Control device for internal combustion engines

Abstract

This reduces the hydrogen concentration inside the crankcase. [Solution] The internal combustion engine 10 includes a throttle valve 28, a supercharger 24, and a blow-by gas treatment mechanism. The blow-by gas treatment mechanism includes a first communication passage 37 that connects the portion of the intake passage upstream of the compressor wheel 24C of the supercharger 24 to the crankcase 19, a third communication passage 62 that connects the portion of the intake passage downstream of the throttle valve 28 to the crankcase 19, and a second PCV valve 64 provided in the third communication passage 62 that opens when the intake pressure, which is the pressure downstream of the throttle valve 28 in the intake passage, becomes higher than the pressure inside the crankcase 19. The control device 100 performs a ventilation process to increase the boost pressure of the supercharger 24 if the intake pressure remains within a predetermined range for a predetermined time or longer.

Description

Technical Field

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

Background Art

[0002] In an internal combustion engine that uses hydrogen as fuel, hydrogen accumulates in the crankcase. Therefore, in the internal combustion engine described in Patent Document 1, for example, the negative pressure in the intake manifold is used to ventilate the hydrogen in the crankcase.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, in the internal combustion engine described in Patent Document 1, the negative pressure is used to ventilate the hydrogen in the crankcase. Therefore, when the pressure in the intake manifold is close to atmospheric pressure, the hydrogen in the crankcase cannot be sufficiently ventilated, so the hydrogen concentration in the crankcase may increase.

Means for Solving the Problems

[0005] A control device for an internal combustion engine that solves the above problems comprises an intake passage, a throttle valve provided in the intake passage, a supercharger equipped with a compressor wheel provided upstream of the throttle valve in the intake passage, and a blow-by gas treatment mechanism, and is applied to an internal combustion engine that uses hydrogen as fuel. The blow-by gas treatment mechanism comprises a first passage that connects the portion of the intake passage upstream of the compressor wheel to the crankcase, a second passage that connects the portion of the intake passage downstream of the throttle valve to the crankcase, a first PCV valve provided in the second passage that opens when the intake pressure, which is the pressure downstream of the throttle valve in the intake passage, becomes lower than the pressure inside the crankcase, a third passage that connects the portion of the intake passage downstream of the throttle valve to the crankcase, and a second PCV valve provided in the third passage that opens when the intake pressure becomes higher than the pressure inside the crankcase. Furthermore, if the intake pressure remains within a predetermined range for a predetermined period of time or longer, the control device performs a ventilation process to increase the boost pressure of the supercharger. [Effects of the Invention]

[0006] This internal combustion engine control system can reduce the hydrogen concentration in the crankcase. [Brief explanation of the drawing]

[0007] [Figure 1] This is a schematic diagram showing the configuration of an internal combustion engine in one embodiment. [Figure 2] This flowchart shows the procedure for 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 comprises a cylinder block 11, a cylinder head 12, and a head cover 13. Inside the cylinder block 11 is a cylinder 16 in which a piston 15 is arranged to reciprocate.

[0009] 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. An intake valve 81 is provided in the intake port 30. An exhaust valve 82 is provided in the exhaust port 70.

[0010] The cylinder head 12 is equipped with a fuel injector 84 that directly injects hydrogen, which is the engine fuel, into the combustion chamber 17, and a spark plug 23. A crankcase 19 is provided at the lower part of the cylinder block 11, which houses the crankshaft 18 of the internal combustion engine 10.

[0011] 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 surge tank 60 is equipped with an intake pressure sensor 53 for detecting the intake pressure PIM. The intake pressure PIM is the pressure inside the surge tank 60, which is the pressure downstream of the throttle valve 28 in the intake passage.

[0012] The intake pipe 20, surge tank 60, and intake manifold 29 constitute the intake passage of the internal combustion engine 10. 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 from the combustion chamber 17, a boost pressure sensor 52, an intercooler 27, and a throttle valve 28.

[0013] The air cleaner 21 filters the intake air taken into the intake manifold 20. The air flow meter 51 detects the intake air volume GA of the internal combustion engine 10. The compressor wheel 24C of the supercharger 24 supercharges the air in the intake manifold 20. The boost pressure sensor 52 detects the boost pressure PTC, which is the pressure in the downstream portion of the compressor wheel 24C in the intake manifold 20. The intercooler 27 cools the air after it has passed through the compressor wheel 24C. The throttle valve 28 is a valve that adjusts the intake air volume of the internal combustion engine 10, and the opening of the valve is changed by an electric motor.

