JPH0321737B2 - - Google Patents

Description

Detailed Description of the Invention (Technical Field) The present invention relates to a post-start fuel supply control method for an internal combustion engine, and in particular to a post-start fuel supply control that sets the fuel increase immediately after cranking to an appropriate value in accordance with changes in engine temperature. Regarding the method.

(Technical background of the invention and its problems) 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 set to It is set in accordance with the product value of the warm-up increase coefficient (hereinafter referred to as ``water temperature increase coefficient K _TW ''), which decreases as the engine water temperature increases, which represents the engine temperature, and the post-start increase coefficient K _AST value. , and then convert this initial increase value to the engine's top dead center (TDC).
The present applicant has already proposed a method in which the amount of fuel is reduced by a fixed amount every time a signal pulse occurs and the amount of fuel set in this manner is supplied to the engine (Japanese Patent Application No. 1983-
No. 147234).

Figure 1 is a diagram explaining the post-start fuel supply control method proposed above.
This figure shows how the product value of the water temperature increase coefficient _TW and the post-start increase coefficient _KAST , which increases the basic fuel amount each time a signal pulse is generated, changes. Initial value of increase coefficient after startup
K _AST0 is the water temperature increase coefficient K _TW value and the engine water temperature Tw
This is the product value of the water temperature coefficient C _AST value, which is set according to the TDC value, and from then on, a fixed value is subtracted every time a TDC signal pulse occurs. According to the above-mentioned proposed method shown by the broken line in Fig. 1, the amount of fuel supplied to the engine decreases from the initial value at the time of completion of cranking t ₀ to a constant value every time a TDC signal pulse occurs, and increases to the increase coefficient after starting. K _AST is
The fuel amount decreases substantially linearly to the fuel amount value at time t ₁ when K _AST = 1.0, and thereafter the fuel amount is supplied to the engine, the water temperature of which is corrected only by the water temperature increase coefficient value K _TW .
In this way, by gradually reducing the amount of fuel supplied during the period from the cranking completion time t ₀ to the t ₁ time (this is referred to as the "post-start fuel increase period"), the cranking operation state returns to normal after the t ₁ time. However, in 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 during a cold period is due to incomplete evaporation of fuel adhering to the cold intake pipe inner wall and cylinder inner wall, resulting in a leaner mixture actually supplied to the engine. However, the temperature of the inner wall of the cylinder increases rapidly with the number of combustions in the same cylinder after starting, and fuel evaporation is also promoted, so it is difficult for the engine to increase during the fuel increase period after starting. The required amount of fuel is the value obtained along the solid line in FIG. However, in the conventional method of decreasing the fuel increase value substantially linearly, the air-fuel mixture becomes rich during the increase period, which has an adverse effect on the plug.

That is, at the time of starting, as mentioned above, it is necessary to make the air-fuel ratio (A/F) a very rich state of 10 or less, taking into account the adhesion of the amount to the wall, the vaporization rate, etc., but after starting, it is necessary to If this condition continues, the plug will smolder, which will have an adverse effect on the plug. On the other hand, after startup, in order to ensure stability of combustion during warm-up, it is preferable to set the air-fuel ratio to such an extent that smoldering of the plug does not occur, and to gradually make it lean.

By the way, when cranking an engine when the engine water temperature is extremely cold, for example, below -10 degrees Celsius, the amount of fuel supplied to the engine is extremely increased to ensure engine starting performance. If the fuel supply amount is reduced to the same degree as shown by the solid line in Figure 1, the air-fuel ratio around the plug will locally become richer, and as a result, the plug will smolder, causing the engine to deteriorate. Stable operation becomes difficult. Therefore, a special control method is required for the amount of fuel supplied to the engine during the post-start fuel increase period when the engine is extremely cold.

(Object of the Invention) The present invention has been made in view of the above-mentioned points, and provides a post-starting system that prevents plug smoldering and fogging while ensuring stable combustion in the engine cylinder during the fuel increase period after starting in extremely cold conditions. The purpose of the present invention is to provide a fuel supply control method.

