JPH11193736A - Fuel injection control system for two cycle engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate a complicated sensor or detection circuit so as to simplify the structure by using an engine speed as a feedback element to set a target idle rotational number, and adjusting the injection amount of the fuel in accordance with the difference between the target idle rotational number and the actual engine speed. SOLUTION: During operation of an engine 1, an ECU 12 obtains an actual engine speed from an output of an electromagnetic pick up coil 10 so as to calculate the difference ΔN between the engine speed and the target idle rotational number. Based on the obtained ΔN, a correction factor Ki for deviation idle rotational number and a correction factor Kidl for idle rotational number are calculated. Then the Kidl is compared with correction limit values of rich and lean which have been respectively set. When the Kidl does not exceed the correction limit value, it is set in a memory. A final fuel injection amount Ti is obtained by adding an ineffective injection time To to the product of Kidl and the injection time Tu after correcting with atmospheric pressure, intake air temperature and the like for controlling an injector 13.

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 a two-stroke engine, and more particularly to a fuel injection control device for a two-stroke engine which improves an idling operation state.

[0002]

2. Description of the Related Art A state in which an engine is operating with no load is called an idling operation state. In the case of an engine in which the fuel injection amount is electronically controlled, if this idle operation state is continued, there may be a difference between the fuel map and the fuel demand of the engine, a variation in the injector or intake air amount, etc. The deviation between the required engine fuel amount and the actually supplied fuel amount is integrated over time, and the air-fuel ratio shifts to a rich (rich) or lean (light) state.

[0003] As the air-fuel ratio becomes richer, the engine speed gradually decreases, the fuel consumption and the state of exhaust gas deteriorate, and a response delay at the time of acceleration from the idle state occurs. When the rich state or the lean state reaches the limit, the engine stops (engine stall). Therefore, in a four-cycle engine for an automobile, a method of adjusting the air-fuel ratio at idle and the engine speed by feedback control is used. Was used.

As a specific example of the adjustment method by the feedback control, for example, an exhaust sensor for detecting the oxygen concentration in the exhaust gas is used, and an air-fuel ratio control is performed by a detection signal of the exhaust sensor, or an operation is performed by an engine speed signal. There is a method of controlling the engine speed by operating a throttle opening or a control valve of an intake air bypass passage with an actuator to be operated.

[0005]

However, in the case of a two-stroke engine used for an outboard motor, a small motorcycle, or the like, due to its structure, it is burned because lubricating oil is mixed with fuel for each combustion. Since the oil becomes carbon-like or tar-like and blocks the detection portion of the exhaust sensor, it is difficult to detect the detection signal of the exhaust sensor over a long period of time.

[0006] Further, the exhaust sensor and its mounting, the provision of a sensor signal detection circuit, the actuator for operating the throttle opening and the control valve of the intake air bypass passage, and the provision of the intake air bypass passage itself are small and lightweight. It is not suitable for a two-stroke engine characterized by low cost.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to provide a fuel injection control device for a two-stroke engine which can improve the idling operation state without equipping complicated sensors and detection circuits. Aim.

Another object of the present invention is to provide a fuel injection control device for a two-stroke engine which makes it possible to improve the idling state with high accuracy even under different conditions.

[0009]

According to a first aspect of the present invention, there is provided a fuel injection control apparatus for a two-stroke engine which electronically controls a fuel injection amount according to the present invention. In the fuel injection control device for a two-stroke engine, a target idle speed is set by using the engine speed as a feedback element, and fuel is injected according to a difference between the target idle speed and the actual engine speed. It is configured to adjust the amount.

In order to solve the above-mentioned problem, the target idle speed is set to a position where the air-fuel ratio is the leanest before the engine speed rapidly increases. Things.

Further, in order to solve the above-mentioned problems,
As described in claim 3, the engine speed used for feedback is set to the average speed in an integral multiple of the intermittent combustion cycle or the long-term average speed at which the effect of the speed fluctuation due to intermittent combustion does not matter. At least one of them.

Further, in order to solve the above-described problem, the target idle speed is changed according to a change in air density.

Further, in order to solve the above-mentioned problems,
According to a fifth aspect, the element of the air density that changes the target idle speed is at least one of the atmospheric pressure and the intake air temperature.

Then, in order to solve the above-mentioned problem,
As described in claim 6, the target idle speed is changed according to the type of fuel.

