JPH01313639A - Fuel injection quantity controller for internal combustion engine - Google Patents

Abstract

PURPOSE:To prevent the shift to the lean side of the air-fuel ratio by estimating the suction pipe pressure when acceleration start is detected and calculating the estimated injection quantity on the basis of the estimated intake pipe pressure and carrying out the asynchronous injection corresponding to the shortage portion in the difference from the synchronous injection quantity before acceleration. CONSTITUTION:A synchronous injection control means M4 calculates the synchronous injection quantity and controls a fuel injection valve M3 on the basis of the revolution speed of an internal combustion engine M1 which is detected by an operating state detecting means M2, intake pipe pressure, etc. When an acceleration judging means M5 judges the acceleration state, a suction pipe pressure estimating means M8 estimates the suction pipe pressure for the future time from the time point of detecting the operation state, and an estimating means M9 judges the estimated injection quantity corresponding to the physical model of an internal combustion engine M1. In asynchronous injection control means M10, the differential fuel quantity between the estimated injection quantity and the synchronous injection quantity is obtained, and the asynchronous injection for the shortage portion is carried out by a fuel injection valve M3. Thus, the shift to the lean side of the air/fuel ratio immediately after acceleration can be prevented.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a fuel injection control device that controls the amount of fuel in an internal combustion engine, and more specifically, the present invention relates to a fuel injection control device that controls the amount of fuel in an internal combustion engine. The present invention relates to a fuel injection amount control device for an internal combustion engine that uses a fuel behavior model to adjust the amount of fuel injection during acceleration.

[Prior art and its problems] Conventionally, as a means of controlling the fuel injection amount of an engine, the pressure in the surge tank is detected, and the synchronous injection amount is calculated based on this detected value and the detected value of the engine rotation speed. There is a technology for controlling the opening time of fuel injection valves. The operating state etc. in this conventional control is shown in FIG. 9, which shows the calculation of the synchronous injection amount of the first to fourth cylinders at times tl to tll.

It shows the timing of execution of synchronous injection and the intake stroke, and the intake pipe pressure at the above times t1 to tit.

It shows the synchronous injection amount and throttle opening.

However, for example, the time t5 at which the operating state such as the intake pipe pressure of the first cylinder is detected, and the time t when the fuel calculated and injected using the operating state data is actually inhaled into the air bacteria.
8 is different by three cycles, so the air-fuel ratio may deviate to the lean side for a predetermined period after acceleration. In other words, when the throttle opening changes and an acceleration state occurs, the intake pipe pressure changes suddenly, but the synchronous injection amount supplied to the first to fourth air shafts of the engine is shown by the dashed line in the figure. The air-fuel ratio may not correspond to the ideal air-fuel ratio, and the engine may not be able to supply the amount of fuel it truly requires. This poses a problem in that the air-fuel ratio is disturbed, which affects emissions, drivability, and the like.

As a technique for dealing with such a problem, for example, a technique described in Japanese Patent Application Laid-Open No. 169647/1983 has been known. That is, the future intake pipe pressure is estimated based on the time-series changes in the intake pipe pressure detected in the past, and the synchronous injection amount is controlled based on the estimated intake pipe pressure.

However, this kind of synchronous injection control technology uses the operating state at a predetermined time to estimate the operating state several cycles after that time.For example, the operating state at time t5 immediately after acceleration shown in FIG. Although it is possible to estimate the operating state at time t8 three cycles later using the state, the operating state such as intake pipe pressure PF6 at time t6 can be accurately estimated from the operating state at time t3 before acceleration. It was difficult to do. Therefore, it was difficult to accurately determine the amount of fuel T6 required at time 6. Therefore, at time t5 immediately after acceleration
~t7, the fuel amounts T5 to T7 calculated using the operating state before acceleration are synchronously injected, and the required fuel amounts TF5 to TF7 cannot be supplied, so the air-fuel ratio shifts to the lean side. was.

In order to compensate for the shortage of the fuel amount T5 to T7 for three cycles immediately after acceleration, a method has been proposed in which the fuel amount is corrected by non-simultaneous injection when an acceleration state is detected (Japanese Patent Application Laid-Open No. 1983-1999- Publication No. 201046 and JP-A-62-15725
(See Publication No. 7). However, in these technologies, the amount of fuel to be injected asynchronously is determined from maps determined in advance according to various operating conditions such as throttle opening and water temperature, and the task of determining the amount of fuel using these maps is complicated. Despite this, it was not always possible to obtain the appropriate amount of fuel.

SUMMARY OF THE INVENTION The present invention aims to solve the above-mentioned conventional problems and provides a device that improves emissions and drivability by executing appropriate fuel injection control immediately after acceleration.

[Means for solving the above problems] As shown in FIG. 1, the fuel injection IflI amount control device for an internal combustion engine according to the present invention, which has been made to achieve the above problems, has the following features: A synchronous injection amount is calculated using an operating state detecting means M2 that detects an operating state including pressure, and the operating state detected by the operating state detecting means M2, and the fuel injection valve M3 is driven based on the calculated amount. A fuel injection amount control device for an internal combustion engine, comprising: synchronous injection control means M4 for controlling fuel injection; Based on the acceleration determination means M5, the acceleration determination means M5 determines the acceleration state, and when the acceleration determination means M5 determines the acceleration state, the driving state indicating the acceleration detected by the driving state detection means M2, and the driving state detected before acceleration. an intake pipe pressure estimating means M6 for estimating the intake pipe pressure after the time of detection of the operating state using at least the intake pipe pressure and the rotational speed; and the intake pipe pressure estimated by the intake pipe pressure estimating means M6; Using the operating state detected by the operating state detection means M2, the fuel behavior is estimated according to a fuel behavior model consisting of a state equation and an output equation that describe the behavior of the fuel in the internal combustion engine, and the operating state after acceleration is estimated. An injection amount estimating means M7 that calculates a corresponding estimated injection amount, and calculates the fuel amount that is the difference between the estimated injection amount calculated by the injection amount estimating means M7 and the synchronous injection amount calculated by the same injection control means M4, and calculates the fuel amount. The gist of the present invention is a fuel injection amount control device for an internal combustion engine, characterized in that it includes asynchronous injection control means M8 that asynchronously injects a difference in fuel amount.