(Summary of the Invention) In order to achieve the above object, in the first invention, when the internal combustion engine is in a low temperature range, an initial fuel amount is increased in accordance with the engine temperature when a predetermined control signal is generated immediately after cranking the engine. After that, each time the predetermined control signal is generated, the initial increase value is decreased by a predetermined degree, and the fuel amount calculated using the decreased increase value is applied to the engine in synchronization with the generation of the control signal. In the post-start fuel supply control method, a predetermined determination value is set according to the initial fuel increase value, and it is determined whether or not the engine temperature during cranking is larger than a predetermined value within a low engine temperature range. When the engine temperature is higher than the predetermined value, a first degree of reduction is applied until the increase value reaches the predetermined judgment value, and a second reduction degree smaller than the first degree is applied after the increase value reaches the predetermined judgment value. When the engine temperature is lower than the predetermined value, the increase value is decreased by a third degree that is greater than the first degree until the increase value reaches the predetermined determination value. In a second aspect of the present invention, there is provided a method for controlling fuel supply after starting of an internal combustion engine, which is characterized in that the increase value is decreased by the second decrease degree after the increase value becomes lower than the initial increase value. setting a first predetermined discriminant value and a second predetermined discriminant value smaller than the first predetermined discriminant value, and determining whether or not the engine temperature during cranking is greater than a predetermined value within a low engine temperature region; When the engine temperature is higher than the predetermined value, the first
When the engine temperature becomes lower than the first predetermined determination value, the increase value is decreased by a second reduction degree smaller than the first degree, and when the engine temperature is lower than the predetermined value, Until the increase value reaches the predetermined criterion value, the third degree of decrease is greater than the first degree, and until the increase value reaches the second predetermined criterion value, the first decrease degree is maintained. The present invention provides a post-start fuel supply control method for an internal combustion engine, characterized in that the increase value is decreased by the second reduction degree after the increase value becomes less than the second predetermined determination value.

(Operation) According to the first invention, until the increase value reaches the predetermined judgment value set according to the initial increase value, the first
When the increase value falls below the predetermined determination value, the increase value is decreased by a second decrease degree smaller than the first degree, and the engine temperature during cranking is reduced to a predetermined value within the low engine temperature range. When the increase value is smaller than the predetermined judgment value, the increase value is decreased at a third degree of decrease that is greater than the first degree until the increase value reaches the predetermined judgment value. The initial increase value, which is set to a large value, can be reduced by a larger degree of reduction to reduce the supplied fuel amount more quickly.

Furthermore, according to the second invention, the first predetermined discriminant value and the second predetermined discriminant value smaller than the first predetermined discriminant value are set according to the initial increase value.
Since substantially the same control as in the invention described above is performed, the amount of fuel to be supplied to the engine during the post-start fuel increase period can be set more accurately.

(Embodiment of the Invention) An embodiment 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 designates, for example, a four-cylinder internal combustion engine, and an intake pipe 2 is connected to the engine 1. A slot body 3 is provided in the middle of the intake pipe 2, and a slot valve 3' is provided inside. A throttle valve opening sensor 4 is connected to the throttle valve 3', and the valve opening of the throttle valve 3' is converted into an electrical signal and sent to an electronic control unit (hereinafter referred to as "ECU") 5. ing.

A fuel injection valve 6 is provided in the intake pipe 2 between the engine 1 and the throttle body 3. The fuel injection valve 6 is provided for each cylinder in the intake pipe 2 slightly upstream of an intake valve (not shown). fuel injection valve 6
is connected to a fuel pump (not shown). The fuel injection valve 6 is electrically connected to the ECU 5,
The valve opening time of fuel injection is controlled by a signal from the ECU 5.

On the other hand, an absolute pressure sensor 8 is provided downstream of the throttle valve 3' of the throttle body 3 via a pipe 7, and the absolute pressure signal converted into an electrical signal by the absolute pressure sensor 8 is transmitted to the ECU 5. sent to.

An engine water temperature sensor 9 is provided in the main body of the engine 1. This sensor 9 is made of a thermistor or the like, and is inserted into the circumferential wall of the engine cylinder filled with cooling water, and supplies its detected water temperature signal to the ECU 5.

