JP2024076657A - Control device for internal combustion engine - Google Patents

Abstract

[Problem] To provide a control device for an internal combustion engine capable of suppressing the hydrogen concentration remaining in the crankcase after the engine is stopped. [Solution] A processor 152 of an ECU 150 includes a hydrogen concentration estimation unit 152b that estimates the hydrogen concentration in the crankcase 19 before the engine is stopped when stopping an internal combustion engine 10 that burns hydrogen, a ventilation control unit 152c that ventilates the crankcase 19 before the engine is stopped under ventilation conditions corresponding to the estimated hydrogen concentration, and exhausts hydrogen-containing gas in the crankcase 19 into the gas in the intake system through a ventilation passage connecting the crankcase 19 and the intake passage, and an engine stop unit 152d that stops the internal combustion engine 10 after ventilation of the crankcase 19. [Selected Figure] Figure 3

Description

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

It is known that hydrogen gas leaking from the combustion chamber into the crankcase is purged by supplying an inert gas into the crankcase in response to the detection value of a hydrogen concentration sensor, thereby suppressing deterioration of lubricating oil and hydrogen embrittlement of parts due to accumulation of hydrogen gas (Patent Document 1).

JP 2006-077639 A

However, with the technology described in the above patent document, the purge stops when the engine is stopped, so there is a problem that hydrogen remains in the crankcase when the engine is stopped. If hydrogen remains in the crankcase when the engine is stopped, there is a possibility that the hydrogen will escape to the outside when the oil filler cap is opened after the engine is stopped to refill the oil, for example. In this case, if a hydrogen sensor installed in the engine compartment detects hydrogen, it may erroneously detect an abnormality even though no abnormality that would cause hydrogen to leak from the internal combustion engine has occurred.

In view of the above problems, the objective of this disclosure is to provide a control device for an internal combustion engine that can keep the hydrogen concentration remaining in the crankcase low after the engine is stopped.

The gist of this disclosure is as follows:

(1) a hydrogen concentration estimation unit that estimates a hydrogen concentration in a crankcase before an internal combustion engine that burns hydrogen is stopped;
a ventilation control unit that ventilates the crankcase before the engine is stopped under ventilation conditions corresponding to the estimated hydrogen concentration, and exhausts the hydrogen-containing gas in the crankcase into the gas in the intake system through a ventilation passage that connects the crankcase and an intake passage;
an engine stopping unit that stops the internal combustion engine after ventilating the crankcase;
A control device for an internal combustion engine comprising:

(2) The control device for an internal combustion engine described in (1) above, in which the ventilation control unit ventilates the crankcase before the engine is stopped after an engine stop request is issued.

(3) The control device for an internal combustion engine described in (1) or (2) above, in which the ventilation control unit ventilates the crankcase for a period of time corresponding to the estimated hydrogen concentration.

(4) A control device for an internal combustion engine described in any one of (1) to (3) above, in which the ventilation control unit ventilates the crankcase with a negative pressure in the intake manifold according to the estimated hydrogen concentration.

(5) A control device for an internal combustion engine described in any one of (1) to (4) above, in which the ventilation control unit ventilates the crankcase before the engine is stopped with a higher ventilation efficiency than during normal operation of the internal combustion engine.

(6) A control device for an internal combustion engine described in any one of (1) to (5) above, in which the engine stop unit stops the internal combustion engine when the hydrogen concentration in the crankcase estimated by ventilation in the crankcase falls below a predetermined value.

This disclosure provides a control device for an internal combustion engine that can keep the hydrogen concentration remaining in the crankcase low after the engine is stopped.

FIG. 1 is a schematic diagram showing a configuration of an internal combustion engine system. FIG. 2 is a schematic diagram showing the gas flow during ventilation before the internal combustion engine is stopped. FIG. 2 is a schematic diagram showing functional blocks of a processor of an ECU. 4 is a characteristic diagram showing a map used when a hydrogen concentration estimation unit estimates the hydrogen concentration in the crankcase. FIG. 4 is a characteristic diagram for explaining ventilation control performed by a ventilation control unit. FIG. FIG. 2 is a schematic diagram showing a specific example of ventilation control by a ventilation control unit. 4 is a flowchart showing a process performed by a processor of the ECU at each predetermined control period.

