JP5637098B2 - Control device for internal combustion engine - Google Patents

Description

  The present invention relates to a control device for an internal combustion engine, and more particularly to a technique applied to a direct injection internal combustion engine that injects fuel directly into a cylinder.

  2. Description of the Related Art Conventionally, an in-cylinder injection type internal combustion engine that directly injects fuel into a cylinder is known. In addition, in a cylinder injection internal combustion engine, particulate matter (PM) is easily discharged by fuel combustion in the engine, and in view of this, various technologies that consider PM discharge have been proposed (for example, Patent Document 1). reference). In Patent Document 1, by adjusting the valve overlap amount between the intake valve and the exhaust valve and the closing timing of the intake valve, the residual gas that has not been discharged from the cylinder during the exhaust stroke is blown back into the intake pipe, and the blow back is also performed. It is disclosed that the fuel injection valve is controlled so that fuel is injected at the piston non-collision injection timing when the residual gas is blown back into the cylinder again in the intake stroke (when the internal EGR effect is obtained). As a result, even when the valve overlap amount is increased so as to obtain the internal EGR effect, it is possible to prevent deposits from being generated in the intake port or the like due to PM being blown back into the intake pipe together with the residual gas. I am doing so.

JP 2008-303799 A

  By the way, the fuel injection timing at which the PM emission amount from the engine is minimized does not necessarily coincide with the fuel injection timing at which the fuel efficiency of the engine is the best. Therefore, if priority is given to PM reduction, deterioration of fuel consumption must be allowed, but it is desirable to minimize the degree of fuel consumption deterioration while keeping the PM emission amount within an allowable range.

  The present invention has been made in view of the above problems, and a main object of the present invention is to provide a control device for an internal combustion engine that can achieve both the suppression of emission of particulate matter and the improvement of fuel efficiency.

  The present invention employs the following means in order to solve the above problems.

The present invention relates to a control device for an internal combustion engine applied to an in-cylinder injection type internal combustion engine in which fuel is directly injected into a cylinder from a fuel injection valve. The invention according to claim 1 is a PM reference timing calculation means for calculating a PM reference injection timing which is a fuel injection timing at which the amount of particulate matter discharged from the internal combustion engine is minimized based on the engine operating state. And a particulate matter amount detecting means for detecting the amount of particulate matter contained in the exhaust gas of the internal combustion engine, and an injection for commanding fuel injection by the fuel injection valve for each fuel injection in a steady operation state of the internal combustion engine From the PM reference injection timing calculated by the PM reference timing calculation means within a range in which the particulate matter amount detected by the particulate matter amount detection means does not exceed a predetermined upper limit value, the current command engine And an injection timing changing means for gradually changing the fuel injection timing toward the best fuel injection timing, which is the fuel injection timing at which the fuel efficiency is optimal in the driving state.

  In short, in a cylinder injection internal combustion engine, there is a correlation between the fuel injection timing and the amount of particulate matter discharged from the internal combustion engine due to the combustion of fuel. Emissions change. Similarly, in the internal combustion engine, there is a correlation between the fuel injection timing and the fuel consumption, and the fuel consumption changes by changing the fuel injection timing. Here, the fuel injection timing at which the particulate matter emission amount is minimized does not necessarily coincide with the fuel injection timing at which the fuel consumption of the internal combustion engine is best. On the other hand, considering the recent stricter regulations on particulate matter and optimization of fuel consumption, it is necessary to achieve both reduction of particulate matter emission and optimization of fuel consumption.

  In view of this point, in the above configuration, the amount of particulate matter discharged from the internal combustion engine is monitored, and the injection timing for each fuel injection is set so that the amount of particulate matter does not exceed the upper limit value. The injection timing is gradually approached from the injection timing at which the amount of exhaust gas is minimized. Thereby, fuel consumption can be improved while suppressing emission of particulate matter.

