JP3497268B2 - Fuel injection control device for underwater exhaust engine - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel injection control device for an underwater exhaust engine in which exhaust gas is discharged into water against a back pressure.

[0002]

2. Description of the Related Art As a fuel injection control device for an engine, there is a so-called open control system for controlling a fuel injection amount based on an engine speed and a throttle opening (engine load). On the other hand, in an underwater exhaust engine such as an engine for an outboard motor, the back pressure on the exhaust side changes greatly.Therefore, when the above open control is adopted, the intake amount decreases as the back pressure increases. The air-fuel ratio becomes rich, and the intake air amount increases when the back pressure becomes small, so the air-fuel ratio becomes lean.

In order to avoid the influence of the back pressure, it is effective to employ a feedback control system for correcting the basic fuel injection amount based on the detected air-fuel ratio. In this feedback control, the fuel amount is controlled in accordance with the change in the intake air amount due to the change in the back pressure, and it can be expected to avoid the rich or lean operation due to the influence of the back pressure.

[0004]

By the way, in the above feedback control, the basic fuel injection amount is corrected within the range of the maximum correction amount (maximum control amount). When the back pressure changes, the sensor output is fixed in a rich or lean state, and the appearance is the same as when the sensor failed. Therefore, when the sensor output is fixed, it is unclear whether the back pressure is an influence or a failure.

If the sensor fails when the sensor output indicates a rich state, the stoichiometry (theoretical air-fuel ratio) is used because the reduction correction is performed until the maximum correction amount is reached.
If the sensor fails in a rich state close to 0, excessive lean operation may occur, and particularly in the case of a two-cycle engine, there is a risk of insufficient lubrication. Further, if the sensor fails when the lean state is close to stoichiometry, excessive rich operation is performed, which causes a problem that engine feeling is deteriorated.

The present invention has been made in view of the above-mentioned conventional problems, and when the sensor output is fixed, it is possible to determine whether it is due to the influence of back pressure or due to a sensor failure. It is an object of the present invention to provide a fuel injection control device for an underwater exhaust engine that can control the fuel injection amount in consideration of the above.

[0007]

The invention according to claim 1 is based on FIG.
As shown in, the basic injection amount setting means 31 that sets the basic fuel injection amount according to the engine operating state, the air-fuel ratio detection sensor 20 that detects the air-fuel ratio, and the basic fuel injection amount based on the detected air-fuel ratio. In a fuel injection control device for an underwater exhaust engine, which includes a feedback fuel correction unit 32 that corrects within a range of the maximum correction amount, a duration detection unit 33 that detects a rich or lean duration of a detected air-fuel ratio, and a rich duration or When the lean duration time exceeds a predetermined value, the sensor determination fuel correction means 34 for correcting the fuel injection amount in the converging direction to decrease or increase, and when the detected air-fuel ratio changes due to the fuel amount correction in the converging direction The air-fuel ratio detection sensor is normal, and when the above change does not occur, the sensor state determination means 35 determines that the air-fuel ratio detection sensor is abnormal.
And in the direction of convergence until the detected air-fuel ratio changes.
Maximum in feedback control according to fuel amount correction value
And a maximum correction amount correction means for correcting the correction amount .

The invention according to claim 2 further comprises a control method switching means 36 for switching the feedback control to the open control when the sensor state determining means 35 determines that the air-fuel ratio detecting sensor 20 is abnormal. It is characterized by that.

[0009]

According to a third aspect of the present invention, in the first aspect, when the sensor state determining means 35 determines that the air-fuel ratio detecting sensor 20 is normal, the basic fuel injection amount correcting means 38 is provided for correcting the basic fuel injection amount. It is characterized by that.

Here, the air-fuel ratio detecting means in the present invention is
It also includes one that indirectly detects the air-fuel ratio by detecting the oxygen concentration, CO concentration, or CO ₂ concentration in the exhaust gas.

[0012]

According to the invention of claim 1, the duration detecting means 3
3 detects the duration of the detected air-fuel ratio in the rich or lean state, and when the rich duration or the lean duration exceeds a predetermined value, the sensor determination fuel correction means 34 reduces or increases the fuel injection amount in the convergent direction. To do. When the sensor state determination means 35 changes the detected air-fuel ratio due to the fuel amount correction in the convergence direction, the air-fuel ratio detection sensor is normal, and when the change does not occur, the air-fuel ratio detection sensor is abnormal. It is determined that

For example, when the sensor output is rich, the fuel should be reduced and corrected to a lean state by the feedback control, but the reason why the rich state continues for a predetermined time or more is to decrease to the maximum correction amount. It is conceivable that the back pressure is large and the air amount is small enough not to invert to the lean side even if the correction is performed, or that the sensor fails when the sensor output indicates rich.

