Control device for internal combustion engine

Abstract

The present invention addresses the problem of reducing the hydrogen concentration in a crankcase. An internal combustion engine includes a throttle valve, a supercharger, and a blow-by gas treatment mechanism. The blow-by gas treatment mechanism is provided with: a first communication passage that communicates with a crankcase and a portion of the intake passage upstream of a compressor impeller of the supercharger; a third communication passage that communicates a portion of the intake passage downstream of the throttle valve with the crankcase; and a second PCV valve that is provided in the third communication passage and that opens when an intake pressure, which is a pressure downstream of the throttle valve in the intake passage, is higher than a pressure in the crankcase. When the state in which the intake pressure is within the prescribed range continues for a prescribed time or longer, the control device executes a ventilation process for increasing the supercharging pressure of the supercharger.

Description

Technical Field

[0001] This invention relates to a control device for an internal combustion engine. Background Technology

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

[0003] Patent Document 1: Japanese Patent Application Publication No. 2024-76657 Summary of the Invention

[0004] However, in the internal combustion engine described in Patent Document 1, negative pressure is used to exchange 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 adequately exchanged, and the hydrogen concentration in the crankcase may increase.

[0005] The control device for an internal combustion engine that solves the above-mentioned problems is applied to an internal combustion engine using hydrogen as fuel. The internal combustion engine includes: an intake passage; a throttle valve disposed in the intake passage; a turbocharger having a compressor impeller disposed upstream of the throttle valve in the intake passage; and a blow-by mechanism. The blow-by mechanism includes: a first passage connecting the upstream portion of the intake passage (below the compressor impeller) to the crankcase; a second passage connecting the downstream portion of the intake passage (below the throttle valve) to the crankcase; a first PCV valve disposed in the second passage, which opens when the intake pressure (a pressure downstream of the throttle valve in the intake passage) is lower than the pressure in the crankcase; a third passage connecting the downstream portion of the intake passage (below the throttle valve) to the crankcase; and a second PCV valve disposed in the third passage, which opens when the intake pressure is higher than the pressure in the crankcase. Furthermore, if the intake pressure remains within the specified range for a specified time or longer, the control device performs a scavenging process to increase the boost pressure of the turbocharger.

[0006] Invention Effects

[0007] The control unit of this internal combustion engine can reduce the hydrogen concentration in the crankcase. Attached Figure Description

[0008] Figure 1 This is a schematic diagram showing the structure of an internal combustion engine in one embodiment.

[0009] Figure 2 This is a flowchart illustrating the steps of the processing performed by the control device in this embodiment. Detailed Implementation

[0010] The following describes one embodiment of a control device for an internal combustion engine mounted in a vehicle.

[0011] <Structure of an Internal Combustion Engine>

[0012] like Figure 1 As shown, the internal combustion engine 10 includes a cylinder block 11, a cylinder head 12, and a cylinder head cover 13. A cylinder 16 is disposed within the cylinder block 11 and configured to allow the piston 15 to reciprocate.

[0013] 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 or an exhaust port 70 for discharging exhaust gas from the combustion chamber 17. An intake valve 81 is provided on the intake port 30. An exhaust valve 82 is provided on the exhaust port 70.

[0014] A fuel injection valve 84 and a spark plug 23 are provided on the cylinder head 12 to directly inject hydrogen, which is used as fuel for the internal combustion engine, into the combustion chamber 17.

[0015] A crankcase 19 is provided at the lower part of the cylinder block 11 to accommodate the crankshaft 18 of the internal combustion engine 10.

[0016] An intake manifold 29 with a pressure regulating chamber 60 is connected upstream of the intake port 30, and an intake pipe 20 is connected upstream of the pressure regulating chamber 60. An intake pressure sensor 53 for detecting the intake pressure PIM is installed on the pressure regulating chamber 60. The intake pressure PIM is the pressure inside the pressure regulating chamber 60, and is the pressure in the intake passage downstream of the throttle valve 28.

