JP2006207453A - Control device of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To smoothen operation in transition from an engine start period to normal operation in an internal combustion engine having an injector for cylinder injection and an injector for intake passage injection. <P>SOLUTION: In the engine 10 having a plurality of cylinders 112#1 to 112#4, in engine starting and in idling operation, only one predetermined injector of the injector 110 for cylinder injection and the injector 120 for intake passage injection is used in each cylinder to inject fuel. When there is concern that air may accumulate in a fuel supply system to the injectors, in first transition to the normal operation period wherein fuel is injected from both the injectors 110, 120, the other injectors are prohibited for a predetermined period in some cylinders and fuel is injected only by the one injectors similarly to the engine start time and the idling operation time. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a control device for an internal combustion engine, and more specifically, to a first fuel injection means (in-cylinder injector) for injecting fuel into a cylinder and an intake passage and / or an intake port. The present invention relates to fuel injection control at the time of start-up in an internal combustion engine provided with second fuel injection means (intake passage injector) for injecting fuel.

  2. Description of the Related Art In recent years, an internal combustion engine that further includes an intake passage injection injector that injects fuel into an intake passage (or intake port) of each cylinder in addition to an in-cylinder injection device that directly injects fuel into a combustion chamber, as in a so-called direct injection engine An engine has been proposed (for example, Patent Documents 1 to 3). In this type of internal combustion engine, it is necessary to appropriately set the fuel injection share ratio between the two injectors.

  For example, Patent Document 1 shows a configuration in which fuel is injected into an internal combustion engine by an intake passage injection injector at the time of engine start with a low fuel pressure supplied from the in-cylinder injector. Further, in Patent Document 2, when the engine is started, the share ratio between the fuel injection amount into the cylinder and the fuel injection amount into the intake passage is appropriately set in consideration of the atomization state of the fuel injection in the cylinder. A technique for improving engine startability and exhaust gas properties is disclosed.

Further, in Patent Document 3, when both the cooling water temperature and the fuel injection pressure are less than a predetermined value when the engine is started, fuel injection is performed from the intake manifold injector in addition to the in-cylinder injector. A configuration for ensuring good startability is disclosed.
JP 2000-265877 A JP 2001-336439 A Japanese Patent Laid-Open No. 10-176574

  In the internal combustion engine having both the in-cylinder injector and the intake manifold injector as described above, the fuel injection sharing ratio between the two is usually set according to the engine conditions. For this reason, in the engine start period including the engine start time and the idling operation time, as disclosed in Patent Document 1, fuel injection is performed from only one injector, while both the injectors are in normal operation after engine start. If the control configuration executes fuel injection, the following problems occur.

  When starting the engine of a finished vehicle at the factory or starting the engine once the fuel tank is empty (so-called out-of-gas condition), air is supplied to the fuel piping for supplying fuel to both injectors. Has accumulated. For this reason, immediately after the start of fuel injection from each injector, fuel injection cannot be performed normally during the “air bleeding period” until air in the fuel pipe is released.

  In the above control structure, one injector used at the time of engine start is the other injector in which fuel injection is started during normal operation after engine start while an air bleeding period is generated at the time of engine start to which driving force is applied by a starter Then, since the air bleeding period occurs in a scene where the engine output torque is large, fuel injection from the other injector is not normally performed at this time, a step occurs in the output torque, or a misfire state occurs, There is a risk of impairing drivability.

  The present invention has been made to solve such problems, and an object of the present invention is to provide a first fuel injection means (in-cylinder injector) for injecting fuel into the cylinder. In an internal combustion engine provided with a second fuel injection means (intake passage injection injector) for injecting fuel into the intake passage and / or the intake port, both from the engine start period in which only one injector is used This is to facilitate the operation of the internal combustion engine at the time of transition to the normal operation in which fuel injection from the injector is permitted.

  An internal combustion engine control apparatus according to the present invention includes a plurality of cylinders classified into a plurality of groups, and a first fuel injection means for injecting fuel into the combustion chamber in each cylinder and fuel in the intake passage. A control device for an internal combustion engine comprising a second fuel injection means for injecting, a start period fuel injection control means, a determination means, a first fuel injection control means, a second fuel injection control means, Is provided. The start-up period fuel injection control means selectively uses only one of the first fuel injection means and the second fuel injection means in each cylinder during the start-up period of the internal combustion engine. The determination unit determines whether or not air is accumulated in the first and second fuel supply systems for distributing fuel to the first and second fuel injection units, respectively, when the internal combustion engine is started. When the first fuel injection control means determines that the air is accumulated by the determination means, the first fuel injection control means is configured to start the start period in a part of the plurality of groups during a predetermined period from the end of the start period. Fuel injection is performed using only one fuel injection means selected by the fuel injection control means. When the determination unit determines that the air is in the accumulated state, the second fuel injection control unit determines whether the first and second groups in the remaining group other than a part of the plurality of groups in a predetermined period. The fuel injection is performed according to the fuel injection sharing ratio set based on the conditions required for the internal combustion engine after enabling both of the fuel injection means.

  In the control apparatus for an internal combustion engine, in fuel injection control in which fuel injection is performed using only one fuel injection means (injector) in each cylinder during the start-up period of the internal combustion engine, there is a concern about air (air) accumulation in the fuel supply system. In this case, at the time of transition to normal operation after the start-up period has ended, the fuel injection from the other fuel injection means (injector) is not permitted at the same time in each cylinder, but only in some cylinders. to approve. Further, in the remaining cylinders, fuel injection by one fuel injection means (injector) similar to that in the start-up period is continued, so that fuel injection failure is caused by the influence of stagnant air immediately after the start of use of the other fuel injection means (injector). Even if it occurs, it is possible to suppress a decrease in output in the entire internal combustion engine. As a result, the engine state is stabilized by preventing a rapid decrease in engine output accompanying air bleeding in the fuel supply system at the transition from the start period (during engine start and idle operation) to normal operation. be able to.

  Preferably, the control device for an internal combustion engine according to the present invention further includes an output difference estimating means, an injection restriction releasing means, and a third fuel injection control means. The output difference estimating means estimates the output difference between the plurality of groups. The injection restriction releasing unit monitors the output difference estimated by the output difference estimating unit during a predetermined period, and ends the predetermined period when the output difference decreases to a predetermined value or less. The third fuel injection control means performs fuel injection according to the fuel injection sharing ratio in each cylinder after enabling the first and second fuel injection means to be used in each cylinder after the end of the predetermined period by the injection restriction releasing means. .

  In the control apparatus for an internal combustion engine, a predetermined period during which the use of the fuel injection means (injector) that is not used in the engine starting period in only some cylinders is permitted is monitored by monitoring the output difference between the groups. Therefore, at this time, the air removal of the fuel supply system corresponding to the fuel injection means used during the engine start period has already been completed. Therefore, fuel injection by both fuel injection means can be normally performed by all the cylinders immediately after the end of the predetermined period. In addition, the length of the predetermined period can be minimized.

  Further preferably, in the control apparatus for an internal combustion engine according to the present invention, the start period of the internal combustion engine includes a start time and an idle operation time of the internal combustion engine, and the start period fuel injection control means When the temperature of the engine is higher than the predetermined temperature, fuel injection is performed using only the first fuel injection means, while when the temperature of the internal combustion engine is lower than the predetermined temperature, fuel injection is performed using only the second fuel injection means. .

  In the control apparatus for an internal combustion engine, when the engine is warm, the in-cylinder injection using only the first fuel injection means can quickly start the engine and perform idle operation while preventing the occurrence of injector clogging. Further, when the engine is cold, port injection using only the second fuel injection means prevents engine from adhering to the cylinder causing exhaust gas deterioration and the like, and the engine is started and the idling operation is maintained with good combustion. Can be performed.

