JP2003155940A - Control device of spark ignition engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent degradation of an exhaust condition by suppressing the discharge of the unburned fuel and remaining of the unburned fuel in an intake port 10a or the like as much as possible when an engine 1 is stopped in a case in which an injector 16 is provided on the intake port 10a of a spark ignition engine 1, and the fuel is injected at the predetermined injection timing in each combustion cycle of a cylinder 2. SOLUTION: When the engine 1 is stopped, an ISC control valve 19 is closed to reduce the intake air volume to the cylinders 2, etc., compared with that during an idling operation (Step SA11), and the fuel injection control by an injector 16 is completed (Step SA12). The fuel mixture sucked from the intake port 10a into the cylinder 2 in the subsequent combustion cycle is ignited and burned. When the engine speed ne reaches the preset ECU stop rotational speed ne* or under (Step SA14), the power supply to an ECU 30 is stopped, and the ignition control for each cylinder 2 is also completed (Step SA16).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a so-called port injection type spark ignition type engine control device having a fuel injection valve in an intake port, and more particularly to a technical field of fuel injection and ignition control when the engine is stopped. Belong to.

[0002]

2. Description of the Related Art Conventionally, in this type of spark ignition type engine, fuel is generally provided at a predetermined timing in synchronization with a combustion cycle of the cylinder by a fuel injection valve provided in an intake port of each cylinder. I am trying to make it jet. In this way, the fuel injected into the intake port is promoted to vaporize in the high temperature intake port, and when the intake valve opens at the end of the exhaust stroke of the cylinder, it is sucked into the cylinder to form a mixture,
After that, it is ignited by the spark plug in the latter half of the compression stroke of the cylinder and burns well.

At this time, in order to obtain a good combustibility of the air-fuel mixture, there is a demand to inject the fuel as early as possible so that the fuel is sufficiently vaporized. Since it is preferable that the time interval from fuel injection to ignition is not too long, fuel injection is normally performed by appropriately selecting the timing from the time when the intake valve is closed in the compression stroke of the cylinder to the next intake stroke. It

When the engine is stopped, for example, when the ignition switch is turned off by the driver, for example, the engine control unit (hereinafter referred to as ECU) is immediately turned off, and fuel such as the above engine is used. Since the injection valve is not actuated and the ignition plug is not energized, if the fuel is injected earlier than the ignition timing of the cylinder as described above, the ECU is injected before the injected fuel is ignited. When the power source is turned off, the unburned fuel may be discharged as it is to the exhaust passage, or may remain in the intake port, the combustion chamber in the cylinder, or the like.

That is, a large amount of unburned gas may be discharged from the cylinder when the engine is stopped, and a part of the unburned gas may pass through the catalyst and be discharged into the atmosphere as it is. Also,
Immediately after starting the engine, the fuel remaining in the intake port or cylinder may be released as unburned gas,
At this time, since the catalyst often does not reach the activation temperature, there is a problem that the exhaust condition deteriorates remarkably even temporarily.

In relation to such a problem, for example, according to an engine control method disclosed in Japanese Patent Laid-Open No. 8-177699, in a direct injection engine in which fuel is directly injected into a cylinder, If the fuel injected into the cylinder remains unignited, this fuel liquefies in the cylinder and dilutes the engine oil, or adheres to the spark plug to impair the startability, and eventually the state of exhaust gas. Paying attention to the problem that it may worsen, even after the ignition switch is turned off, ignition is always performed in the cylinder where fuel was injected before, and the fuel injected into the cylinder is burned. The technical idea of making it do is disclosed.

[0007]

However, unlike the direct injection engine described in the above publication (JP-A-8-177699), in the case of a so-called port injection type engine, the fuel once injected into the intake port is used. Is vaporized and atomized there before being supplied into the cylinder. At this time, a part of the fuel adheres to the wall surface of the intake port and is carried over to the next and subsequent combustion cycles. Even if it is executed, it is only possible to reduce the residual amount of unburned gas in the cylinder, and that alone causes the problem of exhausting unburned gas when the engine is stopped or started as described above. It is hard to say that it can be resolved.

The present invention has been made in view of these points, and an object thereof is to provide a fuel for stopping an engine in a spark ignition type engine in which fuel is injected into an intake port of the engine. The control procedure of injection and ignition is elaborately devised, and at that time, the discharge of unburned fuel and the residual in the intake port are suppressed as much as possible to prevent the deterioration of the exhaust state.

[0009]

In order to achieve the above object, in the solution means of the present invention, when the engine is stopped, after the fuel injection by the fuel injection valve is finished, the cylinder corresponding to the fuel injection valve is stopped. The ignition control of the cylinder is executed until at least two combustion cycles have passed.

Specifically, according to the first aspect of the invention, a fuel injection valve for injecting fuel is provided in the intake port of the engine, and the fuel injection valve is used to inject fuel at a predetermined injection timing for each combustion cycle of the cylinder. And a fuel control means for terminating the fuel injection control by the fuel injection valve when the engine is stopped, and a control of the fuel injection valve by the fuel control means. After completion of the above, the ignition control means performs ignition control of the cylinder until the combustion cycle of the cylinder corresponding to the fuel injection valve has passed at least twice or more.

With the above arrangement, when the ignition switch is turned off and the engine is stopped while the engine is operating, first, the control of the fuel injection valve by the fuel control means is finished, and the fuel supply thereafter is stopped. It will not be done. On the other hand, until the combustion cycle of the cylinder corresponding to the fuel injection valve has passed at least two times or more, the ignition control means performs the ignition control for each cylinder, so that the air-fuel mixture is ignited at a predetermined timing in the cylinder. Done.

That is, when the engine is stopped, the fuel-air mixture is ignited in each cylinder for at least two cycles after the fuel injection to the intake port by the fuel injection valve is terminated. , Of course, the fuel sucked into the cylinder from the intake port in the first combustion cycle after the last fuel injection, as well as the fuel evaporated from the intake port wall surface and sucked into the cylinder by the next second combustion cycle. Can also be burned. As a result, the discharge of unburned fuel when the engine is stopped can be suppressed, and the unburned fuel remaining in the engine after the engine is stopped can be reduced as much as possible to prevent deterioration of the exhaust state at the time of starting.

