JP4974777B2 - Control device for internal combustion engine - Google Patents

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, an intake passage and / or an intake port. The present invention relates to a control device for an internal combustion engine including second fuel injection means (intake passage injection injector) for injecting fuel.

  In an internal combustion engine having an in-cylinder injector that injects fuel directly into the combustion chamber and an intake passage injector that injects fuel into the intake passage and / or the intake port of the cylinder, the intake passage injector When the internal combustion engine is operated only by fuel injection, the in-cylinder injector is always exposed to high-temperature combustion gas, so that the tip of the in-cylinder injector is maintained at a high temperature and deposited in its injection hole or needle. Tends to accumulate.

  If the deposit accumulation amount in the injection hole increases, the fuel spray shape change from the in-cylinder injector, the decrease in the fuel injection amount, etc. will be caused, and the output characteristics of the internal combustion engine will become unstable due to the deterioration of combustibility There is a possibility to make it.

  In order to cope with such a problem, in Japanese Patent Laid-Open No. 2002-364409 (Patent Document 1), in addition to the fuel injection by the intake port injection injector during the homogeneous combustion operation, the fuel injection by the in-cylinder injector is combined. A control configuration to perform is disclosed. Thereby, fuel injection from the in-cylinder injector can be secured, and the injector can be prevented from being maintained at a high temperature.

  Japanese Patent Laying-Open No. 2005-120852 (Patent Document 2) describes an operating state of an internal combustion engine in an internal combustion engine that is used by switching an intake port injector and an in-cylinder injector according to an operating state. A control configuration for forcibly using an in-cylinder injector even in the port injection region is disclosed. Thus, by increasing the frequency of fuel injection from the in-cylinder injector as much as possible, the frequency of removing deposits attached to the injection holes by fuel injection can be increased.

Further, in Japanese Patent Laid-Open No. 2006-132396 (Patent Document 3), based on the estimation of the tip temperature of the in-cylinder injector, when the in-cylinder injector is in a high temperature state, the fuel pressure reaches a predetermined pressure. A control configuration for forcibly injecting at least a part of the total fuel injection amount from the in-cylinder injector is disclosed. Thereby, the deposit accumulation by the temperature rise of the front-end | tip part of the in-cylinder injector can be suppressed.
JP 2002-364409 A JP 2005-120852 A JP 2006-132396 A

  In the internal combustion engine provided with both the intake passage injector and the in-cylinder injector, the technology disclosed in Patent Documents 1 to 3 increases the chance of fuel injection from the in-cylinder injector. It is intended to prevent deposits on the surface.

  However, there is a possibility that the deposit once accumulated cannot be sufficiently removed only by increasing the fuel injection opportunity from the in-cylinder injector. As a result, the accumulated amount of deposit increases cumulatively as the internal combustion engine is operated for a long time, so that the fuel injection amount exceeding the range that can be compensated by the fuel injection amount correction based on the feedback of the air-fuel ratio detection value. There may be a shortage. When such a phenomenon occurs, the air-fuel ratio in the combustion chamber cannot be maintained properly, and there is a concern about the occurrence of combustion fluctuations and the deterioration of emissions.

  Further, when the fuel injection by the in-cylinder injector is required for a relatively long time in order to suppress the deposit in the operation state where the operation by only the intake passage injection is preferable, the fuel injection by only the intake passage injection injector can be executed. There is concern that the period will be greatly limited.

  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 a cylinder and an intake air. In-cylinder injector from fuel injection only by intake passage injection injector in internal combustion engine having second fuel injection means (intake passage injection injector) for injecting fuel into passage and / or intake port Is to suppress the deterioration of the performance of the internal combustion engine due to the increase in the accumulated amount of deposit by enhancing the deposit peeling effect immediately after switching to the fuel injection using.

  An internal combustion engine control apparatus according to the present invention comprises a first fuel injection means for injecting fuel into a cylinder and a second fuel injection means for injecting fuel into an intake passage. The fuel injection sharing control means, the first in-cylinder injection condition setting means, and the second in-cylinder injection condition setting means are provided. The fuel injection sharing control unit controls the fuel injection amount sharing between the first and second fuel injection units with respect to the total fuel injection amount based on the operating state of the internal combustion engine. The first in-cylinder injection condition setting means is configured such that the fuel injection share is controlled by the fuel injection share control means from the first mode in which the total fuel injection quantity is injected by the second fuel injection means. When at least a part is switched to the second mode in which the fuel is injected by the first fuel injection means, the fuel injection condition of the first fuel injection means in the first period from the switching time is set. The second in-cylinder injection condition setting unit is in the second mode and sets the fuel injection condition of the first fuel injection unit after the end of the first period. In particular, the first in-cylinder injection condition setting means has an effect of removing deposits accumulated in the first fuel injection means, at least one of the injection pressure from the first fuel injection means and the number of injections per cycle. A value different from the set value by the second in-cylinder injection condition setting means is set so as to be relatively increased.

  For example, the first in-cylinder injection condition setting unit sets the injection pressure from the first fuel injection unit to be higher than that of the second in-cylinder injection condition setting unit. Alternatively, the first in-cylinder injection condition setting unit sets a larger number of injections per cycle from the first fuel injection unit than the second in-cylinder injection condition setting unit.

