Vehicle control device

Abstract

To finish the injection of required fuel before ignition, and to ensure a time for atomizing the fuel.SOLUTION: A vehicle 90 has: an internal combustion engine 10; a motor generator 82 that is located on a power transmission path from the internal combustion engine 10 to driving wheels 72; and a clutch 81 that switches between a connection state in which the internal combustion engine 10 and the motor generator 82 are connected and a disconnection state in which those are separated. When the clutch 81 is in the disconnection state, an engine rotation speed is larger than zero, and starting of the internal combustion engine 10 is requested while ignition by an ignition plug is stopped, a control device 100 executes processing for calculating a basic injection period of a cylinder injector, processing for calculating an injection period required for the injection of a required injection amount by the cylinder injector, processing for calculating a timing that goes back from a compressed top dead center by a necessary period longer than the injection period as a limiting period, and processing for calculating earlier one of the basis injection period and the limiting period as a final injection period.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a vehicle control device. [Background technology]

[0002] The vehicle disclosed in Patent Document 1 has an internal combustion engine, an electric motor, and a control device. The crankshaft of the internal combustion engine is connected to the electric motor. The control device performs so-called idling stop control, which stops or restarts the internal combustion engine depending on the driving conditions of the vehicle. For example, the control device stops the internal combustion engine while the vehicle is decelerating. Here, after the control device stops the internal combustion engine while the vehicle is decelerating, the driver may request re-acceleration. In this case, the control device restarts the internal combustion engine by cranking the internal combustion engine using the electric motor. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2017-100626 A Summary of the Invention [Problem to be solved by the invention]

[0004] As in Patent Document 1, when restarting an internal combustion engine during deceleration of a vehicle, the internal combustion engine may be restarted without cranking by an electric motor. In this case, since there is no cranking by the electric motor, the internal combustion engine itself needs to generate a large torque. This makes it necessary to increase the rotation speed of the crankshaft. In order to increase the torque of the internal combustion engine, it is effective to advance the ignition timing. On the other hand, in order to suppress spontaneous ignition of fuel, it is desirable to retard the fuel injection timing. However, if the fuel injection timing is retarded after advancing the ignition timing, there is a risk that the ignition timing will be reached before the necessary fuel is injected. [Means for solving the problem]

[0005] A vehicle control device for solving the above problem is applied to a vehicle having an internal combustion engine including an ignition plug for igniting in a cylinder, an injector for directly injecting fuel into the cylinder, and a crankshaft, an electric motor including a rotating shaft, and a clutch interposed between the internal combustion engine and the electric motor and switching between a connected state in which the crankshaft and the rotating shaft are connected, and a disconnected state in which the crankshaft and the rotating shaft are disconnected, and when a start request for the internal combustion engine is made while the clutch is in the disconnected state, the rotational speed of the crankshaft is greater than zero, and ignition by the spark plug is stopped, the cylinder in which fuel is burned first after the start request is made is designated as an initial combustion cylinder, and the injector for the initial combustion cylinder is designated as an initial combustion injector, A process of determining an ignition timing of the spark plug for the initial combustion cylinder to be a timing after a compression top dead center of the initial combustion cylinder; A first process calculates a basic injection timing for the first combustion injector based on the rotation speed of the crankshaft, a second process calculates an injection period required for the first combustion injector to inject a required injection amount according to the rotation speed of the crankshaft, a third process calculates a timing going back from the compression top dead center of the first combustion cylinder by a required period longer than the injection period as a limit timing, and a fourth process calculates an injection timing for the first combustion injector based on the rotation speed of the crankshaft. should start injection and a fourth process for calculating the final injection timing and controlling the initial combustion injector.

[0006] When fuel is injected into a cylinder, the fuel is atomized. When the fuel is ignited, it is mainly the atomized fuel that contributes to the generation of torque. In other words, even if the fuel before atomization is ignited, the fuel before atomization does not effectively contribute to the generation of torque. Therefore, it is preferable that the necessary amount of fuel is injected and that the injected fuel is atomized before ignition by the spark plug.

[0007] Now, ignition by the spark plug occurs after the top dead center of compression. Therefore, if the necessary amount of fuel is injected from the injector before the top dead center of compression and the fuel is atomized, all of the fuel injected by the injector can contribute to torque generation. Therefore, the control device sets the limit timing of the initial combustion injector to a timing that is a necessary period earlier than the top dead center of compression that is a specified time longer than the injection period. Then, the control device starts fuel injection from the initial combustion injector at a timing before this limit timing. In this case, the initial combustion injector can inject all of the fuel for the required injection amount. Also, time can be secured for the injected fuel to atomize. Therefore, the torque required to start the internal combustion engine can be output. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic diagram of a vehicle. [Diagram 2] FIG. 2 is a schematic diagram of an internal combustion engine. [Diagram 3] FIG. 3 is a schematic diagram for explaining the basic injection timing and the limit timing. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, an embodiment of a vehicle control device will be described with reference to the drawings. <Overall vehicle configuration> As shown in FIG. 1, a vehicle 90 has an internal combustion engine 10 , a clutch 81 , a motor generator 82 , a transmission unit 80 , a hydraulic mechanism 86 , a differential 71 , a plurality of drive wheels 72 , an inverter 78 , and a battery 79 .

