JPH06123246A - Fuel controller and fuel nature determining device - Google Patents

Abstract

PURPOSE:To always maintain a target air-fuel ratio by correcting a basic fuel injection amount according to an intake air flow rate so as to correspond to the oxygen concentration in exhaust gas. CONSTITUTION:A fuel controller and a fuel nature determining device are provided with an X.tau calculating part 116, which determines an evaporation constant tau and deposit efficiency X, by employing a detected intake pipe pressure P and a detected number of revolutions N of an engine, a fuel liquid membrane amount estimating part 118, which estimates a fuel liquid membrane amount Mf by using the predetermined evaporation constant tau, the deposit efficiency X, and a liquid membrane model, and a liquid membrane compensation part 112, which corrects a basic fuel injection amount fQ according to the estimated fuel liquid membrane amount Mf, the evaporation constant tau, and the deposit efficiency X.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel control device for controlling a fuel amount supplied to an engine by correcting a basic fuel injection amount determined according to an intake air flow rate according to an oxygen concentration in exhaust gas. And a fuel property determination device used therein.

[0002]

2. Description of the Related Art Conventionally, in an internal combustion engine, the basic fuel amount is calculated from the intake air amount or intake pipe pressure and the rotation speed of the internal combustion engine, and the output of an oxygen concentration sensor installed in the exhaust pipe of the internal combustion engine is calculated. Based on this, the basic fuel is corrected, and the fuel supplied to the internal combustion engine is controlled to have a predetermined target air-fuel ratio. However, even if the feedback control is performed in this way, when the fuel injection amount rapidly increases during the transient state of the internal combustion engine, for example, during the acceleration state, the amount of the fuel liquid film adhering to the wall surface in the intake pipe is reduced. The fuel liquid film increases and is supplied to the cylinder of the internal combustion engine with a delay, so that the fuel liquid film temporarily becomes lean. Further, when the internal combustion engine is in the deceleration state, the fuel injection amount decreases, but the intake pipe pressure decreases, so that the fuel liquid film attached to the intake pipe flows into the cylinder of the internal combustion engine, and temporarily. It will be in a rich state. Therefore, in order to eliminate the fluctuation of the air-fuel ratio at the time of transition, the fuel injection device of the internal combustion engine injects fuel synchronously or asynchronously with the crank angle at the time of acceleration to compensate for the change in the intake pipe fuel liquid film. Further, during acceleration, the basic fuel amount is reduced according to the change in the intake pipe fuel liquid film.
However, when the internal combustion engine changes with time, for example, when a carbon compound or the like adheres to the intake valve or the vicinity of the intake valve, the fuel is adsorbed to the compound or the like, so that the correction amount of the fuel during the transition changes.

For this reason, there is one described in Japanese Patent Application Laid-Open No. 2-256844 as a device that considers the influence of carbon compounds adhering to the intake pipe. This is equipped with an oxygen concentration detector for detecting the oxygen concentration in the exhaust pipe and an acceleration state detecting means for detecting the acceleration state, and based on the detection results of the oxygen concentration detector and the acceleration state detecting means, during acceleration operation. The deviation between the lean time and the rich time of the air-fuel mixture is obtained, and when the lean time of the air-fuel mixture is longer than the rich time and the deviation exceeds a preset set value, the fuel injection amount is increased, while The set value is increased as the acceleration state increases based on the detection result of the acceleration state detection means.

By the way, since the feedback control is performed after a lapse of a certain time after the start, even if the fuel having different fuel properties is supplied to the internal combustion engine, the target air-fuel ratio can be basically maintained. However, at the time of starting the internal combustion engine, it is not possible to accurately grasp the air flow rate supplied to the internal combustion engine due to instability at the time of start-up and the intake air flow rate being absolutely small. Cannot be executed temporarily, and it is not possible to cope with changes in fuel properties. Therefore, when starting,
There is a method in which a property of fuel supplied to a vehicle is assumed in advance and a fuel amount corresponding to the fuel property is injected to cope with the property.

[0005]

However, in the one disclosed in Japanese Patent Laid-Open No. 2-256844, the deviation between the lean time and the rich time of the air-fuel mixture during acceleration operation is
The target air-fuel ratio can be maintained in a certain state, but the target air-fuel ratio can be maintained in a certain state, because the amount of the fuel liquid film is indirectly considered and the temporal change is not considered. Can not. Further, in the prior art, at the time of starting, the fuel injection amount is set according to the fuel property already assumed at the shipping stage of the vehicle, so that the fuel having the property different from the initially assumed property is supplied to the internal combustion engine. If
The flammability at the time of starting deteriorates, and the starting property deteriorates.

That is, the conventional technique has a problem that it is not possible to maintain a good combustion state and it is not possible to purify the exhaust gas. Therefore, an object of the present invention is to provide a fuel control device capable of maintaining a good combustion state and cleaning exhaust gas, and a fuel property determination device used for the fuel control device.