[0015]

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

FIG. 1 is a system schematic diagram of a general electronic fuel injection control device (EFI) used for a two-stroke engine.

The two-stroke engine 1 is a general water-cooled two-cylinder two-stroke engine. A crankshaft 3 is rotatably supported in a crankcase 2 of the engine.
A cylinder 5 is formed in the cylinder block 4, and a piston 6 is slidably inserted in the cylinder 5 in a direction perpendicular to the crankshaft 3. The piston 6 and the crankshaft 3 are connected by a connecting rod 7, and the reciprocating stroke of the piston 6 is
It is to be converted into a rotational motion.

A magnet device 8 is provided at one end of the crankshaft 3. An electromagnetic pickup coil 10 for detecting the cylinder, detecting the rotation angle of the crankshaft 3 and its rotation speed is provided near the periphery of the flywheel magnet 9, for example. Will be installed. An exciter 11 is arranged inside the flywheel magneto 9.

Further, the magneto device 8 outputs AC power, and also supplies power to devices such as a control unit 12, a fuel injector 13, and a fuel pump 14, which will be described later.

On the other hand, for example, the cylinder block 4 is provided with a cooling water temperature sensor 15 for detecting a cooling water temperature of the engine 1. Further, a combustion chamber 17 is formed at a joint between the cylinder head 16 and the cylinder block 4, and a spark plug 18 is attached to the center of the combustion chamber 17 from the outside.

The crankcase 2 has a throttle valve 1
9 is connected. A throttle opening sensor 21 for detecting the opening of the throttle valve 19 is provided, for example, outside the intake passage 20. Further, a fuel injector 13 is attached to the intake passage 20 downstream of the throttle valve 19 from outside. And
The fuel in the fuel tank 22 is pumped up by the fuel pump 14, and guided to the fuel injector 13 through the delivery pipe 23. Further, the fuel pressure in the delivery pipe 23 is adjusted by the pressure regulator 24 so that the fuel pressure applied to the fuel injector 13 is always constant.

The fuel injection by the fuel injector 13 is electronically controlled by the EFI 25 described above. The EFI 25 includes an electronic fuel control unit 12 (hereinafter abbreviated as ECU). E
The CU 12 is based on, for example, an engine rotation signal sent from the electromagnetic pickup coil 10 and an opening signal of the throttle valve 19 sent from the throttle opening sensor 21, and further includes a cooling water temperature sensor 15 provided on the wall of the cylinder block 4. The fuel injection time is controlled so as to obtain an optimum air-fuel ratio by using a correction signal sent from an air temperature sensor 26 provided in the intake passage 20 and an atmospheric pressure sensor 27 provided outside the engine 1. .

Further, the electromagnetic pickup coil 10
The ECU 12 controls the timing for injecting fuel for each cylinder 5 based on the rotation angle signal of the crankshaft 3 sent from the ECU. That is, the fuel injector 13 of each cylinder 5 is controlled so as to inject fuel for a predetermined time at a predetermined time according to a signal from the ECU 12.

In addition to controlling the fuel injection time and timing, the ECU 12 sends an ignition signal to an ignition coil 28 for operating the ignition plug 18 and controls the fuel pump 1
4 is also controlled.

Next, a control method of the fuel injection control device according to the present invention will be described.

In order to improve the idle state of the two-cycle engine 1, it is necessary to first set a target idle speed at which the engine performance such as the fuel consumption rate and the response performance during acceleration from the idle state is good. .
It is necessary to adjust the fuel injection amount, that is, the air-fuel ratio according to the difference between the target idle speed and the actual engine speed.

FIG. 2 is a graph showing how the two-cycle engine speed during idle operation varies with the air-fuel ratio. As shown in FIG. 2, when the air-fuel ratio becomes lean, the engine speed of the two-stroke engine 1 starts to rapidly increase, and when the lean limit is reached, the engine speed is slightly decreased and then the engine stalls. Due to such engine characteristics, the gain with respect to the change in the air-fuel ratio is high, and a sudden change in the engine speed A to B in the drawing occurs.
It is not preferable to set the interval to the target rotation speed.

On the other hand, if the air-fuel ratio is rich, for example, if the target engine speed is set to the right of D in the figure, the fuel consumption rate and the state of the exhaust gas will deteriorate, and the response during acceleration from the idle state will be delayed. Again, this is not preferred. Therefore, in the present embodiment, a point C existing between B and D in the figure where the air-fuel ratio is in the leanest state before the sudden rise in the engine speed is set as the target idle speed.

