JPH089975B2 - Air-fuel ratio control device for internal combustion engine - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an air-fuel ratio control device for an internal combustion engine, which uses an air-fuel ratio sensor capable of detecting from lean to rich to perform air-fuel ratio feedback control. In particular, the stability limit of air-fuel ratio control in the engine power zone near the full opening of the throttle valve is expanded to enable stable engine operation.

[Conventional technology]

FIG. 1 shows a configuration of an air-fuel ratio control system for an internal combustion engine according to a conventional and later-described invention, which will be described with reference to FIG. 1 when describing a conventional air-fuel ratio control system for an internal combustion engine.

In FIG. 1, reference numeral 1 is an internal combustion engine, 2 is an intake pipe connected to the internal combustion engine 1, and 3 is a throttle valve provided in the intake pipe 2.

The pressure in the intake pipe 2 is detected by the pressure sensor 4, and the detected pressure is sent to the AD converter 91.

The rotation sensor 5 uses the rotation of the internal combustion engine 1 as a pulse.
The output of the rotation sensor 5 is sent to the input / output circuit 92.

Further, fuel is injected into the intake pipe 2 by an injector 6, which is an output circuit.
It is designed to be driven by 96 outputs.

Further, an exhaust pipe 7 is connected to the internal combustion engine 1, and an exhaust gas component in the exhaust pipe 7 outputs an output corresponding to the air-fuel ratio from the air-fuel ratio sensor 8 to the AD converter 91.

On the other hand, 9 is a control device that calculates the required fuel amount from the information of the pressure sensor 4, the rotation sensor 5, the air-fuel ratio sensor 8 and the like, and generates the drive pulse width of the injector 6.

The AD converter 91 in the control device 9 is adapted to convert analog signals from the air-fuel ratio sensor 8 and the pressure sensor 4 into digital values and output them to the microprocessor 93.

Further, the input circuit 92 is an input circuit for converting the level of the pulse input signal of the rotation sensor 5, and the output thereof is also sent to the microprocessor 93.

This microprocessor 93 calculates the amount of fuel to be supplied to the internal combustion engine 1 based on the digital and pulse signals obtained from the AD converter 91 and the input circuit 92, and according to the result, the drive pulse width of the injector 6 is calculated. It is what is output.

Pre-set the control procedure and data of this microprocessor 93.
It is stored in the ROM 94, and the data in the calculation process is temporarily stored in the RAM 95. Then, according to the output signal of the microprocessor 93, the output circuit 96
It is designed to drive the Injector 6.

The air-fuel ratio sensor 8 in FIG. 1 is configured as shown in FIG. 4, 81 is an oxygen pump cell, 82 is an oxygen battery cell, 83a and 83b are electrodes made of a porous material, 84 is a diffusion chamber,
Reference numeral 85 is a reference voltage source, 86 is a comparison amplifier, 87 is a pump drive circuit, and 88 is a resistor for detecting the current of the pump. The construction of the air-fuel ratio sensor 8 is already known (Japanese Patent Laid-Open No. 59-190646).
And Japanese Patent Laid-Open No. 60-128349).
The reference voltage source 85 is set to about 0.4 V, this voltage is compared with the voltage of the oxygen battery cell 82 by the comparison amplifier 86, and the oxygen pump cell 81 is set via the pump drive circuit 87 so that the deviation becomes zero.
By flowing an electric current into the exhaust gas, the exhaust gas in the diffusion chamber 84 is caused to act so as to have a stoichiometric air-fuel ratio.

Using such a principle, it is possible to detect both the lean side and the rich side of the theoretical air-fuel ratio, and the measurement results can be taken out as the voltage across the resistor 88. As shown in FIG. It is possible to obtain a linear output voltage with respect to.

Next, a conventional method for controlling the air-fuel ratio feedback using the air-fuel ratio sensor 8 will be described with reference to FIG. FIG. 6 is a flow chart showing the control procedure of the controller 9 shown in FIG.

In step 100, the pulse signal input from the rotation sensor 5, that is, the engine speed Ne is read, and in step 10
In step 1, the value Pb of the intake pipe internal pressure (absolute pressure) obtained from the pressure sensor 4 is read, and in step 102, step 100
Enrichment correction coefficient K _ER that determines the target air-fuel ratio for air-fuel ratio open loop control based on the information read in
To set.

The entrainment correction coefficient K _ER is set so as to have a relationship, for example, as shown in FIG.

