Control device for internal combustion engines

Abstract

A stable negative pressure is formed in the intake passage during engine startup. [Solution] The internal combustion engine 10 includes a fuel injection valve 83 that supplies fuel into the cylinder and a throttle valve 28 provided in the intake passage to adjust the amount of intake air, and an electric motor that performs motoring is connected to the crankshaft 18. The control device 100 performs motoring when the engine starts and controls the opening of the throttle valve 28 and the engine rotation speed to adjust the pressure in the intake passage downstream of the throttle valve 28 to a target value lower than atmospheric pressure, and performs fuel injection from the fuel injection valve 83 after the pressure in the intake passage reaches the target value.

Description

Technical Field

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

Background Art

[0002] Patent Document 1 describes an internal combustion engine in which fuel injection is started after a negative pressure is formed in the intake passage at the time of engine startup, thereby promoting vaporization of the injected fuel.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The fuel injection amount required at the time of engine startup varies depending on the magnitude of the negative pressure in the intake passage. Therefore, if the negative pressure is not stable, there is a risk that an excess or deficiency of the fuel injection amount will occur, resulting in a surge in the engine rotational speed or a startup failure. Therefore, it is desirable to form a stable negative pressure in the intake passage at the time of engine startup.

Means for Solving the Problems

[0005] The control device for an internal combustion engine that solves the above problems includes a fuel injection valve that supplies fuel into a cylinder and a throttle valve that is provided in an intake passage and adjusts the intake air amount, and is applied to an internal combustion engine in which an electric motor for motoring is connected to a crankshaft. The control device controls the opening degree of the throttle valve and the engine rotational speed while performing the motoring at the time of engine startup, so as to adjust the pressure in the intake passage downstream of the throttle valve to a target value lower than the atmospheric pressure, and starts fuel injection from the fuel injection valve after the pressure reaches the target value.

Effects of the Invention

[0006] This internal combustion engine control system can create a stable negative pressure in the intake passage during engine startup. [Brief explanation of the drawing]

[0007] [Figure 1] Figure 1 is a schematic diagram showing the configuration of an internal combustion engine in one embodiment. [Figure 2] Figure 2 is a flowchart showing the procedure of processing performed by the control device of the same embodiment. [Modes for carrying out the invention]

[0008] The following describes one embodiment of a control device for an internal combustion engine installed in a vehicle. <Configuration of an internal combustion engine> As shown in Figure 1, the internal combustion engine 10 includes a cylinder block 11, a cylinder head 12, and a head cover 13, among other components.

[0009] The cylinder block 11 contains cylinders 16, which constitute the cylinders of the internal combustion engine 10. A piston 15 is disposed inside each cylinder 16. The cylinder head 12 is provided with an intake port 30 for introducing intake air into the combustion chamber 17 of the internal combustion engine 10, and an exhaust port 70 for discharging exhaust gas from the combustion chamber 17.

[0010] The intake port 30 is equipped with an intake valve 81, which is an engine valve. The drive system for this intake valve 81 is equipped with an intake-side variable valve timing mechanism 85, which is a variable valve timing mechanism that changes the valve timing of the intake valve 81, namely the opening and closing times.

[0011] The exhaust port 70 is equipped with an exhaust valve 82, which is an engine valve. The drive system for this exhaust valve 82 is equipped with an exhaust-side variable valve timing mechanism 86, which is a variable valve timing mechanism that changes the valve timing of the exhaust valve 82, namely the opening and closing times.

[0012] The internal combustion engine 10 is equipped with fuel injectors that supply fuel into the cylinders. Specifically, the internal combustion engine 10 is equipped with a port injection type fuel injector 83 that injects fuel into the intake port 30 and an in-cylinder injection type fuel injector 84 that injects fuel directly into the combustion chamber 17. In addition, a spark plug 23 is provided in the cylinder head 12.

