JP2591072B2 - Control device for internal combustion engine - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for an internal combustion engine, and more particularly to a control device for an internal combustion engine that controls an operating state by detecting an actual air-fuel ratio in a combustion chamber.

[Conventional technology]

Conventionally, engine load (intake air volume or intake pipe pressure)
The air-fuel ratio feedback correction factor FAF obtained from the output of the O ₂ sensor that detects the basic fuel injection time TP determined according to the engine speed and the residual oxygen concentration in the exhaust gas and outputs an inverted signal at the stoichiometric air-fuel ratio There is known an internal combustion engine equipped with a fuel injection amount control device that performs feedback control of the fuel injection amount so that the combustion air-fuel ratio becomes the stoichiometric air-fuel ratio.

It has also been proposed to provide an O ₂ sensor in the combustion chamber or downstream of the carburetor to detect the air-fuel ratio of the mixer and control the air-fuel ratio (JP-A-54-98421 and JP-A-56-19882). reference). Similarly, there is also known an internal combustion engine provided with an ignition timing control device that calculates a basic ignition timing according to an engine load and an engine speed, and corrects the ignition timing based on an engine cooling water temperature, an intake air temperature, and the like.

[Problems to be solved by the invention]

However. Even if the air-fuel ratio is directly detected, the air-fuel mixture may be uneven depending on the detection timing, and an accurate air-fuel ratio cannot be measured. The above publication does not disclose this detection timing at all, and even if the actual oxygen concentration and air-fuel ratio in the combustion chamber are detected, the values are not definitive air-fuel ratios at the time of combustion. Fuel ratio fluctuation will occur.

In consideration of the above fact, the present invention directly detects the air-fuel ratio when the air-fuel ratio of the air-fuel mixture in the combustion chamber is determined, and controls at least one of the combustion injection amount or the ignition timing based on the air-fuel ratio to control the air-fuel ratio. An object of the present invention is to provide a control device for an internal combustion engine that can suppress fluctuations.

[Means for solving the problem]

The control device for an internal combustion engine according to the present invention includes an air-fuel ratio detection sensor A provided in a combustion chamber and detecting an air-fuel ratio, and a fuel injection valve in an intake system. Air-fuel ratio sampling means B for controlling the injection timing of the fuel injection valve so as to burn, sampling the detection value of the air-fuel ratio detection sensor at a predetermined crank angle from the latter half of the intake stroke to the time of ignition after fuel injection, The control means C controls at least one of the fuel injection amount and the ignition timing so that the combustion fluctuation becomes constant based on the air-fuel ratio sampled by the air-fuel ratio sampling means.
And

[Action]

In the present invention, since the air-fuel ratio sampling by the air-fuel ratio detection sensor A is performed by the air-fuel ratio sampling means B at a predetermined crank angle from the latter half of the intake stroke to the time of ignition, the determined mixture which is actually burned is determined. Can be detected.

In the present invention, a combustion injection valve is provided in the intake system, and the injection timing of the fuel injection valve is controlled so that the intake air and the fuel swirl in the combustion chamber to perform stratified combustion. An air-fuel ratio detection sensor is provided at the position, and can accurately detect the air-fuel ratio.

Based on the air-fuel ratio of this sampled mixture,
By controlling, for example, the fuel injection amount so that the air-fuel ratio becomes the target air-fuel ratio by the control means C, it is possible to improve fuel efficiency and suppress cycle fluctuations of the air-fuel ratio, thereby improving the operation control accuracy of the internal combustion engine. be able to. In addition,
The target air-fuel ratio refers to an air-fuel ratio that makes the combustion fluctuation constant.

Further, the control means C can advance the ignition timing as the air-fuel ratio fluctuation becomes smaller and leaner, and can retard the ignition timing as the air-fuel ratio fluctuation becomes larger and richer.

