Control device for internal combustion engine

Abstract

To prevent a piston and a cylinder wall surface from partially becoming a super cooling state.SOLUTION: An internal combustion engine 1 comprises a water injection valve 70 that injects water into an intake port 9 connected to a combustion chamber 8, and an oil jet 80 that injects lubricant onto a back surface of a piston 5. A control device 100 controls water injection by the water injection valve 70 and oil injection by the oil jet 80. When water injection is performed, the control device 100 implements control to reduce an amount of lubricant injected by oil injection compared to before the start of water injection.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] For example, Patent Documents 1 and 2 disclose internal combustion engines that use hydrogen as fuel. These internal combustion engines are equipped with a water injection valve that injects water into an intake passage connected to the combustion chamber.

[0003] The internal combustion engine described in Patent Document 3 is equipped with an oil jet that cools the piston by injecting lubricating oil onto the back surface of the piston. Incidentally, there are also oil jets that indirectly cool the piston by injecting lubricating oil onto the cylinder wall surface. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-130473 [Patent Document 2] Japanese Patent Publication No. 2022-44553 [Patent Document 3] Japanese Patent Application Laid-Open No. 2009-156186 Summary of the Invention [Problem to be solved by the invention]

[0005] However, some of the water injected into the intake passage from the water injection valve may adhere to the piston top or cylinder wall in liquid form. When the liquid water on the piston top or cylinder wall evaporates, the heat of vaporization causes a partial drop in temperature of the piston top or cylinder wall. Therefore, in an internal combustion engine that uses both water injection and oil injection, if the cooling by water injection and the cooling by oil injection overlap, the piston or cylinder wall may become partially overcooled. [Means for solving the problem]

[0006] A control device for an internal combustion engine that solves the above-mentioned problems is applied to an internal combustion engine equipped with a water injection valve that injects water into an intake passage connected to a combustion chamber and an oil jet that injects lubricating oil onto the back surface of a piston or a cylinder wall. This control device controls water injection by the water injection valve and oil injection by the oil jet. When water injection is performed, the control device controls the amount of lubricating oil injected by the oil jet to be reduced compared to before the water injection started. [Effects of the Invention]

[0007] This control device for an internal combustion engine can prevent the piston and the cylinder wall surface from becoming partially overcooled. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic diagram of an internal combustion engine according to one embodiment. [Figure 2] FIG. 2 is a diagram showing the execution area of ​​water injection. [Figure 3] FIG. 3 is a diagram showing an execution region of oil injection. [Figure 4] 4 is a flowchart showing a procedure of a process executed by the control device of the embodiment. [Figure 5] 5A is a timing chart showing the state of oil injection and water injection in the embodiment, where Fig. 5A shows the transition of engine output, Fig. 5B shows the state of oil injection, and Fig. 5C shows the amount of water injection. DETAILED DESCRIPTION OF THE INVENTION

[0009] An embodiment of a control device for an internal combustion engine will be described below with reference to FIGS. <Configuration of an internal combustion engine> As shown in Fig. 1, a cylinder 4 is provided in a cylinder block 2 of an internal combustion engine 1. A piston 5 is provided in the cylinder 4, and the piston 5 is connected to a crankshaft 7 via a connecting rod 6.

[0010] A cylinder head 3 is attached to the top of the cylinder block 2. A combustion chamber 8 is formed in each cylinder 4 between the top surface of the piston 5 and the cylinder head 3. The cylinder head 3 is also provided with an in-cylinder injection valve 35 that directly injects hydrogen gas, which is the fuel for the internal combustion engine 1, into each cylinder, and a spark plug 11 that spark-ignites the air-fuel mixture in the combustion chamber 8, for each cylinder of the internal combustion engine 1.

[0011] The cylinder head 3 is also provided with an intake port 9 and an exhaust port 10 connected to the combustion chamber 8. The intake port 9 constitutes a part of an intake passage through which intake air flows. The intake port 9 is connected to an intake passage 20 provided with a throttle valve 14 that adjusts the amount of intake air. The intake port 9 is also provided with an intake valve 12 that opens and closes the intake port 9. The cylinder head 3 is also provided with a water injection valve 70 for each cylinder of the internal combustion engine 1 that injects water into the intake port 9.

