JPH0533707A - Air-fuel ratio control device for internal combustion engine - Google Patents

Abstract

PURPOSE:To enhance the exhaust purification performance, the output, and the operation performance by providing an exhaust sensor to a branch exhaust passage communicated with a corresponding air cylinder, and adjusting the quantity of fuel and/or air for each air cylinder by use of a detection signal inputted from each corresponding exhaust sensor. CONSTITUTION:When feedback control of the air-fuel ratio is started, the air-fuel correction quantity is corrected, as a learned value, with respect to each air cylinder, and this corrected value is stored in a storage region for each corresponding air cylinder to renew the learned value. The conditions for executing the renewal of this learned value are two in number, one being that air-fuel ratio feedback control is being made, the other being that a load, which is other than the acceleration/deceleration of an internal combustion engine 2 and which is constant, continues for a specified, or a larger than the specified, time length. A control section 64 operates under control a first to a fourth injection valves 30-1...30-4 provided with respect to a corresponding first to a corresponding fourth air cylinders 18-1...18-4 in response to the detection signals inputted from a first to a fourth oxygen sensors 82-1...82-4 respectively provided to a first to a fourth branch exhaust passages 6-1 to 6-4 communicated with a first to a fourth air cylinders 18-1...18-4 of the engine 2, thereby controlling the air-fuel ratio of an air-fuel mixture being fed to the first to fourth air cylinders 18-1...18-4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an air-fuel ratio control system for an internal combustion engine, and more particularly, it can equalize the air-fuel ratio of the air-fuel mixture supplied to each cylinder of the internal combustion engine. The present invention also relates to an air-fuel ratio control device for an internal combustion engine, which can improve driving performance.

[0002]

2. Description of the Related Art Some internal combustion engines mounted on vehicles have an air-fuel ratio control device. The air-fuel ratio control device is provided with an exhaust sensor for detecting the exhaust gas component value in the exhaust passage, and the fuel amount and / or the air amount is adjusted based on the exhaust gas component value detected by the exhaust gas to adjust the air-fuel ratio of the air-fuel mixture to a target value. The feedback control is performed so that the exhaust purification performance by the catalyst body and the output performance and operation performance of the internal combustion engine are improved.

As disclosed in Japanese Patent Laid-Open No. 63-189647, such an air-fuel ratio control device for an internal combustion engine has an exhaust gas provided in an exhaust passage downstream of an exhaust collecting portion where branch exhaust passages gather. The injection signal calculated from the feedback correction coefficient determined based on the output of the sensor and the basic injection amount determined based on the engine speed, the intake air amount, etc. is sequentially shifted by a fixed amount for each cylinder, and this is caused The actual injection ratio of the fuel injection valve for each cylinder is calculated based on the amount of change in the feedback correction coefficient, and this injection ratio is multiplied by the correction coefficient to correct the injection signal for each cylinder, thereby There is one that compensates for variations in the fuel ratio and controls the same air-fuel ratio.

A fuel injection control device for controlling the fuel injected and supplied to each cylinder is disclosed in Japanese Patent Laid-Open No. 60-204.
As disclosed in Japanese Patent No. 942, in which a fuel injection valve provided for each cylinder is switched between sequential injection and simultaneous injection and used together, each fuel is injected at the transition of fuel injection operation from sequential injection to simultaneous injection. By correcting the injection amount and injection timing of the injection valve, the fuel injection amount to each cylinder at the time of transition from sequential injection to simultaneous injection is made equal to prevent a shock from occurring in the operating state of the internal combustion engine. There is.

[0005]

In the air-fuel ratio feedback control in the conventional air-fuel ratio control device, the fuel amount of the carburetor is adjusted by a duty-controlled solenoid valve or the air sucked in by the intake passage. The quantity is adjusted by a duty-controlled solenoid valve, or the quantity of fuel injected by the fuel injection valve is adjusted.

However, adjustment of the fuel amount of the carburetor provided upstream of the intake manifold of the intake manifold and adjustment of the fuel amount of a single fuel injection valve provided upstream of the intake manifold of the intake manifold. In the air-fuel ratio control device that feedback-controls the air-fuel ratio, the air-fuel ratio of the air-fuel mixture supplied to each cylinder varies due to the influence of the intake manifold and the like, and there is a problem that the air-fuel ratio of each cylinder becomes uneven. ..