Next, a method of obtaining the actual engine speed to be fed back will be described. FIG. 3 is a graph showing the engine speed of the two-cycle engine 1 in an intermittent combustion cycle in which combustion is performed once every three rotations. As shown in FIG.
Since the engine 1 burns at the point A and misfires at the points B and C, the average rotational speeds between the points A and B and between the points C and A are different. , At least one of the average rotation speed in the intermittent combustion cycle interval, the average rotation speed in an integral multiple of the intermittent combustion cycle, or the long-term average rotation speed so that the effect of rotation fluctuation due to intermittent combustion does not matter. It should be the actual engine speed.

Therefore, in the present embodiment, the two-cycle engine 1 having an intermittent combustion cycle in which combustion is performed once every three revolutions
, The average rotation speed for the last thirty rotations is set as the actual engine rotation speed.

Incidentally, the idle speed of the engine 1 may change due to various external factors. FIG. 4 is a graph showing how the two-cycle engine speed during idle operation changes depending on the air-fuel ratio and the atmospheric pressure. As shown in FIG. 4, the tendency that the idle speed changes depending on the air-fuel ratio is not affected by the difference in the atmospheric pressure. However, the engine speed decreases as the atmospheric pressure decreases, that is, as the engine 1 goes to a higher altitude. Therefore, as described above, when the point C existing between B and D in the figure is set as the target idle speed, it is necessary to change the setting of the target speed according to the change in the atmospheric pressure.

Further, although not shown in detail, the temperature of the air taken into the engine 1 and the temperature of the engine 1 are factors that cause a change in the atmospheric pressure, that is, a change in the air density. It is necessary to change the setting of the target rotation speed.

Further, in recent years, there has been an increasing number of occasions in which ethanol is mixed with gasoline for use. However, the output of the engine 1 also varies depending on the mixing ratio of gasoline and ethanol. It is necessary to change the setting of the target rotation speed.

FIGS. 5A and 5B are examples of correction maps in the case where the target rotational speed is corrected in consideration of the above-mentioned external factors. 5 (a) shows the atmospheric pressure (P)
And a map including the intake air temperature (Ta) and the target rotation speed (N) corrected by the atmospheric pressure and the intake air temperature.
pa) can be determined.

FIG. 5B is a map including the mixture ratio (F) of gasoline and ethanol and the engine temperature (Tw), and shows the target rotation speed (corrected by the type of fuel and the engine temperature). Nfw).

Then, the target rotation speed corrected by the atmospheric pressure and the intake air temperature obtained previously and the target rotation speed corrected by the type of fuel and the engine temperature are added to obtain a final rotation speed. The target idle speed (Ni) can be obtained (Ni = Npa + Nfw).

Next, a control method for adjusting the actual engine speed to the target idle speed will be described. The method is to obtain the best air-fuel ratio by correcting the fuel injection amount based on the difference between the target idle speed and the actual engine speed.

FIG. 6 is a flowchart for obtaining the above-mentioned idle correction coefficient for correcting the fuel injection amount. In this routine, the engine 1 is in an idle state, for example, the throttle opening is equal to or less than a set value.
Is recognized, and is executed at every fixed time set separately or at every predetermined rotation of the engine 1.

As shown in FIG. 6, first, in step 1, the difference between the actual engine speed and the target idle speed (rotation speed deviation, ΔN) is calculated. Next, in step 2, an idle rotation deviation correction coefficient (Ki) is calculated based on the above ΔN. FIG. 7 shows an idling rotation deviation correction coefficient (K) based on the rotation speed deviation (△ N) in step 2.
It is an example of a map used when calculating i).

Then, in step 3, an idle rotation correction coefficient (Kidl) is calculated. Here, the new idle rotation correction coefficient is obtained by adding the idle rotation deviation correction coefficient obtained in step 2 to the old idle rotation correction coefficient (Kidl = Kidl + Ki).

In step 4, it is determined whether or not the newly obtained idling rotation correction coefficient (Kidl) has exceeded the separately set rich and lean correction limit values. Here, the correction limit value is set because, for example, if one cylinder of a multi-cylinder engine misfires for some reason, the actual idle speed becomes lower than the target idle speed, and as a result, the ECU 12 is infinitely leaned. This is because there is a possibility that the misfire may be continued in cylinders other than the misfired cylinder by continuing the correction.

