Control device for an internal combustion engine

Abstract

A control device is adapted to an internal combustion engine provided with an oil jet that jets oil toward a back surface of a piston or an inner wall of a cylinder. The control device is provided with a processing circuit that controls an intake pressure of the internal combustion engine and an oil jet amount of the oil jet, and stops the internal combustion engine in accordance with a received instruction to stop the internal combustion engine. The processing circuit executes an intake pressure reduction process and an oil jet amount increase process with a condition that freezing of condensed water that can occur in a combustion chamber of the internal combustion engine after the stop can occur, when the instruction to stop the internal combustion engine is received. In the intake pressure reduction process, the intake pressure of the internal combustion engine is reduced. In the oil jet amount increase process, the oil jet amount of the oil jet is increased. The processing circuit stops the internal combustion engine after the intake pressure reduction process and the oil jet amount increase process are ended.

Description

Technical Field

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

[0002] As shown in Japanese Patent Application Publication No. 2018-178839, it is known that after an internal combustion engine stops, condensate accumulates in the engine's intake system, and therefore, in low outdoor temperatures, this condensate can freeze. Furthermore, this condensate accumulates not only in the engine's intake system but also in the combustion chamber. In particular, in internal combustion engines using hydrogen as fuel, condensate tends to accumulate in the combustion chamber. Summary of the Invention

[0003] If condensation buildup in the combustion chamber enters the grooves that house the piston rings, this condensation will freeze when the engine stops in low outdoor temperatures. If the condensation in the piston ring grooves freezes, it will hinder the movement of the piston rings upon the next start of the engine, preventing them from functioning properly after the engine restarts. Furthermore, if the piston rings cannot function properly, poor gas compression in the combustion chamber can occur, potentially leading to misfire.

[0004] The control device according to the first aspect of the present invention is applicable to an internal combustion engine equipped with a fuel injector that injects fuel into the back of the piston or the inner wall of the cylinder. The device includes a control unit that controls the intake pressure of the internal combustion engine and the fuel injection quantity of the fuel injector, and stops the internal combustion engine upon receiving a command to stop the internal combustion engine. Upon receiving the command to stop the internal combustion engine, the control unit performs an intake pressure reduction process and a fuel injection quantity increase process, assuming that condensate freezing may occur in the combustion chamber of the stopped internal combustion engine. The intake pressure reduction process involves reducing the intake pressure of the internal combustion engine. The fuel injection quantity increase process involves increasing the fuel injection quantity of the fuel injector. After the intake pressure reduction process and the fuel injection quantity increase process are completed, the control unit stops the internal combustion engine.

[0005] Based on the above configuration, upon receiving a command to stop the internal combustion engine, in cases where condensate freezing may occur in the combustion chamber after the engine has stopped, an intake pressure reduction process and a fuel injection quantity increase process are executed. During the intake pressure reduction process, as the intake pressure of the internal combustion engine decreases, the pressure inside the combustion chamber also decreases. Furthermore, after the intake pressure reduction process and the fuel injection quantity increase process are completed, the internal combustion engine stops. By reducing the intake pressure of the internal combustion engine through the intake pressure reduction process and increasing the fuel injection quantity from the injectors through the fuel injection quantity increase process, fuel is intentionally raised to the combustion chamber. As a result, the grooves in the piston that house the piston rings are filled with oil, and this oil mixes with the condensate entering the piston grooves. Thus, by mixing the condensate in the grooves with the oil, the freezing point of the condensate in the grooves decreases, thereby suppressing the freezing of condensate in the piston grooves when the internal combustion engine stops in low outdoor temperatures. Furthermore, it is possible to suppress piston ring malfunction caused by the freezing of condensate in the piston grooves. Attached Figure Description

[0006] Hereinafter, with reference to the accompanying drawings, the features, advantages, and technical and industrial significance of exemplary embodiments of the present invention will be described, in which the same reference numerals denote the same elements, and wherein:

[0007] Figure 1 This is a schematic diagram showing an internal combustion engine and its control device.

[0008] Figure 2 It is an enlarged representation Figure 1 A cross-sectional view near the outer peripheral surface of the piston head in an internal combustion engine.