  Alternatively, preferably, in the control device for an internal combustion engine according to the present invention, the first and second fuel supply systems are provided independently for each of the plurality of groups, and the partial group controlled by the first fuel injection control means is It is determined in consideration of the ease of air accumulation in each fuel supply system, which reflects the difference in the location of the first and second fuel supply systems between the plurality of groups.

  In the control device for an internal combustion engine, air can be released first for a group in which air (air) is relatively likely to accumulate in the fuel supply system. The condition can be normalized earlier.

  More preferably, in the control apparatus for an internal combustion engine according to the present invention, the plurality of cylinders are divided and arranged in a plurality of rows, and the plurality of groups correspond to the plurality of rows, respectively.

  In the control apparatus for an internal combustion engine, the fuel injection control according to the present invention can be applied to the internal combustion engine arranged in a cylinder in a plurality of banks.

  Preferably, in the control device for an internal combustion engine according to the present invention, the determination means is at least one of a start history of the internal combustion engine in the past, a shortage of fuel pressure just before the start, and a shortage of remaining fuel just before the start. Based on this, it is determined whether or not air is accumulated in the first and second fuel supply systems.

  In the control apparatus for an internal combustion engine, whether the air is accumulated in the first and second fuel supply systems (fuel distribution pipe, fuel pipe, etc.) is related to the current state of the internal combustion engine and the past operation history. The determination can be made based on the information without providing a new hardware mechanism (sensor or the like).

  In the control apparatus for an internal combustion engine according to the present invention, the first fuel injection means (in-cylinder injector) for injecting fuel into the cylinder and the first fuel injection in the intake passage and / or the intake port are performed. In an internal combustion engine having two fuel injection means (intake passage injection injectors), an internal combustion engine at the time of transition from an engine start period in which only one injector is used to normal operation in which fuel injection from both injectors is permitted The engine can be operated smoothly.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the following, the same or corresponding parts in the drawings are denoted by the same reference numerals, and detailed description thereof will not be repeated in principle.

[Embodiment 1]
FIG. 1 shows a schematic configuration diagram of an engine system controlled by an engine ECU (Electronic Control Unit) which is a control device for an internal combustion engine according to an embodiment of the present invention. Although FIG. 1 shows an in-line four-cylinder gasoline engine as the engine, the present invention is not limited to such an engine.

  As shown in FIG. 1, an engine (internal combustion engine) 10 includes four cylinders 112 # 1 to 112 # 4. Hereinafter, when the cylinders 112 # 1 to 112 # 4 are collectively described without being distinguished from each other, they are simply referred to as the cylinder 112 or each cylinder 112.

  In the embodiment of the present invention, the plurality of cylinders 112 of the engine are classified into a plurality of groups. In the engine 10 illustrated in FIG. 1, the cylinders 112 # 1 to 112 # 4 are configured to include a group G1 including the cylinders 112 # 1 and 112 # 2 and cylinders 112 # 3 and 112 # 4. And group G2.

  Each cylinder 112 is connected to a common surge tank 30 via a corresponding intake manifold 20. The surge tank 30 is connected to an air cleaner 50 via an intake duct 40, an air flow meter 42 is disposed in the intake duct 40, and a throttle valve 70 driven by an electric motor 60 is disposed. The opening degree of throttle valve 70 is controlled based on the output signal of engine ECU 300 independently of accelerator pedal 100. On the other hand, each cylinder 112 is connected to a common exhaust manifold 80, and this exhaust manifold 80 is connected to a three-way catalytic converter 90.

  For each cylinder 112, an in-cylinder injector 110 for injecting fuel into the cylinder, and an intake passage injection injector 120 for injecting fuel into the intake port or / and the intake passage. And are provided respectively. These injectors 110 and 120 are controlled based on the output signal of engine ECU 300, respectively.

  As shown in FIG. 1, each in-cylinder injector 110 is connected to a common fuel distribution pipe 130. The fuel distribution pipe 130 is connected to an engine-driven high-pressure fuel pump 150 via a check valve 140 that can flow toward the fuel distribution pipe 130. The discharge side of the high-pressure fuel pump 150 is connected to the suction side of the high-pressure fuel pump 150 via an electromagnetic spill valve 152. The smaller the opening of the electromagnetic spill valve 152, the more the fuel distribution pipe 130 is connected to the high-pressure fuel pump 150. When the amount of fuel supplied to the inside is increased and the electromagnetic spill valve 152 is fully opened, the fuel supply from the high-pressure fuel pump 150 to the fuel distribution pipe 130 is stopped. Electromagnetic spill valve 152 is controlled based on the output signal of engine ECU 300.

  On the other hand, each intake passage injector 120 is connected to a common low-pressure fuel distribution pipe 160, and the fuel distribution pipe 160 and the high-pressure fuel pump 150 are connected to a common fuel pressure regulator 170 through an electric motor drive type. The low-pressure fuel pump 180 is connected. Further, the low pressure fuel pump 180 is connected to the fuel tank 200 via a fuel filter 190. The fuel pressure regulator 170 returns a part of the fuel discharged from the low-pressure fuel pump 180 to the fuel tank 200 when the fuel pressure of the fuel discharged from the low-pressure fuel pump 180 becomes higher than a predetermined set fuel pressure. It is configured. Therefore, the fuel pressure supplied to the intake manifold injector 120 and the fuel pressure supplied to the high-pressure fuel pump 150 are prevented from becoming higher than the set fuel pressure.

  As described above, independent fuel distribution pipes 130 and 160 are provided for each in-cylinder injector 110 and each intake passage injector 120. Therefore, even if fuel injection is performed using only one injector, it is difficult to perform air bleeding for discharging the air accumulated in the fuel distribution pipe corresponding to the other injector.

  The engine ECU 300 is composed of a digital computer, and is connected to each other via a bidirectional bus 310, a ROM (Read Only Memory) 320, a RAM (Random Access Memory) 330, a CPU (Central Processing Unit) 340, and an input port 350. And an output port 360.

  The air flow meter 42 generates an output voltage proportional to the amount of intake air, and the output voltage of the air flow meter 42 is input to the input port 350 via the A / D converter 370. A water temperature sensor 380 that generates an output voltage proportional to the engine cooling water temperature is attached to the engine 10, and the output voltage of the water temperature sensor 380 is input to the input port 350 via the A / D converter 390.

  A fuel pressure sensor 400 that generates an output voltage proportional to the fuel pressure in the fuel distribution pipe 130 is attached to the fuel distribution pipe 130, and the output voltage of the fuel pressure sensor 400 is input via the A / D converter 410. Input to port 350. The exhaust manifold 80 upstream of the three-way catalytic converter 90 is provided with an air-fuel ratio sensor 420 that generates an output voltage proportional to the oxygen concentration in the exhaust gas. The output voltage of the air-fuel ratio sensor 420 is converted into an A / D converter. It is input to the input port 350 via 430.

The air-fuel ratio sensor 420 in the engine system according to the present embodiment is a global air-fuel ratio sensor (linear air-fuel ratio sensor) that generates an output voltage proportional to the air-fuel ratio of the air-fuel mixture burned by the engine 10. The air-fuel ratio sensor 420 may be an O ₂ sensor that detects whether the air-fuel ratio of the air-fuel mixture burned in the engine 10 is rich or lean with respect to the stoichiometric air-fuel ratio. Good.