[Operation] In the fuel injection control fall device for an internal combustion engine of the present invention having such a configuration, control of the amount of fuel injection fA is performed by the following series of processes.

First, the operating state detection means M2 detects the operating state including the rotational speed and intake pipe pressure of the internal combustion engine M1, and the same-gate injection control means M4 detects the same-gate injection amount based on the operating state such as the rotational speed and intake pipe pressure. Calculate the fuel injection valve M
3 to control the same gate injection.

On the other hand, if the acceleration determining means M5 determines that the acceleration state is present based on a change in the operating state indicating acceleration, the operating state indicating acceleration and at least the intake pipe pressure and rotational speed detected before acceleration are determined. The intake pipe pressure estimating means M8 estimates the intake pipe pressure after the time of detection of the above operating state.

Furthermore, using the estimated intake pipe pressure and the already measured operating conditions such as rotational speed, the injection amount estimating means M7
An estimated injection amount corresponding to the estimated post-acceleration intake pipe pressure is determined in accordance with a physical model that describes the behavior of the fuel supplied to the internal combustion engine M1, that is, a fuel behavior model consisting of a state equation and an output equation.

Then, the asynchronous injection control means M8 calculates the fuel amount that is the difference between the estimated injection amount and the synchronous injection amount, and injects this difference fuel amount asynchronously, thereby quickly supplying the fuel amount necessary for acceleration to the internal combustion engine M1. and performs suitable fuel injection control.

That is, normally, the synchronous injection amount for a predetermined period of time after the detection of the operating state is calculated and fuel injection is executed, but if an acceleration state of more than a predetermined value is detected, the operating state at the time of the acceleration state is calculated. The intake pipe pressure at the previous point in time is estimated based on the included operating conditions, and the estimated injection amount required for simultaneous injection is determined based on the intake pipe pressure and the like. Then, the difference between this estimated injection amount and the amount of fuel that has already been injected simultaneously is calculated, and the difference in fuel amount is injected asynchronously, so the appropriate amount of fuel is quickly replenished immediately after acceleration, and the air-fuel ratio shifts to the lean side. Fluctuations are prevented.

[Example] An embodiment of the present invention will be described below with reference to the drawings.

FIG. 2 is a schematic configuration diagram showing a four-cylinder (only one cylinder is shown in the figure) engine 1 and its peripheral devices to which the fuel injection amount control device of the embodiment is applied.

As shown in the figure, the engine 1 includes an intake system 7 that mixes intake air and fuel injected from a fuel injection valve 3 and guides the mixture to an intake boat 5, and an intake system 7 that mixes intake air and fuel injected from a fuel injection valve 3 and guides the mixture to an intake boat 5. Cylinder 11 taken out via 10
and an exhaust system 13 that discharges the gas after combustion through an exhaust port 12.

The intake pipe 14 of the intake system 7 is provided with a throttle valve 16 for controlling the amount of intake air and a surge tank for smoothing the pulsating flow of intake air.

This amount of intake air is normally controlled by the opening degree of a throttle valve 16 that is linked to an accelerator pedal (not shown).

Furthermore, the intake system 7 includes various sensors, namely, an atmospheric pressure sensor 19, an intake air temperature sensor 20 that detects intake air temperature, and a throttle position sensor 21 that detects throttle opening.
, an intake pressure sensor 22 for detecting intake pipe pressure, and the like are provided.

The mixture of the air taken in through the throttle valve 16 and the fuel injected from the fuel injection valve 3 is
After being sucked into the cylinder 11 and compressed by the piston 10,
It is ignited by the electric spark from the spark plug 9. The ignited air-fuel mixture is explosively combusted and drives the piston 10, and then is discharged into the exhaust system 13 as exhaust gas, purified by a catalyst device (not shown), and then discharged into the atmosphere. This exhaust system 13 is provided with an oxygen sensor 25 that detects the oxygen concentration in the exhaust gas.

The spark plug 9 provided in each cylinder 11 of the engine 1 is
The igniter 27 is connected to the rotation of the crankshaft (not shown).
Distributor 29 that distributes high voltage generated to
It is connected to the. Disposed within the distributor 29 are a rotational speed sensor 32 that generates a pulse according to the rotational speed of the engine 1, and a cylinder discrimination sensor 34 that generates a pulse at every constant crank angle. Note that the cylinder block 3 of the engine 1 is cooled by circulating cooling water, and the temperature of the cooling water, which is one of the operating conditions of the engine 1, is detected by a water temperature sensor 39 provided on the cylinder block 3. be done.

The outputs of the above-mentioned sensors and various actuators such as the fuel injection valve 3 are connected to an electronic control device 40. This electronic control device 40 includes a well-known CPU 41, ROM 43, R
It is mainly composed of an AM45 and a human output boat 47, and has an estimated value of intake pipe pressure (estimated intake pipe pressure value), which will be described later.
, synchronous and asynchronous injection amounts, etc. are calculated, and furthermore, commands for controlling synchronous and asynchronous injection, etc., are executed based on these values. In addition, the RAM 45 stores operational status data from each sensor for several times, and further uses the data to calculate intake pipe pressure for one shift, synchronous and asynchronous injection, etc.
Calculated values of the amount of errors and the like are also stored several times.

