JP2005264879A - Secondary air supply device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a secondary air supply device for suitably suppressing the deterioration of exhaust emission even when any inconvenience occurs in secondary air supply. <P>SOLUTION: The secondary air supply device comprises a secondary air supply passage 11 communicating with an exhaust pipe 3 of an internal combustion engine 1. In the secondary air supply passage 11, an air cleaner 12, an air pump 13 and an air switching valve 14 are arranged for secondary air. The secondary air supply device performs driving control of the air pump 13 through an electronic control device 15 and opening/closing control of the air switching valve 14 to supply the secondary air to the exhaust pipe 3. At this time, the air pump 13 is controlled to be driven in two operation modes different in torque, depending on a mode for secondary air supply into the exhaust pipe 3. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a secondary air supply device that supplies secondary air for promoting oxidation of exhaust gas to an exhaust system of an internal combustion engine.

  As is well known, the secondary air supply device is connected to the exhaust system in a specific period until the catalyst disposed in the exhaust system of the internal combustion engine is activated, for example, at the start of the internal combustion engine. This device supplies secondary air (oxygen). By supplying such secondary air, the exhaust emission of the internal combustion engine in the specific period is improved, and the catalyst is activated early.

  By the way, during a specific period in which the secondary air supply device supplies secondary air to the exhaust system of the internal combustion engine, the oxygen concentration of the exhaust system is such that the air and fuel introduced into the combustion chamber of the internal combustion engine. It changes without depending on the ratio (air-fuel ratio). For this reason, in the internal combustion engine, the air-fuel ratio is controlled by so-called open loop control without performing air-fuel ratio feedback control for feedback control of the air-fuel ratio during this specific period.

  For this reason, during the specific period in which the secondary air is supplied by the secondary air supply device, some abnormality occurs in the secondary air supply device itself, and the supply of secondary air to the exhaust system of the internal combustion engine is sufficient. Otherwise, the exhaust emission of the internal combustion engine will be significantly reduced. That is, in this case, first of all, since the secondary air is not sufficiently supplied to the exhaust system of the internal combustion engine, improvement of exhaust emission by the supply of the secondary air cannot be expected. Secondly, since the catalyst is not activated, it is not expected to improve exhaust emission by the catalyst. Thirdly, since the air-fuel ratio control in the internal combustion engine is also performed by open loop control, the exhaust emission as the internal combustion engine is inevitably lowered.

Therefore, conventionally, as seen in Patent Document 1 or Patent Document 2, for example, a secondary air supply device that self-detects its own abnormality based on the oxygen concentration of the exhaust system of the internal combustion engine has been proposed. That is, in this secondary air supply device, the oxygen concentration in the exhaust system of the engine is maintained below the allowable value in spite of the specific period in which the secondary air is supplied to the exhaust system of the internal combustion engine. In such a case, this is detected as an abnormality of the device itself.
JP-A-9-137717 JP-A-4-308312

  Thus, according to the conventional secondary air supply device, it is possible to detect the abnormality of the device itself. However, this does not improve the deterioration of exhaust emission as an internal combustion engine.

  The present invention has been made in view of such circumstances, and the purpose thereof is a secondary air supply device that can suitably suppress deterioration of exhaust emission even if any inconvenience occurs in the supply of secondary air. Is to provide.

  In order to achieve such an object, according to the first aspect of the present invention, an air pump that pressurizes and discharges sucked air, and a secondary that supplies air discharged based on driving of the air pump to an exhaust system of the internal combustion engine. A secondary air supply device comprising an air supply path and valve means for opening and closing the secondary air supply path, and supplying secondary air to an exhaust system of an internal combustion engine through driving of the air pump and opening of the valve means As described above, control means for controlling the driving of the air pump in a plurality of operation modes each having a different torque is provided.