Further, in the air-fuel ratio control device which feedback-controls the air-fuel ratio by adjusting the fuel amount of the fuel injection valve provided for each cylinder, the fuel is supplied to each cylinder due to the influence of the production variation of each fuel injection valve. There is a problem that the air-fuel ratio of the air-fuel mixture to be generated varies and the air-fuel ratio of each cylinder becomes uneven.

Therefore, the air-fuel ratio of the exhaust gas flowing into the catalyst body provided in the exhaust passage deviates from the target theoretical air-fuel ratio due to the non-uniformity of the air-fuel ratio of the air-fuel mixture supplied to the respective machine cylinders. However, there is an inconvenience that the exhaust purification performance of the catalyst body is deteriorated and the exhaust harmful component value is deteriorated. Further, the non-uniformity of the air-fuel ratio of the air-fuel mixture supplied to each machine cylinder may cause knocking, resulting in a decrease in output performance due to the cylinder having a thin air-fuel ratio of the air-fuel mixture, and There is the inconvenience of causing a decline.

[0009]

Therefore, according to the present invention, in order to eliminate the above-mentioned inconvenience, the fuel amount and / or the air amount is adjusted based on the exhaust gas component value detected by the exhaust gas sensor provided in the exhaust passage of the internal combustion engine. Then, in the air-fuel ratio control device of the internal combustion engine for performing feedback control so that the air-fuel ratio of the air-fuel mixture becomes the target value, the exhaust sensors are provided in the respective branch exhaust passages communicating with the respective cylinders of the internal combustion engine, and the exhaust sensors are provided. A control means for adjusting the fuel amount and / or the air amount for each cylinder of the internal combustion engine by a detection signal input from the controller to perform feedback control to equalize the air-fuel ratio of the air-fuel mixture supplied to each cylinder is provided. Characterize.

[0010]

According to the structure of the present invention, the control means causes
The fuel amount and / or the air amount for each cylinder of the internal combustion engine is adjusted by a detection signal input from each exhaust sensor provided in each branch exhaust passage communicating with each cylinder of the internal combustion engine, and the fuel is supplied to each cylinder. By performing feedback control to equalize the air-fuel ratio of the air-fuel mixture, it is possible to prevent variations in the air-fuel ratio of the air-fuel mixture in each cylinder due to the influence of intake manifolds and the variation in production of individual fuel injection valves. It is possible to equalize the air-fuel ratio for each cylinder.

[0011]

Embodiments of the present invention will be described in detail below with reference to the drawings.

1 to 6 show an embodiment of the present invention. In FIG. 6, 2 is an internal combustion engine, 4 is an intake passage,
6 is an exhaust passage.

The intake passage 4 of the internal combustion engine 2 has an air cleaner 8 and an air flow meter 10 which are sequentially connected from the upstream side.
It is formed by the throttle body 12 and the intake manifold 14. Intake passage 4 in the throttle body 12
Is equipped with an intake throttle valve 16. Further, as shown in FIG. 1, the intake passage 4 in the intake manifold 14 includes a surge tank portion 4-A which is an intake collecting portion and first to fourth branch intake passages branched from the surge tank portion 4-A. Part 4
-1 to 4-4. The first to fourth branch intake passage portions 4-1 to 4-4 respectively include the first to fourth cylinders 18-1 to 18-1.
18-4, respectively.

Further, the exhaust passage 6 of the internal combustion engine 2 is formed by an exhaust manifold 20, an upstream exhaust pipe 22, a catalytic converter 24 and a downstream exhaust pipe 26 which are sequentially connected from the upstream side. The exhaust passage 6 in the exhaust manifold 20 is
First to fourth branch exhaust passage portions 6-1 to 6-4, which are respectively communicated with the first to fourth cylinders 18-1 to 18-4, and these first to first
The exhaust gas collecting section 6-A is formed by collecting the fourth branch exhaust passage sections 6-1 to 6-4. Also, the catalytic converter 2
A catalyst body 28 is provided in the exhaust passage 6 inside 4.

