JP2002054488A - Fuel control device for spark ignition type engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress deterioration in a combustion state caused by delay of suction in returning from a fuel cut state to idling, improve fuel consumption, and enhance operation feeling in a direct injection engine 1 having a catalyst 32 capable of purifying NOx in the exhaust, changing into a stratified charge combustion mode in low rotation and a low load and into a uniform combustion mode in high rotation or a high load, changing into a fuel cut state under the specified condition in deceleration operation, and in this state, compulsorily closing a throttle valve 22. SOLUTION: When a falling degree of an engine speed N is in a quick deceleration state larger than the previously set decision criterion or an air conditioner is set ON, the engine 1 is idling returned in a uniform combustion state. When it is in a gentle deceleration state and the air conditioner is set OFF, the engine 1 is idling returned in a stratified combustion state. When the temperature of the catalyst 32 is low, the decision criterion DN in the quick deceleration state is corrected to be small.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spark ignition type engine in which the combustion mode of an engine is selectively switched to a stratified combustion state or a uniform combustion state, and fuel cut control is performed under predetermined conditions during engine deceleration operation. The present invention relates to a fuel control device for an engine, and particularly to a technical field of fuel injection control when the fuel cut control is terminated and the operation returns to an idle operation state.

[0002]

2. Description of the Related Art Conventionally, as a fuel control system for a spark ignition type engine of this type, a fuel injection valve for directly injecting fuel into a combustion chamber in a cylinder of the engine is provided, and the fuel is stratified by the fuel injection valve. It is known to selectively switch between injection mainly in the middle stage of the compression stroke of the cylinder so as to achieve a state or injection mainly in the intake stroke of the cylinder so as to achieve a uniform combustion state. Since the amount of air required to obtain the same output greatly differs between the stratified combustion state and the uniform combustion state, a so-called electric throttle valve operated by an electric motor or the like is provided in the intake passage of the engine.

In general, when the accelerator pedal is largely released during high-speed running of the vehicle, a fuel cut control for temporarily stopping the fuel injection supply by the fuel injection valve is performed. This not only enhances the utility of the engine brake but also contributes significantly to improved fuel economy.

[0004] Incidentally, a catalyst for purifying the exhaust of an engine has an activation temperature determined by its composition and structure, and when the temperature is lower than the activation temperature, sufficient exhaust gas purification performance cannot be exhibited. Therefore, when the fuel cut control is performed, the throttle valve is normally closed to forcibly reduce the intake air amount in order to prevent the catalyst from being excessively cooled by low-temperature exhaust gas. This is also effective in increasing the effectiveness of engine braking.

However, if the throttle valve is closed during the execution of the fuel cut control, the fuel cut control is terminated due to a decrease in the engine speed, and the return to the idling state is required. Even if the throttle is opened at the time, the intake charging amount to the cylinder is temporarily insufficient due to the transportation delay in the intake system. As a result, stratification of the air-fuel mixture around the spark plug is hindered, and the air-fuel mixture becomes over-rich, which may significantly deteriorate the combustion state and eventually cause a misfire.

To solve such a problem, see, for example,
In the engine control device disclosed in JP-A-227241, when the fuel cut control is terminated during a deceleration operation of the engine or the like, the fuel is injected by the fuel injection valve in the intake stroke of the cylinder for a certain period of time to obtain a uniform combustion state. By doing so, the deterioration of the combustion state as described above is prevented.

[0007]

However, as in the conventional control device (Japanese Patent Laid-Open No. Hei 10-227241),
When the engine is uniformly set to the uniform combustion state when returning from the fuel cut state, the uniform combustion state may be selected in spite of the situation where the stratified combustion can be stably performed. It is not preferable in terms of efficiency. That is, for example, in a situation where the transmission of the vehicle is held at a relatively high gear position and the vehicle gradually decelerates while coasting, the degree of decrease in engine speed is small, Is not so large, and the flammability is hardly deteriorated at the time of idling return.

Further, since the rotational stability of the engine is high in the above-described slow deceleration state, misfire rarely occurs when the engine returns to the idle state.

Therefore, despite the slow deceleration state, the prior art in which the engine is intentionally brought into a uniform combustion state when returning to the idle state from the fuel cut is said to improve fuel efficiency. This leaves room for improvement from a viewpoint.

When the engine is returned to the idling operation state in the uniform combustion state as in the conventional example, the combustion state of the engine is switched from the uniform combustion state to the stratified combustion state after a lapse of a predetermined time. This means that in the idling operation state where the driver is likely to feel a shock, the combustion state is switched and torque fluctuation occurs even though the driver himself does not perform any driving operation. However, even if the vehicle is small, there is a risk that the driver may feel uncomfortable.

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and an object of the present invention is to forcibly reduce the intake air amount in order to prevent the catalyst from being excessively cooled during the execution of the fuel cut control. The fuel cut control is terminated and the procedure of restarting the fuel injection when returning to the idling state is devised so that the deterioration of the combustion state due to the delay of the intake can be suppressed, while the fuel consumption is reduced. It is intended to further improve the driving feeling.

[0012]

According to a first aspect of the present invention, when the engine returns from the fuel cut control to the idle operation state, the engine is in a sudden deceleration state. In order to avoid deterioration of combustion and occurrence of misfire, a uniform combustion state is set, while a stratified combustion state is set unless a sudden deceleration state occurs.

More specifically, according to the first aspect of the present invention, as shown in FIG. 1, a fuel injection valve 12 for directly injecting fuel into a combustion chamber 6 in a cylinder of the engine 1 is provided. An intake air amount adjusting means (an electric throttle valve in the illustrated example) 22 for adjusting the amount of intake air, a catalyst 32 for purifying exhaust gas from the combustion chamber 6, and a fuel injection mode by the fuel injection valve 12. An injection mode switching means 40a for selectively switching between a first injection mode in which a stratified combustion state is established and a second injection mode in which a uniform combustion state is established according to the operating state of the engine 1,
A fuel cut control means 40b for performing a fuel cut control for stopping fuel injection by the fuel injection valve 12 under predetermined conditions at least during engine deceleration operation; and when the fuel cut control is performed by the fuel cut control means 40b, It is assumed that the fuel control device A of the spark ignition type engine includes an intake air amount control unit 40c that controls the operation of the adjusting unit 22 so as to reduce the flow amount of the intake air. In addition, during the deceleration operation of the engine, there is provided a rapid deceleration state determination unit 40d for determining whether or not the degree of decrease in the engine rotation speed is greater than a predetermined determination criterion, and as the injection mode switching unit 40a, When the rapid deceleration state determination unit 40d determines that the vehicle is in the rapid deceleration state, the fuel injection control by the fuel cut control unit 40b ends, and the second injection mode is changed when the engine 1 enters the idle operation state. On the other hand, when it is not determined that the vehicle is in the rapid deceleration state, the first injection mode is selected.

