JP2006017053A - Fuel injection timing control device for internal combustion engine with supercharger - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel injection timing control device for an internal combustion engine with a supercharger, preventing the blowby of an air-fuel mixture by determining a state to easily cause the blowby of the air-fuel mixture without requiring instrumentation of suction/exhaust pressure by a sensor. <P>SOLUTION: An engine ECU50 changes a fuel injection starting timing Ts from a normal injection starting timing to an injection starting timing that the blow-by of the air-fuel mixture from an intake valve 21 to an exhaust valve 22 may not occur, on the basis of the assist operation of a motor 34 to assist the supercharge operation of a turbocharger 30. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a fuel injection timing control device for an internal combustion engine with a supercharger that controls the fuel injection start timing in an internal combustion engine having a turbocharger as a supercharger.

  Conventionally, an engine with a supercharger also has a variable valve mechanism that controls the opening and closing timing of at least one of an intake valve and an exhaust valve. The variable valve mechanism adjusts valve timing and the like to improve fuel efficiency. And a technique for improving output (filling efficiency) is known. At this time, the valve overlap period during which both valves are open is changed. However, during this valve overlap period, there may occur a phenomenon in which the air-fuel mixture blows from the intake port to the exhaust port and the air-fuel mixture does not stay in the combustion chamber.

  When such air-fuel mixture blow-through occurs, there is a problem that the leanness of the combustion occurs, or misfire occurs in some cases, and the responsiveness of the turbo deteriorates. In addition, the air-fuel mixture blows off, resulting in a deterioration in fuel consumption, and further, the air-fuel mixture (HC) is released into the atmosphere, leading to deterioration in exhaust emission. Therefore, a technique for preventing the air-fuel mixture from being blown through is required. For example, Patent Document 1 discloses the technique.

  In Patent Document 1, a supercharger is used as a supercharger, and a fuel mixture is generated by starting fuel injection before a valve overlap period during non-supercharging operation. Then, the fuel injection start timing is changed during the valve overlap period to generate an air-fuel mixture. Therefore, during this supercharging operation, the air-fuel mixture flows into the combustion chamber at the second half or almost at the end of the valve overlap period, and the exhaust valve is closed immediately thereafter, thereby preventing the air-fuel mixture from being blown out. It is like that.

  By the way, for an engine having a turbocharger, an electric motor is attached to the rotating shaft of the turbocharger to assist the supercharging operation, or an upstream exhaust pipe and a downstream exhaust pipe of the turbocharger (exhaust turbine) A bypass pipe that connects the turbocharger without going through the turbocharger, and a wastegate valve (WG valve) is provided in the bypass pipe, the WG valve is opened at a predetermined timing, and both exhaust pipes are connected to adjust the exhaust pressure. There is something. In such an engine, when the WG valve is opened more than a predetermined opening in a period when the electric motor is assisting more than a predetermined value or in a supercharging operation region, the intake pipe pressure (intake pressure) becomes the exhaust pipe pressure (exhaust pressure). This leads to a worsening of air-fuel mixture blow-through.

  Therefore, in Patent Document 2, for example, an intake pipe pressure sensor and an exhaust pipe pressure sensor are used to measure the intake pressure and the exhaust pressure with the pressure sensors, respectively. When it is likely to occur, fuel injection is performed so that the air-fuel mixture reaches the intake port after the end of the valve overlap period. Therefore, even if the intake pressure is higher than the exhaust pressure and the air-fuel mixture is likely to blow through, the air-fuel mixture will not blow through when the air-fuel mixture reaches the intake port because the exhaust valve is already closed.

However, in the technique of Patent Document 2, since it is necessary to set the fuel injection start timing for preventing blow-through based on the measurement of the intake / exhaust pressure, there is a problem that the calculation load for measuring the intake / exhaust pressure increases. Occurs. There is also a problem that the technique of Patent Document 2 cannot be applied to a system that cannot measure at least the exhaust pressure.
Japanese Patent No. 3044077 Japanese Patent Laid-Open No. 7-151006

  The present invention relates to a fuel injection timing control device for an internal combustion engine with a supercharger that can determine a state in which air-fuel mixture is likely to blow through without requiring measurement of intake / exhaust pressure by a sensor and can prevent the air-fuel mixture from being blown through The main purpose is to provide

  According to the first aspect of the present invention, the supercharger is provided with an electric motor that assists the supercharging operation, and based on the assist operation of the electric motor, the fuel injection start timing is changed from the normal injection start timing to the exhaust valve. The injection timing is changed so that the air-fuel mixture does not blow through. That is, during the valve overlap period in which both the intake valve and the exhaust valve are open, and when the motor that assists the supercharging operation is operated, the intake pressure becomes higher than the exhaust pressure, and the air-fuel mixture blows out. Easy situation. Accordingly, paying attention to the assist operation of the electric motor, and setting the fuel injection start time based on the operation, it is possible to prevent the air-fuel mixture from being blown through. In this case, since the fuel injection start timing for preventing blow-through is set based on the assist operation of the electric motor, it is not necessary to measure the intake and exhaust pressure for preventing blow-through. That is, it is possible to determine a state in which the air-fuel mixture easily blows out without requiring measurement of the intake / exhaust pressure by the sensor, and to prevent the air-fuel mixture from blowing through.

