Control device and control method for internal combustion engine

Abstract

The present application provides a control device and a control method of an internal combustion engine. The control device of the internal combustion engine is configured to execute a first injection process of causing a water injection valve to inject water during an open period of an intake valve, and a second injection process of causing the water injection valve to inject water during a close period of the intake valve. The control device is further configured to increase a pressure of water supplied to the water injection valve in the second injection process, as compared with the first injection process.

Description

Technical Field

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

[0002] Japanese Patent Application Publication No. 2017-218994 discloses an internal combustion engine and its control device. The internal combustion engine disclosed in this publication includes a cylinder, an intake passage connected to the cylinder, and a water injection valve located midway through the intake passage. Furthermore, the control device disclosed in this publication causes the water injection valve to inject water when the internal combustion engine is operating under high load. The water injected by the water injection valve flows into the cylinder through the intake passage. The water evaporates inside the cylinder. During water evaporation, the temperature inside the cylinder decreases due to the heat of vaporization. Summary of the Invention

[0003] The problem that the invention aims to solve

[0004] When water is injected from the water injection valve during the opening phase of the intake valve, which opens and closes the connection between the intake passage and the cylinder, water is supplied to the cylinder through the intake passage. However, depending on the required amount of water, sometimes the water injection valve cannot inject the required amount of water only during the opening phase of the intake valve. As a countermeasure in this case, it is considered to inject water from the water injection valve not only during the opening phase of the intake valve but also during the closing phase before the opening phase of the intake valve.

[0005] During the intake valve's closed state, the water injected by the water injection valve remains in the intake passage until the intake valve opens. During this retention period, the water sometimes adheres to the walls of the intake passage in a film. If a large amount of water adheres to the walls, the liquid film becomes thicker, and the water is difficult to evaporate from the film. If the water forming the liquid film remains in the intake passage, it may be impossible to supply the necessary amount of water to the cylinder.

[0006] Technical solutions for solving the problem

[0007] In one aspect of this disclosure, a control device for an internal combustion engine is provided. The internal combustion engine includes: a cylinder; an intake passage connected to the cylinder; a water injection valve configured to inject water into the intake passage; an intake valve configured to selectively open and close the connection between the intake passage and the cylinder; and a pressure regulating device configured to adjust the pressure of the water supplied to the water injection valve. The control device is configured to perform a first injection process in which the water injection valve injects water during the opening of the intake valve, and a second injection process in which the water injection valve injects water during the closing of the intake valve. The control device is further configured to control the pressure regulating device such that, in the second injection process, the pressure of the water supplied to the water injection valve is higher than that in the first injection process.

[0008] In another aspect of this disclosure, a control method for an internal combustion engine is provided. The internal combustion engine includes: a cylinder; an intake passage connected to the cylinder; a water injection valve configured to inject water into the intake passage; and an intake valve configured to selectively open and close a connection between the intake passage and the cylinder. The control method includes the steps of: performing a first injection process that causes the water injection valve to inject water during the opening of the intake valve; performing a second injection process that causes the water injection valve to inject water during the closing of the intake valve; and in the second injection process, increasing the pressure of the water supplied to the water injection valve compared to the first injection process. Attached Figure Description

[0009] Figure 1 This is a schematic diagram of the internal combustion engine.

[0010] Figure 2 It is a time sequence diagram showing the relationship between the jet treatment method accompanied by water jet control and the water pressure.

[0011] Figure 3 This is a flowchart illustrating the process of water jet control.

[0012] Figure 4 This is a schematic diagram of the spray range of water from the water jet valve.

[0013] Figure 5 This is a schematic diagram showing the distance the water travels from the water jet valve.

[0014] Figure 6 This is a schematic diagram illustrating a modification example of a structure related to a water jet valve. Detailed Implementation

[0015] Hereinafter, one embodiment of the present disclosure will be described with reference to the accompanying drawings.

[0016] <Overview of Internal Combustion Engines>

[0017] like Figure 1 As shown, vehicle 300 has an internal combustion engine 10. The internal combustion engine 10 is the drive source of vehicle 300.

[0018] The internal combustion engine 10 includes a cylinder block 81, multiple cylinders 11, multiple pistons 17, multiple connecting rods 19, a crankshaft chamber 83, and a crankshaft 18. Additionally, in... Figure 1Only one of the multiple cylinders 11 is shown in the diagram. The same applies to the piston 17 and connecting rod 19. There are four cylinders 11. Each cylinder 11 is a space defined within the cylinder block 81. Within the cylinder 11, the mixture of intake air (hereinafter referred to as intake air) and fuel is burned. The crankshaft chamber 83 is a space defined by the cylinder block 81 and an oil pan (not shown). The crankshaft chamber 83 is located below the cylinders 11. The crankshaft chamber 83 communicates with each cylinder 11. The crankshaft chamber 83 houses the crankshaft 18. A piston 17 is provided for each cylinder 11. The piston 17 is located within the cylinder 11. The piston 17 reciprocates within the cylinder 11. The piston 17 is connected to the crankshaft 18 via the connecting rod 19. The crankshaft 18 rotates according to the movement of the piston 17.

[0019] The internal combustion engine 10 has a cylinder head 82, multiple spark plugs 16, and multiple fuel injection valves 15. Additionally, in Figure 1 Only one of the multiple spark plugs 16 is shown in the diagram. The same applies to the fuel injection valve 15. Both the spark plug 16 and the fuel injection valve 15 are mounted on the cylinder head 82. The spark plug 16 is provided for each cylinder 11. The spark plug 16 ignites the air-fuel mixture within the cylinder 11. The fuel injection valve 15 is provided for each cylinder 11. The fuel injection valve 15 injects fuel directly into the cylinder 11 without passing through the intake passage 12 described later.

[0020] The internal combustion engine 10 has an intake passage 12 and a throttle valve 3. The intake passage 12 is a passage for introducing intake air into the cylinders 11. The intake passage 12 is connected to each cylinder 11. Specifically, the downstream portion of the intake passage 12 forms a plurality of intake ports 12A divided inside the cylinder head 82. The intake passage 12 branches into these plurality of intake ports 12A at a midway point. Furthermore, in... Figure 1 Only one of the multiple air intake ports 12A is shown in the diagram. Each air intake port 12A is provided for each cylinder 11. The air intake port 12A is connected to the cylinder 11. The throttle valve 3 is located upstream of the multiple air intake ports 12A within the intake passage 12. The throttle valve 3 adjusts the amount of intake air GA flowing in the intake passage 12.

[0021] The internal combustion engine 10 has multiple water injection valves 14. Each water injection valve 14 is provided for each cylinder 11. The water injection valve 14 is mounted on the cylinder head 82. The front end of the water injection valve 14 is located inside the intake port 12A. The water injection valve 14 injects water into the intake port 12A. The water injected by the water injection valve 14 reaches the cylinder 11 via the intake port 12A.

[0022] The internal combustion engine 10 has an exhaust passage 13. The exhaust passage 13 is a passage for discharging exhaust gas from the cylinders 11. The exhaust passage 13 is connected to each cylinder 11. The upstream portion of the exhaust passage 13 forms a plurality of exhaust ports 13A demarcated within the cylinder head 82. Figure 1Only one of the multiple exhaust ports 13A is shown in the image.

[0023] The internal combustion engine 10 has an intake valve mechanism. The intake valve mechanism includes multiple intake valves 23, multiple intake rocker arms 86, an intake camshaft 25, and an intake valve variable actuator 27. The intake valve mechanism is mounted on the cylinder head 82. Additionally, in... Figure 1 Only one of the multiple intake valves 23 is shown in the diagram. The same applies to the intake rocker arm 86. Each intake valve 23 is provided for each intake port 12A. The intake valve 23 is located at the connection between the intake port 12A and the cylinder 11. The intake valve 23 is connected to the intake camshaft 25 via the intake rocker arm 86. The intake valve 23 operates according to the rotation of the intake camshaft 25, selectively opening and closing the aforementioned connection between the intake port 12A and the cylinder 11. The rotation of the crankshaft 18 is transmitted to the intake camshaft 25. That is, the intake camshaft 25 rotates in conjunction with the crankshaft 18. The variable intake valve device 27 changes the relative rotational position (hereinafter referred to as crankshaft position) Scr of the intake camshaft 25 relative to the crankshaft 18. As a result, the opening and closing timing of the intake valve 23 changes relative to the crankshaft position Scr. The variable intake valve device 27 is, for example, an electric device driven by an electric motor.

