JP2015010500A - Control device for cylinder injection engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve fuel economy and exhaust emission.SOLUTION: An engine 10 is a cylinder injection engine, and includes an injector 21 for directly injecting fuel into a combustion chamber 23, and a variable valve train 31A varying opening and closing timing of an intake valve 31 provided in a suction port. An ECU 40 determines a retarded opening state in which valve opening timing of the intake valve 31 is retarded compared to an intake TDC. Further, the ECU 40 controls driving of the injector 21 so as to start fuel injection in a prescribed time period in which an air flow in the combustion chamber 31 is enhanced by retarded opening of the intake valve 31 when the retarded opening state is determined.

Description

  The present invention relates to a control device for an in-cylinder injection engine.

  Conventionally, in an in-cylinder injection engine that supplies fuel directly into the cylinder, the fuel injection timing has been set in order to make the mixture formation in the cylinder uniform and to suppress the emission of harmful substances such as PM and exhaust emissions. Known to be important. Regarding the setting of the fuel injection timing, for example, in an in-cylinder injection engine that performs an Atkinson cycle operation in which the closing timing of the intake valve is delayed, intake air that flows out from the intake bottom dead center to the intake valve closing via the intake valve There is known a technique that further enhances the tumble flow in the cylinder that is accelerated by (see, for example, Patent Document 1).

Japanese Patent No. 4552922

  By the way, when utilizing the Atkinson cycle to reduce pump loss, for example, in a configuration in which the opening / closing timing of the intake valve is delayed by phase adjustment, not only the closing timing of the intake valve but also the opening timing of the intake valve is retarded. It is conceivable that the valve timing becomes later than the intake top dead center (intake TDC). In this case, it is considered that fuel injection may be performed before the intake valve is opened. For example, in general, the fuel injection timing is set to 40 to 60 ° CA after the intake TDC. However, when the opening timing of the intake valve is 60 ° CA or more after the intake TDC, fuel injection is performed before the intake valve is opened. It will be. When fuel injection is performed before the intake valve is opened as described above, it is feared that fuel cannot be put on the flow of intake air, the mixture formation deteriorates, and the combustion state deteriorates accordingly. The

  The present invention has been made paying attention to the above-mentioned problems, and has as its main object to provide a control device for an in-cylinder injection engine that can improve fuel consumption and exhaust emission.

  Hereinafter, means for solving the above-described problems and the effects thereof will be described.

  The present invention relates to a control apparatus for a direct injection engine, the determining means for determining that the opening timing of the intake valve is in a delayed opening state where the opening timing is later than the intake top dead center, and the delay opening by the determining means A fuel injection control means for controlling the drive of the fuel injection valve so that the fuel injection is started during a predetermined period when the air flow in the combustion chamber is enhanced by the slow opening of the intake valve when it is determined that It is characterized by providing.

  In the above configuration, since the opening timing of the intake valve is made later than the intake top dead center, a negative pressure is generated in the combustion chamber (cylinder) when the intake valve opens after the intake top dead center, The negative pressure can be used to generate a powerful air flow in the combustion chamber. Then, by starting the fuel injection under the state where the airflow is strengthened, the fuel atomization and the homogenization of the air-fuel mixture in the combustion chamber can be appropriately realized. As a result, improvements in fuel consumption and exhaust emissions can be realized.

The block diagram which shows the outline of the engine control system in embodiment of invention. The time chart which shows the opening / closing timing of an intake valve and an exhaust valve. The figure which shows the relationship between the valve opening timing of an intake valve, and an engine load. The time chart which shows the change of the in-cylinder pressure when letting the intake valve open slowly. The flowchart which shows the process sequence of fuel-injection control. The figure for calculating | requiring the frequency | count of fuel injection. The functional block diagram which shows the setting procedure of each injection timing of 1st injection and 2nd injection. The figure for demonstrating the guard process of injection timing. The flowchart which shows the process sequence of fuel pressure control. The figure which shows the relationship between the valve opening timing of an intake valve, and target fuel pressure. The figure for demonstrating the effect by fuel injection timing control. The figure which shows the injection start possible time of fuel injection in another example. The figure which shows the injection start possible time of fuel injection in another example.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, an embodiment of the invention will be described with reference to the drawings. In this embodiment, an in-cylinder injection type multi-cylinder four-cycle gasoline engine (internal combustion engine) mounted on a vehicle is to be controlled, and electronic control of various actuators in the engine is performed. First, the overall schematic configuration of the engine control system will be described with reference to FIG.

