Control device for internal combustion engine

Abstract

To appropriately execute restart processing of an internal combustion engine.SOLUTION: When a restart condition is satisfied, a control device for an internal combustion engine executes restart processing for controlling a throttle valve to an open state and resuming combustion of fuel in a cylinder. When executing the restart processing, the control device executes detection processing for acquiring downstream pressure detected by a pressure sensor as base pressure. When a cylinder in which fuel is burned first at restart of the internal combustion engine from a state where fuel combustion in the cylinder is interrupted is defined as an initial explosion cylinder, the control device executes calculation processing for calculating a fluctuation amount of the downstream pressure from a time of acquiring the base pressure through the detection processing to a time of closing an intake valve of the initial explosion cylinder. The control device executes estimation processing for estimating the downstream pressure at the time of closing the intake valve of the initial explosion cylinder as estimation pressure on the basis of the base pressure and the fluctuation amount. In the restart processing, on the basis of the estimation pressure estimated through the estimation processing, a fuel injection amount of the initial explosion cylinder is calculated.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a control device for an internal combustion engine. [Background technology]

[0002] The internal combustion engine of Patent Document 1 includes a cylinder, an intake passage, an exhaust passage, a piston, and a crankshaft. The cylinder is a space for burning fuel. The intake passage introduces intake air into the cylinder. The exhaust passage discharges exhaust gas from the cylinder. The piston reciprocates within the cylinder. The reciprocating motion of the piston rotates the crankshaft.

[0003] Moreover, the internal combustion engine of Patent Document 1 includes a fuel injection valve, a throttle valve, and a pressure sensor. The fuel injection valve supplies fuel into a cylinder. The throttle valve is located midway through an intake passage. The throttle valve adjusts the amount of intake air flowing through the intake passage. The pressure sensor detects downstream pressure, which is the pressure in the portion of the intake passage downstream from the throttle valve.

[0004] The control device for an internal combustion engine in Patent Document 1 calculates the amount of intake air introduced into a cylinder from an intake passage based on the downstream pressure detected by a pressure sensor. The control device in Patent Document 1 then controls the amount of fuel supplied into the cylinder from the fuel injection valve in accordance with the amount of intake air introduced into the cylinder. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2018-173067 A Summary of the Invention [Problem to be solved by the invention]

[0006] An internal combustion engine control device such as that in Patent Document 1 may execute a restart process to restart the internal combustion engine after stopping the combustion of fuel in the cylinders of the internal combustion engine. Here, an internal combustion engine control device such as that in Patent Document 1 may execute the restart process before the rotation speed of the crankshaft of the internal combustion engine reaches zero after stopping the combustion of fuel in the cylinders of the internal combustion engine. In a situation before the rotation speed of the crankshaft reaches zero, gas flows with the reciprocating motion of the piston, so that if the throttle valve is controlled to be in a closed state, the downstream pressure becomes lower than the atmospheric pressure. When the restart process is started in such a situation, the downstream pressure, which was low relative to the atmospheric pressure, gradually increases and approaches the atmospheric pressure.

[0007] However, the conventional restart process is based on the premise that the crankshaft is stopped. In other words, the conventional restart process assumes that the downstream pressure is stable at the time of restart. Therefore, the conventional restart process cannot perform an appropriate restart process that takes into account fluctuations in the downstream pressure. [Means for solving the problem]

[0008] A control device for an internal combustion engine for solving the above problems is applied to an internal combustion engine including a cylinder for burning fuel, an intake passage for introducing intake air into the cylinder, an exhaust passage for discharging exhaust gas from the cylinder, a piston reciprocating in the cylinder, a crankshaft rotated by the reciprocating motion of the piston, a fuel injection valve for supplying fuel into the cylinder, a throttle valve located in the intake passage and for adjusting the amount of intake air flowing through the intake passage, an intake valve for opening and closing a downstream end of the intake passage, and a pressure sensor for detecting a downstream pressure which is a pressure in a portion of the intake passage downstream as viewed from the throttle valve, and the control device controls a restart of the internal combustion engine, the control device comprising: a stop process for interrupting the combustion of fuel in the cylinder and controlling the throttle valve to a closed state when a predetermined stop condition is satisfied; The present invention is capable of executing the following: a restart process that controls the throttle valve to an open state and resumes combustion of fuel in the cylinder when the exhaust gas pressure is satisfied; a detection process that acquires the downstream pressure detected by the pressure sensor as a base pressure when executing the restart process; a calculation process that calculates an amount of fluctuation in the downstream pressure from the time when the base pressure is acquired by the detection process to the time when the intake valve for the initial explosion cylinder closes, when the cylinder in which fuel is first burned when the internal combustion engine is restarted from a state in which fuel combustion in the cylinder is interrupted, and an estimation process that estimates the downstream pressure at the time when the intake valve for the initial explosion cylinder closes as an estimated pressure based on the base pressure and the amount of fluctuation, and in the restart process, a fuel injection amount for the initial explosion cylinder is calculated based on the estimated pressure estimated by the estimation process.