An engine rotation speed sensor (hereinafter referred to as "Ne sensor") 10 and a cylinder discrimination sensor 11 are installed around the camshaft or crankshaft (not shown) of the engine, and the former 10 is a TDC signal, that is, 180 degrees of the engine crankshaft. The latter 11 outputs one pulse each at a predetermined crank angle position of a specific cylinder at a predetermined crank angle position for each rotation, and these pulse signals are sent to the ECU 5.

A three-way catalyst 13 is disposed in the exhaust pipe 12 of the engine 1, and performs the action of purifying HC, CO, and NOx components in the exhaust gas.

Furthermore, ECU 5 has a function that detects battery voltage.
The V _B sensor 14 is connected to other parameter sensors 15 such as an atmospheric pressure sensor and an engine starter switch 16, and the ECU 5 receives detected value signals from the V _B sensor 14 and other parameter sensors 15, Provided with on/off state signals.

As will be described in detail later, the ECU 5 calculates the opening time T _OUT of the fuel injection valve 6 and supplies the fuel injection valve 6 with a drive signal to open the fuel injection valve 6 based on the calculated value.

FIG. 3 is a block diagram showing the circuit configuration inside the ECU 5 shown in FIG. 2. The engine rotation speed signal from the Ne sensor 10 shown in FIG. (hereinafter referred to as "CPU") 503 and is also supplied to the Me counter 502. The Me counter 502 counts the time interval from when the previous predetermined position signal was input from the Ne sensor 10 to when the current predetermined position signal was input, and the counted value Me is proportional to the reciprocal of the engine rotation speed Ne. Me counter 5
02 supplies this count value Me to the CPU 503 via the data bus 510.

The respective output signals from various sensors such as the absolute pressure sensor 8, engine water temperature sensor 9, and _VB sensor 14 in FIG. is supplied to converter 506. A/
The D converter 506 sequentially converts the output signals from each sensor described above into digital signals and supplies the digital signals to the CPU 503 via the data bus 510.

The on/off state signal from the starter switch 16 in FIG.
The signal is supplied to the CPU 503.

The CPU 503 further provides read-on memory (hereinafter referred to as "ROM") via a data bus 510.
507, random access memory (RAM) 50
8 and the drive circuit 509, and the RAM
508 temporarily stores the calculation results etc. of the CPU 503, and the ROM 507 stores the control program executed by the CPU 503, a water temperature increase coefficient K _TW table determined according to the engine water temperature, which will be described later, and a water temperature coefficient.
C _AST table, etc. is memorized. CPU503 is
According to the control program stored in the ROM 507, the fuel injection time T _OUT of the fuel injection valve 6 is calculated according to the various engine parameter signals described above,
These calculated values are supplied to the drive circuit 509 via the data bus 510. The drive circuit 509 supplies the fuel injection valve 6 with a control signal to open the fuel injection valve 6 according to the calculated value.

Next, the details of the operation of the electronic fuel supply control device of the present invention having the above-mentioned configuration will be explained in detail in the first section described above.
This will be explained with reference to FIGS. 3 to 3 and 4 to 11.

FIG. 4 shows a flowchart when the CPU 503 of FIG. 3 calculates the valve opening time in synchronization with the TDC signal, and the entire system consists of an input signal processing block, a basic control block, and a starting control block. First, in the input signal processing block, when the engine ignition switch is turned on, the ECU
5 initializes (step 1),
When the engine starts, a TDC signal is input (step 2). Next, absolute pressure value P _BA and engine water temperature value are obtained from each sensor, which are all basic analog values.
T _W , battery voltage value V, throttle valve opening value θth
and the ON/OFF state signal of the starter switch 16 are read into the ECU 5 and the necessary values are stored (step 3). Next, count the elapsed time from the first TDC signal to the next TDC signal, calculate the engine speed Ne based on that value, and do the same.
Store in ECU 5 (step 4).

