JPH0559259B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a fuel injection amount control method for an internal combustion engine, and particularly to a method for controlling a fuel injection amount of an internal combustion engine. Set the injection amount according to the engine speed,
The present invention relates to a fuel injection amount control method for an internal combustion engine suitable for performing feedback control to maintain an air-fuel ratio at a set value based on a fuel injection amount limited to a maximum fuel injection amount or less.

[Background of the invention]

In a vehicle engine equipped with an electronically controlled fuel injection device, the basic fuel injection amount is determined from the engine rotation speed and the intake air amount detected by the airflow meter, and the upper limit of the fuel injection amount is determined based on the basic fuel injection amount. The maximum fuel injection amount shown is set according to the engine speed, and the air-fuel ratio is set to the set value based on the fuel injection amount that is limited to the maximum fuel injection amount or less.
For example, feedback control has been used to maintain the stoichiometric air-fuel ratio. If the air-fuel ratio is feedback-controlled to near the stoichiometric air-fuel ratio, the exhaust gas can be purified by the three-way catalyst provided in the exhaust system.

However, when driving at high altitudes, as shown in Figure 1, a deviation occurs between the amount of intake air detected by the airflow meter (characteristic C) and the amount of intake air reduced due to the decrease in air density (characteristic B). Therefore, the air-fuel ratio is changed to the stoichiometric air-fuel ratio (A/
F=14.7), the air-fuel ratio A/F becomes excessively rich. For example, as shown in FIG. 2, if the excess air ratio λ is 1.0 when the stoichiometric air-fuel ratio A/F=14.7 on flat ground, then the excess air ratio λ on a high ground of 1600 m is about 0.91.

Therefore, the fuel injection amount is corrected to be lowered by a high altitude compensation value indicating a fuel reduction value corresponding to the deviation between characteristic C and characteristic B. That is, when driving at high altitudes, when the detected output of the air flow meter reaches the amount of intake air shown in characteristic C in FIG. 1, the fuel injection amount is reduced by the amount of fuel corresponding to the deviation between characteristic C and characteristic B. control was in place. As shown in Figure 2, this high-altitude compensation value is a set value that corrects the air-fuel ratio A/F becoming excessively rich depending on the altitude, and is based on the feedback air-fuel ratio A/F at level ground. It is determined by etc. Then, the high altitude compensation value is varied depending on the altitude based on the detection output of an atmospheric pressure sensor that detects atmospheric pressure, etc., and correction is performed to lower the fuel injection amount.

In this way, by lowering the level of the fuel injection amount when traveling at high altitudes, it is possible to prevent the air-fuel ratio A/F from becoming too rich even when traveling at high altitudes.

However, the high altitude compensation value was set as a value that uniformly changes depending on the detection output of the airflow meter, so in systems to which the conventional method is applied, when driving at high altitudes, the throttle valve is fully open. There were problems in which the air-fuel ratio A/F became excessively rich under load, resulting in poor drivability and poor emission performance.

That is, the output of the air flow meter differs between highlands and flatlands due to the pulsation of the air flow meter, and the fluctuation becomes particularly large when the slot valve is fully open.
For example, at high altitudes, the detection output of the airflow meter becomes as shown in characteristic A in FIG. 1 due to a decrease in air density. In this case, it is necessary to correct the fuel injection amount according to the difference between characteristic A and characteristic B, but conventionally, the fuel injection amount is corrected according to the difference between characteristic C and characteristic B; The air-fuel ratio becomes richer in accordance with the deviation from C.

Such a difference between characteristic A and characteristic B is caused by pulsation of the air flow meter. That is, the effect of a decrease in air density is not only a decrease in the amount of intake air due to a simple change in density, but also affects the pulsation of the air flow meter. This effect is particularly large when the throttle valve is fully opened, which is a high load when comparing highlands and flatlands. Therefore, when the throttle valve is fully open when driving at high altitudes, even if the fuel injection amount is reduced by the high altitude compensation value that is set based on the airflow meter detection output when driving on flat roads, the amount of fuel injection will be reduced. The injection amount is not reduced sufficiently and the air-fuel ratio becomes excessively rich.