If the idling rotation correction coefficient (K
If it is determined that (idl) has exceeded the above-mentioned correction limit value, the rich and lean correction limit data set separately in step 5 uses the idle rotation correction coefficient (K
idl).

If the idling rotation correction coefficient (Kidl) does not exceed the correction limit value in step 4, or after a new idling rotation correction coefficient (Kidl) is set in step 5, the idling rotation correction coefficient (Kidl) is set. ) Is set in memory in step 6. When recognizing that the engine 1 is no longer in the idle state, the idling rotation correction coefficient (Kidl) stops the correction as soon as the throttle opening exceeds a set value, for example, and sets the correction coefficient to 1.

The final injection amount (Ti) of the fuel for performing the idle rotation correction is determined by the normal injection time (Tu) to which the correction coefficient such as the atmospheric pressure, the intake air temperature and the engine temperature is already applied, and the idle rotation. Correction coefficient (Kidl)
By adding the invalid injection time (To) to the product of
i = Tu × Kidl + To).

FIG. 8 is a timing chart showing the operation of the flowchart shown in FIG. As shown in FIG. 8, when the throttle opening becomes equal to or less than a set value (throttle idle determination level) at time t1, the engine 1 is recognized as being in an idle state, and every time the engine 1 rotates a predetermined number of times, an idle rotation correction coefficient is set. (Kidl) is updated.

Also, the idle rotation correction coefficient (Kidl) is clamped to the lean-side correction limit value between times t2 and t3, and the idle rotation correction coefficient (Kidl) is clamped to the rich-side correction limit value between times t4 and t5. Indicates the status that is being performed.

When the throttle opening exceeds the set value (throttle idle determination level) at time t6, it is recognized that the engine 1 has left the idle state, the correction is stopped, and the correction coefficient is set to 1. You.

In the above-described embodiment,
FIG. 5 (a) and FIG.
Although the example using the correction map shown in (b) has been described, a target idle speed can be similarly obtained by providing a reference idle speed in advance and correcting the reference idle speed. To correct the reference idle speed,
For example, a product obtained by multiplying a reference idle speed by an atmospheric pressure idle speed correction coefficient, an intake air temperature idle speed correction factor, an engine temperature idle speed correction factor, and a fuel type idle speed correction factor, There is a value obtained by adding the atmospheric pressure idle correction rotation speed, the intake air temperature idle correction rotation speed, the engine temperature idle correction rotation speed, and the fuel type idle correction rotation speed to the idle rotation speed.

In the above-described embodiment, the control method for adjusting the actual engine speed to the target idle speed is to correct the fuel injection amount based on the difference between the target idle speed and the actual engine speed. FIG. 6 shows a flowchart for obtaining the idling rotation correction coefficient (Kidl). However, as another embodiment, Steps 3 to 5 of the flowchart shown in FIG. The idle rotation deviation correction coefficient (Ki) obtained based on (△ N) may be used as the idle rotation correction coefficient (Kidl). FIG. 9 is a flowchart of this embodiment, and FIG. 10 is a timing chart showing the operation of the flowchart.

The above-described fuel injection control method for the two-stroke engine 1 does not require complicated equipment such as an exhaust sensor, its detection circuit, and an actuator for operating a control valve of the intake air bypass passage, and uses existing sensors. Electronic fuel control unit 12 (EC
This can be done only by changing the programming of U).
As a result, the idle operation state of the two-stroke engine 1 can be improved with a simple structure and without significantly increasing the cost.

Further, the setting of the target idle speed is changed in consideration of the air density and the type of fuel derived from the atmospheric pressure and the intake air temperature. Can be made favorable.

In the above-described embodiment, the rotational speed deviation (ΔN) between the target idle speed and the actual engine speed is obtained, and the fuel injection amount is proportionally controlled (deviation) according to the deviation (ΔN). In this example, feedback control is performed by integral and differential control in addition to proportional control (PID control). In the case of the present invention in which the engine speed is controlled by using as an element, the controllability of the fuel injection amount control may be improved by adding the differential control in addition to the proportional control.

The reason is that a change in the engine speed indicates a first-order lag with respect to a change in the amount of fuel supplied to the engine 1, and this first-order lag can be canceled by adding differential control. . This is because the controllability is improved by canceling the first-order lag, and the actual engine speed is easily stabilized near the target idle speed.