[0007]

In a fuel control system for achieving the above object, a correlation between the amount of a fuel liquid film adhering to an intake valve and the inner surface of an intake pipe in the vicinity thereof and its evaporation rate and adhesion rate is shown. A liquid film amount model storage means for storing the liquid film model shown, and a parameter relationship for storing at least a parameter relationship showing a correlation of the evaporation rate and the adhesion rate of the fuel liquid film with respect to the intake pipe pressure and the engine speed. A storage unit, a parameter setting unit that determines the evaporation rate and the deposition rate of the fuel liquid film by using the detected intake pipe pressure and engine speed and the parameter relationship, and the determined evaporation rate and the deposition rate. Fuel liquid film amount estimating means for estimating the amount of the fuel liquid film using the rate and the liquid film amount model, and at least the estimated amount of the fuel liquid film, the evaporation rate, and the adhesion rate. A liquid film compensating means for correcting the basic fuel injection amount, and a fuel for injecting into the engine an amount corrected for the basic fuel injection amount according to the amount of the fuel liquid film and further corrected for the oxygen concentration. As the injection amount,
And an injection amount instruction means for instructing the fuel injection valve.

Further, another fuel control apparatus for achieving the above object is a transient state grasping means for grasping an engine transient state, and a coefficient showing a correlation between a variation state of the O ₂ feedback correction coefficient and a fuel property. -Coefficient for storing property relationship-Property relationship storage means, fuel injection amount storage means for storing the fuel injection amount according to the temperature of the engine or the temperature of cooling water for each fuel property, and the transient The fuel property estimation for estimating the fuel property from the fluctuation status comprehension means for comprehending the fluctuation status of the correction coefficient at the transition time, which is comprehended by the time comprehension means, and the fuel property estimation from the comprehension status of the correction coefficient and the coefficient-property relationship ascertained. Means for calculating the fuel injection amount according to the estimated fuel property and the temperature of the engine or the temperature of the cooling water. The fuel injection amount setting means for setting the amount as the fuel injection amount at the time of starting, and at the time of starting the fuel injection amount determined by the fuel injection amount setting means as the fuel amount to be injected into the engine. And a fuel instruction means for instructing.
In order to achieve the above-mentioned object, it is preferable that all the means of the above two types of fuel control devices are provided.
Needless to say, the evaporation time constant (the reciprocal of the evaporation rate) may be used instead of the evaporation rate used in the above two types of fuel control devices.

Further, in the fuel property determining device used for fuel control, a correction coefficient for the basic fuel injection amount determined according to the intake air flow rate is determined according to the oxygen concentration in the exhaust gas, and the basic coefficient is used with the correction coefficient. Feedback correction control means for correcting the amount of fuel injection, transient grasping means for grasping the transient state of the engine, and coefficient for storing the coefficient-property relationship indicating the correlation between the variation status of the correction coefficient and the fuel property. -Property relationship storage means, fluctuation status grasping means for grasping the fluctuation status of the correction coefficient at the time of the grasped transition, fuel condition estimation from the fluctuation situation of the correction coefficient and the coefficient-property relationship which have been grasped And a fuel property estimating means.

[0010]

The evaporation rate and the adhesion of the fuel liquid film adhering to the inner surface of the intake pipe, etc. are detected by using the intake pipe pressure and engine speed detected by the parameter setting means and the parameter relations stored in the parameter relation storage means. The rate is required.
The fuel liquid film amount estimating means obtains the liquid film amount by using the obtained evaporation rate and adhesion rate and the liquid film model stored in the liquid film model storage means. Then, the liquid film compensating means corrects the basic fuel injection amount using the obtained evaporation rate, adhesion rate and liquid film amount. That is, the liquid film compensating means substantially grasps the accurate amount of fuel flowing into the cylinder from the fuel liquid film regardless of the passage of time, and in addition to the fuel injected from the fuel injection valve, the accurate amount of fuel from the fuel liquid film to the cylinder The amount of fuel injected from the fuel injection valve is always accurately corrected so that the target air-fuel ratio becomes the target amount of fuel that flows into the cylinder including the amount of fuel that does not flow into the cylinder. Therefore, basically, the target air-fuel ratio can always be maintained.

As described in the prior art, at the time of starting when the feedback control cannot be temporarily executed, it is not possible to cope with the change in the fuel property during that time. Therefore, in the present invention, the fuel injection amount at the time of starting is preset for each fuel property, and this fuel injection amount is supplied to the cylinder at the time of starting to improve the combustibility at the time of starting. I am trying.

