JPS6060235A - Method of controlling fuel supply after starting of internal-combustion engine - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a post-start fuel supply control method for an internal combustion engine, and more particularly to a post-start fuel supply control method for setting an increase in fuel amount immediately after cranking to an appropriate value in accordance with a change in engine temperature.

In order to prevent engine stall after engine start and smooth transition to acceleration immediately after engine start, the initial value of the post-start fuel increase immediately after engine cranking is adjusted according to the rise in engine water temperature, which is representative of engine temperature. It is set corresponding to the product of the decreasing warm-up increase coefficient (hereinafter referred to as "water temperature coefficient KTW") and the post-start increase coefficient KAST value, and then this initial increase value is set at the top dead center (TDC) of the engine.
) A method has already been proposed by the present applicant (Japanese Patent Application No. 57-147234
issue).

FIG. 1 is a diagram for explaining the post-start fuel control method proposed above, in which the product value of the above-mentioned water temperature coefficient KTW and post-start increase coefficient KAST, which increases the TDC signal pulse generation basic fuel amount after the engine starts, is Show how things change. The initial value KASTO of the increase coefficient after startup is the water temperature coefficient KTvi value,
From then on, the TDC signal pulse generation standard value is subtracted from the product value of the coefficient KTW value and the variable value CAST set according to the coefficient KTW value. According to the above-mentioned proposed method indicated by the broken line in Fig. 1, the amount of fuel supplied to the engine decreases from the initial value immediately after cranking to a constant value every time a TDC signal pulse occurs, and the fuel increase coefficient value KAST after startup decreases. The fuel amount is supplied to the engine, which decreases substantially linearly to the fuel amount value at time 1, when Kp, ST = 1.0, and then is directly corrected for the water temperature only by the water temperature coefficient KTW. In this way, by gradually decreasing the amount of fuel supplied during the period from the completion of cranking to time 61 (this is referred to as the 1st post-start fuel increase period), the normal operating state after time 61 is changed from the cranking operating state. However, with the above-mentioned proposed method that uses a substantially linear decrease, the amount of fuel supplied to the engine during the fuel increase period cannot necessarily be the appropriate amount.

Normally, increasing the amount of fuel immediately after cranking when cold is due to incomplete evaporation of fuel adhering to the cold intake pipe wall and inner cylinder wall, resulting in a reduction in the amount of air-fuel mixture actually supplied to the engine. However, the NHA degree of the cylinder inner wall, etc. increases rapidly with the number of combustions in the same cylinder after starting, and fuel evaporation is also promoted. The required amount of fuel is the value obtained along the solid line A in FIG. However, with the conventional method of decreasing iI+ almost linearly, the mixture becomes rich during the fuel increase period, which has a negative impact on combustion. This problem can be solved by setting the fuel increase value to an appropriate value depending on the cylinder inner wall surface temperature.However, since the engine cooling water temperature is normally used as the temperature that represents the engine temperature, there is a time delay in the water temperature change with respect to the cylinder wall surface temperature change. Therefore, it is difficult to accurately detect the wall surface temperature using the engine cooling water temperature.The initial value is set according to the detected value of the engine water temperature sensor, and then TDC
The above-mentioned increase coefficient Khsr for reducing signal pulse generation
In some cases, the fuel increase value during the post-start fuel increase period cannot be set correctly.

Also, in order to approximate the solid line l in Fig. 1, the initial value is 92
One possible method is to set the solid line B in FIG. 1 that is 1 minute smaller and supply the engine with the amount of fuel corresponding to the value obtained along this solid line B. However, since the amount of fuel supplied to the engine changes suddenly immediately after cranking is completed (the amount of change is represented by the amount of fuel corresponding to ΔT in Figure 1), engine operation becomes unstable. Moreover, while the air-fuel mixture becomes lean during the period indicated by the diagonal line I in FIG.
In the period indicated by the diagonal line ■, on the contrary, the situation becomes enriched and a complete solution cannot be achieved.

