JPH0612178Y2 - Secondary air supply controller for multi-cylinder internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a secondary air supply control device for a multi-cylinder internal combustion engine.

[Conventional technology]

A secondary air supply control device is known in which secondary air is supplied into the engine exhaust passage to promote the oxidation reaction of unburned HC and CO, thereby purifying unburned HC and CO. However, the oxidation reaction of unburned HC and CO is an exothermic reaction. Therefore, when a large amount of unburned HC and CO are discharged into the engine exhaust passage, if secondary air is supplied, the catalyst installed in the engine exhaust passage will It causes the problem of overheating. Therefore, when the choke valve does not open and therefore the mixture supplied to the engine cylinder becomes rich and a large amount of unburned HC and CO is discharged into the engine exhaust passage, the supply of secondary air should be stopped. Known internal combustion engine (see Japanese Patent Laid-Open No. 51-137017), the oxygen concentration detector arranged in the exhaust passage of the engine fails and the oxygen concentration detector stops producing an output, and as a result, the engine The air-fuel mixture supplied to the cylinder becomes too rich and a large amount of unburned
An internal combustion engine is known in which the supply of secondary air is stopped when HC and CO are discharged into the engine exhaust passage (see Japanese Utility Model Laid-Open No. 62-117217).

[Problems to be solved by the invention]

However, a large amount of unburned HC and CO is discharged into the engine exhaust passage not only when the choke valve does not open or when the oxygen concentration detector fails, but even when the choke valve opens. Alternatively, it occurs even when the oxygen concentration detector is operating normally. That is, when the air-fuel ratio is controlled to become the stoichiometric air-fuel ratio based on the output signal of the oxygen concentration detector (hereinafter referred to as O ₂ sensor) arranged in the engine exhaust passage, the fuel of some cylinders is controlled. When fuel injection from the injection valve continues to stop, a large amount of fuel is supplied to the remaining cylinders, and a large amount of unburned HC and CO are discharged from those cylinders. Therefore, in this case as well, it is necessary to stop the supply of the secondary air, but the known internal combustion engine described above continues to be supplied with the secondary air even in such a case, thus causing a problem that the catalyst deteriorates.

[Means for solving problems]

In order to solve the above problems, according to the present invention, a fuel supply device is provided for each cylinder, an oxygen concentration detector is arranged in the engine exhaust passage, and the air-fuel ratio is determined based on the output signal of the oxygen concentration detector. Should be supplied in a multi-cylinder internal combustion engine in which the fuel supply amount is controlled so that the target air-fuel ratio becomes, and secondary air is supplied into the engine exhaust passage when the engine is in a predetermined operating state. When the fuel supply from any one of the fuel supply devices is stopped, the fuel supply from any of the fuel supply devices is stopped when the fuel is to be supplied. When the presence of the engine is detected, the supply of the secondary air is stopped regardless of the operating condition of the engine.

〔Example〕

Referring to FIG. 1, 1 is an engine body, 2 is a piston, and 3 is
Is a combustion chamber, 4 is an intake valve, 5 is an intake port, 6 is an exhaust valve,
Denoted at 7 are exhaust ports, respectively. The intake port 5 is connected to a surge tank 9 via a branch pipe 8, and a fuel injection valve 10 is attached to each branch pipe 8. The surge tank 9 is connected to an air cleaner 12 via an intake duct 11, and a throttle valve 13 is arranged in the intake duct 11. The exhaust port 7 is connected to the exhaust manifold 14, and the O ₂ sensor 15 is arranged in the exhaust manifold 14. Further, a secondary air supply device 16 is arranged in the exhaust manifold 14. The secondary air supply device 16 includes a secondary air supply conduit 17 communicating with the exhaust manifold 14, a secondary air control valve 18 disposed in the secondary air supply conduit 17, and a secondary air supply conduit 17. A reed valve 19 that is located and can only flow to the exhaust manifold 14. The secondary air control valve 18 is a valve body 2 that controls the opening and closing of the secondary air supply conduit 17.
0, a diaphragm 21 connected to the valve body 20, and a negative pressure chamber 22. The negative pressure chamber 22 can flow only to the electromagnetic switching valve 23 that can communicate with the atmosphere and the surge tank 9. It is connected to the surge tank 9 via the check valve 24. When the solenoid of the electromagnetic switching valve 23 is deenergized, the negative pressure chamber 22 is opened to the atmosphere. At this time, the valve body 20 shuts off the secondary air supply conduit 17, so that the supply of the secondary air is stopped. On the other hand, when the solenoid of the electromagnetic switching valve 23 is energized, the negative pressure chamber 22 is connected to the inside of the surge tank 9 via the check valve 24, so that the negative pressure chamber 22 becomes negative pressure, and thus the valve body 20 opens the secondary air supply conduit 17.
As a result, when the exhaust manifold has a negative pressure inside the exhaust manifold 14, the secondary air is sucked into the exhaust manifold 14 via the reed valve 19, and thus the secondary air is supplied into the exhaust manifold 14. Will be. The secondary air supply conduit 17 is connected to an engine-driven air pump to
The secondary air discharged from the air pump when the secondary air control valve 18 is opened may be supplied into the exhaust manifold 14. The solenoid of the electromagnetic switching valve 23 is controlled based on the output signal of the electronic control unit 30.