[0009] Figure 3 It means to make Figure 1 A flowchart showing the sequence of autonomous operation and shutdown of an internal combustion engine.

[0010] Figure 4 It is a time series graph showing the cumulative changes in cooling water temperature and fuel injection quantity over time. Detailed Implementation

[0011] The following is for reference. Figures 1 to 4 An embodiment of the control device for an internal combustion engine will be described.

[0012] like Figure 1 As shown, a piston 13 is disposed within the cylinder block 12 of the internal combustion engine 11. The piston 13 is connected to the crankshaft 15 via a connecting rod 14. A cylinder head 16 is assembled at the upper end of the cylinder block 12. A combustion chamber 17 is formed between the cylinder block 12, the piston 13, and the cylinder head 16 in the internal combustion engine 11.

[0013] The cylinder head 16 is equipped with an in-cylinder injection valve 18 that directly injects hydrogen, the fuel of the internal combustion engine 11, into the combustion chamber 17, and a spark plug 19 that ignites the air-fuel mixture in the combustion chamber 17. The in-cylinder injection valve 18 and the spark plug 19 are controlled by the control device 32 of the internal combustion engine 11.

[0014] The intake passage 20 of the internal combustion engine 11 is connected to the combustion chamber 17 via the intake port 21. A throttle valve 23 is installed in the intake passage 20 to regulate the amount of air drawn into the internal combustion engine 11. An intake valve 24 is installed on the cylinder head 16 to open or close the intake port 21. The exhaust passage 25 of the internal combustion engine 11 is connected to the combustion chamber 17 via the exhaust port 26. An exhaust valve 27 is installed on the cylinder head 16 to open or close the exhaust port 26.

[0015] The internal combustion engine 11 is equipped with a fuel injector 28 that injects oil onto the back of the piston 13. The fuel injector 28 receives oil discharged from the fuel pump 29 and injects the oil. The fuel pump 29 draws oil from the oil pan 30 of the internal combustion engine 11 and discharges it to the fuel injector 28, for example, an electric fuel pump could be considered.

[0016] The fuel injector 28 is equipped with a valve 31. When the valve 31 is open, fuel is injected from the fuel injector 28. When the valve 31 is closed, the injection of fuel from the fuel injector 28 is stopped. The fuel injected from the fuel injector 28 by opening or closing the valve 31 is controlled by the control device 32 of the internal combustion engine 11.

[0017] The injection direction of the oil from the injector 28 is set to spray towards the back of the piston 13 and the part located on the side of the exhaust port 26. In this way, by setting the injection direction of the oil from the injector 28, the oil injected from the injector 28 not only reaches the back of the piston 13, but also reaches the cylinder wall in the cylinder block 12.

[0018] Details of Piston 13

[0019] Figure 2 A magnified view shows the area near the outer circumference of the head of piston 13. For example... Figure 2 As shown, a plurality of annular grooves 35 to 37 are formed on the outer peripheral surface of the head of the piston 13. Piston rings 38 to 40 are accommodated in the annular grooves 35 to 37. The piston rings 38 to 40 contact the cylinder wall of the cylinder block 12 to suppress gas leakage from the combustion chamber 17.

[0020] Regarding control device 32

[0021] Figure 1 The control device 32 shown includes a processing circuit 33 that functions as a control unit. The processing circuit 33 includes a CPU that executes various processes according to a program and a memory that stores various programs and data. The processing circuit 33 performs various internal combustion engine controls by having the CPU execute programs stored in the memory.

[0022] Various sensors are connected to the control unit 32. For example, a crankshaft angle sensor 41 that detects the rotation angle of the crankshaft 15, an air flow meter 44 that detects the intake air volume GA, and a coolant temperature sensor 45 that detects the temperature of the coolant after heat exchange in the internal combustion engine 11, i.e., the coolant temperature TW, are all connected to the control unit 32. Furthermore, an intake air temperature sensor 48 that detects the intake air temperature THA, which is the intake air temperature of the internal combustion engine 11, and a throttle sensor 49 that detects the throttle operation amount ACCP, which is the throttle pedal operation amount, are also connected to the control unit 32. In addition, an ignition switch 50 that outputs a command signal IG for stopping or starting the internal combustion engine 11 based on the driver's operation is connected to the control unit 32.