  According to the control apparatus for an internal combustion engine, the fuel injection from only the second fuel injection means (intake passage injection injector) is changed to the in-cylinder injection using the first fuel injection means (in-cylinder injection injector). In the initial period (first period) immediately after switching, the in-cylinder injection condition is set to a specific condition that has a higher deposit peeling effect than the normal time. For example, the deposit removal effect accumulated in the first fuel injection means can be enhanced by increasing the number of injections per cycle or increasing the injection pressure as compared with the normal condition. As a result, even if the internal combustion engine is operated for a long time, it is possible to suppress the cumulative increase in the deposit accumulation amount, so the performance of the internal combustion engine, such as the occurrence of combustion fluctuations due to the increase in the deposit accumulation amount and the deterioration of emissions, etc. Reduction can be suppressed.

  In addition, since the in-cylinder injection period required for deposit removal can be shortened, a longer period during which fuel injection can be executed only by the second fuel injection means is ensured in an operating state where operation by only intake passage injection is preferable. can do.

  Preferably, the first in-cylinder injection condition setting unit sets the number of injections per cycle based on the minimum fuel injection amount from the first fuel injection unit.

  With such a configuration, a large error occurs in the fuel injection amount from the first fuel injection means (in-cylinder injector) in the initial period (first period) for enhancing the deposit isolation effect. The number of injections per cycle can be set to the maximum without causing it to occur.

  Further preferably, the injection sharing control means sets the fuel injection ratio from the first fuel injection means to the total fuel injection amount in the first period after the end of the first period corresponding to the same operating state. Set higher than the fuel injection ratio to be performed. Alternatively, the injection sharing control unit sets the fuel injection amount sharing so that the total fuel injection amount is injected from the first fuel injection unit in the first period.

  By adopting such a configuration, in the initial period (first period) for enhancing the deposit peeling effect, the fuel injection ratio from the first fuel injection means (in-cylinder injector) is set to be higher than normal. By relatively increasing it, it is possible to easily increase the number of injections per cycle, and to enhance the deposit peeling effect of the first fuel injection means.

  Alternatively, preferably, the control device further includes deposit accumulation amount estimation means. The deposit accumulation amount estimation means estimates the deposit accumulation amount of the first fuel injection means based on the mode of the internal combustion engine during the period in which the fuel injection amount sharing is in the first mode. The fuel injection sharing control means performs the first fuel injection amount sharing in response to the estimated deposit accumulated amount by the deposit accumulated amount estimating means being greater than or equal to a predetermined value when the fuel injection amount sharing is in the first mode. The mode is switched from the second mode to the second mode.

  More preferably, the deposit accumulation amount estimation means includes the tip temperature of the first fuel injection means estimated by at least part of the rotational speed of the internal combustion engine, the load and the coolant temperature, and the first mode after the start of the first mode. Based on the elapsed time, an estimated deposit accumulation amount is calculated.

  By adopting such a configuration, the deposit accumulation of the first fuel injection means (in-cylinder injector) is performed during the period in which the fuel injection is performed only by the second fuel injection means (intake passage injection injector). In response to the estimated amount being equal to or greater than the predetermined value, it is possible to forcibly switch to in-cylinder injection using the first fuel injection means (in-cylinder injector). Thereby, the deposit removal amount accumulated in the first fuel injection means can be enhanced while reliably preventing the accumulated amount of the deposit from exceeding a predetermined value.

  Preferably, the control device further includes deposit peeling amount estimation means. The deposit peeling amount estimation means calculates the deposit peeling amount from the first fuel injection means based on at least one of the injection pressure from the first fuel injection means and the number of injections per cycle during the first period. presume. The first period ends based on the estimated deposit peeling amount by the deposit peeling amount estimating means. Alternatively, in the first period, the value obtained by subtracting the estimated deposit peeling amount by the deposit peeling amount estimating means from the estimated deposit cumulative amount at the time of switching from the first mode to the second mode is equal to or less than a predetermined value. Is finished.

  By setting it as such a structure, it can be made to complete | finish appropriately, without setting the period (1st period) to which the in-cylinder injection condition is set to the specific conditions different from normal time too long.

  According to the control apparatus for an internal combustion engine according to the present invention, deposit accumulation is enhanced by enhancing the deposit peeling effect in a certain period immediately after switching from fuel injection using only the intake manifold injector to fuel injection using the in-cylinder injector. It is to suppress the performance deterioration of the internal combustion engine due to the increase in the amount.

  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]
(Engine configuration)
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 Embodiment 1 of the present invention. FIG. 1 shows an in-line four-cylinder gasoline engine as the engine, but the present invention is not limited to such an engine.

  As shown in FIG. 1, the engine (internal combustion engine) 10 includes four cylinders 112, and each cylinder 112 is connected to a common surge tank 30 via a corresponding intake manifold. 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.

  FIG. 2 is a configuration diagram of an engine showing one of the four cylinders 112 shown in FIG. 1 as a representative.

  Referring to FIG. 2, engine 10 includes a cylinder 111 having a cylinder block 101, a cylinder head 102 coupled to the upper portion of cylinder block 101, and a piston 103 that reciprocates within cylinder 111. Is done. The piston 103 is connected to a crankshaft 104 that is an output shaft of the engine 10 via a crank arm 105 and a connecting rod 106. The connecting rod 106 converts the reciprocating motion of the piston 103 into the rotation of the crankshaft 104. In the cylinder 111, a combustion chamber 107 for combusting the air-fuel mixture is defined by the inner wall of the cylinder block 101 and the cylinder head 102 and the top surface of the piston.

  The cylinder head 102 is provided with a spark plug 114 that ignites the air-fuel mixture in a manner protruding into the combustion chamber 107, and an in-cylinder injector 110 that injects and supplies fuel to the combustion chamber 107. Further, the intake passage injector 120 is arranged to inject and supply fuel to an intake manifold, that is, an intake port 22 or / and an intake passage 20 which is a communication portion between the intake passage 20 and the combustion chamber 107.