[0013] A crankcase 19 is provided at the lower part of the cylinder block 11, which houses the crankshaft 18, the output shaft of the internal combustion engine 10. An intake manifold 29 equipped with a surge tank 60 is connected upstream of the intake port 30, and an intake pipe 20 is connected upstream of the surge tank 60. The intake pipe 20, surge tank 60, intake manifold 29, and intake port 30 constitute the intake passage of the internal combustion engine 10.

[0014] The intake manifold 20 is equipped with, in order from upstream, an air cleaner 21, an air flow meter 51, a compressor wheel 24C of a supercharger 24 driven by exhaust gases discharged from the combustion chamber 17, an intercooler 27, a boost pressure sensor 54, and a throttle valve 28. An intake pressure sensor 55 is also installed in the surge tank 60. The throttle valve 28 adjusts the amount of intake air by changing its opening degree using an electric motor. The smaller the opening degree of the throttle valve 28, the less air passes through the throttle valve 28.

[0015] The air cleaner 21 filters the intake air taken into the intake manifold 20. The supercharger 24 supercharges the air in the intake manifold 20. The intercooler 27 cools the air after it has passed through the compressor wheel 24C. The throttle valve 28 regulates the amount of intake air by adjusting the valve opening.

[0016] The air flow meter 51 detects the intake air amount GA. Further, the supercharging pressure sensor 54 detects the supercharging pressure PTC which is the pressure at the downstream portion of the compressor wheel 24C in the intake pipe 20. Further, the intake pressure sensor 55 detects the intake pressure PIM which is the pressure in the surge tank 60. The intake pressure PIM is the pressure in the intake passage downstream of the throttle valve 28.

[0017] Downstream of the exhaust port 70, an exhaust pipe 90 constituting an exhaust passage is connected. In the middle of the exhaust pipe 90, a housing for housing the turbine wheel 24T of the supercharger 24 is connected.

[0018] The crankshaft 18 is mechanically connected to the carrier C of the planetary gear mechanism 300 constituting the power split device. The rotating shaft 310a of the first motor generator 310 is mechanically connected to the sun gear S of the planetary gear mechanism 300. The first motor generator 310 functions as a generator that generates electricity using the engine output, and also functions as a starting starter that cranks the crankshaft 18 at the start of the internal combustion engine 10. This first motor generator 310 is an electric motor that performs a motoring operation to rotate the crankshaft 18.

[0019] The rotating shaft 320a of the second motor generator 320 and the drive wheel 400 are mechanically connected to the ring gear R of the planetary gear mechanism 300. The second motor generator 320 functions as an electric motor that generates the driving force of the drive wheel 400, and also functions as a generator that generates electricity by regeneration when the vehicle decelerates.

[0020] An AC voltage is applied to the terminals of the first motor generator 310 by the inverter 330. Also, an AC voltage is applied to the terminals of the second motor generator 320 by the inverter 340. Thus, the vehicle of the present embodiment is a vehicle equipped with a hybrid system including an internal combustion engine 10 and a motor generator as prime movers.

[0021] The control device 100 operates various operation target devices such as the throttle valve 28, fuel injection valves 83 and 84, ignition plug 23, intake-side variable valve mechanism 85, and exhaust-side variable valve mechanism 86. Further, the control device 100 operates the inverter 330 to control the first motor generator 310. Further, the control device 100 operates the inverter 340 to control the second motor generator 320.

[0022] The control device 100 includes a CPU 110 that performs arithmetic processing, a memory 120 in which control programs and data are stored, and the like. Then, the control device 100 executes processes related to various controls by the CPU 110 executing the programs stored in the memory 120. Although not shown in the figure, the control device 100 is composed of a plurality of control units such as a control unit for the internal combustion engine and control units for the first motor generator 310 and the second motor generator 320.