  According to a second aspect of the present invention, in the first aspect of the present invention, the fuel injection start timing is an injection start timing during which the air-fuel mixture does not blow through during a period in which the electric motor performs an assist operation with an assist power of a predetermined value or more. Changed to That is, since it is possible to determine whether the intake pressure is higher than the exhaust pressure and the air-fuel mixture is likely to blow through based on the assist power supplied to the electric motor, the determination is facilitated.

  In the invention described in claim 3, the exhaust gas is provided in a bypass passage that connects the upstream side exhaust passage and the downstream side exhaust passage of the supercharger without passing through the supercharger, and is opened and closed to adjust the exhaust pressure. When the exhaust pressure adjustment valve is opened more than a predetermined opening change rate in the supercharging operation range due to the operation of the turbocharger, the fuel injection start timing is taken in from the normal injection start timing for a predetermined time thereafter The injection timing is changed so that the air-fuel mixture does not blow through from the valve to the exhaust valve. That is, if the exhaust pressure adjustment valve that adjusts the exhaust pressure suddenly opens during the valve overlap period when both the intake valve and the exhaust valve are open, the intake pressure temporarily becomes higher than the exhaust pressure. Thus, the air-fuel mixture is likely to blow through. Therefore, paying attention to the opening operation of the exhaust pressure adjustment valve, and setting the fuel injection start timing based on the rate of change in the opening degree, it is possible to prevent the air-fuel mixture from being blown through. In this case, since the fuel injection start timing for preventing the blow-through is set based on the rate of change of the opening of the exhaust pressure adjusting valve, it is not necessary to measure the intake / exhaust pressure for preventing the blow-through. That is, it is possible to determine a state in which the air-fuel mixture easily blows out without requiring measurement of the intake / exhaust pressure by the sensor, and to prevent the air-fuel mixture from blowing through.

  According to a fourth aspect of the present invention, in the third aspect of the present invention, the predetermined time for setting the fuel injection start time at which no blow-through occurs is varied according to the operating state of the internal combustion engine. That is, since the time during which the intake pressure becomes higher than the exhaust pressure varies depending on the operating state of the internal combustion engine, the wasted time can be reduced as much as possible by varying the predetermined time. It becomes possible to perform injection control.

  According to a fifth aspect of the present invention, there is provided a vaporization state estimation means for estimating the vaporization quality of the injected fuel in the invention according to any one of the first to fourth aspects, and the fuel injection start timing is based on the estimation. It is set according to the vaporization state of the injected fuel. Therefore, for example, when the fuel vaporization is good, the air-fuel mixture tends to blow through, so the fuel injection start timing is set late, and when the fuel injection is poor, the air-fuel mixture hardly blows through. The fuel injection start time is set earlier. That is, the vaporization state of the injected fuel is one of the factors that set the fuel injection start timing. Therefore, by setting the fuel injection start timing in accordance with the vaporization state of the injected fuel, it is possible to perform optimal fuel injection control at that time.

  According to a sixth aspect of the present invention, in the fifth aspect of the present invention, when the vaporization state estimating means estimates that the fuel vaporization is good, the fuel injection start timing is set after the end of the valve overlap period. . That is, when the injected fuel is well vaporized, the air-fuel mixture is likely to blow through. Therefore, by setting the fuel injection start timing after the valve overlap period, the air-fuel mixture is reliably prevented from being blown through.

  According to a seventh aspect of the invention, in the sixth aspect of the invention, when the vaporization state estimation means estimates that the injected fuel is poorly vaporized, the fuel injection start timing is set when the injected fuel is vaporized well. It is set before the injection start timing. That is, when the injection fuel is poorly vaporized, it is difficult for the air-fuel mixture to blow through. Therefore, even if the fuel injection start time is set before the start time set when the fuel is vaporized well, the air-fuel mixture will blow through. The fuel vaporization time can be secured by advancing the fuel injection start timing, and a good air-fuel mixture can be generated.