The internal combustion engine 2 includes first to fourth cylinders 18
First to fourth fuel injection valves 30-1 to 30-3 for each of -1 to 18-4
0-4 is attached. 1st-4th fuel injection valve 30-
1 to 30-4 are connected to a fuel tank 36 by a fuel supply passage 34 via a fuel distribution passage 32. A fuel pump 38 is provided in the fuel tank 36. The fuel to be pumped by the fuel pump 38 has its dust removed by the fuel filter 40 and is supplied to the fuel distribution passage 32 by the fuel supply passage 34.
It is distributed and supplied to the fuel injection valves 30-1 to 30-4.

The fuel distribution passage 32 is provided with a fuel pressure adjusting section 42 for adjusting the fuel pressure. The fuel pressure adjusting unit 42 adjusts the fuel pressure to a constant value by the intake pressure introduced from the pressure guiding passage 44 communicating with the intake passage 4,
Excess fuel is returned to the fuel tank 36 through the fuel return passage 46.

The fuel tank 36 is provided in communication with the intake passage 4 of the throttle body 12 by a vaporized fuel passage 48, and the fuel tank 36 is provided in the middle of the vaporized fuel passage 48.
A two-way valve 50 and a canister 52 are sequentially provided from the side. Further, a bypass passage 54 that bypasses the intake throttle valve 16 of the throttle body 12 and communicates with the intake passage 4 is provided.
And an idle air amount control valve 56 is provided in the middle of the bypass passage 54. Idle air amount control valve 56
Is for stabilizing the idle rotation speed by opening and closing the bypass passage 54 to increase or decrease the air amount when the idle rotation speed needs to be adjusted at the time of start-up, high temperature, or increase in electric load. Reference numeral 58 is an air regulator, reference numeral 60 is a power steering switch, reference numeral 62.
Is an air amount control valve for power steering.

Incidentally, in FIG. 6, the first branch intake passage section 4-1, the first cylinder 18-1, and the first branch exhaust passage section 6 are provided.
Only -1 is shown.

The air flow meter 10, the first to fourth fuel injection valves 30-1 to 30-4, and the idle air amount control valve 5
6. The power steering air amount control valve 62 is connected to a control unit 64 which is a control means. The control unit 64 includes
A crank angle sensor 66, a distributor 68,
An opening sensor 70 for the intake throttle valve 16 and a knock sensor 72
, A water temperature sensor 74, and a vehicle speed sensor 76 are connected to each other. The distributor 68 is connected to the control unit 64 via an ignition coil 78 and an ignition power unit 80.

Further, the control unit 64 is connected to an oxygen sensor 82, which is an exhaust sensor provided in the exhaust passage 6 for detecting the oxygen concentration which is the exhaust gas component value, and the oxygen concentration which is the exhaust gas component value which is detected by the oxygen sensor 82 is provided. The fuel amount and / or the air amount is adjusted based on the above, and feedback control is performed so that the air-fuel ratio of the air-fuel mixture becomes a target value. In this embodiment, based on the oxygen concentration detected by the oxygen sensor 82,
The first to fourth fuel injection valves 30-1 to 30-4 are operated and controlled to adjust the fuel amount, and feedback control is performed so that the air-fuel ratio of the air-fuel mixture becomes a target value.

In such an air-fuel ratio control system for the internal combustion engine 2, as shown in FIG. 1, the first to fourth branch exhaust passages communicating with the first to fourth cylinders 18-1 to 18-4 of the internal combustion engine 2 are provided. 6-1 to 6-4 respectively include first to fourth oxygen sensors 82-1 to 82-1.
82-4 is provided, and these first to fourth oxygen sensors 82-1 are provided.
82-4 are connected to the controller 64 and provided. Control unit 64
Are the first to fourth cylinders 18 of the internal combustion engine 2 according to the detection signals input from the first to fourth oxygen sensors 82-1 to 82-4.
-1st to 4th fuel injection valves 30 provided for each 1 to 18-4
1 to 30-4 are operated to adjust the fuel amount, and feedback control is performed to equalize the air-fuel ratio of the air-fuel mixture supplied to the first to fourth cylinders 18-1 to 18-4.