  In the in-cylinder injection engine (hereinafter referred to as the engine 10) shown in FIG. 1, an air flow meter 12 for detecting an intake air amount is provided upstream of the intake pipe 11. A throttle valve 14 whose opening degree is adjusted by a throttle actuator 13 such as a DC motor is provided on the downstream side of the air flow meter 12. The opening degree (throttle opening degree) of the throttle valve 14 is built in the throttle actuator 13. It is detected by the throttle opening sensor. A surge tank 16 is provided downstream of the throttle valve 14, and an intake pipe pressure sensor 17 for detecting the intake pipe pressure is provided in the surge tank 16. An intake manifold 18 for introducing air into each cylinder of the engine 10 is connected to the surge tank 16.

  The cylinder block 20 is provided with an electromagnetically driven injector 21 for each cylinder, and fuel is directly injected from the injector 21 into a combustion chamber 23 defined by the cylinder inner wall and the upper surface (top) of the piston 22. The The injector 21 corresponds to a fuel injection valve for in-cylinder injection. High pressure fuel is supplied to the injector 21 from a high pressure fuel system having a high pressure pump.

  The high pressure fuel system will be briefly described. This system mainly includes a low-pressure pump 25 that pumps up fuel in the fuel tank 24, a high-pressure pump 26 that increases the pressure of the low-pressure fuel pumped up by the low-pressure pump 25, and high-pressure fuel that is discharged from the high-pressure pump 26. And a delivery pipe 27 constituting a pressure accumulating chamber for storing the fuel, and the injector 21 of each cylinder is connected to the delivery pipe 27. The high-pressure fuel that has been increased in pressure by the high-pressure pump 26 and stored in the delivery pipe 27 is injected by the injector 21 into the combustion chamber 23 (inside the cylinder). A fuel pressure sensor 29 as a fuel pressure detecting means for detecting fuel pressure (fuel pressure) is provided in the high pressure fuel pipe 28 connecting the high pressure pump 26 and the delivery pipe 27 or the delivery pipe 27.

  The high-pressure pump 26 is a mechanical fuel pump and is driven by the rotation of the cam shaft of the engine 10. The fuel discharge amount of the high-pressure pump 26 is controlled by the opening degree of the fuel pressure control valve 26a provided in the pump 26, and the fuel pressure in the delivery pipe 27 is increased to a maximum of about 20 MPa, for example. The fuel pressure control valve 26a is composed of an intake metering valve for adjusting the amount of fuel sucked into the fuel pressurizing chamber of the high pressure pump 26, or a discharge metering valve for adjusting the amount of fuel discharged from the fuel pressurizing chamber. The fuel pressure in the delivery pipe 27 is variably controlled by adjusting the opening of the fuel pressure control valve 26a.

  An intake valve 31 and an exhaust valve 32 that open and close according to the rotation of a camshaft (not shown) are provided at the intake port and the exhaust port of the engine 10, respectively. The intake air is introduced into the combustion chamber 23 by the opening operation of the intake valve 31, and the exhaust gas after combustion is discharged to the exhaust pipe 33 by the opening operation of the exhaust valve 32. The intake valve 31 and the exhaust valve 32 are provided with variable valve mechanisms 31A and 32A that make the opening / closing timing of these valves variable. The variable valve mechanisms 31A and 32A adjust the relative rotational phase between the crankshaft of the engine 10 and the intake camshaft, and can adjust the phase toward the advance side and the retard side with respect to a predetermined reference position. It has become. As the variable valve mechanisms 31A and 32A, hydraulically driven or electric variable valve mechanisms are used.

  A spark plug 34 is attached to each cylinder of the cylinder head of the engine 10. A high voltage is applied to the spark plug 34 at a desired ignition timing through an ignition coil (not shown). By applying this high voltage, a spark discharge is generated between the opposing electrodes of each spark plug 34, and the fuel is ignited in the combustion chamber 23 and used for combustion.

  The exhaust pipe 33 is provided with a catalyst 35 for purifying exhaust gas. The catalyst 35 is a three-way catalyst that purifies CO, HC, NOx in the exhaust gas, for example. In addition, an air-fuel ratio sensor 36 that detects the air-fuel ratio of the air-fuel mixture is provided upstream of the catalyst 35 in the exhaust pipe 33.