  The accelerator pedal 100 is connected to an accelerator opening sensor 440 that generates an output voltage proportional to the depression amount of the accelerator pedal 100, and the output voltage of the accelerator opening sensor 440 is input to the input port 350 via the A / D converter 450. Is input. The input port 350 is connected to a rotational speed sensor 460 that generates an output pulse representing the engine rotational speed. In the ROM 320 of the engine ECU 300, the value of the fuel injection amount and the engine cooling that are set according to the operating state based on the engine load factor and the engine speed obtained by the accelerator opening sensor 440 and the engine speed sensor 460 described above are stored. Correction values based on the water temperature and the like are previously mapped and stored.

  Crank angle sensor 480 includes a rotor mounted on a crankshaft (not shown) of engine 10 and an electromagnetic pickup that is disposed near the rotor and detects the passage of protrusions provided on the outer periphery of the rotor. Is done. The crank angle sensor 480 is a sensor for detecting the rotational phase (crank angle) of the crankshaft. The output of the crank angle sensor 480 is given to the input port 350 as a pulse signal generated each time the projection passes.

  Engine ECU 300 generates various control signals for controlling the overall operation of the engine system based on signals from the sensors by executing a predetermined program. These control signals are sent to the equipment / circuit group constituting the engine system via the output port 360 and the drive circuit 470.

  In the engine 10 according to the embodiment of the present invention, each cylinder 112 is provided with both the in-cylinder injector 110 and the intake passage injector 120. Therefore, the necessary total fuel injection calculated as described above. Regarding the amount, it is necessary to perform fuel injection sharing control between the in-cylinder injector 110 and the intake passage injector 120.

  In the following, the fuel injection sharing ratio between the two injectors will be indicated by the DI ratio r, which is the ratio of the fuel injection amount from the in-cylinder injector 110 to the total fuel injection amount. That is, “DI ratio r = 100%” means that fuel injection is performed only from in-cylinder injector 110, and “DI ratio r = 0%” means only from intake manifold injector 120. It means that fuel injection is performed. “DI ratio r ≠ 0%”, “DI ratio r ≠ 100%” and “0% <DI ratio r <100%” indicate that in-cylinder injector 110 and intake passage injector 120 perform fuel injection. It means to be shared. In general, the in-cylinder injector 110 contributes to an increase in output performance, and the intake manifold injector 120 contributes to the uniformity of the air-fuel mixture.

  Furthermore, a starting device 500 is provided for the engine 10. Generally, starting device 500 is constituted by an electric motor that is energized in response to an operation command from engine ECU 300. For example, engine ECU 300 generates an operation command for starter 500 in response to an ignition switch being turned on by a driver's key operation. In addition, in a vehicle equipped with a hybrid vehicle or an economy running system in which the engine is intermittently operated, the start command of the starter 500 is automatically generated by the engine ECU 300 according to the driving state, the battery charging state, and the like.

  When an operation command is issued from the engine ECU 300, the starter 500 rotates the flywheel 510 of the engine 10 to start the engine 10. Furthermore, after the engine speed reaches a predetermined injection permission speed, engine driving by fuel combustion by fuel injection and ignition is started.

  Next, the fuel injection control according to the first embodiment by the control device for an internal combustion engine according to the present invention will be described with reference to FIG. In the first embodiment, the fuel injection control in the case where only the port injection by the intake manifold injector 120 is used during the engine start period will be described. In the following description, the “engine start period” includes an engine start time and an idle operation time.

  That is, the fuel injection control shown in FIG. 2 is suitable when the engine is cold. When the engine is cold, atomization of the fuel in the cylinder is difficult to promote, and if the fuel is injected from the in-cylinder injector 110, a large amount of fuel adheres to the top surface of the engine piston or the inner peripheral surface of the cylinder. This may cause adverse effects such as deterioration of the lubrication performance and deterioration of the lubrication performance. For this reason, only the port injection, that is, the fuel injection using only each intake manifold injector 120 is executed when the engine is started.

  The fuel injection control routine according to the flowchart shown in FIG. 2 is executed at predetermined intervals after the engine ECU 300 is powered on and initialized.

  Referring to FIG. 2, first, it is determined whether or not there is an “ON” input of the ignition switch (IG) (step S100).

  Specifically, when the previous fuel injection control routine is executed, IG is OFF, and when the current fuel injection control routine is executed, IG is ON ("YES ON input" is determined) (YES in step S100). The following steps S110 to S130 are executed.

  When there is an IG ON input, an in-delivery air accumulation determination is performed to determine whether or not air is stagnant in the fuel supply system (particularly the fuel distribution pipes 130 and 160) to the injectors 110 and 120. (Step S110). The determination in step S110 is executed as shown in FIG.

  Referring to FIG. 3, in the delivery air accumulation determination routine (step S110), in steps S111 and S112, the past engine start history is determined based on whether or not the vehicle is in a new vehicle state. Specifically, in step S111, it is determined whether the accumulated travel distance of the vehicle is equal to or smaller than the determination value Dr. In step S112, the engine start history so far is confirmed.

  The determination value Dr in step S111 is set near 0 km, and in step S112, the engine start history is determined based on a flag xst indicating whether or not there is a history of normal completion of engine start control in the past. For example, the flag xst is stored in a standby RAM (Random Access Memory) that retains the stored contents as long as the engine ECU 300 is connected to the battery terminal, and a history that the engine start control has been normally completed even once in the past. “On” is set in some cases, and “Off” is set in other cases.

  When both steps S111 and S112 are YES, it is determined that the vehicle is in a “new vehicle state (no engine start history)”. In this case, since it is presumed that air accumulation has occurred in the delivery, the dummy injection request flag xdminj is turned “ON” (step S116), and the in-delivery air accumulation determination routine is ended.

  On the other hand, when any of steps S111 and S112 is NO, it is determined as “non-new vehicle state”, and the out-of-gas state determination in steps S113 to S115 is executed.

  In step S113, it is determined whether or not the current remaining fuel amount is below the fuel shortage warning level by using a flag xfuel that is “ON” when the fuel amount in the fuel tank 200 falls below a predetermined warning level. The Further, in step S114, for example, it is determined whether the fuel pressure in the fuel supply system has reached the required pressure Pr based on the measured value of the fuel pressure sensor 400. Further, in step S115, an engine start abnormality occurs when the flag xcrnk that is “on” is checked when the engine speed does not increase and the engine start control does not end normally even if the cranking continuation time exceeds a predetermined value. It is determined whether or not

  When all of steps S113 to S115 are YES, it is determined as “out of gas”. Also in this case, since it is presumed that air accumulation has occurred in the delivery, the dummy injection request flag xdminj is turned “ON” (step S116), and the in-delivery air accumulation determination routine is ended.

  On the other hand, when any of Steps S113 to S115 is NO, it is determined as “non-gas-out state”, the dummy injection request flag xdminj remains “off”, and the delivery air accumulation determination routine is ended.

  As described above, in the delivery air accumulation determination routine (step S110), the dummy injection request flag xdminj is “on” when “new vehicle state” or “out of gas state”, and the dummy injection request flag xdminj is “ “Off”.

  Referring again to FIG. 2, when the delivery air accumulation determination routine (step S110) is completed, the dummy injection request flag xdminj is checked (step S120).

  When xdminj = “ON” (YES determination in step S120), dummy fuel injection is executed on the port injection side used when the engine is started (step S130). In other words, although fuel injection is not necessary, fuel injection from each intake manifold injector 120 is executed, and thereby air removal for removing the accumulated air in the low-pressure fuel path including the fuel distribution pipe 160 is executed. The

  Note that dummy fuel injection is not executed for the in-cylinder injector 110 that is not used at the time of starting. If the dummy fuel injection by the in-cylinder injector 110 is executed before the engine is started when the engine is cold, the fuel injected into the cylinder as the air is released adheres to the cylinder, and the engine as described above This is because there is a possibility of causing deterioration of exhaust properties and lubricity at start-up and ignition failure due to fuel adhering to a spark plug (not shown).