[0024] The internal combustion engine 10 has an exhaust valve mechanism. The exhaust valve mechanism includes multiple exhaust valves 24, multiple exhaust rocker arms 87, an exhaust camshaft 26, and an exhaust valve variable actuator 28. The exhaust valve mechanism is mounted on the cylinder head 82. Additionally, in... Figure 1 Only one of the multiple exhaust valves 24 is shown in the diagram. The same applies to the exhaust rocker arm 87. Each exhaust valve 24 is provided for each exhaust port 13A. The exhaust valve 24 is located at the connection between the exhaust port 13A and the cylinder 11. The exhaust valve 24 is connected to the exhaust camshaft 26 via the exhaust rocker arm 87. The exhaust valve 24 operates according to the rotation of the exhaust camshaft 26, selectively opening and closing the aforementioned connection between the exhaust port 13A and the cylinder 11. The rotation of the crankshaft 18 is transmitted to the exhaust camshaft 26. That is, the exhaust camshaft 26 rotates in conjunction with the crankshaft 18. The exhaust valve variable device 28 changes the relative rotational position of the exhaust camshaft 26 with respect to the crankshaft position Scr. As a result, the opening and closing timing of the exhaust valve 24 opposite to the crankshaft position Scr changes. The exhaust valve variable device 28 is, for example, an electrical device driven by an electric motor.

[0025] The internal combustion engine 10 has a water supply mechanism 70. The water supply mechanism 70 includes a water tank 78, a supply passage 74, a pump 77, multiple branch passages 75, multiple return passages 79, and multiple regulating valves 76. The water tank 78 stores water. The supply passage 74 extends from the water tank 78. Branch passages 75 are provided for each water injection valve 14. Branch passages 75 branch off from the supply passage 74. Each branch passage 75 is connected to its corresponding water injection valve 14. The pump 77 is located midway through the supply passage 74. The pump 77 is an electric pump driven by an electric motor. The pump 77 pressurizes and delivers water from the water tank 78 to each branch passage 75 via the supply passage 74. Return passages 79 are provided for each branch passage 75. Return passages 79 connect the branch passage 75 to the water tank 78. Return passages 79 are passages for returning water from the branch passage 75 back to the water tank 78. Figure 1 In the diagram, the return path 79 is indicated by a dashed line. An adjusting valve 76 is provided for each return path 79. The adjusting valve 76 is located midway through the return path 79. The adjusting valve 76 is an electrically driven valve, driven by an electric motor. The adjusting valve 76 is a butterfly type. That is, the opening degree D of the adjusting valve 76 can be adjusted. Depending on the opening degree D of the adjusting valve 76, the flow area of ​​the return path 79 changes. Simultaneously, the amount of water returning to the water tank 78 via the return path 79 changes. At the same time, the pressure in the branch path 75 downstream of the connection point with the return path 79, i.e., the pressure of the water supplied to the water jet valve 14, changes. In other words, the adjusting valve 76 is a pressure regulating device that adjusts the pressure of the water supplied to the water jet valve 14. Depending on the opening degree D of each adjusting valve 76, the pressure of the water supplied to the corresponding water jet valve 14 changes. The opening degree D of the adjusting valves 76 can be adjusted independently of each other.

[0026] The internal combustion engine 10 includes a crankshaft position sensor 34, an intake camshaft position sensor 36, an exhaust camshaft position sensor 35, and an air flow meter 31. The crankshaft position sensor 34 detects the crankshaft position Scr. The intake camshaft position sensor 36 detects the rotational position CG of the intake camshaft 25. The exhaust camshaft position sensor 35 detects the rotational position CE of the exhaust camshaft 26. The air flow meter 31 is located upstream of the throttle valve 3 within the intake passage 12. The air flow meter 31 detects the amount of intake air GA flowing through its location within the intake passage 12. These sensors repeatedly send signals corresponding to the information they detect to the control device 100, which will be described later.

[0027] The internal combustion engine 10 has multiple water pressure sensors 30 and multiple opening sensors 32. Additionally, in Figure 1Only one of the multiple water pressure sensors 30 is shown in the diagram. The same applies to the opening sensor 32. A water pressure sensor 30 is provided for each branch passage 75. The water pressure sensor 30 detects the pressure (hereinafter referred to as water pressure) WP of the water supplied to the corresponding water jet valve 14. An opening sensor 32 is provided for each regulating valve 76. The opening sensor 32 detects the opening degree D of the corresponding regulating valve 76. These sensors repeatedly send signals corresponding to the information they detect to the control device 100, which will be described later.

[0028] Vehicle 300 has an accelerometer sensor 38 and a vehicle speed sensor 39. The accelerometer sensor 38 detects the amount of time the accelerometer pedal is depressed, i.e., the accelerometer operation amount ACC. The vehicle speed sensor 39 detects the vehicle speed SP of vehicle 300. These sensors repeatedly send signals corresponding to the information they detect to the control device 100, which will be described later.

[0029] <Brief Structure of the Control Device>

[0030] like Figure 1 As shown, vehicle 300 has a control device 100. The control device 100 may include processing circuitry comprising one or more processors that execute various processes according to a computer program (software). Alternatively, the control device 100 may also include processing circuitry comprising one or more dedicated hardware circuits, such as application-specific integrated circuits (ASICs), that execute at least a portion of the various processes, or processing circuitry comprising a combination of the aforementioned processors and dedicated hardware circuits. The processor includes a CPU 111 and a memory 112, such as RAM and ROM. The memory 112 stores program code or instructions configured to cause the CPU 11 to execute processes. The memory 112, i.e., computer-readable medium, includes any usable medium accessible by a general-purpose or special-purpose computer. The memory 112 includes electrically rewritable non-volatile memory.

[0031] The control unit 100 repeatedly receives detection signals from various sensors in the vehicle 300. Based on the received detection signals, the control unit 100 calculates the following parameters at any time. The control unit 100 calculates the crankshaft speed NE, i.e., the internal combustion engine speed NE, based on the crankshaft position Scr detected by the crankshaft position sensor 34. Additionally, the control unit 100 calculates the engine load rate KL based on the engine speed NE and the intake air volume GA detected by the air flow meter 31. The internal combustion engine load rate KL represents the ratio of the current cylinder air intake volume to the cylinder air intake volume when the internal combustion engine 10 is running stably with the throttle 3 fully open at the current internal combustion engine speed NE. Furthermore, the cylinder air intake volume is the amount of intake air that flows into one cylinder 11 during the intake stroke.

[0032] The control device 100 controls the internal combustion engine 10. Based on accelerator control parameters (ACC), vehicle speed (SP), engine speed (NE), and engine load rate (KL), the control device 100 performs controls related to various aspects of the internal combustion engine 10, such as fuel injection via the fuel injection valve 15, ignition timing of the spark plug 16, and adjustment of the throttle opening 3. Through such control, the control device 100 ensures the air-fuel mixture is sequentially combusted in multiple cylinders 11.