Next, in the basic control block, as will be described in detail later, it is determined whether or not the engine is in a cranking state (step 5). If the answer is yes, the engine is sent to the startup control subroutine of the startup control block, which determines Tic _R based on the engine water temperature value Tw using the Tic _R table (step 6), and also determines the engine speed value Ne. A correction coefficient K _N e is determined using a K _N e table (step 7). Then, the battery voltage correction variable Tv is determined using the Tv table (step 8), and each numerical value is inserted into the following equation (1) to calculate T _OUT (step 9).

T _OUT = Tic _R × K _N e + Tv ... (1) Also, if the answer in step 5 is negative (No)
If so, it is determined whether or not the engine is in a state where a fuel cut should be made (step 10), and if the answer is affirmative (Yes), the value of T _OUT is set to zero and a fuel cut is performed (step 11).

On the other hand, if the answer is determined to be negative (No) in step 10, each correction coefficient K _TW , K _AST , etc. and correction variable Tv, etc. are calculated (step 12). These correction coefficients and correction variables are determined by subroutines, tables, etc., respectively.

Next, a predetermined corresponding map is selected in accordance with each data such as the engine speed value Ne, absolute pressure value P _BA, etc., and Ti is determined based on the map (step 13).
Then, based on the correction coefficient value and correction variable value obtained in steps 12 and 13 above, the following equation (2) is used.
Calculate T _OUT (step 14).

T _OUT = Ti × K _TW × K _AST × K ₁ + K ₂ + Tv ... (2) Here, the coefficient K ₁ and the variable K ₂ are each of the above-mentioned sensors,
That is, a throttle valve opening sensor 4, an absolute pressure sensor 8, a Ne sensor 10, a cylinder discrimination sensor 11, another parameter sensor 15, and a starter switch 16.
Correction coefficients and correction variables that are calculated according to engine parameter signals from the engine, and are designed to optimize various characteristics such as starting characteristics, exhaust gas characteristics, fuel consumption characteristics, and engine acceleration characteristics depending on the engine operating condition. is calculated based on a predetermined calculation formula.
Then, the fuel injection valve 6 is operated based on the T _OUT value thus obtained (step 15).

Next, of the above-mentioned valve opening time control, the start determination subroutine and the post-start fuel increase coefficient K _AST calculation subroutine will be explained.

FIG. 5 shows a flowchart of a subroutine for determining whether or not the engine is in a cranking state in step 5 of FIG. In this cranking determination subroutine, first it is determined whether the starter switch is on or not (step 1), and 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). In this case, it is determined whether the engine rotation speed Ne is less than or equal to a predetermined cranking rotation speed Nc _R (for example, 400 rpm) (step 3), and if the former is greater than the latter, it is determined that cranking is not in progress and the basic control loop is continued. If the former is smaller than the latter, it is determined that cranking is in progress and the process moves to a starting loop (block in FIG. 4) (step 4).

FIG. 6 is a flowchart of a subroutine for calculating the increase coefficient _KAST after starting the engine according to the first invention. First, it is determined whether or not the engine state in the immediately preceding control loop was a cranking state ( Step 1) If in cranking state, water temperature coefficient for calculating initial value of post-start increase coefficient K _AST
C _AST according to the engine water temperature Tw in the ROM507.
(Step 2). This water temperature Tw is determined at the time of the final TDC pulse of the start mode. FIG. 7 is a _CAST table diagram showing an example of the relationship between the engine water temperature Tw and the water temperature coefficient _CAST . Based on the same diagram, the engine water temperature Tw is set to a predetermined extremely low temperature value.
Tw _AS0 (e.g. -10℃) or below, water temperature coefficient
C _AST0 (for example, 1.6) is set as C _AST , C _AST1 (for example, 1.4) when the water temperature Tw is above the cryogenic value Tw _AS0 and below the predetermined low temperature value Tw _AS1 , and water temperature Tw is above the above low temperature value Tw _AS1 . In this case, select C _AST2 (for example, 1.5). This water temperature coefficient C _CAS 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 (3) (step 3).

K _AST = C _AST × K _T w ... (3) K _TW is the water temperature increase coefficient determined from the table based on the water temperature Tw as described above.