[0010] The internal combustion engine 10 is a drive source for the vehicle 90. The detailed structure of the internal combustion engine 10 will be described later. The internal combustion engine 10 has a crankshaft 14. The motor generator 82 is a drive source for the vehicle 90. The motor generator 82 functions as both an electric motor and a generator. The motor generator 82 has a stator 82C, a rotor 82B, and a rotating shaft 82A. The rotor 82B is rotatable relative to the stator 82C. The rotating shaft 82A rotates integrally with the rotor 82B. The motor generator 82 is electrically connected to a battery 79 via an inverter 78. The battery 79 exchanges power with the motor generator 82. The inverter 78 converts DC to AC.

[0011] The clutch 81 is interposed between the internal combustion engine 10 and the motor generator 82. The clutch 81 is operated by hydraulic pressure from a hydraulic mechanism 86 to switch between an engaged and disengaged state. When the clutch 81 receives hydraulic pressure, it enters a connected state in which the crankshaft 14 and the rotating shaft 82A of the motor generator 82 are connected. When the supply of hydraulic pressure is stopped, the clutch 81 enters a disengaged state in which the crankshaft 14 and the rotating shaft 82A are separated from each other.

[0012] The transmission unit 80 has a torque converter 83 and an automatic transmission 85. The torque converter 83 has a pump impeller 83A, a turbine liner 83B, and a lock-up clutch 84. The torque converter 83 is a fluid coupling having a torque amplifying function. The pump impeller 83A rotates integrally with a rotating shaft 82A of the motor generator 82. The turbine liner 83B rotates integrally with an input shaft of the automatic transmission 85. The lock-up clutch 84 receives hydraulic pressure from a hydraulic mechanism 86 and directly connects the pump impeller 83A and the turbine liner 83B.

[0013] The automatic transmission 85 is a stepped transmission in which the gear ratio is changed in multiple stages by changing the gears. The output shaft of the automatic transmission 85 is connected to the left and right drive wheels 72 via the differential 71. The differential 71 allows a difference in rotation speed between the left and right drive wheels 72. The clutch 81, the motor generator 82, and the speed change unit 80 are housed in a single continuous case. In other words, the clutch 81, the motor generator 82, and the speed change unit 80 are configured as an integrated hybrid transaxle. The clutch 81, the motor generator 82, and the speed change unit 80 are located on a power transmission path from the internal combustion engine 10 to the drive wheels 72.

[0014] Vehicle 90 has accelerator pedal 94. Accelerator pedal 94 is a foot pedal that is depressed by the driver. Vehicle 90 has vehicle speed sensor 58 and accelerator sensor 59. Vehicle speed sensor 58 detects the traveling speed of vehicle 90 as vehicle speed SP. Accelerator sensor 59 detects the depression amount of accelerator pedal 94 as accelerator operation amount ACC.

[0015] <General configuration of internal combustion engine> As shown in Fig. 2, the internal combustion engine 10 has four cylinders 11, four pistons 12, four connecting rods 13, and the crankshaft 14. Note that Fig. 2 shows only one of the four cylinders 11. The same is true for the pistons 12 and the connecting rods 13. The pistons 12 and the connecting rods 13 are provided for each cylinder 11.

[0016] The cylinder 11 is a space for burning fuel. The piston 12 is located inside the cylinder 11. The piston 12 reciprocates inside the cylinder 11. The piston 12 is connected to a crankshaft 14 via a connecting rod 13. The crankshaft 14 rotates in response to the reciprocating movement of the piston 12.

[0017] The internal combustion engine 10 has a crank angle sensor 61. The crank angle sensor 61 is located near the crankshaft 14. The crank angle sensor 61 detects the rotational position (hereinafter referred to as the crank position) CR of the crankshaft 14.

[0018] The internal combustion engine 10 has four spark plugs 19. Note that Fig. 2 shows only one of the four spark plugs 19. The spark plug 19 is provided for each cylinder 11. The tip of the spark plug 19 is located inside the cylinder 11. The spark plug 19 ignites the mixture of intake air and fuel.

[0019] The internal combustion engine 10 has four in-cylinder injectors 18. Note that Fig. 2 shows only one of the four in-cylinder injectors 18. The in-cylinder injector 18 is provided for each cylinder 11. The tip of the in-cylinder injector 18 is located inside the cylinder 11. The in-cylinder injector 18 injects fuel directly into the cylinder 11 without passing through an intake passage 15 described below.

