JPS59190431A - Fuel injection quantity control method of internal- combustion engine - Google Patents

Abstract

PURPOSE:To maintain the air-fuel ratio at a preset value under a high load while running on a highland by decreasing the maximum fuel injection quantity when a throttle valve is fully opened during the travel on the highland. CONSTITUTION:A control device 68 reads out the value data of the maximum fuel injection quantity corresponding to the output of a rotation angle sensor 58 from an ROM 74. Next, the product of the correction value determined by the first highland compensation level and the maximum fuel injection quantity is calculated. This value becomes the maximum fuel injection quantity when a throttle valve is fully opened during the travel on the highland. Furthermore, a fuel injection pulse width is compared with the maximum fuel injection pulse width during the travel on the highland, and if the former is larger than the latter, the former is limited to the value of the latter. Thereby, the air-fuel ratio under a high load while running on the highland can be maintained at a preset value.

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 in particular,
In a vehicle engine equipped with an electronically controlled fuel injection device, the maximum fuel injection amount by the fuel injection device is set according to the engine speed, and the fuel injection amount is limited to less than the maximum fuel injection amount. The present invention relates to a fuel injection amount control method for an internal combustion engine suitable for performing feedback control to maintain a fuel ratio at a set value.

[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 amount of intake air detected by the airflow meter.
The maximum fuel injection amount, which indicates the upper limit of the fuel injection amount based on the basic fuel injection amount, is set according to the engine speed, and the air-fuel ratio is set to the set value based on the fuel injection l, which is limited to the maximum fuel injection amount or less. For example, feedback control was performed 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,
Intake air amount based on air flow meter detection output (characteristic A)
and the amount of intake air decreased due to the decrease in air density (Characteristic B)
Therefore, if the air-fuel ratio is controlled to the stoichiometric air-fuel ratio (A/F=14.7) under the same conditions, the air-fuel ratio A/F becomes excessively rich. For example, as shown in Figure 2, when the excess air ratio λ = 1.0 when the stoichiometric air-fuel ratio A/F = 14.7 on flat ground, 1600 m
The excess air ratio λ at high altitudes is about 0.91.

Therefore, a correction has been made to lower the fuel injection amount using a high altitude compensation value indicating a fuel reduction value corresponding to the deviation between characteristic A and characteristic B. That is, when driving at high altitudes, if the detected output of the air flow meter reaches the intake air amount shown in characteristic C in Figure 1, the fuel injection amount is increased by the amount of fuel corresponding to the deviation from characteristic C (!: characteristic B). As shown in Figure 2, this high-altitude compensation value is used as a set value to correct the air-fuel ratio A/F becoming too rich depending on the altitude, and is used as a feedback air-fuel ratio on flat ground. Fuel ratio A/F
It is determined by methods based on 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 above-mentioned high altitude compensation value was set as a value that uniformly changes according to the detection output of the air 70 meter, so in systems to which the conventional method is applied, when driving at high altitudes, the throttle valve is fully opened. There were problems in which the air-fuel ratio became too rich under load, resulting in poor drivability and poor emission performance.

That is, the output of the airflow meter differs between highlands and flatlands due to the vibration of the airflowmeter, and the variation becomes particularly large when the throttle valve is fully opened.

Therefore, when the throttle valve is fully open when driving at high altitudes, the amount of fuel injection will be The amount of fuel 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.
An object of the present invention is to provide a fuel injection amount control method for an internal combustion engine that can improve driver control and emission performance when driving at high altitudes with the throttle valve fully open.

[Summary of the invention]

In order to achieve the above object, the present invention calculates the basic fuel injection amount from the intake air amount based on the engine rotation speed and the detected output of the air flow meter, and also calculates the basic fuel injection amount (the maximum value indicating the upper limit of the fuel injection amount). The fuel injection amount is set according to the engine speed, and based on the fuel injection amount limited to the maximum fuel injection amount, feedback control is performed to maintain the air-fuel ratio at the set value, and air flow meter detection is performed when driving at high altitudes. In the fuel injection control method for an internal combustion engine, the basic fuel injection amount is lowered by a high altitude compensation value indicating a fuel reduction value corresponding to the deviation between the intake air amount due to output and the intake air amount reduced due to a decrease in air density. When the throttle valve is fully open during driving, 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, an air flow meter 14 is installed in the intake system of the engine 1o to detect the amount of intake air from the air cleaner 12.
, an intake temperature sensor 16 for detecting the intake temperature, and a throttle sensor 22 for detecting the opening degree of the throttle valve 2o in response to the operation of the accelerator pedal 18. The intake air supplied via the air cleaner 12 is supplied to an air flow meter 14, a valve 20 to an intic manifold 24, and a fuel injection valve 26 disposed near the ink manifold 24. It mixes with the injected fuel and is supplied to the combustion chamber 30 via the intake valve 28.The air-fuel mixture supplied to the combustion chamber 3o is combusted by the spark plug 34 provided in the cylinder head 32, and the exhaust pulp 36 is discharged to the exhaust pipe 38 through the exhaust pipe 38.