Next, the configuration of the engine 1 and the electronic control device 40 described above will be described.
The following will sequentially describe the processes executed by (I) intake pipe pressure estimation process, (If) synchronous injection amount estimation process, and ([I) asynchronous injection control unit process.

In this embodiment, fuel injection control is performed in a four-cylinder engine 1 by performing simultaneous injection and asynchronous injection. Based on the operating state of the stroke, the intake pipe pressure of the intake stroke is estimated (I), and then, based on the estimated intake pipe pressure and the operating state of the compression explosion stroke, a physical model representing a predetermined fuel behavior is estimated. is carried out (processing ■).

On the other hand, the asynchronous injection amount is calculated by first calculating the amount of fuel required immediately after acceleration using the physical model used to calculate the synchronous injection amount above, and then subtracting the amount of fuel that has already been injected from this fuel amount. However, the difference between the method of calculating the synchronous injection amount in the above process ■ and the method of calculating the amount of fuel required immediately after acceleration in process ■ is that in process ■, when calculating the synchronous injection amount, In contrast to using the operating state a predetermined cycle before the intake stroke, in process ①, to calculate the amount of fuel required immediately after acceleration, the throttle opening immediately after acceleration and the operating state a predetermined cycle before the intake stroke immediately after acceleration are used. is to use.

(I) Process for estimating intake pipe pressure First, in explaining the process for estimating intake pipe pressure, the configuration that is the basis for estimating the intake pipe pressure will be explained with reference to the block diagram in FIG. This process is based on the operating state at the detection time in the sampling period of crank angle 180°@, and the detection time (k
+ i) The intake pipe pressure is estimated. That is, the intake pipe pressure in the intake stroke is estimated based on the operating state of a predetermined cylinder 11 during the compression and explosion stroke.

In FIG. 3, 51 is a sensor group. Among the above sensors, detection signals of the intake pipe pressure PM and the rotational speed ω of the engine 1 are manually inputted to the first estimating section P1, and based on a predetermined map, which will be described later, The estimated air amount Ga of 1 is calculated, while the intake pipe pressure PM and the rotation speed ω.

Throttle opening TA, atmospheric pressure 1)a and intake air temperature TK
Each detection signal is manually input to the second estimating section P2, and a second estimated air amount ρa passing through the throttle valve 16 during one cycle is calculated based on an arithmetic expression described later. 1st above
The first estimated air amount Ca and the second estimated air amount Ma output from the estimating section P1 and the second estimating section P2 are manually input to the first calculating section P3, and are inputted to the first calculating section P3, and are inputted to the coefficient ft multiplication section P4 and the coefficient f.
A square multiplier P5 multiplies the signals by predetermined coefficients f1 and f2.

The multiplication result is output to the first adding section P6, where it is added to the intake pipe pressure P, and the first estimated intake pipe pressure value PM at the previous time (k+i) is output. This first intake pipe pressure estimate PM is input to the delay unit P8 of the difference correction unit P7, delayed by i steps, and input to the second addition unit P9, where it is added to the intake pipe pressure PH. . This addition result is multiplied by a predetermined coefficient f3 in a coefficient f3 multiplier PIO, and then added to the first estimated intake pipe pressure value F'M in a third adder pH. This addition result is output as the second intake pipe pressure estimation 1st shift f15M, and is used for estimating the synchronous injection amount, etc., which will be described later.

Next, each of the above components will be explained in more detail.

[1st estimator P1 The first estimator P1 calculates the amount of air taken into the cylinder 11 during one cycle based on the intake pipe pressure PM and the engine 1
The first estimated air amount Ca is calculated by interpolating a two-dimensional map determined in advance using the rotational speed ω of ω as a parameter.

[2] Second estimating unit P2 The second estimating unit P2 uses an arithmetic expression such as the following equation (2) using intake pipe pressure PM, rotational speed ω, throttle opening TA, atmospheric pressure Pa, and intake air temperature TK as parameters. Based on this, a second estimated air amount ρa corresponding to the amount of air passing through the throttle valve 16 during one cycle is output.

φ=[(d/ (d-1)) ((PM/Pa)"'
d-(PM/Pa) """) ko 1'2-(3
) However, Ca (TA) is the effective opening area of the throttle valve and is a value obtained from TA by one-dimensional map interpolation, d is the specific heat of the intake air, and R is the gas constant.

Here, φ in the above formula (3) is intake pipe pressure PM, atmospheric pressure P
When the intake pipe pressure PM is close to the atmospheric pressure Pa, that is, when the throttle opening is relatively large, the following equation (4
), the above formula (3) is applied as is, while the following formula (5) where the throttle opening is small
In the range that satisfies (range of ■), the following formula (6) is applied.

■ At high throttle opening PM/Pa > (2/Cd + 1))
d"d-"...(4) ■ At low throttle opening PM/Pa≦(2/(d+1)) ""-port...(5) φ=((2/(d+1) )) “Cd-’n-
(2d/ (d+1)) 1'2 ... (6) Second
The reason why the estimated air amount ρa is expressed by the above equation (2) and further divided according to the magnitude of the intake pipe pressure PM is as follows.

The flow of intake air passing through the constriction formed by the inner surface of the intake pipe of the engine 1 and the throttle valve 16 is less affected by viscosity, so the change in the intake air at this time is approximately treated as an isentropic change. be able to.

