Internal combustion engine and control method thereof

Abstract

To provide an internal combustion engine capable of diagnosing water injection under a condition where knocking does not occur, without providing a knocking sensor.SOLUTION: A control device 50 performs first water injection by water injection valves 63A to 63D in an expansion stroke after fuel combustion for each of a plurality of cylinders 45A to 45D. The control device 50 acquires from a temperature sensor 29 a first measurement value indicating a measurement value of a temperature of exhaust gas when the first water injection is performed. Then, the control device 50 determines abnormality of water injection in each of the cylinders 45A to 45D based on change of the first measurement value for each of the plurality of cylinders 45A to 45D.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to an internal combustion engine and a control method thereof. [Background technology]

[0002] In internal combustion engines, the amount of NOx in the exhaust gas increases as the combustion temperature increases, so it is known that the generation of NOx can be suppressed by injecting water into the cylinder (combustion chamber) to lower the combustion temperature.

[0003] Regarding the above-described internal combustion engine, Japanese Patent Laid-Open Publication No. 2017-89622 (Patent Document 1) discloses a method for diagnosing water injection into the combustion chamber of an internal combustion engine. In this method, the knocking tendency of the internal combustion engine is determined from the signal of a knocking sensor when water is injected into the combustion chamber, and the water injection is diagnosed by analyzing the obtained knocking tendency (see Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2017-89622 Summary of the Invention [Problem to be solved by the invention]

[0005] The method described in Patent Document 1 is premised on the use of a knocking sensor and requires the occurrence of knocking, so the conditions under which water injection can be diagnosed are limited.

[0006] The present disclosure has been made to solve such problems, and the purpose of the present disclosure is to provide an internal combustion engine and a control method thereof that do not require a knocking sensor and are capable of diagnosing water injection under conditions where knocking does not occur. [Means for solving the problem]

[0007] The internal combustion engine of the present disclosure includes an engine body having multiple cylinders, a fuel injection device configured to inject fuel into each cylinder, a water injection device configured to inject water into each cylinder, a control device that controls the water injection device, and a sensor that measures the temperature or pressure of exhaust gas discharged from the multiple cylinders. The control device performs a first water injection by the water injection device for each of the multiple cylinders during the expansion stroke after fuel combustion, obtains from the sensor a first measurement value that indicates the measurement value of the temperature or pressure when the first water injection is performed, and determines an abnormality in the water injection for each cylinder based on changes in the first measurement value for each of the multiple cylinders.

[0008] The present disclosure also provides a control method for an internal combustion engine. The internal combustion engine includes an engine body having a plurality of cylinders, a fuel injection device configured to inject fuel into each cylinder, a water injection device configured to inject water into each cylinder, and a sensor that measures the temperature or pressure of exhaust gas discharged from the plurality of cylinders. The control method includes the steps of: performing a first water injection by the water injection device for each of the plurality of cylinders during an expansion stroke after fuel combustion; acquiring, from the sensor, a first measurement value that indicates a measurement value of the temperature or pressure when the first water injection is performed; and determining an abnormality in the water injection for each of the plurality of cylinders based on a change in the first measurement value for each of the plurality of cylinders.

[0009] In the above-described internal combustion engine and control method, since the first water injection is performed during the expansion stroke after fuel combustion, it is possible to determine that the water injection amount is abnormal (small amount abnormal) in a cylinder where the temperature or pressure of the exhaust gas is equal to or relatively high than the reference value. In this way, this internal combustion engine and control method does not require a knocking sensor and can determine whether the water injection is abnormal under conditions where knocking does not occur.

[0010] In the above-mentioned internal combustion engine, the control device may further perform a second water injection using a water injection device for each of a plurality of cylinders during the compression stroke before fuel injection, obtain a second measurement value from a sensor indicating the measurement value of the temperature or pressure when the second water injection is performed, and determine an abnormality in the water injection based on changes in the second measurement value for each of the plurality of cylinders.

[0011] The above control method may further include the steps of performing a second water injection using a water injection device for each of a plurality of cylinders during the compression stroke before fuel injection, obtaining a second measurement value from a sensor indicating the measurement value of the temperature or pressure when the second water injection is performed, and determining an abnormality in the water injection based on changes in the second measurement value for each of the plurality of cylinders.

[0012] In the above-described internal combustion engine and control method, since the second water injection is performed during the compression stroke before fuel injection, it is possible to determine that the water injection amount is abnormal (small amount abnormality) or that the water injection control is abnormal (water is not injected at the targeted position) in a cylinder where the temperature or pressure of the exhaust gas is at or relatively high to the determination reference value. In this way, with this internal combustion engine and control method, it is also possible to determine an abnormality in the water injection control.

[0013] The control device may determine that the amount of water injection by the water injection device is normal and that the water injection control by the water injection device is abnormal for a cylinder in which the water injection is determined to be normal based on the first water injection and the water injection is determined to be abnormal based on the second water injection.

[0014] If the first water injection determines that the water injection is normal, the water injection amount is normal, and if the second water injection determines that the water injection is abnormal, it can be determined that the water injection control is abnormal. In this way, by performing the first water injection and the second water injection, it is possible to distinguish between an abnormality in the water injection amount and an abnormality in the water injection control.

[0015] The control device may determine that the amount of water injection by the water injection device is abnormal for a cylinder in which the water injection is determined to be abnormal due to the first water injection and the water injection is determined to be abnormal due to the second water injection.

[0016] If the first water injection determines that the water injection is abnormal, it is assumed that the water injection amount is abnormal, but if the second water injection also determines that the water injection is abnormal, it can be determined that the water injection amount is abnormal. In this way, by performing the first water injection and the second water injection, it is possible to distinguish between an abnormality in the water injection amount and an abnormality in the water injection control.

[0017] The control device may perform a first water injection for each successive fuel injection of the plurality of cylinders, or may perform a second water injection for each successive fuel injection of the plurality of cylinders.

[0018] This allows for the determination of water injection abnormalities in a short period of time. The control device may perform the first water injection in each cycle for each cylinder so that the cycles in which the first water injection is performed do not overlap among the plurality of cylinders. Alternatively, the control device may perform the second water injection in each cycle for each cylinder so that the cycles in which the second water injection is performed do not overlap among the plurality of cylinders.

[0019] This makes it possible to determine whether there is an abnormality in water injection for each cylinder even if the sensor does not have high responsiveness or resolution.

[0020] The internal combustion engine may further include a NOx sensor that measures the amount of NOx in the exhaust gas. The control device may further perform a second water injection by the water injection device during the compression stroke before fuel injection for each of the plurality of cylinders, obtain a third measurement value from the NOx sensor that indicates a measurement value of the NOx amount when the second water injection is performed, and determine whether the water injection is abnormal based on a change in the third measurement value for each of the plurality of cylinders.

[0021] Regarding the second water injection performed before the combustion of fuel, if the water injection amount is abnormal (small amount abnormal) or the water injection control is abnormal (water is not injected at the targeted position), the combustion temperature will rise and the amount of NOx will increase. Therefore, even with the above method, it is possible to determine that the water injection amount or water injection control is abnormal, for example, in a cylinder where the amount of NOx is equal to or relatively high than the judgment reference value.

[0022] The control device may further determine that a predetermined abnormal mode has occurred when it is determined that the water injection is abnormal due to the second water injection in all of the plurality of cylinders.

