JP4548256B2 - Control device for internal combustion engine - Google Patents

Description

  The present invention includes fuel injection means (in-cylinder injector) for injecting fuel into a cylinder and fuel injection means (intake-path injection injector) for injecting fuel into an intake passage or an intake port. In particular, the present invention relates to a technique for correcting a fuel injection amount based on an air-fuel ratio.

  An injector for injecting intake passage for injecting fuel into the engine intake passage and an in-cylinder injector for injecting fuel at all times into the engine combustion chamber, the engine load being higher than a predetermined set load There is known an internal combustion engine that stops fuel injection from the intake passage injector when the engine load is low and injects fuel from the intake passage injector when the engine load is higher than the set load.

  Even in such an internal combustion engine, the fuel injection amount may not be a desired injection amount due to deposits accumulated in the injector and individual differences during manufacture. That is, the air-fuel ratio may deviate from a desired air-fuel ratio (for example, the theoretical air-fuel ratio). In order to correct the deviation of the fuel injection amount, the fuel injection amount is corrected by feedback control of the air-fuel ratio, similarly to the internal combustion engine in which one injector is provided for one cylinder.

  Japanese Patent Laying-Open No. 3-185242 (Patent Document 1) discloses a fuel injection amount control device for an internal combustion engine that accurately corrects the fuel injection amount in an internal combustion engine having a plurality of fuel injection valves per cylinder. This fuel injection amount control device learns a value based on an output signal from a control unit that controls fuel injection from a plurality of fuel injection valves according to an operating state and an oxygen sensor provided in an exhaust system of the engine. Each learning using a learning unit for correcting the fuel injection amount, a setting unit for setting a plurality of learning regions corresponding to the use states of the plurality of fuel injection valves, and each learning value learned in each of the learning regions And a correction unit that corrects the fuel injection amount in the operation state corresponding to the region.

According to the fuel injection amount control device described in this publication, the fuel injection valve that is used in the learning region matches the fuel injection valve that is used when the fuel injection amount is corrected using the learned value. Therefore, the correction accuracy of the fuel injection amount is improved. Accordingly, the air-fuel ratio followability is improved accordingly, and exhaust emission is improved. Further, since the error from the target air-fuel ratio becomes small, even if the air-fuel ratio is set to the lean side, the possibility of misfire can be reduced and fuel efficiency can be improved.
Japanese Patent Laid-Open No. 3-185242

  In an internal combustion engine that injects fuel from both an in-cylinder injector and an intake manifold injector as in the fuel injection amount control device described in Japanese Patent Application Laid-Open No. 3-185242, an injection ratio of fuel to be injected ( It is conceivable to change the fuel sharing ratio) according to the operating state. In this case, the learning value is calculated for the total injection amount obtained by adding the injection amounts from both injectors. Therefore, for example, if a learning value obtained in a state where the injection amount from one injector is not normal is used at different injection ratios, an appropriate air-fuel ratio is not always obtained. For example, it is assumed that the in-cylinder injector is normal, the learning value is calculated in a state where the injection amount from the intake manifold injector is insufficient, and the total injection amount is corrected to increase. When the injection ratio of the intake passage injection injector is reduced from this state, the amount of deviation from the target injection amount is reduced because the injection amount from the intake passage injection injector is reduced. Therefore, immediately after changing the sharing ratio, the total injection amount can be increased more than necessary by the learning value calculated before the change.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a control device for an internal combustion engine capable of realizing an appropriate fuel injection amount.

  An internal combustion engine control apparatus according to a first aspect of the present invention includes an internal combustion engine having a first fuel injection means for injecting fuel into a cylinder and a second fuel injection means for injecting fuel into an intake passage. Control the engine. The control device includes a detection unit for detecting an air-fuel ratio of the internal combustion engine, a calculation unit for calculating a correction value for the fuel injection amount based on the detected air-fuel ratio, and an amount of fuel corresponding to the correction value. At least one of the control means for controlling the first fuel injection means and the second fuel injection means, and the first fuel injection means and the second fuel injection means. And prohibiting means for prohibiting calculation of the correction value when a condition that the temperature of the fuel injection means is higher than a predetermined temperature is satisfied.

