JPH0826803B2 - Air-fuel ratio control device for internal combustion engine - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an air-fuel ratio control device for an internal combustion engine, and more particularly to an air-fuel ratio for an internal combustion engine that purifies exhaust gas when the engine is in an idle region to an acceleration region. Regarding the control device.

[Prior Art] An internal combustion engine for a vehicle has extremely large fluctuations in the vehicle running speed, that is, the engine rotation speed and the load. Requested. Therefore, it is necessary to make the air-fuel ratio appropriate under various operating conditions.

In order to properly control the air-fuel ratio, the air-fuel ratio is adjusted and controlled by the O ₂ sensor signal that detects the concentration in the exhaust gas, for example, the oxygen concentration, so that the best combustion state is always obtained for the various operating states described above. An air-fuel ratio control device that feedback-controls the air-fuel ratio is used in the above.

[Problems to be Solved by the Invention] By the way, in a conventional air-fuel ratio control apparatus for an internal combustion engine, a two-stage catalyst is used to reduce exhaust gas (especially CO), and secondary air is provided between the catalysts. There are those that are supplied to promote oxidation, and those that use large catalysts.

However, the use of the two-stage catalyst, the large-scale catalyst, and the secondary air supply device has a disadvantage of high cost.

Further, in the air-fuel ratio control device, as shown in FIGS. 7 and 8, the control constants (P and I) of the air-fuel ratio by the feedback control during internal combustion engine acceleration or constant speed are always the same, and the same control is performed. Was there.

As a result, for example, if the drivability at a constant speed is focused on, there is a disadvantage that the CO emission amount from the start of the internal combustion engine to the acceleration increases.

In particular, at high altitudes, the air-fuel ratio becomes unnecessarily rich, so that the emission amount of harmful exhaust gas in feedback control increases.

Therefore, in order to eliminate the above-mentioned inconvenience, an object of the present invention is to provide an altitude sensor for detecting an altitude state in an air-fuel ratio control device for an internal combustion engine by feedback control, so that the throttle opening is accelerated from an idle region. Entering the region and for a predetermined time from the time when the engine speed exceeds the predetermined speed, the air-fuel ratio control amount by the feedback control is adjusted to the lean side at predetermined time intervals according to the altitude by the altitude sensor. By adding a correction signal, it is possible to realize an air-fuel ratio control device for an internal combustion engine that can reduce harmful exhaust gas of CO, HC, and NOx without deteriorating drivability during start acceleration at a predetermined altitude in feedback control. It is in.

Further, in an air-fuel ratio control device for an internal combustion engine by feedback control for controlling a control amount of an air-fuel ratio having a proportional control constant and an integral control constant, an altitude sensor for detecting an altitude state is provided, and a throttle opening is in an idle region. To the acceleration region and the engine speed exceeds a predetermined speed for a predetermined time, depending on the altitude by the altitude sensor, the proportional control constant and integral control of the control amount of the air-fuel ratio by the feedback control. It is intended to realize an air-fuel ratio control device for an internal combustion engine, which can quickly reach the stoichiometric air-fuel ratio by making the constant large, improve the follow-up property during air-fuel ratio control, and reduce the CO emission amount.

[Means for Solving the Problems] In order to achieve this object, the present invention sets the air-fuel ratio of an air-fuel mixture supplied to an engine to a predetermined rich side air-fuel ratio when oxygen in exhaust gas becomes excessive. And the rich side is gradually enriched at a predetermined rate with the passage of time,
When the oxygen in the exhaust gas becomes too small, the air-fuel ratio of the lean side is shifted to a predetermined lean side, and the lean side is gradually leaned at a predetermined rate with the passage of time. An altitude sensor for detecting the state is provided, and the feedback control is performed according to the altitude by the altitude sensor for a predetermined time from the time when the throttle opening enters the acceleration range from the idle range and the engine speed exceeds the predetermined speed. It is characterized in that a correction signal to the lean side is added to the control amount of the air-fuel ratio by the above every predetermined time interval.

Further, the air-fuel ratio of the air-fuel mixture supplied to the engine is shifted to a predetermined rich side air-fuel ratio when the oxygen in the exhaust gas becomes excessive, and the rich side is gradually enriched at a predetermined ratio with the passage of time. When the oxygen in the exhaust gas becomes too small, the air-fuel ratio on the lean side is changed to a predetermined value, and on the lean side, a proportional control constant and an integral control constant are set so as to gradually become lean at a predetermined rate with the passage of time. In an air-fuel ratio control device for an internal combustion engine by feedback control for controlling a controlled amount of an air-fuel ratio, an altitude sensor for detecting an altitude state is provided, a throttle opening enters an acceleration region from an idle region, and an engine speed is a predetermined rotation speed. Depending on the altitude from the altitude sensor for a predetermined time from the time when the number is exceeded,
It is characterized in that a proportional control constant and an integral control constant of the air-fuel ratio control amount by the feedback control are increased.

