JP2002115584A - Fuel injection control device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To highly accurately calculate a fuel injection quantity by reducing the effect of a detection error of an atmospheric pressure sensor in calculating the fuel injection quantity. SOLUTION: After reading an intake pressure PM, the atmospheric pressure PA and an engine rotation speed NE (steps 101-103), this fuel injection control device calculates an intake air pressure correction factor KPM according to the atmospheric pressure PA, and corrects the intake pressure PM by the intake air pressure correction factor KPM into a reference intake air pressure PML under a reference air pressure PAbase (steps 104 and 105). Then, this control device finds a reference relative pressure DPML from a differential pressure between the reference intake air pressure PML and the reference air pressure PAbase and calculates a basic injection time TP from a map, etc., based on the reference relative pressure DPML and the engine rotation speed NE (steps 106 and 107). Secondly, this control device calculates an injection quantity correction factor KPA according to the atmospheric pressure PA, various types of correction factors K, and an invalid injection time TV and calculates a last fuel injection time TAUINJ (steps 108-110).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel injection control device for an internal combustion engine that calculates a fuel injection amount based on an intake pressure, an atmospheric pressure, and a rotation speed of the internal combustion engine.

[0002]

2. Description of the Related Art Conventionally, two-wheeled vehicles employ a collective intake engine in which a throttle valve is provided at an intake collecting portion upstream of an intake manifold of each cylinder, and a throttle valve is provided for each intake manifold of each cylinder. Some have adopted independent intake engines. The independent intake engine has the advantage of higher performance than the collective intake engine because the amount of air charged in each cylinder can be controlled by the throttle valve for each cylinder.However, the intake pressure is lower than the throttle valve downstream of the intake manifold for each cylinder. Therefore, a communication pipe is provided downstream of the throttle valve of the intake manifold of each cylinder so that they can communicate with each other, and an intake pressure sensor is provided in this communication pipe. In the independent intake engine having such a configuration, when the fuel injection amount is calculated from the intake pressure detected by the intake pressure sensor provided in the communication pipe and the engine rotation speed, the fuel injection amount is accurately calculated when the atmospheric pressure changes. Since it cannot be performed, it is necessary to perform correction according to the atmospheric pressure.

In Japanese Patent Application Laid-Open No. 10-280988, a differential pressure (relative pressure) between the intake pressure detected by the intake pressure sensor and the atmospheric pressure detected by the atmospheric pressure sensor is calculated, and the relative pressure is calculated based on the atmospheric pressure. After correcting the basic injection amount based on the corrected relative pressure and the engine speed with the relative pressure correction coefficient according to the relative pressure correction coefficient according to The fuel injection amount is obtained by correcting with various correction coefficients such as an injection amount correction coefficient corresponding to the above.

[0004]

By the way, the output characteristics of the atmospheric pressure sensor and the intake pressure sensor vary with each individual, and the output characteristics change with time and temperature. Further, the output of the atmospheric pressure sensor also changes depending on the degree of contact of the atmospheric pressure introduction opening with the wind, so that the detection error tends to be relatively large.

However, according to the technique disclosed in the above publication, in the process of calculating the basic injection amount, the differential pressure (relative pressure) between the intake pressure and the atmospheric pressure is corrected by a relative pressure correction coefficient corresponding to the atmospheric pressure. The relative pressure including the detection error of the atmospheric pressure sensor is corrected by the relative pressure correction coefficient including the detection error of the atmospheric pressure sensor, whereby the detection error of the atmospheric pressure sensor is multiplied and the error is amplified. Will be. as a result,
The influence of the detection error of the atmospheric pressure sensor on the calculation accuracy of the fuel injection amount increases, and the error of the fuel injection amount due to the change in the atmospheric pressure tends to increase.

In recent years, in motorcycles having a large valve overlap, in order to reduce exhaust emissions,
Since the air-fuel ratio is controlled close to the lean limit, if there is a large error in the fuel injection amount, the air-fuel ratio exceeds the lean limit, which tends to cause poor combustion, which may lead to deterioration in drivability and exhaust emissions. There is.