Therefore, the above equations (2) and (3) are expressed as Sun φ Bunane (S
t, V e n ant) and the gas equation of state.

However, the relationship that satisfies equations (2) and (3) is only in the range of equation (4), and in the range of equation (5), the flow velocity of the throttle valve 16 becomes equal to the speed of sound, and the intake air amount reaches its maximum value. It is maintained. The amount of intake air is the intake pipe pressure P
Throttle valve opening T without depending on M at all
The value depends only on A, that is, the value expressed by the above equation (6). Therefore, in a range where the throttle opening degree TA is large, that is, when the intake pipe pressure PM is close to atmospheric pressure Pa,
Expressed by the above equations (2) and (3), on the other hand, the throttle opening TA
is in a small range, that is, far from atmospheric pressure Pa, it is expressed by the above equations (5) and (6).

[3] First calculation unit P3 In the first calculation unit P3, the first estimated air amount Ca of the first estimation unit P1 is multiplied by a predetermined coefficient f1 in the coefficient f1 multiplication unit P4, and the second estimation A predetermined coefficient f2 is applied to the second estimated air amount ρa of gA1'''2 by a coefficient f2 multiplier P5.
are multiplied, and the results of these calculations are manually input to the first addition section P6. The first adding section P6 adds the intake pipe pressure PM at the time to these values and outputs the first estimated intake pipe pressure PM at the time (k+i). Therefore, the calculation executed by the first calculation unit P3 is expressed by the following equation (7).

PM=PM+fl◆Ca+f2◆Ma −= (
7) The first estimated intake pipe pressure value P is calculated by the error correction section P.
7, the delay unit P8 and the third addition unit pH are input manually.

[4] Error correction section P7 In the error correction FiBP7 described above, the delay section P8 has (k-
i) The first estimated intake pipe pressure value Pl estimated at time point 1 is manually inputted, delayed by time point j, and outputted as the estimated intake pipe pressure value Pl. This estimated value ρ is subtracted from the intake pipe pressure PM in the second correction section P9 as expressed by the following equation (8), and an error Err corresponding to the offset is output.

Mouth rr=door-PM...(
8) The error prr is calculated by the coefficient f3 in the coefficient f3 multiplier PIO.
is multiplied, and the first estimated intake pipe pressure value pH is further added in the third addition section pH, thereby outputting the second estimated intake pipe pressure value p at time (k+i). This calculation is expressed by the following equation (9).

pM=F'M+f3 ◆E r r
= (9) Note that the coefficient f3 in the above formula (9) is the first,
The second estimated air amount Ca, ρa and intake pipe pressure PM are set to 2
It is a parameter of one output of human power, and is determined by the observer design method in modern control theory. According to this method, the coefficient f3 is usually determined within the range of 0≦f3≦1.

Next, the process of calculating the second estimated intake pipe pressure value f5M will be explained based on the flowchart of FIG. 4.

In FIG. 4, first, in step 100, data such as intake pipe pressure PM is read. Next step 11
0, the first estimated air amount Ca taken into the cylinder 11 during one cycle is determined. This process corresponds to the first estimating unit P1 in FIG.
This is executed by determining the first estimated air amount Ca corresponding to the first estimated air amount Ca.

In the following step 120, a second estimated amount of air ρa passing through the throttle valve 16 during one cycle is determined. This process corresponds to the second estimator P2 in FIG.
The second estimated air amount ρa is determined based on the above-mentioned predetermined calculation formula (2) and the like.

In the next step 130, the first estimated intake pipe pressure value F'M at the previous time point (k+i) is determined. This processing corresponds to the calculation section P3 in FIG.

In the following step 140, (k−i
) The error Rrr between the first intake pipe pressure estimated value f'M at the time point estimated at the time point and the intake pipe pressure PM read at the time point is determined.

In the next step 150, the first estimated intake pipe pressure value PM
and the deviation prr, the second
Find the estimated intake pipe pressure flif'M.

This process corresponds to the process of the error correction section P7 in FIG.

That is, by repeating the processing from step 100 to step 150, the second intake pipe pressure estimate 11 can be accurately calculated.
5M can be found.

(TI) Synchronous injection determined for each predetermined crank angle by using the second intake pipe pressure estimate pM described above and the operating state such as the rotational speed ω at the time of detection in the process for estimating the synchronous injection amount. The process of determining the quantity q will be explained.

Here, we first introduce a model for finding synchronous injection 1 [<q,
That is, an example of a fuel behavior model based on so-called modern control theory using state equations, output equations, etc. will be explained. In the model below, the subscript n indicates an intake cycle, and the relationship between the above subscript and n is expressed as n=4.

The amount of fuel fc flowing into the cylinder 11 of the engine 1 is determined by the amount of synchronous injection q from the fuel injection valve 3, the amount of fuel fIA adhering to the wall of the intake pipe 14, and the amount of evaporated fuel f inside the intake pipe 14.
It can be written as in the following equation (10) using v.

fc=aL ◆q+a24w+a3φ fv
= (10) That is, the above fuel amount fc is determined by the direct flow amount α1・q of the injected fuel from the fuel injection valve 3, the indirect flow amount α2・fw from the intake pipe 14 to which the injected fuel adheres, and the injection fuel amount α1・q. Since it is considered to be the sum of the inflow amount α3·fv of evaporated fuel existing inside the intake pipe 14 due to evaporation of fuel or fuel adhering to the wall surface, the amount of fuel flowing into the air Wll as shown in equation (10) above is Therefore, the quantity fc can be described.