Figure 8 shows engine water temperature Tw and water temperature increase coefficient K _TW
It is a _KTW table diagram showing the relationship between First, when the water temperature Tw is between a predetermined value Tw ₅ (e.g. 60°C) to Tw ₆ (e.g. 100°C), K _TW has a value of 1.0, but when it falls below Tw ₅ , the calibration variable 5 levels of temperature Tw ₁ ~
K _TW of 5 points is set for each Tw ₅ ,
When the water temperature Tw takes a value other than each variable value Tw ₁ to Tw ₅ , it is determined by interpolation calculation. Furthermore, when the engine water temperature value Tw exceeds the predetermined value Tw ₆ , bubbles are likely to be generated in the fuel supplied to the fuel injection valve 6 . When the bubbles are generated in the fuel, the bubbles are mixed with the fuel and discharged into the engine 1 from the fuel injection valve 6. As a result, the air-fuel ratio of the air-fuel mixture becomes lean, making it difficult to start the engine. In order to prevent the engine from becoming lean, K _TW is set to increase in a region where the engine water temperature value Tw exceeds a predetermined value Tw ₆ as shown in FIG.

Next, the discriminant value K _ASTR0 is determined (step 4). This discriminant value K _ASTR0 remains large until the K _AST value reaches this discriminant value K _ASTR0 , as described later.
This is set in order to decrease the K _AST value, and to reduce the K _AST value to a small degree if it becomes below the K _ASTR0 value, and is determined by the following formula (4).

K _ASTR0 = (K _AST −1) × R _AST0 +1 ...(4) Here, the K _AST value is the value calculated in the previous step 3,
In other words, it is the initial value of the coefficient _KAST , and _RAST0 is the coefficient value so that the amount of fuel supplied to the engine during the fuel increase period after startup becomes the required amount that adapts to the engine temperature.
_KAST is a predetermined coefficient (for example, 0.5) that is set to approximate the solid line in FIG. This route is only passed once at the end of cranking, and the engine water temperature
Initial value of increase coefficient K _AST according to Tw and the initial value
Determine the discrimination value K _ASTR0 according to K _AST and end this program.

If the determination result in step 1 is negative (No), that is, if the engine state is not in the cranking state in the control loop, the process proceeds to step 5, and the engine water temperature value Tw is set to a predetermined value Tw _AS0 (for example -
10° C.), and if the determination result is affirmative (Yes), proceed to step 7. In step 7, it is determined whether the increase coefficient K _AST is larger than the judgment value K _ASTR0 , and if the judgment result is affirmative (Yes), a predetermined value DK _AST1 is set as the subtraction constant ΔK _AST (step 8), and the judgment is negative. (No), set the subtraction constant ΔK _AST to a predetermined value smaller than the above value DK _AST1 .
Set DK _AST2 (Step 9).

If the determination result in step 5 is negative (No),
That is, when the engine water temperature value is smaller than the predetermined value Tw _AS0 (-10°C), the process proceeds to step 6, where, as in step 7, it is determined whether or not the increase coefficient _KAST is greater than the discrimination value _KASTR0 , and the determination result is affirmative. In the case of (Yes), a predetermined value DK _AST3 larger than the above-mentioned value DK _AST1 is set as the subtraction constant ΔK _AST (step 10),
In case of negation (No), the above value is used as a subtraction constant.
Set DK _AST2 (Step 9).

Next, proceeding to step 11, the increase coefficient value _KAST used in the previous loop is set to a smaller value by the _{ΔKAST value} using the thus set subtraction constant value _ΔKAST . Next, the process proceeds to step 12, where it is determined whether the _KAST value is greater than 1.0, and if the value is greater than 1.0, the program is terminated.

Thereafter, the subtraction in step 11 is repeated every time a TDC signal pulse is generated, and the increase coefficient value _KAST decreases along a center line determined according to the engine water temperature immediately after cranking, such as the solid line shown in Fig. 9. become.