[0014] Downstream of the exhaust port 70, an exhaust passage 90 is connected. A housing for the turbine wheel 24T of the supercharger 24 is connected to the exhaust passage 90. The supercharger 24 is a variable displacement supercharger and is equipped with nozzle vanes 24N driven by an actuator. The nozzle vanes 24N are adjustment mechanisms that regulate the flow rate of exhaust gas supplied to the turbine wheel 24T. By changing the opening of the nozzle vanes 24N via the actuator, the intake boost pressure increased by the supercharger 24 changes.

[0015] The internal combustion engine 10 is equipped with a blow-by gas treatment mechanism that processes blow-by gases that leak from the combustion chamber 17 into the crankcase 19 during the compression stroke and combustion stroke. These blow-by gases include hydrogen fuel, lubricating oil for the internal combustion engine 10, and combustion gases of the fuel-air mixture.

[0016] The blow-by gas treatment mechanism includes a first communication passage 37. One end of the first communication passage 37 is connected to the intake pipe 20 between the air cleaner 21 and the compressor wheel 24C. The first communication passage 37 passes through the head cover 13, through the inside of the cylinder head 12 and cylinder block 11, and connects to the crankcase 19. A separator 38, which is an oil separator installed inside the head cover 13, is provided in the middle of the first communication passage 37. The first communication passage 37 and the separator 38 constitute a first passage that connects the portion of the intake passage upstream of the compressor wheel 24C to the crankcase 19.

[0017] The blow-by gas treatment mechanism includes a second communication passage 32 for guiding blow-by gas in the crankcase 19 to a separator 31 which is an oil separator provided in the head cover 13. The end of the second communication passage 32 connected to the separator 31 opens into the crankcase 19. Incidentally, the separator 31 may be provided in the middle of the second communication passage 32.

[0018] The separator 31 is connected to a surge tank 60 via a first PCV (positive crankcase ventilation) valve 34 which is a differential pressure valve and a PCV passage 35. The first PCV valve 34 opens when the pressure in the surge tank 60 becomes lower than the pressure in the separator 31, allowing blow-by gas to flow from the separator 31 into the surge tank 60. The pressure in the separator 31 is equal to the pressure in the crankcase 19. Therefore, the first PCV valve 34 is a valve that opens when the intake pressure PIM becomes lower than the pressure in the crankcase 19.

[0019] The second communication passage 32, the separator 31, the first PCV valve 34, and the PCV passage 35 constitute a second passage that communicates a portion downstream of the throttle valve 28 in the intake passage with the crankcase 19.

[0020] The blow-by gas treatment mechanism includes a third communication passage 62. One end of the third communication passage 62 is connected to the surge tank 60. The other end of the third communication passage 62 communicates with the inside of the crankcase 19. The third communication passage 62 constitutes a third passage that communicates a portion downstream of the throttle valve 28 in the intake passage with the crankcase 19.

[0021] In the middle of the third communication passage 62, a second PCV valve 64, which is a differential pressure valve, is provided. The second PCV valve 64 opens when the pressure in the surge tank 60 becomes higher than the pressure in the crankcase 19, allowing blow-by gas to flow from the crankcase 19 into the surge tank 60. That is, the second PCV valve 64 is a valve that opens when the intake pressure PIM becomes higher than the pressure in the crankcase 19.

[0022] For example, when the operating state of the internal combustion engine 10 is in the naturally aspirated range and the intake pressure PIM is lower than the atmospheric pressure, the pressure in the surge tank 60 becomes lower than the pressure in the crankcase 19. Therefore, the first PCV valve 34 opens. When the first PCV valve 34 opens, fresh air flows into the crankcase 19 from the intake pipe 20 through the first communication passage 37. Also, blow-by gas in the crankcase 19 is sucked into the surge tank 60 through the second communication passage 32, the separator 31, the first PCV valve 34, and the PCV passage 35. The blow-by gas sucked into the surge tank 60 is sent to the combustion chamber 17 together with the intake air and burned. In the naturally aspirated range, the blow-by gas is processed in this way, so the hydrogen in the crankcase 19 is ventilated, and the hydrogen concentration in the crankcase 19 decreases.

