JPH0422724A - Control method for fuel injection of engine - Google Patents

Abstract

PURPOSE:To compensate the fuel transport delay for each cylinder with good preciseness by providing a process corresponding to the element with the 1st order phase advance and a process corresponding to the element with the 2nd order phase advance for farther, and using either process to perform compensation of fuel transport delay of at least one cylinder. CONSTITUTION:Signals from a pressure sensor, throttle angle sensor, water temp. sensor, crank angle sensor, suction air temp. sensor, and oxygen sensor are fed to a control unit which is equipped with a CPU, ROM, RAM, timer, I/OLSI and another timer, and the fuel injection amount is calculated at certain intervals. In this calculation, either a process with the element of 1st order phase advance or its equivalent or a process with the element of 2nd order or farther phase advance or its equivalent is used to compensate the fuel transport delay of any one cylinder, and in this fashion, fuel transport delays of all cylinders are compensated individually by means of one or both of these processes. Thus the fuel control is made for the cylinders individually so that the fuel transport delay are compensated by cylinders, and thereby precise control of the air fuel ratio for a plurality of cylinders is achieved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an engine fuel injection control method suitable for accurately compensating for fuel transport delays for each cylinder in an engine with a multi-point fuel injection system.

[Conventional technology]

In order to compensate for the fuel transport condition caused by the injected fuel adhering to the intake pipe wall surface etc. in an engine with a multi-point fuel injection system, the present applicant has proposed Japanese Patent Application No. 1-227367.
In this method, all of the injected fuel temporarily adheres to the intake pipe wall, and during the subsequent intake stroke, a portion of the adhered fuel flows into the cylinder to express the fuel transport characteristics. There is. Furthermore, this model is used to control fuel for each cylinder to fully compensate for fuel transport delays.

Furthermore, the amount of retained fuel (the amount of liquid film) representing the fuel condition in the intake pipe is updated once every 22 engine revolutions.

Further, the cylinder for the next fuel injection is determined, and the fuel injection amount is calculated only in the determined cylinder, thereby reducing the calculation load.

[Problem to be solved by the invention]

In the prior art described above, the fuel transport characteristics are approximated by a linear transfer function.

GI: Fuel injection amount (g/5) Gje: Cylinder inflow fuel amount (g/s) T:
From the variable equation (1) that depends on the engine operating state, it can be seen that the fuel transport characteristics are regarded as a first-order lag.

On the other hand, SAE poper 890837 reports that when the intake pipe internal pressure is close to atmospheric pressure or when the water temperature is low, the fuel delay is formulated as a second-order delay.

The behavior of fuel in the intake pipe is very complex, and as reported above, it is thought that in some cases, second-order lag can express the characteristics more accurately in a partial region.

In the above-mentioned conventional technology, since the fuel compensation algorithm compensates for the first-order delay, there is a problem that such second-order or higher-order delays cannot be compensated with high accuracy.

Furthermore, in the prior art, the amount of liquid film is updated once every two rotations of the engine. Two revolutions of the engine corresponds to a time of 120 m5ec, assuming the number of revolutions is 1100 orp. In the case of sudden acceleration at 120 m5ec, although the state inside the intake pipe changes greatly, the above-mentioned conventional technology attempts to estimate this state with only one calculation, resulting in a large estimation error. This poses a problem in that desired control performance cannot be obtained.

Furthermore, in the prior art, the fuel injection amount is calculated only in the cylinder to which fuel is to be injected next time. This calculation cycle is 10
It is m5ec. When the rotation speed is greater than 3000 rpm, from when the fuel injection amount is calculated at a certain time until the next time when the fuel injection amount is calculated, that is, 10m5e.
During c, the crank angle changes by more than 180 degrees. 4
In the case of a cylinder engine, fuel injection may be performed twice during this period. In the prior art, the fuel injection amount is calculated only for the cylinder to which fuel is to be injected next, so in the above case, there is a problem in that the fuel injection amount for the next cylinder to be injected is not calculated.

An object of the present invention is to provide a fuel injection control method for an engine that eliminates the above-mentioned problems.

[Means to solve the problem]

In order to achieve the above purpose, the following means (1) will be provided.

(1) In an engine electronic control device for a multipoint fuel injection system that controls the fuel injection amount based on the intake air amount,
1st order phase advance element or equivalent processing, or 2
Any one of the next or more advanced elements or their equivalent processes compensates for fuel transport delays for one cylinder, and fuel transport delays for all cylinders are compensated for independently by one or more of the above processes.

(2) In the above-mentioned electronic control device, the first-order phase advance element or one of the processes equivalent thereto is used to compensate for the fuel transport delay of one cylinder, and the fuel transport of all cylinders is reduced to one of the above-mentioned processes. Compensate for one or more.

aoS n10a 1 S n-1+ ...+ a
n -1S + a nHere, S nira plus operator n≧1 n≧m≧O an=bmf-0 an-0≠○ However, among the above elements, the following elements are excluded: a□-I S + a n (an-1≠O) b.

(3) In (1) and (2), the fuel transport delay of at least one cylinder is compensated for using a (proportional + differential) element or equivalent processing, and the fuel transport delay of all cylinders is compensated for by the above process. Make sure you don't do it.

(4) In (1) to (3), the fuel transport state is estimated and calculated for each cylinder.

(5) In (4), the fuel transportation state is estimated and calculated at predetermined time synchronization.

(6) In (5), the predetermined time is set so that the predetermined time is less than the time required for two revolutions of the engine at a predetermined rotation speed or less.