With the above configuration, for example, in a situation where the transmission of the vehicle is held at the relatively high gear position and the vehicle gradually decelerates while coasting, the fuel cut control means 40b Fuel cut control is performed, and then when the engine speed drops,
After the fuel cut control ends, the state shifts to the idle operation state. In this case, since the rapid deceleration state determination unit 40d does not determine the rapid deceleration state, the first injection mode is selected by the injection mode switching unit 40a during the idle recovery. That is, in a slow deceleration state in which the delay of intake is relatively small and misfire rarely occurs, the engine 1 is brought into a stratified combustion state from the time of idling return. The fuel efficiency can be further improved, and the combustion state of the engine 1 does not change after returning from the idle state, so that the driving feel is improved.

On the other hand, for example, in a situation where the engine speed suddenly decreases, such as when the vehicle is suddenly stopped, the rapid deceleration state determining means 40d determines that the vehicle is in a rapid deceleration state. At the time of idling return, the second injection mode is selected by the injection mode switching means 40a, and the engine 1 is temporarily brought into a uniform combustion state. This allows
Even if the delay in charging the intake air is large when fuel injection is restarted, the combustion state is not significantly deteriorated, and misfire can be reliably prevented from occurring.

According to the second aspect of the present invention, the fuel cut control means terminates the fuel cut control when the engine rotation speed becomes equal to or lower than a predetermined return rotation speed due to the deceleration operation of the engine. Is that when the engine rotation speed is equal to or lower than the set rotation speed higher than the return rotation speed even during the execution of the fuel cut control by the fuel cut control means, the intake air amount is adjusted so that the flow amount of intake air increases. The means shall be operated and controlled.

Thus, when the fuel cut control ends and the engine returns to the idling operation state, the intake air amount is increased before the fuel injection is restarted by the fuel injection valve to reduce the delay in charging the intake air. can do.

According to a third aspect of the present invention, there is provided a catalyst low-temperature state judging means for judging that the catalyst is in a predetermined low-temperature state with low activity, and when the catalyst is judged to be in a low temperature state by the catalyst low-temperature state judging means. And a criterion correcting means for correcting the criterion for determining the degree of decrease of the engine rotational speed by the rapid deceleration state determining means so as to be relatively small as compared with when it is not so.

With this configuration, when the catalyst is in an inactive state or in a low temperature state in which it is likely to become inactive, the criterion for determining the degree of decrease in the engine rotational speed is corrected by the criterion correction means so as to be relatively small, and the fuel is reduced. When returning from the cut state, the engine often becomes in a uniform combustion state.
Thus, by setting the engine to a uniform combustion state in which the exhaust temperature is relatively high, the temperature of the catalyst in a low temperature state is promoted, and the exhaust purification performance of the catalyst can be enhanced.

According to a fourth aspect of the present invention, an external load determining means for determining that the external load of the engine is greater than a predetermined value, and a rapid deceleration state determination when the external load determining means makes a determination as compared with a non-determining state. And a criterion correcting means for correcting the criterion for determining the degree of decrease in the engine rotational speed by the means so as to be relatively small.

In this configuration, when the external load of the engine is greater than a predetermined value, the criterion for determining the degree of decrease in the engine speed is corrected by the criterion correction means so as to be relatively small, and the return from the fuel cut state is performed. Occasionally, the engine will be in a uniform combustion state. That is, in a state where the external load is large, the engine is returned to the idle state in a uniform combustion state in which relatively high output is easily obtained, so that the engine stall can be reliably prevented.

According to a fifth aspect of the present invention, the catalyst according to the second aspect of the present invention has a NOx absorbing material for absorbing NOx in exhaust gas in an oxygen-excess atmosphere, and the catalyst has a predetermined high-temperature state in which the purification performance is reduced. When the catalyst high-temperature state determining means determines that the catalyst is in the high-temperature state, the set rotational speed at which the intake air amount adjusting means operates is smaller than when it is not. A configuration is provided in which a set rotation speed correction means for correcting the rotation speed to be relatively high is provided.

In this configuration, when the catalyst is in a predetermined high temperature state, the set rotation speed at which the intake air amount adjusting means operates is corrected by the set rotation speed correction means to be relatively high, and the return from the fuel cut state is performed. Sometimes the amount of intake air is increased faster. This makes it possible to sufficiently increase the intake air amount before restarting the fuel injection by the fuel injection valve, appropriately cool the overheated catalyst by this intake air, and improve the exhaust gas purification performance of the catalyst. it can.

Next, according to a second solution of the present invention, when the engine returns from the fuel cut-off state and shifts to the idling operation state, the engine is brought into a uniform combustion state in a situation where the external load of the engine is large. If not, a stratified combustion state is set.

More specifically, according to the invention of claim 6, in the fuel control device for a spark ignition type engine having the same premise as that of the invention of claim 1, the external load of the engine is larger than a predetermined value. When the external load determining means determines that the external load is larger than a predetermined value as the injection mode switching means, the fuel cut control by the fuel cut control means ends. The second injection mode is selected when the engine is in the idling operation state, and the first injection mode is selected when it is not determined that the external load is large.

That is, in general, when the external load is larger than a predetermined value, the degree of decrease of the engine speed becomes large. Therefore, when the engine is returned to the idling state in the stratified combustion state, the delay of the intake air becomes large and the misfire occurs due to the deterioration of combustion. Is likely to occur. Moreover, if a misfire occurs when the external load is large, there is a possibility that engine stall will occur.
Therefore, according to the present invention, when the external load is larger than a predetermined value, the engine is returned to the idle state in the uniform combustion state. Deterioration and misfire can be prevented.

Next, a third solution of the present invention is to provide a catalyst having a NOx absorbing material for absorbing NOx in exhaust gas in an oxygen-excess atmosphere.
Paying attention to a decrease in purification performance, when the catalyst is in a high temperature state, the intake air amount is increased as soon as the engine returns to the idle state from the fuel cut state.

More specifically, according to the invention of claim 7, in the fuel control apparatus for a spark ignition type engine having the same premise as in the above-mentioned claims 1 and 6, the catalyst removes NOx in the exhaust gas in an oxygen-excess atmosphere. The fuel cut control means has a NOx absorbing material to be absorbed, and the fuel cut control means terminates the fuel cut control when the engine rotation speed falls below a predetermined return rotation speed with the deceleration operation of the engine. Even during execution of fuel cut control by the fuel cut control means, when the engine rotation speed is equal to or less than the set rotation speed higher than the return rotation speed,
The operation of the intake air amount adjusting means is controlled so that the flow amount of intake air increases. Then, the catalyst high-temperature state determining means for determining that the catalyst is in a predetermined high-temperature state in which the purification performance is reduced, and the catalyst high-temperature state determining means determine that the catalyst is in the high temperature state during the deceleration operation of the engine. At this time, a configuration is provided that includes a set rotation speed correction unit that corrects the set rotation speed to be relatively higher than when it is not.