[0023] If it is determined that water injection is abnormal in all cylinders, it is not a cylinder-specific abnormality, but rather it is assumed that the abnormality is, for example, a change in the properties of the water (a quality abnormality) or an abnormality in the pump that supplies water to the water injection device. According to the above, such an abnormality can be determined as a predetermined abnormal mode and separated from an abnormality in each cylinder. [Effects of the Invention]

[0024] According to the internal combustion engine and the control method thereof of the present disclosure, a knocking sensor is not required, and it is possible to determine an abnormality in water injection under conditions in which knocking does not occur. [Brief explanation of the drawings]

[0025] [Figure 1] 1 is an overall configuration diagram of an example of an internal combustion engine according to a first embodiment of the present disclosure. [Figure 2] FIG. 2 is a diagram illustrating an example of the arrangement of fuel injection valves and water injection valves in a cylinder. [Figure 3] FIG. 10 is a diagram showing the timing of water injection from the water injection valve in the first measurement. [Figure 4] FIG. 4 is a diagram showing an example of transition of temperature inside a cylinder. [Figure 5] FIG. 6 is a diagram showing an example of the transition of the temperature of the exhaust gas when the first measurement is performed. [Figure 6]FIG. 6 is a diagram showing the exhaust gas temperatures shown in FIG. 5 for each cylinder in the form of a bar graph. [Figure 7] FIG. 10 is a diagram showing the timing of water injection from the water injection valve in the second measurement. [Figure 8] FIG. 4 is a diagram showing an example of transition of temperature inside a cylinder. [Figure 9] FIG. 10 is a diagram showing an example of the transition of the temperature of the exhaust gas when the second measurement is performed. [Figure 10] FIG. 10 is a bar graph showing the extent to which the exhaust gas temperature at the second measurement shown in FIG. 9 decreases from the temperature when water injection is not performed for each cylinder. [Figure 11] 10 is a flowchart showing an example of a processing procedure for a first measurement. [Figure 12] 10 is a flowchart showing an example of a processing procedure for a second measurement. [Figure 13] 10 is a flowchart showing an example of a procedure for isolating a water injection abnormality. [Figure 14] 10 is a flowchart showing an example of a procedure for determining an abnormality in the amount of water injection in Modification 1. [Figure 15] 10 is a flowchart showing an example of a processing procedure for a second measurement in the second embodiment. [Figure 16] 10 is a flowchart showing an example of a processing procedure for a first measurement in Modification 2. [Figure 17] 10 is a flowchart showing an example of a processing procedure for a second measurement in Modification 2. [Figure 18] 11 is a flowchart showing an example of a procedure for abnormality determination processing in Modification 3. DETAILED DESCRIPTION OF THE INVENTION

[0026] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. While several embodiments will be described below, it was originally intended that the configurations described in each embodiment be combined as appropriate. Note that identical or corresponding parts in the drawings will be designated by the same reference numerals, and their description will not be repeated.

[0027] [Embodiment 1] 1 is a diagram illustrating an overall configuration of an example of an internal combustion engine according to a first embodiment of the present disclosure. Note that, although a diesel engine, which is a compression ignition (CI) engine, will be described below as a representative example, the internal combustion engine of the present disclosure may also be a gasoline engine, which is a spark ignition (SI) engine, or the like.

[0028] Referring to FIG. 1, the diesel engine 1 includes an engine body 10, intake pipes 11A and 11B, an intake manifold 11C, an exhaust manifold 12A, exhaust pipes 12B and 12C, a turbocharger 30, an EGR device 13, and a control device 50.

[0029] The diesel engine 1 further includes an intake air flow sensor 21, an intercooler 16, a throttle device 47, and a pressure sensor 24.

[0030] The intake pipe 11A is connected to the inlet side of a compressor 35 of the turbocharger 30, and the intake pipe 11B is connected to the outlet side of the compressor 35. An intake manifold 11C is provided on the intake side of the engine body 10, and the intake pipe 11B is connected to the intake manifold 11C.

[0031] The intake air flow rate sensor 21 is provided in the intake pipe 11A and detects the flow rate of air introduced into the intake pipe 11A. The turbocharger 30 includes a compressor 35 having a compressor impeller 35A and a turbine 36 having a turbine impeller 36A. The compressor impeller 35A is rotationally driven by the turbine impeller 36A, which is rotationally driven by exhaust gas, and supercharges the air taken in through the intake pipe 11A and supplies it to the intake pipe 11B.

[0032] The intercooler 16 is provided in the intake pipe 11B and is an air-cooled or water-cooled heat exchanger that cools the air supercharged by the compressor 35. The throttle device 47 is provided in the intake pipe 11B downstream of the intercooler 16 and adjusts the intake air flow rate by driving a throttle valve 47A based on a control signal from the control device 50. The pressure sensor 24 is provided in the intake pipe 11B downstream of the throttle device 47 and detects the pressure of the intake gas supplied to the intake manifold 11C and outputs the detected pressure to the control device 50.

[0033] The diesel engine 1 further includes a common rail 41, fuel pipes 42A to 42D, fuel injection valves 43A to 43D, a water supply common rail 61, water pipes 62A to 62D, water injection valves 63A to 63D, a supply pipe 65, a pump 66, and a water tank 67.

[0034] The engine body 10 is provided with a plurality of cylinders 45A to 45D. In this example, four cylinders 45A to 45D are shown, but the number of cylinders is not limited to this. In the following, the cylinders 45A to 45D may be referred to as #1 cylinder, #2 cylinder, #3 cylinder, and #4 cylinder, respectively.

[0035] The fuel injection valves 43A to 43D are provided in the cylinders 45A to 45D, respectively. Fuel is supplied to the fuel injection valves 43A to 43D from the common rail 41 through fuel pipes 42A to 42D, respectively. The fuel injection valves 43A to 43D are driven by control signals from the control device 50, and inject fuel into the cylinders 45A to 45D, respectively.

[0036] Water injectors 63A to 63D are also provided in cylinders 45A to 45D, respectively. Water (non-combustible liquid) is supplied to water injectors 63A to 63D from water supply common rail 61 through water pipes 62A to 62D, respectively. Water injectors 63A to 63D are driven by control signals from control device 50, and inject water into cylinders 45A to 45D, respectively.

[0037] The water supply common rail 61 is connected to a water tank 67 through a supply pipe 65. A pump 66 is provided in the supply pipe 65, and the pump 66 supplies water from the water tank 67 through the supply pipe 65 to the water supply common rail 61.

[0038] An exhaust manifold 12A is provided on the exhaust side of the engine body 10, and an exhaust pipe 12B is connected to the exhaust manifold 12A. The outlet side of the exhaust pipe 12B is connected to the inlet side of the turbine 36 of the turbocharger 30, and an exhaust pipe 12C is connected to the outlet side of the turbine 36.

[0039] The diesel engine 1 further includes a temperature sensor 29, a pressure sensor 26, and a NOx sensor 28. The temperature sensor 29 is provided in the exhaust pipe 12B and detects the temperature of exhaust gas discharged from the engine body 10. The pressure sensor 26 is provided in the exhaust pipe 12B and detects the pressure of exhaust gas in the exhaust pipe 12B. The NOx sensor 28 is provided in the exhaust pipe 12C. An exhaust gas purification device (not shown) is provided in the exhaust pipe 12C, and the exhaust gas purification device includes, for example, an oxidation catalyst, a particulate filter, a selective reduction catalyst, etc. The NOx sensor 28 is provided, for example, between the particulate filter and the selective reduction catalyst and detects the amount of NOx (NOx concentration) in the exhaust gas before it is reduced in the selective reduction catalyst. The detected values ​​of the temperature sensor 29, the pressure sensor 26, and the NOx sensor 28 are output to the control device 50.

