JPH05272388A - Control device for internal combustion engine - Google Patents

Abstract

PURPOSE:To provide a control device for an internal combustion engine with which a proper fuel injection quantity can be determined in any case. CONSTITUTION:An intake air passage 7 is provided with a throttle switch 12, an intake air temperature sensor 14, and a thermal type air flow gauge 13. A bypass passage 17 is provided with an ISC valve 18, and a distributer 20 is provided with a rotation speed sensor 22. An ECU 26 is provided with a backup memory 26a, and the memory 26a stores a map of relationship between ISC control quantities and actual intake air quantities. The ECU 26 calculates a fuel injection quantity based on an actual intake air quantity and an engine rotation speed in non-idling, or in idling when change of an intake air temperature is a specified value or less, or it calculates an estimated intake air quantity based on the ISC control quantity using the map to calculate a fuel injection quantity based on the estimated intake air quantity and the engine rotation speed in idling in a thermal transition condition where the change of the intake air temperature exceeds the specified value.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for an internal combustion engine for controlling fuel injection.

[0002]

2. Description of the Related Art Conventionally, various methods have been used to measure the intake air amount of an internal combustion engine. Among them, a thermal type air flow meter generally has a good response and the mass flow rate of air can be measured. It is widely used because it can be done.

This thermal air flow meter is composed of two parts, a thermometer for measuring the intake air temperature and a sensor which is constantly maintained at a predetermined temperature (for example, 200 ° C.). And the amount of heat supplied to the sensor is controlled so as to be balanced. That is, when the intake air amount is large, the heat radiation of the sensor becomes large, and thus a large amount of power supply is required to keep the sensor at the predetermined temperature. Then, this energization amount is converted into the intake air amount.

However, when the temperature of the intake air suddenly changes (hereinafter referred to as a thermal transient state), the intake air amount signal of the thermal air flow meter is disturbed, and in the air cleaner located in front of the thermal air flow meter, Air temperature turbulence such as convection and drift occurs due to the temperature difference. Then, the temperature distribution of the air is different in the thermal air flow meter (for example, warm air at the upper part of the thermal air flow meter and cold air at the lower part). Therefore, the intake air amount signal is disturbed and the thermal air flow meter erroneously detects the result, and as a result, the accuracy of the fuel injection control deteriorates.

In order to solve such a problem, Japanese Patent Publication No. 62-42147 discloses a thermal type air flow meter which detects the deterioration of the accuracy based on the throttle valve opening and the engine speed and uses the thermal type. There is disclosed a control device that determines the supplied fuel amount from the throttle valve opening and the engine speed when the accuracy of the air flow meter deteriorates.

[0006]

However, in the above-mentioned conventional control device (Japanese Patent Publication No. 62-42147), the parameter for determining the fuel injection amount is the engine rotation speed when the throttle valve is in the fully closed state at idle. There will be only numbers. As a result, there may be a case where an appropriate fuel injection amount cannot be obtained.

That is, basically, if the negative pressure in the intake passage is constant, there is a correlation between the engine speed and the intake amount. However, when various loads (air conditioner, power steering, air load, drive range, etc.) are entered, the correlation is broken and the intake air amount is increased while the engine speed remains constant. In such a case, it becomes impossible to estimate the intake air amount only from the engine speed, and it becomes impossible to appropriately control the fuel injection amount.

The present invention has been made by paying attention to the above problems, and an object thereof is to prevent an erroneous detection of a thermal air flow meter in an idle state and a thermal transient state. An object of the present invention is to provide a control device for an internal combustion engine that can obtain an appropriate fuel injection amount by controlling the internal combustion engine.

[0009]