  According to a second aspect of the present invention, when the injection timing command value is gradually changed, it is determined whether or not the amount of the particulate matter detected by the particulate matter amount detection means has reached the predetermined upper limit value. A substance amount determining means, wherein the injection timing changing means determines that the injection timing command value is the best fuel efficiency before the substance amount determining means determines that the amount of the particulate matter has reached the predetermined upper limit value. When it is determined that the amount of the particulate matter has reached the predetermined upper limit value by the substance amount determination means before the injection timing is reached or before the injection timing command value reaches the fuel efficiency best injection timing, At that time, the gradual change of the injection timing command value is stopped, and fuel injection is controlled by the injection timing command value.

  When the injection timing command value is changed in the direction of the best fuel injection timing, the amount of particulate matter reaches the best fuel injection timing before reaching the upper limit of the allowable range, or before the best fuel injection timing is reached. When the amount of particulate matter reaches the upper limit of the allowable range, the fuel injection timing at that time can be said to be the injection timing that can achieve the best fuel consumption when the particulate matter is within the allowable range. Therefore, by maintaining the injection timing command value, it is possible to achieve both particulate matter emission suppression and fuel efficiency optimization.

  The gradual change of the injection timing command value for each fuel injection is preferably performed on condition that the internal combustion engine is in a steady operation state. Accordingly, as in the third aspect of the invention, there is provided an operation state determination unit that determines whether or not the operation state of the internal combustion engine is a steady operation state, and the operation state determination unit determines that the operation state is a steady operation state. If not, the injection timing command value is set as the PM reference injection timing, and when it is determined that the operation is in the steady operation state, the injection timing changing means changes the injection timing command value from the PM reference injection timing. It is preferable to gradually change toward the fuel efficiency best injection timing.

  According to a fourth aspect of the present invention, when the injection timing command value is gradually changed from the PM reference injection timing toward the fuel efficiency best injection timing by the injection timing changing means according to the rotational speed of the internal combustion engine. Set the variable.

  The degree of change (increase rate) in the particulate matter associated with the change in the fuel injection timing differs depending on the engine rotation speed. The higher the engine rotation speed, the more the fuel injection timing becomes the fuel efficiency best injection timing than the PM reference injection timing. When the direction is changed, the amount of particulate matter discharged increases greatly. That is, the higher the engine speed, the higher the sensitivity to changes in the fuel injection timing. Therefore, if the amount of gradual change when the fuel injection timing is gradually changed, if the engine speed is relatively high, the particulate matter increases rapidly due to the high sensitivity, and the engine speed is compared. If the fuel injection timing is low, it may take time to change the fuel injection timing toward the best fuel injection timing. Therefore, with the above configuration, the fuel injection timing can be gradually changed by an appropriate change amount corresponding to the sensitivity to the change of the fuel injection timing.

  According to a fifth aspect of the present invention, there is provided a deviation width calculating means for calculating a deviation width between the PM reference injection timing and the fuel efficiency best injection timing, and the injection is performed based on the deviation width calculated by the deviation width calculating means. A gradual change amount is set when the injection timing command value is gradually changed from the PM reference injection timing toward the fuel efficiency best injection timing by the timing changing means.

  The PM reference injection timing and the best fuel efficiency injection timing differ depending on the operating state of the internal combustion engine. Along with the difference, the deviation width between the PM reference injection timing and the best fuel efficiency injection timing differs depending on the operating state of the internal combustion engine. Accordingly, if the amount of gradual change when the fuel injection timing is gradually changed is constant, it takes time to change the fuel injection timing toward the best fuel injection timing when the deviation is relatively large. Therefore, as in the above configuration, the gradual change amount may be set variably in accordance with the deviation width between the PM reference injection timing and the fuel efficiency best injection timing.

  According to a sixth aspect of the invention, there is provided a deviation width calculating means for calculating a deviation width between the PM reference injection timing and the fuel efficiency best injection timing, and the injection is based on the deviation width calculated by the deviation width calculating means. It is switched whether or not the injection timing command value is gradually changed by the timing changing means.

