JP2007100616A - Fuel injection control device of in-cylinder injection type internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To early increase temperature of an exhaust purifying catalyst while increasing fuel economy in a fuel injection control device of an in-cylinder injection type internal combustion engine allowing injection of fuel in the compression stroke. <P>SOLUTION: This fuel injection control device comprises a control means 11 performing a compression stroke injection mode for jetting a fuel in the compression stroke of the internal combustion engine when first predetermined operating conditions are established and a catalyst temperature rising control means 20 performing the temperature rising control of the exhaust purifying catalyst when second predetermined operating conditions are established during the start of the internal combustion engine. The compression stroke injection mode comprises a first fuel injection mode in which a stable combustion area is more increased as an air-fuel ratio becomes leaner and a second fuel injection mode in which the stable combustion area is more increased as the air-fuel ratio becomes richer. The controls means 11 sets the fuel injection mode to the second fuel injection mode when the second predetermined conditions are determined to be established even if the first predetermined operating conditions are not established. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a fuel injection control device for a direct injection internal combustion engine capable of executing fuel injection during a compression stroke.

2. Description of the Related Art Conventionally, an in-cylinder injection type gasoline engine that directly injects fuel into a cylinder (inside a cylinder) has been put into practical use. Generally, in such a cylinder injection type gasoline engine, a compression stroke injection mode in which fuel is injected in a compression stroke and an intake stroke injection mode in which fuel is injected in an intake stroke are set to be switchable.
Among these, the compression stroke injection mode (compression lean injection mode) is a mode in which fuel is injected while the piston is rising, and fuel is injected toward the spark plug when the piston is near the top dead center of the compression stroke. In this mode, the fuel is directly ignited (spray guide injection mode), and the fuel is injected before the top dead center of the compression stroke. What has (wall guide injection mode) is known.

  The wall guide injection mode is an injection mode that realizes stable combustion at an ultra-lean air fuel ratio by stratified combustion using a stratified intake flow formed in a cylinder. In this injection mode, the combustion spray injected toward the piston is collected by the rise of the piston, and a relatively rich air-fuel mixture is formed in the vicinity of the tip of the spark plug, and a substantially air-only layer is formed around the air-fuel mixture. Is formed. Therefore, as a whole, good combustion can be realized while the air-fuel ratio is extremely lean (for example, A / F 20 to 25), and operation can be performed while saving fuel consumption.

Further, in the spray guide injection mode, the fuel is directly injected toward the spark plug to form a layered lean state in the combustion chamber, and the air / fuel ratio is much leaner than that in the wall guide injection mode described above. A stable combustion state can be obtained at (for example, A / F 25-40).
On the other hand, in the intake stroke injection mode, the fuel is premixed and the air-fuel ratio state of the entire combustion chamber is made uniform, and operation is performed so that stable ignition and reliable flame propagation can be realized and sufficient high output can be obtained. Can do. In the intake stroke injection mode, the stoichiometric mode in which a large output is obtained with the air-fuel ratio in the vicinity of the stoichiometric air-fuel ratio (stoichio), and the air-fuel ratio is made leaner (for example, A / F 15 to 20) than the stoichiometric. There are provided a lean mode for improving the fuel consumption, an enrich mode for temporarily enriching the air-fuel ratio more than that of stoichiometric during sudden acceleration or the like.

  In such an in-cylinder injection engine, the compression stroke injection mode (compression lean mode), the intake stroke injection stoichiometric mode (stoichio mode), the intake stroke injection lean mode (intake) based on the engine speed and the engine load. Each operation mode such as a lean mode and an intake stroke injection rich mode (enrich mode) is switched. For example, during low load operation such as during idle operation, fuel consumption can be reduced by performing fuel injection in the spray guide injection mode.

In Patent Document 1 below, as a compression stroke injection mode, a first operation mode for igniting fuel before colliding with a piston during fuel injection or immediately after fuel injection, and fuel via a piston after completion of fuel injection are disclosed. And a second operation mode for igniting the engine, and a technique for switching these operation modes in accordance with the engine operation state is disclosed.
JP 2004-353594 A

In general, when the engine load increases during idling, the air-fuel ratio A / F is enriched to suppress a decrease in engine speed. However, when the fuel injection mode is the spray guide injection mode, the air-fuel ratio A / F is decreased. If enriched, combustion stability may be deteriorated.
Here, FIG. 7 is a diagram showing combustion characteristics in the spray guide injection mode, in which the horizontal axis represents the fuel injection timing and the vertical axis represents the ignition timing. As shown in the figure, in this operation mode, the smaller the A / F (that is, the richer), the smaller the area indicating the combustion stable region and the lower the combustion stability. Therefore, when the air-fuel ratio is enriched when the load is increased as described above, misfire is caused and engine speed fluctuates and the engine may stall due to misfire.