  According to an eighth aspect of the invention, in the invention according to any of the fifth to seventh aspects, the vaporization state estimating means uses at least one of the temperature of the cooling water circulating through the internal combustion engine and the temperature of the lubricating oil. Guess the quality of vaporization. That is, the temperature of the cooling water and the lubricating oil circulating through the internal combustion engine can grasp the warm-up state of the internal combustion engine, and it can be estimated whether the injected fuel is vaporized. Therefore, it is not necessary to take special measures for estimating whether the injected fuel is vaporized.

(First embodiment)
Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. In this embodiment, an engine control system is constructed for an in-vehicle multi-cylinder gasoline engine that is an internal combustion engine, and the engine of the control system is provided with a turbocharger with an electric motor as a supercharger. First, an overall schematic configuration diagram of the engine control system will be described with reference to FIG.

  In the engine 10 shown in FIG. 1, the intake pipe 11 is provided with a throttle valve 14 whose opening is adjusted by an actuator such as a DC motor, and a throttle opening sensor 15 for detecting the throttle opening. A surge tank 16 is provided downstream of the throttle valve 14, and an intake pipe pressure sensor 17 for detecting an intake pipe pressure (intake pressure) Pm is provided in the surge tank 16. The surge tank 16 is connected to an intake manifold 18 that introduces air into each cylinder of the engine 10. In the intake manifold 18, an electromagnetically driven fuel injection that injects fuel near the intake port of each cylinder. A valve 19 is attached.

  An intake valve 21 and an exhaust valve 22 are respectively provided in the intake port and the exhaust port of the engine 10, and an air / fuel mixture is introduced into the combustion chamber 23 by the opening operation of the intake valve 21, and the exhaust valve 22. The exhaust gas after combustion is discharged into the exhaust pipe 24 by the opening operation. The intake valve 21 and the exhaust valve 22 are provided with variable valve mechanisms 25 and 26, respectively. These variable valve mechanisms 25 and 26 have a structure that allows the valve opening / closing operation conditions such as the lift amount and valve opening timing (valve overlap period) of the valves 21 and 22 to be continuously variable. The valve opening / closing operation conditions are appropriately adjusted according to the accelerator opening degree and engine operating state.

  A spark plug 27 is attached to the cylinder head of the engine 10 for each cylinder, and a high voltage is applied to the spark plug 27 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 27, and the air-fuel mixture introduced into the combustion chamber 23 is ignited and used for combustion. An intake side cam angle sensor 25 a and an exhaust side cam angle sensor 26 a are attached to the cylinder head of the engine 10. The intake side cam angle sensor 25a detects the intake side cam angle in order to calculate the opening / closing timing of the intake valve 21, and the exhaust side cam angle sensor 26a is used to calculate the opening / closing timing of the exhaust valve 22, etc. Is detected.

  A cylinder block of the engine 10 mainly circulates in the crank angle sensor 28 that outputs a rectangular crank angle signal for every predetermined crank angle (for example, at a cycle of 30 ° CA) as the engine 10 rotates. A cooling water temperature sensor 29 for detecting the temperature of the cooling water (cooling water temperature Tw) is attached.

  A turbocharger 30 is disposed between the intake pipe 11 and the exhaust pipe 24. The turbocharger 30 has a compressor impeller 31 provided in the intake pipe 11 and a turbine wheel 32 provided in the exhaust pipe 24, which are connected by a rotary shaft 33. The rotating shaft 33 is provided with a motor 34 as an auxiliary power device. The motor 34 is provided with a temperature sensor 35 for detecting the motor temperature.

  In the turbocharger 30, the turbine wheel 32 is rotated by the exhaust gas flowing through the exhaust pipe 24, and the rotational force is transmitted to the compressor impeller 31 via the rotating shaft 33. The compressor impeller 31 compresses and supercharges intake air flowing through the intake pipe 11. The motor 34 is operated by power supply from a vehicle battery (not shown), and auxiliary power is added to the turbocharger 30 by the operation of the motor 34. The air supercharged by the turbocharger 30 is cooled by the intercooler 36 and then fed downstream. As the intake air is cooled by the intercooler 36, the charging efficiency of the intake air is increased.

  Here, the exhaust power for rotating the turbine wheel 32 rises slightly later than the increase in the throttle opening. That is, since the supercharging pressure rises with a delay due to insufficient exhaust power, auxiliary power is added (assisted) by the motor 34 during a period when the exhaust power is insufficient, so that the supercharging pressure rises early. .