  As described above, the secondary air supply device is used with respect to the exhaust system at the initial start of the engine or the like in order to achieve early activation of the catalyst disposed in the exhaust system (exhaust pipe or the like) of the internal combustion engine. A device for supplying secondary air. For this reason, in such a secondary air supply device, it is not necessary to supply secondary air to the exhaust system of the internal combustion engine after the activation of the catalyst, and the secondary air supply path No secondary air will flow through. However, at this time, conversely, with the operation of the internal combustion engine, high-temperature exhaust gas flows into the secondary air supply path. When the exhaust gas flows into the secondary air supply path in this way, foreign matter may adhere to the connection portion between the secondary air supply path and the exhaust pipe. This obstructs the flow of the secondary air in the secondary air supply path, and thus makes it difficult to properly supply the secondary air to the exhaust system of the internal combustion engine.

  In this regard, according to the above configuration comprising the control means for controlling the driving of the air pump in a plurality of operation modes each having a different torque, even if the foreign matter adheres, for example, than in normal times By driving the air pump in an operation mode with high torque, the adhered foreign matter can be removed, or the foreign matter cannot be removed until the foreign matter is attached. A sufficient amount of secondary air can be supplied to the exhaust system (exhaust pipe) of the engine. Further, by controlling the supply amount of secondary air in such a manner, the above-described deterioration of exhaust emission and the like are suitably suppressed.

  Further, particularly in this case, as described in claim 2, as the control means, an operation mode of the air pump based on a detection output by a sensor that detects a secondary air supply mode to the exhaust system of the internal combustion engine. It is desirable to control the driving of the air pump in the selected operation mode.

  That is, normally, the flow rate of the secondary air supplied to the exhaust system of the internal combustion engine is naturally different between the case where foreign matter is attached to the connecting portion and the like and the case where foreign matter is not attached. In this regard, the above-described configuration in which the operation mode (drive torque) of the air pump is selectively used based on the detection output of the sensor that detects the secondary air supply mode to the exhaust system of the internal combustion engine, that is, the actual secondary air supply mode (supply amount) Accordingly, the operation mode (drive torque) of the air pump is selected and controlled in accordance with the presence or absence of the foreign matter or the amount of the foreign matter, so that a more appropriate failsafe can be achieved particularly when foreign matter is attached. become.

  Furthermore, in view of the fact that the flow rate (supply amount) of the secondary air supplied to the exhaust system of the internal combustion engine decreases as the amount of foreign matter adhering to the connection portion or the like increases, 3, the plurality of operation modes include a first operation mode and a second operation mode having a higher torque than the first operation mode. When the detection output by the sensor when the air pump is driven is less than a reference value of the air amount due to the supply of the secondary air, the second operation mode is selected, and the selected second operation mode is set. Therefore, it is more desirable to control the driving of the air pump in terms of simplicity and practicality of the control.

  In these configurations, the integrated value of the intake air amount sucked into the intake system of the internal combustion engine when the air pump is driven in the second operation mode is used as the control means. The logical product of the predetermined value indicating the active state of the catalyst provided in the exhaust system of the exhaust system and that the detection output by the sensor is equal to or greater than the reference value of the air amount by supplying the secondary air If the air pump is driven in the second operation mode until the condition is satisfied, the fail-safe can be realized accurately.

  That is, the temperature of the catalyst correlates with the integrated value of the intake air amount. In this regard, according to the above configuration, the integrated value of the intake air amount sucked into the intake system of the internal combustion engine becomes a predetermined value indicating the active state of the catalyst, and the detection output by the sensor is secondary air. Since the secondary air is supplied until it is determined that the air amount exceeds the reference value due to the supply of air, both the activation of the catalyst and the suppression of the deterioration of exhaust emission can be accurately achieved. become.

  In these configurations, as described in claim 5, as the control means, when the air pump is driven in the second operation mode, the continuous drive time of the air pump reaches an upper limit time required for fail-safe. Up to this point, the failsafe can be accurately realized by driving the air pump in the second operation mode.

  That is, when the air pump is continuously driven at a high torque, an excessive load is applied to the air pump. This also leads to a decrease in the reliability of the air pump, and its influence cannot be ignored. In this regard, according to such a configuration as the control means, it is possible to secure the maximum supply of the secondary air to the exhaust system of the internal combustion engine while suppressing a decrease in reliability as the air pump. .