[0023] Detection signals from the above-described air flow meter 51, boost pressure sensor 54, and intake pressure sensor 55 are input to the control device 100. Further, detection signals from various other sensors are input to the control device 100. For example, a detection signal from an accelerator operation amount sensor 52 that detects an accelerator operation amount ACCP, which is the operation amount of an accelerator pedal for adjusting the output of the internal combustion engine 10, is input to the control device 100. Further, a detection signal from a throttle sensor 53 that detects a throttle opening TA, which is the opening of the throttle valve 28, is input to the control device 100. Further, a detection signal from a water temperature sensor 57 that detects a cooling water temperature THW, which is the temperature of the cooling water of the internal combustion engine 10, is input to the control device 100. Further, a detection signal from a crank angle sensor 50 that detects the rotation angle (crank angle) of the crankshaft 18 to calculate the engine rotational speed NE and a detection signal from a vehicle speed sensor 56 that detects the vehicle speed SP of the vehicle are input to the control device 100. Further, an output signal Sm1 from a first rotation angle sensor 350 that detects the rotation angle of the first motor generator 310 is input to the control device 100. Further, an output signal Sm2 from a second rotation angle sensor 360 that detects the rotation angle of the second motor generator 320 is input to the control device 100.

[0024] The control device 100 calculates the engine load ratio KL based on the engine rotational speed NE and the intake air volume GA. The engine load ratio KL is a parameter that determines the amount of air filled into the combustion chamber 17, and is the ratio of the amount of air inflow per combustion cycle per cylinder to the standard amount of incoming air. The standard amount of incoming air is set variably according to the engine rotational speed NE.

[0025] The control device 100 calculates the required torque for the vehicle's operation based on the accelerator pedal input (ACCP) and vehicle speed (SP). The control device 100 then controls the required output Pe of the internal combustion engine 10 and the output torques of the first motor generator 310 and the second motor generator 320 to meet the vehicle's required torque. For example, if the required output Pe of the internal combustion engine 10 is "0", the control device 100 stops the operation of the internal combustion engine 10 and performs EV driving, using the output torque of the second motor generator 320 to drive the vehicle. If the required output Pe of the internal combustion engine 10 is greater than "0", the control device 100 operates the internal combustion engine 10 to obtain engine output and performs hybrid driving, using that engine output and the output torque of the second motor generator 320 to drive the vehicle.

[0026] The control device 100 calculates the intake-side target value VTint, which is the target valve timing for the intake valve 81, based on the engine rotational speed NE and the engine load ratio KL. Once this intake-side target value VTint is calculated, the control device 100 controls the drive of the intake-side variable valve timing mechanism 85 so that the actual valve timing of the intake valve 81 matches the intake-side target value VTint. In this embodiment, the initial value "0" is set to the state where the valve timing of the intake valve 81 is at its most retarded timing, and the valve timing of the intake valve 81 is controlled using the amount of advance angle from this initial value.

[0027] The control device 100 calculates the exhaust-side target value VText, which is the target valve timing for the exhaust valve 82, based on the engine rotational speed NE and the engine load ratio KL. Once this exhaust-side target value VText is calculated, the control device 100 controls the drive of the exhaust-side variable valve timing mechanism 86 so that the actual valve timing of the exhaust valve 82 matches the exhaust-side target value VText. In this embodiment, the initial value "0" is set to the state where the valve timing of the exhaust valve 82 is at its most advanced timing, and the valve timing of the exhaust valve 82 is controlled using the amount of valve timing retardation from this initial value.

[0028] <Regarding procedures during engine startup> The control device 100 promotes the vaporization of injected fuel by starting fuel injection only after a predetermined negative pressure is formed in the intake passage when the internal combustion engine 10 is started.

[0029] Figure 2 shows the procedure for the process that the control device 100 starts when a start request for the internal combustion engine 10 is received. The process shown in Figure 2 is realized by the CPU 110 executing a program stored in the memory 120 of the control device 100. In the following, the step number of each process is represented by a number preceded by "S".

[0030] In the series of processes shown in Figure 2, the control device 100 issues a valve timing displacement instruction (S100). In process S100, the control device 100 sets the intake-side target value VTint so that the valve timing of the intake valve 81 becomes the next valve timing. That is, the intake-side target value VTint is set so that when motoring by the first motor generator 310 is performed, the blowback of gas from the cylinder to the intake passage is suppressed. In process S100, for example, the intake-side target value VTint is set so that the closing timing of the intake valve 81 becomes the intake bottom dead center.