[0033] As part of the various controls of the internal combustion engine 10, the control device 100 performs controls related to the opening and closing timing of the intake valve 23 (hereinafter referred to as intake valve timing) and the opening and closing timing of the exhaust valve 24. For example, regarding the control of intake valve timing, the control device 100 performs the following processing. In this embodiment, the control device 100 processes the state where the intake valve timing is the most lagging side as an initial value of "0". Then, the control device 100 adjusts the intake valve timing by adjusting the advance of the intake valve timing from this initial value. When adjusting the intake valve timing, the control device 100 calculates a target advance amount as a target value for the advance amount of the intake valve timing based on the internal combustion engine speed NE and the internal combustion engine load rate KL, etc. Then, the control device 100 controls the intake valve variable device 27 to make the actual advance amount of the intake valve timing consistent with the target advance amount. The control device 100 pre-stores the crankshaft position Scr when the intake valve 23 of each cylinder 11 reaches the valve opening timing TS when the intake valve timing is set to the initial value. Therefore, by calculating the crankshaft position Scr that is advanced by a target advance relative to this crankshaft position Scr, the control device 100 can determine the crankshaft position Scr when the intake valve 23 reaches the valve opening timing TS under the current condition. Similarly, the control device 100 pre-stores the crankshaft position Scr when the intake valve 23 of each cylinder 11 reaches the valve closing timing TC when the intake valve timing is set to the initial value. Therefore, the control device 100 can determine the crankshaft position Scr when the intake valve 23 reaches the valve closing timing TC under the current condition. In this way, based on the crankshaft position Scr corresponding to the initial value and the target advance, the control device 100 always determines the crankshaft position Scr when the intake valve 23 of each cylinder 11 reaches the valve opening timing TS and the crankshaft position Scr when it reaches the valve closing timing TC.

[0034] <Overview of Water Jet Control>

[0035] The control device 100 is capable of performing water injection control. Water injection control is used to control the injection timing, injection quantity, and injection pressure of water from the water injection valve 14. Furthermore, in this embodiment, a combustion cycle is defined as the time from the point when the intake valve 23 closes in a specific cylinder 11 to the point when the intake valve 23 temporarily opens and then closes again. That is, as... Figure 2As shown, a combustion cycle begins with the valve closing timing TC, which is the valve closing time of the intake valve 23, and continues until it becomes the valve closing timing TCA again, which is the valve opening time of the intake valve 23. In this combustion cycle, the aforementioned cylinder 11 experiences one compression stroke, one expansion stroke, one exhaust stroke, and one intake stroke. Hereinafter, the period during which the intake valve 23 is in the closed state, i.e., from the valve closing timing TC of the intake valve 23 to the valve opening timing TS, is referred to as the valve closing period U1 of the intake valve 23. Conversely, the period during which the intake valve 23 is in the open state, i.e., from the valve opening timing TS of the intake valve 23 to the valve closing timing TCA, is referred to as the valve opening period U2 of the intake valve 23.

[0036] The control device 100 is capable of performing target calculation processing as part of water injection control. Target calculation processing is based on the operating state of the internal combustion engine 10, calculating a target value, i.e., a target injection quantity Qs, for the amount of water supplied to one cylinder 11 in one combustion cycle. The control device 100 pre-stores a target water quantity mapping M1 as information for calculating the target injection quantity Qs. The target water quantity mapping M1 represents the relationship between the internal combustion engine speed NE, the internal combustion engine load rate KL, and the amount of water to be supplied to one cylinder 11 in one combustion cycle, i.e., the required water quantity. In the target water quantity mapping M1, the engine speed NE, the engine load rate KL, and the required water quantity are essentially related as follows: When the internal combustion engine load rate KL is less than the set load rate (described later), the required water quantity is "0", regardless of the magnitude of the internal combustion engine speed NE. On the other hand, when the internal combustion engine load rate KL is greater than or equal to the set load rate, the required water quantity is greater than "0", regardless of the magnitude of the internal combustion engine speed NE. In detail, when the internal combustion engine load rate KL is above the set load rate, at a certain internal combustion engine speed NE, the higher the internal combustion engine load rate KL, the more water is required. The water injected by the water injection valve 14 evaporates inside the cylinder 11. During water evaporation, the temperature inside the cylinder 11 decreases due to the heat of vaporization. The required water volume set in the target water volume mapping M1 becomes the value that can achieve the required cooling inside the cylinder 11 according to the operating state of each internal combustion engine. In addition, the aforementioned set load rate is the minimum internal combustion engine load rate KL that needs to be reduced in temperature inside the cylinder 11 by the water supply from the water injection valve 14. The target water volume mapping M1 is created, for example, based on experiments or simulations.

[0037] The control device 100 can perform a determination process as part of the water injection control. The determination process is a process that determines whether, during the opening period U2 of the intake valve 23 in a combustion cycle, a target injection quantity Qs of water can be supplied to the cylinder 11 from the water injection valve 14. Here, the maximum amount of water that can be supplied to a cylinder 11 by water injection from the water injection valve 14 during the opening period U2 of the intake valve 23 in a combustion cycle is called the allowable injection quantity Qv. The allowable injection quantity Qv is determined based on the water pressure WP, which is the value used in the first injection process described later. In the determination process, the control device 100 determines whether the allowable injection quantity Qv is greater than or equal to the target injection quantity Qs. The control device 100 pre-stores the arrival period L as information required when calculating the allowable injection quantity Qv. The arrival period L is the length of time from the time water is injected from the water injection valve 14 to the time the water reaches the cylinder 11. The arrival period L is determined, for example, based on experiments or simulations. In this embodiment, the arrival period L is a constant value. Additionally, the control device 100 pre-stores a spray map M2 as information required for calculating the allowable spray volume Qv. Let's assume that water is sprayed from a water jet valve 14 throughout the entire spraying period at a certain water pressure WP. The amount of water sprayed by the water jet valve 14 at this time is called the sprayable volume. The sprayable volume changes depending on the spraying period. Furthermore, as mentioned above, the spraying period is the period during which water is continuously sprayed from the water jet valve 14. The spray map M2 represents the relationship between the spraying period, water pressure WP, and sprayable volume. In the spray map M2, the spraying period, water pressure WP, and sprayable volume are essentially related as follows: When viewed from a certain water pressure WP, the longer the spraying period, the greater the sprayable volume. Furthermore, when viewed from a certain spraying period, the higher the water pressure WP, the greater the sprayable volume. The spray map M2 is created, for example, based on experiments or simulations.

[0038] The control device 100 can execute a first injection process and a second injection process as part of water injection control. The first injection process is the process of causing the water injection valve 14 to inject water during the opening period U2 of the intake valve 23 in a combustion cycle. The second injection process is the process of causing the water injection valve 14 to inject water during the closing period U1 of the intake valve 23 in a combustion cycle. If the determination result of the determination process is positive, the control device 100 only performs the first injection process. In this case, the control device 100 causes the water injection valve 14 to inject the target injection quantity Qs of water during the first injection process. On the other hand, if the determination result of the determination process is negative, the control device 100, such as... Figure 2As shown, both a first spraying process and a second spraying process are performed. In this case, during the first spraying process, the control device 100 causes the water spray valve 14 to spray water at the permissible spraying amount Qv. On the other hand, during the second spraying process, the control device 100 causes the water spray valve 14 to spray water at a set spraying amount Qr. The set spraying amount Qr is the difference between the permissible spraying amount Qv and the target spraying amount Qs. Thus, if the determination result of the determination process is negative, the control device 100 causes the water spray valve 14 to spray water at the target spraying amount Qs by performing both spraying processes.

[0039] like Figure 2 As shown, the control device 100 sets different water pressures WP in the first and second spray processes. Specifically, during the execution of the first spray process, the control device 100 controls the adjusting valve 76 to make the water pressure WP a first value WP1. During the execution of the second spray process, the control device 100 controls the adjusting valve 76 to make the water pressure WP a second value WP2. The second value WP2 is higher than the first value WP1. That is, the control device 100 controls the adjusting valve 76 so that the water pressure WP is higher in the second spray process compared to the first spray process. This essentially means that the control device 100 increases the spray pressure of the water from the water spray valve 14 in the second spray process compared to the first spray process. The first value WP1 is predetermined, for example, through experimentation or simulation. The second value WP2 is predetermined, for example, through experimentation or simulation. The control device 100 stores the first value WP1 and the second value WP2 in advance. In addition, the reasons for changing the water pressure WP in the first and second spray processes are described in the "Effect" column described later. Along with describing the reasons, the values ​​of the first value WP1 and the second value WP2 are also explained. Furthermore, in this embodiment, the control device 100 maintains the water pressure WP at a first value WP1 throughout the entire execution period of the first spraying process. Additionally, the control device 100 maintains the water pressure WP at a second value WP2 throughout the entire execution period of the second spraying process.