According to a second aspect of the invention, the engine has a plurality of cylinders, and the fuel injection valve is provided for each of the plurality of cylinders. That is, in a multi-cylinder engine having a plurality of cylinders, for example, in the case of a 4-cycle in-line 4-cylinder engine, four cylinders explode (combust) at equal intervals (a crank angle of 180 degrees) while the crankshaft makes two revolutions. Therefore, the fuel injection timing for each combustion cycle is approximately 180 degrees.

Therefore, if the fuel injection and the ignition control are uniformly terminated when the multi-cylinder engine is stopped,
It is conceivable that the fuel that has just been injected into some of the plurality of cylinders will be released as it is, and the deterioration of the exhaust state will be particularly remarkable. Therefore, in such a multi-cylinder engine, it is particularly effective to perform ignition twice or more for each cylinder after completion of fuel injection control as in the present invention.

According to the third aspect of the present invention, the intake air amount adjusting means for adjusting the intake air amount to the engine and the intake air amount adjusting means for making the intake air amount smaller when the engine is stopped than when the engine is idling. And an intake air amount control means for controlling. That is, in general, when the engine is stopped, the fuel injection control is ended and the supply of new fuel is terminated, so that the fuel adhering to the intake port wall surface is sucked into the cylinder in the subsequent cycles. As a result, the air-fuel mixture formed in the cylinder is gradually diluted and the ignitability deteriorates.

On the other hand, according to the present invention, when the engine is stopped, the intake air amount control means controls the intake air amount adjustment means, and the intake air amount of the cylinder becomes smaller than that during the idle operation. Even if the control is ended and the supply of new fuel is terminated, the lean mixture of the air-fuel mixture in the cylinder can be delayed, and thus ignition failure can be prevented.
Moreover, if the intake amount is adjusted by the intake amount adjusting means, the intake flow velocity at the intake port is increased accordingly, and the evaporation of the fuel adhering to the port wall surface and the intake into the cylinder are promoted. This also suppresses the leaning of the air-fuel mixture, whereby the effect of the invention of claim 1 or 2 can be sufficiently obtained.

The intake air amount adjusting means includes a throttle valve provided in an intake passage of the engine and operated by an actuator, and a downstream side of the intake passage (including an intake port for enhancing intake flow in a cylinder). ) May be used, or a variable valve mechanism that changes at least one of the lift amount and valve timing of the intake valve itself may be used.

According to a fourth aspect of the present invention, there is provided rotation speed determination means for determining that the engine rotation speed is less than or equal to the set rotation speed, and the ignition control means is ignited when the determination is made by the rotation speed determination means. The control shall be terminated.

As a result, when the engine is stopped, the supply of new fuel to the cylinder is first cut off, and thereafter, ignition is performed for several cycles in the cylinder while the engine speed is gradually reduced. After that, when it becomes difficult to ignite the air-fuel mixture because the engine rotation speed becomes equal to or lower than the set rotation speed, the ignition control ends. This allows
Unburned fuel can be sufficiently reduced, and power consumption associated with ignition can be suppressed.

According to the fifth aspect of the present invention, a sensor for detecting the air-fuel ratio state of the exhaust gas, and an air-fuel ratio for judging that the air-fuel ratio in the cylinder is leaner than a set value based on a signal from the sensor. The ignition control means is configured to end the ignition control when the air-fuel ratio determination means makes a determination.

As a result, when the engine is stopped, the fuel adhering to the wall surface of the intake port is sucked into the cylinder after the new fuel supply to the cylinder is cut off, and the fuel is mixed into the air-fuel mixture for several cycles. Ignition is performed, and thereafter, when the air-fuel mixture in the cylinder is diluted and the air-fuel ratio becomes leaner than a predetermined value, the ignition control ends. As a result, it is possible to continue the ignition to near the misfire limit and reduce the unburned fuel as much as possible, while suppressing the power consumption accompanying the ignition.

According to the sixth aspect of the present invention, after the control of the fuel injection valve by the fuel control means is completed, a cycle number determination means for determining that the combustion cycle of the cylinder has passed the set number of times is provided, and the ignition control means is Ignition control is terminated when the determination is made by the cycle number determining means.

Thus, when the engine is stopped, after the supply of new fuel to the cylinder is cut off, ignition is further performed for the set number of cycles, and then the ignition control is ended. Therefore, the unburned fuel can be reduced by a simple control procedure, and the power consumption associated with ignition can be suppressed.

[0024]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1) FIG. 1 shows an in-line 4-cylinder 4-cycle gasoline engine 1 according to Embodiment 1 of the present invention. The engine 1 includes a cylinder block 3 having four cylinders 2, 2, ... (Only one is shown), and a cylinder head 4 mounted on the upper surface of the cylinder block 3.
And a piston 5 reciprocally fitted in each cylinder 2, and a combustion chamber 6 is defined in each cylinder 2 by being surrounded by the piston 5 and the cylinder head 3. Further, an ignition plug 7 is provided above the combustion chamber 6, and the ignition plug 7 is connected to an ignition circuit 8 including an igniter and the like. That is, the engine 1 is a spark ignition type engine in which the air-fuel mixture formed in the combustion chamber 6 in each cylinder 2 is ignited by the spark plug 7.