(7) In (4), the fuel transport state is estimated at a predetermined crank angle cycle.

(8) In (7), the predetermined crank angle is set smaller than the crank angle equivalent to two revolutions of the engine.

(9) In (7), the predetermined crank angle is made variable depending on the engine operating state.

(]O) In (1) to (9), the fuel injection amount is calculated at a predetermined time period.

(1, 1,) In (10), at a certain fuel injection amount calculation time, the cylinder to which fuel injection is to be performed is determined by the next fuel injection amount calculation time, and the fuel injection amount is calculated only for the determined cylinder.

(12) In (1) to (1), the latest fuel injection amount is calculated based on the past executed fuel injection amount.

(13) In an engine electronic control device that controls the fuel injection amount based on the intake air amount, the fuel transport delay is compensated for using a third-order or higher phase advance element or equivalent processing.

[Effect]

In the method described above, since the fuel transport delay is accurately calculated using a higher order delay, control performance can be improved.

In addition, the fuel condition in the intake pipe can be estimated in a shorter time period.
Since the information is updated, the accuracy of estimating the fuel condition can be ensured. Thereby, desired control performance can be obtained.

Also, without calculating the fuel injection amount in each cylinder,
There will be no more fuel injection.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 to 9.

In order to construct a fuel control system, it is first necessary to formulate the fuel transport delay characteristics until the injected fuel flows into the cylinder. This method will be explained according to FIGS. 1 to 2.

Here, we will show a modeling method when the fuel system dynamic characteristics are set to a quadratic or less delay as shown in the following equation.

Gf: Fuel injection amount (g/5) Gie: Cylinder fuel amount (g/5) Th (i = 1, 2.3): When the variable characteristics that depend on the engine operating state are expressed as an equation, its modeling The question is how to determine the model parameter T1. The method for setting TI will be explained below.

Expressing equation (2) as a continuous time domain differential equation results in the following equation.

Furthermore, equation (3) is discretized using central difference to obtain the following equation.

2Δt 2Δt i: Time (time 2 corresponds to Δt) Δt: Time step for discretization Also, the intake air amount at time j is Qa(i) - the exhaust air-fuel ratio near the exhaust valve is A/F(i) ), Gze(1) can be obtained from these variables using the following equation.

From the formula, Eliminate ate and get the following formula Ru.

moreover, X in the following formula.

T.

Define Z.

X=T,・ Y = Tx + Ti Z=T3 At this time, The formula is as follows.

−□ [Gt(j+1)−Gz(i−1)] j Z−
Gz(i)202Δt Three variables in equation (10) Q a = A / F, G
All x is measurable. Also, equation (10) is x, y, z
is linear with respect to Therefore, if the intake air amount Q& is a predetermined value and the response A/F of the air-fuel ratio is measured when the fuel injection amount Q is changed under predetermined conditions, then from these time series data, by the maximum /IX square method, Parameters x, y, and z can be uniquely determined using only four arithmetic operations. Furthermore, (7) to (9)
) is used to calculate Ti.

Here, the accuracy of parameter calculation depends on the measurement accuracy of time-series data. The response delay of the air-fuel ratio sensor that measures the exhaust air-fuel ratio is relatively large, and highly accurate parameter calculation cannot be performed unless this is taken into account.

Therefore, an equation is derived that takes into account the response delay characteristics of the air-fuel ratio sensor, and parameters are calculated.

First, the response delay characteristics of the sensor are formulated. FIG. 1 shows the response of the measured air-fuel ratio when changing the air-fuel ratio in steps. is is the response start time, ie is the response end time, and the measured air-fuel ratio at time i is A/F-oO).

The response characteristics of the sensor are formulated using this measured value using a moving average model of the fuel-air ratio. Its characteristic formula is as follows.

A/F: true air-fuel ratio A/F,: measured air-fuel ratio (10) By eliminating A/F from equation (11), the following equation can be obtained that takes into account the response delay characteristics of the sensor.

a(i)・X+b(i)・Y+c(i)・z+d(i)
=0j''j, s A/F, ,: Parameter X by applying the least squares method to the measured air-fuel ratio equation (13).

Y.

Calculate Z.

The evaluation finger $11J is calculated by the equation error. It is defined as the sum of squares using the following formula.

J=Σ(a(i)−X+b(j,)・Y+c(i)4+
d(i))2i (J8) The parameter that minimizes J can be found by solving the following simultaneous equations.

Expressing equation (19) using a matrix gives the following equation.

Using Cramer's formula, Solving the equation The solution is as follows.

Δ When equations (7) to (9) are solved for Ti (i=1.2.3), the following equation is obtained.

Using equation (25), Ti (i=1
．． 2.3) can be calculated.

In order to calculate Ti, time series data of the variables Gi, A/F-, and Qa included in equations (14) to (17) and the value of d are required. These data are measured or set, for example, in a first-order manner.

FIG. 2 shows the response of the measured exhaust air-fuel ratio A/F when the engine is operated with the intake air amount Qa kept constant and the fuel Gi is changed in steps. Time U0 is the time when the fuel is changed stepwise, jS' is the time when the response of the exhaust air-fuel ratio starts, and 1e' is the time when the response ends. ]5
', 1, and e' are determined appropriately by drawing the air-fuel ratio response on a graph and visually observing it.

d, which is the time from intake to exhaust, is i as shown in the figure.
It is calculated from the difference between s' and io. G, and A,/F.

The digital values of the response shown in FIG. 2 are used as the time series data, and the air amount Qa, which is a constant value, is the measured value of an air amount sensor such as a H/W sensor.