  In particular, at the time of engine cold start, the oil temperature of the lubricating oil and the oil temperature of the automatic transmission (especially torque converter) hydraulic oil (ATF) are low, so the viscous resistance is large, and the load is high even in the neutral range. For this reason, since it is conceivable that the output torque is insufficient in the compression stroke injection, if it is determined that the engine is cold start, the compression stroke injection is prohibited and the intake stroke injection is executed.

Incidentally, an exhaust purification catalyst is provided in the exhaust passage of the engine. The exhaust purification catalyst is activated at a predetermined temperature (for example, 350 ° C.) or higher, but it is considered that the exhaust purification catalyst is lowered to the activation temperature or lower when the engine is started in the cold state, and the exhaust gas purification function is lowered.
Therefore, it is necessary to quickly raise the temperature of the exhaust purification catalyst to the activation temperature. However, if fuel injection is executed by intake stroke injection at this time, the A / F is set to be relatively rich, so that it remains in the exhaust. Therefore, there is a problem that even if the additional fuel injection is performed to raise the catalyst temperature, the additional fuel is not completely burned, and the temperature of the exhaust purification catalyst is not raised quickly. . Further, in this case, since the intake stroke injection is executed, there is a problem that fuel efficiency is not good.

  The present invention has been devised in view of the above problems, and provides a fuel injection control device for a direct injection internal combustion engine that is intended to raise the temperature of an exhaust purification catalyst early while improving fuel efficiency. The purpose is to provide.

  A fuel injection control device for a cylinder injection type internal combustion engine according to the present invention is a fuel injection control device for a cylinder injection type internal combustion engine in which fuel is directly injected into a cylinder and ignited by a spark plug. As a compression stroke injection mode for injecting the fuel during the stroke, a first fuel injection mode in which the combustion stable region expands as the air-fuel ratio becomes lean, and a second fuel injection mode in which the combustion stable region expands as the air-fuel ratio becomes richer And a catalyst temperature increase control means for performing temperature increase control of the exhaust purification catalyst when a predetermined operating condition is satisfied at the time of starting the internal combustion engine, the control means includes the first predetermined operating condition. When it is determined that is established, the fuel injection mode is set to the second fuel injection mode (claim 1).

  A fuel injection control device for a cylinder injection type internal combustion engine according to the present invention is a fuel injection control device for a cylinder injection type internal combustion engine in which fuel is directly injected into a cylinder and ignited by an ignition plug. As a compression stroke injection mode for injecting the fuel during the compression stroke, a fuel is injected toward the fuel plug in the vicinity of the top dead center of the compression stroke, and a first fuel injection mode for directly igniting the fuel, Control means for injecting fuel at a timing earlier than the fuel injection timing in the first fuel injection mode, and switching between the second fuel injection mode in which the fuel is collected in the vicinity of the spark plug and ignited by raising the piston; When a predetermined operating condition is satisfied at the time of starting the internal combustion engine, a catalyst temperature increasing control means for executing a temperature raising control of the exhaust purification catalyst is provided, and the control means has the first predetermined operating condition. When There is determined that satisfied, is characterized by setting the fuel injection mode to the fuel injection mode of the second (claim 2).

The predetermined operating condition is within a predetermined time from the cold start of the internal combustion engine, the cooling water temperature of the internal combustion engine is within a predetermined temperature range, and the internal combustion engine is unloaded. It is preferable that the operation state is established and the fuel pressure is equal to or higher than a predetermined pressure (Claim 3).
In addition, it is preferable that the catalyst temperature increase control means execute additional fuel injection during the expansion stroke of the internal combustion engine when the temperature increase control of the exhaust purification catalyst is executed.

The control means sets the fuel injection mode to the second fuel injection mode for a predetermined time when it is determined that the predetermined operating condition is satisfied, and the catalyst temperature increase control means It is preferable to execute the catalyst temperature increase control only for a predetermined time (Claim 5).
Further, it is preferable that the predetermined time is set based on the cooling water temperature of the internal combustion engine.