[0040] The EGR device 13 includes EGR pipes 13A and 13B, a path switching device 14A, an EGR valve 14B, an EGR cooler 15, and a bypass pipe 13C. The EGR pipe 13A is connected to the exhaust pipe 12B, and the EGR pipe 13B is connected to the intake pipe 11B. The exhaust pipe 12B and the intake pipe 11B are connected to each other by the EGR pipes 13A and 13B, and a portion of the exhaust gas (EGR gas) in the exhaust pipe 12B can be recirculated to the intake side of the engine body 10.

[0041] The path switching device 14A is a path switching valve that switches between an EGR cooler path that returns the EGR gas recirculated through the EGR piping 13A to the intake pipe 11B via the EGR cooler 15, and a bypass path that bypasses the EGR cooler 15 via the bypass piping 13C and returns the EGR gas to the intake pipe 11B.

[0042] The EGR valve 14B is provided in the EGR pipe 13B, downstream of the junction with the bypass pipe 13C. The EGR valve 14B adjusts the flow rate of the EGR gas flowing through the EGR pipe 13B (i.e., the flow rate of the EGR gas recirculated to the intake pipe 11B) based on a control signal from the control device 50.

[0043] The EGR cooler 15 is a heat exchanger that is provided between the EGR pipe 13A and the EGR pipe 13B and cools the EGR gas. The EGR cooler 15 cools the EGR gas that flows in from the EGR pipe 13A and discharges the cooled EGR gas into the EGR pipe 13B.

[0044] The control device 50 is configured to include at least a processor 51 and a storage device 53. The processor 51 is configured to include a CPU (Central Processing Unit), an MPU (Micro Processing Unit), etc. The storage device 53 is configured to include a ROM (Read Only Memory), a RAM (Random Access Memory), a hard disk, etc. The ROM stores a processing program to be executed by the processor 51, and the processor 51 loads the processing program stored in the ROM into the RAM and executes it.

[0045] The control device 50 detects the operating state of the diesel engine 1 based on detection signals from various sensors, and controls various actuators including the fuel injection valves 43A to 43D, the water injection valves 63A to 63D, the EGR valve 14B, and the like.

[0046] The diesel engine 1 further includes a rotation angle sensor 22, an atmospheric pressure sensor 23, an accelerator pedal sensor 25, and a vehicle speed sensor 27. The rotation angle sensor 22 detects the rotation angle (crank angle) of the crankshaft of the engine main body 10. The atmospheric pressure sensor 23 detects the ambient atmospheric pressure. The accelerator pedal sensor 25 detects the amount of depression of the accelerator pedal by the driver. The vehicle speed sensor 27 detects the rotation speed of the wheels of the vehicle on which the diesel engine 1 is mounted.

[0047] In the above-mentioned diesel engine 1, the amount of NOx in the exhaust gas increases as the combustion temperature in the combustion chambers formed in the cylinders 45A to 45D increases, so water injection valves 63A to 63D are provided to inject water into the cylinders 45A to 45D (inside the combustion chambers) to lower the combustion temperature.

[0048] 2 is a diagram showing an example of the arrangement of the fuel injector 43A and the water injector 63A in the cylinder 45A. The arrangement of the fuel injector 43B to 43D and the water injector 63B to 63D in the other cylinders 45B to 45D is similar to the arrangement of the fuel injector 43A and the water injector 63A in the cylinder 45A.

[0049] Note that Figure 2 shows an example in which water injection is performed from water injection valve 63A during the compression stroke before fuel injection from fuel injection valve 43A, but as will be described later, in this diesel engine 1, water injection from water injection valve 63A may also be performed during the expansion stroke after combustion of the fuel injected from fuel injection valve 43A in order to determine any abnormality in the water injection by water injection valve 63A (when the "first measurement" described later is performed).

[0050] 2, engine body 10 includes a cylinder block 71 in which cylinder 45A is formed, and a cylinder head 72. A piston 73 that reciprocates within cylinder 45A is provided within cylinder 45A. A combustion chamber 75 in which an air-fuel mixture is burned is formed within cylinder 45A between piston 73 and cylinder head 72. A concave cavity 76 is formed in the top surface of piston 73.

[0051] The fuel injection valve 43A is disposed at the center of the upper wall surface of the combustion chamber 75, and is configured to inject fuel F directly toward the peripheral portion of a cavity 76 formed in the piston 73 (see the lower diagram in FIG. 2). The water injection valve 63A is disposed at an angle relative to the fuel injection valve 43A, on the peripheral portion of the upper wall surface of the combustion chamber 75. The water injection valve 63A is configured to inject water 68 into a predetermined region FL around a plurality (e.g., eight) of fuel injection ports (not shown) of the fuel injection valve 43A (see the upper diagram in FIG. 2). As a result, the predetermined region FL is cooled to a temperature lower than the ignition temperature of the fuel F by the heat of vaporization of the water 68.

[0052] Injecting water into the combustion chamber using the water injection valves can suppress the combustion temperature and thereby reduce the amount of NOx in the exhaust gas. If the water injection from the water injection valves is abnormal (abnormal injection amount or injection position), the combustion temperature cannot be suppressed, and as a result, the amount of NOx cannot be suppressed. Therefore, in the diesel engine 1 according to the first embodiment, first and second measurements described below are performed to determine whether the water injection from the water injection valves 63A to 63D is abnormal.

[0053] <First measurement> In the first measurement, in order to determine whether there is an abnormality in the water injection by the water injectors 63A-63D, water injection (first water injection) is performed by the water injectors 63A-63D for each cylinder 45A-45D during the expansion stroke after fuel combustion. Then, based on the temperature change of the exhaust gas when the water injection is performed, whether there is an abnormality in the water injection by the water injectors 63A-63D. More specifically, in this first measurement, whether there is an abnormality in the water injection amount (small amount abnormality) by the water injectors 63A-63D is determined.

[0054] Since the pressure of the exhaust gas depends on the temperature of the exhaust gas, the pressure of the exhaust gas may be used instead of the temperature of the exhaust gas. In the following, an example in which the temperature of the exhaust gas is used will be described as a representative example. This first measurement will be described in detail below with reference to Figures 3 to 6.

[0055] Figure 3 is a diagram showing the timing of water injection from water injector 63A in the first measurement. The same applies to the other water injectors 63B to 63D. In Figure 3, the horizontal axis represents the crank angle of engine body 10, the upper graph represents the amount of heat generated in cylinder 45A in which water injector 63A is provided, and the lower graph represents the timing of water injection from water injector 63A in the first measurement.

[0056] 3, in the first measurement, water injection from the water injector 63A is performed during the expansion stroke after the combustion of fuel. For example, the timing of water injection is preferably just before bottom dead center (BDC) after the end of combustion. In this first embodiment, water injection is performed in the order of water injectors 63A, 63C, 63D, and 63B in accordance with the combustion order of cylinders 45A to 45D (cylinder #1 to cylinder #4) (for example, in the order of cylinder #1 → cylinder #3 → cylinder #4 → cylinder #2).

[0057] Fig. 4 is a diagram showing an example of the transition of temperature inside cylinder 45A. The same applies to other cylinders 45B to 45D. In Fig. 4, the horizontal axis represents the crank angle of engine body 10, and the vertical axis represents the temperature inside cylinder 45A. Solid line L12 represents the in-cylinder temperature when water injection from water injection valve 63A is performed in the first measurement, and dotted line L13 represents the in-cylinder temperature when water injection from water injection valve 63A is not performed.

