JPH0650075B2 - Fuel supply control method for starting internal combustion engine - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a fuel supply control method for starting an internal combustion engine, and more particularly to a fuel supply control method for improving startability of the internal combustion engine at low temperatures.

(Technical background of the invention and its problems) The opening time of a fuel injection valve during cranking of an internal combustion engine, particularly a gasoline engine, is set so that the fuel injection amount decreases as the engine temperature rises according to the engine temperature. A fuel supply control method in which the reference valve opening time is set to, and the set reference valve opening time is corrected to decrease as the engine speed increases in accordance with the engine speed during cranking ( This is hereinafter referred to as a "fuel supply control method by the start mode", and has been proposed by the present applicant (Japanese Patent Laid-Open No. 57-20673).
No. 6).

In such a fuel supply control method, the reference valve opening time during cranking is set according to the engine temperature because a part of the injected fuel amount adheres to the inner wall of the intake pipe or the inner wall of the cylinder and the fuel evaporates. This is because the amount changes depending on the engine temperature, and particularly when the engine temperature is low, such as during low temperature starting, a large amount of fuel is supplied to the engine to obtain good startability.

The reason why the reference valve opening time is corrected according to the engine speed will be described below. If the throttle opening is constant,
When the engine speed increases, the intake manifold pressure (absolute pressure) decreases, and the intake air amount per intake stroke decreases. Therefore, it is necessary to reduce the amount of fuel when the engine speed is high even if the water temperature is the same. If the engine starter fails to start even though it has been activated and the starter is activated again to perform cranking, or if this operation is repeated, the engine water temperature does not change much,
The frictional resistance of the sliding portion of the engine cylinder decreases, and the engine speed during cranking increases. Therefore, the amount of fuel required for cranking must be set smaller as the engine speed increases. Therefore, if the above correction is not performed, when the cranking operation is repeated, the amount of fuel supplied to the engine during cranking becomes excessive and the fuel rich air-fuel ratio is obtained, so the spark plug gets wet with fuel, Inconvenience (so-called “fog phenomenon”) such as carbon deposition on the spark plug electrode and no reliable ignition spark is formed, which results in a problem in reliable and smooth starting.
For the above reasons, the reference valve opening time is corrected according to the engine speed to obtain good startability.

By the way, when the engine temperature is low, such as during cold start, the viscosity of the engine oil is high, and the engine speed during cranking is low. Therefore, for example, even when the cranking operation is repeated and the inner wall of the cylinder gets wet with fuel and the frictional resistance of the sliding portion of the engine cylinder decreases, the engine speed does not rise unidirectionally, and the engine speed does not increase. If the fuel injection is continued for a long time based on the valve opening time that is corrected in accordance with the above, the fuel amount may become excessive and a fogging phenomenon may occur in the ignition snoop, which deteriorates the startability of the engine.

Further, when the engine is in the complete explosion state and the self-sustaining operation is possible, it is no longer necessary to control the fuel supply by the above-mentioned starting mode, but rather the fuel amount set according to the operation parameter value representing the load of the engine. Of fuel consumption characteristics to shift the fuel supply control to supply fuel to the engine (hereinafter referred to as "fuel supply control in basic mode"),
Desirable in terms of exhaust gas characteristics. However, if it is determined that the engine has left the cranking state when the engine speed becomes equal to or higher than a fixed value, which is a fixed value, the viscosity of the engine oil will be reduced even if the engine reaches a complete explosion state at low temperature start of the engine. Since the engine speed is high and the engine speed at the time of complete explosion is low, it may be determined that the engine is still in the cranking state until the predetermined determination value is reached, and an excessive amount of fuel in the start mode may be supplied. And adversely affect the exhaust gas characteristics.

(Object of the invention) The present invention has been made in view of the above-mentioned points, and aims to improve the startability of an engine under low temperature conditions, and quickly disengages the cranking state after the complete explosion of the engine to achieve the basic mode. An object of the present invention is to provide a fuel supply control method for improving startability and exhaust gas characteristics by performing fuel supply control.

