Control device for internal combustion engines

Abstract

To provide a control device of an internal combustion engine capable of suppressing the concentration of hydrogen remaining in a crankcase after the engine is stopped.SOLUTION: A processor 152 of an ECU 150 includes: a hydrogen concentration estimating section 152b for estimating, when an internal combustion engine 10 burning hydrogen is stopped, hydrogen concentration in a crankcase 19 before stopping of the engine; a ventilation control section 152c for ventilating inside the crankcase 19 before stopping of the engine under a ventilation condition in correspondence with the estimated hydrogen concentration, and discharging gas containing hydrogen in the crankcase 19 to gas of an intake system through a ventilation passage connecting the crankcase 19 and an intake passage by the ventilation; and an engine stop section 152d for stopping the internal combustion engine 10 after ventilating the inside of the crankcase 19.SELECTED DRAWING: Figure 3

Description

Technical Field

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

Background Art

[0002] Conventionally, by supplying an inert gas into the crankcase according to the detection value of a hydrogen concentration sensor, hydrogen gas leaked from the combustion chamber into the crankcase is purged, and deterioration of lubricating oil and hydrogen embrittlement of parts due to accumulation of hydrogen gas are suppressed (Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the technology described in the above patent document, since the purge also stops when the engine stops, there is a problem that hydrogen remains in the crankcase when the engine stops. And if hydrogen remains in the crankcase when the engine stops, there is a possibility that hydrogen may come out when the oil filler cap is opened for oil replenishment or the like after the engine stops. In this case, if a hydrogen sensor provided in the engine room detects hydrogen, there is a possibility that an abnormality may be erroneously detected even though there is no abnormality such as hydrogen leakage from the internal combustion engine.

[0005] In view of the above problems, an object of the present disclosure is to provide a control device for an internal combustion engine capable of suppressing the hydrogen concentration remaining in the crankcase after the engine stops to a low level.

Means for Solving the Problems

[0006] The gist of the present disclosure is as follows.

[0007] (1) A hydrogen concentration estimation unit that estimates the hydrogen concentration in the crankcase before the engine is stopped when an internal combustion engine that burns hydrogen is stopped, A ventilation control unit ventilates the crankcase before engine shutdown under ventilation conditions corresponding to the estimated hydrogen concentration, and discharges the hydrogen-containing gas from the crankcase into the intake system gas through a ventilation passage connecting the crankcase and the intake passage. An engine stop unit that stops the internal combustion engine after ventilation of the crankcase, A control device for an internal combustion engine, equipped with the following features.

[0008] (2) The control device for the internal combustion engine described in (1) above, wherein the ventilation control unit ventilates the inside of the crankcase after an engine stop request has been issued but before the engine has been stopped.

[0009] (3) The control device for an internal combustion engine according to (1) or (2) above, wherein the ventilation control unit ventilates the inside of the crankcase for a period of time corresponding to the estimated hydrogen concentration.

[0010] (4) The control device for an internal combustion engine according to any one of (1) to (3) above, wherein the ventilation control unit ventilates the inside of the crankcase with a negative pressure in the intake manifold corresponding to the estimated hydrogen concentration.

[0011] (5) The control device for an internal combustion engine according to any one of (1) to (4) above, wherein the ventilation control unit ventilates the inside of the crankcase before the engine is stopped with a higher ventilation efficiency than during normal operation of the internal combustion engine.

[0012] (6) The control device for an internal combustion engine according to any one of (1) to (5) above, wherein the engine stopping unit stops the internal combustion engine when the hydrogen concentration in the crankcase, estimated by ventilation in the crankcase, falls below a predetermined value. [Effects of the Invention]

[0013] According to this disclosure, a control device for an internal combustion engine is provided that can keep the hydrogen concentration remaining in the crankcase low after the engine has stopped. [Brief explanation of the drawing]

[0014] [Figure 1] This is a schematic diagram showing the configuration of an internal combustion engine system. [Figure 2] This is a schematic diagram showing the gas flow during ventilation before shutting down an internal combustion engine. [Figure 3] This is a schematic diagram showing the functional blocks of the ECU's processor. [Figure 4] This is a characteristic diagram showing the map used by the hydrogen concentration estimation unit to estimate the hydrogen concentration inside the crankcase. [Figure 5] This is a characteristic diagram illustrating the ventilation control performed by the ventilation control unit. [Figure 6] This is a schematic diagram illustrating a specific example of ventilation control by a ventilation control unit. [Figure 7] This flowchart shows the processes that the ECU's processor performs at predetermined control cycles. [Modes for carrying out the invention]

[0015] Several embodiments of the present invention will be described below with reference to the drawings. However, these descriptions are intended to be merely illustrative of preferred embodiments of the present invention and are not intended to limit the present invention to such specific embodiments. In the following description, similar components will be given the same reference numerals.