[Purpose of the invention]

The present invention has been made in view of the above-mentioned conventional problems, and its purpose is to provide an internal combustion engine that can improve drivability and emission performance when driving at high altitudes when the throttle valve is fully open. An object of the present invention is to provide a method for controlling the fuel injection amount of an engine.

[Summary of the invention]

In order to achieve the above object, the present invention calculates the basic fuel injection amount based on the engine rotation speed and the intake air amount detected by the airflow meter, and also calculates the maximum fuel injection amount that indicates the upper limit of the fuel injection amount based on the basic fuel injection amount. Set the amount according to the engine speed,
Feedback control is performed to maintain the air-fuel ratio at the set value based on the basic fuel injection amount, which is limited to less than the maximum fuel injection amount. When driving at high altitudes, the intake air amount and air density decrease based on the airflow meter's detection output, reducing the amount of intake air. In a fuel injection amount control method for an internal combustion engine in which the basic fuel injection amount is corrected by setting the basic fuel injection amount using a high altitude compensation value indicating a fuel reduction value corresponding to a deviation from the intake air amount that has been determined, the method corresponds to fully opening the throttle valve when driving at high altitudes. When the vehicle enters the operating state, the set value of the maximum fuel injection amount is lowered by a predetermined level, and control is performed to maintain the air-fuel ratio at the set value during high load driving at high altitudes.

[Embodiments of the invention]

Hereinafter, preferred embodiments of the present invention will be described based on the drawings.

FIG. 3 shows the configuration of a control system for a vehicle engine to which the present invention is applied.

In FIG. 3, the intake system of the engine 10 includes an air flow meter 14 that detects the intake air amount from the air cleaner 12, an intake temperature sensor 16 that detects the intake air temperature, and a throttle valve 20 that opens in response to the operation of the accelerator pedal 18. A throttle sensor 22 is provided to detect the engine speed. The intake air supplied through the air cleaner 12 is connected to the air flow meter 1.
4. Fuel is supplied to the intake manifold 24 via the throttle valve 20, mixed with fuel injected from the fuel injection valve 26 disposed near the intake manifold 24, and supplied to the combustion chamber 30 via the intake valve 28. Ru. The air-fuel mixture supplied to the combustion chamber 30 is combusted by a spark plug 34 provided in a cylinder head 32, and is discharged into an exhaust pipe 38 via an exhaust valve 36. The exhaust gas discharged into the exhaust pipe 38 is discharged via a three-way catalytic converter (not shown) provided in the exhaust pipe 38. This exhaust pipe 38 is provided with an oxygen concentration sensor (hereinafter referred to as an O ₂ sensor) 40 that detects the oxygen concentration in the exhaust gas.

Further, a pipe 44 forming an exhaust gas recirculation passage is provided between the exhaust pipe 38 and the surge tank 42 of the intake system, and a duty control type exhaust gas recirculation control valve is installed in the middle of this pipe 44. 46 are provided. This exhaust gas recirculation control valve 46 is operated by a control signal from a control device to be described later.
The flow rate of exhaust gas returned to surge tank 42 via pipe 44 can be controlled.

The intake system is also provided with a bypass pipe 48 that communicates with the intake tube 46 and the surge tank 42 to form an air bypass passage. A bypass flow control valve 50 is provided to control the flow rate.

Further, a distributor 54 that distributes and supplies the ignition signal from the ignition coil 52 to the spark plugs of each cylinder is connected to the crankshaft 5 of the engine.
A rotation angle sensor 58 for detecting the rotation angle of 6 is built-in.

Further, the cylinder block 60 of the engine 10 is equipped with a water temperature sensor 6 for detecting the engine cooling water temperature.
2 is provided.

