Vehicle

Abstract

To provide a vehicle capable of achieving more effective operation by widening a range in which a supercharger can be operated according to the degree of flooding to an exhaust passage of an internal combustion engine, and enhancing the degree of freedom of the operation.SOLUTION: The vehicle 1 includes an engine (internal combustion engine) 2, a low-speed turbocharger included in a turbocharger 10 connected to the engine 2, and a controller (control device) 40 that controls the turbocharger 10 such that the turbocharger 10 is driven in a predetermined operation region of the engine 2. The controller 40 acquires information on the degree of water covering to the exhaust passage of the engine 2, and enlarges a predetermined operation region of the low rotation turbo to a high rotation side of the engine 2 as the degree of water covering is large. With this configuration, as the exhaust passage is cooled by the water and the volume flow rate of the exhaust gas decreases, the operating range of the low speed turbocharger is expanded to the high speed side, so that the low speed turbocharger can be used in a wider range.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a vehicle equipped with an internal combustion engine and a supercharger. [Background technology]

[0002] Conventionally, technologies relating to vehicles equipped with an internal combustion engine and a turbocharger have been known. For example, Patent Document 1 describes a hybrid vehicle that, when water is detected in the engine's exhaust pipe, activates an electric turbocharger and opens a throttle valve and an EGR valve in EV driving mode. In this hybrid vehicle, the electric turbocharger sends air from the intake pipe through the EGR pipe to the exhaust pipe, thereby discharging some or all of the water in the exhaust pipe out of the exhaust pipe. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-101576 Summary of the Invention [Problem to be solved by the invention]

[0004] However, when the exhaust passage of an internal combustion engine is cooled with water, the volumetric flow rate of the exhaust gas that rotates the turbocharger changes. Therefore, it is preferable to more appropriately switch the operating state of the turbocharger depending on the degree of water damage to the exhaust pipe.

[0005] The present invention has been made in consideration of these problems, and its purpose is to provide a vehicle that can be operated more effectively by expanding the range in which the turbocharger can operate and increasing the degree of freedom in its operation depending on the degree of water exposure to the exhaust passage of the internal combustion engine. [Means for solving the problem]

[0006] In order to achieve the above object, the vehicle of the present invention comprises an internal combustion engine, a supercharger connected to the internal combustion engine, and a control device that controls the supercharger so that the supercharger operates within a predetermined operating range of the internal combustion engine, wherein the control device acquires information regarding the degree of water damage to the exhaust passage of the internal combustion engine, and the greater the degree of water damage, the greater the expansion of the predetermined operating range of the supercharger toward the high rotation side of the internal combustion engine. [Effects of the Invention]

[0007] According to the vehicle of the present invention, the area in which the turbocharger can operate can be made wider depending on the degree of water exposure to the exhaust passage of the internal combustion engine, thereby increasing the freedom of operation, thereby enabling more effective operation. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a schematic diagram showing a vehicle according to an embodiment. [Figure 2] FIG. 2 is a schematic diagram of the engine and the intake and exhaust systems as viewed from the vehicle width direction. [Figure 3] 2 is a schematic diagram of the engine and the intake and exhaust system periphery as viewed from the front in the vehicle longitudinal direction. FIG. [Figure 4] FIG. 2 is an explanatory diagram showing the operating ranges of a low-speed turbo and a high-speed turbo. [Figure 5] FIG. 1 is a schematic diagram showing an engine, a low-speed turbo, and a high-speed turbo. [Figure 6] 10 is a flowchart illustrating an example of an operating range change control. [Figure 7] FIG. 4 is an explanatory diagram showing the operating ranges of a low rotation turbo and a high rotation turbo when the water depth level is equal to or greater than a first predetermined value. [Figure 8] 10 is an explanatory diagram showing the operating ranges of the low rotation turbo 20 and the high rotation turbo when the water depth level is equal to or greater than a second predetermined value. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0009] An embodiment of the present invention will be described below with reference to the drawings. Fig. 1 is a schematic diagram showing a vehicle 1 according to the embodiment. Fig. 2 is a schematic diagram of the engine and the vicinity of the intake and exhaust system as viewed from the vehicle width direction. Fig. 3 is a schematic diagram of the engine and the vicinity of the intake and exhaust system as viewed from the front in the vehicle longitudinal direction. The vehicle 1 according to the embodiment is configured to be able to run by driving each wheel 3 with the output of an engine (internal combustion engine) 2. The engine 2 is a gasoline engine or a diesel engine with multiple cylinders.

