JPH0633814A - Fuel control device internal combustion engine - Google Patents

Abstract

PURPOSE:To optimally carry out, switching from a constant amount of fuel supply mode at the time of engine start into a variable fuel amount supply mode applicable to the intake air amount displayed by a hot-wire type air flow meter. CONSTITUTION:In an ECU 25, a fuel amount applicable to an engine cooling water temperature for engine start is supplied to an engine until an engine speed exceeds 500rpm after power is supplied to the hot-wire of a hot-wire type air flow meter 13. And in the case where the output value of the air flow meter 13 is smaller than a specified value when the engine speed exceeds 500rpm, the fuel amount applicable to an intake air amount displayed by the air flow meter 13 and engine speed is supplied. In the ECU 25, in the case where the output value of the air flow meter 13 is larger than the specified value when the engine speed reaches 500rpm, a fuel amount applicable to the engine cooling water temperature for the most suitable fuel injection is supplied for a prescribed time. After the specified time, passes a fuel amount applicable to an intake air amount displayed by the air flow meter 13, and an engine speed is supplied to the engine.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel control system for an internal combustion engine using a hot wire type air flow meter.

[0002]

2. Description of the Related Art In a fuel control system for an internal combustion engine, an air flow meter is used to supply the internal combustion engine with a fuel amount corresponding to the intake air amount. There is a hot-wire type air flow meter as one of the air flow meters. The hot wire type air flow meter measures the intake air flow rate by the heat removal of the platinum hot wire. Therefore, when the heating wire is heated to reach a predetermined temperature, it functions as a normal flowmeter. That is, when the power supply to the heat wire is started, the heat wire is cold, and the output value does not correspond to the intake air amount until the heat wire reaches a predetermined temperature. Such output values are shown. Therefore, in the control system (microcomputer), the supplied fuel amount is calculated based on the erroneous output value of the hot wire air flow meter, and the fuel (rich) that is richer than the required fuel amount is supplied. In this way, problems such as deterioration of emissions, poor drivability immediately after engine start, and engine stall have occurred.

Therefore, as described in JP-A-57-181938, in the conventional system, when the fuel injection amount cannot be calculated from the output of the hot wire type air flow meter, that is, the engine cooling water temperature is kept for a predetermined time after the key switch is turned on. The fuel injection amount is calculated from the intake air amount by the hot-wire air flow meter and the engine speed after that. That is, the time required for heating the heating wire of the heating wire type air flow meter to a predetermined temperature is set in advance.

[0004]

However, in this system, when the internal combustion engine has been started within the heat ray heating set time of the heat ray type air flow meter, even if the engine start is completed, the constant fuel amount corresponding to the engine cooling water temperature is maintained. It is injected in a large amount, resulting in poor controllability. On the contrary, if the internal combustion engine startup is not completed within the hot-wire heating set time of the hot-wire airflow meter, the fuel injection amount is calculated with an incorrect output value of the hot-wire airflow meter when the engine startup is completed. As a result, problems such as emission deterioration, drivability failure, and engine stall occur.

Therefore, an object of the present invention is to optimally switch the fuel constant amount supply mode at the time of engine startup to the variable fuel amount mode according to the intake air amount of the hot wire air flow meter. To provide a controller quantity.

[0006]

As shown in FIG. 12, the present invention is arranged in the intake passage of an internal combustion engine and controls the current so as to keep the temperature of a heating wire heated to a constant temperature constant, and the current value thereof is controlled. Is output as a voltage value, a hot wire type air flow meter M1, a start completion detecting means M2 for detecting the completion of starting the internal combustion engine, a rotation speed detecting means M3 for detecting the rotation speed of the internal combustion engine, and a hot wire type by turning on a key switch. Before the start of the engine is completed by the start completion detecting means M2 after the power supply of the heat wire of the air flow meter M1 is started, the first amount of fuel for starting the engine, which corresponds to at least the cooling water temperature of the internal combustion engine, is supplied to the internal combustion engine. When the output value of the hot-wire air flow meter M1 or a value corresponding thereto is smaller than a predetermined value at the time of completion of engine startup by the control means M4 and the startup completion detection means M2, The supply fuel amount corresponding to the engine speed by-wire air flow meter M1 by the intake air amount and the rotational speed detecting means M3 to the internal combustion engine 2 of the control means M5
When the output value of the hot-wire air flow meter M1 or a value corresponding thereto is larger than a predetermined value at the completion of the engine start by the start completion detecting means M2, at least the internal combustion engine for optimum fuel injection for a predetermined time thereafter. A fuel amount according to the cooling water temperature or a predetermined constant fuel amount is supplied to the internal combustion engine, and after a lapse of a predetermined time, the intake air amount by the hot wire air flow meter M1 and the rotation speed detection means M3.
The gist of the present invention is a fuel control device for an internal combustion engine, which is provided with a third control means M6 for supplying the internal combustion engine with a fuel amount according to the engine speed.

