Control device for internal combustion engine

Abstract

By enhancing the scavenging function when the stop request of the internal combustion engine is detected, it is possible to blow off the moisture generated on the inner wall of the cylinder and suppress the occurrence of misfire.SOLUTION: The control device 11 of the internal combustion engine 10 calculates the target rotational speed so that the lower the engine cooling water temperature is, the more the target rotational speed increases when the stop request of the internal combustion engine 10 is detected. Next, the racing is executed by continuing the fuel injection until the engine rotation speed reaches the target rotation speed in a state where the throttle valve 19 is fully opened. Further, the controller 11 stops the fuel injection in a state where the throttle valve 19 is fully opened when the engine rotational speed reaches the target rotational speed. By rotating the output shaft of the internal combustion engine 10 by inertia to scavenge the inside of the cylinder 12 of the internal combustion engine 10, the moisture generated on the inner wall of the cylinder 12 can be blown off, so that the occurrence of misfire can be suppressed.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] Patent Document 1 describes a control device that reduces deposit buildup on fuel injection valves and spark plugs by promoting scavenging when the internal combustion engine is stopped. The control device increases the crank speed of the internal combustion engine when the engine is stopped. After fuel injection is stopped, the control device increases the throttle opening to increase the amount of fresh air introduced into the combustion chamber. This promotes scavenging and reduces deposit buildup on the fuel injection valves and spark plugs. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-64032 Summary of the Invention [Problem to be solved by the invention]

[0004] In internal combustion engines that use hydrogen gas as fuel, water is generated by the combustion of hydrogen gas, resulting in the burned gas containing moisture. When the burned gas containing moisture comes into contact with the inner walls of the cylinder, the moisture contained in the burned gas cools and condenses. If the moisture generated inside the cylinder adheres to the spark plug, it may cause misfires. [Means for solving the problem]

[0005] A control device for an internal combustion engine that solves the above problem operates an internal combustion engine fueled by hydrogen gas using lean combustion, which burns a lean mixture with an air-fuel ratio higher than the stoichiometric air-fuel ratio. When a stop request is detected, the control device calculates the target rotation speed based on the engine coolant temperature so that the target rotation speed is higher when the engine coolant temperature is low than when the engine coolant temperature is high, performs racing to increase the engine rotation speed until it reaches the target rotation speed by continuing fuel injection with the throttle valve fully open, and, when the engine rotation speed reaches the target rotation speed, stops fuel injection and rotates the output shaft of the internal combustion engine by inertia with the throttle valve fully open to scavenge air inside the cylinders of the internal combustion engine. [Effects of the Invention]

[0006] The control device for the internal combustion engine can suppress the occurrence of misfires by blowing away moisture that has formed on the inner walls of the cylinders. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a diagram showing the configuration of an internal combustion engine and a control device for the internal combustion engine according to one embodiment. [Figure 2] FIG. 2 is a flowchart showing the flow of processing executed by the control device for the internal combustion engine of FIG. 1 when a request to stop the internal combustion engine is detected. [Figure 3] FIG. 3 is an illustrative diagram for explaining the contents of map data for calculating the target rotation speed [rpm]. [Figure 4] FIG. 4 is an illustrative diagram for explaining the contents of map data for calculating the fuel injection amount [mg / st]. [Figure 5] FIG. 5 is a time chart showing the state of the ignition switch when the control device of the internal combustion engine in FIG. 1 detects a request to stop the internal combustion engine, and shows the transitions of (a) the state of the ignition switch, (b) the throttle valve opening, (c) the amount of fuel injection, and (d) the engine rotation speed. DETAILED DESCRIPTION OF THE INVENTION