Also, the range of the summation in formulas (21) to (24) is the lowest]o=
The range is from (is' d) to (ie' d). From the above data, Tj, (i=1.2°3) can be calculated.

The fuel system dynamic characteristics of an engine change depending on the engine operating state and operating environment. The controlling factor is the intake air amount Q
Possible parameters include a, intake pipe internal pressure PM, engine speed N, water temperature Tw, intake temperature TM, atmospheric temperature Ta, and atmospheric pressure P8.

Naturally, when these variables change, the value of parameter T also changes. Therefore.

The parameter T1 is calculated based on data measured by fixing all of the above variables and operating the engine at a steady state. The calculation of the parameter T1 is repeated under various operating conditions and environmental conditions, and from the obtained results, the characteristics of the parameter Ti are formulated as a function of the above variables. Since it is difficult to formulate the equation as a function of all variables, it is defined as a function of only particularly dominant factors. If the factors are PM, N, and Tw, then T is as follows.

TI=fj(PMF NP Tl1) (i=
11 2.3) fl: A function of three variables PM, N, and Tw is a method of modeling fuel system dynamic characteristics in a cylinder in which the order is less than or equal to second order. In an engine with a multi-point fuel injection system, fuel transport characteristics may differ from cylinder to cylinder due to variations in injector characteristics, differences in intake pipe configuration, differences in fuel injection angle, etc. Therefore, modeling is performed for each cylinder using the above method. As a result, if no difference in characteristics is found between cylinders, all cylinders are assumed to have the same characteristics. If there are differences in characteristics,
Set characteristics according to each cylinder.

The fitness of the model when the response of the air-fuel ratio calculated from the obtained parameter Ti and equations (13) to (17) and the response of the measured air-fuel ratio do not match accurately, that is, when the order is set to 2nd order or less If is low, modeling may be performed assuming a higher order delay.

Next, the configuration of a control system for compensating for fuel transport delays will be explained based on the mathematical model obtained according to FIGS. 3 to 5.

FIG. 3 shows a fuel control system for a certain cylinder in a multi-point fuel injection system. Block 31 calculates the fuel injection amount at a predetermined time period. The fuel injection amount Gz(i) at time l is calculated by the following equation.

Here, Qa: Target air intake amount (g/s) A/F: Target air-fuel ratio Gie: Cylinder fuel amount (g/5) aJ, bJ: Variables that depend on the engine operating state Variables aJ, bJ are block 32, the intake pipe internal pressure PM, engine speed N, and water temperature T are determined based on a predetermined calculation formula.
Determined from w.

(27) and the function F1J(ji
, GlJ (i) are determined as follows.

Suppose that when the fuel transport characteristics are assumed to be expressed by equation (2), the model parameters are formulated as shown in equation (26) using the method described above.

From equation (2), the following discrete equation representing the fuel transport characteristics can be obtained.

Replace i with i-1 expression) Get the formula.

j=1 j:0 When the amount of intake air at time i is Qa, the following equation should hold true in order to achieve the desired air-fuel ratio A/F.

(29) and (35) by eliminating -e(i) and Gf(
Solving for x) gives the calculation formula for the fuel injection amount (27)
The formula is obtained.

The functions F1J and G1- of block 32 are (30) to (
By substituting equation (26) into equation (34), it can be obtained as follows.

Fx o (F'p+, N, Tw) Fl, (P+, N, Tw) 2・Δt2 F, 2 (PM, N, TV) Δt-fi (PM, N, Tll+) Ga, (P+, N, Tw) ・f, (PM, N, TV)
+Δt' (f, (Px, N, Tw) + f2 (PM,
N, TV)) q□(PM, N, Tw) 2・Δt”−4・f, (PM, N, TV) ・f2(
PM, N, TV) Zf, (PM, N, Ding w)% (PH
-N-TIJ) 1Δt・(f, (PM, N, Tw) + f
2 (PM, N, TI)) G, 2 (PM, N, TV) 2f, (PM, N, Tw)・f, (P+, N, Tw)
−Δt−(fx (PxlN, TV)+f2 (Ps,
N, Tw)) The value of Δt in the formula is set to be equal to the calculation period of G.

In equation (27), the calculation of the fuel injection amount Gz(i) is as follows:
The past cylinder inflow fuel amount Gze(ij) is used. This value is calculated in block 33 using equation (29).

Furthermore, in calculating the fuel injection amount at(i) in block 31, the past fuel injection amount Gi (1-j, ) t(j=
1.2) In the calculation of the cylinder flow rate in block 32, the fuel injection amount Gx (i-j) from the current time i to two hours ago is used.
(j=o, 1.2) is used. As these values, the calculated values in block 31 are not used as they are, but the values processed in block 34 are used.

In block 34, the time when the latest effective fuel injection amount was calculated in the corresponding cylinder is i. , the time when the previous effective fuel injection amount was calculated is 1. Then, the fuel injection amount Gi(fl) (Q≦i) up to the current time i is set according to the following equation.

The process of block 34 is for calculating the next fuel injection amount and the cylinder inflow fuel amount based on the past executed fuel injection amount.

In block 35, the fuel injection pulse width is calculated based on the fuel injection amount calculated in block 31 according to the following equation.

This concludes the explanation of the fuel control system for a certain cylinder.

In a multi-cylinder engine, the fuel control system shown in FIG. 3 is set for each cylinder to control fuel. for example.