[0016] Figure 1 is a schematic diagram showing the configuration of the internal combustion engine system 100. The internal combustion engine system 100 includes an internal combustion engine 10 that uses hydrogen as fuel. The internal combustion engine system 100 is mounted on a vehicle. For example, the internal combustion engine system 100 is mounted on an automobile driven solely by the driving force of the internal combustion engine 10, or on a hybrid automobile equipped with an internal combustion engine 10 and a motor generator (MG).

[0017] When the vehicle is a hybrid vehicle, the vehicle may be of any type as long as it includes an internal combustion engine 10 and an MG (or motor). Therefore, for example, the vehicle may be configured such that the internal combustion engine is only used for power generation and only the motor drives the vehicle. Also, for example, the vehicle may be configured to have two MGs, one mainly used for driving the vehicle and the other mainly used for power generation.

[0018] As shown in FIG. 1, the internal combustion engine 10 includes a cylinder block 11, a cylinder head 12, a head cover 13, and an oil pan 14. A piston 15 is provided reciprocally in a cylinder 16 of the cylinder block 11. A combustion chamber 17 is formed by a space surrounded by the wall surface of the cylinder 16, the crown surface of the piston 15, and the cylinder head 12. The head cover is provided with a filler cap or the like for injecting oil.

[0019] The cylinder head 12 is rotatably provided with an intake camshaft (not shown) for driving the intake valve to open and close and an exhaust camshaft (not shown) for driving the exhaust valve to open and close. The cylinder head 12 is also provided with a fuel injection valve (not shown).

[0020] A crankcase 19 for rotatably supporting a crankshaft 18 is provided at the lower part of the cylinder block 11. The oil pan 14 for storing lubricating oil is assembled below the crankcase 19.

[0021] An intake manifold 29 including a surge tank 60 is connected to the cylinder head 12, and an intake pipe 20 on which various devices are installed is connected upstream of the surge tank 60. The intake pipe 20, the surge tank 60, and the intake manifold 29 constitute the intake passage of the internal combustion engine 10.

[0022] The intake manifold 20 is equipped with, in order from upstream, an air cleaner 21, an air flow meter 91, a compressor 24C of a supercharger 24 driven by exhaust gases from the combustion chamber 17, an intercooler 27, a pressure sensor 93, and an electrically operated throttle valve 28.

[0023] The air cleaner 21 filters the intake air taken into the intake manifold 20, and the supercharger 24 pressurizes (supercharges) the air taken into the intake manifold 20. In addition, the intercooler 27 cools the air after it has passed through the compressor 24C, and the intake air volume is adjusted by adjusting the opening of the throttle valve 28.

[0024] The internal combustion engine 10 is equipped with a blow-by gas treatment device for processing combustion gases, also known as blow-by gases, that leak from the combustion chamber 17 into the crankcase 19. This blow-by gas treatment device includes a suction passage 32 for guiding the blow-by gases in the crankcase 19 to a main separator 31, which is an oil separator provided in the head cover 13. The suction passage 32 extends through the inside of the cylinder block 11 and cylinder head 12, and a pre-separator 33 for oil separation is provided along its path.

[0025] The main separator 31 is connected to the surge tank 60 via a differential pressure valve, a PCV (positive crankcase ventilation) valve 34, and a PCV passage 35. The PCV valve 34 opens when the pressure in the surge tank 60 becomes lower than the pressure in the main separator 31, allowing blow-by gas to flow from the main separator 31 into the surge tank 60.

[0026] When the internal combustion engine 10 is operating in a non-supercharged state (naturally aspirated state), the pressure in the surge tank 60 is lower than the pressure in the main separator 31. Therefore, blow-by gas in the crankcase 19 is drawn into the surge tank 60 via the intake passage 32, the main separator 31, the PCV valve 34, and the PCV passage 35. The drawn-in blow-by gas is sent to the combustion chamber 17 along with the intake air and burned.