  In these configurations, as described in claim 6, when the detection output from the sensor does not change even though the air pump is driven, the control unit is configured to store a diagnosis code indicating that in the storage unit. By storing it, it becomes possible to easily recognize that any of the components of the secondary air supply device is out of order.

  Further, in these configurations, as described in claim 7, further comprising a pressure sensor that detects a pressure between the air pump and the valve means in the secondary air supply path, and the control means includes the pressure sensor. By identifying the failure content of the secondary air supply device based on the transition of the pressure value detected by the sensor and storing the diagnosis code corresponding to the identified failure content in the storage means, the secondary air supply It is also possible to identify which of the components that make up the device has failed.

  In these configurations, as described in claim 8, when the secondary air supply device is activated as the control unit, when the diagnosis code is stored in the storage unit, the driving of the air pump is not executed. Then, it becomes possible to suppress the progress of deterioration as the secondary air supply device.

  In addition, as a sensor for detecting the secondary air supply mode to the exhaust system of the internal combustion engine, as described in claim 9, an empty air whose detection output changes linearly with respect to a change in the oxygen concentration of the exhaust system. It is desirable to be one of a fuel ratio sensor and an oxygen sensor whose detection output changes in a binary manner. Any of these sensors can detect the supply mode of the secondary air by using a sensor used for normal air-fuel ratio feedback control, and it is not necessary to newly provide any special sensor.

Hereinafter, an embodiment of a secondary air supply device according to the present invention will be described in detail with reference to FIGS.
The apparatus of this embodiment assumes a secondary air supply apparatus applied to an exhaust system of an on-vehicle gasoline engine. FIG. 1 includes the internal combustion engine and the entire configuration of the secondary air supply apparatus. This is shown schematically.

As shown in FIG. 1, the internal combustion engine 1 has a structure in which an intake pipe (intake system) 2 and an exhaust pipe (exhaust system) 3 are connected with a combustion chamber (not shown) as a boundary.
Among these, the intake pipe 2 is provided with an injector 4 for injecting fuel into the intake port of the internal combustion engine 1, and the fuel injected from the injector 4 becomes an air-fuel mixture. And introduced into the combustion chamber of the internal combustion engine 1. The air-fuel mixture is ignited and burned by the spark plug 5 in the combustion chamber. In this embodiment, the amount of air (intake air amount) that is taken into the intake pipe 2 and taken into the combustion chamber via a throttle valve (not shown), precisely, is disposed in the intake pipe 2. The airflow sensor GA is detected.

  On the other hand, the air-fuel mixture (exhaust gas) after combustion is discharged from the combustion chamber of the internal combustion engine 1 to the exhaust pipe 3. The exhaust gas thus discharged from the combustion chamber is purified by a catalyst (for example, a three-way catalyst) 6 provided in the middle of the exhaust pipe 3 and then released to the outside. The exhaust pipe 3 is provided with an A / F (air-fuel ratio) sensor AFS for detecting the air-fuel ratio of the air-fuel mixture provided for combustion from the exhaust gas in the illustrated manner.

  For such an internal combustion engine 1, the secondary air supply device of this embodiment includes a secondary air supply path 11 that communicates with the exhaust pipe 3. The secondary air supply path 11 includes an air cleaner 12 for purifying secondary air, an air pump 13 for pressurizing and discharging the purified and sucked air from the upstream side, and an air for opening and closing the supply path 11. A switching valve 14 (valve means) is provided in order. Further, a pressure sensor PS for detecting the pressure in the supply passage 11 is disposed between the air pump 13 and the air switching valve 14 in the secondary air supply passage 11. In the secondary air supply device, the drive control of the air pump 13 and the open / close control (open / close operation) of the air switching valve 14 are performed through the electronic control device 15.