[0009] In the above configuration, if the crankshaft is rotating immediately after the start of the stop process, gas flows in the order of the intake passage, the cylinder, and the exhaust passage. Also, when the stop process is started, the throttle valve is controlled to a closed state. Therefore, when the stop process is started, the downstream pressure becomes lower than the atmospheric pressure. Thereafter, when the restart process is started, the throttle valve is controlled to an open state. Therefore, the downstream pressure gradually increases and approaches the atmospheric pressure. In this way, immediately after the restart process is started while the crankshaft is rotating, the downstream pressure fluctuates.

[0010] According to the above configuration, the downstream pressure at the time when the intake valve of the initial explosion cylinder closes is estimated based on the amount of fluctuation from when the base pressure is acquired until the intake valve closes. In other words, the downstream pressure at the time when the introduction of intake air from the intake passage into the cylinder is completed is estimated. This allows the fuel injection amount to be calculated taking into account the fluctuation of the downstream pressure from when the base pressure is acquired until the introduction of intake air is completed. As a result, the restart process can be executed appropriately.

[0011] In the above configuration, when the rotation speed of the crankshaft is higher than a predetermined threshold value, the calculation process and the estimation process are executed, and when the rotation speed of the crankshaft is equal to or lower than the threshold value, a setting process is executed to set the base pressure as the estimated pressure.

[0012] When the rotation speed of the crankshaft is equal to or lower than the threshold value, the estimation accuracy of the downstream pressure by the estimation process tends to be lower than when the rotation speed of the crankshaft is higher than the threshold value. Also, when the rotation speed of the crankshaft is equal to or lower than the threshold value, the downstream pressure does not become so low compared to the atmospheric pressure even if the crankshaft is rotating. According to the above configuration, when the rotation speed of the crankshaft is equal to or lower than the threshold value, the base pressure is set as the estimated pressure. That is, in a situation where the estimation accuracy of the downstream pressure by the estimation process is lowered, the base pressure that is likely to be close to the downstream pressure at the time when the intake valve is closed is set as the estimated pressure. Therefore, when the rotation speed of the crankshaft is equal to or lower than the threshold value, the estimated pressure is not far from the actual value. [Brief description of the drawings]

[0013] [Figure 1] FIG. 1 is a schematic configuration diagram of a vehicle. [Diagram 2] 1 is a schematic diagram of an internal combustion engine. [Diagram 3] 4 is a flowchart showing restart control. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] <Vehicle mechanical configuration> An embodiment of the present invention will now be described with reference to Figures 1 to 3. First, the mechanical configuration of a vehicle 100 will be described.

[0015] As shown in Fig. 1, a vehicle 100 includes an internal combustion engine 10. As shown in Fig. 2, the internal combustion engine 10 includes a plurality of cylinders 11, an intake passage 12, an exhaust passage 13, a plurality of pistons 16, a plurality of connecting rods 17, and a crankshaft 18.

[0016] As shown in FIG. 2, the cylinder 11 is a space for burning a mixture of fuel and intake air. In this embodiment, the internal combustion engine 10 includes six cylinders 11. The internal combustion engine 10 is a so-called in-line six-cylinder engine in which the six cylinders 11 are arranged in a row. In the following, when the six cylinders 11 are collectively described, they are simply referred to as cylinders 11. When the six cylinders 11 are individually described, they are referred to as the first cylinder 11A, the second cylinder 11B, the third cylinder 11C, the fourth cylinder 11D, the fifth cylinder 11E, and the sixth cylinder 11F from the end in the order in which the six cylinders 11 are arranged. In FIG. 2, only one cylinder 11 is shown as a representative.

[0017] The piston 16 is located inside the cylinder 11. The piston 16 is connected to a crankshaft 18 via a connecting rod 17. The piston 16 reciprocates inside the cylinder 11 as a mixture of fuel and intake air is burned in the cylinder 11. The reciprocating motion of the piston 16 causes the crankshaft 18 to rotate.

[0018] The intake passage 12 is connected to the cylinders 11. The intake passage 12 introduces intake air from outside the internal combustion engine 10 to each cylinder 11. The exhaust passage 13 is connected to the cylinders 11. The exhaust passage 13 discharges exhaust gas from each cylinder 11 to outside the internal combustion engine 10.

[0019] The internal combustion engine 10 includes a throttle valve 21 , a plurality of port injection valves 22 , a plurality of in-cylinder injection valves 23 , a plurality of ignition devices 24 , a plurality of intake valves 26 , and a plurality of exhaust valves 27 .

[0020] The throttle valve 21 is located in the intake passage 12. The throttle valve 21 adjusts the amount of intake air flowing through the intake passage 12. The port injection valve 22 is located in the intake passage 12 near the cylinder 11. The port injection valve 22 injects fuel into the intake passage 12 to supply fuel into the cylinder 11 via the intake passage 12. The internal combustion engine 10 includes six port injection valves 22 corresponding to the six cylinders 11. A portion including a tip of the in-cylinder injection valve 23 is located inside the cylinder 11. The in-cylinder injection valve 23 injects fuel into the cylinder 11 to supply fuel into the cylinder 11. The internal combustion engine 10 includes six in-cylinder injection valves 23 corresponding to the six cylinders 11. In this embodiment, the port injection valve 22 and the in-cylinder injection valve 23 are fuel injection valves that supply fuel into the cylinder 11.