More specifically, the engine water temperature value Tw is a predetermined value.
When it is larger than Tw _AS0 , the increase coefficient _KAST decreases at a rate of decrease approximately along the solid line in FIG. 9, that is, the solid line in FIG. On the other hand, when the engine water temperature value Tw is smaller than the predetermined value Tw _AS0 (-10°C), as at the time of starting between extremes,
Therefore, when the initial value of the increase coefficient value _KAST is large, the increase coefficient _KAST decreases as shown by the solid line in FIG. That is, until the increase coefficient value K _AST reaches the discriminant value K _ASTR0 , the K _AST value decreases at a greater degree than when it is decreased at the degree of decrease along the solid line in Figure 1 (the broken line' in Figure 9). . In this way, the air-fuel ratio rapidly becomes lean to the extent that engine stall does not occur.
This prevents the plug from smoldering. Thereafter, after the coefficient value _KAST falls below the discrimination value _KASTR0 , the degree of decrease is made smaller and the air-fuel ratio is gradually made leaner, so that stable combustion is ensured.

In other words, since the above-mentioned discrimination values K _ASTR0 and K _ASTR1 are appropriately set according to the initial value of the increase coefficient value K _AST , after the engine is started, the desired fuel supply can be performed from the initial stage to the subsequent warm-up state. This makes it possible to perform control according to engine characteristics.

In addition, in the above embodiment, since the material value after startup is calculated by subtracting the subtraction constant ΔK _AST from its initial value, the increase value is equal to the predetermined discrimination value K _ASTR0 ,
The setting of the increase value after going below K _ASTR1 can be freely set independently from that before going below the discrimination value (i.e., the subtraction constants D _KAST3 , D _KAST1 , D _KAST2
(by appropriately changing the ratio or difference between them), it is possible to increase the amount of fuel after startup in accordance with the characteristics of each engine.

When the subtraction in step 11 is repeatedly executed and the increase coefficient value _KAST becomes a value of 1.0 or less, the determination result in step 12 is negative (No), and it is assumed that the post-start fuel increase period has ended, and the increase coefficient _KAST is set to a value of 1.0. (Step 13) and exit this program.

FIG. 10 is a flowchart of a subroutine for calculating the increase coefficient _KAST after engine start according to the second invention, in which step 20 and step 21 are added to the calculation subroutine according to the first invention shown in FIG. ing.

First, in step 20, following step 4,
A second discriminant value K _ASTR1 , which is smaller than the first discriminant value K _ASTR0 calculated in step 4, is calculated using the following equation.

K _ASTR1 = (K _AST −1)×R _AST1 +1 (5) where R _AST1 is a second predetermined coefficient (for example, 0.3) that is smaller than the first predetermined coefficient R _AST0 .

Next, in step 21, if the engine water temperature value Tw is smaller than the predetermined value Tw _AS0 (the judgment result in step 5 is negative (No)) and the increase coefficient value K _AST is smaller than the first judgment value K _ASTR0 (step 6 (if the discrimination result is negative (No)), _KAST is the second discrimination value
It is determined whether or not the value is larger than K _ASTR1 . If the determination result is positive (Yes), the predetermined value DK _AST1 is set as the subtraction constant ΔK _AST (step 8), and if the determination result is negative (No), the predetermined value DK AST1 is set as the subtraction constant ΔK AST. The predetermined value DK _AST2 is set as ΔK _AST (step 9). It should be noted that the steps other than step 20 and step 21 are the same as those in FIG. 6, so the same reference numerals are given and the explanation thereof will be omitted.

Figure 11 shows that the increase coefficient value K _AST according to the second invention is
FIG. 3 is a diagram showing how the TDC signal changes with the generation of pulses. The solid line shows how the increase coefficient K _AST changes when the engine water temperature value Tw is smaller than the predetermined value Tw _AS0 , and the increase coefficient value K _AST is the first discrimination value.
The degree of decrease in the coefficient value K _AST is increased until it reaches K _ASTR0 , and after it falls below the first discriminant value K _ASTR0 , the degree of decrease is made slightly smaller, and then the second discriminant value K _ASTR1 is further decreased. By making the degree of decrease smaller after turning, it is possible to prevent plug fogging immediately after starting the engine, and also to prevent plug fogging immediately after starting the engine _.
1, an increase coefficient value K _AST is obtained that smoothly transitions to a degree of decrease approximately equal to the degree of decrease along the solid line illustrated in FIG. 1. By applying this increase coefficient value _KAST , it is possible to more accurately set the amount of fuel to be supplied to the engine during the post-start fuel increase period. Note that the dashed lines ' and ' of FIG. 11 indicate the same center-fold lines as the solid lines and solid lines of FIG. 9, respectively.