The configuration of the control system for a four-cylinder engine is shown in FIG. The control system in FIG. 3 is set to blocks 41a to 41d, and the injection pulse width of each cylinder T I JF = 1-+ 2
* Performs the calculation 3+4). Naturally, variables such as Git Gte+aJ+bJ are set independently for each cylinder, and the calculations and updates of these values are performed independently.

The calculation cycle of each block of the control system that controls the fuel injection amount is normally set to 10 msec. This cycle is sufficient to ensure accuracy in estimating the amount of fuel flowing into the cylinder, which indicates the fuel transport state.

In the configuration shown in FIG. 4, the calculation load can be reduced by not calculating the fuel injection amount for all cylinders, but only for the high-quality cylinders determined according to the following conditions.

Here, the calculation cycle of each block of the control system is assumed to be 10 m5ec, which is set in a normal control system. In the case of a 4-cylinder 4-cycle engine, the conditions are as follows.

(1) If the rotational speed detected every 10 m5ec in synchronization with the calculation of the fuel injection amount is within (3000-ΔN) rpm, the fuel injection amount is calculated only in the cylinder in which fuel will be injected next. Here, ΔN is set to several hundred. The fuel injection amount is not calculated for other cylinders.

(2) The above rotation speed is (3000-ΔN) rpm or more, (
6000-2ΔN) rpm, the fuel injection amount is calculated only for the next and subsequent cylinders in which fuel is injected.

(3) The above rotation speed is (6000-2ΔN) rpm or more,
(9000-3ΔN) within rpm.

Calculates the fuel injection amount for all cylinders other than the latest cylinder in which fuel was injected.

(4) When the rotational speed is equal to or higher than (9000-3ΔN) rpm, the fuel injection amount for all cylinders is calculated.

In the case of a 4-cylinder 4-stroke engine, the crank angle change from when the fuel injection amount is calculated at a certain time until the next fuel injection amount is calculated is within 180 degrees if the rotation speed is within 3000 rpm. . Therefore, in the case of a four-cylinder engine, if the rotational speed is within 3000 rpm, fuel injection is performed only once between two fuel injection amount calculation periods. At this time, it is sufficient to calculate the fuel injection amount only in the cylinder to which fuel will be injected next. This is condition (1). The reason why the rotational speed is not within 3000rpm under the condition (1) is that the rotational speed is 3000rpm or less at a certain fuel injection amount calculation time.
Even if it is within pm, the next fuel injection amount calculation time will be 3000.
rpm may be exceeded, and in this case, fuel injection may be performed twice between two calculation periods. In order to ensure that the rotational speed is within 3000 rpm until the next calculation time and to inject fuel only once, the rotational speed is set within (3000-ΔN) under condition (1).

When the rotational speed exceeds 3000 rpm, fuel injection may be performed twice or more between two fuel injection amount calculation periods (10 msec). At this time.

It is necessary to calculate the fuel injection amount for all cylinders that perform fuel injection. In other words, when performing two fuel injections, the fuel injection amount is calculated for the next cylinder and the next cylinder, and when performing three fuel injections, the calculation is performed for all cylinders other than the latest cylinder in which fuel was injected. When performing four fuel injections, it is necessary to calculate the fuel injection amount for all cylinders. These correspond to conditions (2) to (4) above.

Even if we try to reduce the calculation load as described above, each cylinder will be
Since calculations are performed at a cycle of 0 m5ec, it is expected that the amount of calculations will still be large. When the above-mentioned fuel control is performed by a processor with small computing power, there is a possibility that tasks at a lower level of engine control will not be completed. In order to deal with this problem, it is necessary to further reduce the amount of calculations for fuel control. The following method can be used for this purpose.

The amount of calculation for fuel control depends on the calculation cycle.

If the calculation period is increased, the amount of calculation will be reduced. However, if the calculation period is set to a fixed value, the following problem will occur. For example, to reduce the amount of calculation, the calculation cycle is set to 30 m.
Assume that it is set to 5ec. Assume that calculation of the fuel injection amount is completed at a certain time, and then immediately before the calculation of the next injection amount is started, an REF interrupt, which is a fuel injection command, is input. In this case, since the amount of fuel calculated 30 m5ec ago, that is, a long time ago, is injected, there will be an excess or shortage of fuel when the fuel is suddenly reduced. In order to increase the calculation cycle and avoid such problems, it is best to synchronize the calculation cycle with the engine rotation.In the case of a 4-cycle engine, fuel injection is performed at 22.3. ...) If the fuel control system is calculated every rotation, the fuel injection amount can be calculated just around the time when the fuel injection command R, E F interrupt occurs. .

It's time for the next one.

For example, if M=1, that is, the control system calculation is performed only once every two rotations, the above time will be 120 m5ec at 11000 rpm, and 40 m5 at 3000 msec.
It becomes ec. Considering that fast acceleration is on the order of 100-odd msec, the calculation cycle of 120 m5ec is too rough to grasp the fuel shaft transport phenomenon in the above acceleration state. A calculation cycle of at least about 60 m5ec is required.

In order to set the calculation cycle to 60 msec at 11000 rpm, M=2, that is, the calculation should be performed once per rotation. At this time, at 6000 rpm,
The computation cycle is 10 m5ec, and the amount of computation becomes large.

Therefore, the value of M is reset so that the calculation cycle becomes larger at a rotation speed higher than a predetermined number of rotations at which the amount of calculation becomes large.

For example, at 3000 rpm or more, M,=1, that is,
6000 rpm if one rotation calculation is performed every three rotations
But it will be 20 msec.