(Structure of the Invention) According to the first invention, the engine temperature is detected when the internal combustion engine is started, and the reference fuel amount set according to the engine temperature is set according to the engine speed. In the fuel supply control method for correcting the set amount of fuel and supplying the corrected amount of fuel to the internal combustion engine, the correction value for the same engine speed is set smaller when the engine temperature is low than when it is high. A fuel supply control method for starting an internal combustion engine is provided. According to the second aspect of the invention, the engine speed is detected, the engine temperature is detected, and when it is determined that the internal combustion engine is in the starting state, the reference fuel amount set according to the engine temperature is set to the engine speed. In the fuel supply control method of correcting with a correction value set according to the number, and supplying the corrected fuel amount to the internal combustion engine, the internal combustion engine is in the starting state when the engine speed is smaller than a determination rotation value. It is determined that the engine speed is equal to the first reference speed value and the first reference speed value.
Of the second reference speed value which is greater than the reference speed value and does not exceed the determination speed value, the correction value is set to decrease the corrected fuel amount as the engine speed increases. At least one of the first and second reference rotational speed values, and the determination rotational speed value are respectively set to be smaller when the engine temperature is low than when the engine temperature is high, whereby the engine speed is set to the first set value. There is provided a fuel supply control method at the time of starting an internal combustion engine, characterized in that the correction value when it is between a reference rotation speed value of 1 and a second reference rotation speed value is corrected according to the engine temperature. .

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

FIG. 1 is an overall configuration diagram of a fuel supply control device to which the method of the present invention is applied. Reference numeral 1 indicates, for example, an internal combustion engine of four cylinders, and an intake pipe 2 is connected to the engine 1. A throttle body 3 is provided in the middle of the intake pipe 2, and a throttle valve 3 '(not shown) is provided inside. A throttle valve opening (θ _TH ) sensor 4 is connected to the throttle valve 3 ′ so as to convert the valve opening of the throttle valve 3 ′ into an electric signal and send it to an electronic control unit (hereinafter referred to as “ECU”) 5. Has been

A fuel injection valve 6 is provided between the engine 1 and the throttle body 3 of the intake pipe 2. The fuel injection valve 6 is connected to a fuel pump (not shown) and is electrically connected to the ECU 5, and a signal from the ECU 5 controls the opening time of the fuel injection valve 6.

On the other hand, an absolute pressure (P _BA ) 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 electric signal by the absolute pressure sensor 8 is provided. Is sent to the ECU 5.

An engine water temperature sensor (hereinafter referred to as “Tw sensor”) 9 is provided in the main body of the engine 1, and the Tw sensor 9 is composed of a thermistor or the like, and is installed in the engine cylinder peripheral wall filled with cooling water to detect the detected water temperature signal. Supply to the ECU 5. An engine speed sensor (hereinafter referred to as "Ne sensor") 10 is mounted around a cam shaft or a crank shaft (not shown) of the engine, and the Ne sensor 10 has a predetermined crank angle position every 180 ° rotation of the engine crank shaft. That is, the top dead center (T
With respect to DC), a crank angle position signal (hereinafter referred to as “TDC signal”) pulse is output at a crank angle position before a predetermined crank angle, and this pulse signal is E
It is sent to CU5.

An exhaust pipe 11 of the engine 1 is provided with a three-way catalyst 12 for purifying HC, CO, and NOx components in the exhaust gas.

Further, the ECU 5 includes a battery voltage sensor, an O ₂ sensor,
The other parameter sensor 13 such as an atmospheric pressure sensor and the starter switch 14 of the engine are connected, and the ECU 5
Is supplied with the detection value signal from the other parameter sensor 13 and the ON / OFF state signal of the starter switch 14.

Next, the operation of the fuel supply control device configured as described above will be described.

The respective operating parameter signals are supplied from the throttle valve opening sensor 4, the absolute pressure sensor 8, the Tw sensor 9, the Ne sensor 10 and the other parameter sensor 13 to the ECU 5, and E
The CU 5 determines an engine operating state such as cranking based on these engine operating parameter signals and the on / off state signal from the starter / sitter 14, and according to the determined state, the fuel supply amount to the engine 1, that is, The valve opening time Tou _T of the fuel injection valve 6 is calculated.

The valve opening time Tou _T during cranking of the fuel injection valve 6, that is, in the starting mode is given by the following equation.

Tou _T = TiC _R × K _N e + Tv (1) where Tic _R is a reference of the opening time of the fuel injection valve during cranking corresponding to the reference fuel amount set according to the engine water temperature Tw at the time of engine start Value, which is described below in Tic _R
Determined by the table. K _N e is the engine speed N
A correction coefficient set according to e, which is K _N described later.
Determined by the e-table. Tv is a correction variable that is set according to other operating parameters such as the battery voltage.

Further, the valve opening time Tou of the fuel injection valve 6 in the basic mode is
_T is given by the following equation.

To _T = Ti × K ₁ + K ₂ (2) Here, Ti is a reference value of the valve opening time set according to the engine speed Ne and the intake pipe absolute pressure P _BA . or,
K ₁ and K ₂ are a correction coefficient value and a correction variable value that are set according to engine parameter signals from various sensors such as the throttle valve opening sensor 4 described above, respectively. It is set based on a predetermined arithmetic expression so that various characteristics such as gas characteristics are optimized.