  Further, it is preferable that the second fuel injection mode is set to a richer air-fuel ratio than the first fuel injection mode in the lean region.

According to the fuel injection control device for a direct injection type internal combustion engine of the present invention, when the operating condition (predetermined operating condition) for executing the temperature raising control of the exhaust purification catalyst is established, the fuel injection mode is set to the compression stroke injection mode. Since the second fuel injection mode is set in which the combustion stable region is expanded as the air-fuel ratio becomes richer, the temperature of the exhaust purification catalyst can be raised quickly while improving the fuel efficiency.
That is, since the air-fuel ratio in the compression stroke injection mode is much leaner than that in the intake stroke injection mode, the oxygen concentration in the exhaust gas becomes high. Therefore, when the catalyst temperature increase control is necessary, the second fuel injection mode that is the compression stroke injection is executed, so that when the fuel is supplied in an excessive amount for the catalyst temperature increase, the fuel is stably oxidized. Reaction (combustion) can raise the temperature of the catalyst. Further, by executing the compression stroke injection mode, fuel efficiency can be improved.

  Further, according to the fuel injection control device for a direct injection internal combustion engine of the present invention, the fuel injection mode is changed to the compression stroke injection mode when the operating condition (predetermined operating condition) for executing the temperature raising control of the exhaust purification catalyst is established. Since the fuel is collected in the vicinity of the spark plug and ignited by raising the piston, the second fuel injection mode is set. Therefore, even if a large amount of fuel is supplied for raising the temperature of the catalyst, the fuel is stably oxidized. The temperature of the catalyst can be increased.

  Hereinafter, a fuel injection control device for a direct injection type internal combustion engine according to an embodiment of the present invention will be described with reference to FIGS. 1 to 5. FIG. 1 is a schematic block diagram showing a functional configuration of a main part thereof. 2 and 3 are schematic views showing the configuration of the main part of the internal combustion engine. FIG. 2 is a diagram for explaining the first fuel injection mode, and FIG. 3 is for explaining the second fuel injection mode. FIG. 4 is a diagram for explaining the characteristics of the first and second fuel injection modes, and FIG. 5 is a flowchart for explaining the operation thereof.

As shown in FIGS. 2 and 3, the internal combustion engine (engine) applied to the present invention is a cylinder injection type internal combustion engine 1 in which fuel is directly injected into a cylinder and ignited. In the form, a gasoline engine is applied.
As shown in the figure, the combustion chamber 3 of the engine 1 is formed by the lower surface of the cylinder head 8, the wall surface of the cylinder 7, and the top surface of the piston 2. A fuel injection valve (hereinafter simply referred to as an injector) 4 is attached to the cylinder head 8. The injector 4 is arranged so that the tip side thereof faces the combustion chamber 3, and fuel is directly injected into the combustion chamber 3 from the injector 4.

On the other hand, the top surface of the piston 2 forming the lower surface of the combustion chamber 3 is formed with a recess (referred to as a cavity) 6 as shown in the drawing, and this recess 6 is curved downwardly in this embodiment. It is formed in a spherical shape. The shape of the recess 6 is not limited to a spherical surface, and various shapes can be applied.
A spark plug 5 is attached at a position slightly deviated from the center of the cylinder head 8. The injector 4 and the spark plug 5 have a fuel injection direction, a protruding amount of the spark plug 5 and the like so that at least the fuel supplied from the injector 4 can reach the tip of the spark plug 5 directly.

Incidentally, as shown in FIG. 1, the engine 1 is provided with an ECU (control means; controller) 11 for electrically controlling the overall operation.
Further, on the input side of the controller 11, an engine speed sensor 15 for detecting the engine speed, an air flow sensor (AFS) 16 for detecting the intake air amount as an engine load, and an accelerator position sensor (for detecting the accelerator position) APS) 17 is connected.

  Further, a fuel injection mode switching means 12 for switching the fuel injection mode is provided in the controller 11, and the engine speed Ne and the load (which are obtained by the engine speed sensor 15 and the accelerator opening sensor 17) ( The fuel injection mode is set by the fuel injection mode switching means 12 based on the target Pe) obtained from the engine speed Ne and the accelerator opening. A throttle opening sensor or the like may be provided in place of the accelerator opening sensor 17, and the engine load may be detected based on detection information from these sensors.