Several embodiments of the present invention will be described below with reference to the drawings. However, these descriptions are intended to merely exemplify 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 numbers.

Figure 1 is a schematic diagram showing the configuration of an 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 that is driven only by the driving force of the internal combustion engine 10, a hybrid automobile that includes the internal combustion engine 10 and a motor generator (MG), etc.

When the vehicle is a hybrid vehicle, the vehicle may be any type of vehicle equipped with an internal combustion engine 10 and an MG (or a motor). Thus, for example, the vehicle may be configured so that the internal combustion engine is used only for generating electricity and only the motor drives the vehicle. Also, for example, the vehicle may be configured to have two MGs: one used mainly for driving the vehicle, and the other used mainly for generating electricity.

As shown in FIG. 1, an 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 within a cylinder 16 of the cylinder block 11. A combustion chamber 17 is formed by the 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 for injecting oil, etc.

The cylinder head 12 is provided with a rotatable intake camshaft (not shown) that drives the intake valve to open and close, and an exhaust camshaft (not shown) that drives the exhaust valve to open and close. The cylinder head 12 is also provided with a fuel injection valve (not shown).

A crankcase 19 that rotatably supports the crankshaft 18 is provided at the bottom of the cylinder block 11. The oil pan 14 that stores lubricating oil is attached below the crankcase 19.

An intake manifold 29 equipped with a surge tank 60 is connected to the cylinder head 12, and an intake pipe 20 in 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 form the intake passage of the internal combustion engine 10.

In the intake pipe 20, from upstream, there are installed an air cleaner 21, an air flow meter 91, a compressor 24C of a supercharger 24 that is driven by exhaust gas from the combustion chamber 17, an intercooler 27, a pressure sensor 93, and an electric throttle valve 28.

The air cleaner 21 filters the intake air taken into the intake pipe 20, and the turbocharger 24 pressurizes (supercharges) the air taken into the intake pipe 20. The intercooler 27 cools the air after it passes through the compressor 24C, and the amount of intake air is adjusted by adjusting the opening of the throttle valve 28.

The internal combustion engine 10 is provided with a blow-by gas processing device for processing the combustion gas that leaks from the combustion chamber 17 into the crankcase 19, known as blow-by gas. This blow-by gas processing device has a suction passage 32 for directing the blow-by gas 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 the cylinder head 12, and a pre-separator 33, which separates oil, is provided midway.

The main separator 31 is connected to the surge tank 60 via a PCV (positive crankcase ventilation) valve 34, which is a differential pressure valve, 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 to the surge tank 60.

When the internal combustion engine 10 is operated 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, so the blow-by gas in the crankcase 19 is sucked into the surge tank 60 via the suction passage 32, the main separator 31, the PCV valve 34, and the PCV passage 35. The sucked blow-by gas is sent to the combustion chamber 17 together with the intake air and combusted.

The main separator 31 is also connected to an ejector 40 via a connection passage 41. The ejector 40 is provided in the middle of a bypass passage 42 that connects the intake pipe 20 upstream of the compressor 24C with the intake pipe 20 downstream of the compressor 24C. The ejector 40 is a single-stage ejector that has only one throttle section that generates negative pressure, and is provided therein with a flow control valve (not shown) that closes when the flow rate of air flowing through the bypass passage 42 reaches or exceeds a predetermined amount.

The connection passage 41 is provided with an electromagnetic valve 43 that adjusts the flow rate of blow-by gas flowing through the connection 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%" toward "100%," the opening of the electromagnetic valve 43 increases, and the flow rate of blow-by gas flowing through the connection passage 41 increases. When the opening command value Vs is "100%," the electromagnetic valve 43 is controlled to be in a fully open state.

The blow-by gas treatment device also has an air intake passage 37 for introducing air into the crankcase 19. The air intake passage 37 runs from a portion of the intake pipe 20 between the air cleaner 21 and the compressor 24C through the head cover 13, passes through the inside of the cylinder head 12 and the cylinder block 11, and is connected to the crankcase 19. An air-side separator 38, which is an oil separator installed inside the head cover 13, is provided midway along the air intake passage 37.