With the above arrangement, for example, when the vehicle is decelerating, the fuel cut control is performed by the fuel cut control means under a predetermined condition, and the intake air control means is controlled by the intake air control means, so that the intake air into the cylinder is controlled. The amount is forcibly reduced. Then, when the engine speed drops,
First, the intake air amount control means is operated by the intake air amount control means to increase the amount of intake air. Subsequently, fuel injection is restarted by the fuel injection valve, and the engine returns to the idle operation state.

At this time, if the catalyst is in a predetermined high temperature state,
Since the set rotation speed at which the intake air amount adjusting means operates is corrected to be relatively high by the set rotation speed correction means, the intake air amount is increased more quickly when the engine returns to the idle state. Thus, it is possible to almost eliminate the delay in charging the intake air at the time of returning to the idle state. This makes it possible to always return the engine from the fuel cut state to the idling state in the stratified combustion state, thereby improving the fuel efficiency as a whole during running of the vehicle and improving the driving feel. In addition, by increasing the intake air amount in the fuel cut state, the overheated catalyst can be appropriately cooled, and the exhaust gas purification performance of the catalyst can be improved.

[0031]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS (Overall Configuration) FIG. 1 shows a fuel control device A for a spark ignition engine according to an embodiment of the present invention, and 1 is a multi-cylinder engine mounted on a vehicle. The engine 1 has a cylinder block 3 in which a plurality of cylinders 2, 2,... (Only one is shown) are provided in series, and a cylinder head 4 arranged on the cylinder block 3. A piston 5 is inserted into the cylinder 2 so as to be able to reciprocate up and down in the figure, and a combustion chamber 6 is defined in the cylinder 2 between the top surface of the piston 5 and the bottom surface of the cylinder head 4. On the other hand, a crankshaft 7 is rotatably supported in the cylinder block 3 below the piston 5, and the crankshaft 7 and the piston 5 are drivingly connected by a connecting rod. An electromagnetic crank angle sensor 8 for detecting the rotation angle of the crankshaft 7 is provided at one end of the crankshaft 7. The electromagnetic crank angle sensor 8 faces a water jacket in the cylinder block 3 and has a coolant temperature (engine coolant temperature). Is provided.

In the cylinder head 4 above the combustion chamber 6 for each of the cylinders 2, an ignition plug 11 connected to an ignition circuit 10 is mounted so as to face the upper part of the combustion chamber 6. An injector (fuel injection valve) 12 is attached to the section so as to directly inject and supply fuel. That is, although not shown in detail, the combustion chamber 6
Is a so-called pent-roof type combustion chamber having a roof-like shape in which two inclined surfaces of the ceiling are put on each other, and two intake and exhaust ports 13 and 14 are respectively opened on each inclined surface. Are arranged so as to open and close the respective open ends.

The injector 12 is disposed below the two intake ports 13 so as to be sandwiched between the two intake ports 13. The tip side injection hole of this injector 12 is 2
The fuel injection valve is configured to inject fuel into the combustion chamber 6 from the side, facing the periphery of the combustion chamber 6 in proximity to the head portions of the two intake valves 15. On the other hand, the injector 12 is connected to a high-pressure fuel pump 18 via a fuel supply passage 17 common to all cylinders, and the fuel is adjusted to an appropriate pressure state by the high-pressure fuel pump 18 and a high-pressure pressure regulator (not shown). While supplying the fuel to the injector 12. A fuel pressure sensor 19 for detecting the pressure state (fuel pressure) of the fuel inside the fuel supply passage 17 is provided.
Is provided.

When fuel is injected by the injector 12 after the middle stage of the compression stroke of the cylinder 2, the fuel spray is trapped in an oblong cavity 5 a formed on the top surface of the piston 5, and the ignition plug A layer of a relatively rich mixture is formed near 11. On the other hand, when fuel is injected by the injector 12 in the intake stroke of the cylinder 2,
The fuel spray diffuses into the combustion chamber 6 and is sufficiently mixed with the intake air to form a substantially uniform mixture in the combustion chamber 6 by the time of ignition.

As shown in FIG. 1, an intake passage 20 is connected to one side surface (left side surface in the figure) of the engine 1 so as to communicate with the intake port 13. This intake passage 20
Supplies hot air filtered by an air cleaner (not shown) to a combustion chamber 6 of the engine 1, and a hot wire for detecting an intake air amount taken into the engine 1 in order from an upstream side to a downstream side. An airflow sensor 21;
A throttle valve 22 (intake air amount adjusting means) composed of a butterfly valve for restricting the intake passage 20 and a surge tank 23 are provided. The throttle valve 22 is not mechanically connected to an accelerator pedal (not shown), but is of an electric type whose valve shaft is opened and closed by being rotated by an electric motor. Further, a throttle opening sensor 24 for detecting the opening of the throttle valve 22 and the throttle valve 2
An intake pressure sensor 25 for detecting a pressure state of intake air downstream of the intake air pressure sensor 2 is provided.

The intake passage 20 downstream of the surge tank 23 is formed as an independent passage branching for each cylinder 2. The downstream end of each independent passage is further branched into two, and the intake passage 20 is divided into two independent passages. The swirl control valve 26 is provided in one of the branches, which is in communication with the ports 8. When the swirl control valve 26 is closed,
Most of the intake air flows into the combustion chamber 6 only from the other branch passage, and a strong swirl is generated in the combustion chamber 6. On the other hand, when the swirl control valve 26 is opened, the intake air is sucked from both branch paths, so that the tumble component of the intake air becomes stronger and the swirl component becomes weaker.

A compressor 27 for an air conditioner of a vehicle is disposed on one side of the engine 1.
The input shaft of the compressor 27 is drivingly connected to the crankshaft 7 by a pulley (not shown) and a V-belt.
The input shaft of the compressor 27 is provided with an electromagnetic clutch which is switched on or off to transmit or cut off the input from the crankshaft 7.

On the other hand, an exhaust passage 2 for discharging burned gas from the combustion chamber 6 is provided on the other side of the engine 1 (the right side in the figure).
8 are connected. The upstream end of the exhaust passage 28
An exhaust manifold 29 branches off for each cylinder 2 and communicates with the exhaust port 14, and an O2 sensor 30 for detecting the oxygen concentration in the exhaust is provided at the gathering portion of the exhaust manifold 29. The O2 sensor 30 is for detecting the air-fuel ratio based on the oxygen concentration in the exhaust gas, and a so-called lambda O2 sensor whose output is inverted in a stepwise manner at the stoichiometric air-fuel ratio is used. An upstream end of an exhaust pipe 31 is connected to a collecting portion of the exhaust manifold 29, and a catalyst 32 for purifying exhaust gas is connected to a downstream end of the exhaust pipe 31.