  As is well known, the engine ECU 50 is mainly composed of a microcomputer composed of a CPU, ROM, RAM, and the like, and executes various control programs stored in the ROM, so that the engine 10 can be operated in accordance with the engine operating state each time. Implement various controls. That is, the engine ECU 50 receives detection signals from the throttle opening sensor 15, the intake pipe pressure sensor 17, the intake side and exhaust side cam angle sensors 25 a and 26 a, the crank angle sensor 28, and the cooling water temperature sensor 29. In addition, detection signals are also input from the accelerator opening sensor 40 for detecting the amount of depression of the accelerator pedal. Then, the engine ECU 50 calculates the fuel injection amount, the fuel injection start timing Ts, the ignition timing, the valve opening / closing operation timing, and the like based on various detection signals that are input as needed. The drive of the valve mechanisms 25 and 26 is controlled.

  Further, the engine ECU 50 controls the motor 34 of the turbocharger 30 to add auxiliary power to the turbocharger 30 during vehicle acceleration so that a desired supercharging pressure can be obtained quickly. At this time, by monitoring the motor temperature obtained by the temperature sensor 35, the supplied power can be corrected based on the motor temperature characteristics.

  Here, during the valve overlap period in which both the intake valve 21 and the exhaust valve 22 are in the open state, and when accelerating by the electric turbo, more specifically, the motor 34 based on the supply of the assist power W of a predetermined value or more. During acceleration in which the turbocharger 30 is assisted by this assist operation, the intake pipe pressure (intake pressure) Pm becomes higher than the exhaust pipe pressure (exhaust pressure) Pe as shown in FIG. The air-fuel mixture is easily blown into the exhaust valve 22. Accordingly, when the turbocharger 30 is accelerated by the electric turbo, the engine ECU 50 performs the normal injection start timing (for example, the intake valve 21), which is generally the fuel injection start timing Ts according to the processing flow shown in FIG. From the predetermined start time set appropriately before the opening of the fuel gas) to the injection start time at which the air-fuel mixture does not blow through.

  FIG. 3 shows a specific processing flow (processing flow when the electric turbo is activated) of the engine ECU 50 during acceleration by the electric turbo. Incidentally, the engine ECU 50 performs this electric turbo operation processing flow for each fuel injection, and determines the fuel injection start timing Ts of the next cylinder based on the processing result.

  In step S101, it is determined whether or not an electric turbo drive command is generated, that is, whether or not the assist power W is supplied to the motor 34 that assists the turbocharger 30 is determined. When the electric turbo drive command is not generated, the processing flow at the time of operating the electric turbo is ended. On the other hand, if an electric turbo drive command is generated, the process proceeds to step S102.

  In step S102, the current valve overlap amount Vol is calculated. In step S103, a threshold value Wth of the assist power W supplied to the motor 34 is calculated. This threshold value Wth is calculated by the threshold value calculation flow shown in FIG.

  That is, in step S201, the engine speed Ne is measured based on the detection signal from the crank angle sensor 28, and the intake pressure Pm is measured based on the detection signal from the intake pipe pressure sensor 17. In step S202, the threshold value Wth is calculated based on the threshold value calculation map shown in FIG. 5 using the intake pressure Pm and the engine speed Ne. Incidentally, the threshold value Wth of the present embodiment is set such that the value increases as the intake pressure Pm and the engine speed Ne increase. The threshold value Wth is a value at which the intake pressure Pm and the exhaust pressure Pe become substantially the same when the motor 34 is assisted by the assist power W that matches this value. That is, when the motor 34 is assisted by the assist power W exceeding the threshold value Wth, the intake pressure Pm becomes higher than the exhaust pressure Pe. Then, when the threshold value Wth is calculated, the process proceeds to step S104 in the process flow of the electric turbo operation shown in FIG.

  In step S104, it is determined whether or not the assist power W is greater than the threshold value Wth and the valve overlap period is in effect (the valve overlap amount Vol is greater than “0”). If neither of these conditions is satisfied, it is determined that the air-fuel mixture is unlikely to blow through when the intake pressure Pm is lower than the exhaust pressure Pe, and the process is terminated. On the other hand, if both of these conditions are satisfied, it is determined that the intake pressure Pm is higher than the exhaust pressure Pe during the valve overlap period, and the mixture is likely to blow through, and the process proceeds to step S105.

  In step S105, the blow-out prevention process flow shown in FIG. 6 is executed to set the fuel injection start timing Ts so that the air-fuel mixture does not blow through. That is, in step S301, the coolant temperature Tw of the engine 10 is measured based on the detection signal from the coolant temperature sensor 29. That is, by detecting the coolant temperature Tw of the engine 10, the warm-up state of the engine 10 is grasped, and thereby the quality of the vaporization of the injected fuel is estimated (vaporization state estimation means). In step S302, the closing timing Tcl of the exhaust valve 22 is calculated. In step S303, the fuel injection start timing Ts is calculated based on the injection start timing calculation table shown in FIG. 7 using the coolant temperature Tw. The coolant temperature Tw used here can be replaced with the temperature of the lubricating oil (oil temperature To) mainly circulating in the engine 10.

