JPH06336939A - Electronically controlled fuel supply device for internal combustion engine - Google Patents

Abstract

PURPOSE:To perform control, wherein a correction factor for quantity-increase- correcting fuel injection quantity according to cooling water temperature is corrected to a value suitable for use fuel, directly after starting. CONSTITUTION:The judgment level RSTR of surge torque STR is set (S14) with an elapsed time after starting as a parameter PRSTR (S13) in an idle running condition after finishing engine start (S11, S12). Here at directly after starting, the judgment level RSTR is set as a relatively high level. The judgment level RSTR and actually detected surge torque STR are compared with each other (S15), and when lower than the judgment level RSTR, a quantity-increase- correction factor KTW is reducibly corrected (S16), when higher than the judgment level RSTR, the quantity-increase-correction factor KTW is increasingly corrected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronically controlled fuel supply device for an internal combustion engine, and more particularly to a technique for optimizing a correction ratio for increasing and correcting the fuel supply amount when the engine is cold.

[0002]

2. Description of the Related Art In a conventional electronically controlled fuel supply system for an internal combustion engine, the amount of air taken into the engine is detected, and the amount of fuel is supplied so as to form a mixture having a target air-fuel ratio in accordance with the amount of intake air. The fuel injection valve is calculated and calculated so as to drive and control the fuel injection valve according to the fuel supply amount. Further, during cooling, most of the fuel injected from the fuel injection valve adheres to the vicinity of the intake valve in a liquid state, the amount of fuel actually sucked into the cylinder decreases, and the air-fuel ratio of the intake air-fuel mixture becomes lean. I will make it. Therefore, the fuel supply amount is increased and corrected according to the temperature of the cooling water that represents the engine temperature to prevent the air-fuel ratio from becoming lean (actual open Sho 62-1623).
64, etc.).

By the way, the sticking rate, which is the rate of adhering to the vicinity of the intake valve in the fuel injected as described above, and the evaporation rate, which is the rate of evaporating from the adhering fuel and being sucked into the cylinder, are the same. Even the temperature condition varies depending on the properties of the fuel used at that time (mainly easiness of evaporation). For this reason, in the past, even when using a fuel whose air-fuel ratio is most likely to become lean (heavy fuel that is difficult to evaporate),
In order to prevent the misfire and the surge associated with the misfire due to the lean air-fuel ratio, the fuel increase ratio according to the water temperature is set to a large amount with a margin.

Therefore, when a light or ordinary fuel that relatively easily evaporates is used, the fuel amount increase correction becomes excessive, and the air-fuel ratio becomes overrich, which causes deterioration of fuel consumption and exhaust properties. There was a problem. As a technique for compensating the non-conformance of the increase correction due to the difference in the used fuel, a sensor for detecting the fuel property (heavy or light fuel) is provided, and the increase correction ratio by the water temperature is set according to the fuel property detected by the sensor. Although an optimizing system has been proposed (see Japanese Patent Laid-Open No. 1-216040), there is a problem that the cost of the system is increased because the sensor for detecting the fuel property is expensive.

Therefore, the present applicant has previously made a correction by increasing the amount of increase correction corresponding to the water temperature, which is set to a large amount as described above, within a range in which the surge torque does not exceed a certain allowable limit value. We have proposed a device capable of performing the minimum required increase correction corresponding to the fuel used at that time (see Japanese Patent Application No. 4-5846).

[0006]

By the way, as described above, the control for decreasing and correcting the increase correction according to the water temperature based on the detected value of the surge torque is performed in the period in which the increase correction is performed. Therefore, it is preferable to increase the time for executing the reduction correction by performing the correction immediately after the start.

However, immediately after the engine is started, the oil surroundings are insufficient, and the mixture formation is not stable and combustion is unstable. Therefore, the rotation fluctuation is likely to occur and the surge torque originally becomes relatively large. Is. Therefore, immediately after the start, even if a certain amount of time has passed from the start and the surge level required for stable engine operation and the surge torque actually detected are compared, it is possible to determine whether the increase correction is excessive or insufficient. Since it cannot be determined, the correction control was excluded from the target immediately after the start.

