JP6585496B2 - Control device for internal combustion engine - Google Patents

Description

  The present invention relates to a control device that controls a port injection type internal combustion engine that injects fuel toward an intake port connected to a cylinder.

  When operating a port injection type internal combustion engine, the fuel injection timing is switched according to the current engine load. Specifically, in the full load region (Wide Open Throttle) where the accelerator opening is fully open or close to full open, the injector is opened after the exhaust top dead center of the cylinder, and fuel is injected during the intake valve opening period. This reduces the temperature in the combustion chamber of the cylinder. As a result, the ignition timing can be advanced without causing knocking, which contributes to the improvement of the thermomechanical conversion efficiency of the internal combustion engine. On the other hand, in the partial load region where the accelerator opening is not fully opened, the injector is opened before the exhaust top dead center of the cylinder.

  If the fuel injection timing is immediately switched to a timing corresponding to the engine load when the engine load fluctuates, the air-fuel ratio of the air-fuel mixture charged in the cylinder may deviate from the target air-fuel ratio. That is, if the driver of the vehicle depresses the accelerator pedal strongly and the required load changes from partial load to full load, if the fuel injection timing is immediately delayed, an air-fuel ratio lean mixture that does not contain sufficient fuel will be produced. A cycle that is sucked into the cylinder may occur. In addition, if the driver loosens the accelerator pedal and the required load changes from full load to partial load, if the fuel injection timing is immediately advanced, the fuel remaining in the intake port will be newly injected. A cycle in which an air-fuel ratio rich air-fuel mixture combined with fresh fuel is sucked into the cylinder may occur.

  In order to suppress such disturbance of the air-fuel ratio, it is conceivable to change the fuel injection timing by a predetermined amount per unit time toward the timing according to the engine load, that is, gradually change the fuel injection timing. (For example, see the following patent document).

Japanese Patent Laid-Open No. 11-062611

  However, if the fuel injection timing is simply changed gradually, there is a possibility that a feeling of rattling will be produced even if the response to the operation of the driver is delayed. For example, when the driver depresses the accelerator pedal strongly, if the fuel injection timing is gradually retarded, the ignition timing is prevented from being advanced during that time, and the increase in the output of the internal combustion engine is suppressed. Will be.

  The present invention, which has been made paying attention to the above problems, aims to achieve both the suppression of the disturbance of the air-fuel ratio of the air-fuel mixture filled in the cylinder and the improvement of the response of the output performance of the internal combustion engine to the operation of the driver. The intended purpose.

The present invention controls a port injection type internal combustion engine that injects fuel toward an intake port connected to a cylinder, and retards the fuel injection timing when the required load on the internal combustion engine is high. This is because the fuel injection timing is set according to the load of the internal combustion engine so that the fuel injection timing is advanced when the required load is low , and the internal combustion engine load has changed from one value to another. In the transition period in which the fuel injection timing is changed from the time corresponding to the former to the time corresponding to the latter, the fuel injection timing is suddenly changed from the time corresponding to the former to the time corresponding to the latter, and the fuel injection A control device for an internal combustion engine is configured to execute both the process of gradually changing the timing from the timing corresponding to the former toward the timing corresponding to the latter .

  ADVANTAGE OF THE INVENTION According to this invention, coexistence with suppression of the disturbance of the air fuel ratio of the air-fuel mixture with which a cylinder is filled and the improvement of the response of the output performance of the internal combustion engine with respect to a driver | operator's operation can be aimed at.

The figure which shows the structure of the internal combustion engine for vehicles and control apparatus in one Embodiment of this invention. The timing diagram explaining the fuel injection timing of the internal combustion engine of the embodiment. The timing diagram which shows the content of control of the fuel injection timing which the control apparatus of the internal combustion engine of the embodiment performs. The timing diagram which shows the content of the control of the fuel injection timing of the conventional internal combustion engine.