[0040] When the control device 100 controls the water pressure WP according to each jet process as described above, it substantially changes the opening degree D of the adjusting valve 76. Now, let's assume that the pump 77 discharges water at a certain set discharge rate. This state is called the first state. The opening degree D of the adjusting valve 76 required to make the water pressure WP reach the first value WP1 in this first state is called the first opening degree D1. Furthermore, the opening degree D of the adjusting valve 76 required to make the water pressure WP reach the second value WP2 in the first state is called the second opening degree D2. Additionally, the rotational speed of the pump 77 required to make the discharge rate of the pump 77 reach the set discharge rate is called the set rotational speed. The control device 100 pre-stores the first opening degree D1, the second opening degree D2, and the set rotational speed. The first opening degree D1, the second opening degree D2, and the set rotational speed are determined, for example, based on experiments or simulations, taking into account the discharge capacity of the pump 77 and the flow path area corresponding to the opening degree D of the adjusting valve 76. In addition, when the control device 100 changes the opening degree D of the regulating valve 76 to the first opening degree D1 or the second opening degree D2, it controls the electric motor of the regulating valve 76 to the required opening degree D while referring to the detection value of the opening degree sensor 32.

[0041] The control device 100 is capable of performing a first jet timing calculation process as part of the water jet control. The first jet timing calculation process is a process that calculates the start time (hereinafter referred to as the first start time V1A) and the end time (hereinafter referred to as the first end time V1B) of the first jet process. Figure 2 As shown, in the first injection timing calculation process, the control device 100 sets the first start timing V1A to the opening timing TS of the intake valve 23. Additionally, in the first injection timing calculation process, the control device 100 sets the first end timing V1B to before the limit timing. The limit timing is obtained by tracing back the aforementioned arrival period L from the closing timing TCA of the intake valve 23. Furthermore, the closing timing TCA of the intake valve 23 mentioned here refers to the end timing of a combustion cycle.

[0042] The control device 100 is capable of performing a second injection timing calculation process as part of water injection control. The second injection timing calculation process is a process that calculates the start time (hereinafter referred to as the second start time V2A) and the end time (hereinafter referred to as the second end time V2B) of the second injection process. In the second injection timing calculation process, the control device 100 determines the second start time V2A to end the second injection process a predetermined period K earlier than the first start time V1A. To achieve this, the control device 100 determines the second start time V2A and the second end time V2B in the following manner: The control device 100 sets the time that is a predetermined period K earlier than the first start time V1A as the second end time V2B. Furthermore, the time obtained by retrospectively estimating the period required to inject the set injection quantity Qr of water from the water injection valve 14 from the second end time V2B is set as the second start time V2A. The minimum period required for the water pressure WP to change from the second value WP2 to the first value WP1 is called the necessary period. The necessary period is the time required to change the opening degree D of the adjusting valve 76 from the second opening degree D2 to the first opening degree D1. In this embodiment, the control device 100 sets the necessary period to a predetermined period K. The control device 100 stores the necessary period in advance. The necessary period is determined in advance, for example, based on experiments or simulations. Furthermore, regarding... Figure 2 The changes in water pressure WP and the details of each jet treatment process will be explained in the "Function" section below.

[0043] <Specific treatment details for water jet control>

[0044] The following description of the water injection control process per cylinder 11. That is, the control device 100 performs the following water injection control process for each cylinder 11, i.e., each water injection valve 14. The control device 100 repeatedly performs water injection control during the operation of the internal combustion engine 10, i.e., when the engine speed NE is greater than "0". The control device 100 performs one water injection control process per combustion cycle for each cylinder 11. In each combustion cycle, the control device 100 initiates water injection control at the start timing of the combustion cycle, i.e., the valve closing timing TC of the intake valve 23. The control device 100 determines the start timing of water injection control based on the latest crankshaft position Scr received from the crankshaft position sensor 34. That is, the control device 100 determines that the intake valve 23 has reached the valve closing timing TC if the latest crankshaft position Scr matches the crankshaft position Scr at which the intake valve 23 reaches the valve closing timing TC. Although detailed explanations are omitted, the intake valve 23's closing timing TC and opening timing TS, referenced or utilized by the control device 100 in the series of water injection control processes, are for the cylinder 11, which is the target of the water injection control. Furthermore, during the operation of the internal combustion engine 10, the control device 100 controls the pump 77 to match its set speed. Additionally, at the start-up point of the internal combustion engine 10, the control device 100 controls the adjusting valve 76 to match its opening degree D with a first opening degree D1. Therefore, when water injection control is first executed after the internal combustion engine 10 is started, the opening degree D of the adjusting valve 76 at the start time of the water injection control becomes the first opening degree D1.

[0045] like Figure 3 As shown, when the control device 100 initiates water injection control, it first performs step S110. In step S110, the control device 100 calculates the target injection quantity Qs. Specifically, the control device 100 refers to the latest internal combustion engine speed NE, the latest internal combustion engine load rate KL, and the target water quantity mapping M1. As described above, the target water quantity mapping M1 represents the relationship between the internal combustion engine speed NE, the internal combustion engine load rate KL, and the amount of water to be supplied to the cylinder 11, i.e., the required water quantity. Based on this target water quantity mapping M1, the control device 100 calculates the required water quantity corresponding to the latest internal combustion engine speed NE and the latest internal combustion engine load rate KL as the target injection quantity Qs. Then, the control device 100 proceeds to step S120. Furthermore, step S110 is a target calculation process.

[0046] In step S120, the control device 100 calculates the permissible injection quantity Qv. As described below, the permissible injection quantity Qv is the amount of water that the water injection valve 14 can inject during the period excluding the arrival period L during the opening period U2 of the intake valve 23. Furthermore, as mentioned above, the arrival period L is the length of time until the water injected by the water injection valve 14 reaches the cylinder 11. When calculating the permissible injection quantity Qv, the control device 100 first converts the arrival period L into a crankshaft rotation amount corresponding to the latest internal combustion engine speed NE. Then, the control device 100 uses the obtained crankshaft rotation amount as an offset value. The crankshaft rotation amount is the magnitude of the rotation angle of the crankshaft 18 during the period from one rotational position to another. The higher the engine speed NE, the larger the offset value. After calculating the offset value, the control device 100 calculates the limiting crankshaft position. Specifically, the control device 100 calculates the crankshaft position Scr as the limiting crankshaft position by calculating the crankshaft position Scr back offset value from the intake valve 23 to the valve closing timing TCA. For example... Figure 2 As shown, the aforementioned valve closing timing TCA is the end timing of this combustion cycle. After calculating the limiting crankshaft position, the control device 100 calculates the allowable rotational speed. The allowable rotational speed is the crankshaft rotational speed from the crankshaft position Scr where the intake valve 23 reaches the valve opening timing TS to the limiting crankshaft position. After calculating the allowable rotational speed, the control device 100 converts the allowable rotational speed into the length of time corresponding to the latest internal combustion engine speed NE based on the latest internal combustion engine speed NE. Then, the control device 100 uses the obtained value as the allowable period. In addition, for the same allowable rotational speed, the higher the internal combustion engine speed NE, the shorter the allowable period. Afterwards, the control device 100 refers to the water pressure WP for the first injection process, i.e., the first value WP1, and the injection map M2. As mentioned above, the injection map M2 represents the relationship between the injection period, the water pressure WP, and the injectable quantity. Based on the injection map M2, the control device 100 calculates the injectable quantity corresponding to the first value WP1 and the aforementioned allowable period as the allowable injection quantity Qv. At this point, the control device 100 only needs to apply the aforementioned permissible period to the injection period in the injection mapping M2. For example... Figure 3 As shown, after calculating the allowable injection quantity Qv, the control device 100 causes the process to proceed to step S130.