  Here, as shown in the figure, the fuel injection mode switching means 12 includes an intake stroke injection injector control means 13 that outputs an injector drive signal to the injector 4 at a timing suitable for intake stroke injection, and And a compression stroke injection control means 14 for outputting an injector drive signal at a timing suitable for the compression stroke injection.

  The fuel injection mode switching means 12 stores a map (not shown) with the engine speed Ne and the load Pe as parameters, and the fuel injection mode corresponding to these parameters is read from the map. The fuel injection mode is set. When the first predetermined operating condition in which the compression stroke injection mode is possible is established, the compression stroke injection mode is selected, and the intake stroke injection mode is selected otherwise. Here, the first predetermined operating condition is that the throttle opening is closed (equivalent to no load or idle), the water temperature is warm (for example, 80 ° C. or higher), the vehicle is stopped (vehicle speed = 0), and the fuel pressure is a predetermined value. More specifically, this corresponds to a warm idle operation.

When the compression stroke injection mode is selected, a control signal for the injector 4 is output from the compression stroke injection injector control means 14 to control the operation of the injector 4. In this case, fuel injection is performed during the compression stroke, and combustion is performed by forming a super lean mixture as a whole in the combustion chamber.
When the intake stroke injection mode is selected, a control signal for the injector 4 is output from the intake stroke injection injector control means 13, and the operation of the injector 4 is controlled. In this case, fuel injection is performed during the intake stroke, and an air-fuel ratio air-fuel mixture corresponding to the operating state of the engine 1 is formed in the combustion chamber and combustion is performed.

  The fuel injection mode is roughly classified into the compression stroke injection mode and the intake stroke injection mode as described above, and each of these modes is further provided with a plurality of different fuel injection modes. Among these, the compression stroke injection mode (compression lean injection mode) is an injection in which fuel is injected toward the spark plug 5 when the piston 2 is in the vicinity of the compression stroke top dead center, and this fuel is directly ignited. Mode (spray guide injection mode; first fuel injection mode, see FIG. 2), and fuel is injected toward the recess 6 of the piston 2 before the top dead center of the compression stroke. And a mode in which ignition is performed in the vicinity of 5 (wall guide injection mode; second fuel injection mode, see FIG. 3).

  Among these, the wall guide injection mode is an injection mode that realizes stable combustion at an ultra-lean (ultra-lean) air-fuel ratio by stratified combustion using a stratified intake flow formed in a cylinder. In this injection mode, as shown in FIG. 3, the combustion spray injected toward the recess 6 of the piston 2 is collected by the rise of the piston 2 and forms a relatively rich mixture near the tip of the spark plug 5. A substantially air-only layer is formed around the air-fuel mixture. Therefore, as a whole, good combustion can be realized while the air-fuel ratio is extremely lean (for example, A / F 20 to 25), and operation can be performed while saving fuel consumption.

Further, in the spray guide injection mode, as shown in FIG. 2, a layered lean state can be formed in the combustion chamber 3 by directly injecting fuel toward the spark plug 5. A stable combustion state can be obtained at an air / fuel ratio (for example, A / F 25 to 40) that is extremely leaner than that in the injection mode.
In the present embodiment, these two modes (spray guide injection mode and wall guide injection mode) can be switched by changing the timing of starting fuel injection.

  On the other hand, in the intake stroke injection mode, the fuel is premixed and the air-fuel ratio state of the entire combustion chamber is made uniform, and operation is performed so that stable ignition and reliable flame propagation can be realized and sufficient high output can be obtained. Stoichiometric mode in which a large output can be obtained by setting the air-fuel ratio in the vicinity of the stoichiometric air-fuel ratio (stoichio), and a lean mode in which the air-fuel ratio is leaner than stoichio (for example, A / F 15-20) to improve fuel efficiency In addition, an enrichment mode or the like is provided in which the air-fuel ratio is temporarily concentrated (richer) than stoichiometric during sudden acceleration or the like.

Since the intake stroke injection mode has been widely known conventionally, the description of the intake stroke injection mode is omitted.
Next, the main part of the present invention will be described. FIG. 4 is a diagram for explaining the characteristics of the spray guide injection mode and the wall guide injection mode. The horizontal axis indicates the fuel injection timing and the vertical axis indicates the ignition timing. This is shown for each (A / F).

