JPH01211636A - Air-fuel ratio control device for multicylinder internal combustion engine - Google Patents

Abstract

PURPOSE:To enable control of unevenness in an air-fuel ratio of each cylinder, by a method wherein a fuel injection amount is set so that the pressure-in-cylinder maximum value of each cylinder is adjusted to a value equal to the pressure-in-cylinder maximum value of a reference cylinder. CONSTITUTION:In an engine body 1, a pressure-in-cylinder sensors 7 is securely mounted in a position situated facing each of cylinders 2 of cylinder heads 5a and 5b, and a detecting part at the tip thereof faces on each combustion chamber. A exhaust gas sensor 22 is positioned facing on an exhaust gas passage 12 of a specified cylinder, and the cylinder forms a reference cylinder. In which case, an air-fuel ratio control means 20 compares the pressure-in-cylinder maximum value of the reference cylinder with the pressure-in-cylinder maximum value of each cylinder to compute it and outputs a signal responding to a deviation therebetween. Based on the signal, a fuel injection correction amount is regulated so that the pressure-in-cylinder maximum value of each cylinder is adjusted to a value equal to the pressure-in-cylinder maximum value of the reference cylinder with a preset allowable value, and the result is added to a reference fuel injection amount. This constitution keeps all cylinders at a theoretical air-fuel ratio, and prevents production of unevenness in an air-fuel ratio and output torque between the cylinders.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an air-fuel ratio control till device for a multi-cylinder internal combustion TAIIQ that utilizes the maximum value of in-cylinder pressure for each cylinder.

[Prior art and problems to be solved by the invention] Conventionally, engines equipped with an electronically controlled fuel injection system (EGI) have been equipped with a system that maintains the air-fuel ratio in an optimum state in each continuous-vi range. First, the basic fuel injection 3 for each operating region is determined, and then this u wood fuel oblique injection tAfill is corrected using various correction terms depending on the parameters of the engine operating state, and feedback control is used to calculate the actual fuel injection value. An exchange/fuel ratio controller is provided to determine the injection amount.

The basic fuel injection ff1Tp is determined as a function of the intake air IQ and the engine speed N. That is, Tp = -Q/NK: coefficient.

In addition, the actual fuel injection ff1Ti is determined by Ti=Tp-^7F-KFB KA/F: Air-fuel ratio correction coefficient KFB set based on engine speed, cooling water temperature, flow valve opening, etc. It is determined by the air-fuel ratio feedback correction amount determined from the FiI element 'fA degrees in the exhaust gas.

The intake air ff1Q is detected by an air flow meter disposed immediately downstream of the air cleaner or an intake air R sensor such as an intake negative pressure sensor disposed in a chamber downstream of the throttle valve. Further, the air-fuel ratio feedback correction mKFB is detected by an exhaust sensor located in the exhaust passage.

By the way, in general, in a multi-cylinder internal combustion engine, the amount of air taken into each cylinder differs due to (1) the complexity of the shape of the intake pipe or interference between the cylinders of the air taken in;

(2) The combustion temperature differs slightly from cylinder to cylinder due to the cooling route of each cylinder.

(3) Production variations occur in the combustion chamber volume, piston shape, etc. of each cylinder.

(4) Injector #? The air-fuel ratio differs slightly for each cylinder due to a difference in fuel injection amount due to a one-degree error or the like.

Although the above-mentioned problems exist, conventional combustion control at the stoichiometric air-fuel ratio does not have a large effect on operating performance.

However, in high-performance engines, where there is a recent trend toward higher output and lower fuel consumption, even slight variations in the air-fuel ratio of each cylinder, as in the past, have a large impact on the output fluctuations of each cylinder, resulting in energy loss. give birth to

As a result, not only the total output of the engine decreases, but also problems such as output becoming unstable, vibrations being promoted, and air-fuel ratio controllability becoming worse occur.

Additionally, in order to eliminate variations in output due to variations in each component, a cylinder pressure sensor is used to detect the pressure inside the combustion chamber, as disclosed in Japanese Patent Laid-Open No. 60-13943, etc., and the combustion Some control the fuel injection foot using a pressure saw. However, the above-mentioned publication uses the combustion pressure (indicated mean effective pressure) in the combustion chamber to form closed-loop control in operating regions where transient feedback control is not performed, such as when the throttle valve is fully open, and controls fuel injection and other control. This method attempts to eliminate variations in output through control, but it has not yet gone so far as to eliminate variations in air-fuel ratio between cylinders in the region where feedback control is performed, leading to the problem of worsening exhaust emissions.