[0027] Furthermore, an ejector 40 is connected to the main separator 31 via a connecting passage 41. The ejector 40 is located in the middle of a bypass passage 42 that connects the intake pipe 20 upstream of the compressor 24C to the intake pipe 20 downstream of the compressor 24C. The ejector 40 is a single-stage ejector with only one throttling section that generates negative pressure, and is equipped with a flow control valve (not shown) inside that closes when the flow rate of air flowing through the bypass passage 42 exceeds a predetermined amount.

[0028] The connecting passage 41 is equipped with an electromagnetic valve 43 that adjusts the flow rate of blow-by gas flowing through the connecting passage 41. This electromagnetic valve 43 is controlled to be in a closed state (fully closed state) when the opening command value Vs is "0%". As the opening command value Vs increases from "0%" to "100%", the opening of the electromagnetic valve 43 increases, and the flow rate of blow-by gas flowing through the connecting passage 41 increases. When the opening command value Vs is "100%", the electromagnetic valve 43 is controlled to be in a fully open state.

[0029] Furthermore, the blow-by gas treatment device is equipped with an atmospheric intake passage 37 for introducing air into the crankcase 19. The atmospheric intake passage 37 extends from the area between the air cleaner 21 and the compressor 24C in the intake manifold 20, through the head cover 13, through the inside of the cylinder head 12 and cylinder block 11, and connects to the crankcase 19. An atmospheric-side separator 38, which is an oil separator installed inside the head cover 13, is provided along the atmospheric intake passage 37.

[0030] When the internal combustion engine 10 is operating under supercharging conditions, air flows through the bypass passage 42 from downstream to upstream of the compressor 24C, causing air (ejector gas) to circulate between the intake manifold 20 and the bypass passage 42, creating negative pressure in the internal space of the ejector 40. By utilizing the negative pressure generated in the internal space of the ejector 40, blow-by gas from the crankcase 19 is drawn into the ejector 40 via a blow-by gas passage consisting of a suction passage 32, a pre-separator 33, a main separator 31, and a connecting passage 41. The blow-by gas drawn into the ejector 40 is introduced along with air through the bypass passage 42 to the intake manifold 20 upstream of the compressor 24C. The blow-by gas introduced into the intake manifold 20 is sent to the combustion chamber 17 along with the intake air and burned.

[0031] The ECU 150 is a component that controls the entire internal combustion engine system 100, and controls the internal combustion engine 10, performing various controls on the internal combustion engine 10 by operating various controllable devices such as the throttle valve 28, fuel injection valve, and solenoid valve 43. The ECU 150 is one embodiment of a control device for an internal combustion engine and has a processor 152, a memory 154, and a communication interface 156. The processor 152 has one or more CPUs (Central Processing Units) and their peripheral circuits. The processor 152 may further have other arithmetic circuits such as a logic unit, a numerical unit, or a graphics processing unit. The memory 154 has, for example, a volatile semiconductor memory and a non-volatile semiconductor memory, and stores data related to the processing according to this embodiment as needed. The communication interface 156 has an interface circuit for connecting the ECU 150 to an in-vehicle network.

[0032] When performing various control operations, the ECU150 refers to the intake air volume GA detected by the air flow meter 91 and the engine rotation speed calculated from the output signal of the crank angle sensor 92. The ECU150 also refers to the intake pressure detected by the pressure sensor 93. Furthermore, when performing various control operations, the ECU150 refers to the output signal of the accelerator pedal position sensor 94, which detects the amount of accelerator pedal operation (accelerator position) performed by the vehicle driver, and the vehicle speed detected by the vehicle speed sensor 95.

[0033] Furthermore, the ECU 150 is connected to a hydrogen sensor 96 that detects the hydrogen concentration in the engine compartment where the internal combustion engine 10 is located. If hydrogen leaks from the internal combustion engine 10 and the hydrogen concentration in the engine compartment detected by the hydrogen sensor 96 exceeds a predetermined value, the ECU 150 detects an abnormality in the internal combustion engine system 1000. In this case, the ECU 150 takes necessary measures such as stopping (shutting down) the operation of the internal combustion engine system or issuing a warning to the vehicle driver to stop the vehicle. This prevents the internal combustion engine 10 from being operated while hydrogen is leaking.

[0034] The throttle valve 28, solenoid valve 43, fuel injector, and other various devices, as well as the various sensors provided by the internal combustion engine system 100, are connected to the ECU 150 via an in-vehicle network compliant with standards such as the Controller Area Network (CAN).

[0035] Although this example shows an internal combustion engine 10 equipped with a supercharger 24, the internal combustion engine 10 does not necessarily have to be equipped with a supercharger 24. If the internal combustion engine 10 is not equipped with a supercharger 24, components such as the ejector 40 and bypass passage 42 are also unnecessary.