  In an internal combustion engine, there may be a dead zone in which the amount of particulate matter and fuel consumption do not change even when the fuel injection timing is changed. Considering this dead zone, if the difference between the PM reference injection timing and the fuel efficiency best injection timing is not so large, even if the fuel injection timing is changed, for example, the amount of particulate matter will increase, but the fuel efficiency will be improved sufficiently. Things that can't be done can happen. Therefore, the fuel injection timing control in consideration of the dead zone can be realized by adopting the above configuration. Specifically, when the deviation width between the PM reference injection timing and the fuel efficiency best injection timing is equal to or greater than the determination value, the fuel injection timing is gradually changed, and when the deviation width is less than the determination value, the fuel injection timing. The gradual change is not implemented.

  In the invention according to claim 7, when the injection timing command value is gradually changed from the PM reference injection timing toward the fuel efficiency best injection timing by the injection timing changing means, the particulate matter amount detecting means is used. If the injection timing command value reaches the fuel efficiency best injection time before the amount of particulate matter detected reaches the predetermined upper limit value, the fuel efficiency best injection time, or the particulate matter amount detection means When the amount of the particulate matter detected by the engine reaches the predetermined upper limit value before reaching the fuel efficiency best injection timing, the fuel injection timing when the upper limit value is reached is set as the optimum injection timing. Storage means for storing for each operation region, and when the optimum injection timing corresponding to the current engine operating state is stored in the storage means, the optimum injection timing is used as the injection timing command value for fuel To control the injection. According to this configuration, it is possible to suppress particulate matter and optimize fuel efficiency without having to gradually change the injection timing command value from the PM reference injection timing to the fuel efficiency best injection timing every time the engine operating state changes. It is possible to set the optimal fuel injection timing to achieve both. Thereby, controllability can be made favorable.

1 is an overall schematic configuration diagram of an engine control system. The figure which shows a fuel injection timing characteristic. (A) shows the relationship between the fuel injection timing and the PM emission amount, and (b) shows the relationship between the fuel injection timing and the fuel consumption rate. The figure explaining the specific aspect of fuel injection timing control. The flowchart which shows the process sequence of fuel injection timing control.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, embodiments of the invention will be described with reference to the drawings. In the present embodiment, an engine control system is constructed for an in-cylinder injection and spark ignition engine that is an on-vehicle multi-cylinder four-cycle gasoline engine that is an internal combustion engine. In this control system, an electronic control unit (hereinafter referred to as ECU) is used as a center to control the fuel injection amount, control the ignition timing, and the like. FIG. 1 shows an overall schematic configuration diagram of the engine control system.

  In the engine 10 shown in FIG. 1, an air cleaner 12 is provided at the most upstream portion of the intake pipe 11, and an air flow meter 13 for detecting the intake air amount is provided downstream of the air cleaner 12. A throttle valve 14 whose opening degree is adjusted by a throttle actuator 15 such as a DC motor is provided on the downstream side of the air flow meter 13. The opening degree of the throttle valve 14 (throttle opening degree) is detected by a throttle opening degree sensor built in the throttle actuator 15.

  A surge tank 16 is provided on the downstream side of the throttle valve 14, and an intake pipe pressure sensor 17 for detecting the intake pipe pressure is provided in the surge tank 16. An intake manifold 18 for introducing air into each cylinder of the engine 10 is connected to the surge tank 16. The intake manifold 18 is further connected to the intake port of each cylinder.

  An intake valve 21 and an exhaust valve 22 are provided at an intake port and an exhaust port of the engine 10, respectively. The air in the surge tank 16 is introduced into the combustion chamber 23 by the opening operation of the intake valve 21, and the exhaust gas after combustion is discharged to the exhaust pipe 24 by the opening operation of the exhaust valve 22.

  A fuel injection valve 19 that directly supplies fuel into the combustion chamber 23 is attached to the upper part of each cylinder of the engine 10. A fuel tank 38 is connected to the fuel injection valve 19 via a fuel pipe 25. In the fuel pipe 25, an electromagnetically driven feed pump 39 is disposed at the most upstream portion, and a mechanically driven high-pressure pump 26 is disposed downstream of the feed pump 39. The fuel in the fuel tank 38 is pumped up by the feed pump 39 and pressurized to a predetermined feed pressure (for example, 0.3 MPa), and then pumped to the high-pressure pump 26. The feed pressure fuel fed to the high-pressure pump 26 is further increased to a high pressure (for example, 4 to 20 MPa) by the high-pressure pump 26, and then pumped to the delivery pipe 27. The fuel injection valve 19 of each cylinder is delivered from the delivery pipe 27. And is injected from the fuel injection valve 19 into the combustion chamber 23.