  In addition, the cylinder block 20 includes a water temperature sensor 37 that detects the engine water temperature (corresponding to the engine temperature), and a crank that outputs a rectangular crank angle signal at every predetermined crank angle of the engine (for example, at a cycle of 10 ° CA). An angle sensor 38 is attached.

  The outputs of the various sensors described above are input to an electronic control unit (hereinafter referred to as ECU 40) that controls the engine. The ECU 40 includes a microcomputer including a CPU, a ROM, a RAM, and the like, and executes various control programs stored in the ROM, thereby controlling the fuel injection amount of the injector 21 according to the engine operating state. Or the ignition timing of the spark plug 34 is controlled. The ECU 40 constitutes determination means, fuel injection control means, and fuel pressure control means.

  Specifically, regarding the basic control of the fuel injection, the ECU 40 calculates the basic injection amount based on the engine load (for example, the intake air amount) and the engine rotation speed as parameters, and the water temperature with respect to the basic injection amount. The final fuel injection amount (total injection amount) is calculated by appropriately performing correction, air-fuel ratio correction, and the like. Further, the injection timing is determined according to the engine operating state, an injection signal is generated, and the injector 21 is driven by the injection signal.

  Further, the ECU 40 controls the driving of the high-pressure pump 26, thereby performing fuel pressure control so as to maintain the fuel pressure in the delivery pipe 27, that is, the injection pressure, at a desired pressure. Specifically, the ECU 40 sets a target fuel pressure based on each engine operating state, and performs fuel pressure feedback control based on a deviation between the target fuel pressure and the actual fuel pressure detected by the fuel pressure sensor 29.

  In addition, the ECU 40 performs retard control of the opening / closing timing of the intake valve 31 and the exhaust valve 32 in order to reduce the pump loss of the engine 10 and the like. In this embodiment, the valve closing timing of the intake valve 31 is delayed by driving the variable valve mechanism 31A in the middle load region of the engine 10 (the intake valve 31 is closed late), thereby realizing a so-called Atkinson cycle. ing. The specific configuration will be described below.

  FIG. 2 is a time chart showing the opening / closing timing of the intake valve 31 and the exhaust valve 32, and these valves 31, 32 are opened / closed in accordance with the exhaust stroke and the intake stroke of the engine 10. First, the intake valve 31 will be described. In a normal state, the intake valve 31 opens immediately before the intake TDC (intake top dead center), and closes immediately after the intake BDC (intake bottom dead center). On the other hand, in the state in which the retard angle control is performed, the valve opening timing and the valve closing timing of the intake valve 31 are respectively retarded, and the intake valve 31 opens after the intake TDC and before the compression TDC (the second half of the compression stroke) Close the valve. At this time, the closing timing of the intake valve 31 is after 90 ° CA before compression TDC.

  Further, the exhaust valve 32 opens and closes so that it partially overlaps with the valve opening timing when the intake valve 31 is opened, that is, the valve overlap period exists. That is, in the normal state, the exhaust valve 32 opens immediately before the exhaust BDC and closes immediately after the intake TDC. On the other hand, in the state where the retard angle control is performed, the valve opening timing and the valve closing timing of the exhaust valve 32 are respectively retarded, the exhaust valve 32 opens after the exhaust BDC, and the intake valve 31 opens during the intake stroke. Close immediately after the valve.

  FIG. 3 is a diagram showing the relationship between the opening timing of the intake valve 31 and the engine load. The engine load can be roughly divided into a low load region (load 0 to 20%) including an idle operation state, a medium load region (load 20 to 60%), and a high load region (load 60 to 100%). In FIG. 8, the valve opening timing of the intake valve 31 in the low load region is set as a reference (advance angle / retard angle amount = 0), and the retard amount and advance angle amount from the reference timing are shown.

  In FIG. 3, in the middle load region, the valve opening timing of the intake valve 31 is shifted to the retard side. That is, both the valve opening timing and the valve closing timing of the intake valve 31 are shifted to the retard side, so that the intake valve 31 is controlled to be opened and closed slowly. The retard amount for retarding the opening timing of the intake valve 31 may be variable according to the engine speed, and the retard amount may be decreased as the engine speed increases. In the high load region, the valve opening timing of the intake valve 31 is shifted to the advance side at or near the full load (load 100%). That is, both the valve opening timing and the valve closing timing of the intake valve 31 are shifted to the advance side, whereby the intake valve 31 is controlled to be quickly opened and closed.

