JP2006138261A - Abnormality diagnosis device for secondary air supply system for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To perform abnormality diagnosis of a secondary air supply system of a vehicle brought in a service shop or the like irrespective of a temperature condition of an engine. <P>SOLUTION: A service person connects an off-board diagnosis device 38 to a diagnosis connector of ECU 37, turns an ignition switch on, operates the off-board diagnosis device 38 to input off-board diagnosis execution signal into the ECU 37 while stopping the engine 11 under a condition keeping power supply to the secondary air supply system enabled at the service shop or the like. Consequently, the ECU 37 starts operation of an air pump 31 and opens a control valve 35 to start supply of secondary air. Secondary air pressure Ps is detected by a pressure sensor 36 under this condition, then the control valve 35 is closed and secondary air pressure Po is detected by the pressure sensor 36, a normal/abnormal condition of the secondary air supply system 30 is determined based on whether pressure difference thereof (Po-Ps) is a criterion or greater. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an abnormality diagnosis device for a secondary air supply system of an internal combustion engine that supplies secondary air upstream of an exhaust gas purification catalyst in an exhaust passage of the internal combustion engine.

  For example, as shown in Patent Document 1 (Japanese Patent Laid-Open No. 2003-83048) and Patent Document 2 (Japanese Patent Laid-Open No. 2004-11585), the exhaust gas purification catalyst in the exhaust pipe of the internal combustion engine is upstream of the exhaust gas. In addition, there is known a technique in which secondary air is supplied by an air pump to promote purification (oxidation reaction) of HC and CO in exhaust gas, or to accelerate catalyst warm-up by the reaction heat.

When such a secondary air supply system breaks down, exhaust emissions deteriorate. Therefore, in Patent Documents 1 and 2, a pressure sensor is installed in the secondary air supply pipe, and the secondary air supply system operates during engine operation. During the period when the secondary air is supplied, abnormality diagnosis of the secondary air supply system is performed based on the pressure of the secondary air detected by the pressure sensor.
JP 2003-83048 A JP 2004-11585 A

  Conventionally, the abnormality diagnosis of the secondary air supply system was performed during the secondary air supply period during operation of the engine (during the operation of the secondary air supply system). Unless the above is established, the abnormality diagnosis of the secondary air supply system is not performed. In general, the secondary air supply condition (abnormality diagnosis execution condition) is established only in a temperature range where the engine cooling water temperature is low. Therefore, even if the vehicle is brought into a service factory or the like, the engine temperature is high. The abnormality diagnosis of the secondary air supply system could not be performed and had to wait until the engine temperature decreased. For this reason, there is a drawback that it takes a considerable amount of time to reach a temperature state where abnormality diagnosis of a secondary air supply system of a vehicle brought into a service factory or the like is performed, resulting in poor serviceability.

  The present invention has been made in view of such circumstances, and the object thereof is to perform abnormality diagnosis of a secondary air supply system of a vehicle brought into a service factory or the like regardless of the temperature state of the internal combustion engine. An object of the present invention is to provide an abnormality diagnosis device for a secondary air supply system of an internal combustion engine that can improve serviceability.

  In order to achieve the above object, the invention according to claim 1 is provided with a secondary air information detecting means for detecting information relating to the flow rate or pressure of secondary air (hereinafter referred to as “secondary air information”). During the stop, the secondary air supply system is operated by the abnormality diagnosis means, and abnormality diagnosis of the secondary air supply system is performed based on the secondary air information detected by the secondary air information detection means. In this way, the secondary air supply system is operated by the abnormality diagnosing means even under the condition that the normal secondary air supply condition (normal abnormality execution condition during normal internal combustion engine operation) is not satisfied while the internal combustion engine is stopped. Therefore, the abnormality diagnosis of the secondary air supply system of the vehicle brought into the service factory or the like can be performed regardless of the temperature state of the internal combustion engine, and the serviceability can be improved. Further, in the production line inspection process, the abnormality diagnosis of the secondary air supply system can be performed regardless of the temperature state of the internal combustion engine, and the workability of the inspection process can be improved.