  A spark plug 29 is attached to the cylinder head of the engine 10. A high voltage is applied to the spark plug 29 at a desired ignition timing through an ignition device (not shown) including an ignition coil. By applying this high voltage, a spark discharge is generated between the opposing electrodes of each spark plug 29, and the air-fuel mixture in the combustion chamber 23 is ignited and used for combustion.

  The exhaust pipe 24 is provided with a three-way catalyst 31 as a catalyst for purifying CO, HC, NOx and the like in the exhaust gas. Further, the exhaust pipe 24 is provided with an air-fuel ratio sensor 32 for detecting the air-fuel ratio (oxygen concentration) of the air-fuel mixture on the upstream side of the catalyst as the detection target, and is included in the exhaust on the downstream side of the catalyst. A PM sensor 33 that detects the amount of particulate matter (PM) is provided.

  In addition, the engine 10 includes a cooling water temperature sensor 35 that detects the cooling water temperature, a crank angle sensor 36 that outputs a rectangular crank angle signal at every predetermined crank angle of the engine 10 (for example, at a cycle of 10 ° CA), and a delivery pipe. A fuel pressure sensor 37 for detecting the fuel pressure in the fuel tank 27 is attached.

  As is well known, the ECU 50 is mainly composed of a microcomputer (hereinafter referred to as a microcomputer) 51 composed of a CPU, ROM, RAM, etc., and executes various control programs stored in the ROM, so that the engine operation state can be changed each time. In response, various controls of the engine 10 are performed. That is, the microcomputer 51 of the ECU 50 inputs detection signals from the various sensors described above, calculates the fuel injection amount, fuel injection timing, ignition timing, and the like based on the input various detection signals, and the fuel injection valve 19. And controls the driving of the ignition device.

  Regarding the fuel injection timing control, the microcomputer 51 calculates the fuel target injection timing based on the engine operating state (for example, the engine speed and engine load). Further, the drive of the fuel injection valve 19 is controlled by outputting an injection signal (injection timing command value) to the fuel injection valve 19 so that fuel injection is started at the calculated target injection timing. Regarding the injection timing In this embodiment, basically, an intake stroke injection that starts fuel injection in an intake stroke in one combustion cycle (intake stroke → compression stroke → expansion stroke → exhaust stroke) is performed, for example, at the time of engine start In some engine operating conditions such as when the catalyst is warmed up, the compression stroke injection is started to start fuel injection in the compression stroke.

  By the way, in a cylinder injection engine, the correlation between the fuel injection timing and the amount of particulate matter (PM amount) discharged by the combustion of the fuel is strong. For example, in the case of intake stroke injection, FIG. As shown in a), as the fuel injection timing is changed from the vicinity of the intake top dead center (intake TDC) to the retarded angle side, the PM amount contained in the exhaust gas decreases, and the retarded angle side of the intake TDC is retarded by a predetermined angle. The PM amount is minimized near the angular position (A in FIG. 2). For example, in a certain engine operating state (engine speed Va, engine load Qa), as shown in FIG. 2A, the amount of PM discharged from the engine 10 is minimized around 300 ° C. before compression top dead center. Become. Further, when the fuel injection timing is further retarded from the injection timing at which the PM amount is minimized, the PM amount gradually increases with the delay of the fuel injection timing, and a certain angular position (B in FIG. 2) is set. If it exceeds, the amount of PM will increase greatly again. Considering such PM emission characteristics, in order to suppress the PM emission amount, it is preferable to set the minimum PM angular position as a command value for the fuel injection timing.