In step 103, the basic drive pulse width τ ₀ of the injector 6 is calculated based on the value read or set in steps 100, 101 and 102.

The arithmetic expression is represented by τ ₀ = K · K _ER · Pb · ηv, and K
Is a constant, and ηv is a charging efficiency predetermined in correspondence with the intake pressure Pb and the engine speed Ne.

Next, at step 104, the target air-fuel ratio (A / F) S is set. This target air-fuel ratio (A / F) S is preset so as to obtain optimum power performance and fuel efficiency corresponding to the engine speed Ne and the intake pressure Pb, as shown in FIG. In the vicinity, (A / F) S = 13, but it may be changed depending on the temperature of the engine and the acceleration / deceleration state.

At step 105, the output signal (A / F) of the air-fuel ratio sensor 8
R is read and the deviation e of the air-fuel ratio is obtained by step 106, e = (A / F) S- (A / F) R, and this value is integrated with an appropriate gain K _I to obtain the air-fuel ratio feedback correction coefficient C Calculate _FB .

Next, in step 107, the injection pulse width τ is obtained by multiplying the basic injection pulse width τ ₀ previously obtained in step 103 by the air-fuel ratio feedback back correction coefficient C _FB .

The above operation is repeated and the air-fuel ratio becomes the target value (A / F) S
Feedback control is performed so that.

[Problems to be solved by the invention]

In the conventional air-fuel ratio control device for an internal combustion engine as described above, when the engine performs air-fuel ratio feedback in the operating region where the throttle valve is fully opened, the correction coefficient K _{ER for} the target air-fuel ratio of the air-fuel ratio open loop control is set. Becomes 1.3,
Since the fuel increase operation is performed and the target air-fuel ratio of the air-fuel ratio feedback control is the latch ((A / F) S = 13),
Both open and feedback control increase the fuel amount, and especially when the engine is fully opened, the air-fuel ratio becomes over-lit and misfire occurs, which causes engine malfunction and deteriorates driving feeling.

The present invention has been made to solve the above problems, and avoids engine malfunction due to excessive fuel increase even when the engine is fully open, and maintains a desired air-fuel ratio under any operating condition to always achieve good results. It is an object of the present invention to obtain an air-fuel ratio control device for an internal combustion engine, which can obtain various operating feelings.

[Means for solving problems]

The air-fuel ratio control device for an internal combustion engine according to the present invention, when performing air-fuel ratio feedback control, sets the enrichment correction coefficient to
1.0, the feedback correction coefficient is calculated based on the deviation between the target air-fuel ratio and the actual air-fuel ratio, and the injection pulse width is calculated using this enrichment correction coefficient and the feedback correction coefficient to determine the target air-fuel ratio on the open-loop side. A means for controlling the fuel ratio to the stoichiometric air-fuel ratio is provided.

[Work]

In the present invention, in the air-fuel ratio feedback control, the engine correction coefficient K _{ER is set} to 1.0, and the air-fuel ratio of the engine is controlled to the target air-fuel ratio.

〔Example〕

An embodiment of an air-fuel ratio control system for an internal combustion engine of the present invention will be described below with reference to the drawings. Although the configuration of the present invention is exactly the same as that of FIG. The calculation processing and data setting method in the calculation unit centering on 93 is different from the conventional apparatus, and the calculation procedure is shown in the flow chart of FIG.

The process from reading the engine speed Ne of the flow chart step 200 of FIG. 2 to reading of the intake pressure Pb of step 201 is the same as the flow chart steps 101 to 102 of FIG. .

At step 202, it is judged whether or not the air-fuel ratio feedback is performed. This criterion is predetermined based on the intake pressure Pb, the engine speed Ne, the engine cooling water temperature, and the elapsed time after engine start.

If it is determined in step 202 that the air-fuel ratio feedback is to be performed, the process proceeds to step 203, and if it is determined that the air-fuel ratio feedback is not to be performed, step 207 is executed.

If it is determined that the air-fuel ratio feedback is to be executed, in step 203 the enrichment correction coefficient (K _ER ) that sets the target air-fuel ratio on the air-fuel ratio open loop side is set to 1.0 constant to satisfy the relationship shown in FIG. 3, for example. To

Next, in step 204, the target air gap is set so as to satisfy the relationship preset in order to obtain the optimum power performance and fuel efficiency corresponding to the engine speed Ne and the intake pressure Pb, for example, as shown in FIG. Set the fuel ratio (A / F) S.