The present invention has been made in view of such circumstances, and therefore has an object to reduce the influence of the detection error of the atmospheric pressure sensor when calculating the fuel injection amount. It is an object of the present invention to provide a fuel injection control device for an internal combustion engine that can improve the calculation accuracy of a fuel injection amount and prevent deterioration of drivability and exhaust emission.

[0008]

In order to achieve the above object, a fuel injection control apparatus for an internal combustion engine according to a first aspect of the present invention comprises a reference intake pressure calculating means for correcting an intake pressure according to an atmospheric pressure. After calculating the reference intake pressure by correcting with a coefficient, a reference relative pressure, which is a differential pressure between the reference intake pressure and the reference atmospheric pressure, is calculated by reference relative pressure calculating means, and at least the reference relative pressure and the internal combustion engine rotational speed are calculated. And the fuel injection amount is calculated by the fuel injection amount calculation means.

In this case, in the process of calculating the fuel injection amount,
Since only the detected value of the atmospheric pressure sensor is used only when obtaining the intake pressure correction coefficient corresponding to the atmospheric pressure, the detection error of the atmospheric pressure sensor is reduced as in the related art (Japanese Patent Laid-Open No. 10-280988). Multiplication does not amplify the error. For this reason, the influence of the detection error of the atmospheric pressure sensor on the calculation accuracy of the fuel injection amount can be reduced, and the error of the fuel injection amount due to the detection error of the atmospheric pressure sensor can be reduced. And deterioration of exhaust emission can be prevented.

The reference intake pressure is obtained by correcting the intake pressure with an intake pressure correction coefficient corresponding to the atmospheric pressure.
The fuel injection amount may be calculated based on at least the reference intake pressure and the internal combustion engine rotation speed. Even in this case, when calculating the fuel injection amount, the error of the fuel injection amount caused by the detection error of the atmospheric pressure sensor is eliminated because the detection error of the atmospheric pressure sensor is multiplied and the error is not amplified. Can be smaller.

The difference between the first and second aspects is that the first aspect converts a reference intake pressure into a relative pressure (reference relative pressure) using a reference atmospheric pressure as a reference pressure, and converts this into a fuel pressure. A second aspect of the present invention is to use the reference intake pressure as it is as a parameter for calculating the fuel injection amount, while using it as a parameter for calculating the amount. Since the reference atmospheric pressure is a constant value, the relationship between the reference relative pressure and the reference intake pressure corresponds to the relationship between the gauge pressure and the absolute pressure, and both can be used as substantially the same pressure data.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS [Embodiment (1)] An embodiment (1) in which the present invention is applied to a motorcycle will be described below with reference to FIGS. An intake manifold 12 is provided in each intake port 10 of each cylinder of an engine 11 which is an internal combustion engine.
The air box 13 is connected upstream of the intake manifold 12 of each cylinder.
The air sucked into the cylinder is drawn into the intake manifold 12 of each cylinder. An air cleaner 33 is mounted in the air box 13.
An intake air temperature sensor 14 for detecting the intake air temperature is attached.

The engine 11 is an independent intake engine, and a throttle valve 15 is attached in the middle of the intake manifold 12 of each cylinder. The opening of the throttle valve 15 (throttle opening) is measured by a throttle opening sensor 16. Is detected. Further, a fuel injection valve 18 is attached to the intake manifold 12 on the downstream side of the throttle valve 15.

On the other hand, the fuel pump 2
The fuel pumped at 0 is sent to the fuel pipe 21 → the fuel filter 22 → the fuel pipe 23 → the delivery pipe 24,
The fuel is distributed to the fuel injection valves 18 of each cylinder. Excess fuel in the delivery pipe 24 is returned to the fuel tank 19 through a path from the pressure regulator 25 to the return pipe 26.
The pressure regulator 25 adjusts the fuel pressure in the delivery pipe 24 so that the pressure difference between the fuel pressure in the delivery pipe 24 and the intake pressure becomes constant.