Note that fuel stored in a fuel tank 64 is supplied to the fuel injection valve 26 via a pump 66.

The detection outputs of sensors that detect various operating states of the engine, such as the air flow meter 14, intake temperature sensor 16, throttle sensor 22, O ₂ sensor 40, rotation angle sensor 58, and water temperature sensor 62, are transmitted to the control device 6.
8. Moreover, in this example,
An atmospheric pressure sensor 70 that detects atmospheric pressure is provided, and the detection output of the atmospheric pressure sensor 70 is also controlled by the control device 6.
8.

The control device 68 is composed of a microcomputer, an example of which is shown in FIG.

The control device 68 in this embodiment includes a CPU 72,
ROM74, RAM76, 78, A/D converter 8
0 and an I/O port 82, and each part is connected by a bus line 84. The A/D converter 80 has a multiplexer, and the RAM 78 is configured with a memory that retains stored contents even after power supply to the control device 68 is stopped.

The detection outputs of the air flow meter 14, intake temperature sensor 16, water temperature sensor 62, and atmospheric pressure sensor 70 are A/
It is supplied to the D converter 80 and the rotation angle sensor 5
8, the detection outputs of the O ₂ sensor 40 and the throttle sensor 22 are supplied to the I/O port 82. On the other hand, the bypass flow control valve 50, ignition coil 52, fuel injection valve 26, and exhaust gas recirculation control valve 46 are supplied with control signals from the I/O port.

Further, the ROM 74 stores various numerical data such as control programs for performing various controls, numerical data of the maximum fuel injection amount corresponding to the engine speed, and numerical data of the high altitude compensation value.

The control device 68 configured as described above can calculate the basic fuel injection amount based on the intake air amount detected by the air flow meter 14 and the engine rotation speed detected by the rotation angle sensor 58.
In addition, the basic fuel injection amount is corrected according to the intake air temperature detected by the intake air temperature sensor 16, the engine water temperature detected by the water temperature sensor 62, and the oxygen concentration detected by the O ₂ sensor 40, and the air-fuel ratio A is adjusted accordingly. /
F can be feedback-controlled to a set value near the stoichiometric air-fuel ratio. Note that the fuel injection amount at this time is limited to the maximum fuel injection amount or less, and feedback control is performed to maintain the air-fuel ratio at the set value based on the fuel injection amount limited to the maximum fuel injection amount or less. It is done.

Further, when it is detected that the throttle valve 20 is fully closed based on the detection output of the throttle sensor 22, a control signal corresponding to the detection outputs of the intake temperature sensor 16 and the water temperature sensor 62 is sent to the bypass flow rate control valve 50. The amount of bypass intake air according to the intake temperature and engine water temperature is supplied to the bypass pipe 4.
8. Engine 1 via bypass flow control valve 50
0. Then, fuel corresponding to the amount of bypass intake air at this time is injected from the fuel control valve 26 to control the engine.

The control device 68 also controls the optimum ignition based on the fuel injection amount calculated by the CPU 72, the engine rotation speed and crank angle based on the detection output of the rotation angle sensor 58, and the intake air temperature based on the detection output of the intake temperature sensor 16. Numerical timing data is read from the ROM 74, a control signal corresponding to this numerical data is supplied to the ignition coil 52 via the I/O port 82, and the spark plugs of each cylinder can be ignited at the optimum ignition timing. .

Here, the present invention reduces the injection amount using a high altitude compensation value that indicates a fuel reduction value corresponding to the deviation between the intake air amount detected by the airflow meter 14 and the intake air amount reduced due to a decrease in air density during high altitude driving. In addition, when the throttle valve 20 is fully open, the set value of the maximum fuel injection amount is lowered by a predetermined level. A first high altitude compensation level and a second high altitude compensation level that lowers the set value of the maximum fuel injection amount by a predetermined level are stored in the ROM 74. The first and second high-altitude compensation levels are calculated based on the detection output of the atmospheric pressure sensor 70, or are pre-calculated as correction values during high-altitude driving based on the feedback control air-fuel ratio during flat-land driving. .