The present invention has been made to solve the above-mentioned problems, and it determines an initial fuel increase value according to the engine temperature when a pulse of a predetermined control signal is generated immediately after cranking of an internal combustion engine, and then determines an initial fuel increase value according to the engine temperature. In a post-start fuel control method, the initial increase value is decreased by a predetermined degree every time a pulse is generated, and the fuel amount calculated using the decreased increase value is supplied to the engine in synchronization with the generation of the control signal pulse, at a first degree until the increase value reaches a predetermined judgment value,
After falling below the predetermined discrimination value, the increase value is decreased by a second degree smaller than the first degree,
To provide a post-start fuel supply control method for an internal combustion engine, which accurately sets the amount of fuel immediately after starting the engine to an appropriate required value according to the engine temperature, and obtains smoother engine operation.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 2 is an overall configuration diagram of the device of the present invention. Reference numeral 1 indicates, for example, a four-cylinder internal combustion engine. An intake pipe 2 is connected to the engine 1, and in the middle of the intake pipe 2 there is a U throttle body. 3 is provided and an internal throttle valve is provided. This throttle valve has a throttle valve opening sensor 4.
is connected to the electronic control unit (hereinafter referred to as "rEcU") which converts the valve opening of the throttle valve into an electrical signal.
It is set to be sent to 5th.

A fuel injection device 6 is provided in the intake pipe 2 between the engine 1 and the throttle body 3. This fuel injection device 6 is provided for each cylinder slightly upstream of an intake valve (not shown) in the intake pipe. The fuel injection device 6 is connected to a fuel pump (not shown).

The fuel injection device 6 is electrically connected to the ECU 3.
The opening time of the salary injection is controlled by a signal from the ECU 3.

On the other hand, an absolute pressure sensor 8 is provided immediately downstream of the throttle valve of the throttle body 3 via a pipe 7.
The absolute pressure signal converted into an electrical signal by the absolute pressure sensor 8 is sent to the ECU 3. Further, an intake temperature sensor 9 is installed downstream of the intake air temperature sensor 9. This intake air temperature sensor 9 also converts the intake air temperature into an electrical signal and sends it to the ECU 3. An engine water mud sensor 10 is installed on the engine 1 body. This sensor 10 consists of a thermistor, etc., and is inserted into the circumferential wall of an engine cylinder filled with cooling water, and supplies the detected water temperature signal to the ECU 3.

Engine speed sensor (hereinafter referred to as "IVe sensor")
11 and cylinder discrimination sensor 12 are installed around the camshaft (not shown) of the engine or around the crank hole 1.
The former 11 is the TDC signal, ie 18 of the engine crankshaft.
The latter 12 outputs one pulse each at a predetermined crank angle position of a specific cylinder at a predetermined crank angle position every 0° rotation, and these pulses are sent to the ECU 3.

A three-way catalyst 14 is disposed in the exhaust pipe 13 of the engine 1 to purify HC, Co, and NOx components in the exhaust residue. On the upstream side of this three-way catalyst, an O sensor 15 is installed in the exhaust pipe 1.
3, this sensor 15 detects the oxygen concentration in the exhaust gas and supplies the detected value signal f, (1!: Cu2).

Furthermore, a sensor 16 for detecting atmospheric pressure and an engine starter switch 17 are connected to the ECU 3.
, the ECU 3 is supplied with a detected value signal from the sensor 16 and a starter switch ON/OFF state signal.

As will be described in detail later, the ECU 3 calculates the valve opening time TOUT of the fuel injection valve 6, and controls the fuel injection valve 6 based on the calculated value.
A drive signal for opening the fuel injection valve 6 is supplied to the fuel injection valve 6.

Figure 3 is a diagram showing the circuit configuration inside the ECU 3 in Figure 2.
The engine rotation speed signal from the Ne sensor 11 in FIG. Ru. Me
The counter 502 counts the time interval from the input of the previous predetermined accompanying signal from the Ne sensor 11 to the input of the predetermined position # code this time, and the counted value Me is the engine rotational speed H
It is proportional to the reciprocal of e. Me counter 502 supplies this counted value Me to CPU 503 via data bus 510.

The respective output signals from various sensors such as the intake pipe absolute pressure sensor 8, the engine water temperature sensor 10, and the starter switch 17 shown in FIG. A/D
is supplied to converter 506. , 4/D converter 5
06 converts the output signals from each sensor described above into 111 digital signals and supplies the digital signals to the CPU 503 via the data bus 510.

The CPU 503 is further connected to a read-only memory (hereinafter referred to as ROM J) 507, a random access memory (RAM) 508, and a drive circuit 509 via a data bus 510.
The ROM507 temporarily stores the calculation results etc.
It stores a control program executed by U503, a water temperature increase coefficient KTW table determined according to the engine water temperature, a water temperature coefficient CAST table, etc., which will be described later. , C.P.
Is U503 I? According to the control program stored in the 0M507, the fuel injection time TOUT of the fuel injection valve 6 is calculated according to the various engine parameter signals mentioned above, and these calculated values are sent to the drive circuit 509 via the data bus 510.
supply to. The drive circuit 509 supplies a control signal to the fuel injection valve 6 to open the fuel injection valve 6 according to the calculated value.