[0031] Next, the control device 100 calculates the target intake pressure PIMt (S110). The target intake pressure PIMt is the target value of the intake pressure PIM when motoring is performed during engine startup. The target intake pressure PIMt is a suitable value that is lower than atmospheric pressure and promotes the vaporization of fuel injected from the fuel injector. Here, the lower the coolant temperature THW at engine startup, the less likely the fuel is to vaporize. Therefore, the target intake pressure PIMt is variably set so that it becomes a lower pressure as the coolant temperature THW at engine startup decreases.

[0032] Next, the control device 100 calculates the target rotational speed NEt, which is the target value of the engine rotational speed NE when motoring is performed during engine startup (S120). The target rotational speed NEt is variably set so that, for example, the lower the target intake pressure PIMt, the higher the engine rotational speed NE becomes.

[0033] Next, the control device 100 calculates the target throttle opening TAt, which is the target value of the throttle opening TA when motoring is performed during engine startup (S130). The target throttle opening TAt is variably set so that, for example, it becomes smaller as the target intake pressure PIMt decreases.

[0034] Next, the control device 100 drives the first motor generator 310 to perform the motoring (S140). In the process of S140, the control device 100 controls the rotational speed of the first motor generator 310 so that the engine rotational speed NE matches the target rotational speed NEt.

[0035] Next, the control device 100 adjusts the throttle opening TA (S150). In the process of S150, the control device 100 controls the opening of the throttle valve 28 so that the throttle opening TA matches the target throttle opening TAt.

[0036] Next, the control device 100 acquires the intake pressure PIM (S160). Next, the control device 100 determines whether the intake pressure PIM obtained in the process of S160 is less than or equal to the target intake pressure PIMt (S170). If it is determined that the intake pressure PIM is not less than or equal to the target intake pressure PIMt (S170: NO), the control device 100 executes the process of S180.

[0037] In the process of S180, the control device 100 adjusts the intake pressure PIM by changing the target throttle opening TAt and the target rotational speed NEt. When adjusting the intake pressure PIM in S180, the adjustment of the throttle opening TA takes precedence over the adjustment of the engine rotational speed NE. That is, the process of first decreasing the target throttle opening TAt is executed. If the target intake pressure PIMt cannot be obtained even after decreasing the target throttle opening TAt, the process of increasing the target rotational speed NEt is executed.

[0038] After executing the process in S180, the control device 100 then executes the processes from S140 onwards described above again. In the process of S170 described above, if it is determined that the intake pressure PIM is less than or equal to the target intake pressure PIMt (S170: YES), the control device 100 starts fuel injection (S190). In the process of S190, the control device 100 starts fuel injection from the fuel injection valve 83 during the intake stroke.

[0039] Then, when the process described in S190 above is executed, the control device 100 terminates this process. <Operation and Effects of This Embodiment> (1) The control device 100 executes the processes S140, S150, S160, S170, and S180 shown in Figure 2. Accordingly, the control device 100 controls the opening of the throttle valve 28 and the engine rotation speed NE while performing motoring, thereby adjusting the intake pressure PIM to the target intake pressure PIMt.

[0040] Thus, in this embodiment, the pressure in the intake passage is adjusted to a target intake pressure PIMt that is lower than atmospheric pressure during engine startup. Therefore, a stable negative pressure can be formed in the intake passage during engine startup.

[0041] (2) The control device 100 executes the process of S180 described above. As a result, when adjusting the intake pressure PIM, the adjustment of the opening degree of the throttle valve 28 takes precedence over the adjustment of the engine rotation speed NE.

[0042] When adjusting the pressure in the intake passage to the target pressure by controlling the throttle opening TA and engine speed NE, changing the engine speed NE may worsen vibration and noise. On the other hand, changing the throttle opening TA is less likely to worsen vibration and noise.