The fuel property is estimated as follows. When the fuel property changes, the changing state of the correction coefficient for correcting the basic fuel injection amount also changes according to the oxygen concentration during the transition. Therefore, the relationship between the fuel property and the changing condition of the correction coefficient at the time of transition is investigated in advance, and the fuel property is estimated from the changing condition of the correction coefficient.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment according to the present invention will be described below with reference to the drawings. As shown in FIG. 1, around the engine 160, a thermal air flow meter 151 that measures the mass flow rate of the intake air, a throttle valve 165 that adjusts the amount of air intake by the engine 160, and a throttle valve 165 A throttle opening sensor 1156 for detecting the valve opening and a crank angle sensor 1 for detecting the rotational speed of the engine 160.
52, a water temperature sensor 154 for measuring the temperature of the cooling water of the engine 160, a pressure sensor 153 for measuring the pressure in the intake pipe, an idling speed control valve 163 for controlling the idling speed, and an engine 160.
, A three-way catalyst 164 for purifying exhaust gas by redox, and a three-way catalyst 164
Of the oxygen sensor 155 that is installed upstream of the engine for detecting the oxygen concentration in the exhaust gas, and signals from the sensors 151, 152, ... Understand the operating state of the engine 160 and the like, and perform a predetermined procedure based on these information. A control unit 100 that calculates an amount of fuel required by the engine 160 and drives an actuator such as the fuel injection valve 105 is provided.

In terms of hardware, the control unit 100 has various sensors 151, as shown in FIG.
A signal from 152, ... Is input, and is amplified or an amplifier circuit 101 that amplifies a drive signal to an actuator such as a fuel injection valve 162, and an input / output signal is converted into a digital signal so that digital arithmetic processing can be performed. A / D conversion circuit 1
02, a microcomputer that performs digital arithmetic processing, or an arithmetic circuit 103 that is equivalent thereto, a ROM 104 and a RAM 105 that store constants, variables, arithmetic procedures and the like that are also used for arithmetic processing of the arithmetic circuit 203, and contents of the volatile RAM 205. And a backup circuit 106 for holding. The control unit 100 of this embodiment includes a thermal air flow meter 151, a crank angle sensor 152, a pressure sensor 153, and a water temperature sensor 15.
4, oxygen concentration sensor 155, throttle opening sensor 15
6 and a signal from the starter switch 157 are input, and a combustion injection valve drive signal, an ignition timing signal, and an idle speed control signal are output.

In addition, as shown in FIG. 3, the control unit 100 is a basic fuel calculating section for calculating a basic fuel injection amount f _Q by dividing the intake air flow rate Q by the target air-fuel ratio A / F as shown in FIG. 111 and a liquid film compensator 112 for correcting the basic fuel injection amount f _{Q based} on the fuel liquid film amount Mf and the like.
And a Qf calculator 113 that divides the liquid film-compensated fuel injection amount Gfi by the fuel-air ratio F / A, a Ti calculator 114 that calculates the injection valve opening time Ti per engine revolution, and an O ₂ correction coefficient α. O ₂ to determine the O ₂ feedback correction unit 115 for correcting the injection valve opening time Ti, from the deviation between the actual air-fuel ratio and the target air-fuel ratio a / F obtained from the oxygen concentration in the exhaust gas O ₂ correction coefficient α by The feedback correction coefficient calculation unit 120, the fluctuation parameter grasping unit 131 that grasps the parameters d and Td indicating the fluctuation state of the O ₂ compensation coefficient α during the transient state of the engine 160, and the deposition of the fuel liquid film from the parameters d and Td. Correction factors f (d, N) and g (T for rate x and evaporation time constant τ
x · τ correction coefficient calculation unit 132 for obtaining d, N) and a fuel property estimation unit 133 for estimating the fuel property according to the value of the product of these correction coefficients f (d, N) and g (Td, N). And a fuel property storage unit 134 for storing the estimated fuel property, a valve opening time storage unit 135 for starting, which stores the injection valve opening time corresponding to the cooling water temperature Tw for each fuel property, and the estimation. The valve opening time setting part 136 at the time of starting for setting the injection valve opening time according to the measured fuel property and the measured cooling water temperature Tw, and the attachment rate x according to the engine speed N, the intake pipe pressure P and the cooling water temperature Tw. And the X · τ calculation unit 116 for obtaining the evaporation time constant τ, and the adhesion rate x and the adhesion rate x previously obtained using the correction coefficient f (d, N) of the adhesion rate and the correction coefficient g (Td, N) of the evaporation time constant. a parameter correcting portion 117 to correct the evaporation time constant tau, using the corrected deposition rate x ₀ and evaporation time constant tau ₀ such as a fuel liquid film quantity Mf The injection film opening time obtained by the liquid film quantity estimating unit 118 to be obtained and the start time open time setting unit 136 at the time of starting is set as the opening time of the fuel injection valve 162, and at other times, the injection corrected by the opening time correcting unit 115. A valve opening time instruction unit 119 that instructs the fuel injection valve 162 to set the valve opening time Tiout as the opening time of the fuel injection valve 162.
And have.

