JPH0771298A - Abnormal condition detecting device for secondary air supplying device in internal combustion engine - Google Patents

Abstract

PURPOSE:To shorten an abnormal diagnosis time so as to suppress deterioration of exhaust gas to the minimum by changing an air-fuel ratio feedback constant for correcting the air-fuel ratio correction coefficient of an air-fuel ratio feedback means at the time of operation and non operation of a secondary air supplying means. CONSTITUTION:In an engine control device 112, a control signal for controlling a secondary air pump 120 and a vacuum cut valve 121 is outputted on the basis of a parameter showing engine operating condition, and a secondary air supplying amount is controlled by an air cut valve 122. It is thus possible to improve purifying efficiency in an exhaust gas harmful component. In this case, when it is judged there is in a range for carrying out abnormal diagnosis in a secondary air supplying part at the time of air-fuel ratio feedback control, secondary air is ON-supplied for diagnosis. When a passing time is a prescribed value and less after secondary air is ON-supplied, a correction amount is changed so as to judge an air-fuel ratio correction coefficient. When the value is a prescribed value or more, normal condition of secondary air is judged. On the other hand when the value is less than a prescribed value, abnormal condition is judged.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for supplying secondary air for warming up a catalyst of an internal combustion engine and recombusting unburned gas, and more particularly to an abnormality detecting apparatus for a secondary air supply apparatus.

[0002]

2. Description of the Related Art A catalyst has a low purification rate at low temperatures.
Therefore, the secondary air is supplied to the exhaust system passage to accelerate the oxidation reaction of HC and CO of the exhaust gas component, and the reaction heat at this time accelerates the rise of the catalyst temperature and promotes the purification capability of the exhaust gas component. Secondary air supply devices are known.

Incidentally, in an internal combustion engine equipped with a secondary air supply device, due to the occurrence of abnormality, secondary air may not be supplied to the exhaust system and HC and CO may increase. An example of such an abnormality detecting device for a secondary air supply device is Japanese Patent Laid-Open No. 63-143362.
It has been proposed in the publication.

[0004]

However, in the above-mentioned prior art, although the abnormality of the secondary air supply device can be detected by the air-fuel ratio correction coefficient, deterioration of exhaust gas during the detection period is not taken into consideration.

It is an object of the present invention to provide an abnormality detecting device which shortens the diagnosis time and minimizes the deterioration of exhaust gas when the secondary air supply of the secondary air supply device is detected by the air-fuel ratio.

[0006]

In order to achieve the above object, in the present invention, an air-fuel ratio detecting means for detecting an air-fuel ratio of an internal combustion engine, and an air-fuel ratio controlling means for controlling a fuel supply amount based on a signal from the air-fuel ratio detecting means. Fuel ratio feedback means, secondary air supply means for supplying secondary air, means for correcting the air-fuel ratio feedback constant for correcting the air-fuel ratio correction coefficient of the air-fuel ratio feedback means at the time of supplying secondary air, abnormality from the air-fuel ratio correction coefficient An abnormality judgment detecting means for judging is provided.

[0007]

According to the abnormality diagnosing device for the secondary air supply device of the present invention, when the secondary air is supplied, the air-fuel ratio feedback constant that corrects the air-fuel ratio correction coefficient of the air-fuel ratio feedback means is corrected, so that the air condition during the diagnosis period is reduced. The fuel ratio can be adjusted to the target air-fuel ratio, and deterioration of exhaust gas can be prevented.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows the overall system configuration of the secondary air supply apparatus of the present invention. A water temperature sensor 102 for detecting the water temperature of the engine is mounted on the engine body 101, a ring gear 103 for taking in rotation information and a crank angle sensor 104, and a cam shaft (not shown) for identifying a cylinder. Intake passage 10 of engine body 101
7, an air cleaner 108 is provided with an air flow sensor 109 for measuring the amount of intake air, a throttle chamber and a throttle sensor 110, and an idle speed control valve 111 for controlling the idle speed of the engine on the downstream side thereof. The output signals of the above sensors are input to the engine control unit 112, and the crank angle, engine speed, intake air amount, engine water temperature, etc. are measured or calculated, and ignition, fuel, A control amount such as the idle speed is calculated and output to actuators such as the spark plug 113, the fuel injection valve 114, and the idle speed control valve 111 to control the engine.