An ignition plug 27 is attached to the cylinder head of the engine 11 for each cylinder, and a high voltage generated on the secondary side of the ignition coil 28 is applied to the ignition plug 27 of each cylinder at each ignition timing to ignite. You. The engine 11 includes an engine speed sensor 29 (rotation speed detection means) for outputting a pulse signal (crank angle signal) at every predetermined crank angle to detect the engine speed, and a cylinder discrimination sensor for discriminating a specific cylinder. 30 and a water temperature sensor 31 for detecting a cooling water temperature are attached. Also,
An atmospheric pressure sensor 3 for detecting the atmospheric pressure is provided at a predetermined position on the vehicle body.
2 (atmospheric pressure detecting means) is attached.

As shown in FIG. 2, a thin communication pipe 34 is connected to the downstream side of the throttle valve 15 in the intake manifold 12 of each cylinder, and the communication pipe 34 connects the thin communication pipe 34 to the throttle valve 15 of the intake manifold 12 of each cylinder. Is connected to the downstream side. An intake pressure sensor 17 (intake pressure detection means) is provided in the middle of the communication pipe 34, and the intake pressure sensor 17 detects an average value of the intake pressure of the intake manifold 12 of each cylinder.

The output signal of the intake pressure sensor 17 and the output signals of various sensors such as the above-described atmospheric pressure sensor 32 are input to an engine control circuit 35 (see FIG. 1). The engine control circuit 35 is mainly composed of a microcomputer, and a built-in ROM 45 (storage medium) stores an ignition control routine, a fuel injection control routine of FIG. 3, a map data of FIGS. 4 and 5, and the like. Is stored.

The engine control circuit 35 executes the fuel injection control routine shown in FIG. 3 to reduce the intake pressure PM by a reference intake pressure PML with an intake pressure correction coefficient KPM corresponding to the atmospheric pressure PA.
To the reference intake pressure PML and the reference atmospheric pressure PAba.
A reference relative pressure DPML, which is a differential pressure from se, is calculated, and a basic injection time TP (corresponding to a basic injection amount) is calculated based on the reference relative pressure DPML and the engine speed NE. After that, the basic injection time TP is corrected by various correction coefficients such as the injection amount correction coefficient KPA corresponding to the atmospheric pressure PA to obtain the final fuel injection time TAUINJ (corresponding to the fuel injection amount).

The processing of the fuel injection control routine of FIG. 3 will be described below. This routine is executed at every predetermined fuel injection amount calculation timing. When this routine is started, first, in step 101, the intake pressure PM detected by the intake pressure sensor 17 is read, and in the next step 102, the atmospheric pressure PA detected by the atmospheric pressure sensor 32 is read.
In step 103, the engine speed NE detected from the output signal of the engine speed sensor 29 is read.

Thereafter, at step 104, an intake pressure correction coefficient K for correcting the intake pressure PM to the reference intake pressure PML under the condition of the reference atmospheric pressure PAbase (for example, 100 kPa).
PM is calculated according to the atmospheric pressure PA. In the method of calculating the intake pressure correction coefficient KPM, the relationship between the atmospheric pressure PA and the intake pressure correction coefficient KPM is determined in advance by experiment or simulation, and the relationship is determined as map data (see FIG. 4). The intake pressure correction coefficient KPM corresponding to the detected atmospheric pressure PA is obtained by searching the map data.

After calculating the intake pressure correction coefficient KPM, in step 105, the intake pressure PM is multiplied by the intake pressure correction coefficient KPM to correct the intake pressure PM to the reference intake pressure PML under the reference atmospheric pressure PAbase. I do. The processing of step 105 plays a role corresponding to a reference intake pressure calculating means referred to in the claims. PML = PM × KPM

Thereafter, at step 106, the reference intake pressure P
From the differential pressure between ML and the reference atmospheric pressure PAbase, the reference relative pressure DP
Find ML. DPML = PAbase-PML The processing in step 106 plays a role corresponding to a reference relative pressure calculating means described in the claims.