[0023] On the other hand, when the operating state of the internal combustion engine 10 is in the supercharged range and the intake pressure PIM is higher than the atmospheric pressure, the pressure in the surge tank 60 becomes higher than the pressure in the crankcase 19. Therefore, the second PCV valve 64 opens. When the second PCV valve 64 opens, fresh air flows into the crankcase 19 from the surge tank 60 through the third communication passage 62. Also, blow-by gas in the crankcase 19 is discharged to the intake pipe 20 through the first communication passage 37. The blow-by gas discharged to the intake pipe 20 is sent to the combustion chamber 17 together with the intake air and burned. In the supercharged range, the blow-by gas is processed in this way, so the hydrogen in the crankcase 19 is ventilated, and the hydrogen concentration in the crankcase 19 decreases.

[0024] The control device 100 controls the internal combustion engine 10 and operates various controllable components such as the throttle valve 28, fuel injection valve 84, and spark plug 23. The control device 100 includes a CPU 110 that performs calculations, and a memory 120 that stores control programs and data. The control device 100 then executes various control-related processes by having the CPU 110 execute the programs stored in the memory 120.

[0025] The control device 100 receives detection signals from the air flow meter 51, boost pressure sensor 52, and intake pressure sensor 53 described above. The control device 100 also receives detection signals from various other sensors. For example, the control device 100 receives a detection signal from the crank angle sensor 54, which detects the rotation angle (crank angle) of the crankshaft 18 in order to calculate the engine rotation speed NE. The control device 100 also receives a detection signal from the accelerator pedal operation amount sensor 55, which detects the accelerator pedal operation amount ACCP, which is the amount of accelerator pedal operation that adjusts the output of the internal combustion engine 10. The control device 100 also receives a detection signal from the throttle sensor 56, which detects the throttle opening TA, which is the opening degree of the throttle valve 28. The control device 100 also receives a detection signal from the vehicle speed sensor 57, which detects the vehicle speed SP.

[0026] 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.

[0027] The control device 100 calculates the required torque based on the accelerator pedal input amount ACCP and vehicle speed SP. The control device 100 then controls the required output Pe of the internal combustion engine 10 to meet the required torque. Here, hydrogen, the fuel for the internal combustion engine 10, has a wider range of combustible air-fuel mixtures compared to gasoline, and can burn even lean mixtures. Therefore, the control device 100 performs lean combustion, which burns a mixture with an air-fuel ratio greater than the stoichiometric air-fuel ratio, and adjusts the output of the internal combustion engine 10 through the following combustion control.

[0028] In other words, the control device 100 sets the required injection amount Qd based on the requested output Pe. The required injection amount Qd is the target value of the fuel injected from the fuel injector 84. Based on the target air-fuel ratio AFt and the required injection amount Qd, the control device 100 calculates the required air amount GAd, which is the target value of the intake air amount necessary to obtain the target air-fuel ratio AFt. In this embodiment, the target air-fuel ratio AFt is a lean air-fuel ratio, for example, an excess air ratio λ = 2.5 to 3.0. The control device 100 then controls the fuel injector 84 so that the required injection amount Qd is obtained. The control device 100 also controls the opening of the throttle valve 28 and the boost pressure of the supercharger 24 so that the required air amount GAd is obtained.

[0029] When controlling the boost pressure of the supercharger 24, the control device 100 calculates a target boost pressure PTCt. The control device 100 then adjusts the opening of the nozzle vane 24N so that the target boost pressure PTCt is obtained.

[0030] The control device 100 sets the ignition timing of the spark plug 23 based on the engine load ratio KL, engine rotational speed NE, etc. <Ventilation treatment> For example, in operating conditions where the engine load ratio KL is low and the accelerator pedal operation amount ACCP is kept constant, the intake pressure PIM becomes close to atmospheric pressure. When the intake pressure PIM is close to atmospheric pressure, the first PCV valve 34 and the second PCV valve 64 mentioned above become difficult to open, so the crankcase 19 cannot be adequately ventilated, and there is a risk that the hydrogen concentration inside the crankcase 19 will rise.

[0031] Therefore, the control device 100 performs the following process to perform ventilation processing to promote ventilation inside the crankcase 19. Figure 2 shows the procedure for performing the ventilation process. The process shown in Figure 2 is achieved by the CPU 110 repeatedly executing a program stored in the memory 120 of the control device 100 at predetermined intervals. In the following, the step number of each process is represented by a number preceded by "S".

[0032] In the series of processes shown in Figure 2, the control device 100 determines whether the intake pressure PIM is within a predetermined range (S100). This predetermined range is a range suitable for determining that the intake pressure PIM is near atmospheric pressure, and is a preset suitable value.