On one side surface (left side in the drawing) of the engine 1, intake air is introduced into the combustion chamber 6 of each cylinder 2, that is, air (fresh air) introduced into the cylinder 2 from the outside or exhaust gas recirculated from the exhaust system. An intake passage 10 for supplying the above components is connected. The downstream end of the intake passage 10 is connected to the combustion chamber 6 by an intake port 10a formed in the cylinder head 3,
The open end of the intake port 10a to the combustion chamber 6 is the intake valve 9
It is designed to be opened and closed by. On the other hand, the intake passage 1
The upstream end of 0 is connected to an air cleaner 11 for filtering air, and the air cleaner 11 is provided with a temperature sensor 12 for detecting the temperature state of intake air. Further, an air flow sensor 13 that detects the amount of intake air into the engine 1, a throttle valve 14 that throttles the intake passage 10, and a surge tank 15 are arranged in this order from the upstream side of the intake passage 10, and each cylinder 2 Injectors 16, 16, ... (Only one is shown in the drawing) as fuel injection valves are arranged so as to individually inject and supply fuel into each intake port 10a.

The throttle valve 14 is not shown,
When mechanically connected to the accelerator pedal of the vehicle and the accelerator pedal is depressed by the driver of the vehicle,
It is designed to be opened according to the operation amount. Also,
The throttle valve 14 is provided with a throttle opening sensor 17 such as a potentiometer for detecting the opening thereof. Further, an ISC (Idle Speed Control) that connects the intake passage 10 on the upstream side and the downstream side of the throttle valve 14
A bypass passage 18 for the vehicle is provided.
Is provided with an ISC control valve 19 (intake air amount adjusting means) which is an electromagnetic valve so as to reduce the passage area. When the engine 1 is in the idle operation state, the IS
The intake flow rate of the bypass passage 18 is adjusted by the opening / closing operation of the C control valve 19.

On the other hand, on the side surface on the opposite side of the engine 1 (right side surface in the figure), burnt gas (exhaust gas) from the combustion chamber 6 of each cylinder 2 is exhausted.
An exhaust passage 20 for discharging the exhaust gas is connected. An upstream end of the exhaust passage 20 communicates with the combustion chamber 6 via an exhaust port, and an opening end of the exhaust port to the combustion chamber 6 is opened / closed by an exhaust valve 21. Further, in the exhaust passage 20, an O ₂ sensor 22 for detecting the oxygen concentration in the exhaust and a catalytic converter 23 including a three-way catalyst for purifying the exhaust are arranged in this order from the upstream side.

An exhaust gas recirculation passage 24 (hereinafter referred to as an EGR passage) is provided in the exhaust passage 20 upstream of the O ₂ sensor 22 for recirculating a part of the exhaust gas to the intake passage 10.
Of the EGR passage 24 is branched and connected to the intake passage 10 between the throttle valve 14 and the surge tank 15. Further, the EGR passage 24 is connected to the intake passage 10 between the throttle valve 14 and the surge tank 15. An electric exhaust gas recirculation amount control valve 25 (hereinafter referred to as an EGR valve) whose opening degree can be adjusted is provided, and the flow rate of exhaust gas recirculating through the exhaust passage 24 can be adjusted.

In the cylinder block 3 of the engine 1, there is provided a crank angle sensor 26 including an electromagnetic pickup for detecting the rotation angle of a crank shaft (not shown). The crank angle sensor 26 is arranged corresponding to the outer periphery of a plate 27 for detection provided at the end of the crankshaft, and a protrusion provided on the outer periphery of the plate 27 for detection as the plate 27 for detection rotates. A signal of the crank angle position of each cylinder 2 is output according to the passage of parts. Further, a water temperature sensor 28 is provided to face the water jacket (not shown) of the cylinder block 3 to detect the temperature state of the cooling water.

The intake air temperature sensor 12, the air flow sensor 13, the throttle opening sensor 17, the O ₂ sensor 22,
Each output signal from the crank angle sensor 26, the water temperature sensor 28, etc. is an ECU configured by a microcomputer or the like.
(Electronic Control Unit) 30 is input. On the other hand, from the ECU 30, the ignition circuit 8
On the other hand, the ignition control signal is output at a predetermined ignition timing for each cylinder 2, and the injectors 16, 16 ,.
On the other hand, a pulse signal for controlling the fuel injection amount is output at a predetermined injection timing for each cylinder 2. Also, E
The CU 30 outputs to the ISC control valve 19 a control signal mainly for adjusting the intake amount of air during idle operation, and outputs a control signal for the EGR valve 25 to adjust the exhaust gas recirculation amount. It

(Outline of Control by ECU) The ECU 3
The control of the fuel injection amount by 0 basically calculates the load state and the rotation speed of the engine 1 based on the signal from each sensor, and the fuel corresponding to them is injected by the injector 16 for each cylinder 2. The injection is performed at a predetermined injection timing in synchronization with the engine rotation for each combustion cycle of the cylinder 2.

Specifically, the ECU 30 intakes air for each cylinder 2 in accordance with the intake air amount detected by the air flow sensor 13 and the engine speed ne obtained based on the pulse signal from the crank angle sensor 26. The charging efficiency ce is calculated, and a fuel injection amount that achieves a predetermined target air-fuel ratio is calculated with respect to the calculated intake charging efficiency ce. And
A pulse signal having a pulse width corresponding to the calculated fuel injection amount is output to the injector 16.

Further, the number of fuel injections in each combustion cycle is set to two in most warm operating states, and the injection timing (the valve opening start timing of the injector 16) is intake for each cylinder 2. It is set to the middle stage of the compression stroke after the valve 9 is closed (leading injection) and the exhaust stroke after that (trailing injection). Specifically, as shown in FIG. 2, in the engine 1 of this embodiment, the first to fourth four
The first, third, fourth, second, for the two cylinders 2, 2, ...
Combustion is performed in this order, and in a warm steady operation state except during idle operation, each cylinder 2 has four strokes of intake, compression, expansion (combustion), and exhaust.
With respect to one combustion cycle, fuel injection is performed in the compression stroke and the exhaust stroke of the immediately preceding cycle.

Thus, injecting the fuel in two times is required to inject the fuel as early as possible and to sufficiently vaporize it in order to obtain good combustibility of the air-fuel mixture. In order to ensure the responsiveness of the engine 1 at the time of a transition while leading injection of the required amount of fuel in response to the above, there is a demand to change the fuel supply amount in response to changes in operating conditions. The total amount of fuel supply is adjusted by trailing injection.