In addition, in the x · τ correction coefficient calculation unit 132, the functions f and g showing the correlation with the parameters d, Td and the like, the correction coefficient of the fuel liquid film deposition rate x ₀ and the evaporation time constant τ _0. Are stored in advance as a map, and the fuel property determination unit 133 stores in the fuel property determination unit 133 a correction coefficient f (d, N) for the attachment rate and a correction coefficient g for the evaporation time constant
The relationship between the product of (Td, N) and the fuel property (shown in FIG. 12) is stored in advance. Further, the parameter correction unit 117 has an engine speed N, an intake pipe pressure P, and a cooling water temperature Tw.
And a deposition rate x, and a function f ′ indicating the relationship between the engine speed N, the intake pipe pressure P, the cooling water temperature Tw, and the evaporation time constant τ are stored. 118
Are the adhesion rate x _{0, the} evaporation time constant τ _0, etc., and the fuel film amount Mf.
A liquid film model (which will be described later (Equation 3)) indicating the relationship with is stored.

O ₂ feedback correction coefficient calculation unit 120
Is a first-order lag filter 121 that removes noise from the output signal from the oxygen concentration sensor 155, as shown in FIG.
And a threshold value storage unit 123 that stores a threshold value SL for determining the lean air-fuel ratio or the high rich air-fuel ratio, and a target air-fuel ratio memory that stores a value AFH corresponding to the target air-fuel ratio. The section 123a, the comparator 122 for comparing the filtered value with the threshold value SL, and the subtracter 1 for obtaining the difference between the output from the comparator 122 and the value AFH corresponding to the target air-fuel ratio.
24, a differentiator 125 for obtaining the differential value S of the difference, and a differential value gain calculator 127 for obtaining the differential gain KP from the differential value S
And an integrator 126 that obtains an integral value 1 / S of the difference obtained by the subtractor, an integral gain calculator 128 that obtains an integral gain KI from the integrated value 1 / S, and a basic value dB of the O ₂ correction coefficient α. Basic value storage unit 129a to be stored, differential gain KP and integral gain
It is configured to have an adder 129 that adds the KI and the basic value dB to obtain the O ₂ correction coefficient α.

In this embodiment, the liquid film model storage means and the fuel liquid film amount estimation means are composed of the liquid film amount estimation section 118, and the parameter storage means and the parameter setting section are X.
.Tau. Calculation means 116, and the transient grasping means and the variation status grasping means are constituted by the variation parameter grasping section 131. Further, the fuel property estimation means is composed of an x · τ correction coefficient calculation unit 132, an integrator 137, and a fuel property estimation unit 133.

Next, the operation of this embodiment will be described.
First, the calculation of the O ₂ correction coefficient α in the O ₂ feedback correction coefficient calculation unit 120 will be described according to the general flowchart shown in FIG.

In step 1301, the oxygen concentration sensor 15
The output signal is taken in from 5. This signal is passed through a first-order lag filter 121 to remove noise. The filtered value is compared in the comparator 122 with the threshold value SL. The output of the comparator 122 and the target value in the subtractor 124
The difference from AHF is obtained (step 1302). The differential value S of this difference is obtained by the differentiator 125, and the differential gain KP is obtained from the differential value S by the differential value gain calculator 127 (step 1303). Further, the integral value 1 / S of the difference is also calculated by the integrator 126, and the integral gain calculator 128 calculates the integral gain KI.
Is calculated (step 1304). And differential gain
KP, integral gain KI, and basic value dB are added by adder 129, and this is output as O ₂ correction coefficient α (step 1305).

Next, liquid film compensation is applied to the basic fuel injection amount,
Before describing the procedure for obtaining the valve opening time Tiout of the fuel injection valve 162, the fuel liquid film will be described.
As shown in FIG. 5, for example, when fuel is injected from the fuel injection valve 162 while the intake valve 161 is closed,
Of the fuel injected from the fuel injection valve 162, the fuel that does not directly enter the cylinder, that is, the inner surface of the intake pipe or the fuel injection valve 162.
If there is any of the above, the fuel adheres to the fuel injection valve 162 and the inner surface of the intake pipe in the vicinity thereof. When the fuel adheres and grows as the fuel liquid film 170 as described above, the mixing ratio of the fuel and the air, that is, the air-fuel ratio is changed as described in the related art.

FIG. 6 is a model showing the behavior of the fuel liquid film 170. Amount G of fuel injected from the fuel injection valve 162
f adheres to the fuel liquid film 170 at a rate of X (adhesion rate). Further, the fuel liquid film 170 evaporates at a rate of 1 / τ (evaporation rate). Therefore, the liquid film amount Mf can be expressed as in (Equation 1), and the fuel amount Gfe flowing into the cylinder of the engine 160 can be expressed as in (Equation 2).

[0023]

[Equation 1]

[0024]

[Equation 2]

When the mathematical expressions of the liquid film behavior are expressed by the mathematical expressions in the discrete range in performing the digital arithmetic processing, they can be expressed as (Equation 3) and (Equation 4), respectively. This (Equation 3) is stored in advance in the liquid film amount estimation unit 118. Further, (Formula 4) is stored in advance in the liquid film compensation unit 112.

[0026]

[Equation 3]

[0027]

[Equation 4]

If the Mf of (Equation 2) is erased using (Equation 1) and expressed using the Laplace operator, it becomes as shown in (Equation 5).