Thereafter, at step 107, the reference relative pressure D
The basic injection time TP is calculated based on the PML and the engine speed NE. In this calculation method, a relationship between the reference relative pressure DPML, the engine rotation speed NE, and the basic injection time TP is obtained in advance by an experiment or simulation, and the like.
A two-dimensional map of the basic injection time TP is created, and this map is stored in the ROM 45 of the engine control circuit 35,
In step 107, this map is searched to calculate a basic injection time TP according to the reference relative pressure DPML and the engine speed NE at that time.

After calculating the basic injection time TP, step 10
In step 8, an injection amount correction coefficient KPA corresponding to the atmospheric pressure PA is calculated. In this calculation method, the relationship between the atmospheric pressure PA and the injection amount correction coefficient KPA is obtained in advance by experiment or simulation, and the relationship is stored in the ROM 45 of the engine control circuit 35 as map data (see FIG. 5). An injection amount correction coefficient KPA corresponding to the detected atmospheric pressure PA is obtained by searching map data. The injection amount correction coefficient KPA is a correction coefficient for correcting a change in fuel density or a change in back pressure due to a change in atmospheric pressure. Note that the injection amount correction coefficient KPA may be calculated according to the engine rotation speed NE and the intake pressure PM, or the injection amount correction coefficient KPA may be calculated according to the reference intake pressure PML.

Then, in the next step 109, various correction coefficients K other than the injection quantity correction coefficient KPA are calculated. For example, the warm-up increase correction coefficient, the post-start increase correction coefficient, and the intake air temperature sensor 1 according to the output signal (cooling water temperature) of the water temperature sensor 31
Various correction coefficients K such as an intake air temperature correction coefficient corresponding to the output signal (intake air temperature) 4 are calculated.

Thereafter, in step 110, an invalid injection time TV for calculating the response delay time of the fuel injection valve 18 is calculated based on the power supply voltage, and in the next step 111, the injection output to the fuel injection valve 18 is calculated. The final fuel injection time TAUINJ, which is the pulse width of the pulse, is calculated based on a basic injection time TP, an injection amount correction coefficient KPA, various correction coefficients K, and an invalid injection time TV.
Is calculated by the following equation. TAUINJ = TP × KPA × K + TV

Here, the correction coefficient K includes various correction coefficients such as a warm-up increase correction coefficient, a post-start increase correction coefficient, and an intake air temperature correction coefficient. The processing of steps 107 to 111 plays a role corresponding to the fuel injection amount calculation means described in the claims.

According to the embodiment (1) described above, in the process of calculating the basic injection time TP, the atmospheric pressure sensor 32 is used only for the process of obtaining the intake pressure correction coefficient KPM corresponding to the atmospheric pressure PA (step 104). , The detection error of the atmospheric pressure sensor is not multiplied as in the prior art, and the error is not amplified.
The effect of the detection error of No. 2 on the fuel injection time TAUINJ can be reduced. As a result, the calculation accuracy of the fuel injection time TAUINJ can be improved, the error in the fuel injection amount can be reduced, and drivability and exhaust emission can be improved.

[Embodiment (2)] In the embodiment (1), a reference relative pressure DPML, which is a differential pressure between a reference intake pressure PML and a reference atmospheric pressure PAbase, is calculated.
Although the basic injection time TP is calculated based on the ML and the engine speed NE, in the embodiment (2) of the present invention shown in FIG. 6, the basic injection time TP is calculated based on the reference intake pressure PML and the engine speed NE. The injection time TP is calculated. In short, since the reference atmospheric pressure PAbase is a constant value, the relationship between the reference relative pressure DPML and the reference intake pressure PML corresponds to the relationship between the gauge pressure and the absolute pressure, and both are used as substantially the same pressure data. be able to. Therefore, even if the reference intake pressure PML is used as in the embodiment (2) as the intake pressure information used as the calculation parameter of the basic injection time TP, the reference relative pressure DPML is used as in the embodiment (1). You can get the same result as

In the fuel injection control routine of FIG. 6 executed in the embodiment (2), the processing of step 106 in FIG.
The processing in each step other than this is the same as that in FIG. 3. The system configuration of the embodiment (2) is the same as that of the embodiment (1).

