JP3444457B2 - Failure diagnosis device for secondary air supply system of engine - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a failure diagnostic device for a secondary air supply system of an engine that supplies secondary air to an exhaust system.

[0002]

2. Description of the Related Art Conventionally, as a part of an engine exhaust gas purification system, an appropriate amount of secondary air is supplied to the upstream side of a three-way catalyst to oxidize unburned gas in the exhaust system to flow into the three-way catalyst. A system is known in which the purification rate of the three-way catalyst is improved by keeping the fuel ratio constant.

Such a system is provided with a function of diagnosing a failure of the secondary air supply system in order to prevent deterioration of exhaust emission due to a failure or abnormal deterioration of the secondary air supply system. Japanese Patent Laid-Open No. 4-50423 discloses a technique for determining an abnormality when the pressure difference between the inlet side and the outlet side of the secondary air introducing device deviates from a predetermined value.

[0004]

However, as compared with flat land, the pressure difference between the inlet side and the outlet side of the secondary air introducing device becomes small under the environmental conditions where the atmospheric pressure is low, such as in the highlands, so that the level in the flat land is low. If the judgment value or the pressure measurement value is used as it is, there is a risk of erroneous diagnosis.

The present invention has been made in view of the above circumstances, and a failure diagnosis of a secondary air supply system of an engine capable of accurately detecting an abnormality of the secondary air supply system without being affected by atmospheric pressure. The purpose is to provide a device.

[0006]

The invention according to claim 1 is
In a failure diagnosis device for a secondary air supply system of an engine that supplies secondary air to an exhaust system through a secondary air passage,
As shown in the basic configuration diagram of (a), the secondary air passage pressure detecting means for detecting the pressure in the secondary air passage, the atmospheric pressure detecting means for detecting the atmospheric pressure, and the secondary air passage pressure detecting means. Pulsating pressure that calculates the difference between the maximum value and the minimum value of the pressure pulsation in the secondary air passage while the secondary air is being supplied to the exhaust system, based on the data of the passage pressure detected by the means. Difference calculation means, a judgment value setting means for setting a judgment value for judging an abnormality of the secondary air supply system based on the atmospheric pressure data detected by the atmospheric pressure detection means, and the pulsating pressure difference calculation The difference between the maximum value and the minimum value of the pressure pulsation in the secondary air passage calculated by the means is compared with the determination value set by the determination value setting means, and when the difference is the determination value or less, the secondary An abnormality determining means for determining that the air supply system is abnormal. The features.

According to a second aspect of the present invention, in a failure diagnosis device for a secondary air supply system of an engine for supplying secondary air to an exhaust system via a secondary air passage, the basic configuration diagram of FIG. As shown, the secondary air passage pressure detecting means for detecting the pressure in the secondary air passage, the atmospheric pressure detecting means for detecting atmospheric pressure, and the passage pressure detected by the secondary air passage pressure detecting means Based on the data, pulsating pressure difference calculating means for calculating the difference between the maximum value and the minimum value of the pressure pulsation in the secondary air passage in the state where the secondary air supply to the exhaust system is stopped,
Based on the atmospheric pressure data detected by the atmospheric pressure detection means, a determination value setting means for setting a determination value for determining an abnormality of the secondary air supply system, and the pulsation pressure difference calculation means The difference between the maximum value and the minimum value of the pressure pulsation in the secondary air passage is compared with the judgment value set by the judgment value setting means, and when the difference is larger than the judgment value, the secondary air supply system is An abnormality determining means for determining an abnormality is provided.

According to a third aspect of the present invention, there is provided a failure diagnosing device for a secondary air supply system of an engine for supplying secondary air to an exhaust system through a secondary air passage. As shown, the secondary air passage pressure detecting means for detecting the pressure in the secondary air passage, the atmospheric pressure detecting means for detecting atmospheric pressure, and the passage pressure detected by the secondary air passage pressure detecting means Based on the data and the atmospheric pressure data detected by the atmospheric pressure detection means, between the maximum value and the minimum value of the pressure pulsation in the secondary air passage in the state of supplying the secondary air to the exhaust system The difference, the pulsating pressure difference calculating means for calculating by converting into a value under the reference atmospheric pressure for abnormality determination, and the maximum value of the pressure pulsation in the secondary air passage calculated by the pulsating pressure difference calculating means. Compare the difference with the minimum value with the judgment value set in advance under the above standard atmospheric pressure When the difference is below the determination value,
An abnormality determining means for determining that the secondary air supply system is abnormal is provided.

According to a fourth aspect of the present invention, in a failure diagnostic device for a secondary air supply system of an engine for supplying secondary air to an exhaust system via a secondary air passage, a basic configuration diagram of FIG. As shown, the secondary air passage pressure detecting means for detecting the pressure in the secondary air passage, the atmospheric pressure detecting means for detecting atmospheric pressure, and the passage pressure detected by the secondary air passage pressure detecting means Based on the data and the atmospheric pressure data detected by the atmospheric pressure detecting means, between the maximum value and the minimum value of the pressure pulsation in the secondary air passage in the state where the secondary air supply to the exhaust system is stopped. The difference, the pulsating pressure difference calculating means for calculating by converting into a value under the reference atmospheric pressure for abnormality determination, and the maximum value of the pressure pulsation in the secondary air passage calculated by the pulsating pressure difference calculating means. The difference from the minimum value is compared with the judgment value preset under the above standard atmospheric pressure. And, when the difference is greater than the determination value, characterized by comprising an abnormality judging means determines that the secondary air supply system is abnormal.

That is, in the first aspect of the invention, the pressure in the secondary air passage is detected while the secondary air is being supplied to the exhaust system, and the difference between the maximum value and the minimum value of the pressure pulsation is calculated. To do. Then, the calculated difference is compared with a determination value set based on the atmospheric pressure data, and when the difference is less than or equal to this determination value, it is determined that the secondary air supply system is abnormal.