  Here, according to the present inventor, when the intake valve 31 is controlled to be opened slowly, negative pressure is generated in the cylinder immediately before the intake valve 31 is opened, and immediately after the intake valve 31 is opened. Was confirmed to generate a strong airflow at the intake port. Therefore, in the present embodiment, when the intake valve 31 is controlled to open slowly, fuel injection is performed after the valve opening timing, thereby promoting fuel atomization (evaporation) and mixing of fuel and air in the cylinder. , Trying to improve fuel economy and exhaust emissions.

  Further, in order to effectively use the powerful air flow when the intake valve 31 is opened, it is desirable to inject a large amount of fuel before the momentum of the air flow attenuates, that is, to increase the injection rate. Conceivable. Therefore, when the intake valve 31 is controlled to open slowly, the fuel pressure in the delivery pipe 27 is increased and fuel injection is performed in this state.

  FIG. 4 is a time chart showing the change in the in-cylinder pressure when the intake valve 31 is opened slowly. For example, the opening timing of the intake valve 31 is set to around 60 ° CA after the intake TDC. The in-cylinder pressure starts to change to the negative pressure side when the opening degree of the exhaust valve 32 becomes minute after the intake TDC, and the intake valve 31 opens under the condition of the negative pressure generation. Thereafter, the negative pressure level further increases as the in-cylinder volume increases, but as the opening degree of the intake valve 31 increases, the negative pressure level of the in-cylinder pressure gradually decreases. Then, when the intake BDC is exceeded, the negative pressure decreases, and thereafter, the opening degree of the intake valve 31 becomes minute, and further, the in-cylinder pressure changes to a positive pressure. In FIG. 4, the negative pressure level in the cylinder becomes particularly large during the period from the opening of the intake valve 31 to 60 ° CA after the valve opening, and the in-cylinder airflow is strengthened during the same period.

  Assuming such a change in the in-cylinder pressure, a powerful air flow in the intake port is utilized by performing fuel injection immediately after the intake valve 31 is opened. This makes it possible to promote fuel atomization and mixing.

  Next, fuel injection control and fuel pressure control performed by the ECU 40 will be described in detail. FIG. 5 is a flowchart showing a processing procedure of fuel injection control, and this processing is repeatedly performed by the ECU 40 at a predetermined cycle.

  In FIG. 5, in step S11, the engine operating state (engine speed, engine load, water temperature, intake / exhaust valve opening timing, etc.) obtained by detection and calculation of various sensors is read. As for the opening timing of the intake / exhaust valves, control command values for the variable valve mechanisms 31A, 32A may be acquired, or timing detection means (position detection sensors) are provided in the variable valve mechanisms 31A, 32A. The detected value may be acquired.

  Thereafter, in step S12, the total injection amount in the current fuel injection is calculated based on the engine operating state (engine speed, engine load, etc.). In the subsequent step S13, it is determined whether or not the current valve opening timing of the intake valve 31 is after the intake TDC, that is, whether or not the intake valve is in the delayed intake opening state. If step S13 is NO, the process proceeds to step S14, and if YES, the process proceeds to step S15. In step S14, normal processing is performed as control of the fuel injection timing. At this time, an injection timing that is a timing for starting fuel injection is set based on the engine operating state (engine speed, engine load, etc.).

  In step S15, it is determined whether or not to perform split injection based on the engine speed and the engine load. At this time, for example, the number of fuel injections may be obtained using the relationship shown in FIG. According to the relationship of FIG. 6, divided injection (number of injections = 2 times) is performed in an engine operating state with a medium to high load and a predetermined rotational speed or less.

  When performing divided injection, in step S16, each divided injection amount (for example, the first injection amount and the second injection amount) is calculated from the total injection amount calculated in step S12. For example, the total injection amount may be divided at a predetermined ratio, and the first injection amount and the second injection amount may be calculated.

  Thereafter, in step S17, setting processing is performed for the injection timing of the first injection, and in subsequent step S18, setting processing is performed for the injection timing of the second injection. Here, the procedure for setting each injection timing of the first injection and the second injection will be described with reference to the functional block diagram of FIG. Each function shown in FIG. 7 is realized as an arithmetic function of the ECU 40.