[0020] The internal combustion engine 10 has an intake passage 15, a throttle valve 16, four port injection valves 17, and an exhaust passage 21. Note that FIG. 2 shows only one of the four port injection valves 17. The intake passage 15 is a passage for introducing intake air into each cylinder 11. The intake passage 15 is connected to each cylinder 11. The throttle valve 16 is located midway through the intake passage 15. The throttle valve 16 adjusts the amount of intake air flowing through the intake passage 15. The four port injection valves 17 are located downstream of the throttle valve 16 in the intake passage 15. The port injection valve 17 is provided for each cylinder 11. The port injection valve 17 injects fuel into the intake passage 15. The exhaust passage 21 is a passage for discharging exhaust gas from each cylinder 11. The exhaust passage 21 is connected to each cylinder 11.

[0021] The vehicle 90 has a fuel supply system. The fuel supply system has a fuel tank 25, a fuel supply passage 26, a branch passage 27, and a fuel pressure sensor 62. The fuel tank 25 stores fuel. The fuel supply passage 26 connects the fuel tank 25 and each in-cylinder injector 18. Fuel pumped by a pump (not shown) flows through the fuel supply passage 26. The fuel pressure sensor 62 detects the pressure P of the fuel supplied to the in-cylinder injector 18 (hereinafter referred to as fuel pressure). The branch passage 27 branches off from the fuel supply passage 26. The branch passage 27 is connected to each port injection valve 17.

[0022] <Outline of the control device> As shown in FIG. 1, the vehicle 90 has a control device 100. The control device 100 may be configured as one or more processors that execute various processes according to a computer program (software). The control device 100 may be configured as 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 circuit including a combination thereof. The processor includes a CPU 111 and memories such as a RAM and a ROM 112. The memory stores program codes or instructions that are configured to cause the CPU 111 to execute the processes. The memory, i.e., the computer-readable medium, includes any available medium that can be accessed by a general-purpose or dedicated computer. The control device 100 has a storage device that is an electrically rewritable non-volatile memory.

[0023] The control device 100 repeatedly receives detection signals from various sensors in the vehicle 90. Specifically, the control device 100 receives detection signals for the following parameters: Vehicle speed SP detected by the vehicle speed sensor 58 Acceleration amount ACC detected by accelerator sensor 59 The crank position CR detected by the crank angle sensor 61 The fuel pressure P detected by the fuel pressure sensor 62 The control device 100 calculates the engine speed NE based on the crank position CR.

[0024] The control device 100 controls various parts of the vehicle 90. In response to this, the control device 100 switches the driving mode of the vehicle 90 to a first mode or a second mode. In the first mode, the control device 100 stops the operation of the internal combustion engine 10 and disengages the clutch 81. In this case, the control device 100 drives the vehicle 90 using the power of the motor generator 82. On the other hand, in the second mode, the control device 100 operates the internal combustion engine 10 and connects the clutch 81. In this case, the control device 100 drives the vehicle 90 using both the power of the internal combustion engine 10 and the power of the motor generator 82. Note that in the second mode, the control device 100 may also drive the vehicle 90 using only the power of the internal combustion engine 10 by causing the motor generator 82 to generate regenerative power.

[0025] For example, when the charge amount of the battery 79 is sufficient, the control device 100 selects the first mode when the accelerator operation amount ACC is small, and selects the second mode when the accelerator operation amount ACC is large. That is, the control device 100 switches the traveling mode according to the accelerator operation amount ACC. For example, when switching the traveling mode to the second mode, the control device 100 determines that there has been a request to switch to the second mode, that is, a request to start the internal combustion engine 10, when the accelerator operation amount ACC increases to a specified operation amount. Then, the control device 100 performs each process required to switch the traveling mode.

[0026] The above-mentioned prescribed operation amount is a value as follows. The torque that the vehicle 90 should output in response to the accelerator operation amount ACC instructed by the occupant is called the vehicle axle torque. When the internal combustion engine 10 is operated, it is required to operate the internal combustion engine 10 with high combustion efficiency to improve fuel efficiency. Here, the torque of the internal combustion engine 10 when the internal combustion engine 10 is operated with high combustion efficiency is correspondingly large. Therefore, it is not preferable from the viewpoint of fuel efficiency to operate the internal combustion engine 10 when the vehicle axle torque is small. Therefore, it is preferable not to operate the internal combustion engine 10 when the vehicle axle torque is small, and to cover the vehicle axle torque only by the motor generator 82. The above-mentioned prescribed operation amount is, for example, the accelerator operation amount ACC corresponding to the minimum value of the vehicle axle torque at which the internal combustion engine 10 can be operated with high combustion efficiency.

[0027] <About independent start control> After the control device 100 switches the driving mode of the vehicle 90 from the second mode to the first mode, a request to switch to the second mode may occur shortly after. This corresponds to a situation in which the occupant once releases the accelerator pedal 94 from a state in which the occupant has depressed the accelerator pedal 94, but then depresses the accelerator pedal 94 again to instruct re-acceleration. As described above, when the driving mode is the first mode, the control device 100 disengages the clutch 81 and stops the internal combustion engine 10. That is, in the above situation, a request to switch the driving mode to the second mode, i.e., a request to start the internal combustion engine 10, occurs with the clutch 81 in the disengaged state and ignition by the spark plug 19 stopped.