  Incidentally, the fuel injection start timing Ts of the present embodiment is assumed to be when the vaporization of the injected fuel is good when the cooling water temperature Tw is 40 ° C. or more of the reference cooling water temperature, and the exhaust valve obtained as described above. 22 is set to the closing timing Tcl. On the other hand, when the cooling water temperature Tw is less than 40 ° C. of the reference cooling water temperature, it is estimated that the vaporization of the injected fuel is poor, and the fuel injection start timing Ts is reduced as the cooling water temperature Tw decreases. The exhaust valve 22 is set before the closing timing Tcl, such as 0 ° CA (crank angle) at 0 ° C. and −180 ° CA at −40 ° C.

  That is, when the cooling water temperature Tw of the engine 10 is equal to or higher than the reference cooling water temperature of 40 ° C., it is determined that the vaporization of the injected fuel is good and the vaporization is good when the fuel wet is an appropriate amount. When this vaporization is good, blow-through easily occurs, so the fuel injection start timing Ts is set to the closing timing Tcl of the exhaust valve 22. On the other hand, when the cooling water temperature Tw of the engine 10 is lower than 40 ° C. of the reference cooling water temperature, as the cooling water temperature Tw decreases, the vaporization of the injected fuel is poor and the fuel wet gradually increases from an appropriate amount. It is determined that the vaporization is poor. When this vaporization failure occurs, blow-through hardly occurs with a decrease in the cooling water temperature Tw, and more time is required for vaporization. Therefore, the fuel injection start timing Ts is gradually advanced with a decrease in the cooling water temperature Tw. When the fuel injection start timing Ts is calculated in this way, the process returns to the electric turbo operation process flow shown in FIG.

  In this way, the engine ECU 50 performs the processing according to the above-described processing flow during the electric turbo operation, thereby optimizing the fuel injection start timing Ts and preventing the air-fuel mixture from being blown out.

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

  In the present embodiment, the turbocharger 30 is provided with a motor 34 that assists the supercharging operation, and the engine ECU 50 changes the fuel injection start timing Ts from the normal injection start timing to the intake valve based on the assist operation of the motor 34. The time is changed to the injection start timing at which the air-fuel mixture does not blow through from the valve 21 to the exhaust valve 22. That is, during the valve overlap period in which both the intake valve 21 and the exhaust valve 22 are open, and during the operation of the motor 34 that assists the supercharging operation, the intake pressure Pm becomes higher than the exhaust pressure Pe, and mixing is performed. It becomes a situation where a blow-through easily occurs. Accordingly, paying attention to the assist operation of the motor 34 and setting the fuel injection start timing Ts based on the operation, it is possible to prevent the air-fuel mixture from being blown through. In this case, since the fuel injection start timing Ts for preventing the blow-through is set based on the assist operation of the motor 34, it is not necessary to measure the intake and exhaust pressure for preventing the blow-through. That is, it is possible to determine a state in which the air-fuel mixture easily blows out without requiring measurement of the intake / exhaust pressure by the sensor, and to prevent the air-fuel mixture from blowing through.

  Further, in this case, the engine ECU 50 sets the fuel injection start timing Ts to an injection start timing at which the air-fuel mixture does not blow through during a period in which the motor 34 performs the assist operation with the assist power W equal to or greater than a predetermined value. That is, since it can be determined whether the intake pressure Pm is higher than the exhaust pressure Pe and the air-fuel mixture is likely to blow through based on the assist power W supplied to the motor 34, the determination is easy.

  Further, the engine ECU 50 has means for estimating the quality of vaporization of the injected fuel based on the coolant temperature Tw (or oil temperature To) circulating in the engine 10, and the fuel injection start timing Ts is based on the above estimation. Set according to the vaporization state of the injected fuel. Then, when it is estimated that the vaporization of the injected fuel at which the cooling water temperature Tw is equal to or higher than the reference cooling water temperature is good, the fuel injection start timing Ts is set after the valve overlap period ends. That is, when the injected fuel is well vaporized, the air-fuel mixture is likely to blow through. Therefore, by setting the fuel injection start timing Ts after the end of the valve overlap period, it is possible to reliably prevent the air-fuel mixture from being blown through. .