  In FIG. 7, an injection timing setting unit M10 for the first injection and an injection timing setting unit M20 for the second injection are provided. In the injection timing setting unit M10 for the first injection, the basic injection timing setting unit M11 calculates the basic injection timing of the first injection based on the engine speed NE and the engine load, and the correction unit M12 sets the engine water temperature. Based on this, the basic injection timing is corrected. Specifically, in the basic injection timing setting unit M11, for example, using a map determined by adaptation, the basic injection timing is calculated as the advanced timing as the rotation speed is higher and the load is higher. Further, the correction unit M12 performs correction so that the basic injection timing shifts to the advance side as the engine water temperature decreases. According to the water temperature correction, the time required for fuel atomization at a low temperature is extended.

  In the guard processing unit M13, the basic injection timing after the water temperature correction is guarded within a predetermined range, and the injection timing in the main injection is calculated by the guard processing. Specifically, a guard process for the injection timing is performed based on the opening timing of the intake valve 31 using the relationship shown in FIG. In FIG. 8A, the advance side guard value and the retard side guard value are determined, and the time between them is the injection startable time (a period during which fuel injection can be started). In the present embodiment, the valve opening timing of each intake valve 31 is set as the advance side guard value, and the valve opening timing + 60 ° CA is set as the retard side guard value. Thus, the first injection timing is set within a range of 0 to 60 ° CA after the intake valve 31 is opened. At this time, the injection startable time is set as a predetermined negative pressure generation period after the intake valve 31 is opened and the in-cylinder negative pressure is increased by the slow opening of the intake valve 31.

  Also, in the injection timing setting unit M20 for the second injection, the basic injection timing setting unit M21 calculates the basic injection timing of the second injection based on the engine speed NE and the engine load, and the correction unit M22 The basic injection timing is corrected based on the water temperature. Specifically, in the basic injection timing setting unit M21, for example, using a map determined by adaptation, the basic injection timing is calculated as the advanced timing as the rotation speed is higher and the load is higher. Moreover, in the correction | amendment part M22, correction | amendment is performed so that basic injection timing may transfer to an advance side, so that engine water temperature is low.

  In the guard processing unit M23, the basic injection timing after the water temperature correction is guarded within a predetermined range, and the injection timing in the main injection is calculated by the guard processing. Specifically, the injection timing guard process is performed using the relationship shown in FIG. In FIG. 8B, the advance side guard value and the retard side guard value are determined, and the time between them is the injection startable time. In this embodiment, the injection end timing of the first injection is set as the advance side guard value, and the angular position obtained by advancing the injection period with respect to the intake BDC (180 ° CA after intake TDC) is set as the retard side guard value. Yes. Thereby, the second fuel injection is started after the injection end timing of the first injection, and is ended before the intake TDC.

  Although the above demonstrated the example which performed the frequency | count of division | segmentation injection twice, the frequency | count of division | segmentation injection may be 3 times or more. However, in any case, the fuel injection that is the last of the divided injections ends the fuel injection by the intake TDC. When the number of divided injections is set to 3 or more, for the first fuel injection, the injection timing is set so that the fuel injection is started in a period in which the airflow is enhanced after the intake valve 31 is opened, For the last fuel injection, the injection timing is set so that the fuel has been injected by the intake TDC. For intermediate fuel injection, the injection timing may be set so as not to overlap with the preceding and subsequent fuel injection periods.

  On the other hand, when the divided injection is not performed, the process proceeds to step S19, and the fuel injection timing setting process is performed. The setting may be performed in accordance with the setting process for the first injection in the divided injection, and refer to the “injection timing setting unit M10 for the first injection” in FIG. In this case, the fuel injection start timing is limited within a predetermined range determined based on the valve opening timing of the intake valve 31.

  After the injection timing is set in steps S14, S17, S18, and S19, an injection signal generated according to the injection timing is set (step S20). Thereby, the injector 21 is driven at a desired timing, and fuel injection is performed.

  FIG. 9 is a flowchart showing a processing procedure of fuel pressure control, and this processing is repeatedly performed by the ECU 40 at a predetermined cycle.

  In FIG. 9, in step S31, the target fuel pressure is set based on the engine operating state (engine rotational speed and engine load). In the subsequent step S32, it is determined whether or not the current valve opening timing of the intake valve 31 is after the intake TDC, that is, whether or not the intake valve is in the delayed intake opening state. If step S32 is YES, the process proceeds to step S33. In step S33, the target fuel pressure is corrected to the high pressure side. This correction may be performed based on the valve opening timing of the intake valve 31, for example, using the relationship of FIG. In FIG. 10, the target fuel pressure is increased as the opening timing of the intake valve 31 is delayed. However, when the intake air is slowly opened, the target fuel pressure may be increased by a certain pressure for correction.