[0028] In the above scene, it is assumed that the timing of the command to accelerate again after the occupant releases the accelerator pedal 94 is fairly early. In this case, when the command to accelerate again is given, that is, when a request to start the internal combustion engine 10 is made, the crankshaft 14 has not yet stopped and is rotating by inertia. When the engine speed NE when a request to start the internal combustion engine 10 is made is a value equal to or greater than the first threshold value and less than the second threshold value, the control device 100 performs the independent start control. This independent start control is a control for restarting the internal combustion engine 10 only by the torque of the internal combustion engine 10 itself, without using the torque assist of the motor generator 82. When the control device 100 executes the independent start control, the crankshaft 14 rises to or greater than the second threshold value. After completing the execution of this independent start control, the control device 100 brings the clutch 81 into an engaged state.

[0029] The first threshold value is determined in advance, for example, through experiments or simulations, as the maximum engine speed NE at which the internal combustion engine 10 can be started without assistance from the motor generator 82. The second threshold value is the minimum engine speed NE at which the internal combustion engine 10 can operate independently, that is, the idle speed.

[0030] The independent start control includes injection control for controlling the in-cylinder injector 18 and ignition control for controlling the spark plug 19. In this embodiment, the control device 100 performs the injection control and ignition control only for the first cycle of the internal combustion engine 10. Note that one cycle of the internal combustion engine 10 is one in which fuel is burned once in each of the four cylinders 11. In the following description, of the four cylinders 11, the cylinder 11 that burns fuel first after a start request is made to the internal combustion engine 10 is referred to as the initial combustion cylinder. Also, of the four in-cylinder injectors 18, the in-cylinder injector 18 that injects fuel into the initial combustion cylinder is referred to as the initial combustion injector.

[0031] In the ignition control, the control device 100 determines the ignition timing Q of the spark plug 19 and controls the spark plug 19 so that ignition occurs at the determined ignition timing Q. The control device 100 determines the ignition timing Q based on the engine speed NE when a start request is made for the internal combustion engine 10, etc. The ignition timing Q determined by the control device 100 is set as early as possible after the compression top dead center of the cylinder 11 to be ignited.

[0032] In the injection control, the control device 100 performs a first process, a second process, a third process, and a fourth process in this order. Through these processes, the control device 100 determines the injection timing of the in-cylinder injector 18 and controls the in-cylinder injector 18 based on the determined injection timing. This injection timing is some timing between when the piston 12 moves from the bottom dead center to the top dead center in the compression stroke. The control device 100 stores an injection amount map in advance as information for performing the injection control. The injection amount map defines the relationship between the engine rotation speed NE and the required injection amount Y. In the injection amount map, the required injection amount Y is basically larger as the engine rotation speed NE is higher. This is due to the fact that the intake amount increases as the engine rotation speed NE is higher. The required injection amount Y corresponding to each engine rotation speed NE is a value required to output a torque for starting the internal combustion engine 10. For this reason, the required injection amount Y is set to an amount that makes the air-fuel ratio richer than the theoretical air-fuel ratio. The injection amount map is created based on, for example, an experiment or a simulation.

[0033] <Regarding the first process> In the first process, the control device 100 calculates a basic injection timing BJ for the initial combustion injector based on the engine rotation speed NE. As shown in FIG. 3, the basic injection timing BJ is a timing that is a basic period BT back from the ignition timing Q. The basic period BT is an optimal length of time as a period from fuel injection by the in-cylinder injector 18 to ignition by the spark plug 19, when various factors such as protection of the spark plug 19, pre-ignition, and exhaust emissions are taken into consideration. The details of protection of the spark plug 19, etc. will be explained in the section on operation described later. In this embodiment, the control device 100 does not use the basic period BT itself, which is expressed in time, but uses a basic set value BCR that expresses the basic period BT in terms of the amount of rotation of the crankshaft 14 (hereinafter referred to as the amount of crank rotation). The amount of crank rotation is the magnitude of the rotation angle of the crankshaft 14 while the crankshaft 14 rotates from one rotation position to another rotation position.

[0034] The control device 100 stores a first map in advance as information for calculating the basic set value BCR required to calculate the basic injection timing BJ. The first map represents the relationship between the engine speed NE, the fuel pressure P, and the basic set value BCR. More specifically, the first map defines the basic set value BCR for each combination of the engine speed NE and the fuel pressure P in an orthogonal coordinate system with the engine speed NE as the X-axis and the fuel pressure P as the Y-axis. The first map is created, for example, based on an experiment or a simulation.

[0035] The relationship between the engine speed NE, the fuel pressure P, and the basic set value BCR in the first map will be described. As described above, the higher the engine speed NE, the larger the required injection amount Y. In consideration of this, in the first map, if the fuel pressure P is the same, the higher the engine speed NE, the larger the basic set value BCR. In other words, the basic set value BCR is set so that the required injection amount Y can be completely injected by the ignition timing Q. On the other hand, in the first map, if the engine speed NE is the same, the higher the fuel pressure P, the smaller the basic set value BCR. This reflects the fact that the higher the fuel pressure P, the larger the amount of fuel that can be injected from the in-cylinder injector 18 per unit time, and therefore the length of time required to completely inject the required injection amount Y becomes shorter. The first map satisfies such basic relationships between the parameters, and further takes into consideration various factors such as the protection of the ignition plug 19, pre-ignition, and exhaust emissions described above. In other words, the first map is adjusted in consideration of the above-mentioned various factors with respect to the crank rotation amount required to completely inject the required injection amount Y. This adjustment is what makes the first map different from the second map described later.

