JP4345853B2 - Abnormality diagnosis device for intake system sensor - Google Patents

Description

  The present invention relates to an abnormality diagnosis device for an intake system sensor for diagnosing whether there is an abnormality in an intake system sensor that detects an intake pipe pressure or an intake air amount of an internal combustion engine.

  In recent years, the demand for in-cylinder injection engines (so-called direct injection engines) having the features of low fuel consumption, low exhaust emission, and high output has been increasing rapidly. This in-cylinder injection engine switches between the stratified combustion mode and the homogeneous combustion mode according to the engine operating state. In the stratified combustion mode, a small amount of fuel is directly injected into the cylinder in the compression stroke to stratify the mixture ( In the homogeneous combustion mode, the fuel injection amount is increased and the fuel is directly injected into the cylinder in the intake stroke so that the air-fuel mixture is homogeneously combusted (stoichiometric or rich combustion).

  In general, in-cylinder injection engines perform air-fuel ratio control, EGR control (exhaust gas recirculation control), and the like based on the output of the intake pipe pressure sensor during homogeneous combustion mode operation. Therefore, it is necessary to perform abnormality diagnosis of the intake pipe pressure sensor in order to ensure the performance.

Therefore, for example, as shown in Patent Document 1 (Japanese Patent No. 2518317), the intake pipe pressure (detected value) detected by the intake pipe pressure sensor every predetermined period, the intake pipe pressure (based on the throttle opening, etc.) In some cases, the presence or absence of abnormality in the intake pipe pressure sensor is diagnosed.
Japanese Patent No. 2518317 (Page 2 etc.)

  By the way, in the stratified charge combustion mode operation in which lean combustion is performed, the throttle opening is maintained almost fully open and the intake pipe pressure is maintained substantially constant (near atmospheric pressure) during the stratified charge combustion mode operation. Even if the abnormality of the intake pipe pressure sensor is executed during operation, the abnormality diagnosis can be performed only when the intake pipe pressure is near atmospheric pressure, and the response of the intake pipe pressure sensor to changes in the intake pipe pressure Since followability and the like cannot be evaluated, it is impossible to accurately diagnose whether there is an abnormality in the intake pipe pressure sensor.

  On the other hand, during the homogeneous combustion mode operation with stoichiometric or rich combustion, the throttle opening changes according to the accelerator opening etc. and the intake pipe pressure changes, so the abnormality diagnosis of the intake pipe pressure sensor during this homogeneous combustion mode operation It seems that the above problem can be solved by executing.

  From this point of view, it is conceivable to perform abnormality diagnosis of the intake pipe pressure sensor only during the homogeneous combustion mode operation. In this case, depending on the vehicle operation method, traveling pattern, etc., the duration time of the stratified combustion mode operation is considered. Or the frequency of stratified combustion mode operation increases, and the number of times of abnormality diagnosis of the intake pipe pressure sensor executed during homogeneous combustion mode operation decreases. There is a possibility that the execution frequency cannot be secured appropriately. For this reason, even if an abnormality occurs in the intake pipe pressure sensor, there is a possibility that it cannot be detected early. Such a problem can also occur with respect to abnormality diagnosis of an air flow meter that detects the intake air amount.

  The present invention has been made in consideration of such circumstances. Accordingly, the object of the present invention is to ensure the frequency of execution of abnormality diagnosis of intake system sensors (intake pipe pressure sensor, air flow meter, etc.). An object of the present invention is to provide an abnormality diagnosis device for an intake system sensor capable of detecting an abnormality of a sensor at an early stage.

  In order to achieve the above object, an abnormality diagnosis device for an intake system sensor according to claim 1 of the present invention switches between a stratified combustion mode and a homogeneous combustion mode by a combustion mode switching control means in response to a combustion mode switching request, and an internal combustion engine. In the system for diagnosing the presence or absence of abnormality in the intake system sensor for detecting the intake pipe pressure or the intake air amount, the sensor abnormality diagnosis means uses at least the output of the intake system sensor when switching the combustion mode. The combustion mode switching is performed using at least one of the air-fuel ratio detected by the exhaust gas sensor and the estimated air-fuel ratio when diagnosing whether the intake system sensor is abnormal or not. Is to check.

  When switching between the stratified combustion mode and the homogeneous combustion mode, the throttle opening is switched and the intake pipe pressure and the intake air amount change, so the response and follow-up performance of the intake system sensor is based on the output of the intake system sensor. Etc., and the presence or absence of abnormality of the intake system sensor can be diagnosed with high accuracy. Therefore, if the abnormality diagnosis of the intake system sensor is executed during the combustion mode switching, the number of times of the abnormality diagnosis can be increased accordingly, so the frequency of the homogeneous combustion mode operation is reduced and the homogeneous combustion mode is reduced. Even under conditions where the number of abnormality diagnoses executed during operation is reduced, the frequency of abnormality diagnosis can be ensured, and when an abnormality occurs in the intake system sensor, the abnormality can be detected early.

  By the way, if the combustion mode switching is not performed normally due to some cause during abnormality diagnosis of the intake system sensor, the behavior of intake pipe pressure and intake air amount will be different from normal behavior. Even though the intake system sensor is normal, there is a possibility of erroneous diagnosis that the intake system sensor is abnormal.