[0036] In the internal combustion engine system 100 configured as described above, if the internal combustion engine 10 stops while hydrogen is accumulating inside the crankcase 19, the hydrogen accumulated inside the crankcase 19 will be discharged into the engine compartment when the filler cap of the internal combustion engine 10 is opened for oil replenishment or other purposes. In this case, if the hydrogen sensor 96 detects a hydrogen concentration above a predetermined value, the ECU 150 may mistakenly detect an abnormality, even though there is no abnormality causing hydrogen to leak from the internal combustion engine 10.

[0037] During normal operation, blow-by gas is discharged from the crankcase 19 in the manner described above. However, in normal operation, the blow-by gas discharge is basically limited to the amount pushed out of the crankcase 19 by the downward movement of the piston 15. Therefore, hydrogen may accumulate inside the crankcase 19 when the internal combustion engine 10 stops.

[0038] Therefore, in this embodiment, when the driver requests the internal combustion engine 10 to stop (engine stop request) when stopping the vehicle, the inside of the crankcase 19 is ventilated before stopping the internal combustion engine 10, and the internal combustion engine 10 is stopped after ventilation. Note that the engine stop request is issued, for example, when the ignition switch is turned off.

[0039] Figure 2 is a schematic diagram showing the gas flow during ventilation before the internal combustion engine 10 is stopped. When a request is made to stop the internal combustion engine 10, the throttle valve 28 is closed before the engine 10 is stopped, creating a negative pressure in the intake manifold 29. As a result, the gas inside the crankcase 19 flows in the direction of the black arrow A1 shown in Figure 2, passes through the PCV valve 34, and flows into the intake manifold 29. Also, as gas flows from inside the crankcase 19 to the intake manifold 29, fresh air downstream of the air cleaner 21 flows in the direction of the white arrow A2 shown in Figure 2, and a large amount of fresh air flows into the crankcase 19 from the atmospheric intake passage 37. This ventilates the inside of the crankcase 19.

[0040] The gas from the crankcase 19 that flows into the intake manifold 29 is drawn into the combustion chamber 17. As a result, the hydrogen that has been accumulating in the crankcase 19 burns, and the exhaust gas after combustion is discharged into the exhaust manifold.

[0041] Ventilation is performed when the internal combustion engine 10 is running at idle after a stop request has been issued. At this time, the electromagnetic valve 43 is closed.

[0042] In the case of hybrid vehicles, ventilation is performed after a stop request is issued, while the internal combustion engine 10 is being driven by the motor. In this case, hydrogen is not burning in the internal combustion engine 10, and the crankshaft 18 rotates due to the motoring, allowing for more efficient ventilation within the crankcase 19.

[0043] After the crankcase 19 has been ventilated as described above, the internal combustion engine 10 is stopped. This prevents hydrogen from being released from the crankcase 19 when the filler cap is opened to replenish the oil, thereby preventing false detection of hydrogen leaks.

[0044] The hydrogen concentration in the crankcase 19 varies depending on the operating conditions of the internal combustion engine 10 (engine speed, load). The higher the engine speed and load of the internal combustion engine 10, the higher the hydrogen concentration in the crankcase 19. Therefore, the hydrogen concentration in the crankcase 19 is predicted according to the operating conditions of the internal combustion engine 10 before a stop request is issued, and ventilation is controlled according to the hydrogen concentration. The load is determined from the accelerator opening or fuel injection amount.

[0045] During ventilation, further restricting the opening of the throttle valve 28 increases the negative pressure in the intake manifold 29, allowing a larger volume of gas to flow from the crankcase 19 into the intake manifold 29. This shortens the ventilation time.

[0046] Therefore, by determining conditions such as the negative pressure in the intake manifold 29 during ventilation and the ventilation time according to the predicted hydrogen concentration in the crankcase 19, ventilation can be reliably performed in the minimum necessary time.

[0047] Figure 3 is a schematic diagram showing the functional blocks of the processor 152 of the ECU 150 for realizing the above-described processing. The processor 152 of the ECU 150 includes an operating state acquisition unit 152a, a hydrogen concentration estimation unit 152b, a ventilation control unit 152c, and an engine stop unit 152d. Each of these parts of the processor 152 is a functional module realized, for example, by a computer program running on the processor 152. In other words, the functional blocks of the processor 152 consist of the processor 152 and a program (software) to make it function. The program may also be recorded in the memory 154 of the ECU 150 or on an externally connected recording medium. Alternatively, each of these parts of the processor 152 may be a dedicated arithmetic circuit provided in the processor 152.