The catalyst 32 absorbs NOx in an oxygen-excess atmosphere where the oxygen concentration in the exhaust gas is high (for example, 4% or more), and releases the absorbed NOx due to the decrease in the oxygen concentration and reduces and purifies the NOx. This type of catalyst exhibits high exhaust gas purification performance similar to that of a so-called three-way catalyst particularly in the vicinity of the stoichiometric air-fuel ratio. The catalyst 3
2 shows a temperature dependency as shown in an example in FIG. 2, and the temperature state of the catalyst 32 is about 250 to 40.
When the temperature is in the range of about 0 ° C., the NOx purification rate is sufficiently high. However, in a lower temperature state, the lower the temperature, the more rapidly the NOx purification rate decreases. On the other hand, when the temperature of the catalyst becomes 400 ° C. or higher, the NOx purification rate decreases as the temperature increases.

Further, on the upstream side of the exhaust pipe 31, a part of the exhaust gas flowing through the exhaust passage 28 is returned to the intake system.
The upstream end of the GR passage 33 is branched and connected. This EG
The downstream end of the R passage 33 is connected to the intake passage 20 between the throttle valve 22 and the surge tank 23, and an electric EGR valve 34 whose opening can be adjusted is disposed near the intake passage 20. The amount of exhaust gas recirculated by 33 is adjusted.

The operation of the ignition circuit 10, the injector 12, the motor of the throttle valve 22, the actuator of the swirl control valve 26, and the actuator of the EGR valve 34 are controlled by a control unit 40 (hereinafter referred to as ECU). . On the other hand, the ECU 40 includes at least the crank angle sensor 8, the water temperature sensor 9, the air flow sensor 21, and the throttle opening sensor 2.
4. Each output signal of the intake pressure sensor 25 and the O2 sensor 30 is input. In addition, the output signal of the accelerator opening sensor 35 for detecting the opening of the accelerator pedal and the intake signal (not shown) Intake temperature sensor that detects temperature,
Each output signal of an atmospheric pressure sensor or the like for detecting the atmospheric pressure is input.

(Outline of Control) The ECU 40 controls the fuel injection amount and the injection timing of the injector 12 and the throttle valve 22 as control parameters related to the engine output.
, The intake swirl intensity adjusted by the swirl control valve 26, the exhaust gas recirculation ratio adjusted by the EGR valve 34, etc., are controlled in accordance with the operating state of the engine 1, respectively. . Then, the fuel injection mode of the injector 12 is switched according to the operation state of the engine 1, and the engine 1 is operated in a different combustion state (combustion mode).

More specifically, as shown in FIG. 3 which shows an example of a control map in the warm operation region of the engine 1, a predetermined region (a) of low rotation and low load is a stratified combustion region. 4A, the fuel is collectively injected by the injector 12 after the middle stage of the compression stroke of the cylinder 2, that is, for example, during a crank angle period of BTDC 120 ° CA to BTDC 35 ° CA indicated by an arrow in the drawing. Thus, a stratified combustion mode is set in which combustion is performed in a stratified state in which the air-fuel mixture is unevenly distributed in the vicinity of the ignition plug 11. As shown by a virtual line in the drawing, a part of the fuel may be injected during the intake or compression stroke before the crank angle period.

On the other hand, the operating regions (b) and (c) shown in FIG. 3 are uniform combustion regions. As shown in FIGS. 4 (b) and 4 (c), the fuel is injected by the injector 12 during the intake stroke of the cylinder 2. Is injected and mixed sufficiently with the intake air to form a uniform air-fuel mixture in the combustion chamber 6, and the combustion mode is set to a uniform combustion mode. Further, when the engine 1 is in a no-load or minus-load state and the engine rotation speed N is equal to or higher than a predetermined rotation speed N3 at which the fuel cut control is started, for example, when the vehicle starts to decelerate, the engine rotation is then stopped. Until the speed N decreases and reaches the predetermined return rotation speed N1, that is, in the operation region (d) shown in FIG. 3, fuel cut control for temporarily stopping fuel injection by the injectors 12 of the cylinders 2 is performed. I have to.

The operation of the injector 12 is controlled by executing a control program electronically stored in the ROM of the ECU 40 by the CPU.
Is achieved. That is, as described above, the injector 12
The fuel injection mode is selectively switched between a stratified combustion mode (first injection mode) and a uniform combustion mode (second injection mode) according to the operating state of the engine 1. The injection mode switching means 40a is configured by software. Further, the fuel cut control means 40 is implemented in software by a control procedure of stopping the fuel injection by the injector 12 under predetermined conditions.
b.

Next, the control of the throttle valve 22 is as follows.
Basically, the throttle opening is adjusted based on the accelerator opening and the engine rotational speed N so as to obtain required torque characteristics. Specifically, in the stratified combustion mode, the pump of the engine 1 is adjusted. In order to reduce the loss, the throttle valve 22 is opened relatively large. At this time, the average air-fuel ratio of the combustion chamber 6 becomes extremely lean, for example, A / F = about 30 to 140. Further, in the region (b) of the uniform combustion mode, the throttle opening is controlled so that the air-fuel ratio of the air-fuel mixture in the combustion chamber 6 becomes substantially equal to the stoichiometric air-fuel ratio (A / F = 14.7). , Stoichio mode). Further, in the high load or high rotation side region (c) of the uniform combustion mode, the fuel injection amount is increased so that the air-fuel ratio becomes richer than the stoichiometric air-fuel ratio (for example, A / F = 13 to 14). Thus, a large output corresponding to a high load can be obtained (hereinafter, also referred to as an enrich mode). In addition, when the fuel cut control is performed, the throttle valve 22 is set to a substantially fully closed state so as to increase the utility of the engine brake and prevent the catalyst 32 from being overcooled.

The operation control of the throttle valve 33 as described above is also realized by executing a control program electronically stored in the ROM of the ECU 40 by the CPU. In accordance with the control procedure of closing the throttle valve 22 in response to the above, when the fuel cut control is performed, the intake air amount control means 40 controls the operation of the intake air amount adjusting means so as to reduce the flow amount of the intake air.
c is configured as software.

In the region indicated by hatching in FIG. 3, the EGR valve 34 is opened, and a part of the exhaust gas is recirculated to the intake passage 20 through the EGR passage 33. The maximum combustion temperature is appropriately reduced by the recirculation of exhaust gas, so that generation of NOx can be suppressed.
In addition, when the engine is cold, the engine 1 is made to be in a uniform combustion state in all of the operation regions (a), (b), and (c) in order to secure combustion stability.

(Fuel Control During Deceleration Operation) As described above, according to the control device A of this embodiment, the engine 1 is in the stratified combustion mode when the engine 1 is at low rotation and low load, and is uniform when the engine 1 is at high rotation or high load. While in the combustion mode,
Further, under predetermined conditions such as during deceleration operation, fuel cut control is performed. During the execution of the fuel cut control, the throttle valve 22 is set to a substantially fully closed state in order to prevent the catalyst 32 from being excessively cooled by low-temperature exhaust gas.

According to such a configuration, when the engine speed N decreases during the deceleration operation of the engine 1 and the engine 1 returns from the fuel cut state to the idle operation state,
The throttle valve 22 is opened so that a stratified combustion state is achieved, and fuel is injected by the injector 12 during the compression stroke of the cylinder 2. At this time, the intake passage 2
Due to the delay of the intake air transport at 0, the amount of intake air charged into each cylinder 2 may be temporarily insufficient. In this case, the air-fuel mixture cannot be appropriately stratified around the spark plug 10, As described above, the combustion state may be significantly deteriorated or a misfire may be caused.