[0058] 4, it can be seen that the temperature inside the cylinder after fuel combustion is lowered by performing the water injection shown in FIG. 3 compared to when water injection is not performed, which reduces the temperature of the exhaust gas discharged from cylinder 45A in the exhaust stroke after the expansion stroke.

[0059] FIG. 5 is a diagram showing an example of the transition of exhaust gas temperature during the first measurement. The exhaust gas temperature is detected by a temperature sensor 29 (FIG. 1) provided in the exhaust pipe 12B. In FIG. 5, the horizontal axis represents the crank angle of the engine body 10, and the vertical axis represents the exhaust gas temperature. In the diagram, sections #1 to #4 represent sections in which exhaust gas is discharged from cylinders #1 to #4 (cylinders 45A to 45D), respectively. In this example, combustion occurs in the order of cylinder #1 → cylinder #3 → cylinder #4 → cylinder #2. Note that sections #1 to #4 can be distinguished from each other based on the crank angle.

[0060] Referring to Figure 5, in this example, the water injection of the water injection valve 63C provided in the #3 cylinder (cylinder 45C) is abnormal (the water injection amount is abnormally small), so the exhaust temperature in section #3, which indicates the temperature of the exhaust gas from the #3 cylinder, is higher than the exhaust temperatures from the other cylinders (temperatures in sections #1, #2, and #4).

[0061] Fig. 6 is a bar graph showing the exhaust gas temperatures shown in Fig. 5 for each cylinder. In Fig. 6, #1 to #4 (measured values) respectively indicate the exhaust gas temperatures (exhaust gas temperatures from cylinders #1 to #4) in sections #1 to #4 shown in Fig. 5. The temperatures shown are the maximum temperatures in each section, or the average temperatures for a predetermined period including the maximum temperatures in each section.

[0062] The leftmost graph in the figure shows the exhaust gas temperature when water injection is not performed, and the second graph from the left shows the exhaust gas temperature when normal water injection is performed. Note that the exhaust gas temperature varies depending on the operating state of the engine body 10, and the two exhaust temperatures on the left in the figure are reference values ​​(without water injection / with normal water injection) according to the operating state (rotation speed and load) of the engine body 10 at the time of measurement. These reference values ​​are determined in advance for each rotation speed and load of the engine body 10 through prior experiments or simulations, and are stored in advance in the storage device 53 as a map or the like.

[0063] 6, the judgment value Tth is an exhaust gas temperature threshold value used to determine whether water injection is abnormal in the first measurement, and is set appropriately between a reference value when water injection is not performed and a reference value when water injection is performed normally. If water injection is performed in the first measurement, the water injection of a cylinder whose exhaust gas temperature (measurement value of temperature sensor 29) exceeds the judgment value Tth is determined to be abnormal (the water injection amount is small and abnormal). In this example, the exhaust gas temperature in section #3 exceeds the judgment value Tth, and the water injection of the water injection valve 63C provided in cylinder #3 (cylinder 45C) is determined to be abnormal (the target amount cannot be injected).

[0064] In this way, in the first measurement, it is possible to determine whether or not the water injection from the water injection valves 63A to 63D is abnormal (small amount of water injection abnormality).

[0065] <Second measurement> In the second measurement, in order to determine an abnormality in water injection by the water injectors 63A-63D, water injection (second water injection) is performed by the water injectors 63A-63D for each cylinder 45A-45D during the compression stroke before fuel injection (before main injection). Then, based on the temperature change of the exhaust gas when the water injection is performed, an abnormality in water injection by the water injectors 63A-63D is determined. More specifically, in this second measurement, an abnormality in the water injection amount (small amount abnormality) of the water injector 63A-63D or an abnormality in water injection control (water cannot be injected at the targeted position) can be determined.

[0066] In this second measurement, the exhaust gas pressure may be used instead of the exhaust gas temperature. In the following, an example in which the exhaust gas temperature is used will be described as a representative example. This second measurement will be described in detail below with reference to Figures 7 to 10.

[0067] Fig. 7 is a diagram showing the timing of water injection from water injector 63A in the second measurement. The same applies to the other water injectors 63B to 63D. In Fig. 7, the horizontal axis represents the crank angle of engine body 10, the upper graph represents the amount of heat generated in cylinder 45A in which water injector 63A is provided, and the lower graph represents the timing of water injection from water injector 63A in the second measurement.

[0068] 7, in the second measurement, water injection from water injector 63A is performed during the compression stroke before fuel injection (before main injection). For example, the timing of water injection is preferably just before TDC (top dead center) before fuel injection. Water injection is performed in the order of water injectors 63A, 63C, 63D, and 63B in accordance with the combustion order of cylinders 45A to 45D (cylinder #1 to cylinder #4) (for example, cylinder #1 → cylinder #3 → cylinder #4 → cylinder #2).

[0069] Fig. 8 is a diagram showing an example of the transition of the temperature inside cylinder 45A. The same applies to other cylinders 45B to 45D. In Fig. 8, the horizontal axis represents the crank angle of engine body 10, and the vertical axis represents the temperature inside cylinder 45A. Solid line L22 represents the in-cylinder temperature when water injection from water injection valve 63A is performed in the second measurement, and dotted line L23 represents the in-cylinder temperature when water injection from water injection valve 63A is not performed.

[0070] 8, it can be seen that the combustion temperature is lowered by performing the water injection shown in Fig. 7 compared to when water injection is not performed, which reduces the amount of NOx and lowers the temperature of the exhaust gas emitted from cylinder 45A.

[0071] Fig. 9 is a diagram showing an example of the transition of the exhaust gas temperature when the second measurement is performed. In Fig. 9, the horizontal axis represents the crank angle of the engine body 10, and the vertical axis represents the exhaust gas temperature. Sections #1 to #4 represent sections in which exhaust gas is discharged from cylinders #1 to #4 (cylinders 45A to 45D), respectively.

[0072] Referring to Figure 9, in this example too, the water injection of the water injection valve 63C provided in the #3 cylinder (cylinder 45C) is abnormal (abnormally small amount of water injection), so the exhaust temperature in section #3, which indicates the temperature of the exhaust gas from the #3 cylinder, is higher than the exhaust temperatures from the other cylinders (temperatures in sections #1, #2, and #4).

[0073] In this example, the water injection of the water injector 63D provided in the #4 cylinder (cylinder 45D) is also abnormal (abnormal water injection control, and the water is not being injected at the intended location), so the exhaust temperature in section #4, which indicates the temperature of the exhaust gas from the #4 cylinder, is also higher than the exhaust temperatures from the #1 and #2 cylinders (temperatures in sections #1 and #2). Note that an abnormality in the water injection control (abnormality in which the water is not being injected at the intended location) can be caused by, for example, looseness in the water injection valve, malfunction, or the accumulation of deposits.

[0074] Fig. 10 is a bar graph showing the decrease in exhaust gas temperature from the temperature when water injection is not performed for each cylinder during the second measurement shown in Fig. 9. In Fig. 10, #1 to #4 (measured values) respectively indicate the decrease in exhaust gas temperature from the reference temperature in sections #1 to #4 shown in Fig. 9 (exhaust gas temperature from cylinders #1 to #4).