  As a countermeasure, it is confirmed whether or not the combustion mode has been normally switched based on the air-fuel ratio when diagnosing the presence or absence of abnormality in the intake system sensor. At the time of abnormality diagnosis of the intake system sensor, it may be determined whether or not the switching of the combustion mode has been normally performed based on whether or not the air-fuel ratio has become the air-fuel ratio corresponding to the switching-destination combustion mode. As a result, when it is determined that the switching of the combustion mode has not been performed normally, it is not necessary to diagnose that there is an abnormality in the intake system sensor, and erroneous diagnosis can be prevented.

  In this case, the air-fuel ratio used for confirming switching of the combustion mode is at least one of the air-fuel ratio detected by the exhaust gas sensor and the estimated air-fuel ratio. Whether the detected air-fuel ratio or the estimated air-fuel ratio is used, it is possible to accurately determine whether the combustion mode has been switched normally.

<Embodiment (1)>
Hereinafter, an embodiment (1) of the present invention will be described with reference to FIGS. First, a schematic configuration of the entire engine control system will be described with reference to FIG. An air cleaner 13 is provided at the most upstream portion of the intake pipe 12 of the direct injection engine 11 which is an internal combustion engine of the direct injection type, and an air flow meter 14 (detecting an intake air amount) downstream of the air cleaner 13 ( An intake system sensor) is provided. A throttle valve 16 driven by a motor 15 such as a DC motor is provided on the downstream side of the air flow meter 14, and an opening degree (throttle opening degree) of the throttle valve 16 is detected by a throttle opening degree sensor 17.

  A surge tank 18 is provided on the downstream side of the throttle valve 16, and an intake pipe pressure sensor 19 (intake system sensor) for detecting the intake pipe pressure is provided in the surge tank 18. The surge tank 18 is provided with an intake manifold 20 that introduces air into each cylinder of the engine 11, and controls the in-cylinder airflow strength (swirl flow strength and tumble flow strength) in the intake manifold 20 of each cylinder. An airflow control valve 31 is provided.

  A fuel injection valve 21 that directly injects fuel into the cylinder is attached to an upper portion of each cylinder of the engine 11. A spark plug 22 is attached to the cylinder head of the engine 11 for each cylinder, and the air-fuel mixture in the cylinder is ignited by the spark discharge of each spark plug 22. In addition, the intake valve 37 and the exhaust valve 38 of the engine 11 are provided with variable valve timing mechanisms 39 and 40 for varying the valve timing, respectively.

  A knock sensor 32 that detects knocking and a cooling water temperature sensor 23 that detects cooling water temperature are attached to the cylinder block of the engine 11. A crank angle sensor 24 that outputs a crank angle signal at every predetermined crank angle is attached to the outer peripheral side of the crankshaft (not shown). Based on the output signal of the crank angle sensor 24, the crank angle and the engine speed are detected.

  On the other hand, the exhaust pipe 25 of the engine 11 is provided with an upstream catalyst 26 and a downstream catalyst 27 for purifying the exhaust gas, and the air-fuel ratio or rich / lean of the exhaust gas is detected on the upstream side of the upstream catalyst 26. An exhaust gas sensor 28 (air-fuel ratio sensor, oxygen sensor, etc.) is provided. In the present embodiment, a three-way catalyst for purifying CO, HC, NOx and the like in the exhaust gas is provided near the stoichiometric as the upstream catalyst 26, and a NOx occlusion reduction type NOx catalyst is provided as the downstream catalyst 27. . The NOx catalyst 27 stores NOx in the exhaust gas when the air-fuel ratio of the exhaust gas is lean, and reduces and purifies the stored NOx when the air-fuel ratio of the exhaust gas becomes near or rich in the stoichiometric ratio. Has characteristics.

  Further, a part of the exhaust gas is recirculated to the intake side between the downstream side of the upstream catalyst 26 in the exhaust pipe 25 and the surge tank 18 on the downstream side of the throttle valve 16 in the intake pipe 12. An EGR pipe 33 is connected, and an EGR valve 34 for controlling the exhaust gas recirculation amount (EGR amount) is provided in the middle of the EGR pipe 33. Further, the accelerator sensor 36 detects the amount of depression of the accelerator pedal 35 (accelerator opening).

  Further, a brake booster 42 is connected to the surge tank 18 via a negative pressure introduction pipe 41, and a pressure (negative pressure) in the negative pressure chamber is supplied to a negative pressure chamber (not shown) of the brake booster 42. A brake negative pressure sensor 43 for detection is provided. The negative pressure introduction pipe 41 may be connected to the intake pipe 12 between the throttle valve 16 and the surge tank 18.

  Outputs of the various sensors described above are input to an engine control circuit (hereinafter referred to as “ECU”) 30. The ECU 30 is mainly composed of a microcomputer, and executes various control routines stored in a built-in ROM (storage medium) to thereby determine the fuel injection amount and fuel of the fuel injection valve 21 according to the engine operating state. The injection timing, the ignition timing of the spark plug 22 and the like are controlled.

  The ECU 30 functions as a combustion mode switching control means by executing each routine shown in FIGS. 2 to 7 described later, and is harmonized with the stratified combustion mode according to the engine operating state (required torque, engine speed, etc.). Switch between combustion modes. In the stratified combustion mode, a small amount of fuel is directly injected into the cylinder in the compression stroke, and a stratified mixture is formed in the vicinity of the spark plug 22 for stratified combustion (lean combustion), thereby improving fuel efficiency. On the other hand, in the homogeneous combustion mode, the engine output is increased by increasing the fuel injection amount and directly injecting fuel into the cylinder during the intake stroke to form a homogeneous mixture and performing homogeneous combustion (stoichiometric or rich combustion).

