JP2005325825A - Fuel injection controller for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel injection controller for an internal combustion engine capable of improving starting property of the engine even when combustion is worsened and preventing worsening of emission when starting. <P>SOLUTION: In this internal combustion engine provided with an injector 11 for injection into a cylinder and an injector 12 for injection into an intake passage, a ratio of amount of fuel injection from the injector 11 for injection into the cylinder is changed to increase more than an amount of fuel injection from the injector 12 for injection into the intake passage or the amount of fuel injection is switched to the amount of fuel injection from the injector 11 for injection into the cylinder when it is determined that combustion is worsened when starting the engine. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a fuel injection control device for an internal combustion engine, and more particularly, to an in-cylinder injector that injects fuel into a cylinder and an intake-path injector that injects fuel into an intake passage or an intake port. And a so-called dual injection internal combustion engine fuel injection control device.

  Generally, an in-cylinder injector for injecting fuel into the cylinder and an intake-path injector for injecting fuel into the intake passage or the intake port are provided according to the operating state of the engine. By switching and using these injectors, for example, stratified combustion in the low load operation region and homogeneous combustion in the high load operation region were realized, or both were used simultaneously to improve fuel consumption characteristics and output characteristics. A so-called dual injection internal combustion engine is known.

By the way, in such a dual injection type internal combustion engine, for example, a technique described in Patent Document 1 has been proposed in order to improve the startability, particularly the cold startability.
This is equipped with a main fuel injection valve that directly injects fuel into the combustion chamber and an auxiliary fuel injection valve that injects fuel into the intake passage. The fuel is temporarily injected from the fuel injection valve. When fuel is injected from the auxiliary fuel injection valve, the injection is continued until the rotational speed of the internal combustion engine exceeds the specified rotational speed. Is set higher on the low temperature side of the internal combustion engine than on the high temperature side.

JP 2001-3785 A

  However, in the technique described in Patent Document 1, at the time of starting, the injection from the auxiliary fuel injection valve is continued until the rotational speed of the internal combustion engine exceeds the specified rotational speed. Since the injection is performed in the intake passage, when the fuel used is heavy fuel, the vaporization is not sufficiently performed, and the startability may not be improved so much. That is, since the heavy fuel injected into the intake passage has poor volatility, the fuel adhering to the wall surface of the intake passage increases and the air-fuel ratio becomes lean. As a result, combustion may worsen and misfire may occur. It is.

  Further, the cause of the deterioration of the combustion at the start is considered to be a shortage of the amount of fuel supplied to the cylinder due to deposit wall deposition, injector clogging, and the like accompanying engine aging.

  Accordingly, an object of the present invention is to improve engine startability even when heavy fuel is used or when combustion deterioration due to deposit wall deposition occurs, and to cause emission deterioration at start-up. It is an object of the present invention to provide a fuel injection control device for an internal combustion engine.

  A fuel injection control device for an internal combustion engine according to an aspect of the present invention that achieves the above object is an internal combustion engine that includes an in-cylinder injector and an intake manifold injector, and combustion deterioration of the engine during a predetermined period when the engine is started. When is detected, the fuel injection amount ratio from the in-cylinder injector is changed so as to increase.

  Here, the deterioration in combustion may be detected by a fluctuation in the rotation of the engine during a predetermined period when the engine is started.

  Further, the deterioration of combustion may be detected by a change in in-cylinder pressure in a predetermined period when the engine is started.

  Further, the ratio of the fuel injection amount from the in-cylinder injector to the fuel injection amount from the intake passage injector may be 0 to 100%.