  On the other hand, when xdminj = “off” (NO determination in step S120), dummy fuel injection is not executed because there is less risk of air accumulation in the delivery.

  Next, in the fuel injection control, it is determined in step S150 whether or not the engine is being started.

  Whether or not the engine is being started is determined based on whether or not there is a history that the engine speed Ne has reached the engine speed N1 for determining completion of engine start after the ignition switch (IG) is turned on. The history is cleared every time the engine is stopped. That is, after IG ON input, step S150 is determined as YES during the period of engine speed Ne <predetermined speed N1, and once engine speed Ne ≧ N1 is satisfied, step S150 is determined as NO. The rotation speed N1 is generally set to about 500 to 600 rpm.

  When the engine is started (when YES is determined in step S150), the DI ratio r = 0% is set so that fuel injection is executed only by port injection in common with each cylinder 112, that is, groups G1 and G2. Step S160), the fuel injection control routine is ended. Thereby, when the engine is started, fuel injection using only one injector is executed. At this time, by the dummy fuel injection executed in step S130, the port injection at the time of starting the engine can ensure a better fuel injection state than immediately after the start of the injection.

  On the other hand, after the engine is started, that is, when NO is determined in step S150, the fuel injection control described below is performed.

  After the engine is started, it is determined whether the engine is idling based on the idle determination flag xidl (step S170). The idle determination flag xidl is “on” when the opening of the throttle valve 70 (throttle opening) is equal to or less than the reference opening, and is “off” when the opening exceeds the reference opening.

  That is, when the idling determination flag xidl = “on”, the idling operation is performed, and when xidl = “off”, the non-idling operation (normal operation) is performed. The reference opening is set to a value obtained by adding a predetermined value to the “idle opening” corresponding to the throttle opening required to maintain the target idle speed with the accelerator depression amount = 0. Since the target idle speed is set to a different value according to the cooling water temperature, the air conditioner load, the electric load, etc., the reference opening also changes depending on the situation.

  During the idling operation, that is, when YES is determined in step S170, the DI ratio r = 0% is set so that the fuel injection is executed only by the port injection in common with each cylinder 112, that is, the groups G1 and G2, similarly to step S160. In step S175, the fuel injection control routine is terminated. Thus, fuel injection using only one injector is executed even during idle operation. By performing only port injection when the engine is cold, stable idle operation can be performed while avoiding the risk of fuel pressure delay and combustion failure in the high-pressure fuel system.

  That is, during the engine start-up period including engine start and idle operation, fuel injection using only one injector (intake passage injection injector 120) is executed in each cylinder according to step S160 or S175 (DI ratio). r = 0%).

  On the other hand, at the time of non-idle operation (NO determination at step S170), the engine start period is ended. At this time, fuel injection is controlled in accordance with the dummy injection request flag xdminj reflecting the delivery air accumulation determination in step S110 (step S180).

  When the dummy injection request flag xdminj = “off” (NO determination in step S180), since there is a low risk of air accumulation in the delivery, both the in-cylinder injector 110 and the intake manifold injector 120 are set. As appropriate, an appropriate DI ratio r is optimally set within a range of 0 to 100% in accordance with engine operating conditions (rotation speed, load factor, etc.). For example, the DI ratio r for obtaining an optimal engine operating state can be set based on a table or the like set in advance according to the engine speed and the load factor. The setting of a preferred DI ratio during normal operation will be described in detail later.

  On the other hand, when the dummy injection request flag xdminj = “ON” (YES determination in step S180), that is, when it is determined that the risk of air in the delivery is high, the start period (during start-up and idle operation) In the fuel supply system to the in-cylinder injector 110 that is not performing fuel injection, there is a high possibility that air is still accumulated in the pipe. For this reason, if fuel injection from the in-cylinder injector 110 is allowed unconditionally, normal fuel injection cannot be performed immediately after the start of the fuel injection due to the influence of stagnant air, and a step-down engine output decrease occurs. May occur. In order to prevent such a phenomenon from occurring, the following steps S200 to S250 are executed in the fuel injection control according to the first embodiment.

  In step S200, the output torque of each cylinder 112 # 1 to 112 # 4 and the output torque for each of groups G1 and G2 are calculated.

  For example, the output torque calculated value DN (n) of each cylinder 112 # n is obtained based on the following equation (1) (n: natural number of 1 to 4).

DN (n) = ω1 ² −ω2 ² (1)
In the equation (1), ω1 indicates an angular velocity of 60 to 90 degrees crank angle ATDC (after top dead center) in cylinder 112- # n, and ω2 is between crank angles TDC and ATDC 30 degrees in cylinder 112- # n. Indicates angular velocity. These angular velocities ω1 and ω2 are calculated based on the output of the crank angle sensor 480.

  With respect to the output torque calculation value DN (#n) in each cylinder according to the equation (1), the average values of the groups G1 and G2 are obtained by the equations (2) and (3), respectively. Output torque calculated values DN (G1) and DN (G2) are calculated.

DN (G1) = (DN (1) + DN (2)) / 2 (2)
DN (G2) = (DN (3) + DN (4)) / 2 (3)
Furthermore, in step S210, the output torque difference TD between groups is calculated according to the equation (4) from the output torque calculated values DN (G1) and DN (G2) for each group obtained in step S200.

TD = DN (G1) -DL (G2) (4)
Further, based on the output torque difference TD, an output torque difference evaluation value TDSM (i) is calculated according to the following equation (5).

TDSM (i) = TDSM # + (DLDN (i) −TDSM #) · x (5)
In equation (5), TDSM (i) represents an output torque difference evaluation value TDSM at the time of execution of the i-th (i: natural number) fuel injection control routine. Further, DLDN (i) is an integrated value of the output torque difference TD obtained in the previous k fuel injection control routines immediately before, and x is a real number where 0 <x <1.0. TDSM # is the previous value of TDSM.

  Thus, the output torque difference evaluation value TDSM is updated every time the output torque difference TD is integrated k times (for engine k cycles) and the integrated value DLDN is obtained. That is, the output torque calculated value DN and the output torque difference TD are calculated for each engine cycle, while the integrated value DLDN and the output torque difference evaluation value TDSM are updated for each engine k cycle.

  According to the output torque difference evaluation value TDSM shown in the equation (5), instead of directly using the output torque difference TD calculated each time the fuel injection control routine is executed, the change in the integrated value over a certain period is an averaging factor. Since it is gradually reflected according to x, even if the output torque difference TD fluctuates instantaneously, the transition of the output torque difference can be accurately evaluated.

  In step S220, the output torque difference evaluation value TDSM obtained in step S210 is compared with a predetermined reference value TDr.

  When output torque difference evaluation value TDSM> TDr, that is, when the output torque difference between groups is larger than the reference value (NO determination in step S220), in one group G1 (cylinders 112 # 1 and 112 # 2), As in the start-up and idle operation, fuel injection is executed only with port injection (that is, r = 0%) (step S230). On the other hand, in the other group G2 (cylinders 112 # 3 and 112 # 4), as in step S190, both the in-cylinder injector 110 and the intake manifold injector 120 can be used, and the engine operating condition ( The appropriate DI ratio r is optimally set within a range of 0 to 100% according to the rotation speed, load factor, and the like.

  As is understood from the equation (5), the output torque is from the first execution of steps S200 and S210 until the fuel injection control routine is executed k times (that is, during the initial k cycles of the engine). The difference evaluation value TDSM is not calculated. The determination result in step S220 during this period is fixed to “NO”.