  At that time, the ECU 30 executes the NOx purge control for temporarily switching to the homogeneous combustion mode when the NOx purge request is generated during the stratified combustion mode operation to reduce and purify the stored NOx of the NOx catalyst 27, thereby performing the stratified combustion mode operation. When a brake negative pressure request occurs, the brake combustion pressure control is executed to temporarily switch to the homogeneous combustion mode to increase the negative pressure in the intake pipe 12 and secure the negative pressure to be introduced into the brake booster 42.

  Further, the ECU 30 functions as a sensor abnormality diagnosing means by executing the abnormality diagnosis routine of the intake pipe pressure sensor shown in FIGS. 8 and 9. (1) When switching the combustion mode according to the engine operating state ( 2) When switching the combustion mode by NOx purge control, (3) When switching the combustion mode by brake negative pressure control, the presence or absence of abnormality of the intake pipe pressure sensor 19 is diagnosed based on the output change of the intake pipe pressure sensor 19 .

  Hereinafter, processing contents of each routine shown in FIGS. 2 to 9 executed by the ECU 30 will be described.

[Engine control main routine]
The engine control main routine of FIG. 2 is executed at a predetermined cycle after an ignition switch (not shown) is turned on. When the main routine is started, first, in step 100, the required torque is calculated based on the accelerator opening, the engine speed, and the like. After this, the routine proceeds to step 200, the combustion mode determination routine of FIG. 3 is executed to determine the combustion mode, and then the routine proceeds to step 300, where the combustion mode switching control routine of FIG. For example, the combustion mode switching control is executed, and the air system control routine of FIG. 5, the fuel system control routine of FIG. 6, and the ignition system control routine of FIG. The combustion mode is switched by switching the control parameters of the system and the ignition system to the target value of the switching destination combustion mode at the timing described later.

[Combustion mode decision routine]
When the combustion mode determination routine of FIG. 3 is started in step 200 of the engine control main routine of FIG. 2, first, in step 201, the required combustion mode determination map is searched and the current engine operating state (for example, engine speed and Depending on the required torque), either the stratified combustion mode or the homogeneous combustion mode is selected as the required combustion mode. In this required combustion mode determination map, the stratified combustion mode is selected in the low rotation and low torque regions with priority on fuel economy, while the homogeneous combustion mode is selected in the high rotation and high torque regions with priority on engine output. Is set to be.
However, even when the required combustion mode selected according to the engine operating state is the stratified combustion mode, when the NOx purge request is generated or the brake negative pressure request is generated, the required combustion mode is temporarily switched to the homogeneous combustion mode. .

  Thereafter, the process proceeds to step 202, where it is determined whether the required combustion mode is the homogeneous combustion mode. If the required combustion mode is the homogeneous combustion mode, the process proceeds to step 203, where the current actual combustion mode is the homogeneous combustion mode. It is determined whether or not there is. If the current actual combustion mode is not the homogeneous combustion mode, it is necessary to switch the combustion mode. Therefore, the routine proceeds to step 204, the combustion mode switching flag is turned on, and the routine proceeds to step 205, where the air system control mode is made homogeneous. Set to combustion mode. On the other hand, if the current actual combustion mode is the homogeneous combustion mode, it is not necessary to switch the combustion mode. Therefore, the process skips step 204 and proceeds to step 205 to maintain the air system control mode in the homogeneous combustion mode.

  When it is determined in step 202 that the required combustion mode is not the homogeneous combustion mode (stratified combustion mode), the routine proceeds to step 207, where it is determined whether or not the current actual combustion mode is the stratified combustion mode. . If the current actual combustion mode is not the stratified combustion mode, it is necessary to switch the combustion mode. Therefore, the routine proceeds to step 208, the combustion mode switching flag is turned on, and the routine proceeds to step 209, where the air system control mode is made homogeneous. Set to combustion mode. On the other hand, if the current actual combustion mode is the stratified combustion mode, there is no need to switch the combustion mode, so step 208 is skipped and the routine proceeds to step 205 to maintain the air system control mode in the stratified combustion mode.

[Combustion mode switching control routine]
When the combustion mode switching control routine of FIG. 4 is started in step 300 of the engine control main routine of FIG. 2, first, in step 301, the combustion mode switching is being performed depending on whether or not the combustion mode switching flag is ON. If it is not during combustion mode switching, this routine is terminated without performing the subsequent processing.

  On the other hand, if the combustion mode is being switched, the routine proceeds to step 302, where it is determined whether or not the required combustion mode is the stratified combustion mode, and the required combustion mode is not the stratified combustion mode (that is, the required combustion mode is the homogeneous combustion mode). If so, the process proceeds to step 303, where it is determined whether or not the actual air-fuel ratio A / F is in the homogeneous combustion region by determining whether or not the actual air-fuel ratio A / F is richer than the homogeneous combustion region determination value CAF2. . As a result, when it is determined that the actual air-fuel ratio A / F is leaner than the homogeneous combustion region determination value CAF2 (the actual air-fuel ratio A / F is not in the homogeneous combustion region), the subsequent processing is not performed. This routine is terminated.

  Thereafter, when it is determined that the actual air-fuel ratio A / F becomes richer than the homogeneous combustion region determination value CAF2 and the actual air-fuel ratio A / F has entered a region where homogeneous combustion can be performed, the routine proceeds to step 304, where fuel system control is performed. After the mode is set to the homogeneous combustion mode and the fuel injection mode is switched to the intake stroke injection, the combustion mode switching flag is turned OFF and this routine is terminated. As a result, the actual combustion mode is switched to the homogeneous combustion mode.