  In this embodiment, an internal combustion engine in which two injectors 110 and 120 are separately provided will be described. However, one injector having both a cylinder injection function and an intake passage injection function is applied. Is also possible.

  The air-fuel mixture containing the fuel injected into the intake passage 20 and / or the intake port 22 is guided into the combustion chamber 107 during the valve opening period of the intake valve 24. The exhaust after the fuel is combusted by ignition by the spark plug 114 is sent to the three-way catalytic converter 90 (FIG. 1) via the exhaust passage (exhaust manifold) 80 during the valve opening period of the exhaust valve 84. The opening / closing timing (valve timing) of the intake valve 24 and the exhaust valve 84 is controlled by a variable valve control mechanism 490 that operates according to a control signal from the engine ECU 300.

  Referring again to 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.

  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 typically 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. is there. 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 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.

  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 system shown in FIG. 1, two types of injectors having different characteristics are used properly according to the engine operating state. Therefore, regarding the fuel injection amount sharing, the mode in which the total fuel injection amount is injected from the intake manifold injector 120 (PFI mode) and the mode in which the total fuel injection amount is injected from the in-cylinder injector 110 (DI mode) In addition, there is a mode (injection mode) in which fuel injection is performed by both the in-cylinder injector 110 and the intake passage injector 120.

  Of these three modes, in the PFI mode, fuel injection is not executed from the in-cylinder injector 110, so that the in-cylinder injector 110 is exposed to high-temperature fuel gas and its tip portion temperature rises. , Deposits are easier to accumulate. On the other hand, in the PFI mode and the split injection mode, fuel injection from the in-cylinder injector 110 is ensured. Hereinafter, the DI mode and the injection mode are also collectively referred to as “in-cylinder injection mode”. That is, the “in-cylinder injection mode” is a state in which the DI mode or the injection mode is selected. Thus, the PFI mode corresponds to the “first mode” in the present invention, and the DI mode and the ejection mode correspond to the “second mode” in the present invention.

(Deposit suppression control)
In the control apparatus for an internal combustion engine according to the first embodiment of the present invention, in order to suppress the deposit accumulation amount of in-cylinder injector 110, the control configuration described below is used to switch from the PFI mode to the in-cylinder injection mode. Immediately after the switching, the deposit suppression control is executed so that the deposit peeling effect in the in-cylinder injector 110 is enhanced.

  FIG. 3 is a functional block diagram illustrating deposit suppression control according to Embodiment 1 of the present invention. Each functional block shown in FIG. 3 is typically realized by executing a predetermined program stored in ECU 300 in advance.

  Referring to FIG. 3, fuel injection sharing control unit 510 shares the fuel injection amount between in-cylinder injector 110 and intake passage injector 120 with respect to the total fuel injection amount Qttl in accordance with the engine operating state. To decide. In general, the fuel injection amount sharing is also executed by referring to a map created in advance.

  That is, when one of the PFI mode, the DI mode, and the injection mode is selected by the fuel injection sharing control unit 510 and the injection mode is selected, the in-cylinder injector 110 and the intake passage injection are selected. The fuel injection ratio between the injectors 120 is determined. Thus, the in-cylinder fuel injection amount Qdi by the in-cylinder injector 110 and the port fuel injection amount Qpi by the intake passage injector 120 are determined. As described above, Qdi = 0 in the PFI mode and Qpi = 0 in the DI mode.

  The total fuel injection amount Qttl is determined by referring to a map prepared in advance as described above. Alternatively, the map is such that the in-cylinder fuel injection amount Qdi and the port fuel injection amount Qpi are directly set according to the engine operating state, that is, the fuel injection sharing control unit 510 also sets the total fuel injection amount Qttl. May be configured.

  Port injection condition setting unit 520 sets the fuel injection condition from intake manifold injector 120 when port fuel injection amount Qpi ≠ 0. Port injection condition setting unit 520 then issues a control instruction to injector drive unit 540 that controls the opening and closing of intake passage injector 120 so that the set fuel injection condition is realized.

  Similarly, in-cylinder injection condition setting unit 530 sets the fuel injection condition from in-cylinder injector 110 when in-cylinder fuel injection amount Qdi ≠ 0. Then, in-cylinder injection condition setting unit 530 generates a control instruction to injector drive unit 550 that controls opening and closing of in-cylinder injector 110 so that the set fuel injection condition is realized. .

  In-cylinder injection condition setting unit 530 includes a normal condition setting unit 532 for setting a normal fuel injection condition and a deposit peeling condition setting unit 534 for setting a fuel injection condition in a deposit peeling period.

  Separation period setting unit 560 sets a certain period from the time of switching from the PFI mode to the in-cylinder injection mode as the deposit separation period according to the mode determined by fuel injection sharing control unit 510.

  The in-cylinder injection condition setting unit 530 sets the fuel injection condition by the deposit peeling condition setting unit 534 during the deposit peeling period, and sets the fuel injection condition by the normal condition setting part 532 after the deposit peeling period ends. To do. The fuel injection condition set by the deposit peeling condition setting unit 534 has a higher deposit removal effect in the in-cylinder injector 110 than the fuel injection condition set by the normal condition setting unit 532. That is, the deposit peeling condition setting unit 534 corresponds to the “first in-cylinder injection condition setting unit” in the present invention, and the normal condition setting unit 532 is the “second in-cylinder injection condition setting unit” in the present invention. ".

  Here, the relationship between the fuel injection condition and the deposit accumulation amount will be described with reference to FIGS. 4 and 5.