[Operation] With the above-described configuration, the altitude sensor provides the control amount of the air-fuel ratio by the feedback control when the engine enters the acceleration range from the idle range for a predetermined time from the time when the engine speed exceeds the predetermined speed. Depending on the altitude, a correction signal to the lean side is added at predetermined time intervals to prevent unnecessary enrichment of the air-fuel ratio, and reduce exhaust gas such as CO without deteriorating drivability.

Further, when the engine enters the acceleration region from the idle region, the proportional constant control constant of the air-fuel ratio control amount by the feedback control according to the altitude by the altitude sensor for a predetermined time from the time when the engine speed exceeds the predetermined speed. Also, the integral control constant can be increased to obtain good followability during air-fuel ratio control, and CO emissions can be reduced.

Embodiments Embodiments of the present invention will be described in detail below with reference to the drawings.

1 to 6 show an embodiment of the present invention. In FIG. 1, 2 is an air cleaner, 4 is an intake passage, 6 is a carburetor, 8 is an engine, 10 is an exhaust passage, and 12 is a catalytic converter including a three-way catalyst. The carburetor 6 is provided with an electromagnetic valve 16 whose opening and closing is controlled by a controller 14 which will be described later.

Further, in order to detect the engine operating state, an opening sensor 18 for detecting the throttle valve opening and a water temperature switch 20 for detecting the engine temperature are provided. Further, an intake air temperature sensor 22, an atmospheric pressure sensor 24, and an O ₂ sensor 26 which is an exhaust gas sensor for detecting an exhaust gas concentration such as an O ₂ concentration are mounted in the exhaust passage 10. Further, an altitude sensor 28 for detecting the altitude is provided, and an ignition coil 30 is provided so as to detect the engine speed.

The opening sensor 18, the water temperature switch 20, the intake air temperature sensor 2
2, the atmospheric pressure sensor 24, and the control unit 14 that receives detection signals from sensors such as the O ₂ sensor 26.

The control unit 14 shifts the air-fuel ratio of the air-fuel mixture supplied to the engine 8 to a predetermined rich side air-fuel ratio when the oxygen in the exhaust gas becomes excessive, and on the rich side, a predetermined ratio with the passage of time. To gradually enrich the exhaust gas, and when the oxygen in the exhaust gas becomes too small, shift to a predetermined lean side air-fuel ratio,
On the lean side, feedback control is performed in which the lean side is gradually made lean at a predetermined rate as time passes.

Then, the region determined by the throttle opening enters the acceleration region from the idle region, and after the engine speed exceeds a predetermined rotation speed, for example, 1000 rpm, for a predetermined time, for example, T seconds (usually 10 to 30 seconds) A leaning signal ΔP that is a correction signal to the lean side is added to the control amount of the air-fuel ratio by the feedback control according to the altitude of the altitude sensor 28 at predetermined time intervals.

Then, at this time, the leaning width by the leaning signal ΔP is controlled by the magnitude of ΔP% and the time interval ΔT, and at every predetermined time interval, that is, the signal output ratio,
Set once / sec.

Further, the altitude sensor 28 is configured to change ΔP step by step according to the altitude change as shown in the following table. At this time, the lean signal ΔP as the correction signal increases the lean tendency in accordance with the increase in altitude by the altitude sensor 28 (see the following table).

Next, description will be given with reference to the flowchart of FIG.

First, when the vehicle starts, it is judged whether the engine speed is 300 rpm or more from the start.If NO, the output stop mode is executed. If YES, it is judged whether the cooling water temperature is normal. I do. Then, if NO, it is determined whether the intake air temperature sensor 22 is 16 ° C. or lower, and if YES, the O ₂ sensor 26 determines whether O ₂ is activated. If this judgment is NO, it is judged whether or not the intake air temperature sensor 22 similar to that described above is 16 ° C. or lower, and if it is YES, it is judged whether the ID (idle) switch is turned on after being turned on. To do.

Here, the operation after the determination by the intake air temperature sensor 22 will be described. When it is determined whether the intake air temperature sensor 22 is 16 ° C. or lower, if NO, it is determined whether the ID switch is ON, and if YES, the low temperature open loop control is performed.

The low temperature open loop control is control for fixing the air-fuel ratio to the rich side when the intake air temperature sensor 22 has a temperature of 16 ° C. or less (for example, during cold weather or immediately after starting).