[0047] In step S130, the control device 100 determines whether the permissible injection quantity Qv calculated in step S120 is greater than or equal to the target injection quantity Qs calculated in step S110. If the determination is affirmative, during the opening period of the intake valve 23 in one combustion cycle, the U2 can supply water of the target injection quantity Qs from the water injection valve 14 into the cylinder 11. If the permissible injection quantity Qv is greater than or equal to the target injection quantity Qs (step S130: yes), the control device 100 causes the process to proceed to step S140. Furthermore, the process in step S130 is a determination process.

[0048] In step S140, the control device 100 calculates the first injection timing. Specifically, the control device 100 calculates the start timing of the first injection process, i.e., the first start timing V1A, and the end timing of the first injection process, i.e., the first end timing V1B. First, the control device 100 calculates the first start timing V1A. Specifically, the control device 100 sets the crankshaft position Scr at which the intake valve 23 reaches the valve opening timing TS as the crankshaft position Scr of the first start timing V1A. Next, the control device 100 calculates the first end timing V1B. Specifically, the control device 100 refers to the water pressure WP used for the first injection process, i.e., the first value WP1, the target injection quantity Qs calculated in step S110, and the injection mapping M2. Then, based on the injection mapping M2, the control device 100 calculates the injection period corresponding to the first value WP1 and the target injection quantity Qs as the normal injection period. Then, based on the latest internal combustion engine speed NE, the control device 100 converts the normal injection period into the crankshaft rotation amount corresponding to the latest internal combustion engine speed NE. The control device 100 uses the obtained value as the normal rotation amount. Then, the control device 100 calculates the crankshaft position Scr obtained by delaying the normal rotation amount from the crankshaft position Scr at the first start timing V1A as the crankshaft position Scr at the first end timing V1B. After calculating the first end timing V1B, the control device 100 causes the process to proceed to step S150. The process in step S140 is the first injection timing calculation process. In addition, the control device 100 quickly performs the processes from step S110 to step S140 after the water injection control starts. Therefore, the timing of step S150 after the process proceeds is substantially the same as the start time of a combustion cycle.

[0049] In step S150, the control device 100 performs a first injection process. Specifically, the control device 100 waits until the first start time V1A calculated in step S140. Then, when the first start time V1A is reached, the control device 100 causes the water injection valve 14 to start injecting water. After that, the control device 100 continues injecting water until the first end time V1B calculated in step S140. Then, when the first end time V1B is reached, the control device 100 causes the water injection valve 14 to stop injecting water. The water pressure WP during the execution of this first injection process is associated with the processing in step S260 during the previous water injection control and becomes a first value WP1. In addition, when the control device 100 starts the first injection process in step S150, it determines that the first start time V1A has been reached in the following manner: that is, the control device 100 repeatedly refers to the latest crankshaft position Scr received from the crankshaft position sensor 34. Then, the control device 100 determines that the first start timing V1A has been reached based on the fact that the latest crankshaft position Scr matches the crankshaft position Scr of the first start timing V1A. Similarly, the control device 100 determines that the first end timing V1B has been reached based on the fact that the latest crankshaft position Scr matches the crankshaft position Scr of the first end timing V1B. After performing the first injection process, the control device 100 temporarily terminates the series of water injection control processes. Then, when the start timing of a combustion cycle is reached, the control device 100 executes step S110 again.

[0050] On the other hand, in step S130, if the allowable injection quantity Qv is less than the target injection quantity Qs (step S130: no), the control device 100 causes the process to proceed to step S210.

[0051] In step S210, the control device 100 calculates the first injection timing. That is, the control device 100 calculates the first start timing V1A and the first end timing V1B in the same manner as in step S140. In this step S210, the control device 100 also sets the crankshaft position Scr at which the valve opening timing TS of the intake valve 23 is reached as the crankshaft position Scr of the first start timing V1A. The control device 100 sets the first end timing V1B as follows: that is, the control device 100 uses the limit crankshaft position calculated simultaneously with the allowable injection quantity Qv in step S120 as the crankshaft position Scr of the first end timing V1B. Then, the control device 100 causes the process to proceed to step S220. The process in step S210 is the first injection timing calculation process.

[0052] In step S220, the control device 100 calculates the set injection quantity Qr as the difference between the target injection quantity Qs and the allowable injection quantity Qv. Specifically, the control device 100 uses the value obtained by subtracting the allowable injection quantity Qv from the target injection quantity Qs as the set injection quantity Qr. Then, the control device 100 causes the process to proceed to step S230.

[0053] In step S230, the control device 100 calculates the second injection timing. Specifically, the control device 100 calculates the injection start timing, i.e., the second start timing V2A, and the end timing, i.e., the second end timing V2B, for the second injection process. The control device 100 first calculates the second end timing V2B. Specifically, the control device 100 refers to the latest internal combustion engine speed NE and a pre-stored necessary period. Then, based on the latest internal combustion engine speed NE, the control device 100 converts the necessary period into a crankshaft rotation amount corresponding to the latest internal combustion engine speed NE. The control device 100 uses the obtained crankshaft rotation amount as the necessary rotation amount. The higher the engine speed NE, the greater the necessary rotation amount. Then, the control device 100 calculates the crankshaft position Scr obtained by backtracking the necessary rotation amount from the crankshaft position Scr calculated in step S210 as the crankshaft position Scr for the second end timing V2B. Next, the control device 100 calculates the second start timing V2A. Specifically, the control device 100 refers to the water pressure WP used for the second injection process, i.e., the second value WP2, the set injection quantity Qr calculated in step S220, and the injection map M2. Then, based on the injection map M2, the control device 100 calculates the injection period corresponding to the second value WP2 and the set injection quantity Qr calculated in step S220 as the set injection period. Then, based on the latest internal combustion engine speed NE, the control device 100 converts the set injection period into a crankshaft rotation amount corresponding to the latest internal combustion engine speed NE. Then, the control device 100 uses the obtained crankshaft rotation amount as the set rotation amount. Similar to the necessary rotation amount, the higher the internal combustion engine speed NE is relative to the same set injection period, the larger the set rotation amount is. Then, the control device 100 uses the crankshaft position Scr obtained by backtracking the set rotation amount from the crankshaft position Scr calculated above for the second end timing V2B as the crankshaft position Scr for the second start timing V2A. After calculating the second start timing V2A, the control device 100 causes the process to proceed to step S240. The process in step S230 is the second injection timing calculation process. Furthermore, similarly to that described in step S140, the control device 100 rapidly performs the processes from step S110 to step S230 after the water injection control begins. Therefore, the timing of step S240, after which the process begins, is substantially the same as the start time of a combustion cycle.

[0054] In step S240, the control device 100 changes the water pressure WP to a second value WP2. Furthermore, the water pressure WP at the time of entering step S240 is associated with the processing in step S260 during the previous water jet control, and is a first value WP1. Also, the opening degree D of the adjusting valve 76 is a first opening degree D1. As a specific process of step S240, the control device 100 controls the adjusting valve 76 so that the opening degree D of the adjusting valve 76 matches the second opening degree D2. Accompanying this, the opening degree D of the adjusting valve 76 changes from the first opening degree D1 to the second opening degree D2. After executing the processing in step S240, the control device 100 causes the process to proceed to step S250.

[0055] In step S250, the control device 100 performs a second spraying process. Specifically, the control device 100 waits until the second start time V2A calculated in step S230. Then, when the second start time V2A is reached, the control device 100 causes the water spray valve 14 to start spraying water. Afterward, the control device 100 continues spraying water until the second end time V2B calculated in step S230. Then, when the second end time V2B is reached, the control device 100 causes the water spray valve 14 to stop spraying water. Furthermore, the method for determining the second start time V2A and the second end time V2B is the same as the method described in step S150. After performing the second spraying process, the control device 100 proceeds to step S260.

[0056] In step S260, the control device 100 changes the water pressure WP from a second value WP2 to a first value WP1. Specifically, the control device 100 controls the adjusting valve 76 to make its opening degree D match the first opening degree D1. Accompanying this, the opening degree D of the adjusting valve 76 changes from a second opening degree D2 to a first opening degree D1. This change in opening degree requires a necessary period, namely the specified period K of this embodiment. After executing the processing in step S260, the control device 100 moves the processing to step S270. Furthermore, regarding the setting of the second end timing V2B, the crankshaft position Scr at the time point of step S270 after the processing has started becomes the crankshaft position Scr of the first start timing V1A.