  On the other hand, the fuel injection timing at which the PM amount contained in the exhaust of the engine 10 is minimized does not necessarily coincide with the fuel injection timing at which the fuel efficiency of the engine 10 is best (fuel economy best point). For example, in the operating state of the engine speed Va and the engine load Qa, as shown in FIG. 2B, the fuel consumption is minimized when fuel is injected near 325 ° C. A before compression top dead center (C in FIG. 2). ). In view of these matters, when setting the command value for the fuel injection timing, if priority is given to PM reduction, it is necessary to allow fuel consumption deterioration. However, the degree of fuel consumption deterioration falls within the allowable range of PM emissions. It is desirable to minimize it while doing so.

  Further, as shown in FIG. 2 (a), the amount of increase in the PM emission amount with respect to the change amount of the fuel injection timing is more advanced than the fuel injection timing (A in FIG. 2) at which the PM emission amount is minimized. More than the retard side. Therefore, considering the design tolerances of the engine 10 and the fuel injection valve 19 (considering the robustness of PM reduction), the appropriate value for the fuel injection timing is slightly retarded from the injection timing at which the PM amount is minimized. It is desirable to set to. However, as shown in FIG. 2 (b), when the fuel injection timing is set to the retarded side, the fuel consumption is deteriorated. For this reason, when the fuel injection timing is controlled by a predetermined adaptive value, it cannot always be said that deterioration of fuel consumption can be suitably suppressed.

  Therefore, in the present embodiment, the amount of PM contained in the exhaust gas of the engine 10 (PM emission amount) is detected, and the fuel injection for each fuel injection is performed so that the detected PM emission amount does not exceed the upper limit value of the allowable range. From the PM reference injection timing (A in FIG. 2), which is the fuel injection timing at which the amount of PM discharged from the engine 10 is minimized, the fuel injection that provides the best fuel efficiency in the current engine operating state The fuel consumption is gradually changed toward the best fuel efficiency injection timing (C in FIG. 2).

  The fuel injection timing control of this embodiment will be described more specifically with reference to FIG. In the present embodiment, basically, the target injection timing is calculated using, for example, a predetermined adaptation map based on the engine operating state. At this time, in the present embodiment, the PM reference injection timing is set as the target injection timing, and the fuel injection valve 19 is controlled so that fuel is injected at the PM reference injection timing. Then, when the engine 10 shifts to the steady operation state, the target injection timing is changed from the PM reference injection timing to a predetermined gradual change amount α in the direction of the best fuel injection timing (direction of arrow M in FIG. 3) from the PM reference injection timing. Change it step by step. That is, under steady operating conditions, while monitoring the PM discharge amount detected by the PM sensor 33, the fuel injection timing command value is gradually changed by a predetermined amount with respect to the previous value every time the fuel injection valve 19 performs fuel injection. Let In addition, if the fuel injection timing reaches the best fuel injection timing while the control is being executed, the gradual change of the command value of the fuel injection timing is stopped at that time, and the fuel injection at the best fuel injection timing is maintained. To do. However, when the PM emission amount detected by the PM sensor 33 reaches a predetermined upper limit value (reference value TH) before the fuel injection timing reaches the fuel efficiency best injection timing, the point at which the reference value TH is reached. Then, the gradual change of the fuel injection timing is stopped, and the injection timing (In1 in FIG. 3) at that time is maintained.

  Next, the fuel injection timing control of the present embodiment will be described using the flowchart of FIG. This process is executed by the microcomputer 51 of the ECU 50 for each fuel injection in each cylinder (for every 180 ° C. in the case of a 4-cylinder engine).

  In FIG. 4, in step S101, it is determined whether or not the operating state of the engine 10 is a steady state. In the present embodiment, it is determined that the engine is in the steady operation state when the engine rotation speed and the engine load are constant for a predetermined time. If it is determined that the engine is not in the steady operation state, the process proceeds to step S102, and a fuel injection timing (PM reference injection timing) at which the PM emission amount is minimized is calculated based on the engine operation state at that time (PM reference timing calculation). And the calculated PM reference injection timing is set as the target injection timing. In this embodiment, the PM reference injection timing is predetermined and stored as a PM conformity map for each engine operating state. Therefore, here, the PM reference injection timing corresponding to the current engine operating state is read from the PM compatibility map, and the read PM reference injection timing is set as the target injection timing. In step S103, an injection signal is output to the fuel injection valve 19 so that fuel is injected from the fuel injection valve 19 at the set target injection timing.