Next, details of the operation of the electronic fuel injection control device of the present invention having the above-described configuration will be explained with reference to FIGS. 1 to 3 and FIGS.

First, Fig. 4 is a block diagram showing the overall program configuration of the air-fuel ratio control of the present invention, that is, the control content of the valve opening time TOUT of the fuel injection device 6 in the ECU 3.
The fuel control program 1 is based on the engine speed Ne (T
It performs control in synchronization with a DC signal and consists of a starting control subroutine 2 and a basic control program 3.

Basic calculation formula % formula % (
1) It is expressed as. Here, I'iaR is a reference value for the opening time of the fuel injection valve, and is determined by the TiCR table 4. A''N6 is a correction coefficient at the time of starting specified by the rotational motion Ne and is determined by the KNe table 5.T
v is a constant (2) for increasing or decreasing the valve opening time according to changes in battery voltage, and is requested from the 1v table 6.

Also, the basic 3'II notation % in basic control block 3
It is expressed as the formula % ) (2). Here, Ti is a reference value for the opening time of the fuel thrust valve, and is calculated from the basic fi map 7.

7”DEC! and 7’AOO are respectively used when decelerating.
Acceleration and deceleration subroutine 8 using variable values during acceleration and acceleration
determined by KTA, KTW...
The various numbers of strokes, etc., are calculated by the respective tables and subroutines 9. KTA is an intake air temperature correction coefficient calculated from a table based on the actual intake air temperature, KTW is a fuel increase coefficient determined from a table based on the actual engine coolant temperature TW, a P phase increase % coefficient after fuel cut determined by the KAFC subroutine, KPA is an atmospheric pressure correction coefficient determined from a table based on the actual atmospheric pressure, KAS
T is the post-start fuel increase coefficient determined by the subroutine, KWOT is a constant and is the enrichment coefficient of the air-fuel mixture when the throttle valve is fully opened, and Ko is the 02 feedback determined by the subroutine according to the actual oxygen concentration in the exhaust gas. The sleeve positive coefficient, KLS, is a constant, and is a fuel-air mixture uniformity coefficient during lean/stroyer operation. Stoiki is St
o, ichi ometγic is an abbreviation for chemical theory, or stoichiometric air-fuel ratio.

Figure 5 is based on the CPU 503 in Figure 3.
The flowchart shows the flowchart for calculating the valve opening time in synchronization with the input signal processing block I, basic 1b.
It consists of a control block (1) and a start-up control block 10.

First, in the input signal processing block I, when the engine ignition switch is turned on, EC'(C'PU in J5 initializes (Step 1)), and when the engine starts, F)
A TDC signal is input (step 2). Next, all analog values of atmospheric pressure PA, absolute pressure PB from each sensor, engine water yg'w, atmospheric pressure 7°A, battery 1 pressure 11, /(0 liter valve opening oth, o , sensor output type, pressure sensor V, and the on/off state of the starter switch 17 are stored in the ECUS and the necessary values are stored (step 3).Subsequently, from the first TI)C signal to the next 1° Count the elapsed time until the DC signal, and then record the engine speed No. based on 0! itc!?
-1. Similarly, store it in ECUS (step 4).

Next, in the basic control block H, the mouth (field) of this He is
Due to +<+, engine rotation 0 becomes cranking 1+jll
It is determined whether or not it is less than or equal to k,←'(rg; rotational speed during excitation) (step 5). If the answer is affirmative (Yes), it is sent to the startup Rt control subroutine of the startup control s41 block 11, and TicR is determined based on the engine coolant temperature 1゛W using the rioa table (step 6).
In addition, the corrected centering KNg of Ne is determined as 1 (υ) using the He table (step 7).Then, the voltage correction constant TV is determined using the TV table (step 8).
), each numerical value is inserted into both equations (1) to calculate TOUT (step 9).

If the answer in step 5 is no (IVo), it is determined whether the engine is in a state where fuel should be cut (step 10), and the answer is affirmative (YVo).
If yes, set the TOUTO value to zero and try to cut the fuel (step 11).

On the other hand, if the answer is determined to be no (AIO) in step 10, each correction coefficient KTA, KTW, AAFO
.

KPA, KAs'r, zwo'r, KO,
, KLB, KTWT, etc. and correction values TDF2C, TA
G(!, TV, is output for the first time (step 12). These correction coefficients and correction values are determined by subroutines, tables, etc., respectively.