  According to the first invention, the air-fuel ratio is detected, and the correction value for the fuel injection amount is calculated based on the detected air-fuel ratio. The first fuel injection means and the second fuel injection means are controlled so that an amount of fuel corresponding to the correction value is injected. At this time, if the temperature of the fuel injection means increases, the fuel injection amount may become smaller than the target injection amount due to an abnormal operation of the fuel injection means or the fuel boiling. In this case, the total injection amount, which is the sum of the fuels injected from both fuel injection means, becomes smaller than the target injection amount. That is, since the air-fuel ratio becomes lean with respect to the target air-fuel ratio (for example, the stoichiometric air-fuel ratio), the learning value is calculated so as to increase the total injection amount. In such a state that the learning value is obtained, the injection ratio of the fuel injection means from each fuel injection means with respect to the total injection quantity is changed, and the injection ratio of the fuel injection means having a short injection quantity becomes smaller. The amount of deviation from the target injection amount is reduced by the amount by which the injection amount from the fuel injection means that is insufficient is reduced. Therefore, immediately after the change of the spray distribution ratio, the total injection amount is increased more than necessary by the learning value calculated before the change. In order to suppress such increase correction, the condition that the temperature of at least one of the first fuel injection unit and the second fuel injection unit is higher than a predetermined temperature is satisfied. In such a case, calculation of the correction value is prohibited. Thereby, when the injection ratio of the first fuel injection means and the second fuel injection means is changed, the fuel is obtained by the learning value obtained in a state where the injection amount from one fuel injection means can be insufficient. It can be suppressed that the injection amount is corrected to increase more than necessary. Therefore, it is possible to provide a control device for an internal combustion engine that can realize an appropriate fuel injection amount.

  In the control device for an internal combustion engine according to the second invention, in addition to the configuration of the first invention, the prohibiting means has a temperature in advance in addition to the condition that the temperature of the fuel injection means is higher than a predetermined temperature. A means for prohibiting calculation of the correction value is included when the condition that the fuel injection amount from the fuel injection means higher than the predetermined temperature is smaller than the predetermined fuel injection amount is satisfied.

  According to the second aspect of the invention, as the fuel injection amount becomes smaller and the fuel injection time from the fuel injection means becomes shorter, the control becomes easier and the fuel injection amount tends to be insufficient. When the condition that the fuel injection amount is smaller than the predetermined fuel injection amount is satisfied, calculation of the correction value is prohibited. Thereby, when the injection ratio of the first fuel injection means and the second fuel injection means is changed, the fuel is obtained by the learning value obtained in a state where the injection amount from one fuel injection means can be insufficient. It can be suppressed that the injection amount is corrected to increase more than necessary. Therefore, the fuel injection amount can be made appropriate.

  In the control apparatus for an internal combustion engine according to the third invention, in addition to the configuration of the first or second invention, the first fuel injection means is an in-cylinder injector, and the second fuel injection means is: It is an injector for intake passage injection.

  According to a third aspect of the present invention, in an internal combustion engine in which an in-cylinder injector that is a first fuel injection means and an intake passage injection injector that is a second fuel injection means are separately provided to share the injected fuel, The injection amount can be made appropriate.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following description, the same parts are denoted by the same reference numerals. Their names and functions are also the same. Therefore, detailed description thereof will not be repeated.

<First Embodiment>
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 a first embodiment of the present invention. Although FIG. 1 shows an in-line four-cylinder gasoline engine as an engine, the present invention is not limited to such an engine, and various types of engines such as a V-type 6-cylinder engine and a V-type 8-cylinder engine can be used. Applicable to engine.