  In addition, when it is estimated that the injected fuel is poorly vaporized when the coolant temperature Tw is lower than the reference coolant temperature, the fuel injection start timing Ts is set before the start timing Ts set when the injected fuel is vaporized well. Is done. That is, when the injection fuel is poorly vaporized, it is difficult for the air-fuel mixture to blow through. Therefore, even if the fuel injection start time Ts is set before the start time Ts set when the injection fuel is well vaporized, the air-fuel mixture Further, the fuel vaporization time can be secured by advancing the fuel injection start timing Ts, and a good air-fuel mixture can be generated.

  Thus, the vaporization state of the injected fuel is one of the factors that set the fuel injection start timing Ts. Therefore, by setting the fuel injection start timing Ts according to the vaporization state of the injected fuel, it is possible to perform optimal fuel injection control at any time.

  Further, as described above, the engine ECU 50 uses the cooling water temperature Tw (or the oil temperature To) of the engine 10 to estimate whether or not the injected fuel is vaporized. That is, the coolant temperature Tw (or the oil temperature To) of the engine 10 can grasp the warm-up state of the engine 10, and it can be estimated whether the injected fuel is vaporized. Therefore, it is not necessary to take special measures for estimating whether the injected fuel is vaporized.

(Second Embodiment)
Hereinafter, a second embodiment of the present invention will be described with reference to the drawings. In the present embodiment, the description will focus on the differences from the first embodiment.

  In the engine control system of the present embodiment, as shown in FIG. 8, the motor 34 that assists the supercharging operation of the turbocharger 30 is omitted, and the upstream side exhaust pipe 24a of the turbocharger 30 (turbine wheel 32). And the downstream exhaust pipe 24b are connected to each other by a bypass pipe 37 without passing through the turbocharger 30, and the bypass pipe 37 is provided with a waste gate valve (WG valve) 38 as an exhaust pressure adjusting valve. The WG valve 38 is an electric valve whose opening degree can be adjusted, and the opening degree is controlled by the engine ECU 50. The opening of the WG valve 38 is adjusted at a low speed that does not require the function of the turbocharger 30 or at a high speed when the supercharging pressure is excessive, and the flow rate of the exhaust gas passing through the bypass pipe 37 is adjusted. The pressure Pe is adjusted.

  When this WG valve 38 is used, it is in a supercharging operation region (a region where the turbocharger 30 is activated and the intake pressure Pm is greater than the atmospheric pressure), and after a predetermined opening change rate Δθ is suddenly opened for a predetermined time (described later). In the injection timing retardation time t), as shown in FIG. 9, the intake pressure Pm becomes higher than the exhaust pressure Pe, and the air-fuel mixture from the intake valve 21 to the exhaust valve 22 is likely to blow through. . Accordingly, the engine ECU 50 does not cause the air-fuel mixture to blow through the fuel injection start timing Ts from the normal injection start timing for a predetermined time (injection timing delay time t) after the WG valve 38 is opened by a predetermined opening change rate Δθ or more. Change to the injection start time.

  FIG. 10 shows a specific processing flow (processing flow when the WG valve is activated) of the engine ECU 50 when the WG valve is activated. Incidentally, the engine ECU 50 performs the processing flow during WG valve operation for each fuel injection, and determines the fuel injection start timing Ts of the next cylinder based on the processing result.

  In step S401, the current valve overlap amount Vol is calculated. In step S402, it is determined whether or not an injection timing retard flag flag1 described later is “1” and the valve overlap period (the valve overlap amount Vol is greater than “0”). If neither of these conditions is satisfied, the process proceeds to step S403.

  In step S403, an opening change rate Δθ of the WG valve 38 is calculated. In step S404, it is determined whether or not the WG valve 38 is opened by a specified opening change rate k or more. If the WG valve 38 is not opened more than the specific opening degree change rate k, it is determined that the intake air pressure Pm is lower than the exhaust gas pressure Pe and it is difficult for the air-fuel mixture to blow through, and the process is terminated. On the other hand, if the WG valve 38 opens more than the specific opening change rate k, the process proceeds to step S405.

  In step S405, it is determined whether or not the turbocharger 30 is operating in the supercharging operation region and during the valve overlap period (the valve overlap amount Vol is greater than “0”). If neither of these conditions is satisfied, it is determined that the air-fuel mixture is unlikely to blow through in the same manner as described above, and the process ends. On the other hand, if both of these conditions are satisfied, it is determined that the intake pressure Pm is higher than the exhaust pressure Pe during the valve overlap period, and the air-fuel mixture is likely to be blown out. The flag flag1 is set, that is, the flag flag1 is rewritten to “1”, and the process ends.

  If it is determined in step S402 that the injection timing retard flag flag1 is “1” and the valve overlap period is in progress, the process proceeds to step S407.