  On the other hand, when it is determined that the engine 10 is in the steady operation state, an affirmative determination is made in step S101, and the process proceeds to step S104. In step S104, based on the engine operating state at that time, a fuel injection timing (the best fuel injection timing) at which the fuel efficiency of the engine 10 is best is calculated. In this embodiment, the best fuel injection timing is determined and stored in advance as a fuel consumption adaptation map for each engine operation state, and the best fuel injection timing corresponding to the current engine operation state is read from the fuel consumption adaptation map. Calculate the optimal fuel injection timing.

  In step S105, it is determined whether or not the best fuel efficiency injection timing is set as the target injection timing. When a negative determination is made in step S105, the process proceeds to step S106, where the PM discharge amount detected by the PM sensor 33 is acquired, and in step S107, it is determined whether the acquired PM discharge amount is equal to or less than a reference value. . Here, the reference value is an upper limit value of a range allowed as the PM amount contained in the exhaust of the engine 10, and in the present embodiment, it is predetermined and stored for each engine operating state.

  If the PM emission amount is less than or equal to the reference value, an affirmative determination is made in step S107 and the process proceeds to step S108. In step S108, the previous value of the target injection timing is changed by a predetermined gradual change amount α (for example, several degrees C) in the direction of the best fuel injection timing. At this time, for example, when a transition from a state in which the steady operation state is not determined (pre-determination state) to a state in which the steady operation state is determined (post-determination state), first, before the determination The advance side or the retard side is changed with respect to the last target fuel injection timing (PM reference injection timing) in the state, and then the further advance side or retard side with respect to the previous value of the target injection timing Changes to are made. Further, with regard to the direction of changing the target injection timing, specifically, for example, in the case of the engine operating state of FIG. 2, the fuel efficiency best injection timing is on the advance side with respect to the PM reference injection timing. The gradual change amount α is changed to the advance side. On the other hand, when the best fuel injection timing is on the retard side relative to the PM reference injection timing, the previous value of the target injection timing is changed to the retard side. Note that the gradual change amount α is a fixed value in this embodiment. In step S103, an injection signal (injection timing command value) is output to the fuel injection valve 19 so that fuel injection is performed at the set target injection timing.

  On the other hand, when the PM emission amount is larger than the reference value, a negative determination is made in step S107, the process proceeds to step S109, the gradual change of the fuel injection timing is stopped, and the target injection timing (previous value) at that time is held. . In step S103, an injection signal is output to the fuel injection valve 19 so that fuel is injected at the set target injection timing.

  If it is determined in step S105 that the target injection timing is the best fuel consumption injection timing, the process proceeds to step S110, where the target injection timing is held at the optimal fuel consumption injection timing (the previous value is maintained), and in step S103, the best fuel consumption is achieved. An injection signal is output to the fuel injection valve 19 so that fuel is injected at the injection timing.

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

  The amount of PM discharged from the engine 10 is monitored, and the PM amount is in a range that does not exceed the upper limit value, and the fuel injection timing for each fuel injection in each cylinder (fuel injection performed at 180 ° C. for a 4-cylinder engine) The injection timing is gradually changed from the PM reference injection timing at which the PM emission amount is minimized to the best fuel efficiency injection timing at which the fuel efficiency is optimal. In this case, it is possible to inject fuel at a fuel injection timing with better fuel efficiency among fuel injection timings in which the PM emission amount is within an allowable range. Therefore, according to the said structure, fuel consumption can be made favorable, aiming at PM discharge suppression.

  In addition, when the injection timing command value is gradually changed, it is determined that the PM amount has reached the reference value based on the detection value of the PM sensor 33, and it is determined that the PM amount has reached the reference value. If it is determined that the injection timing command value has reached the fuel efficiency best injection timing before, or the PM amount has reached the reference value before the injection timing command value has reached the fuel efficiency best injection timing, then the injection timing command The gradual change of the value is stopped, and the fuel injection is controlled by the injection timing command value. In this case, the fuel injection timing with the best fuel consumption among the fuel injection timings in which the PM emission amount is within the allowable range can be maintained as the command value.