[0007]

The first control means M4 starts at least the internal combustion engine for starting the engine before the engine start is completed by the start completion detecting means M2 after the power supply to the hot wire of the hot wire air flow meter M1 is started by turning on the key switch. The amount of fuel corresponding to the cooling water temperature is supplied to the internal combustion engine. Then, when the output value of the heat ray type air flow meter M1 or a value corresponding thereto is smaller than a predetermined value at the completion of the engine start by the start completion detecting means M2, the second control means M5 takes in the intake air by the heat ray type air flow meter M1. The amount of fuel is supplied to the internal combustion engine in accordance with the amount and the engine speed by the engine speed detecting means M3.
On the other hand, the third control means M6 is a hot-wire type air flow meter M when the engine start is completed by the start completion detecting means M2.
If the output value of 1 or the value corresponding to it is larger than the predetermined value,
After that, a fuel amount corresponding to at least the cooling water temperature of the internal combustion engine or a predetermined constant fuel amount for optimum fuel injection for a predetermined time is supplied to the internal combustion engine, and after the lapse of a predetermined time, the intake air amount by the hot wire air flow meter M1. And a fuel amount corresponding to the engine speed by the engine speed detection means M3 is supplied to the internal combustion engine.

That is, when the heating wire of the heating wire type airflow meter is heated to a constant temperature at the completion of engine startup, the output value of the heating wire type airflow meter is directly reflected in the fuel amount.
On the contrary, if the supply voltage to the hot wire air flow meter is low and it takes time to heat the hot wire to a certain temperature due to some cause, such as a sag in the battery voltage, it will take only a predetermined time after the engine has been started. At least a fuel amount corresponding to the cooling water temperature of the internal combustion engine or a predetermined constant fuel amount for optimal fuel injection is supplied to the internal combustion engine, and then a fuel amount based on the output value of the hot wire air flow meter is supplied to the internal combustion engine. It Therefore, the air-fuel ratio becomes rich when the output value of the hot wire type air flow meter is directly reflected in the fuel amount without the heating wire of the hot wire type air flow meter being heated to a constant temperature at the completion of the engine start. It is avoided.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing an outline of a fuel control device for an internal combustion engine, which is installed in an automobile. A multi-cylinder internal combustion engine (hereinafter referred to as an engine) 1 includes a piston 3 in a cylinder 2. This piston 3
Above the cylinder head 1a, cylinder block 1b
A combustion chamber 4 defined by is formed. Combustion chamber 4
A spark plug 16 is provided in the. Also, the combustion chamber 4
Through the intake valve 5 and the exhaust valve 6 to the intake passage 7
And communicates with the exhaust passage 8.

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 intake air pulsation during intake. There is. A throttle valve 11 that is opened / closed in conjunction with the operation of an accelerator pedal (not shown) is provided on the upstream side of the surge tank 10. By opening / closing the throttle valve 11, the amount of intake air to the intake passage 7 is adjusted. It A throttle sensor 12 that detects the opening degree of the throttle valve 11 is provided near the throttle valve 11. A heat ray type air flow meter 13 is provided upstream of the throttle valve 11.

The configuration of the hot wire type air flow meter 13 is as follows.
As shown in FIG. Platinum heating wire (heating element) in the intake passage 7
14 is arranged, and a temperature compensating resistor 15 is arranged on the downstream side of the platinum heating wire 14. This platinum hot wire 14
The temperature compensating resistor 15 and the like form a bridge circuit, and the control circuit 26 controls the voltage Vs so that the unbalanced voltage Vo is always zero to keep the temperature constant. That is, the platinum hot wire 14 is placed in an air flow, and the current is controlled so as to keep the temperature of the platinum hot wire 14 current-heated at a constant temperature constant, and the current value is output as a voltage value VG.