  According to the fuel injection control device for an internal combustion engine according to one aspect of the present invention, in an internal combustion engine including an in-cylinder injector and an intake manifold injector, combustion deterioration of the engine is detected in a predetermined period when the engine is started. Sometimes, the ratio of the fuel injection amount from the in-cylinder injector is changed to be larger than the fuel injection amount from the intake passage injector, so that the volatility is low when the fuel used is heavy fuel. The amount of heavy fuel adhering to the wall surface of the intake passage is reduced, and at the same time, misfire due to lean air-fuel ratio is suppressed by the in-cylinder injected fuel that is injected at an increased ratio. Further, even in the case of deterioration of combustion due to deposit wall surface adhesion, injector clogging, or the like, fuel in the cylinder is secured, and misfire due to lean air-fuel ratio is suppressed. Thus, it is possible to suppress the deterioration of the emission at the start.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
First, referring to FIG. 1 showing a schematic configuration of a fuel injection control device for a dual injection internal combustion engine according to the present invention, the engine 1 includes four cylinders 1a. Each cylinder 1 a is connected to a common surge tank 3 via a corresponding intake branch pipe 2. The surge tank 3 is connected to an air flow meter 4 a through an intake duct 4, and the air flow meter 4 a is connected to an air cleaner 5. A throttle valve 7 driven by an electric motor 6 is disposed in the intake duct 4. The throttle valve 7 is closed to some extent only when the engine load is extremely low, and is kept fully open when the engine load is slightly increased. On the other hand, each cylinder 1 a is connected to a common exhaust manifold 8, and this exhaust manifold 8 is connected to a three-way catalytic converter 9.

  Each cylinder 1a is provided with an in-cylinder injector 11 for injecting fuel into the cylinder and an intake passage injector 12 for injecting fuel into the intake port or intake passage. ing. These injectors 11 and 12 are controlled based on the output signal of the electronic control unit 30. Further, each in-cylinder injector 11 is connected to a common fuel distribution pipe 13, and this fuel distribution pipe 13 is connected to a fuel distribution pipe 13 through a check valve 14, and is driven by an engine drive type. A high-pressure fuel pump 15 is connected.

  As shown in FIG. 1, the discharge side of the high-pressure fuel pump 15 is connected to the suction side of the high-pressure fuel pump 15 via a spill electromagnetic valve 15a. When the amount of fuel supplied from the pump 15 into the fuel distribution pipe 13 is increased and the spill electromagnetic valve 15a is fully opened, the fuel supply from the high pressure fuel pump 15 to the fuel distribution pipe 13 is stopped. ing. The spill electromagnetic valve 15a is controlled based on the output signal of the electronic control unit 30.

  On the other hand, each intake passage injector 12 is connected to a common fuel distribution pipe 16, and the fuel distribution pipe 16 and the high pressure fuel pump 15 are connected to a common fuel pressure regulator 17 through an electric motor drive type low pressure fuel pump. 18 is connected. Further, the low pressure fuel pump 18 is connected to the fuel tank 20 via the fuel filter 19. The fuel pressure regulator 17 returns a part of the fuel discharged from the low-pressure fuel pump 18 to the fuel tank 20 when the fuel pressure of the fuel discharged from the low-pressure fuel pump 18 becomes higher than a predetermined set fuel pressure. Accordingly, the fuel pressure supplied to the intake manifold injector 12 and the fuel pressure supplied to the high-pressure fuel pump 15 are prevented from becoming higher than the set fuel pressure. Further, as shown in FIG. 1, a flow valve 21 is provided between the high pressure fuel pump 15 and the fuel pressure regulator 17. The flow valve 21 is normally opened. When the flow valve 21 is closed, the fuel supply from the low pressure fuel pump 18 to the high pressure fuel pump 15 is stopped. The opening / closing of the flow valve 21 is controlled based on the output signal of the electronic control unit 30.

  The electronic control unit 30 is composed of a digital computer and includes a ROM (Read Only Memory) 32, a RAM (Random Access Memory) 33, a CPU (Microprocessor) 34, and an input port which are connected to each other via a bidirectional bus 31. 35 and an output port 36. The air flow meter 4 a generates an output voltage proportional to the amount of intake air, and the output voltage of the air flow meter 4 a is input to the input port 35 via the AD converter 37. A water temperature sensor 38 that generates an output voltage proportional to the engine cooling water temperature is attached to the engine 1, and the output voltage of the water temperature sensor 38 is input to the input port 35 via the AD converter 39.

  A fuel pressure sensor 40 that generates an output voltage proportional to the fuel pressure in the fuel distribution pipe 13 is attached to the fuel distribution pipe 13, and the output voltage of the fuel pressure sensor 40 is supplied to the input port 35 via the AD converter 41. Entered. An oxygen concentration sensor 42 that generates an output voltage proportional to the oxygen concentration in the exhaust gas is attached to the exhaust manifold 8 upstream of the catalyst 9. The output voltage of the oxygen concentration sensor 42 is input to an input port 35 via an AD converter 43. Is input. The accelerator pedal 10 is connected to an accelerator opening sensor 44 that generates an output voltage proportional to the depression amount of the accelerator pedal 10, and the output voltage of the accelerator opening sensor 44 is input to the input port 35 via the AD converter 45. . The input port 35 is connected to a rotational speed sensor 46 that generates an output pulse representing the engine rotational speed. Further, a starter switch 49 for detecting a starter on / off signal is connected to the input port 35. In the ROM 32 of the electronic control unit 30, the value of the fuel injection amount set corresponding to the operating state based on the engine load factor and the engine speed obtained by the accelerator opening sensor 44 and the engine speed sensor 46 described above, Correction values and the like based on the engine cooling water temperature are mapped and stored in advance.