The electronic control unit 30 comprises a digital computer, and ROMs connected to each other by a bidirectional bus 31.
(Read-only memory) 32, RAM (random access memory) 33, CPU (microprocessor) 34,
It has an input port 35 and an output port 36. The air flow meter 12 generates an output voltage proportional to the intake air amount, and this output voltage is input to the input port 35 via the AD converter 37. A throttle switch 25 that is turned on when the throttle valve 13 is at an idling opening is attached to the throttle valve 13, and an output signal of the throttle switch 25 is input to an input port 35. A water temperature sensor 26 that generates an output voltage proportional to the engine cooling water temperature is attached to the engine body 1, and the output voltage of the water temperature sensor 26 is input to an input port 35 via an AD converter 38. The output signal of the O ₂ sensor 15 is the AD converter 39.
Is input to the input port 35 via. Further, the input port 35 is connected to a rotation speed sensor 27 that generates an output signal that represents the engine speed and a vehicle speed sensor 28 that generates an output signal that represents the vehicle speed. On the other hand, the output port 16 is connected to each fuel injection valve 10 via the drive circuit 40, and is connected to the solenoid of the electromagnetic switching valve 23 via the drive circuit 41.

The fuel injection amount TAU from the fuel injection valve 10 is basically calculated based on the following equation.

TAU = TP * FAF * K Here, TP shows a basic fuel injection amount, FAF shows a feedback correction coefficient, and K shows an increase correction coefficient. The basic fuel injection amount TP is calculated from, for example, the intake air amount and the engine speed. The feedback correction coefficient FAF is controlled based on the output signal of the O ₂ sensor 15 so that the air-fuel ratio becomes the stoichiometric air-fuel ratio, and the value of this FAF normally fluctuates around 1.0. The increase correction coefficient K is usually 1.0, and is set to a value larger than 1.0, for example, 1.2 when the fuel should be increased, for example, during high load operation. FAF at this time is 1.0
Fixed to. Therefore, the injected fuel is increased during high load operation.

Next, the behavior of the feedback correction coefficient FAF will be described with reference to FIG. In FIG. 2, V indicates the output voltage of the O ₂ sensor 15. The O ₂ sensor 15 generates an output voltage of about 0.9 volt when a rich mixture is supplied to the engine cylinder, that is, when it is rich, and a lean mixture is supplied to the engine cylinder. At the time, that is, when lean, an output voltage of about 0.1 V is generated. The feedback correction coefficient FAF rapidly rises by a constant value when it shifts from rich to lean, that is, skips, and then gradually increases. On the other hand, when shifting from lean to rich, it skips in the decreasing direction and then gradually decreases. When the fuel injection operation from the fuel injection valve 10 is normally performed, the feedback correction coefficient F
The AF moves up and down around 1.0. However, for example, when one of the fuel injection valves 10 is blown off, the fuel supply as a whole becomes excessive and the fuel supply continues to become rich, and thus the FAF continues to decrease as shown in FIG. Reach MIN. Note that MAX and MIN are called guards, and FAF is controlled so as not to be larger than MAX or smaller than MIN. On the other hand, if the fuel injection from any of the fuel injection valves 10 continues to stop, the fuel supply as a whole becomes too small to keep the fuel lean, and in this case, the FAF continues to increase. Reach MAX. Therefore, if FAF becomes MAX or MIN, it is considered that the fuel injection valve 10 is out of order, and a flag indicating that the fuel system is abnormal is set.

Next, with reference to FIG. 3, an abnormality determination process of setting a flag at the time of abnormality will be described. The routine shown in FIG. 3 is executed by interruption at regular intervals.

Referring to FIG. 3, first, at step 50, it is judged if the feedback condition of the air-fuel ratio is satisfied or not. If it is the feedback condition, the routine proceeds to step 51 and the FAFM is executed.
It is determined whether or not it is AX. If FAFMAX, the routine proceeds to step 52, where the abnormality flag is set. If FAF <MAX, the routine proceeds to step 53, where it is judged if FAFMIN or not. If FAFMIN, the routine proceeds to step 52 and the abnormality flag is set. If FAF> MIN, the routine proceeds to step 54, where the abnormality flag is reset.

Whether or not the fuel system is abnormal can be determined by another method. That is, when the normal fuel injection operation is being performed, the FAF is skipped in a certain cycle, but when the fuel system becomes abnormal, the FAF does not skip as shown in FIG. Although not shown in FIG. 2, for example, when the fuel injection valve 10 of a certain cylinder is blown out, the O ₂ sensor 15 generates a spike-shaped rich signal every time the exhaust gas is discharged from the cylinder. Whenever such a spike-shaped rich signal is generated, the FAF is skipped each time, so the number of skips increases. Therefore, it is possible to determine whether the fuel system is out of order from the number of skips that occur within a predetermined time.