[0048] The operating state acquisition unit 152a of the processor 152 acquires the operating state of the internal combustion engine 10 immediately before a request to stop the internal combustion engine 10 is issued. The operating state acquisition unit 152a acquires the operating state for a predetermined period of time in the past, going back from the time the engine stop request was issued.

[0049] The hydrogen concentration estimation unit 152b of the processor 152 estimates the hydrogen concentration in the crankcase 19 before the engine is stopped when the internal combustion engine 10 is stopped. Specifically, the hydrogen concentration estimation unit 152b estimates the hydrogen concentration in the crankcase 19 at the time a request to stop the internal combustion engine 10 is issued, based on the operating state of the internal combustion engine 10 acquired by the operating state acquisition unit 152a. Figure 4 is a characteristic diagram showing the map used by the hydrogen concentration estimation unit 152b when estimating the hydrogen concentration in the crankcase 19. Figure 4 shows characteristic C1 for estimating the hydrogen concentration when the internal combustion engine 10 was operated at high speed and high load immediately before stopping, and characteristic C2 for estimating the hydrogen concentration when the internal combustion engine 10 was operated at low speed and low load immediately before stopping.

[0050] If the internal combustion engine 10 was operating at high speed and high load before being stopped, the hydrogen concentration estimation unit 152b estimates the hydrogen concentration in the crankcase 19 by applying the operating time during which the internal combustion engine 10 was operating at high speed and high load to characteristic C1 in Figure 4. For example, if the internal combustion engine 10 was operating at high speed and high load as described in characteristic C1 during a predetermined period (time 0 to t1) prior to the time when the engine stop request was issued, the hydrogen concentration estimation unit 152b estimates that the hydrogen concentration in the crankcase 19 is d1.

[0051] Furthermore, if the internal combustion engine 10 was operating at low speed and low load before being stopped, the hydrogen concentration estimation unit 152b estimates the hydrogen concentration in the crankcase 19 by applying the operating time during which the internal combustion engine 10 was operating at low speed and low load to characteristic C2 in Figure 4. For example, if the internal combustion engine 10 was operating at low speed and low load as described in characteristic C2 during a predetermined period (time 0 to t1) prior to the time when the engine stop request was issued, the hydrogen concentration estimation unit 152b estimates that the hydrogen concentration in the crankcase 19 is d2.

[0052] Note that the map shown in Figure 4 is just one example, and the map used to estimate the hydrogen concentration in the crankcase 19 may include a variety of other characteristics. For example, the map used to estimate the hydrogen concentration in the crankcase 19 may include characteristics for estimating the hydrogen concentration when the internal combustion engine 10 is operated at medium speed and medium load just before stopping.

[0053] The ventilation control unit 152c of the processor 152 ventilates the crankcase 19 before engine shutdown under ventilation conditions corresponding to the hydrogen concentration estimated by the hydrogen concentration estimation unit 152b, and discharges the hydrogen-containing gas inside the crankcase 19 into the intake system gas through the ventilation passages (suction passage 32, PCV passage 35, connecting passage 41, bypass passage 42) that connect the crankcase 19 to the intake passage. The ventilation control unit 152c may ventilate the crankcase 19 for a period of time corresponding to the estimated hydrogen concentration. Alternatively, the ventilation control unit 152c may ventilate the crankcase 19 using the negative pressure of the intake manifold 29 corresponding to the estimated hydrogen concentration.

[0054] More specifically, the ventilation control unit 152c determines ventilation conditions such as negative pressure in the intake manifold 29 and ventilation time when the hydrogen concentration estimated by the hydrogen concentration estimation unit 152b is above a predetermined value (for example, 4% or more), and performs ventilation in the crankcase 19 according to the ventilation conditions. The ventilation control unit 152c may also perform ventilation in the crankcase 19 when the hydrogen concentration estimated by the hydrogen concentration estimation unit 152b is within a predetermined range (for example, 4% or more and 75% or less). Figure 5 is a characteristic diagram illustrating the ventilation control performed by the ventilation control unit 152c.

