JPS60201042A - Method of controlling air-fuel ratio of engine - Google Patents

Abstract

PURPOSE:To make the operation of an engine smooth at the time of transient operation of the same, by calculating a correction factor for the quantity of fuel to be supplied from the density of vaporized fuel existing in the region from the deownstream side of a throttle valve to the engine. CONSTITUTION:A sensor 2 for detecting the temperature of intake air and an injector 3 are provided at an upstream side of an intake system of an engine 1. The sensor 2 detects the temperature of intake air and produces a signal corresponding to the detected temperature of intake air, while the injector 3 supplies fuel to the engine 1. On the downstream side of the injector 3, there are provided a throttle valve 6 which controls the quantity of air drawn into an intake pssage 5 defined by an intake pipe 4, a pressure sensor 8 which detects the absolute pressure of intake air in the intake passage 5 at the portion thereof located on the downstream side of the throttle valve 6 and produces a signal corresponding to the detected pressure, and a sensor 9 which detects the temperature of liquid film fuel attached to the inner wall surface of the intake pipe 4 in the region from the downstream side of the valve 6 to the engine 1 and produces a signal corresponding to the detectig temperature.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention measures the concentration of evaporated fuel existing in the intake passage downstream of the throttle valve in response to a signal from a sensor that detects engine operating conditions. The present invention relates to an air-fuel ratio control method for an engine, in which the amount of fuel to be supplied is adjusted by a positive coefficient corresponding to the concentration, and the air-fuel ratio of the air-fuel mixture is appropriately controlled in response to an engine malfunction state.

(Prior art) Conventionally, during so-called transient periods such as engine deceleration or acceleration, the absolute pressure in the intake passage downstream of the throttle valve fluctuates rapidly. The area in the intake passage where the amount of evaporation changes rapidly @
As a result of changing the fuel concentration, the air-fuel ratio of the air-fuel mixture may become too rich or too lean, and the air-fuel ratio of the air-fuel mixture depends not only on the above-mentioned absolute pressure change but also on the intake air temperature, flow rate,
Since the amount of fA generated fuel from the liquid film fuel varies depending on the temperature of the liquid film fuel, for example, the difference ΔPn between the intake pipe pressure Pn sampled this time and the intake pipe pressure Pn-1 sampled the previous time is In the method of controlling the amount of injected fuel by setting the fuel injector positive coefficient corresponding to this ΔPn, the formula for calculating the fuel injection correction coefficient written in IiJ is a model formula corresponding to a driving mode with certain characteristics. The drawback is that it is impossible to accurately control the air-fuel ratio over the entire range of vehicle driving conditions.

(Objective of the Invention) The object of the invention is to calculate the concentration of evaporated fuel existing between the downstream of the throttle valve and the engine at arbitrary intervals using a model formula set in advance according to the engine characteristics. , supply fuel to determine the corrected amount of fuel supplied from the engine's fuel supply system! By providing an engine air-fuel ratio control method that calculates a correction coefficient and controls the amount of supplied fuel in accordance with the correction coefficient, engine operation is smoothed during transitions such as acceleration and deceleration. At the same time, prevention of wasteful consumption of fuel,
The goal is to reduce harmful exhaust components.

(Structure of the Invention) As shown in the flowchart shown in FIG. 1 showing the method of the present invention, the present invention includes a rotation speed sensor that generates a signal corresponding to the engine rotation speed, and a pressure sensor that detects absolute pressure and outputs a signal corresponding to the absolute pressure; an intake 4PC temperature sensor that detects the temperature of intake air and outputs a signal corresponding to the temperature;
and a liquid film fuel temperature sensor that detects the temperature of the liquid film fuel adhering to the inner wall between the downstream side of the intake pipe (thrower of the intake pipe forming the intake passage) and the engine and outputs a signal corresponding to the temperature. By inputting the signal output from the evaporative fuel at an arbitrary period (ST101), the evaporative fuel concentration is calculated using the model calculation formula for calculating the evaporative fuel concentration present in the intake passage from the throttle valve downstream to the engine. Calculate the concentration at each arbitrary cycle (
sr1o2), then calculate a supplied fuel amount correction coefficient for determining the corrected amount of fuel supplied from the engine fuel supply device in accordance with the vaporized fuel concentration (S T
103) and the corrected fuel amount is controlled in accordance with the supplied fuel amount correction coefficient (ST104).

(Embodiment of the Invention) Next, the configuration of an embodiment of the wooden invention will be explained with reference to FIGS. 2 to 4.

