reached the set time, the process returns to step S1, and the diagnosis is continued while the conditions of steps S1 to S3 are satisfied.

  Note that the diagnosis end may be determined by integrating the engine speed after the engine is started and determining that the diagnosis is completed when the integrated value of the engine speed reaches a set value.

  On the other hand, if the diagnostic value (NE / Qa) is greater than or equal to the determination threshold value in step S5, the process proceeds to step S8, where the catalyst early warm-up / retarding angle control does not function normally, and the actual ignition timing is set according to the command value. It is not retarded and it is determined that a failure has occurred. For example, as shown by the rough broken line in FIG. 2, when the diagnosis value (NE / Qa) is a failure that greatly exceeds the determination threshold, the retarding is actually delayed with respect to the ignition timing retarding control command. Almost nothing has been done, it is judged that an abnormality has occurred in the ignition system components, etc., the control is forcibly stopped, the details of the failure are recorded in the memory in the ECU 50, and a warning lamp is lit. Encourage repairs by warehousing at service stations.

  In addition, as shown by a thin broken line in FIG. 2, when the diagnosis value (NE / Qa) is a failure that slightly exceeds the determination threshold, the response to the ignition timing retarding control command is slow, Assuming that there is a delay in the retard control due to deterioration or the like, similarly, the failure content is recorded in the memory in the ECU 50, and a warning lamp is turned on so that the driver can go to a service station for inspection. Encourage warehousing.

  As described above, in the present embodiment, it is possible to perform a diagnosis that is not easily affected by the ignition timing control (advance / control stop / retard amount decrease) for catalyst early warm-up control, and the engine is relatively Even when the water temperature is high and the ignition timing retardation amount for the early catalyst warm-up control is small, the abnormality can be reliably detected. Furthermore, a control speed deviation of the ignition timing control such that the ignition timing is retarded can be detected as an abnormality.

  Next, a second embodiment of the present invention will be described. 4 and 5 relate to the second embodiment of the present invention, FIG. 4 is a flowchart of a diagnostic routine, and FIG. 5 is a flowchart showing another diagnostic routine.

  The second form introduces a diagnosis counter that measures the elapsed time after the diagnosis start condition is satisfied, and determines the actual diagnosis execution and termination based on the value of the diagnosis counter.

  For this reason, in the second embodiment, the diagnosis process for the catalyst early warm-up / retard angle control is performed by the diagnosis routine shown in the flowchart of FIG. In this diagnosis routine, in the first steps S11, S12, and S13, as in steps S1, S2, and S3 of the diagnosis routine of the first embodiment (see FIG. 3), the conditions for executing the catalyst early warm-up / retarding angle control are established, Further, it is checked whether the retard amount of the ignition timing is equal to or larger than a set value during the idling operation.

  When the conditions for executing the catalyst early warm-up / retarding angle control are satisfied, and the ignition timing retarding amount is equal to or larger than the set value during the idling operation, the process proceeds from step S13 to step S14, and the diagnostic counter is added. Check whether the diagnostic counter has exceeded the set value. The diagnosis counter starts counting after the diagnosis start condition is satisfied.

  When the diagnosis counter becomes equal to or larger than the set value, the process proceeds from step S15 to step S16, the ratio (NE / Qa) between the engine speed NE and the intake air amount Qa is calculated as the diagnosis value, and the diagnosis value (NE) is calculated in step S17. It is checked whether / Qa) is equal to or greater than the determination threshold. As a result, if the diagnostic value (NE / Qa) is less than the determination threshold, it is determined normal in step S18 and the routine is terminated. If the diagnostic value (NE / Qa) is greater than or equal to the determination threshold, a failure occurs in step S19. And the routine is terminated.

  On the other hand, if the ignition timing is less than the set value in step S13, the process proceeds from step S13 to step S20 to reset the diagnosis counter. In step S21, the diagnosis is made based on whether or not the elapsed time after engine start has reached the set time. If the diagnosis counter has not reached the set value in step S15, the process proceeds from step S15 to step S21 to determine the completion of diagnosis.

  As a result, in step S21, when the elapsed time after engine start has not reached the set time, the process returns to step S11. When the elapsed time after engine start has reached the set time, it is determined that the diagnosis is finished and step S21 is performed. Exit the routine. That is, if the diagnostic counter does not reach the set value within the set time after the engine is started, the diagnostic value is less reliable thereafter, and the process is terminated without making a diagnosis.

  Even if the diagnostic counter does not reach the set value within the set time after the engine is started, as shown by the broken line in the flowchart of FIG. 4, the routine proceeds to step S16 without terminating the routine in step S21. As long as the catalyst early warm-up / retarding angle control and the idling operation are continued, the diagnosis may be performed once after the engine is started. Thereby, the chance of diagnosis can be increased and abnormality can be detected more reliably.

  In this case, as described above, the diagnosis performed when the diagnosis counter does not reach the set value within the set time after the engine is started is a provisional diagnosis in which the diagnostic value is less reliable than the normal diagnosis. It is. Therefore, as shown in the flowchart of FIG. 5, the reference value for diagnosis may be changed between a regular diagnosis and a provisional diagnosis.

  The diagnostic routine shown in the flowchart of FIG. 5 is obtained by adding steps S22 and S23 for provisional diagnosis to the diagnostic routine of FIG. That is, if the diagnostic counter does not reach the set value within the set time after the engine is started, the process proceeds from step S21 to step S22 to tentatively calculate the diagnostic value (NE / Qa), and in step S23 the diagnostic value (NE / Qa) is compared with the second determination threshold value. The second determination threshold value is set to a value higher than the determination threshold value in the normal diagnosis (step S17) in consideration of a decrease in the certainty of the provisional diagnosis value (NE / Qa).