[0036] Here, assuming that the fuel pressure P is the same, the difference between the basic set value BCR (hereinafter referred to as the first basic set value) when the engine speed NE is a first value and the basic set value BCR (hereinafter referred to as the second basic set value) when the engine speed NE is a second value will be considered. The second value is larger than the first value. As described above, the second basic set value is basically larger than the first basic set value, reflecting the relationship that the higher the engine speed NE is, the larger the required injection amount Y is. In addition to this, in this embodiment, since the basic set value BCR is used instead of the basic period BT, the following is reflected in the difference between the first basic set value and the second basic set value. That is, the crank rotation amount during a certain period of time increases as the engine speed NE is higher. Therefore, even if the basic period BT is approximately the same when the engine speed NE is a first value and when it is a second value, the second basic set value is larger than the first basic set value. The first map also reflects such differences in the basic set value BCR according to the relationship between the engine rotation speed NE and the crank rotation amount.

[0037] In the first process, the control device 100 calculates, based on the above-mentioned first map, a basic set value BCR corresponding to the engine speed NE and the fuel pressure P when a start request is made for the internal combustion engine 10. After calculating the basic set value BCR, the control device 100 calculates, as a basic injection timing BJ, a crank position CR that is located back by the basic set value BCR from the ignition timing Q calculated in the ignition control.

[0038] <Regarding the second process> In the second process, the control device 100 calculates the injection period DT. The injection period DT is the length of time required for the initial combustion injector to completely inject the required injection amount Y according to the engine rotation speed NE. Note that the control device 100 actually calculates an injection set value DCR that expresses the injection period DT in terms of the crank rotation amount, rather than the injection period DT itself. As shown in FIG. 3, this injection set value DCR is a parameter required for calculating the limit timing LJ, which will be described later.

[0039] The control device 100 stores a second map in advance as information for calculating the injection set value DCR. The second map represents the relationship between the engine speed NE, the fuel pressure P, and the injection set value DCR. More specifically, the second map defines the injection set value DCR for each combination of the engine speed NE and the fuel pressure P in an orthogonal coordinate system with the engine speed NE as the X-axis and the fuel pressure P as the Y-axis. The second map is created based on, for example, an experiment or a simulation.

[0040] In the second map, the basic relationship between the engine speed NE, the fuel pressure P, and the injection set value DCR is the same as that in the first map. That is, if the fuel pressure P is the same, the higher the engine speed NE, the larger the injection set value DCR. Also, if the engine speed NE is the same, the higher the fuel pressure P, the smaller the injection set value DCR. The second map and the first map differ in the following points. That is, as described above, the first map is created taking into consideration various factors such as protection of the ignition plug 19, pre-ignition, and exhaust emissions. On the other hand, the second map does not take these factors into consideration at all, and simply represents the amount of crank rotation required to completely inject the required injection amount Y as a function of the engine speed NE and the fuel pressure P.

[0041] In the second process, the control device 100 calculates, based on the second map, the injection set value DCR corresponding to the engine speed NE and the fuel pressure P when a start request for the internal combustion engine 10 is made. <About the third process> In the third process, the control device 100 calculates the limit timing LJ. As shown in FIG. 3, the limit timing LJ is a timing that precedes the compression top dead center of the initial explosion cylinder by a necessary period LT that is longer than the injection period DT by a specified time NT. The injection period DT is as described in the second process. The specified time NT is the length of time required for all of the injected fuel to be atomized when the fuel is injected into the cylinder 11 by the in-cylinder injector 18. When calculating the limit timing LJ, the control device 100 uses a specified set value NCR that expresses the specified time NT in terms of the amount of crank rotation, similar to the injection period DT.

[0042] The control device 100 stores a third map in advance as information for calculating the above-mentioned specified set value NCR required for calculating the limit timing LJ. The third map shows the relationship between the engine speed NE and the specified set value NCR. The relationship between the engine speed NE and the specified set value NCR in the third map is as follows. That is, the higher the engine speed NE, the larger the specified set value NCR. Here, although the required injection amount Y for the initial combustion injector varies depending on the engine speed NE, the length of time required for the fuel corresponding to each required injection amount Y to be atomized is approximately constant. This constant value is called the basic atomization time. As described above, the crank rotation amount during a certain period of time increases as the engine speed NE increases. Therefore, when the basic atomization time is converted into the crank rotation amount, the value increases as the engine speed NE increases. Reflecting this, in the third map, the higher the engine speed NE, the larger the specified set value NCR. Furthermore, strictly speaking, the length of time required for the fuel to be atomized can be longer as the required injection amount Y increases. This also contributes to the relationship in which the higher the engine speed NE, the larger the specified set value NCR in map 3. Note that the atomization of fuel is also affected by the way gas swirls in the cylinder 11 according to the difference in engine speed NE. Taking this into consideration, map 3 is created based on, for example, experiments or simulations.