[0057] In step S270, the control device 100 performs a first injection process. Specifically, after entering step S270, the control device 100 quickly starts water injection from the water injection valve 14. Then, the control device 100 continues water injection until the first end timer V1B calculated in step S210. Then, when the first end timer V1B is reached, the control device 100 stops water injection from the water injection valve 14. Furthermore, the method for determining the first start timer V1A and the first end timer V1B is the same as the method described in step S150. After performing the first injection process, the control device 100 temporarily terminates the series of water injection control processes. Then, when the start timer of a combustion cycle is reached, the control device 100 again executes the process of step S110.

[0058] <The Role of the Implementation Method>

[0059] (A) Procedure regarding changes in water jet and water pressure from the water jet valve accompanying water jet control.

[0060] At the beginning of a combustion cycle, i.e., the closing timing TC of intake valve 23, the opening degree D of adjusting valve 76 becomes the first opening degree D1. Accompanying this, as... Figure 2 As shown, at the valve closing timing TC of intake valve 23, water pressure WP becomes the first value WP1. Additionally, due to reasons such as a high target injection quantity Qs or a high internal combustion engine speed NE, sometimes the injection quantity Qv is allowed to be less than the target injection quantity Qs (step S130: No). In this case, such as... Figure 2 As shown, starting from the closing timing TC of the intake valve 23, the control device 100 rapidly changes the opening degree D of the adjusting valve 76 from the first opening degree D1 to the second opening degree D2 (step S240). Simultaneously, the water pressure WP changes from the first value WP1 to the second value WP2. Afterwards, as... Figure 2 As shown, when the water pressure WP is set to the second value WP2, the control device 100 performs the second injection process during the closed period of the intake valve 23 (step S250). Then, the control device 100 causes the water injection valve 14 to inject water at a set injection quantity Qr. The control device 100 ends the second injection process at a timed period K earlier than the opening timing TS of the intake valve 23, i.e., the second end timed period V2B. Then, the control device 100 changes the opening degree D of the adjusting valve 76 from the second opening degree D2 to the first opening degree D1 (step S260). Accompanying this, as Figure 2 As shown, the water pressure WP changes from the second value WP2 to the first value WP1. This change in water pressure WP needs to be set to the necessary period of the specified period K. Therefore, the opening timing TS of the intake valve 23 coincides with the time when the change in water pressure WP ends. Thus, as... Figure 2As shown, the control device 100 performs the first injection process (step S270). Then, during the opening period of the intake valve 23, the control device 100 causes the water injection valve 14 to inject water at the allowed injection amount Qv. By performing both the first and second injection processes in this way, the control device 100 causes the water injection valve 14 to inject the target injection amount Qs of water as a total amount in one combustion cycle.

[0061] In addition, Figure 2 In order to easily understand the situation of changing the water pressure WP between the second injection process and the first injection process, the time required to change the water pressure WP from the second value WP2 to the first value WP1 is exaggerated, i.e., the necessary time. The same applies to the time required to change the water pressure WP from the first value WP1 to the second value WP2. Furthermore, Figure 2 The spray periods for the first and second spray processes shown are merely examples and may not necessarily correspond to actual spray periods.

[0062] (B) Reasons for changing water pressure in the first and second jet treatments

[0063] Now, suppose water is sprayed from the water injection valve 14. Assume the sprayed water concentrates and adheres to a certain part of the wall of the air intake 12A. In this case, the adhered water forms large water droplets at the aforementioned location on the wall of the air intake 12A. Because the liquid film formed by such water droplets is thick, the water droplets are difficult to evaporate. The water droplets thus remain on the wall of the air intake 12A, or flow into the cylinder 11 along with the intake air. If the water droplets flow into the cylinder 11, they eventually flow down the wall of the cylinder 11 into the crankshaft chamber 83. Therefore, they do not contribute to the cooling of the cylinder 11. In addition to large water droplets forming at the air intake 12A flowing into the cylinder 11 as described above, sometimes large water droplets also form directly on the wall of the cylinder 11. For example, suppose water concentrates and adheres to a certain part of the wall of the cylinder 11. In this case, the adhered water forms large water droplets at the aforementioned location on the wall of the cylinder 11. Such water droplets do not essentially evaporate within the cylinder 11 and flow into the crankshaft chamber 83. Furthermore, even in the case of evaporation, the heat of vaporization contributes to the cooling of the cylinder 11 walls themselves, but hardly contributes to the cooling of the gas inside the cylinder 11. Thus, when large water droplets form a thick liquid film at the intake port 12A or inside the cylinder 11, these droplets are unlikely to contribute to the evaporative cooling of the gas inside the cylinder 11. Therefore, even when the water injection valve 14 injects the target injection quantity Qs of water, the formation of such large water droplets makes it impossible to cool the cylinder 11 as intended.

[0064] Therefore, this embodiment studies the water jet control to avoid the formation of large water droplets as described above. Specifically, the water pressure WP is changed in the first and second jet processes. More specifically, the water pressure WP in the second jet process is made higher than the water pressure WP in the first jet process. This essentially means that the jet pressure of the water jet valve 14 in the second jet process is higher than the jet pressure of the water jet valve 14 in the first jet process. The reason for adopting this method will be explained.

[0065] Now, assume that the intake valve 23 is in the closed period U1. Also, assume that the water injection valve 14 is injecting water into the intake port 12A. At this time, when the injection pressure of the water injection valve 14 is high, the water is forcefully dispersed in all directions from the nozzle of the water injection valve 14. Therefore, when the injection pressure of the water injection valve 14 is high, the water injected by the water injection valve 14 is dispersed over a wide area. That is, as... Figure 4 As shown in Y1, the water jet range is greater at higher jet pressures than... Figure 4 Y2 shows a wide spray range under low spray pressure. Even when spraying the same amount of water, if the water spray range is wide, the amount of water adhering to each part of the wall of the air inlet 12A is correspondingly less. Therefore, the thickness of the liquid film formed by the adhering water at each part of the wall of the air inlet 12A is also smaller. If the thickness of the liquid film is small, the liquid film evaporates rapidly. In this way, when the spray pressure of the water jet valve 14 is increased, it is possible to avoid the formation of large water droplets on the wall of the air inlet 12A. From this point of view, the control device 100 sets the water pressure WP, and thus the spray pressure of the water jet valve 14, to a higher level in the second spray process. Here, the spray pressure that can spray water over a wide range to the extent that the formation of large water droplets can be avoided when the air inlet valve 23 is in the closed period U1 is called the second spray pressure J2. The water pressure WP used for the second spray process, i.e., the second value WP2, is the water pressure WP when the spray pressure of the water jet valve 14 becomes the second spray pressure J2. The second value WP2 and the second injection pressure J2 based thereon are predetermined values, for example, through experimentation or simulation. Furthermore, when determining the second injection pressure J2, the intake air pressure corresponding to the engine operating state when the target injection quantity Qs is greater than "0" is considered, for example. The difference between the intake air pressure and the injection pressure from the water injection valve 14 may affect the injection range.