[0021] A part of the ignition device 24 including a tip is located inside the cylinder 11. The ignition device 24 ignites a mixture of fuel and intake air by spark discharge. The internal combustion engine 10 has six ignition devices 24 corresponding to the six cylinders 11. The six ignition devices 24 ignite the first cylinder 11A, the fifth cylinder 11E, the third cylinder 11C, the sixth cylinder 11F, the second cylinder 11B, and the fourth cylinder 11D in this order. In other words, the internal combustion engine 10 goes through a combustion stroke in the order of the first cylinder 11A, the fifth cylinder 11E, the third cylinder 11C, the sixth cylinder 11F, the second cylinder 11B, and the fourth cylinder 11D. Each cylinder 11 repeats an intake stroke, a compression stroke, a combustion stroke, and an exhaust stroke every time the crankshaft 18 rotates twice. Therefore, in the internal combustion engine 10, one of the six cylinders 11 undergoes a new combustion stroke every time the crankshaft 18 rotates through 120 degrees.

[0022] The intake valve 26 is located at the downstream end of the intake passage 12. The intake valve 26 opens and closes the downstream end of the intake passage 12 by a driving force from a valve mechanism (not shown). The internal combustion engine 10 is provided with six intake valves 26 corresponding to the six cylinders 11. The exhaust valve 27 is located at the upstream end of the exhaust passage 13. The exhaust valve 27 opens and closes the upstream end of the exhaust passage 13 by a driving force from a valve mechanism (not shown). The internal combustion engine 10 is provided with six exhaust valves 27 corresponding to the six cylinders 11.

[0023] As shown in FIG. 1, the vehicle 100 includes a clutch 31, a motor generator 40, an automatic transmission 61, a differential mechanism 62, and a plurality of drive wheels 63. The motor generator 40 includes a rotating shaft 41, a rotor 42, and a stator 43. The rotating shaft 41 is connected to the rotor 42. Therefore, the rotating shaft 41 is rotatable relative to the stator 43. The rotating shaft 41 of the motor generator 40 is connected to the crankshaft 18 of the internal combustion engine 10 via a clutch 31. The connection state of the clutch 31 is switched between an engaged state and a released state depending on the pressure of oil supplied to the inside of the clutch 31.

[0024] Furthermore, the rotating shaft 41 of the motor generator 40 is connected to drive wheels 63 via an automatic transmission 61 and a differential mechanism 62. An example of the automatic transmission 61 is a stepped automatic transmission. The automatic transmission 61 can change the gear ratio in stages. The differential mechanism 62 allows a difference in rotation speed to occur between the left and right drive wheels 63.

[0025] <Vehicle Electrical Configuration> 1, the vehicle 100 includes a battery 71 and an inverter 72. When the motor generator 40 functions as a power generator, the battery 71 stores the electric power generated by the motor generator 40. When the motor generator 40 functions as an electric motor, the battery 71 supplies electric power to the motor generator 40. The inverter 72 adjusts the amount of electric power exchanged between the motor generator 40 and the battery 71.

[0026] As shown in Fig. 1, the vehicle 100 is equipped with an accelerator operation amount sensor 81, a vehicle speed sensor 82, a crank angle sensor 83, and a pressure sensor 84. The accelerator operation amount sensor 81 detects an accelerator operation amount ACC, which is the amount of operation of an accelerator pedal (not shown) operated by a driver. The vehicle speed sensor 82 detects a vehicle speed SP, which is the speed of the vehicle 100. The crank angle sensor 83 detects a crank angle SC, which is the angular position of the crankshaft 18. The pressure sensor 84 detects a detected value of a downstream pressure, which is the pressure in the downstream portion of the intake passage 12 as viewed from the throttle valve 21, as a detected downstream pressure PI.

[0027] As shown in Fig. 1, the vehicle 100 is equipped with a control device 90. The control device 90 obtains a signal indicating an accelerator operation amount ACC from an accelerator operation amount sensor 81. The control device 90 obtains a signal indicating a vehicle speed SP from a vehicle speed sensor 82. The control device 90 obtains a signal indicating a crank angle SC from a crank angle sensor 83. The control device 90 calculates an engine rotation speed NE, which is the rotation speed of the crankshaft 18, based on the crank angle SC. The control device 90 obtains a signal indicating a detected downstream pressure PI from a pressure sensor 84.

[0028] The control device 90 calculates the vehicle required driving force, which is a required value of driving force necessary for the vehicle 100 to travel, based on the accelerator operation amount ACC and the vehicle speed SP. The control device 90 determines the torque distribution between the internal combustion engine 10 and the motor generator 40 based on the vehicle required driving force. The control device 90 controls the output of the internal combustion engine 10 and the power running and regeneration of the motor generator 40 based on the torque distribution between the internal combustion engine 10 and the motor generator 40.

[0029] The control device 90 performs various types of control such as adjusting the opening of the throttle valve 21, adjusting the amount of fuel injected from the port injection valve 22, adjusting the amount of fuel injected from the in-cylinder injection valve 23, and adjusting the ignition timing of the ignition device 24 by outputting control signals to the internal combustion engine 10. The control device 90 also outputs a control signal to the inverter 72 in order to control the motor generator 40. The control device 90 then controls the motor generator 40 by adjusting the amount of power exchanged between the motor generator 40 and the battery 71 via the inverter 72.

[0030] The control device 90 outputs a control signal to the clutch 31 to control the connection state of the clutch 31. The control device 90 outputs a control signal to the automatic transmission 61 to control the gear ratio of the automatic transmission 61.