According to the second aspect of the present invention, the pressure in the secondary air passage is detected while the secondary air supply to the exhaust system is stopped, and the difference between the maximum value and the minimum value of the pressure pulsation is calculated. . Then, the calculated difference is compared with a determination value set based on the atmospheric pressure data, and when it is larger than this determination value, it is determined that the secondary air supply system is abnormal.

According to the third aspect of the present invention, the pressure in the secondary air passage while the secondary air is being supplied to the exhaust system is detected, and the atmospheric pressure is also detected to determine the maximum and minimum pressure pulsations. The difference from the value is calculated by converting it to a value under the standard atmospheric pressure for abnormality determination. Then, the calculated difference is compared with a predetermined judgment value under the reference atmospheric pressure, and when it is less than or equal to this judgment value, it is judged that the secondary air supply system is abnormal.

According to the fourth aspect of the present invention, the pressure in the secondary air passage in the state where the secondary air supply to the exhaust system is stopped is detected, and the atmospheric pressure is detected to detect the maximum and minimum pressure pulsations. The difference from the value is calculated by converting it to a value under the standard atmospheric pressure for abnormality determination. Then, the calculated difference is compared with a predetermined judgment value under the reference atmospheric pressure, and when it is larger than this judgment value, it is judged that the secondary air supply system is abnormal.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

3 to 10 relate to the first embodiment of the present invention, FIGS. 3 to 6 are flowcharts of a failure diagnosis routine, FIG. 7 is a flowchart of an atmospheric pressure detection routine, and FIG. 8 is a judgment value table. FIG. 9 is a schematic configuration diagram of the engine control system, and FIG. 10 is a circuit configuration diagram of the electronic control system.

In FIG. 9, reference numeral 1 is an engine,
In the figure, a horizontally opposed four cylinder engine is shown. An intake manifold 3 is communicated with each intake port 2a formed in the cylinder head 2 of the engine 1, a throttle chamber 5 is communicated with the intake manifold 3 through an air chamber 4, and an intake pipe is provided upstream of the throttle chamber 5. An air cleaner 7 is attached via 6.

Further, the air cleaner 7 of the intake pipe 6
An intake air amount sensor 8 of, for example, a hot wire type or a hot film type is provided immediately downstream of the throttle valve 5a provided in the throttle chamber 5 and a throttle opening sensor 9a and a throttle valve fully closed. A throttle sensor 9 having a built-in idle switch 9b that is turned on is connected in series.

Further, an idle speed control (ISC) valve 11 is provided in a bypass passage 10 connecting the upstream side and the downstream side of the throttle valve 5a, and the passage communicating with the intake manifold 3 is
Intake pipe pressure / atmospheric pressure switching solenoid valve 1 that selectively communicates between the inside of the intake manifold 3 and the atmosphere.
2, an intake pipe pressure / atmospheric pressure switching solenoid valve 12 is connected to a pressure sensor (absolute pressure sensor) 13.

The intake pipe pressure / atmospheric pressure switching solenoid valve 12 is an electromagnetic three-way valve having a port communicating with the intake manifold 3 and an atmospheric port. In the present embodiment, the atmospheric port is closed in the OFF state. And open the port communicating with the intake manifold 3 above,
It is possible to measure the suction pipe pressure by the pressure sensor 13. Further, an electronic control unit 40 (ECU; FIG.
When turned on by the reference), the port communicating with the intake manifold 3 is closed to release the atmospheric port,
The pressure sensor 13 can measure the atmospheric pressure, and the pressure sensor 13 is used as an atmospheric pressure detecting means.

Further, an injector 14 is provided immediately upstream of each intake port 2a of each cylinder of the intake manifold 3.
A spark plug 15a whose tip is exposed to the combustion chamber is attached to the cylinder head 2 for each cylinder of the cylinder head 2. An igniter 16 is connected to the ignition coil 15b connected to the ignition plug 15a.

The injector 14 has a fuel supply path 17
The fuel tank 18 is communicated with the fuel tank 18 via the fuel tank 18, and an in-tank type fuel pump 19 is provided in the fuel tank 18. The fuel from the fuel pump 19 is pressure-fed to the injector 14 and the pressure regulator 21 via the fuel filter 20 provided in the fuel supply path 17, and is returned from the pressure regulator 21 to the fuel tank 18 to be injected into the injector. The fuel pressure to 14 is adjusted to a predetermined pressure.

A knock sensor 22 is attached to the cylinder block 1a of the engine 1, and a cooling water temperature sensor 24 is exposed to a cooling water passage 23 that connects the left and right banks of the cylinder block 1a. Further, a front O2 sensor (FO2 sensor) 26a is exposed at a gathering portion of the exhaust manifold 25 communicating with the exhaust port 2b of the cylinder head 2, and a front catalytic converter 27a is interposed downstream of the FO2 sensor 26a. . A rear catalytic converter 27b is provided immediately downstream of the front catalytic converter 27a, and a rear O2 sensor (RO2 sensor) 26b is exposed downstream of the rear catalytic converter 27b.

A secondary air passage 32 for supplying secondary air is opened in the exhaust manifold 25,
In the secondary air passage 32, a secondary air switching valve (Air Suction Valve; AS) including a diaphragm actuator is provided.
V) 33 is interposed. The ASV 33 has a configuration in which a reed valve is provided on the downstream side of the diaphragm valve, the upstream side of the diaphragm valve is communicated with the muffler chamber of the air cleaner 7 via a secondary air passage 34, and the downstream side of the reed valve is the secondary air. It communicates with the inside of the exhaust manifold 25 via a passage 32.