[0043] In the third process, the control device 100 calculates a specified set value NCR corresponding to the engine speed NE and fuel pressure P when a start request for the internal combustion engine 10 is made based on the third map. Then, as shown in FIG. 3, the control device 100 calculates a value obtained by adding this specified set value NCR to the injection set value DCR calculated in the second process as a required set value LCR. Then, the control device 100 calculates a crank position CR that is back by the required set value LCR from the crank position CR at the compression top dead center of the initial explosion cylinder as a limit timing LJ. Note that the above-mentioned required set value LCR corresponds to a required period LT that is longer than the injection period DT by a specified time NT and is expressed in terms of the amount of crank rotation.

[0044] <About the fourth process> In the fourth process, the control device 100 calculates the final injection timing FJ for the initial combustion injector. The control device 100 sets the crank position CR earlier than the compression top dead center of the initial combustion cylinder, out of the basic injection timing BJ calculated in the first process and the limit timing LJ calculated in the third process, as the final injection timing FJ. In other words, the control device 100 sets the earlier of the basic injection timing BJ and the limit timing LJ as the final injection timing FJ. Specifically, in the example of FIG. 3, the control device 100 sets the basic injection timing BJ as the final injection timing FJ. After that, the control device 100 calculates the required injection amount Y corresponding to the engine speed NE when the start request of the internal combustion engine 10 is made, based on the injection amount map already described.

[0045] After calculating the final injection timing FJ and the required injection amount Y, the control device 100 controls the initial combustion injector based on these parameters. That is, the control device 100 starts fuel injection from the initial combustion injector at the final injection timing FJ. The control device 100 also causes the initial combustion injector to inject fuel for the required injection amount Y. After that, the control device 100 injects fuel into the in-cylinder injectors 18 of the three cylinders 11 other than the initial combustion cylinder in the order of the cylinders 11 that undergo the compression stroke. At that time, the control device 100 treats the same timing as the final injection timing FJ of the initial combustion injector as the final injection timing FJ of the other in-cylinder injectors 18 during the compression stroke of each cylinder 11. That is, the control device 100 starts fuel injection for the in-cylinder injector 18 of the cylinder 11 that undergoes the compression stroke next to the initial combustion cylinder at a timing when the crank position CR advances 180 degrees from the final injection timing FJ of the initial combustion injector. The control device 100 also starts fuel injection from the in-cylinder injectors 18 of the remaining two cylinders 11 every time the crank position CR advances by 180 degrees. The control device 100 also causes the in-cylinder injectors 18 of the three cylinders 11 other than the initial combustion cylinder to inject fuel in the required injection amount Y, in the same manner as the initial combustion injector.

[0046] <Embodiment Action 1: Regarding Limit Timing LJ> Explain the concept of limit time LJ. The fuel injected into the cylinder 11 by the in-cylinder injector 18 is atomized within the cylinder 11. When the fuel is ignited, it is mainly the atomized fuel that contributes to the generation of torque. In other words, even if the fuel before atomization is ignited, the fuel before atomization does not effectively contribute to the generation of torque. Therefore, in order to ensure that all of the fuel injected from the in-cylinder injector 18 contributes to the generation of torque without being wasted, it is necessary that the fuel injection is completed and the injected fuel is atomized before ignition by the spark plug 19.

[0047] Now, the limit time LJ is a timing that goes back from the compression top dead center by the injection set value DCR and the specified set value NCR. As described above, the injection set value DCR corresponds to the period required for fuel injection, and the specified set value NCR corresponds to the period required for the injected fuel to be atomized. In other words, the limit time LJ is a timing that goes back from the compression top dead center by the crank rotation amount required to complete both the fuel injection and the atomization. Therefore, if the fuel injection is started before the limit time LJ, the fuel injection and the atomization of the fuel can be completed before the compression top dead center. Here, the ignition by the spark plug 19 is performed at a timing after the compression top dead center. Therefore, if the fuel injection is started before the limit time LJ, the fuel injection and the atomization of the fuel can be completed before the ignition. This allows all the fuel injected from the in-cylinder injector 18 to effectively contribute to the generation of torque. In this way, the limit time LJ is the latest limit time for all the fuel injected from the in-cylinder injector 18 to contribute to the generation of torque.