  An embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows an outline of an internal combustion engine for a vehicle in the present embodiment. The internal combustion engine of the present embodiment is a port injection type four-stroke spark ignition engine, and includes a plurality of cylinders 1 (for example, three cylinders, one of which is shown in FIG. 1). In the vicinity of the intake port of each cylinder 1, an injector 11 for injecting fuel is provided for each cylinder 1. A spark plug 12 is attached to the ceiling of the combustion chamber of each cylinder 1. The spark plug 12 receives spark voltage generated by the ignition coil and causes spark discharge between the center electrode and the ground electrode. The ignition coil is integrally incorporated in a coil case together with an igniter that is a semiconductor switching element.

  The intake passage 3 for supplying intake air takes in air from the outside and guides it to the intake port of each cylinder 1. On the intake passage 3, an air cleaner 31, an electronic throttle valve 32, a surge tank 33, and an intake manifold 34 are arranged in this order from the upstream.

  The exhaust passage 4 for discharging the exhaust guides the exhaust generated as a result of burning the fuel in the cylinder 1 from the exhaust port of each cylinder 1 to the outside. An exhaust manifold 42 and an exhaust purification three-way catalyst 41 are disposed on the exhaust passage 4.

  The external EGR (Exhaust Gas Recirculation) device 2 realizes a so-called high pressure loop EGR, and an external EGR passage 21 that connects the upstream side of the catalyst 41 in the exhaust passage 4 and the downstream side of the throttle valve 32 in the intake passage 3. The EGR cooler 22 provided on the EGR passage 21 and the EGR valve 23 that opens and closes the EGR passage 21 and controls the flow rate of the EGR gas flowing through the EGR passage 21 are used as elements. The inlet of the EGR passage 21 is connected to the exhaust manifold 42 in the exhaust passage 4 or a predetermined location downstream thereof. The outlet of the EGR passage 21 is connected to a predetermined location downstream of the throttle valve 32 in the intake passage 3, particularly to the surge tank 33.

  The internal combustion engine of the present embodiment is accompanied by a VVT (Variable Valve Timing) mechanism 6 that can variably control the opening / closing timing of the intake valve of each cylinder 1. The VVT mechanism 6 is a known electric type (motor drive VVT) in which the rotation phase of the intake camshaft that drives the intake valve of each cylinder 1 with respect to the crankshaft is changed by an electric motor. As is well known, an intake camshaft of an internal combustion engine is supplied with a rotational driving force from a crankshaft that is an output shaft of the internal combustion engine, and rotates following the crankshaft. A winding transmission device (not shown) for transmitting a rotational driving force is interposed between the crankshaft and the intake camshaft. The winding transmission includes a crank sprocket (or pulley) provided on the crankshaft side, a cam sprocket (or pulley) provided on the intake camshaft side, and a timing chain (or pulley) wound around these sprockets (or pulleys). Alternatively, a timing belt is used as an element. The VVT mechanism 6 changes the rotation phase of the intake camshaft relative to the crankshaft by rotating the intake camshaft relative to the cam sprocket, thereby changing the opening / closing timing of the intake valve.

  An ECU (Electronic Control Unit) 0 serving as a control device for an internal combustion engine according to the present embodiment is a microcomputer system having a processor, a memory, an input interface, an output interface, and the like.

  The input interface of the ECU 0 includes a vehicle speed signal a output from a vehicle speed sensor that detects the actual vehicle speed of the vehicle, a crank angle signal b output from a crank angle sensor that detects the rotation angle of the crankshaft and the engine speed, and an accelerator pedal. , An accelerator opening signal c output from a sensor that detects the amount of depression of the engine or the opening of the throttle valve 32 as an accelerator opening (so-called required engine load), an intake passage 3 (in particular, a surge tank 33) connected to the cylinder 1 The intake air temperature / intake pressure signal e output from the temperature / pressure sensor for detecting the intake air temperature and the intake pressure in the inside), the coolant temperature signal f output from the water temperature sensor for detecting the coolant temperature of the internal combustion engine, and the exhaust passage 4 An air-fuel ratio signal g output from an air-fuel ratio sensor for detecting the air-fuel ratio of the flowing exhaust gas, a cylinder block containing the cylinder 1 Vibration signal h or the like is input that is output from the vibration type knock sensor for detecting a magnitude of vibration of the click.

  From the output interface of the ECU 0, an ignition signal i for the igniter 13, a fuel injection signal j for the injector 11, an opening operation signal k for the throttle valve 32, an opening operation signal l for the EGR valve 23, An intake valve timing control signal m or the like is output to the VVT mechanism 6.