[0055] In the example shown in Figure 4, if the hydrogen concentration in the crankcase 19 estimated by the hydrogen concentration estimation unit 152b is d1, the ventilation control unit 152c can control ventilation as shown in characteristics C3 or C4 in Figure 5 by adjusting the opening of the throttle valve 28. Characteristic C3 shows the case where ventilation control is performed by increasing the opening of the throttle valve 28 to lower the negative pressure in the intake manifold 29. When the negative pressure in the intake manifold 29 is low, it takes a relatively long time to discharge the gas in the crankcase 19 to the intake manifold 29. Therefore, when controlling as characteristic C3, the hydrogen concentration in the crankcase 19 reaches 0 at time t11, and ventilation is completed at time t11.

[0056] On the other hand, characteristic C4 represents the case where ventilation control is performed by reducing the opening of the throttle valve 28 and increasing the negative pressure in the intake manifold 29. When the negative pressure in the intake manifold 29 is high, the gas in the crankcase 19 is discharged into the intake manifold 29 in a relatively short time. Therefore, when controlling with characteristic C4, the hydrogen concentration in the crankcase 19 reaches 0 at time t12, earlier than time t11, and ventilation is completed at time t12.

[0057] As described above, when ventilation is performed by increasing the negative pressure in the intake manifold 29 (characteristic C4), the ventilation time is shortened by time T compared to when ventilation is performed by decreasing the negative pressure in the intake manifold 29 (characteristic C3). The ventilation control unit 152c can control the ventilation time by adjusting the opening of the throttle valve. Therefore, ventilation is reliably performed in the minimum necessary time.

[0058] Furthermore, in the example shown in Figure 4, if the hydrogen concentration estimated by the hydrogen concentration estimation unit 152b is d2, the ventilation control unit 152c can perform ventilation control as shown by characteristic C5 in Figure 5. Characteristic C5 shows a case where ventilation control is performed by reducing the opening of the throttle valve 28 and increasing the negative pressure in the intake manifold 29. In this case, the hydrogen concentration in the crankcase 19 reaches 0 at time t13, and ventilation is completed at time t13. Thus, when the hydrogen concentration is relatively low at d2, the ventilation time is shortened compared to when the hydrogen concentration is relatively high at d1. Note that even when the hydrogen concentration is d2, it is possible to extend the ventilation time by increasing the opening of the throttle valve 28.

[0059] As described above, the ventilation control unit 152c can determine ventilation conditions such as the negative pressure in the intake manifold 29 and the ventilation time according to the hydrogen concentration in the crankcase 19, and can control the ventilation in the crankcase 19 based on the determined ventilation conditions. The ventilation control unit 152c controls the negative pressure in the intake manifold 29 by controlling the opening degree of the throttle valve 28. Alternatively, the ventilation control unit 152c may control the negative pressure in the intake manifold 29 by controlling valves other than the throttle valve 28 provided in the intake manifold 29. Furthermore, the ventilation control unit 152c may control the negative pressure in the intake manifold 29 by controlling the valve timing of the intake valve and exhaust valve of the internal combustion engine 10.

[0060] Furthermore, the ventilation control unit 152c may ventilate the crankcase 19 before engine shutdown with a higher ventilation efficiency than during normal operation of the internal combustion engine 10. Ventilation efficiency refers to the decrease in hydrogen concentration in the crankcase 19 per unit time. For example, before engine shutdown, the ventilation control unit 152c may increase the negative pressure in the intake manifold 29 compared to normal operation to ventilate the crankcase 19. Also, before engine shutdown, the ventilation control unit 152c may extend the ventilation time compared to normal operation to ventilate the crankcase 19.

[0061] The engine stop unit 152d of the processor 152 stops the internal combustion engine 10 when an engine stop request is issued. If ventilation of the crankcase 19 is performed by the ventilation control unit 152c before stopping the internal combustion engine 10, the engine stop unit 152d stops the internal combustion engine 10 after ventilation. More specifically, the engine stop unit 152d stops the internal combustion engine 10 when the hydrogen concentration in the crankcase 19, estimated by ventilation, falls below a predetermined value.

[0062] Figure 6 is a schematic diagram showing a specific example of ventilation control by the ventilation control unit 152c. Figure 6 is a schematic diagram showing the relationship between the operating state of the internal combustion engine 10 before the stop request, the hydrogen concentration in the crankcase 19, the negative pressure in the intake manifold 29 during ventilation (intake manifold negative pressure), and the ventilation time. The operating state before the stop request shown in Figure 6 is acquired by the operating state acquisition unit 152a, and the hydrogen concentration in the crankcase 19 is estimated by the hydrogen concentration estimation unit 152b. In addition, the intake manifold negative pressure and ventilation time shown in Figure 6 are controlled by the ventilation control unit 152c.