When the internal combustion engine 10 is operated in a supercharged state, air flows through the bypass passage 42 from the downstream side of the compressor 24C to the upstream side, so that air (ejector gas) circulates through the intake pipe 20 and the bypass passage 42, and negative pressure is generated in the internal space of the ejector 40. Then, by utilizing the negative pressure generated in the internal space of the ejector 40, the blow-by gas in the crankcase 19 is sucked into the inside of the ejector 40 through the blow-by gas passage consisting of the suction passage 32, the pre-separator 33, the main separator 31, and the connection passage 41. The blow-by gas sucked into the ejector 40 is introduced into the intake pipe 20 upstream of the compressor 24C through the bypass passage 42 together with the air. The blow-by gas introduced into the intake pipe 20 is sent to the combustion chamber 17 together with the intake air and combusted.

The ECU 150 is a component that controls the entire internal combustion engine system 100, and controls the internal combustion engine 10 by operating various devices such as the throttle valve 28, the fuel injection valve, and the solenoid valve 43. The ECU 150 is one aspect 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 arithmetic unit, a numerical arithmetic unit, or a graphic 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 necessary. The communication interface 156 has an interface circuit for connecting the ECU 150 to an in-vehicle network.

When carrying out various controls, the ECU 150 refers to the intake air volume GA detected by the air flow meter 91 and the engine speed calculated from the output signal of the crank angle sensor 92. The ECU 150 also refers to the intake air pressure detected by the pressure sensor 93. When carrying out various controls, the ECU 150 also refers to the output signal of the accelerator opening sensor 94, which detects the amount of operation of the accelerator pedal operated by the driver of the vehicle (accelerator opening), and the vehicle speed detected by the vehicle speed sensor 95.

The ECU 150 is also connected to a hydrogen sensor 96 that detects the hydrogen concentration in the engine compartment in which 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 urge him or her to stop the vehicle. This prevents the internal combustion engine 10 from being operated in a state in which hydrogen has leaked.

The throttle valve 28, solenoid valve 43, fuel injection valve, and other devices, as well as the above-mentioned various sensors of the internal combustion engine system 100, are connected to the ECU 150 via an in-vehicle network that conforms to a standard such as the Controller Area Network (CAN).

Note that, although an example in which the internal combustion engine 10 is equipped with a turbocharger 24 has been shown here, the internal combustion engine 10 does not have to be equipped with a turbocharger 24. If the internal combustion engine 10 is not equipped with a turbocharger 24, components such as the ejector 40 and the bypass passage 42 are also not required.

In the internal combustion engine system 100 configured as described above, if the internal combustion engine 10 is stopped with hydrogen remaining inside the crankcase 19, the hydrogen remaining 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 refills, etc. In this case, if the hydrogen sensor 96 detects a hydrogen concentration equal to or greater than a predetermined value, the ECU 150 may erroneously detect an abnormality even though no abnormality that would cause hydrogen to leak from the internal combustion engine 10 has occurred.

During normal operation, blow-by gas is discharged from the crankcase 19 in the manner described above. However, when the blow-by gas is discharged during normal operation, the amount of blow-by gas that is pushed out of the crankcase 19 when the piston 15 descends is basically discharged. For this reason, hydrogen may remain inside the crankcase 19 when the internal combustion engine 10 stops.

For this reason, in this embodiment, when a request to stop the internal combustion engine 10 (engine stop request) is issued, for example, when the driver stops 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.

Figure 2 is a schematic diagram showing the gas flow during ventilation before the internal combustion engine 10 is stopped. When a request to stop the internal combustion engine 10 is issued, the throttle valve 28 is closed before the internal combustion engine 10 is stopped, and the pressure in the intake manifold 29 is made negative. As a result, 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. In addition, 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 air intake passage 37. This ventilates the crankcase 19.

The gas in the crankcase 19 that flows into the intake manifold 29 is drawn into the combustion chamber 17. This causes the hydrogen that has accumulated in the crankcase 19 to burn, and the resulting exhaust gas is discharged into the exhaust manifold.

Ventilation is performed when the internal combustion engine 10 is operating in an idling state after a stop request is issued. At this time, the solenoid valve 43 is closed.

In the case of a hybrid vehicle, ventilation is performed when the internal combustion engine 10 is driven by the motor after a stop request has been issued. In this case, hydrogen is not being burned in the internal combustion engine 10, and the crankshaft 18 is rotated by motoring, so ventilation inside the crankcase 19 can be performed more efficiently.