[0031] When a predetermined stop condition is satisfied, the control device 90 executes a stop process to interrupt the combustion of fuel in the cylinder 11 and control the throttle valve 21 to a closed state. Here, one example of the stop condition is that the accelerator operation amount ACC becomes zero, thereby reducing the vehicle required driving force.

[0032] When a predetermined restart condition is satisfied, the control device 90 controls the throttle valve 21 to an open state and executes a restart process to resume the combustion of fuel in the cylinder 11. Here, one example of the restart condition is that, after the execution of the stop process, the accelerator operation amount ACC becomes greater than zero, thereby increasing the vehicle required driving force.

[0033] Specifically, in the restart process, the control device 90 first controls the connection state of the clutch 31 to an engaged state by outputting a control signal to the clutch 31. Then, the control device 90 applies torque from the rotating shaft 41 of the motor generator 40 to the crankshaft 18 of the internal combustion engine 10 via the clutch 31 by outputting a control signal to the inverter 72. As a result, the engine rotation speed NE increases. The control device 90 also controls the throttle valve 21 to an open state. Furthermore, the control device 90 supplies fuel into the cylinder 11 by controlling the port injection valve 22 and the in-cylinder injection valve 23. The control device 90 also controls the ignition device 24 to ignite the mixture of fuel and intake air in the cylinder 11 by spark discharge. As a result, the internal combustion engine 10 restarts.

[0034] As part of the restart process, the control device 90 executes a determination process for determining the cylinder 11 into which fuel is to be injected next. Specifically, in the determination process, the control device 90 first acquires the position of the piston 16 in the cylinder 11 currently undergoing the intake stroke based on the crank angle SC. Then, when the position of the piston 16 in the cylinder 11 currently undergoing the intake stroke is outside a predetermined specified angle range, the control device 90 determines the cylinder 11 currently undergoing the intake stroke as the cylinder 11 into which fuel is to be injected next. An example of the specified angle range is a range from an angle advanced by several tens of degrees from the injection start timing of the port injection valve 22 to the bottom dead center of the intake stroke. On the other hand, when the position of the piston 16 in the cylinder 11 currently undergoing the intake stroke is within a predetermined specified angle range, the control device 90 determines the cylinder 11 that will undergo the intake stroke next to the cylinder 11 currently undergoing the intake stroke as the cylinder 11 into which fuel is to be injected next. Furthermore, the control device 90 changes the injection determination flag indicating the cylinder 11 that will inject fuel next from OFF to ON. In this embodiment, since the internal combustion engine 10 has six cylinders 11, there are six injection determination flags. For example, when the first cylinder 11A is determined as the cylinder 11 that will inject fuel next, the injection determination flag corresponding to the first cylinder 11A is turned ON. On the other hand, the injection determination flags corresponding to the second cylinder 11B to the sixth cylinder 11F are turned OFF. The control device 90 repeatedly executes the determination process at a predetermined control period. Furthermore, since the internal combustion engine 10 has six cylinders 11 in this embodiment, one cylinder 11 or two cylinders 11 may enter the intake stroke at the same time. When two cylinders 11 are entering the intake stroke, the control device 90 treats the cylinder 11 whose piston 16 is located near the bottom dead center of the intake stroke as the cylinder 11 currently entering the intake stroke.

[0035] The control device 90 may be configured as a circuit including one or more processors that execute various processes according to a computer program (software). The control device 90 may also be configured as a circuit including one or more dedicated hardware circuits, such as an application specific integrated circuit (ASIC), that execute at least a part of the various processes, or a combination thereof. The processor includes a CPU and memories such as RAM and ROM. The memory stores program codes or instructions that are configured to cause the CPU to execute processes. The memory, i.e., computer-readable medium, includes any medium that can be accessed by a general-purpose or dedicated computer.

[0036] <Restart control> Next, the restart control executed by the control device 90 will be described. The control device 90 repeatedly executes the restart control at a predetermined control period from when the restart condition is satisfied until the restart of the internal combustion engine 10 is completed. Here, an example of when the restart of the internal combustion engine 10 is completed is when the total number of times that fuel is burned in the six cylinders 11 since the start of the restart control reaches a predetermined number. Therefore, the control device 90 performs the following series of processes on the cylinders 11 that burn fuel the predetermined number of times, starting from the initial explosion cylinder, which is the cylinder 11 in which fuel is burned first when the internal combustion engine 10 is restarted from a state in which fuel combustion in the cylinders 11 is interrupted.

[0037] As shown in Fig. 3, when the control device 90 starts restart control, the control device 90 proceeds to processing in step S11. In step S11, the control device 90 determines whether or not the engine rotation speed NE is higher than a predetermined threshold value. Here, an example of the threshold value is approximately several tens to several hundreds of rpm. In step S11, if the control device 90 determines that the engine rotation speed NE is higher than the threshold value (S11: YES), the control device 90 proceeds to processing in step S12.