In the fuel injection control routine of FIG. 6, after reading the intake pressure PM, the atmospheric pressure PA, and the engine rotational speed NE in steps 101 to 103, steps 104 to 10 are executed.
5, the intake pressure correction coefficient KPM calculated according to the atmospheric pressure PA
Is used to correct the intake pressure PM to the reference intake pressure PML.

Thereafter, at step 107a, a basic injection time TP is calculated based on the reference intake pressure PML and the engine speed NE. In this calculation method, a relationship between the reference intake pressure PML, the engine rotation speed NE, and the basic injection time TP is obtained in advance by experiment or simulation, and a two-dimensional map of the basic injection time TP is created. The map is stored in the ROM 45 of the circuit 35, and in step 107a, this map is searched to calculate a basic injection time TP according to the reference intake pressure PML and the engine speed NE at that time.

After calculating the basic injection time TP, step 10
8 to 110, the injection amount correction coefficient KPA, various correction coefficients K,
After calculating the invalid injection time TV, in step 111, the final fuel injection time TAUINJ is calculated. TAUINJ = TP × KPA × K + TV

In the embodiment (2) described above, the same effect as in the embodiment (1) can be obtained. In each of the above embodiments, the present invention is applied to an independent intake engine of a motorcycle. However, the present invention may be applied to an independent intake engine other than a motorcycle (for example, a four-wheeled vehicle). May be applied.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an entire engine control system showing an embodiment (1) of the present invention.

FIG. 2 is a diagram showing a schematic configuration of an intake system.

FIG. 3 is a flowchart showing the flow of processing of a fuel injection control routine according to the embodiment (1).

FIG. 4 is a diagram conceptually showing a map of an intake pressure correction coefficient KPM.

FIG. 5 is a diagram conceptually showing a map of an injection amount correction coefficient KPA.

FIG. 6 is a flowchart showing the flow of processing of a fuel injection control routine according to the embodiment (2).

[Explanation of symbols]

11: engine (internal combustion engine), 12: intake manifold, 13: air box, 15: throttle valve, 1
6: throttle opening sensor; 17: intake pressure sensor (intake pressure detecting means); 18: fuel injection valve; 29: engine rotational speed sensor (rotating speed detecting means); 32: atmospheric pressure sensor (atmospheric pressure detecting means); 35 ... Engine control circuit (reference intake pressure calculation means, reference relative pressure calculation means, fuel injection amount calculation means).

Claims (2)

[Claims] An internal combustion engine includes a rotational speed detecting means for detecting a rotational speed, an atmospheric pressure detecting means for detecting an atmospheric pressure, and an intake pressure detecting means for detecting an intake pressure. In a fuel injection control device for an internal combustion engine that calculates a fuel injection amount based on an atmospheric pressure, an atmospheric pressure, and an internal combustion engine rotation speed, the intake pressure detected by the intake pressure detecting means is corrected by an intake pressure correction coefficient corresponding to the atmospheric pressure. Reference intake pressure calculating means for calculating a reference intake pressure, and a reference relative pressure calculating means for calculating a reference relative pressure that is a differential pressure between the reference intake pressure and a reference atmospheric pressure; and at least the reference relative pressure and the internal combustion engine rotation. Fuel injection amount calculating means for calculating a fuel injection amount based on the speed and a fuel injection control device for an internal combustion engine. 2. An engine according to claim 1, further comprising: a rotational speed detecting means for detecting a rotational speed of the internal combustion engine; an atmospheric pressure detecting means for detecting an atmospheric pressure; and an intake pressure detecting means for detecting an intake pressure. In a fuel injection control device for an internal combustion engine that calculates a fuel injection amount based on an atmospheric pressure, an atmospheric pressure, and an internal combustion engine rotation speed, the intake pressure detected by the intake pressure detecting means is corrected by an intake pressure correction coefficient corresponding to the atmospheric pressure. And a fuel injection amount calculating means for calculating a fuel injection amount based on at least the reference suction pressure and a rotation speed of the internal combustion engine. Engine fuel injection control device.