In the exhaust passage 115, the secondary air introduction port 11
6 and a catalytic converter 117 downstream thereof and oxygen concentration sensors 118 and 119 before and after the catalytic converter 117. Although the oxygen concentration sensor is used in this embodiment, it is not limited to the oxygen concentration sensor, and an air-fuel ratio sensor or the like may be used.
In this system, in order to improve the purification rate of harmful exhaust components,
Based on the output signal of the upstream oxygen concentration sensor 118 of the catalytic converter 117, the fuel injection amount of the fuel injection valve 114 is controlled by air-fuel ratio feedback control for controlling the air-fuel ratio of the engine to near the stoichiometric air-fuel ratio.

The secondary air promotes the oxidation reaction of exhaust gas harmful components such as HC and CO that are discharged, and promotes the temperature rise (activation) of the catalyst due to the heat of its chemical reaction, and the exhaust gas harmful components of the exhaust gas due to the catalytic action are promoted. It improves the purification efficiency.

The configuration of the secondary air supply section is based on the parameters indicating the engine operating state, and the engine control unit 11
2 outputs a control signal for controlling the secondary air pump 120 and the vacuum cut solenoid valve 121, and the air cut valve 122 controls the secondary air supply amount. The check valve 123 is responsible for preventing blowback of exhaust gas.

When the secondary air is not supplied due to an abnormality in the secondary air supply portion, the purification efficiency of exhaust gas harmful components is lowered and the exhaust gas is deteriorated.

FIG. 2 is an explanatory view of the diagnosis of the secondary air supply device of the present invention. FIG. 2A shows the supply of secondary air (O
N), secondary air supply stop (OFF). FIG. 2B shows the movement of the air-fuel ratio correction coefficient (ALPHA). When the secondary air supply portion is normal, when the secondary air is supplied (ON) at (t ₁ ), the air-fuel ratio correction coefficient (ALPHA) moves like B or C according to the output of the oxygen concentration sensor 118, At t ₂ ) the supply of secondary air is stopped (OFF)
And the air-fuel ratio correction coefficient (ALPHA) moves like D or E. When the secondary air supply portion is abnormal and the secondary air is not supplied, the air-fuel ratio correction coefficient (ALPHA) becomes A. When the air-fuel ratio correction coefficient (ALPHA) is equal to or smaller than the predetermined value ALPHA1 when the secondary air is supplied (ON), it can be detected that the secondary air supply is abnormal. Although ALPHA1 is set to a predetermined value, the value may be changed according to the driving state.

Here, at (t ₁ ), the air-fuel ratio correction coefficient A
By increasing the correction amount of LPHA for a predetermined time T1, ALPHA moves like C, and the diagnostic waiting time, that is, the time when the air-fuel ratio deviates from the theoretical air-fuel ratio, is T11.
To T1. B shows the movement of ALPHA when the correction amount of ALPHA is not changed. The correction amount is returned after T1. Even when the secondary air supply of (t ₂ ) is stopped, the correction amount of ALPHA is increased during the predetermined time T2. In this case also, the time during which the air-fuel ratio deviates from the stoichiometric air-fuel ratio becomes shorter from T22 to T2. Therefore, deterioration of exhaust gas can be prevented.

FIG. 3 shows a flow chart of the main routine of the secondary air supply system of the present invention. In step 10, the operation status parameters are fetched, and in step 20, 2
The next air supply device is diagnosed, and in step 30, air-fuel ratio feedback control, fuel control, idle speed control,
Normal engine control such as ignition control is performed.