Also, in this embodiment (second invention), since the post-start increase value is calculated by subtracting it from its initial value, similarly to the embodiment according to the first invention,
It is possible to increase the amount of fuel after startup in accordance with individual engine characteristics.

In this example, the case where _RAST0 in step 4 of FIGS. 6 and 10 is the same value is shown, but in order to better match the engine condition during the increase period after engine start, it is preferable to set them to different values. It's okay.

(Effects of the Invention) As detailed above, according to the post-start fuel supply control method for an internal combustion engine of the first invention, the initial period of the post-start fuel increase period is determined when the internal combustion engine is in a low temperature range. A predetermined judgment value is set according to the increase value, and when the engine temperature during cranking is higher than a predetermined value within the low engine temperature range, the fuel increase value during the post-start fuel increase period reaches the predetermined judgment value. When the engine temperature falls below a predetermined determination value at a first reduction degree, the fuel increase value is decreased at a second reduction degree smaller than the first reduction degree, and when the engine temperature is lower than the predetermined value, the fuel increase value is decreased. Until the value reaches the predetermined judgment value, the increase value is decreased by a third reduction degree that is larger than the first degree, and after falling below the predetermined judgment value, the increase value is decreased by the second reduction degree, and the increase value is decreased in this manner. Since the amount of fuel calculated using the increase value is supplied to the engine in synchronization with the generation of pulses of a predetermined control signal, it is possible to reduce the amount of fuel in extremely cold conditions when there is a large amount of injected fuel adhering to the inner wall surface of the intake pipe or the inner wall surface of the cylinder. , a larger initial fuel increase value can be set according to this adhesion amount, and the larger the initial fuel increase value is, the larger the reduction degree is to reduce the amount of fuel to be supplied, and then This makes it possible to prevent the mixture from becoming richer due to fuel evaporation due to the sudden rise in the temperature of the inner wall of the cylinder due to engine combustion, thereby ensuring a stable fuel supply and preventing the plug from smoldering. Furthermore, according to the post-start fuel supply method of the second invention, a first predetermined discrimination value and a second predetermined discrimination value smaller than the first predetermined discrimination value are set according to the initial fuel increase value, It is determined whether or not the engine temperature is higher than a predetermined value, and when the engine temperature is higher than the predetermined value, the increase value is at a first decrease degree until the increase value reaches the first predetermined determination value. , the increase value is decreased by a second reduction degree smaller than the first degree, and when the engine temperature is lower than the predetermined value, the increase value is reduced to the first predetermined value. The third degree of decrease is greater than the second degree until the discriminant value is reached, and the first degree of decrease is maintained until the first predetermined discriminant value is lowered and the second predetermined discriminant value is reached. Since the increase value is decreased by the second decrease degree after falling below the second predetermined determination value, the amount of fuel to be supplied to the engine during the post-start fuel increase period can be set more accurately. This allows for smoother engine operation without causing plug smoldering.

Furthermore, in the first and second aspects of the invention, the increase value can be set after falling below a predetermined discrimination value by calculating the decrease in the increase value by a predetermined subtraction constant from its initial value. , can be set independently of the value before it goes below the discrimination value, making it possible to increase the amount of fuel after startup in accordance with the characteristics of each engine.