[0023] The control unit 32 calculates the internal combustion engine speed NE based on the output signal Scr of the crankshaft angle sensor 41. Furthermore, the control unit 32 calculates the internal combustion engine load rate KL based on the internal combustion engine speed NE and the intake air volume GA. The internal combustion engine load rate KL represents the ratio of the current cylinder air volume to the total cylinder air volume when the internal combustion engine 11 is running stably with the throttle valve 23 fully open at the current internal combustion engine speed NE.

[0024] As part of various internal combustion engine controls, the control device 32 performs fuel injection control from the in-cylinder injection valve 18, spark plug 19 ignition control, and throttle valve 23 opening control. The control device 32 stops fuel injection from the in-cylinder injection valve 18 into the autonomously operating internal combustion engine 11 and stops spark plug 19 ignition, thereby stopping the autonomous operation of the internal combustion engine 11. Furthermore, by performing throttle valve 23 opening control based on the control device 32, the intake pressure of the internal combustion engine 11, in other words, the pressure downstream of the throttle valve 23 in the intake passage 20, is controlled. In addition, as part of various internal combustion engine controls, the control device 32 also controls fuel injection from the fuel injector 28 by opening or closing valve 31 and controls the fuel pump 29's discharge volume.

[0025] In the internal combustion engine 11 using hydrogen as fuel, condensate produced during fuel combustion tends to accumulate in the combustion chamber 17. Furthermore, if the condensate accumulated in the combustion chamber 17 enters the space between the outer circumference of the piston head 13 and the cylinder wall, it also enters the annular grooves 35 to 37 that house the piston rings 38 to 40 within the piston 13. If the condensate enters the annular grooves 35 to 37, it will freeze when the internal combustion engine stops in a low-temperature environment. Thus, if the condensate in the annular grooves 35 to 37 that house the piston rings 38 to 40 freezes, it will hinder the movement of the piston rings 38 to 40 after the next start of the internal combustion engine 11. Therefore, after the aforementioned start of the internal combustion engine 11, the piston rings 38 to 40 cannot function properly. Furthermore, if the piston rings 38 to 40 cannot function properly, poor gas compression may occur in the combustion chamber 17, potentially leading to misfire.

[0026] To address this situation, when the control device 32 receives a command to stop the internal combustion engine 11, it performs an intake pressure reduction process and a fuel injection quantity increase process, assuming that condensate may freeze in the combustion chamber 17 of the stopped internal combustion engine 11. The intake pressure reduction process lowers the intake pressure of the internal combustion engine. The fuel injection quantity increase process increases the fuel injection quantity from the fuel injectors 28. After the intake pressure reduction and fuel injection quantity increase processes are completed, the control device 32 stops the autonomous operation of the internal combustion engine 11.

[0027] Figure 3 This is a flowchart illustrating the sequence of actions to stop the autonomous operation of the internal combustion engine 11. The processing circuit 33 of the control device 32 begins operation when the driver turns off the ignition switch 50—in other words, when a command to stop the internal combustion engine 11 is issued. Figure 3 The series of processes shown.

[0028] The processing circuit 33 determines, based on step 101 (S101) of the series of processes, whether condensate freezing is likely to occur in the combustion chamber 17 of the stopped internal combustion engine 11. The determination of whether condensate freezing is likely to occur in the combustion chamber 17 of the stopped internal combustion engine 11 is made, for example, based on whether all the following conditions (A1) to (A3) are met.

[0029] (A1) The outdoor temperature is lower than the specified value. Furthermore, the outdoor temperature here can be, for example, the intake air temperature (THA), or a value estimated from the intake air temperature (THA). Also, regarding the specified value, as the outdoor temperature at which the aforementioned condensate may freeze after the internal combustion engine 11 stops, a value determined through prior experiments, etc., can be considered.

[0030] (A2) The cooling water temperature TW of the internal combustion engine 11 is lower than the specified value. Regarding the specified value mentioned above, the cooling water temperature at which the aforementioned condensate may freeze after the internal combustion engine 11 is stopped can be determined through prior experiments, etc.