[0012] The exhaust port 10 is provided with an exhaust valve 13 that opens and closes the exhaust port 10. The exhaust port 10 is connected to an exhaust passage 30. The internal combustion engine 1 is equipped with an oil jet 80 that injects lubricating oil onto the back surface of the piston 5. Lubricating oil stored in an oil pan of the internal combustion engine 1 is pumped up by an oil pump and injected from the oil jet 80. The injection direction of the oil jet 80 is set so that the lubricating oil is injected toward a portion of the back surface of the piston 5 that is located on the exhaust port 10 side.

[0013] The oil jet 80 is equipped with a valve 81. When the valve 81 is open, oil injection is performed by injecting lubricating oil from the oil jet 80. When the valve 81 is closed, the injection of lubricating oil from the oil jet 80 is stopped, thereby stopping oil injection.

[0014] <About the control device> The control device 100 includes a CPU 110, a memory 120 in which control programs and data are stored, etc. The CPU 110 executes the programs stored in the memory 120 to perform various engine controls.

[0015] Various sensors are connected to the control device 100. For example, the control device 100 is connected to a crank angle sensor 41 that detects the rotation angle of the crankshaft 7, an air flow meter 44 that detects the intake air amount GA, and a water temperature sensor 45 that detects the coolant temperature TW, which is the temperature of the coolant after heat exchange in the internal combustion engine 1. The control device 100 is also connected to an oil temperature sensor 48 that detects the oil temperature TO, which is the temperature of the lubricating oil supplied to the oil jet 80, and an accelerator sensor 49 that detects the accelerator operation amount ACCP, which is the operation amount of the accelerator pedal.

[0016] The control device 100 calculates the engine speed NE based on the output signal Scr of the crank angle sensor 41. The control device 100 also calculates the engine load factor KL based on the engine speed NE and the intake air amount GA. The engine load factor KL represents the ratio of the current cylinder inflow air amount to the cylinder inflow air amount when the internal combustion engine 1 is operating steadily at the current engine speed NE with the throttle valve 14 fully open. The cylinder inflow air amount is the amount of air that flows into each cylinder during the intake stroke.

[0017] The control device 100 performs various engine controls, such as injection control of fuel injected from the in-cylinder injection valve 35 and ignition control of the spark plug 11. In addition, the control device 100 performs various engine controls, such as water injection control for controlling the water injection amount Qw, which is the amount of water injected from the water injection valve 70, and the injection timing of the water, and oil injection control for the oil jet 80 by controlling the opening and closing of the valve 81.

[0018] <Water injection control> The control device 100 executes a process of calculating the water injection amount Qw as one of the water injection controls.

[0019] 2, a water injection region map M1 is stored in advance in the memory 120 as information for calculating the water injection amount Qw. The water injection region map M1 represents the relationship between the engine speed NE, the required torque Tt, and the water injection amount Qw, which is the amount of water that needs to be supplied to one cylinder in one combustion cycle. The required torque Tt is the torque required by the internal combustion engine 1, which is calculated by the control device 100 based on the accelerator operation amount ACCP, etc.

[0020] In the water injection region map M1, the engine speed NE, the required torque Tt, and the water injection amount Qw basically have the following relationship: When the required torque Tt is less than a predetermined threshold value Ttref, the water injection amount Qw is "0" regardless of the engine speed NE. On the other hand, when the required torque Tt is equal to or greater than the threshold value Ttref, the water injection amount Qw is set to a value greater than "0" and corresponding to the required torque Tt and the engine speed NE in a predetermined operating region defined in advance by the required torque Tt and the engine speed NE. More specifically, when the engine output, which is the product of the required torque Tt and the engine speed NE, is high, the water injection amount Qw is set to a larger value than when the engine output is low. The operating region in which the water injection amount Qw is set to a value greater than "0" is the water injection region in which water injection is performed.

[0021] The control device 100 calculates the water injection amount Qw based on this water injection region map M1 while the engine is running, and then controls the injection of the water injector 70 so that the amount of water corresponding to the calculated water injection amount Qw is injected from the water injector 70.

[0022] The water injected by the water injection valve 70 evaporates inside the cylinder. The heat of vaporization at this time reduces the temperature inside the cylinder. Therefore, by injecting water, it is possible to suppress the occurrence of abnormal combustion such as pre-ignition and to reduce the amount of NOx generated. In the internal combustion engine 1 that uses hydrogen as fuel, the ignitability of the fuel is high. Therefore, compared to an internal combustion engine that uses fuel with low ignitability, the water injection amount Qw required to suppress the occurrence of abnormal combustion is larger.