[0075] More specifically, in the above, the exhaust gas temperatures in sections #1 to #4 are the maximum temperatures in each section, or the average temperatures for a predetermined period including the maximum temperatures in each section. The reference temperature is the exhaust gas temperature when water injection is not performed. The leftmost graph in the figure is the amount of exhaust gas temperature decrease from the reference temperature when water injection is normal in the second measurement. The exhaust gas temperatures including the reference temperature vary depending on the operating state of the engine body 10, and the leftmost temperature decrease is a reference value corresponding to the operating state (rotation speed and load) of the engine body 10 at the time of measurement. The reference temperatures and these reference values ​​are also previously determined for each rotation speed and load of the engine body 10 through prior experiments or simulations, and are previously stored in the storage device 53 as a map or the like.

[0076] 10, the judgment value ΔTth is a threshold value of the exhaust gas temperature decrease for judging whether or not the water injection is abnormal in the second measurement, and is appropriately set to a value smaller than the reference value of the temperature decrease when normal water injection is performed. When water injection is performed in the second measurement, it is judged that the water injection of a cylinder in which the decrease in the exhaust gas temperature (measured by the temperature sensor 29) from the reference temperature is smaller than the judgment value ΔTth is abnormal (abnormality in the water injection amount or water injection control).

[0077] In this example, the temperature drop in sections #3 and #4 is below the judgment value ΔTth, and it is determined that the water injection of water injection valves 63C, 63D provided in cylinder #3 (cylinder 45C) and cylinder #4 (cylinder 45D), respectively, is abnormal (the target amount cannot be injected or the intended location cannot be injected).

[0078] In the first embodiment, the determination result of the second measurement is combined with the determination result of the first measurement to isolate the water injection abnormality. For example, in the example of Figures 3 to 10, the exhaust gas temperature in section #3 is determined to be abnormal in both the first and second measurements, so it can be determined that the water injection amount of the water injection valve 63C provided in the #3 cylinder (cylinder 45C) is abnormal (small amount abnormality).

[0079] On the other hand, the exhaust temperature in section #4 was determined to be normal in the first measurement, but was determined to be abnormal in the second measurement. Therefore, it can be determined that the water injection amount of the water injection valve 63D installed in the #4 cylinder (cylinder 45D) is normal, but the water injection control is abnormal (water is not being injected at the intended position).

[0080] FIG. 11 is a flowchart showing an example of a processing procedure for the first measurement executed by the control device 50. The series of processes shown in this flowchart are executed at predetermined intervals. Referring to FIG. 11, the control device 50 determines whether or not the execution condition for the first measurement is met (step S10). Since the influence of water injection accompanying the first measurement can be relatively suppressed when the engine body 10 is under a high load, the execution condition for the first measurement can be, for example, that the load on the engine body 10 exceeds a predetermined value and that a predetermined time has elapsed since the previous first measurement. If the execution condition for the first measurement is not met (NO in step S10), the process proceeds to the end without executing the subsequent series of processes.

[0081] If it is determined in step S10 that the condition for executing the first measurement is met (YES in step S10), the control device 50 sequentially performs water injection using the water injection valves 63A to 63D for all cylinders 45A to 45D at a predetermined timing (Figure 3) after the expansion stroke (after combustion ends) (step S15).

[0082] Next, the control device 50 acquires the temperature of the exhaust gas when water injection was performed in step S15 using the temperature sensor 29 (step S20). Then, the control device 50 acquires exhaust temperatures T1 to T4 for each of the cylinders 45A to 45D from the temperatures acquired in step S20 based on the crank angle of the engine body 10 (step S25). More specifically, the control device 50 acquires the exhaust temperatures (maximum temperatures or average temperatures for a predetermined period including the maximum temperatures) for each of the sections #1 to #4 shown in Fig. 5 as the exhaust temperatures T1 to T4, respectively.

[0083] When the exhaust gas temperatures T1 to T4 are acquired, the control device 50 sets a counter i to 1 (step S30) and determines whether the exhaust gas temperature Ti (T1) is higher than the determination value Tth (FIG. 6) (step S35). If it is determined that the exhaust gas temperature Ti is higher than the determination value Tth (YES in step S35), the control device 50 determines that the water injection of the water injection valve provided in the #i cylinder corresponding to the section #i is abnormal (step S40).

[0084] On the other hand, when it is determined in step S35 that the exhaust temperature Ti is equal to or lower than the determination value Tth (NO in step S35), control device 50 proceeds to the process in step S45 without executing step S40.

[0085] Next, if counter i is not 4 (NO in step S45), control device 50 counts up counter i (step S50) and returns to step S35. Thereafter, for the other cylinders, the presence or absence of a water injection abnormality is determined based on the comparison result between exhaust temperature Ti and determination value Tth. Then, when counter i becomes 4 (YES in step S45) and the presence or absence of an abnormality has been determined for all cylinders, the first measurement ends.

[0086] 12 is a flowchart showing an example of the processing procedure of the second measurement executed by the control device 50. The series of processes shown in this flowchart is also executed at predetermined intervals. This second measurement is carried out independently of the first measurement shown in FIG.

[0087] 12, the control device 50 determines whether the execution condition for the second measurement is met (step S110). As with the first measurement, the execution condition for the second measurement can be, for example, that the load on the engine body 10 exceeds a predetermined value and that a predetermined time has elapsed since the previous second measurement. If the execution condition for the second measurement is not met (NO in step S110), the process proceeds to the end without executing the subsequent series of processes.

[0088] If it is determined in step S110 that the condition for executing the second measurement is met (YES in step S110), the control device 50 sequentially performs water injection using the water injection valves 63A to 63D at a predetermined timing (Figure 7) during the compression stroke (before fuel injection) for all cylinders 45A to 45D (step S115).

[0089] Next, the control device 50 acquires the temperature of the exhaust gas when water injection was performed in step S115 using the temperature sensor 29 (step S120). Then, the control device 50 acquires exhaust temperatures T1 to T4 for each of the cylinders 45A to 45D from the temperatures acquired in step S120 based on the crank angle of the engine body 10 (step S125). In detail, the control device 50 acquires the exhaust temperatures (maximum temperatures or average temperatures for a predetermined period including the maximum temperatures) for each of the sections #1 to #4 shown in Fig. 9 as the exhaust temperatures T1 to T4, respectively.

[0090] Next, the control device 50 calculates the decrease amounts ΔT1 to ΔT4 of the exhaust gas temperatures T1 to T4 from the reference temperature (step S130). The reference temperatures are exhaust gas temperatures when water injection is not performed, and are obtained in advance for each rotation speed and load of the engine body 10 through prior experiments or simulations, and are stored in advance in the storage device 53 as a map or the like. The control device 50 then obtains the reference temperature corresponding to the rotation speed and load of the engine body 10 at the time of measurement from the map, and calculates the temperature decrease amounts ΔT1 to ΔT4 using the obtained reference temperature.

[0091] After calculating the exhaust gas temperature decreases ΔT1 to ΔT4, the control device 50 sets a counter i to 1 (step S135) and determines whether the temperature decrease ΔTi (ΔT1) is smaller than the determination value ΔTth (FIG. 10) (step S140). If it is determined that the temperature decrease ΔTi is smaller than the determination value ΔTth (YES in step S140), the control device 50 determines that the water injection of the water injector provided in the #i cylinder corresponding to the section #i is abnormal (step S145).

[0092] On the other hand, if it is determined in step S140 that the temperature decrease ΔTi is equal to or greater than the determination value ΔTth (NO in step S140), control device 50 proceeds to step S150 without executing step S145.

[0093] Next, if counter i is not 4 (NO in step S150), control device 50 counts up counter i (step S155) and returns to step S140. Thereafter, for the other cylinders, the presence or absence of a water injection abnormality is determined based on the comparison result between temperature decrease ΔTi and determination value ΔTth. Then, when counter i becomes 4 (YES in step S150) and the presence or absence of an abnormality has been determined for all cylinders, the second measurement ends.

[0094] Fig. 13 is a flowchart showing an example of the procedure for isolating water injection abnormalities executed by the control device 50. The series of processes shown in this flowchart are also executed at predetermined intervals. Referring to Fig. 13, the control device 50 sets counter i to 1 (step S210), and then determines whether or not the water injection of cylinder #i has been determined to be abnormal in the second measurement described in Fig. 12 (step S215).

[0095] If it is determined in the second measurement that there is no water injection abnormality in cylinder #i (NO in step S215), control device 50 determines that water injection in cylinder #i is normal (step S220).

[0096] On the other hand, if the water injection of cylinder #i is determined to be abnormal in the second measurement (YES in step S215), the control device 50 determines whether the water injection of cylinder #i was determined to be abnormal in the first measurement described in Figure 11 (step S225).

[0097] If the water injection of cylinder #i is also determined to be abnormal in the first measurement (YES in step S225), control device 50 determines that the water injection amount of the water injection valve of cylinder #i is abnormal (step S230).

[0098] On the other hand, when it is determined in the first measurement that there is no water injection abnormality in cylinder #i (NO in step S225), control device 50 determines that there is an abnormality in the water injection control of the water injector of cylinder #i (step S235).

[0099] Next, if counter i is not 4 (NO in step S240), control device 50 increments counter i (step S245) and returns to step S215. Thereafter, for the other cylinders, based on the presence or absence of a water injection abnormality in the first and second measurements, it is determined whether the water injection of the relevant cylinder is normal, whether the water injection amount is abnormal, or whether the water injection control is abnormal. Then, when counter i becomes 4 (YES in step S240) and processing has been completed for all cylinders, control proceeds to END.

[0100] As described above, in this first embodiment, a water injection abnormality (a small water injection amount abnormality) can be determined for each cylinder by the first measurement in which water is injected during the expansion stroke after fuel combustion. Furthermore, a water injection abnormality (an abnormality in the water injection amount or water injection control) can also be determined for each cylinder by the second measurement in which water is injected during the compression stroke before fuel injection. Thus, according to this first embodiment, a knocking sensor is not required, and a water injection abnormality can be determined under conditions in which knocking does not occur.

[0101] Furthermore, according to this first embodiment, by combining the judgment results of the first measurement and the judgment results of the second measurement, it is possible to determine for each cylinder whether the abnormality is in the water injection amount or in the water injection control.

[0102] Furthermore, according to the first embodiment, in the first and second measurements, water injection is performed for each successive fuel injection of a plurality of cylinders (FIGS. 5 and 9), so that an abnormality in water injection can be determined in a short period of time.

[0103] [Variation 1] In the first embodiment, the first and second measurements are performed to determine whether a water injection abnormality exists and to isolate the water injection abnormality, but it is possible to perform only the first measurement more simply. In this case, it is not possible to determine whether there is an abnormality in the water injection control (e.g., the water is not being injected at the intended position), but it is possible to determine whether there is an abnormality in the water injection amount.

[0104] In this modified example 1, the first measurement described in Fig. 11 in the first embodiment is carried out. Then, based on the result of determining whether or not there is an abnormality in the water injection amount in the first measurement, an abnormality in the water injection amount is determined.

[0105] Fig. 14 is a flowchart showing an example of the procedure for the process of determining whether the water injection amount is abnormal in Modification 1. The series of processes shown in this flowchart is also executed at predetermined intervals. Referring to Fig. 14, the control device 50 sets counter i to 1 (step S310), and then determines whether the water injection of cylinder #i was determined to be abnormal in the first measurement described in Fig. 11 (step S315).

[0106] If the first measurement determines that the water injection of cylinder #i is abnormal (YES in step S315), the control device 50 determines that the water injection amount of the water injection valve of cylinder #i is abnormal (step S320). On the other hand, if the first measurement determines that the water injection of cylinder #i is not abnormal (NO in step S315), the control device 50 proceeds to step S325 without executing step S320.

[0107] Next, if counter i is not 4 (NO in step S325), control device 50 increments counter i (step S330) and returns to step S315. Thereafter, for the other cylinders, it is determined whether the water injection amount of the corresponding cylinder is normal or not, based on the presence or absence of a water injection abnormality in the first measurement. Then, when counter i becomes 4 (YES in step S325) and processing for all cylinders is completed, the processing proceeds to END.

[0108] As described above, according to this first modification, an abnormality in the water injection amount can be determined for each cylinder by the first measurement.

[0109] [Embodiment 2] For the second measurement based on water injection before fuel injection, a water injection abnormality (abnormal water injection control) may be determined from the measured value of the amount of NOx in the exhaust gas. If water injection is not performed at the intended position (abnormal water injection control), the amount of NOx may increase due to a high combustion temperature. Therefore, in this second embodiment, for the second measurement, a water injection abnormality is determined based on the amount of NOx in the exhaust gas instead of the temperature or pressure of the exhaust gas.

[0110] The overall configuration of the internal combustion engine in this second embodiment is the same as that in the first embodiment shown in Fig. 1. The processing procedure for the first measurement is the same as that in the first embodiment shown in Fig. 11.

[0111] 15 is a flowchart showing an example of the processing procedure of the second measurement executed by the control device 50 in the second embodiment. The series of processing shown in this flowchart is also executed at predetermined intervals. This flowchart corresponds to the flowchart shown in FIG.

[0112] Referring to Fig. 15, the processes of steps S410 and S415 are the same as the processes of steps S110 and S115, respectively, shown in Fig. 12. In this second embodiment, when water injection is performed in step S415, control device 50 obtains the amount of NOx in the exhaust gas when the water injection was performed using NOx sensor 28 (step S420).

[0113] Next, the control device 50 acquires the NOx amounts N1 to N4 for each of the cylinders 45A to 45D from the NOx amounts acquired in step S420 based on the crank angle of the engine body 10 (step S425). Specifically, the control device 50 acquires the NOx amounts (maximum values ​​or average values ​​for a predetermined period including the maximum values) for each of the sections #1 to #4 as the NOx amounts N1 to N4, respectively.

[0114] Then, the control device 50 calculates increases ΔN1 to ΔN4 of the NOx amounts N1 to N4 from the reference NOx amount (step S430). The reference NOx amount is the NOx amount when the water injection in the second measurement is normal, and is obtained in advance for each rotation speed and load of the engine body 10 by prior experiments or simulations, and is stored in advance in the storage device 53 as a map or the like. The control device 50 then obtains from the map the reference NOx amount corresponding to the rotation speed and load of the engine body 10 at the time of measurement, and calculates increases ΔN1 to ΔN4 of the NOx amount using the obtained reference NOx amount.

[0115] When the NOx amount increase amounts ΔN1 to ΔN4 from the reference NOx amount are calculated, the control device 50 sets a counter i to 1 (step S435) and determines whether the NOx amount increase amount ΔNi (ΔN1) is greater than the determination value ΔNth (step S440). If it is determined that the NOx amount increase amount ΔNi is greater than the determination value ΔNth (YES in step S440), the control device 50 determines that the water injection of the water injection valve provided in the #i cylinder corresponding to the section #i is abnormal (step S445).

[0116] On the other hand, when it is determined in step S440 that the NOx amount increase ΔNi is equal to or less than the determination value ΔNth (NO in step S440), control device 50 proceeds to step S450 without executing step S445.