The configuration of the fuel control system that performs the above method, that is, the calculation is performed once per rotation at approximately 3000 rpm or higher, and once every two rotations at approximately 300 rpm or higher, will be explained with reference to FIG.

Block 5A is a configuration of a control system that performs calculations once every rotation, and block 5B is a configuration of a control system that performs calculations once every two rotations.

First, each component of the control system of block 5A will be explained.

In block 51a, the fuel injection amount is calculated according to the following formula.

m: Engine crank angle (1 angle is engine 1
(equivalent to the crank angle of rotation) Qa: intake air amount A, /F: target air-fuel ratio Cn1dwa: variable parameter C1ldn, which depends on the engine operating state, is determined in block 52a by the intake pipe internal pressure PM
, engine rotation speed N, and water temperature Tw.

The formula (44) and the formula for calculating the parameter C1l dn are developed as follows.

The time t (sec) for one rotation of the engine is as follows, where the engine rotation speed is N (rpm).

In equation (28), which is a discrete equation expressing the fuel transport characteristics, in order to set the time of one time in the discrete equation to the above time t, (2
If Δ1=1 in equation 8), the following equation is obtained.

Here, m: Engine crank angle (one angle corresponds to the angle of one revolution) □・T3 CO: 2T,, T2+□・(T1÷T2) 2・(□)2 C1= 2T1T2+□・(T□ten T2) ・T3 C2: 2T, T2+□・(T1+T2) 2・(−) ” −4T1T2 d1= 2T1T2+□・(T1+Tz) 2T,・T, −□・(TI+72) d2= − (5]) 2T, T2+□・(T,+T2) Using the same logic as when formula (27) was derived, formula (44), which is the calculation formula for the fuel injection amount, is derived from formula (46).

The calculation formula for CJ, d is shown in equations (47) to (51),
It is obtained by substituting equation (26).

In block 53a, the cylinder flow rate fuel amount ate (m) is calculated according to equation (46). This calculation result is used to calculate the fuel injection amount in block 51a.

In block 51a, the fuel injection amount ax (m) is calculated using the calculated value G((m-
1) Use G* (m 2). Also, in block 53a, 2 is used to calculate the cylinder flow rate Gfe(m).
Fuel injection amount Gf (m-j) (j=o, 1. before rotation)
Use 2). These fuel injection amounts are determined by block 51
Instead of using the calculated value in block a as is, block 5
4. The actual value of the past fuel injection amount stored in a is used. Specifically, the angle at which the latest effective value of the fuel injection amount was calculated is mfl, and the angle at which the previous effective value was calculated is m.

When, the value Gi(m-j) determined according to the following formula
(j = 0, 1, 2) is used.

The calculations in blocks 51a and 54a described above need only be performed when fuel injection is performed. Therefore, it is performed once every two revolutions. or,
The calculations in blocks 52a and 53a are as follows.

Do this once per revolution. This concludes the explanation of the control system of block 5A that performs calculations every other revolution.

Next, the components of the control system of block 5B, which performs calculations every two revolutions of the engine, will be explained.

In block 51b, fuel injection amount Gi (
m) is calculated.

: Crank angle (one angle corresponds to the crank angle of one revolution of the engine) : Intake air amount A/F : Target air-fuel ratio : Cylinder fuel flow rate ate 07, dJ' are variables that depend on the engine operating state. Calculated in block 52b. The calculation formula % Formula % T+ (i=1.2.3) of formulas (54) to (58) is (
26) is satisfied.

In block 53b, the amount of fuel flowing into each cylinder used for calculating the fuel injection amount is calculated using the following equation.

In block 54b, the calculated values G* (m 2) and Gz (m 4) of the fuel injection amount before two revolutions and four revolutions ago are stored. Since these values are execution values, the calculations in blocks 51b and 53b are performed using these values.

The arithmetic expressions for each component of the block 5B described above are obtained in the same manner as for the block 5A. Blocks 51b, 52
The calculations of b, 53b, and 54b are performed every two revolutions of the engine. Also, the crank angle at which fuel injection is performed and the crank angle at which calculation is performed are naturally made to match.

This completes the explanation of the control system of block 5B that performs calculations every two rotations.

Block 56 selects one of the fuel injection amounts Gz(rn) calculated in block 5A and block 5B. The selection process is performed immediately after fuel injection to select a signal to be used for calculating the next executed fuel injection pulse width. For example, the following selection conditions can be used.

(]-) When the output of 5A was selected in the previous selection process, and the rotation speed is 3200 rpm or more in the current selection process, the output of 5B is selected in the current process.

(2) In the previous selection process, the output of 5B was selected, and in the current selection process, when the rotation speed was 280 Orpm or less, the output of 5A was selected in the current process.

(3) In cases other than the above, the current selection signal is the same as the previous selection signal.

Note that when it is determined in the first selection process that the output of block 5A is to be used for calculating the next fuel injection pulse width, only the calculation of block 5A is performed until the first selection process. The same applies when block 5B is selected.

In the above selection conditions, different rotation speeds are used as conditions for switching the selection signal. The reason why the same rotational speed is not set is to prevent the calculations of blocks 5A and 5B from frequently switching when the actual rotational speed is near the set rotational speed.

Immediately after the calculation is switched from block 5A to block 5B, the latest fuel injection amount Gz (m) is calculated using the past injection amount execution value Gi (m 2), the value of Gl (m-4), and , the calculated value of the past cylinder fuel amount, Fte (
m 2) and Gxe (m 4) are required.