  As shown in FIG. 1, the engine 10 includes four cylinders 112, and each cylinder 112 is connected to a common surge tank 30 via a corresponding intake manifold 20. The surge tank 30 is connected to an air cleaner 50 via an intake duct 40, an air flow meter 42 is disposed in the intake duct 40, and a throttle valve 70 driven by an electric motor 60 is disposed. The opening degree of throttle valve 70 is controlled based on the output signal of engine ECU 300 independently of accelerator pedal 100. On the other hand, each cylinder 112 is connected to a common exhaust manifold 80, and this exhaust manifold 80 is connected to a three-way catalytic converter 90.

  For each cylinder 112, an in-cylinder injector 110 for injecting fuel into the cylinder, and an intake passage injection injector 120 for injecting fuel into the intake port or / and the intake passage. And are provided respectively. These injectors 110 and 120 are controlled based on the output signal of engine ECU 300, respectively. The in-cylinder injectors 110 are connected to a common fuel distribution pipe 130, and this fuel distribution pipe 130 is connected to the fuel distribution pipe 130 through a check valve 140, and is driven by an engine. A high-pressure fuel pump 150 is connected. In the present embodiment, an internal combustion engine in which two injectors are separately provided will be described, but the present invention is not limited to such an internal combustion engine. For example, it may be an internal combustion engine having one injector that has both an in-cylinder injection function and an intake passage injection function.

  As shown in FIG. 1, 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. When the amount of fuel supplied from the pump 150 into the fuel distribution pipe 130 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. ing. 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. Accordingly, 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 a global air-fuel ratio sensor (linear air-fuel ratio sensor) that generates an output voltage proportional to the air-fuel ratio of the air-fuel mixture burned by the engine 10. The air-fuel ratio sensor 420 may be an O ₂ sensor that detects whether the air-fuel ratio of the air-fuel mixture burned in the engine 10 is rich or lean with respect to the stoichiometric air-fuel ratio. Good.

  In the present embodiment, engine ECU 300 calculates a feedback correction amount for the total fuel injection amount based on the output voltage of air-fuel ratio sensor 420. Further, when a predetermined learning condition is satisfied, a learning value of the feedback correction amount (a value representing a constant deviation amount of the fuel injection amount) is calculated. The calculation of the feedback correction amount and its learning value is performed within a predetermined learning region with the intake air amount as a parameter. The learning area will be described in detail later.

  In the present embodiment, when the air-fuel ratio is lean (when leaner than the stoichiometric air-fuel ratio), the feedback correction amount is calculated to increase. When the air-fuel ratio is rich (when it is richer than the theoretical air-fuel ratio), the feedback correction amount is calculated to decrease. As a method for calculating the feedback correction amount, a known general technique may be used. Therefore, detailed description thereof will not be repeated here.

  The learning value is calculated by adding the update amount determined based on the map to the previously calculated learning value or subtracting from the previously calculated learning value when a predetermined learning condition is satisfied. The The predetermined learning condition is, for example, a condition that the average value (control center value) of the feedback correction amount is smaller than the threshold value (1) or the threshold value (2) (threshold value (2)> threshold value. It is a condition that it is larger than (1)).

The learning value is calculated as a smaller value as the fuel injection amount is excessive (as the actual fuel injection amount is larger than the target fuel injection amount). On the other hand, the smaller the fuel injection amount (the smaller the actual fuel injection amount than the target fuel injection amount), the larger the learning value is calculated.
In addition, about the calculation method of a learning value, what is necessary is just to use a well-known general technique, Therefore The further detailed description is not repeated here.

  The fuel injection amount is corrected based on the feedback correction amount and the learned value. That is, the larger the feedback correction amount and the learning value, the more the fuel injection amount is corrected. The smaller the feedback correction amount and the learned value, the smaller the fuel injection amount is corrected. In the present embodiment, the fuel injection amount correction amount (hereinafter also referred to as fuel correction amount) is calculated as the sum of the feedback correction amount and the learning value.

  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. The fuel injection set in the ROM 320 of the engine ECU 300 is set in accordance with the operating state (intake air amount, etc.) 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. A quantity value, a correction value based on the engine coolant temperature, and the like are previously mapped and stored.

