JP2917195B2 - Electronic control fuel supply device for internal combustion engine - Google Patents

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 system for an internal combustion engine, and more particularly, to a technology for making the air-fuel ratio of an intake air-fuel mixture as lean as possible while avoiding generation of a surge torque exceeding an allowable level. About.

[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 supplied is adjusted in accordance with the amount of intake air to form a mixture having a target air-fuel ratio. The calculation is performed, and the drive of the fuel injection valve is controlled in accordance with the fuel supply amount. In addition, when the engine is cold, 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 decreases. I will make it. For this reason, the fuel supply amount is increased and corrected in accordance with the cooling water temperature representing the engine temperature so as to prevent the air-fuel ratio from becoming lean (actual opening 62-1623).
No. 64, etc.).

[0003] Incidentally, the adhesion rate, which is the rate of the fuel injected as described above adhering to the vicinity of the intake valve, and the evaporation rate, which is the rate at which the adhering fuel evaporates and is sucked into the cylinder, are the same. Even temperature conditions vary depending on the properties of the fuel used at that time (mainly, the ease of evaporation). For this reason, conventionally, even when using the fuel whose air-fuel ratio is most likely to be lean (heavy fuel that hardly evaporates),
In order to prevent the occurrence of a misfire or a surge caused by the misfire due to a lean air-fuel ratio, the fuel increase rate according to the water temperature is set to be relatively large in consideration of a margin.

[0004] Therefore, when a light or ordinary fuel which is relatively easy to evaporate is used, the fuel increase correction becomes excessive, causing the air-fuel ratio to become over-rich and deteriorating the fuel consumption and exhaust characteristics. There was a problem. Accordingly, the present applicant has to first correct the increase correction value corresponding to the water temperature which is set in advance in advance in consideration of the allowance as described above so that the surge torque does not exceed a certain allowable limit value. Proposed a device capable of performing the minimum increase correction required for the fuel used at that time (see Japanese Patent Application No. 4-5846).

[0005]

By the way, in a large displacement engine having a large number of cylinders such as eight cylinders, the rotation stability is high,
Of course, since the output torque is large, if the properties of the fuel used are relatively good (light fuel), even if the air-fuel ratio is made leaner than the stoichiometric air-fuel ratio after warm-up, a surge torque exceeding the allowable level is generated. May not.

That is, in a large displacement engine having high rotational stability and large output torque, the target air-fuel ratio of the air-fuel ratio feedback control can be made leaner than the stoichiometric air-fuel ratio. It is possible to improve the fuel efficiency and the exhaust characteristics by adopting the structure. However, as described above, since the leaning is performed under the condition that the properties of the fuel used at that time are good, in a usage environment where only good properties (light) are not necessarily used as the fuel used. However, the target air-fuel ratio could not be made lean.

On the other hand, in the control for correcting the increase correction value based on the water temperature based on the detected value of the surge torque, the increase correction value is adapted to the fuel used at that time, and is set in accordance with the heavy fuel. The properties (heavy and light) of the fuel used can be specified to some extent by the correction ratio with respect to the set initial value. That is, if the initial value adapted to the heavy fuel is reduced and corrected, the fuel used at that time can be estimated to be lighter in accordance with the increase in the reduction correction ratio,
Here, when the use of light fuel is estimated, leaning of the target air-fuel ratio can be realized.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and suppresses increase correction during warm-up and leans a target air-fuel ratio in air-fuel ratio feedback control after warm-up. It is an object of the present invention to provide an electronic control fuel supply device that can be realized while performing the above.

[0009]

Accordingly, an electronic control fuel supply system for an internal combustion engine according to the present invention is configured as shown in FIG. In FIG. 1, the air-fuel ratio detecting means is an engine intake.
The air-fuel ratio of the air-fuel mixture is detected, and the air-fuel ratio feedback control
The stage sets the air-fuel ratio detected by the air-fuel ratio detecting means to the target air-fuel ratio.
Feedback to the engine so that it approaches
Control . In addition, the output fluctuation detecting means detects the output fluctuation of the engine.
The fuel correction means for detecting and changing the output,
When the feedback control means is in the clamped state,
Allowable limit of engine output fluctuation detected by force fluctuation detection means
Increase or decrease the fuel supply to the engine so that it approaches the value.
You.