Further, when the ID switch is ON, the ID open loop control is performed, when the ID switch is OFF, the PT open loop control is performed, and then the WOT switch proceeds to the judgment whether or not it is ON.

The ID open loop control is control that fixes the air-fuel ratio when the ID switch is ON (idle (ID) operation immediately after starting). The PT open loop control is a control that fixes the air-fuel ratio during PT (partial), that is, under partial load.

Judgment is made as to whether or not the ID switch is turned off from the ON state. If YES, it is judged whether or not the engine speed exceeds 1000 rpm, and if NO, the ID switch is turned ON.
Determine whether or not. In the judgment of whether the ID switch is in the ON state or not, if NO, PT closed loop control is performed and YE
In the case of S, it is judged whether the engine speed is 2500 rpm or more.

The PT closed loop control means executing feedback control of the air-fuel ratio during PT (partial), that is, under partial load.

When the engine speed is 2500 rpm or more, deceleration open loop control is performed and the engine speed is 2500 rp.
When it is less than m, the ID closed loop control is performed, and then the process proceeds to the judgment of whether the WOT switch is ON or not.

The deceleration open loop control refers to control for performing fixed condition operation by performing deceleration operation such as fuel cut during deceleration. Also,
The ID closed loop control means executing feedback control of the air-fuel ratio during idle (ID) operation.

When the engine speed exceeds 1000 rpm, it is judged whether it is within T seconds (about 10 to 30 seconds) after the engine speed is exceeded, and only when YES is determined whether the altitude is 500 m or less by a signal from the altitude sensor 28. to decide. Then, in the case of YES, PT closed loop control is performed with ΔP = 0, and in the case of NO, ΔP is set according to the altitude change based on the above table, and PT closed loop control is performed. After that, it is judged whether the WOT switch is ON, and NO
In case of, jump to start, and in case of YES, perform WOT control and then jump to start.

As shown in the above-described flowchart, in the highland, when the internal combustion engine is started and decelerated, as shown in FIG. 4, the air-fuel ratio can be made lean for T seconds by including ΔP in the partial feedback control. .

As a result, as shown in FIGS. 2 and 3, when used in a manual vehicle or an automatic vehicle, the engine performance such as responsiveness can be improved by accurate air-fuel ratio control.

Further, as shown in FIG. 6, by controlling only during acceleration that satisfies a predetermined condition, there is no inconvenience of deteriorating drivability and CO emissions can be reduced, which is practically advantageous.

Furthermore, by providing the altitude sensor 28, it is possible to perform air-fuel ratio control according to altitude changes, which can contribute to reduction of exhaust gas.

Furthermore, the air-fuel ratio control can be satisfactorily achieved only by changing the air-fuel ratio control program, and the cost can be reduced.

Note that the present invention is not limited to the above-described embodiment, and various application modifications are possible.

For example, in the embodiment of the present invention, the lean width is set by ΔP and ΔT, and the air-fuel ratio that is being made rich is lean, but the region determined by the throttle opening is from the idling region to the partial region. When the engine speed exceeds 1000 rpm and enters the region, the P value (P value of the control constant proportional to the control amount of the air-fuel ratio in the feedback control for a period of T seconds (usually 10 to 30 seconds) (P
(R), P (L)) and the I value (I
(R) and I (L) may be increased.

That, O ₂ sensor for detecting the O ₂ concentration in the exhaust gas is intended to determine whether the air-fuel ratio is lean or rich relative to the stoichiometric air-fuel ratio (about 14.7), detected from the O ₂ sensor The signal is used to change the air-fuel ratio to the theoretical air-fuel ratio (about 1
The air-fuel ratio control amount is feedback-controlled to converge to 4.7). At this time, when the P value (P (R), P (L)) of the proportional control constant of the control amount of the air-fuel ratio and the I value (I (R), I (L)) of the integral control constant are set to be large. During the lean and rich conditions, the stoichiometric air-fuel ratio is reached early, the followability during air-fuel ratio control can be improved, and CO emissions can be reduced.

The proportional control constant is P (R) or P (L) in FIG.
The amount of the part is shown, and the integral control constant is I (R) in FIG.
And the inclination of the I (L) part are shown.

Further, in the embodiment of the present invention, the lean signal ΔP is set stepwise according to the altitude change.
As shown in the following table and the one-dot chain line in FIG. 5, the proportional control constant P and the integral control constant I can be set stepwise according to the altitude change.

By doing so, it is possible to perform accurate air-fuel ratio control according to changes in altitude, which can contribute to reduction of harmful exhaust gas such as CO.