[0023] <Oil injection control> The control device 100 executes oil injection control while the engine is running. 3, an oil injection region map M2 is stored in advance in the memory 120 as information for determining whether or not to perform oil injection. The oil injection region map M2 represents the relationship between the engine rotation speed NE, the required torque Tt, and the oil injection region in which oil injection is performed. Note that multiple oil injection region maps M2 are set for each oil temperature, and the control device 100 selects the oil injection region map M2 that corresponds to the acquired oil temperature TO.

[0024] In the oil injection region map M2, the engine speed NE, the required torque Tt, and the oil injection region basically have the following relationship: When the required torque Tt exceeds the threshold value Ttref, the control device 100 closes the valve 81 to stop and disable oil injection. On the other hand, when the required torque Tt is equal to or less than the threshold value Ttref, the control device 100 opens the valve 81 to enable oil injection in a predetermined operating region defined in advance by the required torque Tt and the engine speed NE.

[0025] In this way, the region where oil injection is performed and the region where oil injection is not performed are set with the threshold value Ttref as the boundary, so that the operating region where oil injection is performed and the operating region where water injection is performed do not overlap, i.e., oil injection and water injection are not performed simultaneously.

[0026] The execution of water injection and oil injection based on the water injection region map M1 and the oil injection region map M2 corresponds to the following control executed by the control device 100. In other words, when water injection is executed, it corresponds to control that reduces the amount of lubricating oil injected by oil injection compared to before the start of water injection. Then, the control device 100 executes control that reduces the amount of lubricating oil injected by oil injection by stopping oil injection.

[0027] <Processing performed by the control device when water injection is stopped> Figure 4 shows the procedure of the process executed by the control device 100. The control device 100 starts executing this process when the water injection that was being executed is stopped, that is, when the operating point of the internal combustion engine 1 defined by the engine speed NE and the required torque Tt falls outside the water injection region shown in Figure 2. Note that, hereinafter, step numbers are represented by numbers preceded by "S."

[0028] 2 starts, the control device 100 calculates a waiting time WT (S100). The waiting time WT is the time from when water injection is stopped until the suppression process is released, that is, the time to wait for the start of oil injection when oil injection is to be started after water injection is stopped. The control device 100 sets the waiting time WT based on the water injection amount Qw calculated during water injection and the execution time of water injection. More specifically, the waiting time WT is set so that the value of the waiting time WT increases as the water injection amount Qw increases or the execution time of water injection increases.

[0029] Next, the control device 100 determines whether the waiting time WT has elapsed since the water injection was stopped (S110). If it is determined in the process of S110 that the waiting time WT has not elapsed (S110: NO), the control device 100 repeatedly executes the process of S110 until it determines that the waiting time WT has elapsed.

[0030] In the process of S110, if it is determined that the waiting time WT has elapsed (S110: NYES), the control device 100 acquires the engine rotation speed NE and the required torque Tt (S120).

[0031] Next, the control device 100 determines whether the acquired engine speed NE and required torque Tt are within the oil injection region shown in Fig. 3 (S130). If the control device 100 determines that the acquired engine speed NE and required torque Tt are within the oil injection region (S130: YES), the control device 100 executes oil injection (S140).

[0032] Then, when the process of S140 has been executed, or when a negative determination is made in the process of S130, the control device 100 ends this process. <effect> The operation of this embodiment will be described.

[0033] The execution states of oil injection and water injection are shown in Figure 5. Figure 5(A) shows the transition of engine output, Figure 5(B) shows the execution state of oil injection, and Figure 5(C) shows the transition of the amount of water injection. The engine output increases, and at time t1, when the operating point of the internal combustion engine 1, which is defined by the engine speed NE and the required torque Tt, enters the oil injection region, oil injection is started.

[0034] Then, as the engine output continues to increase and the operating point of the internal combustion engine 1 enters the water injection region at time t2, oil injection is quickly stopped and water injection is started. In this way, by stopping oil injection at the same time as the start of water injection, the work of the oil pump is quickly reduced.

[0035] Thereafter, the engine output decreases, and at time t3, when the operating point of the internal combustion engine 1 deviates from the water injection region, the water injection amount Qw is set to "0" and water injection is stopped. Then, the waiting time WT is calculated.

[0036] At time t4, when the waiting time WT has elapsed since the water injection was stopped, if the operating point of the internal combustion engine 1, defined by the engine speed NE and the required torque Tt, is within the oil injection region, oil injection is started.