In FIG. 1, a hot-wire type air flow meter 13
An intake air temperature sensor 17 for detecting the intake air temperature is provided between the throttle valve 11 and the throttle valve 11. An air cleaner 18 is provided on the upstream side of the hot wire air flow meter 13.

Therefore, the air sucked from the air cleaner 18 flows toward the downstream side of the intake passage 7 via the hot wire type air flow meter 13, the throttle valve 11 and the surge tank 10. And in the middle of the air flow,
It is mixed with fuel injected from the heat material injection valve 9 to form an air-fuel 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 19 that bypasses the throttle valve 11 and connects the upstream side of the throttle valve 11 and the surge tank 10 is provided. An idle speed control valve (hereinafter referred to as ISC valve) 20 is provided in the middle of the bypass passage 19. The ISC valve 20 is always biased by a spring (not shown) so that the valve body 20a closes the seat portion 20b.
0a opens the seat portion 20b. Therefore, the bypass passage 19 is opened by exciting the coil 20c of the ISC valve 20, and the bypass passage 19 is closed by demagnetizing the coil 20c. The opening of this ISC valve 20 is adjusted by duty ratio control based on pulse width modulation.

The distributor 21 is the igniter 2
2 for distributing the high voltage output from 2 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 22. The distributor 21 is provided with a rotation speed sensor 23 that detects a crank angle from the rotation of the rotor of the distributor 21 and outputs a pulse signal. Further, the cylinder block 1b is provided with a water temperature sensor 24 that detects the temperature of the engine cooling water.

Electronic control unit (hereinafter referred to as ECU) 25
Is mainly composed of a microcomputer and includes an A / D converter and the like. The ECU 25 includes a throttle sensor 12, a heat ray type air flow meter 13, an intake air temperature sensor 1
7, the rotation speed sensor 23 and the water temperature sensor 24 are connected,
The signal from each sensor is input. Further, each fuel injection valve 9, ISC valve 20 and igniter 22 are connected to the ECU 25 and output a drive signal to each drive unit.

Further, the ECU 25 is a hot wire type air flow meter 1
The intake air amount QAFM is calculated (converted) from the output value (output voltage value VG) of 3 using a map. In the present embodiment, the ECU 25 constitutes a start completion detecting means, a first control means, a second control means and a third control means, and the rotation speed sensor 23 detects a rotation speed detecting means and a start completion detecting means. Means are configured.

Next, the operation of the fuel control system for an internal combustion engine having the above-described structure will be described. FIG. 3 shows a process (flow chart) executed by the ECU 25. This process is started every predetermined time. FIG. 4 is a time chart showing various signals. Here, in FIG. 4, the key switch is turned on at the timing of t1 to start the application of the battery voltage to the hot wire air flow meter 13, and the starter motor is turned on (driven) at the timing of t2 thereafter. I shall.

The ECU 25 determines in step 100 of FIG. 3 whether or not the speed reaches 500 rpm for the first time after the engine is started.
If it is less than 500 rpm, the process proceeds to step 101.
In step 101, the ECU 25 uses the map shown in FIG. 6 for starting the engine and the engine cooling water temperature Tw at that time
The fuel injection time (opening time of the fuel injection valve) T _{F according} to the above is set. The period from t1 to t3 in FIG.
00 → 101 is repeated.

When the engine speed reaches 500 rpm for the first time after the engine is started (timing t3 in FIG. 4), the ECU 25 proceeds from step 100 to step 102 in FIG. In step 102, the ECU 25 compares the output value VG of the hot wire air flow meter 13 with a predetermined comparison value Vref. Here, as shown in FIG. 4, when the output value VG of the hot-wire air flow meter 13 is smaller than the comparison value Vref, the ECU 25 proceeds to step 103. In step 103, the ECU 25 receives the intake air amount QAFM by the hot-wire air flow meter 13 and the engine speed N by the speed sensor 23.
fuel injection time (fuel injection valve opening time) T according to e
Set _F. After the timing of t3 in FIG. 4, steps 100 → 102 → 103 are repeated.