[0048] <Embodiment Action 2: Various Elements Considered When Creating the First Map> As described above, the fuel injected into the cylinder 11 by the in-cylinder injector 18 is atomized in the cylinder 11. The heat of vaporization at this time cools the periphery of the spark plug 19. When ignition is performed by the spark plug 19, the periphery of the spark plug 19 becomes considerably hot. If the injection timing of the in-cylinder injector 18 is brought as close as possible to the ignition timing of the spark plug 19, ignition can be performed under a condition where the periphery of the spark plug 19 is kept relatively cold by the heat of vaporization. This is effective in suppressing damage to the spark plug 19. That is, when considering protection of the spark plug 19, it is preferable that the period from the injection timing of the in-cylinder injector 18 to the ignition timing of the spark plug 19 is as short as possible. Also, from the viewpoint of preventing so-called pre-ignition, in which fuel spontaneously ignites in the cylinder 11 before ignition by the spark plug 19, it is preferable that the period from the injection timing to the ignition timing is as short as possible. On the other hand, when considering exhaust emissions, it is preferable that the period from the injection timing to the ignition timing is as long as possible. The reason is as follows. If fuel is injected from the in-cylinder injector 18 when the piston 12 is in a position close to the top dead center, the fuel adheres to the top surface of the piston 12, making it difficult to atomize the fuel. Fuel in a liquid state that is not atomized is difficult to burn. For this reason, when the fuel is difficult to atomize as described above, a large amount of fuel is discharged unburned into the exhaust passage 21. This results in a deterioration of exhaust emissions. Therefore, in order to avoid a deterioration of exhaust emissions, it is preferable to inject fuel when the piston 12 is in a position farther from the top dead center, that is, at a timing as far back as possible from the ignition timing.

[0049] In the first map, a basic set value BCR is determined that can be considered to be optimal overall as the length from the fuel injection timing to the ignition timing, taking into account the various factors mentioned above.

[0050] <Effects of the embodiment> (1) In this embodiment, the control device 100 sets the earlier of the limit timing LJ and the basic injection timing BJ as the final injection timing FJ. That is, the control device 100 starts the injection of fuel from the initial combustion injector at a timing before the limit timing LJ. This makes it possible to achieve the following. That is, the initial combustion injector injects all of the fuel equivalent to the required injection amount Y before the compression top dead center. In addition, the injected fuel is all atomized before the compression top dead center. The ignition plug 19 ignites this atomized fuel after the compression top dead center, so that in the initial combustion cylinder, all of the fuel injected from the initial combustion injector effectively contributes to the generation of torque. As for the other three cylinders 11, all of the fuel injected by the in-cylinder injector 18 effectively contributes to the generation of torque, as in the initial combustion cylinder. Therefore, the internal combustion engine 10 can output the torque required to start itself.

[0051] (2) In this embodiment, the specified time NT, which is the length of time required for atomization, is treated as a specified set value NCR as the crank rotation amount. The specified set value NCR is increased or decreased according to the engine speed NE. As described above, even if the specified time NT, which is a value measured in time, is the same, if the engine speed NE is different, the specified set value NCR, which is the crank rotation amount, is different. The higher the engine speed NE, the larger the specified set value NCR becomes. In this embodiment, which takes into account the difference in the crank rotation amount according to the engine speed NE, such a difference in the specified set value NCR according to the engine speed NE can be reflected in the calculation of the limit timing LJ. The same can be said about the injection set value DCR. The configuration of this embodiment can accurately calculate the limit timing LJ. Similarly, the configuration of this embodiment can accurately calculate the basic injection timing BJ.

[0052] <Example of change> The above embodiment can be modified as follows: The above embodiment and the following modifications can be combined with each other to the extent that no technical contradiction occurs.

[0053] The manner in which the basic injection timing BJ is calculated in the first process is not limited to the example of the above embodiment. For example, the relationship between the engine speed NE, the fuel pressure P, and the basic injection timing BJ may be defined in a first map. Then, the basic injection timing BJ may be calculated directly from the first map. If it is known in advance that the fuel pressure P when performing independent start control is determined to a relatively unique value, only the relationship between the engine speed NE and the basic injection timing BJ may be defined in the first map. In the first process, it is sufficient to be able to calculate the basic injection timing BJ based on the engine speed NE.

[0054] The manner in which the injection set value DCR is calculated in the second process is not limited to the example of the embodiment. For example, the relationship between the required injection amount Y, the fuel pressure P, and the injection period DT may be defined in the second map. In this case, the required injection amount Y corresponding to the engine speed NE when the start request of the internal combustion engine 10 is made is first calculated based on the injection amount map. Then, the injection period DT corresponding to the required injection amount Y and the fuel pressure P is calculated based on the second map. Then, the calculated injection period DT is increased or decreased according to the engine speed NE to calculate the injection set value DCR. The injection set value DCR may be calculated in such a manner. If various calculations are performed using time instead of the crank rotation amount as a scale as in the modified example described later, the injection period DT calculated from the second map described in this modified example may be used as it is. In the second process, it is sufficient to be able to calculate the injection period DT according to the required injection amount Y.