  Furthermore, FIG. 2 shows a side sectional view of the cylinder 1a. Referring to FIG. 2, 61 is a cylinder block, 62 is a piston having a recess 62a formed on the top surface, 63 is a cylinder head secured on the cylinder block 61, and 64 is between the piston 62 and the cylinder head 63. The formed combustion chamber, 65 is an intake valve, 66 is an exhaust valve, 67 is an intake port, 68 is an exhaust port, and 69 is an ignition plug. The intake port 67 is formed so that the air flowing into the combustion chamber 64 generates a swirling flow around the cylinder axis. The recess 62 a extends from the peripheral edge of the piston 62 located on the in-cylinder injector 11 side toward the center of the piston 62 and extends upward below the spark plug 69.

  The intake valve 65 and the exhaust valve 66 are linked to an intake valve drive mechanism 70 and an exhaust valve drive mechanism 71, respectively. The intake valve driving mechanism 70 and the exhaust valve driving mechanism 71 use an electromagnetic force generated when a driving force or an excitation current by a normal cam and a hydraulic control mechanism is applied, respectively, and an intake valve 65 and an exhaust valve, respectively. 66, and a mechanical or electromagnetic drive mechanism that drives forward and backward, and based on a signal from the electronic control unit 30, the opening / closing timing and the lift amount can be arbitrarily controlled. Therefore, for example, when the intake valve drive mechanism 70 and / or the exhaust valve drive mechanism 71 are operated based on a signal from the electronic control unit 30, the opening / closing timing of the intake valve 65 and / or the intake valve 65, and thus the open period. Is variably controlled to be long or short.

  Here, the output port 36 of the electronic control unit 30 is connected to the electric motor 6, each in-cylinder injector 11, each intake passage injector 12, the spill solenoid valve 15 a, the flow valve 21, via a corresponding drive circuit 47. The intake valve drive mechanism 70 and the exhaust valve drive mechanism 71 are connected.

  Next, fuel injection control at the time of engine start according to the first embodiment of the present invention having the above-described configuration will be described below with reference to a flowchart shown in FIG. First, when control is started by turning on an accessory switch (not shown), the electric motor driven low-pressure fuel pump 18 is started to drive, the flow valve 21 is opened, and the spill electromagnetic valve 15a is kept closed. Therefore, when the starter switch 49 is turned on and cranking of the engine 1 is started, in the first embodiment, the intake passage or in-port injection by the intake passage injection injector 12 is executed.

  Then, whether or not the engine 1 is being started is determined by the determination in step S31 in the starting fuel injection control routine. Here, whether or not the engine is being started is determined by determining whether the elapsed time or the period t after the time t1 when the rotational speed Ne of the engine 1 exceeds the predetermined value Ne1 and the rotational speed Ne exceeds the predetermined value Ne1 is predetermined. This is done depending on whether the value ts has been exceeded. The predetermined value Ne1 of the rotational speed is Ne1 = 300 to 400 rpm as a guideline that the complete explosion has been performed, and the predetermined value ts of the elapsed time is ts = 1 to 1 as the rotational speed increase period after the complete explosion. It can be 5 seconds. Then, when the engine is starting at the determination in step S31, that is, "Yes", the process proceeds to step S32, and various parameters indicating the operation state are input. The parameters include the cooling water temperature T of the engine 1 that is a detected value from the water temperature sensor 38, the rotational speed Ne that is a calculated value from the rotational speed sensor 46, and the elapsed time t after the above-mentioned complete explosion. it can. Further, in step S33, it is determined whether or not the fuel being used is a heavy fuel as a cause of deterioration in combustion. Here, whether or not the fuel is heavy fuel is determined as follows.