An intake air temperature sensor 2 that detects the temperature of intake air and outputs a signal corresponding to the detected temperature and an injector 6 for supplying fuel to the engine 1 are cut and installed in the upstream part of the intake system of the engine 1. 6, there is a throttle valve 6 that adjusts the air gCt sucked into the intake passage 5 formed by the intake pipe 4, and an intake passage 5 downstream of the throttle valve 6.
A pressure sensor 8 detects the absolute pressure of and outputs a signal corresponding to the detected pressure, and detects the temperature of the liquid film fuel adhering to the inner wall of the intake pipe 4 between the downstream of the throttle valve 6 and the engine 1. A liquid film fuel temperature sensor 9 is provided that outputs an f# number corresponding to the detected temperature.

The ECU calculates the concentration of evaporated fuel present in the intake passage 5 from the downstream side of the throttle valve 6 to the engine 1 using a preset model formula described below, which includes the intake air temperature sensor 2 and a pressure sensor. 8, an output signal from the liquid film fuel temperature sensor 9, and an ibunirashironkoi/
The fuel vapor concentration is calculated by inputting the signal from L'IQ, and the amount of fuel to be supplied is determined in accordance with the fuel vapor concentration to determine the normal suction of the fuel to be supplied from the injector 3. After calculating the correction coefficient, a drive signal corresponding to the supplied fuel amount correction coefficient is output to the injector 3.

The injector 3 is operated by inputting the drive/power signal outputted from the child control unit ECU, and controls the amount of liter and fuel supplied.

Note that 11 is an intake port of the engine 1, and 12 is a combustion chamber of the engine 1.

Fig. 6 shows the internal configuration of the electronic control unit ECU, and the analog signals output from the intake air temperature sensor 2, pressure sensor 8°, and liquid fuel temperature sensor 9 are converted into digital signals. A, 4) The ignition Vgn signal input to the converter 21 and output from the ignition coil 11 is input to the waveform shaper 22.

The output signals of the A/D converter 21 and the waveform shaper 22 are input to the computer CPU, and the computer CPU calculates the mI vaporized fuel concentration and the supplied fuel corner positive coefficient using the model formula described later. A correction signal corresponding to the correction coefficient is output to the drive circuit 26 which outputs a drive signal to the input controller 6.

Inputting the correction signal output from the computer CPU, the drive circuit 26 outputs a drive signal corresponding to the correction signal to the injector 6 to drive it and inject fuel.

FIG. 4 shows a state in which the liquid film fuel temperature sensor 9 is attached to the intake pipe 4. An opening for fitting the liquid film fuel temperature sensor 9 is formed in the intake pipe 4, and the fuel temperature sensor 9 is attached to the intake pipe 4. Attach the sensor 9 with the pin 51. A thermistor 62 is used as a temperature detection element of the liquid film fuel temperature sensor 9, and the detection surface of the thermistor 62 located inside the intake pipe 4 is covered with a glass layer 66.
protected by Lead wires 35 and 36 of the thermistor 32 and thermistor 62 are molded with synthetic resin 37, and the lead wires 35 and 66 of the thermistor 62 are connected to terminals 3a, respectively.
, i9, and is further connected to the throat control sub-unit E C'uK from terminals 38 and 39.

(Effects of the Example) Now, the model equation showing the state of the air-fuel mixture existing in the intake passage 5 is as follows: Mf is e attached to the inner wall of the intake pipe 4, the amount of membrane fuel is
v is the amount of evaporated fuel existing in the intake passage 5 between the throttle valve 6 and the intake port 11, Gft is the fuel flow rate supplied from the injector 6, and Gap is the intake port 1.
The air flowing into the engine 1 from 1 to the intake air path 5 between the throttle valve 6 and the intake port 11 is
dMf/dt, where X is the proportion of the fuel flow rate supplied from the injector 6 that becomes liquid film fuel, and τ is the time constant indicating the time period until the liquid film fuel evaporates. MiX, Gft - (1/τ) @Mf
(1) and dMv/dt = (1/r)-Mf
-(My/Ma)-Gap (2) Here, @X and τ are engine-specific and fuel-specific variables. In other words, since Equation (1) shows the temporal change in the amount of liquid pumped fuel, it shows the amount of fine particles released from the liquid film wall material during each m interval (1/τ
) - Mt is subtracted, and the formula (2) shows the color change of rIj during the dark ivy combustion slope from the throttle valve 6 to the intake port 11, and at each moment. IiJ evaporation@fuel indicates the amount of evaporated material from the liquid film fuel (1/τ)・Mf, from the suction port 1
Engine 1 along with the air taken into Engine 1
(Mv/Ma) - Gap
This shows that the thickness of the material is reduced.

When the fuel concentration Mv existing between the throttle valve 6 and the suction boat 11 is calculated by equations (1) and (2), the vapor concentration My/Ma can be calculated. .