  The processor of the ECU 0 interprets and executes a program stored in the memory in advance, calculates operation parameters, and controls the operation of the internal combustion engine. The ECU 0 acquires various information a, b, c, d, e, f, g, and h necessary for operation control of the internal combustion engine via the input interface, knows the engine speed, and is filled in the cylinder 1. Estimate the intake volume. Based on the engine speed, the intake air amount, etc., the required fuel injection amount, fuel injection timing (including the number of times of fuel injection for one combustion), fuel injection pressure, ignition timing, required EGR rate (or EGR rate) Volume), opening / closing timing of the intake valve, and the like. The ECU 0 applies various control signals i, j, k, l and m corresponding to the operation parameters via the output interface.

The ECU 0 determines a basic injection amount TP commensurate with the amount of intake air (fresh air) charged into the cylinder 1. Next, the basic injection amount TP is corrected with a feedback correction coefficient FAF that is determined based on the deviation between the air-fuel ratio of the exhaust gas flowing into the catalyst 41 and the target air-fuel ratio. The target air-fuel ratio is usually the theoretical air-fuel ratio or the vicinity thereof. Further, the final fuel injection time (energization time for the injector 11) T is calculated in consideration of various correction factors K determined according to the state of the internal combustion engine and the invalid injection time TAUV of the injector 11. The fuel injection time T is
T = TP × FAF × K + TAUV
It becomes. Then, the signal j is input to the injector 11 for the fuel injection time T, and the injector 11 is opened to inject fuel.

  Further, the ECU 0 refers to the vibration signal h output from the knock sensor, determines whether or not knocking has occurred in the expansion stroke of each cylinder 1, and adjusts the ignition timing according to the determination result (so-called knocking). Control system). That is, the ECU 0 compares the current sampling value (the current vibration intensity) of the vibration signal h with the knock determination value, and determines that knocking has occurred in the cylinder 1 if the former exceeds the latter. Conversely, if the sampling value of the vibration signal h is equal to or less than the knock determination value, it is determined that knocking has not occurred in the cylinder 1. In addition, when detecting the occurrence of knocking in the cylinder 1, the ECU 0 gradually retards the ignition timing until knocking does not occur thereafter. On the other hand, when the occurrence of knocking is not sensed, the ignition timing is gradually advanced as long as knocking does not occur.

  Thus, the ECU 0 according to the present embodiment determines the timing of injecting fuel from the injector 11 toward the intake port, in other words, the timing of opening the injector 11, based on the current operating range of the internal combustion engine [engine speed, engine load. ], And the valve overlap amount (or intake valve timing, internal EGR amount) that is the length of the period during which both the intake valve and the exhaust valve are opened.

  In principle, the fuel injection timing is delayed when the accelerator opening is large and the required load on the internal combustion engine is high, and the fuel injection timing is advanced when the accelerator opening is small and the required load on the internal combustion engine is low. More specifically, as shown in FIG. 2, in the full load operation region where the accelerator opening is fully open or close to full open, the exhaust top dead center of the target cylinder 1 is considerably slower (more than the intake bottom dead center). Timing), for example, timing t2 at 200 ° CA (crank angle) after exhaust top dead center is the end of fuel injection, that is, the valve closing timing of the injector 11, and from the valve closing timing t2 by the fuel injection time T described above. The retroactive timing t1 is set as the start timing of fuel injection, that is, the valve opening timing of the injector 11. As a result, during the intake stroke of the cylinder 1, fuel can be directly injected from the injector 11 toward the combustion chamber of the cylinder 1 while the intake valve is open, and the temperature in the combustion chamber is lowered to cause knocking. Risk can be reduced. If the frequency of knocking decreases, the ignition timing can be advanced to approach MBT (Minimum Advance for Best Torque), the thermomechanical conversion efficiency of the internal combustion engine is improved, and the output of the internal combustion engine is further increased.