[0063] As shown in Figure 6, in the operating state of the internal combustion engine 10 before the stop request, if the engine speed is high, the load is high, and the operating time in that state is long, the hydrogen concentration estimation unit 152b estimates that the hydrogen concentration in the crankcase 19 is "high". In this case, the ventilation control unit 152c controls the negative pressure in the intake manifold 29 during ventilation to "medium" and controls the ventilation time to a relatively long "long". Alternatively, as shown in parentheses in Figure 6, the ventilation control unit 152c may control the negative pressure in the intake manifold 29 during ventilation to "high" and control the ventilation time to a shorter "medium".

[0064] Furthermore, as shown in Figure 6, if, in the operating state of the internal combustion engine 10 before the stop request, the engine speed is high, the load is low, and the operating time in that state is short, the hydrogen concentration estimation unit 152b estimates the hydrogen concentration in the crankcase 19 to be "medium". In this case, the ventilation control unit 152c controls the negative pressure in the intake manifold 29 during ventilation to "medium" and controls the ventilation time to "medium". Alternatively, as shown in parentheses in Figure 6, the ventilation control unit 152c may control the negative pressure in the intake manifold 29 during ventilation to "high" and control the ventilation time to a shorter "short" setting.

[0065] Furthermore, as shown in Figure 6, if, in the operating state of the internal combustion engine 10 before the stop request, the engine speed is low, the load is high, and the operating time in that state is long, the hydrogen concentration estimation unit 152b estimates the hydrogen concentration in the crankcase 19 to be "medium". In this case as well, the ventilation control unit 152c controls the negative pressure in the intake manifold 29 during ventilation to "medium" and controls the ventilation time to "medium". Alternatively, as shown in parentheses in Figure 6, the ventilation control unit 152c may control the negative pressure in the intake manifold 29 during ventilation to "high" and control the ventilation time to a shorter "short" setting.

[0066] Furthermore, as shown in Figure 6, if the engine speed is low, the load is low, and the operating time in that state is short, the hydrogen concentration estimation unit 152b estimates that the hydrogen concentration in the crankcase 19 is "low" in the operating state before the request to stop the internal combustion engine 10. In this case, the ventilation control unit 152c controls the negative pressure in the intake manifold 29 during ventilation to "low" and controls the ventilation time to "short". Alternatively, as shown in parentheses in Figure 6, the ventilation control unit 152c may control the negative pressure in the intake manifold 29 during ventilation to "medium" and control the ventilation time to an even shorter "very short" duration.

[0067] As described above, the hydrogen concentration in the crankcase 19 varies depending on the operating state of the internal combustion engine 10. However, in order to ensure ventilation without considering the hydrogen concentration, ventilation must be performed for a long time according to the conditions with the highest concentration, which can result in an excessive amount of time being required from the time a request to stop the engine is issued until the internal combustion engine 10 is stopped. According to this embodiment, as shown in Figure 6, by controlling the negative pressure in the intake manifold 29 and the ventilation time during ventilation according to the hydrogen concentration in the crankcase 19, the time until the internal combustion engine 10 stops can be reduced to the minimum necessary time.

[0068] Furthermore, the higher the engine speed of the internal combustion engine 10 during ventilation, the higher the negative pressure inside the intake manifold 29, and therefore the ventilation time is shortened as the engine speed increases.

[0069] Next, the processing performed by the processor 152 of the ECU 150 will be described. Figure 7 is a flowchart showing the processing performed by the processor 152 of the ECU 150 at predetermined control cycles. First, the operating state acquisition unit 152a acquires the operating state of the internal combustion engine 10 (step S10). The operating state of the internal combustion engine 10 acquired at each control cycle is stored in the memory 154.

[0070] Next, the processor 152 determines whether or not a request to stop the internal combustion engine 10 has been issued (step S12). If a request to stop the internal combustion engine 10 has been issued, the operating state acquisition unit 152a acquires the operating state for a predetermined period in the past, going back from the current time when the engine stop request was issued, from the operating state acquired in step S10 for each control cycle. Also, if a request to stop the internal combustion engine 10 has been issued, the hydrogen concentration estimation unit 152b estimates the hydrogen concentration in the crankcase 19 based on the operating state for a predetermined period in the past, going back from the current time (step S14). On the other hand, if a request to stop the internal combustion engine 10 has not been issued in step S12, the processing for this control cycle ends. Note that in step S14, if ventilation of the crankcase 19 was performed in the previous control cycle, the hydrogen concentration estimation unit 152b estimates the hydrogen concentration in the crankcase 19 by subtracting the hydrogen ventilation amount calculated in the previous step S21 from the hydrogen concentration in the previous step S14.