In addition, the fuel flow rate flowing into the engine 1 from the intake port 11 is Gfp, and Gfp is Gfp==(j-X)-
It is expressed as Gft+(Mv/Ma)Gap (3). The fuel flowing from the throttle valve 6 section to the intake port 11 causes a time lag when the engine 1 accelerates and speeds, so-called peaking, so the fuel flow from the intake port 11 to the engine 1 is reduced. In order to cause the inflow of GftK supplied from the injector 6, the injection force coefficient α must be multiplied. In other words, the fuel flow rate Gft is σ
By easting Gfp in equation (3), Gft [
be equal.

Therefore, equation (3) becomes the following equation.

Gft== (1-X)-Gft-a+(My/Ma)
Gap (4) When formula (4) is transformed, it becomes the following formula.

a = 1. , (1-X)-(1(Gaplof<M
v/M off (5) Here, it is considered that the intake air flow does not cause a time lag, so the air intake from the intake boat 11 (!:, thrower)/the intake air from the Reval Pro is approximately equal. . In other words, if the air flow rate sucked from the throttle valve 6 is Gat, G in Gap is
at is established. Therefore, equation (,5) ノGap/Gat
Gat/Gf t (C1 is equal to Ga
When t/Gft I is not equal to the standard air-fuel ratio (ALP) end, Gat/13f t = (ALP) end stutters.

Gaplof t = Gat/Gf t =+ (A
By substituting LP ) end (a) into equation (5), the injection correction coefficient σ can be determined by the following equation.

a = 1. (1-x> (1-(ALP)end(M
v/Ma)) (7)) In addition, the vote is empty Confucianism (ALP)
The end is set at any time to the optimal frlj according to the transmission conditions.
9 Change the pitch value.

In the example of Mukou1i11i, when calculating the liquid at the moment of Tianwei, the liquid at the moment of Tianwei, the amount of water +t) Mfn, the following formula is used.

Mfn=Mfn-1+(X-Gft(1/)-Mfn
1)-Δt ts) That is, it is determined by integrating the current Mfn over several meters. Here, Δt indicates a total period X that is arbitrarily set according to the characteristics of the engine, and in this embodiment, it is 10 milliseconds.

Furthermore, using Mfn determined by equation (8), the instantaneous fuel vapor concentration Mvn is determined by the following equation.

Mvn = Mvn-1+((1/r)・Mfn%1
/Ma), Gap) -Δt (9) That is,
It can be determined by numerically integrating the current Mvn. Mvn thus determined becomes a variable indicating the state of the air-fuel mixture in the intake passage 5 at every calculation period Δ.

By using the vaporized fuel concentration Mvn determined by the equation (9) in the equation (7)K, the injection correction coefficient a is determined, and the fuel injection class is determined in accordance with this a.

As mentioned above, the computer CPtJij formula (8), (
9), the amount of evaporated Confucianism Mvn is calculated sequentially and the requested M
The injection correction coefficient α is determined from equation (7) using vn, and the injection time of the injector 6 is also calculated.

Next, the computer CP for controlling these air-fuel ratios
The calculation procedure using U will be explained using the flowchart of FIG. In step 201, it is determined whether a certain period of time, for example, 10 milliseconds has elapsed since the previous calculation, and if 10 milliseconds have elapsed since the previous calculation, the calculation is performed. is executed, and if 10 milliseconds have not yet elapsed, the tree! -Jump Chin to execute another p-Chin.

In step 202, the output signals from the intake air temperature sensor 2, the pressure sensor 8, the liquid film fuel temperature sensor 9, and the Ignifushi Pankoi/I/10 are inputted to determine the intake air temperature, the intake passage pressure, and the liquid film temperature. and the engine speed are stored in the memory circuit RAM of the computer CPU. In step 206, a two-dimensional table for calculating X indicating the proportion of the injection charge that becomes a liquid film charge, which is stored in advance on the computer CPUK, is searched from the intake passage pressure and the number of engine revolutions, Determine the current X.

In step 204, based on the liquid film fuel temperature and the intake passage pressure, a two-dimensional table is stored in advance in the computer CPU and is used to calculate a time constant τ indicating the time period until the liquid film fuel evaporates. Determine τ.

In step 205, Mfn
In step 206, Mfn calculated in step 205 is used in the equation (9) to calculate Mvn.

In step 207, Mvn determined in nil step 206 is used in the equation (7) to calculate the injection correction coefficient a.
and store it in RAM. In step 208, the injection time of the injector 3 is calculated in accordance with the requested injection correction coefficient α, and the drive circuit 25 is
A correction signal is output to *@h circuit 23 to output a drive signal to the injector 5 to inject fuel. From step 209, another routine is executed.