  In general, how the rotational speed Ne changes when the engine is started is as shown in the time chart of FIG. Here, t0 is the cranking start time, t1 is the time when the complete explosion is performed and the engine speed Ne reaches the above-mentioned predetermined value Ne1, and t2 is the time after the completion of the predetermined time or period ts after the complete explosion. Represents each. In FIG. 4, the fluctuation of the rotational speed Ne in the case of a fuel having a normal volatility is indicated by a solid line, and the case of a heavy fuel having a low volatility is indicated by a broken line. As can be seen from FIG. 4, in the case of normal fuel, after the rotational speed Ne reaches the predetermined value Ne1 due to complete explosion, the engine rotational speed Ne reaches a specified rotational speed Ne2 (for example, Ne2 = 1000 rpm). It rises smoothly. On the other hand, in the case of heavy fuel, the rotational speed Ne fluctuates up and down even within a predetermined time ts after reaching the predetermined value Ne1.

  Therefore, in the first embodiment of the present invention, using this phenomenon, the combustion caused by the heavy fuel is determined in step S33 depending on whether or not fluctuations in the rotational speed Ne occur within a predetermined time ts. A determination is made as to whether the condition is worse. Specifically, by comparing the rotational speed Ne obtained in the previous control routine cycle with the rotational speed Ne obtained in the current control routine cycle, the state of the fluctuation is grasped and a determination is made based thereon. . If it is determined in step S33 above that the combustion is caused by heavy fuel, that is, "Yes", the process proceeds to step S34, and the injection ratio is calculated.

  Specifically, the fuel injection amount and the injection ratio, which are obtained in advance by experiments or the like from the engine operating state based on the engine load factor and the engine speed and are mapped and stored in the ROM 32, are obtained. In other words, the fuel injection amount injected into the in-cylinder combustion chamber 64 by the in-cylinder injector 11 and the fuel injection amount injected into the intake passage or port by the intake passage injector 12 are respectively in accordance with the injection ratio. It is required. Then, the process proceeds to step S35, and the injection into the combustion chamber 64 and the intake passage injection injector 12 (in-cylinder INJ in FIG. 3) is performed under the above-described injection ratio (indicated in-cylinder INJ in FIG. 3). In FIG. 3, the intake passage or port injection at the port INJ) is executed simultaneously.

  Further, when it is determined that the engine is not starting at the determination in step S31 described above and when it is determined that the combustion is not deteriorated due to heavy fuel in the determination at step S33, the process proceeds to step S36, and the intake manifold injector “Exportex”, which is an injection execution flag by No. 12, is turned on, and 100% intake passage or port injection by the intake passage injection injector 12 in the next step S37 is continuously executed.

  According to the present embodiment where the deterioration of combustion is caused by heavy fuel, the ratio of the amount of heavy fuel with low volatility attached to the wall of the intake passage is reduced, and at the same time, the ratio is increased and the cylinder is injected. The misfire due to the lean air-fuel ratio is suppressed by the internal injection fuel. Moreover, since the necessity of fuel increase in anticipation of low volatility can be reduced, it is possible to suppress the deterioration of emission at the time of starting. This injection ratio may be changed according to the cooling water temperature T. For example, the lower the cooling water temperature T, the higher the injection ratio from the in-cylinder injector 11 compared to the intake passage injection injector 12. Also good.

  Next, fuel injection control at the time of engine start according to the second embodiment of the present invention will be described with reference to a flowchart shown in FIG. Also in the second embodiment, when the starter switch 49 is turned on and cranking of the engine 1 is started, the intake passage or in-port injection by the intake passage injection injector 12 is executed. It is the same.

  Further, in the starting fuel injection control routine, it is determined whether or not the engine 1 is being started in step S51, input of various parameters indicating the operating state in step S52, and whether or not the combustion is deteriorated in step S53. This determination is the same as step S31 to step S33 in the first embodiment described above, and therefore a duplicate description is avoided.

  Therefore, if it is determined in step S53 that the combustion is caused by heavy fuel, that is, if "Yes", the process proceeds to step S54, where "exportex" is an injection execution flag by the intake passage injector 12. "Is turned off, and the process proceeds to step S55, where" exdiex ", which is an injection execution flag by the in-cylinder injector 11, is turned on. In the next step S56, 100% in-cylinder injection by the in-cylinder injector 11 is executed. In other words, in the case of deterioration of combustion caused by heavy fuel, the intake passage or port injection is switched to in-cylinder injection. If it is determined in step S51 that the engine is not starting, or if it is determined in step S53 that the combustion is not deteriorated due to heavy fuel, the process proceeds to step S57, where the intake passage injection injector 12 As in the previous embodiment, “exportex”, which is an injection execution flag, is turned on, and 100% intake passage or port injection is continuously executed by the intake passage injection injector 12 in the next step S58. is there.