[0038] In step S12, the control device 90 determines whether the cylinder 11 into which fuel is to be injected next has been determined. Specifically, when only one of the six injection determination flags is ON, the control device 90 determines that the cylinder 11 into which fuel is to be injected next has been determined. On the other hand, when all of the six injection determination flags are OFF, the control device 90 determines that the cylinder 11 into which fuel is to be injected next has not been determined. Also, when two or more of the six injection determination flags are ON, the control device 90 determines that the cylinder 11 into which fuel is to be injected next has not been determined. Here, an example of a case where all of the six injection determination flags are OFF is a situation where an injection determination flag that was turned ON in the determination process becomes OFF at the time of processing in step S12 due to a bid error or the like. Also, an example of a case where two or more of the six injection determination flags are ON is a situation where an injection determination flag that was turned OFF in the determination process becomes ON at the time of processing in step S12 due to a bid error or the like. Even in these cases, the determination process is normally executed in the next control cycle, and only one of the six injection determination flags is turned ON. In step S12, when the control device 90 determines that the cylinder 11 into which fuel is to be next injected has been determined (S12: YES), the control device 90 advances the process to step S21.

[0039] In step S21, the control device 90 executes a first detection process for acquiring a base pressure PA when restarting the internal combustion engine 10. Specifically, in the first detection process, the control device 90 specifies a crank angle SC that is a first predetermined angle before the crank angle SC at the time of processing step S21. Then, the control device 90 calculates an average value of a plurality of detected downstream pressures PI acquired from the crank angle SC before the first predetermined angle to the time of processing step S21. Then, the control device 90 acquires the calculated average value of the detected downstream pressures PI as the base pressure PA. Note that an example of the first predetermined angle is several hundred degrees to several hundred degrees. Thereafter, the control device 90 advances the process to step S22.

[0040] In step S22, the control device 90 executes a first calculation process for calculating the fluctuation amount PB of the downstream pressure. Specifically, in the first calculation process, the control device 90 first specifies the crank angle SC that is a second predetermined angle before the crank angle SC at the time of processing step S22. The control device 90 also calculates a fluctuation speed C, which is the amount of fluctuation of the detected downstream pressure PI per unit angle of the crank angle SC, based on a plurality of detected downstream pressures PI acquired from the crank angle SC that is the second predetermined angle before until the time of processing step S22. Furthermore, the control device 90 calculates a first fluctuation angle D1, which is the angle width of the crank angle SC that fluctuates from the time of processing step S22 to the time when the intake valve 26 for the cylinder 11 that will next inject fuel is closed. Then, the control device 90 calculates a value obtained by multiplying the fluctuation speed C by the first fluctuation angle D1 as the fluctuation amount PB. That is, the fluctuation amount PB in step S22 is the amount of fluctuation in the downstream pressure from the point in time when the base pressure PA is acquired by the first detection process in step S21 to the point in time when the intake valve 26 for the cylinder 11 that will next inject fuel is closed. Note that an example of the second predetermined angle is several tens of degrees to several hundred degrees. After step S22, the control device 90 advances the process to step S23.

[0041] In step S23, the control device 90 executes a first estimation process for estimating the estimated pressure PZ. Specifically, in the first estimation process, the control device 90 estimates a value obtained by adding the fluctuation amount PB in step S22 to the base pressure PA in step S21 as the estimated pressure PZ. Here, the estimated pressure PZ is an estimate of the downstream pressure at the time when the intake valve 26 of the cylinder 11 that will next inject fuel is closed. Thereafter, the control device 90 advances the process to step S26.

[0042] In step S26, the control device 90 calculates the amount of intake air introduced from the intake passage 12 into the cylinder 11 into which fuel is to be injected next, based on the estimated pressure PZ in step S23. For example, the higher the estimated pressure PZ in step S23, the larger the amount of intake air introduced into the cylinder 11 into which fuel is to be injected next is calculated by the control device 90. In addition, the control device 90 calculates the fuel injection amount for the cylinder 11 into which fuel is to be injected next, based on the amount of intake air introduced into the cylinder 11 into which fuel is to be injected next. For example, the larger the amount of intake air introduced into the cylinder 11 into which fuel is to be injected next is, the larger the value of the fuel injection amount for the cylinder 11 into which fuel is to be injected next is calculated by the control device 90. Note that the control device 90 controls the port injection valve 22 and the in-cylinder injection valve 23 based on the calculated fuel injection amount. As a result, fuel is supplied to the cylinder 11 into which fuel is to be injected next. In this embodiment, the process of step S26 is a process executed as part of the restart process. Therefore, the restart process is a process for calculating the fuel injection amount for the cylinder 11 into which fuel is next injected, based on the estimated pressure PZ estimated in the first estimation process in step S23. After that, the control device 90 ends the current restart control, and causes the process to proceed to step S11 again.

[0043] On the other hand, in step S12 described above, when the control device 90 determines that the cylinder 11 into which fuel is to be injected next has not been determined (S12: NO), the control device 90 advances the process to step S31.

[0044] In step S31, the control device 90 executes a second detection process to acquire a base pressure PA when restarting the internal combustion engine 10. The second detection process in step S31 is similar to the first detection process in step S21. That is, the control device 90 acquires an average value of the detected downstream pressures PI calculated in the second detection process as the base pressure PA. Thereafter, the control device 90 advances the process to step S32.