[0033] If the control device 100 determines that the intake pressure PIM is within the default range (S100: YES), it increments counter C (S110). Counter C is a value that indicates the duration for which the intake pressure PIM was within the default range, and its value increases through the process in S110 each time a positive determination is made in S100 during this process, which is performed at predetermined intervals. Counter C is reset when ventilation is performed.

[0034] Next, the control device 100 determines whether the current counter C, which has been counted up, is equal to or greater than the threshold Cref (S120). The threshold Cref is set to a value that allows for accurate determination of whether the counter C has become large enough to require ventilation treatment, based on whether the counter C is equal to or greater than this threshold Cref.

[0035] In the process of S120, if it is determined that the counter C is equal to or greater than the threshold Cref (S120: YES), the control device 100 executes the processes of S130 and S140 as ventilation processes.

[0036] In the process of S130, the control device 100 performs a process to increase the currently set target boost pressure PTCt by a predetermined value α. The predetermined value α is the amount of increase in boost pressure PTC required to increase the intake pressure PIM and open the second PCV valve 64, and is set in advance. When the target boost pressure PTCt is increased in this way, the boost pressure PTC of the turbocharger 24 changes toward the increased target boost pressure PTCt.

[0037] Next, the control device 100 executes the process in S140. In the process in S140, the control device 100 executes a process to increase the target throttle opening TAt, which is the currently set target opening of the throttle valve 28, by a default value β. The default value β is a value that is set in advance to increase the amount of fresh air flowing through the third communication passage 62 by increasing the amount of fresh air that flows into the surge tank 60 through the throttle valve 28. When the target throttle opening TAt is increased in this way, the opening of the throttle valve 28 changes toward the increased target throttle opening TAt.

[0038] Next, the control device 100 sets the ignition timing according to the excess air ratio λ during the ventilation process (S150). In the process of S150, for example, the control device 100 calculates the excess air ratio λ during the ventilation process based on the required injection amount Qd and the intake air amount GA during the ventilation process. Then, the control device 100 sets the ignition timing so that the torque generated by the internal combustion engine 10 during the ventilation process is the same as the torque before the ventilation process started, based on, for example, the torque generated by the internal combustion engine 10 before the start of the ventilation process and the excess air ratio λ during the ventilation process. This setting of the ignition timing is done by referring to, for example, a pre-set map.

[0039] Then, if the process in S150 is executed, or if the process in S100 is deemed negative, or if the process in S120 is deemed negative, the control device 100 terminates the execution of this process for the current execution cycle.

[0040] <Operation and Effects of This Embodiment> (1) If both the process in S100 and the process in S120 shown in Figure 2 are judged positively, it means that the intake pressure PIM has been within the predetermined range for a predetermined time or longer. Therefore, by setting the predetermined range to a value near atmospheric pressure, it can be determined that such a state continuing is an operating condition in which the hydrogen concentration in the crankcase 19 may increase. If this determination is made, a ventilation process is performed to increase the boost pressure PTC of the turbocharger 24 by increasing the target boost pressure PTCt (S130).

[0041] When the boost pressure PTC is increased from a state where the intake pressure PIM is near atmospheric pressure, the intake pressure PIM becomes higher than atmospheric pressure, causing the second PCV valve 64 to open. When the second PCV valve 64 opens, fresh air flows into the crankcase 19 from the third communication passage 62, and the blow-by gas in the crankcase 19 containing hydrogen is discharged to the intake manifold 20 via the first communication passage 37. Therefore, the hydrogen concentration in the crankcase 19 can be reduced.

[0042] (2) The ventilation process includes increasing the opening of the throttle valve 28 (the process of S140 shown in Figure 2). Therefore, the opening of the throttle valve 28 is increased when the ventilation process is performed. When the opening of the throttle valve 28 is increased, the amount of fresh air flowing through the third communication passage 62 increases. When the amount of fresh air flowing through the third communication passage 62 increases, the amount of hydrogen discharged from the crankcase 19 to the intake manifold 20 via the first communication passage 37 increases. Therefore, the hydrogen concentration in the crankcase 19 can be further reduced compared to the case where the opening of the throttle valve 28 is not increased.

[0043] (3) When the boost pressure PTC of the supercharger 24 is increased or the opening of the throttle valve 28 is increased as part of the ventilation process, the intake air volume GA changes, which in turn changes the excess air ratio λ of the air-fuel mixture. When the excess air ratio λ of the air-fuel mixture changes, there is a risk that the torque generated by the internal combustion engine 10 will change. In this embodiment, the ignition timing of the air-fuel mixture is set so as to suppress the change in the torque generated by the internal combustion engine 10 due to the execution of the ventilation process by performing the process S150 shown in Figure 2.