In the above equation (10), the synchronous injection amount q is determined by the control amount of the fuel injection valve 3, so the amount of fuel adhering to the wall surface of the intake pipe 14 f- and the amount of evaporated fuel within the intake pipe 14 fv are known. If so, the fuel amount fc can be predicted.

Therefore, next, consider the amount of adhered fuel fw and the amount of evaporated fuel fv.

First, the amount of fuel fw adhering to the wall of the intake pipe 14 is partially reduced by α2 in each intake cycle due to the inflow into the cylinder 11 during the intake stroke, and also decreases due to evaporation inside the intake pipe 14. The amount increases due to the adhesion of a portion α4 of the synchronous injection amount q injected from the fuel injection valve 3 in synchronization with the cycle.

Further, the amount of fuel FJP evaporated for each intake stroke can be expressed as α5·Vf/ω. Therefore, the amount of fuel f- adhering to the wall surface of the intake pipe 14 is calculated by the following formula (11
) can be written as shown below.

f w (n+1) = (1-a2) f w (n) + α
4*q(n)-α5・Vf(b)/ω(b)...
(11) On the other hand, the amount of evaporated fuel fν inside the intake pipe 14 decreases by a portion α3 in each intake cycle due to the inflow into the cylinder 11 during the intake stroke, and also by a portion of the synchronous injection amount q. α6 increases due to evaporation, and further increases due to fuel evaporation of the adhering fuel.

Therefore, the evaporated fuel FL amount fv in the intake pipe I4 is calculated by the following formula (12
) can be written as shown below.

f v(n+1)=(1-a3) f v(n)+a
6・q (n) + a5◆Vf(n)/c, +(n)
= (12) Next, the amount of fuel fc sucked into the cylinder 11 of the engine 1 is calculated from the fuel-air ratio input, which can be detected based on the oxygen concentration in the exhaust gas, and the air firm that has flowed into the cylinder 11.
It can be written as shown in the following equation (13).

fc=in・m (13) Therefore, if the coefficients α1 to α6 in each of the above equations are determined by the system identification method, the amount of fuel adhering to the wall of the intake pipe 14 and the amount of evaporated fuel are used as state variables, and the engine The following state equation (14) and output equation (15) expressed as a discrete system can be obtained using one intake cycle as a sampling period, and thereby a physical model representing the fuel behavior of the engine 1 is determined.

+(1-04-α6) q(n)...(15) The amount of evaporation Vf of fuel from the wall surface of the intake pipe 14 in the above model is determined by the saturated vapor pressure of fuel in the intake pipe 14 F)S and the intake air Pipe pressure P
Although it can be obtained as a function of M, here, the second estimated intake pipe pressure value pM obtained in the above process (2) is used instead of the detected intake pipe pressure PM.

Although it is difficult to directly detect the saturated vapor pressure Ps with a sensor, the saturated vapor pressure Ps is a function of the temperature of the fuel adhering to the wall surface of the intake pipe 14, and the adhering fuel temperature is determined by the temperature of the engine 1 over jacket water or the intake boat. Since the temperature can be represented by the cylinder head temperature around 5, the water temperature sensor 39 detects the overjacket water temperature or the cylinder head temperature, and an arithmetic expression such as the following equation (16) using the temperature T as a parameter is used. can be used to determine the saturated vapor pressure Ps.

Ps = β1-T2-β2◆T+β3-(16)
(However, β1, β2, β3: constant) Therefore, the amount of evaporation Vf of fuel from the wall surface of the intake pipe 14 is determined by determining the saturated vapor pressure PS based on the detection signal from the water temperature sensor 39, and calculating the saturated vapor pressure Ps and the second It may be determined using a data map or an arithmetic expression using the estimated intake pipe pressure value f5M as a parameter.

Further, the amount of air flowing into the cylinder 11, m, can be easily calculated using, for example, the following equation (17) using the intake pipe pressure PM, the intake air temperature TK, and the rotational speed ω of the engine 1 as parameters. be able to. Therefore, the amount of air m
can be determined using the above equation (17) based on the intake air temperature TK and rotational speed, using the second intake pipe pressure estimate pM as the intake pipe pressure PM. Also, the second intake pipe pressure estimation f+! The air amount m can also be determined by determining the basic air amount m using a map using H5M and the rotational speed ω as parameters, and correcting the calculation result using the intake air temperature Tk.

Next, the control system used for this control will be explained based on the block diagram shown in FIG.

This control system is designed based on the physical model shown in equations (14) and (15) above.

As shown in FIG. 5, in the control system of this embodiment, the cooling water temperature TR detected by the water temperature sensor 39 is first
is man-powered. In the second calculation section Q1, the manually inputted cooling water temperature signal is converted into the saturated vapor pressure Ps of the fuel in the intake pipe 14 using the above-mentioned calculation formula (16), and furthermore, the converted saturated vapor pressure Ps is Using the vapor pressure Ps, the amount of evaporation Vf of fuel from the wall surface of the intake pipe 14 is determined. In addition, the converted evaporation amount Vf is manually inputted to the dividing section Q2, and the rotational speed ω
divided by Then, the division result Vf/ω is manually input to the coefficient f8 multiplier Q3, and the preset coefficient f8
is multiplied.