After the crankcase 19 has been ventilated in the above manner, the internal combustion engine 10 is stopped. This prevents hydrogen from being discharged from the crankcase 19 when the filler cap is opened to refill oil, and prevents false detection of a hydrogen leak.

The hydrogen concentration in the crankcase 19 varies depending on the operating state (engine speed, load) of the internal combustion engine 10; the higher the internal combustion engine 10 is operated at higher speeds and with a higher load, the higher the hydrogen concentration in the crankcase 19. For this reason, the hydrogen concentration in the crankcase 19 is predicted according to the operating state 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 the amount of fuel injected.

During ventilation, the throttle valve 28 is narrowed further, which increases the negative pressure in the intake manifold 29 and causes a larger amount of gas to flow from inside the crankcase 19 into the intake manifold 29. This shortens the ventilation time.

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 performed reliably in the minimum time required.

Figure 3 is a schematic diagram showing the functional blocks of the processor 152 of the ECU 150 for implementing the above-mentioned processing. The processor 152 of the ECU 150 has 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 units of the processor 152 is a functional module realized by, for example, a computer program running on the processor 152. In other words, the functional blocks of the processor 152 are composed of the processor 152 and a program (software) for making it function. The program may be recorded in the memory 154 of the ECU 150 or in a recording medium connected from the outside. Alternatively, each of these units of the processor 152 may be a dedicated arithmetic circuit provided in the processor 152.

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

When the internal combustion engine 10 is stopped, the hydrogen concentration estimation unit 152b of the processor 152 estimates the hydrogen concentration in the crankcase 19 before the engine is stopped. Specifically, the hydrogen concentration estimation unit 152b estimates the hydrogen concentration in the crankcase 19 at the time when 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. FIG. 4 is a characteristic diagram showing a map used when the hydrogen concentration estimation unit 152b estimates the hydrogen concentration in the crankcase 19. FIG. 4 shows a characteristic C1 for estimating the hydrogen concentration when the internal combustion engine 10 is operated at high speed and high load immediately before being stopped, and a characteristic C2 for estimating the hydrogen concentration when the internal combustion engine 10 is operated at low speed and low load immediately before being stopped.

If the internal combustion engine 10 was operating at high revolutions and high load before it was 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 revolutions and high load to characteristic C1 in Figure 4. For example, if the internal combustion engine 10 was operating at high revolutions and high load as shown by characteristic C1 during a predetermined period (time 0 to t1) before the engine stop request was issued, the hydrogen concentration estimation unit 152b estimates that the hydrogen concentration in the crankcase 19 is d1.

In addition, if the internal combustion engine 10 was operating at low revolutions and low load before it was 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 revolutions and low load to characteristic C2 in Figure 4. For example, if the internal combustion engine 10 was operating at low revolutions and low load as shown by characteristic C2 during a predetermined period (time 0 to t1) before the engine stop request was issued, the hydrogen concentration estimation unit 152b estimates that the hydrogen concentration in the crankcase 19 is d2.

Note that the map shown in FIG. 4 is just one example, and the map used to estimate the hydrogen concentration in the crankcase 19 may further include various 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 immediately before being stopped.

The ventilation control unit 152c of the processor 152 ventilates the crankcase 19 before the engine is stopped under ventilation conditions corresponding to the hydrogen concentration estimated by the hydrogen concentration estimation unit 152b, and exhausts the hydrogen-containing gas in the crankcase 19 into the gas in the intake system through the ventilation passages (suction passage 32, PCV passage 35, connection passage 41, bypass passage 42) that connect the crankcase 19 and the intake passage. The ventilation control unit 152c may ventilate the crankcase 19 for a period of time corresponding to the estimated hydrogen concentration. The ventilation control unit 152c may also ventilate the crankcase 19 with a negative pressure in the intake manifold 29 corresponding to the estimated hydrogen concentration.

More specifically, when the hydrogen concentration estimated by the hydrogen concentration estimation unit 152b is equal to or greater than a predetermined value (e.g., 4% or greater), the ventilation control unit 152c determines ventilation conditions such as the negative pressure in the intake manifold 29 and ventilation time, and ventilates the crankcase 19 according to the ventilation conditions. When the hydrogen concentration estimated by the hydrogen concentration estimation unit 152b is within a predetermined value range (e.g., 4% or greater and 75% or less), the ventilation control unit 152c may ventilate the crankcase 19. Figure 5 is a characteristic diagram for explaining the ventilation control performed by the ventilation control unit 152c.