On the other hand, throttle opening and engine speed
When it is determined that the engine 1 is in an extremely low load operation state such as an idle operation based on ne, the fuel required for one combustion cycle is small, and therefore, as shown in FIG. Only the trailing injection in the exhaust stroke for every 2 is performed.

The fuel injection timing for each cylinder 2 as described above is adjusted according to the operating state of the engine 1.
Further, the ignition timing of each cylinder 2 is also adjusted according to the operating state of the engine 1, and as shown schematically by the arrow in the figure, it is approximately compression top dead center (TDC) in a warm steady operating state.
Before, for example, in the idle operation state, it is set to 10 degrees before the compression top dead center (BTDC 10 ° CA).

By the way, as described above, the fuel to be supplied to each cylinder 2 of the engine 1 in each combustion cycle is supplied to the intake port 10 in the cycle immediately before the cycle.
If the fuel is injected into a, the ignition switch of the vehicle is turned off immediately after the fuel injection, and the ECU 3
When the supply of the main electric power to 0 is stopped, the fuel already injected into the intake port 10a is discharged as unburned gas without being ignited, or the combustion chamber 6 of the cylinder 2 or the intake port 10a is discharged. It adheres to the wall surface and remains there. Therefore, at the next engine start, the engine 1
There was a problem that the residual fuel inside was discharged as unburned gas, and the exhaust condition temporarily deteriorated.

Explaining this problem in detail, for example, when the engine 1 is stopped from a warm idle operation state, fuel injection and ignition are uniformly terminated in response to an off operation of an ignition switch, At this time, the correlation between the change in the combustion state in one cylinder 2 and the change in the exhaust concentration of unburned HC from the cylinder 2 can be obtained by experiments or the like as shown in the graph in FIG.
That is, according to the figure, if the ignition switch is turned off immediately before ignition in the middle of a certain combustion cycle (t = t2), the air-fuel mixture is not ignited in this combustion cycle. Most of the fuel injected (t = t1) into the intake port 10a in the exhaust stroke of the previous combustion cycle is discharged without being ignited, and as a result, from the end timing (t = t3) of the exhaust stroke. The HC concentration in the exhaust gas is rapidly increasing.

Further, a part of the fuel injected into the intake port 10a in the "previous combustion cycle" adheres to the wall surface of the intake port 10a, and the next combustion cycle (the "certain combustion cycle" mentioned above). )), It is not sucked into the cylinder 2, but is sucked into the cylinder 2 in the next combustion cycle, and is similarly discharged as unburned gas. Therefore, the HC concentration in the exhaust gas increases again from the end timing (t = t4) of the exhaust stroke of the “next combustion cycle”. Most of the unburned gas thus discharged from the combustion chamber 6 in the cylinder 2 is purified by the catalytic converter 23 in the exhaust passage 20, but some unburned gas passes through the catalytic converter 23 and is discharged to the atmosphere. Will be released inside.

Further, when the engine 1 is stopped thereafter, a part of the fuel injected into the intake port 10a remains in the combustion chamber 6 in the cylinder 2 as described above, and the intake port 1
Since it remains attached to the wall surface of 0a, the fuel remaining in the intake port 10a and the like is discharged as unburned gas when the engine 1 is started next time. That is, FIG.
As shown in FIG. 3, when the engine is started, first, the starter is operated (t = t1) to rotate the crankshaft, and fuel is injected into the intake port 10a during the first cycle (motoring) (t = t2). ). This fuel is sucked into the cylinder 2 in the next combustion cycle to form a mixture and is ignited (t = t3),
The engine 1 starts rotating by itself.

At that time, during the period from the operation of the starter to the start of motoring (t = t1 to t2), the fuel remaining in the intake port 10a and the cylinder 2 is not burned as the crankshaft starts rotating. The gas is discharged from the cylinder 2 as gas, and the HC concentration in the exhaust gas sharply increases as shown in the figure. Moreover, immediately after the engine is started, the catalytic converter 2 in the exhaust passage 20 is generally used.
Since 3 is often not activated, most of the unburned gas discharged as described above will be released into the atmosphere as it is, and the exhaust condition will deteriorate significantly even for a short time. Become.

Such a problem becomes particularly remarkable in the multi-cylinder engine as in this embodiment. That is, for example, in the case of the 4-cycle in-line 4-cylinder engine as in this embodiment, as shown in FIGS. 2 and 3, the first to fourth four cylinders 2 are provided while the crankshaft makes two revolutions. , 2, ... Combust at equal intervals (180 ° CA) from each other, the ECU is operated even when only the trailing injection is performed as in the idle operation shown in FIG.
4 regardless of the timing of stopping the power supply to 30
This is because it causes a situation in which the injected fuel is not ignited in some of the two cylinders 2, 2, ....

In order to cope with such a problem, in the control device A of the engine 1 according to this embodiment, a feature of the present invention is that the fuel is injected by the injectors 16, 16, ... When the engine 1 is stopped. While the control is immediately ended, the ignition control is continued until at least two or more combustion cycles have passed for each cylinder 2, and then ended when the engine speed ne drops to the set speed. .

(Engine Stop Control) A specific procedure of fuel injection and ignition control by the ECU 30 when the engine 1 is stopped will be described in detail below with reference to the flowchart shown in FIG.

First, in step SA1 after the start of the flow shown in the figure, the output signals from various sensors are accepted and the data and flag values stored in the RAM are read. The RAM data is, for example, the engine speed calculated based on the signal from the crank angle sensor 26, or when the engine 1 is stopped, the injector 16 of each cylinder 2 injects fuel. The value of the fuel stop flag F _INJOFF , which indicates that the fuel injection control should not be performed (end of fuel injection control), is stored.

Then, at step SA2, whether or not the fuel stop flag F _INJOFF is on (F _INJOFF = 1?)
If the determination is Yes and the fuel injection control is completed, the process proceeds to step SA14 described later, while if the determination is No, the process proceeds to step SA3.