[0043] In this respect, in the operation of this embodiment, when adjusting the intake pressure PIM, which is the pressure in the intake passage, adjustment of the throttle opening TA takes precedence over adjustment of the engine rotational speed NE. Therefore, when forming a stable negative pressure in the intake passage, it is possible to suppress the deterioration of vibration and noise.

[0044] (3) The internal combustion engine 10 is equipped with an intake-side variable valve timing mechanism 85 that changes the valve timing of the intake valve 81. When the above motoring is performed, the valve timing is set to a valve timing that suppresses the backflow of gas from the cylinder into the intake passage.

[0045] When motoring is performed during engine startup, if gas blowback occurs from the cylinder into the intake passage, the time it takes for the intake pressure PIM, which is the pressure in the intake passage, to drop to the target intake pressure PIMt will be longer. Consequently, the time required to form negative pressure in the intake passage may be prolonged. In this embodiment, the valve timing of the intake valve 81 of the internal combustion engine 10 is set to a valve timing that suppresses gas blowback from the cylinder into the intake passage. Therefore, the time required to form negative pressure in the intake passage during engine startup can be shortened.

[0046] (4) The valve timing of the intake valve 81 is set so that when motoring is performed the closing time of the intake valve 81 is at the intake bottom dead center. When the intake valve 81 of the internal combustion engine 10 is open during the compression stroke, gas blowback occurs from the cylinder into the intake passage. In this embodiment, the valve timing of the intake valve 81 is set so that the closing timing of the intake valve 81 when motoring is performed coincides with the intake bottom dead center. Therefore, such gas blowback can be suppressed.

[0047] (5) A stable negative pressure can be formed in the intake passage when the engine is started. Therefore, it is possible to suppress the occurrence of engine speed increases or starting problems caused by an excess or deficiency of fuel injected when the engine is started. In addition, the starting performance of the internal combustion engine 10 becomes stable, and emissions during engine starting also become stable.

[0048] <Example of changes> The above embodiment can be implemented with the following modifications. The above embodiment and the following modifications can be combined with each other to the extent that they do not contradict each other technically.

[0049] - If the intake valve 81 of the internal combustion engine 10 is open during the exhaust stroke, gas will be blown back from the cylinder into the intake passage. Therefore, in order to suppress gas blown back from the cylinder into the intake passage when motoring is performed, the valve timing of the intake valve 81 may be set so that the opening time of the intake valve 81 when motoring is performed is at the intake top dead center.

[0050] The valve timing of the exhaust valve 82 may be set to suppress the backflow of gas from the cylinder into the intake passage when motoring is being performed. The valve timing of the intake valve 81 during motoring may be set as follows: By setting the valve timing so that the intake valve 81 is open for a longer time during the intake stroke, while it is open for a shorter time during the compression stroke and exhaust stroke, negative pressure in the intake passage can be efficiently obtained during motoring.

[0051] The valve timing of the intake valve 81 was set to suppress the backflow of gas from the cylinder to the intake passage when motoring is performed, but this valve timing setting may be omitted. Even in this case, effects and benefits other than those described in (3) and (4) above can be obtained.

[0052] When adjusting the intake pressure PIM, the adjustment of the throttle valve 28 opening is given priority over the adjustment of the engine rotation speed NE, but such priority settings may be omitted. For example, when adjusting the intake pressure PIM, both the engine rotation speed NE and the throttle opening TA may be adjusted in the S180 process.

[0053] In the S120 process, the target rotational speed NET was calculated based on the target intake pressure PIMt, but the target rotational speed NET may also be calculated directly based on the coolant temperature THW. • In the S130 process, the target throttle opening TAt was calculated based on the target intake pressure PIMt, but the target throttle opening TAt may also be calculated directly based on the coolant temperature THW.

[0054] • The target intake pressure PIMt was a variable value set based on the coolant temperature THW at engine startup, but it may also be a fixed value. During the process of S190, the control device 100 may start fuel injection from the fuel injector 84 during the intake stroke. Alternatively, during the process of S190, the control device 100 may start fuel injection from the fuel injector 84 during the compression stroke.