[0029]

[Equation 5]

In the above equation, Mf: liquid film amount,
Gf: fuel injection amount, Gfe: inflow amount of fuel into cylinder, 1 / τ;
Evaporation rate, X: Adhesion rate, Δt: Calculation cycle, f _Q : Basic fuel injection amount, s: Laplace operator.

FIG. 7 shows the relationship between the adherence rate X and the intake pipe pressure P for each fuel property, and FIG. 8 shows the evaporation time constant τ (the reciprocal of the evaporation ratio 1 / τ) and the intake pipe pressure P for each fuel property. Shows the relationship. As described above, the attachment rate X and the evaporation time constant τ required for calculating the liquid film amount Mf have a constant relationship with the intake pipe pressure P. Further, the attachment rate X and the evaporation time constant τ also have a constant relationship with the cooling water temperature Tw (which may be the engine temperature) and the engine speed N. Therefore, X
In the τ calculation means 116, a function f ′ indicating the relationship between the attachment rate X and these values and a function g ′ indicating the relationship between the evaporation time constant τ and these values are mapped and stored in advance. .

Further, as shown in FIGS. 7 and 8, the adhesion rate X and the evaporation time constant τ are the fuel properties (in the figure, the triangles indicate heavy fuel and the circles indicate light fuel). It also depends on Therefore, the parameter correction unit 117 corrects the attachment rate X and the evaporation time constant τ in accordance with the fuel property.

FIG. 14 shows the valve opening time T of the fuel injection valve 162.
It is a general flowchart which shows the procedure until it calculates | requires iout. First, take in the intake air flow rate Q (step 1
401). The basic fuel calculation unit 111 uses this intake air flow rate Q.
The divided by the target air-fuel ratio A / F determining a basic fuel injection quantity f _Q (step 1402). Meanwhile, the intake pipe pressure P, the engine speed N, and the cooling water temperature Tw are taken in (step 140
3, 1404, 1405), and the X · τ calculating means 116 retrieves the adhering rate x corresponding to the intake pipe pressure P, the engine speed N and the cooling water temperature Tw from the map of the function f ′, and from the map of the function g ′. The evaporation time constant τ corresponding to the intake pipe pressure P, the engine speed N and the cooling water temperature Tw is searched (step 1406). The adhesion rate X and the evaporation time constant τ are
As described above, the parameter correction unit 117 determines the correction coefficient depending on the fuel property because it depends on the fuel property.
Using f (d, N) and g (Td, N), the attachment rate X and the evaporation time constant τ are corrected as shown in (Equation 6) and (Equation 7). In addition,
The correction coefficients f (d, N) and g (Td, N) will be described later.

X ₀ = X · f (d, N) ... (Equation 6) ) Τ ₀ = τ ・ g (Td, N) ・ ・ ・ ・ ・ ・ ・ ・ (Equation 7) Liquid film The amount estimation unit 118 obtains the liquid film amount Mf using the corrected attachment rate X ₀ and the evaporation time constant τ ₀ and the above-mentioned (Equation 3). The liquid film compensating unit 112 calculates the basic fuel injection amount f _Q obtained in step 1402, the adhesion rate X ₀ and the evaporation time constant τ ₀ obtained in step 1407, and the liquid film amount Mf obtained in step 1408 (Equation 4). And are used to determine the total amount of fuel flowing into the cylinder. That is, liquid film compensation for correcting the basic fuel injection amount f _Q is executed in consideration of the fuel liquid film (step 1409). Subsequently, the Qf calculation unit 113 divides the liquid film-compensated injection amount Gfi by the fuel-air ratio F / A to obtain Qf (step 1410), and the Ti calculation unit 114 uses (Equation 8) to calculate the engine speed per revolution. The injection valve opening time Ti of is calculated.

Ti = K · Qf / N + Ts ... (Equation 8) Is the injection valve coefficient, and Ts is the dead time of the fuel injection valve 162. O ₂ feedback correction unit 115 corrects the injection valve opening time Ti by O ₂ feedback correction coefficient calculator O ₂ correction coefficient calculated in 120 alpha (Step 14
12). Injection valve opening time Tio obtained in step 1412
ut is output from the open time instruction unit 119 to the fuel injection valve 162 during normal traveling (when not starting).

As described above, in the liquid film compensating section 112, the accurate amount of fuel flowing into the cylinder from the fuel liquid film is substantially grasped regardless of the passage of time, and the other amount of fuel injected from the fuel injection valve 162 is also detected. The amount of fuel injected from the fuel injection valve 162 is always accurately corrected so that the target air-fuel ratio becomes the target amount of fuel that flows into the cylinder, including the amount of fuel that does not flow into the cylinder from the fuel liquid film. . Therefore, the target air-fuel ratio can be basically maintained at all times during normal traveling (when not starting).