[0044] <Example of changes> This embodiment can be implemented with the following modifications. This embodiment and the following modifications can be combined with each other to the extent that they do not contradict each other technically.

[0045] The process S140 shown in Figure 2 may be omitted. Even in this case, effects and benefits other than those described in (2) above can be obtained. The process S150 shown in Figure 2 may be omitted. Even in this case, effects and benefits other than those described in (3) above can still be obtained.

[0046] In the above embodiment, the increase in boost pressure PTC due to ventilation was achieved by adjusting the opening of the nozzle vane 24N. Alternatively, if the supercharger 24 has a wastegate valve that adjusts the amount of exhaust gas that flows around the turbine wheel 24T of the supercharger 24, the increase in boost pressure PTC due to ventilation may be achieved by adjusting the opening of the wastegate valve.

[0047] The third connecting passage 62 was connected to the surge tank 60, but the connection point may be changed as appropriate, as long as it is downstream of the throttle valve 28 in the intake passage. The internal combustion engine 10 may be equipped with a fuel injection valve that injects fuel into the intake port 30.

[0048] The control device is not limited to one that includes a CPU 110 and memory 120 and executes software processing. For example, in the above embodiment, it may include a dedicated hardware circuit such as an ASIC that performs hardware processing on at least a portion of what is processed by software. In other words, the control device may have any of the following configurations (a) to (c): (a) It includes a processing unit that executes all of the above processing according to a program and a program storage device such as a ROM that stores the program. (b) It includes a processing unit and a program storage device that execute a portion of the above processing according to a program and a dedicated hardware circuit that executes the remaining processing. (c) It includes a dedicated hardware circuit that executes all of the above processing. Here, the software execution device that includes the processing unit and program storage device and the dedicated hardware circuit may be one or any number of them. [Explanation of symbols]

[0049] 10... Internal combustion engine 19... Crankcase 20... Intake pipe 23... Spark plug 24… Supercharger 24C... Compressor Wheel 24N... Nozzle vane 27…Intercooler 28... Throttle valve 29…Intake manifold 30…Intake port 31... Separator 32…Second communication passage 34…First PCV valve 35…PCV passage 37...1st communication passage 38... Separator 53... Intake pressure sensor 60... Surge Tank 62…Third communication passage 64…2nd PCV valve 81…Intake valve 82... Exhaust valve 84…Fuel injector 100...Control device

Claims

1. A control device for an internal combustion engine that uses hydrogen as fuel, comprising an intake passage, a throttle valve provided in the intake passage, a supercharger equipped with a compressor wheel provided upstream of the throttle valve in the intake passage, and a blow-by gas treatment mechanism, The blow-by gas treatment mechanism includes a first passage connecting the portion of the intake passage upstream of the compressor wheel to the crankcase, a second passage connecting the portion of the intake passage downstream of the throttle valve to the crankcase, a first PCV valve provided in the second passage that opens when the intake pressure, which is the pressure downstream of the throttle valve in the intake passage, becomes lower than the pressure inside the crankcase, a third passage connecting the portion of the intake passage downstream of the throttle valve to the crankcase, and a second PCV valve provided in the third passage that opens when the intake pressure becomes higher than the pressure inside the crankcase. If the intake pressure remains within a predetermined range for a predetermined period of time or longer, a ventilation process is executed to increase the boost pressure of the supercharger. Control device for internal combustion engines.

2. The ventilation process includes a process to increase the opening degree of the throttle valve. A control device for an internal combustion engine according to claim 1.

3. The process of setting the ignition timing of the air-fuel mixture is performed in such a way that the change in torque generated by the internal combustion engine due to the execution of the ventilation process is suppressed. A control device for an internal combustion engine according to claim 1 or 2.

4. The supercharger is a variable-capacity supercharger that changes the boost pressure by changing the opening of the nozzle vanes. The increase in boost pressure due to the ventilation process is achieved through adjustment of the nozzle vane opening. A control device for an internal combustion engine according to claim 1.

5. The supercharger has a wastegate valve that adjusts the amount of exhaust gas that flows around the turbine wheel of the supercharger. The increase in boost pressure due to the ventilation process is achieved through adjustment of the opening of the wastegate valve. A control device for an internal combustion engine according to claim 1.

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