Further, in the ASV 33, a diaphragm chamber in which a spring for urging the diaphragm valve in the closing direction is built is formed by being partitioned by the diaphragm, and the AS is provided through the passage 35 in the diaphragm chamber.
The V operation switching solenoid valve 36 is connected, and further,
The ASV operation switching solenoid valve 36 is connected to the intake manifold 3 via a passage 37.

The ASV operation switching solenoid valve 36
Is the intake pipe pressure / atmospheric pressure switching solenoid valve 1 described above.
Similar to 2, it is a solenoid three-way valve having a port communicating with the intake manifold 3 and an atmospheric port. In the present embodiment, the intake manifold 3 is in the OFF state.
When the ECU 40, which will be described later, turns on the air port, the air port is closed and the port communicating with the intake manifold 3 is released.

That is, when the ASV operation switching solenoid valve 36 is turned on, the negative pressure of the intake manifold 3 is introduced into the diaphragm chamber of the ASV 33, and the diaphragm valve opens against the biasing force of the spring. Then, the reed valve is opened by the negative pressure in the exhaust manifold 25, and the atmosphere (secondary air) is introduced into the exhaust manifold 25 via the air cleaner 7. On the other hand, when the ASV operation switching solenoid valve 36 is OFF, the ASV 33
The diaphragm chamber is opened to the atmosphere, the diaphragm valve is closed by the biasing force of the spring, and the supply of secondary air is stopped.

When the secondary air is supplied or stopped by the ASV 33, the pressure in the secondary air passage 34 is detected by the pressure sensor 38 communicating with the secondary air passage 34. As will be described later, the failure diagnosis of the secondary air supply system is performed based on the difference between the maximum value and the minimum value of the pressure pulsation generated when the secondary air supply is turned on and off. The pressure sensor 38 may be configured to detect the pressure of the secondary air passage 32 on the exhaust side.

On the other hand, a crank rotor 1 is rotatably mounted on a crank shaft 1b supported by the cylinder block 1a, and a magnet for detecting a protrusion (or slit) corresponding to a predetermined crank angle is provided on the outer periphery of the crank rotor 28. A crank angle sensor 29 including a sensor (electromagnetic pickup or the like) or an optical sensor is provided oppositely. Further, a cam rotor 30 is connected to the camshaft 1c of the cylinder head 2, and a cam angle sensor 31 for discriminating a cylinder, which is also composed of a magnetic sensor or an optical sensor, is provided opposite to the cam rotor 30.

Next, based on FIG. 10, an electronic control unit (E
The CU) 40 will be described. The ECU 40 is the CPU 4
1, ROM 42, RAM 43, backup RAM 4
4 and the I / O interface 45 is the bus line 4
6, which is mainly composed of microcomputers connected to each other via a constant voltage circuit 47 for supplying a stabilizing voltage to each section, and driving for driving actuators by signals from the output port of the I / O interface 45. The circuit 48 and peripheral circuits such as an A / D converter 49 for converting an analog signal from the sensors to a digital signal are incorporated.

The constant voltage circuit 47 includes an ECU relay 50.
The relay coil of the ECU relay 50 is connected to the battery 51 via an ignition switch 52.
Further, the constant voltage circuit 47 is directly connected to the battery 51.
When the ignition switch 52 is turned on and the relay contact of the ECU relay 50 is closed, power is supplied from the constant voltage circuit 47 to each part, while the ignition switch 52 is turned on and off.
Regardless of this, backup power is constantly supplied to the backup RAM 44.

The input port of the I / O interface 45 is connected with the idle switch 9b, the knock sensor 22, the crank angle sensor 29, the cam angle sensor 31, and the vehicle speed sensor 39, and the intake air amount sensor. 8, throttle opening sensor 9a, pressure sensor 1
3, 38, cooling water temperature sensor 24, FO2 sensor 26a,
The RO2 sensor 26b is connected via the A / D converter 49, and the voltage VB from the battery 51 is input to the A / D converter 49 for monitoring.

On the other hand, the igniter 16 is connected to the output port of the I / O interface 45, and the ISC valve 11, the intake pipe pressure / atmospheric pressure switching solenoid valve 12, and the injector 14 are connected via the drive circuit 48. , ASV operation switching solenoid valve 36, and an MIL lamp 53 arranged on an instrument panel (not shown) for centrally displaying various alarms.

The ROM 42 stores an engine control program, various failure diagnosis programs, fixed data such as maps, and the RAM 43 processes output signals of the sensors and switches. Later data and data processed by the CPU 41 are stored. Further, various learning maps and the like are stored in the backup RAM 44, and the data is retained even when the ignition switch 52 is OFF.

The CPU 41 calculates the fuel injection amount, the ignition timing, the duty ratio of the drive signal of the ISC valve 11, etc. according to the control program stored in the ROM 42, and the air-fuel ratio feedback control, the ignition timing control, I
In addition to performing various engine controls such as SC control, the ASV operation switching solenoid valve 36 is turned on to open the ASV 33 in a predetermined operating region, and the exhaust manifold 25
By supplying the secondary air to the inside, the oxidation reaction of the exhaust gas in the exhaust manifold 25 is promoted, and the purification efficiency in the front catalytic converter 27a and the rear catalytic converter 27b is improved.

Further, the ECU 40 (the CPU 41
Has a failure diagnosis function (so-called self-diagnosis function) for performing failure diagnosis of the secondary air supply system including the ASV 33 and the ASV operation switching solenoid valve 36, each sensor, each actuator, etc. The trouble data detected by this failure diagnosis function is stored in the backup RAM 44.

The trouble data can be read out to the outside by connecting the serial monitor 60 to the ECU 40 via the connector 54. The serial monitor 60 is disclosed in Japanese Patent Laid-Open No. 2-73131 previously filed by the applicant.
It is described in detail in the publication.