The ECU 5 supplies to the fuel injection valve 6 a drive signal for opening the fuel injection valve 6 based on the valve opening time Tou _T obtained as described above.

FIG. 2 is a diagram showing a circuit configuration inside the ECU 5 of FIG.
The TDC signal from the Ne sensor 10 shown in FIG. 1 is subjected to waveform shaping by the waveform shaping circuit 501, and then is a central processing unit (hereinafter referred to as "CPU") as an interrupt signal for executing a cranking control program or the like which will be described later. It is supplied to 503 as well as to the Me counter 502. The Me counter 502 counts the time interval from the input of the previous TDC signal from the Ne sensor 10 to the input of the current TDC signal, and the count value Me is proportional to the reciprocal of the engine speed Ne. The Me counter 502 supplies this count value Me to the CPU 503 via the data bus 510.

1, the throttle valve opening sensor 4, the absolute pressure sensor 8,
Output signals from the Tw sensor 9 and the other parameter sensor 13 are corrected to a predetermined voltage level by the level correction circuit 504, and then sequentially supplied to the A / D converter 506 by the multiplexer 505. A / D converter 506
Is an output signal from each of the above-described sensors, which is sequentially converted into a digital signal, and the digital signal is transferred via the data bus 510 to C
It is supplied to the PU 503.

The on / off state signal from the starter switch 14 of FIG. 1 is adjusted to a predetermined voltage level by the level correction circuit 512, and then supplied to the CPU 503 via the data bus 510 converted into a predetermined signal by the data input circuit 513. It

The CPU 503 is further connected to a read only memory (hereinafter referred to as “ROM”) 507, a random access memory (RAM) 508, and a drive circuit 509 via a data bus 510, and the RAM 508 temporarily stores the calculation result or the like in the CPU 503. stored in, ROM 506 will be described later control program executed by the CPU 503, Tic _R table stores _{K N} e table or the like. CPU503 is R
According to the control program stored in the OM 507, the valve opening time Tou _T of the fuel injection valve 6 according to the various engine parameter signals described above is calculated, and this calculated value is supplied to the drive circuit 509 via the data bus 510. Drive circuit 5
09 supplies a drive signal for opening the fuel injection valve 6 to the injection valve 6 according to the calculated value.

FIG. 3 shows a flowchart of a cranking time control subroutine executed in the CPU 503 of FIG. 2. First, the engine water temperature value Tw is a predetermined temperature value Twc _R (for example, 0
(° C) is determined (step 1), and the determination result is affirmative (Yes), that is, the engine water temperature value Tw.
Is greater than the predetermined temperature value Twc _R , the process proceeds to step 2 and the cranking determination circuit numerical value Nc _R is set to the predetermined value Xc _RH.
At (for example, 400 rpm), the first and second pure rotational speed values N ₁ and N ₂ are set to predetermined values X _1H (for example 100 rpm) and X _2H (for example 400 rpm), respectively. On the other hand, when the determination result of the step 1 is negative (No), the determination rotational speed Nc _R is set to the predetermined value Xc _RL (eg, 300 rpm) smaller than the Xc _RH value, and the first and second reference rotational speeds N are set.
₁ and N ₂ are predetermined values X _1L (eg 50 rpm) and X _2L (eg 300 rp) smaller than the X _1H value and the X _2H value, respectively.
m) (step 3).

Next, in steps 4 and 5, it is determined whether the engine is in the cranking state. That is, when the starter switch 14 of the engine is on and the engine rotation speed Ne is smaller than the determination rotation speed Nc _R set in step 2 or 3 (when the determination results in steps 4 and 5 are both affirmative (Yes)). ) The engine determines that it is in the cranking state, and proceeds to step 6. On the other hand, when at least one of steps 4 and 5 is negative (No), it is determined that the engine is out of the cranking state, and the engine is controlled by the basic mode applied to the engine operation other than cranking. (Step 7).

In step 6, the fuel injection valve reference valve opening time Ti _cR during cranking is determined. This Ti _cR value is set according to the engine _coolant temperature Tw, and a Tw-Ti _cR table showing the relationship between the Tw and the Ti _cR value is shown in FIG. In this case, as the reference valve opening time _{Ti cR} and the engine coolant temperature Tw calibration variables, as water temperature increases, each predetermined value Tc _R1-5, are set Twc _R1-5, actual water temperature Tw is the value Twc _When it is in the middle of _R1-5 , the reference valve opening time Ti _cR is calculated by interpolation calculation.