[0008] An embodiment of a control device for an internal combustion engine will be described below with reference to FIGS. <Configuration of the internal combustion engine 10> First, with reference to FIG. 1, the configuration of the internal combustion engine 10 controlled by the control device 11 for the internal combustion engine 10 will be described. The internal combustion engine 10 has multiple cylinders 12. FIG. 1 shows only one of the multiple cylinders 12. An air-fuel mixture is combusted in each of the multiple cylinders 12. The internal combustion engine 10 also includes an intake passage 13 through which fresh air is introduced into the multiple cylinders 12, and an exhaust passage 14 through which exhaust gas is discharged from the cylinders 12. Each cylinder 12 includes a piston 15, and a combustion chamber 16 is defined above the piston 15. The combustion chamber 16 includes an in-cylinder injector 17 that injects fuel to form an air-fuel mixture. The combustion chamber 16 also includes an ignition device 18 that ignites the air-fuel mixture in the combustion chamber 16 by spark discharge. A throttle valve 19 is installed in the intake passage 13. The amount of fresh air introduced into the combustion chamber 16 can be adjusted by changing the opening of the throttle valve 19. The internal combustion engine 10 generates driving force for the vehicle by rotating a crankshaft 20, which is an output shaft of the internal combustion engine 10, through combustion of an air-fuel mixture in a combustion chamber 16.

[0009] The internal combustion engine 10 is controlled by a control device 11. Detection results of various sensors for detecting the operating conditions of the internal combustion engine 10 are input to the control device 11. 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.

[0010] The air flow meter 21 is a sensor that detects the intake air volume, which is the flow rate of intake air flowing 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 rotation angle of the crankshaft 20. The control device 11 calculates the engine rotation speed, which is the number of rotations of the crankshaft 20 per minute, based on 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. Based on the detection results of these sensors, the control device 11 controls the fuel injection volume and fuel injection timing of the in-cylinder injector 17, the ignition timing of the ignition device 18, the throttle opening, etc.

[0011] The vehicle is provided with an ignition switch 27 for switching between a driving power supply mode in which the internal combustion engine 10 is operated and a parking power supply mode in which the internal combustion engine 10 is not operated. Switching from the parking power supply mode to the driving power supply mode is performed in response to switching of the ignition switch 27 from off to on. Switching from the driving power supply mode to the parking power supply mode is performed when processing for switching is completed after switching of the ignition switch 27 from on to off. The processing for switching is, for example, processing for stopping the internal combustion engine 10.

[0012] <Processing Executed by the Control Device 11> The processing executed by the control device 11 will be described with reference to FIGS. The process in Fig. 2 is a process in which the control device 11 executes scavenging of the internal combustion engine 10. The control device 11 executes the process in Fig. 2 when it detects a request to stop the internal combustion engine 10. The request to stop the internal combustion engine 10 is output, for example, when the driver switches the ignition switch 27 from on to off.

[0013] As shown in FIG. 2, when the control device 11 detects a stop request for the internal combustion engine 10, it first executes the processing of step S1. In step S1, the control device 11 calculates a target rotation speed of the crankshaft 20. Specifically, the control device 11 calculates the target rotation speed based on the stop water temperature and the start water temperature. The stop water temperature is the temperature of the engine cooling water when the control device 11 detects the stop request. The start water temperature is the temperature of the engine cooling water when the internal combustion engine 10 is started. The control device 11 stores the start water temperature when the internal combustion engine 10 is started.

[0014] Map data for calculating the target rotation speed based on the water temperature at the time of stopping and the water temperature at the time of starting is stored in advance in the control device 11. The control device 11 calculates the target rotation speed based on the water temperature at the time of stopping and the water temperature at the time of starting using this map data.

[0015] As shown in Figure 3, this map data is designed so that the calculated target rotation speed is higher when the stop water temperature is low than when the stop water temperature is high. Moreover, this map data is designed so that the calculated target rotation speed is higher when the start water temperature is low than when the start water temperature is high.

[0016] After calculating the target rotation speed, the control device 11 proceeds to step S2 as shown in FIG. 2. In step S2, the control device 11 calculates the fuel injection amount for racing, which will be described later. Specifically, the control device 11 calculates the fuel injection amount based on the current engine rotation speed and oil temperature. The oil temperature is the oil temperature detected by the oil temperature sensor 26. In other words, the oil temperature indicates the temperature of the lubricating oil in the internal combustion engine 10. The engine rotation speed is the engine rotation speed when the processing of step S2 is executed.

[0017] Map data for calculating the fuel injection amount during racing based on the engine rotation speed and oil temperature is stored in advance in the control device 11. In the process of step S2, the control device 11 uses this map data to calculate the fuel injection amount during racing based on the engine rotation speed and oil temperature at that time.

[0018] As shown in Figure 4, this map data is designed so that the calculated fuel injection amount is larger when the engine speed is low than when the engine speed is high. In addition, this map data is designed so that the calculated fuel injection amount is larger when the oil temperature is low than when the oil temperature is high.

[0019] After calculating the fuel injection amount, the control device 11 advances the process to step S3. In step S3, the control device 11 determines whether the engine cooling water temperature is lower than a predetermined temperature. The predetermined temperature is set based on the dew point temperature so that it can be determined that no moisture is attached to the inner wall of the cylinder 12 when the engine cooling water temperature is equal to or higher than the predetermined temperature. For example, the predetermined temperature is set to a temperature higher than the dew point temperature.

[0020] If the engine cooling water temperature is equal to or higher than the predetermined temperature (step S3: NO), the control device 11 proceeds to step S7 without executing racing. In this case, the control device 11 stops fuel injection in step S7, thereby ending this series of processes. After fuel injection is stopped, the internal combustion engine 10 is stopped.

[0021] On the other hand, if the engine cooling water temperature is lower than the predetermined temperature (step S3: YES), the control device 11 proceeds to step S4. In this case, the control device 11 fully opens the throttle valve 19 in step S4. Once the throttle valve 19 is fully opened, the control device 11 proceeds to step S5.

[0022] In step S5, the control device 11 executes racing. Racing means revving the internal combustion engine 10. Specifically, the control device 11 executes racing by continuing to inject fuel at the fuel injection amount calculated in step S2 with the throttle fully open.

[0023] When racing starts in step S5, the control device 11 advances the process to step S6. In step S6, the control device 11 determines whether the engine rotation speed is equal to or higher than the target rotation speed.

[0024] If the engine rotation speed is lower than the target rotation speed (step S6: NO), the control device 11 returns the process to step S5. In this way, the control device 11 continues racing until the engine rotation speed reaches the target rotation speed.

[0025] On the other hand, when the engine rotation speed reaches the target rotation speed (step S6: YES), the control device 11 proceeds to step S7. In this case, the control device 11 stops fuel injection in step S7. This ends racing. At this time, the throttle valve 19 remains fully open. Because fuel injection is stopped, the engine rotation speed gradually decreases and the internal combustion engine 10 stops. When the internal combustion engine 10 stops, the power supply mode is switched to the parking mode, and power supply is no longer performed, so the throttle valve 19 is fully closed.

[0026] <Operation of this embodiment> As shown in Figure 5(a), when the ignition switch 27 is switched from on to off at time T0, a stop request is output. The control device 11 detects the stop request and starts the series of processes described with reference to Figure 2. Then, as shown in Figures 5(b) and 5(c), the control device 11 performs racing by continuing to inject fuel at the calculated fuel injection amount with the throttle valve 19 fully open.

[0027] As shown in FIG. 5(d), when the control device 11 executes racing, the engine rotation speed increases. When the engine rotation speed reaches the target rotation speed at time T1, the control device 11 stops fuel injection as shown in FIG. 5(c). As shown in FIG. 5(d), when fuel injection is stopped at time T1, the engine rotation speed gradually decreases. When the internal combustion engine 10 stops at time T2, the throttle valve 19 is fully closed as shown in FIG. 5(b).

[0028] When the engine cooling water temperature is low, the temperature of the inner walls of the cylinders 12 decreases, and therefore the amount of moisture generated on the inner walls of the cylinders 12 by the combustion of hydrogen gas increases. In other words, the amount of moisture that needs to be blown away by scavenging increases. Therefore, when a stop request is detected, the control device 11 calculates the target rotation speed so that the target rotation speed increases as the engine cooling water temperature decreases.

[0029] Then, the control device 11 performs racing by continuing fuel injection with the throttle valve 19 fully open until the engine rotation speed reaches the target rotation speed. This reduces the air resistance acting on the fresh air introduced into the combustion chamber 16. As a result, air is more easily introduced into the combustion chamber 16, making it easier to rotate the output shaft of the internal combustion engine 10. This reduces the amount of fuel required to reach the target rotation speed. Also, the time required to rotate the output shaft of the internal combustion engine 10 can be shortened.

[0030] Furthermore, when the engine rotation speed reaches the target rotation speed, the control device 11 stops fuel injection with the throttle valve 19 fully open. Then, the output shaft of the internal combustion engine 10 rotates by inertia based on the engine rotation speed when fuel injection is stopped. At this time, since the throttle valve 19 is fully open, fresh air is introduced into the combustion chamber 16, scavenging the inside of the cylinder 12.

[0031] <Effects of this embodiment> (1) When the engine coolant temperature is low and it is estimated that a large amount of water needs to be blown away by scavenging, the control device 11 increases the engine speed to a higher level before stopping fuel injection. Also, during racing and the subsequent scavenging, the throttle valve 19 is fully opened. As a result, water that has formed on the inner walls of the cylinder 12 can be blown away, thereby suppressing the occurrence of misfires.

[0032] (2) When the control device 11 detects a stop request, if the engine cooling water temperature is equal to or higher than a predetermined temperature set based on the dew point temperature, the control device 11 stops fuel injection without performing racing. If the engine cooling water temperature is equal to or higher than a predetermined temperature set based on the dew point temperature, the temperature of the inner wall of the cylinder 12 is also equal to or higher than the predetermined temperature. In this case, even if hydrogen gas is burned, the temperature of the inner wall of the cylinder 12 is high, so moisture is not generated on the inner wall of the cylinder 12. Therefore, if the engine cooling water temperature is equal to or higher than the predetermined temperature, unnecessary scavenging can be prevented by stopping fuel injection without performing racing.

[0033] (3) As shown in FIG. 3 , the control device 11 calculates the target rotation speed based on the stop water temperature and the start water temperature so that the target rotation speed is higher when the start water temperature, which is the engine coolant temperature at the time of starting the internal combustion engine 10, is low than when the start water temperature is high. Not only the stop water temperature but also the start water temperature affects the temperature of the inner wall of the cylinder 12. That is, when the start water temperature is low, the temperature of the inner wall of the cylinder 12 is also low. Therefore, even when the start water temperature is low, the amount of moisture generated on the inner wall of the cylinder 12 due to the combustion of hydrogen gas increases. In this case, by calculating a higher target rotation speed, the scavenging function is enhanced. As a result, more moisture generated on the inner wall of the cylinder 12 can be blown away, thereby suppressing the occurrence of misfires.

[0034] (4) When a stop request is detected, the control device 11 calculates the fuel injection amount so that the fuel injection amount is larger when the engine rotation speed is low than when the engine rotation speed is high, and executes racing. The larger the fuel injection amount, the greater the increase in engine rotation speed per unit time. If the engine rotation speed when the stop request is detected is low, the difference from the target rotation speed becomes larger. Therefore, by increasing the increase in engine rotation speed per unit time, the time until the engine rotation speed reaches the target rotation speed can be shortened. Therefore, the time until scavenging is completed can be shortened.

[0035] (5) As shown in FIG. 4, the control device 11 calculates the fuel injection amount so that it is greater when the oil temperature is low than when the oil temperature is high. When the oil temperature is low, the viscosity of the engine oil is high, so the amount of energy required for the engine rotation speed to reach the target rotation speed increases. When the oil temperature is low, the control device 11 increases the fuel injection amount, so the amount of energy supplied per unit time increases. As a result, the time required for the engine rotation speed to reach the target rotation speed can be shortened. Therefore, the time required for scavenging to be completed can be shortened.

[0036] <Example of change> This embodiment can be modified as follows: This embodiment and the following modifications can be combined and implemented within the scope of technical compatibility.

[0037] When a stop request is detected, the control device 11 may calculate the target rotation speed based on the engine coolant temperature so that the target rotation speed is higher when the engine coolant temperature is low than when the engine coolant temperature is high. Although the example in which the control device 11 calculates the target rotation speed based on the water temperature at the time of stop and the water temperature at the time of start has been shown, for example, the control device 11 may calculate the target rotation speed based only on the water temperature at the time of stop without referring to the water temperature at the time of start.

[0038] An example has been shown in which the control device 11 calculates the fuel injection amount for racing based on the engine speed and oil temperature when a stop request is detected. However, it is not essential that the control device 11 calculate the fuel injection amount for racing based on the engine speed and oil temperature. For example, the control device 11 may calculate the fuel injection amount for racing based only on the engine speed without referring to the oil temperature. For example, the control device 11 may calculate the fuel injection amount for racing based only on the oil temperature without referring to the engine speed. For example, the control device 11 may omit the process of calculating the fuel injection amount for racing, and may perform racing using a fuel injection amount predetermined at the time of design.

[0039] In the example shown, when the engine cooling water temperature is equal to or higher than a predetermined temperature, the control device 11 does not execute racing, but stops fuel injection and stops the internal combustion engine 10. However, a configuration may be adopted in which the control device 11 always executes racing, performs scavenging, and then stops the internal combustion engine 10, without referring to the engine cooling water temperature.

[0040] The internal combustion engine 10 may be any internal combustion engine equipped with a throttle valve 19. For example, the internal combustion engine 10 may be an internal combustion engine that uses gasoline as fuel. For example, the internal combustion engine 10 may be an internal combustion engine that uses a mixed fuel that is a mixture of gasoline and alcohol fuel as fuel. For example, the internal combustion engine 10 may be an internal combustion engine that uses hydrogen as fuel. In particular, application of the control device 11 described above is particularly effective for internal combustion engines that use hydrogen as fuel, because water is produced by burning the hydrogen.

[0041] The vehicle may be a vehicle equipped with only the internal combustion engine 10 as a driving force source. The vehicle may be a hybrid vehicle equipped with a motor as a driving force source in addition to the internal combustion engine 10. The vehicle may be an electric vehicle equipped with the internal combustion engine 10 for generating electricity and using a motor as a driving force source only. [Explanation of symbols]

[0042] 10...internal combustion engine, 11...control device, 12...cylinder, 13...intake passage, 14...exhaust passage, 15...piston, 16...combustion chamber, 17...in-cylinder injector, 18...ignition device, 19...throttle valve, 20...crankshaft, 21...air flow meter, 22...vehicle speed sensor, 23...accelerator position sensor, 24...crank angle sensor, 25...water temperature sensor, 26...oil temperature sensor, 27...ignition switch

Claims

1. A control device for an internal combustion engine that uses hydrogen gas as fuel and operates the engine by lean combustion, in which a lean mixture having an air-fuel ratio higher than the stoichiometric air-fuel ratio is burned, When a stop request is detected, calculating the target rotation speed based on the engine cooling water temperature such that the target rotation speed is higher when the engine cooling water temperature is low than when the engine cooling water temperature is high; executing racing to increase the engine rotation speed until the engine rotation speed reaches the target rotation speed by continuing fuel injection with the throttle valve fully open; When the engine rotation speed reaches the target rotation speed, fuel injection is stopped and the throttle valve is fully opened, and an output shaft of the internal combustion engine is rotated by inertia to scavenge the inside of a cylinder of the internal combustion engine. Run Control device for internal combustion engines.

2. When the stop request is detected, if the engine cooling water temperature is equal to or higher than a predetermined temperature set based on a dew point temperature, the racing is not performed and fuel injection is stopped. The control device for an internal combustion engine according to claim 1.

3. The target rotation speed is calculated based on a stop water temperature, which is the engine cooling water temperature at the time of detecting a stop request, and the start-up water temperature, so that the target rotation speed is larger when the start-up water temperature, which is the engine cooling water temperature at the time of starting the internal combustion engine, is low than when the start-up water temperature is high. The control device for an internal combustion engine according to claim 1.

4. When the stop request is detected, the fuel injection amount is calculated so that the fuel injection amount is larger when the engine rotation speed is low than when the engine rotation speed is high, and the racing is performed with the calculated fuel injection amount. The control device for an internal combustion engine according to any one of claims 1 to 3.

5. The fuel injection amount is calculated so that the fuel injection amount is larger when the oil temperature is low than when the oil temperature is high. The control device for an internal combustion engine according to claim 4.

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