Hereinafter, the effects of the present invention will be explained based on a flowchart.

FIG. 5 shows an example of a processing routine performed by the control device 68.

The routine shown in FIG. 5 is a routine synchronized with the crank angle. First, in step 100, when driving at high altitudes, the first and second
The high altitude compensation level is read into the CPU 72, and the process moves to step 102. In step 102, the maximum fuel injection amount T _P is determined according to the detection output of the rotation angle sensor 58.
The numerical data of MAX is supplied from the ROM 74 to the CPU 72, and the process moves to step 104. In step 104, the correction value f (FHAC) determined from the first high altitude compensation level and the maximum fuel injection amount T P MAX are integrated, and the maximum fuel injection amount T _P MAX when the throttle valve is fully open is calculated. Fuel injection amount ET _P
An operation is performed to find MAX. That is, a calculation is performed to lower the set value of the maximum fuel injection amount to the second high altitude compensation level.

After step 104, the process moves to step 106, where the current basic fuel injection amount T _P is calculated based on the detected output of the rotation angle sensor 58 and the air flow meter 14, and the process moves to step 108.

In step 108, it is determined whether the basic fuel injection amount T _P calculated in step 106 is less than the maximum fuel injection amount E _P MAX calculated in step 104. At this step, it is judged as YES and T _P < ET _P
When the throttle valve 20 is at MAX, it is assumed that the throttle valve 20 is not fully open and the process moves on to other processing.

On the other hand, the determination in step 108 is NO, and T _P
If it is larger than ET _P MAX, it is assumed that the throttle valve 20 is fully open and the process moves to step 110.

In step 110, the maximum fuel injection amount ET _P MAX calculated in step 104 is set as the basic fuel injection amount.
Set to _TP . Feedback control is then performed to maintain the air-fuel ratio at the set value based on the fuel injection amount, which is limited to less than the maximum fuel injection amount _ETP MAX calculated in step 104.

In this embodiment, the fuel injection amount is lowered by the first high altitude compensation level when driving at high altitudes, and when the throttle valve 20 is fully open, the maximum fuel injection amount is reduced to the first high altitude compensation level. It is lowered by the high altitude compensation level of 2. Therefore, even when the throttle valve 20 is fully open, the amount of intake air is set to be the amount of intake air corresponding to the amount of intake air shown at point D in FIG. Since the air-fuel ratio is maintained at the set value by the control, even if the throttle valve 20 is fully open when driving at high altitudes, the air-fuel ratio will not become excessively rich and the air-fuel ratio will be maintained at the set value. This makes it possible to improve drivability and emission performance even when driving at high altitudes when the throttle valve 20 is fully open.

FIG. 6 shows a flow chart for explaining the operation of another embodiment of the present invention.

The processing routine shown in FIG. 6 is also performed in synchronization with the crank angle. First, in step 200,
When driving at high altitudes, the first high altitude compensation level is imported from the ROM 74, and the numerical data of the maximum fuel injection amount based on the detection output of the rotation angle sensor 58 is also acquired.
The process moves to a loading step 202 from the ROM 74.

In step 202, it is determined whether the first high altitude compensation level is smaller than the reference value A.
For example, if the applicable air-fuel ratio A/F is 13.0 when the throttle valve 20 is fully open at a high altitude of 1,600 m, then the limit value of the emission performance when the throttle valve 20 is fully open is the same as the standard value A. Since the fuel ratio A/F is 12, the value is set to be 8% richer than the compatible air fuel ratio A/F.