[0017] The intake pipe 20, the pressure regulating chamber 60, and the intake manifold 29 constitute the intake passage of the internal combustion engine 10.

[0018] In the intake manifold 20, from upstream, there are an air filter 21, an air flow meter 51, a compressor impeller 24C of a turbocharger 24 driven by exhaust gas from the combustion chamber 17, a boost pressure sensor 52, an intercooler 27, and a throttle valve 28.

[0019] Air filter 21 filters the intake air entering the intake manifold 20. Air flow meter 51 detects the intake air volume GA of the internal combustion engine 10. Compressor impeller 24C of turbocharger 24 pressurizes the air in the intake manifold 20. Boost pressure sensor 52 detects the boost pressure PTC, which is the pressure downstream of compressor impeller 24C in the intake manifold 20. Intercooler 27 cools the air after passing through compressor impeller 24C. Throttle valve 28 is a valve that regulates the intake air volume of the internal combustion engine 10, and its opening is changed by an electric motor.

[0020] An exhaust passage 90 is connected downstream of the exhaust port 70. A housing accommodating the turbine impeller 24T of the turbocharger 24 is connected midway through the exhaust passage 90. The turbocharger 24 is a variable capacity turbocharger, equipped with nozzle blades 24N driven by an actuator. The nozzle blades 24N are a regulating mechanism for adjusting the amount of exhaust gas supplied to the turbine impeller 24T. By changing the opening of the nozzle blades 24N via the actuator, the boost pressure of the intake air increased by the turbocharger 24 will change.

[0021] The internal combustion engine 10 is equipped with a blow-by gas treatment mechanism to treat blow-by gas that leaks from the combustion chamber 17 into the crankcase 19 during the compression stroke or combustion stroke. This blow-by gas contains hydrogen as fuel, lubricating oil of the internal combustion engine 10, combustion gases of the air-fuel mixture, etc.

[0022] The blow-by mechanism includes a first connecting passage 37. One end of the first connecting passage 37 is connected to the intake pipe 20 between the air filter 21 and the compressor impeller 24C. The first connecting passage 37 passes through the cylinder head cover 13, through the interior of the cylinder head 12 and the cylinder block 11, and connects to the crankcase 19. A separator 38, which serves as an oil separator housed within the cylinder head cover 13, is provided midway through the first connecting passage 37. The first connecting passage 37 and the separator 38 constitute a first passage connecting the portion of the intake passage upstream of the compressor impeller 24C to the crankcase 19.

[0023] The blow-by gas treatment mechanism includes a second connecting passage 32 for guiding blow-by gas in the crankcase 19 to a separator 31, which serves as an oil separator located within the cylinder head cover 13. The end of the second connecting passage 32, which is connected to the separator 31, opens into the crankcase 19. Alternatively, the separator 31 may be installed midway through the second connecting passage 32.

[0024] The separator 31 is connected to the pressure regulating chamber 60 via a first PCV (positive crankcase ventilation) valve 34, which functions as a differential pressure valve, and a PCV passage 35. When the pressure in the pressure regulating chamber 60 is lower than the pressure in the separator 31, the first PCV valve 34 opens, allowing blow-by gas to flow from the separator 31 into the pressure regulating chamber 60. The pressure in the separator 31 is equal to the pressure in the crankcase 19. Therefore, the first PCV valve 34 is the valve that opens when the intake pressure PIM is lower than the pressure in the crankcase 19.

[0025] The second connecting passage 32, separator 31, first PCV valve 34 and PCV passage 35 constitute the part of the intake passage that is downstream of throttle valve 28 and the second passage of crankcase 19.

[0026] The blow-by mechanism includes a third connecting passage 62. One end of the third connecting passage 62 is connected to the pressure regulating chamber 60. The other end of the third connecting passage 62 is connected to the crankcase 19. The third connecting passage 62 constitutes a third passage connecting the portion of the intake passage downstream of the throttle valve 28 to the crankcase 19.