  On the other hand, in the partial load operation region where the accelerator opening is not fully opened, the timing immediately after the exhaust top dead center of the target cylinder 1, for example, the timing t4 of 30 ° CA after the exhaust top dead center is set as the valve closing timing of the injector 11. A timing t3 that goes back by the fuel injection time T from the valve closing timing t4 is set as the valve opening timing of the injector 11. As a result, fuel injection is started prior to the opening of the intake valve, and the intake and fuel can be sufficiently mixed in the intake port and then sucked into the combustion chamber of the cylinder 1 to burn the mixture. Improves stability.

  In addition to the above, the optimum fuel injection timing also varies depending on the engine speed and the valve overlap amount at that time. In the memory of the ECU 0, map data defining the relationship between the engine speed, the engine load, the valve overlap amount, and the like and the valve closing timing of the injector 11 is stored in advance. The ECU 0 that controls the fuel injection timing searches the map using the current engine speed, engine load, valve overlap amount, etc. as keys, and knows the valve closing timing of the injector 11 to be set.

  By the way, when the required load on the internal combustion engine fluctuates, if the fuel injection timing is immediately switched to a timing corresponding to the required load, the air-fuel ratio of the air-fuel mixture filled in the cylinder 1 deviates from the target air-fuel ratio and becomes lean. Or it may become rich. For example, as shown in FIG. 4, when the driver of the vehicle depresses the accelerator pedal strongly and the required load changes from partial load to full load, the valve closing timing of the injector 11 is immediately set to 30 after exhaust top dead center. When switching from CA to 200 CA after exhaust top dead center, a cycle in which an air-fuel ratio lean air-fuel mixture that does not contain sufficient fuel is sucked into the cylinder 1 may occur.

  Further, at the time TC when the driver loosens the accelerator pedal and the required load changes from full load to partial load, the valve closing timing of the injector 11 is immediately changed from 200 ° CA after exhaust top dead center to after exhaust top dead center. When switching to 30 ° CA, a cycle in which an air-fuel ratio rich air-fuel mixture in which newly injected fuel is combined with fuel remaining in the intake port may be sucked into the cylinder 1 may occur. Such disturbance of the air-fuel ratio of the air-fuel mixture is not preferable because it leads to deterioration of internal combustion engine emission and induction of knocking.

  In order to prevent disturbance of the air-fuel ratio, the fuel injection timing should not be changed suddenly when the load of the internal combustion engine fluctuates, but gradually retarded or advanced toward the timing corresponding to the fluctuating load. However, if the fuel injection timing is simply changed gradually, there is a concern that the output performance of the internal combustion engine desired by the driver cannot be quickly achieved.

  Therefore, the ECU 0 of the present embodiment causes the fuel injection timing to change from the time corresponding to the former to the time corresponding to the latter due to the load of the internal combustion engine changing from one value to another value. In addition, a process of suddenly changing the fuel injection timing and a process of gradually changing the fuel injection timing are successively executed.

  That is, as shown in FIG. 3, the ECU 0 of the present embodiment first determines the closing timing of the injector 11 after the time point TO at which the load of the internal combustion engine transitions from partial load to full load or a high load close to full load. The timing is immediately retarded by a predetermined skip amount A1 from the timing A corresponding to the partial load. Thereafter, a gradual change period in which the valve closing timing of the injector 11 is retarded by a predetermined amount A2 per unit crank angle or unit time is provided. After that, the valve closing timing of the injector 11 is delayed by a predetermined skip amount A3, thereby changing to the timing A ′ corresponding to the full load or a high load close to the full load.

  In principle, the skip amount (retard amount) A1 and A3 of the valve closing timing of the injector 11 is based on the change amount (retard amount) A2 of the valve closing timing of the injector 11 per unit crank angle or unit time during the gradual change period. Is also big. However, similarly to the valve closing timings A and A ′ of the injector 11 corresponding to the load of the internal combustion engine, the optimum skip amounts A1 and A3 and the gradual change speed A2 are also the current operation range and valve overlap amount of the internal combustion engine. Influenced by etc. Depending on the operating region and the valve overlap amount, either the skip amount A1 or the skip amount A3 may be smaller than the change amount A2 per unit crank angle or unit time. Furthermore, either the skip amount A1 or the skip amount A3 may be zero.