  Thereafter, in step S34, fuel pressure feedback control is performed based on the deviation between the target fuel pressure and the actual fuel pressure detected by the fuel pressure sensor 29. According to the present fuel pressure control, the fuel pressure is controlled to be higher in the intake slow-open state than in the non-slow-open state (the state where the opening timing of the intake valve 31 is before the intake TDC).

  As a means for increasing the fuel pressure in the delivery pipe 27 when the intake valve 31 is controlled to open slowly, in addition to correcting the target fuel pressure as described above, the fuel pressure feedback control is temporarily stopped to increase the fuel pressure. The fuel discharge amount of the pump 26 may be increased (the control duty ratio of the fuel pressure control valve 26a is increased).

  FIG. 11 is a diagram showing the effect obtained by the fuel injection timing control of the present embodiment using fuel efficiency as an index. FIG. 11 shows the fuel consumption when the fuel injection start timing is changed within the range of ATDC 20 ° CA to ATDC 160 ° CA. The solid line in the figure shows the result when the intake valve 31 is opened slowly (when the opening timing of the intake valve 31 is set to ATDC 40 ° CA), and the alternate long and short dash line shows the case where the intake valve 31 is not opened slowly (the intake valve 31). (When valve opening timing = before intake TDC) is shown.

  When the intake is not slowly opened (dashed line), the fuel efficiency is best at ATDC 60 ° CA (A1 in the figure), and when the intake is slowly opened (solid line), the fuel efficiency is best at ATDC 80 ° CA (A2 in the figure). . Comparing these two, it can be seen that the fuel consumption is better in the latter case. This is presumably due to the utilization of the Atkinson cycle and the optimization of the fuel injection timing.

  According to the embodiment described in detail above, the following excellent effects can be obtained.

  In the above configuration, since the opening timing of the intake valve 31 is made later than the intake TDC, a negative pressure is generated in the cylinder after the intake TDC and the intake valve 31 is opened, and the negative pressure is used. This can generate a powerful air flow in the cylinder. And fuel atomization in the cylinder and homogenization of the air-fuel mixture can be appropriately realized by starting fuel injection under the state where the airflow is strengthened. As a result, improvements in fuel consumption and exhaust emissions can be realized.

  Since the predetermined negative pressure generation period in which the in-cylinder negative pressure is increased due to the slow opening of the intake valve 31 when the intake valve 31 is opened in the case of the intake slow opening state is set as the injection startable timing, Fuel injection can be performed at a time when the airflow is strongest after the valve 31 is opened. Thereby, the improvement of a combustion state is realizable.

  Since the injector 21 finishes injecting fuel (fuel supplied for the next combustion) before the piston position becomes the intake TDC, fuel injection is performed before the in-cylinder pressure changes to a positive pressure, that is, in a negative pressure state. Is called. In this case, it is possible to realize an advantageous configuration for promoting fuel atomization and air-fuel mixture formation.

  Since the fuel pressure is controlled at a higher pressure in the intake slow-open state than in the state not in the slow-open state, fuel injection with strong penetration is performed before the strong airflow generated after the intake valve 31 opens is attenuated It is possible to realize an advantageous configuration for improving the combustion state.

(Other embodiments)
You may change the said embodiment as follows, for example.

  For the fuel injection immediately after the intake valve 31 is opened (first injection in the case of split injection), the injection startable timing of the fuel injection may be determined as shown in FIG. In FIG. 12, the advance side guard value at the timing at which injection can be started is retarded by a predetermined angle with respect to the opening timing of the intake valve 31.

  -It is considered that the situation of the change in the in-cylinder negative pressure differs depending on the opening timing of the intake valve 31 in the case of the intake slow opening state. In other words, it is considered that the period during which the airflow is enhanced changes. Therefore, for fuel injection immediately after opening of the intake valve 31 (first injection in the case of split injection), the injection startable timing of the fuel injection may be set variably based on the opening timing of the intake valve 31.