Then, select a predetermined corresponding map according to each take of rotation speed Ne and absolute pressure PB, and according to the map, g>I'i
is determined (step 13). Therefore, step 1 above
2. Calculate TOUT using both equations (2) based on the correction number and correction value obtained in step 14.
). Then, based on the TOUT value obtained in this way, 11r (injector!) of the fuel injection device 6 is activated (step 15).
.

Next, of the above-mentioned valve opening time control, the start]+4+ determination subroutine and the 3PH output subroutine of the increase mooring after starting KAST will be explained.

FIG. 6 shows a flowchart of a subroutine for determining whether or not the engine is in a cranking state in the valve 5 of FIG. In this cranking determination subroutine, the first step is to determine whether or not the starter switch is on (step 1). If it is not on, it is assumed that cranking is not in progress, and the process moves on to the basic control loop (step 2). Engine rotation speed he
is 19'r constant cranking rotation speed NC,R (for example, 4
If the former is smaller than the latter, it is assumed that cranking is not in progress and the process moves to the basic control loop, and if the former is smaller than the latter, then step 3) It is determined that cranking is in progress and the process moves to a starting loop (block 111 in FIG. 5) (step 4).

FIG. 7 is a flowchart of a subroutine for calculating the increase coefficient 1 (AFET) after the engine starts. First, it is determined whether or not the engine state in the immediately preceding control loop was in the cranking state. Step 1) If there is, the water temperature coefficient CABT for calculating the initial value of ABT after starting is set to the above-mentioned ROJ according to the engine water temperature.
Read from i507 (step 2). Figure 8 shows an example of the relationship between engine water temperature Tw and water temperature coefficient CAST.
It is an AST table diagram. Based on the same figure, engine water temperature T
If W is below TWASO (e.g. 0°C), is the water temperature responsible? t
As Cp, Sr (:'ASTO (for example, 1.2),
If the water temperature TW is 7'WAEIG or more and TWAS1 or less, set CASTI (e.g. 1.0).
”CAST2 (for example, 0.8) if WAS1 or higher
Select each. This water temperature coefficient CAST table can be set in various ways depending on the characteristics of the engine.

Next, using the water temperature coefficient CAST obtained in step 2, the initial value of the increase coefficient KAST is calculated by the following equation (step 3).

KAf3T = CABT XXTW・・・・・・・・・
・・・・・・・・・・・・・・・・・・・・・(3)K
As mentioned above, TW is the water wetting and clarifying coefficient determined by the water temperature Tw.

FIG. 9 is a KTW table diagram showing the relationship between the engine water temperature TW and the number of water temperature increases KTW. First, when the water temperature TW exceeds fnTW 5 (for example, 60℃), I (TW remains at 1, but when it falls below 7'W5, the five-stage QK established as a calibration variable is set.
'fL '' 5Kjσ)KT for 1 to 5 respectively
W is set, and the water temperature Tw is set for each reason (1 to 7' to 7
When taking a value other than 1 to 5, it is determined by interpolation calculation.

Next, a determination j[lKA S T R is made (step 4). This discriminant value KAsTR is the AAS
It is set to reduce the KAST value to a large degree until the T value reaches this discrimination value KASTH, and to reduce the KAST value to a small degree until the T value reaches the fAsTR value or less.
This is determined by the following η equation (4).

KAsTR=(fAST-1)×RAST+1...
...(4) In particular, the KAST value is the value calculated in the previous step 3, that is, the initial value of the coefficient KAST, and R
AsT is a predetermined value that is set so that the coefficient value KhsT approximates the solid line A in Fig. 1 so that the amount of fuel supplied to the engine during the fuel increase U, Jυj after startup becomes the required amount adapted to the engine temperature. ratio (eg 0.5).

Next, the process proceeds to step 5, where it is determined whether the value of the increase coefficient KAsT is greater than 1 or not. In this loop, step 3
Since the initial values have just been set, the determination result in this step is naturally affirmative (Yg, r), and the program ends.

When the determination result in step 1 is negative (A'0),
That is, if the engine state is not in the cranking state in the previous control loop, the process proceeds to step 6, and it is determined whether the increase coefficient KAST in the previous loop is larger than the discriminant value A"Al9TR set in step 4. Then, if the determination result is positive (yg-t), the subtraction constant Δ
A predetermined value DKAsTo is set in KABT (step 7
), in the case of negative (No), a predetermined value DKAST1, which is smaller than the DKASTo, is set (step 8).