[0031] (A3) The cumulative value of fuel injection quantity from the start of the internal combustion engine 11; in other words, the cumulative value of fuel injection quantity during the operation of the internal combustion engine 11 from the opening operation of the ignition switch 50 to the closing operation is less than a predetermined threshold. This cumulative value of fuel injection quantity is related to the heat generated during the operation of the internal combustion engine 11. Regarding this threshold, a value corresponding to the heat generated that may cause the freezing of condensate after the internal combustion engine 11 stops can be considered, determined through prior experiments, etc.

[0032] like Figure 4 As shown, if the internal combustion engine 11 starts at time T1, the coolant temperature TH gradually increases over time, and the cumulative value of the fuel injection quantity gradually increases. Furthermore, if a command to stop the internal combustion engine 11 is received at time T2, the coolant temperature TW at time T2 is used to determine whether condition (A2) is met. Additionally, the aforementioned cumulative value at time T2 is used to determine whether condition (A3) is met.

[0033] If at least one of the conditions (A1) to (A3) above is not met, it is determined that no condensate will freeze in the combustion chamber 17 of the stopped internal combustion engine 11. In this case, proceed to S104. The processing circuit 33 stops the autonomous operation of the internal combustion engine 11 by stopping fuel injection based on the in-cylinder injection valve 18 and ignition based on the spark plug 19 as the process in S104. Then, the processing circuit 33 ends the series of processes.

[0034] When all conditions (A1) to (A3) above are met, it is determined that condensate freezing may occur in the combustion chamber 17 of the stopped internal combustion engine 11. In this case, S102, equivalent to the intake pressure reduction process described above, is entered. As part of S102, the processing circuit 33 reduces the intake pressure of the internal combustion engine 11 by controlling the throttle valve 23 of the internal combustion engine 11 to the closed side. As the intake pressure decreases, the pressure in the combustion chamber 17 also decreases. Then, S103, equivalent to the fuel injection quantity increase process described above, is entered. As part of S103, the processing circuit 33 controls the fuel pump 29 to increase the fuel discharge quantity, thereby opening the valve 31 and increasing the fuel injection quantity when injecting fuel from the fuel injector 28. Then, the processing circuit 33 performs the processes described above from S104 onwards.

[0035] Next, the effects of the control device for the internal combustion engine 11 in this embodiment will be explained.

[0036] (1) Upon receiving an instruction to stop the internal combustion engine 11, if condensate freezing may occur in the combustion chamber 17 of the stopped internal combustion engine 11, an intake pressure reduction process and a fuel injection quantity increase process are performed. Furthermore, after the intake pressure reduction process and fuel injection quantity increase process are completed, the internal combustion engine 11 stops. Through the reduction of the intake pressure of the internal combustion engine 11 and the increase of the fuel injection quantity from the fuel injector 28, oil is intentionally generated to rise into the combustion chamber 17. As a result, the annular grooves 35 to 37 in the piston 13, which house the piston rings 38 to 40, are filled with oil, and this oil mixes with the condensate entering the annular grooves 35 to 37 of the piston 13. Thus, by mixing the condensate in the annular grooves 35 to 37 with the oil, the freezing point of the condensate in the annular grooves 35 to 37 decreases, thereby suppressing the freezing of condensate in the annular grooves 35 to 37 of the piston 13 when the internal combustion engine stops in a low outdoor temperature environment. Furthermore, it can suppress the functional impairment of piston rings 38 to 40 caused by the freezing of condensate in the ring grooves 35 to 37 of piston 13.

[0037] (2) Upon receiving an instruction to stop the internal combustion engine 11, condensate may freeze in the combustion chamber 17 of the stopped internal combustion engine 11 under the following conditions: Specifically, if the outdoor temperature and the coolant temperature TW are both below specified values ​​and the cumulative fuel injection quantity since the start of the internal combustion engine 11 is less than a specified threshold, condensate may freeze in the combustion chamber 17 of the stopped internal combustion engine 11. In this case, intake pressure reduction and fuel injection quantity increase processing can be accurately performed.

[0038] (3) In the intake pressure reduction process, the throttle valve 23 of the internal combustion engine 11 is controlled to be closed. As a result, the intake pressure of the internal combustion engine 11 can be effectively reduced.