  If the diagnostic value (NE / Qa) is greater than or equal to the second determination threshold, it is determined to be normal in step S18, and if the diagnostic value (NE / Qa) is less than the second determination threshold, in step S19. Judge as failure. As a result, after the engine is started, a diagnosis is always performed once to increase the chance of detecting an abnormality, and the reliability of the diagnosis can be maintained.

  In the second mode, as in the first mode, it is possible not only to make a diagnosis that is not easily influenced by the ignition timing control for the catalyst early warm-up control, but also to increase the chances of the diagnosis, thereby increasing the probability of detecting an abnormality. Can be improved.

  Next, a third embodiment of the present invention will be described. FIG. 6 is a flowchart of a diagnostic routine according to the third embodiment of the present invention.

  The third form changes the diagnosis start condition for the catalyst early warm-up control with respect to the first form, and adds the integrated value of the engine speed as the diagnosis start condition.

  The diagnosis routine of the third form is shown in the flowchart of FIG. 6. In this diagnosis routine, the first steps S31, S32, S33 are the steps S1, S2, S3 of the first form diagnosis routine (see FIG. 3). Similarly, it is checked whether or not the conditions for executing the catalyst early warm-up / retarding angle control are satisfied and the ignition timing retardation amount is equal to or larger than the set value during the idling operation. If the conditions for executing the catalyst early warm-up / retard angle control are satisfied and the ignition timing retard amount is equal to or larger than the set value during the idling operation, the engine speed is integrated in step S34. The integration of the engine speed is performed after the engine is started.

  Subsequently, it progresses to step S35 and it is investigated whether an engine speed integrated value is more than a setting value. If the engine speed integrated value is less than the set value, the process returns from step S35 to step S31. If the engine speed integrated value is greater than or equal to the set value, the process proceeds to step S36 and the engine speed NE and the intake air are increased. A ratio (NE / Qa) to the quantity Qa is calculated as a diagnostic value. In step S36, the diagnosis value (NE / Qa) is compared with the determination threshold value. If the diagnosis value (NE / Qa) is equal to or greater than the determination threshold value, it is determined normal in step S37, and the diagnosis value (NE / Qa). Is less than the determination threshold, it is determined as a failure in step S38.

  The third mode for determining the start of diagnosis based on the integrated value of the engine speed is effective when a diagnosis is desired in a short time after the engine is started. That is, when an abnormality occurs, the actual ignition timing is not retarded according to the command value, and the engine speed rises faster than normal. For this reason, it is possible to make an early diagnosis by adding the engine rotation speed integrated value to the diagnosis start condition, and to increase the chance of detecting an abnormality.

Schematic configuration diagram of an engine system according to the first embodiment of the present invention. The same as above, explanatory diagram showing the relationship between the change in engine speed and intake air amount by the ignition timing retard control and the diagnostic value Same as above, flowchart of diagnostic routine The flowchart of a diagnostic routine according to the second embodiment of the present invention. Same as above, flowchart of other diagnostic routines The flowchart of a diagnostic routine according to the third embodiment of the present invention.

Explanation of symbols

1 engine 9 catalyst 50 electronic control device (catalyst early warm-up control means, abnormality diagnosis means)
NE Engine speed Qa Intake air amount NE / Qa Diagnostic value

Claims (8)

Catalyst early warm-up control means for performing catalyst early warm-up control for increasing the exhaust heat amount of the engine and promoting warm-up of the catalyst interposed in the exhaust system of the engine;
An abnormality diagnosing means for diagnosing whether or not the catalyst early warm-up control means is abnormal is based on a ratio between the engine load during idling and the engine speed that changes with the execution of the catalyst early warm-up control. An engine control device.   2. The engine control device according to claim 1, wherein the engine load is an intake air amount or an intake pipe pressure of the engine. The catalyst early warm-up control means includes
At least by retarding the ignition timing of the engine, the exhaust heat amount of the engine is increased and the catalyst early warm-up control is executed.
The abnormality diagnosis means includes
3. The engine according to claim 1, wherein the diagnosis is started when a set time elapses after the engine is started or when an ignition timing fluctuation amount in the ignition timing control becomes a set value or more. Control device. The abnormality diagnosis means includes
4. The engine control apparatus according to claim 3, wherein the diagnosis is started after a set time has elapsed after an ignition timing fluctuation amount in the ignition timing control becomes equal to or greater than a set value. The abnormality diagnosis means includes
5. The diagnosis is ended when a set time has elapsed after the start of the engine or when an integrated value of the engine speed becomes equal to or greater than a set value. 6. Engine control device. The abnormality diagnosis means includes
2. The provisional diagnosis is performed in which the diagnosis is tentatively performed when the set time has elapsed after the engine is started if the diagnosis is not started within a set time after the engine is started. The control apparatus of the engine as described in any one of -4.   The engine control apparatus according to claim 6, wherein the provisional diagnosis is performed under conditions different from the diagnosis. The abnormality diagnosis means includes
4. The engine control according to claim 3, wherein the diagnosis is started when an integrated value of the engine speed becomes a set value or more after an ignition timing fluctuation amount in the ignition timing control becomes a set value or more. apparatus.

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