[First Embodiment] FIG. 2 shows an internal combustion engine to which a first embodiment of the present invention is applied. Cylinder bore 11 formed in engine body 10
A piston 12 is slidably housed in the
A combustion chamber 13 is formed above 12. An end of the intake passage 14 on the combustion chamber 13 side is opened and closed by an intake valve 15. In the intake passage 14, a fuel injection valve 16 as combustion injection means is disposed on the upstream side of the intake valve 15, and a pressure sensor 17 is provided from a surge tank upstream of the fuel injection valve 16 via a communication pipe. Is provided. A swirl control valve 38 is provided downstream of the fuel injection valve 16 and upstream of the combustion chamber 13, so that the air-fuel mixture fed into the combustion substance 13 is swirled. Thus, combustion can be stabilized, and operation can be performed at a leaner air-fuel ratio.

An intake throttle valve 18 is provided upstream of the pressure sensor 17, and an idle control valve 20 is provided in a bypass passage 19 that bypasses the intake throttle valve 18. The idle control valve 20 is driven to open and close by a stepper motor 21 and has a function of making the idle speed substantially constant when the intake throttle valve 18 is fully closed.

On the other hand, the end of the exhaust passage 22 on the combustion chamber 13 side is opened and closed by an exhaust valve 23. The water jacket 25 of the engine body 10 is provided with a water temperature sensor 26, and a spark plug.
A distributor 28 connected to 27 is provided with a rotation speed sensor 29 for detecting the engine rotation speed.

An air-fuel ratio detection sensor 50 for detecting an air-fuel ratio in the combustion chamber 13 is attached near the ignition plug 27. As shown in FIG. 3, the air-fuel ratio detection sensor 50 has an A / F sensor element 54 joined to a distal end of a metal housing 52, and the A / F sensor element 54 Lead wires 56 and 58 for applying a predetermined voltage to the sensor element 54 are connected. The lead wires 56 and 58 pass through the inner space of the housing 52, are taken out from the air opening hole 60 provided at the upper end thereof, and are connected to the electronic control unit (ECU) 30.

The A / F sensor element 54 has a structure in which a Pt electrode 64, a zirconia 66, and a Pt electrode 68 are sequentially stacked on the upper surface thereof based on the porous ceramics 62 serving as a gas diffusion-controlling layer,
By applying a predetermined voltage (for example, 0.2 to 1.0 V) at a predetermined temperature or higher (for example, 600 ° C. or higher), the air-fuel ratio (A / A
_A voltage value V _{A / F} corresponding to F) can be detected. A heater 70 is attached to the lower surface of the porous ceramics 62 (see FIG. 4), and a catalyst layer 72 is provided so as to cover the heater 70.
700 ° C for porous ceramics 62 and zirconia 66
Heating can be performed before and after, and the combustion of the air-fuel mixture in the A / F sensor element 54 can be promoted by the catalyst layer 72.

The relationship between the voltage value V _{A / F} and the air-fuel ratio A / F has characteristics as shown in FIG. 5, and details thereof are described in SAE Paper 86.
0408.

The electronic control (ECU) 30 includes an MPU 31, a ROM 32, a RAM 36, an input port 33, an output port 34, and a bus 35 connecting these. The pressure sensor 17, the stepper motor 21, the water temperature sensor 26, and the rotation speed sensor 29 are connected to the input port 33. Further, a fuel injection valve 16 is connected to the output port.

 The operation of the first embodiment will be described below.

First, the fuel injection routine will be described with reference to the flowchart of FIG.

In step 100, the engine speed NE and the intake pipe pressure PM, as well as calculating a basic fuel injection quantity T _P, determine the reference voltage V ₀ based on the target air-fuel ratio. This reference voltage V
₀ is set to the lean limit air-fuel ratio in the case of lean control.

In the next step 102, it is determined whether or not the crank angle is a predetermined crank angle for detecting the actual air-fuel ratio in the fuel chamber 13. If the determination is affirmative, the process proceeds to step 104, where the air-fuel ratio detection sensor 5
Based on 0, the voltage value _{VA / F} based on the air-fuel ratio is detected, and the routine proceeds to step 106.

In step 106, the reference voltage V ₀ and the detected voltage V _{A / F} is compared, when it is determined that V _{A / F} ≦ V _0, the actual air-fuel ratio is changed to be leaner than the target air-fuel ratio Is reached, the process proceeds to step 108, where the feedback correction coefficient FAF
And a variation ΔAF is added to
If it is determined that the _{A / F>} V _0, is determined to be varied in Ritsuchi side, the routine proceeds to step 110, subtracts the variation ΔAF from fed back correction coefficient FAF, respectively proceeds to step 112. If a negative determination is made in step 102, the process skips steps 106, 108, and 110 and proceeds to step 112.