  In this case, various execution conditions can be considered for starting the abnormality diagnosis of the secondary air supply system while the internal combustion engine is stopped. For example, the abnormality diagnosis of the secondary air supply system is automatically executed after a predetermined time elapses from when the ignition switch is turned off (when the internal combustion engine is stopped) or when a predetermined execution condition is satisfied, so that the frequency of abnormality diagnosis is increased. Or, as in claim 2, when an offboard diagnosis execution signal is input from the offboard diagnosis device, an abnormality diagnosis of the secondary air supply system may be performed. In this way, in the inspection process of the service factory or production line, the abnormality diagnosis of the secondary air supply system can be executed by the off-board diagnosis device at any time while the internal combustion engine is stopped.

  According to another aspect of the present invention, when an offboard diagnosis execution signal is input from the offboard diagnostic device during operation of the internal combustion engine, an abnormality diagnosis of the secondary air supply system is performed with the internal combustion engine being operated. You may do it. In this way, it is possible to diagnose the abnormality of the secondary air supply system when the internal combustion engine is stopped or operating in the inspection process of the service factory or production line, etc. This can be further improved.

  By the way, when the abnormality diagnosis of the secondary air supply system is performed while the internal combustion engine is stopped, the pressure on the outlet side of the secondary air supply pipe is equivalent to the atmospheric pressure, while the secondary air supply system is operating during the operation of the internal combustion engine. When performing abnormality diagnosis of the air supply system, the pressure on the outlet side of the secondary air supply pipe becomes the exhaust pressure, so the discharge pressure (pump rotation speed) of the air pump is the same when the internal combustion engine is stopped and during operation. Even so, the secondary air supply flow rate into the exhaust passage changes. For this reason, if the determination condition for abnormality diagnosis while the internal combustion engine is stopped is the same as the determination condition for abnormality diagnosis during operation of the internal combustion engine, the determination of normality / abnormality of the secondary air supply system may be erroneously determined. is there.

  As a countermeasure, it is preferable that the abnormality diagnosis determination condition during stoppage of the internal combustion engine is made different from the abnormality diagnosis determination condition during operation of the internal combustion engine. In this way, the determination condition for the abnormality diagnosis while the internal combustion engine is stopped uses the determination condition considering that the pressure on the outlet side of the secondary air supply pipe is equivalent to the atmospheric pressure, and the internal combustion engine is operating. As a judgment condition for abnormality diagnosis, it is possible to use a judgment condition that takes into account that the pressure on the outlet side of the secondary air supply pipe becomes the exhaust pressure, regardless of whether the internal combustion engine is stopped or in operation. The normal / abnormality of the secondary air supply system can be accurately determined.

  By the way, if the abnormality diagnosis of the secondary air supply system and the abnormality diagnosis of other systems (for example, the leak diagnosis of the evaporation purge system) are simultaneously executed while the internal combustion engine is stopped, the burden of the battery serving as the power source of those systems is reduced. Since the power supply voltage is increased and the power supply voltage is decreased, the secondary air supply flow rate (air pump rotation speed) of the secondary air supply system may be decreased, and the normal / abnormality of the secondary air supply system may be erroneously determined. .

  As a countermeasure, when the abnormality diagnosis of the secondary air supply system is executed while the internal combustion engine is stopped as in claim 5, the other system (for example, leak diagnosis of the evaporative purge system) during the abnormality diagnosis period. It is advisable to prohibit abnormality diagnosis. In this way, when the abnormality diagnosis of the secondary air supply system is executed while the internal combustion engine is stopped, the power supply voltage drop due to the abnormality diagnosis of the other system can be prevented in advance, and the normal / An erroneous determination of abnormality can be prevented.

  Hereinafter, two Examples 1 and 2, which embody the best mode for carrying out the present invention, will be described.

  A first embodiment 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 engine 11 that is an internal combustion engine, and an air flow meter 14 that detects the intake air amount is provided downstream of the air cleaner 13. On the downstream side of the air flow meter 14, a throttle valve 16 whose opening is adjusted by a motor 15 such as a DC motor, and a throttle opening sensor 17 for detecting the throttle opening are provided.

  Further, a surge tank 18 is provided on the downstream side of the throttle valve 16, and an intake pipe pressure sensor 19 for detecting the intake pipe pressure is provided in the surge tank 18. The surge tank 18 is provided with an intake manifold 20 for introducing air into each cylinder of the engine 11, and a fuel injection valve 21 for injecting fuel is attached in the vicinity of the intake port of the intake manifold 20 of each cylinder. Yes. A spark plug 22 is attached to the cylinder head of the engine 11 for each cylinder.