Immediately after the start, the air-fuel ratio becomes extremely rich due to sagging after the increased fuel injection during the start, and in such a rich state, the correlation between the air-fuel ratio and the surge torque is reversed (see FIG. 6). ). Therefore, in the configuration in which the excess / deficiency of the increase correction is determined based on the comparison between the surge torque and a constant determination value, the accuracy of the excess / deficiency determination may be deteriorated. Was excluded from the target.

As described above, immediately after the start, control is performed to correct the excessive increase correction to the minimum necessary amount by comparing the detected surge torque with the constant judgment value (the allowable limit value of the surge torque). Since it cannot be performed as expected, engine operation (air-fuel ratio
(Combustion), the correction control is executed after a lapse of time expected to be stable.
There is a problem in that the maximum control effect cannot be maximized because the period during which the increase correction according to the water temperature is performed can be corrected to the optimum increase correction level is limited.

The present invention has been made in view of the above-mentioned problems, and the control for correcting the increase correction according to the water temperature to a necessary minimum corresponding to the fuel used can be performed immediately after the start, and the correction is performed. The purpose is to maximize the effect of control.

[0011]

Therefore, an electronically controlled fuel supply system for an internal combustion engine according to the present invention is constructed as shown in FIG. In FIG. 1, the increase correction value storage means stores an increase correction value for increasing and correcting the fuel supply amount to the engine according to the engine temperature.

Then, the increase correction means refers to the increase correction value storage means on the basis of the engine temperature detected by the engine temperature detection means, and sends the increase correction value to the engine based on the increase correction value corresponding to the engine temperature at that time. Correct the fuel supply amount. On the other hand, the increase correction value correcting means stores the increase correction value stored in the increase correction value storage means so that the output fluctuation of the engine detected by the output fluctuation detecting means approaches a permissible limit value in a predetermined steady operation state of the engine. Correct the value.

Here, the permissible limit value varying means changes the permissible limit value in the increase correction value correcting means in accordance with the engine operating conditions.

[0014]

With this configuration, by correcting the increase correction value according to the engine temperature so that the output fluctuation of the engine approaches the allowable limit value, the output correction is suppressed to the allowable level while the increase correction value is the minimum necessary value. This is corrected to the limit, and as a result, it is corrected to the increase correction level corresponding to the increase correction request that differs depending on the fuel used.

Here, the permissible limit value of the output fluctuation which is the target of the correction control is changed according to the engine operating condition, whereby the increase correction is made for each of the operating conditions in which the generation level of the output fluctuation is different. It becomes possible to judge whether the value is excessive or insufficient, and even in the extremely rich region where the correlation between the air-fuel ratio and the output fluctuation (surge torque) is reversed, the desired correction is made by setting a higher limit value. It becomes possible.

[0016]

EXAMPLES Examples of the present invention will be described below. In FIG. 2 showing an embodiment, air is drawn into an internal combustion engine 1 from an air cleaner 2 through an intake duct 3, a throttle valve 4 and an intake manifold 5. At each branch portion of the intake manifold 5, a fuel injection valve 6 is provided for each cylinder. The fuel injection valve 6 is an electromagnetic fuel injection valve that is opened by energizing a solenoid, and is closed by deenergizing, and is opened by being energized by an injection pulse signal from a control unit 12 described later. Fuel, which is pressure-fed from a fuel pump (not shown) and adjusted to a predetermined pressure by a pressure regulator, is intermittently injected and supplied to the engine 1.

A spark plug 7 is provided in each combustion chamber of the engine 1 to spark-ignite and ignite and burn the air-fuel mixture. Exhaust gas is discharged from the engine 1 through the exhaust manifold 8, the exhaust duct 9, the catalyst 10 and the muffler 11. The control unit 12 provided for electronically controlling the fuel supply to the engine includes a CPU, ROM, RA
Equipped with a microcomputer including an M, A / D converter, an input / output interface, etc., receives input signals from various sensors, performs arithmetic processing as described later, and controls the operation of the fuel injection valve 6. To do.

As the various sensors, the intake duct 3 is used.
An air flow meter 13 is provided therein and outputs a signal according to the intake air flow rate Q of the engine 1. Further, a crank angle sensor 14 is provided and outputs a reference angle signal REF for each reference angle position (for example, for each TDC) and a unit angle signal POS for each 1 ° or 2 °. Here, the engine rotation speed Ne can be calculated by measuring the cycle of the reference angle signal REF or the number of generated unit angle signals POS within a predetermined time.