On the other hand, the target air-fuel ratio setting means controls the output fluctuation.
Based on the rate at which the fuel supply was
A target in the air-fuel ratio feedback control means.
Set the air-fuel ratio variably.

[0011]

According to this structure, the air-fuel ratio feedback system is used.
Allows engine output fluctuations when the control means is clamped
Increase or decrease the fuel supply to the engine so that it approaches the limit
Therefore, the correction result indicates that the output fluctuation does not exceed the allowable level.
The minimum required fuel supply is within this range. The required minimum fuel amount varies depending on the properties of the fuel. If the output fluctuation exceeding the allowable limit does not occur even with a small amount of fuel, leaning is possible even as the target air-fuel ratio of the air-fuel ratio feedback control. It is estimated that there is.

Therefore, the air-fuel ratio feedback control means
In the clamped state, the output fluctuation of the engine approaches the allowable limit.
To increase or decrease the fuel supply to the engine
Based on the target air-fuel ratio for air-fuel ratio feedback control,
And set the target air-fuel ratio according to the fuel properties.
In the air-fuel ratio feedback control state,
Lean while avoiding lux
Was.

[0013]

Embodiments of the present invention will be described below. In FIG. 2 showing one embodiment, air is sucked 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. In each branch 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 energized by a solenoid and opens, and is deenergized and closed by being energized by an injection pulse signal from a control unit 12 described later. The fuel which is pressure-fed by a fuel pump (not shown) and adjusted to a predetermined pressure by a pressure regulator is intermittently injected and supplied to the engine 1.

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

The various sensors include an intake duct 3
An air flow meter 13 is provided therein, and outputs a signal corresponding 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 period of the reference angle signal REF or the number of occurrences of the unit angle signal POS within a predetermined time.

Further, a water temperature sensor 15 for detecting a cooling water temperature Tw of the water jacket of the engine 1 is provided.
Further, each of the ignition plugs 7 is provided with an in-cylinder pressure sensor 16 of a type mounted as a washer of the ignition plug 7 as disclosed in Japanese Utility Model Application Laid-Open No. 63-17432. The internal pressure (combustion pressure) can be detected.

The in-cylinder pressure sensor 16 is of a type which is mounted as a washer of the ignition plug 7 as described above, or a type which detects the in-cylinder pressure as an absolute pressure by directing a sensor portion directly into the combustion chamber. It may be. The throttle valve 4 is provided with an idle switch 17 which is turned on when the throttle valve 4 is fully closed (idle position).

An oxygen sensor 18 as an air-fuel ratio detecting means is provided at a collecting portion of the exhaust manifold 8. The oxygen sensor 18 is a known sensor that generates an electromotive force _VO2 according to the ratio of the oxygen partial pressure in the exhaust gas to the oxygen partial pressure in the reference gas (atmosphere). By utilizing the rapid change in the oxygen concentration of the exhaust gas, it is possible to detect the rich / lean ratio of the exhaust air-fuel ratio to the stoichiometric air-fuel ratio.

Here, the CPU of the microcomputer built in the control unit 12 calculates the injection pulse width Ti (fuel supply amount) as follows, and converts the injection pulse signal of the injection pulse width Ti into a predetermined value. Output to the fuel injection valve 6 at the injection timing, and the fuel injection by the fuel injection valve 6 is electronically controlled. The control unit 12
Intake air flow rate Q detected by the air flow meter 13
And the basic injection pulse width T based on the engine rotation speed Ne calculated based on the detection signal from the crank angle sensor 14.
p (← K × Q / Ne: K is a constant) is calculated.