[0027] A second PCV valve 64, acting as a differential pressure valve, is installed midway through the third connecting passage 62. When the pressure inside the pressure regulating chamber 60 is higher than the pressure inside the crankcase 19, the second PCV valve 64 opens, allowing blow-by gas to flow from the crankcase 19 into the pressure regulating chamber 60. In other words, the second PCV valve 64 is the valve that opens when the intake pressure PIM is higher than the pressure inside the crankcase 19.

[0028] For example, when the internal combustion engine 10 is operating in the naturally aspirated region and the intake pressure PIM is lower than atmospheric pressure, the pressure in the pressure regulating chamber 60 is 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 from the intake manifold 20 into the crankcase 19 via the first connecting passage 37. Furthermore, blow-by gas in the crankcase 19 is drawn into the pressure regulating chamber 60 via the second connecting passage 32, the separator 31, the first PCV valve 34, and the PCV passage 35. The blow-by gas drawn into the pressure regulating chamber 60 is sent to the combustion chamber 17 for combustion along with the intake air. In the naturally aspirated region, by handling the blow-by gas in this way, the hydrogen in the crankcase 19 is replaced, thus reducing the hydrogen concentration in the crankcase 19.

[0029] On the other hand, when the internal combustion engine 10 is operating in the boost region and the intake pressure PIM is higher than atmospheric pressure, the pressure in the pressure regulating chamber 60 is 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 from the pressure regulating chamber 60 into the crankcase 19 via the third connecting passage 62. Furthermore, blow-by gas in the crankcase 19 is discharged to the intake manifold 20 via the first connecting passage 37. The blow-by gas discharged to the intake manifold 20 is sent into the combustion chamber 17 for combustion along with the intake air. In the boost region, by handling the blow-by gas in this way, the hydrogen in the crankcase 19 is replaced, thus reducing the hydrogen concentration in the crankcase 19.

[0030] The control device 100 uses the internal combustion engine 10 as the controlled object and operates various operating objects such as the throttle valve 28, the fuel injection valve 84, and the spark plug 23.

[0031] The control device 100 includes a CPU 110 for performing calculations and a memory 120 for storing control programs or data. Furthermore, the control device 100 performs various control-related processes by executing the programs stored in the memory 120 through the CPU 110.

[0032] The control unit 100 receives detection signals from the air flow meter 51, boost pressure sensor 52, and intake pressure sensor 53. It also receives detection signals from various other sensors. For example, the control unit 100 receives a detection signal from the crankshaft angle sensor 54, which detects the crankshaft angle (crankshaft rotation angle) of the crankshaft 18 to calculate the internal combustion engine speed NE. It also receives a detection signal from the throttle operation amount sensor 55, which detects the throttle operation amount (ACCP) of the throttle pedal, which regulates the output of the internal combustion engine 10. Furthermore, the control unit 100 receives a detection signal from the throttle sensor 56, which detects the throttle opening amount (TA), which is the opening degree of the throttle valve 28. Finally, the control unit 100 receives a detection signal from the vehicle speed sensor 57, which detects the vehicle speed (SP).

[0033] The control device 100 calculates the internal combustion engine load rate KL based on the internal combustion engine speed NE and the intake air volume GA. The internal combustion engine load rate KL is a parameter that determines the amount of air filling the combustion chamber 17, and is the ratio of the inflow air volume for a single cylinder and a single combustion cycle to the reference inflow air volume. The reference inflow air volume can be set variably according to the internal combustion engine speed NE.