  Incidentally, in this embodiment, the electronic control unit 15 controls the internal combustion engine 1 such as control of the fuel injection timing and fuel injection amount (air-fuel ratio) by the injector 4, and control of the ignition timing by an ignition plug (not shown). It is a device that governs the control over the entire operation. And as a part of those controls, control with respect to the said air pump 13 and the air switching valve 14 is performed collectively.

  That is, the electronic control unit 15 recognizes the current engine operating state based on signals taken from various sensors such as the air flow sensor GA, the A / F sensor AFS, and the pressure sensor PS. Based on the recognized engine operating state, the driving of the injector 4, spark plug 5, air pump 13, air switching valve 14 and the like is controlled. The electronic control unit 15 of this embodiment is configured to drive the air pump 13 and open the air switching valve 14 during a specific period in which the catalyst 6 is not yet activated, such as when the engine is started. Secondary air is supplied to the tube 3. Thus, the exhaust emission of the internal combustion engine 1 during the specific period is improved, and the catalyst 6 is activated early.

  By the way, in such a secondary air supply device, it is not necessary to supply secondary air to the exhaust pipe 3 after the activation of the catalyst 6, and the secondary air supply path 11 is connected to the secondary air supply path 11. Secondary air will not flow. However, at this time, conversely, along with the operation of the internal combustion engine, high-temperature exhaust gas flows into the secondary air supply path 11. At this time, as shown in FIG. Foreign matters (such as unburned components) F may adhere to the connection with the exhaust pipe 3 or the like. Such adhesion of the foreign matter F obstructs the flow of the secondary air in the secondary air supply passage 11 and thus makes it difficult to appropriately supply the secondary air to the exhaust pipe 3 of the internal combustion engine. .

  Therefore, in this embodiment, the electronic control device 15 which is also a control means of the secondary air supply device is provided with a function of controlling the driving of the air pump 13 in two operation modes with different torques. ing. As a result, even when the foreign matter F is attached to the connection portion or the like, a sufficient amount of the exhaust pipe 3 is connected to the exhaust pipe 3 by driving the air pump in an operation mode having a higher torque than usual. The secondary air can be supplied.

  FIG. 2 is a flowchart showing the control procedure of the drive control of the air pump 13 by the electronic control unit 15. Next, the drive control of the air pump 13 will be described in detail with reference to FIG.

  In the same control, the electronic control unit 15 first determines whether there is a request for supplying secondary air to the exhaust pipe 3 as a process of step S1. As a result, when it is determined that there is no secondary air supply request, such as when the catalyst 6 has already been activated, the electronic control unit 15 then drives the air pump 13 as a process of step S2. Is stopped (not performed) and the air switching valve 14 is closed to end this control.

  On the other hand, in the process of step S1, when it is determined that the catalyst 6 is in an inactive state and there is a request for supplying secondary air, such as when the internal combustion engine 1 is started, the electronic control unit 15 performs the next step S3. In the process, it is determined whether or not there is a failure in the secondary air supply device.

  That is, when it is determined in the past processing that the secondary air supply device has a failure, the electronic control device 15 displays a diagnosis code indicating that fact in its own storage device (storage means) comprising a nonvolatile raw memory. I remember it. When these diagnostic codes are read from the storage device, the electronic control unit 15 performs the process of step S2 without performing the process for supplying secondary air to the exhaust pipe 3, This control is terminated.

  On the other hand, when the diagnosis code is not read from the storage device in the process of step S3, that is, when it is determined that there is no failure in the secondary air supply device, the electronic control device 15 performs the exhaust pipe 3 Secondary air is supplied to the above, and thereby the following processing from step S4 is executed in order to activate the catalyst 5 at an early stage.

  That is, first, as the process of step S4, the air-fuel ratio feedback control is stopped and switched to the air-fuel ratio control by the open loop control. Thereafter, as a process of step S5, supply of secondary air to the exhaust pipe 3 of the internal combustion engine is started. Specifically, the electronic control unit 15 selects the operation mode of the air pump 13 as a normal operation mode (first operation mode), and performs drive control of the air pump 13 in the selected operation mode. At this time, the electronic control unit 15 also performs valve opening control (opening operation) of the air switching valve 14.