  The above-described start time fuel injection control of the present invention will be further described with reference to a time chart shown in FIG. First, as described above, when the accessory switch is turned on, the electric motor driven low-pressure fuel pump 18 is started to drive, and the fuel pressure P1 is generated in the fuel distribution pipes 13 and 16. Thus, when the starter switch 49 is turned on and cranking by the starter is performed at time t0, and the starter signal is input at the same time, the port INJ injection by the intake passage injector 12 is performed. Then, due to a complete explosion in a certain cylinder, the rotational speed Ne reaches a predetermined value Ne1 at time t1. Therefore, if it is determined that the combustion is deteriorated due to heavy fuel at time tx based on the vertical fluctuation of the rotational speed Ne within the predetermined time ts after reaching the predetermined value Ne1, the port INJ injection is prohibited, In-cylinder INJ injection is executed. As a result, the rotational speed Ne stabilizes without up and down fluctuations as indicated by the thick line.

  In the second embodiment, the low-volatility heavy fuel does not adhere to the intake passage wall surface, and the in-cylinder injected fuel that is injected in its entirety suppresses misfiring due to the lean air-fuel ratio. . Moreover, since the necessity of fuel increase in anticipation of low volatility can be reduced, it is possible to suppress the deterioration of emission at the time of starting.

  Next, in addition to the determination of whether or not the fuel is a heavy fuel as a cause of combustion deterioration in the first and second embodiments described above, it is possible to determine or determine combustion deterioration caused by deposit wall surface adhesion, etc. This procedure will be further described with reference to FIG. 7 and subsequent drawings as third to fifth embodiments.

  Therefore, in the combustion deterioration determination routine as the third embodiment shown in the flowchart of FIG. 7, in the case of a four-cylinder engine, a predetermined angle from the top dead center (for example, a crank angle is displayed as 30 °, hereinafter 30 ° CA). Time required for rotation (for example, when the predetermined angle is 30 °, this is referred to as 30 ° CA time) and time required to rotate the angle corresponding to the predetermined angle at 180 ° before top dead center The rotation fluctuation ΔT is obtained from the difference between the two and the combustion deterioration is determined based on whether or not the rotation fluctuation ΔT exceeds a predetermined value. The worse the combustion, the longer the 30 ° CA time. In the flowchart of FIG. 7, the predetermined angle is 30 °.

  Therefore, in this combustion deterioration determination routine, in step S71, it is determined whether or not the crank angle is at the 30 ° CA timing position set every 30 ° from the reference angle position. If “No”, this routine is terminated. On the other hand, if “Yes”, the process proceeds to step S72, where the 30 ° CA time T30, which is the time required for the 30 ° CA rotation, subtracts the previous 30 ° CA time from the current 30 ° CA time. Is required. Then, in the next step S73, it is determined whether or not it is at the 30 ° CA timing position after the top dead center. If not, that is, if “No”, this routine is ended. On the other hand, if “Yes”, the process proceeds to step S74, and the change amount ΔT of the 30 ° CA time T30 is obtained by subtracting the previous 30 ° CA time T30old from the current 30 ° CA time T30. Further, in step S75, the current 30 ° CA time T30 is stored as the previous 30 ° CA time T30old, and then the process proceeds to step S76 to determine whether or not a predetermined time has elapsed after a certain delay time after the complete explosion. If it is determined and has elapsed, that is, if “Yes”, this routine is terminated. On the other hand, if “No”, the process proceeds to step S77 to determine whether or not the engine 1 is in the idling operation state, and when not in the idling operation state, that is, “No”, this routine is ended. When the engine is in an idling state, ie, “Yes”, the process proceeds to step S78, where it is determined whether or not the change amount ΔT of the 30 ° CA time T30 obtained in step S74 exceeds a predetermined value. That is, if “No”, this routine is terminated. When the amount of change ΔT exceeds a predetermined value, that is, “Yes”, the process proceeds to step S79, where it is determined that the combustion has deteriorated, the combustion deterioration flag “exnerough” is turned on, and the routine is ended.