[0117] Next, if counter i is not 4 (NO in step S450), control device 50 counts up counter i (step S455) and returns to step S440. Thereafter, for the other cylinders, the presence or absence of a water injection abnormality is determined based on the comparison result between NOx amount increase ΔNi and determination value ΔNth. Then, when counter i becomes 4 (YES in step S450) and the presence or absence of an abnormality has been determined for all cylinders, the second measurement ends.

[0118] As described above, the second embodiment can also achieve the same effects as the first embodiment.

[0119] [Variation 2] In each of the above embodiments and variants, in the first measurement, water injection is performed sequentially for all cylinders 45A to 45D at a predetermined timing after the expansion stroke (after the end of combustion), and in the second measurement, water injection is performed sequentially for all cylinders at a predetermined timing after the compression stroke (before fuel injection).

[0120] However, if the responsiveness or resolution of the temperature sensor 29, pressure sensor 26, or NOx sensor 28 used to detect the measured values ​​is low, it may be impossible to separate (detect) the measured values ​​for each cylinder. Therefore, water injection may be performed for each cylinder cycle so that the cycles in which water injection is performed do not overlap between cylinders. That is, for the first measurement, water injection is performed during the expansion stroke of one cylinder, and after one cycle of that cylinder is completed, water injection is performed during the expansion stroke of the other cylinders. This is performed sequentially for all four cylinders. For the second measurement, water injection is performed during the compression stroke of one cylinder, and after one cycle of that cylinder is completed, water injection is performed during the compression stroke of the other cylinders. This is performed sequentially for all four cylinders. For example, the measured values ​​for each cylinder may be the average value of the sensor detection values ​​over one cycle. With this measurement method, even if a sensor with low responsiveness or resolution is used, measurements for each cylinder can be obtained and an abnormality in water injection can be determined for each cylinder.

[0121] In the following, a typical example will be described in which the determination of water injection abnormality is made based on the exhaust temperature detected by the temperature sensor 29, but the exhaust gas pressure detected by the pressure sensor 26 may be used instead of the exhaust temperature. Furthermore, for the second measurement, the determination of abnormality may be made based on the amount of NOx in the exhaust gas detected by the NOx sensor 28 instead of the exhaust temperature.

[0122] 16 is a flowchart showing an example of the processing procedure of the first measurement executed by the control device 50 in this modified example 2. The series of processing shown in this flowchart is also executed at predetermined intervals. This flowchart corresponds to the flowchart shown in FIG.

[0123] Referring to Fig. 16, the process of step S510 is the same as the process of step S10 shown in Fig. 11. Then, when it is determined in step S510 that the condition for performing the first measurement is met (YES in step S510), control device 50 sets counter i to 1 (step S515), and performs water injection from the water injector for cylinder #i (cylinder #1) at a predetermined timing (Fig. 3) after the expansion stroke (after the end of combustion) (step S520).

[0124] Next, the control device 50 acquires the temperature Ti of the exhaust gas discharged from this cylinder #i using the temperature sensor 29 (step S525). Then, the control device 50 calculates the one-cycle average temperature of the acquired temperature Ti, i.e., the average temperature Tai of the cylinder #i in one cycle (step S530).

[0125] When the average temperature Tai of the #i cylinder is calculated, the control device 50 determines whether the average temperature Tai is higher than the determination value Tth (FIG. 6) (step S535). If it is determined that the average temperature Tai is higher than the determination value Tth (YES in step S535), the control device 50 determines that the water injection of the water injection valve provided in the #i cylinder corresponding to the section #i is abnormal (step S540).

[0126] On the other hand, when it is determined in step S535 that the average temperature Taii is equal to or lower than the determination value Tth (NO in step S535), control device 50 proceeds to step S545 without executing step S540.

[0127] Next, if counter i is not 4 (NO in step S545), control device 50 counts up counter i (step S550) and returns to step S520. Thereafter, for the other cylinders, the presence or absence of a water injection abnormality is determined based on the comparison result between average temperature Tai and determination value Tth. Then, when counter i becomes 4 (YES in step S545) and the presence or absence of an abnormality has been determined for all cylinders, the first measurement ends.

[0128] 17 is a flowchart showing an example of the processing procedure of the second measurement executed by the control device 50 in Modification 2. The series of processes shown in this flowchart is also executed at predetermined intervals. This flowchart corresponds to the flowchart shown in FIG.

[0129] Referring to Fig. 17, the process of step S610 is the same as the process of step S110 shown in Fig. 12. Then, when it is determined in step S610 that the condition for performing the second measurement is met (YES in step S610), control device 50 sets counter i to 1 (step S615), and performs water injection from the water injector for cylinder #i (cylinder #1) at a predetermined timing (see Fig. 7) during the compression stroke (before fuel injection) (step S620).

[0130] Next, the control device 50 acquires the temperature Ti of the exhaust gas discharged from this cylinder #i using the temperature sensor 29 (step S625). Then, the control device 50 calculates the one-cycle average temperature of the acquired temperature Ti, i.e., the one-cycle average temperature Tai of the cylinder #i (step S630).

[0131] After calculating the average temperature Tai of cylinder #i, the control device 50 calculates the decrease ΔTai of the average temperature Tai from the reference temperature (step S630). The reference temperature is the same as the reference temperature described in step S130 of FIG.

[0132] When the decrease ΔTai of the average temperature Tai from the reference temperature is calculated, the control device 50 determines whether the temperature decrease ΔTai is smaller than the determination value ΔTth (FIG. 10) (step S640). If it is determined that the temperature decrease ΔTai is smaller than the determination value ΔTth (YES in step S640), the control device 50 determines that the water injection of the water injector provided in the #i cylinder corresponding to the section #i is abnormal (step S645).

[0133] On the other hand, if it is determined in step S640 that the temperature decrease ΔTai is equal to or greater than the determination value ΔTth (NO in step S640), control device 50 proceeds to step S650 without executing step S645.

[0134] Next, if counter i is not 4 (NO in step S650), control device 50 counts up counter i (step S655) and returns to step S620. Thereafter, for the other cylinders, the presence or absence of a water injection abnormality is determined based on the comparison result between temperature decrease ΔTai and determination value ΔTth. Then, when counter i becomes 4 (YES in step S650) and the presence or absence of an abnormality has been determined for all cylinders, the second measurement ends.

[0135] As described above, according to the second modification, even if a sensor (temperature sensor 29, pressure sensor 26, or NOx sensor 28) does not have high responsiveness or resolution, it is possible to determine an abnormality in water injection for each cylinder.

[0136] [Variation 3] In each of the above embodiments and modifications, if it is determined that water injection is abnormal for all cylinders, it may be determined that another abnormal mode (an abnormality other than an abnormality in the water injection amount / water injection control) has occurred. If it is determined that water injection is abnormal for all cylinders, it may be assumed that there is an abnormality not in each cylinder, but in the pump 66 that supplies water to the water injection valves 63A-63D, for example, and it may be determined that such an abnormality has occurred.

[0137] Fig. 18 is a flowchart showing an example of the procedure for the abnormality determination process in Modification 3. The series of processes shown in this flowchart is also executed at predetermined intervals. Referring to Fig. 18, the control device 50 sets counter i to 1 (step S710), and then determines whether or not the water injection from the water injector of cylinder #i is abnormal in the first measurement or the second measurement (step S715).

[0138] If it is determined in step S715 that the water injection of cylinder #i is abnormal (YES in step S715), the control device 50 determines that the water injection of the water injector of cylinder #i is abnormal (step S720). On the other hand, if it is determined that the water injection of cylinder #i is not abnormal (NO in step S715), the control device 50 proceeds to step S725 without executing step S720.