[0066] Furthermore, as mentioned above, increasing the injection pressure from the water injection valve 14 is effective in preventing the formation of large water droplets on the wall of the air intake 12A. On the other hand, increasing the injection pressure from the water injection valve 14 is not effective in preventing the formation of large water droplets on the wall of the cylinder 11. The reason will be explained. Now, suppose the air intake valve 23 is in the open period U2. Suppose that in this condition, the water injection valve 14 injects water at a high injection pressure. In this case, associated with the increased water injection range, the water reaches a farther distance. Moreover, during the open period U2 of the air intake valve 23, there is an intake air flow toward the cylinder 11. The water injected by the water injection valve 14 flows toward the cylinder 11 through this intake air flow. When the situation of the intake air flow toward the cylinder 11 overlaps with the situation of the water injection valve 14 injecting water to a farther distance, the water injected by the water injection valve 14 flows forcefully into the cylinder 11. At the same time, as Figure 5 As shown in Z1, the water travels a longer distance. Furthermore, the water can reach the wall of cylinder 11. At this time, when the water locally concentrates and adheres to the wall of cylinder 11, the adhered water forms large droplets. That is, when U2 increases the injection pressure of the water injection valve 14 during the opening of the intake valve 23, it may actually lead to the formation of large droplets. Regarding this, when the injection pressure of the water from the water injection valve 14 is reduced, as... Figure 5 As shown in Z2, the travel distance of the water injected from the water injection valve 14 is correspondingly shortened. In this case, it is possible to avoid the water reaching the wall of the cylinder 11. From this point of view, the control device 100 sets the water pressure WP, and thus the injection pressure of the water injection valve 14, to a lower level in the second injection process. Here, the injection pressure at which the water injected from the water injection valve 14 will not reach the wall of the cylinder 11 when the intake valve 23 is in the open period U2 is called the first injection pressure J1. The water pressure WP used for the first injection process, i.e., the first value WP1, is the water pressure WP when the injection pressure of the water injection valve 14 becomes the first injection pressure J1. The first value WP1 and the first injection pressure J1 based thereon are values ​​predetermined, for example, through experiments or simulations. When determining the first injection pressure J1, for example, the intake air quantity GA corresponding to the internal combustion engine operating state when the target injection quantity Qs is greater than "0" is considered. The intake air quantity GA may affect the travel distance of the water injected from the water injection valve 14.

[0067] <Effects of the Implementation Method>

[0068] (1) When the allowable injection quantity Qv is less than the target injection quantity Qs, the control device 100 performs a first injection process during the opening period U2 of the intake valve 23 and a second injection process during the closing period U1 of the intake valve 23. Thus, the control device 100 causes the water injection valve 14 to inject water at the target injection quantity Qs in one combustion cycle. In this way, based on the injection processes performed during both the opening period U2 and the closing period U1 of the intake valve 23, the control device 100 sets a water pressure WP suitable for avoiding the formation of large water droplets in each injection process. Therefore, most of the water at the target injection quantity Qs injected from the water injection valve 14 does not become large water droplets but flows into the cylinder 11 in a particulate state. Therefore, this embodiment enables approximately all of the water at the target injection quantity Qs to contribute to evaporation within the cylinder 11.

[0069] (2) The control device 100 sets the end time of the second injection process, i.e., the second end time V2B, to a time obtained by retrospectively counting back a predetermined period K from the start time of the first injection process, i.e., the first start time V1A. In this case, it is possible to ensure that the opening degree D of the adjusting valve 76 is changed from the second opening degree D2 to the first opening degree D1 during the period from the end of the second injection process to the start of the first injection process. That is, it is possible to ensure the period for changing the water pressure WP. Thus, when the water pressure WP is changed between the two injection processes, the following can be achieved: In the second injection process, the water pressure WP can be maintained at the second value WP2 until the second end time V2B, which is the end time of the second injection process. That is, the second injection pressure J2 can be maintained until the end time of the second injection process. In addition, in the first injection process, the water pressure WP can be made to the first value WP1 from the first start time V1A, which is the start time of the first injection process. That is, the first injection pressure J1 can be used from the start time of the first injection process. Therefore, the control device 100 can utilize different injection pressures throughout the entire period of performing the second injection process and throughout the entire period of performing the first injection process. As a result, it is possible to more reliably obtain the effect (1) that makes approximately all of the water in the target injection quantity Qs contribute to evaporation within the cylinder 11.

[0070] (3) In order to minimize the amount of water adhering to the wall of the air inlet 12A and thus minimize the formation of large water droplets, the following requirements are made: When water is injected by the U1 water injection valve 14 during the closing period of the air inlet valve 23 in the second injection process, the period during which the injected water remains in the air inlet 12A needs to be shortened as much as possible. For this purpose, the second injection process needs to be performed at a timing as close as possible to the opening timing TS of the air inlet valve 23.

[0071] In this embodiment, the period K from the second end timer V2B to the first start timer V1A, i.e., the predetermined period, is set as the minimum period required for changing the water pressure WP, i.e., the necessary period. Therefore, when changing the water pressure WP during the period from the second end timer V2B to the first start timer V1A, the period from the second end timer V2B to the first start timer V1A can be limited to the minimum. Therefore, based on the structure described above (2) that uses different injection pressures during the entire period of performing the second injection process and the entire period of performing the first injection process, the second injection process can be performed at a timing as close as possible to the valve opening timing TS of the intake valve 23. This more effectively prevents the formation of large water droplets on the wall surface of the intake port 12A.

[0072] <Example of Change>

[0073] Furthermore, the above-described embodiments can be implemented by modification as follows. The above-described embodiments and the following modifications can be combined with each other to implement them within the scope of technical non-contradiction.

[0074] • The water pressure WP can also be changed during the execution of the first injection process, or during the execution of the second injection process. For example, the operating state of the internal combustion engine 10 may change during the execution of these injection processes. Correspondingly, the injection pressure of the water injection valve 14, which is suitable for preventing the formation of large water droplets, may also change during the execution of the injection process. Taking this into consideration, the water pressure WP can also be changed according to the operating state of the internal combustion engine 10. For example, if a mapping representing the relationship between the operating state of the internal combustion engine 10 and the optimal water pressure WP is created in advance, the water pressure WP can also be changed during the execution of the injection process.

[0075] The specified period K is not limited to the examples of the above embodiments. That is, the specified period K can also be set to a length of time different from the necessary period. For example, the specified period K can also be longer than the necessary period. In this case, the water pressure WP can be changed from the second value WP2 to the first value WP1 before the first start time V1A. Therefore, in the second injection process, the water pressure WP can be kept at the second value WP2 until the end time of the second injection process. In addition, in the first injection process, the water pressure WP can be kept at the first value WP1 from the start time of the first injection process. When the specified period K is longer than the necessary period, the water pressure WP can be changed at any time within the specified period K. For example, the opening degree D of the regulating valve 76 can be changed after a predetermined period has elapsed from the second end time V2B. In addition, the timing for changing the opening degree D of the regulating valve 76 can be calculated based on the operating state of the internal combustion engine 10.

[0076] • The specified period K can also be abolished. Furthermore, the second and first spraying processes can be continuous. In this case, for example, the water pressure WP can be reduced midway through the second spraying process, and the water pressure WP can be set to a value suitable for the first spraying process at the start time of the first spraying process. This is only necessary as long as the water pressure WP is higher than the water pressure WP for at least a portion of the execution period of the second spraying process. This prevents the formation of large water droplets, at least for a portion of the time.

[0077] • The first start timing V1A is not limited to the examples of the above embodiments. That is, the first start timing V1A can also be set to a timing later than the valve opening timing TS of the intake valve 23. For example, when the target injection quantity Qs is correspondingly less than the allowable injection quantity Qv, even if the first start timing V1A is set to a timing later than the valve opening timing TS of the intake valve 23, the following situation can be achieved: that is, the target injection quantity Qs of water can be injected from the water injection valve 14 during the valve opening period of the intake valve 23.

[0078] The structure of the water supply mechanism 70 is not limited to the example of the above embodiment. The water supply mechanism 70 can be configured to appropriately adjust the water pressure WP for the water jet valves 14. For example, instead of providing a return passage 79 for each branch passage 75 as in the above embodiment, only one return passage can be provided in the water supply mechanism 70. At the same time, only one regulating valve 76 can be provided in the water supply mechanism 70. In this case, as in the above embodiment, a pump 77 is provided midway along the supply passage 74 extending from the water tank 78, and each branch passage 75 branches from the supply passage 74. Based on this, the portion of the supply passage 74 downstream of the pump 77 and upstream of the branching portion to each branch passage 75 is connected to the water tank 78 via the return passage. Furthermore, a regulating valve 76 is provided midway along the return passage. In this case, the water pressure downstream of the pump 77 in the supply passage 74 changes according to the opening degree D of the regulating valve 76. Consequently, the water pressure WP for all water jet valves 14 changes. In this way, a common adjusting valve can be set for all water injection valves 14, and the water pressure WP for all water injection valves 14 can be changed through this adjusting valve. As long as the target injection quantity Qs in the target water volume mapping M1 is taken into account, and it is determined in advance that the period of performing the first injection process on a certain cylinder 11 does not overlap with the period of performing the second injection process on other cylinders 11, the above-described method can be used.