On the other hand, as shown in FIG. 5, if the output value VG of the hot-wire air flow meter 13 is larger than the comparison value Vref in step 102, the ECU 25 executes step 1 of FIG.
Move to 04. The ECU 25 starts the timer 25a when it reaches 500 rpm for the first time after the engine is started in step 104.
The timing operation (shown in FIG. 1) is started, and it is determined whether or not the elapsed time has reached a preset set time tset. If the set time tset has not elapsed, the ECU 25 proceeds to step 105 and uses the map shown in FIG. 7 for the optimum fuel injection to determine the fuel injection time (fuel injection valve's corresponding to the engine cooling water temperature Tw at that time). Set the valve opening time) T _F. During the period from t3 to t4 in FIG. 5, steps 100 → 102 → 104 → 105 in FIG. 3 are repeated.

After that, the ECU 25 executes step 1
When the elapsed time after the engine speed reaches 500 rpm for the first time at 04 reaches the set time tset (timing t4 in FIG. 5), the routine proceeds to step 103, where the intake air amount QAFM by the hot-wire air flow meter 13 and the rotation speed sensor 23.
The fuel injection time (valve opening time of the fuel injection valve) _TF is set in accordance with the engine rotation speed Ne. After the timing of t4 in FIG. 5, steps 100 → 102 → 104 → 10.
3 or steps 100 → 102 → 103 are repeated.

Then, steps 101, 103, and
The fuel injection time (valve opening time of the fuel injection valve) T _F set in 105 is injected from the fuel injection valve 9 at a predetermined fuel injection timing.

As described above, in the present embodiment, the ECU 25 (starting completion detecting means, first, second and third control means) determines whether or not the engine speed Ne becomes 500 rpm for the first time after the engine is started. Determines whether the engine has been started. Then, the ECU 25 supplies to the engine a fuel amount corresponding to the engine cooling water temperature Tw for starting the engine before the engine start is completed after the electric power supply to the hot wire of the hot wire air flow meter 13 is started by turning on the key switch. . Further, the ECU 25 outputs the output value VG of the hot wire air flow meter 13 at the completion of the engine start.
Is smaller than a predetermined value (comparative value Vref), the intake air amount QAFM by the hot-wire air flow meter 13 and the rotation speed sensor 2
A fuel amount corresponding to the engine speed Ne of 3 is supplied to the engine. On the other hand, when the output value VG of the hot-wire air flow meter 13 is larger than the predetermined value Vref at the completion of engine start, the ECU 25 responds to the engine cooling water temperature Tw for optimum fuel injection for a predetermined time (set time tset) thereafter. The amount of fuel is supplied to the engine, and after a lapse of a predetermined time, the intake air amount QAFM by the hot wire air flow meter 13 and the engine speed N by the speed sensor 23.
The fuel amount corresponding to e is supplied to the engine.

That is, when the heating wire of the heating wire type air flow meter 13 is heated to a constant temperature at the completion of engine start,
The output value of the hot wire type air flow meter 13 is directly reflected in the fuel amount. As a result, for example, even when the engine is warmed up and restarted, the output value of the hot-wire air flow meter 13 can be reflected in the fuel amount at an optimum timing. In this way, the value when the output of the hot-wire air flow meter 13 is normal can be used effectively as much as possible.

On the contrary, the supply voltage Vs to the hot wire type air flow meter 13 is rated at 12 in FIG. 4 due to some cause, for example, as shown in FIG.
When it takes time to heat the heating wire to a constant temperature as low as 8 volts with respect to the bolt, the cooling water temperature Tw for optimum fuel injection using the map of FIG. 7 is set for a predetermined time (tset) after completion of engine start. A corresponding amount of fuel is supplied to the engine, and then the output value VG of the hot wire air flow meter 13
To supply the engine with a fuel amount based on. Therefore, the air-fuel ratio becomes rich when the output value of the hot wire air flow meter 13 is directly reflected on the fuel amount without the hot wire of the hot wire air flow meter 13 being heated to a constant temperature at the completion of the engine start. According to it, it is avoided. That is,
When the heating of the heating wire of the heating wire type air flow meter 13 is not completed, that is, when the output of the heating wire type air flow meter 13 shows a value larger than the actual air flow rate, the output of the heating wire type air flow meter 13 is not used. Therefore, the air-fuel ratio does not become rich, and it is possible to prevent deterioration of emission and occurrence of defects such as drivability failure and engine stall immediately after the engine is started.