As can be seen from this figure, in the spray guide injection mode, the air-fuel ratio at which stable combustion can be obtained is about 25 to 40, and the combustion stable region is widened as the air-fuel ratio becomes leaner. On the other hand, in the wall guide injection mode, the air-fuel ratio at which stable combustion can be obtained is about 20 to 25, and the combustion stable region becomes wider as the air-fuel ratio becomes richer.
In such a spray guide injection mode, the air-fuel ratio is very lean at 25 to 40, so that the fuel consumption can be improved. However, during idling, it is easily affected by a slight load fluctuation, and the rotation fluctuation Is likely to occur.

When the load on the engine 1 increases and the engine speed decreases, the throttle opening is usually increased to increase the engine speed and the target air-fuel ratio A / F is reduced (riched) to increase the engine speed. In the spray guide injection mode, when the fuel is enriched as shown in FIG. 4, the stable combustion region is narrowed, and an engine stall occurs due to misfire.
Therefore, when the load increases, the wall guide injection mode can be switched to obtain stable combustion even if the air-fuel ratio is enriched.

  By the way, at the time of engine cold start, since the oil temperature of the lubricating oil and the oil temperature of the hydraulic oil of the automatic transmission (particularly the torque converter) are low, the viscous resistance is large, and the load becomes high even in the neutral range. For this reason, it is conceivable to switch to the wall guide injection mode even at the time of such cold engine start, but at the time of cold engine start, the first predetermined operating condition described above is not satisfied, so the intake stroke injection mode is set. Can be switched.

  This is because the first predetermined operating condition is originally provided to prohibit the compression stroke injection mode at the cold start. That is, since the generated torque is small in the compression stroke injection mode, the spray guide injection is performed when the load is large even in the idling operation as in the cold start (that is, when a relatively large torque is required). The compression stroke injection mode having the mode and the wall guide injection mode is prohibited, and the intake stroke injection mode capable of outputting a large torque is selected.

On the other hand, although not shown, an exhaust gas purification catalyst (hereinafter simply referred to as a catalyst) for purifying exhaust gas is provided in the exhaust passage of the engine. The exhaust purification catalyst is activated at a predetermined temperature (for example, 350 ° C.) or higher, but it is considered that the exhaust purification catalyst is lowered to the activation temperature or lower when the engine is started in the cold state, and the exhaust gas purification function is lowered.
Therefore, it is necessary to quickly raise the exhaust purification catalyst to the activation temperature, but at the time of such cold start, if fuel injection is executed in the intake stroke injection mode, the air-fuel ratio A / F is set to be relatively rich. Therefore, oxygen remaining in the exhaust gas is reduced. Therefore, even if the additional fuel injection is executed to raise the catalyst temperature, the additional fuel is not completely burned, and the temperature of the exhaust purification catalyst is not rapidly raised. Further, the fuel consumption reduction effect cannot be obtained by the intake stroke injection.

Therefore, in the present embodiment, for example, when it is determined that the temperature of the catalyst needs to be increased even if the first predetermined operating condition is not satisfied by the cold start, the wall guide for the compression stroke injection is determined. The injection mode is executed.
Hereinafter, in detail, as shown in FIG. 1, the controller 11 is provided with a catalyst temperature increase control means 20 that performs catalyst temperature increase control. In addition to the engine speed sensor 15 and the air flow sensor 16 described above, the controller 11 detects an ignition switch 21 that detects start of the engine 1, an idle switch 22 that detects accelerator off, and a temperature Tw of engine coolant. A water temperature sensor 23, a vehicle speed sensor 24 for detecting the traveling speed of the vehicle, and a fuel pressure sensor 24 for detecting the fuel pressure P are connected.

  When the catalyst temperature increase control means 20 determines that the ignition is on based on the information from the ignition switch 21, the catalyst temperature increase control means 20 starts counting a timer (not shown). Further, when the ignition is on, the information from the water temperature sensor is taken in, and if it is equal to or higher than a predetermined temperature (80 ° C. in this case), it is determined as a warm start, and if it is lower than the predetermined temperature, it is determined as a cold start. Further, when it is determined that the cold start (Tw <80 ° C.), it is determined whether the water temperature Tw is within a predetermined temperature range (for example, 10 ° C. <Tw <50 ° C.).