[Effects of the Invention] As described in detail above, according to the present invention, in the air-fuel ratio control device for an internal combustion engine by feedback control,
An altitude sensor for detecting an altitude state is provided, and the feedback is provided in accordance with the altitude by the altitude sensor for a predetermined time from the time when the throttle opening enters the acceleration range from the idle range and the engine speed exceeds a predetermined speed. Since the correction signal to the lean side is added to the control amount of the air-fuel ratio by the control at every predetermined time interval, harmful exhaust gases such as CO, HC and NOx can be reduced without deteriorating the drivability. Further, the air-fuel ratio control can be easily performed only by changing the air-fuel ratio control computer, and the cost can be reduced. Furthermore, this air-fuel ratio control device can be installed in a manual vehicle or an automatic vehicle, which is practically advantageous. Furthermore, by providing the altitude sensor, it is possible to perform accurate air-fuel ratio control according to altitude changes, which can contribute to reduction of exhaust gas at all altitudes.

Further, in an air-fuel ratio control device for an internal combustion engine by feedback control for controlling a control amount of an air-fuel ratio having a proportional control constant and an integral control constant, an altitude sensor for detecting an altitude state is provided, and a throttle opening is in an idle region. To the acceleration region and the engine speed exceeds a predetermined speed for a predetermined time, depending on the altitude by the altitude sensor, the proportional control constant and integral control of the control amount of the air-fuel ratio by the feedback control. Since the constant is increased, the stoichiometric air-fuel ratio can be reached at an early stage, the followability during air-fuel ratio control can be improved, and the CO emission amount can be reduced.

[Brief description of drawings]

1 to 6 show an embodiment of the present invention, FIG. 1 shows a control state of an internal combustion engine, FIG. 2 shows air-fuel ratio control of an automatic vehicle, and FIG. 3 shows an air-fuel ratio of a manual vehicle. Figure showing control, Figure 4 is a figure showing duty during air-fuel ratio control, Figure 5 is a flow chart of air-fuel ratio control, and Figure 6 is CO
It is a figure which shows the discharge amount. 7 and 8 show the prior art of the present invention, FIG. 7 is a diagram showing the duty during air-fuel ratio control, and FIG. 8 is a diagram showing the CO emission amount. In the figure, 2 is an air cleaner, 4 is an intake passage, 6 is a carburetor, 8 is an engine, 10 is an exhaust passage, 12 is a catalytic converter, 14 is a control unit, 16 is a solenoid valve, 18 is an opening sensor, 20 is water temperature. Switch, 22 is intake air temperature sensor, 24 is atmospheric pressure sensor, 26
Is an O ₂ sensor, 28 is an altitude sensor, and 30 is an ignition coil.

Claims (2)

[Claims] 1. An air-fuel ratio of an air-fuel mixture supplied to an engine is shifted to a predetermined rich side air-fuel ratio when oxygen in the exhaust gas becomes excessive, and the rich side is gradually increased at a predetermined ratio with the lapse of time. Air-fuel ratio control of the internal combustion engine by feedback control that makes the air-fuel ratio richer and shifts to a predetermined lean side air-fuel ratio when the oxygen in the exhaust gas becomes too small, and gradually leans at a predetermined rate with the passage of time on the lean side. The apparatus is provided with an altitude sensor for detecting an altitude state, and the throttle opening is changed from the idle range to the acceleration range and the engine speed exceeds a predetermined speed for a predetermined time, depending on the altitude detected by the altitude sensor. An air-fuel ratio control device for an internal combustion engine, wherein a lean side correction signal is added to a control amount of the air-fuel ratio by the feedback control at predetermined time intervals. 2. The air-fuel ratio of the air-fuel mixture supplied to the engine is shifted to a predetermined rich side air-fuel ratio when oxygen in the exhaust gas becomes excessive, and the rich side is gradually increased at a predetermined ratio with the lapse of time. When the amount of oxygen in the exhaust gas becomes excessively small, the air-fuel ratio is shifted to a predetermined lean side air-fuel ratio, and the lean side is gradually leaned at a predetermined rate with the passage of time. In an air-fuel ratio control device for an internal combustion engine by feedback control for controlling an air-fuel ratio control amount having a constant, an altitude sensor for detecting an altitude state is provided, and a throttle opening enters an acceleration region from an idle region and an engine speed. For a predetermined time from the time when exceeds a predetermined number of revolutions, according to the altitude by the altitude sensor, a proportional control constant of the control amount of the air-fuel ratio by the feedback control and Air-fuel ratio control system for an internal combustion engine, characterized by increasing the partial content control constants.