In the example shown in FIG. 4, when the hydrogen concentration in the crankcase 19 estimated by the hydrogen concentration estimation unit 152b is d1, the ventilation control unit 152c can perform ventilation control as shown in characteristic C3 or C4 in FIG. 5 by adjusting the opening of the throttle valve 28. Characteristic C3 shows a case where ventilation control is performed by increasing the opening of the throttle valve 28 and lowering 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 control of characteristic C3 is performed, the hydrogen concentration in the crankcase 19 reaches 0 at time t11, and ventilation is completed at time t11.

On the other hand, characteristic C4 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. When the negative pressure in the intake manifold 29 is high, it takes a relatively short time to discharge the gas in the crankcase 19 to the intake manifold 29. Therefore, when control according to characteristic C4 is performed, the hydrogen concentration in the crankcase 19 reaches 0 at time t12, which is earlier than time t11, and ventilation is completed at time t12.

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.

In the example shown in FIG. 4, when 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 FIG. 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. In this way, when the hydrogen concentration is relatively low at d2, the ventilation time is shorter than when the hydrogen concentration is relatively high at d1. Note that even when the hydrogen concentration is d2, it is possible to lengthen the ventilation time by increasing the opening of the throttle valve 28.

As described above, the ventilation control unit 152c can determine ventilation conditions such as the negative pressure and ventilation time in the intake manifold 29 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 of the throttle valve 28. On the other hand, the ventilation control unit 152c may control the negative pressure in the intake manifold 29 by controlling a valve other than the throttle valve 28 provided in the intake manifold 29. The ventilation control unit 152c may also 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.

The ventilation control unit 152c may also ventilate the crankcase 19 before the engine is stopped with a higher ventilation efficiency than during normal operation of the internal combustion engine 10. Note that ventilation efficiency refers to the amount of decrease in hydrogen concentration in the crankcase 19 per unit time. For example, the ventilation control unit 152c may ventilate the crankcase 19 before the engine is stopped by increasing the negative pressure in the intake manifold 29 compared to during normal operation. The ventilation control unit 152c may also ventilate the crankcase 19 before the engine is stopped by making the ventilation time longer than during normal operation.

When an engine stop request is issued, the engine stop unit 152d of the processor 152 stops the internal combustion engine 10. If the ventilation control unit 152c ventilates the crankcase 19 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.

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 before a stop request of the internal combustion engine 10, the hydrogen concentration in the crankcase 19, the negative pressure (intake manifold negative pressure) of the intake manifold 29 during ventilation, 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.

As shown in FIG. 6, in the operating state before a stop request is made for the internal combustion engine 10, 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." Also, as shown in parentheses in FIG. 6, the ventilation control unit 152c may control the negative pressure in the intake manifold 29 during ventilation to "large" and control the ventilation time to a shorter "medium."

Also, as shown in FIG. 6, in the operating state before a stop request for the internal combustion engine 10, if the engine speed is high, the load is low, and the operating time in this 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". Also, as shown in parentheses in FIG. 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 an even shorter "short".

Also, as shown in FIG. 6, in the operating state before a stop request for the internal combustion engine 10, if 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". Even 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". Also, as shown in parentheses in FIG. 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 an even shorter "short".

Also, as shown in FIG. 6, in the operating state before a stop request for the internal combustion engine 10, 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 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". Also, as shown in parentheses in FIG. 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" time.

As described above, the hydrogen concentration in the crankcase 19 varies depending on the operating state of the internal combustion engine 10. In order to reliably perform ventilation without considering the hydrogen concentration, it is necessary to perform long-term ventilation according to the conditions with the highest concentration, and this may result in an excessively long time being required from when an engine stop request is issued until the internal combustion engine 10 is stopped. According to this embodiment, as shown in FIG. 6, the negative pressure in the intake manifold 29 during ventilation and the ventilation time are controlled according to the hydrogen concentration in the crankcase 19, making it possible to reduce the time until the internal combustion engine 10 is stopped to the minimum necessary time.