[0010] A supercharger 10 is provided downstream of an exhaust manifold 5, which is part of an exhaust passage of the engine 2. As shown in FIG. 2 , the supercharger includes a low-speed turbocharger (low-speed supercharger) 20 (hereinafter referred to as low-speed turbo 20) and a high-speed turbocharger (high-speed supercharger) 30 (hereinafter referred to as high-speed turbo 30). The low-speed turbo 20 has a turbine 21 and a compressor 22. The high-speed turbo 30 has a turbine 31 and a compressor 32, and is connected to the low-speed turbo 20. The high-speed turbo 30 is provided above the low-speed turbo 20.

[0011] As shown by the two-dot chain arrows in FIG. 2 , exhaust gas discharged from the exhaust manifold 5 passes through the turbine 21 or turbine 31, passes through the purification device 6 including a catalyst, and is then discharged to the outside from the exhaust pipe 7. At this time, the exhaust gas drives the turbine 21 or turbine 31 to rotate, which in turn rotates the compressor 22 or compressor 32. As a result, as shown by the solid arrows in FIGS. 2 and 3 , air from the outside is drawn into the compressor 22 or compressor 32 via the air cleaner 8 ( FIG. 3 ) and is then compressed and sent to the intake side of the engine 2. Note that an intercooler 9 that cools the air is disposed between the compressors 22 and 32 and the engine 2. The illustration of the intercooler 9 is omitted in FIG. 3 . The compressor 32 is connected to the air cleaner 8 via an intake passage, and the compressor 22 is connected to the intercooler 9 via an intake passage. The intake air that passes through the compressor 22 or compressor 32 is cooled by the intercooler 9 and supplied to the engine 2. Furthermore, the turbine 21 is connected to the exhaust manifold 5 via an exhaust passage, and the turbine 31 is connected to the purification device 6 via an exhaust passage.

[0012] FIG. 4 is an explanatory diagram showing the operating ranges of the low-speed turbocharger 20 and the high-speed turbocharger 30. As shown in the figure, the low-speed turbocharger 20 and the high-speed turbocharger 30 each have their own operating range defined within the operating range of the engine 2, with the horizontal axis representing the engine speed and the vertical axis representing torque (load). In FIG. 4, the low-speed region A1 represents the region where the speed and torque are lower than the dashed line DL1, the medium-speed region A2 represents the region surrounded by the dashed lines DL1 and DL2, and the high-speed region A3 represents the region where the speed and torque are higher than the dashed line DL2. The low-speed turbocharger 20 is a small-capacity turbocharger used in the region of the engine 2 that includes the low-speed region A1 to the medium-speed region A2. On the other hand, the high-speed turbocharger 30 is a large-capacity turbocharger used in the region of the engine 2 that includes the medium-speed region A2 to the high-speed region A3. The medium-speed region A2 is a region where both the low-speed turbocharger 20 and the high-speed turbocharger 30 can be used.

[0013] 5 is a schematic diagram showing the engine 2, the low-speed turbo 20, and the high-speed turbo 30. As shown in the figure, the intake passage 2A of the engine 2 is provided with a bypass passage 2A1 that allows intake air to flow into the engine 2, bypassing the compressor 22 of the low-speed turbo 20, and the bypass passage 2A1 is provided with a bypass valve 61 that opens and closes the bypass passage 2A1. The exhaust passage 2B of the engine 2 is provided with a bypass passage 2B1 that allows exhaust gas from the engine 2 to flow, bypassing the turbine 21 of the low-speed turbo 20, and the bypass passage 2B1 is provided with a bypass valve 62 that opens and closes the bypass passage 2B1. The exhaust passage 2B is further provided with a bypass passage 2B2 that allows exhaust gas from the engine 2 to flow, bypassing the turbine 31 of the high-speed turbo 30, and the bypass passage 2B2 is provided with a wastegate valve 63 that opens and closes the bypass passage 2B2.