  Further, when the combustion mode is being switched and it is determined that the required combustion mode is the stratified combustion mode (when both the determinations in steps 301 and 302 are “Yes”), the routine proceeds to step 306 and the actual air-fuel ratio A Whether or not the actual air-fuel ratio A / F is in the stratified combustion region is determined by whether / F is leaner than the stratified combustion region determination value CAF1. As a result, when it is determined that the actual air-fuel ratio A / F is richer than the stratified combustion region determination value CAF1 (the actual air-fuel ratio A / F does not enter the stratified combustion region), the subsequent processing is performed. This routine is terminated.

  Thereafter, when it is determined that the actual air-fuel ratio A / F is leaner than the stratified charge combustion region determination value CAF1 and the actual air-fuel ratio A / F has entered a region where stratified combustion is possible, the routine proceeds to step 308, where fuel system control is performed. After the mode is set to the stratified combustion mode and the fuel injection mode is switched to the compression stroke injection, the combustion mode switching flag is turned OFF and this routine is terminated. As a result, the actual combustion mode is switched to the stratified combustion mode.

[Air control routine]
When the air system control routine of FIG. 5 is started in step 400 of the engine control main routine of FIG. 2, first, in step 401, it is determined whether or not the air system control mode is the homogeneous combustion mode. If so, the process proceeds to step 402, and the target value for the homogeneous combustion mode according to the engine operating state is used as the target value of the control parameter (throttle opening degree, etc.) of the air system using the map for the homogeneous combustion mode, respectively. calculate.

  On the other hand, if it is determined in step 401 that the air system control mode is not the homogeneous combustion mode (the stratified combustion mode), the process proceeds to step 403, where the target value of the air system control parameter is used for the stratified combustion mode. The target value for the stratified combustion mode corresponding to the engine operating state is calculated using the map of FIG.

[Fuel system control routine]
When the fuel system control routine of FIG. 6 is started in step 500 of the engine control main routine of FIG. 2, first, in step 501, it is determined whether or not the fuel system control mode is the homogeneous combustion mode, and the homogeneous combustion mode is determined. If so, the process proceeds to step 502, and the homogeneity corresponding to the engine operating state is obtained by using a map for the homogeneous combustion mode as a target value of the fuel system control parameters (fuel injection amount, fuel injection timing, fuel pressure, etc.). A target value for the combustion mode is calculated.

  If it is determined in step 501 that the fuel system control mode is not the homogeneous combustion mode (stratified combustion mode), the process proceeds to step 503, where the target value of the control parameter of the fuel system is used for the stratified combustion mode. The target value for the stratified combustion mode corresponding to the engine operating state is calculated using the map of FIG.

[Ignition system control routine]
When the ignition system control routine of FIG. 7 is started in step 600 of the engine control main routine of FIG. 2, first, in step 601, it is determined whether or not the ignition system control mode (= fuel system control mode) is the homogeneous combustion mode. If it is the homogeneous combustion mode, the process proceeds to step 602, and the target value of the ignition system control parameter (ignition timing) is used for the homogeneous combustion mode according to the engine operating state using a map for the homogeneous combustion mode or the like. The target value of is calculated.

  If it is determined in step 601 that the ignition system control mode is not the homogeneous combustion mode (stratified combustion mode), the process proceeds to step 603, where the target value of the ignition system control parameter is set for the stratified combustion mode. A target value for the stratified combustion mode corresponding to the engine operating state is calculated using a map or the like.

[Intake pipe pressure sensor abnormality diagnosis routine]
The abnormality diagnosis routine for the intake pipe pressure sensor shown in FIGS. 8 and 9 is executed at a predetermined cycle after the ignition switch (not shown) is turned on. When this routine is started, first, in steps 701 to 703, it is determined whether the throttle control system, the EGR control system, and the valve timing control system are all normal based on the diagnosis result of the vehicle self-diagnosis function. To do. As a result, if any one of the throttle control system, the EGR control system, and the valve timing control system is determined to be abnormal, it is determined that it is not possible to diagnose the abnormality of the intake pipe pressure sensor 19. The routine is terminated without executing the processing relating to the abnormality diagnosis of the intake pipe pressure sensor 19 after step 704.

  On the other hand, if it is determined in steps 701 to 703 that the throttle control system, the EGR control system, and the valve timing control system are all normal, the processing related to abnormality diagnosis of the intake pipe pressure sensor 19 in step 704 and subsequent steps is performed. Do as follows.

  First, in step 704, it is determined whether or not the combustion mode is being switched based on whether or not the combustion mode switching flag is ON. If it is determined that the combustion mode is being switched, the process proceeds to step 705, where an abnormality is detected. Whether or not diagnosis is being performed is determined by whether or not the abnormality diagnosis flag is ON.

  The first time after it is determined that the combustion mode is being switched (that is, at the start of the combustion mode switching), since the abnormality diagnosis flag is OFF, it is determined in step 705 that the abnormality is not being diagnosed. After reading the output value MAP0 of the intake pipe pressure sensor 19 at the start of mode switching, the routine proceeds to step 707, where the abnormality diagnosing flag is turned on, and this routine ends.

  After the abnormality diagnosis flag is turned on, it is determined in step 705 that abnormality diagnosis is in progress. Therefore, the routine is terminated without performing the processing in steps 706 and 707.

  Thereafter, when the switching of the fuel mode is completed and it is determined in step 704 that the combustion mode is not being switched, the process proceeds to step 708 in FIG. 9 to determine whether or not an abnormality diagnosis is being performed.