At Step SA3, it is judged whether or not the ignition switch of the vehicle is turned off (IG-SW is off?). If the judgment is Yes, engine stop control (step described later) for stopping the engine in operation (Step S3) is performed. S
On the other hand, if the determination is No, the normal operation control of the engine 1 is performed. That is, step S
In A4, the fuel injection pulse width is calculated according to the operating state of the engine 1, the fuel injection timing is similarly calculated in step SA5, and the ignition timing is calculated in step SA6.

Subsequently, the routine proceeds to step SA7, where it is judged whether or not the fuel injection timing has come for each cylinder 2, wait until the injection timing comes (No in the judgment), and if the injection timing comes (Yes in the judgment). In step SA8, the injector 16 causes the fuel injection operation. Then, the process proceeds to step SA9, it is determined whether the ignition timing has come for each cylinder 2, wait until the ignition timing comes (the determination is No), and if the ignition timing comes (the determination is Yes), the process proceeds to step SA10. Each cylinder 2
Each time, the spark plug 7 is energized to ignite the air-fuel mixture, and then the process returns.

On the other hand, in step SA11, which is determined that the ignition switch is turned off (Yes) in step SA3, the ISC control valve 1
9 to close the bypass passage 18 to close the engine 1
Make sure that the amount of intake air into the engine is less than that during idle operation. Subsequently, in step SA12, the fuel stop flag F _INJOFF is turned on (F _INJOFF ← 1), and thereafter, the fuel injection operation by the injector 16 is not performed, and in the subsequent step SA13, the ignition timing for each cylinder is set. Calculate Then, the process proceeds to steps SA9 and SA10 described above, ignition is executed for each cylinder 2 at the calculated ignition timing, and then the process returns.

That is, when the engine 1 is stopped, first, the ISC control valve 19 is closed to reduce the intake air amount to the cylinders 2, 2 ,.
The fuel injection control is terminated by stopping the new fuel supply to the intake port 10a, and in the subsequent combustion cycle, the fuel sucked into the cylinder 2 from the intake port 10a is ignited.

At this time, since the intake air amount is reduced by the control of the ISC control valve 19 as described above, even after the supply of new fuel is cut off, the lean dilution of the air-fuel mixture due to this is relatively caused. Even after the fuel injection control ends, the mixture can be ignited at least twice. Moreover, the ISC control valve 19 is closed and the intake air is throttled. As a result, the intake air flow velocity at the intake port 10a increases, so that the fuel adhering to the wall surface of the intake port 10a evaporates and enters the cylinder 2. Intake is promoted, which also suppresses the leaning of the air-fuel mixture in the cylinder 2 and increases the certainty of ignition.

Further, the ignition timing at that time is set to a more advanced side than usual so that the ignitability of the air-fuel mixture in the cylinder 2 is made as high as possible in response to the leaning of the air-fuel mixture. There is.

On the other hand, in step SA14, which has proceeded after determining in step SA2 that the fuel stop flag F _INJOFF is ON (Yes), the engine rotation speed ne is a preset ECU stop rotation speed ne * (set rotation speed). It is determined whether or not the following has occurred, and if the result of this determination is No, the control procedure of steps SA13, SA9, SA10 is executed, while the engine speed ne decreases and EC
If the U stop rotation speed is below ne * (determination result is Yes
s), the flow proceeds to step SA15 and the fuel stop flag F _IN
Turn off _JOFF (F _INJOFF = 0) and continue to step SA1
In 6, the ignition control for each cylinder 2 is terminated, and thereafter, the power supply to the ECU 30 is stopped.

That is, if the fuel stop flag F _INJOFF is on (F _INJOFF = 1), it is determined that the engine 1 is under stop control, and the ignition control for each cylinder 2 is continued. Then, the engine rotation speed ne gradually decreases and the ECU stop rotation speed
If ne * or less, the ignition control ends.

In the flow chart shown in FIG. 6, the intake air amount control means for controlling the ISC control valve 19 so that the intake air amount becomes smaller when the engine 1 is stopped than when the engine 1 is idle by the control procedure of step SA11. 30a
In addition, the control procedure of step SA12 constitutes fuel control means 30b that terminates the fuel injection control by the injector 16 when the engine 1 is stopped.

Further, according to the control procedure of step SA14, when the engine 1 is stopped, the engine rotation speed
A rotation speed determination unit 30c is configured to determine that ne is equal to or less than a preset ECU stop rotation speed ne *.

Further, the steps SA14 to SA13, SA9, SA10, or step SA1.
5, when the engine 1 is stopped by the control procedure of advancing to SA16, the ignition control means 30d is configured to execute the ignition control for each cylinder 2 for at least two cycles after the end of the fuel injection control. Control means 30
When the engine rotation speed ne becomes equal to or lower than the ECU stop rotation speed ne *, d ends the ignition control.

Therefore, according to the control device A for the spark ignition engine according to this embodiment, as shown in FIG. 7, when the engine 1 is in the warm idle operation state, the ignition switch of the vehicle is turned on. When it is turned off, the fuel injection control by the injector 16 is immediately ended in response to this (t = t2), and although not shown, the ISC control valve 19 is closed and intake air to the cylinders 2, 2 ,. Reduce the amount. Here, only the trailing injection is performed in the idle operation state, and if the ignition switch is turned off in the intake stroke of the cylinder 2 as shown in the figure, the injection (t) is performed to the intake port 10a in the exhaust stroke of the combustion cycle before that. = T0, t1) is sucked into the cylinder 2 to form an air-fuel mixture. Then, after the ignition (t = t3) is performed, the air-fuel mixture is burned.