[0037] Then, at time t5, when the operating point moves out of the oil injection region, oil injection is stopped. <Effects> The effects of this embodiment will be described.

[0038] (1) When water injection is performed, control is implemented to reduce the amount of lubricating oil injected by oil injection compared to before the start of water injection. Therefore, when water injection is performed, the amount of lubricating oil injected by oil injection is reduced. Therefore, it is possible to prevent the piston 5 and the wall surface of the cylinder 4 from becoming partially supercooled due to the execution of water injection and oil injection.

[0039] (2) If the piston 5 or the wall surface of the cylinder 4 becomes partially supercooled, the temperature distribution will vary greatly and the difference in the amount of thermal deformation between parts will increase, which may cause abnormal noise such as piston slapping and increase the risk of wear on the cylinder 4. In this regard, in this embodiment, it is possible to prevent the wall surfaces of the piston 5 or the cylinder 4 from becoming partially supercooled, thereby suppressing the generation of such abnormal noise and wear on the cylinder 4.

[0040] (3) The control to reduce the amount of lubricating oil injected by oil injection is performed by stopping oil injection, so that cooling by oil injection can be reliably stopped when water injection is performed.

[0041] (4) The temperature of the piston 5 and the wall surface of the cylinder 4, which is located on the exhaust port 10 side, tends to be higher than the temperature of the wall surface of the piston 5 and the cylinder 4, which is located on the intake port 9 side. Therefore, in this embodiment, an oil jet 80 is provided that injects lubricating oil toward the back surface of the piston 5, which is located on the exhaust port side, to cool these high-temperature areas.

[0042] Here, due to the influence of penetration force and tumble flow within the cylinder, some of the water injected from the water injection valve 70 into the intake port 9 may adhere in liquid form to the top surface of the piston 5 on the exhaust port 10 side or to the wall surface of the cylinder 4 on the exhaust port 10 side. When the liquid water adhering to the top surface of the piston 5 or the wall surface of the cylinder 4 vaporizes, the temperature of the top surface of the piston 5 and the wall surface of the cylinder 4 drops due to the heat of vaporization. Therefore, when water injection is performed, the parts of the piston 5 and the wall surface of the cylinder 4 that are located on the exhaust port 10 side are likely to be cooled. Therefore, if both oil injection and water injection are performed, the parts of the piston 5 and the wall surface of the cylinder 4 that are located on the exhaust port 10 side are likely to become supercooled.

[0043] In this regard, in this embodiment, when water injection is performed, oil injection is stopped, so that the amount of lubricating oil injected from the oil jet 80 is set to "0." Therefore, it is possible to prevent the piston 5 and the wall surface of the cylinder 4 located on the exhaust port 10 side from becoming overcooled.

[0044] (5) When water injection is stopped, the piston 5 and the wall surfaces of the cylinder 4 are cooled by the water injection that was performed immediately before. Therefore, if the suppression process is immediately released and oil injection is started when water injection is stopped, there is a risk that the wall surfaces of the piston 5 and the cylinder 4 may be overcooled. In this regard, in this embodiment, after the waiting time WT has elapsed since water injection was stopped, the control that suppresses the amount of lubricating oil injected by oil injection is released and oil injection is started. Therefore, oil injection is started after the temperature of the wall surfaces of the piston 5 and the cylinder 4, which have been lowered by water injection, has risen to a certain level. Therefore, partial overcooling can be suppressed when oil injection is started after water injection is stopped.

[0045] (6) The degree of cooling of the piston 5 and the wall surfaces of the cylinder 4 by water injection is correlated with the water injection amount Qw during water injection and the execution time of water injection. Therefore, in this embodiment, the waiting time WT is set based on the water injection amount Qw and the execution time of water injection, which are correlated with the degree of cooling of the wall surfaces of the piston 5 and the cylinder 4. Therefore, the waiting time WT can be appropriately set in accordance with the degree of cooling of the piston 5 and the wall surfaces of the cylinder 4 by water injection.

[0046] (7) As described above, in an internal combustion engine 1 that uses hydrogen as fuel, the fuel has high ignitability. Therefore, a larger water injection amount Qw is required to suppress the occurrence of abnormal combustion compared to an internal combustion engine that uses fuel with low ignitability. Therefore, partial supercooling on the wall surfaces of the piston 5 and the cylinder 4 as described above is likely to occur. In this regard, in this embodiment, in such an internal combustion engine 1 that uses hydrogen as fuel, when water injection is performed, the amount of lubricating oil injected by oil injection is reduced compared to before the start of water injection. Therefore, even in an internal combustion engine 1 that is prone to partial supercooling, it is possible to suppress the occurrence of partial supercooling on the wall surfaces of the piston 5 and the cylinder 4.