  As shown in FIG. 4, when the number of fuel injections per cycle (hereinafter simply referred to as “the number of injections”) and the injection pressure are changed and the changes in the deposit accumulation amount are compared, the number of injections is large and the injection The higher the pressure, the lower the deposit accumulation. When experimenting the characteristics shown in FIGS. 4 and 5, the deposit accumulation amount is estimated from the degree of decrease in the fuel injection amount from the in-cylinder injector 110 without actually measuring it. Can do.

  As shown in FIG. 5, when the number of fuel injections is changed, the deposit accumulation amount decreases as the number of injections increases as in FIG. On the other hand, if the number of injections is the same, the length of the injection period does not significantly affect the deposit accumulation amount.

  Therefore, based on the knowledge obtained through experiments by the inventors shown in FIGS. 4 and 5, in order to increase the deposit peeling effect, in-cylinder injection is performed so that the injection pressure is high and the number of injections is increased. It will be understood that the fuel injection condition of the injector 110 may be set. For example, during the deposit peeling period, the fuel injection pressure is set to the maximum operating pressure, and the number of injections is set to the maximum value within the possible range.

  On the other hand, raising the injection pressure more than necessary is not preferable from the viewpoint of fuel consumption and the like. Also, if the number of injections is increased, problems such as variations in fuel injection amount and coarsening of injected fuel may occur due to responsiveness problems at the time of on-off valves. This is not preferable from the combustion aspect of the engine.

  Therefore, in the embodiment of the present invention, the injection pressure is set to an appropriate pressure under the normal in-cylinder injection conditions, and the number of injections is normally set to one, and the deposit peeling period is compared with the normal time. Then, the fuel injection condition in which at least one of the injection pressure increase and the injection frequency increase is realized is set. As a result, at the time of transition from the PFI mode in which in-cylinder injection is stopped and deposits are accumulated in the in-cylinder injector 110 to the in-cylinder injection mode, fuel injection conditions with a high deposit peeling effect are temporarily set. The deposit accumulated in the PFI mode period can be positively peeled off.

  In order to ensure the maximum number of injections, it is preferable to set the fuel injection amount by one fuel injection as the minimum fuel injection amount of the injector. This minimum fuel injection amount corresponds to the minimum value of the fuel injection amount that can ensure the linearity between the pulse width of the valve opening instruction signal of the injector and the fuel injection amount. In this way, the maximum number of fuel injections per cycle can be ensured without causing a large error in the fuel injection amount from the in-cylinder injector 110.

  Further, by increasing the fuel injection ratio from the in-cylinder injector 110 during the deposit separation period, it is possible to secure a larger number of fuel injections. Therefore, in the deposit separation period, the fuel injection ratio from the in-cylinder injector 110 is increased so that the in-cylinder fuel injection amount Qdi set corresponding to the same engine operating state is increased as compared with the normal time. Is preferably increased. For example, in the deposit separation period, the DI mode is selected regardless of the engine operating state, and the entire fuel injection amount is injected from the in-cylinder injector 110.

  Referring to FIG. 3 again, stripping period setting unit 560 further includes a deposit stripping amount estimation unit 570.

  The deposit peeling amount estimation unit 570 estimates the deposit peeling amount during the deposit peeling period according to the fuel injection conditions. For example, a map that calculates the estimated deposit separation amount based on the number of injections and the injection pressure can be configured based on the characteristics shown in FIG.

  Deposit peeling amount estimation unit 570 calculates estimated total deposit peeling amount Dtr # by accumulating the estimated deposit peeling amount during the deposit peeling period.

  Stripping period setting unit 560 sets a condition for terminating the deposit stripping period based on estimated total deposit stripping amount Dtr # by deposit stripping amount estimating unit 570. For example, the deposit peeling period can be terminated when the estimated total deposit peeling amount Dtr # is equal to or greater than a predetermined value.

  It is also possible to adopt a configuration in which the deposit peeling period is terminated in response to elapse of a predetermined time or a predetermined number of cycles from the time of switching to the in-cylinder injection mode. However, by terminating the deposit stripping period based on the estimated total deposit stripping amount Dtr # as described above, the deposit stripping period can be appropriately terminated without setting it excessively long. As a result, it is possible to increase the deposit suppressing effect while preventing the setting of the fuel injection condition for enhancing the deposit peeling effect from excessively affecting the engine performance.

  FIG. 7 is a flowchart for executing the deposit suppression control according to the first embodiment by the engine ECU.

  Referring to FIG. 7, in step S100, ECU 300 reads the engine operating state, specifically, the engine speed, the load, the coolant temperature, and the like. In step S110, ECU 300 determines the total fuel injection amount Qttl based on the read engine operating state by referring to a map or the like, and further sets the fuel injection amount sharing by referring to the map or the like in step S120. Thereby, the port fuel injection amount Qpi and the in-cylinder fuel injection amount Qdi are determined. That is, the processing in steps S100 to S120 or S100 and S120 corresponds to the function of the fuel injection sharing control unit 510 shown in FIG.

  In step S130, ECU 300 determines whether or not it is the in-cylinder injection mode based on the fuel injection sharing determined in step S120. When the PFI mode is selected, step S130 is NO, and when the DI mode or spray mode is selected, step S130 is YES.

  In step S140, ECU 300 determines whether or not peeling period flag FLG is set to “1”. The separation period flag FLG is initialized to “0” at the time of NO determination in step S130 (when the PFI mode is selected), while at the time of transition from the PFI mode to the in-cylinder injection mode (DI mode or injection mode). Transition from “0” to “1”.