[Object of the Invention] The present invention has been made in view of the above circumstances, and aims to improve the total output of the engine, improve J3, and achieve stable output characteristics.
! ? It is an object of the present invention to provide an air-fuel ratio control device for a multi-cylinder internal combustion engine that not only achieves high fuel efficiency but also achieves low fuel consumption and a reduction in transmission.

[Means and operations for solving the problems] The air-fuel ratio control device for a multi-cylinder internal combustion engine according to the present invention calculates the basic fuel ratio based on the output signal No. 3 from the intake air amount sensor and the output signal from the rotation speed sensor. A basic fuel injection 0J foot calculation unit that calculates noise suspension, and a feedback correction unit that calculates the feedback correction amount of the reference cylinder based on the output signal from the exhaust sensor facing the exhaust passage of a specific reference cylinder. A spherical semi-fuel injection system that sends out a fuel nozzle i'pl from the fuel injection port to the reference cylinder based on the output signal from the basic fuel injection a calculation section and the output signal from the feedback correction calculation section. an arithmetic unit;
A cylinder-specific maximum cylinder pressure value output unit that receives the output signal q from the cylinder pressure sensor installed in each cylinder and calculates the maximum value of the cylinder pressure for each cylinder, and An in-cylinder pressure comparator section that compares and calculates the maximum in-cylinder pressure value for each cylinder, and an output signal from the in-cylinder pressure sensor Ω section, calculates the maximum in-cylinder pressure value for each cylinder by calculating the maximum in-cylinder pressure value for each cylinder. Fuel r at which the internal pressure reaches the maximum value
The cylinder-specific fuel injection correction unit calculates the copper loss per cylinder for each cylinder, and controls the air-fuel ratio of each cylinder based on the output signal from the internal pressure sensor of each station, 115 to eliminate variations.

[Embodiments of the Invention] The present invention will be described in detail below with reference to the drawings. The drawings show embodiments of the present invention; FIG. 1 is a schematic diagram of the main parts of the engine, FIG. 2 is a schematic plan view of the engine, FIG. 3 is a sectional view taken along the line ■-■ of FIG. 2, and FIG. is an IV-rV sectional view of FIG. 3, FIG. 5 is a block diagram of the air-fuel ratio control means, FIG. 6 is a block diagram of the air-fuel ratio control means, and FIG.
p HAX), a correlation diagram showing the air-fuel ratio (A/F) on the horizontal axis,
FIG. 8 is a flowchart showing the operating procedure of the air-fuel ratio control means.

Reference numeral 1 in the figure indicates a four-cylinder horizontally opposed engine body, which is an example of a multi-cylinder internal combustion engine.
-1) It is divided into two banks.

Furthermore, a water temperature sensor 24 is placed on the water jacket, and the 8 air fF sensors 12a, 2b, 2c, and 2 installed in the LH bank and RH bank of the cylinder block 2 are connected to the water temperature sensor 24.
Each piston 4 inserted into the crankshaft 3
are connected to each other via a connecting rod (not shown). Further, the pistons 4 of each of the cylinders 2a to 2d
A combustion chamber 6a is located in a portion of the cylinder heads 5a and 5b that is classified as 1Tl1.

6b, 6c, and 6d are formed respectively.

Further, each cylinder 2 of each cylinder head 5a, 5b
Cylinder pressure pins 7 are mounted and fixed via adapters 8 at positions corresponding to a to 2d, and the tip detection portions of these cylinder pressure sensors face each of the combustion chambers 68 to 6d. Further, each of the cylinder heads 5a, 5b is equipped with a spark plug 9 corresponding to the 8-cylinder tires 2a to 2d.

Note that this cylinder pressure sensor 7 is connected to the cylinder head 5a,
It may be directly fixed to 5b.

Further, injectors 10a and 10b are provided in the suction boat 1a that communicates with the combustion chambers 68 to 6d, respectively.