The failure diagnosis of the secondary air supply system by the ECU 40 is carried out in the secondary air passage 34 based on the pressure data in the secondary air passage 34 detected by the pressure sensor 38 as the secondary air passage pressure detecting means. Abnormality of the secondary air supply system is determined based on the atmospheric pressure data detected by the pulsation pressure difference calculation means for calculating the difference between the maximum value and the minimum value of the pressure pulsation and the pressure sensor 13 as the atmospheric pressure detection means. Judgment value setting means for setting a judgment value for operating the secondary air passage 3
The difference between the maximum value and the minimum value of the pressure pulsation in 4 is compared with the judgment value set by the judgment value setting means, and is executed by each function of the abnormality judgment means for judging an abnormality.
The MIL lamp 53 as a warning means is turned on (or blinks) to warn the driver.

The processing relating to the failure diagnosis of the secondary air supply system by the ECU 40 will be described below with reference to the flow charts of FIGS.

FIG. 7 shows an atmospheric pressure detection routine executed by interruption at predetermined time intervals. In this routine, first, in step S51, it is determined whether the atmospheric pressure measurement mode or the intake pipe pressure measurement mode. Each measurement mode is switched at every set time by referring to a flag set or cleared at the end of each measurement mode, and the intake pipe pressure / atmospheric pressure switching solenoid valve 12 is turned on every set time.
Although turned off and the pressure sensor 13 alternately measures the intake pipe pressure and the atmospheric pressure, the intake pipe pressure detection process is similar to the atmospheric pressure detection process and is not directly involved in the failure diagnosis of the secondary air supply system. Therefore, the description thereof is omitted.

Then, in step S51, when the atmospheric pressure measurement mode is not set, the routine is directed. When in the atmospheric pressure measurement mode, the process proceeds from step S51 to step S52, and the intake pipe pressure / atmospheric pressure switching solenoid valve 12 is turned on.
When the atmosphere port is opened by N and the atmosphere side and the pressure sensor 13 are made to communicate with each other, in steps S53 and S54, stabilization waiting after turning on the intake pipe pressure / atmospheric pressure switching solenoid valve 12 is performed.

That is, the count value C is incremented in step S53 (C ← C + 1), and in step S54 it is checked whether or not the count value C is equal to or more than the set value CS1.
When C <CS1, the routine is exited, and when C ≧ CS1,
After the intake pipe pressure / atmospheric pressure switching solenoid valve 12 is turned on to release the atmospheric port, when it can be considered that the pressure has been stabilized for a sufficient amount of time for pressure measurement, the process proceeds to step S55.

In step S55, the analog signal from the pressure sensor 13 is input and A / D converted, and in step S56 A
Atmospheric pressure data PA
Is calculated, the atmospheric pressure data PA is integrated to obtain an integrated value SUM (initial value is 0) in step S57 (SUM ← SUM + PA).

In a succeeding step S58, the count value i for counting the number of times of integration is counted up, and in a step S59, it is checked whether or not the count value i has reached the set number n. Then, when i <n, the routine is exited,
When i ≧ n, the process proceeds from step S59 to step S60, the integrated value SUM is divided by the number of times of integration n to obtain an average value, and this average value is used as atmospheric pressure data PA (PA ← SU
M / n) Store at a predetermined address in the backup RAM 44.

After that, the process proceeds to step S61 and subsequent steps, and in each of steps S61, S62, S63, the count value C, i and the integrated value SUM are cleared (C ← 0, i ← 0, SU
M ← 0), exit the routine. In addition, backup RAM
The atmospheric pressure data PA stored in 44 may be weighted average processing.

Next, the failure diagnosis routine of FIGS. 3 to 6 will be described. This failure diagnosis is an interrupt routine executed every predetermined time, and when the routine is started, the flag F1 which is set to 1 when the diagnosis when the secondary air supply is ON is completed is referred to in step S101. . And F
When the diagnosis when the secondary air supply is ON is not completed with 1 = 0, the process proceeds to step S102 and subsequent steps, and when the diagnosis when the secondary air supply is ON is completed with F1 = 1, the secondary air supply is OFF. In order to execute the diagnosis, the process proceeds to step S130 and thereafter.

Each flag, each count value, and each variable used in this failure diagnosis routine are initialized to 0 at the time of system initialization. Therefore, the routine proceeds to step S101 to step S102 and subsequent steps with F1 = 0 until the first routine and the diagnosis when the secondary air supply is turned on are completed.

First, the secondary air supply O after step S102
The diagnosis process at N hours will be described. In step S102,
Check whether the engine operating condition satisfies the predetermined diagnostic conditions. This diagnostic condition is, for example, that fuel cut is being executed at the time of deceleration of low load and high rotation, that each sensor and the ASV operation switching solenoid valve 36 are normal, and the diagnostic condition is the above-mentioned step S102. If not satisfied, the above steps S102 to S160
Flag F which is set to 1 when the diagnosis is executed.
See 2.

As a result, in step S160, F
When 2 = 0, the routine is exited, and when the operating state changes during the execution of the diagnosis with F2 = 1, the diagnosis is temporarily stopped and the state before the diagnosis is restored.
It is checked whether or not the V operation switching solenoid valve 36 is turned on. Then, when the ASV operation switching solenoid valve 36 is OFF, the routine jumps to step S163, and the ASV
When the operation switching solenoid valve 36 is ON, step
After the ASV operation switching solenoid valve 36 is turned off in S162, the process proceeds to step S163.

In step S163, when the flag F2 is cleared (F2 ← 0), count values C1 and C2, a flag F3, and a variable (minimum value) MI, which will be described later in steps S164 to S168, are set.
N, variable (maximum value) MAX is cleared (C1 ← 0, C2
← 0, F3 ← 0, MIN ← 0, MAX ← 0), exit the routine.