As for the actual value of the fuel injection amount, the value stored in block 54a is used. In addition, the calculated value G((
m 2), Gt (m 4) was previously block 5
Use the value calculated and stored in step 3a. Also, block 5A
The cylinder inflow fuel amount ate (m) at the angle m immediately after the calculation is switched from block 5B to block 5B is also calculated using the same value.

Conversely, the calculation of the fuel injection amount Gz (m) at the angle m immediately after the calculation is switched from block 5B to block 5A is as follows.
Actual values of past injection amounts Gi (m 1), Gf (m
2) and the cylinder fuel amount Gie (m-1), (Gie
The value of (m 2) is required. In block 5B only 2 angles, i.e. every 2 rotations.

The values of Gi and Gie are not calculated. Therefore, Gi(m-
The actual value of 2) is not stored in block 54b, and furthermore, Gie(m 2) is not computed in block 53b. Since the actual value of the injection amount at angle (m-2) is equal to the actual value at angle (m-3), the value of Gz (m 3) is used instead of Gz (m 2). Also, the angle m
-2 cylinder inflow fuel amount Gze (m 2) is obtained by the following interpolation calculation from the value aze (m-3) one revolution before and the value Gze (m 1) one revolution after which a calculated value exists.

Gze(-12): -(Gie(m-1) 10 Gie(
m-3) (60) Calculate Gi(m) using the above values.

The values of G and e(m) are also calculated using similar values.

In block 55, the fuel injection pulse width is calculated from the fuel injection amount Gz(m) calculated and selected by the above method using the following equation.

Here, k: various correction coefficients N: engine rotational speed Ts: invalid injection time or more, this concludes the explanation of the operation of the control system for a certain cylinder configured as shown in FIG. In a multi-cylinder engine, the control system shown in FIG. 5 is set for each cylinder as shown in FIG. 4, and fuel is controlled independently.

In the control system shown in FIG. 5, calculation of the fuel injection amount is started at the crank angle at which fuel injection should be performed.

Therefore, there is a delay equal to the calculation time until actual injection is performed. In order to perform fuel injection without a delay in calculation time, a secondary method may be used.

In blocks 5A and 5B of FIG. 5, originally block 51a
, 51b are performed once every two rotations. In contrast, calculation of the fuel injection amount is performed at predetermined time intervals, for example, every 10 m5ec. block 51
In a, the fuel injection amount Gz (m) is calculated based on equation (44), but Gte (m-j), C31 (C5
1 ((j = 1, 2) is the original value, Qa,
Calculation of Gz(m) is performed every 10 m5ec using only the latest values of A/F, Ci, and dJ.

Although the fuel injection amount may be calculated for all cylinders simultaneously as described above, the calculation amount can also be reduced by the method of P23-2. In this method, fuel injection is performed based on the latest Gz (m) at the crank angle at which fuel injection is performed. Let this Gf (m) be the actual value of the fuel injection amount at this crank angle.

In the above method, although the calculation load increases slightly, fuel injection can be performed immediately at a predetermined crank angle.

Next, the overall configuration of the control system and the operation of the control program when the control shown in FIGS. 3 to 5 is realized by a digital control unit will be explained with reference to FIGS. 6 to 9.

FIG. 6 shows an overall configuration diagram of a control system when the present invention is applied to a four-cylinder engine of the D-Jetronic system.

The control unit includes CPtJ, ROM, RAM, timer,
It is equipped with an Ilo LSI, a timer, and a bus that electrically connects them. The timer generates an interrupt request to the CPU at regular intervals, and the CPU responds to this by executing a control program stored in the ROM. Engineering/
○ Signals from a pressure sensor, throttle angle sensor, water temperature sensor, crank angle sensor, intake temperature sensor, and oxygen sensor are input to the LSI. Also, from ■／○ LSI,
A signal to the injector is output.

Next, with reference to FIGS. 6 and 7, a description will be given of the operation of a control program that implements the processing of the control system shown in FIGS. 3 and 4, that is, a control program that calculates the fuel injection amount at regular time intervals.

When an interrupt signal every 10m5ec is input, step 70
1, the latest measured values of intake pipe internal pressure PM, engine speed N, and water temperature Tw are stored.

Next, in step 702, a predetermined table is searched using the intake pipe internal pressure and rotational speed obtained in step 701 as parameters, and an intake air amount Qa is determined and stored.

Next, in step 703, from T+ (i=1, 2.3) formulated for each cylinder using the method described above, (30)
Using equation (34), the parameter aaHb for each cylinder is
Find i.

Next, in step 704, it is determined whether the rotation speed stored in step 701 is within 2800 rpm. 280
If it is within 0 rpm, the process from step 705 is performed, otherwise the process from step 706 is performed.

In step 705, the value obtained in step 703 is determined.

The parameter is the cylinder fuel amount Gie (i J) (j=
1.2), the injection amount Gi (i-j) (j = 1.2) determined according to the formula (41) from the execution fuel injection amount Gi (10) and Gi (xx) stored in another program.
), the fuel injection amount G of the cylinder to which fuel will be injected next is determined from the value of each variable corresponding to the cylinder to which fuel will be injected next! (
j) is calculated using equation (44).

In step 706, it is determined whether the rotation speed stored in step 701 is within 5600 rpm. 5600r
If it is within pm, perform the processing from step 707,
Otherwise, the process from step 708 onwards is performed.

In step 707, the fuel injection amount of the next and subsequent cylinders to be injected is calculated using equation (44). The values of various variables such as a4, b4, Gi, etc. used to calculate the fuel injection amount for each cylinder are, of course, values corresponding to each cylinder.