[0045] In step S32, the control device 90 executes a second calculation process for calculating the fluctuation amount PB of the downstream pressure. Specifically, in the second calculation process, the control device 90 first specifies the crank angle SC that is a second predetermined angle before the crank angle SC at the time of processing step S32. The control device 90 also calculates a fluctuation speed C, which is the amount of fluctuation of the detected downstream pressure PI per unit angle of the crank angle SC, based on a plurality of detected downstream pressures PI acquired from the crank angle SC that is the second predetermined angle before the time of processing step S32. Furthermore, the control device 90 acquires a second fluctuation angle D2, which is the angle width of the crank angle SC that fluctuates from the injection start timing of the port injection valve 22 for the cylinder 11 that is in the intake stroke to the time when the intake valve 26 for that cylinder 11 closes. The situation in which the process of step S32 is executed is a situation in which the cylinder 11 to which fuel is next injected has not been determined. However, the crank angle SC at the injection start timing of the port injection valve 22 for the cylinder 11 undergoing the intake stroke is determined with respect to the bottom dead center of the intake stroke, regardless of whether the cylinder 11 to which fuel is to be injected next has been determined. Similarly, the crank angle SC at the time when the intake valve 26 for the cylinder 11 undergoing the intake stroke is closed is determined with respect to the bottom dead center of the intake stroke. Therefore, the control device 90 pre-stores a value grasped at the design stage of the internal combustion engine 10, for example, as a value to be used for the second fluctuation angle D2. Then, the control device 90 acquires the pre-stored value as the second fluctuation angle D2. In addition, the control device 90 calculates a value obtained by multiplying the fluctuation speed C by the second fluctuation angle D2 as the fluctuation amount PB. As described above, in this embodiment, the specified angle range used in the determination process is a range from an angle advanced by several tens of degrees from the injection start timing of the port injection valve 22 to the bottom dead center of the intake stroke. Therefore, the second adjustment angle D2 in step S32 is a smaller value than the first adjustment angle D1 in step S22. After that, the control device 90 advances the process to step S33.

[0046] In step S33, the control device 90 executes a second estimation process to estimate the estimated pressure PZ. The second estimation process in step S33 is similar to the first estimation process in step S23. That is, in the second estimation process, the control device 90 estimates a value obtained by adding the fluctuation amount PB in step S32 to the base pressure PA in step S31 as the estimated pressure PZ. Thereafter, the control device 90 advances the process to step S36.

[0047] In step S36, the control device 90 calculates the amount of intake air introduced from the intake passage 12 into the cylinder 11 into which fuel is to be injected next, based on the estimated pressure PZ in step S33. For example, the higher the estimated pressure PZ in step S33, the larger the amount of intake air introduced into the cylinder 11 into which fuel is to be injected next is calculated by the control device 90. Also, the control device 90 calculates the fuel injection amount for the cylinder 11 into which fuel is to be injected next, based on the amount of intake air introduced into the cylinder 11 into which fuel is to be injected next. For example, the larger the amount of intake air introduced into the cylinder 11 into which fuel is to be injected next, the larger the value of the fuel injection amount for the cylinder 11 into which fuel is to be injected next is calculated by the control device 90. In this embodiment, the process of step S36 is a process executed as part of the restart process. Therefore, the restart process is a process of calculating the fuel injection amount for the cylinder 11 into which fuel is to be injected next, based on the estimated pressure PZ estimated in the second estimation process in step S33. Thereafter, the control device 90 ends the current restart control, and advances the process to step S11 again.

[0048] On the other hand, in the above-mentioned step S11, when the control device 90 determines that the engine rotation speed NE is equal to or lower than the threshold value (S11: NO), the control device 90 advances the process to step S41.

[0049] In step S41, the control device 90 executes a third detection process for acquiring a base pressure PA when restarting the internal combustion engine 10. The third detection process in step S41 is similar to the first detection process in step S21. That is, the control device 90 acquires an average value of the detected downstream pressures PI calculated in the third detection process as the base pressure PA. Thereafter, the control device 90 advances the process to step S42.

[0050] In step S42, the control device 90 executes a setting process. Specifically, in the setting process, the control device 90 sets the base pressure PA in step S41 as the estimated pressure PZ as is. After that, the control device 90 advances the process to step S46.

[0051] In step S46, the control device 90 calculates the amount of intake air introduced from the intake passage 12 into the cylinder 11 into which fuel is to be injected next, based on the estimated pressure PZ in step S42. For example, the control device 90 calculates a larger value as the amount of intake air introduced into the cylinder 11 into which fuel is to be injected next, as the estimated pressure PZ in step S42 is higher. In addition, the control device 90 calculates the fuel injection amount for the cylinder 11 into which fuel is to be injected next, based on the amount of intake air introduced into the cylinder 11 into which fuel is to be injected next. For example, the control device 90 calculates a larger value as the fuel injection amount for the cylinder 11 into which fuel is to be injected next, as the amount of intake air introduced into the cylinder 11 into which fuel is to be injected next is larger. In this embodiment, the process of step S46 is a process executed as part of the restart process. Thereafter, the control device 90 ends the current restart control, and advances the process to step S11 again.