To cope with such a problem, the fuel control apparatus A of this embodiment first sets the throttle position before the engine speed N reaches the return speed N1, that is, before the fuel injection by the injector 12 is restarted. By opening the valve 22, the delay in charging the intake air into each cylinder 2 is reduced,
Nevertheless, when there is a risk that the combustion state may deteriorate, for example, when the engine 1 is in a rapid deceleration state or when the compressor of the air conditioner is operating, the engine 1 is forcibly brought into a uniform combustion state at the time of idling return. I try to make it.

Hereinafter, the procedure of the fuel injection control mainly when the engine is decelerated will be specifically described with reference to the flowchart shown in FIG.

First, in step S1 after the start, various sensor signals such as the crank angle sensor 8, the water temperature sensor 9, the air flow sensor 21, and the accelerator opening sensor 35 are input, and various data are read from the memory of the ECU 40. Subsequently, in step S2, it is determined based on the accelerator opening and the engine speed N whether or not a predetermined condition for performing the fuel cut control is satisfied. That is, if the engine rotation speed N is equal to or higher than the start rotation speed N3 of the fuel cut control and the accelerator pedal is in the fully-closed deceleration state in which the accelerator pedal is fully closed (determination YES), the process proceeds to step S6, while if the determination is NO. Proceeding to step S3, the current operating region of the engine 1 is determined. If YES in the stratified combustion region (A), the process proceeds to step S4 to set the stratified combustion mode. Thereafter, the process returns. If NO in the uniform combustion region (B), the process proceeds to step S5 to proceed to the uniform combustion mode. And then return.

On the other hand, in step S6, where it is determined that the predetermined condition for performing the fuel cut control is YES, the process proceeds to step S6, it is determined whether the compressor 27 of the air conditioner is operating (the air conditioner is on). If the air conditioner is turned on and the answer is YES, step S described later
On the other hand, if the air conditioner is turned off and NO is determined, the process proceeds to step S7, and it is determined whether the catalyst 32 is in a predetermined low temperature state with low activity. That is, the catalyst temperature Tcat is estimated based on the engine water temperature and the operation history of the engine 1, and it is determined whether or not the estimated temperature Tcat is equal to or lower than a preset temperature (for example, 250 ° C.). If this determination is YES and the catalyst 32 is inactive or at a low temperature close to it, the process proceeds to step S8, while the determination is N
If the catalyst 32 has been sufficiently activated by O, the process proceeds to step S9.

In step S8, the engine speed reduction rate criterion DN (predetermined criterion) serving as a criterion for determining the rapid deceleration state of the engine 1 is set to a relatively small value DN1. In step S9, the decrease rate determination reference DN is set to a relatively large value DN2. That is, when the temperature state of the catalyst 32 is low, it is easy to determine that the engine 1 is in the rapid deceleration state. Then, in step S10 following both steps, the current engine rotational speed reduction rate ΔN
Is smaller than the decrease rate determination reference DN. If this determination is NO and it is determined that the engine rotational speed is in a rapid deceleration state in which the decrease rate ΔN is large, step S15 described later is performed.
On the other hand, if the determination is YES and the vehicle is in the slow deceleration state, the process proceeds to step S11.

Subsequently, in step S11, it is determined whether or not the engine speed N has decreased to become equal to or lower than the set speed N2. If N> N2 and the determination is NO, step S11 is executed.
Then, the program proceeds to step 12, where fuel cut control is performed, and the throttle valve 22 is forcibly set to a substantially fully closed state. That is, when the engine rotation speed N is sufficiently high (N> N3) during the deceleration operation of the engine 1 and the accelerator pedal is returned to be in a substantially fully closed state, the fuel injection by the injector 12 is temporarily stopped. The throttle valve 22 is forcibly closed in order to prevent wasteful consumption of fuel and to prevent the catalyst 32 from being excessively cooled by low-temperature exhaust at this time.

If the engine speed N drops below the set speed N2 (eg, 1200 rpm) (N ≦ N2), YES is determined in step S11 and the process proceeds to step S13. In step S13, the throttle valve 22 closed as described above is opened in preparation for the return of the engine 1 to the idling operation state, and the flow rate of the intake air in the intake passage 20 corresponds to the stratified combustion state during idling. The predetermined value α is set. Subsequently, in step S14, it is determined whether or not the engine rotation speed N has become equal to or lower than the return rotation speed N1 (for example, 900 rpm).
While N> N1, the process proceeds to step S12 to continue the fuel cut control. On the other hand, when N ≦ N1, the process proceeds to step S4, and the injector 12 restarts fuel injection after the middle stage of the compression stroke of each cylinder 2. Let it.

That is, the engine 1 is not in a sudden deceleration state,
In addition, if the air conditioner is off, when the engine speed N drops due to the deceleration operation, the throttle valve 22 is opened in advance before the fuel injection by the injector 12 is restarted,
The amount of intake air charged into each cylinder 2 is increased, and then the engine 1 is returned to the idling operation state in the stratified combustion state according to the control map (see FIG. 3).

On the other hand, in step S6, it is determined whether the air conditioner is turned on or in step S10.
If it is determined in step S15 that the vehicle is in a rapid deceleration state, it is first determined in step S15 whether the engine speed N has become equal to or lower than the set speed N2 as in step S11. Control and close the throttle valve 22 (step S1).
2). On the other hand, if the engine rotation speed N drops and becomes equal to or lower than the set rotation speed N2 (N ≦ N2), the process proceeds to step S16, in preparation for the return of the engine 1 to the idle operation state,
The throttle valve 22 is opened. At this time, the intake passage 2
The flow rate of the intake air at 0 is set to a predetermined value β smaller than the value α in the stratified combustion state so as to correspond to the uniform combustion state during idling.

Subsequently, in step S17, it is determined whether or not the engine rotation speed N has become equal to or lower than the return rotation speed N1, and while N> N1, the process proceeds to step S12.
While the fuel cut control is continued, if N ≦ N1, the routine proceeds to step S18, where the injector 12 restarts the fuel injection in the intake stroke of each cylinder 2. The counting of the timer is started simultaneously with the restart of the fuel injection, and after the counting of the timer is completed, the engine 1 is switched to the stratified combustion state.

That is, when the engine 1 is in a rapid deceleration state or when the air conditioner is on, when the fuel cut control is terminated and the fuel injection by the injector 12 is restarted, the engine 1 is forced to be in the uniform combustion mode. It returns to idle in the combustion state.

Steps S3 to S5, S18 of the above flow
Corresponds to an injection mode switching unit 40a for selectively switching the fuel injection mode by the injector 12, and the injection mode switching unit 40a is configured such that the external load of the engine 1 is larger than a predetermined value when the air conditioner is on, or When it is determined that the engine 1 is in the rapid deceleration state, the engine 1 is configured to select the idle return in the uniform combustion state.