On the other hand, the rotational speed ω is also manually input to the third calculation unit Q4 along with the second estimated intake pipe pressure value pM outputted from the RAM 45 and the intake air temperature Tk detected by the intake air temperature sensor 13. This third calculation unit Q4 calculates the amount of air flowing into the cylinder 11 based on the rotational speed, the second estimated intake pipe pressure value 119M, and the intake air temperature TK using a calculation formula such as the above-mentioned formula (17). This is for calculating m, and the calculation result is
It is output to the fourth arithmetic unit Q5 and the fifth arithmetic unit Q6. Then, in the fourth calculation section Q5, the fuel-air ratio λ of the fuel mixture that has flowed into the cylinder 11 detected by the oxygen sensor 25 is multiplied by the air amount m calculated in the third calculation section Q4. The amount of fuel actually flowing into the cylinder 11 (actual fuel amount) λm is calculated.

Further, in the fifth calculation section Q6, the target fuel/air ratio input set according to the load of the engine 1 is multiplied by the air amount m calculated in the third calculation section Q4. The desired fuel amount (target fuel amount) λ'm is calculated. Then, the target fuel amount large rm calculated by the fifth calculation section Q6 is manually inputted to the coefficient f7 multiplication section Q7, and multiplied by a preset coefficient f7. be done.

Further, the calculation results of the fourth calculation unit Q5 and the fifth calculation unit Q6 are both manually inputted to the deviation calculation unit Q8, and the deviation m(λ−λr)
is calculated. Then, the calculation results are sequentially added in an adding section Q9, and the calculation results are multiplied by a preset coefficient f6 in a coefficient f6 multiplication section QIO.

On the other hand, the actual fuel amount λm calculated by the fourth calculation unit Q5 and the division result Vf/ω of the division unit Q2 are also output to the observer Qll. The observer Qll calculates the actual fuel amount λm and the division result V of the division unit Q2 using a preset arithmetic expression.
f/ω, the synchronous injection amount q from the fuel injection valve 3, and the previously estimated amount of fuel adhering to the wall of the intake pipe 14? enemy and intake pipe 1
Amount of evaporated fuel in 4? This is for estimating the amount of adhering fuel f- and the amount of evaporated fuel fv from V, and the estimation result?
Enemy? V is multiplied by coefficients f4 and f5 by a coefficient f4 multiplier Q12 and a coefficient f5 multiplier fl (Q13), respectively.

The multiplication results from these multiplication units Q12 and Q13 are added together with the multiplication results from other multiplication units Q3, Q7, and QIO in addition units 014 to Q17, thereby making it possible to estimate the synchronous injection amount q. can.

In this example, Smith-Da
vison) using the design method described in (14) above,
Based on the physical model shown in equation (15), the following (1
A formula for calculating the synchronous injection amount q shown in the following formula is derived.

q=f4・fw+f5◆fv+soft f6◆m(j)sha(λ
(j) - input r) +f7◆m input "+f8・vf/ω...(1st) As for the design method of this kind of control system, for example, the system "Digital control of real systems" written by Katsuhisa Furuta and Control, Vol.
, 2B, (A30.12 (1984) Society of Instrument and Control Engineers, Special JMI No. 62-189889, etc.), so the process of deriving the formula (1st) will be omitted here.

Furthermore, since the observer Qll cannot directly measure the amount fw of fuel adhering to the wall surface of the intake pipe 14 and the amount fv of evaporated fuel within the intake pipe 14, it is used to estimate the values thereof. As an estimation method using this observer, for example,
Minimal 0rder 0
bserver), same-dimensional observer (Identi
ty 0bsr, rver), finitely settled observer (D
eadBeat 0bserver), Linear Function Observer (Linear Function 0bserver)
er) or an adaptive observer (Adapt i veOb
"Basic System Theory" by Katsuhisa Furuta et al. (1978) Corona Publishing, or "Mechanical System Control" by Katsuhisa Furuta et al. (1988) Ohm Publishing, etc.
It can be constructed using the well-known design method detailed in .

Next, a method of designing the observer Q11 used in the above control system will be explained. The Gobibus design method is known as a design method for this observer Q11, and is detailed in "Basic System Theory" (cited above). Here, we will briefly explain how to design a minimum dimension observer.

The general system of the observer of the physical model in this example is expressed by the following equation (
19).

x(n+1)=A・x(n)+ ]R−y(n)+f
f·u(n) (19) Therefore, the observer Qll of this embodiment can be designed as shown in the following equation (20), and thereby the amount of attached fuel fw and the amount of evaporated fuel fv can be estimated.

Next, a process for determining the synchronous injection amount q based on the above-mentioned fuel behavior model will be explained based on the flowchart of FIG. 6.

In FIG. 6, first, step 200 and step 2
10ζ At this point, initial values are set. That is, step 200
So, how much fuel is attached? Wow, amount of evaporated fuel? The VO is initially set to 0 and the synchronous injection amount q@qO is set, and in the subsequent step 210, the integral value Smλ of the deviation between the actual fuel amount λm and the target fuel amount λrm is determined.
Set to O.

Next, in step 220, step 10 in FIG.
0 to the second estimated intake pipe pressure pM calculated in step 150, and further reads the rotational speed sensor 32. Water temperature sensor 39. From the output signals of the intake air temperature sensor 20, oxygen sensor 25, etc., the rotational speed ω of the engine 1, the cooling water temperature TR,
Read operating conditions such as intake air temperature Tk and fuel/air ratio λ.

In the next step 230, a target fuel-air ratio input according to the load of the engine 1 is calculated based on the second estimated intake pipe pressure value pM and the rotational speed ω read in step 220.

When the target fuel/air ratio input is set in step 230, the process moves to step 240, and the second intake pipe pressure estimated value PM
Based on the intake air temperature i and rotational speed ω, the above (17)
The amount m of air flowing into the cylinder 11 is calculated using the arithmetic expression or data map shown in the following equation. That is, it executes processing as the third calculation unit Q4.