Various correction coefficients COEF (← 1 + K _TW +) including an increase correction coefficient K _TW for increasing the basic injection pulse width Tp according to the cooling water temperature Tw at the time of cold operation.
..) Are calculated to set a voltage correction Ts for correcting a change in the effective valve opening time of the fuel injection valve 6 due to a change in the battery voltage (power supply voltage of the fuel injection valve 6). Further, when the predetermined feedback control condition is satisfied, the exhaust air-fuel ratio approaches the target air-fuel ratio based on the rich / lean ratio with respect to the stoichiometric air-fuel ratio detected from the output value of the oxygen sensor 18. Fuel ratio feedback correction coefficient α
(Initial value 1.0) is set by proportional / integral control.

Further, in a predetermined idle operation state (predetermined steady state), as described later, a surge torque of the engine is detected, and a surge torque feedback correction is performed in a direction in which the surge torque approaches a predetermined value (allowable limit value). Coefficient SC
OEF (initial value 1.0) is integrated and controlled. Then, the basic injection pulse width Tp is corrected by the various correction coefficients COEF, the voltage correction amount Ts, the air-fuel ratio feedback correction coefficient α, and the surge torque feedback correction coefficient SCOEF to obtain a final injection pulse width Ti (← Tp × COEF ×
SCOEF × α + Ts) is calculated.

FIG. 3 shows how the control unit 12 calculates the air-fuel ratio feedback correction coefficient α and the surge torque feedback correction coefficient SCOEF.
This will be described with reference to the flowcharts of FIGS. In this embodiment, the air-fuel ratio feedback control means, output fluctuation
The functions of the fuel correction means and the target air-fuel ratio setting means are provided in the control unit 12 as shown in the flowcharts of FIGS. 3 to 5, and the output fluctuation detecting means is shown in the flowchart of FIG. This is realized by the software function of the control unit 12 and the in-cylinder pressure sensor 16.

The program shown in the flowchart of FIG. 3 is for calculating the surge torque STR of the engine 1. In the flowchart of FIG. 3, first, in step 1 (S1 in the figure, the same applies hereinafter),
A 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 in-cylinder pressure sensor 16
Is integrated in a predetermined crank angle range to calculate an average effective pressure equivalent value MPi (see FIG. 6). Step 3
Then, the average effective pressure equivalent value MPi newly calculated this time
Is set to Pi as the latest value, while the previous value is set to Pi.
Set to _-1 . Then, in the next step 4, a variation component ΔPi of the average effective pressure is obtained by subtracting the previous value Pi ₋₁ from the current value Pi.

In step 5, a filtering process for extracting only the specific frequency component of the fluctuation component ΔPi is performed. Here, the specific frequency component is a frequency range corresponding to a main component of torsional vibration of a vehicle drive system caused by an output fluctuation of an engine, and overlaps a frequency range (for example, 2 Hz) that a passenger of the vehicle feels most sensitive. To 10 Hz).

In the next step 6, the fluctuation component ΔPi subjected to the filtering processing is set in the STR as a surge torque equivalent value. In the flowchart of FIG. 3, the output fluctuation (surge torque) of the engine is determined based on the in-cylinder pressure (combustion pressure), but may be determined based on, for example, rotation fluctuation. However, the invention is not limited to the configuration using the in-cylinder pressure.

FIG. 4 shows a program for calculating the surge torque feedback correction coefficient SCOEF and the air-fuel ratio feedback correction coefficient α. In the flowchart of FIG.
At 13, it is determined whether or not the engine 1 is in the idling operation state in which the engine 1 is not being started and a predetermined time has elapsed since the start of the engine 1.

If it is determined in steps 11 to 13 that all three conditions are satisfied, the routine proceeds to step 14, where the surge torque STR calculated in the flowchart of FIG. Tolerable limit)
Compare with When the surge torque STR detected in the predetermined idle operation state is equal to or more than a predetermined value,
Proceeding to step 15, the surge torque feedback correction coefficient SCOEF is increased by a predetermined value ΔCOE.

The initial value of the surge torque feedback correction coefficient SCOEF is 1.0, and the correction coefficient SCOEF
The fuel injection amount is increased and corrected by the increase correction of the EF, thereby stabilizing the combustion and reducing the surge torque STR. On the other hand, if the surge torque STR detected in the predetermined idle operation state is less than the predetermined value, the process proceeds to step 16, where the surge torque feedback correction coefficient SCOEF is reduced by the predetermined value ΔCOE.