  This combustion deterioration determination routine corresponds to the determination routine as to whether or not the combustion deterioration is caused by the heavy fuel in steps S33 and S53 in the first and second embodiments described above, and when it is determined that the combustion deterioration has occurred. As in the first and second embodiments, the ratio of the fuel injection amount from the in-cylinder injector is changed or the intake passage or port injection is switched to in-cylinder injection. .

  Next, in the same manner as the combustion deterioration determination routine due to rotation fluctuation in the third embodiment described above, another procedure that can determine or determine combustion deterioration by rotation fluctuation will be described as a fourth embodiment with reference to FIG. To do.

  Therefore, in the combustion deterioration determination routine as the fourth embodiment shown in the flowchart of FIG. 8A, the target rotational speed deviation “DLNT” is calculated from the difference between the target rotational speed and the current rotational speed. Combustion deterioration is determined based on whether or not the deviation amount exceeds a predetermined value. The target rotational speed deviation “DLNT” increases as the combustion deteriorates.

  Therefore, in this combustion deterioration determination routine, in step S81, the cooling water temperature of the engine 1 is detected from the water temperature sensor 38, and the target rotational speed NT is obtained from a map or the like based on this cooling water temperature. Then, in step S82, it is determined whether or not a predetermined time has elapsed after a certain delay time after the complete explosion. If it has elapsed, that is, if "Yes", this routine is terminated. On the other hand, if “No”, the process proceeds to step S83 to determine whether or not the engine 1 is in the idling operation state, and when not in the idling operation state, ie, “No”, this routine is ended. When the engine is in an idling state, ie, “Yes”, the process proceeds to step S84, and the target rotational speed deviation “DLNT” is calculated based on the difference between the target rotational speed NT obtained in step S81 and the current rotational speed NE. Calculated. Next, in step S85, it is determined whether or not the target rotational speed deviation “DLNT” exceeds a predetermined value. If not, that is, if “No”, this routine is terminated. When the target rotational speed deviation “DLNT” exceeds a predetermined value, that is, “Yes”, the routine proceeds to step S86 where it is determined that the combustion has deteriorated, the combustion deterioration flag “exnerough” is turned on, and the routine is ended. . A mode of determination based on the above-described target rotational speed deviation “DLNT” is shown in the time chart of FIG.

  The combustion deterioration determination routine based on the target rotational speed deviation “DLNT” corresponds to the determination routine as to whether or not the fuel is heavy fuel in steps S33 and S53 in the first and second embodiments described above. When it is determined that the combustion has deteriorated, the ratio of the fuel injection amount from the in-cylinder injector is increased or the intake passage or the in-port injection is performed, as in the first and second embodiments. Switching from in-cylinder injection is the same as in the third embodiment.

  Further, a combustion deterioration determination routine as the fifth embodiment will be described with reference to a flowchart of FIG. In this combustion deterioration determination routine, a cylinder pressure due to combustion is detected using a cylinder pressure sensor (not shown), and a cylinder in a predetermined crank angle section (for example, a section of 30 ° CA from the top dead center) by the previous and current ignitions. The pressure fluctuation ΔP is calculated from the change amount of the internal pressure maximum value Pmax, and the deterioration of combustion is determined based on whether or not the pressure fluctuation ΔP exceeds a predetermined value. As the combustion worsens, the in-cylinder pressure maximum value Pmax decreases, and the generation position of the in-cylinder pressure maximum value Pmax changes to the delay side.

  Therefore, in the combustion deterioration determination routine based on the pressure fluctuation ΔP, the cylinder pressure Pcyl is measured and read by a cylinder pressure sensor (not shown) in step S901. Then, in the next step S902, it is determined whether or not the crank position is between 30 ° CA after top dead center and if not, that is, if “No”, this routine is terminated. To do. On the other hand, if "Yes", the process proceeds to step S903, and the in-cylinder pressure Pcyl read in step S901 is compared with a previous value of a later-described in-cylinder pressure maximum value Pmax. If the current in-cylinder pressure Pcyl is not greater than the previous value of the in-cylinder pressure maximum value Pmax, that is, if “No”, this routine is terminated. On the other hand, if "Yes", the process proceeds to step S904, and the current in-cylinder pressure Pcyl is set as the current in-cylinder pressure maximum value Pmax. In step S905, it is determined whether or not the crank position is at the 30 ° CA timing position after top dead center. If the crank position is not at that position, that is, if “No”, this routine is terminated. On the other hand, if “Yes”, the process proceeds to step S906, and the pressure fluctuation ΔP is obtained by subtracting the previous in-cylinder pressure maximum value Pmax from the current in-cylinder pressure maximum value Pmax.