Then applied to a Ne-K N _e table first and second reference rotational speed value N ₁ and N ₂ to a value in the step 8 step 2 or 3 is set shown in Figure 5, against the engine rotational speed value Ne The correction coefficient value K _N e is determined. That is, the correction coefficient value K _N e is the engine speed numerical value Ne being the first
A reference rotational speed value _{N 1} or less when the predetermined value K _N e ₁ (e.g. 1.0), the predetermined value K _N e ₂ (eg 0.5) when Ne value is N ₂ or the second reference speed value , Ne value is N ₁ value and N
_In the case of an intermediate value between the _two values, the correction coefficient value K _N e is calculated by interpolation calculation. At this time, the correction coefficient value K _N e is calculated so as to decrease as the Ne value increases. As a result, the valve opening time T _OUT corrected by applying the correction coefficient value K _N e to the equation (1) decreases as the Ne value increases. By setting the N ₁ value and the N ₂ value according to the engine water temperature value Tw as described above, when Ne is between the N ₁ value and the N ₂ value, as is clear from FIG. , The K _N e value according to the same engine speed is corrected according to the engine water temperature Tw, that is, when the engine Tw is lower than the predetermined temperature Twc _{R, the} K _N e value becomes smaller than when it is higher.

In step 9, Tic _R set in steps 6 and 8 above
Value and K _N e value are applied to the equation (1) to calculate the valve opening time Tou _T of the fuel injection valve 6 during cranking,
This program ends. In the fuel supply control method at the time of engine start of the above embodiment, when the engine water temperature Tw is lower than the predetermined value Tw _CR , the engine speed becomes lower due to the increase in the viscosity of the engine oil as compared to when it is higher. , When the engine speed Ne is between the N ₁ value and the N ₂ value, the valve opening time T _OUT for the same engine speed Ne
Is set so that even if the engine continues to run at low speed for a long time during cranking, it is possible to prevent the supplied fuel amount from becoming excessive. In addition, the above-mentioned discriminating rotation speed value N _CR is set to be smaller when the engine water temperature Tw is lower than the predetermined value Tw _CR as compared to when it is high. However, since this is quickly discriminated and the fuel supply control based on the basic mode is entered, good fuel consumption characteristics and exhaust gas characteristics can be obtained.

In the present embodiment, the determination of the cranking state is made based on the engine speed and the on / off state of the starter switch, but it may be made based only on the engine speed.

(Effects of the Invention) As described in detail above, according to the fuel supply control method for starting the internal combustion engine of the present invention, the cold startability of the engine under low temperature conditions is improved, and the fuel consumption characteristics and the exhaust gas characteristics are improved. Can be improved.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an overall configuration diagram of a fuel supply control device for an internal combustion engine to which the method of the present invention is applied, and FIG. 2 is a block diagram showing an internal configuration of the electronic control unit of FIG. FIG. 3 is a flowchart of a cranking control subroutine according to the present invention, FIG. 4 is a Tw-Tic _R table diagram, and FIG. 5 is N.
It is an e-K _N e table figure. 1 ... Internal combustion engine, 5 ... Electronic control unit (ECU), 6 ... Fuel injection valve, 9 ... Engine water temperature sensor (Tw sensor), 10 ... Engine speed sensor (Ne sensor), 14 ... Starter Switch, 503 ...
... Central processing unit (CPU), 507 ... Read only memory (ROM), 508 ... Random access memory (RAM).

Claims (2)

[Claims] 1. When an internal combustion engine is started, the engine temperature is detected, a reference fuel amount set according to the engine temperature is corrected by a correction value set according to the engine speed, and the corrected fuel is corrected. In the fuel supply control method for supplying a quantity to the internal combustion engine, the correction value for the same engine speed is set to be smaller when the engine temperature is low than when the engine temperature is high. Control method. 2. When the engine speed is detected, the engine temperature is detected, and when it is determined that the internal combustion engine is in a starting state, a reference fuel amount set according to the engine temperature is set according to the engine speed. In the fuel supply control method for supplying the corrected amount of fuel to the internal combustion engine, the internal combustion engine is determined to be in the starting state when the engine speed is smaller than the determination speed value. Along with the increase of the engine speed when the engine speed is between the first reference speed value and the second reference speed value that is greater than the first reference speed value and does not exceed the determination speed value. The correction value is set so as to reduce the corrected fuel amount, and at least one of the first and second reference rotational speed values, and the determination rotational speed value When the engine temperature is low, it is set smaller than when it is high, whereby the correction value when the engine speed is between the set first reference speed value and the second reference speed value is set. A method for controlling fuel supply at the time of starting an internal combustion engine, which is modified according to the engine temperature.