In order to achieve the above object, a control device for an internal combustion engine according to the present invention, as shown in FIG. 6, uses an auxiliary air passage M3 that bypasses a throttle valve M2 in an intake passage M1. An auxiliary air amount adjusting actuator M4 that is provided and adjusts the auxiliary air amount during idling
And the engine speed detection means M6 for detecting the rotation speed of the internal combustion engine M5, the target idle speed, and the engine speed detected by the engine speed detection means M6 so that the auxiliary air amount adjustment is performed. Control means M7 for controlling the actuator M4, a thermal air flow meter M8 provided in the intake passage M1 for detecting the intake air amount, and an intake air temperature detection means provided in the intake passage M1 for detecting the intake air temperature M9 and the auxiliary air amount adjusting actuator M4
When the variation of the intake air temperature by the intake air temperature detection means M9 is within a predetermined value, the storage means M10 stores the relationship between the value according to the control amount of the intake air amount and the intake air amount. First, a first fuel injection amount calculation means M12 for calculating the fuel injection amount of the fuel injection valve M11 from the intake air amount by the thermal air flow meter M8 and the engine speed by the engine speed detection means M6, and an idle At the time, and when the intake air temperature detection means M9 is in a thermal transient state in which the fluctuation of the intake air temperature exceeds a predetermined value, the data in the storage means M10 is used to use the auxiliary air amount adjusting actuator M4 at that time. Second fuel injection amount calculation for calculating the fuel injection amount of the fuel injection valve M11 from the intake air amount and the engine speed detected by the engine speed detection means M6. And a stage M13.

Further, the data of the storage means M10 shows that when the change in intake air temperature during idling is within a predetermined value,
It is learned from a value according to the control amount of the auxiliary air amount adjusting actuator M4 and the intake amount by the thermal air flow meter M8.

[0011]

According to the above construction, when the intake air temperature detecting means M9 varies the intake air temperature within a predetermined value even when the engine is not idle, or when idle, the first fuel injection amount calculating means M12 uses the thermal equation. The fuel injection amount of the fuel injection valve M11 is calculated from the intake air amount by the air flow meter M8 and the engine speed by the engine speed detection means M6. Further, when the engine is idle, and the intake air temperature detecting means M9 varies the intake air temperature by more than a predetermined value, the second fuel injection amount calculating means M1.
3 uses the data of the storage means M10 to obtain the intake air amount from the value corresponding to the control amount of the auxiliary air amount adjusting actuator M4 at that time, and the intake air amount and the engine speed by the engine speed detecting means M6. The fuel injection amount is calculated from

That is, the second fuel injection amount calculation means M13
Thus, at the time of idling and when the intake air temperature suddenly changes, the fuel injection amount can be obtained without using the intake air amount by the thermal air flow meter M8 that may cause erroneous detection.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a schematic configuration of a fuel control device for an internal combustion engine. A multi-cylinder internal combustion engine (hereinafter referred to as an engine) 1 includes a piston 3 in a cylinder 2,
A combustion chamber 4 defined by a cylinder head 1a and a cylinder block 1b is formed above the piston 3. A spark plug 16 is provided in the combustion chamber 4.
Further, the combustion chamber 4 communicates with an intake passage 7 and an exhaust passage 8 via an intake valve 5 and an exhaust valve 6.

The fuel injection valve 9 for each cylinder is provided in the intake passage 7, and the intake passage 7 upstream of the fuel injection valve 9 is provided with a surge tank 10 for suppressing air pulsation during intake. There is. On the upstream side of the surge tank 10, a throttle valve 11 that is opened / closed in association with the operation of an accelerator pedal (not shown) is provided. It A throttle switch 12 for detecting that the throttle valve 11 is fully closed (idle state) is provided near the throttle valve 11. A thermal air flow meter 13 is provided upstream of the throttle valve 11, and the measured air intake amount G _AV introduced into the intake passage 7 is detected by the thermal air flow meter 13.

Thermal air flow meter 13 and throttle valve 1
1, an intake air temperature sensor 14 for detecting the intake air temperature.
Is provided. An air cleaner 15 is provided on the upstream side of the thermal air flow meter 13.

Therefore, the air taken in from the air cleaner 15 is supplied to the thermal air flow meter 13, the throttle valve 11,
It is sent toward the downstream side of the intake passage 7 via the surge tank 10, and at the downstream side of the intake passage 7, the fuel injection valve 9
It is mixed with the fuel injected from the fuel cell to form a mixture. The air-fuel mixture is introduced into the combustion chamber 4 via the intake valve 5.
Then, the engine 1 explodes the air-fuel mixture in the combustion chamber 4 by the spark plug 16 to obtain a driving force, and then discharges the exhaust gas to the exhaust passage 8 via the exhaust valve 6.