On the other hand, when the diagnosis condition is satisfied in step S102 and the process proceeds from step S102 to step S103, an abnormality determination is made by referring to the flag FNGON of the backup RAM 44 up to the last time when the secondary air supply was turned on. Check whether or not. And FNGON = 1
If it is determined that there is an abnormality in the diagnosis when the secondary air supply is turned on up to the previous time, the above step S103
To step S123, the flag F1 is set (F1 ← 1), and the routine is exited to shift to the diagnosis when the secondary air supply is OFF as the end of the diagnosis when the secondary air supply is ON.

Further, in the above step S103, FNGO
If N = 0, and it is determined to be normal in the initial diagnosis or in the diagnosis when the secondary air supply is turned on up to the previous time, the process proceeds from step S103 to step S104 to indicate that the diagnosis is being executed. When F2 is set (F2 ← 1), the process proceeds to step S105, the ASV operation switching solenoid valve 36 is turned on to forcibly turn on the secondary air supply to the exhaust system.

In subsequent steps S106 and S107, after the ASV operation switching solenoid valve 36 is turned from OFF to ON,
Standby processing is performed until the pressure in the secondary air passage 34 is stabilized. That is, in step S106, the count value C1 is incremented (C1 ← C1 + 1) in order to measure the elapsed time after the ASV operation switching solenoid valve 36 is turned from OFF to ON.
1 is compared with the set value TMON, and when C1 <TMON, the routine is exited, and when C1 ≧ TMON, the pressure in the secondary air passage 34 is considered to be stabilized, and the routine proceeds to step S108.

In step S108, the flag F3 indicating that the initial setting for obtaining the minimum value and the maximum value of the pressure pulsation in the secondary air passage 34 within the set time is made. Initial setting is not completed at the beginning of processing (F
3 = 0), the process proceeds from step S108 to step S109,
The minimum value MIN is initialized by the current pressure measurement value PON when the secondary air supply is ON by the pressure sensor 38 (M
Along with IN ← PON, the maximum value MAX is initialized by the pressure measurement value PON in step S110 (MAX ←
PON), and in step S111, the flag F3 is set to 1 to indicate the end of the initial setting (F3 ← 1) and the routine exits.

When the above initial setting is completed and the routine is started again to reach step S108, since F3 = 1, the process proceeds from step S108 to step S112, and the pressure measurement value PON is compared with the minimum value MIN. When MIN> PON, the process proceeds from step S112 to step S113 to set the minimum value MIN as the pressure measurement value PON (MIN ← PO
N) Proceed to step S116, and if MIN≤PON, proceed to step S114 from step S112 to measure pressure P
Compare ON with the maximum value MAX.

In step S114, if MAX ≧ PON, the process proceeds to step S116, and if MAX <PON, the process proceeds to step S115 to set the maximum value MAX as the pressure measurement value PON (MAX ← PON), and the process proceeds to step S116. And
When the count value C2 is counted up in step S116 (C2 ← C2 + 1), the count value C2 is compared with the set value CTON in step S117 to determine the minimum and maximum values of the pressure in the secondary air passage 34 within the set time. It is checked whether or not the requested processing has been completed.

In step S117, C2 <CTO
When N, exit the routine, and when C2 ≧ CTON,
Proceed to step S118, and the secondary air passage 3 within the set time
The difference D between the maximum value MAX and the minimum value MIN of the pressure pulsation within 4
When LTPON is calculated (DLTPON ← MAX-MI
N), in step S119, the latest atmospheric pressure data PA is read from the backup RAM 44, and the determination value (secondary air supply ON side determination value) ASVGNON at the atmospheric pressure at the time of executing this diagnosis is set based on this atmospheric pressure data PA. , In step S120, this secondary air supply ON side determination value ASVNGO
By comparing N with the difference DLTPON, the abnormality determination on the secondary air supply ON side is performed.

Secondary air supply ON side determination value ASVNG
ON means that the engine operating state is a predetermined operating state, for example,
When the fuel cut is executed during deceleration of low load and high rotation, and the pressure pulsation in the secondary air passage 34 when the secondary air supply is ON is the smallest, the maximum value and the minimum value And the value under each atmospheric pressure is stored in the ROM as shown in FIG.
It is stored in the table 42. That is, the pressure pulsation in the secondary air passage 34 becomes relatively large when the atmospheric pressure becomes high during lowland traveling or the like, and becomes relatively small when the atmospheric pressure becomes low during highland traveling.
The judgment value is set according to the atmospheric pressure measured by.

When the secondary air supply is ON, DL
In the case of TPON> ASVNGON, it can be determined that the minimum secondary air flow rate is secured and the secondary air supply system is normal, and conversely, in the case of DLTPON ≦ ASVNGON, the valve opening failure of the ASV33, Leakage occurs in the secondary air supply system due to malfunction of the ASV operation switching solenoid valve 36, piping leakage, etc., and deterioration of parts constituting the secondary air supply system over time, so that pressure pulsation in the secondary air passage 34 is normal. It can be judged that it is smaller than time.

Therefore, in step S119, DLTPON
When> ASVNGON, it is determined that the secondary air supply system is normal, and in step S123 a flag F1 is set to indicate the end of diagnosis when the secondary air supply is ON (F1 ← 1).
The routine exits through steps S164 to S168 described above. On the other hand, the comparison result in step S120 is DLTPON ≦ A.
In the case of SVNGON, it is determined that an abnormality has occurred in the secondary air supply system, the process proceeds from step S120 to step S121, and a flag FNGON indicating a trouble occurrence when the secondary air supply of the secondary air supply system is ON is set ( FNGON ← 1)
When the data is stored in a predetermined address of the backup RAM 44, the MIL lamp 53 is turned on (or blinks) in step S122 to warn the driver of the occurrence of an abnormality, and the routine exits via step S123.