  Referring to FIGS. 2 and 3, the injection ratio of in-cylinder injector 110 and intake manifold injector 120 (hereinafter referred to as DI ratio (r)), which is information corresponding to the operating state of engine 10, is also referred to. Will be described). These maps are stored in the ROM 320 of the engine ECU 300. FIG. 2 is a map for the warm of the engine 10, and FIG. 3 is a map for the cold of the engine 10.

  As shown in FIG. 2 and FIG. 3, these maps are expressed in percentages where the engine 10 rotational speed is on the horizontal axis, the load factor is on the vertical axis, and the share ratio of the in-cylinder injector 110 is the DI ratio r. It is shown.

  As shown in FIGS. 2 and 3, the DI ratio r is set for each operation region determined by the rotation speed and load factor of the engine 10. “DI ratio r = 100%” means a region where fuel injection is performed only from in-cylinder injector 110, and “DI ratio r = 0%” means from intake manifold injector 120. This means that only the region where fuel injection is performed. “DI ratio r ≠ 0%”, “DI ratio r ≠ 100%” and “0% <DI ratio r <100%” indicate that in-cylinder injector 110 and intake passage injector 120 perform fuel injection. It means that the area is shared. In general, the in-cylinder injector 110 contributes to an increase in output performance, and the intake manifold injector 120 contributes to the uniformity of the air-fuel mixture. By using two types of injectors having different characteristics depending on the rotation speed and load factor of the engine 10, the engine 10 is in a normal operation state (for example, when the catalyst is warmed up at idle when the engine 10 is in an abnormal state other than the normal operation state). In this case, only homogeneous combustion is performed.

  Further, as shown in FIG. 2 and FIG. 3, the DI share ratio r of the in-cylinder injector 110 and the intake manifold injector 120 is defined by dividing it into a warm map and a cold map. did. If the temperature of the engine 10 is different, the temperature of the engine 10 is detected by detecting the temperature of the engine 10 using a map set so that the control areas of the in-cylinder injector 110 and the intake manifold injector 120 are different. If it is equal to or higher than a predetermined temperature threshold value, the warm time map shown in FIG. 2 is selected. Otherwise, the cold time map shown in FIG. 3 is selected. Based on the selected maps, the in-cylinder injector 110 and / or the intake manifold injector 120 are controlled based on the rotation speed and load factor of the engine 10.

  In the present embodiment, the fuel injection amount from in-cylinder injector 110 and the fuel from intake manifold injector 120 are based on DI ratio r so that the total fuel injection amount becomes a desired injection amount. The injection amount is determined.

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

  When FIG. 2 and FIG. 3 are compared, NE (3) of the map for cold shown in FIG. 3 is higher than NE (1) of the map for warm shown in FIG. This indicates that as the temperature of the engine 10 is lower, the control range of the intake manifold injector 120 is expanded to a higher engine speed range. That is, since the engine 10 is in a cold state, deposits are unlikely to accumulate at the injection port of the in-cylinder injector 110 (even if fuel is not injected from the in-cylinder injector 110). For this reason, it sets so that the area | region which injects a fuel using the intake manifold injector 120 may be expanded, and a homogeneity can be improved.

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

  In the warm map shown in FIG. 2, only the in-cylinder injector 110 is used below the load factor KL (1). This indicates that when the temperature of the engine 10 is high, only the in-cylinder injector 110 is used in a predetermined low load region. This is because when the engine 10 is warm, the engine 10 is in a warm state, and deposits are likely to accumulate at the injection port of the in-cylinder injector 110. However, since the injection port temperature can be lowered by injecting fuel using the in-cylinder injector 110, it is conceivable to avoid deposit accumulation, and the minimum fuel injection amount of the in-cylinder injector Therefore, it is conceivable that the in-cylinder injector 110 is not blocked, and for this reason, the in-cylinder injector 110 is used as an area.