[0055] As described in the modified example of the first process, the second process may not require calculation taking the fuel pressure P into consideration. The manner in which the limit timing LJ is calculated in the third process is not limited to the example of the embodiment. For example, instead of setting the specified set value NCR variably according to the engine speed NE, the specified set value NCR may be a certain fixed value regardless of the magnitude of the engine speed NE. In this case, a value that can be considered to be somewhat general as the length of time required for the fuel to be atomized may be determined by experiment. Even when such a fixed value is used, since a certain amount of time for atomization can be secured, a larger portion of the fuel injected from the in-cylinder injector 18 can be contributed to the generation of torque. In the third process, it is sufficient to calculate the timing that goes back from the compression top dead center by the necessary period LT that is longer than the injection period DT by the specified time NT as the limit timing LJ.

[0056] When calculating the limit timing LJ, it is not essential to use parameters that are scaled by the amount of crank rotation, such as the injection set value DCR and the specified set value NCR. In other words, the limit timing LJ may be calculated using parameters that are scaled by time, such as the injection period DT and the specified time NT. In this case, the limit timing LJ is expressed not in terms of the crank position CR, but in terms of time, such as a point in time several milliseconds before the compression top dead center. The basic injection timing BJ can be expressed in a similar manner. Here, the range of the engine speed NE when performing the independent start control is somewhat limited. For this reason, even if the above-mentioned mode is adopted, it is possible to perform injection at a timing that is more or less as desired.

[0057] The number of cycles of the internal combustion engine 10 targeted by the independent start control is not limited to the example in the above embodiment. For example, independent start control may be performed for two cycles of the internal combustion engine 10. Furthermore, the number of cylinders 11 targeted by the independent start control does not have to be determined in cycle units. In other words, the number of cylinders 11 may be a number other than a multiple of the total number of cylinders. It is sufficient that independent start control is performed for the number of cylinders 11 required to start the internal combustion engine 10.

[0058] The number of in-cylinder injectors 18 to be controlled in the fourth process varies depending on the number of cylinders 11 to be subjected to the independent start control. The fourth process only needs to perform the following at a minimum: Calculation of the final injection timing FJ for the initial combustion injector, and control of the initial combustion injector based on the final injection timing FJ.

[0059] The range of the engine speed NE that is the start condition for the independent start control is not limited to the example in the above embodiment. The engine speed NE that is the start condition may be any speed greater than zero. By performing independent start control, the required injection amount Y, injection timing, ignition timing, etc. may be determined according to the engine speed NE when a start request for the internal combustion engine 10 is made so that the internal combustion engine 10 can be started without assistance from the motor generator 82.

[0060] The method of determining the prescribed operation amount that serves as the threshold for switching from the first mode to the second mode is not limited to the example in the above embodiment. The prescribed operation amount may be any value that allows the driving mode to be switched in an appropriate situation in consideration of the fuel efficiency and electricity consumption of the vehicle 90.

[0061] The configuration of the internal combustion engine 10 is not limited to the example of the above embodiment. For example, the number of cylinders 11 may be changed. The internal combustion engine 10 only needs to have the spark plugs 19, the in-cylinder injectors 18, and the crankshaft 14.

[0062] The overall configuration of the vehicle 90 is not limited to the example of the above embodiment. The vehicle 90 only needs to have the motor generator 82 located on the power transmission path from the internal combustion engine 10 to the drive wheels 72, and the clutch 81 interposed between the internal combustion engine 10 and the motor generator 82 for connecting and disconnecting them. For example, a continuously variable automatic transmission may be used instead of the stepped automatic transmission 85.

[0063] Each map does not have to be a graph, but can be a table or a formula. [Explanation of symbols]

[0064] 10. Internal combustion engine 11…Cylinder 14…Crankshaft 18...In-cylinder injector 19…Spark plug 72...Drive wheel 81…Clutch 82...Motor generator 90…Vehicle 100...Control device

Claims

[Claim 1] an internal combustion engine including a spark plug for igniting fuel in a cylinder, an injector for directly injecting fuel into the cylinder, and a crankshaft; an electric motor having a rotating shaft, the electric motor being located on a power transmission path from the internal combustion engine to a drive wheel; a clutch interposed between the internal combustion engine and the electric motor, the clutch being switched between a connected state in which the crankshaft and the rotating shaft are connected and a disconnected state in which the crankshaft and the rotating shaft are disconnected, When a request to start the internal combustion engine is received while the clutch is in the disengaged state, the rotational speed of the crankshaft is greater than zero, and ignition by the spark plug is stopped, When the cylinder in which fuel is first burned after the start request is issued is defined as an initial combustion cylinder, and the injector for the initial combustion cylinder is defined as an initial combustion injector, A process of determining an ignition timing of the spark plug for the initial combustion cylinder to be a timing after a compression top dead center of the initial combustion cylinder; a first process for calculating a basic injection timing for the first combustion injector based on a rotation speed of the crankshaft; a second process of calculating an injection period required for the first combustion injector to inject a required injection amount corresponding to a rotation speed of the crankshaft; a third process for calculating a timing going back from the compression top dead center of the first combustion cylinder by a necessary period that is a specified time longer than the injection period as a limit timing; a fourth process of calculating an earlier one of the basic injection timing and the limit timing as a final injection timing at which the initial combustion injector should start injection, and controlling the initial combustion injector; Run Vehicle control device.

Images