If the determination in step 202 is YES, the process moves to step 206, and if the determination in step 202 is NO, the process moves to step 204. That is, step 204
In step 202, it is determined that the first high altitude compensation level is greater than the reference value A, so calculations are performed to compensate for when the throttle valve 20 is fully open. That is, ROM
The second high altitude compensation level is taken in from step 74, the maximum fuel injection amount T _P MAX obtained in step 200 and the second high altitude compensation level are integrated, and the corrected maximum fuel injection amount ET _P MAX is calculated. will be carried out. The second high altitude compensation level at this time is the first
Fuel injection amount corrected by the high altitude compensation level of
A value of about 0.92 is used to further lower T _P by 8%. After step 204, the process moves to step 206. In step 206, the current basic fuel injection amount T _P is calculated based on the detection outputs of the rotation angle sensor 58 and the air flow meter 14, and the process moves to step 208. In step 208, the basic fuel injection amount T _P calculated in step 206 is
It is determined whether the maximum fuel injection amount ET _P MAX calculated in step 204 is reached. If the determination in step 208 is YES, the process moves to other processing, and if the determination is NO, the process moves to step 210. step 210
In this case, the maximum fuel injection amount ET _P MAX calculated in step 204 is set as the basic fuel injection amount T _P , and the fuel injection amount is limited to less than the maximum fuel injection amount ET _P MAX calculated in step 204. Based on this, control is performed to maintain the air-fuel ratio at the set value.

In this embodiment, as in the previous embodiment, even when driving at high altitudes with the throttle valve 20 fully open, the detected output of the air flow meter 14 is equal to the intake air amount corresponding to point D shown in FIG. Since the air-fuel ratio is maintained at the set value based on the fuel injection amount corresponding to the intake air amount, the air-fuel ratio will not become too rich even when driving at high altitudes when the throttle valve 20 is fully open. It is possible to improve the stability and the emission performance.

〔Effect of the invention〕

As explained above, according to the present invention, when the throttle valve is fully open while driving at high altitudes, the fuel injection amount corrected by the first high altitude compensation level is changed by the second high altitude compensation level. The air-fuel ratio is further lowered to maintain the air-fuel ratio at the set value during high-load driving at high altitudes, improving drivability and emission performance when driving at high altitudes when the throttle valve is fully open. It has the excellent effect of being able to

[Brief explanation of the drawing]

Fig. 1 is a diagram showing the relationship between the detection output of the airflow meter and the intake air amount, Fig. 2 is a diagram showing the relationship between altitude and air-fuel ratio, and Fig. 3 is a diagram showing the relationship between the altitude and the air-fuel ratio. FIG. 4 is a configuration diagram for explaining the configuration of the control device shown in FIG. 3, FIG. 5 is a flowchart showing an embodiment of the present invention, and FIG. 1 is a flowchart showing an example of the following. 10... Engine, 14... Air flow meter,
16...Intake temperature sensor, 20...Throttle valve, 22...Throttle sensor, 26...Fuel injection valve, 40... _O2 sensor, 58...Rotation angle sensor, 62...Water temperature sensor, 68... …Control device.

Claims (1)

[Scope of Claims] 1. The basic fuel injection amount is determined based on the engine rotational speed and the amount of intake air detected by the airflow meter, and the maximum fuel injection amount, which indicates the upper limit of the fuel injection amount based on the basic fuel injection amount, is calculated based on the engine speed. Feedback control is performed to maintain the air-fuel ratio at the set value based on the basic fuel injection amount, which is set according to the number of fuel injections and is limited to less than the maximum fuel injection amount. In a fuel injection control method for an internal combustion engine, the basic fuel injection amount is corrected by setting the basic fuel injection amount using a high altitude compensation value indicating a fuel reduction value corresponding to a deviation between the intake air amount and the intake air amount reduced due to a decrease in air density. During driving, when the operating state corresponds to a fully open throttle valve, the set value of the maximum fuel injection amount is lowered by a predetermined level, and control is performed to maintain the air-fuel ratio at the set value during high load when driving at high altitudes. A method for controlling fuel injection amount for an internal combustion engine.