Next, the relationship between the operating condition of the engine and the injection correction coefficient a in this embodiment will be explained using FIG. At 21:00, throttle valve 6 1iFJ degree B to opening degree A
When K opens, which corresponds to acceleration, the injection correction coefficient changes as shown by the debris in the 1d1 section.

In addition, the broken line in the ■ section is the same as when it is a solid line.
This accommodates changes in the injection correction coefficient σ when the liquid film fuel temperature in the intake pipe 4 is low.

At 22:00, the throttle valve 6 is opened from A to ri.
When closing to N degrees B, which corresponds to deceleration,
The injection correction coefficient α changes as shown in section J and acts to reduce the injected fuel.

Next, if you repeatedly pull the throttle valve 6 → close → open and close it from 23:00 to 25:00,
The temporal change in the injection correction coefficient α in the section h is the same as the initial change in the previous construction section, but when the injection correction coefficient a shown in the M section is 11 when the throttle valve 6 is opened at 25:00. Since the monthly change is affected by the evaporated fuel of LIXllil which corresponds to the time of deceleration, the injection correction coefficient aI7) maximum value also becomes smaller than that in the K section.

In this way, since the current vaporized fuel amount Mvn is calculated sequentially from the previous state, the requested injection correction coefficient α always adjusts the air-fuel ratio of the air-fuel mixture in the intake passage 5 to the engine The target air-fuel ratio (A
/F)and is an appropriate value for controlling to approach it.

Further, as another example, a control example will be shown in which the side air-fuel ratio is changed depending on the operating conditions of the engine 1.

For example, if the operating conditions of the engine 1 change and the air-fuel ratio of the mixture changes from a state close to the ideal air-fuel ratio to a lean burn state, or conversely, from a lean burn state to an immediate air-fuel ratio state, Equation (7) is shown in order to reduce the drop in torque when shifting to the rabbit mode (A/F).
end (By changing D fI, the fuel injected from the injector 3 can be sterilized.

Furthermore, as another example, when driving a torque converter vehicle, when shifting from the neutral range to the drive range, the engine speed drops due to load changes, so the air-fuel ratio becomes lean. By applying the control method of the present invention, it is possible to prevent a drop in torque.

(Effects of the Invention) The present invention provides that if the evaporative fuel concentration existing between the downstream of the throttle valve and the engine is calculated at any arbitrary cycle using a model 2 set in advance in accordance with the engine characteristics, the engine Supply fuel to determine the Ura Masakage of the fuel supplied from the fuel supply device of! By calculating the correction coefficient and controlling the amount of correction fuel in accordance with the total correction coefficient of the supplied fuel, the engine operation during transients such as acceleration and deceleration is streamlined, and fuel is not wasted. It has the effect of preventing consumption and reducing harmful exhaust components.

[Brief explanation of drawings]

FIG. 1 is a flowchart diagram clearly showing the method of the present invention, FIG. 2 is a system diagram showing the structure of an embodiment of the present invention, and FIG. 6 is a block diagram of an electronic control unit of an embodiment of the present invention. FIG. 4 is a cross-sectional view showing a mounting structure of a liquid-simulating fuel temperature sensor according to an embodiment of the present invention, FIG. 5 is a flowchart showing a calculation and control method according to an embodiment of the present invention, and No. FIG. 6 is an explanatory diagram of a state in which a change in the injection correction coefficient α is erased according to an embodiment of the invention. ST 101 to ST 104...Flowchart step entry Person Aisan Industries Co., Ltd. Agent Patent attorney Hidehiko Okada

Claims (1)

[Scope of Claims] A rotation speed sensor that generates a signal corresponding to the engine rotation speed, a pressure sensor that detects the absolute pressure in the intake passage downstream of the throttle valve and outputs a signal corresponding to the absolute pressure, and an intake An intake air temperature sensor that detects the temperature of the air and outputs a signal corresponding to the temperature; and an intake air temperature sensor that detects the temperature of the liquid film fuel adhering to the wall of the throttle valve of the intake pipe forming the intake passage and outputs a signal corresponding to the temperature. A model calculation formula for calculating the concentration of vaporized fuel present in the intake passage from downstream of the throttle valve to the engine by inputting the signals output from each of the liquid film fuel temperature sensors and the liquid film fuel temperature sensor that outputs signals at an arbitrary period. After calculating the evaporated fuel concentration at each arbitrary cycle in the first period, calculate the supplied fuel amount correction coefficient for determining the correction amount of fuel supplied from the engine fuel supply device in accordance with the evaporated fuel concentration. An air-fuel ratio control method for an engine, which controls a corrected fuel amount in accordance with the supplied fuel Momoura positive coefficient.