(Other embodiments)
The present invention is not limited to the description of the above embodiment, and may be implemented as follows, for example.

  In the above embodiment, the gradual change amount (the gradual change amount α of the target injection timing) when the command value of the fuel injection timing is changed from the PM reference injection timing toward the fuel efficiency best injection timing for each fuel injection is a fixed value. In this embodiment, the gradual change amount is variably set in accordance with the engine rotation speed (the engine rotation speed in the engine steady operation state). The influence (sensitivity) on the PM emission amount when the fuel injection timing is changed differs depending on the engine rotation speed. The higher the engine rotation speed, the fuel injection timing is set to the fuel efficiency best injection timing than the PM reference injection timing. When the direction is changed, the PM increase amount (slope) increases. In this case, when the engine speed is high, the sensitivity of the PM emission amount associated with the change of the fuel injection timing is high, so it is desirable to make the change amount of the fuel injection timing as small as possible. On the other hand, when the engine speed is low, if the gradual change amount is too small, it takes time to change the fuel injection timing toward the best fuel injection timing. Therefore, in the present embodiment, the gradual change amount is set to be smaller as the engine rotation speed is higher. Thereby, the gradual change amount according to the engine rotation speed can be set, and fuel injection timing control suitable for each operation state can be realized.

  -When the deviation width between the PM reference injection timing and the best fuel efficiency injection timing is calculated, and the fuel injection timing is changed from the PM reference injection timing toward the best fuel efficiency injection timing for each fuel injection based on the calculated deviation width The gradual variation amount (gradual variation amount α of the target injection timing) is variably set. At this time, it is better to set the gradual change amount as the deviation width is larger.

  -About the engine 10, it is possible that there exists a dead zone in which PM emission amount and fuel consumption do not change only by slightly changing the fuel injection timing. In view of this, whether or not to gradually change the fuel injection timing (command value) from the PM reference injection timing to the fuel efficiency best injection timing is switched based on the deviation width between the PM reference injection timing and the fuel efficiency best injection timing. The configuration. Specifically, when the deviation width between the PM reference injection timing and the fuel efficiency best injection timing is less than the determination value, the fuel injection timing is not gradually changed. For example, fuel injection is performed with the PM reference injection timing as the target injection timing. carry out. On the other hand, when the deviation width is equal to or larger than the determination value, the fuel injection timing is gradually changed by, for example, the processing of FIG.

  In the above embodiment, the target injection timing is gradually changed from the PM reference injection timing to the fuel economy best injection timing by a predetermined amount, whereby the command value of the fuel injection timing is directed from the PM reference injection timing to the fuel economy best injection timing. However, the configuration for changing the command value of the fuel injection timing is not limited to this. For example, the difference between the PM reference injection timing and the best fuel efficiency injection timing is calculated, and the change amount of the injection timing command value is calculated based on the difference. At this time, the change amount of the injection timing command value in each fuel injection is limited, that is, the change amount is calculated so that the command value of the fuel injection timing is changed minutely (for example, by several degrees C).

  When the command value of the fuel injection timing is gradually changed from the PM reference injection timing toward the fuel efficiency best injection timing, before the PM emission amount detected by the PM sensor 33 reaches a predetermined upper limit value (reference value TH) When the fuel injection timing reaches the best fuel injection timing, the best fuel injection timing or the PM emission detected by the PM sensor 33 reaches a predetermined upper limit value before reaching the best fuel injection timing. In this case, the fuel injection timing when the upper limit value is reached is acquired as the optimal injection timing, and the acquired optimal injection timing is stored for each engine operating state (storage means). At this time, the optimum injection timing is stored in correspondence with the engine operating state for which the optimum injection timing has been acquired. When the optimum injection timing corresponding to the current engine operating state is stored during operation of the engine 10, the optimum injection timing is set as the target fuel injection timing, and the set target injection timing is set. An injection signal (injection timing command value) is output to the fuel injection valve 19 so that fuel is injected. According to this configuration, even when the fuel injection timing is not gradually changed every time the engine operating state changes, an optimal fuel injection timing is set to achieve both PM emission suppression and fuel efficiency optimization. And controllability can be improved.