  The first time after it is determined that the combustion mode is not being switched (that is, at the end of the combustion mode switching), since the abnormality diagnosis flag is ON, it is determined in step 708 that the abnormality diagnosis is being performed, and the routine proceeds to step 709 where combustion is performed. After reading the output value MAP1 of the intake pipe pressure sensor 19 at the end of mode switching, the process proceeds to step 710, and the abnormality diagnosis flag is turned OFF.

  Thereafter, the process proceeds to step 711, where the output value MAP0 of the intake pipe pressure sensor 19 at the start of the combustion mode switching and the output value at the end of the combustion mode switching are obtained as information on the output change of the intake pipe pressure sensor 19 that occurs during the combustion mode switching. An absolute value ΔMAP of a difference from MAP1 (output change amount before and after switching of the combustion mode) is calculated.

ΔMAP = | MAP0−MAP1 |
Thereafter, it is determined whether or not the output change amount ΔMAP of the intake pipe pressure sensor 19 before and after switching the combustion mode is smaller than the abnormality determination value K. Since the behavior of the output of the intake pipe pressure sensor 19 during the switching of the combustion mode changes according to the engine operating state, the abnormality determination value K is determined by a map or a mathematical formula or the like according to the engine operating state (for example, the engine rotation speed and the required torque). Is set.

  As a result, if it is determined that the output change amount ΔMAP of the intake pipe pressure sensor 19 is smaller than the abnormality determination value K, the process proceeds to step 713 and it is determined that there is an abnormality (failure or the like) in the intake pipe pressure sensor 19. The abnormality flag is turned on and a warning lamp (not shown) provided on the instrument panel of the driver's seat is turned on, or a warning is displayed on the warning display section (not shown) of the instrument panel. Is also stored in the backup RAM (not shown) of the ECU 30 and the routine is terminated.

  On the other hand, when it is determined in step 712 that the output change amount ΔMAP of the intake pipe pressure sensor 19 is equal to or greater than the abnormality determination value K, the process proceeds to step 714 where there is no abnormality in the intake pipe pressure sensor 19 ( The normal diagnosis flag is turned OFF, and this routine is terminated.

  After the abnormality diagnosis flag is turned off, it is determined in step 708 that the abnormality diagnosis is not in progress. Therefore, the routine is terminated without performing the processing of steps 709 to 714.

  An execution example of this embodiment (1) described above will be described with reference to the time charts of FIGS. The output of the intake pipe pressure sensor 19 at the start of combustion mode switching when the required combustion mode is switched and the combustion mode switching flag is turned ON according to any of the engine operating state, NOx purge request, or brake negative pressure request Read the value MAP0. Thereafter, when the actual combustion mode is switched and the combustion mode switching flag is turned OFF, the output value MAP1 of the intake pipe pressure sensor 19 at the end of the combustion mode switching is read, and the sensor output value MAP0 at the start of the combustion mode switching is read. Using the sensor output value MAP1 at the end of the combustion mode switching, the output change amount ΔMAP = | MAP0−MAP1 | of the intake pipe pressure sensor 19 before and after the combustion mode switching is obtained.

  Then, the output change amount ΔMAP of the intake pipe pressure sensor 19 is compared with the abnormality determination value K. If the output change amount ΔMAP is greater than or equal to the abnormality determination value K as shown in FIG. It is determined that there is no abnormality (normal). On the other hand, as shown in FIG. 11, when the output change amount ΔMAP of the intake pipe pressure sensor 19 is smaller than the abnormality determination value K, it is determined that there is an abnormality (failure or the like) in the intake pipe pressure sensor 19.

When switching between the stratified combustion mode and the homogeneous combustion mode, the throttle opening is switched and the intake pipe pressure changes. Therefore, if the change in the output of the intake pipe pressure sensor 19 during the switching of the combustion mode is monitored, the intake pipe pressure sensor 19 can be accurately evaluated, and the presence or absence of abnormality of the intake pipe pressure sensor 19 can be diagnosed with high accuracy. Focusing on this point, in the present embodiment (1), since abnormality diagnosis of the intake pipe pressure sensor 19 is executed at the time of switching the combustion mode, not only the switching of the combustion mode according to the engine operating state but also the NOx purge is performed. An abnormality diagnosis of the intake pipe pressure sensor 19 can be executed using switching of the combustion mode by control and switching of the combustion mode by brake negative pressure control. Thereby, even under the condition that the time of the stratified combustion mode operation becomes longer and the frequency of the homogeneous combustion mode operation decreases, the frequency of executing the abnormality diagnosis of the intake pipe pressure sensor 19 can be secured. When an abnormality occurs, the abnormality can be detected early.
In addition to executing abnormality diagnosis of the intake pipe pressure sensor 19 at the time of switching the combustion mode, abnormality diagnosis of the intake pipe pressure sensor 19 is executed every time a predetermined diagnosis execution condition is satisfied during the homogeneous combustion mode operation. Anyway.

<Embodiment (2)>
By the way, when abnormality of the intake pipe pressure sensor 19 is diagnosed and switching of the combustion mode is not normally performed due to some cause, the intake pipe pressure sensor 19 is normal although the intake pipe pressure sensor 19 is normal. There is a possibility of erroneous diagnosis that the sensor 19 is abnormal.