Subsequently, in the subsequent combustion cycle, the fuel evaporated from the wall surface of the intake port 10a is transferred to the cylinder 2
Is inhaled into the mixture to form an air-fuel mixture, and ignition (t = t4, t
5) It is burnt. At that time, since the intake air is throttled by the control of the ISC control valve 19 as described above, the amount of air taken into the cylinder 2 is relatively small, while the flow velocity of the intake port 10a is high, so that the wall surface Of the fuel and the intake of the fuel into the cylinder 2 are promoted, whereby the air-fuel ratio of the air-fuel mixture in the cylinder 2 is maintained at a ignitable concentration for a while even after the fuel injection control is completed. Thus, ignition / combustion is continued at least twice.

In this way, in the engine 1 of this embodiment, the fuel that is once injected into the intake port 10a of the engine 1 is ignited for at least two cycles or more for each cylinder 2 even after the ignition switch is turned off. As a result, the HC concentration in the exhaust gas is not increased, unlike the conventional example shown in FIG. Then, when the combustion energy gradually decreases, the engine rotation speed ne gradually decreases, and when the engine stop rotation speed ne * is equal to or lower than a preset value, the ignition control is also terminated and the ECU
The main power supply to 30 is stopped.

That is, in this embodiment, when the engine 1 is stopped, irrespective of the timing when the ignition switch is turned off, most of the fuel injected once into the intake port 10a of each cylinder 2 is burned, It is possible to prevent the exhaust state from being deteriorated due to the discharge of unburned gas.

Further, after the engine 1 is stopped, the unburned fuel remaining in the intake port 10a and the cylinder 2 is almost eliminated. Therefore, as in the conventional example shown in FIG. 5, a large amount of unburned gas is discharged when the engine is started. As a result, deterioration of the exhaust state can be prevented even before the catalytic converter 23 is warmed up.

In FIG. 7, the HC concentration in the exhaust gas slightly increases after the ignition switch is turned off because the exhaust gas flow rate decreases as the crankshaft rotation speed decreases. Only the detected value required is increased, and it is considered that the HC concentration in the exhaust gas is substantially maintained at the same level as during idle operation.

Further, as described above, when the engine 1 is stopped in this embodiment, when the fuel control by the ECU 30 ends and then the engine rotation speed ne becomes equal to or lower than the preset ECU stop rotation speed ne *. To
The ignition control is ended, but not limited to this,
For example, based on the signal from the crank angle sensor 26, it is determined that the combustion cycle has passed a set number of times after the end of fuel control for each cylinder 2, and the ignition control is terminated when this determination is made. May be. In this way, the control procedure becomes extremely simple.

Specifically, the control procedure as shown in the flowchart of FIG. 8 may be used. That is, when the ignition switch is turned off during operation of the engine 1 (Yes in step SA3), the ISC control valve 19 is first closed (step S3), as in the above embodiment.
A11), and subsequently, the fuel stop flag F _INJOFF is turned on to end the fuel control (step SA12). Then, the number NIG of combustion cycles for each cylinder 2 thereafter is counted (step SA20: NIG = NIG + 1), ignition timing is calculated for each cylinder (step SA13), and ignition is executed at the ignition timing ( Steps SA9 and SA1
0), then return.

Then, after the fuel control is completed (Yes in step SA2), the number of combustion cycles NIG for each cylinder 2 is increased.
Until the preset number of times exceeds KIG (step SA
14, No), the steps SA20, SA13, SA
9. If the number of combustion cycles NIG exceeds the set number KIG by repeating the procedure of 9 and SA10 (Y at step SA14).
es), the fuel stop flag F _INJOFF is turned off (step _SA15 ), the _count value of the combustion cycle is cleared (step SA21: NIG = 0), and then the ignition control is also ended (step SA16).

In the flow shown in FIG. 8, when the engine 1 is stopped by the control procedure of step SA14, it is determined that the combustion cycle for each cylinder 2 has passed the set number of times KIG after the end of the fuel injection control. The number determination means 30e is configured. And step SA
As is clear from the procedure of 14, the ignition control means 30d
Is configured to terminate the ignition control when the determination is made by the cycle number determination means 30e.

(Second Embodiment) FIG. 9 shows a procedure of engine stop control by a control device according to a second embodiment of the present invention. In the second embodiment, the spark ignition engine 1 is stopped under a predetermined condition while the vehicle is stopped (so-called idle stop), and the engine stop control of the present invention is applied when the idle stop is performed. It is something that is done. Therefore, since the configuration of the engine 1 itself is the same as that of the first embodiment, the same members are designated by the same reference numerals and the description thereof will be omitted.

The specific procedure of the engine stop control of the second embodiment will be described with reference to the flowchart of FIG. 9. First, in step SB1 after the start, the flow of the first embodiment (see FIG. 6). Step S
Accepts output signals from various sensors, similar to A1, R
Read the values of data and flags from AM. Subsequently, in step SB2, it is determined whether or not the engine 1 is started from the idle stop (engine start command?). This is performed based on, for example, the traveling speed of the vehicle (vehicle speed) and the operating state of the brake, clutch, shift lever, etc., and the driver's intention to start is estimated to determine whether the engine has started. If the determination in step SB2 is No, the engine 1 has not started, and therefore the process proceeds to step SB11 described below. On the other hand, the determination is Yes
If s, the process proceeds to step SB3 and the fuel stop flag F
_Turn off _INJOFF (F _INJOFF = 0), step SB4 ~
The routine proceeds to SB10, where fuel and ignition control at the time of starting is executed.

Further, in step SB2, the process proceeds to step SB1 which is judged as No when the engine is not started.
In No. 1, it is determined whether the fuel stop flag F _INJOFF is turned on (F _INJOFF = 1?). If the result is Yes, it means that the engine 1 is in the idle stop control, so the process proceeds to step SB16, which will be described later. If No, the process proceeds to step SB12. In this step SB12, similarly to the above-described determination at the time of starting the engine, it is determined whether or not to idle stop based on the vehicle speed and the driving operation status (engine stop command?). Proceeding to steps SB4 to SB10, normal fuel and ignition control corresponding to the operating state of the engine 1 is performed.