FIG. 9 is a graph showing changes with time of the output of the oxygen concentration sensor 155 and the O ₂ correction coefficient α. The air-fuel ratio indicated by the output of the oxygen concentration sensor 155 is the target air-fuel ratio A /
When it is higher than F, the O ₂ correction coefficient α increases by the integral amount, and when it is lower than the target air-fuel ratio A / F, it decreases. In addition,
When the output of the oxygen concentration sensor 155 crosses a value corresponding to the target air-fuel ratio A / F, the increment / decrement changes stepwise due to the integral.

FIG. 10 is a graph showing changes in the O ₂ correction coefficient α, the throttle valve opening θ, and the intake pipe pressure P during the transient state of the engine 160. When the throttle valve opening θ changes as shown in the figure, the intake pipe pressure P also changes.
By the way, as described in the prior art, the air-fuel ratio is most affected by the fuel liquid film during the transition. Therefore, the oxygen concentration in the exhaust gas also changes significantly during the transition, and as a result,
As shown in the figure, the O ₂ correction coefficient α also changes. Therefore, the property of the fuel changes (if the property changes, naturally,
The adhesion rate and evaporation time constant also change. ), If the amount of liquid film attached to the inner surface of the intake pipe changes, the O ₂ correction coefficient α deviates from an appropriate value. Therefore, conversely, if the change state of the O ₂ correction coefficient α during transition is grasped, the fuel property can be grasped.

In the present embodiment, as the parameter indicating the variation of the O ₂ correction coefficient α, the maximum value d of the deviation amount from the central value of the correction coefficient α and the maximum value thereof are reached as shown in FIG. The time Td from when to return to the central value is used. Although the fuel property may be immediately estimated from these values, here, in order to correct the deposition rate and the evaporation rate of the fuel liquid film, the correction rate f (d, N )
And the correction coefficient g (Td, N) of the evaporation time constant are obtained, and the fuel properties are grasped from these.

FIG. 15 is a general flow chart showing the procedure for acquiring the parameter indicating the variation of the O ₂ correction coefficient α during the transient state of the engine 160. Note that the processing described below is all executed by the variation parameter grasping unit 131. First, the throttle valve opening θ is taken in (step 1501), and it is determined whether the throttle valve opening θ is changing (step 1502). If it is not changing, the processing is ended without executing the following processing, and if it is changing, the intake pipe pressure P is taken in (step 1503). Then, it is judged whether or not the intake pipe pressure P is changing (step 1504), and if it is not changing, it is judged that it is not a transient time, and the process ends. If it is changing, it is judged that it is a transient time, and O ₂ Read the correction coefficient α (step 1505). In step 1506,
A weighted average is applied to the read O ₂ correction coefficient α. continue,
The peak position of the O ₂ correction coefficient α is detected (step 150
7) The maximum value deviation d is calculated (step 1508).
After that, the return time Td from the maximum value is calculated (step 1509).

FIG. 16 shows a general flow chart for determining the fuel property. First, the x · τ correction coefficient calculation unit 132
Reads the maximum value d of the O ₂ correction coefficient α and the return time Td from the fluctuation parameter grasping section 131 (step 160
1), the maximum value d and the return time Td from the correction coefficient map
The correction coefficient g (Td, N) of the evaporation time constant and the correction coefficient f (d, N) of the attachment rate corresponding to are retrieved (step 1602). Both correction factors g (Td, N) and f (d, N) are multiplied by an integrator (step 1603).

By the way, as shown in FIG. 12, when the product g (Td, N) f (d, N) of these correction coefficients exceeds 1, it is a heavy fuel, and when it is around 1, the standard is heavy fuel. It has been confirmed by tests that the fuel is a light fuel when the fuel is less than 1.
Therefore, the fuel property estimation unit 133 refers to a table as shown in FIG. 12, and determines whether the fuel is heavy or standard, according to the product g (Td, N) · f (d, N) of both correction coefficients. Determine if it is light (Step 1
604, 1605), and the corresponding flag in the fuel property storage unit 134 is set (steps 1606, 1607,
1608).

FIG. 18 is a general flow chart for setting the fuel injection amount (injection valve opening time) at the time of starting. It is determined whether or not the starter switch 157 has been pressed (step 1701). If it is not turned on, the process ends. If it is turned on, the start-time open time setting unit 136 takes in the cooling water temperature Tw and the fuel property storage unit 134. The fuel property is read from (steps 1702 and 1703). The startup valve opening time setting unit 136 further searches the startup opening time storage unit 135 for an injection valve opening time corresponding to the fuel property and the cooling water temperature Tw. Then, the injection valve opening time is indicated by the valve opening time indicating section 1
It is output from 19 to the fuel injection valve 162. in this way,
At the time of starting, since the fuel injection amount according to the fuel property is injected, the combustibility at the time of starting can be improved.

In this embodiment, FIGS. 13 to 1 are used.
The flow up to 7 is executed in time synchronization, but may be executed in event synchronization. Also,
In the present embodiment, when determining the valve opening time at startup,
Although the cooling water temperature is used, the present invention is not limited to this, and the engine temperature may be used.