  Comparing FIG. 2 and FIG. 3, the region of “DI ratio r = 0%” exists only in the cold map of FIG. 3. This indicates that when the temperature of the engine 10 is low, only the intake manifold injector 120 is used in a predetermined low load region (KL (3) or less). This is because the engine 10 is cold and the load on the engine 10 is low and the intake air amount is low, so that the fuel is difficult to atomize. In such a region, it is difficult to perform good combustion with the fuel injection by the in-cylinder injector 110. In particular, a high output using the in-cylinder injector 110 is required in the region of low load and low rotation speed. Therefore, only the intake passage injector 120 is used without using the in-cylinder injector 110.

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

  With reference to FIG. 4 and FIG. 5, the learning region in which the feedback correction amount and its learning value are calculated will be described. FIG. 4 shows a learning region in the warm map, and FIG. 5 shows a learning region in the cold map.

  In FIG. 4 and FIG. 5, a region sandwiched by curves indicated by alternate long and short dashed lines is a learning region. The learning area is divided according to the intake air amount. The reason why the learning area is set according to the intake air amount is that the error in the output of the air flow meter 42 differs depending on the intake air amount.

  In the present embodiment, four learning areas from learning areas (1) to (4) are provided. The intake air amount increases in the order of the learning area (1), the learning area (2), the learning area (3), and the learning area (4). Note that the number of learning regions is not limited to four.

  In the present embodiment, in addition to the learning area, the injection area ("DI ratio r = 100%" area, "0% <DI ratio r <100%" area, and "DI ratio r = 0%" area) ), The feedback correction amount and its learning value are calculated. That is, for each injection region, a feedback correction amount is calculated for each learning region, and a learning value is calculated corresponding to the injection region and the learning region as shown in FIG. FIG. 6 shows a state in which one learning value is calculated for each learning region in each injection region. Square points in FIG. 6 indicate learning values in the region of “DI ratio r = 100%”. Circle points indicate learning values in the region of “0% <DI ratio r <100%”. Triangular points indicate learning values in the region of “DI ratio r = 0%”. The calculated learning value is stored in the RAM 330.

  With reference to FIG. 7, a control structure of a program executed when engine ECU 300 which is the control device for the internal combustion engine according to the present embodiment calculates a learning value will be described.

  In step (hereinafter, step is abbreviated as S) 100, engine ECU 300 determines DI ratio r based on the maps shown in FIGS. In S102, engine ECU 300 detects the air-fuel ratio based on the signal transmitted from air-fuel ratio sensor 420. In S104, engine ECU 300 calculates a feedback correction amount for the fuel injection amount based on the detected air-fuel ratio.

  In S106, engine ECU 300 determines whether or not 0% <DI ratio r <100%. If 0% <DI ratio r <100% (YES in S106), the process proceeds to S108. If not (NO in S106), the process proceeds to S116.

  In S108, engine ECU 300 detects temperature T of intake passage injector 120. The temperature of the intake manifold injector 120 is detected using a map created in advance using, for example, the fuel injection amount, engine speed NE, load, fuel temperature, DI ratio, and the like as parameters.

  In S110, engine ECU 300 determines whether or not temperature T of intake manifold injector 120 is higher than threshold value T (0). If temperature T of intake passage injector 120 is higher than threshold value T (0) (YES in S110), the process proceeds to S112. If not (NO in S110), the process proceeds to S116.

  In S112, engine ECU 300 determines whether or not injection amount Q from intake passage injector 120 is smaller than threshold value Q (0). Whether or not the injection amount Q from the intake manifold injector 120 is smaller than the threshold value Q (0) is determined based on the target total injection amount and the DI ratio. If the injection amount Q from intake manifold injector 120 is smaller than threshold value Q (0) (YES in S112), the process proceeds to S114. If not (NO in S112), the process proceeds to S116.

  In S114, engine ECU 300 prohibits calculation (update) of the learning value. Thereafter, this process ends.