At step 205, the output signal (A / F) R of the air-fuel ratio sensor 8
Reading, and at step 206, the air-fuel ratio deviation e = (A / F) S-
(A / F) R is obtained, and this value is integrated with an appropriate gain to calculate the feed back coefficient C _FB .

On the other hand, when it is determined in step 202 that the air-fuel ratio feedback is not executed, in step 207, the entrainment correction coefficient (K _ER ) is set in correspondence with the engine speed Ne and the intake pressure Pb, for example, as shown in FIG. To be Next, at step 208, the air-fuel ratio feedback coefficient C _{FB is set} to 1.0.

The injection pulse width τ is calculated using the en-rich coefficient K _ER and the feed back correction coefficient C _FB determined in steps 203 and 206 or steps 207 and 208. This arithmetic expression is expressed by τ = K × K _ER × C _FB × Pb × ηv, where K is a constant and ηv is a packing efficiency.

By repeating the above operation, the air-fuel ratio is controlled so that the air-fuel ratio deviation becomes zero.

Further, in the above embodiment, when calculating the feedback back correction coefficient C _FB in step 206, the value of C _FB was not limited, but, for example, the upper limit should be set so that the relationship of C _FB 1.3 is satisfied.
A lower limit may be added.

Furthermore, in the description of the above embodiments, the fuel injection system is a specific example of a fuel injection device of the speed density type, but it can be said that the present invention is also applicable to a fuel injection device using an air flow sensor and an electronically controlled carburetor. There is no end.

〔The invention's effect〕

As described above, according to the present invention, the air-fuel ratio control device is configured to control the target air-fuel ratio of the open-loop control to the stoichiometric air-fuel ratio when performing the air-fuel ratio feedback control. It is possible to eliminate the interference between the control and the conventional air-fuel ratio open loop control, and it is possible to obtain a good operating feeling at low cost without causing misfiring due to the air-fuel ratio becoming overlit.

[Brief description of drawings]

FIG. 1 is a diagram showing the construction of an air-fuel ratio control device for an internal combustion engine of the present invention and a conventional device, FIG. 2 is a flow chart showing the operation of the air-fuel ratio control device for an internal combustion engine of the present invention, and FIG. 3 is this invention. FIG. 4 is a characteristic diagram of an enrichment correction coefficient of air-fuel ratio open loop control in the air-fuel ratio control device for an internal combustion engine, FIG. 4 is a diagram showing a configuration of an air-fuel ratio sensor in the air-fuel ratio control device for an internal combustion engine according to the present invention, and FIG. FIG. 6 is a characteristic diagram of an air-fuel ratio sensor in an air-fuel ratio control system for an internal combustion engine according to the present invention. FIG. 6 is a flow chart showing the operation of an air-fuel ratio control system for a conventional internal combustion engine. FIG. 3 is a diagram showing a relationship between an engine speed and an intake pressure in an air-fuel ratio control device for an internal combustion engine according to the related art and the present invention, respectively. 1 ... Internal combustion engine, 2 ... Intake pipe, 4 ... Pressure sensor, 5
...... Rotation sensor, 6 …… Injector, 8 …… Air-fuel ratio sensor, 9 …… Control device, 81 …… Oxygen pump cell, 82 ……
Oxygen battery cell, 93 …… Microprocessor, 94 …… RO
M, 95 ... RAM.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Haruji Wataya 840 Chiyoda-cho, Himeji City, Hyogo Prefecture Mitsubishi Electric Co., Ltd. Himeji Works (56) References JP 62-182457 (JP, A)

Claims (1)

[Claims] 1. An air-fuel ratio sensor capable of detecting the rich-side and lean-side air-fuel ratios from an exhaust gas component of an internal combustion engine, and a feedback control of the air-fuel ratio so that an output signal of the air-fuel ratio sensor and a target air-fuel ratio match. When performing air-fuel ratio feedback control in an internal combustion engine equipped with an air-fuel ratio control means, the feedback based on the deviation between the target air-fuel ratio set as the enrichment correction coefficient of 1.0 and the actual air-fuel ratio obtained from the air-fuel ratio sensor. A means for calculating a correction coefficient, calculating an injection pulse width using the enrichment correction coefficient and the feedback correction coefficient, and controlling the target air-fuel ratio on the air-fuel ratio open loop side to be the theoretical air-fuel ratio is provided. An air-fuel ratio control device for an internal combustion engine, which is characterized.