  When separation period flag FLG = “0” (NO determination in S140), ECU 300 sets a normal condition for the fuel injection condition of in-cylinder injector 110 in step S160. At this time, the injection pressure is set to a predetermined pressure P2 (appropriate operating pressure), and the number of injections in one cycle is set to N2.

  On the other hand, when peeling period flag FLG = “1” (when YES is determined in S140), ECU 300 sets a fuel injection condition for deposit peeling in step S150. At this time, the injection pressure is set to P1 (P1> P2), and the number of injections is set to N1 (N1> N2). For example, as described above, the injection pressure P1 is set to the maximum operating pressure, and the number of injections N1 is set based on the minimum fuel injection amount of the injector.

  That is, steps S150 and S160 correspond to the function of in-cylinder injection condition setting unit 530 shown in FIG. 3, in particular, step S150 corresponds to the function of deposit peeling condition setting unit 534, and step S160 is a normal condition setting unit. This corresponds to the function 532.

  In the deposit peeling period, ECU 300 further determines in step S170 whether a condition for terminating the deposit peeling period is satisfied. As described above, the determination in step S170 is performed based on the elapsed time or the number of elapsed cycles from the time of switching to the in-cylinder injection mode, or the estimated value Dtr # of the deposit separation amount.

  Until the end condition is satisfied, ECU 300 determines that step S170 is NO, and maintains peeling period flag FLG at “1” in step S180. Thus, the fuel injection condition for deposit peeling is set in step S150 until the end condition is satisfied. On the other hand, when the end condition is satisfied, ECU 300 determines YES in step S170 and changes peeling period flag FLG to “0” in step S190. Thereby, the subsequent in-cylinder injection is executed under the normal fuel injection conditions set in step S160.

FIG. 8 is a waveform diagram for explaining the effect of deposit suppression control according to the first embodiment.
Referring to FIG. 8, the PFI mode is selected in each period of time t0 to t1, t3 to t4, and t6 to t7, and fuel injection by only intake manifold injector 120 is executed.

  In the PFI mode period, the deposit accumulation amount of the in-cylinder injector 110 increases with time. Note that an estimated value is also used for the deposit accumulation amount shown in FIG. Further, the injection amount correction amount by the air-fuel ratio learning is based on the difference between the actual air-fuel ratio measured by the air-fuel ratio sensor 420 and the target air-fuel ratio (typically the theoretical air-fuel ratio). The fuel is increased when lean, and the fuel is decreased when the actual air-fuel ratio is lean. Therefore, the injection amount correction amount of in-cylinder fuel injection has a characteristic of increasing (increasing side) in conjunction with an increase in deposit accumulation amount and decreasing (increasing amount) in conjunction with a decrease in deposit accumulation amount.

  At time t1, t4, t7, the fuel injection by the in-cylinder injector 110 is started by shifting from the PFI mode to the DI mode. That is, times t1, t4, and t7 correspond to the “switching time” in the present invention. In the prior art, control for correcting the shortage of the fuel injection amount by air-fuel ratio learning is performed in the DI mode period, but the fuel injection condition is fixed to the normal condition in the present embodiment.

  As a result, as shown by the dotted line in FIG. 8, the deposit accumulation amount of the in-cylinder injector 110 decreases during the DI mode period, but the rate of decrease is relatively slow, so that the injection performance is restored. There is concern that it will take time. Further, since the DI mode is required for a long time to secure the deposit peeling amount, the deposit accumulated in the PFI mode cannot be completely removed in the DI mode period, and the engine is operated for a long period of time. As a result, the accumulated amount of deposit may increase cumulatively.

  As described above, in the DI mode period, the injection amount correction amount by the air-fuel ratio learning changes according to the deposit accumulation amount of the in-cylinder injector 110. However, when the deposit accumulation amount increases cumulatively, the injection amount correction amount May exceed the upper limit set in the control (time t4, t7 in FIG. 8). When such a phenomenon occurs, the fuel injection amount cannot be corrected by the air-fuel ratio learning, so that the fuel injection from the in-cylinder injector 110 becomes insufficient, and the air-fuel ratio in the combustion chamber becomes lean, resulting in combustion fluctuations. Will occur.

  On the other hand, according to the deposit suppression control according to the present invention, the deposit peeling period is at the initial period after the shift to the DI mode, specifically, at times t1 to t2, t4 to t5, and t7 to t8 in FIG. Provided. As described above, in the deposit stripping period, the fuel injection conditions having a higher deposit stripping effect than the normal time are set. As a result, as shown by the solid line in FIG. 8, it is possible to secure the deposit peeling amount during the DI mode period, and thus it is easy to remove the deposit accumulated during the PFI mode period during the DI mode period. Become.

  As a result, even if the engine is operated for a long period of time, it becomes easy to shift the deposit accumulation amount of the in-cylinder injector 110 within a range where the injection amount correction amount with respect to the theoretical air-fuel ratio does not reach the upper limit value. It is possible to continue the engine operation with the engine properly maintained. As a result, the occurrence of large combustion fluctuations can be prevented.

  As described above, according to the control apparatus for an internal combustion engine according to the first embodiment of the present invention, the period for setting the special fuel injection condition that enhances the deposit peeling effect is provided at the time of transition from the PFI mode to the in-cylinder injection mode. As a result, even if the engine is continuously operated for a long time, it is possible to suppress the cumulative accumulation amount from increasing. As a result, it is possible to suppress engine performance degradation such as occurrence of combustion fluctuations and deterioration of emissions due to an increase in the accumulated amount of deposit.