The present invention is not limited to the above embodiment, and for example, in the above embodiment, step 1 of FIG.
Although the fuel amount for the optimum fuel injection in 05 is the fuel amount according to the cooling water temperature of the engine, a predetermined constant fuel amount may be supplied to the engine.

Further, the comparison value Vre in step 102 of FIG.
f is at least the engine cooling water temperature T as shown in FIG.
It may be a value according to w. Further, step 1 in FIG.
As shown in FIG. 9, the set time tset from when the engine speed becomes 500 rpm for the first time in 04, is the average battery voltage value after the key switch is turned on until the engine start is completed (it becomes 500 rpm for the first time after engine start). B
The value corresponding to av, the value corresponding to the battery voltage value B when the engine start is completed as shown in FIG. 10, the output of the heat ray type air flow meter 13 when the engine start is completed as shown in FIG. It may be a value corresponding to the value VG. Alternatively, the set time tset may be obtained using a two-dimensional map having the battery voltage value B at the time of engine start completion and the output value VG of the hot wire air flow meter 13 as factors. Alternatively, the set time tset may be obtained using a two-dimensional map having the average battery voltage value Bav and the output value VG of the hot-wire air flow meter 13 as factors after the key switch is turned on until the engine start is completed.

The start of the engine may be completed when the drive of the starter motor is stopped (timing shown by t4 in FIG. 4). Further, in the above-described embodiment, the output value VG of the heat ray type air flow meter 13 is compared with the predetermined value (comparison value Vref) in step 102 of FIG.
Intake air amount (conversion value to air amount after ECU processing)
May be compared with a predetermined value.

[0030]

As described above in detail, according to the present invention,
It has an excellent effect that it is possible to optimally switch from the fixed amount fuel supply mode at the time of engine start to the variable fuel amount mode according to the intake air amount of the hot wire type air flow meter.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a fuel control device for an internal combustion engine.

FIG. 2 is a diagram showing a hot wire type air flow meter.

FIG. 3 is a flowchart for explaining an operation.

FIG. 4 is a time chart for explaining the operation.

FIG. 5 is a time chart for explaining the operation.

FIG. 6 is a map for obtaining a fuel injection time.

FIG. 7 is a map for obtaining a fuel injection time.

FIG. 8 is a map for obtaining a comparison value.

FIG. 9 is a map for obtaining a set time.

FIG. 10 is a map for obtaining a set time.

FIG. 11 is a map for obtaining a set time.

FIG. 12 is a claim correspondence diagram.

[Explanation of symbols]

Reference Signs List 7 air intake passage 13 hot wire type air flow meter 14 hot wire 23 rotation speed sensor constituting rotation speed detection means and start completion detection means 25 start completion detection means and ECUs constituting first, second and third control means

Claims (1)

[Claims] 1. A hot wire type air flow meter which is arranged in an intake passage of an internal combustion engine and which controls a current to output a current value as a voltage value so as to keep the temperature of a hot wire heated to a constant temperature constant, Start completion detection means for detecting start completion, rotation speed detection means for detecting the rotation speed of the internal combustion engine, and engine start by the start completion detection means after the start of power supply of the heat wire of the hot wire type air flow meter by turning on the key switch Before completion, first control means for supplying at least an amount of fuel corresponding to the cooling water temperature of the internal combustion engine for starting the engine to the internal combustion engine, and at the completion of engine startup by the start completion detecting means,
When the output value of the hot-wire airflow meter or a value corresponding thereto is smaller than a predetermined value, a fuel amount is supplied to the internal combustion engine according to the intake air amount by the hot-wire airflow meter and the engine rotation speed by the rotation speed detection means. When the engine start is completed by the second control means and the start completion detecting means,
When the output value of the hot-wire air flow meter or a value corresponding to it is larger than a predetermined value, a fuel amount corresponding to at least the cooling water temperature of the internal combustion engine or a predetermined constant fuel amount for optimal fuel injection for a predetermined time thereafter A third control means is provided for supplying to the engine, and after a lapse of a predetermined time, supplying to the internal combustion engine a fuel quantity according to the intake air quantity by the hot wire air flow meter and the engine speed by the speed detecting means. A fuel control device for an internal combustion engine, comprising: