Control device for internal combustion engine

Abstract

When a stop request for the internal combustion engine is detected, a control device for the internal combustion engine calculates a target rotational speed such that the target rotational speed increases as the engine coolant temperature decreases. Next, in a state in which the throttle valve is fully opened, the fuel injection is continued and idling is performed until the engine rotation speed reaches the target rotation speed. Furthermore, when the engine rotation speed reaches the target rotation speed, the control device stops the fuel injection in a state in which the throttle valve is fully opened. According to the present invention, an output shaft of an internal combustion engine is rotated due to inertia to scavenge the inside of a cylinder of the internal combustion engine, so that moisture generated on the inner wall of the cylinder can be blown away, and the occurrence of misfire can be suppressed.

Description

TECHNICAL FIELD

[0001] The present application relates to a control device of an internal combustion engine. BACKGROUND

[0002] In Japanese Patent Application Publication No. 2007-64032, a control device is described that reduces the adhesion of deposits on a fuel injection valve or a spark plug by promoting scavenging at the time of stopping an internal combustion engine. The control device increases the crank speed of the internal combustion engine at the time of stopping the internal combustion engine. The control device increases the amount of fresh air introduced into the combustion chamber by increasing the throttle opening after stopping fuel injection. Thereby, scavenging can be promoted, and the adhesion of deposits on the fuel injection valve or the spark plug can be reduced. SUMMARY

[0003] In the case of an internal combustion engine that uses hydrogen gas as fuel, water is produced by the combustion of hydrogen gas, and thus moisture is contained in the burned gas. The burned gas containing moisture comes into contact with the inner wall of the cylinder, and thus the moisture contained in the burned gas is cooled and dew condensation occurs. If the moisture produced in the cylinder adheres to the spark plug, misfire can occur.

[0004] A control device of an internal combustion engine that solves the above-described problem operates an internal combustion engine that uses hydrogen gas as fuel by lean burn that burns lean mixture having an air-fuel ratio greater than a theoretical air-fuel ratio. The control device, upon detecting a stop request, executes the following steps:

[0005] calculates a target speed of an output shaft of the internal combustion engine based on the temperature of the cooling water of the internal combustion engine such that the target speed is greater in the case where the temperature of the cooling water of the internal combustion engine is low than in the case where the temperature of the cooling water of the internal combustion engine is high;

[0006] continues fuel injection and executes idling that increases the speed of the internal combustion engine until the speed of the internal combustion engine reaches the target speed in a state where the throttle is fully open; and

[0007] stops the fuel injection and rotates the output shaft of the internal combustion engine by inertia in a state where the throttle is fully open to perform scavenging in the cylinder of the internal combustion engine if the speed of the internal combustion engine reaches the target speed.

[0008] The control device of the internal combustion engine can suppress the occurrence of misfire by blowing off the moisture produced on the inner wall in the cylinder. BRIEF DESCRIPTION OF DRAWINGS

[0009] Hereinafter, features, advantages, and technical and industrial significance of exemplary embodiments of the present application will be described with reference to the accompanying drawings, in which like numerals denote like elements, and wherein:

[0010] Figure 1This is a diagram showing the control device and structure of an internal combustion engine according to one embodiment.

[0011] Figure 2 It means Figure 1 The flowchart shows the processing flow executed by the control unit of the internal combustion engine when it detects a stop request from the internal combustion engine.

[0012] Figure 3 This is an exemplary illustration diagram used to explain the contents of the mapping data used to calculate the target rotational speed [rpm].

[0013] Figure 4 This is an exemplary illustration diagram used to explain the contents of the mapping data used to calculate the fuel injection quantity [mg / st].

[0014] Figure 5 yes Figure 1 The timing diagram of the internal combustion engine control unit when it detects a stop request from the internal combustion engine. Parts (a), (b), (c) and (d) represent the state of the ignition switch, the throttle opening, the fuel injection quantity and the changes in the internal combustion engine speed, respectively. Detailed Implementation

[0015] The following is for reference. Figures 1 to 5 An embodiment of the control device for an internal combustion engine will be described.

[0016] Structure of internal combustion engine 10

[0017] First, refer to Figure 1 The structure of the internal combustion engine 10, controlled by the control device 11 of the internal combustion engine 10, will be described. The internal combustion engine 10 has multiple cylinders 12. Figure 1 Only one of the multiple cylinders 12 is shown. Combustion of the air-fuel mixture occurs in each of the multiple cylinders 12. The internal combustion engine 10 includes an intake passage 13, which is an intake path for introducing fresh air into the multiple cylinders 12, and an exhaust passage 14, which is an exhaust path for discharging exhaust gases from the cylinders 12. A piston 15 is disposed within each cylinder 12, and a combustion chamber 16 is formed above the piston 15. An in-cylinder injector 17 is disposed in the combustion chamber 16 to inject fuel for forming the air-fuel mixture. An ignition device 18 is disposed in the combustion chamber 16 to ignite the air-fuel mixture within the combustion chamber 16 by spark discharge. A throttle valve 19 is disposed in the intake passage 13. By changing the opening of the throttle valve 19, the amount of fresh air introduced into the combustion chamber 16 can be adjusted. The combustion of the air-fuel mixture in the combustion chamber 16 causes the crankshaft 20, which serves as the output shaft of the internal combustion engine 10, to rotate, thereby generating driving force for the vehicle.

[0018] The internal combustion engine 10 is controlled by a control device 11. The control device 11 has input thereinto detection results of various sensors for detecting the operating state of the internal combustion engine 10. The various sensors include an air flow meter 21, a vehicle speed sensor 22, an accelerator position sensor 23, a crank angle sensor 24, a water temperature sensor 25, and an oil temperature sensor 26.

[0019] The air flow meter 21 is a sensor that detects the intake air amount, which is the flow rate of intake air that flows through the intake passage 13. The vehicle speed sensor 22 is a sensor that detects the speed of the vehicle. The accelerator position sensor 23 is a sensor that detects the depression amount of the accelerator pedal. The crank angle sensor 24 is a sensor that detects the crank angle, which is the rotational angle of the crankshaft 20. The control device 11 calculates the engine speed, which is the number of rotations per minute of the crankshaft 20, on the basis of the crank angle. The water temperature sensor 25 is a sensor that detects the temperature of the cooling water of the internal combustion engine 10. The oil temperature sensor 26 is a sensor that detects the oil temperature, which is the temperature of the lubricating oil of the internal combustion engine 10. The control device 11 controls the fuel injection amount and the fuel injection timing of the in-cylinder injector 17, the ignition timing of the ignition device 18, the throttle opening degree, and the like on the basis of the detection results of these sensors.

[0020] A ignition switch 27 is provided on the vehicle, and is used to switch between a running power source mode in which the internal combustion engine 10 is operated, and a parking power source mode in which the internal combustion engine 10 is not operated. The switching from the parking power source mode to the running power source mode is performed in accordance with the switching of the ignition switch 27 from off to on. After the ignition switch 27 is switched from on to off, the switching from the running power source mode to the parking power source mode is performed when the processing for the switching is completed. The processing for the switching is, for example, processing for stopping the internal combustion engine 10.

[0021] Processing performed by the control device 11

[0022] Reference Figures 2 to 4 The processing performed by the control device 11 will be described.

[0023] Figure 2 The processing of the internal combustion engine 10 is the processing of scavenging the internal combustion engine 10, which is performed by the control device 11. The control device 11 performs the processing of the internal combustion engine 10 when a stop request of the internal combustion engine 10 is detected. Figure 2 The stop request of the internal combustion engine 10 is output, for example, when the driver switches the ignition switch 27 from on to off.

[0024] As described above, the processing of the internal combustion engine 10 is the processing of scavenging the internal combustion engine 10, which is performed by the control device 11. Figure 2As shown, if a stop request from the internal combustion engine 10 is detected, the control device 11 first executes the process S1. In S1, the control device 11 calculates the target speed of the crankshaft 20. Specifically, the control device 11 calculates the target speed based on the coolant temperature at the time of stop and the coolant temperature at the time of start. The coolant temperature at the time of stop is the temperature of the internal combustion engine coolant when the control device 11 detects the stop request. The coolant temperature at the time of start is the temperature of the internal combustion engine coolant when the internal combustion engine 10 is started. When starting the internal combustion engine 10, the control device 11 stores the coolant temperature at the time of start.

[0025] The control device 11 pre-stores mapping data for calculating the target speed based on the water temperature at the time of stopping and the water temperature at the time of starting. The control device 11 uses the mapping data to calculate the target speed based on the water temperature at the time of stopping and the water temperature at the time of starting.

[0026] like Figure 3 As shown, the mapping data is designed such that the target speed calculated when the water temperature is low at the time of shutdown is greater than the target speed calculated when the water temperature is high at the time of shutdown. Furthermore, the mapping data is designed such that the target speed calculated when the water temperature is low at the time of startup is greater than the target speed calculated when the water temperature is high at the time of startup.

[0027] If the target rotational speed is calculated, then as follows: Figure 2 As shown, control device 11 initiates process S2. In S2, control device 11 calculates the fuel injection quantity during idling, as described later. Specifically, control device 11 calculates the fuel injection quantity based on the current internal combustion engine speed and oil temperature. The oil temperature is detected by oil temperature sensor 26. That is, the oil temperature represents the temperature of the lubricating oil in the internal combustion engine 10. The internal combustion engine speed is the speed of the internal combustion engine at the time of executing process S2.

[0028] The control device 11 stores pre-contained mapping data for calculating the fuel injection quantity during idling based on the internal combustion engine speed and oil temperature. In the processing of S2, the control device 11 uses the mapping data and calculates the fuel injection quantity during idling based on the current internal combustion engine speed and oil temperature.

[0029] like Figure 4 As shown, the mapping data is designed such that the fuel injection quantity calculated at low engine speeds is greater than the fuel injection quantity calculated at high engine speeds. Furthermore, the mapping data is designed such that the fuel injection quantity calculated at low oil temperatures is greater than the fuel injection quantity calculated at high oil temperatures.

[0030] If the fuel injection quantity is calculated, the control device 11 causes the processing to proceed to S3.

[0031] In S3, the control device 11 determines whether the internal combustion engine coolant temperature is lower than a predetermined temperature. The predetermined temperature is set based on the dew point temperature so that if the internal combustion engine coolant temperature is above the predetermined temperature, it can be determined that there is no moisture adhering to the inner wall of the cylinder 12. For example, the predetermined temperature is set to a temperature higher than the dew point temperature.

[0032] If the internal combustion engine coolant temperature is above a predetermined temperature (S3: No), the control device 11 does not perform idling and proceeds to S7. In this case, the control device 11 stops fuel injection in S7, thereby ending the series of processes. If fuel injection is stopped, the internal combustion engine 10 subsequently stops.

[0033] On the other hand, if the internal combustion engine coolant temperature is lower than a predetermined temperature (S3: Yes), the control device 11 causes the process to proceed to S4. In this case, in S4, the control device 11 fully opens the throttle valve 19. If the throttle valve 19 is fully opened, the control device 11 causes the process to proceed to S5.

[0034] In S5, control device 11 performs idling. Idling refers to running the internal combustion engine 10 idle. Specifically, with the throttle fully open, control device 11 continues to inject fuel according to the fuel injection amount calculated in S2 and idles.

[0035] If idling begins in S5, the control device 11 causes the processing to proceed to S6.

[0036] In S6, the control device 11 determines whether the internal combustion engine speed is above the target speed.

[0037] If the internal combustion engine speed is lower than the target speed (S6: No), the control device 11 returns the process to S5. Then, the control device 11 continues to idle until the internal combustion engine speed reaches the target speed.

[0038] On the other hand, if the internal combustion engine speed reaches the target speed (S6: Yes), the control device 11 initiates the process in S7. In this case, in S7, the control device 11 stops fuel injection. Thus, idling ends. At this time, the throttle valve 19 remains fully open. Due to the cessation of fuel injection, the internal combustion engine speed gradually decreases, and the internal combustion engine 10 stops. If the internal combustion engine 10 stops, the power mode is switched to parking mode, and power supply is not possible, so the throttle valve 19 becomes fully closed.

[0039] The function of this implementation method

[0040] like Figure 5 As shown in part (a), if the ignition switch 27 switches from on to off at time T0, a stop request is output. Control device 11 detects the stop request and begins reference...Figure 2 The series of processes explained above. Then, as shown in Figure 5 (b) and (c) of FIG. 10, in a state where the throttle valve 19 is fully opened, the control device 11 continues to inject fuel with the calculated fuel injection amount and executes idling.

[0041] As shown in (d) of FIG. 10, if the control device 11 executes idling, the engine speed rises. If the engine speed reaches the target speed at time Tl, the control device 11 stops fuel injection as shown in (c) of FIG. 10. As shown in (d) of FIG. 10, if fuel injection is stopped at time Tl, the engine speed gradually decreases. If the engine 10 is stopped at time T2, the throttle valve 19 becomes fully closed as shown in (b) of FIG. 10. Figure 5 Figure 5 Figure 5 Figure 5

[0042] In the case where the engine cooling water temperature is low, the temperature of the inner wall in the cylinder 12 becomes low, and therefore the amount of moisture generated on the inner wall in the cylinder 12 due to the combustion of hydrogen gas increases. That is, the amount of moisture to be blown away by scavenging increases. Therefore, the control device 11, upon detecting a stop request, calculates the target speed so that the lower the engine cooling water temperature, the higher the target speed.

[0043] Then, in a state where the throttle valve 19 is fully opened, the control device 11 continues fuel injection and executes idling until the engine speed reaches the target speed. Thereby, the air resistance acting on the fresh air introduced into the combustion chamber 16 becomes small. As a result, air is easily introduced into the combustion chamber 16, and therefore the output shaft of the engine 10 can be easily rotated. Therefore, the amount of fuel required until the target speed is reached can be reduced. Also, the time required to rotate the output shaft of the engine 10 can be shortened.

[0044] Furthermore, the control device 11, upon the engine speed reaching the target speed, stops fuel injection in a state where the throttle valve 19 is fully opened. Then, based on the engine speed at the time of fuel injection stop, the output shaft of the engine 10 rotates due to inertia. At this time, by fully opening the throttle valve 19, fresh air is introduced into the combustion chamber 16, thereby scavenging the inside of the cylinder 12.

[0045] Effects of the present embodiment

[0046] (1) The control device 11 makes the engine speed rise higher and then stops fuel injection, the lower the engine cooling water temperature and the more the amount of moisture estimated to be required to be blown away by scavenging. Also, during idling and the subsequent scavenging, the throttle valve 19 is fully opened. As a result, the moisture generated on the inner wall in the cylinder 12 can be blown away, and therefore the occurrence of misfire can be suppressed. ​​​​

[0047] (2) When the control device 11 detects a stop request, it stops fuel injection without idling if the internal combustion engine coolant temperature is above a predetermined temperature set based on the dew point temperature. When the internal combustion engine coolant temperature is above the predetermined temperature set based on the dew point temperature, the temperature of the inner wall of the cylinder 12 is also above the predetermined temperature. At this time, even if hydrogen is burned, the temperature of the inner wall of the cylinder 12 is high, so no moisture is generated on the inner wall of the cylinder 12. Therefore, by stopping fuel injection without idling when the internal combustion engine coolant temperature is above the predetermined temperature, unnecessary scavenging can be prevented.

[0048] (3) Figure 3 As shown, the control device 11 calculates the target speed based on the coolant temperature at startup and the coolant temperature at rest, ensuring that the target speed is higher when the coolant temperature is low at startup than when the coolant temperature is high at startup. The coolant temperature at startup is the temperature of the cooling water in the internal combustion engine 10 when it starts. Not only the coolant temperature at rest, but also the coolant temperature at startup affects the temperature of the inner wall of the cylinder 12. That is, when the coolant temperature is low at startup, the temperature of the inner wall of the cylinder 12 is also low. Therefore, when the coolant temperature is low at startup, the amount of water generated on the inner wall of the cylinder 12 due to hydrogen combustion also increases. At this time, by calculating a higher target speed, the scavenging function is enhanced. As a result, a large amount of water generated on the inner wall of the cylinder 12 can be blown away, thus suppressing misfires.

[0049] (4) Upon detecting a stop request, the control device 11 calculates the fuel injection quantity, ensuring that the fuel injection quantity is greater when the internal combustion engine speed is low than when the internal combustion engine speed is high, and then performs idling. The greater the fuel injection quantity, the greater the increase in internal combustion engine speed per unit time. When the internal combustion engine speed is low at the time the stop request is detected, the difference between the target speed and the target speed becomes larger. Therefore, by increasing the increase in internal combustion engine speed per unit time, the time until the internal combustion engine speed reaches the target speed can be shortened. Thus, the time until scavenging is completed can be shortened.

[0050] (5) Figure 4 As shown, the control device 11 calculates the fuel injection quantity, ensuring that the fuel injection quantity is greater at low oil temperatures than at high oil temperatures. At low oil temperatures, the engine oil viscosity is high, thus increasing the energy required for the internal combustion engine to reach the target speed. By increasing the fuel injection quantity at low oil temperatures, the control device 11 increases the energy supply per unit time. As a result, the time required for the internal combustion engine to reach the target speed is shortened. Therefore, the time required to complete scavenging is also shortened.

[0051] Change Example

[0052] This embodiment can be implemented in the following manner. This embodiment and the following modified examples can be implemented in combination with each other within a range that does not contradict in technology.

[0053] Upon detection of the stop request, the control device 11 can calculate the target rotation speed based on the engine coolant temperature such that the target rotation speed in the case where the engine coolant temperature is low is greater than the target rotation speed in the case where the engine coolant temperature is high. An example is shown in which the control device 11 calculates the target rotation speed based on the stop-time water temperature and the start-time water temperature, but for example, a configuration can be adopted in which the control device 11 calculates the target rotation speed based on only the stop-time water temperature without referring to the start-time water temperature.

[0054] An example is shown in which, upon detection of the stop request, the control device 11 calculates the fuel injection amount at the time of idling based on the engine rotation speed and the oil temperature. In contrast to this, a configuration in which the control device 11 calculates the fuel injection amount at the time of idling based on the engine rotation speed and the oil temperature is not necessarily required. For example, a configuration can be adopted in which the control device 11 calculates the fuel injection amount at the time of idling based on only the engine rotation speed without referring to the oil temperature. For example, a configuration can be adopted in which the control device 11 calculates the fuel injection amount at the time of idling based on only the oil temperature without referring to the engine rotation speed. For example, a process in which the control device 11 calculates the fuel injection amount at the time of idling can be omitted, and a configuration can be adopted in which the control device 11 performs idling with a fuel injection amount that is set in advance at the time of design.

[0055] An example is shown in which, in the case where the engine coolant temperature is equal to or higher than a predetermined temperature, the control device 11 does not perform idling but directly stops the fuel injection and stops the engine 10. In contrast to this, a configuration can be adopted in which the control device 11 always performs idling after scavenging and stops the engine 10 without referring to the engine coolant temperature.

[0056] The engine 10 can be an engine provided with the throttle valve 19. For example, the engine 10 can be an engine that uses gasoline as fuel. For example, the engine 10 can be an engine that uses a mixed fuel obtained by mixing gasoline and alcohol fuel as fuel. For example, the engine 10 can be an engine that uses hydrogen as fuel. In particular, in the engine that uses hydrogen as fuel, water is generated due to combustion of hydrogen, and therefore, if the control device 11 as described above is applied, it is particularly effective.

[0057] The vehicle can be a vehicle that mounts only the engine 10 as a driving force source. The vehicle can be a hybrid electric vehicle that mounts, in addition to the engine 10, a motor as a driving force source. The vehicle can be an electrified vehicle that mounts the engine 10 for power generation and uses only the motor as a driving force source.

Claims

1. A control device for an internal combustion engine, which operates a hydrogen-fueled internal combustion engine through lean combustion, wherein the lean combustion results in the combustion of a lean mixture with an air-fuel ratio greater than the stoichiometric air-fuel ratio, the control device being characterized in that... Upon detecting a stop request, perform the following steps: The target rotational speed of the output shaft of the internal combustion engine is calculated based on the internal combustion engine cooling water temperature, such that the target rotational speed when the internal combustion engine cooling water temperature is low is greater than the target rotational speed when the internal combustion engine cooling water temperature is high. With the throttle fully open, fuel injection continues and idling is performed, which causes the internal combustion engine speed to increase until the internal combustion engine speed reaches the target speed; and If the internal combustion engine reaches the target speed, fuel injection is stopped and the output shaft of the internal combustion engine is rotated due to inertia with the throttle fully open to scavenge the cylinders of the internal combustion engine.

2. The control device for an internal combustion engine according to claim 1, characterized in that, Upon detecting the stop request, if the internal combustion engine coolant temperature is above a predetermined temperature set based on the dew point temperature, the idling is not performed and fuel injection is stopped.

3. The control device for an internal combustion engine according to claim 1, characterized in that, The target speed is calculated based on the water temperature at the time of stopping and the water temperature at the time of starting, such that the target speed when the water temperature at the time of starting is low is greater than the target speed when the water temperature at the time of starting is high. The water temperature at the time of starting is the cooling water temperature of the internal combustion engine when the internal combustion engine starts, and the water temperature at the time of stopping is the cooling water temperature of the internal combustion engine when the stop request is detected.

4. The control device for an internal combustion engine according to any one of claims 1 to 3, characterized in that, Upon detecting the stop request, the fuel injection quantity is calculated such that the fuel injection quantity at low engine speed is greater than the fuel injection quantity at high engine speed, and the idling is performed with the fuel injection quantity.

5. The control device for an internal combustion engine according to claim 4, characterized in that, The fuel injection quantity is calculated such that the fuel injection quantity is greater when the oil temperature (which is the temperature of the lubricating oil in the internal combustion engine) is low than when the oil temperature is high.

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