  When the dummy injection request flag xdminj = “on”, that is, when there is a concern about air accumulation in the delivery, at the end of the start-up period, that is, at the time of switching from idle operation to non-idle operation (normal operation), at start-up and idle operation There is a possibility that a fuel injection failure may occur at the start of fuel injection from the in-cylinder injector 110, which was sometimes not used. Accordingly, in a predetermined period from the end of the start period, all the groups are not permitted to start using the in-cylinder injector 110 at the same time, and some groups (that is, some cylinders) start and idle operation. Continue port injection in the same way as time. Thereby, even if the fuel injection from the in-cylinder injector 110 is insufficient or defective in the remaining cylinders that have started in-cylinder injection, it is possible to suppress a drop in the output of the engine 10 as a whole. Thereby, the remarkable deterioration of drivability is avoided.

  On the other hand, when the output torque difference evaluation value TDSM ≦ TDr, that is, when the output torque difference between the groups is equal to or smaller than the reference value (YES determination in step S220), the dummy injection request flag xdminj is changed from “ON” to “OFF”. It is changed (step S250). That is, when the group that has started in-cylinder injection completes bleeding of the fuel path corresponding to in-cylinder injector 110 and the output torque difference TD or the output torque difference evaluation value TDSM gradually decreases, the dummy injection request flag xdminj is “off”.

  As a result, the determination in step S180 is “NO” from the next execution of the fuel injection control routine. Therefore, according to step S190, both the in-cylinder injector 110 and the intake manifold injector 120 can be used in both groups G1 and G2, and the DI ratio r common to each cylinder 112 is within the range of 0 to 100%. Set optimally. That is, the predetermined period during which the in-cylinder injection in some cylinders is not permitted at this time is ended.

  As described above, since the output torque difference between the groups is monitored and the predetermined period is ended, the air bleeding of the fuel path corresponding to the in-cylinder injector 110 has already been completed at this time. Therefore, the remaining cylinders of the group G1 can normally perform fuel injection immediately after the start of in-cylinder injection. In addition, the length of the predetermined period can be minimized.

  FIG. 4 shows an example of the operation of the fuel injection control shown in FIG. FIG. 4 shows an example of the control operation in the case where it is determined in step S110 that the dummy injection request flag xdminj is “ON”, that is, an air pool is generated in the delivery.

  Referring to FIG. 4, at time t0, ignition switch IG is turned “ON” from “OFF”. In response to this, when step S110 of FIG. 2 is executed and the dummy injection request flag xdminj is turned “ON”, dummy fuel injection in step S130 is executed in each intake passage injector 120 after time t0. Is done.

  In the period (time t0 to t1) from when the engine is started at time t0 until the engine speed Ne reaches a predetermined speed N1 for determining completion of engine start at time t1, each cylinder is operated according to step S160 in FIG. In 112, the DI ratio r = 0% is set, and fuel injection from the intake manifold injector 120 alone is executed. When the engine speed Ne reaches the predetermined speed N1, the engine ECU 300 recognizes the completion of the engine start, and the ignition switch IG is “off”.

  Between times t1 and t2, since the throttle opening is equal to or less than the reference opening, the flag xidl = “on” is maintained and the idle operation is performed. Even during this period, the DI ratio r = 0% is set for each cylinder in accordance with step S175. Thus, at the time of engine start (time t0 to t1) and idling operation (time t1 to t2), the DI ratio settings r (G1) and r (G2) in the groups G1 and G2 are each 0%. Is set.

  At time t2, the throttle opening becomes equal to or greater than the reference opening, and the idle determination flag xidl changes from “on” to “off”. Thereby, step S170 becomes NO judgment and an engine starting period is complete | finished. That is, in the operation example of FIG. 4, the times t0 to t2 correspond to the “engine start period”.

  Since the dummy injection request flag xdminj = “on” is set at the end of the engine start period, steps S200 to S250 are executed, and the DI ratio r (G1) in one group G1 is 0%. On the other hand, the DI ratio r (G2) in the other group G2 can be set to an arbitrary value in the range of 0% to 100%. In response to this, calculation of the output torque difference evaluation value TDSM is started.

  After time t2, the start of in-cylinder injection is permitted in group G2, while a predetermined period in which port injection is executed in a fixed manner is provided in group G1. At the start of in-cylinder injection, a fuel injection failure from the in-cylinder injector 110 may occur due to the accumulation of air in the delivery. As a result, an output torque difference is generated between the group G1 in which port injection is normally performed and the group G2 at the start of in-cylinder injection. As a result, the output of the engine 10 also decreases, but a drop in the output of the entire engine 10 is suppressed as compared with the case where in-cylinder injection is started in all the cylinders simultaneously and a fuel injection failure occurs.

  After the time t2, when the in-cylinder injection in the group G2 proceeds and the bleeding of the fuel path corresponding to the in-cylinder injector 110 is completed, the output torque difference evaluation value TDSM gradually decreases. From time t3 when the output torque difference evaluation value TDSM becomes smaller than the reference value TDr, fuel injection from the in-cylinder injector 110 is permitted also in the group G1. That is, since the predetermined period in which in-cylinder injection is not permitted in some cylinders ends at time t3, in the operation example of FIG. 4, time t2 to t3 corresponds to the “predetermined period”.

  After time t3, the DI ratios r (G1) and r (G2) in the groups G1 and G2 can both be set to arbitrary values in the range of 0% to 100%. Accordingly, both the in-cylinder injector 110 and the intake manifold injector 120 can be used, and an appropriate DI ratio r is in the range of 0 to 100% depending on the engine operating conditions (rotation speed, load factor, etc.). Are commonly set in each cylinder 112.

  As described above, in the control device for an internal combustion engine according to the embodiment of the present invention, in the fuel injection control in which fuel injection is performed using only one injector in each cylinder during the start period (starting time and idling operation), When there is a concern about delivery of air in the delivery, the fuel injection from the other injector is allowed in stages from some cylinders without allowing the cylinders to start fuel injection all at once. As a result, it is possible to prevent the engine output from rapidly decreasing due to air bleeding in the fuel supply system, and to stabilize the operation state at the time of switching from the engine start period to the normal operation.

[Embodiment 2]
In the fuel injection control according to the first embodiment, the fuel injection control suitable for the engine cold time in which only the port injection is performed in each cylinder during the engine start period has been described. In contrast, in the second embodiment, fuel injection control in which only in-cylinder injection is performed in each cylinder during the engine start period will be described.

  FIG. 5 is a flowchart illustrating fuel injection control according to the second embodiment of the present invention.

  The fuel injection control routine according to the flowchart shown in FIG. 5 is also executed by engine ECU 300 at predetermined intervals after the system is powered on and initialized.

  5 is compared with FIG. 2, in the fuel injection control according to the second embodiment, steps S130 #, S160 #, S175 # and S230 # are executed in place of steps S130, S160, S175 and S230 in FIG. The Other steps in the flowchart shown in FIG. 5 are the same as those in the flowchart shown in FIG. 2, and thus detailed description will not be repeated.

  In step S130 #, only in-cylinder injection is used when the engine is started. When xdminj = “ON” (YES determination in step S120), each in-cylinder injector 110 performs dummy fuel injection. Is executed. As a result, air bleeding for removing the accumulated air in the high-pressure fuel path including the fuel distribution pipe 130 is executed. In this case, if the dummy fuel injection is performed on the port side, the fuel that flows out from each intake manifold injector 120 during air bleeding may cause engine start failure. The dummy fuel injection is executed only by the injector 110 for the engine.