Step S12 corresponds to the fuel cut control means 40b for executing the fuel cut control under a predetermined condition at the time of engine deceleration. Speed N1
The fuel cut control is terminated when the following occurs. Further, steps S11 → S13, S
The control procedure from S15 to S16 is such that when the engine speed N becomes equal to or lower than the set speed N2 which is higher than the return speed N1, the intake air amount is set such that the throttle valve 22 is opened so as to increase the flow rate of the intake air. It corresponds to the control by the control means 40c.

Further, step S10 of the above flow
Thus, during the deceleration operation of the engine 1, the rapid deceleration state determination is performed to determine whether or not the decrease rate ΔN (degree of decrease) of the engine rotation speed N is greater than a preset decrease rate determination reference DN (determination reference). Means 40d are configured. Step S7 constitutes a catalyst low-temperature state determination unit 40e that determines that the catalyst 32 is in a predetermined low-temperature state with low activity.
9, a determination criterion for correcting the decrease rate determination criterion DN to be relatively small when the catalyst 32 is determined to be in a low temperature state by the catalyst low temperature state determination means 40e as compared with when it is not. The correction means 40f is configured.

In addition, the external load determining means 40g for determining that the external load of the engine 1 is larger than a predetermined value is constituted by step S6 of the flow,
The external load determining means 40g is configured to determine that the external load is large when the compressor 27 for the air conditioner of the vehicle is operating.

(Operation and Effect) Next, the operation and effect of the above embodiment will be described.

FIG. 6 shows a change in the engine rotation speed N when the engine 1 returns from the fuel cut state to the idle operation state when the vehicle is decelerated, and the opening degree and the throttle valve 22 of the throttle valve 22 which are controlled correspondingly. The change in the flow rate of intake air is shown in comparison with each other.

First, when the driver largely releases the accelerator pedal while the vehicle is running and the vehicle is almost fully closed, the engine rotation speed N at this time becomes equal to the start rotation speed N3 of the fuel cut control.
If so, the fuel cut control for stopping the fuel injection by the injector 12 of each cylinder 2 is performed. At this time,
For example, if the vehicle transmission is held at a relatively high gear position, the vehicle is gradually decelerating while coasting, and the air conditioner is off, the broken line in FIG. , The engine speed N
Is gentle, and the decrease rate ΔN is smaller than the decrease rate determination reference DN. In this case, it is not determined that the vehicle is in the rapid deceleration state.

When the engine speed N reaches the set speed N2 (t = t3), the throttle valve 22 is opened, and the throttle valve 22 is relatively opened to correspond to a stratified combustion state. And the intake flow rate is set to α
become. Subsequently, the engine rotation speed N becomes the return rotation speed N
When it becomes 1 (t = t4), fuel is injected by the injector 12 after the middle stage of the compression stroke of each cylinder 2, and the engine 1 returns to the idle state in a favorable stratified combustion state.

On the other hand, for example, when the driver tries to stop the car suddenly by applying a sudden brake, the engine speed N suddenly decreases as shown by a solid line in the figure. At this time, since the decrease rate ΔN of the engine rotation speed is equal to or greater than the decrease rate determination reference DN, it is determined that the vehicle is in a rapid deceleration state. In this case, the engine rotation speed N is reduced to the set rotation speed N
2 (t = t1), is opened, and subsequently, when the engine rotation speed N reaches the return rotation speed N1 (t = t1).
t2) At the intake stroke of each cylinder 2 by the injector 12, fuel is injected, and the engine 1 returns to the idle state in a uniform combustion state. Also, when the air conditioner is turned on, the engine 1 returns to the idle state in the uniform combustion state as described above.

That is, in the rapid deceleration state, as shown in the figure, the time Δt (t2−t1) from when the throttle valve 22 is opened to when fuel injection is restarted is extremely short.
Even if the throttle valve 22 is opened in advance, the amount of intake air will be insufficient at the time of resuming fuel injection.
However, the amount of intake air required in the uniform combustion state is smaller than that in the stratified combustion state, and in the case of uniform combustion, even if the intake air is insufficient, the air-fuel ratio of the air-fuel mixture as a whole is the stoichiometric air-fuel ratio. However, the air-fuel ratio around the plug becomes over-rich as in the case of stratified charge combustion, and misfire does not occur.

Furthermore, the fact that the air-fuel ratio of the homogeneous air-fuel mixture is slightly richer than the stoichiometric air-fuel ratio means that the engine 1
Therefore, the engine stall can be reliably prevented even in a rapid deceleration state in which the degree of decrease of the engine speed N is large.

Therefore, according to the fuel control system A for the spark ignition engine according to this embodiment, when the engine 1 returns from the fuel cut state to the idle operation state during the deceleration operation, first, the engine speed N is reduced to the return rotation speed. Speed N
Since the throttle valve 22 was opened before the pressure became 1, that is, before the fuel injection was restarted by the injector 12,
It is possible to reduce the delay of charging the intake air into each cylinder 2 at the time of restarting the fuel injection. As a result, it is possible to improve the fuel economy as a whole during running of the vehicle by increasing the idling return in the stratified combustion state while suppressing the deterioration of the combustion state, and to cut off the combustion state of the engine 1 after the idling return. The driving feeling is also improved, since there is less switching.

Further, as described above, after the delay in charging the intake air at the time of returning from the idle state is reduced, the combustion state may still be deteriorated, that is, when the engine 1 is suddenly decelerated or the air conditioner is turned on. In a situation where the external load is particularly large, for example, the engine 1 is forcibly returned to the idle state in the uniform combustion state, whereby it is possible to reliably prevent the combustion from deteriorating to misfire, and also to prevent engine stall.

At this time, especially when the temperature of the catalyst 32 is low and the catalyst 32 is in an inactive state or close to the inactive state, the criterion DN for decreasing the engine speed N is corrected to a relatively small value. Since the determination that the engine 1 is in the sudden deceleration state is made easy to be performed, in this case, the engine 1 is more likely to be in the uniform combustion state at the time of the return from the idle state. Catalyst 3
2 can be promoted to enhance the exhaust gas purifying performance of the catalyst 32.

(Other Embodiments) The present invention is not limited to the above-described embodiment, but includes other various embodiments. That is, in the embodiment,
In steps S7 to S9 of the flow of FIG.
Is corrected when the temperature of the engine is low, but the invention is not limited to this. The content of step S6 of the flow is applied to step S7, and for example, the engine 1 is turned on, such as turning on the air conditioner. When the external load is larger than a predetermined value, the reduction rate determination reference DN may be corrected so as to be relatively small.

With this arrangement, when the external load of the engine 1 is large, the engine 1 often returns to the idle state in the uniform combustion state. In this uniform combustion state, it is easier to obtain a high output than in the stratified combustion state. In addition, even if the external load is large, the occurrence of engine stall can be reliably prevented.