[0055] The internal combustion engine 10 does not need to be equipped with a supercharger 24. • The vehicle's hybrid system is not limited to the one shown in Figure 1; other hybrid systems may also be used.

[0056] The number of motor generators equipped in the vehicle can be changed as needed. The vehicle may be equipped only with an internal combustion engine 10 as the prime mover. In this modified example, the motoring described above can be performed, for example, by driving a starter motor that rotates the crankshaft 18 when the engine is started.

[0057] The control device 100 is not limited to one that includes a CPU and memory and performs software processing. For example, the control device 100 may include a dedicated hardware circuit, such as an ASIC, that performs hardware processing for at least a portion of what is processed by software in the above embodiment. That is, the control device 100 may include a processing circuit having any of the following configurations (a) to (c): (a) A processing circuit comprising one or more processing units that perform all of the above processing according to a program, and one or more program storage devices such as ROMs that store the program. (b) A processing circuit comprising one or more processing units and one or more program storage devices that perform a portion of the above processing according to a program, and one or more dedicated hardware circuits that perform the remaining processing. (c) A processing circuit comprising one or more dedicated hardware circuits that perform all of the above processing. The program storage device, i.e., computer-readable medium, includes any available medium that can be accessed by a general-purpose or dedicated computer. [Explanation of Symbols]

[0058] 10...Internal combustion engine 11...Cylinder block 12...Cylinder head 13...Head cover 15...Piston 16...Cylinder 17...Combustion chamber 18...Crankshaft 19...Crankcase 20...Intake pipe 21...Air cleaner 23...Spark plug 24...Supercharger 24C...Compressor wheel 24T...Turbine wheel 27...Intercooler 28...Throttle valve 29...Intake manifold 30...Intake port 50...Crank angle sensor 51...Air flow meter 52...Accelerator pedal position sensor 53...Throttle sensor 54...Boost pressure sensor 55...Intake pressure sensor 56...Vehicle speed sensor 57...Water temperature sensor 60...Surge tank 70...Exhaust port 81...Intake valve 82...Exhaust valve 83...Fuel injector 84...Fuel injector 85...Intake side variable valve timing mechanism 86…Variable valve timing mechanism on the exhaust side 90…Exhaust pipe 100…Control device 110…CPU 120…Memory 300…Planetary gear mechanism 310…First motor generator 310a…Rotating shaft 320…Second motor generator 320a…Rotating shaft 330…Inverter 340…Inverter 350…First rotation angle sensor 360…Second rotation angle sensor 400…Drive wheel

Claims

1. A control device applied to an internal combustion engine that includes a fuel injection valve for supplying fuel into the cylinder, a throttle valve provided in the intake passage for adjusting the amount of intake air, and an electric motor connected to the crankshaft for motoring, A process to adjust the pressure in the intake passage downstream of the throttle valve to a target value lower than atmospheric pressure by controlling the opening of the throttle valve and the engine rotation speed while performing the motoring during engine startup, The process of starting fuel injection from the fuel injector after the pressure reaches the target value is executed. Control device for internal combustion engines.

2. When adjusting the pressure, adjusting the opening degree of the throttle valve takes precedence over adjusting the engine rotation speed. A control device for an internal combustion engine according to claim 1.

3. The aforementioned internal combustion engine is equipped with a variable valve timing mechanism that changes the valve timing of the engine valves. When the motoring described above is performed, the valve timing is set to a valve timing that suppresses the backflow of gas from the cylinder to the intake passage. A control device for an internal combustion engine according to claim 1 or 2.

4. The engine valve is the intake valve of the internal combustion engine, The valve timing is set so that when the motoring is being performed, the closing time of the intake valve is at the intake bottom dead center. The control device for an internal combustion engine according to claim 3.

5. The engine valve is the intake valve of the internal combustion engine, The valve timing is set so that the opening time of the intake valve when the motoring is performed coincides with the intake top dead center. The control device for an internal combustion engine according to claim 3.

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