[0034] The control device 100 calculates the required torque based on the throttle input (ACCP) and vehicle speed (SP). Furthermore, the control device 100 controls the required output Pe of the internal combustion engine 10 to meet the required torque. Here, hydrogen, as fuel for the internal combustion engine 10, has a wider range of combustible mixtures compared to gasoline, and can even burn lean mixtures. Therefore, the control device 100 performs lean combustion of a mixture with an air-fuel ratio greater than the stoichiometric air-fuel ratio, and regulates the output of the internal combustion engine 10 through the following combustion control.

[0035] That is, the control device 100 sets the required injection quantity Qd based on the required output Pe. The required injection quantity Qd is the target value of fuel injected from the fuel injection valve 84. The control device 100 calculates the target value of the intake air volume required to obtain the target air-fuel ratio AFt, i.e., the required air volume GAd, based on the target air-fuel ratio AFt and the required injection quantity Qd. In this embodiment, the target air-fuel ratio AFt is, for example, a lean air-fuel ratio with an excess air coefficient λ of 2.5 to 3.0. Furthermore, the control device 100 controls the fuel injection valve 84 to obtain the required injection quantity Qd. In addition, the control device 100 controls the opening degree of the throttle valve 28 or the boost pressure of the turbocharger 24 to obtain the required air volume GAd.

[0036] When controlling the boost pressure of the booster 24, the control device 100 calculates the target boost pressure PTCt. Furthermore, the control device 100 adjusts the opening of the nozzle blades 24N to obtain the target boost pressure PTCt.

[0037] The control device 100 sets the ignition timing of the spark plug 23 based on the internal combustion engine load rate KL or the internal combustion engine speed NE.

[0038] <Ventilation Treatment>

[0039] For example, under operating conditions such as a low internal combustion engine load rate KL and a constant throttle input ACCP, the intake pressure PIM becomes close to atmospheric pressure. When the intake pressure PIM is close to atmospheric pressure, the aforementioned first PCV valve 34 or second PCV valve 64 is difficult to open, thus insufficient air exchange within the crankcase 19 can occur, potentially leading to an increase in the hydrogen concentration within the crankcase 19.

[0040] Therefore, in order to perform a ventilation process that promotes air exchange within the crankcase 19, the control device 100 performs the following process.

[0041] Figure 2 The diagram shows the processing steps used to perform the ventilation process. Figure 2 The processing shown is achieved by the CPU 110 repeatedly executing the program stored in the memory 120 of the control device 100 at predetermined cycles. Furthermore, the step numbers of each process will be indicated below by numbers beginning with "S".

[0042] exist Figure 2 In the series of processes shown, the control device 100 determines whether the intake pressure PIM is within a specified range (S100). This specified range is a pressure range suitable for determining that the intake pressure PIM is near atmospheric pressure, and is a preset calibration value.

[0043] If the intake pressure PIM is determined to be within the specified range (S100: YES), the control device 100 increments the counter C (S110). The counter C represents the duration for which the intake pressure PIM remains within the specified range. During the execution of this process according to a predetermined cycle, the value increases through the process in S110 whenever a positive result is obtained in S100. Furthermore, the counter C is reset when an air exchange process is performed.

[0044] Next, the control device 100 determines whether the current counter C, which is being incremented, is above or above the threshold Cref (S120). The value of the threshold Cref is preset so that it can be accurately determined that the counter C has reached a level requiring ventilation based on the fact that the counter C is above or above the threshold Cref.

[0045] In the process of S120, if it is determined that the counter C is above the threshold Cref (S120: YES), the control device 100 performs the processes of S130 and S140 as ventilation processing.

[0046] In the process of S130, the control device 100 performs a process that increases 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 to open the second PCV valve 64, and is preset. Thus, when the target boost pressure PTCt increases, the boost pressure PTC of the booster 24 changes toward the increased target boost pressure PTCt.

[0047] Next, the control device 100 executes the process of S140. In the process of S140, the control device 100 executes a process that increases the target throttle opening TAt, which is the currently set target opening of the throttle valve 28, by a predetermined value β. The predetermined value β is a value that increases the amount of fresh air flowing through the third connecting passage 62 by increasing the amount of fresh air flowing into the pressure regulating chamber 60 through the throttle valve 28. Thus, when the target throttle opening TAt increases, the opening of the throttle valve 28 changes toward the increased target throttle opening TAt.