[0014] The bypass valves 61, 62 and the wastegate valve 63 are controlled to open and close by a controller (control device 40). Specifically, when the low-speed turbo 20 is used, the bypass valves 61, 62 are closed and the wastegate valve 63 is open. On the other hand, when the high-speed turbo 30 is used, the bypass valves 61, 62 are open and the wastegate valve 63 is closed. This allows switching between the low-speed turbo 20 and the high-speed turbo 30 to be used.

[0015] The controller 40 is a control device that performs overall control of the vehicle 1, including the operation of the engine 2 and the turbocharger 10, and is configured to include input / output devices, storage devices (ROM, RAM, non-volatile RAM, etc.), a central processing unit (CPU), etc. The controller 40 switches between the operation of the low rotation turbo 20 and the high rotation turbo 30 for each predetermined operating range. In this embodiment, as an example, it is assumed that the predetermined operating range AL, which is shaded in Fig. 4, is set so that the low rotation turbo 20 operates in the low rotation range A1, and the high rotation turbo 30 operates in the medium rotation range A2 and the high rotation range A3.

[0016] In the vehicle 1 configured as described above, the controller 40 acquires information relating to the extent of water coverage on the outer surface of the exhaust passage of the engine 2, and changes the operating range AL of the low rotation turbo 20 based on this information. The information relating to the extent of water coverage on the exhaust passage is, for example, a water depth level L, which is the height of water present around the vehicle body from the road surface. The vehicle 1 is provided with a water depth level sensor 52 (FIG. 1) that detects the water depth level L, and information on the water depth level L (FIG. 1) detected by the water depth level sensor 52 is output to the controller 40. Note that the controller 40 may acquire the water depth level L by estimation using other well-known methods, not limited to detection by the water depth level sensor 52.

[0017] Based on the acquired water depth level L, the controller 40 acquires the degree of water damage to the exhaust passage due to flooding into the engine compartment. The relationship between the degree of water damage and the water depth level L may be determined in advance through experiments, analysis, or the like. Even if the engine compartment is flooded and water could splash onto the exhaust passage, the devices and components of the vehicle 1 that should be protected from water are protected by waterproofing. As such, when the degree of water damage to the exhaust passage increases, the exhaust passage cools, thereby reducing the volumetric flow rate of exhaust gas even if the engine 2 rotation speed remains the same. As a result, the low-speed turbo 20 can be operated above its normal upper limit of rotation speed.

[0018] Therefore, the controller 40 expands the operating range AL of the low rotation turbo 20 toward the higher rotation side of the engine 2 as the water depth level L increases, for example, as shown in FIG. 1 with a first predetermined value (first predetermined value) L1, a second predetermined value L2, and a third predetermined value (second predetermined value) L3. Hereinafter, with reference to the drawings, a description will be given of control for changing the operating range AL of the low rotation turbo 20. FIG. 6 is a flowchart showing an example of the operating range change control. The process shown in FIG. 6 is repeatedly executed by the controller 40 every unit time (for example, every few msec) while the engine 2 is running.

[0019] First, the controller 40 determines whether or not the engine 2 has just been started (step ST1). "Immediately after the engine 2 has been started" refers to the period from when the engine 2 has been started until the temperature of the low rotation turbo 20 has not yet risen sufficiently due to exhaust gas. If the controller 40 determines that the engine 2 has not just been started (Yes in step ST1), it determines whether or not the water depth level L is equal to or greater than a first predetermined value L1 (FIG. 1) (step ST2). The first predetermined value L1 is, for example, a water depth level L in the engine compartment at which the lower end of the low rotation turbo 20 is submerged.

[0020] If the controller 40 determines that the water depth level L is equal to or greater than the first predetermined value L1 (step ST2), it then determines whether the water depth level L is less than a third predetermined value L3 (FIG. 1) (step ST3). The third predetermined value L3 is a water depth level L at which priority should be given to escaping the vehicle 1 from the surrounding water rather than expanding the operating range AL of the low rotation turbo 20. The third predetermined value L3 is, for example, approximately the height of the hood of the vehicle 1.