In step 708, it is determined whether the rotation speed stored in step 701 is within 8400 rpm. 8400r
If it is within pm, the process of step 709 is performed; otherwise, the process of step 710 is performed.

In step 709, the fuel injection amounts for all cylinders other than the latest cylinder in which fuel injection was performed are calculated using equation (44).

In step 710, fuel injection for all cylinders is calculated using equation (44).

Next, in step 711, the fuel injection pulse width of all the cylinders for which the fuel injection amount was calculated in the previous step is calculated as (4
2) Calculate and store using formulas. The calculated value of the fuel injection amount for each cylinder is used to calculate the pulse width for each cylinder.

Finally, in step 712, the parameters a5 and bJ obtained in step 703 and the execution injection amount Gi (jo) t Gt (11) to (4
1) Fuel injection Gt (i-j) determined according to the formula; cylinder smoke amount Gze (i
From the value of j) for each cylinder, the cylinder fuel amount G for each cylinder is calculated using equation (29).

(i) is calculated and stored. This completes the process and waits until the next interrupt request.

Next, the operation of the control program for storing and updating the executed fuel injection amount will be explained with reference to FIG.

This program is designed to be executed immediately after fuel injection is performed.

First, in step 801, Gr(i6
) is assigned to Gi(il).

In step 802, the latest effective fuel injection amount in the corresponding cylinder is substituted into Gi(xo). This completes the process.

Note that the variables Gi (in) and Gi (5) are set for each cylinder as the latest effective injection amount and the immediately preceding effective injection amount.

This concludes the explanation of the control program that calculates the fuel injection amount at predetermined time intervals.

Next, referring to FIG. 9, the operation of a program for controlling fuel for each cylinder, in which the configuration shown in FIG. 5 is set for each cylinder, will be explained.

This program is executed every time an REF interrupt, which is a fuel injection command, occurs, that is, every half revolution.

First, in step 901, the latest measured values of intake pipe internal pressure PM, rotational speed N, and water temperature Tw are stored.

Next, in step 902, a predetermined table is searched using the intake pipe internal pressure and rotational speed stored in step 901 as parameters to obtain the intake air amount Qa.

Next, in step 903, the cylinder to which fuel is to be injected during the current interruption is determined.

Next, in step 904, if it is determined that the output of block 5A of the control system in FIG. When the output of block 5B is used for the processing, step 9
Perform the processing from 10 onwards. This signal selection process is done by this program.

This is performed in step 915, which will be described later.

Steps 905 to 909 are a program of the processing performed in block 5A of FIG.

First, in step 905, from the intake pipe internal pressure PM, rotation speed N, and water temperature Tw stored in step 901, (47) to
Using equations (51) and (26), the parameters CJ,l corresponding to the cylinder determined in step 503 are calculated.

Next, in step 906, the parameters Ca and d* calculated in step 905 are used, and the cylinder flow rate Gre (m −j ) of the judgment cylinder, which has been calculated and stored using a predetermined calculation formula until the previous program execution. (j=1.2)
, the actual fuel injection amount Gi (me) of the past determination cylinder,
Fuel injection amount at (m-j) (j=1°2) determined according to equation (52) from Gi (ml) (44)
The fuel injection amount Gr(m) is calculated using the formula. Furthermore, this value is stored as the latest fuel injection amount execution value for that cylinder.

Next, in step 907, the fuel injection pulse width T of the determined cylinder is calculated from the fuel injection amount Gz(m) calculated in step 906 using equation (62).

Further, in step 908, the pulse is sent to the injector to inject fuel into the cylinder to be determined.

Next, in step 909, the cylinder flow rate fuel amount Gf(m) of the determined cylinder is calculated using equation (46).

Remember. This value is used to calculate the fuel injection amount when executing the program from next time onwards.

The processing from step 910 to step 9U4 is
This is a program of the processing performed in block 5B of the figure. This processing is all for the cylinder determined in step 903, and various calculations are performed using the variables set for that cylinder.

First, in step 910, equations (54) to (58), (
26) Calculate the parameter CJ'ldJ using equation.

Next, in step 911, the fuel injection amount Gz(m) is calculated using equation (53) and stored as an execution value.

Next, in step 912, the fuel injection pulse width Ti is calculated using equation (61).

Next, in step 913, the calculated pulse is sent to the injector, and fuel is injected into the cylinder determined in step 903.

Next, in step 914, the cylinder inflow fuel amount ate (m) is calculated using equation (59) and stored.

In step 915, step 9
It is determined whether the output of block 5A or block 5B is used to calculate the next executed fuel injection pulse width for the determination cylinder in step 03, and this result is stored.

Next, in step 916, the cylinder in which fuel was injected one revolution before is determined.

Furthermore, in step 917, it is checked whether to use the fuel injection amount of block 5A or block 5B to calculate the next execution fuel injection pulse width for the cylinder determined in step 916. Information regarding which block's injection amount is to be used is stored in a predetermined location by the process of step 915 during the previous program execution. When using the injection amount of block 5B, all processing is completed and the system waits until the next interrupt signal is input.

If the injection amount of block 5A is used, step 918
Perform subsequent processing.

In step 918, (47) to (51) are calculated from the intake pipe internal pressure PM, rotational speed N, and water temperature Tw stored in step 901.
The parameter CJ-d< is determined using the equation (26). Note that T+ (i=1−.
2.3) uses a formula corresponding to the cylinder to be determined in step 916.

Next, in step 919, the amount of fuel flowing into the cylinder determined in step 916 is calculated using equation (46) and stored.