On the other hand, when it is determined Yes in step SB12 that the engine is idling, the engine 1 is stopped. At this time, as in the first embodiment, first, the ISC control valve 19 is closed to close the cylinder 2, The amount of intake air to 2, ... is reduced (step SB13), and the fuel injection control by the injector 16 is ended (step SB13).
14) After that, ignition control is executed for each cylinder 2 (steps SB15, SB9, SB10), and then the process returns. That is, most of the fuel injected into the intake port 10a of the engine 1 is once burned by ending the fuel injection control for each cylinder 2 first and then continuing the ignition control for a while.

Then, in the subsequent control cycle,
In step SB11 of the flow, it is determined that the engine stop control is in progress (F _INJOFF = 1 and Yes), and step SB16
And the engine speed ne becomes E in this step.
Determine whether the CU stop rotation speed ne * or less,
If the determination result is No, the above-mentioned steps SB15 and SB
9. While the control procedure of 9 and SB10 is repeated, if the engine rotation speed ne decreases and becomes equal to or lower than the ECU stop rotation speed ne * (determination result is Yes), the ignition control ends and returns.

In the flow shown in FIG. 9, the intake amount control means 30a is controlled by the control procedure of step SB13, and the fuel control means 3 is controlled by the control procedure of step SB14.
0b is configured respectively. Also, step SB1
The rotation speed determination means 30c is configured by the control procedure of No. 6, and the steps SB16 to SB1 are further performed.
The ignition control means 30d is constituted by the control procedure for proceeding to 5, SB9, SB10 and so on.

Therefore, according to the control device A of the second embodiment, when the so-called idle stop is carried out in the spark ignition type engine 1, the fuel injection control is first terminated even at the idle stop, By continuing the ignition control for a while after that, it is possible to prevent the deterioration of the exhaust state due to the discharge of unburned gas at the time of idling stop, and also to suppress the intake port 10a of the engine 1 and the cylinder 2
Almost all unburned fuel remains inside. With this,
Even if the number of times the engine 1 is stopped or restarted dramatically increases due to the idling stop, the exhaust state does not deteriorate due to that.

Also in the second embodiment, when the engine 1 is stopped, the ignition control may be ended after the combustion cycle has reached the set number of times after the end of the fuel control for each cylinder 2. . That is, as shown in the flowchart of FIG.
The C control valve 19 is closed (step SB13), the fuel stop flag F _INJOFF is turned on to end the fuel control (step SB14), and the number NIG of combustion cycles for each cylinder 2 thereafter is counted (step SB21). . Then, until the number of combustion cycles NIG for each cylinder 2 after the fuel control ends exceeds the set number of times KIG (N in step SB16
o), the ignition control is continued (steps SB15, SB9,
SB10), if the combustion cycle number NIG exceeds the set number KIG (Yes in step SB16), the ignition control is ended and the process returns.

When the engine 1 is subsequently restarted (Yes in step SB2), the fuel stop flag F _{INJOFF is set.}
After turning off (step SB3), the count value of the combustion cycle may be cleared (step SB2).
0: NIG = 0).

In the flow shown in FIG. 10, the cycle number determination means 30e is executed by the control procedure of step SB16.
The ignition control means 30d is configured to terminate the ignition control when the determination by the cycle number determination means 30e is performed.

(Other Embodiments) The structure of the present invention is not limited to those of the first and second embodiments, and includes various other structures. That is, in each of the above-described embodiments, fuel is supplied by the injector 16 for each combustion cycle of each cylinder 2 in most operating conditions during engine temperature.
Although the injection is divided into two times, the reading and the trailing, it is needless to say that the injection form and the injection timing are not limited, and the fuel injection timing by the injector 16 is, in short, every combustion cycle of the cylinder 2. The fuel may be injected at a predetermined injection timing.

In the first embodiment, the control when the engine 1 is stopped by turning off the ignition switch of the vehicle is explained, and the second embodiment is also explained.
The idle stop control is described above. However, in addition to this, for example, in a hybrid vehicle, when the driving force of the vehicle is switched from the engine to the electric motor to temporarily stop the engine, A stop control procedure can be applied.

Further, in the first embodiment, the engine 1
When the engine rotation speed ne becomes equal to or lower than the ECU stop rotation speed ne * when the engine is stopped, the ignition control is finished. In the second embodiment, the combustion cycle is completed after the fuel control is finished for each cylinder 2. Although the ignition control is terminated when the set number of times has passed, the present invention is not limited to this. That is, although not shown, a sensor for detecting the air-fuel ratio state of the exhaust (for example, the concentration of a predetermined gas component in the exhaust such as the O ₂ concentration and the HC concentration) is provided in the exhaust passage 20, and based on the signal from this sensor. It is also possible to estimate the air-fuel ratio in the cylinder 2 of the engine 1 and terminate the ignition control when the estimated air-fuel ratio becomes leaner than a preset value. With this configuration, the unburned fuel can be reduced as much as possible by continuing the ignition until the air-fuel mixture in the cylinder 2 is diluted and reaches the so-called misfire limit.

Furthermore, in the above embodiment, the intake flow rate is adjusted by operating the ISC control valve 19 provided in the intake passage 10. However, the present invention is not limited to this, and the intake valve adjusting means may be a throttle valve. A so-called electric throttle valve in which 14 itself is actuated by an actuator, an on-off valve disposed downstream of the intake passage 10 to enhance intake flow in the cylinder 2, or the like may be used, or Alternatively, a variable valve mechanism that changes the lift amount or valve timing of the intake valve 9 may be used.

[0083]

As described above, according to the control device for a spark ignition type engine according to the invention of claim 1, the fuel injection valve for injecting fuel to the intake port of the engine is provided, and the control device is provided for each combustion cycle of the cylinder. In a spark ignition engine control device that injects fuel at a predetermined injection timing, when stopping the engine, after the fuel injection by the fuel injection valve is completed, the combustion cycle of the cylinder corresponding to the fuel injection valve is By performing the ignition control of the cylinder until at least two times have passed, it is possible to burn the fuel sucked into the cylinder from the intake port after the last fuel injection and suppress the discharge of unburned fuel. ,
Unburned fuel remaining after the engine is stopped can be reduced as much as possible, so that deterioration of the exhaust state at the time of engine start can be prevented.