  In addition, the cylinder block of the engine 11 includes a coolant temperature sensor 23 that detects the coolant temperature, and a crank angle that outputs a rotation angle signal pulse every time the crankshaft of the engine 11 rotates by a predetermined crank angle (for example, 30 ° C. A). A sensor 24 is attached. Based on the output signal pulse of the crank angle sensor 24, the crank angle and the engine speed are detected.

  On the other hand, the exhaust pipe 25 (exhaust passage) of the engine 11 is provided with a catalyst 26 such as a three-way catalyst for purifying CO, HC, NOx, etc. in the exhaust gas. Exhaust gas sensors 27 and 28 (air-fuel ratio sensor, oxygen sensor, etc.) for detecting the air-fuel ratio or rich / lean of the exhaust gas are provided.

  Next, the configuration of the secondary air supply system 30 that supplies secondary air to the upstream side of the catalyst 26 in the exhaust pipe 25 will be described. The secondary air supply system 30 discharges secondary air discharged from an air pump 31 driven by an electric motor through a discharge pipe 32 (secondary air supply passage) to a secondary air supply nozzle 33 (secondary air supply passage) of each cylinder. To the exhaust manifold 34 (exhaust passage) of each cylinder. The discharge pipe 32 of the air pump 31 is provided with a control valve 35 (electromagnetic valve) that opens and closes the discharge pipe 32, and secondary air information is provided between the control valve 35 of the discharge pipe 32 and the air pump 31. A pressure sensor 36 (secondary air information detection means) is provided as detection means.

  The air pump 31 and the control valve 35 of the secondary air supply system 30 are controlled by an engine control circuit (hereinafter referred to as “ECU”) 37. The ECU 37 reads the output signals of various sensors (for example, the crank angle sensor 24, the intake pipe pressure sensor 19, the water temperature sensor 23, etc.) that detect the engine operating state, detects the engine operating state, and according to the engine operating state. The fuel injection amount and ignition timing of each cylinder are controlled.

  Further, the ECU 37 executes a secondary air supply / abnormality diagnosis routine of FIG. 2 to be described later, thereby executing the secondary air supply operation and abnormality diagnosis processing of the secondary air supply system 30 during engine operation. When an offboard diagnosis execution signal is input from the offboard diagnosis device 38 during the stop, the abnormality diagnosis process of the secondary air supply system 30 is executed with the engine 11 stopped.

  Here, the abnormality diagnosis method of the secondary air supply system 30 of the present Example 1 is demonstrated using the time chart of FIG. In the present embodiment, the secondary air supply operation of the secondary air supply system 30 and the timing for executing the abnormality diagnosis process are turned off from the offboard diagnostic device 38 mainly during the early catalyst warm-up control immediately after engine startup and during engine stop. This is when a board diagnosis execution signal is input.

  For example, in an inspection process of a service factory or a production line, an operator connects the off-board diagnostic device 38 to the diagnostic connector of the ECU 37, turns on the ignition switch (time t1), and then enters the secondary air supply system 30. When the offboard diagnosis device 38 is operated and the offboard diagnosis execution signal is input to the ECU 37 (time t2) while the engine 11 is stopped, the ECU 37 is connected to the air pump 31. While starting the operation (ON), the control valve 35 is opened and the supply of secondary air is started.

  At a time t3 when a predetermined time has elapsed from the start of the operation (ON) of the air pump 31, the control valve 35 is closed and the supply of secondary air into the exhaust manifold 34 is stopped. In order to diagnose an abnormality in the supply system 30, the air pump 31 is continuously operated for a predetermined time. In the following description, a period (t2 to t3) from the start of operation of the air pump 31 to the closing of the control valve 35 is referred to as a “first detection period”, and thereafter a period until the operation of the air pump 31 is stopped ( t3 to t4) is called a "second detection period".