Further, as shown in FIG. 2, the exhaust gas purifying catalyst 32 in the above-described embodiment has a characteristic that the purifying performance is lowered even when the temperature becomes too high. The estimated temperature of the catalyst 32 is, for example, 400
In a high temperature state of not less than ° C, the throttle valve 22 may be opened earlier at the time of idling return. That is, as shown in an example in the flow of FIG. 7, it is determined whether or not the estimated temperature Tcat of the catalyst 32 is equal to or higher than a set temperature (for example, 400 ° C.) in step S7 ′. If the temperature is lower than the predetermined high temperature, the process proceeds to step S8 ', and the set rotation speed N2 is corrected to a relatively high value N2'.

In this case, the throttle valve 22 is opened earlier when the engine 1 returns to the idle state, the intake air amount is increased, and the overheating of the catalyst 32 is suppressed by the intake air.
Its purification performance can be enhanced. In addition, since the delay in charging the intake air can be almost eliminated, the frequency of the idling return in the stratified combustion state is increased as much as possible to further improve the fuel efficiency.
This can be improved, and if there is no delay in charging the intake air, the controllability of the air-fuel ratio improves, so that the exhaust harmful components can be further reduced.

Steps S1-S of the flow shown in FIG.
6 and the control procedures in steps S10 to S18 are the same as those in the above embodiment. Further, according to the control procedure of step S7 ′, the catalyst high-temperature state determining unit 40h that determines that the catalyst 32 is in the predetermined high-temperature state in which the purification performance decreases.
Is formed, and the catalyst 3 is obtained by the control procedure of step S8 ′.
A set rotation speed correction means 40i for correcting the set rotation speed N2 for opening the throttle valve 22 to be relatively higher than when it is not in a high temperature state is provided.

Further, as described above, if the timing for opening the throttle valve 22 is advanced when the catalyst 32 is in a high temperature state, a rapid deceleration state or the like is determined as in the above-described embodiment. It is not always necessary to switch the fuel injection mode at the time of idling return based on the result. At the time of idling return from the fuel cut state, the engine 1 may be set to the stratified combustion state at any time.

That is, as shown in an example in the flow of FIG. 8, the estimated temperature Tcat of the catalyst 32 is determined in step S20.
Is higher than or equal to a set temperature (for example, 400 ° C.). If the determination is YES and the catalyst 32 is at a predetermined high temperature where the purification performance is reduced, the process proceeds to step S21.
The set rotation speed N2 is corrected to a relatively high value N2 '. Then, in each of steps S22 to S25, a control procedure similar to that of steps S11 to S14 of the above embodiment is executed.

In this way, as shown in an example in FIG. 9, when the engine 1 returns to the idle state from the fuel cut state, the set rotation speed N2 for opening the throttle valve 22 is corrected to be relatively high. (N2 → N2 ′), the timing of opening the throttle valve 22 becomes earlier (t1 → t2), and when fuel injection by the injector 12 is restarted (t3), the intake charge delay is eliminated.
A good stratified combustion state results. As a result, fuel consumption can be further improved as a whole during driving of the vehicle, and the driving feel can be improved. Moreover, since the temperature of the catalyst 32 is high,
Even if the throttle valve 22 is opened in the fuel cut state, there is no fear of overcooling, but rather, the overheating of the catalyst 32 can be suppressed and the purification performance can be improved.

Incidentally, step S1 of the flow shown in FIG.
The control procedure of steps S5 to S5 is the same as that of the above embodiment. Step S20 is the catalyst high temperature state determination means 40.
h, and step S21 is the set rotation speed correction means 4
0i.

[0085]

As described above, according to the fuel control system for a spark ignition type engine according to the first aspect of the present invention, the amount of intake air is forcibly reduced in order to prevent the catalyst from being excessively cooled in the fuel cut state. On the other hand, when the engine returns to the idle state, the engine 1 is temporarily brought into a uniform combustion state if it is suddenly decelerated when the engine is returned to the idling state, thereby preventing deterioration of the combustion state and misfiring. By setting the engine in a stratified combustion state, it is possible to achieve an improvement in overall fuel efficiency and an improvement in operation feeling during idling operation.

According to the second aspect of the present invention, the delay in charging the intake air can be reduced by increasing the amount of intake air before restarting fuel injection when the engine returns to idle.

According to the third aspect of the present invention, when the catalyst is in a low-temperature state with low activity, the engine is more likely to return to an idle state in a uniform combustion state, and the catalyst is promoted to increase in temperature.
Exhaust gas purification performance can be improved.

According to the fourth aspect of the invention, when the external load of the engine is large, the chances of the engine returning to the idle state in the uniform combustion state are increased, and the engine stall can be reliably prevented.

According to the fifth aspect of the present invention, attention is paid to the fact that the purification performance of the catalyst having the NOx absorbent deteriorates at a high temperature, and the amount of intake air is increased earlier when the catalyst is at a high temperature. By appropriately cooling the overheated catalyst, the exhaust gas purification performance can be improved.

According to the fuel control apparatus for a spark ignition engine according to the present invention, when the engine returns from the fuel cut state and shifts to the idle operation state,
In the situation where the external load of the engine is large, the engine is set to the uniform combustion state. Otherwise, the engine is set to the stratified combustion state. Therefore, even if the external load is large, the misfire and engine stall can be prevented. It is possible to improve the driving feel during idling operation.

Further, according to the fuel control apparatus for a spark ignition type engine according to the present invention, it is noted that the catalyst having the NOx absorbent has a low purification performance at a predetermined high temperature, and In this case, the intake air amount is increased earlier so that the intake charge delay when the engine returns from the fuel cut state to the idle state is almost eliminated, and the idle return can always be performed in the good stratified combustion state. it can. In addition, by increasing the intake air amount in the fuel cut state, the overheated catalyst can be appropriately cooled, and its purification performance can be improved.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of a fuel control device for a spark ignition engine according to an embodiment of the present invention.

FIG. 2 is a diagram showing a change characteristic of a NOx purification rate with respect to a change in a temperature state of a catalyst.

FIG. 3 is a diagram showing an example of a control map in which a stratified combustion region, a uniform combustion region, and a region for performing fuel cut control of an engine are set.

FIG. 4 is a view schematically showing a fuel injection mode of an engine.

FIG. 5 is a flowchart mainly showing a procedure of fuel injection control during engine deceleration operation.

FIG. 6 is a time chart showing changes in engine speed, throttle valve opening, and intake air flow rate when the vehicle is decelerated, in comparison with each other.

7 is a diagram corresponding to FIG. 5 according to another embodiment in which the opening operation of the throttle valve is hastened when the temperature of the catalyst is high.

FIG. 8 is a diagram corresponding to FIG. 5 according to another embodiment in which the opening operation of the throttle valve is advanced when the temperature of the catalyst is high, and the determination of the rapid deceleration state is not performed.