  As a countermeasure, in the embodiment (2) of the present invention shown in FIGS. 12 to 14, the presence or absence of abnormality of the intake pipe pressure sensor 19 is diagnosed based on the output change amount of the intake pipe pressure sensor 19 before and after the combustion mode switching. At this time, it is confirmed whether or not the switching of the combustion mode has been normally performed based on the air-fuel ratio A / F, and if it is determined that the switching of the combustion mode has not been performed normally, the intake pipe pressure sensor Nineteen abnormalities are not diagnosed.

In the present embodiment (2), a routine in which the process in FIG. 9 is replaced with the process in FIG. 12 in the abnormality diagnosis routine for the intake pipe pressure sensor in FIG. 8 and FIG. 9 described in the above embodiment (1) is executed. The routine of FIG. 12 is obtained by adding the processing of steps 712a, 712b, and 712c after step 712 of the routine of FIG. 9 described in the embodiment (1), and the processing of other steps is shown in FIG. Is the same.
In the routine of FIG. 12, when it is determined in step 712 that the output change amount ΔMAP of the intake pipe pressure sensor 19 is smaller than the abnormality determination value K (when abnormality of the intake pipe pressure sensor 19 is suspected), step 712a Then, it is determined whether or not the required combustion mode is the stratified combustion mode. As a result, when it is determined that the required combustion mode is the stratified combustion mode, that is, when the homogeneous combustion mode is switched to the stratified combustion mode, the routine proceeds to step 712b and the air-fuel ratio A / detected by the exhaust gas sensor 28 is reached. It is determined whether F is leaner than the stratified combustion mode determination value A1. The air-fuel ratio A / F may be an estimated air-fuel ratio calculated based on the intake air amount and the fuel injection amount.

  As a result, when it is determined that the air-fuel ratio A / F is leaner than the stratified combustion mode determination value A1, it is determined that the switching of the combustion mode has been performed normally, the process proceeds to step 713, and the above step 712 is performed. The abnormality diagnosis result by is used as the final diagnosis result as it is, and it is diagnosed that there is an abnormality (failure or the like) in the intake pipe pressure sensor 19, and the abnormality flag is turned ON.

  On the other hand, when it is determined that the air-fuel ratio A / F is not leaner than the stratified combustion mode determination value A1, the combustion mode switching is not performed normally, so the intake pipe pressure sensor 19 Therefore, the process proceeds to step 714, invalidates the abnormality diagnosis result in step 712, and finally determines that there is no abnormality in the intake pipe pressure sensor 19 and turns off the abnormality flag. To do.

  On the other hand, when it is determined in step 712a that the required combustion mode is not the stratified combustion mode (ie, the homogeneous combustion mode), that is, when the stratified combustion mode is switched to the homogeneous combustion mode, the process proceeds to step 712c. It is determined whether the air-fuel ratio A / F is richer than the homogeneous combustion mode determination value A0.

  As a result, when it is determined that the air-fuel ratio A / F is richer than the homogeneous combustion mode determination value A0, it is determined that the switching of the combustion mode has been performed normally, the process proceeds to step 713, and finally Then, it is determined that there is an abnormality (failure or the like) in the intake pipe pressure sensor 19, and the abnormality flag is turned ON.

  On the other hand, if it is determined that the air-fuel ratio A / F is not richer than the homogeneous combustion mode determination value A0, the air system combustion mode switching is not performed normally, so the intake pipe pressure If it is determined that there is no situation in which the abnormality diagnosis of the sensor 19 can be performed, the process proceeds to step 714 to determine that there is no abnormality in the intake pipe pressure sensor 19 and the abnormality flag is turned OFF.

  According to this embodiment (2) described above, as shown in FIGS. 13 and 14, the air-fuel ratio A / F is higher than the homogeneous combustion mode determination value A0 when the stratified combustion mode is switched to the homogeneous combustion mode. If rich (or if the air-fuel ratio A / F is leaner than the stratified combustion mode determination value A1 when the homogeneous combustion mode is switched to the stratified combustion mode), it is determined that the combustion mode has been switched normally. When the output change amount ΔMAP of the intake pipe pressure sensor 19 is equal to or greater than the abnormality determination value K, it is determined that there is no abnormality in the intake pipe pressure sensor 19 (see FIG. 13), and the output change amount ΔMAP of the intake pipe pressure sensor 19 is If it is smaller than the abnormality determination value K, it is determined that there is an abnormality in the intake pipe pressure sensor 19 (see FIG. 14).

  On the other hand, if the air-fuel ratio A / F is leaner than the homogeneous combustion mode determination value A0 when the stratified combustion mode is switched to the homogeneous combustion mode (or the air-fuel ratio is switched to the stratified combustion mode from the homogeneous combustion mode). If A / F is richer than the stratified combustion mode determination value A1), it is determined that the combustion mode has not been switched normally, and the output change amount ΔMAP of the intake pipe pressure sensor 19 is greater than the abnormality determination value K. Is smaller, it is determined that there is no abnormality in the intake pipe pressure sensor 19. As a result, when the combustion mode is not switched normally, it is possible to prevent the intake pipe pressure sensor 19 from being erroneously diagnosed as being abnormal although the intake pipe pressure sensor 19 is normal. be able to.

  In each of the above embodiments (1) and (2), the output change amount ΔMAP before and after the combustion mode switching of the intake pipe pressure sensor 19 is calculated as information on the output change of the intake pipe pressure sensor 19 that occurs during the combustion mode switching. However, instead of the output change amount ΔMAP, the output change rate (output change rate) of the intake pipe pressure sensor 19 during the combustion mode switching is calculated, and the output change rate of the intake pipe pressure sensor 19 is determined to be abnormal. The presence or absence of abnormality of the intake pipe pressure sensor 19 may be diagnosed by comparing with the value.