[0048] Next, the control device 100 sets the ignition timing based on the excess air coefficient λ during the aforementioned scavenging process (S150). In S150, for example, the control device 100 calculates the excess air coefficient λ during the scavenging process based on the required injection quantity Qd and the intake air quantity GA during the scavenging process. Furthermore, the control device 100 sets the ignition timing, for example, based on the torque generated by the internal combustion engine 10 before the start of the scavenging process and the excess air coefficient λ during the scavenging process, so that the torque generated by the internal combustion engine 10 during the scavenging process is the same as the torque before the start of the scavenging process. This ignition timing setting is performed, for example, by referring to a pre-set mapping table (MAP).

[0049] Furthermore, if the processing of S150 is performed, or if the processing of S100 is determined to be negative, or if the processing of S120 is determined to be negative, the control device 100 terminates the execution of this processing in the current execution cycle.

[0050] <Function and Effects of This Implementation Method>

[0051] (1) In Figure 2In both S100 and S120, the condition is determined to be positive when the intake pressure PIM remains within a specified range for a specified time or longer. Therefore, by setting the specified range to a value near atmospheric pressure, it can be determined that the continued existence of this state is an operating state that may cause an increase in the hydrogen concentration in the crankcase 19. Therefore, when such a determination can be made, a scavenging process (S130) is performed to increase the boost pressure PTC of the turbocharger 24 by increasing the target boost pressure PTCt.

[0052] 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, thus opening the second PCV valve 64. When the second PCV valve 64 is open, fresh air flows into the crankcase 19 through the third connecting passage 62, thereby expelling the hydrogen-containing blow-by gas in the crankcase 19 to the intake manifold 20 via the first connecting passage 37. Therefore, the hydrogen concentration in the crankcase 19 can be reduced.

[0053] (2) The ventilation treatment includes increasing the opening of the throttle valve 28. Figure 2 (The process shown is S140). Therefore, during the scavenging process, the opening of the throttle valve 28 is increased. When the opening of the throttle valve 28 is increased, the amount of fresh air flowing through the third connecting passage 62 increases. When the amount of fresh air flowing through the third connecting passage 62 increases, the amount of hydrogen discharged from the crankcase 19 to the intake manifold 20 via the first connecting passage 37 increases. Therefore, compared to the case where the opening of the throttle valve 28 is not increased, the hydrogen concentration in the crankcase 19 can be further reduced.

[0054] (3) As a scavenging process, when the boost pressure PTC of the turbocharger 24 is increased or the opening of the throttle valve 28 is increased, the intake air volume GA changes, and therefore the excess air coefficient λ of the air-fuel mixture changes. When the excess air coefficient λ of the air-fuel mixture changes, the torque generated in the internal combustion engine 10 may change. In this respect, in this embodiment, by performing... Figure 2 The S150 process shown sets the ignition timing of the air-fuel mixture to suppress changes in the torque generated by the internal combustion engine 10 caused by the scavenging process. Therefore, it is possible to suppress changes in the torque generated by the internal combustion engine 10 caused by an increase in the boost pressure PTC or an increase in the opening of the throttle valve 28.

[0055] <Example of Change>

[0056] Furthermore, this embodiment can be implemented with the following modifications. This embodiment and the following modifications can be combined with each other within the scope of technical non-contradiction.

[0057] • Can be omitted Figure 2The processing of S140 shown. Even in this case, it is possible to obtain effects and benefits other than those described in (2).

[0058] • Can be omitted Figure 2 The processing of S150 shown. Even in this case, effects and benefits other than those described in (3) can be obtained.