Further, a water temperature sensor 15 for detecting the cooling water temperature Tw of the water jacket of the engine 1 is provided.
The cooling water temperature Tw is a parameter representing the engine temperature, and the water temperature sensor 15 corresponds to the engine temperature detecting means in this embodiment. Furthermore, in each of the spark plugs 7,
An in-cylinder pressure sensor 16 of the type mounted as a washer of the spark plug 7 as disclosed in Japanese Utility Model Laid-Open No. 63-17432 is provided so that the in-cylinder pressure (combustion pressure) for each cylinder can be detected. Has become. The in-cylinder pressure sensor 16 is of a type that is mounted as a washer of the spark plug 7 as described above, or of a type that directly detects the in-cylinder pressure in the combustion chamber and detects the in-cylinder pressure as an absolute pressure. Is also good.

Further, the throttle valve 4 is provided with an idle switch 17 which is turned on at the fully closed position (idle position) of the throttle valve 4. Here, the CPU of the microcomputer incorporated in the control unit 12 basically uses the intake air flow rate Q detected by the air flow meter 13 and the engine rotation speed Ne calculated based on the detection signal from the crank angle sensor 14. The ejection pulse width Tp (← K × Q / Ne: K is a constant) is calculated.

Further, various correction coefficients COEF (including an increase correction coefficient K _TW (increase correction value) for correcting the basic injection pulse width (basic fuel injection amount) Tp according to the cooling water temperature Tw (engine temperature). ← 1 + K _TW + ...) is set, and the basic injection pulse width Tp is corrected by the various correction coefficients COEF to calculate the effective injection pulse width Te (← Tp × COEF). The function of the increase correction calculation based on the increase correction coefficient K _TW by the control unit 12 corresponds to the increase correction means in this embodiment.

Further, a voltage correction amount Ts for correcting the change in the effective valve opening time of the fuel injection valve 6 due to the battery voltage is set, and the voltage correction amount T is set to the effective injection pulse width Te.
s is added and the final injection pulse width Ti (← Te + T
s) is obtained. Then, the injection pulse signal having the injection pulse width Ti is output to the fuel injection valve 6 at a predetermined injection timing to electronically control the fuel injection by the fuel injection valve 6.

Here, the increase correction coefficient K _TW is stored in advance in a map using the cooling water temperature Tw as a parameter, and as an initial value, it is allowable even when a heavy fuel for which the increase request is the largest is used. A large value with allowance is set so that surge torque (output fluctuation) exceeding the level does not occur. Therefore, when the light fuel is normally used, the increase correction coefficient K _TW becomes an excessive increase correction, so that the control unit 12
As shown in the flowcharts of FIGS. 3 and 4, it has a function of correcting the increase correction coefficient K _TW to the minimum level required in accordance with the fuel used at that time.

In this embodiment, the control unit 12 is provided with software as functions of the increasing correction value correcting means and the allowable limit value varying means as shown in the flow chart of FIG. The means is
Control unit shown in the flow chart of FIG.
It is realized by 12 software functions and the cylinder pressure sensor 16. A memory (not shown) such as RAM or ROM provided in the control unit 12 corresponds to the increase correction value storage means.

In the flowchart of FIG. 3, first, in step 1 (denoted as S1 in the figure, the same applies hereinafter),
The detection signal output from the in-cylinder pressure sensor 16 according to the in-cylinder pressure P is A / D converted and read. In the next step 2, the average effective pressure equivalent value MPi is calculated by integrating the output of the in-cylinder pressure sensor 16 within a predetermined crank angle range (see FIG. 5).

At step 3, the newly calculated average effective pressure equivalent value MPi is set to Pi as the latest value, while the previous value is set to Pi _-1 . Then, in the next step 4, the previous value Pi ₋₁ is subtracted from the current value Pi to obtain the fluctuation component ΔPi of the average effective pressure. In step 5, filtering processing is performed to extract only the specific frequency component of the fluctuation component ΔPi.