  Then, as a process of step S6, the electronic control unit 15 takes in the sensor output (corresponding to the oxygen concentration in the exhaust pipe 3) from the A / F sensor AFS, and the exhaust pipe 3 based on the taken-in sensor output. It is determined whether the secondary air supply mode is normal.

  That is, when secondary air is normally supplied to the exhaust pipe 3, as shown in FIG. 3 as an example of transition of sensor output by the A / F sensor AFS after the start of supply of secondary air, The sensor output of the / F sensor AFS (sensor output AF1 in FIG. 3) changes to the lean side as time elapses from the start of the supply of secondary air. The sensor output AF1 is saturated after a predetermined time has elapsed from the start of the supply of the secondary air.

  On the other hand, when the secondary air is not sufficiently supplied to the exhaust pipe 3, such as when foreign matter F adheres to the connection part, the sensor output of the A / F sensor AFS (sensor output AF2 in FIG. 3) is 2 It changes to the lean side as time elapses from the start of the supply of the next air. However, the sensor output AF2 has a slower movement that changes to the lean side than the sensor output AF1, and the level that saturates after the lapse of the predetermined time is also richer than the sensor output AF1.

  On the other hand, when the air pump 13 itself or the air switching valve 14 itself is out of order, or when the connecting portion is completely blocked by the foreign matter F, the exhaust pipe 3 is Secondary air is not introduced. Accordingly, in this case, the sensor output of the A / F sensor AFS (sensor output AF3 in FIG. 3) does not change.

  Therefore, in the electronic control unit 15, as shown in FIG. 3, the saturation level of the sensor output AF1 (when normal) and the saturation level of the sensor output AF2 (when secondary air is not sufficiently supplied) A reference value SL is preset between them. Then, by comparing this reference value SL with the saturation level of the sensor output of the A / F sensor AFS, it is determined whether or not the secondary air supply mode is normal.

  That is, when it is determined that the sensor output of the A / F sensor AFS is leaner than the reference value SL, it is possible to determine that the secondary air supply mode is also normal. Accordingly, in this case, the electronic control unit 15 continues to operate the air pump 13 in the normal operation mode until it is determined that the catalyst 6 is activated in the next steps S7 and S8. Control the drive.

  Here, in view of the fact that the temperature of the catalyst 6 correlates with the integrated value of the intake air amount, the electronic control unit 15 sets the integrated value of the air amount necessary for activating the catalyst 6 as the specified value GA1. It is set in advance. Then, the electronic control unit 15 takes in the intake air amount to the intake pipe 2 detected through the air flow sensor GA, and compares the integrated value of the taken-in intake air amount with the specified value GA1 to determine the activity of the catalyst 6. Determine whether or not When it is determined in step S8 that the integrated value of the intake air amount is equal to or greater than the specified value GA1, the electronic control unit 15 determines that the catalyst 6 has been activated and performs the process in step S2. To finish this control.

  On the other hand, if it is determined in step S6 that the sensor output of the A / F sensor AFS is on the rich side with respect to the reference value SL (FIG. 3), the secondary air supply mode is abnormal. It will be. Therefore, at this time, the electronic control unit 15 determines whether or not the sensor output of the A / F sensor AFS is changed by controlling the drive of the air pump 13 in the normal operation mode as the process of step S9. To do.

  That is, for example, when the sensor output of the A / F sensor AFS is changed to the lean side as in the sensor output AF2 shown in FIG. 3, the exhaust emission of the internal combustion engine 1 is insufficient to improve the exhaust emission. However, secondary air having a certain flow rate is introduced into the exhaust pipe 3. In such a case, there is a high possibility that the circulation of the secondary air in the secondary air supply path 11 is hindered by the foreign matter F adhering to the connection part or the like. Therefore, the electronic control unit 15 then switches the drive mode of the air pump 13 to a high torque operation mode (second operation mode) with respect to the normal operation mode as a process of step S10. The air pump 13 is driven in the operation mode. As a result, the foreign matter F adhering to the connecting portion or the like is removed, or a sufficient amount of secondary air is supplied to the exhaust pipe 3 even if the foreign matter F is not removed. .