[Brief explanation of the drawing]

FIG. 1 is a diagram illustrating a fuel increase supply control method in the post-start fuel increase period, FIG. 2 is an overall configuration diagram of a fuel supply control device to which the method of the present invention is applied,
Fig. 3 is a circuit diagram showing the internal configuration of the electronic control unit (ECU) 5 shown in Fig. 2, Fig. 4 is a flowchart for calculating the fuel injection valve opening time T _OUT , and Fig. 5 is the same as Fig. 4. The flowchart of the included cranking determination subroutine, FIG.
FIG. 7 is a flowchart for calculating the fuel increase coefficient after startup _KAST according to the invention, and FIG. 7 shows the relationship between the water temperature coefficient _CAST used to calculate the fuel increase coefficient after startup _KAST and the engine water temperature Tw _. Table diagram, No. 8
The figure is a _KTW table diagram showing the relationship between the water temperature increase coefficient _KTW and the engine water temperature Tw, and Figure 9 shows how the post-start fuel increase coefficient value _KAST according to the first invention changes with the generation of the TDC signal pulse. Figure 10 is a flowchart for calculating the post-start fuel increase coefficient _KAST according to the second invention, Figure 11 is TDC.
FIG. 7 is a diagram showing how the post-start fuel increase coefficient value _KAST according to the second invention changes with the generation of a signal pulse. 1... Internal combustion engine, 5... Electronic control unit (ECU), 6... Fuel injection valve, 9... Engine water temperature sensor, 10... Engine rotation speed sensor, 16... Starter switch, 503... Central processing unit (CPU), 507... Read only memory (ROM), 508... Random access memory (RAM).

Claims (1)

[Claims] 1. When the internal combustion engine is in a low temperature range, determining an initial fuel increase value according to the engine temperature when a predetermined control signal is generated immediately after cranking the engine;
Thereafter, each time the predetermined control signal is generated, the initial fuel increase value is decreased by a predetermined degree, and the fuel amount calculated using the reduced image fuel increase value is supplied to the engine in synchronization with the generation of the control signal after starting. In the fuel supply control method, a predetermined determination value is set according to the initial fuel increase value, it is determined whether the engine temperature during cranking is higher than a predetermined value within a low engine temperature range, and the engine temperature is When it is larger than the predetermined value, the amount is increased at the first degree of decrease until the increase value reaches the predetermined judgment value, and after it falls below the predetermined judgment value, the amount is increased at a second degree of decrease that is smaller than the first degree. and when the engine temperature is lower than the predetermined value, a third degree larger than the first degree is maintained until the increase value reaches the predetermined determination value.
A method for controlling fuel supply after startup of an internal combustion engine, characterized in that the increase value is decreased by a second decrease degree after the increase value becomes less than the predetermined determination value by a decrease degree of . 2. The post-movement fuel supply control method for an internal combustion engine according to claim 1, wherein the predetermined discrimination value is set by multiplying the initial fuel increase value by a predetermined coefficient. 3. When the internal combustion engine is in a low temperature range, determining an initial fuel increase value according to the engine temperature when a predetermined control signal is generated immediately after cranking the engine;
Thereafter, each time the predetermined control signal is generated, the initial increase value is decreased by a predetermined degree, and the amount of fuel calculated using the decreased increase value is supplied to the engine in synchronization with the generation of the control signal. In the supply control method, a first predetermined discrimination value and a second predetermined discrimination value smaller than the first predetermined discrimination value are determined according to the initial increase value.
It is determined whether the engine temperature during cranking is greater than a predetermined value within the low engine temperature range, and when the engine temperature is greater than the predetermined value, the increase value is set to the first increase value. The increase value is decreased at a first degree of decrease until reaching a predetermined judgment value of When the temperature is lower than the predetermined value, until the increase value reaches the first predetermined determination value, the first
Until the amount falls below a predetermined judgment value and reaches the second predetermined judgment value, the first reduction degree is applied, and after the amount falls below the second predetermined judgment value, the increase value is increased at the second reduction degree. A method for controlling fuel supply after startup of an internal combustion engine, characterized in that: 4. After starting the internal combustion engine according to claim 3, the first and second predetermined discrimination values are set by multiplying the initial increase value by first and second predetermined coefficients. Fuel supply control method. 5. The post-start fuel supply control method for an internal combustion engine according to claim 1 or 3, wherein the increase value is decreased by subtracting a predetermined subtraction constant from the increase value.