Next, the processing when the diagnosis when the secondary air supply is ON is completed, the flag F1 is set to 1 and the process proceeds from step S101 to step S130 and thereafter will be described.

In step S130, when executing the diagnosis when the secondary air is OFF, it is checked whether or not the diagnosis condition is satisfied, as in the case where the diagnosis is executed when the secondary air is ON, and when the diagnosis condition is not satisfied, If the diagnosis condition is satisfied by branching to step S163 or later, whether the abnormality determination has been made in the previous diagnosis when the secondary air supply is turned off by referring to the flag FNGOF of the backup RAM 44 when the diagnosis condition is satisfied. Check whether or not. And FNG
When OF = 1, and when it is determined that there is an abnormality in the diagnosis when the secondary air supply is turned off up to the previous time, a jump is made from the above step S131 to step S150 in order to stop the diagnosis when the secondary air supply is turned off. F1 is cleared (F1 ← 0), and the routine exits through steps S163 to S168 described above.

On the other hand, in step S131, FNGOF =
0, and when it is judged to be normal in the diagnosis at the time of turning off the secondary air supply for the first time or at the previous diagnosis at the time of turning off the secondary air supply, the process proceeds from step S131 to step S132, and the ASV operation switching solenoid valve is executed. Three
6 is turned off, and the secondary air supply to the exhaust system is stopped.

Next, in step S133, the count value C1 is counted up (C1 in order to count the elapsed time after the ASV operation switching solenoid valve 36 is turned off).
← C1 + 1), and it is checked in step S134 whether the count value C1 has reached the set value TMOF. When C1 <TMOF in step S134, the routine is exited,
When C1 ≧ TMOF and the set time has elapsed, the routine proceeds to step S135, where the initial setting for obtaining the minimum value and the maximum value of the pressure pulsation in the secondary air passage 34 in the secondary air supply OFF state is made. Reference is made to the flag F3 indicating that there is.

When F3 = 0, the above step S1
The process branches from 35 to step S136, and when F3 = 1, the process proceeds from step S135 to step 139. At the stage where the initial setting for obtaining the minimum value and the maximum value has not been made, in steps S136 and S137, the minimum value M is determined by the current pressure measurement value POF by the pressure sensor 38 when the secondary air supply is OFF.
Initially setting IN and maximum value MAX (MIN
← POF, MAX ← POF), and in step S138, the flag F3 is set to 1 to indicate the end of initialization (F3 ←
1) Exit the routine.

Next, the routine is started again and the step
When the process proceeds to S135 and F3 = 1 and proceeds to step S139, the pressure measurement value POF is compared with the minimum value MIN. And MI
When N> POF, the above steps S139 to S140
Go to step S143 and set the minimum value MIN with the current pressure measurement value POF (MIN ← POF), and go to step S143, where MIN≤
In the case of POF, the process proceeds from step S139 to step S141 to compare the pressure measurement value POF with the maximum value MAX.

In step S141, if MAX ≧ POF, the process proceeds to step S143, and if MAX <POF,
In step S142, the maximum value MAX is set to the current pressure measurement value POF.
Set with (MAX ← POF), and proceed to step S143. Then, when the count value C2 is incremented in step S143 (C2 ← C2 + 1), the count value C2 is compared with the set value CTOF in step S144, and the minimum and maximum values of the pressure in the secondary air passage 34 within the set time are set. It is checked whether or not the processing for obtaining the value is completed.

In step S144, C2 <CTO
When F, exit the routine, and when C2 ≧ CTOF,
In step S145, the maximum value MAX and the minimum value M of the pressure pulsation in the secondary air passage 34 in the secondary air supply OFF state.
When the difference DLPOF from IN is calculated (DLTPOF ←
MAX-MIN), backup RAM in step S146
The latest atmospheric pressure data PA is read from 44, and the determination value (secondary air supply OFF side determination value) ASVNGOF at the atmospheric pressure at the time of executing this diagnosis is set based on this atmospheric pressure data PA, and in step S147, this value is set. By comparing the next air supply OFF side determination value ASVNGOF and the difference DLTPOF, the abnormality determination on the second air supply OFF side is performed.

Secondary air supply OFF side determination value ASVN
The GOF is in a predetermined operating state, for example, in an operating range where fuel cut is executed at the time of deceleration of low load and high rotation, and is shut off from the exhaust system by the valve closing of the ASV 33, so that the engine suction negative pressure is reduced. In the state in which the pressure pulsation in the secondary air passage 34 caused by the above is the largest, the difference between the maximum value and the minimum value is previously obtained by an experiment or the like, and each atmospheric pressure is determined similarly to the secondary air supply ON side determination value ASVNGON. The values below are stored in the table of the ROM 42.

It should be noted that each of the above judgment values ASVNGON, ASV
The NGOF is not stored in a table having atmospheric pressure as a parameter, and values under atmospheric pressure (hereinafter referred to as reference atmospheric pressure; for example, standard atmospheric pressure) serving as a reference for abnormality determination are obtained in advance and stored in the ROM 42. Alternatively, the value may be converted into a value at the atmospheric pressure at the time of executing the diagnosis by storing it in the.

When the secondary air supply is OFF, D
When LTPOF ≤ ASVNGOF, the secondary air passage 34
Is completely shut off from the exhaust system, and it can be determined that it is normal. If DLTPOF> ASVNGOF, A
It may be determined that the secondary air passage 34 is not completely shut off from the exhaust system due to a valve closing failure of the SV 33, an operation failure of the ASV operation switching solenoid valve 36, etc., and the pressure pulsation is larger than in the normal state. it can.