[0021] If the controller 40 determines that the water depth level L is less than the third predetermined value L3 (Yes in step ST3), it expands the operating range AL of the low rotation turbo 20 toward the high rotation side (step ST4) and executes the processing from step ST1 onwards again. Fig. 7 is an explanatory diagram showing an example of the operating ranges of the low rotation turbo 20 and the high rotation turbo 30 when the water depth level L is equal to or greater than the first predetermined value L1. When the water depth level L is equal to or greater than the first predetermined value L1, the controller 40 expands the operating range AL of the low rotation turbo 20 into the medium rotation range A2, which is higher than normal, as shown by the hatched range in Fig. 7.

[0022] Furthermore, when the water depth level L is equal to or greater than a first predetermined value L1 and less than a third predetermined value L3, the controller 40 may further increase the amount by which the operating range AL of the low rotation turbo 20 is expanded toward the high rotation side compared to normal operation as the water depth level L increases, i.e., the degree of submersion increases. Figure 8 is an explanatory diagram showing an example of the operating ranges of the low rotation turbo 20 and the high rotation turbo 30 when the water depth level L is equal to or greater than a second predetermined value L2. When the water depth level L is equal to or greater than a second predetermined value L2 that is greater than the first predetermined value L1, the controller 40 expands the operating range AL of the low rotation turbo 20 further into the high rotation range A3, as shown by the hatched range in Figure 8, than when the water depth level L is equal to or greater than the first predetermined value L1 and less than the second predetermined value L2.

[0023] In this way, by operating the low rotation turbo 20 at a higher rotation speed as the water depth level L increases, the frequency of switching from the low rotation turbo 20 to the high rotation turbo 30 can be reduced. Therefore, torque fluctuations associated with switching can be suppressed. Furthermore, by reducing the number of valve controls required for switching, valve wear and energy consumption for valve drive can be suppressed, enabling more efficient operation of the turbocharger 10. The upper limit rotation speed for expanding the operating range AL may be set in advance through experiments, analysis, etc. Furthermore, the expansion of the operating range AL relative to the water depth level L may be either a stepwise change or a continuous change.

[0024] In contrast, if the controller 40 determines that the engine 2 has just started (No in step ST1), it skips steps ST2 to ST4, does not expand the operating range AL of the low rotation turbo 20, and executes the processes from step ST1 onwards again. If the temperature of the low rotation turbo 20 has not yet risen sufficiently, there is a risk of condensation occurring in the low rotation turbo 20. Therefore, by not actively expanding the operating range AL of the low rotation turbo 20, it is possible to suppress the occurrence of condensation in the low rotation turbo 20. In this case, the high rotation turbo 30, which is located above the low rotation turbo 20 and is less likely to be exposed to water and generate condensation, operates in its normal operating range (here, the medium rotation range A2 and the high rotation range A3).

[0025] Furthermore, if the controller 40 determines that the water depth level L is less than the first predetermined value L1 (No in step ST2), it skips steps ST3 and ST4, does not expand the operating range AL of the low rotation turbo 20, and executes the processes from step ST1 onwards again. In other words, if the water depth level L is less than the first predetermined value L1 and there is little possibility that water will splash onto the exhaust passage of the engine 2, the operating range AL of the low rotation turbo 20 is not expanded. This prevents the low rotation turbo 20 from operating beyond the upper limit of rotation speed, thereby enabling the low rotation turbo 20 to be appropriately protected.

[0026] Furthermore, if the controller 40 determines that the water depth level L is equal to or greater than the third predetermined value L3 (Yes in step ST3), it skips step ST4, does not expand the operating range AL of the low-speed turbo 20, and executes the processes from step ST1 onwards again. When the water depth level L is equal to or greater than the third predetermined value L3, it is desirable to prioritize getting the vehicle 1 out of the surrounding flooded road. Therefore, in this case, the operating range AL of the low-speed turbo 20 is not actively expanded, and the high-speed turbo 30 is maintained in an operating state within its normal operating range. This ensures the driving force of the vehicle 1 by utilizing the high output of the high-speed turbo 30, enabling the vehicle 1 to quickly escape from the surrounding water.

[0027] As described above, the vehicle 1 of the embodiment includes the engine (internal combustion engine) 2, the low rotation turbo 20 included in the supercharger 10 connected to the engine 2, and the controller (control device) 40 that controls the supercharger 10 so that the low rotation turbo 20 is driven in a predetermined operating range of the engine 2. The controller 40 acquires information relating to the degree of water damage to the exhaust passage of the engine 2, and expands the predetermined operating range AL of the low rotation turbo 20 toward the high rotation side of the engine 2 as the degree of water damage increases.