  In step S160 #, the engine is started by in-cylinder injection only (DI ratio r = 100%) for each cylinder. Further, in step S175 #, during idling (when YES is determined in step S170), fuel injection is executed by only in-cylinder injection (DI ratio r = 100%) in each cylinder as in the engine start.

  As a result, the engine is started by in-cylinder injection whose start-up time is shortened in consideration of the good spray state during in-cylinder fuel injection when the engine is warm. Further, during idle operation, by performing fuel injection from the in-cylinder injector 110, it is possible to suppress the temperature rise at the front end portion of the in-cylinder injector 110 and to prevent clogging at the front end portion of the injector.

  Further, in step S230 #, corresponding to the fact that only in-cylinder injection is executed during the engine start period (starting time and idling operation), the same applies to the group G1 where the use of both injectors is not permitted. In addition, the fuel injection is executed only by the in-cylinder injection (that is, r = 100%).

  As described above, also in the fuel injection control in which only the in-cylinder injection is performed during the engine start period, as in the first embodiment, when there is a concern about the accumulation of air in the delivery, the fuel injection from the intake manifold injector The start is permitted in stages from a part of the cylinders without allowing the start in each cylinder at once. As a result, it is possible to prevent the engine output from rapidly decreasing due to air bleeding in the fuel supply system, and to stabilize the operation state at the time of switching from the engine start period to the normal operation.

  Here, the correspondence between the flowcharts shown in FIGS. 2 and 5 and the configuration of the present invention will be described. Step S110 (FIGS. 2 and 3) corresponds to the “determination means” in the present invention, and steps S160, S175 (FIG. 2), S160 #, and S175 # (FIG. 5) correspond to “starting period fuel injection control means” in the present invention. Further, steps S230 (FIG. 2) and S230 # (FIG. 5) correspond to the “first fuel injection control means” in the present invention, and steps S240 (FIG. 2) and S240 # (FIG. 5) correspond to the present invention. Step S190 (FIGS. 2 and 5) corresponds to the “third fuel injection control means” in the present invention. Step S210 (FIGS. 2 and 5) corresponds to “output difference estimating means” in the present invention, and steps S220 and S250 (FIGS. 2 and 5) correspond to “injection restriction releasing means” in the present invention. To do.

  As described above, the fuel injection control according to the first embodiment is suitable when the engine is cold, and the fuel injection control according to the second embodiment is suitable when the engine is warm. Therefore, the engine temperature, specifically, when the engine coolant temperature measured by the water temperature sensor 380 is higher than the reference temperature is defined as “when the engine is warm”, and when it is lower than the reference temperature, it is defined as “when the engine is cold”. Thus, it is preferable that the fuel injection control according to the second embodiment is executed when the engine is warm, while the fuel injection control according to the first embodiment is executed when the engine is cold.

  In the first and second embodiments, an example in which four cylinders are divided into two groups has been shown. However, an arbitrary number of cylinders are divided into two or more arbitrary numbers of groups to start the engine. It is good also as a control structure which gives the usage permission of both the injectors 110 and 120 in the end of a period in steps for every group.

[Applicable to engines with multiple banks]
The fuel injection control according to the present invention described in the first and second embodiments can be applied regardless of the arrangement form as long as the engine 10 has a plurality of cylinders that can be divided into a plurality of groups.

  Therefore, not only an engine in which a plurality of cylinders shown in FIG. 1 are arranged in series, but also an engine in which a plurality of cylinders are divided and arranged in a plurality of rows, that is, a plurality of banks, as shown in FIG. The fuel injection control according to can be applied.

  In engine 10 # shown in FIG. 6, six cylinders 112 # 1- # 6 are divided and arranged in two banks a and b. Cylinders # 2, # 4, and # 6 are arranged in a row so as to form bank a on the left side with respect to the traveling direction Fr of the automobile, and cylinders # 1, # 3, and # 5 are traveling directions of the automobile. They are arranged in a row so as to form a bank b on the right side of Fr. Note that the cylinder arrangement direction is not limited to the vehicle front-rear direction as shown in FIG. 6, but may be other directions.

  In engine 10 #, for example, by making bank a and bank b correspond to groups G1 and G2, respectively, similar fuel injection control according to the first or second embodiment can be executed.

  Further, in engine # 10 in which a plurality of cylinders are arranged in a plurality of banks, a fuel distribution pipe may be provided independently for each bank.

  Referring to FIG. 7, corresponding to bank a including cylinders 112 # 2, # 4, and # 6, fuel distribution pipe 130a is provided for in-cylinder injector 110, and intake manifold injector 120 is provided. On the other hand, a fuel distribution pipe 160a is provided. Similarly, a fuel distribution pipe 130 b is provided for in-cylinder injector 110 corresponding to bank b including cylinders 112 # 1, # 3, and # 5, and fuel distribution for intake manifold injector 120 is provided. A pipe 160b is provided.

  Since bank a and bank b correspond to groups G1 and G2 in the first and second embodiments, respectively, in the configuration shown in FIG. 7, independent fuel distribution pipes and fuel pipes are arranged for groups G1 and G2. It becomes composition.

  Low pressure fuel is supplied from the low pressure supply system 400L of the fuel supply system shown in FIG. 1 to the fuel distribution pipes 160a and 160b, and high pressure fuel is supplied to the fuel distribution pipes 130a and 160a by the high pressure supply system 400H. Is done. Note that the low-pressure supply system 400L and the high-pressure supply system 400H may be provided independently for each bank.

  Even in such a fuel supply configuration, by applying the fuel injection control shown in the first embodiment (FIG. 2) and / or the second embodiment (FIG. 5), only one of the injectors during start-up and idling operation is used. Thus, fuel injection is performed to ensure good drivability at start-up and idling, and a sudden drop in engine output immediately after the start of use of the other injector at the time of transition to normal operation can be prevented.

  In the configuration in which the fuel distribution pipe and the fuel pipe (that is, the “fuel supply path”) are divided and arranged for each bank (each group) as described above, the arrangement position of each fuel distribution pipe and each fuel pipe is considered. Thus, the fuel injection permission in each group in the fuel injection control according to the first and second embodiments may be determined.

  For example, in the configuration example of FIG. 7, air tends to accumulate in the fuel distribution pipe and the fuel pipe on the side of the group G2 where the fuel pumping distance is relatively long. Alternatively, when engine 10 # is disposed in a slant, air is likely to accumulate in the fuel distribution pipe and the fuel pipe that are positioned relative to each other when viewed in the vertical direction.

  In these cases, the bank (that is, the group) in which air is relatively easily accumulated in the fuel distribution pipe and the fuel pipe (fuel supply path) is the target of step S240 or S240 # before the other groups. Allow fuel injection with both injectors. On the other hand, the bank (that is, the group) in which air is relatively less likely to accumulate in the fuel distribution pipe and the fuel pipe (fuel supply path) is usually the target of step S230 or S230 # from the time of engine start and idle operation. Even during a predetermined period after the initial transition to operation, fuel injection from only one injector used at the time of engine start and idle operation is permitted.

  As a result, air can be removed from the fuel distribution pipe and the fuel pipe (fuel supply path) first for the bank on which air is relatively likely to accumulate.

[Preferable DI ratio setting during normal operation]
Next, the setting of a preferable DI ratio according to the engine conditions during normal operation according to step S190 (FIGS. 2 and 5) will also be described.

  In the engine system shown in FIG. 1, when two types of injectors having different characteristics are used depending on the rotation rate and load factor of the engine 10 as described below, the engine 10 is in a normal operation state. Homogeneous combustion is mainly performed. On the other hand, when the engine 10 is in an abnormal operation state such as when the catalyst is warmed up during idling, stratified combustion is performed.