Therefore, in the above step S147, DLTPOF
When ≤ ASVNGOF, it is determined that the secondary air supply system is normal, the process proceeds to step S150, and the flag F1 is cleared (F1 ← 0). Then, after passing through step S163 described above, each count value, each flag, and each variable are set. Clear and exit the routine. On the other hand, in step S147, DLTPOF> ASV
In the case of NGOF, it is determined that an abnormality has occurred in the secondary air supply system, the process branches from step S147 to step S148, and a flag F indicating that an abnormality has occurred on the secondary air supply OFF side is generated.
When NGOF is set (FNGOF ← 1) and stored in a predetermined address of the backup RAM 44, step S1
At 49, the MIL lamp 53 is turned on (or blinks) to warn of the occurrence of an abnormality, and similarly, after the flag F1 is cleared at step S150, the routine jumps to step S163.

That is, when the secondary air supply is ON, the abnormality is judged based on the magnitude of the pressure pulsation due to the actual flow of the secondary air in the secondary air passage 34. When the secondary air supply is OFF, the abnormality is judged. When the secondary air does not flow in the secondary air passage 34 and the determination is made based on the pressure pulsation that accompanies the intake cycle of the engine, the air-fuel ratio between the cylinders varies, the misfire occurs, or It is possible to reliably detect an abnormality in the secondary air supply system even in an operating region where the secondary air flow rate is small, such as in a low load region.
At this time, since the determination value is set according to the atmospheric pressure, the influence of the atmospheric pressure can be eliminated and the accurate determination can be always performed regardless of the highland and the lowland, and the reliability can be improved.

The secondary air supply to the exhaust system is turned on and off
The pressure in each state is detected by the secondary air passage 32 on the exhaust side, and the secondary air supply OFF side judgment value is determined based on the pressure pulsation in the secondary air passage 32 in the state where the secondary air passage 32 is completely cut off from the intake system. May be set.

FIG. 11 and FIG. 12 are flowcharts relating to the second embodiment of the present invention and showing a modified part of the failure diagnosis routine.

In this embodiment, a part of the failure diagnosis function for the secondary air supply system in the above-mentioned first embodiment is changed, and the secondary air passage 34 detected by the pressure sensor 38 as the secondary air passage pressure detecting means. Based on the internal pressure data and the atmospheric pressure data detected by the pressure sensor 13 as the atmospheric pressure detection means, the difference between the maximum value and the minimum value of the pressure pulsation in the secondary air passage 34 is used for abnormality determination. Pulsating pressure difference calculating means for converting to a value under the standard atmospheric pressure, and the difference between the maximum value and the minimum value of the pressure pulsation in the secondary air passage 34 calculated by this pulsating pressure difference calculating means The abnormality diagnosis is performed by the abnormality determination means for determining abnormality by comparing with a preset determination value under atmospheric pressure.

That is, in contrast to the first mode in which the judgment value for the abnormality judgment is set according to the actual atmospheric pressure at the time of diagnosis,
In this embodiment, the pressure in the secondary air passage 34 measured at the time of diagnosis is set to the reference atmospheric pressure (for example,
(Standard atmospheric pressure), and the difference between the maximum value and the minimum value of the pressure pulsation in the secondary air passage 34 under the reference atmospheric pressure is a judgment value set as a value under the reference atmospheric pressure in advance. By comparing, the abnormality determination is performed.

Therefore, in the failure diagnosis routine of this embodiment, steps S119 and S120 of the failure diagnosis routine of the first embodiment described above are changed to steps S1190 and S1200, and steps S146 and S147 are changed to steps S1460 and S1470. To do. The changed part will be described below.

As shown in FIG. 11, in step S1190, the difference between the maximum value MAX and the minimum value MIN of the pressure pulsation in the secondary air passage 34 is based on the latest atmospheric pressure data PA stored in the backup RAM 44. DLTPON
Is converted to a value at the standard atmospheric pressure, and in step S1200,
By comparing the converted difference DLTPON with the secondary air supply ON side determination value ASVNGON which is set in advance under the standard atmospheric pressure and stored in the ROM 42, the abnormality determination on the secondary air supply ON side is performed. .

Further, as shown in FIG. 12, step S146
At 0, based on the latest atmospheric pressure data PA stored in the backup RAM 44, the difference DLTP between the maximum value MAX and the minimum value MIN of the pressure pulsation in the secondary air passage 34.
The OF is converted into a value at the standard atmospheric pressure, and step S1470
Then, by comparing the converted difference DLTPOF with the secondary air supply OFF side determination value ASVNGOF which is set in advance under the reference atmospheric pressure and stored in the ROM 42, the abnormality determination on the secondary air supply OFF side is performed. I do.

The difference DLT between the maximum value MAX and the minimum value MIN of the pressure pulsation in each state of the secondary air supply ON and OFF.
PON and DLPPOF can be converted into values at the standard atmospheric pressure as follows, assuming that the standard atmospheric pressure is the standard atmospheric pressure. However, the maximum value MAX and the minimum value MIN in each state are as follows.
Needless to say, may be converted into a value at the standard atmospheric pressure and the difference may be obtained.

DLTPON ← DLTPON × 760 / PA DLTPOF ← DLTPOF × 760 / PA In this embodiment as well, the same as in the first embodiment described above, the influence of atmospheric pressure can be eliminated and accurate determination can always be performed regardless of highland or lowland. If the air-fuel ratio among the cylinders varies, if a misfire occurs, or even in an operating region where the secondary air flow rate is low, such as in the low load region, it is possible to reliably detect an abnormality in the secondary air supply system. it can.

[0082]

As described above, according to the present invention, the difference between the maximum value and the minimum value of the pressure pulsation in the secondary air passage is calculated, and the calculated difference is set based on the atmospheric pressure data. By comparing with the judgment value, the abnormality of the secondary air supply system is judged,
Alternatively, the difference between the maximum value and the minimum value of the pressure pulsation in the secondary air passage is converted to a value under the standard atmospheric pressure for abnormality determination, and the calculated difference is preset under the standard atmospheric pressure. Since the abnormality of the secondary air supply system is determined by comparing with the determined value, the air-fuel ratio between the cylinders varies, a misfire occurs, or the secondary air flow rate in the low load region is small. The influence of atmospheric pressure on the operating area and the like can be eliminated to enable accurate determination at all times regardless of highland or lowland, and reliability can be improved.