[0028] With this configuration, the operating range AL of the low rotation turbo 20 can be expanded toward the high rotation side as the exhaust passage is cooled by water and the volumetric flow rate of the exhaust gas decreases, making it possible to use the low rotation turbo 20 in a wider range. Therefore, according to the vehicle 1 of the embodiment, the range in which the low rotation turbo 20 can operate can be made wider depending on the degree of water exposure to the exhaust passage of the engine 2, and the degree of freedom in its operation can be increased, making it possible to achieve more effective operation.

[0029] The vehicle 1 is further provided with a water depth level sensor (water depth level acquisition unit) 52 that acquires the water depth level L around the vehicle body, and the controller 40 acquires the degree of water coverage based on the water depth level L. With this configuration, the degree of water coverage of the exhaust passage can be easily and accurately acquired based on the water depth level L.

[0030] The supercharger 10 also includes a low-speed turbo (low-speed supercharger) 20 and a high-speed turbo (high-speed supercharger) 30 that is used in a higher speed range of the engine 2 than the low-speed turbo 20 and is positioned above the low-speed turbo 20, and when the water depth level L is equal to or greater than a first predetermined value (first predetermined value) L1, the controller 40 expands the operating range AL of the low-speed turbo 20 toward the high speed side, and does not expand the operating range AL of the low-speed turbo 20 regardless of the water depth level L immediately after starting the engine 2.

[0031] This configuration reduces the frequency of switching between the low-speed turbo 20 and the high-speed turbo 30, suppressing torque fluctuations while reducing the number of valve controls and improving controllability. Also, by not actively expanding the operating range AL of the low-speed turbo 20 immediately after starting the engine 2, it is possible to suppress the generation of condensed water.

[0032] Furthermore, when the water depth level is equal to or greater than a third predetermined value (second predetermined value) L3 that is greater than the first predetermined value L1, the controller 40 does not expand the operating range AL of the low rotation turbo 20. This configuration makes it possible to maintain a state in which it is easy to ensure the driving force of the vehicle 1 by using the high rotation turbo 30, and to quickly get the vehicle 1 out of the surrounding water.

[0033] Here, when expanding the operating range AL of the low-speed turbo 20, the controller 40 may take into consideration the following factors in addition to the water depth level L. For example, as the vehicle speed increases, the attitude of the vehicle 1 and the movement of water in the engine compartment tend to change more significantly, and therefore water in the engine compartment tends to get into the exhaust passage. Therefore, the controller 40 may determine, based on the vehicle speed detected by a vehicle speed sensor 54 (FIG. 1) provided on the vehicle 1, that the higher the vehicle speed, the greater the degree of water exposure to the exhaust passage, and expand the operating range AL of the low-speed turbo 20 toward the higher speed side as the vehicle speed increases. This allows the degree of water exposure to the exhaust passage, i.e., the degree of reduction in exhaust flow rate, to be obtained more accurately and reflected in the expansion of the operating range AL of the low-speed turbo 20. Note that the controller 40 may also determine that the degree of water exposure to the exhaust passage increases as the acceleration, yaw rate, pitch angle, roll angle, etc. of the vehicle 1 increase, as other index values ​​that indicate the tendency for the attitude of the vehicle 1 and the movement of water in the engine compartment to change.

[0034] Furthermore, the longer the exhaust passage is exposed to water, the more likely the temperature of the exhaust passage will drop. Therefore, the controller 40 may measure the time that has elapsed since the water depth level L became equal to or greater than the first predetermined value L1, and may expand the operating range AL of the low rotation turbo 20 toward the higher rotation side as the time elapses. This allows the degree of reduction in the exhaust flow rate to be obtained more accurately and reflected in the expansion of the operating range AL of the low rotation turbo 20.

[0035] Furthermore, the lower the temperature of the water in the exhaust passage, the more easily the temperature of the exhaust passage decreases. Therefore, the controller 40 may expand the operating range AL of the low-speed turbo 20 toward the higher rotation speed side as the water temperature decreases, based on the water temperature acquired by a water temperature sensor (temperature acquisition unit) 56 (FIG. 1) that detects the temperature of the water around the vehicle body. For example, if the water temperature is lower than a predetermined temperature when the water depth level L is equal to or higher than a first predetermined value L1, the controller 40 may perform control such that the operating range AL of the low-speed turbo 20 is expanded toward the higher rotation speed side compared to when the water temperature is equal to or higher than the predetermined temperature. This allows the degree of reduction in exhaust flow rate to be acquired more accurately and reflected in the expansion of the operating range AL of the low-speed turbo 20.