  The ECU 37 detects the secondary air pressure in the discharge pipe 32 of the air pump 31 with the pressure sensor 36 at a predetermined sampling period during the first detection period (t2 to t3), and the secondary of the first detection period. The air pressure Ps (average value or annealing value) is calculated. Thereafter, during the second detection period (t3 to t4), the secondary air pressure in the discharge pipe 32 of the air pump 31 is detected by the pressure sensor 36 at a predetermined sampling period, and the secondary air in the second detection period is detected. The pressure Po (average value or annealing value) is obtained. Thereafter, a pressure difference (Po-Ps) between the secondary air pressure Po in the second detection period and the secondary air pressure Ps in the first detection period is calculated, and the pressure difference (Po-Ps) is equal to or greater than a determination value. Whether the secondary air supply system 30 is normal or abnormal is determined based on whether or not

  By the way, when the abnormality diagnosis of the secondary air supply system 30 is performed while the engine is stopped, the pressure on the outlet side of the secondary air supply nozzle 33 is equivalent to the atmospheric pressure, whereas the secondary air supply is performed during engine operation. When the abnormality diagnosis of the system 30 is performed, the pressure on the outlet side of the secondary air supply nozzle 33 becomes the exhaust pressure, so that the discharge pressure (pump rotation speed) of the air pump 31 is the same when the engine is stopped and during operation. Even if it exists, the secondary air supply flow rate into the exhaust manifold 34 changes. For this reason, if the determination value for abnormality diagnosis during engine stop (determination value for offboard) is the same as the determination value for abnormality diagnosis during engine operation (determination value for normal diagnosis), the secondary air supply system 30 There is a possibility of misjudging the normal / abnormal judgment.

  Thus, in the first embodiment, the abnormality diagnosis determination value while the engine is stopped is made different from the abnormality diagnosis determination value during engine operation. That is, the determination value for abnormality diagnosis while the engine is stopped uses an off-board determination value considering that the pressure on the outlet side of the secondary air supply nozzle 33 is equivalent to atmospheric pressure, and abnormality diagnosis during engine operation is performed. As the determination value, a determination value for normal diagnosis in consideration of the fact that the pressure on the outlet side of the secondary air supply nozzle 33 becomes the exhaust pressure is used. Thereby, it is possible to accurately determine whether the secondary air supply system 30 is normal / abnormal even when the engine is stopped or operating.

  The abnormality diagnosis process of the secondary air supply system 30 of the first embodiment described above is executed by the ECU 37 according to the secondary air supply control / abnormality diagnosis routine of FIG. This routine is periodically executed during the ON period of the ignition switch, and plays a role as abnormality diagnosis means in the claims. When this routine is started, first, in step 101, it is determined whether or not an offboard diagnosis execution signal is input from the offboard diagnosis device 38. If no offboard diagnosis execution signal is input, the process proceeds to step 102. Then, it is determined according to the following conditions (1) to (4) whether or not a normal abnormality diagnosis execution condition (hereinafter referred to as “normal diagnosis execution condition”) to be performed during engine operation is satisfied.

(1) Secondary air supply is not complete
(2) The cooling water temperature detected by the water temperature sensor 23 is within a predetermined range.
(3) The engine speed must be within the idle range.
(4) The engine load is light. If all of these conditions (1) to (4) are satisfied, the normal diagnosis execution condition is satisfied. If any one of these conditions is not satisfied, the normal diagnosis is executed. The condition is not satisfied, and this routine is terminated without performing the subsequent processing.

  On the other hand, if all of the above conditions (1) to (4) are satisfied and the normal diagnosis execution condition is satisfied, the process proceeds to step 103, the control valve 35 is opened, and the air pump 31 is turned on in the next step 104. Then, the secondary air is supplied into the exhaust manifold 34, and in the subsequent step 105, the secondary air pressure Ps (average value or smoothed value) in the first detection period is calculated. Specifically, the secondary air pressure detected by the pressure sensor 36 during the first detection period is integrated, and the integrated value is divided by the number of integrations to average the secondary air pressure Ps during the first detection period. Or the secondary air pressure detected by the pressure sensor 36 during the first detection period is smoothed to determine the smoothing value of the secondary air pressure Ps during the first detection period. The processes in steps 103 to 105 are repeated until a predetermined time corresponding to the first detection period elapses (step 106), and the secondary air pressure Ps (average value or annealing value) in the first detection period is increased. Calculated.