10c and 10d are facing, and furthermore, the upstream side of each intake boat 1a is an intake manifold, and a throttle chamber 14 in which a throttle valve 13 is installed via an intake manifold 11.
The upstream side of the throttle chamber 14 is connected to an air cleaner 17 via an intake pipe 15.

Furthermore, on the downstream side of the throttle valve 13, an intake negative pressure sensor 25, which is an example of an intake air sensor, is connected. This suction negative pressure sensor 25 measures the suction negative pressure generated downstream of the throttle valve, outputs a measurement signal @PO, and determines the intake aeration.

Further, a rotation speed sensor 18 is connected to the crankshaft 3 to detect the engine rotation speed N and the crank angle Crθ. Note that reference numeral 19 is a throttle position sensor that detects the throttle opening degree θ.

On the other hand, an exhaust sensor 22 faces the air passage 12 of a specific cylinder of the engine main body 1, and this cylinder is defined as a reference cylinder. In addition, the code|symbol 23 is a catalytic converter.

Further, reference numeral 20 indicates an air-fuel ratio control means, and the central U unit CPLJ40. A read-on memory ROM 41, a random access memory RAM 42, an input port 44, and an output port 46 are connected to each other by a system bus 43. Furthermore, as noted above, the boat 44 converts analog signals from each sensor into analog-to-digital converters. The above input boat 4
An A/D converter 45 is connected to the input terminal 4. Among the above-mentioned sensors, throttle position sensor 19° water temperature sensor 24. The cylinder pressure sensor 7 to which the suction negative pressure sensor 25 and the engine block 48 are connected is connected to the A/D converter 45, and the rotation speed sensor 18 and the exhaust sensor 22
is connected to the input port 44 through a waveform shaping circuit (not shown) provided as necessary. Also from above]
The port 46 includes injector drive units 38a, 38b',
38c and 38d are connected to the injector 10a.
~10d are each driven independently.

Further, the air-fuel ratio control means 20 includes a basic fuel injection calculation unit 3o, an air-fuel ratio correction coefficient calculation unit 32, a feedback correction ω calculation unit 33, a reference fuel injection suspension calculation unit 31,
Cylinder-specific cylinder pressure maximum value n mountain portion 34 and cylinder pressure comparison calculation section 3
5, a cylinder-by-cylinder fuel injection correction section 36, an air-fuel ratio learning map 37, and injector drive sections 38a to 38d.

Basic fuel injection above! ) The J 硲 calculation unit 30 calculates the reference fuel injection group ( (pulse width) Tp is processed.

Further, in the air-fuel ratio correction coefficient calculating section 32, the above-mentioned output signal N
The air-fuel ratio correction coefficient K A/F is calculated from the output signal Tw indicating the cooling water temperature from the water temperature sensor 24 and the output signal θ indicating the throttle opening from the throttle position sensor 19. On the other hand, the feedback correction a calculation unit 33 performs air-fuel ratio feedback correction a K based on the output signal E indicating the air-fuel ratio feedback value from the exhaust sensor 22.
Calculate FB.

Then, the reference fuel injection O calculation unit 31 calculates the actual fuel injection value obtained by correcting the basic fuel injection amount 'r T p using the air-fuel ratio correction coefficient K A/F and the air-fuel ratio feedback correction U K FB. Based on the calculated value, the injector drive unit 38a outputs the base 1? =Output η to the injector 10a disposed in the cylinder, with an optimum fuel injection pulse width Ti matching the intake air ω.

The above shows that the known feedback control is applied to the reference cylinder.

In addition, in the cylinder-by-cylinder maximum in-cylinder pressure calculation unit 34, the pressure signal 11 in each air 'kl from the in-cylinder pressure sensor 7 disposed in each cylinder 11 corresponds to the crank angle from the rotation speed sensor 18.
6, and the suction pipe pressure signal PO from the suction negative pressure sensor 25
The cylinder pressure maximum value PHAX corresponding to the crank angle of each cylinder is detected. In addition, the suction negative pressure sensor "25
The absolute value of cylinder pressure is zero-point corrected by the signal from.