  When the cold start (ignition on) is within the first predetermined time t1 and the cooling water temperature is within the predetermined temperature range, the idle switch 22 is on (no load operation state). When the fuel pressure obtained by the fuel pressure sensor 24 is equal to or higher than a predetermined pressure and the vehicle speed obtained by the vehicle speed sensor is equal to or lower than a predetermined vehicle speed (for example, 2 km / h) (that is, the vehicle is stopped), the catalyst temperature increase control is performed. A possible second predetermined operating condition (corresponding to the predetermined operating condition described in the claims) is established, and the catalyst temperature increase control means 20 instructs the catalyst to execute the temperature increase control. ing.

In this case, the fuel injection mode switching means 12 selects the compression stroke injection mode even if the first predetermined operating condition is not satisfied, and the wall guide injection mode is selected from the compression stroke injection mode. Is supposed to be selected.
That is, as described above, the wall guide injection mode is set to a lean air guide ratio with a relatively low air-fuel ratio when the cooling water temperature is within the predetermined temperature range and the idling operation is performed within the predetermined time t1 from the cold start. As a result, the oxygen concentration in the exhaust gas is increased, and when the temperature increase control such as additional fuel injection (two-stage combustion) is executed, the additional fuel is stably burned so that the temperature of the catalyst can be raised quickly. Become.

  Here, the wall guide injection mode is selected for the following reason. That is, at the time of cold start, since the oil temperature of the lubricating oil or ATF is low and the viscous resistance is large as described above, the output torque may be insufficient in the spray guide injection mode, and rotation may be reduced. This is because in the intake stroke injection, the oxygen concentration in the exhaust gas decreases, and even if additional fuel is supplied to raise the temperature of the catalyst, the additional fuel may not be stably burned.

Therefore, as in this embodiment, the wall guide injection mode is selected when the catalyst temperature increase control is executed at the time of cold start, so that the engine can be stably operated while the temperature of the catalyst is rapidly increased. it can.
Even at the time of cold start, when the water temperature Tw is below a predetermined range (Tw ≦ 10 ° C.) or above a predetermined range (Tw ≧ 50 ° C.), such wall guide injection is performed. Mode selection and catalyst temperature rise control are not executed. This is because if the water temperature Tw is equal to or lower than the predetermined temperature range, the viscosity resistance of the lubricating oil or ATF is too large, and the engine speed may decrease even if fuel injection is executed in the wall guide injection mode. . Further, if the temperature is equal to or higher than the predetermined temperature range, it is considered that the temperature of the catalyst is raised immediately after the normal operation while the water temperature rises quickly in the normal operation.

In the present embodiment, the conditions for establishing such a second operating state include a condition that the fuel pressure is equal to or higher than a predetermined pressure and a condition that the vehicle is stopped. Or it is not necessary to provide both. Moreover, the above-mentioned predetermined pressure is a minimum pressure at which compression stroke injection is possible.
When the timer counted by the catalyst temperature increase control means 21 reaches the second predetermined time t2, the wall guide injection mode + catalyst temperature increase control ends (or is canceled) and depends on the original engine operating state. The fuel injection mode is set.

  Moreover, this 2nd predetermined time t2 is set according to water temperature according to the map shown, for example in FIG. That is, the predetermined time t2 is basically set to be longer as the cooling water temperature is lower, and the predetermined time t2 is set to be shorter as the temperature is higher. The predetermined time t2 is stored as the execution time of the catalyst activation control that is the minimum necessary for the catalyst to be activated. This map is stored in the catalyst temperature rise control means 20.

The fuel injection control device for a direct injection type internal combustion engine according to one embodiment of the present invention is configured as described above, and its operation will be described below with reference to the flowchart shown in FIG. This flowchart is repeatedly executed at predetermined intervals (for example, 100 msec).
First, it is determined whether or not it is immediately after the cold start based on the detection information of the ignition 21 and the information from the water temperature sensor 23 (step S1). Specifically, when the elapsed time from the ignition on is within a preset time (first predetermined time t1) and the water temperature Tw is lower than the predetermined temperature (80 ° C.), judge.

If it is immediately after the cold start, it is next determined whether or not the idle switch (ID SW) 22 is on (step S2). If the idle switch is on, that is, in the no-load operation state, the coolant temperature Tw is determined. Is in a predetermined temperature range (10 ° C. to 50 ° C.) (step S3).
If the coolant temperature Tw is within the predetermined temperature range, it is determined whether or not the vehicle is stopped based on information from the vehicle speed sensor 24 (step S4), and the fuel pressure is determined based on information from the fuel pressure sensor 25. It is determined whether the pressure is higher than a predetermined pressure (step S5).