  Specifically, as shown in FIG. 13, it is preferable that the injection startable range is determined. In FIG. 13, the range of the injection startable timing is increased as the opening timing of the intake valve 31 is retarded. In particular, in FIG. 13, as the valve opening timing of the intake valve 31 is retarded, the retard side guard value is further away from the valve opening timing of the intake valve 31 to increase the range of timing at which injection can be started. In other words, as the valve opening timing of the intake valve 31 is advanced, the retard side guard value is made closer to the valve opening timing of the intake valve 31 to reduce the range of the injection startable timing. That is, comparing the case where the opening timing of the intake valve 31 is close to the intake TDC and the case where the intake valve 31 is far, it is considered that the in-cylinder negative pressure becomes larger when the intake valve 31 is far (when the retard amount is larger than the intake TDC). . In this case, it is considered that the period during which the airflow is enhanced is relatively long. In view of this point, the relationship of FIG. 13 is determined.

  By adopting a configuration in which the injection startable timing (specifically, the retard side guard value of the first injection timing) is variably set according to the opening timing of the intake valve 31, the cylinder is set according to the opening timing of the intake valve 31. Even if the change state of the internal negative pressure changes, the fuel injection can be performed at an appropriate time by following the change.

  In the relationship of FIG. 13, it is also possible to retard the advance side guard value of the injection startable timing by a predetermined angle with respect to the opening timing of the intake valve 31 as shown in FIG. 12. .

  In the above embodiment, the valve opening timing is variable for both the intake valve 31 and the exhaust valve 32. Alternatively, the valve opening timing may be variable only for the intake valve 31. Good.

  In the above embodiment, the phase adjustment type variable valve mechanisms 31A and 32A are used as the variable valve means. However, in addition to this, the intake / exhaust valves are opened and closed by a cam switching type variable valve mechanism or an electric actuator. It is also possible to use a variable valve mechanism. In these variable valve mechanisms, it is possible not only to change the opening / closing timing, but also to change the valve opening timing from opening to closing to a wide angle or a narrow angle.

  DESCRIPTION OF SYMBOLS 10 ... Engine, 21 ... Injector (fuel injection valve), 23 ... Combustion chamber, 31 ... Intake valve, 31A ... Variable valve mechanism (variable valve operation means), 40 ... ECU (determination means, fuel injection control means).

Claims (6)

In-cylinder provided with a fuel injection valve (21) for directly injecting fuel into the combustion chamber (23) and variable valve operating means (31A) for varying the opening and closing timing of the intake valve (31) provided in the intake port A control device (40) for an injection engine (10),
Determination means for determining that the valve opening timing of the intake valve is in a delayed opening state that is later than the intake top dead center;
When it is determined by the determination means that the valve is in the slow open state, fuel injection is performed during a predetermined period after the intake valve is opened and the air flow in the combustion chamber is strengthened by the slow opening of the intake valve. Fuel injection control means for controlling the drive of the fuel injection valve to be started;
A control apparatus for an in-cylinder injection engine comprising: The predetermined period is a predetermined negative pressure generation period in which the in-cylinder negative pressure is increased by the slow opening of the intake valve after the intake valve is opened in the slow opening state,
The fuel injection control means sets the negative pressure generation period as an injection startable timing at which fuel injection by the fuel injection valve can be started, and the fuel injection is started at the injection startable timing. The in-cylinder injection engine control device according to claim 1, which controls driving of the injection valve.   The in-cylinder injection engine according to claim 2, further comprising means for variably setting the injection startable timing of the fuel injection immediately after the intake valve is opened based on the opening timing of the intake valve. Control device.   4. The fuel injection control unit according to claim 1, wherein the fuel injection control unit performs fuel injection by the fuel injection valve such that fuel supplied for the next combustion finishes being injected before intake bottom dead center. In-cylinder injection engine control device.   The fuel injection control means performs split injection that divides the fuel injection by the fuel injection valve into a plurality of times, so that the fuel injection that is the last of the split injection finishes the injection by the bottom dead center of intake air. The in-cylinder injection engine control device according to claim 4. A pressure accumulation chamber (27) capable of accumulating fuel in a high pressure state; and a fuel pump (26) for increasing the pressure of fuel supplied from a low pressure side and supplying the fuel to the pressure accumulation chamber, Applied to a fuel injection system that directly injects into the combustion chamber by a fuel injection valve;
A fuel pressure control means for variably controlling the fuel pressure in the pressure accumulating chamber by controlling the driving of the fuel pump;
When the fuel pressure control means is determined by the determination means to be in the delayed opening state, the fuel pressure control means is not in the delayed opening state but in the opening timing of the intake valve before the intake top dead center, The in-cylinder injection engine control device according to any one of claims 1 to 5, wherein the fuel pressure is controlled at a high pressure.

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