In FIG. 6, reference numeral 84 is a dashpot, reference numeral 86 is a battery, reference numeral 88 is a thermofuse, reference numeral 90 is an alarm relay, reference numeral 92 is a warning light, and reference numeral 94 is a main switch.

Next, the control by the air-fuel ratio control device will be described with reference to FIG.
2 will be described with reference to FIG.

When the internal combustion engine 2 is started (step 100) and the battery 86 is switched from off to on, initial values of the learning value and the feedback value are set (step 10).
1) Do. At this time, if the previous learning value is erased by turning off the battery 86, the initial value of the learning value is set to 1.0 without the correction value, and the initial value of the feedback value is set to 1.0.

Next, normally, when the previous learning value is stored in the storage area for each cylinder as shown in FIG. 4,
Until the air-fuel ratio feedback control is started,
Learning correction for each of the fourth cylinders 18-1 to 18-4 (step 1
02) is performed.

Further, in order to correct the distribution of each cylinder of the internal combustion engine 2 in the cold state according to the water temperature, as shown in FIG. 5, the water temperature is set for each of the first to fourth cylinders 18-1 to 18-4. Distribution correction (step 103) is performed according to the load.

When the warm-up of the internal combustion engine 2 is completed,
Air-fuel ratio feedback control starts (step 104)
To be done.

When the air-fuel ratio feedback control is started, the air-fuel ratio correction amount is corrected as a learning value for each cylinder, and the value is stored in a storage area for each cylinder as shown in FIG. Update (step 105) is performed. The condition for executing the update of the learned value is that the condition that the feedback control of the air-fuel ratio is being performed and that the constant load other than the acceleration / deceleration of the internal combustion engine 2 is continued for a predetermined time or longer is satisfied. In addition,
The determination that the load is constant is made by, for example, the intake throttle valve 16
And the pressure in the intake passage 4, etc.

As described above, the control section 64 is provided in each of the first to fourth branch exhaust passages 6-1 to 6-4 communicating with the first to fourth cylinders 18-1 to 18-4 of the internal combustion engine 2. 1st to 4th
The first to fourth fuel injection valves 30-1 to 30-4 provided for each of the first to fourth cylinders 18-1 to 18-4 are operated by the detection signals input from the oxygen sensors 82-1 to 82-4. By controlling and adjusting the fuel amount as shown in FIG. 3, the first to fourth cylinders 18-
Feedback control is performed to equalize the air-fuel ratio of the air-fuel mixture supplied to 1 to 18-4.

As a result, the first to fourth cylinders 18-1 to 18-1 to 18-1 to 18-1 to 18-4 are caused by the influence of the intake manifold 14 and the like and the influence of variations in production of the individual first to fourth fuel injection valves 30-1 to 30-4.
It is possible to prevent variations in the air-fuel ratio of the air-fuel mixture to 18-4, and it is possible to equalize the air-fuel ratio for each of the first to fourth cylinders 18-1 to 18-4.

Therefore, the first to fourth cylinders 18-1 to 18-18
By equalizing the air-fuel ratio of the air-fuel mixture supplied to -4, it is possible to prevent the air-fuel ratio of the exhaust gas flowing into the catalyst body 28 in the catalytic converter 24 provided in the exhaust passage 6 from deviating from the target theoretical air-fuel ratio. This can be prevented, and the exhaust gas purification performance of the catalyst body 28 can be improved. Also, the first to fourth cylinders 18
By equalizing the air-fuel ratios of the air-fuel mixture supplied to -1 to 18-4, it is possible to avoid the possibility of causing knocking and improve output performance and operating performance.

In this embodiment, the internal combustion engine 2
First to fourth cylinders 18-1 to 18-4 are provided with first to fourth fuel injection valves 30-1 to 30-4, respectively.
Although the air-fuel ratio was controlled by adjusting the fuel amount for each of 8-1 to 18-4, a single carburetor and a fuel injection valve (not shown) were provided on the upstream side of the intake manifold 14 in the intake manifold. In this case, the intake-air amount of each of the first to fourth cylinders 18-1 to 18-4 can be adjusted by a duty-controlled solenoid valve (not shown) to control the air-fuel ratio.