When the sensor is normal and the back pressure is high, the sensor output is reversed to the lean side when the fuel is further reduced. Therefore, when the sensor output is reversed by the fuel correction for the sensor state determination, the sensor is It can be judged as normal. on the other hand,
If the sensor output is not reversed even with the above amount reduction, it can be determined that the sensor is abnormal. Also, the air-fuel ratio detection sensor 20 is
If it is determined that there is,
Since the maximum amount of feedback correction was corrected, the back pressure
Can respond to movement.

In the invention of claim 2, the air-fuel ratio detection sensor 2
When it is determined that 0 is abnormal, the control method switching unit 36 switches the feedback control to the open control, so that the operation in the excessive lean or excessive rich state can be avoided. For example, if the feedback control is continued when a failure occurs in the state where the sensor output indicates rich, the operation is performed in a state where the maximum correction amount is reduced, and therefore excessive lean may occur in some cases. It can be avoided.

In the invention of claim 3, the air-fuel ratio detection sensor 2
If 0 is determined to be normal. Thus correcting the basic fuel injection amount, it is possible to correspond to the amount of change of the back pressure can always be maintained engine in good condition.

[0017]

Embodiments of the present invention will be described below with reference to the drawings. 1 and 2 are views for explaining a fuel injection amount control device for an underwater exhaust engine according to an embodiment of the inventions of claims 1 to 4, FIG. 1 is a diagram showing the entire configuration, and FIG. 2 is an operation. FIG. 4 is a diagram showing changes in sensor output and fuel injection amount for explaining the above.

In FIG. 1, reference numeral 1 denotes an outboard motor having a built-in engine 2 of the present embodiment. The outboard motor 1 has a trim angle β and a mount height H variably attached to the tail of the hull. The engine 2 is a water-cooled two-cycle three-cylinder crankshaft vertical type, in which the crankcase 4 is connected to the front joint surface of the cylinder block 3 and the cylinder head 5 is connected to the rear joint surface thereof to form the cylinder block 3. A piston 6 is inserted into each of the three cylinders to be connected, and is connected to a crankshaft 8 by a connecting rod 7. Reference numeral 9 is a spark plug.

The above three cylinders are arranged as shown in the sectional view taken along the line AA in FIG. 1, and ignition is performed in this order. Also, each exhaust port 5a from each cylinder
The collecting exhaust pipe 5 connected to the collecting portion of the cylinder is opened in the muffler 10, and the exhaust gas from each of the cylinders is collected by the collecting exhaust pipe 5.
Through the muffler 10 and the exhaust pipe 11 through the thruster 12
The water is discharged through the periphery of the rotating shaft 12a.

An intake pipe 13 communicates with each cylinder crank chamber of the crankcase 4, and the intake pipe 13 has a backflow preventing reed valve 14, a fuel injection valve 15,
A throttle valve 16 is provided. Reference numeral 17 is a fuel supply system for supplying high-pressure fuel to the fuel injection valve 15.

Further, the engine 1 of this embodiment includes a crank angle sensor 18 for detecting the engine speed and a throttle valve 1.
A throttle sensor 19 for detecting the opening degree (load) of 6;
An O ₂ sensor 20 for detecting the oxygen concentration in the upper cylinder, and thus the air-fuel ratio, a back pressure sensor 21 for detecting the pressure (back pressure) of the exhaust gas acting on the exhaust passage, and the amount of air supplied to the entire engine. And an intake sensor 22 for detecting

The O ₂ sensor 20 is connected to the downstream end of an exhaust extraction passage 20a formed so as to open from the exhaust port 5a of the upper end cylinder to the combustion chamber side, and as a result, substantially no blow-through gas is contained. The oxygen concentration of only the burnt gas is detected, and by extension, the air-fuel ratio of the air-fuel mixture supplied to the upper end cylinder is detected. Therefore, in this embodiment, the cylinder is the air-fuel ratio detection cylinder, and the cylinders are the non-air-fuel ratio detection cylinders.

The back pressure sensor 21 is arranged at the upper end of the muffler 10 and detects back pressure which changes depending on the speed of the hull, cloak height (water depth) H, trim angle β and the like.