If the fuel injection valve 10 fails and blows off, or if the injection action continues to stop, a large amount of unburned HC, CO is discharged into the exhaust manifold 14 in either case as described above. At this time, if the secondary air is supplied, the catalyst will be overheated. Therefore, in the present invention, when the fuel injection valve 10 fails and the abnormality flag is set, the secondary air is discharged regardless of the operating state of the engine. We are trying to stop the supply.

Next, the secondary air supply control routine will be described with reference to FIGS. 4 and 5. It should be noted that this routine is performed by interruption at every constant crank angle.

Referring to FIGS. 4 and 5, first step 6
At 0, it is determined whether or not the abnormality flag is set. If the abnormality flag is set, the routine proceeds to step 61, where the solenoid of the solenoid operated directional control valve 23 is deenergized, and thus the supply of secondary air is stopped. On the other hand, if the abnormality flag is not set, the secondary air supply determination processing 62 is performed to determine whether or not the secondary air should be supplied according to the operating state of the engine. In this process 62, when the operating state in which the secondary air is not to be supplied is in effect, the routine proceeds to step 61, where the supply of the secondary air is stopped, and when in the operating state in which the secondary air is to be supplied, the routine proceeds to step 63 and the electromagnetic switching valve 23. Is energized, thereby supplying secondary air. That is, at step 64, whether the engine speed N is lower than a preset value N ₀ ,
That is, it is determined whether or not the engine is starting, and if the engine is starting, the supply of secondary air is stopped. If the engine is not started, the routine proceeds to step 65, where the engine is started for a certain period of time, for example,
It is determined whether 1.5 seconds have elapsed. If 1.5 seconds have not elapsed, the supply of secondary air is stopped, and if 1.5 seconds have elapsed, the routine proceeds to step 66. At step 66, it is judged if another abnormality flag is set. If another abnormality flag is set, the supply of secondary air is stopped. If another abnormality flag is set, the routine proceeds to step 67, where the engine cooling water temperature T is -10 ° C <T <
It is determined whether or not it is in the range of 35 ° C. -10 ° C <T
If <35 ° C., the routine proceeds to step 68, where it is judged if the fuel is being increased, that is, if the above-mentioned increase correction coefficient K is larger than 1.0. When the fuel amount is not increased, the secondary air is supplied.

On the other hand, -10 ° C <T <35 ° C, or -10 ° C
Even if <T <35 ° C., if the fuel is being increased, step 6
In step 9, it is determined whether the engine cooling water temperature T is higher than 10 ° C. If T10 ° C., the supply of secondary air is stopped, and if T> 10 ° C., the process proceeds to step 70. At step 70, it is judged if the throttle switch 25 is on, that is, if the throttle valve 13 is at the idling opening degree. If the throttle switch 25 is off, the supply of secondary air is stopped, and if the throttle switch 25 is on, the routine proceeds to step 71. In step 71, the engine speed N is 1200r.pm <N <3200r.
Whether it is in the range of pm or not is determined, and if it is in this range, the secondary air is supplied. If it is not within this range, the routine proceeds to step 72, where it is judged if the engine speed N is lower than 3200 rpm. If N3200r.pm, secondary air supply is stopped, and if N <3200r.pm, step 7
Go to 3. At step 73, it is judged if the vehicle speed V is faster than 2 km / h. If V> 2 km / h, the supply of secondary air is performed, and if V2 km / h, the supply of secondary air is stopped.

[Effect of device]

When the supply of fuel from the fuel supply device provided to one of the cylinders is stopped and a large amount of unburned HC, CO is discharged, the secondary air supply is stopped, so the catalyst Can be prevented from overheating, thus preventing the catalyst from deteriorating and preventing the catalyst from melting.

[Brief description of drawings]

FIG. 1 is an overall view of an internal combustion engine, FIG. 2 is a diagram showing the behavior of a feedback correction coefficient, FIG. 3 is a flow chart for executing a fuel system abnormality determination, and FIGS. It is a flow chart for performing air supply control. 9 ... Surge tank, 10 ... Fuel injection valve, 14 ... Exhaust manifold, 16 ... Secondary air supply device, 18 ... Secondary air control valve, 19 ... Reed valve.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Creator Naoto Sugimoto 1-1, Showamachi, Kariya city, Aichi Nihon Denso Co., Ltd. (56) Reference JP-A-63-212750 (JP, A)

Claims (1)

[Scope of utility model registration request] 1. A fuel supply device is provided for each cylinder,
An oxygen concentration detector is arranged in the engine exhaust passage, and the fuel supply amount is controlled so that the air-fuel ratio becomes the target air-fuel ratio based on the output signal of the oxygen concentration detector, and when the engine operating condition is predetermined. In a multi-cylinder internal combustion engine configured to supply secondary air into the engine exhaust passage, a detection means for detecting that fuel supply from any fuel supply device is stopped when fuel should be supplied is provided. When the supply of fuel is to be supplied, when the supply of fuel from any of the fuel supply devices is detected to be stopped, the supply of secondary air is stopped regardless of the operating state of the engine. Secondary air supply control device for a multi-cylinder internal combustion engine.