Next, it is determined whether or not the elapsed time since the start of this control is within the temperature increase control execution time (second predetermined time t2) obtained from the map shown in FIG. 6 (step S6).
When all of the above-described steps S1 to S6 are Yes, the fuel injection mode is set to the wall guide injection mode of the compression stroke injection regardless of whether or not the first predetermined operation condition is satisfied. (Step S7).

Further, so-called two-stage combustion (catalyst temperature rise control) is performed in which fuel is injected in the latter stage of the expansion stroke of the engine and this fuel is combusted in the exhaust passage (step S8). By executing the two-stage combustion in such a wall guide injection mode, the additional fuel supplied in the exhaust gas can be stably burned, and the temperature of the catalyst can be increased.
Further, such two-stage combustion is executed until any of Steps S1 to S6 becomes No. And if it becomes No in any of step S1-S6, while complete | finishing temperature rising control of a catalyst, it progresses to step S9 and a normal driving | running is performed.

  Here, the normal operation refers to an operation in a fuel injection mode corresponding to the operating state of the engine. That is, in this case, if the engine operating condition satisfies the first predetermined operating condition, the compression stroke injection mode is set as the fuel injection mode, and the spray guide injection is performed according to the engine speed and load. The mode and the wall guide injection mode are switched. Further, if the engine operating state does not satisfy the first predetermined operating condition, the intake stroke injection mode is set, and the stoichiometric mode, the lean mode, and the enrich mode are switched according to the engine speed and load. .

Note that the order of determination in steps S2 to S6 is not particularly significant, and these steps may be executed in any order. As described in detail above, according to an embodiment of the present invention. According to the fuel injection control device for a direct injection internal combustion engine, it is possible to quickly raise the temperature of the exhaust purification catalyst at the time of cold start while improving the fuel efficiency.

  That is, when the compression stroke injection mode is originally leaner than the intake stroke injection mode, the oxygen concentration in the exhaust gas is high. Therefore, when the catalyst temperature increase control is required, the first predetermined operation is performed. By executing the compression stroke injection mode with priority over the establishment of conditions, the fuel stably oxidizes (combusts) when a large amount of fuel is supplied to raise the catalyst temperature, thereby raising the temperature of the catalyst. Can do.

  In addition, fuel efficiency can be improved by executing fuel injection in the compression stroke injection mode. Also, as the compression stroke injection mode, the wall guide injection mode (second fuel injection mode) in which the combustion stable region becomes wider as the air-fuel ratio becomes richer is selected. Enrichment can suppress engine rotation fluctuations while realizing stable combustion. In this case, even if the air-fuel ratio is enriched, the overall air-fuel ratio is about 25 to 30, so that the fuel consumption is less than that of the intake stroke injection, and the fuel efficiency is improved.

In addition, since the time t2 for executing the two-stage combustion (catalyst temperature increase control) is set according to the cooling water temperature, the minimum time necessary for the temperature increase is set as the execution time of the compression stroke injection mode at the cold start. And can ensure stable combustion of the engine.
Further, since the wall guide injection mode and the two-stage combustion (catalyst temperature rise control) are executed only when the cooling water is within the predetermined temperature range, there are the following advantages. In other words, when the cooling water is below a predetermined temperature range (10 ° C. or lower), it takes too much time for the catalyst to rise, and if the compression stroke injection is executed in such a long time during the cooling state, the output torque becomes the load (main In contrast, the combustion oil may become unstable due to the loss of the viscous resistance of hydraulic oil or ATF.

Therefore, when the cooling water is below the predetermined temperature range, the temperature of the catalyst is raised in a short time without executing the wall guide injection mode and the two-stage combustion (catalyst temperature rise control) in consideration of the combustion stability of the engine. The catalyst temperature rise control is executed when the temperature is within a predetermined temperature range.
Further, if the temperature is not lower than a predetermined temperature range (50 ° C. or higher), the temperature is quickly raised to the activation temperature in a normal operation without intentionally performing the temperature increase control of the catalyst. By not performing additional fuel supply, fuel efficiency is further improved.

While the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention. For example, in addition to performing additional fuel injection in the expansion stroke as catalyst temperature increase control, a separate injector may be provided in the exhaust path, and fuel may be added directly from this injector.