According to the second aspect of the present invention, in the multi-cylinder engine in which the fuel just injected when the engine is stopped is likely to be released as it is, the number of cylinders is 2 for each cylinder after the end of the fuel injection control as in the first aspect of the present invention. It is particularly effective to ignite more than once.

According to the third aspect of the present invention, when the engine is stopped, the intake air amount is controlled to be smaller than that during the idle operation, so that the lean air-fuel mixture in the cylinder is maintained even after the fuel injection control is completed. The ignition can be delayed to prevent misfire, whereby the effect of the invention of claim 1 or 2 can be sufficiently obtained.

According to the fourth aspect of the present invention, when the engine is stopped, the unburned fuel can be sufficiently reduced by terminating the ignition control when the engine speed becomes equal to or lower than the set speed. Also, power consumption associated with ignition can be suppressed.

According to the fifth aspect of the present invention, when the engine is stopped, the ignition control is ended when the air-fuel ratio in the cylinder becomes leaner than the set value after the end of the fuel injection control. It is possible to suppress the power consumption due to ignition while continuing to ignite to the vicinity and reducing unburned fuel as much as possible.

According to the sixth aspect of the present invention, when the engine is stopped, the ignition control is terminated when the combustion cycle of the cylinders has passed the set number of times after the fuel injection control is terminated. While reducing unburned fuel, it is possible to suppress power consumption due to ignition.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram of an engine according to a first embodiment of the present invention.

FIG. 2 is an explanatory diagram schematically showing an example of fuel injection timing when the combustion order of each cylinder in a four-cylinder engine is used.

FIG. 3 is a diagram corresponding to FIG. 2 when the engine is in an idle operation state.

FIG. 4 shows how the combustion state of a cylinder and the HC concentration in exhaust change with the passage of time when fuel injection and ignition control are uniformly terminated as engine stop control. It is a time chart figure shown in contrast with each other.

FIG. 5 is a view corresponding to FIG. 4 when the engine is started.

FIG. 6 is a flowchart showing a procedure of fuel injection and ignition control when the engine is stopped.

FIG. 7 is a diagram corresponding to FIG. 4 when the ignition control is continued for a predetermined period after ending the fuel injection control as the engine stop control.

FIG. 8 is a view corresponding to FIG. 6 according to a modification of the first embodiment.

FIG. 9 is a view corresponding to FIG. 6 according to the second embodiment.

FIG. 10 is a view corresponding to FIG. 6 according to a modification of the second embodiment.

[Explanation of symbols]

1 engine Two cylinder 10a intake port 16 injectors (fuel injection valve) 19 ISC control valve (intake quantity control means) 30 ECU 30a Intake amount control means 30b Fuel control means 30c Rotational speed determination means 30d ignition control means 30e Cycle number determination means

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) F02D 41/04 310 F02D 41/04 310H 315 315 320 320 320 330 330H 43/00 301 43/00 301A 301H 301K 45 / 00 310 45/00 310G 310N 314 314Z 368 368G F02P 5/15 F02P 5/15 EF Term (reference) 3G022 CA10 GA05 3G065 CA12 EA06 GA00 GA10 GA43 3G084 BA05 BA06 BA13 BA16 BA23 CA07 DA10 FA02 FA01 EC01 FA03 FA03 FA29 FA33 FA38 3G092 AA01 AA11 AA17 BA01 BA08 BB10 CA01 CB04 CB05 DA01 DA03 DC01 DC04 EA17 EB04 EC01 FA18 FA26 GA10 HA01Z HA04Z HA06Z HD05Z HE01Z HE03Z HE08Z PEZ PA02 PA01 PA01 LA02 LA01 MA02 LA01 LA01 LA01 LA04 LA01 LA04 LA01 LA01 LA04 LA01 LA01 LA04

Claims (6)

[Claims] 1. A control device for a spark ignition engine, comprising a fuel injection valve for injecting fuel into an intake port of an engine, wherein the fuel injection valve is used to inject fuel at a predetermined injection timing for each combustion cycle of a cylinder. In the above, when the engine is stopped, the fuel control means for ending the fuel injection control by the fuel injection valve, and the cylinder of the cylinder corresponding to the fuel injection valve after the control of the fuel injection valve by the fuel control means are completed. A spark ignition engine control device, comprising: ignition control means for controlling ignition of the cylinder until at least two combustion cycles have elapsed. 2. The control of a spark ignition engine according to claim 1, wherein the engine has a plurality of cylinders, and a fuel injection valve is provided for each of the plurality of cylinders. apparatus. 3. The intake air amount adjusting means for adjusting the intake air amount to the engine according to claim 1, and the intake air amount to be smaller when the engine is stopped than when the engine is idling. A control device for a spark ignition engine, comprising: an intake air amount control means for controlling the intake air amount adjusting means. 4. The rotation speed determination means for determining that the engine rotation speed is equal to or lower than a set rotation speed according to any one of claims 1 to 3, and the ignition control means determines by the rotation speed determination means. A control device for a spark ignition engine, characterized in that the ignition control is terminated when the control is performed. 5. The sensor according to claim 1, wherein a sensor for detecting an air-fuel ratio state of the exhaust gas and a signal from the sensor make the air-fuel ratio in the cylinder leaner than a set value. Spark ignition, characterized in that the ignition control means is configured to terminate the ignition control when the determination by the air-fuel ratio determination means is made. Type engine control device. 6. The method according to claim 1, wherein after the control of the fuel injection valve by the fuel control means is completed,
A cycle number determination means for determining that the combustion cycle of the cylinder has passed a set number of times is provided, and the ignition control means is configured to end the ignition control when the determination by the cycle number determination means is performed. A control device for a spark ignition engine, which is characterized in that