[0052] <Action of this embodiment> In the vehicle 100, when the stop process is started, the throttle valve 21 is controlled to a closed state. However, even if the throttle valve 21 is controlled to a closed state, a small amount of gas can generally flow through the intake passage 12. Then, immediately after the stop process is started, the crankshaft 18 is rotating. When the crankshaft 18 is rotating, each cylinder 11 repeats an intake stroke, a compression stroke, a combustion stroke, and an exhaust stroke, so that gas flows through the intake passage 12, the cylinder 11, and the exhaust passage 13 in this order. When gas flows in this manner, the downstream pressure, which is the pressure of the portion downstream of the throttle valve 21 in the intake passage 12, becomes lower than the atmospheric pressure. Thereafter, when the restart process is started while the crankshaft 18 is rotating, the throttle valve 21 is controlled to an open state. Then, the downstream pressure gradually increases and approaches the atmospheric pressure. Therefore, when the restart process is started while the crankshaft 18 is rotating, the downstream pressure fluctuates immediately after the restart process is started.

[0053] Here, in the restart process, the fuel injected from the port injection valve 22 is supplied from the intake passage 12 to the cylinder 11 together with the intake air introduced from the intake passage 12 to the cylinder 11 during the intake stroke of the target cylinder 11. Therefore, the fuel injection amount from the port injection valve 22 needs to be calculated before the intake valve 26 for the target cylinder 11 closes. However, if the downstream pressure fluctuates immediately after the start of the restart process, there is a possibility that the detected downstream pressure PI detected by the pressure sensor 84 before the fuel injection amount is calculated will deviate from the downstream pressure at the time the intake valve 26 for the target cylinder 11 closes.

[0054] <Effects of this embodiment> (1) In the first calculation process of step S22, the control device 90 calculates the fluctuation amount PB of the downstream pressure from the time when the base pressure PA is acquired by the first detection process of step S21 to the time when the intake valve 26 of the cylinder 11 that will inject fuel next is closed. Then, in the first estimation process of step S23, the control device 90 estimates a value obtained by adding the fluctuation amount PB of step S22 to the base pressure PA of step S21 as the estimated pressure PZ. Therefore, based on the fluctuation amount PB from the acquisition of the base pressure PA to the closing of the intake valve 26, the downstream pressure at the time when the intake valve 26 of the cylinder 11 that will inject fuel next is closed is estimated as the estimated pressure PZ. In other words, the downstream pressure at the time when the introduction of the intake air from the intake passage 12 into the cylinder 11 is completed is estimated. Thereby, the fuel injection amount is calculated taking into account the fluctuation of the downstream pressure from the acquisition of the base pressure PA to the completion of the introduction of the intake air. As a result, the restart process can be appropriately executed.

[0055] (2) In the first calculation process of step S22, a first fluctuation angle D1 is calculated to calculate the fluctuation amount PB. This first fluctuation angle D1 is the angle width of the crank angle SC that fluctuates from the time of the process of step S22 to the time when the intake valve 26 for the cylinder 11 that will inject fuel next is closed. Therefore, for example, when all six injection determination flags are OFF due to a bid error or the like, that is, when the cylinder 11 that will inject fuel next has not been determined, the first fluctuation angle D1 cannot be calculated. As a result, in the first calculation process of step S22, the control device 90 cannot calculate the fluctuation amount PB.

[0056] In this regard, in the second calculation process of step S32, the control device 90 calculates the fluctuation amount PB using the second fluctuation angle D2. Here, the second fluctuation angle D2 is the angle width of the crank angle SC that fluctuates from the injection start timing of the port injection valve 22 for the cylinder 11 that is in the intake stroke to the time when the intake valve 26 for that cylinder 11 closes. The second fluctuation angle D2 is a value that is determined regardless of whether the cylinder 11 that will inject fuel next has been determined. As a result, even in a situation where the cylinder 11 that will inject fuel next has not been determined, the fluctuation amount PB can be calculated by using the second fluctuation angle D2.

[0057] (3) When the engine speed NE when the internal combustion engine 10 is restarted is equal to or lower than a threshold value, the estimation accuracy of the estimated pressure PZ by the first estimation process or the like tends to decrease compared to when the engine speed NE is higher than the threshold value. In addition, when the engine speed NE is equal to or lower than the threshold value, the amount of intake air flowing through the intake passage 12 is also small. For this reason, when the engine speed NE is equal to or lower than the threshold value, the downstream pressure does not become significantly lower than the atmospheric pressure even if the crankshaft 18 is rotating.

[0058] In this regard, in the setting process of step S41, when the engine speed NE is equal to or lower than the threshold value, the control device 90 sets the base pressure PA as the estimated pressure PZ as it is. In other words, in a situation where the estimation accuracy of the estimated pressure PZ by the first estimation process or the like is reduced, the base pressure PA, which is likely to be close to the downstream pressure at the time when the intake valve 26 closes, is set as the estimated pressure PZ. Therefore, when the engine speed NE of the crankshaft 18 is equal to or lower than the threshold value, the estimated pressure PZ is not estimated to be far from the actual value.

[0059] (4) In this embodiment, for example, in step S21, the base pressure PA is set to the average value of multiple detected downstream pressures PI obtained from the crank angle SC before the first predetermined angle until the processing of step S21. Therefore, even if the downstream pressure at the processing of step S21 momentarily becomes an abnormal value, for example, the influence of this can be reduced.

[0060] <Example of change> This embodiment can be modified as follows: This embodiment and the following modifications can be combined with each other to the extent that there is no technical contradiction.

[0061] In the above embodiment, the restart control may be changed. For example, as long as each process in the restart control is executed for the cylinder that produces the initial explosion, it does not have to be executed for the cylinder 11 that burns for the second or subsequent times.