[0071] After step S14, the processor 152 determines whether the hydrogen concentration estimated in step S14 is above a predetermined value (step S16). If the hydrogen concentration is above the predetermined value, the processor continues to operate the internal combustion engine 10 without stopping it at this point (step S18).

[0072] Next, the ventilation control unit 152c of the processor 152 determines ventilation conditions such as the negative pressure in the intake manifold 29 and the ventilation time, based on the hydrogen concentration in the crankcase 19 estimated in step S14 (step S20). Next, if ventilation in the crankcase 19 was performed in the previous control cycle, the ventilation control unit 152c calculates the amount of hydrogen ventilation from the previous control cycle to the current control cycle. The amount of hydrogen ventilation is the change in hydrogen concentration, which can be determined by applying, for example, the hydrogen concentration estimated at the time the engine stop request was issued, the negative pressure in the intake manifold 29 during ventilation, and the elapsed time from the previous control cycle to the current control cycle to the map in Figure 4. Alternatively, the amount of hydrogen ventilation (change in hydrogen concentration) may be a value experimentally determined in relation to the negative pressure in the intake manifold 29 during ventilation, engine speed, etc. Next, the ventilation control unit 152c performs ventilation in the crankcase 19 according to the ventilation conditions determined in step S20 (step S22).

[0073] If the hydrogen concentration is below a predetermined value in step S16, the ventilation control unit 152c of the processor 152 stops ventilation in the crankcase 19 if ventilation was performed in the previous control cycle (step S24). If ventilation in the crankcase 19 was not performed in the previous control cycle, the ventilation is kept stopped. Next, the engine stop unit 152d of the processor 152 stops the internal combustion engine 10 (step S26).

[0074] As described above, according to this embodiment, the hydrogen concentration in the crankcase 19 after the engine is stopped is reduced. Therefore, when the oil filler cap is opened after the engine is stopped, hydrogen is prevented from escaping to the outside, and a false alarm is prevented from occurring even though there is no abnormality such as hydrogen leaking from the internal combustion engine 10. [Explanation of symbols]

[0075] 10 Internal combustion engine 19 Crankcase 20 Intake pipe 32 Suction path 35 PCV passage 41 Connecting passage 42 Bypass passage 100 Internal Combustion Engine Systems ECU 150 152 processors 152a Operating status acquisition unit 152b Hydrogen concentration estimation unit 152c Ventilation Control Unit 152d Engine Stop Section

Claims

1. When stopping an internal combustion engine that burns hydrogen, a hydrogen concentration estimation unit estimates the hydrogen concentration in the crankcase before the engine stops, A ventilation control unit ventilates the crankcase before engine shutdown under ventilation conditions corresponding to the estimated hydrogen concentration, and discharges the hydrogen-containing gas from the crankcase into the intake system gas through a ventilation passage connecting the crankcase and the intake passage. An engine stop unit that stops the internal combustion engine after ventilation of the crankcase, Equipped with, The ventilation control unit is a control device for an internal combustion engine that increases the negative pressure in the intake manifold to ventilate the crankcase as the operating state of the internal combustion engine during a predetermined period before the engine stop request is high load and high rotation speed.

2. The control device for an internal combustion engine according to claim 1, wherein the ventilation control unit ventilates the inside of the crankcase after an engine stop request has been issued but before the engine has been stopped.

3. The control device for an internal combustion engine according to claim 1 or 2, wherein the ventilation control unit ventilates the inside of the crankcase for a period of time corresponding to the estimated hydrogen concentration.

4. The control device for an internal combustion engine according to claim 1 or 2, wherein the ventilation control unit ventilates the inside of the crankcase with a negative pressure in the intake manifold corresponding to the estimated hydrogen concentration.

5. The control device for an internal combustion engine according to claim 1 or 2, wherein the ventilation control unit ventilates the inside of the crankcase before the engine is stopped with a higher ventilation efficiency than during normal operation of the internal combustion engine.

6. The control device for an internal combustion engine according to claim 1 or 2, wherein the engine stopping unit stops the internal combustion engine when the hydrogen concentration in the crankcase, estimated by ventilation in the crankcase, falls below a predetermined value.

Images