A throttle valve 11 is provided in the intake passage 7.
A bypass passage 17 is provided as a supplementary air passage that bypasses the throttle valve 11 and connects the upstream side of the throttle valve 11 and the surge tank 10. An idle speed control valve (hereinafter referred to as an ISC valve) 18 as an auxiliary air amount adjusting actuator is provided in the middle of the bypass passage 17. The ISC valve 18 is a spring (not shown)
Thus, the valve body 18a is always biased in the direction of closing the seat portion 18b, but the valve body 18a opens the seat portion 18b by exciting the coil 18c.
Therefore, the bypass passage 17 is opened by exciting the coil 18c of the ISC valve 18, and the bypass passage 17 is closed by demagnetizing the coil 18c. This ISC valve 1
The opening degree 8 is adjusted by the duty ratio control based on the pulse width modulation.

The distributor 20 is the igniter 2
1 for distributing the high voltage output from 1 to each spark plug 16 in synchronization with the crank angle of the engine 1.
The ignition timing of each spark plug 16 is determined by the high voltage output timing from the igniter 21. The distributor 20 is provided with a rotation speed sensor 22 as an operation state detecting unit that detects a crank angle from the rotation of the rotor of the distributor 20 and outputs a pulse signal.

The electronic control unit (hereinafter referred to as ECU) 26 constituting the actuator control means, the first and second fuel injection amount calculation means, and the storage means includes a throttle switch 12, a thermal air flow meter 13, an intake air temperature. The sensor 14 and the rotation speed sensor 22 are connected, the signals from the respective sensors are input, the fuel injection valves 9, the ISC valve 18 and the igniter 21 are connected, and a drive signal is output to each drive unit.

Further, the ECU 26 has a backup memory 2
6a is provided, and a map having the characteristic line L (shown in FIG. 2) is stored in the memory 26a. In this map, the horizontal axis represents the ISC control amount G _I described later, and the vertical axis represents the measured intake air amount G _AV . Hereinafter, this map is referred to as the GI-GAV map. The data of the G _I -G _AV map (characteristic line L) is made rewritable.

Next, the operation of the control device for the internal combustion engine configured as described above will be described. The ECU 26 performs ISC control when idle. That is, when the throttle switch 12 is turned on to enter the idle state, the opening degree of the ISC valve 18 (hereinafter referred to as ISC control amount G so that the engine speed Ne by the rotation speed sensor 22 and the predetermined target idle speed match). _{Called I} ).

3 to 5 show flowcharts executed by the ECU 26. FIG. 3 shows a routine for calculating the fuel injection amount, and this processing is started every predetermined time or every predetermined crank angle. First, the ECU 26 executes step 10
At 0, the engine speed Ne is detected by the engine speed sensor 22. Then, in step 110, the ECU 26 detects the intake air temperature in the intake passage 7 by the intake air temperature sensor 14 and determines whether or not the engine 1 is in the thermal transient state based on the change in the intake air temperature. That is, it is determined whether or not the fluctuation of the intake air temperature is larger than a predetermined value, and if it is large, it is determined that the thermal transient state exists. Then, the ECU 26 proceeds to step 120 if it is in the thermal transient state, or proceeds to step 140 if it is not in the thermal transient state. Then, in step 120, the ECU 26 determines whether or not the throttle valve 11 is fully closed by the throttle switch 12 and the engine 1 is in the idle state,
If it is in the idle state, the process proceeds to step 130, and if it is not in the idle state, the process proceeds to step 140.

Next, in step 130, the ECU 26 executes an estimated intake air amount G _K calculation process. This process is shown in FIG. First, read the ISC control amount G _I described above in step 131, G _I -G in FIG 2 at step 132
_The measured intake air amount G _AV corresponding to the ISC control amount G _I is obtained using the _AV map. Then, the measured intake air amount G _AV is set as the estimated intake air amount G _K. In step 140, the actually measured intake air amount G _AV measured by the thermal air flow meter 13 is read.

Subsequently, the ECU 26 executes steps 130, 1
After processing 40, in step 150, step
Engine speed Ne read at 100 and step
Estimated intake air amount G read at 130_K, Or step 14
Measured intake air amount G read at 0 _AVAnd fuel injection amount TAU
Is calculated, and the series of routines is ended.

Then, the ECU 26 injects fuel from the fuel injection valve 9 based on the fuel injection amount TAU calculated by the above routine. Further, since G _I -G _AV map of FIG. 2, corresponding to the change in leakage amount of air intake system during idling (aging), or to absorb the variations in the control at any time, the data (characteristic line L ) Can be rewritten. The flowchart for rewriting G _I -G _AV data shown in FIG.