[0045]

According to the present invention, the accurate amount of fuel flowing into the cylinder from the fuel liquid film is substantially grasped regardless of the passage of time, and in addition to the fuel injected from the fuel injection valve, the fuel liquid film The amount of fuel injected from the fuel injection valve is always corrected accurately so that the target air-fuel ratio is the same as the amount of fuel that flows into the cylinder, including the amount of fuel that does not flow into the cylinder. The air-fuel ratio can be constantly maintained. According to another aspect of the present invention, the fuel property is determined, the fuel injection amount at the time of starting is determined according to the determined fuel property, and this fuel injection amount is injected at the time of starting, so the fuel property is changed. Even in this case, the combustibility at the time of starting can be improved.

Therefore, any of these inventions can maintain a good combustion state and clean the exhaust gas.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a configuration around an engine according to an embodiment of the present invention.

FIG. 2 is a circuit block diagram of a control unit of one embodiment according to the present invention.

FIG. 3 is a functional block diagram of a control unit according to an embodiment of the present invention.

FIG. 4 is a logic circuit diagram of an O ₂ feedback correction coefficient calculation unit according to an embodiment of the present invention.

FIG. 5 is an explanatory diagram showing a state near the intake valve.

FIG. 6 is an explanatory diagram showing a liquid film model of one example according to the present invention.

FIG. 7 is a graph showing a relationship between an intake pipe pressure and an adhesion rate for each fuel property according to an embodiment of the present invention.

FIG. 8 is a graph showing a relationship between an intake pipe pressure and an evaporation time constant for each fuel property according to an embodiment of the present invention.

FIG. 9 is a graph showing changes over time in the output of the oxygen concentration sensor and the O ₂ correction coefficient α.

FIG. 10 is an O ₂ correction coefficient α during engine transient;
7 is a graph showing changes in throttle valve opening θ and intake pipe pressure P.

FIG. 11 is an explanatory diagram for explaining a parameter indicating a change situation of the O ₂ correction coefficient α according to the embodiment of the present invention.

FIG. 12 is an explanatory diagram showing the relationship between the product of the correction coefficient of the attachment rate and the correction coefficient of the evaporation time constant and the fuel property according to the embodiment of the present invention.

FIG. 13 is a flowchart showing a procedure for calculating an O ₂ correction coefficient α according to an embodiment of the present invention.

FIG. 14 is a flowchart showing a procedure for calculating a final fuel injection amount (injection valve opening time) according to the embodiment of the present invention.

FIG. 15 is a flowchart showing a procedure of acquiring a parameter indicating a change in the O ₂ correction coefficient α according to the embodiment of the present invention.

FIG. 16 is a flowchart of fuel property determination according to an embodiment of the present invention.

FIG. 17 is a flowchart showing a procedure for setting a fuel injection amount (injection valve opening time) at the time of starting of one embodiment according to the present invention.

[Explanation of symbols]

100 ... Control unit, 103 ... Arithmetic circuit, 1
04 ... ROM, 105 ... RAM, 111 ... Basic fuel calculation unit, 112 ... Liquid film compensation unit, 115 ... O ₂ feedback correction unit, 116 ... X · τ calculation unit, 117 ... Parameter correction unit, 118 ... Liquid film amount estimation Section, 119 ... Valve opening time instruction section, 120 ... O ₂ feedback correction coefficient calculation section, 13
DESCRIPTION OF SYMBOLS 1 ... Fluctuation parameter grasping part, 132 ... x * (tau) correction coefficient calculation part, 133 ... Fuel property estimation part, 134 ... Fuel property storage part, 135 ... Start valve opening time storage part, 136 ... Start valve opening time setting part , 151 ... Thermal air flow meter, 152 ... Crank angle sensor, 153 ... Pressure sensor, 154 ... Water temperature sensor, 155 ... Oxygen concentration sensor, 156 ... Throttle opening sensor, 157 ... Starter switch, 160 ... Engine, 161, ... Intake Valve, 162 ... Fuel injection valve, 170 ... Fuel liquid film.

Claims (8)