  In addition, the presence or absence of abnormality of the intake pipe pressure sensor 19 may be diagnosed using other information related to the output change of the intake pipe pressure sensor 19 and various information related to the output of the intake pipe pressure sensor 19. good.

<Embodiment (3)>
Next, an embodiment (3) of the present invention will be described with reference to FIGS. In the system that executes the brake negative pressure control described above, the negative pressure in the intake pipe 12 is increased by the brake negative pressure control (switching from the stratified combustion mode to the homogeneous combustion mode), and the negative pressure is introduced into the brake booster 42. Therefore, if the intake pipe pressure sensor 19 is normal, the output of the intake pipe pressure sensor 19 and the output of the brake negative pressure sensor 43 should exhibit substantially the same behavior during execution of the brake negative pressure control.

  Focusing on this point, in the present embodiment (3), an abnormality diagnosis routine of the intake pipe pressure sensor of FIG. 15 described later is executed, so that the output of the intake pipe pressure sensor 19 can be obtained during execution of the brake negative pressure control. The output of the brake negative pressure sensor 43 is compared to diagnose whether the intake pipe pressure sensor 19 is abnormal.

  The abnormality diagnosis routine for the intake pipe pressure sensor in FIG. 15 is executed at a predetermined cycle after an ignition switch (not shown) is turned on. When this routine is started, first, in steps 801 to 803, it is determined whether the throttle control system, the EGR control system, and the valve timing control system are all normal based on the diagnosis result of the vehicle self-diagnosis function. To do. As a result, if any one of the throttle control system, the EGR control system, and the valve timing control system is determined to be abnormal, it is determined that it is not possible to diagnose the abnormality of the intake pipe pressure sensor 19. Without executing the processing related to abnormality diagnosis of the intake pipe pressure sensor 19 after step 804, the routine proceeds to step 812, where an abnormality counter to be described later is cleared, and this routine is terminated.

  On the other hand, if it is determined in steps 801 to 803 that the throttle control system, the EGR control system, and the valve timing control system are all normal, the processing related to abnormality diagnosis of the intake pipe pressure sensor 19 in step 804 and subsequent steps is performed. Do as follows.

  First, at step 804, it is determined whether or not the brake negative pressure control is being performed. If it is determined that the brake negative pressure control is not being performed, the routine proceeds to step 812, the abnormality counter is cleared, and this routine is terminated.

  Thereafter, when it is determined in step 804 that the brake negative pressure control is being performed, the process proceeds to step 805, where the output value MAP of the intake pipe pressure sensor 19 is read and the output value BRP of the brake negative pressure sensor 43 is read. Thereafter, the routine proceeds to step 806, where it is determined whether or not the differential pressure (MAP-BRP) between the output value MAP of the intake pipe pressure sensor 19 and the output value BRP of the brake negative pressure sensor 43 is greater than a predetermined value DP.

  As a result, if the differential pressure (MAP-BRP) is larger than the predetermined value DP, the process proceeds to step 807, and the abnormal counter is counted up. On the other hand, if the differential pressure (MAP-BRP) is less than or equal to the predetermined value DP, the process proceeds to step 808 and the abnormal counter is counted down.

  Thereafter, the process proceeds to step 809, where it is determined whether or not the count value of the abnormality counter is larger than the abnormality determination value KT. As a result, when it is determined that the count value of the abnormality counter is larger than the abnormality determination value KT, the process proceeds to step 810, where it is determined that there is an abnormality (failure or the like) in the intake pipe pressure sensor 19, and the abnormality flag is turned ON. A warning lamp (not shown) provided on the instrument panel of the driver's seat is turned on, or a warning is displayed on a warning display (not shown) of the instrument panel, and the driver is warned. Abnormal information (such as an abnormal code) is stored in a backup RAM (not shown) of the ECU 30, and this routine is terminated.

  On the other hand, if it is determined in step 809 that the count value of the abnormality counter is equal to or less than the abnormality determination value KT, it is not yet determined that the intake pipe pressure sensor 19 is abnormal, and the process proceeds to step 811. Then, it is determined that there is no abnormality (normal) in the intake pipe pressure sensor 19, the abnormality flag is maintained in the OFF state, and this routine is terminated.

  According to this embodiment (3) described above, as shown in FIGS. 16 and 17, the output value MAP of the intake pipe pressure sensor 19 and the output value of the brake negative pressure sensor 43 in a predetermined cycle during the brake negative pressure control. The differential pressure (MAP-BRP) with BRP is calculated, and if this differential pressure (MAP-BRP) is larger than the predetermined value DP, the abnormal counter is counted up and the differential pressure (MAP-BRP) is below the predetermined value DP. If so, the abnormality counter is counted down.

  Then, as shown in FIG. 16, when the count value of the abnormality counter does not exceed the abnormality determination value KT, it is determined that the intake pipe pressure sensor 19 is not abnormal (normal). On the other hand, as shown in FIG. 17, when the count value of the abnormality counter exceeds the abnormality determination value KT, it is determined that there is an abnormality (failure or the like) in the intake pipe pressure sensor 19.

  Even in the present embodiment (3) described above, it is possible to accurately diagnose the presence or absence of abnormality in the intake pipe pressure sensor 19, and to increase the number of times abnormality diagnosis is performed. The execution frequency can be secured, and the abnormality of the intake pipe pressure sensor 19 can be detected at an early stage.