  While supplying a sufficient amount of secondary air into the exhaust pipe 3, the electronic control unit 15 then outputs the sensor output of the A / F sensor AFS as the reference value SL (FIG. 3) as the processing of step S 11. As described above, it is determined whether or not the logical product condition of the change to the lean side and the activation of the catalyst 6 is satisfied.

  Incidentally, whether or not the catalyst 6 is activated is determined by comparing the integrated value of the intake air amount detected through the air flow sensor GA with the specified value GA1, as described above.

  Then, the electronic control unit 15 continuously (continuously) drives and controls the air pump 13 in the high torque operation mode until it is determined that the logical product condition is satisfied in the process of step S11. .

  However, when the air pump 13 is continuously driven at a high torque, an excessive load is applied to the air pump 13. This also leads to a decrease in the reliability of the air pump 13, and its influence cannot be ignored. Therefore, in this embodiment, the electronic control unit 15 is necessary for the limit time that can affect the reliability of the air pump 13 when the air pump 13 is continuously driven at a high torque, in other words, for fail-safe in this way. Is set in advance as an upper limit time. When the air pump 13 is continuously driven in the process of step S11, the upper limit time and the continuous drive time of the air pump 13 in the high torque operation mode are compared with the process of the next step S12. I am doing so. After that, the electronic control unit 15 stops driving the air pump 13 when it is determined that the continuous drive time of the air pump 13 has reached the upper limit time. As a result, the air pump 13 can be driven at a high torque while suppressing a decrease in the reliability of the air pump 13, and fail-safe against the adhesion of the foreign matter F can be performed.

  In the process of step S12, when it is determined that the logical product condition is satisfied in the process of step S11 before it is determined that the continuous drive time of the air pump 13 has reached the upper limit time. At that time, the process of step S2 is performed and this control is terminated.

  Incidentally, in the process of step S9, it is determined that the sensor output of the A / F sensor AFS has not changed even though the air pump 13 is driven as in the sensor output AF3 shown in FIG. 3, for example. Sometimes. In this case, as described above, it is considered that the air pump 13 or the air switching valve 14 itself has failed, or the connecting portion is completely blocked by the foreign matter F. For this reason, in such a case, the electronic control unit 15 first identifies the cause of the change in the sensor output of the A / F sensor AFS based on the output of the pressure sensor PS as the process of step S13. Specifically, the electronic control unit 15 identifies the cause based on the transition of the output value as exemplified in FIG. 4 by the pressure sensor PS. That is, as shown in FIG. 4, when the air pump 13 is out of order and the pump 13 is not driven, the pressure value (pressure value PS1 in FIG. 4) output from the pressure sensor PS is It does not change.

  On the other hand, even if the air pump 13 is normal, if the air switching valve 14 is broken and the valve 14 does not open, the pressure value output from the pressure sensor PS (the pressure value in FIG. 4). PS2) increases rapidly as the air pump 13 is driven. Then, it saturates to a predetermined value in a relatively short time from the start of driving of the air pump 13.

  On the other hand, when the connection portion is completely blocked by the foreign matter F, the pressure value output from the pressure sensor PS is as shown in FIG. 4 as long as the air pump 13 and the air switching valve 14 are normal. As shown in the figure, the value gradually increases with the start of driving of the air pump 13 although it is delayed by the length of the secondary air supply path 11. Eventually, saturation occurs at a predetermined pressure value. In FIG. 4, the transition of the pressure value at the normal time is shown as a pressure value PS0 for reference.

  As described above, in the process of step S13, the electronic control unit 15 identifies a failure of the air pump 13 when the pressure value by the pressure sensor PS does not change. Further, when the pressure value by the pressure sensor PS changes, for example, the failure of the air switching valve 14 itself based on the determination of whether or not the transition of the pressure value from the start of driving of the air pump 13 is abrupt. Or the apparatus abnormality by adhesion of the foreign material F is specified.