  In S116, engine ECU 300 determines whether or not a learning value learning condition is satisfied. As described above, the learning condition is, for example, the condition that the average value (control center value) of the feedback correction amount is smaller than the threshold value (1) or the threshold value (2) (threshold value (2)> threshold. The condition is that it is larger than the value (1)). If the learning condition is satisfied (YES in S116), the process proceeds to S118. Otherwise (NO in S116), this process ends.

  In S118, engine ECU 300 updates the learning value. As described above, the learning value is updated by adding the update amount determined based on the map to the learning value calculated last time or subtracting it from the learning value calculated last time. Thereafter, this process ends.

  The operation of engine ECU 300 that is the control device for the internal combustion engine according to the present embodiment based on the above-described structure and flowchart will be described.

  During engine operation, the DI ratio is determined based on the maps shown in FIGS. 2 and 3 (S100), and the air-fuel ratio is detected based on the signal transmitted from the air-fuel ratio sensor 420 (S102). Based on this air-fuel ratio, a feedback correction amount for the fuel injection amount is calculated (S104).

  When 0% <DI ratio r <100% (S106), the feedback correction amount is calculated for the total injection amount that is the sum of the injection amounts from the in-cylinder injector 110 and the intake manifold injector 120. The The learning value is updated based on the feedback correction amount.

  In normal times, for example, the condition that the average value (control center value) of the feedback correction amount is smaller than the threshold value (1) or the threshold value (2) (threshold value (2)> threshold value (1)) When a learning condition such as a condition of greater than is satisfied (YES in S116), the learning value is updated (S118). If the learning condition is not satisfied (NO in S116), the learning value is not updated.

  By the way, when the temperature of the intake passage injector 120 becomes high, a valve opening / closing operation failure occurs due to a failure in energization of the coil or the fuel boils in the vicinity of the injection hole. The injection amount Q can be smaller than the target injection amount. Such a phenomenon appears remarkably when the injection amount Q (target injection amount) of the intake manifold injector 120 is small. This is because when the injection amount Q (target injection amount) of the intake passage injector 120 is small, the valve opening time is shortened, so that the valve opening control of the intake passage injector 120 becomes difficult.

  In such a state, since the total injection amount is insufficient and the air-fuel ratio becomes lean with respect to the target air-fuel ratio (for example, the theoretical air-fuel ratio), the feedback correction amount is calculated so that the total injection amount is increased. The

  In a state where the learning value is calculated from such a feedback correction amount, when the DI ratio r increases, the injection amount from the intake manifold injector 120 decreases. Therefore, the deviation amount of the actual injection amount with respect to the target injection amount is reduced. In this case, immediately after the DI ratio r is changed, the total injection amount is increased more than necessary by the learning value before the DI ratio r is changed.

  In order to suppress such an increase correction, when 0% <DI ratio r <100% (YES in S106), that is, in a state where fuel is injected from both injectors, intake manifold injector 120 When temperature T is higher than threshold value T (0) (YES in S110) and injection amount Q is lower than threshold value Q (0) (YES in S112), updating of the learning value is prohibited. (S114).

  Thereby, when the DI ratio is changed, it is possible to prevent the total injection amount from being corrected to increase more than necessary by the learning value obtained in a state where the injection amount from the intake manifold injector 120 may be insufficient. Can do. Therefore, the fuel injection amount can be made appropriate.

  As described above, according to the engine ECU which is the control device for the internal combustion engine according to the present embodiment, when 0% <DI ratio r <100%, that is, in a state where fuel is injected from both injectors. When the temperature T of the intake manifold injector is higher than the threshold value T (0) and the injection amount Q is lower than the threshold value Q (0), updating of the learning value is prohibited. Thereby, when the DI ratio is changed, it is possible to prevent the total injection amount from being corrected to increase more than necessary by the learning value obtained in a state where the injection amount from the intake manifold injector can be insufficient. it can. Therefore, the fuel injection amount can be made appropriate.