  During the homogeneous combustion operation, the fuel injection amount sharing ratio between the in-cylinder injector 110 and the intake passage injector 120 with respect to the total fuel injection amount calculated as described above is controlled as described below. The

  8 and 9 are maps for setting the fuel injection amount sharing ratio (injection ratio) between the in-cylinder injector 110 and the intake manifold injector 120 during the homogeneous combustion operation in the engine system shown in FIG. It is a figure explaining the 1st example of.

  Referring to FIGS. 8 and 9, the injection ratio of in-cylinder injector 110 and intake manifold injector 120 (hereinafter also referred to as DI ratio r), which is information corresponding to the operating state of engine 10. .) Will be described. These maps are stored in the ROM 320 of the engine ECU 300. FIG. 8 is a warm map of the engine 10, and FIG. 9 is a cold map of the engine 10.

  As shown in FIG. 8 and FIG. 9, these maps show that the share ratio of the in-cylinder injector 110 is the DI ratio, with the rotational speed of the engine (internal combustion engine) 10 as the horizontal axis and the load factor as the vertical axis. It is shown as a percentage as r.

  As shown in FIGS. 8 and 9, the DI ratio r is set for each operation region determined by the rotational speed and load factor of the engine 10. As already described, in-cylinder injector 110 generally contributes to an increase in output performance, and intake manifold injector 120 contributes to the uniformity of the air-fuel mixture. By using the two types of injectors having different characteristics depending on the rotational speed and load factor of the engine 10, homogeneous combustion is performed when the engine 10 is in a normal operation state.

  Further, as shown in FIGS. 8 and 9, the DI share ratio r of the in-cylinder injector 110 and the intake manifold injector 120 is defined by dividing it into a warm map and a cold map. did. If the temperature of the engine 10 is different, the temperature of the engine 10 is detected by detecting the temperature of the engine 10 using a map set so that the control areas of the in-cylinder injector 110 and the intake manifold injector 120 are different. If it is equal to or higher than a predetermined temperature threshold, the map at the time of warm in FIG. 8 is selected, and if not, the map at the time of cold shown in FIG. 9 is selected. Based on the selected maps, the in-cylinder injector 110 and / or the intake manifold injector 120 are controlled based on the rotation speed and load factor of the engine 10.

  The engine speed and load factor of engine 10 set in FIGS. 8 and 9 will be described. In FIG. 8, NE (1) is set to 2500 to 2700 rpm, KL (1) is set to 30 to 50%, and KL (2) is set to 60 to 90%. Further, NE (3) in FIG. 9 is set to 2900-3100 rpm. That is, NE (1) <NE (3). In addition, NE (2) in FIG. 8 and KL (3) and KL (4) in FIG. 9 are also set as appropriate.

  Comparing FIG. 8 and FIG. 9, NE (3) of the cold map shown in FIG. 9 is higher than NE (1) of the warm map shown in FIG. This indicates that as the temperature of the engine 10 is lower, the control range of the intake manifold injector 120 is expanded to a higher engine speed range. That is, since the engine 10 is in a cold state, deposits are unlikely to accumulate at the injection port of the in-cylinder injector 110 (even if fuel is not injected from the in-cylinder injector 110). For this reason, it sets so that the area | region which injects a fuel using the intake manifold injector 120 may be expanded, and a homogeneity can be improved.

8 and FIG. 9, in the region where the rotational speed of the engine 10 is NE (1) or more in the warm map and in the region where NE (3) or more in the cold map,
DI ratio r = 100% ”. Further, the load factor is “DI ratio r = 100%” in the region of KL (2) or higher in the warm map and in the region of KL (4) or higher in the cold map. This indicates that only the in-cylinder injector 110 is used in a predetermined high engine speed region, and only the in-cylinder injector 110 is used in a predetermined high engine load region. . That is, in the high speed region and the high load region, even if the fuel is injected only by the in-cylinder injector 110, the engine 10 has a high rotational speed and load, and the intake amount is large. It is because it is easy to homogenize. Thus, the fuel injected from the in-cylinder injector 110 is vaporized with latent heat of vaporization (sucking heat from the combustion chamber) in the combustion chamber. Thereby, the temperature of the air-fuel mixture at the compression end is lowered. As a result, the knocking performance is improved. Further, since the temperature of the combustion chamber is lowered, the suction efficiency is improved and high output can be expected.

  In the warm map shown in FIG. 8, only the in-cylinder injector 110 is used at a load factor KL (1) or less. This indicates that when the temperature of the engine 10 is high, only the in-cylinder injector 110 is used in a predetermined low load region. Since the engine 10 is in a warm state during the warm period, deposits are likely to accumulate at the injection port of the in-cylinder injector 110. However, since the injection port temperature can be lowered by injecting fuel using the in-cylinder injector 110, it is conceivable to avoid deposit accumulation, and the minimum fuel injection amount of the in-cylinder injector It is also conceivable that the in-cylinder injector 110 is not blocked by ensuring the above. For this reason, in this region, fuel injection using the in-cylinder injector 110 is performed.

  Comparing FIG. 8 and FIG. 9, there is an area of “DI ratio r = 0%” only in the cold map of FIG. This indicates that when the temperature of the engine 10 is low, only the intake manifold injector 120 is used in a predetermined low load region (KL (3) or less). This is because the engine 10 is cold and the load on the engine 10 is low and the intake air amount is low, so that the fuel is difficult to atomize. In such a region, it is difficult to perform good combustion with the fuel injection by the in-cylinder injector 110. In particular, a high output using the in-cylinder injector 110 is required in the region of low load and low rotation speed. Therefore, only the intake passage injector 120 is used without using the in-cylinder injector 110.

  In addition, in the case other than the normal operation, when the engine 10 is idling when the catalyst is warmed up (when the engine 10 is in a non-normal operation state), the in-cylinder injector 110 is controlled to perform stratified combustion. By causing stratified charge combustion only during such catalyst warm-up operation, catalyst warm-up is promoted and exhaust emission is improved.

  10 and 11 show a second example of the DI ratio r setting map in the engine system shown in FIG.

  The setting maps shown in FIG. 10 (during warm) and FIG. 11 (during cold) are compared with the setting maps shown in FIG. 8 and FIG. 9 and the DI ratio in the high load region in the low engine speed region. The settings are different.

  In the engine 10, in the high load region of the low engine speed region, mixing of the air-fuel mixture formed by the fuel injected from the in-cylinder injector 110 is not good, and the air-fuel mixture in the combustion chamber is not homogeneous and combustion Has a tendency to become unstable. For this reason, the injection ratio of the in-cylinder injector is increased with the shift to the high rotation speed region where such a problem does not occur. In addition, the injection ratio of the in-cylinder injector 110 is decreased as the engine shifts to a high load region where such a problem occurs. These changes in the DI ratio r are indicated by cross arrows in FIGS.

  If it does in this way, the fluctuation | variation of the output torque of an engine resulting from combustion being unstable can be suppressed. It should be noted that these things can be achieved by reducing the injection ratio of the in-cylinder injector 110 as the engine shifts to the predetermined low rotational speed region, or by the in-cylinder injection as the vehicle shifts to the predetermined low load region. The fact that it is substantially equivalent to increasing the injection ratio of the injector 110 for operation will be described. Further, areas other than such areas (areas where the crossed arrows are described in FIGS. 10 and 11) and areas where fuel is injected only by the in-cylinder injector 110 (high rotation side, low load) On the other hand, it is easy to homogenize the air-fuel mixture with the in-cylinder injector 110 alone. Thus, the fuel injected from the in-cylinder injector 110 is vaporized with latent heat of vaporization (sucking heat from the combustion chamber) in the combustion chamber. Thereby, the temperature of the air-fuel mixture at the compression end is lowered. As a result, the knocking performance is improved. Further, since the temperature of the combustion chamber is lowered, the suction efficiency is improved and high output can be expected.