  The electronic control unit 15 that has identified the cause of the change in the air-fuel ratio in the exhaust pipe 3 thus stores the diagnostic code corresponding to the identified cause in its own storage device. And as a process of step S14, after lighting the warning lamp provided in the instrument panel etc. of a vehicle interior, the process of said step S2 is performed and this control is complete | finished.

As described above, according to the secondary air supply apparatus according to this embodiment, many excellent effects as described below can be obtained.
(1) When the air pump 13 is driven in the normal operation mode, when the sensor output of the A / F sensor AFS provided in the exhaust pipe 3 is on the rich side with respect to the reference value SL, The air pump 13 is driven and controlled in an operation mode having a higher torque than the operation mode. For this reason, even if it is a case where supply of secondary air cannot be performed properly due to adhesion of foreign matter F or the like, a sufficient amount of secondary air can be supplied to the exhaust pipe 3 as a fail safe. As a result, deterioration of exhaust emission and the like are preferably suppressed.

  (2) Until it is determined that the sensor output of the A / F sensor AFS is leaner than the reference value SL and the integrated value of the intake air amount detected through the airflow sensor GA is equal to or greater than the specified value GA1. The air pump 13 is driven and controlled with high torque. For this reason, the deterioration suppression of the exhaust emission as the fail safe is more accurately realized.

  (3) When it is determined that the continuous drive time of the air pump 13 in the high torque operation mode has reached the upper limit time required for the failsafe, the drive of the air pump 13 is stopped. As a result, it is possible to suitably suppress the decrease in the reliability of the air pump 13 while maximizing the above fail-safe.

  (4) When the sensor output of the A / F sensor AFS does not change despite the air pump 13 being driven, the cause is determined based on the output of the pressure sensor PS provided between the air pump 13 and the air switching valve 14. The diagnostic code corresponding to the identified cause is stored. For this reason, it becomes possible to easily determine the failure of the air pump 13, the failure of the air switching valve 14, and the abnormality of the device due to the adhesion of the foreign matter F.

  (5) In addition, when the diagnosis code is stored, the air pump 13 is not driven, that is, the air pump 13 is not driven, so that the progress of deterioration as the secondary air supply device is suppressed. Will be able to.

  (6) As a sensor for detecting the supply mode of the secondary air, an A / F sensor AFS whose sensor output changes linearly with respect to a change in oxygen concentration in the exhaust pipe 3 is adopted. For this reason, the supply mode of the secondary air to the exhaust pipe 3 can be easily detected. In addition, this A / F sensor AFS is a sensor that is normally used in air-fuel ratio feedback control, and by adding such a sensor to the prohibited period of the feedback control, any special sensor is added. In addition, the supply mode of the secondary air can be detected.

In addition, the said embodiment can also be changed and implemented as follows.
When the sensor output of the A / F sensor AFS does not change, a diagnosis code indicating that fact (secondary air supply abnormality) may be stored without necessarily identifying the cause. This also makes it possible to recognize the failure of the secondary air supply device.

-Moreover, when specifying the cause of secondary air supply abnormality, you may make it perform the process (step S13 of FIG. 2) concerning the identification independently of the process (control) illustrated in FIG.
-As a sensor which detects the supply aspect of the secondary air with respect to the exhaust pipe 3, not only the said A / F sensor AFS but arbitrary sensors, such as a flow sensor, can be used. However, in terms of diverting a sensor that is normally used for engine operation control, a sensor whose sensor output changes in a binary manner with respect to a change in oxygen concentration, such as an O2 sensor, is also employed as appropriate. be able to. In this case, first, the sensor output of the sensor is set to the rich side at the start of the supply of secondary air. And the supply mode of the secondary air with respect to the exhaust pipe 3 is detected by measuring the time from the supply start of secondary air until the sensor output of the sensor changes to the lean side.

  -Regarding the determination of the activation of the catalyst 6 based on the integrated value of the intake air amount, the engine temperature may also be referred to. Thereby, activation of the catalyst 6 can be determined more accurately. As the engine temperature, for example, the temperature of cooling water for cooling the internal combustion engine can be used.