[0059] In the above embodiment, the increase in boost pressure PTC based on air exchange is performed by adjusting the opening degree of the nozzle blade 24N. Alternatively, if the booster 24 has an exhaust gas bypass valve that adjusts the amount of exhaust gas flowing around the turbine impeller 24T of the booster 24, the increase in boost pressure PTC based on air exchange can be performed by adjusting the opening degree of the exhaust gas bypass valve.

[0060] • The third connecting channel 62 is connected to the pressure regulating chamber 60, but as long as it is a part of the intake channel that is further downstream than the throttle valve 28, its connection point can be appropriately changed.

[0061] The internal combustion engine 10 may be equipped with a fuel injection valve that injects fuel into the air intake 30.

[0062] • The control device is not limited to a device that includes a CPU 110 and a memory 120 and performs software processing. For example, it may include a dedicated hardware circuit such as an ASIC that performs hardware processing on at least a portion of the software processing in the above embodiment. That is, the control device may be any of the following structures (a) to (c): (a) A processing device that performs all of the above processing according to a program and a program storage device such as a ROM that stores the program. (b) A processing device that performs a portion of the above processing according to a program, a program storage device, and a dedicated hardware circuit that performs the remaining processing. (c) A dedicated hardware circuit that performs all of the above processing. Here, the software execution device or dedicated hardware circuit that includes the processing device and the program storage device may be one or any multiple.

[0063] Symbol Explanation

[0064] 10-Internal combustion engine, 19-Crankcase, 20-Intake manifold, 23-Spark plug, 24-Turbocharger, 24C-Compressor impeller, 24N-Nozzle blade, 27-Intercooler, 28-Throttle valve, 29-Intake manifold, 30-Intake port, 31-Separator, 32-Second connecting channel, 34-First PCV valve, 35-PCV channel, 37-First connecting channel, 38-Separator, 53-Intake pressure sensor, 60-Pressure chamber, 62-Third connecting channel, 64-Second PCV valve, 81-Intake valve, 82-Exhaust valve, 84-Fuel injection valve, 100-Control device.

Claims

1. A control device for an internal combustion engine, characterized in that, An internal combustion engine used as hydrogen fuel, the internal combustion engine having: An intake passage; a throttle valve disposed in the intake passage; a turbocharger having a compressor impeller disposed in the intake passage upstream of the throttle valve; and a blow-by mechanism, wherein... The gas leakage treatment mechanism has: A first channel connects the portion of the intake passage upstream of the compressor impeller to the crankcase; a second channel connects the portion of the intake passage downstream of the throttle valve to the crankcase; a first PCV valve, located in the second channel, opens when the intake pressure (the pressure downstream of the throttle valve in the intake passage) is lower than the pressure in the crankcase; a third channel connects the portion of the intake passage downstream of the throttle valve to the crankcase; and a second PCV valve, located in the third channel, opens when the intake pressure is higher than the pressure in the crankcase. If the intake pressure remains within the specified range for a specified time or longer, a scavenging process is performed to increase the boost pressure of the turbocharger.

2. The control device for an internal combustion engine according to claim 1, characterized in that, The ventilation process includes increasing the opening of the throttle valve.

3. The control device for an internal combustion engine according to claim 1 or 2, characterized in that, The process of setting the ignition timing of the air-fuel mixture is performed to suppress changes in the torque generated by the internal combustion engine caused by the scavenging process.

4. The control device for an internal combustion engine according to claim 1, characterized in that, The intensifier is a variable-capacity intensifier that changes the boost pressure by altering the opening of the nozzle blades. The increase in boost pressure based on the ventilation process is performed by adjusting the opening of the nozzle blades.

5. The control device for an internal combustion engine according to claim 1, characterized in that, The turbocharger has an exhaust bypass valve that regulates the amount of exhaust gas flowing around the turbine impeller of the turbocharger. The increase in boost pressure based on the ventilation process is performed by adjusting the opening degree of the waste gas bypass valve.

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