  DESCRIPTION OF SYMBOLS 10 ... Engine, 19 ... Fuel injection valve, 29 ... Spark plug, 50 ... ECU, 51 ... Microcomputer (PM reference | standard timing calculation means, particulate matter amount detection means, injection timing change means, substance amount determination means, operation state determination means , Deviation width calculation means, storage means).

Claims (7)

Applied to an in-cylinder internal combustion engine that injects fuel directly into a cylinder from a fuel injection valve,
PM reference timing calculation means for calculating a PM reference injection timing, which is a fuel injection timing that minimizes the amount of particulate matter discharged from the internal combustion engine, based on the engine operating state;
Particulate matter amount detection means for detecting the amount of particulate matter contained in the exhaust gas of the internal combustion engine;
In a steady operation state of the internal combustion engine, an injection timing command value for instructing fuel injection by the fuel injection valve for each fuel injection, and the amount of particulate matter detected by the particulate matter amount detecting means is a predetermined upper limit value. The injection timing is gradually changed from the PM reference injection timing calculated by the PM reference timing calculation means toward the best fuel injection timing that is the best fuel injection timing in the current engine operating state without exceeding Change means,
A control device for an internal combustion engine, comprising: A substance amount determination means for determining whether or not the amount of the particulate matter detected by the particulate matter amount detection means has reached the predetermined upper limit value when the injection timing command value is gradually changed;
The injection timing changing means is configured such that the injection timing command value reaches the fuel efficiency best injection timing before the substance amount determining means determines that the amount of the particulate matter has reached the predetermined upper limit value, or If the amount of the particulate matter has reached the predetermined upper limit by the substance amount determination means before the injection timing command value reaches the fuel efficiency best injection timing, the injection timing command at that time 2. The control device for an internal combustion engine according to claim 1, wherein the gradual change of the value is stopped and the fuel injection is controlled by the injection timing command value. An operating state determining means for determining whether or not the operating state of the internal combustion engine is a steady operating state;
The injection timing command value is set as the PM reference injection timing when the operation state determination unit does not determine that the operation state is a steady operation state, and when it is determined that the operation state is the steady operation state, the injection timing change unit The control device for an internal combustion engine according to claim 1 or 2, wherein the injection timing command value is gradually changed from the PM reference injection timing toward the fuel efficiency best injection timing.   4. A gradual change amount is set when the injection timing change means gradually changes the injection timing command value from the PM reference injection timing toward the fuel efficiency best injection timing according to the rotational speed of the internal combustion engine. The control apparatus for an internal combustion engine according to any one of the above. A deviation width calculating means for calculating a deviation width between the PM reference injection timing and the fuel efficiency best injection timing;
Based on the deviation width calculated by the deviation width calculating means, a gradual change amount is set when the injection timing command value is gradually changed from the PM reference injection timing toward the fuel efficiency best injection timing by the injection timing changing means. The control device for an internal combustion engine according to any one of claims 1 to 3. A deviation width calculating means for calculating a deviation width between the PM reference injection timing and the fuel efficiency best injection timing;
6. The internal combustion engine according to claim 1, wherein whether or not to gradually change the injection timing command value by the injection timing changing means is switched based on the deviation width calculated by the deviation width calculating means. Engine control device. When the injection timing change means gradually changes the injection timing command value from the PM reference injection timing toward the fuel efficiency best injection timing, the amount of particulate matter detected by the particulate matter amount detection means is If the injection timing command value reaches the fuel efficiency best injection timing before reaching the predetermined upper limit value, the fuel efficiency best injection timing, or the amount of particulate matter detected by the particulate matter amount detection means Storage means for storing the fuel injection timing when the upper limit value is reached before reaching the fuel efficiency best injection timing for each operating region of the internal combustion engine as the optimum injection timing Prepared,
The fuel injection is controlled by using the optimum injection timing as the injection timing command value when the storage means stores the optimum injection timing corresponding to the current engine operating state. The control apparatus for an internal combustion engine according to the item.

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