  In the present embodiment, when the temperature T of the intake manifold injector 120 is higher than the threshold value T (0) and the injection amount Q is lower than the threshold value Q (0), the learning value is updated. However, if the temperature T of the intake manifold injector 120 is higher than the threshold value T (0) even if the injection amount Q is larger than the threshold value Q (0), the learning value Update may be prohibited.

  Further, when the temperature T of the in-cylinder injector 110 is higher than the threshold value T (0), or when the temperature T of the in-cylinder injector 110 is higher than the threshold value T (0), the injection is performed. When the amount Q is smaller than the threshold value Q (0), the learning value may be prohibited from being updated.

<Second Embodiment>
The second embodiment of the present invention will be described with reference to FIGS. In the present embodiment, the DI ratio r is calculated using a map different from that of the first embodiment.

  Other structures and processing flow are the same as those in the first embodiment. The function about them is the same. Therefore, detailed description thereof will not be repeated here.

  With reference to FIGS. 8 and 9, a map representing the injection ratio of in-cylinder injector 110 and intake manifold injector 120, which is information corresponding to the operating state of engine 10, will be described. These maps are stored in the ROM 320 of the engine ECU 300. FIG. 8 is a warm map of the engine 10, and FIG. 9 is a cold map of the engine 10.

  8 and 9 differ from FIGS. 2 and 3 in the following points. The rotational speed of the engine 10 is “DI ratio r = 100%” in the region of NE (1) or more in the warm map and in the region of NE (3) or more in the cold map. In the region where the load factor is KL (2) or higher excluding the low rotational speed region in the warm map, and in the region where KL (4) is higher than the low rotational speed region in the cold map, “DI” Ratio r = 100% ”. This is because only the in-cylinder injector 110 is used in a predetermined high engine speed region, and only the in-cylinder injector 110 is used in a predetermined high engine load region. Indicates. However, in the high load region of the low engine speed region, mixing of the air-fuel mixture formed by the fuel injected from the in-cylinder injector 110 is not good, and the air-fuel mixture in the combustion chamber is inhomogeneous and combustion is unstable. Tend to be. For this reason, the injection ratio of the in-cylinder injector is increased with the shift to the high rotation speed region where such a problem does not occur. In addition, the injection ratio of the in-cylinder injector 110 is decreased as the engine shifts to a high load region where such a problem occurs. These changes in the DI ratio r are indicated by cross arrows in FIGS. If it does in this way, the fluctuation | variation of the output torque of an engine resulting from combustion being unstable can be suppressed. It should be noted that these things can be achieved by reducing the injection ratio of the in-cylinder injector 110 as the engine shifts to the predetermined low rotational speed region, or by the in-cylinder injection as the vehicle shifts to the predetermined low load region. The fact that it is substantially equivalent to increasing the injection ratio of the injector 110 for operation will be described. Further, areas other than such areas (areas where the crossed arrows are described in FIGS. 8 and 9) and areas where fuel is injected only by the in-cylinder injector 110 (high rotation side, low load) On the other hand, it is easy to homogenize the air-fuel mixture with the in-cylinder injector 110 alone. Thus, the fuel injected from the in-cylinder injector 110 is vaporized with latent heat of vaporization (sucking heat from the combustion chamber) in the combustion chamber. Thereby, the temperature of the air-fuel mixture at the compression end is lowered. As a result, the knocking performance is improved. Further, since the temperature of the combustion chamber is lowered, the suction efficiency is improved and high output can be expected.

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

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

  In the engine described in the first and second embodiments, the timing of fuel injection by the in-cylinder injector 110 is preferably performed in the compression stroke for the following reason. However, in the engine 10 described above, in a basic most region (a weak operation that is performed only when the catalyst is warmed up, the intake passage injection injector 120 is injected in the intake stroke and the in-cylinder injector 110 is compressed in the compression stroke. The timing of fuel injection by the in-cylinder injector 110 other than the stratified combustion region is a basic region) is the intake stroke. However, for the following reasons, the fuel injection timing of the in-cylinder injector 110 may be temporarily set to the compression stroke injection for the purpose of stabilizing the combustion.