It is a typical block diagram which shows the function structure of the fuel-injection control apparatus of the cylinder injection type internal combustion engine concerning one Embodiment of this invention. FIG. 3 is a schematic diagram showing a configuration of a main part of a direct injection internal combustion engine applied to the present invention, for explaining a first fuel injection mode. It is a schematic diagram which shows the principal part structure of the cylinder injection type internal combustion engine applied to this invention, Comprising: It is a figure for demonstrating 2nd fuel-injection mode. It is a figure for demonstrating the characteristic of the 1st and 2nd fuel injection mode of the fuel-injection control apparatus of the cylinder injection type internal combustion engine concerning one Embodiment of this invention. It is a flowchart for demonstrating the effect | action of the fuel-injection control apparatus of the cylinder injection type internal combustion engine concerning one Embodiment of this invention. It is a figure for demonstrating the effect | action of the fuel-injection control apparatus of the cylinder injection type internal combustion engine concerning one Embodiment of this invention. It is a figure for demonstrating the subject of a prior art, Comprising: It is a figure which shows the change of the stable combustion area | region when an air fuel ratio fluctuates.

Explanation of symbols

1 engine (internal combustion engine)
2 Piston 3 Combustion chamber 4 Injector (fuel injection valve)
5 Spark plug 6 Recess 7 Cylinder 8 Cylinder head 11 Controller (control means)
Reference Signs List 12 fuel injection mode switching means 13 intake stroke injection injector control means 14 compression stroke injection injector control means 15 engine speed sensor (engine speed detection means)
20 Catalyst temperature rise control means

Claims (7)

A fuel injection control device for an in-cylinder injection internal combustion engine in which fuel is directly injected into a cylinder and ignited by an ignition plug,
As a compression stroke injection mode for injecting the fuel during the compression stroke of the internal combustion engine, a first fuel injection mode in which the combustion stable region expands as the air-fuel ratio becomes lean, and a combustion stable region that expands as the air-fuel ratio becomes richer. Control means for switching between two fuel injection modes;
A catalyst temperature increase control means for performing temperature increase control of the exhaust purification catalyst when a predetermined operating condition is satisfied at the start of the internal combustion engine;
The control means sets the fuel injection mode to the second fuel injection mode when it is determined that the predetermined operating condition is satisfied, and the fuel injection of the direct injection internal combustion engine is characterized in that Control device. A fuel injection control device for an in-cylinder injection internal combustion engine in which fuel is directly injected into a cylinder and ignited by an ignition plug,
As a compression stroke injection mode for injecting the fuel during the compression stroke of the internal combustion engine, a first fuel injection mode for injecting fuel toward the fuel plug near the top dead center of the compression stroke and directly igniting the fuel; During the compression stroke, fuel is injected at an earlier timing than the fuel injection timing of the first fuel injection mode, and the second fuel injection mode is switched between collecting the fuel in the vicinity of the spark plug and igniting it by raising the piston. Control means;
A catalyst temperature increase control means for performing temperature increase control of the exhaust purification catalyst when a predetermined operating condition is satisfied at the start of the internal combustion engine;
The control means sets the fuel injection mode to the second fuel injection mode when it is determined that the predetermined operating condition is satisfied, and the fuel injection of the direct injection internal combustion engine is characterized in that Control device. Within a predetermined time from the cold start of the internal combustion engine, the cooling water temperature of the internal combustion engine is within a predetermined temperature range, the internal combustion engine is in a no-load operation state, and the fuel pressure 3. The fuel injection control device for a direct injection internal combustion engine according to claim 1, wherein when the pressure is equal to or higher than a predetermined pressure, the predetermined operating condition is satisfied. The in-cylinder injection internal combustion engine according to any one of claims 1 to 3, wherein the catalyst temperature increase control means executes additional fuel injection during an expansion stroke of the internal combustion engine when temperature increase control of the exhaust purification catalyst is executed. Engine fuel injection control device. The control means sets the fuel injection mode to the second fuel injection mode for a predetermined time when it is determined that the predetermined operating condition is satisfied, and the catalyst temperature increase control means The fuel injection control device for a direct injection internal combustion engine according to any one of claims 1 to 4, wherein the catalyst temperature increase control is executed only. 6. The fuel injection control device for a direct injection internal combustion engine according to claim 5, wherein the predetermined time is set based on a cooling water temperature of the internal combustion engine. The in-cylinder injection internal combustion engine according to claim 1 or 2, wherein the second fuel injection mode is set to a richer air-fuel ratio than the first fuel injection mode in the lean region. Fuel injection control device.

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