  By increasing the deposit removal capability during the DI mode period, the PFI mode can be actively applied during an operation state in which operation by only intake passage injection is preferred. During the PFI mode, the engine noise can be reduced because the high-pressure fuel pump 150 for in-cylinder injection can be stopped. Therefore, the engine noise can be reduced by actively utilizing the PFI mode in an operation state in which the combustion noise is small and the operation sound of the engine actuator is likely to be surfaced, such as during idle operation or low load range operation.

  In order to start the deposit peeling period immediately after switching to the in-cylinder injection mode, it is necessary to secure a certain amount of injection pressure on the in-cylinder injection side even in the PFI mode period. Therefore, in a case where there is a concern about an increase in the accumulated amount of deposit, such as when the PFI mode period continues for a predetermined time or more, it is preferable to operate the high-pressure fuel pump 150 in advance during the PFI mode period.

  Also, during the deposit peeling period, it is preferable to enhance the deposit peeling effect while ensuring the stability of the combustion state of the engine. For example, under conditions where the required fuel injection amount is low, such as during idle operation or low load range operation, increasing the number of fuel injections per cycle may cause variations in the fuel injection amount, resulting in combustion fluctuations. There is. Therefore, when the total fuel injection amount is less than or equal to a predetermined value, the deposit separation condition is subdivided, such as relatively decreasing the number of injections N1 or ensuring the number of injections N1 after relatively reducing the injection pressure. It is preferable to aim for.

[Embodiment 2]
As shown in FIG. 8, the upper limit value Dmax of the allowable deposit accumulation amount can be set in correspondence with the situation where the injection amount correction amount by the air-fuel ratio learning reaches the upper limit value. In the second embodiment, deposit suppression control for more reliably preventing the deposit accumulation amount from exceeding the upper limit value Dmax will be described. In the second embodiment, only the deposit suppression control executed by engine ECU 300 is different from the first embodiment, and the configuration of the engine system and the like are the same as in the first embodiment.

  FIG. 9 is a functional block diagram illustrating deposit suppression control according to Embodiment 2 of the present invention.

  Referring to FIG. 9, the control configuration according to the second embodiment further includes a deposit accumulation amount estimation unit 580 and a boost instruction unit 590 as compared with the control configuration according to the first embodiment shown in FIG. 3.

  Deposit accumulation amount estimation unit 580 calculates estimated deposit accumulation amount Dpa # based on the tip temperature estimation of in-cylinder injector 110 that has a large influence on deposit generation. The tip temperature of in-cylinder injector 110 is affected by engine coolant temperature, engine speed, and engine load.

  Here, as shown in FIG. 10, under the same engine cooling water temperature conditions, the tip temperature Tinj tends to increase as the engine speed increases and the engine load increases. Therefore, the tip temperature Tinj of the in-cylinder injector 110 can be estimated based on the engine operating conditions by creating a map based on the characteristics shown in FIG. 10 in advance for each engine coolant temperature. .

  Further, as shown in FIG. 11, the accumulated deposit amount of in-cylinder injector 110 is the elapsed time from when in-cylinder injection is stopped, that is, the duration of PFI mode, and the tip of in-cylinder injector 110. It has been found by experiments by the inventors that the temperature Tinj is greatly affected. Note that the accumulated deposit amount shown in FIG. 11 can also be estimated from the degree of decrease in the fuel injection amount from the in-cylinder injector 110 without actually measuring it.

  More specifically, as shown in FIG. 11, the deposit generation rate varies depending on the tip temperature Tinj, and the deposit generation amount also varies depending on the duration of the PFI mode. Such characteristics occur because the deposit properties differ depending on the tip temperature Tinj, and the adhesive force differs. Further, it is known that the deposit accumulation amount is gradually saturated and has a certain upper limit value.

  For this reason, the estimated deposit accumulation amount Dpa # during the PFI mode period can be calculated based on the estimated tip temperature Tinj and the duration of the PFI mode so as to reflect the characteristics shown in FIG. The deposit accumulation amount can be estimated every elapse of a predetermined time or every predetermined cycle of the engine (for example, every cycle).

  In particular, if a map of the deposit generation rate corresponding to the slope of the characteristic line shown in FIG. 11 is created, the deposit generation amount per unit time is estimated based on the deposit generation rate, and the deposit generation amount is integrated. In addition, it is possible to estimate with high accuracy reflecting the change of the engine state over time.

  FIG. 12 is a flowchart for executing deposit accumulation amount estimation by deposit accumulation amount estimation unit 580 of FIG.

  Referring to FIG. 12, in step S300, ECU 300 executes reading of the engine operating state similar to step S100. In step S310, ECU 300 determines whether the PFI mode is being selected. When the PFI mode is not selected (when NO is determined in S310), since it is not necessary to estimate the deposit accumulation amount based on the injector tip temperature estimation, ECU 300 ends the process without executing the following steps.

  In contrast, when PFI mode is selected (YES in S130), ECU 300 calculates estimated value Tinj # of the tip temperature of the in-cylinder injector in accordance with the characteristics shown in FIG. 10 in step S320. . In step S330, ECU 300 calculates the PFI mode duration, and in steps S340 and S350, calculates current estimated deposit accumulation amount Dpa # based on the characteristics shown in FIG.

  Referring to FIG. 9 again, estimated deposit accumulation amount Dpa # calculated by deposit accumulation amount estimation unit 580 is sent to fuel injection sharing control unit 510 and boosting instruction unit 590. The fuel injection sharing control unit 510 selects the DI mode / PFI mode / injection mode based on the engine operating state in the same manner as in the first embodiment, and the estimated deposit accumulation amount Dpa # is set during the PFI mode period. When the upper limit value Dmax is exceeded, the PFI mode is forcibly terminated and the in-cylinder injection mode (preferably the DI mode) is selected.