[Brief description of drawings]

FIG. 1 is a basic configuration diagram of the present invention.

FIG. 2 is a basic configuration diagram of the present invention.

FIG. 3 is a flowchart (part 1) of a failure diagnosis routine according to the first embodiment of the invention.

FIG. 4 is a flowchart of a failure diagnosis routine (part 2).

FIG. 5 is a flowchart of the failure diagnosis routine (part 3).

FIG. 6 is a flowchart of a failure diagnosis routine (Part 4).

FIG. 7 is a flowchart of an atmospheric pressure detection routine of the same as above.

FIG. 8 is an explanatory diagram of a judgment value table same as above.

FIG. 9 is a schematic configuration diagram of an engine control system.

FIG. 10 is a circuit configuration diagram of an electronic control system.

FIG. 11 is a flow chart showing a modified part of the failure diagnosis routine according to the second embodiment of the present invention.

FIG. 12 is a flowchart showing a modified part of the failure diagnosis routine of the above.

[Explanation of symbols]

1 ... Engine 13 ... Pressure sensor (atmospheric pressure detection means) 34 ... Secondary air passage 38 ... Pressure sensor (secondary air passage pressure detection means) 40 ... Electronic control device PA ... Atmospheric pressure data DLTPON, DLTPOF ... Maximum pressure pulsation Difference between value and minimum value ASVNGON, ASVNGOF ... Judgment value

Claims (4)

(57) [Claims] 1. A failure diagnosis device for a secondary air supply system of an engine, which supplies secondary air to an exhaust system through a secondary air passage, wherein a secondary air passage pressure for detecting a pressure in the secondary air passage. The detecting means, the atmospheric pressure detecting means for detecting the atmospheric pressure, and the above-mentioned state in the state where the secondary air is being supplied to the exhaust system based on the data of the pressure inside the passage detected by the above-mentioned secondary air passage pressure detecting means. Based on the atmospheric pressure data detected by the pulsating pressure difference calculating means for calculating the difference between the maximum value and the minimum value of the pressure pulsation in the secondary air passage and the atmospheric pressure detecting means, the secondary air supply system Judgment value setting means for setting a judgment value for judging abnormality, and the difference between the maximum value and the minimum value of the pressure pulsation in the secondary air passage calculated by the pulsation pressure difference calculation means is the judgment value setting means. Compared with the judgment value set in, The following case, the secondary air supply system failure diagnosis apparatus for an engine characterized by comprising an abnormality judging means determines that the secondary air supply system is abnormal. 2. A failure diagnosis device for a secondary air supply system of an engine, which supplies secondary air to an exhaust system through a secondary air passage, wherein a secondary air passage pressure for detecting a pressure in the secondary air passage. The detection means, the atmospheric pressure detection means for detecting the atmospheric pressure, and the above-mentioned state in the state where the secondary air supply to the exhaust system is stopped based on the data of the passage pressure detected by the secondary air passage pressure detection means. Based on the atmospheric pressure data detected by the pulsating pressure difference calculating means for calculating the difference between the maximum value and the minimum value of the pressure pulsation in the secondary air passage and the atmospheric pressure detecting means, the secondary air supply system Judgment value setting means for setting a judgment value for judging abnormality, and the difference between the maximum value and the minimum value of the pressure pulsation in the secondary air passage calculated by the pulsation pressure difference calculation means is the judgment value setting means. Compared with the judgment value set in When greater than the value, the secondary air supply system failure diagnosis apparatus for an engine characterized by comprising an abnormality judging means determines that the secondary air supply system is abnormal. 3. A failure diagnosis device for a secondary air supply system of an engine, which supplies secondary air to an exhaust system through a secondary air passage, wherein a secondary air passage pressure for detecting a pressure in the secondary air passage. An exhaust gas based on the data of the pressure in the passage detected by the secondary air passage pressure detection means and the data of the atmospheric pressure detected by the atmospheric pressure detection means; Calculated by converting the difference between the maximum value and the minimum value of the pressure pulsation in the secondary air passage while supplying the secondary air to the system to the value under the standard atmospheric pressure for abnormality determination. Pulsating pressure difference calculating means, and the difference between the maximum value and the minimum value of the pressure pulsation in the secondary air passage calculated by the pulsating pressure difference calculating means is compared with a judgment value preset under the reference atmospheric pressure. , When the difference is less than or equal to the determination value, the secondary air supply system The secondary air supply system of the failure diagnosis apparatus for an engine characterized by comprising an abnormality judging means for judging that the normal. 4. A failure diagnosis device for a secondary air supply system of an engine, which supplies secondary air to an exhaust system via a secondary air passage, wherein a secondary air passage pressure for detecting a pressure in the secondary air passage. An exhaust gas based on the data of the pressure in the passage detected by the secondary air passage pressure detection means and the data of the atmospheric pressure detected by the atmospheric pressure detection means; Calculated by converting the difference between the maximum value and the minimum value of the pressure pulsation in the secondary air passage when the secondary air supply to the system is stopped into a value under the standard atmospheric pressure for abnormality determination. Pulsating pressure difference calculating means, and the difference between the maximum value and the minimum value of the pressure pulsation in the secondary air passage calculated by the pulsating pressure difference calculating means is compared with a judgment value preset under the reference atmospheric pressure. , When the difference is larger than the judgment value, the secondary air Feeding system secondary air supply system failure diagnosis apparatus for an engine characterized by comprising an abnormality judging means for judging as abnormal.