The predetermined value is the allowable surge torque ST
Since the actual surge torque STR is smaller than the predetermined value, it is estimated that the air-fuel ratio of the engine intake air-fuel mixture can be further made leaner. As described above, the correction coefficient SCOEF is reduced to reduce the fuel injection amount. When the surge torque feedback correction coefficient SCOEF is controlled as described above, the generated surge torque converges to a value near the allowable limit, and the convergence value depends on the properties of the fuel used at that time. .

In particular, during warm-up in which the increase correction by the increase correction coefficient K _TW is set, for example, when the correction coefficient K _TW is adapted to a heavy fuel which requires a relatively high increase correction request, If the fuel used is relatively light, excessive increase correction by the correction coefficient K _TW
It is corrected by the correction coefficient SCOEF, and converges to the correction of the level required by the fuel used at that time.

That is, when a high-quality fuel having good atomization properties is used, a high flammability can be maintained even if the injection amount is small, so that the correction coefficient SCOEF is used.
Is expected to converge to a relatively small value. vice versa,
When a poor fuel with poor atomization properties is used, if the injection amount is small, good mixture formation cannot be achieved and the surge torque increases, so the correction coefficient SCOE is used.
It is expected that a relatively large value is required for F.

Here, the surge torque feedback correction coefficient SCOEF is controlled in a state where an air-fuel ratio feedback control described later is clamped. However, the fuel property predicted by the value of the correction coefficient SCOEF is as described above. , Can be reflected in the air-fuel ratio feedback control. That is, when a high-quality fuel having good atomization properties is used, especially when the engine 1 is an engine having a large displacement such as an eight-cylinder engine, the rotation stability is high and the output torque is large. Therefore, it is estimated that even if the target air-fuel ratio of the air-fuel ratio feedback control is made lean, surge torque exceeding an allowable level will not be generated.Conversely, if poor fuel is used, combustion will be stabilized. In order to make the target air-fuel ratio rich, it is determined that the target air-fuel ratio should be enriched.

Therefore, in step 17, the proportional components P _R and P _L used for proportional control of the air-fuel ratio feedback correction coefficient α are variably set in accordance with the level of the surge torque feedback correction coefficient SCOEF. The proportional component P
_R, as shown in FIG. 7, when the air-fuel ratio is inverted from rich to lean state than the stoichiometric air-fuel ratio is a value used to increase control of the correction coefficient alpha, conversely, the proportional portion P _L is ,
When the air-fuel ratio is richly inverted from a state leaner than the stoichiometric air-fuel ratio, this is a value used for control to decrease the correction coefficient α.

In step 17, the correction coefficient SCO
When EF is large, larger the proportional portion P _R, set to a small relatively proportional portion P _L, conversely, the correction coefficient SCO
When EF is small, smaller the proportional portion P _R, is adapted to set large relative proportional amount P _L. For example the correction coefficient SCOEF large, in the state where it can not be said that good properties of the fuel used, but it is desirable to stabilize the combustion by enriching the air-fuel ratio, as described above, by increasing the proportional part P _R, Conversely, if the proportional component P _L is set small, the control point of the air-fuel ratio feedback control will shift to the rich side, and it will be possible to respond to the enrichment request.

That is, the variable setting of the proportional components P _R and P _{L in} the step 17 changes the target air-fuel ratio of the air-fuel ratio feedback control according to the correction coefficient SCOEF, and the correction coefficient SCOEF is used as a parameter. Thus, the target air-fuel ratio is set in accordance with the properties of the fuel used at that time. When the proportional components P _R and P _L are variably set according to the correction coefficient SCOEF, the following step 18
Then, it is determined whether or not a condition for executing the air-fuel ratio feedback control (λ / C) is satisfied.