Here, the specific frequency component is a frequency range corresponding to the main component of the torsional vibration of the vehicle drive system caused by the output fluctuation of the engine, and the frequency range overlapping with the frequency range most sensitive to the occupant of the vehicle. (For example, 2Hz-10H
z) is preferred. In the next step 6, the fluctuation component ΔPi subjected to the filtering process is set in STR as a surge torque equivalent value.

In the flow chart of FIG. 3, the output fluctuation (surge torque) of the engine is calculated based on the cylinder pressure (combustion pressure), but in addition to this, for example, it is calculated based on the rotation fluctuation. However, the configuration is not limited to the configuration using the in-cylinder pressure. On the other hand, the program shown in the flow chart of FIG. 4 shows the contents of arithmetic processing of the control unit 12 for optimizing the increase correction coefficient K _TW in accordance with the vaporization (heavy and light) of the fuel used.

The increase correction coefficient K _TW is used to increase the injection pulse width (injection amount) according to the increase. In the flowchart of FIG. 4, first, in step 11, whether or not the engine is starting (cranking) is checked by turning on / off a starter switch (not shown).
And the engine rotation speed Ne.

If the engine is not starting, go to step 12.
Go to the engine eye where the idle switch 17 is ON.
Judge whether it is in the dollar operation state (predetermined steady operation state)
Separate. Then, when in idle operation,
Proceed to step 13 to judge the surge torque STR.
Judgment level R_STRPR for determining
_STRTo set.

As will be described later, the judgment level R_STRYo
If the actual surge torque STR is higher than
Positive coefficient K_TWA large surge torque will be generated if the
Correction coefficient K_TWIs fixed
Meanwhile, the judgment level R _STRThan a real surge
If surge torque is low, surge torque increases
Increase correction coefficient K_TWIt is presumed that
Correction coefficient K_TWWill be corrected to decrease
Therefore, the judgment level R_STRTo the actual surge
Increment correction coefficient K to bring the STR closer_TWIs fixed
It Therefore, the judgment level R_STRIs an acceptable service
It is required to set the limit value (permissible limit value) of the torque.
It

As the parameter PR _STR , most preferably, the elapsed time from the start end (start switch OFF) is set. That is, immediately after the start is short after the start, the oil around is insufficient and the combustion is unstable, and a large surge torque is originally generated, which is a relatively large surge immediately after the start. Torque has the property of being tolerated.

Immediately after the start, there is a condition that the air-fuel ratio becomes extremely rich due to the post sag due to the increase in fuel during the start,
Under such a rich condition, a phenomenon may occur in which the normal correlation between the air-fuel ratio and the surge torque is reversed, that is, the surge torque increases as the air-fuel ratio becomes leaner (see FIG. 6). Therefore, immediately after the start as described above, it is preferable to set a relatively high surge torque as a control target, and in the next step 4, the smaller the parameter PR _STR is, in other words, the elapsed time from the start. The determination level R _STR is set to increase as it becomes shorter.

If the determination level R _STR immediately after the start is set to a high value as described above, at least under the operating condition where the surge torque is relatively large, at least the increase correction coefficient K _{TW is obtained.}
Since it is possible to determine the increase of the surge level due to the under setting, the increase correction ratio by the increase correction coefficient K _TW can be reduced within a range where the under setting is not made. However, since a relatively large surge torque tends to be allowed immediately after the start, the setting of the higher determination level R _STR does not pose a problem.

Even if the air-fuel ratio becomes extremely rich immediately after starting and the correlation between the surge torque and the air-fuel ratio is reversed (see FIG. 6), the surge torque target is set to a high value. , Judgment level R by leaning the air-fuel ratio
It is possible to avoid falling below _STR and ensure the determination accuracy. Thus, the determination level R immediately after the start
_By setting _STR higher, it is possible to correct the increase correction coefficient K _TW based on the surge torque determination result immediately after the start.

Further, when the elapsed time from the start becomes the time when the shift to stable operation of the engine 1 is expected, operating conditions under which lower surge torque can be controlled by appropriately setting the increase correction coefficient K _TW. Therefore, the judgment level R
_{The STR} is lowered to suppress the surge torque to a sufficiently low level, and the increase correction coefficient K _TW is corrected to a minimum value.