Next, proceed to step 9, and set the subtraction constant value ΔK
The value related to the increase used in the previous loop by AST KAS
T(I?ΔzAs'r value is set to a smaller value. Then, the process proceeds to step 5, where it is determined whether or not the fAsT value is greater than 1. If it is greater than 1, the program is terminated.

Thereafter, the subtraction in step 9 is repeatedly executed when the TDC pulse is generated, and the increased H value KAtor is determined by the cranking 1@ of the solid lines 1, 11, 11+, etc. shown in Fig. 10.
It decreases along the center fold 1 determined according to the subsequent engine cooling water temperature. With help, each center fold ig shown in Figure 10! -! The increase h1 coefficient value KAsT set along [, U, ill, etc. is RAsT, ΔKAST
By setting OΔKAST1, the solid line A illustrated in FIG.
To? The amount of fuel to be supplied to the engine during the fuel increase period after startup can be set more accurately by applying this total KABT.

The reduction yL in step 9 is repeatedly executed to reduce the ligation coefficient value K.
When hsT becomes a value of 1.0 or less, the determination result in step 5 becomes negative (IvO), and it is assumed that the post-start fuel increase period has ended, and the fuel increase coefficient KAST is set to 1.0 (step 10), and this program is executed. finish.

Note that the present invention is not limited to the above-described embodiments, and may be applied to, for example, an internal combustion engine that includes a main combustion chamber and a sub-combustion chamber that communicates with the main combustion chamber.

As described in detail above, according to the post-start fuel supply control method for an internal combustion engine of the present invention, the fuel increase value during the post-start fuel increase period is n [at the first degree until reaching the fixed judgment value, After falling below a predetermined discrimination value, the fuel increase value is decreased by a second degree smaller than the first degree, and the fuel amount calculated using the thus decreased increase value is synchronized with the pulse generation of a predetermined control signal. Since the fuel is supplied to the engine, it is possible to accurately set the required fuel U to adapt to the engine operating condition immediately after a cold start, and smooth engine operation can be achieved.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram illustrating the fuel increase supply control method during the post-start fuel increase period, Fig. 2 is an overall configuration diagram of a fuel supply control system to which the method of the present invention is applied, and Fig. 3 is the same as Fig. 2. city,
A circuit diagram showing the internal configuration of the child control unit (ECU) 5, Fig. 4 is a block diagram of the overall program configuration of the TOUT control contents of the valve opening time of the fuel injection device in the ECU, and Fig. 5 shows the valve opening of the fuel injector. Time TOUT
FIG. 6 is a 70-chart of the cranking determination subroutine included in FIG. 5, FIG. 7 is a flowchart for calculating the post-start fuel increase coefficient KAST, and FIG. 8 is a flow chart for calculating the post-start fuel increase coefficient KAST. ? 71 key sentence KA
A CAST table diagram showing the relationship between the water temperature coefficient CAST used to calculate ST and the engine water temperature TW, and Figure 9 shows the water temperature increase h (K showing the relationship between the coefficient KTW and the engine water temperature 7W).
TW chifur diagram, Figure 10 is 7' I) With the generation of Cii ij pulse, the fuel increase coefficient KAS after starting according to the present invention
It is approximately 1 indicating how T changes. 1... Inner PI engine 5... = 1 child control unit (ECU), 6... Fuel injection valve, 10... Engine water temperature sensor, 11... Engine rotation speed sensor,
17...Starter switch, 503...C'l)U,
507...RΔM0 White person Honda Motor Co., Ltd. agent Patent attorney

Claims (1)

[Claims] 1. An initial fuel increase value is determined in accordance with the engine temperature when a pulse of a predetermined control signal is generated immediately after cranking of the internal combustion engine, and thereafter the initial fuel increase value is determined every time a pulse of the predetermined control signal is generated. In the post-start fuel control method, the amount of fuel is decreased by a predetermined degree and the amount of fuel calculated using the increased value thus decreased is supplied to the engine in synchronization with the generation of the control signal pulse, wherein the increased amount reaches a predetermined determination value. A post-start fuel supply control method for an internal combustion engine, characterized in that the increase value is decreased at a first degree until the increase value falls below the predetermined determination value, and at a second degree smaller than the first degree. 2. The post-start fuel supply control method for an internal combustion engine according to claim 1, wherein the predetermined discrimination value is a product value obtained by multiplying the initial fuel increase value by a predetermined ratio. 3. The internal combustion engine according to claim 1 or 2, wherein the predetermined control signal is a pulse signal output at every predetermined crank angle position in synchronization with the rotation of the engine. A fuel supply control method after startup.