  By setting the fuel injection timing from the in-cylinder injector 110 during the compression stroke, the air-fuel mixture is cooled by fuel injection at a time when the in-cylinder temperature is higher. Since the cooling effect is enhanced, knock resistance can be improved. Furthermore, if the fuel injection timing from the in-cylinder injector 110 is in the compression stroke, the time from the fuel injection to the ignition timing is short, so that the air flow can be strengthened by spraying and the combustion speed can be increased. From these improvement in knocking property and increase in combustion speed, combustion fluctuation can be avoided and combustion stability can be improved.

  Furthermore, regardless of the temperature of the engine 10 (that is, whether the engine is warm or cold), it is off-idle (when the idle switch is off or the accelerator pedal is depressed). May use the warm map shown in FIG. 2 or FIG. 8 (the in-cylinder injector 110 is used in the low load region regardless of the cold warm).

  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.

It is a schematic block diagram of the engine system controlled by the control apparatus which concerns on the 1st Embodiment of this invention. It is a figure showing DI ratio map at the time of warm memorized by engine ECU which is a control device concerning a 1st embodiment of the present invention. It is a figure showing the DI ratio map at the time of cold memorized by engine ECU which is a control device concerning a 1st embodiment of the present invention. It is FIG. (1) which shows the learning area | region of the fuel injection quantity memorize | stored in engine ECU which is a control apparatus which concerns on the 1st Embodiment of this invention. FIG. 8 is a diagram (No. 2) illustrating a fuel injection amount learning region stored in the engine ECU that is the control device according to the first embodiment of the present invention. It is a figure which shows the state by which the learning value was calculated for every learning area | region about each injection area | region. It is a flowchart which shows the control structure of the program which engine ECU which is a control apparatus which concerns on the 1st Embodiment of this invention performs. It is a figure showing the DI ratio map at the time of warm memorize | stored in engine ECU which is a control apparatus which concerns on the 2nd Embodiment of this invention. It is a figure showing DI ratio map at the time of cold memorized by engine ECU which is a control device concerning a 2nd embodiment of the present invention.

Explanation of symbols

  10 engine, 20 intake manifold, 30 surge tank, 40 air intake duct, 42 air flow meter, 50 air cleaner, 60 electric motor, 70 throttle valve, 80 exhaust manifold, 90 three-way catalytic converter, 100 accelerator pedal, 110 in-cylinder injector , 112 cylinder, 120 Injector injector, 130 Fuel distribution pipe, 140 Check valve, 150 High pressure fuel pump, 152 Electromagnetic spill valve, 160 Fuel distribution pipe (low pressure side), 170 Fuel pressure regulator, 180 Low pressure fuel pump, 190 fuel filter, 200 fuel tank, 300 engine ECU, 310 bidirectional bus, 320 ROM, 330 RAM, 340 CPU, 350 input port, 360 output port, 370, 39 , 410,430,450 A / D converter, 380 a water temperature sensor, 400 a fuel pressure sensor, 420 an air-fuel ratio sensor, 440 an accelerator opening sensor, 460 rpm sensor.

Claims (2)

A control device 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,
Detecting means for detecting an air-fuel ratio of the internal combustion engine;
Calculation means for calculating a correction value of the fuel injection amount based on the detected air-fuel ratio;
Control means for controlling the first fuel injection means and the second fuel injection means so that an amount of fuel corresponding to the correction value is injected;
In a state where fuel is injected from both the first fuel injection means and the second fuel injection means, a condition that the temperature of the second fuel injection means is higher than a predetermined temperature; And a prohibiting unit for prohibiting the calculation of the correction value when a condition that the fuel injection amount from the fuel injection unit is smaller than a predetermined fuel injection amount is satisfied. apparatus. The first fuel injection means is an in-cylinder injector,
The control apparatus for an internal combustion engine according to claim 1, wherein the second fuel injection means is an intake passage injection injector.

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