In addition, in this embodiment, the first to fourth
The feedback control of the air-fuel ratio was performed for each of the cylinders 18-1 to 18-4, but the detection signal of one oxygen sensor provided in the branch exhaust passage communicating with one specific cylinder is used as a reference signal. The air-fuel ratio of the air-fuel mixture to all the cylinders is feedback-controlled, and the difference between the detection signals of the residual oxygen sensors respectively provided in the branch exhaust passages communicating with the residual cylinders and the reference signal is applied to the residual cylinders. It is also possible to calculate the air-fuel ratio correction amount of the air-fuel mixture and perform feedback control of the air-fuel ratio of the air-fuel mixture to the remaining cylinders.

Further, in this embodiment, the oxygen sensor 82 is provided as the exhaust gas sensor, but the air-fuel ratio sensor capable of covering the entire region is connected to the first to fourth cylinders 18-1 to 18-4. -The fourth branch exhaust passages 6-1 to 6-4 are respectively provided, and according to the air-fuel ratios detected by these air-fuel ratio sensors,
It is also possible to perform feedback control so that the air-fuel ratio becomes the target value in all regions regardless of the water temperature.

[0035]

As described above in detail, according to the present invention, the variation of the air-fuel ratio of the air-fuel mixture in each cylinder due to the influence of the intake manifold or the variation in the production of individual fuel injection valves is prevented. Therefore, the air-fuel ratio of each cylinder can be equalized.

Therefore, by equalizing the air-fuel ratio of the air-fuel mixture supplied to each machine cylinder, it is possible to prevent the air-fuel ratio of the exhaust gas flowing into the catalyst provided in the exhaust passage from deviating from the theoretical air-fuel ratio which is the target value. As a result, the exhaust gas purification performance of the catalyst body can be improved. Further, by equalizing the air-fuel ratio of the air-fuel mixture supplied to each machine cylinder, it is possible to avoid the risk of causing knocking,
It is possible to improve output performance and driving performance.

[Brief description of drawings]

FIG. 1 is a configuration diagram of essential parts of an air-fuel ratio control device for an internal combustion engine showing an embodiment of the present invention.

FIG. 2 is a flowchart of control by a fuel injection valve for each cylinder.

FIG. 3 is a time chart of control by a fuel injection valve for each cylinder.

FIG. 4 is an explanatory diagram of an air-fuel ratio learning storage area for each cylinder.

FIG. 5 is an explanatory diagram of distribution correction based on water temperature.

FIG. 6 is a schematic structural diagram of an air-fuel ratio control device for an internal combustion engine.

[Explanation of symbols]

 2 Internal combustion engine 4 Intake passage 4-A Surge tank section 4-1 to 4-4 First to fourth branch intake passage section 6 Exhaust passage 6-A Exhaust collecting section 6-1 to 6-4 First to fourth branch Exhaust passage part 12 Throttle body 14 Intake manifold 16 Intake throttle valve 18-1 to 18-4 First to fourth cylinder 20 Exhaust manifold 24 Catalytic converter 30-1 to 30-1 First to fourth fuel injection valve 64 Control part 66 crank angle sensor 68 distributor 70 opening sensor 72 knock sensor 74 water temperature sensor 76 vehicle speed sensor 82-1 to 82-4 first to fourth oxygen sensor

Claims (1)

Claims: 1. An air-fuel ratio of a mixture becomes a target value by adjusting a fuel amount and / or an air amount based on an exhaust component value detected by an exhaust sensor provided in an exhaust passage of an internal combustion engine. In the air-fuel ratio control device for an internal combustion engine that performs feedback control as described above, the exhaust sensors are provided in the respective branch exhaust passages that communicate with the respective cylinders of the internal combustion engine, and the cylinders of the internal combustion engine are detected by the detection signals input from the respective exhaust sensors. An air-fuel ratio control device for an internal combustion engine, comprising: a control unit that adjusts the fuel amount and / or the air amount for each cylinder to perform feedback control to equalize the air-fuel ratio of the air-fuel mixture supplied to each cylinder.