[0139] Next, if counter i is not 4 (NO in step S725), control device 50 counts up counter i (step S730) and returns the process to step S715. Thereafter, determinations as to whether or not water injection is abnormal are made for the other cylinders as well.

[0140] Then, when counter i reaches 4 (YES in step S725) and the water injection abnormality determination for all cylinders is completed, control device 50 determines whether or not water injection for all cylinders has been determined to be abnormal (step S735). If water injection for all cylinders has been determined to be abnormal (YES in step S735), control device 50 diagnoses that another abnormal mode has occurred (step S740). As described above, another abnormal mode is not an abnormality for each cylinder, but is, for example, an abnormality in which the properties of water change (quality abnormality) or an abnormality in pump 66 that supplies water to water injection valves 63A-63D.

[0141] As described above, according to the third modification, abnormalities in the water quality and abnormalities in the pump 66 can be determined separately from abnormalities in each cylinder.

[0142] The embodiments disclosed herein are intended to be combined as appropriate within the scope of any technical inconsistency. The embodiments disclosed herein should be considered to be illustrative and not restrictive in all respects. The technical scope of the present disclosure is defined by the claims, not the description of the above-described embodiments, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0143] 1 diesel engine, 10 engine body, 11A, 11B intake pipe, 11C intake manifold, 12A exhaust manifold, 12B, 12C exhaust pipe, 13 EGR device, 13A, 13B EGR piping, 13C bypass piping, 14A path switching device, 14B EGR valve, 15 EGR cooler, 16 intercooler, 21 intake air flow sensor, 22 rotation angle sensor, 23 atmospheric pressure sensor, 24, 26 pressure sensor, 25 accelerator pedal sensor, 27 vehicle speed sensor, 28 NOx sensor, 29 temperature sensor, 30 turbocharger, 35 compressor, 35A compressor impeller, 36 turbine, 36A turbine impeller, 41 common rail, 42A to 42D fuel piping, 43A to 43D fuel injection valve, 45A to 45D cylinder, 47 Throttle device, 47A throttle valve, 50 control device, 51 processor, 53 storage device, 61 water supply common rail, 62A-62D water piping, 63A-63D water injection valve, 65 supply pipe, 66 pump, 67 water tank, 71 cylinder block, 72 cylinder head, 73 piston, 75 combustion chamber, 76 cavity.

Claims

1. An engine body having a plurality of cylinders; a fuel injector configured to inject fuel into each of the plurality of cylinders; a water injection device configured to inject water into each of the plurality of cylinders; a control device for controlling the water injection device; a sensor for measuring the temperature or pressure of exhaust gas discharged from the plurality of cylinders; The control device performing a first water injection by the water injection device during an expansion stroke after fuel combustion for each of the plurality of cylinders; acquiring a first measurement value from the sensor that indicates a measurement value of the temperature or pressure when the first water injection is performed; determining an abnormality in water injection for each of the plurality of cylinders based on a change in the first measurement value for each of the plurality of cylinders; The control device further a second water injection by the water injection device during a compression stroke before fuel injection for each of the plurality of cylinders; acquiring a second measurement value from the sensor indicating the measurement value of the temperature or pressure when the second water injection is performed; The abnormality is determined based on a change in the second measurement value for each of the plurality of cylinders.

2. 2. The internal combustion engine according to claim 1, wherein the control device determines that the amount of water injection by the water injection device is normal and that the water injection control by the water injection device is abnormal for a cylinder for which the water injection is determined to be normal based on the first water injection and the water injection is determined to be abnormal based on the second water injection.

3. 3. The internal combustion engine according to claim 1, wherein the control device determines that the amount of water injection by the water injection device is abnormal for a cylinder in which water injection is determined to be abnormal due to the first water injection and water injection is determined to be abnormal due to the second water injection.

4. 4. The internal combustion engine according to claim 1, wherein the control device performs the second water injection for each successive fuel injection of the plurality of cylinders.

5. 5. The internal combustion engine according to claim 1, wherein the control device performs the first water injection for each successive fuel injection of the plurality of cylinders.

6. 4. The internal combustion engine according to claim 1, wherein the control device performs the second water injection for each cycle of the plurality of cylinders so that the cycles in which the second water injection is performed do not overlap among the plurality of cylinders.

7. 7. The internal combustion engine according to claim 1, wherein the control device performs the first water injection for each cycle of the plurality of cylinders so that the cycles in which the first water injection is performed do not overlap among the plurality of cylinders.

8. An engine body having a plurality of cylinders; a fuel injector configured to inject fuel into each of the plurality of cylinders; a water injection device configured to inject water into each of the plurality of cylinders; a control device for controlling the water injection device; a sensor for measuring the temperature or pressure of exhaust gas discharged from the plurality of cylinders; The control device performing a first water injection by the water injection device during an expansion stroke after fuel combustion for each of the plurality of cylinders; acquiring a first measurement value from the sensor that indicates a measurement value of the temperature or pressure when the first water injection is performed; determining an abnormality in water injection for each of the plurality of cylinders based on a change in the first measurement value for each of the plurality of cylinders; The control device performs the first water injection in each cycle of the plurality of cylinders so that the cycles in which the first water injection is performed do not overlap among the plurality of cylinders.

9. An engine body having a plurality of cylinders; a fuel injector configured to inject fuel into each of the plurality of cylinders; a water injection device configured to inject water into each of the plurality of cylinders; a control device for controlling the water injection device; a sensor for measuring the temperature or pressure of exhaust gas discharged from the plurality of cylinders; a NOx sensor that measures the amount of NOx in the exhaust gas; The control device performing a first water injection by the water injection device during an expansion stroke after fuel combustion for each of the plurality of cylinders; acquiring a first measurement value from the sensor that indicates a measurement value of the temperature or pressure when the first water injection is performed; determining an abnormality in water injection for each of the plurality of cylinders based on a change in the first measurement value for each of the plurality of cylinders; The control device further a second water injection by the water injection device during a compression stroke before fuel injection for each of the plurality of cylinders; acquiring a third measurement value from the NOx sensor, the third measurement value indicating the measurement value of the NOx amount when the second water injection is performed; The abnormality is determined based on a change in the third measurement value for each of the plurality of cylinders.

10. 4. The internal combustion engine according to claim 1, wherein the control device further determines that a predetermined abnormal mode has occurred when it is determined that water injection is abnormal due to the first water injection or the second water injection in all of the plurality of cylinders.

11. A control method for an internal combustion engine, comprising: The internal combustion engine includes: an engine body having a plurality of cylinders; a fuel injector configured to inject fuel into each of the plurality of cylinders; a water injection device configured to inject water into each of the plurality of cylinders; a sensor for measuring the temperature or pressure of exhaust gas discharged from the plurality of cylinders; The control method includes: performing a first water injection by the water injection device for each of the plurality of cylinders during an expansion stroke after fuel combustion; obtaining a first measurement value from the sensor indicating a measurement value of the temperature or pressure when the first water injection is performed; determining an abnormality in water injection in each of the plurality of cylinders based on a change in the first measurement value for each of the plurality of cylinders; performing a second water injection by the water injection device during a compression stroke before fuel injection for each of the plurality of cylinders; obtaining a second measurement value from the sensor indicating the measurement value of the temperature or pressure when the second water injection is performed; determining whether or not an abnormality exists based on a change in the second measurement value for each of the plurality of cylinders.

Images