FIG. 4 shows a flow chart of the abnormality diagnosing routine of the secondary air supply system in step 20 of FIG. In step 201, it is determined whether or not the air-fuel ratio feedback control is being performed. In step 201, if air-fuel ratio feedback control is in progress, the process proceeds to step 202, and if feedback is not in progress, the diagnosis of the secondary air supply unit ends. In step 202, it is determined whether or not it is an area for diagnosing an abnormality in the secondary air supply unit. If it is an area for diagnosing an abnormality, the procedure proceeds to step 203, and if it is not an area for diagnosing an abnormality, the procedure proceeds to step 211. In step 203, secondary air is turned on (supplied) for diagnosis, and the process proceeds to step 204. In step 204, the counter CT1 when ON is updated,
The counter CT2 at the time of OFF is cleared, and step 205
Go to. In step 205, if the elapsed time CT1 after turning on the secondary air is less than the predetermined value T1, the process proceeds to step 207 and AL
The values of the PHA correction amounts I1 and I2 are changed to the equations (1) and (2), respectively.

I1 = I12 (1) I2 = I22 (2) If CT1 is greater than or equal to T1 in step 205, step 20
6, the values of I1 and I2 are returned to the expressions (3) and (4).

I1 = I11 (3) I2 = I21 (4) After the secondary air is turned on, the values of the correction amounts I1 and I2 of ALPHA change for a predetermined time T1. Where I12> I11,
I22> I21. The predetermined value T1 may be a variable of the engine operating state parameter.

After step 206, the routine proceeds to step 208, where the air-fuel ratio correction coefficient ALPHA is judged. ALPHA
Is greater than or equal to the predetermined value ALPHA1, step 209
Then, the process proceeds to step S2 and the secondary air normality reporting flag FLAGOK = 1 is set. If ALPHA is less than ALPHA1 at step 208, the routine proceeds to step 210, where a secondary air abnormality report flag FLAGNG = 1 is set.

At step 211, the supply of secondary air is stopped (OFF), and the routine proceeds to step 212. Step 21
At 2, the on-time counter CT1 is cleared, the off-time counter CT2 is updated, and the routine proceeds to step 213. In step 213, it is determined whether or not the OFF counter CT2 is equal to or larger than the predetermined value T2. If CT2 is less than T2, step 21
4, the air-fuel ratio feedback constants I1 and I2 are changed to equations (5) and (6). I13> I12, I23
> I22.

I1 = I13 (5) I2 = I23 (6) In step 213, the OFF-time counter CT2 is set to the predetermined value T.
If it is 2 or more, the routine proceeds to step 215, where the feedback constants I1 and I2 are returned to the equations (3) and (4). After the secondary air is turned off, the air / fuel ratio feedback constant changes within a predetermined time T2, and the flow returns after T2.

I11, 112, I13, I21, I2
Although 2 and I23 are set to predetermined values, they may be changed according to the driving state.

FIG. 5 shows a flow chart of the air-fuel ratio control routine of the secondary air supply system in the engine control of step 30 of FIG. In step 301, it is determined whether or not the condition is for air-fuel ratio control. If the condition is for air-fuel ratio control, the process proceeds to step 302, and if it is not for air-fuel ratio control, the process ends. In step 302, the oxygen concentration sensor 11
The air-fuel ratio of the engine is judged by whether or not the output O _{2 of} 8 is a judgment value SL or more. If O ₂ is SL or more, the routine proceeds to step 303, and if O ₂ is less than SL, the routine proceeds to step 306. Although the determination value SL is set to a predetermined value, it may be changed according to the operating state.

In step 303, if the previous O ₂ is less than SL, the previous air-fuel ratio is lean, and step 3
In step 04, the air-fuel ratio feedback constant P1 is subtracted from the air-fuel ratio correction coefficient ALPHA. If the previous O ₂ is SL or more in step 303, the process proceeds to step 305,
The air-fuel ratio feedback constant I1 is subtracted from the air-fuel ratio correction coefficient ALPHA.

In step 306, if the previous O ₂ is SL or more, the previous air-fuel ratio is rich, and step 3
In step 07, the air-fuel ratio feedback constant P2 is added to the air-fuel ratio correction coefficient ALPHA. If the previous O ₂ is less than SL in step 306, the process proceeds to step 308, and the air-fuel ratio correction coefficient ALPHA is sent to the air-fuel ratio feedback constant I.
Add 2

In the above embodiment, the diagnosis time can be shortened by changing the air-fuel ratio feedback constant when the secondary air supply is turned from ON to OFF and from OFF to ON at the time of abnormality diagnosis, and the harmful exhaust gas to the atmosphere is reduced. The emission of components can be suppressed.

[0028]

According to the present invention, the diagnostic time for detecting an abnormality in the secondary air supply device can be shortened, and the discharge of harmful exhaust gas components into the atmosphere can be suppressed.

[Brief description of drawings]

FIG. 1 is an overall system configuration diagram of a secondary air supply device of the present invention.

FIG. 2 is an explanatory diagram of secondary air supply device diagnosis of the present invention.

FIG. 3 is a flowchart of a main routine of the secondary air supply device of the invention.

FIG. 4 is a flowchart of an abnormality diagnosing routine of the secondary air supply device of the invention.

FIG. 5 is a flowchart of an air-fuel ratio control routine of the secondary air supply system of the invention.

[Explanation of symbols]

101 ... Engine body, 102 ... Water temperature sensor, 104 ...
Crank angle sensor, 109 ... Air flow sensor, 110
... Throttle chamber and throttle sensor, 111 ...
Idle speed control valve, 113 ... Spark plug, 114 ... Fuel injection valve, 116 ... Secondary air inlet,
117 ... Catalytic converter, 120 ... Secondary air pump.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Internal reference number for FI FI technical display location F02D 45/00 368 G (72) Inventor Toshio Ishii 2520 Takaba, Katsuta City, Ibaraki Hitachi, Ltd. Mfg. Co., Ltd. Automotive Equipment Division (72) Inventor Akito Numata 2477 Kashima Yatsu Kashima, Katsuta City, Ibaraki Pref. 3 Hitachi Automotive Engineering Co., Ltd.

Claims (6)

[Claims] 1. An air-fuel ratio detecting means for detecting an air-fuel ratio of an engine, an operating state detecting means for detecting an operating state of the engine, and information on an air-fuel ratio signal from the operating state detecting means and the air-fuel ratio detecting means. Based on the air-fuel ratio feedback means for controlling the fuel supply amount of the engine based on the air-fuel ratio, the secondary air supply means for supplying air to the exhaust system, and the air-fuel ratio correction coefficient of the air-fuel ratio feedback means when the secondary air supply means operates. An abnormality detection device for a secondary air supply device of an internal combustion engine having an abnormality determination means for determining whether the air-fuel ratio correction means corrects an air-fuel ratio correction coefficient of the air-fuel ratio feedback means depending on whether the secondary air supply means is operating or not. An abnormality detection device for a secondary air supply device of an internal combustion engine, characterized by changing an air-fuel ratio feedback constant. 2. The diagnostic apparatus according to claim 1, wherein an air-fuel ratio feedback constant for correcting the air-fuel ratio correction coefficient of the air-fuel ratio feedback means is set according to the operating state of the engine when the secondary air supply means is operating and when it is not operating. An abnormality detection device for a secondary air supply device of an internal combustion engine, characterized in that 3. The diagnostic device according to claim 1 or 2, wherein
Abnormality of the secondary air supply device of the internal combustion engine, characterized in that the air-fuel ratio feedback constant for correcting the air-fuel ratio correction coefficient of the air-fuel ratio feedback means is changed in an increasing direction when the secondary air supply means is deactivated. Detection device. 4. The diagnostic device according to claim 1 or 2, wherein 2
Abnormality of the secondary air supply device of the internal combustion engine, characterized in that when the operation of the secondary air supply means is changed from the operation to the non-operation, the air-fuel ratio feedback constant for correcting the air-fuel ratio correction coefficient of the air-fuel ratio feedback means is changed in an increasing direction. Detection device. 5. The diagnostic device according to claim 3 or 2, wherein 2
Changing the air-fuel ratio feedback constant for increasing the air-fuel ratio correction coefficient of the air-fuel ratio feedback means for a predetermined period when the secondary air supply means changes from inactive to inactive or from inactive to inactive An abnormality detection device for a secondary air supply device of an internal combustion engine, comprising: 6. The air-fuel ratio correction coefficient of the air-fuel ratio feedback means in the diagnostic device according to claim 5, when the operation of the secondary air supply means changes from inoperative to inactive An abnormality detection device for a secondary air supply device of an internal combustion engine, characterized in that an air-fuel ratio feedback constant to be corrected is changed in an increasing direction.