[0036] Although the description of the embodiment has been completed above, aspects of the present invention are not limited to this embodiment. For example, in this embodiment, the present invention is applied to a vehicle 1 that can run using the output of the engine 2, but the present invention may also be applied to hybrid vehicles, plug-in hybrid vehicles, and the like. Note that a plug-in hybrid vehicle is a vehicle that is capable of external charging, in which power is supplied from an external power source to a power storage device mounted on the vehicle for charging, and external power feeding, in which power is supplied from the power storage device to electrical appliances outside the vehicle.

[0037] Furthermore, in this embodiment, the present invention is applied to a vehicle 1 equipped with a low-speed turbo 20 and a high-speed turbo 30, but the present invention may also be applied to a vehicle equipped with a single supercharger. Even in this case, as described above, the greater the degree of water exposure to the exhaust passage, the wider the operating range of the supercharger can be expanded to the high-speed side, thereby enabling the supercharger to be used in a wider range. Furthermore, the number of times the valve is controlled to switch between using and not using the supercharger can be reduced, improving the controllability of the supercharger.

[0038] Furthermore, in this embodiment, it is assumed that the extent to which water present around the vehicle body is exposed to the engine compartment changes depending on the amount of water that is exposed to the outer surface of the exhaust passage of the engine 2. However, a water supply device that supplies water to the outer surface of the exhaust passage of the engine 2 may be installed in the engine compartment, and the operating range of the turbocharger may be expanded to the high rotation speed side depending on the amount of water that is exposed to the exhaust passage by the water supply device. [Explanation of symbols]

[0039] 1 vehicle 2. Engine (internal combustion engine) 5 Exhaust manifold (exhaust passage) 10. Turbocharger 20 Low-speed turbo (low-speed turbocharger: low-speed supercharger) 30 High-speed turbo (high-speed turbocharger: high-speed supercharger) 40 Controller (control device) 52 Water depth level sensor (water depth level acquisition unit) 56 Water temperature sensor (temperature acquisition part) L Water depth level L1 First predetermined value (first predetermined value) L2 Second predetermined value L3 Third predetermined value (second predetermined value)

Claims

1. an internal combustion engine; a supercharger connected to the internal combustion engine; a control device that controls the supercharger so that the supercharger is driven in a predetermined operating region of the internal combustion engine; Equipped with The control device acquires information relating to the degree of water damage to the exhaust passage of the internal combustion engine, and expands the predetermined operating range toward higher rotation speeds of the internal combustion engine as the degree of water damage increases.

2. Further provided is a water depth level acquisition unit for acquiring the water depth level around the vehicle body, the control device expands the predetermined operating range of the turbocharger to a higher rotation side as the water depth level increases as information about the degree of water damage increases, The vehicle of claim 1 .

3. 3. The vehicle according to claim 2, wherein the control device expands the predetermined operating range toward the high rotation speed side as the time that has elapsed since the water depth level became equal to or greater than a first predetermined value increases.

4. a temperature acquisition unit that acquires the temperature of water around the vehicle body, the control device expands the predetermined operating range toward the high rotation speed side as the water temperature acquired by the temperature acquisition unit decreases.

3. The vehicle of claim 2.

5. the supercharger includes a low-speed supercharger and a high-speed supercharger that is used in a higher speed region of the internal combustion engine than the low-speed supercharger and is disposed above the low-speed supercharger, the control device expands the predetermined operating range of the low rotation supercharger toward the high rotation side when the water depth level is equal to or greater than a first predetermined value, and does not expand the predetermined operating range of the low rotation supercharger immediately after start of the internal combustion engine regardless of the water depth level. A vehicle according to any one of claims 2 to 4.

6. 6. The vehicle according to claim 5, wherein the control device does not expand the predetermined operating range of the low-speed supercharger when the water depth level is equal to or greater than a second predetermined value that is greater than the first predetermined value.

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