  The activation of the catalyst 6 can also be determined based on the load of the internal combustion engine 1 and the engine speed, not limited to the integrated value of the intake air amount. Furthermore, the temperature of the catalyst 6 may be directly monitored.

  In the above embodiment, the operation mode of the air pump 13 has two modes, and these are selectively used selectively. However, such a configuration is not necessarily required. In short, if the driving of the air pump 13 is controlled in a plurality of operation modes each having a different torque, the fail safe according to the above embodiment can be realized.

The block diagram which shows the structure about one Embodiment of the secondary air supply apparatus concerning this invention. The flowchart which shows the control procedure about the drive control of the air pump by the secondary air control apparatus of the embodiment. The time chart which shows the transition example of the sensor output by an A / F sensor. The time chart which shows the transition example of the output value by a pressure sensor.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Engine, 2 ... Intake pipe, 3 ... Exhaust pipe, 4 ... Injector, 5 ... Spark plug, 6 ... Catalyst, 11 ... Secondary air supply path, 12 ... Air cleaner, 13 ... Air pump, 14 ... Air switching valve, 15 ... electronic control unit, GA ... air flow sensor, AFS ... A / F sensor, PS ... pressure sensor.

Claims (9)

An air pump that pressurizes and discharges the sucked air, a secondary air supply path that supplies the discharged air to the exhaust system of the internal combustion engine based on driving of the air pump, and a valve means that opens and closes the secondary air supply path A secondary air supply device for supplying secondary air to an exhaust system of an internal combustion engine through driving of the air pump and opening operation of the valve means,
A secondary air supply device comprising: control means for controlling driving of the air pump in a plurality of operation modes each having a different torque. The control means selects an operation mode of the air pump based on a detection output by a sensor that detects a secondary air supply mode to an exhaust system of the internal combustion engine, and controls driving of the air pump in the selected operation mode. The secondary air supply device according to claim 1. The plurality of operation modes include a first operation mode and a second operation mode having a higher torque than the first operation mode, and the control means controls the air pump in the first operation mode. When the detection output by the sensor when driven is less than the reference value of the air amount due to the supply of the secondary air, the second operation mode is selected, and the second operation mode is selected in the selected second operation mode. The secondary air supply device according to claim 2, wherein the driving of the air pump is controlled. When the air pump is driven in the second operation mode, the control means indicates the active state of the catalyst provided in the exhaust system of the engine, wherein the integrated value of the intake air amount sucked into the intake system of the internal combustion engine The air pump is operated in the second operation until a logical product condition of satisfying a predetermined value and that a detection output by the sensor is equal to or greater than a reference value of an air amount by supplying the secondary air is satisfied. The secondary air supply device according to claim 3, wherein the secondary air supply device is driven in a mode. When the air pump is driven in the second operation mode, the control means drives the air pump in the second operation mode until the continuous drive time of the air pump reaches an upper limit time required for fail-safe. The secondary air supply device according to claim 3. The said control means memorize | stores the diagnostic code which shows that in the memory | storage means, when the detection output by the said sensor does not change in spite of driving the said air pump. Secondary air supply device. In the secondary air supply device according to any one of claims 1 to 6,
A pressure sensor for detecting a pressure between the air pump and the valve means in the secondary air supply path, wherein the control means is configured to supply the secondary air based on a transition of a pressure value detected by the pressure sensor; A secondary air supply device characterized by specifying a failure content of the device and storing a diagnosis code corresponding to the specified failure content in a storage means. The secondary air supply device according to claim 6 or 7, wherein when the secondary air supply device is activated, the control unit does not execute the driving of the air pump when a diagnostic code is stored in the storage device. . The sensor for detecting the secondary air supply mode to the exhaust system of the internal combustion engine includes an air-fuel ratio sensor whose detection output changes linearly with respect to a change in oxygen concentration of the exhaust system, and a binary detection output. The secondary air supply device according to any one of claims 2 to 8, wherein the secondary air supply device is one of oxygen sensors that change.

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