  In addition, the ECU 0 of the present embodiment first sets the valve closing timing of the injector 11 close to the full load or the full load after the time TC when the load of the internal combustion engine transits from the full load or the high load close to the full load to the partial load. The timing is immediately advanced by a predetermined skip amount A4 from timing A ′ corresponding to a high load. Thereafter, a gradual change period in which the valve closing timing of the injector 11 is advanced by a predetermined amount A5 per unit crank angle or unit time is provided. Thereafter, the valve closing timing of the injector 11 is advanced by a predetermined skip amount A6 to change to the timing A corresponding to the partial load.

  As a general rule, the skip amount (advance amount) A4, A6 of the valve closing timing of the injector 11 is based on the change amount (advance amount) A5 per unit crank angle or unit time of the valve closing timing of the injector 11 during the gradual change period. Is also big. However, the optimum skip amounts A4 and A6 and the gradual change speed A5 are also affected by the current operating range of the internal combustion engine, the valve overlap amount, and the like. Depending on the operating region and valve overlap amount, either the skip amount A4 or the skip amount A6 may be smaller than the change amount A5 per unit crank angle or unit time. Furthermore, either the skip amount A4 or the skip amount A6 may be zero. As indicated by a chain line in FIG. 3, in a specific engine speed range, the skip amount A4 immediately after the time point TC when the required load decreases may be zero.

  In the memory of the ECU 0, map data defining the relationship between the engine speed, the engine load, the valve overlap amount, etc., and the skip amounts A1, A3, A4, A6 and the gradual change speeds A2, A4 is stored in advance. ing. The ECU 0 that controls the fuel injection timing searches the map using the current engine speed, engine load, valve overlap amount, and the like as keys, and sets the valve closing timing of the injector 11 to timings A and A ′ corresponding to the required load. The skip amounts A1, A3, A4, A6 and the gradual change speeds A2, A4 when changing in the direction are known.

  In the present embodiment, a port injection type internal combustion engine that injects fuel toward an intake port connected to the cylinder 1 is controlled, and the fuel injection timing is set in accordance with the load of the internal combustion engine. Due to the change in the load of the internal combustion engine from a certain value to another value, the fuel injection timing is changed from the timing A corresponding to the former to the timing A ′ and A corresponding to the latter, Control of an internal combustion engine that executes both a process for suddenly changing the fuel injection timing (skip by skip amounts A1, A3, A4, and A6) and a process for gradually changing the fuel injection timing (gradual change by gradually changing speeds A2 and A4) Device 0 was configured.

  According to this embodiment, the internal combustion engine with respect to the operation of the driver is optimized by optimizing the skip amounts A1, A3, A4, A6 and the gradual change speeds A2, A4 according to the operation region of the internal combustion engine, the valve overlap amount, and the like. The disturbance of the air-fuel ratio of the air-fuel mixture filled in the cylinder 1 can be suppressed without impairing the response of the engine output performance. As a result, it is possible to achieve both improved drivability and improved emissions.

  The present invention is not limited to the embodiment described in detail above. Various modifications can be made to the specific configuration of each part, processing procedure, and the like without departing from the spirit of the present invention.

  The present invention can be used for controlling an internal combustion engine mounted on a vehicle or the like.

0 ... Control unit (ECU)
DESCRIPTION OF SYMBOLS 1 ... Cylinder 11 ... Injector 32 ... Throttle valve b ... Crank angle signal c ... Accelerator opening signal j ... Fuel injection signal m ... Control signal of intake valve timing

Claims (1)

Controlling a port injection type internal combustion engine that injects fuel toward an intake port connected to a cylinder,
The fuel injection timing is set according to the load of the internal combustion engine so that the fuel injection timing is retarded when the required load on the internal combustion engine is high and the fuel injection timing is advanced when the required load on the internal combustion engine is low And
In transition to change to timing corresponding to the latter fuel injection timing resulted from the variation from a certain value when the load of the internal combustion engine to a different value from the timing corresponding to the former, the corresponding fuel injection timing in the former a process of the time to sudden change toward a timing corresponding to the latter, the control apparatus for an internal combustion engine together and a process for gradually changing toward a timing corresponding to the latter from the time the corresponding fuel injection timing in the former.

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