[0039] (4) In the process of increasing the amount of fuel injected, the amount of fuel discharged from the fuel pump 29 can be increased by controlling the fuel pump 29, which is an electric fuel pump. As a result, the amount of fuel injected from the fuel injector 28 when the valve 31 is opened can be effectively increased.

[0040] Furthermore, the above-described embodiments can also be modified as follows. The above-described embodiments and the following modifications can be combined with each other to implement them without creating technical inconsistencies.

[0041] Alternatively, the oil pump 29 can be a mechanical oil pump driven by the internal combustion engine 11 instead of an electric oil pump. In this case, the oil pump 29 is driven by the rotation of the crankshaft 15, and oil is discharged from the oil pump 29. The oil discharge rate of the oil pump 29 increases with the increase of the internal combustion engine speed. Furthermore, the processing circuit 33 of the control device 32 controls the internal combustion engine 11 as a fuel injection quantity increase process, so that the fuel discharge rate from the oil pump 29 increases with the increase of the internal combustion engine speed. According to this configuration, the internal combustion engine speed is increased by controlling the internal combustion engine 11 in the fuel injection quantity increase process. As a result, the fuel discharge rate from the oil pump 29 can be increased, and therefore the fuel injection rate from the fuel injector 28 can be effectively increased.

[0042] • As a way to reduce intake pressure, the intake pressure of the internal combustion engine 11 is reduced by controlling the throttle valve 23 to the closed side. However, it is also possible to reduce the intake pressure of the internal combustion engine 11 by changing the opening or closing time of the intake valve 24 instead.

[0043] • To determine whether condensate freezing might occur in the combustion chamber 17 of the stopped internal combustion engine 11, all conditions (A1) to (A3) described above are checked for compliance, but the present invention is not limited thereto. For example, it is also possible to determine whether condensate freezing might occur in the combustion chamber 17 of the stopped internal combustion engine 11 based on the compliance of two of the conditions (A1) to (A3). Furthermore, it is also possible to determine whether condensate freezing might occur in the combustion chamber 17 of the stopped internal combustion engine 11 based on the compliance of only one of the conditions (A1) to (A3).

[0044] The internal combustion engine 11 does not necessarily have to use hydrogen as fuel; it can also use other fuels such as gasoline.

Claims

1. A control device for an internal combustion engine, characterized in that, The system includes a control unit adapted to an internal combustion engine equipped with a fuel injector that sprays fuel onto the back of a piston or the inner wall of a cylinder. This control unit controls the intake pressure of the internal combustion engine and the fuel injection quantity from the fuel injector, and stops the internal combustion engine upon receiving a command to stop it. When the control unit receives a command to stop the internal combustion engine, it performs an intake pressure reduction process to reduce the intake pressure of the internal combustion engine and an injection quantity increase process to increase the injection quantity of the fuel injectors, based on the condition that condensate may freeze in the combustion chamber of the stopped internal combustion engine. After the intake pressure reduction process and the injection quantity increase process are completed, the internal combustion engine is stopped.

2. The control device for an internal combustion engine according to claim 1, characterized in that, When the control unit receives a command to stop the internal combustion engine, it determines that condensate freezing may occur in the combustion chamber of the stopped internal combustion engine based on the fact that the outdoor temperature and the cooling water temperature of the internal combustion engine are both lower than the specified values ​​and the cumulative value of fuel injection since the start of the internal combustion engine is less than the specified threshold. Then, it executes the intake pressure reduction process and the fuel injection quantity increase process.

3. The control device for an internal combustion engine according to claim 1 or 2, characterized in that, The intake pressure reduction process involves controlling the throttle valve of the internal combustion engine to the closed side.

4. The control device for an internal combustion engine according to claim 1 or 2, characterized in that, The fuel injector receives fuel dispensed from the electric fuel pump and sprays the fuel. The fuel injection quantity increase process controls the electric fuel pump to increase the fuel discharge volume of the electric fuel pump.

5. The control device for an internal combustion engine according to claim 1 or 2, characterized in that, The fuel injector receives fuel from a mechanical fuel pump driven by an internal combustion engine and injects the fuel. The increased fuel injection quantity control process of the internal combustion engine increases the fuel output from the mechanical fuel pump by increasing the engine speed.

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