The stop (clamp) conditions for the air-fuel ratio feedback control are idle operation, low water temperature, start, deceleration, high load operation of the engine, and the like. as an air-fuel ratio feedback control condition is satisfied, the process proceeds to step 19, step 17 with the set proportional portion P _R, thereby calculating the air-fuel ratio feedback correction coefficient α using P _L.

The calculation of the correction coefficient α in step 19 is shown in the flowchart of FIG. In the flowchart of FIG. 5, first, in step 21, the output V _O2 of the oxygen sensor 18 is read. Then, in the next step 22, the slice level SL corresponding to the stoichiometric air-fuel ratio is determined.
Is compared with the output V _O2 read in step (1) to determine whether the air-fuel ratio is rich or lean.

Here, when it is determined that the output V _O2 is equal to or higher than the slice level SL and richer than the stoichiometric air-fuel ratio, the process proceeds to step 23, and it is determined whether or not the rich determination is the first time, that is, from lean. It is determined whether it is the time of inversion to rich. When it is the first time of rich judgment,
The process proceeds to step 24, decreases the proportional portion P _L by the correction coefficient alpha (see FIG. 7).

On the other hand, if it is determined in step 23 that it is not the first time, step 24 is jumped to step 25 where the correction coefficient α is reduced by a predetermined integral Δα. Further, in step 22, when the air-fuel ratio lower than the output V _O2 is a slice level SL is determined to be leaner than the stoichiometric air-fuel ratio, similarly to the rich determination, the first by a proportional amount P _R The increase correction is executed, and thereafter, the increase correction by the integral Δα is continued until the inversion is made rich (step 26).
~ Step 28).

In the above embodiment, the control point in the air-fuel ratio feedback control is corrected in the rich or lean direction by changing the proportional components P _R and P _L , and the target air-fuel ratio is substantially made rich or lean. In addition, the slice level SL is changed,
The control point (target air-fuel ratio) of the air-fuel ratio feedback control can also be changed by changing the delay time from the detection of rich / lean reversal to the stoichiometric air-fuel ratio to the execution of proportional control. Parameters that can change the air-fuel ratio (slice level S
L, delay time) may be variably set according to the correction coefficient SCOEF.

[0042]

As described above, according to the present invention, an empty space is provided.
In the clamp state of the fuel ratio feedback control, by correcting the fuel supply amount so that the output fluctuation approaches the allowable limit value, the increase correction is corrected to a necessary minimum particularly during warm-up, while the correction depending on the fuel property is performed. Since the target air-fuel ratio in the air-fuel ratio feedback control is changed based on the control result, it is possible to make the target air-fuel ratio in the air-fuel ratio feedback control lean while avoiding the occurrence of surge torque when the fuel properties are good. Thus, there is an effect that the fuel efficiency and the exhaust properties during the air-fuel ratio feedback control can be improved.

[Brief description of the drawings]

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

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

FIG. 3 is a flowchart showing detection control of surge torque.

FIG. 4 is a flowchart showing feedback control of a fuel supply amount.

FIG. 5 is a flowchart showing air-fuel ratio feedback control.

FIG. 6 is a diagram showing a state of integration of a combustion pressure.

FIG. 7 is a time chart showing a state of air-fuel ratio feedback control.

[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 18 oxygen sensor

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁶ , DB name) F02D 41/14 310 F02D 41/04 305 F02D 45/00 368

Claims (1)

(57) [Claims] An air-fuel ratio for detecting an air-fuel ratio of an engine intake air-fuel mixture.
Detection means, and the air-fuel ratio detected by the air-fuel ratio detection means is set close to the target air-fuel ratio.
Feedback control of the amount of fuel supplied to the engine
Air-fuel ratio feedback control means, output fluctuation detection means for detecting engine output fluctuation, and the air-fuel ratio feedback control means
The output fluctuation of the engine detected by the output fluctuation detecting means.
Fuel supply to the engine so that
The fuel supply means is corrected by a fuel correction means based on output fluctuation for increasing or decreasing
The air-fuel ratio feedback control means based on the
Target air-fuel ratio setting means for variably setting the target air-fuel ratio in the vehicle
And an electronically controlled fuel supply device for an internal combustion engine.