<Embodiment (4)>
In the embodiment (4) of the present invention shown in FIG. 18, the output of the intake pipe pressure sensor 19 and the output of the brake negative pressure sensor 43 are compared during brake negative pressure control to determine whether the intake pipe pressure sensor 19 is abnormal. At the time of diagnosis, it is confirmed whether or not the switching of the combustion mode has been normally performed based on the air-fuel ratio A / F, and if it is determined that the switching of the combustion mode has not been performed normally, the intake pipe The pressure sensor 19 is not diagnosed as having an abnormality.

  The abnormality diagnosis routine of the intake pipe pressure sensor of FIG. 18 executed in the present embodiment (4) is obtained by adding the processing of step 806a after step 806 of the routine of FIG. 15 described in the above embodiment (3). Yes, the processing of each step other than that is the same as FIG.

  In the routine of FIG. 18, when it is determined in step 806 that the differential pressure (MAP−BRP) between the output value MAP of the intake pipe pressure sensor 19 and the output value BRP of the brake negative pressure sensor 43 is greater than a predetermined value DP. In step 806a, it is determined whether the air-fuel ratio A / F detected by the exhaust gas sensor 28 is richer than the homogeneous combustion mode determination value A0. The air-fuel ratio A / F may be an estimated air-fuel ratio calculated based on the intake air amount and the fuel injection amount.

  As a result, if it is determined that the air-fuel ratio A / F is richer than the homogeneous combustion mode determination value A0, it is determined that switching of the combustion mode has been performed normally, and the routine proceeds to step 807, where the abnormality counter is set. Count up.

  On the other hand, if it is determined that the air-fuel ratio A / F is not richer than the homogeneous combustion mode determination value A0, the combustion mode is not switched normally, so the intake pipe pressure sensor 19 If it is determined that the abnormality cannot be diagnosed, the process proceeds to step 808 to count down the abnormality counter. Thereby, the count value of the abnormality counter is prevented from exceeding the abnormality determination value KT.

In the present embodiment (4) described above, the intake pipe pressure sensor 19 is not diagnosed as being abnormal when the switching of the combustion mode is not performed normally during brake negative pressure control. Even though 19 is normal, it is possible to prevent the intake pipe pressure sensor 19 from being erroneously diagnosed as having an abnormality.
In the above embodiments (1) to (4), the present invention is applied to the abnormality diagnosis of the intake pipe pressure sensor 19, but the present invention may be applied to the abnormality diagnosis of the air flow meter 14.

  In addition, the present invention is not limited to a cylinder injection type engine, but can be similarly applied to a lean burn engine (an intake port injection engine capable of switching a combustion mode).

Schematic configuration diagram of the entire engine control system in the embodiment (1) of the present invention Flowchart showing the flow of processing of the engine control main routine Flow chart showing the flow of processing of the combustion mode determination routine Flowchart showing the flow of processing of the combustion mode switching control routine Flow chart showing process flow of air system control routine Flow chart showing the flow of processing of the fuel system control routine Flowchart showing the processing flow of the ignition system control routine Flowchart showing the flow of processing of the abnormality diagnosis routine of the intake pipe pressure sensor of the embodiment (1) (No. 1) Flowchart showing the flow of processing of the abnormality diagnosis routine of the intake pipe pressure sensor of the embodiment (1) (No. 2) The time chart which shows the example of execution at the time of normal intake pipe pressure sensor of embodiment (1) Time chart showing an execution example when the intake pipe pressure sensor is abnormal in the embodiment (1) The flowchart which shows the flow of a process of the principal part of the abnormality diagnosis routine of the intake pipe pressure sensor of Embodiment (2). Time chart showing an execution example of the embodiment (2) when the intake pipe pressure sensor is normal Time chart showing an execution example when the intake pipe pressure sensor is abnormal in the embodiment (2) The flowchart which shows the flow of a process of the abnormality diagnosis routine of the intake pipe pressure sensor of Embodiment (3). Time chart showing an execution example of the embodiment (3) when the intake pipe pressure sensor is normal Time chart showing an execution example when the intake pipe pressure sensor is abnormal in the embodiment (3) The flowchart which shows the flow of a process of abnormality diagnosis routine of the intake pipe pressure sensor of Embodiment (4).

Explanation of symbols

  DESCRIPTION OF SYMBOLS 11 ... Engine (internal combustion engine), 12 ... Intake pipe, 14 ... Air flow meter (intake system sensor), 16 ... Throttle valve, 19 ... Intake pipe pressure sensor (intake system sensor), 21 ... Fuel injection valve, 22 ... Ignition plug 25 ... exhaust pipe, 26 ... upstream catalyst (three-way catalyst), 27 ... NOx catalyst, 30 ... ECU (sensor abnormality diagnosis means, combustion mode switching control means).

Claims (1)

Combustion mode switching control means for switching between stratified combustion mode and homogeneous combustion mode according to the combustion mode switching request, and sensor abnormality diagnosis for diagnosing the presence or absence of abnormality in the intake system sensor for detecting the intake pipe pressure or intake air amount of the internal combustion engine In an abnormality diagnosis apparatus for an intake system sensor comprising means,
The sensor abnormality diagnosing means executes an abnormality diagnosis of the intake system sensor using at least the output of the intake system sensor at the time of switching the combustion mode, and is an exhaust gas sensor when diagnosing the presence or absence of the abnormality of the intake system sensor. An abnormality diagnosis apparatus for an intake system sensor, wherein switching of the combustion mode is confirmed using at least one of a detected air-fuel ratio and an estimated air-fuel ratio.

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