[0079] Pump 77 is not limited to a pump driven by an electric motor. Pump 77 may also be of the type driven by crankshaft 18, for example. Even in this case, it is sufficient to adjust the opening degree D of regulating valve 76 according to the driving state of pump 77 to obtain an appropriate water pressure WP.

[0080] The structure of the regulating valve 76 is not limited to the example described above. The regulating valve 76 can be any structure capable of changing the water pressure WP. For example, a ball valve can also be used as the regulating valve 76.

[0081] The pressure regulating device is not limited to the examples described above. For example, the water pressure WP can be changed by altering both the discharge rate of pump 77 and the opening degree D of regulating valve 76. In this case, pump 77 and regulating valve 76 constitute the pressure regulating device. Alternatively, the water pressure WP can be changed by changing only the discharge rate of pump 77. In this case, pump 77 constitutes the pressure regulating device. The pressure regulating device can also be a device other than a pump or valve. The pressure regulating device only needs to be able to appropriately change the water pressure WP. The control device 100 only needs to appropriately control the pressure regulating device according to its structure. Depending on the structure of the pressure regulating device, feedback control of the pressure regulating device can be performed while referring to the detection value of water pressure sensor 30 to achieve an appropriate water pressure WP.

[0082] The arrival period L may not be a constant value, but may vary, for example, based on the intake air volume GA. The arrival period L may also be set to "0". Even in this case, a large amount of water from the target injection volume Qs will reach the cylinder 11.

[0083] The content of the target water volume mapping M1 is not limited to the examples of the above embodiments. The target water volume mapping M1 can be set to inject the water required to cool the cylinder 11 to the necessary degree according to the operating state of the internal combustion engine.

[0084] The method for determining the crankshaft position Scr at which the intake valve 23 reaches its opening timing TS is not limited to the examples described above. For instance, the crankshaft position Scr at which the intake valve 23 reaches its opening timing TS can also be determined using the detection values ​​of the crankshaft position sensor 34 and the intake camshaft position sensor 36. The method is not limited as long as the crankshaft position Scr at which the intake valve 23 reaches its opening timing TS can be properly determined. The same applies to the crankshaft position Scr at which the intake valve 23 reaches its closing timing TC.

[0085] The overall structure of the internal combustion engine 10 is not limited to the example of the above embodiment. For example, the number of cylinders 11 can be changed. The internal combustion engine 10 only needs to have a water injection valve 14, an intake valve 23, and a pressure adjustment device.

[0086] The number of water injection valves 14 in each cylinder 11 is not limited to the examples described in the above embodiments. For example, such as... Figure 6 As shown, two water injection valves 14 can also be provided for one cylinder 11. Furthermore, the two water injection valves 14 can inject water into one cylinder 11 via the air inlet 12A. Hereinafter, these two water injection valves 14 will be referred to as the first water injection valve 14A and the second water injection valve 14B. When the first water injection valve 14A and the second water injection valve 14B are provided for one cylinder 11, the following configuration can be adopted: The water supply mechanism 70A is configured to supply water at their respective water pressures WP to the first water injection valve 14A and the second water injection valve 14B. Specifically, the first water injection valve 14A is connected to a first passage 171 extending from the water tank 78. The second water injection valve 14B is connected to a second passage 172 extending from the water tank 78. For example, a first pump is provided as a first pressure regulating device 191 in the middle of the first passage 171. For example, a second pump is provided as a second pressure regulating device 192 in the middle of the second passage 172. Furthermore, the control device 100 controls the drive of the first pump so that the water pressure WP supplied to the first water jet valve 14A is the aforementioned first value WP1. Additionally, the control device 100 controls the drive of the second pump so that the water pressure WP supplied to the second water jet valve 14B is the aforementioned second value WP2, which is greater than the first value WP1. The control device 100 utilizes the first water jet valve 14A as a dedicated water jet valve 14 for the first jetting process and the second water jet valve 14B as a dedicated water jet valve 14 for the second jetting process. In this configuration, unlike the embodiment described above where a common water jet valve 14 is used for both the first and second jetting processes, it is not necessary to change the water pressure WP using a pressure adjusting device corresponding to the execution of each jetting process. Therefore, even without setting a predetermined period K for changing the water pressure WP, the respective jetting pressures can be used throughout the entire period of executing the second jetting process and the entire period of executing the first jetting process. That is, the respective jetting pressures can be used throughout the entire period of both jetting processes, and the second and first jetting processes can be executed continuously. Furthermore, in Figure 6 Only one cylinder 11 is shown in the diagram, but the same applies to the other cylinders 11. A first water jet valve 14A and a second water jet valve 14B can be provided for each cylinder 11. Furthermore, the first water jet valve 14A corresponding to the other cylinders 11 only needs to be connected to a first branch passage 181, which branches downstream of the first pressure adjusting device 191 from the first passage 171. Similarly, the second water jet valve 14B corresponding to the other cylinders 11 only needs to be connected to a second branch passage 182, which branches downstream of the second pressure adjusting device 192 from the second passage 172. Moreover, the structure of the water supply mechanism is not limited to the case where there are multiple water jet valves 14 for each cylinder 11. Figure 6The example shown illustrates this. The water supply mechanism simply needs to be configured to supply water at the appropriate water pressure WP to each water jet valve 14.

[0087] • The overall structure of vehicle 300 is not limited to the examples of the above embodiments. For example, vehicle 300 may also have not only an internal combustion engine 10 but also a generator motor as the drive source of vehicle 300.

[0088] The amount of water injected from the water injection valve 14 in the first injection process is not limited to the example of the above embodiment. Similarly, the amount of water injected from the water injection valve 14 in the second injection process is not limited to the example of the above embodiment. For example, if the allowable injection quantity Qv is less than the target injection quantity Qs, the amount of water injected from the water injection valve 14 in the first injection process can be less than the allowable injection quantity Qv. Furthermore, the set injection quantity Qr injected from the water injection valve 14 in the second injection process can be increased accordingly.

[0089] • When comparing the second injection process of a combustion cycle with the first injection process of other combustion cycles, the difference in their water pressures (WP) is effective in preventing the formation of large water droplets. Considering this, for example, the following structure can be considered: In a combustion cycle, only the second injection process (either the first or second injection process) is performed. In this case, the water pressure (WP) of this second injection process is made higher than the water pressure (WP) of the first injection process in other combustion cycles.

Claims

1. A control device for an internal combustion engine, wherein, The internal combustion engine has the following features: cylinder; An intake passage, connected to the cylinder; A water jet valve is configured to jet water into the air intake passage; The intake valve is configured to selectively open and close the connection between the intake passage and the cylinder; and The pressure regulating device is configured to adjust the pressure of the water supplied to the water jet valve. The control device is configured to perform a first injection process in which the water jet valve injects water during the opening of the intake valve, and a second injection process in which the water jet valve injects water during the closing of the intake valve, and to control the pressure adjustment device such that, in the second injection process, the pressure of the water supplied to the water jet valve is higher than that in the first injection process. The control device is configured to set the start time of the second spraying process to end before the start time of the first spraying process by a predetermined period.

2. The control device for an internal combustion engine according to claim 1, wherein, The control device is configured to, during the execution of the first injection process, control the pressure adjusting device to make the pressure of the water supplied to the water injection valve a predetermined first value, and during the execution of the second injection process, control the pressure adjusting device to make the pressure of the water supplied to the water injection valve a predetermined second value, and set the predetermined period as the minimum period required for the pressure adjusting device to change the water pressure from the second value to the first value.

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