  In the next step S907, the current in-cylinder pressure maximum value Pmax is stored as the previous in-cylinder pressure maximum value Pmax, and then the process proceeds to step S908, where a predetermined time has elapsed after a certain delay time after the complete explosion. This routine is terminated when the time elapses, i.e., "Yes". On the other hand, if “No”, the process proceeds to step S909 to determine whether or not the engine 1 is in the idling operation state, and when not in the idling operation state, ie, “No”, this routine is terminated. When the engine is in an idle operation state, ie, “Yes”, the process proceeds to step S910, where it is determined whether or not the pressure fluctuation ΔP obtained in step S906 exceeds a predetermined value. If this is the case, this routine is terminated. When the pressure fluctuation ΔP exceeds a predetermined value, ie, “Yes”, the process proceeds to step S911, where it is determined that the combustion has deteriorated, and the combustion deterioration flag “exnerough” is turned on, and the routine is ended.

  The combustion deterioration determination routine based on the pressure fluctuation ΔP corresponds to the determination routine as to whether or not the combustion deterioration is caused by heavy fuel in steps S33 and S53 in the first and second embodiments described above. When it is determined that the combustion has deteriorated, the ratio of the fuel injection amount from the in-cylinder injector is increased or the intake passage or the in-port injection is performed, as in the first and second embodiments. Switching from in-cylinder injection is the same as in the third and fourth embodiments described above.

  A mode of combustion deterioration determination based on the pressure fluctuation ΔP described above is shown in the time chart of FIG. When the combustion is normal, the in-cylinder pressure maximum value Pmax appears between 30 ° CA and the top dead center, while the in-cylinder pressure maximum value Pmax decreases and decreases when the combustion deteriorates. It will be understood that the position changes to the lag side.

  Needless to say, the control according to the present invention is not limited to a four-cylinder engine, and can be performed by a multi-cylinder engine having more cylinders.

1 is a schematic diagram showing a schematic configuration diagram of a fuel injection control device for a dual injection internal combustion engine according to the present invention. It is a sectional side view of the engine shown in FIG. It is a flowchart which shows an example of the fuel injection control routine at the time of start in the 1st Embodiment of this invention. It is a time chart which shows the mode of the rotation speed Ne at the time of engine starting. It is a flowchart which shows an example of the fuel injection control routine at the time of start in the 2nd Embodiment of this invention. It is a time chart which shows the relationship between the form of control in the 2nd Embodiment of this invention, and engine speed Ne. It is a flowchart which shows an example of the combustion deterioration determination routine in the 3rd Embodiment of this invention. (A) is a flowchart which shows an example of the combustion deterioration determination routine in the 4th Embodiment of this invention, (B) is a time chart which shows the aspect of the determination. It is a flowchart which shows an example of the combustion deterioration determination routine in the 5th Embodiment of this invention. It is a time chart which shows the aspect of the combustion deterioration determination in the 5th Embodiment of this invention.

Explanation of symbols

11 In-cylinder injector 12 Intake passage injector 30 Electronic control unit 44 Accelerator opening sensor (load sensor)
46 Rotational speed sensor 49 Starter switch

Claims (4)

In an internal combustion engine comprising an in-cylinder injector and an intake manifold injector,
A fuel injection control device for an internal combustion engine, wherein the ratio of the fuel injection amount from the in-cylinder injector is changed so as to increase when combustion deterioration of the engine is detected in a predetermined period when the engine is started.   2. The fuel injection control device for an internal combustion engine according to claim 1, wherein the deterioration of combustion is detected by engine rotational fluctuation in a predetermined period when the engine is started.   2. The fuel injection control device for an internal combustion engine according to claim 1, wherein the deterioration of combustion is detected by a change in in-cylinder pressure during a predetermined period when the engine is started. 4. The internal combustion engine according to claim 1, wherein the ratio of the fuel injection amount from the in-cylinder injector to the fuel injection amount from the intake passage injector is 0 to 100%. 5. Fuel injection control device.

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