This concludes the explanation of the control program shown in FIG.

The configuration of the control system and the operation of the control program when the fuel transportability is formulated as a quadratic or less delay in equation (2,) have been described above.

Fuel transport characteristics can generally be expressed by the following transfer function.

Gi(S) aO5" + a, S"-"+-+ an-, 6S +
an However, n ≧ l, n ≧ m ≧Oa,
≠ o, bo f-.

a n ” b m ≠ O When the fuel system dynamic characteristics are expressed by equation (62), the model parameters a+ (i=1+
2. ""t n), ba F=1.2. ..., m)
can be determined and its characteristics can be formulated.

Furthermore, a control system can be constructed from the discrete equations of the obtained model using the same logic as described above.

In addition, in the above embodiment, fuel compensation is performed using a secondary advance element for all cylinders, but for some cylinders, a primary advance element,
It is also possible to change the compensation method for each cylinder, such as using a third-order advance element for other cylinders.

This method is effective when each cylinder cannot be accurately modeled with the same order using the method described above.

C Effects of the Invention According to the present invention, the fuel transport characteristics of each cylinder are accurately modeled, and the model is used to control the fuel of each cylinder to compensate for fuel transport delays, so that the air-fuel ratio control of each cylinder is improved. It is possible to achieve more precision.

[Brief explanation of drawings]

Figure 1 shows the response of the air-fuel ratio sensor output to a step input, Figure 2 shows the response of the exhaust air-fuel ratio to a step change in the fuel injection amount, and Figure 3 shows the response of the cylinder control system that calculates the fuel injection amount at a predetermined time period. Configuration diagram, Figure 4 is a configuration diagram of the control system when the control system in Figure 3 is applied to each cylinder of a 4-cylinder engine,
FIG. 5 is a configuration diagram of a control system for a certain cylinder that calculates the fuel injection amount at a predetermined crank angle, FIG. 6 is an overall configuration diagram of a control system when the present invention is implemented with a digital control unit, and FIG. FIG. 8 is a flowchart of a control program when the control system of FIG. 4 is implemented by a digital control unit. FIG. 9 is a flowchart of a control program when the control system of FIG. 5 is implemented by a digital control unit. S Ei1 1,, C 81 Darkness 1 Tsun Q N S N e Last time 4r ψ Ron 11 N (] 1 ~ Shi / To pump: supply (, (! ni Kechiroa〒(Ding″′

Claims (1)

[Claims] 1. An engine electronic control method for a multipoint fuel injection system that controls a fuel injection amount based on an intake air amount, comprising: 1.
Either the process corresponding to the next phase advance element or the process corresponding to the second or higher phase advance element compensates for the fuel transport delay of at least one cylinder, and the fuel transport delay of all cylinders is compensated for as described above. A fuel injection control method for an engine, characterized in that at least one of the processes independently compensates and calculates the fuel injection amount. 2. In an engine electronic control method for a multi-point fuel injection system that controls the fuel injection amount based on the intake air amount, one of the processes corresponding to the phase advance element A below is used to reduce the fuel transport delay for one cylinder. compensating for the fuel transport delay of all cylinders by at least one of the processes corresponding to element A;
A fuel injection control method for an engine, the method comprising calculating a fuel injection amount. A=(a_0S^n+a_1S^n^-^1+...+
a_n_-_1S+a_n)/(b_0S^m+b_1
S^m^-^1+...+b_m_-_1S+b_m)
Here S: Laplace operator n≧1 n≧m≧0 a_n=b_m≠0 a_n_−_1≠0 However, among the above elements, the following element is excluded (a_n_−_1S+a_n)/b_m Here a_n_−_1≠ 0 3. Compensate for fuel transport delay for at least one cylinder (
2. A fuel injection control method for an engine according to claim 1, wherein said processing is performed by a process corresponding to a proportional + differential (proportional + differential) element, and said process does not compensate for a delay in fuel transport to all cylinders. 4. The engine fuel injection control method according to claim 1 or 2, wherein the process of calculating the fuel injection amount includes a process of estimating and calculating a fuel transport state for each cylinder. 5. The engine fuel injection control method according to claim 4, wherein the estimation and calculation process is performed at a predetermined time period. 6. The above time period is below the predetermined rotation speed, and the engine 2
6. The fuel injection control method for an engine according to claim 5, wherein the time is set to be shorter than the time required for rotation. 7. The engine fuel injection control method according to claim 5, wherein the time period is a predetermined crank angle period. 8. The method for controlling fuel injection for an engine according to claim 7, wherein the crank angle is set smaller than a crank angle corresponding to two revolutions of the engine. 9. The fuel injection control method for an engine according to claim 7, wherein the crank angle is made variable depending on the engine operating state. 10. The engine fuel injection control method according to claim 1 or 2, wherein the process of calculating the fuel injection amount is performed at a predetermined time period. 11. The calculation process is characterized in that, at a fuel injection amount calculation time, a cylinder in which fuel injection is to be performed is determined by the next fuel injection amount calculation time, and the fuel injection amount is calculated only for the determined cylinder. engine fuel injection control method. 12. The fuel injection control method for an engine according to claim 1 or 2, wherein in the process of calculating the fuel injection amount, the latest fuel injection amount is calculated based on the past executed fuel injection amount. 13. In an engine electronic control device that controls the fuel injection amount based on the intake air amount, the engine fuel injection control is characterized in that a delay in fuel transport is compensated by a third-order or higher phase advance element or processing equivalent thereto. Method.