The exhaust gas extracted 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 O2 sensor) 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 is provided.3 This exhaust gas recirculation control valve 46 is actuated by a control signal from a control device to be described later, and can control the flow rate of exhaust gas returned to the surge tank 42 via the pipe 44. .

In addition, the intake system includes an intake tube 46 and a surge tank 42.
a bypass pipe 4 communicating with the air bypass pipe 4 to form an air bypass passage;
The surge tank 42 is provided with a bypass flow control valve 5o that controls the flow rate of intake air flowing through the bypass pipe 48.

Further, a distributor 5 distributes and supplies the ignition signal from the ignition coil 52 to the spark plugs of each cylinder.
4 has a built-in rotation angle sensor 58 that detects the rotation angle of the crankshaft 56 of the engine.

Further, the cylinder block 6o of the engine 10 is provided with a water temperature sensor 62 that detects the engine cooling water temperature.

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

Air flow meter 14, intake air temperature sensor 16, throttle sensor 22.02 sensor 40. Detection outputs from sensors that detect various operating states of the engine, such as the rotation angle sensor 58 and the water temperature sensor 62, are supplied to the control device 68. Furthermore, in this embodiment, an atmospheric pressure sensor 70 that detects atmospheric pressure is used.
is provided, and the detection output of the atmospheric pressure sensor 70 is also supplied to the control device 68.

The control bag ft68 has a microcomputer configuration, an example of which is shown in FIG.

The control device 68 in this embodiment includes a CPU 72, a ROM
74, RAM76.78, A/D converter f30. I10
It is composed of a boat 82, and each part has a pass line 84.
connected with. , the A/D converter 80 has a multiplexer, and the RAM 78 is constituted by a memory that retains stored contents even after power supply to the control device 68 is stopped.

Air flow meter 14, intake temperature sensor 16, water wetness sensor 6
2. The detection output of the atmospheric pressure sensor 70 is supplied to the A/D converter 80, and the rotation angle sensor 58.02 sensor 40,
The detection output of the throttle sensor 22 is supplied to the I10 boat 82, while the bypass flow control valve 50, ignition coil 52, fuel injection valve 26, and exhaust gas recirculation control valve 46 receive control signals from the I10 boat. is supplied.

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 in this manner can calculate the basic fuel injection amount based on the intake air amount based on the detection output of the air flow meter 14 and the engine rotation speed based on the detection output of 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 02 sensor 40, and the air-fuel ratio A/ F
can be feedback-controlled to a set value near the stoichiometric air-fuel ratio. In addition, the fuel injection amount at this time must be limited to the maximum fuel injection amount or less, and the feed/fuel ratio is maintained at the set value based on the fuel injection amount limited to the maximum fuel injection amount or less. control is performed.

Further, when it is detected that the throttle valve 20 is fully open based on the detection output of the throttle sensor 22, the control signal according to the detection outputs of the intake air flow sensor 16 and the water wetness sensor 62 is /< , 1 /< Bypass intake air intake is supplied to the flow control valve 50 and is supplied to the engine 10 via the bypass pipe 48 and the bypass flow discharge control valve 50 in accordance with the intake air flow and engine water temperature. And at this time...
(Fuel corresponding to the intake air pressure is also injected from the fuel control valve 26 to control the engine.

Further, the control device 68 determines the optimum ignition timing 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 flow rate based on the detection output of the intake air temperature sensor 16. Numerical data is read out from the ROM 74, and a control signal corresponding to this numerical data is supplied to the ignition coil 52 via the ignition coil 52 (10 baud) to ignite the spark plugs of each cylinder at the optimum ignition timing.

Here, the present invention uses a high altitude compensation value that indicates a fuel loss value corresponding to the deviation between the intake air bank determined by the detection output of the airflow meter 14 during high altitude driving and the intake air acid which has decreased due to a decrease in air density. In this implementation, the above-mentioned high altitude compensation A first high altitude compensation level corresponding to the value 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 ROM 7.
It is completely stored in 4. 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 operation according to 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, and first, in step 100, when traveling at high altitude, the first and second high altitude compensation levels are read from the ROM 74 into the CPU 72, and the process moves to step 102. In step 102), the numerical data of the maximum fuel injection amount TpMAX according to the detection output of the rotation angle sensor 58 is stored in the ROM 7.
4 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 TpMA are
Maximum fuel injection amount ETp when driving at high altitude when the throttle valve is fully open after integration with X.
An operation is performed to determine 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 Tp is calculated based on the detection output of the rotation angle sensor 58 and the detection output of the air flow meter 14, and the process moves to step 108.

In step 108, +1J determination is made to determine whether the basic fuel injection 11Tp calculated in step 106<the maximum fuel injection amount E'I'pMAX calculated in step 104. It is determined as YES in this step and Tp(ETp
When the throttle valve 20 is at MAX, it is assumed that the throttle valve 20 is not fully open and the process moves to other processing.