  Boost instruction unit 590 sets estimated deposit accumulation amount Dpa # to a predetermined reference value lower than upper limit value Dmax so that in-cylinder injection can be started quickly when estimated deposit accumulation amount Dpa # becomes equal to or greater than upper limit value Dmax. In response, the high pressure fuel pump 150 starts to operate. In this way, as compared with the first embodiment, the injection pressure can be reliably ensured from the start of the deposit peeling period. That is, it is possible to enhance the deposit peeling effect at the time of in-cylinder injection while minimizing the operation period of the high-pressure fuel pump 150 during the PFI mode period.

  Further, the deposit accumulation amount estimation unit 580 determines the deposit accumulation amount at the start of the PFI mode based on the fuel amount correction amount by the air-fuel ratio learning at the time of switching from the in-cylinder injection mode to the PFI mode, that is, at the end of the in-cylinder injection mode. The initial value of can be estimated. Then, the accumulated deposit value Dpa # is calculated by calculating the estimated accumulated deposit amount Dpa # based on the sum of the initial value thus obtained and the estimated accumulated deposit amount during the PFI mode according to the characteristics shown in FIG. Can be more reliably predicted to reach the upper limit.

  Since other control configurations in the second embodiment are the same as those in FIG. 3, detailed description thereof will not be repeated.

  FIG. 13 is a flowchart for executing the deposit suppression control according to the second embodiment by the engine ECU.

  Referring to FIG. 13, in the deposit suppression control according to the second embodiment, step S120 # is executed in place of step S120 and step S170 is executed as compared with the flowchart according to the first embodiment shown in FIG. Instead, step S170 # is different. Furthermore, steps S152 and S154 are executed after step S150. Since other steps are the same as those in the first embodiment (FIG. 7), detailed description will not be repeated.

  In step S120 #, ECU 300 performs in-cylinder injection from the PFI mode in response to the estimated deposit accumulation amount Dpa # being equal to or greater than the upper limit value Dmax in addition to the fuel injection amount sharing setting based on the engine operating state in step S120. Force transition to mode.

  Further, in the deposit peeling period (when YES is determined in S130), ECU 300 calculates an estimated total deposit peeling amount Dtr # within the deposit peeling period in steps S152 and S154 after setting the deposit peeling condition in step S150.

  In step S170 #, ECU 300 subtracts estimated total deposit peeling amount Dtr # calculated in step S154 from estimated deposit accumulation amount Dpa # at the end of PFI mode, that is, current estimated deposit accumulation amount ( It is determined whether or not (Dpa # -Dtr #) is equal to or less than threshold value Dth.

  That is, in the deposit suppression control according to the second embodiment, the condition for ending the deposit stripping period is determined depending on whether or not the estimated deposit accumulation amount (Dpa # −Dtr #) after stripping has decreased to a threshold value Dth or less. The

  When the estimated deposit accumulation amount after peeling becomes equal to or less than threshold value Dth (when YES is determined in S170 #), ECU 300 changes peeling period flag FLG to “0” in step S190. Thereby, the deposit peeling period is ended.

  On the other hand, when the estimated deposit accumulation amount after peeling is large enough to be the threshold value Dth (when YES is determined in S170 #), ECU 300 maintains peeling period flag FLG at “1” in step S180, and deposit peeling. Continue the period.

  As described above, according to the deposit suppression control according to the second embodiment, it is possible to shift from the PFI mode to the in-cylinder injection mode based on the estimation of the deposit accumulation amount. Therefore, the deposit accumulation amount is more than the upper limit value. It can be surely prevented. Further, as with the deposit suppression control according to the first embodiment, the deposit removal effect can be enhanced by setting the deposit peeling period, so the deposit accumulation amount can be increased more stably than the deposit suppression control according to the first embodiment. It is possible to suppress the engine performance deterioration caused by.

  In addition, the PFI mode can be more actively applied in an operating state in which operation by only intake passage injection is preferable.

  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 a control device for an internal combustion engine according to Embodiment 1 of the present invention. FIG. It is a block diagram of each cylinder shown by FIG. 5 is a functional block diagram for explaining deposit suppression control according to Embodiment 1. FIG. It is a 1st figure which shows the relationship between fuel-injection conditions and the deposit accumulation amount. It is a 2nd figure which shows the relationship between fuel-injection conditions and the deposit accumulation amount. It is a figure which shows the relationship between the frequency | count of injection, injection pressure, and deposit peeling amount. 5 is a flowchart for executing deposit suppression control according to the first embodiment by an engine ECU. FIG. 6 is a waveform diagram for explaining the effect of deposit suppression control according to the first embodiment. FIG. 10 is a functional block diagram illustrating deposit suppression control according to a second embodiment. It is a figure which shows the relationship between an engine driving | running state and the front-end | tip temperature of the injector for cylinder injection. It is a figure explaining the relationship between the front-end | tip temperature of the injector for cylinder injection, the continuous operation time of PFI mode, and the deposit accumulation amount. It is a flowchart for performing deposit accumulation amount estimation by engine ECU. 6 is a flowchart for executing deposit suppression control according to a second embodiment by an engine ECU.