The above judgment level R _STR (allowable limit value of surge torque) is compared with the actual surge torque STR obtained in the flow chart of FIG. 3 in step 15, and if the surge torque STR is below the judgment level R _STR the, the process proceeds to step 16, the increase correction coefficient K _TW decreases corrected by a predetermined value [Delta] K _TW, conversely, when the surge torque STR exceeds the judgment level R _STR is generated, the program proceeds to a step 17, The increase correction coefficient K _TW is reduced by a predetermined value ΔK _TW to prevent the occurrence of surge exceeding the allowable level.

It should be noted, than the predetermined value [Delta] K _TW increasing modify the enrichment coefficient K _TW, it is preferable to set small predetermined value [Delta] K _TW decreasing modified, also increase correction factor corresponding to the appropriate water temperature Tw K _TW In addition, it is preferable to simultaneously correct the increase correction coefficient K _TW corresponding to other water temperature conditions at the same rate. By such correction control, it is possible to correct the increase correction ratio to the minimum necessary value corresponding to the fuel used at that time while suppressing the surge torque to the allowable limit value, and to avoid extra increase correction. , Fuel consumption and exhaust properties are improved. Here, in this embodiment, as described above, the correction control is executed immediately after the start by changing the determination level R _STR according to the elapsed time from the start, so that the correction control is executed. Make the time longer,
It is possible to maximize the effects of improving fuel economy and exhaust properties.

In the above description, the elapsed time from the start is used as the parameter PR _STR (engine operating condition) for determining the determination level R _STR. Speed, engine load, etc. may be used. That is, the lower the cooling water temperature Tw, the more easily the rotation fluctuation occurs, and it is predicted that a relatively large surge torque will be tolerated at a low temperature. Level R
_{It is sufficient} to set _STR and execute the correction control of the increase correction coefficient K _TW immediately after the start.

Further, since the air amount is generally controlled so that the idling speed becomes higher as the engine cools down, the idling speed or the engine load is set as the parameter PR _STR and the judgment level R is set.
It may be configured to determine _STR . Furthermore, it may be configured for determining the decision level R _{ST R} by combining a plurality of said parameters (engine operating conditions).

[0041]

As described above, according to the present invention, in the control for correcting the increase correction that is added according to the engine temperature so that the output fluctuation of the engine approaches the predetermined allowable limit value, the allowable limit value is set. By changing according to the engine operating conditions, it becomes possible to perform correction control immediately after starting,
There is an effect that the period during which the correction control is executed is lengthened to maximize the effect of improving the fuel economy and the exhaust property by the correction control.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of the present invention.

FIG. 2 is a system schematic diagram showing an embodiment of the present invention.

FIG. 3 is a flowchart showing the processing contents for obtaining a surge torque.

FIG. 4 is a flowchart showing correction control of an increase correction coefficient according to water temperature.

FIG. 5 is a diagram showing how the combustion pressure is integrated.

FIG. 6 is a diagram showing a correlation between an air-fuel ratio and surge torque.

[Explanation of symbols]

 1 Engine 6 Fuel Injection Valve 12 Control Unit 13 Air Flow Meter 14 Crank Angle Sensor 15 Water Temperature Sensor 16 Cylinder Pressure Sensor 17 Idle Switch

Continuation of front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display area F02D 45/00 368 S

Claims (1)

[Claims] 1. An engine temperature detecting means for detecting an engine temperature, an increase correction value storage means for storing an increase correction value for increasing and correcting an amount of fuel supplied to the engine according to the engine temperature, and the engine temperature detecting means. An increase correction means for referring to the increase correction value storage means on the basis of the engine temperature detected by the means, and for increasing and correcting the fuel supply amount to the engine on the basis of the increase correction value corresponding to the engine temperature at that time; Output fluctuation detection means for detecting the output fluctuation of the engine, and stored in the increase correction value storage means so that the output fluctuation of the engine detected by the output fluctuation detection means in a predetermined steady operating state of the engine approaches an allowable limit value. The increase correction value correcting means for correcting the increase correction value being corrected, and the allowable limit value changing means for changing the allowable limit value in the increase correction value correcting means according to the engine operating conditions. Electronically controlled fuel supply system for an internal combustion engine, characterized in that the.