Generally, in the partial region, as shown in Figure 7, PHAX is maximum at the stoichiometric air-fuel ratio (A/
F=14.7). In the operating range where the air-fuel ratio of the reference cylinder is maintained at the stoichiometric air-fuel ratio by feedback control, if the maximum value of the cylinder pressure of the reference cylinder is PHAXo, then the maximum cylinder pressure of the other cylinders PHAX is the cylinder pressure of the reference cylinder. By controlling to approach the maximum value p HAXo, all cylinders will approach the stoichiometric air-fuel ratio.

Based on the above, the cylinder pressure comparison calculation unit 35 compares and calculates the maximum cylinder pressure value pHAXO of the reference cylinder with the maximum cylinder pressure value pHAX of each cylinder for each cylinder, and calculates the maximum cylinder pressure value pHAXO of the reference air. Maximum in-cylinder pressure of each cylinder r HA
A signal corresponding to the deviation ΔP of X is outputted to the cylinder-specific fuel rJR injection correction unit 36.

Then, the cylinder-specific fuel injection side correction section 36 calculates the cylinder pressure maximum value PHA of each cylinder based on the signal from the cylinder pressure comparison calculation section 35, with respect to the cylinder pressure maximum value PHAXo of the reference cylinder.
The fuel injection correction ffmKLRN is increased or decreased so that
-"T 1-KLRN), outputs a signal to the injector drive units 38b, 38c, and 38d provided independently for each cylinder to drive the injectors 10b, 10c, and 10d.Furthermore, stores fuel injection correction ff1KLRN. The air-fuel ratio learning map 37 is rewritten, and the fuel injection correction f
f1KLRN is under learning control. The air-fuel ratio learning map 37 is specifically stored in the RAM 42.

Through the above operations, the maximum cylinder pressure of each cylinder other than the reference cylinder is controlled to be equal to the maximum cylinder pressure of a single cylinder, and as is clear from FIG. 7, all cylinders are 1! I! The stoichiometric air-fuel ratio is maintained, eliminating variations in air-fuel ratio and output torque between cylinders.

Next, the air-fuel ratio control operation of each cylinder by the air-fuel ratio control means will be explained according to the flowchart of FIG.

When the engine is running and all cylinders are being operated by the signal from the reference fuel output section, an exhaust sensor placed in the exhaust passage of the reference cylinder indicates that the reference cylinder is -
02 When the operating range is reached where the stoichiometric air-fuel ratio is maintained under feedback control, the maximum in-cylinder pressure of the reference cylinder P HAXo is determined in step 100 from the output signal of each in-cylinder pressure sensor.
is detected, and then in step 101, X is detected to reach the maximum cylinder pressure value PH for each cylinder. Next, in step 102, the cylinder pressure maximum value P HAX for each cylinder is compared with the cylinder pressure maximum value P HAXo of the ν quasi-cylinder, p HAXo,! =(7)
The difference Δp=p HAXo-p HAX is calculated and stored. Next, in step 103, this ΔP is r[capacity value ΔP
It is determined whether the air-fuel ratio is within INTT, that is, whether each cylinder is within the variation range of the air-fuel ratio relative to the reference cylinder. △
It is determined that the cylinder for which P≦ΔPINIT is within the allowable value, and the process returns to step 100 without making any correction to the fuel injection correction can KLRN.
Return to

On the other hand, for a cylinder where ΔP>ΔP INIT, it is assumed that the air-fuel ratio is lean, and the fuel injection ω of the cylinder is
Increase by X% (for example, M stored in the map depending on the size of ΔP) for the hot semi-fuel injection level (
K L RN - + -
X is detected, and then the process moves to step 106. Similarly, in step 106, the maximum cylinder pressure p HAX of the reference cylinder is determined.
O,! : (1) Difference A P' = PHAXo -P
)IAX wo comparison D5-46゜Proceeds to step 107, where ΔP' and Δ stored in step 102
P is compared, and if ΔP≧ΔP′, the process proceeds to step 108, where the fuel injection ω of that cylinder is roughly increased by X%C)
(KLRN+X), 1', 11 semi-combustible If
In kj M Increase the hanging by 2X%, step 11
Transition to 0.