  Thereafter, when a predetermined time corresponding to the first detection period has elapsed, “Yes” is determined in Step 106, the process proceeds to Step 107, the control valve 35 is closed, and the secondary flow into the exhaust manifold 34 is performed. Shut off the air supply. Thereafter, the air pump 31 is continuously operated (ON) for abnormality diagnosis of the secondary air supply system 30, and the secondary air pressure Po (average value or smoothed value) in the second detection period is calculated. The processes in steps 107 to 108 are repeated until a predetermined time corresponding to the second detection period has elapsed (step 109), and the secondary air pressure Po (average value or smoothed value) in the second detection period is increased. Calculated.

  Thereafter, when a predetermined time corresponding to the second detection period has elapsed, “Yes” is determined in Step 109, the process proceeds to Step 110, and the secondary air supply system 30 is determined using the determination value for normal diagnosis. Determine the normality / abnormality. Specifically, the pressure difference (Po−Ps) between the secondary air pressure Po in the second detection period and the secondary air pressure Pa in the first detection period is compared with a determination value for normal diagnosis. If the difference (Po−Ps) is larger than the normal diagnosis determination value, it is determined that the secondary air supply system 30 is normal. On the other hand, if the pressure difference (Po-Ps) is equal to or less than the determination value for normal diagnosis, it is determined that the secondary air supply system 30 is abnormal, and a warning lamp (not shown) is turned on or blinked. Or, a warning is displayed on the display unit of the instrument panel of the driver's seat, and abnormality information such as an abnormality code is stored in a rewritable nonvolatile memory such as a backup RAM of the ECU 37. Thereafter, the routine proceeds to step 111, where the air pump 31 is turned off and this routine is terminated.

  On the other hand, if it is determined in step 101 that an offboard diagnosis execution signal is input from the offboard diagnosis device 38, the process proceeds to step 112, and it is determined whether or not an offboard diagnosis execution condition is satisfied. Here, the offboard diagnosis execution condition is, for example, that the engine is stopped, the battery voltage is equal to or higher than a predetermined value, and if all of these conditions are satisfied, the offboard diagnosis execution condition is satisfied, If any one of the conditions is not satisfied, the offboard diagnosis execution condition is not satisfied, and this routine is terminated without performing the subsequent processing.

  On the other hand, if it is determined in step 112 that the offboard diagnosis execution condition is satisfied, the process proceeds to step 113, the control valve 35 is opened, and the air pump 31 is turned on in the next step 114. Then, the secondary air is discharged from the air pump 31, and in the subsequent step 115, the secondary air pressure Ps (average value or smoothing value) in the first detection period is calculated. The processes in steps 113 to 115 are repeated until a predetermined time corresponding to the first detection period has elapsed (step 116), and the secondary air pressure Ps (average value or smoothed value) in the first detection period is increased. Calculated.

  Thereafter, when a predetermined time corresponding to the first detection period has elapsed, “Yes” is determined in Step 116, the process proceeds to Step 117, the control valve 35 is closed, and the secondary flow into the exhaust manifold 34 is performed. Shut off the air supply. Thereafter, the air pump 31 is continuously operated (ON) for abnormality diagnosis of the secondary air supply system 30, and the secondary air pressure Po (average value or smoothed value) in the second detection period is calculated. The processing in steps 117 to 118 is repeated until a predetermined time corresponding to the second detection period has elapsed (step 119), and the secondary air pressure Po (average value or annealing value) in the second detection period is increased. Calculated.

  Thereafter, when a predetermined time corresponding to the second detection period has elapsed, “Yes” is determined in Step 119, the process proceeds to Step 120, and the secondary air supply system 30 is determined using the determination value for offboard. Determine the normality / abnormality. Specifically, the pressure difference (Po-Ps) between the secondary air pressure Po in the second detection period and the secondary air pressure Pa in the first detection period is compared with the determination value for offboard, and this pressure If the difference (Po−Ps) is larger than the determination value for offboard, it is determined that the secondary air supply system 30 is normal, and the determination result is transmitted to the offboard diagnostic device 38. On the other hand, if the pressure difference (Po−Ps) is equal to or less than the determination value for offboard, it is determined that the secondary air supply system 30 is abnormal, and the determination result is transmitted to the offboard diagnostic device 38. . After this, the routine proceeds to step 121 where the air pump 31 is turned off and this routine is terminated.