Note that the higher the engine speed of the internal combustion engine 10 during ventilation, the higher the negative pressure in the intake manifold 29 becomes, so the higher the engine speed is, the shorter the ventilation time becomes.

Next, the processing performed by the processor 152 of the ECU 150 will be described. FIG. 7 is a flowchart showing the processing performed by the processor 152 of the ECU 150 at each predetermined control cycle. 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.

Next, the processor 152 determines whether a request to stop the internal combustion engine 10 has been issued (step S12). When 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 of time going back from the current time when the engine stop request was issued from the operating states acquired in step S10 for each control cycle. When 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 of time going back from the current time (step S14). On the other hand, when a request to stop the internal combustion engine 10 has not been issued in step S12, the processing for this control cycle ends. In addition, in step S14, when ventilation in 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.

After step S14, the processor 152 determines whether the hydrogen concentration estimated in step S14 is equal to or greater than a predetermined value (step S16), and if the hydrogen concentration is equal to or greater than the predetermined value, the processor 152 continues to operate the internal combustion engine 10 without stopping the internal combustion engine 10 at this point (step S18).

Next, the ventilation control unit 152c of the processor 152 determines ventilation conditions such as the negative pressure in the intake manifold 29 and 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 hydrogen ventilation amount from the previous control cycle to the current control cycle. The hydrogen ventilation amount is, for example, the amount of change in hydrogen concentration calculated by applying the hydrogen concentration estimated at the time when 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 FIG. 4. In addition, the hydrogen ventilation amount (amount of change in hydrogen concentration) may be a value experimentally determined according to the relationship with the negative pressure in the intake manifold 29 during ventilation, the 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).

If the hydrogen concentration is less than the predetermined value in step S16, the ventilation control unit 152c of the processor 152 stops ventilation if ventilation was performed inside the crankcase 19 in the previous control cycle (step S24). Note that if ventilation was not performed inside the crankcase 19 in the previous control cycle, the ventilation stopped state is maintained. Next, the engine stop unit 152d of the processor 152 stops the internal combustion engine 10 (step S26).

As described above, according to this embodiment, the hydrogen concentration in the crankcase 19 after the engine is stopped is reduced. This prevents hydrogen from escaping to the outside when the oil filler cap is opened after the engine is stopped, and prevents erroneous detection of an abnormality even when no abnormality that would cause hydrogen to leak from the internal combustion engine 10 has occurred.

REFERENCE SIGNS LIST 10 Internal combustion engine 19 Crankcase 20 Intake pipe 32 Suction passage 35 PCV passage 41 Connection passage 42 Bypass passage 100 Internal combustion engine system ECU 150
152 Processor 152a Operating state acquisition unit 152b Hydrogen concentration estimation unit 152c Ventilation control unit 152d Engine stop unit

Claims (6)

a hydrogen concentration estimation unit that estimates a hydrogen concentration in a crankcase before an internal combustion engine that burns hydrogen is stopped when the engine is stopped;
a ventilation control unit that ventilates the crankcase before the engine is stopped under ventilation conditions corresponding to the estimated hydrogen concentration, and exhausts the hydrogen-containing gas in the crankcase into the gas in the intake system through a ventilation passage that connects the crankcase and an intake passage;
an engine stopping unit that stops the internal combustion engine after ventilating the crankcase;
A control device for an internal combustion engine comprising: The control device for an internal combustion engine according to claim 1, wherein the ventilation control unit ventilates the crankcase after an engine stop request is issued and before the engine is stopped. The control device for an internal combustion engine according to claim 1 or 2, wherein the ventilation control unit ventilates the crankcase for a period of time corresponding to the estimated hydrogen concentration. The control device for an internal combustion engine according to claim 1 or 2, wherein the ventilation control unit ventilates the crankcase with a negative pressure in the intake manifold according to the estimated hydrogen concentration. The control device for an internal combustion engine according to claim 1 or 2, wherein the ventilation control unit ventilates the crankcase before the engine is stopped with a higher ventilation efficiency than during normal operation of the internal combustion engine. The control device for an internal combustion engine according to claim 1 or 2, wherein the engine stop unit stops the internal combustion engine when the hydrogen concentration in the crankcase estimated by ventilation in the crankcase falls below a predetermined value.

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