The engine 2 of the present embodiment is equipped with an ECU 23 for controlling the operating state of the engine. This ECU 23
Reads the detection values of the sensors 18 to 22 and functions as ignition timing control means for controlling the ignition timing based on the engine speed and the throttle opening, and further has the following functions.

That is, basic injection amount setting means for setting the basic fuel injection amount according to the engine operating state, feedback fuel correction means for correcting the basic fuel injection amount within the range of the maximum correction amount based on the detected air-fuel ratio, Duration detection means for detecting the rich or lean duration of the detected air-fuel ratio, the sensor determination fuel correction means for correcting the fuel injection amount in the convergent direction to decrease or increase when the rich duration or the lean duration exceeds a predetermined value, If the detected air-fuel ratio changes due to the correction of the fuel amount in the convergence direction, the air-fuel ratio detection sensor is normal, and if the above change does not occur, the air-fuel ratio detection sensor is judged to be abnormal. Means, control method switching means for switching the feedback control to open control when the sensor is abnormal, and feedback control when the sensor is normal. Maximum correction amount correction means for correcting the large correction amount or basic fuel injection amount, functions as a basic injection quantity correcting means.

Next, the function and effect of this embodiment will be described. In the engine 2 of this embodiment, the ECU 23 causes
Open control is performed during sudden acceleration, avoidance of an emergency, etc., and feedback control is performed during normal operation. At the time of the open control, the basic fuel injection amount is calculated from the engine operating state-fuel injection amount map built in the ECU 23 based on the engine speed and the throttle opening.
The fuel is supplied from the fuel injection valve 15. In this case, the basic fuel injection amount is controlled to a fuel amount that provides a slightly rich basic air-fuel ratio as shown by the solid line in FIG.

In the open control, the propulsion device 1 is used.
When the back pressure changes depending on the water depth H of 2, the trim angle β, or the boat speed, the amount of air introduced into the cylinder changes, and the air-fuel ratio of the air-fuel mixture deviates from the basic air-fuel ratio. For example, when the back pressure increases, the intake air amount decreases, and when the above basic fuel injection amount is supplied,
2 becomes excessively rich as indicated by the broken line, and conversely when the back pressure becomes small, the intake air amount increases and becomes excessively lean as indicated by the alternate long and short dash line in FIG.

When the open control is switched to the feedback control at time t1 when the back pressure is high, the sensor output is rich at this time, so the fuel injection amount is reduced from the basic fuel injection amount. Is done. In this case, the sensor output reverses to the lean side at time t2 in the normal back pressure state, and thereafter, the increase correction is performed.

When the back pressure is abnormally large, the values shown in FIG.
As indicated by A ', even if the reduction correction is performed up to the maximum correction amount ΔQ, the sensor output does not reverse to the lean side and the rich state continues. When the duration of the rich state exceeds the predetermined time T (for example, 10 seconds), the sensor state determination fuel correction is performed in order to determine whether the influence of back pressure or the sensor malfunctions. In this case, first, as shown by B and B ′ in FIG. 2, the amount is reduced by Δq, and if the sensor output does not reverse even after a certain time elapses, Δq is further increased a preset number of times.
The amount is gradually reduced. When the sensor output is inverted as shown by C and C'in FIG. 2 by this reduction correction,
The sensor output did not reverse during the predetermined time T because the intake air amount was small due to the influence of back pressure, and it is determined that the air-fuel ratio detection sensor 20 is functioning normally.

When it is determined that the air-fuel ratio detecting sensor 20 is normal, the maximum correction amount ΔQ or the basic fuel injection amount is corrected so as to cope with the change in the air amount due to the influence of the back pressure. That is, in the case of the present embodiment, the maximum correction amount is corrected to about (ΔQ + 2Δq). In addition, ΔQ is about ± 15% of the basic injection charge, and Δq is about ± 5%. Further, the basic fuel injection amount is corrected to about -25%. It should be noted that these corrections are continued until the engine is stopped, and are restored to their original values the next time the engine is started.

On the other hand, if the sensor output is not reversed even after the reduction correction is performed a predetermined number of times, it is determined that the air-fuel ratio detection sensor 20 is malfunctioning and the sensor is abnormal. If this sensor abnormality is determined, the engine speed,
An open control is performed in which the basic fuel injection amount is calculated based on the throttle opening and the amount of fuel is injected.

When the back pressure is abnormally small, the increase correction is performed based on the same idea as when the back pressure is abnormally large. That is, when the duration of the lean state exceeds the predetermined time T, the increase correction of Δq is performed a preset number of times, and if the sensor output is reversed from the lean side to the rich side during that time, the sensor is normal, and the case is not reversed. Is determined to be a sensor abnormality. When the sensor is abnormal, the feedback control is switched to the open control, and when the sensor is normal, the maximum correction amount is increased or the basic fuel injection amount is increased.