  According to the first embodiment described above, an abnormality diagnosis (offboard diagnosis) of the secondary air supply system 30 is performed by inputting an offboard diagnosis execution signal from the offboard diagnosis device 38 to the ECU 37 while the engine is stopped. Since it can be performed, the abnormality diagnosis of the secondary air supply system 31 can be forcibly performed even under conditions where the normal secondary air supply condition (normal diagnosis execution condition) is not satisfied while the engine is stopped. It becomes possible. Thereby, the abnormality diagnosis of the secondary air supply system 31 of the vehicle brought into the service factory or the like can be performed at any time regardless of the temperature state of the engine 11, and the serviceability can be improved. Also, in the inspection process of the production line, the abnormality diagnosis of the secondary air supply system 30 can be performed at any time regardless of the temperature state of the engine 11, and the workability of the inspection process can be improved.

  Moreover, in the first embodiment, the determination value for abnormality diagnosis while the engine is stopped uses an off-board determination value that takes into account that the pressure on the outlet side of the secondary air supply nozzle 33 is equivalent to atmospheric pressure, As the judgment value for abnormality diagnosis during engine operation, a judgment value for normal diagnosis that takes into account that the pressure on the outlet side of the secondary air supply nozzle 33 becomes the exhaust pressure is used. In any of the cases, it is possible to accurately determine whether the secondary air supply system 30 is normal or abnormal.

  In the first embodiment, the off-board diagnosis of the secondary air supply system 30 is performed with the engine 11 stopped. However, in the second embodiment of the present invention shown in FIG. The off-board diagnosis can be performed both when the engine is stopped and during operation.

  The secondary air supply control / abnormality diagnosis routine of FIG. 4 executed in the second embodiment is different from the first embodiment (FIG. 2) only in steps 112a to 112d and step 120a in the offboard diagnosis processing. The other processes are the same as those in the first embodiment.

  In the secondary air supply control / abnormality diagnosis routine of FIG. 4, if it is determined in step 101 that an offboard diagnosis execution signal has been input from the offboard diagnosis device 38, the process proceeds to step 112 a and an offboard diagnosis execution condition (for example, If the off-board diagnosis execution condition is not satisfied, the routine is terminated without performing the subsequent processing.

  On the other hand, if it is determined in step 112a that the offboard diagnosis execution condition is satisfied, the process proceeds to step 112b to determine whether or not the engine is stopped. Proceeding to step 112c, the determination value at the time of engine stop is selected as the determination value for offboard. If the engine is operating, the process proceeds to step 112d, and the determination value at the time of engine operation is determined as the determination value for offboard. select.

  Thereafter, the secondary air pressure Ps (average value or smoothed value) in the first detection period is calculated by the process of steps 113 to 116 in the same manner as in the first embodiment, and the following steps 117 to 119 are performed. By processing, the secondary air pressure Po (average value or smoothed value) in the second detection period is calculated in the same manner as in the first embodiment.

  Thereafter, the process proceeds to step 120a, and the normal / abnormality of the secondary air supply system 30 is determined by the same method as in the first embodiment, using the offboard determination value selected in step 112c or 112d. That is, if the engine is stopped, an abnormality diagnosis is performed using the determination value when the engine is stopped, and if the engine is operating, an abnormality diagnosis is performed using the determination value when the engine is operating. 38. After this, the routine proceeds to step 121 where the air pump 31 is turned off and this routine is terminated.

  According to the second embodiment described above, it is possible to perform an abnormality diagnosis of the secondary air supply system 30 when the engine is stopped or in operation in the inspection process of the service factory or the production line. Serviceability and inspection can be further improved.

  By the way, if the abnormality diagnosis of the secondary air supply system 30 and the abnormality diagnosis of other systems (for example, the leakage diagnosis of the evaporation purge system) are executed at the same time while the engine is stopped, the burden on the battery serving as the power source of those systems becomes large. Therefore, since the power supply voltage is lowered, the secondary air supply flow rate (air pump rotation speed) of the secondary air supply system 39 is lowered, and the normal / abnormality of the secondary air supply system may be erroneously determined. .