On the other hand, if ΔP - ΔP', the process moves to step 109, and in order to avoid correcting the assumption that the air-fuel ratio is lean in step 104, the fuel s'a an ai m is set as the reference fuel. % decrease fnl (KLRN-Y). Here, as is clear from FIG. 7, the Y% reduction has already been done in step 104.
Y = 3, including the amount increased by % and shifted to the rich side
A weight loss of X% is appropriate. Step 110'r
is the fuel injection correction fi stored in the air-fuel ratio learning map
t, K l-RN is rewritten and the program is terminated.

As described above, in this embodiment, an example has been described in which fuel injection ♀ for cylinders other than the reference cylinder is corrected with respect to reference fuel injection B, which is a fuel injection award for the reference cylinder, but the present invention is limited to this. For example, correlation data between the maximum in-cylinder pressure and fuel injection height, which has been determined in advance based on experiments, is stored as map data in the ROM in the air-fuel ratio control means, and the map data in the ROM is referred to as appropriate. Another possible method is to determine the fuel injection rAfil to the cylinder.

[Effects of the Invention] As explained above, according to the present invention, the maximum cylinder pressure of the gold cylinder is calculated, and the fuel 1 is calculated so that the maximum cylinder pressure of each cylinder becomes the maximum cylinder pressure of the reference cylinder. By setting the injection a, it is possible to control variations in the air-fuel ratio of each cylinder, resulting in less vibration and energy loss, improving the engine's total output and achieving stable output characteristics. Not only does it reduce fuel consumption, it also ensures quietness and reduces emissions.

[Brief explanation of the drawing]

The drawings show one embodiment of the present invention, and FIG. 1 is a schematic diagram of the main parts of the engine, FIG. 2 is a schematic plan view of the engine, FIG. 3 is a sectional view taken along the line ■-■ of FIG. 2, and FIG. Fig. 3 is a cross-sectional view of IV-TV, Fig. 5 is a block diagram of the air-fuel ratio control means, Fig. 6 is a block diagram of the air-fuel ratio control means, and Fig. 7 is the maximum in-cylinder pressure (p) on the t and L vertical axes. FIG. 8 is a flowchart showing the operating procedure of the air-fuel ratio control means. 2...Cylinder block, 2a-2d...Cylinder, 7
. . . Cylinder pressure sensor, 30 . . . Basic fuel injection amount calculation section, 31 . . . Reference fuel injection ttJm calculation section, 32 . . . Air fuel ratio correction coefficient calculation section, 33 .
Performance section, 34... Maximum in-cylinder pressure for each cylinder Takuyama section, 35.
...Cylinder pressure comparison calculation section, 36...Separate fuel injection correction section, 37...Air-fuel ratio learning map, P HAXo...
Maximum cylinder pressure of the reference cylinder, PHAX... Maximum cylinder pressure of each cylinder, N, Q. Crθ, Tw, θ, E, PO, P...output signal. Agent Patent Attorney Susumu Ito Figure 7 Figure 8 TART PMAXW4 of Kikyo's PMAXO Fighter Each Kiba Calculate PMAXO-02 ΔP>ΔPINITN. P' 06 Mamoru/107

Claims (1)

[Scope of Claims] A basic fuel injection amount calculating section that calculates a basic fuel injection amount based on an output signal from an intake air amount sensor and an output signal from a rotation speed sensor; a feedback correction amount calculation unit that calculates a feedback correction amount for the reference cylinder based on an output signal from the exhaust sensor, and an output signal from the basic fuel injection amount calculation unit and an output signal from the feedback correction amount calculation unit. A reference fuel injection amount calculation unit that calculates the fuel injection amount to the reference cylinder, and a cylinder-specific cylinder pressure unit that calculates the maximum value of the cylinder pressure for each cylinder by taking in the output signal of the cylinder pressure sensor installed in each cylinder. a maximum value calculation section; an in-cylinder pressure comparison calculation section that compares and calculates the maximum cylinder pressure value of the reference cylinder with the maximum cylinder pressure value of each cylinder; and an output signal from the cylinder pressure comparison calculation section that takes in the output signal from the cylinder pressure comparison calculation section An air-fuel ratio control device for a multi-cylinder internal combustion engine, comprising: a cylinder-by-cylinder fuel injection correction unit that calculates, for each cylinder, a fuel injection amount such that the maximum cylinder pressure of the reference cylinder becomes the maximum cylinder pressure of the reference cylinder.