FIG. 9 is a diagram corresponding to FIG. 6, according to another embodiment shown in FIG. 8;

[Explanation of symbols]

 A fuel control device for a spark ignition type engine 1 engine 2 cylinder 6 combustion chamber 12 injector (fuel injection valve) 22 throttle valve (intake amount adjustment means) 32 catalyst 40 control unit (ECU) 40a injection mode switching means 40b fuel cut control means 40c intake air amount control means 40d rapid deceleration state determination means 40e catalyst low temperature state determination means 40f determination reference correction means 40g external load determination means 40h catalyst high temperature state determination means 40i set rotation speed correction means

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (reference) F02D 41/12 335 F02D 41/12 335 45/00 312 45/00 312R 312L F term (reference) 3G065 AA04 AA06 AA07 CA12 CA13 DA05 DA06 DA15 EA03 EA05 GA00 GA01 GA05 GA09 GA10 GA26 GA27 GA37 GA46 HA21 HA22 JA04 JA09 JA11 KA02 3G084 BA05 BA13 BA15 CA03 CA06 DA02 DA05 DA15 EA11 EB12 FA00 FA01 FA02 FA08 FA10 FA11 FA20 FA29 FA33 FA38 FA38 JA12 KA18 KA26 LA00 LA03 MA11 MA18 MA24 MA25 ND02 ND03 NE20 PA04Z PA07Z PA09Z PA10Z PA11Z PB08Z PD02Z PD12Z PE01Z PE03Z PE08Z PF03Z

Claims (7)

[Claims] A fuel is directly injected into a combustion chamber in a cylinder of an engine.
A fuel injection valve for injecting and supplying, an intake air amount adjusting means for adjusting a flow amount of intake air to the combustion chamber, a catalyst for purifying exhaust gas from the combustion chamber, and a fuel injection mode by the fuel injection valve. An injection mode switching means for selectively switching between a first injection mode in which a stratified combustion state is established and a second injection mode in which a uniform combustion mode is established according to an operating state of the engine; Fuel cut control means for performing fuel cut control for stopping fuel injection by a fuel injection valve; and when the fuel cut control means performs fuel cut control, operating the intake air amount adjusting means so as to reduce the flow rate of intake air. In a fuel control device for a spark ignition type engine having an intake air amount control means for controlling, a degree of decrease of an engine rotation speed is set in advance during an engine deceleration operation. A rapid deceleration state determining unit that determines whether or not the vehicle is in a rapid deceleration state greater than a fixed reference; wherein the injection mode switching unit determines that the vehicle is in a rapid deceleration state by the rapid deceleration state determination unit. The second injection mode is selected when the fuel cut control unit terminates the fuel cut control and the engine enters an idling operation state, and the first injection mode is selected when the rapid deceleration state is not determined. A fuel control device for a spark ignition engine. 2. The fuel cut control device according to claim 1, wherein the fuel cut control means is configured to execute the fuel cut control when the engine rotational speed falls below a predetermined return rotational speed due to the deceleration operation of the engine.
The fuel cut control is ended, and the intake air amount control means determines that the engine rotation speed has become equal to or lower than the set rotation speed higher than the return rotation speed even while the fuel cut control is being performed by the fuel cut control means. A fuel control device for a spark ignition engine, wherein the operation amount of the intake air amount adjusting means is controlled so that the flow amount of the intake air sometimes increases. 3. The catalyst according to claim 1, wherein the catalyst is in a predetermined low temperature state with low activity, and the catalyst low state determination means determines that the catalyst is in a low temperature state. And a criterion correcting means for correcting the criterion for determining the degree of decrease of the engine rotational speed by the rapid deceleration state determining means to be relatively small as compared with when it is not so. Fuel control system for traction engines. 4. An external load determining means for determining that an external load of an engine is greater than a predetermined value, and a sudden deceleration state determination when the external load determining means makes a determination as compared with a non-determining state. And a criterion correction means for correcting the criterion for determining the degree of decrease in the engine rotation speed by the means to be relatively small. 5. The catalyst according to claim 2, wherein the catalyst absorbs NOx in exhaust gas in an oxygen-excess atmosphere.
A catalyst high-temperature state determining unit that has an Ox absorbent and determines that the catalyst is in a predetermined high-temperature state in which purification performance is reduced; and when the catalyst is determined to be in a high-temperature state by the catalyst high-temperature state determining unit. And a set rotation speed correction means for correcting the set rotation speed at which the intake air amount adjustment means operates so as to be relatively high as compared with a case other than the above case. Control device. 6. The fuel is directly supplied to an in-cylinder combustion chamber of an engine.
A fuel injection valve for injecting and supplying, an intake air amount adjusting means for adjusting a flow amount of intake air to the combustion chamber, a catalyst for purifying exhaust gas from the combustion chamber, and a fuel injection mode by the fuel injection valve. An injection mode switching means for selectively switching between a first injection mode in which a stratified combustion state is established and a second injection mode in which a uniform combustion mode is established according to an operating state of the engine; Fuel cut control means for performing fuel cut control for stopping fuel injection by a fuel injection valve; and when the fuel cut control means performs fuel cut control, operating the intake air amount adjusting means so as to reduce the flow rate of intake air. In the fuel control system for a spark ignition type engine provided with an intake air amount control means for controlling, it is determined that an external load of the engine is in a state larger than a predetermined value. When the external load determining unit determines that the external load is large, the injection mode switching unit terminates fuel cut control by the fuel cut control unit and sets the engine to an idle operation state. A fuel control apparatus for a spark ignition engine, wherein the first injection mode is selected when the external load is not determined to be large while the second injection mode is selected. 7. Fuel is directly supplied to a combustion chamber in a cylinder of an engine.
A fuel injection valve for injecting and supplying, an intake air amount adjusting means for adjusting a flow amount of intake air to the combustion chamber, a catalyst for purifying exhaust gas from the combustion chamber, and a fuel injection mode by the fuel injection valve. An injection mode switching means for selectively switching between a first injection mode in which a stratified combustion state is established and a second injection mode in which a uniform combustion state is established according to an operation state of the engine; Fuel cut control means for performing fuel cut control for stopping fuel injection by a fuel injection valve; and when fuel cut control is performed by the fuel cut control means, the intake air amount adjusting means is operated so as to reduce the flow rate of intake air. A fuel control device for a spark ignition type engine, comprising: an intake air amount control means for controlling the amount of intake air; The fuel cut control means terminates the fuel cut control when the engine rotation speed becomes equal to or lower than a predetermined return rotation speed due to the deceleration operation of the engine. Even during execution of fuel cut control by the fuel cut control means, when the engine rotation speed becomes equal to or lower than the set rotation speed higher than the return rotation speed, the intake air amount adjustment means is configured to increase the flow amount of intake air. Operation control, the catalyst high-temperature state determining means for determining that the catalyst is in a predetermined high-temperature state in which the purification performance is reduced, and the catalyst high-temperature state determining means during the deceleration operation of the engine. Setting rotation speed correction means for correcting the set rotation speed to be relatively high when it is determined that there is, compared to when it is not. Fuel control apparatus for a spark ignition engine, wherein the door.