  In step S407, the blow-out prevention processing flow shown in FIG. 6 is executed to set the fuel injection start timing Ts so that the air-fuel mixture does not blow through, and the fuel injection start timing Ts corresponding to the coolant temperature Tw is set. In step S408, counting up of the injection timing retardation time t is started.

  In step S409, it is determined whether or not the injection timing retardation time t that has started counting up is within a specific time Tth. In the present embodiment, the specific time Tth varies according to variations in the intake pressure Pm and the engine speed Ne. If the injection timing retardation time t is within the specific time Tth, the process is terminated. On the other hand, when the injection timing retardation time t becomes longer than the specific time Tth, the process proceeds to step S410, the injection timing retardation flag flag1 is reset, that is, the flag flag1 is rewritten to “0”, and the counter is reset, that is, the injection timing is delayed. The angular time t is set to “0”. In step S408 to step S410, the injection timing retardation time t is measured until the specific time Tth is reached.

  In this way, the engine ECU 50 performs the processing according to the above-described processing flow when the WG valve is operated, thereby optimizing the fuel injection start timing Ts and preventing the air-fuel mixture from being blown out.

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

  In the present embodiment, a WG that is provided in a bypass pipe 37 that communicates the upstream exhaust pipe 24a and the downstream exhaust pipe 24b of the turbocharger 30 without passing through the turbocharger 30 and is opened and closed to adjust the exhaust pressure. When the opening change rate Δθ of the WG valve 38 opens more than a specific opening k in the supercharging operation region due to the operation of the turbocharger 30, the engine ECU 50 is provided with a predetermined time (injection timing delay time). The fuel injection start timing Ts is set to an injection start timing at which the air-fuel mixture does not blow from the intake valve 21 to the exhaust valve 22 from the normal injection start timing. That is, if the WG valve 38 for adjusting the exhaust pressure is suddenly opened during the valve overlap period, the intake pressure Pm temporarily becomes higher than the exhaust pressure Pe, and the air-fuel mixture is likely to blow through. . Therefore, focusing on the opening operation of the WG valve 38 and setting the fuel injection start timing Ts based on the opening change rate Δθ, it is possible to prevent the air-fuel mixture from blowing through. In this case, since the fuel injection start timing Ts for preventing the blow-through is set based on the opening degree change rate Δθ of the WG valve 38, it is not necessary to measure the intake / exhaust pressure for preventing the blow-through in this embodiment. . That is, it is possible to determine a state in which the air-fuel mixture easily blows out without requiring measurement of the intake / exhaust pressure by the sensor, and to prevent the air-fuel mixture from blowing through.

  Further, in this case, the engine ECU 50 sets the predetermined time (specific time Tth) for setting the fuel injection start timing Ts at which no blow-through occurs to the operating state of the engine 10 (in this embodiment, the intake pressure Pm and the engine speed Ne). Fluctuating). That is, since the time during which the intake pressure Pm described above becomes higher than the exhaust pressure Pe varies depending on the operating state of the engine 10, it is possible to reduce wasted time as much as possible by varying this predetermined time. Optimal fuel injection control can be performed.

  In addition, this invention is not limited to the content of description of the said embodiment, For example, you may implement as follows.

  In the first embodiment, when the assist power W supplied to the motor 34 exceeds the threshold value Vth, the fuel injection start time Ts is adjusted to a time when no blow-through occurs. For example, it may be performed based on the number of rotations (rotational speed) of the motor 34 or simply on / off of the motor 34.

  In the first embodiment, as shown in the threshold value calculation map of FIG. 5, the threshold value Wth is calculated using the intake pressure Pm and the engine speed Ne. However, the present invention is not limited to this. For example, the threshold value Wth may be calculated using only one of the intake pressure Pm and the engine speed Ne. Further, the threshold value Wth may be calculated using detection values other than these.

  In the second embodiment, the predetermined time (specific time Tth) for setting the fuel injection start timing Ts at which no blow-through occurs is changed according to changes in the intake pressure Pm and the engine speed Ne. For example, the specific time Tth may be set using only one of the intake pressure Pm and the engine speed Ne. Further, the specific time Tth may be set using detection values other than these. The specific time Tth may be a fixed value set in advance.

  In each of the above embodiments, the reference cooling water temperature is set to 40 ° C. in the injection start timing calculation table of FIG. 7, but is not limited to this, and may be changed as appropriate. Further, when the temperature is equal to or higher than the reference cooling water temperature, the fuel injection start timing Ts is set to the closing timing Tcl of the exhaust valve 22, but at least if the blow-through does not occur, the air-fuel mixture enters the combustion chamber 23 at the closing timing Tcl of the exhaust valve 22, for example. The fuel injection start timing Ts can also be advanced earlier than the closing timing Tcl of the exhaust valve 22 by taking into account the delay time for the air-fuel mixture to reach the combustion chamber 23 as it reaches.