[0054]

As described above, according to the fuel injection control apparatus for a two-cycle engine according to the present invention, in the fuel injection control apparatus for a two-cycle engine that electronically controls the fuel injection amount, the rotation of the engine is controlled. In addition to setting the target idle speed as a feedback element and setting the target idle speed and adjusting the fuel injection amount according to the difference between the target idle speed and the actual engine speed, complicated sensors and detection The idle operation state of the two-stroke engine can be improved with a simple structure without providing a circuit or the like.

Further, since the target idle speed is set at the point where the air-fuel ratio is the leanest before the sudden increase in the engine speed occurs, the engine is not stalled and the fuel consumption rate and the state of the exhaust gas are reduced. There is no deterioration, and the response at the time of acceleration from the idle state is not delayed.

Further, the engine speed used for the feedback is at least one of the average speed in an integral multiple of the intermittent combustion cycle or the long-term average speed at which the influence of the speed fluctuation due to the intermittent combustion does not matter. Therefore, even if intermittent combustion occurs during idling, an optimum engine speed for feedback can be obtained.

Further, since the target idle speed is changed according to the change in the air density, the optimum target idle speed can be set even if the engine output changes due to the change in the air density.

Further, since the element of the air density that changes the target idle speed is at least one of the atmospheric pressure and the intake air temperature, even if the engine output changes due to the change in the atmospheric pressure or the intake air, the optimum value is obtained. The target idle speed can be set.

Since the target idle speed is changed according to the type of fuel, it is possible to use the gasoline mixed with ethanol and to set the optimum target idle speed even if the mixture ratio is different. it can.

[Brief description of the drawings]

FIG. 1 is a system schematic diagram of a general electronic fuel injection control device (EFI) used in a two-cycle engine, showing an embodiment of a two-cycle engine fuel injection control device according to the present invention.

FIG. 2 is a graph showing how a two-cycle engine speed during idling operation varies with an air-fuel ratio.

FIG. 3 shows an intermittent combustion cycle in which combustion is performed once every three rotations.
4 is a graph showing an engine speed of a cycle engine.

FIG. 4 is a graph showing a state in which a two-cycle engine speed during idle operation changes depending on an air-fuel ratio and atmospheric pressure.

FIGS. 5A and 5B are examples of a correction map in a case where a target rotation speed is corrected in consideration of an external factor;
(A) is a map composed of atmospheric pressure and intake air temperature, (b)
Is a map consisting of the mixture ratio of gasoline and ethanol and the engine temperature.

FIG. 6 is a flowchart for calculating an idle correction coefficient for correcting a fuel injection amount.

FIG. 7 is an example of a map used for calculating an idle rotation deviation correction coefficient based on a rotation speed deviation.

FIG. 8 is a timing chart showing the operation of the flowchart shown in FIG. 6;

FIG. 9 is a flowchart of another embodiment for obtaining an idle correction coefficient for correcting a fuel injection amount.

FIG. 10 is a timing chart showing the operation of the flowchart shown in FIG. 9;

[Explanation of symbols]

Reference Signs List 1 2 cycle engine 8 Magnetic device 10 Electromagnetic pickup coil 12 Electronic fuel control unit (ECU) 13 Fuel injector 14 Fuel pump 15 Cooling water temperature sensor 21 Throttle opening degree sensor 25 Electronic fuel injection control device (EFI) 26 Air temperature sensor 27 Large Barometric pressure sensor

Claims (6)

[Claims] In a fuel injection control device for a two-stroke engine that electronically controls a fuel injection amount, a target idle speed is set by using the engine speed as a feedback element. A fuel injection control device for a two-stroke engine, wherein the fuel injection amount is adjusted according to a difference from an actual engine speed. 2. The fuel injection control device for a two-stroke engine according to claim 1, wherein the target idle speed is set to a point where the air-fuel ratio is the leanest before the engine speed rapidly increases. 3. The engine speed used for feedback is at least one of an average speed in an integral multiple of an intermittent combustion cycle or a long-term average speed that does not cause a problem of rotation fluctuation due to intermittent combustion. 3. The fuel injection control device for a two-stroke engine according to claim 1, wherein: 4. The fuel injection control device for a two-stroke engine according to claim 1, wherein the target idle speed is changed according to a change in air density. 5. The method according to claim 1, wherein the element of the air density for changing the target idle speed is at least one of the atmospheric pressure and the intake air temperature.
Fuel injection control device for cycle engine. 6. The fuel injection control device for a two-stroke engine according to claim 1, wherein the target idle speed is changed according to the type of fuel.