In step 112, the basic fuel injection quantity T _P, feedback correction coefficient FAF and other correction coefficients α and invalid injection amount β
The fuel injection amount TAU is calculated based on the above, and the routine proceeds to step 114. In step 114, the fuel injection start time t _i is read from the engine speed NE and the intake pipe pressure PM, and in the next step 116, the fuel injection end time t _c is changed to the fuel injection start item t _i and the fuel injection time TAU. After the interruption is permitted in step 118, the process proceeds to step 120, where the fuel injection start time t _i is set.

FIG. 7 shows a chart based on the crank angle when fuel is actually injected based on the values set as described above. The range indicated by arrow A in FIG. 7 is a range in which the actual air-fuel ratio is detected by the air-fuel ratio detection sensor 50, and any range may be used as long as it is within this range. The range from the end of this detection range to the start of fuel injection (the range indicated by arrow B in FIG. 7) corresponds to each calculation processing time shown in FIG. 6, and the end of this range is the fuel injection start time t _i. .

As described above, since the actual air-fuel ratio is detected immediately before the ignition of each cycle to correct the fuel injection amount, the accuracy of the air-fuel ratio control is improved, and engine control excellent in fuel efficiency and drivability is performed. be able to.

Second Embodiment Hereinafter, a second embodiment of the present invention will be described. In addition,
The components are the same as those of the first embodiment shown in FIG. 2 and only the control is different, so that the description of the configuration is omitted. The feature of the second embodiment is that the fuel injection amount is increased when the fluctuation is equal to or more than a predetermined value in order to prevent misfire occurring when the fluctuation of the air-fuel ratio is large. The operation will be described below with reference to FIG.

In step 150, the basic fuel injection amount _TP is calculated from the engine speed NE and the intake pipe pressure PM, and the reference voltage deviation ΔV ₀ based on the allowable deviation of the target air-fuel ratio is obtained.
In the next step 152, it is determined whether or not a predetermined crank angle for detecting the actual air-fuel ratio in the fuel chamber 13 is obtained. If the determination is affirmative, the process proceeds to step 154, where the air-fuel ratio is detected by the air-fuel ratio detection sensor 50. Voltage value V _{A / F} based on the
Move to 6.

In step 156, the detected voltage value _{VA / F} is temporarily stored, and then in step 158, it is determined whether the voltage value _{VA / F} has been stored n times. If the determination in step 158 is affirmative, the process proceeds to step 160, where the detection voltage deviation ΔV _{A / F} is calculated from the maximum value and the minimum value of the voltage value _{VA / F} for n times.
In the next step 162, the detected voltage deviation ΔV _{A / F} is compared with the reference voltage deviation ΔV _0, and if it is determined that ΔV _{A / F} > ΔV ₀ , the air-fuel ratio greatly fluctuates and the possibility of misfire Then, the process proceeds to step 164, where a predetermined value is added to the feedback correction coefficient FAF, and the process proceeds to step 166.
If it is determined in step 162 that ΔV _{A / F} ≦ ΔV _0, it is determined that the variation of the air-fuel ratio is within a predetermined range and there is no danger of misfiring, and step 164 is skipped.
Move to.

At the following step 166, the basic fuel injection quantity T _P, based on the fed back correction coefficient FAF and other correction coefficient α and the ineffective injection quantity beta, the fuel injection amount TAU is calculated, step 1
Move to 68. If a negative determination is made in step 152 or a negative determination is made in step 158, the process directly proceeds to step 168 without performing the above processing.

In step 168, the engine speed NE and the intake pipe pressure PM
The fuel injection start time t _i is read from
In 170, the fuel injection end time t _e is calculated from the fuel injection start time t _i and the fuel injection time TAU, and then after the interrupt enable is made in step 172, the start transition to the fuel injection to the step 174 the time t _i Is set.