In the subsequent step 250, the amount of evaporation Vf of fuel from the wall surface of the intake pipe 14 is determined based on the cooling water temperature TR, the value is divided by the rotational speed ω of the engine 1, and 1 of the intake stroke salt from the previous intake stroke to the next intake stroke is calculated. The amount of evaporation Vfw (ie, Vf/ω) from the wall surface of the intake pipe 14 that evaporates during the cycle is calculated.

Then, in step 260, the fuel-air ratio λ is multiplied by the air amount m obtained in step 240 to calculate the actual fuel amount λm that flowed into the cylinder 11 during the previous intake stroke, and the fourth calculation unit Execute the process as Q5 and proceed to step 27.
Transition to 0.

Step 270 includes the actual fuel amount λm obtained in step 260, the previous synchronous injection amount q, and step 250.
The amount of evaporation of fuel from the wall surface of the intake pipe 14 in one cycle, Vf-, which was determined by ?, and the amount of adhering fuel, which was determined last time? wo and evaporated fuel amount? Based on VO, the amount of adhering fuel is calculated using the formula (20) above. W and amount of evaporated fuel? Processing as an observer Qll to estimate ν is executed.

Then, in the following step 280, the step 230
After executing the process as the fifth calculation unit Q6, which calculates the target fuel amount λrm flowing into the cylinder 11 by multiplying the target fuel air ratio input set in step 240 by the air amount m obtained in step 240 above. , transition to step 290.

In step 290, the integral value Smλ of the deviation between the previously determined actual fuel amount λm and the target fuel amount large rm and the step 2
The amount of attached fuel found in 70? - and amount of evaporated fuel? V, the target fuel amount λ"m obtained in step 280, and step 2
From the fuel evaporation amount Vfw of one cycle found in 50,
The synchronous injection amount q is calculated using the above-mentioned equation (19), and the process moves to step 300.

Then, in step 300, at the fuel injection timing determined based on the detection signal from the crank angle sensor 34,
According to the synchronous injection amount q calculated in step 290,
The fuel injection valve 3 is opened to perform synchronous injection control.

In the following step 310, the actual fuel amount λm obtained in step 260 and the target fuel amount λ" obtained in step 280 are determined.
The process as a sequential addition unit Q9 is executed to obtain an integral value Smλ by adding the deviation from m to the previously determined integral value 8m people, and the process moves to step 320.

Then, in step 320, the amount of attached fuel is determined in the next process?
amount of fuel and vaporized fuel? What are the standard values for the amount of attached fuel and amount of evaporated fuel used to estimate V? wo, as YVO,
The amount of adhering fuel found in step 270 above this time? W and amount of evaporated fuel? V is set, and the process moves to step 220 again.

That is, by the processing of steps 200 to 320 described above, the synchronous injection amount q is appropriately calculated based on the second estimated intake pipe pressure value pM according to the operating state i cycles ahead from the time when the operating state is detected. can do.

(III) Asynchronous injection control processing The asynchronous injection control processing executed after it is determined that the vehicle is in an acceleration state will be described based on the flowchart of FIG. 7.

At step 400 in FIG. 7, the throttle opening TA
data is read every 16 m5, for example.

In step 410, the current throttle opening TA is compared with the previously read throttle opening TA to determine whether the increase ΔTA in the throttle opening within a certain period of time is greater than or equal to a predetermined value. Here, the increase in throttle opening △
If it is determined that TA is greater than a predetermined value, that is, the acceleration state is determined, the process proceeds to step 420, while if it is determined that the acceleration state is not, the present process is temporarily terminated.

In step 420, the increase amount Δ of the throttle opening is
The second estimated intake pipe pressure value PM immediately after acceleration is determined again from TA and the operating state such as the rotational speed ω several cycles before immediately after acceleration, which is stored in the RAM 45.

In the following step 430, the sixth intake pipe pressure estimation value f5M is calculated based on the second estimated intake pipe pressure value f5M immediately after acceleration obtained in step 420, and the data of the operating state several cycles before immediately after acceleration.
Processing similar to steps 220 to 290 for determining the synchronous injection amount q shown in the figure is performed to determine the estimated injection amount qi required immediately after acceleration.

In the subsequent step 440, a fuel amount Δq is calculated as the difference between the estimated injection amount qi calculated in step 430 and the synchronous injection amount q calculated or injected in step 290 of FIG. 6 above before this calculation.

In the subsequent step 450, a process is performed to asynchronously inject this difference in fuel amount Δq, and the process is temporarily terminated.

Next, the processes performed in steps 400 to 450 will be described in detail using the graph shown in FIG. 8 showing changes in operating conditions.

As shown in the figure, immediately after time tt4, the throttle opening TA
When an acceleration state is detected from the increase ΔTA, the second estimated intake pipe pressure value pM at time tt5 is changed again.
Find 5. As data when calculating this second intake pipe pressure estimate pM5, the throttle opening TA immediately after acceleration and the data of the operating state at time tt2 are used, and the same steps as steps 100 to 150 shown in FIG. 4 are performed. The process is performed to obtain the first estimated air amount Ca and the second estimated air amount 1'la, and calculate the second estimated air amount Ca corresponding to time tt5 immediately after acceleration.
This is to obtain the estimated intake pipe pressure value pM5.

Next, based on the second estimated intake pipe pressure value PM5 and the operating state at time 112, processing similar to step 220 to step 290 shown in FIG. 6 above is performed,
Estimated injection amount qi5 required at time tt5 is calculated.