On the other hand, the determination in step 108 is No, and TP is ETp.
If it is larger than 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 ETpMAX calculated in step 104 is changed to the basic fuel injection amount tTp.
Set to . Then, 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 ETpMAX calculated in step 104 or less.

As described above, in this embodiment, the fuel injection amount is lowered by the first high altitude compensation level when driving at high altitude, and when the throttle valve 20 is fully open, the maximum fuel injection amount is lowered to the second high altitude compensation level. Reduced by compensation level. Therefore, when the throttle valve 2o is fully open, the amount of intake air is set to the amount of intake air corresponding to the amount of intake air shown at point D in Figure 1, and the amount of fuel injection corresponding to this amount of intake air is Since the fuel ratio is controlled to be maintained at the set value, even if the throttle valve 2o is fully open when driving at high altitudes, the air-fuel ratio will not become excessively rich and the air-fuel ratio can be maintained at the set value. It is possible to improve drivability and emission performance even when driving at high altitudes when 2o is fully open.

FIG. 6 shows a flowchart illustrating 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 traveling at a high altitude, the first high altitude compensation level is set 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 fetched from the ROM 74, and the process moves to step 202.

In step 202, it is determined whether the first high altitude compensation level is also smaller than the reference value A.

This reference value A is, for example, when the adaptive air-fuel ratio A/F is 13° when the throttle valve 20 is fully open at a high altitude of 1600 m, and when the throttle valve 20 is
The limit value of emission performance when fully opened is 1 at air fuel ratio A/F.
2, the adaptive air-fuel ratio A/FjI) is also set to a value that is 8% richer.

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, in step 204, since it was determined in step 202 that the first high altitude compensation level was greater than the reference value A, the throttle valve 2
Calculation is performed to compensate for the case where the valve o is fully open. That is, the second high altitude compensation level is fetched from the ROM 74, the maximum fuel injection amount TPMAX obtained in step 200 and the second high altitude compensation level are integrated, and the corrected maximum fuel injection amount ETPMAX is calculated. will be carried out. The second high altitude compensation level at this time is
Fuel injection amount T corrected by the first high altitude compensation level
A value of about 0.92 is used to further reduce P by 8%. After step 204, the process moves to step 206. In step 206, the detected outputs of the rotation angle sensor 58 and the air flow meter 14 are The current basic fuel injection - EiTp is calculated and step 2
Move on to 08. In step 208, step 20
Basic fuel injection amount Tp calculated in step 6<calculated in step 204]! It is determined whether the large fuel injection amount ETpMAX is large or not. 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. In step 210 - the maximum fuel injection amount ETPMAX calculated in step 204;
is set as the basic fuel injection amount tTp, and control is performed to maintain the air-fuel ratio at the set value based on the fuel injection amount limited to below the maximum fuel injection amount ETpMAX calculated in step 204.

In this embodiment as well, even when driving at high altitudes with the throttle valve 20 fully open, the detected output of the airflow meter 14 is equal to the I 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 this intake air amount, the air-fuel ratio will not become excessively rich even when driving at high altitudes when the throttle valve 20 is fully open. It is possible to improve drivability and 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 further reduced by the second high altitude compensation level, Control is performed to maintain the air-fuel ratio at the set value during high-load driving, which has the excellent effect of improving drivability and emission performance when driving at high altitudes with the throttle valve fully open. There is.

[Brief explanation of drawings]

Figure 1 is a diagram showing the relationship between air 70 meter detection output and intake air amount, Figure 2 is a miniature diagram showing the relationship between altitude and air-fuel ratio, and Figure 3 is a vehicle engine to which the present invention is applied. FIG. 4 is a configuration diagram for explaining the configuration of the control device shown in FIG. 3, and FIG.
Flowchart 1, which shows an example, and FIG.
This is a flowchart showing one example of Kj.10...Engine, 14...Airflow, Evening, 16
...Intake inkstone sensor, 20...Throttle valve, 22
・・Throttle sensor sweet, 26・・Fuel injection valve, 40・・
・02+Nza, 58... Kaisho" angle sensor, 62...
Water temperature sensor, 68...control device. Agent: Tatsuyuki Kugenuma (and 1 other person) Figure 1 Figure 2 Figure 4 68 Figure 5

Claims (1)

[Claims] (1) Determine the basic fuel injection amount based on the intake air amount determined by the engine speed and the detected output of the airflow meter. Based on the fuel injection bone, which is set according to the number of fuel injections and is limited to less than the maximum fuel injection amount, feedback control is performed to maintain the air-fuel ratio at the set value, and when driving at high altitudes, the intake air amount and In a fuel injection amount 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 from an intake air amount reduced due to a decrease in air density. When the throttle valve is fully open while driving at high altitudes, the set value of the maximum fuel injection amount is lowered by a predetermined one novel, and control is performed to maintain the air-fuel ratio at the set value during high load driving at high altitudes. A fuel injection amount control method for an internal combustion engine.