  As a countermeasure, in the first and second embodiments, when the abnormality diagnosis of the secondary air supply system 30 is executed while the engine is stopped, another system (for example, a leak diagnosis of the evaporation purge system) during the abnormality diagnosis period. It is advisable to prohibit abnormality diagnosis. In this way, when the abnormality diagnosis of the secondary air supply system 30 is executed while the engine is stopped, the power supply voltage drop due to the abnormality diagnosis of other systems can be prevented in advance, and the normal / An erroneous determination of abnormality can be prevented.

  In the first and second embodiments, in order to improve diagnosis accuracy, the secondary air pressure Ps in the first detection period and the secondary air pressure Po in the second detection period are parameters (exhaust gas) that affect them. Pressure, battery voltage, intake air temperature, etc.), or the determination value may be corrected with the parameter.

  In the first and second embodiments, the determination value is changed between the normal diagnosis and the offboard diagnosis. However, the secondary air pressure Ps in the first detection period and the secondary air pressure in the second detection period. You may make it correct | amend Po according to a diagnostic method.

  In the first and second embodiments, the secondary air pressure is detected by the pressure sensor 36 as the secondary air information. However, the flow rate of the secondary air discharged from the air pump 31 may be detected. good.

  In addition, the present invention automatically performs abnormality diagnosis of the secondary air supply system 30 after a predetermined time elapses from when the ignition switch is turned off (when the engine is stopped) or when a predetermined execution condition is satisfied, thereby performing the abnormality diagnosis. The frequency may be increased.

  In addition, the present invention can be implemented with various modifications such that the abnormality diagnosis method of the secondary air supply system 30 may be appropriately changed.

It is a figure which shows the whole structure of the engine control system in Example 1 of this invention. 6 is a flowchart for explaining a processing flow of a secondary air supply / abnormality diagnosis routine according to the first embodiment. It is a time chart explaining an example of abnormality diagnosis processing. 7 is a flowchart for explaining a processing flow of a secondary air supply / abnormality diagnosis routine according to a second embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 11 ... Engine (internal combustion engine), 12 ... Intake pipe, 25 ... Exhaust pipe (exhaust passage), 26 ... Catalyst, 30 ... Secondary air supply system, 31 ... Air pump, 32 ... Discharge pipe (secondary air supply passage), 33 ... Secondary air supply nozzle (secondary air supply passage), 34 ... Exhaust manifold (exhaust passage), 35 ... Control valve, 36 ... Pressure sensor (secondary air information detection means), 37 ... ECU (abnormality diagnosis means) 38. Off-board diagnostic device

Claims (5)

In the secondary air supply system for an internal combustion engine that supplies secondary air upstream of the exhaust gas purification catalyst in the exhaust passage of the internal combustion engine,
Secondary air information detection means for detecting information on the flow rate or pressure of secondary air (hereinafter referred to as “secondary air information”);
An abnormality diagnosis means for operating the secondary air supply system while the internal combustion engine is stopped and performing an abnormality diagnosis of the secondary air supply system based on the secondary air information detected by the secondary air information detection means. An abnormality diagnosis device for a secondary air supply system of an internal combustion engine characterized by comprising:   2. The secondary air of the internal combustion engine according to claim 1, wherein the abnormality diagnosis unit performs abnormality diagnosis of the secondary air supply system when an offboard diagnosis execution signal is input from an offboard diagnosis device. Supply system abnormality diagnosis device.   When the offboard diagnosis execution signal is input from the offboard diagnosis device during operation of the internal combustion engine, the abnormality diagnosis means performs abnormality diagnosis of the secondary air supply system while the internal combustion engine is operated. The abnormality diagnosis device for a secondary air supply system of an internal combustion engine according to claim 2.   The abnormality diagnosing means is configured such that a determination condition for abnormality diagnosis of the secondary air supply system executed while the internal combustion engine is stopped differs from a determination condition for abnormality diagnosis of the secondary air supply system executed during operation of the internal combustion engine. The abnormality diagnosis device for a secondary air supply system of an internal combustion engine according to claim 3, wherein   2. The abnormality diagnosis unit, when executing abnormality diagnosis of the secondary air supply system while the internal combustion engine is stopped, prohibits abnormality diagnosis of other systems during the abnormality diagnosis period. The abnormality diagnosis device for a secondary air supply system of an internal combustion engine according to any one of claims 1 to 4.

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