Then, the difference between the estimated injection amount qi5 obtained in this way and the synchronous injection amount q5 that has already been injected is determined, and the fuel amount Δq5 corresponding to the difference is injected asynchronously, thereby quickly supplying the insufficient amount of fuel. be able to.

Therefore, the lack of fuel immediately after acceleration (time tt5) can be quickly compensated for, thereby preventing the air-fuel ratio from shifting toward the lean side immediately after acceleration.

By repeating the same process, time 116,
Second intake pipe pressure estimate PM6.1'M at tt7
7 can be found, and based on their operating conditions,
Appropriate estimated injection amount qi6. By calculating qi7, it is possible to compensate for the lack of fuel for several cycles immediately after acceleration.

Therefore, by performing the above-described processing, the following effects can be obtained.

When an acceleration state is detected due to a change in the throttle opening TA, the process of calculating the second intake pipe pressure estimate pM is performed again, so that an appropriate second intake pipe pressure estimate 15M can be obtained according to the acceleration state. I can do it. Furthermore, since the estimated injection amount qi is calculated using the second estimated intake pipe pressure value f5M, it is possible to accurately calculate the amount of fuel actually required immediately after acceleration.

Then, this calculated estimated injection amount qi is compared with the synchronous fuel amount q actually injected just before acceleration by synchronous injection, and the shortfall in fuel amount is quickly supplied by asynchronous injection. The fuel injection can be appropriately controlled, and the air-fuel ratio can be prevented from shifting toward the lean side. Therefore, driveability and emissions can be maintained suitably.

Note that in this embodiment, the second estimated intake pipe pressure value PM was used to calculate the synchronous injection amount q, but the first estimated intake pipe pressure value P
M may also be used. Furthermore, to calculate the synchronous injection amount q, the intake pipe pressure may be estimated using a model of intake pipe pressure other than the physical model of this embodiment, and the synchronous injection amount q may be calculated based on the estimated value. . Furthermore, the accelerator opening corresponding to the throttle opening TA may be used to detect the acceleration state.

Furthermore, in the above embodiment, depending on the asynchronous injection amount supplied during acceleration, the amount of adhering fuel used to calculate the synchronous injection amount q? - and amount of evaporated fuel? The value of ν may be reset. This amount of attached fuel? and amount of evaporated fuel? By correcting (1) by 11, the fuel behavior can be expressed more accurately, so the fuel injection amount can be controlled more appropriately.

[Effects of the Invention] As explained above, according to the present invention, when an acceleration state is detected, the intake pipe pressure is estimated, the estimated injection amount is calculated based on the estimated intake pipe pressure, and the estimated injection amount is calculated based on the estimated intake pipe pressure. Since the difference between the amount of fuel and the synchronous injection amount already calculated or injected before acceleration is determined, and the insufficient amount is injected asynchronously, appropriate fuel injection control can be performed immediately after acceleration. This prevents the air-fuel ratio from shifting toward the lean side immediately after acceleration, so drivability and emissions can be maintained suitably.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing an example of the basic configuration of the present invention, Fig. 2 is a block diagram showing an engine and peripheral control device according to an embodiment of the present invention, and Fig. 3 is a control system for estimating intake pipe pressure. Figure 4 is a flowchart showing the process of estimating the intake pipe pressure, Figure 5 is a flowchart of the control system that calculates the synchronous injection amount, and Figure 6 is the process of calculating the synchronous injection amount. FIG. 7 is a flowchart showing processing for controlling the asynchronous injection amount, FIG. 8 is a graph showing changes in intake pipe pressure and synchronous injection amount, and FIG. 9 is an explanatory diagram of the prior art. Ml...Internal combustion engine M2...Operating state detection means M3...Fuel injection valve M4...Synchronized injection control means M5...Acceleration determination means M6...Intake pipe pressure estimation means M7...Injection Quantity estimating means M8... Asynchronous injection means 1... Engine 19... Atmospheric pressure sensor 20... Intake temperature sensor 21... Throttle position sensor 22... Intake pressure sensor 32... Rotational speed sensor 40...Electronic control device agent Patent attorney Tsutomu Sadatsu (and 2 others) Figure 1 Figure 4 Figure 6

Claims (1)

[Scope of Claims] Operating state detection means for detecting the operating state including the rotational speed and intake pipe pressure of the internal combustion engine, and calculating the synchronous injection amount using the operating state detected by the operating state detection means. A fuel injection amount control device for an internal combustion engine, comprising: synchronous injection control means for controlling fuel injection by driving a fuel injection valve based on the amount of fuel injection; , an acceleration determination means for determining whether or not the acceleration state is present based on a change in the driving state indicating acceleration; and when the acceleration determination means determines that the acceleration state is present, the acceleration detected by the driving state detection means is detected. an intake pipe pressure estimating means for estimating the intake pipe pressure beyond the time of detection of the operating state using the operating state shown and at least the intake pipe pressure and rotational speed detected before acceleration; and the intake pipe pressure estimating means Estimated intake pipe pressure and
Using the operating state detected by the operating state detection means, the fuel behavior is estimated according to a fuel behavior model consisting of a state equation and an output equation that describe the behavior of the fuel in the internal combustion engine, and the result is adapted to the operating state after acceleration. an injection amount estimating means for calculating the estimated injection amount; and an injection amount estimating means for calculating the fuel amount difference between the estimated injection amount calculated by the injection amount estimating means and the synchronous injection amount calculated by the synchronous injection control means, and determining the fuel amount for the difference. 1. A fuel injection amount control device for an internal combustion engine, comprising: asynchronous injection control means for asynchronously injecting;