[0047] <Example of change> The above embodiment can be modified as follows: The above embodiment and the following modifications can be combined with each other within the scope of technical compatibility.

[0048] In the water injection region map M1 shown in FIG. 2, the required torque Tt may be replaced with the engine load factor KL. In the oil injection region map M2 shown in FIG. 3, the required torque Tt may be replaced with the engine load factor KL.

[0049] The injection direction of the oil jet 80 may be set so that the lubricating oil is injected toward a portion of the wall surface of the cylinder 4 that is located on the exhaust port 10 side. The injection direction of the oil jet 80 may be set so that the lubricating oil is injected toward a portion of the back surface of the piston 5 or the wall surface of the cylinder 4 that is different from the portion located on the exhaust port 10 side. Even in this case, effects other than the above (4) can be obtained.

[0050] In the oil injection region, the amount of lubricating oil injected from the oil jet 80 may be adjusted by changing the opening of the valve 81 in various ways. When water injection is being performed, oil injection is stopped to reduce the amount of lubricating oil injected by oil injection. Alternatively, when water injection is being performed, oil injection may be continued while controlling the amount of lubricating oil injected from the oil jet 80 so that the amount of lubricating oil is less than that before water injection began. Even in this case, effects other than (3) above can be obtained.

[0051] Although the internal combustion engine 1 is an internal combustion engine that uses hydrogen as fuel, it may be an internal combustion engine that uses a fuel other than hydrogen. Even in this case, effects other than the above (7) can be obtained. The control device 100 includes a CPU 110 and a memory 120 and executes software processing. However, this is merely an example. The control device 100 may also include a dedicated hardware circuit (e.g., an ASIC) that processes at least part of the software processing executed in the above embodiment. That is, the control device 100 may have any of the following configurations (a) to (c): (a) a processing device that executes all of the above processing according to a program and a program storage device such as a memory that stores the program; (b) a processing device and program storage device that executes part of the above processing according to a program and a dedicated hardware circuit that executes the remaining processing; or (c) a dedicated hardware circuit that executes all of the above processing. Here, there may be multiple software circuits and dedicated hardware circuits that include a processing device and a program storage device. That is, the above processing may be executed by a processing circuit that includes at least one software circuit and one or more dedicated hardware circuits. The program storage device, i.e., computer-readable medium, includes any available medium that can be accessed by a general-purpose or dedicated computer. [Explanation of symbols]

[0052] 1...Internal combustion engine 2...Cylinder block 3...Cylinder head 4...Cylinder 5...Piston 6...Connecting rod 7...Crankshaft 8...Combustion chamber 9...Intake port 10...Exhaust port 12...Intake valve 13...Exhaust valve 14...Throttle valve 20...Intake passage 30...Exhaust passage 35...In-cylinder injection valve 41...Crank angle sensor 44...Air flow meter 45...Water temperature sensor 48...Oil temperature sensor 49...Accelerator sensor 70...Water injection valve 80...Oil jet 81...Valve 100...Control device

Claims

1. 1. A device for controlling water injection by the water injection valve and oil injection by the oil jet, which is applied to an internal combustion engine equipped with a water injection valve that injects water into an intake passage connected to a combustion chamber and an oil jet that injects lubricating oil onto a back surface of a piston or a cylinder wall, comprising: When the water injection is performed, a control is performed to reduce the amount of the lubricating oil injected in the oil injection compared to before the water injection started. Control device for internal combustion engines.

2. The oil jet injects the lubricating oil toward a portion of the rear surface of the piston that is located on the exhaust port side or a portion of the cylinder wall that is located on the exhaust port side. The control device for an internal combustion engine according to claim 1.

3. After a waiting time has elapsed since the water injection was stopped, the control for suppressing the amount of lubricating oil is released. The control device for an internal combustion engine according to claim 1.

4. The waiting time is set based on the amount of water injected during the execution of the water injection and the execution time of the water injection. The control device for an internal combustion engine according to claim 3.

5. By stopping the oil injection, the amount of lubricating oil is controlled to be reduced. The control device for an internal combustion engine according to claim 1.

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