Explanation of symbols

  10 engine, 20 intake passage, 22 intake port, 24 intake valve, 30 surge tank, 40 intake duct, 42 air flow meter, 50 air cleaner, 60 electric motor, 70 throttle valve, 80 exhaust manifold, 84 exhaust valve, 90 three-way catalyst Converter, 100 Accelerator pedal, 101 Cylinder block, 102 Cylinder head, 103 Piston, 104 Crankshaft, 105 Crank arm, 106 Connecting rod, 107 Combustion chamber, 110 In-cylinder injector, 111 cylinder, 112 cylinder, 114 Spark plug, 120 Injector injector for injection passage, 130, 160 Fuel distribution pipe, 140 Check valve, 150 High pressure fuel pump, 152 Electromagnetic spill valve, 170 Fuel pressure regulator, 180 Low pressure Fuel pump, 190 Fuel filter, 200 Fuel tank, 300 Engine ECU, 310 Bidirectional bus, 350 input port, 360 output port, 370, 390, 410, 430, 450 A / D converter, 380 Water temperature sensor, 400 Fuel Pressure sensor, 420 Air-fuel ratio sensor, 440 Accelerator opening sensor, 460 Rotational speed sensor, 470 Drive circuit, 490 Variable valve control mechanism, 510 Fuel injection sharing control unit, 520 Port injection condition setting unit, 530 In-cylinder injection condition setting , 532 normal condition setting unit, 534 deposit peeling condition setting unit, 540 injector driving unit (PFI), 550 injector driving unit (DI), 560 peeling period setting unit, 570 deposit peeling amount estimation unit, 580 deposit accumulation amount estimation unit 590 Step-up instruction unit, Dm x Upper limit value (deposit accumulation amount), Dpa # estimated deposit accumulation amount, Dth threshold value (deposit accumulation amount), Dtr # estimated total deposit peeling amount, Qdi In-cylinder fuel injection amount, Qpi port fuel injection amount, Qttl Total fuel Injection amount, Tinj Tip temperature (in-cylinder injector).

Claims (10)

A control apparatus for an internal combustion engine, comprising: a first fuel injection means for injecting fuel into a cylinder; and a second fuel injection means for injecting fuel into an intake passage,
Fuel injection sharing control means for controlling the fuel injection amount sharing between the first and second fuel injection means for the total fuel injection amount based on the operating state of the internal combustion engine;
From the first mode in which the fuel injection amount sharing is controlled by the fuel injection sharing control means so that the total fuel injection amount is injected by the second fuel injection means, at least a part of the total fuel injection amount is A first in-cylinder injection that sets a fuel injection condition of the first fuel injection means in a first period from the switching time when the mode is switched to the second mode of injection by one fuel injection means. Condition setting means;
A second in-cylinder injection condition setting means for setting a fuel injection condition of the first fuel injection means in the second mode and after the end of the first period;
The first in-cylinder injection condition setting unit is configured to remove at least one of the injection pressure from the first fuel injection unit and the number of injections per cycle from the deposit accumulated in the first fuel injection unit. A control device for an internal combustion engine, which is set to a value different from a set value by the second in-cylinder injection condition setting means so that the value is relatively increased.   The internal combustion engine according to claim 1, wherein the first in-cylinder injection condition setting means sets an injection pressure from the first fuel injection means to be higher than that of the second in-cylinder injection condition setting means. Control device.   2. The first in-cylinder injection condition setting unit sets the number of injections per cycle from the first fuel injection unit to be larger than that of the second in-cylinder injection condition setting unit. The internal combustion engine control device described.   The control device for an internal combustion engine according to claim 3, wherein the first in-cylinder injection condition setting means sets the number of injections per cycle based on a minimum fuel injection amount from the first fuel injection means. .   The injection sharing control means sets the fuel injection ratio from the first fuel injection means to the total fuel injection amount in the first period after the end of the first period corresponding to the same operating state. The control device for an internal combustion engine according to any one of claims 1 to 4, wherein the control device is set to be higher than the fuel injection ratio to be set in (1).   5. The fuel injection amount sharing unit according to claim 1, wherein the fuel injection amount control unit sets the fuel injection amount sharing so that the total fuel injection amount is injected from the first fuel injection unit in the first period. The control apparatus for an internal combustion engine according to the item. A deposit accumulation amount estimating means for estimating a deposit accumulation amount of the first fuel injection means based on a mode of the internal combustion engine in a period in which the fuel injection amount sharing is in the first mode;
The fuel injection sharing control means responds to the fact that when the fuel injection amount sharing is in the first mode, the estimated fuel accumulation amount estimated by the deposit accumulation amount estimation means becomes equal to or greater than a predetermined value. The control device for an internal combustion engine according to claim 1, wherein the quantity sharing is switched from the first mode to the second mode. During the first period, the amount of deposit peeling from the first fuel injection unit is estimated based on at least one of the injection pressure from the first fuel injection unit and the number of injections per cycle. A deposit peeling amount estimating means for
In the first period, a value obtained by subtracting the estimated deposit peeling amount by the deposit peeling amount estimating means from the estimated deposit accumulated amount at the time of switching from the first mode to the second mode becomes a predetermined value or less. 8. The control device for an internal combustion engine according to claim 7, wherein the control device is terminated accordingly.   The deposit accumulation amount estimating means includes a tip temperature of the first fuel injection means estimated from at least a part of the rotational speed, load and cooling water temperature of the internal combustion engine, and the first mode after the start of the first mode. The control device for an internal combustion engine according to claim 7 or 8, wherein the estimated deposit accumulation amount is calculated based on an elapsed time. During the first period, the amount of deposit peeling from the first fuel injection unit is estimated based on at least one of the injection pressure from the first fuel injection unit and the number of injections per cycle. A deposit peeling amount estimating means for
The control apparatus for an internal combustion engine according to claim 1, wherein the first period is ended based on an estimated deposit separation amount by the deposit separation amount estimation means.

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