  In the engine 10 described with reference to FIGS. 8 to 11, the homogeneous combustion is basically performed by setting the fuel injection timing of the in-cylinder injector 110 to the intake stroke, and the stratified combustion is performed by the in-cylinder injector. This can be realized by setting the fuel injection timing of 110 as the compression stroke. That is, by setting the fuel injection timing of the in-cylinder injector 110 as the compression stroke, stratified combustion is realized in which the rich air-fuel mixture is unevenly distributed around the spark plug and the entire combustion chamber ignites a lean air-fuel mixture. Can do. Further, even when the fuel injection timing of the in-cylinder injector 110 is set to the intake stroke, if rich air-fuel mixture can be unevenly distributed around the spark plug, stratified combustion can be realized even with the intake stroke injection.

  Further, the stratified combustion here includes both stratified combustion and weakly stratified combustion described below. In the weak stratified combustion, the intake passage injector 120 is injected with fuel in the intake stroke to produce a lean and homogeneous mixture in the entire combustion chamber, and the in-cylinder injector 110 is injected with fuel in the compression stroke. A rich air-fuel mixture is generated around the spark plug to improve the combustion state. Such weak stratified combustion is preferable when the catalyst is warmed up. This is due to the following reason. That is, it is necessary to significantly retard the ignition timing and maintain a good combustion state (idle state) in order to allow high-temperature combustion gas to reach the catalyst during catalyst warm-up. Moreover, it is necessary to supply a certain amount of fuel. Even if this is done by stratified combustion, there is a problem that the amount of fuel is small, and even if this is done by homogeneous combustion, there is a problem that the retard amount is small compared to stratified combustion in order to maintain good combustion. is there. From such a viewpoint, it is preferable to use the above-described weak stratified combustion at the time of warming up the catalyst, but either stratified combustion or weak stratified combustion may be used.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

1 is a schematic configuration diagram of an engine system controlled by an engine ECU which is a control device for an internal combustion engine according to an embodiment of the present invention. It is a flowchart explaining the fuel-injection control by Embodiment 1 of this invention. FIG. 3 is a flowchart for explaining the details of the determination of air accumulation in the delivery shown in FIG. 2. FIG. It is a wave form diagram explaining the operation example of the fuel-injection control by Embodiment 1 of this invention. It is a flowchart explaining the fuel-injection control by Embodiment 2 of this invention. It is a conceptual diagram explaining application of the present invention to an internal combustion engine provided with a plurality of cylinders arranged in a plurality of banks. It is a block diagram explaining the structural example of the fuel supply system in the internal combustion engine shown in FIG. FIG. 3 is a diagram for explaining a first example of a DI ratio setting map (when the engine is warm) during homogeneous combustion operation in the engine system shown in FIG. 1. FIG. 3 is a diagram for explaining a first example of a DI ratio setting map (when the engine is cold) during homogeneous combustion operation in the engine system shown in FIG. 1. It is a figure explaining the 2nd example of DI ratio setting map (at the time of engine warm) at the time of homogeneous combustion operation in the engine system shown in FIG. It is a figure explaining the 2nd example of DI ratio setting map (at the time of engine cold) at the time of homogeneous combustion operation in the engine system shown in FIG.

Explanation of symbols

10, 10 # engine, 20 intake manifold, 30 surge tank, 40
Intake duct, 42 Air flow meter, 50 Air cleaner, 60 Electric motor, 70
Throttle valve, 80 exhaust manifold, 90 three-way catalytic converter, 100 accelerator pedal, 110 in-cylinder injector, 112 # 1 to 112 # 6 cylinder, 120 intake manifold injector, 130, 130a, 130b Fuel distribution pipe (cylinder) Inner injection side), 140 check valve, 150 high pressure fuel pump, 152 electromagnetic spill valve, 160, 160a, 160b fuel distribution pipe (port injection side), 170 fuel pressure regulator, 180 low pressure fuel pump, 190 fuel filter, 200 fuel Tank, 300 Engine ECU, 380 Water temperature sensor, 400 Fuel pressure sensor, 400L Low pressure supply system, 400H High pressure supply system, 420 Air-fuel ratio sensor, 440 Accelerator opening sensor, 460 Rotational speed sensor, 480 Crank angle sensor, 500 Starter, 510 Flywheel, Fr traveling direction, G1, G2 group (cylinder), N1 predetermined speed (for engine start completion judgment), Ne engine speed, rDI ratio, TD output torque difference between groups, TDr reference value (intergroup output) Torque difference), TDSM output torque difference evaluation value, xdminj
Dummy injection request flag, xidl idle determination flag.

Claims (6)

A first fuel injection means for injecting fuel into the combustion chamber and a second fuel injection means for injecting fuel into the intake passage, each having a plurality of cylinders classified into a plurality of groups An internal combustion engine control device comprising:
A start period fuel injection control means for performing fuel injection selectively using only one of the first fuel injection means and the second fuel injection means in each cylinder in the start period of the internal combustion engine;
Determining means for determining at the start of the internal combustion engine whether or not air is accumulated in the first and second fuel supply systems for distributing fuel to the first and second fuel injection means, respectively; ,
When it is determined by the determination means that the air is in a accumulated state, in a predetermined period from the end of the start period, the start period fuel injection control means in some groups of the plurality of groups. First fuel injection control means for performing fuel injection using only one selected fuel injection means;
The first and second fuel injection means in the remaining group other than the partial group of the plurality of groups in the predetermined period when it is determined by the determination means that air is accumulated. And a second fuel injection control means for injecting fuel according to a fuel injection sharing ratio set based on conditions required for the internal combustion engine. An output difference estimating means for estimating an output difference between the plurality of groups;
An injection restriction releasing unit that monitors the output difference estimated by the output difference estimating unit during the predetermined period and ends the predetermined period when the output difference decreases to a predetermined value or less;
After the end of the predetermined period by the injection restriction releasing means, a third fuel injection is performed in each cylinder according to the fuel injection sharing ratio after enabling both the first and second fuel injection means. The control apparatus for an internal combustion engine according to claim 1, further comprising a fuel injection control means. The start-up period of the internal combustion engine includes the start-up time of the internal combustion engine and the idle operation time,
The start-up period fuel injection control means performs fuel injection using only the first fuel injection means when the temperature of the internal combustion engine is higher than a predetermined temperature during the start-up and the idling operation. The control apparatus for an internal combustion engine according to claim 1, wherein when the temperature of the engine is equal to or lower than a predetermined temperature, fuel injection is performed using only the second fuel injection means. The first and second fuel supply systems are provided independently for each of the plurality of groups,
The partial group controlled by the first fuel injection control means may be different in each fuel supply system that reflects a difference in arrangement positions of the first and second fuel supply systems between the plurality of groups. The control device for an internal combustion engine according to claim 1, wherein the control device is determined in consideration of easiness of air accumulation. The plurality of cylinders are divided and arranged in a plurality of rows,
The control device for an internal combustion engine according to claim 1, wherein the plurality of groups respectively correspond to the plurality of columns.   The determination means is based on at least one of a start history of the internal combustion engine in the past, a shortage of fuel pressure just before the start, and a shortage of fuel remaining just before the start. 2. The control device for an internal combustion engine according to claim 1, wherein it is determined whether or not air is accumulated in the fuel supply system.

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