As described above, in the engine 2 of the present embodiment, in the feedback control, when the rich or lean duration of the sensor output continues for a predetermined time or longer, the fuel is reduced or increased in the direction of converging the sensor output, Since the fuel correction for the sensor state determination that determines whether the sensor is normal or abnormal is performed based on the change in the sensor output, it can be determined whether the rich or lean state continues due to the back pressure or the sensor failure.

Further, since it is possible to determine whether the sensor is normal or abnormal, appropriate control can be performed based on the determination result. For example, when the sensor is abnormal, the control is switched to open control, so it is possible to avoid excessive lean or excessive rich engine operation, and excessive rich operation leads to insufficient lubricating oil and overheating of the engine, or excessive rich operation. It is possible to prevent the engine feeling from being deteriorated.

Further, when the sensor is normal, the maximum correction amount and the basic fuel injection amount in the feedback control are corrected, so that the feedback control corresponding to the fluctuation of the back pressure becomes possible.

[0036]

As described above, according to the invention of claim 1,
When the rich or lean duration of the detected air-fuel ratio exceeds a predetermined value, the fuel injection amount is reduced or increased in the converging direction, and when the detected air-fuel ratio changes due to the fuel amount correction in this converging direction, the Since the fuel ratio detection sensor is normal and the air-fuel ratio detection sensor is determined to be abnormal if the above change does not occur, it is possible to reliably determine whether the sensor is normal or abnormal when the sensor output does not change. is there. Well
Also, depending on the fuel amount correction value until the sensor output changes
The maximum correction amount of feedback control was corrected.
Therefore, it can respond to back pressure fluctuations and always keeps the engine in good condition.
Can be maintained in a good state.

According to the second aspect of the invention, when it is determined that the air-fuel ratio detection sensor is abnormal, the feedback control is switched to the open control, so that the operation in the excessive lean or excessive rich state can be avoided. It has the effect of avoiding engine overheating and deterioration of engine feeling.

According to the third aspect of the present invention, when the air-fuel ratio detection sensor is determined to be normal , the basic fuel injection amount is corrected, so that a large change in back pressure can be accommodated. This has the effect of keeping the engine in good condition at all times.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing a fuel injection control device according to an embodiment of the present invention.

FIG. 2 is a characteristic diagram showing changes in sensor output and fuel injection amount for explaining the operation of the apparatus of the above embodiment.

FIG. 3 is a claim correspondence diagram for explaining the scope of the claims of the present invention.

[Explanation of symbols]

2 engine 20 Air-fuel ratio detection sensor 31 Basic injection amount setting means 32 Feedback fuel correction means 33 Duration detection means 34 Sensor determination fuel correction means 35 Sensor status determination means 36 Control system switching means 37 Maximum correction amount correction means 38 Basic injection amount correction means

Claims (3)

(57) [Claims] 1. A basic injection amount setting means for setting a basic fuel injection amount according to an engine operating state, an air-fuel ratio detection sensor for detecting an air-fuel ratio, and a maximum correction of the basic fuel injection amount based on the detected air-fuel ratio. In a fuel injection control device for an underwater exhaust engine having feedback fuel correction means for correcting within a range of amount, duration detection means for detecting rich or lean duration of the detected air-fuel ratio, and rich duration or lean duration Exceeds a predetermined value, the fuel amount for sensor determination corrects the amount of fuel injection to decrease or increase in the convergent direction, and the air-fuel ratio detection sensor if the detected air-fuel ratio changes due to the correction of the fuel amount in the convergent direction. Is normal, and if the above change does not occur, the sensor state determination means for determining that the air-fuel ratio detection sensor is abnormal, and the detected air-fuel ratio change
Depending on the fuel amount correction value in the direction of convergence until
Maximum compensation to compensate the maximum compensation amount in feedback control
A fuel injection control device for an underwater exhaust engine, comprising: a positive amount correcting means . 2. The underwater exhaust engine according to claim 1, further comprising control method switching means for switching the feedback control to open control when the sensor state determination means determines that the air-fuel ratio detection sensor is abnormal. Fuel injection control device. 3. The method of claim 1, when the sensor state determining means determines that the normal air-fuel ratio detection sensor, the group
A fuel injection control device for an underwater exhaust engine, comprising a basic injection amount correction means for correcting the fuel injection amount .