First, the ECU 26 executes steps 300, 31.
At 0, it is determined whether the engine 1 is in the thermal transient state and in the idle state based on the intake air temperature detected by the intake air temperature sensor 14 (these steps are referred to as step 11 in FIG. 3).
The same as 0,120).

Then, the ECU 26 executes steps 300, 3
When it is determined in 10 that the engine 1 is not in the heat transient state and is in the idle state, the ISC control amount G _I is read in step 320, and the measured intake air amount G _AV by the thermal air flow meter 13 is read in step 330. ..

[0028] Thus, G _I -G _AV map is not the thermal transient condition, and only when it is idle, the data on the map is rewritten. Thus, the aging caused by clogging of the intake system can be incorporated into the G _I -G _AV map, thereby enabling more accurate control.

As described above, in the control device of this embodiment,
In the thermal transient state and the idle state, the measured intake air amount G _AV measured by the thermal air flow meter 13
Instead of using the G _I − stored in the ECU 26
Using the estimated intake air amount G _K obtained from the G _AV map,
It is configured to calculate the fuel injection amount TAU. Therefore,
It is possible to solve the problem caused by the erroneous detection of the thermal air flow meter 13 as in the related art, and thereby it is possible to perform highly accurate fuel injection control.

The present invention is not limited to the above-mentioned embodiment. For example, in the above-mentioned embodiment, the estimated intake air amount G _K is determined from the ISC control amount G _I using the GI-GAV map. Instead of the amount G _I , another value depending on the control amount of the ISC valve 18 may be used. For example, ISC
The estimated intake air amount G _K may be determined using the actual opening of the valve 18 or the duty ratio applied to the ISC valve 18.

[0031]

According to the present invention, an excellent effect that an appropriate fuel injection amount can be obtained is exhibited.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a control device for an internal combustion engine of an embodiment.

2 is a diagram showing a G _I -G _AV map.

FIG. 3 is a flowchart showing a routine for calculating a fuel injection amount.

FIG. 4 is a flowchart showing a routine for obtaining an estimated intake air amount.

5 is a flowchart showing a routine for G _I -G _AV map of rewriting.

FIG. 6 is a diagram corresponding to the claims of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Engine as an internal combustion engine, 7 ... Intake passage, 9 ... Fuel injection valve, 11 ... Throttle valve, 13 ... Thermal air flow meter, 17 ... Bypass passage as auxiliary air passage, 18
... an idle speed control valve (ISC valve) as an auxiliary air amount adjusting actuator, 22 ... a speed sensor as an engine speed detecting means, 26 ... an actuator controlling means,
An electronic control unit (ECU) as a storage unit, a learning unit, and first and second fuel injection amount calculation units.

Claims (2)

[Claims] 1. An auxiliary air amount adjusting actuator, which is provided in an auxiliary air passage bypassing a throttle valve in an intake passage, and adjusts an auxiliary air amount during idling; and an engine speed detection for detecting an engine speed of an internal combustion engine. Means, a target idle speed, and an actuator control means for controlling the auxiliary air amount adjusting actuator so that the engine speed detected by the engine speed detecting means coincides with each other, and provided in the intake passage, A thermal air flow meter for detecting an intake air amount, an intake air temperature detecting means provided in the intake passage for detecting an intake air temperature, and a relationship between a value according to a control amount of the auxiliary air amount adjusting actuator and the intake air amount. When the variation of the intake air temperature by the intake air temperature detecting means is within a predetermined value even during non-idle or idle time, First fuel injection amount calculation means for calculating the fuel injection amount of the fuel injection valve from the intake air amount by the air flow meter and the engine speed by the engine speed detection means; When the fluctuation of the intake air temperature by the air temperature detecting means exceeds a predetermined value in a thermal transient state, the data of the storage means is used to determine the intake air quantity from the value according to the control quantity of the auxiliary air quantity adjusting actuator at that time. And a second fuel injection amount calculation means for calculating the fuel injection amount of the fuel injection valve from the intake air amount and the engine speed detected by the engine speed detection means. Fuel control device. 2. The data of the storage means includes a value according to a control amount of the auxiliary air amount adjusting actuator when the variation of the intake air temperature during idling is within a predetermined value, and the thermal air flow meter. The control device for an internal combustion engine according to claim 1, wherein the control device is learned from the intake air amount by