  In each of the above-described embodiments, the variable valve mechanisms 25 and 26 are provided on the intake valve 21 and the exhaust valve 22, but the variable valve mechanism is provided on one of the intake valve 21 and the exhaust valve 22. May be.

It is a lineblock diagram showing the outline of the engine control system in a 1st embodiment. It is a wave form chart for explaining change of intake and exhaust pressure accompanying operation of a motor. It is a flow figure showing processing at the time of electric turbo operation. It is a flowchart which shows the process which calculates the threshold value of assist electric power. It is a figure which shows the threshold value calculation map of assist electric power. It is a flowchart which shows the process of blow-out prevention. It is a figure which shows the injection start time calculation table. It is a block diagram which shows the outline of the engine control system in 2nd Embodiment. It is a wave form diagram for explaining change of intake and exhaust pressure accompanying operation of a WG valve. It is a flow figure showing processing at the time of WG valve operation.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Engine (internal combustion engine), 21 ... Intake valve, 22 ... Exhaust valve, 24a ... Upstream exhaust pipe (upstream exhaust passage), 24b ... Downstream exhaust pipe (downstream exhaust passage), 30 ... Supercharger Turbocharger, 34 ... motor (electric motor), 37 ... bypass pipe (bypass passage), 38 ... wastegate valve (exhaust pressure adjusting valve), 50 ... engine ECU (including vaporization state estimating means), Ts ... start of fuel injection Timing, t ... Injection timing retardation time (predetermined time), Tth ... specific time (predetermined time), Tw ... cooling water temperature, To ... oil temperature, W ... assist power, Δθ ... opening degree change rate.

Claims (8)

A fuel injection timing control device for an internal combustion engine that has a supercharger that supercharges intake air by exhaust power and that has a valve overlap period in which both an intake valve and an exhaust valve are open,
The supercharger includes an electric motor that assists the supercharging operation,
Based on the assist operation of the electric motor, the fuel injection start timing is changed from a normal injection start timing to an injection start timing at which no air-fuel mixture blows from the intake valve to the exhaust valve. A fuel injection timing control device for an internal combustion engine.   2. The turbocharger according to claim 1, wherein the fuel injection start timing is changed to an injection start timing in which air-fuel mixture blow-out does not occur during a period in which the electric motor performs an assist operation with an assist power of a predetermined value or more. A fuel injection timing control device for an internal combustion engine. A fuel injection timing control device for an internal combustion engine that has a supercharger that supercharges intake air by exhaust power and that has a valve overlap period in which both an intake valve and an exhaust valve are open,
Provided with a bypass passage that connects the upstream exhaust passage and the downstream exhaust passage of the supercharger without going through the supercharger, and includes an exhaust pressure adjusting valve that is opened and closed to adjust the exhaust pressure. ,
When the exhaust pressure adjustment valve is opened more than a predetermined opening change rate in the supercharging operation region due to the operation of the supercharger, the fuel injection start timing is changed from the normal injection start timing to the exhaust valve from the intake valve for a predetermined time thereafter. A fuel injection timing control device for an internal combustion engine with a supercharger, wherein the fuel injection timing is changed so that the air-fuel mixture does not blow through the valve.   4. The fuel injection timing control device for an internal combustion engine with a supercharger according to claim 3, wherein the predetermined time is varied in accordance with an operating state of the internal combustion engine. Provided with a vaporization state estimation means for estimating the vaporization quality of the injected fuel,
The fuel injection timing control device for an internal combustion engine with a supercharger according to any one of claims 1 to 4, wherein the fuel injection start timing is set according to a vaporization state of the injected fuel based on the estimation.   6. The internal combustion engine with a supercharger according to claim 5, wherein when the vaporization state estimating means estimates that the vaporization of the injected fuel is good, the fuel injection start timing is set after the valve overlap period ends. Engine fuel injection timing control device.   The fuel injection start timing is set before the injection start timing set when the injection fuel is in good vaporization when the vaporization state estimation means estimates that the fuel is poorly vaporized. Item 7. The fuel injection timing control device for an internal combustion engine with a supercharger according to Item 6.   The vaporization state estimation means estimates the vaporization quality of the injected fuel by using at least one of the temperature of cooling water and lubricating oil circulating in the internal combustion engine. Fuel injection timing control device for an internal combustion engine with a supercharger.

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