As described above, when the fluctuation of the actual air-fuel ratio in each cycle becomes larger than a predetermined value, the feedback correction coefficient is corrected to the rich side, so that the cycle fluctuation is suppressed and no misfire occurs.

Therefore, when the engine is operated with a lean air-fuel mixture, the lean burn limit can be increased by reducing the possibility of misfire.

[Third Embodiment] A feature of the third embodiment resides in that the ignition timing of the air-fuel mixture in the combustion chamber is controlled in accordance with the air-fuel ratio of the air-fuel mixture before ignition. And the time chart of FIG.

First, in step 200, a basic ignition advance θ _BASE is calculated from the engine speed NE and the intake pipe pressure PM, and a reference voltage V ₀ corresponding to a target air-fuel ratio is obtained. This reference voltage may be searched from a map based on the intake pipe pressure PM and the engine speed NE, or if the fuel supply amount is F / B controlled so as to have a desired air-fuel ratio. Alternatively, the output value of the past air-fuel ratio detection sensor may be averaged.
In the next step 202, a correction advance amount θ _COM is calculated based on the engine cooling water temperature, the intake air temperature, etc., and then in step 204, the effective ignition advance θi is calculated according to the following equation.

θi = θ _BASE + θ _{COM In the} next step 206, steps 152 to 160 in FIG.
The voltage V _{A / F} is calculated by performing the same processing as the processing indicated by. At the following step 208, this is the voltage V _{A / F} and the voltage V _O is compared, when it is determined that V _{A / F>} voltage V _O, step
The routine proceeds to 210, where the effective ignition advance θi is retarded, and V _{A / F} ≦
If it is determined that the voltage V _O, by advancing the execution spark advance θi operation proceeds to step 212, respectively proceeds to step 214. In step 214, the ignition start time t _i ′ and the ignition end time t _e ′ are calculated, then an interrupt is permitted in step 216, and the routine proceeds to step 218, where the ignition start time t _i ′ is calculated.
Set _i '.

The flowchart shown in FIG. 10 is a routine for setting the ignition end time. In step 250, after the interruption is inhibited, the ignition end time t _e 'is set in step 252.

As described above, since the air-fuel ratio of the air-fuel mixture before combustion is detected and the ignition timing is controlled based on the fluctuation of the air-fuel ratio, fluctuations in combustion of the engine can be prevented, leading to improvement in vehicle operability.

〔The invention's effect〕

As described above, the control device for an internal combustion engine according to the present invention directly detects the air-fuel ratio when the air-fuel ratio of the air-fuel mixture in the combustion chamber is determined, and controls the fuel injection amount based on this air-fuel ratio to control the air-fuel ratio. It has an excellent effect that fluctuation can be suppressed.

[Brief description of the drawings]

1 is a block diagram showing the configuration of the present invention, FIG. 2 is a schematic configuration diagram of an internal combustion engine applied to this embodiment, FIG. 3 is a cross-sectional view of an air-fuel ratio detection sensor, and FIG. 4 is FIG. Bottom view, fifth
FIG. 6 is a characteristic diagram showing the relationship between the voltage value V _{A / F} and the air-fuel ratio A / F. FIG. 6 is a fuel injection amount control flow chart according to the first embodiment. FIG. FIG. 8 is a flow chart showing a fuel injection amount control according to the second embodiment, FIG. 9 is a flowchart showing an ignition timing control according to the third embodiment, and FIG.
FIG. 11 is a flow chart for setting the ignition end time of the third embodiment. 10 ... engine body, 16 ... fuel injection valve, 30 ... EUC, 50 ...
... Air-fuel ratio detection sensor.

Claims (1)

(57) [Claims] An air-fuel ratio detection sensor provided in a combustion chamber and detecting an air-fuel ratio, and a fuel injection valve in an intake system, wherein a fuel injection valve is provided so that intake air and fuel swirl in the combustion chamber to perform stratified combustion. The air-fuel ratio sampling means controls the injection timing of the air-fuel ratio, and samples the detection value of the air-fuel ratio detection sensor at a predetermined crank angle from the latter half of the intake stroke after the fuel injection to the ignition timing. A control means for controlling at least one of the fuel injection amount and the ignition timing so that the combustion fluctuation becomes constant based on the air-fuel ratio.