[0062] For example, depending on the structure of the internal combustion engine 10, the estimation accuracy of the estimated pressure PZ by the first estimation process or the like may not be likely to decrease even if the engine speed NE when the internal combustion engine 10 is restarted is equal to or lower than a threshold value. In this case, the control device 90 may proceed to step S12 when restart control is started. In this configuration, the processes of step S11 and steps S41 to S46 can be omitted.

[0063] For example, the processes of step S12 and steps S31 to S36 may be omitted. As a specific example, if the injection determination flag is normally turned ON and OFF, there is no particular problem even if the above steps are omitted.

[0064] For example, in step S21, the configuration for acquiring the base pressure PA may be changed. As a specific example, the control device 90 may acquire the most recently detected downstream pressure PI detected at the time of processing step S21 as the base pressure PA. Similarly, the processing of steps S31 and S41 may be changed.

[0065] For example, in step S22, the way of calculating the fluctuation amount PB can be appropriately changed. As a specific example, immediately before the intake valve 26 for the cylinder 11 that will inject fuel next closes in the first fluctuation angle D1, the opening degree of the intake valve 26 becomes small, which makes it difficult for intake air to be introduced from the intake passage 12 to the cylinder 11. If the flow of intake air in the intake passage 12 is stagnated, the actual fluctuation amount of the downstream pressure also becomes small. Therefore, the control device 90 may set the value obtained by further correcting the fluctuation amount PB calculated based on the fluctuation speed C and the first fluctuation angle D1 as the final fluctuation amount PB. Examples of such correction include a correction in which a predetermined constant value is subtracted from the fluctuation amount PB, a correction in which a predetermined coefficient less than 1 is multiplied by the fluctuation amount PB, and the like. The process of step S32 can also be changed in a similar manner.

[0066] In the above embodiment, the configuration of the vehicle 100 may be changed. For example, the vehicle 100 does not need to include the motor generator 40. Even in this configuration, if the engine rotation speed NE is relatively high when the restart condition is satisfied, it is possible to restart the internal combustion engine 10 without applying torque from the motor generator 40. Also, if the engine rotation speed NE is zero when the restart condition is satisfied, it is possible to restart the internal combustion engine 10 by cranking using a starter motor, for example.

[0067] For example, the internal combustion engine 10 may have five or fewer cylinders 11, or may have seven or more cylinders 11. In addition, for example, the internal combustion engine 10 does not have to have an in-cylinder injection valve 23. [Explanation of symbols]

[0068] PA: Base pressure PB: Fluctuation amount PI: Detected downstream pressure PZ: Estimated pressure 10. Internal combustion engine 11…Cylinder 12…Intake passage 13...Exhaust passage 16…Piston 17…Connecting rod 18…Crankshaft 21...Throttle valve 22...Port injection valve 23...In-cylinder injection valve 24...Ignition device 26…Intake valve 27…Exhaust valve 31…Clutch 40…Motor generator 61…Automatic transmission 62…Differential mechanism 63...Drive wheel 71…Battery 72…Inverter 81...Accelerator operation amount sensor 82...Vehicle speed sensor 83...Crank angle sensor 84...Pressure sensor 90...Control device 100…Vehicle

Claims

1. 1. A control device that is applied to an internal combustion engine including: a cylinder that combusts fuel; an intake passage that introduces intake air into the cylinder; an exhaust passage that discharges exhaust gas from the cylinder; a piston that reciprocates in the cylinder; a crankshaft that rotates by the reciprocating motion of the piston; a fuel injection valve that supplies fuel into the cylinder; a throttle valve that is located in the intake passage and adjusts the amount of intake air flowing through the intake passage; an intake valve that opens and closes a downstream end of the intake passage; and a pressure sensor that detects a downstream pressure, which is a pressure in a portion of the intake passage downstream from the throttle valve, and controls a restart of the internal combustion engine, a stop process for stopping the combustion of fuel in the cylinder and controlling the throttle valve to a closed state when a predetermined stop condition is satisfied; a restart process for controlling the throttle valve to an open state and restarting combustion of fuel in the cylinder when a predetermined restart condition is satisfied; a detection process of acquiring the downstream pressure detected by the pressure sensor as a base pressure when executing the restart process; a calculation process for calculating a fluctuation amount of the downstream pressure from a time point at which the base pressure is acquired by the detection process to a time point at which the intake valve of the initial explosion cylinder is closed, when the cylinder in which fuel is first burned when the internal combustion engine is restarted from a state in which fuel combustion in the cylinder has been interrupted is determined as an initial explosion cylinder; an estimation process for estimating, as an estimated pressure, the downstream pressure at a time point when the intake valve of the initial explosion cylinder closes, based on the base pressure and the fluctuation amount; It is possible to execute In the restart process, a fuel injection amount for the initial explosion cylinder is calculated based on the estimated pressure estimated in the estimation process. A control device for an internal combustion engine.

2. When the rotation speed of the crankshaft is higher than a predetermined threshold value, the calculation process and the estimation process are executed. When the rotation speed of the crankshaft is equal to or lower than the threshold value, a setting process is executed to set the base pressure as the estimated pressure. The control device for an internal combustion engine according to claim 1.

Images