[Claims] 1. A fuel control device for controlling a fuel amount supplied to an engine by correcting a basic fuel injection amount determined according to an intake air flow rate according to an oxygen concentration in exhaust gas. Liquid film model storage means for storing a liquid film model showing the correlation between the amount of the fuel liquid film attached to the inner surface of the nearby intake pipe and its evaporation rate and adhesion rate; and the liquid pipe model storage means for the intake pipe pressure and engine speed. The fuel liquid film is formed by using a parameter relation storage unit that stores a parameter relation indicating a correlation between the evaporation rate and the adhesion rate of the fuel liquid film, and the detected intake pipe pressure and engine speed and the parameter relation. Parameter setting means for determining the evaporation rate and the adhesion rate of the fuel liquid film, and a fuel liquid film amount estimating means for estimating the amount of the fuel liquid film by using the evaporation rate and the adhesion rate and the liquid film model which are determined. A liquid film compensating means for correcting the basic fuel injection amount according to at least the estimated amount of the fuel liquid film, the evaporation rate, and the adhesion rate; and the basic fuel injection amount by the liquid film compensating means. And an injection amount instructing means for instructing the fuel injection valve that the fuel injection amount is an amount that is corrected according to the oxygen concentration and is an amount to be injected into the engine. Fuel control device. 2. A transient state grasping means for grasping a transient state of the engine, and O showing a correlation between a variation state of a correction coefficient for compensating the basic fuel injection amount according to the oxygen concentration and a fuel property. ₍₂ ) Coefficient-property relationship storage means for storing the coefficient-property relationship storage means, and fuel injection amount storage means for storing the starting fuel injection quantity with respect to the temperature of the engine or the temperature of the cooling water for each fuel property. And a change state grasping means for grasping the change state of the correction coefficient at the time of the grasped transition, and the fuel property estimation for estimating the fuel property from the grasped change state of the correction coefficient and the O ₂ coefficient-property relationship. Means and among those stored in the fuel injection amount storage means,
And a fuel injection amount setting means for determining a fuel injection amount according to the estimated fuel property and the detected engine temperature or the temperature of the cooling water thereof, and setting the fuel injection amount as a fuel injection amount at the time of starting, The injection amount instructing means instructs the fuel injection valve at the time of starting as the fuel injection amount obtained by the fuel injection amount setting means as the fuel injection amount to be injected into the engine. 1. The fuel control device according to 1. 3. The O ₂ coefficient-property relationship stored in the coefficient-property relationship storage means is a correlation between the variation status of the correction coefficient and the evaporation rate correction coefficient and the adhesion rate correction coefficient. O ₂ coefficient-X · τ coefficient relationship, and X / τ coefficient-property relationship that is a correlation between the correction coefficient of the evaporation rate and the correction coefficient of the attachment rate and the fuel property. Is obtained from the grasped change status of the correction coefficient and the O ₂ coefficient-X · τ coefficient relationship, and obtains the correction coefficient for the evaporation rate and the correction coefficient for the adhesion rate. Adhesion rate correction coefficient and the X / τ coefficient
-Parameter correction means for estimating the fuel property from the property relationship and correcting the evaporation rate and the adhesion rate by using the correction coefficient of the evaporation rate and the correction coefficient of the adhesion rate obtained by the fuel property estimation means The fuel control device according to claim 2, further comprising: 4. The parameter relationship stored in the parameter relationship storage means is the evaporation rate and adhesion of the fuel liquid film with respect to the temperature of the engine or the temperature of the cooling water, the intake pipe pressure and the engine speed. Is a correlation of the ratio, the parameter setting means, the intake pipe pressure, the engine speed and the temperature of the engine or the temperature of the cooling water thereof, and the parameter relationship, the evaporation rate of the fuel liquid film The fuel control device according to claim 1, 2, or 3, characterized in that the adhesion rate is determined. 5. A correction coefficient for the basic fuel injection amount determined according to the intake air flow rate is determined according to the oxygen concentration in the exhaust gas, and the basic fuel injection amount is corrected by the correction coefficient and supplied to the engine. In the fuel control device for controlling the amount of fuel to be controlled, a transient state grasping unit that grasps the transient state of the engine, and a coefficient that stores a coefficient-property relationship indicating a correlation between the variation status of the correction coefficient and the fuel property. -Property relation storage means, fuel injection amount storage means for storing the starting fuel injection amount for the engine temperature or the temperature of the cooling water for each of the fuel properties, and the correction coefficient at the grasped transition time And a fuel property estimating means for estimating the fuel property from the comprehended fluctuation condition of the correction coefficient and the coefficient-property relationship. Among those stored in,
Fuel injection amount setting means for obtaining a fuel injection amount according to the estimated fuel property and the detected engine temperature or the temperature of its cooling water, and setting the fuel injection amount as a fuel injection amount at the time of starting, and at the time of starting Assuming that the fuel injection amount obtained by the fuel injection amount setting means is the fuel amount to be injected into the engine,
A fuel control device comprising: a fuel instructing means for instructing the fuel injection valve. 6. The transient grasping means judges from the amount of change in throttle valve opening.
4. The fuel control device according to 4 or 5. 7. The transient grasping means judges from the amount of change in intake pipe pressure.
Alternatively, the fuel control device according to item 6. 8. A feedback correction control means for determining a correction coefficient for the basic fuel injection amount determined according to the intake air flow rate according to the oxygen concentration in the exhaust gas, and correcting the basic fuel injection amount with the correction coefficient. A transient grasping means for grasping an engine transient time, a coefficient-property relation storing means for storing a coefficient-property relation indicating a correlation between the fluctuation state of the correction coefficient and the fuel property, and a grasped transient And a fuel property estimating means for estimating a fuel property from the learned fluctuation condition of the correction coefficient and the coefficient-property relationship. A fuel property determination device characterized by: