JP2570287B2 - Function diagnosis display device for secondary air supply device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an abnormality diagnosis display device for a secondary air supply device of an internal combustion engine.

(Prior art)

In an engine equipped with a three-way catalytic converter, an air-fuel ratio sensor is provided in the exhaust system, and the air-fuel ratio of the combustion air-fuel mixture is set to a target air-fuel ratio (for example, a stoichiometric It is well known that the control is performed based on the fuel ratio.

The applicant of the present application firstly disclosed a secondary air supply capable of supplying secondary air to the exhaust system when the engine is cold, so that the three-way catalyst can exhibit its function even when the engine is cold. A device was proposed (Japanese Utility Model Application Laid-Open No. 52-160010).

[Problems to be solved by the invention]

In this secondary air supply device, when the secondary air supply cannot be stopped after the engine is warmed up due to a foreign matter such as a deposit being caught in a control valve or a reed valve of the device, the exhaust gas is removed from the secondary air supply device. , And the air-fuel ratio sensor always outputs a lean signal, so that the feedback control of the air-fuel ratio becomes inaccurate and the exhaust emission deteriorates. Further, since the learning control value of the air-fuel ratio is deviated, the air-fuel ratio at the time of the open control becomes excessively rich, leading to a decrease in engine output, or a shortage of secondary air injection during a cold period, which also deteriorates exhaust emissions.

An object of the present invention is to diagnose an abnormality of a secondary air supply device,
In the event of an abnormality, the fact is displayed to the vehicle driver to prompt repair and inspection, thereby contributing to exhaust gas measures.

[Means for solving the problem]

As shown in FIG. 1, a function diagnosis display device for a secondary air supply device according to the present invention includes: an idle state determination unit that determines whether an engine is in an idle operation state; Stop means for stopping, alarm means for displaying an abnormality of the secondary air supply device, diagnosis of the function of the secondary air supply device only during idling operation, and air-fuel ratio sensor lean for a predetermined time after secondary air supply is stopped. Operating means for diagnosing that the function of the secondary air supply device is abnormal when outputting the signal and activating the alarm means.

〔Example〕

Referring to FIG. 2, in FIG.
Is a piston, 14 is a combustion chamber, 16 is a spark plug, 18 is an intake valve, 20
Represents an exhaust valve. As in the conventional case, the intake system of the engine includes an air flow meter 22, an intake pipe 24, a throttle body 26, a surge tank 28, and an intake manifold 30. An idle switch 34 is provided for the throttle valve 32 of the throttle body 26.
The idle switch 34 is set to the throttle valve 32
A signal is output when fully closed.

The fuel supply device is configured as an electronically controlled fuel injection device (EFI). The electronically controlled fuel injection device includes an injector 38 that is electronically controlled by a control circuit 36, and the injector 38 injects fuel into an intake air flow in an intake passage 40.

The exhaust system of the engine is an exhaust manifold 42, an exhaust pipe 44,
A catalytic converter 46 is provided, and the catalytic converter 46 contains a three-way catalyst. An air-fuel ratio sensor (oxygen sensor) 48 is provided in the exhaust pipe 44 upstream of the converter 46 to detect the oxygen concentration in the exhaust gas.

The control circuit 36 is composed of a microcomputer, and includes a CPU,
It consists of ROM, RAM, interface, and drive circuit. The coolant temperature of the engine is detected by a water temperature sensor 50, and the crank angle is detected by crank angle sensors 54 and 56 of the distributor 52. Air flow meter 22,
Idle switch 34, air-fuel ratio sensor 48, water temperature sensor 50,
Signals from the crank angle sensors 54 and 56 are input to the control circuit 36. The control circuit 36 calculates the fuel injection amount based on these signals, and at a predetermined time, the injector 38 for a predetermined time.
To form a combustion mixture having a desired air-fuel ratio. The control circuit 36 also controls the ignition timing via the igniter 58.

The secondary air supply device 60 includes a secondary air supply passage 62 communicating with the exhaust manifold 42, an air filter 64, and a reed valve.
66, and a control valve 68 for controlling the flow rate of the secondary air flowing through the passage 62. The control valve 68 is a negative pressure responsive control valve, and the negative pressure chamber 70 is connected to a negative pressure source 74 via a negative pressure transmission passage 72. An electromagnetic valve 76 controlled by the control circuit 36 is provided in the middle of the negative pressure transmission passage 72. When the electromagnetic valve 76 is excited, a negative pressure is applied to the negative pressure chamber 70 of the control valve 68 so that the control valve 68
Are opened, and secondary air is injected into the exhaust manifold 42. When the excitation of the solenoid valve 76 is released,
The atmosphere is bleed into the negative pressure chamber 70, and the control valve 68 is opened to stop the supply of the secondary air.

The control circuit 36 also constitutes a part of a device for diagnosing and displaying an abnormality in the secondary air supply device 60, and turns on an abnormality display means, for example, a display lamp 78 when an abnormality occurs.

A part of the diagnostic display device of the present invention is realized by the control circuit 36 executing the program shown in the flowcharts of FIGS. 3 and 4.

The flowchart of FIG. 3 shows a secondary air control routine, which is executed as an interruption routine every 8 milliseconds. In step 300, the water temperature sensor 50
It is determined whether or not the cooling water temperature _TW is equal to or higher than 10 ° C. and equal to or lower than 30 ° C. based on the signal from the controller. If YES, the solenoid valve 76 is excited in step 310. As a result, secondary air is injected into the exhaust manifold 42, so that the catalytic converter 46 functions sufficiently even when the air-fuel ratio is excessively rich. Next, after setting the solenoid valve position display flag to 1 in step 320, the control routine is terminated. This flag is used in the diagnosis display routine of FIG. 4 described later.

If it is determined in step 300 that the cooling water temperature _TW is out of the range, the process proceeds to step 330 to determine whether or not the idle switch 34 is closed.

If YES, proceed to step 340, where the crank angle sensors 54, 5
The engine speed is set to a set value (for example, 1
000 rpm) or less. Judgment result is YES
If so, it indicates that the engine is in idle operation,
NO indicates that the vehicle is in a deceleration state. If NO, step
Proceed to 310. If the determination result of step 330 is NO, and if the determination result of step 340 is YES, step
After the solenoid valve 76 is turned off at 350, the solenoid valve position display flag is set to zero at step 360. By turning off the solenoid valve 76, the injection of the secondary air is stopped.

FIG. 4 shows a routine for diagnosing and displaying an abnormality in the secondary air supply device 60, and this routine can also be executed every 8 milliseconds. In step 400, a diagnosis similar to steps 330 and 340 in the flowchart of FIG.
It is determined whether or not the engine is in an idling operation state, and the process proceeds to step 410 only when the engine is in an idling operation state. This is to avoid an erroneous determination because the air-fuel ratio greatly fluctuates during the acceleration / deceleration operation. In step 410, it is determined whether or not the secondary air supply is stopped based on the above-described solenoid valve position display flag.
To determine whether the air-fuel ratio sensor 48 is outputting a lean signal. As described with reference to the flowchart of FIG. 3, when the engine is in the idling operation state, the supply of the secondary air must be stopped. Therefore, in the determination in step 420, the air-fuel ratio sensor 48 outputs the lean signal. The output means that foreign matter is caught in the control valve 68 and secondary air is leaking.

If no lean signal is output, go to step 43
At 0, the counter C for measuring the lean signal duration is reset to zero, and the diagnostic display routine ends.

If a lean signal is output, go to step 440
In step 450, it is determined whether the value of the counter C has reached a set value. When the counter C has reached the set value, the control valve 68 is not operated abnormally due to foreign matter being caught or the like.
It is determined that the next air has been released, and step 460 is performed.
Turns on the abnormality display lamp 78.

〔The invention's effect〕

As described above, according to the present invention, in the internal combustion engine provided with the secondary air supply device, the abnormality of the secondary air supply device is diagnosed and the abnormality is displayed, so that the repair can be prompted. Therefore, it is possible to minimize the deterioration of the exhaust emission and the deterioration of the output performance at the time of abnormality.

[Brief description of the drawings]

FIG. 1 is a functional block diagram of the diagnostic display device of the present invention, FIG. 2 is a schematic diagram of an internal combustion engine to which the diagnostic display device of the present invention is applied, a part of which is a cross section, and FIG. FIG. 4 is a flowchart of an air control routine, and FIG. 4 is a flowchart of an abnormality diagnosis display routine. 36: control circuit, 60: secondary air supply device, 62: secondary air supply passage, 68: secondary air control valve, 78: abnormality indicator lamp.

Claims (1)

(57) [Claims] An air-fuel ratio sensor provided in an exhaust system of an internal combustion engine for outputting a signal indicating whether an air ratio of a combustion air-fuel mixture is rich or lean according to an oxygen concentration in exhaust gas; Equipped with an electronic control fuel supply device that controls the air-fuel ratio of the air-fuel mixture based on the signal from the fuel-ratio sensor with the target air-fuel ratio as the center, and supplies secondary air to the exhaust system upstream of the air-fuel ratio sensor when the engine is cold An idle state determining means for diagnosing and displaying the function of the secondary air supply device of the internal combustion engine provided with the secondary air supply device, which determines whether the engine is in an idle operation state; Stopping means for stopping the secondary air supply during idle operation; alarm means for displaying an abnormality of the secondary air supply apparatus; diagnosing the function of the secondary air supply apparatus only during idle operation; stop Operating means for diagnosing that the function of the secondary air supply device is abnormal when the air-fuel ratio sensor outputs a lean signal for a predetermined time after the stop and activating the alarm means. Functional diagnostic display.